Science.gov

Sample records for galactic superluminal jet

  1. Accretion Disk Spectra of the Ultra-luminous X-ray Sources in Nearby Spiral Galaxies and Galactic Superluminal Jet Sources

    NASA Technical Reports Server (NTRS)

    White, Nicholas E. (Technical Monitor); Ebisawa, Ken; Zycki, Piotr; Kubota, Aya; Mizuno, Tsunefumi; Watarai, Ken-ya

    2003-01-01

    Ultra-luminous Compact X-ray Sources (ULXs) in nearby spiral galaxies and Galactic superluminal jet sources share the common spectral characteristic that they have unusually high disk temperatures which cannot be explained in the framework of the standard optically thick accretion disk in the Schwarzschild metric. On the other hand, the standard accretion disk around the Kerr black hole might explain the observed high disk temperature, as the inner radius of the Kerr disk gets smaller and the disk temperature can be consequently higher. However, we point out that the observable Kerr disk spectra becomes significantly harder than Schwarzschild disk spectra only when the disk is highly inclined. This is because the emission from the innermost part of the accretion disk is Doppler-boosted for an edge-on Kerr disk, while hardly seen for a face-on disk. The Galactic superluminal jet sources are known to be highly inclined systems, thus their energy spectra may be explained with the standard Kerr disk with known black hole masses. For ULXs, on the other hand, the standard Kerr disk model seems implausible, since it is highly unlikely that their accretion disks are preferentially inclined, and, if edge-on Kerr disk model is applied, the black hole mass becomes unreasonably large (greater than or approximately equal to 300 Solar Mass). Instead, the slim disk (advection dominated optically thick disk) model is likely to explain the observed super- Eddington luminosities, hard energy spectra, and spectral variations of ULXs. We suggest that ULXs are accreting black holes with a few tens of solar mass, which is not unexpected from the standard stellar evolution scenario, and their X-ray emission is from the slim disk shining at super-Eddington luminosities.

  2. Jet Stability and the Generation of Superluminal and Stationary Components

    NASA Technical Reports Server (NTRS)

    Agudo, Ivan; Gomez, Jose-Luis; Marti, Jose-Maria; Ibanez, Jose-Maria; Marscher, Alan P.; Alberdi, Antonio; Aloy, Miguel-Angel; Hardee, Philip E.

    2001-01-01

    We present a numerical simulation of the response of an expanding relativistic jet to the ejection of a superluminal component. The simulation has been performed with a relativistic time-dependent hydrodynamical code from which simulated radio maps are computed by integrating the transfer equations for synchrotron radiation. The interaction of the superluminal component with the underlying jet results in the formation of multiple conical shocks behind the main perturbation. These trailing components can be easily distinguished because they appear to be released from the primary superluminal component instead of being ejected from the core. Their oblique nature should also result in distinct polarization properties. Those appearing closer to the core show small apparent motions and a very slow secular decrease in brightness and could be identified as stationary components. Those appearing farther downstream are weaker and can reach superluminal apparent motions. The existence of these trailing components indicates that not all observed components necessarily represent major perturbations at the jet inlet; rather, multiple emission components can be generated by a single disturbance in the jet. While the superluminal component associated with the primary perturbation exhibits a rather stable pattern speed, trailing components have velocities that increase with distance from the core but move at less than the jet speed. The trailing components exhibit motion and structure consistent with the triggering of pinch modes by the superluminal component. The increase in velocity of the trailing components is an indirect consequence of the acceleration of the expanding fluid, which is assumed to be relativistically hot; if observed, such accelerations would therefore favor an electron-positron (as opposed to proton rest mass) dominated jet.

  3. The Trails of Superluminal Jet Components in 3C 111

    NASA Technical Reports Server (NTRS)

    Kadler, M.; Ros, E.; Perucho, M.; Kovalev, Y. Y.; Homan, D. C.; Agudo, I.; Kellermann, K. I.; Aller, M. F.; Aller, H. D.; Lister, M. L.; Zensus, J. A.

    2007-01-01

    The parsec-scale radio jet of the broad-line radio galaxy 3C 111 has been monitored since 1995 as part of the 2cm Survey and MOJAVE monitoring observations conducted with the VLBA. Here, we present results from 18 epochs of VLBA observations of 3C 111 and from 18 years of radio flux density monitoring observations conducted at the University of Michigan. A major radio flux-density outburst of 3C 111 occurred in 1996 and was followed by a particularly bright plasma ejection associated with a superluminal jet component. This major event allows us to study a variety of processes associated with outbursts of radio-loud AGN in much greater detail than possible in other cases: the primary perturbation gives rise to the formation of a forward and a backward-shock, which both evolve in characteristically different ways and allow us to draw conclusions about the workflow of jet-production events; the expansion, acceleration and recollimation of the ejected jet plasma in an environment with steep pressure and density gradients are revealed; trailing components are formed in the wake of the primary perturbation as a result of Kelvin- Helmholtz instabilities from the interaction of the jet with the external medium. The jet-medium interaction is further scrutinized by the linear-polarization signature of jet components traveling along the jet and passing a region of steep pressure/density gradients.

  4. Superluminal Jets and Other Properties of Black Holes Binaries

    NASA Technical Reports Server (NTRS)

    Harmon, Alan

    1997-01-01

    Discoveries in the past few years of radio jets in Galactic black hole candidates have provided a link between active galactic nuclei (AGNS) and the compact stars in binary systems. The availability of binary systems relatively close by is an opportunity to learn about the jet production mechanism on a timescale a million times shorter than that of an AGN. Evidence is clearly seen of correlated high energy X-ray and gamma ray emission to radio emission from jets, linking the accretion and jet production mechanisms. objects such as GRS 1915+105, GRO J1655-40 and Cyg X-3 show striking properties which distinguish them from other black hole candidates. Our theoretical understanding of these systems is still in the formative stages. I review some of the most recent multiwavelength data and point out questions raised by these observations.

  5. Broadband High-Energy Observations of the Superluminal Jet Source GRO J1655-40 During an Outburst

    NASA Technical Reports Server (NTRS)

    Zhang, S. N.; Ebisawa, K.; Sunyaev, R.; Ueda, Y.; Harmon, B. A.; Sazonov, S.; Fishman, G. J.; Inoue, H.; Paciesas, W. S.; Takahash, T.

    1997-01-01

    The X-ray/radio transient superluminal jet source GRO J1655-40 was recently suggested to contain a black hole from optical observations. Because it is a relatively close-by system (d approximately 3.2 kpc), it can likely provide us with rich information about the physics operating in both Galactic and extragalactic jet sources. We present the first simultaneous broadband high-energy observations of GRO J1655-40 during the 1995 July-August outburst by three instruments: ASCA, WATCH/Granat, and BATSE/CGRO, in the energy band from 1 keV to 2 MeV. Our observations strengthen the interpretation that GRO J1655-40 contains a black hole. We detected a two-component energy spectrum, commonly seen from other Galactic black hole binaries, but never detected from a neutron star system. Combining our results with the mass limits derived from optical radial velocity and orbital period measurements, we further constrain the mass of the central object to be between 3.3 and 5.8 solar mass, above the well-established mass upper limit of 3.2 solar mass for a neutron star (the optical mass function for GRO J1655-40 is 3.16 + 0.2 solar mass). This system is therefore the first Galactic superluminal jet source for which there is strong evidence that the system contains a stellar mass black hole. The inclination angle of the binary system is constrained to be between 76 deg and 87 deg, consistent with estimates obtained from optical light curves and radio jet kinematics.

  6. X-ray Dips Followed by Superluminal Ejections as Evidence for An Accretion Disc Feeding the Jet in A Radio Galaxy

    NASA Technical Reports Server (NTRS)

    Marscher, Alan P.; Jorstad, Svetlana G.; Gomez, Jose-Luis; Aller, Margo F.; Terasranta, Harri; Lister, Matthew L.; Stirling, Alastair, M.

    2002-01-01

    Accretion onto black holes is thought to power the relativistic jets and other high-energy phenomena in both active galactic nuclei (AGNs) and the "microquasar" binary systems located in our Galaxy. However, until now there has been insufficient multifrequency monitoring to establish a direct observational link between the black hole and the jet in an AGE. This contrasts with the case of microquasars, in which superluminal features appear and propagate down the radio jet shortly after sudden decreases in the X-ray flux. Such an X-ray dip is most likely caused by the disappearance of a section of the inner accretion disc, part of which falls past the event horizon and the remainder of which is injected into the jet. This infusion of energy generates a disturbance that propagates down the jet, creating the appearance of a superluminal bright spot. Here we report the results of three years of intensive monitoring of the X-ray and radio emission of the Seyfert-like radio galaxy 3C 120. As in the case of microquasars, dips in the X-ray emission are followed by ejections of bright superluminal knots in the radio jet. Comparison of the characteristic length and time scales allows us to infer that the rotational states of the black holes in these two objects are different.

  7. Flashing superluminal components in the jet of the radio galaxy 3C120

    PubMed

    Gomez; Marscher; Alberdi; Jorstad; Garcia-Miro

    2000-09-29

    A 16-month sequence of radio images of the active galaxy 3C120 with the Very Long Baseline Array reveals a region in the relativistic jet where superluminal components flash on and off over time scales of months, while the polarization angle rotates. This can be explained by interaction between the jet and an interstellar cloud located about 8 parsecs from the center of the galaxy. The cloud, which rotates the polarization direction and possibly eclipses a section of the jet, represents a "missing link" between the ultradense broad-emission-line clouds closer to the center and the lower density narrow-emission-line clouds seen on kiloparsec scales. PMID:11009410

  8. Superluminal Motions at 500 Mpc: New Results on Nearby AGN Jets with HST

    NASA Astrophysics Data System (ADS)

    Meyer, Eileen T.; Georganopoulos, Markos; Sparks, William B.; Biretta, John A.; Van Der Marel, Roeland P.; Anderson, Jay; Chiaberge, Marco; Perlman, Eric S.; Norman, Colin Arthur

    2015-01-01

    I will present results from recent HST observations of several nearby AGN Jets. Using over 20 years of archival data in combination with the most recent deep ACS/WFC imaging, we have found evidence for superluminal motions in optical kpc-scale jets, beyond the only previously reported case of M87. Our observations show that relativistic bulk motions extend to the outermost parts of these jets, and our continuous refinement of astrometric techniques suggests that the reach of Hubble observations, and the constraints on jet models implied by these measurements, may extend beyond 500 Mpc. The presentation will include movies of these jets in which the motions of the plasma can be seen by eye.

  9. "New Proper Motion Measurements of the Superluminal Velocities in the M87 Optical Jet with HST"

    NASA Astrophysics Data System (ADS)

    Meyer, Eileen T.; Sparks, W. B.; Biretta, J. A.; Sohn, S.; Anderson, J.; Van Der Marel, R. P.; Norman, C. A.; Nakamura, M.

    2014-01-01

    Using over 13 years of archival HST observations of the relativistic jet in the archetypal radio galaxy M87, we have produced astrometric speed measurements of the optically bright synchrotron emitting plasma components in the jet with unprecedented accuracy. Building on previous work showing the superluminal nature of the jet in the optical, we have found that the jet motion is incredibly complex, with both transverse motions and flux variations which can be seen very clearly by eye in the timeseries of deep exposures. These observations of M87 provide us with a unique dataset with which to refine theoretical models of the largescale jet structure, potentially addressing open questions such as the jet collimation mechanism, bulk acceleration and deceleration in the jet, and the presence of a helical structure. I will also present very recent results using data from the HST archive on the optical counterjet and nuclear regions of M87 and discuss the larger implications of these detailed studies of one of the most nearby AGN jets.

  10. Superluminal non-ballistic jet swing in the quasar NRAO 150 revealed by mm-VLBI

    NASA Astrophysics Data System (ADS)

    Agudo, I.; Bach, U.; Krichbaum, T. P.; Marscher, A. P.; Gonidakis, I.; Diamond, P. J.; Perucho, M.; Alef, W.; Graham, D. A.; Witzel, A.; Zensus, J. A.; Bremer, M.; Acosta-Pulido, J. A.; Barrena, R.

    2007-12-01

    Context: NRAO 150, a compact and bright radio to mm source showing core/jet structure, has been recently identified as a quasar at redshift z = 1.52 through a near-IR spectral observation. Aims: To study the jet kinematics on the smallest accessible scales and to compute the first estimates of its basic physical properties. Methods: We have analysed the ultra-high-resolution images from a new monitoring program at 86 GHz and 43 GHz with the Global mm VLBI Array and the VLBA, respectively. An additional archival calibration VLBA data set, covering the period from 1997 to 2007, has been used. Results: Our data show an extreme projected counter-clockwise jet position angle swing at an angular rate of up to ≈11° yr within the inner ≈ 3 pc of the jet, which is associated with a non-ballistic superluminal motion of the jet within this region. Conclusions: The results suggest that the magnetic field could play an important role in the dynamics of the jet in NRAO 150, which is supported by the large values of the magnetic field strength obtained from our first estimates. The extreme characteristics of the jet swing make NRAO 150 a prime source to study the jet wobbling phenomenon. Tables 1-3 and the movie are only available in electronic form at http://www.aanda.org

  11. Batse Triggered Observations of Galactic Superluminal Sources GROJ1655-40

    NASA Technical Reports Server (NTRS)

    Zhang, Shuang Nan

    2002-01-01

    We have analyzed multiwavelength data of galactic superluminal sources including GROJ1655-40. Currently there are thirteen X-ray binaries, in which the masses of the invisible and compact objects have been determined to be much higher than three solar masses, the well-known upper limit to the mass of a neutron star. Because no stable and compact objects are believed to exist above this limit, these compact objects are consequently considered as stellar mass black holes, though clean evidence of strong gravity effects around the assumed black holes is very rare. From optical and radio observations, their system inclination angles have been determined to range between 25 degrees and 80 degrees, but peaked between 60-70 degrees. This peak is not explained in the frame work of Newtonian gravity in these systems. However, this peak is reproduced naturally if we model the observed X-ray radiation as being produced in the accretion disks very close to the black hole horizons, where the extremely strong general and special relativistic effects, caused by the extremely strong gravity near the black hole horizons, modify the local radiation significantly as the X-rays propagate to the remote observer.

  12. DISCOVERY OF SUB- TO SUPERLUMINAL MOTIONS IN THE M87 JET: AN IMPLICATION OF ACCELERATION FROM SUB-RELATIVISTIC TO RELATIVISTIC SPEEDS

    SciTech Connect

    Asada, Keiichi; Nakamura, Masanori; Inoue, Makoto; Doi, Akihiro; Nagai, Hiroshi E-mail: nakamura@asiaa.sinica.edu.tw

    2014-01-20

    The velocity field of the M87 jet from milli-arcsecond (mas) to arcsecond scales is extensively investigated together with new radio images taken from European VLBI Network (EVN) observations. We detected proper motions of components located at between 160 mas from the core and the HST-1 complex for the first time. Newly derived velocity fields exhibit a systematic increase from sub- to superluminal speeds in the upstream of HST-1. If we assume that the observed velocities reflect the bulk flow, here we suggest that the M87 jet may be gradually accelerated through a distance of 10{sup 6} times the Schwarzschild radius of the supermassive black hole. The acceleration zone is co-spatial with the jet parabolic region, which is interpreted as the collimation zone of the jet. The acceleration and collimation take place simultaneously, which we suggest is characteristic of magnetohydrodynamic flows. The distribution of the velocity field has a peak at HST-1, which is considered as the site of over-collimation, and shows a deceleration downstream of HST-1 where the jet is conical. Our interpretation of the velocity map in the M87 jet provides a hypothesis for active galactic nuclei which suggests that the acceleration and collimation zone of relativistic jets extends over the whole scale within the sphere of influence of the supermassive black hole.

  13. Launching of Active Galactic Nuclei Jets

    NASA Astrophysics Data System (ADS)

    Tchekhovskoy, Alexander

    As black holes accrete gas, they often produce relativistic, collimated outflows, or jets. Jets are expected to form in the vicinity of a black hole, making them powerful probes of strong-field gravity. However, how jet properties (e.g., jet power) connect to those of the accretion flow (e.g., mass accretion rate) and the black hole (e.g., black hole spin) remains an area of active research. This is because what determines a crucial parameter that controls jet properties—the strength of large-scale magnetic flux threading the black hole—remains largely unknown. First-principles computer simulations show that due to this, even if black hole spin and mass accretion rate are held constant, the simulated jet powers span a wide range, with no clear winner. This limits our ability to use jets as a quantitative diagnostic tool of accreting black holes. Recent advances in computer simulations demonstrated that accretion disks can accumulate large-scale magnetic flux on the black hole, until the magnetic flux becomes so strong that it obstructs gas infall and leads to a magnetically-arrested disk (MAD). Recent evidence suggests that central black holes in jetted active galactic nuclei and tidal disruptions are surrounded by MADs. Since in MADs both the black hole magnetic flux and the jet power are at their maximum, well-defined values, this opens up a new vista in the measurements of black hole masses and spins and quantitative tests of accretion and jet theory.

  14. Stellar and galactic jets - Theoretical issues

    NASA Technical Reports Server (NTRS)

    Konigl, A.

    1986-01-01

    Theoretical issues pertaining to the modelling of jets in young stellar objects and in active galactic nuclei are reviewed. The strong morphological similarities between these two types of sources are emphasized, and observational constraints on the basic physical mechanisms that may be responsible for the jet phenomenon are outlined. Particular attention is given to the 'momentum-discharge problem' in molecular-cloud outflows and to its possible resolution in terms of a centrifugally driven magnetohydrodynamic wind from an accretion disk. In addition, various propagation effects are discussed, and the relevance to stellar jets of the de Laval collimation mechanism and of the accelerated-clump model for emission knots is assessed. The review concludes with a brief list of potentially useful observational tests.

  15. Intrinsic physical conditions and structure of relativistic jets in active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Nokhrina, E. E.; Beskin, V. S.; Kovalev, Y. Y.; Zheltoukhov, A. A.

    2015-03-01

    The analysis of the frequency dependence of the observed shift of the cores of relativistic jets in active galactic nuclei (AGNs) allows us to evaluate the number density of the outflowing plasma ne and, hence, the multiplicity parameter λ = ne/nGJ, where nGJ is the Goldreich-Julian number density. We have obtained the median value for λmed = 3 × 1013 and the median value for the Michel magnetization parameter σM, med = 8 from an analysis of 97 sources. Since the magnetization parameter can be interpreted as the maximum possible Lorentz factor Γ of the bulk motion which can be obtained for relativistic magnetohydrodynamic (MHD) flow, this estimate is in agreement with the observed superluminal motion of bright features in AGN jets. Moreover, knowing these key parameters, one can determine the transverse structure of the flow. We show that the poloidal magnetic field and particle number density are much larger in the centre of the jet than near the jet boundary. The MHD model can also explain the typical observed level of jet acceleration. Finally, casual connectivity of strongly collimated jets is discussed.

  16. Pulsars in the Laboratory: Practical Superluminal Emitters Mimic Their Galactic Cousins

    NASA Astrophysics Data System (ADS)

    Singleton, John; Schmidt, A. C.; Middleditch, J.; Redman, S.; Wigger, J.; Ardavan, H.; Ardavan, A.

    2013-06-01

    Maxwell's equations establish that polarization currents can be animated to travel faster than the speed of light in vacuo, and that these superluminal distribution patterns emit tightly focused packets of electromagnetic radiation that are fundamentally different from those emitted by conventional means. A polarization current occurs when a polarized region moves or is changed with time t its density is ∂P/∂t and it has the same dimensions as a conventional current density of electrons. If a polarization current oscillates or accelerates, it will emit electromagnetic radiation, just as an accelerated or oscillating current of electrons does. However, unlike electrons, which possess rest mass and are therefore limited to speeds less than c, the speed of light, polarization currents may travel arbitrarily fast, as the displacement of their constituent elements is minimal; while the radiation source travels faster than c, the individual massive particles’ speeds remain subluminal. In the past few years, several superluminal light sources have been built in the laboratory, generating polarization currents that move at up to 20 times the speed of light. Here we compare the emitted radiation from these well-characterized, ground-based experiments to observational pulsar data. Comparisons are also made with theoretical predictions of the Superluminal Model for Pulsars, which invokes emission by polarization currents that travel faster than light in a circular orbit through the pulsar’s plasma “atmosphere.” Using this single, dominant emission mechanism, which accounts for the properties of the laboratory-based sources, we show that many of the most enigmatic features of pulsar radiation are merely qualities intrinsic to a faster- than-light source: (i) the apparent radiation temperature and pulse shape; (ii) the unusual polarization properties (e.g. swing in position angle); and (iii) the broadband radiation spectrum.

  17. The radiative deceleration of ultrarelativistic jets in active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Melia, Fulvio; Konigl, Arieh

    1989-05-01

    A detailed study of the dynamical interaction between a highly relativistic jet and the thermal radiation field from an AGN accretion disk is reported, and the Comptonized spectrum arising from this interaction is self-consistently determined. A simple model that captures the essential radiative and geometrical features of realistic disk configurations is presented, and the disk radiation field is calculated. The results confirm Phinney's (1987) suggestion that the thermal radiation field produced by accretion in an AGN could be very effective in decelerating ultrarelativistic jets that are accreted by electromagnetic or hydromagnetic forces closer to the central black hole. Terminal Lorentz factors are consistent with the values inferred in superluminal radio sources are readily produced in this model for plausible disk and jet parameters without additional acceleration in the interaction zone. A new interpretation of the hard X-ray component detected in BL Lac spectra is proposed.

  18. ASCA Observation of the Superluminal Jet Source GRO J1655-40 in the 1997 Outburst

    NASA Technical Reports Server (NTRS)

    Yamaoka, Kazutaka; Ueda, Yoshihiro; Hajime, Inoue; Nagase, Fumiski; Ebisawa, Ken; Kotani, Taro; Tanaka, Yasuo; Zhang, Shang Nan

    2001-01-01

    We report on the results of an ASCA observation of the Galactic jet source GRO 51655-40 performed from 1997 February 25 to February 28 covering a full orbital period (2.62 d). The averaged 2-10 keV flux was about 1.1 Crab. An absorption line feature centered at 6.8 keV was detected both in the GIS and SIS spectra. We interpret this as a blend of two resonance-absorption K alpha lines from H-like and He-like iron ions. We can consistently explain both the ASCA spectra and the simultaneous RXTE/PCA spectrum by a combination of K-absorption lines and K-absorption edges of iron ions. The fact that the absorption line is stably present over the whole orbital phase implies that the distribution of the highly ionized plasma is not affected by the companion star, which is consistent with its presence around the black hole. A curve of growth analysis shows that the plasma contains velocity dispersion along the line-of-sight larger than 300 km/s attributed to bulk motions. It is probably a part of a geometrically thick accretion flow in turbulent motions with velocities of 500-1600 km/s at an estimated radius of sim 10(exp 10)/cm.

  19. Radio jet refraction in galactic atmospheres with static pressure gradients

    NASA Technical Reports Server (NTRS)

    Henriksen, R. N.; Vallee, J. P.; Bridle, A. H.

    1981-01-01

    A theory of double radio sources which have a 'Z' or 'S' morphology is proposed, based on the refraction of radio jets in the extended atmosphere of an elliptical galaxy. The model describes a collimated jet of supersonic material bending self-consistently under the influence of external static pressure gradients. Gravity and magnetic fields are neglected in the simplest case except insofar as they determine the static pressure distribution. The calculation is a straightforward extension of a method used to calculate a ram-pressure model for twin radio trails ('C' morphology). It may also be described as a continuous-jet version of a buoyancy model proposed in 1973. The model has the added virtue of invoking a galactic atmosphere similar to those already indicated by X-ray measurements of some other radio galaxies and by models for the collimation of other radio jets.

  20. Baldwin Effect and Additional BLR Component in AGN with Superluminal Jets

    NASA Astrophysics Data System (ADS)

    Patiño Álvarez, Víctor; Torrealba, Janet; Chavushyan, Vahram; Cruz González, Irene; Arshakian, Tigran; León Tavares, Jonathan; Popovic, Luka

    2016-06-01

    We study the Baldwin Effect (BE) in 96 core-jet blazars with optical and ultraviolet spectroscopic data from a radio-loud AGN sample obtained from the MOJAVE 2cm survey. A statistical analysis is presented of the equivalent widths W_lambda of emission lines H beta 4861, Mg II 2798, C IV 1549, and continuum luminosities at 5100, 3000, and 1350 angstroms. The BE is found statistically significant (with confidence level c.l. > 95%) in H beta and C IV emission lines, while for Mg II the trend is slightly less significant (c.l. = 94.5%). The slopes of the BE in the studied samples for H beta and Mg II are found steeper and with statistically significant difference than those of a comparison radio-quiet sample. We present simulations of the expected BE slopes produced by the contribution to the total continuum of the non-thermal boosted emission from the relativistic jet, and by variability of the continuum components. We find that the slopes of the BE between radio-quiet and radio-loud AGN should not be different, under the assumption that the broad line is only being emitted by the canonical broad line region around the black hole. We discuss that the BE slope steepening in radio AGN is due to a jet associated broad-line region.

  1. Variability in Active Galactic Nuclei from Propagating Turbulent Relativistic Jets

    NASA Astrophysics Data System (ADS)

    Pollack, Maxwell; Pauls, David; Wiita, Paul J.

    2016-03-01

    We use the Athena hydrodynamics code to model propagating two-dimensional relativistic jets as approximations to the growth of radio-loud active galactic nuclei for various input jet velocities and jet-to-ambient matter density ratios. Using results from these simulations we estimate the changing synchrotron emission by summing the fluxes from a vertical strip of zones behind the reconfinement shock, which is nearly stationary, and from which a substantial portion of the flux variability should arise. We explore a wide range of timescales by considering two light curves from each simulation; one uses a relativistic turbulence code with bulk velocities taken from our simulations as input, while the other uses the bulk velocity data to compute fluctuations caused by variations in the Doppler boosting due to changes in the direction and the speed of the flow through all zones in the strip. We then calculate power spectral densities (PSDs) from the light curves for both turbulent and bulk velocity origins for variability. The range of the power-law slopes of the PSDs for the turbulence induced variations is -1.8 to -2.3, while for the bulk velocity produced variations this range is -2.1 to -2.9 these are in agreement with most observations. When superimposed, these power spectra span a very large range in frequency (about five decades), with the turbulent fluctuations yielding most of the shorter timescale variations and the bulk flow changes dominating the longer periods.

  2. Large-scale X-ray jets from Galactic black holes

    NASA Astrophysics Data System (ADS)

    Kaaret, P.; Corbel, S.; Tomsick, J. A.; Butt, Y.; Fender, R. P.; Lazendic, J.; Miller, J. M.; Orosz, J. A.; Tzioumis, A. K.; Wijnands, Rudy

    2004-06-01

    Observations of jets from stellar-mass sources located in our Galaxy offer a unique opportunity to study the dynamical evolution of relativistic jets on time scales inaccessible for active galactic nuclei jets, with implications for our understanding of the dynamics and energetics of relativistic jets from Galactic x-ray binaries and active galactic nuclei. We review recent observations of X-ray jets from Galactic black hole candidates. Spatially resolved X-ray spectra from SS 433 have provided evidence for re-heating in a hadronic jet and may offer an observational probe of jet collimation. A large-scale jet from the now quiescent transient 4U 1755-33 appears to indicate continual jet formation over a period of 10-30 years. Detection of a jet from XTE J1550-564 has provided the first direct measurement of gradual deceleration of a jet from a black hole and strong evidence for the re-energization of jet particles to energies up to 10 TeV at sites far from the jet origin.

  3. Errarum: Detection of Absorption-Line Features in the X-Ray Spectra of the Galactic Superluminal Source GRO J1655-40

    NASA Astrophysics Data System (ADS)

    Ueda, Y.; Inoue, H.; Tanaka, Y.; Ebisawa, K.; Nagase, F.; Kotani, T.; Gehrels, N.

    1998-06-01

    In the paper ``Detection of Absorption-Line Features in the X-Ray Spectra of the Galactic Superluminal Source GRO J1655-40'' by Y. Ueda, H. Inoue, Y. Tanaka, K. Ebisawa, F. Nagase, T. Kotani, and N. Gehrels (ApJ, 492, 782 [1998]), there is an error in the curve of growth for the Kα absorption line (Fig. 4). The revised version of Figure 4 given here replaces Figure 4 in the paper. Several numbers derived from the figure should be corrected accordingly, but the conclusion of the paper is not affected. In the third paragraph of the discussion section (page 786), the iron column density of the plasma should be 1019-1020 cm-2, which corresponds to a hydrogen column density of 3 × 1023-3 × 1024 cm-2. The final limit on the hydrogen column density of the line-absorbing plasma should be changed to 3 × 1023 cm-2 < NH < 1024 cm-2.

  4. Discovery of a Superluminal Fe K Echo at the Galactic Center: The Glorious Past of Sgr A* Preserved by Molecular Clouds

    NASA Astrophysics Data System (ADS)

    Ponti, G.; Terrier, R.; Goldwurm, A.; Belanger, G.; Trap, G.

    2010-05-01

    We present the result of a study of the X-ray emission from the galactic center (GC) molecular clouds (MCs) within 15 arcmin from Sgr A*. We use XMM-Newton data (about 1.2 Ms of observation time) spanning about eight years. The MC spectra show all the features characteristic of reflection: (1) intense Fe Kα, with equivalent width of about 0.7-1 keV, and the associated Kβ line; (2) flat power-law continuum, and (3) a significant Fe K edge (τ ~ 0.1-0.3). The diffuse low ionization Fe K emission follows the MC distribution, nevertheless not all MC are Fe K emitters. The long baseline monitoring allows the characterization of the temporal evolution of the MC emission. A complex pattern of variations is shown by the different MCs, with some having constant Fe K emission, some increasing, and some decreasing. In particular, we observe an apparent superluminal motion of a light front illuminating a molecular nebula. This might be due to a source outside the MC (such as Sgr A* or a bright and long outburst of a X-ray binary), though it cannot be due to low energy cosmic rays or a source located inside the cloud. We also observe a decrease of the X-ray emission from G0.11-0.11, behavior similar to that of Sgr B2. The line intensities, clouds dimensions, columns densities, and positions with respect to Sgr A* are consistent with being produced by the same Sgr A* flare. The required high luminosity (about 1.5 × 1039 erg s-1) can hardly be produced by a binary system, while it is in agreement with a flare of Sgr A* fading about 100 years ago. The low intensity of the Fe K emission coming from the 50 and the 20 km s-1 MC places an upper limit of 1036 erg s-1 to the mean luminosity of Sgr A* in the last 60-90 years. The Fe K emission and variations from these MC might have been produced by a single flare of Sgr A*.

  5. Evidence of parsec-scale jets in low-luminosity active galactic nuclei

    SciTech Connect

    Mezcua, M.; Prieto, M. A.

    2014-05-20

    The nuclear radio emission of low-luminosity active galactic nuclei (LLAGNs) is often associated with unresolved cores. In this paper we show that most LLAGNs present extended jet radio emission when observed with sufficient angular resolution and sensitivity. They are thus able to power, at least, parsec-scale radio jets. To increase the detection rate of jets in LLAGNs, we analyze subarcsecond resolution data of three low-ionization nuclear emission regions. This yields the detection of extended jet-like radio structures in NGC 1097 and NGC 2911 and the first resolved parsec-scale jet of NGC 4594 (Sombrero). The three sources belong to a sample of nearby LLAGNs for which high-spatial-resolution spectral energy distribution of their core emission is available. This allows us to study their accretion rate and jet power (Q {sub jet}) without drawing on (most) of the ad hoc assumptions usually considered in large statistical surveys. We find that those LLAGNs with large-scale radio jets (>100 pc) have Q {sub jet} > 10{sup 42} erg s{sup –1}, while the lowest Q {sub jet} correspond to those LLAGNs with parsec-scale (≤100 pc) jets. The Q {sub jet} is at least as large as the radiated bolometric luminosity for all LLAGN, in agreement with previous statistical studies. Our detection of parsec-scale jets in individual objects further shows that the kinematic jet contribution is equally important in large- or parsec-scale objects. We also find that the Eddington-scaled accretion rate is still highly sub-Eddingtonian (<10{sup –4}) when adding the Q {sub jet} to the total emitted luminosity (radiated plus kinetic). This indicates that LLAGNs are not only inefficient radiators but that they also accrete inefficiently or are very efficient advectors.

  6. Evidence of Parsec-scale Jets in Low-luminosity Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Mezcua, M.; Prieto, M. A.

    2014-05-01

    The nuclear radio emission of low-luminosity active galactic nuclei (LLAGNs) is often associated with unresolved cores. In this paper we show that most LLAGNs present extended jet radio emission when observed with sufficient angular resolution and sensitivity. They are thus able to power, at least, parsec-scale radio jets. To increase the detection rate of jets in LLAGNs, we analyze subarcsecond resolution data of three low-ionization nuclear emission regions. This yields the detection of extended jet-like radio structures in NGC 1097 and NGC 2911 and the first resolved parsec-scale jet of NGC 4594 (Sombrero). The three sources belong to a sample of nearby LLAGNs for which high-spatial-resolution spectral energy distribution of their core emission is available. This allows us to study their accretion rate and jet power (Q jet) without drawing on (most) of the ad hoc assumptions usually considered in large statistical surveys. We find that those LLAGNs with large-scale radio jets (>100 pc) have Q jet > 1042 erg s-1, while the lowest Q jet correspond to those LLAGNs with parsec-scale (<=100 pc) jets. The Q jet is at least as large as the radiated bolometric luminosity for all LLAGN, in agreement with previous statistical studies. Our detection of parsec-scale jets in individual objects further shows that the kinematic jet contribution is equally important in large- or parsec-scale objects. We also find that the Eddington-scaled accretion rate is still highly sub-Eddingtonian (<10-4) when adding the Q jet to the total emitted luminosity (radiated plus kinetic). This indicates that LLAGNs are not only inefficient radiators but that they also accrete inefficiently or are very efficient advectors.

  7. Radio jet refraction in galactic atmospheres with static pressure gradients

    NASA Technical Reports Server (NTRS)

    Henriksen, R. N.; Vallee, J. P.; Bridle, A. H.

    1981-01-01

    A theory based on the refraction of radio jets in the extended atmosphere of an elliptical galaxy, is proposed for double radio sources with a Z or S morphology. The model describes a collimated jet of supersonic material that bends self-consistently under the influence of external static pressure gradients, and may alternatively be seen as a continuous-jet version of the buoyancy model proposed by Gull (1973). Emphasis is placed on (1) S-shaped radio sources identified with isolated galaxies, such as 3C 293, whose radio structures should be free of distortions resulting from motion relative to a cluster medium, and (2) small-scale, galaxy-dominated rather than environment-dominated S-shaped sources such as the inner jet structure of Fornax A.

  8. Polarimetric Observations of 15 Active Galactic Nuclei at High Frequencies: Jet Kinematics from Bimonthly Monitoring with the Very Long Baseline Array

    NASA Astrophysics Data System (ADS)

    Jorstad, Svetlana G.; Marscher, Alan P.; Lister, Matthew L.; Stirling, Alastair M.; Cawthorne, Timothy V.; Gear, Walter K.; Gómez, José L.; Stevens, Jason A.; Smith, Paul S.; Forster, James R.; Robson, E. Ian

    2005-10-01

    We present total and polarized intensity images of 15 active galactic nuclei obtained with the Very Long Baseline Array at 7 mm wavelength at 17 epochs from 1998 March to 2001 April. At some epochs the images are accompanied by nearly simultaneous polarization measurements at 3 mm, 1.35/0.85 mm, and optical wavelengths. Here we analyze the 7 mm images to define the properties of the jets of two radio galaxies, five BL Lac objects, and eight quasars on angular scales >~0.1 mas. We determine the apparent velocities of 106 features in the jets. For many of the features we derive Doppler factors using a new method based on a comparison of the timescale of decline in flux density with the light-travel time across the emitting region. This allows us to estimate the Lorentz factors (Γ), intrinsic brightness temperatures, and viewing angles of 73 superluminal knots, as well as the opening angle of the jet for each source. The Lorentz factors of the jet flows in the different blazars range from Γ~5 to 40 with the majority of the quasar components having Γ~16-18, while the values in the BL Lac objects are more uniformly distributed. The brightest knots in the quasars have the highest apparent speeds, while the more slowly moving components are pronounced in the BL Lac objects. The quasars in our sample have similar opening angles and marginally smaller viewing angles than the BL Lacs. The two radio galaxies have lower Lorentz factors and wider viewing angles than the blazars. Opening angle and Lorentz factor are inversely proportional, as predicted by gasdynamical models. The brightness temperature drops more abruptly with distance from the core in the BL Lac objects than in the quasars and radio galaxies, perhaps owing to stronger magnetic fields in the former resulting in more severe synchrotron losses of the highest energy electrons. In nine sources we detect statistically meaningful deviations from ballistic motion, with the majority of components accelerating with

  9. WHAT GOVERNS THE BULK VELOCITY OF THE JET COMPONENTS IN ACTIVE GALACTIC NUCLEI?

    SciTech Connect

    Chai Bo; Cao Xinwu; Gu Minfeng E-mail: cxw@shao.ac.cn

    2012-11-10

    We use a sample of radio-loud active galactic nuclei (AGNs) with measured black hole masses to explore the jet formation mechanisms in these sources. Based on Koenigl's inhomogeneous jet model, the jet parameters, such as the bulk motion Lorentz factor, magnetic field strength, and electron density in the jet, can be estimated with the very long baseline interferometry and X-ray data.. We find a significant correlation between black hole mass and the bulk Lorentz factor of the jet components for this sample, while no significant correlation is present between the bulk Lorentz factor and the Eddington ratio. The massive black holes will be spun up through accretion, as the black holes acquire mass and angular momentum simultaneously through accretion. Recent investigation indeed suggested that most supermassive black holes in elliptical galaxies have on average higher spins than the black holes in spiral galaxies, where random, small accretion episodes (e.g., tidally disrupted stars, accretion of molecular clouds) might have played a more important role. If this is true, then the correlation between black hole mass and the bulk Lorentz factor of the jet components found in this work implies that the motion velocity of the jet components is probably governed by the black hole spin. No correlation is found between the magnetic field strength at 10R {sub S} (R {sub S} = 2GM/c {sup 2} is the Schwarzschild radius) in the jets and the bulk Lorentz factor of the jet components for this sample. This is consistent with the black hole spin scenario, i.e., the faster moving jets are magnetically accelerated by the magnetic fields threading the horizon of more rapidly rotating black holes. The results imply that the Blandford-Znajek mechanism may dominate over the Blandford-Payne mechanism for the jet acceleration, at least in these radio-loud AGNs.

  10. MOJAVE: Monitoring of Jets in Active Galactic Nuclei with VLBA Experiments. XI. Spectral Distributions

    NASA Astrophysics Data System (ADS)

    Hovatta, Talvikki; Aller, Margo F.; Aller, Hugh D.; Clausen-Brown, Eric; Homan, Daniel C.; Kovalev, Yuri Y.; Lister, Matthew L.; Pushkarev, Alexander B.; Savolainen, Tuomas

    2014-06-01

    We have obtained milliarcsecond-scale spectral index distributions for a sample of 190 extragalactic radio jets through the Monitoring of Jets in Active Galactic Nuclei with the VLBA Experiments (MOJAVE) project. The sources were observed in 2006 at 8.1, 8.4, 12.1, and 15.4 GHz, and we have determined spectral index maps between 8.1 and 15.4 GHz to study the four-frequency spectrum in individual jet features. We have performed detailed simulations to study the effects of image alignment and (u, v)-plane coverage on the spectral index maps to verify our results. We use the spectral index maps to study the spectral index evolution along the jet and determine the spectral distributions in different locations of the jets. The core spectral indices are on average flat with a mean value of +0.22 ± 0.03 for the sample, while the jet spectrum is in general steep with a mean index of -1.04 ± 0.03. A simple power-law fit is often inadequate for the core regions, as expected if the cores are partially self-absorbed. The overall jet spectrum steepens at a rate of about -0.001 to -0.004 per deprojected parsec when moving further out from the core with flat spectrum radio quasars having significantly steeper spectra (mean -1.09 ± 0.04) than the BL Lac objects (mean -0.80 ± 0.05). However, the spectrum in both types of objects flattens on average by ~0.2 at the locations of the jet components indicating particle acceleration or density enhancements along the jet. The mean spectral index at the component locations of -0.81 ± 0.02 corresponds to a power-law index of ~2.6 for the electron energy distribution. We find a significant trend that jet components with linear polarization parallel to the jet (magnetic field perpendicular to the jet) have flatter spectra, as expected for transverse shocks. Compared to quasars, BL Lacs have more jet components with perpendicular magnetic field alignment, which may explain their generally flatter spectra. The overall steepening of the

  11. MOJAVE: Monitoring of jets in active galactic nuclei with VLBA experiments. XI. Spectral distributions

    SciTech Connect

    Hovatta, Talvikki; Aller, Margo F.; Aller, Hugh D.; Clausen-Brown, Eric; Kovalev, Yuri Y.; Pushkarev, Alexander B.; Savolainen, Tuomas; Homan, Daniel C.; Lister, Matthew L.

    2014-06-01

    We have obtained milliarcsecond-scale spectral index distributions for a sample of 190 extragalactic radio jets through the Monitoring of Jets in Active Galactic Nuclei with the VLBA Experiments (MOJAVE) project. The sources were observed in 2006 at 8.1, 8.4, 12.1, and 15.4 GHz, and we have determined spectral index maps between 8.1 and 15.4 GHz to study the four-frequency spectrum in individual jet features. We have performed detailed simulations to study the effects of image alignment and (u, v)-plane coverage on the spectral index maps to verify our results. We use the spectral index maps to study the spectral index evolution along the jet and determine the spectral distributions in different locations of the jets. The core spectral indices are on average flat with a mean value of +0.22 ± 0.03 for the sample, while the jet spectrum is in general steep with a mean index of –1.04 ± 0.03. A simple power-law fit is often inadequate for the core regions, as expected if the cores are partially self-absorbed. The overall jet spectrum steepens at a rate of about –0.001 to –0.004 per deprojected parsec when moving further out from the core with flat spectrum radio quasars having significantly steeper spectra (mean –1.09 ± 0.04) than the BL Lac objects (mean –0.80 ± 0.05). However, the spectrum in both types of objects flattens on average by ∼0.2 at the locations of the jet components indicating particle acceleration or density enhancements along the jet. The mean spectral index at the component locations of –0.81 ± 0.02 corresponds to a power-law index of ∼2.6 for the electron energy distribution. We find a significant trend that jet components with linear polarization parallel to the jet (magnetic field perpendicular to the jet) have flatter spectra, as expected for transverse shocks. Compared to quasars, BL Lacs have more jet components with perpendicular magnetic field alignment, which may explain their generally flatter spectra. The overall

  12. Superluminal sources.

    PubMed Central

    Vermeulen, R C

    1995-01-01

    Predictions for the apparent velocity statistics under simple beaming models are presented and compared to the observations. The potential applications for tests of unification models and for cosmology (source counts, measurements of the Hubble constant H0 and the deceleration parameter q0) are discussed. First results from a large homogeneous survey are presented. The data do not show compelling evidence for the existence of intrinsically different populations of galaxies, BL Lacertae objects, or quasars. Apparent velocities betaapp in the range 1-5 h-1, where h = H0/100 km.s-1.Mpc-1 [1 megaparsec (Mpc) = 3.09 x 10(22) m], occur with roughly equal frequency; higher values, up to betaapp = 10 h-1, are rather more scarce than appeared to be the case from earlier work, which evidently concentrated on sources that are not representative of the general population. The betaapp distribution suggests that there might be a skewed distribution of Lorentz factors over the sample, with a peak at gammab approximately 2 h-1 and a tail up to at least gammab approximately 10 h-1. There appears to be a clearly rising upper envelope to the betaapp distribution when plotted as a function of observed 5-GHz luminosity; a combination of source counts and the apparent velocity statistics in a larger sample could provide much insight into the properties of radio jet sources. PMID:11607604

  13. Probing the Relativistic Jets of Active Galactic Nuclei with Multiwavelength Monitoring

    NASA Technical Reports Server (NTRS)

    Marscher, Alan P.; Jorstad, Svetlana G.; Aller, Margo

    2005-01-01

    The work completed includes the analysis of observations obtained during Cycle 7 (March 2002-February 2003) of the Rossi X-ray Timing Explorer (RXTE). The project was part of a longer-term, continuing program to study the X-ray emission process in blazars and radio galaxies in collaboration with Dr. Ian McHardy (U. of Southampton, UK) and Prof. Thomas Balonek (Colgate U.). The goals of the program are to study the X-ray emission mechanism in blazars and radio galaxies and the relation of the X-ray emission to changes in the relativistic jet. The program includes contemporaneous brightness and linear polarization monitoring at radio and optical wavelengths, total and polarized intensity imaging at at 43 GHz with a resolution of 0.1 milliarcseconds with the VLBA, and well-sampled X-ray light curves obtained from a series of approved RXTE programs. The objects studied in the time period covered by the grant were 3C 120, 3C 279, PKS 1510-089, and 3C 273, all with radio jets containing bright knots that appear to move at superluminal speeds. During RXTE Cycle 7, the project was awarded RXTE time to monitor PKS 1510-089 two times per week, 3C 273 and 3C 279 three times per week, and 3C 120 four times per week. In addition, 3C273 and 3C 279 were observed several times per day during a ten-day period in April 2002. The X-ray data, including those from earlier cycles, were compared with radio measurements obtained in the centimeter-wave band by the monitoring program of Drs. Margo and Hugh Aller at the University of Michigan Radio Astronomy Observatory, monthly imaging observations with the VLBA at 43 GHz, and optical observations obtained at several telescopes around the world.

  14. NUCLEAR RADIO JET FROM A LOW-LUMINOSITY ACTIVE GALACTIC NUCLEUS IN NGC 4258

    SciTech Connect

    Doi, Akihiro; Kohno, Kotaro; Nakanishi, Kouichiro; Kameno, Seiji; Inoue, Makoto; Hada, Kazuhiro; Sorai, Kazuo

    2013-03-01

    The nearby low-luminosity active galactic nucleus (LLAGN) NGC 4258 has a weak radio continuum component at the galactic center. We investigate its radio spectral properties on the basis of our new observations using the Nobeyama Millimeter Array at 100 GHz and archival data from the Very Large Array at 1.7-43 GHz and the James Clerk Maxwell telescope at 347 GHz. The NGC 4258 nuclear component exhibits (1) an intra-month variable and complicated spectral feature at 5-22 GHz and (2) a slightly inverted spectrum at 5-100 GHz ({alpha} {approx} 0.3; F {sub {nu}}{proportional_to}{nu}{sup {alpha}}) in time-averaged flux densities, which are also apparent in the closest LLAGN M81. These similarities between NGC 4258 and M81 in radio spectral natures in addition to previously known core shift in their AU-scale jet structures produce evidence that the same mechanism drives their nuclei. We interpret the observed spectral property as the superposition of emission spectra originating at different locations with frequency-dependent opacity along the nuclear jet. Quantitative differences between NGC 4258 and M81 in terms of jet/counter jet ratio, radio loudness, and degree of core shift can be consistently understood by fairly relativistic speeds ({Gamma} {approx}> 3) of jets and their quite different inclinations. The picture established from the two closest LLAGNs is useful for understanding the physical origin of unresolved and flat/inverted spectrum radio cores that are prevalently found in LLAGNs, including Sgr A*, with starved supermassive black holes in the present-day universe.

  15. Nuclear Radio Jet from a Low-luminosity Active Galactic Nucleus in NGC 4258

    NASA Astrophysics Data System (ADS)

    Doi, Akihiro; Kohno, Kotaro; Nakanishi, Kouichiro; Kameno, Seiji; Inoue, Makoto; Hada, Kazuhiro; Sorai, Kazuo

    2013-03-01

    The nearby low-luminosity active galactic nucleus (LLAGN) NGC 4258 has a weak radio continuum component at the galactic center. We investigate its radio spectral properties on the basis of our new observations using the Nobeyama Millimeter Array at 100 GHz and archival data from the Very Large Array at 1.7-43 GHz and the James Clerk Maxwell telescope at 347 GHz. The NGC 4258 nuclear component exhibits (1) an intra-month variable and complicated spectral feature at 5-22 GHz and (2) a slightly inverted spectrum at 5-100 GHz (α ~ 0.3; F νvpropνα) in time-averaged flux densities, which are also apparent in the closest LLAGN M81. These similarities between NGC 4258 and M81 in radio spectral natures in addition to previously known core shift in their AU-scale jet structures produce evidence that the same mechanism drives their nuclei. We interpret the observed spectral property as the superposition of emission spectra originating at different locations with frequency-dependent opacity along the nuclear jet. Quantitative differences between NGC 4258 and M81 in terms of jet/counter jet ratio, radio loudness, and degree of core shift can be consistently understood by fairly relativistic speeds (Γ >~ 3) of jets and their quite different inclinations. The picture established from the two closest LLAGNs is useful for understanding the physical origin of unresolved and flat/inverted spectrum radio cores that are prevalently found in LLAGNs, including Sgr A*, with starved supermassive black holes in the present-day universe.

  16. Three-dimensional relativistic MHD simulations of active galactic nuclei jets: magnetic kink instability and Fanaroff-Riley dichotomy

    NASA Astrophysics Data System (ADS)

    Tchekhovskoy, Alexander; Bromberg, Omer

    2016-09-01

    Energy deposition by active galactic nuclei jets into the ambient medium can affect galaxy formation and evolution, the cooling of gas flows at the centres of galaxy clusters, and the growth of the supermassive black holes. However, the processes that couple jet power to the ambient medium and determine jet morphology are poorly understood. For instance, there is no agreement on the cause of the well-known Fanaroff-Riley (FR) morphological dichotomy of jets, with FRI jets being shorter and less stable than FRII jets. We carry out global 3D magnetohydrodynamic simulations of relativistic jets propagating through the ambient medium. We show that the flat density profiles of galactic cores slow down and collimate the jets, making them susceptible to the 3D magnetic kink instability. We obtain a critical power, which depends on the galaxy core mass and radius, below which jets become kink-unstable within the core, stall, and inflate cavities filled with relativistically hot plasma. Jets above the critical power stably escape the core and form powerful backflows. Thus, the kink instability controls the jet morphology and can lead to the FR dichotomy. The model-predicted dependence of the critical power on the galaxy optical luminosity agrees well with observations.

  17. Three-dimensional Relativistic MHD Simulations of Active Galactic Nuclei Jets: Magnetic Kink Instability and Fanaroff-Riley Dichotomy

    NASA Astrophysics Data System (ADS)

    Tchekhovskoy, Alexander; Bromberg, Omer

    2016-04-01

    Energy deposition by active galactic nuclei jets into the ambient medium can affect galaxy formation and evolution, the cooling of gas flows at the centres of galaxy clusters, and the growth of the supermassive black holes. However, the processes that couple jet power to the ambient medium and determine jet morphology are poorly understood. For instance, there is no agreement on the cause of the well-known Fanaroff-Riley (FR) morphological dichotomy of jets, with FRI jets being shorter and less stable than FRII jets. We carry out global 3D magnetohydrodynamic simulations of relativistic jets propagating through the ambient medium. We show that the flat density profiles of galactic cores slow down and collimate the jets, making them susceptible to the 3D magnetic kink instability. We obtain a critical power, which depends on the galaxy core mass and radius, below which jets become kink-unstable within the core, stall, and inflate cavities filled with relativistically-hot plasma. Jets above the critical power stably escape the galaxy cores and form powerful backflows. Thus, the kink instability controls the jet morphology and can lead to the FR dichotomy. The model-predicted dependence of the critical power on the galaxy optical luminosity agrees well with observations.

  18. Precessing Gamma Jets in the extended and evaporating galactic halo as the sources of GRBs

    NASA Astrophysics Data System (ADS)

    Fargion, Daniele; Salis, Andrea

    1996-08-01

    Precessing Gamma Jets (GJ) in binary systems located in extended or evaporating galactic halos should be the sources of GRBs. The GJ are born by Inverse Compton Scattering (ICS) of thermal photons (optical, infrared,...) onto (power law) electron jets (from GeV energies and above) produced by spinning pulsars or black holes. The thermal photons are emitted by the binary companion (or by their nearby accreting disk). The collimated GJ beam is trembling with the characteristic pulsar millisecond period and it is bent by the companion magnetic field interactions, as a lighthouse, in a nearly conical shape within the characteristic Keplerian period; an additional nutation due to the asymmetric inertial momentum may lead, in general, to aperiodic behaviour of GRB signals. SGRs are GRBs seen at the periphery of the hard energy GJ beam core. The original birth locations of GJ (SNRs, planetary nebulae, globular clusters,...) are smeared out by the high escape velocity of the system; the Neutron Star (NS) high velocity is possibly due to the asymmetric jet precession, and consequent ``rowing'' acceleration, related to the eccentricity of the binary system. The GJ power is, for realistic parameters, comparable to that needed for GRBs in an extended or evaporating galactic halo. Their detailed spectra and time evolution fit the observed data. The expected GRB source number (within present BATSE sensitivity) is tens of thousands, compatible with the allowed presence of 10-20% GRB repeaters.

  19. THE MICROARCSECOND STRUCTURE OF AN ACTIVE GALACTIC NUCLEUS JET VIA INTERSTELLAR SCINTILLATION

    SciTech Connect

    Macquart, J.-P.; Godfrey, L. E. H.; Bignall, H. E.

    2013-03-10

    We describe a new tool for studying the structure and physical characteristics of ultracompact active galactic nucleus (AGN) jets and their surroundings with {mu}as precision. This tool is based on the frequency dependence of the light curves observed for intra-day variable radio sources, where the variability is caused by interstellar scintillation. We apply this method to PKS 1257-326 to resolve the core-shift as a function of frequency on scales well below {approx}12 {mu}as. We find that the frequency dependence of the position of the scintillating component is r{proportional_to}{nu}{sup -0.1{+-}0.24} (99% confidence interval) and the frequency dependence of the size of the scintillating component is d{proportional_to}{nu}{sup -0.64{+-}0.006}. Together, these results imply that the jet opening angle increases with distance along the jet: d{proportional_to}r{sup n{sub d}} with n{sub d} > 1.8. We show that the flaring of the jet, and flat frequency dependence of the core position is broadly consistent with a model in which the jet is hydrostatically confined and traversing a steep pressure gradient in the confining medium with p{proportional_to}r{sup -n{sub p}} and n{sub p} {approx}> 7. Such steep pressure gradients have previously been suggested based on very long baseline interferometry studies of the frequency dependent core shifts in AGNs.

  20. On Radiative Acceleration of Relativistic Jets

    NASA Astrophysics Data System (ADS)

    Inoue, S.; Takahara, F.

    1997-10-01

    The formation and acceleration of relativistic jets by radiative forces in black hole systems are investigated. Under a variety of circumstances, we calculate the bulk acceleration and radiative cooling of a confined plasma cell, immersed in different types of radiation fields and interacting by Compton scattering. Both non-relativistic (cold) and relativistic (hot) jet plasma, comprising mixtures of electron-proton and electron-positron components, are treated. We pay attention to some conceivable effects, previously neglected, which may possibly enhance the bulk acceleration; among them are an anisotropically radiating accretion disk surface, beamed secondary radiation from the inner jet, and scattering in the energy dependent Klein-Nishina regime. Our results are discussed in the context of relativistic jets in active galactic nuclei and Galactic black hole candidates, and the conditions necessary for successfully reproducing their observed properties are highlighted. In particular, the velocities of the recently discovered superluminal jets in Galactic black hole candidates (Lorentz factors of Γ ~ 2.5) are readily and very robustly accounted for if the jet is composed primarily of electron-positron pairs and the disk luminosity is near the Eddington value; the jet kinetic power can be consistent with optical depth and pair annihilation constraints. On the other hand, severe difficulty is met in attaining the velocities of AGN jets (Γ ~ 10), which can only be realized when a significant amount of beamed secondary radiation is present. We also contemplate additional important issues, such as global energetics.

  1. A PHYSICAL LINK BETWEEN JET FORMATION AND HOT PLASMA IN ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Wu Qingwen; Wang Dingxiong; Cao Xinwu; Ho, Luis C. E-mail: dxwang@hust.edu.cn E-mail: lho@obs.carnegiescience.edu

    2013-06-10

    Recent observations suggest that in black hole X-ray binaries jet/outflow formation is related to the hot plasma in the vicinity of the black hole, either in the form of an advection-dominated accretion flow at low accretion rates or in a disk corona at high accretion rates. We test the viability of this scenario for supermassive black holes using two samples of active galactic nuclei distinguished by the presence (radio-strong) and absence (radio-weak) of well-collimated, relativistic jets. Each is centered on a narrow range of black hole mass but spans a very broad range of Eddington ratios, effectively simulating in a statistical manner the behavior of a single black hole evolving across a wide spread in accretion states. Unlike the relationship between the radio and optical luminosity, which shows an abrupt break between high- and low-luminosity sources at an Eddington ratio of {approx}1%, the radio emission-a measure of the jet power-varies continuously with the hard X-ray (2-10 keV) luminosity, roughly as L{sub R} {proportional_to} L{sub X}{sup 0.6-0.75}. This relation, which holds for both radio-weak and radio-strong active galaxies, is similar to the one seen in X-ray binaries. Jet/outflow formation appears to be closely linked to the conditions that give rise to the hot, optically thin coronal emission associated with accretion flows, both in the regime of low and high accretion rates.

  2. Proton-synchrotron radiation of large-scale jets in active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Aharonian, F. A.

    2002-05-01

    The X-radiation of large-scale extragalactic jets poses a serious challenge for the conventional electron-synchrotron or inverse Compton models suggested to explain the overall non-thermal emission of the resolved knots and hotspots. In this paper I propose an alternative mechanism for X-ray emission - synchrotron radiation by extremely high-energy protons - and discuss implications of this model for the extended jet features resolved by Chandra in several prominent radio galaxies and active galactic nuclei (AGN) - Pictor A, 3C 120, PKS 0637-752 and 3C 273. I show that if protons are indeed accelerated to energies E p >=1018 eV, it is possible to construct a realistic model that allows an effective cooling of protons via synchrotron radiation on quite `comfortable' time-scales of about 107 -108 yr, i.e. on time-scales that provide effective propagation of protons over the jet structures on kpc scales. This explains quite naturally the diffuse character of the observed X-ray emission, as well as the broad range of spectral X-ray indices observed from different objects. Yet, as long as the proton synchrotron cooling time is comparable with both the particle escape time and the age of the jet, the proton-synchrotron model offers an adequate radiation efficiency. The model requires relatively large magnetic field of about 1mG, and proton acceleration rates ranging from L p ~1043 to 1046 ergs-1 . These numbers could be reduced significantly if the jet structures are moving relativistically towards the observer. I discuss also possible contributions of synchrotron radiation by secondary electrons produced at interactions of relatively low energy (E p <=1013 eV) protons with the compressed gas in the jet structures. This is an interesting possibility which however requires a very large product of the ambient gas density and total amount of accelerated protons. Therefore it could be treated as a viable working hypothesis only if one can reduce the intrinsic X

  3. Superluminal motion (review)

    NASA Astrophysics Data System (ADS)

    Malykin, G. B.; Romanets, E. A.

