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Sample records for grb afterglow emission

  1. GRB off-axis afterglows and the emission from the accompanying supernovae

    NASA Astrophysics Data System (ADS)

    Kathirgamaraju, Adithan; Barniol Duran, Rodolfo; Giannios, Dimitrios

    2016-09-01

    Gamma-ray burst (GRB) afterglows are likely produced in the shock that is driven as the GRB jet interacts with the external medium. Long-duration GRBs are also associated with powerful supernovae (SNe). We consider the optical and radio afterglows of long GRBs for both blasts viewed along the jet axis (`on-axis' afterglows) and misaligned observes (`off-axis' afterglows). Comparing the optical emission from the afterglow with that of the accompanying SN, using SN 1998bw as an archetype, we find that only a few per cent of afterglows viewed off-axis are brighter than the SN. For observable optical off-axis afterglows, the viewing angle is at most twice the half-opening angle of the GRB jet. Radio off-axis afterglows should be detected with upcoming radio surveys within a few hundred Mpc. We propose that these surveys will act as `radio triggers', and that dedicated radio facilities should follow-up these sources. Follow-ups can unveil the presence of the radio SN remnant, if present. In addition, they can probe the presence of a mildly relativistic component, either associated with the GRB jet or the SN ejecta, expected in these sources.

  2. Multiwavelength Observations of GRB 110731A: GeV Emission from Onset to Afterglow

    NASA Astrophysics Data System (ADS)

    Ackermann, M.; Ajello, M.; Asano, K.; Baldini, L.; Barbiellini, G.; Baring, M. G.; Bastieri, D.; Bellazzini, R.; Blandford, R. D.; Bonamente, E.; Borgland, A. W.; Bottacini, E.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Cecchi, C.; Charles, E.; Chaves, R. C. G.; Chekhtman, A.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; Cutini, S.; D'Ammando, F.; de Angelis, A.; de Palma, F.; Dermer, C. D.; Silva, E. do Couto e.; Drell, P. S.; Drlica-Wagner, A.; Favuzzi, C.; Fegan, S. J.; Focke, W. B.; Franckowiak, A.; Fukazawa, Y.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Giglietto, N.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Granot, J.; Greiner, J.; Grenier, I. A.; Grove, J. E.; Guiriec, S.; Hadasch, D.; Hanabata, Y.; Hayashida, M.; Hays, E.; Hughes, R. E.; Jackson, M. S.; Jogler, T.; Jóhannesson, G.; Johnson, A. S.; Knödlseder, J.; Kocevski, D.; Kuss, M.; Lande, J.; Larsson, S.; Latronico, L.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Mazziotta, M. N.; McEnery, J. E.; Mehault, J.; Mészáros, P.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Monte, C.; Monzani, M. E.; Moretti, E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Naumann-Godo, M.; Norris, J. P.; Nuss, E.; Nymark, T.; Ohno, M.; Ohsugi, T.; Omodei, N.; Orienti, M.; Orlando, E.; Paneque, D.; Perkins, J. S.; Pesce-Rollins, M.; Piron, F.; Pivato, G.; Racusin, J. L.; Rainò, S.; Rando, R.; Razzano, M.; Razzaque, S.; Reimer, A.; Reimer, O.; Romoli, C.; Roth, M.; Ryde, F.; Sanchez, D. A.; Sgrò, C.; Siskind, E. J.; Sonbas, E.; Spinelli, P.; Stamatikos, M.; Takahashi, H.; Tanaka, T.; Thayer, J. G.; Thayer, J. B.; Tibaldo, L.; Tinivella, M.; Tosti, G.; Troja, E.; Usher, T. L.; Vandenbroucke, J.; Vasileiou, V.; Vianello, G.; Vitale, V.; Waite, A. P.; Winer, B. L.; Wood, K. S.; Yang, Z.; Gruber, D.; Bhat, P. N.; Bissaldi, E.; Briggs, M. S.; Burgess, J. M.; Connaughton, V.; Foley, S.; Kippen, R. M.; Kouveliotou, C.; McBreen, S.; McGlynn, S.; Paciesas, W. S.; Pelassa, V.; Preece, R.; Rau, A.; van der Horst, A. J.; von Kienlin, A.; Kann, D. A.; Filgas, R.; Klose, S.; Krühler, T.; Fukui, A.; Sako, T.; Tristram, P. J.; Oates, S. R.; Ukwatta, T. N.; Littlejohns, O.

    2013-02-01

    We report on the multiwavelength observations of the bright, long gamma-ray burst GRB 110731A, by the Fermi and Swift observatories, and by the MOA and GROND optical telescopes. The analysis of the prompt phase reveals that GRB 110731A shares many features with bright Large Area Telescope bursts observed by Fermi during the first three years on-orbit: a light curve with short time variability across the whole energy range during the prompt phase, delayed onset of the emission above 100 MeV, extra power-law component and temporally extended high-energy emission. In addition, this is the first GRB for which simultaneous GeV, X-ray, and optical data are available over multiple epochs beginning just after the trigger time and extending for more than 800 s, allowing temporal and spectral analysis in different epochs that favor emission from the forward shock in a wind-type medium. The observed temporally extended GeV emission is most likely part of the high-energy end of the afterglow emission. Both the single-zone pair transparency constraint for the prompt signal and the spectral and temporal analysis of the forward-shock afterglow emission independently lead to an estimate of the bulk Lorentz factor of the jet Γ ~ 500-550.

  3. Synchrotron and inverse-Compton emissions from pairs formed in GRB afterglows (analytical treatment)

    SciTech Connect

    Panaitescu, A.; Vestrand, W. T.

    2014-10-01

    We calculate the synchrotron and inverse-Compton emissions from pairs formed in gamma-ray burst (GRB) afterglows from high-energy photons (above 100 MeV), assuming a power-law photon spectrum C {sub ν}∝ν{sup –2} and considering only the pairs generated from primary high-energy photons. The essential properties of these pairs (number, minimal energy, cooling energy, distribution with energy) and of their emission (peak flux, spectral breaks, spectral slope) are set by the observables GeV fluence Φ(t) = Ft and spectrum, and by the Lorentz factor, Γ, and magnetic field, B, of the source of high-energy photons, at observer time, t. Optical and X-ray pseudo light curves, F {sub ν}(Γ), are calculated for the given B; proper synchrotron self-Compton light curves are calculated by setting the dynamics Γ(t) of the high-energy photon source to be that of a decelerating, relativistic shock. It is found that the emission from pairs can accommodate the flux and decays of the optical flashes measured during the prompt (GRB) phase, but it decays faster than the X-ray plateaus observed during the delayed (afterglow) phase. The brightest pair optical emission is obtained for 100 < Γ < 500, and depends mostly on the GeV fluence, being independent of the source redshift. Emission from pairs formed during the GRB phase offers an alternate explanation to reverse-shock optical flashes. These two models may be distinguished based on their corresponding flux decay index-spectral slope relations, different correlations with the Large Area Telescope fluence, or through modeling of the afterglow multiwavelength data.

  4. PANCHROMATIC OBSERVATIONS OF THE TEXTBOOK GRB 110205A: CONSTRAINING PHYSICAL MECHANISMS OF PROMPT EMISSION AND AFTERGLOW

    SciTech Connect

    Zheng, W.; Shen, R. F.; Sakamoto, T.; Beardmore, A. P.; De Pasquale, M.; Wu, X. F.; Zhang, B.; Gorosabel, J.; Urata, Y.; Sugita, S.; Pozanenko, A.; Sahu, D. K.; Im, M.; Ukwatta, T. N.; Andreev, M.; Klunko, E. E-mail: rfshen@astro.utoronto.ca; and others

    2012-06-01

    We present a comprehensive analysis of a bright, long-duration (T{sub 90} {approx} 257 s) GRB 110205A at redshift z = 2.22. The optical prompt emission was detected by Swift/UVOT, ROTSE-IIIb, and BOOTES telescopes when the gamma-ray burst (GRB) was still radiating in the {gamma}-ray band, with optical light curve showing correlation with {gamma}-ray data. Nearly 200 s of observations were obtained simultaneously from optical, X-ray, to {gamma}-ray (1 eV to 5 MeV), which makes it one of the exceptional cases to study the broadband spectral energy distribution during the prompt emission phase. In particular, we clearly identify, for the first time, an interesting two-break energy spectrum, roughly consistent with the standard synchrotron emission model in the fast cooling regime. Shortly after prompt emission ({approx}1100 s), a bright (R = 14.0) optical emission hump with very steep rise ({alpha} {approx} 5.5) was observed, which we interpret as the reverse shock (RS) emission. It is the first time that the rising phase of an RS component has been closely observed. The full optical and X-ray afterglow light curves can be interpreted within the standard reverse shock (RS) + forward shock (FS) model. In general, the high-quality prompt and afterglow data allow us to apply the standard fireball model to extract valuable information, including the radiation mechanism (synchrotron), radius of prompt emission (R{sub GRB} {approx} 3 Multiplication-Sign 10{sup 13} cm), initial Lorentz factor of the outflow ({Gamma}{sub 0} {approx} 250), the composition of the ejecta (mildly magnetized), the collimation angle, and the total energy budget.

  5. THERMAL EMISSIONS SPANNING THE PROMPT AND THE AFTERGLOW PHASES OF THE ULTRA-LONG GRB 130925A

    SciTech Connect

    Basak, Rupal; Rao, A. R. E-mail: arrao@tifr.res.in

    2015-07-01

    GRB 130925A is an ultra-long gamma-ray burst (GRB), and it shows clear evidence for thermal emission in the soft X-ray data of the Swift/X-ray Telescope (XRT; ∼0.5 keV), lasting until the X-ray afterglow phase. Due to the long duration of the GRB, the burst could be studied in hard X-rays with high-resolution focusing detectors (NuSTAR). The blackbody temperature, as measured by the Swift/XRT, shows a decreasing trend until the late phase (Piro et al.) whereas the high-energy data reveal a significant blackbody component during the late epochs at an order of magnitude higher temperature (∼5 keV) compared to contemporaneous low energy data (Bellm et al.). We resolve this apparent contradiction by demonstrating that a model with two black bodies and a power law (2BBPL) is consistent with the data right from the late prompt emission to the afterglow phase. Both blackbodies show a similar cooling behavior up to late times. We invoke a structured jet, having a fast spine and a slower sheath layer, to identify the location of these blackbodies. Independent of the physical interpretation, we propose that the 2BBPL model is a generic feature of the prompt emission of all long GRBs, and the thermal emission found in the afterglow phase of different GRBs reflects the lingering thermal component of the prompt emission with different timescales. We strengthen this proposal by pointing out a close similarity between the spectral evolutions of this GRB and GRB 090618, a source with significant wide band data during the early afterglow phase.

  6. Radio rebrightening of the GRB afterglow by the accompanying supernova

    NASA Astrophysics Data System (ADS)

    Barniol Duran, R.; Giannios, D.

    2015-12-01

    The gamma-ray burst (GRB) jet powers the afterglow emission by shocking the surrounding medium, and radio afterglow can now be routinely observed to almost a year after the explosion. Long-duration GRBs are accompanied by supernovae (SNe) that typically contain much more energy than the GRB jet. Here we consider the fact that the SN blast wave will also produce its own afterglow (supernova remnant emission), which will peak at much later time (since it is non-relativistic), when the SN blast wave transitions from a coasting phase to a decelerating Sedov-Taylor phase. We predict that this component will peak generally a few tens of years after the explosion and it will outshine the GRB powered afterglow well-before its peak emission. In the case of GRB 030329, where the external density is constrained by the ˜10-year coverage of the radio GRB afterglow, the radio emission is predicted to start rising over the next decade and to continue to increase for the following decades up to a level of ˜ mJy. Detection of the SN-powered radio emission will greatly advance our knowledge of particle acceleration in ˜0.1c shocks.

  7. SYNCHROTRON SELF-COMPTON EMISSION AS THE ORIGIN OF THE GAMMA-RAY AFTERGLOW OBSERVED IN GRB 980923

    SciTech Connect

    Fraija, N.; Gonzalez, M. M.; Lee, W. H. E-mail: magda@astro.unam.mx

    2012-05-20

    GRB 980923 was one of the brightest bursts observed by the Burst and Transient Source Experiment. Previous studies have detected two distinct components in addition to the main prompt episode, which is well described by a Band function. The first of these is a tail with a duration of {approx_equal} 400 s, while the second is a high-energy component lasting {approx_equal} 2 s. We summarize the observations and argue for a unified model in which the tail can be understood as the early {gamma}-ray afterglow from forward shock synchrotron emission, while the high-energy component arises from synchrotron self-Compton from the reverse shock. Consistency between the main assumption of thick shell emission and agreement between the observed and computed values for fluxes, break energies, starting times, and spectral indices leads to a requirement that the ejecta must be highly magnetized.

  8. GRB050525A : Multiband modelling of the afterglow

    NASA Astrophysics Data System (ADS)

    Resmi, Lekshmi; Misra, Kuntal; Castro-Tirado, Alberto

    2011-08-01

    The Swift era has posed a challenge to the standard blast-wave model of Gamma Ray Burst afterglows. The achromatic steepening of the afterglow lightcurves (`jet break') considered in the model as the signature of outflow collimation, has become almost rare. Several afterglows exhibited complex lightcurves that did not confirm by the predicted spectral--temporal `closure relations' of the blastwave model. Here we present optical observations and broadband modelling of the afterglow of GRB0505025A, a bright burst detected and followed up by Swift. We find that the overall evolution of the afterglow can not be explained by a single forward shock emission, though the late time evolution is compatible with the predictions of the standard afterglow model, including a jet break. We explain the afterglow evolution based on a two-component jet model and estimate the physical parameters.

  9. Panchromatic Observations of the Textbook GRB 110205A: Constraining Physical Mechanisms of Prompt Emission and Afterglow

    NASA Technical Reports Server (NTRS)

    Zheng, W.; Shen, R. F.; Sakamoto, T.; Beardmore, A. P.; De Pasquale, M.; Wu, X. F.; Gorosabel, J.; Urata, Y.; Sugita, S.; Zhang, B.; Pozanenko, A.; Nissinen, M.; Sahu, D. K.; Im, M.; Ukwatta, T. N.; Andreev, M.; Klunko, E.; Volnova, A.; Akerlof, C. W.; Anto, P.; Barthelmy, S. D.; Breeveld, A.; Carsenty, U.; Gehrels, N.; Sonbas, E.

    2011-01-01

    We present a comprehensive analysis of a bright, long duration (T(sub 90) approx. 257 s) GRB 110205A at redshift z = 2.22. The optical prompt emission was detected by Swift/UVOT, ROTSE-IIIb and BOOTES telescopes when the GRB was still radiating in the gamma-ray band. Thanks to its long duration, nearly 200 s of observations were obtained simultaneously from optical, X-ray to gamma-ray (1 eV - 5 MeV), which makes it one of the exceptional cases to study the broadband spectral energy distribution across 6 orders of magnitude in energy during the prompt emission phase. In particular, by fitting the time resolved prompt spectra, we clearly identify, for the first time, an interesting two-break energy spectrum, roughly consistent with the standard GRB synchrotron emission model in the fast cooling regime. Although the prompt optical emission is brighter than the extrapolation of the best fit X/ -ray spectra, it traces the -ray light curve shape, suggesting a relation to the prompt high energy emission. The synchrotron + synchrotron self-Compton (SSC) scenario is disfavored by the data, but the models invoking a pair of internal shocks or having two emission regions can interpret the data well. Shortly after prompt emission (approx. 1100 s), a bright (R = 14.0) optical emission hump with very steep rise ( alpha approx. 5.5) was observed which we interpret as the emission from the reverse shock. It is the first time that the rising phase of a reverse shock component has been closely observed.

  10. The Supercritical Pile GRB Model: The Prompt to Afterglow Evolution

    NASA Technical Reports Server (NTRS)

    Kazanas, Demosthenes

    2008-01-01

    The 'Supercritical Pile' is a very economical gamma ray burst (GRB) model that provides for the efficient conversion of the energy stored in the protons of a Relativistic Blast Wave (RBW) into radiation and at the same time produces - in the prompt GRB phase, even in the absence of any particle acceleration - a spectral peak at an energy sim 1 MeV. We extend this model to include also the evolution of the RBW Lorentz factor Gamma and thus follow the spectral and temporal features of this model into the early GRB afterglow stage. One of the novel features of the present treatment is the inclusion of the feedback of the GRB produced radiation on the evolution of Gamma with radius. This feedback and the presence of kinematic and dynamic thresholds in the model can be the sources of rich time evolution which we have begun to explore. In particular, one can this way obtain afterglow light curves with steep decays followed by the more conventional flatter afterglow slopes, while at the same time preserving the desirable features of the model, i.e. the well defined relativistic electron source and radiative processes that produce the proper peak in the nu F spectra. Furthermore, the existence of a kinematic threshold in this model provides for a operational distinction of the prompt and afterglow GRB stages; in fact, the afterglow stage sets in when the RBW Lorentz factor cannot anymore fulfill the kinematic condition for pair formation in the photon - proton pair production reactions that constitute the fundamental process for the dissipation of the blast wave kinetic energy. We present the results of a specific set of parameters of this model with emphasis on the multiwavelength prompt emission and transition to the early afterglow.

  11. The Supercritical Pile GRB Model: The Prompt to Afterglow Evolution

    NASA Technical Reports Server (NTRS)

    Mastichiadis, A.; Kazanas, D.

    2009-01-01

    The "Supercritical Pile" is a very economical GRB model that provides for the efficient conversion of the energy stored in the protons of a Relativistic Blast Wave (RBW) into radiation and at the same time produces - in the prompt GRB phase, even in the absence of any particle acceleration - a spectral peak at energy approx. 1 MeV. We extend this model to include the evolution of the RBW Lorentz factor Gamma and thus follow its spectral and temporal features into the early GRB afterglow stage. One of the novel features of the present treatment is the inclusion of the feedback of the GRB produced radiation on the evolution of Gamma with radius. This feedback and the presence of kinematic and dynamic thresholds in the model can be the sources of rich time evolution which we have began to explore. In particular. one can this may obtain afterglow light curves with steep decays followed by the more conventional flatter afterglow slopes, while at the same time preserving the desirable features of the model, i.e. the well defined relativistic electron source and radiative processes that produce the proper peak in the (nu)F(sub nu), spectra. In this note we present the results of a specific set of parameters of this model with emphasis on the multiwavelength prompt emission and transition to the early afterglow.

  12. Prompt, early and afterglow optical observations of five γ-ray bursts: GRB 100901A, GRB 100902A, GRB 100905A, GRB 100906A and GRB 101020A

    NASA Astrophysics Data System (ADS)

    Gorbovskoy, E. S.; Lipunova, G. V.; Lipunov, V. M.; Kornilov, V. G.; Belinski, A. A.; Shatskiy, N. I.; Tyurina, N. V.; Kuvshinov, D. A.; Balanutsa, P. V.; Chazov, V. V.; Kuznetsov, A.; Zimnukhov, D. S.; Kornilov, M. V.; Sankovich, A. V.; Krylov, A.; Ivanov, K. I.; Chvalaev, O.; Poleschuk, V. A.; Konstantinov, E. N.; Gress, O. A.; Yazev, S. A.; Budnev, N. M.; Krushinski, V. V.; Zalozhnich, I. S.; Popov, A. A.; Tlatov, A. G.; Parhomenko, A. V.; Dormidontov, D. V.; Senik, V.; Yurkov, V. V.; Sergienko, Yu. P.; Varda, D.; Kudelina, I. P.; Castro-Tirado, A. J.; Gorosabel, J.; Sánchez-Ramírez, R.; Jelinek, M.; Tello, J. C.

    2012-04-01

    We present the results of the prompt, early and afterglow optical observations of five γ-ray bursts (GRBs): GRB 100901A, GRB 100902A, GRB 100905A, GRB 100906A and GRB 101020A. These observations were made with the Mobile Astronomical System of TElescope-Robots in Russia (MASTER-II Net), the 1.5-m telescope of the Sierra Nevada Observatory and the 2.56-m Nordic Optical Telescope. For two sources, GRB 100901A and GRB 100906A, we detected optical counterparts and obtained light curves starting before the cessation of γ-ray emission, at 113 and 48 s after the trigger, respectively. Observations of GRB 100906A were conducted in two polarizing filters. Observations of the other three bursts gave the upper limits on the optical flux; their properties are briefly discussed. A more detailed analysis of GRB 100901A and GRB 100906A, supplemented by Swift data, provides the following results and indicates different origins for the prompt optical radiation in the two bursts. The light-curve patterns and spectral distributions suggest that there is a common production site for the prompt optical and high-energy emission in GRB 100901A. The results of the spectral fits for GRB 100901A in the range from optical to X-ray favour power-law energy distributions and a consistent value of the optical extinction in the host galaxy. GRB 100906A produced a smoothly peaking optical light curve, suggesting that the prompt optical radiation in this GRB originated in a front shock. This is supported by a spectral analysis. We have found that the Amati and Ghirlanda relations are satisfied for GRB 100906A. We obtain an upper limit on the value of the optical extinction on the host of GRB 100906A.

  13. Short GRB Prompt and Afterglow Correlations

    NASA Technical Reports Server (NTRS)

    Gehrels, Neil

    2007-01-01

    The Swift data set on short GRBs has now grown large enough to study correlations of key parameters. The goal is to compare long and short bursts to better understand similarities and differences in the burst origins. In this study we consider the both prompt and afterglow fluxes. It is found that the optical, X-ray and gamma-ray emissions are linearly correlated - stronger bursts tend to have brighter afterglows, and bursts with brighter X-ray afterglow tend to have brighter optical afterglow. Both the prompt and afterglow fluxes are, on average, lower for short bursts than for long. Although there are short GRBs with undetected optical emission, there is no evidence for "dark" short bursts with anomalously low opt/X ratios. The weakest short bursts have a low X-ray/gamma-ray ratio.

  14. The distribution of equivalent widths in long GRB afterglow spectra

    NASA Astrophysics Data System (ADS)

    de Ugarte Postigo, A.; Fynbo, J. P. U.; Thöne, C. C.; Christensen, L.; Gorosabel, J.; Milvang-Jensen, B.; Schulze, S.; Jakobsson, P.; Wiersema, K.; Sánchez-Ramírez, R.; Leloudas, G.; Zafar, T.; Malesani, D.; Hjorth, J.

    2012-12-01

    Context. The extreme brightness of gamma-ray burst (GRB) afterglows and their simple spectral shape make them ideal beacons to study the interstellar medium of their host galaxies through absorption line spectroscopy at almost any redshift. Aims: We describe the distribution of rest-frame equivalent widths (EWs) of the most prominent absorption features in GRB afterglow spectra, providing the means to compare individual spectra to the sample and identify its peculiarities. Methods: Using 69 low-resolution GRB afterglow spectra, we conduct a study of the rest-frame EWs distribution of features with an average rest-frame EW larger than 0.5 Å. To compare an individual GRB with the sample, we develop EW diagrams as a graphical tool, and we give a catalogue with diagrams for the 69 spectra. We introduce a line strength parameter (LSP) that allows us to quantify the strength of the absorption features in a GRB spectrum as compared to the sample by a single number. Using the distributions of EWs of single-species features, we derive the distribution of their column densities by a curve of growth (CoG) fit. Results: We find correlations between the LSP and the extinction of the GRB, the UV brightness of the host galaxies and the neutral hydrogen column density. However, we see no significant evolution of the LSP with the redshift. There is a weak correlation between the ionisation of the absorbers and the energy of the GRB, indicating that, either the GRB event is responsible for part of the ionisation, or that galaxies with high-ionisation media produce more energetic GRBs. Spectral features in GRB spectra are, on average, 2.5 times stronger than those seen in QSO intervening damped Lyman-α (DLA) systems and slightly more ionised. In particular we find a larger excess in the EW of C ivλλ1549 relative to QSO DLAs, which could be related to an excess of Wolf-Rayet stars in the environments of GRBs. From the CoG fitting we obtain an average number of components in the

  15. Radio observations of GRB 100418a: Test of an energy injection model explaining long-lasting GRB afterglows

    SciTech Connect

    Moin, A.; Wang, Z.; Chandra, P.; Miller-Jones, J. C. A.; Tingay, S. J.; Reynolds, C.; Taylor, G. B.; Frail, D. A.; Phillips, C. J.

    2013-12-20

    We present the results of our radio observational campaign of gamma-ray burst (GRB) 100418a, for which we used the Australia Telescope Compact Array, the Very Large Array, and the Very Long Baseline Array. GRB 100418a was a peculiar GRB with unusual X-ray and optical afterglow profiles featuring a plateau phase with a very shallow rise. This observed plateau phase was believed to be due to a continued energy injection mechanism that powered the forward shock, giving rise to an unusual and long-lasting afterglow. The radio afterglow of GRB 100418a was detectable several weeks after the prompt emission. We conducted long-term monitoring observations of the afterglow and attempted to test the energy injection model advocating that the continuous energy injection is due to shells of material moving at a wide range of Lorentz factors. We obtained an upper limit of γ < 7 for the expansion rate of the GRB 100418a radio afterglow, indicating that the range-of-Lorentz factor model could only be applicable for relatively slow-moving ejecta. A preferred explanation could be that continued activity of the central engine may have powered the long-lasting afterglow.

  16. The ultra-long GRB 111209A. II. Prompt to afterglow and afterglow properties

    SciTech Connect

    Stratta, G.; Gendre, B.; Boër, M.; Atteia, J. L.; Coward, D. M.; Howell, E.; De Pasquale, M.; Oates, S.; Klotz, A.; Piro, L.

    2013-12-10

    The 'ultra-long' gamma-ray burst GRB 111209A at redshift z = 0.677 is the longest GRB ever observed thus far, with a rest frame prompt emission duration of ∼4 hr. In order to explain the burst exceptional longevity, a low-metallicity blue supergiant progenitor was invoked. In this article we further constrain the phenomenology and progenitor properties of this peculiar GRB by performing a multiband temporal and spectral analysis of both the prompt and the afterglow emission. We use proprietary and publicly available data from Swift, Konus WIND, XMM-Newton, and TAROT, as well as from other ground-based optical and radio telescopes. We find some peculiar properties that are possibly connected to the exceptional nature of this burst, namely: (1) an unprecedented large optical delay of 410 ± 50 s between the peak time in gamma-rays and the peak time in the optical of a marked multiwavelength flare; (2) multiwavelength prompt emission spectral modeling requires a certain amount of dust in the circumburst environment. The dust produces a rest frame visual extinction of A{sub V} = 0.3-1.5 mag, and may undergo destruction at late times; and (3) we detect the presence of a hard spectral extra power-law component at the end of the X-ray steep steep decay phase and before the start of the X-ray afterglow, which has never been revealed thus far in past GRBs. The optical afterglow shows more usual properties; it has a flux power-law decay with an index of 1.6 ± 0.1 and a late rebrightening feature observed at ∼1.1 the day after the first Burst Alert Telescope trigger. We discuss our findings in the context of several possible interpretations that have been given thus far of the complex multiband GRB phenomenology and propose a binary channel formation for the blue supergiant progenitor.

  17. GRB 030329: 3 years of radio afterglow monitoring.

    PubMed

    van der Horst, A J; Kamble, A; Wijers, R A M J; Resmi, L; Bhattacharya, D; Rol, E; Strom, R; Kouveliotou, C; Oosterloo, T; Ishwara-Chandra, C H

    2007-05-15

    Radio observations of gamma-ray burst (GRB) afterglows are essential for our understanding of the physics of relativistic blast waves, as they enable us to follow the evolution of GRB explosions much longer than the afterglows in any other wave band. We have performed a 3-year monitoring campaign of GRB 030329 with the Westerbork Synthesis Radio Telescopes and the Giant Metrewave Radio Telescope. Our observations, combined with observations at other wavelengths, have allowed us to determine the GRB blast wave physical parameters, such as the total burst energy and the ambient medium density, as well as to investigate the jet nature of the relativistic outflow. Further, by modelling the late-time radio light curve of GRB 030329, we predict that the Low-Frequency Array (30-240 MHz) will be able to observe afterglows of similar GRBs, and constrain the physics of the blast wave during its non-relativistic phase.

  18. GRB 030329: 3 years of radio afterglow monitoring.

    PubMed

    van der Horst, A J; Kamble, A; Wijers, R A M J; Resmi, L; Bhattacharya, D; Rol, E; Strom, R; Kouveliotou, C; Oosterloo, T; Ishwara-Chandra, C H

    2007-05-15

    Radio observations of gamma-ray burst (GRB) afterglows are essential for our understanding of the physics of relativistic blast waves, as they enable us to follow the evolution of GRB explosions much longer than the afterglows in any other wave band. We have performed a 3-year monitoring campaign of GRB 030329 with the Westerbork Synthesis Radio Telescopes and the Giant Metrewave Radio Telescope. Our observations, combined with observations at other wavelengths, have allowed us to determine the GRB blast wave physical parameters, such as the total burst energy and the ambient medium density, as well as to investigate the jet nature of the relativistic outflow. Further, by modelling the late-time radio light curve of GRB 030329, we predict that the Low-Frequency Array (30-240 MHz) will be able to observe afterglows of similar GRBs, and constrain the physics of the blast wave during its non-relativistic phase. PMID:17293318

  19. The SEDs and Host Galaxies of the Dustiest GRB Afterglows

    NASA Technical Reports Server (NTRS)

    Kruhler, T.; Greiner, J.; Schady, P.; Savaglio, S.; Afonso, P. M. J.; Clemens, C.; Elliott, J.; Filgas, R.; Gruber, D.; Kann, D. A.; Klose, S.; Kupcu-Yoldas, A.; McBreen, S.; Olivares, E.; Pierini, D.; Rau, A.; Rossi, A.; Nardini, M.; Nicuesa Guelbenzu, A.; Sudilovsky, V.; Updike, A. C.

    2011-01-01

    The afterglows and host galaxies of long gamma-ray bursts (GRBs) offer unique opportunities to study star-forming galaxies in the high-z Universe, Until recently, however. the information inferred from GRB follow-up observations was mostly limited to optically bright afterglows. biasing all demographic studies against sight-lines that contain large amounts of dust. Aims. Here we present afterglow and host observations for a sample of bursts that are exemplary of previously missed ones because of high visual extinction (A(sub v) (Sup GRB) approx > 1 mag) along the sight-line. This facilitates an investigation of the properties, geometry and location of the absorbing dust of these poorly-explored host galaxies. and a comparison to hosts from optically-selected samples. Methods. This work is based on GROND optical/NIR and Swift/XRT X-ray observations of the afterglows, and multi-color imaging for eight GRB hosts. The afterglow and galaxy spectral energy distributions yield detailed insight into physical properties such as the dust and metal content along the GRB sight-line as well as galaxy-integrated characteristics like the host's stellar mass, luminosity. color-excess and star-formation rate. Results. For the eight afterglows considered in this study we report for the first time the redshift of GRBs 081109 (z = 0.97S7 +/- 0.0005). and the visual extinction towards GRBs 0801109 (A(sub v) (Sup GRB) = 3.4(sup +0.4) (sub -0.3) mag) and l00621A (A(sub v) (Sup GRB) = 3.8 +/- 0.2 mag), which are among the largest ever derived for GRB afterglows. Combined with non-extinguished GRBs. there is a strong anti-correlation between the afterglow's metals-to-dust ratio and visual extinction. The hosts of the dustiest afterglows are diverse in their properties, but on average redder(((R - K)(sub AB)) approximates 1.6 mag), more luminous ( approximates 0.9 L (sup *)) and massive ((log M(sup *) [M(solar]) approximates 9.8) than the hosts of optically-bright events. We hence probe

  20. REM observations of GRB 060418 and GRB 060607A: the onset of the afterglow and the initial fireball Lorentz factor determination

    NASA Astrophysics Data System (ADS)

    Molinari, E.; Vergani, S. D.; Malesani, D.; Covino, S.; D'Avanzo, P.; Chincarini, G.; Zerbi, F. M.; Antonelli, L. A.; Conconi, P.; Testa, V.; Tosti, G.; Vitali, F.; D'Alessio, F.; Malaspina, G.; Nicastro, L.; Palazzi, E.; Guetta, D.; Campana, S.; Goldoni, P.; Masetti, N.; Meurs, E. J. A.; Monfardini, A.; Norci, L.; Pian, E.; Piranomonte, S.; Rizzuto, D.; Stefanon, M.; Stella, L.; Tagliaferri, G.; Ward, P. A.; Ihle, G.; Gonzalez, L.; Pizarro, A.; Sinclaire, P.; Valenzuela, J.

    2007-07-01

    Context: Gamma-ray burst (GRB) emission is believed to originate in highly relativistic fireballs. Aims: Currently, only lower limits were securely set to the initial fireball Lorentz factor Γ_0. We aim to provide a direct measure of Γ_0. Methods: The early-time afterglow light curve carries information about Γ_0, which determines the time of the afterglow peak. We have obtained early observations of the near-infrared afterglows of GRB 060418 and GRB 060607A with the REM robotic telescope. Results: For both events, the afterglow peak could be clearly singled out, allowing a firm determination of the fireball Lorentz of Γ_0˜ 400, fully confirming the highly relativistic nature of GRB fireballs. The deceleration radius was inferred to be R_dec ≈ 1017 cm. This is much larger than the internal shocks radius (believed to power the prompt emission), thus providing further evidence for a different origin of the prompt and afterglow stages of the GRB. Tables 2 and 3 are only available in electronic form at http://www.aanda.org

  1. Circular polarization in the optical afterglow of GRB 121024A.

    PubMed

    Wiersema, K; Covino, S; Toma, K; van der Horst, A J; Varela, K; Min, M; Greiner, J; Starling, R L C; Tanvir, N R; Wijers, R A M J; Campana, S; Curran, P A; Fan, Y; Fynbo, J P U; Gorosabel, J; Gomboc, A; Götz, D; Hjorth, J; Jin, Z P; Kobayashi, S; Kouveliotou, C; Mundell, C; O'Brien, P T; Pian, E; Rowlinson, A; Russell, D M; Salvaterra, R; di Serego Alighieri, S; Tagliaferri, G; Vergani, S D; Elliott, J; Fariña, C; Hartoog, O E; Karjalainen, R; Klose, S; Knust, F; Levan, A J; Schady, P; Sudilovsky, V; Willingale, R

    2014-05-01

    Gamma-ray bursts (GRBs) are most probably powered by collimated relativistic outflows (jets) from accreting black holes at cosmological distances. Bright afterglows are produced when the outflow collides with the ambient medium. Afterglow polarization directly probes the magnetic properties of the jet when measured minutes after the burst, and it probes the geometric properties of the jet and the ambient medium when measured hours to days after the burst. High values of optical polarization detected minutes after the burst of GRB 120308A indicate the presence of large-scale ordered magnetic fields originating from the central engine (the power source of the GRB). Theoretical models predict low degrees of linear polarization and no circular polarization at late times, when the energy in the original ejecta is quickly transferred to the ambient medium and propagates farther into the medium as a blast wave. Here we report the detection of circularly polarized light in the afterglow of GRB 121024A, measured 0.15 days after the burst. We show that the circular polarization is intrinsic to the afterglow and unlikely to be produced by dust scattering or plasma propagation effects. A possible explanation is to invoke anisotropic (rather than the commonly assumed isotropic) electron pitch-angle distributions, and we suggest that new models are required to produce the complex microphysics of realistic shocks in relativistic jets.

  2. Circular polarization in the optical afterglow of GRB 121024A

    NASA Astrophysics Data System (ADS)

    Wiersema, K.; Covino, S.; Toma, K.; van der Horst, A. J.; Varela, K.; Min, M.; Greiner, J.; Starling, R. L. C.; Tanvir, N. R.; Wijers, R. A. M. J.; Campana, S.; Curran, P. A.; Fan, Y.; Fynbo, J. P. U.; Gorosabel, J.; Gomboc, A.; Götz, D.; Hjorth, J.; Jin, Z. P.; Kobayashi, S.; Kouveliotou, C.; Mundell, C.; O'Brien, P. T.; Pian, E.; Rowlinson, A.; Russell, D. M.; Salvaterra, R.; di Serego Alighieri, S.; Tagliaferri, G.; Vergani, S. D.; Elliott, J.; Fariña, C.; Hartoog, O. E.; Karjalainen, R.; Klose, S.; Knust, F.; Levan, A. J.; Schady, P.; Sudilovsky, V.; Willingale, R.

    2014-05-01

    Gamma-ray bursts (GRBs) are most probably powered by collimated relativistic outflows (jets) from accreting black holes at cosmological distances. Bright afterglows are produced when the outflow collides with the ambient medium. Afterglow polarization directly probes the magnetic properties of the jet when measured minutes after the burst, and it probes the geometric properties of the jet and the ambient medium when measured hours to days after the burst. High values of optical polarization detected minutes after the burst of GRB 120308A indicate the presence of large-scale ordered magnetic fields originating from the central engine (the power source of the GRB). Theoretical models predict low degrees of linear polarization and no circular polarization at late times, when the energy in the original ejecta is quickly transferred to the ambient medium and propagates farther into the medium as a blast wave. Here we report the detection of circularly polarized light in the afterglow of GRB 121024A, measured 0.15 days after the burst. We show that the circular polarization is intrinsic to the afterglow and unlikely to be produced by dust scattering or plasma propagation effects. A possible explanation is to invoke anisotropic (rather than the commonly assumed isotropic) electron pitch-angle distributions, and we suggest that new models are required to produce the complex microphysics of realistic shocks in relativistic jets.

  3. Circular polarization in the optical afterglow of GRB 121024A.

    PubMed

    Wiersema, K; Covino, S; Toma, K; van der Horst, A J; Varela, K; Min, M; Greiner, J; Starling, R L C; Tanvir, N R; Wijers, R A M J; Campana, S; Curran, P A; Fan, Y; Fynbo, J P U; Gorosabel, J; Gomboc, A; Götz, D; Hjorth, J; Jin, Z P; Kobayashi, S; Kouveliotou, C; Mundell, C; O'Brien, P T; Pian, E; Rowlinson, A; Russell, D M; Salvaterra, R; di Serego Alighieri, S; Tagliaferri, G; Vergani, S D; Elliott, J; Fariña, C; Hartoog, O E; Karjalainen, R; Klose, S; Knust, F; Levan, A J; Schady, P; Sudilovsky, V; Willingale, R

    2014-05-01

    Gamma-ray bursts (GRBs) are most probably powered by collimated relativistic outflows (jets) from accreting black holes at cosmological distances. Bright afterglows are produced when the outflow collides with the ambient medium. Afterglow polarization directly probes the magnetic properties of the jet when measured minutes after the burst, and it probes the geometric properties of the jet and the ambient medium when measured hours to days after the burst. High values of optical polarization detected minutes after the burst of GRB 120308A indicate the presence of large-scale ordered magnetic fields originating from the central engine (the power source of the GRB). Theoretical models predict low degrees of linear polarization and no circular polarization at late times, when the energy in the original ejecta is quickly transferred to the ambient medium and propagates farther into the medium as a blast wave. Here we report the detection of circularly polarized light in the afterglow of GRB 121024A, measured 0.15 days after the burst. We show that the circular polarization is intrinsic to the afterglow and unlikely to be produced by dust scattering or plasma propagation effects. A possible explanation is to invoke anisotropic (rather than the commonly assumed isotropic) electron pitch-angle distributions, and we suggest that new models are required to produce the complex microphysics of realistic shocks in relativistic jets. PMID:24776800

  4. The afterglow of GRB 130427A from 1 to 10{sup 16} GHz

    SciTech Connect

    Perley, D. A.; Cenko, S. B.; Corsi, A.; Tanvir, N. R.; Wiersema, K.; Levan, A. J.; Kann, D. A.; Greiner, J.; Sonbas, E.; Zheng, W.; Clubb, K. I.; Zhao, X.-H.; Bai, J.-M.; Chang, L.; Bremer, M.; Castro-Tirado, A. J.; Fruchter, A.; Göğüş, E.; Güver, T.; and others

    2014-01-20

    We present multiwavelength observations of the afterglow of GRB 130427A, the brightest (in total fluence) gamma-ray burst (GRB) of the past 29 yr. Optical spectroscopy from Gemini-North reveals the redshift of the GRB to be z = 0.340, indicating that its unprecedented brightness is primarily the result of its relatively close proximity to Earth; the intrinsic luminosities of both the GRB and its afterglow are not extreme in comparison to other bright GRBs. We present a large suite of multiwavelength observations spanning from 300 s to 130 days after the burst and demonstrate that the afterglow shows relatively simple, smooth evolution at all frequencies, with no significant late-time flaring or rebrightening activity. The entire data set from 1 GHz to 10 GeV can be modeled as synchrotron emission from a combination of reverse and forward shocks in good agreement with the standard afterglow model, providing strong support to the applicability of the underlying theory and clarifying the nature of the GeV emission observed to last for minutes to hours following other very bright GRBs. A tenuous, wind-stratified circumburst density profile is required by the observations, suggesting a massive-star progenitor with a low mass-loss rate, perhaps due to low metallicity. GRBs similar in nature to GRB 130427A, inhabiting low-density media and exhibiting strong reverse shocks, are probably not uncommon but may have been difficult to recognize in the past owing to their relatively faint late-time radio emission; more such events should be found in abundance by the new generation of sensitive radio and millimeter instruments.

  5. GRB afterglows in the nonrelativistic phase

    NASA Astrophysics Data System (ADS)

    Huang, Y. F.; Lu, T.

    2008-10-01

    When discussing the afterglows of gamma-ray bursts analytically, it is usually assumed that the external shock is always ultra-relativisitc, with the bulk Lorentz factor much larger than 1. However, we show that the deceleration of the external shock is actually very quick. The afterglow may typically enter the nonrelativistic phase in several days to teens of days, and may even enter the deep Newtonian phase in tens of days to several months. One thus should be careful in using those familiar analytical expressions that are derived only under the ultra-relativistic assumption. To explain the observed afterglows that typically last for a few weeks to several months, we need to consider the dynamics and radiation in the nonrelativisitic phase.

  6. Spectroscopic Observations of the Bright Afterglow of GRB021004

    NASA Astrophysics Data System (ADS)

    Harrison, Fiona

    2001-09-01

    One of the holy grails of gamma-ray burst research is to detect X-ray line signatures from an afterglow with high statistical significance. Of all possible observations, this perhaps offers the best chance of constraining the GRB mechanism and environment, and could provide the "smoking gun" signature connecting GRBs to massive stellar deaths. In order to accomplish this, we know long observations within one day of the event are necessary.

  7. The Late Afterglow and Host Galaxy of GRB 990712.

    PubMed

    Hjorth; Holland; Courbin; Dar; Olsen; Scodeggio

    2000-05-10

    We present deep Hubble Space Telescope (HST) imaging, as well as ground-based imaging and spectroscopy, of the optical afterglow associated with the long-duration gamma-ray burst GRB 990712 and its host galaxy. The data were obtained 48-123 days after the burst occurred. The magnitudes of the host (R=21.9, V=22.5) and optical afterglow (R=25.4, V=25.8, 47.7 days after the burst) favor a scenario in which the optical light follows a pure power-law decay with an index of alpha approximately -1.0. We find no evidence for a contribution from a supernova like SN 1998bw. This suggests that either there are multiple classes of long-duration gamma-ray bursts or that the peak luminosity of the supernova was more than 1.5 mag fainter than SN 1998bw. The HST images and EFOSC2 spectra indicate that the gamma-ray burst was located in a bright, extended feature (possibly a star-forming region) 1.4 kpc from the nucleus of a 0.2L*B galaxy at z=0.434, possibly a Seyfert 2 galaxy. The late-time afterglow and host galaxy of GRB 990712 bear some resemblance to those of GRB 970508. PMID:10813669

  8. The Supercritical Pile Gamma-Ray Burst Model: The GRB Afterglow Steep Decline and Plateau Phase

    NASA Technical Reports Server (NTRS)

    Sultana, Joseph; Kazanas, D.; Mastichiadis, A.

    2013-01-01

    We present a process that accounts for the steep decline and plateau phase of the Swift X-Ray Telescope (XRT) light curves, vexing features of gamma-ray burst (GRB) phenomenology. This process is an integral part of the "supercritical pile" GRB model, proposed a few years ago to account for the conversion of the GRB kinetic energy into radiation with a spectral peak at E(sub pk) is approx. m(sub e)C(exp 2). We compute the evolution of the relativistic blast wave (RBW) Lorentz factor Gamma to show that the radiation-reaction force due to the GRB emission can produce an abrupt, small (approx. 25%) decrease in Gamma at a radius that is smaller (depending on conditions) than the deceleration radius R(sub D). Because of this reduction, the kinematic criticality criterion of the "supercritical pile" is no longer fulfilled. Transfer of the proton energy into electrons ceases and the GRB enters abruptly the afterglow phase at a luminosity smaller by approx. m(sub p)/m(sub e) than that of the prompt emission. If the radius at which this slow-down occurs is significantly smaller than R(sub D), the RBW internal energy continues to drive the RBW expansion at a constant (new) Gamma and its X-ray luminosity remains constant until R(sub D) is reached, at which point it resumes its more conventional decay, thereby completing the "unexpected" XRT light curve phase. If this transition occurs at R is approx. equal to R(sub D), the steep decline is followed by a flux decrease instead of a "plateau," consistent with the conventional afterglow declines. Besides providing an account of these peculiarities, the model suggests that the afterglow phase may in fact begin before the RBW reaches R is approx. equal to R(sub D), thus providing novel insights into GRB phenomenology.

  9. The Supercritical Pile Gamma-Ray Burst Model: The GRB Afterglow Steep Decline and Plateau Phase

    NASA Astrophysics Data System (ADS)

    Sultana, J.; Kazanas, D.; Mastichiadis, A.

    2013-12-01

    We present a process that accounts for the steep decline and plateau phase of the Swift X-Ray Telescope (XRT) light curves, vexing features of gamma-ray burst (GRB) phenomenology. This process is an integral part of the "supercritical pile" GRB model, proposed a few years ago to account for the conversion of the GRB kinetic energy into radiation with a spectral peak at E pk ~ mec 2. We compute the evolution of the relativistic blast wave (RBW) Lorentz factor Γ to show that the radiation-reaction force due to the GRB emission can produce an abrupt, small (~25%) decrease in Γ at a radius that is smaller (depending on conditions) than the deceleration radius RD . Because of this reduction, the kinematic criticality criterion of the "supercritical pile" is no longer fulfilled. Transfer of the proton energy into electrons ceases and the GRB enters abruptly the afterglow phase at a luminosity smaller by ~mp /me than that of the prompt emission. If the radius at which this slow-down occurs is significantly smaller than RD , the RBW internal energy continues to drive the RBW expansion at a constant (new) Γ and its X-ray luminosity remains constant until RD is reached, at which point it resumes its more conventional decay, thereby completing the "unexpected" XRT light curve phase. If this transition occurs at R ~= RD , the steep decline is followed by a flux decrease instead of a "plateau," consistent with the conventional afterglow declines. Besides providing an account of these peculiarities, the model suggests that the afterglow phase may in fact begin before the RBW reaches R ~= RD , thus providing novel insights into GRB phenomenology.

  10. CALORIMETRY OF GRB 030329: SIMULTANEOUS MODEL FITTING TO THE BROADBAND RADIO AFTERGLOW AND THE OBSERVED IMAGE EXPANSION RATE

    SciTech Connect

    Mesler, Robert A.; Pihlstroem, Ylva M.

    2013-09-01

    We perform calorimetry on the bright gamma-ray burst GRB 030329 by fitting simultaneously the broadband radio afterglow and the observed afterglow image size to a semi-analytic MHD and afterglow emission model. Our semi-analytic method is valid in both the relativistic and non-relativistic regimes, and incorporates a model of the interstellar scintillation that substantially effects the broadband afterglow below 10 GHz. The model is fitted to archival measurements of the afterglow flux from 1 day to 8.3 yr after the burst. Values for the initial burst parameters are determined and the nature of the circumburst medium is explored. Additionally, direct measurements of the lateral expansion rate of the radio afterglow image size allow us to estimate the initial Lorentz factor of the jet.

  11. Optical and X-Ray Observations of GRB 060526: A Complex Afterglow Consistent with an Achromatic Jet Break

    NASA Technical Reports Server (NTRS)

    Dai, X.; Halpern, J. P.; Morgan, N. D.; Armstrong, E.; Mirabal, N.; Haislip. J. B.; Reichart, D. E.; Stanek, K. Z.

    2007-01-01

    We obtained 98 R-band and 18 B, r', i' images of the optical afterglow of GRB 060526 (z = 3.21) with the MDM 1.3 m, 2.4 m, and the PROMPT telescopes at CTIO over the five nights following the burst trigger. Combining these data with other optical observations reported in GCN and the Swift XRT observations, we compare the optical and X-ray afterglow light curves of GRB 060526. Both the optical and X-ray afterglow light curves show rich features, such as flares and breaks. The densely sampled optical observations provide very good coverage at T > 10(exp 4) s. We observed a break at 2.4 x 10(exp 5) sin the optical afterglow light curve. Compared with the X-ray afterglow light curve, the break is consistent with an achromatic break supporting the beaming models of GRBs. However, the prebreak and postbreak temporal decay slopes are difficult to explain in simple afterglow models. We estimated a jet angle of theta(sub j) approx. 7deg and a prompt emission size of R(sub prompt) approx. 2 x 10(exp 14) cm. In addition, we detected several optical flares with amplitudes of (Delta)m approx. 0.2,0.6, and 0.2 mag. The X-ray afterglows detected by Swift have shown complicated decay patterns. Recently, many well-sampled optical afterglows also show decays with flares and multiple breaks. GRB 060526 provides an additional case of such a complex, well-observed optical afterglow. The accumulated well-sampled afterglows indicate that most of the optical afterglows are complex.

  12. A possible explanation for the radio afterglow of GRB 980519: the dense medium effect

    NASA Astrophysics Data System (ADS)

    Wang, X. Y.; Dai, Z. G.; Lu, T.

    2000-09-01

    GRB 980519 is characterized by its rapidly declining optical and X-ray afterglows. Explanations of this behaviour include models invoking a dense medium environment, which makes the shock wave evolve quickly into the subrelativistic phase, a jet-like outflow, and a wind-shaped circumburst medium environment. Recently, Frail et al. found that the latter two cases are consistent with the radio afterglow of this burst. Here, by considering the transrelativistic shock hydrodynamics, we show that the dense medium model can also account for the radio light curve quite well. The potential virtue of the dense medium model for GRB 980519 is that it implies a smaller angular size of the afterglow, which is essential for interpreting the strong modulation of the radio light curve. Optical extinction arising from the dense medium is not important if the prompt optical-UV flash accompanying the γ-ray emission can destroy dust by sublimation out to an appreciable distance. Comparisons with some other radio afterglows are also discussed.

  13. THE UNUSUAL RADIO AFTERGLOW OF THE ULTRA-LONG GAMMA-RAY BURST GRB 130925A

    SciTech Connect

    Horesh, Assaf; Cenko, S. Bradley; Perley, Daniel A.; Kulkarni, S. R.; Hallinan, Gregg; Bellm, Eric

    2015-10-10

    GRB 130925A is one of the recent additions to the growing family of ultra-long gamma-ray bursts (GRBs; T90 ≳1000 s). While the X-ray emission of ultra-long GRBs have been studied extensively in the past, no comprehensive radio data set has been obtained so far. We report here the early discovery of an unusual radio afterglow associated with the ultra-long GRB 130925A. The radio emission peaks at low-frequencies (∼7 GHz) at early times, only 2.2 days after the burst occurred. More notably, the radio spectrum at frequencies above 10 GHz exhibits a rather steep cut-off, compared to other long GRB radio afterglows. This cut-off can be explained if the emitting electrons are either mono-energetic or originate from a rather steep, dN/dE ∝ E{sup −4}, power-law energy distribution. An alternative electron acceleration mechanism may be required to produce such an electron energy distribution. Furthermore, the radio spectrum exhibits a secondary underlying and slowly varying component. This may hint that the radio emission we observed is comprised of emission from both a reverse and a forward shock. We discuss our results in comparison with previous works that studied the unusual X-ray spectrum of this event and discuss the implications of our findings on progenitor scenarios.

  14. Shocked by the Very Bright Radio Flare and Afterglow of GRB 130427A

    NASA Astrophysics Data System (ADS)

    van der Horst, Alexander J.

    2014-01-01

    Gamma-ray burst (GRB) 130427A was extremely bright across the electromagnetic spectrum, with emission spanning 16 orders of magnitude in observing frequency, from almost 100 GeV gamma-rays down to the GHz radio regime. While the intrinsic luminosity of this GRB was not extreme compared to other GRBs, it displayed the largest measured fluence of the last three decades due to its proximity with a redshift of 0.34. One of the most notable characteristics of this GRB was its bright radio emission, in particular the radio flare which has been observed only a few times in other GRBs and is usually attributed to the reverse shock moving back into the GRB jet. Here we present radio observations with unprecedented temporal coverage at three observing frequencies obtained with the Westerbork Synthesis Radio Telescope (WSRT) and the Arcminute Microkelvin Imager (AMI). AMI had the earliest radio detection at 8 hours after the initial flash of gamma-rays, catching the radio flare on the rise. The 12-hour WSRT observations in the first few days enabled a detailed study of the short time-scale behavior at radio wavelengths. Besides our observations of the radio flare and afterglow up to three months after the gamma-ray trigger, we present our results for modeling the radio light curves together with the broadband data set in various other wavelength regimes, enabling us to determine physical parameters of both the reverse and forward shock of this enigmatic GRB.

  15. Anatomy of a dark burst - the afterglow of GRB 060108

    NASA Astrophysics Data System (ADS)

    Oates, S. R.; Mundell, C. G.; Piranomonte, S.; Page, K. L.; de Pasquale, M.; Monfardini, A.; Melandri, A.; Zane, S.; Guidorzi, C.; Malesani, D.; Gomboc, A.; Bannister, N.; Blustin, A. J.; Capalbi, M.; Carter, D.; D'Avanzo, P.; Kobayashi, S.; Krimm, H. A.; O'Brien, P. T.; Page, M. J.; Smith, R. J.; Steele, I. A.; Tanvir, N.

    2006-10-01

    We present a multiwavelength study of GRB 060108 - the 100th gamma-ray burst discovered by Swift. The X-ray flux and light curve (three segments plus a flare) detected with the X-ray Telescope are typical of Swift long bursts. We report the discovery of a faint optical afterglow detected in deep BVRi'-band imaging obtained with the Faulkes Telescope North beginning 2.75 min after the burst. The afterglow is below the detection limit of the Ultraviolet/Optical Telescope within 100 s of the burst, while is evident in K-band images taken with the United Kingdom Infrared Telescope 45 min after the burst. The optical light curve is sparsely sampled. Observations taken in the R and i' bands can be fitted either with a single power-law decay in flux, F(t) ~ t-α where α = 0.43 +/- 0.08, or with a two-segment light curve with an initial steep decay α1 < 0.88 +/- 0.2, flattening to a slope α2 ~ 0.31 +/- 0.12. A marginal evidence for rebrightening is seen in the i' band. Deep R-band imaging obtained ~12 d post-burst with the Very Large Telescope reveals a faint, extended object (R ~ 23.5mag) at the location of the afterglow. Although the brightness is compatible with the extrapolation of the slow decay with index α2, significant flux is likely due to a host galaxy. This implies that the optical light curve had a break before 12 d, akin to what observed in the X-rays. We derive the maximum photometric redshift z < 3.2 for GRB 060108. We find that the spectral energy distribution at 1000 s after the burst, from the optical to the X-ray range, is best fitted by a simple power law, Fν ~ ν-β, with βOX = 0.54 and a small amount of extinction. The optical to X-ray spectral index (βOX) confirms GRB 060108 to be one of the optically darkest bursts detected. Our observations rule out a high redshift as the reason for the optical faintness of GRB 060108. We conclude that a more likely explanation is a combination of an intrinsic optical faintness of the burst, a hard optical

  16. GRB 080503 LATE AFTERGLOW RE-BRIGHTENING: SIGNATURE OF A MAGNETAR-POWERED MERGER-NOVA

    SciTech Connect

    Gao, He; Ding, Xuan; Wu, Xue-Feng; Dai, Zi-Gao; Zhang, Bing E-mail: xfwu@pmo.ac.cn E-mail: zhang@physics.unlv.edu

    2015-07-10

    GRB 080503 is a short gamma-ray burst (GRB) detected by Swift and has been classified as a GRB originating from a compact star merger. The soft extended emission and the simultaneous late re-brightening in both the X-ray and optical afterglow light curves raise interesting questions regarding its physical origin. We show that the broadband data of GRB 080503 can be well explained within the framework of the double neutron star merger model, provided that the merger remnant is a rapidly rotating massive neutron star with an extremely high magnetic field (i.e., a millisecond magnetar). We show that the late optical re-brightening is consistent with the emission from a magnetar-powered “merger-nova.” This adds one more case to the growing sample of merger-novae associated with short GRBs. The soft extended emission and the late X-ray excess emission are well connected through a magnetar dipole spin-down luminosity evolution function, suggesting that direct magnetic dissipation is the mechanism to produce these X-rays. The X-ray emission initially leaks from a hole in the merger ejecta pierced by the short GRB jet. The hole subsequently closes after the magnetar spins down and the magnetic pressure drops below ram pressure. The X-ray photons are then trapped behind the merger-nova ejecta until the ejecta becomes optically thin at a later time. This explains the essentially simultaneous re-brightening in both the optical and X-ray light curves. Within this model, future gravitational-wave sources could be associated with a bright X-ray counterpart along with the merger-nova, even if the short GRB jet beams away from Earth.

  17. Modeling the Early Afterglow in the Short and Hard GRB 090510

    NASA Astrophysics Data System (ADS)

    Fraija, N.; Lee, W. H.; Veres, P.; Barniol Duran, R.

    2016-11-01

    The bright, short, and hard GRB 090510 was detected by all instruments aboard the Fermi and Swift satellites. The multiwavelength observations of this burst presented similar features to the Fermi-LAT-detected gamma-ray bursts. In the framework of the external shock model of early afterglow, a leptonic scenario that evolves in a homogeneous medium is proposed to revisit GRB 090510 and explain the multiwavelength light curve observations presented in this burst. These observations are consistent with the evolution of a jet before and after the jet break. The long-lasting LAT, X-ray, and optical fluxes are explained in the synchrotron emission from the adiabatic forward shock. Synchrotron self-Compton emission from the reverse shock is consistent with the bright LAT peak provided that the progenitor environment is entrained with strong magnetic fields. It could provide compelling evidence of magnetic field amplification in the neutron star merger.

  18. The 'Supercritical Pile' GRB Model: Afterglows and GRB, XRR, XRF Unification

    NASA Technical Reports Server (NTRS)

    Kazanas, D.

    2007-01-01

    We present the general notions and observational consequences of the "Supercritical Pile" GRB model; the fundamental feature of this model is a detailed process for the conversion of the energy stored in relativistic protons in the GRB Relativistic Blast Waves (RBW) into relativistic electrons and then into radiation. The conversion is effected through the $p \\, \\gamma \\rightarrow p \\, e circumflex + e circumflex -$ reaction, whose kinematic threshold is imprinted on the GRB spectra to provide a peak of their emitted luminosity at energy \\Ep $\\sim 1$ MeV in the lab frame. We extend this model to include, in addition to the (quasi--)thermal relativistic post-shock protons an accelerated component of power law form. This component guarantees the production of $e circumflex +e circumflex- - $pairs even after the RBW has slowed down to the point that its (quasi-) thermal protons cannot fulfill the threshold of the above reaction. We suggest that this last condition marks the transition from the prompt to the afterglow GRB phase. We also discuss conditions under which this transition is accompanied by a significant drop in the flux and could thus account for several puzzling, recent observations. Finally, we indicate that the same mechanism applied to the late stages of the GRB evolution leads to a decrease in \\Ep $\\propto \\Gamma circumflex 2(t)\\propto t circumflex {-3/4}$, a feature amenable to future observational tests.

  19. GRB 110731A: Early Afterglow in Stellar Wind Powered By a Magnetized Outflow

    NASA Astrophysics Data System (ADS)

    Fraija, N.

    2015-05-01

    One of the most energetic gamma-ray bursts, GRB 110731A, was observed from an optical to GeV energy range. Previous analysis of the prompt phase revealed similarities between the Large Area Telescope (LAT) bursts observed by Fermi: (1) a delayed onset of the high-energy emission (\\gt 100 MeV), (2) a short-lasting bright peak at later times, and (3) a temporally extended component from this phase, lasting hundreds of seconds. Additionally to the prompt phase, multiwavelength observations over different epochs showed that the spectral energy distribution was better fitted by a wind afterglow model. We present a leptonic model based on an early afterglow that evolves in a stellar wind of its progenitor. We apply this model to interpret the temporally extended LAT emission and the brightest LAT peak exhibited by the prompt phase of GRB 110731A. Additionally, using the same set of parameters, we describe the multiwavelength afterglow observations. The origin of the temporally extended LAT, X-ray, and optical flux is explained through synchrotron radiation from the forward shock (FS) and the brightest LAT peak is described, evoking the synchrotron self-Compton emission from the reverse shock (RS). The bulk Lorentz factor required in this model (Γ ≃ 520) lies in the range of values demanded for most LAT-detected GRBs. We show that the strength of the magnetic field in the RS region is ∼50 times stronger than that in the FS region. This result suggests that, for GRB 110731A, the central engine is likely entrained with strong magnetic fields.

  20. Discovery of the Low-Redshift Afterglow of GRB 011121 and Its Progenitor Supernova 2001ke

    NASA Astrophysics Data System (ADS)

    Garnavich, P. M.; Stanek, K. Z.; Wyrzykowski, L.; Infante, L.; Bendek, E.; Holland, S. T.; Bersier, D.; Jha, S.; Matheson, T.; Kirshner, R. P.; Phillips, M. M.; Krisciunas, K.; Carlberg, R.

    2002-05-01

    We identify and present the first optical observations of the afterglow of the Gamma-Ray Burst (GRB) 011121. Images were obtained with the OGLE 1.3m telescope in BVRI passbands, starting 10.3;hours after the burst. The temporal analysis of our data indicates a steep decay, independent of wavelength with Fν t{-1.72+/- 0.05}. There is no evidence for a break in the light curve earlier than 2.5 days after the burst. The spectral energy distribution determined from the early broad-band photometry is a power-law with Fν ν {-0.46+/- 0.10} after correcting for a large Galactic extinction. Spectra, obtained with the Magellan 6.5m Baade telescope, reveal narrow emission lines from the host galaxy and these provide a redshift of z=0.36, which is the lowest measured redshift for an optical afterglow. We also present late R and J-band observations of the afterglow ~ 14;days after the burst. The late-time photometry shows a large deviation from the initial decline and our data combined with Hubble Space Telescope photometry provide strong evidence for a supernova peaking less than 10 rest-frame days after the GRB. This is the best evidence to date that classical, long gamma-ray bursts are generated by core-collapse supernovae. This work is partially supported by NASA LTSA grant NAG5-9364.

  1. GRB Discoveries with Swift

    NASA Technical Reports Server (NTRS)

    Gehrels, Neil

    2008-01-01

    This brief presentation presents Swift Observatory recordings of gamma ray burst (GRB) activity. Long and short GRBs and afterglows are highlighted. Recordings of GRB emission, afterglow, optical/IR brightness, and flux density are presented. The time structure and current status of short GRB structures is also included.

  2. A search for absorption features in the afterglow of the unusual GRB 130925A

    NASA Astrophysics Data System (ADS)

    Bellm, Eric

    2012-09-01

    GRB 130925A produced several emission episodes triggering Swift-BAT, Fermi-GBM, and MAXI. The extraordinary length of this emission--over 10^4 seconds--would give GRB 130925A one of the highest total durations ever observed for a gamma-ray burst. While the initial bursting phase was similar to that of the the relativistic tidal disruption event Swift J1644+57, starting at 10^4 seconds after the trigger this event has entered a steady decay phase without new bursts (www.swift.ac.uk/xrt_curves/00571830/). Its classification is thus uncertain, as neither the long GRB class nor Swift J1644 provide direct parallels. Our NuSTAR spectroscopy during the decay phase has revealed evidence for a broad absorption feature never previously observed for either GRB afterglows or for tidal disruption events. Chandra observations will enable searches for lower-energy lines which may constrain the ionization state of this unprecedented event.

  3. A possible macronova in the late afterglow of the long-short burst GRB 060614

    NASA Astrophysics Data System (ADS)

    Yang, Bin; Jin, Zhi-Ping; Li, Xiang; Covino, Stefano; Zheng, Xian-Zhong; Hotokezaka, Kenta; Fan, Yi-Zhong; Piran, Tsvi; Wei, Da-Ming

    2015-06-01

    Long-duration (>2 s) γ-ray bursts that are believed to originate from the death of massive stars are expected to be accompanied by supernovae. GRB 060614, that lasted 102 s, lacks a supernova-like emission down to very stringent limits and its physical origin is still debated. Here we report the discovery of near-infrared bump that is significantly above the regular decaying afterglow. This red bump is inconsistent with even the weakest known supernova. However, it can arise from a Li-Paczyński macronova--the radioactive decay of debris following a compact binary merger. If this interpretation is correct, GRB 060614 arose from a compact binary merger rather than from the death of a massive star and it was a site of a significant production of heavy r-process elements. The significant ejected mass favours a black hole-neutron star merger but a double neutron star merger cannot be ruled out.

  4. A possible macronova in the late afterglow of the long-short burst GRB 060614.

    PubMed

    Yang, Bin; Jin, Zhi-Ping; Li, Xiang; Covino, Stefano; Zheng, Xian-Zhong; Hotokezaka, Kenta; Fan, Yi-Zhong; Piran, Tsvi; Wei, Da-Ming

    2015-06-11

    Long-duration (>2 s) γ-ray bursts that are believed to originate from the death of massive stars are expected to be accompanied by supernovae. GRB 060614, that lasted 102 s, lacks a supernova-like emission down to very stringent limits and its physical origin is still debated. Here we report the discovery of near-infrared bump that is significantly above the regular decaying afterglow. This red bump is inconsistent with even the weakest known supernova. However, it can arise from a Li-Paczyński macronova--the radioactive decay of debris following a compact binary merger. If this interpretation is correct, GRB 060614 arose from a compact binary merger rather than from the death of a massive star and it was a site of a significant production of heavy r-process elements. The significant ejected mass favours a black hole-neutron star merger but a double neutron star merger cannot be ruled out.

  5. The puzzling afterglow of GRB 050721: a rebrightening seen in the optical but not in the X-ray

    SciTech Connect

    Antonelli, L. A.; Romano, P.; Testa, V.; D'Elia, V.; Guetta, D.; Torii, K.; Malesani, D.

    2007-08-21

    We present here the analysis of the early and late multiwavelength afterglow emission, as observed by Swift a small robotic telescope, and the VLT. We compare early observations with late afterglow observations obtained with Swift and the VLT and we observe an intense rebrightening in the optical band at about one day after the burst which is not present in the X-ray band. The lack of detection in X-ray of such a strong rebrightening at lower energies may be described with a variable external density profile. In such a scenario, the combined X-ray and optical observations allow us to derive that the matter density located at {approx} 1017 cm from the burst is about a factor of 10 higher than in the inner region. This is the first time in which a rebrightening has been observed in the optical afterglow of a GRB that is clearly absent in the X-ray afterglow.

  6. An inverse Compton origin for the 55 GeV photon in the late afterglow of GRB 130907A

    SciTech Connect

    Tang, Qing-Wen; Wang, Xiang-Yu; Tam, Pak-Hin Thomas E-mail: phtam@phys.nthu.edu.tw

    2014-06-20

    The extended high-energy gamma-ray (>100 MeV) emission which occurs well after the prompt gamma-ray bursts (GRBs) is usually explained as the afterglow synchrotron radiation. Here we report the analysis of Fermi Large Area Telescope observations of GRB 130907A. A 55 GeV photon compatible with the position of the burst was found about 5 hr after the prompt phase. The probability that this photon is associated with GRB 130907A is higher than 99.96%. The energy of this photon exceeds the maximum synchrotron photon energy at this time and its occurrence thus challenges the synchrotron mechanism as the origin for the extended high-energy >10 GeV emission. Modeling of the broadband spectral energy distribution suggests that such high energy photons can be produced by the synchrotron self-Compton emission of the afterglow.

  7. Evidence for a Canonical GRB Afterglow Light Curve in the Swift/XRT Data

    NASA Technical Reports Server (NTRS)

    Nousek, J. A.; Kouveliotou, C.; Grupe, D.; Page, K.; Granot, J.; Ramirez-Ruiz, E.; Patel, S. K.; Burrows, D. N.; Mangano, V.; Barthelmy, S.

    2005-01-01

    We present new observations of the early X-ray afterglows of the first 27 gamma-ray bursts (GRBs) detected with the Swift X-ray Telescope (XRT). The early X-ray afterglows show a canonical behavior, where the light curve broadly consists of three distinct power law segments. These power law segments are separated by two corresponding break times. On top of this canonical behavior of the early X-ray light curve, many events have superimposed X-ray flares, which are most likely caused by internal shocks due to long lasting sporadx activity of the central engine, up to several hours after the GRB. We find that the initial steep decay is consistent with it being the tail of the prompt emission: from photons that are radiated at large angles relative to our line of sight. The first break in the light curve takes place when the forward shock emission becomes dominant, with the intermediate shallow flux decay likely caused by the continuous energy injection into the external shock. When this energy injection stops, a second break is then observed in the light curve. This energy injection increases the energy of the afterglow shock by at least a factor of f greater than or approx. equal to 4, and augments the already severe requirements for the efficiency of the prompt gamma-ray emission.

  8. Constraints on an Optical Afterglow and on Supernova Light Following the Short Burst GRB 050813

    NASA Technical Reports Server (NTRS)

    Ferrero, P.; Sanchez, S. F.; Kann, D. A.; Klose, S.; Greiner, J.; Gorosabel, J.; Hartmann, D. H.; Henden, A. A.; Moller, P.; Palazzi, E.; Rau, A.; Stecklum, B.; Castro-Tirado, A. J.; Fynbok J. P. U.; Hjorth, J.; Jakobsson, P.; Kouveliotou, C.; Masetti, N.; Pian, E.; Tanvir, N. R.; Wijers, R. A. M. J.

    2006-01-01

    We report early follow-up observations of the error box of the short burst 050813 using the telescopes at Calar Alto and at Observatorio Sierra Nevada (OSN), followed by deep VLT/FORS2 I-band observations obtained under very good seeing conditions 5.7 and 11.7 days after the event. No evidence for a GRB afterglow was found in our Calar Alto and OSN data, no rising supernova component was detected in our FORS2 images. A potential host galaxy can be identified in our FORS2 images, even though we cannot state with certainty its association with GRB 050813. IN any case, the optical afterglow of GRB 050813 was very faint, well in agreement with what is known so far about the optical properties of afterglows of short bursts. We conclude that all optical data are not in conflict with the interpretation that GRB 050813 was a short burst.

  9. Signature of a Spin-up Magnetar from Multi-band Afterglow Rebrightening of GRB 100814A

    NASA Astrophysics Data System (ADS)

    Yu, Y. B.; Huang, Y. F.; Wu, X. F.; Xu, M.; Geng, J. J.

    2015-06-01

    In recent years, more and more gamma-ray bursts (GRBs) with late rebrightenings in their multi-band afterglows have revealed the late-time activity of their central engines. GRB 100814A is a special case among the well-sampled events, with complex temporal and spectral evolution. The single power-law shallow decay index of the optical light curve observed by GROND between 640 s and 10 ks is {{α }opt}=0.57+/- 0.02, which apparently conflicts with expectations from the simple external shock model. In particular, there is remarkable rebrightening in the optical to near-infrared bands at late times, challenging the external shock model with synchrotron emission coming from the interaction of the blast wave with the surrounding interstellar medium. In this paper, we invoke a magnetar with spin evolution to explain the complex multi-band afterglow emission of GRB 100814A. The initial shallow decay phase in the optical bands and the plateau in the X-ray can be explained as being due to energy injection from a spin-down magnetar. At late times, with materials from the fall-back disk falling onto the central object of the burster, the angular momentum of the accreted materials is transferred to the magnetar, which leads to a spin up process. As a result, the magnetic dipole radiation luminosity will increase, resulting in significant rebrightening of the optical afterglow. We show that the model can well reproduce the observed multi-band afterglow emission.

  10. THE PROPERTIES OF THE 2175 A EXTINCTION FEATURE DISCOVERED IN GRB AFTERGLOWS

    SciTech Connect

    Zafar, Tayyaba; Watson, Darach; Eliasdottir, Ardis; Fynbo, Johan P. U.; Kruehler, Thomas; Leloudas, Giorgos; Schady, Patricia; Greiner, Jochen; Jakobsson, Pall; Thoene, Christina C.; Perley, Daniel A.; Morgan, Adam N.; Bloom, Joshua E-mail: darach@dark-cosmology.dk

    2012-07-01

    The unequivocal, spectroscopic detection of the 2175 A bump in extinction curves outside the Local Group is rare. To date, the properties of the bump have been examined in only two gamma-ray burst (GRB) afterglows (GRB 070802 and GRB 080607). In this work, we analyze in detail the detections of the 2175 Angstrom-Sign extinction bump in the optical spectra of two further GRB afterglows: GRB 080605 and 080805. We gather all available optical/near-infrared photometric, spectroscopic, and X-ray data to construct multi-epoch spectral energy distributions (SEDs) for both GRB afterglows. We fit the SEDs with the Fitzpatrick and Massa model with a single or broken power law. We also fit a sample of 38 GRB afterglows, known to prefer a Small Magellanic Cloud (SMC)-type extinction curve, with the same model. We find that the SEDs of GRB 080605 and GRB 080805 at two epochs are fit well with a single power law with a derived extinction of A{sub V} = 0.52{sup +0.13}{sub -0.16} and 0.50{sup +0.13}{sub -0.10}, and 2.1{sup +0.7}{sub -0.6} and 1.5 {+-} 0.2, respectively. While the slope of the extinction curve of GRB 080805 is not well constrained, the extinction curve of GRB 080605 has an unusual very steep far-UV rise together with the 2175 A bump. Such an extinction curve has previously been found in only a small handful of sightlines in the Milky Way. One possible explanation of such an extinction curve may be dust arising from two different regions with two separate grain populations, however we cannot distinguish the origin of the curve. We finally compare the four 2175 A bump sightlines to the larger GRB afterglow sample and to Local Group sightlines. We find that while the width and central positions of the bumps are consistent with what is observed in the Local Group, the relative strength of the detected bump (A{sub bump}) for GRB afterglows is weaker for a given A{sub V} than for almost any Local Group sightline. Such dilution of the bump strength may offer tentative

  11. THE AFTERGLOW AND ENVIRONMENT OF THE SHORT GRB 111117A

    SciTech Connect

    Margutti, R.; Berger, E.; Fong, W.; Zauderer, B. A.; Soderberg, A. M.; Milisavljevic, D.; Sanders, N.; Cenko, S. B.; Greiner, J.; Cucchiara, A.

    2012-09-01

    We present multi-wavelength observations of the afterglow of the short GRB 111117A, and follow-up observations of its host galaxy. From rapid optical and radio observations, we place limits of r {approx}> 25.5 mag at {delta}t Almost-Equal-To 0.55 days and F{sub {nu}}(5.8 GHz) {approx}< 18 {mu}Jy at {delta}t Almost-Equal-To 0.50 days, respectively. However, using a Chandra observation at {delta}t Almost-Equal-To 3.0 days we locate the absolute position of the X-ray afterglow to an accuracy of 0.''22 (1{sigma}), a factor of about six times better than the Swift/XRT position. This allows us to robustly identify the host galaxy and to locate the burst at a projected offset of 1.''25 {+-} 0.''20 from the host centroid. Using optical and near-IR observations of the host galaxy we determine a photometric redshift of z = 1.3{sup +0.3}{sub -0.2}, one of the highest for any short gamma-ray burst (GRB), leading to a projected physical offset for the burst of 10.5 {+-} 1.7 kpc, typical of previous short GRBs. At this redshift, the isotropic {gamma}-ray energy is E{sub {gamma},iso} Almost-Equal-To 3.0 Multiplication-Sign 10{sup 51} erg (rest-frame 23-2300 keV) with a peak energy of E{sub pk} Almost-Equal-To 850-2300 keV (rest-frame). In conjunction with the isotropic X-ray energy, GRB 111117A appears to follow our recently reported E{sub x,iso}-E{sub {gamma},iso}-E{sub pk} universal scaling. Using the X-ray data along with the optical and radio non-detections, we find that for a blastwave kinetic energy of E{sub K,iso} Almost-Equal-To E{sub {gamma},iso} erg, the circumburst density is n{sub 0} Almost-Equal-To 3 Multiplication-Sign 10{sup -4} - 1 cm{sup -3} (for a range of {epsilon}{sub B} = 0.001-0.1). Similarly, from the non-detection of a break in the X-ray light curve at {delta}t {approx}< 3 days, we infer a minimum opening angle for the outflow of {theta}{sub j} {approx}> 3-10 Degree-Sign (depending on the circumburst density). We conclude that Chandra observations of short

  12. Study of GRB Light-curve Decay Indices in the Afterglow Phase

    NASA Astrophysics Data System (ADS)

    Del Vecchio, Roberta; Dainotti, Maria Giovanna; Ostrowski, Michał

    2016-09-01

    In this work, we study the distribution of temporal power-law decay indices, α, in the gamma-ray burst (GRB) afterglow phase, fitted for 176 GRBs (139 long GRBs, 12 short GRBs with extended emission, and 25 X-ray flashes) with known redshifts. These indices are compared with the temporal decay index, α W , derived with the light-curve fitting using the Willingale et al. model. This model fitting yields similar distributions of α W to the fitted α, but for individual bursts a difference can be significant. Analysis of (α, L a ) distribution, where L a is the characteristic luminosity at the end of the plateau, reveals only a weak correlation of these quantities. However, we discovered a significant regular trend when studying GRB α values along the Dainotti et al. correlation between L a and the end time of the plateau emission in the rest frame, {T}a* , hereafter LT correlation. We note a systematic variation of the α parameter distribution with luminosity for any selected {T}a* . We analyze this systematics with respect to the fitted LT correlation line, expecting that the presented trend may allow us to constrain the GRB physical models. We also attempted to use the derived correlation of α ({T}a) versus {L}a({T}a) to diminish the luminosity scatter related to the variations of α along the LT distribution, a step forward in the effort of standardizing GRBs. A proposed toy model accounting for this systematics applied to the analyzed GRB distribution results in a slight increase of the LT correlation coefficient.

  13. The afterglow and the host galaxy of GRB 011211

    NASA Astrophysics Data System (ADS)

    Jakobsson, P.; Hjorth, J.; Fynbo, J. P. U.; Gorosabel, J.; Pedersen, K.; Burud, I.; Levan, A.; Kouveliotou, C.; Tanvir, N.; Fruchter, A.; Rhoads, J.; Grav, T.; Hansen, M. W.; Michelsen, R.; Andersen, M. I.; Jensen, B. L.; Pedersen, H.; Thomsen, B.; Weidinger, M.; Bhargavi, S. G.; Cowsik, R.; Pandey, S. B.

    2003-09-01

    We present optical, near-infrared, and X-ray observations of the optical afterglow (OA) of the X-ray rich, long-duration gamma-ray burst GRB 011211. Hubble Space Telescope (HST) data obtained 14, 26, 32, and 59 days after the burst, show the host galaxy to have a morphology that is fairly typical of blue galaxies at high redshift. We measure its magnitude to be R = 24.95 +/- 0.11. We detect a break in the OA R-band light curve which is naturally accounted for by a collimated outflow geometry. By fitting a broken power-law to the data we find a best fit with a break 1.56 +/- 0.02 days after the burst, a pre-break slope of alpha1 = -0.95 +/- 0.02, and a post-break slope of alpha2 = -2.11 +/- 0.07. The UV-optical spectral energy distribution (SED) around 14 hours after the burst is best fit with a power-law with index beta = -0.56 +/- 0.19 reddened by an SMC-like extinction law with a modest AV = 0.08 +/- 0.08 mag. By comparison, from the XMM-Newton X-ray data at around the same time, we find a decay index of alphaX = -1.62 +/- 0.36 and a spectral index of betaX = -1.21+0.10-0.15. Interpolating between the UV-optical and X-ray implies that the cooling frequency is located close to ~ 1016 Hz in the observer frame at the time of the observations. We argue, using the various temporal and spectral indices above, that the most likely afterglow model is that of a jet expanding into an external environment that has a constant mean density rather than a wind-fed density structure. We estimate the electron energy index for this burst to be p ~ 2.3. Based on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden. Based on observations made with ESO Telescopes at the Paranal Observatory by GRACE under programme ID 69.D-0701. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the

  14. The First Swift Ultraviolet/Optical Telescope GRB Afterglow Catalog

    NASA Astrophysics Data System (ADS)

    Roming, P. W. A.; Koch, T. S.; Oates, S. R.; Porterfield, B. L.; Vanden Berk, D. E.; Boyd, P. T.; Holland, S. T.; Hoversten, E. A.; Immler, S.; Marshall, F. E.; Page, M. J.; Racusin, J. L.; Schneider, D. P.; Breeveld, A. A.; Brown, P. J.; Chester, M. M.; Cucchiara, A.; DePasquale, M.; Gronwall, C.; Hunsberger, S. D.; Kuin, N. P. M.; Landsman, W. B.; Schady, P.; Still, M.

    2009-01-01

    We present the first Swift Ultraviolet/Optical Telescope (UVOT) gamma-ray burst (GRB) afterglow catalog. The catalog contains data from over 64,000 independent UVOT image observations of 229 GRBs first detected by Swift, the High Energy Transient Explorer 2 (HETE2), the International Gamma-Ray Astrophysics Laboratory (INTEGRAL), and the Interplanetary Network (IPN). The catalog covers GRBs occurring during the period from 2005 January 17 to 2007 June 16 and includes ~86% of the bursts detected by the Swift Burst Alert Telescope (BAT). The catalog provides detailed burst positional, temporal, and photometric information extracted from each of the UVOT images. Positions for bursts detected at the 3σ level are provided with a nominal accuracy, relative to the USNO-B1 catalog, of ~0farcs25. Photometry for each burst is given in three UV bands, three optical bands, and a "white" or open filter. Upper limits for magnitudes are reported for sources detected below 3σ. General properties of the burst sample and light curves, including the filter-dependent temporal slopes, are also provided. The majority of the UVOT light curves, for bursts detected at the 3σ level, can be fit by a single power-law, with a median temporal slope (α) of 0.96, beginning several hundred seconds after the burst trigger and ending at ~1 × 105 s. The median UVOT v-band (~5500 Å) magnitude at 2000 s for a sample of "well"-detected bursts is 18.02. The UVOT flux interpolated to 2000 s after the burst, shows relatively strong correlations with both the prompt Swift BAT fluence, and the Swift X-ray flux at 11 hr after the trigger.

  15. Evidence for a Canonical GRB Afterglow Light Curve in the Swift/XRT Data

    SciTech Connect

    Nousek, J.A.; Kouveliotou, C.; Grupe, D.; Page, K.; Granot, J.; Ramirez-Ruiz, E.; Patel, S.K.; Burrows, D.N.; Mangano, V.; Barthelmy, S.; Beardmore, A.P.; Campana, S.; Capalbi, M.; Chincarini, G.; Cusumano, G.; Falcone, A.D.; Gehrels, N.; Giommi, P.; Goad, M.; Godet, O.; Hurkett, C.; /Penn State U., Astron. Astrophys. /NASA, Marshall /Leicester U. /KIPAC, Menlo Park /Princeton, Inst. Advanced Study /NASA, Marshall /IASF, Palermo /Brera Observ. /Frascati /Milan Bicocca U. /NASA, Goddard

    2005-08-17

    We present new observations of the early X-ray afterglows of the first 27 gamma-ray bursts (GRBs) detected with the Swift X-ray Telescope (XRT). The early X-ray afterglows show a canonical behavior, where the light curve broadly consists of three distinct power law segments: (1) an initial very steep decay ({infinity} t{sup -a} with 3 {approx}< a{sub 1} {approx}< 5) , followed by (2) a very shallow decay (0.2 {approx}< a{sub 2} {approx}< 0.8), and finally (3) a somewhat steeper decay (1 {approx}< a{sub 3} {approx}< 1.5). These power law segments are separated by two corresponding break times, 300 s {approx}< t{sub break,1} {approx}< 500 s and 10{sup 3} s {approx}< t{sub break,2} {approx}< 10{sup 4} s. On top of this canonical behavior of the early X-ray light curve, many events have superimposed X-ray flares, which are most likely caused by internal shocks due to long lasting sporadic activity of the central engine, up to several hours after the GRB. We find that the initial steep decay is consistent with it being the tail of the prompt emission, from photons that are radiated at large angles relative to our line of sight. The first break in the light curve (t{sub break,1}) takes place when the forward shock emission becomes dominant, with the intermediate shallow flux decay (a{sub 2}) likely caused by the continuous energy injection into the external shock. When this energy injection stops, a second break is then observed in the light curve (t{sub break,2}). This energy injection increases the energy of the afterglow shock by at least a factor of f {approx}> 4, and augments the already severe requirements for the efficiency of the prompt gamma-ray emission.

  16. Very Large Telescope/Ultraviolet and Visual Echelle Spectrograph and FORS2 spectroscopy of the GRB 081008 afterglow

    NASA Astrophysics Data System (ADS)

    D'Elia, V.; Campana, S.; Covino, S.; D'Avanzo, P.; Piranomonte, S.; Tagliaferri, G.

