Swift-BAT: Transient Source Monitoring

NASA Astrophysics Data System (ADS)

Barbier, L. M.; Barthelmy, S.; Cummings, J.; Gehrels, N.; Krimm, H.; Markwardt, C.; Mushotzky, R.; Parsons, A.; Sakamoto, T.; Tueller, J.; Fenimore, E.; Palmer, D.; Skinner, G.; Swift-BAT Team

2005-12-01

The Burst Alert Telescope (BAT) on the Swift satellite is a large field of view instrument that continually monitors the sky to provide the gamma-ray burst trigger for Swift. An average of more than 70% of the sky is observed on a daily basis. The survey mode data is processed on two sets of time scales: from one minute to one day as part of the transient monitor program, and from one spacecraft pointing ( ˜20 minutes) to the full mission duration for the hard X-ray survey program. In the transient monitor program, sky images are processed to detect astrophysical sources in six energy bands covering 15-350 keV. The detected flux or upper limit in each energy band is calculated for >300 objects on time scales up to one day. In addition, the monitor is sensitive to an outburst from a new or unknown source. Sensitivity as a function of time scale for catalog and unknown sources will be presented. The daily exposure for a typical source is ˜1500 - 3000 seconds, with a 1-sigma sensitivity of ˜4mCrab. 90% of the sources are sampled at least every 16 days, but many sources are sampled daily. The BAT team will soon make the results of the transient monitor public to the astrophysical community through the Swift mission web page. It is expected that the Swift-BAT transient monitor will become an important resource for the high energy astrophysics community.

VizieR Online Data Catalog: Short GRBs with Fermi GBM and Swift BAT (Burns+, 2016)

NASA Astrophysics Data System (ADS)

Burns, E.; Connaughton, V.; Zhang, B.-B.; Lien, A.; Briggs, M. S.; Goldstein, A.; Pelassa, V.; Troja, E.

2018-01-01

Compact binary system mergers are expected to generate gravitational radiation detectable by ground-based interferometers. A subset of these, the merger of a neutron star with another neutron star or a black hole, are also the most popular model for the production of short gamma-ray bursts (GRBs). The Swift Burst Alert Telescope (BAT) and the Fermi Gamma-ray Burst Monitor (GBM) trigger on short GRBs (SGRBs) at rates that reflect their relative sky exposures, with the BAT detecting 10 per year compared to about 45 for GBM. We examine the SGRB populations detected by Swift BAT and Fermi GBM. (4 data files).

BAT AGN Spectroscopic Survey. V. X-Ray Properties of the Swift/BAT 70-month AGN Catalog

NASA Astrophysics Data System (ADS)

Ricci, C.; Trakhtenbrot, B.; Koss, M. J.; Ueda, Y.; Del Vecchio, I.; Treister, E.; Schawinski, K.; Paltani, S.; Oh, K.; Lamperti, I.; Berney, S.; Gandhi, P.; Ichikawa, K.; Bauer, F. E.; Ho, L. C.; Asmus, D.; Beckmann, V.; Soldi, S.; Baloković, M.; Gehrels, N.; Markwardt, C. B.

2017-12-01

Hard X-ray (≥10 keV) observations of active galactic nuclei (AGNs) can shed light on some of the most obscured episodes of accretion onto supermassive black holes. The 70-month Swift/BAT all-sky survey, which probes the 14-195 keV energy range, has currently detected 838 AGNs. We report here on the broadband X-ray (0.3-150 keV) characteristics of these AGNs, obtained by combining XMM-Newton, Swift/XRT, ASCA, Chandra, and Suzaku observations in the soft X-ray band (≤slant 10 keV) with 70-month averaged Swift/BAT data. The nonblazar AGNs of our sample are almost equally divided into unobscured ({N}{{H}}< {10}22 {{cm}}-2) and obscured ({N}{{H}}≥slant {10}22 {{cm}}-2) AGNs, and their Swift/BAT continuum is systematically steeper than the 0.3-10 keV emission, which suggests that the presence of a high-energy cutoff is almost ubiquitous. We discuss the main X-ray spectral parameters obtained, such as the photon index, the reflection parameter, the energy of the cutoff, neutral and ionized absorbers, and the soft excess for both obscured and unobscured AGNs.

The Third Swift Burst Alert Telescope Gamma-Ray Burst Catalog

NASA Astrophysics Data System (ADS)

Lien, Amy; Sakamoto, Takanori; Barthelmy, Scott D.; Baumgartner, Wayne H.; Cannizzo, John K.; Chen, Kevin; Collins, Nicholas R.; Cummings, Jay R.; Gehrels, Neil; Krimm, Hans A.; Markwardt, Craig. B.; Palmer, David M.; Stamatikos, Michael; Troja, Eleonora; Ukwatta, T. N.

2016-09-01

To date, the Burst Alert Telescope (BAT) onboard Swift has detected ˜1000 gamma-ray bursts (GRBs), of which ˜360 GRBs have redshift measurements, ranging from z = 0.03 to z = 9.38. We present the analyses of the BAT-detected GRBs for the past ˜11 years up through GRB 151027B. We report summaries of both the temporal and spectral analyses of the GRB characteristics using event data (I.e., data for each photon within approximately 250 s before and 950 s after the BAT trigger time), and discuss the instrumental sensitivity and selection effects of GRB detections. We also explore the GRB properties with redshift when possible. The result summaries and data products are available at http://swift.gsfc.nasa.gov/results/batgrbcat/index.html. In addition, we perform searches for GRB emissions before or after the event data using the BAT survey data. We estimate the false detection rate to be only one false detection in this sample. There are 15 ultra-long GRBs (˜2% of the BAT GRBs) in this search with confirmed emission beyond ˜1000 s of event data, and only two GRBs (GRB 100316D and GRB 101024A) with detections in the survey data prior to the starting of event data.

The Swift/BAT Hard X-Ray Survey

NASA Technical Reports Server (NTRS)

Tueller, Jack; Markwardt, C. B.; Mushotzky, R. F.; Barthelmy, S. D.; Gehrels, N.; Krimm, H. A.; Skinner, G. K.; Falcone, A.; Kennea, J. A.

2006-01-01

The BAT instrument on Swift is a wide field (70 deg. '100 deg.) coded aperture instrument with a CdZnTe detector array sensitive to energies of 14-200 keV. Each day, the BAT survey typically covers 60% of the sky to a detection limit of 30 millicrab. BAT makes hard X-ray light curves of similar sensitivity and coverage to the X-ray light curves from XTE/ASM, but in an energy range where sources show remarkably different behavior. Integrating the BAT data produces an all sky map with a source detection limit at 15 months of a few 10(exp -11) ergs per square centimeter per second, depending on the exposure. This is the first uniform all-sky survey at energies high enough to be unaffected by absorption since HEAO 1 in 1977-8. BAT has detected greater than 200 AGN and greater than 180 galactic sources. At high galactic latitudes, the BAT sources are usually easy to identify, but many are heavily absorbed and there are a few quite surprising identifications. The BAT selected galaxies can be used to calculate LogN/LogS and the luminosity function for AGN which are complete and free from common systematics. Several crucial parameters for understanding the cosmic hard x-ray background are now determined.

The 105 month Swift-BAT data release

NASA Astrophysics Data System (ADS)

Oh, Kyuseok; Koss, Michael; Markwardt, Craig B.; Schawinski, Kevin; Baumgartner, Wayne H.; Barthelmy, Scott D.; Cenko, Bradley; Gehrels, Neil; Mushotzky, Richard; Petulante, Abigail; Ricci, Claudio; Lien, Amy; Trakhtenbrot, Benny; NASA GSFC Swift BAT team, BAT AGN Spectroscopic Survey (BASS)

2018-01-01

We present a new catalog of hard X-ray sources detected in the first 105 months of observations with the Burst Alert Telescope (BAT) on board the Swift observatory. The 105 month Swift-BAT survey is a uniform hard X-ray all-sky survey with a sensitivity of 8.40×10-12 erg s-1 cm-2 over 90% of the sky and 7.24×10-12 erg s-1 cm-2 over 50% of the sky in the 14‑195 keV band. The Swift-BAT 105 month catalog provides 1632 (422 new detections) hard X-ray sources in the 14 ‑ 195 keV band above the 4.8σ significance level. Adding to the previously known hard X-ray sources, 34% (144/422) of the new detections are identified as Seyfert AGN in nearby galaxies (z < 0.2). The majority of the remaining identified sources are X-ray binaries (7%, 31) and blazars/BL Lac objects (10%, 43). As part of this new edition of the Swift-BAT catalog, we release eight-channel spectra and monthly sampled light curves for each object in the online journal and at the Swift-BAT 105 month Web site.

THE THIRD SWIFT BURST ALERT TELESCOPE GAMMA-RAY BURST CATALOG

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lien, Amy; Baumgartner, Wayne H.; Cannizzo, John K.

2016-09-20

To date, the Burst Alert Telescope (BAT) onboard Swift has detected ∼1000 gamma-ray bursts (GRBs), of which ∼360 GRBs have redshift measurements, ranging from z = 0.03 to z = 9.38. We present the analyses of the BAT-detected GRBs for the past ∼11 years up through GRB 151027B. We report summaries of both the temporal and spectral analyses of the GRB characteristics using event data (i.e., data for each photon within approximately 250 s before and 950 s after the BAT trigger time), and discuss the instrumental sensitivity and selection effects of GRB detections. We also explore the GRB propertiesmore » with redshift when possible. The result summaries and data products are available at http://swift.gsfc.nasa.gov/results/batgrbcat/index.html. In addition, we perform searches for GRB emissions before or after the event data using the BAT survey data. We estimate the false detection rate to be only one false detection in this sample. There are 15 ultra-long GRBs (∼2% of the BAT GRBs) in this search with confirmed emission beyond ∼1000 s of event data, and only two GRBs (GRB 100316D and GRB 101024A) with detections in the survey data prior to the starting of event data.« less

Swift Gamma-Ray Burst Explorer: Mission Design for Rapid, Accurate Location of Gamma-ray Bursts

NASA Technical Reports Server (NTRS)

Bundas, David J.

2004-01-01

The Swift Gamma-ray Burst Explorer is a NASA Mid-sized Explorer (MIDEX) with the primary mission of determining the origins of Gamma-Ray Bursts (GRBs). It will be the first mission to autonomously respond to newly-discovered GRBs and provide immediate follow-up narrow field instruments capable of multi-wavelength (UV, Optical, X-ray) observations. The characteristics of GRBs that are the key mission design drivers, are their non-repeating and brief duration bursts of multi-wavelength photons. In addition, rapid notification of the location and characteristics of the GRBs to ground-and-space- based observatories drive the end-to-end data analysis and distribution requirements. The Swift mission is managed by the GSFC, and includes an international team of contributors that each bring their unique perspective that have proven invaluable to the mission. The spacecraft bus, provided by Spectrum Astro, Inc. was procured through a Rapid Spacecraft Development Office (RSDO) contract by the GSFC. There are three instruments: the Burst Alert Telescope (BAT) provided by the GSFC; the X-Ray Telescope (XRT) provided by a team led by the Pennsylvania State University (PSU); and the Ultra-Violet Optical Telescope (UVOT), again managed by PSU. The Mission Operations Center (MOC) was developed by and is located at PSU. Science archiving and data analysis centers are located at the GSFC, in the UK and in Italy.

Evidence of the Exponential Decay Emission in the Swift Gamma-ray Bursts

NASA Technical Reports Server (NTRS)

Sakamoto, T.; Sato, G.; Hill, J.E.; Krimm, H.A.; Yamazaki, R.; Takami, K.; Swindell, S.; Osborne, J.P.

2007-01-01

We present a systematic study of the steep decay emission of gamma-ray bursts (GRBs) observed by the Swift X-Ray Telescope (XRT). In contrast to the analysis in recent literature, instead of extrapolating the data of Burst Alert Telescope (BAT) down into the XRT energy range, we extrapolated the XRT data up to the BAT energy range, 15-25 keV, to produce the BAT and XRT composite light curve. Based on our composite light curve fitting, we have confirmed the existence of an exponential decay component which smoothly connects the BAT prompt data to the XRT steep decay for several GRBs. We also find that the XRT steep decay for some of the bursts can be well fitted by a combination of a power-law with an exponential decay model. We discuss that this exponential component may be the emission from an external shock and a sign of the deceleration of the outflow during the prompt phase.

The Swift Gamma-ray Burst Explorer: Early Views into Black-hole Creation

NASA Technical Reports Server (NTRS)

Hill, Joe

2007-01-01

This viewgraph presentation reviews the discovery of Gamma-ray Bursts (GRBs) in the 1960's and early 1970's, and the characteristics of GRBs. Theoretical predictions and explanations are reviewed. The first observation of a GRB by the Beppo-SAX is discussed, and then the need develop a Gamma Ray Burst detector with a larger field of view, that has rapid follow-up capabilities and has the ability to rapidly get localized positions to the ground. The Swift instruments (i.e., the Burst Alert Telescope (BAT), the X-Ray Telescope (XRT) and the UV/Optical Telescope (UVOT)) are shown and described. The scenario for observing of GRBs is reviewed. Many charts of the some of the GRBs data and GRB spectra are shown.

The Swift-BAT Hard X-Ray Transient Monitor

NASA Technical Reports Server (NTRS)

Krimm, H. A.; Holland, S. T.; Corbet, R. H. D.; Pearlman, A. B.; Romano, P.; Kennea, J. A.; Bloom, J. S.; Barthelmy, S. D.; Baumgartner, W. H.; Cummings, J. R.;

The Swift/BAT Hard X-ray Transient Monitor

NASA Technical Reports Server (NTRS)

Krimm, H. A.; Holland, S. T.; Corbet, R.H.D.; Pearlman, A. B.; Romano, P.; Kennea, J. A.; Bloom, J. S.; Barthelmy, S. D.; Baumgartner, W. H.; Cummings, J. R.;

THE SWIFT/BAT HARD X-RAY TRANSIENT MONITOR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krimm, H. A.; Holland, S. T.; Corbet, R. H. D.

2013-11-01

The Swift/Burst Alert Telescope (BAT) hard X-ray transient monitor provides near real-time coverage of the X-ray sky in the energy range 15-50 keV. The BAT observes 88% of the sky each day with a detection sensitivity of 5.3 mCrab for a full-day observation and a time resolution as fine as 64 s. The three main purposes of the monitor are (1) the discovery of new transient X-ray sources, (2) the detection of outbursts or other changes in the flux of known X-ray sources, and (3) the generation of light curves of more than 900 sources spanning over eight years. Themore » primary interface for the BAT transient monitor is a public Web site. Between 2005 February 12 and 2013 April 30, 245 sources have been detected in the monitor, 146 of them persistent and 99 detected only in outburst. Among these sources, 17 were previously unknown and were discovered in the transient monitor. In this paper, we discuss the methodology and the data processing and filtering for the BAT transient monitor and review its sensitivity and exposure. We provide a summary of the source detections and classify them according to the variability of their light curves. Finally, we review all new BAT monitor discoveries. For the new sources that are previously unpublished, we present basic data analysis and interpretations.« less

The HEASARC Swift Gamma-Ray Burst Archive: The Pipeline and the Catalog

NASA Technical Reports Server (NTRS)

Donato, Davide; Angelini, Lorella; Padgett, C.A.; Reichard, T.; Gehrels, Neil; Marshall, Francis E.; Sakamoto, Takanori

2012-01-01

Since its launch in late 2004, the Swift satellite triggered or observed an average of one gamma-ray burst (GRB) every 3 days, for a total of 771 GRBs by 2012 January. Here, we report the development of a pipeline that semi automatically performs the data-reduction and data-analysis processes for the three instruments on board Swift (BAT, XRT, UVOT). The pipeline is written in Perl, and it uses only HEAsoft tools and can be used to perform the analysis of a majority of the point-like objects (e.g., GRBs, active galactic nuclei, pulsars) observed by Swift. We run the pipeline on the GRBs, and we present a database containing the screened data, the output products, and the results of our ongoing analysis. Furthermore, we created a catalog summarizing some GRB information, collected either by running the pipeline or from the literature. The Perl script, the database, and the catalog are available for downloading and querying at the HEASARC Web site.

The HEASARC Swift Gamma-Ray Burst Archive: The Pipeline and the Catalog

NASA Astrophysics Data System (ADS)

Donato, D.; Angelini, L.; Padgett, C. A.; Reichard, T.; Gehrels, N.; Marshall, F. E.; Sakamoto, T.

2012-11-01

Since its launch in late 2004, the Swift satellite triggered or observed an average of one gamma-ray burst (GRB) every 3 days, for a total of 771 GRBs by 2012 January. Here, we report the development of a pipeline that semi-automatically performs the data-reduction and data-analysis processes for the three instruments on board Swift (BAT, XRT, UVOT). The pipeline is written in Perl, and it uses only HEAsoft tools and can be used to perform the analysis of a majority of the point-like objects (e.g., GRBs, active galactic nuclei, pulsars) observed by Swift. We run the pipeline on the GRBs, and we present a database containing the screened data, the output products, and the results of our ongoing analysis. Furthermore, we created a catalog summarizing some GRB information, collected either by running the pipeline or from the literature. The Perl script, the database, and the catalog are available for downloading and querying at the HEASARC Web site.

Gamma-Ray Bursts in the Swift Era

NASA Technical Reports Server (NTRS)

Gehrels, Neil; Ramirez-Ruiz, E.; Fox, D. B.

2010-01-01

With its rapid-response capability and multiwavelength complement of instruments, the Swift satellite has transformed our physical understanding of gamma-ray bursts. Providing high-quality observations of hundreds of bursts, and facilitating a wide range of follow-up observations within seconds of each event, Swift has revealed an unforeseen richness in observed burst properties, shed light on the nature of short-duration bursts, and helped realize the promise of gamma-ray bursts as probes of the processes and environments of star formation out to the earliest cosmic epochs. These advances have opened new perspectives on the nature and properties of burst central engines, interactions with the burst environment from microparsec to gigaparsec scales, and the possibilities for non-photonic signatures. Our understanding of these extreme cosmic sources has thus advanced substantially; yet more than forty years after their discovery, gamma-ray bursts continue to present major challenges on both observational and theoretical fronts.

On the detection of very high redshift gamma-ray bursts with Swift

NASA Astrophysics Data System (ADS)

Salvaterra, R.; Campana, S.; Chincarini, G.; Tagliaferri, G.; Covino, S.

2007-09-01

We compute the probability of detecting long gamma-ray bursts (GRBs) at z >= 5 with Swift, assuming that GRBs form preferentially in low-metallicity environments. The model fits both the observed Burst and Transient Source Experiment (BATSE) and Swift GRB differential peak flux distributions well and is consistent with the number of z >= 2.5 detections in the 2-yr Swift data. We find that the probability of observing a burst at z >= 5 becomes larger than 10 per cent for photon fluxes P < 1 ph s-1 cm-2, consistent with the number of confirmed detections. The corresponding fraction of z >= 5 bursts in the Swift catalogue is ~10-30 per cent depending on the adopted metallicity threshold for GRB formation. We propose to use the computed probability as a tool to identify high-redshift GRBs. By jointly considering promptly available information provided by Swift and model results, we can select reliable z >= 5 candidates in a few hours from the BAT detection. We test the procedure against last year Swift data: only three bursts match all our requirements, two being confirmed at z >= 5. Another three possible candidates are picked up by slightly relaxing the adopted criteria. No low-z interloper is found among the six candidates.

Gamma Ray Burst Discoveries by the Swift Mission

NASA Technical Reports Server (NTRS)

Gehrels, Neil

2006-01-01

Gamma-ray bursts are among the most fascinating occurrences in the cosmos. They are thought to be the birth cries of black holes throughout the universe. The NASA Swift mission is an innovative new multiwavelength observatory designed to determine the origin of bursts and use them to probe the early Universe. Swift is now in orbit after a beautiful launch on November 20, 2004. A new-technology wide-field gamma-ray camera detects more than a hundred bursts per year. Sensitive narrow-field X-ray and UV/optical telescopes, built in collaboration with UK and Italian partners and calibrated in Germany, are pointed at the burst location in 20 to 70 sec by an autonomously controlled "swift" spacecraft. For each burst, arcsec positions are determined and optical/UV/X-ray/gamma-ray spectrophotometry performed. Information is also rapidly sent to the ground to a team of more than 50 observers at telescopes around the world. Early results from the mission will be presented. The long-standing mystery of short GRBs has been solved, and the answer is the most interesting possible scenario. High redshift bursts have been detected leading to a better understanding of star formation rates and distant galaxy environments. GRBs have been found with giant X-ray flares occurring in their afterglow. Observations of magnetars, galactic transients, supernovae, AGN and many other types of sources are also being performed

Gamma Ray Burst Discoveries by the Swift Mission

NASA Astrophysics Data System (ADS)

Gehrels, N.; Swift Team

2005-12-01

Gamma-ray bursts are among the most fascinating occurrences in the cosmos. They are thought to be the birth cries of black holes throughout the universe. The NASA Swift mission is an innovative new multiwavelength observatory designed to determine the origin of bursts and use them to probe the early Universe. Swift is now in orbit after a beautiful launch on November 20, 2004. A new-technology wide-field gamma-ray camera detects more than a hundred bursts per year. Sensitive narrow-field X-ray and UV/optical telescopes, built in collaboration with UK and Italian partners, are pointed at the burst location in 20 to 70 sec by an autonomously controlled "swift" spacecraft. For each burst, arcsec positions are determined and optical/UV/X-ray/gamma-ray spectrophotometry performed. Information is also rapidly sent to the ground to a team of more than 50 observers at telescopes around the world. The first year of findings from the mission will be presented. The long-standing mystery of short GRBs has been solved, and the answer is the most interesting possible scenario. High redshift bursts have been detected leading to a better understanding of star formation rates and distant galaxy environments. GRBs have been found with giant X-ray flares occurring in their afterglow. These, and other topics, will be discussed.

Gamma Ray Burst Discoveries by the Swift Mission

NASA Astrophysics Data System (ADS)

Gehrels, Neil

2006-04-01

Gamma-ray bursts are among the most fascinating occurrences in the cosmos. They are thought to be the birth cries of black holes throughout the universe. The NASA Swift mission is an innovative new multiwavelength observatory designed to determine the origin of bursts and use them to probe the early Universe. Swift is now in orbit since November 20, 2004 and all hardware is performing well. A new-technology wide-field gamma-ray camera is detecting a hundred bursts per year. Sensitive narrow-field X-ray and UV/optical telescopes, built in collaboration with UK and Italian partners, are pointed at the burst location in 50-100 sec by an autonomously controlled ``swift'' spacecraft. For each burst, arcsec positions are determined and optical/UV/X-ray/gamma-ray spectrophotometry performed. Information is also rapidly sent to the ground to a team of more than 50 observers at telescopes around the world. The first year of findings from the mission will be presented. There has been a break-through in the long-standing mystery of short GRBs; they appear to be caused by merging neutron stars. High redshift bursts have been detected leading to a better understanding of star formation rates and distant galaxy environments. GRBs have been found with giant X-ray flares occurring in their afterglow.

Gamma Ray Burst Discoveries by the Swift Mission

NASA Technical Reports Server (NTRS)

Gehrels, Neil

2006-01-01

Gamma-ray bursts are among the most fascinating occurrences in the cosmos. They are thought to be the birth cries of black holes throughout the universe. The NASA swift mission is an innovative new multiwavelength observatory designed to determine the origin of bursts and use them to probe the early Universe. Swift is now in orbit since November 20, 2004 and all hardware is performing well. A new-technology wide-field gamma-ray camera is detecting a hundred bursts per year. sensitive narrow-field X-ray and uv/optical telescopes, built in collaboration with UK and Italian partners, are pointed at the burst location in 50-100 sec by an autonomously controlled "swift" spacecraft. For each burst, arcsec positions are determined and optical/UV/X-ray/gamma-ray spectrophotometry performed. Information is also rapidly sent to the ground to a team of more than 50 observers at telescopes around the world. The first year of findings from the mission will be presented. There has been a break-through in the longstanding mystery of short GRBs; they appear to be caused by merging neutron stars. High redshift bursts have been detected leading to a better understanding of star formation rates and distant galaxy environments. GRBs have been found with giant X-ray flares occurring in their afterglow.

Gamma Ray Burst Discoveries by the Swift Mission

NASA Technical Reports Server (NTRS)

Gehrels, Neil

2006-01-01

Gamma-ray bursts are among the most fascinating occurrences in the cosmos. They are thought to be the birth cries of black holes throughout the universe. The NASA Swift mission is an innovative new multiwavelength observatory designed to determine the origin of bursts and use them to probe the early Universe. Swift is now in orbit after a beautiful launch on November 20, 2004. A new-technology wide-field gamma-ray camera detects more than a hundred bursts per year. Sensitive narrow-field X-ray and UV/optical telescopes, built in collaboration with UK and Italian partners, are pointed at the burst location in 20 to 70 sec by an autonomously controlled "swift" spacecraft. For each burst, arcsec positions are determined and optical/UV/X-ray/gamma-ray spectrophotometry performed. Information is also rapidly sent to the ground to a team of more than 50 observers at telescopes around the world. The first year of findings from the mission will be presented. The long-standing mystery of short GRBs has been solved, and the answer is the most interesting possible scenario. High redshift bursts have been detected leading to a better understanding of star formation rates and distant galaxy environments. GRBs have been found with giant X-ray flares occurring in their afterglow. These, and other topics, will be discussed.

Gamma-ray burst theory after Swift.

PubMed

Piran, Tsvi; Fan, Yi-Zhong

2007-05-15

Afterglow observations in the pre-Swift era confirmed to a large extend the relativistic blast wave model for gamma-ray bursts (GRBs). Together with the observations of properties of host galaxies and the association with (type Ic) SNe, this has led to the generally accepted collapsar origin of long GRBs. However, most of the afterglow data was collected hours after the burst. The X-ray telescope and the UV/optical telescope onboard Swift are able to slew to the direction of a burst in real time and record the early broadband afterglow light curves. These observations, and in particular the X-ray observations, resulted in many surprises. While we have anticipated a smooth transition from the prompt emission to the afterglow, many observed that early light curves are drastically different. We review here how these observations are changing our understanding of GRBs.

Analysis of the observed and intrinsic durations of Swift/BAT gamma-ray bursts

NASA Astrophysics Data System (ADS)

Tarnopolski, Mariusz

2016-07-01

The duration distribution of 947 GRBs observed by Swift/BAT, as well as its subsample of 347 events with measured redshift, allowing to examine the durations in both the observer and rest frames, are examined. Using a maximum log-likelihood method, mixtures of two and three standard Gaussians are fitted to each sample, and the adequate model is chosen based on the value of the difference in the log-likelihoods, Akaike information criterion and Bayesian information criterion. It is found that a two-Gaussian is a better description than a three-Gaussian, and that the presumed intermediate-duration class is unlikely to be present in the Swift duration data.

The SWIFT Gamma-Ray Burst X-Ray Telescope

NASA Technical Reports Server (NTRS)

Hill, J. E.; Burrows, D. N.; Nousek, J. A.; Wells, A.; Chincarini, G.; Abbey, A. F.; Angelini, L.; Beardmore, A.; Brauninger, H. W.; Chang, W.

2006-01-01

The Swift Gamma-Ray Burst Explorer is designed to make prompt multi-wavelength observations of Gamma-Ray Bursts and GRB afterglows. The X-ray Telescope enables Swift to determine GRB positions with a few arcseconds accuracy within 100 seconds of the burst onset. The XRT utilizes a mirror set built for JET-X and an XMM-Newton/ EPIC MOS CCD detector to provide a sensitive broad-band (0.2-10 keV) X-ray imager with an effective area of more than 120 sq cm at 1.5 keV, a field of view of 23.6 x 23.6 arcminutes, and an angular resolution of 18 arcseconds (HPD). The detection sensitivity is 2x10(exp 14) erg/sq cm/s in 10(exp 4) seconds. The instrument provides automated source detection and position reporting within 5 seconds of target acquisition. It can also measure the redshifts of GRBs with Iron line emission or other spectral features. The XRT operates in an auto-exposure mode, adjusting the CCD readout mode automatically to optimize the science return as the source intensity fades. The XRT measures spectra and lightcurves of the GRB afterglow beginning about a minute after the burst and follows each burst for days or weeks. We provide an overview of the X-ray Telescope scientific background from which the systems engineering requirements were derived, with specific emphasis on the design and qualification aspects from conception through to launch. We describe the impact on cleanliness and vacuum requirements for the instrument low energy response and to maintain the high sensitivity to the fading signal of the Gamma-ray Bursts.

The Swift/BAT Hard X-ray Transient Monitor: A Status Report

NASA Astrophysics Data System (ADS)

Krimm, Hans A.; Bloom, J. S.; Markwardt, C.; Miler-Jones, J.; Gehrels, N.; Kennea, J. A.; Holland, S.; Sivakoff, G. R.; Swift/BAT Team

2013-04-01

The Swift/Burst Alert Telescope (BAT) hard X-ray transient monitor provides near real-time coverage of the X-ray sky in the energy range 15-50 keV. This monitor was first announced at the 2006 HEAD meeting. Seven years later, it continues to operate and provides near real-time light curves of more than 900 astrophysical sources. The BAT observes ~75% of the sky each day with a 3-sigma detection sensitivity of 7 mCrab for a full-day observation and a time resolution as fine as 64 seconds. The three main purposes of the monitor are (1) the discovery of new transient X-ray sources, (2) the detection of outbursts or other changes in the flux of known X-ray sources, and (3) the generation of archival light curves spanning nearly seven years. The primary interface for the BAT transient monitor is a public web page. Since February 2005, 223 sources have been detected in the monitor, 142 of them persistent and 81 detected only in outburst. From 2006-2013, fourteen new sources have been discovered by the BAT transient monitor. We will describe the methodology of the transient monitor, present a summary of its statistics, and discuss the detection of known and newly discovered sources.

The Swift/BAT Hard X-ray Transient Monitor: A Status Report

NASA Astrophysics Data System (ADS)

Krimm, Hans A.; Swift/BAT Team

2011-09-01

The Swift/Burst Alert Telescope (BAT) hard X-ray transient monitor provides near real-time coverage of the X-ray sky in the energy range 15-50 keV. This monitor was first announced at the 2006 HEAD meeting. Five years later, it continues to operate and provides near real-time light curves of more than 900 astrophysical sources. The BAT observes 75% of the sky each day with a 3-sigma detection sensitivity of 7 mCrab for a full-day observation and a time resolution as fine as 64 seconds. The three main purposes of the monitor are (1) the discovery of new transient X-ray sources, (2) the detection of outbursts or other changes in the flux of known X-ray sources, and (3) the generation of archival light curves spanning nearly seven years. The primary interface for the BAT transient monitor is a public web page. Since February 2005, 172 sources have been detected in the monitor, 89 of them persistent and 83 detected only in outburst. From 2006-2011, nine new sources have been discovered by the BAT transient monitor. We will describe the methodology of the transient monitor, present a summary of its statistics, and discuss the detection of known and newly discovered sources.

Exploring the Pulse Structure of the Gamma-Ray Bursts from the Swift Burst Alert Telescop

NASA Astrophysics Data System (ADS)

Martinez, Juan-Carlos; Team 1: Jon Hakkila, Amy Lien, Judith, Racusin, Team 2: Antonino Cucchiara, David Morris

2018-01-01

Gamma-ray bursts (GRBs) are one of the brightest and most intense explosions in our universe. For this project, we studied the shape of 400 single pulse GRBs using data gathered from Swift's Burst Alert Telescope (BAT). Hakkila et al. (2015) have discovered a mathematical Model that describes the GRB’s pulse shapes. Following the method in Hakkila et al. (2015), we fit GRB pulses with the Norris function and examined the residual in the fitting, to see whether the results are consistent with the one reported in Hakkila et al. (2015).

The nature of fifty Palermo Swift-BAT hard X-ray objects through optical spectroscopy

NASA Astrophysics Data System (ADS)

Rojas, A. F.; Masetti, N.; Minniti, D.; Jiménez-Bailón, E.; Chavushyan, V.; Hau, G.; McBride, V. A.; Bassani, L.; Bazzano, A.; Bird, A. J.; Galaz, G.; Gavignaud, I.; Landi, R.; Malizia, A.; Morelli, L.; Palazzi, E.; Patiño-álvarez, V.; Stephen, J. B.; Ubertini, P.

2017-07-01

We present the nature of 50 unidentified hard X-ray emitting objects detected with Swift-BAT and listed as of unidentified nature in the 54-month Palermo BAT catalogue. We found 45 extragalactic sources: 26 type 1 AGN, 15 type 2 AGN, one type 1 QSO, one starburst galaxy, one X-ray bright optically normal galaxy, and one LINER. We report 30 new redshift measurements, 13 confirmations and 2 more accurate redshift values. The remaining five objects are galactic sources: three are Cataclismic Variables, one is a X-ray Binary, and one is an active star.

The Swift Gamma Ray Burst Mission

NASA Technical Reports Server (NTRS)

Gehrels, N.; Chincarini, G.; Giommi, P.; Mason, K. O.; Nousek, J. A.; Wells, A. A.; White, N. E.; Barthelmy, S. D.; Burrows, D. N.; Cominsky, L. R.

2004-01-01

The Swift mission: scheduled for launch in early 2004: is a multiwavelength observatory for gamma-ray burst (GRB) astronomy. It is the first-of-its-kind autonomous rapid-slewing satellite for transient astronomy and pioneers the way for future rapid-reaction and multiwavelength missions. It will be far more powerful than any previous GRB mission, observing more than 100 bursts per year and performing detailed X-ray and UV/optical afterglow observations spanning timescales from 1 minute to several days after the burst. The objectives are to: 1) determine the origin of GFU3s; 2) classify GRBs and search for new types; 3) study the interaction of the ultra-relativistic outflows of GRBs with their surrounding medium; and 4) use GRBs to study the early universe out to z greater than 10. The mission is being developed by a NASA-led international collaboration. It will carry three instruments: a new-generation wide-field gamma-ray (15-150 keV) detector that will detect bursts, calculate 1-4 arcmin positions: and trigger autonomous spacecraft slews; a narrow-field X-ray telescope that will give 5 arcsec positions and perform spectroscopy in the 0.2 to 10 keV band; and a narrow-field UV/optical telescope that will operate in the 170-600 nm band and provide 0.3 arcsec positions and optical finding charts. Redshift determinations will be made for most bursts. In addition to the primary GRB science, the mission will perform a hard X-ray survey to a sensitivity of approx. 1 mCrab (approx. 2 x l0(exp -11) erg/sq cm s in the 15-150 keV band), more than an order of magnitude better than HEAO A-4. A flexible data and operations system will allow rapid follow-up observations of all types of high-energy transients. with rapid data downlink and uplink available through the NASA TDRSS system. Swift transient data will be rapidly distributed to the astronomical community and all interested observers are encouraged to participate in follow-up measurements. A Guest Investigator program

AGN classification for X-ray sources in the 105 month Swift/BAT survey

NASA Astrophysics Data System (ADS)

Masetti, N.; Bassani, L.; Palazzi, E.; Malizia, A.; Stephen, J. B.; Ubertini, P.

2018-03-01

We here provide classifications for 8 hard X-ray sources listed as 'unknown AGN' in the 105 month Swift/BAT all-sky survey catalogue (Oh et al. 2018, ApJS, 235, 4). The corresponding optical spectra were extracted from the 6dF Galaxy Survey (Jones et al. 2009, MNRAS, 399, 683).

Fermi-LAT Gamma-ray Bursts and Insight from Swift

NASA Technical Reports Server (NTRS)

Racusin, Judith L.

2011-01-01

A new revolution in GRB observation and theory has begun over the last 3 years since the launch of the Fermi gamma-ray space telescope. The new window into high energy gamma-rays opened by the Fermi-LAT is providing insight into prompt emission mechanisms and possibly also afterglow physics. The LAT detected GRBs appear to be a new unique subset of extremely energetic and bright bursts. In this talk I will discuss the context and recent discoveries from these LAT GRBs and the large database of broadband observations collected by Swift over the last 7 years and how through comparisons between the Swift, GBM, and LAT GRB samples, we can learn about the unique characteristics and relationships between each population.

XMM Observations of 'New' Swift BAT Sources

NASA Technical Reports Server (NTRS)

Mushotzky, Richard F.

2008-01-01

Because the E> 15 keV band is unaffected by absorption this band offers the best hope of obtaining an unbiased sample of AGN. The Swift BAT survey has produced the first large sample of hard x-ray bright AGN in the local universe providing the data necessary to determine the true characteristics of the AGN population. However to use this data one needs to obtain the x-ray spectral properties of these objects.We will present the complete sample of x-ray spectra of the BAT objects and the implications of these data.

Modeling the Swift BAT Trigger Algorithm with Machine Learning

NASA Technical Reports Server (NTRS)

Graff, Philip B.; Lien, Amy Y.; Baker, John G.; Sakamoto, Takanori

2015-01-01

To draw inferences about gamma-ray burst (GRB) source populations based on Swift observations, it is essential to understand the detection efficiency of the Swift burst alert telescope (BAT). This study considers the problem of modeling the Swift BAT triggering algorithm for long GRBs, a computationally expensive procedure, and models it using machine learning algorithms. A large sample of simulated GRBs from Lien et al. (2014) is used to train various models: random forests, boosted decision trees (with AdaBoost), support vector machines, and artificial neural networks. The best models have accuracies of approximately greater than 97% (approximately less than 3% error), which is a significant improvement on a cut in GRB flux which has an accuracy of 89:6% (10:4% error). These models are then used to measure the detection efficiency of Swift as a function of redshift z, which is used to perform Bayesian parameter estimation on the GRB rate distribution. We find a local GRB rate density of eta(sub 0) approximately 0.48(+0.41/-0.23) Gpc(exp -3) yr(exp -1) with power-law indices of eta(sub 1) approximately 1.7(+0.6/-0.5) and eta(sub 2) approximately -5.9(+5.7/-0.1) for GRBs above and below a break point of z(sub 1) approximately 6.8(+2.8/-3.2). This methodology is able to improve upon earlier studies by more accurately modeling Swift detection and using this for fully Bayesian model fitting. The code used in this is analysis is publicly available online.

A 10 Day Period in IGR J16328-4726 from Swift/BAT Observations

NASA Astrophysics Data System (ADS)

Corbet, R. H. D.; Barthelmy, S. D.; Baumgartner, W. H.; Krimm, H. A.; Markwardt, C. B.; Skinner, G. K.; Tueller, J.

2010-04-01

IGR J16328-4726 is a little studied X-ray source. It is listed as a "blended" variable source in the 4th IBIS/ISGRI Catalog (Bird et al. 2010, ApJ Supp, 186, 1) but is not present in the Swift BAT 22 month all-sky survey (Tueller et al. 2010, ApJ Supp, 186, 378). Grupe et al. (2009, ATel #2075) report a flare detected with the Swift BAT which was followed up with Swift XRT observations. We have analyzed the Swift BAT 58 month survey (Baumgartner et al.

AGN in the Swift/BAT and INTEGRAL Hard X-ray Surveys

NASA Technical Reports Server (NTRS)

Beckmann, Volker; Tueller, Jack; Baumgartner, Wayne; Markwardt, Craig; Mushotzky, Richard; Skinner, Gerry

2008-01-01

Two hard X-ray surveys are in progress at this time. They provide a unique new window on compact objects and black holes. I will discuss how these two surveys complement each other and the potential for improved coordination that could yield significant near term results in both sensitivity and time coverage. I will pay particular attention to the discovery of faint sources including new results from the 36 month survey from Swift/Burst Alert Telescope (BAT).

Modeling the Swift Bat Trigger Algorithm with Machine Learning

NASA Technical Reports Server (NTRS)

Graff, Philip B.; Lien, Amy Y.; Baker, John G.; Sakamoto, Takanori

2016-01-01

To draw inferences about gamma-ray burst (GRB) source populations based on Swift observations, it is essential to understand the detection efficiency of the Swift burst alert telescope (BAT). This study considers the problem of modeling the Swift / BAT triggering algorithm for long GRBs, a computationally expensive procedure, and models it using machine learning algorithms. A large sample of simulated GRBs from Lien et al. is used to train various models: random forests, boosted decision trees (with AdaBoost), support vector machines, and artificial neural networks. The best models have accuracies of greater than or equal to 97 percent (less than or equal to 3 percent error), which is a significant improvement on a cut in GRB flux, which has an accuracy of 89.6 percent (10.4 percent error). These models are then used to measure the detection efficiency of Swift as a function of redshift z, which is used to perform Bayesian parameter estimation on the GRB rate distribution. We find a local GRB rate density of n (sub 0) approaching 0.48 (sup plus 0.41) (sub minus 0.23) per cubic gigaparsecs per year with power-law indices of n (sub 1) approaching 1.7 (sup plus 0.6) (sub minus 0.5) and n (sub 2) approaching minus 5.9 (sup plus 5.7) (sub minus 0.1) for GRBs above and below a break point of z (redshift) (sub 1) approaching 6.8 (sup plus 2.8) (sub minus 3.2). This methodology is able to improve upon earlier studies by more accurately modeling Swift detection and using this for fully Bayesian model fitting.

SWIFT BAT Survey of AGN

NASA Technical Reports Server (NTRS)

Tueller, J.; Mushotzky, R. F.; Barthelmy, S.; Cannizzo, J. K.; Gehrels, N.; Markwardt, C. B.; Skinner, G. K.; Winter, L. M.

2008-01-01

We present the results1 of the analysis of the first 9 months of data of the Swift BAT survey of AGN in the 14-195 keV band. Using archival X-ray data or follow-up Swift XRT observations, we have identified 129 (103 AGN) of 130 objects detected at [b] > 15deg and with significance > 4.8-delta. One source remains unidentified. These same X-ray data have allowed measurement of the X-ray properties of the objects. We fit a power law to the logN - log S distribution, and find the slope to be 1.42+/-0.14. Characterizing the differential luminosity function data as a broken power law, we find a break luminosity logL*(ergs/s)= 43.85+/-0.26. We obtain a mean photon index 1.98 in the 14-195 keV band, with an rms spread of 0.27. Integration of our luminosity function gives a local volume density of AGN above 10(exp 41) erg/s of 2.4x10(exp -3) Mpc(sup -3), which is about 10% of the total luminous local galaxy density above M* = -19.75. We have obtained X-ray spectra from the literature and from Swift XRT follow-up observations. These show that the distribution of log nH is essentially flat from nH = 10(exp 20)/sq cm to 10(exp 24)/sq cm, with 50% of the objects having column densities of less than 10(exp 22)/sq cm. BAT Seyfert galaxies have a median redshift of 0.03, a maximum log luminosity of 45.1, and approximately half have log nH > 22.

Thermal Assessment of Swift BAT Instrument Thermal Control System in Flight

NASA Technical Reports Server (NTRS)

Choi, Michael K.

2005-01-01

THE BAT is the primary instrument on the Swift spacecraft. The Swift mission is part of the National Aeronautics and Space Administration (NASA) Medium-Size Explorer (MIDEX) Program, and is managed by Goddard Space Flight Center (GSFC). It is designed to detect gamma ray burst over a broad region of the sky in a low Earth orbit of 600-km altitude and quickly align the telescopes on the spacecraft to the gamma ray source. It was successfully launched into orbit on November 20, 2004. The Swift mission is a first of its kind of multi-wavelength transient observatory for gamma ray burst astronomy. Its mission life is 2 years. The inclination is 22 deg maximum. The spacecraft bus voltage to the instruments is in the 24 V to 35 V range. The instruments will be turned off when the voltage is below 27 V. The BAT is mounted to the optical bench through five titanium flexures. The BAT has been developed at GSFC. Its telescope assembly consists of 256 Detector Modules (DMs) in the Detector Array. There are 16 Detector Array Blocks. Each Block holds 16 DMs, 3 Block Voltage Regulator (BVR) units and 3 Block Command & Data Handling (BCDH) units. The power dissipation of each Block has been measured to be 13 W. Therefore the total power dissipation of the 16 Blocks is 208 W. The DAP is 1.3 m (4.3 ft) x 1 m (3.3 ft), accommodates all the 16 Blocks. It also provides the mounting surface and the positional stability for the Blocks. The DMs are located at the top (+X side) of the DAP and is enclosed by graded-Z shields on the sides and a coded mask at the top. The BVRs and BCDHs are located at the bottom (-X side) of the DAP. Eight Blocks are located at the front (-Z side or radiator side) of the DAP, and eight are located at the rear (+Z side) of the DAP. The DMs and top of DAP are insulated with a 7-layer multi-layer insulation (MLI). There is a 5.08 cm (2 in) x 5.08 cm (2 in) MLI cutout over each Block heater controller so that heat radiates from the heater controller to the mask

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.

Swift Gamma-Ray Burst Explorer: Mission Design for Rapid, Accurate Location of Gamma-ray Bursts

NASA Technical Reports Server (NTRS)

Bundas, David J.

2004-01-01

The Swift Gamma-ray Burst Explorer is a NASA Mid-sized Explorer (MIDEX) with the primary mission of determining the origins of Gamma-Ray Bursts (GRBs). It will be the first mission to autonomously respond to newly-discovered GRBs and provide immediate follow-up with narrow field instruments capable of multi-wavelength (UV, Optical, X-ray) observations. The characteristics of GRBs that are the key mission design drivers, are their non-repeating and brief duration bursts of multi-wavelength photons. In addition, rapid notification of the location and characteristics of the GRBs to ground-and-space-based observatories drive the end-to-end data analysis and distribution requirements.

Swift Gamma-ray Burst Explorer: Mission Design for Rapid, Accurate Location of Gamma-ray Bursts

NASA Technical Reports Server (NTRS)

Bundas, David J.

2005-01-01

The Swift Gamma-ray Burst Explorer is a NASA Mid-sized Explorer (MIDEX) with the primary mission of determining the origins of Gamma-Ray Bursts (GRBs). It will be the first mission to autonomously respond to newly-discovered GRBs and provide immediate follow-up with narrow field instruments capable of multi-wavelength (UT, Optical, X-ray) observations. The characteristics of GRBs that are the key mission design drivers, are their non-repeating and brief duration bursts of multi-wavelength photons. In addition, rapid notification of the location and characteristics of the GRBs to ground-and-space-based observatories drive the end-to-end data analysis and distribution requirements.

X-RAY PROPERTIES OF THE NORTHERN GALACTIC CAP SOURCES IN THE 58 MONTH SWIFT/BAT CATALOG

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vasudevan, Ranjan V.; Mushotzky, Richard F.; Shimizu, Thomas T.

2013-02-15

We present a detailed X-ray spectral analysis of the non-beamed, hard X-ray selected active galactic nuclei (AGNs) in the northern Galactic cap of the 58 month Swift Burst Alert Telescope (Swift/BAT) catalog, consisting of 100 AGNs with b > 50 Degree-Sign . This sky area has excellent potential for further dedicated study due to a wide range of multi-wavelength data that are already available, and we propose it as a low-redshift analog to the 'deep field' observations of AGNs at higher redshifts (e.g., CDFN/S, COSMOS, Lockman Hole). We present distributions of luminosity, absorbing column density, and other key quantities formore » the catalog. We use a consistent approach to fit new and archival X-ray data gathered from XMM-Newton, Swift/XRT, ASCA, and Swift/BAT. We probe to deeper redshifts than the 9 month BAT catalog ((z) = 0.043 compared to (z) = 0.03 for the 9 month catalog), and uncover a broader absorbing column density distribution. The fraction of obscured (log N {sub H} {>=} 22) objects in the sample is {approx}60%, and 43%-56% of the sample exhibits 'complex' 0.4-10 keV spectra. We present the properties of iron lines, soft excesses, and ionized absorbers for the subset of objects with sufficient signal-to-noise ratio. We reinforce previous determinations of the X-ray Baldwin (Iwasawa-Taniguchi) effect for iron K{alpha} lines. We also identify two distinct populations of sources; one in which a soft excess is well-detected and another where the soft excess is undetected, suggesting that the process responsible for producing the soft excess is not at work in all AGNs. The fraction of Compton-thick sources (log N {sub H} > 24.15) in our sample is {approx}9%. We find that 'hidden/buried AGNs' (which may have a geometrically thick torus or emaciated scattering regions) constitute {approx}14% of our sample, including seven objects previously not identified as hidden. Compton reflection is found to be important in a large fraction of our sample using joint

Host Galaxy Properties of the Swift BAT Ultra Hard X-Ray Selected AGN

NASA Technical Reports Server (NTRS)

Koss, Michael; Mushotzky, Richard; Veilleux, Sylvain; Winter, Lisa M.; Baumgartner, Wayne; Tueller, Jack; Gehrels, Neil; Valencic, Lynne

2011-01-01

We have assembled the largest sample of ultra hard X-ray selected (14-195 keV) AGN with host galaxy optical data to date, with 185 nearby (z<0.05), moderate luminosity AGN from the Swift Burst Alert Telescope (BAT) sample. The BAT AGN host galaxies have intermediate optical colors (u -- r and g -- r) that are bluer than a comparison sample of inactive galaxies and optically selected AGN from the Sloan Digital Sky Survey (SDSS) which are chosen to have the same stellar mass. Based on morphological classifications from the RC3 and the Galaxy Zoo, the bluer colors of BAT AGN are mainly due to a higher fraction of mergers and massive spirals than in the comparison samples. BAT AGN in massive galaxies (log Stellar Mass >10.5) have a 5 to 10 times higher rate of spiral morphologies than in SDSS AGN or inactive galaxies. We also see enhanced far-IR emission in BAT AGN suggestive of higher levels of star formation compared to the comparison samples. BAT AGN are preferentially found in the most massive host galaxies with high concentration indexes indicative of large bulge-to-disk ratios and large supermassive black holes. The narrow-line (NL) BAT AGN have similar intrinsic luminosities as the SDSS NL Seyferts based on measurements of [O III] Lambda 5007. There is also a correlation between the stellar mass and X-ray emission. The BAT AGN in mergers have bluer colors and greater ultra hard X-ray emission compared to the BAT sample as whole. In agreement with the Unified Model of AGN, and the relatively unbiased nature of the BAT sources, the host galaxy colors and morphologies are independent of measures of obscuration such as X-ray column density or Seyfert type. The high fraction of massive spiral galaxies and galaxy mergers in BAT AGN suggest that host galaxy morphology is related to the activation and fueling of local AGN.

Swift J181723.1-164300 is likely a new bursting neutron star low-mass X-ray binary

NASA Astrophysics Data System (ADS)

Parikh, Aastha; Wijnands, Rudy; Degenaar, Nathalie; Altamirano, Diego

2017-08-01

On 28 July 2017 Swift/BAT triggered (#00765081) on an event corresponding to a previously unknown source (Barthelmy et al. 2017, GCN #21369, #21385). Its properties suggested it was likely a Galactic source and not a gamma-ray burst.

STUDYING FAINT ULTRA-HARD X-RAY EMISSION FROM AGN IN GOALS LIRGS WITH SWIFT/BAT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koss, Michael; Casey, Caitlin M.; Mushotzky, Richard

2013-03-10

We present the first analysis of the all-sky Swift Burst Alert Telescope (BAT) ultra-hard X-ray (14-195 keV) data for a targeted list of objects. We find that the BAT data can be studied at three-times-fainter limits than in previous blind detection catalogs based on prior knowledge of source positions and using smaller energy ranges for source detection. We determine the active galactic nucleus (AGN) fraction in 134 nearby (z < 0.05) luminous infrared galaxies (LIRGs) from the GOALS sample. We find that LIRGs have a higher detection frequency than galaxies matched in stellar mass and redshift at 14-195 keV andmore » 24-35 keV. In agreement with work at other wavelengths, the AGN detection fraction increases strongly at high IR luminosity with half of the high-luminosity LIRGs (50%, 6/12, log L{sub IR}/L{sub Sun} > 11.8) detected. The BAT AGN classification shows 97% (37/38) agreement with Chandra and XMM-Newton AGN classification using hardness ratios or detection of an iron K{alpha} line. This confirms our statistical analysis and supports the use of the Swift/BAT all-sky survey to study fainter populations of any category of sources in the ultra-hard X-ray band. BAT AGNs in LIRGs tend to show higher column densities with 40% {+-} 9% showing 14-195 keV/2-10 keV hardness flux ratios suggestive of high or Compton-thick column densities (log N{sub H} > 24 cm{sup -2}), compared to only 12% {+-} 5% of non-LIRG BAT AGNs. We also find that using specific energy ranges of the BAT detector can yield additional sources over total band detections with 24% (5/21) of detections in LIRGs at 24-35 keV not detected at 14-195 keV.« less

Gamma Ray Burst Discoveries with the Swift Mission

NASA Technical Reports Server (NTRS)

Gehrels, Neil

2008-01-01

Gamma-ray bursts (GRBs) are among the most fascinating occurrences in the universe. They are powerful explosions, visible to high redshift, and thought to be the signature of black hole formation. The Swift Observatory has been detecting 100 bursts per year for 3 years and has greatly stimulated the field with new findings. Observations are made of the X-ray and optical afterglow from - 1 minute after the burst, continuing for days. Evidence is building that the long and short duration subcategories of GRBs have very different origins: massive star core collapse to a black hole for long bursts and binary neutron star coalescence to a black hole for short bursts. The similarity to Type I1 and Ia supernovae originating from young and old stellar progenitors is striking. Bursts are providing a new tool to study the high redshift universe. Swift has detected several events at z>5 and one at z=6.3 giving metallicity measurements and other data on galaxies at previously inaccessible distances. The talk will present the latest results from Swift in GRB astronomy.