    2012-06-01

    Prior to the development of Special Relativity, no restrictions were imposed on the velocity of the motion of particles and material bodies, as well as on energy transfer and signal propagation. At the end of the 19th century and the beginning of the 20th century, it was shown that a charge that moves at a velocity faster than the speed of light in an optical medium, in particular, in vacuum, gives rise to impact radiation, which later was termed the Vavilov-Cherenkov radiation. Shortly after the development of Special Relativity, some researchers considered the possibility of superluminal motion. In 1923, the Soviet physicist L.Ya. Strum suggested the existence of tachyons, which, however, have not been discovered yet. Superluminal motions can occur only for images, e.g., for so-called "light spots," which were considered in 1972 by V.L. Ginzburg and B.M. Bolotovskii. These spots can move with a superluminal phase velocity but are incapable of transferring energy and information. Nevertheless, these light spots may induce quite real generation of microwave radiation in closed waveguides and create the Vavilov-Cherenkov radiation in vacuum. In this work, we consider various paradoxes, illusions, and artifacts associated with superluminal motion.

  4. MOJAVE: Monitoring of Jets in Active Galactic Nuclei with VLBA Experiments. VI. Kinematics Analysis of a Complete Sample of Blazar Jets

    NASA Astrophysics Data System (ADS)

    Lister, M. L.; Cohen, M. H.; Homan, D. C.; Kadler, M.; Kellermann, K. I.; Kovalev, Y. Y.; Ros, E.; Savolainen, T.; Zensus, J. A.

    2009-12-01

    We discuss the jet kinematics of a complete flux-density-limited sample of 135 radio-loud active galactic nuclei (AGNs) resulting from a 13 year program to investigate the structure and evolution of parsec-scale jet phenomena. Our analysis is based on new 2 cm Very Long Baseline Array (VLBA) images obtained between 2002 and 2007, but includes our previously published observations made at the same wavelength, and is supplemented by VLBA archive data. In all, we have used 2424 images spanning the years 1994-2007 to study and determine the motions of 526 separate jet features in 127 jets. The data quality and temporal coverage (a median of 15 epochs per source) of this complete AGN jet sample represent a significant advance over previous kinematics surveys. In all but five AGNs, the jets appear one-sided, most likely the result of differential Doppler boosting. In general, the observed motions are directed along the jet ridge line, outward from the optically thick core feature. We directly observe changes in speed and/or direction in one third of the well-sampled jet components in our survey. While there is some spread in the apparent speeds of separate features within an individual jet, the dispersion is about three times smaller than the overall dispersion of speeds among all jets. This supports the idea that there is a characteristic flow that describes each jet, which we have characterized by the fastest observed component speed. The observed maximum speed distribution is peaked at ~10c, with a tail that extends out to ~50c. This requires a distribution of intrinsic Lorentz factors in the parent population that range up to ~50. We also note the presence of some rare low-pattern speeds or even stationary features in otherwise rapidly flowing jets that may be the result of standing re-collimation shocks, and/or a complex geometry and highly favorable Doppler factor.

  5. THE INVARIANT TWIST OF MAGNETIC FIELDS IN THE RELATIVISTIC JETS OF ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Contopoulos, Ioannis; Christodoulou, Dimitris M.; Kazanas, Demosthenes E-mail: dimitris_christodoulou@uml.edu E-mail: gabuzda@physics.ucc.ie

    2009-09-10

    The origin of cosmic magnetic (B) fields remains an open question. It is generally believed that very weak primordial B fields are amplified by dynamo processes, but it appears unlikely that the amplification proceeds fast enough to account for the fields presently observed in galaxies and galaxy clusters. In an alternative scenario, cosmic B fields are generated near the inner edges of accretion disks in active galactic nuclei (AGNs) by azimuthal electric currents due to the difference between the plasma electron and ion velocities that arises when the electrons are retarded by interactions with photons. While dynamo processes show no preference for the polarity of the (presumably random) seed field that they amplify, this alternative mechanism uniquely relates the polarity of the poloidal B field to the angular velocity of the accretion disk, resulting in a unique direction for the toroidal B field induced by disk rotation. Observations of the toroidal fields of 29 AGN jets revealed by parsec-scale Faraday rotation measurements show a clear asymmetry that is consistent with this model, with the probability that this asymmetry came about by chance being less than 1%. This lends support to the hypothesis that the universe is seeded by B fields that are generated in AGNs via this mechanism and subsequently injected into intergalactic space by the jet outflows.

  6. Photon-axion mixing within the jets of active galactic nuclei and prospects for detection

    SciTech Connect

    Harris, J.; Chadwick, P.M. E-mail: p.m.chadwick@durham.ac.uk

    2014-10-01

    Very high energy γ-ray observations of distant active galactic nuclei (AGN) generally result in higher fluxes and harder spectra than expected, resulting in some tension with the level of the extragalactic background light (EBL). If hypothetical axions or axion-like particles (ALPs) were to exist, this tension could be relieved since the oscillation of photons to ALPs would mitigate the effects of EBL absorption and lead to softer inferred intrinsic AGN spectra. In this paper we consider the effect of photon-ALP mixing on observed spectra, including the photon-ALP mixing that would occur within AGN jets. We then simulate observations of three AGN with the Cherenkov Telescope Array (CTA), a next generation γ-ray telescope, to determine its prospects for detecting the signatures of photon-ALP mixing on the spectra. We conclude that prospects for CTA detecting these signatures or else setting limits on the ALP parameter space are quite promising. We find that prospects are improved if photon-ALP mixing within the jet is properly considered and that the best target for observations is PKS 2155-304.

  7. Large-scale jets from active galactic nuclei as a source of intracluster medium heating: cavities and shocks

    NASA Astrophysics Data System (ADS)

    Perucho, Manel; Martí, José-María; Quilis, Vicent; Ricciardelli, Elena

    2014-12-01

    The evolution of powerful extragalactic jets is not only interesting by itself, but also for its impact on the evolution of the host galaxy and its surroundings. We have performed long-term axisymmetric numerical simulations of relativistic jets with different powers to study their evolution through an environment with a pressure and density gradient. Our results show key differences in the evolution of jets with different powers in terms of the spatial and temporal scales of energy deposition. According to our results, the observed morphology in X-ray cavities requires that an important fraction of the jet's energetic budget is in the form of internal energy. Thus, light, lepton-dominated jets are favoured. In all cases, heating is mainly produced by shocks. Cavity overpressure is sustained by an important population of thermal particles. Our simulations reproduce the cool-core structure in projected, luminosity-weighted temperature. We have performed an additional simulation of a slow, massive jet and discuss the differences with its relativistic counterparts. Important qualitative and quantitative differences are found between the non-relativistic and the relativistic jets. Our conclusions point towards a dual mode of active galactic nuclei kinetic feedback, depending on the jet power.

  8. THE FERMI BUBBLES: SUPERSONIC ACTIVE GALACTIC NUCLEUS JETS WITH ANISOTROPIC COSMIC-RAY DIFFUSION

    SciTech Connect

    Yang, H.-Y. K.; Ruszkowski, M.; Ricker, P. M.; Zweibel, E.; Lee, D.

    2012-12-20

    The Fermi Gamma-Ray Space Telescope reveals two large bubbles in the Galaxy, which extend nearly symmetrically {approx}50 Degree-Sign above and below the Galactic center. Using three-dimensional (3D) magnetohydrodynamic simulations that self-consistently include the dynamical interaction between cosmic rays (CRs) and thermal gas and anisotropic CR diffusion along the magnetic field lines, we show that the key characteristics of the observed gamma-ray bubbles and the spatially correlated X-ray features in the ROSAT 1.5 keV map can be successfully reproduced by recent jet activity from the central active galactic nucleus. We find that after taking into account the projection of the 3D bubbles onto the sky the physical heights of the bubbles can be much smaller than previously thought, greatly reducing the formation time of the bubbles to about a Myr. This relatively small bubble age is needed to reconcile the simulations with the upper limit of bubble ages estimated from the cooling time of high-energy electrons. No additional physical mechanisms are required to suppress large-scale hydrodynamic instabilities because the evolution time is too short for them to develop. The simulated CR bubbles are edge-brightened, which is consistent with the observed projected flat surface brightness distribution. Furthermore, we demonstrate that the sharp edges of the observed bubbles can be due to anisotropic CR diffusion along magnetic field lines that drape around the bubbles during their supersonic expansion, with suppressed perpendicular diffusion across the bubble surface. Possible causes of the slight bends of the Fermi bubbles to the west are also discussed.

  9. Evidence for a Parsec-scale Jet from the Galactic Center Black Hole: Interaction with Local Gas

    NASA Astrophysics Data System (ADS)

    Li, Zhiyuan; Morris, Mark R.; Baganoff, Frederick K.

    2013-12-01

    Despite strong physical reasons that they should exist and decades of searching, jets from the Galactic center black hole, Sgr A*, have not yet been convincingly detected. Based on high-resolution Very Large Array images and ultra-deep imaging-spectroscopic data produced by the Chandra X-ray Observatory, we report new evidence for the existence of a parsec-scale jet from Sgr A*, by associating a linear feature G359.944-0.052, previously identified in X-ray images of the Galactic center, with a radio shock front on the Eastern Arm of the Sgr A West H II region. We show that the shock front can be explained in terms of the impact of a jet having a sharp momentum peak along the Galaxy's rotation axis, whereas G359.944-0.052, a quasi-steady feature with a power-law spectrum, can be understood as synchrotron radiation from shock-induced ultra-relativistic electrons cooling in a finite post-shock region downstream along the jet path. Several interesting implications of the jet properties are discussed.

  10. The host galaxies of active galactic nuclei with powerful relativistic jets

    NASA Astrophysics Data System (ADS)

    Olguín-Iglesias, A.; León-Tavares, J.; Kotilainen, J. K.; Chavushyan, V.; Tornikoski, M.; Valtaoja, E.; Añorve, C.; Valdés, J.; Carrasco, L.

    2016-08-01

    We present deep near-infrared (NIR) images of a sample of 19 intermediate-redshift (0.3 < z < 1.0) radio-loud active galactic nuclei (AGN) with powerful relativistic jets (L1.4 GHz > 1027 W Hz-1), previously classified as flat-spectrum radio quasars. We also compile host galaxy and nuclear magnitudes for blazars from literature. The combined sample (this work and compilation) contains 100 radio-loud AGN with host galaxy detections and a broad range of radio luminosities L1.4 GHz ˜ 1023.7-1028.3 W Hz-1, allowing us to divide our sample into high-luminosity blazars (HLBs) and low-luminosity blazars (LLBs). The host galaxies of our sample are bright and seem to follow the μe-Reff relation for ellipticals and bulges. The two populations of blazars show different behaviours in the MK,nuclear -MK,bulge plane, where a statistically significant correlation is observed for HLBs. Although it may be affected by selection effects, this correlation suggests a close coupling between the accretion mode of the central supermassive black hole and its host galaxy, which could be interpreted in terms of AGN feedback. Our findings are consistent with semi-analytical models where low-luminosity AGN emit the bulk of their energy in the form of radio jets, producing a strong feedback mechanism, and high-luminosity AGN are affected by galaxy mergers and interactions, which provide a common supply of cold gas to feed both nuclear activity and star formation episodes.

  11. Signs of active galactic nucleus quenching in a merger remnant with radio jets

    NASA Astrophysics Data System (ADS)

    Ichikawa, Kohei; Ueda, Junko; Shidatsu, Megumi; Kawamuro, Taiki; Matsuoka, Kenta

    2016-02-01

    We investigate optical, infrared, and radio active galactic nucleus (AGN) signs in the merger remnant Arp 187, which hosts luminous jets launched in the order of 105 yr ago but whose present-day AGN activity is still unknown. We find AGN signs from the optical Baldwin-Phillips-Telervich diagram and infrared [O IV] 25.89 μm line, originating from the narrow line regions of AGN. On the other hand, Spitzer/IRS show host galaxy dominated spectra, suggesting that the thermal emission from the AGN torus is considerably small or already diminished. Combining the black hole mass, the upper limit of radio luminosity of the core, and the fundamental plane of the black hole enables us to estimate X-ray luminosity, which gives <1040 erg s-1. Those results suggest that the AGN activity of Arp 187 has already been quenched, but the narrow line region is still alive owing to the time delay of emission from the past AGN activity.

  12. The Invariant Twist of Magnetic Fields in the Relativistic Jets of Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Contopoulos, Ioannis; Christodoulou, Dimitris M.; Kazanas, Demosthenes; Gabuzda, Denise C.

    2009-01-01

    The origin of cosmic magnetic (B) fields remains an open question. It is generally believed that very weak primordial B fields are amplified by dynamo processes, but it appears unlikely that the amplification proceeds fast enough to account for the fields presently observed in galaxies and galaxy clusters. In an alternative scenario, cosmic B fields are generated near the inner edges of accretion disks in Active Galactic Nuclei (AGNs) by azimuthal electric currents due to the difference between the plasma electron and ion velocities that arises when the electrons are retarded by interactions with photons. While dynamo processes show no preference for the polarity of the (presumably random) seed field that they amplify, this alternative mechanism uniquely relates the polarity of the poloidal B field to the angular velocity of the accretion disk, resulting in a unique direction for the toroidal B field induced by disk rotation. Observations of the toroidal fields of 29 AGN jets revealed by parsec-scale Faraday rotation measurements show a clear asymmetry that is consistent with this model, with the probability that this asymmetry came about by chance being less than 1 %. This lends support to the hypothesis that the Universe is seeded by B fields that are generated in AGN via this mechanism

  13. Milliarcsecond polarization structure of the superluminal quasar 3C 273

    NASA Astrophysics Data System (ADS)

    Roberts, David H.; Kollgaard, Ronald I.; Brown, Leslie F.; Gabuzda, Denise C.; Wardle, John F. C.

    1990-09-01

    A 2 x 10 marcsec-resolution determination is presented for the total intensity and linear polarization structures of the superluminal quasar 3C 273 at 5 GHz. Substantial polarized flux was detected from several superluminal components of the jet, whose fractional polarization increased symmetrically with distance from the core; the most distant component is highly polarized and exhibits a highly ordered magnetic field. Within a few marcsec of the core, the inferred magnetic field orientation varies rapidly with position along the jet. The primarily longitudinal magnetic field orientation is concluded to become established within 20 marcsec of the core. A highly disorganized magnetic field is the most plausible explanation for the low degree of polarization in the innermost regions of the jet.

  14. A jet model for Galactic black-hole X-ray sources: The correlation between cutoff energy and phase lag

    NASA Astrophysics Data System (ADS)

    Reig, P.; Kylafis, N. D.

    2015-12-01

    Context. Galactic black-hole X-ray binaries emit a compact, optically thick, mildy relativistic radio jet when they are in the hard and hard-intermediate states, that is, typically at the beginning and the end of an X-ray outburst. In a series of papers, we have developed a jet model and have shown through Monte Carlo simulations that our model can explain many observational results. Aims: In this work, we investigate one more constraining relationship between the cutoff energy and the phase lag during the early stages of an X-ray outburst of the black-hole X-ray binary GX 339-4: the cutoff energy decreases while the phase lag increases during the brightening of the hard state. Methods: We performed Monte Carlo simulations of the Compton upscattering of soft accretion-disk photons in the jet and computed the phase lag between soft and hard photons and the cutoff energy of the resulting high-energy power law. Results: We demonstrate that our jet model naturally explains the above correlation, with a minor modification consisting of introducing an acceleration zone at the base of the jet. Conclusions: The observed correlation between the cutoff energy and the phase lag in the black-hole binary GX 339-4 suggests that the lags are produced by the hard component. Here we show that this correlation arises naturally if Comptonization in the jet produces these two quantities.

  15. FROM THE BLAZAR SEQUENCE TO THE BLAZAR ENVELOPE: REVISITING THE RELATIVISTIC JET DICHOTOMY IN RADIO-LOUD ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Meyer, Eileen T.; Fossati, Giovanni; Georganopoulos, Markos; Lister, Matthew L.

    2011-10-20

    We revisit the concept of a blazar sequence that relates the synchrotron peak frequency ({nu}{sub peak}) in blazars with synchrotron peak luminosity (L{sub peak}, in {nu}L{sub {nu}}) using a large sample of radio-loud active galactic nuclei. We present observational evidence that the blazar sequence is formed from two populations in the synchrotron {nu}{sub peak}-L{sub peak} plane, each forming an upper edge to an envelope of progressively misaligned blazars, and connecting to an adjacent group of radio galaxies having jets viewed at much larger angles to the line of sight. When binned by jet kinetic power (L{sub kin}; as measured through a scaling relationship with extended radio power), we find that radio core dominance decreases with decreasing synchrotron L{sub peak}, revealing that sources in the envelope are generally more misaligned. We find population-based evidence of velocity gradients in jets at low kinetic powers ({approx}10{sup 42}-10{sup 44.5} erg s{sup -1}), corresponding to Fanaroff-Riley (FR) I radio galaxies and most BL Lac objects. These low jet power 'weak-jet' sources, thought to exhibit radiatively inefficient accretion, are distinguished from the population of non-decelerating, low synchrotron-peaking (LSP) blazars and FR II radio galaxies ('strong' jets) which are thought to exhibit radiatively efficient accretion. The two-population interpretation explains the apparent contradiction of the existence of highly core-dominated, low-power blazars at both low and high synchrotron peak frequencies, and further implies that most intermediate synchrotron peak sources are not intermediate in intrinsic jet power between LSP and high synchrotron-peaking (HSP) sources, but are more misaligned versions of HSP sources with similar jet powers.

  16. The inner jet of an active galactic nucleus as revealed by a radio-to-gamma-ray outburst.

    PubMed

    Marscher, Alan P; Jorstad, Svetlana G; D'Arcangelo, Francesca D; Smith, Paul S; Williams, G Grant; Larionov, Valeri M; Oh, Haruki; Olmstead, Alice R; Aller, Margo F; Aller, Hugh D; McHardy, Ian M; Lähteenmäki, Anne; Tornikoski, Merja; Valtaoja, Esko; Hagen-Thorn, Vladimir A; Kopatskaya, Eugenia N; Gear, Walter K; Tosti, Gino; Kurtanidze, Omar; Nikolashvili, Maria; Sigua, Lorand; Miller, H Richard; Ryle, Wesley T

    2008-04-24

    Blazars are the most extreme active galactic nuclei. They possess oppositely directed plasma jets emanating at near light speeds from accreting supermassive black holes. According to theoretical models, such jets are propelled by magnetic fields twisted by differential rotation of the black hole's accretion disk or inertial-frame-dragging ergosphere. The flow velocity increases outward along the jet in an acceleration and collimation zone containing a coiled magnetic field. Detailed observations of outbursts of electromagnetic radiation, for which blazars are famous, can potentially probe the zone. It has hitherto not been possible to either specify the location of the outbursts or verify the general picture of jet formation. Here we report sequences of high-resolution radio images and optical polarization measurements of the blazar BL Lacertae. The data reveal a bright feature in the jet that causes a double flare of radiation from optical frequencies to TeV gamma-ray energies, as well as a delayed outburst at radio wavelengths. We conclude that the event starts in a region with a helical magnetic field that we identify with the acceleration and collimation zone predicted by the theories. The feature brightens again when it crosses a standing shock wave corresponding to the bright 'core' seen on the images. PMID:18432239

  17. Complete multiwavelength evolution of Galactic black hole transients during outburst decay. I. Conditions for 'compact' jet formation

    SciTech Connect

    Kalemci, E.; Dinçer, T.; Chun, Y. Y.; Tomsick, J. A.; Buxton, M. M.; Bailyn, C. D.

    2013-12-20

    Compact, steady jets are observed in the near infrared and radio bands in the hard state of Galactic black hole transients as their luminosity decreases and the source moves toward a quiescent state. Recent radio observations indicate that the jets turn off completely in the soft state; therefore, multiwavelength monitoring of black hole transients is essential to probe the formation of jets. In this work, we conducted a systematic study of all black hole transients with near infrared and radio coverage during their outburst decays. We characterized the timescales of changes in X-ray spectral and temporal properties and also in near infrared and/or in radio emission. We confirmed that state transitions occur in black hole transients at a very similar fraction of their respective Eddington luminosities. We also found that the near infrared flux increase that could be due to the formation of a compact jet is delayed by a time period of days with respect to the formation of a corona. Finally, we found a threshold disk Eddington luminosity fraction for the compact jets to form. We explain these results with a model such that the increase in the near infrared flux corresponds to a transition from a patchy, small-scale height corona along with an optically thin outflow to a large-scale height corona that allows for collimation of a steady compact jet. We discuss the timescale of jet formation in terms of transport of magnetic fields from the outer parts of the disk, and we also consider two alternative explanations for the multiwavelength emission: hot inner accretion flows and irradiation.

  18. Superluminous X-Rays from a Superluminous Supernova

    NASA Astrophysics Data System (ADS)

    Levan, A. J.; Read, A. M.; Metzger, B. D.; Wheatley, P. J.; Tanvir, N. R.

    2013-07-01

    The discovery of a population of superluminous supernovae (SLSNe), with peak luminosities a factor of ~100 brighter than normal supernovae (SNe; typically SLSNe have MV < -21), has shown an unexpected diversity in core-collapse SN properties. Numerous models have been postulated for the nature of these events, including a strong interaction of the shockwave with a dense circumstellar environment, a re-energizing of the outflow via a central engine, or an origin in the catastrophic destruction of the star following a loss of pressure due to pair production in an extremely massive stellar core (so-called pair instability SNe). Here we consider constraints that can be placed on the explosion mechanism of hydrogen-poor SLSNe (SLSNe-I) via X-ray observations, with XMM-Newton, Chandra, and Swift, and show that at least one SLSN-I is likely the brightest X-ray SN ever observed, with LX ~ 1045 erg s-1, ~150 days after its initial discovery. This is a luminosity three orders of magnitude higher than seen in other X-ray SNe powered via circumstellar interactions. Such high X-ray luminosities are sufficient to ionize the ejecta and markedly reduce the optical depth, making it possible to see deep into the ejecta and any source of emission that resides there. Alternatively, an engine could have powered a moderately relativistic jet external to the ejecta, similar to those seen in gamma-ray bursts. If the detection of X-rays does require an engine it implies that these SNe do create compact objects, and that the stars are not completely destroyed in a pair instability event. Future observations will determine which, if any, of these mechanisms are at play in SLSNe.

  19. Cosmology with superluminous supernovae

    NASA Astrophysics Data System (ADS)

    Scovacricchi, D.; Nichol, R. C.; Bacon, D.; Sullivan, M.; Prajs, S.

    2016-02-01

    We predict cosmological constraints for forthcoming surveys using superluminous supernovae (SLSNe) as standardizable candles. Due to their high peak luminosity, these events can be observed to high redshift (z ˜ 3), opening up new possibilities to probe the Universe in the deceleration epoch. We describe our methodology for creating mock Hubble diagrams for the Dark Energy Survey (DES), the `Search Using DECam for Superluminous Supernovae' (SUDSS) and a sample of SLSNe possible from the Large Synoptic Survey Telescope (LSST), exploring a range of standardization values for SLSNe. We include uncertainties due to gravitational lensing and marginalize over possible uncertainties in the magnitude scale of the observations (e.g. uncertain absolute peak magnitude, calibration errors). We find that the addition of only ≃100 SLSNe from SUDSS to 3800 Type Ia Supernovae (SNe Ia) from DES can improve the constraints on w and Ωm by at least 20 per cent (assuming a flat wCDM universe). Moreover, the combination of DES SNe Ia and 10 000 LSST-like SLSNe can measure Ωm and w to 2 and 4 per cent, respectively. The real power of SLSNe becomes evident when we consider possible temporal variations in w(a), giving possible uncertainties of only 2, 5 and 14 per cent on Ωm, w0 and wa, respectively, from the combination of DES SNe Ia, LSST-like SLSNe and Planck. These errors are competitive with predicted Euclid constraints, indicating a future role for SLSNe for probing the high-redshift Universe.

  20. MOJAVE: MONITORING OF JETS IN ACTIVE GALACTIC NUCLEI WITH VLBA EXPERIMENTS. V. MULTI-EPOCH VLBA IMAGES

    SciTech Connect

    Lister, M. L.; Aller, H. D.; Aller, M. F. E-mail: haller@umich.edu

    2009-03-15

    We present images from a long-term program (MOJAVE: Monitoring of Jets in active galactic nuclei (AGNs) with VLBA Experiments) to survey the structure and evolution of parsec-scale jet phenomena associated with bright radio-loud active galaxies in the northern sky. The observations consist of 2424 15 GHz Very Long Baseline Array (VLBA) images of a complete flux-density-limited sample of 135 AGNs above declination -20{sup 0}, spanning the period 1994 August to 2007 September. These data were acquired as part of the MOJAVE and 2 cm Survey programs, and from the VLBA archive. The sample-selection criteria are based on multi-epoch parsec-scale (VLBA) flux density, and heavily favor highly variable and compact blazars. The sample includes nearly all the most prominent blazars in the northern sky, and is well suited for statistical analysis and comparison with studies at other wavelengths. Our multi-epoch and stacked-epoch images show 94% of the sample to have apparent one-sided jet morphologies, most likely due to the effects of relativistic beaming. Of the remaining sources, five have two-sided parsec-scale jets, and three are effectively unresolved by the VLBA at 15 GHz, with essentially all of the flux density contained within a few tenths of a milliarcsecond.

  1. DRIVING OUTFLOWS WITH RELATIVISTIC JETS AND THE DEPENDENCE OF ACTIVE GALACTIC NUCLEUS FEEDBACK EFFICIENCY ON INTERSTELLAR MEDIUM INHOMOGENEITY

    SciTech Connect

    Wagner, A. Y.; Umemura, M.; Bicknell, G. V.

    2012-10-01

    We examine the detailed physics of the feedback mechanism by relativistic active galactic nucleus (AGN) jets interacting with a two-phase fractal interstellar medium (ISM) in the kpc-scale core of galaxies using 29 three-dimensional grid-based hydrodynamical simulations. The feedback efficiency, as measured by the amount of cloud dispersal generated by the jet-ISM interactions, is sensitive to the maximum size of clouds in the fractal cloud distribution but not to their volume filling factor. Feedback ceases to be efficient for Eddington ratios P{sub jet}/L{sub edd} {approx}< 10{sup -4}, although systems with large cloud complexes {approx}> 50 pc require jets of Eddington ratio in excess of 10{sup -2} to disperse the clouds appreciably. Based on measurements of the bubble expansion rates in our simulations, we argue that sub-grid AGN prescriptions resulting in negative feedback in cosmological simulations without a multi-phase treatment of the ISM are good approximations if the volume filling factor of warm-phase material is less than 0.1 and the cloud complexes are smaller than {approx}25 pc. We find that the acceleration of the dense embedded clouds is provided by the ram pressure of the high-velocity flow through the porous channels of the warm phase, flow that has fully entrained the shocked hot-phase gas it has swept up, and is additionally mass loaded by ablated cloud material. This mechanism transfers 10% to 40% of the jet energy to the cold and warm gas, accelerating it within a few 10 to 100 Myr to velocities that match those observed in a range of high- and low-redshift radio galaxies hosting powerful radio jets.

  2. MOJAVE: MONITORING OF JETS IN ACTIVE GALACTIC NUCLEI WITH VLBA EXPERIMENTS. VIII. FARADAY ROTATION IN PARSEC-SCALE AGN JETS

    SciTech Connect

    Hovatta, Talvikki; Lister, Matthew L.; Aller, Margo F.; Aller, Hugh D.; Homan, Daniel C.; Kovalev, Yuri Y.

    2012-10-01

    We report observations of Faraday rotation measures for a sample of 191 extragalactic radio jets observed within the MOJAVE program. Multifrequency Very Long Baseline Array observations were carried out over 12 epochs in 2006 at four frequencies between 8 and 15 GHz. We detect parsec-scale Faraday rotation measures in 149 sources and find the quasars to have larger rotation measures on average than BL Lac objects. The median core rotation measures are significantly higher than in the jet components. This is especially true for quasars where we detect a significant negative correlation between the magnitude of the rotation measure and the de-projected distance from the core. We perform detailed simulations of the observational errors of total intensity, polarization, and Faraday rotation, and concentrate on the errors of transverse Faraday rotation measure gradients in unresolved jets. Our simulations show that the finite image restoring beam size has a significant effect on the observed rotation measure gradients, and spurious gradients can occur due to noise in the data if the jet is less than two beams wide in polarization. We detect significant transverse rotation measure gradients in four sources (0923+392, 1226+023, 2230+114, and 2251+158). In 1226+023 the rotation measure is for the first time seen to change sign from positive to negative over the transverse cuts, which supports the presence of a helical magnetic field in the jet. In this source we also detect variations in the jet rotation measure over a timescale of three months, which are difficult to explain with external Faraday screens and suggest internal Faraday rotation. By comparing fractional polarization changes in jet components between the four frequency bands to depolarization models, we find that an external purely random Faraday screen viewed through only a few lines of sight can explain most of our polarization observations, but in some sources, such as 1226+023 and 2251+158, internal

  3. Coupling hydrodynamics and radiation calculations for star-jet interactions in active galactic nuclei

    NASA Astrophysics Data System (ADS)

    de la Cita, V. M.; Bosch-Ramon, V.; Paredes-Fortuny, X.; Khangulyan, D.; Perucho, M.

    2016-06-01

    Context. Stars and their winds can contribute to the non-thermal emission in extragalactic jets. Because of the complexity of jet-star interactions, the properties of the resulting emission are closely linked to those of the emitting flows. Aims: We simulate the interaction between a stellar wind and a relativistic extragalactic jet and use the hydrodynamic results to compute the non-thermal emission under different conditions. Methods: We performed relativistic axisymmetric hydrodynamical simulations of a relativistic jet interacting with a supersonic, non-relativistic stellar wind. We computed the corresponding streamlines out of the simulation results and calculated the injection, evolution, and emission of non-thermal particles accelerated in the jet shock, focusing on electrons or e±-pairs. Several cases were explored, considering different jet-star interaction locations, magnetic fields, and observer lines of sight. The jet luminosity and star properties were fixed, but the results are easily scalable when these parameters are changed. Results: Individual jet-star interactions produce synchrotron and inverse Compton emission that peaks from X-rays to MeV energies (depending on the magnetic field), and at ~100-1000 GeV (depending on the stellar type), respectively. The radiation spectrum is hard in the scenarios explored here as a result of non-radiative cooling dominance, as low-energy electrons are efficiently advected even under relatively high magnetic fields. Interactions of jets with cold stars lead to an even harder inverse Compton spectrum because of the Klein-Nishina effect in the cross section. Doppler boosting has a strong effect on the observer luminosity. Conclusions: The emission levels for individual interactions found here are in the line of previous, more approximate, estimates, strengthening the hypothesis that collective jet-star interactions could significantly contribute at high energies under efficient particle acceleration.

  4. NEW CLASS OF VERY HIGH ENERGY {gamma}-RAY EMITTERS: RADIO-DARK MINI SHELLS SURROUNDING ACTIVE GALACTIC NUCLEUS JETS

    SciTech Connect

    Kino, Motoki; Kawakatu, Nozomu; Orienti, Monica

    2013-02-20

    We explore non-thermal emission from a shocked interstellar medium, which is identified as an expanding shell, driven by a relativistic jet in active galactic nuclei (AGNs). In this work, we particularly focus on parsec-scale size mini shells surrounding mini radio lobes. From the radio to X-ray band, the mini radio lobe emission dominates the faint emission from the mini shell. On the other hand, we find that inverse-Compton (IC) emission from the shell can overwhelm the associated lobe emission at the very high energy (VHE; E > 100 GeV) {gamma}-ray range, because energy densities of synchrotron photons from the lobe and/or soft photons from the AGN nucleus are large and IC scattering works effectively. The predicted IC emission from nearby mini shells can be detected with the Cherenkov Telescope Array and they are potentially a new class of VHE {gamma}-ray emitters.

  5. Radiation Mechanism and Jet Composition of Gamma-Ray Bursts and GeV-TeV-selected Radio-loud Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Zhang, Jin; Liang, En-Wei; Sun, Xiao-Na; Zhang, Bing; Lu, Ye; Zhang, Shuang-Nan

    2013-09-01

    Gamma-ray bursts (GRBs) and GeV-TeV-selected radio-loud active galactic nuclei (AGNs) are compared based on our systematic modeling of the observed spectral energy distributions of a sample of AGNs with a single-zone leptonic model. We show that the correlation between the jet power (P jet) and the prompt gamma-ray luminosity (L jet) of GRBs is consistent, within the uncertainties, with the correlation between jet power and the synchrotron peak luminosity (L s, jet) of flat spectrum radio quasars (FSRQs). Their radiation efficiencies (ε) are also comparable (>10% for most sources), which increase with the bolometric jet luminosity (L bol, jet) for FSRQs and with the L jet for GRBs with similar power-law indices. BL Lac objects (BL Lacs) do not follow the P jet-L s, jet relation of FSRQs. They have lower ε and L bol, jet values than FSRQs, and a tentative L bol, jet-ε relation is also found, with a power-law index different from that of the FSRQs. The magnetization parameters (σ) of FSRQs are on average larger than that of BL Lacs. They are anti-correlated with ε for the FSRQs, but positively correlated with ε for the BL Lacs. GeV narrow-line Seyfert 1 galaxies potentially share similar properties with FSRQs. Based on the analogy between GRBs and FSRQs, we suggest that the prompt gamma-ray emission of GRBs is likely produced by the synchrotron process in a magnetized jet with high radiation efficiency, similar to FSRQs. The jets of BL Lacs, on the other hand, are less efficient and are likely more matter-dominated.

  6. X ray emission from relativistic jets in AGNs and statistical implications

    NASA Astrophysics Data System (ADS)

    Melia, Fulvio; Koenigl, Arieh

    1989-11-01

    Calculations of the Compton scattering interaction between an ultrarelativistic jet and a thermal radiation field, in an Active Galactic Nuclei (AGN), are presented. This process can be effective in decelerating ultrarelativistic jets that are accelerated by electromagnetic or hydromagnetic forces closer in to the central black hole. A narrow distribution of terminal Lorentz factors gammainfinity, consistent with the values inferred in superluminal radio sources, arises naturally in this model. The hard X-ray component detected in the spectra of 3C273 and several BL Lac objects may be due to the inverse Compton radiation produced in the course of the initial deceleration of their relativistic jets. The requirement that the luminosity of the hard X-ray component must exceed the total power in the associated jet is considered.

  7. THE ROLE OF THE ACCRETION DISK, DUST, AND JETS IN THE IR EMISSION OF LOW-LUMINOSITY ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Mason, R. E.; Ramos Almeida, C.; Alonso-Herrero, A.

    2013-11-10

    We use recent high-resolution infrared (IR; 1-20 μm) photometry to examine the origin of the IR emission in low-luminosity active galactic nuclei (LLAGN). The data are compared with published model fits that describe the spectral energy distribution (SED) of LLAGN in terms of an advection-dominated accretion flow, truncated thin accretion disk, and jet. The truncated disk in these models is usually not luminous enough to explain the observed IR emission, and in all cases its spectral shape is much narrower than the broad IR peaks in the data. Synchrotron radiation from the jet appears to be important in very radio-loud nuclei, but the detection of strong silicate emission features in many objects indicates that dust must also contribute. We investigate this point by fitting the IR SED of NGC 3998 using dusty torus and optically thin (τ{sub mid-IR} ∼ 1) dust shell models. While more detailed modeling is necessary, these initial results suggest that dust may account for the nuclear mid-IR emission of many LLAGN.

  8. Diffuse neutrino intensity from the inner jets of active galactic nuclei: Impacts of external photon fields and the blazar sequence

    NASA Astrophysics Data System (ADS)

    Murase, Kohta; Inoue, Yoshiyuki; Dermer, Charles D.

    2014-07-01

    We study high-energy neutrino production in inner jets of radio-loud active galactic nuclei (AGN), taking into account effects of external photon fields and the blazar sequence. We show that the resulting diffuse neutrino intensity is dominated by quasar-hosted blazars, in particular, flat spectrum radio quasars, and that PeV-EeV neutrino production due to photohadronic interactions with broadline and dust radiation is unavoidable if the AGN inner jets are ultrahigh-energy cosmic-ray (UHECR) sources. Their neutrino spectrum has a cutoff feature around PeV energies since target photons are due to Lyα emission. Because of infrared photons provided by the dust torus, neutrino spectra above PeV energies are too hard to be consistent with the IceCube data unless the proton spectral index is steeper than 2.5, or the maximum proton energy is ≲100 PeV. Thus, the simple model has difficulty in explaining the IceCube data. For the cumulative neutrino intensity from blazars to exceed ˜10-8 GeV cm-2 s-1 sr-1, their local cosmic-ray energy generation rate would be ˜10-100 times larger than the local UHECR emissivity but is comparable to the averaged γ-ray blazar emissivity. Interestingly, future detectors such as the Askaryan Radio Array can detect ˜0.1-1 EeV neutrinos even in more conservative cases, allowing us to indirectly test the hypothesis that UHECRs are produced in the inner jets. We find that the diffuse neutrino intensity from radio-loud AGN is dominated by blazars with γ-ray luminosity of ≳1048 erg s-1, and the arrival directions of their ˜1-100 PeV neutrinos correlate with the luminous blazars detected by Fermi.

  9. RELATIONSHIP BETWEEN THE KINETIC POWER AND BOLOMETRIC LUMINOSITY OF JETS: LIMITATION FROM BLACK HOLE X-RAY BINARIES, ACTIVE GALACTIC NUCLEI, AND GAMMA-RAY BURSTS

    SciTech Connect

    Ma, Renyi; Hou, Shujin; Xie, Fu-Guo E-mail: fgxie@shao.ac.cn

    2014-01-01

    The correlation between the kinetic power P {sub jet} and intrinsic bolometric luminosity L {sub jet} of jets may reveal the underlying jet physics in various black hole systems. Based on the recent work by Nemmen et al., we re-investigate this correlation with additional sources of black hole X-ray binaries (BXBs) in hard/quiescent states and low-luminosity active galactic nuclei (LLAGNs). The new sample includes 29 sets of data from 7 BXBs and 20 LLAGNs, with P {sub jet} and L {sub jet} being derived from spectral modeling of the quasi-simultaneous multi-band spectra under the accretion jet scenario. Compared to previous works, the range of luminosity is now enlarged to more than 20 decades, i.e., from ∼10{sup 31} erg s{sup –1} to ∼10{sup 52} erg s{sup –1}, which allows for better constraining of the correlation. One notable result is that the jets in BXBs and LLAGNs almost follow the same P {sub jet}-L {sub jet} correlation that was obtained from blazars and gamma-ray bursts. The slope indices we derived are 1.03 ± 0.01 for the whole sample, 0.85 ± 0.06 for the BXB subsample, 0.71 ± 0.11 for the LLAGN subsample, and 1.01 ± 0.05 for the LLAGN-blazar subsample, respectively. The correlation index around unit implies the independence of jet efficiency on the luminosity or kinetic power. Our results may further support the hypothesis that similar physical processes exist in the jets of various black hole systems.

  10. Relationship between the Kinetic Power and Bolometric Luminosity of Jets: Limitation from Black Hole X-Ray Binaries, Active Galactic Nuclei, and Gamma-Ray Bursts

    NASA Astrophysics Data System (ADS)

    Ma, Renyi; Xie, Fu-Guo; Hou, Shujin

    2014-01-01

    The correlation between the kinetic power P jet and intrinsic bolometric luminosity L jet of jets may reveal the underlying jet physics in various black hole systems. Based on the recent work by Nemmen et al., we re-investigate this correlation with additional sources of black hole X-ray binaries (BXBs) in hard/quiescent states and low-luminosity active galactic nuclei (LLAGNs). The new sample includes 29 sets of data from 7 BXBs and 20 LLAGNs, with P jet and L jet being derived from spectral modeling of the quasi-simultaneous multi-band spectra under the accretion jet scenario. Compared to previous works, the range of luminosity is now enlarged to more than 20 decades, i.e., from ~1031 erg s-1 to ~1052 erg s-1, which allows for better constraining of the correlation. One notable result is that the jets in BXBs and LLAGNs almost follow the same P jet-L jet correlation that was obtained from blazars and gamma-ray bursts. The slope indices we derived are 1.03 ± 0.01 for the whole sample, 0.85 ± 0.06 for the BXB subsample, 0.71 ± 0.11 for the LLAGN subsample, and 1.01 ± 0.05 for the LLAGN-blazar subsample, respectively. The correlation index around unit implies the independence of jet efficiency on the luminosity or kinetic power. Our results may further support the hypothesis that similar physical processes exist in the jets of various black hole systems.

  11. Vainshtein solutions without superluminal modes

    NASA Astrophysics Data System (ADS)

    Gabadadze, Gregory; Kimura, Rampei; Pirtskhalava, David

    2015-06-01

    The Vainshtein mechanism suppresses the fifth force at astrophysical distances, while enabling it to compete with gravity at cosmological scales. Typically, Vainshtein solutions exhibit superluminal perturbations. However, a restricted class of solutions with special boundary conditions was shown to be devoid of the faster-than-light modes. Here we extend this class by finding solutions in a theory of quasidilaton, amended by derivative terms consistent with its symmetries. Solutions with Minkowski asymptotics are not stable, while the ones that exhibit the Vainshtein mechanism by transitioning to cosmological backgrounds are free of ghosts, tachyons, gradient instability, and superluminality, for all propagating modes present in the theory. These solutions require a special choice of the strength and signs of nonlinear terms, as well as a choice of asymptotic cosmological boundary conditions.

  12. Unidentified Active Galactic Nuclei in the Fermi-2LAC catalogue: identification of candidate sources

    NASA Astrophysics Data System (ADS)

    Klindt, L.; van Soelen, B.; Meintjes, P. J.

    Blazars constitute the most violent astronomical objects with jet emitting radiation at all frequencies. In order to fully understand and model blazars and in particular the accretion-black hole system and superluminal jet structure, multi-wavelength observations are required. In the search for Very High Energy (VHE) sources a target sample of twenty unidentified sources with possible blazar characteristics has been constructed from sources listed in the Fermi-2LAC catalogue. The selected targets are all at high galactic latitude (|b| > 10°) with optical/radio counterparts within the Fermi 95% error circle. The selection criteria, which are based on source properties including radio brightness, photon spectral indices, undetermined redshifts, observability and variability, are presented along with the twenty identified sources.

  13. Disk-Jet quenching of the Galactic Black Hole Swift J1753.5-0127

    NASA Astrophysics Data System (ADS)

    Rushton, A. P.; Shaw, A. W.; Fender, R. P.; Altamirano, D.; Gandhi, P.; Uttley, P.; Charles, P. A.; Kolehmainen, M.; Anderson, G. E.; Rumsey, C.; Titterington, D. J.

    2016-08-01

    We report on radio and X-ray monitoring observations of the BHC Swift J1753.5-0127 taken over a ˜10 year period. Presented are daily radio observations at 15 GHz with the AMI-LA and X-ray data from Swift XRT and BAT. Also presented is a deep 2hr JVLA observation taken in an unusually low-luminosity soft-state (with a low disk temperature). We show that although the source has remained relatively radio-quiet compared to XRBs with a similar X-ray luminosity in the hard-state, the power-law relationship scales as ζ = 0.96 ± 0.06 i.e. slightly closer to what has been considered for radiatively inefficient accretion disks. We also place the most stringent limit to date on the radio-jet quenching in an XRB soft-state, showing the connection of the jet quenching to the X-ray power-law component; the radio flux in the soft-state was found to be <21~μJy, which is a quenching factor of ≳ 25.

  14. THE GALACTIC SUPERNOVA REMNANT W49B LIKELY ORIGINATES FROM A JET-DRIVEN, CORE-COLLAPSE EXPLOSION

    SciTech Connect

    Lopez, Laura A.; Castro, Daniel; Ramirez-Ruiz, Enrico; Pearson, Sarah

    2013-02-10

    We present results from a 220 ks observation of the Galactic supernova remnant (SNR) W49B using the Advanced CCD Imaging Spectrometer on board the Chanrda X-ray Observatory. We exploit these data to perform detailed spatially resolved spectroscopic analyses across the SNR with the aim to investigate the thermodynamic properties and explosive origin of W49B. We find substantial variation in the electron temperature and absorbing column toward W49B, and we show that the mean metal abundances are consistent with the predicted yields in models of bipolar/jet-driven core-collapse SNe. Furthermore, we set strict upper limits on the X-ray luminosity of any undetected point sources, and we exclude the presence of a neutron star associated with W49B. We conclude that the morphological, spectral, and environmental characteristics of W49B are indicative of a bipolar Type Ib/Ic SN origin, making it the first of its kind to be discovered in the Milky Way.

  15. The Stored Energy of Gravitational Collapse Powers Gamma Ray Bursts, Active Galactic Nuclei and Jets

    NASA Astrophysics Data System (ADS)

    Greyber, Howard

    2004-05-01

    The recent discovery of almost 100% polarization of the prompt gamma ray emission from GRB021206 (1) confirms my ````Strong'' Magnetic Field'' model (SMF). In SMF, Storage Ring (SR) particles were accelerated during the gravitational collapse of the pregalactic/prequasar plasma that is permeated by a large-scale primordial magnetic field (2.3). The enormous, intense, slender, relativistic, stable, coherent Astrophysical Storage Ring stores a small fraction of the gravitational collapse energy in an almost radiationless state, unless disturbed. Galactic morphology varies as the ratio of magnetic energy to rotational energy in each object. GRB are due to a ``rock'' i.e. white dwarf,ordinary star,neutron star,planet,etc. falling through the SR and being rapidly vaporized into a hot plasma fireball. The fireball speeds on into the huge organized magnetic field surrounding the current ring, thus generating very highly polarized prompt gamma ray emission from the synchrotron radiation process. The timing fits the GRB observations. A ``rock'' racing at 1000 km/sec across a 20,000 km path in the beam produces a twenty second burst. Tracking across a short chord yields a short burst. Typical currents in space are sometimes made of many slender filaments. Thus the puzzling less than one millisecond spikes observed in some GRB are simply describing the structure of that particular SR at that time. 1. W. Coburn & S. E. Boggs, Nature 423, 425 (2003) 2. H. D. Greyber in After the Dark Ages:When Galaxies Were Young, AIP Conf. Proc. 470, eds. S. Holt & E. Smith, (1998) 3. H. D. Greyber in a Space Telescope Science Institute Report from their 2001 Spring Symposium, ``The Dark Universe: Matter, Energy and Gravity'', ed. Mario Livio, published March 2003.

  16. Weak Energy Condition Violation and Superluminal Travel

    NASA Astrophysics Data System (ADS)

    Lobo, Francisco; Crawford, Paulo

    Recent solutions to the Einstein Field Equations involving negative energy densities, i.e., matter violating the weak-energy-condition, have been obtained, namely traversable wormholes, the Alcubierre warp drive and the Krasnikov tube. These solutions are related to superluminal travel, although locally the speed of light is not surpassed. It is difficult to define faster-than-light travel in generic space-times, and one can construct metrics which apparently allow superluminal travel, but are in fact flat Minkowski space-times. Therefore, to avoid these difficulties it is important to provide an appropriate definition of superluminal travel.We investigate these problems and the relationship between weak-energy-condition violation and superluminal travel.

  17. Against dogma: On superluminal propagation in classical electromagnetism

    NASA Astrophysics Data System (ADS)

    Weatherall, James Owen

    2014-11-01

    It is deeply entrenched dogma that relativity theory prohibits superluminal propagation. It is also experimentally well-established that under some circumstances, classical electromagnetic fields propagate through a dielectric medium with superluminal group velocities and superluminal phase velocities. But it is usually claimed that these superluminal velocities do not violate the relativistic prohibition. Here I analyze electromagnetic fields in a dielectric medium within a framework for understanding superluminal propagation recently developed by Geroch (1996, 2011) and elaborated by Earman (2014). I will argue that for some parameter values, electromagnetic fields do propagate superluminally in the Geroch-Earman sense.

  18. Constraints and Tests of the OPERA Superluminal Neutrinos

    NASA Astrophysics Data System (ADS)

    Bi, Xiao-Jun; Yin, Peng-Fei; Yu, Zhao-Huan; Yuan, Qiang

    2011-12-01

    The superluminal neutrinos detected by OPERA indicate Lorentz invariance violation (LIV) of the neutrino sector at the order of 10-5. We study the implications of the result in this work. We find that such a large LIV implied by OPERA data will make the neutrino production process π→μ+νμ kinematically forbidden for a neutrino energy greater than about 5 GeV. The OPERA detection of neutrinos at 40 GeV can constrain the LIV parameter to be smaller than 3×10-7. Furthermore, the neutrino decay in the LIV framework will modify the neutrino spectrum greatly. The atmospheric neutrino spectrum measured by the IceCube Collaboration can constrain the LIV parameter to the level of 10-12. The future detection of astrophysical neutrinos of galactic sources is expected to be able to give an even stronger constraint on the LIV parameter of neutrinos.

  19. Model fitting of the kinematics of ten superluminal components in blazar 3C 279

    NASA Astrophysics Data System (ADS)

    Qian, Shan-Jie

    2013-07-01

    The kinematics of ten superluminal components (C11- C16, C18, C20, C21 and C24) of blazar 3C 279 are studied from VLBI observations. It is shown that their initial trajectory, distance from the core and apparent speed can be well fitted by the precession model proposed by Qian. Combined with the results of the model fit for the six superluminal components (C3, C4, C7a, C8, C9 and C10) already published, the kinematics of sixteen superluminal components can now be consistently interpreted in the precession scenario with their ejection times spanning more than 25 yr (or more than one precession period). The results from model fitting show the possible existence of a common precessing trajectory for these knots within a projected core distance of ~0.2-0.4 mas. In the framework of the jet-precession scenario, we can, for the first time, identify three classes of trajectories which are characterized by their collimation parameters. These different trajectories could be related to the helical structure of magnetic fields in the jet. Through fitting the model, the bulk Lorentz factor, Doppler factor and viewing angle of these knots are derived. It is found that there is no evidence for any correlation between the bulk Lorentz factor of the components and their precession phase (or ejection time). In a companion paper, the kinematics of another seven components (C5a, C6, C7, C17, C19, C22 and C23) have been derived from model fitting, and a binary black-hole/jet scenario was envisaged. The precession model proposed by Qian would be useful for understanding the kinematics of superluminal components in blazar 3C 279 derived from VLBI observations, by disentangling different mechanisms and ingredients. More generally, it might also be helpful for studying the mechanism of jet swing (wobbling) in other blazars.

  20. THE JET-DRIVEN OUTFLOW IN THE RADIO GALAXY SDSS J1517+3353: IMPLICATIONS FOR DOUBLE-PEAKED NARROW-LINE ACTIVE GALACTIC NUCLEUS

    SciTech Connect

    Rosario, D. J.; Taylor, G. B. E-mail: shieldsga@mail.utexas.ed E-mail: krista@mail.utexas.ed

    2010-06-10

    We report on the study of an intriguing active galaxy that was selected as a potential multiple supermassive black hole merger in the early-type host SDSS J151709.20+335324.7 (z = 0.135) from a complete search for double-peaked [O III] lines from the SDSS spectroscopic quasi-stellar object (QSO) database. Ground-based SDSS imaging reveals two blue structures on either side of the photometric center of the host galaxy, separated from each other by about 5.7 kpc. From a combination of SDSS fiber and Keck/HIRES long-slit spectroscopy, it is demonstrated that, in addition to these two features, a third distinct structure surrounds the nucleus of the host galaxy. All three structures exhibit highly ionized line emission with line ratios characteristic of Seyfert II active galactic nuclei. The analysis of spatially resolved emission-line profiles from the HIRES spectrum reveal three distinct kinematic subcomponents, one at rest and the other two moving at -350 km s{sup -1} and 500 km s{sup -1} with respect to the systemic velocity of the host galaxy. A comparison of imaging and spectral data confirm a strong association between the kinematic components and the spatial knots, which implies a highly disturbed and complex active region in this object. A comparative analysis of the broadband positions, colors, kinematics, and spectral properties of the knots in this system lead to two plausible explanations: (1) a multiple active galactic nucleus (AGN) produced due to a massive dry merger, or (2) a very powerful radio jet-driven outflow. Subsequent VLA radio imaging reveals a clear jet aligned with the emission-line gas, confirming the latter explanation. We use the broadband radio measurements to examine the impact of the jet on the interstellar medium of the host galaxy, and find that the energy in the radio lobes can heat a significant fraction of the gas to the virial temperature. Finally, we discuss tests that may help future surveys distinguish between jet

  1. PAGaN II: The Evolution of AGN Jets on Sub-Parsec Scales

    NASA Astrophysics Data System (ADS)

    Oh, Junghwan; Trippe, Sascha; Kang, Sincheol; Kim, Jae-Young; Park, Jong-Ho; Lee, Taeseok; Kim, Daewon; Kino, Motoki; Lee, Sang-Sung; Sohn, Bong Won

    2015-10-01

    We report first results from KVN and VERA Array (KaVA) VLBI observations obtained in the frame of our Plasma-physics of Active Galactic Nuclei (PAGaN) project. We observed eight selected AGN at 22 and 43 GHz in single polarization (LCP) between March 2014 and April 2015. Each source was observed for 6 to 8 hours per observing run to maximize the uv coverage. We obtained a total of 15 deep high-resolution images permitting the identification of individual circular Gaussian jet components and three spectral index maps of BL Lac, 3C~111 and 3C~345 from simultaneous dual-frequency observations. The spectral index maps show trends in agreement with general expectations -- flat core and steep jets -- while the actual value of the spectral index for jets shows indications for a dependence on AGN type. We analyzed the kinematics of jet components of BL Lac and 3C~111, detecting superluminal proper motions with maximum apparent speeds of about 5c. This constrains the lower limits of the intrinsic component velocities to ˜0.98c and the upper limits of the angle between jet and line of sight to ˜20°. In agreement with global jet expansion, jet components show systematically larger diameters d at larger core distances r, following the global relation d≈0.2r, albeit within substantial scatter.

  2. Superluminal subway: The Krasnikov tube

    NASA Astrophysics Data System (ADS)

    Everett, Allen E.; Roman, Thomas A.

    1997-08-01

    The ``warp drive'' metric recently presented by Alcubierre has the problem that an observer at the center of the warp bubble is causally separated from the outer edge of the bubble wall. Hence such an observer can neither create a warp bubble on demand nor control one once it has been created. In addition, such a bubble requires negative energy densities. One might hope that elimination of the first problem might ameliorate the second as well. We analyze and generalize a metric, originally proposed by Krasnikov for two spacetime dimensions, which does not suffer from the first difficulty. As a consequence, the Krasnikov metric has the interesting property that, although the time for a one-way trip to a distant star cannot be shortened, the time for a round trip, as measured by clocks on Earth, can be made arbitrarily short. In our four-dimensional extension of this metric, a ``tube'' is constructed along the path of an outbound spaceship, which connects the Earth and the star. Inside the tube spacetime is flat, but the light cones are opened out so as to allow superluminal travel in one direction. We show that, although a single Krasnikov tube does not involve closed timelike curves, a time machine can be constructed with a system of two nonoverlapping tubes. Furthermore, it is demonstrated that Krasnikov tubes, like warp bubbles and traversable wormholes, also involve unphysically thin layers of negative energy density, as well as large total negative energies, and, therefore, probably cannot be realized in practice.

  3. Particle Acceleration in Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Miller, James A.

    1997-01-01

    The high efficiency of energy generation inferred from radio observations of quasars and X-ray observations of Seyfert active galactic nuclei (AGNs) is apparently achieved only by the gravitational conversion of the rest mass energy of accreting matter onto supermassive black holes. Evidence for the acceleration of particles to high energies by a central engine is also inferred from observations of apparent superluminal motion in flat spectrum, core-dominated radio sources. This phenomenon is widely attributed to the ejection of relativistic bulk plasma from the nuclei of active galaxies, and accounts for the existence of large scale radio jets and lobes at large distances from the central regions of radio galaxies. Reports of radio jets and superluminal motion from galactic black hole candidate X-ray sources indicate that similar processes are operating in these sources. Observations of luminous, rapidly variable high-energy radiation from active galactic nuclei (AGNs) with the Compton Gamma Ray Observatory show directly that particles are accelerated to high energies in a compact environment. The mechanisms which transform the gravitational potential energy of the infalling matter into nonthermal particle energy in galactic black hole candidates and AGNs are not conclusively identified, although several have been proposed. These include direct acceleration by static electric fields (resulting from, for example, magnetic reconnection), shock acceleration, and energy extraction from the rotational energy of Kerr black holes. The dominant acceleration mechanism(s) operating in the black hole environment can only be determined, of course, by a comparison of model predictions with observations. The purpose of the work proposed for this grant was to investigate stochastic particle acceleration through resonant interactions with plasma waves that populate the magnetosphere surrounding an accreting black hole. Stochastic acceleration has been successfully applied to the

  4. Discrete knot ejection from the jet in a nearby low-luminosity active galactic nucleus, M81*

    NASA Astrophysics Data System (ADS)

    King, Ashley L.; Miller, Jon M.; Bietenholz, Michael; Gültekin, Kayhan; Reynolds, Mark T.; Mioduszewski, Amy; Rupen, Michael; Bartel, Norbert

    2016-08-01

    Observational constraints of the relativistic jets from black holes have largely come from the most powerful and extended jets, leaving the nature of the low-luminosity jets a mystery. M81* is one of the nearest low-luminosity jets and it emitted an extremely large radio flare in 2011, allowing us to study compact core emission with unprecedented sensitivity and linear resolution. Using a multiwavelength campaign, we were able to track the flare as it re-brightened and became optically thick. Simultaneous X-ray observations indicated that the radio re-brightening was preceded by a low-energy X-ray flare at least 12 days earlier. Associating the time delay (tdelay) between the two bands with the cooling time in a synchrotron flare, we find that the magnetic field strength was 1.9 < B < 9.2 G, which is consistent with magnetic field estimate from spectral energy distribution modelling, B < 10.2 G. In addition, Very Long Baseline Array observations at 23 GHz clearly illustrate a discrete knot moving at a low relativistic speed of vapp/c = 0.51 +/- 0.17 associated with the initial radio flare. The observations indicate radial jet motions for the first time in M81*. This has profound implications for jet production, as it means radial motion can be observed in even the lowest-luminosity AGN, but at slower velocities and smaller radial extents (≍104 RG).

  5. Cosmic jets

    NASA Technical Reports Server (NTRS)

    Rees, M. J.

    1986-01-01

    The evidence that active galactic nuclei produce collimated plasma jets is summarised. The strongest radio galaxies are probably energised by relativistic plasma jets generated by spinning black holes interacting with magnetic fields attached to infalling matter. Such objects can produce e(+)-e(-) plasma, and may be relevant to the acceleration of the highest-energy cosmic ray primaries. Small-scale counterparts of the jet phenomenon within our own galaxy are briefly reviewed.

  6. Superluminal cascade spectra of TeV {gamma}-ray sources

    SciTech Connect

    Tomaschitz, Roman . E-mail: tom@geminga.org

    2007-03-15

    Astrophysical radiation sources are scrutinized in search of superluminal {gamma}-rays. The tachyonic spectral densities generated by ultra-relativistic electrons in uniform motion are fitted to the high-energy spectra of Galactic supernova remnants, such as RX J0852.0-4622 and the pulsar wind nebulae in G0.9+0.1 and MSH 15-52. The superluminal spectral maps of the unidentified TeV {gamma}-ray sources HESS J1303-631, TeV J2032+4130 and HESS J1825-137 are inferred from EGRET, HEGRA and HESS data. Tachyonic cascade spectra are quite capable of generating the spectral curvature seen in double-logarithmic plots, as well as the extended spectral plateaus defined by EGRET flux points in the GeV band. The curvature of the TeV spectra is intrinsic, caused by the Boltzmann factor in the source densities. The spectral averaging with thermal and exponentially cut power-law electron densities can be done in closed form, and systematic high- and low-temperature expansions of the superluminal spectral densities are derived. Estimates on the electron/proton populations generating the tachyon flux are obtained from the spectral fits, such as power-law indices, temperature and source counts. The cutoff temperatures of the source densities suggest ultra-high-energy protons in MSH 15-52, HESS J1825-137 and TeV J2032+4130.