    2011-11-01

    We aim at studying the gamma-ray burst (GRB), GRB 081008, environment by analysing the spectra of its optical afterglow. Ultraviolet and Visual Echelle Spectrograph/Very Large Telescope (UVES/VLT) high-resolution spectroscopy of GRB 081008 was secured ˜5 h after the Swift-BAT trigger. Our data set also comprises three VLT/FORS2 nearly simultaneous spectra of the same source. The availability of nearly simultaneous high- and low-resolution spectra for a GRB afterglow is an extremely rare event. The GRB-damped Lyman α system at z= 1.9683 shows that the interstellar medium (ISM) of the host galaxy is constituted by at least three components which contribute to the line profiles. Component I is the redmost one, and is 20 and 78 km s-1 redward components II and III, respectively. We detect several ground state and excited absorption features in components I and II. These features have been used to compute the distances between the GRB and the absorbers. Component I is found to be 52 ± 6 pc away from the GRB, while component II presents few excited transitions and its distance is 200+60- 80 pc. Component III only features a few, low-ionization and saturated lines suggesting that it is even farther from the GRB. Component I represents the closest absorber ever detected near a GRB. This (relatively) low distance can possibly be a consequence of a dense GRB environment, which prevents the GRB prompt/afterglow emission to strongly affect the ISM up to higher distances. The hydrogen column density associated with GRB 081008 is log NH/cm-2= 21.11 ± 0.10, and the metallicity of the host galaxy is in the range of [X/H] =-1.29 to -0.52. In particular, we found [Fe/H] =-1.19 ± 0.11 and [Zn/H] =-0.52 ± 0.11 with respect to solar values. This discrepancy can be explained by the presence of dust in the GRB ISM, given the opposite refractory properties of iron and zinc. By deriving the depletion pattern for GRB 081008, we find the optical extinction in the visual band to be AV

  17. THE AFTERGLOW AND ULIRG HOST GALAXY OF THE DARK SHORT GRB 120804A

    SciTech Connect

    Berger, E.; Zauderer, B. A.; Margutti, R.; Laskar, T.; Fong, W.; Chornock, R.; Dupuy, T. J.; Levan, A.; Tunnicliffe, R. L.; Mangano, V.; Fox, D. B.; Tanvir, N. R.; Menten, K. M.; Hjorth, J.; Roth, K.

    2013-03-10

    We present the optical discovery and subarcsecond optical and X-ray localization of the afterglow of the short GRB 120804A, as well as optical, near-IR, and radio detections of its host galaxy. X-ray observations with Swift/XRT, Chandra, and XMM-Newton extending to {delta}t Almost-Equal-To 19 days reveal a single power-law decline. The optical afterglow is faint, and comparison to the X-ray flux indicates that GRB 120804A is ''dark'', with a rest-frame extinction of A {sup host}{sub V} Almost-Equal-To 2.5 mag (at z = 1.3). The intrinsic neutral hydrogen column density inferred from the X-ray spectrum, N{sub H,{sub int}}(z = 1.3) Almost-Equal-To 2 Multiplication-Sign 10{sup 22} cm{sup -2}, is commensurate with the large extinction. The host galaxy exhibits red optical/near-IR colors. Equally important, JVLA observations at Almost-Equal-To 0.9-11 days reveal a constant flux density of F{sub {nu}}(5.8 GHz) = 35 {+-} 4 {mu}Jy and an optically thin spectrum, unprecedented for GRB afterglows, but suggestive instead of emission from the host galaxy. The optical/near-IR and radio fluxes are well fit with the scaled spectral energy distribution of the local ultraluminous infrared galaxy (ULIRG) Arp 220 at z Almost-Equal-To 1.3, with a resulting star formation rate of x Almost-Equal-To 300 M{sub Sun} yr{sup -1}. The inferred extinction and small projected offset (2.2 {+-} 1.2 kpc) are also consistent with the ULIRG scenario, as is the presence of a companion galaxy at the same redshift and with a separation of about 11 kpc. The limits on radio afterglow emission, in conjunction with the observed X-ray and optical emission, require a circumburst density of n {approx} 10{sup -3} cm{sup -3}, an isotropic-equivalent energy scale of E{sub {gamma},{sub iso}} Almost-Equal-To E{sub K,{sub iso}} Almost-Equal-To 7 Multiplication-Sign 10{sup 51} erg, and a jet opening angle of {theta}{sub j} {approx}> 11 Degree-Sign . The expected fraction of luminous infrared galaxies in the short GRB

  18. Towards understanding magnetic field generation in relativistic shocks with GRB afterglow observations and the GRB radiation mechanism with photospheric simulations and the X-ray flare radiation mechanism

    NASA Astrophysics Data System (ADS)

    Santana, Rodolfo

    2015-12-01

    In this thesis, we present three projects on open questions in the Gammaray Burst (GRB) field. In the first project, we used X-ray and optical observations to determine the amount of amplification of the ISM magnetic field needed to explain the GRB afterglow observations. We determined that mild amplification is required, at a level stronger than shock-compression but weaker than predicted by the Weibel mechanism. In the second project, we present a Monte Carlo code we wrote from scratch to perform realistic simulations of the photospheric process, one of the mechanisms considered to explain the GRB gamma-ray emission. We determined that photospheric emission can explain the GRB gamma-ray spectrum above the peak-energy if the photons are taken to have a temperature much smaller than the electron temperature and if the interactions between photons and electrons take place at a large optical depth. In the third project, we used multi-wavelength observations to constrain the X-ray flare radiation mechanism. We determined that synchrotron from a Poynting jet and the Photospheric process are the best candidates to explain the X-ray flare observations.

  19. A possible macronova in the late afterglow of the long–short burst GRB 060614

    PubMed Central

    Yang, Bin; Jin, Zhi-Ping; Li, Xiang; Covino, Stefano; Zheng, Xian-Zhong; Hotokezaka, Kenta; Fan, Yi-Zhong; Piran, Tsvi; Wei, Da-Ming

    2015-01-01

    Long-duration (>2 s) γ-ray bursts that are believed to originate from the death of massive stars are expected to be accompanied by supernovae. GRB 060614, that lasted 102 s, lacks a supernova-like emission down to very stringent limits and its physical origin is still debated. Here we report the discovery of near-infrared bump that is significantly above the regular decaying afterglow. This red bump is inconsistent with even the weakest known supernova. However, it can arise from a Li-Paczyński macronova—the radioactive decay of debris following a compact binary merger. If this interpretation is correct, GRB 060614 arose from a compact binary merger rather than from the death of a massive star and it was a site of a significant production of heavy r-process elements. The significant ejected mass favours a black hole–neutron star merger but a double neutron star merger cannot be ruled out. PMID:26065563

  20. A possible macronova in the late afterglow of the long-short burst GRB 060614.

    PubMed

    Yang, Bin; Jin, Zhi-Ping; Li, Xiang; Covino, Stefano; Zheng, Xian-Zhong; Hotokezaka, Kenta; Fan, Yi-Zhong; Piran, Tsvi; Wei, Da-Ming

    2015-01-01

    Long-duration (>2 s) γ-ray bursts that are believed to originate from the death of massive stars are expected to be accompanied by supernovae. GRB 060614, that lasted 102 s, lacks a supernova-like emission down to very stringent limits and its physical origin is still debated. Here we report the discovery of near-infrared bump that is significantly above the regular decaying afterglow. This red bump is inconsistent with even the weakest known supernova. However, it can arise from a Li-Paczyński macronova--the radioactive decay of debris following a compact binary merger. If this interpretation is correct, GRB 060614 arose from a compact binary merger rather than from the death of a massive star and it was a site of a significant production of heavy r-process elements. The significant ejected mass favours a black hole-neutron star merger but a double neutron star merger cannot be ruled out. PMID:26065563

  1. Measuring the beaming angle of GRB 030329 by fitting the rebrightenings in its multiband afterglow

    NASA Astrophysics Data System (ADS)

    Deng, Wei; Huang, Yong-Feng; Kong, Si-Wei

    2010-11-01

    Multiple rebrightenings have been observed in the multiband afterglow of GRB 030329. In particular, a marked and quick rebrightening occurred at about t ~ 1.2 × 105 s. Energy injection from late and slow shells seems to be the best interpretation for these rebrightenings. Usually it is assumed that the energy is injected into the whole external shock. However, in the case of GRB 030329, the rebrightenings are so quick that the usual consideration fails to give a satisfactory fit to the observed light curves. Actually, since these late/slow shells freely coast in the wake of the external shock, they should be cold and may not expand laterally. The energy injection then should only occur at the central region of the external shock. Considering this effect, we numerically re-fit the quick rebrightenings observed in GRB 030329. By doing this, we were able to derive the beaming angle of the energy injection process. Our result, with a relative residual of only 5% - 10% during the major rebrightening, is better than any previous modeling. The derived energy injection angle is about 0.035. We assume that these late shells are ejected by the central engine via the same mechanism as those early shells that produce the prompt gamma-ray burst. The main difference is that their velocities are much slower, so that they catch up with the external shock relatively late and are manifested as the observed quick rebrightenings. If this were true, then the derived energy injection angle can give a good measure of the beaming angle of the prompt γ-ray emission. Our study may hopefully provide a novel method to measure the beaming angle of gamma-ray bursts.

  2. GRB 070125 and the environments of spectral-line poor afterglow absorbers

    NASA Astrophysics Data System (ADS)

    De Cia, A.; Starling, R. L. C.; Wiersema, K.; van der Horst, A. J.; Vreeswijk, P. M.; Björnsson, G.; de Ugarte Postigo, A.; Jakobsson, P.; Levan, A. J.; Rol, E.; Schulze, S.; Tanvir, N. R.

    2011-11-01

    GRB 070125 is among the most energetic bursts detected and the most extensively observed so far. Nevertheless, unresolved issues are still open in the literature on the physics of the afterglow and on the gamma-ray burst (GRB) environment. In particular, GRB 070125 was claimed to have exploded in a galactic halo environment, based on the uniqueness of the optical spectrum and the non-detection of an underlying host galaxy. In this work we collect all publicly available data and address these issues by modelling the near-infrared to X-ray spectral energy distribution (SED) and studying the high signal-to-noise ratio Very Large Telescope/FOcal Reducer/low dispersion Spectrograph afterglow spectrum in comparison with a larger sample of GRB absorbers. The SED reveals a synchrotron cooling break in the ultraviolet, low equivalent hydrogen column density and little reddening caused by a Large Magellanic Cloud type or Small Magellanic Cloud type extinction curve. From the weak Mg II absorption at z= 1.5477 in the spectrum, we derived log N(Mg II) = 12.96+0.13- 0.18 and upper limits on the ionic column density of several metals. These suggest that the GRB absorber is most likely a Lyman limit system with a 0.03 < Z < 1.3 Z⊙ metallicity. The comparison with other GRB absorbers places GRB 070125 at the low end of the absorption-line equivalent width distribution, confirming that weak spectral features and spectral-line poor absorbers are not so uncommon in afterglow spectra. Moreover, we show that the effect of photoionization on the gas surrounding the GRB, combined with a low N(H I) along a short segment of the line of sight within the host galaxy, can explain the lack of spectral features in GRB 070125. Finally, the non-detection of an underlying galaxy is consistent with a faint GRB host galaxy, well within the GRB host brightness distribution. Thus, the possibility that GRB 070125 is simply located in the outskirts of a gas-rich, massive star-forming region inside its

  3. GRB 021211 as a Faint Analogue of GRB 990123: Exploring the Similarities and Differences in the Optical Afterglows

    NASA Technical Reports Server (NTRS)

    Holland, Stephen T.; Bersier, David; Bloom, J. S.; Garnavich, Peter M.; Caldwell, Nelson; Challis, Peter; Kirshner, Robert; Luhman, Kevin; McLeod, Brian; Stanek, K. Z.

    2004-01-01

    We present BVR(sub c)JHK(sub s) photometry of the optical afterglow of the gamma-ray burst GRB 021211 taken at the Magellan, MMT, and WIYN observatories between 0.7 and 50 days after the burst. We find an intrinsic spectral slope at optical and near-infrared wavelengths of 0.69 +/- 0.14 at 0.87 days. The optical decay during the first day is almost identical to that of GRB 990123 except that GRB 021211's optical afterglow was intrinsically approximately 38 times fainter and the transition from the reverse shock to the forward shock may have occurred earlier than it did for GRB 990123. We find no evidence for a jet break or the cooling break passing through optical frequencies during the first day after the burst. There is weak evidence for a break in the J-band decay between 0.89 and 1.87 days which may be due to a jet. The optical and infrared data are consistent with a relativistic fireball where the shocked electrons are in the slow cooling regime and the electron index is 2.3 +/- 0.1. The burst appears to have occurred in a homogeneous ambient medium. Our analysis suggests that the jet of GRB 021211 may have a small opening angle (1.4 deg-4.4 deg) and that the total gamma-ray energy is much less than the canonical value of 1.33 x 10(exp 51) erg. If, this is the case then most of the energy of the burst may be in another form such as a frozen magnetic field, in supernova ejecta, or in a second jet component. The host galaxy of GRB 021211 is subluminous and has a star formation rate of at least 1 solar mass/yr.

  4. DISCOVERY OF SMOOTHLY EVOLVING BLACKBODIES IN THE EARLY AFTERGLOW OF GRB 090618: EVIDENCE FOR A SPINE–SHEATH JET?

    SciTech Connect

    Basak, Rupal; Rao, A. R. E-mail: arrao@tifr.res.in

    2015-10-20

    GRB 090618 is a bright gamma-ray burst (GRB) with multiple pulses. It shows evidence of thermal emission in the initial pulses as well as in the early afterglow phase. Because high-resolution spectral data from the Swift/X-ray Telescope (XRT) are available for the early afterglow, we investigate the shape and evolution of the thermal component in this phase using data from the Swift/Burst Alert Telescope (BAT), the Swift/XRT, and the Fermi/Gamma-ray Burst Monitor detectors. An independent fit to the BAT and XRT data reveals two correlated blackbodies with monotonically decreasing temperatures. Hence, we investigated the combined data with a model consisting of two blackbodies and a power law (2BBPL), a model suggested for several bright GRBs. We elicit the following interesting features of the 2BBPL model: (1) the same model is applicable from the peak of the last pulse in the prompt emission to the afterglow emission, (2) the ratio of temperatures and the fluxes of the two blackbodies remains constant throughout the observations, (3) the blackbody temperatures and fluxes show a monotonic decrease with time, with the BB fluxes dropping about a factor of two faster than that of the power-law (PL) emission, and (4) attributing the blackbody emission to photospheric emissions, we find that the photospheric radii increase very slowly with time, and the lower-temperature blackbody shows a larger emitting radius than that of the higher-temperature blackbody. We find some evidence that the underlying shape of the nonthermal emission is a cutoff power law rather than a PL. We sketch a spine–sheath jet model to explain our observations.

  5. GRB Orphan Afterglows in Present and Future Radio Transient Surveys

    NASA Astrophysics Data System (ADS)

    Ghirlanda, G.; Burlon, D.; Ghisellini, G.; Salvaterra, R.; Bernardini, M. G.; Campana, S.; Covino, S.; D'Avanzo, P.; D'Elia, V.; Melandri, A.; Murphy, T.; Nava, L.; Vergani, S. D.; Tagliaferri, G.

    2014-05-01

    Orphan Afterglows (OA) are slow transients produced by Gamma Ray Bursts seen off-axis that become visible on timescales of days/years at optical/NIR and radio frequencies, when the prompt emission at high energies (X and γ rays) has already ceased. Given the typically estimated jet opening angle of GRBs θjet ~ 3°, for each burst pointing to the Earth there should be a factor ~ 700 more GRBs pointing in other directions. Despite this, no secure OAs have been detected so far. Through a population synthesis code we study the emission properties of the population of OA at radio frequencies. OAs reach their emission peak on year-timescales and they last for a comparable amount of time. The typical peak fluxes (which depend on the observing frequency) are of few μJy in the radio band with only a few OA reaching the mJy level. These values are consistent with the upper limits on the radio flux of SN Ib/c observed at late times. We find that the OA radio number count distribution has a typical slope - 1.7 at high fluxes and a flatter ( - 0.4) slope at low fluxes with a break at a frequency-dependent flux. Our predictions of the OA rates are consistent with the (upper) limits of recent radio surveys and archive searches for radio transients. Future radio surveys like VAST/ASKAP at 1.4 GHz should detect ~ 3 × 10- 3 OA deg- 2 yr- 1, MeerKAT and EVLA at 8.4 GHz should see ~ 3 × 10- 1 OA deg- 2 yr- 1. The SKA, reaching the μJy flux limit, could see up to ~ 0.2 - 1.5 OA deg- 2 yr- 1. These rates also depend on the duration of the OA above a certain flux limit and we discuss this effect with respect to the survey cadence.

  6. Electron and ion acceleration in relativistic shocks with applications to GRB afterglows

    NASA Astrophysics Data System (ADS)

    Warren, Donald C.; Ellison, Donald C.; Bykov, Andrei M.; Lee, Shiu-Hang

    2015-09-01

    We have modelled the simultaneous first-order Fermi shock acceleration of protons, electrons, and helium nuclei by relativistic shocks. By parametrizing the particle diffusion, our steady-state Monte Carlo simulation allows us to follow particles from particle injection at non-relativistic thermal energies to above PeV energies, including the non-linear smoothing of the shock structure due to cosmic ray (CR) backpressure. We observe the mass-to-charge (A/Z) enhancement effect believed to occur in efficient Fermi acceleration in non-relativistic shocks and we parametrize the transfer of ion energy to electrons seen in particle-in-cell (PIC) simulations. For a given set of environmental and model parameters, the Monte Carlo simulation determines the absolute normalization of the particle distributions and the resulting synchrotron, inverse Compton, and pion-decay emission in a largely self-consistent manner. The simulation is flexible and can be readily used with a wide range of parameters typical of γ-ray burst (GRB) afterglows. We describe some preliminary results for photon emission from shocks of different Lorentz factors and outline how the Monte Carlo simulation can be generalized and coupled to hydrodynamic simulations of GRB blast waves. We assume Bohm diffusion for simplicity but emphasize that the non-linear effects we describe stem mainly from an extended shock precursor where higher energy particles diffuse further upstream. Quantitative differences will occur with different diffusion models, particularly for the maximum CR energy and photon emission, but these non-linear effects should be qualitatively similar as long as the scattering mean-free path is an increasing function of momentum.

  7. The Late-time Afterglow of the Extremely Energetic Short Burst GRB 090510 Revisited

    NASA Technical Reports Server (NTRS)

    Guelbenzu, A. Nicuesa; Klose, S.; Kruehler, T.; Greiner, J.; Rossi, A.; Kann, D. A.; Olivares, F.; Rau, A.; Afonso, P. M. J.; Elliott, J.; Filgas, R.; Yoldas, A. Kuepcue; McBreen, S.; Nardini, M.; Schady, P.; Schmidl, S.; Sudilovsky, V.; Updike, A. C.; Yoldas, A.

    2012-01-01

    Context. The Swift discovery of the short burst GRB 090510 has raised considerable attention mainly because of two reasons: first, it had a bright optical afterglow, and second it is among the most energetic events detected so far within the entire GRB population (long plus short). The afterglow of GRB 090510 was observed with Swift/UVOT and Swift/XRT and evidence of a jet break around 1.5 ks after the burst has been reported in the literature, implying that after this break the optical and X-ray light curve should fade with the same decay slope. Aims. As noted by several authors, the post-break decay slope seen in the UVOT data is much shallower than the steep decay in the X-ray band, pointing to a (theoretically hard to understand) excess of optical flux at late times. We assess here the validity of this peculiar behavior. Methods. We reduced and analyzed new afterglow light-curve data obtained with the multichannel imager GROND. These additional g'r'i'z' data were then combined with the UVOT and XRT data to study the behavior of the afterglow at late times more stringently. Results. Based on the densely sampled data set obtained with GROND, we find that the optical afterglow of GRB 090510 did indeed enter a steep decay phase starting around 22 ks after the burst. During this time the GROND optical light curve is achromatic, and its slope is identical to the slope of the X-ray data. In combination with the UVOT data this implies that a second break must have occurred in the optical light curve around 22 ks post burst, which, however, has no obvious counterpart in the X-ray band, contradicting the interpretation that this could be another jet break. Conclusions. The GROND data provide the missing piece of evidence that the optical afterglow of GRB 090510 did follow a post-jet break evolution at late times. The break seen in the optical light curve around 22 ks in combination with its missing counterpart in the X-ray band could be due to the passage of the

  8. A possible bright blue supernova in the afterglow of GRB020305

    SciTech Connect

    Gorosabel, J.; Fynbo, J.P.U.; Fruchter, A.; Levan, A.; Hjorth,J.; Nugent, P.; Castro-Tirado, A.J.; Castro Ceron, J.M.; Rhoads, J.; Bersier, D.; Burud, I.

    2005-07-01

    We report on ground-based and HST(+STIS) imaging of the afterglow and host galaxy of the Gamma-Ray Burst (GRB) of March 5, 2002. The GRB occurred in a R=25.17+-0.14 galaxy, which apparently is part of an interacting system. The light curve of the optical afterglow shows are brightening, or at least a plateau, 12-16 days after the gamma-ray event. UBVRIK' multi-band imaging of the afterglow {approx}12 days after the GRB reveals a blue spectral energy distribution (SED). The SED is consistent with a power-law with a spectral index of beta=-0.63+-0.16,but there is tentative evidence for deviations away from a power-law. Unfortunately, a spectroscopic redshift has not been secured for GRB020305. From the SED we impose a redshift upper limit of z<{approx}2.8,hence excluding the pseudo redshift of 4.6 reported for this burst. We discuss the possibilities for explaining the light curve, SED and host galaxy properties for GRB 020305. The most natural interpretation of the light curve and the SED is an associated supernova (SN). Our data can not precisely determine the redshift of the GRB. The most favored explanation is a low redshift (z{approx}0.2) SN, but a higher redshift(z>{approx}0.5) SN can not be excluded. We also discuss less likely scenarios not based on SNe, like a burst occurring in a z=2.5 galaxy with an extinction curve similar to that of the Milky Way.

  9. GRB 131231A: IMPLICATIONS OF THE GeV EMISSION

    SciTech Connect

    Liu, Bin; Chen, Wei; Liang, Yun-Feng; Zhou, Bei; He, Hao-Ning; Jin, Zhi-Ping; Fan, Yi-Zhong; Wei, Da-Ming; Tam, Pak-Hin Thomas; Shao, Lang E-mail: beizhou@pmo.ac.cn E-mail: dmwei@pmo.ac.cn

    2014-05-20

    GRB 131231A was detected by the Large Area Telescope on board the Fermi Space Gamma-ray Telescope. The high-energy gamma-ray (>100 MeV) afterglow emission spectrum is F {sub ν}∝ν{sup –0.54} {sup ±} {sup 0.15} in the first ∼1300 s after the trigger and the most energetic photon has an energy of ∼62 GeV, arriving at t ∼ 520 s. With reasonable parameters of the gamma-ray burst (GRB) outflow as well as the density of the circum-burst medium, the synchrotron radiation of electrons or protons accelerated at an external forward shock have difficulty accounting for the data. Rather, the synchrotron self-Compton radiation of the forward shock-accelerated electrons can account for both the spectrum and temporal behavior of the GeV afterglow emission. We also show that the prospect for detecting GRB 131231A-like GRBs with the Cherenkov Telescope Array is promising.

  10. Spectral softening in the X-RAY afterglow of GRB 130925A as predicted by the dust scattering model

    SciTech Connect

    Zhao, Yi-Nan; Shao, Lang

    2014-07-01

    Gamma-ray bursts (GRBs) usually occur in a dense star-forming region with a massive circumburst medium. The small-angle scattering of intense prompt X-ray emission off the surrounding dust grains will have observable consequences and sometimes can dominate the X-ray afterglow. In most of the previous studies, only the Rayleigh-Gans (RG) approximation is employed for describing the scattering process, which works accurately for the typical size of grains (with radius of a ≤ 0.1 μm) in the diffuse interstellar medium. When the size of the grains may significantly increase, as in a more dense region where GRBs would occur, the RG approximation may not be valid enough for modeling detailed observational data. In order to study the temporal and spectral properties of the scattered X-ray emission more accurately with potentially larger dust grains, we provide a practical approach using the series expansions of anomalous diffraction (AD) approximation based on the complicated Mie theory. We apply our calculations to understand the puzzling X-ray afterglow of recently observed GRB 130925A that showed a significant spectral softening. We find that the X-ray scattering scenarios with either AD or RG approximation adopted could well reproduce both the temporal and spectral profile simultaneously. Given the plateau present in the early X-ray light curve, a typical distribution of smaller grains as in the interstellar medium would be suggested for GRB 130925A.

  11. Spectral Softening in the X-Ray Afterglow of GRB 130925A as Predicted by the Dust Scattering Model

    NASA Astrophysics Data System (ADS)

    Zhao, Yi-Nan; Shao, Lang

    2014-07-01

    Gamma-ray bursts (GRBs) usually occur in a dense star-forming region with a massive circumburst medium. The small-angle scattering of intense prompt X-ray emission off the surrounding dust grains will have observable consequences and sometimes can dominate the X-ray afterglow. In most of the previous studies, only the Rayleigh-Gans (RG) approximation is employed for describing the scattering process, which works accurately for the typical size of grains (with radius of a <= 0.1 μm) in the diffuse interstellar medium. When the size of the grains may significantly increase, as in a more dense region where GRBs would occur, the RG approximation may not be valid enough for modeling detailed observational data. In order to study the temporal and spectral properties of the scattered X-ray emission more accurately with potentially larger dust grains, we provide a practical approach using the series expansions of anomalous diffraction (AD) approximation based on the complicated Mie theory. We apply our calculations to understand the puzzling X-ray afterglow of recently observed GRB 130925A that showed a significant spectral softening. We find that the X-ray scattering scenarios with either AD or RG approximation adopted could well reproduce both the temporal and spectral profile simultaneously. Given the plateau present in the early X-ray light curve, a typical distribution of smaller grains as in the interstellar medium would be suggested for GRB 130925A.

  12. VLBI AND ARCHIVAL VLA AND WSRT OBSERVATIONS OF THE GRB 030329 RADIO AFTERGLOW

    SciTech Connect

    Mesler, Robert A.; Pihlstroem, Ylva M.; Taylor, Greg B.; Granot, Johnathan

    2012-11-01

    We present VLBI and archival Karl G. Jansky Very Large Array (VLA) and Westerbork Synthesis Radio Telescope (WSRT) observations of the radio afterglow from the gamma-ray burst (GRB) of 2003 March 29 (GRB 030329) taken between 672 and 2032 days after the burst. The VLA and WSRT data suggest a simple power-law decay in the flux at 5 GHz, with no clear signature of any rebrightening from the counterjet. We report an unresolved source at day 2032 of size 1.18 {+-} 0.13 mas, which we use in conjunction with the expansion rate of the burst to argue for the presence of a uniform, interstellar-medium-like circumburst medium. A limit of <0.067 mas yr{sup -1} is placed on the proper motion, supporting the standard afterglow model for gamma-ray bursts.

  13. iPTF14yb: The First GRB Discovered Outside the Gamma-Ray Bandpass and the Rate of Orphan Afterglows

    NASA Astrophysics Data System (ADS)

    Cenko, Stephen

    2015-04-01

    We report here the discovery by the Intermediate Palomar Transient Factory (iPTF) of iPTF14yb, the first unambiguous detection of an afterglow-like transient identified outside the γ-ray bandpass. Subsequent to our discovery announcement, the ``parent'' γ-ray burst GRB 140226A was identified by the InterPlanetary Network of high-energy detectors. We demonstrate an association between iPTF14yb and GRB 140226A based both on probabilistic arguments and by comparing iPTF14yb with the known population of long GRB afterglows and host galaxies. We furthermore estimate the rate of iPTF14yb-like transients based on iPTF observations, and demonstrate it is consistent with the rate of on-axis long GRBs. Finally, we briefly discuss the implications of the non-detection to date of bona fide ``orphan'' afterglows (i.e., those lacking entirely in high-energy emission) on GRB beaming and the degree of baryon loading in these relativistic jets.

  14. The origin of the plateau and late rebrightening in the afterglow of GRB 120326A

    SciTech Connect

    Hou, S. J.; Lu, J. F.; Geng, J. J.; Wang, K.; Huang, Y. F.; Dai, Z. G.; Wu, X. F.

    2014-04-20

    GRB 120326A is an unusual gamma-ray burst (GRB) that has a long plateau and a very late rebrightening in both X-ray and optical bands. The similar behavior of the optical and X-ray light curves suggests that they may share a common origin. The long plateau starts at several hundred seconds and ends at tens of thousands of seconds, and the peak time of the late rebrightening is about 30,000 s. We analyze the energy injection model by means of numerical and analytical solutions, considering both the wind environment and the interstellar medium environment for GRB afterglows. We particularly study the influence of the injection starting time, ending time, stellar wind density (or density of the circumburst environment), and injection luminosity on the shape of the afterglow light curves, respectively. In the wind model, we find that the light curve is largely affected by the parameters and that there is a 'bump' in the late stage. In the wind environment, we found that the longer the energy is injected, the more obvious the rebrightening will be. We also find that the peak time of the bump is determined by the stellar wind density. We use the late continuous injection model to interpret the unusual afterglow of GRB 120326A. The model fits the observational data well; however, we find that the timescale of the injection must be higher than 10,000 s, which implies that the timescale of the central engine activity must also be more than 10,000 s. This information can give useful constraints on the central engines of GRBs—we consider a newborn millisecond pulsar with a strong magnetic field to be the central engine. On the other hand, our results suggest that the circumburst environment of GRB 120326A is very likely a stellar wind.

  15. An Achromatic Break in the Afterglow of the Short GRB 140903A: Evidence for a Narrow Jet

    NASA Astrophysics Data System (ADS)

    Troja, E.; Sakamoto, T.; Cenko, S. B.; Lien, A.; Gehrels, N.; Castro-Tirado, A. J.; Ricci, R.; Capone, J.; Toy, V.; Kutyrev, A.; Kawai, N.; Cucchiara, A.; Fruchter, A.; Gorosabel, J.; Jeong, S.; Levan, A.; Perley, D.; Sanchez-Ramirez, R.; Tanvir, N.; Veilleux, S.

    2016-08-01

    We report the results of our observing campaign on GRB 140903A, a nearby (z = 0.351) short-duration (T 90 ˜ 0.3 s) gamma-ray burst discovered by Swift. We monitored the X-ray afterglow with Chandra up to 15 days after the burst and detected a steeper decay of the X-ray flux after t j ≈ 1 day. Continued monitoring at optical and radio wavelengths showed a similar decay in flux at nearly the same time, and we interpret it as evidence of a narrowly collimated jet. By using the standard fireball model to describe the afterglow evolution, we derive a jet opening angle θ j ≈ 5° and a collimation-corrected total energy release E ≈ 2 × {10}50 erg. We further discuss the nature of the GRB progenitor system. Three main lines disfavor a massive star progenitor: the properties of the prompt gamma-ray emission, the age and low star formation rate of the host galaxy, and the lack of a bright supernova. We conclude that this event likely originated from a compact binary merger.

  16. The Discovery and Broadband Follow-Up of the Transient Afterglow of GRB 980703

    NASA Technical Reports Server (NTRS)

    Bloom, J. S.; Frail, D. A.; Kulkarni, S. R.; Djorgovski, S. G.; Halpern, J. P.; Marzke, R. O.; Patton, D. R.; Oke, J. B.; Horne, K. D.; Gomer, R.; Goodrich, R.; Campbell, R.; Moriarity-Schieven, G. H.; Redman, R. O.; Feldman, P. A.; Costa, E.; Masetti, N.

    1998-01-01

    We report on the discovery of the radio, infrared, and optical transient coincident with an X-ray transient proposed to be the afterglow of GRB 980703. At later times when the transient has faded below detection, we see an underlying galaxy with R = 22.6; this galaxy is the brightest host galaxy (by nearly 2 mag) of any cosmological gamma-ray burst (GRB) thus far. In keeping with an established trend, the GRB is not significantly offset from the host galaxy. Interpreting the multiwavelength data in the framework of the popular fireball model requires that the synchrotron cooling break was between the optical and X-ray bands on 1998 July 8.5 UT and that the intrinsic extinction of the transient is A(sub v) = 0.9. This is somewhat higher than the extinction for the galaxy as a whole, as estimated from spectroscopy.

  17. On the afterglow and host galaxy of GRB 021004: A comprehensivestudy with the Hubble Space Telescope1

    SciTech Connect

    Fynbo, J.P.U.; Gorosabel, J.; Smette, A.; Fruchter, A.; Hjorth,J.; Pedersen, K.; Levan, A.; Burud, I.; Sahu, K.; Vreeswijk, P.M.; Bergeron, E.; Kouveliotou1, C.; Tanvir, N.; Thorsett11, S.E.; Wijers,R.A.M.J.; Castro Ceron, J.M.; Castro-Tirado, A.; Garnavich, P.; Holland,S.T.; Jakobsson, P.; Moller, P.; Nugent, P.; Pian, E.; Rhoads, J.; Thomsen, B.; Watson, D.; Woosley, S.

    2004-12-01

    We report on Hubble Space Telescope (HST) observations of the late-time afterglow and host galaxy of GRB 021004 (z = 2.33).Although this gamma-ray burst (GRB) is one of the best observed so far in terms of sampling in the time domain, multi-wavelength coverage and polarimetric observations, there is large disagreement between different measurements and interpretations of this burst in the literature. We have observed the field of GRB 021004 with the HST at multiple epochs from 3 days until almost 10 months after the burst. With STI S prism and G430L spectroscopy we cover the spectral region from about 2000 Angstrom to 5700 Angstrom corresponding to 600 1700 Angstrom in the rest frame. From the limit on the flux recovery bluewards of the Lyman-limit we constrain the H I column density to be above 1 x 1018 cm-2 (5 sigma). Based on ACS and N ICMOS imaging we find that the afterglow evolved a chromatically within the errors (any variation must be less then 5 percent) during the period of HST observations. The color changes observed by other authors during the first four days must be related to a 'noisy' phenomenon superimposed on an afterglow component with a constant spectral shape. This also means that the cooling break has remained on the blue side of the optical part of the spectrum for at least two weeks after the explosion. The optical to X-ray slope OX is consistent with being the same at 1.4 and 52.4 days after the burst. This indicates that the cooling frequency is constant and hence, according to fireball models, that the circumburst medium has a constant density profile. The late-time slope of the light curve (alpha 2, F nu proportional to t-alpha2) is in the range 2 = 1.8-1.9, although inconsistent with a single power-law. This could be due to a late-time flattening caused by the transition to non-relativistic expansion or due to excess emission (a 'bump' in the light curve) about 7 days afterburst. The host galaxy is like most previously studied GRB hosts

  18. Modeling the Multi-band Afterglow of GRB 130831A: Evidence for a Spinning-down Magnetar Dominated by Gravitational Wave Losses?

    NASA Astrophysics Data System (ADS)

    Zhang, Q.; Huang, Y. F.; Zong, H. S.

    2016-06-01

    The X-ray afterglow of GRB 130831A shows an “internal plateau” with a decay slope of ˜0.8, followed by a steep drop at around 105 s with a slope of ˜6. After the drop, the X-ray afterglow continues with a much shallower decay. The optical afterglow exhibits two segments of plateaus separated by a luminous optical flare, followed by a normal decay with a slope basically consistent with that of the late-time X-ray afterglow. The decay of the internal X-ray plateau is much steeper than what we expect in the simplest magnetar model. We propose a scenario in which the magnetar undergoes gravitational-wave-driven r-mode instability, and the spin-down is dominated by gravitational wave losses up to the end of the steep plateau, so that such a relatively steep plateau can be interpreted as the internal emission of the magnetar wind and the sharp drop can be produced when the magnetar collapses into a black hole. This scenario also predicts an initial X-ray plateau lasting for hundreds of seconds with an approximately constant flux which is compatible with observation. Assuming that the magnetar wind has a negligible contribution in the optical band, we interpret the optical afterglow as the forward shock emission by invoking the energy injection from a continuously refreshed shock following the prompt emission phase. It is shown that our model can basically describe the temporal evolution of the multi-band afterglow of GRB 130831A.

  19. Probing a GRB Progenitor at a Redshift of z=2: A Comprehensive Observing Campaign of the Afterglow of GRB 030226l

    NASA Technical Reports Server (NTRS)

    Klose, S.; Greiner, J.; Rau, A.; Henden, A. A.; Hartmann, D. H.; Zeh, A.; Ries, C.; Masetti, N.; Malesani, D.; Guenther, E.

    2004-01-01

    We report results from a comprehensive optical/near-infrared follow-up observing campaign of the afterglow of GRB 030226, including VLT spectroscopy and polarimetry, supplemented by Chandra X-ray and BOOTES-1 rapid response observations. First observations at ESO started 0.2 days after the burst when the afterglow was at a magnitude of R approx. 19. The multi-color light curve of the afterglow, with a break around 1 day after the burst, is achromatic within the observational uncertainties even during episodes of short-term fluctuations. Close to the break time the degree of linear polarization of the afterglow light was less than 1.1%, consistent with low intrinsic polarization observed in other afterglows. VLT spectra show a foreground absorber of Mg II at a redshift z=1.042 and two absorption line systems at redshifts z=1.962+/-0.001 and at z=1.986+/-0.001, placing the lower limit for the redshift of the GRB close to 2. The kinematics and the composition of the absorbing clouds is very similar to those observed in the afterglow of GRB 021004, supporting the view that at least some GRBs are physically related to the explosion of a Wolf-Rayet star.

  20. Extremely Soft X-Ray Flash as the Indicator of Off-axis Orphan GRB Afterglow

    NASA Astrophysics Data System (ADS)

    Urata, Yuji; Huang, Kuiyun; Yamazaki, Ryo; Sakamoto, Takanori

    2015-06-01

    We verified the off-axis jet model of X-ray flashes (XRFs) and examined a discovery of off-axis orphan gamma-ray burst (GRB) afterglows. The XRF sample was selected on the basis of the following three factors: (1) a constraint on the lower peak energy of the prompt spectrum {E}{obs}{src}, (2) redshift measurements, and (3) multicolor observations of an earlier (or brightening) phase. XRF 020903 was the only sample selected on the basis of these criteria. A complete optical multicolor afterglow light curve of XRF 020903 obtained from archived data and photometric results in the literature showed an achromatic brightening around 0.7 days. An off-axis jet model with a large observing angle (0.21 rad, which is twice the jet opening half-angle, {θ }{jet}) can naturally describe the achromatic brightening and the prompt X-ray spectral properties. This result indicates the existence of off-axis orphan GRB afterglow light curves. Events with a larger viewing angle (\\gt ∼ 2{θ }{jet}) could be discovered using an 8 m class telescope with wide-field imagers such as the Subaru Hyper-Suprime-Cam and the Large Synoptic Survey Telescope.

  1. Unified GRB Paradigm: Correlation between Afterglow Beaming Fraction and Gamma-ray Spectral Lag

    NASA Astrophysics Data System (ADS)

    Norris, J. P.

    2001-12-01

    Without redshifts, studies of the pulse structures in gamma-ray bursts (GRBs) were largely phenomenological. Now that approximately twenty GRBs have associated redshifts, it is clear that cosmological GRBs exhibit a large dynamic range in observed luminosity and total energy. Thus from afterglow measurements, inferences on the physics of GRB spectral/temporal properties become possible. For a subset of bursts where redshifts and BATSE data are available, a correlation between luminosity and spectral lag has been reported (Norris, Marani & Bonnell 2001, ApJ 534, 248). It has also been demonstrated from breaks in GRB afterglow temporal decays (e.g., Frail et al. 2001, ApJL, accepted) that GRBs manifest a wide dynamic range in opening angle, or beaming fraction -- implying more uniform isotropic luminosities and energies for GRBs. Even more exciting, the beaming fraction and average spectral lag appear to be correlated (both being related to luminosity), signaling a profound, but indirect, link between the gamma-ray and afterglow phases. While the sample is still small, and the analysis techniques for beaming fraction and spectral lag are still being refined, it is possible to extend observed BATSE distributions and prognosticate on distributional properties of GRBs, such as luminosity and redshift, that should be observable by Swift.

  2. Prior Emission Model for X-ray Plateau Phase of Gamma-Ray Burst Afterglows

    NASA Astrophysics Data System (ADS)

    Yamazaki, Ryo

    2009-01-01

    The two-component emission model to explain the plateau phase of the X-ray afterglows of gamma-ray bursts (GRBs) is proposed. One component, which is responsible for the plateau and subsequent normal decay phase of the X-ray afterglow, is the prior emission via outflow ejected from the central engine before the main burst. The other is the main outflow, which causes the prompt GRB emission and the initial steep decay phase of the X-ray afterglow. In this model, the transition from the plateau to the subsequent normal decay phase is an artifact of the choice of the zero of time. For events with distinct plateau phase, the central engine is active 103-104 s before the launch of the main outflow. According to this model, a prior emission in the X-ray and/or optical bands 103-104 s before the prompt GRB emission is possibly seen, which will be tested by near-future instruments such as Monitor of All-sky X-ray Image (MAXI), WIDe-field telescope for GRB Early Timing (WIDGET), and so on.

  3. Optical light curve of GRB 121011A: a textbook for the onset of GRB afterglow in a mixture of ISM and wind-type medium

    NASA Astrophysics Data System (ADS)

    Xin, Li-Ping; Wei, Jian-Yan; Qiu, Yu-Lei; Deng, Jin-Song; Wang, Jing; Han, Xu-Hui

    2016-01-01

    We report the optical observations of GRB 121011A by the 0.8m TNT facility at Xinglong observatory, China. The light curve of the optical afterglow shows a smooth and featureless bump during the epoch of ∼130 s and ∼5000 s with a rising index of 1.57 ± 0.28 before the break time of 539 ± 44 s, and a decaying index of about 1.29 ± 0.07 up to the end of our observations. Moreover, the X-ray light curve decays in a single power-law with a slope of about 1.51 ± 0.03 observed by XRT onboard Swift from 100 s to about 10 000 s after the burst trigger. The featureless optical light curve could be understood as an onset process under the external-shock model. The typical frequency has been below or near the optical one before the deceleration time, and the cooling frequency is located between the optical and X-ray wavelengths. The external medium density has a transition from a mixed stage of ISM and wind-type medium before the peak time to the ISM at the later phase. The joint-analysis of X-ray and optical light curves shows that the emissions from both frequencies are consistent with the prediction of the standard afterglow model without any energy injections, indicating that the central engine has stopped its activity and does not restart anymore after the prompt phase.

  4. GRB 110530A: Peculiar Broad Bump and Delayed Plateau in Early Optical Afterglows

    NASA Astrophysics Data System (ADS)

    Zhong, Shu-Qing; Xin, Li-Ping; Liang, En-Wei; Wei, Jian-Yan; Urata, Yuji; Huang, Kui-Yun; Qiu, Yu-Lei; Deng, Can-Min; Wang, Yuan-Zhu; Deng, Jin-Song

    2016-11-01

    We report our very early optical observations of GRB 110530A and investigate its jet properties together with its X-ray afterglow data. A peculiar broad onset bump followed by a plateau is observed in its early R band afterglow light curve. The optical data in the other bands and the X-ray data are well consistent with the temporal feature of the R band light curve. Our joint spectral fits of the optical and X-ray data show that they are in the same regime, with a photon index of ∼1.70. The optical and X-ray afterglow light curves are well fitted with the standard external shock model by considering a delayed energy injection component. Based on our modeling results, we find that the radiative efficiency of the gamma-ray burst jet is ∼ 1 % and the magnetization parameter of the afterglow jet is \\lt 0.04 with a derived extremely low {ε }B (the ratio of shock energy to the magnetic field) of (1.64+/- 0.25)× {10}-6. These results indicate that the jet may be matter dominated. A discussion on delayed energy injection from the accretion of the late fall-back material of its pre-supernova star is also presented.

  5. Detailed afterglow modelling and host galaxy properties of the dark GRB 111215A

    NASA Astrophysics Data System (ADS)

    van der Horst, A. J.; Levan, A. J.; Pooley, G. G.; Wiersema, K.; Krühler, T.; Perley, D. A.; Starling, R. L. C.; Curran, P. A.; Tanvir, N. R.; Wijers, R. A. M. J.; Strom, R. G.; Kouveliotou, C.; Hartoog, O. E.; Xu, D.; Fynbo, J. P. U.; Jakobsson, P.

    2015-02-01

    Gamma-ray burst (GRB) 111215A was bright at X-ray and radio frequencies, but not detected in the optical or near-infrared (nIR) down to deep limits. We have observed the GRB afterglow with the Westerbork Synthesis Radio Telescope and Arcminute Microkelvin Imager at radio frequencies, with the William Herschel Telescope and Nordic Optical Telescope in the nIR/optical, and with the Chandra X-ray Observatory. We have combined our data with the Swift X-Ray Telescope monitoring, and radio and millimetre observations from the literature to perform broad-band modelling, and determined the macro- and microphysical parameters of the GRB blast wave. By combining the broad-band modelling results with our nIR upper limits we have put constraints on the extinction in the host galaxy. This is consistent with the optical extinction we have derived from the excess X-ray absorption, and higher than in other dark bursts for which similar modelling work has been performed. We also present deep imaging of the host galaxy with the Keck I telescope, Spitzer Space Telescope, and Hubble Space Telescope (HST), which resulted in a well-constrained photometric redshift, giving credence to the tentative spectroscopic redshift we obtained with the Keck II telescope, and estimates for the stellar mass and star formation rate of the host. Finally, our high-resolution HST images of the host galaxy show that the GRB afterglow position is offset from the brightest regions of the host galaxy, in contrast to studies of optically bright GRBs.

  6. On the Afterglow and Host Galaxy of GRB 021004: A Comprehensive Study with the Hubble Space Telescope

    NASA Astrophysics Data System (ADS)

    Fynbo, J. P. U.; Gorosabel, J.; Smette, A.; Fruchter, A.; Hjorth, J.; Pedersen, K.; Levan, A.; Burud, I.; Sahu, K.; Vreeswijk, P. M.; Bergeron, E.; Kouveliotou, C.; Tanvir, N.; Thorsett, S. E.; Wijers, R. A. M. J.; Castro Cerón, J. M.; Castro-Tirado, A.; Garnavich, P.; Holland, S. T.; Jakobsson, P.; Møller, P.; Nugent, P.; Pian, E.; Rhoads, J.; Thomsen, B.; Watson, D.; Woosley, S.

    2005-11-01

    We report on Hubble Space Telescope (HST) observations of the late-time afterglow and host galaxy of GRB 021004 (z=2.33). Although this gamma-ray burst (GRB) is one of the best observed so far in terms of sampling in the time domain, multiwavelength coverage, and polarimetric observations, there is substantial disagreement between different interpretations of data sets on this burst in the literature. We have observed the field of GRB 021004 with the HST at multiple epochs from 3 days until almost 10 months after the burst. With the STIS PRISM and G430L spectroscopy, we cover the spectral region from about 2000 to 5700 Å, corresponding to 600-1700 Å in the rest frame. From the limit on the flux recovery blueward of the Lyman limit, we constrain the H I column density to be above 1×1018 cm-2 (5 σ). On the basis of ACS and NICMOS imaging, we find that the afterglow evolved achromatically within the errors (any variation must be less than 5%) during the period of the HST observations. The color changes observed by other authors during the first 4 days must be related to a stochastic phenomenon superimposed on an afterglow component with a constant spectral shape. This achromaticity implies that the cooling break has remained on the blue side of the optical part of the spectrum for at least 2 weeks after the explosion. The optical-to-X-ray slope βOX is consistent with being the same at 1.4 and 52.4 days after the burst. This indicates that the cooling frequency is constant and, hence, according to fireball models, that the circumburst medium has a constant density profile. The late-time slope of the light curve (α2, Fν~t-α2) is in the range α2=1.8-1.9 and is inconsistent with a single power law. This could be due to a late-time flattening caused by the transition to nonrelativistic expansion or could be due to excess emission (a ``bump'' in the light curve) about 7 days after the burst. The host galaxy is, like most previously studied GRB hosts, a (very) blue

  7. The Achromatic Light Curve of the Optical Afterglow of GRB 030226 at a Redshift of z Approximately 2

    NASA Technical Reports Server (NTRS)

    Klose, S.; Greiner, J.; Rau, A.; Henden, A. A.; Hartmann, D. H.; Zeh, A.; Masetti, N.; Guenther, E.; Stecklum, B.; Lindsay, K.

    2003-01-01

    Abstract. We report on optical and near-infrared (NIR) follow-up observations of the afterglow of GRB 030226, mainly performed with the telescopes at ESO La Silla and Paranal, with additional data obtained at other places. Our first observations started 0.2 days after the burst when the afterglow was at a magnitude of R approximately equal to 19 . One week later the magnitude of the afterglow had fallen to R=25, and at two weeks after the burst it could no longer be detected (R > 26). Our VLT blueband spectra show two absorption line systems at redshifts z = 1.962 +/- 0.001 and at z = 1.986 +/- 0.001, placing the redshift of the burster close to 2. Within our measurement errors no evidence for variations in the line strengths has been found between 0.2 and 1.2 days after the burst. An overabundance of alpha-group elements might indicate that the burst occurred in a chemically young interstellar region shaped by the nucleosynthesis from type II supernovae. The spectral slope of the afterglow shows no signs for cosmic dust along the line of sight in the GRB host galaxy, which itself remained undetected (R > 26.2). At the given redshift no supernova component affected the light from the GRB afterglow, so that the optical transient was essentially only powered by the radiation from the GRB fireball, allowing for a detailed investigation of the color evolution of the afterglow light. In our data set no obvious evidence for color changes has been found before, during, or after the smooth break in the light curve approximately 1 day after the burst. In comparison with investigations by others, our data favor the interpretation that the afterglow began to develop into a homogeneous interstellar medium before the break in the light curve became apparent.

  8. Strategies for Prompt Searches for GRB Afterglows: The Discovery of GRB 001011 Optical/Near-Infrared Counterpart Using Colour-Colour Selection

    NASA Technical Reports Server (NTRS)

    Gorosabel, J.; Fynbo, J. U.; Hjorth, J.; Wolf, C.; Andersen, M. I.; Pedersen, H.; Christensen, L.; Jensen, B. L.; Moller, P.; Afonso, J.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    We report the discovery of the optical and near-infrared counterpart to GRB 001011. The GRB 001011 error box determined by Beppo-SAX was simultaneously imaged in the near-infrared by the 3.58-m. New Technology Telescope and in the optical by the 1.54-m Danish Telescope - 8 hr after the gamma-ray event. We implement the colour-colour discrimination technique proposed by Rhoads (2001) and extend it using near-IR data as well. We present the results provided by an automatic colour-colour discrimination pipe-line developed to discern the different populations of objects present in the GRB 001011 error box. Our software revealed three candidates based on single-epoch images. Second-epoch observations carried out approx. 3.2 days after the burst revealed that the most likely candidate had faded thus identifying it with the counterpart to the GRB. In deep R-band images obtained 7 months after the burst a faint (R=25.38 plus or minus 0.25) elongated object, presumably the host galaxy of GRB 001011, was detected at the position of the afterglow. The GRB 001011 afterglow is the first discovered with the assistance of colour-colour diagram techniques. We discuss the advantages of using this method and its application to boxes determined by future missions.

  9. Determination of Cosmological Parameters from GRB Correlation between E_iso (gamma) and Afterglow Flux

    NASA Astrophysics Data System (ADS)

    Hannachi, Zitouni; Guessoum, Nidhal; Azzam, Walid

    2016-07-01

    Context: We use the correlation relations between the energy emitted by the GRBs in their prompt phases and the X-ray afterglow fluxes, in an effort to constrain cosmological parameters and construct a Hubble diagram at high redshifts, i.e. beyond those found in Type Ia supernovae. Methods: We use a sample of 128 Swift GRBs, which we have selected among more than 800 ones observed until July 2015. The selection is based on a few observational constraints: GRB flux higher than 0.4 photons/cm^2/s in the band 15-150 keV; spectrum fitted with simple power law; redshift accurately known and given; and X-ray afterglow observed and flux measured. The statistical method of maximum likelihood is then used to determine the best cosmological parameters (Ω_M, Ω_L) that give the best correlation between the isotropic gamma energies E_{iso} and the afterglow fluxes at the break time t_{b}. The χ^2 statistical test is also used as a way to compare results from two methods. Results & Conclusions: Although the number of GRBs with high redshifts is rather small, and despite the notable dispersion found in the data, the results we have obtained are quite encouraging and promising. The values of the cosmological parameters obtained here are close to those currently used.

  10. GRB 081029: A Gamma-Ray Burst with a Multi-Component Afterglow

    NASA Technical Reports Server (NTRS)

    Holland, Stephen T.; DePasquale, Massimiliano; Mao, Jirong; Sakamoto, Taka; Shady, Patricia; Covino, Stefano; Yi-Zhong, Fan; Zhi-Ping, Jin; D'Avanzo, Paolo; Antonelli, Angelo; D'Elia, Valerio; Chincarini, Guido; Fiore, Fabrizio; Pandey, Shashi Bhushan

    2011-01-01

    We present an analysis of the unusual optical light curve of the gamma-ray burst GRB 081029, a long-soft burst with a redshift of z = 3.8479. We combine X-ray and optical observations from the Swift X-Ray Telescope and the Swift UltraViolet Optical Telescope with ground-based optical and infrared data obtained using the REM and ROTSE telescopes to construct a detailed data set extending from 86 s to approx. 100000 s after the BAT trigger. Our data cover a wide energy range, from 10 keV to 0.77 eV (1.24 A to 16000 A). The X-ray afterglow shows a shallow initial decay followed by a rapid decay starting at about 18000 s. The optical and infrared afterglow, however, shows an uncharacteristic rise at about 5000 s that does not correspond to any feature in the X-ray light curve. Our data are not consistent with synchrotron radiation from a jet interacting with an external medium, a two-component jet, or continuous energy injection from the central engine. We find that the the optical light curves can be broadly explained by a collision between two ejecta shells within a two-component jet. A growing number of gamma-ray burst afterglows are consistent with complex jets, which suggests that some (or all) gamma-ray burst jets are complex and will require detailed modelling to fully understand them.

  11. GRB 081029: A GAMMA-RAY BURST WITH A MULTI-COMPONENT AFTERGLOW

    SciTech Connect

    Holland, Stephen T.; Sakamoto, Takanori; De Pasquale, Massimiliano; Schady, Patricia; Mao, Jirong; Covino, Stefano; Jin, Zhi-Ping; D'Avanzo, Paolo; Chincarini, Guido; Fan, Yi-Zhong; Antonelli, Angelo; D'Elia, Valerio; Fiore, Fabrizio; Pandey, Shashi Bhushan; Cobb, Bethany E.

    2012-01-20

    We present an analysis of the unusual optical light curve of the gamma-ray burst GRB 081029, a long-soft burst with a redshift of z = 3.8479. We combine X-ray and optical observations from the Swift X-Ray Telescope and the Swift UltraViolet/Optical Telescope with ground-based optical and infrared data obtained using the REM, ROTSE, and CTIO 1.3 m telescopes to construct a detailed data set extending from 86 s to {approx}100000 s after the BAT trigger. Our data cover a wide energy range from 10 keV to 0.77 eV (1.24 A-16000 A). The X-ray afterglow shows a shallow initial decay followed by a rapid decay starting at about 18000 s. The optical and infrared afterglow, however, shows an uncharacteristic rise at about 3000 s that does not correspond to any feature in the X-ray light curve. Our data are not consistent with synchrotron radiation from a jet interacting with an external medium, a two-component jet, or continuous energy injection from the central engine. We find that the optical light curves can be broadly explained by a collision between two ejecta shells within a two-component jet. A growing number of gamma-ray-burst afterglows are consistent with complex jets, which suggests that some (or all) gamma-ray-burst jets are complex and will require detailed modeling to fully understand them.

  12. X-ray plateaus in the context of the one-zone SSC model for GRB afterglows

    SciTech Connect

    Petropoulou, M.; Mastichiadis, A.

    2010-10-15

    We investigate the impact that the upper cutoff of the electron distribution has on the multiwavelength GRB afterglow spectra and on the corresponding X-ray light curves. We show under which conditions X-ray light curves with a plateau phase can be produced in this picture.

  13. Analysis of two scenarios for the early optical emission of the gamma-ray burst afterglows 990123 and 021211

    NASA Astrophysics Data System (ADS)

    Panaitescu, A.; Kumar, P.

    2004-09-01

    The optical light curves of gamma-ray burst (GRB) afterglows 990123 and 021211 exhibit a steep decay at 100-600 s after the burst, the decay becoming slower after about 10 min. We investigate two scenarios for the fast decaying early optical emission of these GRB afterglows. In the reverse-forward shock scenario, this emission arises in the reverse shock crossing the GRB ejecta, the mitigation of the light-curve decay occurring when the forward shock emission overtakes that from the reverse shock. Both a homogeneous and wind-like circumburst medium are considered. In the wind-bubble scenario, the steeply decaying, early optical emission arises from the forward shock interacting with a r-2 bubble, with a negligible contribution from the reverse shock, the slower decay starting when the blast wave reaches the bubble termination shock and enters a homogeneous region of the circumburst medium. We determine the shock microphysical parameters, ejecta kinetic energy and circumburst density, which accommodate the radio and optical measurements of the GRB afterglows 990123 and 021211. We find that, for a homogeneous medium, the radio and optical emissions of the afterglow 990123 can be accommodated by the reverse-forward shock scenario if the microphysical parameters behind the two shocks differ substantially. A wind-like circumburst medium also allows the reverse-forward shock scenario to account for the radio and optical properties of the afterglows 990123 and 021211, but the required wind densities are at least 10 times smaller than those of Galactic Wolf-Rayet stars. The wind-bubble scenario requires a variation of the microphysical parameters when the afterglow fireball reaches the wind termination shock, which seems a contrived feature.

  14. GRB 020410: A Gamma-ray burst afterglow discovered by its supernova light

    SciTech Connect

    Levan, Andrew; Nugent, Peter; Fruchter, Andrew; Burud, Ingunn; Branch, David; Rhoads, James; Castro-Tirado, Alberto; Gorosabel, Javier; Ceron, Jose Maria Castro; Thorsett, Stephen E.; Kouveliotou, Chryssa; Golenetskii, Sergey; Fynbo, Johan; Garnavich, Peter; Holland, Stephen; Hjorth, Jens; Moller, Palle; Pian, Elena; Tanvir, Nial; Ulanov, Mihail; Wijers, Ralph; Woosley, Stan

    2004-03-19

    We present the discovery and monitoring of the optical transient (OT) associated with GRB 020410. The fading OT was found by Hubble Space Telescope (HST) observations taken 28 and 65 days after burst at a position consistent with the X-ray afterglow. Subsequent re-examination of early ground based observations revealed that a faint OT was present 6 hours after burst, confirming the source association with GRB 020410. A deep non-detection after one week requires that the OT re-brightened between day 7 and day 28, and further late time HST data taken approximately 100 days after burst imply that it is very red (F{sub nu} proportional to nu-2.7). We compare both the flux and color of the excess with supernova models and show that the data are best explained by the presence of a Type I b/c supernova at a redshift z approx. equal 0.5, which occurred roughly coincident with the day of GRB.

  15. THE MAGNETIZATION DEGREE OF THE OUTFLOW POWERING THE HIGHLY POLARIZED REVERSE-SHOCK EMISSION OF GRB 120308A

    SciTech Connect

    Zhang, Shuai; Jin, Zhi-Ping; Wei, Da-Ming E-mail: dmwei@pmo.ac.cn

    2015-01-01

    GRB 120308A, a long duration γ-ray burst (GRB) detected by Swift, was distinguished by a highly polarized early optical afterglow emission that strongly suggests an ordered magnetic field component in the emitting region. In this work, we model the optical and X-ray emission in the reverse and forward shock scenario and show that the strength of the magnetic field in the reverse-shock region is ∼10 times stronger than that in the forward shock region. Consequently, the outflow powering the highly polarized reverse-shock optical emission was mildly magnetized at a degree of σ ∼ a few percent. Considering the plausible magnetic energy dissipation in both the acceleration and prompt emission phases of the GRB outflow, the afterglow data of GRB 120308A provides us with compelling evidence that, at least for some GRBs, a nonignorable fraction of the energy was released in the form of Poynting flux, confirming the finding first made in the reverse-forward shock emission modeling of the optical afterglow of GRB 990123 by Fan et al. in 2002 and Zhang et al. in 2003.

  16. Rapid UBVRI Follow-up of the Highly Collimated Optical Afterglow of GRB 010222

    NASA Astrophysics Data System (ADS)

    Stanek, Krzysztof Z.; Garnavich, Peter M.; Jha, Saurabh; Kilgard, Roy E.; McDowell, Jonathan C.; Bersier, David; Challis, Peter M.; Falco, Emilio; Quinn, Jason L.

    2001-12-01

    We present the earliest optical observations of the optical counterpart to the gamma-ray burst (GRB) 010222, obtained with the Fred L. Whipple Observatory 1.2 m telescope in UBVRI passbands, starting 3.64 hr after the burst (0.4 hr after public notification of the burst localization). We also present late R-band observations of the afterglow obtained with the 1.8 m Vatican Advanced Technology Telescope ~25 days after the burst. The temporal analysis of our data joined with published data indicates a steepening decay, independent of wavelength, asymptotically approaching Fν~t-0.80+/-0.05 at early times (t<<1 day) and Fν~t-1.30+/-0.05 at late times, with a sharp break at tb=0.72+/-0.10 days. This is the second earliest observed break of any afterglow (after GRB 980519), which clearly indicates the importance of rapid multiband follow-up for GRB afterglow research. The optical spectral energy distribution, corrected for small Galactic reddening, can be fitted fairly well by a single power law with Fν~ν-1.07+/-0.09. However, when we fit using our BVRI data only, we obtain a shallower slope of -0.88+/-0.10, in excellent agreement with the slope derived from our low-resolution spectrum (-0.89+/-0.03). The spectral slope and light-curve decay slopes we derive are not consistent with a jet model despite the presence of a temporal break. Significant host dust extinction with a starburst reddening law would flatten the spectral index to match jet predictions and still be consistent with the observed spectral energy distribution. We derive an opening angle of 2.1d, smaller than any listed in the recent compilation of Frail et al. The total beamed energy corrected for the jet geometry is 4×1050 ergs, very close to the ``standard'' value of 5×1050 ergs found by Frail et al. for a number of other bursts with light-curve breaks. Based on observations collected at the FLWO 1.2 m telescope and the 1.8 m VATT.

  17. The Radio Afterglow of GRB030329 at Centimetre Wavelengths: Evidence for Multiple Jets or a Structured Jet. Chapter 6

    NASA Technical Reports Server (NTRS)

    Rol, E.; vanderHorst, A. J.; Wijers, R. A. M. J.; Strom, R.; Kaper, L.; Kouveliotou, C.; vandenHeuvel, E. P. J.

    2003-01-01

    We present our centimetre wavelength (1.4, 2.3 and 4.9 GHz) light curves of the afterglow of GRB030329, which were obtained with the Westerbork Synthesis Radio Telescope. Modelling the data according to a collimated afterglow results in a jet-break time t(sub j) of 17 days. This is in contrast with earlier results obtained at higher frequencies, which indicate t(sub j) to be around 10 days. Furthermore, with respect to the afterglow model, some additional flux at the lower frequencies is present when these light curves reach their maximum. We subsequently show that the afterglow can be modelled with two or more components with progressively later jet breaks. From these results we infer that the jet is in fact a structured or a layered jet, where the ejecta with lower Lorentz factors produce additional flux which becomes visible at late times in the lowest frequency bands.

  18. Photohadronic Instability Model for GRB Prompt Emission

    NASA Astrophysics Data System (ADS)

    Dimitrakoudis, S.

    2013-09-01

    Τhe mechanisms behind gamma-ray bursts (GRBs) are not yet well understood. Here we investigate a model where a spectral energy distribution (SED) that looks surprisingly like a typical GRB prompt emission is generated starting with merely high energy protons and a magnetic field. Using a selfconsistent, time-dependent code we show that when the density of such protons exceeds a certain threshold their energy is converted explosively to lower energy photons through a series of positive feedback loops. At even higher densities, Compton scattering of cold electrons shapes the low energy part of the SED into the familiar Band function, a distinctive peak between 1-10 keV (in the comoving frame) in GRB observations. This approach, although similar to the photospheric GRB model, also allows us to investigate the neutrino emission, which can be compared with recent ICECUBE limits.

  19. Happy Birthday Swift: Ultra-long GRB 141121A and Its Broadband Afterglow

    NASA Astrophysics Data System (ADS)

    Cucchiara, A.; Veres, P.; Corsi, A.; Cenko, S. B.; Perley, D. A.; Lien, A.; Marshall, F. E.; Pagani, C.; Toy, V. L.; Capone, J. I.; Frail, D. A.; Horesh, A.; Modjaz, M.; Butler, N. R.; Littlejohns, O. M.; Watson, A. M.; Kutyrev, A. S.; Lee, W. H.; Richer, M. G.; Klein, C. R.; Fox, O. D.; Prochaska, J. X.; Bloom, J. S.; Troja, E.; Ramirez-Ruiz, E.; de Diego, J. A.; Georgiev, L.; González, J.; Román-Zúñiga, C. G.; Gehrels, N.; Moseley, H.

    2015-10-01

    We present our extensive observational campaign on the Swift-discovered GRB 141121A, almost 10 years after its launch. Our observations cover radio through X-rays and extend for more than 30 days after discovery. The prompt phase of GRB 141121A lasted 1410 s and, at the derived redshift of z = 1.469, the isotropic energy is Eγ,iso = 8.0 × 1052 erg. Due to the long prompt duration, GRB 141121A falls into the recently discovered class of ultra-long GRBs (UL-GRBs). Peculiar features of this burst are (1) a flat early-time optical light curve and (2) a radio-to-X-ray rebrightening around three days after the burst. The latter is followed by a steep optical-to-X-ray decay and a much shallower radio fading. We analyze GRB 141121A in the context of the standard forward-reverse shock (FS, RS) scenario and we disentangle the FS and RS contributions. Finally, we comment on the puzzling early-time (t ≲ 3 days) behavior of GRB 141121A, and suggest that its interpretation may require a two-component jet model. Overall, our analysis confirms that the class of UL-GRBs represents our best opportunity to firmly establish the prominent emission mechanisms in action during powerful gamma-ray burst explosions, and future missions (like SVOM, XTiDE, or ISS-Lobster) will provide many more of such objects.

  20. Happy Birthday Swift: Ultra-long GRB 141121A and Its Broadband Afterglow

    NASA Astrophysics Data System (ADS)

    Cucchiara, A.; Veres, P.; Corsi, A.; Cenko, S. B.; Perley, D. A.; Lien, A.; Marshall, F. E.; Pagani, C.; Toy, V. L.; Capone, J. I.; Frail, D. A.; Horesh, A.; Modjaz, M.; Butler, N. R.; Littlejohns, O. M.; Watson, A. M.; Kutyrev, A. S.; Lee, W. H.; Richer, M. G.; Klein, C. R.; Fox, O. D.; Prochaska, J. X.; Bloom, J. S.; Troja, E.; Ramirez-Ruiz, E.; de Diego, J. A.; Georgiev, L.; González, J.; Román-Zúñiga, C. G.; Gehrels, N.; Moseley, H.

    2015-10-01

    We present our extensive observational campaign on the Swift-discovered GRB 141121A, almost 10 years after its launch. Our observations cover radio through X-rays and extend for more than 30 days after discovery. The prompt phase of GRB 141121A lasted 1410 s and, at the derived redshift of z = 1.469, the isotropic energy is Eγ,iso = 8.0 × 1052 erg. Due to the long prompt duration, GRB 141121A falls into the recently discovered class of ultra-long GRBs (UL-GRBs). Peculiar features of this burst are (1) a flat early-time optical light curve and (2) a radio-to-X-ray rebrightening around three days after the burst. The latter is followed by a steep optical-to-X-ray decay and a much shallower radio fading. We analyze GRB 141121A in the context of the standard forward–reverse shock (FS, RS) scenario and we disentangle the FS and RS contributions. Finally, we comment on the puzzling early-time (t ≲ 3 days) behavior of GRB 141121A, and suggest that its interpretation may require a two-component jet model. Overall, our analysis confirms that the class of UL-GRBs represents our best opportunity to firmly establish the prominent emission mechanisms in action during powerful gamma-ray burst explosions, and future missions (like SVOM, XTiDE, or ISS-Lobster) will provide many more of such objects.

  1. HAPPY BIRTHDAY SWIFT: ULTRA-LONG GRB 141121A AND ITS BROADBAND AFTERGLOW

    SciTech Connect

    Cucchiara, A.; Veres, P.; Corsi, A.; Cenko, S. B.; Marshall, F. E.; Kutyrev, A. S.; Perley, D. A.; Horesh, A.; Lien, A.; Pagani, C.; Toy, V. L.; Capone, J. I.; Frail, D. A.; Modjaz, M.; Butler, N. R.; Littlejohns, O. M.; Watson, A. M.; Lee, W. H.; Richer, M. G.; Klein, C. R.; and others

    2015-10-20

    We present our extensive observational campaign on the Swift-discovered GRB 141121A, almost 10 years after its launch. Our observations cover radio through X-rays and extend for more than 30 days after discovery. The prompt phase of GRB 141121A lasted 1410 s and, at the derived redshift of z = 1.469, the isotropic energy is E{sub γ,iso} = 8.0 × 10{sup 52} erg. Due to the long prompt duration, GRB 141121A falls into the recently discovered class of ultra-long GRBs (UL-GRBs). Peculiar features of this burst are (1) a flat early-time optical light curve and (2) a radio-to-X-ray rebrightening around three days after the burst. The latter is followed by a steep optical-to-X-ray decay and a much shallower radio fading. We analyze GRB 141121A in the context of the standard forward–reverse shock (FS, RS) scenario and we disentangle the FS and RS contributions. Finally, we comment on the puzzling early-time (t ≲ 3 days) behavior of GRB 141121A, and suggest that its interpretation may require a two-component jet model. Overall, our analysis confirms that the class of UL-GRBs represents our best opportunity to firmly establish the prominent emission mechanisms in action during powerful gamma-ray burst explosions, and future missions (like SVOM, XTiDE, or ISS-Lobster) will provide many more of such objects.

  2. GRB 081029: A Gamma-Ray Burst with a Multi-Component Afterglow

    NASA Technical Reports Server (NTRS)

    Holland, Stephen T.; De Pasquale, Massimiliano; Mao, Jirong; Sakamoto, Takanori; Schady, Patricia; Covino, Stefano; Fan, Yi-Zhong; Jin, Zhi-Ping; D'Avanzo, Paolo; Antonelli, Angelo; D'Elia, Valerio; Ohincarini, Guido; Fiore, Fabrizio; Pandey, Shashi Bhushan; Cobb, Bethany E.

    2012-01-01

    We present an analysis of the unusual optical light curve of the gamma-ray burst GRB 081029, a long-soft burst with a redshift of z = 3.8479. We combine X-ray and optical observations from the Swift X-Ray Telescope and the Swift Ultra Violet/Optical Telescope with ground-based optical and infrared data obtained using the REM, ROTSE, and CTIO 1.3-m telescopes to construct a detailed data set extending from 86 s to approx.100,000 s after the BAT trigger. Our data covers a wide energy range, from 10 keV to 0.77 eV (1.24 A to 16000 A). The X-ray afterglow shows a shallow initial decay followed by a rapid decay starting at about 18,000 s. The optical and infrared afterglow, however, shows an uncharacteristic rise at about 3000 s that does not correspond to any feature in the X-ray light curve. Our data are not consistent with synchrotron radiation from a jet interacting with an external medium, a two-component jet, or continuous energy injection from the central engine. We find that the optical light curves can be broadly explained by a collision between two ejecta shells within a two-component jet. A growing number of gamma-ray burst afterglows are consistent with complex jets, which suggests that some (or all) gamma-ray burst jets are complex and will require detailed modelling to fully understand them.injection

  3. Probing the bright radio flare and afterglow of GRB 130427A with the Arcminute Microkelvin Imager

    NASA Astrophysics Data System (ADS)

    Anderson, G. E.; van der Horst, A. J.; Staley, T. D.; Fender, R. P.; Wijers, R. A. M. J.; Scaife, A. M. M.; Rumsey, C.; Titterington, D. J.; Rowlinson, A.; Saunders, R. D. E.

    2014-05-01

    We present one of the best sampled early-time light curves of a gamma-ray burst (GRB) at radio wavelengths. Using the Arcminute Mircrokelvin Imager (AMI), we observed GRB 130427A at the central frequency of 15.7 GHz between 0.36 and 59.32 d post-burst. These results yield one of the earliest radio detections of a GRB and demonstrate a clear rise in flux less than one day after the γ-ray trigger followed by a rapid decline. This early-time radio emission probably originates in the GRB reverse shock so our AMI light curve reveals the first ever confirmed detection of a reverse shock peak in the radio domain. At later times (about 3.2 d post-burst), the rate of decline decreases, indicating that the forward shock component has begun to dominate the light curve. Comparisons of the AMI light curve with modelling conducted by Perley et al. show that the most likely explanation of the early-time 15.7 GHz peak is caused by the self-absorption turn-over frequency, rather than the peak frequency, of the reverse shock moving through the observing bands.

  4. GRB 080503: IMPLICATIONS OF A NAKED SHORT GAMMA-RAY BURST DOMINATED BY EXTENDED EMISSION

    SciTech Connect

    Perley, D. A.; Metzger, B. D.; Butler, N. R.; Bloom, J. S.; Miller, A. A.; Filippenko, A. V.; Li, W.; Granot, J.; Sakamoto, T.; Gehrels, N.; Ramirez-Ruiz, E.; Bunker, A.; Chen, H.-W.; Glazebrook, K.; Hall, P. B.; Hurley, K. C.; Kocevski, D.; Norris, J.

    2009-05-10

    We report on observations of GRB 080503, a short gamma-ray burst (GRB) with very bright extended emission (about 30 times the gamma-ray fluence of the initial spike) in conjunction with a thorough comparison to other short Swift events. In spite of the prompt-emission brightness, however, the optical counterpart is extraordinarily faint, never exceeding 25 mag in deep observations starting at {approx}1 hr after the Burst Alert Telescope (BAT) trigger. The optical brightness peaks at {approx}1 day and then falls sharply in a manner similar to the predictions of Li and Paczynski (1998) for supernova-like emission following compact binary mergers. However, a shallow spectral index and similar evolution in X-rays inferred from Chandra observations are more consistent with an afterglow interpretation. The extreme faintness of this probable afterglow relative to the bright gamma-ray emission argues for a very low density medium surrounding the burst (a 'naked' GRB), consistent with the lack of a coincident host galaxy down to 28.5 mag in deep Hubble Space Telescope imaging. The late optical and X-ray peak could be explained by a slightly off-axis jet or by a refreshed shock. Our observations reinforce the notion that short GRBs generally occur outside regions of active star formation, but demonstrate that in some cases the luminosity of the extended prompt emission can greatly exceed that of the short spike, which may constrain theoretical interpretation of this class of events. This extended emission is not the onset of an afterglow, and its relative brightness is probably either a viewing-angle effect or intrinsic to the central engine itself. Because most previous BAT short bursts without observed extended emission are too faint for this signature to have been detectable even if it were present at typical level, conclusions based solely on the observed presence or absence of extended emission in the existing Swift sample are premature.

  5. Prompt and Afterglow Emission Properties of Gamma-Ray Bursts with Spectroscopically Identified Supernovae

    NASA Technical Reports Server (NTRS)

    Kaneko, Yuki; Ramirez-Ruiz, Enrico; Patel, Sandeep K.; Kouveliotou, Chryssa; Granot, Jonathan; Rol, Evert; Woosley, Stan; in'tZand, Jean J. M.; vanderHorst, Alexander; Wijers, Ralph A. M. J.; Strom, Richard

    2006-01-01

    We present a detailed spectral analysis of the prompt and afterglow emission of four nearby GRBs (GRBs 980425, 030329, 031203, and 060218) that were spectroscopically found to be associated with type Ib/c supernovae. For each event, we investigated its spectral and luminosity evolution and estimated the total energy budget based on the broadband observations. We discuss the properties of the four events in comparison to general burst population, and infer the physical parameters involved in creation of these nearby GRB-SN events

  6. X-Ray Spectral Components Observed in the Afterglow of GRB 130925A

    NASA Technical Reports Server (NTRS)

    Bellm, Eric C.; Barriere, Nicolas M.; Bhalerao, Varun; Boggs, Steven E.; Cenko, S. Bradley; Christensen, Finn E.; Craig, William W.; Forster, Karl; Fryer, Chris L.; Hailey, Charles J.; Harrison, Fiona A.; Horesh, Assaf; Kouveliotou, Chryssa; Madsen, Kristin K.; Miller, Jon M.; Ofek, Eran O.; Perley, Daniel A.; Rana, Vikram R.; Miller, Jon M.; Stern, Daniel; Tomsick, John A.; Zhang, William W.

    2014-01-01

    We have identified spectral features in the late-time X-ray afterglow of the unusually long, slow-decaying GRB 130925A using NuSTAR, Swift/X-Ray Telescope, and Chandra. A spectral component in addition to an absorbed power law is required at greater than 4 less than 1 significance, and its spectral shape varies between two observation epochs at 2 x 10 (sup 5) and 10 (sup 6) seconds after the burst. Several models can fit this additional component, each with very different physical implications. A broad, resolved Gaussian absorption feature of several kiloelectronvolts width improves the fit, but it is poorly constrained in the second epoch. An additive blackbody or second power-law component provide better fits. Both are challenging to interpret: the blackbody radius is near the scale of a compact remnant (10 (sup 8) centimeters), while the second power-law component requires an unobserved high-energy cutoff in order to be consistent with the non-detection by Fermi/Large Area Telescope.

  7. Emission spectrum of a sporadic fireball afterglow

    NASA Astrophysics Data System (ADS)

    Madiedo, J.; Trigo-Rodríguez, J.

    2014-07-01

    A mag. -11 fireball was imaged over southern Spain on April 14, 2013 at 22:35:49.8 ± 0.1s UTC. Its emission spectrum was also obtained. This event was assigned the SPMN code 140413 after the recording date. By the end of its atmospheric path, it exhibited a very bright flare which resulted in a persistent train whose spectrum was recorded. Here we present a preliminary analysis of this event and focus special attention on the evolution of the main emission lines in the spectrum of the afterglow. An array of low-lux CCD video devices (models 902H and 902H Ultimate from Watec Co.) operating from our stations at Sevilla and El Arenosillo was employed to record the SPMN140413 fireball. The operation of these systems is explained in [1,2]. Some of these are configured as spectrographs by attaching holographic diffraction gratings (1000 lines/mm) to the objective lens [3]. To calculate the atmospheric trajectory, radiant, and orbit we have employed our AMALTHEA software, which follows the planes intersection method [4]. The spectrum was analyzed with our CHIMET application [5]. The parent meteoroid impacted the atmosphere with an initial velocity of 28.9 ± 0.3 km/s and the fireball began at a height of 104.4 ± 0.5 km. The event ended at 80.7 ± 0.5 km above the ground level, with the main flare taking place at 83 ± 0.5 km. The calculated radiant and orbital parameters confirm the sporadic nature of the bolide. The calibrated emission spectrum shows that the most important contributions correspond to the Na I-1 (588.9 nm) and Mg I-2 (517.2 nm) multiplets. In the ultraviolet, the contribution from the H and K lines from Ca was also identified. As usual in meteor spectra, most of the lines correspond to Fe I. The train spectrum was recorded during about 0.12 seconds. This provided the evolution with time of the intensity of the emission lines in this signal. The contributions from Mg I, Na I, Ca I, Fe I, Ca II, and O I were identified in the afterglow, with the Na I-1

  8. Probing a Gamma-Ray Burst Progenitor at a Redshift of z = 2: A Comprehensive Observing Campaign Campaign of the Afterglow of GRB 030226

    NASA Technical Reports Server (NTRS)

    Klose, S.; Greiner, J.; Rau, A.; Henden, A. A.; Hartmann, D. H.; Zeh, A.; Ries, C.; Masetti, N.; Malesani, D.; Guenther, E.

    2004-01-01

    We report results from a comprehensive follow-up observing campaign of the afterglow of GRB 030226 including VLT spectroscopy, VLT polarimetry, and Chandra X-ray observations. In addition, we present BOOTES-1 wide-field observations at the time of the occurrence of the burst. First observations at ESO started 0.2 days after the event when the gamma ray burst (GRB) afterglow was at a magnitude of R approximately 19 and continued until the afterglow had faded below the detection threshold (R greater than 26). No underlying host galaxy was found. The optical light curve shows a break around 0.8 days after the burst, which is achromatic within the observational errors, supporting the view that it was due to a jetted explosion. Close to the break time the degree of linear polarization of the afterglow light was less than 1.1%, which favors a uniform-jet model rather than a structured one. VLT spectra show two absorption line systems at redshifts z = 1.962 plus or minus 0.001 and 1.986 plus or minus 0.001, placing the lower limit for the redshift of the GRB close to 2. We emphasize that the kinematics and the composition of the absorbing clouds responsible for these line systems are very similar to those observed in the afterglow of GRB 021004. This corroborates the picture in which at least some GRBs are physically related to the explosion of a Wolf-Rayet star.

  9. ON THE FORMATION OF Lyalpha EMISSION FROM RESONANTLY SCATTERED CONTINUUM PHOTONS OF GAMMA-RAY BURST's AFTERGLOW

    SciTech Connect

    Xu Wen; Wu Xiangping

    2010-02-20

    The continuum spectrum of gamma-ray burst's (GRB) afterglow at Lyalpha wavelength is known to be otherwise featureless except for the existence of a pair of smooth damping wings. Resonant scattering of photons with the ambient neutral hydrogen around the GRB may alter this picture. We study the formation and evolution of the spectral imprint of these resonantly scattered photons in the context of GRB's afterglow. Based on an analytic model that includes photons that are scattered only once, as well as a complete treatment of all the scatterings using Monte Carlo simulations, we are able to calculate the spectrum and luminosity of this Lyalpha emission from a very early moment up to a late epoch. We find that the amount, the motion, and the geometry of the neutral hydrogen around the GRB, together with the time behavior of the source are the crucial factors that affect the predicted luminosity and spectral profile. The flux of the Lyalpha emission is found to be mainly contributed by photons that are scattered only once. The flux is of the order 10{sup -4}-10{sup -9} relative to the undecayed maximum flux of the transmitted continuum, making the feature negligible but potentially observable. If not obscured by the host galaxy's damped Lyalpha absorption systems or intergalactic neutral hydrogen, the feature may appear sometime from 1 hr to several years when the directly transmitted light has faded away. This scattered emission feature can be distinguished from Lyalpha photons of other origins by its luminosity evolution and by its gradual narrowing of profile with time. The typical timescale for spectral variance is that of the light crossing time of a hydrogen clump close to the GRB. If observed, the resonant peaks' time-dependent behavior is a scanning probe on the distribution of neutral hydrogen in GRB's immediate neighborhood.

  10. Phenomenology of reverse-shock emission in the optical afterglows of gamma-ray bursts

    SciTech Connect

    Japelj, J.; Kopač, D.; Gomboc, A.; Kobayashi, S.; Harrison, R.; Virgili, F. J.; Mundell, C. G.; Guidorzi, C.; Melandri, A. E-mail: andreja.gomboc@fmf.uni-lj.si

    2014-04-20

    We use a parent sample of 118 gamma-ray burst (GRB) afterglows, with known redshift and host galaxy extinction, to separate afterglows with and without signatures of dominant reverse-shock (RS) emission and to determine which physical conditions lead to a prominent reverse-shock emission. We identify 10 GRBs with reverse-shock signatures: 990123, 021004, 021211, 060908, 061126, 080319B, 081007, 090102, 090424, and 130427A. By modeling their optical afterglows with reverse- and forward-shock analytic light curves and using Monte Carlo simulations, we estimate the parameter space of the physical quantities describing the ejecta and circumburst medium. We find that physical properties cover a wide parameter space and do not seem to cluster around any preferential values. Comparing the rest-frame optical, X-ray, and high-energy properties of the larger sample of non-RS-dominated GRBs, we show that the early-time (<1 ks) optical spectral luminosity, X-ray afterglow luminosity, and γ-ray energy output of our reverse-shock dominated sample do not differ significantly from the general population at early times. However, the GRBs with dominant reverse-shock emission have fainter than average optical forward-shock emission at late times (>10 ks). We find that GRBs with an identifiable reverse-shock component show a high magnetization parameter R {sub B} = ε{sub B,r}/ε{sub B,f} ∼ 2-10{sup 4}. Our results are in agreement with the mildly magnetized baryonic jet model of GRBs.

  11. DISCOVERY AND REDSHIFT OF AN OPTICAL AFTERGLOW IN 71 deg{sup 2}: iPTF13bxl AND GRB 130702A

    SciTech Connect

    Singer, Leo P.; Brown, Duncan A.; Bradley Cenko, S.; Gehrels, Neil; McEnery, Julie; Kasliwal, Mansi M.; Mulchaey, John; Perley, Daniel A.; Kulkarni, S. R.; Bellm, Eric; Barlow, Tom; Cao, Yi; Horesh, Assaf; Ofek, Eran O.; Arcavi, Iair; Nugent, Peter E.; Bloom, Joshua S.; Corsi, Alessandra; Frail, Dale A.; Masci, Frank J.; and others

    2013-10-20

    We report the discovery of the optical afterglow of the γ-ray burst (GRB) 130702A, identified upon searching 71 deg{sup 2} surrounding the Fermi Gamma-ray Burst Monitor (GBM) localization. Discovered and characterized by the intermediate Palomar Transient Factory, iPTF13bxl is the first afterglow discovered solely based on a GBM localization. Real-time image subtraction, machine learning, human vetting, and rapid response multi-wavelength follow-up enabled us to quickly narrow a list of 27,004 optical transient candidates to a single afterglow-like source. Detection of a new, fading X-ray source by Swift and a radio counterpart by CARMA and the Very Large Array confirmed the association between iPTF13bxl and GRB 130702A. Spectroscopy with the Magellan and Palomar 200 inch telescopes showed the afterglow to be at a redshift of z = 0.145, placing GRB 130702A among the lowest redshift GRBs detected to date. The prompt γ-ray energy release and afterglow luminosity are intermediate between typical cosmological GRBs and nearby sub-luminous events such as GRB 980425 and GRB 060218. The bright afterglow and emerging supernova offer an opportunity for extensive panchromatic follow-up. Our discovery of iPTF13bxl demonstrates the first observational proof-of-principle for ∼10 Fermi-iPTF localizations annually. Furthermore, it represents an important step toward overcoming the challenges inherent in uncovering faint optical counterparts to comparably localized gravitational wave events in the Advanced LIGO and Virgo era.

  12. Search for VHE emission from GRB with Milagro

    SciTech Connect

    Saz Parkinson, P.M.

    2005-02-21

    The Milagro gamma-ray observatory employs a water Cherenkov detector to observe extensive air showers produced by high-energy particles impacting in the Earth's atmosphere. Milagro is uniquely capable of searching for very high-energy emission from gamma-ray bursts (GRB) during the prompt emission phase because of its wide field of view and high duty cycle, monitoring the northern sky almost continuously in the 100 GeV to 100 TeV energy range. 33 satellite-triggered GRB have occurred within the field of view of Milagro between January 2000 and December 2003. We have searched for counterparts to these GRB and found no significant emission from any of these burst positions. In the case of GRB 010921, the redshift is low enough (0.45) that our upper limit on the fluence places an observational constraint on potential GRB models.