Gamma Ray Burst Discoveries with the Swift Mission

NASA Technical Reports Server (NTRS)

Gehrels, Neil

2008-01-01

Gamma-ray bursts (GRBs) are among the most fascinating occurrences in the universe. They are powerful explosions, visible to high redshift, and thought to be the signature of black hole formation. The Swift Observatory has been detecting 100 bursts per year for 3 years and has greatly stimulated the field with new findings. Observations are made of the X-ray and optical afterglow from approximately 1 minute after the burst, continuing for days. Evidence is building that the long and short duration subcategories of GRBs have very different origins: massive star core collapse to a black hole for long bursts and binary neutron star coalescence to a black hole for short bursts. The similarity to Type II and Ia supernovae originating from young and old stellar progenitors is striking. Bursts are providing a new tool to study the high redshift universe. Swift has detected several events at z greater than 5 and one at z=6.3 giving metallicity measurements and other data on galaxies at previously inaccessible distances. The talk will present the latest results from Swift in GRB astronomy.

Gamma Ray Burst Discoveries with the Swift Mission

NASA Technical Reports Server (NTRS)

Gehrels, Neil

2009-01-01

Gamma-ray bursts (GRBs) are among the most fascinating occurrences in the universe. They are powerful explosions, visible to high redshift, and thought to be the signature of black hole formation. The Swift Observatory has been detecting 100 bursts per year for 4 years and has greatly stimulated the field with new findings. Observations are made of the X-ray and optical afterglow from approximately 1 minute after the burst, continuing for days. Evidence is building that the long and short duration subcategories of GRBs have very different origins: massive star core collapse to a black hole for long bursts and binary neutron star coalescence to a black hole for short bursts. The similarity to Type II and Ia supernovae originating from young and old stellar progenitors is striking. Bursts are providing a new tool to study the high redshift universe. Swift has detected several events at z>5 and one at z=6.7 giving metallicity measurements and other data on galaxies at previously inaccessible distances. The talk will present the latest results from Swift in GRB astronomy.

[Results from the X-ray and Optical Follow-up Observations of the Swift BAT AGN Survey

NASA Technical Reports Server (NTRS)

Mushotzky, R.

2008-01-01

I will present results from the x-ray and optical follow-up observations of the Swift BAT ACN survey. I will discuss the nature of obscuration in these objects, the relationship to optical properties and the change of properties with luminosity and galaxy type and how they will influence the design of XO.

Swift/BAT X-ray monitoring indicates a new outburst of the black hole transient H 1743-322

NASA Astrophysics Data System (ADS)

Zhang, Hui; Yu, Wenfei; Yan, Zhen; Lin, Jie

2017-07-01

H 1743-322 is a black hole X-ray binary with frequent outbursts. Recent Swift/BAT monitoring observations (Krimm et al. 2013) show that this source has turned into a new outburst after been in quiescence for about nine months since the most recent outburst in 2016.

Swift/BAT confirms the giant outburst of H 1417-624

NASA Astrophysics Data System (ADS)

Krimm, H. A.; Barthelmy, S. D.; Cummings, J. R.; Lien, A. Y.; Markwardt, C. B.; Palmer, D. M.; Sakamoto, T.; Stamatikos, M.; Ukwatta, T. N.

2018-04-01

The Swift/BAT transient monitor confirms the current outburst from the Be/X-ray binary pulsar, H 1417-624 ( = 2S 1417-624) (Nakajima et al., ATel #11479). In the BAT 15-50 keV energy band, the outburst began approximately on 20 March 2018 (MJD 57467) and the count rate has been steadily rising since that time.

Swift detection of increased X-ray activity from gamma-ray flaring blazar PKS 1424-41

NASA Astrophysics Data System (ADS)

Ciprini, Stefano; Cutini, Sara

2013-01-01

Following enduring gamma-ray flaring activity of the flat spectrum radio quasar PKS 1424-41 (also known as 2FGL J1428.0-4206, Nolan et al. 2012, ApJS, 199, 31) detected by Fermi LAT during January 2013, two Swift target of opportunity observations were performed on January 24 and 27, 2013. Recent gamma-ray and X-ray flaring activity from the source was observed on January 6 and January 7 (ATel#4714 and ATel #4717).

The Early Life Of A Gamma-ray Burst

NASA Astrophysics Data System (ADS)

O'Brien, P. T.; Willingale, D.

2006-09-01

We present results for 100 gamma-ray bursts observed promptly by the Swift satellite. Combining the early gamma-ray and X-ray data from the BAT and XRT, we show that although individual GRBs can display complex light curves, including a variety of decay phases and flares, their early emission can be described by a relatively simple combination of central engine activity and the interaction of a relativistic jet with the surrounding environment. We also discuss the later fading, which in the optical/IR has traditionally been explained as a jet-break. The Swift data reveal many bursts have a relatively early break in their X-ray light curves contradicting the standard jet break model derived from optical data. We discuss the implications of this for GRB jet models and for using GRBs as standard candles.

Thermal Design to Meet Stringent Temperature Gradient/Stability Requirements of SWIFT BAT Detectors

NASA Technical Reports Server (NTRS)

Choi, Michael K.

2000-01-01

The Burst Alert Telescope (BAT) is an instrument on the National Aeronautics and Space Administration (NASA) SWIFT spacecraft. It is designed to detect gamma ray burst over a broad region of the sky and quickly align the telescopes on the spacecraft to the gamma ray source. The thermal requirements for the BAT detector arrays are very stringent. The maximum allowable temperature gradient of the 256 cadmium zinc telluride (CZT) detectors is PC. Also, the maximum allowable rate of temperature change of the ASICs of the 256 Detector Modules (DMs) is PC on any time scale. The total power dissipation of the DMs and Block Command & Data Handling (BCDH) is 180 W. This paper presents a thermal design that uses constant conductance heat pipes (CCHPs) to minimize the temperature gradient of the DMs, and loop heat pipes (LHPs) to transport the waste heat to the radiator. The LHPs vary the effective thermal conductance from the DMs to the radiator to minimize heater power to meet the heater power budget, and to improve the temperature stability. The DMs are cold biased, and active heater control is used to meet the temperature gradient and stability requirements.

Swift/BAT and MAXI/GSC monitoring indicate a new outburst of black hole transient H 1743-322

NASA Astrophysics Data System (ADS)

Zhang, Hui; Yu, Wenfei; Lin, Jie; Zhang, Wenda; Yan, Zhen

2015-06-01

Swift/BAT and MAXI/GSC monitoring in the X-rays show that the black hole binary transient H 1743-322 has started a new outburst. The Swift/BAT X-ray intensity increased from 0.007+/-0.003 counts/s/cm^2 (0.029+/-0.012 Crab) on MJD 57177 to 0.024+/-0.002 counts/s/cm^2 (0.105+/-0.007 Crab) on MJD 57181 in 15-50 keV.

HOST GALAXY PROPERTIES OF THE SWIFT BAT ULTRA HARD X-RAY SELECTED ACTIVE GALACTIC NUCLEUS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koss, Michael; Mushotzky, Richard; Veilleux, Sylvain

We have assembled the largest sample of ultra hard X-ray selected (14-195 keV) active galactic nucleus (AGN) with host galaxy optical data to date, with 185 nearby (z < 0.05), moderate luminosity AGNs from the Swift BAT sample. The BAT AGN host galaxies have intermediate optical colors (u - r and g - r) that are bluer than a comparison sample of inactive galaxies and optically selected AGNs from the Sloan Digital Sky Survey (SDSS) which are chosen to have the same stellar mass. Based on morphological classifications from the RC3 and the Galaxy Zoo, the bluer colors of BATmore » AGNs are mainly due to a higher fraction of mergers and massive spirals than in the comparison samples. BAT AGNs in massive galaxies (log M{sub *} >10.5) have a 5-10 times higher rate of spiral morphologies than in SDSS AGNs or inactive galaxies. We also see enhanced far-infrared emission in BAT AGN suggestive of higher levels of star formation compared to the comparison samples. BAT AGNs are preferentially found in the most massive host galaxies with high concentration indexes indicative of large bulge-to-disk ratios and large supermassive black holes. The narrow-line (NL) BAT AGNs have similar intrinsic luminosities as the SDSS NL Seyferts based on measurements of [O III] {lambda}5007. There is also a correlation between the stellar mass and X-ray emission. The BAT AGNs in mergers have bluer colors and greater ultra hard X-ray emission compared to the BAT sample as a whole. In agreement with the unified model of AGNs, and the relatively unbiased nature of the BAT sources, the host galaxy colors and morphologies are independent of measures of obscuration such as X-ray column density or Seyfert type. The high fraction of massive spiral galaxies and galaxy mergers in BAT AGNs suggest that host galaxy morphology is related to the activation and fueling of local AGN.« less

The 999th Swift gamma-ray burst: Some like it thermal. A multiwavelength study of GRB 151027A

NASA Astrophysics Data System (ADS)

Nappo, F.; Pescalli, A.; Oganesyan, G.; Ghirlanda, G.; Giroletti, M.; Melandri, A.; Campana, S.; Ghisellini, G.; Salafia, O. S.; D'Avanzo, P.; Bernardini, M. G.; Covino, S.; Carretti, E.; Celotti, A.; D'Elia, V.; Nava, L.; Palazzi, E.; Poppi, S.; Prandoni, I.; Righini, S.; Rossi, A.; Salvaterra, R.; Tagliaferri, G.; Testa, V.; Venturi, T.; Vergani, S. D.

2017-02-01

We present a multiwavelength study of GRB 151027A. This is the 999th gamma-ray burst detected by the Swift satellite and it has a densely sampled emission in the X-ray and optical band and has been observed and detected in the radio up to 140 days after the prompt. The multiwavelength light curve from 500 s to 140 days can be modelled through a standard forward shock afterglow, but it requires an additional emission component to reproduce the early X-ray and optical emission. We present optical observations performed with the Telescopio Nazionale Galileo (TNG) and the Large Binocular Telescope (LBT) 19.6, 33.9, and 92.3 days after the trigger which show a bump with respect to a standard afterglow flux decay and are interpreted as possibly due to the underlying supernova and host galaxy (at a level of 0.4 μJy in the optical R band, RAB 25). Radio observations, performed with the Sardinia Radio Telescope (SRT) and Medicina in single-dish mode and with the European Very Long Baseline Interferometer (VLBI) Network and the Very Long Baseline Array (VLBA), between day 4 and 140 suggest that the burst exploded in an environment characterized by a density profile scaling with the distance from the source (wind profile). A remarkable feature of the prompt emission is the presence of a bright flare 100 s after the trigger, lasting 70 s in the soft X-ray band, which was simultaneously detected from the optical band up to the MeV energy range. By combining Swift-BAT/XRT and Fermi-GBM data, the broadband (0.3-1000 keV) time resolved spectral analysis of the flare reveals the coexistence of a non-thermal (power law) and thermal blackbody components. The blackbody component contributes up to 35% of the luminosity in the 0.3-1000 keV band. The γ-ray emission observed in Swift-BAT and Fermi-GBM anticipates and lasts less than the soft X-ray emission as observed by Swift-XRT, arguing against a Comptonization origin. The blackbody component could either be produced by an outflow

Swift Observations Of High-z Radio-loud Quasars Detected With Bat

NASA Technical Reports Server (NTRS)

Sambruna, Rita M.; Tueller, J.; Markwardt, C.; Mushotzky, R.; Tavecchio, F.

2006-01-01

We present follow-up Swift observations of 4 high-z radio-loud quasars detected with the BAT during the 15-month survey in 15-150 keV. The 0.5-8-keV spectra are best fitted either with a power law with no excess absorption over the Galactic value (0212+735, 0836+710, 2149--307 in higher state) or by a downward-curved broken power law model (0537--286, 2149--307 in lower state). The BAT spectra integrated over the whole 15 months of the survey are fitted with a single power law, with a range of spectral slopes, Gamma=l.3-2.3. Comparison with previous SAX observations shows that there is a trend for the 15-150-keV continuum to soften with fading intensity; on the contrary, little or no spectral variations are observed at medium-hard X-rays. This may suggest either/both dramatic variability above 10-keV, or/and two separate spectral components.

Swift/BAT Detects Increase in Hard X-ray Emission from the Ultra-compact X-ray Binary 4U 1543-624

NASA Astrophysics Data System (ADS)

Ludlam, Renee; Miller, Jon M.; Miller-Jones, James; Reynolds, Mark

2017-08-01

The Swift/BAT detected an increase in hard X-ray emission (15-50 keV) coming from the ultra-compact X-ray binary 4U 1543-624 around 2017 August 9. The MAXI daily monitoring also shows a gradual increase in 2.0-20.0 keV X-ray intensity as of 2017 August 19. Swift/XRT ToO monitoring of the source was triggered and shows an increase in unabsorbed flux to 1.06E-9 ergs/cm2/s in the 0.3-10.0 keV energy band as of 2017 August 26. ATCA performed ToO observations for approximately 4 hours in the 5.5 GHz and 9.0 GHz bands while the antennas were in the 1.5A array configuration from 11:25-16:09 UTC on 2017 August 23. The source was not detected in either band.

Host Galaxy Properties Of The Swift Bat Hard X-ray Survey Of Agn

NASA Astrophysics Data System (ADS)

Koss, Michael; Mushotzky, R.; Veilleux, S.; Winter, L.

2010-03-01

Surveys of AGN taken in the optical, UV, and soft X-rays miss an important population of obscured AGN only visible in the hard X-rays and mid-IR wavelengths. The SWIFT BAT survey in the hard X-ray range (14-195 keV) has provided a uniquely unbiased sample of AGN unaffected by galactic or circumnuclear absorption. Optical imaging of this unbiased sample provides a new opportunity to understand how the environments of the host galaxies are linked to AGN. In 2008, we observed 90 of these targets at Kitt Peak with the 2.1m in the SDSS ugriz bands over 17 nights. Using these observations and SDSS data we review the relationships between color, morphology, merger activity, stellar mass, star formation, and AGN luminosity for a sample of 145 AGN Hard X-ray Selected AGN.

Testing the E(sub peak)-E(sub iso) Relation for GRBs Detected by Swift and Suzaku-WAM

NASA Technical Reports Server (NTRS)

Krimm, H. A.; Yamaoka, K.; Sugita, S.; Ohno, M.; Sakamoto, T.; Barthelmy, S. D.; Gehrels, N.; Hara, R.; Onda, K.; Sato, G.;

Gamma Ray Bursts in the Swift-Fermi Era

NASA Technical Reports Server (NTRS)

Gehrels, Neil; Razzaque, Soebur

2013-01-01

Gamma-ray bursts (GRBs) are among the most violent occurrences in the universe. They are powerful explosions, visible to high redshift, and thought to be the signature of black hole birth. They are highly luminous events and provide excellent probes of the distant universe. GRB research has greatly advanced over the past 10 years with the results from Swift, Fermi and an active follow-up community. In this review we survey the interplay between these recent observations and the theoretical models of the prompt GRB emission and the subsequent afterglows.

The Swift BAT Hard X-ray Survey - A New Window on the Local AGN Universe

NASA Technical Reports Server (NTRS)

Mushotzky, Richard

2009-01-01

The Swift Burst and Transient telescope (BAT) has surveyed the entire sky for the last 3.5 years obtaining the first sensitive all sky survey of the 14-195 keV sky. At high galactic latitudes the vast majority of the detected sources are AGN. Since hard x-rays penetrate all but Compton thick obscuring material (Column densities of 1.6E24 atms/cm2) this survey is unbiased with respect to obscuration, host galaxy type, optical , radio or IR properties. We will present results on the broad band x-ray properties, the nature of the host galaxies, the luminosity function and will discuss a few of the optical, IR and x-ray results in detail.

OPTICAL STUDIES OF 13 HARD X-RAY SELECTED CATACLYSMIC BINARIES FROM THE SWIFT-BAT SURVEY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Halpern, Jules P.; Thorstensen, John R.

2015-12-15

From a set of 13 cataclysmic binaries that were discovered in the Swift Burst Alert Telescope (BAT) survey, we conducted time-resolved optical spectroscopy and/or time-series photometry of 11, with the goal of measuring their orbital periods and searching for spin periods. Seven of the objects in this study are new optical identifications. Orbital periods are found for seven targets, ranging from 81 minutes to 20.4 hr. PBC J0706.7+0327 is an AM Herculis star (polar) based on its emission-line variations and large amplitude photometric modulation on the same period. Swift J2341.0+7645 may be a polar, although the evidence here is lessmore » secure. Coherent pulsations are detected from two objects, Swift J0503.7−2819 (975 s) and Swift J0614.0+1709 (1412 s and 1530 s, spin and beat periods, respectively), indicating that they are probable intermediate polars (DQ Herculis stars). For two other stars, longer spin periods are tentatively suggested. We also present the discovery of a 2.00 hr X-ray modulation from RX J2015.6+3711, possibly a contributor to Swift J2015.9+3715, and likely a polar.« less

The Swift Burst and Transient Telescope (BAT)

NASA Technical Reports Server (NTRS)

Mushotzky, Richard

2008-01-01

The Swift Burst and Transient telescope (BAT) has surveyed the entire sky for the last 3.5 years obtaining the first sensitive all sky survey of the 14-195 kev sky. At high galactic latitudes the vast majority of the detected sources are AGN. Since hard x-rays penetrate all but Compton thick obscuring material (Column densities of 1.6324 atms/sq cm) this survey is unbiased with respect to obscuration, host galaxy type, optical , radio or IR properties. We will present results on the broad band x-ray properties, the nature of the host galaxies, the luminosity function and will discuss a few of the optical, IR and x-ray results in detail.

Properties of Supergiant Fast X-Ray Transients as Observed by Swift

NASA Technical Reports Server (NTRS)

Romano, P.; Vercellone, S.; Krimm, H. A.; Esposito, P.; Cusumano, C.; LaParola, V.; Mangano, V.; Kennea, J. A.; Burrows, D. N.; Pagani, C.;

The unique observing capabilities of the Swift x-ray telescope

NASA Astrophysics Data System (ADS)

Hill, J. E.; Angelini, L.; Morris, D. C.; Burrows, D. N.; Abbey, A. F.; Campana, S.; Capalbi, M.; Cusumano, G.; Kennea, J. A.; Klar, R.; Mangels, C.; Moretti, A.; Osborne, J. P.; Perri, M.; Racusin, J.; Tagliaferri, G.; Tamburelli, F.; Wood, P.; Nousek, J. A.; Wells, A.

2005-08-01

The XRT is a sensitive, autonomous X-ray imaging spectrometer onboard the Swift Gamma-Ray Burst Observatory. The unique observing capabilities of the XRT allow it to autonomously refine the Swift BAT positions (~1-4' uncertainty) to better than 2.5 arcsec in XRT detector coordinates, within 5 seconds of target acquisition by the Swift Observatory for typical bursts, and to measure the flux, spectrum, and light curve of GRBs and afterglows over a wide dynamic range covering more than seven orders of magnitude in flux (62 Crab to < 1 mCrab). The results of the rapid positioning capability of the XRT are presented here for both known sources and newly discovered GRBs, demonstrating the ability to automatically utilise one of two integration times according to the burst brightness, and to correct the position for alignment offsets caused by the fast pointing performance and variable thermal environment of the satellite as measured by the Telescope Alignment Monitor. The onboard results are compared to the positions obtained by groundbased follow-up. After obtaining the position, the XRT switches between four CCD readout modes, automatically optimising the scientific return from the source depending on the flux of the GRB. Typical data products are presented here.

The unique observing capabilities of the Swift x-ray telescope

NASA Astrophysics Data System (ADS)

Hill, J. E.; Angelini, L.; Morris, D. C.; Burrows, D. N.; Abbey, A. F.; Campana, S.; Cusumano, G.; Kennea, J. A.; Klar, R.; Mangels, C.; Moretti, A.; Perri, M.; Racusin, J.; Tagliaferri, G.; Tamburelli, F.; Wood, P.; Nousek, J. A.; Wells, A.

2005-01-01

The XRT is a sensitive, autonomous X-ray imaging spectrometer onboard the Swift Gamma-Ray Burst Observatory. The unique observing capabilities of the XRT allow it to autonomously refine the Swift BAT positions (~1-4' uncertainty) to better than 2.5 arcsec in XRT detector coordinates, within 5 seconds of target acquisition by the Swift Observatory for typical bursts, and to measure the flux, spectrum, and light curve of GRBs and afterglows over a wide dynamic range covering more than seven orders of magnitude in flux (62 Crab to < 1 mCrab). The results of the rapid positioning capability of the XRT are presented here for both known sources and newly discovered GRBs, demonstrating the ability to automatically utilise one of two integration times according to the burst brightness, and to correct the position for alignment offsets caused by the fast pointing performance and variable thermal environment of the satellite as measured by the Telescope Alignment Monitor. The onboard results are compared to the positions obtained by groundbased follow-up. After obtaining the position, the XRT switches between four CCD readout modes, automatically optimising the scientific return from the source depending on the flux of the GRB. Typical data products are presented here.

Correlations of Prompt and Afterglow Emission in Swift Long and Short Gamma Ray Bursts

NASA Technical Reports Server (NTRS)

Gehrel, Neil; Barthelmy, S. d.; Burrows, D. N.; Cannizzo, J. K.; Chincarini, G.; Feinmore, E.; Kouveliotou, C.; O'Brien, P.; Palmer, D. M.; Racusin, J.;

Swift Observatory Space Simulation Testing

NASA Technical Reports Server (NTRS)

Espiritu, Mellina; Choi, Michael K.; Scocik, Christopher S.

2004-01-01

The Swift Observatory is a Middle-Class Explorer (MIDEX) mission that is a rapidly re-pointing spacecraft with immediate data distribution capability to the astronomical community. Its primary objectives are to characterize and determine the origin of Gamma Ray Bursts (GRBs) and to use the collected data on GRB phenomena in order to probe the universe and gain insight into the physics of black hole formation and early universe. The main components of the spacecraft are the Burst Alert Telescope (BAT), Ultraviolet and Optical Telescope (UVOT), X-Ray Telescope (XRT), and Optical Bench (OB) instruments coupled with the Swift spacecraft (S/C) bus. The Swift Observatory will be tested at the Space Environment Simulation (SES) chamber at the Goddard Space Flight Center from May to June 2004 in order to characterize its thermal behavior in a vacuum environment. In order to simulate the independent thermal zones required by the BAT, XRT, UVOT, and OB instruments, the spacecraft is mounted on a chariot structure capable of maintaining adiabatic interfaces and enclosed in a modified, four section MSX fixture in order to accommodate the strategic placement of seven cryopanels (on four circuits), four heater panels, and a radiation source burst simulator mechanism. There are additionally 55 heater circuits on the spacecraft. To mitigate possible migration of silicone contaminants from BAT to the XRT and UVOT instruments, a contamination enclosure is to be fabricated around the BAT at the uppermost section of the MSX fixture. This paper discuses the test requirements and implemented thermal vacuum test configuration for the Swift Observatory.

Host Galaxy Morphologies Of Hard X-ray Selected AGN From The Swift BAT Survey

NASA Astrophysics Data System (ADS)

Koss, Michael; Mushotzky, R.; Veilleux, S.

2009-01-01

Surveys of AGN taken in the optical, UV, and soft X-rays miss an important population of obscured AGN only visible in the hard X-rays and mid-IR wavelengths. The SWIFT BAT survey in the hard X-ray range (14-195 keV) has provided a uniquely unbiased sample of 258 AGN unaffected by galactic or circumnuclear absorption. Optical imaging of this unbiased sample provides a new opportunity to understand how the environments of the host galaxies are linked to AGN. For these host galaxies, only a fraction, 29%, have high quality optical images, predominately from the SDSS. In addition, about 33% show peculiar morphologies and interaction. In 2008, we observed 110 of these targets at Kitt Peak with the 2.1m in the SDSS bands over 17 nights. Using these observations and SDSS data we review the relationships between color, morphology, merger activity, star formation, and AGN luminosity.

The All-Sky Swift - INTEGRAL X-Ray Survey

NASA Astrophysics Data System (ADS)

Michelson, Peter

All-sky surveys at hard X-ray energies (above 15 keV) have proven to be a powerful technique in detecting Galactic and extragalactic source populations. Most of the radiation at hard X-ray energies originates in non-thermal processes. These processes take place in extreme conditions of gravitational fields, of electromagnetic field, and also in explosive events. Such extreme conditions can be found in the Milk Way in the vicinity of neutron stars, black holes, and supernovae. Also extragalactic sources are known to be hard X-ray emitters like Active Galactic Nuclei (AGNs), blazars, and Clusters of Galaxies. Currently the most sensitive flying hard X-ray detectors are the Burst Alert Telescope (BAT) on board the NASA mission Swift and the INTEGRAL Soft-Gamma Ray Imager (IBIS/ISGRI) on board the ESA mission INTEGRAL. BAT and IBIS/ISGRI are coded- mask telescopes that shed continuously light on the Galactic and the extragalactic source populations. However, coded-mask telescopes suffer from heavy systematic effects (errors) preventing them from reaching their theoretical limiting sensitivity. Furthermore, by design, they block ~50% of the incident photons causing and increase of statistical noise. As a consequence BAT and IBIS/ISGRI are not sensitive enough to detect faint objects. In addition it has been proven that the Galactic survey of these instruments is limited by systematic uncertainties. Therefore, further observations on the Galactic plane will not improve the sensitivity of the survey of BAT and IBIS/ISGRI. In this project we show that it is possible to overcome the limits of BAT and of IBIS/ISGRI by combining their observations in the 18 55 keV energy range. We call it the SIX survey that stands for Swift - INTEGRAL X-ray survey. Two major advantages are obtained by merging the observations of BAT and IBIS/ISGRI: 1) the exposure is greatly enhanced (sum of BAT and IBIS/ISGRI) and therefore the sensitivity is improved; 2) the systematic errors of both

Swift J1112.2-8238: a candidate relativistic tidal disruption flare

NASA Astrophysics Data System (ADS)

Brown, G. C.; Levan, A. J.; Stanway, E. R.; Tanvir, N. R.; Cenko, S. B.; Berger, E.; Chornock, R.; Cucchiaria, A.

2015-10-01

We present observations of Swift J1112.2-8238, and identify it as a candidate relativistic tidal disruption flare. The outburst was first detected by Swift/Burst Alert Telescope (BAT) in 2011 June as an unknown, long-lived (order of days) gamma-ray transient source. We show that its position is consistent with the nucleus of a faint galaxy for which we establish a likely redshift of z = 0.89 based on a single emission line that we interpret as the blended [O II] λ3727 doublet. At this redshift, the peak X-ray/gamma-ray luminosity exceeded 1047 erg s-1, while a spatially coincident optical transient source had i' ˜ 22 (Mg ˜ -21.4 at z = 0.89) during early observations, ˜20 d after the Swift trigger. These properties place Swift J1112.2-8238 in a very similar region of parameter space to the two previously identified members of this class, Swift J1644+57 and Swift J2058+0516. As with those events the high-energy emission shows evidence for variability over the first few days, while late-time observations, almost 3 yr post-outburst, demonstrate that it has now switched off. Swift J1112.2-8238 brings the total number of such events observed by Swift to three, interestingly all detected by Swift over a ˜3 month period (<3 per cent of its total lifetime as of 2015 March). While this suggests the possibility that further examples may be uncovered by detailed searches of the BAT archives, the lack of any prime candidates in the years since 2011 means these events are undoubtedly rare.

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.;

Swift and Fermi observations of the early afterglow of the short gamma-ray burst 090510

DOE PAGES

De Pasquale, M.

2010-01-14

Here, we present the observations of GRB090510 performed by the Fermi Gamma-Ray Space Telescope and the Swift observatory. In a GeV range, we detected a bright, short burst that shows an extended emission. Furthermore, its optical emission initially rises, a feature so far observed only in long bursts, while the X-ray flux shows an initial shallow decrease, followed by a steeper decay. This exceptional behavior enables us to investigate the physical properties of the gamma-ray burst outflow, poorly known in short bursts. Here, we discuss internal and external shock models for the broadband energy emission of this object.

The Successful Synergy of Swift and Fermi/GBM in Magnetars

NASA Technical Reports Server (NTRS)

Kouveliotou, Chryssa

2011-01-01

The magnetar rate of discovery has increased dramatically in the last decade. Five sources were discovered in the last three years alone as a result of the very efficient synergy among three X- and .gamma-ray instruments on NASA satellites: the Swift/Burst Alert Telescope (BAT), the Fermi/Gamma ray Burst Monitor (GBM), and the Rossi X-Ray Timing Explorer; RXTE/Proportional Counter Array (PCA). To date, there are approx. 25 magnetar candidates, of which two are (one each) in the Large and Small Magellanic Cloud and the rest reside on the Galactic plane of our Milky Way. I will discuss here the main properties of the Magnetar Population and the common projects that can be achieved with the synergy of Swift and GBM.

The hard X-ray spectrum of MAXI J1820+070 observed by Swift/BAT

NASA Astrophysics Data System (ADS)

Del Santo, Melania; Segreto, Alberto

2018-03-01

We have analysed the Swift/BAT data of the new transient MAXI J1820+070 (Atel #11399,#11400, #11403, #11404, #11406, #11418, #11420, #11421, #11423,#11424, #11425, #11425) collected from 2018-03-07 00:41:07 until 2018-03-15 06:20:58.

Swift/BAT and RXTE Observations of the Peculiar X-ray Binary 4U 2206+54 - Disappearance of the 9.6 Day Modulation

NASA Technical Reports Server (NTRS)

Corbet, R. H. D.; Markwardt, C.; Tueller, J.

2007-01-01

Observations of the high-mass X-ray binary 4U 2206+54 with the Swift Burst Alert Telescope (BAT) do not show modulation at the previously reported period of 9.6 days found from observations made with the Rossi X-ray Timing Explorer (RXTE) All-Sky Monitor (ASM). Instead, the strongest peak in the power spectrum of the BAT light curve occurs at a period of 19.25+/-0.08 days, twice the period found with the RXTE ASM. The maximum of the folded BAT light curve is also delayed compared to the maximum of the folded ASM light curve. The most recent ASM data folded on twice the 9.6 day period show 'similar morphology to the folded BAT light curve. This suggests that the apparent period doubling is a recent secular change rather than an energy-dependent effect. The 9.6 day period is thus not a permanent strong feature of the light curve. We suggest that the orbital period of 4U 2206+54 may be twice the previously proposed value.

The nature of 50 Palermo Swift-BAT hard X-ray objects through optical spectroscopy

NASA Astrophysics Data System (ADS)

Rojas, A. F.; Masetti, N.; Minniti, D.; Jiménez-Bailón, E.; Chavushyan, V.; Hau, G.; McBride, V. A.; Bassani, L.; Bazzano, A.; Bird, A. J.; Galaz, G.; Gavignaud, I.; Landi, R.; Malizia, A.; Morelli, L.; Palazzi, E.; Patiño-Álvarez, V.; Stephen, J. B.; Ubertini, P.

2017-06-01

We present the nature of 50 hard X-ray emitting objects unveiled through an optical spectroscopy campaign performed at seven telescopes in the northern and southern hemispheres. These objects were detected with the Burst Alert Telescope (BAT) instrument onboard the Swift satellite and listed as of unidentified nature in the 54-month Palermo BAT catalogue. In detail, 45 sources in our sample are identified as active galactic nuclei of which, 27 are classified as type 1 (with broad and narrow emission lines) and 18 are classified as type 2 (with only narrow emission lines). Among the broad-line emission objects, one is a type 1 high-redshift quasi-stellar object, and among the narrow-line emission objects, one is a starburst galaxy, one is a X-ray bright optically normal galaxy, and one is a low ionization nuclear emission line region. We report 30 new redshift measurements, 13 confirmations and 2 more accurate redshift values. The remaining five objects are galactic sources: three are Cataclismic Variables, one is a X-ray Binary probably with a low mass secondary star, and one is an active star. Based on observations obtained from the following observatories: Cerro Tololo Interamerican Observatory (Chile); Astronomical Observatory of Bologna in Loiano (Italy); Observatorio Astronómico Nacional (San Pedro Mártir, Mexico); Radcliffe telescope of the South African Astronomical Observatory (Sutherland, South Africa); Sloan Digital Sky Survey; Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias (Canary Islands, Spain) and New Technology Telescope (NTT) of La Silla Observatory, Chile.

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.;

X-ray Afterglows of Short Gamma-Ray Bursts

NASA Astrophysics Data System (ADS)

Burrows, David N.

2006-12-01

The Swift Burst Alert Telescope (BAT) has discovered about 20 short GRBs in its first two years of operation. The Swift X-ray Telescope (XRT) has detected X-ray afterglows for roughly 75% of these, allowing host galaxies, redshifts and source characteristics to be studied for the first time. As a result, our knowledge of the properties of short GRBs and their afterglows has increased tremendously in the past year and a half. I will discuss the X-ray afterglows of short GRBs as observed by the Swift XRT and by Chandra. These afterglows are generally much fainter than those of long GRBs, and therefore fade rapidly below detection thresholds. However, some brighter, long-lived afterglows provide intriguing insights into the properties of the progenitors and their environments.

VizieR Online Data Catalog: Gamma Ray Bursts detected by Swift (2004-2015) (Buchner+, 2017)

NASA Astrophysics Data System (ADS)

Buchner, J.; Schulze, S.; Bauer, F.

2016-04-01

Gamma Ray Bursts (GRB) typically show intrinsic LOS column densities of 1021-23cm2. We performed a thorough statistical analysis of all available X-ray spectra of Swift-detected GRBs. In the associated paper we use sub-samples to analyse the population properties of LGRB and concluded that the obscuration is due to large-scale gas inside the GRB host galaxy, due to the shape of the column density distribution and its correlation with host stellar mass. This catalogue presents X-ray spectral analysis of all Swift-detected GRBs. It includes information about the GRB (ID, Swift Trigger ID, duration, RA/Dec in J2000, galactic coordinates, Milky Way column density). Those properties are taken from the http://www.swift.ac.uk/ and http://gcn.gsfc.nasa.gov/ websites. We removed prompt emission and flares, leaving only a certain time interval for spectral extraction. We use two models to analyse X-ray spectra: TBABS and SPHERE. Both include updated abundances and cross-sections as compared to previous works. The latter includes the effects of Compton-scattering and FeKa fluorescence relevant at high column densities. Columns list the posterior mean, standard deviation, 10% and 90% quantiles. Note that the column densities are converted to hydrogen assuming local ISM abundances, but are derived primarily from photo-electric absorption of e.g. Fe and O, and therefore primarily measure metal gas. (2 data files).

A Temporal Correlation in Quiescent Gamma-Ray Burst Prompt Emission: Evidence for Prognitor Memory

NASA Astrophysics Data System (ADS)

Patton, Thomas L.; Giblin, Timothy; Hakkila, Jon E.

2018-06-01

In spite of the insight gained into the nature of the Gamma-Ray Bursts (GRB) from early and late-time X-Ray observations in the Swift era, GRB prompt emission continues to provide clues and new insight into the activity of the central engine. A comprehensive understanding of all emission components observed in GRBs, from the traditional prompt GRB emission to the long lived X-Ray and optical decay super- imposed with late-time flaring activity, currently remains allusive. Using data from the Swift Burst Alert Telescope (BAT), we've identified and measured durations observed in GRBs that exhibit multi-episodic prompt emission behavior. Duration analysis of the burst attributes revealed no significant correlations between emissions and quiet time durations. This variability allows us to extrapolate that the central engine is constantly active.

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;

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;

X-ray View of Four High-Luminosity Swift-BAT AGN: Unveiling Obscuration and Reflection with Suzaku

NASA Technical Reports Server (NTRS)

Fiorettil, V.; Angelini, L.; Mushotzky, R. F.; Koss, M.; Malaguti, G.

2013-01-01

Aims. A complete census of obscured Active Galactic Nuclei (AGN) is necessary to reveal the history of the super massive black hole (SMBH) growth and galaxy evolution in the Universe given the complex feedback processes and the fact that much of this growth occurs in an obscured phase. In this context, hard X-ray surveys and dedicated follow-up observations represent a unique tool for selecting highly absorbed AGN and for characterizing the obscuring matter surrounding the SMBH. Here we focus on the absorption and reflection occurring in highly luminous, quasar-like AGN, to study the relation between the geometry of the absorbing matter and the AGN nature (e.g. X-ray, optical, and radio properties), and to help to determine the column density dependency on the AGN luminosity. Methods. The Swift/BAT nine-month survey observed 153 AGN, all with ultra-hard X-ray BAT fluxes in excess of 10(exp -11) erg per square centimeter and an average redshift of 0.03. Among them, four of the most luminous BAT AGN (44.73 less than LogLBAT less than 45.31) were selected as targets of Suzaku follow-up observations: J2246.0+3941 (3C 452), J0407.4+0339 (3C 105), J0318.7+6828, and J0918.5+0425. The column density, scattered/reflected emission, the properties of the Fe K line, and a possible variability are fully analyzed. For the latter, the spectral properties from Chandra, XMM-Newton and Swift/XRT public observations were compared with the present Suzaku analysis, adding an original spectral analysis when non was available from the literature. Results. Of our sample, 3C 452 is the only certain Compton-thick AGN candidate because of i) the high absorption (N(sub H) approximately 4 × 10(exp 23) per square centimeter) and strong Compton reflection; ii) the lack of variability; iii) the "buried" nature, i.e. the low scattering fraction (less than 0.5%) and the extremely low relative [OIII] luminosity. In contrast 3C 105 is not reflection-dominated, despite the comparable column density

The Swift Burst Alert Telescope Detected Seyfert 1 Galaxies: X-Ray Broadband Properties and Warm Absorbers

NASA Technical Reports Server (NTRS)

Winter, Lisa M.; Veilleux, Sylvain; McKernan, Barry; Kallman, T.

2012-01-01

We present results from an analysis of the broadband, 0.3-195 keV, X-ray spectra of 48 Seyfert 1-1.5 sources detected in the very hard X-rays with the Swift Burst Alert Telescope (BAT). This sample is selected in an all-sky survey conducted in the 14-195 keV band. Therefore, our sources are largely unbiased toward both obscuration and host galaxy properties. Our detailed and uniform model fits to Suzaku/BAT and XMM-Newton/BAT spectra include the neutral absorption, direct power-law, reflected emission, soft excess, warm absorption, and narrow Fe I K[alpha] emission properties for the entire sample. We significantly detect O VII and O VIII edges in 52% of our sample. The strength of these detections is strongly correlated with the neutral column density measured in the spectrum. Among the strongest detections, X-ray grating and UV observations, where available, indicate outflowing material. The ionized column densities of sources with O VII and O VIII detections are clustered in a narrow range with Nwarm [approx] 1021 cm-2, while sources without strong detections have column densities of ionized gas an order of magnitude lower. Therefore, we note that sources without strong detections likely have warm ionized outflows present but at low column densities that are not easily probed with current X-ray observations. Sources with strong complex absorption have a strong soft excess, which may or may not be due to difficulties in modeling the complex spectra of these sources. Still, the detection of a flat [Gamma] [approx] 1 and a strong soft excess may allow us to infer the presence of strong absorption in low signal-to-noise active galactic nucleus spectra. Additionally, we include a useful correction from the Swift BAT luminosity to bolometric luminosity, based on a comparison of our spectral fitting results with published spectral energy distribution fits from 33 of our sources.

The Prompt-afterglow Connection in Gamma-ray Bursts: a Comprehensive Statistical Analysis of Swift X-ray Light-curves

NASA Technical Reports Server (NTRS)

Margutti, R.; Zaninoni, E.; Bernardini, M. G.; Chincarini, G.; Pasotti, F.; Guidorzi, C.; Angelini, Lorella; Burrows, D. N.; Capalbi, M.; Evans, P. A.;

The prompt-afterglow connection in gamma-ray bursts: a comprehensive statistical analysis of Swift X-ray light curves

NASA Astrophysics Data System (ADS)

Margutti, R.; Zaninoni, E.; Bernardini, M. G.; Chincarini, G.; Pasotti, F.; Guidorzi, C.; Angelini, L.; Burrows, D. N.; Capalbi, M.; Evans, P. A.; Gehrels, N.; Kennea, J.; Mangano, V.; Moretti, A.; Nousek, J.; Osborne, J. P.; Page, K. L.; Perri, M.; Racusin, J.; Romano, P.; Sbarufatti, B.; Stafford, S.; Stamatikos, M.

2013-01-01

We present a comprehensive statistical analysis of Swift X-ray light curves of gamma-ray bursts (GRBs) collecting data from more than 650 GRBs discovered by Swift and other facilities. The unprecedented sample size allows us to constrain the rest-frame X-ray properties of GRBs from a statistical perspective, with particular reference to intrinsic time-scales and the energetics of the different light-curve phases in a common rest-frame 0.3-30 keV energy band. Temporal variability episodes are also studied and their properties constrained. Two fundamental questions drive this effort: (i) Does the X-ray emission retain any kind of `memory' of the prompt γ-ray phase? (ii) Where is the dividing line between long and short GRB X-ray properties? We show that short GRBs decay faster, are less luminous and less energetic than long GRBs in the X-rays, but are interestingly characterized by similar intrinsic absorption. We furthermore reveal the existence of a number of statistically significant relations that link the X-ray to prompt γ-ray parameters in long GRBs; short GRBs are outliers of the majority of these two-parameter relations. However and more importantly, we report on the existence of a universal three-parameter scaling that links the X-ray and the γ-ray energy to the prompt spectral peak energy of both long and short GRBs: EX, iso∝E1.00 ± 0.06γ, iso/E0.60 ± 0.10pk.

Swift Gamma Ray Observatory Observations Of The Comet 73P/Schwassmann-Wachmann 3

NASA Astrophysics Data System (ADS)

Brown, Gregory V.; Beiersdorfer, P.; Bodewits, D.; Porter, F.; Willingale, R.

2007-05-01

The XRT on the Swift Gamma Ray Observatory has been used to observe fragment C of the comet 73P/Schwassmann-Wachmann 3 on 19 different days over the course of May and June of 2006. During these observations, comet 73P/SW3C was near perihelion and passed within 0.1 AU of the Earth. The XRT spectra show distinct line emission from helium-like and hydrogenic oxygen. This line emission is caused by charge exchange recombination between solar wind ions and cometary neutrals. Our observations also include monitoring of the comet with Swift's UV/Optical Telescope. An overview of our observation, the XRT spectra, and the current status of our data analysis will be presented. Work at LLNL was completed under the auspices of the U.S. D.o.E by the University of California Lawrence Livermore National Laboratory under contract W-7405-Eng-48.

Future Hard X-ray and Gamma-Ray Missions

NASA Astrophysics Data System (ADS)

Krawczynski, Henric; Physics of the Cosmos (PCOS) Gamma Ray Science Interest Group (GammaSIG) Team

2017-01-01

With four major NASA and ESA hard X-ray and gamma-ray missions in orbit (Swift, NuSTAR, INTEGRAL, and Fermi) hard X-ray and gamma-ray astronomy is making major contributions to our understanding of the cosmos. In this talk, I will summarize the current and upcoming activities of the Physics of the Cosmos Gamma Ray Science Interest Group and highlight a few of the future hard X-ray and gamma-ray mission discussed by the community. HK thanks NASA for the support through the awards NNX14AD19G and NNX16AC42G and for PCOS travel support.

Searching for New γ-Ray Blazar Candidates in the Third Palermo BAT Hard X-Ray Catalog with WISE

NASA Astrophysics Data System (ADS)

Maselli, A.; Massaro, F.; Cusumano, G.; D'Abrusco, R.; La Parola, V.; Paggi, A.; Segreto, A.; Smith, Howard A.; Tosti, G.

2013-06-01

We searched for γ-ray blazar candidates among the 382 unidentified hard X-ray sources of the third Palermo BAT Catalog (3PBC) obtained from the analysis of 66 months of Swift Burst Alert Telescope (BAT) survey data and listing 1586 sources. We adopted a recently developed association method based on the peculiar infrared colors that characterize the γ-ray blazars included in the second catalog of active galactic nuclei detected by the Fermi Large Area Telescope. We used this method exploiting the data of the all-sky survey performed by the Wide-field Infrared Survey Explorer (WISE) to establish correspondences between unidentified 3PBC sources and WISE γ-ray blazar candidates located within the BAT positional uncertainty region at a 99% confidence level. We obtained a preliminary list of candidates for which we analyzed all the available data in the Swift archive to complement the information in the literature and in the radio, infrared, and optical catalogs with the information on their optical-UV and soft X-ray emission. Requiring the presence of radio and soft X-ray counterparts consistent with the infrared positions of the selected WISE sources, as well as a blazar-like radio morphology, we finally obtained a list of 24 γ-ray blazar candidates.

THE SWIFT BAT SURVEY DETECTS TWO OPTICAL BROAD LINE, X-RAY HEAVILY OBSCURED ACTIVE GALAXIES: NVSS 193013+341047 AND IRAS 05218-1212

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hogg, J. Drew; Winter, Lisa M.; Mushotzky, Richard F.

2012-06-20

The Swift Burst Alert Telescope (BAT) is discovering interesting new objects while monitoring the sky in the 14-195 keV band. Here we present the X-ray properties and spectral energy distributions (SEDs) for two unusual active galactic nucleus sources. Both NVSS 193013+341047 and IRAS 05218-1212 are absorbed, Compton-thin, but heavily obscured (N{sub H} {approx} 10{sup 23} cm{sup -2}), X-ray sources at redshifts <0.1. The SEDs reveal these galaxies to be very red, with high extinction in the optical and UV. A similar SED is seen for the extremely red objects (EROs) detected in the higher redshift universe. This suggests that thesemore » unusual BAT-detected sources are a low-redshift (z << 1) analog to EROs, which recent evidence suggests are a class of the elusive type II quasars. Studying the multi-wavelength properties of these sources may reveal the properties of their high-redshift counterparts.« less

Gamma-Ray Bursts in the Swift Era

NASA Technical Reports Server (NTRS)

Gehrels, Neil; Cannizzo, John K.; Norris, Jay P.

2007-01-01

GRB research has undergone a revolution in the last two years. The launch of Swift, with its rapid slewing capability, has greatly increased the number and quality of GRB localizations and X-ray and optical afterglow lightcurves. Over 160 GRBs have been detected, and nearly all that have been followed up with the on-board narrow field telescopes. Advances in our understanding of short GRBs have been spectacular. The detection of X-ray afterglows has led to accurate localizations from ground based observatories, which have given host identifications and redshifts. Theoretical models for short GRB progenitors have, for the first time, been placed on a sound foundation. The hosts for the short GRBs differ in a fundamental way from the long GRB hosts: short GRBs tend to occur in non-star forming galaxies or regions, whereas long GRBs are strongly concentrated within star forming regions. Observations are consistent with a binary neutron star merger model, but other models involving old stellar populations are also viable. Swift has greatly increased the redshift range of GRB detection. The highest redshift GRBs, at zeta approx. 5-6, are approaching the era of reionization. Ground-based deep optical spectroscopy of high redshift bursts is giving metallicity measurements and other information on the source environment to much greater distance than other techniques. The localization of GRB 060218 to a nearby galaxy, and association with SN 2006aj, added a valuable member to the class of GRBs with detected supernova. The prospects for future progress are excellent given the >10 year orbital lifetime of the Swift satellite.

"Short, Hard Gamma-Ray Bursts - Mystery Solved?????"

NASA Technical Reports Server (NTRS)

Parsons, A.

2006-01-01

After over a decade of speculation about the nature of short-duration hard-spectrum gamma-ray bursts (GRBs), the recent detection of afterglow emission from a small number of short bursts has provided the first physical constraints on possible progenitor models. While the discovery of afterglow emission from long GRBs was a real breakthrough linking their origin to star forming galaxies, and hence the death of massive stars, the progenitors, energetics, and environments for short gamma-ray burst events remain elusive despite a few recent localizations. Thus far, the nature of the host galaxies measured indicates that short GRBs arise from an old (> 1 Gyr) stellar population, strengthening earlier suggestions and providing support for coalescing compact object binaries as the progenitors. On the other hand, some of the short burst afterglow observations cannot be easily explained in the coalescence scenario. These observations raise the possibility that short GRBs may have different or multiple progenitors systems. The study of the short-hard GRB afterglows has been made possible by the Swift Gamma-ray Burst Explorer, launched in November of 2004. Swift is equipped with a coded aperture gamma-ray telescope that can observe up to 2 steradians of the sky and can compute the position of a gamma-ray burst to within 2-3 arcmin in less than 10 seconds. The Swift spacecraft can slew on to this burst position without human intervention, allowing its on-board x ray and optical telescopes to study the afterglow within 2 minutes of the original GRB trigger. More Swift short burst detections and afterglow measurements are needed before we can declare that the mystery of short gamma-ray burst is solved.

Discovery of an Extreme MeV Blazar with the Swift Burst Alert Telescope

NASA Technical Reports Server (NTRS)

Sambruna, R. M.; Markwardt, C. B.; Mushotzky, R. F.; Tueller, J.; Hartman, R.; Brandt, W. N.; Schneider, D> P.; Falcone, A.; Cucchiara, A.;

Mid- and Near-infrared spectral properties of a sample of Swift-BAT X-ray selected AGNs

NASA Astrophysics Data System (ADS)

Castro, Angel; Miyaji, Takamitsu; Malkan, Matthew A.; Ichikawa, Kohei; Ueda, Yoshihiro; Shirahata, M.; Nakagawa, Takao; Imanishi, Masatoshi; Oyabu, Shinki

2015-08-01

We present a comparative study of the mid- (MIR) to near-infrared (NIR) properties of a sample of X-ray selected AGNs from the Swift/Burst Alert Telescope (BAT) 70-month all-sky hard X-ray (14-195 keV) survey. For a sample of 78 AGNs, including both Seyfert 1 and Seyfert 2 sources with black hole masses derived from 2MASS K-band magnitudes and literature, we obtain spectroscopic data from the IRC (2.5 - 5 μm) and IRS (in the 5-14 μm band) instruments onboard the Akari and Spitzer satellites, respectively. We test possible correlations between the 3.3, 6.2, 7.7, 8.6, 11.2 and 12.7 μm polycyclic aromatic hydrocarbon (PAH) emission features, the continuum slope and CO optical depth, as well as CO2, H2O, and amorphous silicates. Using the 3.3, 6.2 and 11.3 μm PAH emission features as a proxy for the star-formation rate (SFR) we report the AGN type and Eddington-ratio dependences of circum-nuclear star formation.

Gamma-Ray Bursts, their Hosts, and their Supernovae

NASA Astrophysics Data System (ADS)

Bersier, David; Rhoads, James; Rest, Armin; Merrill, Michael; Levan, Andrew; Fruchter, Andrew; Gorosabel Urkia, Javier; Kouveliotou, Chryssa; Hjorth, Jens; Castro Cerón, J. M.; Patel, Sandeep; Strolger, Lou; Tanvir, Nial

2005-08-01

We request rapid optical and near-IR followup observations of gamma ray bursts (GRBs), which will exploit unique NOAO capabilities to obtain (a) rapid afterglow identifications and (b) detailed physical information on selected events. We will use the Mosaic cameras on the 4m telescopes for rapid identification of GRB afterglows. These instruments provide unsurpassed sensitivity over a wide field. This cycle, they will (a) help identify low-redshift bursts found by HETE-2, which may constitute a large fraction of low-z bursts even in the Swift era; and (b) search for Swift bursts found by the hard X-ray BAT instrument in case the Swift narrow- field instruments do not find a bright counterpart. Afterglow IDs from this program will provide targets for our imaging and spectroscopy programs with Spitzer and Gemini. Large area near-IR imaging with ISPI and FLAMINGOS, and simultaneous multicolor imaging with SQIID, will help address several open questions about GRBs and their afterglows: (1) Are ``dark'' GRBs (without detected optical afterglows) a consequence of dust absorption in the GRB environment? (2) Are observed breaks in GRB light curves truly wavelength-independent, as predicted under models of beamed burst afterglows? (3) Can IR observations find bursts at extreme redshifts? (4) How well do afterglow models stand up to detailed comparison with high precision spectral slope and light curve measurements?