  7. Complete multiwavelength evolution of galactic black hole transients during outburst decay. II. Compact jets and X-ray variability properties

    SciTech Connect

    Dinçer, T.; Kalemci, E.; Tomsick, J. A.; Buxton, M. M.; Bailyn, C. D.

    2014-11-01

    We investigated the relation between compact jet emission and X-ray variability properties of all black hole transients with multiwavelength coverage during their outburst decays. We studied the evolution of all power spectral components (including low-frequency quasi-periodic oscillations; QPOs), and related this evolution to changes in jet properties tracked by radio and infrared observations. We grouped sources according to their tracks in the radio/X-ray luminosity relation and show that the standards show stronger broadband X-ray variability than outliers at a given X-ray luminosity when the compact jet turns on. This trend is consistent with the internal shock model and can be important for the understanding of the presence of tracks in the radio/X-ray luminosity relation. We also observed that the total and the QPO rms amplitudes increase together during the earlier part of the outburst decay, but after the compact jet turns, either the QPO disappears or its rms amplitude decreases significantly while the total rms amplitudes remain high. We discuss these results with a scenario including a variable corona and a non-variable disk with a mechanism for the QPO separate from the mechanism that creates broad components. Finally, we evaluated the timing predictions of the magnetically dominated accretion flow model that can explain the presence of tracks in the radio/X-ray luminosity relation.

  8. Non-Ballistic Motions in Relativistic Jets

    NASA Astrophysics Data System (ADS)

    Homan, D. C.

    2002-12-01

    We present results from the 2cm Very Long Baseline Array (VLBA) survey of motions in relativistic jets (Kellermann et al. 1998; Zensus et al. 2002). In particular, we discuss the distribution of non-ballistic motions and present several examples from our sample. The non-ballistic motions we observe are generally in the direction of the downstream jet emission, providing evidence that jet features follow streaming flows in curved, bent jets. We also discuss the jet of the quasar 3C279, which displays a distinct change in the motion of a bright superluminal component. The new motion for this component is along a parallel track to the motion of an older superluminal component, suggesting collimation of the jet may still be occurring at radii (de-projected) of a kiloparsec or more.

  9. Retardation magnification and the appearance of relativistic jets

    NASA Astrophysics Data System (ADS)

    Jester, Sebastian

    2008-10-01

    Thanks to the availability of high-resolution high-sensitivity telescopes such as the Very Large Array, the Hubble Space Telescope and the Chandra X-Ray Observatory, there is now a wealth of observational data on relativistic jets from active galactic nuclei (AGN) as well as galactic sources such as black hole X-ray binaries. Since the jet speeds cannot be constrained well from observations, but are generally believed to be relativistic, physical quantities inferred from observables are commonly expressed in terms of the unknown beaming parameters: the bulk Lorentz factor and the line-of-sight angle, usually in their combination as relativistic Doppler factor. This paper aims to resolve the discrepancies existing in the literature about such `debeaming' of derived quantities, in particular regarding the minimum-energy magnetic field estimate. The discrepancies arise because the distinction is not normally made between the case of a fixed source observed with different beaming parameters and the case where the source projection on the sky is held fixed. The former is usually considered, but it is the latter that corresponds to interpreting actual jet observations. Furthermore, attention is drawn to the fact that apparent superluminal motion has a spatial corollary, here called `retardation magnification', which implies that most parts of a relativistic jet that are actually present in the observer's frame (a `world map' in relativity terminology) are in fact hidden on the observer's image (the `world picture' in general, or `supersnapshot' in the special case of astronomy). Portions of this work were carried at the Particle Astrophysics Center, Fermilab MS 127, PO Box 500, Batavia, IL 60510, USA; and while the author was an Otto Hahn fellow of the Max-Planck-Gesellschaft at the Department of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ. E-mail: jester@mpia.de

  10. Superluminal periodic orbits in the Lorenz system

    NASA Astrophysics Data System (ADS)

    Algaba, A.; Merino, M.; Rodríguez-Luis, A. J.

    2016-10-01

    In this work we present, for the Lorenz system, analytical and numerical results on the existence of periodic orbits with unbounded amplitude and whose period tends to zero. Since a particle moving on these periodic orbits would be faster-than-light, we call them superluminal periodic orbits. To achieve this goal, we first find analytical expressions for the period in three different situations, where Hopf and Takens-Bogdanov bifurcations of infinite codimension occur. Thus, taking limit in the corresponding expressions allows to demonstrate the existence of superluminal periodic orbits for finite values of the parameter ρ (in a region where the other two parameters σ and b are negative). Moreover, we numerically show, in other two different cases of physical interest, that these orbits also exist when the parameter ρ tends to infinity. Finally, the presence of superluminal periodic orbits in the widely studied Chen and Lü systems follows directly from our results, taking into account that they are, generically, particular cases of the Lorenz system, as can be proved with a linear scaling in time and state variables.

  11. VLBI limits on the proper motion of the 'core' of the superluminal quasar 3C345

    NASA Technical Reports Server (NTRS)

    Bartel, N.; Herring, T. A.; Ratner, M. I.; Shapiro, I. I.; Corey, B. E.

    1986-01-01

    VLBI (very-long-baseline interferometry) observations between 1971 and 1983 have been used to determine the positions of the 'core' of the quasar 3C345 relative to the more distant compact quasar NRAO512 with a fractional uncertainty as small as two parts in a hundred million. The core of 3C345 appears stationary in right ascension to within 20 arc microsec/yr, a subluminal bound corresponding to 0.7c. The apparent velocities of the jets are superluminal, up to 14c in magnitude.

  12. Quaternionic Analysis of Generalized Electromagnetic Fields of Superluminal Dyons

    SciTech Connect

    Bisht, P. S.; Negi, O. P. S.

    2008-04-21

    Superluminal electromagnetic fields of dyons are described in T{sup 4}--space and Quaternion formulation of various quantum equations is derived. It is shown that on passing from subluminal to superluminal realm via quaternion the theory of dyons becomes the Tachyonic dyons. Corresponding field Equations of Tachyonic dyons are derived in consistent, compact and simpler form.

  13. Interaction of ultraviolet and X-ray radiation with gamma rays produced by a jet in active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Zbyszewska, Magda

    1994-01-01

    Recent observations by the Compton Gamma-Ray Observatory give evidence for the existence of a type of blazar with strong gamma-ray emission. Data obtained by EGRET for the quasar 3C 279 show a spectrum between 100 MeV and 10 GeV. Photons of such energies should interact with the X-rays and produce positron/electron pairs. If the optical depth against pair production for the gamma rays is large (tau(gamma gamma) greater than 1), the gamma-ray spectrum should be affected. The importance of this process has been pointed out by, e.g., Maraschi, Ghisellini, & Celotti (1992). Several works (e.g., Dermer 1993; Zbyszewska 1993; Sikora, Begelman, & Rees 1993) concerning gamma-ray radiation from quasar 3C 279 have proposed a model in which the gamma rays are produced via interaction between a moving cloud of relativistic electrons and external soft photons. The presence of gamma rays in active galactic nuclei spectra gives constraints on the localization and the luminosity of the medium which produces ultraviolet/X-ray photons. We investigate what conditions should be fulfilled in the above model to avoid the absorption of the gamma rays due to pair production.

  14. Grs 1915+105: a superluminal source in the Galaxy.

    PubMed Central

    Rodríguez, L F; Mirabel, I F

    1995-01-01

    We present the results of additional observations of the high energy source GRS 1915+105, which produces ejecta with apparent superluminal motions. The observations reported here were carried out with the Very Large Array at 3.5 cm and 20 cm. The 3.5-cm observations made during 1994 May allowed us to continue following the proper motions of the bright 1994 March 19 ejecta, as well as those of a subsequent, fainter ejection. The proper motions of the 1994 March 19 ejecta continued to be ballistic (i.e., constant) over the period of about 75 days where they remained detectable. From the observations in 1994 March-May we have identified three ejections of pairs of plasma clouds moving ballistically in approximately the same direction on the sky with similar proper motions. The 20-cm observations made during 1994 November and December were used to search, yet unsuccessfully, for extended jets or lobes associated with GRS 1915+105. PMID:11607605

  15. Comparison of ejection events in the jet and accretion disc outflows in 3C 111

    NASA Astrophysics Data System (ADS)

    Tombesi, F.; Sambruna, R. M.; Marscher, A. P.; Jorstad, S. G.; Reynolds, C. S.; Markowitz, A.

    2012-07-01

    We present a comparison of the parameters of accretion disc outflows and the jet of the broad-line radio galaxy 3C 111 on subparsec (sub-pc) scales. We make use of published X-ray observations of ultra-fast outflows (UFOs) and new 43-GHz Very Long Baseline Array images to track the jet knot ejection. We find that the superluminal jet coexists with the mildly relativistic outflows on sub-pc scales, possibly indicating a transverse stratification of a global flow. The two are roughly in pressure equilibrium, with the UFOs potentially providing additional support for the initial jet collimation. The UFOs are much more massive than the jet, but their kinetic power is probably about an order of magnitude lower, at least for the observations considered here. However, their momentum flux is equivalent and both of them are powerful enough to exert a concurrent feedback impact on the surrounding environment. A link between these components is naturally predicted in the context of magnetohydrodynamic models for jet/outflow formation. However, given the high radiation throughput of active galactic nuclei, radiation pressure should also be taken into account. From the comparison with the long-term 2-10 keV Rossi X-ray Timing Explorer light curve, we find that the UFOs are preferentially detected during periods of increasing flux. We also find the possibility to place the UFOs within the known X-ray dips-jet ejection cycles, which has been shown to be a strong proof of the disc-jet connection, in analogue with stellar mass black holes. However, given the limited number of observations presently available, these relations are only tentative and additional spectral monitoring is needed to test them conclusively.

  16. Superluminal group velocity in a birefringent crystal

    SciTech Connect

    Halvorsen, Tore Gunnar; Leinaas, Jon Magne

    2008-02-15

    We examine the effect of superluminal signal propagation through a birefringent crystal, where the effect is not due to absorption or reflection, but to the filtration of a special polarization component. We first examine the effect by a stationary phase analysis, with results consistent with those of an earlier analysis of the system. We supplement this analysis by considering the transit of a Gaussian wave and find bounds for the validity of the stationary phase result. The propagation of the Gaussian wave is illustrated by figures.

  17. Multiepoch VLBI observations of 4C 39.25 - Superluminal motion amid stationary structure

    NASA Technical Reports Server (NTRS)

    Shaffer, David B.; Marscher, Alan P.; Marcaide, Jon; Romney, Jonathan D.

    1987-01-01

    Eight VLBI maps of the quasar 4C 39.25 are presented, covering the time interval November 1979 to July 1985. During this period the compact components at the eastern and western ends of the source remained roughly stationary with respect to each other. A third component emerged from the western component in 1982 and proceeded to move (relative to the other two components) eastward at a rate of 0.16 + or - 0.02 marcsec per year. This corresponds to an average apparent speed between 3.2c and 8.4c for Hubble's constant between 100 and 50 km/s Mpc and q0 between 1 and 0. This superluminal motion contrasts with the stationary structure observed in the 1970s and also still observed between the eastern and western ends of the source. Possible explanations include superluminal feeding of a stationary compact counterpart to a classical radio lobe, an obstacle in a relativistic jet, a relativistic jet which alternatively expands and contracts owing to gradients in the confining pressure, and gravitational lensing of the compact radio emission.

  18. Gain-assisted superluminal light propagation

    PubMed

    Wang; Kuzmich; Dogariu

    2000-07-20

    Einstein's theory of special relativity and the principle of causality imply that the speed of any moving object cannot exceed that of light in a vacuum (c). Nevertheless, there exist various proposals for observing faster-than-c propagation of light pulses, using anomalous dispersion near an absorption line, nonlinear and linear gain lines, or tunnelling barriers. However, in all previous experimental demonstrations, the light pulses experienced either very large absorption or severe reshaping, resulting in controversies over the interpretation. Here we use gain-assisted linear anomalous dispersion to demonstrate superluminal light propagation in atomic caesium gas. The group velocity of a laser pulse in this region exceeds c and can even become negative, while the shape of the pulse is preserved. We measure a group-velocity index of n(g) = -310(+/- 5); in practice, this means that a light pulse propagating through the atomic vapour cell appears at the exit side so much earlier than if it had propagated the same distance in a vacuum that the peak of the pulse appears to leave the cell before entering it. The observed superluminal light pulse propagation is not at odds with causality, being a direct consequence of classical interference between its different frequency components in an anomalous dispersion region. PMID:10917523

  19. Superluminal Sweeping Spot Pair Events in Astronomical Settings

    NASA Astrophysics Data System (ADS)

    Nemiroff, Robert J.

    2015-01-01

    Sweeping beams of light can cast spots that move superluminally across scattering surfaces. Such faster-than-light speeds are well-known phenomena that do not violate special relativity. It is shown that under certain circumstances, superluminal spot pair creation and annihilation events can occur that provide unique information to observers. These spot pair events are not particle pair events -- they are the sudden creation or annihilation of a pair of relatively illuminated spots on a scattering surface. Astronomical settings where superluminal spot pairs might be found include Earth's Moon, passing asteroids, pulsars, and variable nebula. Potentially recoverable information includes three dimensional imaging, relative geometric size factors, and distances.

  20. On Superluminal Particles and the Extended Relativity Theories

    NASA Astrophysics Data System (ADS)

    Castro, Carlos

    2012-09-01

    Superluminal particles are studied within the framework of the Extended Relativity theory in Clifford spaces ( C-spaces). In the simplest scenario, it is found that it is the contribution of the Clifford scalar component π of the poly-vector-valued momentum which is responsible for the superluminal behavior in ordinary spacetime due to the fact that the effective mass {M} = sqrt{ M2 - π2 } is imaginary (tachyonic). However, from the point of view of C-space, there is no superluminal (tachyonic) behavior because the true physical mass still obeys M 2>0. Therefore, there are no violations of the Clifford-extended Lorentz invariance and the extended Relativity principle in C-spaces. It is also explained why the charged muons (leptons) are subluminal while its chargeless neutrinos may admit superluminal propagation. A Born's Reciprocal Relativity theory in Phase Spaces leads to modified dispersion relations involving both coordinates and momenta, and whose truncations furnish Lorentz-violating dispersion relations which appear in Finsler Geometry, rainbow-metrics models and Double (deformed) Special Relativity. These models also admit superluminal particles. A numerical analysis based on the recent OPERA experimental findings on alleged superluminal muon neutrinos is made. For the average muon neutrino energy of 17 GeV, we find a value for the magnitude |{M } | = 119.7 MeV that, coincidentally, is close to the mass of the muon m μ =105.7 MeV.

  1. MOJAVE: XIII. Parsec-scale AGN Jet Kinematics Analysis Based on 19 years of VLBA Observations at 15 GHz

    NASA Astrophysics Data System (ADS)

    Lister, M. L.; Aller, M. F.; Aller, H. D.; Homan, D. C.; Kellermann, K. I.; Kovalev, Y. Y.; Pushkarev, A. B.; Richards, J. L.; Ros, E.; Savolainen, T.

    2016-07-01

    We present 1625 new 15 GHz (2 cm) VLBA images of 295 jets associated with active galactic nuclei (AGNs) from the MOJAVE and 2 cm VLBA surveys, spanning observations between 1994 August 31 and 2013 August 20. For 274 AGNs with at least 5 VLBA epochs, we have analyzed the kinematics of 961 individual bright features in their parsec-scale jets. A total of 122 of these jets have not been previously analyzed by the MOJAVE program. In the case of 451 jet features that had at least 10 epochs, we also examined their kinematics for possible accelerations. At least half of the well-sampled features have non-radial and/or accelerating trajectories, indicating that non-ballistic motion is common in AGN jets. Since it is impossible to extrapolate any accelerations that occurred before our monitoring period, we could only determine reliable ejection dates for ∼ 24 % of those features that had significant proper motions. The distribution of maximum apparent jet speeds in all 295 AGNs measured by our program to date is peaked below 5c, with very few jets with apparent speeds above 30c. The fastest speed in our survey is ∼ 50c, measured in the jet of the quasar PKS 0805‑07, and is indicative of a maximum jet Lorentz factor of ∼50 in the parent population. An envelope in the maximum jet speed versus redshift distribution of our sample provides additional evidence of this upper limit to the speeds of radio-emitting regions in parsec-scale AGN jets. The Fermi-LAT-detected gamma-ray AGNs in our sample have, on average, higher jet speeds than non-LAT-detected AGNs, indicating a strong correlation between parsec-scale jet speed and the gamma-ray Doppler boosting factor. We have identified 11 moderate-redshift (z\\lt 0.35) AGNs with fast apparent speeds (\\gt 10c) that are strong candidates for future TeV gamma-ray detection. Of the five gamma-ray loud narrow-lined Seyfert I AGNs in our sample, three show highly superluminal jet motions, while the others have sub-luminal speeds

  2. Particle Acceleration in Jets

    NASA Technical Reports Server (NTRS)

    Nishikawa, Ken-Ichi

    2005-01-01

    Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., active galactic nuclei (AGNs), gamma ray burst (GRBs), and Galactic microquasar systems usually have power-law emission spectra. Fermi acceleration is the mechanism usually assumed for the acceleration of particles in astrophysical environments.

  3. Nonlocal Quantum Information Transfer Without Superluminal Signalling and Communication

    NASA Astrophysics Data System (ADS)

    Walleczek, Jan; Grössing, Gerhard

    2016-01-01

    It is a frequent assumption that—via superluminal information transfers—superluminal signals capable of enabling communication are necessarily exchanged in any quantum theory that posits hidden superluminal influences. However, does the presence of hidden superluminal influences automatically imply superluminal signalling and communication? The non-signalling theorem mediates the apparent conflict between quantum mechanics and the theory of special relativity. However, as a `no-go' theorem there exist two opposing interpretations of the non-signalling constraint: foundational and operational. Concerning Bell's theorem, we argue that Bell employed both interpretations, and that he finally adopted the operational position which is associated often with ontological quantum theory, e.g., de Broglie-Bohm theory. This position we refer to as "effective non-signalling". By contrast, associated with orthodox quantum mechanics is the foundational position referred to here as "axiomatic non-signalling". In search of a decisive communication-theoretic criterion for differentiating between "axiomatic" and "effective" non-signalling, we employ the operational framework offered by Shannon's mathematical theory of communication, whereby we distinguish between Shannon signals and non-Shannon signals. We find that an effective non-signalling theorem represents two sub-theorems: (1) Non-transfer-control (NTC) theorem, and (2) Non-signification-control (NSC) theorem. Employing NTC and NSC theorems, we report that effective, instead of axiomatic, non-signalling is entirely sufficient for prohibiting nonlocal communication. Effective non-signalling prevents the instantaneous, i.e., superluminal, transfer of message-encoded information through the controlled use—by a sender-receiver pair —of informationally-correlated detection events, e.g., in EPR-type experiments. An effective non-signalling theorem allows for nonlocal quantum information transfer yet—at the same time

  4. Superluminality and parelectricity: The ammonia maser revisited

    NASA Astrophysics Data System (ADS)

    Chiao, R. Y.; Boyce, J.; Mitchell, M. W.

    1995-02-01

    It is well known that the inversion of populations in the ammonia maser leads to stimulated emission, and hence amplification, of microwaves. However, it is not well known that an inverted medium also leads to the superluminal propagation of off-resonance, finite-band-width wave packets, whose phase, group, energy, and “signal” velocities, as defined by Sommerfeld and Brillouin, all exceed the vacuum speed of light c. Einstein causality is not violated, since the front velocity is c. The inversion of populations also implies a parelectric medium with negative electric susceptibility. ( Parelectric media should not be confused with paraelectric media, which are ferroelectrics just above their Curie points.) The existence of a parelectric medium implies the possibility of the levitation of an electrical charge in the vacuum above this medium, as well as stable electrostatic configurations of charges placed inside an evacuated cavity surrounded by this medium. The apparent violation of Earn-shaw's theorem will be discussed. Numerical estimates for a proposed experiment to observe parelectricity will be given.

  5. Superluminous supernovae: no threat from eta Carinae.

    PubMed

    Thomas, Brian C; Melott, Adrian L; Fields, Brian D; Anthony-Twarog, Barbara J

    2008-02-01

    Recently, Supernova 2006gy was noted as the most luminous ever recorded, with a total radiated energy of approximately 10(44) Joules. It was proposed that the progenitor may have been a massive evolved star similar to eta Carinae, which resides in our own Galaxy at a distance of about 2.3 kpc. eta Carinae appears ready to detonate. Although it is too distant to pose a serious threat as a normal supernova, and given that its rotation axis is unlikely to produce a gamma-ray burst oriented toward Earth, eta Carinae is about 30,000 times nearer than 2006gy, and we re-evaluate it as a potential superluminous supernova. We have found that, given the large ratio of emission in the optical to the X-ray, atmospheric effects are negligible. Ionization of the atmosphere and concomitant ozone depletion are unlikely to be important. Any cosmic ray effects should be spread out over approximately 10(4) y and similarly unlikely to produce any serious perturbation to the biosphere. We also discuss a new possible effect of supernovae-e-ndocrine disruption induced by blue light near the peak of the optical spectrum. This is a possibility for nearby supernovae at distances too large to be considered "dangerous" for other reasons. However, due to reddening and extinction by the interstellar medium, eta Carinae is unlikely to trigger such effects to any significant degree. PMID:18199005

  6. Superluminous Supernovae: No Threat from Eta Carinae

    NASA Astrophysics Data System (ADS)

    Thomas, Brian; Melott, A. L.; Fields, B. D.; Anthony-Twarog, B. J.

    2008-05-01

    Recently Supernova 2006gy was noted as the most luminous ever recorded, with a total radiated energy of 1044 Joules. It was proposed that the progenitor may have been a massive evolved star similar to η Carinae, which resides in our own galaxy at a distance of about 2.3 kpc. η Carinae appears ready to detonate. Although it is too distant to pose a serious threat as a normal supernova, and given its rotation axis is unlikely to produce a Gamma-Ray Burst oriented toward the Earth, η Carinae is about 30,000 times nearer than 2006gy, and we re-evaluate it as a potential superluminous supernova. We find that given the large ratio of emission in the optical to the X-ray, atmospheric effects are negligible. Ionization of the atmosphere and concomitant ozone depletion are unlikely to be important. Any cosmic ray effects should be spread out over 104 y, and similarly unlikely to produce any serious perturbation to the biosphere. We also discuss a new possible effect of supernovae, endocrine disruption induced by blue light near the peak of the optical spectrum. This is a possibility for nearby supernovae at distances too large to be considered "dangerous” for other reasons. However, due to reddening and extinction by the interstellar medium, η Carinae is unlikely to trigger such effects to any significant degree.

  7. Particle Acceleration in Superluminal Strong Waves

    NASA Astrophysics Data System (ADS)

    Teraki, Yuto; Ito, Hirotaka; Nagataki, Shigehiro

    2015-06-01

    We calculate the electron acceleration in random superluminal strong waves (SLSWs) and radiation from them using numerical methods in the context of the termination shocks of pulsar wind nebulae. We pursue the orbit of electrons by solving the equation of motion in the analytically expressed electromagnetic turbulences. These consist of a primary SLS and isotropically distributed secondary electromagnetic waves. Under the dominance of the secondary waves, all electrons gain nearly equal energy. On the other hand, when the primary wave is dominant, selective acceleration occurs. The phase of the primary wave for electrons moving nearly along the wavevector changes very slowly compared with the oscillation of the wave, which is “phase-locked,” and such electrons are continuously accelerated. This acceleration by SLSWs may play a crucial role in pre-shock acceleration. In general, the radiation from the phase-locked population is different from the synchro-Compton radiation. However, when the amplitude of the secondary waves is not extremely weaker than that of the primary wave, the typical frequency can be estimated from synchro-Compton theory using the secondary waves. The primary wave does not contribute to the radiation because the SLSW accelerates electrons almost linearly. This radiation can be observed as a radio knot at the upstream of the termination shocks of the pulsar wind nebulae without counterparts in higher frequency ranges.

  8. Testing the OPERA Superluminal Neutrino Anomaly at the LHC

    SciTech Connect

    Davoudiasl, Hooman; Rizzo, Thomas G.; /SLAC

    2012-03-15

    The OPERA collaboration has reported the observation of superluminal muon neutrinos, whose speed v{sub {nu}} exceeds that of light c, with (v{sub {nu}}-c)/c {approx_equal} 2.5 x 10{sup -5}. In a recent work, Cohen and Glashow (CG) have refuted this claim by noting that such neutrinos will lose energy, by pair-emission of particles, at unacceptable rates. Following the CG arguments, we point out that pair-emissions consistent with the OPERA anomaly can lead to detectable signals for neutrinos originating from decays of highly boosted top quarks at the LHC, allowing an independent test of the superluminal neutrino hypothesis.

  9. Spectrum formation in superluminous supernovae (Type I)

    NASA Astrophysics Data System (ADS)

    Mazzali, P. A.; Sullivan, M.; Pian, E.; Greiner, J.; Kann, D. A.

    2016-06-01

    The near-maximum spectra of most superluminous supernovae (SLSNe) that are not dominated by interaction with a H-rich circum-stellar medium (SLSN-I) are characterized by a blue spectral peak and a series of absorption lines which have been identified as O II. SN 2011kl, associated with the ultra-long gamma-ray burst GRB111209A, also had a blue peak but a featureless optical/ultraviolet (UV) spectrum. Radiation transport methods are used to show that the spectra (not including SN 2007bi, which has a redder spectrum at peak, like ordinary SNe Ic) can be explained by a rather steep density distribution of the ejecta, whose composition appears to be typical of carbon-oxygen cores of massive stars which can have low metal content. If the photospheric velocity is ˜10 000-15 000 km s-1, several lines form in the UV. O II lines, however, arise from very highly excited lower levels, which require significant departures from local thermodynamic equilibrium to be populated. These SLSNe are not thought to be powered primarily by 56Ni decay. An appealing scenario is that they are energized by X-rays from the shock driven by a magnetar wind into the SN ejecta. The apparent lack of evolution of line velocity with time that characterizes SLSNe up to about maximum is another argument in favour of the magnetar scenario. The smooth UV continuum of SN 2011kl requires higher ejecta velocities (˜20 000 km s-1): line blanketing leads to an almost featureless spectrum. Helium is observed in some SLSNe after maximum. The high-ionization near-maximum implies that both He and H may be present but not observed at early times. The spectroscopic classification of SLSNe should probably reflect that of SNe Ib/c. Extensive time coverage is required for an accurate classification.

  10. Studying Absorption Line Feature in the Relativistic Jet Source GRS 1915+105

    NASA Technical Reports Server (NTRS)

    Tavani, Marco

    1998-01-01

    The galactic superluminal source GRS 1915+105 is among the most interesting objects in our Galaxy. It is subject to erratic accretion instabilities with energization of relativistic jets producing X-ray, optical and radio emission. This source was observed by ASCA on Sept. 27, 1994, April 20, 1995, October 23, 1996 and April 25, 1997 as part of a long timescale investigation. We detected strong variability of the source, and in particular the existence of burst/dip structure in October 1996 and April 1997. Clear evidence of transient absorption features at 6.7, 7.0 and 8.0 keV was obtained for the first time in September 1994 and April 1995. Given the phenomenology of plasmoid energization and ejection, these transient spectral features might be produced by material entrained in the radio jets or in other high-velocity outflows. Our contribution to the interpretation is to incorporate these observations into a overall theoretical picture for GRS 1915+105 also taking into account other observations by XTE and BSAX. The emerging picture is complex. The central source is subject to (most likely) super-Eddington instabilities mediated by magnetic field build-up, reconnection and dissipation in the form of blobs that eventually leads to the formation of transient spectral features from the surrounding of the plasmoid emitting region. A comprehensive theoretical investigation is in progress.

  11. Doppler effect of subluminal and superluminal sources in eight dimensions

    NASA Astrophysics Data System (ADS)

    Chandola, H. C.; Rajput, B. S.

    1984-06-01

    The study of the relativistic Doppler effect of subliminal and superluminal sources has been undertaken in the eight-dimensional space. It has been shown that correct Doppler shifts are obtained in the external spaces of these sources and the conformal correspondence between Doppler effect curves holds in case of approaching and receeding sources but not in the transverse case.

  12. The introduction of Superluminal Lorentz transformations: A revisitation

    NASA Astrophysics Data System (ADS)

    Maccarrone, G. D.; Recami, Erasmo

    1984-05-01

    We revisit the introduction of the Superluminal Lorentz transformations which carry from “bradyonic” inertial frames to “tachyonic” inertial frames, i.e., which transform time-like objects into space-like objects, and vice versa. It has long been known that special relativity can be extended to Superluminal observers only by increasing the number of dimensions of the space-time or—which is in a sense equivalent—by releasing the reality condition (i.e., introducing also imaginary quantities). In the past we always adopted the latter procedure. Here we show the connection between that procedure and the former one. In other words, in order to clarify the physical meaning of the imaginary units entering the classical theory of tachyons, we have temporarily to call into play an auxiliary six-dimensional space-time M (3, 3); however, we are eventually able to go back to the four-dimensional Minkowski space-time. We revisit the introduction of the Superluminal Lorentz transformations also under another aspect. In fact, the generalized Lorentz transformations had been previously written down in a form suited only for the simple case of collinear boosts (e.g., they formed a group just for collinear boosts). We express now the Superluminal Lorentz transformations in a more general form, so that they constitute a group together with the ordinary—orthochronous and antichronous—Lorentz transformations, and reduce to the previous form in the case of collinear boosts. Our approach introduces either real or imaginary quantities, with exclusion of (generic) complex quantities. In the present context, a procedure—in two steps—for interpreting the imaginary quantities is put forth and discussed. In the case of a chain of generalized Lorentz transformations, such a procedure (when necessary) is to be applied only at the end of the chain. Finally, we justify why we call “transformations” also the Superluminal ones.

  13. SN 2012au: A GOLDEN LINK BETWEEN SUPERLUMINOUS SUPERNOVAE AND THEIR LOWER-LUMINOSITY COUNTERPARTS

    SciTech Connect

    Milisavljevic, Dan; Soderberg, Alicia M.; Margutti, Raffaella; Drout, Maria R.; Marion, G. Howie; Sanders, Nathan E.; Lunnan, Ragnhild; Chornock, Ryan; Berger, Edo; Foley, Ryan J.; Challis, Pete; Kirshner, Robert P.; Dittmann, Jason; Bieryla, Allyson; Kamble, Atish; Chakraborti, Sayan; Hsiao, Eric Y.; Fesen, Robert A.; Parrent, Jerod T.; Levesque, Emily M.; and others

    2013-06-20

    We present optical and near-infrared observations of SN 2012au, a slow-evolving supernova (SN) with properties that suggest a link between subsets of energetic and H-poor SNe and superluminous SNe. SN 2012au exhibited conspicuous Type-Ib-like He I lines and other absorption features at velocities reaching Almost-Equal-To 2 Multiplication-Sign 10{sup 4} km s{sup -1} in its early spectra, and a broad light curve that peaked at M{sub B} = -18.1 mag. Models of these data indicate a large explosion kinetic energy of {approx}10{sup 52} erg and {sup 56}Ni mass ejection of M{sub Ni} Almost-Equal-To 0.3 M{sub Sun} on par with SN 1998bw. SN 2012au's spectra almost one year after explosion show a blend of persistent Fe II P-Cyg absorptions and nebular emissions originating from two distinct velocity regions. These late-time emissions include strong [Fe II], [Ca II], [O I], Mg I], and Na I lines at velocities {approx}> 4500 km s{sup -1}, as well as O I and Mg I lines at noticeably smaller velocities {approx}< 2000 km s{sup -1}. Many of the late-time properties of SN 2012au are similar to the slow-evolving hypernovae SN 1997dq and SN 1997ef, and the superluminous SN 2007bi. Our observations suggest that a single explosion mechanism may unify all of these events that span -21 {approx}< M{sub B} {approx}< -17 mag. The aspherical and possibly jetted explosion was most likely initiated by the core collapse of a massive progenitor star and created substantial high-density, low-velocity Ni-rich material.

  14. SN 2012au: A Golden Link between Superluminous Supernovae and Their Lower-luminosity Counterparts

    NASA Astrophysics Data System (ADS)

    Milisavljevic, Dan; Soderberg, Alicia M.; Margutti, Raffaella; Drout, Maria R.; Howie Marion, G.; Sanders, Nathan E.; Hsiao, Eric Y.; Lunnan, Ragnhild; Chornock, Ryan; Fesen, Robert A.; Parrent, Jerod T.; Levesque, Emily M.; Berger, Edo; Foley, Ryan J.; Challis, Pete; Kirshner, Robert P.; Dittmann, Jason; Bieryla, Allyson; Kamble, Atish; Chakraborti, Sayan; De Rosa, Gisella; Fausnaugh, Michael; Hainline, Kevin N.; Chen, Chien-Ting; Hickox, Ryan C.; Morrell, Nidia; Phillips, Mark M.; Stritzinger, Maximilian

    2013-06-01

    We present optical and near-infrared observations of SN 2012au, a slow-evolving supernova (SN) with properties that suggest a link between subsets of energetic and H-poor SNe and superluminous SNe. SN 2012au exhibited conspicuous Type-Ib-like He I lines and other absorption features at velocities reaching ≈2 × 104 km s-1 in its early spectra, and a broad light curve that peaked at MB = -18.1 mag. Models of these data indicate a large explosion kinetic energy of ~1052 erg and 56Ni mass ejection of M Ni ≈ 0.3 M ⊙ on par with SN 1998bw. SN 2012au's spectra almost one year after explosion show a blend of persistent Fe II P-Cyg absorptions and nebular emissions originating from two distinct velocity regions. These late-time emissions include strong [Fe II], [Ca II], [O I], Mg I], and Na I lines at velocities >~ 4500 km s-1, as well as O I and Mg I lines at noticeably smaller velocities <~ 2000 km s-1. Many of the late-time properties of SN 2012au are similar to the slow-evolving hypernovae SN 1997dq and SN 1997ef, and the superluminous SN 2007bi. Our observations suggest that a single explosion mechanism may unify all of these events that span -21 <~ MB <~ -17 mag. The aspherical and possibly jetted explosion was most likely initiated by the core collapse of a massive progenitor star and created substantial high-density, low-velocity Ni-rich material.

  15. Kinetic power of quasars and statistical excess of MOJAVE superluminal motions

    NASA Astrophysics Data System (ADS)

    López-Corredoira, M.; Perucho, M.

    2012-08-01

    Aims: The MOJAVE (MOnitoring of Jets in AGN with VLBA Experiments) survey contains 101 quasars with a total of 354 observed radio components that are different from the radio cores, among which 95% move with apparent projected superluminal velocities with respect to the core, and 45% have projected velocities larger than 10c (with a maximum velocity 60c). We try to determine whether this distribution is statistically probable, and we make an independent measure of the kinetic power required in the quasars to produce such powerful ejections. Methods: Doppler boosting effects are analyzed to determine the statistics of the superluminal motions. We integrate over all possible values of the Lorentz factor, the values of the kinetic energy corresponding to each component. The calculation of the mass in the ejection is carried out by assuming the minimum energy state, i.e., that the magnetic field and particle energy distributions are arranged in the most efficient way to produce the observed synchrotron emission. This kinetic energy is multiplied by the frequency at which the portions of the jet fluid identified as "blobs" are produced. Hence, we estimate the average total power released by the quasars in the form of kinetic energy in the long term on pc-scales. Results: A selection effect in which both the core and the blobs of the quasar are affected by huge Doppler-boosting enhancement increases the probability of finding a jet ejected within 10 degrees of the line of sight ≳ 40 times above what one would expect for a random distribution of ejection, which explains the ratios of the very high projected velocities given above. The average total kinetic power of each MOJAVE quasar should be very high to obtain this distribution: ~ 7 × 1047 erg/s. This amount is much higher than previous estimates of kinetic power on kpc-scales based on the analysis of cavities in X-ray gas or radio lobes in samples of objects of much lower radio luminosity but similar black hole

  16. Inverse Compton X-ray emission from the superluminal quasar 3C 345

    NASA Technical Reports Server (NTRS)

    Unwin, S. C.; Wehrle, A. E.; Urry, C. M.; Gilmore, D. M.; Barton, E. J.; Kjerulf, B. C.; Zensus, J. A.; Rabaca, C. R.

    1994-01-01

    In quasars with strong radio cores, the inverse-Compton process is believed to be the dominant source X-ray emission. For objects with parsec-scale radio jets, simple models have predicted that components in the jet emerging from the quasar nucleus generate the observed X-ray emission. We have tested this hypothesis in detail for the quasar 3C 345 using a ROSAT X-ray observation in 1990 July, together with quasi-simultaneous very long base interferometry (VLBI) imaging of the parsec-scale jet at five frequencies. The ROSAT spectrum is well fitted by a power law with index alpha = -0.96 +/- -0.13, consistent with models in which the X-ray emission results from inverse-Compton scattering of radio radiation from high-energy electrons in compact components. We show that the radio properties of brightest `knot' in the jet (`C5') can be fitted with a homogeneous sphere model whose parameters require bulk relativistic motion of the emitting material; otherwise the predicted model whose parameters require bulk relativistic motion of the emitting material; otherwise the predicted inverse-Compton X-ray emission exceeds the observed flux. If C5 is the origin of the X-ray emission, then it has a Doppler factor delta = 7.5((sup +3 sub -2)). If the nucleus or other components contribute to the X-ray emission, then this becomes a firm lower limit to delta. The inhomogeneous jet model of Koenigl is a good fit both to the barely resolved (less than 1 pc) flat-spectrum nucleus in the radio, and also to the ROSAT X-ray spectrum. The synchrotron and inverse-Compton emitting fluid moves down a narrow cone (opening angle 2 phi approximately 5 deg) nucleus relativistically, with delta approximately 4.6. Doppler factors for the nucleus and C5, derived from our ROSAT observation, provide evidence for bulk relativistic motion in the jet. By combining these constraints with well-known superluminal motion of jet components, we can deduce geometry. For epoch 1990.5 we infer the Lorentz factor

  17. Impossibility of superluminal travel in Lorentz violating theories

    NASA Astrophysics Data System (ADS)

    Coutant, Antonin; Finazzi, Stefano; Liberati, Stefano; Parentani, Renaud

    2012-03-01

    Warp drives are space-times allowing for superluminal travel. However, they are quantum mechanically unstable because they produce a Hawking-like radiation which is blue shifted at their front wall without any bound. We reexamine this instability when local Lorentz invariance is violated at ultrahigh energy by dispersion, as in some theories of quantum gravity. Interestingly, even though the ultraviolet divergence is now regulated, warp drives are still unstable. Moreover the type of instability is different whether one uses a subluminal or a superluminal dispersion relation. In the first case, a black-hole laser yields an exponential amplification of the emitted flux whereas, in the second, infrared effects produce a linear growth of that flux. These results suggest that chronology could still be protected when violating Lorentz invariance.

  18. Multi-Epoch Spectroscopy of Hydrogen-Poor Superluminous Supernovae

    NASA Astrophysics Data System (ADS)

    Quimby, Robert; De Cia, Annalisa; Gal-Yam, Avishay; Leloudas, Giorgos; Lunnan, Ragnhild; Perley, Daniel A.; Vreeswijk, Paul; Yan, Lin

    2016-06-01

    A growing sample of intrinsically rare supernovae is being uncovered by wide-field synoptic surveys, such as the Palomar Transient Factory (PTF). A fraction of these events have been labeled "superluminous supernovae" due to their peak luminosities, which can exceed normal supernovae by factors of 10 to 100. The power sources for these events and thus their connection to normal luminosity supernovae remains uncertain. Here we present results from 134 spectroscopic observations of 17 hydrogen-poor superluminous supernovae (SLSN-I) discovered by PTF. We select our targets from the full PTF sample using only spectroscopic information; we do not employ the traditional cut in absolute magnitude (e.g. M < -21) to avoid potential bias. Using our multi-epoch observations, we identify the ion species contributing to the spectroscopic features, and we perform parametric modeling to estimate photospheric velocities. Finally we discuss the physical insights into the nature of these explosions offered by this unique dataset.

  19. The hypothesis of superluminal neutrinos: Comparing OPERA with other data

    NASA Astrophysics Data System (ADS)

    Drago, A.; Masina, I.; Pagliara, G.; Tripiccione, R.

    2012-01-01

    The OPERA Collaboration reported evidence for muonic neutrinos traveling slightly faster than light in vacuum. While waiting further checks from the experimental community, here we aim at exploring some theoretical consequences of the hypothesis that muonic neutrinos are superluminal, considering in particular the tachyonic and the Coleman-Glashow cases. We show that a tachyonic interpretation is not only hardly reconciled with OPERA data on energy dependence, but that it clashes with neutrino production from pion and with neutrino oscillations. A Coleman-Glashow superluminal neutrino beam would also have problems with pion decay kinematics for the OPERA setup; it could be easily reconciled with SN1987a data, but then it would be very problematic to account for neutrino oscillations.

  20. Ultraviolet complete Lorentz-invariant theory with superluminal signal propagation

    NASA Astrophysics Data System (ADS)

    Cooper, Patrick; Dubovsky, Sergei; Mohsen, Ali

    2014-04-01

    We describe a UV complete asymptotically fragile Lorentz-invariant theory exhibiting superluminal signal propagation. Its low energy effective action contains "wrong" sign higher dimensional operators. Nevertheless, the theory gives rise to an S matrix, which is defined at all energies. As expected for a nonlocal theory, the corresponding scattering amplitudes are not exponentially bounded on the physical sheet, but otherwise are healthy. We study some of the physical consequences of this S matrix.

  1. ''Superluminal'' transmission via entanglement, superoscillations, and quasi-Dirac distributions

    SciTech Connect

    Sokolovski, D.; Mayato, R. Sala

    2010-02-15

    We analyze a system in which, due to entanglement between the spin and spatial degrees of freedom, the reduced transmitted state has the shape of the freely propagating pulse translated in the complex coordinate plane. In the case an apparently ''superluminal'' advancement of the pulse, the delay amplitude distribution is found to be a peculiar approximation to the Dirac {delta} function, and the transmission coefficient exhibits a well-defined superoscillatory window. Analogies with potential tunneling and Wheeler's delayed choice experiment are highlighted.

  2. Selectively Bringing Down the Curtain on OPERA Superluminal Neutrino Papers

    NASA Astrophysics Data System (ADS)

    Garisto, Robert

    2012-03-01

    Picture this: instead of watching from afar the daily flow of superluminal proposals trying to explain OPERA's preliminary data, you are the PRL Editor charged with deciding, via a peer review process, what to do with each paper. How do you address the validity of a manuscript whose starting point involves circumventing Einstein? I'll discuss the general issues of controversial claims and data-driven floods of theory papers through the unusual lens of the OPERA-motivated papers.

  3. Superluminal propagation of solitary kinklike waves in amplifying media.

    PubMed

    Janowicz, Maciej; Mostowski, Jan

    2006-04-01

    It is shown that solitary-wave, kinklike structures can propagate superluminally in two- and four-level amplifying media with strongly damped oscillations of coherences. This is done by solving analytically the Maxwell-Bloch equations in the kinetic limit. It is also shown that the true wave fronts--unlike the pseudo wave fronts of the kinks--must propagate with velocity c, so that no violation of special relativity is possible. The conditions of experimental verification are discussed. PMID:16711948

  4. Galactic dynamos

    NASA Astrophysics Data System (ADS)

    Moss, David

    There is a broad agreement between the predictions of galactic dynamo theory and observations; although there are still some unresolved difficulties, the theory appears to be robust. Now attention is turning from generic models to studies of particular features of the large-scale magnetic fields, and also to models for specific galaxies. The effects of noncircular flows, for example driven by the interaction of spiral arms and galactic bars with the dynamo, are of current interest.

  5. Panchromatic Views of Large-Scale Extragalactic Jets

    SciTech Connect

    Cheung, C.C.; /KIPAC, Menlo Park

    2007-06-01

    Highlights of recent observations of extended jets in AGN are presented. Specifically, we discuss new spectral constraints enabled by Spitzer, studies of the highest-redshift (z{approx}4) radio/X-ray quasar jets, and a new VLBA detection of superluminal motion in the M87 jet associated with a recent dramatic X-ray outburst. Expanding on the title, inverse Compton emission from extended radio lobes is considered and a testable prediction for the gamma-ray emission in one exemplary example is presented. Prospects for future studies with ALMA and low-frequency radio interferometers are briefly described.

  6. Six-dimensional formulation of the quantum theory of superluminal particles

    SciTech Connect

    Patty, C.E. Jr.

    1983-01-01

    By operating in a six dimensional spacetime, transformations which relate superluminal to subluminal observers and do not introduce imaginary numbers are developed. These transformations preserve the Lorentz invariance of physical quantities. A six dimensional quantum theory is built upon this spacetime. All formal properties and the operators of the four dimensional Dirac quantum theory are duplicated. In addition, the extended quantum theory predicts the known behavior of subliminal matter and permits the calculation of the behavior of superluminal matter. The most distinctive characteristics of superluminal matter are found to be a spatial polarization during interactions with subluminal matter and an intrensic multi-temporal nature. The theory is applied to the Rutherford scattering problem for an incident beam of electrons. The results of the calculation indicate that the behavior of superluminal matter differs in an unambigious way from that of subluminal matter. The superluminal state is detectable.

  7. OPTICAL PROPER MOTION MEASUREMENTS OF THE M87 JET: NEW RESULTS FROM THE HUBBLE SPACE TELESCOPE

    SciTech Connect

    Meyer, Eileen T.; Sparks, W. B.; Biretta, J. A.; Anderson, Jay; Sohn, Sangmo Tony; Van der Marel, Roeland P.; Norman, Colin; Nakamura, Masanori

    2013-09-10

    We report new results from a Hubble Space Telescope archival program to study proper motions in the optical jet of the nearby radio galaxy M87. Using over 13 yr of archival imaging, we reach accuracies below 0.1c in measuring the apparent velocities of individual knots in the jet. We confirm previous findings of speeds up to 4.5c in the inner 6'' of the jet, and report new speeds for optical components in the outer part of the jet. We find evidence of significant motion transverse to the jet axis on the order of 0.6c in the inner jet features, and superluminal velocities parallel and transverse to the jet in the outer knot components, with an apparent ordering of velocity vectors possibly consistent with a helical jet pattern. Previous results suggested a global deceleration over the length of the jet in the form of decreasing maximum speeds of knot components from HST-1 outward, but our results suggest that superluminal speeds persist out to knot C, with large differentials in very nearby features all along the jet. We find significant apparent accelerations in directions parallel and transverse to the jet axis, along with evidence for stationary features in knots D, E, and I. These results are expected to place important constraints on detailed models of kiloparsec-scale relativistic jets.

  8. Galactic Winds

    NASA Astrophysics Data System (ADS)

    Veilleux, Sylvain

    Galactic winds have become arguably one of the hottest topics in extragalactic astronomy. This enthusiasm for galactic winds is due in part to the detection of winds in many, if not most, high-redshift galaxies. Galactic winds have also been invoked by theorists to (1) suppress the number of visible dwarf galaxies and avoid the "cooling catastrophe" at high redshift that results in the overproduction of massive luminous galaxies, (2) remove material with low specific angular momentum early on and help enlarge gas disks in CDM + baryons simulations, (3) reduce the dark mass concentrations in galaxies, (4) explain the mass-metallicity relation of galaxies from selective loss of metal-enriched gas from smaller galaxies, (5) enrich and "preheat" the ICM, (6) enrich the IGM without disturbing the Lyαforest significantly, and (7) inhibit cooling flows in galaxy clusters with active cD galaxies. The present paper highlights a few key aspects of galactic winds taken from a recent ARAA review by Veilleux, Cecil, &Bland-Hawthorn (2005; herafter VCBH). Readers interested in a more detailed discussion of this topic are encouraged to refer to the original ARAA article.

  9. Towards Parsec-Scale Jet Speed Measurements for the Full TeV Blazar Sample

    NASA Astrophysics Data System (ADS)

    Piner, B. Glenn; Edwards, Phillip

    2016-06-01

    We present new multi-epoch Very Long Baseline Array (VLBA) observations of TeV blazars drawn from our VLBA program to monitor all TeV-detected high-frequency peaked BL Lac objects (HBLs) at the parsec scale. Many of these sources are faint in the radio (flux densities of a few millijanskys) so they have not been previously well observed with VLBI techniques by other surveys. Our previous measurements of apparent jet speeds in of order a dozen TeV HBLs showed apparent jet speeds that were subluminal or barely superluminal; suggesting jets with velocity structures at the parsec-scale. Here we present apparent jet speed measurements for eight new sources, which for the first time show a superluminal tail to the apparent speed distribution for the TeV HBLs.

  10. Superluminal Spot Pair Events in Astronomical Settings: Sweeping Beams

    NASA Astrophysics Data System (ADS)

    Nemiroff, Robert J.

    2015-02-01

    Sweeping beams of light can cast spots moving with superluminal speeds across scattering surfaces. Such faster-than-light speeds are well-known phenomena that do not violate special relativity. It is shown here that under certain circumstances, superluminal spot pair creation and annihilation events can occur that provide unique information to observers. These spot pair events are not particle pair events-they are the sudden creation or annihilation of a pair of relatively illuminated spots on a scattering surface. Real spot pair illumination events occur unambiguously on the scattering surface when spot speeds diverge, while virtual spot pair events are observer dependent and perceived only when real spot radial speeds cross the speed of light. Specifically, a virtual spot pair creation event will be observed when a real spot's speed toward the observer drops below c, while a virtual spot pair annihilation event will be observed when a real spot's radial speed away from the observer rises above c. Superluminal spot pair events might be found angularly, photometrically, or polarimetrically, and might carry useful geometry or distance information. Two example scenarios are briefly considered. The first is a beam swept across a scattering spherical object, exemplified by spots of light moving across Earth's Moon and pulsar companions. The second is a beam swept across a scattering planar wall or linear filament, exemplified by spots of light moving across variable nebulae including Hubble's Variable Nebula. In local cases where the sweeping beam can be controlled and repeated, a three-dimensional map of a target object can be constructed. Used tomographically, this imaging technique is fundamentally different from lens photography, radar, and conventional lidar.

  11. Conditions for Lorentz-invariant superluminal information transfer without signaling

    NASA Astrophysics Data System (ADS)

    Grössing, G.; Fussy, S.; Mesa Pascasio, J.; Schwabl, H.

    2016-03-01

    We understand emergent quantum mechanics in the sense that quantum mechanics describes processes of physical emergence relating an assumed sub-quantum physics to macroscopic boundary conditions. The latter can be shown to entail top-down causation, in addition to usual bottom-up scenarios. With this example it is demonstrated that definitions of “realism” in the literature are simply too restrictive. A prevailing manner to define realism in quantum mechanics is in terms of pre-determination independent of the measurement. With our counter-example, which actually is ubiquitous in emergent, or self-organizing, systems, we argue for realism without pre-determination. We refer to earlier results of our group showing how the guiding equation of the de Broglie-Bohm interpretation can be derived from a theory with classical ingredients only. Essentially, this corresponds to a “quantum mechanics without wave functions” in ordinary 3-space, albeit with nonlocal correlations. This, then, leads to the central question of how to deal with the nonlocality problem in a relativistic setting. We here show that a basic argument discussing the allegedly paradox time ordering of events in EPR-type two-particle experiments falls short of taking into account the contextuality of the experimental setup. Consequently, we then discuss under which circumstances (i.e. physical premises) superluminal information transfer (but not signaling) may be compatible with a Lorentz-invariant theory. Finally, we argue that the impossibility of superluminal signaling - despite the presence of superluminal information transfer - is not the result of some sort of conspiracy (á la “Nature likes to hide”), but the consequence of the impossibility to exactly reproduce in repeated experimental runs a state's preparation, or of the no-cloning theorem, respectively.

  12. Slow Light and Superluminality in Kerr Media without a Pump

    NASA Astrophysics Data System (ADS)

    Yang, Qiguang; Seo, Jae Tae; Tabibi, Bagher; Wang, Huitian

    2005-08-01

    Subluminal and superluminal propagation of a light pulse in Kerr materials has been investigated. Group velocities as slow as much less than 1 mm per second to as fast as negative several thousands meters per second can easily be obtained in the Kerr medium, which possesses a large nonlinear refractive index and long relaxation time, such as Cr3+-doped alexandrite, ruby, and GdAlO3. The physical mechanism is the strong highly dispersive coupling between different frequency components of the pulse.

  13. Dynamics of relativistic jets

    NASA Astrophysics Data System (ADS)

    Nishikawa, K.-I.; Frank, J.; Christodoulou, D. M.; Koide, S.; Sakai, J.-I.; Sol, Hélène; Mutel, Robert L.

    1998-12-01

    We discuss the structure and relativistic kinematics that develop in three spatial dimensions when a moderately hot, supersonic jet propagates into a denser background medium and encounters resistance from an oblique magnetic field. Our simulations incorporate relativistic MHD in a four-dimensional spacetime and clearly show that (a) relatively weak, oblique fields (at 1/16 of the equipartition value) have only a negligible influence on the propagating jet and they are passively pushed away by the relativistically moving head; (b) oblique fields in equipartition with the ambient plasma provide more resistance and cause bending at the jet head, but the magnitude of this deflection and the associated backflow are small compared to those identified by previous studies. The new results are understood as follows: Relativistic simulations have consistently shown that these jets are effectively heavy and so they do not suffer substantial momentum losses and are not decelerated as efficiently as their nonrelativistic counterparts. In addition, the ambient magnetic field, however strong, can be pushed aside with relative ease by the beam, provided that the degrees of freedom associated with all three spatial dimensions are followed self-consistently during the simulations. The effect is analogous to pushing Japanese "noren" or vertical Venetian blinds out of the way while the slats are allowed to bend and twist in 3-D space. Applied to relativistic extragalactic jets from blazars, the new results are encouraging since superluminal outflows exhibit bending near their sources and their environments are profoundly magnetized - but observations do not provide support for irregular kinematics such as large-scale vortical motions and pronounced reverse flows near the points of origin.

  14. Superluminal Neutrinos from Special Relativity with de Sitter Spacetime Symmetry

    NASA Astrophysics Data System (ADS)

    Yan, Mu-Lin; Xiao, Neng-Chao; Huang, Wei; Hu, Sen

    2012-05-01

    We explore the recent OPERA experiment of superluminal neutrinos in the framework of special relativity with de Sitter spacetime symmetry (dS-SR). According to Einstein, a photon is treated as a massless particle in the framework of special relativity. In special relativity (SR) we have the universal parameter c, the photon velocity cphoton and the phase velocity of a light wave in vacuum cwave = λν. Due to the null experiments of Michelson-Morley we have c = cwave. The parameter cphoton is determined by the Noether charges corresponding to the spacetime symmetries of SR. In Einstein's special relativity (E-SR) we have c = cphoton. In dS-SR, i.e. the special relativity with SO(4, 1) de Sitter spacetime symmetry, we have cphoton > c. In this paper, the OPERA datum are examined in the framework of dS-SR. We show that OPERA anomaly is in agreement with the prediction of dS-SR with R≃1.95×1012 l.y. Based on the p-E relation of dS-SR, we also prove that the Cohen and Glashow's argument of possible superluminal neutrino's Cherenkov-like radiation is forbidden. We conclude that OPERA and ICARUS results are consistent and they are explained in the dS-SR framework.

  15. Radiation from Relativistic Jets

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.-I.; Mizuno, Y.; Hardee, P.; Sol, H.; Medvedev, M.; Zhang, B.; Nordlund, A.; Frederiksen, J. T.; Fishman, G. J.; Preece, R.

    2008-01-01

    Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., gamma-ray bursts (GRBs), active galactic nuclei (AGNs), and Galactic microquasar systems usually have power-law emission spectra. Recent PIC simulations of relativistic electron-ion (electron-positron) jets injected into a stationary medium show that particle acceleration occurs within the downstream jet. In the presence of relativistic jets, instabilities such as the Buneman instability, other two-streaming instability, and the Weibel (filamentation) instability create collisionless shocks, which are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the jet head. The 'jitter' radiation from deflected electrons in small-scale magnetic fields has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation, a case of diffusive synchrotron radiation, may be important to understand the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.

  16. Superluminal motion in the double-lobed quasar 3C263

    NASA Technical Reports Server (NTRS)

    Zensus, J. A.; Hough, D. H.; Porcas, R. W.

    1987-01-01

    The detection of superluminal motion in the quasar 3C263 is reported. The milliarcsecond structure of this source consists of two nearly unresolved components whose separation is increasing at a rate of 0.06 + or - 0.02 marcsec/yr. This corresponds to an expansion speed of 2.7 + or - 0.9 c (H/0/ = 55 km/s/Mpc, q/0/ = 0.05). This quasar is the weakest superluminal source found so far, and there are indications that superluminal motion occurs frequently in this class of object.

  17. Towards Observational Astronomy of Jets in Active Galaxies from General Relativistic Magnetohydrodynamic Simulations

    NASA Astrophysics Data System (ADS)

    Anantua, Richard; Roger Blandford, Jonathan McKinney and Alexander Tchekhovskoy

    2016-01-01

    We carry out the process of "observing" simulations of active galactic nuclei (AGN) with relativistic jets (hereafter called jet/accretion disk/black hole (JAB) systems) from ray tracing between image plane and source to convolving the resulting images with a point spread function. Images are generated at arbitrary observer angle relative to the black hole spin axis by implementing spatial and temporal interpolation of conserved magnetohydrodynamic flow quantities from a time series of output datablocks from fully general relativistic 3D simulations. We also describe the evolution of simulations of JAB systems' dynamical and kinematic variables, e.g., velocity shear and momentum density, respectively, and the variation of these variables with respect to observer polar and azimuthal angles. We produce, at frequencies from radio to optical, fixed observer time intensity and polarization maps using various plasma physics motivated prescriptions for the emissivity function of physical quantities from the simulation output, and analyze the corresponding light curves. Our hypothesis is that this approach reproduces observed features of JAB systems such as superluminal bulk flow projections and quasi-periodic oscillations in the light curves more closely than extant stylized analytical models, e.g., cannonball bulk flows. Moreover, our development of user-friendly, versatile C++ routines for processing images of state-of-the-art simulations of JAB systems may afford greater flexibility for observing a wide range of sources from high power BL-Lacs to low power quasars (possibly with the same simulation) without requiring years of observation using multiple telescopes. Advantages of observing simulations instead of observing astrophysical sources directly include: the absence of a diffraction limit, panoramic views of the same object and the ability to freely track features. Light travel time effects become significant for high Lorentz factor and small angles between

  18. Constraining neutrino superluminality from searches for sterile neutrino decays

    NASA Astrophysics Data System (ADS)

    Gorbunov, D. S.; Nugaev, E. Ya.

    2012-07-01

    Superluminal neutrinos are expected to lose energy due to bremsstrahlung. It is dominated by e+e--pair production if kinematically allowed. The same signature was used in searches for 3-body decays of hypothetical heavy sterile neutrinos. From the published analyses of these searches performed by CERN PS191 and CHARM experiments we set upper limits on the neutrino velocity in the energy range from 0.2 GeV to 280 GeV. Our limits are well below the neutrino velocity favored by the recent OPERA results. For energy-independent neutrino velocity the limits obtained in this Letter are stronger than those coming from ICARUS experiment and observations of Supernova SN1987a.