  13. Detailed optical and near-infrared polarimetry, spectroscopy and broad-band photometry of the afterglow of GRB 091018: polarization evolution

    NASA Astrophysics Data System (ADS)

    Wiersema, K.; Curran, P. A.; Krühler, T.; Melandri, A.; Rol, E.; Starling, R. L. C.; Tanvir, N. R.; van der Horst, A. J.; Covino, S.; Fynbo, J. P. U.; Goldoni, P.; Gorosabel, J.; Hjorth, J.; Klose, S.; Mundell, C. G.; O'Brien, P. T.; Palazzi, E.; Wijers, R. A. M. J.; D'Elia, V.; Evans, P. A.; Filgas, R.; Gomboc, A.; Greiner, J.; Guidorzi, C.; Kaper, L.; Kobayashi, S.; Kouveliotou, C.; Levan, A. J.; Rossi, A.; Rowlinson, A.; Steele, I. A.; de Ugarte Postigo, A.; Vergani, S. D.

    2012-10-01

    Follow-up observations of large numbers of gamma-ray burst (GRB) afterglows, facilitated by the Swift satellite, have produced a large sample of spectral energy distributions and light curves, from which their basic micro- and macro-physical parameters can in principle be derived. However, a number of phenomena have been observed that defy explanation by simple versions of the standard fireball model, leading to a variety of new models. Polarimetry can be a major independent diagnostic of afterglow physics, probing the magnetic field properties and internal structure of the GRB jets. In this paper we present the first high-quality multi-night polarimetric light curve of a Swift GRB afterglow, aimed at providing a well-calibrated data set of a typical afterglow to serve as a benchmark system for modelling afterglow polarization behaviour. In particular, our data set of the afterglow of GRB 091018 (at redshift z = 0.971) comprises optical linear polarimetry (R band, 0.13-2.3 d after burst); circular polarimetry (R band) and near-infrared linear polarimetry (Ks band). We add to that high-quality optical and near-infrared broad-band light curves and spectral energy distributions as well as afterglow spectroscopy. The linear polarization varies between 0 and 3 per cent, with both long and short time-scale variability visible. We find an achromatic break in the afterglow light curve, which corresponds to features in the polarimetric curve. We find that the data can be reproduced by jet break models only if an additional polarized component of unknown nature is present in the polarimetric curve. We probe the ordered magnetic field component in the afterglow through our deep circular polarimetry, finding Pcirc < 0.15 per cent (2σ), the deepest limit yet for a GRB afterglow, suggesting ordered fields are weak, if at all present. Our simultaneous R- and Ks-band polarimetry shows that dust-induced polarization in the host galaxy is likely negligible.

  14. Hubble space telescope observations of the afterglow, supernova, and host galaxy associated with the extremely bright GRB 130427A

    SciTech Connect

    Levan, A. J.; Tanvir, N. R.; Wiersema, K.; Fruchter, A. S.; Hounsell, R. A.; Graham, J.; Hjorth, J.; Fynbo, J. P. U.; Pian, E.; Mazzali, P.; Perley, D. A.; Cano, Z.; Cenko, S. B.; Kouveliotou, C.; Misra, K.

    2014-09-10

    We present Hubble Space Telescope (HST) observations of the exceptionally bright and luminous Swift gamma-ray burst (GRB), GRB 130427A. At z = 0.34, this burst affords an excellent opportunity to study the supernova (SN) and host galaxy associated with an intrinsically extremely luminous burst (E {sub iso} > 10{sup 54} erg): more luminous than any previous GRB with a spectroscopically associated SN. We use the combination of the image quality, UV capability, and invariant point-spread function of HST to provide the best possible separation of the afterglow, host, and SN contributions to the observed light ∼17 rest-frame days after the burst, utilizing a host subtraction spectrum obtained one year later. Advanced Camera for Surveys grism observations show that the associated SN, SN 2013cq, has an overall spectral shape and luminosity similar to SN 1998bw (with a photospheric velocity, v {sub ph} ∼ 15, 000 km s{sup –1}). The positions of the bluer features are better matched by the higher velocity SN 2010bh (v {sub ph} ∼ 30, 000 km s{sup –1}), but this SN is significantly fainter and fails to reproduce the overall spectral shape, perhaps indicative of velocity structure in the ejecta. We find that the burst originated ∼4 kpc from the nucleus of a moderately star forming (1 M {sub ☉} yr{sup –1}), possibly interacting disk galaxy. The absolute magnitude, physical size, and morphology of this galaxy, as well as the location of the GRB within it, are also strikingly similar to those of GRB 980425/SN 1998bw. The similarity of the SNe and environment from both the most luminous and least luminous GRBs suggests that broadly similar progenitor stars can create GRBs across six orders of magnitude in isotropic energy.

  15. Hubble Space Telescope Observations of the Afterglow, Supernova, and Host Galaxy Associated with the Extremely Bright GRB 130427A

    NASA Astrophysics Data System (ADS)

    Levan, A. J.; Tanvir, N. R.; Fruchter, A. S.; Hjorth, J.; Pian, E.; Mazzali, P.; Hounsell, R. A.; Perley, D. A.; Cano, Z.; Graham, J.; Cenko, S. B.; Fynbo, J. P. U.; Kouveliotou, C.; Pe'er, A.; Misra, K.; Wiersema, K.

    2014-09-01

    We present Hubble Space Telescope (HST) observations of the exceptionally bright and luminous Swift gamma-ray burst (GRB), GRB 130427A. At z = 0.34, this burst affords an excellent opportunity to study the supernova (SN) and host galaxy associated with an intrinsically extremely luminous burst (E iso > 1054 erg): more luminous than any previous GRB with a spectroscopically associated SN. We use the combination of the image quality, UV capability, and invariant point-spread function of HST to provide the best possible separation of the afterglow, host, and SN contributions to the observed light ~17 rest-frame days after the burst, utilizing a host subtraction spectrum obtained one year later. Advanced Camera for Surveys grism observations show that the associated SN, SN 2013cq, has an overall spectral shape and luminosity similar to SN 1998bw (with a photospheric velocity, v ph ~ 15, 000 km s-1). The positions of the bluer features are better matched by the higher velocity SN 2010bh (v ph ~ 30, 000 km s-1), but this SN is significantly fainter and fails to reproduce the overall spectral shape, perhaps indicative of velocity structure in the ejecta. We find that the burst originated ~4 kpc from the nucleus of a moderately star forming (1 M ⊙ yr-1), possibly interacting disk galaxy. The absolute magnitude, physical size, and morphology of this galaxy, as well as the location of the GRB within it, are also strikingly similar to those of GRB 980425/SN 1998bw. The similarity of the SNe and environment from both the most luminous and least luminous GRBs suggests that broadly similar progenitor stars can create GRBs across six orders of magnitude in isotropic energy.

  16. Ambient magnetic field amplification in shock fronts of relativistic jets: an application to GRB afterglows

    NASA Astrophysics Data System (ADS)

    Rocha da Silva, G.; Falceta-Gonçalves, D.; Kowal, G.; de Gouveia Dal Pino, E. M.

    2015-01-01

    Strong downstream magnetic fields of the order of ˜1 G, with large correlation lengths, are believed to cause the large synchrotron emission at the afterglow phase of gamma-ray bursts (GRBs). Despite the recent theoretical efforts, models have failed to fully explain the amplification of the magnetic field, particularly in a matter-dominated scenario. We revisit the problem by considering the synchrotron emission to occur at the expanding shock front of a weakly magnetized relativistic jet over a magnetized surrounding medium. Analytical estimates and a number of high-resolution 2D relativistic magnetohydrodynamical (RMHD) simulations are provided. Jet opening angles of θ = 0°-20°, and ambient to jet density ratios of 10-4-102 were considered. We found that most of the amplification is due to compression of the ambient magnetic field at the contact discontinuity between the reverse and forward shocks at the jet head, with substantial pile-up of the magnetic field lines as the jet propagates sweeping the ambient field lines. The pile-up is maximum for θ → 0, decreasing with θ, but larger than in the spherical blast problem. Values obtained for certain models are able to explain the observed intensities. The maximum correlation lengths found for such strong fields is of lcorr ≤ 1014 cm, 2-6 orders of magnitude larger than the found in previous works.

  17. Hubble Space Telescope Observations of the Afterglow, Supernova and Host Galaxy Associated with the Extremely Bright GRB 130427A

    NASA Technical Reports Server (NTRS)

    Levan, A.J.; Tanvir, N. R.; Fruchter, A. S.; Hjorth, J.; Pian, E.; Mazzali, P.; Hounsell, R. A.; Perley, D. A.; Cano, Z.; Graham, J.; Cenko, S. B.; Fynbo, J. P. U.; Kouveliotou, C.; Pe'er, A.; Misra, K.; Wiersema, K.

    2014-01-01

    We present Hubble Space Telescope (HST) observations of the exceptionally bright and luminous Swift gamma-ray burst, GRB 130427A. At z=0.34 this burst affords an excellent opportunity to study the supernova and host galaxy associated with an intrinsically extremely luminous burst (E(sub iso) greater than 10(exp 54) erg): more luminous than any previous GRB with a spectroscopically associated supernova. We use the combination of the image quality, UV capability and and invariant PSF of HST to provide the best possible separation of the afterglow, host and supernova contributions to the observed light approximately 17 rest-frame days after the burst utilising a host subtraction spectrum obtained 1 year later. Advanced Camera for Surveys (ACS) grism observations show that the associated supernova, SN 2013cq, has an overall spectral shape and luminosity similar to SN 1998bw (with a photospheric velocity, vph approximately 15,000 kilometers per second). The positions of the bluer features are better matched by the higher velocity SN 2010bh (vph approximately 30,000 kilometers per second), but SN 2010bh (vph approximately 30,000 kilometers per second but this SN is significantly fainter, and fails to reproduce the overall spectral shape, perhaps indicative of velocity structure in the ejecta. We find that the burst originated approximately 4 kpc from the nucleus of a moderately star forming (1 Solar Mass yr(exp-1)), possibly interacting disc galaxy. The absolute magnitude, physical size and morphology of this galaxy, as well as the location of the GRB within it are also strikingly similar to those of GRB980425SN 1998bw. The similarity of supernovae and environment from both the most luminous and least luminous GRBs suggests broadly similar progenitor stars can create GRBs across six orders of magnitude in isotropic energy.

  18. EARLY-TIME VLA OBSERVATIONS AND BROADBAND AFTERGLOW ANALYSIS OF THE FERMI/LAT DETECTED GRB 130907A

    SciTech Connect

    Veres, Péter; Corsi, Alessandra; Frail, Dale A.; Cenko, S. Bradley; Perley, Daniel A.

    2015-09-01

    We present multi-wavelength observations of the hyper-energetic gamma-ray burst (GRB) 130907A, a Swift-discovered burst with early radio observations starting at ≈4 hr after the γ-ray trigger. GRB 130907A was also detected by the Fermi/LAT instrument and at late times showed a strong spectral evolution in X-rays. We focus on the early-time radio observations, especially at >10 GHz, to attempt to identify reverse shock signatures. While our radio follow-up of GRB 130907A ranks among the earliest observations of a GRB with the Karl G. Jansky Very Large Array, we did not see an unambiguous signature of a reverse shock. While a model with both reverse and forward shock can correctly describe the observations, the data is not constraining enough to decide upon the presence of the reverse-shock component. We model the broadband data using a simple forward-shock synchrotron scenario with a transition from a wind environment to a constant density interstellar medium (ISM) in order to account for the observed features. Within the confines of this model, we also derive the underlying physical parameters of the fireball, which are within typical ranges except for the wind density parameter (A{sub *}), which is higher than those for bursts with wind-ISM transition, but typical for the general population of bursts. We note the importance of early-time radio observations of the afterglow (and of well-sampled light curves) for unambiguously identifying the potential contribution of the reverse shock.

  19. Constraints on Very High Energy Emission from GRB 130427A

    NASA Astrophysics Data System (ADS)

    Aliu, E.; Aune, T.; Barnacka, A.; Beilicke, M.; Benbow, W.; Berger, K.; Biteau, J.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cardenzana, J. V.; Cerruti, M.; Chen, X.; Ciupik, L.; Connaughton, V.; Cui, W.; Dickinson, H. J.; Eisch, J. D.; Errando, M.; Falcone, A.; Federici, S.; Feng, Q.; Finley, J. P.; Fleischhack, H.; Fortin, P.; Fortson, L.; Furniss, A.; Galante, N.; Gillanders, G. H.; Griffin, S.; Griffiths, S. T.; Grube, J.; Gyuk, G.; Håkansson, N.; Hanna, D.; Holder, J.; Hughes, G.; Humensky, T. B.; Johnson, C. A.; Kaaret, P.; Kar, P.; Kertzman, M.; Khassen, Y.; Kieda, D.; Krawczynski, H.; Krennrich, F.; Lang, M. J.; Madhavan, A. S.; Maier, G.; McArthur, S.; McCann, A.; Meagher, K.; Millis, J.; Moriarty, P.; Mukherjee, R.; Nieto, D.; O'Faoláin de Bhróithe, A.; Ong, R. A.; Otte, A. N.; Park, N.; Pohl, M.; Popkow, A.; Prokoph, H.; Pueschel, E.; Quinn, J.; Ragan, K.; Rajotte, J.; Reyes, L. C.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Sembroski, G. H.; Shahinyan, K.; Smith, A. W.; Staszak, D.; Telezhinsky, I.; Tucci, J. V.; Tyler, J.; Varlotta, A.; Vassiliev, V. V.; Vincent, S.; Wakely, S. P.; Weiner, O. M.; Weinstein, A.; Welsing, R.; Wilhelm, A.; Williams, D. A.; Zitzer, B.; McEnery, J. E.; Perkins, J. S.; Veres, P.; Zhu, S.

    2014-11-01

    Prompt emission from the very fluent and nearby (z = 0.34) gamma-ray burst GRB 130427A was detected by several orbiting telescopes and by ground-based, wide-field-of-view optical transient monitors. Apart from the intensity and proximity of this GRB, it is exceptional due to the extremely long-lived high-energy (100 MeV to 100 GeV) gamma-ray emission, which was detected by the Large Area Telescope on the Fermi Gamma-Ray Space Telescope for ~70 ks after the initial burst. The persistent, hard-spectrum, high-energy emission suggests that the highest-energy gamma rays may have been produced via synchrotron self-Compton processes though there is also evidence that the high-energy emission may instead be an extension of the synchrotron spectrum. VERITAS, a ground-based imaging atmospheric Cherenkov telescope array, began follow-up observations of GRB 130427A ~71 ks (~20 hr) after the onset of the burst. The GRB was not detected with VERITAS; however, the high elevation of the observations, coupled with the low redshift of the GRB, make VERITAS a very sensitive probe of the emission from GRB 130427A for E > 100 GeV. The non-detection and consequent upper limit derived place constraints on the synchrotron self-Compton model of high-energy gamma-ray emission from this burst.

  20. CONSTRAINTS ON VERY HIGH ENERGY EMISSION FROM GRB 130427A

    SciTech Connect

    Aliu, E.; Errando, M.; Aune, T.; Barnacka, A.; Beilicke, M.; Buckley, J. H.; Bugaev, V.; Benbow, W.; Cerruti, M.; Berger, K.; Biteau, J.; Byrum, K.; Cardenzana, J. V; Dickinson, H. J.; Eisch, J. D.; Chen, X.; Ciupik, L.; Connaughton, V.; Cui, W.; Falcone, A. E-mail: sjzhu@umd.edu; and others

    2014-11-01

    Prompt emission from the very fluent and nearby (z = 0.34) gamma-ray burst GRB 130427A was detected by several orbiting telescopes and by ground-based, wide-field-of-view optical transient monitors. Apart from the intensity and proximity of this GRB, it is exceptional due to the extremely long-lived high-energy (100 MeV to 100 GeV) gamma-ray emission, which was detected by the Large Area Telescope on the Fermi Gamma-Ray Space Telescope for ∼70 ks after the initial burst. The persistent, hard-spectrum, high-energy emission suggests that the highest-energy gamma rays may have been produced via synchrotron self-Compton processes though there is also evidence that the high-energy emission may instead be an extension of the synchrotron spectrum. VERITAS, a ground-based imaging atmospheric Cherenkov telescope array, began follow-up observations of GRB 130427A ∼71 ks (∼20 hr) after the onset of the burst. The GRB was not detected with VERITAS; however, the high elevation of the observations, coupled with the low redshift of the GRB, make VERITAS a very sensitive probe of the emission from GRB 130427A for E > 100 GeV. The non-detection and consequent upper limit derived place constraints on the synchrotron self-Compton model of high-energy gamma-ray emission from this burst.

  1. Confronting GRB prompt emission with a model for subphotospheric dissipation

    NASA Astrophysics Data System (ADS)

    Ahlgren, Björn; Larsson, Josefin; Nymark, Tanja; Ryde, Felix; Pe'er, Asaf

    2015-11-01

    The origin of the prompt emission in gamma-ray bursts (GRBs) is still an unsolved problem and several different mechanisms have been suggested. Here, we fit Fermi GRB data with a photospheric emission model which includes dissipation of the jet kinetic energy below the photosphere. The resulting spectra are dominated by Comptonization and contain no significant contribution from synchrotron radiation. In order to fit to the data, we span a physically motivated part of the model's parameter space and create DREAM (Dissipation with Radiative Emission as A table Model), a table model for XSPEC. We show that this model can describe different kinds of GRB spectra, including GRB 090618, representing a typical Band function spectrum, and GRB 100724B, illustrating a double peaked spectrum, previously fitted with a Band+blackbody model, suggesting they originate from a similar scenario. We suggest that the main difference between these two types of bursts is the optical depth at the dissipation site.

  2. Prompt Emission of GRB 121217A from Gamma-Rays to the Near-Infrared

    NASA Technical Reports Server (NTRS)

    Elliott, J.; Yu, H.-F.; Schmidl, S.; Greiner, J.; Gruber, D.; Oates, S.; Kobayashi, S.; Zhang, B.; Cummings, J. R.; Filgas, R.; Gehrels, N.

    2014-01-01

    The mechanism that causes the prompt-emission episode of gamma-ray bursts (GRBs) is still widely debated despite there being thousands of prompt detections. The favoured internal shock model relates this emission to synchrotron radiation. However, it does not always explain the spectral indices of the shape of the spectrum, which is often fit with empirical functions, such as the Band function. Multi-wavelength observations are therefore required to help investigate the possible underlying mechanisms that causes the prompt emission. We present GRB 121217A, for which we were able to observe its near-infrared (NIR) emission during a secondary prompt-emission episode with the Gamma-Ray burst Optical Near-infrared Detector (GROND) in combination with the Swift and Fermi satellites, which cover an energy range of 5 orders of magnitude (10(exp -3) keV to 100 keV). We determine a photometric redshift of z = 3.1 +/- 0.1 with a line-of-sight with little or no extinction (AV approx. 0 mag) utilising the optical/NIR SED. From the afterglow, we determine a bulk Lorentz factor of Gamma(sub 0) approx. 250 and an emission radius of R < 1018 cm. The prompt-emission broadband spectral energy distribution is well fit with a broken power law with beta1 = -0.3 +/- 0.1 and beta2 = 0.6 +/- 0.1 that has a break at E = 6.6 +/- 0.9 keV, which can be interpreted as the maximum injection frequency. Self-absorption by the electron population below energies of Ea < 6 keV suggest a magnetic field strength of B approx. 10(exp 5) G. However, all the best fit models underpredict the flux observed in the NIR wavelengths, which also only rebrightens by a factor of approx. 2 during the second prompt emission episode, in stark contrast to the X-ray emission, which rebrightens by a factor of approx. 100. This suggests an afterglow component is dominating the emission. We present GRB 121217A, one of the few GRBs that has multi-wavelength observations of the prompt-emission period and shows that it can

  3. NuSTAR OBSERVATIONS OF GRB 130427A ESTABLISH A SINGLE COMPONENT SYNCHROTRON AFTERGLOW ORIGIN FOR THE LATE OPTICAL TO MULTI-GEV EMISSION

    SciTech Connect

    Kouveliotou, C.; Racusin, J. L.; Gehrels, N.; McEnery, J. E.; Zhang, W. W.; Bellm, E.; Harrison, F. A.; Vianello, G.; Oates, S.; Fryer, C. L.; Boggs, S. E.; Craig, W. W.; Christensen, F. E.; Dermer, C. D.; Hailey, C. J.; Melandri, A.; Tagliaferri, G.; Mundell, C. G.; Stern, D. K. E-mail: granot@openu.ac.il

    2013-12-10

    GRB 130427A occurred in a relatively nearby galaxy; its prompt emission had the largest GRB fluence ever recorded. The afterglow of GRB 130427A was bright enough for the Nuclear Spectroscopic Telescope ARray (NuSTAR) to observe it in the 3-79 keV energy range long after its prompt emission (∼1.5 and 5 days). This range, where afterglow observations were previously not possible, bridges an important spectral gap. Combined with Swift, Fermi, and ground-based optical data, NuSTAR observations unambiguously establish a single afterglow spectral component from optical to multi-GeV energies a day after the event, which is almost certainly synchrotron radiation. Such an origin of the late-time Fermi/Large Area Telescope >10 GeV photons requires revisions in our understanding of collisionless relativistic shock physics.

  4. THERMAL EMISSION IN THE EARLY X-RAY AFTERGLOWS OF GAMMA-RAY BURSTS: FOLLOWING THE PROMPT PHASE TO LATE TIMES

    SciTech Connect

    Friis, Mette; Watson, Darach E-mail: darach@dark-cosmology.dk

    2013-07-01

    Thermal radiation, peaking in soft X-rays, has now been detected in a handful of gamma-ray burst (GRB) afterglows and has to date been interpreted as shock break-out of the GRB's progenitor star. We present a search for thermal emission in the early X-ray afterglows of a sample of Swift bursts selected by their brightness in X-rays at early times. We identify a clear thermal component in eight GRBs and track the evolution. We show that at least some of the emission must come from highly relativistic material since two show an apparent super-luminal expansion of the thermal component. Furthermore, we determine very large luminosities and high temperatures for many of the components-too high to originate in a supernova shock break-out. Instead, we suggest that the component may be modeled as late photospheric emission from the jet, linking it to the apparently thermal component observed in the prompt emission of some GRBs at gamma-ray and hard X-ray energies. By comparing the parameters from the prompt emission and the early afterglow emission, we find that the results are compatible with the interpretation that we are observing the prompt quasi-thermal emission component in soft X-rays at a later point in its evolution.

  5. A Correlated Optical and Gamma Emission from GRB 081126A

    SciTech Connect

    Gendre, B.; Klotz, A.; Atteia, J. L.; Boeer, M.; Coward, D. M.; Imerito, A. C.

    2010-10-15

    We present an analysis of time-resolved optical emissions observed from the gamma-ray burst GRB 081126 during the prompt phase. The analysis employed time-resolved photometry using optical data obtained by the TAROT telescope, BAT data from the Swift spacecraft and time-resolved spectroscopy at high energies from the GBM instrument onboard the Fermi spacecraft. The optical emission of GRB 081126 is found to be compatible with the second gamma emission pulse shifted by a positive time-lag of 8.4{+-}3.9 sec. This is the first well resolved observation of a time lag between optical and gamma emissions during a gamma-ray burst. Our observations could potentially provide new constraints on the fireball model for gamma ray burst early emissions. Furthermore, observations of time-lags between optical and gamma ray photons provides an exciting opportunity to constrain quantum gravity theories.

  6. Decay of the GRB 990123 optical afterglow: implications for the fireball model

    PubMed

    Castro-Tirado; Zapatero-Osorio; Caon; Cairos; Hjorth; Pedersen; Andersen; Gorosabel; Bartolini; Guarnieri; Piccioni; Frontera; Masetti; Palazzi; Pian; Greiner; Hudec; Sagar; Pandey; Mohan; Yadav; Nilakshi; Bjornsson; Jakobsson; Burud; et

    1999-03-26

    Broad-band (ultraviolet to near-infrared) observations of the intense gamma ray burst GRB 990123 started approximately 8.5 hours after the event and continued until 18 February 1999. When combined with other data, in particular from the Robotic Telescope and Transient Source Experiment (ROTSE) and the Hubble Space Telescope (HST), evidence emerges for a smoothly declining light curve, suggesting some color dependence that could be related to a cooling break passing the ultraviolet-optical band at about 1 day after the high-energy event. The steeper decline rate seen after 1.5 to 2 days may be evidence for a collimated jet pointing toward the observer.

  7. Self organized criticality in an one dimensional magnetized grid. Application to GRB X-ray afterglows

    NASA Astrophysics Data System (ADS)

    Harko, Tiberiu; Mocanu, Gabriela; Stroia, Nicoleta

    2015-05-01

    A simplified one dimensional grid is used to model the evolution of magnetized plasma flow. We implement diffusion laws similar to those so-far used to model magnetic reconnection with Cellular Automata. As a novelty, we also explicitly superimpose a background flow. The aim is to numerically investigate the possibility that Self-Organized Criticality appears in a one dimensional magnetized flow. The cellular automaton's cells store information about the parameter relevant to the evolution of the system being modelled. Under the assumption that this parameter stands for the magnetic field, the magnetic energy released by one grid cell during one individual relaxation event is also computed. Our results show that indeed in this system Self-Organized Criticality is established. The possible applications of this model to the study of the X-ray afterglows of GRBs is also briefly considered.

  8. Search for TeV Gamma-ray Emission from GRB 100621A, an extremely bright GRB in X-rays, with H.E.S.S.

    NASA Astrophysics Data System (ADS)

    H.E.S.S. Collaboration; Abramowski, A.; Aharonian, F.; Ait Benkhali, F.; Akhperjanian, A. G.; Angüner, E.; Anton, G.; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Becker Tjus, J.; Bernlöhr, K.; Birsin, E.; Bissaldi, E.; Biteau, J.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bordas, P.; Brucker, J.; Brun, F.; Brun, P.; Bulik, T.; Carrigan, S.; Casanova, S.; Cerruti, M.; Chadwick, P. M.; Chalme-Calvet, R.; Chaves, R. C. G.; Cheesebrough, A.; Chrétien, M.; Colafrancesco, S.; Cologna, G.; Conrad, J.; Couturier, C.; Dalton, M.; Daniel, M. K.; Davids, I. D.; Degrange, B.; Deil, C.; deWilt, P.; Dickinson, H. J.; Djannati-Ataï, A.; Domainko, W.; O'C. Drury, L.; Dubus, G.; Dutson, K.; Dyks, J.; Dyrda, M.; Edwards, T.; Egberts, K.; Eger, P.; Espigat, P.; Farnier, C.; Fegan, S.; Feinstein, F.; Fernandes, M. V.; Fernandez, D.; Fiasson, A.; Fontaine, G.; Förster, A.; Füßling, M.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Giebels, B.; Glicenstein, J. F.; Grondin, M.-H.; Grudzińska, M.; Häffner, S.; Hahn, J.; Harris, J.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hervet, O.; Hillert, A.; Hinton, J. A.; Hofmann, W.; Hofverberg, P.; Holler, M.; Horns, D.; Jacholkowska, A.; Jahn, C.; Jamrozy, M.; Janiak, M.; Jankowsky, F.; Jung, I.; Kastendieck, M. A.; Katarzyński, K.; Katz, U.; Kaufmann, S.; Khélifi, B.; Kieffer, M.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Kneiske, T.; Kolitzus, D.; Komin, Nu.; Kosack, K.; Krakau, S.; Krayzel, F.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lefaucheur, J.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J.-P.; Lennarz, D.; Lohse, T.; Lopatin, A.; Lu, C.-C.; Marandon, V.; Marcowith, A.; Marx, R.; Maurin, G.; Maxted, N.; Mayer, M.; McComb, T. J. L.; Méhault, J.; Menzler, U.; Meyer, M.; Moderski, R.; Mohamed, M.; Moulin, E.; Murach, T.; Naumann, C. L.; de Naurois, M.; Niemiec, J.; Nolan, S. J.; Oakes, L.; O'Brien, P. T.; Ohm, S.; de Oña Wilhelmi, E.; Opitz, B.; Ostrowski, M.; Oya, I.; Panter, M.; Parsons, R. D.; Paz Arribas, M.; Pekeur, N. W.; Pelletier, G.; Perez, J.; Petrucci, P.-O.; Peyaud, B.; Pita, S.; Poon, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Raue, M.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Rieger, F.; Rob, L.; Romoli, C.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Sanchez, D. A.; Santangelo, A.; Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schwanke, U.; Schwarzburg, S.; Schwemmer, S.; Sol, H.; Spengler, G.; Spies, F.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stinzing, F.; Stycz, K.; Sushch, I.; Szostek, A.; Tam, P. H. T.; Tavernet, J.-P.; Tavernier, T.; Taylor, A. M.; Terrier, R.; Tluczykont, M.; Trichard, C.; Valerius, K.; van Eldik, C.; Vasileiadis, G.; Venter, C.; Viana, A.; Vincent, P.; Völk, H. J.; Volpe, F.; Vorster, M.; Wagner, S. J.; Wagner, P.; Ward, M.; Weidinger, M.; Weitzel, Q.; White, R.; Wierzcholska, A.; Willmann, P.; Wörnlein, A.; Wouters, D.; Zacharias, M.; Zajczyk, A.; Zdziarski, A. A.; Zech, A.; Zechlin, H.-S.

    2014-05-01

    The long gamma-ray burst (GRB) 100621A, at the time the brightest X-ray transient ever detected by Swift-XRT in the 0.3-10 keV range, has been observed with the H.E.S.S. imaging air Cherenkov telescope array, sensitive to gamma radiation in the very-high-energy (VHE, >100 GeV) regime. Due to its relatively small redshift of z ~ 0.5, the favourable position in the southern sky and the relatively short follow-up time (<700 s after the satellite trigger) of the H.E.S.S. observations, this GRB could be within the sensitivity reach of the H.E.S.S. instrument. The analysis of the H.E.S.S. data shows no indication of emission and yields an integral flux upper limit above ~380 GeV of 4.2 × 10-12 cm-2 s-1 (95% confidence level), assuming a simple Band function extension model. A comparison to a spectral-temporal model, normalised to the prompt flux at sub-MeV energies, constraints the existence of a temporally extended and strong additional hard power law, as has been observed in the other bright X-ray GRB 130427A. A comparison between the H.E.S.S. upper limit and the contemporaneous energy output in X-rays constrains the ratio between the X-ray and VHE gamma-ray fluxes to be greater than 0.4. This value is an important quantity for modelling the afterglow and can constrain leptonic emission scenarios, where leptons are responsible for the X-ray emission and might produce VHE gamma rays.

  9. A Bulk Comptonization Model for the Prompt GRB Emission and its Relation to the Fermi GRB Spectra

    NASA Technical Reports Server (NTRS)

    Kazanas, Demosthenes

    2010-01-01

    We present a model in which the GRB prompt emission at E E(sub peak) is due to bulk Comptonization by the relativistic blast wave motion of either its own synchrotron photons of ambient photons of the stellar configuration that gave birth to the GRB. The bulk Comptonization process then induces the production of relativistic electrons of Lorentz factor equal to that of the blast wave through interactions with its ambient protons. The inverse compton emission of these electrons produces a power law component that extends to multi GeV energies in good agreement with the LAT GRB observations.

  10. GRB 081007 AND GRB 090424: THE SURROUNDING MEDIUM, OUTFLOWS, AND SUPERNOVAE

    SciTech Connect

    Jin Zhiping; Covino, Stefano; Fugazza, Dino; Melandri, Andrea; Campana, Sergio; D'Avanzo, Paolo; Della Valle, Massimo; Ferrero, Patrizia; Malesani, Daniele; Fynbo, Johan P. U.; Hjorth, Jens; Pian, Elena; Salvaterra, Ruben; Bersier, David; Cano, Zach; Castro-Tirado, Alberto J.; Gorosabel, Javier; Guidorzi, Cristiano; Haislip, Joshua B.; and others

    2013-09-10

    We discuss the results of the analysis of multi-wavelength data for the afterglows of GRB 081007 and GRB 090424, two bursts detected by Swift. One of them, GRB 081007, also shows a spectroscopically confirmed supernova, SN 2008hw, which resembles SN 1998bw in its absorption features, while the maximum magnitude may be fainter, up to 0.7 mag, than observed in SN 1998bw. Bright optical flashes have been detected in both events, which allows us to derive solid constraints on the circumburst-matter density profile. This is particularly interesting in the case of GRB 081007, whose afterglow is found to be propagating into a constant-density medium, yielding yet another example of a gamma-ray burst (GRB) clearly associated with a massive-star progenitor which did not sculpt the surroundings with its stellar wind. There is no supernova component detected in the afterglow of GRB 090424, likely due to the brightness of the host galaxy, comparable to the Milky Way. We show that the afterglow data are consistent with the presence of both forward- and reverse-shock emission powered by relativistic outflows expanding into the interstellar medium. The absence of optical peaks due to the forward shock strongly suggests that the reverse-shock regions should be mildly magnetized. The initial Lorentz factor of outflow of GRB 081007 is estimated to be {Gamma} {approx} 200, while for GRB 090424 a lower limit of {Gamma} > 170 is derived. We also discuss the prompt emission of GRB 081007, which consists of just a single pulse. We argue that neither the external forward-shock model nor the shock-breakout model can account for the prompt emission data and suggest that the single-pulse-like prompt emission may be due to magnetic energy dissipation of a Poynting-flux-dominated outflow or to a dissipative photosphere.

  11. Effect of secondary emission on the argon plasma afterglow with large dust density

    SciTech Connect

    Denysenko, I. B.; Azarenkov, N. A.; Burmaka, G. P.; Stefanović, I.

    2015-02-15

    A zero-dimensional, space-averaged model for argon plasma afterglow with large dust density is developed. In the model, three groups of electrons in the plasma afterglow are assumed: (i) thermal electrons with Maxwellian distribution, (ii) energetic electrons generated by metastable-metastable collisions (metastable pooling), and (iii) secondary electrons generated at collisions of ions with the electrodes, which have sufficiently large negative voltages in the afterglow. The model calculates the time-dependencies for electron densities in plasma afterglow based on experimental decay times for metastable density and electrode bias. The effect of secondary emission on electron density in the afterglow is estimated by varying secondary emission yields. It is found that this effect is less important than metastable pooling. The case of dust-free plasma afterglow is considered also, and it is found that in the afterglow the effect of secondary emission may be more important than metastable pooling. The secondary emission may increase thermal electron density n{sub e} in dust-free and dusty plasma afterglows on a few ten percentages. The calculated time dependencies for n{sub e} in dust-free and dusty plasma afterglows describe well the experimental results.

  12. Decay of the GRB 990123 optical afterglow: implications for the fireball model

    PubMed

    Castro-Tirado; Zapatero-Osorio; Caon; Cairos; Hjorth; Pedersen; Andersen; Gorosabel; Bartolini; Guarnieri; Piccioni; Frontera; Masetti; Palazzi; Pian; Greiner; Hudec; Sagar; Pandey; Mohan; Yadav; Nilakshi; Bjornsson; Jakobsson; Burud; et

    1999-03-26

    Broad-band (ultraviolet to near-infrared) observations of the intense gamma ray burst GRB 990123 started approximately 8.5 hours after the event and continued until 18 February 1999. When combined with other data, in particular from the Robotic Telescope and Transient Source Experiment (ROTSE) and the Hubble Space Telescope (HST), evidence emerges for a smoothly declining light curve, suggesting some color dependence that could be related to a cooling break passing the ultraviolet-optical band at about 1 day after the high-energy event. The steeper decline rate seen after 1.5 to 2 days may be evidence for a collimated jet pointing toward the observer. PMID:10092226

  13. DETECTION OF HIGH-ENERGY GAMMA-RAY EMISSION DURING THE X-RAY FLARING ACTIVITY IN GRB 100728A

    SciTech Connect

    Abdo, A. A.; Ackermann, M.; Ajello, M.; Bechtol, K.; Berenji, B.; Blandford, R. D.; Borgland, A. W.; Baldini, L.; Bellazzini, R.; Bregeon, J.; Ballet, J.; Baring, M. G.; Bastieri, D.; Bhat, P. N.; Bissaldi, E.; Bonamente, E.; Bonnell, J.; Bouvier, A.; Brigida, M. E-mail: Julie.E.McEnery@nasa.gov E-mail: vlasios.vasileiou@univ-montp2.fr

    2011-06-20

    We present the simultaneous Swift and Fermi observations of the bright GRB 100728A and its afterglow. The early X-ray emission is dominated by a vigorous flaring activity continuing until 1 ks after the burst. In the same time interval, high-energy emission is significantly detected by the Fermi/Large Area Telescope. Marginal evidence of GeV emission is observed up to later times. We discuss the broadband properties of this burst within both the internal and external shock scenarios, with a particular emphasis on the relation between X-ray flares, the GeV emission, and a continued long-duration central engine activity as their power source.

  14. MITSuME: multicolor optical/NIR telescopes for GRB afterglows

    SciTech Connect

    Shimokawabe, Takashi; Kawai, Nobuyuki; Kotani, Taro; Yatsu, Yoichi; Ishimura, Takuto; Vasquez, Nicolas; Mori, Yuki; Kudo, Yusuke; Yoshida, Michitoshi; Yanagisawa, Kenshi; Nagayama, Shogo; Toda, Hiroyuki; Shimozu, Yasuhiro; Kuroda, Daisuke; Watanabe, Junichi; Fukushima, Hideo; Mori, Masaki

    2008-05-22

    Multicolor Imaging Telescopes for Survey and Monstrous Explosions (MITSuME) is built to perform multi-color photometry of NIR/optical afterglow covering the wavebands from K{sub s} to g' allowing the photometric redshift measurements up to z{approx_equal}10.Two 50 cm optical telescopes are built at Akeno, Yamanashi in eastern Japan, and at OAO, Okayama in western Japan. Each telescope has a Tricolor Camera, which allows us to take simultaneous images in g', R{sub c} and I{sub c} bands. These telescopes respond to GCN alerts and start taking series of tricolor images, which are immediately processed through the analys is pipeline on site. The pipeline consists of source finding, catalog matching, sky coordinates mapping to the image pixels, and photometry of the found sources. In addition, an automated search for an optical counterpart is performed.In addition, a wide-field (1 deg.) 91 cm NIR telescope is being built at OAO with filters in K{sub s}, H, J, and y bands.Summary of early results will be also presented.

  15. Broadband Study of GRB 091127: A Sub-Energetic Burst at Higher Redshift?

    NASA Technical Reports Server (NTRS)

    Troja, E.; Sakamoto, T.; Guidorzi, C.; Norris, J. P.; Panaitescu, A.; Kobayashi, S.; Omodei, N.; Brown, J. C.; Burrows, D. N.; Evans, P. A.; Gehrels, N.; Marshall, F. E.; Mawson, N.; Melandri,; Mundell, C. G.; Oates, S. R.; Pal'shin, V.; Preece, R. D.; Racusin, J. L.; Steele, I. A.; Tanvir, N. R.; Vasileiou, V.; Wilson-Hodge, C.

    2012-01-01

    GRB 091127 is a bright gamma-ray burst (GRB) detected by Swift at a redshift z=0.49 and associated with SN 2009nz. We present the broadband analysis of the GRB prompt and afterglow emission and study its high-energy properties in the context of the GRB/SN association. While the high luminosity of the prompt emission and standard afterglow behavior are typical of cosmological long GRBs, its low energy release (E(sub gamma),<3x10(exp 49) erg), soft spectrum and unusual spectral lag connect this GRB to the class of sub-energetic bursts. We discuss the suppression of high-energy emission in this burst, and investigate whether this behavior could be connected with the sub-energetic nature of the explosion. Subject headings: gamma-ray bursts: individual (GRB 091127)

  16. The Optical Afterglow of a Short Gamma-ray Burst

    NASA Technical Reports Server (NTRS)

    Hjorth, Jens; Watson, Darach; Flynbo, Johan P.U.; Price, Paul A.; Jensen, Brian L.; Jorgensen, Uffe G.; Kubas, Daniel; Gorosabel, Javier; Jakobssonk, Pall; Sollerman, Jesper

    2005-01-01

    It has long been known that there are two classes of gamma-ray bursts (GRBs), principally distinguished by their durations. The breakthrough in our understanding of long-duration GRBs (greater than 2 seconds in duration), that ultimately linked them with energetic Type Ic supernovae, came about from the discovery of their long-lived X-ray and optical "afterglow", when precise and rapid localizations of the sources could finally be obtained. Recently, X-ray localizations have become available for short (less than 2 seconds in duration) GRBs, a hitherto elusive GRB population, that has evaded optical detection for more than thirty years. Here we report the discovery of transient optical emission (R approximately 23 mag) associated with a short GRB. This first short GRB afterglow is localized with sub-arcsecond accuracy onto the outskirts of a blue dwarf galaxy. Unless the optical and X-ray afterglow arise from different mechanisms our observations 33 h after the GRB suggest that, analogously to long GRBs, we observe synchrotron emission from ultrarelativistic ejecta (ZZZ CAN WE LIMIT GAMMA?). In contrast, we did not detect a bright supernova, as found in most nearby long GRB afterglows, which suggests a different origidstrongly constrain the nature of the short GRB progenitors.

  17. Prompt and Afterglow Emission Properties of Gamma-Ray Bursts with Spectroscopically Identified Supernovae

    NASA Technical Reports Server (NTRS)

    Kaneko, Yuki; Ramirez-Ruiz, Enrico; Granot, Jonathan; Kouveliotou, Chryssa; Woosley, Stan E.; Patel, Sandeep K.; Rol, Evert; In'TZand, Jean J. M.; VanDerHorst, Alexander J.; Wuers, Ralph A. M. J.; Strom, Richard

    2007-01-01

    We present a detailed spectral analysis of the prompt and afterglow emission of four nearby long-soft gamma-ray bursts (GRBs 980425,030329,031203, and 060218) that were spectroscopically found to be associated with Type Ic supernovae and compare them to the general GRB population. For each event, we investigate the spectral and luminosity evolution and estimate the total energy budget based on broadband observations. The observational inventory for these events has become rich enough to allow estimates of their energy content in relativistic and subrelativistic form. The result is a global portrait of the effects of the physical processes responsible for producing long-soft GRBs. In particular, we find that the values of the energy released in mildly relativistic outflows appears to have a significantly smaller scatter than those found in highly relativistic ejecta. This is consistent with a picture in which the energy released inside the progenitor star is roughly standard, while the fraction of that energy that ends up in highly relativistic ejecta outside the star can vary dramatically between different events.

  18. Prompt and Afterglow Emission Properties of Gamma-Ray Bursts with Spectroscopically Identified Supernovae

    SciTech Connect

    Kaneko, Yuki; Ramirez-Ruiz, E.; Granot, J.; Kouveliotou, C.; Woosley, S.E.; Patel, S.K.; Rol, E.; Zand, J.J.M.in't; a; Wijers, R.A.M.J.; Strom, R.; /USRA, Huntsville /Princeton, Inst. Advanced Study /UC, Santa Cruz /KIPAC, Menlo Park /NASA, Marshall /Leicester U. /SRON, Utrecht /Utrecht, Astron. Inst. /Amsterdam U., Astron. Inst. /NFRA, Dwingeloo

    2006-07-12

    We present a detailed spectral analysis of the prompt and afterglow emission of four nearby long-soft gamma-ray bursts (GRBs 980425, 030329, 031203, and 060218) that were spectroscopically found to be associated with type Ic supernovae, and compare them to the general GRB population. For each event, we investigate the spectral and luminosity evolution, and estimate the total energy budget based upon broadband observations. The observational inventory for these events has become rich enough to allow estimates of their energy content in relativistic and sub-relativistic form. The result is a global portrait of the effects of the physical processes responsible for producing long-soft GRBs. In particular, we find that the values of the energy released in mildly relativistic outflows appears to have a significantly smaller scatter than those found in highly relativistic ejecta. This is consistent with a picture in which the energy released inside the progenitor star is roughly standard, while the fraction of that energy that ends up in highly relativistic ejecta outside the star can vary dramatically between different events.

  19. GRB 050826: A Subluminous Event at z=0.296 Finds Its Place in the Luminosity Distribution of Gamma-Ray Burst Afterglows

    NASA Technical Reports Server (NTRS)

    Mirabal, N.; Halpern J. P.; O'Brien, P. T.

    2007-01-01

    We present the optical identification and spectroscopy of the host galaxy of GRB 050826 at redshift z = 0.296 +/- 0.001. Image subtraction among observations obtained on three consecutive nights reveals a fading object 5 hr after the burst, confirming its identification as the optical afterglow of this event. Deep imaging shows that the optical afterglow is offset by 0.4" (1.76 kpc) from the center of its irregular host galaxy, which is typical for long-duration gamma-ray bursts. Combining these results with X-ray measurements acquired by the Swift XRT instrument, we find that GRB 050826 falls entirely within the subluminous, subenergetic group of long gamma-ray bursts at low redshift (z less than or equal to 0.3). The results are discussed in the context of models that possibly account for this trend, including the nature of the central engine, the evolution of progenitor properties as a function of redshift, and incompleteness in current gamma-ray burst samples.

  20. Radiative Mechanisms in GRB Prompt Emission

    NASA Astrophysics Data System (ADS)

    Pe'er, A.

    2013-07-01

    Motivated by the Fermi gamma-ray space telescope results, in recent years immense efforts were given to understanding the mechanism that leads to the prompt emission observed. The failure of the optically thin emission models (synchrotron and synchrotron self Compton) increased interest in alternative models. Optically thick models, while having several advantages, also face difficulty in capturing several key observables. Theoretical efforts are focused in two main directions: (1) mechanisms that act to broaden the Planck spectrum; and (2) combining the optically thin and optically thick models to a hybrid model that could explain the key observables.

  1. GRB 070724B: the first Gamma Ray Burst localized by SuperAGILE

    SciTech Connect

    Del Monte, E.; Costa, E.; Donnarumma, I.; Feroci, M.; Lapshov, I.; Lazzarotto, F.; Soffitta, P.; Argan, A.; Pucella, G.; Trois, A.; Vittorini, V.; Evangelista, Y.; Rapisarda, M.; Barbiellini, G.; Longo, F.; Basset, M.; Foggetta, L.; Vallazza, E.; Bulgarelli, A.; Di Cocco, G.

    2008-05-22

    GRB070724B is the first Gamma Ray Burst localized by the SuperAGILE instrument aboard the AGILE space mission. The SuperAGILE localization has been confirmed after the after-glow observation by the XRT aboard the Swift satellite. No significant gamma ray emission above 50 MeV has been detected for this GRB. In this paper we describe the SuperAGILE capabilities in detecting Gamma Ray Burst and the AGILE observation of GRB 070724B.

  2. Luminosity Correlations for Gamma-Ray Bursts and Implications for Their Prompt and Afterglow Emission Mechanisms

    NASA Astrophysics Data System (ADS)

    Sultana, J.; Kazanas, D.; Fukumura, K.

    2012-10-01

    We present the relation between the (z- and k-corrected) spectral lags, τ, for the standard Swift energy bands 50-100 keV and 100-200 keV and the peak isotropic luminosity, L iso (a relation reported first by Norris et al.), for a subset of 12 long Swift gamma-ray bursts (GRBs) taken from a recent study of this relation by Ukwatta et al. The chosen GRBs are also a subset of the Dainotti et al. sample, a set of Swift GRBs of known redshift, employed in establishing a relation between the (GRB frame) luminosity, LX , of the shallow (or constant) flux portion of the typical X-Ray Telescope GRB-afterglow light curve and the (GRB frame) time of transition to the normal decay rate, T brk. We also present the LX -T brk relation using only the bursts common in the two samples. The two relations exhibit a significant degree of correlation (ρ = -0.65 for the L iso-τ and ρ = -0.88 for the LX -T brk relation) and have surprisingly similar best-fit power-law indices (-1.19 ± 0.17 for L iso-τ and -1.10 ± 0.03 for LX -T brk). Even more surprisingly, we noted that although τ and T brk represent different GRB time variables, it appears that the first relation (L iso-τ) extrapolates into the second one for timescales τ ~= T brk. This fact suggests that these two relations have a common origin, which we conjecture to be kinematic. This relation adds to the recently discovered relations between properties of the prompt and afterglow GRB phases, indicating a much more intimate relation between these two phases than hitherto considered.

  3. GRB 120711A: an intense INTEGRAL burst with long-lasting soft γ-ray emission and a powerful optical flash

    NASA Astrophysics Data System (ADS)

    Martin-Carrillo, A.; Hanlon, L.; Topinka, M.; LaCluyzé, A. P.; Savchenko, V.; Kann, D. A.; Trotter, A. S.; Covino, S.; Krühler, T.; Greiner, J.; McGlynn, S.; Murphy, D.; Tisdall, P.; Meehan, S.; Wade, C.; McBreen, B.; Reichart, D. E.; Fugazza, D.; Haislip, J. B.; Rossi, A.; Schady, P.; Elliott, J.; Klose, S.

    2014-07-01

    A long and intense γ-ray burst (GRB) was detected by INTEGRAL on 11 July 2012 with a duration of ~115 s and fluence of 2.8 × 10-4 erg cm-2 in the 20 keV-8 MeV energy range. GRB 120711A was at z ~ 1.405 and produced soft γ-ray emission (>20 keV) for at least ~10 ks after the trigger. The GRB was observed by several ground-based telescopes that detected a powerful optical flash peaking at an R-band brightness of ~11.5 mag at ~126 s after the trigger, or ~9th magnitude when corrected for the host galaxy extinction (AV ~ 0.85). The X-ray afterglow was monitored by the Swift, XMM-Newton, and Chandra observatories from 8 ks to 7 Ms and provides evidence for a jet break at ~0.9 Ms. We present a comprehensive temporal and spectral analysis of the long-lasting soft γ-ray emission detected in the 20-200 keV band with INTEGRAL/IBIS, the Fermi/LAT post-GRB detection above 100 MeV, the soft X-ray afterglow and the optical/near-infrared detections from Watcher, Skynet/PROMPT, GROND, and REM. The prompt emission had a very hard spectrum (Epeak ~ 1 MeV) and yields an Eγ,iso ~ 1054 erg (1 keV-10 MeV rest frame), making GRB 120711A one of the most energetic GRBs detected so far. We modelled the long-lasting soft γ-ray emission using the standard afterglow scenario, which indicates a forward shock origin. The combination of data extending from the near-infrared to GeV energies suggest that the emission is produced by a broken power-law spectrum consistent with synchrotron radiation. The afterglow is well modelled using a stratified wind-like environment with a density profile k ~ 1.2, suggesting a massive star progenitor (i.e. Wolf-Rayet) with a mass-loss rate between ~10-5-10-6 M⊙ yr-1 depending on the value of the radiative efficiency (ηγ = 0.2 or 0.5). The analysis of the reverse and forward shock emission reveals an initial Lorentz factor of ~120-340, a jet half-opening angle of ~2°-5°, and a baryon load of ~10-5 - 10-6 M⊙ consistent with the expectations of the

  4. BROADBAND STUDY OF GRB 091127: A SUB-ENERGETIC BURST AT HIGHER REDSHIFT?

    SciTech Connect

    Troja, E.; Sakamoto, T.; Brown, J. C.; Gehrels, N.; Marshall, F. E.; Racusin, J. L.; Guidorzi, C.; Norris, J. P.; Panaitescu, A.; Kobayashi, S.; Mawson, N.; Melandri, A.; Mundell, C. G.; Steele, I. A.; Omodei, N.; Burrows, D. N.; Evans, P. A.; Oates, S. R.; Pal'shin, V.; Preece, R. D.; and others

    2012-12-10

    GRB 091127 is a bright gamma-ray burst (GRB) detected by Swift at a redshift z = 0.49 and associated with SN 2009nz. We present the broadband analysis of the GRB prompt and afterglow emission and study its high-energy properties in the context of the GRB/SN association. While the high luminosity of the prompt emission and standard afterglow behavior are typical of cosmological long GRBs, its low-energy release (E{sub {gamma}} < 3 Multiplication-Sign 10{sup 49} erg), soft spectrum, and unusual spectral lag connect this GRB to the class of sub-energetic bursts. We discuss the suppression of high-energy emission in this burst, and investigate whether this behavior could be connected with the sub-energetic nature of the explosion.

  5. Ten per cent polarized optical emission from GRB090102

    NASA Astrophysics Data System (ADS)

    Steele, I. A.; Mundell, C. G.; Smith, R. J.; Kobayashi, S.; Guidorzi, C.

    2009-12-01

    The nature of the jets and the role of magnetic fields in gamma-ray bursts (GRBs) remains unclear. In a baryon-dominated jet only weak, tangled fields generated in situ through shocks would be present. In an alternative model, jets are threaded with large-scale magnetic fields that originate at the central engine and that accelerate and collimate the material. To distinguish between the models the degree of polarization in early-time emission must be measured; however, previous claims of gamma-ray polarization have been controversial. Here we report that the early optical emission from GRB090102 was polarized at 10+/-1 per cent, indicating the presence of large-scale fields originating in the expanding fireball. If the degree of polarization and its position angle were variable on timescales shorter than our 60-second exposure, then the peak polarization may have been larger than ten per cent.

  6. Fermi-LAT Observations of the Gamma-Ray Burst GRB 130427A

    NASA Technical Reports Server (NTRS)

    Ackermann, M.; Ajello, M.; Asano, K.; Atwood, W. B.; Axelsson, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Baring, M. G.; Bastieri, D.; Gehrels, Cornelis

    2013-01-01

    The observations of the exceptionally bright gamma-ray burst (GRB) 130427A by the Large Area Telescope aboard the Fermi Gamma-ray Space Telescope provide constraints on the nature of these unique astrophysical sources. GRB 130427A had the largest fluence, highest-energy photon (95 GeV), longest gamma-ray duration (20 hours), and one of the largest isotropic energy releases ever observed from a GRB. Temporal and spectral analyses of GRB 130427A challenge the widely accepted model that the nonthermal high-energy emission in the afterglow phase of GRBs is synchrotron emission radiated by electrons accelerated at an external shock.

  7. Fermi-LAT Observations of the Gamma-Ray Burst GRB 130427A

    NASA Astrophysics Data System (ADS)

    Ackermann, M.; Ajello, M.; Asano, K.; Atwood, W. B.; Axelsson, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Baring, M. G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Bissaldi, E.; Bonamente, E.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Burgess, J. Michael; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Cecchi, C.; Chaplin, V.; Charles, E.; Chekhtman, A.; Cheung, C. C.; Chiang, J.; Chiaro, G.; Ciprini, S.; Claus, R.; Cleveland, W.; Cohen-Tanugi, J.; Collazzi, A.; Cominsky, L. R.; Connaughton, V.; Conrad, J.; Cutini, S.; D'Ammando, F.; de Angelis, A.; DeKlotz, M.; de Palma, F.; Dermer, C. D.; Desiante, R.; Diekmann, A.; Di Venere, L.; Drell, P. S.; Drlica-Wagner, A.; Favuzzi, C.; Fegan, S. J.; Ferrara, E. C.; Finke, J.; Fitzpatrick, G.; Focke, W. B.; Franckowiak, A.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gehrels, N.; Germani, S.; Gibby, M.; Giglietto, N.; Giles, M.; Giordano, F.; Giroletti, M.; Godfrey, G.; Granot, J.; Grenier, I. A.; Grove, J. E.; Gruber, D.; Guiriec, S.; Hadasch, D.; Hanabata, Y.; Harding, A. K.; Hayashida, M.; Hays, E.; Horan, D.; Hughes, R. E.; Inoue, Y.; Jogler, T.; Jóhannesson, G.; Johnson, W. N.; Kawano, T.; Knödlseder, J.; Kocevski, D.; Kuss, M.; Lande, J.; Larsson, S.; Latronico, L.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Mayer, M.; Mazziotta, M. N.; McEnery, J. E.; Michelson, P. F.; Mizuno, T.; Moiseev, A. A.; Monzani, M. E.; Moretti, E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nemmen, R.; Nuss, E.; Ohno, M.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orienti, M.; Paneque, D.; Pelassa, V.; Perkins, J. S.; Pesce-Rollins, M.; Petrosian, V.; Piron, F.; Pivato, G.; Porter, T. A.; Racusin, J. L.; Rainò, S.; Rando, R.; Razzano, M.; Razzaque, S.; Reimer, A.; Reimer, O.; Ritz, S.; Roth, M.; Ryde, F.; Sartori, A.; Parkinson, P. M. Saz; Scargle, J. D.; Schulz, A.; Sgrò, C.; Siskind, E. J.; Sonbas, E.; Spandre, G.; Spinelli, P.; Tajima, H.; Takahashi, H.; Thayer, J. G.; Thayer, J. B.; Thompson, D. J.; Tibaldo, L.; Tinivella, M.; Torres, D. F.; Tosti, G.; Troja, E.; Usher, T. L.; Vandenbroucke, J.; Vasileiou, V.; Vianello, G.; Vitale, V.; Winer, B. L.; Wood, K. S.; Yamazaki, R.; Younes, G.; Yu, H.-F.; Zhu, S. J.; Bhat, P. N.; Briggs, M. S.; Byrne, D.; Foley, S.; Goldstein, A.; Jenke, P.; Kippen, R. M.; Kouveliotou, C.; McBreen, S.; Meegan, C.; Paciesas, W. S.; Preece, R.; Rau, A.; Tierney, D.; van der Horst, A. J.; von Kienlin, A.; Wilson-Hodge, C.; Xiong, S.; Cusumano, G.; La Parola, V.; Cummings, J. R.

    2014-01-01

    The observations of the exceptionally bright gamma-ray burst (GRB) 130427A by the Large Area Telescope aboard the Fermi Gamma-ray Space Telescope provide constraints on the nature of these unique astrophysical sources. GRB 130427A had the largest fluence, highest-energy photon (95 GeV), longest γ-ray duration (20 hours), and one of the largest isotropic energy releases ever observed from a GRB. Temporal and spectral analyses of GRB 130427A challenge the widely accepted model that the nonthermal high-energy emission in the afterglow phase of GRBs is synchrotron emission radiated by electrons accelerated at an external shock.

  8. The 80 Ms follow-up of the X-ray afterglow of GRB 130427A challenges the standard forward shock model

    NASA Astrophysics Data System (ADS)

    De Pasquale, M.; Page, M. J.; Kann, D. A.; Oates, S. R.; Schulze, S.; Zhang, B.; Cano, Z.; Gendre, B.; Malesani, D.; Rossi, A.; Troja, E.; Piro, L.; Boër, M.; Stratta, G.; Gehrels, N.

    2016-10-01

    GRB 130427A was the brightest gamma-ray burst detected in the last 30 yr. With an equivalent isotropic energy output of 8.5 × 1053 erg and redshift z = 0.34, it uniquely combined very high energetics with a relative proximity to Earth. As a consequence, its X-ray afterglow has been detected by sensitive X-ray observatories such as XMM-Newton and Chandra for a record-breaking baseline longer than 80 million seconds. We present the X-ray light curve of this event over such an interval. The light curve shows a simple power-law decay with a slope α = 1.309 ± 0.007 over more than three decades in time (47 ks-83 Ms). We discuss the consequences of this result for a few models proposed so far to interpret GRB 130427A, and more in general the significance of this outcome in the context of the standard forward shock model. We find that this model has difficulty in explaining our data, in both cases of constant density and stellar-wind circumburst media, and requires far-fetched values for the physical parameters involved.

  9. IN SEARCH OF PROGENITORS FOR SUPERNOVALESS GAMMA-RAY BURSTS 060505 AND 060614: RE-EXAMINATION OF THEIR AFTERGLOWS

    SciTech Connect

    Xu, D.; Fynbo, J. P. U.; Sollerman, J.; Watson, D.; Hjorth, J.; Starling, R. L. C.; O'Brien, P. T.; Yost, S.; Foley, S.

    2009-05-01

    GRB 060505 and GRB 060614 are nearby long-duration gamma-ray bursts (LGRBs) without accompanying supernovae (SNe) down to very strict limits. They thereby challenge the conventional LGRB-SN connection and naturally give rise to the question: are there other peculiar features in their afterglows which would help shed light on their progenitors? To answer this question, we combine new observational data with published data and investigate the multiband temporal and spectral properties of the two afterglows. We find that both afterglows can be well interpreted within the framework of the jetted standard external shock wave model, and that the afterglow parameters for both bursts fall well within the range observed for other LGRBs. Hence, from the properties of the afterglows there is nothing to suggest that these bursts should have another progenitor than other LGRBs. Recently, Swift-discovered GRB 080503 also has the spike + tail structure during its prompt {gamma}-ray emission seemingly similar to GRB 060614. We analyze the prompt emission of this burst and find that this GRB is actually a hard-spike + hard-tail burst with a spectral lag of 0.8 {+-} 0.4 s during its tail emission. Thus, the properties of the prompt emission of GRB 060614 and GRB 080503 are clearly different, motivating further thinking of GRB classification (and even identification of faint core-collapse SNe). Finally, we note that, whereas the progenitor of the two SN-less bursts remains uncertain, the core-collapse origin for the SN-less bursts would be quite certain if a windlike environment can be observationally established, e.g., from an optical decay faster than the X-ray decay in the afterglow's slow cooling phase.

  10. GABI: a compact detector for GRB prompt emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Natalucci, L.; Ubertini, P.; Bazzano, A.; Federici, M.; Fiocchi, M. T.; Lotti, S.; Grindlay, J. E.; Gehrels, N.; Uslenghi, M.; Fiorini, M.; Perotti, F.

    Triggering on sky transient events can be efficiently accomplished by coded mask instruments, which can also provide positions with arcmin or sub-arcmin accuracy, but at the expense of weight and power. On the other hand good broadband spectroscopy is possible using much lighter systems, that could also provide a coarse positioning capability (˜ degrees). We present the concept of a compact, light detector based on NaI(Tl) scintillator, that can be used to complement other soft X-ray or IR/optical telescopes in detecting transients and characterizing them. The Gamma-Ray Burst Imager (GABI) will operate in the energy range 8-1000 keV that is optimal for the detection of the prompt emission of Gamma-Ray Bursts (GRB). GABI is being proposed for accomodation on board Lobster, a candidate mission of the NASA Explorer Program.

  11. LUMINOSITY CORRELATIONS FOR GAMMA-RAY BURSTS AND IMPLICATIONS FOR THEIR PROMPT AND AFTERGLOW EMISSION MECHANISMS

    SciTech Connect

    Sultana, J.; Kazanas, D.; Fukumura, K.

    2012-10-10

    We present the relation between the (z- and k-corrected) spectral lags, {tau}, for the standard Swift energy bands 50-100 keV and 100-200 keV and the peak isotropic luminosity, L{sub iso} (a relation reported first by Norris et al.), for a subset of 12 long Swift gamma-ray bursts (GRBs) taken from a recent study of this relation by Ukwatta et al. The chosen GRBs are also a subset of the Dainotti et al. sample, a set of Swift GRBs of known redshift, employed in establishing a relation between the (GRB frame) luminosity, L{sub X} , of the shallow (or constant) flux portion of the typical X-Ray Telescope GRB-afterglow light curve and the (GRB frame) time of transition to the normal decay rate, T{sub brk}. We also present the L{sub X} -T{sub brk} relation using only the bursts common in the two samples. The two relations exhibit a significant degree of correlation ({rho} = -0.65 for the L{sub iso}-{tau} and {rho} = -0.88 for the L{sub X} -T{sub brk} relation) and have surprisingly similar best-fit power-law indices (-1.19 {+-} 0.17 for L{sub iso}-{tau} and -1.10 {+-} 0.03 for L{sub X} -T{sub brk}). Even more surprisingly, we noted that although {tau} and T{sub brk} represent different GRB time variables, it appears that the first relation (L{sub iso}-{tau}) extrapolates into the second one for timescales {tau} {approx_equal} T{sub brk}. This fact suggests that these two relations have a common origin, which we conjecture to be kinematic. This relation adds to the recently discovered relations between properties of the prompt and afterglow GRB phases, indicating a much more intimate relation between these two phases than hitherto considered.

  12. GRB 130427A: A Nearby Ordinary Monster

    NASA Technical Reports Server (NTRS)

    Maselli, A.; Melandri, A.; Nava, L.; Mundell, C. G.; Kawai, N.; Campana, S.; Covino, S.; Cummings, J. R.; Cusumano, G.; Evans, P. A.; Ghirlander, G.; Ghisellini, G.; Guidorzi, C.; Kobayashi, S.; Kuin, P.; La Parola, V.; Mangano, V.; Oates, S.; Barthelmy, S.; Gehrels, N.; Marshall, F.; Wiegand, B.

    2014-01-01

    Long-duration gamma-ray bursts (GRBs) are an extremely rare outcome of the collapse of massive stars and are typically found in the distant universe. Because of its intrinsic luminosity (L approx. 3 x 10(exp 53) ergs/s and its relative proximity (z = 0.34), GRB 130427A reached the highest fluence observed in the gamma-ray band. Here, we present a comprehensive multiwavelength view of GRB 130427A with Swift, the 2-meter Liverpool and Faulkes telescopes, and by other ground-based facilities, highlighting the evolution of the burst emission from the prompt to the afterglow phase. The properties of GRB 130427A are similar to those of the most luminous, high-redshift GRBs, suggesting that a common central engine is responsible for producing GRBs in both the contemporary and the early universe and over the full range of GRB isotropic energies.

  13. GRB 130427A: A Nearby Ordinary Monster

    NASA Astrophysics Data System (ADS)

    Maselli, A.; Melandri, A.; Nava, L.; Mundell, C. G.; Kawai, N.; Campana, S.; Covino, S.; Cummings, J. R.; Cusumano, G.; Evans, P. A.; Ghirlanda, G.; Ghisellini, G.; Guidorzi, C.; Kobayashi, S.; Kuin, P.; La Parola, V.; Mangano, V.; Oates, S.; Sakamoto, T.; Serino, M.; Virgili, F.; Zhang, B.-B.; Barthelmy, S.; Beardmore, A.; Bernardini, M. G.; Bersier, D.; Burrows, D.; Calderone, G.; Capalbi, M.; Chiang, J.; D'Avanzo, P.; D'Elia, V.; De Pasquale, M.; Fugazza, D.; Gehrels, N.; Gomboc, A.; Harrison, R.; Hanayama, H.; Japelj, J.; Kennea, J.; Kopac, D.; Kouveliotou, C.; Kuroda, D.; Levan, A.; Malesani, D.; Marshall, F.; Nousek, J.; O'Brien, P.; Osborne, J. P.; Pagani, C.; Page, K. L.; Page, M.; Perri, M.; Pritchard, T.; Romano, P.; Saito, Y.; Sbarufatti, B.; Salvaterra, R.; Steele, I.; Tanvir, N.; Vianello, G.; Weigand, B.; Wiersema, K.; Yatsu, Y.; Yoshii, T.; Tagliaferri, G.

    2014-01-01

    Long-duration gamma-ray bursts (GRBs) are an extremely rare outcome of the collapse of massive stars and are typically found in the distant universe. Because of its intrinsic luminosity (L ˜ 3 × 1053 ergs per second) and its relative proximity (z = 0.34), GRB 130427A reached the highest fluence observed in the γ-ray band. Here, we present a comprehensive multiwavelength view of GRB 130427A with Swift, the 2-meter Liverpool and Faulkes telescopes, and by other ground-based facilities, highlighting the evolution of the burst emission from the prompt to the afterglow phase. The properties of GRB 130427A are similar to those of the most luminous, high-redshift GRBs, suggesting that a common central engine is responsible for producing GRBs in both the contemporary and the early universe and over the full range of GRB isotropic energies.

  14. Revisiting the dispersion measure of fast radio bursts associated with gamma-ray burst afterglows

    SciTech Connect

    Yu, Yun-Wei

    2014-12-01

    Some fast radio bursts (FRBs) are expected to be associated with the afterglow emission of gamma-ray bursts (GRBs), while a short-lived, supermassive neutron star (NS) forms during the GRBs. I investigate the possible contributions to the dispersion measure (DM) of the FRBs from the GRB ejecta and the wind blown from the precollapsing NS. On the one hand, sometimes an internal X-ray plateau afterglow could be produced by the NS wind, which indicates that a great number of electron-positron pairs are carried by the wind. If the pair-generation radius satisfies a somewhat rigorous condition, the relativistic and dense wind would contribute a high DM to the associated FRB, which can be comparable to and even exceed the DM contributed by the intergalactic medium. On the other hand, if the wind only carries a Goldreich-Julian particle flux, its DM contribution would become negligible; meanwhile, the internal plateau afterglow would not appear. Alternatively, the FRB should be associated with a GRB afterglow produced by the GRB external shock, i.e., an energy-injection-caused shallow-decay afterglow or a normal single-power-law afterglow if the impulsive energy release of the GRB is high enough. In the latter case, the DM contributed by the high-mass GRB ejecta could be substantially important, in particular, for an environment of main-sequence stellar wind. In summary, a careful assessment on the various DM contributors could be required for the cosmological application of the expected FRB-GRB association. The future DM measurements of GRB-associated FRBs could provide a constraint on the physics of NS winds.

  15. Bright x-ray flares in gamma-ray burst afterglows.

    PubMed

    Burrows, D N; Romano, P; Falcone, A; Kobayashi, S; Zhang, B; Moretti, A; O'brien, P T; Goad, M R; Campana, S; Page, K L; Angelini, L; Barthelmy, S; Beardmore, A P; Capalbi, M; Chincarini, G; Cummings, J; Cusumano, G; Fox, D; Giommi, P; Hill, J E; Kennea, J A; Krimm, H; Mangano, V; Marshall, F; Mészáros, P; Morris, D C; Nousek, J A; Osborne, J P; Pagani, C; Perri, M; Tagliaferri, G; Wells, A A; Woosley, S; Gehrels, N

    2005-09-16

    Gamma-ray burst (GRB) afterglows have provided important clues to the nature of these massive explosive events, providing direct information on the nearby environment and indirect information on the central engine that powers the burst. We report the discovery of two bright x-ray flares in GRB afterglows, including a giant flare comparable in total energy to the burst itself, each peaking minutes after the burst. These strong, rapid x-ray flares imply that the central engines of the bursts have long periods of activity, with strong internal shocks continuing for hundreds of seconds after the gamma-ray emission has ended.

  16. Evidence of Bulk Acceleration of the GRB X-Ray Flare Emission Region

    NASA Astrophysics Data System (ADS)

    Uhm, Z. Lucas; Zhang, Bing

    2016-06-01

    Applying our recently developed generalized version of the high-latitude emission theory to the observations of X-ray flares in gamma-ray bursts (GRBs), here we present clear observational evidence that the X-ray flare emission region is undergoing rapid bulk acceleration as the photons are emitted. We show that both the observed X-ray flare light curves and the photon index evolution curves can be simultaneously reproduced within a simple physical model invoking synchrotron radiation in an accelerating emission region far from the GRB central engine. Such an acceleration process demands an additional energy dissipation source other than kinetic energy, which points toward a significant Poynting flux in the emission region of X-ray flares. As the X-ray flares are believed to share a similar physical mechanism as the GRB prompt emission, our finding here hints that the GRB prompt emission jets may also carry a significant Poynting flux in their emitting region.

  17. VLT/X-Shooter spectroscopy of the afterglow of the Swift GRB 130606A. Chemical abundances and reionisation at z ~ 6

    NASA Astrophysics Data System (ADS)

    Hartoog, O. E.; Malesani, D.; Fynbo, J. P. U.; Goto, T.; Krühler, T.; Vreeswijk, P. M.; De Cia, A.; Xu, D.; Møller, P.; Covino, S.; D'Elia, V.; Flores, H.; Goldoni, P.; Hjorth, J.; Jakobsson, P.; Krogager, J.-K.; Kaper, L.; Ledoux, C.; Levan, A. J.; Milvang-Jensen, B.; Sollerman, J.; Sparre, M.; Tagliaferri, G.; Tanvir, N. R.; de Ugarte Postigo, A.; Vergani, S. D.; Wiersema, K.; Datson, J.; Salinas, R.; Mikkelsen, K.; Aghanim, N.

    2015-08-01

    Context. The reionisation of the Universe is a process that is thought to have ended around z ~ 6, as inferred from spectroscopy of distant bright background sources, such as quasars (QSO) and gamma-ray burst (GRB) afterglows. Furthermore, spectroscopy of a GRB afterglow provides insight in its host galaxy, which is often too dim and distant to study otherwise. Aims: For the Swift GRB 130606A at z = 5.913 we have obtained a high S/N spectrum covering the full optical and near-IR wavelength region at intermediate spectral resolution with VLT/X-Shooter. We aim to measure the degree of ionisation of the intergalactic medium (IGM) between z = 5.02-5.84 and to study the chemical abundance pattern and dust content of its host galaxy. Methods: We estimated the UV continuum of the GRB afterglow using a power-law extrapolation, then measured the flux decrement due to absorption at Lyα,β, and γ wavelength regions. Furthermore, we fitted the shape of the red damping wing of Lyα. The hydrogen and metal absorption lines formed in the host galaxy were fitted with Voigt profiles to obtain column densities. We investigated whether ionisation corrections needed to be applied. Results: Our measurements of the Lyα-forest optical depth are consistent with previous measurements of QSOs, but have a much smaller uncertainty. The analysis of the red damping wing yields a neutral fraction xH i< 0.05 (3σ). We obtain column density measurements of H, Al, Si, and Fe; for C, O, S and Ni we obtain limits. The ionisation due to the GRB is estimated to be negligible (corrections <0.03 dex), but larger corrections may apply due to the pre-existing radiation field (up to 0.4 dex based on sub-DLA studies). Assuming that [ Si/Fe ] = +0.79 ± 0.13 is due to dust depletion, the dust-to-metal ratio is similar to the Galactic value. Conclusions: Our measurements confirm that the Universe is already predominantly ionised over the redshift range probed in this work, but was slightly more neutral at z

  18. Shock-wave-induced enhancement of optical emission in nitrogen afterglow plasma

    SciTech Connect

    Siefert, N.; Ganguly, B.N.; Bletzinger, P.

    2005-12-15

    This paper reports measurements of optical emission enhancement at the shock front of Mach 1.5 to Mach 3.5 shockwaves propagating in the afterglow of a 0.75 Torr nitrogen glow discharge. Electrically-generated shocks pass through the afterglow and create noticeable enhancements of the B {sup 3}{pi}{sub g}-A {sup 3}{sigma}{sub u}{sup +} and C {sup 3}{pi}{sub u}-B {sup 3}{pi}{sub g} transitions of nitrogen. Under our discharge conditions, the electron Debye length was approximately the same magnitude as the shock thickness; this allows the possibility of a space-charge region extending beyond the neutral shockwave discontinuity. Previous researchers have measured enhancement in the B {sup 3}{pi}{sub g}-A {sup 3}{sigma}{sub u}{sup +} optical emission at the shock front, but only in the active discharge. Fibers connected to photomultipler tubes measure the optical emission from the discharge. Laser deflection measures the shock velocity. The data reveals that the emission enhancement increases with Mach number, and also indicates that the emission enhancement decreases exponentially with time in the afterglow. Since the discharge voltage has already been shut off, the energy needed to create the emission enhancement cannot come from the power supply. We conclude that under our discharge conditions there is an increase in the already non-equilibrium energy of the electrons at the shock front via a shockwave-induced strong double layer.

  19. Shock-wave-induced enhancement of optical emission in nitrogen afterglow plasma.

    PubMed

    Siefert, N; Ganguly, B N; Bletzinger, P

    2005-12-01

    This paper reports measurements of optical emission enhancement at the shock front of Mach 1.5 to Mach 3.5 shockwaves propagating in the afterglow of a 0.75 Torr nitrogen glow discharge. Electrically-generated shocks pass through the afterglow and create noticeable enhancements of the B 3Pig-A 3Sigma+u and C 3Piu-B 3Pig transitions of nitrogen. Under our discharge conditions, the electron Debye length was approximately the same magnitude as the shock thickness; this allows the possibility of a space-charge region extending beyond the neutral shockwave discontinuity. Previous researchers have measured enhancement in the B 3Pig-A 3Sigma+u optical emission at the shock front, but only in the active discharge. Fibers connected to photomultipler tubes measure the optical emission from the discharge. Laser deflection measures the shock velocity. The data reveals that the emission enhancement increases with Mach number, and also indicates that the emission enhancement decreases exponentially with time in the afterglow. Since the discharge voltage has already been shut off, the energy needed to create the emission enhancement cannot come from the power supply. We conclude that under our discharge conditions there is an increase in the already non-equilibrium energy of the electrons at the shock front via a shockwave-induced strong double layer.

  20. The ``Christmas burst'' GRB 101225A revisited

    NASA Astrophysics Data System (ADS)

    Thöne, C. C.; de Ugarte Postigo, A.; Fryer, C. L.; Kann, D. A.

    2015-03-01

    Long GRBs are related to the death of massive stars and reveal themselves through synchrotron emission from highly relativistic jets. The `Christmas Burst' GRB 101225A was an exceptionally long GRB with a thermal afterglow, very different from the standard GRB. Initially, no spectroscopic redshift could be obtained and SED modeling yielded z=0.33. A plausible model was a He-NS star merger where the He-star had ejected part of its envelope in the common envelope phase during inspiral. The interaction between the jet and the previously ejected shell can explains the thermal emission. We obtained deep spectroscopy of the host galaxy which leads to a correction of the redshift to z=0.847. Despite the higher redshift, our model is still valid and theoretically better justified than the alternative suggestion of a blue supergiant progenitor proposed by Levan et al. (2014) for several ``ultra-long'' GRBs.

  1. The potential for detecting gamma-ray burst afterglows from population III stars with the next generation of infrared telescopes

    SciTech Connect

    Macpherson, D.; Coward, D. M.; Zadnik, M. G.

    2013-12-10

    We investigate the detectability of a proposed population of gamma-ray bursts (GRBs) from the collapse of Population III (Pop III) stars. The James Webb Space Telescope (JWST) and Space Infrared Telescope for Cosmology and Astrophysics (SPICA) will be able to observe the late time infrared afterglows. We have developed a new method to calculate their detectability, which takes into account the fundamental initial mass function and formation rates of Pop III stars, from which we find the temporal variability of the afterglows and ultimately the length of time JWST and SPICA can detect them. In the range of plausible Pop III GRB parameters, the afterglows are always detectable by these instruments during the isotropic emission, for a minimum of 55 days and a maximum of 3.7 yr. The average number of detectable afterglows will be 2.96× 10{sup –5} per SPICA field of view (FOV) and 2.78× 10{sup –6} per JWST FOV. These are lower limits, using a pessimistic estimate of Pop III star formation. An optimal observing strategy with SPICA could identify a candidate orphan afterglow in ∼1.3 yr, with a 90% probability of confirmation with further detailed observations. A beamed GRB will align with the FOV of the planned GRB detector Energetic X-ray Imaging Survey Telescope once every 9 yr. Pop III GRBs will be more easily detected by their isotropic emissions (i.e., orphan afterglows) rather than by their prompt emissions.

  2. The Potential for Detecting Gamma-Ray Burst Afterglows from Population III Stars with the Next Generation of Infrared Telescopes

    NASA Astrophysics Data System (ADS)

    Macpherson, D.; Coward, D. M.; Zadnik, M. G.

    2013-12-01

    We investigate the detectability of a proposed population of gamma-ray bursts (GRBs) from the collapse of Population III (Pop III) stars. The James Webb Space Telescope (JWST) and Space Infrared Telescope for Cosmology and Astrophysics (SPICA) will be able to observe the late time infrared afterglows. We have developed a new method to calculate their detectability, which takes into account the fundamental initial mass function and formation rates of Pop III stars, from which we find the temporal variability of the afterglows and ultimately the length of time JWST and SPICA can detect them. In the range of plausible Pop III GRB parameters, the afterglows are always detectable by these instruments during the isotropic emission, for a minimum of 55 days and a maximum of 3.7 yr. The average number of detectable afterglows will be 2.96× 10-5 per SPICA field of view (FOV) and 2.78× 10-6 per JWST FOV. These are lower limits, using a pessimistic estimate of Pop III star formation. An optimal observing strategy with SPICA could identify a candidate orphan afterglow in ~1.3 yr, with a 90% probability of confirmation with further detailed observations. A beamed GRB will align with the FOV of the planned GRB detector Energetic X-ray Imaging Survey Telescope once every 9 yr. Pop III GRBs will be more easily detected by their isotropic emissions (i.e., orphan afterglows) rather than by their prompt emissions.

  3. The Early Optical Brightening in the GRB 071010B

    SciTech Connect

    Wang, J H; Schwamb, M E; Huang, K Y; Wen, C Y; Zhang, Z W; Wang, S Y; Chen, W P; Bianco, F B; Dave, R; Lehner, M J; Marshall, S L; Porrata, R; Alcock, C; Byun, Y I; Cook, K H; King, S K; Lee, T; Urata, Y

    2008-04-08

    We report the detection of early (60-230 s) optical emission of the gamma-ray burst afterglow of GRB071010B. No significant correlation with the prompt {gamma}-ray emission was found. Our high time-resolution data combining with other measurements within 2 days after the burst indicate that GRB071010B is composed of a weak early brightening ({alpha} {approx} 0.6), probably caused by the peak frequency passing through the optical wavelengths, followed by a decay ({alpha} {approx} -0.51), attributed to continuous energy injection by patchy jets.

  4. A COMPREHENSIVE STUDY OF GAMMA-RAY BURST OPTICAL EMISSION. II. AFTERGLOW ONSET AND LATE RE-BRIGHTENING COMPONENTS

    SciTech Connect

    Liang Enwei; Li Liang; Liang Yunfeng; Tang Qingwen; Chen Jiemin; Lu Ruijing; Lue Lianzhong; Gao He; Zhang, Bing; Lue Houjun; Wu Xuefeng; Yi Shuangxi; Dai Zigao; Zhang Jin; Wei Jianyan E-mail: zhang@physics.unlv.edu

    2013-09-01

    We continue our systematic statistical study of various components of gamma-ray burst (GRB) optical light curves. We decompose the early onset bump and the late re-brightening bump with empirical fits and analyze their statistical properties. Among the 146 GRBs that have well-sampled optical light curves, the onset and re-brightening bumps are observed in 38 and 26 GRBs, respectively. It is found that the typical rising and decaying slopes for both the onset and re-brightening bumps are {approx}1.5 and {approx} - 1.15, respectively. No early onset bumps in the X-ray band are detected to be associated with the optical onset bumps, while an X-ray re-brightening bump is detected for half of the re-brightening optical bumps. The peak luminosity is anti-correlated with the peak time L{sub p}{proportional_to}t{sub p}{sup -1.81{+-}0.32} for the onset bumps and L{sub p}{proportional_to}t{sub p}{sup -0.83{+-}0.17} for the re-brightening bumps. Both L{sub p} and the isotropic energy release of the onset bumps are correlated with E{sub {gamma},iso}, whereas no similar correlation is found for the re-brightening bumps. These results suggest that the afterglow onset bumps are likely due to the deceleration of the GRB fireballs. Taking the onset bumps as probes for the properties of the fireballs and their ambient medium, we find that the typical power-law index of the relativistic electrons is 2.5 and the medium density profile behaves as n{proportional_to}r {sup -1} within the framework of the synchrotron external shock models. With the medium density profile obtained from our analysis, we also confirm the correlation between the initial Lorentz factor ({Gamma}{sub 0}) and E{sub iso,{gamma}} in our previous work. The jet component that produces the re-brightening bump seems to be on-axis and independent of the prompt emission jet component. Its typical kinetic energy budget would be about one order of magnitude larger than the prompt emission component, but with a lower {Gamma

  5. Direct and bulk-scattered forward-shock emissions: sources of X-ray afterglow diversity

    SciTech Connect

    Panaitescu, A.

    2008-05-22

    I describe the modifications to the standard forward-shock model required to account for the X-ray light-curve features discovered by Swift in the early afterglow emission and propose that a delayed, pair-enriched, and highly relativistic outflow, which bulk-scatters the forward-shock synchrotron emission, yields sometimes a brighter X-ray emission, producing short-lived X-ray flares, X-ray light-curve plateaus ending with chromatic breaks, and fast post-plateau decays.

  6. Optical polarimetric observations of GRB prompt emissions by MASTER robots-telescopes net.

    NASA Astrophysics Data System (ADS)

    Gorbovskoy, Evgeny; Lipunov, Vladimir; Kornilov, Victor; Shatskij, Nikolaj; Kuvshi-Nov, Dmitry; Tyurina, Nataly; Belinski, Alexander; Krylov, Alexander; Balanutsa, Pavel; Chazov, Vadim; Kuznetsov, Artem; Zimnuhov, Dmitry; Balanutsa, Pavel; Kortunov, Petr; Sankovich, Anatoly; Tlatov, An-Drey; Parkhomenko, A.; Krushinsky, Vadim; Zalozhnyh, Ivan; Popov, A.; Kopytova, Taisia; Ivanov, Kirill; Yazev, Sergey; Yurkov, Vladimir

    The main goal of the MASTER-Net project is to produce a unique fast sky survey with all sky observed over a single night down to a limiting magnitude of 19 -20mag. Such a survey will make it possible to address a number of fundamental problems: search for dark energy via the discovery and photometry of supernovas (including SNIa), search for exoplanets, microlensing effects, discovery of minor bodies in the Solar System and space-junk monitoring. All MASTER telescopes can be guided by alerts, and we plan to observe prompt optical emission from gamma-ray bursts synchronously in several filters and in several polarization planes. Observations on telescopes capable to observ polarisation of GRB prompt emission have been begun in the summer of 2009. Since summer of 2009 an observations of several GRB have been made. In particular for GRB0910 and GRB091127 optical polarisation has been measured. So, for GRB091127 which supervision have begun all through 91 sec polarisation at level of several tens percent has been registered. (GCN 10231, GCN 10052, GCN 10203)

  7. Emissive sheath measurements in the afterglow of a radio frequency plasma

    SciTech Connect

    Sheehan, J. P. Hershkowitz, N.; Barnat, E. V.; Weatherford, B. R.; Kaganovich, I. D.