On the Connection of Gamma-Ray Bursts and X-Ray Flashes

NASA Astrophysics Data System (ADS)

Ripa, J.; Meszaros, A.

2017-12-01

Classification of gamma-ray bursts (GRBs) into groups has been intensively studied by various statistical tests since 1998. It has been suggested that next to the groups of short/hard and long/soft GRBs there could be another class of intermediate durations. For the Swift/BAT database Veres et al. 2010 (ApJ, 725, 1955) it was found that the intermediate-duration bursts might be related to X-ray flashes (XRFs). On the other hand, Ripa and Meszaros 2016 (Ap&SS, 361, 370) and Ripa et al. 2012 (ApJ, 756, 44) found that the intermediate-duration GRBs in the RHESSI database are spectrally too hard to be given by XRFs. Also, in the BATSE database the intermediate-duration GRBs can be only partly populated by XRFs. The key ideas of the Ripa and Meszaros 2016 (Ap&SS, 361, 370) article are summarized in this poster.

Can a Double Component Outflow Explain the X-Ray and Optical Lightcurves of Swift Gamma-Ray Bursts?

NASA Technical Reports Server (NTRS)

De Pasquale, Massimiliano; Evans, P.; Oates, S.; Page, M.; Zane, S.; Schady, P.; Breeveld, A.; Holland, S.; Still, M.

2011-01-01

An increasing sample of Gamma-Ray Bursts (GRBs) observed by Swift show evidence of 'chromatic breaks', i.e. breaks that are present in the X-ray but not in the optical. We find that in a significant fraction of these GRB afterglows the X-ray and the optical emission cannot be produced by the same component. We propose that these afterglow lightcurves are the result of a two-component jet, in which both components undergo energy injection for the whole observation and the X-ray break is due to a jet break in the narrow outflow. Bursts with chromatic breaks also explain another surprising finding, the paucity of late achromatic breaks. We propose a model that may explain the behaviour of GRB emission in both X-ray and optical bands. This model can be a radical and noteworthy alternative to the current interpretation for the 'canonical' XRT and UVOT lightcurves, and it bears fundamental implications for GRB physics.

Suzaku View of the Swift/BAT Active Galactic Nuclei (I): Spectral Analysis of Six AGNs and Evidence for Two Types of Obscured Population

NASA Technical Reports Server (NTRS)

Eguchi, Satoshi; Ueda, Yoshihiro; Terashima, Yuichi; Mushotzky, Richard F.; Tueller, Jack

2009-01-01

We present a systematic spectral analysis with Suzaku of six AGNs detected in the Swift/BAT hard X-ray (15-200 keV) survey, Swift J0138.6-4001, J0255.2-0011, J0350.1-5019, J0505.7-2348, J0601.9-8636, and J1628.1-5145. This is considered to be a representative sample of new AGNs without X-ray spectral information before the BAT survey. We find that the 0.5-200 keV spectra of these sources can be uniformly fit with a base model consisting of heavily absorbed (log NH >23.5/sq cm) transmitted components, scattered lights, a reflection component, and an iron-K emission line. There are two distinct groups, three "new type" AGNs (including the two sources reported by Ueda et al. 2007) with an extremely small scattered fraction (f(sub scat) < 0:5%) and strong reflection component (R = omega/2pi > or equal to 0.8 where omega is the solid angle of the reflector), and three "classical type" ones with f(sub scat > 0.5% and R < or approx. 0.8. The spectral parameters suggest that the new type has an optically thick torus for Thomson scattering (N(sub H) approx. 10(exp 25)/sq cm) with a small opening angle theta approx. 20deg viewed in a rather face-on geometry, while the classical type has a thin torus (N(sub H) approx. 10(exp 23-24)/sq cm) with theta > or approx. 30deg. We infer that a significant number of new type AGNs with an edge-on view is missing in the current all-sky hard X-ray surveys. Subject headings: galaxies: active . gamma rays: observations . X-rays: galaxies . X-rays: general

Superorbital Periodic Modulation in Wind-Accretion High-Mass X-Ray Binaries from Swift Burst Alert Telescope Observations

NASA Technical Reports Server (NTRS)

Corbet, Robin H. D.; Krimm, Hans A.

2013-01-01

We report the discovery using data from the Swift-Burst Alert Telescope (BAT) of superorbital modulation in the wind-accretion supergiant high-mass X-ray binaries 4U 1909+07 (= X 1908+075), IGR J16418-4532, and IGR J16479-4514. Together with already known superorbital periodicities in 2S 0114+650 and IGR J16493-4348, the systems exhibit a monotonic relationship between superorbital and orbital periods. These systems include both supergiant fast X-ray transients and classical supergiant systems, and have a range of inclination angles. This suggests an underlying physical mechanism which is connected to the orbital period. In addition to these sources with clear detections of superorbital periods, IGR J16393-4643 (= AX J16390.4-4642) is identified as a system that may have superorbital modulation due to the coincidence of low-amplitude peaks in power spectra derived from BAT, Rossi X-Ray Timing Explorer Proportional Counter Array, and International Gamma-Ray Astrophysics Laboratory light curves. 1E 1145.1-6141 may also be worthy of further attention due to the amount of low-frequency modulation of its light curve. However, we find that the presence of superorbital modulation is not a universal feature of wind-accretion supergiant X-ray binaries.

Continued X-ray Monitoring of Magnetar Candidate SWIFT J1822.3-1606

NASA Astrophysics Data System (ADS)

Scholz, P.; Livingstone, M. A.; Kaspi, V. M.

2011-08-01

We report on Swift/XRT and RXTE/PCA observations of the new 8.4-s Galactic magnetar candidate SWIFT J1822.3-1606, also referred to as SGR J1822.3-1606 (ATELs #3488, #3489, #3490, #3493, #3495, #3496, #3501, #3503, #3543). The persistent X-ray flux from the source continues to fade in ongoing XRT monitoring observations. For data in the MJD range 55757 to 55781, the best-fit power-law index, alpha, for the decay of the absorbed 1-10 keV flux is -0.47 ± 0.02, assuming a decay of functional form F(t) = F0 + F0*(t-T)^alpha, where T is the epoch of the Swift/BAT trigger (ATEL #3488).

Seeing Through the Clouds: AGN Geometry with the Swift BAT Sample

NASA Astrophysics Data System (ADS)

Glikman, Eilat; Urry, M.; Schawinski, K.; Koss, M. J.; Winter, L. M.; Elitzur, M.; Wilkin, W. H.

2011-01-01

We investigate the intrinsic structure of the clouds surrounding AGN which give rise to their X-ray and optical emission properties. Using a complete sample of Swift BAT AGN selected in hard X-rays (14-195 keV), which is unbiased with respect to obscuration and extinction, we compute the reddening in the broad line region along the line of sight to the nucleus of each source using Balmer decrement from the ratio of the broad components of H-alpha/H-beta. We compare reddening from dust in the broad line clouds to the hydrogen column density (NH) obtained from their X-ray spectra. The distribution of the gas-to-dust ratios over many lines of sight allow us to test models of AGN structure and probe the immediate environment of the accreting supermassive black holes.

A Comparison of the Variability of the Symbiotic X-ray Binaries GX 1+4, 4U 1954+31, and 4U 1700+24 from Swift/BAT and RXTE/ASM Observations

NASA Technical Reports Server (NTRS)

Corbet, R. H. D.; Sokoloski, J. L.; Mukai, K.; Markwardt, C. B.; Tueller, J.

2007-01-01

We present an analysis of the X-ray variability of three symbiotic X-ray binaries, GX 1+4, 4U 1700+24, and 4U 1954+31, using observations made with the Swift Burst Alert Telescope (BAT) and the Rossi X-ray Timing Explorer (RXTE) All-Sky Monitor (ASM). Observations of 4U 1954+31 with the Swift BAT show modulation at a period near 5 hours. Models to explain this modulation are discussed including the presence of an exceptionally slow X-ray pulsar in the system and accretion instabilities. We conclude that the most likely interpretation is that 4U 1954+31 contains one of the slowest known X-ray pulsars. Unlike 4U 1954+31, neither GX 1+4 nor 4U 1700+24 show any evidence for modulation on a timescale of hours. An analysis of the RXTE ASM light curves of GX l+4, 4U 1700+24, and 4U 1954+31 does not show the presence of periodic modulation in any source, although there is considerable variability on long timescales for all three sources. There is no modulation in GX 1+4 on either the optical 1161 day orbital period or a previously reported 304 day X-ray period. For 4U 1700+24 we do not confirm the 404 day period previously proposed for this source from a shorter duration ASM light curve.

Swift and GLAST Cooperative Efforts

NASA Technical Reports Server (NTRS)

Thompson, D. J.

2007-01-01

Because gamma-ray astrophysics depends in many ways on multiwavelength studies, the Gamma-ray Large Area Space Telescope (GLAST) instrument teams are eagerly anticipating coordinated observations with the Swift observatory. Swift and GLAST combined cover most of twelve orders of magnitude in the electromagnetic spectrum, offering numerous opportunities for cooperation. Three of the high-priority interests are: (1) gamma-ray burst studies; (2) broad-spectrum studies of blazars in both quiescent and flaring states; and (3) identification and detailed study of unidentified gamma-ray sources.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perley, D. A.; Metzger, B. D.; Butler, N. R.

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,more » 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.« less

Merging and Clustering of the Swift BAT AGN Sample

NASA Astrophysics Data System (ADS)

Koss, Michael; Mushotzky, Richard; Veilleux, Sylvain; Winter, Lisa

2010-06-01

We discuss the merger rate, close galaxy environment, and clustering on scales up to an Mpc of the Swift BAT hard X-ray sample of nearby (z<0.05), moderate-luminosity active galactic nuclei (AGNs). We find a higher incidence of galaxies with signs of disruption compared to a matched control sample (18% versus 1%) and of close pairs within 30 kpc (24% versus 1%). We also find a larger fraction with companions compared to normal galaxies and optical emission line selected AGNs at scales up to 250 kpc. We hypothesize that these merging AGNs may not be identified using optical emission line diagnostics because of optical extinction and dilution by star formation. In support of this hypothesis, in merging systems we find a higher hard X-ray to [O III] flux ratio, as well as emission line diagnostics characteristic of composite or star-forming galaxies, and a larger IRAS 60 μm to stellar mass ratio.

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.;

Study of Swift/Bat Selected Low-luminosity Active Galactic Nuclei Observed with Suzaku

NASA Astrophysics Data System (ADS)

Kawamuro, Taiki; Ueda, Yoshihiro; Tazaki, Fumie; Terashima, Yuichi; Mushotzky, Richard

2016-11-01

We systematically analyze the broadband (0.5-200 keV) X-ray spectra of hard X-ray (>10 keV) selected local low-luminosity active galactic nuclei (LLAGNs) observed with Suzaku and Swift/BAT. The sample consists of 10 LLAGNs detected with Swift/BAT with intrinsic 14-195 keV luminosities smaller than 1042 erg s-1 available in the Suzaku archive, covering a wide range of the Eddington ratio from 10-5 to 10-2. The overall spectra can be reproduced with an absorbed cut-off power law, often accompanied by reflection components from distant cold matter, and/or optically thin thermal emission from the host galaxy. In all of the objects, relativistic reflection components from the innermost disk are not required. Eight objects show a significant narrow iron-Kα emission line. Comparing their observed equivalent widths with the predictions from the Monte-Carlo-based torus model by Ikeda et al. (2009), we constrain the column density in the equatorial plane to be {log} {N}{{H}}{{eq}}\\gt 22.7, or the torus half-opening angle θ oa < 70°. We infer that the Eddington ratio (λ Edd) is a key parameter that determines the torus structure of LLAGNs: the torus becomes large at λ Edd ≳ 2 × 10-4, whereas at lower accretion rates it is little developed. The luminosity correlation between the hard X-ray and mid-infrared (MIR) bands of the LLAGNs follows the same correlation as for more luminous AGNs. This implies that mechanisms other than AGN-heated dust are responsible for the MIR emission in low Eddington ratio LLAGNs.

DISCOVERY OF A TRANSIENT GAMMA-RAY COUNTERPART TO FRB 131104

DOE Office of Scientific and Technical Information (OSTI.GOV)

DeLaunay, J. J.; Murase, K.; Mészáros, P.

We report our discovery in Swift satellite data of a transient gamma-ray counterpart (3.2 σ confidence) to the fast radio burst (FRB) FRB 131104, the first such counterpart to any FRB. The transient has a duration T {sub 90} ≳ 100 s and a fluence S{sub γ} ≈ 4 × 10{sup −6} erg cm{sup −2}, increasing the energy budget for this event by more than a billion times; at the nominal z ≈ 0.55 redshift implied by its dispersion measure, the burst’s gamma-ray energy output is E{sub γ} ≈ 5 × 10{sup 51} erg. The observed radio to gamma-ray fluencemore » ratio for FRB 131104 is consistent with a lower limit we derive from Swift observations of another FRB, which is not detected in gamma-rays, and with an upper limit previously derived for the brightest gamma-ray flare from SGR 1806−20, which was not detected in the radio. X-ray, ultraviolet, and optical observations beginning two days after the FRB do not reveal any associated afterglow, supernova, or transient; Swift observations exclude association with the brightest 65% of Swift gamma-ray burst (GRB) X-ray afterglows, while leaving the possibility of an associated supernova at much more than 10% the FRB’s nominal distance, D ≳ 320 Mpc, largely unconstrained. Transient high-luminosity gamma-ray emission arises most naturally in a relativistic outflow or shock breakout, such as, for example, from magnetar flares, GRBs, relativistic supernovae, and some types of galactic nuclear activity. Our discovery thus bolsters the case for an extragalactic origin for some FRBs and suggests that future rapid-response observations might identify long-lived counterparts, resolving the nature of these mysterious phenomena and realizing their promise as probes of cosmology and fundamental physics.« less

Simultaneous Planck, Swift, and Fermi Observations of X-ray and Gamma-ray Selected Blazars

NASA Technical Reports Server (NTRS)

Giommi, P.; Polenta, G.; Laehteenmaeki, A.; Thompson, D. J.; Capalbi, M.; Cutini, S.; Gasparrini, D.; Gonzalez, Nuevo, J.; Leon-Tavares, J.; Lopez-Caniego, M.;

Probing the Cosmic Gamma-Ray Burst Rate with Trigger Simulations of the Swift Burst Alert Telescope

NASA Technical Reports Server (NTRS)

Lien, Amy; Sakamoto, Takanori; Gehrels, Neil; Palmer, David M.; Barthelmy, Scott D.; Graziani, Carlo; Cannizzo, John K.

2013-01-01

The gamma-ray burst (GRB) rate is essential for revealing the connection between GRBs, supernovae and stellar evolution. Additionally, the GRB rate at high redshift provides a strong probe of star formation history in the early universe. While hundreds of GRBs are observed by Swift, it remains difficult to determine the intrinsic GRB rate due to the complex trigger algorithm of Swift. Current studies of the GRB rate usually approximate the Swift trigger algorithm by a single detection threshold. However, unlike the previously own GRB instruments, Swift has over 500 trigger criteria based on photon count rate and additional image threshold for localization. To investigate possible systematic biases and explore the intrinsic GRB properties, we develop a program that is capable of simulating all the rate trigger criteria and mimicking the image threshold. Our simulations show that adopting the complex trigger algorithm of Swift increases the detection rate of dim bursts. As a result, our simulations suggest bursts need to be dimmer than previously expected to avoid over-producing the number of detections and to match with Swift observations. Moreover, our results indicate that these dim bursts are more likely to be high redshift events than low-luminosity GRBs. This would imply an even higher cosmic GRB rate at large redshifts than previous expectations based on star-formation rate measurements, unless other factors, such as the luminosity evolution, are taken into account. The GRB rate from our best result gives a total number of 4568 +825 -1429 GRBs per year that are beamed toward us in the whole universe.

Gamma-Ray Bursts: A Mystery Story

NASA Technical Reports Server (NTRS)

Parsons, Ann

2007-01-01

With the success of the Swift Gamma-Ray Burst Explorer currently in orbit, this is quite an exciting time in the history of Gamma Ray Bursts (GRBs). The study of GRBs is a modern astronomical mystery story that began over 30 years ago with the serendipitous discovery of these astronomical events by military satellites in the late 1960's. Until the launch of BATSE on the Compton Gamma-ray Observatory, astronomers had no clue whether GRBs originated at the edge of our solar system, in our own Milky Way Galaxy or incredibly far away near the edge of the observable Universe. Data from BATSE proved that GRBs are distributed isotropically on the sky and thus could not be the related to objects in the disk of our Galaxy. Given the intensity of the gamma-ray emission, an extragalactic origin would require an astounding amount of energy. Without sufficient data to decide the issue, a great debate continued about whether GRBs were located in the halo of our own galaxy or were at extragalactic - even cosmological distances. This debate continued until 1997 when the BeppoSAX mission discovered a fading X-ray afterglow signal in the same location as a GRB. This discovery enabled other telescopes, to observe afterglow emission at optical and radio wavelengths and prove that GRBs were at cosmological distances by measuring large redshifts in the optical spectra. Like BeppoSAX Swift, slews to new GRB locations to measure afterglow emission. In addition to improved GRB sensitivity, a significant advantage of Swift over BeppoSAX and other missions is its ability to slew very quickly, allowing x-ray and optical follow-up measurements to be made as early as a minute after the gamma-ray burst trigger rather than the previous 6-8 hour delay. Swift afterglow measurements along with follow-up ground-based observations, and theoretical work have allowed astronomers to identify two plausible scenarios for the creation of a GRB: either through core collapse of super massive stars or

Heterogeneity in Short Gamma-Ray Bursts

NASA Astrophysics Data System (ADS)

Norris, Jay P.; Gehrels, Neil; Scargle, Jeffrey D.

2011-07-01

We analyze the Swift/BAT sample of short gamma-ray bursts, using an objective Bayesian Block procedure to extract temporal descriptors of the bursts' initial pulse complexes (IPCs). The sample is comprised of 12 and 41 bursts with and without extended emission (EE) components, respectively. IPCs of non-EE bursts are dominated by single pulse structures, while EE bursts tend to have two or more pulse structures. The medians of characteristic timescales—durations, pulse structure widths, and peak intervals—for EE bursts are factors of ~2-3 longer than for non-EE bursts. A trend previously reported by Hakkila and colleagues unifying long and short bursts—the anti-correlation of pulse intensity and width—continues in the two short burst groups, with non-EE bursts extending to more intense, narrower pulses. In addition, we find that preceding and succeeding pulse intensities are anti-correlated with pulse interval. We also examine the short burst X-ray afterglows as observed by the Swift/X-Ray Telescope (XRT). The median flux of the initial XRT detections for EE bursts (~6×10-10 erg cm-2 s-1) is gsim20× brighter than for non-EE bursts, and the median X-ray afterglow duration for EE bursts (~60,000 s) is ~30× longer than for non-EE bursts. The tendency for EE bursts toward longer prompt-emission timescales and higher initial X-ray afterglow fluxes implies larger energy injections powering the afterglows. The longer-lasting X-ray afterglows of EE bursts may suggest that a significant fraction explode into denser environments than non-EE bursts, or that the sometimes-dominant EE component efficiently powers the afterglow. Combined, these results favor different progenitors for EE and non-EE short bursts.

Suzaku Wide-band All-sky Monitor measurements of duration distributions of gamma-ray bursts

NASA Astrophysics Data System (ADS)

Ohmori, Norisuke; Yamaoka, Kazutaka; Ohno, Masanori; Sugita, Satoshi; Kinoshita, Ryuuji; Nishioka, Yusuke; Hurley, Kevin; Hanabata, Yoshitaka; Tashiro, Makoto S.; Enomoto, Junichi; Fujinuma, Takeshi; Fukazawa, Yasushi; Iwakiri, Wataru; Kawano, Takafumi; Kokubun, Motohide; Makishima, Kazuo; Matsuoka, Shunsuke; Nagayoshi, Tsutomu; Nakagawa, Yujin E.; Nakaya, Souhei; Nakazawa, Kazuhiro; Takahashi, Tadayuki; Takeda, Sawako; Terada, Yukikatsu; Urata, Yuji; Yabe, Seiya; Yasuda, Tetsuya; Yamauchi, Makoto

2016-06-01

We report on the T90 and T50 duration distributions and their relations with spectral hardness using 1464 gamma-ray bursts (GRBs), which were observed by the Suzaku Wide-band All-sky Monitor (WAM) from 2005 August 4 to 2010 December 29. The duration distribution is clearly bimodal in three energy ranges (50-120, 120-250, and 250-550 keV), but is unclear in the 550-5000 keV range, probably because of the limited sample size. The WAM durations decrease with energy according to a power-law index of -0.058(-0.034, +0.033). The hardness-duration relation reveals the presence of short-hard and long-soft GRBs. The short:long event ratio tends to be higher with increasing energy. We compared the WAM distribution with ones measured by eight other GRB instruments. The WAM T90 distribution is very similar to those of INTEGRAL/SPI-ACS and Granat/PHEBUS, and least likely to match the Swift/BAT distribution. The WAM short:long event ratio (0.25:0.75) is much different from Swift/BAT (0.08:0.92), but is almost the same as CGRO/BATSE (0.25:0.75). To explain this difference for BAT, we examined three effects: BAT trigger types, energy dependence of the duration, and detection sensitivity differences between BAT and WAM. As a result, we found that the ratio difference could be explained mainly by energy dependence including soft extended emissions for short GRBs and much better sensitivity for BAT which can detect weak/long GRBs. The reason for the same short:long event ratio for BATSE and WAM was confirmed by calculation using the trigger efficiency curve.

Gamma Ray Bursts

NASA Technical Reports Server (NTRS)

Gehrels, Neil; Meszaros, Peter

2012-01-01

Gamma-ray bursts (GRBs) are bright flashes of gamma-rays coming from the cosmos. They occur roughly once per day ,last typically lOs of seconds and are the most luminous events in the universe. More than three decades after their discovery, and after pioneering advances from space and ground experiments, they still remain mysterious. The launch of the Swift and Fermi satellites in 2004 and 2008 brought in a trove of qualitatively new data. In this review we survey the interplay between these recent observations and the theoretical models of the prompt GRB emission and the subsequent afterglows.

Probing the cosmic gamma-ray burst rate with trigger simulations of the swift burst alert telescope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lien, Amy; Cannizzo, John K.; Sakamoto, Takanori

The gamma-ray burst (GRB) rate is essential for revealing the connection between GRBs, supernovae, and stellar evolution. Additionally, the GRB rate at high redshift provides a strong probe of star formation history in the early universe. While hundreds of GRBs are observed by Swift, it remains difficult to determine the intrinsic GRB rate due to the complex trigger algorithm of Swift. Current studies of the GRB rate usually approximate the Swift trigger algorithm by a single detection threshold. However, unlike the previously flown GRB instruments, Swift has over 500 trigger criteria based on photon count rate and an additional imagemore » threshold for localization. To investigate possible systematic biases and explore the intrinsic GRB properties, we develop a program that is capable of simulating all the rate trigger criteria and mimicking the image threshold. Our simulations show that adopting the complex trigger algorithm of Swift increases the detection rate of dim bursts. As a result, our simulations suggest that bursts need to be dimmer than previously expected to avoid overproducing the number of detections and to match with Swift observations. Moreover, our results indicate that these dim bursts are more likely to be high redshift events than low-luminosity GRBs. This would imply an even higher cosmic GRB rate at large redshifts than previous expectations based on star formation rate measurements, unless other factors, such as the luminosity evolution, are taken into account. The GRB rate from our best result gives a total number of 4568{sub −1429}{sup +825} GRBs per year that are beamed toward us in the whole universe.« less

Confirmation of the E(sup src)(sub Peak)-E(sub iso) (Amati) relation from the x-ray flash XRF 050416A observed by the Swift burst alert telescope

NASA Technical Reports Server (NTRS)

Sakamoti, T.; Barbier, L.; Barthelmy, S. D.; Cummings, J. R.; Fenimore, E. E.; Gehrels, N.; Hullinger, D.; Krimm, H. A.; Markwardt, C. B.

2006-01-01

We report Swift Burst Alert Telescope (BAT) observations of the X-ray flash (XRF) XRF 050416A. The fluence ratio between the 15-25 and 25-50 keV energy bands of this event is 1.5, thus making it the softest gamma-ray burst (GRB) observed by BAT so far. The spectrum is well fitted by a Band function with E(sup obs)(sub peak) of 15.0(sup +2.3)(sub -2.7) keV. Assuming the redshift of the host galaxy (z = 0.6535), the isotropic equivalent radiated energy E(sub iso) and the peak energy at the GRB rest frame (E(sup src)(sub peak)) of XRF 050416A are not only consistent with the correlation found by Amati et al. and extended to XRFs by Sakamoto et al. but also fill in the gap of this relation around the 30-80 keV range of E(sup src)(sub peak). This result tightens the validity of the E(sup src)(sub Peak)-E(sup src)(sub peak) relation from XRFs to GRBs. We also find that the jet break time estimated using the empirical relation between E(sup src)(sub peak) and the collimation corrected energy E(sub gamma), is inconsistent with the afterglow observation by the Swift X-Ray Telescope. This could be due to the extra external shock emission overlaid around the jet break time or to the nonexistence of a jet break feature for XRFs, which might be a further challenge for GRB jet emission models and XRF/GRB unification scenarios.

Early On-Orbit Operation of the Loop Heat Pipe System on the Swift BAT Instrument

NASA Technical Reports Server (NTRS)

Ottenstein, Laura; Ku, Jentung; Choi, Mike; Feenan, Dave

2005-01-01

The Burst Alert Telescope (BAT) is one of three instruments on the Swift satellite. Two Loop Heat Pipes (LHP's), one at either side of the BAT's Detector Array Plate (DAP), transfer heat to a common radiator for rejection to space. This viewgraph presentation provides information on LHP design for the BAT, and the performance of the LHPs in orbit.

Heterogeneity in Short Gamma-Ray Bursts

NASA Technical Reports Server (NTRS)

Norris, Jay P.; Gehrels Neil; Scargle, Jeffrey D.

2011-01-01

We analyze the Swift/BAT sample of short gamma-ray bursts, using an objective Bayesian Block procedure to extract temporal descriptors of the bursts' initial pulse complexes (IPCs). The sample comprises 12 and 41 bursts with and without extended emission (EE) components, respectively. IPCs of non-EE bursts are dominated by single pulse structures, while EE bursts tend to have two or more pulse structures. The medians of characteristic timescales - durations, pulse structure widths, and peak intervals - for EE bursts are factors of approx 2-3 longer than for non-EE bursts. A trend previously reported by Hakkila and colleagues unifying long and short bursts - the anti-correlation of pulse intensity and width - continues in the two short burst groups, with non-EE bursts extending to more intense, narrower pulses. In addition we find that preceding and succeeding pulse intensities are anti-correlated with pulse interval. We also examine the short burst X-ray afterglows as observed by the Swift/XRT. The median flux of the initial XRT detections for EE bursts (approx 6 X 10(exp -10) erg / sq cm/ s) is approx > 20 x brighter than for non-EE bursts, and the median X-ray afterglow duration for EE bursts (approx 60,000 s) is approx 30 x longer than for non-EE bursts. The tendency for EE bursts toward longer prompt-emission timescales and higher initial X-ray afterglow fluxes implies larger energy injections powering the afterglows. The longer-lasting X-ray afterglows of EE bursts may suggest that a significant fraction explode into more dense environments than non-EE bursts, or that the sometimes-dominant EE component efficiently p()wers the afterglow. Combined, these results favor different progenitors for EE and non-EE short bursts.

X-Ray Enhancement and Long-term Evolution of Swift J1822.3-1606

NASA Astrophysics Data System (ADS)

Benli, Onur; Çalışkan, Ş.; Ertan, Ü.; Alpar, M. A.; Trümper, J. E.; Kylafis, N. D.

2013-12-01

We investigate the X-ray enhancement and the long-term evolution of the recently discovered second "low-B magnetar" Swift J1822.3-1606 in the frame of the fallback disk model. During a soft gamma burst episode, the inner disk matter is pushed back to larger radii, forming a density gradient at the inner disk. Subsequent relaxation of the inner disk could account for the observed X-ray enhancement light curve of Swift J1822.3-1606. We obtain model fits to the X-ray data with basic disk parameters similar to those employed to explain the X-ray outburst light curves of other anomalous X-ray pulsars and soft gamma repeaters. The long period (8.4 s) of the neutron star can be reached by the effect of the disk torques in the long-term accretion phase ((1-3) × 105 yr). The currently ongoing X-ray enhancement could be due to a transient accretion epoch, or the source could still be in the accretion phase in quiescence. Considering these different possibilities, we determine the model curves that could represent the long-term rotational and the X-ray luminosity evolution of Swift J1822.3-1606, which constrain the strength of the magnetic dipole field to the range of (1-2) × 1012 G on the surface of the neutron star.

Host Galaxy Properties of SWIFT Hard X-ray Selected AGN

NASA Astrophysics Data System (ADS)

Koss, Michael; Mushotzky, R.; Veilleux, S.; Winter, L.

2010-01-01

Surveys of AGN taken in the optical, UV, and soft X-rays miss an important population of obscured AGN only visible in the hard X-rays and mid-IR wavelengths. The SWIFT BAT survey in the hard X-ray range (14-195 keV) has provided a uniquely unbiased sample of 258 AGN unaffected by galactic or circumnuclear absorption. Optical imaging of this unbiased sample provides a new opportunity to understand how the environments of the host galaxies are linked to AGN. In 2008, we observed 110 of these targets at Kitt Peak with the 2.1m in the SDSS ugriz bands over 17 nights. Using these observations and SDSS data we review the relationships between color, morphology, merger activity, star formation, and AGN luminosity.

Simultaneous Planck, Swift, and Fermi Observations of X-Ray and gamma-Ray Selected Blazars

NASA Technical Reports Server (NTRS)

Giommi, P.; Polenta, G.; Laehteenmaeki, A.; Thompson, D. J.; Capalbi, M.; Cutini, S.; Gasparrini, D.; Gonzalez-Nuevo, J.; Leon-Tavares, J.; Lopez-Caniego, M.;

The Swift Gamma-ray Burst Explorer: Early views into Black-hole Creation

NASA Technical Reports Server (NTRS)

Hill, Joe

2006-01-01

Swift has exceeded every pre-launch predicted advance in GRB science. It has discovered the farthest GRB ever seen and identified new GRBs at a rate of 100/year. It has also explored a brand new time interval in GRB light curves by revealing unpredicted phenomena of GRB flares and rapid x-ray afterglow declines. Swift has conducted 20,00o successful slews to sources and is predicted to stay in orbit until 2022.

Solving the Mystery of Short Gamma Ray Bursts

NASA Technical Reports Server (NTRS)

Gehrels, Neil

2006-01-01

Gamma-ray bursts are among the most fascinating occurrences in the cosmos. Until this year, the origin of short gamma-ray bursts was a complete mystery. A new NASA satellite named Swift has now captured the first images of these events and found that they are caused by tremendous explosions in the distant universe.

The Swift BAT Perspective on Non-Thermal Emission in HIFLUGCS Galaxy Clusters

NASA Technical Reports Server (NTRS)

Wik, Daniel R.

2011-01-01

The search for diffuse non-thermal, inverse Compton (IC) emission from galaxy clusters at hard X-ray energies has been underway for many years, with most detections being either of low significance or controversial. Until recently, comprehensive surveys of hard X-ray emission from clusters were not possible; instead, individually proposed-for. long observations would be collated from the archive. With the advent of the Swift BAT all sky survey, any c1u,;ter's emission above 14 keV can be probed with nearly uniform sensitivity. which is comparable to that of RXTE, Beppo-SAX, and Suzaku with the 58-month version of the survey. In this work. we search for non-thermal excess emission above the exponentially decreasing, high energy thermal emission in the flux-limited HIFLUGCS sample. The BAT emission from many of the detected clusters is marginally extended; we are able to extract the total flux for these clusters using fiducial models for their spatial extent. To account for thermal emission at BAT energies, XMM-Newton EPIC spectra are extracted from coincident spatial regions so that both the thermal and non-thermal spectral components can be determined simultaneou,;ly in joint fits. We find marginally significant IC components in 6 clusters, though after closer inspection and consideration of systematic errors we are unable to claim a clear detection in any of them. The spectra of all clusters are also summed to enhance a cumulative non-thermal signal not quite detectable in individual clusters. After constructing a model based on single temperature

Machine- z: Rapid machine-learned redshift indicator for Swift gamma-ray bursts

DOE PAGES

Ukwatta, T. N.; Wozniak, P. R.; Gehrels, N.

2016-03-08

Studies of high-redshift gamma-ray bursts (GRBs) provide important information about the early Universe such as the rates of stellar collapsars and mergers, the metallicity content, constraints on the re-ionization period, and probes of the Hubble expansion. Rapid selection of high-z candidates from GRB samples reported in real time by dedicated space missions such as Swift is the key to identifying the most distant bursts before the optical afterglow becomes too dim to warrant a good spectrum. Here, we introduce ‘machine-z’, a redshift prediction algorithm and a ‘high-z’ classifier for Swift GRBs based on machine learning. Our method relies exclusively onmore » canonical data commonly available within the first few hours after the GRB trigger. Using a sample of 284 bursts with measured redshifts, we trained a randomized ensemble of decision trees (random forest) to perform both regression and classification. Cross-validated performance studies show that the correlation coefficient between machine-z predictions and the true redshift is nearly 0.6. At the same time, our high-z classifier can achieve 80 per cent recall of true high-redshift bursts, while incurring a false positive rate of 20 per cent. With 40 per cent false positive rate the classifier can achieve ~100 per cent recall. As a result, the most reliable selection of high-redshift GRBs is obtained by combining predictions from both the high-z classifier and the machine-z regressor.« less

Machine-z: Rapid Machine-Learned Redshift Indicator for Swift Gamma-Ray Bursts

NASA Technical Reports Server (NTRS)

Ukwatta, T. N.; Wozniak, P. R.; Gehrels, N.

2016-01-01

Studies of high-redshift gamma-ray bursts (GRBs) provide important information about the early Universe such as the rates of stellar collapsars and mergers, the metallicity content, constraints on the re-ionization period, and probes of the Hubble expansion. Rapid selection of high-z candidates from GRB samples reported in real time by dedicated space missions such as Swift is the key to identifying the most distant bursts before the optical afterglow becomes too dim to warrant a good spectrum. Here, we introduce 'machine-z', a redshift prediction algorithm and a 'high-z' classifier for Swift GRBs based on machine learning. Our method relies exclusively on canonical data commonly available within the first few hours after the GRB trigger. Using a sample of 284 bursts with measured redshifts, we trained a randomized ensemble of decision trees (random forest) to perform both regression and classification. Cross-validated performance studies show that the correlation coefficient between machine-z predictions and the true redshift is nearly 0.6. At the same time, our high-z classifier can achieve 80 per cent recall of true high-redshift bursts, while incurring a false positive rate of 20 per cent. With 40 per cent false positive rate the classifier can achieve approximately 100 per cent recall. The most reliable selection of high-redshift GRBs is obtained by combining predictions from both the high-z classifier and the machine-z regressor.

Diverse Long-Term Variability of Five Candidate High-Mass X-Ray Binaries from Swift Burst Alert Telescope Observations

NASA Technical Reports Server (NTRS)

Corbet, Robin H. D.; Coley, Joel B.; Krimm, Hans A.

2017-01-01

We present an investigation of long-term modulation in the X-ray light curves of five little-studied candidate high-mass X-ray binaries using the Swift Burst Alert Telescope (SWIFT-BAT). IGR J14488-5942 and AX J1700.2-4220 show strong modulation at periods of 49.6 and 44 days, respectively, which are interpreted as orbital periods of Be star systems. For IGR J14488-5942, observations with the Swift X-ray Telescope show a hint of pulsations at 33.4 seconds. For AX J1700.2-4220, 54 second-pulsations were previously found with XMM-Newton. Swift J1816.7-1613 exhibits complicated behavior. The strongest peak in the power spectrum is at a period near 150 days, but this conflicts with a determination of a period of 118.5 days by La Parola et al. AX J1820.5-1434 has been proposed to exhibit modulation near 54 days, but the extended BAT observations suggest modulation at slightly longer than double this at approximately 111 days. There appears to be a long-term change in the shape of the modulation near 111 days, which may explain the apparent discrepancy. The X-ray pulsar XTE J1906+090,which was previously proposed to be a Be star system with an orbital period of approximately 30 days from pulse timing, shows peaks in the power spectrum at 81 and 173 days. The origins of these periods are unclear, although theymight be the orbital period and a superorbital period respectively. For all five sources, the long-term variability, together with the combination of orbital and proposed pulse periods, suggests that the sources contain Be starmass donors.

GRB 120729A: External Shock Origin for Both the Prompt Gamma-Ray Emission and Afterglow

NASA Astrophysics Data System (ADS)

Huang, Li-Ye; Wang, Xiang-Gao; Zheng, WeiKang; Liang, En-Wei; Lin, Da-bin; Zhong, Shu-Qing; Zhang, Hai-Ming; Huang, Xiao-Li; Filippenko, Alexei V.; Zhang, Bing

2018-06-01

Gamma-ray burst (GRB) 120729A was detected by Swift/BAT and Fermi/GBM, and then rapidly observed by Swift/XRT, Swift/UVOT, and ground-based telescopes. It had a single long and smooth γ-ray emission pulse, which extends continuously to the X-rays. We report Lick/KAIT observations of the source, and make temporal and spectral joint fits of the multiwavelength light curves of GRB 120729A. It exhibits achromatic light-curve behavior, consistent with the predictions of the external shock model. The light curves are decomposed into four typical phases: onset bump (Phase I), normal decay (Phase II), shallow decay (Phase III), and post-jet break (Phase IV). The spectral energy distribution (SED) evolves from prompt γ-ray emission to the afterglow with a photon index from Γ γ = 1.36 to Γ ≈ 1.75. There is no obvious evolution of the SED during the afterglow. The multiwavelength light curves from γ-ray to optical can be well modeled with an external shock by considering energy injection, and a time-dependent microphysics model with {ε }B\\propto {t}{α B} for the emission at early times, T< {T}0+157 {{s}}. Therefore, we conclude that both the prompt γ-ray emission and afterglow of GRB 120729A have the same external shock physical origin. Our model indicates that the ɛ B evolution can be described as a broken power-law function with α B,1 = 0.18 ± 0.04 and α B,2 = 0.84 ± 0.04. We also systematically investigate single-pulse GRBs in the Swift era, finding that only a small fraction of GRBs (GRBs 120729A, 051111, and 070318) are likely to originate from an external shock for both the prompt γ-ray emission and afterglow.

Swift and Fermi Observations of X-Ray Flares: The Case of Late Internal Shock

NASA Technical Reports Server (NTRS)

Troja, E.; Piro, L.; Vasileiou, V.; Omodei, N.; Burgess, J. M.; Cutini, S.; Connaughton, V.; McEnery, J. E.

2015-01-01

Simultaneous Swift and Fermi observations of gamma-ray bursts (GRBs) offer a unique broadband view of their afterglow emission, spanning more than 10 decades in energy. We present the sample of X-ray flares observed by both Swift and Fermi during the first three years of Fermi operations. While bright in the X-ray band, X-ray flares are often undetected at lower (optical), and higher (MeV to GeV) energies. We show that this disfavors synchrotron self-Compton processes as the origin of the observed X-ray emission. We compare the broadband properties of X-ray flares with the standard late internal shock model, and find that in this scenario, X-ray flares can be produced by a late-time relativistic (gamma greater than 50) outflow at radii R approximately 10(exp 13) - 10(exp 14) cm. This conclusion holds only if the variability timescale is significantly shorter than the observed flare duration, and implies that X-ray flares can directly probe the activity of the GRB central engine.

X-ray Properties of an Unbiased Hard X-ray Detected Sample of AGN

NASA Technical Reports Server (NTRS)

Winter, Lisa M.; Mushotzky, Richard F.; Tueller, Jack; Markwardt, Craig

2007-01-01

The SWIFT gamma ray observatory's Burst Alert Telescope (BAT) has detected a sample of active galactic nuclei (AGN) based solely on their hard X-ray flux (14-195keV). In this paper, we present for the first time XMM-Newton X-ray spectra for 22 BAT AGXs with no previously analyzed X-ray spectra. If our sources are a representative sample of the BAT AGN, as we claim, our results present for the first time global X-ray properties of an unbiased towards absorption (n(sub H) < 3 x 10(exp 25)/sq cm), local (< z >= 0.03), AGN sample. We find 9/22 low absorption (n(sub H) < 10(exp 23)/sq cm), simple power law model sources, where 4 of these sources have a statistically significant soft component. Among these sources, we find the presence of a warm absorber statistically significant for only one Seyfert 1 source, contrasting with the ASCA results of Reynolds (1997) and George et al. (1998), who find signatures of warm absorption in half or more of their Seyfert 1 samples at similar redshifts. Additionally, the remaining sources (13122) have more complex spectra, well-fit by an absorbed power law at E > 2.0 keV. Five of the complex sources (NGC 612, ESO 362-G018, MRK 417, ESO 506-G027, and NGC 6860) are classified as Compton-thick candidates. Further, we find four more sources (SWIFT J0641.3+3257, SWIFT J0911.2+4533, SWIFT J1200.8+0650, and NGC 4992) with properties consistent with the hidden/buried AGN reported by Ueda et al. (2007). Finally, we include a comparison of the XMM EPIC spectra with available SWIFT X-ray Telescope (XRT) observations. From these comparisons, we find 6/16 sources with varying column densities, 6/16 sources with varying power law indices, and 13/16 sources with varying fluxes, over periods of hours to months. Flux and power law index are correlated for objects where both parameters vary.

The Zone of Avoidance as an X-ray absorber - the role of the galactic foreground modelling Swift XRT spectra

NASA Astrophysics Data System (ADS)

Racz, I. I.; Bagoly, Z.; Tóth, L. V.; Balázs, L. G.; Horvath, I.; Zahorecz, S.

2018-05-01

Gamma-ray bursts (GRBs) are the most powerful explosive events in the Universe. The prompt gamma emission is followed by an X-ray afterglow that is also detected for over nine hundred GRBs by the Swift BAT and XRT detectors. The X-ray afterglow spectrum bears essential information about the burst, and the surrounding interstellar medium (ISM). Since the radiation travels through the line of sight intergalactic medium and the ISM in the Milky Way, the observed emission is influenced by extragalactic and galactic components. The column density of the Galactic foreground ranges several orders of magnitudes, due to both the large scale distribution of ISM and its small scale structures. We examined the effect of local HI column density on the penetrating X-ray emission, as the first step towards a precise modeling of the measured X-ray spectra. We fitted the X-ray spectra using the Xspec software, and checked how the shape of the initially power low spectrum changes with varying input Galactic HI column density. The total absorbing HI column is a sum of the intrinsic and Galactic component. We also investigated the model results for the intrinsic component varying the Galactic foreground. We found that such variations may alter the intrinsic hydrogen column density up to twenty-five percent. We will briefly discuss its consequences.

NuSTAR constraints on coronal cutoffs in Swift-BAT selected Seyfert 1 AGN

NASA Astrophysics Data System (ADS)

Kamraj, Nikita; Harrison, Fiona; Balokovic, Mislav; Brightman, Murray; Stern, Daniel

2017-08-01

The continuum X-ray emission from Active Galactic Nuclei (AGN) is believed to originate in a hot, compact corona above the accretion disk. Compton upscattering of UV photons from the inner accretion disk by coronal electrons produces a power law X-ray continuum with a cutoff at energies determined by the electron temperature. The NuSTAR observatory, with its high sensitivity in hard X-rays, has enabled detailed broadband modeling of the X-ray spectra of AGN, thereby allowing tight constraints to be placed on the high-energy cutoff of the X-ray continuum. Recent detections of low cutoff energies in Seyfert 1 AGN in the NuSTAR band have motivated us to pursue a systematic search for low cutoff candidates in Swift-BAT detected Seyfert 1 AGN that have been observed with NuSTAR. We use our constraints on the cutoff energy to map out the location of these sources on the compactness - temperature diagram for AGN coronae, and discuss the implications of low cutoff energies for the cooling and thermalization mechanisms in the corona.

The Operation and Evolution of the Swift X-ray Telescope

NASA Technical Reports Server (NTRS)

Kennea, Jamie; Burrows, D. N.; Pagani, C.; Hill, Joanne; Racusin, J. L.; Morris, D. C.; Abbey, A. F.; Beardmore, A. P.; Campana, G.; Chincarini, G.;

Probing the Properties of AGN Clustering in the Local Universe with Swift-BAT

NASA Astrophysics Data System (ADS)

Powell, M.; Cappelluti, N.; Urry, M.; Koss, M.; Allevato, V.; Ajello, M.

2017-10-01

I present the benchmark measurement of AGN clustering in the local universe with the all-sky Swift-BAT survey. The hard X-ray selection (14-195 keV) allows for the detection of some of the most obscured AGN, providing the largest, most unbiased sample of local AGN to date. We derive for the first time the halo occupation distribution (HOD) of the sample in various bins of black hole mass, accretion rate, and obscuration. In doing so, we characterize the cosmic environment of growing supermassive black holes with unprecedented precision, and determine which black hole parameters depend on environment. We then compare our results to the current evolutionary models of AGN.

Enhanced high-energy gamma-ray emission from the microquasar Cygnus X-3 detected by Fermi/LAT

NASA Astrophysics Data System (ADS)

Loh, Alan; Corbel, Stephane

2017-02-01

Following the recent decrease of the hard X-ray emission from the high-mass X-ray binary Cygnus X-3 as seen by the Swift/Burst Alert Telescope (https://swift.gsfc.nasa.gov/results/transients/CygX-3/), the Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed significant gamma-ray emission originating from the microquasar.

PKS 2123-463: A Confirmed Gamma-ray Blazar at High Redshift

NASA Technical Reports Server (NTRS)

DAmmando, F.; Rau, A.; Schady, P.; Finke, J.; Orienti, M.; Greiner, J.; Kann, D. A.; Ojha, R.; Foley, A. R.; Stevens, J.;

Candidate counterparts to the soft gamma-ray flare in the direction of LS I +61 303

NASA Astrophysics Data System (ADS)

Muñoz-Arjonilla, A. J.; Martí, J.; Combi, J. A.; Luque-Escamilla, P.; Sánchez-Sutil, J. R.; Zabalza, V.; Paredes, J. M.

2009-04-01

Context: A short duration burst reminiscent of a soft gamma-ray repeater/anomalous X-ray pulsar behaviour was detected in the direction of LS I +61 303 by the Swift satellite. While the association with this well known gamma-ray binary is likely, a different origin cannot be excluded. Aims: We explore the error box of this unexpected flaring event and establish the radio, near-infrared and X-ray sources in our search for any peculiar alternative counterpart. Methods: We carried out a combined analysis of archive Very Large Array radio data of LS I +61 303 sensitive to both compact and extended emission. We also reanalysed previous near infrared observations with the 3.5 m telescope of the Centro Astronómico Hispano Alemán and X-ray observations with the Chandra satellite. Results: Our deep radio maps of the LS I +61 303 environment represent a significant advancement on previous work and 16 compact radio sources in the LS I +61 303 vicinity are detected. For some detections, we also identify near infrared and X-ray counterparts. Extended emission features in the field are also detected and confirmed. The possible connection of some of these sources with the observed flaring event is considered. Based on these data, we are unable to claim a clear association between the Swift-BAT flare and any of the sources reported here. However, this study represents the most sophisticated attempt to determine possible alternative counterparts other than LS I +61 303.

Gamma Ray Bursts and the Birth of Black Holes

NASA Technical Reports Server (NTRS)

Gehrels, Neil

2009-01-01

Black holes have been predicted since the 1940's from solutions of Einstein's general relativity field equation. There is strong evidence of their existence from astronomical observations, but their origin has remained an open question of great interest. Gamma-ray bursts may the clue. They are powerful explosions, visible to high redshift, and appear to be the birth cries of black holes. The Swift and Fermi missions are two powerful NASA observatories currently in orbit that are discovering how gamma-ray bursts work. Evidence is building that the long and short duration subcategories of GRBs have very different origins: massive star core collapse to a black hole for long bursts and binary neutron star coalescence to a black hole for short bursts. The similarity to Type II and Ia supernovae originating from young and old stellar progenitors is striking. Bursts are tremendously luminous and are providing a new tool to study the high redshift universe. One Swift burst at z=8.3 is the most distant object known in the universe. The talk will present the latest gamma-ray burst results from Swift and Fermi and will highlight what they are teaching us about black holes and jet outflows.

Building A New Kind of Graded-Z Shield for Swift's Burst Alert Telescope

NASA Technical Reports Server (NTRS)

Robinson, David W.

2002-01-01

The Burst Alert Telescope (BAT) on Swift has a graded-Z Shield that closes out the volume between the coded aperture mask and the Cadmium-Zinc-Telluride (CZT) detector array. The purpose of the 37 kilogram shield is to attenuate gamma rays that have not penetrated the coded aperture mask of the BAT instrument and are therefore a major source of noise on the detector array. Unlike previous shields made from plates and panels, this shield consists of multiple layers of thin metal foils (lead, tantalum, tin, and copper) that are stitched together much like standard multi-layer insulation blankets. The shield sections are fastened around BAT, forming a curtain around the instrument aperture. Strength tests were performed to validate and improve the design, and the shield will be vibration tested along with BAT in late 2002. Practical aspects such as the layup design, methods of manufacture, and testing of this new kind of graded-Z Shield are presented.

PKS 2123-463: A Confirmed Gamma-ray Blazar at High Redshift

NASA Technical Reports Server (NTRS)

D'Ammando, F.; Rau, A.; Schady, P.; Finke, J.; Orienti, M.; Greiner, J.; Kann, D. A.; Ojha, R.; Foley, A. R.; Stevens, J.;

VizieR Online Data Catalog: Swift Master Catalog (HEASARC, 2004-)

NASA Astrophysics Data System (ADS)

Nasa; Heasarc

2018-01-01

This table records high-level information for each Swift observation and provides access to the data archive. Each record is associated with a single observation that contains data from all instruments on board Swift. The BAT is the large field of view instrument and operates in the 10-300 keV energy band. The narrow field instruments, XRT and UVOT, operate in the X-ray and UV/optical regime, respectively. An observation is defined as a collection of snapshots, where a snapshot is defined as the time spent observing the same position continuously. Because of observing constraints, the length of a snapshot can be shorter than a single orbit and it can be interrupted because the satellite will point in a different direction of the sky or because the time allocated to that observation ends. The typical Swift observing strategy for a Gamma Ray Burst (GRB) and/or afterglow, consists of a serious of observations aimed at following the GRB and its afterglow evolution. This strategy is achieved with two different type of observations named Automatic Targets and Pre-Planned Targets. The Automatic Target is initiated on board soon after an event is triggered by the BAT. The Figure of Merit (FOM) algorithm, part of the observatory's autonomy, decides if it is worth requesting a slew maneuver to point the narrow field instruments (NFI) on Swift, XRT and UVOT, in the direction of the trigger. If the conditions to slew to the new position are satisfied, the Automatic Target observation takes place; all the instruments have a pre-set standard configuration of operating modes and filters and about 20000 seconds on source will be collected. The Pre-Planned Target observations instead are initiated from the ground once the trigger is known. These observations are planned on ground and uploaded onto the spacecraft. (1 data file).

VizieR Online Data Catalog: New gamma-ray blazar candidates in the 3PBC (Maselli+, 2013)

NASA Astrophysics Data System (ADS)

Maselli, A.; Massaro, F.; Cusumano, G.; D'Abrusco, R.; La Parola, V.; Paggi, A.; Segreto, A.; Smith, H. A.; Tosti, G.