  19. PROPAGATION AND STABILITY OF SUPERLUMINAL WAVES IN PULSAR WINDS

    SciTech Connect

    Mochol, Iwona; Kirk, John G. E-mail: john.kirk@mpi-hd.mpg.de

    2013-07-01

    Nonlinear electromagnetic waves with superluminal phase velocity can propagate in the winds around isolated pulsars, and around some pulsars in binary systems. Using a short-wavelength approximation, we find and analyze an integrable system of equations that govern their evolution in spherical geometry. A confined mode is identified that stagnates to finite pressure at large radius and can form a precursor to the termination shock. Using a simplified criterion, we find this mode is stable for most isolated pulsars, but may be unstable if the external pressure is high, such as in the pulsar wind nebulae in starburst galaxies and in W44. Pulsar winds in eccentric binary systems, such as PSR 1259-63, may go through phases with stable and unstable electromagnetic precursors, as well as phases in which the density is too high for these modes to propagate.

  20. Swift X-Ray Telescope Observations of Superluminous Supernovae

    NASA Astrophysics Data System (ADS)

    Kae Batara Olaes, Melanie; Quimby, Robert

    2016-06-01

    Superluminous Supernovae (SLSNe) are a part of an emerging class of exceptionally bright supernovae with peak luminosities 10 times brighter than typical Type Ia supernovae. Similar to supernovae, SLSNe are divided into two subclasses: hydrogen poor SLSN-I and hydrogen rich SLSN-II. However, the luminosity of these events is far too high to be explained by the models for normal supernovae. New models developed to explain SLSNe predict high luminosity X-ray emission at late times. A consistent analysis of incoming SLSNe is essential in order to place constraints on the mechanisms behind these events. Here we present the results of X-ray analysis on SLSNe using a Bayesian method of statistical inference for low count rate events.

  1. Quantum interactions with closed timelike curves and superluminal signaling

    NASA Astrophysics Data System (ADS)

    Bub, Jeffrey; Stairs, Allen

    2014-02-01

    There is now a significant body of results on quantum interactions with closed timelike curves (CTCs) in the quantum information literature, for both the Deutsch model of CTC interactions (D-CTCs) and the projective model (P-CTCs). As a consequence, there is a prima facie argument exploiting entanglement that CTC interactions would enable superluminal and, indeed, effectively instantaneous signaling. In cases of spacelike separation between the sender of a signal and the receiver, whether a receiver measures the local part of an entangled state or a disentangled state to access the signal can depend on the reference frame. We propose a consistency condition that gives priority to either an entangled perspective or a disentangled perspective in spacelike-separated scenarios. For D-CTC interactions, the consistency condition gives priority to frames of reference in which the state is disentangled, while for P-CTC interactions the condition selects the entangled state. Using the consistency condition, we show that there is a procedure that allows Alice to signal to Bob in the past via relayed superluminal communications between spacelike-separated Alice and Clio, and spacelike-separated Clio and Bob. This opens the door to time travel paradoxes in the classical domain. Ralph [T. C. Ralph, arXiv:1107.4675 [quant-ph].] first pointed this out for P-CTCs, but we show that Ralph's procedure for a "radio to the past" is flawed. Since both D-CTCs and P-CTCs allow classical information to be sent around a spacetime loop, it follows from a result by Aaronson and Watrous [S. Aaronson and J. Watrous, Proc. R. Soc. A 465, 631 (2009), 10.1098/rspa.2008.0350] for CTC-enhanced classical computation that a quantum computer with access to P-CTCs would have the power of PSPACE, equivalent to a D-CTC-enhanced quantum computer.

  2. Radio Jet Interactions with Massive Clouds

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Wiita, P. J.; Joyce, J.; Hooda, J. S.

    1998-12-01

    Rather high resolution three-dimensional simulations of hydrodynamical jets are computed using the Zeus-3D code. The parameters we employ are suitable for moderate to high power radio jets emerging through a galactic atmosphere or halo, and eventually crossing a tilted pressure matched interface with a hotter intracluster medium. Before they cross this interface, these simulations aim the jets so that they hit massive clouds within the galactic halo, with densities 10 or more times higher than the ambient atmospheric density, and 100's of times the jet density. Such clouds are set up with radii several times that of the jet, and could correspond to giant molecular cloud complexes or small cannibalized galaxies. We find that powerful jets eventually disperse the clouds, but that, for off-center collisions, non-axisymmetric instabilities are induced in those jets. Those instabilities grow faster for lower Mach number jets, and can produce disruptions substantially sooner than occurred in our earlier work on jets crossing tilted interfaces in the absence of collisions with massive clouds. Such interactions, particularly with weaker jets, could be related to some Compact Steep Spectrum source morphologies. Very weak jets can be effectively halted by reasonably massive clouds, and this may have relevance for the paucity of radio jets in spiral galaxies. The possibility of jets being bent, yet remaining stable, after such collisions is also investigated. This work was supported by NPACI allocation GSU200 on the Cray T90 and by RPE funds at Georgia State University.

  3. Galactic Evolution

    NASA Astrophysics Data System (ADS)

    Brekke, Stewart

    2013-04-01

    All galaxies began as spiral galaxies. The early universe began with sets of two or more pre-galactic arms orbiting each other. As gravitational attraction between the arms took effect, the fore-sections of the arms tangentially collided forming spiral galaxies when they attached with the orbital motion of the arms being converted to the rotational motion of the newly formed spiral galaxies or (Iφ)arm1+ (Iφ)arm2+ ...+ (Iφ)armn= (Iφ)galaxy. If the centripetal force on the arms is more than the gravitational force on the arms, the spiral galaxy remains a spiral galaxy i.e. mv^2/r>=Gmarmmgalaxy/r^2. If the galaxy is slowly rotating, the spiral arms collapse into the body of the galaxy because the gravitational force is greater than the centripetal force on the arms and an elliptical galaxy is formed i.e. mv^2/r < Gmarmsmgalaxy/r^2.

  4. The Parsec-Scale Jet of Quasar 3C345

    NASA Astrophysics Data System (ADS)

    Zensus, J. A.; Rabaca, C. R.

    1993-12-01

    We discuss the parsec-scale structure of the superluminal quasar 3C345. Monitoring of the structure with VLBI at cm and mm wavelengths has shown apparent superluminal motion of at least four distinct emission features, over a distance of more than 40 pc from the stationary core (Zensus, Cohen, and Unwin, submitted to APJ). Near the core, the projected trajectories are curved and different for individual components, indicative of more complicated flow patterns than previously suspected, and consistent with motion along helical paths. The motion accelerates with increasing separation from the core, as the jet curves towards the extended kiloparsec structure. The flux evolution of individual components can be described using a generalized shock model. We apply this to component C4 and discuss the impact of orientation effects and implications for specific shock models.

  5. On particle acceleration in astrophysical relativistic jets

    NASA Astrophysics Data System (ADS)

    Medvedev, Mikhail

    2015-11-01

    Relativistic jets, e.g., in active galactic nuclei, are believed to be accelerators of high-energy cosmic rays. This is a lore but no justification of it exists. We investigate this problem from the first principles and present arguments that ``no-jets'' are better accelerators than the jets themselves. Supported by grant DOE grant DE-FG02-07ER54940 and NSF grant AST-1209665.

  6. Twin Jet

    NASA Technical Reports Server (NTRS)

    Henderson, Brenda; Bozak, Rick

    2010-01-01

    Many subsonic and supersonic vehicles in the current fleet have multiple engines mounted near one another. Some future vehicle concepts may use innovative propulsion systems such as distributed propulsion which will result in multiple jets mounted in close proximity. Engine configurations with multiple jets have the ability to exploit jet-by-jet shielding which may significantly reduce noise. Jet-by-jet shielding is the ability of one jet to shield noise that is emitted by another jet. The sensitivity of jet-by-jet shielding to jet spacing and simulated flight stream Mach number are not well understood. The current experiment investigates the impact of jet spacing, jet operating condition, and flight stream Mach number on the noise radiated from subsonic and supersonic twin jets.

  7. Blazar Jets Push Closer to Cosmic Speed Limit

    NASA Astrophysics Data System (ADS)

    2005-01-01

    Astronomers using the National Science Foundation's Very Long Baseline Array (VLBA) have discovered jets of plasma blasted from the cores of distant galaxies at speeds within one-tenth of one percent of the speed of light, placing these plasma jets among the fastest objects yet seen in the Universe. "This tells us that the physical processes at the cores of these galaxies, called blazars, are extremely energetic and are capable of propelling matter very close to the absolute cosmic speed limit," said Glenn Piner of Whittier College in Whittier, California. Piner, who worked on the project with student Dipesh Bhattari, also of Whittier College, Philip Edwards of the Japan Aerospace Exploration Agency, and Dayton Jones of NASA's Jet Propulsion Laboratory, presented their findings to the American Astronomical Society's meeting in San Diego, California. According to Einstein's Special Theory of Relativity, no object with mass can be accelerated to the speed of light. To get even close to the speed of light requires enormous amounts of energy. "For example, to accelerate a bowling ball to the speed newly measured in these blazars would require all the energy produced in the world for an entire week," Piner said, "and the blobs of plasma in these jets are at least as massive as a large planet". Blazars are active galactic nuclei -- energetic regions surrounding massive black holes at the centers of galaxies. Material being drawn into the black hole forms a spinning disk called an accretion disk. Powerful jets of charged particles are ejected at high speeds along the poles of accretion disks. When these jets happen to be aimed nearly toward the Earth, the objects are called blazars. Taking advantage of the extremely sharp radio "vision" of the continent-wide VLBA, the scientists tracked individual features in the jets of three blazars at distances from Earth ranging from 7.3 to 9 billion light-years. A Boston University team led by Svetlana Jorstad earlier had identified

  8. CONNECTION BETWEEN THE ACCRETION DISK AND JET IN THE RADIO GALAXY 3C 111

    SciTech Connect

    Chatterjee, Ritaban; Marscher, Alan P.; Jorstad, Svetlana G.; Harrison, Brandon; Agudo, Ivan; Taylor, Brian W.; Markowitz, Alex; Rivers, Elizabeth; Rothschild, Richard E.; McHardy, Ian M.; Aller, Margo F.; Aller, Hugh D.; Laehteenmaeki, Anne; Tornikoski, Merja; Gomez, Jose L.; Gurwell, Mark

    2011-06-10

    We present the results of extensive multi-frequency monitoring of the radio galaxy 3C 111 between 2004 and 2010 at X-ray (2.4-10 keV), optical (R band), and radio (14.5, 37, and 230 GHz) wave bands, as well as multi-epoch imaging with the Very Long Baseline Array (VLBA) at 43 GHz. Over the six years of observation, significant dips in the X-ray light curve are followed by ejections of bright superluminal knots in the VLBA images. This shows a clear connection between the radiative state near the black hole, where the X-rays are produced, and events in the jet. The X-ray continuum flux and Fe line intensity are strongly correlated, with a time lag shorter than 90 days and consistent with zero. This implies that the Fe line is generated within 90 lt-day of the source of the X-ray continuum. The power spectral density function of X-ray variations contains a break, with a steeper slope at shorter timescales. The break timescale of 13{sup +12}{sub -6} days is commensurate with scaling according to the mass of the central black hole based on observations of Seyfert galaxies and black hole X-ray binaries (BHXRBs). The data are consistent with the standard paradigm, in which the X-rays are predominantly produced by inverse Compton scattering of thermal optical/UV seed photons from the accretion disk by a distribution of hot electrons-the corona-situated near the disk. Most of the optical emission is generated in the accretion disk due to reprocessing of the X-ray emission. The relationships that we have uncovered between the accretion disk and the jet in 3C 111, as well as in the Fanaroff-Riley class I radio galaxy 3C 120 in a previous paper, support the paradigm that active galactic nuclei and Galactic BHXRBs are fundamentally similar, with characteristic time and size scales proportional to the mass of the central black hole.

  9. Superluminous Supernovae: A Pan-STARRS1 Perspective

    NASA Astrophysics Data System (ADS)

    Lunnan, Ragnhild; Chornock, Ryan; Berger, Edo; Pan-Starrs1 Cfa/Jhu Transient Team

    2015-01-01

    Wide-field optical time-domain surveys like Pan-STARRS and PTF provide an opportunity to discover and decipher new types of transients. One such discovery in the past decade is a new class of "superluminous" supernovae (SLSNe), which have bolometric luminosities 10-100 times those of normal core-collapse and Type Ia SN and spectra that do not match known supernova classes. These SLSNe represent a challenge to our understanding of the deaths of massive stars, the mechanism for powering optical emission in SNe, and to the standard core-collapse picture. In this talk, I will present results from the Pan-STARRS1 Medium Deep Survey, which has discovered ~20 SLSNe out to redshift 1.6 in its four years of operation. I will address the nature of SLSNe from two angles: 1) by characterizing the explosions themselves and comparing the observed properties to model predictions, and 2) by constraining the progenitor population through a comprehensive study of SLSN host galaxy environments.

  10. Rapidly Rising Transients in the Supernova—Superluminous Supernova Gap

    NASA Astrophysics Data System (ADS)

    Arcavi, Iair; Wolf, William M.; Howell, D. Andrew; Bildsten, Lars; Leloudas, Giorgos; Hardin, Delphine; Prajs, Szymon; Perley, Daniel A.; Svirski, Gilad; Gal-Yam, Avishay; Katz, Boaz; McCully, Curtis; Cenko, S. Bradley; Lidman, Chris; Sullivan, Mark; Valenti, Stefano; Astier, Pierre; Balland, Cristophe; Carlberg, Ray G.; Conley, Alex; Fouchez, Dominique; Guy, Julien; Pain, Reynald; Palanque-Delabrouille, Nathalie; Perrett, Kathy; Pritchet, Chris J.; Regnault, Nicolas; Rich, James; Ruhlmann-Kleider, Vanina

    2016-03-01

    We present observations of four rapidly rising (trise ≈ 10 days) transients with peak luminosities between those of supernovae (SNe) and superluminous SNe (Mpeak ≈ -20)—one discovered and followed by the Palomar Transient Factory (PTF) and three by the Supernova Legacy Survey. The light curves resemble those of SN 2011kl, recently shown to be associated with an ultra-long-duration gamma-ray burst (GRB), though no GRB was seen to accompany our SNe. The rapid rise to a luminous peak places these events in a unique part of SN phase space, challenging standard SN emission mechanisms. Spectra of the PTF event formally classify it as an SN II due to broad Hα emission, but an unusual absorption feature, which can be interpreted as either high velocity Hα (though deeper than in previously known cases) or Si ii (as seen in SNe Ia), is also observed. We find that existing models of white dwarf detonations, CSM interaction, shock breakout in a wind (or steeper CSM), and magnetar spin down cannot readily explain the observations. We consider the possibility that a “Type 1.5 SN” scenario could be the origin of our events. More detailed models for these kinds of transients and more constraining observations of future such events should help to better determine their nature.

  11. Astronomy. ASASSN-15lh: A highly super-luminous supernova.

    PubMed

    Dong, Subo; Shappee, B J; Prieto, J L; Jha, S W; Stanek, K Z; Holoien, T W-S; Kochanek, C S; Thompson, T A; Morrell, N; Thompson, I B; Basu, U; Beacom, J F; Bersier, D; Brimacombe, J; Brown, J S; Bufano, F; Chen, Ping; Conseil, E; Danilet, A B; Falco, E; Grupe, D; Kiyota, S; Masi, G; Nicholls, B; Olivares E, F; Pignata, G; Pojmanski, G; Simonian, G V; Szczygiel, D M; Woźniak, P R

    2016-01-15

    We report the discovery of ASASSN-15lh (SN 2015L), which we interpret as the most luminous supernova yet found. At redshift z = 0.2326, ASASSN-15lh reached an absolute magnitude of Mu ,AB = -23.5 ± 0.1 and bolometric luminosity Lbol = (2.2 ± 0.2) × 10(45) ergs s(-1), which is more than twice as luminous as any previously known supernova. It has several major features characteristic of the hydrogen-poor super-luminous supernovae (SLSNe-I), whose energy sources and progenitors are currently poorly understood. In contrast to most previously known SLSNe-I that reside in star-forming dwarf galaxies, ASASSN-15lh appears to be hosted by a luminous galaxy (MK ≈ -25.5) with little star formation. In the 4 months since first detection, ASASSN-15lh radiated (1.1 ± 0.2) × 10(52) ergs, challenging the magnetar model for its engine. PMID:26816375

  12. ASASSN-15lh: A highly super-luminous supernova

    NASA Astrophysics Data System (ADS)

    Dong, Subo; Shappee, B. J.; Prieto, J. L.; Jha, S. W.; Stanek, K. Z.; Holoien, T. W.-S.; Kochanek, C. S.; Thompson, T. A.; Morrell, N.; Thompson, I. B.; Basu, U.; Beacom, J. F.; Bersier, D.; Brimacombe, J.; Brown, J. S.; Bufano, F.; Chen, Ping; Conseil, E.; Danilet, A. B.; Falco, E.; Grupe, D.; Kiyota, S.; Masi, G.; Nicholls, B.; Olivares E., F.; Pignata, G.; Pojmanski, G.; Simonian, G. V.; Szczygiel, D. M.; Woźniak, P. R.

    2016-01-01

    We report the discovery of ASASSN-15lh (SN 2015L), which we interpret as the most luminous supernova yet found. At redshift z = 0.2326, ASASSN-15lh reached an absolute magnitude of Mu,AB = -23.5 ± 0.1 and bolometric luminosity Lbol = (2.2 ± 0.2) × 1045 ergs s-1, which is more than twice as luminous as any previously known supernova. It has several major features characteristic of the hydrogen-poor super-luminous supernovae (SLSNe-I), whose energy sources and progenitors are currently poorly understood. In contrast to most previously known SLSNe-I that reside in star-forming dwarf galaxies, ASASSN-15lh appears to be hosted by a luminous galaxy (MK ≈ -25.5) with little star formation. In the 4 months since first detection, ASASSN-15lh radiated (1.1 ± 0.2) × 1052 ergs, challenging the magnetar model for its engine.

  13. Radio jet interactions with massive clouds

    NASA Astrophysics Data System (ADS)

    Wiita, Paul J.; Wang, Zhongxiang; Hooda, Jagbir S.

    2002-05-01

    Three-dimensional simulations of light hydrodynamic jets are computed using the Zeus-3D code. We employ parameters corresponding to moderate to high power radio jets emerging through a galactic atmosphere or halo, and eventually crossing a tilted pressure matched interface with a hotter intracluster medium. These simulations aim the jets so that they hit massive dense clouds within the galactic halo. Such clouds are set up with radii several times that of the jet, and nominally correspond to giant molecular cloud complexes or small cannibalized galaxies. We find that powerful jets eventually disperse the clouds, but that, for the off-center collisions considered, non-axisymmetric instabilities are induced in those jets. Those instabilities grow faster for lower Mach number jets, and can produce disruptions substantially sooner than occurred in our earlier work on jets in the absence of collisions with massive clouds. Such interactions could be related to some Compact Steep Spectrum source morphologies. Very weak jets can be effectively halted by reasonably massive clouds, and this may have relevance for the paucity of radio jets in spiral galaxies. Slow, dense jets may be bent, yet remain stable for fairly extended times, thereby explaining some Wide-Angle-Tail and most "dog-leg" morphologies.

  14. Jet shielding of jet noise

    NASA Technical Reports Server (NTRS)

    Simonich, J. C.; Amiet, R. K.; Schlinker, R. H.

    1986-01-01

    An experimental and theoretical study was conducted to develop a validated first principle analysis for predicting the jet noise reduction achieved by shielding one jet exhaust flow with a second, closely spaced, identical jet flow. A generalized fuel jet noise analytical model was formulated in which the acoustic radiation from a source jet propagates through the velocity and temperature discontinuity of the adjacent shielding jet. Input variables to the prediction procedure include jet Mach number, spacing, temperature, diameter, and source frequency. Refraction, diffraction, and reflection effects, which control the dual jet directivity pattern, are incorporated in the theory. The analysis calculates the difference in sound pressure level between the dual jet configuration and the radiation field based on superimposing two independent jet noise directivity patterns. Jet shielding was found experimentally to reduce noise levels in the common plane of the dual jet system relative to the noise generated by two independent jets.

  15. The peculiar case of the “double-humped" super-luminous supernova SN 2006oz

    NASA Astrophysics Data System (ADS)

    Ouyed, Rachid; Leahy, Denis

    2013-10-01

    SN 2006oz is a super-luminous supernova with a mysterious bright precursor that has resisted explanation in standard models. However, such a precursor has been predicted in the dual-shock quark nova model of super-luminous supernovae — the precursor is the supernova event while the main light curve of the super-luminous supernova is powered by the Quark-Nova (explosive transition of the neutron star to a quark star). As the supernova is fading, the Quark-Nova re-energizes the supernova ejecta, producing a “double-humped" light curve. We show that the quark nova model successfully reproduces the observed light curve of SN 2006oz.

  16. A note on observational signatures in superluminal unified dark matter models

    SciTech Connect

    Urakawa, Yuko; Kobayashi, Tsutomu E-mail: tsutomu@gravity.phys.waseda.ac.jp

    2010-07-01

    We explore the possibility that the dark matter and dark energy are mimicked by a single fluid or by a single k-essence-like scalar field. The so called Chaplygin gas unified dark matter models can reproduce the observed matter power spectrum by adding a baryon component. It has been argued that the evolution of the baryon fluctuations is particularly favoured for the ''superluminal'' case where the sound speed of the Chaplygin gas exceeds the speed of light at late times, as well as for the models with the negligibly small sound speed. In this note we compute the integrated Sachs-Wolfe signal in the Chaplygin gas models, focusing on the superluminal case which has not been investigated before because of the premature understanding of causality. It is shown that the superluminal model leads to large enhancement of the integrated Sachs-Wolfe effect, which is inconsistent with the CMB measurements.

  17. Inverse Doppler shift and control field as coherence generators for the stability in superluminal light

    NASA Astrophysics Data System (ADS)

    Ghafoor, Fazal; Bacha, Bakht Amin; Khan, Salman

    2015-05-01

    A gain-based four-level atomic medium for the stability in superluminal light propagation using control field and inverse Doppler shift as coherence generators is studied. In regimes of weak and strong control field, a broadband and multiple controllable transparency windows are, respectively, identified with significantly enhanced group indices. The observed Doppler effect for the class of high atomic velocity of the medium is counterintuitive in comparison to the effect of the class of low atomic velocity. The intensity of each of the two pump fields is kept less than the optimum limit reported in [M. D. Stenner and D. J. Gauthier, Phys. Rev. A 67, 063801 (2003), 10.1103/PhysRevA.67.063801] for stability in the superluminal light pulse. Consequently, superluminal stable domains with the generated coherence are explored.

  18. Blazar Jets Push Closer to Cosmic Speed Limit

    NASA Astrophysics Data System (ADS)

    2005-01-01

    Astronomers using the National Science Foundation's Very Long Baseline Array (VLBA) have discovered jets of plasma blasted from the cores of distant galaxies at speeds within one-tenth of one percent of the speed of light, placing these plasma jets among the fastest objects yet seen in the Universe. "This tells us that the physical processes at the cores of these galaxies, called blazars, are extremely energetic and are capable of propelling matter very close to the absolute cosmic speed limit," said Glenn Piner of Whittier College in Whittier, California. Piner, who worked on the project with student Dipesh Bhattari, also of Whittier College, Philip Edwards of the Japan Aerospace Exploration Agency, and Dayton Jones of NASA's Jet Propulsion Laboratory, presented their findings to the American Astronomical Society's meeting in San Diego, California. According to Einstein's Special Theory of Relativity, no object with mass can be accelerated to the speed of light. To get even close to the speed of light requires enormous amounts of energy. "For example, to accelerate a bowling ball to the speed newly measured in these blazars would require all the energy produced in the world for an entire week," Piner said, "and the blobs of plasma in these jets are at least as massive as a large planet". Blazars are active galactic nuclei -- energetic regions surrounding massive black holes at the centers of galaxies. Material being drawn into the black hole forms a spinning disk called an accretion disk. Powerful jets of charged particles are ejected at high speeds along the poles of accretion disks. When these jets happen to be aimed nearly toward the Earth, the objects are called blazars. Taking advantage of the extremely sharp radio "vision" of the continent-wide VLBA, the scientists tracked individual features in the jets of three blazars at distances from Earth ranging from 7.3 to 9 billion light-years. A Boston University team led by Svetlana Jorstad earlier had identified

  19. Comment on 'Alternative perspective on photonic tunneling' and 'Theoretical evidence for the superluminality of evanescent waves'

    SciTech Connect

    Winful, Herbert G.

    2007-11-15

    In a pair of related papers, Wang et al. [Phys. Rev. A 75, 013813 (2007); 75, 042105 (2007)] claim to present evidence, based on quantum field theory, for the superluminality of evanescent modes in undersized waveguides. Here we show that the conclusion of the authors is false and is based on an error: they mistake a nonzero propagator for a nonzero commutator. The commutator of the field operator at two points separated by a spacelike interval is strictly zero, which makes true superluminality impossible.

  20. Superluminal and slow light propagation in a room-temperature solid.

    PubMed

    Bigelow, Matthew S; Lepeshkin, Nick N; Boyd, Robert W

    2003-07-11

    We have observed both superluminal and ultraslow light propagation in an alexandrite crystal at room temperature. Group velocities as slow as 91 meters per second to as fast as -800 meters per second were measured and attributed to the influence of coherent population oscillations involving chromium ions in either mirror or inversion sites within the crystal lattice. Namely, ions in mirror sites are inversely saturable and cause superluminal light propagation, whereas ions in inversion sites experience conventional saturable absorption and produce slow light. This technique for producing large group indices is considerably easier than the existing methods to implement and is therefore suitable for diverse applications. PMID:12855803

  1. Observation of dissipative superluminous solitons in a Brillouin fiber ring laser

    NASA Astrophysics Data System (ADS)

    Picholle, Eric; Montes, Carlos; Leycuras, Claude; Legrand, Olivier; Botineau, Jean

    1991-03-01

    It has been demonstrated that nonstationary stimulated Brillouin backscattering in a large-gain optical-fiber ring-cavity laser exhibits superluminous Stokes pulses of quasi-soliton type and partial self-induced transparency for the pump. Experimental data (confirmed by numerical simulation with the three-wave coherent model, taking acoustic-wave dynamics into account) indicate that this class of long transients occurs even with a CW-coupled pump wave. The contribution of the dissipative superluminous quasi-solitons to the stabilization of the Stokes output is demonstrated.

  2. Luminous Blue Variables and Superluminous Supernovae from Binary Mergers

    NASA Astrophysics Data System (ADS)

    Justham, Stephen; Podsiadlowski, Philipp; Vink, Jorick S.

    2014-12-01

    Evidence suggests that the direct progenitor stars of some core-collapse supernovae (CCSNe) are luminous blue variables (LBVs), perhaps including some Type II "superluminous supernovae" (SLSNe). We examine models in which massive stars gain mass soon after the end of core hydrogen burning. These are mainly intended to represent mergers following a brief contact phase during early Case B mass transfer, but may also represent stars which gain mass in the Hertzsprung Gap or extremely late during the main-sequence phase for other reasons. The post-accretion stars spend their core helium-burning phase as blue supergiants (BSGs), and many examples are consistent with being LBVs at the time of core collapse. Other examples are yellow supergiants at explosion. We also investigate whether such post-accretion stars may explode successfully after core collapse. The final core properties of post-accretion models are broadly similar to those of single stars with the same initial mass as the pre-merger primary star. More surprisingly, when early Case B accretion does affect the final core properties, the effect appears likely to favor a successful SN explosion, i.e., to make the core properties more like those of a lower-mass single star. However, the detailed structures of these cores sometimes display qualitative differences to any single-star model we have calculated. The rate of appropriate binary mergers may match the rate of SNe with immediate LBV progenitors; for moderately optimistic assumptions we estimate that the progenitor birthrate is ~1% of the CCSN rate.

  3. The Volumetric Rate of Superluminous Supernovae at z ˜ 1

    NASA Astrophysics Data System (ADS)

    Prajs, S.; Sullivan, M.; Smith, M.; Levan, A.; Karpenka, N. V.; Edwards, T. D. P.; Walker, C. R.; Wolf, W. M.; Balland, C.; Carlberg, R.; Howell, A.; Lidman, C.; Pain, R.; Pritchet, C.; Ruhlmann-Kleider, V.

    2016-08-01

    We present a measurement of the volumetric rate of superluminous supernovae (SLSNe) at z˜1.0, measured using archival data from the first four years of the Canada-France-Hawaii Telescope Supernova Legacy Survey (SNLS). We develop a method for the photometric classification of SLSNe to construct our sample. Our sample includes two previously spectroscopically-identified objects, and a further new candidate selected using our classification technique. We use the point-source recovery efficiencies from Perrett et al. (2010) and a Monte Carlo approach to calculate the rate based on our SLSN sample. We find that the three identified SLSNe from SNLS give a rate of 91^{+76}_{-36} SNe Yr-1 Gpc-3 at a volume-weighted redshift of z = 1.13. This is equivalent to 2.2^{+1.8}_{-0.9}× 10^{-4} of the volumetric core collapse supernova rate at the same redshift. When combined with other rate measurements from the literature, we show that the rate of SLSNe increases with redshift in a manner consistent with that of the cosmic star formation history. We also estimate the rate of ultra-long gamma ray bursts (ULGRBs) based on the events discovered by the Swift satellite, and show that it is comparable to the rate of SLSNe, providing further evidence of a possible connection between these two classes of events. We also examine the host galaxies of the SLSNe discovered in SNLS, and find them to be consistent with the stellar-mass distribution of other published samples of SLSNe.

  4. Luminous blue variables and superluminous supernovae from binary mergers

    SciTech Connect

    Justham, Stephen; Podsiadlowski, Philipp; Vink, Jorick S. E-mail: podsi@astro.ox.ac.uk

    2014-12-01

    Evidence suggests that the direct progenitor stars of some core-collapse supernovae (CCSNe) are luminous blue variables (LBVs), perhaps including some Type II 'superluminous supernovae' (SLSNe). We examine models in which massive stars gain mass soon after the end of core hydrogen burning. These are mainly intended to represent mergers following a brief contact phase during early Case B mass transfer, but may also represent stars which gain mass in the Hertzsprung Gap or extremely late during the main-sequence phase for other reasons. The post-accretion stars spend their core helium-burning phase as blue supergiants (BSGs), and many examples are consistent with being LBVs at the time of core collapse. Other examples are yellow supergiants at explosion. We also investigate whether such post-accretion stars may explode successfully after core collapse. The final core properties of post-accretion models are broadly similar to those of single stars with the same initial mass as the pre-merger primary star. More surprisingly, when early Case B accretion does affect the final core properties, the effect appears likely to favor a successful SN explosion, i.e., to make the core properties more like those of a lower-mass single star. However, the detailed structures of these cores sometimes display qualitative differences to any single-star model we have calculated. The rate of appropriate binary mergers may match the rate of SNe with immediate LBV progenitors; for moderately optimistic assumptions we estimate that the progenitor birthrate is ∼1% of the CCSN rate.

  5. Blue supergiant model for ultra-long gamma-ray burst with superluminous-supernova-like bump

    SciTech Connect

    Nakauchi, Daisuke; Nakamura, Takashi; Kashiyama, Kazumi; Suwa, Yudai

    2013-11-20

    Long gamma-ray bursts (LGRBs) have a typical duration of ∼30 s, and some of them are associated with hypernovae, such as Type Ic SN 1998bw. Wolf-Rayet stars are the most plausible LGRB progenitors, since the free fall time of the envelope is consistent with the duration, and the natural outcome of the progenitor is a Type Ic SN. While a new population of ultra-long GRBs (ULGRBs), GRB 111209A, GRB 101225A, and GRB 121027A, has a duration of ∼10{sup 4} s, two of them are accompanied by superluminous-supernova-like (SLSN-like) bumps, which are ≲ 10 times brighter than typical hypernovae. Wolf-Rayet progenitors cannot explain ULGRBs because of durations that are too long and SN-like bumps that are too bright. A blue supergiant (BSG) progenitor model, however, can explain the duration of ULGRBs. Moreover, SLSN-like bumps can be attributed to the so-called cocoon fireball photospheric emissions (CFPEs). Since a large cocoon is inevitably produced during the relativistic jet piercing though the BSG envelope, this component can be smoking gun evidence of the BSG model for ULGRBs. In this paper, we examine u-, g-, r-, i-, and J-band light curves of three ULGRBs and demonstrate that they can be fitted quite well by our BSG model with the appropriate choices of the jet opening angle and the number density of the ambient gas. In addition, we predict that for 121027A, SLSN-like bump could have been observed for ∼20-80 days after the burst. We also propose that some SLSNe might be CFPEs of off-axis ULGRBs without visible prompt emissions.

  6. THE ROLE OF SUPERLUMINAL ELECTROMAGNETIC WAVES IN PULSAR WIND TERMINATION SHOCKS

    SciTech Connect

    Amano, Takanobu; Kirk, John G.

    2013-06-10

    The dynamics of a standing shock front in a Poynting-flux-dominated relativistic flow is investigated by using a one-dimensional, relativistic, two-fluid simulation. An upstream flow containing a circularly polarized, sinusoidal magnetic shear wave is considered, mimicking a wave driven by an obliquely rotating pulsar. It is demonstrated that this wave is converted into large-amplitude electromagnetic waves with superluminal phase speeds by interacting with the shock when the shock-frame frequency of the wave exceeds the proper plasma frequency. The superluminal waves propagate in the upstream, modify the shock structure substantially, and form a well-developed precursor region ahead of a subshock. Dissipation of Poynting flux occurs in the precursor as well as in the downstream region through a parametric instability driven by the superluminal waves. The Poynting flux remaining in the downstream region is carried entirely by the superluminal waves. The downstream plasma is therefore an essentially unmagnetized, relativistically hot plasma with a non-relativistic flow speed, as suggested by observations of pulsar wind nebulae.

  7. Superluminal and Ultra-Slow Light Propagation in Room-Temperature Solids

    NASA Astrophysics Data System (ADS)

    Boyd, Robert W.; Bigelow, Matthew S.; Lepeshkin, Nick N.

    2004-12-01

    We have observed ultra-slow light propagation (57 m s-1) in ruby and superluminal (-800 m s-1) light propagation in alexandrite at room temperature. The modified light speed results from the rapid variation in refractive index associated with spectral holes and antiholes produced by the process of coherent population oscillations.

  8. Observation of image pair creation and annihilation from superluminal scattering sources.

    PubMed

    Clerici, Matteo; Spalding, Gabriel C; Warburton, Ryan; Lyons, Ashley; Aniculaesei, Constantin; Richards, Joseph M; Leach, Jonathan; Henderson, Robert; Faccio, Daniele

    2016-04-01

    The invariance of the speed of light is one of the foundational pillars of our current understanding of the universe. It implies a series of consequences related to our perception of simultaneity and, ultimately, of time itself. Whereas these consequences are experimentally well studied in the case of subluminal motion, the kinematics of superluminal motion lack direct evidence or even a clear experimental approach. We investigate kinematic effects associated with the superluminal motion of a light source. By using high-temporal-resolution imaging techniques, we directly demonstrate that if the source approaches an observer at superluminal speeds, the temporal ordering of events is inverted and its image appears to propagate backward. Moreover, for a source changing its speed and crossing the interface between subluminal and superluminal propagation regions, we observe image pair annihilation and creation, depending on the crossing direction. These results are very general and show that, regardless of the emitter speed, it is not possible to unambiguously determine the kinematics of an event from imaging and time-resolved measurements alone. This has implications not only for light, but also, for example, for sound and other wave phenomena. PMID:27152347

  9. Observation of image pair creation and annihilation from superluminal scattering sources

    PubMed Central

    Clerici, Matteo; Spalding, Gabriel C.; Warburton, Ryan; Lyons, Ashley; Aniculaesei, Constantin; Richards, Joseph M.; Leach, Jonathan; Henderson, Robert; Faccio, Daniele

    2016-01-01

    The invariance of the speed of light is one of the foundational pillars of our current understanding of the universe. It implies a series of consequences related to our perception of simultaneity and, ultimately, of time itself. Whereas these consequences are experimentally well studied in the case of subluminal motion, the kinematics of superluminal motion lack direct evidence or even a clear experimental approach. We investigate kinematic effects associated with the superluminal motion of a light source. By using high-temporal-resolution imaging techniques, we directly demonstrate that if the source approaches an observer at superluminal speeds, the temporal ordering of events is inverted and its image appears to propagate backward. Moreover, for a source changing its speed and crossing the interface between subluminal and superluminal propagation regions, we observe image pair annihilation and creation, depending on the crossing direction. These results are very general and show that, regardless of the emitter speed, it is not possible to unambiguously determine the kinematics of an event from imaging and time-resolved measurements alone. This has implications not only for light, but also, for example, for sound and other wave phenomena. PMID:27152347

  10. Revealing the binary origin of Type Ic superluminous supernovae through nebular hydrogen emission

    NASA Astrophysics Data System (ADS)

    Moriya, Takashi J.; Liu, Zheng-Wei; Mackey, Jonathan; Chen, Ting-Wan; Langer, Norbert

    2015-12-01

    We propose that nebular Hα emission, as detected in the Type Ic superluminous supernova iPTF13ehe, stems from matter that is stripped from a companion star when the supernova ejecta collide with it. The temporal evolution, the line broadening, and the overall blueshift of the emission are consistent with this interpretation. We scale the nebular Hα luminosity predicted for Type Ia supernovae in single-degenerate systems to derive the stripped mass required to explain the Hα luminosity of iPTF13ehe. We find a stripped mass of 0.1-0.9 solar masses, assuming that the supernova luminosity is powered by radioactivity or magnetar spin down. Because a central heating source is required to excite the Hα emission, an interaction-powered model is not favored for iPTF13ehe if the Hα emission is from stripped matter. We derive a companion mass of more than 20 solar masses and a binary separation of less than about 20 companion radii based on the stripping efficiency during the collision, indicating that the supernova progenitor and the companion formed a massive close binary system. If Type Ic superluminous supernovae generally occur in massive close binary systems, the early brightening observed previously in several Type Ic superluminous supernovae may also be due to the collision with a close companion. Observations of nebular hydrogen emission in future Type Ic superluminous supernovae will enable us to test this interpretation.

  11. Radio observations of the γ-ray quasar 0528+134. Superluminal motion and an extreme scattering event.

    NASA Astrophysics Data System (ADS)

    Pohl, M.; Reich, W.; Krichbaum, T. P.; Standke, K.; Britzen, S.; Reuter, H. P.; Reich, P.; Schlickeiser, R.; Fiedler, R. L.; Waltman, E. B.; Ghigo, F. D.; Johnston, K. J.

    1995-11-01

    We report on multifrequency radio observations made with the Effelsberg 100-m telescope, the IRAM 30-m telescope and the Green Bank Interferometer between 1992 and 1994 of the γ-ray quasar 0528+134. We present a new VLBI based map of 0528+134 at 22GHz with sub-mas angular resolution observed in November 1992. At that time the source was in a phase of brightening at all of our observing frequencies above 3GHz. The increase of brightness may be related to activity in the unresolved core component of the quasar. The VLBI map at 22GHz (epoch 1992.85) shows a one-sided core jet structure of ~5mas length. A new component close to the core indicates an apparent transverse velocity of β_app_<=20 (H_0_=100km/s/Mpc, q_0_=0.5). A second component, seen also previously at 8.4GHz & 22GHz, shows apparent superluminal motion with β_app_=4.4+/-1.7. Superluminal motion is expected since strong Doppler boosting in this source is required in view of the γ-ray luminosity and the variability timescale, which violate the compactness limit. In summer 1993 we observed a major outburst at all frequencies higher than a few GHz, which peaked a few months after a strong outburst in high energy γ-rays and showed the canonical time evolution of a cooling and/or expanding electron distribution. Our data indicate that the outburst in the EGRET range originated very close to the central object of the AGN and that a remnant of this outburst moved further outward in the jet until it became optically thin at radio frequencies after a few months. During the flare in July 1993 we observed with the Effelsberg 100-m telescope an unusually strong decrease of the flux density by about 50% at 4.75GHz and 10.55GHz and slightly less at 2.695GHz. This behaviour is also seen in the monitoring data at 2.25GHz and 8.3GHz taken with the Green Bank Interferometer (NRL-GBI). The event lasted less than three days at the higher frequencies and more than two weeks at 2.25GHz. For the case that this event is

  12. Subluminal and superluminal parametric doppler effects in the case of light reflection from a moving smooth medium inhomogeneity

    SciTech Connect

    Rozanov, N. N.

    2012-12-15

    The reflection of test radiation from a smooth inhomogeneity of medium characteristics propagating with a subluminal or superluminal velocity is analyzed. The equations describing the propagation of the forward- and counter-propagating waves in such an inhomogeneous medium are derived. Quasi-phase conjugation is demonstrated in the case of superluminal inhomogeneities. The Bragg resonance conditions are formulated and the conditions for increasing the reflection coefficient of radiation from an inhomogeneity are discussed.

  13. Fuzzy jets

    DOE PAGESBeta

    Mackey, Lester; Nachman, Benjamin; Schwartzman, Ariel; Stansbury, Conrad

    2016-06-01

    Here, collimated streams of particles produced in high energy physics experiments are organized using clustering algorithms to form jets . To construct jets, the experimental collaborations based at the Large Hadron Collider (LHC) primarily use agglomerative hierarchical clustering schemes known as sequential recombination. We propose a new class of algorithms for clustering jets that use infrared and collinear safe mixture models. These new algorithms, known as fuzzy jets , are clustered using maximum likelihood techniques and can dynamically determine various properties of jets like their size. We show that the fuzzy jet size adds additional information to conventional jet taggingmore » variables in boosted topologies. Furthermore, we study the impact of pileup and show that with some slight modifications to the algorithm, fuzzy jets can be stable up to high pileup interaction multiplicities.« less

  14. Fuzzy jets

    NASA Astrophysics Data System (ADS)

    Mackey, Lester; Nachman, Benjamin; Schwartzman, Ariel; Stansbury, Conrad

    2016-06-01

    Collimated streams of particles produced in high energy physics experiments are organized using clustering algorithms to form jets. To construct jets, the experimental collaborations based at the Large Hadron Collider (LHC) primarily use agglomerative hierarchical clustering schemes known as sequential recombination. We propose a new class of algorithms for clustering jets that use infrared and collinear safe mixture models. These new algorithms, known as fuzzy jets, are clustered using maximum likelihood techniques and can dynamically determine various properties of jets like their size. We show that the fuzzy jet size adds additional information to conventional jet tagging variables in boosted topologies. Furthermore, we study the impact of pileup and show that with some slight modifications to the algorithm, fuzzy jets can be stable up to high pileup interaction multiplicities.

  15. STRUCTURE OF THE INNER JET OF OJ287 FROM VLBA DATA AT 15 GHz IN SUPER-RESOLUTION MODE

    SciTech Connect

    Tateyama, Claudio E.

    2013-04-01

    In this work we show the results obtained from the Very Long Baseline Array data at 15 GHz of OJ287 in super-resolution mode. The data showed a jet configuration in the form of a 'fork' where superluminal components emerge via stationary components at the northwest and the southeast close to the core to form parallel trajectories along the southwest direction in the plane of sky. This agrees with a source structure of an extended, broad morphology of OJ287.

  16. A search for new galactic microquasars

    NASA Astrophysics Data System (ADS)

    Tsarevsky, G. S.; Pavlenko, E. P.; Stathakis, R. A.; Kardashev, N. S.; Slee, O. B.

    2002-01-01

    The population of microquasars in our Galaxy} Accretion onto a supermassive black hole with a strong surrounding magnetic field can supply the necessary energy for AGNs (Kardashev 1995). Inside our own galaxy, accretion from a stellar component onto a black hole (or neutron star) in a close binary system can produce a similar kind of phenomenon. X-ray observations made by UHURU in 1978 attracted attention to the peculiar object SS 433 located in the very centre of the supernova remnant W50. When the orbital period was first determined, Shklovski (1978) suggested that SS 433 is a binary system associated with the ejection of relativistic particles, which are responsible for the strong, periodic radio emission. Many observations of SS 433 led to the conclusion that the system is a close binary consisting of a massive OB star and a neutron star or a black hole surrounded by a bright accretion disk opaque to X-rays. SS 433 and similar objects have been assigned to a special class called "microquasars" (see comprehensive review by Mirabel & Rodriguez, 1999). Only about 30 of ~280 known X-ray binaries (XRBs) have been detected in radio (Fender et al. 1997), and only a few of them have characteristic radio emission and morphology associated with the microquasars' family. Radio images of such objects bear a striking similarity to the structures of AGN: they have a compact core and two-sided jets of relativistic particles. Flux variability and superluminal motions are also quite common for the microquasars. GRO J1655--40 is a representative object of this class (Tingay at al. 1995). First discovered in X-rays, it produces relativistic radio jets with β = 0.92, and has an angular extent of 1arcsec. It is the intention of the project described here to search for similar features with the aim of increasing the number of known microquasars.

  17. The Making of a Galactic Parallelogram

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This image taken by NASA's Spitzer Space Telescope shows in unprecedented detail the galaxy Centaurus A's last big meal: a spiral galaxy seemingly twisted into a parallelogram-shaped structure of dust. Spitzer's ability to both see dust and see through it allowed the telescope to peer into the center of Centaurus A and capture this galactic remnant as never before.

    An elliptical galaxy located 11 million light-years from Earth, Centaurus A is one of the brightest sources of radio waves in the sky. These radio waves indicate the presence of a supermassive black hole, which may be 'feeding' off the leftover galactic meal.

    A high-speed jet of gas can be seen shooting above the plane of the galaxy (the faint, fuzzy feature pointing from the center toward the upper left). Jets are a common feature of galaxies, and this one is probably receiving an extra boost from the galactic remnant.

    Scientists have created a model that explains how such a strangely geometric structure could arise. In this model, a spiral galaxy falls into an elliptical galaxy, becoming warped and twisted in the process. The folds in the warped disc create the parallelogram-shaped illusion.

  18. The UKIDSS Galactic Plane Survey

    NASA Astrophysics Data System (ADS)

    Lucas, P. W.; Hoare, M. G.; Longmore, A.; Schröder, A. C.; Davis, C. J.; Adamson, A.; Bandyopadhyay, R. M.; de Grijs, R.; Smith, M.; Gosling, A.; Mitchison, S.; Gáspár, A.; Coe, M.; Tamura, M.; Parker, Q.; Irwin, M.; Hambly, N.; Bryant, J.; Collins, R. S.; Cross, N.; Evans, D. W.; Gonzalez-Solares, E.; Hodgkin, S.; Lewis, J.; Read, M.; Riello, M.; Sutorius, E. T. W.; Lawrence, A.; Drew, J. E.; Dye, S.; Thompson, M. A.

    2008-11-01

    The UKIDSS Galactic Plane Survey (GPS) is one of the five near-infrared Public Legacy Surveys that are being undertaken by the UKIDSS consortium, using the Wide Field Camera on the United Kingdom Infrared Telescope. It is surveying 1868 deg2 of the northern and equatorial Galactic plane at Galactic latitudes -5° < b < 5° in the J, H and K filters and a ~200-deg2 area of the Taurus-Auriga-Perseus molecular cloud complex in these three filters and the 2.12 μm (1-0) H2 filter. It will provide data on ~2 × 109 sources. Here we describe the properties of the data set and provide a user's guide for its exploitation. We also present brief Demonstration Science results from DR2 and from the Science Verification programme. These results illustrate how GPS data will frequently be combined with data taken in other wavebands to produce scientific results. The Demonstration Science comprises six studies. (1) A GPS-Spitzer-GLIMPSE cross-match for the star formation region G28.983-0.603 to identify YSOs. This increases the number of YSOs identified by a factor of 10 compared to GLIMPSE alone. (2) A wide-field study of the M17 nebula, in which an extinction map of the field is presented and the effect of source confusion on luminosity functions in different subregions is noted. (3) H2 emission in the ρ Ophiuchi dark cloud. All the molecular jets are traced back to a single active clump containing only a few protostars, which suggests that the duration of strong jet activity and associated rapid accretion in low-mass protostars is brief. (4) X-ray sources in the nuclear bulge. The GPS data distinguishes local main-sequence counterparts with soft X-ray spectra from nuclear bulge giant counterparts with hard X-ray spectra. (5) External galaxies in the zone of avoidance. The galaxies are clearly distinguished from stars in fields at longitudes l > 90°. (6) IPHAS-GPS optical-infrared spectrophotometric typing. The (i' - J) versus (J - H) diagram is used to distinguish A-F type

  19. Synchrotron radiation from the jet of 3C 273. 3: The speed and direction of the jet

    NASA Astrophysics Data System (ADS)

    Conway, R. G.; Davis, R. J.

    1994-04-01

    The jet of 3C 273 is interpreted as synchrotron plasma moving at a mildly relativistic speed up to a terminal shock, identified with the brightest radio component, H2, in the head. The Mach number of the flow can be deduced from the brightness contrast of the shocked gas compared with the upstream portions of the flow, after making due allowance for the effects of the Doppler beaming. This shows that the jet speed is approximately equals 0.8 c, while the speed of the shocked gas is approximately equals 0.4 c. By comparing the linear polarization of the jet (18%, with B parallel to the jet axis), and that of the shocked gas (23% with B transverse), it is shown that the direction of the jet must be 30 deg - 35 deg to the line of sight. The Doppler shift of the shocked gas in the head is less than or equal to 1.5, and is insufficient to hide a hypothetical counter-jet by a factor of about 2000. The direction of the jet differs by 20 deg - 30 deg from that deduced from the superluminal proper motion detected in the core, most probably because of a bend situated at a distance between 8 and 20 mas from the core. We suggest that the virtual absence of optical emission from H2 can be explained if there has been a recent disconnection event, as suggested by the 'Dentist's Drill' model of Cox, Gull & Scheuer.

  20. Relativistic jet feedback in high-redshift galaxies - I. Dynamics

    NASA Astrophysics Data System (ADS)

    Mukherjee, Dipanjan; Bicknell, Geoffrey V.; Sutherland, Ralph; Wagner, Alex

    2016-09-01

    We present the results of 3D relativistic hydrodynamic simulations of interaction of active galactic nucleus jets with a dense turbulent two-phase interstellar medium, which would be typical of high-redshift galaxies. We describe the effect of the jet on the evolution of the density of the turbulent interstellar medium (ISM). The jet-driven energy bubble affects the gas to distances up to several kiloparsecs from the injection region. The shocks resulting from such interactions create a multiphase ISM and radial outflows. One of the striking result of this work is that low-power jets (Pjet ≲ 1043 ergs-1), although less efficient in accelerating clouds, are trapped in the ISM for a longer time and hence affect the ISM over a larger volume. Jets of higher power drill through with relative ease. Although the relativistic jets launch strong outflows, there is little net mass ejection to very large distances, supporting a galactic fountain scenario for local feedback.

  1. Disk-Jet Connection in the Radio Galaxy 3C 120

    NASA Astrophysics Data System (ADS)

    Chatterjee, Ritaban; Marscher, Alan P.; Jorstad, Svetlana G.; Olmstead, Alice R.; McHardy, Ian M.; Aller, Margo F.; Aller, Hugh D.; Lähteenmäki, Anne; Tornikoski, Merja; Hovatta, Talvikki; Marshall, Kevin; Miller, H. Richard; Ryle, Wesley T.; Chicka, Benjamin; Benker, A. J.; Bottorff, Mark C.; Brokofsky, David; Campbell, Jeffrey S.; Chonis, Taylor S.; Gaskell, C. Martin; Gaynullina, Evelina R.; Grankin, Konstantin N.; Hedrick, Cecelia H.; Ibrahimov, Mansur A.; Klimek, Elizabeth S.; Kruse, Amanda K.; Masatoshi, Shoji; Miller, Thomas R.; Pan, Hong-Jian; Petersen, Eric A.; Peterson, Bradley W.; Shen, Zhiqiang; Strel'nikov, Dmitriy V.; Tao, Jun; Watkins, Aaron E.; Wheeler, Kathleen

    2009-10-01

    We present the results of extensive multi-frequency monitoring of the radio galaxy 3C 120 between 2002 and 2007 at X-ray (2-10 keV), optical (R and V bands), and radio (14.5 and 37 GHz) wave bands, as well as imaging with the Very Long Baseline Array (VLBA) at 43 GHz. Over the 5 yr of observation, significant dips in the X-ray light curve are followed by ejections of bright superluminal knots in the VLBA images. Consistent with this, the X-ray flux and 37 GHz flux are anti-correlated with X-ray leading the radio variations. Furthermore, the total radiative output of a radio flare is related to the equivalent width of the corresponding X-ray dip. This implies that, in this radio galaxy, the radiative state of accretion disk plus corona system, where the X-rays are produced, has a direct effect on the events in the jet, where the radio emission originates. The X-ray power spectral density of 3C 120 shows a break, with steeper slope at shorter timescale and the break timescale is commensurate with the mass of the central black hole (BH) based on observations of Seyfert galaxies and black hole X-ray binaries (BHXRBs). These findings provide support for the paradigm that BHXRBs and both radio-loud and radio-quiet active galactic nuclei are fundamentally similar systems, with characteristic time and size scales linearly proportional to the mass of the central BH. The X-ray and optical variations are strongly correlated in 3C 120, which implies that the optical emission in this object arises from the same general region as the X-rays, i.e., in the accretion disk-corona system. We numerically model multi-wavelength light curves of 3C 120 from such a system with the optical-UV emission produced in the disk and the X-rays generated by scattering of thermal photons by hot electrons in the corona. From the comparison of the temporal properties of the model light curves to that of the observed variability, we constrain the physical size of the corona and the distances of the

  2. Active galactic nuclei

    PubMed Central

    Fabian, Andrew C.

    1999-01-01

    Active galactic nuclei are the most powerful, long-lived objects in the Universe. Recent data confirm the theoretical idea that the power source is accretion into a massive black hole. The common occurrence of obscuration and outflows probably means that the contribution of active galactic nuclei to the power density of the Universe has been generally underestimated. PMID:10220363

  3. Controlling the Radiation Parameters of a Resonant Medium Excited by a Sequence of Ultrashort Superluminal Pulses

    NASA Astrophysics Data System (ADS)

    Arkhipov, R. M.; Arkhipov, M. V.; Belov, P. A.; Babushkin, I.; Tolmachev, Yu. A.

    2016-03-01

    We investigate the possibility of controlling the radiation parameters of a spatially periodic one-dimensional medium consisting of classical harmonic oscillators by means of a sequence of ultrashort pulses that propagate through the medium with a superluminal velocity. We show that, in the spectrum of the transient process, in addition to the radiation at a resonant frequency of oscillators, new frequencies arise that depend on the period of the spatial distribution of the oscillator density, the excitation velocity, and the angle of observation. We have examined in detail the case of excitation of the medium by a periodic sequence of ultrashort pulses that travel with a superluminal velocity. We show that it is possible to excite oscillations of complex shapes and to control the radiation parameters of the resonant medium by changing the relationship between the pulse repetition rate, the medium resonant frequency, and the new frequency.

  4. Gravitational Lorentz violation and superluminality via AdS/CFT duality

    SciTech Connect

    Sundrum, Raman

    2008-04-15

    A weak quantum mechanical coupling is constructed permitting superluminal communication within a preferred region of a gravitating AdS{sub 5} spacetime. This is achieved by adding a spatially nonlocal perturbation of a special kind to the Hamiltonian of a four-dimensional conformal field theory with a weakly coupled AdS{sub 5} dual, such as maximally supersymmetric Yang-Mills theory. In particular, two issues are given careful treatment: (1) the UV-completeness of our deformed conformal field theory (CFT), guaranteeing the existence of a ''deformed string theory'' AdS dual and (2) the demonstration that superluminal effects can take place in AdS, both on its boundary as well as in the bulk. Exotic Lorentz-violating properties such as these may have implications for tests of general relativity, addressing the cosmological constant problem, or probing behind horizons. Our construction may give insight into the interpretation of wormhole solutions in Euclidean AdS gravity.

  5. Superluminal motion in the double-lobed quasar 3C 245

    NASA Technical Reports Server (NTRS)

    Hough, D. H.; Readhead, A. C. S.

    1987-01-01

    VLBI observations of 3C 245 obtained at 10.7 GHz with the Mark III array at five epochs in 1981-1986 are reported. The data-reduction and model-fitting procedures are explained, and the results are presented in tables, graphs, and maps along with previously published data on 11 other superluminal sources. The central component of the quasar is found to have an apparent transverse velocity of (3.1 + or - 1.4) c/h, assuming H0 = 100h km/s Mpc and q0 = 0.5. From the apparent source orientation (based on R, variability, apparent curvature, and projected linear size) it is inferred that the apparent transverse velocity is anticorrelated with the angle to the line of sight, as predicted by relativistic-beaming models of superluminal motion.

  6. RADIATIVE DAMPING AND EMISSION SIGNATURES OF STRONG SUPERLUMINAL WAVES IN PULSAR WINDS

    SciTech Connect

    Mochol, Iwona; Kirk, John G. E-mail: john.kirk@mpi-hd.mpg.de

    2013-10-10

    We analyze the damping of strong, superluminal electromagnetic waves by radiation reaction and Compton drag in the context of pulsar winds. The associated radiation signature is found by estimating the efficiency and the characteristic radiation frequencies. Applying these estimates to the gamma-ray binary containing PSR B1259–63, we show that the GeV flare observed by the Fermi Large Area Telescope can be understood as inverse-Compton emission by particles scattering photons from the companion star, if the pulsar wind termination shock acquires a precursor of superluminal waves roughly 30 days after periastron. This requirement constrains the mass-loading factor of the wind μ=L/ N-dot mc{sup 2}, where L is the luminosity and N-dot is the rate of loss of electrons and positrons, to be roughly 6 × 10{sup 4}.

  7. Apparatus and method for phase fronts based on superluminal polarization current

    DOEpatents

    Singleton, John; Ardavan, Houshang; Ardavan, Arzhang

    2012-02-28

    An apparatus and method for a radiation source involving phase fronts emanating from an accelerated, oscillating polarization current whose distribution pattern moves superluminally (that is, faster than light in vacuo). Theoretical predictions and experimental measurements using an existing prototype superluminal source show that the phase fronts from such a source can be made to be very complex. Consequently, it will be very difficult for an aircraft imaged by such a radiation to detect where this radiation has come from. Moreover, the complexity of the phase fronts makes it almost impossible for electronics on an aircraft to synthesize a rogue reflection. A simple directional antenna and timing system should, on the other hand, be sufficient for the radar operators to locate the aircraft, given knowledge of their own source's speed and modulation pattern.

  8. MEASURING THE JET POWER OF FLAT-SPECTRUM RADIO QUASARS

    SciTech Connect

    Shabala, S. S.; Santoso, J. S.; Godfrey, L. E. H.

    2012-09-10

    We use frequency-dependent position shifts of flat-spectrum radio cores to estimate the kinetic power of active galactic nucleus (AGN) jets. We find a correlation between the derived jet powers and AGN narrow-line luminosity, consistent with the well-known relation for radio galaxies and steep spectrum quasars. This technique can be applied to intrinsically weak jets even at high redshift.