    2014-01-15

    The difference between the plasma potential and the floating potential of a highly emissive planar surface was measured in the afterglow of a radio frequency discharge. A Langmuir probe was used to measure the electron temperature and an emissive probe was used to measure the spatial distribution of the potential using the inflection point in the limit of zero emission technique. Time-resolved measurements were made using the slow-sweep method, a technique for measuring time-resolved current-voltage traces. This was the first time the inflection point in the limit of zero emission was used to make time-resolved measurements. Measurements of the potential profile of the presheath indicate that the potential penetrated approximately 50% farther into the plasma when a surface was emitting electrons. The experiments confirmed a recent kinetic theory of emissive sheaths, demonstrating that late in the afterglow as the plasma electron temperature approached the emitted electron temperature, the emissive sheath potential shrank to zero. However, the difference between the plasma potential and the floating potential of a highly emissive planar surface data appeared to be much less sensitive to the electron temperature ratio than the theory predicts.

  8. Emissive sheath measurements in the afterglow of a radio frequency plasma

    NASA Astrophysics Data System (ADS)

    Sheehan, J. P.; Barnat, E. V.; Weatherford, B. R.; Kaganovich, I. D.; Hershkowitz, N.

    2014-01-01

    The difference between the plasma potential and the floating potential of a highly emissive planar surface was measured in the afterglow of a radio frequency discharge. A Langmuir probe was used to measure the electron temperature and an emissive probe was used to measure the spatial distribution of the potential using the inflection point in the limit of zero emission technique. Time-resolved measurements were made using the slow-sweep method, a technique for measuring time-resolved current-voltage traces. This was the first time the inflection point in the limit of zero emission was used to make time-resolved measurements. Measurements of the potential profile of the presheath indicate that the potential penetrated approximately 50% farther into the plasma when a surface was emitting electrons. The experiments confirmed a recent kinetic theory of emissive sheaths, demonstrating that late in the afterglow as the plasma electron temperature approached the emitted electron temperature, the emissive sheath potential shrank to zero. However, the difference between the plasma potential and the floating potential of a highly emissive planar surface data appeared to be much less sensitive to the electron temperature ratio than the theory predicts.

  9. The LAGO Collaboration: Searching for high energy GRB emissions in Latin America

    NASA Astrophysics Data System (ADS)

    Barros, H.; Lago Collaboration

    2012-02-01

    During more than a decade Gamma Ray Bursts (GRB a cosmological phenomena of tremendous power) have been extensively studied in the keV - MeV energy range. However, the higher energy emission still remains a mystery. The Large Aperture GRB Observatory (L.A.G.O.) is an international collaboration started in 2005 aiming at a better understanding of the GRB by studying their emission at high energies (> 1 GeV), where the fluxes are low and measurements by satellites are difficult. This is done using the Single Particle Technique, by means of ground-based Water Cherenkov Detectors (WCD) at sites of high altitude. At those altitudes it is possible to detect air showers produced by high energy photons from the GRB, i. e. a higher rate of events on a short time scale, of the order of the second. The Pierre Auger Observatory could detect such GRB given its large number of detectors, but at 1400 m.a.s.l. the expected signal is quite small. At higher altitudes, similar performance is expected with only a very small number of WCD. As of 2011, high altitude WCD are in operation at Sierra Negra (Mexico, 4650 m.a.s.l.), Chacaltaya (Bolivia, 5200 m.a.s.l.), Maracapomacocha (Peru, 4200 m.a.s.l.), and new WCDs are being installed in Venezuela (Pico Espejo, 4750 m.a.s.l.), Argentina, Brazil, Chile, Colombia and Guatemala. Most of the new WCDs will not be at high enough altitude to detect GRB, never the less it will allow obtaining valuable measurements of secondaries at ground level, which are relevant for solar physics. The LAGO sensitivity to GRB is determined from simulations (under a sudden increase of 1 GeV - 1 TeV photons from a GRB) of the gamma initiated particle shower in the atmosphere and the WCD response to secondaries. We report on WDC calibration and operation at high altitude, GRB detectability, background rates, search for bursts in several months of preliminary data, as well as search for signals at ground level when satellite burst is reported, all these show the

  10. An Off-Axis Model for GRB 031203

    NASA Technical Reports Server (NTRS)

    Ramirez-Ruiz, Enrico; Granot, Jonathan; Kouveliotou, Chryssa; Woosley, S. E.; Patel, Sandy K.; Mazzali, Paolo A.

    2004-01-01

    The low luminosity radio emission of the unusually faint GRB 031203 has been argued to support the idea of a class of intrinsically sub-energetic gamma-ray bursts (GRBs), currently comprising two members. While low energy GRBs probably exist, we show that the collective prompt and multiwavelength observations of the afterglow of GRB 031203, do not necessarily require a sub-energetic nature for that event. In fact, the data are more consistent with a typical, powerful GRB seen at an angle of about twice the opening angle of the central jet. The (redshift corrected) peak energy, E(sub p), of GRB 031203 then becomes approximately 2 MeV, similar to many other GRBs.

  11. A Unified Model for GRB Prompt Emission from Optical to γ-Rays: Exploring GRBs as Standard Candles

    NASA Astrophysics Data System (ADS)

    Guiriec, S.; Kouveliotou, C.; Hartmann, D. H.; Granot, J.; Asano, K.; Mészáros, P.; Gill, R.; Gehrels, N.; McEnery, J.

    2016-11-01

    The origin of prompt emission from gamma-ray bursts (GRBs) remains to be an open question. Correlated prompt optical and γ-ray emission observed in a handful of GRBs strongly suggests a common emission region, but failure to adequately fit the broadband GRB spectrum prompted the hypothesis of different emission mechanisms for the low- and high-energy radiations. We demonstrate that our multi-component model for GRB γ-ray prompt emission provides an excellent fit to GRB 110205A from optical to γ-ray energies. Our results show that the optical and highest γ-ray emissions have the same spatial and spectral origin, which is different from the bulk of the X- and softest γ-ray radiation. Finally, our accurate redshift estimate for GRB 110205A demonstrates promise for using GRBs as cosmological standard candles.

  12. Observational Signatures of High-Energy Emission during the Shallow Decay Phase of Gamma-Ray Burst X-Ray Afterglows

    NASA Astrophysics Data System (ADS)

    Yu, Y. W.; Liu, X. W.; Dai, Z. G.

    2007-12-01

    The widely existing shallow decay phase of the X-ray afterglows of gamma-ray bursts (GRBs) is generally accepted to be due to long-lasting energy injection. The outflows carrying the injecting energy, based on the component that is dominant in energy, fall into two possible types: baryon-dominated and lepton-dominated ones. The former type of outflow could be ejecta that is ejected during the prompt phase of a GRB and consists of a series of baryonic shells with a distribution of Lorentz factors, and the latter type could be an electron-positron pair wind that is driven by the postburst central engine. We here provide a unified description for the dynamics of fireballs based on these two types of energy injection and calculate the corresponding high-energy photon emission by considering synchrotron radiation and inverse Compton scattering (including synchrotron self-Compton and combined inverse Compton) of electrons. We find that, in the two energy-injection models, there is a plateau (even a hump) in high-energy light curves during the X-ray shallow decay phase. In particular, a considerable fraction of the injecting energy in the lepton-dominated model can be shared by the long-lasting reverse shock since it is relativistic. Furthermore, almost all of the energy of the reverse shock is carried by leptons, and thus, the inverse Compton emission is enhanced dramatically. Therefore, this model predicts more significant high-energy afterglow emission than the baryon-dominated model. We argue that these observational signatures would be used to discriminate between different energy-injection models in the upcoming Gamma-Ray Large Area Space Telescope (GLAST) era.

  13. GRB 090727 AND GAMMA-RAY BURSTS WITH EARLY-TIME OPTICAL EMISSION

    SciTech Connect

    Kopac, D.; Gomboc, A.; Japelj, J.; Kobayashi, S.; Mundell, C. G.; Bersier, D.; Cano, Z.; Smith, R. J.; Steele, I. A.; Virgili, F. J.; Guidorzi, C.; Melandri, A.

    2013-07-20

    We present a multi-wavelength analysis of Swift gamma-ray burst GRB 090727, for which optical emission was detected during the prompt gamma-ray emission by the 2 m autonomous robotic Liverpool Telescope and subsequently monitored for a further two days with the Liverpool and Faulkes Telescopes. Within the context of the standard fireball model, we rule out a reverse shock origin for the early-time optical emission in GRB 090727 and instead conclude that the early-time optical flash likely corresponds to emission from an internal dissipation process. Putting GRB 090727 into a broader observational and theoretical context, we build a sample of 36 gamma-ray bursts (GRBs) with contemporaneous early-time optical and gamma-ray detections. From these GRBs, we extract a sub-sample of 18 GRBs, which show optical peaks during prompt gamma-ray emission, and perform detailed temporal and spectral analysis in gamma-ray, X-ray, and optical bands. We find that in most cases early-time optical emission shows sharp and steep behavior, and notice a rich diversity of spectral properties. Using a simple internal shock dissipation model, we show that the emission during prompt GRB phase can occur at very different frequencies via synchrotron radiation. Based on the results obtained from observations and simulation, we conclude that the standard external shock interpretation for early-time optical emission is disfavored in most cases due to sharp peaks ({Delta}t/t < 1) and steep rise/decay indices, and that internal dissipation can explain the properties of GRBs with optical peaks during gamma-ray emission.

  14. HIGH-ENERGY EMISSION OF GRB 130427A: EVIDENCE FOR INVERSE COMPTON RADIATION

    SciTech Connect

    Fan, Yi-Zhong; Zhang, Fu-Wen; He, Hao-Ning; Zhou, Bei; Yang, Rui-Zhi; Jin, Zhi-Ping; Wei, Da-Ming; Tam, P. H. T.; Liang, Yun-Feng E-mail: fwzhang@pmo.ac.cn

    2013-10-20

    A nearby superluminous burst GRB 130427A was simultaneously detected by six γ-ray space telescopes (Swift, the Fermi GLAST Burst Monitor (GBM)/Large Area Telescope, Konus-Wind, SPI-ACS/INTEGRAL, AGILE, and RHESSI) and by three RAPTOR full-sky persistent monitors. The isotropic γ-ray energy release is ∼10{sup 54} erg, rendering it the most powerful explosion among gamma-ray bursts (GRBs) with a redshift z ≤ 0.5. The emission above 100 MeV lasted about one day, and four photons are at energies greater than 40 GeV. We show that the count rate of 100 MeV-100 GeV emission may be mainly accounted for by the forward shock synchrotron radiation and the inverse Compton radiation likely dominates at GeV-TeV energies. In particular, an inverse Compton radiation origin is favored for the ∼(95.3, 47.3, 41.4, 38.5, 32) GeV photons arriving at t ∼ (243, 256.3, 610.6, 3409.8, 34366.2) s after the trigger of Fermi-GBM. Interestingly, the external inverse Compton scattering of the prompt emission (the second episode, i.e., t ∼ 120-260 s) by the forward-shock-accelerated electrons is expected to produce a few γ-rays at energies above 10 GeV, while five were detected in the same time interval. A possible unified model for the prompt soft γ-ray, optical, and GeV emission of GRB 130427A, GRB 080319B, and GRB 090902B is outlined. Implications of the null detection of >1 TeV neutrinos from GRB 130427A by IceCube are discussed.

  15. Emission and afterglow properties of an expanding RF plasma with nonuniform neutral gas density

    NASA Astrophysics Data System (ADS)

    Chaplin, Vernon H.; Bellan, Paul M.

    2016-08-01

    We describe some notable aspects of the light emission and afterglow properties in pulsed, high-density ( 1018-1020 m-3 ) argon inductively coupled discharges initiated following fast gas injection. The plasma was created in a long, narrow discharge tube and then expanded downstream of the radiofrequency (RF) antenna into a large chamber. Fast camera images of the expanding plasma revealed a multi-phase time-dependent emission pattern that did not follow the ion density distribution. Dramatic differences in visible brightness were observed between discharges with and without an externally applied magnetic field. These phenomena were studied by tracking excited state populations using passive emission spectroscopy and are discussed in terms of the distinction between ionizing and recombining phase plasmas. Additionally, a method is presented for inferring the unknown neutral gas pressure in the discharge tube from the time-dependent visible and infrared emission measured by a simple photodiode placed near the antenna. In magnetized discharges created with fast gas injection, the downstream ion density rose by Δni˜1018 m-3 in the first ˜100 μs after the RF power was turned off. The conditions conducive to this afterglow density rise are investigated in detail, and the effect is tentatively attributed to pooling ionization.

  16. EVIDENCE FOR A PHOTOSPHERIC COMPONENT IN THE PROMPT EMISSION OF THE SHORT GRB 120323A AND ITS EFFECTS ON THE GRB HARDNESS-LUMINOSITY RELATION

    SciTech Connect

    Guiriec, S.; McEnery, J.; Gehrels, N.; Daigne, F.; Hascoeet, R.; Mochkovitch, R.; Vianello, G.; Ryde, F.; Kouveliotou, C.; Foley, S.; McGlynn, S.; Gruber, D.

    2013-06-10

    The short GRB 120323A had the highest flux ever detected with the Gamma-Ray Burst Monitor on board the Fermi Gamma-Ray Space Telescope. Here we study its remarkable spectral properties and their evolution using two spectral models: (1) a single emission component scenario, where the spectrum is modeled by the empirical Band function (a broken power law), and (2) a two-component scenario, where thermal (a Planck-like function) emission is observed simultaneously with a non-thermal component (a Band function). We find that the latter model fits the integrated burst spectrum significantly better than the former, and that their respective spectral parameters are dramatically different: when fit with a Band function only, the E{sub peak} of the event is unusually soft for a short gamma-ray burst (GRB; 70 keV compared to an average of 300 keV), while adding a thermal component leads to more typical short GRB values (E{sub peak} {approx} 300 keV). Our time-resolved spectral analysis produces similar results. We argue here that the two-component model is the preferred interpretation for GRB 120323A based on (1) the values and evolution of the Band function parameters of the two component scenario, which are more typical for a short GRB, and (2) the appearance in the data of a significant hardness-intensity correlation, commonly found in GRBs, when we employee two-component model fits; the correlation is non-existent in the Band-only fits. GRB 110721A, a long burst with an intense photospheric emission, exhibits the exact same behavior. We conclude that GRB 120323A has a strong photospheric emission contribution, observed for the first time in a short GRB. Magnetic dissipation models are difficult to reconcile with these results, which instead favor photospheric thermal emission and fast cooling synchrotron radiation from internal shocks. Finally, we derive a possibly universal hardness-luminosity relation in the source frame using a larger set of GRBs (L{sub i}{sup Band

  17. The AAVSO International GRB Network

    NASA Astrophysics Data System (ADS)

    Price, Aaron

    2003-04-01

    The AAVSO International GRB Network provides services to both amateurs and professionals to help detect GRB afterglows. The network leverages the unique abilities of amateur astronomers to offer global coverage to eliminate geographic and climatic restrictions to GRB alert reaction times. Additionally, public outreach is a critical component of the network and automated online chart making procedures have made it a useful tool for professionals. The financial support of NASA and the Curry Foundation is gratefully appreciated.

  18. GRB Prompt Optical Observations by Master and Lomonosov

    NASA Astrophysics Data System (ADS)

    Gorbovskoy, Evgeny

    We present the results of the prompt, early and afterglow optical observations of five γ-ray bursts (GRBs): GRB 100901A, GRB 100902A, GRB 100905A, GRB 100906A and GRB 101020A. These observations were made with the Mobile Astronomical System of TElescope-Robots in Russia (MASTER-II Net), the 1.5-m telescope of the Sierra Nevada Observatory and the 2.56-m Nordic Optical Telescope. For two sources, GRB 100901A and GRB 100906A, we detected optical counterparts and obtained light curves starting before the cessation of γ-ray emission, at 113 and 48 s after the trigger, respectively. Observations of GRB 100906A were conducted in two polarizing filters. Observations of the other three bursts gave the upper limits on the optical flux; their properties are briefly discussed. A more detailed analysis of GRB 100901A and GRB 100906A, supplemented by Swift data, provides the following results and indicates different origins for the prompt optical radiation in the two bursts. The light-curve patterns and spectral distributions suggest that there is a common production site for the prompt optical and high-energy emission in GRB 100901A. The results of the spectral fits for GRB 100901A in the range from optical to X-ray favour power-law energy distributions and a consistent value of the optical extinction in the host galaxy. GRB 100906A produced a smoothly peaking optical light curve, suggesting that the prompt optical radiation in this GRB originated in a front shock. This is supported by a spectral analysis. We have found that the Amati and Ghirlanda relations are satisfied for GRB 100906A. We obtain an upper limit on the value of the optical extinction on the host of GRB 100906A. Also we consider prompt observation of dark gamma ray bursts for which on very widefield cameras MASTER-VWF and MASTER-II telescopes upper limits were received. We represent SHOCK experiment onboard the spacecraft Lomonosov.

  19. Fermi Observations of High-energy Gamma-ray Emission from GRB 090217A

    NASA Astrophysics Data System (ADS)

    Ackermann, M.; Ajello, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Baring, M. G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Bhat, P. N.; Bissaldi, E.; Blandford, R. D.; Bonamente, E.; Borgland, A. W.; Bouvier, A.; Bregeon, J.; Brez, A.; Briggs, M. S.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Carrigan, S.; Casandjian, J. M.; Cecchi, C.; Çelik, Ö.; Charles, E.; Chekhtman, A.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Connaughton, V.; Conrad, J.; Cutini, S.; Dermer, C. D.; de Angelis, A.; de Palma, F.; Digel, S. W.; Silva, E. do Couto e.; Drell, P. S.; Dubois, R.; Favuzzi, C.; Fegan, S. J.; Ferrara, E. C.; Frailis, M.; Fukazawa, Y.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Germani, S.; Giglietto, N.; Giommi, P.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Granot, J.; Grenier, I. A.; Grove, J. E.; Guillemot, L.; Guiriec, S.; Hadasch, D.; Hays, E.; Horan, D.; Hughes, R. E.; Jóhannesson, G.; Johnson, A. S.; Johnson, W. N.; Kamae, T.; Katagiri, H.; Kippen, R. M.; Knödlseder, J.; Kocevski, D.; Kuss, M.; Lande, J.; Latronico, L.; Lee, S.-H.; Llena Garde, M.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Makeev, A.; Mazziotta, M. N.; McBreen, S.; McEnery, J. E.; McGlynn, S.; Meegan, C.; Mehault, J.; Mészáros, P.; Michelson, P. F.; Mizuno, T.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Moretti, E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nakajima, H.; Nakamori, T.; Naumann-Godo, M.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohno, M.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orlando, E.; Ormes, J. F.; Ozaki, M.; Paciesas, W. S.; Paneque, D.; Panetta, J. H.; Parent, D.; Pelassa, V.; Pepe, M.; Pesce-Rollins, M.; Petrosian, V.; Piron, F.; Porter, T. A.; Preece, R.; Racusin, J. L.; Rainò, S.; Rando, R.; Rau, A.; Razzano, M.; Razzaque, S.; Reimer, A.; Reimer, O.; Ripken, J.; Roth, M.; Ryde, F.; Sadrozinski, H. F.-W.; Sander, A.; Scargle, J. D.; Schalk, T. L.; Sgrò, C.; Siskind, E. J.; Smith, P. D.; Spandre, G.; Spinelli, P.; Stamatikos, M.; Strickman, M. S.; Suson, D. J.; Tajima, H.; Takahashi, H.; Tanaka, T.; Thayer, J. B.; Thayer, J. G.; Tibaldo, L.; Torres, D. F.; Tosti, G.; Tramacere, A.; Uehara, T.; Usher, T. L.; Vandenbroucke, J.; van der Horst, A. J.; Vasileiou, V.; Vilchez, N.; Vitale, V.; von Kienlin, A.; Waite, A. P.; Wang, P.; Wilson-Hodge, C.; Winer, B. L.; Wood, K. S.; Wu, X. F.; Yamazaki, R.; Yang, Z.; Ylinen, T.; Ziegler, M.; Fermi LAT Collaboration; Fermi GBM Collaboration

    2010-07-01

    The Fermi observatory is advancing our knowledge of gamma-ray bursts (GRBs) through pioneering observations at high energies, covering more than seven decades in energy with the two on-board detectors, the Large Area Telescope (LAT) and the Gamma-ray Burst Monitor (GBM). Here, we report on the observation of the long GRB 090217A which triggered the GBM and has been detected by the LAT with a significance greater than 9σ. We present the GBM and LAT observations and on-ground analyses, including the time-resolved spectra and the study of the temporal profile from 8 keV up to ~1 GeV. All spectra are well reproduced by a Band model. We compare these observations to the first two LAT-detected, long bursts GRB 080825C and GRB 080916C. These bursts were found to have time-dependent spectra and exhibited a delayed onset of the high-energy emission, which are not observed in the case of GRB 090217A. We discuss some theoretical implications for the high-energy emission of GRBs.

  20. Gamma-ray Burst Reverse Shock Emission in Early Radio Afterglows

    NASA Astrophysics Data System (ADS)

    Resmi, Lekshmi; Zhang, Bing

    2016-07-01

    Reverse shock (RS) emission from gamma-ray bursts is an important tool in investigating the nature of the ejecta from the central engine. If the magnetization of the ejecta is not high enough to suppress the RS, a strong RS emission component, usually peaking in the optical/IR band early on, would provide an important contribution to early afterglow light curve. In the radio band, synchrotron self-absorption may suppress early RS emission and also delay the RS peak time. In this paper, we calculate the self-absorbed RS emission in the radio band under different dynamical conditions. In particular, we stress that the RS radio emission is subject to self-absorption in both RSs and forward shocks (FSs). We calculate the ratio between the RS to FS flux at the RS peak time for different frequencies, which is a measure of the detectability of the RS emission component. We then constrain the range of physical parameters for a detectable RS, in particular the role of magnetization. We notice that unlike optical RS emission which is enhanced by moderate magnetization, moderately magnetized ejecta do not necessarily produce a brighter radio RS due to the self-absorption effect. For typical parameters, the RS emission component would not be detectable below 1 GHz unless the medium density is very low (e.g., n < 10-3 cm-3 for the interstellar medium and A * < 5 × 10-4 for wind). These predictions can be tested using the afterglow observations from current and upcoming radio facilities such as the Karl G. Jansky Very Large Array, the Low-Frequency Array, the Five Hundred Meter Aperture Spherical Telescope, and the Square Kilometer Array.

  1. The Detectability of Orphan Afterglows

    NASA Astrophysics Data System (ADS)

    Nakar, Ehud; Piran, Tsvi; Granot, Jonathan

    2002-11-01

    The realization that gamma-ray bursts (GRBs) release a constant amount of energy implies that post-jet-break afterglow evolution is largely universal. For a given redshift, all afterglows should be detected up to a fixed observer angle. We estimate the observed magnitude and the implied detectability of orphan afterglows. We show that for reasonable limiting magnitudes (mlim=25), orphan afterglows will typically be detected from small (~10°) angles away from the GRB jet axis. A detected orphan afterglow generally corresponds to a ``near miss'' of a GRB whose jet is pointing just slightly away from us. With our most optimistic parameters, we expect that 15 orphan afterglows will be recorded in the Sloan Digital Sky Survey, and 35 transients will be recorded in a dedicated 2 m class telescope operating full time for a year in an orphan afterglow search. The rate is smaller by a factor of 15 for our ``canonical'' parameters. We show that for a given facility, an optimal survey should be shallower, covering a larger area, rather than deeper. The limiting magnitude should not be, however, lower than ~23, as in this case, more transients from on-axis GRBs will be discovered than orphan afterglows. About 15% of the transients could be discovered with a second exposure of the same area provided that it follows after 3, 4, and 8 days for mlim=23, 25, and 27, respectively.

  2. Neutral beam model for the anomalous γ-ray emission component in GRB 941017

    NASA Astrophysics Data System (ADS)

    Dermer, C. D.; Atoyan, A.

    2004-04-01

    González et al. (\\cite{gon03}) have reported the discovery of an anomalous radiation component from ≈1-200 MeV in GRB 941017. This component varies independently of and contains ⪆3× the energy found in the prompt ˜50 keV-1 MeV radiation component that is well described by the relativistic synchrotron-shock model. Acceleration of hadrons to very high energies can give rise to two additional emission components, one produced inside the GRB blast wave and one associated with an escaping beam of ultra-high energy (UHE; ⪆1014 eV) neutrons, γ rays, and neutrinos. The first component extending to ˜100 MeV is from a pair-photon cascade induced by photomeson processes with the internal synchrotron photons coincident with the prompt radiation. The outflowing UHE neutral beam can undergo further interactions with external photons from the backscattered photon field to produce a beam of hyper-relativistic electrons that lose most of their energy during a fraction of a gyroperiod in the assumed Gauss-strength magnetic fields of the circumburst medium. The synchrotron radiation of these electrons has a spectrum with ν Fν index equal to +1 that can explain the anomalous component in GRB 941017. This interpretation of the spectrum of GRB 941017 requires a high baryon load of the accelerated particles in GRB blast waves. It implies that most of the radiation associated with the anomalous component is released at ⪆500 MeV, suitable for observations with GLAST, and with a comparable energy fluence in ˜100 TeV neutrinos that could be detected with a km-scale neutrino telescope like IceCube.

  3. CONSTRAINTS ON THE EMISSION MODEL OF THE 'NAKED-EYE BURST' GRB 080319B

    SciTech Connect

    Abdo, A. A.; Abeysekara, A. U.; Linnemann, J. T.; Allen, B. T.; Chen, C.; Aune, T.; Berley, D.; Goodman, J. A.; Christopher, G. E.; Kolterman, B. E.; Mincer, A. I.; DeYoung, T.; Dingus, B. L.; Hoffman, C. M.; Ellsworth, R. W.; Gonzalez, M. M.; Granot, J.; Hays, E.; McEnery, J. E.; Huentemeyer, P. H.; and others

    2012-07-10

    On 2008 March 19, one of the brightest gamma-ray bursts (GRBs) ever recorded was detected by several ground- and space-based instruments spanning the electromagnetic spectrum from radio to gamma rays. With a peak visual magnitude of 5.3, GRB 080319B was dubbed the 'naked-eye' GRB, as an observer under dark skies could have seen the burst without the aid of an instrument. Presented here are results from observations of the prompt phase of GRB 080319B taken with the Milagro TeV observatory. The burst was observed at an elevation angle of 47 Degree-Sign . Analysis of the data is performed using both the standard air shower method and the scaler or single-particle technique, which results in a sensitive energy range that extends from {approx}5 GeV to >20 TeV. These observations provide the only direct constraints on the properties of the high-energy gamma-ray emission from GRB 080319B at these energies. No evidence for emission is found in the Milagro data, and upper limits on the gamma-ray flux above 10 GeV are derived. The limits on emission between {approx}25 and 200 GeV are incompatible with the synchrotron self-Compton model of gamma-ray production and disfavor a corresponding range (2 eV-16 eV) of assumed synchrotron peak energies. This indicates that the optical photons and soft ({approx}650 keV) gamma rays may not be produced by the same electron population.

  4. Electromagnetic afterglows associated with gamma-ray emission coincident with binary black hole merger event GW150914

    NASA Astrophysics Data System (ADS)

    Yamazaki, Ryo; Asano, Katsuaki; Ohira, Yutaka

    2016-05-01

    The Fermi Gamma-ray Burst Monitor reported the possible detection of the gamma-ray counterpart of a binary black hole merger event, GW150914. We show that the gamma-ray emission is caused by a relativistic outflow with Lorentz factor larger than 10. Subsequently, debris outflow pushes the ambient gas to form a shock, which is responsible for the afterglow synchrotron emission. We find that the 1.4 GHz radio flux peaks at {˜ }10^5 s after the burst trigger. If the ambient matter is dense enough, with density larger than {˜ }10^{-2} cm^{-3}, then the peak radio flux is {˜ }0.1 mJy, which is detectable with radio telescopes such as the Very Large Array. The optical afterglow peaks earlier than the radio, and if the ambient matter density is larger than {˜ }0.1 cm^{-3}, the optical flux is detectable with large telescopes such as the Subaru Hyper Suprime-Cam. To reveal the currently unknown mechanisms of the outflow and its gamma-ray emission associated with the binary black hole merger event, follow-up electromagnetic observations of afterglows are important. Detection of the afterglow will localize the sky position of the gravitational wave and gamma-ray emissions, and it will support the physical association between them.

  5. Fermi observations of high-energy gamma-ray emission from GRB 080916C.

    PubMed

    Abdo, A A; Ackermann, M; Arimoto, M; Asano, K; Atwood, W B; Axelsson, M; Baldini, L; Ballet, J; Band, D L; Barbiellini, G; Baring, M G; Bastieri, D; Battelino, M; Baughman, B M; Bechtol, K; Bellardi, F; Bellazzini, R; Berenji, B; Bhat, P N; Bissaldi, E; Blandford, R D; Bloom, E D; Bogaert, G; Bogart, J R; Bonamente, E; Bonnell, J; Borgland, A W; Bouvier, A; Bregeon, J; Brez, A; Briggs, M S; Brigida, M; Bruel, P; Burnett, T H; Burrows, D; Busetto, G; Caliandro, G A; Cameron, R A; Caraveo, P A; Casandjian, J M; Ceccanti, M; Cecchi, C; Celotti, A; Charles, E; Chekhtman, A; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Cominsky, L R; Connaughton, V; Conrad, J; Costamante, L; Cutini, S; Deklotz, M; Dermer, C D; de Angelis, A; de Palma, F; Digel, S W; Dingus, B L; do Couto E Silva, E; Drell, P S; Dubois, R; Dumora, D; Edmonds, Y; Evans, P A; Fabiani, D; Farnier, C; Favuzzi, C; Finke, J; Fishman, G; Focke, W B; Frailis, M; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Gehrels, N; Germani, S; Giebels, B; Giglietto, N; Giommi, P; Giordano, F; Glanzman, T; Godfrey, G; Goldstein, A; Granot, J; Greiner, J; Grenier, I A; Grondin, M-H; Grove, J E; Guillemot, L; Guiriec, S; Haller, G; Hanabata, Y; Harding, A K; Hayashida, M; Hays, E; Hernando Morat, J A; Hoover, A; Hughes, R E; Jóhannesson, G; Johnson, A S; Johnson, R P; Johnson, T J; Johnson, W N; Kamae, T; Katagiri, H; Kataoka, J; Kavelaars, A; Kawai, N; Kelly, H; Kennea, J; Kerr, M; Kippen, R M; Knödlseder, J; Kocevski, D; Kocian, M L; Komin, N; Kouveliotou, C; Kuehn, F; Kuss, M; Lande, J; Landriu, D; Larsson, S; Latronico, L; Lavalley, C; Lee, B; Lee, S-H; Lemoine-Goumard, M; Lichti, G G; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Madejski, G M; Makeev, A; Marangelli, B; Mazziotta, M N; McBreen, S; McEnery, J E; McGlynn, S; Meegan, C; Mészáros, P; Meurer, C; Michelson, P F; Minuti, M; Mirizzi, N; Mitthumsiri, W; Mizuno, T; Moiseev, A A; Monte, C; Monzani, M E; Moretti, E; Morselli, A; Moskalenko, I V; Murgia, S; Nakamori, T; Nelson, D; Nolan, P L; Norris, J P; Nuss, E; Ohno, M; Ohsugi, T; Okumura, A; Omodei, N; Orlando, E; Ormes, J F; Ozaki, M; Paciesas, W S; Paneque, D; Panetta, J H; Parent, D; Pelassa, V; Pepe, M; Perri, M; Pesce-Rollins, M; Petrosian, V; Pinchera, M; Piron, F; Porter, T A; Preece, R; Rainò, S; Ramirez-Ruiz, E; Rando, R; Rapposelli, E; Razzano, M; Razzaque, S; Rea, N; Reimer, A; Reimer, O; Reposeur, T; Reyes, L C; Ritz, S; Rochester, L S; Rodriguez, A Y; Roth, M; Ryde, F; Sadrozinski, H F-W; Sanchez, D; Sander, A; Saz Parkinson, P M; Scargle, J D; Schalk, T L; Segal, K N; Sgrò, C; Shimokawabe, T; Siskind, E J; Smith, D A; Smith, P D; Spandre, G; Spinelli, P; Stamatikos, M; Starck, J-L; Stecker, F W; Steinle, H; Stephens, T E; Strickman, M S; Suson, D J; Tagliaferri, G; Tajima, H; Takahashi, H; Takahashi, T; Tanaka, T; Tenze, A; Thayer, J B; Thayer, J G; Thompson, D J; Tibaldo, L; Torres, D F; Tosti, G; Tramacere, A; Turri, M; Tuvi, S; Usher, T L; van der Horst, A J; Vigiani, L; Vilchez, N; Vitale, V; von Kienlin, A; Waite, A P; Williams, D A; Wilson-Hodge, C; Winer, B L; Wood, K S; Wu, X F; Yamazaki, R; Ylinen, T; Ziegler, M

    2009-03-27

    Gamma-ray bursts (GRBs) are highly energetic explosions signaling the death of massive stars in distant galaxies. The Gamma-ray Burst Monitor and Large Area Telescope onboard the Fermi Observatory together record GRBs over a broad energy range spanning about 7 decades of gammaray energy. In September 2008, Fermi observed the exceptionally luminous GRB 080916C, with the largest apparent energy release yet measured. The high-energy gamma rays are observed to start later and persist longer than the lower energy photons. A simple spectral form fits the entire GRB spectrum, providing strong constraints on emission models. The known distance of the burst enables placing lower limits on the bulk Lorentz factor of the outflow and on the quantum gravity mass.

  6. Plastic Damping of Alfvén Waves in Magnetar Flares and Delayed Afterglow Emission

    NASA Astrophysics Data System (ADS)

    Li, Xinyu; Beloborodov, Andrei M.

    2015-12-01

    Magnetar flares generate Alfvén waves bouncing in the closed magnetosphere with energy up to ∼ {10}46 erg. We show that on a timescale of 10 ms the waves are transmitted into the star and form a compressed packet of high energy density. This packet strongly shears the stellar crust and initiates a plastic flow, heating the crust and melting it hundreds of meters below the surface. A fraction of the deposited plastic heat is eventually conducted to the stellar surface, contributing to the surface afterglow months to years after the flare. A large fraction of heat is lost to neutrino emission or conducted into the core of the neutron star.

  7. The status of the AGILE GRB observations and the noticeable case of GRB 080514B

    SciTech Connect

    Del Monte, E.; Costa, E.; Donnarumma, I.; Lapshov, I.; Lazzarotto, F.; Pacciani, L.; Soffitta, P.; Argan, A.; Feroci, M.; Pucella, G.; Trois, A.; Vittorini, V.; Evangelista, Y.; Fornari, F.; Giuliani, A.; Mereghetti, S.; Vercellone, S.; Caraveo, P.; Chen, A.; Pellizzoni, A.

    2009-05-25

    Since Summer 2007, the AGILE mission is successfully detecting and localizing Gamma Ray Bursts by using its wide-field hard X-ray monitor SuperAGILE (17-60 keV) and its CsI Minicalorimeter (0.3-20 MeV). Moreover, all the events with a known localization in the field of view of the Gamma Ray Imaging Detector are searched for in the 30 MeV-50 GeV energy range. Among the several bursts occurred in the field of view of the Gamma Ray Imaging Detector during more than one year of operations, at the time of writing the remarkable GRB 080514B is detected at high significance and GRB 080721 and GRB 081001 are detected at low significance. GRB 080514B is the first Gamma Ray Burst showing a significant emission above 20 MeV after EGRET, and the first ever associated with an afterglow, measured at X-rays and in the IR/Optical/UV. Significant upper limits are derived for the other GRBs. In this paper we report about the status and the scientific performances of the AGILE instrumentation in the study of GRBs and we discuss the properties of GRB 080514B in the context of the long Gamma Ray Bursts.

  8. On the Electron Energy Distribution Index of Swift Gamma-ray Burst Afterglows

    NASA Astrophysics Data System (ADS)

    Curran, P. A.; Evans, P. A.; de Pasquale, M.; Page, M. J.; van der Horst, A. J.

    2010-06-01

    The electron energy distribution index, p, is a fundamental parameter of the synchrotron emission from a range of astronomical sources. Here we examine one such source of synchrotron emission, gamma-ray burst (GRB) afterglows observed by the Swift satellite. Within the framework of the blast wave model, we examine the constraints placed on the distribution of p by the observed X-ray spectral indices and parameterize the distribution. We find that the observed distribution of spectral indices are inconsistent with an underlying distribution of p composed of a single discrete value but consistent with a Gaussian distribution centered at p = 2.36 and having a width of 0.59. Furthermore, accepting that the underlying distribution is a Gaussian, we find that the majority (gsim94%) of GRB afterglows in our sample have cooling break frequencies less than the X-ray frequency.

  9. Probing the Environment of Gravitational-wave Transient Sources with TeV Afterglow Emission

    NASA Astrophysics Data System (ADS)

    Zhu, Qin-Yu; Wang, Xiang-Yu

    2016-09-01

    Recently, the Advanced Laser Interferometer Gravitational-wave Observatory detected gravitational-wave (GW) transients from mergers of binary black holes (BHs). The system may also produce a wide-angle, relativistic outflow if the claimed short gamma-ray burst detected by GBM is in real association with GW150914. It was suggested that mergers of double neutron stars (or neutron star-black hole binaries), another promising source of GW transients, also produce fast, wide-angle outflows. In this paper, we calculate the high-energy gamma-ray emission arising from the blast waves driven by these wide-angle outflows. We find that TeV emission arising from the inverse-Compton process in the relativistic outflow, originating from mergers of binary BHs that are similar to those in GW150914, could be detectable by ground-based Imaging Atmospheric Cherenkov Telescopes such as the Cherenkov Telescope Array (CTA) if the sources occur in a dense medium with a density of n≳ 0.3 {{cm}}-3. For neutron star–neutron star (NS–NS) and NS–BH mergers, TeV emission from the wide-angle, mildly relativistic outflow could be detected as well, if it occurs in a dense medium with n≳ 10{--}100 {{cm}}-3. Thus, TeV afterglow emission could be a useful probe of the environment of the GW transients, which could shed light on the evolution channels of the progenitors of GW transients.

  10. Probing the Environment of Gravitational-wave Transient Sources with TeV Afterglow Emission

    NASA Astrophysics Data System (ADS)

    Zhu, Qin-Yu; Wang, Xiang-Yu

    2016-09-01

    Recently, the Advanced Laser Interferometer Gravitational-wave Observatory detected gravitational-wave (GW) transients from mergers of binary black holes (BHs). The system may also produce a wide-angle, relativistic outflow if the claimed short gamma-ray burst detected by GBM is in real association with GW150914. It was suggested that mergers of double neutron stars (or neutron star-black hole binaries), another promising source of GW transients, also produce fast, wide-angle outflows. In this paper, we calculate the high-energy gamma-ray emission arising from the blast waves driven by these wide-angle outflows. We find that TeV emission arising from the inverse-Compton process in the relativistic outflow, originating from mergers of binary BHs that are similar to those in GW150914, could be detectable by ground-based Imaging Atmospheric Cherenkov Telescopes such as the Cherenkov Telescope Array (CTA) if the sources occur in a dense medium with a density of n≳ 0.3 {{cm}}-3. For neutron star-neutron star (NS-NS) and NS-BH mergers, TeV emission from the wide-angle, mildly relativistic outflow could be detected as well, if it occurs in a dense medium with n≳ 10{--}100 {{cm}}-3. Thus, TeV afterglow emission could be a useful probe of the environment of the GW transients, which could shed light on the evolution channels of the progenitors of GW transients.

  11. Experimental and numerical studies on Xe2* VUV emission in fast electric discharge afterglow

    NASA Astrophysics Data System (ADS)

    Lo, Dennis; Shangguan, Cheng; Kochetov, Igor; Napartovich, Anatoly

    2002-10-01

    Optical and electrical properties of a fast ( 50 ns) high-pressure discharge in pure Xe and Xe-Ne mixtures were studied experimentally and simulated numerically. Afterglow VUV emission was revealed lasting for a few microseconds. Its duration depended on gas pressure and Xe content. Observations of VUV emission intensity across the discharge aperture demonstrated a good uniformity with sizes 4.5x 2 mm2. The length of the discharge was 42 cm. Operation of the discharge was limited in gas pressure by development of instability. The highest pressure for stable discharge run was 0.55 bar for pure Xe and 5 bar for xenon-lean mixture. A detailed kinetic model of discharge plasma was developed, which calculated self-consistently electron energy distribution function and excited states including excimer population dynamics. VUV emission dynamics observed experimentally can be explained theoretically only in a model with an essentially increased number of electronic states taken into account. Calculated discharge voltage history and VUV emission dynamics agree satisfactory with measurements.

  12. A magnetar powering the ordinary monster GRB 130427A?

    NASA Astrophysics Data System (ADS)

    Bernardini, M. G.; Campana, S.; Ghisellini, G.; D'Avanzo, P.; Calderone, G.; Covino, S.; Cusumano, G.; Ghirlanda, G.; La Parola, V.; Maselli, A.; Melandri, A.; Salvaterra, R.; Burlon, D.; D'Elia, V.; Fugazza, D.; Sbarufatti, B.; Vergani, S. D.; Tagliaferri, G.

    2014-03-01

    We present the analysis of the extraordinarily bright gamma-ray burst (GRB) 130427A under the hypothesis that the GRB central engine is an accretion-powered magnetar. In this framework, initially proposed to explain GRBs with precursor activity, the prompt emission is produced by accretion of matter on to a newly born magnetar, and the observed power is related to the accretion rate. The emission is eventually halted if the centrifugal forces are able to pause accretion. We show that the X-ray and optical afterglow is well explained as the forward shock emission with a jet break plus a contribution from the spin-down of the magnetar. Our modelling does not require any contribution from the reverse shock, that may still influence the afterglow light curve at radio and mm frequencies, or in the optical at early times. We derive the magnetic field (B ˜ 1016 G) and the spin period (P ˜ 20 ms) of the magnetar and obtain an independent estimate of the minimum luminosity for accretion. This minimum luminosity results well below the prompt emission luminosity of GRB 130427A, providing a strong consistency check for the scenario where the entire prompt emission is the result of continuous accretion on to the magnetar. This is in agreement with the relatively long spin period of the magnetar. GRB 130427A was a well-monitored GRB showing a very standard behaviour and, thus, is a well-suited benchmark to show that an accretion-powered magnetar gives a unique view of the properties of long GRBs.

  13. Super-LOTIS/LOTIS/LITE: Prompt GRB Followup Experiments

    SciTech Connect

    Park, H S; Ables, E; Barthelmy, S; Bradshaw, M; Cline, T; Gehrels, N; Hartmann, D; Hurley, K; Nemiroff, R; Pereira, W; Perez-Ramirez, D; Williams, G G; Ziock, K

    2001-06-25

    LOTIS (Livermore Optical Transient Imaging System) and Super-LOTIS are automatic telescope systems that measure very prompt optical emission occurring within seconds of the gamma-ray energy release during a Gamma Ray Burst (GRB). Unlike hour-to-days delayed afterglow measurements, very early measurements will contain information about the GRB progenitor. To accomplish this, we developed and have been operating automated telescopes that rapidly image GRB coordinate error boxes in response to triggers distributed by the GRB Coordinate Distribution Network (GCN). LOTIS, located in California, consists of 4 cameras each with a different astronomical filter (B, V, R, open) that can respond to GRB triggers within 5 s. Super-LOTIS can point to any part of the sky within 30 s upon receipt of a GCN trigger and its sensitivity is as deep as V = 17-19 depending on the integration times. Since the shutdown of the CGRO, there has been no real-time GRE3 triggers that enable the LOTIS systems to measure real-time GRE3 counterpart fluxes as of May 2001. This paper describes performance of these systems. We also present our plan to replace the current optical CCD camera on the Super-LOTIS to a near infrared camera to be able to probe dusty GRB environment.

  14. GRB 011121: A Collimated Outflow into Wind-Blown Surroundings

    NASA Technical Reports Server (NTRS)

    Greiner, J.; Klose, S.; Salvato, M.; Zeh, A.; Schwarz, R.; Hartmann, D. H.; Masetti, N.; Stecklum, B.; Lamer, G.; Lodieu, N.; Burud, I.; Rhoads, J.; Fruchter, A.

    2003-01-01

    We report optical and near-infrared follow-up observations of GRB 011121 collected predominantly at ESO telescopes in Chile. We discover a break in the afterglow light curve after 1.3 days, which implies an initial jet opening angle of about 9 deg. The jet origin of this break is supported by the fact that the spectral energy distribution is achromatic during the first four days. During later phases, GRB 011121 shows significant excess emission above the flux predicted by a power law, which we interpret as additional light from an underlying supernova. In particular, the spectral energy distribution of the optical transient approximately 2 weeks after the burst is clearly not of power-law type, but can be presented by a black body with a temperature of approx. 6000 K. The deduced parameters for the decay slope as well as the spectral index favor a wind scenario, i.e. an outflow into a circum-burst environment shaped by the stellar wind of a massive GRB progenitor. Due to its low redshift of z=0.36, GRB 011121 has been the best example for the GRB-supernova connection until GRB 030329, and provides compelling evidence for a circum-burster wind region expected to exist if the progenitor was a massive star.

  15. THE LONG AND THE SHORT OF THE HIGH-ENERGY EMISSION IN GRB090926A: AN EXTERNAL SHOCK

    SciTech Connect

    Sacahui, J. R.; Fraija, N.; Gonzalez, M. M.; Lee, W. H. E-mail: nifraija@astro.unam.mx E-mail: wlee@astro.unam.mx

    2012-08-20

    Synchrotron self-Compton (SSC) emission from a reverse shock has been suggested as the origin for the high-energy component lasting 2 s in the prompt phase of GRB98080923. The model describes spectral indices, fluxes, and the duration of the high-energy component as well as a long keV tail present in the prompt phase of GRB980923. Here, we present an extension of this model to describe the high-energy emission of GRB090926A. We argue that the emission consists of two components, one with a duration less than 1 s during the prompt phase, and a second, longer-lasting GeV phase lasting hundred of seconds after the prompt phase. The short high-energy phase can be described as SSC emission from a reverse shock similar to that observed in GRB980923, while the longer component arises from the forward shock. The main assumption is that the jet is magnetized and evolves in the thick-shell case, and the calculated fluxes and break energies are all consistent with the observed values. A comparison between the resulting parameters obtained for GRB980923 and GRB090926A suggests differences in burst tails that could be attributable to the circumburst medium, and this could account for previous analyses reported in the literature for other bursts. We find that the density of the surrounding medium inferred from the observed values associated with the forward shock agrees with standard values for host galaxies such as the one associated with GRB090926A.

  16. DETECTION OF GAMMA-RAY POLARIZATION IN PROMPT EMISSION OF GRB 100826A

    SciTech Connect

    Yonetoku, Daisuke; Murakami, Toshio; Sakashita, Tomonori; Morihara, Yoshiyuki; Takahashi, Takuya; Fujimoto, Hirofumi; Kodama, Yoshiki; Gunji, Shuichi; Toukairin, Noriyuki; Mihara, Tatehiro; Toma, Kenji; Kubo, Shin

    2011-12-20

    We report the polarization measurement in prompt {gamma}-ray emission of GRB 100826A with the Gamma-Ray Burst Polarimeter on board the small solar-power-sail demonstrator IKAROS. We detected the firm change of polarization angle (PA) during the prompt emission with 99.9% (3.5{sigma}) confidence level, and the average polarization degree ({Pi}) of 27% {+-} 11% with 99.4% (2.9{sigma}) confidence level. Here the quoted errors are given at 1{sigma} confidence level for the two parameters of interest. The systematic errors have been carefully included in this analysis, unlike other previous reports. Such a high {Pi} can be obtained in several emission models of gamma-ray bursts (GRBs), including synchrotron and photospheric models. However, it is difficult to explain the observed significant change of PA within the framework of axisymmetric jet as considered in many theoretical works. The non-axisymmetric (e.g., patchy) structures of the magnetic fields and/or brightness inside the relativistic jet are therefore required within the observable angular scale of {approx}{Gamma}{sup -1}. Our observation strongly indicates that the polarization measurement is a powerful tool to constrain the GRB production mechanism, and more theoretical works are needed to discuss the data in more detail.

  17. The Ultraluminous GRB 110918A

    NASA Astrophysics Data System (ADS)

    Frederiks, D. D.; Hurley, K.; Svinkin, D. S.; Pal'shin, V. D.; Mangano, V.; Oates, S.; Aptekar, R. L.; Golenetskii, S. V.; Mazets, E. P.; Oleynik, Ph. P.; Tsvetkova, A. E.; Ulanov, M. V.; Kokomov, A. A.; Cline, T. L.; Burrows, D. N.; Krimm, H. A.; Pagani, C.; Sbarufatti, B.; Siegel, M. H.; Mitrofanov, I. G.; Golovin, D.; Litvak, M. L.; Sanin, A. B.; Boynton, W.; Fellows, C.; Harshman, K.; Enos, H.; Starr, R.; von Kienlin, A.; Rau, A.; Zhang, X.; Goldstein, J.

    2013-12-01

    GRB 110918A is the brightest long gamma-ray burst (GRB) detected by Konus-WIND during its almost 19 yr of continuous observations and the most luminous GRB ever observed since the beginning of the cosmological era in 1997. We report on the final Interplanetary Network localization of this event and its detailed multiwavelength study with a number of space-based instruments. The prompt emission is characterized by a typical duration, a moderate peak energy of the time-integrated spectrum, and strong hard-to-soft evolution. The high observed energy fluence yields, at z = 0.984, a huge isotropic-equivalent energy release E iso = (2.1 ± 0.1) × 1054 erg. The record-breaking energy flux observed at the peak of the short, bright, hard initial pulse results in an unprecedented isotropic-equivalent luminosity L iso = (4.7 ± 0.2) × 1054 erg s-1. A tail of the soft γ-ray emission was detected with temporal and spectral behavior typical of that predicted by the synchrotron forward-shock model. The Swift/X-Ray Telescope and the Swift/Ultraviolet Optical Telescope observed the bright afterglow from 1.2 to 48 days after the burst and revealed no evidence of a jet break. The post-break scenario for the afterglow is preferred from our analysis, with a hard underlying electron spectrum and interstellar-medium-like circumburst environment implied. We conclude that, among the multiple reasons investigated, the tight collimation of the jet must have been a key ingredient to produce this unusually bright burst. The inferred jet opening angle of 1.°7-3.°4 results in reasonable values of the collimation-corrected radiated energy and the peak luminosity, which, however, are still at the top of their distributions for such tightly collimated events. We estimate a detection horizon for a similar ultraluminous GRB of z ~ 7.5 for Konus-WIND and z ~ 12 for the Swift/Burst Alert Telescope, which stresses the importance of GRBs as probes of the early Universe.

  18. The ultraluminous GRB 110918A

    SciTech Connect

    Frederiks, D. D.; Svinkin, D. S.; Pal'shin, V. D.; Aptekar, R. L.; Golenetskii, S. V.; Mazets, E. P.; Oleynik, Ph. P.; Tsvetkova, A. E.; Ulanov, M. V.; Kokomov, A. A.; Hurley, K.; Mangano, V.; Burrows, D. N.; Sbarufatti, B.; Siegel, M. H.; Oates, S.; Cline, T. L.; Krimm, H. A.; Pagani, C.; Mitrofanov, I. G. [Space Research Institute, Profsoyuznaya 84 and others

    2013-12-20

    GRB 110918A is the brightest long gamma-ray burst (GRB) detected by Konus-WIND during its almost 19 yr of continuous observations and the most luminous GRB ever observed since the beginning of the cosmological era in 1997. We report on the final Interplanetary Network localization of this event and its detailed multiwavelength study with a number of space-based instruments. The prompt emission is characterized by a typical duration, a moderate peak energy of the time-integrated spectrum, and strong hard-to-soft evolution. The high observed energy fluence yields, at z = 0.984, a huge isotropic-equivalent energy release E {sub iso} = (2.1 ± 0.1) × 10{sup 54} erg. The record-breaking energy flux observed at the peak of the short, bright, hard initial pulse results in an unprecedented isotropic-equivalent luminosity L {sub iso} = (4.7 ± 0.2) × 10{sup 54} erg s{sup –1}. A tail of the soft γ-ray emission was detected with temporal and spectral behavior typical of that predicted by the synchrotron forward-shock model. The Swift/X-Ray Telescope and the Swift/Ultraviolet Optical Telescope observed the bright afterglow from 1.2 to 48 days after the burst and revealed no evidence of a jet break. The post-break scenario for the afterglow is preferred from our analysis, with a hard underlying electron spectrum and interstellar-medium-like circumburst environment implied. We conclude that, among the multiple reasons investigated, the tight collimation of the jet must have been a key ingredient to produce this unusually bright burst. The inferred jet opening angle of 1.°7-3.°4 results in reasonable values of the collimation-corrected radiated energy and the peak luminosity, which, however, are still at the top of their distributions for such tightly collimated events. We estimate a detection horizon for a similar ultraluminous GRB of z ∼ 7.5 for Konus-WIND and z ∼ 12 for the Swift/Burst Alert Telescope, which stresses the importance of GRBs as probes of the early

  19. Gamma ray burst outflows and afterglows

    NASA Astrophysics Data System (ADS)

    Morsony, Brian J.

    2008-08-01

    We carry out a theoretical investigation of jet propagation in Gamma Ray Bursts and examine the jitter radiation mechanism as a means of producing prompt and afterglow emission. We study the long-term evolution of relativistic jets in collapsars and examine the effects of viewing angle on the subsequent gamma ray bursts. Our simulations allow us to single out three phases in the jet evolution: a precursor phase in which relativistic material turbulently shed from the head of the jet first emerges from the star; a shocked jet phase where a fully shocked jet of material is emerging; and an unshocked jet phase where the jet consists of a free-streaming, unshocked core surrounded by a thin boundary layer of shocked jet material. We also carry out a series of simulations with central engines that vary on long time periods comparable to the breakout time of the jet, on short time periods (0.1s) much less than the breakout time, and finally that decay as a power law at late times. We conclude that rapid variability seen in prompt GRB emission, as well as shallow decays and flares seen in the X-ray afterglow, can be caused by central engine variability. Finally, we present a detailed computation of the jitter radiation spectrum, including self-absorption, for electrons inside Weibel-like shock- generated magnetic fields. We apply our results to the case of the prompt and afterglow emission of gamma-ray bursts. We conclude that jitter and synchrotron afterglows can be distinguished from each other with good quality observations. However, it is unlikely that the difference can explain the peculiar behavior of several recent observations, such as flat X-ray slopes and uncorrelated optical and X-ray behavior.

  20. A Fe K Line in GRB 970508

    NASA Astrophysics Data System (ADS)

    Protassov, R.; van Dyk, D.; Connors, A.; Kashyap, V.; Siemiginowska, A.

    2000-12-01

    We examine the x-ray spectrum of the afterglow of GRB 970508, analyzed for Fe line emission by Piro et al (1999, ApJL, 514, L73). This is a difficult and extremely important measurement: the detection of x-ray afterglows from γ -ray bursts is at best a tricky business, relying on near-real satellite time response to unpredictable events; and a great deal of luck in catching a burst bright enough for a useful spectral analysis. Detecting a clear atomic (or cyclotron) line in the generally smooth and featureless afterglow (or burst) emission not only gives one of the few very specific keys to the physics local to the emission region, but also provides clues or confirmation of its distance (via redshift). Unfortunately, neither the likelihood ratio test or the related F-statistic commonly used to detect spectral lines adhere to their nominal Chi square and F-distributions. Thus we begin by calibrating the F-statistic used in Piro et al (1999, ApJL, 514, L73) via a simulation study. The simulation study relies on a completely specified source model, i.e. we do Monte Carlo simulations with all model parameters fixed (so--called ``parametric bootstrapping''). Second, we employ the method of posterior predictive p-values to calibrate a LRT statistic while accounting for the uncertainty in the parameters of the source model. Our analysis reveals evidence for the Fe K line.

  1. DETECTION OF A THERMAL SPECTRAL COMPONENT IN THE PROMPT EMISSION OF GRB 100724B

    SciTech Connect

    Guiriec, Sylvain; Connaughton, Valerie; Briggs, Michael S.; Burgess, Michael; Goldstein, Adam; Bhat, P.N.; Chaplin, Vandiver; Ryde, Felix; Daigne, Frederic; Meszaros, Peter; McEnery, Julie; Omodei, Nicola; Bissaldi, Elisabetta; Diehl, Roland; Foley, Suzanne; Greiner, Jochen; Camero-Arranz, Ascension; Fishman, Gerald

    2011-02-01

    Observations of GRB 100724B with the Fermi Gamma-Ray Burst Monitor find that the spectrum is dominated by the typical Band functional form, which is usually taken to represent a non-thermal emission component, but also includes a statistically highly significant thermal spectral contribution. The simultaneous observation of the thermal and non-thermal components allows us to confidently identify the two emission components. The fact that these seem to vary independently favors the idea that the thermal component is of photospheric origin while the dominant non-thermal emission occurs at larger radii. Our results imply either a very high efficiency for the non-thermal process or a very small size of the region at the base of the flow, both quite challenging for the standard fireball model. These problems are resolved if the jet is initially highly magnetized and has a substantial Poynting flux.

  2. Detection of a Thermal Spectral Component in the Prompt Emission of GRB 100724B

    NASA Astrophysics Data System (ADS)

    Guiriec, Sylvain; Connaughton, Valerie; Briggs, Michael S.; Burgess, Michael; Ryde, Felix; Daigne, Frédéric; Mészáros, Peter; Goldstein, Adam; McEnery, Julie; Omodei, Nicola; Bhat, P. N.; Bissaldi, Elisabetta; Camero-Arranz, Ascensión; Chaplin, Vandiver; Diehl, Roland; Fishman, Gerald; Foley, Suzanne; Gibby, Melissa; Giles, Misty M.; Greiner, Jochen; Gruber, David; von Kienlin, Andreas; Kippen, Marc; Kouveliotou, Chryssa; McBreen, Sheila; Meegan, Charles A.; Paciesas, William; Preece, Robert; Rau, Arne; Tierney, Dave; van der Horst, Alexander J.; Wilson-Hodge, Colleen

    2011-02-01

    Observations of GRB 100724B with the Fermi Gamma-Ray Burst Monitor find that the spectrum is dominated by the typical Band functional form, which is usually taken to represent a non-thermal emission component, but also includes a statistically highly significant thermal spectral contribution. The simultaneous observation of the thermal and non-thermal components allows us to confidently identify the two emission components. The fact that these seem to vary independently favors the idea that the thermal component is of photospheric origin while the dominant non-thermal emission occurs at larger radii. Our results imply either a very high efficiency for the non-thermal process or a very small size of the region at the base of the flow, both quite challenging for the standard fireball model. These problems are resolved if the jet is initially highly magnetized and has a substantial Poynting flux.

  3. Physical Processes Shaping Gamma-Ray Burst X-Ray Afterglow Light Curves: Theoretical Implications from the Swift X-Ray Telescope Observations

    NASA Astrophysics Data System (ADS)

    Zhang, Bing; Fan, Y. Z.; Dyks, Jaroslaw; Kobayashi, Shiho; Mészáros, Peter; Burrows, David N.; Nousek, John A.; Gehrels, Neil

    2006-05-01

    With the successful launch of the Swift Gamma-Ray Burst Explorer, a rich trove of early X-ray afterglow data has been collected by its onboard X-Ray Telescope (XRT). Some interesting features are emerging, including a distinct rapidly decaying component preceding the conventional afterglow component in many sources, a shallow decay component before the more ``normal'' decay component observed in a good fraction of GRBs, and X-ray flares in nearly half of the afterglows. In this paper we systematically analyze the possible physical processes that shape the properties of the early X-ray afterglow light curves and use the data to constrain various models. We suggest that the steep decay component is consistent with the tail emission of the prompt gamma-ray bursts and/or the X-ray flares. This provides strong evidence that the prompt emission and afterglow emission are likely two distinct components, supporting the internal origin of the GRB prompt emission. The shallow decay segment observed in a group of GRBs suggests that very likely the forward shock keeps being refreshed for some time. This might be caused by either a long-lived central engine, or a wide distribution of the shell Lorentz factors, or else possibly the deceleration of a Poynting flux-dominated flow. X-ray flares suggest that the GRB central engine is very likely still active after the prompt gamma-ray emission is over, but with a reduced activity at later times. In some cases, the central engine activity even extends to days after the burst triggers. Analyses of early X-ray afterglow data reveal that GRBs are indeed highly relativistic events and that early afterglow data of many bursts, starting from the beginning of the XRT observations, are consistent with the afterglow emission from an ISM environment.

  4. The Very Bright and Nearby GRB130427A: the Extra Hard Spectral Component and Implications for Very High-Energy Gamma-Ray Observations of Gamma-Ray Bursts

    NASA Astrophysics Data System (ADS)

    Tam, Pak-Hin Thomas

    2014-03-01

    The extended high-energy gamma-ray (>100 MeV) emission occurring after the prompt gamma-ray bursts (GRBs) is usually characterized by a single power-law spectrum, which has been explained as the afterglow synchrotron radiation. We report on the Fermi Large Area Telescope (LAT) observations of the >100 MeV emission from the very bright and nearby GRB 130427A, up to 100 GeV. By performing time-resolved spectral fits of GRB 130427A, we found a strong evidence of an extra hard spectral component above a few GeV that exists in the extended high-energy emission of this GRB. This extra spectral component may represent the first clear evidence of the long sought-after afterglow inverse Compton emission. Prospects for observations at the very high-energy gamma-rays, i.e., above 100 GeV, are described.

  5. TWO POPULATIONS OF GAMMA-RAY BURST RADIO AFTERGLOWS

    SciTech Connect

    Hancock, P. J.; Gaensler, B. M.; Murphy, T.

    2013-10-20

    The detection rate of gamma-ray burst (GRB) afterglows is ∼30% at radio wavelengths, much lower than in the X-ray (∼95%) or optical (∼70%) bands. The cause of this low radio detection rate has previously been attributed to limited observing sensitivity. We use visibility stacking to test this idea, and conclude that the low detection rate is instead due to two intrinsically different populations of GRBs: radio-bright and radio-faint. We calculate that no more than 70% of GRB afterglows are truly radio-bright, leaving a significant population of GRBs that lack a radio afterglow. These radio-bright GRBs have higher gamma-ray fluence, isotropic energies, X-ray fluxes, and optical fluxes than the radio-faint GRBs, thus confirming the existence of two physically distinct populations. We suggest that the gamma-ray efficiency of the prompt emission is responsible for the difference between the two populations. We also discuss the implications for future radio and optical surveys.

  6. The Gamma-Ray Burst Afterglow Modeling Project: Foundational Statistics and Absorption & Extinction Models

    NASA Astrophysics Data System (ADS)

    Trotter, Adam Somers

    The Gamma-Ray Burst (GRB) Afterglow Modeling Project (AMP) will model, in a statistically sound and self-consistent way, every GRB afterglow observed since the first detection in 1997, using all available radio, infrared, optical, ultraviolet and X-ray data. The result will be a catalog of fitted empirical model parameters describing the intrinsic afterglow emission, and extinction due to dust and absorption due to gas along the line of sight to the GRB. This ever-growing catalog of fitted model parameters will allow us to infer the astrophysical properties of GRBs and their environments, and to explore their variety and evolution over the history of the universe. First, I present a new, broadly applicable statistical technique, the TRF statistic, for fitting model distributions to data in two dimensions, where the data have intrinsic uncertainties in both dimensions, and extrinsic scatter in both dimensions that is greater than can be accounted for by the intrinsic uncertainties alone. I demonstrate the properties of the TRF statistic, which is invertible but not scalable, and present an algorithm for obtaining an optimum scale for fits to a given data set. I then apply the TRF statistic to observations of interstellar extinction of stars along various Milky Way and Magellanic Cloud lines of sight, and to observations of Lyalpha forest flux deficits in quasars, to construct a comprehensive empirical model for extinction due to interstellar dust in the source frame and in the Milky Way, and absorption due to gas in the source frame and in the intergalactic medium. Combined with theoretical models of synchrotron emission from GRB jets, the resulting parameterization provides a framework for modeling the observed emission from most GRB afterglows. Furthermore, the extinction and absorption models are broadly applicable, in that they may be used to model observations of any extragalactic point source of radiation. Finally, I describe the results of model fitting to

  7. The Correlation of Spectral Lag Evolution with Prompt Optical Emission in GRB 080319B

    NASA Astrophysics Data System (ADS)

    Stamatikos, Michael; Ukwatta, Tilan N.; Sakamoto, Takanori; Dhuga, Kalvir S.; Toma, Kenji; Pe'Er, Asaf; Mészáros, Peter; Band, David L.; Norris, Jay P.; Barthelmy, Scott D.; Gehrels, Neil

    2009-05-01

    We report on observations of correlated behavior between the prompt γ-ray and optical emission from GRB 080319B, which confirm that (i) they occurred within the same astrophysical source region and (ii) their respective radiation mechanisms were dynamically coupled. Our results, based upon a new cross-correlation function (CCF) methodology for determining the time-resolved spectral lag, are summarized as follows. First, the evolution in the arrival offset of prompt γ-ray photon counts between Swift-BAT 15-25 keV and 50-100 keV energy bands (intrinsic γ-ray spectral lag) appears to be anti-correlated with the arrival offset between prompt 15-350 keV γ-rays and the optical emission observed by TORTORA (extrinsic optical/γ-ray spectral lag), thus effectively partitioning the burst into two main episodes at ~T+28+/-2 sec. Second, the rise and decline of prompt optical emission at ~T+10+/-1 sec and ~T+50+/-1 sec, respectively, both coincide with discontinuities in the hard to soft evolution of the photon index for a power law fit to 15-150 keV Swift-BAT data at ~T+8+/-2 sec and ~T+48+/-1 sec. These spectral energy changes also coincide with intervals whose time-resolved spectral lag values are consistent with zero, at ~T+12+/-2 sec and ~T+50+/-2 sec. These results, which are robust across heuristic permutations of Swift-BAT energy channels and varying temporal bin resolution, have also been corroborated via independent analysis of Konus-Wind data. This potential discovery may provide the first observational evidence for an implicit connection between spectral lags and GRB emission mechanisms in the context of canonical fireball phenomenology. Future work includes exploring a subset of bursts with prompt optical emission to probe the unique or ubiquitous nature of this result.

  8. AGILE DETECTION OF DELAYED GAMMA-RAY EMISSION FROM THE SHORT GAMMA-RAY BURST GRB 090510

    SciTech Connect

    Giuliani, A.; Vianello, G.; Mereghetti, S.; Caraveo, P.; Chen, A. W.; Contessi, T.; Barbiellini, G.; Longo, F.; Moretti, E.; Cattaneo, P. W.

    2010-01-10

    Short gamma-ray bursts (GRBs), typically lasting less than 2 s, are a special class of GRBs of great interest. We report the detection by the AGILE satellite of the short GRB 090510 which shows two clearly distinct emission phases: a prompt phase lasting {approx}200 ms and a second phase lasting tens of seconds. The prompt phase is relatively intense in the 0.3-10 MeV range with a spectrum characterized by a large peak/cutoff energy near 3 MeV; in this phase, no significant high-energy gamma-ray emission is detected. At the end of the prompt phase, intense gamma-ray emission above 30 MeV is detected showing a power-law time decay of the flux of the type t {sup -1.3} and a broadband spectrum remarkably different from that of the prompt phase. It extends from sub-MeV to hundreds of MeV energies with a photon index {alpha} {approx_equal} 1.5. GRB 090510 provides the first case of a short GRB with delayed gamma-ray emission. We present the timing and spectral data of GRB 090510 and briefly discuss its remarkable properties within the current models of gamma-ray emission of short GRBs.

  9. From a Better Understanding of GRB Prompt Emission to a New Type of Standard Candles?

    NASA Astrophysics Data System (ADS)

    Guiriec, Sylvain

    2016-07-01

    Recent results revealed the simultaneous existence of multiple components in the prompt emission of gamma-ray bursts (GRBs) leading to a unified spectro-temporal model for the broadband spectrum from the optical regime up to higher gamma rays. Unexpectedly, we discovered a relation intrinsic to one specific component of this model: its luminosity is strongly and tightly correlated to its spectral break energy. This new luminosity-hardness relation has the same index for all GRBs when fitted to a power law. In addition, this relation seems to have the same normalization for all GRBs; therefore, this is a promising and physically motivated tool that may establish GRBs as cosmological standard candles. During this presentation, I will introduce this new relation, which might eventually be used to (i) estimate GRB distances, (ii) to support searches for gravitational waves and cosmic high-energy neutrinos, and (iii) constrain the cosmological parameters. I will give a few examples of GRB redshift estimates using this relation and I will show why this new result cannot solely be explain by instrumental selection effects and/or measurement/analysis biases.

  10. Shallow Decay of Early X-Ray Afterglows from Inhomogeneous Gamma-Ray Burst Jets

    NASA Astrophysics Data System (ADS)

    Toma, Kenji; Ioka, Kunihito; Yamazaki, Ryo; Nakamura, Takashi

    2006-04-01

    Almost all the X-ray afterglows of γ-ray bursts (GRBs) observed by the Swift satellite have a shallow decay phase in their first few thousand seconds. We show that in an inhomogeneous-jet model (multiple-subjet or patchy-shell), the superposition of the afterglows of off-axis subjets (patchy shells) can produce the shallow decay phase. The necessary condition for obtaining the shallow decay phase is that γ-ray-bright subjets (patchy shells) have γ-ray efficiencies higher than previously estimated and that they be surrounded by γ-ray-dim subjets (patchy shells) with low γ-ray efficiency. Our model predicts that events with dim prompt emission will have a conventional afterglow light curve without a shallow decay phase, like GRB 050416A.

  11. GRB neutrino search with MAGIC

    SciTech Connect

    Becker, Julia K.; Rhode, Wolfgang; Gaug, Markus

    2008-05-22

    The Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescope was designed for the detection of photon sources > or approx. 50 GeV. The measurement of highly-inclined air showers renders possible the search for high-energy neutrinos, too. Only neutrinos can traverse the Earth without interaction, and therefore, events close to the horizon can be identified as neutrino-induced rather than photon-induced or hadronic events. In this paper, Swift-XRT-detected GRBs with given spectral information are used in order to calculate the potential neutrino energy spectrum from prompt and afterglow emission for each individual GRB. The event rate in MAGIC is estimated assuming that the GRB happens within the field of view of MAGIC. A sample of 568 long GRBs as detected by BATSE is used to compare the detection rates with 163 Swift-detected bursts. BATSE has properties similar to the Gamma-ray Burst Monitor (GBM) on board of GLAST. Therefore the estimated rates give an estimate for the possibilities of neutrino detection with MAGIC from GLAST-triggered bursts.

  12. Toward an Understanding of GRB Prompt Emission Mechanism. I. The Origin of Spectral Lags

    NASA Astrophysics Data System (ADS)

    Uhm, Z. Lucas; Zhang, Bing

    2016-07-01

    Despite decades of investigations, the physical mechanism that powers the bright prompt γ-ray emission from gamma-ray bursts (GRBs) is still not identified. One important observational clue that still has not been properly interpreted is the existence of time lags of broad light curve pulses in different energy bands, referred to as “spectral lags.” Here, we show that the traditional view invoking the high-latitude emission “curvature effect” of a relativistic jet cannot account for spectral lags. Rather, the observed spectral lags demand the sweep of a spectral peak across the observing energy band in a specific manner. The duration of the broad pulses and inferred typical Lorentz factor of GRBs require that the emission region be in an optically thin emission region far from the GRB central engine. We construct a simple physical model invoking synchrotron radiation from a rapidly expanding outflow. We show that the observed spectral lags appear naturally in our model light curves given that (1) the gamma-ray photon spectrum is curved (as observed), (2) the magnetic field strength in the emitting region decreases with radius as the region expands in space, and (3) the emission region itself undergoes rapid bulk acceleration as the prompt γ-rays are produced. These requirements are consistent with a Poynting-flux-dominated jet abruptly dissipating magnetic energy at a large distance from the engine.

  13. Investigating the Impact of Optical Selection Effects on Observed Rest-frame Prompt GRB Properties

    NASA Astrophysics Data System (ADS)

    Turpin, D.; Heussaff, V.; Dezalay, J.-P.; Atteia, J.-L.; Klotz, A.; Dornic, D.

    2016-11-01

    Measuring gamma-ray burst (GRB) properties in their rest frame is crucial for understanding the physics at work in GRBs. This can only be done for GRBs with known redshifts. Since redshifts are usually measured from the optical spectrum of the afterglow, correlations between prompt and afterglow emissions may introduce biases into the distribution of the rest-frame properties of the prompt emission, especially considering that we measure the redshift of only one-third of Swift GRBs. In this paper, we study the optical flux of GRB afterglows and its connection to various intrinsic properties of GRBs. We also discuss the impact of the optical selection effect on the distribution of rest-frame prompt properties of GRBs. Our analysis is based on a sample of 90 GRBs with good optical follow-up and well-measured prompt emission. Seventy-six of them have a measure of redshift and 14 have no redshift. We compare the rest-frame prompt properties of GRBs with different afterglow optical fluxes in order to check for possible correlations between the promt properties and the optical flux of the afterglow. The optical flux is measured two hours after the trigger, which is a typical time for the measure of the redshift. We find that the optical flux of GRB afterglows in our sample is mainly driven by their optical luminosity and depends only slightly on their redshift. We show that GRBs with low and high afterglow optical fluxes have similar E {}{{pi}}, E {}{{iso}}, and L {}{{iso}}, indicating that the rest-frame distributions computed from GRBs with a redshift are not significantly distorted by optical selection effects. However, we found that the {T}90{rest} distribution is not immune to optical selection effects, which favor the selection of GRBs with longer durations. Finally, we note that GRBs well above the E {}{{pi}}–E {}{{iso}} relation have lower optical fluxes and we show that optical selection effects favor the detection of GRBs with bright optical afterglows

  14. Soft X-ray observation of the prompt emission of GRB 100418A

    NASA Astrophysics Data System (ADS)

    Imatani, Ritsuko; Tomida, Hiroshi; Nakahira, Satoshi; Kimura, Masashi; Sakamoto, Takanori; Arimoto, Makoto; Morooka, Yoshitaka; Yonetoku, Daisuke; Kawai, Nobuyuki; Tsunemi, Hiroshi

    2016-06-01

    We have observed the prompt emission of GRB 100418A from its beginning captured by the MAXI SSC (0.7-7 keV) on board the International Space Station followed by the Swift XRT (0.3-10 keV) observation. The light curve can be fitted by a combination of a power-law component and an exponential component (the decay constant is 31.6 ± 1.6 s). The X-ray spectrum is well expressed by the Band function with Ep ≤ 8.3 keV. This is the brightest gamma-ray burst showing a very low value of Ep. It satisfies the Yonetoku relation (Ep-Lp). It is also consistent with the Amati relation (Ep-Eiso) within a 2.5σ level.

  15. Near-extremal Black Holes as Initial Conditions of Long GRB Supernovae and Probes of Their Gravitational Wave Emission

    NASA Astrophysics Data System (ADS)

    van Putten, Maurice H. P. M.

    2015-09-01

    Long gamma-ray bursts (GRBs) associated with supernovae and short GRBs with extended emission (SGRBEE) from mergers are probably powered by black holes as a common inner engine, as their prompt GRB emission satisfies the same Amati correlation in the Ep,i-Eiso plane. We introduce modified Bardeen equations to identify hyper-accretion driving newly formed black holes in core-collapse supernovae to near-extremal spin as a precursor to prompt GRB emission. Subsequent spin-down is observed in the BATSE catalog of long GRBs. Spin-down provides a natural unification of long durations associated with the lifetime of black hole spin for normal long GRBs and SGRBEEs, given the absence of major fallback matter in mergers. The results point to major emissions unseen in high frequency gravitational waves. A novel matched filtering method is described for LIGO-Virgo and KAGRA broadband probes of nearby core-collapse supernovae at essentially maximal sensitivity.

  16. GRB 060714: No Clear Dividing Line Between Prompt Emission and X-Ray Flares

    SciTech Connect

    Krimm, Hans A.; Granot, J.; Marshal, F.; Perri, M.; Barthelmy, S.D.; Burrows, D.N.; Gehrels, N.; Meszaros, P.; Morris, D.; /Penn State U., Astron. Astrophys.

    2007-02-26

    The long gamma-ray burst GRB 060714 was observed to exhibit a series of five X-ray flares beginning {approx} 70 s after the burst trigger T{sub 0} and continuing until {approx} T{sub 0} + 200 s. The first two flares were detected by the Burst Alert Telescope (BAT) on the Swift satellite, before Swift had slewed to the burst location, while the last three flares were strongly detected by the X-Ray Telescope (XRT) but only weakly detected by the BAT. This burst provides an unusual opportunity to track a complete sequence of flares over a wide energy range. The flares were very similar in their light curve morphology, showing power-law rise and fall components, and in most cases significant sub-structure. The flares also showed strong evolution with time, both spectrally and temporally. The small time scale and large amplitude variability observed are incompatible with an external shock origin for the flares, and support instead late time sporadic activity either of the central source or of localized dissipation events within the outflow. We show that the flares in GRB 060714 cannot be the result of internal shocks in which the contrast in the Lorentz factor of the colliding shells is very small, and that this mechanism faces serious difficulties in most Swift GRBs. The morphological similarity of the flares and the prompt emission and the gradual and continual evolution of the flares with time makes it difficult and arbitrary to draw a dividing line between the prompt emission and the flares.

  17. GRB 141221A: gone is the wind

    NASA Astrophysics Data System (ADS)

    Bardho, O.; Gendre, B.; Rossi, A.; Amati, L.; Haislip, J.; Klotz, A.; Palazzi, E.; Reichart, D.; Trotter, A. S.; Boër, M.

    2016-06-01

    GRB 141221A was observed from infrared to soft gamma-ray bands. Here, we investigate its properties, in light of the standard model. We find that the optical light curve of the afterglow of this burst presents an unusual steep/quick rise. The broad-band spectral energy distribution taken near the maximum of the optical emission presents either a thermal component or a spectral break. In the former case, the properties of the afterglow are then very unusual, but could explain the lack of apparent jet breaks in the Swift light curves. In the latter case, the afterglow properties of this burst are more usual, and we can see in the light curves the passing through of the injection and cooling frequencies within the optical bands, not masked by a reverse shock. This model also excludes the presence of a stellar wind, challenging either the stellar progenitor properties, or the very stellar nature of the progenitor itself. In all cases, this burst may be a part of a Rosetta stone that could help to explain some of the most striking features discovered by Swift during the last 10 years.

  18. Afterglow Population Studies from Swift Follow-Up Observations of Fermi LAT GRBs

    NASA Technical Reports Server (NTRS)

    Racusin, Judith L.; Oates, S. R.; McEnery, J.; Vasileiou, V.; Troja, E.; Gehrels, N.

    2010-01-01

    The small population of Fermi LAT detected GRBs discovered over the last year has been providing interesting and unexpected clues into GRB prompt and afterglow emission mechanisms. Over the last 5 years, it has been Swift that has provided the robust data set of UV/optical and X-ray afterglow observations that opened many windows into other components of GRB emission structure. We explore the new ability to utilize both of these observatories to study the same GRBs over 10 orders of magnitude in energy, although not always concurrently. Almost all LAT GRBs that have been followed-up by Swift within 1-day have been clearly detected and carefully observed. We will present the context of the lower-energy afterglows of this special subset of GRBs that has > 100 MeV emission compared to the hundreds in the Swift database that may or may not have been observed by LAT, and theorize upon the relationship between these properties and the origin of the high energy gamma-ray emission.

  19. GRB 110205A: ANATOMY OF A LONG GAMMA-RAY BURST

    SciTech Connect

    Gendre, B.; Stratta, G.; Atteia, J. L.; Klotz, A.; Boeer, M.; Colas, F.; Vachier, F.; Kugel, F.; Rinner, C.; Laas-Bourez, M.

    2012-03-20

    The Swift burst GRB 110205A was a very bright burst visible in the Northern Hemisphere. GRB 110205A was intrinsically long and very energetic and it occurred in a low-density interstellar medium environment, leading to delayed afterglow emission and a clear temporal separation of the main emitting components: prompt emission, reverse shock, and forward shock. Our observations show several remarkable features of GRB 110205A: the detection of prompt optical emission strongly correlated with the Burst Alert Telescope light curve, with no temporal lag between the two; the absence of correlation of the X-ray emission compared to the optical and high-energy gamma-ray ones during the prompt phase; and a large optical re-brightening after the end of the prompt phase, that we interpret as a signature of the reverse shock. Beyond the pedagogical value offered by the excellent multi-wavelength coverage of a gamma-ray burst with temporally separated radiating components, we discuss several questions raised by our observations: the nature of the prompt optical emission and the spectral evolution of the prompt emission at high energies (from 0.5 keV to 150 keV); the origin of an X-ray flare at the beginning of the forward shock; and the modeling of the afterglow, including the reverse shock, in the framework of the classical fireball model.

  20. The Swift XRT: Observations of Early X-ray Afterglows

    SciTech Connect

    Burrows, David N.; Kennea, J. A.; Nousek, J. A.; Osborne, J. P.; O'Brien, P. T.; Chincarini, G.; Tagliaferri, G.; Giommi, P.; Zhang, B.

    2006-05-19

    During the first year of operations of the Swift observatory, the X-ray Telescope has made a number of discoveries concerning the nature of X-ray afterglows of both long and short GRBs. We highlight the key findings, which include rapid declines at early times, a standard template of afterglow light curve shapes, common flaring, and the discovery of the first short GRB afterglow.

  1. GRB 100614A and GRB 100615A: two extremely dark gamma-ray bursts

    NASA Astrophysics Data System (ADS)

    D'Elia, V.; Stratta, G.

    2011-08-01

    Context. Dark gamma-ray bursts (GRBs) are sources with no or faint optical/near infrared (NIR) afterglow with respect to the X-ray one. Three possible explanations of this optical darkness have been proposed, namely: i) the GRB might be at high redshift, such that the Lyman α absorption prevents optical identifications; ii) dust in the GRB host galaxy may absorb the optical/NIR wavelengths; and iii) the optical faintness might have an intrinsic origin. Aims: We study two dark GRBs discovered by Swift, namely, GRB 100614A and GRB 100615A. These sources are bright in the X-rays, but no optical/NIR afterglow has been detected for either source, despite the efforts of several follow-up campaigns that have been performed since soon after the GRB explosion. Methods: We analyze the X-ray data and collect all the optical/NIR upper limits in literature for these bursts. We then build optical-to-X-ray spectral energy distributions (SEDs) at the times at which the reddest upper limits are available, and we model our SEDs with the attenuation curves of the Milky Way (MW), Small Magellanic Cloud (SMC), and one obtained for a sample of starburst galaxies. Results: We find that to explain the deepest NIR upper limits assuming either a MW or SMC extinction law, the visual extinction towards GRB 100614A is AV > 47 mag, while for GRB 100615A we obtain AV > 58 mag using data taken within one day after the burst and AV > 22 mag even 9.2 days after the trigger. Conclusions: If these bursts were strongly extincted by dust, these results imply that a MW or SMC-like dust obscuration is unlikely to be able to explain their optical darkness. Since both GRBs are bright in X-rays, explanation iii) also cannot explain their dark classification, unless optical radiation and X-rays are not part of the same synchrotron spectrum. In particular, the X-ray emission during the first 100 - 10 000 s after the burst, shows in ~70% of the cases a "shallow phase" unexpected by the fireball model

  2. Identification and Properties of the Photospheric Emission in GRB090902B

    NASA Astrophysics Data System (ADS)

    Ryde, F.; Axelsson, M.; Zhang, B. B.; McGlynn, S.; Pe'er, A.; Lundman, C.; Larsson, S.; Battelino, M.; Zhang, B.; Bissaldi, E.; Bregeon, J.; Briggs, M. S.; Chiang, J.; de Palma, F.; Guiriec, S.; Larsson, J.; Longo, F.; McBreen, S.; Omodei, N.; Petrosian, V.; Preece, R.; van der Horst, A. J.

    2010-02-01

    The Fermi Gamma-ray Space Telescope observed the bright and long GRB090902B, lying at a redshift of z = 1.822. Together the Large Area Telescope (LAT) and the Gamma-ray Burst Monitor (GBM) cover the spectral range from 8 keV to >300 GeV. Here we show that the prompt burst spectrum is consistent with emission from the jet photosphere combined with nonthermal emission described by a single power law with photon index -1.9. The photosphere gives rise to a strong quasi-blackbody spectrum which is somewhat broader than a single Planck function and has a characteristic temperature of ~290 keV. We model the photospheric emission with a multicolor blackbody, and its shape indicates that the photospheric radius increases at higher latitudes. We derive the averaged photospheric radius R ph = (1.1 ± 0.3) × 1012 Y 1/4 cm and the bulk Lorentz factor of the flow, which is found to vary by a factor of 2 and has a maximal value of Γ = 750 Y 1/4. Here, Y is the ratio between the total fireball energy and the energy emitted in the gamma rays. We find that during the first quarter of the prompt phase the photospheric emission dominates, which explains the delayed onset of the observed flux in the LAT compared to the GBM. We interpret the broadband emission as synchrotron emission at R ~ 4 × 1015 cm. Our analysis emphasizes the importance of having high temporal resolution when performing spectral analysis on gamma-ray bursts, since there is strong spectral evolution.

  3. Fermi and Swift Gamma-Ray Burst Afterglow Population Studies

    NASA Technical Reports Server (NTRS)

    Racusin, J. L.; Oates, S. R.; Schady, P.; Burrows, D. N.; de Pasquale, M.; Donato, D.; Gehrels, N.; Koch, S.; McEnery, J.; Piran, T.; Roming, P.; Sakamoto, T.; Swenson, C.; Virgili, F.; Wanderman, D.; Zhang, B.

    2011-01-01

    The new and extreme population of GRBs detected by Fermi-LAT shows several new features in high energy gamma-rays that are providing interesting and unexpected clues into GRB prompt and afterglow emission mechanisms. Over the last 6 years, it has been Swift that has provided the robust data set of UV/optical and X-ray afterglow observations that opened many windows into components of GRB emission structure. The relationship between the LAT GRBs and the well studied, fainter, less energetic GRBs detected by Swift-BAT is only beginning to be explored by multiwavelength studies. We explore the large sample of GRBs detected by BAT only, BAT and Fermi-GBM, and GBM and LAT, focusing on these samples separately in order to search for statistically significant differences between the populations, using only those GRBs with measured redshifts in order to physically characterize these objects. We disentangle which differences are instrumental selection effects versus intrinsic properties, in order to better understand the nature of the special characteristics of the LAT bursts.