2013-06-01

We searched for γ-ray blazar candidates among the 382 unidentified hard X-ray sources of the third Palermo BAT Catalog (3PBC) obtained from the analysis of 66 months of Swift Burst Alert Telescope (BAT) survey data and listing 1586 sources. We adopted a recently developed association method based on the peculiar infrared colors that characterize the γ-ray blazars included in the second catalog of active galactic nuclei detected by the Fermi Large Area Telescope. We used this method exploiting the data of the all-sky survey performed by the Wide-field Infrared Survey Explorer (WISE) to establish correspondences between unidentified 3PBC sources and WISE γ-ray blazar candidates located within the BAT positional uncertainty region at a 99% confidence level. We obtained a preliminary list of candidates for which we analyzed all the available data in the Swift archive to complement the information in the literature and in the radio, infrared, and optical catalogs with the information on their optical-UV and soft X-ray emission. Requiring the presence of radio and soft X-ray counterparts consistent with the infrared positions of the selected WISE sources, as well as a blazar-like radio morphology, we finally obtained a list of 24 γ-ray blazar candidates. (2 data files).

The Spitzer/Swift Gamma-Ray Burst Host Galaxy Extended Legacy Survey

NASA Astrophysics Data System (ADS)

Perley, Daniel; Berger, Edo; Butler, Nathaniel; Cenko, S. Bradley; Chary, Ranga-Ram; Cucchiara, Antonino; Ellis, Richard; Fong, Wen-fai; Fruchter, Andrew; Fynbo, Johan; Gehrels, Neil; Graham, John; Greiner, Jochen; Hjorth, Jens; Hunt, Leslie; Jakobsson, Pall; Kruehler, Thomas; Laskar, Tanmoy; Le Floc'h, Emerich; Levan, Andrew; Levesque, Emily; Littlejohns, Owen; Malesani, Daniele; Michalowski, Michal; Prochaska, J. Xavier; Salvaterra, Ruben; Schulze, Steve; Schady, Patricia; Tanvir, Nial; de Ugarte Postigo, Antonio; Vergani, Susanna

2014-12-01

Long-duration gamma-ray bursts act as beacons to the sites of star-formation in the distant universe. GRBs reveal galaxies too faint and star-forming regions too dusty to characterize in detail using any other method, and provide a powerful independent constraint on the evolution of the cosmic star-formation rate density at high-redshift. However, a full understanding of the GRB phenomenon and its relation to cosmic star-formation requires connecting the observations obtained from GRBs to the properties of the galaxies hosting them. The large majority of GRBs originate at moderate to high redshift (z>1) and Spitzer has proven crucial for understanding the host population, given its unique ability to observe the rest-frame NIR and its unrivaled sensitivity and efficiency. We propose to complete a comprehensive public legacy survey of the Swift GRB host population to build on our earlier successes and push beyond the statistical limits of previous, smaller efforts. Our survey will enable a diverse range of GRB and galaxy science including: (1) to quantitatively and robustly map the connection between GRBs and cosmic star-formation to constrain the GRB progenitor and calibrate GRB rate-based measurements of the high-z cosmic star-formation rate; (2) to constrain the luminosity function of star-forming galaxies at the faint end and at high redshift; (3) to understand how the ISM properties seen in absorption in high-redshift galaxies unveiled by GRBs - metallicity, dust column, dust properties - connect to global properties of the host galaxies such as mass and age. Building on a decade of experience at both observatories, our observations will create an enduring joint Swift-Spitzer legacy sample and provide the definitive resource with which to examine all aspects of the GRB/galaxy connection for years and possibly decades to come.

A Correlated Optical and Gamma Emission from GRB 081126A

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gendre, B.; Klotz, A.; CESR, Observatoire Midi-Pyrenees, CNRS, Universite de Toulouse, BP 4346, F-31028-Toulouse Cedex 04

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 couldmore » 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.« less

Technology Needs for Gamma Ray Astronomy

NASA Technical Reports Server (NTRS)

Gehrels, Neil

2011-01-01

Gamma ray astronomy is currently in an exciting period of multiple missions and a wealth of data. Results from INTEGRAL, Fermi, AGILE, Suzaku and Swift are making large contributions to our knowledge of high energy processes in the universe. The advances are due to new detector and imaging technologies. The steps to date have been from scintillators to solid state detectors for sensors and from light buckets to coded aperture masks and pair telescopes for imagers. A key direction for the future is toward focusing telescopes pushing into the hard X-ray regime and Compton telescopes and pair telescopes with fine spatial resolution for medium and high energy gamma rays. These technologies will provide finer imaging of gamma-ray sources. Importantly, they will also enable large steps forward in sensitivity by reducing background.

Swift J1822.3-1606: refined X-ray timing and spectral parameters

NASA Astrophysics Data System (ADS)

Rea, N.; Esposito, P.; Israel, G. L.; Tiengo, A.; Zan, S.

2011-07-01

Between 2011 July 15-19 Swift-XRT continued its monitoring of the new SGR discovered by Swift-BAT, namely Swift J1822.3-1606 (Cummings et al. Atel #3488). Using the first four available Swift-XRT observations we find a best period of 8.437716(5)s. No evidence for a period derivative has been observed in the first days of monitoring, yielding a Pdot limit of about a few 10-10 s/s, still consistent with the SGR nature of this new transient.

Fermi and Swift as supernova alarms: Alert, localization, and diagnosis of future Galactic Type Ia explosions

NASA Astrophysics Data System (ADS)

Wang, Xilu; Fields, Brian D.; Lien, Amy Y.

2017-01-01

A Galactic SNIa event could go entirely unnoticed due to the large optical and near-IR extinction in the Milky Way plane, low radio and X-ray luminosities, and a weak neutrino signal. But the recent SN2014J confirms that Type Ia supernovae emit nuclear γ- ray lines, from the 56Ni → 56Co → 56Fe radioactive decay. The energy released in these decays powers the SNIa UVOIR light curve at times after ~1 week, leading to an exponential decline. Importantly for Swift and Fermi, these decays are accompanied by γ-ray line emission, with distinct series of lines for both the 56Ni and 56Co decays, spanning 158 keV to 2.6 MeV. These lines are squarely within the Fermi/GBM energy range, and the 56Ni 158 keV line is detectable by Swift/BAT. The Galaxy is optically thin to γ-rays, so the supernova line flux will suffer negligible extinction. Both GBM and BAT have continuous and nearly all-sky coverage. Thus GBM and BAT are ideal Galactic SNIa monitors and early warning systems. We will illustrate expected GBM and BAT light curves and spectra, based on our model for SNIa γ-ray emission and transfer. We show that the supernova signal emerges as distinct from the GBM background within days after the explosion in the SN2014J shell model. Therefore, if a Galactic SNIa were to explode, there are two possibilities of confirming and sounding the alert: 1) Swift/BAT discovers the SNIa first and localizes it within arcminutes; 2) Fermi/GBM finds the SNIa first and localizes it to within ~1 degree, using the Earth occultation technique, followed up by BAT to localize it within arcminutes. After the alert of either BAT or GBM, Swift localizes it to take spectra in optical, UV, soft and hard X-rays simultaneously with both XRT and UVOT instruments.

Catalogue of isolated emission episodes in gamma-ray bursts from Fermi, Swift and BATSE

NASA Astrophysics Data System (ADS)

Charisi, M.; Márka, S.; Bartos, I.

2015-04-01

We report a comprehensive catalogue of emission episodes within long gamma-ray bursts (GRBs) that are separated by a quiescent period during which gamma-ray emission falls below the background level. We use a fully automated identification method for an unbiased, large-scale and expandable search. We examine a comprehensive sample of long GRBs from the BATSE (Burst and Transient Source Experiment), Swift and Fermi missions, assembling a total searched set of 2710 GRBs, the largest catalogue of isolated emission episodes so far. Our search extends out to [-1000 s, 750 s] around the burst trigger, expanding the covered time interval beyond previous studies and far beyond the nominal durations (T90) of most bursts. We compare our results to previous works by identifying pre-peak emission (or precursors), defined as isolated emission periods prior to the episode with the highest peak luminosity of the burst. We also systematically search for similarly defined periods after the burst's peak emission. We find that the pre-peak and post-peak emission periods are statistically similar, possibly indicating a common origin. For the analysed GRBs, we identify 24 per cent to have more than one isolated emission episode, with 11 per cent having at least one pre-peak event and 15 per cent having at least one post-peak event. We identify GRB activity significantly beyond their T90, which can be important for understanding the central engine activity as well as, e.g. gravitational-wave searches.

Discovering highly obscured AGN with the Swift-BAT 100-month survey

NASA Astrophysics Data System (ADS)

Marchesi, Stefano; Ajello, Marco; Comastri, Andrea; Cusumano, Giancarlo; La Parola, Valentina; Segreto, Alberto

2017-01-01

In this talk, I present a new technique to find highly obscured AGN using the 100-month Swift-BAT survey. I will show the results of the combined Chandra and BAT spectral analysis in the 0.3-150 keV band of seven Seyfert 2 galaxies selected from the 100-month BAT catalog. We selected nearby (z<0.03) sources lacking of a ROSAT counterpart and never previously observed in the 0.3-10 keV energy range. All the objects are significantly obscured, having NH>1E23 cm-2 at a >99% confidence level, and one to three sources are candidate Compton thick Active Galactic Nuclei (CT-AGN), i.e., have NH>1E24 cm-2.Since the selection criteria we adopted have been extremely effective in detecting highly obscured AGN, further observations of these and other Seyfert 2 galaxies selected from the BAT 100-month catalog will allow us to create a statistically significant sample of highly obscured AGN, therefore better understanding the physics of the obscuration processes.

The Swift Supergiant Fast X-ray Transient Project

NASA Astrophysics Data System (ADS)

Romano, P.; Barthelmy, S.; Bozzo, E.; Burrows, D.; Ducci, L.; Esposito, P.; Evans, P.; Kennea, J.; Krimm, H.; Vercellone, S.

2017-10-01

We present the Swift Supergiant Fast X-ray Transients project, a systematic study of SFXTs and classical supergiant X-ray binaries (SGXBs) through efficient long-term monitoring of 17 sources including SFXTs and classical SGXBs across more than 4 orders of magnitude in X-ray luminosity on timescales from hundred seconds to years. We derived dynamic ranges, duty cycles, and luminosity distributions to highlight systematic differences that help discriminate between different theoretical models proposed to explain the differences between the wind accretion processes in SFXTs and classical SGXBs. Our follow-ups of the SFXT outbursts provide a steady advancement in the comprehension of the mechanisms triggering the high X-ray level emission of these sources. In particular, the observations of the outburst of the SFXT prototype IGR J17544-2619, when the source reached a peak X-ray luminosity of 3×10^{38} erg s^{-1}, challenged for the first time the maximum theoretical luminosity achievable by a wind-fed neutron star high mass X-ray binary. We propose that this giant outburst was due to the formation of a transient accretion disc around the compact object. We also created a catalogue of over 1000 BAT flares which we use to predict the observability and perspectives with future missions.

Gamma ray sources observation with the ARGO-YBJ detector

NASA Astrophysics Data System (ADS)

Vernetto, S.; ARGO-YBJ Collaboration

2011-02-01

In this paper we report on the observations of TeV gamma ray sources performed by the air shower detector ARGO-YBJ. The objects studied in this work are the blazar Markarian 421 and the extended galactic source MGROJ1908+06, monitored during ~2 years of operation. Mrk421 has been detected by ARGO-YBJ with a statistical significance of ~11 standard deviations. The observed TeV emission was highly variable, showing large enhancements of the flux during active periods. The study of the spectral behaviour during flares revealed a positive correlation of the hardness with the flux, as already reported in the past by the Whipple telescope, suggesting that this is a long term property of the source. ARGO-YBJ observed a strong correlation between TeV gamma rays and the X-ray flux measured by RXTM/ASM and SWIFT/BAT during the whole period, with a time lag compatible with zero, supporting the one-zone SSC model to describe the emission mechanism. MGROJ1908+06 has been detected by ARGO-YBJ with ~5 standard deviation of significance. From our data the source appears extended and the measured extension is σext = 0.48° --> σext = 0.48° -0.28+0.26 --> -0.28+0.26, in agreement with a previous HESS observation. The average flux is in marginal agreement with that reported by MILAGRO, but significantly higher than that obtained by HESS, suggesting a possible flux variability.

Global Properties of X-Ray Flashes and X-Ray-Rich Gamma-Ray Bursts Observed by Swift

NASA Astrophysics Data System (ADS)

Sakamoto, Takanori; Yamazaki, Ryo; Barthelmy, Scott; Gehrels, Neil; Osborne, Julian; Hullinger, Derek; Sato, Goro; Barbier, Louis; Cummings, Jay; Fenimore, Ed; Krimm, Hans; Lamb, Don; Markwardt, Craig; Palmer, David; Parsons, Ann; Stamatikos, Michael; Tueller, Jack

Takanori Sakamoto, Taka.Sakamoto@nasa.gov NASA Goddard Space Flight Center, Greenbelt, Maryland, United States Ryo Yamazaki, ryo@theo.phys.sci.hiroshima-u.ac.jp Hiroshima University, Higashi-Hiroshima, Japan Scott Barthelmy, scott@milkyway.gsfc.nasa.gov NASA GSFC, Greenbelt, Maryland, United States Neil Gehrels, gehrels@milkyway.gsfc.nasa.gov NASA Goddard Space Flight Center, Greenbelt, Maryland, United States Julian Osborne, julo@star.le.ac.uk University of Leicester, Leicester, United Kingdom Derek Hullinger, derek.hullinger@gmail.com Moxtek, Inc, Orem, Utah, United States Goro Sato, Goro.Sato@nasa.gov Goddard Space Flight Center, Greenbelt, Maryland, United States Louis Barbier, lmb@milkyway.gsfc.nasa.gov Goddard Space Flight Center, Greenbelt, Maryland, United States Jay Cummings, jayc@milkyway.gsfc.nasa.gov Goddard Space Flight Center, Greenbelt, Maryland, United States Ed Fenimore, efenimore@lanl.gov Los Alamos National Laboratory, Los Alamos, California, United States Hans Krimm, hans.krimm@nasa.gov Goddard Space Flight Center, Greenbelt, Maryland, United States Don Lamb, d-lamb@uchicago.edu University of Chicago, Chicago, Illinois, United States Craig Markwardt, Craig.Markwardt@nasa.gov Goddard Space Flight Center, Greenbelt, Maryland, United States David Palmer, palmer@lanl.gov Los Alamos National Laboratory, Los Alamos, California, United States Ann Parsons, Ann.M.Parsons@nasa.gov Goddard Space Flight Center, Greenbelt, Maryland, United States Michael Stamatikos, michael@milkyway.gsfc.nasa.gov Goddard Space Flight Center, Greenbelt, Maryland, United States Jack Tueller, jack.tueller@nasa.gov Goddard Space Flight Center, Greenbelt, Maryland, United States We present the spectral and temporal characteristics of the prompt emission and X-ray afterglow emission of X-ray flashes (XRFs) and X-ray-rich gamma-ray bursts (XRRs) detected and observed by Swift between December 2004 and September 2006. We compare these characteristics to a sample of conventional

Supergiant fast X-ray transients with Swift: Spectroscopic and temporal properties

NASA Astrophysics Data System (ADS)

Romano, P.; Mangano, V.; Ducci, L.; Esposito, P.; Farinelli, R.; Ceccobello, C.; Vercellone, S.; Burrows, D. N.; Kennea, J. A.; Krimm, H. A.; Gehrels, N.

2012-12-01

Supergiant fast X-ray transients (SFXTs) are a class of high-mass X-ray binaries with possible counterparts in the high energy gamma rays. The Swift SFXT Project1 has conducted a systematic investigation of the properties of SFTXs on timescales ranging from minutes to years and in several intensity states (from bright flares, to intermediate intensity states, and down to almost quiescence). We also performed broad-band spectroscopy of outbursts, and intensity-selected spectroscopy outside of outbursts. We demonstrated that while the brightest phase of the outburst only lasts a few hours, further activity is observed at lower fluxes for a remarkably longer time, up to weeks. Furthermore, we assessed the fraction of the time these sources spend in each phase, and their duty cycle of inactivity. We present the most recent results from our investigation. The spectroscopic and, most importantly, timing properties of SFXTs we have uncovered with Swift will serve as a guide in search for the high energy emission from these enigmatic objects.

Swift J1822.3-1606: A Probable New SGR in Ground Analysis of BAT Data

NASA Astrophysics Data System (ADS)

Cummings, J. R.; Burrows, D.; Campana, S.; Kennea, J. A.; Krimm, H. A.; Palmer, D. M.; Sakamoto, T.; Zan, S.

2011-07-01

At 2011-07-14 at 12:47:47.1 UTC, Swift-BAT triggered (#457261) on a previously unknown source, Swift J1822.3-1606. This was at the same time as Fermi-GBM trigger #332340476. Only a subthreshold source was detected onboard. There were two subsequent rate increases of similar size, probably from the same source at about T+26 sec and T+308 sec, the latter also causing a rate trigger with no significant source found onboard (#457263).

Characterization and Evolution of the Swift X-ray Telescope Instrumental Background

NASA Technical Reports Server (NTRS)

Hill, Joanne; Pagani, C.; Morris, D. C.; Racusin, J.; Grupe, D.; Vetere, L.; Stroh, M.; Falcone, A.; Kennea, J.; Burrows, D. N.;

Radio-gamma-ray connection and spectral evolution in 4C +49.22 (S4 1150+49): the Fermi, Swift and Planck view

DOE PAGES

Cutini, S.; Ciprini, S.; Orienti, M.; ...

2014-11-07

We report the Large Area Telescope on board the Fermi Gamma-ray Space Telescope detected a strong γ-ray flare on 2011 May 15 from a source identified as 4C +49.22, a flat spectrum radio quasar (FSRQ) also known as S4 1150+49. This blazar, characterized by a prominent radio–optical–X-ray jet, was in a low γ-ray activity state during the first years of Fermi observations. Simultaneous observations during the quiescent, outburst and post-flare γ-ray states were obtained by Swift, Planck and optical–IR–radio telescopes (Instituto Nacional de Astrofísica, Óptica y Electrónica, Catalina Sky Survey, Very Long Baseline Array [VLBA], Metsähovi). The flare is observedmore » from microwave to X-ray bands with correlated variability and the Fermi, Swift and Planck data for this FSRQ show some features more typical of BL Lac objects, like the synchrotron peak in the optical band that outshines the thermal blue-bump emission, and the X-ray spectral softening. Multi-epoch VLBA observations show the ejection of a new component close in time with the GeV γ-ray flare. In conclusion, the radio-to-γ-ray spectral energy distribution is modelled and fitted successfully for the outburst and the post-flare epochs using either a single flaring blob with two emission processes (synchrotron self-Compton (SSC), and external-radiation Compton), and a two-zone model with SSC-only mechanism.« less

Rapid Identification of GRB Afterglows with Swift/UVOT

NASA Technical Reports Server (NTRS)

Marshall, F. E.

2006-01-01

As part of the automated response to a new gamma-ray burst (GRB), the Ultraviolet and Optical Telescope (UVOT) instrument on Swift starts a 200-second exposure with the V filter within approximately 100 seconds of the BAT burst trigger. The instrument searches for sources in a 8' x 8' region, and sends the list of sources and a 160" x 160" sub-image centered on the burst position to the ground via Tracking and Data Relay Satellite System (TDRSS). These raw products and additional products calculated on the ground are then distributed through the GCN within a few minutes of the trigger. We describe the sensitivity of these data for detecting afterglows, summarize current results, and outline plans for rapidly distributing future detections.

Discovery and Evolution of the New Black Hole Candidate Swift J1539.2-6227 During Its 2008 Outburst

NASA Technical Reports Server (NTRS)

Krimm, H. A.; Tomsick, J. A.; Markwardt, C. B.; Brocksopp, C.; Grise, F.; Kaaret, P.; Romano, P.

2010-01-01

We report on the discovery by the Swift Gamma-Ray Burst Explorer of the black hole candidate Swift J1539.2-6227 and the subsequent course of an outburst beginning in November 2008 and lasting at least seven months. The source was discovered during normal observations with the Swift Burst Alert Telescope (BAT) on 2008 November 25. An extended observing campaign with the Rossi X-Ray Timing Explorer (RXTE) and Swift provided near-daily coverage over 176 days, giving us a rare opportunity to track the evolution of spectral and timing parameters with fine temporal resolution through a series of spectral states. The source was first detected in a hard state during which strong low-frequency quasiperiodic oscillations (QPOs) were detected. The QPOs persisted for about 35 days and a signature of the transition from the hard to soft intermediate states was seen in the timing data. The source entered a short-lived thermal state about 40 days after the start of the outburst. There were variations in spectral hardness as the source flux declined and returned to a hard state at the end of the outburst. The progression of spectral states and the nature of the timing features provide strong evidence that Swift J1539.2-6227 is a candidate black hole in a low-mass X-ray binary system.

Hard X-ray Variations in the Crab Nebula

NASA Technical Reports Server (NTRS)

Wilson-Hodge, Colleen A.; Cherry, M. L.; Case, G. L.; Baumgartner, W. H.; Beklen, E.; Bhat, P. N.; Briggs, M. S.; Camero-Arranz, A.; Chaplin, V.; Connaughton, V.;

Hard X-ray Variations in the Crab Nebula

NASA Technical Reports Server (NTRS)

Wilson-Hodge, Colleen A.; Cherry, M. L.; Case, G. L.; Baumgarter, W. H.; Beklen, E.; Bhat, P. N.; Briggs, M. S.; Camero-Arranz, A.; Chaplin, V.; Connaughton, V.;

Hard X-ray Variations in the Crab Nebula

NASA Technical Reports Server (NTRS)

Wilson-Hodge, Colleen A.; Cherry, M. L.; Case, G. L.; Baumgartner, W. H.; Beklen, E.; Bhat, P. N.; Briggs, M. S.; Camero-Arranz, A.; Connaughton, V.; Finger, M. H.;

Finding X-ray counterparts for unidentified sources in the 105 months BAT survey - 1

NASA Astrophysics Data System (ADS)

Stephen, J. B.; Bassani, L.; Malizia, A.; Masetti, N.; Ubertini, P.

2018-02-01

We provide X-ray counterparts for the unidentified Swift/BAT sources listed in the 105 month catalogue (Oh et al. 2018, ApJS in press). These associations were found by cross-correlating the list of U1,U2 and U3 sources with the ROSAT Bright (RASSBSC, Voges et al. 1999, A & A, 349, 389) and the XMM-Newton Slew (XMMSlew, Saxton et al. 2008, A & A, 480, 611) catalogues.

Development of a Spectral Model Based on Charge Transport for the Swift/BAT 32K CdZnTe Detector Array

NASA Technical Reports Server (NTRS)

Sato, Goro; Parsons, Ann; Hillinger, Derek; Suzuki, Masaya; Takahashi, Tadayuki; Tashiro, Makoto; Nakazawa, Kazuhiro; Okada, Yuu; Takahashi, Hiromitsu; Watanabe, Shin

2005-01-01

The properties of 32K CdZnTe (4 x 4 sq mm large, 2 mm thick) detectors have been studied in the pre-flight calibration of the Burst Alert Telescope (BAT) on-board the Swift Gamma-ray Burst Explorer (scheduled for launch in November 2004). In order to understand the energy response of the BAT CdZnTe array, we first quantify the mobility-lifetime (mu tau) products of carriers in individual CdZnTe detectors, which produce a position dependency in the charge induction efficiency and results in a low energy tail in the energy spectrum. Based on a new method utilizing (57)Co spectra obtained at different bias voltages, the mu tau for electrons ranges from 5.0 x 10(exp -4) to 1.0 x 10(exp -2) sq cm/V while the mu tau for holes ranges from 1.3 x 10(exp -5 to 1.8 x 10(exp -4) sq cm/V. We find that this wide distribution of mu tau products explains the large diversity in spectral shapes between CdZnTe detectors well. We also find that the variation of mu tau products can be attributed to the difference of crystal ingots or manufacturing harness. We utilize the 32K sets of extracted mu tau products to develop a spectral model of the detector. In combination with Monte Carlo simulations, we can construct a spectral model for any photon energy or any incident angle.

A missing population of short duration gamma-ray bursts

NASA Astrophysics Data System (ADS)

Troja, Eleonora

Short duration gamma-ray bursts (GRBs) are brief and intense flashes of gamma-ray radiation located at cosmological distances. NASA s Swift mission provided the first breakthrough observations connecting these high-energy transients to the coalescence of two compact objects, either two neutron stars (NSs) or a NS and a black hole (BH). Short GRBs are therefore prime candidate electromagnetic counterparts of gravitational wave sources detectable by advanced LIGO. Unfortunately, only a fraction of short GRBs visible by Swift is promptly identified by the on-board trigger system. A larger number of events fails to pass the on-board trigger selection and goes unnoticed. Luckily, this subset of events is not lost. It is instead downlinked through a low-priority channel and then archived. The goal of this ADAP proposal is to harvest this rich population of gamma-ray transients buried in the data archive. We propose to 1) systematically mine this untapped resource of the Swift archive in order to discover new short GRBs; 2) correlate the Swift untriggered dataset with signals detected by other facilities (e.g Fermi, INTEGRAL), at other wavelengths (e.g. fast radio bursts) or with other messengers (e.g. gravitational waves); 3) develop and release the relevant tools and documentation to the community in order to facilitate the exploitation of this valuable dataset in future years. The proposed research will significantly expand the current database of short GRBs, and aid multimessenger searches of transient phenomena. By studying the behavior of matter in extreme physical conditions, the formation of new black holes, and gravity, this project directly addresses NASA Strategic Objective 1.6, a key science goal in the area of Cosmic Origins.

Post-Launch Analysis of Swift's Gamma-Ray Burst Detection Sensitivity

NASA Technical Reports Server (NTRS)

Band, David L.

2005-01-01

The dependence of Swift#s detection sensitivity on a burst#s temporal and spectral properties shapes the detected burst population. Using s implified models of the detector hardware and the burst trigger syste m I find that Swift is more sensitive to long, soft bursts than CGRO# s BATSE, a reference mission because of its large burst database. Thu s Swift has increased sensitivity in the parameter space region into which time dilation and spectral redshifting shift high redshift burs ts.

The Evolution of Swift/BAT blazars and the origin of the MeV background

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ajello, M.; /SLAC /KIPAC, Menlo Park; Costamante, L.

2009-10-17

We use 3 years of data from the Swift/BAT survey to select a complete sample of X-ray blazars above 15 keV. This sample comprises 26 Flat-Spectrum Radio Quasars (FSRQs) and 12 BL Lac objects detected over a redshift range of 0.03 < z < 4.0. We use this sample to determine, for the first time in the 15-55 keV band, the evolution of blazars. We find that, contrary to the Seyfert-like AGNs detected by BAT, the population of blazars shows strong positive evolution. This evolution is comparable to the evolution of luminous optical QSOs and luminous X-ray selected AGNs. Wemore » also find evidence for an epoch-dependence of the evolution as determined previously for radio-quiet AGNs. We interpret both these findings as a strong link between accretion and jet activity. In our sample, the FSRQs evolve strongly, while our best-fit shows that BL Lacs might not evolve at all. The blazar population accounts for 10-20% (depending on the evolution of the BL Lacs) of the Cosmic X-ray background (CXB) in the 15-55 keV band. We find that FSRQs can explain the entire CXB emission for energies above 500 keV solving the mystery of the generation of the MeV background. The evolution of luminous FSRQs shows a peak in redshift (z{sub c} = 4.3 {+-} 0.5) which is larger than the one observed in QSOs and X-ray selected AGNs. We argue that FSRQs can be used as tracers of massive elliptical galaxies in the early Universe.« less

On the nature of the SWIFT/INTEGRAL source SWIFT J1508.6-4953 (also PMN J1508-4953)

NASA Astrophysics Data System (ADS)

Landi, R.; Bassani, L.; Masetti, N.; Bazzano, A.; Parisi, P.; Drave, S.; Goossens, M.

2012-06-01

This source is listed in the recent INTEGRAL/IBIS 9-year Galactic Hard X-ray Survey (Krivonos et al. 2012, arXiv:1205.3941) and also appears in the BAT 58-month catalogue (http://heasarc.nasa.gov/docs/swift/results/bs58mon/). It has been associated with the radio source PMN J1508-4953, also reported as a GeV emitter in the 2nd Fermi catalogue (Nolan et al. 2012, ApJS, 199, 31). We use archival Swift/XRT data to investigate its nature.

Bimodal Long-lasting Components in Short Gamma-Ray Bursts: Promising Electromagnetic Counterparts to Neutron Star Binary Mergers

NASA Astrophysics Data System (ADS)

Kisaka, Shota; Ioka, Kunihito; Sakamoto, Takanori

2017-09-01

Long-lasting emission of short gamma-ray bursts (GRBs) is crucial to reveal the physical origin of the central engine as well as to detect electromagnetic (EM) counterparts to gravitational waves (GWs) from neutron star binary mergers. We investigate 65 X-ray light curves of short GRBs, which is six times more than previous studies, by combining both Swift/BAT and XRT data. The light curves are found to consist of two distinct components at >5σ with bimodal distributions of luminosity and duration, I.e., extended (with a timescale of ≲103 s) and plateau emission (with a timescale of ≳103 s), which are likely the central engine activities, but not afterglows. The extended emission has an isotropic energy comparable to the prompt emission, while the plateau emission has ˜0.01-1 times this energy. Half (50%) of our sample has both components, while the other half is consistent with having both components. This leads us to conjecture that almost all short GRBs have both the extended and plateau emission. The long-lasting emission can be explained by the jets from black holes with fallback ejecta, and could power macronovae (or kilonovae) like GRB 130603B and GRB 160821B. Based on the observed properties, we quantify the detectability of EM counterparts to GWs, including the plateau emission scattered to the off-axis angle, with CALET/HXM, INTEGRAL/SPI-ACS, Fermi/GBM, MAXI/GSC, Swift/BAT, XRT, the future ISS-Lobster/WFI, Einstein Probe/WXT, and eROSITA.

Bimodal Long-lasting Components in Short Gamma-Ray Bursts: Promising Electromagnetic Counterparts to Neutron Star Binary Mergers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kisaka, Shota; Sakamoto, Takanori; Ioka, Kunihito, E-mail: kisaka@phys.aoyama.ac.jp, E-mail: tsakamoto@phys.aoyama.ac.jp, E-mail: kunihito.ioka@yukawa.kyoto-u.ac.jp

Long-lasting emission of short gamma-ray bursts (GRBs) is crucial to reveal the physical origin of the central engine as well as to detect electromagnetic (EM) counterparts to gravitational waves (GWs) from neutron star binary mergers. We investigate 65 X-ray light curves of short GRBs, which is six times more than previous studies, by combining both Swift /BAT and XRT data. The light curves are found to consist of two distinct components at >5 σ with bimodal distributions of luminosity and duration, i.e., extended (with a timescale of ≲10{sup 3} s) and plateau emission (with a timescale of ≳10{sup 3} s),more » which are likely the central engine activities, but not afterglows. The extended emission has an isotropic energy comparable to the prompt emission, while the plateau emission has ∼0.01–1 times this energy. Half (50%) of our sample has both components, while the other half is consistent with having both components. This leads us to conjecture that almost all short GRBs have both the extended and plateau emission. The long-lasting emission can be explained by the jets from black holes with fallback ejecta, and could power macronovae (or kilonovae) like GRB 130603B and GRB 160821B. Based on the observed properties, we quantify the detectability of EM counterparts to GWs, including the plateau emission scattered to the off-axis angle, with CALET /HXM, INTEGRAL /SPI-ACS, Fermi /GBM, MAXI /GSC, Swift /BAT, XRT, the future ISS-Lobster /WFI, Einstein Probe /WXT, and eROSITA .« less

Finding X-ray counterparts for unidentified sources in the 105 months BAT survey - 2

NASA Astrophysics Data System (ADS)

Stephen, J. B.; Bassani, L.; Malizia, A.; Masetti, N.; Ubertini, P.

2018-02-01

We provide X-ray counterparts for unidentified Swift/BAT sources in the 105 month catalogue (Oh et al. 2018, ApJS in press). They were found by cross-correlating the list of U1,U2 and U3 sources with the ROSAT Bright (RASSBSC, Voges et al. 1999, A & A, 349, 389) and XMM-Newton Slew (XMMSlew, Saxton et al. 2008, A & A, 480, 611) catalogues and optically identified as reported in Atel #11340.

Swift AND Fermi observations of x-ray flares: The case of late internal shock

DOE PAGES

Troja, Eleonora; Piro, Luigi; Vasileiou, Vlasios; ...

2015-04-07

Simultaneous Swift and Fermi observations of gamma-ray bursts (GRBs) offer a unique broadband view of their afterglow emission, spanning more than 10 decades in energy. We present the sample of X-ray flares observed by both Swift and Fermi during the first three years of Fermi operations. While bright in the X-ray band, X-ray flares are often undetected at lower (optical), and higher (MeV to GeV) energies. We show that this disfavors synchrotron self-Compton processes as the origin of the observed X-ray emission. We compare the broadband properties of X-ray flares with the standard late internal shock model, and find thatmore » in this scenario, X-ray flares can be produced by a late-time relativistic (Γ > 50) outflow at radii R ~ 10 13-10 14 cm. As a result, this conclusion holds only if the variability timescale is significantly shorter than the observed flare duration, and implies that X-ray flares can directly probe the activity of the GRB central engine.« less

SWIFT AND FERMI OBSERVATIONS OF X-RAY FLARES: THE CASE OF LATE INTERNAL SHOCK

DOE Office of Scientific and Technical Information (OSTI.GOV)

Troja, E.; Piro, L.; Vasileiou, V.

2015-04-10

Simultaneous Swift and Fermi observations of gamma-ray bursts (GRBs) offer a unique broadband view of their afterglow emission, spanning more than 10 decades in energy. We present the sample of X-ray flares observed by both Swift and Fermi during the first three years of Fermi operations. While bright in the X-ray band, X-ray flares are often undetected at lower (optical), and higher (MeV to GeV) energies. We show that this disfavors synchrotron self-Compton processes as the origin of the observed X-ray emission. We compare the broadband properties of X-ray flares with the standard late internal shock model, and find thatmore » in this scenario, X-ray flares can be produced by a late-time relativistic (Γ > 50) outflow at radii R ∼ 10{sup 13}-10{sup 14} cm. This conclusion holds only if the variability timescale is significantly shorter than the observed flare duration, and implies that X-ray flares can directly probe the activity of the GRB central engine.« less

Swift detection of an X-ray flare from the flaring blazar PKS 0502+049

NASA Astrophysics Data System (ADS)

Ojha, Roopesh; Dutka, Michael

2013-03-01

Following the recent gamma-ray flaring activity of the flat spectrum radio quasar PKS 0502+049 (also known as 2FGL J0505.5+0501, Nolan et al. 2012, ApJS, 199, 31), detected by Fermi LAT on 2013 March 2 (ATel#4858), a Swift target of opportunity observation was performed on March 13.

Swift Multi-wavelength Observing Campaigns: Strategies and Outcomes

NASA Technical Reports Server (NTRS)

Krimm, Hans A.

2007-01-01

The Swift gamma-ray burst explorer has been operating since December 2004 as both a gamma-ray burst (GRB) monitor and telescope and a multi-wavelength observatory, covering the energy range from V band and near UV to hard X rays above 150 keV. It is designed to rapidly repoint to observe newly discovered GRBs, and this maneuverability, combined with an easily changed observing program, allows Swift to also be an effective multiwavelength observatory for non-GRB targets, both as targets of opportunity and pre-planned multi-wavelength observing campaigns. Blazars are particularly attractive targets for coordinated campaigns with TeV experiments since many blazars are bright in both the hard X-ray and TeV energy ranges. Successful coordinated campaigns have included observations of 3C454.3 during its 2005 outburst. The latest Swift funding cycles allow for non- GRB related observations to be proposed. The Burst Alert Telescope on Swift also serves as a hard X-ray monitor with a public web page that includes light curves for over 400 X-ray sources and is used to alert the astronomical community about increased activity from both known and newly discovered sources. This presentation mill include Swift capabilities, strategies and policies for coordinated multi-wavelength observations as well as discussion of the potential outcomes of such campaigns.

On the connection of gamma-ray bursts and X-ray flashes in the BATSE and RHESSI databases

NASA Astrophysics Data System (ADS)

Řípa, J.; Mészáros, A.

2016-12-01

Classification of gamma-ray bursts (GRBs) into groups has been intensively studied by various statistical tests in previous years. It has been suggested that there was a distinct group of GRBs, beyond the long and short ones, with intermediate durations. However, such a group is not securely confirmed yet. Strangely, concerning the spectral hardness, the observations from the Swift and RHESSI satellites give different results. For the Swift/BAT database it is found that the intermediate-duration bursts might well be related to so-called X-ray flashes (XRFs). On the other hand, for the RHESSI dataset the intermediate-duration bursts seem to be spectrally too hard to be given by XRFs. The connection of the intermediate-duration bursts and XRFs for the BATSE database is not clear as well. The purpose of this article is to check the relation between XRFs and GRBs for the BATSE and RHESSI databases, respectively. We use an empirical definition of XRFs introduced by other authors earlier. For the RHESSI database we also use a transformation between the detected counts and the fluences based on the simulated detector response function. The purpose is to compare the hardnesses of GRBs with the definition of XRFs. There is a 1.3-4.2 % fraction of XRFs in the whole BATSE database. The vast majority of the BATSE short bursts are not XRFs because only 0.7-5.7 % of the short bursts can be given by XRFs. However, there is a large uncertainty in the fraction of XRFs among the intermediate-duration bursts. The fraction of 1-85 % of the BATSE intermediate-duration bursts can be related to XRFs. For the long bursts this fraction is between 1.0 % and 3.4 %. The uncertainties in these fractions are large, however it can be claimed that all BATSE intermediate-duration bursts cannot be given by XRFs. At least 79 % of RHESSI short bursts, at least 53 % of RHESSI intermediate-duration bursts, and at least 45 % of RHESSI long bursts should not be given by XRFs. A simulation of XRFs

The most luminous type 2 Active Galactic Nuclei of the Swift/ BAT catalog : Are they different?

NASA Astrophysics Data System (ADS)

Baer, Rudolf Erik; Oh, Kyuseok; Koss, Michael; Wong, Ivy; Schawinski, Kevin

2018-01-01

We present an analysis of the most luminous obscured AGN of the Swift/BAT 70 month catalog, which is based on an all-sky survey in the 14 – 195 keV energy range. This survey identified 838 AGN. Excluding Blazars and AGN close ( |gb| < 6o ) to the Galactic plane we select a sample of the 30 most luminous type 2 AGN. We analyze their emission line properties in the optical and infrared range and their radio properties using data in the 150 MHz to 22 GHz range. We obtained their black hole masses from the Swift/ BAT 70 month catalog and from a specific observation campaign in order to analyze the relationship of their luminosity to black hole mass and their Eddington ratios. We discuss whether these most luminous type 2 AGN have common characteristics, which differentiate them from all the type 2 AGN in the 70 month catalog.

Radial Angular Momentum Transfer and Magnetic Barrier for Short-type Gamma-Ray-burst Central Engine Activity

NASA Astrophysics Data System (ADS)

Liu, Tong; Liang, En-Wei; Gu, Wei-Min; Hou, Shu-Jin; Lei, Wei-Hua; Lin, Lin; Dai, Zi-Gao; Zhang, Shuang-Nan

2012-11-01

Soft extended emission (EE) following initial hard spikes up to 100 s was observed with Swift/BAT for about half of known short-type gamma-ray bursts (SGRBs). This challenges the conversional central engine models of SGRBs, i.e., compact star merger models. In the framework of black-hole-neutron-star merger models, we study the roles of radial angular momentum transfer in the disk and the magnetic barrier around the black hole in the activity of SGRB central engines. We show that radial angular momentum transfer may significantly prolong the lifetime of the accretion process, which may be divided into multiple episodes by the magnetic barrier. Our numerical calculations based on models of neutrino-dominated accretion flows suggest that disk mass is critical for producing the observed EE. In the case of the mass being ~0.8 M ⊙, our model can reproduce the observed timescale and luminosity of both the main and the EE episodes in a reasonable parameter set. The predicted luminosity of the EE component is lower than the observed EE within about one order of magnitude and the timescale is shorter than 20 s if the disk mass is ~0.2 M ⊙. Swift/BAT-like instruments may be not sensitive enough to detect the EE component in this case. We argue that the EE component could be a probe for the merger process and disk formation for compact star mergers.

Chandra and NuSTAR Follow-up Observations of Swift-BAT-selected AGNs

NASA Astrophysics Data System (ADS)

Marchesi, S.; Tremblay, L.; Ajello, M.; Marcotulli, L.; Paggi, A.; Cusumano, G.; La Parola, V.; Segreto, A.

2017-10-01

Based on current models of the cosmic X-ray background (CXB), heavily obscured active galactic nuclei (AGNs) are expected to make up ˜10% of the peak emission of the CXB and ˜20% of the total population of AGNs, yet few of these sources have been recorded and characterized in current surveys. Here we present the Chandra follow-up observation of 14 AGNs detected by Swift-BAT. For five sources in the sample, NuSTAR observations in the 3-80 keV band are also available. The X-ray spectral fitting over the 0.3-150 keV energy range allows us to determine the main X-ray spectral parameters, such as the photon index and the intrinsic absorption, of these objects and to make hypotheses on the physical structures responsible for the observed spectra. We find that 13 of the 14 objects are absorbed AGNs, and one is a candidate Compton-thick AGN, having intrinsic absorption {N}{{H}}> {10}24 cm-2. Finally, we verified that the use of NuSTAR observations is strategic to strongly constrain the properties of obscured AGNs, since the best-fit values we obtained for parameters such as the power-law photon index Γ and the intrinsic absorption {N}{{H}} changed sometimes significantly fitting the spectra with and without the use of NuSTAR data.

SWIFT-BAT HARD X-RAY SKY MONITORING UNVEILS THE ORBITAL PERIOD OF THE HMXB IGR J18219–1347

DOE Office of Scientific and Technical Information (OSTI.GOV)

La Parola, V.; Cusumano, G.; Segreto, A.

2013-09-20

IGR J18219–1347 is a hard X-ray source discovered by INTEGRAL in 2010. We have analyzed the X-ray emission of this source exploiting the Burst Alert Telescope (BAT) survey data up to 2012 March and the X-Ray Telescope (XRT) data that include also an observing campaign performed in early 2012. The source is detected at a significance level of ∼13 standard deviations in the 88 month BAT survey data, and shows a strong variability along the survey monitoring, going from high intensity to quiescent states. A timing analysis on the BAT data revealed an intensity modulation with a period of Pmore » {sub 0} = 72.44 ± 0.3 days. The significance of this modulation is about seven standard deviations in Gaussian statistics. We interpret it as the orbital period of the binary system. The light curve folded at P {sub 0} shows a sharp peak covering ∼30% of the period, superimposed to a flat level roughly consistent with zero. In the soft X-rays the source is detected only in 5 out of 12 XRT observations, with the highest recorded count rate corresponding to a phase close to the BAT folded light-curve peak. The long orbital period and the evidence that the source emits only during a small fraction of the orbit suggests that the IGR J18219–1347 binary system hosts a Be star. The broadband XRT+BAT spectrum is well modeled with a flat absorbed power law with a high-energy exponential cutoff at ∼11 keV.« less

The Swift Gamma-Ray Burst Host Galaxy Legacy Survey. I. Sample Selection and Redshift Distribution

NASA Technical Reports Server (NTRS)

Perley, D. A.; Kruhler, T.; Schulze, S.; Postigo, A. De Ugarte; Hjorth, J.; Berger, E.; Cenko, S. B.; Chary, R.; Cucchiara, A.; Ellis, R.;

NuSTAR Resolves the First Dual AGN above 10 keV in SWIFT J2028.5+2543

NASA Astrophysics Data System (ADS)

Koss, Michael J.; Glidden, Ana; Baloković, Mislav; Stern, Daniel; Lamperti, Isabella; Assef, Roberto; Bauer, Franz; Ballantyne, David; Boggs, Steven E.; Craig, William W.; Farrah, Duncan; Fürst, Felix; Gandhi, Poshak; Gehrels, Neil; Hailey, Charles J.; Harrison, Fiona A.; Markwardt, Craig; Masini, Alberto; Ricci, Claudio; Treister, Ezequiel; Walton, Dominic J.; Zhang, William W.

2016-06-01

We have discovered heavy obscuration in the dual active galactic nucleus (AGN) in the Swift/Burst Alert Telescope (BAT) source SWIFT J2028.5+2543 using Nuclear Spectroscopic Telescope Array (NuSTAR). While an early XMM-Newton study suggested the emission was mainly from NGC 6921, the superior spatial resolution of NuSTAR above 10 keV resolves the Swift/BAT emission into two sources associated with the nearby galaxies MCG +04-48-002 and NGC 6921 (z = 0.014) with a projected separation of 25.3 kpc (91″). NuSTAR's sensitivity above 10 keV finds both are heavily obscured to Compton-thick levels (N H ≈ (1-2) × 1024 cm-2) and contribute equally to the BAT detection ({L}10-50 {keV}{{int}} ≈ 6 × 1042 erg s-1). The observed luminosity of both sources is severely diminished in the 2-10 keV band ({L} 2-10 {keV}{{obs}}\\lt 0.1× {L} 2-10 {keV}{{int}}), illustrating the importance of >10 keV surveys like those with NuSTAR and Swift/BAT. Compared to archival X-ray data, MCG +04-48-002 shows significant variability (>3) between observations. Despite being bright X-ray AGNs, they are difficult to detect using optical emission-line diagnostics because MCG +04-48-002 is identified as a starburst/composite because of the high rates of star formation from a luminous infrared galaxy while NGC 6921 is only classified as a LINER using line detection limits. SWIFT J2028.5+2543 is the first dual AGN resolved above 10 keV and is the second most heavily obscured dual AGN discovered to date in the X-rays other than NGC 6240.

Galactic and extragalactic hydrogen in the X-ray spectra of Gamma Ray Bursts

NASA Astrophysics Data System (ADS)

Rácz, I. I.; Bagoly, Z.; Tóth, L. V.; Balázs, L. G.; Horváth, I.; Pintér, S.

2017-07-01

Two types of emission can be observed from gamma-ray bursts (GRBs): the prompt emission from the central engine which can be observed in gamma or X-ray (as a low energy tail) and the afterglow from the environment in X-ray and at shorter frequencies. We examined the Swift XRT spectra with the XSPEC software. The correct estimation of the galactic interstellar medium is very important because we observe the host emission together with the galactic hydrogen absorption. We found that the estimated intrinsic hydrogen column density and the X-ray flux depend heavily on the redshift and the galactic foreground hydrogen. We also found that the initial parameters of the iteration and the cosmological parameters did not have much effect on the fitting result.

Thermal Vacuum/Balance Test Results of Swift BAT with Loop Heat Pipe Thermal System

NASA Technical Reports Server (NTRS)

Choi, Michael K.

2004-01-01

The Swift Burst Alert Telescope (BAT) Detector Array is thermally well coupled to eight constant conductance heat pipes (CCHPs) embedded in the Detector Array Plate PAP), and two loop heat pipes (LHPs) transport heat from the CCHPs to a radiator. The CCHPs have ammonia as the working fluid and the LHPs have propylene as the working fluid. Precision heater controllers, which have adjustable set points in flight, are used to control the LHP compensation chamber and Detector Array xA1 ASIC temperatures. The radiator has AZ-Tek's AZW-LA-II low solar absorptance white paint as the thermal coating, and is located on the anti-sun side of the spacecraft. A thermal balance (T/B) test on the BAT was successfully completed. It validated that the thermal design satisfies the temperature requirements of the BAT in the flight thermal environments. Instrument level and observatory level thermal vacuum (TN) cycling tests of the BAT Detector Array by using the LHP thermal system were successfully completed. This paper presents the results of the T/B test and T N cycling tests.

Observations of short gamma-ray bursts.

PubMed

Fox, Derek B; Roming, Peter W A

2007-05-15

We review recent observations of short-hard gamma-ray bursts and their afterglows. The launch and successful ongoing operations of the Swift satellite, along with several localizations from the High-Energy Transient Explorer mission, have provoked a revolution in short-burst studies: first, by quickly providing high-quality positions to observers; and second, via rapid and sustained observations from the Swift satellite itself. We make a complete accounting of Swift-era short-burst localizations and proposed host galaxies, and discuss the implications of these observations for the distances, energetics and environments of short bursts, and the nature of their progenitors. We then review the physical modelling of short-burst afterglows: while the simplest afterglow models are inadequate to explain the observations, there have been several notable successes. Finally, we address the case of an unusual burst that threatens to upset the simple picture in which long bursts are due to the deaths of massive stars, and short bursts to compact-object merger events.

A Correlation Between the Intrinsic Brightness and Average Decay Rate of Gamma-Ray Burst X-Ray Afterglow Light Curves

NASA Technical Reports Server (NTRS)

Racusin, J. L.; Oates, S. R.; De Pasquale, M.; Kocevski, D.

2016-01-01

We present a correlation between the average temporal decay (alpha X,avg, greater than 200 s) and early-time luminosity (LX,200 s) of X-ray afterglows of gamma-ray bursts as observed by the Swift X-ray Telescope. Both quantities are measured relative to a rest-frame time of 200 s after the gamma-ray trigger. The luminosity â€" average decay correlation does not depend on specific temporal behavior and contains one scale-independent quantity minimizing the role of selection effects. This is a complementary correlation to that discovered by Oates et al. in the optical light curves observed by the Swift Ultraviolet Optical Telescope. The correlation indicates that, on average, more luminous X-ray afterglows decay faster than less luminous ones, indicating some relative mechanism for energy dissipation. The X-ray and optical correlations are entirely consistent once corrections are applied and contamination is removed. We explore the possible biases introduced by different light-curve morphologies and observational selection effects, and how either geometrical effects or intrinsic properties of the central engine and jet could explain the observed correlation.

A targeted LIGO-Virgo search for gravitational waves associated with gamma-ray bursts using low-threshold swift GRB triggers

NASA Astrophysics Data System (ADS)

Harstad, Emelie D.

Gamma-ray bursts (GRBs) are short, intense ashes of 0.1-1 MeV electromagnetic radiation that are routinely observed by Earth orbiting satellites. The sources of GRBs are known to be extragalactic and located at cosmological distances. Due to the extremely high isotropic equivalent energies of GRBs, which are on the order of Eiso˜1054 erg, the gamma-ray emission is believed to be collimated, making them observable only when they are directed towards Earth. The favored progenitor models of GRBs are also believed to emit gravitational waves that would be observable by the current generation of ground-based interferometric gravitational wave detectors. The LIGO (Laser Interferometer Gravitational-Wave Observatory) and Virgo instruments operated near design sensitivity and collected more than a year of triple coincident data during the S5/VSR1 science run, which spanned the two year interval between November 2005 and October 2007. During this time, GRB detections were being made by the NASA/Goddard Swift Burst Alert Telescope at a rate of approximately 0.3 per day, producing a collection of triggers that has since been used in a coincident GRB-GW burst search with data from the LIGO-Virgo interferometer network. This dissertation describes the search for gravitational waves using the times and locations of 123 below-threshold potential GRB triggers from Swift over the same time period. Although most of the below-threshold triggers are likely false alarms, there is reason to believe that some are the result of actual faintly-observed GRB events. Recent GRB observations indicate that the local rate of low-luminosity GRBs is much higher than previously believed. This result, combined with the possibility of discovering a rare nearby GRB event accompanied by gravitational waves, is what motivates this search. The analysis results indicate no evidence for gravitational waves associated with any of the below-threshold triggers. A median distance lower limit of ˜16 Mpc was

The Chase to Capture Gamma Ray Bursts

NASA Technical Reports Server (NTRS)

Gehrels, Neil

2008-01-01

Gamma-ray bursts are the most powerful explosions in the universe, thought to be the birth cries of black holes. It has taken 40 years of international cooperation and competition to begin to unravel the mystery of their origin. The most recent chapter in this field is being written by the SWIFT mission, a fast-response satellite with 3 power telescopes. An international team from countries all over the world participates in the chase to capture the fading light of bursts detected by SWIFT. This talk will discuss the challenges and excitement of building this space observatory. New results will be presented on our growing understanding of exploding stars and fiery mergers of orbiting stars.

VizieR Online Data Catalog: IR photometry of AGNs in Swift/BAT 70 month cat. (Ichikawa+, 2017)

NASA Astrophysics Data System (ADS)

Ichikawa, K.; Ricci, C.; Ueda, Y.; Matsuoka, K.; Toba, Y.; Kawamuro, T.; Trakhtenbrot, B.; Koss, M. J.