  9. Superluminal media formed by photonic crystals for transformation optics-based invisibility cloaks

    NASA Astrophysics Data System (ADS)

    Semouchkina, Elena; Duan, Ran; Gandji, Navid P.; Jamilan, Saeid; Semouchkin, George; Pandey, Ravi

    2016-04-01

    We have developed an approach to building superluminal medium for transformation optics-based devices, including invisibility cloaks, from photonic crystals. Analysis of dispersion diagrams of 2D arrays composed from dielectric rods has shown that at frequencies corresponding to the second bands formed due to bandgap opening at increase of rod permittivity, the medium formed by arrays exhibits refractive indices providing for superluminal phase velocities of propagating waves. It is further demonstrated that rod arrays with various lattice constants could be used for realizing a range of superluminal index values prescribed by transformation optics for cylindrical cloaks at arbitrary chosen operating frequency. The performed studies allowed for solving a row of problems with employment rod arrays in the cloak medium: in particular, formulating transformation optics-based prescriptions for refractive index dispersion in the cloaking shell, defining the dimensions of array fragments capable of responding similar to infinite arrays, finding optimal distribution of linear arrays sets at their coiling to form concentric material layers in the cloaking shell, and employing interaction between neighboring array sets with various lattice constants to assist the realization of prescribed index dispersion. The performance of the superluminal medium formed by rod array sets was demonstrated on an example of a cloaking shell developed for microwave frequency range. In contrast to metamaterial-based cloak media, the developed media requires neither material homogenization, nor obtaining the effective parameters with peculiar values and Lorentz’s type resonances in rods. Combination of these advantages and low losses makes photonic crystals perspective materials for invisibility cloaks operating in THz and optical ranges.

  10. Superluminal and stopped light due to mode coupling in confined hyperbolic metamaterial waveguides

    NASA Astrophysics Data System (ADS)

    Neira, Andres D.; Wurtz, Gregory A.; Zayats, Anatoly V.

    2015-12-01

    Anisotropic metamaterials with hyperbolic dispersion can be used to design waveguides with unusual properties. We show that, in contrast to planar waveguides, geometric confinement leads to coupling of ordinary (forward) and extraordinary (backward) modes and formation of hybrid waveguided modes, which near the crossing point may exhibit slow, stopped or superluminal behavior accompanied by very strong group velocity dispersion. These modes can be used for designing stopped-light nanolasers for nanophotonic applications and dispersion-facilitated signal reshaping in telecom applications.

  11. Fundamental role of the retarded potential in the electrodynamics of superluminal sources: reply to comment

    SciTech Connect

    Singleton, John; Fasel, Joseph H; Schmidt, Andrea C; Ardavan, Houshang; Ardavan, Arzhang

    2009-01-01

    Neither Eq. (6.52) of Jackson [Classical Electrodynamics, 3rd ed. (Wiley, 1999)], or Hannay's derivation of that dquation in the preceding Comment [J. Opt. Soc. Am. A, ... (2009)], are applicable to a source whose distribution pattern moves faster than light in vacuo with nonzero acceleration. It is assumed in Hannay's derivation that the retarded distribution of the density of any moving source would be smooth and differentiable if its rest-frame distribution is. By working out an explicit example of a rotating superluminal source with a bounded and smooth density profile, we show that this assumption is erroneous. The retarded distribution of a rotating source with a moderate superluminal speed is, in general, spread over three disjoint volumes (differing in shape from each other and from the volume occupied by the source in its rest frame) whose boundaries depend on the spacetime position of the observer. Hannay overlooks the fact that the limits of integration in his expression for the retarded potential (which delineate the boundaries of the retarded distribution of the source) are not differentiable functions of the coordinates of the observer at those points on the source boundary that approach the observer, along the radiation direction, with the speed of light at the retarded time. In the superluminal regime, derivatives of the integral representing the retarded potential are well defined only as generalized functions.

  12. Superluminous supernovae at redshifts of 2.05 and 3.90.

    PubMed

    Cooke, Jeff; Sullivan, Mark; Gal-Yam, Avishay; Barton, Elizabeth J; Carlberg, Raymond G; Ryan-Weber, Emma V; Horst, Chuck; Omori, Yuuki; Díaz, C Gonzalo

    2012-11-01

    A rare class of 'superluminous' supernovae that are about ten or more times more luminous at their peaks than other types of luminous supernova has recently been found at low to intermediate redshifts. A small subset of these events have luminosities that evolve slowly and result in radiated energies of up to about 10(51) ergs. Therefore, they are probably examples of 'pair-instability' or 'pulsational pair-instability' supernovae with estimated progenitor masses of 100 to 250 times that of the Sun. These events are exceedingly rare at low redshift, but are expected to be more common at high redshift because the mass distribution of the earliest stars was probably skewed to high values. Here we report the detection of two superluminous supernovae, at redshifts of 2.05 and 3.90, that have slowly evolving light curves. We estimate the rate of events at redshifts of 2 and 4 to be approximately ten times higher than the rate at low redshift. The extreme luminosities of superluminous supernovae extend the redshift limit for supernova detection using present technology, previously 2.36 (ref. 8), and provide a way of investigating the deaths of the first generation of stars to form after the Big Bang. PMID:23123848

  13. Cosmic jets

    SciTech Connect

    Blandford, R.D.; Begelman, M.C.; Rees, M.J.

    1982-05-01

    Observations with radio telescopes have revealed that the center of many galaxies is a place of violent activity. This activity is often manifested in the production of cosmic jets. Each jet is a narrow stream of plasma that appears to squirt out of the center of a galaxy emitting radiowaves as it does so. New techniques in radio astronomy have shown how common jets are in the universe. These jets take on many different forms. The discovery of radio jets has helped in the understanding of the double structure of the majority of extragalactic radio sources. The morphology of some jets and explanations of how jets are fueled are discussed. There are many difficulties plaguing the investigation of jets. Some of these difficulties are (1) it is not known how much power the jets are radiating, (2) it is hard to tell whether a jet delieated by radio emission is identical to the region where ionized gas is flowing, and (3) what makes them. (SC)

  14. Pondermotive acceleration of charged particles along the relativistic jets of an accreting blackhole

    NASA Astrophysics Data System (ADS)

    Ebisuzaki, T.; Tajima, T.

    2014-05-01

    Accreting blackholes such as miniquasars and active galactic nuclei can contribute to the highest energy components of intra- (˜1015 eV) galactic and extra-galactic components (˜1020 eV) of cosmic rays. Alfven wave pulses which are excited in the accretion disk around blackholes propagate in relativistic jets. Because of their highly non-linear nature of the waves, charged particles (protons, ions, and electrons) can be accelerated to high energies in relativistic jets in accreting blackhole systems, the central engine of miniquasars and active galactic nuclei.

  15. Fermi-LAT Observations of Galactic Transients

    NASA Technical Reports Server (NTRS)

    Hays, Elizabeth

    2011-01-01

    This slide presentation reviews the observations of Galactic transients by the Large Area Telescope (LAT) on the Fermi Gamma Ray Space Telescope. The LAT is producing spectacular results for the GeV transient sky, some of which are shown and reviewed. Some of the results in the GeV range that are discussed in this presentation are: (1) New blazars and unidentified transients (2) the jet of the Cygnus X-3 microquasar (3) gamma rays from V407 Cygni nova (4) Fast high-energy gamma-ray flares from the Crab Nebula

  16. Nearly degenerate electron distributions and superluminal radiation densities

    NASA Astrophysics Data System (ADS)

    Tomaschitz, Roman

    2010-02-01

    Polylogarithmic fugacity expansions of the partition function, the caloric and thermal equations of state, and the specific heat of fermionic power-law distributions are derived in the nearly degenerate low-temperature/high-density quantum regime. The spectral functions of an ultra-relativistic electron plasma are obtained by averaging the tachyonic radiation densities of inertial electrons with Fermi power-laws, whose entropy is shown to be extensive and stable. The averaged radiation densities are put to test by performing tachyonic cascade fits to the γ-ray spectrum of the TeV blazar Markarian 421 in a low and high emission state. Estimates of the thermal electron plasma in this active galactic nucleus are extracted from the spectral fits, such as temperature, number count, and internal energy. The tachyonic cascades reproduce the quiescent as well as a burst spectrum of the blazar obtained with imaging atmospheric Cherenkov detectors. Double-logarithmic plots of the differential tachyon flux exhibit intrinsic spectral curvature, caused by the Boltzmann factor of the electron gas.

  17. Water Jetting

    NASA Technical Reports Server (NTRS)

    1985-01-01

    Hi-Tech Inc., a company which manufactures water jetting equipment, needed a high pressure rotating swivel, but found that available hardware for the system was unsatisfactory. They were assisted by Marshall, which had developed water jetting technology to clean the Space Shuttles. The result was a completely automatic water jetting system which cuts rock and granite and removes concrete. Labor costs have been reduced; dust is suppressed and production has been increased.

  18. Jet-intracluster medium interaction in Hydra A - I. Estimates of jet velocity from inner knots

    NASA Astrophysics Data System (ADS)

    Nawaz, M. A.; Wagner, A. Y.; Bicknell, G. V.; Sutherland, R. S.; McNamara, B. R.

    2014-10-01

    We present the first stage of an investigation of the interactions of the jets in the radio galaxy Hydra A with the intracluster medium. We consider the jet kinetic power, the galaxy and cluster atmosphere and the inner structure of the radio source. Analysing radio observations of the inner lobes of Hydra A by Taylor et al. we confirm the jet power estimates ˜1045 erg s-1 derived by Wise et al. from dynamical analysis of the X-ray cavities. With this result and a model for the galaxy halo, we explore the jet-intracluster medium interactions occurring on a scale of 10 kpc using two-dimensional, axisymmetric, relativistic pure hydrodynamic simulations. A key feature is that we identify the three bright knots in the northern jet as biconical reconfinement shocks, which result when an overpressured jet starts to come into equilibrium with the galactic atmosphere. Through an extensive parameter space study we deduce that the jet velocity is approximately 0.8c at a distance 0.5 kpc from the black hole. The combined constraints of jet power, the observed jet radius profile along the jet and the estimated jet pressure and jet velocity imply a value of the jet density parameter χ ≈ 13 for the northern jet. We show that for a jet β = 0.8 and θ = 42°, an intrinsic asymmetry in the emissivity of the northern and southern jet is required for a consistent brightness ratio ≈7 estimated from the 6-cm Very Large Array image of Hydra A.

  19. Fermi Galactic Center Zoom

    NASA Video Gallery

    This animation zooms into an image of the Milky Way, shown in visible light, and superimposes a gamma-ray map of the galactic center from NASA's Fermi. Raw data transitions to a view with all known...

  20. Galactic cosmic ray composition

    NASA Technical Reports Server (NTRS)

    Meyer, J. P.

    1986-01-01

    An assessment is given of the galactic cosmic ray source (GCRS) elemental composition and its correlation with first ionization potential. The isotopic composition of heavy nuclei; spallation cross sections; energy spectra of primary nuclei; electrons; positrons; local galactic reference abundances; comparison of solar energetic particles and solar coronal compositions; the hydrogen; lead; nitrogen; helium; and germanium deficiency problems; and the excess of elements are among the topics covered.

  1. Jets in AGN at extremely high redshifts

    NASA Astrophysics Data System (ADS)

    Gurvits, Leonid I.; Frey, Sándor; Paragi, Zsolt

    2015-03-01

    The jet phenomenon is a trademark of active galactic nuclei (AGN). In most general terms, the current understanding of this phenomenon explains the jet appearance by effects of relativistic plasma physics. The fundamental source of energy that feeds the plasma flow is believed to be the gravitational field of a central supermassive black hole. While the mechanism of energy transfer and a multitude of effects controlling the plasma flow are yet to be understood, major properties of jets are strikingly similar in a broad range of scales from stellar to galactic. They are supposed to be controlled by a limited number of physical parameters, such as the mass of a central black hole and its spin, magnetic field induction and accretion rate. In a very simplified sense, these parameters define the formation of a typical core-jet structure observed at radio wavelengths in the region of the innermost central tens of parsecs in AGN. These core-jet structures are studied in the radio domain by Very Long Baseline Interferometry (VLBI) with milli- and sub-milliarcsecond angular resolution. Such structures are detectable at a broad range of redshifts. If observed at a fixed wavelength, a typical core-jet AGN morphology would appear as having a steep-spectrum jet fading away with the increasing redshift while a flat-spectrum core becoming more dominant. If core-jet AGN constitute the same population of objects throughout the redshift space, the apparent ``prominence'' of jets at higher redshifts must decrease (Gurvits 1999): well pronounced jets at high z must appear less frequent than at low z.

  2. Active Galactic Nuclei:. Sources for Ultra High Energy Cosmic Rays

    NASA Astrophysics Data System (ADS)

    Biermann, P. L.; Becker, J. K.; Caramete, L.; Gergely, L.; Mariş, I. C.; Meli, A.; de Souza, V.; Stanev, T.

    Ultra high energy cosmic ray events presently show a spectrum, which we interpret here as galactic cosmic rays due to a starburst, in the radio galaxy Cen A which is pushed up in energy by the shock of a relativistic jet. The knee feature and the particles with energy immediately higher in galactic cosmic rays then turn into the bulk of ultra high energy cosmic rays. This entails that all ultra high energy cosmic rays are heavy nuclei. This picture is viable if the majority of the observed ultra high energy events come from the radio galaxy Cen A, and are scattered by intergalactic magnetic fields across much of the sky.

  3. Unconditional jetting.

    PubMed

    Gañán-Calvo, Alfonso M

    2008-08-01

    Capillary jetting of a fluid dispersed into another immiscible phase is usually limited by a critical capillary number, a function of the Reynolds number and the fluid property ratios. Critical conditions are set when the minimum spreading velocity of small perturbations v_{-};{*} along the jet (marginal stability velocity) is zero. Here we identify and describe parametric regions of high technological relevance, where v_{-};{*}>0 and the jet flow is always supercritical independently of the dispersed liquid flow rate; within these relatively broad regions, the jet does not undergo the usual dripping-jetting transition, so that either the jet can be made arbitrarily thin (yielding droplets of any imaginably small size), or the issuing flow rate can be made arbitrarily small. In this work, we provide illustrative analytical studies of asymptotic cases for both negligible and dominant inertia forces. In this latter case, requiring a nonzero jet surface velocity, axisymmetric perturbation waves "surf" downstream for all given wave numbers, while the liquid bulk can remain static. In the former case (implying small Reynolds flow) we found that the jet profile small slope is limited by a critical value; different published experiments support our predictions. PMID:18850933

  4. Energetic and radiative constraints on highly relativistic jets

    NASA Technical Reports Server (NTRS)

    Begelman, Mitchell C.; Rees, Martin J.; Sikora, Marek

    1994-01-01

    We examine constraints on the energetics and radiative efficiencies of highly relativistic, synchrotron-emitting jets. If the observed intraday radio variability of compact radio sources is intrinsic and results from incoherent synchrotron radiation, then the associated jets must have bulk Lorentz factors in the range Gamma varies approximately 30 to 100, several times larger than the largest values inferred from superluminal expansion, and larger even than the values required to avoid the synchrotron self-Compton catastrophe. We show that such highly relativistic jets produce synchrotron radiation with extremely low radiative efficiency. As a result they must carry enormous kinetic energy fluxes, L(sub j) approximately greater than 10(exp 47)(Delta Omega/0.1 sr), where Delta Omega is the solid angle subtended by the jet, in order to produce 'apparent' synchrotron brightness temperatures approximately greater than 10(exp 16) K. Energy losses by such jets should be strongly dominated by Compton scattering of diffuse ambient radiation, and they should produce large X-ray and gamma-ray fluxes.

  5. Slowly fading super-luminous supernovae that are not pair-instability explosions.

    PubMed

    Nicholl, M; Smartt, S J; Jerkstrand, A; Inserra, C; McCrum, M; Kotak, R; Fraser, M; Wright, D; Chen, T-W; Smith, K; Young, D R; Sim, S A; Valenti, S; Howell, D A; Bresolin, F; Kudritzki, R P; Tonry, J L; Huber, M E; Rest, A; Pastorello, A; Tomasella, L; Cappellaro, E; Benetti, S; Mattila, S; Kankare, E; Kangas, T; Leloudas, G; Sollerman, J; Taddia, F; Berger, E; Chornock, R; Narayan, G; Stubbs, C W; Foley, R J; Lunnan, R; Soderberg, A; Sanders, N; Milisavljevic, D; Margutti, R; Kirshner, R P; Elias-Rosa, N; Morales-Garoffolo, A; Taubenberger, S; Botticella, M T; Gezari, S; Urata, Y; Rodney, S; Riess, A G; Scolnic, D; Wood-Vasey, W M; Burgett, W S; Chambers, K; Flewelling, H A; Magnier, E A; Kaiser, N; Metcalfe, N; Morgan, J; Price, P A; Sweeney, W; Waters, C

    2013-10-17

    Super-luminous supernovae that radiate more than 10(44) ergs per second at their peak luminosity have recently been discovered in faint galaxies at redshifts of 0.1-4. Some evolve slowly, resembling models of 'pair-instability' supernovae. Such models involve stars with original masses 140-260 times that of the Sun that now have carbon-oxygen cores of 65-130 solar masses. In these stars, the photons that prevent gravitational collapse are converted to electron-positron pairs, causing rapid contraction and thermonuclear explosions. Many solar masses of (56)Ni are synthesized; this isotope decays to (56)Fe via (56)Co, powering bright light curves. Such massive progenitors are expected to have formed from metal-poor gas in the early Universe. Recently, supernova 2007bi in a galaxy at redshift 0.127 (about 12 billion years after the Big Bang) with a metallicity one-third that of the Sun was observed to look like a fading pair-instability supernova. Here we report observations of two slow-to-fade super-luminous supernovae that show relatively fast rise times and blue colours, which are incompatible with pair-instability models. Their late-time light-curve and spectral similarities to supernova 2007bi call the nature of that event into question. Our early spectra closely resemble typical fast-declining super-luminous supernovae, which are not powered by radioactivity. Modelling our observations with 10-16 solar masses of magnetar-energized ejecta demonstrates the possibility of a common explosion mechanism. The lack of unambiguous nearby pair-instability events suggests that their local rate of occurrence is less than 6 × 10(-6) times that of the core-collapse rate. PMID:24132291

  6. Slowly fading super-luminous supernovae that are not pair-instability explosions

    NASA Astrophysics Data System (ADS)

    Nicholl, M.; Smartt, S. J.; Jerkstrand, A.; Inserra, C.; McCrum, M.; Kotak, R.; Fraser, M.; Wright, D.; Chen, T.-W.; Smith, K.; Young, D. R.; Sim, S. A.; Valenti, S.; Howell, D. A.; Bresolin, F.; Kudritzki, R. P.; Tonry, J. L.; Huber, M. E.; Rest, A.; Pastorello, A.; Tomasella, L.; Cappellaro, E.; Benetti, S.; Mattila, S.; Kankare, E.; Kangas, T.; Leloudas, G.; Sollerman, J.; Taddia, F.; Berger, E.; Chornock, R.; Narayan, G.; Stubbs, C. W.; Foley, R. J.; Lunnan, R.; Soderberg, A.; Sanders, N.; Milisavljevic, D.; Margutti, R.; Kirshner, R. P.; Elias-Rosa, N.; Morales-Garoffolo, A.; Taubenberger, S.; Botticella, M. T.; Gezari, S.; Urata, Y.; Rodney, S.; Riess, A. G.; Scolnic, D.; Wood-Vasey, W. M.; Burgett, W. S.; Chambers, K.; Flewelling, H. A.; Magnier, E. A.; Kaiser, N.; Metcalfe, N.; Morgan, J.; Price, P. A.; Sweeney, W.; Waters, C.

    2013-10-01

    Super-luminous supernovae that radiate more than 1044 ergs per second at their peak luminosity have recently been discovered in faint galaxies at redshifts of 0.1-4. Some evolve slowly, resembling models of `pair-instability' supernovae. Such models involve stars with original masses 140-260 times that of the Sun that now have carbon-oxygen cores of 65-130 solar masses. In these stars, the photons that prevent gravitational collapse are converted to electron-positron pairs, causing rapid contraction and thermonuclear explosions. Many solar masses of 56Ni are synthesized; this isotope decays to 56Fe via 56Co, powering bright light curves. Such massive progenitors are expected to have formed from metal-poor gas in the early Universe. Recently, supernova 2007bi in a galaxy at redshift 0.127 (about 12 billion years after the Big Bang) with a metallicity one-third that of the Sun was observed to look like a fading pair-instability supernova. Here we report observations of two slow-to-fade super-luminous supernovae that show relatively fast rise times and blue colours, which are incompatible with pair-instability models. Their late-time light-curve and spectral similarities to supernova 2007bi call the nature of that event into question. Our early spectra closely resemble typical fast-declining super-luminous supernovae, which are not powered by radioactivity. Modelling our observations with 10-16 solar masses of magnetar-energized ejecta demonstrates the possibility of a common explosion mechanism. The lack of unambiguous nearby pair-instability events suggests that their local rate of occurrence is less than 6 × 10-6 times that of the core-collapse rate.

  7. Higher Dimensional Spacetimes for Visualizing and Modeling Subluminal, Luminal and Superluminal Flight

    SciTech Connect

    Froning, H. David; Meholic, Gregory V.

    2010-01-28

    This paper briefly explores higher dimensional spacetimes that extend Meholic's visualizable, fluidic views of: subluminal-luminal-superluminal flight; gravity, inertia, light quanta, and electromagnetism from 2-D to 3-D representations. Although 3-D representations have the potential to better model features of Meholic's most fundamental entities (Transluminal Energy Quantum) and of the zero-point quantum vacuum that pervades all space, the more complex 3-D representations loose some of the clarity of Meholic's 2-D representations of subluminal and superlumimal realms. So, much new work would be needed to replace Meholic's 2-D views of reality with 3-D ones.

  8. On the Extended Lorentz Transformation Model and Its Application to Superluminal Neutrinos

    NASA Astrophysics Data System (ADS)

    Hamieh, Salah D.

    2012-09-01

    In this paper, we consider the apparent superluminal speed of neutrinos in their travel from CERN to Gran Susso, as measured by the OPERA experiment, within the framework of the Extended Lorentz Transformation Model. The model is based on a natural extension of Lorentz transformation by wick rotation. Scalar and Dirac's fields are considered and invariance under the new Lorentz group is discussed. Moreover, an extension of quantum mechanics to accommodate new particles is considered using the newly proposed Generalized-C quantum mechanics. A two dimensional represen- tation of the new Dirac's equation is therefore formulated and its solution is calculated.

  9. On Determination of the Geometric Cosmological Constant from the Opera Experiment of Superluminal Neutrinos

    NASA Astrophysics Data System (ADS)

    Yan, Mu-Lin; Hu, Sen; Huang, Wei; Xiao, Neng-Chao

    The recent OPERA experiment of superluminal neutrinos has deep consequences in cosmology. In cosmology a fundamental constant is the cosmological constant. From observations one can estimate the effective cosmological constant Λeff which is the sum of the quantum zero point energy Λdark energy and the geometric cosmological constant Λ. The OPERA experiment can be applied to determine the geometric cosmological constant Λ. It is the first study to distinguish the contributions of Λ and Λdark energy from each other by experiment. The determination is based on an explanation of the OPERA experiment in the framework of Special Relativity with de Sitter spacetime symmetry.

  10. Superluminal and stopped light due to mode coupling in confined hyperbolic metamaterial waveguides.

    PubMed

    Neira, Andres D; Wurtz, Gregory A; Zayats, Anatoly V

    2015-01-01

    Anisotropic metamaterials with hyperbolic dispersion can be used to design waveguides with unusual properties. We show that, in contrast to planar waveguides, geometric confinement leads to coupling of ordinary (forward) and extraordinary (backward) modes and formation of hybrid waveguided modes, which near the crossing point may exhibit slow, stopped or superluminal behavior accompanied by very strong group velocity dispersion. These modes can be used for designing stopped-light nanolasers for nanophotonic applications and dispersion-facilitated signal reshaping in telecom applications. PMID:26643503

  11. Sub- and Superluminal Propagation of Intense Pulses in Media with Saturated and Reverse Absorption

    NASA Astrophysics Data System (ADS)

    Agarwal, G. S.; Dey, Tarak Nath

    2004-05-01

    We develop models for the propagation of intense pulses in solid state media which can have either saturated absorption or reverse absorption. We model subluminal propagation in ruby and superluminal propagation in alexandrite as three and four level systems, respectively, coupled to Maxwell's equations. We present results well beyond the traditional pump-probe approach and explain the experiments of Bigelow et al. [

    Phys. Rev. Lett.PRLTAO0031-9007 90, 113903 (2003); 10.1103/PhysRevLett.90.113903
    ScienceSCIEAS0036-8075 301, 200 (2003)
    ] on solid state materials.

  12. Universe of superluminal velocities: tests of astrophysics, from dogma-to reality

    NASA Astrophysics Data System (ADS)

    Chechelnitsky, A.

    The Barrier of speed of light is the most chained and, perhaps, the most unreasonable Interdiction of the standard (astro) physics and cosmology. Its theoretical bases are speculative and unconvincing, and it actually has not been proved by observations from the very beginning of its promulgations. Moreover, it is gradually increase a stream of the observational data frankly contradicting to the Barrier. This monumental Dogma substantially holds down the initiative of researchers and development of sciences about the Universe. Resolving proofs of absence of the Barrier and real existence of superluminal velocities can come, most likely, from the side of observational astrophysics, when appear fair predictions, based on the alternative theory. Predictions and observational Tests, in particular, are those. The advanced astrophysical researches will lead to accumulation of the precision data and construction of histograms of the velocities observable in the Universe (in the centers of galaxies, AGN, blazàrs, BL Lac, etc), which will show: i) Distribution of the transversal (in a picture plane) superluminal velocities has distinct peaks near to the values specified by the alternative theory: (in G[ -6] Shell) β =v/c: 1.77; 1.48; 1.25; 1.05; 0.88; 0.74; 0.62; 0.52; 0.44; (G[ -7] Shell) β =v/c:: 6.48 ; 5.45; 4.58; 3.85; 3.24; 2.72; 2.29; 1.92; 1.62; (G[ -8] Shell) β =v/c: 23.79; 20.00; 16.82; 14.14; 11.89; 10.00; 8.41; 7.07; 5.95 ii) The same peaks are available (already now, - and it can be shown on the basis of the spectroscopic data) in distribution (histograms) of beam (radial) superluminal velocities (with the same multiplicator M = 2 = 1.1892). iii) The predicted property of discreteness, quantization of superluminal velocities (as well as subluminal) velocities is the exclusive pattern, essentially distinguishing alternative representations (Wave Universe Concept [Chechelnitsky 1980-2004]; see, in particular, the bibliography in Advances in Space Research, v

  13. Interaction of Relativistic Jets with Their Environments

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna; Begelman, M. C.

    2014-01-01

    Relativistic jets such as those emitted by active galactic nuclei are observed to be collimated over great distances, but the cause of this collimation is uncertain. Also not fully understood are the means by which these jets become accelerated to their extreme velocities. To probe these questions, I examine the possibility of collimation and acceleration of relativistic jets by the pressure of the ambient medium surrounding the jet base, in the limit in which the jet interior has lost causal contact with its surroundings. I model the jet with an ultrarelativistic equation of state, injected into an ambient medium that has a pressure that decreases as a power of spherical radius, p ~ r^-n. Within the range 2jet interior will be out of causal contact, but the outer layers of the jet gradually collimate toward the jet axis, leading to the formation of a shocked boundary layer. By constructing partially self-similar solutions to the fluid equations within this boundary layer, I examine the impact of the external pressure profile on the behavior of the fluid in the layer. I determine both the structure of the jet and the rate of energy conversion from internal to kinetic as the jet propagates outward, establishing both the collimation and acceleration profiles of the jet. I will discuss the differences in predicted jet behavior based on whether the jet is purely hydrodynamic or whether the model also includes the effects of a toroidal magnetic field threading the jet interior. I will also describe the conditions that create specific observed jet morphology, such as the "hollow cone" structure seen in jets such as M87. Finally, I will discuss the specific application of these models to describe the relativistic jets that are created by some tidal disruption events --- events in which a star passing near a supermassive black hole (SMBH) is torn apart by tidal forces, and the star material then accretes back onto the SMBH --- such as in the observations of Swift

  14. Asteroseismology and Galactic Archaeology

    NASA Astrophysics Data System (ADS)

    Chiappini, C.

    2015-02-01

    Galactic Archeology is a coined term to describe the fact that the Milky Way's history is encoded both in the amounts of various chemical elements seen in the spectra of stellar atmospheres (abundances), and in stellar motions. One of the pillars of Galactic Archaeology is the use of stellar abundance ratios as an indirect age estimator, which although imprecise, has been proved useful in providing relative ages between the different galactic components. The lack of more precise age determination for large samples of field stars is one of the main reasons why different scenarios for the formation of our Galaxy can still be accommodated to current observational constraints, thus preventing a clear picture of the Milky Way's assembling history. Another difficulty is that most of the available information (especially on ages) has been confined to a region close to the Sun. These two main obstacles can now start to be overcome thanks to a) large spectroscopic and photometric surveys covering larger portions of the Milky Way, and b) the combination of the photometric and spectroscopic information with that coming from asteroseismology. The latter promises a breakthrough in the field of Galactic Archaeology, as it brings the opportunity to, for the first time, measure ages for large samples of distant field giant stars, which cover a large age-baseline. When combining this information with that soon available from Gaia, the field of Galactic Archaeology will be shaken and modelers will certainly have less flexibility in finding models that comply to these precious new observational constraints. The goal of these short lectures is to put Asteroseismology in the context of Galactic Archaeology.

  15. Interaction of Hydra A jets with the intracluster medium

    NASA Astrophysics Data System (ADS)

    Nawaz, Mohammad Ali; Bicknell, Geoffrey Vincent; Wagner, Alex; Slatyer Sutherland, Ralph; McNamara, Brian

    2015-08-01

    An important research area of modern astronomy is to understand the physics of jets from Active Galactic Nuclei (AGN) and their interaction with the interstellar medium (ISM) or intracluster medium (ICM). The aims of our project is to understand the energetics and composition of the jet near its origin, and its interaction with the ICM, focusing on detailed models of the inner structure of a spectacular radio source Hydra A. The key features of our modelling are that 1) We identify the four bright knots in the northern jet of Hydra A as biconical reconfinement shocks, which result when an over-pressured jet starts to come into equilibrium whit the galactic atmosphere 2) The curved morphology of the source and the turbulent transition of the jet to a plume are produced by the dynamical interaction of a precessing jet with the ICM. We provided an innovative theoretical approach to estimate the jet velocity from the information of the inner jet knots and the oscillation of the jet boundary. We also explored the complex morphology of the source and the heating of the ambient medium via the forward shock using a three dimensional precessing jet-ICM interaction model. With the 3D models We successfully reproduced key features of the source, for example, i) Four bright knots along the jet trajectory at approximately correct locations, 2) The curvature of the jet within 10 kpc, 3) The turbulent transition of the jet to a plume, and 4) A misaligned bright knot in the turbulent flaring zone. From our model we determined that the heating of the atmosphere by the jet would be gentle, which is consistent with the assessment of the physics of cooling flow.

  16. Magnetohydrodynamic Simulations of the Formation of Molecular Columns Found toward the Double Helix Nebulae in the Galactic Center

    NASA Astrophysics Data System (ADS)

    Asahina, Yuta; Matsumoto, Ryoji; Ogawa, Takayuki

    NANTEN2 observations of the galactic molecular gas revealed that molecular columns surround the double helix nebulae at our Galactic center (Enokiya et al. 2014). In order to study the formation mechanism of the double helix nebulae and molecular columns, we carried out magnetohydrodynamic (MHD) simulations of the interaction of a magnetic tower jet ejected from the galactic center with interstellar neutral hydrogen (HI) gas taking into account the interstellar cooling. The HI gas compressed by the bow shock ahead of the jet is cooled down by cooling instability triggered by the density enhancement. As a result, cold, dense region is formed around the helical magnetic tower jet. These molecular columns can be the evidences of the past activity near the galactic center black hole.

  17. ANATOMY OF HELICAL EXTRAGALACTIC JETS: THE CASE OF S5 0836+710

    SciTech Connect

    Perucho, M.; Kovalev, Y. Y.; Lobanov, A. P.; Hardee, P. E.; Agudo, I.

    2012-04-10

    Helical structures are common in extragalactic jets. They are usually attributed in the literature to periodical phenomena in the source (e.g., precession). In this work, we use very long baseline interferometry data of the radio jet in the quasar S5 0836+710 and hypothesize that the ridgeline of helical jets like this corresponds to a pressure maximum in the jet and assume that the helically twisted pressure maximum is the result of a helical wave pattern. For our study, we use observations of the jet in S5 0836+710 at different frequencies and epochs. The results show that the structures observed are physical and not generated artificially by the observing arrays. Our hypothesis that the observed intensity ridgeline can correspond to a helically twisted pressure maximum is confirmed by our observational tests. This interpretation allows us to explain jet misalignment between parsec and kiloparsec scales when the viewing angle is small, and also brings us to the conclusion that high-frequency observations may show only a small region of the jet flow concentrated around the maximum pressure ridgeline observed at low frequencies. Our work provides a potential explanation for the apparent transversal superluminal speeds observed in several extragalactic jets by means of transversal shift of an apparent core position with time.

  18. Emerging jets

    NASA Astrophysics Data System (ADS)

    Schwaller, Pedro; Stolarski, Daniel; Weiler, Andreas

    2015-05-01

    In this work, we propose a novel search strategy for new physics at the LHC that utilizes calorimeter jets that (i) are composed dominantly of displaced tracks and (ii) have many different vertices within the jet cone. Such emerging jet signatures are smoking guns for models with a composite dark sector where a parton shower in the dark sector is followed by displaced decays of dark pions back to SM jets. No current LHC searches are sensitive to this type of phenomenology. We perform a detailed simulation for a benchmark signal with two regular and two emerging jets, and present and implement strategies to suppress QCD backgrounds by up to six orders of magnitude. At the 14 TeV LHC, this signature can be probed with mediator masses as large as 1.5 TeV for a range of dark pion lifetimes, and the reach is increased further at the high-luminosity LHC. The emerging jet search is also sensitive to a broad class of long-lived phenomena, and we show this for a supersymmetric model with R-parity violation. Possibilities for discovery at LHCb are also discussed.

  19. A wind-type model for the generation of astrophysical jets

    NASA Technical Reports Server (NTRS)

    Ferrari, A.; Habbal, S. R.; Rosner, R.; Tsinganos, K.

    1984-01-01

    Wind-type solutions for the generation of astrophysical jets from active galactic nuclei and stellar sources, such as those associated with SS 433 and protostellar objects, are discussed. Acceleration, collimation, and morphology are consistently interpreted in terms of a flow starting from the galactic or stellar core inside the 'throat' of a thick accretion disk.

  20. Self-accelerating massive gravity: Superluminality, Cauchy surfaces, and strong coupling

    NASA Astrophysics Data System (ADS)

    Motloch, Pavel; Hu, Wayne; Joyce, Austin; Motohashi, Hayato

    2015-08-01

    Self-accelerating solutions in massive gravity provide explicit, calculable examples that exhibit the general interplay between superluminality, the well-posedness of the Cauchy problem, and strong coupling. For three particular classes of vacuum solutions, one of which is new to this work, we construct the conformal diagram for the characteristic surfaces on which isotropic stress-energy perturbations propagate. With one exception, all solutions necessarily possess spacelike characteristics, indicating perturbative superluminality. Foliating the spacetime with these surfaces gives a pathological frame where kinetic terms of the perturbations vanish, confusing the Hamiltonian counting of degrees of freedom. This frame dependence distinguishes the vanishing of kinetic terms from strong coupling of perturbations or an ill-posed Cauchy problem. We give examples where spacelike characteristics do and do not originate from a point where perturbation theory breaks down and where spacelike surfaces do or do not intersect all characteristics in the past light cone of a given observer. The global structure of spacetime also reveals issues that are unique to theories with two metrics: in all three classes of solutions, the Minkowski fiducial space fails to cover the entire de Sitter spacetime allowing worldlines of observers to end in finite proper time at determinant singularities. Characteristics run tangent to these surfaces requiring ad hoc rules to establish continuity across singularities.

  1. Superfast Cosmic Jet "Hits the Wall"

    NASA Astrophysics Data System (ADS)

    1999-01-01

    A superfast jet of subatomic particles presumably powered by the gravitational energy of a black hole has collided with nearby material, been slowed dramatically and released much of its energy in the collision, radio astronomers report. The astronomers used the National Science Foundation's Very Large Array (VLA) radio telescope to observe the jet's motion. This is the first time such a collision has been seen within our own Milky Way Galaxy, and the collision may shed new light on the physics of cosmic jets. Robert Hjellming, Michael Rupen and Frank Ghigo of the National Radio Astronomy Observatory (NRAO); Amy Mioduszewski of the Joint Institute for VLBI in Europe; Don Smith of MIT's Space Research Lab; Alan Harmon of Marshall Space Flight Center, and Elizabeth Waltman of the Naval Research Laboratory reported their findings today at the American Astronomical Society's meeting in Austin, TX. The cosmic jet comes from an object called XTE J1748-288, at least 30,000 light-years away in the constellation Sagittarius, near the center of the Milky Way. XTE J1748-288, discovered on June 4, 1998, by Don Smith, using the RXTE satellite, is a "black hole candidate," probably consisting of a black hole drawing material from a companion star and accelerating jets of material outward in the process. A series of VLA images showed a "blob" of material in the jet moving at an apparent speed at least 50 percent greater than that of light. This is only the third such "superluminal" jet seen in our own Galaxy. The apparent faster-than-light motion is an illusion created by geometric effects when jets move at nearly the speed of light and are aligned so that their motion is somewhat toward Earth. The two other Milky Way objects whose jets show such rapid motion are dubbed "microquasars," because their behavior mimics that of quasars -- much larger objects seen at the cores of very distant galaxies. A series of VLA images showed material ejected as a jet from the core of XTE J1748

  2. Synthetic Jets

    NASA Technical Reports Server (NTRS)

    Milanovic, Ivana M.

    2003-01-01

    Current investigation of synthetic jets and synthetic jets in cross-flow examined the effects of orifice geometry and dimensions, momentum-flux ratio, cluster of orifices, pitch and yaw angles as well as streamwise development of the flow field. This comprehensive study provided much needed experimental information related to the various control strategies. The results of the current investigation on isolated and clustered synthetic jets with and without cross-flow will be further analyzed and documented in detail. Presentations at national conferences and publication of peer- reviewed journal articles are also expected. Projected publications will present both the mean and turbulent properties of the flow field, comparisons made with the data available in an open literature, as well as recommendations for the future work.

  3. Relativistic jet feedback in high-redshift galaxies I: Dynamics

    NASA Astrophysics Data System (ADS)

    Mukherjee, Dipanjan; Bicknell, Geoffrey V.; Sutherland, Ralph; Wagner, Alex

    2016-06-01

    We present the results of three dimensional relativistic hydrodynamic simulations of interaction of AGN jets with a dense turbulent two-phase interstellar medium, which would be typical of high redshift galaxies. We describe the effect of the jet on the evolution of the density of the turbulent ISM. The jet driven energy bubble affects the gas to distances up to several kiloparsecs from the injection region. The shocks resulting from such interactions create a multi-phase ISM and radial outflows. One of the striking result of this work is that low power jets (Pjet ≲ 1043ergs-1) although less efficient in accelerating clouds, are trapped in the ISM for a longer time and hence affect the ISM over a larger volume. Jets of higher power drill through with relative ease. Although the relativistic jets launch strong outflows, there is little net mass ejection to very large distances, supporting a galactic fountain scenario for local feedback.

  4. eRMHD simulations of jets with helical magnetic fields

    NASA Astrophysics Data System (ADS)

    Roca-Sogorb, M.; Perucho, M.; Gómez, J. L.; Martí, J. M.; Antón, L.; Aloy, M. A.; Agudo, I.

    We present numerical magnetohydrodynamic and emission (eRMHD) simulations of relativistic jets in active galactic nuclei. We focus our study on the role played by the magnetic field in the dynamics of the jet, analyzing the balance of the main driving forces which determine the jet evolution. Overpressured jets with different magnetizations are considered in order to study their influence in the jet collimation, confinement and overall stability. Computation of the synchrotron emission from these models allows a direct comparison with actual sources. We find that the relative brightness of the knots associated with the recollimation shocks decreases with increasing magnetization, suggesting that overpressured jets presenting stationary components may have a relatively weak magnetization, with magnetic fields of the order of equipartition or below.

  5. Simulations of Relativistic Extragalactic Jets

    NASA Astrophysics Data System (ADS)

    Hughes, P. A.; Duncan, G. C.

    1994-05-01

    We present results for 2-D, axisymmetric simulations of flows with Lorentz factors ~ 5 -- 10, typical of values inferred for superluminal BL Lacs and QSOs. The simulations were performed with a numerical hydrodynamic code that admits relativistic flow speed. We exploit the property that the relativistic Euler equations for mass, momentum and total energy densities in the laboratory frame have the same form as the nonrelativistic equations, to solve for laboratory frame variables using a conventional Godunov-type scheme with approximate Riemann solver: the HLLE method. The relativistic nature of the flow is incorporated by performing a Lorentz transformation at every step, at each cell center or cell boundary where pressure, sound speed or velocity are required. Determination of the velocity in this manner is a robust algebraic procedure within which we can ensure that vjet radii, the Kelvin-Helmholtz instability at the contact surface is much less evident in the high Lorentz factor cases, supporting the contention that relativistic flows are less prone to such instability. We describe how the morphology of the cocoon and shocked ambient gas change with increasing Lorentz factor. This work was supported by NSF grant AST 9120224 and by the Ohio Supercomputer Center from a Cray Research Software Development Grant.

  6. Abundances of planetary nebulae in the Galactic bulge

    NASA Astrophysics Data System (ADS)

    Pottasch, S. R.; Bernard-Salas, J.

    2015-11-01

    Context. Planetary nebulae (PNe) abundances are poorly known for those nebulae in the Galactic bulge. This is because of the high and uneven extinction in the bulge which makes visual spectral measurements difficult. In addition, the extinction corrections may be unreliable. Elements considered are O, N, Ne, S, Ar, and Cl. Aims: We determine the abundances in 19 PNe, 18 of which are located in the bulge. This doubles the number of PNe abundance determinations in the bulge. The Galactic abundance gradient is discussed for five elements. Methods: The mid-infrared spectra measured by the Spitzer Space Telescope are used to determine the abundances. This part of the spectrum is little affected by extinction for which an uncertain correction is no longer necessary. In addition the connection with the visible and ultraviolet spectrum becomes simpler because hydrogen lines are observed both in the infrared and in the visible spectra. In this way we more than double the number of PNe with reliable abundances. Results: Reliable abundances are obtained for O, N, Ne, S, and Ar for Galactic bulge PNe. Conclusions: The Galactic abundance gradient is less steep than previously thought. This is especially true for oxygen. The sulfur abundance is reliable because all stages of ionization expected have been measured. It is not systematically low compared to oxygen as has been found for some Galactic PNe. Based on observations with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology.

  7. Bulk Comptonization of the Cosmic Microwave Background by Extragalactic Jets as a Probe of their Matter Content

    NASA Technical Reports Server (NTRS)

    Georganopoulos, Markos; Kazanas, Demosthenes; Perlman, Eric; Stecker, Floyd W.

    2004-01-01

    We propose a method for estimating the composition, i.e. the relative amounts of leptons and protons, of extragalactic jets which exhibit Chandra - detected knots in their kpc scale jets. The method relies on measuring, or setting upper limits on, the component of the Cosmic Microwave Background (CMB) radiation that is bulk-Comptonized by the cold electrons in the relativistically flowing jet. These measurements, along with modeling of the broadband knot emission that constrain the bulk Lorentz factor GAMMA of the jets, can yield estimates of the jet power carried by protons and leptons. We provide an explicit calculation of the spectrum of the bulk-Comptonized (BC) CMB component and apply these results to PKS 0637 - 752 and 3C 273, two superluminal quasars with Chandra - detected large scale jets. What makes these sources particularly suited for such a procedure is the absence of significant non-thermal jet emission in the 'bridge', the region between the core and the first bright jet knot, which guarantees that most of the electrons are cold there, leaving the BC scattered CMB radiation as the only significant source of photons in this region. At lambda = 3.6 - 8.0 microns, the most likely band to observe the BC scattered CMB emission, the Spitzer angular resolution (approximately 1" - 3") is considerably smaller than the the 'bridges' of these jets (approximately 10"), making it possible to both measure and resolve this emission.

  8. Relativistic MHD Simulations of Poynting Flux-driven Jets

    NASA Astrophysics Data System (ADS)

    Guan, Xiaoyue; Li, Hui; Li, Shengtai

    2014-01-01

    Relativistic, magnetized jets are observed to propagate to very large distances in many active galactic nuclei (AGNs). We use three-dimensional relativistic MHD simulations to study the propagation of Poynting flux-driven jets in AGNs. These jets are already assumed to be being launched from the vicinity (~103 gravitational radii) of supermassive black holes. Jet injections are characterized by a model described in Li et al., and we follow the propagation of these jets to ~parsec scales. We find that these current-carrying jets are always collimated and mildly relativistic. When α, the ratio of toroidal-to-poloidal magnetic flux injection, is large the jet is subject to nonaxisymmetric current-driven instabilities (CDI) which lead to substantial dissipation and reduced jet speed. However, even with the presence of instabilities, the jet is not disrupted and will continue to propagate to large distances. We suggest that the relatively weak impact by the instability is due to the nature of the instability being convective and the fact that the jet magnetic fields are rapidly evolving on Alfvénic time scales. We present the detailed jet properties and show that far from the jet launching region, a substantial amount of magnetic energy has been transformed into kinetic energy and thermal energy, producing a jet magnetization number σ < 1. In addition, we have also studied the effects of a gas pressure supported "disk" surrounding the injection region, and qualitatively similar global jet behaviors were observed. We stress that jet collimation, CDIs, and the subsequent energy transitions are intrinsic features of current-carrying jets.

  9. Simulations of Galactic Dynamos

    NASA Astrophysics Data System (ADS)

    Brandenburg, Axel

    We review our current understanding of galactic dynamo theory, paying particular attention to numerical simulations both of the mean-field equations and the original three-dimensional equations relevant to describing the magnetic field evolution for a turbulent flow. We emphasize the theoretical difficulties in explaining non-axisymmetric magnetic fields in galaxies and discuss the observational basis for such results in terms of rotation measure analysis. Next, we discuss nonlinear theory, the role of magnetic helicity conservation and magnetic helicity fluxes. This leads to the possibility that galactic magnetic fields may be bi-helical, with opposite signs of helicity and large and small length scales. We discuss their observational signatures and close by discussing the possibilities of explaining the origin of primordial magnetic fields.

  10. The Galactic Bulge

    NASA Astrophysics Data System (ADS)

    Barbuy, B.

    2016-06-01

    The Galactic bulge is the least studied component of our Galaxy. Yet, its formation and evolution are key to understand the formation of the Galaxy itself. Studies on the Galactic bulge have increased significantly in the last years, but still there are many points of controversy. This volume contains several contributions from experts in different aspects of the bulge. Issues discussed include the following: the presence of an old spheroidal bulge, or identification of its old stellar population with the thick disk or halo; fraction of stars younger than 10 Gyr is estimated to be of < 5 to 22% depending on method and authors; multiple populations or only a metal-poor and a metal-rich ones; spheroidal or ellipsoidal distribution of RR Lyrae; formation of the bulge from early mergers or from secular evolution of the bar; different methods of mapping extinction; selection and identification of bulge globular clusters.

  11. Galactic-scale civilization

    NASA Technical Reports Server (NTRS)

    Kuiper, T. B. H.

    1980-01-01

    Evolutionary arguments are presented in favor of the existence of civilization on a galactic scale. Patterns of physical, chemical, biological, social and cultural evolution leading to increasing levels of complexity are pointed out and explained thermodynamically in terms of the maximization of free energy dissipation in the environment of the organized system. The possibility of the evolution of a global and then a galactic human civilization is considered, and probabilities that the galaxy is presently in its colonization state and that life could have evolved to its present state on earth are discussed. Fermi's paradox of the absence of extraterrestrials in light of the probability of their existence is noted, and a variety of possible explanations is indicated. Finally, it is argued that although mankind may be the first occurrence of intelligence in the galaxy, it is unjustified to presume that this is so.

  12. Topics in galactic dynamics

    NASA Astrophysics Data System (ADS)

    Little, Frank Blane

    1989-01-01

    The distant satellites of the Milky Way Galaxy are used to probe the distribution of dark matter in the Galactic halo. A new method of statistical analysis based on Bayes' theorem was devised, which directly yields confidence intervals for the mass of the Galaxy once the eccentricity distribution of the satellites is specified. Assuming an isotropic velocity distribution for 10 objects at distances of 50 to 140 kiloparsecs, mass results suggest that the Galaxy's massive dark halo extends to approximately less than 50 kiloparsecs from the Galactic center. A model galaxy with an artificial bar is used to explore the effect of dynamical friction on a galactic bar. An analytic formula is provided which correctly predicts angular momentum changes for a bar in interaction with a non self-gravitating disk. N-body simulations further show that disk self-gravity tends to make a bar without inner Lindblad resonances spin down more rapidly, and tends to make a bar dominated by inner Lindblad resonances spin up less rapidly. The long-term dynamical evolution of galactic bars is investigated using fully self gravitating bar-unstable disk-halo models. The models develop rapidly rotating bars which then slow down through transfers of angular momentum both to the outer disk and to the halo. The models suggest that the distance between the end of a bar and its corotation circle is proportional to the bar's age, and an approximate formula is presented which expresses this relationship. It is also concluded that the average tangential velocity within a barlike object drops by a factor of about 2 over approximately 45 initial rotation periods.

  13. Modeling Relativistic Jets Using the Athena Hydrodynamics Code

    NASA Astrophysics Data System (ADS)

    Pauls, David; Pollack, Maxwell; Wiita, Paul

    2014-11-01

    We used the Athena hydrodynamics code (Beckwith & Stone 2011) to model early-stage two-dimensional relativistic jets as approximations to the growth of radio-loud active galactic nuclei. We analyzed variability of the radio emission by calculating fluxes from a vertical strip of zones behind a standing shock, as discussed in the accompanying poster. We found the advance speed of the jet bow shock for various input jet velocities and jet-to-ambient density ratios. Faster jets and higher jet densities produce faster shock advances. We investigated the effects of parameters such as the Courant-Friedrichs-Lewy number, the input jet velocity, and the density ratio on the stability of the simulated jet, finding that numerical instabilities grow rapidly when the CFL number is above 0.1. We found that greater jet input velocities and higher density ratios lengthen the time the jet remains stable. We also examined the effects of the boundary conditions, the CFL number, the input jet velocity, the grid resolution, and the density ratio on the premature termination of Athena code. We found that a grid of 1200 by 1000 zones allows the code to run with minimal errors, while still maintaining an adequate resolution. This work is supported by the Mentored Undergraduate Summer Experience program at TCNJ.

  14. Galactic Diffuse Emissions

    SciTech Connect

    Digel, Seth W.; /SLAC

    2007-10-25

    Interactions of cosmic rays with interstellar nucleons and photons make the Milky Way a bright, diffuse source of high-energy {gamma}-rays. Observationally, the results from EGRET, COMPTEL, and OSSE have now been extended to higher energies by ground-based experiments, with detections of diffuse emission in the Galactic center reported by H.E.S.S. in the range above 100 GeV and of diffuse emission in Cygnus by MILAGRO in the TeV range. In the range above 100 keV, INTEGRAL SPI has found that diffuse emission remains after point sources are accounted for. I will summarize current knowledge of diffuse {gamma}-ray emission from the Milky Way and review some open issues related to the diffuse emission -- some old, like the distribution of cosmic-ray sources and the origin of the 'excess' of GeV emission observed by EGRET, and some recently recognized, like the amount and distribution of molecular hydrogen not traced by CO emission -- and anticipate some of the advances that will be possible with the Large Area Telescope on GLAST. We plan to develop an accurate physical model for the diffuse emission, which will be useful for detecting and accurately characterizing emission from Galactic point sources as well as any Galactic diffuse emission from exotic processes, and for studying the unresolved extragalactic emission.

  15. Galactic oscillator symmetry

    NASA Technical Reports Server (NTRS)

    Rosensteel, George

    1995-01-01

    Riemann ellipsoids model rotating galaxies when the galactic velocity field is a linear function of the Cartesian coordinates of the galactic masses. In nuclear physics, the kinetic energy in the linear velocity field approximation is known as the collective kinetic energy. But, the linear approximation neglects intrinsic degrees of freedom associated with nonlinear velocity fields. To remove this limitation, the theory of symplectic dynamical symmetry is developed for classical systems. A classical phase space for a self-gravitating symplectic system is a co-adjoint orbit of the noncompact group SP(3,R). The degenerate co-adjoint orbit is the 12 dimensional homogeneous space Sp(3,R)/U(3), where the maximal compact subgroup U(3) is the symmetry group of the harmonic oscillator. The Hamiltonian equations of motion on each orbit form a Lax system X = (X,F), where X and F are elements of the symplectic Lie algebra. The elements of the matrix X are the generators of the symplectic Lie algebra, viz., the one-body collective quadratic functions of the positions and momenta of the galactic masses. The matrix F is composed from the self-gravitating potential energy, the angular velocity, and the hydostatic pressure. Solutions to the hamiltonian dynamical system on Sp(3,R)/U(3) are given by symplectic isospectral deformations. The Casimirs of Sp(3,R), equal to the traces of powers of X, are conserved quantities.

  16. The generation of bipolar jets of astrophysical relevance using the OMEGA facility

    NASA Astrophysics Data System (ADS)

    Gourdain, P.-A.; Blackman, E. G.; Frank, A.; Meyerhofer, D. M.; Seyler, C. E.

    2015-11-01

    Bipolar astrophysical plasma jets are generated by young stellar objects, active galactic nuclei and proto-planetary nebulae. They are not only born in harsh environments, they can encounter extreme conditions along the way. Recent observations have made apparent that electron physics impacts the overall dynamics of bipolar plasma jets. For instance, the Hall effect together with Ohmic resistivity can change completely the magnetic field structure inside protoplanetary disks and can alter significantly the magneto-rotational instabilities in the inner regions of the disks. The Hall effect plays a critical role in the magnetic polarity of galactic jets. The numerical simulations presented here show how the OMEGA laser can be used to produce bipolar plasma jets with large Reynolds, magnetic Reynolds and Mach numbers. It will also show how electron physics can break the jet symmetry. A discussion will follow on how to generate similar jets using pulsed-power generators. Research partially supported by the NSF grant PHY-1102471.

  17. Galactic diffuse gamma rays from galactic plane

    NASA Astrophysics Data System (ADS)

    Tateyama, N.; Nishimura, J.

    2001-08-01

    The dominant part of the diffuse gamma rays from the Galactic plane, with energy greater than 1TeV, has been thought as due to the inverse Compton scattering of the interstellar photons with the high-energy cosmic electrons. In these energy regions, the diffuse gamma-ray observation gives us unique infor-mation on the energy spectrum of the high-energy electrons in the interstellar space, since we cannot observe those electrons directly. This provides us information on the cosmicray source, production mechanism and propagation in the Galaxy. We discuss the implication of our results by comparing with the work of Porter and Protheroe, and also compare with the data observed by the most recent extensive air showers. It is also pointed out that the patchy structure of gammaray distribution will appear at high-energy side, if we observe the distribution with a higher angular resolution of a few arc degrees. This patchy structure will become clear beyond 10TeV of IC gamma rays, where the number of contributing sources of parent decrease and the diffusion distance of the electrons become smaller.

  18. THE ACCELERATING JET OF 3C 279

    SciTech Connect

    Bloom, S. D.; Fromm, C. M.; Ros, E.

    2013-01-01

    Analysis of the proper motions of the subparsec scale jet of the quasar 3C 279 at 15 GHz with the Very Long Baseline Array shows significant accelerations in four of nine superluminal features. Analysis of these motions is combined with the analysis of flux density light curves to constrain values of Lorentz factor and viewing angle (and their derivatives) for each component. The data for each of these components are consistent with significant changes to the Lorentz factor, viewing angle, and azimuthal angle, suggesting jet bending with changes in speed. We see that for these observed components Lorentz factors are in the range {Gamma} = 10-41, viewing angles are in the range thetav = 0. Degree-Sign 1-5. Degree-Sign 0, and intrinsic (source frame) flux density is in the range, F{sub {nu},int} 1.5 Multiplication-Sign 10{sup -9}-1.5 Multiplication-Sign 10{sup -5} Jy. Considering individual components, the Lorentz factors vary from {Gamma} = 11-16 for C1, {Gamma} = 31-41 for C5, {Gamma} = 29-41 for C6, and {Gamma} = 9-12 for C8, indicating that there is no single underlying flow speed to the jet and likely we are seeing pattern speeds from shocks in the jet. The viewing angles vary in time from 0. Degree-Sign 6 to 1. Degree-Sign 5 in the case of C1 (the least extreme example), from 0. Degree-Sign 5 to 5. Degree-Sign 0 in the case of C8, and from 0. Degree-Sign 1 to 0. Degree-Sign 9 for C5 (the last two being the most extreme examples). The intrinsic flux density varies by factors from 1.4 for C8 and 430 for C5. Theoretical analysis of the accelerations also indicates potential jet bending. In addition, for one component, C5, polarization measurements also set limits to the trajectory of the jet.

  19. On using Greenberger-Horne-Zeilinger three-particle states for superluminal communication

    SciTech Connect

    Jensen, Raymond

    2010-01-28

    Using a three-particle entangled system (triple) of photons, it is possible in principle to transmit signals faster than the speed of light from sender to receiver in the following manner: First, let there be an emitter of triples between sender and receiver. For every triple, photons 1 and 2 are sent to the receiver and 3, to the sender. The sender is given the choice of whether to (a) measure polarization of photon 3 or (b) destroy such information. On the other hand, the receiver measures photon correlation vs. relative polarization angle between photons 1 and 2. These correlation statistics depend on whether photon 3 polarization was (a) measured or (b) destroyed. Since this dependence is nonlocal, it is a basis for superluminal i.e. faster-than-light communication.

  20. Experimental demonstration of slow and superluminal light in semiconductor optical amplifiers.

    PubMed

    Pesala, Bala; Chen, Zhangyuan; Uskov, Alexander V; Chang-Hasnain, Connie

    2006-12-25

    Tunable delays in semiconductor optical amplifiers are achieved via four wave mixing between a strong pump beam and a modulated probe beam. The delay of the probe beam can be controlled both electrically, by changing the SOA bias, and optically, by varying the pump power or the pump-probe detuning. For sinusoidal modulated signal at 0.5 GHz, a tunable delay of 1.6 ns is achieved. This corresponds to a RF phase change of 1.6 pi. For 1.3 ns optical pulses propagating through the SOA a delay of 0.59 ns is achieved corresponding to a delay-bandwidth product exceeding 0.45. For both the cases, slow light and superluminal light are observed as the pump-probe detuning is varied. PMID:19532190

  1. Influence of nanorod absorption spectrum width on superluminality effect for laser pulse propagation

    NASA Astrophysics Data System (ADS)

    Trofimov, Vyacheslav A.; Lysak, Tatiana M.

    2016-03-01

    We investigate the influence of the finite absorption spectrum width on the soliton formation and superluminality phenomenon at a femtosecond pulse propagation in a medium with noble nanoparticles. These effects take place if a positive phase-amplitude grating is induced by laser radiation. We take into account the two-photon absorption (TPA) of laser radiation by nanorods, and time-dependent nanorod aspect ratio changing due to their melting or reshaping because of laser energy absorption, and the nanorod absorption spectrum width. On the basis of computer simulation we demonstrate these effects in a medium with positive phase-amplitude grating, induced by laser radiation, if a weak laser energy absorption takes place on the laser pulse dispersion length.

  2. The superluminal limit as a consequence of the classical causality principle

    NASA Astrophysics Data System (ADS)

    Cutolo, A.