  4. Fermi and Swift Gamma-Ray Burst Afterglow Population Studies

    NASA Technical Reports Server (NTRS)

    Racusin, Judith I.

    2011-01-01

    The new and extreme population of GRBs detected by Fermi-LAT shows several new features in high energy gamma-rays that are providing interesting and unexpected clues into GRB prompt and afterglow emission mechanisms. Over the last 6 years, it has been Swift that has provided the robust data set of UV/optical and X-ray afterglow observations that opened many windows into components of GRB emission structure. The relationship between the LAT GRBs and the well studied, fainter, less energetic GRBs detected by Swift-BAT is only beginning to be explored by multi-wavelength studies. We explore the large sample of GRBs detected by BAT only, BAT and Fermi-GBM, and GBM and LAT, focusing on these samples separately in order to search for statistically significant differences between the populations, using only those GRBs with measured redshifts in order to physically characterize these objects. We disentangle which differences are instrumental selection effects versus intrinsic properties, in order to better understand the nature of the special characteristics of the LAT bursts.

  5. Fermi and Swift Gamma-Ray Burst Afterglow Population Studies

    NASA Technical Reports Server (NTRS)

    Racusin, Judith L.; Oates, S. R.; Schady, P.; Burrows, D. N.; dePasquale, M.; Donato, D.; Gehrels, N.; Koch, S.; McEnery, J.; Piran, T.; Roming, P.; Sakamoto, T.; Swenson, C.; Troja, E.; Vasileiou, V.; Virgili, F.; Wanderman, D.; Zhang, B.

    2011-01-01

    The new and extreme population of GRBs detected by Fermi -LAT shows several new features in high energy gamma-rays that are providing interesting and unexpected clues into GRB prompt and afterglow emission mechanisms. Over the last 6 years, it has been Swift that has provided the robust dataset of UV/optical and X-ray afterglow observations that opened many windows into components of GRB emission structure. The relationship between the LAT detected GRBs and the well studied, fainter, less energetic GRBs detected by Swift -BAT is only beginning to be explored by multi-wavelength studies. We explore the large sample of GRBs detected by BAT only, BAT and Fermi -GBM, and GBM and LAT, focusing on these samples separately in order to search for statistically significant differences between the populations, using only those GRBs with measured redshifts in order to physically characterize these objects. We disentangle which differences are instrumental selection effects versus intrinsic properties, in order to better understand the nature of the special characteristics of the LAT bursts.

  6. PROSPECTS FOR GRB SCIENCE WITH THE FERMI LARGE AREA TELESCOPE

    SciTech Connect

    Band, D. L.; Axelsson, M.; Baldini, L.; Bellazzini, R.; Barbiellini, G.; Baring, M. G.; Bastieri, D.; Battelino, M.; Bissaldi, E.; Bogaert, G.; Chiang, J.; Do Couto e Silva, E.; Cohen-Tanugi, J.; Cutini, S.; De Palma, F.; Dingus, B. L.; Fishman, G.

    2009-08-20

    The Large Area Telescope (LAT) instrument on the Fermi mission will reveal the rich spectral and temporal gamma-ray burst (GRB) phenomena in the >100 MeV band. The synergy with Fermi's Gamma-ray Burst Monitor detectors will link these observations to those in the well explored 10-1000 keV range; the addition of the >100 MeV band observations will resolve theoretical uncertainties about burst emission in both the prompt and afterglow phases. Trigger algorithms will be applied to the LAT data both onboard the spacecraft and on the ground. The sensitivity of these triggers will differ because of the available computing resources onboard and on the ground. Here we present the LAT's burst detection methodologies and the instrument's GRB capabilities.

  7. A Deep Search for Prompt Radio Emission from the Short GRB 150424A with the Murchison Widefield Array

    NASA Astrophysics Data System (ADS)

    Kaplan, D. L.; Rowlinson, A.; Bannister, K. W.; Bell, M. E.; Croft, S. D.; Murphy, T.; Tingay, S. J.; Wayth, R. B.; Williams, A.

    2015-12-01

    We present a search for prompt radio emission associated with the short-duration gamma-ray burst (GRB) 150424A using the Murchison Widefield Array (MWA) at frequencies from 80 to 133 MHz. Our observations span delays of 23 s-30 minutes after the GRB, corresponding to dispersion measures of 100-7700 {pc} {{cm}}-3. We see no excess flux in images with timescales of 4 s, 2 minutes, or 30 minutes and set a 3σ flux density limit of 3.0 Jy at 132 MHz on the shortest timescales: some of the most stringent limits to date on prompt radio emission from any type of GRB. We use these limits to constrain a number of proposed models for coherent emission from short-duration GRBs, although we show that our limits are not particularly constraining for fast radio bursts because of reduced sensitivity for this pointing. Finally, we discuss the prospects for using the MWA to search for prompt radio emission from gravitational wave (GW) transients and find that while the flux density and luminosity limits are likely to be very constraining, the latency of the GW alert may limit the robustness of any conclusions.

  8. The X-ray afterglows of Gamma-Ray Bursts

    NASA Astrophysics Data System (ADS)

    Watson, D.

    2014-07-01

    Gamma-ray bursts are renowned for being the brightest explosions since the Big Bang. They are extremely useful probes with which to study the cosmos, primarily because of their bright afterglows. While the afterglow is panchromatic, the X-ray afterglow has proved extremely useful: the first localisations of both short and long-duration GRBs were made via their X-ray afterglows, an X-ray afterglow is associated with almost every burst, and spectroscopy of the X-ray afterglow informs us of the material close to the GRB as well as providing an unobscured measurement of the afterglow flux for virtually every GRB. We now have an incredibly rich database of ten years worth of GRBs and their afterglows from the Swift satellite, where its rapid autonomous repointing has allowed its X-Ray Telescope to be on target only minutes after the GRB. Here I will review what we have learnt from the X-ray afterglows of GRBs and describe some exciting recent results.

  9. Constraints on the Bulk Lorentz Factors of GRB X-Ray Flares

    NASA Astrophysics Data System (ADS)

    Yi, Shuang-Xi; Wu, Xue-Feng; Wang, Fa-Yin; Dai, Zi-Gao

    2015-07-01

    X-ray flares were discovered in the afterglow phase of gamma-ray bursts (GRBs) by the Swift satellite a decade ago and are known as a canonical component in GRB X-ray afterglows. In this paper, we constrain the Lorentz factors of GRB X-ray flares using two different methods. For the first method, we estimate the lower limit on the bulk Lorentz factor with the flare duration and jet break time. In the second method, the upper limit on the Lorentz factor is derived by assuming that the X-ray flare jet has undergone saturated acceleration. We also re-estimate the initial Lorentz factor with GRB afterglow onsets, and find the coefficient of the theoretical Lorentz factor is 1.67 rather than the commonly used 2 for the interstellar medium (ISM) and 1.44 for the wind case. We find that the correlation between the limited Lorentz factor and the isotropic radiation energy of X-ray flares in the ISM case is more consistent with that of prompt emission than the wind case in a statistical sense. For a comparison, the lower limit on the Lorentz factor is statistically larger than the extrapolation from prompt bursts in the wind case. Our results indicate that X-ray flares and prompt bursts are produced by the same physical mechanism.

  10. CONSTRAINTS ON THE BULK LORENTZ FACTORS OF GRB X-RAY FLARES

    SciTech Connect

    Yi, Shuang-Xi; Wang, Fa-Yin; Dai, Zi-Gao; Wu, Xue-Feng

    2015-07-01

    X-ray flares were discovered in the afterglow phase of gamma-ray bursts (GRBs) by the Swift satellite a decade ago and are known as a canonical component in GRB X-ray afterglows. In this paper, we constrain the Lorentz factors of GRB X-ray flares using two different methods. For the first method, we estimate the lower limit on the bulk Lorentz factor with the flare duration and jet break time. In the second method, the upper limit on the Lorentz factor is derived by assuming that the X-ray flare jet has undergone saturated acceleration. We also re-estimate the initial Lorentz factor with GRB afterglow onsets, and find the coefficient of the theoretical Lorentz factor is 1.67 rather than the commonly used 2 for the interstellar medium (ISM) and 1.44 for the wind case. We find that the correlation between the limited Lorentz factor and the isotropic radiation energy of X-ray flares in the ISM case is more consistent with that of prompt emission than the wind case in a statistical sense. For a comparison, the lower limit on the Lorentz factor is statistically larger than the extrapolation from prompt bursts in the wind case. Our results indicate that X-ray flares and prompt bursts are produced by the same physical mechanism.

  11. A HOT COCOON IN THE ULTRALONG GRB 130925A: HINTS OF A POPIII-LIKE PROGENITOR IN A LOW-DENSITY WIND ENVIRONMENT

    SciTech Connect

    Piro, Luigi; Troja, Eleonora; Kidd, Lauren A.; Ghisellini, Gabriele; Ricci, Roberto; Bannister, Keith; Fiore, Fabrizio; Piranomonte, Silvia; Wieringa, Mark H.

    2014-08-01

    GRB 130925A is a peculiar event characterized by an extremely long gamma-ray duration (≈7 ks), as well as dramatic flaring in the X-rays for ≈20 ks. After this period, its X-ray afterglow shows an atypical soft spectrum with photon index Γ ∼ 4, as observed by Swift and Chandra, until ≈10{sup 7} s, when XMM-Newton observations uncover a harder spectral shape with Γ ∼ 2.5, commonly observed in gamma-ray burst (GRB) afterglows. We find that two distinct emission components are needed to explain the X-ray observations: a thermal component, which dominates the X-ray emission for several weeks, and a non-thermal component, consistent with a typical afterglow. A forward shock model well describes the broadband (from radio to X-rays) afterglow spectrum at various epochs. It requires an ambient medium with a very low-density wind profile, consistent with that expected from a low-metallicity blue supergiant (BSG). The thermal component has a remarkably constant size and a total energy consistent with those expected by a hot cocoon surrounding the relativistic jet. We argue that the features observed in this GRB (its ultralong duration, the thermal cocoon, and the low-density wind environment) are associated with a low metallicity BSG progenitor and, thus, should characterize the class of ultralong GRBs.

  12. Constraining the Geometry and Energetics of the Exceptionally Energetic GRB070125

    NASA Astrophysics Data System (ADS)

    Frail, Dale

    2006-09-01

    The IPN and Swift-localized GRB070125, the brightest radio afterglow seen in almost four years, exhibits a steep spectrum from GHz frequencies up to ~1 mm, indicating a dense local environment (n >~ 100 cm^-3) and an extreme isotropic-equivalent afterglow energy (~10^54 erg). Depending solely on the angle of collimation (i.e. "jet opening angle") derived for this burst, it may easily become the highest-energy release GRB seen to date, straining the capacity of collapsar models and sounding the death knell for the "standard energy reservoir" of GRBs (Frail et al., ApJ, 562, 2001). We have an extensive set of optical and radio data for this burst that show a likely jet break at t~5 days; at this same epoch, the X-ray afterglow fades below the detection limit of Swift. We request a single 30-ksec observation with Chandra to distinguish jet-break from no-break models for the X-ray emission, and therefore to enable measurement of the prompt and afterglow energies for this remarkable event.

  13. Fermi Observations of High-energy Gamma-ray Emission from GRB 080825C

    NASA Astrophysics Data System (ADS)

    Abdo, A. A.; Ackermann, M.; Asano, K.; Atwood, W. B.; Axelsson, M.; Baldini, L.; Ballet, J.; Band, D. L.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Bhat, P. N.; Bissaldi, E.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bouvier, A.; Bregeon, J.; Brez, A.; Briggs, M. S.; Brigida, M.; Bruel, P.; Burnett, T. H.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Casandjian, J. M.; Cecchi, C.; Chaplin, V.; Chekhtman, A.; Cheung, C. C.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Cominsky, L. R.; Connaughton, V.; Conrad, J.; Cutini, S.; Dermer, C. D.; de Angelis, A.; de Palma, F.; Digel, S. W.; Silva, E. do Couto e.; Drell, P. S.; Dubois, R.; Dumora, D.; Farnier, C.; Favuzzi, C.; Focke, W. B.; Frailis, M.; Fukazawa, Y.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Germani, S.; Gibby, L.; Giebels, B.; Giglietto, N.; Giordano, F.; Glanzman, T.; Godfrey, G.; Goldstein, A.; Granot, J.; Grenier, I. A.; Grondin, M.-H.; Grove, J. E.; Guillemot, L.; Guiriec, S.; Hanabata, Y.; Harding, A. K.; Hayashida, M.; Hays, E.; Hughes, R. E.; Jóhannesson, G.; Johnson, A. S.; Johnson, W. N.; Kamae, T.; Katagiri, H.; Kataoka, J.; Kawai, N.; Kerr, M.; Knödlseder, J.; Kocevski, D.; Komin, N.; Kouveliotou, C.; Kuehn, F.; Kuss, M.; Latronico, L.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Makeev, A.; Mazziotta, M. N.; McBreen, S.; McEnery, J. E.; McGlynn, S.; Meegan, C.; Meurer, C.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Monte, C.; Monzani, M. E.; Moretti, E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nakamori, T.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohno, M.; Ohsugi, T.; Omodei, N.; Orlando, E.; Ormes, J. F.; Ozaki, M.; Paciesas, W. S.; Paneque, D.; Panetta, J. H.; Parent, D.; Pelassa, V.; Pepe, M.; Pesce-Rollins, M.; Piron, F.; Porter, T. A.; Preece, R.; Rainò, S.; Rando, R.; Razzano, M.; Razzaque, S.; Reimer, O.; Reposeur, T.; Ritz, S.; Rochester, L. S.; Rodriguez, A. Y.; Roth, M.; Ryde, F.; Sadrozinski, H. F.-W.; Sanchez, D.; Sander, A.; Saz Parkinson, P. M.; Scargle, J. D.; Sgrò, C.; Siskind, E. J.; Smith, D. A.; Smith, P. D.; Spandre, G.; Spinelli, P.; Stamatikos, M.; Strickman, M. S.; Suson, D. J.; Tajima, H.; Takahashi, H.; Tanaka, T.; Thayer, J. B.; Thayer, J. G.; Tibaldo, L.; Torres, D. F.; Tosti, G.; Tramacere, A.; Uchiyama, Y.; Usher, T. L.; van der Horst, A. J.; Vasileiou, V.; Vilchez, N.; Vitale, V.; von Kienlin, A.; Waite, A. P.; Wang, P.; Wilson-Hodge, C.; Winer, B. L.; Wood, K. S.; Ylinen, T.; Ziegler, M.

    2009-12-01

    The Fermi Gamma-ray Space Telescope has opened a new high-energy window in the study of gamma-ray bursts (GRBs). Here we present a thorough analysis of GRB 080825C, which triggered the Fermi Gamma-ray Burst Monitor (GBM), and was the first firm detection of a GRB by the Fermi Large Area Telescope (LAT). We discuss the LAT event selections, background estimation, significance calculations, and localization for Fermi GRBs in general and GRB 080825C in particular. We show the results of temporal and time-resolved spectral analysis of the GBM and LAT data. We also present some theoretical interpretation of GRB 080825C observations as well as some common features observed in other LAT GRBs.

  14. Chandra Observations of the X-ray Environs of SN 1998bw/GRB 980425

    NASA Technical Reports Server (NTRS)

    Kouveliotou, C.; Woosley, S. E.; Patel, S. K.; Levan, A.; Blandford, R.; Ramirez-Ruiz, E.; Wijers, R. A. M. J.; Weisskopf, M. C.; Tennant, A.; Pian, E.

    2004-01-01

    We report X-ray studies of the environs of SN 1998bw and GRB 980425 using the Chandra X-Ray Observatory 1281 days after the gamma-ray burst (GRB). Eight X-ray point sources were localized, three and five each in the original error boxes, S1 and S2, assigned for variable X-ray counteparts to the GRB by BeppoSAX. The sum of the discrete X-ray sources plus continuous emission in S2 observed by Chandra on day 1281 is within a factor of 1.5 of the maximum and the upper limits seen by BeppoSAX. We conclude that S2 is the sum of several variable sources that have not disappeared and therefore is not associated with the GRB. Within S1, clear evidence is seen for a decline of approximately a factor of 12 between day 200 and day 1281. One of the sources in S 1, S 1 a, is coincident with the well-determined radio location of SN 1998bw and is certainly the remnant of that explosion. The nature of the other sources is also discussed. Combining our observation of the supernova with others of the GRB afterglow, a smooth X-ray light curve, spanning approx. 1400 days, is obtained by assuming that the burst and supernova were coincident at 35.6 Mpc. When this X-ray light curve is compared with those of the X-ray af "erglows" of ordinary GRBs, X-ray flashes, and ordinary supernovae, evidence emerges for at least two classes of light curves, perhaps bounding a continuum. By 3-10 yr, all these phenomena seem to converge on a common X-ray luminosity, possibly indicative of the supernova underlying them all. This convergence strengthens the conclusion that SN 1998 bw aid GRB 980425 took place in the same object.One possible explanation for the two classes is that a (nearly) standard GRB was observed at different angles, in which case X-ray afterglows with intermediate luminosities should eventually be discovered. Finally, we comment on the contribution of GRB afterglows to the ultraluminous X-ray source population.

  15. GRB 091127: The Cooling Break Race on Magnetic Fuel

    NASA Technical Reports Server (NTRS)

    Filgas, R.; Greiner, J.; Schady, P.; Kruhler, T.; Updike, A. C.; Klose, S.; Nardini, M.; Kann, D. A.; Rossi, A.; Sudilovsky, V.; Afonso, P. M. J.; Clemens, C.; Elliott, J.; Nicuesa Guelbenzu, A.; Olivares, F.; Rau, A.

    2011-01-01

    Using high-quality, broad-band afterglow data for GRB 091127, we investigate the validity of the synchrotron fireball model for gamma-ray bursts, and infer physical parameters of the ultra-relativistic outflow. Methods. We used multi-wavelength (NIR to X-ray) follow-up observations obtained with GROND simultaneously in the g' r' t' i' z' JH filters and the XRT onboard the Swift satellite in the 0.3 to 10 keY energy range. The resulting afterglow light curve is of excellent accuracy with relative photometric errors as low as 1 %, and the spectral energy distribution (SED) is well-sampled over 5 decades in energy. These data present one of the most comprehensive observing campaigns for a single GRB afterglow and allow us to test several proposed emission models and outflow characteristics in unprecedented detail. Results. Both the multi-color light curve and the broad-band SED of the afterglow of GRB 091127 show evidence of a cooling break moving from high to lower energies. The early light curve is well described by a broken power-law, where the initial decay in the optical/NlR wavelength range is considerably flatter than at X-rays. Detailed fitting of the time-resolved SED shows that the break is very smooth with a sharpness index of 2.2 +/- 0.2, and evolves towards lower frequencies as a power-law with index -1.23 +/- 0.06. These are the first accurate and contemporaneous measurements of both the sharpness of the spectral break and its time evolution. Conclusions. The measured evolution of the cooling break (V(sub c) varies as t(sup -1.2) is not consistent with the predictions of the standard model, wherein V(sub c) varies as t(sup -05) is expected. A possible explanation for the observed behavior is a time dependence of the microphysical parameters, in particular the fraction of the total energy in the magnetic field epsilon(sub Beta). This conclusion provides further evidence that the standard fireball model is too simplistic, and time-dependent micro

  16. The high-redshift gamma-ray burst GRB 140515A

    SciTech Connect

    Melandri, A.; Bernardini, M. G.; D'Avanzo, P. D.; Sanchez-Ramirez, R.; Nappo, F.; Nava, L.; Japelj, J.; de Ugarte Postigo, A.; Oates, S.; Campana, S.; Covino, S.; D'Elia, V.; Ghirlanda, G.; Gafton, E.; Ghisellini, G.; Gnedin, N.; Goldoni, P.; Gorosabel, J.; Libbrecht, T.; Malesani, D.; Salvaterra, R.; Thone, C. C.; Vergani, S. D.; Xu, D.; Tagliaferri, G.

    2015-09-09

    High-redshift gamma-ray bursts (GRBs) offer several advantages when studying the distant Universe, providing unique information about the structure and properties of the galaxies in which they exploded. Spectroscopic identification with large ground-based telescopes has improved our knowledge of this kind of distant events. We present the multi-wavelength analysis of the high-zSwift GRB GRB 140515A (z = 6.327). The best estimate of the neutral hydrogen fraction of the intergalactic medium towards the burst is xHI ≤ 0.002. The spectral absorption lines detected for this event are the weakest lines ever observed in GRB afterglows, suggesting that GRB 140515A exploded in a very low-density environment. Its circum-burst medium is characterised by an average extinction (AV ~ 0.1) that seems to be typical of z ≥ 6 events. The observed multi-band light curves are explained either with a very hard injected spectrum (p = 1.7) or with a multi-component emission (p = 2.1). In the second case a long-lasting central engine activity is needed in order to explain the late time X-ray emission. Furthermore, the possible origin of GRB 140515A in a Pop III (or in a Pop II star with a local environment enriched by Pop III) massive star is unlikely.

  17. The high-redshift gamma-ray burst GRB 140515A

    DOE PAGESBeta

    Melandri, A.; Bernardini, M. G.; D'Avanzo, P. D.; Sanchez-Ramirez, R.; Nappo, F.; Nava, L.; Japelj, J.; de Ugarte Postigo, A.; Oates, S.; Campana, S.; et al

    2015-09-09

    High-redshift gamma-ray bursts (GRBs) offer several advantages when studying the distant Universe, providing unique information about the structure and properties of the galaxies in which they exploded. Spectroscopic identification with large ground-based telescopes has improved our knowledge of this kind of distant events. We present the multi-wavelength analysis of the high-zSwift GRB GRB 140515A (z = 6.327). The best estimate of the neutral hydrogen fraction of the intergalactic medium towards the burst is xHI ≤ 0.002. The spectral absorption lines detected for this event are the weakest lines ever observed in GRB afterglows, suggesting that GRB 140515A exploded in amore » very low-density environment. Its circum-burst medium is characterised by an average extinction (AV ~ 0.1) that seems to be typical of z ≥ 6 events. The observed multi-band light curves are explained either with a very hard injected spectrum (p = 1.7) or with a multi-component emission (p = 2.1). In the second case a long-lasting central engine activity is needed in order to explain the late time X-ray emission. Furthermore, the possible origin of GRB 140515A in a Pop III (or in a Pop II star with a local environment enriched by Pop III) massive star is unlikely.« less

  18. Observations of GRB 990123 by the Compton Gamma Ray Observatory

    NASA Technical Reports Server (NTRS)

    Briggs, M. S.; Band, D. L.; Kippen, R. M.; Preece, R. D.; Kouveliotou, C.; vanParadijs, J.; Share, G. H.; Murphy, R. J.; Matz, S. M.; Connors, A.

    1999-01-01

    GRB 990123 was the first burst from which simultaneous optical, X-ray, and gamma-ray emission was detected; its afterglow has been followed by an extensive set of radio, optical, and X-ray observations. We have studied the gamma-ray burst itself as observed by the Compton Gamma Ray Observatory detectors. We find that gamma-ray fluxes are not correlated with the simultaneous optical observations and that the gamma-ray spectra cannot be extrapolated simply to the optical fluxes. The burst is well fitted by the standard four-parameter GRB function, with the exception that excess emission compared with this function is observed below approx. 15 keV during some time intervals. The burst is characterized by the typical hard-to-soft and hardness-intensity correlation spectral evolution patterns. The energy of the peak of the vf (sub v), spectrum, E (sub p), reaches an unusually high value during the first intensity spike, 1470 plus or minus 110 keV, and then falls to approx. 300 keV during the tail of the burst. The high-energy spectrum above approx. 1 MeV is consistent with a power law with a photon index of about -3. By fluence, GRB 990123 is brighter than all but 0.4% of the GRBs observed with BATSE (Burst and Transient Source Experiment), clearly placing it on the -3/2 power-law portion of the intensity distribution. However, the redshift measured for the afterglow is inconsistent with the Euclidean interpretation of the -3/2 power law. Using the redshift value of greater than or equal to 1.61 and assuming isotropic emission, the gamma-ray energy exceeds 10 (exp 54) ergs.

  19. NEAR-EXTREMAL BLACK HOLES AS INITIAL CONDITIONS OF LONG GRB SUPERNOVAE AND PROBES OF THEIR GRAVITATIONAL WAVE EMISSION

    SciTech Connect

    Van Putten, Maurice H. P. M.

    2015-09-01

    Long gamma-ray bursts (GRBs) associated with supernovae and short GRBs with extended emission (SGRBEE) from mergers are probably powered by black holes as a common inner engine, as their prompt GRB emission satisfies the same Amati correlation in the E{sub p,i}–E{sub iso} plane. We introduce modified Bardeen equations to identify hyper-accretion driving newly formed black holes in core-collapse supernovae to near-extremal spin as a precursor to prompt GRB emission. Subsequent spin-down is observed in the BATSE catalog of long GRBs. Spin-down provides a natural unification of long durations associated with the lifetime of black hole spin for normal long GRBs and SGRBEEs, given the absence of major fallback matter in mergers. The results point to major emissions unseen in high frequency gravitational waves. A novel matched filtering method is described for LIGO–Virgo and KAGRA broadband probes of nearby core-collapse supernovae at essentially maximal sensitivity.

  20. Simulation Study Of Early Afterglows Observed With Swift

    NASA Astrophysics Data System (ADS)

    Nishikawa, Ken-Ichi; Hededal, C.; Hardee, P.; Mizuno, Y.; Fishman, G. J.

    2006-09-01

    A 3-D relativistic particle-in-cell code has been used to simulate the dynamics of forward and reverse shocks with thin and thick shells within the parameter constraints provided by present Swift observations and the present models of GRB emission. Our 3-D RPIC simulations have provided the dynamics of collisionless shocks in electron-ion and electron-positron plasmas with and without initial ambient magnetic fields and revealed the importance of ``jitter radiation'' with prompt and afterglow spectra due to the inhomogeneous magnetic fields generated by the Weibel instability. It is different from synchrotron radiation, which is usually assumed to be the dominant radiation process. We have investigated gamma-ray burst emissions from prompt, early, and late afterglows considering microscopic processes. Based on our previous investigation of the Weibel instability for each stage of evolution of ejecta propagating in the ISM, we have incorporated the plasma conditions (relativistic jets) with the density and composition of the plasmas, the magnetic field strength ($\\sigma$-values (the ratio of the electromagnetic energy flux to the particle energy flux)) and its direction, and the Lorentz factor for the different stages in prompt and afterglows. Systematic simulation studies of the relativistic collisionless shocks, associated particle acceleration, magnetic field generation and self-consistent radiation provide insight into undetermined issues in prompt and afterglows observed by Swift. Self-consistently calculated lightcurves, spectra, spectral evolutions, and polarization as function of viewing angle will be done to light a shed on recent new observations by Swift, in particular, X-ray flares, early steep decay, and shallow decay.

  1. Understanding Grb Physics With Multi-Wavelength Data

    NASA Astrophysics Data System (ADS)

    Zhang, Bing

    /XRT, Chandra), and optical (ground-based and HST) properties of all short GRBs, and apply multi-wavelength observational criteria to constrain the possible progenitor(s) of them. 3. The GRB central engine is still not identified. Growing observational data and theoretical modeling suggest that at least some GRBs may host a magnetar (in contrast to a hyper-accreting black hole) central engine. We propose to carry out a statistical study of the prompt emission and afterglow properties of GRBs that show possible evidence of magnetar behavior and compare their properties with those that do not show such evidence. We will define three samples: a gold sample that show a steady X-ray emission followed by a rapid decline, which are likely powered by internal dissipation of a magnetar wind, a silver sample showing a shallow decay segment followed by a normal decay, which can be interpreted as external shock emission with a magnetar continuous energy injection into the blastwave, and a sample that includes other GRBs that do not show any evidence of magnetar. We will compare various observational properties (e.g. isotropic energy/luminosity, jet-corrected energy/luminosity, jet opening angle, peak energy) of these samples and investigate whether there are noticeable differences among these samples. The results would shed light onto the difficult problem of GRB central engine, addressing whether different engines work in GRBs, and if so, what difference. The program conforms to NASA's Strategic Plan, and will make use of the public archival data of many NASA missions, including Fermi, Swift, HST, and Chandra.

  2. SWIFT Discovery of Gamma-ray Bursts without Jet Break Feature in their X-ray Afterglows

    NASA Technical Reports Server (NTRS)

    Sato, G.; Yamazaki, R.; Sakamoto, T.; Takahashi, T; Nakazawa, K.; Nakamura, T.; Toma, K.; Hullinger, D.; Tashiro, M.; Parsons, A. M.; Krimm, H. A.; Barthelmy, S. D.; Gehrels, N.; Burrows, D. N.; O'Brien, P. T.; Osborne, J. P.; Chincarini, G.; Lamb, D. Q.

    2007-01-01

    We analyze Swift gamma-ray bursts (GRBs) and X-ray afterglows for three GRBs with spectroscopic redshift determinations - GRB 050401, XRF 050416a, and GRB 050525a. We find that the relation between spectral peak energy and isotropic energy of prompt emissions (the Amati relation) is consistent with that for the bursts observed in pre-Swift era. However, we find that the X-ray afterglow lightcurves, which extend up to 10 - 70 days, show no sign of the jet break that is expected in the standard framework of collimated outflows. We do so by showing that none of the X-ray afterglow lightcurves in our sample satisfies the relation between the spectral and temporal indices that is predicted for the phase after jet break. The jet break time can be predicted by inverting the tight empirical relation between the peak energy of the spectrum and the collimation-corrected energy of the prompt emission (the Ghirlanda relation). We find that there are no temporal breaks within the predicted time intervals in X-ray band. This requires either that the Ghirlanda relation has a larger scatter than previously thought, that the temporal break in X-rays is masked by some additional source of X-ray emission, or that it does not happen because of some unknown reason.

  3. GRB 050717: A Long, Short-Lag Burst Observed by Swift and Konus

    SciTech Connect

    Krimm, H. A.; Hurkett, C.; Osborne, J. P.; Pal'shin, V.; Golenetskii, S.; Norris, J. P.; Barthelmy, S. D.; Gehrels, N.; Parsons, A. M.; Zhang, B.; Burrows, D. N.; Perri, M.

    2006-05-19

    The long burst GRB 050717 was observed simultaneously by the Burst Alert Telescope (BAT) on Swift and the Konus instrument on Wind. Significant hard to soft spectral evolution was seen. Early gamma-ray and X-ray emission was detected by both BAT and the X-Ray Telescope (XRT) on Swift. The XRT continued to observe the burst for 7.1 days and detect it for 1.4 days. The X-ray light curve showed a classic decay pattern including evidence of the onset of the external shock emission at {approx} 45 s after the trigger; the afterglow was too faint for a jet break to be detected. No optical, infrared or ultraviolet counterpart was discovered despite deep searches within 14 hours of the burst. The spectral lag for GRB 050717 was determined to be 2.5 {+-} 2.6 ms, consistent with zero and unusually short for a long burst. This lag measurement suggests that this burst has a high intrinsic luminosity and hence is at high redshift (z > 2.7). GRB 050717 provides a good example of classic prompt and afterglow behavior for a gamma-ray burst.

  4. Energies of GRB blast waves and prompt efficiencies as implied by modelling of X-ray and GeV afterglows

    NASA Astrophysics Data System (ADS)

    Beniamini, Paz; Nava, Lara; Duran, Rodolfo Barniol; Piran, Tsvi

    2015-11-01

    We consider a sample of 10 gamma-ray bursts with long-lasting ( ≳ 102 s) emission detected by Fermi/Large Area Telescope and for which X-ray data around 1 d are also available. We assume that both the X-rays and the GeV emission are produced by electrons accelerated at the external forward shock, and show that the X-ray and the GeV fluxes lead to very different estimates of the initial kinetic energy of the blast wave. The energy estimated from GeV is on average ˜50 times larger than the one estimated from X-rays. We model the data (accounting also for optical detections around 1 d, if available) to unveil the reason for this discrepancy and find that good modelling within the forward shock model is always possible and leads to two possibilities: (i) either the X-ray emitting electrons (unlike the GeV emitting electrons) are in the slow-cooling regime or (ii) the X-ray synchrotron flux is strongly suppressed by Compton cooling, whereas, due to the Klein-Nishina suppression, this effect is much smaller at GeV energies. In both cases the X-ray flux is no longer a robust proxy for the blast wave kinetic energy. On average, both cases require weak magnetic fields (10-6 ≲ ɛB ≲ 10-3) and relatively large isotropic kinetic blast wave energies 10^{53} erg<{E}_{0,kin}<10^{55} erg corresponding to large lower limits on the collimated energies, in the range 10^{52} erg<{E}_{θ ,kin}<5× 10^{52} erg for an ISM (interstellar medium) environment with n ˜ 1 cm-3 and 10^{52} erg<{E}_{θ ,kin}<10^{53} erg for a wind environment with A* ˜ 1. These energies are larger than those estimated from the X-ray flux alone, and imply smaller inferred values of the prompt efficiency mechanism, reducing the efficiency requirements on the still uncertain mechanism responsible for prompt emission.

  5. GRB 140606B/iPTF14bfu: detection of shock-breakout emission from a cosmological γ-ray burst?

    NASA Astrophysics Data System (ADS)

    Cano, Zach; de Ugarte Postigo, A.; Perley, D.; Krühler, T.; Margutti, R.; Friis, M.; Malesani, D.; Jakobsson, P.; Fynbo, J. P. U.; Gorosabel, J.; Hjorth, J.; Sánchez-Ramírez, R.; Schulze, S.; Tanvir, N. R.; Thöne, C. C.; Xu, D.

    2015-09-01

    We present optical and near-infrared photometry of GRB 140606B (z = 0.384), and optical photometry and spectroscopy of its associated supernova (SN). The results of our modelling indicate that the bolometric properties of the SN (MNi = 0.4 ± 0.2 M⊙, Mej = 5 ± 2 M⊙, and EK = 2 ± 1 × 1052 erg) are fully consistent with the statistical averages determined for other γ-ray burst (GRB)-SNe. However, in terms of its γ-ray emission, GRB 140606B is an outlier of the Amati relation, and occupies the same region as low luminosity (ll) and short GRBs. The γ-ray emission in llGRBs is thought to arise in some or all events from a shock breakout (SBO), rather than from a jet. The measured peak photon energy (Ep ≈ 800 keV) is close to that expected for γ-rays created by an SBO (≳ 1 MeV). Moreover, based on its position in the MV, p-Liso, γ plane and the EK-Γβ plane, GRB 140606B has properties similar to both SBO-GRBs and jetted-GRBs. Additionally, we searched for correlations between the isotropic γ-ray emission and the bolometric properties of a sample of GRB-SNe, finding that no statistically significant correlation is present. The average kinetic energy of the sample is bar{E}_K = 2.1× 10^{52} erg. All of the GRB-SNe in our sample, with the exception of SN 2006aj, are within this range, which has implications for the total energy budget available to power both the relativistic and non-relativistic components in a GRB-SN event.

  6. Chandra Observations of the X-ray Environs of SN 1998bw/GRB 980425

    NASA Technical Reports Server (NTRS)

    Kouveliotou, C.; Woosley, S. E.; Patel, S. K.; Levan, A.; Blandford, R.; Ramirez-Ruiz, E.; Wijers, R. A. M. J.; Weisskopf, M. C.; Tennant, A.; Pian, E.

    2004-01-01

    We report X-ray studies of the environs of SN 1998bw and GRB 980425 using the Chandra X-Ray Observatory 1281 days after the GRB. Eight X-ray point sources were localized, three and five each in the original error boxes - S1 and S2 - assigned for variable X-ray counterparts to the GRB by BeppoSAX. The sum of the discrete X-ray sources plus continuous emission in S2 observed by CXO on day 1281 is within a factor of 1.5 of the maximum and the upper limits seen by BeppoSAX. We conclude that S2 is the sum of several variable sources that have not disappeared, and therefore is not associated with the GRB. Within S1, clear evidence is seen for a decline of approximately a factor of 12 between day 200 and day 1281. One of the sources in S1, Sla, is coincident with the well-determined radio location of SN 1998bw, and is certainly the remnant of that explosion. The nature of the other sources is also discussed. Combining our observation of the supernova with others of the GRB afterglow, a smooth X-ray light curve, spanning approximately 1300 days, is obtained by assuming the burst and supernova were coincident at 35.6 Mpc. When this X-ray iight curve is compared with those of the X-ray afterglows of ordinary GRBs, X-ray Flashes, and ordinary supernovae, evidence emerges for at least two classes of lightcurves, perhaps bounding a continuum. By three to ten years, all these phenomena seem to converge on a common X-ray luminosity, possibly indicative of the supernova underlying them all. This convergence strengthens the conclusion that SN 1998bw and GRB 980425 took place in the same object. One possible explanation for the two classes is a (nearly) standard GRB observed at different angles, in which case X-ray afterglows with intermediate luminosities should eventually be discovered. Finally, we comment on the contribution of GRBs to the ULX source population.

  7. A Reverse Shock in GRB 130427A

    NASA Astrophysics Data System (ADS)

    Laskar, Tanmoy; Berger, Edo; Zauderer, B. Ashley; Margutti, Raffaella; Soderberg, Alicia Margarita; Lunnan, Ragnhild; Chornock, Ryan

    2014-06-01

    We present extensive radio and millimeter observations of the unusually bright GRB 130427A at z=0.340, spanning 0.67 to 12 days after the burst. Taken in conjunction with detailed multi-band UV, optical, NIR, and X-ray observations we find that the broad-band afterglow emission is composed of distinct reverse shock and forward shock contributions. The reverse shock emission dominates in the radio/millimeter and at <0.1 days in the UV/optical/NIR, while the forward shock emission dominates in the X-rays and at >0.1 days in the UV/optical/NIR. We further find that the optical and X-ray data require a Wind circumburst environment, pointing to a massive star progenitor. Using the combined forward and reverse shock emission we find that the parameters of the burst are an isotropic kinetic energy of E_Kis 2e53 erg, a mass loss rate of Mdo 3e-8 Msun/yr (for a wind velocity of 1,000 km/s), and a Lorentz factor at the deceleration time of Gamma(200s 130. Due to the low density and large isotropic energy, the absence of a jet break to ~15 days places only a weak constraint on the opening angle of theta_j>2.5 deg, and therefore a total energy of E_gamma+E_K>1.2e51 erg, similar to other GRBs. The reverse shock emission is detectable in this burst due to the low circumburst density, which leads to a slow cooling shock. We speculate that this is a required property for the detectability of reverse shocks in the radio and millimeter bands. Following on GRB 130427A as a benchmark event, observations of future GRBs with the exquisite sensitivity of VLA and ALMA, coupled with detailed modeling of the reverse and forward shock contributions will test this hypothesis.

  8. A Bulk Comptonization Model for the Prompt GRM Emission

    NASA Technical Reports Server (NTRS)

    Kazanas, Demos; Mastichiadis, A.

    2010-01-01

    The "Supercritical Pile" is a very economical GRB model that provides for the efficient conversion of the energy stored in the protons of a Relativistic Blast Wave (RBW) into radiation and at the same time produces - in the prompt GRB phase, even in the absence of any particle acceleration - a spectral peak at energy approximately 1 MeV. We extend this model to include the evolution of the RBW Lorentz factor F and thus follow its spectral and temporal features into the early GRB afterglow stage. One of the novel features of the present treatment is the inclusion of the feedback of the GRB produced radiation on the evolution of Gamma with radius. This feedback and the presence of kinematic and dynamic thresholds in the model are sources of potentially very rich time evolution which we have began to explore. In particular, one can this way obtain afterglow light curves with steep decays followed by the more conventional flatter afterglow slopes, while at the same time preserving the desirable features of the model, i.e. the well defined relativistic electron source and radiative processes that produce the proper peak in the nu F(sub nu) spectra. In this note we present the results of a specific set of parameters of this model with emphasis on the multiwavelength prompt emission and transition to the early afterglow.

  9. iPTF14yb: The First Discovery of a Gamma-Ray Burst Afterglow Independent of a High-Energy Trigger

    DOE PAGESBeta

    Cenko, S. Bradley; Urban, Alex L.; Perley, Daniel A.; Horesh, Assaf; Corsi, Alessandra; Fox, Derek B.; Cao, Yi; Kasliwal, Mansi M.; Lien, Amy; Arcavi, Iair; et al

    2015-04-20

    We report here the discovery by the Intermediate Palomar Transient Factory (iPTF) of iPTF14yb, a luminous (Msub>r ≈ ₋27.8 mag), cosmological (redshift 1.9733), rapidly fading optical transient. We demonstrate, based on probabilistic arguments and a comparison with the broader population, that iPTF14yb is the optical afterglow of the long-duration gamma-ray burst GRB140226A. This marks the rst unambiguous discovery of a GRB afterglow prior to (and thus entirely independent of) an associated high-energy trigger. We estimate the rate of iPTF14yb-like sources (i.e., cosmologically dis- tant relativistic explosions) based on iPTF observations, inferring an all-sky value ofmore » $$R_{rel}$$ = 610yr-1 (68% con dence interval of 110{2000 yr-1). Our derived rate is consistent (within the large uncer- tainty) with the all-sky rate of on-axis GRBs derived by the Swift satellite. Finally, we brie y discuss the implications of the nondetection to date of bona de \\orphan" afterglows (i.e., those lacking de- tectable high-energy emission) on GRB beaming and the degree of baryon loading in these relativistic jets.« less

  10. iPTF14yb: The First Discovery of a Gamma-Ray Burst Afterglow Independent of a High-Energy Trigger

    SciTech Connect

    Cenko, S. Bradley; Urban, Alex L.; Perley, Daniel A.; Horesh, Assaf; Corsi, Alessandra; Fox, Derek B.; Cao, Yi; Kasliwal, Mansi M.; Lien, Amy; Arcavi, Iair; Bloom, Joshua S.; Butler, Nat R.; Cucchiara, Antonino; Diego, José A. de; Filippenko, Alexei V.; Gal-Yam, Avishay; Gehrels, Neil; Georgiev, Leonid; Gonzalez, J. Jesus; Graham, John F.; Greiner, Jochen; Kann, D. Alexander; Klein, Christopher R.; Knust, Fabian; Kulkarni, S. R.; Kutyrev, Alexander; Laher, Russ; Lee, William H.; Nugent, Peter E.; Xavier Prochaska, J.; Rubin, Adam; Urata, Yuji; Varela, Karla; Watson, Alan M.; Wozniak, Przemek R.

    2015-04-20

    We report here the discovery by the Intermediate Palomar Transient Factory (iPTF) of iPTF14yb, a luminous (Msub>r ≈ ₋27.8 mag), cosmological (redshift 1.9733), rapidly fading optical transient. We demonstrate, based on probabilistic arguments and a comparison with the broader population, that iPTF14yb is the optical afterglow of the long-duration gamma-ray burst GRB140226A. This marks the rst unambiguous discovery of a GRB afterglow prior to (and thus entirely independent of) an associated high-energy trigger. We estimate the rate of iPTF14yb-like sources (i.e., cosmologically dis- tant relativistic explosions) based on iPTF observations, inferring an all-sky value of $R_{rel}$ = 610yr-1 (68% con dence interval of 110{2000 yr-1). Our derived rate is consistent (within the large uncer- tainty) with the all-sky rate of on-axis GRBs derived by the Swift satellite. Finally, we brie y discuss the implications of the nondetection to date of bona de \\orphan" afterglows (i.e., those lacking de- tectable high-energy emission) on GRB beaming and the degree of baryon loading in these relativistic jets.

  11. iPTF14yb: The First Discovery of a Gamma-Ray Burst Afterglow Independent of a High-Energy Trigger

    NASA Technical Reports Server (NTRS)

    Cenko, S. Bradley; Urban, Alex L.; Perley, Daniel A.; Horesh, Assaf; Corsi, Alessandra; Fox, Derek B.; Cao, Yi; Kasliwal, Mansi M.; Lien, Amy; Arcavi, Iair; Bloom, Joshua S.; Butler, Nat R.; Cucchiara, Antonino; De Diego, Jose A.; Filippenko, Alexei V.; Gal-Yam, Avishay; Gehrels, Neil; Georgiev, Leonid; Gonzalez, J. Jesus; Graham, John F.; Greiner, Jochen; Kann, D. Alexander; Klein, Christopher R.; Knust, Fabian; Kutyrev, Alexander

    2015-01-01

    We report here the discovery by the Intermediate Palomar Transient Factory (iPTF) of iPTF14yb, a luminous (Mr >> -27.8 mag), cosmological (redshift 1.9733), rapidly fading optical transient. We demonstrate, based on probabilistic arguments and a comparison with the broader population, that iPTF14yb is the optical afterglow of the long-duration gamma-ray burst GRB 140226A. This marks the first unambiguous discovery of a GRB afterglow prior to (and thus entirely independent of) an associated high-energy trigger. We estimate the rate of iPTF14yb-like sources (i.e., cosmologically distant relativistic explosions) based on iPTF observations, inferring an all-sky value of Rrel = 610/yr (68% confidence interval of 110-2000/yr). Our derived rate is consistent (within the large uncertainty) with the all-sky rate of on-axis GRBs derived by the Swift satellite. Finally, we briefly discuss the implications of the nondetection to date of bona fide "orphan" afterglows (i.e., those lacking detectable high-energy emission) on GRB beaming and the degree of baryon loading in these relativistic jets.

  12. iPTF14yb: The First Discovery of a Gamma-Ray Burst Afterglow Independent of a High-energy Trigger

    NASA Astrophysics Data System (ADS)

    Cenko, S. Bradley; Urban, Alex L.; Perley, Daniel A.; Horesh, Assaf; Corsi, Alessandra; Fox, Derek B.; Cao, Yi; Kasliwal, Mansi M.; Lien, Amy; Arcavi, Iair; Bloom, Joshua S.; Butler, Nat R.; Cucchiara, Antonino; de Diego, José A.; Filippenko, Alexei V.; Gal-Yam, Avishay; Gehrels, Neil; Georgiev, Leonid; Jesús González, J.; Graham, John F.; Greiner, Jochen; Kann, D. Alexander; Klein, Christopher R.; Knust, Fabian; Kulkarni, S. R.; Kutyrev, Alexander; Laher, Russ; Lee, William H.; Nugent, Peter E.; Prochaska, J. Xavier; Ramirez-Ruiz, Enrico; Richer, Michael G.; Rubin, Adam; Urata, Yuji; Varela, Karla; Watson, Alan M.; Wozniak, Przemek R.

    2015-04-01

    We report here the discovery by the Intermediate Palomar Transient Factory (iPTF) of iPTF14yb, a luminous ({{M}r}≈ -27.8 mag), cosmological (redshift 1.9733), rapidly fading optical transient. We demonstrate, based on probabilistic arguments and a comparison with the broader population, that iPTF14yb is the optical afterglow of the long-duration gamma-ray burst GRB 140226A. This marks the first unambiguous discovery of a GRB afterglow prior to (and thus entirely independent of) an associated high-energy trigger. We estimate the rate of iPTF14yb-like sources (i.e., cosmologically distant relativistic explosions) based on iPTF observations, inferring an all-sky value of {{\\Re }rel}=610 yr-1 (68% confidence interval of 110-2000 yr-1). Our derived rate is consistent (within the large uncertainty) with the all-sky rate of on-axis GRBs derived by the Swift satellite. Finally, we briefly discuss the implications of the nondetection to date of bona fide “orphan” afterglows (i.e., those lacking detectable high-energy emission) on GRB beaming and the degree of baryon loading in these relativistic jets.

  13. Extremely dark GRBs: the case of GRB 100614A and GRB 100615A.

    NASA Astrophysics Data System (ADS)

    D'Elia, V.; Stratta, G.

    Dark gamma-ray bursts (GRBs) are sources with a low optical-to-X-ray flux ratio. Proposed explanations for this darkness are: i) the GRB is at high redshift ii) dust in the GRB host galaxy absorbs the optical/NIR flux iii) GRBs have an intrinsically faint afterglow emission. Within this framework, GRB 100614A and GRB 100615A are extreme. In fact, they are bright in the X-rays, but no optical/NIR afterglow has been detected for either source, despite several follow-up campaigns began early after the triggers. We analyze the X-ray data and collect all the optical/NIR upper limits in literature for these bursts. We then build optical-to-X-ray spectral energy distributions (SEDs) at the times at which the reddest upper limits are available, and we model our SEDs with the extinction curves of the Milky Way (MW), Small Magellanic Cloud (SMC), and the attenuation curve obtained for a sample of starburst galaxies. We find that to explain the deepest NIR upper limits assuming either a MW or SMC extinction law, a visual extinction of A_V > 50 is required, which is extremely unlikely. Since both GRBs are bright in X-rays, explanation iii) also cannot explain their dark classification, unless optical radiation and X-rays are not part of the same synchrotron spectrum. An alternative, or complementary explanation of the previous possibility, involves greyer extinction laws. A starburst attenuation curve gives A_V>10, which is less extreme, despite still very high. Assuming high redshift in addition to extinction, implies an A_V>10 at z=2 and A_V>4-5 at z=5, regardless of the adopted extinction recipe. A different, exotic possibility would be an extremely high redshift origin (z>17 given the missing K detections). Population III stars are expected to emerge at z ˜ 20 and can produce GRBs with energies well above those inferred for our GRBs at these redshifts. Mid- and far-IR observations of these extreme class of GRBs can help us to differentiate between the proposed scenarios.

  14. GRB 070714B—Discovery of the Highest Spectroscopically Confirmed Short Burst Redshift

    NASA Astrophysics Data System (ADS)

    Graham, J. F.; Fruchter, A. S.; Levan, A. J.; Melandri, A.; Kewley, L. J.; Levesque, E. M.; Nysewander, M.; Tanvir, N. R.; Dahlen, T.; Bersier, D.; Wiersema, K.; Bonfield, D. G.; Martinez-Sansigre, A.

    2009-06-01

    We detect the optical afterglow and host galaxy of GRB 070714B. Our observations of the afterglow show an initial plateau in the light curve for approximately the first 5-25 minutes, and then steepening to a power-law decay with index α = 0.86 ± 0.10 for the period between 1 and 24 hr postburst. This is consistent with the X-ray light curve which shows an initial plateau followed by a similar subsequent decay. At late time, we detect a host galaxy at the location of the optical transient. Gemini Nod & Shuffle spectroscopic observations of the host show a single emission line at 7167 Å which, based on a griz JHK photometric redshift, we conclude is the 3727 Å [O II] line. We therefore find a redshift of z = 0.923. This redshift, as well as a subsequent probable spectroscopic redshift determination of GRB 070429B at z = 0.904 by two other groups significantly exceeds the previous highest spectroscopically confirmed short burst redshift of z = 0.546 for GRB 051221. This dramatically moves back the time at which we know short bursts were being formed and suggests that the present evidence for an old progenitor population may be observationally biased.

  15. A SUPRAMASSIVE MAGNETAR CENTRAL ENGINE FOR GRB 130603B

    SciTech Connect

    Fan, Yi-Zhong; Jin, Zhi-Ping; Wei, Da-Ming; Yu, Yun-Wei; Xu, Dong; Wu, Xue-Feng; Zhang, Bing E-mail: zhang@physics.unlv.edu

    2013-12-20

    We show that the peculiar early optical emission and, in particular, the X-ray afterglow emission of the short-duration burst GRB 130603B can be explained by continuous energy injection into the blastwave from a supramassive magnetar central engine. The observed energetics and temporal/spectral properties of the late infrared bump (i.e., the {sup k}ilonova{sup )} are also found to be consistent with emission from the ejecta launched during a neutron star (NS)-NS merger and powered by a magnetar central engine. The isotropic-equivalent kinetic energies of both the gamma-ray burst (GRB) blastwave and the kilonova are approximately E{sub k} ∼ 10{sup 51} erg, consistent with being powered by a near-isotropic magnetar wind. However, this relatively small value requires that most of the initial rotational energy of the magnetar (∼a few × 10{sup 52} erg) is carried away by gravitational wave radiation. Our results suggest that (1) the progenitor of GRB 130603B was a NS-NS binary system, the merger product of which would have been a supramassive NS that lasted for about ∼1000 s; (2) the equation of state of the nuclear matter should be stiff enough to allow the survival of a long-lived supramassive NS; thus this suggested that the detection of the bright electromagnetic counterparts of gravitational wave triggers without short GRB associations is promising in the upcoming Advanced LIGO/VIRGO era.

  16. INTEGRAL and XMM-Newton observations of GRB 040106

    NASA Astrophysics Data System (ADS)

    Moran, L.; Mereghetti, S.; Götz, D.; Hanlon, L.; von Kienlin, A.; McBreen, B.; Tiengo, A.; Preece, R.; Williams, O. R.; Bennett, K.; Kippen, R. M.; McBreen, S.; McGlynn, S.

    2005-03-01

    On January 6th 2004, the IBAS burst alert system triggered the 8th gamma-ray burst (GRB) to be located by the INTEGRAL satellite. The position was determined and publicly distributed within 12 s, prompting ESA's XMM-Newton to execute a ToO observation just 5 h later, during which an X-ray afterglow was detected. The GRB had a duration ~52 s with two distinct pulses separated by ~42 s. Here we present the results of imaging and spectral analyses of the prompt emission from INTEGRAL data and the X-ray afterglow from XMM-Newton data. The γ-ray spectrum is consistent with a single power-law of photon index -1.72 ± 0.15. The fluence (20-200 keV) was 8.2 × 10-7 erg cm-2. The X-ray afterglow (Fν(t) ∝ ν-β_X t-δ) was extremely hard with βX = 0.47 ± 0.01 and δ = 1.46 ± 0.04. The 2-10 keV flux 11 h after the burst was 1.1 × 10-12 erg cm-2 s-1. The time profile of the GRB is consistent with the observed trends from previous analysis of BATSE GRBs. We find that the X-ray data are not well-fit by either a simple spherical fireball or by a speading jet, expanding into a homogeneous medium or a wind environment. Based on previously determined correlations between GRB spectra and redshift, we estimate a redshift of ~0.9+0.5-0.4 (1σ) and a lower limit on the isotropic radiated energy of ~5 × 1051 erg in this burst. Based on observations with INTEGRAL, an ESA project with instruments and science data centre funded by ESA member states (especially the PI countries: Denmark, France, Germany, Italy, Switzerland, Spain), Czech Republic and Poland, and with the participation of Russia and the USA.

  17. Swift Observations of the X-Ray-Bright GRB 050315

    NASA Astrophysics Data System (ADS)

    Vaughan, S.; Goad, M. R.; Beardmore, A. P.; O'Brien, P. T.; Osborne, J. P.; Page, K. L.; Barthelmy, S. D.; Burrows, D. N.; Campana, S.; Cannizzo, J. K.; Capalbi, M.; Chincarini, G.; Cummings, J. R.; Cusumano, G.; Giommi, P.; Godet, O.; Hill, J. E.; Kobayashi, S.; Kumar, P.; La Parola, V.; Levan, A.; Mangano, V.; Mészáros, P.; Moretti, A.; Morris, D. C.; Nousek, J. A.; Pagani, C.; Palmer, D. M.; Racusin, J. L.; Romano, P.; Tagliaferri, G.; Zhang, B.; Gehrels, N.

    2006-02-01

    This paper discusses Swift observations of the γ-ray burst GRB 050315 (z=1.949) from 80 s to 10 days after the onset of the burst. The X-ray light curve displayed a steep early decay (t-5) for ~200 s and several breaks. However, both the prompt hard X-ray/γ-ray emission (observed by the BAT) and the first ~300 s of X-ray emission (observed by the XRT) can be explained by exponential decays, with similar decay constants. Extrapolating the BAT light curve into the XRT band suggests that the rapidly decaying, early X-ray emission was simply a continuation of the fading prompt emission; this strong similarity between the prompt γ-ray and early X-ray emission may be related to the simple temporal and spectral character of this X-ray-rich GRB. The prompt (BAT) spectrum was steep down to ~15 keV and appeared to continue through the XRT bandpass, implying a low peak energy, inconsistent with the Amati relation. Following the initial steep decline, the X-ray afterglow did not fade for ~1.2×104 s, after which time it decayed with a temporal index of α~0.7, followed by a second break at ~2.5×105 s to a slope of α~2. The apparent ``plateau'' in the X-ray light curve, after the early rapid decay, makes this one of the most extreme examples of the steep-flat-steep X-ray light curves revealed by Swift. If the second afterglow break is identified with a jet break, then the jet opening angle was θ0~5deg, implying Eγ>~1050 ergs.

  18. Evidence for Filamentary Jet Structure: The Light Curve of GRB 011211

    NASA Technical Reports Server (NTRS)

    Jakobsson, P.; Hjorth, J.; Ramirez-Ruiz, E.; Kouveliotou, C.; Pedersen, K.; Fynbo, J. P. U.; Gorosabel, J.; Watson, D.; Jensen, B. L.; Gray, T.

    2003-01-01

    We report on the discovery of the optical afterglow of the X-ray rich, long-duration gamma-ray burst GRB 011211, and the oscillatory behavior present in its optical and X-ray afterglow light curve. The time scale of the fluctuations, -1 hour, is much smaller than the time of the observations, -12 hours from the onset of the gamma-ray burst. The character and strength of the fluctuations visible in the optical data are unprecedented, and are inconsistent with causally connected variations in the emission of a symmetric, relativistic blast wave. Moreover, the differential time lag between the short-term variations in X-ray and optical energies suggests they do not arise from the same emitting region. Such variability may imply that local spherical symmetry is broken because the energy content across the jet-emitting surface is not uniform, indicating the detection of a small scale substructure within the jet itself.

  19. The Sub-Energetic GRB 031203 as a Cosmic Analogue to GRB 980425

    SciTech Connect

    Soderberg, A

    2004-08-27

    Over the six years since the discovery of the {gamma}-ray burst GRB 980425, associated with the nearby (distance {approx}40 Mpc) supernova 1998bw, astronomers have fiercely debated the nature of this event. Relative to bursts located at cosmological distances, (redshift, z {approx} 1), GRB 980425 was under-luminous in {gamma}-rays by three orders of magnitude. Radio calorimetry showed the explosion was sub-energetic by a factor of 10. Here, the authors report observations of the radio and X-ray afterglow of the recent z = 0.105 GRB031203 and demonstrate that it too is sub-energetic. The result, when taken together with the low {gamma}-ray luminosity, suggest that GRB031203 is the first cosmic analogue to GRB980425. They find no evidence that this event was a highly collimated explosion viewed off-axis. Like GRB980425, GRB031203 appears to be an intrinsically sub-energetic {gamma}-burst. Such sub-energetic events have faint afterglows. Intensive follow-up of faint bursts with smooth {gamma}-ray light curves (common to both GRBs 031203 and 980425) may enable the authors to reveal their expected large population.

  20. Gamma-Ray Bursts and Afterglows: a Multi-Wavelength Study in the Swift Era

    NASA Astrophysics Data System (ADS)

    Yu, Y. W.

    2010-01-01

    Gamma-ray bursts (GRBs), which are generally followed by long-lasting low-frequency afterglow emission, are short and intense pulses of gamma-rays observed from the sky in arbitrary directions. In order to observe the multi-wavelength emission at the early afterglow phase and even the prompt emission phase, NASA launched the Swift satellite on Nov. 20th 2004. Swift can localize GRBs within about 10 seconds. A brief review on the recent progress in observations and theories in the Swift era is given in Chapter 1. This paper focuses on the features of the early afterglows and the multi-wavelength prompt emission. In Chapters 2 and 3, we try to explain the shallow-decaying X-ray afterglows and X-ray flares, both of which are unaccountable in the standard afterglow model. (1) It is widely accepted that the shallow decay phase indicates a continuous energy injection into the GRB blast wave, and this energy could be released from the central engine after the burst. Based on the knowledge of the evolution of a pulsar wind, we argue that the injected flow interacting with the GRB blast wave is an ultra-relativistic kinetic-energy flow (i.e., wind) rather than pure electromagnetic waves. Therefore, a relativistic wind bubble (RWB) including a pair of shocks will be formed. Our numerical calculations and the fitting results show that the emission from an RWB can well account for the X-ray shallow decay phase. (2) For the X-ray flares that are attributed to some intermediate late activities of the central engine, we analyze the detailed dynamics of late internal shocks which directly produce the flare emission. Comparing the theoretical results with the lower limits of the observational luminosities and the profiles of the flare light curves, we find some constraints on the properties of the pre-collision shells, which are directly determined by the central object. In Chapter 4, we investigate the high-energy afterglow emission during the shallow decay phase in two models, i

  1. IDENTIFYING THE LOCATION IN THE HOST GALAXY OF THE SHORT GRB 111117A WITH THE CHANDRA SUBARCSECOND POSITION

    SciTech Connect

    Sakamoto, T.; Troja, E.; Aoki, K.; Guiriec, S.; Barthelmy, S. D.; Im, M.; Jeon, Y.; Leloudas, G.; Malesani, D.; De Ugarte Postigo, A.; Andersen, M. I.; Melandri, A.; D'Avanzo, P.; Urata, Y.; Xu, D.; Gorosabel, J.; Sanchez-Ramirez, R.; Briggs, M. S.; Foley, S.; and others

    2013-03-20

    We present our successful Chandra program designed to identify, with subarcsecond accuracy, the X-ray afterglow of the short GRB 111117A, which was discovered by Swift and Fermi. Thanks to our rapid target of opportunity request, Chandra clearly detected the X-ray afterglow, though no optical afterglow was found in deep optical observations. The host galaxy was clearly detected in the optical and near-infrared band, with the best photometric redshift of z=1.31{sub -0.23}{sup +0.46} (90% confidence), making it one of the highest known short gamma-ray burst (GRB) redshifts. Furthermore, we see an offset of 1.0 {+-} 0.2 arcsec, which corresponds to 8.4 {+-} 1.7 kpc, between the host and the afterglow position. We discuss the importance of using Chandra for obtaining subarcsecond X-ray localizations of short GRB afterglows to study GRB environments.

  2. Jet or Shock Breakout? The Low-Luminosity GRB 060218

    NASA Astrophysics Data System (ADS)

    Irwin, Christopher; Chevalier, Roger

    2016-01-01

    We consider a model for the long-duration, low-luminosity gamma-ray burst GRB 060218 that plausibly accounts for multiwavelength observations to day 20. The components of our model are: (1) a long-lived (tj ~ 3000 s) central engine and accompanying low-luminosity (Lj ~ 1045 erg s-1), mildly relativistic jet; (2) a low-mass (~ 10-2 Msun) envelope surrounding the progenitor star; and (3) a modest amount of dust (AV ~ 0.1) in the circumstellar or interstellar environment. Blackbody emission from the transparency radius in a low-power jet outflow can fit the prompt thermal X-ray emission, and the prompt nonthermal X-rays and γ-rays may be produced via Compton scattering of thermal photons from hot leptons in the jet interior or the external shocks. The later mildly relativistic phase of this outflow can produce the radio emission via synchrotron radiation from the forward shock. Meanwhile, interaction of the associated SN 2006aj with a circumstellar envelope extending to ~ 1013 cm can explain the early optical peak. The X-ray afterglow can be interpreted as a light echo of the prompt emission from dust at ~ 30 pc. Our model is a plausible alternative to that of Nakar, who recently proposed shock breakout of a jet smothered by an extended envelope as the source of prompt emission. Both our results and Nakar's suggest that ultra-long bursts such as GRB 060218 and GRB 100316D may originate from unusual progenitors with extended circumstellar envelopes, and that a jet is necessary to decouple the prompt high-energy emission from the supernova.

  3. Gamma-Ray Bursts and Afterglows: a Multi-Wavelength Study in the Swift Era

    NASA Astrophysics Data System (ADS)

    Yu, Y. W.

    2010-01-01

    Gamma-ray bursts (GRBs), which are generally followed by long-lasting low-frequency afterglow emission, are short and intense pulses of gamma-rays observed from the sky in arbitrary directions. In order to observe the multi-wavelength emission at the early afterglow phase and even the prompt emission phase, NASA launched the Swift satellite on Nov. 20th 2004. Swift can localize GRBs within about 10 seconds. A brief review on the recent progress in observations and theories in the Swift era is given in Chapter 1. This paper focuses on the features of the early afterglows and the multi-wavelength prompt emission. In Chapters 2 and 3, we try to explain the shallow-decaying X-ray afterglows and X-ray flares, both of which are unaccountable in the standard afterglow model. (1) It is widely accepted that the shallow decay phase indicates a continuous energy injection into the GRB blast wave, and this energy could be released from the central engine after the burst. Based on the knowledge of the evolution of a pulsar wind, we argue that the injected flow interacting with the GRB blast wave is an ultra-relativistic kinetic-energy flow (i.e., wind) rather than pure electromagnetic waves. Therefore, a relativistic wind bubble (RWB) including a pair of shocks will be formed. Our numerical calculations and the fitting results show that the emission from an RWB can well account for the X-ray shallow decay phase. (2) For the X-ray flares that are attributed to some intermediate late activities of the central engine, we analyze the detailed dynamics of late internal shocks which directly produce the flare emission. Comparing the theoretical results with the lower limits of the observational luminosities and the profiles of the flare light curves, we find some constraints on the properties of the pre-collision shells, which are directly determined by the central object. In Chapter 4, we investigate the high-energy afterglow emission during the shallow decay phase in two models, i

  4. Broad band simulation of Gamma Ray Bursts (GRB) prompt emission in presence of an external magnetic field

    NASA Astrophysics Data System (ADS)

    Ziaeepour, Houri; Gardner, Brian

    2011-12-01

    The origin of prompt emission in GRBs is not yet well understood. The simplest and most popular model is Synchrotron Self-Compton (SSC) emission produced by internal shocks inside an ultra-relativistic jet. However, recent observations of a delayed high energy component by the Fermi-LAT instrument have encouraged alternative models. Here we use a recently developed formulation of relativistic shocks for GRBs to simulate light curves and spectra of synchrotron and self-Compton emissions in the framework of internal shock model. This model takes into account the evolution of quantities such as densities of colliding shells, and fraction of kinetic energy transferred to electrons and to induced magnetic field. We also extend this formulation by considering the presence of a precessing external magnetic field. These simulations are very realistic and present significant improvement with respect to previous phenomenological GRB simulations. They reproduce light curves of separate peaks of real GRBs and variety of spectral slopes at E > Epeak observed by the Fermi-LAT instrument. The high energy emission can be explained by synchrotron emission and a subdominant contribution from inverse Compton. We also suggest an explanation for extended tail emission and relate it to the screening of the magnetic field and/or trapping of accelerated electrons in the electromagnetic energy structure of the plasma in the shock front. Spectral slopes of simulated bursts at E << Epeak are consistent with theoretical prediction and at E < Epeak can be flatter if the spectrum of electrons is roughly flat or has a shallow slope at low energies. The observed flat spectra at soft gamma-ray and hard x-ray bands is the evidence that there is a significant contribution at E < Epeak from lower Lorentz factor wing of electron distribution which have a roughly random acceleration rather than being thermal. This means that the state of matter in the jet at the time of ejection is most probably

  5. GRB 091024A and the nature of ultra-long gamma-ray bursts

    SciTech Connect

    Virgili, F. J.; Mundell, C. G.; Harrison, R.; Kobayashi, S.; Steele, I. A.; Mottram, C. J.; Clay, N. R.; Pal'shin, V.; Guidorzi, C.; Margutti, R.; Chornock, R.; Melandri, A.; Updike, A. C.; Cenko, S. B.; Tanvir, N. R.; Cucchiara, A.; Levan, A.; Cano, Z.; and others

    2013-11-20

    We present a broadband study of gamma-ray burst (GRB) 091024A within the context of other ultra-long-duration GRBs. An unusually long burst detected by Konus-Wind (KW), Swift, and Fermi, GRB 091024A has prompt emission episodes covering ∼1300 s, accompanied by bright and highly structured optical emission captured by various rapid-response facilities, including the 2 m autonomous robotic Faulkes North and Liverpool Telescopes, KAIT, S-LOTIS, and the Sonoita Research Observatory. We also observed the burst with 8 and 10 m class telescopes and determine the redshift to be z = 1.0924 ± 0.0004. We find no correlation between the optical and γ-ray peaks and interpret the optical light curve as being of external origin, caused by the reverse and forward shock of a highly magnetized jet (R{sub B} ≈ 100-200). Low-level emission is detected throughout the near-background quiescent period between the first two emission episodes of the KW data, suggesting continued central-engine activity; we discuss the implications of this ongoing emission and its impact on the afterglow evolution and predictions. We summarize the varied sample of historical GRBs with exceptionally long durations in gamma-rays (≳1000 s) and discuss the likelihood of these events being from a separate population; we suggest ultra-long GRBs represent the tail of the duration distribution of the long GRB population.

  6. GRB 091024A and the Nature of Ultra-long Gamma-Ray Bursts

    NASA Astrophysics Data System (ADS)

    Virgili, F. J.; Mundell, C. G.; Pal'shin, V.; Guidorzi, C.; Margutti, R.; Melandri, A.; Harrison, R.; Kobayashi, S.; Chornock, R.; Henden, A.; Updike, A. C.; Cenko, S. B.; Tanvir, N. R.; Steele, I. A.; Cucchiara, A.; Gomboc, A.; Levan, A.; Cano, Z.; Mottram, C. J.; Clay, N. R.; Bersier, D.; Kopač, D.; Japelj, J.; Filippenko, A. V.; Li, W.; Svinkin, D.; Golenetskii, S.; Hartmann, D. H.; Milne, P. A.; Williams, G.; O'Brien, P. T.; Fox, D. B.; Berger, E.

    2013-11-01

    We present a broadband study of gamma-ray burst (GRB) 091024A within the context of other ultra-long-duration GRBs. An unusually long burst detected by Konus-Wind (KW), Swift, and Fermi, GRB 091024A has prompt emission episodes covering ~1300 s, accompanied by bright and highly structured optical emission captured by various rapid-response facilities, including the 2 m autonomous robotic Faulkes North and Liverpool Telescopes, KAIT, S-LOTIS, and the Sonoita Research Observatory. We also observed the burst with 8 and 10 m class telescopes and determine the redshift to be z = 1.0924 ± 0.0004. We find no correlation between the optical and γ-ray peaks and interpret the optical light curve as being of external origin, caused by the reverse and forward shock of a highly magnetized jet (RB ≈ 100-200). Low-level emission is detected throughout the near-background quiescent period between the first two emission episodes of the KW data, suggesting continued central-engine activity; we discuss the implications of this ongoing emission and its impact on the afterglow evolution and predictions. We summarize the varied sample of historical GRBs with exceptionally long durations in gamma-rays (gsim1000 s) and discuss the likelihood of these events being from a separate population; we suggest ultra-long GRBs represent the tail of the duration distribution of the long GRB population.

  7. On the optical and X-ray afterglows of gamma ray bursts

    NASA Astrophysics Data System (ADS)

    Dado, S.; Dar, A.; De Rújula, A.

    2002-06-01

    We severely criticize the consuetudinary analysis of the afterglows of gamma-ray bursts (GRBs) in the conical-ejection fireball scenarios. We argue that, instead, recent observations imply that the long-duration GRBs and their afterglows are produced by highly relativistic jets of cannonballs (CBs) emitted in supernova explosions. The CBs are heated by their collision with the supernova shell. The GRB is the boosted surface radiation the CBs emit as they reach the transparent outskirts of the shell. The exiting CBs further decelerate by sweeping up interstellar matter (ISM). The early X-ray afterglow is dominated by thermal bremsstrahlung from the cooling CBs, the optical afterglow by synchrotron radiation from the ISM electrons swept up by the CBs. We show that this model fits simply and remarkably well all the measured optical afterglows of the 15 GRBs with known redshift, including that of GRB 990123, for which unusually prompt data are available. We demonstrate that GRB 980425 was a normal GRB produced by SN1998bw, with standard X-ray and optical afterglows. We find that the very peculiar afterglow of GRB 970508 can be explained if its CBs encountered a significant jump in density as they moved through the ISM. The afterglows of the nearest 8 of the known-redshift GRBs show various degrees of evidence for an association with a supernova akin to SN1998bw. In all other cases such an association, even if present, would have been undetectable with the best current photometric sensitivities. This gives strong support to the proposition that most, maybe all, of the long-duration GRBs are associated with supernovae. Although our emphasis is on optical afterglows, we also provide an excellent description of X-ray afterglows. Figures \\ref{fig228} to \\ref{X1216} are only available in electronic form at http:/www.edpsciences.org

  8. The Decay of Optical Emission from the gamma-Ray Burst GRB970228

    NASA Technical Reports Server (NTRS)

    Galama, T.; Groot, P. J.; vanParadijs, J.; Kouveliotou, C.; Robinson, C. R.; Fishman, G. J.; Meegan, C. A.; Sahu, K. C.; Livio, M.; Petro, L.; Macchetto, F. D.; Heise, J.; Int Zand, J.; Strom, R. G.; Telting, J.; Rutten, R. G. M.; Pettini, M.; Tanvir, N.; Bloom, J.

    1997-01-01

    The origin of gamma-ray bursts has been one of the great unsolved mysteries in high-energy astrophysics for almost 30 years. The recent discovery of fading sources at X-ray and optical wavelengths coincident with the location of the gamma-ray burst GRB970228 therefore provides an unprecedented opportunity to probe the nature of these high-energy events. The optical counterpart appears to be a transient point source embedded in a region of extended nebulosity, the latter having been tentatively identified as a high-redshift galaxy. This would seem to favour models that place gamma-ray bursts at cosmological distances, although a range of mechanisms for producing the bursts is still allowed. A crucial piece of information for distinguishing between such models is how the brightness of the optical counterpart evolves with time. Here we re-evaluate the existing photometry of the optical counterpart of GRB970228 to construct an optical light curve for the transient event. We find that between 21 hours and six days after the burst, the R-band brightness decreased by a factor of approximately 40, with any subsequent decrease in brightness occurring at a much slower rate. As the point source faded, it also became redder. The initial behaviour of the source appears to be consistent with the 'fireball' model, but the subsequent decrease in the rate of fading may prove harder to explain.

  9. The central engine of GRB 130831A and the energy breakdown of a relativistic explosion

    NASA Astrophysics Data System (ADS)

    De Pasquale, M.; Oates, S. R.; Racusin, J. L.; Kann, D. A.; Zhang, B.; Pozanenko, A.; Volnova, A. A.; Trotter, A.; Frank, N.; Cucchiara, A.; Troja, E.; Sbarufatti, B.; Butler, N. R.; Schulze, S.; Cano, Z.; Page, M. J.; Castro-Tirado, A. J.; Gorosabel, J.; Lien, A.; Fox, O.; Littlejohns, O.; Bloom, J. S.; Prochaska, J. X.; de Diego, J. A.; Gonzalez, J.; Richer, M. G.; Román-Zúñiga, C.; Watson, A. M.; Gehrels, N.; Moseley, H.; Kutyrev, A.; Zane, S.; Hoette, V.; Russell, R. R.; Rumyantsev, V.; Klunko, E.; Burkhonov, O.; Breeveld, A. A.; Reichart, D. E.; Haislip, J. B.

    2016-01-01

    Gamma-ray bursts (GRBs) are the most luminous explosions in the Universe, yet the nature and physical properties of their energy sources are far from understood. Very important clues, however, can be inferred by studying the afterglows of these events. We present optical and X-ray observations of GRB 130831A obtained by Swift, Chandra, Skynet, Reionization And Transients Infra-Red camera, Maidanak, International Scientific Optical-Observation Network, Nordic Optical Telescope, Liverpool Telescope and Gran Telescopio Canarias. This burst shows a steep drop in the X-ray light curve at ≃105 s after the trigger, with a power-law decay index of α ˜ 6. Such a rare behaviour cannot be explained by the standard forward shock (FS) model and indicates that the emission, up to the fast decay at 105 s, must be of `internal origin', produced by a dissipation process within an ultrarelativistic outflow. We propose that the source of such an outflow, which must produce the X-ray flux for ≃1 d in the cosmological rest frame, is a newly born magnetar or black hole. After the drop, the faint X-ray afterglow continues with a much shallower decay. The optical emission, on the other hand, shows no break across the X-ray steep decrease, and the late-time decays of both the X-ray and optical are consistent. Using both the X-ray and optical data, we show that the emission after ≃105 s can be explained well by the FS model. We model our data to derive the kinetic energy of the ejecta and thus measure the efficiency of the central engine of a GRB with emission of internal origin visible for a long time. Furthermore, we break down the energy budget of this GRB into the prompt emission, the late internal dissipation, the kinetic energy of the relativistic ejecta, and compare it with the energy of the associated supernova, SN 2013 fu.

  10. GRB Studies with Fermi

    NASA Technical Reports Server (NTRS)

    Meegan, Charles A.

    2008-01-01

    This slide presentation reviews the studies of Gamma Ray Bursts (GRB) with the Fermi Gamma Ray Space Telescope. Included are pictures of the observatory, with illustrations of the Large Area Telescope (LAT), and the Gamma-ray Burst Monitor (GBM) including information about both their capabilities. Graphs showing the GBM count rate over time after the GBM trigger for three GRBs, preliminary charts showing the multiple detector light curves the spectroscopy of the main LAT peak and the spectral evolution of GRB 080916C Burst Temporally-extended LAT emission.

  11. GRB 050117: Simultaneous Gamma-ray and X-ray Observations with the Swift Satellite

    NASA Technical Reports Server (NTRS)

    Hill, J. E.; Morris, D. C.; Sakamoto, T.; Sato, G.; Burrows, D. N.; Angelini, L.; Pagani, C.; Moretti, A.; Abbey, A. F.; Barthelmy, S.

    2005-01-01

    The Swift Gamma-Ray Burst Explorer performed its first autonomous, X-ray follow-up to a newly detected GRB on 2005 January 17, within 193 seconds of the burst trigger by the Swift Burst Alert Telescope. While the burst was still in progress, the X-ray Telescope obtained a position and an image for an un-catalogued X-ray source; simultaneous with the gamma-ray observation. The XRT observed flux during the prompt emission was 1.1 x 10(exp -8) ergs/sq cm/s in the 0.5-10 keV energy band. The emission in the X-ray band decreased by three orders of magnitude within 700 seconds, following the prompt emission. This is found to be consistent with the gamma-ray decay when extrapolated into the XRT energy band. During the following 6.3 hours, the XRT observed the afterglow in an automated sequence for an additional 947 seconds, until the burst became fully obscured by the Earth limb. A faint, extremely slowly decaying afterglow, alpha=-0.21, was detected. Finally, a break in the lightcurve occurred and the flux decayed with alpha<-1.2. The X-ray position triggered many follow-up observations: no optical afterglow could be confirmed, although a candidate was identified 3 arcsecs from the XRT position.

  12. A search for pulsations from the compact object of GRB 060218

    NASA Astrophysics Data System (ADS)

    Mirabal, N.; Gotthelf, E. V.

    2010-02-01

    Aims: A fraction of massive stars are expected to collapse into compact objects (accreting black holes or rapidly rotating neutron stars) that successfully produce gamma-ray bursts (GRBs). We examine the possibility of directly observing these gamma-ray burst compact objects (GCOs) using post-explosion observations of past and future GRB sites. Methods: We present a search for early pulsations from the nearby (z=0.0335) gamma-ray burst GRB 060218, which exhibited features possibly consistent with a rapidly spinning neutron star as its underlying GCO. We also consider alternative techniques that could potentially achieve a detection of GCOs either in the Local Volume or near the plane of our own Galaxy. Results: We report the non-detection of pulsations from the GCO of GRB 060218. In particular, fast fourier transform analysis applied to the light curve shows no significant power over the range of frequencies 0.78 mHz < f < 227 Hz with an upper limit on the pulsed fraction of ~2%. In addition, we present detection limits of current high-resolution archival X-ray images of galaxies within the Local Volume. The existing data could be harnessed to rule out the presence of any background contaminants at the GRB position of future nearby events. Conclusions: The null detection of pulsations from the GCO of GRB 060218 is most likely explained by the fact that the afterglow emission occurs near the head of the jet and should be far removed from the compact object. We also find that the comparison of pre- and post-explosion explosion images of future GRBs within the Local Volume, as well as the firm identification of a GCO within an ancient GRB remnant near the Galactic plane are extremely challenging with current GeV/TeV capabilities. Finally, we conclude that only under some very exceptional circumstances will it be possible to directly detect the compact object responsible for gamma-ray bursts.

  13. GRB 050717: A Long, Short-Lag Burst Observed by Swift and Konus

    NASA Technical Reports Server (NTRS)

    Krimm, H. A.; Hurkett, C.; Pal'shin, V.; Norris, J. P.; Zhang, B.; Barthelmy, S. D.; Burrows, D. N.; Gehrels, N.; Golenetskii, S.; Osborne, J. P.; Parsons, A. M.; Perri, M.; Willingale, R.

    2005-01-01

    The long burst GRB 050717 was observed simultaneously by the Burst Alert Telescope (BAT) on Swift and the Konus instrument on Wind. Significant hard to soft spectral evolution was seen. Early gamma-ray and X-ray emission was detected by both BAT and the X-Ray Telescope (XRT) on Swift. The XRT continued to observe the burst for 7.1 days and detect it for 1.4 days. The X-ray light curve showed a classic decay pattern including evidence of the onset of the external shock emission at approx. 50 s after the trigger; the afterglow was too faint for a jet break to be detected. No optical, infrared or ultraviolet counterpart was discovered despite deep searches within 14 hours of the burst. The spectral lag for GRB 050717 was determined to be 2.5 +/- 2.6 ms, consistent, with zero and unusually short for a long burst. This lag measurement suggests that this burst has a high intrinsic luminosity and hence is at high redshift (z > 2.7). 050717 provides a good example of classic prompt and afterglow behavior for a gamma-ray burst.

  14. RAPTOR: Closed-Loop monitoring of the night sky and the earliest optical detection of GRB 021211

    NASA Astrophysics Data System (ADS)

    Vestrand, W. T.; Borozdin, K.; Casperson, D. J.; Fenimore, E.; Galassi, M.; McGowan, K.; Starr, D.; White, R. R.; Wozniak, P.; Wren, J.

    2004-10-01

    We discuss the RAPTOR (Rapid Telescopes for Optical Response) sky monitoring system at Los Alamos National Laboratory. RAPTOR is a fully autonomous robotic system that is designed to identify and make follow-up observations of optical transients with durations as short as one minute. The RAPTOR design is based on Biomimicry of Human Vision. The sky monitor is composed of two identical arrays of telescopes, separated by 38 kilometers, which stereoscopically monitor a field of about 1300 square-degrees for transients. Both monitoring arrays are carried on rapidly slewing mounts and are composed of an ensemble of wide-field telescopes clustered around a more powerful narrow-field telescope called the ``fovea'' telescope. All telescopes are coupled to real-time analysis pipelines that identify candidate transients and relay the information to a central decision unit that filters the candidates to find real celestial transients and command a response. When a celestial transient is found, the system can point the fovea telescopes to any position on the sky within five seconds and begin follow-up observations. RAPTOR also responds to Gamma Ray Burst (GRB) alerts generated by GRB monitoring spacecraft. Here we present RAPTOR observations of GRB 021211 that constitute the earliest detection of optical emission from that event and are the second fastest achieved for any GRB. The detection of bright optical emission from GRB021211, a burst with modest gamma-ray fluence, indicates that prompt optical emission, detectable with small robotic telescopes, is more common than previously thought. Further, the very fast decline of the optical afterglow from GRB 021211 suggests that some so-called ``optically dark'' GRBs were not detected only because of the slow response of the follow-up telescopes.

  15. CGRO/BATSE Data Support the New Paradigm for GRB Prompt Emission and the New LinTh-Epeak,inTh,rest Relation

    NASA Astrophysics Data System (ADS)

    Guiriec, S.; Gonzalez, M. M.; Sacahui, J. R.; Kouveliotou, C.; Gehrels, N.; McEnery, J.

    2016-03-01

    The paradigm for gamma-ray burst (GRB) prompt emission is changing. Since early in the Compton Gamma Ray Observatory (CGRO) era, the empirical Band function has been considered a good description of the keV-MeV γ-ray prompt emission spectra despite the fact that its shape was very often inconsistent with the theoretical predictions, especially those expected in pure synchrotron emission scenarios. We have recently established a new observational model analyzing data of the NASA Fermi Gamma-ray Space Telescope. In this model, GRB prompt emission would be a combination of three main emission components: (i) a thermal-like component that we have interpreted so far as emission from the jet photosphere, (ii) a non-thermal component that we have interpreted so far as either synchrotron radiation from the propagating and accelerated charged particles within the jet or reprocessed jet photospheric emission, and (iii) an additional non-thermal (cutoff) power law (PL) extending from low to high energies in γ-rays and most likely of inverse Compton origin. In this article we reanalyze some of the bright GRBs, namely GRBs 941017, 970111, and 990123, observed with the Burst And Transient Source Experiment (BATSE) on board CGRO with the new model. We conclude that BATSE data for these three GRBs are fully consistent with the recent results obtained with Fermi: some bright BATSE GRBs exhibit three separate components during the prompt phase with similar spectral parameters as those reported from Fermi data. In addition, the analysis of the BATSE GRBs with the new prompt emission model results in a relation between the time-resolved energy flux of the non-thermal component, {F}{{i}}{nTh}, and its corresponding νF{}ν spectral peak energy, {E}{peak,{{i}}}{nTh} (i.e., {F}{{i}}{nTh}-{E}{peak,{{i}}}{nTh}), which has a similar index—when fitted to a PL—as the one initially derived from Fermi data. For GRBs with known redshifts (z) this results in a possible universal relation

  16. The Decay of Optical Emission Form the Gamma-Ray Burst GRB 970228

    NASA Technical Reports Server (NTRS)

    Galama, T.; Groot, P. J.; vanParadijs, J.; Kouvellotou, C.; Robinson, C. R.; Fishmans, G. J.; Meegan, C. A.; Sahu, K. C.; Livio, M.; Petro, L.