2017-08-01

Our initial sample contains the 834 AGNs reported in the 70 month Swift/BAT catalog (Baumgartner+ 2013, J/ApJS/207/19), 105 of which are blazars. Of the remaining 729 sources, 697 sources have secure redshift information as presented in Ricci et al. (2016, ApJ, submitted). Next, we removed galaxy pairs or interacting galaxies not resolved in the BAT survey. Further, the 606 sources located at higher galactic latitudes with |b|>10° were selected to reduce the contamination in the crowded region through IR catalog matching. (1 data file).

The Swift MIDEX Education and Public Outreach Program

NASA Astrophysics Data System (ADS)

Feigelson, E. D.; Cominsky, L. R.; Whitlock, L. A.

1999-12-01

The Swift satellite is dedicated to an understanding of gamma-ray bursts, the most powerful explosions in the Universe since the Big Bang. A multifaceted E/PO program associated with Swift is planned. Web sites will be constructed, including sophisticated interactive learning environments for combining science concepts with with exploration and critical thinking for high school students. The award-winning instructional television program "What's in the News?", produced by Penn State Public Broadcasting and reaching several million 4th-7th graders, will create a series of broadcasts on Swift and space astronomy. A teachers' curricular guide on space astronomy will be produced by UC-Berkeley's Lawrence Hall of Science as part of their highly successful GEMS guides promoting inquiry-based science education. Teacher workshops will be conducted in the Appalachian region and nationwide to testbed and disseminate these products. We may also assist the production of gamma-ray burst museum exhibits. All aspects of the program will be overseen by a Swift Education Committee and assessed by a professional educational evaluation firm. This effort will be supported by the NASA Swift MIDEX contract to Penn State.

The Swift X-Ray Te1escope: Status and Performance

NASA Technical Reports Server (NTRS)

Burrows, David N.; Kennea, J.A.; Abbey, A.F.; Beardmore, A.; Campana, S.; Capalbi, M.; Chincarini, G.; Cusumano, G.; Evans, P.A.; Hill, J.E.;

Hard X-ray spectral investigations of gamma-ray bursts 120521C and 130606A at high-redshift z ˜ 6

NASA Astrophysics Data System (ADS)

Yasuda, T.; Urata, Y.; Enomoto, J.; Tashiro, M. S.

2017-04-01

This study presents a temporal and spectral analysis of the prompt emission of two high-redshift gamma-ray bursts (GRBs), 120521C at z ˜ 6 and 130606A at z ˜ 5.91, using data obtained from the Swift-XRT/BAT and the Suzaku-WAM simultaneously. Based on follow-up XRT observations, the longest durations of the prompt emissions were approximately 80 s (120521C) and 360 s (130606A) in the rest-frames of the two GRBs. These objects are thus categorized as long-duration GRBs; however, the durations are short compared with the predicted duration of GRBs originating from first-generation stars. Because of the wide bandpass of the instruments, covering the ranges 15 keV-5 MeV (BAT-WAM) and 0.3 keV-5.0 MeV (XRT-BAT-WAM), we could successfully determine the νFν peak energies E_peak^src in the rest-frame and isotropic-equivalent radiated energies Eiso; E^src_peak = 682^{+845}_{-207} keV and E_iso = (8. 25^{+2.24}_{-1.96}) × 10^{52} erg for 120521C, and E^src_peak = 1209^{+553}_{-304} keV and E_iso = (2.82^{+0.17}_{-0.71}) × 10^{53} erg for 130606A. These obtained characteristic parameters are in accordance with the well-known relationship between E_peak^src and Eiso (Amati relationship). In addition, we examined the relationships between E_peak^src and the 1-s peak luminosity, Lp, and between E_peak^src and the geometrical corrected radiated energy, Eγ, and confirmed the E_peak^src-Lp (Yonetoku) and E_peak^src-Eγ (Ghirlanda) relationships. The results imply that these high-redshift GRBs at z ˜ 6, which are expected to have radiated during the reionization epoch, have properties similar to those of low-redshift GRBs regarding X-ray prompt emission.

VizieR Online Data Catalog: Unidentified gamma-ray sources. IV. X-ray (Paggi+, 2013)

NASA Astrophysics Data System (ADS)

Paggi, A.; Massaro, F.; D'Abrusco, R.; Smith, H. A.; Masetti, N.; Giroletti, M.; Tosti, G.; Funk, S.

2013-11-01

The initial sample considered in our analysis is constituted by the 299 unidentified gamma-ray sources (UGSs) in the 2FGL catalog that do not present any γ-ray analysis flag (Nolan et al. 2012, Cat. J/ApJS/199/31). After Fermi was launched, the Swift XRT Survey of Fermi Unassociated Sources was started in order to perform follow-up observations of the unidentified gamma-ray sources (UGSs) in an attempt to find their potential X-ray counterparts (PI: A. Falcone). We analyze all data collected between the beginning of the follow-up program until 2013 March 31. We note that 203 of the 205 UGSs that constitute our sample have been also observed in the optical and UV by UVOT. We then produced for each X-ray observation the corresponding merged UVOT event files, adopting standard procedures. (6 data files).

The first ten years of Swift supernovae

NASA Astrophysics Data System (ADS)

Brown, Peter J.; Roming, Peter W. A.; Milne, Peter A.

2015-09-01

The Swift Gamma Ray Burst Explorer has proven to be an incredible platform for studying the multiwavelength properties of supernova explosions. In its first ten years, Swift has observed over three hundred supernovae. The ultraviolet observations reveal a complex diversity of behavior across supernova types and classes. Even amongst the standard candle type Ia supernovae, ultraviolet observations reveal distinct groups. When the UVOT data is combined with higher redshift optical data, the relative populations of these groups appear to change with redshift. Among core-collapse supernovae, Swift discovered the shock breakout of two supernovae and the Swift data show a diversity in the cooling phase of the shock breakout of supernovae discovered from the ground and promptly followed up with Swift. Swift observations have resulted in an incredible dataset of UV and X-ray data for comparison with high-redshift supernova observations and theoretical models. Swift's supernova program has the potential to dramatically improve our understanding of stellar life and death as well as the history of our universe.

Searching for high-energy gamma-ray counterparts to gravitational-wave sources with Fermi-LAT: A needle in a haystack

DOE PAGES

Vianello, G.; Omodei, N.; Chiang, J.; ...

2017-05-20

At least a fraction of gravitational-wave (GW) progenitors are expected to emit an electromagnetic (EM) signal in the form of a short gamma-ray burst (sGRB). Discovering such a transient EM counterpart is challenging because the LIGO/VIRGO localization region is much larger (several hundreds of square degrees) than the field of view of X-ray, optical, and radio telescopes. The Fermi Large Area Telescope (LAT) has a wide field of view (~2.4 sr) and detects ~2–3 sGRBs per year above 100 MeV. It can detect them not only during the short prompt phase, but also during their long-lasting high-energy afterglow phase. If other wide-field, high-energy instruments such as Fermi-GBM, Swift-BAT, or INTEGRAL-ISGRI cannot detect or localize with enough precision an EM counterpart during the prompt phase, the LAT can potentially pinpoint it withmore » $$\\lesssim 10$$ arcmin accuracy during the afterglow phase. This routinely happens with gamma-ray bursts. Moreover, the LAT will cover the entire localization region within hours of any triggers during normal operations, allowing the γ-ray flux of any EM counterpart to be measured or constrained. As a result, we illustrate two new ad hoc methods to search for EM counterparts with the LAT and their application to the GW candidate LVT151012.« less

Searching for high-energy gamma-ray counterparts to gravitational-wave sources with Fermi-LAT: A needle in a haystack

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vianello, G.; Omodei, N.; Chiang, J.

At least a fraction of gravitational-wave (GW) progenitors are expected to emit an electromagnetic (EM) signal in the form of a short gamma-ray burst (sGRB). Discovering such a transient EM counterpart is challenging because the LIGO/VIRGO localization region is much larger (several hundreds of square degrees) than the field of view of X-ray, optical, and radio telescopes. The Fermi Large Area Telescope (LAT) has a wide field of view (~2.4 sr) and detects ~2–3 sGRBs per year above 100 MeV. It can detect them not only during the short prompt phase, but also during their long-lasting high-energy afterglow phase. If other wide-field, high-energy instruments such as Fermi-GBM, Swift-BAT, or INTEGRAL-ISGRI cannot detect or localize with enough precision an EM counterpart during the prompt phase, the LAT can potentially pinpoint it withmore » $$\\lesssim 10$$ arcmin accuracy during the afterglow phase. This routinely happens with gamma-ray bursts. Moreover, the LAT will cover the entire localization region within hours of any triggers during normal operations, allowing the γ-ray flux of any EM counterpart to be measured or constrained. As a result, we illustrate two new ad hoc methods to search for EM counterparts with the LAT and their application to the GW candidate LVT151012.« less

Search for very high-energy gamma-ray emission from the microquasar Cygnus X-1 with the MAGIC telescopes

NASA Astrophysics Data System (ADS)

Ahnen, M. L.; Ansoldi, S.; Antonelli, L. A.; Arcaro, C.; Babić, A.; Banerjee, B.; Bangale, P.; Barres de Almeida, U.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Bernardini, E.; Berti, A.; Bhattacharyya, W.; Biasuzzi, B.; Biland, A.; Blanch, O.; Bonnefoy, S.; Bonnoli, G.; Carosi, R.; Carosi, A.; Chatterjee, A.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; Cumani, P.; da Vela, P.; Dazzi, F.; de Angelis, A.; de Lotto, B.; de Oña Wilhelmi, E.; di Pierro, F.; Doert, M.; Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Einecke, S.; Eisenacher Glawion, D.; Elsaesser, D.; Engelkemeier, M.; Fallah Ramazani, V.; Fernández-Barral, A.; Fidalgo, D.; Fonseca, M. V.; Font, L.; Fruck, C.; Galindo, D.; García López, R. J.; Garczarczyk, M.; Gaug, M.; Giammaria, P.; Godinović, N.; Gora, D.; Guberman, D.; Hadasch, D.; Hahn, A.; Hassan, T.; Hayashida, M.; Herrera, J.; Hose, J.; Hrupec, D.; Ishio, K.; Konno, Y.; Kubo, H.; Kushida, J.; Kuveždić, D.; Lelas, D.; Lindfors, E.; Lombardi, S.; Longo, F.; López, M.; Maggio, C.; Majumdar, P.; Makariev, M.; Maneva, G.; Manganaro, M.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martínez, M.; Mazin, D.; Menzel, U.; Minev, M.; Mirzoyan, R.; Moralejo, A.; Moreno, V.; Moretti, E.; Neustroev, V.; Niedzwiecki, A.; Nievas Rosillo, M.; Nilsson, K.; Ninci, D.; Nishijima, K.; Noda, K.; Nogués, L.; Paiano, S.; Palacio, J.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Paredes-Fortuny, X.; Pedaletti, G.; Peresano, M.; Perri, L.; Persic, M.; Prada Moroni, P. G.; Prandini, E.; Puljak, I.; Garcia, J. R.; Reichardt, I.; Rhode, W.; Ribó, M.; Rico, J.; Righi, C.; Saito, T.; Satalecka, K.; Schroeder, S.; Schweizer, T.; Sitarek, J.; Šnidarić, I.; Sobczynska, D.; Stamerra, A.; Strzys, M.; Surić, T.; Takalo, L.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Torres, D. F.; Torres-Albà, N.; Treves, A.; Vanzo, G.; Vazquez Acosta, M.; Vovk, I.; Ward, J. E.; Will, M.; Zarić, D.; MAGIC Collaboration; Bosch-Ramon, V.; Pooley, G. G.; Trushkin, S. A.; Zanin, R.

2017-12-01

The microquasar Cygnus X-1 displays the two typical soft and hard X-ray states of a black hole transient. During the latter, Cygnus X-1 shows a one-sided relativistic radio-jet. Recent detection of the system in the high energy (HE; E ≳ 60 MeV) gamma-ray range with Fermi-LAT associates this emission with the outflow. Former MAGIC observations revealed a hint of flaring activity in the very high-energy (VHE; E ≳ 100 GeV) regime during this X-ray state. We analyse ∼97 h of Cygnus X-1 data taken with the MAGIC telescopes between July 2007 and October 2014. To shed light on the correlation between hard X-ray and VHE gamma rays as previously suggested, we study each main X-ray state separately. We perform an orbital phase-folded analysis to look for variability in the VHE band. Additionally, to place this variability behaviour in a multiwavelength context, we compare our results with Fermi-LAT, AGILE, Swift-BAT, MAXI, RXTE-ASM, AMI and RATAN-600 data. We do not detect Cygnus X-1 in the VHE regime. We establish upper limits for each X-ray state, assuming a power-law distribution with photon index Γ = 3.2. For steady emission in the hard and soft X-ray states, we set integral upper limits at 95 per cent confidence level for energies above 200 GeV at 2.6 × 10-12 photons cm-2 s-1 and 1.0 × 10-11 photons cm-2 s-1, respectively. We rule out steady VHE gamma-ray emission above this energy range, at the level of the MAGIC sensitivity, originating in the interaction between the relativistic jet and the surrounding medium, while the emission above this flux level produced inside the binary still remains a valid possibility.

Gamma-Ray Emission from the Broad-Line Radio Galaxy 3C 111

NASA Technical Reports Server (NTRS)

Hartman, Robert C.; Kadler, M.; Tueller, Jack

2008-01-01

The broad-line radio galaxy 3C 111 has been suggested as the counterpart of the y-ray source 3EG J0416+3650. While 3C 111 meets most of the criteria for a high-probability identification, like a bright flat-spectrum radio core and a blazar-like broadband SED, in the Third EGRET Catalog, the large positional offset of about 1.5' put 3C 111 outside the 99% probability region for 3EG J0416+3650, making this association questionable. We present a re-analysis of all available archival data for 3C 111 from the EGRET archives, resulting in detection of variable hard-spectrum high-energy gamma-ray emission above 1000 MeV from a position close to the nominal position of 3C 111, in three separate viewing periods (VPs), at a 3sigma level in each. A second variable hard-spectrum source is present nearby. At >100 MeV, one variable soft-spectrum source seems to account for most of the EGRET-detected emission of 3EG J0416+3650. A follow-up Swift UVOT/XRT observation reveals one moderately bright X-ray source in the error box of 3EG J0416+3650, but because of the large EGRET position uncertainty, it is not certain that the X-ray and gamma-ray sources are associated. Another Swift observation near the second (unidentified) hard gamma-ray source detected no X-ray source nearby.

Automatic Analysis of Swift-XRT data

NASA Astrophysics Data System (ADS)

Evans, P. A.; Tyler, L. G.; Beardmore, A. P.; Osborne, J. P.

2008-08-01

The Swift spacecraft detects and autonomously observes ˜100 Gamma Ray Bursts (GRBs) per year, ˜96% of which are detected by the X-ray telescope (XRT). GRBs are accompanied by optical transients and the field of ground-based follow-up of GRBs has expanded significantly over the last few years, with rapid response instruments capable of responding to Swift triggers on timescales of minutes. To make the most efficient use of limited telescope time, follow-up astronomers need accurate positions of GRBs as soon as possible after the trigger. Additionally, information such as the X-ray light curve, is of interest when considering observing strategy. The Swift team at Leicester University have developed techniques to improve the accuracy of the GRB positions available from the XRT, and to produce science-grade X-ray light curves of GRBs. These techniques are fully automated, and are executed as soon as data are available.

Identification of the Hard X-Ray Source Dominating the E > 25 keV Emission of the Nearby Galaxy M31

NASA Technical Reports Server (NTRS)

Yukita, M.; Ptak, A.; Hornschemeier, A. E.; Wik, D.; Maccarone, T.J.; Pottschmidt, Katja; Zezas, A.; Antoniou, V.; Ballhausen, R.; Lehmer, B.D.;

Identification of the Hard X-Ray Source Dominating the E > 25 keV Emission of the Nearby Galaxy M31

NASA Technical Reports Server (NTRS)

Yukita, M.; Ptak, A.; Hornschemeier, A. E.; Wik, D.; Maccarone, T. J.; Pottschmidt, K.; Zezas, A.; Antoniou, V.; Ballhausen, R.; Lehmer, B. D.;

The Swift Era

NASA Technical Reports Server (NTRS)

Gehrels, Neil; Burrows, David N.

2011-01-01

The study of gamma-ray bursts (GRBs) remains highly dependent on the capabilities of the observatories that carry out the measurements. The large detector size of BATSE produced an impressively large sample of GRBs for duration and sky distribution studies. The burst localization and repointing capabilities of BeppoSAX led to breakthroughs in host and progenitor understanding. The next phase in our understanding of GRBs is being provided by the Swift mission. In this chapter we discuss the capabilities and findings of the Swift mission and their relevance to our understanding of GRBs. We also examine what is being learned about star formation, supernovae and the early Universe from the new results. In each section of the chapter, we close with a discussion of the new questions and issues raised by the Swift findings.

Gamma Ray Bursts - Observations

NASA Technical Reports Server (NTRS)

Gehrels, N.; Cannizzo, J. K.

2010-01-01

We are in an exciting period of discovery for gamma-ray bursts. The Swift observatory is detecting 100 bursts per year, providing arcsecond localizations and sensitive observations of the prompt and afterglow emission. The Fermi observatory is observing 250 bursts per year with its medium-energy GRB instrument and about 10 bursts per year with its high-energy LAT instrument. In addition, rapid-response telescopes on the ground are providing new capabilities to study optical emission during the prompt phase and spectral signatures of the host galaxies. The combined data set is enabling great advances in our understanding of GRBs including afterglow physics, short burst origin, and high energy emission.

NASA's Swift Education and Public Outreach Program

NASA Astrophysics Data System (ADS)

Plait, P.; Silva, S.; Graves, T.; Simonnet, A.; Cominsky, L.

2003-05-01

Few astronomical objects excite students more than big explosions and black holes. Gamma Ray Bursts (GRBs) are both: powerful explosions that signal the births of black holes. NASA's Swift satellite mission, set for launch in December 2003, will detect hundreds of black holes over its two-year nominal mission timeline. The NASA Education and Public Outreach (E/PO) group at Sonoma State University is leading the Swift E/PO effort, using the Swift mission to engage students in science and math learning. We have partnered with the Lawrence Hall of Science to create a "Great Explorations in Math and Science" guide entitled "Invisible Universe: from Radio Waves to Gamma Rays," which uses GRBs to introduce students to the electromagnetic spectrum and the scale of energies in the Universe. Three to four segments about Swift are being broadcast each year to millions of middle-school children as part of "What's In The News," an educational television series based at Penn State University. We are also creating new standards-based activities for grades 9-12 using GRBs: one activity puts the students in the place of astronomers 20 years ago, trying to sort out various types of stellar explosions that create high-energy radiation. Another mimics the use of the Interplanetary Network to let students figure out the direction to a GRB. Post-launch materials will include magazine articles about Swift and GRBs, more formal educational activities, and additions to the Swift E/PO website (http://swift.sonoma.edu) that will excite and inspire students to learn more about space science.

VizieR Online Data Catalog: GRB Swift X-ray light curves analysis (Margutti+, 2013)

NASA Astrophysics Data System (ADS)

Margutti, R.; Zaninoni, E.; Bernardini, M. G.; Chincarini, G.; Pasotti, F.; Guidorzi, C.; Angelini, L.; Burrows, D. N.; Capalbi, M.; Evans, P. A.; Gehrels, N.; Kennea, J.; Mangano, V.; Moretti, A.; Nousek, J.; Osborne, J. P.; Page, K. L.; Perri, M.; Racusin, J.; Romano, P.; Sbarufatti, B.; Stafford, S.; Stamatikos, M.

2013-11-01

We present a comprehensive statistical analysis of Swift X-ray light curves of gamma-ray bursts (GRBs) collecting data from more than 650 GRBs discovered by Swift and other facilities. The unprecedented sample size allows us to constrain the rest-frame X-ray properties of GRBs from a statistical perspective, with particular reference to intrinsic time-scales and the energetics of the different light-curve phases in a common rest-frame 0.3-30keV energy band. Temporal variability episodes are also studied and their properties constrained. Two fundamental questions drive this effort: (i) Does the X-ray emission retain any kind of 'memory' of the prompt γ-ray phase? (ii) Where is the dividing line between long and short GRB X-ray properties? We show that short GRBs decay faster, are less luminous and less energetic than long GRBs in the X-rays, but are interestingly characterized by similar intrinsic absorption. We furthermore reveal the existence of a number of statistically significant relations that link the X-ray to prompt γ-ray parameters in long GRBs; short GRBs are outliers of the majority of these two-parameter relations. However and more importantly, we report on the existence of a universal three-parameter scaling that links the X-ray and the γ-ray energy to the prompt spectral peak energy of both long and short GRBs: EX,iso{prop.to}E1.00+/-0.06γ,iso/E0.60+/-0.10pk. (3 data files).

Introduction: recent developments in the study of gamma-ray bursts.

PubMed

Wells, Alan; Wijers, Ralph A M J; Rees, Martin J

2007-05-15

Gamma-ray bursts (GRBs) are immensely powerful explosions, originating at cosmological distances, whose outbursts persist for durations ranging from milliseconds to tens of seconds or more. In these brief moments, the explosions radiate more energy than the Sun will release in its entire 10Gyr lifetime. Current theories attribute these phenomena to the final collapse of a massive star, or the coalescence of a binary system induced by gravity wave emission. New results from Swift and related programmes offer fresh understanding of the physics of GRBs, and of the local environments and host galaxies of burst progenitors. Bursts found at very high red shifts are new tools for exploring the intergalactic medium, the first stars and the earliest stages of galaxy formation. This Royal Society Discussion Meeting has brought together leading figures in the field, together with young researchers and students, to discuss and review the latest results from NASA's Swift Gamma-ray Burst Observatory and elsewhere, and to examine their impact on current understanding of the observed phenomena.

NASA's Swift Education and Public Outreach Program

NASA Astrophysics Data System (ADS)

Cominsky, L. R.; Graves, T.; Plait, P.; Silva, S.; Simonnet, A.

2004-08-01

Few astronomical objects excite students more than big explosions and black holes. Gamma Ray Bursts (GRBs) are both: powerful explosions that signal the births of black holes. NASA's Swift satellite mission, set for launch in Fall 2004, will detect hundreds of black holes over its two-year nominal mission timeline. The NASA Education and Public Outreach (E/PO) group at Sonoma State University is leading the Swift E/PO effort, using the Swift mission to engage students in science and math learning. We have partnered with the Lawrence Hall of Science to create a ``Great Explorations in Math and Science" guide entitled ``Invisible Universe: from Radio Waves to Gamma Rays," which uses GRBs to introduce students to the electromagnetic spectrum and the scale of energies in the Universe. We have also created new standards-based activities for grades 9-12 using GRBs: one activity puts the students in the place of astronomers 20 years ago, trying to sort out various types of stellar explosions that create high-energy radiation. Another mimics the use of the Interplanetary Network to let students figure out the direction to a GRB. Post-launch materials will include magazine articles about Swift and GRBs, and live updates of GRB information to the Swift E/PO website that will excite and inspire students to learn more about space science.

DISCOVERY OF HIGH-ENERGY AND VERY HIGH ENERGY {gamma}-RAY EMISSION FROM THE BLAZAR RBS 0413

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aliu, E.; Archambault, S.; Arlen, T.

2012-05-10

We report on the discovery of high-energy (HE; E > 0.1 GeV) and very high energy (VHE; E > 100 GeV) {gamma}-ray emission from the high-frequency-peaked BL Lac object RBS 0413. VERITAS, a ground-based {gamma}-ray observatory, detected VHE {gamma} rays from RBS 0413 with a statistical significance of 5.5 standard deviations ({sigma}) and a {gamma}-ray flux of (1.5 {+-} 0.6{sub stat} {+-} 0.7{sub syst}) Multiplication-Sign 10{sup -8} photons m{sup -2} s{sup -1} ({approx}1% of the Crab Nebula flux) above 250 GeV. The observed spectrum can be described by a power law with a photon index of 3.18 {+-} 0.68{sub stat}more » {+-} 0.30{sub syst}. Contemporaneous observations with the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope detected HE {gamma} rays from RBS 0413 with a statistical significance of more than 9{sigma}, a power-law photon index of 1.57 {+-} 0.12{sub stat}+{sup 0.11}{sub -0.12sys}, and a {gamma}-ray flux between 300 MeV and 300 GeV of (1.64 {+-} 0.43{sub stat}{sup +0.31}{sub -0.22sys}) Multiplication-Sign 10{sup -5} photons m{sup -2} s{sup -1}. We present the results from Fermi-LAT and VERITAS, including a spectral energy distribution modeling of the {gamma}-ray, quasi-simultaneous X-ray (Swift-XRT), ultraviolet (Swift-UVOT), and R-band optical (MDM) data. We find that, if conditions close to equipartition are required, both the combined synchrotron self-Compton/external-Compton and the lepto-hadronic models are preferred over a pure synchrotron self-Compton model.« less

Gamma-Ray Bursts and Cosmology

NASA Technical Reports Server (NTRS)

Norris, Jay P.

2003-01-01

The unrivalled, extreme luminosities of gamma-ray bursts (GRBs) make them the favored beacons for sampling the high redshift Universe. To employ GRBs to study the cosmic terrain -- e.g., star and galaxy formation history -- GRB luminosities must be calibrated, and the luminosity function versus redshift must be measured or inferred. Several nascent relationships between gamma-ray temporal or spectral indicators and luminosity or total energy have been reported. These measures promise to further our understanding of GRBs once the connections between the luminosity indicators and GRB jets and emission mechanisms are better elucidated. The current distribution of 33 redshifts determined from host galaxies and afterglows peaks near z $\\sim$ 1, whereas for the full BATSE sample of long bursts, the lag-luminosity relation predicts a broad peak z $\\sim$ 1--4 with a tail to z $\\sim$ 20, in rough agreement with theoretical models based on star formation considerations. For some GRB subclasses and apparently related phenomena -- short bursts, long-lag bursts, and X-ray flashes -- the present information on their redshift distributions is sparse or entirely lacking, and progress is expected in Swift era when prompt alerts become numerous.

Diverse Long-term Variability of Five Candidate High-mass X-Ray Binaries from Swift Burst Alert Telescope Observations

NASA Astrophysics Data System (ADS)

Corbet, Robin H. D.; Coley, Joel B.; Krimm, Hans A.

2017-09-01

We present an investigation of long-term modulation in the X-ray light curves of five little-studied candidate high-mass X-ray binaries using the Swift Burst Alert Telescope. IGR J14488-5942 and AX J1700.2-4220 show strong modulation at periods of 49.6 and 44 days, respectively, which are interpreted as orbital periods of Be star systems. For IGR J14488-5942, observations with the Swift X-ray Telescope show a hint of pulsations at 33.4 s. For AX J1700.2-4220, 54 s pulsations were previously found with XMM-Newton. Swift J1816.7-1613 exhibits complicated behavior. The strongest peak in the power spectrum is at a period near 150 days, but this conflicts with a determination of a period of 118.5 days by La Parola et al. AX J1820.5-1434 has been proposed to exhibit modulation near 54 days, but the extended BAT observations suggest modulation at slightly longer than double this at approximately 111 days. There appears to be a long-term change in the shape of the modulation near 111 days, which may explain the apparent discrepancy. The X-ray pulsar XTE J1906+090, which was previously proposed to be a Be star system with an orbital period of ˜30 days from pulse timing, shows peaks in the power spectrum at 81 and 173 days. The origins of these periods are unclear, although they might be the orbital period and a superorbital period respectively. For all five sources, the long-term variability, together with the combination of orbital and proposed pulse periods, suggests that the sources contain Be star mass donors.

Diverse Long-Term Variability of Five Candidate High-Mass X-ray Binaries from Swift Burst Alert Telescope Observations

NASA Astrophysics Data System (ADS)

Corbet, Robin; Coley, Joel Barry; Krimm, Hans A.

2017-08-01

We present an investigation of long-term modulation in the X-ray light curves of five little-studied candidate high-mass X-ray binaries using the Swift Burst Alert Telescope. IGR J14488-5942 and AX J1700.2-4220 show strong modulation at periods of 49.6 and 44 days, respectively, which are interpreted as orbital periods of Be star systems. For IGR J14488-5942, observations with Swift X-ray Telescope show a hint of pulsations at 33.4 s. For AX J1700.2-4220, 54 s pulsations were previously found with XMM-Newton. Swift J1816.7-1613 exhibits complicated behavior. The strongest peak in the power spectrum is at a period near 150 days, but this conflicts with a determination of a period of 118.5 days by La Parola et al. (2014). AX J1820.5-1434 has been proposed to exhibit modulation near 54 days, but the extended BAT observations suggest modulation at slightly longer than double this at approximately 111 days. There appears to be a long-term change in the shape of the modulation near 111 days, which may explain the apparent discrepancy. The X-ray pulsar XTE J1906+090, which was previously proposed to be a Be star system with an orbital period of ˜30 days from pulse timing, shows peaks in the power spectrum at 81 and 173 days. The origins of these periods are unclear, although they might be the orbital period and a superorbital period respectively. For all five sources, the long-term variability, together with the combination of orbital and proposed pulse periods, suggests that the sources contain Be star mass donors.

When a Standard Candle Flickers: Crab Nebula Variations in Hard X-rays

NASA Technical Reports Server (NTRS)

Wilson-Hodge, Colleen A.; Cherry, M. L.; Case, G. L.; Baumgartner, W. H.; Beklen, E.; Bhat, P. N.; Briggs, M. S.; Camero-Arranz, A.; Chaplin, V.; Connaughton, V.;

When a Standard Candle Flickers: Hard X-Ray Variations in the Crab Nebula

NASA Technical Reports Server (NTRS)

Wilson-Hodge, Colleen A.; Cherry, M. L.; Case, G. L.; Baumgartner, W. H.; Beklen, E.; Bhat, P. N.; Briggs, M. S.; Camaro-Arranz, A.; Connaughton, V.; Diehl, R.;

MULTIBAND DIAGNOSTICS OF UNIDENTIFIED 1FGL SOURCES WITH SUZAKU AND SWIFT X-RAY OBSERVATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Takeuchi, Y.; Kataoka, J.; Maeda, K.

2013-10-01

We have analyzed all the archival X-ray data of 134 unidentified (unID) gamma-ray sources listed in the first Fermi/LAT (1FGL) catalog and subsequently followed up by the Swift/XRT. We constructed the spectral energy distributions (SEDs) from radio to gamma-rays for each X-ray source detected, and tried to pick up unique objects that display anomalous spectral signatures. In these analyses, we target all the 1FGL unID sources, using updated data from the second Fermi/LAT (2FGL) catalog on the Large Area Telescope (LAT) position and spectra. We found several potentially interesting objects, particularly three sources, 1FGL J0022.2–1850, 1FGL J0038.0+1236, and 1FGL J0157.0–5259,more » which were then more deeply observed with Suzaku as a part of an AO-7 program in 2012. We successfully detected an X-ray counterpart for each source whose X-ray spectra were well fitted by a single power-law function. The positional coincidence with a bright radio counterpart (currently identified as an active galactic nucleus, AGN) in the 2FGL error circles suggests these sources are definitely the X-ray emission from the same AGN, but their SEDs show a wide variety of behavior. In particular, the SED of 1FGL J0038.0+1236 is not easily explained by conventional emission models of blazars. The source 1FGL J0022.2–1850 may be in a transition state between a low-frequency peaked and a high-frequency peaked BL Lac object, and 1FGL J0157.0–5259 could be a rare kind of extreme blazar. We discuss the possible nature of these three sources observed with Suzaku, together with the X-ray identification results and SEDs of all 134 sources observed with the Swift/XRT.« less

Gamma-Ray Emision from the Broad-Line Radio Galaxy 3C 111

NASA Technical Reports Server (NTRS)

Hartman, Robert C.; Kadler, Matthias; Tueller, Jack

2008-01-01

The broad-line radio galaxy 3C 111 has been suggested as the counterpart of the Gamma-ray source 3EGJ0416+3650. While 3C 111 meets most of the criteria for a high-probability identification, like a bright fla t-spectrum radio core and a blazarlike broadband SED, in the Third EG RET Catalog, the large positional offset of about 1.5 degrees put 3C1 11 outside the 99% probability region for 3EG J0416+3650, making this association questionable. We present a re-analysis of all available data for 3C111 from the EGRET archives, resulting in probable detection of high-energy Gamma-ray emission above 1000MeV from a position clo se to the nominal position of 3C 111, in two separate viewing periods (VPs), at a 3sigma level in each. A new source, GROJ0426+3747, appea rs to be present nearby, seen only in the >1000MeV data. For >100MeV, the data are in agreement with only one source (at the original cata log position) accounting for most of the EGRET-detected emission of 3 EGJ0416+3650. A follow-up Swift UVOT/XRT observation reveals one mode rately bright X-ray source in the error box of 3EGJ0416+3650, but bec ause of the large EGRET position uncertainty, it is not certain that the X-ray and Gamma-ray sources are associated. A Swift observation of GROJ0426+3747 detected no X.ray source nearby.

Individual power density spectra of Swift gamma-ray bursts

NASA Astrophysics Data System (ADS)

Guidorzi, C.; Dichiara, S.; Amati, L.

2016-05-01

Context. Timing analysis can be a powerful tool with which to shed light on the still obscure emission physics and geometry of the prompt emission of gamma-ray bursts (GRBs). Fourier power density spectra (PDS) characterise time series as stochastic processes and can be used to search for coherent pulsations and, more in general, to investigate the dominant variability timescales in astrophysical sources. Because of the limited duration and of the statistical properties involved, modelling the PDS of individual GRBs is challenging, and only average PDS of large samples have been discussed in the literature thus far. Aims: We aim at characterising the individual PDS of GRBs to describe their variability in terms of a stochastic process, to explore their variety, and to carry out for the first time a systematic search for periodic signals and for a link between PDS properties and other GRB observables. Methods: We present a Bayesian procedure that uses a Markov chain Monte Carlo technique and apply it to study the individual PDS of 215 bright long GRBs detected with the Swift Burst Alert Telescope in the 15-150 keV band from January 2005 to May 2015. The PDS are modelled with a power-law either with or without a break. Results: Two classes of GRBs emerge: with or without a unique dominant timescale. A comparison with active galactic nuclei (AGNs) reveals similar distributions of PDS slopes. Unexpectedly, GRBs with subsecond-dominant timescales and duration longer than a few tens of seconds in the source frame appear to be either very rare or altogether absent. Three GRBs are found with possible evidence for a periodic signal at 3.0-3.2σ (Gaussian) significance, corresponding to a multi-trial chance probability of ~1%. Thus, we found no compelling evidence for periodic signal in GRBs. Conclusions: The analogy between the PDS of GRBs and of AGNs could tentatively indicate similar stochastic processes that rule BH accretion across different BH mass scales and objects

Modelling the luminosity function of long gamma-ray bursts using Swift and Fermi

NASA Astrophysics Data System (ADS)

Paul, Debdutta

2018-01-01

I have used a sample of long gamma-ray bursts (GRBs) common to both Swift and Fermi to re-derive the parameters of the Yonetoku correlation. This allowed me to self-consistently estimate pseudo-redshifts of all the bursts with unknown redshifts. This is the first time such a large sample of GRBs from these two instruments is used, both individually and in conjunction, to model the long GRB luminosity function. The GRB formation rate is modelled as the product of the cosmic star formation rate and a GRB formation efficiency for a given stellar mass. An exponential cut-off power-law luminosity function fits the data reasonably well, with ν = 0.6 and Lb = 5.4 × 1052 ergs- 1, and does not require a cosmological evolution. In the case of a broken power law, it is required to incorporate a sharp evolution of the break given by Lb ∼ 0.3 × 1052(1 + z)2.90 erg s- 1, and the GRB formation efficiency (degenerate up to a beaming factor of GRBs) decreases with redshift as ∝ (1 + z)-0.80. However, it is not possible to distinguish between the two models. The derived models are then used as templates to predict the distribution of GRBs detectable by CZT Imager onboard AstroSat as a function of redshift and luminosity. This demonstrates that via a quick localization and redshift measurement of even a few CZT Imager GRBs, AstroSat will help in improving the statistics of GRBs both typical and peculiar.

LFlGRB: Luminosity function of long gamma-ray bursts

NASA Astrophysics Data System (ADS)

Paul, Debdutta

2018-04-01

LFlGRB models the luminosity function (LF) of long Gamma Ray Bursts (lGRBs) by using a sample of Swift and Fermi lGRBs to re-derive the parameters of the Yonetoku correlation and self-consistently estimate pseudo-redshifts of all the bursts with unknown redshifts. The GRB formation rate is modeled as the product of the cosmic star formation rate and a GRB formation efficiency for a given stellar mass.

Hydration effect on ion exchange resin irradiated by swift heavy ions and gamma rays

NASA Astrophysics Data System (ADS)

Boughattas, I.; Labed, V.; Gerenton, A.; Ngono-Ravache, Y.; Dannoux-Papin, A.

2018-06-01

Gamma radiolysis of ion exchange resins (IER) is widely studied since the sixties, as a function of different parameters (resin type, dose, atmosphere, water content …). However, to our knowledge, there are very few data concerning hydrogen emission from anionic and cationic resins irradiated at high Linear Energy Transfers (LET). In the present work, we focus on the influence of hydration on hydrogen emission, in anionic and cationic resins irradiated under inert atmosphere using Swift Heavy Ions (SHI) and gamma irradiations. The radiation chemical yield of molecular hydrogen is nonlinear with water content for both resins. The molecular hydrogen production depends first on the water form in IER (free or linked) and second on the solubility of degradation products. Three steps have been observed: at lower water content where G(H2) is stable, at 50%, G(H2) increases due to reactions between water radiolytic species and the resin functional groups and at high water content, G(H2) decreases probably due to its accumulation in water and its consumption by hydroxyl radicals in the supernatant.

Fermi GBM: Highlights from the First Year

NASA Technical Reports Server (NTRS)

Wilson-Hodge, Colleen A.

2009-01-01

The Fermi Gamma ray Burst Monitor is an all-sky instrument sensitive to photons from about 8 keV to 40 MeV. I will summarize highlights from the first year, including triggered observations of gamma ray bursts, soft gamma ray repeaters, and terrestrial gamma flashes, and observations in the continuous data of X-ray binaries and accreting X-ray pulsars. GBM provides complementary observations to Swift/BAT, observing many of the same sources, but over a wider energy range.

The new magnetar Swift J1822.3-1606

NASA Astrophysics Data System (ADS)

Scholz, P.; Ng, C.-Y.; Livingstone, M. A.; Kaspi, V. M.; Cumming, A.; Archibald, R.

2013-03-01

On 2011 July 14, a transient X-ray source, Swift J1822.3-1606, was detected by Swift BAT via its burst activities. It was subsequently identified as a new magnetar upon the detection of a pulse period of 8.4 s. Using follow-up RXTE, Swift, and Chandra observations, we have determined a spin-down rate of Ṗ ~ 3 × 10-13, implying a dipole magnetic field of ~ 5 × 1013 G, second lowest among known magnetars, although our timing solution is contaminated by timing noise. The post-outburst flux evolution is well modelled by surface cooling resulting from heat injection in the outer crust, although we cannot rule out other models. We measure an absorption column density similar to that of the open cluster M17 at 10' away, arguing for a comparable distance of ~1.6 kpc. If confirmed, this could be the nearest known magnetar.

Search for gamma-ray emission from AE Aquarii with seven year of Fermi LAT observations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Jian; Torres, Diego F.; Rea, Nanda

2016-11-14

AE Aquarii (AE Aqr) is a cataclysmic binary hosting one of the fastest rotating (more » $${P}_{\\mathrm{spin}}$$ = 33.08 s) white dwarfs (WDs) known. Based on seven years of Fermi Large Area Telescope (LAT) Pass 8 data, we report on a deep search for gamma-ray emission from AE Aqr. When using X-ray observations from ASCA, XMM-Newton, Chandra, Swift, Suzaku, and NuSTAR, spanning 20 years, we substantially extend and improve the spin ephemeris of AE Aqr. Using this ephemeris, we searched for gamma-ray pulsations at the spin period of the WD. We detected no gamma-ray pulsations above 3σ significance. Neither phase-averaged gamma-ray emission nor gamma-ray variability of AE Aqr is detected by Fermi LAT. We also impose the most restrictive upper limit to the gamma-ray flux from AE Aqr to date: $$1.3\\times {10}^{-12}$$ erg cm -2 s -1 in the 100 MeV–300 GeV energy range, providing constraints on models.« less

Seven years with the Swift Supergiant Fast X-ray Transients project

NASA Astrophysics Data System (ADS)

Romano, P.

2015-09-01

Supergiant Fast X-ray Transients (SFXTs) are HMXBs with OB supergiant companions. I review the results of the Swift SFXT project, which since 2007 has been exploiting Swift's capabilities in a systematic study of SFXTs and supergiant X-ray binaries (SGXBs) by combining follow-ups of outbursts, when detailed broad-band spectroscopy is possible, with long-term monitoring campaigns, when the out-of-outburst fainter states can be observed. This strategy has led us to measure their duty cycles as a function of luminosity, to extract their differential luminosity distributions in the soft X-ray domain, and to compare, with unprecedented detail, the X-ray variability in these different classes of sources. I also discuss the ;seventh year crisis;, the challenges that the recent Swift observations are making to the prevailing models attempting to explain the SFXT behavior.

The Nature of the X-Ray Binary IGR J19294+1816 from INTEGRAL, RXTE, and Swift Observations

NASA Technical Reports Server (NTRS)

Rodriquez, J.; Tomsick, J. A.; Bodaghee, A.; ZuritaHeras, J.-A.; Chaty, S.; Paizis, A.; Corbel, S.

2009-01-01

We report the results of a high-energy multi-instrumental campaign with INTEGRAL, RXTE, and Swift of the recently discovered INTEGRAL source IGR J19294+ 1816. The Swift/XRT data allow us to refine the position of the source to R.A. (J2000) = 19h 29m 55.9s, Decl. (J2000) = +18 deg 18 feet 38 inches . 4 (+/- 3 inches .5), which in turn permits us to identify a candidate infrared counterpart. The Swift and RXTE spectra are well fitted with absorbed power laws with hard (Gamma approx 1) photon indices. During the longest Swift observation, we obtained evidence of absorption in true excess to the Galactic value, which may indicate some intrinsic absorption in this source. We detected a strong (P = 40%) pulsations at 12.43781 (+/- 0.00003) s that we interpret as the spin period of a pulsar. All these results, coupled with the possible 117 day orbital period, point to IGR J19294+ 1816 being an high-mass X-ray binary (HMXB) with a Be companion star. However, while the long-term INTEGRAL/IBIS/ISGRI 18-40 keV light curve shows that the source spends most of its time in an undetectable state, we detect occurrences of short (2000-3000 s) and intense flares that are more typical of supergiant fast X-ray transients. We therefore cannot make firm conclusions on the type of system, and we discuss the possible implication of IGR J19294+1816 being an Supergiant Fast X-ray Transient (SFXT).

Local Swift-BAT active galactic nuclei prefer circumnuclear star formation

NASA Astrophysics Data System (ADS)

Lutz, D.; Shimizu, T.; Davies, R. I.; Herrera-Camus, R.; Sturm, E.; Tacconi, L. J.; Veilleux, S.

2018-01-01

We use Herschel data to analyze the size of the far-infrared 70 μm emission for z < 0.06 local samples of 277 hosts of Swift-BAT selected active galactic nuclei (AGN), and 515 comparison galaxies that are not detected by BAT. For modest far-infrared luminosities 8.5 BAT hosts that is only half that of comparison galaxies of same far-infrared luminosity. The result mostly reflects a more compact distribution of star formation (and hence gas) in the AGN hosts, but compact AGN heated dust may contribute in some extremely AGN dominated systems. Our findings are in support of an AGN-host coevolution where accretion onto the central black hole and star formation are fed from the same gas reservoir, with more efficient black hole feeding if that reservoir is more concentrated. The significant scatter in the far-infrared sizes emphasizes that we are mostly probing spatial scales much larger than those of actual accretion, and that rapid accretion variations can smear the distinction between the AGN and comparison categories. Large samples are hence needed to detect structural differences that favor feeding of the black hole. No size difference between AGN host and comparison galaxies is observed at higher far-infrared luminosities log(LFIR [L⊙]) > 10.5 (star formation rates ≳6 M⊙ yr-1), possibly because these are typically reached in more compact regions. Full Table A.1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/609/A9

The 2014 X-Ray Minimum of Eta Carinae as Seen by Swift

NASA Technical Reports Server (NTRS)

Corcoran, M. F.; Liburd, J.; Morris, D.; Russell, C. M. P.; Hamaguchi, K.; Gull, T. R.; Madura, T. I.; Teodoro, M.; Moffat, A. F. J.; Richardson, N. D.

2017-01-01

We report on Swift X-ray Telescope observations of Eta Carinae ( Car), an extremely massive, long-period, highly eccentric binary obtained during the 2014.6 X-ray minimumperiastron passage. These observations show that Car may have been particularly bright in X-rays going into the X-ray minimum state, while the duration of the 2014 X-ray minimum was intermediate between the extended minima seen in 1998.0 and 2003.5 by Rossi X-Ray Timing Explorer (RXTE), and the shorter minimum in 2009.0. The hardness ratios derived from the Swift observations showed a relatively smooth increase to a peak value occurring 40.5 days after the start of the X-ray minimum, though these observations cannot reliably measure the X-ray hardness during the deepest part of the X-ray minimum when contamination by the central constant emission component is significant. By comparing the timings of the RXTE and Swift observations near the X-ray minima, we derive an updated X-ray period of P X equals 2023.7 +/- 0.7 days, in good agreement with periods derived from observations at other wavelengths, and we compare the X-ray changes with variations in the He ii lambda 4686 emission. The middle of the Deep Minimum interval, as defined by the Swift column density variations, is in good agreement with the time of periastron passage derived from the He ii 4686 line variations.

The 2014 X-Ray Minimum of η Carinae as Seen by Swift

DOE Office of Scientific and Technical Information (OSTI.GOV)

Corcoran, M. F.; Hamaguchi, K.; Liburd, J.

We report on Swift X-ray Telescope observations of Eta Carinae ( η Car), an extremely massive, long-period, highly eccentric binary obtained during the 2014.6 X-ray minimum/periastron passage. These observations show that η Car may have been particularly bright in X-rays going into the X-ray minimum state, while the duration of the 2014 X-ray minimum was intermediate between the extended minima seen in 1998.0 and 2003.5 by Rossi X-Ray Timing Explorer ( RXTE ), and the shorter minimum in 2009.0. The hardness ratios derived from the Swift observations showed a relatively smooth increase to a peak value occurring 40.5 days aftermore » the start of the X-ray minimum, though these observations cannot reliably measure the X-ray hardness during the deepest part of the X-ray minimum when contamination by the “central constant emission” component is significant. By comparing the timings of the RXTE and Swift observations near the X-ray minima, we derive an updated X-ray period of P {sub X} = 2023.7 ± 0.7 days, in good agreement with periods derived from observations at other wavelengths, and we compare the X-ray changes with variations in the He ii 4686 emission. The middle of the “Deep Minimum” interval, as defined by the Swift column density variations, is in good agreement with the time of periastron passage derived from the He ii λ 4686 line variations.« less

Detection of Highly-Absorbed X-rays from Nova Mus 2018 with Swift

NASA Astrophysics Data System (ADS)

Nelson, Thomas; Kuin, Paul; Mukai, Koji; Page, Kim; Chomiuk, Laura; Kawash, Adam; Sokoloski, J. L.; Linford, Justin; Rupen, Michael P.; Mioduszewski, Amy

2018-03-01

We report the detection of X-rays from Nova Mus 2018 with the Swift XRT instrument. We have been carrying out weekly monitoring of the nova with Swift since its discovery on 2018 Jan 15 (see ATel #11220), and observations up to 2018 Feb 24 yielded X-ray non-detections.

Light Dawns on Dark Gamma-ray Bursts

NASA Astrophysics Data System (ADS)

2010-12-01

Gamma-ray bursts are among the most energetic events in the Universe, but some appear curiously faint in visible light. The biggest study to date of these so-called dark gamma-ray bursts, using the GROND instrument on the 2.2-metre MPG/ESO telescope at La Silla in Chile, has found that these gigantic explosions don't require exotic explanations. Their faintness is now fully explained by a combination of causes, the most important of which is the presence of dust between the Earth and the explosion. Gamma-ray bursts (GRBs), fleeting events that last from less than a second to several minutes, are detected by orbiting observatories that can pick up their high energy radiation. Thirteen years ago, however, astronomers discovered a longer-lasting stream of less energetic radiation coming from these violent outbursts, which can last for weeks or even years after the initial explosion. Astronomers call this the burst's afterglow. While all gamma-ray bursts [1] have afterglows that give off X-rays, only about half of them were found to give off visible light, with the rest remaining mysteriously dark. Some astronomers suspected that these dark afterglows could be examples of a whole new class of gamma-ray bursts, while others thought that they might all be at very great distances. Previous studies had suggested that obscuring dust between the burst and us might also explain why they were so dim. "Studying afterglows is vital to further our understanding of the objects that become gamma-ray bursts and what they tell us about star formation in the early Universe," says the study's lead author Jochen Greiner from the Max-Planck Institute for Extraterrestrial Physics in Garching bei München, Germany. NASA launched the Swift satellite at the end of 2004. From its orbit above the Earth's atmosphere it can detect gamma-ray bursts and immediately relay their positions to other observatories so that the afterglows could be studied. In the new study, astronomers combined Swift

Swift J045106.8-694803: A Highly Magnetised Neutron Star in the Large Magellanic Cloud

NASA Technical Reports Server (NTRS)

Klus, H.; Bartlett, E. S.; Bird, A. J.; Coe, M.; Corbet, R. H. D.; Udalski, A.

2013-01-01

We report the analysis of a highly magnetised neutron star in the Large Magellanic Cloud (LMC). The high mass X-ray binary pulsar Swift J045106.8-694803 has been observed with Swift X-ray telescope (XRT) in 2008, The Rossi X-ray Timing Explorer (RXTE) in 2011 and the X-ray Multi-Mirror Mission - Newton (XMM-Newton) in 2012. The change in spin period over these four years indicates a spin-up rate of 5.010.06 s/yr, amongst the highest observed for an accreting pulsar. This spin-up rate can be accounted for using Ghosh and Lambs (1979) accretion theory assuming it has a magnetic field of (1.2 +/= 0.20/0.7) x 10(exp 14) Gauss. This is over the quantum critical field value. There are very few accreting pulsars with such high surface magnetic fields and this is the first of which to be discovered in the LMC. The large spin-up rate is consistent with Swift Burst Alert Telescope (BAT) observations which show that Swift J045106.8-694803 has had a consistently high X-ray luminosity for at least five years. Optical spectra have been used to classify the optical counterpart of Swift J045106.8-694803 as a B0-1 III-V star and a possible orbital period of 21.631 +/- 0.005 days has been found from MACHO optical photometry.