    2012-01-01

    The superluminal limit states that no physical object can overpass the velocity of the light in vacuum. This limit is usually considered a consequence of the special theory of relativity (STR). In contrast with the basic hypotheses chosen by Albert Einstein, many authors wrongly consider it a basic assumption of the STR. Here, we revise this limit by showing that it can be derived as a consequence of the classical causality principle without invoking any additional hypotheses. It will be demonstrated to hold true in any kind of medium even in those exhibiting either a phase or group velocity of the light greater than that of light in vacuum. The behavior of some neutral particles ( e.g. neutrinos, photons) is shown to be fully consistent with this model. The validity of our discussion rests on the hypotheses of a gravitationless vacuum.

  3. Generalised Einstein mass-variation formulae: II Superluminal relative frame velocities

    NASA Astrophysics Data System (ADS)

    Hill, James M.; Cox, Barry J.

    In part I of this paper we have deduced generalised Einstein mass variation formulae assuming relative frame velocities v < c . Here we present corresponding new expressions for superluminal relative frame velocities v > c . We again use the notion of the residual mass m0 (v) which for v > c is defined by the equation m (v) =m0 (v)[(v / c) 2 - 1 ] - 1 / 2 for the actual mass m (v) . The residual mass is essentially the actual mass with the Einstein factor removed, and we emphasise that we make no restrictions on m0 (v) . Using this formal device we deduce corresponding new mass variation formulae applicable to superluminal relative frame velocities, assuming only the extended Lorentz transformations and their consequences, and two invariants that are known to apply in special relativity. The present authors have previously speculated a dual framework such that both the rest mass m0∗ and the residual mass at infinite velocity m∞∗ (by which we mean p∞∗ / c , assuming finite momentum at infinity) are equally important parameters in the specification of mass as a function of its velocity, and the two arbitrary constants can be so determined. The new formulae involving two arbitrary constants may also be exploited so that the mass remains finite at the speed of light, and two distinct mass profiles are determined as functions of their velocity with the rest mass assumed to be alternatively prescribed at the origin of either frame. The two profiles so obtained (M (U), m (u)) and (M∗ (U),m∗ (u)) although distinct have a common ratio M (U) /M∗ (U) = m (u) /m∗ (u) that is a function of v > c , indicating that observable mass depends upon the frame in which the rest mass is prescribed.

  4. Two-dimensional radiation hydrodynamics simulations of superluminous interacting supernovae of Type IIn

    NASA Astrophysics Data System (ADS)

    Vlasis, Alkiviadis; Dessart, Luc; Audit, Edouard

    2016-05-01

    Some interacting supernovae (SNe) of Type IIn show a sizeable continuum polarization suggestive of a large-scale asymmetry in the circumstellar medium (CSM) and/or the SN ejecta. Here, we extend the recent work of Dessart et al. on superluminous SNe IIn and perform axially-symmetric (i.e. 2D) multigroup radiation hydrodynamics simulations to explore the impact of an imposed large-scale density asymmetry. When the CSM is asymmetric, the latitudinal variation of the radial optical depth τ introduces a strong flux redistribution from the higher density CSM regions, where the shock luminosity is larger, towards the lower density CSM regions where photons escape more freely - this redistribution ceases when τ ≲ 1. Along directions where the CSM density is larger, the shock deceleration is stronger and its progression slower, producing a non-spherical cold-dense shell (CDS). For an oblate CSM density distribution, the photosphere (CDS) has an oblate (prolate) morphology when τ ≳ 1. When the CSM is symmetric and the ejecta asymmetric, the flux redistribution within the CSM now tends to damp the latitudinal variation of the luminosity at the shock. It then requires a larger ejecta asymmetry to produce a sizeable latitudinal variation in the emergent flux. When the interaction is between a SN ejecta and a relic disc, the luminosity boost at early times scales with the disc opening angle - forming a superluminous SN IIn this way requires an unrealistically thick disc. In contrast, interaction with a disc of modest thickness/mass can yield a power that rivals radioactive decay of a standard SN II at nebular times.

  5. Two Superluminous Supernovae from the Early Universe Discovered by the Supernova Legacy Survey

    NASA Astrophysics Data System (ADS)

    Howell, D. A.; Kasen, D.; Lidman, C.; Sullivan, M.; Conley, A.; Astier, P.; Balland, C.; Carlberg, R. G.; Fouchez, D.; Guy, J.; Hardin, D.; Pain, R.; Palanque-Delabrouille, N.; Perrett, K.; Pritchet, C. J.; Regnault, N.; Rich, J.; Ruhlmann-Kleider, V.

    2013-12-01

    We present spectra and light curves of SNLS 06D4eu and SNLS 07D2bv, two hydrogen-free superluminous supernovae (SNe) discovered by the Supernova Legacy Survey. At z = 1.588, SNLS 06D4eu is the highest redshift superluminous SN with a spectrum, at MU = -22.7 it is one of the most luminous SNe ever observed, and it gives a rare glimpse into the rest-frame ultraviolet where these SNe put out their peak energy. SNLS 07D2bv does not have a host galaxy redshift, but on the basis of the SN spectrum, we estimate it to be at z ~ 1.5. Both SNe have similar observer-frame griz light curves, which map to rest-frame light curves in the U band and UV, rising in ~20 rest-frame days or longer and declining over a similar timescale. The light curves peak in the shortest wavelengths first, consistent with an expanding blackbody starting near 15,000 K and steadily declining in temperature. We compare the spectra with theoretical models, and we identify lines of C II, C III, Fe III, and Mg II in the spectra of SNLS 06D4eu and SCP 06F6 and find that they are consistent with an expanding explosion of only a few solar masses of carbon, oxygen, and other trace metals. Thus, the progenitors appear to be related to those suspected for SNe Ic. A high kinetic energy, 1052 erg, is also favored. Normal mechanisms of powering core-collapse or thermonuclear SNe do not seem to work for these SNe. We consider models powered by 56Ni decay and interaction with circumstellar material, but we find that the creation and spin-down of a magnetar with a period of 2 ms, a magnetic field of 2 × 1014 G, and a 3 M ⊙ progenitor provides the best fit to the data.

  6. Extreme Supernova Models for the Super-luminous Transient ASASSN-15lh

    NASA Astrophysics Data System (ADS)

    Chatzopoulos, E.; Wheeler, J. C.; Vinko, J.; Nagy, A. P.; Wiggins, B. K.; Even, W. P.

    2016-09-01

    The recent discovery of the unprecedentedly super-luminous transient ASASSN-15lh (or SN 2015L) with its UV-bright secondary peak challenges all the power-input models that have been proposed for super-luminous supernovae. Here we examine some of the few viable interpretations of ASASSN-15lh in the context of a stellar explosion, involving combinations of one or more power inputs. We model the light curve of ASASSN-15lh with a hybrid model that includes contributions from magnetar spin-down energy and hydrogen-poor circumstellar interaction. We also investigate models of pure circumstellar interaction with a massive hydrogen-deficient shell and discuss the lack of interaction features in the observed spectra. We find that, as a supernova, ASASSN-15lh can be best modeled by the energetic core-collapse of an ∼40 M ⊙ star interacting with a hydrogen-poor shell of ∼20 M ⊙. The circumstellar shell and progenitor mass are consistent with a rapidly rotating pulsational pair-instability supernova progenitor as required for strong interaction following the final supernova explosion. Additional energy injection by a magnetar with an initial period of 1–2 ms and magnetic field of 0.1–1 × 1014 G may supply the excess luminosity required to overcome the deficit in single-component models, but this requires more fine-tuning and extreme parameters for the magnetar, as well as the assumption of efficient conversion of magnetar energy into radiation. We thus favor a single-input model where the reverse shock formed in a strong SN ejecta–circumstellar matter interaction following a very powerful core-collapse SN explosion can supply the luminosity needed to reproduce the late-time UV-bright plateau.

  7. The parsec-scale jet of PKS 1749+096

    NASA Astrophysics Data System (ADS)

    Lu, R.-S.; Shen, Z.-Q.; Krichbaum, T. P.; Iguchi, S.; Lee, S.-S.; Zensus, J. A.

    2012-08-01

    Context.PKS 1749+096 is a BL Lac object showing weak extended jet emission to the northeast of the compact VLBI core on parsec scales. Aims: We aim at better understanding the jet kinematics and variability of this source and finding clues that may applicable to other BL Lac objects. Methods: The jet was studied with multi-epoch multi-frequency high-resolution VLBI observations. Results: The jet is characterized by a one-sided curved morphology at all epochs and all frequencies. The VLBI core, located at the southern end of the jet, was identified based on its spectral properties. The equipartition magnetic field of the core was investigated, through which we derived a Doppler factor of 5, largely consistent with that derived from kinematics (component C5). The study of the detailed jet kinematics at 22 and 15 GHz, spanning a period of more than 10 years, indicates the possible existence of a bimodal distribution of the jet apparent speed. Ballistic and non-ballistic components are found to coexist in the jet. Superluminal motions in the range of 5-21 c were measured in 11 distinct components. We estimated the physical jet parameters with the minimum Lorentz factor of 10.2 and Doppler factors in the range of 10.2-20.4 (component C5). The coincidence in time of the component's ejection and flares supports the idea that, at least in PKS 1749+096, ejection of new jet components is connected with major outbursts in flux density. For the best-traced component (C5) we found that the flux density decays rapidly as it travels downstream the jet, accompanied by a steepening of its spectra, which argues in favor of a contribution of inverse Compton cooling. These properties make PKS 1749+096 a suitable target for an intensive monitoring to decipher the variability phenomenon of BL Lac objects. Figure A.1 and Tables A.1, A.2 are available in electronic form at http://www.aanda.org

  8. Jets in air-jet family

    NASA Technical Reports Server (NTRS)

    Navia, C. E.; Sawayanagi, K.

    1985-01-01

    The A-jet families on Chacaltaya emulsion chamber experiments were analyzed by the study of jets which are reconstructed by a grouping procedure. It is demonstrated that large-E sub J R sub J events are characterized by small number of jets and two-jet like asymmetric shape, binocular events and the other type. This type has a larger number of jets and more symmetrical shape in the P sub t plane.

  9. Marine Jet

    NASA Technical Reports Server (NTRS)

    1978-01-01

    The marine turbine pump pictured is the Jacuzzi 12YJ, a jet propulsion system for pleasure or commercial boating. Its development was aided by a NASA computer program made available by the Computer Software Management and Information Center (COSMIC) at the University of Georgia. The manufacturer, Jacuzzi Brothers, Incorporated, Little Rock, Arkansas, used COSMIC'S Computer Program for Predicting Turbopump Inducer Loading, which enabled substantial savings in development time and money through reduction of repetitive testing.

  10. Galactic distribution of pulsars

    NASA Technical Reports Server (NTRS)

    Seiradakis, J. H.

    1977-01-01

    The density distributions of pulsars in luminosity, period, Z-distance, and galactocentric distance were derived, using a uniform sample of pulsars detected during a 408-MHz pulsar survey at Jodrell Bank. There are indications of a fine-scale structure in the spatial distributions and evidence that there is a general correlation with other galactic populations and the overall spiral structure. The electron layer in our galaxy is shown to be wider than the pulsar layer and uniform on a large scale. The number of pulsars in the galaxy has been estimated and used to derive the pulsar birthrate.

  11. Galactic distribution of pulsars

    NASA Technical Reports Server (NTRS)

    Seiradakis, J. H.

    1976-01-01

    The density distributions of pulsars in luminosity, period, Z-distance, and galactocentric distance were derived using a uniform sample of pulsars detected during a 408 MHz pulsar survey at Jodrell Bank. There are indications of a fine scale structure in the spatial distribution and evidence that there is a general correlation with other galactic populations and the overall spiral structure. The electron layer in the galaxy is shown to be wider than the pulsar layer and uniform on a large scale. The number of pulsars in the galaxy was estimated and used to derive the pulsar birthrate.

  12. DICHOTOMY OF SOLAR CORONAL JETS: STANDARD JETS AND BLOWOUT JETS

    SciTech Connect

    Moore, Ronald L.; Cirtain, Jonathan W.; Sterling, Alphonse C.; Falconer, David A.

    2010-09-01

    By examining many X-ray jets in Hinode/X-Ray Telescope coronal X-ray movies of the polar coronal holes, we found that there is a dichotomy of polar X-ray jets. About two thirds fit the standard reconnection picture for coronal jets, and about one third are another type. We present observations indicating that the non-standard jets are counterparts of erupting-loop H{alpha} macrospicules, jets in which the jet-base magnetic arch undergoes a miniature version of the blowout eruptions that produce major coronal mass ejections. From the coronal X-ray movies we present in detail two typical standard X-ray jets and two typical blowout X-ray jets that were also caught in He II 304 A snapshots from STEREO/EUVI. The distinguishing features of blowout X-ray jets are (1) X-ray brightening inside the base arch in addition to the outside bright point that standard jets have, (2) blowout eruption of the base arch's core field, often carrying a filament of cool (T {approx} 10{sup 4} - 10{sup 5} K) plasma, and (3) an extra jet-spire strand rooted close to the bright point. We present cartoons showing how reconnection during blowout eruption of the base arch could produce the observed features of blowout X-ray jets. We infer that (1) the standard-jet/blowout-jet dichotomy of coronal jets results from the dichotomy of base arches that do not have and base arches that do have enough shear and twist to erupt open, and (2) there is a large class of spicules that are standard jets and a comparably large class of spicules that are blowout jets.

  13. Dichotomy of Solar Coronal Jets: Standard Jets and Blowout Jets

    NASA Technical Reports Server (NTRS)

    Moore, R. L.; Cirtain, J. W.; Sterling, A. C.; Falconer, D. A.

    2010-01-01

    By examining many X-ray jets in Hinode/XRT coronal X-ray movies of the polar coronal holes, we found that there is a dichotomy of polar X-ray jets. About two thirds fit the standard reconnection picture for coronal jets, and about one third are another type. We present observations indicating that the non-standard jets are counterparts of erupting-loop H alpha macrospicules, jets in which the jet-base magnetic arch undergoes a miniature version of the blowout eruptions that produce major CMEs. From the coronal X-ray movies we present in detail two typical standard X-ray jets and two typical blowout X-ray jets that were also caught in He II 304 Angstrom snapshots from STEREO/EUVI. The distinguishing features of blowout X-ray jets are (1) X-ray brightening inside the base arch in addition to the outside bright point that standard jets have, (2) blowout eruption of the base arch's core field, often carrying a filament of cool (T 10(exp 4) - 10(exp 5) K) plasma, and (3) an extra jet-spire strand rooted close to the bright point. We present cartoons showing how reconnection during blowout eruption of the base arch could produce the observed features of blowout X-ray jets. We infer that (1) the standard-jet/blowout-jet dichotomy of coronal jets results from the dichotomy of base arches that do not have and base arches that do have enough shear and twist to erupt open, and (2) there is a large class of spicules that are standard jets and a comparably large class of spicules that are blowout jets.

  14. Soliton Formation and Superluminality Effect due to Nonlinear Absorption of Femtosecond Laser Pulse Energy by the Medium Containing Nanorods

    NASA Astrophysics Data System (ADS)

    Trofimov, Vyacheslav A.; Lysak, Tatiana M.

    2016-02-01

    We investigate a femtosecond pulse propagation in a medium, containing nanorods, with taking into account the dependence of multi-photon absorption from the aspect ratio of nanorods. Nanorods melting due to the laser energy absorption leads to the non-stationary interaction of laser pulse with the medium and time-dependent nanorod aspect ratio changing. Under certain conditions, we found out the soliton-like mode of a laser pulse propagation and the superluminality effect: acceleration of light (fast light) in comparison with light propagation in a linear medium. We discuss a physical mechanism of superluminality effect for considering laser pulse propagation. Using spatio-temporal analogy, one can see the similarity between the pulse centre evolution along longitudinal coordinate and the beam centre evolution under the infrared optical radiation propagation in a cloud, or fog, which moves across the beam, with taking into account its thermal blooming.

  15. Radio crickets: chirping jets from black hole binaries entering their gravitational wave inspiral

    NASA Astrophysics Data System (ADS)

    Kulkarni, Girish; Loeb, Abraham

    2016-03-01

    We study a novel electromagnetic signature of supermassive black hole (BH) binaries whose inspiral starts being dominated by gravitational wave (GW) emission. Recent simulations suggest that the binary's member BHs can continue to accrete gas from the circumbinary accretion disc in this phase of the binary's evolution, all the way until coalescence. If one of the binary members produces a radio jet as a result of accretion, the jet precesses along a biconical surface due to the binary's orbital motion. When the binary enters the GW phase of its evolution, the opening angle widens, the jet exhibits milliarcsecond-scale wiggles, and the conical surface of jet precession is twisted due to apparent superluminal motion. The rapidly increasing orbital velocity of the binary gives the jet an appearance of a `chirp'. This helical chirping morphology of the jet can be used to infer the binary parameters. For binaries with mass 107-1010 M⊙ at redshifts z < 0.5, monitoring these features in current and archival data will place a lower limit on sources that could be detected by Evolved Laser Interferometer Space Antenna and Pulsar Timing Arrays. In the future, microarcsecond interferometry with the Square Kilometre Array will increase the potential usefulness of this technique.

  16. Discovery of superluminal velocities of X-rays and Bharat Radiation challenging the validity of Einstein's formula E= mc2

    NASA Astrophysics Data System (ADS)

    Rao, M. A. Padmanabha

    2013-09-01

    The current paper reports discovery of superluminal velocities of X-rays, and Bharat Radiation in 12.87 to 31 nm range from solar spectra. The discovery challenges the 100 year old Albert Einstein's assertion that nothing can go faster than velocity of light c in vacuum while formulating E = mc2 in his special theory of relativity reported in 1905 [1]. Several solar spectra recorded at various wavelengths by Woods et al in 2011 demonstrated GOES X-rays arriving earlier than 13.5 nm emission, which in turn arriving earlier than 33.5 nm emission [2]. Finally, the investigators faced difficulty in concluding that short wavelengths traveled fast because of lack of information whether all the three emissions originated from the same source and at the same time. Very recently the author has reported GOES X-rays (7.0 nm) cause 13.5 nm (Bharat Radiation), which in turn causes 33.5 nm Extreme ultraviolet (EUV) emission from same excited atoms present in solar flare by Padmanabha Rao Effect [3, 4]. Based on these findings, the author succeeded in explaining how the solar spectral findings provide direct evidences on superluminal velocities of GOES X-ray and 13.5 nm Bharat Radiation emissions, when 33.5 nm EUV emission is considered travelling at velocity of light c. Among X-ray wavelengths, the short wavelength 7.0 nm X-rays traveled faster than 9.4 nm X-rays, while X-rays go at superluminal velocities. Among Bharat radiation wavelengths, short wavelengths showed fast travel, while Bharat Radiation goes at superluminal velocities as compared to 33.5 EUV emission.

  17. Magnetohydrodynamic simulations of a jet drilling an H I cloud: Shock induced formation of molecular clouds and jet breakup

    SciTech Connect

    Asahina, Yuta; Ogawa, Takayuki; Matsumoto, Ryoji; Kawashima, Tomohisa; Furukawa, Naoko; Enokiya, Rei; Yamamoto, Hiroaki; Fukui, Yasuo

    2014-07-01

    The formation mechanism of the jet-aligned CO clouds found by NANTEN CO observations is studied by magnetohydrodynamical (MHD) simulations taking into account the cooling of the interstellar medium. Motivated by the association of the CO clouds with the enhancement of H I gas density, we carried out MHD simulations of the propagation of a supersonic jet injected into the dense H I gas. We found that the H I gas compressed by the bow shock ahead of the jet is cooled down by growth of the cooling instability triggered by the density enhancement. As a result, a cold dense sheath is formed around the interface between the jet and the H I gas. The radial speed of the cold, dense gas in the sheath is a few km s{sup –1} almost independent of the jet speed. Molecular clouds can be formed in this region. Since the dense sheath wrapping the jet reflects waves generated in the cocoon, the jet is strongly perturbed by the vortices of the warm gas in the cocoon, which breaks up the jet and forms a secondary shock in the H I-cavity drilled by the jet. The particle acceleration at the shock can be the origin of radio and X-ray filaments observed near the eastern edge of the W50 nebula surrounding the galactic jet source SS433.

  18. Probing the connection between the accretion disk, outflows and the jet in 3C111

    NASA Astrophysics Data System (ADS)

    Tombesi, Francesco

    2011-10-01

    Recent XMM-Newton and Suzaku observations of 3C111 demonstrated the presence of ultra-fast outflows (UFOs) with v~0.1c and their relation with the accretion disk. Independent studies found that X-ray dips are followed by ejection of superluminal radio knots, therefore providing a proof of the disk-jet connection. We acquired evidence that UFOs are preferentially present between X-ray dips and new knots, possibly indicating also a link between disk outflows and the jet. The goal of this XMM-Newton proposal is to confirm this evidence. Given the strong correlation with X-rays, we will use an ongoing optical monitoring campaign to trigger a 90ks observation within two days of a dip to detect a UFO and we request a possible additional 60ks >15 days after to compare with the non-dipped state.

  19. Testing Galactic Cosmic Ray Models

    NASA Technical Reports Server (NTRS)

    Adams, James H., Jr.

    2010-01-01

    Models of the Galactic Cosmic Ray Environment are used for designing and planning space missions. The exising models will be reviewed. Spectral representations from these models will be compared with measurements of galactic cosmic ray spectra made on balloon flights and satellite flights over a period of more than 50 years.

  20. Testing Galactic Cosmic Ray Models

    NASA Technical Reports Server (NTRS)

    Adams, James H., Jr.

    2009-01-01

    Models of the Galactic Cosmic Ray Environment are used for designing and planning space missions. The existing models will be reviewed. Spectral representations from these models will be compared with measurements of galactic cosmic ray spectra made on balloon flights and satellite flights over a period of more than 50 years.

  1. Galactic cosmic rays and nucleosynthesis

    SciTech Connect

    Kiener, Juergen

    2010-03-01

    The nucleosynthesis of the light elements Li, Be and B by galactic cosmic rays is presented. Observations of cosmic rays and the nuclear reactions responsible for Li, Be and B nucleosynthesis are described, followed by some words on propagation. At the end, some open questions concerning galactic cosmic rays are discussed.

  2. MAGNETIC FLUX PARADIGM FOR RADIO LOUDNESS OF ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Sikora, Marek; Begelman, Mitchell C. E-mail: mitch@jila.colorado.edu

    2013-02-20

    We argue that the magnetic flux threading the black hole (BH), rather than BH spin or Eddington ratio, is the dominant factor in launching powerful jets and thus determining the radio loudness of active galactic nuclei (AGNs). Most AGNs are radio quiet because the thin accretion disks that feed them are inefficient in depositing magnetic flux close to the BH. Flux accumulation is more likely to occur during a hot accretion (or thick disk) phase, and we argue that radio-loud quasars and strong emission-line radio galaxies occur only when a massive, cold accretion event follows an episode of hot accretion. Such an event might be triggered by the merger of a giant elliptical galaxy with a disk galaxy. This picture supports the idea that flux accumulation can lead to the formation of a so-called magnetically choked accretion flow. The large observed range in radio loudness reflects not only the magnitude of the flux pressed against the BH, but also the decrease in UV flux from the disk, due to its disruption by the ''magnetosphere'' associated with the accumulated flux. While the strongest jets result from the secular accumulation of flux, moderate jet activity can also be triggered by fluctuations in the magnetic flux deposited by turbulent, hot inner regions of otherwise thin accretion disks, or by the dissipation of turbulent fields in accretion disk coronae. These processes could be responsible for jet production in Seyferts and low-luminosity AGNs, as well as jets associated with X-ray binaries.

  3. Formation of Relativistic Jets : Magnetohydrodynamics and Synchrotron Radiation

    NASA Astrophysics Data System (ADS)

    Porth, Oliver J. G.

    2011-11-01

    In this thesis, the formation of relativistic jets is investigated by means of special relativistic magnetohydrodynamic simulations and synchrotron radiative transfer. Our results show that the magnetohydrodynamic jet self-collimation paradigm can also be applied to the relativistic case. In the first part, jets launched from rotating hot accretion disk coronae are explored, leading to well collimated, but only mildly relativistic flows. Beyond the light-cylinder, the electric charge separation force balances the classical trans-field Lorentz force almost entirely, resulting in a decreased efficiency of acceleration and collimation in comparison to non-relativistic disk winds. In the second part, we examine Poynting dominated flows of various electric current distributions. By following the outflow for over 3000 Schwarzschild radii, highly relativistic jets of Lorentz factor 8 and half-opening angles below 1 degree are obtained, providing dynamical models for the parsec scale jets of active galactic nuclei. Applying the magnetohydrodynamic structure of the quasi-stationary simulation models, we solve the relativistically beamed synchrotron radiation transport. This yields synthetic radiation maps and polarization patterns that can be used to confront high resolution radio and (sub-) mm observations of nearby active galactic nuclei. Relativistic motion together with the helical magnetic fields of the jet formation site imprint a clear signature on the observed polarization and Faraday rotation. In particular, asymmetries in the polarization direction across the jet can disclose the handedness of the magnetic helix and thus the spin direction of the central engine. Finally, we show first results from fully three-dimensional, high resolution adaptive mesh refinement simulations of jet formation from a rotating magnetosphere and examine the jet stability. Relativistic field-line rotation leads to an electric charge separation force that opposes the magnetic Lorentz

  4. Galactic Hearts of Glass

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Click on image for larger graph

    This artist's concept shows delicate greenish crystals sprinkled throughout the violent core of a pair of colliding galaxies. The white spots represent a thriving population of stars of all sizes and ages. NASA's Spitzer Space Telescope detected more than 20 bright and dusty galactic mergers like the one depicted here, all teeming with the tiny gem-like crystals.

    When galaxies collide, they trigger the birth of large numbers of massive stars. Astronomers believe these blazing hot stars act like furnaces to produce silicate crystals in the same way that glass is made from sand. The stars probably shed the crystals as they age, and as they blow apart in supernovae explosions.

    At the same time the crystals are being churned out, they are also being destroyed. Fast-moving particles from supernova blasts easily convert silicates crystals back to their amorphous, or shapeless, form.

    How is Spitzer seeing the crystals if they are rapidly disappearing? Astronomers say that, for a short period of time at the beginning of galactic mergers, massive stars might be producing silicate crystals faster than they are eliminating them. When our own galaxy merges with the Andromeda galaxy in a few billion years, a similar burst of massive stars and silicate crystals might occur.

    Crystal Storm in Distant Galaxy The graph (see inset above) of infrared data from NASA's Spitzer Space Telescope tells astronomers that a distant galaxy called IRAS 08752+3915 is experiencing a storm of tiny crystals made up of silicates. The crystals are similar to the glass-like grains of sand found on Earth's many beaches.

    The data were taken by Spitzer's infrared spectrograph, which splits light open to reveal its rainbow-like components. The resulting spectrum shown here reveals the signatures of both crystalline (green) and non-crystalline (brown) silicates.

    Spitzer detected the same

  5. The Role of Magnetic Fields in Relativistic Astrophysical Jets

    NASA Astrophysics Data System (ADS)

    Hamlin, Nathaniel; Newman, W. I.

    2012-05-01

    We explore, analytically and by numerical simulation, the evolution of the Kelvin-Helmholtz (KH) instability in a relativistic magnetized astrophysical jet. Our results successfully reproduce numerous magnetohydrodynamic features observed in relativistic astrophysical environments. The KH instability arises from a variation in flow speed orthogonal to the flow. Many astrophysical jets are relativistic, evidenced by apparent superluminal motion, and are likely collimated by a magnetic field, according to commonly accepted models. We find convergence of our numerical results between the hydrodynamic, magnetohydrodynamic, relativistic hydrodynamic, and relativistic magnetohydrodynamic regimes. We observe complementarity between fluid flow and magnetic field behavior. The early nonlinear regime corresponds to the formation of large vortices connected by a dual filamentary structure reminiscent of the cosmic double helix in the extragalactic jet 3C 273. These vortices are disrupted by the field, followed by a complex turbulent regime, and then an approach to an equilibrium configuration consisting of flow-aligned filaments. For stronger fields, this process occurs more rapidly, and sufficiently strong fields suppress vortices entirely. The jet also widens and decelerates by an amount depending on field strength. These results are in qualitative agreement with observations of numerous jets, including NGC 5128, 3C 273, and HH 30. Relativistic flows break synchronicity between longitudinal and transverse motions, thereby destabilizing the system, and enhancing the complexity of vortex disruption and turbulent breakdown. This desynchronization also causes early numerical breakdown at high Lorentz factors, a long-standing problem. Using a uniform-flow model, we provide the first mathematical analysis showing that for sufficiently high Lorentz factors, artificial diffusion not only fails to suppress numerical instability, but introduces growing modes which destabilize the

  6. 3-D Relativistic MHD Simulations of Extragalactic Jets

    NASA Astrophysics Data System (ADS)

    Nishikawa, K.-I.; Koide, S.; Sakai, J.-I.; Frank, J.; Christodoulou, D. M.; Sol, H.; Mutel, R. L.

    1997-12-01

    We present the numerical simulations of relativistic jets propagating initially oblique to the field lines of a magnetized ambient medium. Our simulations incorporate relativistic MHD in a four-dimensional spacetime and clearly show that (a) relatively weak, oblique fields (at 1/16 of the equipartition value) have only a negligible influence on the propagating jet and they are passively pushed away by the relativistically moving head; (b) oblique fields in equipartition with the ambient plasma provide more resistance and cause bending at the jet head, but the magnitude of this deflection and the associated backflow are small compared to those identified by previous studies with a 2-D slab model. The new results are understood as follows: Relativistic simulations have consistently shown that these jets are effectively heavy and so they do not suffer substantial momentum losses and are not decelerated as efficiently as their nonrelativistic counterparts. In addition, the ambient magnetic field, however strong, can be pushed aside with relative ease by the beam, provided that the degrees of freedom associated with all three spatial dimensions are followed self-consistently during the simulations. The effect is analogous to pushing Japanese ``noren'' or vertical Venetian blinds out of the way while the slats are allowed to bend in 3-D space rather than as a 2-D slab structure. Applied to relativistic extragalactic jets from blazars, the new results are encouraging since superluminal outflows exhibit bending near their sources and their environments are profoundly magnetized---but observations do not provide support for irregular kinematics such as large-scale vortical motions and pronounced reverse flows near the points of origin.

  7. Two superluminous supernovae from the early universe discovered by the supernova legacy survey

    SciTech Connect

    Howell, D. A.; Kasen, D.; Lidman, C.; Sullivan, M.; Conley, A.; Astier, P.; Balland, C.; Guy, J.; Hardin, D.; Pain, R.; Regnault, N.; Carlberg, R. G.; Fouchez, D.; Palanque-Delabrouille, N.; Rich, J.; Ruhlmann-Kleider, V.; Pritchet, C. J.

    2013-12-20

    We present spectra and light curves of SNLS 06D4eu and SNLS 07D2bv, two hydrogen-free superluminous supernovae (SNe) discovered by the Supernova Legacy Survey. At z = 1.588, SNLS 06D4eu is the highest redshift superluminous SN with a spectrum, at M{sub U} = –22.7 it is one of the most luminous SNe ever observed, and it gives a rare glimpse into the rest-frame ultraviolet where these SNe put out their peak energy. SNLS 07D2bv does not have a host galaxy redshift, but on the basis of the SN spectrum, we estimate it to be at z ∼ 1.5. Both SNe have similar observer-frame griz light curves, which map to rest-frame light curves in the U band and UV, rising in ∼20 rest-frame days or longer and declining over a similar timescale. The light curves peak in the shortest wavelengths first, consistent with an expanding blackbody starting near 15,000 K and steadily declining in temperature. We compare the spectra with theoretical models, and we identify lines of C II, C III, Fe III, and Mg II in the spectra of SNLS 06D4eu and SCP 06F6 and find that they are consistent with an expanding explosion of only a few solar masses of carbon, oxygen, and other trace metals. Thus, the progenitors appear to be related to those suspected for SNe Ic. A high kinetic energy, 10{sup 52} erg, is also favored. Normal mechanisms of powering core-collapse or thermonuclear SNe do not seem to work for these SNe. We consider models powered by {sup 56}Ni decay and interaction with circumstellar material, but we find that the creation and spin-down of a magnetar with a period of 2 ms, a magnetic field of 2 × 10{sup 14} G, and a 3 M {sub ☉} progenitor provides the best fit to the data.

  8. Galactic Diffuse Polarized Emission

    NASA Astrophysics Data System (ADS)

    Carretti, Ettore

    2011-12-01

    Diffuse polarized emission by synchrotron is a key tool to investigate magnetic fields in the Milky Way, particularly the ordered component of the large scale structure. Key observables are the synchrotron emission itself and the RM is by Faraday rotation. In this paper the main properties of the radio polarized diffuse emission and its use to investigate magnetic fields will be reviewed along with our current understanding of the galactic magnetic field and the data sets available. We will then focus on the future perspective discussing RM-synthesis - the new powerful instrument devised to unlock the information encoded in such an emission - and the surveys currently in progress like S-PASS and GMIMS.

  9. The Galactic Nucleus

    NASA Astrophysics Data System (ADS)

    Melia, Fulvio

    Exciting new broadband observations of the galactic nucleus have placed the heart of the Milky Way under intense scrutiny in recent years. This has been due in part to the growing interest from theorists motivated to study the physics of black hole accretion, magnetized gas dynamics, and unusual star formation. The center of our Galaxy is now known to harbor the most compelling supermassive black hole candidate, weighing in at 3-4 million solar masses. Its nearby environment is comprised of a molecular dusty ring, clusters of evolved and young stars, diffuse hot gas, ionized gas streamers, and several supernova remnants. This chapter will focus on the physical makeup of this dynamic region and the feasibility of actually imaging the black hole's shadow in the coming decade with mm interferometry.

  10. The Galactic center wind

    NASA Technical Reports Server (NTRS)

    Chevalier, Roger A.

    1992-01-01

    The combined effect of winds from a cluster of stars in the central 0.8 pc of the Galaxy is modeled as uniform power and mass input over the central region. The flow becomes supersonic outside the central region, and the expected decrease in pressure is in approximate accord with observations. The pressure variations on a larger scale suggest that the Galactic center wind passes through a shock front at a radius of a few pc, leading to a shocked wind bubble on a scale of 100 pc. The tangential magnetic field can come to dominate the pressure in the shocked wind flow even if the energy density of the magnetic field in the initial wind is only 0.1 percent of the wind kinetic energy density. The magnetic region produced in this way may be related to some of the apparently magnetized structures observed in the central region of the Galaxy.

  11. Galactic antiprotons from photinos

    NASA Technical Reports Server (NTRS)

    Stecker, F. W.; Rudaz, S.; Walsh, T. F.

    1985-01-01

    Stable photinos, the photino being the supersymmetry partner of the photon, can explain both the 'missing mass' in galactic halos and the cosmic-ray antiproton spectrum up to the highest energies observed so far. This requires a photino mass around 15 GeV; significantly higher masses are cosmologically disfavored. As a consequence, the observed cosmic-ray antiproton-to-proton ratio is predicted to decrease abruptly just above the measured energy range, at E = m(x). If observed, this striking effect would strongly support the hypothesis that photinos make up the missing matter in the galaxy and also lead to a measurement of the photino mass from cosmic-ray data.

  12. Great Galactic Buddies

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Click on image for poster [figure removed for brevity, see original site] [figure removed for brevity, see original site] [figure removed for brevity, see original site] [figure removed for brevity, see original site] 8.15 Billion Lightyears8.59 Billion Lightyears8.98 Billion Lightyears 9.09 Billion Lightyears

    Like great friends, galaxies stick together. Astronomers using NASA's Spitzer Space Telescope have spotted a handful of great galactic pals bonding back when the universe was a mere 4.6 billion years old. The universe is believed to be 13.7 billion years old.

    Collectively, these great galactic buddies are called galaxy clusters. A typical galaxy cluster can contain hundreds of galaxies and trillions of stars.

    In this false-color composite, some of the oldest galaxy clusters in the universe pose for Spitzer's infrared array camera. The individual galaxies that make up the distant clusters are shown as red dots in all four images.

    The green blobs are Milky Way stars along the line of sight, and the blue specks are faint galaxies at various distances along the line of sight. The green and blue data are from a visible-light, ground-based telescope.

    The cluster at 9.1 billion light-years away (lower right panel) is currently the most distant galaxy cluster ever detected.

    These images are three-color composites, in which blue represents visible light with a wavelength of 0.4 microns, and green indicates visible light of 0.8 microns. The visible data were captured by the ground-based Mosaic I camera at the Kitt Peak National Observatory in Tucson, Ariz. Red represents infrared light of 4.5 microns, captured by Spitzer's infrared array camera.

  13. The Galactic Bulge

    NASA Astrophysics Data System (ADS)

    Rich, R. M.

    2015-05-01

    Observations at Cerro Tololo Inter-American Observatory (CTIO) have had a critical formative impact on the study of the Galactic bulge, much of the work being inspired and supported by Victor Blanco and collaborators, which is presented in a historical overview. Recent observations at CTIO include the Blanco 4m/Hydra Bulge Radial Velocity Assay (BRAVA) that has mapped the Galactic bulge velocity field from -10

  14. Relativistic Doppler Beaming and Misalignments in AGN Jets

    NASA Astrophysics Data System (ADS)

    Singal, Ashok K.

    2016-08-01

    Radio maps of active galactic nuclei often show linear features, called jets, on both parsec and kiloparsec scales. These jets supposedly possess relativistic motion and are oriented close to the line of sight of the observer, and accordingly the relativistic Doppler beaming makes them look much brighter than they really are in their respective rest frames. The flux boosting due to the relativistic beaming is a very sensitive function of the jet orientation angle, as seen by the observer. Sometimes, large bends are seen in these jets, with misalignments being 90° or more, which might imply a change in the orientation angle that should cause a large change in the relativistic beaming factor. Hence, if relativistic beaming does play an important role in these jets such large bends should usually show high contrast in the brightness of the jets before and after the bend. It needs to be kept in mind that sometimes a small intrinsic change in the jet angle might appear as a much larger misalignment due to the effects of geometrical projection, especially when seen close to the line of sight. What really matters are the initial and final orientation angles of the jet with respect to the observer’s line of sight. Taking the geometrical projection effects properly into account, we calculate the consequences of the presumed relativistic beaming and demonstrate that there ought to be large brightness ratios in jets before and after the observed misalignments.

  15. The formation of slow-massive-wide jets

    NASA Astrophysics Data System (ADS)

    Soker, Noam

    2008-07-01

    I propose a model for the formation of slow-massive-wide (SMW) jets by accretion disks around compact objects. This study is motivated by claims for the existence of SMW jets in some astrophysical objects such as in planetary nebulae (PNs) and in some active galactic nuclei in galaxies and in cooling flow clusters. In this model the energy still comes from accretion onto a compact object. The accretion disk launches two opposite jets with velocity of the order of the escape velocity from the accreting object and with mass outflow rate of ˜1-20% of the accretion rate as in most popular models for jet launching; in the present model these are termed fast-first-stage (FFS) jets. However, the FFS jets encounter surrounding gas that originates in the mass accretion process, and are terminated by strong shocks close to their origin. Two hot bubbles are formed. These bubbles accelerate the surrounding gas to form two SMW jets that are more massive and slower than the FFS jets. There are two conditions for this mechanism to work. Firstly, the surrounding gas should be massive enough to block the free expansion of the FFS jets. Most efficiently this condition is achieved when the surrounding gas is replenished. Secondly, the radiative energy losses must be small.

  16. Causality and stability of cosmic jets

    NASA Astrophysics Data System (ADS)

    Porth, Oliver; Komissarov, Serguei S.

    2015-09-01

    In stark contrast to their laboratory and terrestrial counterparts, cosmic jets appear to be very stable. They are able to penetrate vast spaces, which exceed by up to a billion times the size of their central engines. We propose that the reason behind this remarkable property is the loss of causal connectivity across these jets, caused by their rapid expansion in response to fast decline of external pressure with the distance from the `jet engine'. In atmospheres with power-law pressure distribution, pext ∝ z-κ, the total loss of causal connectivity occurs, when κ > 2 - the steepness which is expected to be quite common for many astrophysical environments. This conclusion does not seem to depend on the physical nature of jets - it applies both to relativistic and non-relativistic flows, both magnetically dominated and unmagnetized jets. In order to verify it, we have carried out numerical simulations of moderately magnetized and moderately relativistic jets. The results give strong support to our hypothesis and provide with valuable insights. In particular, we find that the z-pinched inner cores of magnetic jets expand slower than their envelopes and become susceptible to instabilities even when the whole jet is stable. This may result in local dissipation and emission without global disintegration of the flow. Cosmic jets may become globally unstable when they enter flat sections of external atmospheres. We propose that the Fanaroff-Riley (FR) morphological division of extragalactic radio sources into two classes is related to this issue. In particular, we argue that the low power FR-I jets become reconfined, causally connected and globally unstable on the scale of galactic X-ray coronas, whereas more powerful FR-II jets reconfine much further out, already on the scale of radio lobes and remain largely intact until they terminate at hotspots. Using this idea, we derived the relationship between the critical jet power and the optical luminosity of the host

  17. An X-ray IMAGING SURVEY OF QUASAR JETS: TESTING THE INVERSE COMPTON MODEL

    SciTech Connect

    Marshall, H. L.; Gelbord, J. M.; Schwartz, D. A.; Worrall, D. M.; Birkinshaw, M.; Murphy, D. W.; Godfrey, L.; Jauncey, D. L.; Lovell, J. E. J.; Perlman, E. S. E-mail: jgelbord@astro.psu.edu E-mail: D. Worrall@bristol.ac.uk E-mail: david.murphy@jpl.nasa.gov E-mail: David.Jauncey@csiro.au E-mail: eperlman@fit.edu

    2011-03-15

    We present results from continued Chandra X-ray imaging and spectroscopy of a flux-limited sample of flat spectrum radio-emitting quasars with jet-like extended structure. X-rays are detected from 24 of the 39 jets observed so far. We compute the distribution of {alpha} {sub rx}, the spectral index between the X-ray and radio bands, showing that it is broad, extending at least from 0.8 to 1.2. While there is a general trend that the radio brightest jets are detected most often, it is clear that predicting the X-ray flux from the radio knot flux densities is risky, so a shallow X-ray survey is the most effective means for finding jets that are X-ray bright. We test the model in which the X-rays result from inverse Compton (IC) scattering of cosmic microwave background (CMB) photons by relativistic electrons in the jet moving with a high bulk Lorentz factor nearly along the line of sight. Depending on how the jet magnetic fields vary with z, the observed X-ray to radio flux ratios do not follow the redshift dependence expected from the IC-CMB model. For a subset of our sample with known superluminal motion based on VLBI observations, we estimate the angle of the kiloparsec-scale jet to the line of sight by considering the additional information in the bends observed between parsec- and kiloparsec-scale jets. These angles are sometimes much smaller than estimates based on the IC-CMB model with a Lorentz factor of 15, indicating that these jets may decelerate significantly from parsec scales to kiloparsec scales.

  18. Inclusive Jets in PHP

    NASA Astrophysics Data System (ADS)

    Roloff, P.

    Differential inclusive-jet cross sections have been measured in photoproduction for boson virtualities Q^2 < 1 GeV^2 with the ZEUS detector at HERA using an integrated luminosity of 300 pb^-1. Jets were identified in the laboratory frame using the k_T, anti-k_T or SIScone jet algorithms. Cross sections are presented as functions of the jet pseudorapidity, eta(jet), and the jet transverse energy, E_T(jet). Next-to-leading-order QCD calculations give a good description of the measurements, except for jets with low E_T(jet) and high eta(jet). The cross sections have the potential to improve the determination of the PDFs in future QCD fits. Values of alpha_s(M_Z) have been extracted from the measurements based on different jet algorithms. In addition, the energy-scale dependence of the strong coupling was determined.

  19. VLBA Movies Reveal New Details of Cosmic Jets

    NASA Astrophysics Data System (ADS)

    2008-01-01

    Astronomers have known for decades that supermassive black holes at the cores of galaxies can shoot out jets of subatomic particles at tremendous speeds. However, details about the physics of such jets, including how they are generated, how the high-speed flows are shaped into jets, and how fast the particles are moving, among many others, have remained elusive. An international team of researchers now is making an unprecedented long-term study of the motions of these giant jets, using the super-sharp imaging capabilities of the National Science Foundation's Very Long Baseline Array (VLBA). "We're making images of 200 galactic jets at regular intervals, tracking their motions and studying their magnetic-field properties. This is making major contributions to our understanding of such jets," said Matthew Lister, of Purdue University. MOJAVE Poster Click image for high-resolution file (11.9 MB) The research team has produced time-lapse movies of 100 of the jets, allowing measurement of the speed and direction of motion. "The results of these VLBA observations are going into a rich and still-growing set of data that is available to the entire astronomical research community as a tool for understanding the many unresolved questions we have about these jets," Lister said. The jet study is called MOJAVE -- Monitoring Of Jets in Active galactic nuclei with VLBA Experiments -- and began in 2002. It is a successor to an earlier VLBA study that regularly made images of nearly 200 jets from 1994 to 2002. The jets are powered by the gravitational energy of black holes containing hundreds of millions times more mass than the Sun. Black holes are concentrations of mass so dense that not even light can escape them. As these monsters draw material toward them, the material falls into a circular disk orbiting the black hole. The jets are propelled outward along the poles of the disk. The MOJAVE movies have given astronomers some surprises and also have spurred follow-on studies of

  20. CCD Pictures of Peculiar Galaxies with Jets or Extensions

    NASA Astrophysics Data System (ADS)

    Sol, H.

    1983-06-01

    The phenomenon of "jets" seems to be rather universal in astrophysics. The astrophysical jets are seen in different wavelengths, from radio to X-rays. Their more general definitioni is "some emitting material weil collimated along a straight Or curved line". Such features appear on very different scales. Jets having a length of the order of a megaparsec and of a kiloparsec have been detected in different extragalactic systems, respectively aso (e. g. 4C18.68; Gower, Hutchings, Ap. J. 253, L1, 1982) and radio galaxies (e. g. PKS 0521-36; Danziger et al. MNRAS, 188,415, 1979). Jets of a few parsecs have also been suspected in galactic objects as the exotic SS 433, Sco X-1 and R Aquarii. Königl (Ap. J., 261, 115, 1982) even proposed to call jets the asymmetrical outflows which appear in the models of bipolar nebulae, bipolar CO emission lobes and aligned Herbig-Haro objects. Part of the galactic jets could be miniature models of some of the extragalactic ones.

  1. QUASI-STAR JETS AS UNIDENTIFIED GAMMA-RAY SOURCES

    SciTech Connect

    Czerny, Bozena; Sikora, Marek; Janiuk, Agnieszka

    2012-08-10

    Gamma-ray catalogs contain a considerable amount of unidentified sources. Many of these are located out of the Galactic plane and therefore may have extragalactic origin. Here we assume that the formation of massive black holes in galactic nuclei proceeds through a quasi-star stage and consider the possibility of jet production by such objects. Those jets would be the sources of collimated synchrotron and Compton emission, extending from radio to gamma rays. The expected lifetimes of quasi-stars are of the order of million of years while the jet luminosities, somewhat smaller than that of quasar jets, are sufficient to account for the unidentified gamma-ray sources. The jet emission dominates over the thermal emission of a quasi-star in all energy bands, except when the jet is not directed toward an observer. The predicted synchrotron emission peaks in the IR band, with the flux close to the limits of the available IR all sky surveys. The ratio of the gamma-ray flux to the IR flux is found to be very large ({approx}60), much larger than in BL Lac objects but reached by some radio-loud quasars. On the other hand, radio-loud quasars show broad emission lines while no such lines are expected from quasi-stars. Therefore, the differentiation between various scenarios accounting for the unidentified gamma-ray sources will be possible at the basis of the photometry and spectroscopy of the IR/optical counterparts.

  2. Particle Acceleration, Magnetic Field Generation and Emission from Relativistic Jets

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.-I.; Hardee, P.; Hededal, C.; Mizuno, Yosuke; Fishman, G. Jerry; Hartmann, D. H.

    2006-01-01

    Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., active galactic nuclei (AGNs), gamma-ray bursts (GRBs), supernova remnants, and Galactic microquasar systems usually have power-law emission spectra. Fermi acceleration is the mechanism usually assumed for the acceleration of particles in astrophysical environments. Recent PIC simulations using injected relativistic electron-ion (electro-positron) jets show that particle acceleration occurs within the downstream jet, rather than by the scattering of particles back and forth across the shock as in Fermi acceleration. Shock acceleration' is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, other two-streaming instability, and the Weibel instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the jet head. The "jitter" radiation from deflected electrons has different spectral properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants. We will review recent PIC simulations of relativistic jets and try to make a connection with observations.

  3. Observations of diffuse galactic gamma rays

    NASA Technical Reports Server (NTRS)

    Simpson, G. A.

    1979-01-01

    The observations of galactic diffuse gamma radiation are reviewed. The connections of the gamma ray observations with galactic structure and cosmic rays are discussed. The high latitude galactic component and the low latitude emission from the galactic plane are examined. The observations in other regions of the gamma ray spectrum are discussed.

  4. Constraining the ellipticity of strongly-magnetized neutron stars powering superluminous supernovae

    NASA Astrophysics Data System (ADS)

    Moriya, Takashi J.; Tauris, Thomas M.

    2016-04-01

    Superluminous supernovae (SLSNe) have been suggested to be powered by strongly-magnetized, rapidly-rotating neutron stars which are often called magnetars. In this process, rotational energy of the magnetar is radiated via magnetic dipole radiation and heats the supernova ejecta. However, if magnetars are highly distorted in their geometric shape, rotational energy is mainly lost as gravitational wave radiation and thus such magnetars cannot power SLSNe. By simply comparing electromagnetic and gravitational wave emission timescales, we constrain upper limits to the ellipticity of magnetars by assuming that they power the observed SLSNe. We find that their ellipticity typically needs to be less than about a few 10-3. This indicates that the toroidal magnetic field strengths in these magnetars are typically less than a few 1016 G so that their distortions remain small. Because light-curve modeling of SLSNe shows that their dipole magnetic field strengths are of the order of 1014 G, the ratio of poloidal to toroidal magnetic field strengths is found to be larger than ˜0.01 in magnetars powering SLSNe.

  5. Seeing double: the frequency and detectability of double-peaked superluminous supernova light curves

    NASA Astrophysics Data System (ADS)

    Nicholl, M.; Smartt, S. J.

    2016-03-01

    The discovery of double-peaked light curves in some superluminous supernovae (SLSNe) offers an important new clue to their origins. We examine the published photometry of all Type Ic SLSNe, finding 14 objects with constraining data or limits around the time of explosion. Of these, eight (including the already identified SN 2006oz and LSQ14bdq) show plausible flux excess at the earliest epochs, which deviate by 2-9σ from polynomial fits to the rising light curves. Simple scaling of the LSQ14bdq data show that they are all consistent with a similar double-peaked structure. PS1-10pm provides multicolour UV data indicating a temperature of Tbb = 25000 ± 5000 K during the early `bump' phase. We find that a double-peak cannot be excluded in any of the other six objects, and that this behaviour may be ubiquitous. The homogeneity of the observed bumps is unexpected for interaction-powered models. Engine-powered models can explain the observations if all progenitors have extended radii or the central engine drives shock breakout emission several days after the supernova explosion.

  6. Compared propagation characteristics of superluminal and slow light in SOA and EDFA based on rectangle signals

    NASA Astrophysics Data System (ADS)

    Wang, Fu; Wang, Zhi; Wu, Chongqing; Sun, Zhenchao; Mao, Yaya; Liu, Lanlan; Li, Qiang

    2015-10-01

    Based on the general mechanism of the coherent population oscillations (CPO) in the Semiconductor optical amplifiers (SOA) and Erbium doped fiber amplifiers (EDFA), the group time delay of rectangle signal propagating in the active media is deduced. Compared with the sinusoidal signal, the time delay difference between the fundamental harmonics (FHFD: fundamental harmonic fractional delay) is first investigated in detail for the rectangle signal which is more popularly used in the digital signal systems. The plenty of simulations based on the propagation equations and some experiments for the sinusoidal and rectangle signals are used to analyze the differences and evaluate the slow and superluminal light effects. Furthermore, the time delay/advance always takes place accompanying with the signal distortion, which is evaluated by the total harmonic distortion (THD). The distortion caused by the SOA is smaller than that by the EDFA. A factor Q which is defined to evaluate the trade-off between the FHFD and the THD, shows that higher input power or higher optical gain is better for optical signal processing and optical telecommunications, and the SOA is more suitable for the higher modulation frequency (>10 GHz).

  7. Apparent Lorentz violation with superluminal Majorana-tachyonic neutrinos at OPERA?

    NASA Astrophysics Data System (ADS)

    Tamburini, F.; Laveder, M.

    2012-03-01

    From the controversial data release of the OPERA-CNGS experiment (The OPERA collaboration 2011 arXiv:1109.4897), publicly announced on 23 September 2011 where muonic neutrinos seem to propagate at a speed faster than light, we cast a phenomenological model describing the behaviour of such a tachyonic neutrino, carrying an imaginary mass based on the Majorana tower of particles described in 1932. If the interpretation of OPERA data is correct and considering the strong constraints from the observations of the supernova SN1987a, we show that the tachyonic behaviour of the neutrino can occur only when it is propagating inside matter. Following this idea, within the experimental errors, we fit the data released by OPERA with those of MINOS and by assuming a superluminal propagation inside the matter of SN1987a, confirm our ansatz with stellar structure models of the supernova precursor. Monte Carlo simulations based on this fit agree well with the new OPERA data. Possible violations of Lorentz invariance due to quantum gravity effects have been considered.

  8. A Triple-energy-source Model for Superluminous Supernova iPTF13ehe

    NASA Astrophysics Data System (ADS)

    Wang, S. Q.; Liu, L. D.; Dai, Z. G.; Wang, L. J.; Wu, X. F.

    2016-09-01

    Almost all superluminous supernovae (SLSNe) whose peak magnitudes are ≲ -21 mag can be explained by the 56Ni-powered model, the magnetar-powered (highly magnetized pulsar) model, or the ejecta-circumstellar medium (CSM) interaction model. Recently, iPTF13ehe challenged these energy-source models, because the spectral analysis shows that ∼ 2.5{M}ȯ of 56Ni have been synthesized, but are inadequate to power the peak bolometric emission of iPTF13ehe, while the rebrightening of the late-time light curve (LC) and the Hα emission lines indicate that the ejecta-CSM interaction must play a key role in powering the late-time LC. Here we propose a triple-energy-source model, in which a magnetar together with some amount (≲ 2.5{M}ȯ ) of 56Ni may power the early LC of iPTF13ehe, while the late-time rebrightening can be quantitatively explained by an ejecta-CSM interaction. Furthermore, we suggest that iPTF13ehe is a genuine core-collapse supernova rather than a pulsational pair-instability supernova candidate. Further studies on similar SLSNe in the future would eventually shed light on their explosion and energy-source mechanisms.

  9. Light reversing and folding based on a superluminal flying mirror in a plasma with increasing density

    NASA Astrophysics Data System (ADS)

    Bu, Zhigang; Shen, Baifei; Huang, Shan; Li, Shun; Zhang, Hao

    2016-07-01

    A superluminal flying mirror (SFM) is proposed using the electron density spike in the tail of a wake-field excited in a plasma with an increasing density profile. The wavelength of the wake-field is shrunk in the direction of the increasing plasma density, which increases the phase velocity of the wake wave—namely the flying mirror velocity—in excess of the speed of light. The SFM exhibits some novel characteristics. When it up-shifts the light frequency, just as with a normal flying mirror, because the velocity of the SFM is quicker than light, the reflected light penetrates the electron density spike and propagates behind it. The transmitted light can gain extra energy from the wake wave so that the transmission coefficient is higher than one. Most interestingly, the reflected light may be reversed or folded in time during the reflection, if the SFM velocity gradually decreases and goes through the speed of light. The proposed SFM mechanism can provide potential applications in the production of high-frequency ultrashort pulses.

  10. Constraining the ellipticity of strongly magnetized neutron stars powering superluminous supernovae

    NASA Astrophysics Data System (ADS)

    Moriya, Takashi J.; Tauris, Thomas M.

    2016-07-01

    Superluminous supernovae (SLSNe) have been suggested to be powered by strongly magnetized, rapidly rotating neutron stars which are often called magnetars. In this process, rotational energy of the magnetar is radiated via magnetic dipole radiation and heats the supernova ejecta. However, if magnetars are highly distorted in their geometric shape, rotational energy is mainly lost as gravitational wave radiation and thus such magnetars cannot power SLSNe. By simply comparing electromagnetic and gravitational wave emission time-scales, we constrain upper limits to the ellipticity of magnetars by assuming that they power the observed SLSNe. We find that their ellipticity typically needs to be less than about a few 10-3. This indicates that the toroidal magnetic field strengths in these magnetars are typically less than a few 1016 G so that their distortions remain small. Because light-curve modelling of SLSNe shows that their dipole magnetic field strengths are of the order of 1014 G, the ratio of poloidal to toroidal magnetic field strengths is found to be larger than ˜0.01 in magnetars powering SLSNe.

  11. Corporate Jet

    NASA Technical Reports Server (NTRS)

    1991-01-01

    Gulfstream Aerospace Corporation, Savannah, GA, used a version of a NASA program called WIBCO to design a wing for the Gulfstream IV (G-IV) which will help to reduce transonic drag (created by shock waves that develop as an airplane approaches the speed of sound). The G-IV cruises at 88 percent of the speed of sound, and holds the international record in its class for round-the-world flight. They also used the STANS5 and Profile programs in the design. They will use the NASA program GASP to help determine the gross weight, range, speed, payload and optimum wing area of an intercontinental supersonic business jet being developed in cooperation with Sukhoi Design Bureau, a Soviet organization.

  12. On Building a 3D Model of the M87 Jet

    NASA Astrophysics Data System (ADS)

    Li, Kunyang; Kosak, Katie; Avachat, Sayali S.; Perlman, Eric S.

    2016-01-01

    Optical and radio images of the M87 jet show a huge variety of parsec-scale bends and helical distortion from HST-1 to knot C. The sinusoidal pattern in the outer jet is observed in both bands, suggesting a possible double helical structure. We developed a mathematical model that converts the observed 2D projection of the jet to a 3D configuration by using three inputs: the viewing angle (estimated from 20 years of HST monitoring of the jet), distances and relative angles between bends measured from the HST optical and VLA/VLBA radio images of the M87 jet. Our model is written in Python, combining nonlinear optimization methods and computer graphics to describe and demonstrate the jet geometry. We are extensively testing the scripts to compare stability of the model, optimization techniques, and model with the data of galactic jets, focusing on M87.

  13. AGN jets under the microscope: A divide? Doctoral Thesis Award Lecture 2011

    NASA Astrophysics Data System (ADS)

    Karouzos, M.; Britzen, S.; Witzel, A.; Zensus, A. J.; Eckart, A.

    2012-06-01

    A new paradigm for active galactic jet kinematics has emerged through detailed investigations of BL Lac objects using very long baseline radio interferometry. In this new scheme, most, if not all, jet components appear to remain stationary with respect to the core but show significant non-radial motions. This paper presents results from our kinematic investigation of the jets of a statistically complete sample of radio-loud flat-spectrum active galaxies, focusing on the comparison between the jet kinematic properties of BL Lacs and flat-spectrum radio-quasars. It is shown that there is a statistically significant difference between the kinematics of the two AGN classes, with BL Lacs showing more bent jets, that are wider and show slower movement along the jet axis, compared to flat-spectrum radio-quasars. This is interpreted as evidence for helically structured jets.

  14. Jet inclusive cross sections

    SciTech Connect

    Del Duca, V.