    1997-01-01

    The origin of gamma-ray bursts has been one of the great unsolved mysteries in high-energy astrophysics for almost 30 years. The recent discovery of fading sources at X-ray and optical wave-lengths coincident with the location of the gamma-ray burst GRB970228 therefore provides an unprecedented opportunity to probe the nature of these high-energy events. The optical counterpart appears to be a transient point source embedded in a region of extended nebulosity, the latter having been tentatively identified as a high-redshift galaxy. This would seem to favour models that place gamma-ray bursts at cosmological distances, although a range of mechanisms for producing the bursts is still allowed. A crucial piece of information for distinguishing between such models is how the brightness of the optical counterpart evolves with time. Here we re-evaluate the existing photometry of the optical counterpart of GRB970228 to construct an optical light curve for the transient event. We find that between 21 hours and six days after the burst, the R-band brightness decreased by a factor of approx. 50, with any subsequent decrease in brightness occurring at a much slower rate. As the point source faded, it also became redder. The initial behaviour of the source appears to be consistent with the 'fireball' model, in which the burst results from the merger of two neutron stars, but the subsequent decrease in the rate of fading may prove harder to explain. The gamma-ray burst of 28 February 1997, detected with the Gamma-Ray Burst Monitor on board the BeppoSAX satellite, and located with an approx. 3 feet radius position with the Wide Field Camera on the same satellite, was the first for which a fading X-ray and optical counterpart were discovered. The optical Counterpart was discovered from a comparison of V- and I-band images taken with the William Herschel Telescope (WHT) on February 28.99 UT, and the Isaac Newton Telescope (INT; V band) and the WHT (I band) on March 8.8 uT.

  17. High energy emission of GRB 130821A: Constraining the density profile of the circum-burst medium as well as the initial Lorentz factor of the outflow

    SciTech Connect

    Liang, Yun-Feng; Zhou, Bei; He, Hao-Ning; Fan, Yi-Zhong; Wei, Da-Ming; Tam, Pak-Hin Thomas

    2014-02-01

    GRB 130821A was detected by Fermi-GBM/LAT, Konus-WIND, SPI-ACS/INTEGRAL, RHESSI and Mars Odyssey-HEND. Although the data of GRB 130821A are very limited, we show in this work that the high energy γ-ray emission (i.e., above 100 MeV) alone imposes tight constraint on the density profile of the circum-burst medium as well as the initial Lorentz factor of the outflow. The temporal behavior of the high energy γ-ray emission is consistent with the forward shock synchrotron radiation model, and the circum-burst medium likely has a constant-density profile. The Lorentz factor is about a few hundred, similar to other bright GRBs.

  18. Spectroscopy of the short-hard GRB 130603B. The host galaxy and environment of a compact object merger

    NASA Astrophysics Data System (ADS)

    de Ugarte Postigo, A.; Thöne, C. C.; Rowlinson, A.; García-Benito, R.; Levan, A. J.; Gorosabel, J.; Goldoni, P.; Schulze, S.; Zafar, T.; Wiersema, K.; Sánchez-Ramírez, R.; Melandri, A.; D'Avanzo, P.; Oates, S.; D'Elia, V.; De Pasquale, M.; Krühler, T.; van der Horst, A. J.; Xu, D.; Watson, D.; Piranomonte, S.; Vergani, S. D.; Milvang-Jensen, B.; Kaper, L.; Malesani, D.; Fynbo, J. P. U.; Cano, Z.; Covino, S.; Flores, H.; Greiss, S.; Hammer, F.; Hartoog, O. E.; Hellmich, S.; Heuser, C.; Hjorth, J.; Jakobsson, P.; Mottola, S.; Sparre, M.; Sollerman, J.; Tagliaferri, G.; Tanvir, N. R.; Vestergaard, M.; Wijers, R. A. M. J.

    2014-03-01

    Context. Short duration gamma-ray bursts (SGRBs) are thought to be related to the violent merger of compact objects, such as neutron stars or black holes, which makes them promising sources of gravitational waves. The detection of a "kilonova"-likesignature associated to the Swift-detected GRB 130603B has suggested that this event is the result of a compact object merger. Aims: Our knowledge on SGRB has been, until now, mostly based on the absence of supernova signatures and the analysis of the host galaxies to which they cannot always be securely associated. Further progress has been significantly hampered by the faintness and rapid fading of their optical counterparts (afterglows), which has so far precluded spectroscopy of such events. Afterglow spectroscopy is the key tool to firmly determine the distance at which the burst was produced, crucial to understand its physics, and study its local environment. Methods: Here we present the first spectra of a prototypical SGRB afterglow in which both absorption and emission features are clearly detected. Together with multi-wavelength photometry we study the host and environment of GRB 130603B. Results: From these spectra we determine the redshift of the burst to be z = 0.3565 ± 0.0002, measure rich dynamics both in absorption and emission, and a substantial line of sight extinction of AV = 0.86 ± 0.15 mag. The GRB was located at the edge of a disrupted arm of a moderately star forming galaxy with near-solar metallicity. Unlike for most long GRBs (LGRBs), NHX/AV is consistent with the Galactic ratio, indicating that the explosion site differs from those found in LGRBs. Conclusions: The merger is not associated with the most star-forming region of the galaxy; however, it did occur in a dense region, implying a rapid merger or a low natal kick velocity for the compact object binary. Appendices are available in electronic form at http://www.aanda.org

  19. Super-solar metallicity at the position of the ultra-long GRB 130925A

    NASA Astrophysics Data System (ADS)

    Schady, P.; Krühler, T.; Greiner, J.; Graham, J. F.; Kann, D. A.; Bolmer, J.; Delvaux, C.; Elliott, J.; Klose, S.; Knust, F.; Nicuesa Guelbenzu, A.; Rau, A.; Rossi, A.; Savaglio, S.; Schmidl, S.; Schweyer, T.; Sudilovsky, V.; Tanga, M.; Tanvir, N. R.; Varela, K.; Wiseman, P.

    2015-07-01

    Over the last decade there has been immense progress in the follow-up of short and long gamma-ray bursts (GRBs), resulting in a significant rise in the detection rate of X-ray and optical afterglows, in the determination of GRB redshifts, and of the identification of the underlying host galaxies. Nevertheless, our theoretical understanding of the progenitors and central engines powering these vast explosions is lagging behind, and a newly identified class of ultra-long GRBs has fuelled speculation on the existence of a new channel of GRB formation. In this paper we present high signal-to-noise X-Shooter observations of the host galaxy of GRB 130925A, which is the fourth unambiguously identified ultra-long GRB, with prompt γ-ray emission detected for ~20 ks. The GRB line of sight was close to the host galaxy nucleus, and our spectroscopic observations cover this region along the bulge/disk of the galaxy and a bright star-forming region within the outskirts of the galaxy. From our broad wavelength coverage, we obtain accurate metallicity and dust-extinction measurements at the galaxy nucleus and at an outer star-forming region, and measure a super-solar metallicity at both locations, placing this galaxy within the 10-20% most metal-rich GRB host galaxies. Such a high metal enrichment has significant implications on the progenitor models of both long and ultra-long GRBs, although the edge-on orientation of the host galaxy does not allow us to rule out a large metallicity variation along our line of sight. The spatially resolved spectroscopic observations presented in this paper offer important insight into variations in the metal and dust abundance within GRB host galaxies. However, they also illustrate the need for integral field unit observations on a larger sample of GRB host galaxies of a variety of metallicities to provide a more quantitative view on the relation between the GRB circumburst environment and the galaxy-whole properties. Based on observations taken

  20. PROMPT GeV EMISSION FROM RESIDUAL COLLISIONS IN GAMMA-RAY BURST OUTFLOWS: EVIDENCE FROM FERMI OBSERVATIONS OF GRB 080916c

    SciTech Connect

    Li Zhuo

    2010-01-20

    The gamma-rays from gamma-ray bursts (GRBs) are believed to be produced by internal shocks driven by small timescale, approx1 ms, variation in the GRB outflows, and a pair-production spectral cutoff is generally expected around the GeV range. However, the observed optical flashes accompanying GRBs suggest that the delayed residual collisions due to large timescale variation continue to accelerate electrons. We show here that the inverse-Compton (IC) scattering of the prompt gamma-rays by these residual internal shock electrons leads to a high-energy emission beyond the previously thought spectral cutoff, in agreement with the previous detections of GeV photons by EGRET in several GRBs in conjunction with MeV emission. We expect a spectral break due to the transition from the primary to residual internal shock emission at the previously thought spectral cutoff and expect systematic time delays of high-energy photons relative to MeV emission, the discovery of which would provide stringent constraint on the outflow properties, but requires large enough collection of high-energy photons by, e.g., Fermi and AGILE satellites. The recent Fermi-detected bright GRB 080916c unambiguously shows the shifting of the prompt emission toward later times as the photon energy increases. The second-scale shifting at >100 MeV is much longer than the MeV variability time, as predicted in the residual collision model. The observations imply that there should be emission above 70 GeV in the source frame, which may not be produced by primary internal shocks but by IC emission in residual collisions. With the method involving time delays of high-energy emission, the bulk Lorentz factor of GRB 080916c is determined to be GAMMA approx 300.

  1. Jet or shock breakout? The low-luminosity GRB 060218

    NASA Astrophysics Data System (ADS)

    Irwin, Christopher M.; Chevalier, Roger A.

    2016-08-01

    We consider a model for the low-luminosity gamma-ray burst GRB 060218 that plausibly accounts for multiwavelength observations to day 20. The model components are: (1) a long-lived (tj ˜ 3000 s) central engine and accompanying low-luminosity (Lj ˜ 1047 erg s-1), mildly relativistic (γ ˜ 10) jet; (2) a low-mass (˜4 × 10-3 M⊙) envelope surrounding the progenitor star; and (3) a modest amount of dust (AV ˜ 0.1 mag) in the circumstellar or interstellar environment. Blackbody emission from the transparency radius in a low-power jet outflow can fit the prompt thermal X-ray emission, and the non-thermal X-rays and gamma-rays may be produced via Compton scattering of thermal photons from hot leptons in the jet interior or the external shocks. The later mildly relativistic phase of this outflow can produce the radio emission via synchrotron radiation from the forward shock. Meanwhile, interaction of the associated SN 2006aj with a circumstellar envelope extending to ˜1013 cm can explain the early optical emission. The X-ray afterglow can be interpreted as a light echo of the prompt emission from dust at ˜30 pc. Our model is a plausible alternative to that of Nakar, who recently proposed shock breakout of a jet smothered by an extended envelope as the source of prompt emission. Both our results and Nakar's suggest that bursts such as GRB 060218 may originate from unusual progenitors with extended circumstellar envelopes, and that a jet is necessary to decouple the prompt emission from the supernova.

  2. The plateau phase of gamma-ray burst afterglows in the thick-shell scenario

    NASA Astrophysics Data System (ADS)

    Leventis, K.; Wijers, R. A. M. J.; van der Horst, A. J.

    2014-01-01

    We present analytic calculations of synchrotron radiation from the forward and the reverse shock of gamma-ray burst blast waves, in the thick-shell scenario (i.e. when the reverse shock is relativistic). We show that this scenario can naturally account for the plateau phase, observed early in the afterglows of about half the bursts detected by Swift. We generalize our approach to include power-law luminosity of the central engine and show that when radiation from both regions (forward and reverse shock) is taken into account, a wide range of possibilities emerge, including chromatic and achromatic breaks, frequency-dependent spectral evolution during the injection break and widely varying decay indices in different bands. For both the forward and the reverse shock, we derive formulas for the spectral parameters and the observed flux in different power-law segments of the spectrum, as a function of observer time. We explore the Fb-tb relation (between the observed time of the end of the plateau phase and the flux at that point) in the framework of the presented model and show that model predictions favour the reverse shock as the dominant source of emission in both optical and X-rays. As case studies, we present simultaneous fits to X-ray and optical/IR afterglow data of GRB 080928 and GRB 090423. We identify the end of the plateau phase with the cessation of energy injection and infer the corresponding upper limits to central-engine activity, which are about 1 h for the former and 1.5 h for the latter. We conclude that smooth energy injection through the reverse shock is a plausible explanation for the plateau phase of gamma-ray burst afterglows. During that phase, radiation from the reverse shock is likely to be important, or even dominant, and should be taken into account when fitting model parameters to observations.

  3. The circumburst density profile around GRB progenitors: a statistical study

    NASA Astrophysics Data System (ADS)

    Schulze, S.; Klose, S.; Björnsson, G.; Jakobsson, P.; Kann, D. A.; Rossi, A.; Krühler, T.; Greiner, J.; Ferrero, P.

    2011-02-01

    According to our present understanding, long gamma-ray bursts (GRBs) originate from the collapse of massive stars, while short bursts are caused by to the coalescence of compact stellar objects. Because the afterglow evolution is determined by the circumburst density profile, n(r), traversed by the fireball, it can be used to distinguish between a constant density medium, n(r) = const., and a free stellar wind, n(r) ∝ r-2. Our goal is to derive the most probable circumburst density profile for a large number of Swift-detected bursts using well-sampled afterglow light curves in the optical and X-ray bands. We combined all publicly available optical and Swift/X-ray afterglow data from June 2005 to September 2009 to find the best-sampled late-time afterglow light curves. After applying several selection criteria, our final sample consists of 27 bursts, including one short burst. The afterglow evolution was then studied within the framework of the fireball model. We find that the majority (18) of the 27 afterglow light curves are compatible with a constant density medium (ISM case). Only 6 of the 27 afterglows show evidence of a wind profile at late times. In particular, we set upper limits on the wind termination-shock radius, RT, for GRB fireballs that are propagating into an ISM profile and lower limits on RT for those that were found to propagate through a wind medium. Observational evidence for ISM profiles dominates in GRB afterglow studies, implying that most GRB progenitors might have relatively small wind termination-shock radii. A smaller group of progenitors, however, seems to be characterised by significantly more extended wind regions. Appendices are only available in electronic form at http://www.aanda.org

  4. GRB 080319B: A Naked-Eye Stellar Blast from the Distant Universe

    SciTech Connect

    Racusin, J. L.; Burrows, D. N.

    2008-10-22

    On behalf of a large international collaboration [1], we present the unprecedented broadband observations of GRB 080319B, whose prompt optical emission peaked at a visual magnitude of 5.3, making it briefly visible with the naked eye. GRB 080319B was discovered by Swift and captured in exquisite detail by ground based wide-field telescopes, imaging the burst location from before the time of the explosion. The combination of these unique optical data with simultaneous {gamma}-ray observations provides powerful diagnostics of the detailed physics of this explosion within seconds of its formation. We show that the prompt optical and {gamma}-ray emissions from this event arise from different spectral components within the same physical region located at a large distance from the source, implying an extremely relativistic outflow. Our observations also provide good evidence for a bright reverse shock component. The chromatic behavior of the broadband afterglow is consistent with viewing the GRB down the very narrow inner core of a two-component jet that is expanding into a wind-like environment consistent with the massive star origin of long GRBs.

  5. Prompt GRB optical follow-up experiments

    SciTech Connect

    Park, H-S; Williams, G; Ables, E; Band, D; Barthelmy, S; Bionta, R; Cline, T; Gehrels, N; Hartmann, D; Hurley, K; Kippen, M; Nemiroff, R; Pereira, W; Porrata, R

    2000-11-13

    Gamma Ray Bursts (GRBs) are brief, randomly located, releases of gamma-ray energy from unknown celestial sources that occur almost daily. The study of GRBs has undergone a revolution in the past three years due to an international effort of follow-up observations of coordinates provided by Beppo/SAX and IPN GRB. These follow-up observations have shown that GRBs are at cosmological distances and interact with surrounding material as described by the fireball model. However, prompt optical counterparts have only been seen in one case and are therefore very rare or much dimmer than the sensitivity of the current instruments. Unlike later time afterglows, prompt optical measurements would provide information on the GRB progenitor. LOTIS is the very first automated and dedicated telescope system that actively utilizes the GRB Coordinates Network (GCN) and it attempts to measure simultaneous optical light curve associated with GRBs. After 3 years of running, LOTIS has responded to 75 GRB triggers. The lack of any optical signal in any of the LOTIS images places numerical limits on the surrounding matter density, and other physical parameters in the environment of the GRB progenitor. This paper presents LOTIS results and describes other prompt GRB follow-up experiments including the Super-LOTIS at Kitt Peak in Arizona.

  6. Broadband observations of the naked-eye gamma-ray burst GRB 080319B.

    PubMed

    Racusin, J L; Karpov, S V; Sokolowski, M; Granot, J; Wu, X F; Pal'shin, V; Covino, S; van der Horst, A J; Oates, S R; Schady, P; Smith, R J; Cummings, J; Starling, R L C; Piotrowski, L W; Zhang, B; Evans, P A; Holland, S T; Malek, K; Page, M T; Vetere, L; Margutti, R; Guidorzi, C; Kamble, A P; Curran, P A; Beardmore, A; Kouveliotou, C; Mankiewicz, L; Melandri, A; O'Brien, P T; Page, K L; Piran, T; Tanvir, N R; Wrochna, G; Aptekar, R L; Barthelmy, S; Bartolini, C; Beskin, G M; Bondar, S; Bremer, M; Campana, S; Castro-Tirado, A; Cucchiara, A; Cwiok, M; D'Avanzo, P; D'Elia, V; Valle, M Della; de Ugarte Postigo, A; Dominik, W; Falcone, A; Fiore, F; Fox, D B; Frederiks, D D; Fruchter, A S; Fugazza, D; Garrett, M A; Gehrels, N; Golenetskii, S; Gomboc, A; Gorosabel, J; Greco, G; Guarnieri, A; Immler, S; Jelinek, M; Kasprowicz, G; La Parola, V; Levan, A J; Mangano, V; Mazets, E P; Molinari, E; Moretti, A; Nawrocki, K; Oleynik, P P; Osborne, J P; Pagani, C; Pandey, S B; Paragi, Z; Perri, M; Piccioni, A; Ramirez-Ruiz, E; Roming, P W A; Steele, I A; Strom, R G; Testa, V; Tosti, G; Ulanov, M V; Wiersema, K; Wijers, R A M J; Winters, J M; Zarnecki, A F; Zerbi, F; Mészáros, P; Chincarini, G; Burrows, D N

    2008-09-11

    Long-duration gamma-ray bursts (GRBs) release copious amounts of energy across the entire electromagnetic spectrum, and so provide a window into the process of black hole formation from the collapse of massive stars. Previous early optical observations of even the most exceptional GRBs (990123 and 030329) lacked both the temporal resolution to probe the optical flash in detail and the accuracy needed to trace the transition from the prompt emission within the outflow to external shocks caused by interaction with the progenitor environment. Here we report observations of the extraordinarily bright prompt optical and gamma-ray emission of GRB 080319B that provide diagnostics within seconds of its formation, followed by broadband observations of the afterglow decay that continued for weeks. We show that the prompt emission stems from a single physical region, implying an extremely relativistic outflow that propagates within the narrow inner core of a two-component jet.

  7. A NEW CORRELATION BETWEEN GRB X-RAY FLARES AND THE PROMPT EMISSION

    SciTech Connect

    Sonbas, E.; MacLachlan, G. A.; Shenoy, A.; Dhuga, K. S.; Parke, W. C.

    2013-04-20

    From a sample of gamma-ray bursts (GRBs) detected by the Fermi and Swift missions, we have extracted the minimum variability timescales for temporal structures in the light curves associated with the prompt emission and X-ray flares. A comparison of this variability timescale with pulse parameters such as rise times, determined via pulse-fitting procedures, and spectral lags, extracted via the cross-correlation function, indicates a tight correlation between these temporal features for both the X-ray flares and the prompt emission. These correlations suggest a common origin for the production of X-ray flares and the prompt emission in GRBs.

  8. A Statistical Study of GRB X-Ray Flares: Evidence of Ubiquitous Bulk Acceleration in the Emission Region

    NASA Astrophysics Data System (ADS)

    Jia, Lan-Wei; Uhm, Z. Lucas; Zhang, Bing

    2016-07-01

    When emission in a conical relativistic jet ceases abruptly (or decays sharply), the observed decay light curve is controlled by the high-latitude “curvature effect.” Recently, Uhm & Zhang found that the decay slopes of three gamma-ray burst (GRB) X-ray flares are steeper than what the standard model predicts. This requires bulk acceleration of the emission region, which is consistent with a Poynting-flux-dominated outflow. In this paper, we systematically analyze a sample of 85 bright X-ray flares detected in 63 Swift GRBs and investigate the relationship between the temporal decay index α and spectral index β during the steep decay phase of these flares. The α values depend on the choice of the zero time point t 0. We adopt two methods. “Method I” takes {t}0{{I}} as the first rising data point of each flare and is the most conservative approach. We find that at the 99.9% confidence level 56/85 flares have decay slopes steeper than the simplest curvature effect prediction and therefore are in the acceleration regime. “Method II” extrapolates the rising light curve of each flare backward until the flux density is three orders of magnitude lower than the peak flux density, and it defines the corresponding time as the zero time point ({t}0{{II}}). We find that 74/85 flares fall into the acceleration regime at the 99.9% confidence level. This suggests that bulk acceleration is common and may even be ubiquitous among X-ray flares, pointing toward a Poynting-flux-dominated jet composition for these events.

  9. A REVERSE SHOCK IN GRB 130427A

    SciTech Connect

    Laskar, T.; Berger, E.; Zauderer, B. A.; Margutti, R.; Soderberg, A. M.; Chakraborti, S.; Lunnan, R.; Chornock, R.; Chandra, P.; Ray, A.

    2013-10-20

    We present extensive radio and millimeter observations of the unusually bright GRB 130427A at z = 0.340, spanning 0.67-12 days after the burst. We combine these data with detailed multi-band UV, optical, NIR, and Swift X-ray observations and find that the broadband afterglow emission is composed of distinct reverse shock and forward shock contributions. The reverse shock emission dominates in the radio/millimeter and at ∼< 0.1 days in the UV/optical/NIR, while the forward shock emission dominates in the X-rays and at ∼> 0.1 days in the UV/optical/NIR. We further find that the optical and X-ray data require a wind circumburst environment, pointing to a massive star progenitor. Using the combined forward and reverse shock emission, we find that the parameters of the burst include an isotropic kinetic energy of E{sub K,{sub iso}} ≈ 2 × 10{sup 53} erg, a mass loss rate of M-dot ∼3×10{sup -8} M{sub ☉} yr{sup –1} (for a wind velocity of 1000 km s{sup –1}), and a Lorentz factor at the deceleration time of Γ(200 s) ≈ 130. Due to the low density and large isotropic energy, the absence of a jet break to ≈15 days places only a weak constraint on the opening angle, θ{sub j} ∼> 2.°5, and therefore a total energy of E{sub γ} + E{sub K} ∼> 1.2 × 10{sup 51} erg, similar to other gamma-ray bursts (GRBs). The reverse shock emission is detectable in this burst due to the low circumburst density, which leads to a slow cooling shock. We speculate that this property is required for the detectability of reverse shocks in radio and millimeter bands. Following on GRB 130427A as a benchmark event, observations of future GRBs with the exquisite sensitivity of the Very Large Array and ALMA, coupled with detailed modeling of the reverse and forward shock contributions, will test this hypothesis.

  10. ON PARTICLE ACCELERATION RATE IN GAMMA-RAY BURST AFTERGLOWS

    SciTech Connect

    Sagi, Eran; Nakar, Ehud

    2012-04-10

    It is well known that collisionless shocks are major sites of particle acceleration in the universe, but the details of the acceleration process are still not well understood. The particle acceleration rate, which can shed light on the acceleration process, is rarely measured in astrophysical environments. Here, we use observations of gamma-ray burst (GRB) afterglows, which are weakly magnetized relativistic collisionless shocks in ion-electron plasma, to constrain the rate of particle acceleration in such shocks. We find, based on X-ray and GeV afterglows, an acceleration rate that is most likely very fast, approaching the Bohm limit, when the shock Lorentz factor is in the range of {Gamma} {approx} 10-100. In that case X-ray observations may be consistent with no amplification of the magnetic field in the shock upstream region. We examine the X-ray afterglow of GRB 060729, which is observed for 642 days showing a sharp decay in the flux starting about 400 days after the burst, when the shock Lorentz factor is {approx}5. We find that inability to accelerate X-ray-emitting electrons at late time provides a natural explanation for the sharp decay, and that also in that case acceleration must be rather fast, and cannot be more than a 100 times slower than the Bohm limit. We conclude that particle acceleration is most likely fast in GRB afterglows, at least as long as the blast wave is ultrarelativistic.

  11. Linear and circular polarimetry observations of gamma-ray burst afterglows

    NASA Astrophysics Data System (ADS)

    Wiersema, K.

    2013-07-01

    Follow-up observations of large numbers of gamma-ray burst (GRB) afterglows, facilitated by the Swift satellite, have produced a large sample of spectral energy distributions and light curves, from which the basic micro- and macrophysical parameters of afterglows may be derived. However, a number of phenomena have been observed that defy explanation by simple versions of the standard fireball model, leading to a variety of new models. Polarimetry has shown great promise as a diagnosis of afterglow physics, probing the magnetic field properties of the afterglow and geometrical effects (e.g. jet breaks). Unfortunately, high quality polarimetry of a significant sample of afterglows is difficult to acquire, requiring specialised instrumentation and observing modes. In this talk I will review the recent successes in afterglow polarimetry, also showing first results of new instruments and observing campaigns. I will particularly focus on jet breaks.

  12. GLAST Prospects for Swift-Era Afterglows

    SciTech Connect

    Gou, L.J.; Meszaros, P.; /Penn State U.

    2011-11-23

    We calculate the GeV spectra of gamma-ray burst afterglows produced by inverse Compton scattering of these objects sub-MeV emission. We improve on earlier treatments by using refined afterglow parameters and new model developments motivated by recent Swift observations. We present time-dependent GeV spectra for standard, constant-parameter models, as well as for models with energy injection and with time-varying parameters, for a range of burst parameters. We evaluate the limiting redshift to which such afterglows can be detected by the GLAST Large Area Telescope, as well as by AGILE.

  13. Constraining Gamma-ray Burst Initial Lorentz Factor with the Afterglow Onset Feature and Discovery of a Tight Γ0-E γ,iso Correlation

    NASA Astrophysics Data System (ADS)

    Liang, En-Wei; Yi, Shuang-Xi; Zhang, Jin; Lü, Hou-Jun; Zhang, Bin-Bin; Zhang, Bing

    2010-12-01

    The onset of gamma-ray burst (GRB) afterglow is characterized by a smooth bump in the early afterglow light curve as the GRB fireball is decelerated by the circumburst medium. We extensively search for GRBs with such an onset feature in their optical and X-ray light curves from the literature and from the catalog established with the Swift/XRT. Twenty optically selected GRBs and 12 X-ray-selected GRBs are obtained, among which 17 optically selected and 2 X-ray-selected GRBs have redshift measurements. We fit these light curves with a smooth broken power law and measure the width (w), rising timescale (t r), and decaying timescale (t d) at full width at half-maximum. Strong mutual correlations among these timescales and with the peak time (t p) are found. The ratio t r/t d is almost universal among bursts, but the ratio t r/t p varies from 0.3 to ~1. The optical peak luminosity in the R band (L R,p) is anti-correlated with t p and w in the burst frame, indicating a dimmer and broader bump peaking at a later time. The isotropic prompt gamma-ray energy (E γ,iso) is also tightly correlated with L R,p and t p in the burst frame. Assuming that the bumps signal the deceleration of the GRB fireballs in a constant density medium, we calculate the initial Lorentz factor (Γ0) and the deceleration radius (R d) of the GRBs with redshift measurements. The derived Γ0 is typically a few hundreds, and the deceleration radius is R dec ~ 2 × 1017 cm. More intriguingly, a tight correlation between Γ0 and E γ,iso is found, namely Γ0 ~= 182(E γ,iso/1052 erg)0.25. This correlation also applies to the small sample of GRBs which show the signature of the afterglow onset in their X-ray afterglow, and to two bursts (GRBs 990123 and 080319B) whose early optical emission is dominated by a reverse shock. The lower limits of Γ0 derived from a sample of optical afterglow light curves showing a decaying feature from the beginning of the observation are also generally consistent with such

  14. Gamma-ray burst radio afterglows from Population III stars: simulation methods and detection prospects with SKA precursors

    NASA Astrophysics Data System (ADS)

    Macpherson, D.; Coward, D.

    2015-10-01

    We investigate the prospects of detecting radio afterglows from long Gamma-Ray Bursts (GRBs) from Population III (Pop III) progenitors using the Square Kilometre Array (SKA) precursor instruments MWA (Murchison Widefield Array) and ASKAP (Australian SKA Pathfinder). We derive a realistic model of GRB afterglows that encompasses the widest range of plausible physical parameters and observation angles. We define the best case scenario of Pop III GRB energy and redshift distributions. Using probability distribution functions fitted to the observed microphysical parameters of long GRBs, we simulate a large number of Pop III GRB afterglows to find the global probability of detection. We find that ASKAP may be able to detect 35 per cent of Pop III GRB afterglows in the optimistic case, and 27 per cent in the pessimistic case. A negligible number will be detectable by MWA in either case. Detections per image for ASKAP, found by incorporating intrinsic rates with detectable time-scales, are as high as ˜6000 and as low as ˜11, which shows the optimistic case is unrealistic. We track how the afterglow flux density changes over various time intervals and find that, because of their very slow variability, the cadence for blind searches of these afterglows should be as long as possible. We also find Pop III GRBs at high redshift have radio afterglow light curves that are indistinguishable from those of regular long GRBs in the more local Universe.

  15. Detection of GRB 060927 at zeta = 5.47: Implications for the Use of Gamma-Ray Bursts as Probes of the End of the Dark Ages

    NASA Technical Reports Server (NTRS)

    Ruiz-Velasco, A. E.; Swan, H.; Troja, E.; Malesani, D.; Fynbo, J. P. U.; Sterling, R. L. C.; Xu, D.; Aharonian, F.; Akerlof, C.; Andersen, M. I.; Ashley, M. C. B.; Barthelmy, S. D.; Bersier, D.; CastroCeron, J. M.; Castro-Tirado, A. J.; Gehrels, N.; Gogus, E.; Gorosabel, J.; Guidorzi, C.; Guver, T.; Hjorth, J.; Horns, D.; Huang, K. Y.; Jakobsson, P.; Jensen, B. L.

    2007-01-01

    We report on follow-up observations of the gamma-ray burst GRB 060927 using the robotic ROTSE-IIIa telescope and a suite of larger aperture groundbased telescopes. An optical afterglow was detected 20 s after the burst, the earliest rest-frame detection of optical emission from any GRB. Spectroscopy performed with the VLT about 13 hours after the trigger shows a continuum break at lambda approx. equals 8070 A, produced by neutral hydrogen absorption at zeta = 5.6. We also detect an absorption line at 8158 A which we interpret as Si II lambda 1260 at zeta = 5.467. Hence, GRB 060927 is the second most distant GRB with a spectroscopically measured redshift. The shape of the red wing of the spectral break can be fitted by a damped Ly(alpha) profile with a column density with log(N(sub HI)/sq cm) = 22.50 +/- 0.15. We discuss the implications of this work for the use of GRBs as probes of the end of the dark ages and draw three main conclusions: i) GRB afterglows originating from zeta greater than or approx. equal to 6 should be relatively easy to detect from the ground, but rapid near-infrared monitoring is necessary to ensure that they are found; ii) The presence of large H I column densities in some GRBs host galaxies at zeta > 5 makes the use of GRBs to probe the reionization epoch via spectroscopy of the red damping wing challenging; iii) GRBs appear crucial to locate typical star-forming galaxies at zeta > 5 and therefore the type of galaxies responsible for the reionization of the universe.

  16. Gamma-Ray Bursts: The Afterglow Revolution

    NASA Astrophysics Data System (ADS)

    Galama, Titus J.; Sari, Re'em

    GRBs were discovered with the Vela satellites, whose main purpose was to verify compliance with the 1963 Limited Nuclear Test Ban Treaty. Since their discovery these events, which emit the bulk of their energy in the 0.1 - 1.0 MeV range, and whose durations span milliseconds to tens of minutes, posed one of the great unsolved problems in astrophysics. GRBs are formed in extreme relativistic outflows and provide important information about highly relativistic acceleration mechanisms. Until 1997, no counterparts (quiescent as well as transient) could be found and observations did not provide a direct measurement of their distance. The breakthrough came in early 1997, when the Wide Field Cameras aboard the Italian-Dutch BeppoSAX satellite allowed rapid and accurate localization of GRBs. Follow-up on these positions resulted in the discovery of X-ray, optical and radio afterglows. These observations revealed that GRBs come from 'cosmological' distances, and that they are by far the most luminous photon sources in the Universe, with peak luminosities in γ rays up to 1052 erg/s, and total energy budgets up to several times 1053-54 erg (for assumed isotropic emission). Evidence is accumulating, however, that GRB outflow is collimated in the form of jets and when corrected for the geometry of the outflow the energies of GRBs appear to cluster around 5 x 1050 ergs- very comparable to that of supernovae. GRBs are rare phenomena with an overall rate about 2000 times smaller than that of supernovae. Indirect evidence in the last several years shows that a fraction of GRBs may be related to a peculiar type of supernova explosions. Theoretical work has shown that these supernovae most likely mark the birth events of stellar mass black holes as the final products of the evolution of very massive stars. A fundamental question is whether there are also other processes that can drive such an engine, for example the coalescence of a double neutron-star system. Finally, the

  17. Induced gravitational collapse in the BATSE era: The case of GRB 970828

    NASA Astrophysics Data System (ADS)

    Ruffini, R.; Izzo, L.; Bianco, C. L.; Rueda, J. A.; Barbarino, C.; Dereli, H.; Enderli, M.; Muccino, M.; Penacchioni, A. V.; Pisani, G. B.; Wang, Y.

    2015-07-01

    Following the recently established "Binary-driven HyperNova" (BdHN) model, we here interpret GRB 970828 in terms of the four episodes typical of such a model. The "Episode 1," up to 40 s after the trigger time t 0, with a time varying thermal emission and a total energy of Eiso,1st = 2.60 × 1053 erg, is interpreted as due to the onset of an hyper-critical accretion process onto a companion neutron star, triggered by the companion star, an FeCO core undergoing a SN explosion. The "Episode 2," observed up t 0 + 90 s, is interpreted as a canonical gamma ray burst, with an energy of erg, a baryon load of B = 7× 10-3 and a bulk Lorentz factor at transparency of G = 142.5. From this Episode 2, we infer that the GRB exploded in an environment with a large average particle density ≈103 particles/cm3 and dense clouds characterized by typical dimensions of (4-8) × 1014 cm and δn/n ~ 10. The "Episode 3" is identified from t 0 +90 s all the way up to 105-6 s: despite the paucity of the early X-ray data, typical in the BATSE, pre-Swift era, we find extremely significant data points in the late X-ray afterglow emission of GRB 970828, which corresponds to the ones observed in all BdHNe sources. The "Episode 4," related to the Supernova emission, does not appear to be observable in this source, due to the presence of darkening from the large density of the GRB environment, also inferred from the analysis of the Episode 2.

  18. An External Shock Origin of GRB 141028A

    NASA Astrophysics Data System (ADS)

    Burgess, J. Michael; Bégué, Damien; Ryde, Felix; Omodei, Nicola; Pe'er, Asaf; Racusin, J. L.; Cucchiara, A.

    2016-05-01

    The prompt emission of the long, smooth, and single-pulsed gamma-ray burst, GRB 141028A, is analyzed under the guise of an external shock model. First, we fit the γ-ray spectrum with a two-component photon model, namely, synchrotron+blackbody, and then fit the recovered evolution of the synchrotron νF ν peak to an analytic model derived considering the emission of a relativistic blast wave expanding into an external medium. The prediction of the model for the νF ν peak evolution matches well with the observations. We observe the blast wave transitioning into the deceleration phase. Furthermore, we assume the expansion of the blast wave to be nearly adiabatic, motivated by the low magnetic field deduced from the observations. This allows us to recover within an order of magnitude the flux density at the νF ν peak, which is remarkable considering the simplicity of the analytic model. Under this scenario we argue that the distinction between prompt and afterglow emission is superfluous as both early-time emission and late-time emission emanate from the same source. While the external shock model is clearly not a universal solution, this analysis opens the possibility that at least some fraction of GRBs can be explained with an external shock origin of their prompt phase.

  19. Limits on Optical Polarization during the Prompt Phase of GRB 140430A

    NASA Astrophysics Data System (ADS)

    Kopač, D.; Mundell, C. G.; Japelj, J.; Arnold, D. M.; Steele, I. A.; Guidorzi, C.; Dichiara, S.; Kobayashi, S.; Gomboc, A.; Harrison, R. M.; Lamb, G. P.; Melandri, A.; Smith, R. J.; Virgili, F. J.; Castro-Tirado, A. J.; Gorosabel, J.; Järvinen, A.; Sánchez-Ramírez, R.; Oates, S. R.; Jelínek, M.

    2015-11-01

    Gamma-ray burst GRB 140430A was detected by the Swift satellite and observed promptly with the imaging polarimeter RINGO3 mounted on the Liverpool Telescope, with observations beginning while the prompt γ-ray emission was still ongoing. In this paper, we present densely sampled (10-s temporal resolution) early optical light curves (LCs) in 3 optical bands and limits to the degree of optical polarization. We compare optical, X-ray, and gamma-ray properties and present an analysis of the optical emission during a period of high-energy flaring. The complex optical LC cannot be explained merely with a combination of forward and reverse shock emission from a standard external shock, implying additional contribution of emission from internal shock dissipation. We estimate an upper limit for time averaged optical polarization during the prompt phase to be as low as P < 12% (1σ). This suggests that the optical flares and early afterglow emission in this GRB are not highly polarized. Alternatively, time averaging could mask the presence of otherwise polarized components of distinct origin at different polarization position angles.

  20. LIMITS ON OPTICAL POLARIZATION DURING THE PROMPT PHASE OF GRB 140430A

    SciTech Connect

    Kopac, D.; Mundell, C. G.; Arnold, D. M.; Steele, I. A.; Kobayashi, S.; Lamb, G. P.; Smith, R. J.; Virgili, F. J.; Japelj, J.; Gomboc, A.; Guidorzi, C.; Dichiara, S.; Harrison, R. M.; Melandri, A.; Castro-Tirado, A. J.; Gorosabel, J.; Sánchez-Ramírez, R.; Oates, S. R.; Jelínek, M.

    2015-11-01

    Gamma-ray burst GRB 140430A was detected by the Swift satellite and observed promptly with the imaging polarimeter RINGO3 mounted on the Liverpool Telescope, with observations beginning while the prompt γ-ray emission was still ongoing. In this paper, we present densely sampled (10-s temporal resolution) early optical light curves (LCs) in 3 optical bands and limits to the degree of optical polarization. We compare optical, X-ray, and gamma-ray properties and present an analysis of the optical emission during a period of high-energy flaring. The complex optical LC cannot be explained merely with a combination of forward and reverse shock emission from a standard external shock, implying additional contribution of emission from internal shock dissipation. We estimate an upper limit for time averaged optical polarization during the prompt phase to be as low as P < 12% (1σ). This suggests that the optical flares and early afterglow emission in this GRB are not highly polarized. Alternatively, time averaging could mask the presence of otherwise polarized components of distinct origin at different polarization position angles.

  1. The signature of the central engine in the weakest relativistic explosions: GRB 100316D

    SciTech Connect

    Margutti, R.; Soderberg, A. M.; Sironi, L.; Zauderer, B. A.; Milisavljevic, D.; Kamble, A.; Wieringa, M. H.; Edwards, P. G.; Chevalier, R. A.; Morsony, B. J.; Duran, R. Barniol; Pian, E.

    2013-11-20

    We present late-time radio and X-ray observations of the nearby sub-energetic gamma-ray burst (GRB)100316D associated with supernova (SN) 2010bh. Our broad-band analysis constrains the explosion properties of GRB 100316D to be intermediate between highly relativistic, collimated GRBs and the spherical, ordinary hydrogen-stripped SNe. We find that ∼10{sup 49} erg is coupled to mildly relativistic (Γ = 1.5-2), quasi-spherical ejecta, expanding into a medium previously shaped by the progenitor mass-loss with a rate of M-dot ∼ 10{sup −5} M{sub ⊙} yr{sup −1} (for an assumed wind density profile and wind velocity v{sub w} = 1000 km s{sup –1}). The kinetic energy profile of the ejecta argues for the presence of a central engine and identifies GRB 100316D as one of the weakest central-engine-driven explosions detected to date. Emission from the central engine is responsible for an excess of soft X-ray radiation that dominates over the standard afterglow at late times (t > 10 days). We connect this phenomenology with the birth of the most rapidly rotating magnetars. Alternatively, accretion onto a newly formed black hole might explain the excess of radiation. However, significant departure from the standard fall-back scenario is required.

  2. On the Afterglow and Progenitor of FRB 150418

    NASA Astrophysics Data System (ADS)

    Zhang, Bing

    2016-05-01

    Keane et al. recently detected a fading radio source following FRB 150418, leading to the identification of a putative host galaxy at z = 0.492 ± 0.008. Assuming that the fading source is the afterglow of FRB 150418, I model the afterglow and constrain the isotropic energy of the explosion to be a few 1050 erg, comparable to that of a short-duration gamma-ray burst (GRB). The outflow may have a jet opening angle of ˜0.22 rad, so that the beaming-corrected energy is below 1049 erg. The results rule out most fast radio burst (FRB) progenitor models for this FRB, but may be consistent with either of the following two scenarios. The first scenario invokes a merger of an NS-NS binary, which produced an undetected short GRB and a supra-massive neutron star, which subsequently collapsed into a black hole, probably hundreds of seconds after the short GRB. The second scenario invokes a merger of a compact star binary (BH-BH, NS-NS, or BH-NS) system whose pre-merger dynamical magnetospheric activities made the FRB, which is followed by an undetected short GRB-like transient. The gravitational-wave (GW) event GW 150914 would be a sister of FRB 150418 in this second scenario. In both cases, one expects an exciting prospect of GW/FRB/GRB associations.

  3. GRB 090510: A DISGUISED SHORT GAMMA-RAY BURST WITH THE HIGHEST LORENTZ FACTOR AND CIRCUMBURST MEDIUM

    SciTech Connect

    Muccino, M.; Ruffini, R.; Bianco, C. L.; Izzo, L.; Penacchioni, A. V.; Pisani, G. B.

    2013-07-20

    GRB 090510, observed by both Fermi and AGILE satellites, is the first bright short-hard gamma-ray burst (GRB) with an emission from the keV up to the GeV energy range. Within the Fireshell model, we interpret the faint precursor in the light curve as the emission at the transparency of the expanding e {sup +} e {sup -} plasma: the Proper-GRB. From the observed isotropic energy, we assume a total plasma energy E{sup tot}{sub e{sup +}e{sup -}}=(1.10{+-}0.06) Multiplication-Sign 10{sup 53} erg and derive a Baryon load B = (1.45 {+-} 0.28) Multiplication-Sign 10{sup -3} and a Lorentz factor at transparency {Gamma}{sub tr} = (6.7 {+-} 1.6) Multiplication-Sign 10{sup 2}. The main emission {approx}0.4 s after the initial spike is interpreted as the extended afterglow, due to the interaction of the ultrarelativistic baryons with the CircumBurst Medium (CBM). Using the condition of fully radiative regime, we infer a CBM average spherically symmetric density of (n{sub CBM}) = (1.85 {+-} 0.14) Multiplication-Sign 10{sup 3} particles cm{sup -3}, one of the highest found in the Fireshell model. The value of the filling factor, 1.5 Multiplication-Sign 10{sup -10}{<=}R{<=}3.8 Multiplication-Sign 10{sup -8}, leads to the estimate of filaments with densities n{sub fil} = n{sub CBM}/R approx. (10{sup 6}-10{sup 14}) particles cm{sup -3}. The sub-MeV and the MeV emissions are well reproduced. When compared to the canonical GRBs with (n{sub CBM}) Almost-Equal-To 1 particles cm{sup -3} and to the disguised short GRBs with (n{sub CBM}) Almost-Equal-To 10{sup -3} particles cm{sup -3}, the case of GRB 090510 leads to the existence of a new family of bursts exploding in an overdense galactic region with (n{sub CBM}) Almost-Equal-To 10{sup 3} particles cm{sup -3}. The joint effect of the high {Gamma}{sub tr} and the high density compresses in time and 'inflates' in intensity the extended afterglow, making it appear as a short burst, which we here define as a 'disguised short GRB by excess

  4. Prompt and Afterglow Emmision Properties of Gamma-ray Bursts with Spectroscopically Identified Supernovae

    NASA Technical Reports Server (NTRS)

    Kaneko, Yuki; Ramirez-Ruiz, Enrico; Granot, Jonathan; Kouveliotou, Chryssa; Woosley, Stan E.; Patel, Sandeep K.; Rol, Evert; In'TZant, Jean J. M.; VanDerHorst, Alexander J.; Wijers, Ralph A. M. J.; Strom, Richard

    2007-01-01

    We present a detailed spectral analysis of the prompt and afterglow emission of four nearby long-soft gamma-ray bursts (GRBs 980425,030329,031203, and 060218) that were spectroscopically found to be associated with Type IC supernovae and compare them to the general GRB population. For each event, we investigate the spectral and luminosity evolution and estimate the total energy budget based on broadband observations. The observational inventory for these events has become rich enough to allow estimates of their energy content in relativistic and subrelativistic form. The result is a global portrait of the effects of the physical processes responsible for producing long-soft GRBs. In particular, we find that the values of the energy released in mildly relativistic out8ows appears to have a sigruficantly smaller scatter than those found in highly relativistic ejecta. This is consistent with a picture in which the energy released inside the progenitor star is roughly standard, while the fracti

  5. A late-time flattening of light curves in gamma-ray burst afterglows

    SciTech Connect

    Sironi, Lorenzo; Giannios, Dimitrios E-mail: dgiannio@purdue.edu

    2013-12-01

    The afterglow emission from gamma-ray bursts (GRBs) is usually interpreted as synchrotron radiation from relativistic electrons accelerated at the GRB external shock. We investigate the temporal decay of the afterglow emission at late times, when the bulk of the shock-accelerated electrons are non-relativistic (the 'deep Newtonian phase', as denoted by Huang and Cheng). We assume that the electron spectrum in the deep Newtonian phase is a power-law distribution in momentum with slope p, as dictated by the theory of Fermi acceleration in non-relativistic shocks. For a uniform circumburst medium, the deep Newtonian phase begins at t{sub DN}∼3 ϵ{sub e,−1}{sup 5/6}t{sub ST}, where t {sub ST} marks the transition of the blast wave to the non-relativistic, spherically symmetric Sedov-Taylor (ST) solution, and ε {sub e} = 0.1 ε {sub e,–1} quantifies the amount of shock energy transferred to the electrons. For typical parameters, the deep Newtonian stage starts ∼0.5 to several years after the GRB. The radio flux in this phase decays as F {sub ν}∝t {sup –3(p+1)/10}∝t {sup –(0.9÷1.2)}, for a power-law slope 2 < p < 3. This is shallower than the scaling F {sub ν}∝t {sup –3(5p–7)/10}∝t {sup –(0.9÷2.4)} derived by Frail et al., which only applies if the GRB shock is non-relativistic, but the electron distribution still peaks at ultra-relativistic energies (a regime that is relevant for a narrow time interval, and only if t {sub DN} ≳ t {sub ST}, namely, ε {sub e} ≳ 0.03). We discuss how the deep Newtonian phase can be reliably used for GRB calorimetry, and we comment on the good detection prospects of trans-relativistic blast waves at 0.1÷10 GHz with the Karl G. Jansky Very Large Array and LOw-Frequency ARray.

  6. A Late-time Flattening of Light Curves in Gamma-Ray Burst Afterglows

    NASA Astrophysics Data System (ADS)

    Sironi, Lorenzo; Giannios, Dimitrios

    2013-12-01

    The afterglow emission from gamma-ray bursts (GRBs) is usually interpreted as synchrotron radiation from relativistic electrons accelerated at the GRB external shock. We investigate the temporal decay of the afterglow emission at late times, when the bulk of the shock-accelerated electrons are non-relativistic (the "deep Newtonian phase," as denoted by Huang and Cheng). We assume that the electron spectrum in the deep Newtonian phase is a power-law distribution in momentum with slope p, as dictated by the theory of Fermi acceleration in non-relativistic shocks. For a uniform circumburst medium, the deep Newtonian phase begins at t{_{\\scriptsize {DN}}}\\sim 3\\,\\epsilon _{e,-1}^{5/6}t{_{\\scriptsize {ST}}}, where t ST marks the transition of the blast wave to the non-relativistic, spherically symmetric Sedov-Taylor (ST) solution, and epsilon e = 0.1 epsilon e, -1 quantifies the amount of shock energy transferred to the electrons. For typical parameters, the deep Newtonian stage starts ~0.5 to several years after the GRB. The radio flux in this phase decays as F νvpropt -3(p + 1)/10vpropt -(0.9÷1.2), for a power-law slope 2 < p < 3. This is shallower than the scaling F νvpropt -3(5p - 7)/10vpropt -(0.9÷2.4) derived by Frail et al., which only applies if the GRB shock is non-relativistic, but the electron distribution still peaks at ultra-relativistic energies (a regime that is relevant for a narrow time interval, and only if t DN >~ t ST, namely, epsilon e >~ 0.03). We discuss how the deep Newtonian phase can be reliably used for GRB calorimetry, and we comment on the good detection prospects of trans-relativistic blast waves at 0.1÷10 GHz with the Karl G. Jansky Very Large Array and LOw-Frequency ARray.

  7. GRB070610: A Curious Galactic Transient

    NASA Technical Reports Server (NTRS)

    Kasliwal, M. M.; Kulkrarni. S. R.; Cameron, P. B.; Nakar, E.; Ofek, E. O.; Rau, A.; Soderberg, A. M.; Campana, S.; Bloom, J. S.; Perley, D. A.; Pollack, L. K.; Barthelmy, S.; Cummings, J.; Gehrels, N.; Krimm, H. A.; Markwardt, C. B.; Sato, G.; Chandra, P.; Frail, D.; Fox, D. B.; Price, P. A.; Berger, E.; Krivonos, R. A.; Grebenev, S. A.; Sunyaev, R. A.

    2007-01-01

    GRB 070610 is a typical high-energy event with a duration of 5s.Yet within the burst localization we detect a highly unusual X-ray and optical transient, SwiftJ195509.6+261406. We see high amplitude X-ray and optical variability on very short time scares even at late times. Using near-infrared imaging assisted by a laser guide star and adaptive optics, we identified the counterpart of SwiftJl95509.6+261406. Late-time optical and near-infrared imaging constrain the spectral type of the counterpart to be fainter than a K-dwarf assuming it is of Galactic origin. It is possible that GRB 070610 and Swift J195509.6+261406 are unrelated sources. However, the absence of a typical X-ray afterglow from GRB 070610 in conjunction with the spatial and temporal coincidence of the two motivate us to suggest that the sources are related. The closest (imperfect) analog to Swift J195509.6+261406 is V4641 Sgr, an unusual black hole binary. We suggest that Swift J195509.6+261406 along with V4641 Sgr define a sub-class of stellar black hole binaries -- the fast X-ray novae. We further suggest that fast X-ray novae are associated with bursts of gamma-rays. If so, GRB 070610 defines a new class of celestial gamma-ray bursts and these bursts dominate the long-duration GRB demographics

  8. GRB 071112C: A Case Study of Different Mechanisms in X-Ray and Optical Temporal Evolution

    NASA Astrophysics Data System (ADS)

    Huang, K. Y.; Urata, Y.; Tung, Y. H.; Lin, H. M.; Xin, L. P.; Yoshida, M.; Zheng, W.; Akerlof, C.; Wang, S. Y.; Ip, W. H.; Lehner, M. J.; Bianco, F. B.; Kawai, N.; Kuroda, D.; Marshall, S. L.; Schwamb, M. E.; Qiu, Y.; Wang, J. H.; Wen, C. Y.; Wei, J.; Yanagisawa, K.; Zhang, Z. W.

    2012-03-01

    We present a study on GRB 071112C X-ray and optical light curves. In these two wavelength ranges, we have found different temporal properties. The R-band light curve showed an initial rise followed by a single power-law decay, while the X-ray light curve was described by a single power-law decay plus a flare-like feature. Our analysis shows that the observed temporal evolution cannot be described by the external shock model in which the X-ray and optical emission are produced by the same emission mechanism. No significant color changes in multi-band light curves and a reasonable value of the initial Lorentz factor (Γ0 = 275 ± 20) in a uniform interstellar medium support the afterglow onset scenario as the correct interpretation for the early R band rise. The result suggests that the optical flux is dominated by afterglow. Our further investigations show that the X-ray flux could be created by an additional feature related to energy injection and X-ray afterglow. Different theoretical interpretations indicate the additional feature in X-ray can be explained by either late internal dissipation or local inverse-Compton scattering in the external shock.

  9. An External Shock Origin of GRB 141028A

    NASA Astrophysics Data System (ADS)

    Burgess, Michael; Bégué, Damien

    2016-07-01

    The prompt emission of the long, smooth, and single-pulsed gamma-ray burst, GRB 141028A, is analyzed under the guise of an external shock model. First, we fit the γ-ray spectrum with a two-component photon model, namely synchrotron+blackbody, and then fit the recovered evolution of the synchrotron ν F_{ν} peak to an analytic model derived considering the emission of a relativistic blast-wave expanding into an external medium. The prediction of the model for the ν F_{ν} peak evolution matches well with the observations. We observe the blast-wave transitioning into the deceleration phase. Further we assume the expansion of the magnetic field deduced from the observations. This allows us to recover within an order of magnitude the flux density at the ν F_{ν} peak, which is remarkable considering the simplicity of the analytic model. Under this scenario we argue that the distinction between prompt and afterglow emission is superfluous as both early and late time emission emanate from the same source. While the external shock model is clearly not a universal solution, this analysis opens the possibility that at least some fraction of GRBs can be explained with an external shock origin of their prompt phase.

  10. DISCOVERY OF A TIGHT CORRELATION FOR GAMMA-RAY BURST AFTERGLOWS WITH 'CANONICAL' LIGHT CURVES

    SciTech Connect

    Dainotti, Maria Giovanna; Ostrowski, Michal; Willingale, Richard; Capozziello, Salvatore; Cardone, Vincenzo Fabrizio E-mail: mio@oa.uj.edu.p E-mail: capozziello@na.infn.i

    2010-10-20

    Gamma-ray bursts (GRBs) observed up to redshifts z>8 are fascinating objects to study due to their still unexplained relativistic outburst mechanisms and their possible use to test cosmological models. Our analysis of 77 GRB afterglows with known redshifts revealed a physical subsample of long GRBs with the canonical plateau breaking to power-law light curves with a significant luminosity L*{sub X}-break time T*{sub a} correlation in the GRB rest frame. This subsample forms approximately the upper envelope of the studied distribution. We have also found a similar relation for a small sample of GRB afterglows that belong to the intermediate class between the short and the long ones. It proves that within the full sample of afterglows there exist physical subclasses revealed here by tight correlations of their afterglow properties. The afterglows with regular ('canonical') light curves obey not only the mentioned tight physical scaling, but-for a given T*{sub a}-the more regular progenitor explosions lead to preferentially brighter afterglows.

  11. Fermi/GBM observations of the ultra-long GRB 091024. A burst with an optical flash

    NASA Astrophysics Data System (ADS)

    Gruber, D.; Krühler, T.; Foley, S.; Nardini, M.; Burlon, D.; Rau, A.; Bissaldi, E.; von Kienlin, A.; McBreen, S.; Greiner, J.; Bhat, P. N.; Briggs, M. S.; Burgess, J. M.; Chaplin, V. L.; Connaughton, V.; Diehl, R.; Fishman, G. J.; Gibby, M. H.; Giles, M. M.; Goldstein, A.; Guiriec, S.; van der Horst, A. J.; Kippen, R. M.; Kouveliotou, C.; Lin, L.; Meegan, C. A.; Paciesas, W. S.; Preece, R. D.; Tierney, D.; Wilson-Hodge, C.

    2011-04-01

    Aims: In this paper we examine gamma-ray and optical data of GRB 091024, a gamma-ray burst (GRB) with an extremely long duration of T90 ≈ 1020 s, as observed with the Fermi Gamma-ray Burst Monitor (GBM). Methods: We present spectral analysis of all three distinct emission episodes using data from Fermi/GBM. Because of the long nature of this event, many ground-based optical telescopes slewed to its location within a few minutes and thus were able to observe the GRB during its active period. We compare the optical and gamma-ray light curves. Furthermore, we estimate a lower limit on the bulk Lorentz factor from the variability and spectrum of the GBM light curve and compare it with that obtained from the peak time of the forward shock of the optical afterglow. Results: From the spectral analysis we note that, despite its unusually long duration, this burst is similar to other long GRBs, i.e. there is spectral evolution (both the peak energy and the spectral index vary with time) and spectral lags are measured. We find that the optical light curve is highly anti-correlated to the prompt gamma-ray emission, with the optical emission reaching the maximum during an epoch of quiescence in the prompt emission. We interpret this behavior as the reverse shock (optical flash), expected in the internal-external shock model of GRB emission but observed only in a handful of GRBs so far. The lower limit on the initial Lorentz factor deduced from the variability time scale (Γmin = 195_{-110+90}) is consistent within the error to the one obtained using the peak time of the forward shock (Γ0 = 120) and is also consistent with Lorentz factors of other long GRBs.

  12. Imprints of Electron-Positron Winds on the Multiwavelength Afterglows of Gamma-ray Bursts

    NASA Astrophysics Data System (ADS)

    Geng, J. J.; Wu, X. F.; Huang, Y. F.; Li, L.; Dai, Z. G.

    2016-07-01

    Optical rebrightenings in the afterglows of some gamma-ray bursts (GRBs) are unexpected within the framework of the simple external shock model. While it has been suggested that the central engines of some GRBs are newly born magnetars, we aim to relate the behaviors of magnetars to the optical rebrightenings. A newly born magnetar will lose its rotational energy in the form of Poynting-flux, which may be converted into a wind of electron-positron pairs through some magnetic dissipation processes. As proposed by Dai, this wind will catch up with the GRB outflow and a long-lasting reverse shock (RS) would form. By applying this scenario to GRB afterglows, we find that the RS propagating back into the electron-positron wind can lead to an observable optical rebrightening and a simultaneous X-ray plateau (or X-ray shallow decay). In our study, we select four GRBs (i.e., GRB 080413B, GRB 090426, GRB 091029, and GRB 100814A), of which the optical afterglows are well observed and show clear rebrightenings. We find that they can be well interpreted. In our scenario, the spin-down timescale of the magnetar should be slightly smaller than the peak time of the rebrightening, which can provide a clue to the characteristics of the magnetar.

  13. Fast-response optical and near-infrared GRB science with RATIR and RIMAS

    NASA Astrophysics Data System (ADS)

    Capone, John; RIMAS Collaboration, RATIR project Team

    2016-01-01

    As the Universe's most luminous transient events, long gamma-ray bursts (GRBs) are observed at cosmological distances. The afterglow emission generated by the burst's interaction with the surrounding medium presents the opportunity to study the local environment, as well as intervening systems. The transient nature of these events requires observations starting within minutes of the GRB to maximize the scientific opportunities.This dissertation work comprises efforts to advance the field with a new instrument, the Rapid Infrared Imager and Spectrograph (RIMAS). The optical design is complicated by the broad band coverage (0.97 to 2.39 microns) and the necessity of transmissive optics due to space and weight limitations on the telescope. Additionally, the entire optical system must be cooled to cryogenic temperatures to decrease the background from thermal emission. The completed instrument will be permanently installed on Lowell Observatory's new 4.3 meter Discovery Channel Telescope (DCT) located in Happy Jack, Arizona. The fast slew time of the telescope, combined with the instrument's ability to image in two bands simultaneously and switch to spectroscopic configurations in under a minute will allow observers to obtain photometric data within minutes and spectra within ~ ten minutes.In addition to instrumentation work on RIMAS's optics, early time photometric light curves have been studied primarily using data from the Reionization and Transients Infrared/Optical Project (RATIR). Early time photometric data in six optical and near-infrared (NIR) bands has allowed a study of color evolution in the early to late time SEDs. This study probes possible impacts of the GRB on the local medium as well as intrinsic changes in the afterglow emission.This work is made possible by the RATIR and RIMAS collaborations as well as financial support by the NSF.

  14. Afterglow Complex Plasma

    SciTech Connect

    Samarian, A. A.; Boufendi, L.; Mikikian, M.

    2008-09-07

    The review of the first detailed experimental and theoretical studies of complex plasma in RF discharge afterglow is presented. The studies have been done in a frame of FAST collaborative research project between Complex Plasma Laboratory of the University of Sydney and the GREMI laboratory of Universite d'Orleans. We examined the existing models of plasma decay, presents experimental observations of dust dynamics under different afterglow complex plasma conditions, presents the experimental data obtained (in particular the presence of positively charged particles in discharge afterglow), discusses the use of dust particles as a probe to study the diffusion losses in afterglow plasmas.

  15. An optical spectrum of the afterglow of a gamma-ray burst at a redshift of z = 6.295.

    PubMed

    Kawai, N; Kosugi, G; Aoki, K; Yamada, T; Totani, T; Ohta, K; Iye, M; Hattori, T; Aoki, W; Furusawa, H; Hurley, K; Kawabata, K S; Kobayashi, N; Komiyama, Y; Mizumoto, Y; Nomoto, K; Noumaru, J; Ogasawara, R; Sato, R; Sekiguchi, K; Shirasaki, Y; Suzuki, M; Takata, T; Tamagawa, T; Terada, H; Watanabe, J; Yatsu, Y; Yoshida, A

    2006-03-01

    The prompt gamma-ray emission from gamma-ray bursts (GRBs) should be detectable out to distances of z > 10 (ref. 1), and should therefore provide an excellent probe of the evolution of cosmic star formation, reionization of the intergalactic medium, and the metal enrichment history of the Universe. Hitherto, the highest measured redshift for a GRB has been z = 4.50 (ref. 5). Here we report the optical spectrum of the afterglow of GRB 050904 obtained 3.4 days after the burst; the spectrum shows a clear continuum at the long-wavelength end of the spectrum with a sharp cut-off at around 9,000 A due to Lyman alpha absorption at z approximately 6.3 (with a damping wing). A system of absorption lines of heavy elements at z = 6.295 +/- 0.002 was also detected, yielding the precise measurement of the redshift. The Si ii fine-structure lines suggest a dense, metal-enriched environment around the progenitor of the GRB.

  16. An optical spectrum of the afterglow of a gamma-ray burst at a redshift of z = 6.295.

    PubMed

    Kawai, N; Kosugi, G; Aoki, K; Yamada, T; Totani, T; Ohta, K; Iye, M; Hattori, T; Aoki, W; Furusawa, H; Hurley, K; Kawabata, K S; Kobayashi, N; Komiyama, Y; Mizumoto, Y; Nomoto, K; Noumaru, J; Ogasawara, R; Sato, R; Sekiguchi, K; Shirasaki, Y; Suzuki, M; Takata, T; Tamagawa, T; Terada, H; Watanabe, J; Yatsu, Y; Yoshida, A

    2006-03-01

    The prompt gamma-ray emission from gamma-ray bursts (GRBs) should be detectable out to distances of z > 10 (ref. 1), and should therefore provide an excellent probe of the evolution of cosmic star formation, reionization of the intergalactic medium, and the metal enrichment history of the Universe. Hitherto, the highest measured redshift for a GRB has been z = 4.50 (ref. 5). Here we report the optical spectrum of the afterglow of GRB 050904 obtained 3.4 days after the burst; the spectrum shows a clear continuum at the long-wavelength end of the spectrum with a sharp cut-off at around 9,000 A due to Lyman alpha absorption at z approximately 6.3 (with a damping wing). A system of absorption lines of heavy elements at z = 6.295 +/- 0.002 was also detected, yielding the precise measurement of the redshift. The Si ii fine-structure lines suggest a dense, metal-enriched environment around the progenitor of the GRB. PMID:16525466

  17. Multiwavelength observations of the energetic GRB 080810: detailed mapping of the broad-band spectral evolution

    NASA Astrophysics Data System (ADS)

    Page, K. L.; Willingale, R.; Bissaldi, E.; Postigo, A. De Ugarte; Holland, S. T.; McBreen, S.; O'Brien, P. T.; Osborne, J. P.; Prochaska, J. X.; Rol, E.; Rykoff, E. S.; Starling, R. L. C.; Tanvir, N. R.; van der Horst, A. J.; Wiersema, K.; Zhang, B.; Aceituno, F. J.; Akerlof, C.; Beardmore, A. P.; Briggs, M. S.; Burrows, D. N.; Castro-Tirado, A. J.; Connaughton, V.; Evans, P. A.; Fynbo, J. P. U.; Gehrels, N.; Guidorzi, C.; Howard, A. W.; Kennea, J. A.; Kouveliotou, C.; Pagani, C.; Preece, R.; Perley, D.; Steele, I. A.; Yuan, F.

    2009-11-01

    GRB 080810 was one of the first bursts to trigger both Swift and the Fermi Gamma-ray Space Telescope. It was subsequently monitored over the X-ray and UV/optical bands by Swift, in the optical by Robotic Optical Transient Search Experiment (ROTSE) and a host of other telescopes, and was detected in the radio by the Very Large Array. The redshift of z = 3.355 +/- 0.005 was determined by Keck/High Resolution Echelle Spectrometer (HIRES) and confirmed by RTT150 and NOT. The prompt gamma/X-ray emission, detected over 0.3-103 keV, systematically softens over time, with Epeak moving from ~600 keV at the start to ~40 keV around 100s after the trigger; alternatively, this spectral evolution could be identified with the blackbody temperature of a quasi-thermal model shifting from ~60 to ~3keV over the same time interval. The first optical detection was made at 38s, but the smooth, featureless profile of the full optical coverage implies that this is originated from the afterglow component, not from the pulsed/flaring prompt emission. Broad-band optical and X-ray coverage of the afterglow at the start of the final X-ray decay (~8ks) reveals a spectral break between the optical and X-ray bands in the range of 1015-2 × 1016Hz. The decay profiles of the X-ray and optical bands show that this break initially migrates blueward to this frequency and then subsequently drifts redward to below the optical band by ~3 × 105s. GRB 080810 was very energetic, with an isotropic energy output for the prompt component of 3 × 1053 and 1.6 × 1052 erg for the afterglow; there is no evidence for a jet break in the afterglow up to 6d following the burst. This paper is dedicated to the memory of Professor Martin Turner, who sadly passed away during its writing. Martin was an influential figure in X-ray Astronomy and an excellent PhD supervisor. He will be greatly missed. E-mail: kpa@star.le.ac.uk ‡ NASA postdoctoral program fellow.

  18. GRB 101225A: an unusual stellar death on Christmas Day

    NASA Astrophysics Data System (ADS)

    Thöne, C. C.; de Ugarte Postigo, A.; Fryer, C. L.; Page, K. L.; Gorosabel, J.; Aloy, M.; Perley, D.

    2013-05-01

    Gamma-ray bursts are usually followed by afterglows produced by synchrotron radiation which makes them detectable out to the far Universe. Here we present the unusual GRB 101225A, also named the ``Christmas burst'', an extremely long γ-ray burst followed by a bright X-ray afterglow and a peculiar optical counterpart. The X-ray spectrum shows an additional thermal component while the UV-optical-IR SED evolves as a cooling, expanding black-body until 10 days, after which a faint supernova emerges. With GTC/OSIRIS, we detect an extremely faint host galaxy 6 months after the burst.

  19. The Swift/Fermi GRB 080928 from 1 eV to 150 keV

    NASA Technical Reports Server (NTRS)

    Sonbas, Eda; Rossi, A.; Schulze, S.; Klose, S.; Kann, D. A.; Ferrero, P.; NicuesaGuelbenzu, A.; Rau, A.; Kruehler, T.; Greiner, J.; Schady, P.; Afonso, P. M. J.; Clemens, C.; Filgas, R.; KuepcuYoldas, A.; McBreen, S.; Olivares, F.; Szokoly, G.; Yoldas, A.; Krimm, H. A.; Johannesson, G.; Panaitescu, A.; Yuan, F.; Pandey, S. B.; Akerlof, C. W.

    2010-01-01

    We present the results of a comprehensive study of the Gamma-Ray Burst 080928 and of its afterglow. GRB 08092 was a long burst detected by Swift/BAT and Fermi/GBM, It is one of the exceptional cases where optical emission was already detected when the GRB itself was still radiating in the gamma-ray band. for nearly 100 seconds simultaneous optical X-ray and gamma-ray data provide a coverage of the spectral energy distribution of the transient source from about 1 eV to 150 keV. Here we analyze the prompt emission, constrain its spectral propertIes. and set lower limits on the initial Lorentz factor of the relativistic outflow, In particular. we show that the SED during the main prompt emission phase is in agreement with synchrotron radiation. We construct the optical/near-infrared light curve and the spectral energy distribution based on Swift/UVOT. ROTSE-Illa (Australia) and GROND (La Silla) data and compare it to the X-ray light curve retrieved from the Swift/XRT repository. We show that its bumpy shape can be modeled by multiple energy injections into the forward shock. Furthermore, we provide evidence that the temporal and spectral evolution of the first strong flare seen in the early X-ray light curve can be explained by large-angle emission. Finally, we report on the results of our search for the GRB host galaxy, for which only a deep upper limit can be provided.

  20. The radiative efficiency of relativistic jet and wind: a case study of GRB 070110

    NASA Astrophysics Data System (ADS)

    Du, Shuang; Lü, Hou-Jun; Zhong, Shu-Qing; Liang, En-Wei

    2016-11-01

    A rapidly spinning, strongly magnetized neutron star (NS) is invoked as the central engine for some gamma-ray bursts (GRBs), especially, the `internal plateau' feature of X-ray afterglow. However, for these `internal plateau' GRBs, how to produce their prompt emission remains an open question. Two different physical processes have been proposed in the literature, (1) a new-born NS is surrounded by a hyper-accreting and neutrino cooling disc, the GRB jet can be powered by neutrino annihilation aligning the spin axis; (2) a differentially rotating millisecond pulsar was formed due to different angular velocity between the interior core and outer shell parts of the NS, which can power an episodic GRB jet. In this paper, by analysing the data of one peculiar GRB 070110 (with internal plateau), we try to test which model is being favoured. By deriving the physical parameters of magnetar with observational data, the parameter regime for initial period (P0) and surface polar cap magnetic field (Bp) of the central NS are 0.96 ˜ 1.2 ms and (2.4 ˜ 3.7) × 1014 G, respectively. The radiative efficiency of prompt emission is about ηγ ˜ 6 per cent. However, the radiative efficiency of internal plateau (ηX) is larger than 31 per cent assuming the MNS ˜ 1.4 M⊙ and P0˜ 1.2 ms. The clear difference between the radiation efficiencies of prompt emission and internal plateau implies that they maybe originated from different components (e.g. prompt emission from the relativistic jet powered by neutrino annihilation, while the internal plateau from the magnetic outflow wind).

  1. Synchrotron radiation and diffusive shock acceleration - A short review and GRB perspective

    SciTech Connect

    Karlica, Mile

    2015-12-17

    In this talk we present the sponge” model and its possible implications on the GRB afterglow light curves. “Sponge” model describes source of GRB afterglow radiation as fragmented GRB ejecta where bubbles move through the rarefied medium. In the first part of the talk a short introduction to synchrotron radiation and Fermi acceleration was presented. In the assumption that X-ray luminosity of GRB afterglow phase comes from the kinetic energy losses of clouds in ejecta medium radiated as synchrotron radiation we solved currently very simple equation of motion to find which combination of cloud and medium regime describes the afterglow light curve the best. We proposed for the first step to watch simple combinations of expansion regimes for both bubbles and surrounding medium. The closest case to the numerical fit of GRB 150403A with time power law index k = 1.38 is the combination of constant bubbles and Sedov like expanding medium with time power law index k = 1.25. Of course the question of possible mixture of variuos regime combinations is still open within this model.

  2. The hidden X-ray breaks in afterglow light curves

    SciTech Connect

    Curran, P. A.; Wijers, R. A. M. J.; Horst, A. J. van der; Starling, R. L. C.

    2008-05-22

    Gamma-Ray Burst (GRB) afterglow observations in the Swift era have a perceived lack of achromatic jet breaks compared to the BeppoSAX, or pre-Swift era. Specifically, relatively few breaks, consistent with jet breaks, are observed in the X-ray light curves of these bursts. If these breaks are truly missing, it has serious consequences for the interpretation of GRB jet collimation and energy requirements, and the use of GRBs as standard candles.Here we address the issue of X-ray breaks which are possibly 'hidden' and hence the light curves are misinterpreted as being single power-laws. We show how a number of precedents, including GRB 990510 and GRB 060206, exist for such hidden breaks and how, even with the well sampled light curves of the Swift era, these breaks may be left misidentified. We do so by synthesising X-ray light curves and finding general trends via Monte Carlo analysis. Furthermore, in light of these simulations, we discuss how to best identify achromatic breaks in afterglow light curves via multi-wavelength analysis.

  3. Swift and GRB's: Unveiling the Relativistic Universe

    NASA Technical Reports Server (NTRS)

    Marshall, Francis E.

    2006-01-01

    We report Swift observations of GRB 051109A, a bright, long burst detected with BAT. A bright afterglow was quickly detected with the X-Ray Telescope and Ultraviolet and Optical Telescope, and observations continued for more than 10 days. The X-ray light is complex with a rapid initial decay followed by a more gradual decay. There is evidence for a jet break with an indicated opening angle of a few degrees. UVOT observations with the V filter are consistent with a power-law day for the first 10 ks. We discuss the observations in light of current models.

  4. THE ANTICIPATED SUPERNOVA ASSOCIATED WITH GRB 090618

    SciTech Connect

    Dado, Shlomo; Dar, Arnon E-mail: arnon@physics.technion.ac.il

    2010-01-10

    We use the cannonball model of gamma-ray bursts (GRBs) and public data from the first day of observations of GRB 090618 to predict its X-ray and optical light curves until very late times, and, in particular, the emergence of a photometric and spectroscopic signature of an SN akin to SN1998bw in its optical afterglow with an anticipated peak brightness of magnitude {approx}23.2 in the R band around 2009 July 10, if extinction in the host galaxy can be neglected.

  5. Gamma-ray burst afterglows as probes of their host galaxies and the cosmos

    NASA Astrophysics Data System (ADS)

    Cucchiara, Antonino

    2010-12-01

    Gamma-ray Bursts (GRBs) represent the sole class of catastrophic phenomena seen over almost the entire history of the Universe. Their extreme luminosities in high energy gamma-ray radiation make them readily detectable, even with relatively small satellite-based detectors, out to the earliest cosmic epochs. Moreover, the brilliance of their fading afterglow light, routinely observed in X-ray, optical, near-infrared, and radio wavelengths, allows them to be exploited -- for hours, days, or weeks -- as cosmic lighthouses, probing the conditions of gas and dust along the line of sight, through their host galaxies and the cosmos at large. Since the November 2004 launch of Swift, this GRB-focused NASA mission has discovered more than 500 GRBs, in almost all cases reporting the burst coordinates to ground-based observers within seconds of the event. The availability of prompt burst positions from Swift, combined with promptly-reported flux measurements from instruments on Swift and an array of ground-based robotic telescopes, have enabled targeted spectroscopic campaigns that have gathered detailed observations of the young, bright afterglows of hundreds of these events. This thesis reports the results of my own efforts over the past 5 years, analyzing imaging and spectroscopic observations of Swift-detected GRBs as triggered according to my own requests, or as gathered from public data archives. In Chapter 2, I discuss our follow-up campaign for GRB090429B, one of our best "extreme redshift" (z > 8) candidates. This burst followed closely on the spectroscopicallyconfirmed z = 8.2 GRB090423, and our multiwavelength observations and SED modeling demonstrate the value and limitation of such studies, in cases where a spectroscopic redshift cannot be gathered in a timely fashion. I also address the importance of such extreme-redshift events from a cosmological perspective. In Chapter 3, I use high-resolution GRB afterglow spectra to study the properties of intervening

  6. GAMMA-RAY BURSTS IN THE FERMI ERA: THE SPECTRAL ENERGY DISTRIBUTION OF THE PROMPT EMISSION

    SciTech Connect

    Massaro, F.; Grindlay, J. E.; Paggi, A.

    2010-05-10

    Gamma-ray bursts (GRBs) show evidence of different light curves, duration, afterglows, and host galaxies and explode within a wide redshift range. However, their spectral energy distributions (SEDs) appear to be very similar, showing a curved shape. Band et al. proposed a phenomenological description of the integrated spectral shape for the GRB prompt emission, the so-called Band function. In this Letter, we suggest an alternative scenario to explain the curved shape of GRB SEDs: the log-parabolic model. In comparison with the Band spectral shape our model is statistically favored because it fits the GRB spectra with one parameter less than the Band function and is motivated by a theoretical acceleration scenario. The new Fermi observations of GRBs will be crucial for disentangling these two models.

  7. UNUSUAL CENTRAL ENGINE ACTIVITY IN THE DOUBLE BURST GRB 110709B

    SciTech Connect

    Zhang Binbin; Burrows, David N.; Meszaros, Peter; Falcone, Abraham D.; Zhang Bing; Wang Xiangyu; Stratta, Giulia; D'Elia, Valerio; Frederiks, Dmitry; Golenetskii, Sergey; Cummings, Jay R.; Barthelmy, Scott D.; Gehrels, Neil; Norris, Jay P.

    2012-04-01

    The double burst, GRB 110709B, triggered the Swift/Burst Alert Telescope (BAT) twice at 21:32:39 UT and 21:43:45 UT, respectively, on 2011 July 9. This is the first time we observed a gamma-ray burst (GRB) with two BAT triggers. In this paper, we present simultaneous Swift and Konus-WIND observations of this unusual GRB and its afterglow. If the two events originated from the same physical progenitor, their different time-dependent spectral evolution suggests they must belong to different episodes of the central engine, which may be a magnetar-to-BH accretion system.

  8. Unusual Central Engine Activity in the Double Burst GRB 110709B

    NASA Technical Reports Server (NTRS)

    Zhang, Bin-Bin; Burrows, David N.; Zhang, Bing; Meszaros, Peter; Stratta, Giulia; D'Elia, Valerio; Frederiks, Dmitry; Golenetskii, S.; Cummings, Jay R.; Wang, Xiang-Yu; Falcone, Abraham D.; Barthelmy, Scott D.; Gehrels, Neil

    2011-01-01

    The double burst, GRB 110709B, triggered Swift/BAT twice at 21:32:39 UT and 21:43:45 UT, respectively, on 9 July 2011. This is the first time we observed a GRB with two BAT triggers. In this paper, we present simultaneous Swift and Konus-WIND observations of this unusual GRB and its afterglow. If the two events are from the same physical origin, their different time-dependent spectral evolution suggest they must belong to different episodes of the central engine, which may be a magnetar-to-BH accretion system.

  9. IS THE LATE NEAR-INFRARED BUMP IN SHORT-HARD GRB 130603B DUE TO THE LI-PACZYNSKI KILONOVA?

    SciTech Connect

    Jin, Zhi-Ping; Fan, Yi-Zhong; Wei, Da-Ming; Xu, Dong; Wu, Xue-Feng

    2013-09-20

    Short-hard gamma-ray bursts (GRBs) are widely believed to be produced by the merger of two binary compact objects, specifically by two neutron stars or by a neutron star orbiting a black hole. According to the Li-Paczynski kilonova model, the merger would launch sub-relativistic ejecta and a near-infrared/optical transient would then occur, lasting up to days, which is powered by the radioactive decay of heavy elements synthesized in the ejecta. The detection of a late bump using the Hubble Space Telescope (HST) in the near-infrared afterglow light curve of the short-hard GRB 130603B is indeed consistent with such a model. However, as shown in this Letter, the limited HST near-infrared light curve behavior can also be interpreted as the synchrotron radiation of the external shock driven by a wide mildly relativistic outflow. In such a scenario, the radio emission is expected to peak with a flux of ∼100 μJy, which is detectable for current radio arrays. Hence, the radio afterglow data can provide complementary evidence on the nature of the bump in GRB 130603B. It is worth noting that good spectroscopy during the bump phase in short-hard bursts can test the validity of either model above, analogous to spectroscopy of broad-lined Type Ic supernova in long-soft GRBs.

  10. DIVERSITY OF SHORT GAMMA-RAY BURST AFTERGLOWS FROM COMPACT BINARY MERGERS HOSTING PULSARS

    SciTech Connect

    Holcomb, Cole; Ramirez-Ruiz, Enrico; De Colle, Fabio; Montes, Gabriela

    2014-07-20

    Short-duration gamma-ray bursts (sGRBs) are widely believed to result from the mergers of compact binaries. This model predicts an afterglow that bears the characteristic signatures of a constant, low-density medium, including a smooth prompt-afterglow transition, and a simple temporal evolution. However, these expectations are in conflict with observations for a non-negligible fraction of sGRB afterglows. In particular, the onset of the afterglow phase for some of these events appears to be delayed and, in addition, a few of them exhibit late-time rapid fading in their light curves. We show that these peculiar observations can be explained independently of ongoing central engine activity if some sGRB progenitors are compact binaries hosting at least one pulsar. The Poynting flux emanating from the pulsar companion can excavate a bow-shock cavity surrounding the binary. If this cavity is larger than the shock deceleration length scale in the undisturbed interstellar medium, then the onset of the afterglow will be delayed. Should the deceleration occur entirely within the swept-up thin shell, a rapid fade in the light curve will ensue. We identify two types of pulsar that can achieve the conditions necessary for altering the afterglow: low-field, long-lived pulsars, and high-field pulsars. We find that a sizable fraction (≈20%-50%) of low-field pulsars are likely to reside in neutron star binaries based on observations, while their high-field counterparts are not. Hydrodynamical calculations motivated by this model are shown to be in good agreement with observations of sGRB afterglow light curves.

  11. Closing in on a Short-Hard Burst Progenitor: Constraints From Early-Time Optical Imaging and Spectroscopy of a Possible Host Galaxy of GRB 050509b

    SciTech Connect

    Bloom, Joshua S.; Prochaska, J.X.; Pooley, D.; Blake, C.W.; Foley, R.J.; Jha, S.; Ramirez-Ruiz, E.; Granot, J.; Filippenko, A.V.; Sigurdsson, S.; Barth, A.J.; Chen, H.-W.; Cooper, M.C.; Falco, E.E.; Gal, R.R.; Gerke, B.F.; Gladders, M.D.; Greene, J.E.; Hennanwi, J.; Ho, L.C.; Hurley, K.; /UC, Berkeley, Astron. Dept. /Lick Observ. /Harvard-Smithsonian Ctr. Astrophys. /Princeton, Inst. Advanced Study /KIPAC, Menlo Park /Penn State U., Astron. Astrophys. /UC, Irvine /MIT, MKI /UC, Davis /UC, Berkeley /Carnegie Inst. Observ. /UC, Berkeley, Space Sci. Dept. /Michigan U. /LBL, Berkeley /Spitzer Space Telescope

    2005-06-07

    The localization of the short-duration, hard-spectrum gamma-ray burst GRB050509b by the Swift satellite was a watershed event. Never before had a member of this mysterious subclass of classic GRBs been rapidly and precisely positioned in a sky accessible to the bevy of ground-based follow-up facilities. Thanks to the nearly immediate relay of the GRB position by Swift, we began imaging the GRB field 8 minutes after the burst and have continued during the 8 days since. Though the Swift X-ray Telescope (XRT) discovered an X-ray afterglow of GRB050509b, the first ever of a short-hard burst, thus far no convincing optical/infrared candidate afterglow or supernova has been found for the object. We present a re-analysis of the XRT afterglow and find an absolute position of R.A. = 12h36m13.59s, Decl. = +28{sup o}59'04.9'' (J2000), with a 1{sigma} uncertainty of 3.68'' in R.A., 3.52'' in Decl.; this is about 4'' to the west of the XRT position reported previously. Close to this position is a bright elliptical galaxy with redshift z = 0.2248 {+-} 0.0002, about 1' from the center of a rich cluster of galaxies. This cluster has detectable diffuse emission, with a temperature of kT = 5.25{sub -1.68}{sup +3.36} keV. We also find several ({approx}11) much fainter galaxies consistent with the XRT position from deep Keck imaging and have obtained Gemini spectra of several of these sources. Nevertheless we argue, based on positional coincidences, that the GRB and the bright elliptical are likely to be physically related. We thus have discovered reasonable evidence that at least some short-duration, hard-spectra GRBs are at cosmological distances. We also explore the connection of the properties of the burst and the afterglow, finding that GRB050509b was underluminous in both of these relative to long-duration GRBs. However, we also demonstrate that the ratio of the blast-wave energy to the {gamma}-ray energy is consistent with that of long-duration GRBs. We thus find plausible

  12. ALMA SUBMILLIMETER CONTINUUM IMAGING OF THE HOST GALAXIES OF GRB 021004 AND GRB 080607

    SciTech Connect

    Wang, Wei-Hao; Huang, Kui-Yun; Chen, Hsiao-Wen

    2012-12-20

    We report 345 GHz continuum observations of the host galaxies of gamma-ray bursts (GRBs) 021004 and 080607 at z > 2 using the Atacama Large Millimeter/Submillimeter Array (ALMA) in Cycle 0. Of the two bursts, GRB 021004 is one of the few GRBs that originate in a Lyman limit host, while GRB 080607 is classified as a 'dark burst' and its host galaxy is a candidate of dusty star-forming galaxy at z {approx} 3. With an order of magnitude improvement in the sensitivities of the new imaging searches, we detect the host galaxy of GRB 080607 with a flux of S{sub 345} = 0.31 {+-} 0.09 mJy and a corresponding infrared luminosity of L{sub IR} = (2.4-4.5) Multiplication-Sign 10{sup 11} L{sub Sun }. However, the host galaxy of GRB 021004 remains undetected and the ALMA observations allow us to place a 3{sigma} upper limit of L{sub IR} < 3.1 Multiplication-Sign 10{sup 11} L{sub Sun} for the host galaxy. The continuum imaging observations show that the two galaxies are not ultraluminous infrared galaxies, but are at the faintest end of the dusty galaxy population that gives rise to the submillimeter extragalactic background light. The derived star formation rates of the two GRB host galaxies are less than 100 M{sub Sun} yr{sup -1}, which are broadly consistent with optical measurements. The result suggests that the large extinction (A{sub V} {approx} 3) in the afterglow of GRB 080607 is confined along its particularly dusty sight line, and not representative of the global properties of the host galaxy.

  13. The Supercritical Pile Model: Prompt Emission Across the Electromagnetic Spectrum

    NASA Technical Reports Server (NTRS)

    Kazanas, Demos; Mastichiadis, A.

    2008-01-01

    The "Supercritical Pile" GRB model is an economical model that provides the dissipation necessary to convert explosively the energy stored in relativistic protons in the blast wave of a GRB into radiation; at the same time it produces spectra whose luminosity peaks at 1 MeV in the lab frame, the result of the kinematics of the proton-photon - pair production reaction that effects the conversion of proton energy to radiation. We outline the fundamental notions behind the "Supercritical Pile" model and discuss the resulting spectra of the prompt emission from optical to gamma-ray energies of order Gamma^2 m_ec^2, (Gamma is the Lorentz factor of the blast wave) present even in the absence of an accelerated particle distribution and compare our results to bursts that cover this entire energy range. Particular emphasis is given on the emission at the GLAST energy range both in the prompt and the afterglow stages of the burst.