SWIFT OBSERVATIONS OF GAMMA-RAY BURST PULSE SHAPES: GRB PULSE SPECTRAL EVOLUTION CLARIFIED

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hakkila, Jon; Lien, Amy; Sakamoto, Takanori

Isolated Swift gamma-ray burst (GRB) pulses, like their higher-energy BATSE counterparts, emit the bulk of their pulsed emission as a hard-to-soft component that can be fitted by the Norris et al. empirical pulse model. This signal is overlaid by a fainter, three-peaked signal that can be modeled by the residual fit of Hakkila and Preece: the two fits combine to reproduce GRB pulses with distinctive three-peaked shapes. The precursor peak appears on or before the pulse rise and is often the hardest component, the central peak is the brightest, and the decay peak converts exponentially decaying emission into a long,more » soft, power-law tail. Accounting for systematic instrumental differences, the general characteristics of the fitted pulses are remarkably similar. Isolated GRB pulses are dominated by hard-to-soft evolution; this is more pronounced for asymmetric pulses than for symmetric ones. Isolated GRB pulses can also exhibit intensity tracking behaviors that, when observed, are tied to the timing of the three peaks: pulses with the largest maximum hardnesses are hardest during the precursor, those with smaller maximum hardnesses are hardest during the central peak, and all pulses can re-harden during the central peak and/or during the decay peak. Since these behaviors are essentially seen in all isolated pulses, the distinction between “hard-to-soft and “intensity-tracking” pulses really no longer applies. Additionally, the triple-peaked nature of isolated GRB pulses seems to indicate that energy is injected on three separate occasions during the pulse duration: theoretical pulse models need to account for this.« less

When A Standard Candle Flickers

NASA Technical Reports Server (NTRS)

Wilson-Hodge, Colleen A.; Cherry, Michael L.; Case, Gary L.; Baumgartner, Wayne H.; Beklen Elif; Bhat, P. Narayana; Briggs, Michael S.; Camero-Arranz, Ascension; Chaplin, Vandiver; Connaughton, Valerie;

When a Standard Candle Flickers: Hard X-ray Variations in the Crab Nebula

NASA Technical Reports Server (NTRS)

Wilson-Hodge, Colleen; Cherry, Michael L.; Case, Gary L.; Baumgartner, Wayne H.; Beklen, Elif; Bhat, Narayana P.; Briggs, Michael S.; Buehler, Rolf; Camero-Arranz, Ascension; Connaughton, Valerie;

Search for Very-high-energy Emission from Gamma-Ray Bursts Using the First 18 Months of Data from the HAWC Gamma-Ray Observatory

NASA Astrophysics Data System (ADS)

Alfaro, R.; Alvarez, C.; Álvarez, J. D.; Arceo, R.; Arteaga-Velázquez, J. C.; Avila Rojas, D.; Ayala Solares, H. A.; Barber, A. S.; Bautista-Elivar, N.; Becerril, A.; Belmont-Moreno, E.; BenZvi, S. Y.; Bernal, A.; Braun, J.; Brisbois, C.; Caballero-Mora, K. S.; Capistrán, T.; Carramiñana, A.; Casanova, S.; Castillo, M.; Cotti, U.; Cotzomi, J.; Coutiño deLeón, S.; De la Fuente, E.; De León, C.; DeYoung, T.; Diaz Hernandez, R.; Dingus, B. L.; DuVernois, M. A.; Díaz-Vélez, J. C.; Ellsworth, R. W.; Engel, K.; Fiorino, D. W.; Fraija, N.; García-González, J. A.; Garfias, F.; Gerhardt, M.; González Muñoz, A.; González, M. M.; Goodman, J. A.; Hampel-Arias, Z.; Harding, J. P.; Hernandez-Almada, A.; Hernandez, S.; Hona, B.; Hui, C. M.; Hüntemeyer, P.; Iriarte, A.; Jardin-Blicq, A.; Joshi, V.; Kaufmann, S.; Kieda, D.; Lauer, R. J.; Lee, W. H.; Lennarz, D.; León Vargas, H.; Linnemann, J. T.; Longinotti, A. L.; Raya, G. Luis; Luna-García, R.; López-Coto, R.; Malone, K.; Marinelli, S. S.; Martinez, O.; Martinez-Castellanos, I.; Martínez-Castro, J.; Martínez-Huerta, H.; Matthews, J. A.; Miranda-Romagnoli, P.; Moreno, E.; Mostafá, M.; Nellen, L.; Newbold, M.; Noriega-Papaqui, R.; Pelayo, R.; Pérez-Pérez, E. G.; Pretz, J.; Ren, Z.; Rho, C. D.; Rivière, C.; Rosa-González, D.; Rosenberg, M.; Ruiz-Velasco, E.; Salazar, H.; Salesa Greus, F.; Sandoval, A.; Schneider, M.; Schoorlemmer, H.; Sinnis, G.; Smith, A. J.; Springer, R. W.; Surajbali, P.; Taboada, I.; Tibolla, O.; Tollefson, K.; Torres, I.; Ukwatta, T. N.; Vianello, G.; Weisgarber, T.; Westerhoff, S.; Wood, J.; Yapici, T.; Younk, P. W.; Zepeda, A.; Zhou, H.; HAWC Collaboration

2017-07-01

The High Altitude Water Cherenkov (HAWC) Gamma-ray Observatory is an extensive air shower detector operating in central Mexico that has recently completed its first two years of full operations. If for a burst like GRB 130427A at a redshift of 0.34 and a high-energy component following a power law with index 1.66, the high-energy component is extended to higher energies with no cutoff other than that from extragalactic background light attenuation, HAWC would observe gamma-rays with a peak energy of ˜300 GeV. This paper reports the results of HAWC observations of 64 gamma-ray bursts (GRBs) detected by Swift and Fermi, including 3 GRBs that were also detected by the Large Area Telescope (Fermi-LAT). An ON/OFF analysis method is employed, searching on the timescale given by the observed light curve at keV-MeV energies and also on extended timescales. For all GRBs and timescales, no statistically significant excess of counts is found and upper limits on the number of gamma-rays and the gamma-ray flux are calculated. GRB 170206A, the third brightest short GRB detected by the Gamma-ray Burst Monitor on board the Fermi satellite (Fermi-GBM) and also detected by the LAT, occurred very close to zenith. The LAT measurements can neither exclude the presence of a synchrotron self-Compton component nor constrain its spectrum. Instead, the HAWC upper limits constrain the expected cutoff in an additional high-energy component to be less than 100 {GeV} for reasonable assumptions about the energetics and redshift of the burst.

When a Standard Candle Flickers: Crab Nebula Variations in Hard X-rays

NASA Technical Reports Server (NTRS)

Wilson-Hodge, Collen A.; Cherry, M. L.; Case, G. L.; Baumgartner, W. H.; Beklen, E.; Bhat, P. N.; Briggs, M. S.; Camero-Arranz, A.; Chaplin, V.; Connaughton, V.;

The BAT AGN Spectroscopic Survey (BASS)

NASA Astrophysics Data System (ADS)

Koss, Michael

2017-08-01

We present the Swift BAT AGN Spectroscopic Survey (BASS) and discus the first four papers. The catalog represents an unprecedented census of hard-X-ray selected AGN in the local universe, with ~90% of sources at z<0.2. Starting from an all-sky catalog of AGN detected based on their 14-195 keV flux from the 70-month Swift/BAT catalog, we analyze a total of 1279 optical spectra, taken from twelve different telescopes, for a total of 642 spectra of unique AGN. We present the absorption and emission line measurements as well as black hole masses and accretion rates for the majority of obscured and un-obscured AGN (473), representing more than a factor of 10 increase from past studies. Consistent with previous surveys, we find an increase in the fraction of un-obscured (type 1) AGN, as measured from broad Hbeta and Halpha, with increasing 14-195 keV and 2-10 keV luminosity. We find the FWHM of the emission lines to show broad agreement with the X-ray obscuration measurements. Compared to narrow line AGN in the SDSS, the X-ray selected AGN in our sample with emission lines have a larger fraction of dustier galaxies suggesting these types of galaxies are missed in optical AGN surveys using emission line diagnostics.

Swift reports a recent brightening of XTE J1543-568

NASA Astrophysics Data System (ADS)

Krimm, H. A.; Barthelmy, S. D.; Baumgartner, W.; Cummings, J.; Fenimore, E.; Gehrels, N.; Markwardt, C. B.; Palmer, D.; Sakamoto, T.; Skinner, G.; Stamatikos, M.; Tueller, J.; Ukwatta, T.

2012-03-01

The Swift/BAT hard X-ray transient monitor has recorded a recent flux increase from the transient X-ray pulsar and likely Be binary system XTE J1543-568. In the 15-50 keV band, the source was first detected in an 8-day integration covering 2012 March 9-16 (MJD 55995-56002) with a rate of 0.0016 ± 0.0003 ct/s/cm2. The peak day in the light curve was 2012 March 22 when the rate was 0.0043 ± 0.001 ct/s/cm2 (~20 mCrab).

Spectroscopic and Temporal Properties of Supergiant Fast X-ray Transients with Swift

NASA Astrophysics Data System (ADS)

Romano, Patrizia; Kennea, J. A.; Vercellone, S.; Burrows, D. N.; Cusumano, G.; Esposito, P.; Farinelli, R.; Krimm, H. A.; La Parola, V.; Mangano, V.; Pagani, C.; Gehrels, N.

2011-09-01

We present a review of the Swift Supergiant Fast X-ray Transients (SFXT) project. Swift has recently opened a brand new way of investigating this class of High-Mass X-ray Binaries whose optical counterparts are O or B supergiant stars, and whose X-ray outbursts are about 4 orders of magnitude brighter than the quiescent state. Thanks to its scheduling flexibility, Swift has allowed us to regularly monitor a small sample of SFXTs with 2-3 observations per week (1-2 ks) with the X-Ray Telescope (XRT) over their entire visibility period (9 months/year) for over 2 years. This intense monitoring has allowed us to study them throughout all phases of their lives (outbursts, intermediate level, and quiescence) and to determine the long-term properties and their duty cycles, through very sensitive and non-serendipitous observations. We also monitored one source along its whole orbital period. Furthermore, thanks to its autonomous and rapid repointing, Swift has allowed us for the first time to catch and study, from optical to hard X-ray, the bright outbursts, and to follow them in the X-ray for days, thus determining the actual duration of the outburst episodes and the shape of their X-ray spectra through simultaneous broadband spectroscopy. We acknowledge financial contribution from the agreement ASI-INAF I/009/10/0.

Unidentified Gamma-Ray Sources: Hunting Gamma-Ray Blazars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Massaro, F.; D'Abrusco, R.; Tosti, G.

2012-04-02

One of the main scientific objectives of the ongoing Fermi mission is unveiling the nature of the unidentified {gamma}-ray sources (UGSs). Despite the large improvements of Fermi in the localization of {gamma}-ray sources with respect to the past {gamma}-ray missions, about one third of the Fermi-detected objects are still not associated to low energy counterparts. Recently, using the Wide-field Infrared Survey Explorer (WISE) survey, we discovered that blazars, the rarest class of Active Galactic Nuclei and the largest population of {gamma}-ray sources, can be recognized and separated from other extragalactic sources on the basis of their infrared (IR) colors. Basedmore » on this result, we designed an association method for the {gamma}-ray sources to recognize if there is a blazar candidate within the positional uncertainty region of a generic {gamma}-ray source. With this new IR diagnostic tool, we searched for {gamma}-ray blazar candidates associated to the UGS sample of the second Fermi {gamma}-ray catalog (2FGL). We found that our method associates at least one {gamma}-ray blazar candidate as a counterpart each of 156 out of 313 UGSs analyzed. These new low-energy candidates have the same IR properties as the blazars associated to {gamma}-ray sources in the 2FGL catalog.« less

UNIDENTIFIED {gamma}-RAY SOURCES: HUNTING {gamma}-RAY BLAZARS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Massaro, F.; Ajello, M.; D'Abrusco, R.

2012-06-10

One of the main scientific objectives of the ongoing Fermi mission is unveiling the nature of unidentified {gamma}-ray sources (UGSs). Despite the major improvements of Fermi in the localization of {gamma}-ray sources with respect to the past {gamma}-ray missions, about one-third of the Fermi-detected objects are still not associated with low-energy counterparts. Recently, using the Wide-field Infrared Survey Explorer survey, we discovered that blazars, the rarest class of active galactic nuclei and the largest population of {gamma}-ray sources, can be recognized and separated from other extragalactic sources on the basis of their infrared (IR) colors. Based on this result, wemore » designed an association method for the {gamma}-ray sources to recognize if there is a blazar candidate within the positional uncertainty region of a generic {gamma}-ray source. With this new IR diagnostic tool, we searched for {gamma}-ray blazar candidates associated with the UGS sample of the second Fermi {gamma}-ray LAT catalog (2FGL). We found that our method associates at least one {gamma}-ray blazar candidate as a counterpart to each of 156 out of 313 UGSs analyzed. These new low-energy candidates have the same IR properties as the blazars associated with {gamma}-ray sources in the 2FGL catalog.« less

X-ray rebrightening of the Be/X-ray transient Swift J0243.6+6124

NASA Astrophysics Data System (ADS)

Rouco Escorial, A.; Degenaar, N.; van den Eijnden, J.; Wijnands, R.

2018-04-01

Swift J0243.6+6124 is a Be/X-ray transient that was discovered in October 2017 when it started a giant, type-II outburst (Atel #10809, Atel #10822). After reaching the peak around November 5th 2017, the source luminosity started to decay slowly over & sim;135 days, although the decay rate increased significantly around two weeks ago. To investigate how exactly the source would decay and potentially transit back into quiescence, we triggered a monitoring program (PI: Degenaar) on the system using the Neil Gehrels Swift observatory (Swift).

Multi-wavelength Observations of the Flaring Gamma-ray Blazar 3C 66A in 2008 October

NASA Astrophysics Data System (ADS)

Abdo, A. A.; Ackermann, M.; Ajello, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Blandford, R. D.; Bonamente, E.; Borgland, A. W.; Bouvier, A.; Bregeon, J.; Brez, A.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Carrigan, S.; Casandjian, J. M.; Cavazzuti, E.; Cecchi, C.; Çelik, Ö.; Charles, E.; Chekhtman, A.; Cheung, C. C.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; Costamante, L.; Cutini, S.; Davis, D. S.; Dermer, C. D.; de Palma, F.; Digel, S. W.; do Couto e Silva, E.; Drell, P. S.; Dubois, R.; Dumora, D.; Favuzzi, C.; Fegan, S. J.; Fortin, P.; Frailis, M.; Fuhrmann, L.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Germani, S.; Giglietto, N.; Giommi, P.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Grenier, I. A.; Grove, J. E.; Guillemot, L.; Guiriec, S.; Hadasch, D.; Hayashida, M.; Hays, E.; Horan, D.; Hughes, R. E.; Itoh, R.; Jóhannesson, G.; Johnson, A. S.; Johnson, T. J.; Johnson, W. N.; Kamae, T.; Katagiri, H.; Kataoka, J.; Knödlseder, J.; Kuss, M.; Lande, J.; Latronico, L.; Lee, S.-H.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Makeev, A.; Mazziotta, M. N.; McEnery, J. E.; Mehault, J.; Michelson, P. F.; Mizuno, T.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nakamori, T.; Naumann-Godo, M.; Nestoras, I.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orlando, E.; Ormes, J. F.; Ozaki, M.; Paneque, D.; Panetta, J. H.; Parent, D.; Pelassa, V.; Pepe, M.; Pesce-Rollins, M.; Piron, F.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Reimer, A.; Reimer, O.; Reyes, L. C.; Ripken, J.; Ritz, S.; Romani, R. W.; Roth, M.; Sadrozinski, H. F.-W.; Sanchez, D.; Sander, A.; Scargle, J. D.; Sgrò, C.; Shaw, M. S.; Smith, P. D.; Spandre, G.; Spinelli, P.; Strickman, M. S.; Suson, D. J.; Takahashi, H.; Tanaka, T.; Thayer, J. B.; Thayer, J. G.; Thompson, D. J.; Tibaldo, L.; Torres, D. F.; Tosti, G.; Tramacere, A.; Usher, T. L.; Vandenbroucke, J.; Vasileiou, V.; Vilchez, N.; Vitale, V.; Waite, A. P.; Wang, P.; Winer, B. L.; Wood, K. S.; Yang, Z.; Ylinen, T.; Ziegler, M.; Acciari, V. A.; Aliu, E.; Arlen, T.; Aune, T.; Beilicke, M.; Benbow, W.; Böttcher, M.; Boltuch, D.; Bradbury, S. M.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cannon, A.; Cesarini, A.; Christiansen, J. L.; Ciupik, L.; Cui, W.; de la Calle Perez, I.; Dickherber, R.; Errando, M.; Falcone, A.; Finley, J. P.; Finnegan, G.; Fortson, L.; Furniss, A.; Galante, N.; Gall, D.; Gillanders, G. H.; Godambe, S.; Grube, J.; Guenette, R.; Gyuk, G.; Hanna, D.; Holder, J.; Hui, C. M.; Humensky, T. B.; Imran, A.; Kaaret, P.; Karlsson, N.; Kertzman, M.; Kieda, D.; Konopelko, A.; Krawczynski, H.; Krennrich, F.; Lang, M. J.; LeBohec, S.; Maier, G.; McArthur, S.; McCann, A.; McCutcheon, M.; Moriarty, P.; Mukherjee, R.; Ong, R. A.; Otte, A. N.; Pandel, D.; Perkins, J. S.; Pichel, A.; Pohl, M.; Quinn, J.; Ragan, K.; Reynolds, P. T.; Roache, E.; Rose, H. J.; Schroedter, M.; Sembroski, G. H.; Senturk, G. Demet; Smith, A. W.; Steele, D.; Swordy, S. P.; Tešić, G.; Theiling, M.; Thibadeau, S.; Varlotta, A.; Vassiliev, V. V.; Vincent, S.; Wakely, S. P.; Ward, J. E.; Weekes, T. C.; Weinstein, A.; Weisgarber, T.; Williams, D. A.; Wissel, S.; Wood, M.; Villata, M.; Raiteri, C. M.; Gurwell, M. A.; Larionov, V. M.; Kurtanidze, O. M.; Aller, M. F.; Lähteenmäki, A.; Chen, W. P.; Berduygin, A.; Agudo, I.; Aller, H. D.; Arkharov, A. A.; Bach, U.; Bachev, R.; Beltrame, P.; Benítez, E.; Buemi, C. S.; Dashti, J.; Calcidese, P.; Capezzali, D.; Carosati, D.; Da Rio, D.; Di Paola, A.; Diltz, C.; Dolci, M.; Dultzin, D.; Forné, E.; Gómez, J. L.; Hagen-Thorn, V. A.; Halkola, A.; Heidt, J.; Hiriart, D.; Hovatta, T.; Hsiao, H.-Y.; Jorstad, S. G.; Kimeridze, G. N.; Konstantinova, T. S.; Kopatskaya, E. N.; Koptelova, E.; Leto, P.; Ligustri, R.; Lindfors, E.; Lopez, J. M.; Marscher, A. P.; Mommert, M.; Mujica, R.; Nikolashvili, M. G.; Nilsson, K.; Palma, N.; Pasanen, M.; Roca-Sogorb, M.; Ros, J. A.; Roustazadeh, P.; Sadun, A. C.; Saino, J.; Sigua, L. A.; Sillanää, A.; Sorcia, M.; Takalo, L. O.; Tornikoski, M.; Trigilio, C.; Turchetti, R.; Umana, G.; Belloni, T.; Blake, C. H.; Bloom, J. S.; Angelakis, E.; Fumagalli, M.; Hauser, M.; Prochaska, J. X.; Riquelme, D.; Sievers, A.; Starr, D. L.; Tagliaferri, G.; Ungerechts, H.; Wagner, S.; Zensus, J. A.; Fermi LAT Collaboration; VERITAS Collaboration; GASP-WEBT Consortium

2011-01-01

The BL Lacertae object 3C 66A was detected in a flaring state by the Fermi Large Area Telescope (LAT) and VERITAS in 2008 October. In addition to these gamma-ray observations, F-GAMMA, GASP-WEBT, PAIRITEL, MDM, ATOM, Swift, and Chandra provided radio to X-ray coverage. The available light curves show variability and, in particular, correlated flares are observed in the optical and Fermi-LAT gamma-ray band. The resulting spectral energy distribution can be well fitted using standard leptonic models with and without an external radiation field for inverse Compton scattering. It is found, however, that only the model with an external radiation field can accommodate the intra-night variability observed at optical wavelengths.

SEARCH FOR GAMMA-RAY EMISSION FROM X-RAY-SELECTED SEYFERT GALAXIES WITH FERMI-LAT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ackermann, M.; Ajello, M.; Allafort, A.

We report on a systematic investigation of the {gamma}-ray properties of 120 hard X-ray-selected Seyfert galaxies classified as 'radio-quiet' objects, utilizing the three-year accumulation of Fermi Large Area Telescope (LAT) data. Our sample of Seyfert galaxies is selected using the Swift Burst Alert Telescope 58 month catalog, restricting the analysis to the bright sources with average hard X-ray fluxes F{sub 14-195keV} {>=} 2.5 Multiplication-Sign 10{sup -11} erg cm{sup -2} s{sup -1} at high Galactic latitudes (|b| > 10 Degree-Sign ). In order to remove 'radio-loud' objects from the sample, we use the 'hard X-ray radio loudness parameter', R{sub rX}, definedmore » as the ratio of the total 1.4 GHz radio to 14-195 keV hard X-ray energy fluxes. Among 120 X-ray bright Seyfert galaxies with R{sub rX} <10{sup -4}, we did not find a statistically significant {gamma}-ray excess (TS > 25) positionally coincident with any target Seyferts, with possible exceptions of ESO 323-G077 and NGC 6814. The mean value of the 95% confidence level {gamma}-ray upper limit for the integrated photon flux above 100 MeV from the analyzed Seyferts is {approx_equal} 4 Multiplication-Sign 10{sup -9} photons cm{sup -2} s{sup -1} , and the upper limits derived for several objects reach {approx_equal} 1 Multiplication-Sign 10{sup -9} photons cm{sup -2} s{sup -1} . Our results indicate that no prominent {gamma}-ray emission component related to active galactic nucleus activity is present in the spectra of Seyferts around GeV energies. The Fermi-LAT upper limits derived for our sample probe the ratio of {gamma}-ray to X-ray luminosities L{sub {gamma}}/L{sub X} < 0.1, and even <0.01 in some cases. The obtained results impose novel constraints on the models for high-energy radiation of 'radio-quiet' Seyfert galaxies.« less

VizieR Online Data Catalog: Swift and NuSTAR obs. of the BL Lac Mrk 421 (Kapanadze+, 2016)

NASA Astrophysics Data System (ADS)

Kapanadze, B.; Dorner, D.; Vercellone, S.; Romano, P.; Aller, H.; Aller, M.; Hughes, P.; Reynolds, M.; Kapanadze, S.; Tabagari, L.

2017-01-01

We retrieved the Swift-XRT data from the publicly available archive, maintained by HEASARC. We present the results of X-ray observations of the high-energy peaked BL Lac (HBL) source Mrk421 performed by Swift-XRT and NuSTAR during 2013 January-June. Along with the 0.3-10keV and 3-79keV data obtained with the Swift-XRT and NuSTAR instruments, we have processed and analyzed those obtained with the Ultraviolet-Optical Telescope (UVOT) and Large Area Telescope (LAT) onboard Fermi. We have also used the publicly available light curves from the observations performed with the Burst Alert Telescope (BAT) onboard Swift, Monitor of All Sky X-ray Image (MAXI), MAGIC, First G-APD Cherenkov Telescope (FACT), and the OVRO 40m telescope during the 2013 January-June period to draw conclusions about the interband correlations. (8 data files).

Population III Gamma-ray Burst Afterglows: Constraints on Stellar Masses and External Medium Densities

NASA Astrophysics Data System (ADS)

Toma, Kenji; Sakamoto, Takanori; Mészáros, Peter

2011-04-01

Population (Pop.) III stars are theoretically expected to be prominent around redshifts z ~ 20, consisting of mainly very massive stars with M * >~ 100 M sun, though there is no direct observational evidence for these objects. They may produce collapsar gamma-ray bursts (GRBs), with jets driven by magnetohydrodynamic processes, whose total isotropic-equivalent energy could be as high as E iso >~ 1057 erg over a cosmological-rest-frame duration of td >~ 104 s, depending on the progenitor mass. Here, we calculate the afterglow spectra of such Pop. III GRBs based on the standard external shock model and show that they will be detectable with the Swift Burst Alert Telescope (BAT)/XRT and Fermi Large Area Telescope (LAT) instruments. We find that in some cases a spectral break due to electron-positron pair creation will be observable in the LAT energy range, which can put constraints on the ambient density of the pre-collapse Pop. III star. Thus, high-redshift GRB afterglow observations could be unique and powerful probes of the properties of Pop. III stars and their environments. We examine the trigger threshold of the BAT instrument in detail, focusing on the image trigger system, and show that the prompt emission of Pop. III GRBs could also be detected by BAT. Finally we briefly show that the late-time radio afterglows of Pop. III GRBs for typical parameters, despite the large distances, can be very bright: ~= 140 mJy at 1 GHz, which may lead to a constraint on the Pop. III GRB rate from the current radio survey data, and ~= 2.4 mJy at 70 MHz, which implies that Pop. III GRB radio afterglows could be interesting background source candidates for 21 cm absorption line detections.

Multiwavelength Studies of Dual AGN in the Swift/BAT Sample

NASA Astrophysics Data System (ADS)

Treister, Ezequiel; Privon, George; Sartori, Lia; Nagar, Neil; Bauer, Franz Erik; Schawinski, Kevin; Ricci, Claudio; U, Vivian; Comerford, Julie; Muller-Sanchez, Francisco; Evans, Aaron; Koss, Michael; Sanders, David B.; Urry, Meg; MODA Collaboration

2018-01-01

For the last 30 years there has been growing evidence for a strong connection between major galaxy mergers and simultaneous episodes ofstrong star formation and signicant central supermassive black hole (SMBH) growth. A natural consequence of this scenario is that dual Active Galactic Nuclei (AGN), i.e., systems in which the two nuclear SMBHs are growing simultaneously at separations <10 kpc should be relatively common. This particular stage in a major galaxy merger, albeit short at ~hundreds Myears, is very relevant for galaxy evolution.Here we present the first results from an ongoing survey aimed to study the multiwavelength properties of the dual AGN in the neary universe, z<0.1 selected from mostly-unbiased observations at hard X-rays, E>10 keV, obtained from the Swift-BAT extragalactic survey and complemented by NuSTAR observations. Our work focuses on the study of the physical properties of the ionized, atomic and molecular gas and the dust in confirmed dual AGN by combining observations with ALMA, VLT/MUSE and SINFONI and Keck/OSIRIS among others. In addition to providing general properties of this poulation, we will further focus on two remarkable systems, NGC6240 and Mrk 463. Both systems show evidence of large kpc-scale tidal features, complex gas dynamics and kinematical evidence for both inflows and outflows.These results clearly show the importance of performing high resolution multi wavelength studies covering kpc scales in order to understandthe complex connection between black hole growth and galaxy evolution in this critical phase.Support from this work has been provided by CONICYT FONDECYT 1160999 and PFB-06/2007.

Swift observations of GS 1826-238

NASA Astrophysics Data System (ADS)

Ji, L.; Santangelo, A.; Zhang, S.; Ducci, L.; Suleimanov, V.

2018-02-01

GS 1826-238 is a well-studied low-mass X-ray binary neutron star. This source was in a persistent hard state since its discovery in 1988 and until 2014 June. After that, the source exhibited several softer periods of enhanced intensity in the energy range 2-20 keV. We studied the long-term light curves of MAXI (Monitor of All Sky X-ray Image) and Swift/BAT, and found clearly two branches in the MAXI-BAT and hardness-intensity diagrams, which correspond to the persistent state and softer periods, respectively. We analysed 21 Swift/XRT observations, of which four were located in the persistent state while the others were in softer periods or in a state between them. The XRT spectra could be generally fitted by using an absorbed Comptonization model with no other components required. We found a peculiar relationship between the luminosity and the hardness in the energy range of 0.6-10 keV: when the luminosity is larger (smaller) than 4 per cent-6 per cent Ledd, the hardness is anti-correlated (correlated) with luminosity. We also estimated the variability for each observation by using the fractional rms in the 0.1-10 Hz range. We found that the observations in the persistent state had a large fractional rms of ˜25 per cent, similar to other low-mass X-ray binaries. However, the variability is mainly found in the range of 5 per cent-20 per cent during softer periods. We suggest that GS 1826-238 did not evolve into the soft state of atoll sources, and all the observed XRT observations during the softer periods resemble a peculiar intermediate state of atoll sources.

Very high-energy gamma rays from gamma-ray bursts.

PubMed

Chadwick, Paula M

2007-05-15

Very high-energy (VHE) gamma-ray astronomy has undergone a transformation in the last few years, with telescopes of unprecedented sensitivity having greatly expanded the source catalogue. Such progress makes the detection of a gamma-ray burst at the highest energies much more likely than previously. This paper describes the facilities currently operating and their chances for detecting gamma-ray bursts, and reviews predictions for VHE gamma-ray emission from gamma-ray bursts. Results to date are summarized.

Multi-wavelength observations of the flaring gamma-ray blazar 3C 66A in 2008 October

DOE PAGES

Abdo, A. A.; Ackermann, M.; Ajello, M.; ...

2010-12-14

We report that Tthe BL Lacertae object 3C 66A was detected in a flaring state by the Fermi Large Area Telescope (LAT) and VERITAS in 2008 October. In addition to these gamma-ray observations, F-GAMMA, GASP-WEBT, PAIRITEL, MDM, ATOM, Swift, and Chandra provided radio to X-ray coverage. The available light curves show variability and, in particular, correlated flares are observed in the optical and Fermi-LAT gamma-ray band. The resulting spectral energy distribution can be well fitted using standard leptonic models with and without an external radiation field for inverse Compton scattering. It is found, however, that only the model with anmore » external radiation field can accommodate the intra-night variability observed at optical wavelengths.« less

X-Ray Flare Candidates in Short Gamma-Ray Bursts

NASA Technical Reports Server (NTRS)

Margutti, R.; Chincarini, G.; Granot, J.; Guidorzi, C.; Berger, E.; Bernardini, M. G.; Geherls, N.; Soderberg, A. M.; Stamatikos, M.; Zaninoni, E.

2012-01-01

We present the first systematic study of X-ray flare candidates in short gamma-ray bursts (SGRBs) exploiting the large 6-year Swift database with the aim to constrain the physical nature of such fluctuations. We find that flare candidates appear in different types of SGRB host galaxy environments and show no clear correlation with the X-ray afterglow lifetime; flare candidates are detected both in SGRBs with a bright extended emission in the soft gamma-rays and in SGRBs which do not show such component. We furthermore show that SGRB X-ray flare candidates only partially share the set of observational properties of long GRB (LGRB) flares. In particular, the main parameter driving the duration evolution of X-ray variability episodes in both classes is found to be the elapsed time from the explosion, with very limited dependence on the different progenitors, environments, central engine life-times, prompt variability time-scales and energy budgets. On the contrary, SGRB flare candidates significantly differ from LGRB flares in terms of peak luminosity, isotropic energy, flare-to-prompt luminosity ratio and relative variability flux. However, these differences disappear when the central engine time-scales and energy budget are accounted for, suggesting that (i) flare candidates and prompt pulses in SGRBs likely have a common origin; (ii) similar dissipation and/or emission mechanisms are responsible for the prompt and flare emission in long and short GRBs, with SGRBs being less energetic albeit faster evolving versions of the long class. Finally, we show that in strict analogy to the SGRB prompt emission, flares candidates fall off the lag-luminosity relation defined by LGRBs, thus strengthening the SGRB flare-prompt pulse connection.

Investigation of redshift- and duration-dependent clustering of gamma-ray bursts

DOE PAGES

Ukwatta, T. N.; Woźniak, P. R.

2015-11-05

Gamma-ray bursts (GRBs) are detectable out to very large distances and as such are potentially powerful cosmological probes. Historically, the angular distribution of GRBs provided important information about their origin and physical properties. As a general population, GRBs are distributed isotropically across the sky. However, there are published reports that once binned by duration or redshift, GRBs display significant clustering. We have studied the redshift- and duration-dependent clustering of GRBs using proximity measures and kernel density estimation. Utilizing bursts detected by Burst and Transient Source Experiment, Fermi/gamma-ray burst monitor, and Swift/Burst Alert Telescope, we found marginal evidence for clustering inmore » very short duration GRBs lasting less than 100 ms. As a result, our analysis provides little evidence for significant redshift-dependent clustering of GRBs.« less

Suzaku  Observations of Heavily Obscured (Compton-thick) Active Galactic Nuclei Selected by the Swift/BAT Hard X-Ray Survey

NASA Astrophysics Data System (ADS)

Tanimoto, Atsushi; Ueda, Yoshihiro; Kawamuro, Taiki; Ricci, Claudio; Awaki, Hisamitsu; Terashima, Yuichi

2018-02-01

We present a uniform broadband X-ray (0.5–100.0 keV) spectral analysis of 12 Swift/Burst Alert Telescope selected Compton-thick ({log}{N}{{H}}/{{cm}}-2≥slant 24) active galactic nuclei (CTAGNs) observed with Suzaku. The Suzaku data of three objects are published here for the first time. We fit the Suzaku and Swift spectra with models utilizing an analytic reflection code and those utilizing the Monte-Carlo-based model from an AGN torus by Ikeda et al. The main results are as follows: (1) The estimated intrinsic luminosity of a CTAGN strongly depends on the model; applying Compton scattering to the transmitted component in an analytic model may largely overestimate the intrinsic luminosity at large column densities. (2) Unabsorbed reflection components are commonly observed, suggesting that the tori are clumpy. (3) Most of CTAGNs show small scattering fractions (<0.5%), implying a buried AGN nature. (4) Comparison with the results obtained for Compton-thin AGNs suggests that the properties of these CTAGNs can be understood as a smooth extension from Compton-thin AGNs with heavier obscuration; we find no evidence that the bulk of the population of hard-X-ray-selected CTAGNs are different from less obscured objects.

Spin and Flux Evolution of the New Magnetar Swift J1822.3-1606

NASA Astrophysics Data System (ADS)

Ng, Stephen C.-Y.; Kaspi, Victoria; Cumming, Andrew; Livingstone, Margaret; Scholz, Paul; Archibald, Robert

2012-07-01

On 2011 July 14, a transient X-ray source, Swift J1822.3-1606, was first detected by Swift BAT via its burst activities. It was subsequently identified as a new magnetar upon the detection of a pulse period of 8.4s. Using follow-up RXTE, Swift, and Chandra observations, we determined a spin-down rate of ~1.6e-13, giving a dipole magnetic field of ~3.8e13G, second lowest among known magnetars. The post-outburst flux evolution can be model by a double exponential decay with timescales of 11 and 58 days. We found an absorption column density similar to that of the open cluster M17 at 16' away, arguing a comparable distance of ~1.6kpc for Swift J1823.3-1606. If confirmed, this will be the nearest magnetar observed. We also discuss the possibility that the magnetar progenitor was born in M17.

Testing the anisotropy in the angular distribution of Fermi/GBM gamma-ray bursts

NASA Astrophysics Data System (ADS)

Tarnopolski, M.

2017-12-01

Gamma-ray bursts (GRBs) were confirmed to be of extragalactic origin due to their isotropic angular distribution, combined with the fact that they exhibited an intensity distribution that deviated strongly from the -3/2 power law. This finding was later confirmed with the first redshift, equal to at least z = 0.835, measured for GRB970508. Despite this result, the data from CGRO/BATSE and Swift/BAT indicate that long GRBs are indeed distributed isotropically, but the distribution of short GRBs is anisotropic. Fermi/GBM has detected 1669 GRBs up to date, and their sky distribution is examined in this paper. A number of statistical tests are applied: nearest neighbour analysis, fractal dimension, dipole and quadrupole moments of the distribution function decomposed into spherical harmonics, binomial test and the two-point angular correlation function. Monte Carlo benchmark testing of each test is performed in order to evaluate its reliability. It is found that short GRBs are distributed anisotropically in the sky, and long ones have an isotropic distribution. The probability that these results are not a chance occurrence is equal to at least 99.98 per cent and 30.68 per cent for short and long GRBs, respectively. The cosmological context of this finding and its relation to large-scale structures is discussed.

Status Of The Swift Burst Alert Telescope Hard X-ray Transient Monitor

NASA Astrophysics Data System (ADS)

Krimm, Hans A.; Barthelmy, S. D.; Baumgartner, W. H.; Cummings, J.; Fenimore, E.; Gehrels, N.; Markwardt, C. B.; Palmer, D.; Sakamoto, T.; Skinner, G. K.; Stamatikos, M.; Tueller, J.

2010-01-01

The Swift Burst Alert Telescope hard X-ray transient monitor has been operating since October 1, 2006. More than 700 sources are tracked on a daily basis and light curves are produced and made available to the public on two time scales: a single Swift pointing (approximately 20 minutes) and the weighted average for each day. Of the monitored sources, approximately 33 are detected daily and another 100 have had one or more outburst during the Swift mission. The monitor is also sensitive to the detection of previously undiscovered sources and we have reported the discovery of four galactic sources and one source in the Large Magellanic Cloud. Follow-up target of opportunity observations with Swift and the Rossi X-Ray Timing Explorer have revealed that three of these new sources are pulsars and two are black hole candidates. In addition, the monitor has led to the announcement of significant outbursts from 24 different galactic and extra-galactic sources, many of which have had follow-up Swift XRT, UVOT and ground based multi-wavelength observations. The transient monitor web pages currently receive an average of 21 visits per day. We will report on the most important results from the transient monitor and also on detection and exposure statistics and outline recent and planned improvements to the monitor. The transient monitor web page is http://swift.gsfc.nasa.gov/docs/swift/results/transients/.

The Swift satellite lives up to its name, revealing cosmic explosions as they happen.

PubMed

Starling, Rhaana L C

2008-12-13

Gamma-ray bursts are the most powerful objects in the Universe. Discovered in the 1960s as brief flashes of gamma radiation, we now know that they emit across the entire electromagnetic spectrum, are located in distant galaxies and comprise two distinct populations, one of which may originate in the deaths of massive stars. The launch of the Swift satellite in 2004 brought a flurry of new discoveries, advancing our understanding of these sources and the galaxies that host them. I highlight a number of important results from the Swift era thus far.

AN EVOLVING STELLAR INITIAL MASS FUNCTION AND THE GAMMA-RAY BURST REDSHIFT DISTRIBUTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, F. Y.; Dai, Z. G.

2011-02-01

Recent studies suggest that Swift gamma-ray bursts (GRBs) may not trace an ordinary star formation history (SFH). Here, we show that the GRB rate turns out to be consistent with the SFH with an evolving stellar initial mass function (IMF). We first show that the latest Swift sample of GRBs reveals an increasing evolution in the GRB rate relative to the ordinary star formation rate at high redshifts. We then assume only massive stars with masses greater than the critical value to produce GRBs and use an evolving stellar IMF suggested by Dave to fit the latest GRB redshift distribution.more » This evolving IMF would increase the relative number of massive stars, which could lead to more GRB explosions at high redshifts. We find that the evolving IMF can well reproduce the observed redshift distribution of Swift GRBs.« less

Swift X-ray monitoring of stellar coronal variability

NASA Astrophysics Data System (ADS)

Miller, Brendan; Hagen, Cedric; Gallo, Elena; Wright, Jason T.

2018-01-01

We used California Planet Search Ca II H and K core emission measurements to identify and characterize chromospheric activity cycles in a sample of main-sequence FGK stars. About a dozen of these with existing ROSAT archival data were targeted with Swift to obtain a current epoch X-ray flux. We find that coronal variability by a factor of several is common on decade-long timescales (we attempt to link to the chromospheric cycle phase) but can also occur on short timescales between Swift visits to a given target, presumably related to stellar rotation and coronal inhomogeneity or to small flares. Additionally, we present new Swift monitoring observations of two M dwarfs with known exoplanets: GJ 15A and GJ 674. GJ 15A b is around 5.3 Earth masses with an 11.4 day orbital period, while GJ 674 is around 11.1 Earth masses with a 4.7 day orbital period. GJ 15A was observed several times in late 2014 and then monitored at approximately weekly intervals for several months in early 2016, for a total exposure of 18 ks. GJ 674 was monitored at approximately weekly intervals for most of 2016, for a total exposure of 40 ks. We provide light curves and hardness ratios for both sources, and also compare to earlier archival X-ray data. Both sources show significant X-ray variability, including between consecutive observations. We quantify the energy distribution for coronal flaring, and compare to optical results for M dwarfs from Kepler. Finally, we discuss the implications of M dwarf coronal activity for exoplanets orbiting within the nominal habitable zone.

Swift X-ray monitoring of stellar coronal variability

NASA Astrophysics Data System (ADS)

Miller, Brendan P.; Gallo, Elena; Wright, Jason; Hagen, Cedric

2017-08-01

We used California Planet Search Ca II H and K core emission measurements to identify and characterize chromospheric activity cycles in a sample of main-sequence FGK stars. About a dozen of these with existing ROSAT archival data were targeted with Swift to obtain a current epoch X-ray flux. We find that coronal variability by a factor of several is common on decade-long timescales (we attempt to link to the chromospheric cycle phase) but can also occur on short timescales between Swift visits to a given target, presumably related to stellar rotation and coronal inhomogeneity or to small flares.Additionally, we present new Swift monitoring observations of two M dwarfs with known exoplanets: GJ 15A and GJ 674. GJ 15A b is around 5.3 Earth masses with an 11.4 day orbital period, while GJ 674 is around 11.1 Earth masses with a 4.7 day orbital period. GJ 15A was observed several times in late 2014 and then monitored at approximately weekly intervals for several months in early 2016, for a total exposure of 18 ks. GJ 674 was monitored at approximately weekly intervals for most of 2016, for a total exposure of 40 ks. We provide light curves and hardness ratios for both sources, and also compare to earlier archival X-ray data. Both sources show significant X-ray variability, including between consecutive observations. We quantify the energy distribution for coronal flaring, and compare to optical results for M dwarfs from Kepler. Finally, we discuss the implications of M dwarf coronal activity for exoplanets orbiting within the nominal habitable zone.

The Lag-Luminosity Relation in the GRB Source Frame: An Investigation with Swift BAT Bursts

NASA Technical Reports Server (NTRS)

Ukwatta, T. N.; Dhuga, K. S.; Stamatikos, M.; Dermer, C. D.; Sakamoto, T.; Sonbas, E.; Parke, W. C.; Maximon, L. C.; Linnemann, J. T.; Bhat, P. N.;

Comparison Of Optical, UV, X-ray, And Gamma-ray Variations Of Selected Blazars In 2011

NASA Astrophysics Data System (ADS)

Consiglio, Santina; Marscher, A. P.; Jorstad, S. G.; Walker, G.

2012-01-01

We present multi-wavelength observations of several gamma-ray bright blazars. We combine optical data obtained at Maria Mitchell Observatory on Nantucket Island with space- and ground-based observations carried out with a variety of instruments. These include a number of other optical telescopes, the Fermi Gamma-ray Space Telescope at photon energies of 0.1-200 GeV, the Rossi X-Ray Timing Explorer at 2.4-10 keV, and the Swift satellite at 0.3-10 keV plus optical and UV wavelengths. Three of the observed blazars proved to be particularly active - BL Lac, 3C 279, and PKS 1510-089. BL Lac was of special interest, varying greatly in optical brightness from night to night. In addition, as reported by the VERITAS group, it exhibited a remarkable, short-lived flare at TeV gamma-ray energies on one of the nights. We cross-correlate the variations in the different wavebands in an effort to guide theoretical interpretations of the optical and high-energy emission from blazars. This project was supported by NSF/REU grant AST-0851892 and by the Nantucket Maria Mitchell Association. The research at Boston University was supported in part by NSF grants AST-0907893, and by NASA through Fermi grants NNX08AV65G and NNX11AQ03G.

Swift Publication Statistics: A Comparison With Other Major Observatories

NASA Astrophysics Data System (ADS)

Savaglio, S.; Grothkopf, U.

2013-03-01

Swift is a satellite equipped with γ-ray, X-ray, and optical-UV instruments aimed at discovering, localizing, and collecting data from gamma-ray bursts (GRBs). Launched at the end of 2004, this small-size mission finds about a hundred GRBs per year, totaling more than 700 events as of 2012. In addition to GRBs, Swift observes other energetic events, such as active galactic nuclei (AGNs), novae, and supernovae. Here we look at its success using bibliometric tools; that is, the number of papers using Swift data and their impact (i.e., number of citations to those papers). We derived these from the publication years 2005 to 2011, and compared them with the same numbers for other major observatories. Swift provided data for 1101 papers in the interval 2005-2011, with 24 in the first year, to 287 in the last year. In 2011, Swift had more than double the number of publications as Subaru, it overcame Gemini by a large fraction, and reached Keck. It is getting closer to the ˜400 publications of the successful high-energy missions XMM-Newton and Chandra, but is still far from the most productive telescopes, VLT (over 500) and HST (almost 800). The overall average number of citations per paper, as of 2012 November, is 28.3, which is comparable to the others, but lower than Keck (41.8). The science topics covered by Swift publications have changed from the first year, when over 80% of the papers were about GRBs, falling to less than 30% in 2011.

Gamma-ray bursts and their use as cosmic probes

PubMed Central

2017-01-01

Since the launch of the highly successful and ongoing Swift mission, the field of gamma-ray bursts (GRBs) has undergone a revolution. The arcsecond GRB localizations available within just a few minutes of the GRB alert has signified the continual sampling of the GRB evolution through the prompt to afterglow phases revealing unexpected flaring and plateau phases, the first detection of a kilonova coincident with a short GRB, and the identification of samples of low-luminosity, ultra-long and highly dust-extinguished GRBs. The increased numbers of GRB afterglows, GRB-supernova detections, redshifts and host galaxy associations has greatly improved our understanding of what produces and powers these immense, cosmological explosions. Nevertheless, more high-quality data often also reveal greater complexity. In this review, I summarize some of the milestones made in GRB research during the Swift era, and how previous widely accepted theoretical models have had to adapt to accommodate the new wealth of observational data. PMID:28791158

Recovering Swift-XRT Energy Resolution through CCD Charge Trap Mapping

NASA Technical Reports Server (NTRS)

Pagani, C.; Beardmore, A. P.; Abbey, A. F.; Mountford, C.; Osborne, J. P.; Capalbi, M.; Perri, M.; Angelini, L.; Burrows, D. N.; Campana, S.;

A Soft X-Ray Spectral Episode for the Clocked Burster, GS 1826-24 as Measured by Swift and NuSTAR

NASA Technical Reports Server (NTRS)

Chenvez, J.; Galloway, D. K.; Zand, J. J. M. In 'T; Tomsick, J. A.; Barret, D.; Chakrabarty, D.; Fuerst, F.; Boggs, S. E.; Christensen, F. E.; Craig, W. W.;

The Search for Neutrinos from Gamma Ray Bursts with AMANDA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuehn, Kyler

2006-05-19

We report on the combined analysis of over 400 GRB time periods that occurred during seven years of AMANDA observations. AMANDA has seen no neutrinos correlated with these bursts, thus we report a neutrino flux limit that is the most stringent observational limit to date. In light of the new observational opportunities afforded by Swift, we also discuss the future potential for GRB neutrino detection with AMANDA'S successor, IceCube. Finally, we briefly discuss the expansion of AMANDA'S transient point-source search to other phenomena, such as jet-driven supernovae and gamma-ray dark bursts.

Swift follow-up of the flaring blazar OJ 248

NASA Astrophysics Data System (ADS)

D'Ammando, F.; Orienti, M.

2012-10-01

Following the gamma-ray flaring activity of the flat spectrum radio quasar OJ 248 (also known as 2FGL J0830.5+2407, Nolan et al. 2012, ApJS, 199, 31) detected by Fermi LAT starting from 2012 September 23 (ATel #4421) a Swift target of opportunity observation was performed on September 28.

Cosmic Gamma-Rays

Science.gov Websites

[Argonne Logo] [DOE Logo] Cosmic Gamma-Rays Home Publications Talks People Students Argonne > ; HEP > Cosmic Gamma-Rays Projects VERITAS Past Projects TrICE What's New CTA Cosmic Gamma-Rays The

Gamma-ray Irradiation Effects on InAs/GaSb-based nBn IR Detector

DTIC Science & Technology

2011-01-01

very low noise performance. When properly passivated, conventional mercury cadmium telluride ( MCT )?based infrared detectors have been shown to...Gamma-ray Irradiation Effects on InAs/GaSb-based nBn IR Detector Vincent M. Cowan*1, Christian P. Morath1, Seth M. Swift1, Stephen Myers2...2Center for High Technology Materials, University of New Mexico, Albuquerque, NM 87106, USA ABSTRACT IR detectors operated in a space environment are

Swift XRT Observation of 1E 1841-045

NASA Astrophysics Data System (ADS)

Archibald, Robert; Scholz, Paul; Kaspi, Victoria

2013-09-01

We report on Swift XRT observations made following an X-ray/soft gamma-ray burst detected by Fermi-GBM on 13 September 2013 (GCNs 15245, 15228) from the direction of magnetar 1E 1841-045 in the supernova remnant Kes 73. As part of an ongoing monitoring campaign of 1E 1841-045, as well as several other magnetars with the Swift XRT, we observed the source on 16 September 2013 for 4.4 ks. We detect no significant change in the X-ray flux relative to pre-burst epochs: we measure an absorbed 2-10 keV flux of 2.48^(+0.07)_(-0.09) E-11 ergs/s/cm^2 for the 16 September 2013 observation, compared with an average of 2.484^(+0.006)_(-0.06) E-11 ergs/s/cm^2 for observations for the 2 years prior, or 2.39^(+0.10)_(-0.17) E-11 ergs/s/cm^2 for the prior observation on 24 August, 2013.

VizieR Online Data Catalog: SPIRE observations of Herschel-BAT sample (Shimizu+, 2016)

NASA Astrophysics Data System (ADS)

Shimizu, T. T.; Melendez, M.; Mushotzky, R. F.; Koss, M. J.; Barger, A. J.; Cowie, L. L.

2016-09-01

We selected our sample of 313 AGN from the 58 month Swift/BAT Catalogue (https://swift.gsfc.nasa.gov/results/bs58mon) (Baumgartner et al., 2012, in prep.), imposing a redshift cutoff of z<0.05. All different types of AGN were chosen only excluding Blazars/BL Lac objects which most likely introduce complicated beaming effects. To determine their AGN type, for 252 sources we used the classifications from the BAT AGN Spectroscopic Survey (Koss et al., in preparation) which compiled and analysed optical spectra for the Swift/BAT 70 month catalogue (Berney et al., 2015MNRAS.454.3622B). (2 data files).

The BAT AGN Spectroscopic Survey (BASS)

NASA Astrophysics Data System (ADS)

Koss, Michael; Trakhtenbrot, Benny; Ricci, Claudio; Lamperti, Isabella; Oh, Kyuseok; Berney, Simon; Schawinski, Kevin; Balokovic, Mislav; Baronchelli, Linda; Gehrels, Neil; Stern, Daniel; Mushotzky, Richard; Veilleux, Sylvain; Ueda, Yoshihiro; Crenshaw, D. Michael; Harrison, Fiona; Fischer, Travis C.; Treister, Ezequiel; BASS Team; Swift BAT Team

2017-01-01

We present the Swift BAT AGN Spectroscopic Survey (BASS) and discus the first four papers. The catalog represents an unprecedented census of hard-X-ray selected AGN in the local universe, with ~90% of sources at z<0.2. Starting from an all-sky catalog of AGN detected based on their 14-195 keV flux from the 70-month Swift/BAT catalog, we analyze a total of 1279 optical spectra, taken from twelve dierent telescopes, for a total of 642 spectra of unique AGN. We present the absorption and emission line measurements as well as black hole masses and accretion rates for the majority of obscured and un-obscured AGN (473), representing more than a factor of 10 increase from past studies. Consistent with previous surveys, we find an increase in the fraction of un-obscured (type 1) AGN, as measured from broad Hbeta and Halpha, with increasing 14-195 keV and 2-10 keV luminosity. We find the FWHM of the emission lines to show broad agreement with the X-ray obscuration measurements. Compared to narrow line AGN in the SDSS, the X-ray selected AGN in our sample with emission lines have a larger fraction of dustier galaxies suggesting these types of galaxies are missed in optical AGN surveys using emission line diagnostics. Additionally, we discuss follow-on efforts to study the variation of [OIII] to Xray measurements, a new method to measure accretion rates from using line ratios, a sample of 100 AGN observed with NIR spectroscopy, and an effort to measure the accretion rates and obscuration with merger stage in a subsample of mergers.

The Diverse Environments of Gamma-Ray Bursts

NASA Astrophysics Data System (ADS)

Perley, Daniel Alan

I present results from several years of concerted observations of the afterglows and host galaxies of gamma-ray bursts (GRBs), the most energetic explosions in the Universe. Short gamma-ray bursts originate from a wide variety of environments, including disk galaxies, elliptical galaxies, galaxy haloes, and intracluster and intergalactic space. Long gamma ray bursts associate almost exclusively with star-forming hosts, but the properties of these galaxies also vary widely. Some are hosted in extremely small galaxies, difficult to identify directly in emission or infer from the absorption of afterglow light, but the host luminosity distribution extends up to very luminous (> L*) systems as well. A significant fraction of long GRBs are observed along highly dust-obscured sightlines through their host medium. Some of these events are hosted within conspicuously dusty galaxies, although the hosts of other dust-obscured events show no outward signs of significant internal dust content. By measuring the wavelength dependence of dust absorption profiles using a few well-observed GRB afterglows, I provide evidence for ordinary dust with properties similar to those of dust in the Milky Way in a system at z ˜ 3, but a very different absorption profile from the dust in a galaxy at z ˜ 5, providing tentative evidence to support a transition in dust composition early in the history of the Universe. I present an observationally-determined redshift distribution for Swift GRBs, showing few to originate from high redshifts (z ≳ 5). I also provide the first photometric and spectroscopic catalogs from one of the largest GRB host-galaxy surveys ever conducted, including observations of almost 150 distinct GRB fields.