    1992-11-01

    Minijet production in jet inclusive cross sections at hadron colliders, with large rapidity intervals between the tagged jets, is evaluated by using the BFKL pomeron. We describe the jet inclusive cross section for an arbitrary number of tagged jets, and show that it behaves like a system of coupled pomerons.

  15. An irradiated jet in M 17

    NASA Astrophysics Data System (ADS)

    Comerón, F.; Pasquali, A.; Alves de Oliveira, C.

    2013-04-01

    Context. M 17 is one of the best studied giant HII regions in our galactic neighborhood. It should also provide a suitable environment for the class of fully ionized jets externally irradiated by the presence of nearby hot stars. However, no such jets have been observed thus far in M 17. Aims: We report on a visible imaging survey of the M 17 nebula with the goal of identifying likely shock-excited nebulosities. Methods: We imaged M 17 through narrow-band filters centered on the most intense visible lines of [OIII], Hα+[NII], [SII], and Hβ. We obtained follow-up spectroscopy of the only jet-like structure identified in the images. We also used published X-ray observations of M 17 obtained with the Chandra X-ray Observatory, as well as infrared data obtained with the Very Large Telescope and with the Spitzer Space Telescope, to look for evidence of a jet-driving source. Results: We have detected what appears to be the first jet identified in M 17 visible HII region. The jet is composed of a set of knots, two of which have significant radial velocities with respect to the HII region, and a distant arc-like bright nebulosity that may represent an early episode of intense mass loss by the jet-driving source. The follow-up spectra of the structures composing the jet, including the arc, support this interpretation by revealing intense forbidden lines of [NII] and [SII] due to enhanced collisional excitation in shocks. The presence of a X-ray source, most likely a young stellar object, at a position where the jet launching source should be expected to lie reinforces the interpretation. We identify a tentative near-infrared counterpart of the X-ray source, although it is offset by 1".9 from the nominal position of the X-ray source, which is almost three times the radius of its positional uncertainty. The very weak [OI] emission in the spectra of the jet knots and the arc suggests that they are nearly fully ionized, in agreement with the environment in which the jet is

  16. Long wavelength superluminal pulse propagation in a defect slab doped with GaAs/AlGaAs multiple quantum well nanostructure

    NASA Astrophysics Data System (ADS)

    Panahi, M.; Solookinejad, G.; Sangachin, E. Ahmadi; Asadpour, S. H.

    2015-12-01

    In this paper, long wavelength superluminal and subluminal properties of pulse propagation in a defect slab medium doped with four-level GaAs/AlGaAs multiple quantum wells (MQWs) with 15 periods of 17.5 nm GaAs wells and 15 nm Al0.3Ga0.7As barriers is theoretically discussed. It is shown that exciton spin relaxation (ESR) between excitonic states in MQWs can be used for controlling the superluminal and subluminal light transmissions and reflections at different wavelengths. We also show that reflection and transmission coefficients depend on the thickness of the slab for the resonance and nonresonance conditions. Moreover, we found that the ESR for nonresonance condition lead to superluminal light transmission and subluminal light reflection.

  17. Supersonic gas jets

    NASA Astrophysics Data System (ADS)

    Dulov, V. G.

    The papers presented in this volume provide an overview of the current state of research in the gas dynamics of jet flows. In particular, attention is given to free supersonic jets and to the interaction of supersonic jets with one another and with obstacles under stationary and nonstationary flow conditions. Papers are presented on a method for calculating a weakly anisotropic supersonic turbulent jet in a subsonic slipstream; composite supersonic jets; the principal gas-dynamic characteristics of the processes occurring in gas-jet-driven shock-wave generators; and the construction of models for supersonic jet flows. For individual items see A84-16902 to A84-16918

  18. Spiral Galactic Formation and Evolution

    NASA Astrophysics Data System (ADS)

    Brekke, Stewart

    2009-05-01

    Before the period of galactic formation the uiverse consisted of a vast number of pre-formed systems consisting of two or more pre-galactic arms, the arms orbiting each other. As the orbits of the arms decayed the sides of the fore-sections of the arms tangentially collided and joined and thereby forming multi-armed spiral galaxies which began to rotate.The rotation resulted from the conversion of the orbital motion of the individual arms when joined into faster rotational motion of the newly formed galaxy. The spiral arms were maintained by the centripital force of the rapidly rotational motion of the galaxy system. As the rotational motion of the galaxy slowed down the arms of the spiral galaxy collapsed towards the body of the galaxy due to lessening of centripetal force on the arms and elliptical galaxies were formed and with further lessening of galactic rotational motion galactic disks were formed. One can see in galaxies M51, M100, NGC2336 and NGC4939 the galactic arms came from external orbit, not disks or instabilities in support of this theory. Also in support of this theory of galactic evolution is that spiral galaxies rotate faster than ellipticals or disks.

  19. "Waveguidability" of idealized jets

    NASA Astrophysics Data System (ADS)

    Manola, Iris; Selten, Frank; Vries, Hylke; Hazeleger, Wilco

    2013-09-01

    It is known that strong zonal jets can act as waveguides for Rossby waves. In this study we use the European Center for Medium-Range Weather Forecasts (ECMWF) reanalysis data to analyze the connection between jets and zonal waves at timescales beyond 10 days. Moreover, a barotropic model is used to systematically study the ability of idealized jets to trap Rossby wave energy ("waveguidability") as a function of jet strength, jet width, and jet location. In general, strongest waveguidability is found for narrow, fast jets. In addition, when the stationary wave number is integer, a resonant response is found through constructive interference. In Austral summer, the Southern Hemispheric jet is closest to the idealized jets considered and it is for this season that similar jet-zonal wave relationships are identified in the ECMWF reanalysis data.

  20. Galactic planetary science.

    PubMed

    Tinetti, Giovanna

    2014-04-28

    Planetary science beyond the boundaries of our Solar System is today in its infancy. Until a couple of decades ago, the detailed investigation of the planetary properties was restricted to objects orbiting inside the Kuiper Belt. Today, we cannot ignore that the number of known planets has increased by two orders of magnitude nor that these planets resemble anything but the objects present in our own Solar System. Whether this fact is the result of a selection bias induced by the kind of techniques used to discover new planets--mainly radial velocity and transit--or simply the proof that the Solar System is a rarity in the Milky Way, we do not know yet. What is clear, though, is that the Solar System has failed to be the paradigm not only in our Galaxy but even 'just' in the solar neighbourhood. This finding, although unsettling, forces us to reconsider our knowledge of planets under a different light and perhaps question a few of the theoretical pillars on which we base our current 'understanding'. The next decade will be critical to advance in what we should perhaps call Galactic planetary science. In this paper, I review highlights and pitfalls of our current knowledge of this topic and elaborate on how this knowledge might arguably evolve in the next decade. More critically, I identify what should be the mandatory scientific and technical steps to be taken in this fascinating journey of remote exploration of planets in our Galaxy. PMID:24664916

  1. Galactic planetary science

    PubMed Central

    Tinetti, Giovanna

    2014-01-01

    Planetary science beyond the boundaries of our Solar System is today in its infancy. Until a couple of decades ago, the detailed investigation of the planetary properties was restricted to objects orbiting inside the Kuiper Belt. Today, we cannot ignore that the number of known planets has increased by two orders of magnitude nor that these planets resemble anything but the objects present in our own Solar System. Whether this fact is the result of a selection bias induced by the kind of techniques used to discover new planets—mainly radial velocity and transit—or simply the proof that the Solar System is a rarity in the Milky Way, we do not know yet. What is clear, though, is that the Solar System has failed to be the paradigm not only in our Galaxy but even ‘just’ in the solar neighbourhood. This finding, although unsettling, forces us to reconsider our knowledge of planets under a different light and perhaps question a few of the theoretical pillars on which we base our current ‘understanding’. The next decade will be critical to advance in what we should perhaps call Galactic planetary science. In this paper, I review highlights and pitfalls of our current knowledge of this topic and elaborate on how this knowledge might arguably evolve in the next decade. More critically, I identify what should be the mandatory scientific and technical steps to be taken in this fascinating journey of remote exploration of planets in our Galaxy. PMID:24664916

  2. Comparison of Ejection Events in the Jet and Accretion Disc Outflows in 3C 111

    NASA Technical Reports Server (NTRS)

    Tombesi, F.; Sambruna, R. M.; Marscher, A. P.; Jorstad, S. G.; Reynolds, C. S.; Markowtiz, A.

    2012-01-01

    We present a comparison of the parameters of accretion disc outflows and the jet of the broad-line radio galaxy 3C 111 on sub-pc scales. We make use of published X-ray observations of ultra-fast outflows (UFOs) and new 43 GHz VLBA images to track the jet knots ejection. We find that the superluminal jet coexists with the mildly relativistic outflows on sub-pc scales, possibly indicating a transverse stratification of a global flow. The two are roughly in pressure equilibrium, with the UFOs potentially providing additional support for the initial jet collimation. The UFOs are much more massive than the jet, but their kinetic power is probably about an order of magnitude lower, at least for the observations considered here. However, their momentum flux is equivalent and both of them are powerful enough to exert a concurrent feedback impact on the surrounding environment. A link between these components is naturally predicted in the context of MHD models for jet/outflow formation. However, given the high radiation throughput of AGNs, radiation pressure should also be taken into account. From the comparison with the long-term 2-10 keV RXTE light curve we find that the UFOs are preferentially detected during periods of increasing flux. We also find the possibility to place the UFOs within the known X-ray dips-jet ejection cycles, which has been shown to be a strong proof of the disc-jet connection, in analogue with stellar-mass black holes. However, given the limited number of observations presently available, these relations are only tentative and additional spectral monitoring is needed to test them conclusively.

  3. Stellar signatures of AGN-jet-triggered star formation

    SciTech Connect

    Dugan, Zachary; Silk, Joseph; Bryan, Sarah; Gaibler, Volker; Haas, Marcel

    2014-12-01

    To investigate feedback between relativistic jets emanating from active galactic nuclei and the stellar population of the host galaxy, we analyze the long-term evolution of the orbits of the stars formed in the galaxy-scale simulations by Gaibler et al. of jets in massive, gas-rich galaxies at z ∼ 2-3. We find strong, jet-induced differences in the resulting stellar populations of galaxies that host relativistic jets and galaxies that do not, including correlations in stellar locations, velocities, and ages. Jets are found to generate distributions of increased radial and vertical velocities that persist long enough to effectively augment the stellar structure of the host. The jets cause the formation of bow shocks that move out through the disk, generating rings of star formation within the disk. The bow shock often accelerates pockets of gas in which stars form, yielding populations of stars with significant radial and vertical velocities, some of which have large enough velocities to escape the galaxy. These stellar population signatures can serve to identify past jet activity as well as jet-induced star formation.

  4. EVIDENCE FOR GAMMA-RAY JETS IN THE MILKY WAY

    SciTech Connect

    Su Meng; Finkbeiner, Douglas P.

    2012-07-01

    Although accretion onto supermassive black holes in other galaxies is seen to produce powerful jets in X-ray and radio, no convincing detection has ever been made of a kpc-scale jet in the Milky Way. The recently discovered pair of 10 kpc tall gamma-ray bubbles in our Galaxy may be signs of earlier jet activity from the central black hole. In this paper, we identify a gamma-ray cocoon feature in the southern bubble, a jet-like feature along the cocoon's axis of symmetry, and another directly opposite the Galactic center in the north. Both the cocoon and jet-like feature have a hard spectrum with spectral index {approx} - 2 from 1 to 100 GeV, with a cocoon total luminosity of (5.5 {+-} 0.45) Multiplication-Sign 10{sup 35} and luminosity of the jet-like feature of (1.8 {+-} 0.35) Multiplication-Sign 10{sup 35} erg s{sup -1} at 1-100 GeV. If confirmed, these jets are the first resolved gamma-ray jets ever seen.

  5. A search for the analogue to Cherenkov radiation by high energy neutrinos at superluminal speeds in ICARUS

    NASA Astrophysics Data System (ADS)

    ICARUS Collaboration; Antonello, M.; Aprili, P.; Baibussinov, B.; Baldo Ceolin, M.; Benetti, P.; Calligarich, E.; Canci, N.; Carbonara, F.; Centro, S.; Cesana, A.; Cieslik, K.; Cline, D. B.; Cocco, A. G.; Dabrowska, A.; Dequal, D.; Dermenev, A.; Dolfini, R.; Farnese, C.; Fava, A.; Ferrari, A.; Fiorillo, G.; Gibin, D.; Gigli Berzolari, A.; Gninenko, S.; Guglielmi, A.; Haranczyk, M.; Holeczek, J.; Ivashkin, A.; Kisiel, J.; Kochanek, I.; Lagoda, J.; Mania, S.; Mannocchi, G.; Menegolli, A.; Meng, G.; Montanari, C.; Otwinowski, S.; Periale, L.; Piazzoli, A.; Picchi, P.; Pietropaolo, F.; Plonski, P.; Rappoldi, A.; Raselli, G. L.; Rossella, M.; Rubbia, C.; Sala, P. R.; Scantamburlo, E.; Scaramelli, A.; Segreto, E.; Sergiampietri, F.; Stefan, D.; Stepaniak, J.; Sulej, R.; Szarska, M.; Terrani, M.; Varanini, F.; Ventura, S.; Vignoli, C.; Wang, H.; Yang, X.; Zalewska, A.; Zaremba, K.; Cohen, A.

    2012-05-01

    The OPERA Collaboration (2011) [1] has reported evidence of superluminal νμ propagation between CERN and the LNGS. Cohen and Glashow (2011) [2] argued that such neutrinos should lose energy by producing photons and e+e- pairs, through Z0 mediated processes analogous to Cherenkov radiation. In terms of the parameter δ≡(vν2-vc2)/vc2, the OPERA result corresponds to δ≈5ṡ10-5. For this value (note that (vν-vc)/vc≈δ2≈2.5ṡ10-5) of δ, a very significant deformation of the neutrino energy spectrum and an abundant production of photons and e+e- pairs should be observed at LNGS. We present an analysis based on the 2010 and part of the 2011 data sets from the ICARUS experiment, located at Gran Sasso National Laboratory and using the same neutrino beam from CERN. We find that the rates and deposited energy distributions of neutrino events in ICARUS agree with the expectations for an unperturbed spectrum of the CERN neutrino beam, as also reported by OPERA. Our results therefore refute a superluminal interpretation of the OPERA result according to the Cohen and Glashow (2011) prediction [2] for a weak current analog to Cherenkov radiation. In a dedicated search, no superluminal Cherenkov-like e+e- pair or γ emission event has been directly observed inside the fiducial volume of the "bubble chamber-like" ICARUS TPC-LAr detector, setting the much stricter limit of δ<2.5ṡ10-8 at the 90% confidence level, comparable with the one due to the observations from the SN1987a (M.J. Longo, 1987 [4]). The observations of high energy neutrino events by Super-Kamiokande and IceCube are also pointing to a much stricter limit on δ.

  6. THE HOST GALAXY OF THE SUPER-LUMINOUS SN 2010gx AND LIMITS ON EXPLOSIVE {sup 56}Ni PRODUCTION

    SciTech Connect

    Chen, Ting-Wan; Smartt, Stephen J.; Kotak, Rubina; McCrum, Matt; Fraser, Morgan; Bresolin, Fabio; Kudritzki, Rolf-Peter; Pastorello, Andrea; Valenti, Stefano

    2013-02-01

    Super-luminous supernovae have a tendency to occur in faint host galaxies which are likely to have low mass and low metallicity. While these extremely luminous explosions have been observed from z = 0.1 to 1.55, the closest explosions allow more detailed investigations of their host galaxies. We present a detailed analysis of the host galaxy of SN 2010gx (z = 0.23), one of the best studied super-luminous type Ic supernovae. The host is a dwarf galaxy (M{sub g} = -17.42 {+-} 0.17) with a high specific star formation rate. It has a remarkably low metallicity of 12 + log (O/H) = 7.5 {+-} 0.1 dex as determined from the detection of the [O III] {lambda}4363 line. This is the first reliable metallicity determination of a super-luminous stripped-envelope supernova host. We collected deep multi-epoch imaging with Gemini + GMOS between 240 and 560 days after explosion to search for any sign of radioactive {sup 56}Ni, which might provide further insights on the explosion mechanism and the progenitor's nature. We reach griz magnitudes of m{sub AB} {approx} 26, but do not detect SN 2010gx at these epochs. The limit implies that any {sup 56}Ni production was similar to or below that of SN 1998bw (a luminous type Ic SN that produced around 0.4 M{sub Sun} of {sup 56}Ni). The low volumetric rates of these supernovae ({approx}10{sup -4} of the core-collapse population) could be qualitatively matched if the explosion mechanism requires a combination of low-metallicity (below 0.2 Z{sub Sun }), high progenitor mass (>60 M{sub Sun }) and high rotation rate (fastest 10% of rotators).

  7. Multi-epoch multi-frequency VLBI study of the parsec-scale jet in the blazar 3C 66A

    SciTech Connect

    Zhao, Guang-Yao; Chen, Yong-Jun; Shen, Zhi-Qiang; Sudou, Hiroshi; Iguchi, Satoru

    2015-02-01

    We present observational results of the γ-ray blazar 3C 66A at 2.3, 8.4, and 22 GHz at four epochs during 2004–2005 with the VLBA. The resulting images show an overall core-jet structure extending roughly to the south, with two intermediate breaks occurring in the region near the core. By model-fitting to the visibility data, the northmost component, which is also the brightest, is identified as the core according to its relatively flat spectrum and its compactness. Combining our results with previous results to investigate the proper motions of the jet components, we found the kinematics of 3C 66A to be quite complicated, with components of inward and outward, subluminal and superluminal motions all detected in the radio structure. The superluminal motions indicate strong Doppler boosting exists in the jet. The apparent inward motions of the innermost components last for at least 10 years and could not be caused by newborn components. A possible reason could be non-stationarity of the core due to opacity change.

  8. Switching from subluminal to superluminal light propagation via a coherent pump field in a four-level atomic system

    SciTech Connect

    Kuang Shangqi; Wan Rengang; Kou Jun; Jiang Yun; Gao Jinyue

    2009-12-15

    We theoretically investigate the influence of a coherent pump field on the propagation of a weak light pulse of a probe field in a four-level atomic system. Due to the modulation of the pump field, the light pulse can be manipulated from subluminal to superluminal with negligible distortion. This scheme can be realized in both the ultracold and Doppler-broadened atomic systems. We also demonstrate that the spectral linewidth with an anomalous dispersion is reduced by thermal averaging; therefore, one can obtain a larger negative group refractive index in room-temperature vapor than the largest value achieved in ultracold atomic gas.

  9. The connection between the parsec-scale radio jet and γ-ray flares in the blazar 1156+295

    NASA Astrophysics Data System (ADS)

    Ramakrishnan, Venkatessh; León-Tavares, Jonathan; Rastorgueva-Foi, Elizaveta A.; Wiik, Kaj; Jorstad, Svetlana G.; Marscher, Alan P.; Tornikoski, Merja; Agudo, Iván; Lähteenmäki, Anne; Valtaoja, Esko; Aller, Margo F.; Blinov, Dmitry A.; Casadio, Carolina; Efimova, Natalia V.; Gurwell, Mark A.; Gómez, José L.; Hagen-Thorn, Vladimir A.; Joshi, Manasvita; Järvelä, Emilia; Konstantinova, Tatiana S.; Kopatskaya, Evgenia N.; Larionov, Valeri M.; Larionova, Elena G.; Larionova, Liudmilla V.; Lavonen, Niko; MacDonald, Nicholas R.; McHardy, Ian M.; Molina, Sol N.; Morozova, Daria A.; Nieppola, Elina; Tammi, Joni; Taylor, Brian W.; Troitsky, Ivan S.

    2014-12-01

    The blazar 1156+295 was active at γ-ray energies, exhibiting three prominent flares during the year 2010. Here, we present results using the combination of broad-band (X-ray through mm single-dish) monitoring data and radio-band imaging data at 43 GHz on the connection of γ-ray events to the ejections of superluminal components and other changes in the jet of 1156+295. The kinematics of the jet over the interval 2007.0-2012.5 using 43 GHz Very Long Baseline Array observations reveal the presence of four moving and one stationary component in the inner region of the blazar jet. The propagation of the third and fourth components in the jet corresponds closely in time to the active phase of the source in γ-rays. We briefly discuss the implications of the structural changes in the jet for the mechanism of γ-ray production during bright flares. To localize the γ-ray emission site in the blazar, we performed the correlation analysis between the 43 GHz radio core and the γ-ray light curve. The time lag obtained from the correlation constrains the γ-ray emitting region in the parsec-scale jet.

  10. Finding Distant Galactic HII Regions

    NASA Astrophysics Data System (ADS)

    Anderson, L. D.; Armentrout, W. P.; Johnstone, B. M.; Bania, T. M.; Balser, Dana S.; Wenger, Trey V.; Cunningham, V.

    2015-12-01

    The WISE Catalog of Galactic H ii Regions contains ˜2000 H ii region candidates lacking ionized gas spectroscopic observations. All candidates have the characteristic H ii region mid-infrared morphology of WISE 12 μ {{m}} emission surrounding 22 μ {{m}} emission, and additionally have detected radio continuum emission. We here report Green Bank Telescope hydrogen radio recombination line and radio continuum detections in the X-band (9 GHz; 3 cm) of 302 WISE H ii region candidates (out of 324 targets observed) in the zone 225^\\circ ≥slant {\\ell }≥slant -20^\\circ , | {\\text{}}b| ≤slant 6^\\circ . Here we extend the sky coverage of our H ii region Discovery Survey, which now contains nearly 800 H ii regions distributed across the entire northern sky. We provide LSR velocities for the 302 detections and kinematic distances for 131 of these. Of the 302 new detections, 5 have ({\\ell },{\\text{}}b,v) coordinates consistent with the Outer Scutum-Centaurus Arm (OSC), the most distant molecular spiral arm of the Milky Way. Due to the Galactic warp, these nebulae are found at Galactic latitudes >1° in the first Galactic quadrant, and therefore were missed in previous surveys of the Galactic plane. One additional region has a longitude and velocity consistent with the OSC but lies at a negative Galactic latitude (G039.183-01.422 -54.9 {km} {{{s}}}-1). With Heliocentric distances >22 kpc and Galactocentric distances >16 kpc, the OSC H ii regions are the most distant known in the Galaxy. We detect an additional three H ii regions near {\\ell }≃ 150^\\circ whose LSR velocities place them at Galactocentric radii >19 kpc. If their distances are correct, these nebulae may represent the limit to Galactic massive star formation.

  11. JASMINE: galactic structure surveyor

    NASA Astrophysics Data System (ADS)

    Gouda, Naoteru; Kobayashi, Yukiyasu; Yamada, Yoshiyuki; Yano, Taihei; Tsujimoto, Takuji; Suganuma, Masahiro; Niwa, Yoshito; Yamauchi, Masahiro; Kawakatsu, Yasuhiro; Matsuhara, Hideo; Noda, Atsushi; Tsuiki, Atsuo; Utashima, Masayoshi; Ogawa, Akira

    2006-06-01

    We introduce a Japanese plan of infrared(z-band:0.9μm) space astrometry(JASMINE-project). JASMINE is the satellite (Japan Astrometry Satellite Mission for INfrared Exploration) which will measure distances and apparent motions of stars around the center of the Milky Way with yet unprecedented precision. It will measure parallaxes, positions with the accuracy of 10 micro-arcsec and proper motions with the accuracy of ~ 4microarcsec/ year for stars brighter than z=14mag. JASMINE can observe about ten million stars belonging to the bulge components of our Galaxy, which are hidden by the interstellar dust extinction in optical bands. Number of stars with σ/π < 0.1 in the direction of the Galactic central bulge is about 1000 times larger than those observed in optical bands, where π is a parallax and σ is an error of the parallax. With the completely new "map of the bulge in the Milky Way", it is expected that many new exciting scientific results will be obtained in various fields of astronomy. Presently, JASMINE is in a development phase, with a target launch date around 2015. We adopt the following instrument design of JASMINE in order to get the accurate positions of many stars. A 3-mirrors optical system(modified Korsch system)with a primary mirror of~ 0.85m is one of the candidate for the optical system. On the astro-focal plane, we put dozens of new type of CCDs for z-band to get a wide field of view. The accurate measurements of the astrometric parameters requires the instrument line-of-sight highly stability and the opto-mechanical highly stability of the payload in the JASMINE spacecraft. The consideration of overall system(bus) design is now going on in cooperation with Japan Aerospace Exploration Agency(JAXA).

  12. Galactic Habitable Orbits

    NASA Astrophysics Data System (ADS)

    Rahimi, A.; Mao, S.; Kawata, D.

    2014-03-01

    The fossil record shows that the Earth has experienced several mass extinctions over the past 500 million years1, and it has been suggested that there is a periodicity in extinction events on timescales of tens1 and/or hundreds of millions of years. Various hypotheses have been proposed to explain the cause of the mass extinctions, including the suggestion that the Earth's ozone layer may have been destroyed by intense radiation from a nearby supernovae2- 3, exposing the Earth's surface to damaging UV radiation. Recent observations of cores taken from the ocean floor revealed atoms of a very rare isotope of iron (60Fe) believed to have arrived on Earth around 2 million years ago as fallout from a nearby supernovae4. Astronomical evidence for that past supernovae was recently found in the debris of a young cluster of massive stars5, by tracing its past orbit, putting it at the right place at the right time to explain the mild extinction event. Here we report new high-resolution (both in space and time) N-body chemodynamical simulations (carried out with our novel code GCD+6) of the evolution of a model Milky Way Galaxy, tracing the orbit of èsun-like' stars over a 500 million year period, checking the proximity to supernovae throughout the history of the orbit and comparing the times when this occurs with past mass extinctions on Earth. We additionally explain the important effects of the spiral arm pattern, radial migration of stars and Galactic chemistry on habitability.

  13. The Bubbling Galactic Disk

    NASA Astrophysics Data System (ADS)

    Churchwell, E.; Povich, M. S.; Allen, D.; Taylor, M. G.; Meade, M. R.; Babler, B. L.; Indebetouw, R.; Watson, C.; Whitney, B. A.; Wolfire, M. G.; Bania, T. M.; Benjamin, R. A.; Clemens, D. P.; Cohen, M.; Cyganowski, C. J.; Jackson, J. M.; Kobulnicky, H. A.; Mathis, J. S.; Mercer, E. P.; Stolovy, S. R.; Uzpen, B.; Watson, D. F.; Wolff, M. J.

    2006-10-01

    A visual examination of the images from the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) has revealed 322 partial and closed rings that we propose represent partially or fully enclosed three-dimensional bubbles. We argue that the bubbles are primarily formed by hot young stars in massive star formation regions. We have found an average of about 1.5 bubbles per square degree. About 25% of the bubbles coincide with known radio H II regions, and about 13% enclose known star clusters. It appears that B4-B9 stars (too cool to produce detectable radio H II regions) probably produce about three-quarters of the bubbles in our sample, and the remainder are produced by young O-B3 stars that produce detectable radio H II regions. Some of the bubbles may be the outer edges of H II regions where PAH spectral features are excited and may not be dynamically formed by stellar winds. Only three of the bubbles are identified as known SNRs. No bubbles coincide with known planetary nebulae or W-R stars in the GLIMPSE survey area. The bubbles are small. The distribution of angular diameters peaks between 1' and 3' with over 98% having angular diameters less than 10' and 88% less than 4'. Almost 90% have shell thicknesses between 0.2 and 0.4 of their outer radii. Bubble shell thickness increases approximately linearly with shell radius. The eccentricities are rather large, peaking between 0.6 and 0.7; about 65% have eccentricities between 0.55 and 0.85.

  14. A Disturbed Galactic Duo

    NASA Astrophysics Data System (ADS)

    2011-04-01

    The galaxies in this cosmic pairing, captured by the Wide Field Imager on the MPG/ESO 2.2-metre telescope at the La Silla Observatory in Chile, display some curious features, demonstrating that each member of the duo is close enough to feel the distorting gravitational influence of the other. The gravitational tug of war has warped the spiral shape of one galaxy, NGC 3169, and fragmented the dust lanes in its companion NGC 3166. Meanwhile, a third, smaller galaxy to the lower right, NGC 3165, has a front-row seat to the gravitational twisting and pulling of its bigger neighbours. This galactic grouping, found about 70 million light-years away in the constellation Sextans (The Sextant), was discovered by the English astronomer William Herschel in 1783. Modern astronomers have gauged the distance between NGC 3169 (left) and NGC 3166 (right) as a mere 50 000 light-years, a separation that is only about half the diameter of the Milky Way galaxy. In such tight quarters, gravity can start to play havoc with galactic structure. Spiral galaxies like NGC 3169 and NGC 3166 tend to have orderly swirls of stars and dust pinwheeling about their glowing centres. Close encounters with other massive objects can jumble this classic configuration, often serving as a disfiguring prelude to the merging of galaxies into one larger galaxy. So far, the interactions of NGC 3169 and NGC 3166 have just lent a bit of character. NGC 3169's arms, shining bright with big, young, blue stars, have been teased apart, and lots of luminous gas has been drawn out from its disc. In NGC 3166's case, the dust lanes that also usually outline spiral arms are in disarray. Unlike its bluer counterpart, NGC 3166 is not forming many new stars. NGC 3169 has another distinction: the faint yellow dot beaming through a veil of dark dust just to the left of and close to the galaxy's centre [1]. This flash is the leftover of a supernova detected in 2003 and known accordingly as SN 2003cg. A supernova of this

  15. A Disturbed Galactic Duo

    NASA Astrophysics Data System (ADS)

    2011-04-01

    The galaxies in this cosmic pairing, captured by the Wide Field Imager on the MPG/ESO 2.2-metre telescope at the La Silla Observatory in Chile, display some curious features, demonstrating that each member of the duo is close enough to feel the distorting gravitational influence of the other. The gravitational tug of war has warped the spiral shape of one galaxy, NGC 3169, and fragmented the dust lanes in its companion NGC 3166. Meanwhile, a third, smaller galaxy to the lower right, NGC 3165, has a front-row seat to the gravitational twisting and pulling of its bigger neighbours. This galactic grouping, found about 70 million light-years away in the constellation Sextans (The Sextant), was discovered by the English astronomer William Herschel in 1783. Modern astronomers have gauged the distance between NGC 3169 (left) and NGC 3166 (right) as a mere 50 000 light-years, a separation that is only about half the diameter of the Milky Way galaxy. In such tight quarters, gravity can start to play havoc with galactic structure. Spiral galaxies like NGC 3169 and NGC 3166 tend to have orderly swirls of stars and dust pinwheeling about their glowing centres. Close encounters with other massive objects can jumble this classic configuration, often serving as a disfiguring prelude to the merging of galaxies into one larger galaxy. So far, the interactions of NGC 3169 and NGC 3166 have just lent a bit of character. NGC 3169's arms, shining bright with big, young, blue stars, have been teased apart, and lots of luminous gas has been drawn out from its disc. In NGC 3166's case, the dust lanes that also usually outline spiral arms are in disarray. Unlike its bluer counterpart, NGC 3166 is not forming many new stars. NGC 3169 has another distinction: the faint yellow dot beaming through a veil of dark dust just to the left of and close to the galaxy's centre [1]. This flash is the leftover of a supernova detected in 2003 and known accordingly as SN 2003cg. A supernova of this

  16. ASASSN-15lh: A Superluminous Ultraviolet Rebrightening Observed by Swift and Hubble

    NASA Astrophysics Data System (ADS)

    Brown, Peter J.; Yang, Yi; Cooke, Jeff; Olaes, Melanie; Quimby, Robert M.; Baade, Dietrich; Gehrels, Neil; Hoeflich, Peter; Maund, Justyn; Mould, Jeremy; Wang, Lifan; Wheeler, J. Craig

    2016-09-01

    We present and discuss ultraviolet and optical photometry from the Ultraviolet/Optical Telescope, X-ray limits from the X-Ray Telescope on Swift, and imaging polarimetry and ultraviolet/optical spectroscopy with the Hubble Space Telescope, all from observations of ASASSN-15lh. It has been classified as a hydrogen-poor superluminous supernova (SLSN I), making it more luminous than any other supernova observed. ASASSN-15lh is not detected in the X-rays in individual or co-added observations. From the polarimetry we determine that the explosion was only mildly asymmetric. We find the flux of ASASSN-15lh to increase strongly into the ultraviolet, with an ultraviolet luminosity 100 times greater than the hydrogen-rich, ultraviolet-bright SLSN II SN 2008es. We find that objects as bright as ASASSN-15lh are easily detectable beyond redshifts of ∼4 with the single-visit depths planned for the Large Synoptic Survey Telescope. Deep near-infrared surveys could detect such objects past a redshift of ∼20, enabling a probe of the earliest star formation. A late rebrightening—most prominent at shorter wavelengths—is seen about two months after the peak brightness, which is itself as bright as an SLSN. The ultraviolet spectra during the rebrightening are dominated by the continuum without the broad absorption or emission lines seen in SLSNe or tidal disruption events (TDEs) and the early optical spectra of ASASSN-15lh. Our spectra show no strong hydrogen emission, showing only Lyα absorption near the redshift previously found by optical absorption lines of the presumed host. The properties of ASASSN-15lh are extreme when compared to either SLSNe or TDEs. Based on observations with the NASA/ESA Hubble Space Telescope (HST) obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555.

  17. Are superluminous supernovae and long GRBs the products of dynamical processes in young dense star clusters?

    SciTech Connect

    Van den Heuvel, E. P. J.; Portegies Zwart, S. F.

    2013-12-20

    Superluminous supernovae (SLSNe) occur almost exclusively in small galaxies (Small/Large Magellanic Cloud (SMC/LMC)-like or smaller), and the few SLSNe observed in larger star-forming galaxies always occur close to the nuclei of their hosts. Another type of peculiar and highly energetic supernovae are the broad-line Type Ic SNe (SN Ic-BL) that are associated with long-duration gamma-ray bursts (LGRBs). Also these have a strong preference for occurring in small (SMC/LMC-like or smaller) star-forming galaxies, and in these galaxies LGRBs always occur in the brightest spots. Studies of nearby star-forming galaxies that are similar to the hosts of LGRBs show that these brightest spots are giant H II regions produced by massive dense young star clusters with many hundreds of O- and Wolf-Rayet-type stars. Such dense young clusters are also found in abundance within a few hundred parsecs from the nucleus of larger galaxies like our own. We argue that the SLSNe and the SNe Ic-BL/LGRBs are exclusive products of two types of dynamical interactions in dense young star clusters. In our model the high angular momentum of the collapsing stellar cores required for the engines of an SN Ic-BL results from the post-main-sequence mergers of dynamically produced cluster binaries with almost equal-mass components. The merger produces a critically rotating single helium star with sufficient angular momentum to produce an LGRB; the observed 'metal aversion' of LGRBs is a natural consequence of the model. We argue that, on the other hand, SLSNe could be the products of runaway multiple collisions in dense clusters, and we present (and quantize) plausible scenarios of how the different types of SLSNe can be produced.

  18. SN 2015BN: A Detailed Multi-wavelength View of a Nearby Superluminous Supernova

    NASA Astrophysics Data System (ADS)

    Nicholl, M.; Berger, E.; Smartt, S. J.; Margutti, R.; Kamble, A.; Alexander, K. D.; Chen, T.-W.; Inserra, C.; Arcavi, I.; Blanchard, P. K.; Cartier, R.; Chambers, K. C.; Childress, M. J.; Chornock, R.; Cowperthwaite, P. S.; Drout, M.; Flewelling, H. A.; Fraser, M.; Gal-Yam, A.; Galbany, L.; Harmanen, J.; Holoien, T. W.-S.; Hosseinzadeh, G.; Howell, D. A.; Huber, M. E.; Jerkstrand, A.; Kankare, E.; Kochanek, C. S.; Lin, Z.-Y.; Lunnan, R.; Magnier, E. A.; Maguire, K.; McCully, C.; McDonald, M.; Metzger, B. D.; Milisavljevic, D.; Mitra, A.; Reynolds, T.; Saario, J.; Shappee, B. J.; Smith, K. W.; Valenti, S.; Villar, V. A.; Waters, C.; Young, D. R.

    2016-07-01

    We present observations of SN 2015bn (=PS15ae = CSS141223-113342+004332 = MLS150211-113342+004333), a Type I superluminous supernova (SLSN) at redshift z = 0.1136. As well as being one of the closest SLSNe I yet discovered, it is intrinsically brighter ({M}U≈ -23.1) and in a fainter galaxy ({M}B≈ -16.0) than other SLSNe at z∼ 0.1. We used this opportunity to collect the most extensive data set for any SLSN I to date, including densely sampled spectroscopy and photometry, from the UV to the NIR, spanning ‑50 to +250 days from optical maximum. SN 2015bn fades slowly, but exhibits surprising undulations in the light curve on a timescale of 30–50 days, especially in the UV. The spectrum shows extraordinarily slow evolution except for a rapid transformation between +7 and +20–30 days. No narrow emission lines from slow-moving material are observed at any phase. We derive physical properties including the bolometric luminosity, and find slow velocity evolution and non-monotonic temperature and radial evolution. A deep radio limit rules out a healthy off-axis gamma-ray burst, and places constraints on the pre-explosion mass loss. The data can be consistently explained by a ≳ 10 M {}ȯ stripped progenitor exploding with ∼ {10}51 erg kinetic energy, forming a magnetar with a spin-down timescale of ∼20 days (thus avoiding a gamma-ray burst) that reheats the ejecta and drives ionization fronts. The most likely alternative scenario—interaction with ∼20 M {}ȯ of dense, inhomogeneous circumstellar material—can be tested with continuing radio follow-up.

  19. SUPER-LUMINOUS TYPE Ic SUPERNOVAE: CATCHING A MAGNETAR BY THE TAIL

    SciTech Connect

    Inserra, C.; Smartt, S. J.; Jerkstrand, A.; Fraser, M.; Wright, D.; Smith, K.; Chen, T.-W.; Kotak, R.; Nicholl, M.; Valenti, S.; Pastorello, A.; Benetti, S.; Bresolin, F.; Kudritzki, R. P.; Burgett, W. S.; Chambers, K. C.; Flewelling, H.; Botticella, M. T.; Ergon, M.; Fynbo, J. P. U.; and others

    2013-06-20

    We report extensive observational data for five of the lowest redshift Super-Luminous Type Ic Supernovae (SL-SNe Ic) discovered to date, namely, PTF10hgi, SN2011ke, PTF11rks, SN2011kf, and SN2012il. Photometric imaging of the transients at +50 to +230 days after peak combined with host galaxy subtraction reveals a luminous tail phase for four of these SL-SNe. A high-resolution, optical, and near-infrared spectrum from xshooter provides detection of a broad He I {lambda}10830 emission line in the spectrum (+50 days) of SN2012il, revealing that at least some SL-SNe Ic are not completely helium-free. At first sight, the tail luminosity decline rates that we measure are consistent with the radioactive decay of {sup 56}Co, and would require 1-4 M{sub Sun} of {sup 56}Ni to produce the luminosity. These {sup 56}Ni masses cannot be made consistent with the short diffusion times at peak, and indeed are insufficient to power the peak luminosity. We instead favor energy deposition by newborn magnetars as the power source for these objects. A semi-analytical diffusion model with energy input from the spin-down of a magnetar reproduces the extensive light curve data well. The model predictions of ejecta velocities and temperatures which are required are in reasonable agreement with those determined from our observations. We derive magnetar energies of 0.4 {approx}< E(10{sup 51} erg) {approx}< 6.9 and ejecta masses of 2.3 {approx}< M{sub ej}(M{sub Sun }) {approx}< 8.6. The sample of five SL-SNe Ic presented here, combined with SN 2010gx-the best sampled SL-SNe Ic so far-points toward an explosion driven by a magnetar as a viable explanation for all SL-SNe Ic.

  20. On the diversity of superluminous supernovae: ejected mass as the dominant factor

    NASA Astrophysics Data System (ADS)

    Nicholl, M.; Smartt, S. J.; Jerkstrand, A.; Inserra, C.; Sim, S. A.; Chen, T.-W.; Benetti, S.; Fraser, M.; Gal-Yam, A.; Kankare, E.; Maguire, K.; Smith, K.; Sullivan, M.; Valenti, S.; Young, D. R.; Baltay, C.; Bauer, F. E.; Baumont, S.; Bersier, D.; Botticella, M.-T.; Childress, M.; Dennefeld, M.; Della Valle, M.; Elias-Rosa, N.; Feindt, U.; Galbany, L.; Hadjiyska, E.; Le Guillou, L.; Leloudas, G.; Mazzali, P.; McKinnon, R.; Polshaw, J.; Rabinowitz, D.; Rostami, S.; Scalzo, R.; Schmidt, B. P.; Schulze, S.; Sollerman, J.; Taddia, F.; Yuan, F.

    2015-10-01

    We assemble a sample of 24 hydrogen-poor superluminous supernovae (SLSNe). Parameterizing the light-curve shape through rise and decline time-scales shows that the two are highly correlated. Magnetar-powered models can reproduce the correlation, with the diversity in rise and decline rates driven by the diffusion time-scale. Circumstellar interaction models can exhibit a similar rise-decline relation, but only for a narrow range of densities, which may be problematic for these models. We find that SLSNe are approximately 3.5 mag brighter and have light curves three times broader than SNe Ibc, but that the intrinsic shapes are similar. There are a number of SLSNe with particularly broad light curves, possibly indicating two progenitor channels, but statistical tests do not cleanly separate two populations. The general spectral evolution is also presented. Velocities measured from Fe II are similar for SLSNe and SNe Ibc, suggesting that diffusion time differences are dominated by mass or opacity. Flat velocity evolution in most SLSNe suggests a dense shell of ejecta. If opacities in SLSNe are similar to other SNe Ibc, the average ejected mass is higher by a factor 2-3. Assuming κ = 0.1 cm2 g-1, we estimate a mean (median) SLSN ejecta mass of 10 M⊙ (6 M⊙), with a range of 3-30 M⊙. Doubling the assumed opacity brings the masses closer to normal SNe Ibc, but with a high-mass tail. The most probable mechanism for generating SLSNe seems to be the core collapse of a very massive hydrogen-poor star, forming a millisecond magnetar.

  1. SN 2015BN: A Detailed Multi-wavelength View of a Nearby Superluminous Supernova

    NASA Astrophysics Data System (ADS)

    Nicholl, M.; Berger, E.; Smartt, S. J.; Margutti, R.; Kamble, A.; Alexander, K. D.; Chen, T.-W.; Inserra, C.; Arcavi, I.; Blanchard, P. K.; Cartier, R.; Chambers, K. C.; Childress, M. J.; Chornock, R.; Cowperthwaite, P. S.; Drout, M.; Flewelling, H. A.; Fraser, M.; Gal-Yam, A.; Galbany, L.; Harmanen, J.; Holoien, T. W.-S.; Hosseinzadeh, G.; Howell, D. A.; Huber, M. E.; Jerkstrand, A.; Kankare, E.; Kochanek, C. S.; Lin, Z.-Y.; Lunnan, R.; Magnier, E. A.; Maguire, K.; McCully, C.; McDonald, M.; Metzger, B. D.; Milisavljevic, D.; Mitra, A.; Reynolds, T.; Saario, J.; Shappee, B. J.; Smith, K. W.; Valenti, S.; Villar, V. A.; Waters, C.; Young, D. R.

    2016-07-01

    We present observations of SN 2015bn (=PS15ae = CSS141223-113342+004332 = MLS150211-113342+004333), a Type I superluminous supernova (SLSN) at redshift z = 0.1136. As well as being one of the closest SLSNe I yet discovered, it is intrinsically brighter ({M}U≈ -23.1) and in a fainter galaxy ({M}B≈ -16.0) than other SLSNe at z˜ 0.1. We used this opportunity to collect the most extensive data set for any SLSN I to date, including densely sampled spectroscopy and photometry, from the UV to the NIR, spanning ‑50 to +250 days from optical maximum. SN 2015bn fades slowly, but exhibits surprising undulations in the light curve on a timescale of 30–50 days, especially in the UV. The spectrum shows extraordinarily slow evolution except for a rapid transformation between +7 and +20–30 days. No narrow emission lines from slow-moving material are observed at any phase. We derive physical properties including the bolometric luminosity, and find slow velocity evolution and non-monotonic temperature and radial evolution. A deep radio limit rules out a healthy off-axis gamma-ray burst, and places constraints on the pre-explosion mass loss. The data can be consistently explained by a ≳ 10 M {}ȯ stripped progenitor exploding with ˜ {10}51 erg kinetic energy, forming a magnetar with a spin-down timescale of ˜20 days (thus avoiding a gamma-ray burst) that reheats the ejecta and drives ionization fronts. The most likely alternative scenario—interaction with ˜20 M {}ȯ of dense, inhomogeneous circumstellar material—can be tested with continuing radio follow-up.

  2. Superluminous Supernovae Powered by Magnetars: Late-time Light Curves and Hard Emission Leakage

    NASA Astrophysics Data System (ADS)

    Wang, S. Q.; Wang, L. J.; Dai, Z. G.; Wu, X. F.

    2015-01-01

    Recently, research performed by two groups has revealed that the magnetar spin-down energy injection model with full energy trapping can explain the early-time light curves of SN 2010gx, SN 2013dg, LSQ12dlf, SSS120810, and CSS121015 but fails to fit the late-time light curves of these superluminous supernovae (SLSNe). These results imply that the original magnetar-powered model is challenged in explaining these SLSNe. Our paper aims to simultaneously explain both the early- and late-time data/upper limits by considering the leakage of hard emissions. We incorporate quantitatively the leakage effect into the original magnetar-powered model and derive a new semianalytical equation. Comparing the light curves reproduced by our revised magnetar-powered model with the observed data and/or upper limits of these five SLSNe, we found that the late-time light curves reproduced by our semianalytical equation are in good agreement with the late-time observed data and/or upper limits of SN 2010gx, CSS121015, SN 2013dg, and LSQ12dlf and the late-time excess of SSS120810, indicating that the magnetar-powered model might be responsible for these SLSNe and that the gamma-ray and X-ray leakages are unavoidable when the hard photons were down-Comptonized to softer photons. To determine the details of the leakage effect and unveil the nature of SLSNe, more high-quality bolometric light curves and spectra of SLSNe are required.

  3. ASASSN-15lh: A Superluminous Ultraviolet Rebrightening Observed by Swift and Hubble

    NASA Astrophysics Data System (ADS)

    Brown, Peter J.; Yang, Yi; Cooke, Jeff; Olaes, Melanie; Quimby, Robert M.; Baade, Dietrich; Gehrels, Neil; Hoeflich, Peter; Maund, Justyn; Mould, Jeremy; Wang, Lifan; Wheeler, J. Craig

    2016-09-01

    We present and discuss ultraviolet and optical photometry from the Ultraviolet/Optical Telescope, X-ray limits from the X-Ray Telescope on Swift, and imaging polarimetry and ultraviolet/optical spectroscopy with the Hubble Space Telescope, all from observations of ASASSN-15lh. It has been classified as a hydrogen-poor superluminous supernova (SLSN I), making it more luminous than any other supernova observed. ASASSN-15lh is not detected in the X-rays in individual or co-added observations. From the polarimetry we determine that the explosion was only mildly asymmetric. We find the flux of ASASSN-15lh to increase strongly into the ultraviolet, with an ultraviolet luminosity 100 times greater than the hydrogen-rich, ultraviolet-bright SLSN II SN 2008es. We find that objects as bright as ASASSN-15lh are easily detectable beyond redshifts of ˜4 with the single-visit depths planned for the Large Synoptic Survey Telescope. Deep near-infrared surveys could detect such objects past a redshift of ˜20, enabling a probe of the earliest star formation. A late rebrightening—most prominent at shorter wavelengths—is seen about two months after the peak brightness, which is itself as bright as an SLSN. The ultraviolet spectra during the rebrightening are dominated by the continuum without the broad absorption or emission lines seen in SLSNe or tidal disruption events (TDEs) and the early optical spectra of ASASSN-15lh. Our spectra show no strong hydrogen emission, showing only Lyα absorption near the redshift previously found by optical absorption lines of the presumed host. The properties of ASASSN-15lh are extreme when compared to either SLSNe or TDEs. Based on observations with the NASA/ESA Hubble Space Telescope (HST) obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555.

  4. Can pair-instability supernova models match the observations of superluminous supernovae?

    NASA Astrophysics Data System (ADS)

    Kozyreva, Alexandra; Blinnikov, S.

    2015-12-01

    An increasing number of so-called superluminous supernovae (SLSNe) are discovered. It is believed that at least some of them with slowly fading light curves originate in stellar explosions induced by the pair instability mechanism. Recent stellar evolution models naturally predict pair instability supernovae (PISNe) from very massive stars at wide range of metallicities (up to Z = 0.006, Yusof et al.). In the scope of this study, we analyse whether PISN models can match the observational properties of SLSNe with various light-curve shapes. Specifically, we explore the influence of different degrees of macroscopic chemical mixing in PISN explosive products on the resulting observational properties. We artificially apply mixing to the 250 M⊙ PISN evolutionary model from Kozyreva et al. and explore its supernova evolution with the one-dimensional radiation hydrodynamics code STELLA. The greatest success in matching SLSN observations is achieved in the case of an extreme macroscopic mixing, where all radioactive material is ejected into the hydrogen-helium outer layer. Such an extreme macroscopic redistribution of chemicals produces events with faster light curves with high photospheric temperatures and high photospheric velocities. These properties fit a wider range of SLSNe than non-mixed PISN model. Our mixed models match the light curves, colour temperature, and photospheric velocity evolution of two well-observed SLSNe PTF12dam and LSQ12dlf. However, these models' extreme chemical redistribution may be hard to realize in massive PISNe. Therefore, alternative models such as the magnetar mechanism or wind-interaction may still to be favourable to interpret rapidly rising SLSNe.

  5. Are Superluminous Supernovae and Long GRBs the Products of Dynamical Processes in Young Dense Star Clusters?

    NASA Astrophysics Data System (ADS)

    van den Heuvel, E. P. J.; Portegies Zwart, S. F.

    2013-12-01

    Superluminous supernovae (SLSNe) occur almost exclusively in small galaxies (Small/Large Magellanic Cloud (SMC/LMC)-like or smaller), and the few SLSNe observed in larger star-forming galaxies always occur close to the nuclei of their hosts. Another type of peculiar and highly energetic supernovae are the broad-line Type Ic SNe (SN Ic-BL) that are associated with long-duration gamma-ray bursts (LGRBs). Also these have a strong preference for occurring in small (SMC/LMC-like or smaller) star-forming galaxies, and in these galaxies LGRBs always occur in the brightest spots. Studies of nearby star-forming galaxies that are similar to the hosts of LGRBs show that these brightest spots are giant H II regions produced by massive dense young star clusters with many hundreds of O- and Wolf-Rayet-type stars. Such dense young clusters are also found in abundance within a few hundred parsecs from the nucleus of larger galaxies like our own. We argue that the SLSNe and the SNe Ic-BL/LGRBs are exclusive products of two types of dynamical interactions in dense young star clusters. In our model the high angular momentum of the collapsing stellar cores required for the engines of an SN Ic-BL results from the post-main-sequence mergers of dynamically produced cluster binaries with almost equal-mass components. The merger produces a critically rotating single helium star with sufficient angular momentum to produce an LGRB; the observed "metal aversion" of LGRBs is a natural consequence of the model. We argue that, on the other hand, SLSNe could be the products of runaway multiple collisions in dense clusters, and we present (and quantize) plausible scenarios of how the different types of SLSNe can be produced.

  6. ANALYTICAL LIGHT CURVE MODELS OF SUPERLUMINOUS SUPERNOVAE: {chi}{sup 2}-MINIMIZATION OF PARAMETER FITS

    SciTech Connect

    Chatzopoulos, E.; Wheeler, J. Craig; Vinko, J.; Horvath, Z. L.; Nagy, A.

    2013-08-10

    We present fits of generalized semi-analytic supernova (SN) light curve (LC) models for a variety of power inputs including {sup 56}Ni and {sup 56}Co radioactive decay, magnetar spin-down, and forward and reverse shock heating due to supernova ejecta-circumstellar matter (CSM) interaction. We apply our models to the observed LCs of the H-rich superluminous supernovae (SLSN-II) SN 2006gy, SN 2006tf, SN 2008am, SN 2008es, CSS100217, the H-poor SLSN-I SN 2005ap, SCP06F6, SN 2007bi, SN 2010gx, and SN 2010kd, as well as to the interacting SN 2008iy and PTF 09uj. Our goal is to determine the dominant mechanism that powers the LCs of these extraordinary events and the physical conditions involved in each case. We also present a comparison of our semi-analytical results with recent results from numerical radiation hydrodynamics calculations in the particular case of SN 2006gy in order to explore the strengths and weaknesses of our models. We find that CS shock heating produced by ejecta-CSM interaction provides a better fit to the LCs of most of the events we examine. We discuss the possibility that collision of supernova ejecta with hydrogen-deficient CSM accounts for some of the hydrogen-deficient SLSNe (SLSN-I) and may be a plausible explanation for the explosion mechanism of SN 2007bi, the pair-instability supernova candidate. We characterize and discuss issues of parameter degeneracy.

  7. A Hubble Space Telescope survey of the host galaxies of Superluminous Supernovae

    NASA Astrophysics Data System (ADS)

    Angus, C. R.; Levan, A. J.; Perley, D. A.; Tanvir, N. R.; Lyman, J. D.; Stanway, E. R.; Fruchter, A. S.

    2016-05-01

    We present Hubble Space Telescope (HST) Wide Field Camera 3 UV and near-IR (nIR) imaging of 21 Superluminous Supernovae (SLSNe) host galaxies, providing a sensitive probe of star formation and stellar mass within the hosts. Comparing the photometric and morphological properties of these host galaxies with those of core-collapse supernovae (CCSNe) and long-duration gamma-ray bursts (LGRBs), we find SLSN hosts are fainter and more compact at both UV and nIR wavelengths, in some cases we barely recover hosts with absolute magnitude around MV ≈ -14. With the addition of ground based optical observations and archival results, we produce spectral energy distribution fits to these hosts, and show that SLSN hosts possess lower stellar mass and star formation rates. This is most pronounced for the hydrogen deficient Type-I SLSN hosts, although Type-II H-rich SLSN host galaxies remain distinct from the bulk of CCSNe, spanning a remarkably broad range of absolute magnitudes, with ˜30 per cent of SLSNe-II arising from galaxies fainter than MnIR ˜ -14. The detection of our faintest SLSN hosts increases the confidence that SLSNe-I hosts are distinct from those of LGRBs in star formation rate and stellar mass, and suggests that apparent similarities in metallicity may be due to the limited fraction of hosts for which emission line metallicity measurements are feasible. The broad range of luminosities of SLSN-II hosts is difficult to describe by metallicity cuts, and does not match the expectations of any reasonable UV-weighted luminosity function, suggesting additional environmental constraints are likely necessary to yield hydrogen rich SLSNe.

  8. Superluminal paradox’ in wave packet propagation and its quantum mechanical resolution

    SciTech Connect

    Sokolovski, D.; Akhmatskaya, E.

    2013-12-15

    We analyse in detail the reshaping mechanism leading to apparently ‘superluminal’ advancement of a wave packet traversing a classically forbidden region. In the coordinate representation, a barrier is shown to act as an effective beamsplitter, recombining envelopes of the freely propagating pulse with various spacial shifts. Causality ensures that none of the constituent envelopes are advanced with respect to free propagation, yet the resulting pulse is advanced due to a peculiar interference effect, similar to the one responsible for ‘anomalous’ values which occur in Aharonov’s ‘weak measurements’. In the momentum space, the effect is understood as a bandwidth phenomenon, where the incident pulse probes local, rather than global, analytical properties of the transmission amplitude T(p). The advancement is achieved when T(p) mimics locally an exponential behaviour, similar to the one occurring in Berry’s ‘superoscillations’. Seen in a broader quantum mechanical context, the ‘paradox’ is but a consequence of an attempt to obtain ‘which way?’ information without destroying the interference between the pathways of interest. This explains, to a large extent, the failure to adequately describe tunnelling in terms of a single ‘tunnelling time’. -- Highlights: •Apparent superluminality is described in the language of quantum measurements. •A barrier acts as a beamsplitter delaying copies of the initial pulse. •In the coordinate space the effect is similar to what occurs in ‘weak measurements’. •In the momentum space it relies on superoscillations in the transmission amplitude. •It is an interference effect, unlikely to be explained in simpler physical terms.

  9. THE FERMI BUBBLES. I. POSSIBLE EVIDENCE FOR RECENT AGN JET ACTIVITY IN THE GALAXY

    SciTech Connect

    Guo Fulai; Mathews, William G.

    2012-09-10

    The Fermi Gamma-ray Space Telescope reveals two large gamma-ray bubbles in the Galaxy, which extend about 50 Degree-Sign ({approx}10 kpc) above and below the Galactic center (GC) and are symmetric about the Galactic plane. Using axisymmetric hydrodynamic simulations with a self-consistent treatment of the dynamical cosmic ray (CR)-gas interaction, we show that the bubbles can be created with a recent active galactic nucleus (AGN) jet activity about 1-3 Myr ago, which was active for a duration of {approx}0.1-0.5 Myr. The bipolar jets were ejected into the Galactic halo along the rotation axis of the Galaxy. Near the GC, the jets must be moderately light with a typical density contrast 0.001 {approx}< {eta} {approx}< 0.1 relative to the ambient hot gas. The jets are energetically dominated by kinetic energy, and overpressured with either CR or thermal pressure which induces lateral jet expansion, creating fat CR bubbles as observed. The sharp edges of the bubbles imply that CR diffusion across the bubble surface is strongly suppressed. The jet activity induces a strong shock, which heats and compresses the ambient gas in the Galactic halo, potentially explaining the ROSAT X-ray shell features surrounding the bubbles. The Fermi bubbles provide plausible evidence for a recent powerful AGN jet activity in our Galaxy, providing new insights into the origin of the halo CR population and the channel through which massive black holes in disk galaxies release feedback energy during their growth.

  10. Stretched Inertial Jets

    NASA Astrophysics Data System (ADS)

    Ghabache, Elisabeth; Antkowiak, Arnaud; Seon, Thomas; Villermaux, Emmanuel

    2015-11-01

    Liquid jets often arise as short-lived bursting liquid flows. Cavitation or impact-driven jets, bursting champagne bubbles, shaped-charge jets, ballistospores or drop-on-demand inkjet printing are a few examples where liquid jets are suddenly released. The trademark of all these discharge jets is the property of being stretched, due to the quenching injection. the present theoretical and experimental investigation, the structure of the jet flow field will be unraveled experimentally for a few emblematic occurrences of discharge jets. Though the injection markedly depends on each flow configuration, the jet velocity field will be shown to be systematically and rapidly attracted to the universal stretching flow z/t. The emergence of this inertial attractor actually only relies on simple kinematic ingredients, and as such is fairly generic. The universality of the jet velocity structure will be discussed.

  11. The Stability of Radiatively Cooling Jets I. Linear Analysis

    NASA Technical Reports Server (NTRS)

    Hardee, Philip E.; Stone, James M.