  14. Toward a Better Understanding of the GRB Phenomenon: a New Model for GRB Prompt Emission and its Effects on the New LiNT- Epeak,irest,NT Relation

    NASA Astrophysics Data System (ADS)

    Guiriec, S.; Kouveliotou, C.; Daigne, F.; Zhang, B.; Hascoët, R.; Nemmen, R. S.; Thompson, D. J.; Bhat, P. N.; Gehrels, N.; Gonzalez, M. M.; Kaneko, Y.; McEnery, J.; Mochkovitch, R.; Racusin, J. L.; Ryde, F.; Sacahui, J. R.; Ünsal, A. M.

    2015-07-01

    Gamma-ray burst (GRB) prompt emission spectra in the keV-MeV energy range are usually considered to be adequately fitted with the empirical Band function. Recent observations with the Fermi Gamma-ray Space Telescope (Fermi) revealed deviations from the Band function, sometimes in the form of an additional blackbody (BB) component, while on other occasions in the form of an additional power law (PL) component extending to high energies. In this article we investigate the possibility that the three components may be present simultaneously in the prompt emission spectra of two very bright GRBs (080916C and 090926A) observed with Fermi, and how the three components may affect the overall shape of the spectra. While the two GRBs are very different when fitted to a single Band function, they look like “twins” in the three-component scenario. Through fine-time spectroscopy down to the 100 ms timescale, we follow the evolution of the various components. We succeed in reducing the number of free parameters in the three-component model, which results in a new semi-empirical model—but with physical motivations—to be competitive with the Band function in terms of number of degrees of freedom. From this analysis using multiple components, the Band function is globally the most intense component, although the additional PL can overpower the others in sharp time structures. The Band function and the BB component are the most intense at early times and globally fade across the burst duration. The additional PL is the most intense component at late time and may be correlated with the extended high-energy emission observed thousands of seconds after the burst with Fermi/Large Area Telescope. Unexpectedly, this analysis also shows that the additional PL may be present from the very beginning of the burst, where it may even overpower the other components at low energy. We investigate the effect of the three components on the new time-resolved luminosity-hardness relation in

  15. Afterglow Radiation from Gamma Ray Bursts

    SciTech Connect

    Desmond, Hugh; /Leuven U. /SLAC

    2006-08-28

    Gamma-ray bursts (GRB) are huge fluxes of gamma rays that appear randomly in the sky about once a day. It is now commonly accepted that GRBs are caused by a stellar object shooting off a powerful plasma jet along its rotation axis. After the initial outburst of gamma rays, a lower intensity radiation remains, called the afterglow. Using the data from a hydrodynamical numerical simulation that models the dynamics of the jet, we calculated the expected light curve of the afterglow radiation that would be observed on earth. We calculated the light curve and spectrum and compared them to the light curves and spectra predicted by two analytical models of the expansion of the jet (which are based on the Blandford and McKee solution of a relativistic isotropic expansion; see Sari's model [1] and Granot's model [2]). We found that the light curve did not decay as fast as predicted by Sari; the predictions by Granot were largely corroborated. Some results, however, did not match Granot's predictions, and more research is needed to explain these discrepancies.

  16. Black Hole Physics and Astrophysics: The GRB-Supernova Connection and URCA-1 - URCA-2

    NASA Astrophysics Data System (ADS)

    Ruffini, R.; Bernardini, M. G.; Bianco, C. L.; Vitagliano, L.; Xue, S.-S.; Chardonnet, P.; Fraschetti, F.; Gurzadyan, V.

    2006-02-01

    We outline the confluence of three novel theoretical fields in our modeling of Gamma-Ray Bursts (GRBs): 1) the ultrarelativistic regime of a shock front expanding with a Lorentz gamma factor ~ 300; 2) the quantum vacuum polarization process leading to an electron-positron plasma originating the shock front; and 3) the general relativistic process of energy extraction from a black hole originating the vacuum polarization process. There are two different classes of GRBs: the long GRBs and the short GRBs. We here address the issue of the long GRBs. The theoretical understanding of the long GRBs has led to the detailed description of their luminosities in fixed energy bands, of their spectral features and made also possible to probe the astrophysical scenario in which they originate. We are specially interested, in this report, to a subclass of long GRBs which appear to be accompanied by a supernova explosion. We are considering two specific examples: GRB980425/SN1998bw and GRB030329/SN2003dh. While these supernovae appear to have a standard energetics of 1049 ergs, the GRBs are highly variable and can have energetics 104 - 105 times larger than the ones of the supernovae. Moreover, many long GRBs occurs without the presence of a supernova. It is concluded that in no way a GRB can originate from a supernova. The precise theoretical understanding of the GRB luminosity we present evidence, in both these systems, the existence of an independent component in the X-ray emission, usually interpreted in the current literature as part of the GRB afterglow. This component has been observed by Chandra and XMM to have a strong decay on scale of months. We have named here these two sources respectively URCA-1 and URCA-2, in honor of the work that George Gamow and Mario Shoenberg did in 1939 in this town of Urca identifying the basic mechanism, the Urca processes, leading to the process of gravitational collapse and the formation of a neutron star and a supernova. The further

  17. MULTI-WAVELENGTH AFTERGLOWS OF FAST RADIO BURSTS

    SciTech Connect

    Yi, Shuang-Xi; Gao, He; Zhang, Bing

    2014-09-01

    The physical origin of fast radio bursts (FRBs) is unknown. Detecting electromagnetic counterparts to FRBs in other wavelengths is essential to measure their distances and to determine their physical origin. Assuming that at least some of them are of cosmological origin, we calculate their afterglow light curves in multiple wavelengths (X-rays, optical, and radio) by assuming a range of total kinetic energies and redshifts. We focus on forward shock emission, but also consider the possibility that some of the FRBs might have bright reverse shock emission. In general, FRB afterglows are too faint to be detected by current detectors. Only if an FRB has a very low radiative efficiency in radio (hence, a very large kinetic energy), and when it is close enough to observe can its afterglow be detected in the optical and radio bands. We discuss observational strategies for detecting these faint afterglows using future telescopes such as Large Synoptic Survey Telescope and Expanded Very Large Array.

  18. ENERGETIC FERMI/LAT GRB 100414A: ENERGETIC AND CORRELATIONS

    SciTech Connect

    Urata, Yuji; Tsai, Patrick P.; Huang, Kuiyun; Yamaoka, Kazutaka; Tashiro, Makoto S.

    2012-03-20

    This study presents multi-wavelength observational results for energetic GRB 100414A with GeV photons. The prompt spectral fitting using Suzaku/WAM data yielded spectral peak energies of E{sup src}{sub peak} of 1458.7{sup +132.6}{sub -106.6} keV and E{sub iso} of 34.5{sup +2.0}{sub -1.8} Multiplication-Sign 10{sup 52} erg with z = 1.368. The optical afterglow light curves between 3 and 7 days were effectively fitted according to a simple power law with a temporal index of {alpha} = -2.6 {+-} 0.1. The joint light curve with earlier Swift/UVOT observations yields a temporal break at 2.3 {+-} 0.2 days. This was the first Fermi/LAT detected event that demonstrated the clear temporal break in the optical afterglow. The jet opening angle derived from this temporal break was 5.{sup 0}8, consistent with those of other well-observed long gamma-ray bursts (GRBs). The multi-wavelength analyses in this study showed that GRB 100414A follows E{sup src}{sub peak}-E{sub iso} and E{sup src}{sub peak}-E{sub {gamma}} correlations. The late afterglow revealed a flatter evolution with significant excesses at 27.2 days. The most straightforward explanation for the excess is that GRB 100414A was accompanied by a contemporaneous supernova. The model light curve based on other GRB-SN events is marginally consistent with that of the observed light curve.

  19. ON THE ORIGIN OF > 10 GeV PHOTONS IN GAMMA-RAY BURST AFTERGLOWS

    SciTech Connect

    Wang Xiangyu; Liu Ruoyu; Lemoine, Martin

    2013-07-10

    Fermi/LAT has detected long-lasting high-energy photons (>100 MeV) from gamma-ray bursts (GRBs), with the highest energy photons reaching about 100 GeV. One proposed scenario is that they are produced by high-energy electrons accelerated in GRB forward shocks via synchrotron radiation. We study the maximum synchrotron photon energy in this scenario, considering the properties of the microturbulence magnetic fields behind the shock, as revealed by recent particle-in-cell simulations and theoretical analyses of relativistic collisionless shocks. Due to the small-scale nature of the microturbulent magnetic field, the Bohm acceleration approximation, in which the scattering mean free path is equal to the particle Larmor radius, breaks down at such high energies. This effect leads to a typical maximum synchrotron photon of a few GeV at 100 s after the burst and this maximum synchrotron photon energy decreases quickly with time. We show that the fast decrease of the maximum synchrotron photon energy leads to a fast decay of the synchrotron flux. The 10-100 GeV photons detected after the prompt phase cannot be produced by the synchrotron mechanism. They could originate from the synchrotron self-Compton emission of the early afterglow if the circumburst density is sufficiently large, or from the external inverse Compton process in the presence of central X-ray emission, such as X-ray flares and prompt high-latitude X-ray emission.

  20. Comparison of Three Afterglow Morphologies

    SciTech Connect

    Salmonson, J D; Rossi, E; Lazzati, D

    2003-12-23

    Herein we compare three functional families for afterglow morphologies: the homogeneous afterglow with constant shock surface energy density, the structured afterglow for which the energy density decays as a power-law as a function of viewer angle, and the gaussian afterglow which has an exponential decay of energy density with viewer angle. We simulate observed lightcurves and polarization curves for each as seen from a variety of observer vantage points. We find that the homogeneous jet is likely inconsistent with observations and suggest that the future debate on the structure of afterglow jets will be between the other two candidates.

  1. The dark nature of GRB 130528A and its host galaxy

    NASA Astrophysics Data System (ADS)

    Jeong, S.; Castro-Tirado, A. J.; Bremer, M.; Winters, J. M.; Gorosabel, J.; Guziy, S.; Pandey, S. B.; Jelínek, M.; Sánchez-Ramírez, R.; Sokolov, Ilya V.; Orekhova, N. V.; Moskvitin, A. S.; Tello, J. C.; Cunniffe, R.; Lara-Gil, O.; Oates, S. R.; Pérez-Ramírez, D.; Bai, J.; Fan, Y.; Wang, C.; Park, I. H.

    2014-09-01

    Aims: We study the dark nature of GRB 130528A through multi-wavelength observations and conclude that the main reason for the optical darkness is local extinction inside of the host galaxy. Methods: Automatic observations were performed at the Burst Optical Observer and Transient Exploring System (BOOTES)-4/MET robotic telescope. We also triggered target of opportunity (ToO) observations at Observatorio de Sierra Nevada (OSN), IRAM Plateau de Bure Interferometer (PdBI) and Gran Telescopio Canarias (GTC + OSIRIS). The host galaxy photometric observations in optical to near-infrared (nIR) wavelengths were achieved through large ground-based aperture telescopes, such as 10.4 m Gran Telescopio Canarias (GTC), 4.2 m William Herschel Telescope (WHT), 6 m Bolshoi Teleskop Alt-azimutalnyi (BTA) telescope, and 2 m Liverpool Telescope (LT). Based on these observations, spectral energy distributions (SED) for the host galaxy and afterglow were constructed. Results: Thanks to millimetre (mm) observations at PdBI, we confirm the presence of a mm source within the XRT error circle that faded over the course of our observations and identify the host galaxy. However, we do not find any credible optical source within early observations with BOOTES-4/MET and 1.5 m OSN telescopes. Spectroscopic observation of this galaxy by GTC showed a single faint emission line that likely corresponds to [OII] 3727 Å at a redshift of 1.250 ± 0.001, implying a star formation rate (M⊙/yr) > 6.18 M⊙/yr without correcting for dust extinction. The probable line-of-sight extinction towards GRB 130528A is revealed through analysis of the afterglow SED, resulting in a value of A^GRBV≥ 0.9 at the rest frame; this is comparable to extinction levels found among other dark GRBs. The SED of the host galaxy is explained well (χ2/d.o.f. = 0.564) by a luminous (MB = -21.16), low-extinction (AV = 0, rest frame), and aged (2.6 Gyr) stellar population. We can explain this apparent contradiction in global and

  2. A tale of two GRB-SNe at a common redshift of z=0.54

    NASA Astrophysics Data System (ADS)

    Cano, Z.; Bersier, D.; Guidorzi, C.; Margutti, R.; Svensson, K. M.; Kobayashi, S.; Melandri, A.; Wiersema, K.; Pozanenko, A.; van der Horst, A. J.; Pooley, G. G.; Fernandez-Soto, A.; Castro-Tirado, A. J.; Postigo, A. De Ugarte; Im, M.; Kamble, A. P.; Sahu, D.; Alonso-Lorite, J.; Anupama, G.; Bibby, J. L.; Burgdorf, M. J.; Clay, N.; Curran, P. A.; Fatkhullin, T. A.; Fruchter, A. S.; Garnavich, P.; Gomboc, A.; Gorosabel, J.; Graham, J. F.; Gurugubelli, U.; Haislip, J.; Huang, K.; Huxor, A.; Ibrahimov, M.; Jeon, Y.; Jeon, Y.-B.; Ivarsen, K.; Kasen, D.; Klunko, E.; Kouveliotou, C.; Lacluyze, A.; Levan, A. J.; Loznikov, V.; Mazzali, P. A.; Moskvitin, A. S.; Mottram, C.; Mundell, C. G.; Nugent, P. E.; Nysewander, M.; O'Brien, P. T.; Park, W.-K.; Peris, V.; Pian, E.; Reichart, D.; Rhoads, J. E.; Rol, E.; Rumyantsev, V.; Scowcroft, V.; Shakhovskoy, D.; Small, E.; Smith, R. J.; Sokolov, V. V.; Starling, R. L. C.; Steele, I.; Strom, R. G.; Tanvir, N. R.; Tsapras, Y.; Urata, Y.; Vaduvescu, O.; Volnova, A.; Volvach, A.; Wijers, R. A. M. J.; Woosley, S. E.; Young, D. R.

    2011-05-01

    We present ground-based and Hubble Space Telescope optical observations of the optical transients (OTs) of long-duration Gamma Ray Bursts (GRBs) 060729 and 090618, both at a redshift of z= 0.54. For GRB 060729, bumps are seen in the optical light curves (LCs), and the late-time broad-band spectral energy distributions (SEDs) of the OT resemble those of local Type Ic supernovae (SNe). For GRB 090618, the dense sampling of our optical observations has allowed us to detect well-defined bumps in the optical LCs, as well as a change in colour, that are indicative of light coming from a core-collapse SN. The accompanying SNe for both events are individually compared with SN1998bw, a known GRB supernova, and SN1994I, a typical Type Ic supernova without a known GRB counterpart, and in both cases the brightness and temporal evolution more closely resemble SN1998bw. We also exploit our extensive optical and radio data for GRB 090618, as well as the publicly available Swift-XRT data, and discuss the properties of the afterglow at early times. In the context of a simple jet-like model, the afterglow of GRB 090618 is best explained by the presence of a jet-break at t-to > 0.5 d. We then compare the rest-frame, peak V-band absolute magnitudes of all of the GRB and X-Ray Flash (XRF)-associated SNe with a large sample of local Type Ibc SNe, concluding that, when host extinction is considered, the peak magnitudes of the GRB/XRF-SNe cannot be distinguished from the peak magnitudes of non-GRB/XRF SNe.

  3. Applying an accurate spherical model to gamma-ray burst afterglow observations

    NASA Astrophysics Data System (ADS)

    Leventis, K.; van der Horst, A. J.; van Eerten, H. J.; Wijers, R. A. M. J.

    2013-05-01

    We present results of model fits to afterglow data sets of GRB 970508, GRB 980703 and GRB 070125, characterized by long and broad-band coverage. The model assumes synchrotron radiation (including self-absorption) from a spherical adiabatic blast wave and consists of analytic flux prescriptions based on numerical results. For the first time it combines the accuracy of hydrodynamic simulations through different stages of the outflow dynamics with the flexibility of simple heuristic formulas. The prescriptions are especially geared towards accurate description of the dynamical transition of the outflow from relativistic to Newtonian velocities in an arbitrary power-law density environment. We show that the spherical model can accurately describe the data only in the case of GRB 970508, for which we find a circumburst medium density n ∝ r-2. We investigate in detail the implied spectra and physical parameters of that burst. For the microphysics we show evidence for equipartition between the fraction of energy density carried by relativistic electrons and magnetic field. We also find that for the blast wave to be adiabatic, the fraction of electrons accelerated at the shock has to be smaller than 1. We present best-fitting parameters for the afterglows of all three bursts, including uncertainties in the parameters of GRB 970508, and compare the inferred values to those obtained by different authors.

  4. The air afterglow revisited

    NASA Technical Reports Server (NTRS)

    Kaufman, F.

    1972-01-01

    The air afterglow, 0 + NO2 chemiluminescence, is discussed in terms of fluorescence, photodissociation, and quantum theoretical calculations of NO2. The experimental results presented include pressure dependence, M-dependence, spectral dependence of P and M, temperature dependence, and infrared measurements. The NO2 energy transfer model is also discussed.

  5. Towards an optimal search strategy of optical and gravitational wave emissions from binary neutron star coalescence

    NASA Astrophysics Data System (ADS)

    Coward, D. M.; Gendre, B.; Sutton, P. J.; Howell, E. J.; Regimbau, T.; Laas-Bourez, M.; Klotz, A.; Boër, M.; Branchesi, M.

    2011-07-01

    Observations of an optical source coincident with gravitational wave emission detected from a binary neutron star coalescence will improve the confidence of detection, provide host galaxy localization and test models for the progenitors of short gamma-ray bursts. We employ optical observations of three short gamma-ray bursts, 050724, 050709 and 051221, to estimate the detection rate of a coordinated optical and gravitational wave search of neutron star mergers. Model R-band optical afterglow light curves of these bursts that include a jet-break are extrapolated for these sources at the sensitivity horizon of an Advanced LIGO/Virgo network. Using optical sensitivity limits of three telescopes, namely TAROT (m = 18), Zadko (m = 21) and an 8-10 m class telescope (m = 26), we approximate detection rates and cadence times for imaging. We find a median coincident detection rate of 4 yr-1 for the three bursts. GRB 050724 like bursts, with wide opening jet angles, offer the most optimistic rate of 13 coincident detections per year, and would be detectable by Zadko up to 5 d after the trigger. Late-time imaging to m = 26 could detect off-axis afterglows for GRB 051221 like bursts several months after the trigger. For a broad distribution of beaming angles, the optimal strategy for identifying the optical emissions triggered by gravitational wave detectors is rapid response searches with robotic telescopes followed by deeper imaging at later times if an afterglow is not detected within several days of the trigger.

  6. Discovery of an Afterglow Extension of the Prompt Phase of Two Gamma Ray Bursts Observed by Swift

    NASA Technical Reports Server (NTRS)

    Barthelmy, S. D.; Cannizzo, J. K.; Gehrels, N.; Cusumano, G.; O'Brien, P.; Vaughan, S.; Zhang, B.; Burrows, D. N.; Campana, S.; Chincarini, G.

    2005-01-01

    Contemporaneous BAT and XRT observations of two recent well-covered GRBs observed by Swift, GRB 050315 and GRB 050319, show clearly a prompt component of the afterglow emission. The rapid slewing capability of the spacecraft enables X-ray observations immediately after the burst, typically approximately 100 s following the initiation of the prompt gamma-ray phase. By fitting a power law form to the gamma-ray spectrum, we extrapolate the time dependent fluxes measured by the BAT, in the energy band 15 - 350 keV, into the spectral regime observed by the XRT, 0.2 - 10 keV, and examine the functional form of the rate of decay of the two light curves. We find that the BAT and XRT light curves merge to form a unified curve. There is a period of steep decay up to approximately 300 s, followed by a flatter decay. The duration of the steep decay, approximately 100 s in the source frame after correcting for cosmological time dilation, agrees with a theoretical estimate for the deceleration time of the relativistic ejecta as it interacts with circumstellar material. For GRB 050315, the steep decay can be characterized by an exponential form, where T(sub e),(BAT)approximately equal to 24 plus or minus 2 s, and T(sub e)(XRT) approximately equal to 35 plus or minus 2 s. For GRB 050319 a power law decay -d lnf/d lnt = n, where n approximately equal to 3, provides a reasonable fit. The early time X-ray fluxes are consistent with representing the lower energy tail of the prompt emission, and provide our first quantitative measure of the decay of the prompt gamma-ray emission over a large dynamic range. The initial steep decay is expected from the high latitude emission from a curved shell of relativistic plasma illuminated only for a short interval. The overall conclusion is that the prompt phase of GRBs lasts for hundreds of seconds longer than previously thought.

  7. Radio and X-ray observations of the Ultra-long GRB 150518A

    NASA Astrophysics Data System (ADS)

    Johnson, Louis; Kamble, Atish; Margutti, Raffaella; Soderberg, Alicia Margarita; Supernova Forensics

    2016-01-01

    Gamma Ray Burst (GRB) 150518A, discovered on 2015 May 18 by the MAXI and KONUS-Wind satellites, lasted for about 1000s, making it an important addition to the recently established class of very long duration GRBs. We report on the JVLA radio observations of the afterglow of GRB 150518A. Additionally, we report the analysis of Xray afterglow observations by Swift-XRT. Multi-band light curves of the radio afterglow display an unusual, conspicuous rise around 10 days after the burst, possibly due to enhanced mass-loss from the progenitor in the final stages of evolution before the GRB. The X-ray afterglow spectrum is significantly soft (photon index Γx > 3) and heavily absorbed (NHx,i > 8 × 10^{21}/cm^2). These properties suggest peculiar behavior that is different from the predictions of the standard fireball model of GRBs. In the light of these properties, we compare different models of progenitors for very long duration GRBs. This work was supported in part by the NSF REU and DoD ASSURE programs under NSF grant no. 1262851 and by the Smithsonian Institution.

  8. GRB070125: The First Long-Duration Gamma-Ray Burst in a Halo Environment

    NASA Technical Reports Server (NTRS)

    Bradley, Cenko S.; Fox, Derek B.; Penprase, Brian E.; Kulkarni, Shri R.; Price, Paul A.; Berger, Edo; Kulkarni, Shri R.; Harrison, Fiona A.; Gal-Yam, Avishay; Ofek, Eran O.; Rau, Arne; Chandra, Poonam; Frail, Dale A.; Kasliwal, Mansi M.; Schmidt, Brian P.; Soderberg, Alicia M.; Cameron, P. Brian; Roth, Kathy C.

    2007-01-01

    We present the discovery and high signal-to-noise spectroscopic observations of the optical afterglow of the long-duration gamma-ray burst GRB070125. Unlike all previously observed long-duration afterglows in the redshift range 0.5 < z < 2.0, we find no strong (rest-frame equivalent width W > 1.0 A) absorption features in the wavelength range 4000 - 10000 A. The sole significant feature is a weak doublet we identify as Mg 11 2796 (W = 0.18 +/- 0.02 A), 2803 (W = 0.08 +0I.-01 ) at z = 1.5477 +/- 0.0001. The low observed Mg II and inferred H I column densities are typically observed in galactic halos, far away from the bulk of massive star formation. Deep ground-based imaging reveals no host directly underneath the afterglow to a limit of R > 25.4 mag. Either of the two nearest blue galaxies could host GRB070125; the large offset (d >= 27 kpc) would naturally explain the low column density. To remain consistent with the large local (i.e. parsec scale) circum-burst density inferred from broadband afterglow observations, we speculate GRB070125 may have occurred far away from the disk of its host in a compact star-forming cluster. Such distant stellar clusters, typically formed by dynamical galaxy interactions, have been observed in the nearby universe, and should be more prevalent at z>l where galaxy mergers occur more frequently.

  9. Analytically useful spectra excited in an atmospheric pressure active nitrogen afterglow

    SciTech Connect

    Rice, G.W.; D'Silva, A.P.; Fassel, V.A.

    1984-03-01

    An atmospheric pressure active nitrogen (APAN) discharge has been utilized for producing characteristic molecular emissions from nonmetallic species introduced into the afterglow region of the discharge. The addition of inorganic S-, P-, B-, Cl-, and Br-containing compounds into the afterglow has resulted in the formation of excited S/sub 2/, PN, BO, NCl, and NBr species, respectively. Intense molecular Br/sub 2/ emission and I/sub 2/ emission, as well as atomic I emission, have also been observed. Preliminary analytical utilization of the molecular or atomic emissions observed revealed that the APAN afterglow may serve as a potentially useful detector for the aforementioned elements.

  10. The high-redshift gamma-ray burst GRB 140515A. A comprehensive X-ray and optical study

    NASA Astrophysics Data System (ADS)

    Melandri, A.; Bernardini, M. G.; D'Avanzo, P.; Sánchez-Ramírez, R.; Nappo, F.; Nava, L.; Japelj, J.; de Ugarte Postigo, A.; Oates, S.; Campana, S.; Covino, S.; D'Elia, V.; Ghirlanda, G.; Gafton, E.; Ghisellini, G.; Gnedin, N.; Goldoni, P.; Gorosabel, J.; Libbrecht, T.; Malesani, D.; Salvaterra, R.; Thöne, C. C.; Vergani, S. D.; Xu, D.; Tagliaferri, G.

    2015-09-01

    High-redshift gamma-ray bursts (GRBs) offer several advantages when studying the distant Universe, providing unique information about the structure and properties of the galaxies in which they exploded. Spectroscopic identification with large ground-based telescopes has improved our knowledge of this kind of distant events. We present the multi-wavelength analysis of the high-zSwift GRB GRB 140515A (z = 6.327). The best estimate of the neutral hydrogen fraction of the intergalactic medium towards the burst is xHI ≤ 0.002. The spectral absorption lines detected for this event are the weakest lines ever observed in GRB afterglows, suggesting that GRB 140515A exploded in a very low-density environment. Its circum-burst medium is characterised by an average extinction (AV ~ 0.1) that seems to be typical of z ≥ 6 events. The observed multi-band light curves are explained either with a very hard injected spectrum (p = 1.7) or with a multi-component emission (p = 2.1). In the second case a long-lasting central engine activity is needed in order to explain the late time X-ray emission. The possible origin of GRB 140515A in a Pop III (or in a Pop II star with a local environment enriched by Pop III) massive star is unlikely. Based on observations collected at the European Southern Observatory, ESO, the VLT/Kueyen telescope, Paranal, Chile (proposal code: 093.A-0069), on observations made with the Nordic Optical Telescope, operated by the Nordic Optical Telescope Scientific Association at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofísica de Canarias (programme 49-008), and on observations made with the Italian 3.6-m Telescopio Nazionale Galileo (TNG), operated by the Fundación Galileo Galilei of the INAF (Instituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofísica de Canarias (programme A26TAC_63).Appendix A is available in electronic form at

  11. The Macronova in GRB 050709 and the GRB-macronova connection

    PubMed Central

    Jin, Zhi-Ping; Hotokezaka, Kenta; Li, Xiang; Tanaka, Masaomi; D'Avanzo, Paolo; Fan, Yi-Zhong; Covino, Stefano; Wei, Da-Ming; Piran, Tsvi

    2016-01-01

    GRB 050709 was the first short Gamma-ray Burst (sGRB) with an identified optical counterpart. Here we report a reanalysis of the publicly available data of this event and the discovery of a Li-Paczynski macronova/kilonova that dominates the optical/infrared signal at t>2.5 days. Such a signal would arise from 0.05 r-process material launched by a compact binary merger. The implied mass ejection supports the suggestion that compact binary mergers are significant and possibly main sites of heavy r-process nucleosynthesis. Furthermore, we have reanalysed all afterglow data from nearby short and hybrid GRBs (shGRBs). A statistical study of shGRB/macronova connection reveals that macronova may have taken place in all these GRBs, although the fraction as low as 0.18 cannot be ruled out. The identification of two of the three macronova candidates in the I-band implies a more promising detection prospect for ground-based surveys. PMID:27659791

  12. Discovery of an Afterglow Extension of the Prompt Phase of Two Gamma Ray Bursts Observed by Swift

    NASA Technical Reports Server (NTRS)

    Bathelmy, S. D.; Cannizzo, J. K.; Gehrels, N.; Cusumano, G.; OBrien, P. T.; Vaughan, S.; Zhang, B.; Burrows, D. N.; Campana, S.; Chincarini, G.

    2005-01-01

    Contemporaneous BAT and XRT observations of two recent well-covered GRBs observed by Swift, GRB 050315 and GRB 050319, show clearly a prompt component joining the onset of the afterglow emission. The rapid slewing capability of the spacecraft enables X-ray observations immediately after the burst, typically 100 s following the initiation of the prompt y-ray phase. By fitting a power law form to the y-ray spectrum, we extrapolate the time dependent fluxes measured by the BAT, in the energy band 15 - 350 keV, into the spectral regime observed by the XRT 0.2 - 10 keV, and examine the functional form of the rate of decay of the two light curves. We find that the BAT and XRT light curves merge to form a unified curve. There is a period of steep decay up to 300 s, followed by a flatter decay. The duration of the steep decay, 100 s in the source frame after correcting for cosmological time dilation, agrees roughly with a theoretical estimate for the deceleration time of the relativistic ejecta as it interacts with circumstellar material. For GRB 050315, the steep decay can be characterized by an exponential form, where one e-folding decay time Te (BAT) = 24 f 2 s, and Te,(XRT) = 35 f 2 s. For GRB 050319, a power law decay - d l n f / d l n t = n, where n approx. = 3, provides a reasonable fit. The early time X-ray fluxes are consistent with representing the lower energy tail of the prompt emission, and provide our first quantitative measure of the decay of the prompt y-ray emission over a large dynamic range in flux. The initial steep decay is expected due to the delayed high latitude photons from a curved shell of relativistic plasma illuminated only for a short interval. The overall conclusion is that the prompt phase of GRBs remains observable for hundreds of seconds longer than previously thought.

  13. Long-Duration Gamma-Ray Burst Host Galaxies in Emission and Absorption

    NASA Astrophysics Data System (ADS)

    Perley, Daniel A.; Niino, Yuu; Tanvir, Nial R.; Vergani, Susanna D.; Fynbo, Johan P. U.

    2016-03-01

    The galaxy population hosting long-duration GRBs provides a means to constrain the progenitor and an opportunity to use these violent explosions to characterize the nature of the high-redshift universe. Studies of GRB host galaxies in emission reveal a population of star-forming galaxies with great diversity, spanning a wide range of masses, metallicities, and redshifts. However, as a population GRB hosts are significantly less massive and poorer in metals than the hosts of other core-collapse transients, suggesting that GRB production is only efficient at metallicities significantly below Solar. GRBs may also prefer compact galaxies, and dense and/or central regions of galaxies, more than other types of core-collapse explosion. Meanwhile, studies of hosts in absorption against the luminous GRB optical afterglow provide a unique means of unveiling properties of the ISM in even the faintest and most distant galaxies; these observations are helping to constrain the chemical evolution of galaxies and the properties of interstellar dust out to very high redshifts. New ground- and space-based instrumentation, and the accumulation of larger and more carefully-selected samples, are continually enhancing our view of the GRB host population.

  14. Chemical abundances associated with gamma-ray bursts: nucleosynthesis in afterglows

    NASA Astrophysics Data System (ADS)

    Hu, Tao; Wang, Min

    2014-03-01

    Gamma-ray burst (GRB) ejecta carries huge amounts of energy expanding into the surrounding medium and heats up these materials, making it possible that nucleosynthesis can take place in such hot sites in afterglow stage. Here, we study possible changes in chemical abundances in the GRB afterglow processes of Wolf-Rayet (WR) star wind environments (Case A) and constant density surroundings (Case B). We find that the light element of lithium-beryllium-boron could occur in the afterglows via He+He process and spallation reactions. Some isotopes of F, Ne, Mg, Al, Si, P, S and Fe-group elements are also new species formed in the afterglows via proton-, neutron- and α-capture. The results show that the nucleosynthetic yields might be a diagnostic of the GRB's ambient environment. Our calculations indicate that Mg, Al, Si, P, Cr, Mn, Fe and Co have trended to appear in Case A, while Ne, Ti and Ni trend to occur in Case B. Furthermore, although some species have occurred both in Cases A and B, their mass fractions are quite different in these two cases. Here, we show that the mass fractions of 7Li, 7Be, 24Mg and 30Si are higher in Case A than that in Case B, but 18F gives an opposite conclusion. Nucleosynthetic outputs might also be an indice to estimate the luminosity-temperature relation factor β. In this study, when β reduces, the mass abundances of 11B and 20Ne are higher in Case B than that in Case A; in contrast, as the β becomes larger, this trend would be reversed; therefore, perhaps we could select the above elements as the indicators to estimate the properties of the surroundings around the GRBs. We also suggest that the spectroscopic observations of a GRB afterglow could only reveal the nucleosynthetic outputs from the interaction site between the GRB jet and its ambient matter, but could not represent the original composition of the pre-GRB surrounding medium.

  15. Evolution of dust content in galaxies probed by gamma-ray burst afterglows

    NASA Astrophysics Data System (ADS)

    Kuo, Tzu-Ming; Hirashita, Hiroyuki; Zafar, Tayyaba

    2013-12-01

    Because of their brightness, gamma-ray burst (GRB) afterglows are viable targets for investigating the dust content in their host galaxies. Simple intrinsic spectral shapes of GRB afterglows allow us to derive the dust extinction. Recently, the extinction data of GRB afterglows are compiled up to redshift z = 6.3, in combination with hydrogen column densities and metallicities. This data set enables us to investigate the relation between dust-to-gas ratio and metallicity out to high redshift for a wide metallicity range. By applying our evolution models of dust content in galaxies, we find that the dust-to-gas ratios derived from GRB afterglow extinction data are excessively high such that they can be explained with a fraction of gas-phase metals condensed into dust (fin) ˜ 1, while theoretical calculations on dust formation in the wind of asymptotic giant branch stars and in the ejecta of Type II supernovae suggest a much more moderate condensation efficiency (fin ˜ 0.1). Efficient dust growth in dense clouds has difficulty in explaining the excessive dust-to-gas ratio at metallicities Z/Z⊙ < ɛ, where ɛ is the star formation efficiency of the dense clouds. However, if ɛ is as small as 0.01, the dust-to-gas ratio at Z ˜ 10-2 Z⊙ can be explained with nH ≳ 106 cm-3. Therefore, a dense environment hosting dust growth is required to explain the large fraction of metals condensed into dust, but such clouds should have low star formation efficiencies to avoid rapid metal enrichment by stars.

  16. A global study of X-Ray afterglows of GRBs after the plateau

    NASA Astrophysics Data System (ADS)

    Bardho, Onelda; Boer, Michel; Gendre, Bruce

    We have investigated the behavior and correlations in X-ray light curves of GRB afterglows following the earlier results from Boer and Gendre (2000) and Gendre and Boer (2008). We have used data from 160 GRBs observed by Swift, corrected from distance effects. We have applied several statistical tests on this extended data. We discuss the correlations present in the sample and the possible origin of them.

  17. The Onset of Gamma-Ray Burst Afterglow

    NASA Astrophysics Data System (ADS)

    Kobayashi, Shiho; Zhang, Bing

    2007-02-01

    We discuss the reference time t0 of afterglow light curves in the context of the standard internal-external shock model. The decay index of early afterglow is very sensitive to the reference time one chooses. In order to understand the nature of early afterglow, it is essential to take a correct reference time. Our simple analytic model provides a framework for understanding special relativistic effects involved in early afterglow phase. We evaluate light curves of reverse shock emission as well as those of forward shock emission, based on full hydrodynamic calculations. We show that the reference time does not shift significantly even in the thick-shell case. For external shock emission components, measuring times from the beginning of the prompt emission is a good approximation and it does not cause an early steep decay. In the thin-shell case, the energy transfer time from fireball ejecta to ambient medium typically extends to thousands of seconds. This might be related to the shallow decay phases observed in early X-ray afterglow at least for some bursts.

  18. Numerical models of blackbody-dominated gamma-ray bursts - II. Emission properties

    NASA Astrophysics Data System (ADS)

    Cuesta-Martínez, C.; Aloy, M. A.; Mimica, P.; Thöne, C.; de Ugarte Postigo, A.

    2015-01-01

    Blackbody-dominated (BBD) gamma-ray bursts (GRBs) are events characterized by long durations and the presence of a significant thermal component following the prompt emission, as well as by the absence of a typical afterglow. GRB 101225A is the most prominent member of this class. A plausible progenitor system for it and for BBD-GRBs is the merger a neutron star and a helium core of an evolved, massive star. Using relativistic hydrodynamic simulations we model the propagation of ultrarelativistic jets through the environments created by such mergers. In a previous paper we showed that the thermal emission in BBD-GRBs is linked to the interaction of an ultrarelativistic jet with the ejected envelope of the secondary star of the binary. Here we focus on explaining the emission properties of BBD-GRBs computing the whole radiative signature (both thermal and non-thermal) of the jet dynamical evolution. The non-thermal emission of the forward shock of the jet is dominant during the early phases of the evolution, when that shock is moderately relativistic. Our models do not produce a classical afterglow because the quick deceleration of the jet results primarily from the mass entrainment in the beam, and not from the process of plowing mass from the external medium in front of the GRB ejecta. The contribution of the reverse shock is of the same magnitude than that of the forward shock during the first 80 min after the GRB. Later, it quickly fades because the jet/environment interaction chocks the ultrarelativistic jet beam and effectively dumps the reverse shock. In agreement with observations, we obtain rather flat light curves during the first 2 d after the GRB, and a spectral evolution consistent with the observed reddening of the system.

  19. Simulations of Gamma-Ray Burst Jets in a Stratified External Medium: Dynamics, Afterglow Light Curves, Jet Breaks, and Radio Calorimetry

    NASA Astrophysics Data System (ADS)

    De Colle, Fabio; Ramirez-Ruiz, Enrico; Granot, Jonathan; Lopez-Camara, Diego

    2012-05-01

    The dynamics of gamma-ray burst (GRB) jets during the afterglow phase is most reliably and accurately modeled using hydrodynamic simulations. All published simulations so far, however, have considered only a uniform external medium, while a stratified external medium is expected around long duration GRB progenitors. Here, we present simulations of the dynamics of GRB jets and the resulting afterglow emission for both uniform and stratified external media with ρextvpropr -k for k = 0, 1, 2. The simulations are performed in two dimensions using the special relativistic version of the Mezcal code. Common to all calculations is the initiation of the GRB jet as a conical wedge of half-opening angle θ0 = 0.2 whose radial profile is taken from the self-similar Blandford-McKee solution. The dynamics for stratified external media (k = 1, 2) are broadly similar to those derived for expansion into a uniform external medium (k = 0). The jet half-opening angle is observed to start increasing logarithmically with time (or radius) once the Lorentz factor Γ drops below θ-1 0. For larger k values, however, the lateral expansion is faster at early times (when Γ > θ-1 0) and slower at late times with the jet expansion becoming Newtonian and slowly approaching spherical symmetry over progressively longer timescales. We find that, contrary to analytic expectations, there is a reasonably sharp jet break in the light curve for k = 2 (a wind-like external medium), although the shape of the break is affected more by the viewing angle (for θobs <= θ0) than by the slope of the external density profile (for 0 <= k <= 2). Steeper density profiles (i.e., increasing k values) are found to produce more gradual jet breaks while larger viewing angles cause smoother and later appearing jet breaks. The counterjet becomes visible as it becomes sub-relativistic, and for k = 0 this results in a clear bump-like feature in the light curve. However, for larger k values the jet decelerates more

  20. Estimates for Lorentz factors of gamma-ray bursts from early optical afterglow observations

    SciTech Connect

    Hascoët, Romain; Beloborodov, Andrei M.; Daigne, Frédéric; Mochkovitch, Robert

    2014-02-10

    The peak time of optical afterglow may be used as a proxy to constrain the Lorentz factor Γ of the gamma-ray burst (GRB) ejecta. We revisit this method by including bursts with optical observations that started when the afterglow flux was already decaying; these bursts can provide useful lower limits on Γ. Combining all analyzed bursts in our sample, we find that the previously reported correlation between Γ and the burst luminosity L {sub γ} does not hold. However, the data clearly show a lower bound Γ{sub min} that increases with L {sub γ}. We suggest an explanation for this feature: explosions with large jet luminosities and Γ < Γ{sub min} suffer strong adiabatic cooling before their radiation is released at the photosphere; they produce weak bursts, barely detectable with present instruments. To test this explanation, we examine the effect of adiabatic cooling on the GRB location in the L {sub γ} – Γ plane using a Monte Carlo simulation of the GRB population. Our results predict detectable on-axis 'orphan' afterglows. We also derive upper limits on the density of the ambient medium that decelerates the explosion ejecta. We find that the density in many cases is smaller than expected for stellar winds from normal Wolf-Rayet progenitors. The burst progenitors may be peculiar massive stars with weaker winds, or there might exist a mechanism that reduces the stellar wind a few years before the explosion.

  1. Optical flashes from internal pairs formed in gamma-ray burst afterglows

    DOE PAGESBeta

    Panaitescu, A.

    2015-06-09

    We develop a numerical formalism for calculating the distribution with energy of the (internal) pairs formed in a relativistic source from unscattered MeV–TeV photons. For gamma-ray burst (GRB) afterglows, this formalism is more suitable if the relativistic reverse shock that energizes the ejecta is the source of the GeV photons. The number of pairs formed is set by the source GeV output (calculated from the Fermi-LAT fluence), the unknown source Lorentz factor, and the unmeasured peak energy of the LAT spectral component. We show synchrotron and inverse-Compton light curves expected from pairs formed in the shocked medium and identify some criteria for testing a pair origin of GRB optical counterparts. Pairs formed in bright LAT afterglows with a Lorentz factor in the few hundreds may produce bright optical counterparts (more » $$R\\lt 10$$) lasting for up to one hundred seconds. As a result, the number of internal pairs formed from unscattered seed photons decreases very strongly with the source Lorentz factor, thus bright GRB optical counterparts cannot arise from internal pairs if the afterglow Lorentz factor is above several hundreds.« less

  2. Estimates for Lorentz Factors of Gamma-Ray Bursts from Early Optical Afterglow Observations

    NASA Astrophysics Data System (ADS)

    Hascoët, Romain; Beloborodov, Andrei M.; Daigne, Frédéric; Mochkovitch, Robert

    2014-02-01

    The peak time of optical afterglow may be used as a proxy to constrain the Lorentz factor Γ of the gamma-ray burst (GRB) ejecta. We revisit this method by including bursts with optical observations that started when the afterglow flux was already decaying; these bursts can provide useful lower limits on Γ. Combining all analyzed bursts in our sample, we find that the previously reported correlation between Γ and the burst luminosity L γ does not hold. However, the data clearly show a lower bound Γmin that increases with L γ. We suggest an explanation for this feature: explosions with large jet luminosities and Γ < Γmin suffer strong adiabatic cooling before their radiation is released at the photosphere; they produce weak bursts, barely detectable with present instruments. To test this explanation, we examine the effect of adiabatic cooling on the GRB location in the L γ - Γ plane using a Monte Carlo simulation of the GRB population. Our results predict detectable on-axis "orphan" afterglows. We also derive upper limits on the density of the ambient medium that decelerates the explosion ejecta. We find that the density in many cases is smaller than expected for stellar winds from normal Wolf-Rayet progenitors. The burst progenitors may be peculiar massive stars with weaker winds, or there might exist a mechanism that reduces the stellar wind a few years before the explosion.

  3. Optical flashes from internal pairs formed in gamma-ray burst afterglows

    SciTech Connect

    Panaitescu, A.

    2015-06-09

    We develop a numerical formalism for calculating the distribution with energy of the (internal) pairs formed in a relativistic source from unscattered MeV–TeV photons. For gamma-ray burst (GRB) afterglows, this formalism is more suitable if the relativistic reverse shock that energizes the ejecta is the source of the GeV photons. The number of pairs formed is set by the source GeV output (calculated from the Fermi-LAT fluence), the unknown source Lorentz factor, and the unmeasured peak energy of the LAT spectral component. We show synchrotron and inverse-Compton light curves expected from pairs formed in the shocked medium and identify some criteria for testing a pair origin of GRB optical counterparts. Pairs formed in bright LAT afterglows with a Lorentz factor in the few hundreds may produce bright optical counterparts ($R\\lt 10$) lasting for up to one hundred seconds. As a result, the number of internal pairs formed from unscattered seed photons decreases very strongly with the source Lorentz factor, thus bright GRB optical counterparts cannot arise from internal pairs if the afterglow Lorentz factor is above several hundreds.

  4. Altitudinal dependence of meteor radio afterglows measured via optical counterparts

    NASA Astrophysics Data System (ADS)

    Obenberger, K. S.; Holmes, J. M.; Dowell, J. D.; Schinzel, F. K.; Stovall, K.; Sutton, E. K.; Taylor, G. B.

    2016-09-01

    Utilizing the all-sky imaging capabilities of the first station of the Long Wavelength Array along with a host of all-sky optical cameras, we have now observed 44 optical meteor counterparts to radio afterglows. Combining these observations, we have determined the geographic positions of all 44 afterglows. Comparing the number of radio detections as a function of altitude above sea level to the number of expected bright meteors, we find a strong altitudinal dependence characterized by a cutoff below ˜90 km, below which no radio emission occurs, despite the fact that many of the observed optical meteors penetrated well below this altitude. This cutoff suggests that wave damping from electron collisions is an important factor for the evolution of radio afterglows. This finding agrees with the hypothesis that the emission is the result of electron plasma wave emission.

  5. Machine Learning Search for Gamma-Ray Burst Afterglows in Optical Images

    NASA Astrophysics Data System (ADS)

    Topinka, M.

    2016-06-01

    Thanks to the advances in robotic telescopes, time domain astronomy leads to a large number of transient events detected in images every night. Data mining and machine learning tools used for object classification are presented. The goal is to automatically classify transient events for both further follow-up by a larger telescope and for statistical studies of transient events. Special attention is given to the identification of gamma-ray burst afterglows. Machine learning techniques are used to identify GROND gamma-ray burst afterglow among the astrophysical objects present in the SDSS archival images based on the g'-r', r'-i' and i'-z' color indices. The performance of the support vector machine, random forest and neural network algorithms is compared. A joint meta-classifier, built on top of the individual classifiers, can identify GRB afterglows with the overall accuracy of ≳ 90%.

  6. GRB Catalog: Bursts from Vela to Swift

    NASA Technical Reports Server (NTRS)

    Angelini, L.

    2008-01-01

    Gamma ray burst (GRB) astronomy started when the first event was recorded on July 2, 1967 by Vela 4a and 4b. Since then many missions have flown experiments capable of detecting GRBs. The events collected by these older experiments are mostly available in paper copy, each containing a few ten to a few hundred bursts. No systematic effort in cataloging of these bursts has been available. In some cases the information is unpublished and in others difficult to retrieve. The first major GRB catalog was obtained by GRO with the BATSE experiment. It contains more than 2000 bursts and includes homogeneous information for each of the bursts. With the launch of Swift, the first Gamma-ray/X-ray mission dedicated to the study of GRBs and their afterglows, a wealth of information is collected by the Swift instrument as well as from ground-based telescopes. This talk will describe the efforts to create a comprehensive GRBCAT and its current status and future prospective.

  7. Study of argon-oxygen flowing afterglow

    NASA Astrophysics Data System (ADS)

    Mazánková, V.; Trunec, D.; Navrátil, Z.; Raud, J.; Krčma, F.

    2016-06-01

    The reaction kinetics in argon-oxygen flowing afterglow (post-discharge) was studied using NO titration and optical emission spectroscopy. The flowing DC post-discharge in argon-oxygen mixture was created in a quartz tube at the total gas pressure of 1000 Pa and discharge power of 90 W. The O(3P) atom concentration was determined by NO titration at different places along the flow tube. The optical emission spectra were also measured along the flow tube. Argon spectral lines, oxygen lines at 777 nm and 844.6 nm and atmospheric A-band of {{\\text{O}}2} were identified in the spectra. Rotational temperature of {{\\text{O}}2} was determined from the oxygen atmospheric A-band and also the outer wall temperature of the flow tube was measured by a thermocouple and by an IR thermometer. A zero-dimensional kinetic model for the reactions in the afterglow was developed. This model allows the time dependencies of particle concentrations and of gas temperature to be calculated. The wall recombination probability for O(3P) atoms {γ\\text{O≤ft(\\text{P}\\right)}}=≤ft(1.63+/- 0.06\\right)× {{10}-3} and wall deactivation probability for {{\\text{O}}2} (b {{}1}Σ\\text{g}+ ) molecules {γ{{\\text{O}2}≤ft(\\text{b}\\right)}}=≤ft(1.7+/- 0.1\\right)× {{10}-3} were determined from the fit of model results to experimental data. Sensitivity analysis was applied for the analysis of kinetic model in order to reveal the most important reactions in the model. The calculated gas temperature increases in the afterglow and then decreases at later afterglow times after reaching the maximum. This behavior is in good agreement with the spatial rotational temperature dependence. A similar trend was also observed at outer wall temperature measurement.

  8. Study of argon–oxygen flowing afterglow

    NASA Astrophysics Data System (ADS)

    Mazánková, V.; Trunec, D.; Navrátil, Z.; Raud, J.; Krčma, F.

    2016-06-01

    The reaction kinetics in argon–oxygen flowing afterglow (post-discharge) was studied using NO titration and optical emission spectroscopy. The flowing DC post-discharge in argon–oxygen mixture was created in a quartz tube at the total gas pressure of 1000 Pa and discharge power of 90 W. The O(3P) atom concentration was determined by NO titration at different places along the flow tube. The optical emission spectra were also measured along the flow tube. Argon spectral lines, oxygen lines at 777 nm and 844.6 nm and atmospheric A-band of {{\\text{O}}2} were identified in the spectra. Rotational temperature of {{\\text{O}}2} was determined from the oxygen atmospheric A-band and also the outer wall temperature of the flow tube was measured by a thermocouple and by an IR thermometer. A zero-dimensional kinetic model for the reactions in the afterglow was developed. This model allows the time dependencies of particle concentrations and of gas temperature to be calculated. The wall recombination probability for O(3P) atoms {γ\\text{O≤ft(\\text{P}\\right)}}=≤ft(1.63+/- 0.06\\right)× {{10}-3} and wall deactivation probability for {{\\text{O}}2} (b {{}1}Σ\\text{g}+ ) molecules {γ{{\\text{O}2}≤ft(\\text{b}\\right)}}=≤ft(1.7+/- 0.1\\right)× {{10}-3} were determined from the fit of model results to experimental data. Sensitivity analysis was applied for the analysis of kinetic model in order to reveal the most important reactions in the model. The calculated gas temperature increases in the afterglow and then decreases at later afterglow times after reaching the maximum. This behavior is in good agreement with the spatial rotational temperature dependence. A similar trend was also observed at outer wall temperature measurement.

  9. LATE-TIME OBSERVATIONS OF GRB 080319B: JET BREAK, HOST GALAXY, AND ACCOMPANYING SUPERNOVA

    SciTech Connect

    Tanvir, N. R.; O'Brien, P. T.; Wiersema, K.; Starling, R. L. C.; Rol, E.; Levan, A. J.; Svensson, K.; Fruchter, A. S.; Granot, J.; Jakobsson, P.; Fynbo, J.; Hjorth, J.; Curran, P. A.; Burrows, D. N.; Genet, F.

    2010-12-10

    The Swift-discovered GRB 080319B was by far the most distant source ever observed at naked-eye brightness, reaching a peak apparent magnitude of 5.3 at a redshift of z = 0.937. We present our late-time optical (Hubble Space Telescope, Gemini, and Very Large Telescope) and X-ray (Chandra) observations, which confirm that an achromatic break occurred in the power-law afterglow light curve at {approx}11 days post-burst. This most likely indicates that the gamma-ray burst (GRB) outflow was collimated, which for a uniform jet would imply a total energy in the jet E{sub jet} {approx}> 10{sup 52} erg. Our observations also show a late-time excess of red light, which is well explained if the GRB was accompanied by a supernova (SN), similar to those seen in some other long-duration GRBs. The latest observations are dominated by light from the host and show that the GRB took place in a faint dwarf galaxy (r(AB) {approx} 27.0, rest frame M{sub B} {approx} -17.2). This galaxy is small even by the standards of other GRB hosts, which is suggestive of a low-metallicity environment. Intriguingly, the properties of this extreme event-a small host and bright SN-are entirely typical of the very low luminosity bursts such as GRB 980425 and GRB 060218.

  10. Late-time Observations of GRB 080319B: Jet Break, Host Galaxy, and Accompanying Supernova

    NASA Astrophysics Data System (ADS)

    Tanvir, N. R.; Rol, E.; Levan, A. J.; Svensson, K.; Fruchter, A. S.; Granot, J.; O'Brien, P. T.; Wiersema, K.; Starling, R. L. C.; Jakobsson, P.; Fynbo, J.; Hjorth, J.; Curran, P. A.; van der Horst, A. J.; Kouveliotou, C.; Racusin, J. L.; Burrows, D. N.; Genet, F.

    2010-12-01

    The Swift-discovered GRB 080319B was by far the most distant source ever observed at naked-eye brightness, reaching a peak apparent magnitude of 5.3 at a redshift of z = 0.937. We present our late-time optical (Hubble Space Telescope, Gemini, and Very Large Telescope) and X-ray (Chandra) observations, which confirm that an achromatic break occurred in the power-law afterglow light curve at ~11 days post-burst. This most likely indicates that the gamma-ray burst (GRB) outflow was collimated, which for a uniform jet would imply a total energy in the jet E jet >~ 1052 erg. Our observations also show a late-time excess of red light, which is well explained if the GRB was accompanied by a supernova (SN), similar to those seen in some other long-duration GRBs. The latest observations are dominated by light from the host and show that the GRB took place in a faint dwarf galaxy (r(AB) ≈ 27.0, rest frame MB ≈ -17.2). This galaxy is small even by the standards of other GRB hosts, which is suggestive of a low-metallicity environment. Intriguingly, the properties of this extreme event—a small host and bright SN—are entirely typical of the very low luminosity bursts such as GRB 980425 and GRB 060218.

  11. GRB hosts through cosmic time. VLT/X-Shooter emission-line spectroscopy of 96 γ-ray-burst-selected galaxies at 0.1

    NASA Astrophysics Data System (ADS)

    Krühler, T.; Malesani, D.; Fynbo, J. P. U.; Hartoog, O. E.; Hjorth, J.; Jakobsson, P.; Perley, D. A.; Rossi, A.; Schady, P.; Schulze, S.; Tanvir, N. R.; Vergani, S. D.; Wiersema, K.; Afonso, P. M. J.; Bolmer, J.; Cano, Z.; Covino, S.; D'Elia, V.; de Ugarte Postigo, A.; Filgas, R.; Friis, M.; Graham, J. F.; Greiner, J.; Goldoni, P.; Gomboc, A.; Hammer, F.; Japelj, J.; Kann, D. A.; Kaper, L.; Klose, S.; Levan, A. J.; Leloudas, G.; Milvang-Jensen, B.; Nicuesa Guelbenzu, A.; Palazzi, E.; Pian, E.; Piranomonte, S.; Sánchez-Ramírez, R.; Savaglio, S.; Selsing, J.; Tagliaferri, G.; Vreeswijk, P. M.; Watson, D. J.; Xu, D.

    2015-09-01

    We present data and initial results from VLT/X-Shooter emission-line spectroscopy of 96 galaxies selected by long γ-ray bursts (GRBs) at 0.1 GRB host spectra available to date. Most of our GRBs were detected by Swift and 76% are at 0.5 emission-line widths (σ). We study GRB hosts up to z ~ 3.5 and find a strong change in their typical physical properties with redshift. The median SFR of our GRB hosts increases from SFRmed ~ 0.6 M⊙ yr-1 at z ~ 0.6 up to SFRmed ~ 15 M⊙ yr-1 at z ~ 2. A higher ratio of [O iii]/[O ii] at higher redshifts leads to an increasing distance of GRB-selected galaxies to the locus of local galaxies in the Baldwin-Phillips-Terlevich diagram. There is weak evidence for a redshift evolution in AV and σ, with the highest values seen at z ~ 1.5 (AV) or z ~ 2 (σ). Oxygen abundances of the galaxies are distributed between 12 + log (O/H) = 7.9 and 12 + log (O/H) = 9.0 with a median 12 + log (O/H)med ~ 8.5. The fraction of GRB-selected galaxies with super-solar metallicities is ~20% at z< 1 in the adopted metallicity scale. This is significantly less than the fraction of total star formation in similar galaxies, illustrating that GRBs are scarce in high metallicity environments. At z ~ 3, sensitivity limits us to probing only the most luminous GRB hosts for which we derive metallicities of Z ≲ 0.5 Z⊙. Together with a high incidence of Z ~ 0.5 Z⊙ galaxies at z ~ 1.5, this indicates that a metallicity dependence at low redshift will not be dominant at z ~ 3. Significant correlations exist between the hosts' physical properties. Oxygen abundance, for example, relates to AV (12 + log (O/H) ∝ 0.17·AV), line width (12 + log (O/H) ∝ σ0.6), and SFR (12 + log (O/H) ∝ SFR0.2). In the

  12. Constraining properties of GRB magnetar central engines using the observed plateau luminosity and duration correlation

    NASA Astrophysics Data System (ADS)

    Rowlinson, A.; Gompertz, B. P.; Dainotti, M.; O'Brien, P. T.; Wijers, R. A. M. J.; van der Horst, A. J.

    2014-09-01

    An intrinsic correlation has been identified between the luminosity and duration of plateaus in the X-ray afterglows of gamma-ray bursts (GRBs; Dainotti et al. 2008), suggesting a central engine origin. The magnetar central engine model predicts an observable plateau phase, with plateau durations and luminosities being determined by the magnetic fields and spin periods of the newly formed magnetar. This paper analytically shows that the magnetar central engine model can explain, within the 1σ uncertainties, the correlation between plateau luminosity and duration. The observed scatter in the correlation most likely originates in the spread of initial spin periods of the newly formed magnetar and provides an estimate of the maximum spin period of ˜35 ms (assuming a constant mass, efficiency and beaming across the GRB sample). Additionally, by combining the observed data and simulations, we show that the magnetar emission is most likely narrowly beamed and has ≲20 per cent efficiency in conversion of rotational energy from the magnetar into the observed plateau luminosity. The beaming angles and efficiencies obtained by this method are fully consistent with both predicted and observed values. We find that short GRBs and short GRBs with extended emission lie on the same correlation but are statistically inconsistent with being drawn from the same distribution as long GRBs, this is consistent with them having a wider beaming angle than long GRBs.

  13. Soft X-ray absorption excess in gamma-ray burst afterglow spectra: Absorption by turbulent ISM

    NASA Astrophysics Data System (ADS)

    Tanga, M.; Schady, P.; Gatto, A.; Greiner, J.; Krause, M. G. H.; Diehl, R.; Savaglio, S.; Walch, S.

    2016-10-01

    Two-thirds of long duration gamma-ray bursts (GRBs) show soft X-ray absorption in excess of the Milky Way. The column densities of metals inferred from UV and optical spectra differ from those derived from soft X-ray spectra, at times by an order of magnitude, with the latter being higher. The origin of the soft X-ray absorption excess observed in GRB X-ray afterglow spectra remains a heavily debated issue, which has resulted in numerous investigations on the effect of hot material both internal and external to the GRB host galaxy on our X-ray afterglow observations. Nevertheless, all models proposed so far have either only been able to account for a subset of our observations (i.e. at z> 2), or they have required fairly extreme conditions to be present within the absorbing material. In this paper, we investigate the absorption of the GRB afterglow by a collisionally ionised and turbulent interstellar medium (ISM). We find that a dense (3 cm-3) collisionally ionised ISM could produce UV/optical and soft X-ray absorbing column densities that differ by a factor of 10. However the UV/optical and soft X-ray absorbing column densities for such sightlines are 2-3 orders of magnitude lower in comparison to the GRB afterglow spectra. For those GRBs with a larger soft X-ray excess by up to an order of magnitude, the contribution in absorption from a turbulent ISM as considered here would ease the required conditions of additional absorbing components, such as the GRB circumburst medium and intergalactic medium.

  14. On binary driven hypernovae and their nested late X-ray emission

    NASA Astrophysics Data System (ADS)

    Muccino, Marco; Ruffini, Remo; Bianco, Carlo Luciano; Enderli, Maxime; Kovacevic, Milos; Izzo, Luca; Penacchioni, Ana Virginia; Pisani, Giovanni Battista; Rueda, Jorge A.; Wang, Yu

    2015-07-01

    The induced gravitational collapse (IGC) paradigm addresses energetic (1052-1054 erg), long gamma-ray bursts (GRBs) associated to supernovae (SNe) and proposes as their progenitors tight binary systems composed of an evolved FeCO core and a companion neutron star (NS). Their emission is characterized by four specific episodes: Episode 1, corresponding to the on-set of the FeCO SN explosion and the accretion of the ejecta onto the companion NS; Episode 2, related the collapse of the companionNS to a black hole (BH) and to the emission of a long GRB; Episode 3, observed in X-rays and characterized by a steep decay, a plateau phase and a late power-law decay; Episode 4, corresponding to the optical SN emission due to the 56Ni decay. We focus on Episode 3 and we show that, from the thermal component observed during the steep decay of the prototype GRB 090618, the emission region has a typical dimension of ~1013 cm, which is inconsistent with the typical size of the emitting region of GRBs, e.g., ~1016 cm. We propose, therefore, that the X-ray afterglow emission originates from a spherically symmetric SN ejecta expanding at G ˜ 2 or, possibly, from the accretion onto the newly formed black hole, and we name these systems "binary driven hypernovae" (BdHNe). This interpretation is alternative to the traditional afterglow model based on the GRB synchrotron emission from a collimated jet outflow, expanding at ultra-relativistic Lorentz factor of G ~ 102-103 and originating from the collapse of a single object. We show then that the rest-frame energy band 0.3-10 keV X-ray luminosities of three selected BdHNe, GRB 060729, GRB 061121, and GRB 130427A, evidence a precisely constrained "nested" structure and satisfy precise scaling laws between the average prompt luminosity, < Liso>, and the luminosity at the end of the plateau, La, as functions of the time at the end of the plateau. All these features extend the applicability of the "cosmic candle" nature of Episode 3. The

  15. Discovery of the nearby long, soft GRB 100316D with an associated supernova

    NASA Astrophysics Data System (ADS)

    Starling, R. L. C.; Wiersema, K.; Levan, A. J.; Sakamoto, T.; Bersier, D.; Goldoni, P.; Oates, S. R.; Rowlinson, A.; Campana, S.; Sollerman, J.; Tanvir, N. R.; Malesani, D.; Fynbo, J. P. U.; Covino, S.; D'Avanzo, P.; O'Brien, P. T.; Page, K. L.; Osborne, J. P.; Vergani, S. D.; Barthelmy, S.; Burrows, D. N.; Cano, Z.; Curran, P. A.; de Pasquale, M.; D'Elia, V.; Evans, P. A.; Flores, H.; Fruchter, A. S.; Garnavich, P.; Gehrels, N.; Gorosabel, J.; Hjorth, J.; Holland, S. T.; van der Horst, A. J.; Hurkett, C. P.; Jakobsson, P.; Kamble, A. P.; Kouveliotou, C.; Kuin, N. P. M.; Kaper, L.; Mazzali, P. A.; Nugent, P. E.; Pian, E.; Stamatikos, M.; Thöne, C. C.; Woosley, S. E.

    2011-03-01

    We report the Swift discovery of the nearby long, soft gamma-ray burst GRB 100316D, and the subsequent unveiling of its low-redshift host galaxy and associated supernova. We derive the redshift of the event to be z= 0.0591 ± 0.0001 and provide accurate astrometry for the gamma-ray burst (GRB) supernova (SN). We study the extremely unusual prompt emission with time-resolved γ-ray to X-ray spectroscopy and find that the spectrum is best modelled with a thermal component in addition to a synchrotron emission component with a low peak energy. The X-ray light curve has a remarkably shallow decay out to at least 800 s. The host is a bright, blue galaxy with a highly disturbed morphology and we use Gemini-South, Very Large Telescope and Hubble Space Telescope observations to measure some of the basic host galaxy properties. We compare and contrast the X-ray emission and host galaxy of GRB 100316D to a subsample of GRB-SNe. GRB 100316D is unlike the majority of GRB-SNe in its X-ray evolution, but resembles rather GRB 060218, and we find that these two events have remarkably similar high energy prompt emission properties. Comparison of the host galaxies of GRB-SNe demonstrates, however, that there is a great diversity in the environments in which GRB-SNe can be found. GRB 100316D is an important addition to the currently sparse sample of spectroscopically confirmed GRB-SNe, from which a better understanding of long GRB progenitors and the GRB-SN connection can be gleaned.

  16. First Detection of a Foreground Damped Ly-Alpha Absorber Along a GRB Line of Sight?

    NASA Technical Reports Server (NTRS)

    Vreeswijk, P. M.; Fruchter, A. S.; Pian, E.; Rol, E.; Wijers, R. A. M. J.; Kouveliotou, C.; Kaper, L.; Palazzi, E.; Masetti, N.; Frontera, F.; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    We present a VLT spectrum of the optical afterglow of GRB 991216, taken 1.5 days after the burst, and HST (Hubble Space Telescope) imaging of the host galaxy, obtained four months later. The spectrum contains three metal absorption-line systems with redshifts z = 1.024, z = 0.803, and z = 0.771, where the highest redshift most likely reflects the distance to the host galaxy. For the z = 1.024 and z = 0.803 systems we tentatively detect MgI which suggests a dense environment at these redshifts. This and the strength of the z = 0.803 Fe lines indicate that this system very likely is a damped Ly-alpha absorber (DLA), which would be the first foreground DLA to be detected along a GRB afterglow sight line. The HST images are consistent with these findings: they show two blobs of light, one underneath the projected OT position, the presumed host galaxy, and the other 0.6" away, which is probably responsible for the absorption lines at z = 0.803. The lowest redshift system can be explained by either one of the two galaxies that are located roughly 2" away from the transient. Including these newly found systems, the total number of DLAS and Lyman limit systems along GRB afterglow sight lines is consistent with the number expected from QSO (quasi-stellar object) absorption line studies. We expect early spectroscopy of GRB afterglows to significantly increase the number of detected foreground absorption systems, and we discuss some advantages over QSO lines of sight.

  17. VizieR Online Data Catalog: GRB 130606A VLT/X-shooter spectroscopy (Hartoog+, 2015)

    NASA Astrophysics Data System (ADS)

    Hartoog, O. E.; Malesani, D.; Fynbo, J. P. U.; Goto, T.; Kruhler, T.; Vreeswijk, P. M.; De Cia, A.; Xu, D.; Moller, P.; Covino, S.; D'Elia, V.; Flores, H.; Goldoni, P.; Hjorth, J.; Jakobsson, P.; Krogager, J.-K.; Kaper, L.; Ledoux, C.; Levan, A. J.; Milvang-Jensen, B.; Sollerman, J.; Sparre, M.; Tagliaferri, G.; Tanvir, N. R.; de Ugarte Postigo, A.; Vergani, S. D.; Wiersema, K.; Datson, J.; Salinas, R.; Mikkelsen, K.; Aghanim, N.

    2015-06-01

    Reduced visual (VIS) and Near-IR (NIR) VLT/X-shooter spectra (before normalization) of the afterglow of GRB130606A (Pipeline produced, see headers of the fits files for additional info). The original data files and calibrations can be found on http://archive.eso.org/wdb/wdb/eso/xshooter/form under program 091.C-0934(C) querying the following coordinates: coord1 = 16 37 35.188 coord2 = +29 47 47.03 (2 data files).

  18. GRB 131014A: A Laboratory for Studying the Thermal-like and Non-thermal Emissions in Gamma-Ray Bursts, and the New LnThi-EnTh,restpeak,i Relation

    NASA Astrophysics Data System (ADS)

    Guiriec, S.; Mochkovitch, R.; Piran, T.; Daigne, F.; Kouveliotou, C.; Racusin, J.; Gehrels, N.; McEnery, J.

    2015-11-01

    Over the past few years, evidence has been accumulated in support of the existence of a thermal-like component during the prompt phase of gamma-ray bursts (GRBs). However, this component, which is often associated with the GRB jet's photosphere, is usually subdominant compared to a much stronger non-thermal one. The prompt emission of GRB 131014A—detected by the Fermi Gamma-ray Space Telescope (hereafter Fermi)—provides a unique opportunity to trace the history of this thermal-like component. Indeed, the thermal emission in GRB 131014A is much more intense than in other GRBs and a pure thermal episode is observed during the initial 0.16 s. The thermal-like component cools monotonically during the first second while the non-thermal emission kicks off. The intensity of the non-thermal component progressively increases until being energetically dominant at late time, similar to what is typically observed. This is a perfect scenario to disentangle the thermal component from the non-thermal component. The initial decaying and cooling phase of the thermal-like component is followed by a strong re-brightening and a re-heating episode; however, despite a much brighter second emission phase, the temperature of the thermal component does not reach its initial value. This re-brightening episode is followed by a global constant cooling until the end of the burst. We note that there is a shallower low-energy spectral slope than the typical index value +1, corresponding to a pure Planck function, which better matches with the thermal-like spectral shape; a spectral index around +0.6 seems to be in better agreement with the data. The non-thermal component is adequately fitted with a Band function whose low- and high-energy power-law indices are ˜-0.7 and <˜-3, respectively; this is also statistically globally equivalent to a cutoff power law with a ˜-0.7 index. This is in agreement with our previous results. Finally, a strong correlation is observed between the time

  19. GRB 090313 AND THE ORIGIN OF OPTICAL PEAKS IN GAMMA-RAY BURST LIGHT CURVES: IMPLICATIONS FOR LORENTZ FACTORS AND RADIO FLARES

    SciTech Connect

    Melandri, A.; Kobayashi, S.; Mundell, C. G.; Guidorzi, C.; Bersier, D.; Steele, I. A.; Smith, R. J.; De Ugarte Postigo, A.; Pooley, G.; Yoshida, M.; Castro-Tirado, A. J.; Gorosabel, J.; Kubanek, P.; Sota, A.; Gomboc, A.; Bremer, M.; Winters, J. M.; De Gregorio-Monsalvo, I.; GarcIa-Appadoo, D.

    2010-11-10

    We use a sample of 19 gamma-ray bursts (GRBs) that exhibit single-peaked optical light curves to test the standard fireball model by investigating the relationship between the time of the onset of the afterglow and the temporal rising index. Our sample includes GRBs and X-ray flashes for which we derive a wide range of initial Lorentz factors (40 < {Gamma} < 450). Using plausible model parameters, the typical frequency of the forward shock is expected to lie close to the optical band; within this low typical frequency framework, we use the optical data to constrain {epsilon}{sub e} and show that values derived from the early time light-curve properties are consistent with published typical values derived from other afterglow studies. We produce expected radio light curves by predicting the temporal evolution of the expected radio emission from forward and reverse shock components, including synchrotron self-absorption effects at early time. Although a number of GRBs in this sample do not have published radio measurements, we demonstrate the effectiveness of this method in the case of Swift GRB 090313, for which millimetric and centimetric observations were available, and conclude that future detections of reverse-shock radio flares with new radio facilities such as the EVLA and ALMA will test the low-frequency model and provide constraints on magnetic models.

  20. How Can The SN-GRB Time Delay Be Measured?

    NASA Technical Reports Server (NTRS)

    Norris, J. P.; Bonnell, J. T.

    2003-01-01

    The connection between SNe and GRBs, launched by SN 1998bw / GRB 980425 and clinched by SN 2003dh / GRB 030329-with the two GRBs differing by a factor of approximately 50000 in luminosity-so far suggests a rough upper limit of approximately 1-2 days for the delay between SN and GRB. Only four SNe have had nonnegligible coverage in close coincidence with the initial explosion, near the W shock breakout: two Qpe II, and two Type IC, SN 1999ex and SN 1998bw. For the latter, only a hint of the minimum between the UV maximum and the radioactivity bump served to help constrain the interval between SN and GRB. Swift GRB alerts may provide the opportunity to study many SNe through the UV breakout phase: GRB 980425 look dikes -apparently nearby, low- luminosity, soft-spectrum, long-lag GRBs-accounted for half of BATSE bursts near threshold, and may dominate the Swift yield near threshold, since it has sensitivity to lower energies than did BATSE. The SN to GRB delay timescale should be better constrained by prompt UV/optical observations alerted by these bursts. Definitive delay measurements may be obtained if long-lag bursters are truly nearby: The SNe/GRBs could emit gravitational radiation detectable by LIGO-II if robust non-axisymmetric bar instabilities develop during core collapse, and/or neutrino emission may be detectable as suggested by Meszaros et al.

  1. Polarization of the prompt gamma-ray emission from the gamma-ray burst of 6 December 2002.

    PubMed

    Coburn, Wayne; Boggs, Steven E

    2003-05-22

    Observations of the afterglows of gamma-ray bursts (GRBs) have revealed that they lie at cosmological distances, and so correspond to the release of an enormous amount of energy. The nature of the central engine that powers these events and the prompt gamma-ray emission mechanism itself remain enigmatic because, once a relativistic fireball is created, the physics of the afterglow is insensitive to the nature of the progenitor. Here we report the discovery of linear polarization in the prompt gamma-ray emission from GRB021206, which indicates that it is synchrotron emission from relativistic electrons in a strong magnetic field. The polarization is at the theoretical maximum, which requires a uniform, large-scale magnetic field over the gamma-ray emission region. A large-scale magnetic field constrains possible progenitors to those either having or producing organized fields. We suggest that the large magnetic energy densities in the progenitor environment (comparable to the kinetic energy densities of the fireball), combined with the large-scale structure of the field, indicate that magnetic fields drive the GRB explosion.

  2. Multi-wavelength Observations of GRB 111228A and Implications for the Fireball and its Environment

    NASA Astrophysics Data System (ADS)

    Xin, Li-Ping; Wang, Yuan-Zhu; Lin, Ting-Ting; Liang, En-Wei; Lü, Hou-Jun; Zhong, Shu-Qing; Urata, Yuji; Zhao, Xiao-Hong; Wu, Chao; Wei, Jian-Yan; Huang, Kui-Yun; Qiu, Yu-Lei; Deng, Jin-Song

    2016-02-01

    Observations of very early multi-wavelength afterglows are critical to reveal the properties of the radiating fireball and its environment as well as the central engine of gamma-ray bursts (GRBs). We report our optical observations of GRB 111228A from 95 s to about 50 hr after the burst trigger and investigate its properties of the prompt gamma-rays and the ambient medium using our data and the data from the Swift and Fermi missions. Our joint optical and X-ray spectral fits to the afterglow data show that the ambient medium features a low dust-to-gas ratio. Incorporating the energy injection effect, our best fit to the afterglow light curves with the standard afterglow model via the Markov Chain Monte Carlo technique shows that {ɛ }e=(6.9+/- 0.3)× {10}-2, {ɛ }B=(7.73+/- 0.62)× {10}-6,{E}K=(6.32+/- 0.86)× {10}53 {erg}, n=0.100+/- 0.014 cm-3. The low medium density likely implies that the afterglow jet may be in a halo or in a hot ISM. A chromatic shallow decay segment observed in the optical and X-ray bands is well explained with the long-lasting energy injection from the central engine, which would be a magnetar with a period of about 1.92 ms inferred from the data. The Ep of its time-integrated prompt gamma-ray spectrum is ˜26 KeV. Using the initial Lorentz factor ({{{Γ }}}0={476}-237+225) derived from our afterglow model fit, it is found that GRB 111228A satisfies the {L}{{iso}}-{E}p,z-{{{Γ }}}0 relation and bridges the typical GRBs and low luminosity GRBs in this relation.

  3. Discovery of a cosmological, relativistic outburst via its rapidly fading optical emission

    SciTech Connect

    Cenko, S. Bradley; Nugent, Peter E.; Miller, Adam A.; Bloom, Joshua S.; Filippenko, Alexei V.; Kulkarni, S. R.; Horesh, Assaf; Carpenter, John; Perley, Daniel A.; Groot, Paul J.; Hallinan, G.; Corsi, Alessandra; Fox, Derek B.; Frail, Dale A.; Gruber, D.; Rau, Arne; Gal-Yam, Avishay; Ofek, Eran O.; MacLeod, Chelsea L.; Kasliwal, Mansi M.; and others

    2013-06-01

    We report the discovery by the Palomar Transient Factory (PTF) of the transient source PTF11agg, which is distinguished by three primary characteristics: (1) bright (R {sub peak} = 18.3 mag), rapidly fading (ΔR = 4 mag in Δt = 2 days) optical transient emission; (2) a faint (R = 26.2 ± 0.2 mag), blue (g' – R = 0.17 ± 0.29 mag) quiescent optical counterpart; and (3) an associated year-long, scintillating radio transient. We argue that these observed properties are inconsistent with any known class of Galactic transients (flare stars, X-ray binaries, dwarf novae), and instead suggest a cosmological origin. The detection of incoherent radio emission at such distances implies a large emitting region, from which we infer the presence of relativistic ejecta. The observed properties are all consistent with the population of long-duration gamma-ray bursts (GRBs), marking the first time such an outburst has been discovered in the distant universe independent of a high-energy trigger. We searched for possible high-energy counterparts to PTF11agg, but found no evidence for associated prompt emission. We therefore consider three possible scenarios to account for a GRB-like afterglow without a high-energy counterpart: an 'untriggered' GRB (lack of satellite coverage), an 'orphan' afterglow (viewing-angle effects), and a 'dirty fireball' (suppressed high-energy emission). The observed optical and radio light curves appear inconsistent with even the most basic predictions for off-axis afterglow models. The simplest explanation, then, is that PTF11agg is a normal, on-axis long-duration GRB for which the associated high-energy emission was simply missed. However, we have calculated the likelihood of such a serendipitous discovery by PTF and find that it is quite small (≈2.6%). While not definitive, we nonetheless speculate that PTF11agg may represent a new, more common (>4 times the on-axis GRB rate at 90% confidence) class of relativistic outbursts lacking associated high

  4. DETERMINATION OF THE INTRINSIC LUMINOSITY TIME CORRELATION IN THE X-RAY AFTERGLOWS OF GAMMA-RAY BURSTS

    SciTech Connect

    Dainotti, Maria Giovanna; Petrosian, Vahe'; Singal, Jack; Ostrowski, Michal E-mail: vahep@stanford.edu E-mail: dainotti@oa.uj.edu.pl

    2013-09-10

    Gamma-ray bursts (GRBs), which have been observed up to redshifts z Almost-Equal-To 9.5, can be good probes of the early universe and have the potential to test cosmological models. Dainotti's analysis of GRB Swift afterglow light curves with known redshifts and a definite X-ray plateau shows an anti-correlation between the rest-frame time when the plateau ends (the plateau end time) and the calculated luminosity at that time (or approximately an anti-correlation between plateau duration and luminosity). Here, we present an update of this correlation with a larger data sample of 101 GRBs with good light curves. Since some of this correlation could result from the redshift dependences of these intrinsic parameters, namely, their cosmological evolution, we use the Efron-Petrosian method to reveal the intrinsic nature of this correlation. We find that a substantial part of the correlation is intrinsic and describe how we recover it and how this can be used to constrain physical models of the plateau emission, the origin of which is still unknown. The present result could help to clarify the debated nature of the plateau emission.

  5. A MISSING-LINK IN THE SUPERNOVA–GRB CONNECTION: THE CASE OF SN 2012ap

    SciTech Connect

    Chakraborti, Sayan; Soderberg, Alicia; Kamble, Atish; Margutti, Raffaella; Milisavljevic, Dan; Dittmann, Jason; Chomiuk, Laura; Yadav, Naveen; Ray, Alak; Hurley, Kevin; Bietenholz, Michael; Brunthaler, Andreas; Pignata, Giuliano; Pian, Elena; Mazzali, Paolo; Fransson, Claes; Bartel, Norbert; Hamuy, Mario; Levesque, Emily; MacFadyen, Andrew; and others

    2015-06-01

    Gamma-ray bursts (GRBs) are characterized by ultra-relativistic outflows, while supernovae are generally characterized by non-relativistic ejecta. GRB afterglows decelerate rapidly, usually within days, because their low-mass ejecta rapidly sweep up a comparatively larger mass of circumstellar material. However, supernovae with heavy ejecta can be in nearly free expansion for centuries. Supernovae were thought to have non-relativistic outflows except for a few relativistic ones accompanied by GRBs. This clear division was blurred by SN 2009bb, the first supernova with a relativistic outflow without an observed GRB. However, the ejecta from SN 2009bb was baryon loaded and in nearly free expansion for a year, unlike GRBs. We report the first supernova discovered without a GRB but with rapidly decelerating mildly relativistic ejecta, SN 2012ap. We discovered a bright and rapidly evolving radio counterpart driven by the circumstellar interaction of the relativistic ejecta. However, we did not find any coincident GRB with an isotropic fluence of more than one-sixth of the fluence from GRB 980425. This shows for the first time that central engines in SNe Ic, even without an observed GRB, can produce both relativistic and rapidly decelerating outflows like GRBs.

  6. Pair-dominated GeV-Optical Flash in GRB 130427A

    NASA Astrophysics Data System (ADS)

    Vurm, Indrek; Hascoët, Romain; Beloborodov, Andrei M.

    2014-07-01

    We show that the light curve of the double GeV+optical flash in GRB 130427A is consistent with radiation from the blast wave in a wind-type medium with density parameter A = ρr 2 ~ 5 × 1010 g cm-1. The peak of the flash is emitted by copious e ± pairs created and heated in the blast wave; our first-principle calculation determines the pair-loading factor and temperature of the shocked plasma. Using detailed radiative transfer simulations, we reconstruct the observed double flash. The optical flash is dominated by synchrotron emission from the thermal plasma behind the forward shock, and the GeV flash is produced via inverse Compton (IC) scattering by the same plasma. The seed photons for IC scattering are dominated by the prompt MeV radiation during the first tens of seconds, and by the optical to X-ray afterglow thereafter. IC cooling of the thermal plasma behind the forward shock reproduces all GeV data from a few seconds to ~1 day. We find that the blast wave Lorentz factor at the peak of the flash is Γ ≈ 200, and the forward shock magnetization is ɛB ~ 2 × 10-4. An additional source is required by the data in the optical and X-ray bands at times >102 s we speculate that this additional source may be a long-lived reverse shock in the explosion ejecta.

  7. Observações das explosões cósmicas de raios gama GRB021004 e GRB021211 com o satélite HETE

    NASA Astrophysics Data System (ADS)

    Braga, J.; Ricker, G.; Hurley, K.; Lamb, D.; Grew, G.; et al.

    2003-08-01

    O High Energy Transient Explorer (HETE) é o primeiro satélite inteiramente dedicado ao estudo das explosões cósmicas de raios gama (ECRGs). Lançado em 9 de outubro de 2000, o HETE possui instrumentação capaz de observar as ECRGs desde o UV até raios gama e localizá-las com precisão de ~ 1-10 minutos de arco. As localizações das ECRGs detectadas são disseminadas rapidamente (em alguns segundos) pela Internet através de uma rede de estações de recepção ao longo do equador. A participação brasileira nesse projeto se dá através da montagem e operação de uma estação de recepção em Natal, RN, e da participação na equipe científica da missão. Neste trabalho são apresentados resultados da observação pelo HETE de duas ECRGs: GRB 021004 e GRB 021211. A GRB021004 foi detectada em raios gama pelo HETE em 4 de outubro de 2002 e localizada em raios-X em apenas 48 s, quando a emissão de raios gama ainda estava se processando. A explosão, relativamente brilhante e longa, durou aproximadamente 100 s. Um transiente óptico de magnitude 15 foi detectado no local da explosão nove minutos após o evento, e observações realizadas após 7 horas determinaram um desvio para o vermelho de absorção de 1,6. O GRB021004 foi o burst mais bem observado até o momento e suas observações em vários comprimentos de onda têm sido fundamentais para o aprimoramento dos modelos de ECRGs. O GRB21211, um burst brilhante e rico em raios-X, foi detectado em 11 de dezembro de 2002 e localizado em raios-X em 22 s após o início do evento. A duração do burst foi de 2,3 s em altas energias (85 a 400 keV) e de 8,5 s em baixas energias (2 a 10 keV). Caso essa explosão não tivesse sido rapidamente localizada pelo HETE, ela teria sido classificada como "opticamente escura", já que o transiente óptico decaiu rapidamente de R < 14 a R»19 dentro dos primeiros 20 minutos e já estava mais fraco do que R»23 depois de 24 horas da ocorrência do burst. Ser

  8. Green chemistry-mediated synthesis of nanostructures of afterglow phosphor

    NASA Astrophysics Data System (ADS)

    Sharma, Pooja; Haranath, D.; Chander, Harish; Singh, Sukhvir

    2008-04-01

    Various nanostructures of SrAl 2O 4:Eu 2+, Dy 3+ (SAC) afterglow phosphor were prepared in a single-step reaction using a green chemistry-mediated modified combustion process. The evolution of hazardous NxOx gases during the customary combustion reaction was completely eliminated by employing an innovative complex formation route. Another fascinating feature of the process was that, a slight change in the processing conditions ensured the synthesis of either nanoparticles or nanowires. The photoluminescence spectrum of nanophosphor showed a slight blue shift in emission (˜511 nm) as compared to the bulk phosphor (˜520 nm). The afterglow (decay) profiles of SAC nanoparticles, nanowires and bulk phosphor were compared. The chemistry underlying the nanostructure synthesis and the probable afterglow mechanism were discussed.

  9. Identifying the Location in the Host Galaxy of Short GRB 1111l7A with the Chandra Sub- Arcsecond Position

    NASA Technical Reports Server (NTRS)

    Sakamoto, Takanori; Troja, E.; Aoki, K.; Guiriec, S.; Im, M.; Leloudas, G.; Malesani, D.; Melandri, A.; deUgartePostigo, A.; Urata, Y.; Xu, D.; DAvanzo, P.; Gorosabel, J.; Anderson, M. I.; Fynbo, J. P. U.; Aoki, K.; Sanchez-Ramirez, R.