Long-Lag, Wide-pulse Gamma-Ray Bursts

NASA Technical Reports Server (NTRS)

Norris, J. P.; Bonnell, J. T.; Kazanas, D.; Scargle, . D.; Hakkila, J.; Giblin, T. W.

2004-01-01

Currently, the best available probe of the early phase of gamma-ray burst (GRB) jet attributes is the prompt gamma-ray emission, in which several intrinsic and extrinsic variables determine GRB pulse evolution. Bright, usually complex bursts have many narrow pulses that are difficult to model due to overlap. However, the relatively simple, long spectral lag, wide-pulse bursts may have simpler physics and are easier to model. In this work we analyze the temporal and spectral behavior of wide pulses in 24 long-lag bursts, using a pulse model with two shape parameters - width and asymmetry - and the Band spectral model with three shape parameters. We find that pulses in long-lag bursts are distinguished both temporally and spectrally from those in bright bursts: the pulses in long spectral lag bursts are few in number, and approximately 100 times wider (10s of seconds), have systematically lower peaks in vF(v), harder low-energy spectra and softer high-energy spectra. We find that these five pulse descriptors are essentially uncorrelated for our long-lag sample, suggesting that at least approximately 5 parameters are needed to model burst temporal and spectral behavior. However, pulse width is strongly correlated with spectral lag; hence these two parameters may be viewed as mutual surrogates. We infer that accurate formulations for estimating GRB luminosity and total energy will depend on several gamma-ray attributes, at least for long-lag bursts. The prevalence of long-lag bursts near the BATSE trigger threshold, their predominantly low vF(v) spectral peaks, and relatively steep upper power-law spectral indices indicate that Swift will detect many such bursts.

Measurement of the Shape of the Optical-IR Spectrum of Prompt Emission from Gamma-Ray Bursts

NASA Astrophysics Data System (ADS)

Grossan, Bruce; Kistaubayev, M.; Smoot, G.; Scherr, L.

2017-06-01

While the afterglow phase of gamma-ray bursts (GRBs) has been extensively measured, detections of prompt emission (i.e. during bright X-gamma emission) are more limited. Some prompt optical measurements are regularly made, but these are typically in a single wide band, with limited time resolution, and no measurement of spectral shape. Some models predict a synchrotron self-absorption spectral break somewhere in the IR-optical region. Measurement of the absorption frequency would give extensive information on each burst, including the electron Lorentz factor, the radius of emission, and more (Shen & Zhang 2008). Thus far the best prompt observations have been explained invoking a variety of models, but often with a non-unique interpretation. To understand this apparently heterogeneous behavior, and to reduce the number of possible models, it is critical to add data on the optical - IR spectral shape.Long GRB prompt X-gamma emission typically lasts ~40-80 s. The Swift BAT instrument rapidly measures GRB positions to within a few arc minutes and communicates them via the internet within a few seconds. We have measured the time for a fast-moving D=700 mm telescope to point and settle to be less than 9 s anywhere on the observable sky. Therefore, the majority of prompt optical-IR emission can be measured responding to BAT positions with this telescope. In this presentation, we describe our observing and science programs, and give our design for the Burst Simultaneous Three-channel Instrument (BSTI), which uses dichroics to send eparate bands to 3 cameras. Two EMCCD cameras, give high-time resolution in B and V; a third camera with a HgCdTe sensor covers H band, allowing us to study extinguished bursts. For a total exposure time of 10 s, we find a 5 sigma sensitivity of 21.3 and 20.3 mag in B and R for 1" seeing and Kitt Peak sky brightness, much fainter than typical previous prompt detections. We estimate 5 sigma H-band sensitivity for an IR optimized telescope to be

Sneaky Gamma-Rays: Using Gravitational Lensing to Avoid Gamma-Gamma-Absorption

NASA Astrophysics Data System (ADS)

Boettcher, Markus; Barnacka, Anna

2014-08-01

It has recently been suggested that gravitational lensing studies of gamma-ray blazars might be a promising avenue to probe the location of the gamma-ray emitting region in blazars. Motivated by these prospects, we have investigated potential gamma-gamma absorption signatures of intervening lenses in the very-high-energy gamma-ray emission from lensedblazars. We considered intervening galaxies and individual stars within these galaxies. We find that the collective radiation field of galaxies acting as sources of macrolensing are not expected to lead to significant gamma-gamma absorption. Individual stars within intervening galaxies could, in principle, cause a significant opacity to gamma-gamma absorption for VHE gamma-rays if the impact parameter (the distance of closest approach of the gamma-ray to the center of the star) is small enough. However, we find that the curvature of the photon path due to gravitational lensing will cause gamma-ray photons to maintain a sufficiently large distance from such stars to avoid significant gamma-gamma absorption. This re-inforces the prospect of gravitational-lensing studies of gamma-ray blazars without interference due to gamma-gamma absorption due to the lensing objects.

The Lag-Luminosity Relation in the GRB Source-Frame: An Investigation with Swift BAT Bursts

NASA Technical Reports Server (NTRS)

Ukwatta, T. N.; Dhuga, K. S.; Stamatikos, M.; Dermer, C. D.; Sakamoto, T.; Sonbas, E.; Parke, W. C.; Maximon, L. C.; Linnemann, J. T.; Bhat, P. N.;

An Indication of Anisotropy in Arrival Directions of Ultra-high-energy Cosmic Rays through Comparison to the Flux Pattern of Extragalactic Gamma-Ray Sources

NASA Astrophysics Data System (ADS)

Aab, A.; Abreu, P.; Aglietta, M.; Albuquerque, I. F. M.; Allekotte, I.; Almela, A.; Alvarez Castillo, J.; Alvarez-Muñiz, J.; Anastasi, G. A.; Anchordoqui, L.; Andrada, B.; Andringa, S.; Aramo, C.; Arsene, N.; Asorey, H.; Assis, P.; Avila, G.; Badescu, A. M.; Balaceanu, A.; Barbato, F.; Barreira Luz, R. J.; Beatty, J. J.; Becker, K. H.; Bellido, J. A.; Berat, C.; Bertaina, M. E.; Bertou, X.; Biermann, P. L.; Biteau, J.; Blaess, S. G.; Blanco, A.; Blazek, J.; Bleve, C.; Boháčová, M.; Bonifazi, C.; Borodai, N.; Botti, A. M.; Brack, J.; Brancus, I.; Bretz, T.; Bridgeman, A.; Briechle, F. L.; Buchholz, P.; Bueno, A.; Buitink, S.; Buscemi, M.; Caballero-Mora, K. S.; Caccianiga, L.; Cancio, A.; Canfora, F.; Caruso, R.; Castellina, A.; Catalani, F.; Cataldi, G.; Cazon, L.; Chavez, A. G.; Chinellato, J. A.; Chudoba, J.; Clay, R. W.; Cobos Cerutti, A. C.; Colalillo, R.; Coleman, A.; Collica, L.; Coluccia, M. R.; Conceição, R.; Consolati, G.; Contreras, F.; Cooper, M. J.; Coutu, S.; Covault, C. E.; Cronin, J.; D’Amico, S.; Daniel, B.; Dasso, S.; Daumiller, K.; Dawson, B. R.; de Almeida, R. M.; de Jong, S. J.; De Mauro, G.; de Mello Neto, J. R. T.; De Mitri, I.; de Oliveira, J.; de Souza, V.; Debatin, J.; Deligny, O.; Díaz Castro, M. L.; Diogo, F.; Dobrigkeit, C.; D’Olivo, J. C.; Dorosti, Q.; dos Anjos, R. C.; Dova, M. T.; Dundovic, A.; Ebr, J.; Engel, R.; Erdmann, M.; Erfani, M.; Escobar, C. O.; Espadanal, J.; Etchegoyen, A.; Falcke, H.; Farmer, J.; Farrar, G.; Fauth, A. C.; Fazzini, N.; Fenu, F.; Fick, B.; Figueira, J. M.; Filipčič, A.; Freire, M. M.; Fujii, T.; Fuster, A.; Gaïor, R.; García, B.; Gaté, F.; Gemmeke, H.; Gherghel-Lascu, A.; Ghia, P. L.; Giaccari, U.; Giammarchi, M.; Giller, M.; Głas, D.; Glaser, C.; Golup, G.; Gómez Berisso, M.; Gómez Vitale, P. F.; González, N.; Gorgi, A.; Grillo, A. F.; Grubb, T. D.; Guarino, F.; Guedes, G. P.; Halliday, R.; Hampel, M. R.; Hansen, P.; Harari, D.; Harrison, T. A.; Haungs, A.; Hebbeker, T.; Heck, D.; Heimann, P.; Herve, A. E.; Hill, G. C.; Hojvat, C.; Holt, E.; Homola, P.; Hörandel, J. R.; Horvath, P.; Hrabovský, M.; Huege, T.; Hulsman, J.; Insolia, A.; Isar, P. G.; Jandt, I.; Johnsen, J. A.; Josebachuili, M.; Jurysek, J.; Kääpä, A.; Kambeitz, O.; Kampert, K. H.; Keilhauer, B.; Kemmerich, N.; Kemp, E.; Kemp, J.; Kieckhafer, R. M.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Krause, R.; Krohm, N.; Kuempel, D.; Kukec Mezek, G.; Kunka, N.; Kuotb Awad, A.; Lago, B. L.; LaHurd, D.; Lang, R. G.; Lauscher, M.; Legumina, R.; Leigui de Oliveira, M. A.; Letessier-Selvon, A.; Lhenry-Yvon, I.; Link, K.; Lo Presti, D.; Lopes, L.; López, R.; López Casado, A.; Lorek, R.; Luce, Q.; Lucero, A.; Malacari, M.; Mallamaci, M.; Mandat, D.; Mantsch, P.; Mariazzi, A. G.; Mariş, I. C.; Marsella, G.; Martello, D.; Martinez, H.; Martínez Bravo, O.; Masías Meza, J. J.; Mathes, H. J.; Mathys, S.; Matthews, J.; Matthiae, G.; Mayotte, E.; Mazur, P. O.; Medina, C.; Medina-Tanco, G.; Melo, D.; Menshikov, A.; Merenda, K.-D.; Michal, S.; Micheletti, M. I.; Middendorf, L.; Miramonti, L.; Mitrica, B.; Mockler, D.; Mollerach, S.; Montanet, F.; Morello, C.; Morlino, G.; Mostafá, M.; Müller, A. L.; Müller, G.; Muller, M. A.; Müller, S.; Mussa, R.; Naranjo, I.; Nellen, L.; Nguyen, P. H.; Niculescu-Oglinzanu, M.; Niechciol, M.; Niemietz, L.; Niggemann, T.; Nitz, D.; Nosek, D.; Novotny, V.; Nožka, L.; Núñez, L. A.; Oikonomou, F.; Olinto, A.; Palatka, M.; Pallotta, J.; Papenbreer, P.; Parente, G.; Parra, A.; Paul, T.; Pech, M.; Pedreira, F.; Pȩkala, J.; Pelayo, R.; Peña-Rodriguez, J.; Pereira, L. A. S.; Perlin, M.; Perrone, L.; Peters, C.; Petrera, S.; Phuntsok, J.; Pierog, T.; Pimenta, M.; Pirronello, V.; Platino, M.; Plum, M.; Poh, J.; Porowski, C.; Prado, R. R.; Privitera, P.; Prouza, M.; Quel, E. J.; Querchfeld, S.; Quinn, S.; Ramos-Pollan, R.; Rautenberg, J.; Ravignani, D.; Ridky, J.; Riehn, F.; Risse, M.; Ristori, P.; Rizi, V.; Rodrigues de Carvalho, W.; Rodriguez Fernandez, G.; Rodriguez Rojo, J.; Roncoroni, M. J.; Roth, M.; Roulet, E.; Rovero, A. C.; Ruehl, P.; Saffi, S. J.; Saftoiu, A.; Salamida, F.; Salazar, H.; Saleh, A.; Salina, G.; Sánchez, F.; Sanchez-Lucas, P.; Santos, E. M.; Santos, E.; Sarazin, F.; Sarmento, R.; Sarmiento-Cano, C.; Sato, R.; Schauer, M.; Scherini, V.; Schieler, H.; Schimp, M.; Schmidt, D.; Scholten, O.; Schovánek, P.; Schröder, F. G.; Schröder, S.; Schulz, A.; Schumacher, J.; Sciutto, S. J.; Segreto, A.; Shadkam, A.; Shellard, R. C.; Sigl, G.; Silli, G.; Šmída, R.; Snow, G. R.; Sommers, P.; Sonntag, S.; Soriano, J. F.; Squartini, R.; Stanca, D.; Stanič, S.; Stasielak, J.; Stassi, P.; Stolpovskiy, M.; Strafella, F.; Streich, A.; Suarez, F.; Suarez Durán, M.; Sudholz, T.; Suomijärvi, T.; Supanitsky, A. D.; Šupík, J.; Swain, J.; Szadkowski, Z.; Taboada, A.; Taborda, O. A.; Theodoro, V. M.; Timmermans, C.; Todero Peixoto, C. J.; Tomankova, L.; Tomé, B.; Torralba Elipe, G.; Travnicek, P.; Trini, M.; Ulrich, R.; Unger, M.; Urban, M.; Valdés Galicia, J. F.; Valiño, I.; Valore, L.; van Aar, G.; van Bodegom, P.; van den Berg, A. M.; van Vliet, A.; Varela, E.; Vargas Cárdenas, B.; Vázquez, R. A.; Veberič, D.; Ventura, C.; Vergara Quispe, I. D.; Verzi, V.; Vicha, J.; Villaseñor, L.; Vorobiov, S.; Wahlberg, H.; Wainberg, O.; Walz, D.; Watson, A. A.; Weber, M.; Weindl, A.; Wiedeński, M.; Wiencke, L.; Wilczyński, H.; Wirtz, M.; Wittkowski, D.; Wundheiler, B.; Yang, L.; Yushkov, A.; Zas, E.; Zavrtanik, D.; Zavrtanik, M.; Zepeda, A.; Zimmermann, B.; Ziolkowski, M.; Zong, Z.; Zuccarello, F.; The Pierre Auger Collaboration

2018-02-01

A new analysis of the data set from the Pierre Auger Observatory provides evidence for anisotropy in the arrival directions of ultra-high-energy cosmic rays on an intermediate angular scale, which is indicative of excess arrivals from strong, nearby sources. The data consist of 5514 events above 20 {EeV} with zenith angles up to 80° recorded before 2017 April 30. Sky models have been created for two distinct populations of extragalactic gamma-ray emitters: active galactic nuclei from the second catalog of hard Fermi-LAT sources (2FHL) and starburst galaxies from a sample that was examined with Fermi-LAT. Flux-limited samples, which include all types of galaxies from the Swift-BAT and 2MASS surveys, have been investigated for comparison. The sky model of cosmic-ray density constructed using each catalog has two free parameters, the fraction of events correlating with astrophysical objects, and an angular scale characterizing the clustering of cosmic rays around extragalactic sources. A maximum-likelihood ratio test is used to evaluate the best values of these parameters and to quantify the strength of each model by contrast with isotropy. It is found that the starburst model fits the data better than the hypothesis of isotropy with a statistical significance of 4.0σ, the highest value of the test statistic being for energies above 39 {EeV}. The three alternative models are favored against isotropy with 2.7σ–3.2σ significance. The origin of the indicated deviation from isotropy is examined and prospects for more sensitive future studies are discussed. Any correspondence should be addressed to .

An Indication of Anisotropy in Arrival Directions of Ultra-high-energy Cosmic Rays through Comparison to the Flux Pattern of Extragalactic Gamma-Ray Sources

DOE PAGES

Aab, A.; Abreu, P.; Aglietta, M.; ...

2018-02-02

A new analysis of the dataset from the Pierre Auger Observatory provides evidence for anisotropy in the arrival directions of ultra-high-energy cosmic rays on an intermediate angular scale, which is indicative of excess arrivals from strong, nearby sources. The data consist of 5514 events above 20 EeV with zenith angles up to 80 deg recorded before 2017 April 30. Sky models have been created for two distinct populations of extragalactic gamma-ray emitters: active galactic nuclei from the second catalog of hard Fermi-LAT sources (2FHL) and starburst galaxies from a sample that was examined with Fermi-LAT. Flux-limited samples, which include allmore » types of galaxies from the Swift-BAT and 2MASS surveys, have been investigated for comparison. The sky model of cosmic-ray density constructed using each catalog has two free parameters, the fraction of events correlating with astrophysical objects and an angular scale characterizing the clustering of cosmic rays around extragalactic sources. A maximum-likelihood ratio test is used to evaluate the best values of these parameters and to quantify the strength of each model by contrast with isotropy. It is found that the starburst model fits the data better than the hypothesis of isotropy with a statistical significance of 4.0 sigma, the highest value of the test statistic being for energies above 39 EeV. The three alternative models are favored against isotropy with 2.7-3.2 sigma significance. The origin of the indicated deviation from isotropy is examined and prospects for more sensitive future studies are discussed.« less

An Indication of Anisotropy in Arrival Directions of Ultra-high-energy Cosmic Rays through Comparison to the Flux Pattern of Extragalactic Gamma-Ray Sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aab, A.; Abreu, P.; Aglietta, M.

A new analysis of the dataset from the Pierre Auger Observatory provides evidence for anisotropy in the arrival directions of ultra-high-energy cosmic rays on an intermediate angular scale, which is indicative of excess arrivals from strong, nearby sources. The data consist of 5514 events above 20 EeV with zenith angles up to 80 deg recorded before 2017 April 30. Sky models have been created for two distinct populations of extragalactic gamma-ray emitters: active galactic nuclei from the second catalog of hard Fermi-LAT sources (2FHL) and starburst galaxies from a sample that was examined with Fermi-LAT. Flux-limited samples, which include allmore » types of galaxies from the Swift-BAT and 2MASS surveys, have been investigated for comparison. The sky model of cosmic-ray density constructed using each catalog has two free parameters, the fraction of events correlating with astrophysical objects and an angular scale characterizing the clustering of cosmic rays around extragalactic sources. A maximum-likelihood ratio test is used to evaluate the best values of these parameters and to quantify the strength of each model by contrast with isotropy. It is found that the starburst model fits the data better than the hypothesis of isotropy with a statistical significance of 4.0 sigma, the highest value of the test statistic being for energies above 39 EeV. The three alternative models are favored against isotropy with 2.7-3.2 sigma significance. The origin of the indicated deviation from isotropy is examined and prospects for more sensitive future studies are discussed.« less

The status of BAT detector

NASA Astrophysics Data System (ADS)

Lien, Amy; Markwardt, Craig B.; Krimm, Hans Albert; Barthelmy, Scott D.; Cenko, Bradley

2018-01-01

We will present the current status of the Swift/BAT detector. In particular, we will report the updated detector gain calibration, the number of enable detectors, and the global bad time intervals with potential calibration issues. We will also summarize the results of the yearly BAT calibration using the Crab nebula. Finally, we will discuss the effects on the BAT survey, such as the sensitivity, localization, and spectral analysis, due to the changes in detector status.

Two Active States of the Narrow-Line Gamma-Ray-Loud AGN GB 1310 + 487

NASA Technical Reports Server (NTRS)

Sokolovsky, K. V.; Schinzel, F. K.; Tanaka, Y. T.; Abolmasov, P. K.; Angelakis, E.; Bulgarelli, A.; Carrasco, L.; Cenko, S. B.; Cheung, C. C.; Clubb, K. I.;

SWIFT BAT Loop Heat Pipe Thermal System Characteristics and Ground/Flight Operation Procedure

NASA Technical Reports Server (NTRS)

Choi, Michael K.

2003-01-01

The SWIFT Burst Alert Telescope (BAT) Detector Array has a total power dissipation of 208 W. To meet the stringent temperature gradient and thermal stability requirements in the normal operational mode, and heater power budget in both the normal operational and safehold modes, the Detector Array is thermally well coupled to eight constant conductance heat pipes (CCHPs) embedded in the Detector Array Plate (DAP), and two loop heat pipes (LHPs) transport heat fiom the CCHPs to a radiator. The CCHPs have ammonia as the working fluid and the LHPs have propylene as the working fluid. Precision heater controllers, which have adjustable set points in flight, are used to control the LHP compensation chamber and Detector Array XA1 ASIC temperatures. The radiator has the AZ-Tek AZW-LA-II low-alpha white paint as the thermal coating and is located on the anti-sun side of the spacecraft. This paper presents the characteristics, ground operation and flight operation procedures of the LHP thermal system.

Studying The Spectral Shape And The X-ray/uv Variability Of Active Galactic Nuclei With Data From Swift And Xmm Archives

NASA Astrophysics Data System (ADS)

Turriziani, Sara

2011-01-01

Many efforts have been made in understanding the underlying origin of variability in Active Galactic Nuclei (AGN), but at present they could give still no conclusive answers. Since a deeper knowledge of variability will enable to understand better the accretion process onto supermassive black holes, I built the first ensemble struction function analysis of the X-ray variability of samples of quasars with data from Swift and XMM-Newton archives in order to study the average properties of their variability. Moreover, it is known that UV and X-ray luminosities of quasars are correlated and recent studies quantified this relation across 5 orders of magnitude. In this context, I presents results on the X-ray/UV ratio from simultaneous observations in UV and X-ray bands of a sample of quasars with data from XMM-Newton archive. Lastly, I will present a complete sample of Swift/SDSS faint blazars and other non-thermal dominated AGNs. I used this sample to calculate the general statistical properties of faint blazars and radio galaxies and in particular their Radio LogN-LogS with fluxes down to 10 mJy, in order to gain knowledge on the contribution to Cosmic Microwave Background (CMB) and gamma-ray background radiation from the faint tail of the radio population. I acknowledge financial support through Grant ASI I/088/06/0.

Discovery of the Accretion-Powered Millisecond Pulsar SWIFT 51756.9-2508 with a Low-Mass Companion

NASA Technical Reports Server (NTRS)

Krimm, H.A.; Markwardt, C.B.; Deloye, C.J.; Romano, P.; Chakrabarty, S.; Campana. S.; Cummings, J.C.; Galloway, D.K.; Gehrels, N.; Hartman, J.M.;

Correlative Analysis of GRBs detected by Swift, Konus and HETE

NASA Technical Reports Server (NTRS)

Krimm, Hans A.; Barthelmy, S. D.; Gehrels, N.; Hullinger, D.; Sakamoto, T.; Donaghy, T.; Lamb, D. Q.; Pal'shin, V.; Golenetskii, S.; Ricker, G. R.

2005-01-01

Swift has now detected a large enough sample of gamma-ray bursts (GRBs) to allow correlation studies of burst parameters. Such studies of earlier data sets have yielded important results leading to further understanding of burst parameters and classifications. This work focuses on seventeen Swift bursts that have also been detected either by Konus-Wind or HETE-II, providing high energy spectra and fits to E(sub peak). Eight of these bursts have spectroscopic redshifts and for others we can estimate redshifts using the variability/luminosity relationship. We can also compare E(sub peak) with E(sub iso), and for those bursts for which a jet break was observed in the afterglow we can derive E(sub g) and test the relationship between E(peak) and E(sub gamma). For all bursts we can derive durations and hardness ratios from the prompt emission.

Recent Progress on GRBs with Swift

NASA Technical Reports Server (NTRS)

Gehrels, N.; Cannizzo, J. K.

2010-01-01

We are in an exciting period of discovery for gamma-ray bursts. The Swift observatory is detecting 100 bursts per year, providing arcsecond localizations and sensitive observations of the prompt and afterglow emission. In addition, rapid-response telescopes on the ground have new capabilities to study optical emission during the prompt phase and spectral signatures of the host galaxies. The combined data set is enabling great advances in our understanding of GRBs including afterglow physics, short burst origin, and supernova physics.

Swift, INTEGRAL, RXTE, and Spitzer Reveal IGR J16283-4838

NASA Technical Reports Server (NTRS)

Beckmann, V.; Gehrels, N.; Markwardt, C.; Barthelmy S.; Soldi, S.; Paizis, A.; Mowlavi, N.; Kennca, J. A.; Burrows, D. N.; Chester, M.

2005-01-01

We present the first combined study of the recently discovered source IGR J16283-4838 with Swift, INTEGRAL, and RXTE. The source, discovered by INTEGRAL on April 7, 2005, shows a highly absorbed (variable N(sub H) = 0.4-1.7 x 10(exp 23) /sq cm) and flat (Gamma approx. 1) spectrum in the Swift/XRT and RXTE/PCA data. No optical counterpart is detectable (V > 20 mag), but a possible infrared counterpart within the Swift/XRT error radius is detected in the 2MASS and Spitzer/GLIMPSE survey. The observations suggest that IGR J16283-4838 is a high mass X-ray binary containing a neutron star embedded in Compton thick material. This makes IGR J16283-4838 a member of the class of highly absorbed HMXBs, discovered by INTEGRAL.

Prompt optical emission from gamma-ray bursts with multiple timescale variability of central engine activities

NASA Astrophysics Data System (ADS)

Xu, Si-Yao; Li, Zhuo

2014-04-01

Complete high-resolution light curves of GRB 080319B observed by Swift present an opportunity for detailed temporal analysis of prompt optical emission. With a two-component distribution of initial Lorentz factors, we simulate the dynamical process of shells being ejected from the central engine in the framework of the internal shock model. The emitted radiations are decomposed into different frequency ranges for a temporal correlation analysis between the light curves in different energy bands. The resulting prompt optical and gamma-ray emissions show similar temporal profiles, with both showing a superposition of a component with slow variability and a component with fast variability, except that the gamma-ray light curve is much more variable than its optical counterpart. The variability in the simulated light curves and the strong correlation with a time lag between the optical and gamma-ray emissions are in good agreement with observations of GRB 080319B. Our simulations suggest that the variations seen in the light curves stem from the temporal structure of the shells injected from the central engine of gamma-ray bursts. Future observations with high temporal resolution of prompt optical emission from GRBs, e.g., by UFFO-Pathfinder and SVOM-GWAC, will provide a useful tool for investigating the central engine activity.

The gamma-ray observatory

NASA Technical Reports Server (NTRS)

1991-01-01

An overview is given of the Gamma Ray Observatory (GRO) mission. Detection of gamma rays and gamma ray sources, operations using the Space Shuttle, and instruments aboard the GRO, including the Burst and Transient Source Experiment (BATSE), the Oriented Scintillation Spectrometer Experiment (OSSE), the Imaging Compton Telescope (COMPTEL), and the Energetic Gamma Ray Experiment Telescope (EGRET) are among the topics surveyed.

Gamma-Ray Bursts: Characteristics and Prospects

NASA Astrophysics Data System (ADS)

Azzam, W. J.; Zitouni, H.; Guessoum, N.

2017-06-01

Gamma-ray bursts (GRBs) are the most powerful explosions in the universe. They have remained the object of intense research ever since their discovery was declassified in the early 1970s. Several space-borne missions have been dedicated to their study, including the Compton Gamma-Ray Burst Observatory (CGRO) in the 1990s and the current Swift and Fermi satellites. However, despite several decades of focused research, the precise mechanisms behind these enigmatic explosions have not been fully established. In the first part of this paper, we review what is currently known about GRBs. This includes: GRB light-curves and spectra; the different progenitor models, i.e., the "collapsar" and "merger" models; and the afterglow characteristics, including external shocks and the surrounding medium. In the second part of the paper, we present our work, which focuses on utilizing GRBs as cosmological probes. GRBs are ideal cosmological tools, because they have been observed to great distances (redshifts up to z = 9.4) and their radiation is unencumbered by any intervening dust. Although GRBs are not standard candles, the discovery of several energy and luminosity correlations, like the Amati relation which correlates the intrinsic spectral peak energy, Ep,i to the equivalent isotropic energy, Eiso , has ushered in a new era in which GRBs are used to investigate cosmological issues like the star formation rate and the value of the matter-density parameter, ΩM.

ON THE LATE-TIME SPECTRAL SOFTENING FOUND IN X-RAY AFTERGLOWS OF GAMMA-RAY BURSTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Yuan-Zhu; Liang, En-Wei; Lu, Zu-Jia

2016-02-20

Strong spectral softening has been revealed in the late X-ray afterglows of some gamma-ray bursts (GRBs). The scenario of X-ray scattering around the circumburst dusty medium has been supported by previous works due to its overall successful prediction of both the temporal and spectral evolution of some X-ray afterglows. To further investigate the observed feature of spectral softening we now systematically search the X-ray afterglows detected by the X-ray telescope aboard Swift and collect 12 GRBs with significant late-time spectral softening. We find that dust scattering could be the dominant radiative mechanism for these X-ray afterglows regarding their temporal andmore » spectral features. For some well-observed bursts with high-quality data, the time-resolved spectra could be well-produced within the scattering scenario by taking into account the X-ray absorption from the circumburst medium. We also find that during spectral softening the power-law index in the high-energy end of the spectra does not vary much. The spectral softening is mainly manifested by the spectral peak energy continually moving to the soft end.« less

Alternative temporal classification of long Gamma Ray Bursts

NASA Astrophysics Data System (ADS)

Alejandro Vasquez, Nicolas; Baquero, Andres; Andrade, David

2015-08-01

In order to increase the understanding on Gamma Ray Bursts, many attempts of classification have been proposed. Starting with the canonical classification into long and short GRBs, alternative classifications taking into account the cosmological origin of GRBs have been analyzed. In the present work we propose an alternative classification based on two temporal estimators, the Auto Correlation Function (ACF) of the light curves and the emission time which considered the time where the bursts engine is active. The time estimators chosen reflects the internal evolution of the GRB and the internal structure. Using a sample of 61 bright GRBs detected by SWIFT satellite with known redshift, we proposed a bimodal distribution of long bursts. The two types of bursts have different internal structure suggesting different progenitors.

Statistical Distributions of Optical Flares from Gamma-Ray Bursts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yi, Shuang-Xi; Yu, Hai; Wang, F. Y.

2017-07-20

We statistically study gamma-ray burst (GRB) optical flares from the Swift /UVOT catalog. We compile 119 optical flares, including 77 flares with redshift measurements. Some tight correlations among the timescales of optical flares are found. For example, the rise time is correlated with the decay time, and the duration time is correlated with the peak time of optical flares. These two tight correlations indicate that longer rise times are associated with longer decay times of optical flares and also suggest that broader optical flares peak at later times, which are consistent with the corresponding correlations of X-ray flares. We alsomore » study the frequency distributions of optical flare parameters, including the duration time, rise time, decay time, peak time, and waiting time. Similar power-law distributions for optical and X-ray flares are found. Our statistic results imply that GRB optical flares and X-ray flares may share the similar physical origin, and both of them are possibly related to central engine activities.« less

Testing gamma-ray burst models with the afterglow of GRB 090102

NASA Astrophysics Data System (ADS)

Gendre, B.; Klotz, A.; Palazzi, E.; Krühler, T.; Covino, S.; Afonso, P.; Antonelli, L. A.; Atteia, J. L.; D'Avanzo, P.; Boër, M.; Greiner, J.; Klose, S.

2010-07-01

We present the observations of the afterglow of gamma-ray burst GRB 090102. Optical data taken by the Telescope a Action Rapide pour les Objets Transitoires (TAROT), Rapid Eye Mount (REM), Gamma-Ray burst Optical/Near-Infrared Detector (GROND), together with publicly available data from Palomar, Instituto de Astrofísica de Canarias (IAC) and Nordic Optical Telescope (NOT) telescopes, and X-ray data taken by the XRT instrument on board the Swift spacecraft were used. This event features an unusual light curve. In X-rays, it presents a constant decrease with no hint of temporal break from 0.005 to 6d after the burst. In the optical, the light curve presents a flattening after 1ks. Before this break, the optical light curve is steeper than that of the X-ray. In the optical, no further break is observed up to 10d after the burst. We failed to explain these observations in light of the standard fireball model. Several other models, including the cannonball model were investigated. The explanation of the broad-band data by any model requires some fine-tuning when taking into account both optical and X-ray bands. Based on observations obtained with TAROT, REM, GROND. E-mail: bruce.gendre@asdc.asi.it ‡ Present address: ASDC, Via Galileo Galilei, 00044 Frascati, Italy.

Gamma ray transients

NASA Technical Reports Server (NTRS)

Cline, Thomas L.

1987-01-01

The discovery of cosmic gamma ray bursts was made with systems designed at Los Alamos Laboratory for the detection of nuclear explosions beyond the atmosphere. HELIOS-2 was the first gamma ray burst instrument launched; its initial results in 1976, seemed to deepen the mystery around gamma ray transients. Interplanetary spacecraft data were reviewed in terms of explaining the behavior and source of the transients.

X-ray and gamma ray astronomy detectors

NASA Technical Reports Server (NTRS)

Decher, Rudolf; Ramsey, Brian D.; Austin, Robert

1994-01-01

X-ray and gamma ray astronomy was made possible by the advent of space flight. Discovery and early observations of celestial x-rays and gamma rays, dating back almost 40 years, were first done with high altitude rockets, followed by Earth-orbiting satellites> once it became possible to carry detectors above the Earth's atmosphere, a new view of the universe in the high-energy part of the electromagnetic spectrum evolved. Many of the detector concepts used for x-ray and gamma ray astronomy were derived from radiation measuring instruments used in atomic physics, nuclear physics, and other fields. However, these instruments, when used in x-ray and gamma ray astronomy, have to meet unique and demanding requirements related to their operation in space and the need to detect and measure extremely weak radiation fluxes from celestial x-ray and gamma ray sources. Their design for x-ray and gamma ray astronomy has, therefore, become a rather specialized and rapidly advancing field in which improved sensitivity, higher energy and spatial resolution, wider spectral coverage, and enhanced imaging capabilities are all sought. This text is intended as an introduction to x-ray and gamma ray astronomy instruments. It provides an overview of detector design and technology and is aimed at scientists, engineers, and technical personnel and managers associated with this field. The discussion is limited to basic principles and design concepts and provides examples of applications in past, present, and future space flight missions.

Basics of Gamma Ray Detection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stinnett, Jacob; Venkataraman, Ram

The objective of this training is to explain the origin of x-rays and gamma rays, gamma ray interactions with matter, detectors and electronics used in gamma ray-spectrometry, and features of a gamma-ray spectrum for nuclear material that is safeguarded.

Implications of Gamma-Ray Transparency Constraints in Blazars: Minimum Distances and Gamma-Ray Collimation

NASA Technical Reports Server (NTRS)

Becker, Peter A.; Kafatos, Menas

1995-01-01

We develop a general expression for the gamma - gamma absorption coefficient, alpha(sub gamma(gamma)) for gamma-rays propagating in an arbitrary direction at an arbitrary point in space above an X-ray-emitting accretion disk. The X-ray intensity is assumed to vary as a power law in energy and radius between the outer disk radius, R(sub 0), and the inner radius, R(sub ms) which is the radius of marginal stability for a Schwarzschild black hole. We use our result for alpha(sub gamma(gamma)) to calculate the gamma - gamma optical depth, tau(sub gamma(gamma)) for gamma - rays created at height z and propagating at angle Phi relative to the disk axis, and we show that for Phi = 0 and z greater than or approx equal to R(sub 0), tau(sub gamma(gamma)) proportional to Epsilon(sup alpha)z(sup -2(alpha) - 3), where alpha is the X-ray spectral index and Epsilon is the gamma - ray energy. As an application, we use our formalism to compute the minimum distance between the central black hole and the site of production of the gamma-rays detected by EGRET during the 1991 June flare of 3C 279. In order to obtain an upper limit, we assume that all of the X-rays observed contemporaneously by Ginga were emitted by the disk. Our results suggest that the observed gamma - rays may have originated within less than or approx equal to 45 GM/sq c from a black hole of mass greater than or approx equal to 10(exp 9) solar mass, perhaps in active plasma located above the central funnel of the accretion disk. This raises the possibility of establishing a direct connection between the production of the observed gamma - rays and the accretion of material onto the black hole. We also consider the variation of the optical depth as a function of the angle of propagation Phi. Our results indicate that the "focusing" of the gamma - rays along the disk axis due to pair production is strong enough to explain the observed degree of alignment in blazar sources. If the gamma - rays are produced isotropically

Method of incident low-energy gamma-ray direction reconstruction in the GAMMA-400 gamma-ray space telescope

NASA Astrophysics Data System (ADS)

Kheymits, M. D.; Leonov, A. A.; Zverev, V. G.; Galper, A. M.; Arkhangelskaya, I. V.; Arkhangelskiy, A. I.; Suchkov, S. I.; Topchiev, N. P.; Yurkin, Yu T.; Bakaldin, A. V.; Dalkarov, O. D.

2016-02-01

The GAMMA-400 gamma-ray space-based telescope has as its main goals to measure cosmic γ-ray fluxes and the electron-positron cosmic-ray component produced, theoretically, in dark-matter-particles decay or annihilation processes, to search for discrete γ-ray sources and study them in detail, to examine the energy spectra of diffuse γ-rays — both galactic and extragalactic — and to study gamma-ray bursts (GRBs) and γ-rays from the active Sun. Scientific goals of GAMMA-400 telescope require fine angular resolution. The telescope is of a pair-production type. In the converter-tracker, the incident gamma-ray photon converts into electron-positron pair in the tungsten layer and then the tracks are detected by silicon- strip position-sensitive detectors. Multiple scattering processes become a significant obstacle in the incident-gamma direction reconstruction for energies below several gigaelectronvolts. The method of utilising this process to improve the resolution is proposed in the presented work.

Gamma Ray Astronomy

NASA Technical Reports Server (NTRS)

Wu, S. T.

2000-01-01

The project has progressed successfully during this period of performance. The highlights of the Gamma Ray Astronomy teams efforts are: (1) Support daily BATSE data operations, including receipt, archival and dissemination of data, quick-look science analysis, rapid gamma-ray burst and transient monitoring and response efforts, instrument state-of-health monitoring, and instrument commanding and configuration; (2) On-going scientific analysis, including production and maintenance of gamma-ray burst, pulsed source and occultation source catalogs, gamma-ray burst spectroscopy, studies of the properties of pulsars and black holes, and long-term monitoring of hard x-ray sources; (3) Maintenance and continuous improvement of BATSE instrument response and calibration data bases; (4) Investigation of the use of solid state detectors for eventual application and instrument to perform all sky monitoring of X-Ray and Gamma sources with high sensitivity; and (5) Support of BATSE outreach activities, including seminars, colloquia and World Wide Web pages. The highlights of this efforts can be summarized in the publications and presentation list.

Swift J1822.3-1606: Optical spectroscopy of the counterpart candidates from the 10.4m GTC

NASA Astrophysics Data System (ADS)

de Ugarte Postigo, A.; Munoz-Darias, T.

2011-07-01

We have performed optical spectroscopy of the two objects (S1 and S2; ATEL #3496, #3502) present within the Swift/XRT error circle of the Soft Gamma-ray Repeater (SGR) candidate, Swift J1822.3-1606 (ATEL #3488, #3489, #3490, #3491, #3493, #3501, #3503). Observations were performed on July 20, 2011 using the OSIRIS spectrograph at the 10.4m Gran Telescopio de Canarias (GTC) telescope in La Palma, Spain.

The two-component afterglow of Swift GRB 050802

NASA Astrophysics Data System (ADS)

Oates, S. R.; de Pasquale, M.; Page, M. J.; Blustin, A. J.; Zane, S.; McGowan, K.; Mason, K. O.; Poole, T. S.; Schady, P.; Roming, P. W. A.; Page, K. L.; Falcone, A.; Gehrels, N.

2007-09-01

This paper investigates GRB 050802, one of the best examples of a Swift gamma-ray burst afterglow that shows a break in the X-ray light curve, while the optical counterpart decays as a single power law. This burst has an optically bright afterglow of 16.5 mag, detected throughout the 170-650nm spectral range of the Ultraviolet and Optical Telescope (UVOT) onboard Swift. Observations began with the X-ray Telescope and UVOT telescopes 286s after the initial trigger and continued for 1.2 ×106s. The X-ray light curve consists of three power-law segments: a rise until 420s, followed by a slow decay with α =0.63 +/-0.03 until 5000s, after which, the light curve decays faster with a slope of α3 =1.59 +/-0.03. The optical light curve decays as a single power law with αO =0.82 +/-0.03 throughout the observation. The X-ray data on their own are consistent with the break at 5000s being due to the end of energy injection. Modelling the optical to X-ray spectral energy distribution, we find that the optical afterglow cannot be produced by the same component as the X-ray emission at late times, ruling out a single-component afterglow. We therefore considered two-component jet models and find that the X-ray and optical emission is best reproduced by a model in which both components are energy injected for the duration of the observed afterglow and the X-ray break at 5000s is due to a jet break in the narrow component. This bright, well-observed burst is likely a guide for interpreting the surprising finding of Swift that bursts seldom display achromatic jet breaks.

X-ray detection of Nova Del 2013 with Swift

NASA Astrophysics Data System (ADS)

Castro-Tirado, Alberto J.; Martin-Carrillo, Antonio; Hanlon, Lorraine

2013-08-01

Continuous X-ray monitoring by Swift of Nova Del 2013 (see CBET #3628) shows an increase of X-ray emission at the source location compared to previous observations (ATEL #5283, ATEL #5305) during a 3.9 ksec observation at UT 2013-08-22 12:05. With the XRT instrument operating in window timing mode, 744 counts were extracted from a 50 pixel long source region and 324 counts from a similar box for a background region, resulting in a 13-sigma detection with a net count rate of 0.11±0.008 counts/sec.

Swift/XRT follow-up of the flaring blazar PKS 1424-41

NASA Astrophysics Data System (ADS)

D'Ammando, F.; Orienti, M.

2013-01-01

Following the optical and gamma-ray flaring activity of the flat spectrum radio quasar PKS 1424-41 (also known as 2FGL J1428.0-4206, Nolan et al. 2012, ApJS, 199, 31) detected by ATOM and Fermi LAT on 2013 January 6 (ATel #4714), a Swift target of opportunity observation was performed on January 7.

Broad-band characteristics of seven new hard X-ray selected cataclysmic variables

NASA Astrophysics Data System (ADS)

Bernardini, F.; de Martino, D.; Mukai, K.; Russell, D. M.; Falanga, M.; Masetti, N.; Ferrigno, C.; Israel, G.

2017-10-01

We present timing and spectral analysis of a sample of seven hard X-ray selected cataclysmic variable candidates based on simultaneous X-ray and optical observations collected with XMM-Newton, complemented with Swift/BAT and INTEGRAL /IBIS hard X-ray data and ground-based optical photometry. For six sources, X-ray pulsations are detected for the first time in the range of ˜296-6098 s, identifying them as members of the magnetic class. Swift J0927.7-6945, Swift J0958.0-4208, Swift J1701.3-4304, Swift J2113.5+5422 and possibly PBC J0801.2-4625 are intermediate polars (IPs), while Swift J0706.8+0325 is a short (1.7 h) orbital period polar, the 11th hard X-ray-selected identified so far. X-ray orbital modulation is also observed in Swift J0927.7-6945 (5.2 h) and Swift J2113.5+5422 (4.1 h). Swift J1701.3-4304 is discovered as the longest orbital period (12.8 h) deep eclipsing IP. The spectra of the magnetic systems reveal optically thin multitemperature emission between 0.2 and 60 keV. Energy-dependent spin pulses and the orbital modulation in Swift J0927.7-6945 and Swift J2113.5+5422 are due to intervening local high-density absorbing material (NH ˜ 1022 - 23 cm-2). In Swift J0958.0-4208 and Swift J1701.3-4304, a soft X-ray blackbody (kT ˜ 50 and ˜80 eV) is detected, adding them to the growing group of `soft' IPs. White dwarf masses are determined in the range of ˜ 0.58-1.18 M⊙, indicating massive accreting primaries in five of them. Most sources accrete at rates lower than the expected secular value for their orbital period. Formerly proposed as a long-period (9.4 h) nova-like CV, Swift J0746.3-1608 shows peculiar spectrum and light curves suggesting either an atypical low-luminosity CV or a low-mass X-ray binary.

Swift detection of MAXI J1820+070

NASA Astrophysics Data System (ADS)

Kennea, J. A.; Marshall, F. E.; Page, K. L.; Palmer, D. M.; Siegel, M. H.; Neil Gehrels Swift Observatory Team

2018-03-01

This is reposted from GCN #22471 as it is of interest to the transient community. At 00:11:39 UT, the Swift Burst Alert Telescope (BAT) triggered and located MAXI J1820+070 (Kawamuro et al, 2018; ATel #11399) (trigger=813771, retriggering as trigger=813772).

Swift BAT Thermal Recovery After Loop Heat Pipe #0 Secondary Heater Controller Failure in October 2015

NASA Technical Reports Server (NTRS)

Choi, Michael K.

2016-01-01

The Swift BAT LHP #0 primary heater controller failed on March 31, 2010. It has been disabled. On October 31, 2015, the secondary heater controller of this LHP failed. On November 1, 2015, the LHP #0 CC temperature increased to as 18.6 C, despite that the secondary heater controller set point was 8.8 C. It caused the average DM XA1 temperature to increase to 25.9 C, which was 5 C warmer than nominal. As a result, the detectors became noisy. To solve this problem, the LHP #1 secondary heater controller set point was decreased in 0.5 C decrements to 2.2 C. The set-point decrease restored the average DM XA1 temperature to a nominal value of 19.7 C on November 21.

Probing the Nature of Short Swift Bursts via Deep INTEGRAL Monitoring of GRB 050925

NASA Technical Reports Server (NTRS)

Sakamoto, T.; Barbier, L.; Barthelmy, S. D.; Cummings, J. R.; Fenimore, E. E.; Gehrels, N.; Krimm, H. A.; Markwardt, C. B.; Palmer, D. M.; Parsons, A. M.;

Gamma ray camera

DOEpatents

Perez-Mendez, Victor

1997-01-01

A gamma ray camera for detecting rays emanating from a radiation source such as an isotope. The gamma ray camera includes a sensor array formed of a visible light crystal for converting incident gamma rays to a plurality of corresponding visible light photons, and a photosensor array responsive to the visible light photons in order to form an electronic image of the radiation therefrom. The photosensor array is adapted to record an integrated amount of charge proportional to the incident gamma rays closest to it, and includes a transparent metallic layer, photodiode consisting of a p-i-n structure formed on one side of the transparent metallic layer, and comprising an upper p-type layer, an intermediate layer and a lower n-type layer. In the preferred mode, the scintillator crystal is composed essentially of a cesium iodide (CsI) crystal preferably doped with a predetermined amount impurity, and the p-type upper intermediate layers and said n-type layer are essentially composed of hydrogenated amorphous silicon (a-Si:H). The gamma ray camera further includes a collimator interposed between the radiation source and the sensor array, and a readout circuit formed on one side of the photosensor array.

Crab Nebula Variations in Hard X-rays

NASA Technical Reports Server (NTRS)

Wilson-Hodge, Colleen A.

2012-01-01

The Crab Nebula was surprisingly variable from 2001-2010, with less variability before 2001 and since mid-2010. We presented evidence for spectral softening from RXTE, Swift/BAT, and Fermi GBM during the mid-2008-2010 flux decline. We see no clear connections between the hard X-ray variations and the GeV flares

Swift follow-up of the flaring NLSy1 1H 0323+342

NASA Astrophysics Data System (ADS)

D'Ammando, Filippo; Carpenter, Bryce; Ojha, Roopesh

2013-09-01

Following the gamma-ray flaring activity of the narrow-line Seyfert 1 galaxy 1H 0323+342 (also known as 2FGL J0324.8+3408; Nolan et al. 2012, ApJS, 199, 31) detected by Fermi LAT on 2013 August 28 (ATel #5344), a Swift target of opportunity observation was performed on August 30.

Predictions for Swift Follow-up Observations of Advanced LIGO/Virgo Gravitational Wave Sources

NASA Astrophysics Data System (ADS)

Racusin, Judith; Evans, Phil; Connaughton, Valerie

2015-04-01

The likely detection of gravitational waves associated with the inspiral of neutron star binaries by the upcoming advanced LIGO/Virgo observatories will be complemented by searches for electromagnetic counterparts over large areas of the sky by Swift and other observatories. As short gamma-ray bursts (GRB) are the most likely electromagnetic counterpart candidates to these sources, we can make predictions based upon the last decade of GRB observations by Swift and Fermi. Swift is uniquely capable of accurately localizing new transients rapidly over large areas of the sky in single and tiled pointings, enabling ground-based follow-up. We describe simulations of the detectability of short GRB afterglows by Swift given existing and hypothetical tiling schemes with realistic observing conditions and delays, which guide the optimal observing strategy and improvements provided by coincident detection with observatories such as Fermi-GBM.

ON THE LACK OF TIME DILATION SIGNATURES IN GAMMA-RAY BURST LIGHT CURVES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kocevski, Daniel; Petrosian, Vahe

2013-03-10

We examine the effects of time dilation on the temporal profiles of gamma-ray burst (GRB) pulses. By using prescriptions for the shape and evolution of prompt gamma-ray spectra, we can generate a simulated population of single-pulsed GRBs at a variety of redshifts and observe how their light curves would appear to a gamma-ray detector here on Earth. We find that the observer frame duration of individual pulses does not increase with redshift as 1 + z, which one would expect from cosmological expansion. This time dilation is masked by an opposite and often stronger effect: with increasing redshift and decreasingmore » signal-to-noise ratio only the brightest portion of the light curve can be detected. The results of our simulation are consistent with the fact that the simple time dilation of GRB light curves has not materialized in either the Swift or Fermi detected GRBs with known redshift. We show that the measured durations and associated E{sub iso} estimates for GRBs detected near the instrument's detection threshold should be considered lower limits to the true values. Furthermore, we conclude that attempts at distinguishing between long and short GRBs, at even moderate redshifts, cannot be done based on a burst's temporal properties alone.« less

SGR J1745-29: Swift Discovery and Monitoring of a New SGR Near Sgr A*

NASA Technical Reports Server (NTRS)

Kennea, Jamie A.; Burrows, David N.; Kouveliotou, Chryssa; Palmer, David; Kaneko, Yuki; Evans, Phil; Degenaar, Nathalie; Reynolds, Mark; Miller, Jon M.; Wijnands, Rudy;

The Gamma-ray Sky with Fermi

NASA Technical Reports Server (NTRS)

Thompson, David

2012-01-01

Gamma rays reveal extreme, nonthermal conditions in the Universe. The Fermi Gamma-ray Space Telescope has been exploring the gamma-ray sky for more than four years, enabling a search for powerful transients like gamma-ray bursts, novae, solar flares, and flaring active galactic nuclei, as well as long-term studies including pulsars, binary systems, supernova remnants, and searches for predicted sources of gamma rays such as dark matter annihilation. Some results include a stringent limit on Lorentz invariance derived from a gamma-ray burst, unexpected gamma-ray variability from the Crab Nebula, a huge gamma-ray structure associated with the center of our galaxy, surprising behavior from some gamma-ray binary systems, and a possible constraint on some WIMP models for dark matter.

Gamma ray camera

DOEpatents

Perez-Mendez, V.

1997-01-21

A gamma ray camera is disclosed for detecting rays emanating from a radiation source such as an isotope. The gamma ray camera includes a sensor array formed of a visible light crystal for converting incident gamma rays to a plurality of corresponding visible light photons, and a photosensor array responsive to the visible light photons in order to form an electronic image of the radiation therefrom. The photosensor array is adapted to record an integrated amount of charge proportional to the incident gamma rays closest to it, and includes a transparent metallic layer, photodiode consisting of a p-i-n structure formed on one side of the transparent metallic layer, and comprising an upper p-type layer, an intermediate layer and a lower n-type layer. In the preferred mode, the scintillator crystal is composed essentially of a cesium iodide (CsI) crystal preferably doped with a predetermined amount impurity, and the p-type upper intermediate layers and said n-type layer are essentially composed of hydrogenated amorphous silicon (a-Si:H). The gamma ray camera further includes a collimator interposed between the radiation source and the sensor array, and a readout circuit formed on one side of the photosensor array. 6 figs.