    2012-01-01

    We present our successful program using Chandra for identifying the X-ray afterglow with sub-arcsecond accuracy for the short GRB 111117A d iscovered by Swift and Fermi. Thanks to our rapid target of opportuni ty request, Chandra clearly detected the X-ray afterglow, whereas no optical afterglow was found in deep optical observations. Instead, we clearly detect the host galaxy in optica; and also in near-infrared b ands. We found that the best photometric redshift fitofthe host is z = 1.31:(+0.46/-0.23) (90% confidence), making it one of the highest redshift short GRBs. Furthermore, we see an offset of 1.0+/-O.2 arcseco nds, which corresponds to 8.4+/-1.7 kpc aSBuming z= 1.31, between the host and the afterglow position. We discuss the importance of using Chandra for obtaining sub-arcsecond localization of the afterglow in X -rays for short GRBs to study GRB environments in great detail.

  10. AN IMAGING AND SPECTROSCOPIC STUDY OF FOUR STRONG Mg II ABSORBERS REVEALED BY GRB 060418

    SciTech Connect

    Pollack, L. K.; Prochaska, J. X.; Chen, H.-W.; Bloom, J. S.

    2009-08-20

    We present results from an imaging and spectroscopic study of four strong Mg II absorbers of W(2796) {approx}> 1 A revealed by the afterglow of GRB 060418 at z{sub GRB} = 1.491. These absorbers, at z = 0.603, 0.656, 1.107, and z {sub GRB}, exhibit large ion abundances that suggest neutral gas columns characteristic of damped Ly{alpha} systems. The imaging data include optical images obtained using Low-Resolution Imaging Spectrometer (LRIS) on the Keck I telescope and using Advanced Camera for Surveys on board Hubble Space Telescope, and near-infrared H-band images obtained using Persson's Auxiliary Nasmyth Infrared Camera on the Magellan Baade Telescope and K'-band images obtained using NIRC2 with laser guide star adaptive optics on the Keck II telescope. These images reveal six distinct objects at {delta} {theta} {approx}< 3.''5 of the afterglow's position, two of which exhibit well-resolved mature disk morphology, one shows red colors, and three are blue compact sources. Follow-up spectroscopic observations using LRIS confirm that one of the disk galaxies coincides with the Mg II absorber at z = 0.656. The observed broadband spectral energy distributions of the second disk galaxy and the red source indicate that they are associated with the absorbers at z = 0.603 and z = 1.107, respectively. These results show that strong Mg II absorbers identified in gamma-ray burst (GRB) afterglow spectra are associated with typical galaxies of luminosity {approx}0.1 - 1 L{sub *} at impact parameter of {rho} {approx}< 10 h {sup -1} kpc. The close angular separation would preclude easy detections toward a bright quasar. Finally, we associate the remaining three blue compact sources with the GRB host galaxy, noting that they are likely star-forming knots located at projected distances of {rho} = 2 - 12 h {sup -1} kpc from the afterglow. At the afterglow's position, we derive a 2{sigma} upper limit to the underlying star-formation rate intensity of 0.0074 M{sub sun} yr{sup -1} kpc

  11. GRB 120422A/SN 2012bz: Bridging the gap between low- and high-luminosity gamma-ray bursts

    NASA Astrophysics Data System (ADS)

    Schulze, S.; Malesani, D.; Cucchiara, A.; Tanvir, N. R.; Krühler, T.; de Ugarte Postigo, A.; Leloudas, G.; Lyman, J.; Bersier, D.; Wiersema, K.; Perley, D. A.; Schady, P.; Gorosabel, J.; Anderson, J. P.; Castro-Tirado, A. J.; Cenko, S. B.; De Cia, A.; Ellerbroek, L. E.; Fynbo, J. P. U.; Greiner, J.; Hjorth, J.; Kann, D. A.; Kaper, L.; Klose, S.; Levan, A. J.; Martín, S.; O'Brien, P. T.; Page, K. L.; Pignata, G.; Rapaport, S.; Sánchez-Ramírez, R.; Sollerman, J.; Smith, I. A.; Sparre, M.; Thöne, C. C.; Watson, D. J.; Xu, D.; Bauer, F. E.; Bayliss, M.; Björnsson, G.; Bremer, M.; Cano, Z.; Covino, S.; D'Elia, V.; Frail, D. A.; Geier, S.; Goldoni, P.; Hartoog, O. E.; Jakobsson, P.; Korhonen, H.; Lee, K. Y.; Milvang-Jensen, B.; Nardini, M.; Nicuesa Guelbenzu, A.; Oguri, M.; Pandey, S. B.; Petitpas, G.; Rossi, A.; Sandberg, A.; Schmidl, S.; Tagliaferri, G.; Tilanus, R. P. J.; Winters, J. M.; Wright, D.; Wuyts, E.

    2014-06-01

    Context. At low redshift, a handful of gamma-ray bursts (GRBs) have been discovered with luminosities that are substantially lower (Liso ≲ 1048.5 erg s-1) than the average of more distant ones (Liso ≳ 1049.5 erg s-1). It has been suggested that the properties of several low-luminosity (low-L) GRBs are due to shock break-out, as opposed to the emission from ultrarelativistic jets. This has led to much debate about how the populations are connected. Aims: The burst at redshift z = 0.283 from 2012 April 22 is one of the very few examples of intermediate-L GRBs with a γ-ray luminosity of Liso ~ 1049.6-49.9 erg s-1 that have been detected up to now. With the robust detection of its accompanying supernova SN 2012bz, it has the potential to answer important questions on the origin of low- and high-L GRBs and the GRB-SN connection. Methods: We carried out a spectroscopy campaign using medium- and low-resolution spectrographs with 6-10-m class telescopes, which covered a time span of 37.3 days, and a multi-wavelength imaging campaign, which ranged from radio to X-ray energies over a duration of ~270 days. Furthermore, we used a tuneable filter that is centred at Hα to map star-formation in the host and the surrounding galaxies. We used these data to extract and model the properties of different radiation components and fitted the spectral energy distribution to extract the properties of the host galaxy. Results: Modelling the light curve and spectral energy distribution from the radio to the X-rays revealed that the blast wave expanded with an initial Lorentz factor of Γ0 ~ 50, which is a low value in comparison to high-L GRBs, and that the afterglow had an exceptionally low peak luminosity density of ≲2 × 1030 erg s-1 Hz-1 in the sub-mm. Because of the weak afterglow component, we were able to recover the signature of a shock break-out in an event that was not a genuine low-L GRB for the first time. At 1.4 hr after the burst, the stellar envelope had a blackbody

  12. Energy Injection in Gamma-Ray Burst Afterglows

    NASA Astrophysics Data System (ADS)

    Laskar, Tanmoy; Berger, Edo; Margutti, Raffaella; Perley, Daniel; Zauderer, B. Ashley; Sari, Re'em; Fong, Wen-fai

    2015-11-01

    We present multi-wavelength observations and modeling of gamma-ray bursts (GRBs) that exhibit a simultaneous re-brightening in their X-ray and optical light curves, and are also detected at radio wavelengths. We show that the re-brightening episodes can be modeled by injection of energy into the blastwave and that in all cases the energy injection rate falls within the theoretical bounds expected for a distribution of energy with ejecta Lorentz factor. Our measured values of the circumburst density, jet opening angle, and beaming-corrected kinetic energy are consistent with the distribution of these parameters for long-duration GRBs at both z˜ 1 and z≳ 6, suggesting that the jet launching mechanism and environment of these events are similar to that of GRBs that do not have bumps in their light curves. However, events exhibiting re-brightening episodes have lower radiative efficiencies than average, suggesting that a majority of the kinetic energy of the outflow is carried by slow-moving ejecta, which is further supported by steep measured distributions of the ejecta energy as a function of Lorentz factor. We do not find evidence for reverse shocks over the energy injection period, implying that the onset of energy injection is a gentle process. We further show that GRBs exhibiting simultaneous X-ray and optical re-brightenings are likely the tail of a distribution of events with varying rates of energy injection, forming the most extreme events in their class. Future X-ray observations of GRB afterglows with Swift and its successors will thus likely discover several more such events, while radio follow-up and multi-wavelength modeling of similar events will unveil the role of energy injection in GRB afterglows.

  13. Implications of the Early X-Ray Afterglow Light Curves of Swift GRBs

    SciTech Connect

    Granot, Jonathan; Konigl, Arieh; Piran, Tsvi; /Hebrew U.

    2006-01-17

    According to current models, gamma-ray bursts (GRBs) are produced when the energy carried by a relativistic outflow is dissipated and converted into radiation. The efficiency of this process, {epsilon}{sub {gamma}}, is one of the critical factors in any GRB model. The X-ray afterglow light curves of Swift GRBs show an early stage of flattish decay. This has been interpreted as reflecting energy injection. When combined with previous estimates, which have concluded that the kinetic energy of the late ({approx}> 10 hr) afterglow is comparable to the energy emitted in {gamma}-rays, this interpretation implies very high values of {epsilon}{sub {gamma}}, corresponding to {approx}> 90% of the initial energy being converted into {gamma}-rays. Such a high efficiency is hard to reconcile with most models, including in particular the popular internal-shocks model. We re-analyze the derivation of the kinetic energy from the afterglow X-ray flux and re-examine the resulting estimates of the efficiency. We confirm that, if the flattish decay arises from energy injection and the pre-Swift broad-band estimates of the kinetic energy are correct, then {epsilon}{sub {gamma}} {approx}> 0.9. We discuss various issues related to this result, including an alternative interpretation of the light curve in terms of a two-component outflow model, which we apply to the X-ray observations of GRB 050315. We point out, however, that another interpretation of the flattish decay--a variable X-ray afterglow efficiency (e.g., due to a time dependence of afterglow shock microphysical parameters)--is possible. We also show that direct estimates of the kinetic energy from the late X-ray afterglow flux are sensitive to the assumed values of the shock microphysical parameters and suggest that broad-band afterglow fits might have underestimated the kinetic energy (e.g., by overestimating the fraction of electrons that are accelerated to relativistic energies). Either one of these possibilities implies a

  14. GRB Simulations in GLAST

    SciTech Connect

    Omodei, Nicola; Battelino, Milan; Komin, Nukri; Longo, Francesco; McEnery, Julie; Ryde, Felix; /Denver U.

    2007-10-22

    The Gamma-ray Large Area Space Telescope (GLAST), scheduled to be launched in fall of 2007, is the next generation satellite for high-energy gamma-ray astronomy. The Large Area Telescope (LAT) is a pair conversion telescope built with a high precision silicon tracker, a segmented CsI electromagnetic calorimeter and a plastic anticoincidence shield. The LAT will survey the sky in the energy range between 20 MeV to more than 300 GeV, shedding light on many issues left open by its highly successful predecessor EGRET. LAT will observe Gamma-Ray Bursts (GRB) in an energy range never explored before; to tie these frontier observations to the better-known properties at lower energies, a second instrument, the GLAST Burst Monitor (GBM) will provide important spectra and timing in the 10 keV to 30 MeV range. We briefly present the instruments onboard the GLAST satellite, their synergy in the GRB observations and the work done so far by the collaboration in simulation, analysis, and GRB sensitivity estimation.

  15. Implications for the Origin of GRB 070201 from LIGO Observations

    NASA Astrophysics Data System (ADS)

    Abbott, B.; Abbott, R.; Adhikari, R.; Agresti, J.; Ajith, P.; Allen, B.; Amin, R.; Anderson, S. B.; Anderson, W. G.; Arain, M.; Araya, M.; Armandula, H.; Ashley, M.; Aston, S.; Aufmuth, P.; Aulbert, C.; Babak, S.; Ballmer, S.; Bantilan, H.; Barish, B. C.; Barker, C.; Barker, D.; Barr, B.; Barriga, P.; Barton, M. A.; Bayer, K.; Betzwieser, J.; Beyersdorf, P. T.; Bhawal, B.; Bilenko, I. A.; Billingsley, G.; Biswas, R.; Black, E.; Blackburn, K.; Blackburn, L.; Blair, D.; Bland, B.; Bogenstahl, J.; Bogue, L.; Bork, R.; Boschi, V.; Bose, S.; Brady, P. R.; Braginsky, V. B.; Brau, J. E.; Brinkmann, M.; Brooks, A.; Brown, D. A.; Bullington, A.; Bunkowski, A.; Buonanno, A.; Burmeister, O.; Busby, D.; Byer, R. L.; Cadonati, L.; Cagnoli, G.; Camp, J. B.; Cannizzo, J.; Cannon, K.; Cantley, C. A.; Cao, J.; Cardenas, L.; Castaldi, G.; Cepeda, C.; Chalkley, E.; Charlton, P.; Chatterji, S.; Chelkowski, S.; Chen, Y.; Chiadini, F.; Christensen, N.; Clark, J.; Cochrane, P.; Cokelaer, T.; Coldwell, R.; Conte, R.; Cook, D.; Corbitt, T.; Coyne, D.; Creighton, J. D. E.; Croce, R. P.; Crooks, D. R. M.; Cruise, A. M.; Cumming, A.; Dalrymple, J.; D'Ambrosio, E.; Danzmann, K.; Davies, G.; DeBra, D.; Degallaix, J.; Degree, M.; Demma, T.; Dergachev, V.; Desai, S.; DeSalvo, R.; Dhurandhar, S.; Díaz, M.; Dickson, J.; Di Credico, A.; Diederichs, G.; Dietz, A.; Doomes, E. E.; Drever, R. W. P.; Dumas, J.-C.; Dupuis, R. J.; Dwyer, J. G.; Ehrens, P.; Espinoza, E.; Etzel, T.; Evans, M.; Evans, T.; Fairhurst, S.; Fan, Y.; Fazi, D.; Fejer, M. M.; Finn, L. S.; Fiumara, V.; Fotopoulos, N.; Franzen, A.; Franzen, K. Y.; Freise, A.; Frey, R.; Fricke, T.; Fritschel, P.; Frolov, V. V.; Fyffe, M.; Galdi, V.; Garofoli, J.; Gholami, I.; Giaime, J. A.; Giampanis, S.; Giardina, K. D.; Goda, K.; Goetz, E.; Goggin, L. M.; González, G.; Gossler, S.; Grant, A.; Gras, S.; Gray, C.; Gray, M.; Greenhalgh, J.; Gretarsson, A. M.; Grosso, R.; Grote, H.; Grunewald, S.; Guenther, M.; Gustafson, R.; Hage, B.; Hammer, D.; Hanna, C.; Hanson, J.; Harms, J.; Harry, G.; Harstad, E.; Hayler, T.; Heefner, J.; Heng, I. S.; Heptonstall, A.; Heurs, M.; Hewitson, M.; Hild, S.; Hirose, E.; Hoak, D.; Hosken, D.; Hough, J.; Hoyland, D.; Huttner, S. H.; Ingram, D.; Innerhofer, E.; Ito, M.; Itoh, Y.; Ivanov, A.; Johnson, B.; Johnson, W. W.; Jones, D. I.; Jones, G.; Jones, R.; Ju, L.; Kalmus, P.; Kalogera, V.; Kasprzyk, D.; Katsavounidis, E.; Kawabe, K.; Kawamura, S.; Kawazoe, F.; Kells, W.; Keppel, D. G.; Khalili, F. Ya.; Kim, C.; King, P.; Kissel, J. S.; Klimenko, S.; Kokeyama, K.; Kondrashov, V.; Kopparapu, R. K.; Kozak, D.; Krishnan, B.; Kwee, P.; Lam, P. K.; Landry, M.; Lantz, B.; Lazzarini, A.; Lei, M.; Leiner, J.; Leonhardt, V.; Leonor, I.; Libbrecht, K.; Lindquist, P.; Lockerbie, N. A.; Longo, M.; Lormand, M.; Lubinski, M.; Lück, H.; Machenschalk, B.; MacInnis, M.; Mageswaran, M.; Mailand, K.; Malec, M.; Mandic, V.; Marano, S.; Márka, S.; Markowitz, J.; Maros, E.; Martin, I.; Marx, J. N.; Mason, K.; Matone, L.; Matta, V.; Mavalvala, N.; McCarthy, R.; McClelland, D. E.; McGuire, S. C.; McHugh, M.; McKenzie, K.; McWilliams, S.; Meier, T.; Melissinos, A.; Mendell, G.; Mercer, R. A.; Meshkov, S.; Messenger, C. J.; Meyers, D.; Mikhailov, E.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Miyakawa, O.; Mohanty, S.; Moreno, G.; Mossavi, K.; MowLowry, C.; Moylan, A.; Mudge, D.; Mueller, G.; Mukherjee, S.; Müller-Ebhardt, H.; Munch, J.; Murray, P.; Myers, E.; Myers, J.; Nash, T.; Newton, G.; Nishizawa, A.; Numata, K.; O'Reilly, B.; O'Shaughnessy, R.; Ottaway, D. J.; Overmier, H.; Owen, B. J.; Pan, Y.; Papa, M. A.; Parameshwaraiah, V.; Patel, P.; Pedraza, M.; Penn, S.; Pierro, V.; Pinto, I. M.; Pitkin, M.; Pletsch, H.; Plissi, M. V.; Postiglione, F.; Prix, R.; Quetschke, V.; Raab, F.; Rabeling, D.; Radkins, H.; Rahkola, R.; Rainer, N.; Rakhmanov, M.; Ramsunder, M.; Ray-Majumder, S.; Re, V.; Rehbein, H.; Reid, S.; Reitze, D. H.; Ribichini, L.; Riesen, R.; Riles, K.; Rivera, B.; Robertson, N. A.; Robinson, C.; Robinson, E. L.; Roddy, S.; Rodriguez, A.; Rogan, A. M.; Rollins, J.; Romano, J. D.; Romie, J.; Route, R.; Rowan, S.; Rüdiger, A.; Ruet, L.; Russell, P.; Ryan, K.; Sakata, S.; Samidi, M.; Sancho de la Jordana, L.; Sandberg, V.; Sannibale, V.; Saraf, S.; Sarin, P.; Sathyaprakash, B. S.; Sato, S.; Saulson, P. R.; Savage, R.; Savov, P.; Schediwy, S.; Schilling, R.; Schnabel, R.; Schofield, R.; Schutz, B. F.; Schwinberg, P.; Scott, S. M.; Searle, A. C.; Sears, B.; Seifert, F.; Sellers, D.; Sengupta, A. S.; Shawhan, P.; Shoemaker, D. H.; Sibley, A.; Siemens, X.; Sigg, D.; Sinha, S.; Sintes, A. M.; Slagmolen, B. J. J.; Slutsky, J.; Smith, J. R.; Smith, M. R.; Somiya, K.; Strain, K. A.; Strom, D. M.; Stuver, A.; Summerscales, T. Z.; Sun, K.-X.; Sung, M.; Sutton, P. J.; Takahashi, H.; Tanner, D. B.; Taylor, R.; Taylor, R.; Thacker, J.; Thorne, K. A.; Thorne, K. S.; Thüring, A.; Tokmakov, K. V.; Torres, C.; Torrie, C.; Traylor, G.; Trias, M.; Tyler, W.; Ugolini, D.; Urbanek, K.; Vahlbruch, H.; Vallisneri, M.; Van Den Broeck, C.; Varvella, M.; Vass, S.; Vecchio, A.; Veitch, J.; Veitch, P.; Villar, A.; Vorvick, C.; Vyachanin, S. P.; Waldman, S. J.; Wallace, L.; Ward, H.; Ward, R.; Watts, K.; Weidner, A.; Weinert, M.; Weinstein, A.; Weiss, R.; Wen, S.; Wette, K.; Whelan, J. T.; Whitcomb, S. E.; Whiting, B. F.; Wilkinson, C.; Willems, P. A.; Williams, L.; Willke, B.; Wilmut, I.; Winkler, W.; Wipf, C. C.; Wise, S.; Wiseman, A. G.; Woan, G.; Woods, D.; Wooley, R.; Worden, J.; Wu, W.; Yakushin, I.; Yamamoto, H.; Yan, Z.; Yoshida, S.; Yunes, N.; Zanolin, M.; Zhang, J.; Zhang, L.; Zhao, C.; Zotov, N.; Zucker, M.; zur Mühlen, H.; Zweizig, J.; LIGO Scientific Collaboration; Hurley, K. C.

    2008-07-01

    We analyzed the available LIGO data coincident with GRB 070201, a short-duration, hard-spectrum γ-ray burst (GRB) whose electromagnetically determined sky position is coincident with the spiral arms of the Andromeda galaxy (M31). Possible progenitors of such short, hard GRBs include mergers of neutron stars or a neutron star and a black hole, or soft γ-ray repeater (SGR) flares. These events can be accompanied by gravitational-wave emission. No plausible gravitational-wave candidates were found within a 180 s long window around the time of GRB 070201. This result implies that a compact binary progenitor of GRB 070201, with masses in the range 1 M⊙ < m1 < 3 M⊙ and 1 M⊙ < m2 < 40 M⊙, located in M31 is excluded at >99% confidence. If the GRB 070201 progenitor was not in M31, then we can exclude a binary neutron star merger progenitor with distance D < 3.5 Mpc, assuming random inclination, at 90% confidence. The result also implies that an unmodeled gravitational-wave burst from GRB 070201 most probably emitted less than 4.4 × 10-4 M⊙c2 (7.9 × 1050 ergs) in any 100 ms long period within the signal region if the source was in M31 and radiated isotropically at the same frequency as LIGO's peak sensitivity (f ≈ 150 Hz). This upper limit does not exclude current models of SGRs at the M31 distance.

  16. The Late Peaking Afterglow of GR8 100418A

    NASA Technical Reports Server (NTRS)

    Marshall, Frank; Antonelli, L. A.; Burrows, D. N.; Covino, S.; dePasquale, M.; Evans, P. A.; Fugazza, D.; Holland, S. T.; Liang, E. W.; OBrien, P. T.; Osborne, J. P.; Pagani, C.; Sakamoto, T.; Siegel, M. H.; Wu, X. F.; Zhang, B.

    2010-01-01

    GRB 100418A is a long Gamma-Ray Burst at redshift z=0.6235 discovered with the Swift Gamma-Ray Burst Explorer with unusual optical and X-ray light curves ' After an initial short-lived, rapid decline in X-rays, the optical and X-ray light curves observed with Swift are approximately flat or rising slightly out to at least approx.7 ks after the trigger, peak at approx.50 ks, and then follow an approximately power-law decay. Such a long optical plateau and late peaking is rarely seen in 6R8 afterglows. Observations with REM during a gap in the Swift coverage indicate a bright optical flare at approx.25 ks, The long plateau phase of the afterglow is interpreted using either a model with continuous injection of energy into the forward shock of the burst or a model in which the 'et of the burst is viewed off-axis. In both models the isotropic kinetic energy in the late afterglow after the plateau phase is >100 times the 10(exp 51) erg of the prompt isotropic gamma-ray energy release. The energy injection model is favored because the off-axis 'et model would require the intrinsic $T f801$ for the GR8 'et viewed on-axis to be very short, approx.10 ms, and the intrinsic isotropic gamma-ray energy release and the true jet energy to be much higher than the typical values of known short GRBs^ The non-detection of a 'et break up to approx.2 Ms indicates a jet half-opening angle of at least 14 degrees, and a relatively high collimation-corrected 'et energy of at least 10(exp 52) erg.

  17. A Search for Early High-Energy Afterglows in BATSE Gamma-Ray Bursts

    NASA Technical Reports Server (NTRS)

    Giblin, Timothy W.

    2003-01-01

    The scope of this project was to perform a detailed search for the early high-energy afterglow component of gamma-ray bursts (GRBs) in the BATSE GRB data archive. GRBs are believed to be the product of shock waves generated in a relativistic outflow from the demise of extremely massive stars and/or binary neutron star mergers. The outflow undeniably encounters the ambient medium of the progenitor object and another shock wave is set up. A forward shock propagates into the medium and a reverse shock propagates through the ejecta. This "external" shock dissipates the kinetic energy of the ejecta in the form of radiation via synchrotron losses and slows the outflow eventually to a non-relativistic state. Radiation from the forward external shock is therefore expected to be long-lived, lasting days, weeks, and even months. This radiation is referred to as the 'afterglow'.

  18. CORRELATED SPECTRAL AND TEMPORAL BEHAVIOR OF LATE-TIME AFTERGLOWS OF GAMMA-RAY BURSTS

    SciTech Connect

    Dado, Shlomo; Dar, Arnon

    2012-12-20

    The cannonball (CB) model of gamma-ray bursts (GRBs) predicts that the asymptotic behavior of the spectral energy density of GRB afterglows is a power law in time and in frequency, and the difference between the temporal and spectral power-law indices, {alpha}{sub X} - {beta}{sub X}, is restricted to the values 0, 1/2, and 1. Here we report the distributions of the values {alpha}{sub X} and {beta}{sub X}, and their difference for a sample of 315 Swift GRBs. This sample includes all Swift GRBs that were detected before 2012 August 1, whose X-ray afterglow extended well beyond 1 day and the estimated error in {alpha}{sub X} - {beta}{sub X} was {<=}0.25. The values of {alpha}{sub X} were extracted from the CB-model fits to the entire light curves of their X-ray afterglow while the spectral index was extracted by the Swift team from the time-integrated X-ray afterglow of these GRBs. We found that the distribution of the difference {alpha}{sub X} - {beta}{sub X} for these 315 Swift GRBs has three narrow peaks around 0, 1/2, and 1 whose widths are consistent with being due to the measurement errors, in agreement with the CB-model prediction.

  19. Polarization Evolution of Early Optical Afterglows of Gamma-Ray Bursts

    NASA Astrophysics Data System (ADS)

    Lan, Mi-Xiang; Wu, Xue-Feng; Dai, Zi-Gao

    2016-01-01

    The central engine and jet composition of gamma-ray bursts (GRBs) remain mysterious. Here we suggest that observations on the polarization evolution of early optical afterglows may shed light on these questions. We first study the dynamics of a reverse shock and a forward shock that are generated during the interaction of a relativistic jet and its ambient medium. The jet is likely magnetized with a globally large-scale magnetic field from the central engine. The existence of the reverse shock requires that the magnetization degree of the jet should not be high (σ ≤ 1), so that the jet is mainly composed of baryons and leptons. We then calculate the light curves and polarization evolution of early optical afterglows and find that when the polarization position angle changes by 90° during the early afterglow, the polarization degree is zero for a toroidal magnetic field but is very likely to be nonzero for an aligned magnetic field. This result would be expected to provide a probe for the central engine of GRBs because an aligned field configuration could originate from a magnetar central engine and a toroidal field configuration could be produced from a black hole via the Blandford-Znajek mechanism. Finally, for such two kinds of magnetic field configurations, we fit the observed data of the early optical afterglow of GRB 120308A equally well.

  20. Afterglow processes responsible for memory effect in nitrogen

    SciTech Connect

    Pejovic, M. M.; Nesic, N. T.; Pejovic, M. M.; Zivanovic, E. N.

    2012-07-01

    The mechanisms responsible for memory effect in nitrogen at 6.6 mbars have been analysed based on experimental data of electrical breakdown time delay as a function of afterglow period. The analysis has shown that positive ions remaining from previous discharge, as well as metastable and highly vibrationally excited molecules, are responsible for memory effect in the early afterglow. These molecules lead to the formation of positive ions in mutual collisions in the afterglow. Positive ions initiate secondary electron emission from the cathode of a nitrogen-filled tube when voltage higher than static breakdown voltage is applied on the electrodes. On the other hand, N({sup 4}S) atoms have a large influence on memory effect in late afterglow. They recombine on the cathode surface forming metastable molecules, which release secondary electrons in collision with the cathode. The higher values of electrical breakdown time delay in the case of the tube with borosilicate glass walls than in the case of the tube with copper walls are a consequence of faster de-excitation of neutral active particles on the glass. Indirect confirmation of this assumption has been obtained when the tubes were irradiated with gamma radiation.

  1. Afterglow processes responsible for memory effect in nitrogen

    NASA Astrophysics Data System (ADS)

    Pejović, M. M.; Nešić, N. T.; Pejović, M. M.; Živanović, E. N.

    2012-07-01

    The mechanisms responsible for memory effect in nitrogen at 6.6 mbars have been analysed based on experimental data of electrical breakdown time delay as a function of afterglow period. The analysis has shown that positive ions remaining from previous discharge, as well as metastable and highly vibrationally excited molecules, are responsible for memory effect in the early afterglow. These molecules lead to the formation of positive ions in mutual collisions in the afterglow. Positive ions initiate secondary electron emission from the cathode of a nitrogen-filled tube when voltage higher than static breakdown voltage is applied on the electrodes. On the other hand, N(S4) atoms have a large influence on memory effect in late afterglow. They recombine on the cathode surface forming N2(AΣ3u+) metastable molecules, which release secondary electrons in collision with the cathode. The higher values of electrical breakdown time delay in the case of the tube with borosilicate glass walls than in the case of the tube with copper walls are a consequence of faster de-excitation of neutral active particles on the glass. Indirect confirmation of this assumption has been obtained when the tubes were irradiated with gamma radiation.

  2. Spectrophotometric analysis of gamma-ray burst afterglow extinction curves with X-Shooter

    NASA Astrophysics Data System (ADS)

    Japelj, J.; Covino, S.; Gomboc, A.; Vergani, S. D.; Goldoni, P.; Selsing, J.; Cano, Z.; D'Elia, V.; Flores, H.; Fynbo, J. P. U.; Hammer, F.; Hjorth, J.; Jakobsson, P.; Kaper, L.; Kopač, D.; Krühler, T.; Melandri, A.; Piranomonte, S.; Sánchez-Ramírez, R.; Tagliaferri, G.; Tanvir, N. R.; de Ugarte Postigo, A.; Watson, D.; Wijers, R. A. M. J.

    2015-07-01

    We use gamma-ray burst (GRB) afterglow spectra observed with the VLT/X-Shooter spectrograph to measure rest-frame extinction in GRB lines-of-sight by modelling the broadband near-infrared (NIR) to X-ray afterglow spectral energy distributions (SEDs). Our sample consists of nine Swift GRBs, of which eight belong to the long-duration and one to the short-duration class. Dust is modelled using the average extinction curves of the Milky Way and the two Magellanic Clouds. We derive the rest-frame extinction of the entire sample, which fall in the range 0 ≲ AV ≲ 1.2. Moreover, the SMC extinction curve is the preferred extinction curve template for the majority of our sample, a result that is in agreement with those commonly observed in GRB lines of sights. In one analysed case (GRB 120119A), the common extinction curve templates fail to reproduce the observed extinction. To illustrate the advantage of using the high-quality, X-Shooter afterglow SEDs over the photometric SEDs, we repeat the modelling using the broadband SEDs with the NIR-to-UV photometric measurements instead of the spectra. The main result is that the spectroscopic data, thanks to a combination of excellent resolution and coverage of the blue part of the SED, are more successful in constraining extinction curves and therefore dust properties in GRB hosts with respect to photometric measurements. In all cases but one the extinction curve of one template is preferred over the others. We show that themodelled values of the extinction AV and the spectral slope, obtained through spectroscopic and photometric SED analysis, can differ significantly for individual events, though no apparent trend in the differences is observed. Finally we stress that, regardless of the resolution of the optical-to-NIR data, the SED modelling gives reliable results only when the fit is performed on a SED covering a broader spectral region (in our case extending to X-rays). Based on observations collected at the European

  3. ROSAT Imaging of GRB920525 and GRB930118

    NASA Technical Reports Server (NTRS)

    McNamara, Bernie

    1997-01-01

    For this effort we requested ROSAT images of two small gamma-ray burst (GRB) error boxes. Our goal was to search for sources that might be associated with the quiescent site of a GRB. More than 1000 GRBs have been detected in the twenty five years since their discovery, yet their origin remains a mystery. No real-time or quiescent counterparts at any wavelength have been identified as sources of GRBs despite considerable follow-up efforts. Ground based campaigns to examine GRB error boxes shortly after the bursts have revealed no transient, or highly variable objects at optical and radio wavelengths in the time period of more than 7 hours after the burst. Due to the heavy demand on X-ray satellite time, and the difficulty of re-scheduling observations, rapid follow-up observations at high energies have not been obtained as quickly as the ground based-efforts. In fact, X-ray images of GRB error boxes are normally obtained months-years after burst detection. The current fastest X-ray response time is over two weeks. Deep imaging of GRB error boxes at X-ray wavelengths is an additional observational approach that can be used to constrain models of the origin of GRBs. We combined the results of our investigation of the GRB920525 error box with that of a prior ROSAT PSPC observation of GRB910814 and submitted them for publication. We conclude that based upon our efforts and those of others, deep X-ray observations obtained long after the GRB are not likely to yield further productive results until smaller GRB error boxes become available. It may be possible to obtain such small error boxes in the near future from XTE, HETE and an augmented IPN.

  4. The statistics of BAT-to-XRT flux ratio in GRB:Evidence for a characteristic value and its implications

    NASA Astrophysics Data System (ADS)

    Kazanas, Demosthenes; Racusin, Judith L.

    2016-04-01

    We present the statistics of the ratio, R, between the prompt and afterglow ``plateau" fluxes of GRB. This we define as the ratio between the mean prompt energy flux inSwift BAT and the Swift XRT one, immediately following the steep transition between these two states and the beginning of the afterglow stage referred to as the ``plateau". Like the distribution of many other GRB observables, the histogram of R is log-normal with maximum at a value Rm ~ 2000, FWHM of about 2 decades and with the entire distribution spanning about 5 decades in the value of R. We note that the peak of the distribution is close to the proton-to-electron mass ratio Rm ~ mp/me=1836 , as proposed to be the case, on the basis of a specific model of the GRB dissipation process. It therefore appears that, in addition to the values of the energy of peak luminosity Ep ~ mec2, GRB present us with one more quantity with an apparent characteristic value. The fact that the values of both these quantities (Ep and R ) are consistent with the same specific model invoked to account for the efficient conversion of their relativistic proton energies to electrons, argues favorably for its underlying assumptions.

  5. An investigation into the role of metastable argon atoms in the afterglow plasma of a low pressure discharge

    NASA Astrophysics Data System (ADS)

    Strauss, J. A.; Ferreira, N. P.; Human, H. G. C.

    An investigation into the behaviour of metastable argon atoms in a low pressure (250 Pa) pulsed electrical discharge was undertaken in an effort to find the cause of the persisting emission from sputtered metal atoms in the afterglow of an atomic fluorimeter. Results obtained by time-resolved emission and absorption measurements of several argon and copper spectral lines indicate that low energy electrons in the afterglow are converted to high energy electrons via the recombination of electrons with argon ions and the subsequent collisions of pairs of metastable argon atoms. The high energy electrons excite the sputtered metal atoms to give rise to a slow decaying emission tail in the afterglow. A probable change in the electron energy distribution in the afterglow may also have an effect on the observed emission. This phenomenon may be reduced by the use of a suitable quenching gas.

  6. Perspective on Afterglows: Numerically Computed Views, Light Curves, and the Analysis of Homogeneous and Structured Jets with Lateral Expansion

    NASA Astrophysics Data System (ADS)

    Salmonson, Jay D.

    2003-08-01

    Herein I present numerical calculations of light curves of homogeneous and structured afterglows with various lateral expansion rates as seen from any vantage point. Such calculations allow for direct simulation of observable quantities for complex afterglows with arbitrary energy distributions and lateral expansion paradigms. A simple, causal model is suggested for lateral expansion of the jet as it evolves: namely, that the lateral expansion kinetic energy derives from the forward kinetic energy. As such, the homogeneous jet model shows that lateral expansion is important at all times in the afterglow evolution and that analytical scaling laws do a poor job at describing the afterglow decay before and after the break. In particular, I find that lateral expansion does not cause a break in the light curve as had been predicted. A primary purpose of this paper is to study structured afterglows, which do a good job of reproducing global relationships and correlations in the data and thus suggest the possibility of a universal afterglow model. Simulations of structured jets show a general trend in which jet breaks become more pronounced with increasing viewing angle with respect to the jet axis. In fact, under certain conditions a bump can occur in the light curve at the jet-break time. I derive scaling relations for this bump and suggest that it may be a source of some bumps in observed light curves such as that of GRB 000301C. A couple of lateral expansion models are tested over a range of efficiencies and viewing angles, and it is found that lateral expansion can, in some cases, substantially sharpen the jet break. I show flux surface contour maps and simulated images of the afterglows that give insight into how they evolve and determine their light curves.

  7. Study of argon flowing afterglow with nitrogen injection

    SciTech Connect

    Mazánková, V.; Krčma, F.; Trunec, D.

    2013-10-28

    In this work, the reaction kinetics in argon flowing afterglow with nitrogen addition was studied by optical emission spectroscopy. The DC flowing post-discharge in pure argon was created in quartz tube at the total gas pressure of 1000 Pa and discharge power of 60 W. The nitrogen was added into the afterglow at the distance of 9 cm behind the active discharge. The optical emission spectra were measured along the flow tube. The argon spectral lines and after nitrogen addition also nitrogen second positive system (SPS) were identified in the spectra. The measurement of spatial dependence of SPS intensity showed a very slow decay of the intensity and the decay rate did not depend on the nitrogen concentration. In order to explain this behavior a kinetic model for reaction in afterglow was developed. This model showed that C {sup 3}Π{sub u} state of molecular nitrogen, which is the upper state of SPS emission, is produced by excitation transfer from argon metastables to nitrogen molecules. However, the argon metastables are also produced at Ar{sub 2}{sup +} ion recombination with electrons and this limits the decay of argon metastable concentration and it results in very slow decay of SPS intensity.

  8. Spectrophotometric redshifts. A new approach to the reduction of noisy spectra and its application to GRB 090423

    NASA Astrophysics Data System (ADS)

    Stefanon, M.; Fernandez-Soto, A.; Fugazza, D.

    2011-01-01

    Context. The measurement of redshifts for objects on the verge of instrumental observability is difficult and prone to error. This is especially true for almost featureless spectra, as is the case for GRB afterglows. They can be detected out to the farthest distances, and usually spectroscopy poses a serious problem because they fade quickly. Aims: We have developed a new method that is close in philosophy to the photometric redshift technique, which can be applied to spectral data with a very low signal-to-noise ratio. We intend to measure redshifts, while minimising the dangers posed by the usual extraction techniques. Methods: GRB afterglows have generally very simple optical spectra, which can be described well by a pure power law, over which the separate effects of absorption and reddening in the GRB host, the intergalactic medium, and our own Galaxy are superimposed. We model all these effects over a series of template afterglow spectra to produce a set of clean spectra that reproduce what would reach our telescope. We also carefully model the effects of the telescope-spectrograph combination and the properties of noise in the data, which are then applied to the template spectra. The final templates are compared to the two-dimensional spectral data, and the basic parameters (redshift, spectral index, hydrogen absorption column) are estimated with statistical tools. Results: We show how our method works by applying it to our data of the NIR afterglow of Swift GRB 090423. At z ≈ 8.2, this was the most distant object ever observed. Our team took a spectrum using the Telescopio Nazionale Galileo, which we use in this article to derive its redshift and its intrinsic neutral hydrogen column density. Our best fit yields z = 8.4+0.05-0.03 and N(HI < 5 × 1020 cm-2, but with a highly non-Gaussian uncertainty including the redshift range z ∈ [6.7, 8.5] at the 2-sigma confidence level. Conclusions: Our method will be useful for maximising the recovered information

  9. Spectral lag features of GRB 060814 from swift bat and Suzaku observations

    SciTech Connect

    Roychoudhury, Arundhati; Sarkar, Samir K.; Bhadra, Arunava E-mail: samirksarkar@rediffmail.com

    2014-02-20

    This work reports a study on the spectral lag of the prompt emission spectrum of a multi-pulse gamma-ray burst (GRB) GRB 060814 (z = 0.84) using the observations of the Swift Burst Alert Telescope and the Suzaku Wide Area Monitor. We found that the spectral lag for GRB 060814 is positive for the first two and the fourth pulses, while the third pulse exhibits negative lag. However, the time variation of the E {sub peak} of all the stated pulses shows a similar trend. The leading models for spectral lags in GRBs are thus found inadequate to explain the observed spectral lag features of GRB 060814. Probable causes of the spectral lag characteristics of GRB 060814 are discussed.

  10. Synchrotron Origin of the Typical GRB Band Function

    NASA Astrophysics Data System (ADS)

    Zhang, Binbin

    2016-07-01

    We perform a time-resolved spectral analysis of GRB 130606B within the framework of a fast-cooling synchrotron radiation model with magnetic field strength in the emission region decaying with time, as proposed by Uhm & Zhang. The data from all time intervals can be successfully fit by the model. The same data can be equally well fit by the empirical Band function with typical parameter values. Our results, which involve only minimal physical assumptions, offer one natural solution to the origin of the observed GRB spectra and imply that, at least some, if not all, Band-like GRB spectra with typical Band parameter values can indeed be explained by synchrotron radiation.

  11. GRB 080319B: Naked-eye Astronomy from z=1

    NASA Astrophysics Data System (ADS)

    Burrows, David N.

    2008-05-01

    The Swift Gamma-Ray Burst Explorer has revolutionized our view of gamma-ray bursts through its rapid localizations and detailed X-ray and optical light curves, while also contributing to many other areas of astronomy including AGN, SNe, CVs, stellar flares, comets, and galactic transients. Its multiwavelength capability, rapid slewing and flexible schedule make it a powerful observatory for many types of transient phenomena or multiwavelength monitoring campaigns. I will discuss some of the major accomplishments of Swift in its first 3 years of operation, and then will turn my attention to the phenomenal GRB 080319B, the first gamma-ray burst visible to the naked eye, and the only naked eye object ever "seen” at z 1. The combination of Swift's unique capabilities, a new generation of ground-based robotic telescopes, and a world-wide followup effort have resulted in the best multicolor observations ever obtained on a GRB afterglow. This unique object illustrates the potential power of GRBs as high-z tracers of cosmic structure, and points the way to future missions designed to use GRBs as background sources to measure the structure of the Universe well beyond the reionization era.

  12. The optical rebrightening of GRB100814A: an interplay of forward and reverse shocks?

    NASA Astrophysics Data System (ADS)

    De Pasquale, Massimiliano; Kuin, N. P. M.; Oates, S.; Schulze, S.; Cano, Z.; Guidorzi, C.; Beardmore, A.; Evans, P. A.; Uhm, Z. L.; Zhang, B.; Page, M.; Kobayashi, S.; Castro-Tirado, A.; Gorosabel, J.; Sakamoto, T.; Fatkhullin, T.; Pandey, S. B.; Im, M.; Chandra, P.; Frail, D.; Gao, H.; Kopač, D.; Jeon, Y.; Akerlof, C.; Huang, K. Y.; Pak, S.; Park, W.-K.; Gomboc, A.; Melandri, A.; Zane, S.; Mundell, C. G.; Saxton, C. J.; Holland, S. T.; Virgili, F.; Urata, Y.; Steele, I.; Bersier, D.; Tanvir, N.; Sokolov, V. V.; Moskvitin, A. S.

    2015-05-01

    We present a wide data set of gamma-ray, X-ray, UV/Opt/IR (UVOIR), and radio observations of the Swift GRB100814A. At the end of the slow decline phase of the X-ray and optical afterglow, this burst shows a sudden and prominent rebrightening in the optical band only, followed by a fast decay in both bands. The optical rebrightening also shows chromatic evolution. Such a puzzling behaviour cannot be explained by a single component model. We discuss other possible interpretations, and we find that a model that incorporates a long-lived reverse shock and forward shock fits the temporal and spectral properties of GRB100814 the best.

  13. WIDGET: System Performance and GRB Prompt Optical Observations

    NASA Astrophysics Data System (ADS)

    Urata, Yuji; Tashiro, Makoto S.; Tamagawa, Toru; Usui, Fumihiko; Kuwahara, Makoto; Lin, Hungmiao; Kageyama, Shoichi; Iwakiri, Wataru; Sugasahara, Takako; Takahara, Kazuki; Kodaka, Natsuki; Abe, Keiichi; Masuno, Keisuke; Onda, Kaori

    2011-02-01

    The WIDeField telescope for Gamma-ray burst Early Timing (WIDGET) is used for a fully automated, ultra-wide-field survey aimed at detecting the prompt optical emission associated with Gamma-ray Bursts (GRBs). WIDGET surveys the HETE-2 and Swift/BAT pointing directions, covering a total field of view of 62° × 62° every 10 secounds using a unfiltered system. This monitoring survey allows the exploration of optical emission before the γ-ray trigger. The unfiltered magnitude is well converted to the SDSS r' system at a 0.1 mag level. Since 2004, WIDGET has made a total of ten simultaneous and one pre-trigger GRB observations. The efficiency of synchronized observations with HETE-2 is four-times better than that of Swift. There has been no bright optical emission similar to that from GRB 080319B. A statistical analysis implies that GRB 080319B is a rare event. This paper summarizes the design and operation of the WIDGET system and the simultaneous GRB observations obtained with this instrument.

  14. GRB 120521C at z ∼ 6 and the properties of high-redshift γ-ray bursts

    SciTech Connect

    Laskar, Tanmoy; Berger, Edo; Zauderer, B. Ashley; Margutti, Raffaella; Fong, Wen-fai; Tanvir, Nial; Wiersema, Klaas; Levan, Andrew; Perley, Daniel; Menten, Karl; Hrudkova, Marie

    2014-01-20

    We present optical, near-infrared, and radio observations of the afterglow of GRB 120521C. By modeling the multi-wavelength data set, we derive a photometric redshift of z ≈ 6.0, which we confirm with a low signal-to-noise ratio spectrum of the afterglow. We find that a model with a constant-density environment provides a good fit to the afterglow data, with an inferred density of n ≲ 0.05 cm{sup –3}. The radio observations reveal the presence of a jet break at t {sub jet} ≈ 7 d, corresponding to a jet opening angle of θ{sub jet} ≈ 3°. The beaming-corrected γ-ray and kinetic energies are E {sub γ} ≈ E{sub K} ≈ 3 × 10{sup 50} erg. We quantify the uncertainties in our results using a detailed Markov Chain Monte Carlo analysis, which allows us to uncover degeneracies between the physical parameters of the explosion. To compare GRB 120521C to other high-redshift bursts in a uniform manner we re-fit all available afterglow data for the two other bursts at z ≳ 6 with radio detections (GRBs 050904 and 090423). We find a jet break at t {sub jet} ≈ 15 d for GRB 090423, in contrast to previous work. Based on these three events, we find that γ-ray bursts (GRBs) at z ≳ 6 appear to explode in constant-density environments, and exhibit a wide range of energies and densities that span the range inferred for lower redshift bursts. On the other hand, we find a hint for narrower jets in the z ≳ 6 bursts, potentially indicating a larger true event rate at these redshifts. Overall, our results indicate that long GRBs share a common progenitor population at least to z ∼ 8.

  15. GRB 090417B and its Host Galaxy: A Step Towards an Understanding of Optically-Dark Gamma-Ray Bursts

    NASA Technical Reports Server (NTRS)

    Holland, Stephen T.; Sbarufatti, Boris; Shen, Rongfeng; Schady, Patricia; Cummings, Jay R.; Fonseca, Emmanuel; Fynbo, Johan P. U.; Jakobsson, Pall; Leitet, Elisabet; Linne, Staffan; Roming, Peter W.A.; Still, Martin; Zhang, Bing

    2009-01-01

    GRB 090417B was an unusually long burst with a T(sub 90) duration of at least 2130 s and a multi-peaked light curve at energies of 15-150 keV. It was optically dark and has been convincingly associated with a bright star-forming galaxy at a redshift of 0.345 that is broadly similar to the Milky Way. This is one of the few cases where a host galaxy has been clearly identified for a dark gamma-ray burst and thus an ideal candidate for studying the origin of dark bursts. We find that the dark nature of GRB 090417B can not be explained by high redshift, incomplete observations, or unusual physics in the production of the afterglow. The Swift/XRT X-ray data are consistent with the afterglow being obscured by a dense, localized sheet of dust approximately 30-80 pc from the burst along the line of sight. Assuming the standard relativistic fireball model for the afterglow we find that the optical flux is at least 2.5 mag fainter than predicted by the X -ray flux. We are able to explain the lack of an optical afterglow, and the evolution of the X -ray spectrum, by assuming that there is a sheet of dust along the line of sight approximately 30-80 pc from the progenitor. Our results suggest that this dust sheet imparts an extinction of A(sub v)> or = 12 mag, which is sufficient to explain the missing optical flux. GRB 090417B is an example of a gamma-ray burst that is dark due to the localized dust structure in its host galaxy.

  16. Spectroscopic Evidence for SN 2010ma Associated with GRB 101219B

    NASA Astrophysics Data System (ADS)

    Sparre, M.; Sollerman, J.; Fynbo, J. P. U.; Malesani, D.; Goldoni, P.; de Ugarte Postigo, A.; Covino, S.; D'Elia, V.; Flores, H.; Hammer, F.; Hjorth, J.; Jakobsson, P.; Kaper, L.; Leloudas, G.; Levan, A. J.; Milvang-Jensen, B.; Schulze, S.; Tagliaferri, G.; Tanvir, N. R.; Watson, D. J.; Wiersema, K.; Wijers, R. A. M. J.

    2011-07-01

    We report on the spectroscopic detection of supernova SN 2010ma associated with the long gamma-ray burst GRB 101219B. We observed the optical counterpart of the GRB on three nights with the X-shooter spectrograph at the Very Large Telescope. From weak absorption lines, we measure a redshift of z = 0.55. The first-epoch UV-near-infrared afterglow spectrum, taken 11.6 hr after the burst, is well fit by a power law consistent with the slope of the X-ray spectrum. The second- and third-epoch spectra (obtained 16.4 and 36.7 days after the burst), however, display clear bumps closely resembling those of the broad-lined type-Ic SN 1998bw if placed at z = 0.55. Apart from demonstrating that spectroscopic SN signatures can be observed for GRBs at these large distances, our discovery makes a step forward in establishing a general connection between GRBs and SNe. In fact, unlike most previous unambiguous GRB-associated SNe, GRB 101219B has a large gamma-ray energy (E iso = 4.2 × 1051 erg), a bright afterglow, and obeys the "Amati" relation, thus being fully consistent with the cosmological population of GRBs. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile, under program 086.A-0073(B). Also based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência e Tecnologia (Brazil), and Ministerio de Ciencia, Tecnología e Innovacón Productiva (Argentina).

  17. A cross-correlation search for intermediate-duration gravitational waves from GRB magnetars

    NASA Astrophysics Data System (ADS)

    Coyne, Robert

    2015-04-01

    Since the discovery of the afterglow in 1997, the progress made in our understanding of gamma-ray bursts (GRBs) has been spectacular. Yet a direct proof of GRB progenitors is still missing. In the last few years, evidence for a long-lived and sustained central engine in GRBs has mounted. This has called attention to the so-called millisecond-magnetar model, which proposes that a highly magnetized, rapidly-rotating neutron star may exist at the heart of some of these events. The advent of advanced gravitational wave detectors such as LIGO and Virgo may enable us to probe directly, for the first time, the nature of GRB progenitors and their byproducts. In this context, we describe a novel application of a generalized cross-correlation technique optimized for the detection of long-duration gravitational wave signals that may be associated with bar-like deformations of GRB magnetars. The detection of these signals would allow us to answer some of the most intriguing questions on the nature of GRB progenitors, and serve as a starting point for a new class of intermediate-duration gravitational wave searches.

  18. Searching for Progenitor Clues in the Local Environments of Long GRB Hosts

    NASA Astrophysics Data System (ADS)

    Blanchard, Peter; Berger, Edo

    2015-01-01

    This study explores the sub-galactic environments in the host galaxies of Long Gamma-Ray Bursts (GRBs) to shed light on their progenitor population. Pre-Swift studies indicate GRB positions to be correlated with star formation, consistent with the standard picture of long GRBs originating from massive star explosions. We set out to test this using data accumulated over the last decade for Swift bursts. Using late-time HST imaging of a sample of 100 long GRB events and relative astrometry from ground-based afterglow detections we measure the projected offsets of long GRBs from their host centers. As the host centers are often not well-defined for the typically disturbed and irregular morphologies of long GRB hosts, we also employ a morphology-independent technique of assessing the relative brightness of the GRB site compared to the total host light distribution. As this study is currently in progress, preliminary results will be presented. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship Program under Grant No. DGE1144152.

  19. Kinematics of Gamma-Ray Burst and their Relationship to Afterglows

    SciTech Connect

    Salmonson, J D

    2001-12-17

    A strong correlation is reported between gamma-ray burst (GRB) pulse lags and afterglow jet-break times for the set of bursts (seven) with known redshifts, luminosities, pulse lags, and jet-break times. This may be a valuable clue toward understanding the connection between the burst and afterglow phases of these events. The relation is roughly linear (i.e. doubling the pulse lag in turn doubles the jet break time) and thus implies a simple relationship between these quantities. We suggest that this correlation is due to variation among bursts of emitter Doppler factor. Specifically, an increased speed or decreased angle of velocity, with respect to the observed line-of-site, of burst ejecta will result in shorter perceived pulse lags in GRBs as well as quicker evolution of the external shock of the afterglow to the time when the jet becomes obvious, i.e. the jet-break time. Thus this observed variation among GRBs may result from a perspective effect due to different observer angles of a morphologically homogeneous populations of GRBs. Also, a conjecture is made that peak luminosities not only vary inversely with burst timescale, but also are directly proportional to the spectral break energy. If true, this could provide important information for explaining the source of this break.

  20. Development of wide-band GRB detectors and the GRB monitor for the CALET Experiment

    NASA Astrophysics Data System (ADS)

    Yoshida, Atsumasa; Yamaoka, Kazutaka; Nakagawa, Yujin; Nakahira, Satoshi; Sugita, Satoshi; Tomida, Hiroshi; Torii, Shoji

    Many previous observations revealed radiations from GRBs to be widely emitted in electromagnetic energy band form less than a keV to over a GeV range, and peak-energies of νFν spectra to be distributed rather more widely than expected before. Those includes soft events explored by Ginga, BeppoSAX and HETE-2, and delayed GeV emissions and additional hard continuum detected by EGRET. It is very important to have a GRB monitor in space to be sensitive to photons in continuously wide energy range. We are developing wide-band GRB detectors utilizing several kinds of scintillator and X-ray CCD for future space missions. One of these detectors is that proposed as a GRB Monitor for the CALorimetric Electron Telescope (CALET) mission that was selected for Phase A/B studies as a next experiment for JEM-EF of ISS. The GRB Monitor (GBM) is a part of this experiment to extend scientific products achieved by CALET which can detect gamma-rays in a range from about 20MeV to TeV by itself and is potentially sensitive to hard radiations from GRBs. GBM is designed as multiple scintillation counters made of BGO and LaBr3 (Ce) to detect GRBs in a few keV to about 20MeV range alone, and to cover the energy band continuously up-to TeV region together with the CALET's main instruments, Imaging Calorimeter (IMC) and Total Absorption Calorimeter (TASC); one can expect sensitive range of nine orders of magnitude for GRBs inside the IMC's FOV of about 1.8 str. We present current status of our study including preliminary experimental results for LaBr3 (Ce) using a proton accelerator, and the design and expected ability of CALET-GBM.

  1. A Reverse Shock in GRB 160509A

    NASA Astrophysics Data System (ADS)

    Laskar, T.; Alexander, K. D.; Berger, E.

    2016-10-01

    Through detailed multi-wavelength observations and modeling, we present the discovery and characterization a reverse shock in GRB 160509A. This result highlights the unique power of radio observations in the study of GRB reverse shocks.

  2. The properties of a novel green long afterglow phosphor Zn2GeO4:Mn2+, Pr3+

    NASA Astrophysics Data System (ADS)

    Wan, Minhua; Wang, Yinhai; Wang, Xiansheng; Zhao, Hui; Hu, Zhengfa

    2014-01-01

    Novel Zn2GeO4:Mn2+, Pr3+ long afterglow phosphor was successfully synthesized by the high temperature solid state reaction. Long afterglow properties of the sample has been investigated in detail by measuring the X-ray diffraction (XRD), excitation spectrum, emission spectrum, afterglow spectrum, decay curve and thermoluminescence curve. The X-ray diffraction phases indicate that the co-doped Mn2+, Pr3+ have little influence on the crystal structure of Zn2GeO4. According to the emission spectra, we found that the Zn2GeO4:Mn2+, Pr3+ exhibit a narrow band emission with the peak at 532 nm, which could be ascribed to Mn2+ transition between 4T1 and 6A1 electron configurations. The green long afterglow of Zn2GeO4:Mn2+, Pr3+ could be observed for three hours by naked eyes at room temperature under 254 nm UV excitation. The thermoluminescence (TL) curve is employed for the discussion of the origin of the traps and the mechanism of the persistent luminescence. The results suggest that Zn2GeO4 may be an excellent host material for Mn2+-based long afterglow. Furthermore, the function of co-doped Pr3+ ions is confirmed as trap center, which can greatly postpone the afterglow emission properties of Mn2+.

  3. Implications for the Origin of GRB 070201 from LIGO Observations

    SciTech Connect

    Abbott, B.; Abbott, R.; Adhikari, R.; Agresti, J.; Anderson, S. B.; Araya, M.; Armandula, H.; Ballmer, S.; Barish, B. C.; Ajith, P.; Allen, B.; Amin, R.; Anderson, W. G.; Arain, M.; Ashley, M.; Aston, S.; Aufmuth, P.; Aulbert, C.; Babak, S.; Bantilan, H.

    2008-07-10

    We analyzed the available LIGO data coincident with GRB 070201, a short-duration, hard-spectrum {gamma}-ray burst (GRB) whose electromagnetically determined sky position is coincident with the spiral arms of the Andromeda galaxy (M31). Possible progenitors of such short, hard GRBs include mergers of neutron stars or a neutron star and a black hole, or soft {gamma}-ray repeater (SGR) flares. These events can be accompanied by gravitational-wave emission. No plausible gravitational-wave candidates were found within a 180 s long window around the time of GRB 070201. This result implies that a compact binary progenitor of GRB 070201, with masses in the range 1 M{sub sun} < m{sub 1} < 3 M{sub sun} and 1 M{sub sun} < m{sub 2} < 40 M{sub sun}, located in M31 is excluded at >99% confidence. If the GRB 070201 progenitor was not in M31, then we can exclude a binary neutron star merger progenitor with distance D < 3.5 Mpc, assuming random inclination, at 90% confidence. The result also implies that an unmodeled gravitational-wave burst from GRB 070201 most probably emitted less than 4.4 x 10{sup -4} M{sub sun}c{sup 2} (7.9 x 10{sup 50} ergs) in any 100 ms long period within the signal region if the source was in M31 and radiated isotropically at the same frequency as LIGO's peak sensitivity (f {approx} 150 Hz). This upper limit does not exclude current models of SGRs at the M31 distance.

  4. The low-extinction afterglow in the solar-metallicity host galaxy of γ-ray burst 110918A

    NASA Astrophysics Data System (ADS)

    Elliott, J.; Krühler, T.; Greiner, J.; Savaglio, S.; Olivares, F.; Rau, E. A.; de Ugarte Postigo, A.; Sánchez-Ramírez, R.; Wiersema, K.; Schady, P.; Kann, D. A.; Filgas, R.; Nardini, M.; Berger, E.; Fox, D.; Gorosabel, J.; Klose, S.; Levan, A.; Nicuesa Guelbenzu, A.; Rossi, A.; Schmidl, S.; Sudilovsky, V.; Tanvir, N. R.; Thöne, C. C.

    2013-08-01

    Galaxies selected through long γ-ray bursts (GRBs) could be of fundamental importance when mapping the star formation history out to the highest redshifts. Before using them as efficient tools in the early Universe, however, the environmental factors that govern the formation of GRBs need to be understood. Metallicity is theoretically thought to be a fundamental driver in GRB explosions and energetics, but it is still, even after more than a decade of extensive studies, not fully understood. This is largely related to two phenomena: a dust-extinction bias, which prevented high-mass and thus likely high-metallicity GRB hosts from being detected in the first place, and a lack of efficient instrumentation, which limited spectroscopic studies, including metallicity measurements, to the low-redshift end of the GRB host population. The subject of this work is the very energetic GRB 110918A (Eγ,iso = 1.9 × 1054 erg), for which we measure a redshift of z = 0.984. GRB 110918A gave rise to a luminous afterglow with an intrinsic spectral slope of β = 0.70, which probed a sight-line with little extinction (AGRBV = 0.16 mag) and soft X-ray absorption (NH,X = (1.6 ± 0.5) × 1021 cm-2) typical of the established distributions of afterglow properties. However, photometric and spectroscopic follow-up observations of the galaxy hosting GRB 110918A, including optical/near-infrared photometry with the Gamma-Ray burst Optical Near-infrared Detector and spectroscopy with the Very Large Telescope/X-shooter, reveal an all but average GRB host in comparison to the z ~ 1 galaxies selected through similar afterglows to date. It has a large spatial extent with a half-light radius of R1/2 ~ 10 kpc, the highest stellar mass for z < 1.9 (log (M∗/M⊙) = 10.68 ± 0.16), and an Hα-based star formation rate of SFRHα = 41+28-16M⊙ yr-1. We measure a gas-phase extinction of AgasV ~ 1.8 mag through the Balmer decrement and one of the largest host-integrated metallicities ever of around solar

  5. The Case for Anisotropic Afterglow Efficiency Within Gamma-Ray Burst Jets

    SciTech Connect

    Eichler, David; Granot, Jonathan; /KIPAC, Menlo Park

    2005-10-05

    Early X-ray afterglows recently detected by Swift frequently show a phase of very shallow flux decay lasting from a few hundred seconds up to {approx} 10{sup 4} s, followed by a steeper, more familiar decay. We suggest that the flat early part of the light curve may be a combination of the decaying tail of the prompt emission and the delayed onset of the afterglow emission observed from viewing angles slightly outside the edge of the jet, as predicted previously. This would imply that a significant fraction of viewers have a very small external shock energy along their line of sight and a very high {gamma}-ray to kinetic energy ratio. The early flat phase in the afterglow light curve implies, according to this or other interpretations, a very large {gamma}-ray efficiency, typically {approx}> 90%, which is very difficult to produce by internal shocks.

  6. The late X-ray afterglow of gamma-ray bursts.

    PubMed

    Willingale, Richard; O'Brien, Paul T

    2007-05-15

    We have developed a functional fit which can be used to represent the entire temporal decay of the X-ray afterglow of gamma-ray bursts (GRBs). The fit delineates and parameterizes well-defined phases for the decay: the prompt emission; an initial steep decay; a shallow plateau phase; and finally, a powerlaw afterglow. For 20% of GRBs, the plateau phase is weak, or not seen, and the initial powerlaw decay becomes the final afterglow.We compare the temporal decay parameters and X-ray spectral indices for 107 GRBs discovered by Swift with the expectations of the standard fireball model including a search for possible jet breaks. For approximately 50% of GRBs, the observed afterglow is in accord with the model, but for the rest the temporal and spectral properties are not as expected. We identify a few possible jet breaks, but there are many examples where such breaks are predicted but are absent. We also find that the start time of the final afterglow decay, Ta, is associated with the peak of the prompt gamma-ray emission spectrum, Epeak, just as optical jet-break times, tj, are associated with Epeak in the Ghirlanda relation.

  7. GRB 051008: a long, spectrally hard dust-obscured GRB in a Lyman-break galaxy at z ≈ 2.8

    NASA Astrophysics Data System (ADS)

    Volnova, A. A.; Pozanenko, A. S.; Gorosabel, J.; Perley, D. A.; Frederiks, D. D.; Kann, D. A.; Rumyantsev, V. V.; Biryukov, V. V.; Burkhonov, O.; Castro-Tirado, A. J.; Ferrero, P.; Golenetskii, S. V.; Klose, S.; Loznikov, V. M.; Minaev, P. Yu.; Stecklum, B.; Svinkin, D. S.; Tsvetkova, A. E.; de Ugarte Postigo, A.; Ulanov, M. V.

    2014-08-01

    We present observations of the dark gamma-ray burst GRB 051008 provided by Swift/BAT, Swift/XRT, Konus-WIND, INTEGRAL/SPI-ACS in the high-energy domain and the Shajn, Swift/UVOT, Tautenburg, NOT, Gemini and Keck I telescopes in the optical and near-infrared bands. The burst was detected only in gamma- and X-rays and neither a prompt optical nor a radio afterglow was detected down to deep limits. We identified the host galaxy of the burst, which is a typical Lyman-break galaxy (LBG) with R-magnitude of 24.06 ± 0.10 mag. A redshift of the galaxy of z = 2.77_{-0.20}^{+0.15} is measured photometrically due to the presence of a clear, strong Lyman-break feature. The host galaxy is a small starburst galaxy with moderate intrinsic extinction (AV = 0.3) and has a star formation rate of ˜60 M⊙ yr-1 typical for LBGs. It is one of the few cases where a GRB host has been found to be a classical LBG. Using the redshift we estimate the isotropic-equivalent radiated energy of the burst to be Eiso = (1.15 ± 0.20) × 1054 erg. We also provide evidence in favour of the hypothesis that the darkness of GRB 051008 is due to local absorption resulting from a dense circumburst medium.

  8. UHECR acceleration at GRB internal shocks

    NASA Astrophysics Data System (ADS)

    Globus, N.; Allard, D.; Mochkovitch, R.; Parizot, E.

    2015-07-01

    Recent results from the Pierre Auger Observatory suggest that nuclei heavier than protons might be present in significant amounts among ultrahigh-energy cosmic rays (UHECRs). It is therefore interesting to investigate the acceleration both protons and nuclei in relativistic jets. We calculate the acceleration of a mixed composition of cosmic rays at Gamma-ray burst (GRB) internal shocks, taking into account the relevant energy loss processes. 3D trajectories during the relativistic Fermi cycles are simulated following previous works by Niemiec & Ostrowski. We use the internal shock model of Daigne & Mochkovitch to derive the evolution of the relevant physical quantities (magnetic fields, baryon and photon densities, shock velocity). We consider different phenomenological hypotheses about the sharing of the dissipated energy between accelerated cosmic rays, electrons and the magnetic field. For various choices of the parameters, we calculate the spectrum of cosmic rays escaping from the GRB environment as well as secondary particles produced either during the acceleration or extragalactic propagation of UHECRs. Only models where (i) the prompt emission represents only a small fraction of the energy dissipated at internal shocks and (ii) most of this dissipated energy is communicated to cosmic rays, are able to reproduce the magnitude of the UHECR flux observed on Earth. For these models, however, the observed shape of the UHECR spectrum can be well reproduced above the ankle, with an evolution of the composition compatible with the trend suggested by Auger, and associated diffuse fluxes of secondary particles which do not violate current observational limits.

  9. the Large Aperture GRB Observatory

    SciTech Connect

    Bertou, Xavier

    2009-04-30

    The Large Aperture GRB Observatory (LAGO) aims at the detection of high energy photons from Gamma Ray Bursts (GRB) using the single particle technique (SPT) in ground based water Cherenkov detectors (WCD). To reach a reasonable sensitivity, high altitude mountain sites have been selected in Mexico (Sierra Negra, 4550 m a.s.l.), Bolivia (Chacaltaya, 5300 m a.s.l.) and Venezuela (Merida, 4765 m a.s.l.). We report on the project progresses and the first operation at high altitude, search for bursts in 6 months of preliminary data, as well as search for signal at ground level when satellites report a burst.

  10. Estimating Long GRB Jet Opening Angles and Rest-Frame Energetics

    NASA Astrophysics Data System (ADS)

    Goldstein, Adam; Connaughton, Valerie; Briggs, Michael; Burns, Eric

    2016-03-01

    We present a method to estimate the jet opening angles of long Gamma-Ray Bursts (GRBs) using the prompt gamma-ray energetics and a correlation between the time-integrated peak energy of the GRB prompt spectrum and the collimation-corrected energy in gamma rays. The derived jet opening angles using this method match well with the corresponding inferred jet opening angles obtained when a break in the afterglow is observed. Furthermore, using a model of the predicted long GRB redshift probability distribution observable by the Fermi Gamma-ray Burst Monitor (GBM), we estimate the probability distributions for the jet opening angle and rest-frame energetics for a large sample of GBM GRBs for which the redshifts have not been observed. Previous studies have only used a handful of GRBs to estimate these properties due to the paucity of observed afterglow jet breaks, spectroscopic redshifts, and comprehensive prompt gamma-ray observations, and we expand the number of GRBs that can be used in this analysis by more than an order of magnitude. We also present an inferred distribution of jet breaks which indicates that a large fraction of jet breaks are not observable with current instrumentation and observing strategies. A.G. is funded by the NASA Postdoctoral Program through USRA.

  11. Estimating Long GRB Jet Opening Angles and Rest-Frame Energetics

    NASA Astrophysics Data System (ADS)

    Goldstein, Adam; Connaughton, Valerie; Briggs, Michael Stephen; Burns, Eric

    2016-04-01

    We present a method to estimate the jet opening angles of long duration Gamma-Ray Bursts (GRBs) using the prompt gamma-ray energetics and a correlation between the time-integrated peak energy of the GRB prompt spectrum and the collimation-corrected energy in gamma rays. The derived jet opening angles using this method match well with the corresponding inferred jet opening angles obtained when a break in the afterglow is observed. Furthermore, using a model of the predicted long GRB redshift probability distribution observable by the Fermi Gamma-ray Burst Monitor (GBM), we estimate the probability distributions for the jet opening angle and rest-frame energetics for a large sample of GBM GRBs for which the redshifts have not been observed. Previous studies have only used a handful of GRBs to estimate these properties due to the paucity of observed afterglow jet breaks, spectroscopic redshifts, and comprehensive prompt gamma-ray observations, and we expand the number of GRBs that can be used in this analysis by more than an order of magnitude. In this analysis, we also present an inferred distribution of jet breaks which indicates that a large fraction of jet breaks are not observable with current instrumentation and observing strategies. We present simple parameterizations for the jet angle, energetics, and jet break distributions so that they may be used in future studies.

  12. Numerical Study on GRB-Jet Formation in Collapsars

    SciTech Connect

    Nagataki, Shigehiro; Takahashi, Rohta; Mizuta, Akira; Takiwaki, Tomoya; /Tokyo U.

    2006-08-22

    Two-dimensional magnetohydrodynamic simulations are performed using the ZEUS-2D code to investigate the dynamics of a collapsar that generates a GRB jet, taking account of realistic equation of state, neutrino cooling and heating processes, magnetic fields, and gravitational force from the central black hole and self gravity. It is found that neutrino heating processes are not so efficient to launch a jet in this study. It is also found that a jet is launched mainly by B{sub {phi}} fields that are amplified by the winding-up effect. However, since the ratio of total energy relative to the rest mass energy in the jet is not so high as several hundred, we conclude that the jets seen in this study are not be a GRB jet. This result suggests that general relativistic effects, which are not included in this study, will be important to generate a GRB jet. Also, the accretion disk with magnetic fields may still play an important role to launch a GRB jet, although a simulation for much longer physical time {approx} 10-100 s is required to confirm this effect. It is shown that considerable amount of {sup 56}Ni is synthesized in the accretion disk. Thus there will be a possibility for the accretion disk to supply sufficient amount of {sup 56}Ni required to explain the luminosity of a hypernova. Also, it is shown that neutron-rich matter due to electron captures with high entropy per baryon is ejected along the polar axis. Moreover, it is found that the electron fraction becomes larger than 0.5 around the polar axis near the black hole by {nu}{sub e} capture at the region. Thus there will be a possibility that r-process and r/p-process nucleosynthesis occur at these regions. Finally, much neutrons will be ejected from the jet, which suggests that signals from the neutron decays may be observed as the delayed bump of the light curve of the afterglow or gamma-rays.

  13. A Broader Perspective on the GRB-SN Connection

    NASA Astrophysics Data System (ADS)

    Soderberg, Alicia M.

    2006-05-01

    Over the last few years our understanding of local Type Ibc supernovae and their connection to long-duration gamma-ray bursts has been revolutionized. Recent discoveries have shown that the emerging picture for core-collapse explosions is one of diversity. Compiling data from our dedicated radio survey of SNe Ibc and our comprehensive HST survey of GRB-SNe together with ground-based follow-up campaigns, I review our current understanding of the GRB-SN connection. In particular, I compare local SNe Ibc with GRB-SNe based on the following criteria: (1) the distribution of optical peak magnitudes which serve as a proxy for the mass of 56Ni produced in the explosion, (2) radio luminosity at early time (few days to weeks) which provides a measure of the energy coupled to on-axis relativistic ejecta, and (3) radio luminosity at late time (several years) which constrains the emission from GRB jets initially directed away from our line-of-sight. By focusing on these three points, I will describe the complex picture of stellar death that is emerging.

  14. Two Variable Radio Sources Near the Position of GRB 940301

    NASA Technical Reports Server (NTRS)

    Galama, T. J.; DeBruyn, A. G.; vanParadijs, J.; Hanlon, L.; Groot, P. J.; VanDerKlis, M.; Strom, R.; Spoelstra, T.; Bennett, K.; Fishman, G. J.; Hurley, K.

    1997-01-01

    We report on the results of a search for a radio counterpart to the strong gamma-ray burst GRB 940301. Observations with the Westerbork Synthesis Radio Telescope of the Compton Telescope error box region of GRB 940301 began on March 4, 1994, at 21 cm and April 2, 1994, at 92 cm. No flux density variations were detected at 92 cm above S= 10 mJy (5 (sigma)) within a period of 1 to 4 months after the burst. However, when we compared the field with Westerbork Northern Sky Survey data, taken two years prior to GRB 940301, we found two radio sources with significantly increased flux densities. These sources, only 17 min. apart, are located at the 2.3 and 2.6(sigma) Compton Telescope confidence contours. Their separation from the Inter Planetary Network annulus virtually excludes association with GRB 940301. Further observations in January 1996 reveal that the sources continued to change in flux density. The relatively large flux density variations at 92 cm, compared to those at higher frequencies, and the inverted spectra in the frequency range from 325-38O MHz make the sources somewhat unusual. Because the sources were already detected at 5 GHz in 1986 most, if not all, of the radio emission is probably associated with activity in Active Galactic Nuclei in distant galaxies.

  15. GRB 060505: A Possible Short-Duration Gamma-Ray Burst in a Star Forming Region at Redshift of 0.09

    NASA Technical Reports Server (NTRS)

    Ofek, E. O.; Cenko, S. B.; Gal-Yam, A.; Fox, D. B.; Nakar, E.; Rau, A.; Frail, D. A.; Kullkarni, S. R.; Price, P. A.; Schmidt, B. P.; Soderberg, A. M.; Peterson, B.; Berger, E.; Sharon, K.; Shemmer, O.; Penprase, B. E.; Chevalier, R. A.; Brown, P. J.; Burrows, D. N.; Gehrels, N.; Harrison, F.; Holland, S. T.

    2007-01-01

    On May 5, 2006 a four-second duration, low-energy, approximately 10(exp 59) erg, Gamma-Ray Burst (GRB) was observed, spatially associated with a z=0.0894 galaxy. Here, we report the discovery of the GRB optical afterglow and observations of its environment using gemini-south, Hubble Space Telescope (HST), Chandra, Swift and the Very Large Array. The optical afterglow of this GRB is spatially associated with a prominent star forming region in the Sc-type galaxy 2dFGRS S173Z112. Its proximity to a star forming region suggests that the progenitor delay time, from birth to explosion, is smaller than about 10 Myr. Our HST deep imaging rules out the presence of a supernova brighter than an absolute magnitude of about -11 (or -126 in case of 'maximal' extinction) at about two weeks after the burst, and limits the ejected mass of radioactive Nickel 56 to be less than about 2x10(exp -4) solar mass (assuming no extinction). Although it was suggested that GRB 060505 may belong to a new class of long-duration GRBs with no supernova, we argue that the simplest interpretation is that the physical mechanism for this burst is the same as for short-duration GRBs.

  16. Optical studies of gamma-ray burst fields. 3: GRB 790613 and GRB 781124

    NASA Technical Reports Server (NTRS)

    Harrison, Thomas E.; Mcnamara, Bernard J.; Klemola, Arnold R.

    1994-01-01

    An optical photometric and proper motion study of the fields of the gamma-ray bursts GRB 790613 and GRB 781124 is presented. No objects were visible on our Charge Coupled Devices (CCD) images inside the GRB 790613 error box. About 15 objects are visible on our CCD images inside the GRB 781124 error box. Two of these objects were found to be faint galaxies. Two stars with sizeable proper motions were identified near, but outside of the GRB 781124 error box. No large proper motion objects were found in the area surrounding the GRB 790613 error box.

  17. Numerical models of blackbody-dominated gamma-ray bursts - I. Hydrodynamics and the origin of the thermal emission

    NASA Astrophysics Data System (ADS)

    Cuesta-Martínez, C.; Aloy, M. A.; Mimica, P.

    2015-01-01

    GRB 101225A is a prototype of the class of blackbody-dominated (BBD) gamma-ray bursts (GRBs). It has been suggested that BBD-GRBs result from the merger of a binary system formed by a neutron star and the helium core of an evolved star. We have modelled the propagation of ultrarelativistic jets through the environment left behind the merger by means of relativistic hydrodynamic simulations. In this paper, the output of our numerical models is post-processed to obtain the (thermal) radiative signature of the resulting outflow. We outline the most relevant dynamical details of the jet propagation and connect them to the generation of thermal radiation in GRB events akin to that of GRB 101225A. A comprehensive parameter study of the jet/environment interaction has been performed and synthetic light curves are confronted with the observational data. The thermal emission in our models originates from the interaction between the jet and the hydrogen envelope ejected during the neutron star/He core merger. We find that the lack of a classical afterglow and the accompanying thermal emission in BBD-GRBs can be explained by the interaction of an ultrarelativistic jet with a toroidally shaped ejecta whose axis coincides with the binary rotation axis. The spectral inversion and reddening happening at about 2 d in GRB 101225A can be related to the time at which the massive shell ejected in an early phase of the common envelope evolution of the progenitor system is completely ablated by the ultrarelativistic jet.

  18. Processes in afterglow responsible for initiation of electrical breakdown in xenon at low pressure

    NASA Astrophysics Data System (ADS)

    Pejović, Momčilo M.; Spasić, Ivana V.; Pejović, Milić M.; Nešić, Nikola T.; Brajović, Dragan V.; Brajović

    2013-10-01

    The processes responsible for initiation of electrical breakdown in xenon-filled tube with two spherical iron electrodes at 2.7-mbar pressure have been analyzed. The analysis is based on the experimental data of electrical breakdown time delay as a function of afterglow period. It is shown that positive ions remaining from previous discharge, as well as positive ions created in mutual collisions of metastable atoms in afterglow, have a dominant role in secondary emission of electrons from the cathode which lead to initiation of breakdown in early afterglow. In late afterglow, dominant role in initiation of breakdown is taken by N(4S) atoms formed during the discharge by dissociation of ground state nitrogen molecules that are present as impurities in xenon. When the concentration of N(4S) atoms decreases sufficiently, the initiation of breakdown is caused by cosmic radiation. Small doses of gamma-ray irradiation also contribute to the initiation of breakdown, but only for large values of the afterglow period.

  19. Dust Cloud Dynamics in Complex Plasma Afterglow

    SciTech Connect

    Layden, B.; Samarian, A. A.; Vladimirov, S. V.; Coueedel, L.

    2008-09-07

    Experimental observations of dust cloud dynamics in a RF discharge afterglow are presented. Image analysis is used to extract information from videos taken of the plasma. Estimations of the mean confining electric field have been made for different experimental conditions using a model for the contraction of the dust cloud. Dust particle trajectories in the late afterglow evidence the co-existence of positively and negatively charged dust particles.

  20. Characterization of the flowing afterglows of an N2 O2 reduced-pressure discharge: setting the operating conditions to achieve a dominant late afterglow and correlating the NOβ UV intensity variation with the N and O atom densities

    NASA Astrophysics Data System (ADS)

    Boudam, M. K.; Saoudi, B.; Moisan, M.; Ricard, A.

    2007-03-01

    The flowing afterglow of an N2-O2 discharge in the 0.6-10 Torr range is examined in the perspective of achieving sterilization of medical devices (MDs) under conditions ensuring maximum UV intensity with minimum damage to polymer-based MDs. The early afterglow is shown to be responsible for creating strong erosion damage, requiring that the sterilizer be operated in a dominant late-afterglow mode. These two types of afterglow can be characterized by optical emission spectroscopy: the early afterglow is distinguished by an intense emission from the N_{2}^{+} 1st negative system (band head at 391.4 nm) while the late afterglow yields an overpopulation of the v' = 11 ro-vibrational level of the N2(B) state, indicating a reduced contribution from the early afterglow N2 metastable species. We have studied the influence of operating conditions (pressure, O2 content in the N2-O2 mixture, distance of the discharge from the entrance to the afterglow (sterilizer) chamber) in order to achieve a dominant late afterglow that also ensures maximum and almost uniform UV intensity in the sterilization chamber. As far as operating conditions are concerned, moving the plasma source sufficiently far from the chamber entrance is shown to be a practical means for significantly reducing the density of the characteristic species of the early afterglow. Using the NO titration method, we obtain the (absolute) densities of N and O atoms in the afterglow at the NO injection inlet, a few cm before the chamber entrance: the N atom density goes through a maximum at approximately 0.3-0.5% O2 and then decreases, while the O atom density increases regularly with the O2 percentage. The spatial variation of the N atom (relative) density in the chamber is obtained by recording the emission intensity from the 1st positive system at 580 nm: in the 2-5 Torr range, this density is quite uniform everywhere in the chamber. The (relative) densities of N and O atoms in the discharge are determined by using

  1. On binary-driven hypernovae and their nested late X-ray emission

    NASA Astrophysics Data System (ADS)

    Ruffini, R.; Muccino, M.; Bianco, C. L.; Enderli, M.; Izzo, L.; Kovacevic, M.; Penacchioni, A. V.; Pisani, G. B.; Rueda, J. A.; Wang, Y.

    2014-05-01

    Context. The induced gravitational collapse (IGC) paradigm addresses the very energetic (1052-1054 erg) long gamma-ray bursts (GRBs) associated to supernovae (SNe). Unlike the traditional "collapsar" model, an evolved FeCO core with a companion neutron star (NS) in a tight binary system is considered as the progenitor. This special class of sources, here named "binary-driven hypernovae" (BdHNe), presents a composite sequence composed of four different episodes with precise spectral and luminosity features. Aims: We first compare and contrast the steep decay, the plateau, and the power-law decay of the X-ray luminosities of three selected BdHNe (GRB 060729, GRB 061121, and GRB 130427A). Second, to explain the different sizes and Lorentz factors of the emitting regions of the four episodes, for definiteness, we use the most complete set of data of GRB 090618. Finally, we show the possible role of r-process, which originates in the binary system of the progenitor. Methods: We compare and contrast the late X-ray luminosity of the above three BdHNe. We examine correlations between the time at the starting point of the constant late power-law decay t*a, the average prompt luminosity ⟨ Liso ⟩, and the luminosity at the end of the plateau La. We analyze a thermal emission (~ 0.97-0.29 keV), observed during the X-ray steep decay phase of GRB 090618. Results: The late X-ray luminosities of the three BdHNe, in the rest-frame energy band 0.3-10 keV, show a precisely constrained "nested" structure. In a space-time diagram, we illustrate the different sizes and Lorentz factors of the emitting regions of the three episodes. For GRB 090618, we infer an initial dimension of the thermal emitter of ~ 7 × 1012 cm, expanding at Γ ≈ 2. We find tighter correlations than the Dainotti-Willingale ones. Conclusions: We confirm a constant slope power-law behavior for the late X-ray luminosity in the source rest frame, which may lead to a new distance indicator for BdHNe. These results

  2. Implications of Lag-Luminosity Relationship for Unified GRB Paradigms

    NASA Technical Reports Server (NTRS)

    Norris, J. P.; White, Nicholas E. (Technical Monitor)

    2002-01-01

    Spectral lags (tau(sub lag)) are deduced for 1437 long (T(sub 90) greater than 2 s) BATSE gamma-ray bursts (GRBs) with peak flux F(sub p) greater than 0.25 photons cm(sup -2)/s, near to the BATSE trigger threshold. The lags are modeled to approximate the observed distribution in the F(sub p)-T(sub lag) plane, realizing a noise-free representation. Assuming a two-branch lag-luminosity relationship, the lags are self-consistently corrected for cosmological effects to yield distributions in luminosity, distance, and redshift. The results have several consequences for GRB populations and for unified gamma-ray/afterglow scenarios which would account for afterglow break times and gamma-ray spectral evolution in terms of jet opening angle, viewing angle, or a profiled jet with variable Lorentz factor: A component of the burst sample is identified - those with few, wide pulses, lags of a few tenths to several seconds, and soft spectra - whose Log[N]-Log[F(sub p)] distribution approximates a -3/2 power-law, suggesting homogeneity and thus relatively nearby sources. The proportion of these long-lag bursts increases from negligible among bright BATSE bursts to approx. 50% at trigger threshold. Bursts with very long lags, approx. 1-2 less than tau(sub lag) (S) less than 10, show a tendency to concentrate near the Supergalactic Plane with a quadrupole moment of approx. -0.10 +/- 0.04. GRB 980425 (SN 1998bw) is a member of this subsample of approx. 90 bursts with estimated distances less than 100 Mpc. The frequency of the observed ultra-low luminosity bursts is approx. 1/4 that of SNe Ib/c within the same volume. If truly nearby, the core-collapse events associated with these GRBs might produce gravitational radiation detectable by LIGO-II. Such nearby bursts might also help explain flattening of the cosmic ray spectrum at ultra-high energies, as observed by AGASA.

  3. Exploring the first stars with rapid GRB follow-up observations

    NASA Astrophysics Data System (ADS)

    Cucchiara, Antonino; Cenko, Stephen; Schmidt, Brian; Perley, Daniel; Berger, Edo; Fox, Derek; Fruchter, Andrew; Bloom, Joshua; Prochaska, Jason X.; Lopez, Sebastian; Cobb, Bethany; Roth, Kathy; Levan, Andrew; Tanvir, Nial; Rapoport, Sharon; Yuan, Fang; Chornock, Ryan; Wen-Fai, Fong; Morgan, Adam; Wiersema, Klaas

    2013-02-01

    GRBs provide a unique window on exotic, highly relativistic physics. Our discovery of cosmic explosions like GRB090423 at z=8.2, breaking the record for the most distant known object, also demonstrates the power of using GRBs as lighthouses visible into the epoch of re-ionization, pinpointing the earliest stars and galaxies. Therefore, we intend (i) to observe GRBs at very high-z, in order to explore the IGM during reionization and place fundamental constraints on the early epochs of star-formation; (ii) to study in detail the class of short-dura