Fourth Workshop on Science with the New Generation of High Energy Gamma-ray Experiments

NASA Astrophysics Data System (ADS)

Massai, Marco Maria; Omodei, Nicola; Spandre, Gloria

I. Space-based telescope. Integral-4 years in orbit / P. Umbertini, P. Caraveo. The Suzaku mission / K. Yamaoka. The Swift mission: two years of operation / A. Moretti. Gamma-ray astrophysics with AGILE / F.Longo et al., The AGILE collaboration. The GLAST mission / J.E. McEnery -- II. Ground-based telescope. Recent results from CANGAROO / M. Mori for the CANGAROO team. The H.E.S.S. project / C. Masterson for the H.E.S.S. collaboration. The MAGIC experiment / N. Turini for the MAGIC collaboration. VERITAS: status and performance / J. Holder for the VERITAS collaboration -- III. Galactic variable sources. Galactic variable sky with EGRET and GLAST / S. Digel. Galactic variable sources observed with H.E.S.S. / N. Komin for the H.E.S.S collaboration. Gamma ray pulsars in the GLAST era / M. Razzano. Solving the riddle of unidentified high-energy gamma-ray sources / P. Caraveo. Supernovae and gamma-ray burst / M. Della Valle. First cycle of MAGIC galactic observations / J. Cortina for the MAGIC collaboration. Gamma-rays and neutrinos from a SNR in the galactic center / V. Cavasinni, D. Grasso, L. Maccione. Solving GRBs and SGRs puzzles by precessing jets / D. Fargion, O. Lanciano, P. Oliva -- IV. Extragalactic sources. Multiwavelength observations and theories of blazers / G. Tosti. AGN observations with the MAGIC telescope / C. Bigongiari for the MAGIC collaboration. Gamma ray bursts/ L. Amati. X-rays and GeV flares in GRB light curves / A. Galli ... [et al.]. The highest energy emission from gamma ray bursts: MILAGRO's constraints and HAWC's potential / B. Dingus for the MILAGRO and HAWC collaborations. Observation of GRB with the MAGIC telescope / N. Galante, P. Piccioli for the MAGIC collaboration. GRB 060218 and the outliers with respect to the E-E correlation / G. Ghirlanda, G. Ghibellini -- V. Poster session. Study of the performance and calibration of the GLAST-LAT silicon tracker / M. Brigida, N. Giglietto, P. Spinelli. The online monitor for the GLAST

Spinning-Up: the Case of the Symbiotic X-Ray Binary 3A 1954+319

NASA Technical Reports Server (NTRS)

Fuerst, F.; Marcu, D. M.; Pottschmidt, K.; Grinberg, V.; Wilms, J.; CadolleBel, M.

2011-01-01

We present a timing and spectral analysis of the variable X-ray source 3A 1954+319. Our analysis is mainly based on an outburst serendipitously observed during INTEGRAL Key Program observations of the Cygnus region in 2008 fall and on the Swift/BAT longterm light curve. Previous observations, though sparse, have identified the source to be one of only nine known symbiotic X-ray binaries, i.e., systems composed of an accreting neutron star orbiting in a highly inhomogeneous medium around an M-giant companion. The spectrum of3A 1954+319 above > 20 keV can be best described by a broken power law model. The extremely long pulse period of approx.5.3 hours is clearly visible in the INTEGRAL/ISGRI light curve and confirmed through an epoch folding period search. Furthermore, the light curve allows us to determine a very strong spin up of -2 x 10(exp -4) h/h during the outburst. This spin up is confirmed by the pulse period evolution calculated from Swift/BAT data. The Swift/BAT data also show a long spin-down trend prior to the 2008 outburst, which is confirmed in archival INTEGRAL/ISGRI data. We discuss possible accretion models and geometries allowing for the transfer of such large amounts of angular momentum and investigate the harder spectrum of this outburst compared to previously published results.

Spinning-Up: The Case of the Symbiotic X-Ray Binary 3A 1954+319

NASA Technical Reports Server (NTRS)

Fuerst, F.; Marcu, D. M.; Pottschmidt, K.; Grinberg, V.; Wilms, J.; Bel, M. Cadolle

2010-01-01

We present a timing and spectral analysis of the variable X-ray source 3A 1954+319, Our analysis is mainly based on an outburst serendipitously observed during INTEGRAL Key Program observations of the Cygnus region in 2008 fall and on the Swift/BAT longterm light curve, Previous observations, though sparse, have identified the source to be one of only nine known symbiotic X-ray binaries, i.e., systems composed of an accreting neutron star orbiting in a highly inhomogeneous medium around an M-giant companion. The spectrum of 3A 1954+319 above 20 keY can be best described by a broken power law model. The extremely long pulse period of approx.5.3 hours is clearly visible in the INTEGRAL/ISGRI light curve and confirmed through an epoch folding period search. Furthermore, the light curve allows us to determine a very strong spin up of -2x10(exp 4)h/h during the outburst. This spin up is confirmed by the pulse period evolution calculated from Swift/BAT data. The Swift/BAT data also show a long spin-down trend prior to the 2008 outburst. which is confirmed in archival INTEGRAL/ISGRI data. We discuss possible accretion models and geometries allowing for the transfer of such large amounts of angular momentum and investigate the harder spectrum of this outburst compared to previously published results.

UNCOVERING THE INTRINSIC VARIABILITY OF GAMMA-RAY BURSTS

NASA Astrophysics Data System (ADS)

Golkhou, V. Zach; Butler, Nathaniel R

2014-08-01

We develop a robust technique to determine the minimum variability timescale for gamma-ray burst (GRB) light curves, utilizing Haar wavelets. Our approach averages over the data for a given GRB, providing an aggregate measure of signal variation while also retaining sensitivity to narrow pulses within complicated time series. In contrast to previous studies using wavelets, which simply define the minimum timescale in reference to the measurement noise floor, our approach identifies the signature of temporally smooth features in the wavelet scaleogram and then additionally identifies a break in the scaleogram on longer timescales as a signature of a true, temporally unsmooth light curve feature or features. We apply our technique to the large sample of Swift GRB gamma-ray light curves and for the first time—due to the presence of a large number of GRBs with measured redshift—determine the distribution of minimum variability timescales in the source frame. We find a median minimum timescale for long-duration GRBs in the source frame of Δtmin = 0.5 s, with the shortest timescale found being on the order of 10 ms. This short timescale suggests a compact central engine (3000 km). We discuss further implications for the GRB fireball model and present a tantalizing correlation between the minimum timescale and redshift, which may in part be due to cosmological time dilation.

Terrestrial Gamma-Ray Flashes (TGFs)

NASA Technical Reports Server (NTRS)

Fishman, Gerald J.

2010-01-01

This slide presentation reviews the observation of Terrestrial Gamma Ray Flashes (TGFs) by Gamma-Ray Telescopes. These were: (1) BATSE /Compton Observatory, (2) Solar Spectroscopic Imager, (3) AGILE Gamma-ray Telescope, and (4) Gamma-ray Burst Monitor (GBM) on the Fermi Gamma-ray Space Telescope. It contains charts which display the counts over time, a map or the TGFs observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). and a map showing the latitude and longitude of 85 of the TGFs observed by the Fermi GBM.

Cygnus X-3 Returns to an Active State

NASA Astrophysics Data System (ADS)

McCollough, Michael L.; Koljonen, Karri; Gurwell, Mark A.; Trushkin, Sergei; Pooley, Guy G.

2017-08-01

Cygnus X-3 is a well-known microquasar composed of a mass-donating Wolf-Rayet star and a compact object. Recently, Cygnus X-3 has been in a quiescent state for an extended period of time (2011-2016) but returned to an active state on two occasions during 2016/2017 including quenched/hypersoft states, gamma-ray emission, and major radio flares. During these two periods of activity, we undertook multi-wavelength observing campaigns with observations in the radio (RATAN-600, AMI-LA, Metsähovi), submillimeter (SMA, EHT), X-ray (Swift/XRT, MAXI), hard X-ray (Swift/BAT, NuSTAR), and gamma-ray (AGILE, Fermi, VERITAS). At the peak of the major radio flare in April 2017 observations were made with VERITAS (TeV), NuSTAR (hard X-ray), and the Event Horizon Telescope (submillimeter). In this presentation, I will review these observing campaigns and the insights they provide about Cygnus X-3.

Gamma-ray astrophysics

NASA Technical Reports Server (NTRS)

Stecker, F. W. (Editor); Trombka, J. I. (Editor)

1973-01-01

Conference papers on gamma ray astrophysics are summarized. Data cover the energy region from about 0.3 MeV to a few hundred GeV and theoretical models of production mechanisms that give rise to both galactic and extragalactic gamma rays.

The Gamma-ray Universe through Fermi

NASA Technical Reports Server (NTRS)

Thompson, David J.

2012-01-01

Gamma rays, the most powerful form of light, reveal extreme conditions in the Universe. The Fermi Gamma-ray Space Telescope and its smaller cousin AGILE have been exploring the gamma-ray sky for several years, enabling a search for powerful transients like gamma-ray bursts, novae, solar flares, and flaring active galactic nuclei, as well as long-term studies including pulsars, binary systems, supernova remnants, and searches for predicted sources of gamma rays such as dark matter annihilation. Some results include a stringent limit on Lorentz invariance derived from a gamma-ray burst, unexpected gamma-ray variability from the Crab Nebula, a huge ga.nuna-ray structure associated with the center of our galaxy, surprising behavior from some gamma-ray binary systems, and a possible constraint on some WIMP models for dark matter.

Gamma-ray astronomy

NASA Technical Reports Server (NTRS)

Ramaty, R.; Lingenfelter, R. E.

1982-01-01

Cosmic gamma rays, the physical processes responsible for their production and the astrophysical sites from which they were seen are reported. The bulk of the observed gamma ray emission is in the photon energy range from about 0.1 MeV to 1 GeV, where observations are carried out above the atmosphere. There are also, however, gamma ray observations at higher energies obtained by detecting the Cerenkov light produced by the high energy photons in the atmosphere. Gamma ray emission was observed from sources as close as the Sun and the Moon and as distant as the quasar 3C273, as well as from various other galactic and extragalactic sites. The radiation processes also range from the well understood, e.g. energetic particle interactions with matter, to the still incompletely researched, such as radiation transfer in optically thick electron positron plasmas in intense neutron star magnetic fields.

X-Ray and Multi-Wavelength Observations of Gamma Ray Bursts (GRBs)

NASA Technical Reports Server (NTRS)

Kouveliotou, Chryssa

2009-01-01

The launch of the Italian (with Dutch participation) satellite BeppoSAX in 1996 enabled the detection of the first X-ray GRB afterglow, which in turn led to GRB counterpart detection in multiple wavelengths. This breakthrough firmly established the cosmological nature of GRBs. However, afterglow observations of GRBs took off in large numbers after the launch of NASA's Swift satellite in 2004. Swift enabled multiple major discoveries, such as the early lightcurves of X-ray afterglows, the first detection of a short GRB afterglow and opened more questions such as where are the elusive breaks in afterglow light curves. I will describe here these results and will discuss future opportunities and improvements in the field.

Swift follow-up of the flaring blazar PKS 0250-225

NASA Astrophysics Data System (ADS)

Dutka, Michael; Ojha, Roopesh; Donato, DavidePottschmidt, Katja

2012-11-01

Following the gamma-ray flaring activity of the flat spectrum radio quasar PKS 0250-225 (also known as 2FGL J0252.7-2218, Nolan et al. 2012, ApJS, 199, 31) detected by Fermi LAT on 2012 November 13 (ATel #4574) two Swift target of opportunity observations were performed on November 14 and 16. As no significant differences were found between the two epochs the combined results are reported here.

Topics in gamma ray astronomy

NASA Technical Reports Server (NTRS)

Ramaty, R.; Lingenfelter, R. E.

1986-01-01

Observations of gamma rays from solar flares, gamma ray bursts, the Galactic center, galactic nucleosynthesis, SS433, and Cygnus X-3, and their effects on astrophysical problems are discussed. It is observed that gamma ray spectra from solar flares are applicable to the study of particle acceleration and confinement and the determination of chemical abundances in the solar atmosphere. The gamma ray lines from the compact galactic object SS433 are utilized to examine the acceleration of jets, and analysis of the gamma ray lines of Cygnus X-3 reveal that particles can be accelerated in compact sources to ultrahigh energies.

Gamma-ray Bursts May Originate in Star-Forming Regions

NASA Astrophysics Data System (ADS)

2001-04-01

than that expected by the standard scenario of a fireball in a low-density medium - an important clue that the explosion occurred in a dense region. Next, on February 22, 2001, Piro said that Chandra observations of the burst's afterglow, one of the brightest bursts ever observed by BeppoSAX, provided evidence of a fireball expanding in a very dense gas. These recent results supported data from four other gamma-ray bursts observed by BeppoSAX and Chandra (GRB970508, GRB990705, GRB991216, and GRB000214). In these bursts, Piro and his team found evidence indicating that the burst had encountered an extremely dense gas. The properties of this gas suggest that it originated from a very massive progenitor before it exploded as a gamma-ray burst. A key element in the success of these observations has been the perfect timing and liaison between the two satellites, Chandra and BeppoSAX, according to Piro. Piro is the Mission Scientist for BeppoSAX, the instrument that first detected X-ray afterglows from gamma-ray bursts. Currently, astronomers are not usually notified about gamma-ray bursts until an hour or so after they occur. These bursts last only for a few milliseconds to about a minute, although their afterglow can linger in X-ray and optical light for days or weeks. The HETE-2 satellite, launched in October 2000, and Swift, scheduled for a 2003 launch, will provide nearly instant notification of bursts in action, providing satellites such as Chandra a better opportunity to study the afterglow phenomenon in depth. The ACIS X-ray camera was developed for NASA by Penn State and the Massachusetts Institute of Technology. The High Energy Transmission Grating Spectrometer was built by MIT. NASA's Marshall Space Flight Center in Huntsville, AL, manages the Chandra program. TRW, Inc., Redondo Beach, California, is the prime contractor for the spacecraft. The Smithsonian's Chandra X-ray Center controls science and flight operations from Cambridge, MA. Images associated with this

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.

Analysis of the X-ray emission of nine Swift afterglows

NASA Astrophysics Data System (ADS)

Panaitescu, A.; Mészáros, P.; Gehrels, N.; Burrows, D.; Nousek, J.

2006-03-01

The X-ray light curves of nine Swift XRT afterglows (050126, 050128, 050219A, 050315, 050318, 050319, 050401, 050408 and 050505) display a complex behaviour: a steep t-3.0+/-0.3 decay until ~400 s, followed by a significantly slower t-0.65+/-0.20 fall-off, which at 0.2-2 day after the burst evolves into a t-1.7+/-0.5 decay. We consider three possible models for the geometry of relativistic blast-waves (spherical outflows, non-spreading jets and spreading jets), two possible dynamical regimes for the forward shock (adiabatic and fully radiative), and we take into account a possible angular structure of the outflow and delayed energy injection in the blast-wave to identify the models which reconcile the X-ray light-curve decay with the slope of the X-ray continuum for each of the above three afterglow phases. By piecing together the various models for each phase in a way that makes physical sense, we identify possible models for the entire X-ray afterglow. The major conclusion of this work is that a long-lived episode of energy injection in the blast-wave, during which the shock energy increases at t1.0+/-0.5, is required for five afterglows and could be at work in the other four as well. For some afterglows, there may be other mechanisms that can explain the t < 400 s fast falling-off X-ray light curve (e.g. the large-angle gamma-ray burst emission), the 400 s to 5 h slow decay (e.g. a structured outflow), or the steepening at 0.2-2 day (e.g. a jet-break, a collimated outflow transiting from a wind with a r-3 radial density profile to a homogeneous or outward-increasing density region). Optical observations in conjunction with the X-ray can distinguish among these various models. Our simple tests allow the determination of the location of the cooling frequency relative to the X-ray domain and, thus, of the index of the electron power-law distribution with energy in the blast-wave. The resulting indices are clearly inconsistent with a universal value.

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.

Compton Gamma-Ray Observatory

NASA Technical Reports Server (NTRS)

1991-01-01

This photograph shows the Compton Gamma-Ray Observatory (GRO) being deployed by the Remote Manipulator System (RMS) arm aboard the Space Shuttle Atlantis during the STS-37 mission in April 1991. The GRO reentered Earth atmosphere and ended its successful mission in June 2000. For nearly 9 years, the GRO Burst and Transient Source Experiment (BATSE), designed and built by the Marshall Space Flight Center (MSFC), kept an unblinking watch on the universe to alert scientists to the invisible, mysterious gamma-ray bursts that had puzzled them for decades. By studying gamma-rays from objects like black holes, pulsars, quasars, neutron stars, and other exotic objects, scientists could discover clues to the birth, evolution, and death of stars, galaxies, and the universe. The gamma-ray instrument was one of four major science instruments aboard the Compton. It consisted of eight detectors, or modules, located at each corner of the rectangular satellite to simultaneously scan the entire universe for bursts of gamma-rays ranging in duration from fractions of a second to minutes. In January 1999, the instrument, via the Internet, cued a computer-controlled telescope at Las Alamos National Laboratory in Los Alamos, New Mexico, within 20 seconds of registering a burst. With this capability, the gamma-ray experiment came to serve as a gamma-ray burst alert for the Hubble Space Telescope, the Chandra X-Ray Observatory, and major gound-based observatories around the world. Thirty-seven universities, observatories, and NASA centers in 19 states, and 11 more institutions in Europe and Russia, participated in the BATSE science program.

Compton Gamma-Ray Observatory

NASA Technical Reports Server (NTRS)

1991-01-01

This photograph shows the Compton Gamma-Ray Observatory being released from the Remote Manipulator System (RMS) arm aboard the Space Shuttle Atlantis during the STS-35 mission in April 1991. The GRO reentered the Earth's atmosphere and ended its successful mission in June 2000. For nearly 9 years, GRO's Burst and Transient Source Experiment (BATSE), designed and built by the Marshall Space Flight Center, kept an unblinking watch on the universe to alert scientist to the invisible, mysterious gamma-ray bursts that had puzzled them for decades. By studying gamma-rays from objects like black holes, pulsars, quasars, neutron stars, and other exotic objects, scientists could discover clues to the birth, evolution, and death of star, galaxies, and the universe. The gamma-ray instrument was one of four major science instruments aboard the Compton. It consisted of eight detectors, or modules, located at each corner of the rectangular satellite to simultaneously scan the entire universe for bursts of gamma-rays ranging in duration from fractions of a second to minutes. In January 1999, the instrument, via the Internet, cued a computer-controlled telescope at Las Alamos National Laboratory in Los Alamos, New Mexico, within 20 seconds of registering a burst. With this capability, the gamma-ray experiment came to serve as a gamma-ray burst alert for the Hubble Space Telescope, the Chandra X-Ray Observatory, and major gound-based observatories around the world. Thirty-seven universities, observatories, and NASA centers in 19 states, and 11 more institutions in Europe and Russia, participated in BATSE's science program.

Gamma rays from Centaurus A

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gupta, Nayantara, E-mail: nayan@phy.iitb.ac.in

2008-06-15

Centaurus A, the cosmic ray accelerator a few Mpc away from us, is possibly one of the nearest sources of extremely high energy cosmic rays. We investigate whether the gamma ray data currently available from Centaurus A in the GeV-TeV energy band can be explained with only proton-proton interactions. We show that for a single power law proton spectrum, mechanisms of {gamma}-ray production other than proton-proton interactions are needed inside this radio-galaxy to explain the gamma ray flux observed by EGRET, upper limits from HESS/CANGAROO-III and the correlated extremely energetic cosmic ray events observed by the Pierre Auger experiment. Inmore » future, with better {gamma}-ray data, and simultaneous observation with {gamma}-ray and cosmic ray detectors, it will be possible to carry out such studies on different sources in more detail.« less

Gamma Ray Bursts as Cosmological Probes with EXIST

NASA Astrophysics Data System (ADS)

Hartmann, Dieter; EXIST Team

2006-12-01

The EXIST mission, studied as a Black Hole Finder Probe within NASA's Beyond Einstein Program, would, in its current design, trigger on 1000 Gamma Ray Bursts (GRBs) per year (Grindlay et al, this meeting). The redshift distribution of these GRBs, using results from Swift as a guide, would probe the z > 7 epoch at an event rate of > 50 per year. These bursts trace early cosmic star formation history, point to a first generation of stellar objects that reionize the universe, and provide bright beacons for absorption line studies with groundand space-based observatories. We discuss how EXIST, in conjunction with other space missions and future large survey programs such as LSST, can be utilized to advance our understanding of cosmic chemical evolution, the structure and evolution of the baryonic cosmic web, and the formation of stars in low metallicity environments.

Future prospects for gamma-ray

NASA Technical Reports Server (NTRS)

Fichtel, C.

1980-01-01

Astrophysical phenomena discussed are: the very energetic and nuclear processes associated with compact objects; astrophysical nucleo-synthesis; solar particle acceleration; the chemical composition of the planets and other bodies of the solar system; the structure of our galaxy; the origin and dynamic pressure effects of the cosmic rays; the high energy particles and energetic processes in other galaxies, especially active ones; and the degree of matter antimater symmetry of the universe. The gamma ray results of GAMMA-I, the gamma ray observatory, the gamma ray burst network, solar polar, and very high energy gamma ray telescopes on the ground provide justification for more sophisticated telescopes.

Early Results from Swift AGN and Cluster Survey

NASA Astrophysics Data System (ADS)

Dai, Xinyu; Griffin, Rhiannon; Nugent, Jenna; Kochanek, Christopher S.; Bregman, Joel N.

2016-04-01

The Swift AGN and Cluster Survey (SACS) uses 125 deg^2 of Swift X-ray Telescope serendipitous fields with variable depths surrounding gamma-ray bursts to provide a medium depth (4 × 10^-15 erg cm^-2 s^-1) and area survey filling the gap between deep, narrow Chandra/XMM-Newton surveys and wide, shallow ROSAT surveys. Here, we present the first two papers in a series of publications for SACS. In the first paper, we introduce our method and catalog of 22,563 point sources and 442 extended sources. SACS provides excellent constraints on the AGN and cluster number counts at the bright end with negligible uncertainties due to cosmic variance, and these constraints are consistent with previous measurements. The depth and areal coverage of SACS is well suited for galaxy cluster surveys outside the local universe, reaching z > 1 for massive clusters. In the second paper, we use SDSS DR8 data to study the 203 extended SACS sources that are located within the SDSS footprint. We search for galaxy over-densities in 3-D space using SDSS galaxies and their photometric redshifts near the Swift galaxy cluster candidates. We find 103 Swift clusters with a > 3σ over-density. The remaining targets are potentially located at higher redshifts and require deeper optical follow-up observations for confirmations as galaxy clusters. We present a series of cluster properties including the redshift, BCG magnitude, BCG-to-X-ray center offset, optical richness, X-ray luminosity and red sequences. We compare the observed redshift distribution of the sample with a theoretical model, and find that our sample is complete for z ≤ 0.3 and 80% complete for z ≤ 0.4, consistent with the survey depth of SDSS. These analysis results suggest that our Swift cluster selection algorithm presented in our first paper has yielded a statistically well-defined cluster sample for further studying cluster evolution and cosmology. In the end, we will discuss our ongoing optical identification of z>0.5 cluster

Swift: 10 Years of Discovery

NASA Astrophysics Data System (ADS)

2014-12-01

The conference Swift: 10 years of discovery was held in Roma at La Sapienza University on Dec. 2-5 2014 to celebrate 10 years of Swift successes. Thanks to a large attendance and a lively program, it provided the opportunity to review recent advances of our knowledge of the high-energy transient Universe both from the observational and theoretical sides. When Swift was launched on November 20, 2004, its prime objective was to chase Gamma-Ray Bursts and deepen our knowledge of these cosmic explosions. And so it did, unveiling the secrets of long and short GRBs. However, its multi-wavelength instrumentation and fast scheduling capabilities made it the most versatile mission ever flown. Besides GRBs, Swift has observed, and contributed to our understanding of, an impressive variety of targets including AGNs, supernovae, pulsars, microquasars, novae, variable stars, comets, and much more. Swift is continuously discovering rare and surprising events distributed over a wide range of redshifts, out to the most distant transient objects in the Universe. Such a trove of discoveries has been addressed during the conference with sessions dedicated to each class of events. Indeed, the conference in Rome was a spectacular celebration of the Swift 10th anniversary. It included sessions on all types of transient and steady sources. Top scientists from around the world gave invited and contributed talks. There was a large poster session, sumptuous lunches, news interviews and a glorious banquet with officials attending from INAF and ASI. All the presentations, as well as several conference pictures, can be found in the conference website (http://www.brera.inaf.it/Swift10/Welcome.html). These proceedings have been collected owing to the efforts of Paolo D’Avanzo who has followed each paper from submission to final acceptance. Our warmest thanks to Paolo for all his work. The Conference has been made possible by the support from La Sapienza University as well as from the ARAP

Gamma ray astrophysics to the year 2000. Report of the NASA Gamma Ray Program Working Group

NASA Technical Reports Server (NTRS)

1988-01-01

Important developments in gamma-ray astrophysics up to energies of 100 GeV during the last decade are reviewed. Also, the report seeks to define the major current scientific goals of the field and proposes a vigorous program to pursue them, extending to the year 2000. The goals of gamma-ray astronomy include the study of gamma rays which provide the most direct means of studying many important problems in high energy astrophysics including explosive nucleosynthesis, accelerated particle interactions and sources, and high-energy processes around compact objects. The current research program in gamma-ray astronomy in the U.S. including the space program, balloon program and foreign programs in gamma-ray astronomy is described. The high priority recommendations for future study include an Explorer-class high resolution gamma-ray spectroscopy mission and a Get Away Special cannister (GAS-can) or Scout class multiwavelength experiment for the study of gamma-ray bursts. Continuing programs include an extended Gamma Ray Observatory mission, continuation of the vigorous program of balloon observations of the nearby Supernova 1987A, augmentation of the balloon program to provide for new instruments and rapid scientific results, and continuation of support for theoretical research. Long term recommendations include new space missions using advanced detectors to better study gamma-ray sources, the development of these detectors, continued study for the assembly of large detectors in space, collaboration with the gamma-ray astronomy missions initiated by other countries, and consideration of the Space Station attached payloads for gamma-ray experiments.

X-ray Follow-ups of XSS J12270-4859: A Low-mass X-ray Binary with Gamma-ray Fermi-LAT Association

NASA Technical Reports Server (NTRS)

deMartino, D.; Belloni, T.; Falanga, M.; Papitto, A.; Motta, S.; Pellizzoni, A.; Evangelista, Y.; Piano, G.; Masetti, N.; Mouchet, M.;

The Swift/BAT AGN Spectroscopic Survey. IX. The Clustering Environments of an Unbiased Sample of Local AGNs

NASA Astrophysics Data System (ADS)

Powell, M. C.; Cappelluti, N.; Urry, C. M.; Koss, M.; Finoguenov, A.; Ricci, C.; Trakhtenbrot, B.; Allevato, V.; Ajello, M.; Oh, K.; Schawinski, K.; Secrest, N.

2018-05-01

We characterize the environments of local accreting supermassive black holes by measuring the clustering of AGNs in the Swift/BAT Spectroscopic Survey (BASS). With 548 AGN in the redshift range 0.01 < z < 0.1 over the full sky from the DR1 catalog, BASS provides the largest, least biased sample of local AGNs to date due to its hard X-ray selection (14–195 keV) and rich multiwavelength/ancillary data. By measuring the projected cross-correlation function between the AGN and 2MASS galaxies, and interpreting it via halo occupation distribution and subhalo-based models, we constrain the occupation statistics of the full sample, as well as in bins of absorbing column density and black hole mass. We find that AGNs tend to reside in galaxy group environments, in agreement with previous studies of AGNs throughout a large range of luminosity and redshift, and that on average they occupy their dark matter halos similar to inactive galaxies of comparable stellar mass. We also find evidence that obscured AGNs tend to reside in denser environments than unobscured AGNs, even when samples were matched in luminosity, redshift, stellar mass, and Eddington ratio. We show that this can be explained either by significantly different halo occupation distributions or statistically different host halo assembly histories. Lastly, we see that massive black holes are slightly more likely to reside in central galaxies than black holes of smaller mass.

Comparing Data from Telescopic X-Ray Instruments: Can We Trust All Satellites?

NASA Astrophysics Data System (ADS)

Joyce, Quianah T.; Fortenberry, Alexander; Gendre, Bruce

2017-01-01

In astronomy and astrophysics, X-ray emissions from cosmic entities aid in revealing what type of sources they emanate from. Swift, NASA’s latest X-ray satellite, has not been operating at its intended configurations. The satellite is experiencing difficulties maintaining a stable temperature in its charge capture device. This research intends to determine if this complication causes discrepancies in Swift’s collected data by using gamma-ray burst data. Gamma-ray bursts are excellent comparison candidates due to their brightness and fluctuations. We compared archived data of GRB 130427A and GRB 090423A from Swift and the European Space Agency’s XMM-Newton observatory. Next, we reduced the data and produced the respective spectra. We then analyzed and compared the spectra to one another to find any discrepancies. We have determined, based on data analysis of the spectra, that Swift is working properly despite the cooling malfunction.

Gamma ray detector shield

DOEpatents

Ohlinger, R.D.; Humphrey, H.W.

1985-08-26

A gamma ray detector shield comprised of a rigid, lead, cylindrical-shaped vessel having upper and lower portions with an pneumatically driven, sliding top assembly. Disposed inside the lead shield is a gamma ray scintillation crystal detector. Access to the gamma detector is through the sliding top assembly.

Gamma-Ray Bursts: An Overview

NASA Technical Reports Server (NTRS)

Fishman, Gerald J.

1995-01-01

A history and overview of the observed properties of gamma-ray bursts are presented. The phenomenon of gamma-ray bursts is without precedent in astronomy, having no observed property that would be a direct indicator of their distance and no counterpart object in another wavelength region. Their brief, random appearance only in the gamma-ray region has made their study difficult. The observed time profiles, spectral properties, and durations of gamma-ray bursts cover a wide range. All proposed models for their origin must be considered speculative. It is humbling to think that even after 25 years since their discovery, the distance scale of gamma-ray bursts is still very much debatable.

High energy gamma ray astronomy

NASA Technical Reports Server (NTRS)

Fichtel, Carl E.

1987-01-01

High energy gamma ray astronomy has evolved with the space age. Nonexistent twenty-five years ago, there is now a general sketch of the gamma ray sky which should develop into a detailed picture with the results expected to be forthcoming over the next decade. The galactic plane is the dominant feature of the gamma ray sky, the longitude and latitude distribution being generally correlated with galactic structural features including the spiral arms. Two molecular clouds were already seen. Two of the three strongest gamma ray sources are pulsars. The highly variable X-ray source Cygnus X-3 was seen at one time, but not another in the 100 MeV region, and it was also observed at very high energies. Beyond the Milky Way Galaxy, there is seen a diffuse radiation, whose origin remains uncertain, as well as at least one quasar, 3C 273. Looking to the future, the satellite opportunities for high energy gamma ray astronomy in the near term are the GAMMA-I planned to be launched in late 1987 and the Gamma Ray Observatory, scheduled for launch in 1990. The Gamma Ray Observatory will carry a total of four instruments covering the entire energy range from 30,000 eV to 3 x 10 to the 10th eV with over an order of magnitude increase in sensitivity relative to previous satellite instruments.

X-Ray Spectral Properties of Seven Heavily Obscured Seyfert 2 Galaxies

NASA Astrophysics Data System (ADS)

Marchesi, S.; Ajello, M.; Comastri, A.; Cusumano, G.; La Parola, V.; Segreto, A.

2017-02-01

We present the combined Chandra and Swift-BAT spectral analysis of seven Seyfert 2 galaxies selected from the Swift-BAT 100 month catalog. We selected nearby (z ≤ 0.03) sources lacking a ROSAT counterpart that never previously been observed with Chandra in the 0.3-10 keV energy range, and targeted these objects with 10 ks Chandra ACIS-S observations. The X-ray spectral fitting over the 0.3-150 keV energy range allows us to determine that all the objects are significantly obscured, with N H ≥ 1023 cm-2 at a >99% confidence level. Moreover, one to three sources are candidate Compton-thick Active Galactic Nuclei (CT-AGNs; I.e., N H ≥ 1024 cm-2). We also test the recent spectral curvature method developed by Koss et al. to find candidate CT-AGNs, finding a good agreement between our results and their predictions. Because the selection criteria we adopted were effective in detecting highly obscured AGNs, further observations of these and other Seyfert 2 galaxies selected from the Swift-BAT 100 month catalog will allow us to create a statistically significant sample of highly obscured AGNs, therefore providing a better understanding of the physics of the obscuration processes.

Bats: Swift Shadows in the Twilight. The Wonder Series.

ERIC Educational Resources Information Center

Cooper, Ann C.

This curriculum guide is all about bats and provides information through the telling of stories about bats and their history and folklore. The activities contained in this guide employ an interdisciplinary approach and use mazes, puzzles, model-building, and board games to interest and inform students. Topics covered include the physical…

Gamma-sky.net: Portal to the gamma-ray sky

NASA Astrophysics Data System (ADS)

Voruganti, Arjun; Deil, Christoph; Donath, Axel; King, Johannes

2017-01-01

http://gamma-sky.net is a novel interactive website designed for exploring the gamma-ray sky. The Map View portion of the site is powered by the Aladin Lite sky atlas, providing a scalable survey image tesselated onto a three-dimensional sphere. The map allows for interactive pan and zoom navigation as well as search queries by sky position or object name. The default image overlay shows the gamma-ray sky observed by the Fermi-LAT gamma-ray space telescope. Other survey images (e.g. Planck microwave images in low/high frequency bands, ROSAT X-ray image) are available for comparison with the gamma-ray data. Sources from major gamma-ray source catalogs of interest (Fermi-LAT 2FHL, 3FGL and a TeV source catalog) are overlaid over the sky map as markers. Clicking on a given source shows basic information in a popup, and detailed pages for every source are available via the Catalog View component of the website, including information such as source classification, spectrum and light-curve plots, and literature references. We intend for gamma-sky.net to be applicable for both professional astronomers as well as the general public. The website started in early June 2016 and is being developed as an open-source, open data project on GitHub (https://github.com/gammapy/gamma-sky). We plan to extend it to display more gamma-ray and multi-wavelength data. Feedback and contributions are very welcome!

Space instrumentation for gamma-ray astronomy

NASA Astrophysics Data System (ADS)

Teegarden, B. J.

1999-02-01

The decade of the 1990s has witnessed a renaissance in the field of gamma-ray astronomy. The seminal event was the launch of the Compton Gamma-Ray Observatory (CGRO) in April 1991. There have been a flood of major discoveries from CGRO including breakthroughs in gamma-ray bursts, annihilation radiation, and blazars. The Italian SAX satellite was launched in April 1996. Although not primarily a gamma-ray mission, it has added a new dimension to our understanding of gamma-ray bursts. Along with these new discoveries a firm groundwork has been laid for missions and new technology development that should maintain a healthy and vigorous field throughout most of the next decade. These include the ESA INTEGRAL mission (INTErnational Gamma-Ray Astrophysics Laboratory, to be launched in mid-2001) and the NASA GLAST mission (Gamma-Ray Large Area Space Telescope) with a likely launch in the middle of the next decade. These two missions will extend the observational capabilities well beyond those of CGRO. New technologies (to gamma-ray astronomy), such as cooled germanium detectors, silicon strip detectors, and CdTe detectors are planned for these new missions. Additional promising new technologies such as CdZnTe strip detectors, scintillator fibers, and a gamma-ray lens for future gamma-ray astronomy missions are under development in laboratories around the world.

Detection of potential periodicities in the unique hard X-ray source Swift J0042.6+4112, dominating the hard X-ray emission in M31

NASA Astrophysics Data System (ADS)

Yukita, Mihoko; Tzanavaris, Panayiotis; Corbet, Robin; Ptak, Andrew; Hornschemeier, Ann; Pottschmidt, Katja; Ballhausen, Ralf; Enoto, Teruaki; Antoniou, Vallia; Lehmer, Bret; Maccarone, Thomas J.; Wik, Daniel; Williams, Ben; Zezas, Andreas

2018-01-01

Recent NuSTAR-Swift observations revealed that a single resolved X-ray source, Swift J0042.6+4112, with Lx of a few times 1038 erg/s dominates the hard X-ray emission from the Andromeda galaxy. HST-based stellar population synthesis modeling combined with the 0.5-50 keV spectral shape suggests that this might be an X-ray pulsar with an intermediate- (or low-) mass donor. Here we further explore the alternative scenario of a symbiotic or ultracompact X-ray binary, based on long-term variability from Swift observations between 2005 and 2016. We find that the soft (0.3-8.0 keV) X-ray flux varies within a factor of 4 but does not exhibit transient behavior. Its power spectrum suggests a 6.1-day period. Additionally, we find a strong 3s-period candidate from both NuSTAR and XMM observations taken in 2017. If interpreted as an orbital and spin period respectively, the source's temporal behavior would not support either the symbiotic or the ultracompact X-ray binary scenario. Rather, it is more consistent with an accreting pulsar with a higher mass donor.

Central-engine-powered Bright X-Ray Flares in Short Gamma-Ray Bursts: A Hint of a Black Hole–Neutron Star Merger?

NASA Astrophysics Data System (ADS)

Mu, Hui-Jun; Gu, Wei-Min; Mao, Jirong; Hou, Shu-Jin; Lin, Da-Bin; Liu, Tong

2018-05-01

Short gamma-ray bursts may originate from the merger of a double neutron star (NS) or the merger of a black hole (BH) and an NS. We propose that the bright X-ray flare related to the central engine reactivity may indicate a BH–NS merger, since such a merger can provide more fallback materials and therefore a more massive accretion disk than the NS–NS merger. Based on the 49 observed short bursts with the Swift/X-ray Telescope follow-up observations, we find that three bursts have bright X-ray flares, among which three flares from two bursts are probably related to the central engine reactivity. We argue that these two bursts may originate from the BH–NS merger rather than the NS–NS merger. Our suggested link between the central-engine-powered bright X-ray flare and the BH–NS merger event can be checked by future gravitational wave detections from advanced LIGO and Virgo.

CHANDRA AND SWIFT X-RAY OBSERVATIONS OF THE X-RAY PULSAR SMC X-2 DURING THE OUTBURST OF 2015

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, K. L.; Hu, C.-P; Lin, L. C. C.

2016-09-10

We report the Chandra /HRC-S and Swift /XRT observations for the 2015 outburst of the high-mass X-ray binary pulsar in the Small Magellanic Cloud, SMC X-2. While previous studies suggested that either an O star or a Be star in the field is the high-mass companion of SMC X-2, our Chandra /HRC-S image unambiguously confirms the O-type star as the true optical counterpart. Using the Swift /XRT observations, we extracted accurate orbital parameters of the pulsar binary through a time of arrivals analysis. In addition, there were two X-ray dips near the inferior conjunction, which are possibly caused by eclipsesmore » or an ionized high-density shadow wind near the companion’s surface. Finally, we propose that an outflow driven by the radiation pressure from day ∼10 played an important role in the X-ray/optical evolution of the outburst.« less

The Gamma-Ray Imager GRI

NASA Astrophysics Data System (ADS)

Wunderer, Cornelia B.; GRI Collaboration

2006-09-01

Observations of the gamma-ray sky reveal the most powerful sources and the most violent events in the Universe. While at lower wavebands the observed emission is generally dominated by thermal processes, the gamma-ray sky provides us with a view on the non-thermal Universe. Here particles are accelerated to extreme relativistic energies by mechanisms which are still poorly understood, and nuclear reactions are synthesizing the basic constituents of our world. Cosmic accelerators and cosmic explosions are the major science themes that are addressed in the gamma-ray regime. With the INTEGRAL observatory, ESA has provided a unique tool to the astronomical community revealing hundreds of sources, new classes of objects, extraordinary views of antimatter annihilation in our Galaxy, and fingerprints of recent nucleosynthesis processes. While INTEGRAL provides the global overview over the soft gamma-ray sky, there is a growing need to perform deeper, more focused investigations of gamma-ray sources. In soft X-rays a comparable step was taken going from the Einstein and the EXOSAT satellites to the Chandra and XMM/Newton observatories. Technological advances in the past years in the domain of gamma-ray focusing using Laue diffraction and multilayer coated mirror techniques have paved the way towards a gamma-ray mission, providing major improvements compared to past missions regarding sensitivity and angular resolution. Such a future Gamma-Ray Imager will allow to study particle acceleration processes and explosion physics in unprecedented detail, providing essential clues on the innermost nature of the most violent and most energetic processes in the Universe.

NASA's Swift Satellite Catches First Supernova in The Act of Exploding

NASA Astrophysics Data System (ADS)

2008-05-01

constellation Lynx. At 9:33 a.m. EST they spotted an extremely bright 5-minute X-ray outburst in NGC 2770. They quickly recognized that the X-rays were coming from another location in the same galaxy. People Who Read This Also Read... Black Holes Have Simple Feeding Habits Jet Power and Black Hole Assortment Revealed in New Chandra Image Chandra Data Reveal Rapidly Whirling Black Holes Ghostly Glow Reveals a Hidden Class of Long-Wavelength Radio Emitters In a paper submitted to Nature, Soderberg and 38 colleagues show that the energy and pattern of the X-ray outburst is consistent with a shock wave bursting through the surface of the progenitor star. This marks the birth of the supernova now known as SN 2008D. Although astronomers were lucky that Swift was observing NGC 2770 just at the moment when SN 2008D’s shock wave was blowing up the star, Swift is well equipped to study such an event because of its multiple instruments observing in gamma rays, X-rays, and ultraviolet light. "It was a gift of nature for Swift to be observing that patch of sky when the supernova exploded. But thanks to Swift's flexibility, we have been able to trace its evolution in detail every day since," says Swift lead scientist Neil Gehrels of NASA’s Goddard Space Flight Center in Greenbelt, Md. Due to the significance of the X-ray outburst, Soderberg immediately mounted an international observing campaign to study SN 2008D. Observations were made with major telescopes such as the Hubble Space Telescope, the Chandra X-ray Observatory, the Very Large Array in New Mexico, the Gemini North telescope in Hawaii, the Keck I telescope in Hawaii, the 200-inch and 60-inch telescopes at the Palomar Observatory in California, and the 3.5-meter telescope at the Apache Point Observatory in New Mexico. The combined observations helped Soderberg and her colleagues pin down the energy of the initial X-ray outburst, which will help theorists better understand supernovae. The observations also show that SN 2008D is

Gamma Ray Pulsars: Multiwavelength Observations

NASA Technical Reports Server (NTRS)

Thompson, David J.

2004-01-01

High-energy gamma rays are a valuable tool for studying particle acceleration and radiation in the magnetospheres of energetic pulsars. The seven or more pulsars seen by instruments on the Compton Gamma Ray Observatory (CGRO) show that: the light curves usually have double-peak structures (suggesting a broad cone of emission); gamma rays are frequently the dominant component of the radiated power; and all the spectra show evidence of a high-energy turnover. For all the known gamma-ray pulsars, multiwavelength observations and theoretical models based on such observations offer the prospect of gaining a broad understanding of these rotating neutron stars. The Gamma-ray Large Area Space Telescope (GLAST), now in planning for a launch in 2006, will provide a major advance in sensitivity, energy range, and sky coverage.

Observational difference between gamma and X-ray properties of optically dark and bright GRBs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balazs, L. G.; Horvath, I.; Bagoly, Zs.

2008-05-22

Using the discriminant analysis of the multivariate statistical analysis we compared the distribution of the physical quantities of the optically dark and bright GRBs, detected by the BAT and XRT on board of the Swift Satellite. We found that the GRBs having detected optical transients (OT) have systematically higher peak fluxes and lower HI column densities than those without OT.

Gamma ray pulsars

NASA Technical Reports Server (NTRS)

Oegelman, H.; Ayasli, S.; Hacinliyan, A.

1976-01-01

Recent data from the high energy gamma ray experiment have revealed the existence of four pulsars emitting photons above 35 MeV. An attempt is made to explain the gamma ray emission from these pulsars in terms of an electron-photon cascade that develops in the magnetosphere of the pulsar. Although there is very little material above the surface of the pulsar, the very intense magnetic fields correspond to many radiation lengths which cause electrons to emit photons via magnetic bremsstrahlung and these photons to pair produce. The cascade develops until the mean photon energy drops below the pair production threshold which happens to be in the gamma ray range; at this stage the photons break out from the source.

Limits to the Fraction of High-energy Photon Emitting Gamma-Ray Bursts

NASA Astrophysics Data System (ADS)

Akerlof, Carl W.; Zheng, WeiKang

2013-02-01

After almost four years of operation, the two instruments on board the Fermi Gamma-ray Space Telescope have shown that the number of gamma-ray bursts (GRBs) with high-energy photon emission above 100 MeV cannot exceed roughly 9% of the total number of all such events, at least at the present detection limits. In a recent paper, we found that GRBs with photons detected in the Large Area Telescope have a surprisingly broad distribution with respect to the observed event photon number. Extrapolation of our empirical fit to numbers of photons below our previous detection limit suggests that the overall rate of such low flux events could be estimated by standard image co-adding techniques. In this case, we have taken advantage of the excellent angular resolution of the Swift mission to provide accurate reference points for 79 GRB events which have eluded any previous correlations with high-energy photons. We find a small but significant signal in the co-added field. Guided by the extrapolated power-law fit previously obtained for the number distribution of GRBs with higher fluxes, the data suggest that only a small fraction of GRBs are sources of high-energy photons.

The Swift GRB Host Galaxy Legacy Survey

NASA Astrophysics Data System (ADS)

Perley, Daniel A.

2015-01-01

I introduce the Swift Host Galaxy Legacy Survey (SHOALS), a comprehensive multiwavelength program to characterize the demographics of the GRB host population across its entire redshift range. Using unbiased selection criteria we have designated a subset of 130 Swift gamma-ray bursts which are now being targeted with intensive observational follow-up. Deep Spitzer imaging of every field has already been obtained and analyzed, with major programs ongoing at Keck, GTC, and Gemini to obtain complementary optical/NIR photometry to enable full SED modeling and derivation of fundamental physical parameters such as mass, extinction, and star-formation rate. Using these data I will present an unbiased measurement of the GRB host-galaxy luminosity and mass functions and their evolution with redshift between z=0 and z=5, compare GRB hosts to other star-forming galaxy populations, and discuss implications for the nature of the GRB progenitor and the ability of GRBs to probe cosmic star-formation.

Gamma-Ray Astronomy Technology Needs

NASA Technical Reports Server (NTRS)

Gehrels, N.; Cannizzo, J. K.

2012-01-01

In recent decades gamma-ray observations have become a valuable tool for studying the universe. Progress made in diverse 8re1lS such as gamma-ray bursts (GRBs), nucleosynthesis, and active galactic nuclei (AGNs) has complimented and enriched our astrophysical understanding in many ways. We present an overview of current and future planned space y-ray missions and discussion technology needs for- the next generation of space gamma-ray instruments.

A hard X-ray view of the soft excess in AGN

NASA Astrophysics Data System (ADS)

Boissay, R.; Ricci, C.; Paltani, S.

2017-10-01

A soft X-ray emission in excess of the extrapolation of the hard X-ray continuum is detected in many Seyfert 1 galaxies below 1 keV. To understand the uncertain nature of this soft excess, which could be due to warm Comptonization or to blurred ionized reflection, we consider the different behaviors of these models above 10 keV. We present the results of a study done on 102 Seyfert 1s from the Swift BAT 70-Month Hard X-ray Survey catalog. We have performed the joint spectral analysis of Swift/BAT and XMM-Newton data in order to get a hard X-ray view of the soft excess. We discuss the links between the soft-excess strength and the reflection at high energy, the slope of the continuum and the Eddington ratio. We compare our results to simulations of blurred ionized-reflection models and show that they are in contradiction. Indeed, we do not find the expected correlation between the reflection and the soft-excess strengths, neither in individual, nor in stacked spectra. We also present our current project of broadband fitting, using different models explaining the soft excess, to simultaneous XMM-Newton and NuSTAR observations of about ten objects of our sample.

THE BRIGHTEST GAMMA-RAY FLARING BLAZAR IN THE SKY: AGILE AND MULTI-WAVELENGTH OBSERVATIONS OF 3C 454.3 DURING 2010 NOVEMBER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vercellone, S.; Romano, P.; Striani, E.

2011-08-01

Since 2005, the blazar 3C 454.3 has shown remarkable flaring activity at all frequencies, and during the last four years it has exhibited more than one {gamma}-ray flare per year, becoming the most active {gamma}-ray blazar in the sky. We present for the first time the multi-wavelength AGILE, Swift, INTEGRAL, and GASP-WEBT data collected in order to explain the extraordinary {gamma}-ray flare of 3C 454.3 which occurred in 2010 November. On 2010 November 20 (MJD 55520), 3C 454.3 reached a peak flux (E >100 MeV) of F{sup p}{sub {gamma}} = (6.8 {+-} 1.0) x 10{sup -5} photons cm{sup -2} s{supmore » -1} on a timescale of about 12 hr, more than a factor of six higher than the flux of the brightest steady {gamma}-ray source, the Vela pulsar, and more than a factor of three brighter than its previous super-flare on 2009 December 2-3. The multi-wavelength data make possible a thorough study of the present event: the comparison with the previous outbursts indicates a close similarity to the one that occurred in 2009. By comparing the broadband emission before, during, and after the {gamma}-ray flare, we find that the radio, optical, and X-ray emission varies within a factor of 2-3, whereas the {gamma}-ray flux by a factor of 10. This remarkable behavior is modeled by an external Compton component driven by a substantial local enhancement of soft seed photons.« less

The Andromeda galaxy in gamma-rays

NASA Technical Reports Server (NTRS)

Oezel, M. E.; Berkhuijsen, E. M.

1987-01-01

Implications of high-energy gamma-ray observations of the Andromeda galaxy with the next generation of satellites Gamma-1 and GRO are discussed in the context of the origin of cosmic rays and gamma-ray processes. The present estimate of the total gamma-ray flux of this galaxy at energies above 100 MeV is a factor of about three less than previous estimates.

Gamma-ray burster recurrence timescales

NASA Technical Reports Server (NTRS)

Schaefer, B. E.; Cline, T. L.

1984-01-01

Three optical transients have been found which are associated with gamma-ray bursters (GRBs). The deduced recurrence timescale for these optical transients (tau sub opt) will depend on the minimum brightness for which a flash would be detected. A detailed analysis using all available data of tau sub opt as a function of E(gamma)/E(opt) is given. For flashes similar to those found in the Harvard archives, the best estimate of tau sub opt is 0.74 years, with a 99% confidence interval from 0.23 years to 4.7 years. It is currently unclear whether the optical transients from GRBs also give rise to gamma-ray events. One way to test this association is to measure the recurrence timescale of gamma-ray events tau sub gamma. A total of 210 gamma-ray error boxes were examined and it was found that the number of observed overlaps is not significantly different from the number expected from chance coincidence. This observation can be used to place limits on tau sub gamma for an assumed luminosity function. It was found that tau sub gamma is approx. 10 yr if bursts are monoenergetic. However, if GRBs have a power law luminosity function with a wide dynamic range, then the limit is tau sub gamma 0.5 yr. Hence, the gamma-ray data do not require tau sub gamma and tau sub opt to be different.

GRI: The Gamma-Ray Imager mission

NASA Astrophysics Data System (ADS)

Knödlseder, J.; Gri Consortium

Observations of the gamma-ray sky reveal the most powerful sources and the most violent events in the Universe While at lower wavebands the observed emission is generally dominated by thermal processes the gamma-ray sky provides us with a view on the non-thermal Universe Here particles are accelerated to extreme relativistic energies by mechanisms which are still poorly understood and nuclear reactions are synthesizing the basic constituents of our world Cosmic accelerators and cosmic explosions are the major science themes that are addressed in the gamma-ray regime With the INTEGRAL observatory ESA has provided a unique tool to the astronomical community and has put Europe in the lead in the field of gamma-ray astronomy INTEGRAL provides an unprecedented survey of the soft gamma-ray sky revealing hundreds of sources new classes of objects extraordinary views of antimatter annihilation in our Galaxy and fingerprints of recent nucleosynthesis processes While INTEGRAL has provided the global overview over the soft gamma-ray sky there is a growing need to perform deeper more focused investigations of gamma-ray sources In soft X-rays a comparable step was taken going from the Einstein satellite to the XMM Newton observatory Technological advances in the past years in the domain of gamma-ray focusing using Laue diffraction and multilayer-coated mirror techniques have paved the way towards a gamma-ray mission providing major improvements compared to past missions regarding sensitivity and angular resolution Such a