    1997-01-01

    The results of a spatial stability analysis of a two-dimensional slab jet, in which optically thin radiative cooling is dynamically important, are presented. We study both magnetized and unmagnetized jets at external Mach numbers of 5 and 20. We model the cooling rate by using two different cooling curves: one appropriate to interstellar gas, and the other to photoionized gas of reduced metallicity. Thus, our results will be applicable to both protostellar (Herbig-Haro) jets and optical jets from active galactic nuclei. We present analytical solutions to the dispersion relations in useful limits and solve the dispersion relations numerically over a broad range of perturbation frequencies. We find that the growth rates and wavelengths of the unstable Kelvin-Helmholtz (K-H) modes are significantly different from the adiabatic limit, and that the form of the cooling function strongly affects the results. In particular, if the cooling curve is a steep function of temperature in the neighborhood of the equilibrium state, then the growth of K-H modes is reduced relative to the adiabatic jet. On the other hand, if the cooling curve is a shallow function of temperature, then the growth of K-H modes can be enhanced relative to the adiabatic jet by the increase in cooling relative to heating in overdense regions. Inclusion of a dynamically important magnetic field does not strongly modify the important differences between an adiabatic jet and a cooling jet, provided the jet is highly supermagnetosonic and not magnetic pressure-dominated. In the latter case, the unstable modes behave more like the transmagnetosonic magnetic pressure-dominated adiabatic limit. We also plot fluid displacement surfaces associated with the various waves in a cooling jet in order to predict the structures that might arise in the nonlinear regime. This analysis predicts that low-frequency surface waves and the lowest order body modes will be the most effective at producing observable features in

  12. Microscopic Processes On Radiation from Accelerated Particles in Relativistic Jets

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.-I.; Hardee, P. E.; Mizuno, Y.; Medvedev, M.; Zhang, B.; Sol, H.; Niemiec, J.; Pohl, M.; Nordlund, A.; Fredriksen, J.; Lyubarsky, Y.; Hartmann, D. H.; Fishman, G. J.

    2009-01-01

    Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., gamma-ray bursts (GRBs), active galactic nuclei (AGNs), and Galactic microquasar systems usually have power-law emission spectra. Recent PIC simulations of relativistic electron-ion (electro-positron) jets injected into a stationary medium show that particle acceleration occurs within the downstream jet. In the collisionless relativistic shock particle acceleration is due to plasma waves and their associated instabilities (e.g., the Buneman instability, other two-streaming instability, and the Weibel (filamentation) instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the jet head. The jitter'' radiation from deflected electrons has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.

  13. Where Galactic Snakes Live

    NASA Technical Reports Server (NTRS)

    2006-01-01

    This infrared image from NASA's Spitzer Space Telescope shows what astronomers are referring to as a 'snake' (upper left) and its surrounding stormy environment. The sinuous object is actually the core of a thick, sooty cloud large enough to swallow dozens of solar systems. In fact, astronomers say the 'snake's belly' may be harboring beastly stars in the process of forming.

    The galactic creepy crawler to the right of the snake is another thick cloud core, in which additional burgeoning massive stars might be lurking. The colorful regions below the two cloud cores are less dense cloud material, in which dust has been heated by starlight and glows with infrared light. Yellow and orange dots throughout the image are monstrous developing stars; the red star on the 'belly' of the snake is 20 to 50 times as massive as our sun. The blue dots are foreground stars.

    The red ball at the bottom left is a 'supernova remnant,' the remains of massive star that died in a fiery blast. Astronomers speculate that radiation and winds from the star before it died, in addition to a shock wave created when it exploded, might have played a role in creating the snake.

    Spitzer was able to spot the two black cloud cores using its heat-seeking infrared vision. The objects are hiding in the dusty plane of our Milky Way galaxy, invisible to optical telescopes. Because their heat, or infrared light, can sneak through the dust, they first showed up in infrared images from past missions. The cloud cores are so thick with dust that if you were to somehow transport yourself into the middle of them, you would see nothing but black, not even a star in the sky. Now, that's spooky!

    Spitzer's new view of the region provides the best look yet at the massive embryonic stars hiding inside the snake. Astronomers say these observations will ultimately help them better understand how massive stars form. By studying the clustering and range of masses of the stellar embryos, they hope

  14. The acceleration and collimation of jets.

    PubMed Central

    Begelman, M C

    1995-01-01

    I will discuss several issues related to the acceleration, collimation, and propagation of jets from active galactic nuclei. Hydromagnetic stresses provide the best bet for both accelerating relativistic flows and providing a certain amount of initial collimation. However, there are limits to how much "self-collimation" can be achieved without the help of an external pressurized medium. Moreover, existing models, which postulate highly organized poloidal flux near the base of the flow, are probably unrealistic. Instead, a large fraction of the magnetic energy may reside in highly disorganized "chaotic" fields. Such a field can also accelerate the flow to relativistic speeds, in some cases with greater efficiency than highly organized fields, but at the expense of self-collimation. The observational interpretation of jet physics is still hampered by a dearth of unambiguous diagnostics. Propagating disturbances in flows, such as the oblique shocks that may constitute the kiloparsec-scale "knots" in the M87 jet, may provide a wide range of untapped diagnostics for jet properties. PMID:11607615

  15. A New Relativistic Jet Model of Blazars

    NASA Astrophysics Data System (ADS)

    Webb, James; Benitez, Erika; Howard, Emily

    1998-11-01

    The subclass of Active galaxies called Blazars encompass the most intrinsically luminous and rapidly variable sources known to astrophysicists. Attempts to model these sources has largely been frustrated due in part to observational difficulties, but also due to the lack of theoretical models capable of explaining the different characteristics of the observed sources. Leading candidate models all incorporate a massive, rotating black hole which is accreting galactic material, with some of this material being ejected out the ratational axis of the hole in the form of relativistically expanding jets. These jets are thought to emit energy via the synchrotron process across the entire spectrum from radio frequences all the way through the GEV (sometimes TEV) gamma-ray frequencies. Attempts to model these sources with single relativistic jets has proven difficult. We present a new model which features concentric interacting jets that do a much better job of explaining the types of Blazars we observe. We also discuss ways of testing this new model against multifreuqency observations.

  16. Fano line-shape control and superluminal light using cavity quantum electrodynamics with a partially transmitting element

    NASA Astrophysics Data System (ADS)

    Li, Jiahua; Yu, Rong; Liu, Jiuyang; Ding, Chunling; Wu, Ying

    2016-05-01

    We study the probe-field transmission in cavity quantum electrodynamics (cavity-QED) systems with a partially transmitting element (PTE), where the PTE is used to control and tune the amplitude of the weak probe field propagating along a single waveguide channel in the structure. We derive analytic formulas utilized to determine the transmission coefficient of the probe field within the framework of quantum optics. Using experimentally accessible parameters, it is clearly shown that the asymmetric Fano-resonance line shape can be formed and manipulated by means of the added PTE. Furthermore, we reveal that there exists superluminal light with large intensity transmission in the transport spectrum of the waveguide-coupled cavity-QED system. This superluminal-light propagation effect, which exhibits the anomalous phase shift and is characterized by the negative group delay, can be enhanced by properly choosing the system parameters. The obtained results may be used for designing switching, modulation, and sensing for nanophotonic applications and ultrafast on-chip signal processing in telecom applications.

  17. Observing the next galactic supernova

    SciTech Connect

    Adams, Scott M.; Kochanek, C. S.; Beacom, John F.; Stanek, K. Z.; Vagins, Mark R.

    2013-12-01

    No supernova (SN) in the Milky Way has been observed since the invention of the optical telescope, instruments for other wavelengths, neutrino detectors, or gravitational wave observatories. It would be a tragedy to miss the opportunity to fully characterize the next one. To aid preparations for its observations, we model the distance, extinction, and magnitude probability distributions of a successful Galactic core-collapse supernova (ccSN), its shock breakout radiation, and its massive star progenitor. We find, at very high probability (≅ 100%), that the next Galactic SN will easily be detectable in the near-IR and that near-IR photometry of the progenitor star very likely (≅ 92%) already exists in the Two Micron All Sky Survey. Most ccSNe (98%) will be easily observed in the optical, but a significant fraction (43%) will lack observations of the progenitor due to a combination of survey sensitivity and confusion. If neutrino detection experiments can quickly disseminate a likely position (∼3°), we show that a modestly priced IR camera system can probably detect the shock breakout radiation pulse even in daytime (64% for the cheapest design). Neutrino experiments should seriously consider adding such systems, both for their scientific return and as an added and internal layer of protection against false triggers. We find that shock breakouts from failed ccSNe of red supergiants may be more observable than those of successful SNe due to their lower radiation temperatures. We review the process by which neutrinos from a Galactic ccSN would be detected and announced. We provide new information on the EGADS system and its potential for providing instant neutrino alerts. We also discuss the distance, extinction, and magnitude probability distributions for the next Galactic Type Ia supernova (SN Ia). Based on our modeled observability, we find a Galactic ccSN rate of 3.2{sub −2.6}{sup +7.3} per century and a Galactic SN Ia rate of 1.4{sub −0.8}{sup +1.4} per

  18. Galactic gamma-ray observations and galactic structure

    NASA Technical Reports Server (NTRS)

    Stecker, F. W.

    1975-01-01

    Recent observations of gamma-rays originating in the galactic disk together with radio observations, support an emerging picture of the overall structure of our galaxy with higher interstellar gas densities and star formation rates in a region which corresponds to that of the inner arms. The emerging picture is one where molecular clouds make up the dominant constituent of the interstellar gas in the inner galaxy and play a key role in accounting for the gamma-rays and phenomena associated with the production of young stars and other population 1 objects. In this picture, cosmic rays are associated with supernovae and are primarily of galactic origin. These newly observed phenomena can be understood as consequences of the density wave theories of spiral structure. Based on these new developments, the suggestion is made that a new galactic population class, Population O, be added to the standard Populations 1 and 2 in order to recognize important differences in dynamics and distribution between diffuse galactic H1 and interstellar molecular clouds.

  19. The Heliosphere and Galactic Cosmic Rays

    NASA Video Gallery

    The heliosphere deflects galactic cosmic rays from entering the system. Galactic cosmic rays are a very high energy form of particle radiation that are extremely difficult to shield against and are...

  20. Do Jets Precess... or Even Move at All?

    NASA Astrophysics Data System (ADS)

    Nixon, Chris; King, Andrew

    2013-03-01

    Observations of accreting black holes often provoke suggestions that their jets precess. The precession is usually supposed to result from a combination of the Lense-Thirring effect and accretion disk viscosity. We show that this is unlikely for any type of black hole system, as the disk generally has too little angular momentum compared with a spinning hole to cause any significant movement of the jet direction across the sky on short timescales. Uncorrelated accretion events, as in the chaotic accretion picture of active galactic nuclei (AGNs), change AGN jet directions only on timescales >~ 107 yr. In this picture AGN jet directions are stable on shorter timescales, but uncorrelated with any structure of the host galaxy, as observed. We argue that observations of black hole jets precessing on timescales short compared to the accretion time would be a strong indication that the accretion disk, and not the standard Blandford-Znajek mechanism, is responsible for driving the jet. This would be particularly convincing in a tidal disruption event. We suggest that additional disk physics is needed to explain any jet precession on timescales short compared with the accretion time. Possibilities include the radiation warping instability, or disk tearing.

  1. A Study of Radio Polarization in Protostellar Jets

    NASA Astrophysics Data System (ADS)

    Cécere, Mariana; Velázquez, Pablo F.; Araudo, Anabella T.; De Colle, Fabio; Esquivel, Alejandro; Carrasco-González, Carlos; Rodríguez, Luis F.

    2016-01-01

    Synchrotron radiation is commonly observed in connection with shocks of different velocities, ranging from relativistic shocks associated with active galactic nuclei, gamma-ray bursts, or microquasars, to weakly or non-relativistic flows such as those observed in supernova remnants. Recent observations of synchrotron emission in protostellar jets are important not only because they extend the range over which the acceleration process works, but also because they allow us to determine the jet and/or interstellar magnetic field structure, thus giving insights into the jet ejection and collimation mechanisms. In this paper, we compute for the first time polarized (synchrotron) and non-polarized (thermal X-ray) synthetic emission maps from axisymmetrical simulations of magnetized protostellar jets. We consider models with different jet velocities and variability, as well as a toroidal or helical magnetic field. Our simulations show that variable, low-density jets with velocities of ˜1000 km s-1 and ˜10 times lighter than the environment can produce internal knots with significant synchrotron emission and thermal X-rays in the shocked region of the leading bow shock moving in a dense medium. While models with a purely toroidal magnetic field show a very large degree of polarization, models with a helical magnetic field show lower values and a decrease of the degree of polarization, in agreement with observations of protostellar jets.

  2. Investigating the Dynamics of Canonical Flux Tubes in Jet Geometry

    NASA Astrophysics Data System (ADS)

    Lavine, Eric; You, Setthivoine

    2014-10-01

    Highly collimated plasma jets are frequently observed at galactic, stellar, and laboratory scales. Some models suppose these jets are magnetohydrodynamically-driven magnetic flux tubes filled with flowing plasma, but they do not agree on a collimation process. Some evidence supporting a universal MHD pumping mechanism has been obtained from planar electrode experiments with aspect ratios of ~10:1 however, these jets are subject to kink instabilities beyond a certain length and are unable to replicate the remarkable aspect ratios (10-1000:1) seen in astrophysical systems. Other models suppose these jets are flowing Z-pinch plasmas and experiments that use stabilizing shear flows have achieved aspect ratios of ~30:1, but are line tied at both ends. Can both collimation and stabilization mechanisms work together to produce long jets without kink instabilities and only one end tied to the central object? This question is evaluated from the point of view of canonical flux tubes and canonical helicity transport, indicating that jets can become long and collimated due to a combination of strong helical shear flows and conversion of magnetic helicity into kinetic helicity. The MOCHI LabJet experiment is designed to study this in the laboratory. Supported by US DoE Early Career Grant DE-SC0010340.

  3. ERRATIC JET WOBBLING IN THE BL LACERTAE OBJECT OJ287 REVEALED BY SIXTEEN YEARS OF 7 mm VLBA OBSERVATIONS

    SciTech Connect

    Agudo, Ivan; Gomez, Jose L.; Marscher, Alan P.; Jorstad, Svetlana G.; Perucho, Manel; Piner, B. Glenn; Rioja, Maria; Dodson, Richard

    2012-03-01

    We present the results from an ultra-high-resolution 7 mm Very Long Baseline Array study of the relativistic jet in the BL Lacertae object OJ287 from 1995 to 2011 containing 136 total intensity images. Analysis of the image sequence reveals a sharp jet-position-angle swing by >100 Degree-Sign during [2004,2006], as viewed in the plane of the sky, which we interpret as the crossing of the jet from one side of the line of sight to the other during a softer- and longer-term swing of the inner jet. Modulating such long-term swing, our images also show for the first time a prominent erratic wobbling behavior of the innermost {approx}0.4 mas of the jet with fluctuations in position angle of up to {approx}40 Degree-Sign over timescales {approx}2 yr. This is accompanied by highly superluminal motions along non-radial trajectories, which reflect the remarkable non-ballistic nature of the jet plasma on these scales. The erratic nature and short timescales of the observed behavior rule out scenarios such as binary black hole systems, accretion disk precession, and interaction with the ambient medium as possible origins of the phenomenon on the scales probed by our observations, although such processes may cause longer-term modulation of the jet direction. We propose that variable asymmetric injection of the jet flow, perhaps related to turbulence in the accretion disk, coupled with hydrodynamic instabilities leads to the non-ballistic dynamics that causes the observed non-periodic changes in the direction of the inner jet.

  4. NASA Jet Noise Research

    NASA Technical Reports Server (NTRS)

    Henderson, Brenda

    2012-01-01

    The presentation highlights jet-noise research conducted in the Subsonic Fixed Wing, Supersonics, and Environmentally Responsible Aviation Projects in the Fundamental Aeronautics Program at NASA. The research efforts discussed include NASA's updated Aircraft NOise Prediction Program (ANOPP2), acoustic-analogy-based prediction tools, jet-surface-interaction studies, plasma-actuator investigations, N+2 Supersonics Validation studies, rectangular-jet experiments, twin-jet experiments, and Hybrid Wind Body (HWB) activities.

  5. Jets of incipient liquids

    NASA Astrophysics Data System (ADS)

    Reshetnikov, A. V.; Mazheiko, N. A.; Skripov, V. P.

    2000-05-01

    Jets of incipient water escaping into the atmosphere through a short channel are photographed. In some experiments. complete disintegration of the jet is observed. The relationship of this phenomenon with intense volume incipience is considered. The role of the Coanda effect upon complete opening of the jet is revealed. Measurement results of the recoil force R of the jets of incipient liquids are presented. Cases of negative thrust caused by the Coanda effect are noted. Generalization of experimental data is proposed.

  6. On the Importance of Very Light Internally Subsonic AGN Jets in Radio-mode AGN Feedback

    NASA Astrophysics Data System (ADS)

    Guo, Fulai

    2016-07-01

    Radio-mode active galactic nucleus (AGN) feedback plays a key role in the evolution of galaxy groups and clusters. Its physical origin lies in the kiloparsec-scale interaction of AGN jets with the intracluster medium. Large-scale jet simulations often initiate light internally supersonic jets with density contrast 0.01 < η < 1. Here we argue for the first time for the importance of very light (η < 0.01) internally subsonic jets. We investigated the shapes of young X-ray cavities produced in a suite of hydrodynamic simulations, and found that bottom-wide cavities are always produced by internally subsonic jets, while internally supersonic jets inflate cylindrical, center-wide, or top-wide cavities. We found examples of real cavities with shapes analogous to those inflated in our simulations by internally subsonic and internally supersonic jets, suggesting a dichotomy of AGN jets according to their internal Mach numbers. We further studied the long-term cavity evolution, and found that old cavities resulted from light jets spread along the jet direction, while those produced by very light jets are significantly elongated along the perpendicular direction. The northwestern ghost cavity in Perseus is pancake shaped, providing tentative evidence for the existence of very light jets. Our simulations show that very light internally subsonic jets decelerate faster and rise much slower in the intracluster medium than light internally supersonic jets, possibly depositing a larger fraction of jet energy to cluster cores and alleviating the problem of low coupling efficiencies found previously. The internal Mach number points to the jet’s energy content, and internally subsonic jets are energetically dominated by non-kinetic energy, such as thermal energy, cosmic rays, or magnetic fields.

  7. Connection Between X-Ray Dips and Superluminal Ejections in the Radio Galaxy 3C 120

    NASA Technical Reports Server (NTRS)

    Aller, Margo F.

    2005-01-01

    This work represents a part of a long-term study of the X-ray flux variability of 3C 120 and its relation to flux and structural changes in the radio jet of this galaxy. The grant included fiinding for the rediiction and analysis of data obt,ained during the time pwiod of Rossi XTE cycle 8 (March 1, 2003-February 29, 2004). Prior RXTE observations, combined with single dish monitoring at centimeter wavelengths and 43 GHz mapping (monthly until February 1999 and bimonthly thereafter) of the inner jet with the VLBA, had identified the presence of X-ray dips in the light curves and X-ray spectral hardening 4 weeks prior to the ejection of new VLBI components in the radio jet. This suggested a picture in which the radio jet was fed by accretion events near the black hole. The specific goals of the cycle 8 observations were to better define the relation between the X-ray dips and the radio events using higher sampling, to include more events in the correlation and hence improve the statistics, to look for a possible optical X-ray connection, and to search for quasi periodicities on timescales of 1-3 days. In cycle 8 this project was awarded time for 4 pointings weekly with RXTE.

  8. Prewhirl Jet Model

    NASA Technical Reports Server (NTRS)

    Meng, S. Y.; Jensen, M.; Jackson, E. D.

    1985-01-01

    Simple accurate model of centrifugal or rocket engine pumps provides information necessary to design inducer backflow deflector, backflow eliminator and prewhirl jet in jet mixing zones. Jet design based on this model shows improvement in inducer suction performance and reduced cavitation damage.

  9. Large scale radio/X-ray jets in microquasars

    NASA Astrophysics Data System (ADS)

    Corbel, Stephane; Tzioumis, Anastasios; Fender, Rob; Kaaret, Philip; Orosz, Jerry; Tomsick, John; Loh, Alan

    2014-10-01

    The discovery with ATCA of large scale radio lobes around the microquasar XTE J1550-564 has led to the discovery with Chandra (for the first time) of moving relativistic X-ray jets in a galactic accreting source. The lobes are likely due to the interaction of relativistic plasma with the ISM. This ATCA proposal has allowed similar discovery in H 1743-322, and therefore that it maybe a common occurrence in the Galaxy. Recently, we have witnessed with ATCA the formation of similar lobes in the black hole GX 339-4. We propose to use the Compact Array to continue our search for radio lobes in microquasars that have been active in the past years. The proposed observations are optimized to discover and study (flux evolution, morphology, SED, proper motion, ...) new radio lobes from microquasars. This will have implications not only for the study of jets from Galactic X-ray binaries, but also for our understanding of relativistic jets from active galactic nuclei (AGN).

  10. DES13S2cmm: The first superluminous supernova from the Dark Energy Survey

    DOE PAGESBeta

    Papadopoulos, A.; Plazas, A. A.; D"Andrea, C. B.; Sullivan, M.; Nichol, R. C.; Barbary, K.; Biswas, R.; Brown, P. J.; Covarrubias, R. A.; Finley, D. A.; et al

    2015-03-23

    We present DES13S2cmm, the first spectroscopically-confirmed superluminous supernova (SLSN) from the Dark Energy Survey (DES). We briefly discuss the data and search algorithm used to find this event in the first year of DES operations, and outline the spectroscopic data obtained from the European Southern Observatory (ESO) Very Large Telescope to confirm its redshift (z = 0.663 ± 0.001 based on the host-galaxy emission lines) and likely spectral type (type I). Using this redshift, we find MpeakU = –21.05+0.10–0.09 for the peak, rest-frame U-band absolute magnitude, and find DES13S2cmm to be located in a faint, low-metallicity (sub-solar), low stellar-mass hostmore » galaxy (log(M/M⊙) = 9.3 ± 0.3), consistent with what is seen for other SLSNe-I. We compare the bolometric light curve of DES13S2cmm to fourteen similarly well-observed SLSNe-I in the literature and find it possesses one of the slowest declining tails (beyond +30 days rest frame past peak), and is the faintest at peak. Moreover, we find the bolometric light curves of all SLSNe-I studied herein possess a dispersion of only 0.2–0.3 magnitudes between +25 and +30 days after peak (rest frame) depending on redshift range studied; this could be important for ‘standardising’ such supernovae, as is done with the more common type Ia. We fit the bolometric light curve of DES13S2cmm with two competing models for SLSNe-I – the radioactive decay of ⁵⁶Ni, and a magnetar – and find that while the magnetar is formally a better fit, neither model provides a compelling match to the data. Although we are unable to conclusively differentiate between these two physical models for this particular SLSN-I, further DES observations of more SLSNe-I should break this degeneracy, especially if the light curves of SLSNe-I can be observed beyond 100 days in the rest frame of the supernova.« less

  11. DES13S2cmm: The first superluminous supernova from the Dark Energy Survey

    SciTech Connect

    Papadopoulos, A.; Plazas, A. A.; D"Andrea, C. B.; Sullivan, M.; Nichol, R. C.; Barbary, K.; Biswas, R.; Brown, P. J.; Covarrubias, R. A.; Finley, D. A.; Fischer, J. A.; Foley, R. J.; Goldstein, D.; Gupta, R. R.; Kessler, R.; Kovacs, E.; Kuhlmann, S. E.; Lidman, C.; March, M.; Nugent, P. E.; Sako, M.; Smith, R. C.; Spinka, H.; Wester, W.; Abbott, T. M. C.; Abdalla, F.; Allam, S. S.; Banerji, M.; Bernstein, J. P.; Bernstein, R. A.; Carnero, A.; da Costa, L. N.; DePoy, D. L.; Desai, S.; Diehl, H. T.; Eifler, T.; Evrard, A. E.; Flaugher, B.; Frieman, J. A.; Gerdes, D.; Gruen, D.; Honscheid, K.; James, D.; Kuehn, K.; Kuropatkin, N.; Lahav, O.; Maia, M. A. G.; Makler, M.; Marshall, J. L.; Merritt, K. W.; Miller, C. J.; Miquel, R.; Ogando, R.; Roe, N. A.; Romer, A. K.; Rykoff, E.; Sanchez, E.; Santiago, B. X.; Scarpine, V.; Schubnell, M.; Sevilla, I.; Soares-Santos, M.; Suchyta, E.; Swanson, M.; Tarle, G.; Thaler, J.; Tucker, L. D.; Wechsler, R. H.; Zuntz, J.

    2015-03-23

    We present DES13S2cmm, the first spectroscopically-confirmed superluminous supernova (SLSN) from the Dark Energy Survey (DES). We briefly discuss the data and search algorithm used to find this event in the first year of DES operations, and outline the spectroscopic data obtained from the European Southern Observatory (ESO) Very Large Telescope to confirm its redshift (z = 0.663 ± 0.001 based on the host-galaxy emission lines) and likely spectral type (type I). Using this redshift, we find MpeakU = –21.05+0.10–0.09 for the peak, rest-frame U-band absolute magnitude, and find DES13S2cmm to be located in a faint, low-metallicity (sub-solar), low stellar-mass host galaxy (log(M/M⊙) = 9.3 ± 0.3), consistent with what is seen for other SLSNe-I. We compare the bolometric light curve of DES13S2cmm to fourteen similarly well-observed SLSNe-I in the literature and find it possesses one of the slowest declining tails (beyond +30 days rest frame past peak), and is the faintest at peak. Moreover, we find the bolometric light curves of all SLSNe-I studied herein possess a dispersion of only 0.2–0.3 magnitudes between +25 and +30 days after peak (rest frame) depending on redshift range studied; this could be important for ‘standardising’ such supernovae, as is done with the more common type Ia. We fit the bolometric light curve of DES13S2cmm with two competing models for SLSNe-I – the radioactive decay of ⁵⁶Ni, and a magnetar – and find that while the magnetar is formally a better fit, neither model provides a compelling match to the data. Although we are unable to conclusively differentiate between these two physical models for this particular SLSN-I, further DES observations of more SLSNe-I should break this degeneracy, especially if the light curves of SLSNe-I can be observed beyond 100 days in the rest frame of the supernova.

  12. Limiting Superluminal Electron and Neutrino Velocities Using the 2010 Crab Nebula Flare and the IceCube PeV Neutrino Events

    NASA Technical Reports Server (NTRS)

    Stecker, Floyd W.

    2014-01-01

    The observation of two PetaelectronVolt (PeV)-scale neutrino events reported by Ice Cube allows one to place constraints on Lorentz invariance violation (LIV) in the neutrino sector. After first arguing that at least one of the PetaelectronVolt IceCube events was of extragalactic origin, I derive an upper limit for the difference between putative superluminal neutrino and electron velocities of less than or equal to approximately 5.6 x 10(exp -19) in units where c = 1, confirming that the observed PetaelectronVolt neutrinos could have reached Earth from extragalactic sources. I further derive a new constraint on the superluminal electron velocity, obtained from the observation of synchrotron radiation from the Crab Nebula flare of September, 2010. The inference that the greater than 1 GigaelectronVolt gamma-rays from synchrotron emission in the flare were produced by electrons of energy up to approx. 5.1 PetaelectronVolt indicates the nonoccurrence of vacuum Cerenkov radiation by these electrons. This implies a new, strong constraint on superluminal electron velocities delta(sub e) less than or equal to approximately 5 x 10(exp -21). It immediately follows that one then obtains an upper limit on the superluminal neutrino velocity alone of delta(sub v) less than or equal to approximately 5.6 x 10(exp -19), many orders of magnitude better than the time-of-flight constraint from the SN1987A neutrino burst. However, if the electrons are subluminal the constraint on the absolute value of delta(sub e) less than or equal to approximately 8 x 10(exp -17), obtained from the Crab Nebula gamma-ray spectrum, places a weaker constraint on superluminal neutrino velocity of delta(sub v) less than or equal to approximately 8 x 10(exp -17).

  13. Very-long-baseline radio interferometry surveys of the compact structure in active galactic nuclei.

    PubMed Central

    Wilkinson, P N

    1995-01-01

    Very-long-baseline radio interferometry (VLBI) imaging surveys have been undertaken since the late 1970s. The sample sizes were initially limited to a few tens of objects but the snapshot technique has now allowed samples containing almost 200 sources to be studied. The overwhelming majority of powerful compact sources are asymmetric corejects of one form or another, most of which exhibit apparent superluminal motion. However 5-10% of powerful flat-spectrum sources are 100-parsec (pc)-scale compact symmetric objects; these appear to form a continuum with the 1-kpc-scale double-lobed compact steep-spectrum sources, which make up 15-20% of lower frequency samples. It is likely that these sub-galactic-size symmetric sources are the precursors to the large-scale classical double sources. There is a surprising peak around 90 degrees in the histogram of misalignments between the dominant source axes on parsec and kiloparsec scales; this seems to be associated with sources exhibiting a high degree of relativistic beaming. VLBI snapshot surveys have great cosmological potential via measurements of both proper motion and angular size vs. redshift as well as searches for gravitational "millilensing." PMID:11607594

  14. PIPER and Polarized Galactic Foregrounds

    NASA Technical Reports Server (NTRS)

    Chuss, David

    2009-01-01

    In addition to probing inflationary cosmology, PIPER will measure the polarized dust emission from the Galaxy. PIPER will be capable of full (I,0,U,V) measurement over four frequency bands ' These measurements will provide insight into the physics of dust grains and a probe of the Galactic magnetic field on large and intermediate scales.

  15. Dust in the galactic environment

    NASA Astrophysics Data System (ADS)

    Whittet, D. C. B.

    An overview of dust in the galactic environment is given which covers general concepts, methods of investigation, important results and their significance, relevant literature, and suggestions for future research. The general topics addressed include: element abundances and depletions, interstellar extinction and scattering, interstellar polarization and grain alignment, spectral absorption features, continuum and line emission, and the origin and evolution of interstellar grains.

  16. Spectral Energy Distribution Models for Low-Luminosity Active Galactic Nuclei in LINERs

    NASA Technical Reports Server (NTRS)

    Nemmen, Rodrigo S.; Storchi-Bergmann, Thaisa; Eracleous, Michael

    2012-01-01

    Low-luminosity active galactic nuclei (LLAGNs) represent the bulk of the AGN population in the present-day universe and they trace the low-level accreting supermassive black holes. In order to probe the accretion and jet physical properties in LLAGNs as a class, we model the broadband radio to X-rays spectral energy distributions (SEDs) of 21 LLAGNs in low-ionization nuclear emission-line regions (LINERs) with a coupled accretion-jet model. The accretion flow is modeled as an inner ADAF outside of which there is a truncated standard thin disk. We find that the radio emission is severely underpredicted by ADAF models and is explained by the relativistic jet. The origin of the X-ray radiation in most sources can be explained by three distinct scenarios: the X-rays can be dominated by emission from the ADAF, or the jet, or the X-rays can arise from a jet-ADAF combination in which both components contribute to the emission with similar importance. For 3 objects both the jet and ADAF fit equally well the X-ray spectrum and can be the dominant source of X-rays whereas for 11 LLAGNs a jet-dominated model accounts better than the ADAF-dominated model for the data. The individual and average SED models that we computed can be useful for different studies of the nuclear emission of LLAGNs. From the model fits, we estimate important parameters of the central engine powering LLAGNs in LINERs, such as the mass accretion rate and the mass-loss rate in the jet and the jet power - relevant for studies of the kinetic feedback from jets.

  17. The galactic cycle of extinction

    NASA Astrophysics Data System (ADS)

    Gillman, Michael; Erenler, Hilary

    2008-01-01

    Global extinction and geological events have previously been linked with galactic events such as spiral arm crossings and galactic plane oscillation. The expectation that these are repeating predictable events has led to studies of periodicity in a wide set of biological, geological and climatic phenomena. Using data on carbon isotope excursions, large igneous provinces and impact craters, we identify three time zones of high geological activity which relate to the timings of the passage of the Solar System through the spiral arms. These zones are shown to include a significantly large proportion of high extinction periods. The mass extinction events at the ends of the Ordovician, Permian and Cretaceous occur in the first zone, which contains the predicted midpoints of the spiral arms. The start of the Cambrian, end of the Devonian and end of the Triassic occur in the second zone. The pattern of extinction timing in relation to spiral arm structure is supported by the positions of the superchrons and the predicted speed of the spiral arms. The passage times through an arm are simple multiples of published results on impact and fossil record periodicity and galactic plane half-periods. The total estimated passage time through four arms is 703.8 Myr. The repetition of extinction events at the same points in different spiral arm crossings suggests a common underlying galactic cause of mass extinctions, mediated through galactic effects on geological, solar and extra-solar processes. The two largest impact craters (Sudbury and Vredefort), predicted to have occurred during the early part of the first zone, extend the possible pattern to more than 2000 million years ago.

  18. The Formation of Galactic Bulges

    NASA Astrophysics Data System (ADS)

    Carollo, C. Marcella; Ferguson, Henry C.; Wyse, Rosemary F. G.

    2000-03-01

    Part I. Introduction: What are galactic bulges?; Part II. The Epoch of Bulge Formation: Origin of bulges; Deep sub-mm surveys: High-z ULIRGs and the formation of spheroids; Ages and metallicities for stars in the galactic bulge; Integrated stellar populations of bulges: First results; HST-NICMOS observations of galactic bulges: Ages and dust; Inside-out bulge formation and the origin of the Hubble sequence; Part III. The Timescales of Bulge Formation: Constraints on the bulge formation timescale from stellar populations; Bulge building with mergers and winds; Role of winds, starbursts, and activity in bulge formation; Dynamical timescales of bulge formation; Part IV. Physical Processes in Bulge Formation: the role of bars for secular bulge formation; Bars and boxy/peanut-shaped bulges: an observational point of view; Boxy- and peanut-shaped bulges; A new class of bulges; The role of secondary bars in bulge formation; Radial transport of molecular gas to the nuclei of spiral galaxies; Dynamical evolution of bulge shapes; Two-component stellar systems: Phase-space constraints; Central NGC 2146 - a firehose-type bending instability?; Bulge formation: the role of the multi-phase ISM; Global evolution of a self-gravitating multi-phase ISM in the central kpc region of galaxies; Part V. Bulge Phenomenology: Bulge-disk decomposition of spiral galaxies in the near-infrared; The triaxial bulge of NGC 1371; The bulge-disk orthogonal decoupling in galaxies: NGC 4698 and NGC 4672; The kinematics and the origin of the ionized gas in NGC 4036; Optically thin thermal plasma in the galactic bulge; X-ray properties of bulges; The host galaxies of radio-loud AGN; The centers of radio-loud early-type galaxies with HST; Central UV spikes in two galactic spheroids; Conference summary: where do we stand?

  19. Aeroacoustics of hot jets

    NASA Astrophysics Data System (ADS)

    Viswanathan, K.

    2004-10-01

    A systematic study has been undertaken to quantify the effect of jet temperature on the noise radiated by subsonic jets. Nozzles of different diameters were tested to uncover the effects of Reynolds number. All the tests were carried out at Boeing's Low Speed Aeroacoustic Facility, with simultaneous measurement of thrust and noise. It is concluded that the change in spectral shape at high jet temperatures, normally attributed to the contribution from dipoles, is due to Reynolds number effects and not dipoles. This effect has not been identified before. A critical value of the Reynolds number that would need to be maintained to avoid the effects associated with low Reynolds number has been estimated to be {˜}400 000. It is well-known that large-scale structures are the dominant generators of noise in the peak radiation direction for high-speed jets. Experimental evidence is presented that shows the spectral shape at angles close to the jet axis from unheated low subsonic jets to be the same as from heated supersonic jets. A possible mechanism for the observed trend is proposed. When a subsonic jet is heated with the Mach number held constant, there is a broadening of the angular sector in which peak radiation occurs. Furthermore, there is a broadening of the spectral peak. Similar trends have been observed at supersonic Mach numbers. The spectral shapes in the forward quadrant and in the near-normal angles from unheated and heated subsonic jets also conform to the universal shape obtained from supersonic jet data. Just as for unheated jets, the peak frequency at angles close to the jet axis is independent of jet velocity as long as the acoustic Mach number is less than unity. The extensive database generated in the current test programme is intended to provide test cases with high-quality data that could be used for the evaluation of theoretical/semi-theoretical jet noise prediction methodologies.

  20. A kiloparsec-scale internal shock collision in the jet of a nearby radio galaxy.

    PubMed

    Meyer, Eileen T; Georganopoulos, Markos; Sparks, William B; Perlman, Eric; van der Marel, Roeland P; Anderson, Jay; Sohn, Sangmo Tony; Biretta, John; Norman, Colin; Chiaberge, Marco

    2015-05-28

    Jets of highly energized plasma with relativistic velocities are associated with black holes ranging in mass from a few times that of the Sun to the billion-solar-mass black holes at the centres of galaxies. A popular but unconfirmed hypothesis to explain how the plasma is energized is the 'internal shock model', in which the relativistic flow is unsteady. Faster components in the jet catch up to and collide with slower ones, leading to internal shocks that accelerate particles and generate magnetic fields. This mechanism can explain the variable, high-energy emission from a diverse set of objects, with the best indirect evidence being the unseen fast relativistic flow inferred to energize slower components in X-ray binary jets. Mapping of the kinematic profiles in resolved jets has revealed precessing and helical patterns in X-ray binaries, apparent superluminal motions, and the ejection of knots (bright components) from standing shocks in the jets of active galaxies. Observations revealing the structure and evolution of an internal shock in action have, however, remained elusive, hindering measurement of the physical parameters and ultimate efficiency of the mechanism. Here we report observations of a collision between two knots in the jet of nearby radio galaxy 3C 264. A bright knot with an apparent speed of (7.0 ± 0.8)c, where c is the speed of light in a vacuum, is in the incipient stages of a collision with a slower-moving knot of speed (1.8 ± 0.5)c just downstream, resulting in brightening of both knots--as seen in the most recent epoch of imaging. PMID:26017450

  1. Theory of laminar viscous jets

    NASA Astrophysics Data System (ADS)

    Martynenko, O. G.; Korovkin, V. N.; Sokovishin, Iu. A.

    Results of recent theoretical studies of laminar jet flows of a viscous incompressible fluid are reviewed. In particular, attention is given to plane, fan-shaped, axisymmetric, and swirling jet flows; jet flows behind bodies; and slipstream jet flows. The discussion also covers dissipation of mechanical energy in jet flows, jet flows with a zero excess momentum, and asymptotic series expansions in the theory of jet flows.

  2. The importance of jet bending in gamma-ray AGNs—revisited

    SciTech Connect

    Graham, P. J.; Tingay, S. J.

    2014-04-01

    We investigate the hypothesis that γ-ray-quiet active galactic nuclei (AGNs) have a greater tendency for jet bending than γ-ray-loud AGNs, revisiting the analysis of Tingay et al. We perform a statistical analysis using a large sample of 351 radio-loud AGNs along with γ-ray identifications from the Fermi Large Area Telescope (LAT). Our results show no statistically significant differences in jet-bending properties between γ-ray-loud and γ-ray-quiet populations, indicating that jet bending is not a significant factor for γ-ray detection in AGNs.

  3. Observational signatures of galactic winds powered by active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Nims, Jesse; Quataert, Eliot; Faucher-Giguère, Claude-André

    2015-03-01

    We predict the observational signatures of galaxy scale outflows powered by active galactic nuclei (AGN). Most of the emission is produced by the forward shock driven into the ambient interstellar medium (ISM) rather than by the reverse shock. AGN-powered galactic winds with energetics suggested by phenomenological feedback arguments should produce spatially extended ˜1-10 keV X-ray emission ˜ 1041-44 erg s- 1, significantly in excess of the spatially extended X-ray emission associated with normal star-forming galaxies. The presence of such emission is a direct test of whether AGN outflows significantly interact with the ISM of their host galaxy. We further show that even radio-quiet quasars should have a radio luminosity comparable to or in excess of the far-infrared-radio correlation of normal star-forming galaxies. This radio emission directly constrains the total kinetic energy flux in AGN-powered galactic winds. Radio emission from AGN wind shocks can also explain the recently highlighted correlations between radio luminosity and the kinematics of AGN narrow-line regions in radio-quiet quasars.

  4. Relativistic MHD simulations of core-collapse GRB jets: 3D instabilities and magnetic dissipation

    NASA Astrophysics Data System (ADS)

    Bromberg, Omer; Tchekhovskoy, Alexander

    2016-02-01

    Relativistic jets are associated with extreme astrophysical phenomena, like the core collapse of massive stars in gamma-ray bursts (GRBs) and the accretion on to supermassive black holes in active galactic nuclei. It is generally accepted that these jets are powered electromagnetically, by the magnetized rotation of a central compact object (black hole or neutron star). However, how the jets produce the observed emission and survive the propagation for many orders of magnitude in distance without being disrupted by current-driven instabilities is the subject of active debate. We carry out time-dependent 3D relativistic magnetohydrodynamic (MHD) simulations of relativistic, Poynting-flux-dominated jets. The jets are launched self-consistently by the rotation of a strongly magnetized central object. This determines the natural degree of azimuthal magnetic field winding, a crucial factor that controls jet stability. We find that the jets are susceptible to two types of instability: (i) a global, external kink mode that grows on long time-scales. It bodily twists the jet, reducing its propagation velocity. We show analytically that in flat density profiles, like the ones associated with galactic cores, the external mode grows and may stall the jet. In the steep profiles of stellar envelopes the external kink weakens as the jet propagates outward. (ii) a local, internal kink mode that grows over short time-scales and causes small-angle magnetic reconnection and conversion of about half of the jet electromagnetic energy flux into heat. We suggest that internal kink instability is the main dissipation mechanism responsible for powering GRB prompt emission.

  5. Giant Kerr nonlinearity and superluminal and subluminal polaritonic solitons in a Bose-Einstein condensate via superradiant scattering

    NASA Astrophysics Data System (ADS)

    Hang, Chao; Gabadadze, Gregory; Huang, Guoxiang

    2015-09-01

    We propose a setup to generate giant Kerr nonlinearity and polaritonic solitons via matter-wave superradiant scattering. The system we consider is a long cigar-shaped Bose-Einstein condensate (BEC), pumped by a red-detuned laser field with a space-dependent intensity distribution in transverse directions. The pump and the scattered fields propagate along the longitudinal direction. We show that by means of the atom-photon and atom-atom interactions in the system it is possible to produce a giant nonlinear optical effect. We further show that a backward scattering of the laser field from the BEC is favorable for the formation and stable propagation of polaritonic solitons, which are collective nonlinear excitations of the BEC coupled with the scattered laser field. In the case of backward Stokes (anti-Stokes) scattering the system may support robust bright (dark) polaritonic solitons propagating with superluminal (subluminal) velocity.

  6. Superluminal and slow light in {lambda}-type three-level atoms via squeezed vacuum and spontaneously generated coherence

    SciTech Connect

    Carreno, F.; Calderon, Oscar G.; Anton, M.A.

    2005-06-15

    We study the dispersion and absorption spectra of a weak probe in a {lambda}-type three-level atomic system with closely ground sublevels driven by a strong field and damped by a broadband squeezed vacuum. We analyze the interplay between the spontaneous generated coherence and the squeezed field on the susceptibility of the atomic system. We find that by varying the intensity of the squeezed field the group velocity of a weak pulse can change from subluminal to superluminal. In addition we exploit the fact that the properties of the atomic medium can be dramatically modified by controlling the relative phase between the driving field and the squeezed field, allowing us to manipulate the group velocity at which light propagates. The physical origin of this phenomenon corresponds to a transfer of the atomic coherence from electromagnetically induced transparency to electromagnetically induced absorption. Besides, this phenomenon is achieved under nearly transparency conditions and with negligible distortion of the propagation pulse.

  7. Jet Substructure Without Trees

    SciTech Connect

    Jankowiak, Martin; Larkoski, Andrew J.; /SLAC /Stanford U., ITP

    2011-08-19

    We present an alternative approach to identifying and characterizing jet substructure. An angular correlation function is introduced that can be used to extract angular and mass scales within a jet without reference to a clustering algorithm. This procedure gives rise to a number of useful jet observables. As an application, we construct a top quark tagging algorithm that is competitive with existing methods. In preparation for the LHC, the past several years have seen extensive work on various aspects of collider searches. With the excellent resolution of the ATLAS and CMS detectors as a catalyst, one area that has undergone significant development is jet substructure physics. The use of jet substructure techniques, which probe the fine-grained details of how energy is distributed in jets, has two broad goals. First, measuring more than just the bulk properties of jets allows for additional probes of QCD. For example, jet substructure measurements can be compared against precision perturbative QCD calculations or used to tune Monte Carlo event generators. Second, jet substructure allows for additional handles in event discrimination. These handles could play an important role at the LHC in discriminating between signal and background events in a wide variety of particle searches. For example, Monte Carlo studies indicate that jet substructure techniques allow for efficient reconstruction of boosted heavy objects such as the W{sup {+-}} and Z{sup 0} gauge bosons, the top quark, and the Higgs boson.

  8. Relativistic HD and MHD modelling for AGN jets

    NASA Astrophysics Data System (ADS)

    Keppens, R.; Porth, O.; Monceau-Baroux, R.; Walg, S.

    2013-12-01

    Relativistic hydro and magnetohydrodynamics (MHD) provide a continuum fluid description for plasma dynamics characterized by shock-dominated flows approaching the speed of light. Significant progress in its numerical modelling emerged in the last two decades; we highlight selected examples of modern grid-adaptive, massively parallel simulations realized by our open-source software MPI-AMRVAC (Keppens et al 2012 J. Comput. Phys. 231 718). Hydrodynamical models quantify how energy transfer from active galactic nuclei (AGN) jets to their surrounding interstellar/intergalactic medium (ISM/IGM) gets mediated through shocks and various fluid instability mechanisms (Monceau-Baroux et al 2012 Astron. Astrophys. 545 A62). With jet parameters representative for Fanaroff-Riley type-II jets with finite opening angles, we can quantify the ISM volumes affected by jet injection and distinguish the roles of mixing versus shock-heating in cocoon regions. This provides insight in energy feedback by AGN jets, usually incorporated parametrically in cosmological evolution scenarios. We discuss recent axisymmetric studies up to full 3D simulations for precessing relativistic jets, where synthetic radio maps can confront observations. While relativistic hydrodynamic models allow one to better constrain dynamical parameters like the Lorentz factor and density contrast between jets and their surroundings, the role of magnetic fields in AGN jet dynamics and propagation characteristics needs full relativistic MHD treatments. Then, we can demonstrate the collimating properties of an overal helical magnetic field backbone and study differences between poloidal versus toroidal field dominated scenarios (Keppens et al 2008 Astron. Astrophys. 486 663). Full 3D simulations allow one to consider the fate of non-axisymmetric perturbations on relativistic jet propagation from rotating magnetospheres (Porth 2013 Mon. Not. R. Astron. Soc. 429 2482). Self-stabilization mechanisms related to the detailed

  9. Structure of Magnetic Tower Jets in Stratified Atmospheres

    NASA Astrophysics Data System (ADS)

    Nakamura, Masanori; Li, Hui; Li, Shengtai

    2006-12-01

    Using a new approach to modeling the magnetically dominated outflows from active galactic nuclei, we study the propagation of magnetic tower jets in gravitationally stratified atmospheres (such as a galaxy cluster environment) at large scales (more than tens of kiloparsecs) by performing three-dimensional MHD simulations. We present the detailed analysis of the MHD waves, the cylindrical radial force balance, and the collimation of magnetic tower jets. As magnetic energy is injected into a small central volume over a finite amount of time, the magnetic fields expand down the background density gradient, forming a collimated jet and an expanded ``lobe'' due to the gradually decreasing background density and pressure. Both the jet and lobes are magnetically dominated. In addition, the injection and expansion produce a hydrodynamic shock wave that moves ahead of and encloses the magnetic tower jet. This shock can eventually break the hydrostatic equilibrium in the ambient medium and cause a global gravitational contraction. This contraction produces a strong compression at the head of the magnetic tower front and helps to collimate the jet radially to produce a slender body. At the outer edge of the jet, the magnetic pressure is balanced by the background (modified) gas pressure, without any significant contribution from the hoop stress. On the other hand, along the central axis of the jet, hoop stress is the dominant force in shaping the central collimation of the poloidal current. The system, which possesses a highly wound helical magnetic configuration, never quite reaches a force-free equilibrium state, although the evolution becomes much slower at late stages. The simulations were performed without any initial perturbations, so the overall structures of the jet remain mostly axisymmetric.

  10. General Relativistic Magnetohydrodynamic Simulations of Jets from Black Hole Accretions Disks: Two-Component Jets Driven by Nonsteady Accretion of Magnetized Disks

    NASA Astrophysics Data System (ADS)

    Koide, Shinji; Shibata, Kazunari; Kudoh, Takahiro

    1998-03-01

    The radio observations have revealed the compelling evidence of the existence of relativistic jets not only from active galactic nuclei but also from ``microquasars'' in our Galaxy. In the cores of these objects, it is believed that a black hole exists and that violent phenomena occur in the black hole magnetosphere, forming the relativistic jets. To simulate the jet formation in the magnetosphere, we have newly developed the general relativistic magnetohydrodynamic code. Using the code, we present a model of these relativistic jets, in which magnetic fields penetrating the accretion disk around a black hole play a fundamental role of inducing nonsteady accretion and ejection of plasmas. According to our simulations, a jet is ejected from a close vicinity to a black hole (inside 3rS, where rS is the Schwarzschild radius) at a maximum speed of ~90% of the light velocity (i.e., a Lorentz factor of ~2). The jet has a two-layered shell structure consisting of a fast gas pressure-driven jet in the inner part and a slow magnetically driven jet in the outer part, both of which are collimated by the global poloidal magnetic field penetrating the disk. The former jet is a result of a strong pressure increase due to shock formation in the disk through fast accretion flow (``advection-dominated disk'') inside 3rS, which has never been seen in the nonrelativistic calculations.

  11. Galactic Fountains and Gas Accretion

    NASA Astrophysics Data System (ADS)

    Marinacci, F.; Binney, J.; Fraternali, F.; Nipoti, C.; Ciotti, L.; Londrillo, P.

    2010-06-01

    Star-forming disc galaxies such as the Milky Way need to accrete >~1 Msolar of gas each year to sustain their star formation. This gas accretion is likely to come from the cooling of the hot corona, however it is still not clear how this process can take place. We present simulations supporting the idea that this cooling and the subsequent accretion are caused by the passage of cold galactic-fountain clouds through the hot corona. The Kelvin-Helmholtz instability strips gas from these clouds and the stripped gas causes coronal gas to condense in the cloud's wake. For likely parameters of the Galactic corona and of typical fountain clouds we obtain a global accretion rate of the order of that required to feed the star formation.

  12. INTEGRAL Galactic bulge monitoring program

    NASA Astrophysics Data System (ADS)

    Kuulkers, E.; Kouveliotou, C.; van der Horst, A. J.; Belloni, T.; Chenevez, J.; Ibarra, A.; Munoz-Darias, T.; Bazzano, A.; Cadolle Bel, M.; De Cesare, G.; Diaz Trigo, M.; Jourdain, E.; Lubinski, P.; Natalucci, L.; Ness, J. U.; Parmar, A.; Pollock, A. M. T.; Rodriguez, J.; Roques, J. P.; Sanchez-Fernandez; C.; Ubertini, P.; Winkler, C.

    2010-12-01

    The central region of our Galaxy, the Galactic bulge, is a rich host of variable high-energy X-ray and gamma-ray point sources. These sources include bright and relatively faint X-ray transients, X-ray bursters, persistent neutron star and black-hole candidate binaries, high-mass X-ray binaries, etc.. We have a program to monitor the Galactic bulge region regularly and frequently with the gamma-ray observatory INTEGRAL, whenever it is observable. As a service to the scientific community the high-energy light curves of sources present, as well as the images of the region are made available through the WWW at http://integral.esac.esa.int/BULGE/ as soon as possible after the observations have been performed. We show the ongoing results of this exciting program.

  13. The Chandra Galactic Bulge Survey

    NASA Astrophysics Data System (ADS)

    Torres, Manuel

    2014-11-01

    The Chandra Galactic Bulge Survey (GBS) is a shallow survey with a flux limit of 1e-14 erg/cm2/s (0.5-10.0 keV) that covers a pair of 6 sq. deg. areas centred 1.5 deg. above and below the Galactic Center. The extinction and crowding in these regions are such that optical/infrared counterparts to the 1640 X-ray sources found with Chandra are accessible to detailed follow-up. The GBS is designed to set constraints on four important areas in astrophysics: stellar-mass black hole formation, the neutron star equation of state, the nature of the progenitors of type Ia supernovae and the common envelope evolution. Here I present the survey properties and goals, our multiwavelength methods to identify and clasify the counterparts to the X-ray sources and the first scientific results.

  14. Discovery in the Galactic Bulge

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2015-11-01

    In our efforts to map our galaxys structure, one region has remained very difficult to probe: the galactic center. A new survey, however, uses infrared light to peer through the gas and dust in the galactic plane, searching for variable stars in the bulge of the galaxy. This study has discovered a population of very young stars in a thin disk in the galactic center, providing clues to the star formation history of the Milky Way over the last 100 million years.Obscured CenterThe center of the Milky Way is dominated by a region known as the galactic bulge. Efforts to better understand this region in particular, its star formation history have been hindered by the stars, gas, and dust of the galactic disk, which prevent us from viewing the galactic bulge at low latitudes in visible light.The positions of the 35 classical Cepheids discovered in VVV data, projected onto an image of the galactic plane. Click for a better look! The survey area is bounded by the blue lines, and the galactic bar is marked with a red curve. The bottom panel shows the position of the Cepheids overlaid on the VVV bulge extinction map. [Dkny et al. 2015]Infrared light, however, can be used to probe deeper through the dust than visible-light searches. A new survey called VISTA Variables in the Via Lactea (VVV) uses the VISTA telescope in Chile to search, in infrared, for variable stars in the inner part of the galaxy. The VVV survey area spans the Milky Way bulge and an adjacent section of the mid-plane where star formation activity is high.Led by Istvn Dkny, a researcher at the Millennium Institute of Astrophysics and the Pontifical Catholic University of Chile, a team has now used VVV data to specifically identify classical Cepheid variable stars in the bulge. Why? Cepheids are pulsating stars with a very useful relation between their periods and luminosities that allows them to be used as distance indicators. Moreover, classical Cepheids are indicators of young stellar populations which can

  15. Constraints from orbital motions around the Earth of the environmental fifth-force hypothesis for the OPERA superluminal neutrino phenomenology

    NASA Astrophysics Data System (ADS)

    Iorio, L.

    2012-05-01

    It has been recently suggested by Dvali and Vikman that the superluminal neutrino phenomenology of the OPERA experiment may be due to an environmental feature of the Earth, naturally yielding a long-range fifth force of gravitational origin whose coupling with the neutrino is set by the scale M *, in units of reduced Planck mass. Its characteristic length λ should not be smaller than one Earth's radius R e, while its upper bound is expected to be slightly smaller than the Earth-Moon distance (60 R e). We analytically work out some orbital effects of a Yukawa-type fifth force for a test particle moving in the modified field of a central body. Our results are quite general since they are not restricted to any particular size of λ; moreover, they are valid for an arbitrary orbital configuration of the particle, i.e. for any value of its eccentricity e. We find that the dimensionless strength coupling parameter α is constrained to |α| ≲ 1 × 10-10 - 4 × 10-9 for 1 R e ≤ λ ≤ 10 R e by the laser data of the Earth's artificial satellite LAGEOS II, corresponding to M * ≳ 4 × 109 - 1 .6 × 1010. The Moon perigee allows to obtain |α| ≲ 3 × 10-11 for the Earth-Moon pair in the range 15 R e ≲ λ ≲ 60 R e, which translates as M * ≳ 3 × 1010 - 4 .5 × 1010. Our results are neither necessarily limited to the superluminal OPERA scenario nor to the Dvali-Vikman model, in which it is M * ~ 10-6 at λ ~ 1 R e, in contrast with our bounds: they generally extend to any theoretical scenario implying a fifth-force of Yukawa-type.

  16. DES14X3taz: A Type I Superluminous Supernova Showing a Luminous, Rapidly Cooling Initial Pre-peak Bump

    NASA Astrophysics Data System (ADS)

    Smith, M.; Sullivan, M.; D'Andrea, C. B.; Castander, F. J.; Casas, R.; Prajs, S.; Papadopoulos, A.; Nichol, R. C.; Karpenka, N. V.; Bernard, S. R.; Brown, P.; Cartier, R.; Cooke, J.; Curtin, C.; Davis, T. M.; Finley, D. A.; Foley, R. J.; Gal-Yam, A.; Goldstein, D. A.; González-Gaitán, S.; Gupta, R. R.; Howell, D. A.; Inserra, C.; Kessler, R.; Lidman, C.; Marriner, J.; Nugent, P.; Pritchard, T. A.; Sako, M.; Smartt, S.; Smith, R. C.; Spinka, H.; Thomas, R. C.; Wolf, R. C.; Zenteno, A.; Abbott, T. M. C.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Buckley-Geer, E.; Carnero Rosell, A.; Carrasco Kind, M.; Carretero, J.; Crocce, M.; Cunha, C. E.; da Costa, L. N.; Desai, S.; Diehl, H. T.; Doel, P.; Estrada, J.; Evrard, A. E.; Flaugher, B.; Fosalba, P.; Frieman, J.; Gerdes, D. W.; Gruen, D.; Gruendl, R. A.; James, D. J.; Kuehn, K.; Kuropatkin, N.; Lahav, O.; Li, T. S.; Marshall, J. L.; Martini, P.; Miller, C. J.; Miquel, R.; Nord, B.; Ogando, R.; Plazas, A. A.; Reil, K.; Romer, A. K.; Roodman, A.; Rykoff, E. S.; Sanchez, E.; Scarpine, V.; Schubnell, M.; Sevilla-Noarbe, I.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Walker, A. R.; Wester, W.; DES Collaboration

    2016-02-01

    We present DES14X3taz, a new hydrogen-poor superluminous supernova (SLSN-I) discovered by the Dark Energy Survey (DES) supernova program, with additional photometric data provided by the Survey Using DECam for Superluminous Supernovae. Spectra obtained using Optical System for Imaging and low-Intermediate-Resolution Integrated Spectroscopy on the Gran Telescopio CANARIAS show DES14X3taz is an SLSN-I at z = 0.608. Multi-color photometry reveals a double-peaked light curve: a blue and relatively bright initial peak that fades rapidly prior to the slower rise of the main light curve. Our multi-color photometry allows us, for the first time, to show that the initial peak cools from 22,000 to 8000 K over 15 rest-frame days, and is faster and brighter than any published core-collapse supernova, reaching 30% of the bolometric luminosity of the main peak. No physical 56Ni-powered model can fit this initial peak. We show that a shock-cooling model followed by a magnetar driving the second phase of the light curve can adequately explain the entire light curve of DES14X3taz. Models involving the shock-cooling of extended circumstellar material at a distance of ≃400 {\\text{}}{R}⊙ are preferred over the cooling of shock-heated surface layers of a stellar envelope. We compare DES14X3taz to the few double-peaked SLSN-I events in the literature. Although the rise times and characteristics of these initial peaks differ, there exists the tantalizing possibility that they can be explained by one physical interpretation.

  17. DES14X3taz: A type I superluminous supernova showing a luminous, rapidly cooling initial pre-peak bump

    DOE PAGESBeta

    Smith, M.

    2016-02-03

    Here, we present DES14X3taz, a new hydrogen-poor superluminous supernova (SLSN-I) discovered by the Dark Energy Survey (DES) supernova program, with additional photometric data provided by the Survey Using DECam for Superluminous Supernovae. Spectra obtained using Optical System for Imaging and low-Intermediate-Resolution Integrated Spectroscopy on the Gran Telescopio CANARIAS show DES14X3taz is an SLSN-I at z = 0.608. Multi-color photometry reveals a double-peaked light curve: a blue and relatively bright initial peak that fades rapidly prior to the slower rise of the main light curve. Our multi-color photometry allows us, for the first time, to show that the initial peak cools from 22,000more » to 8000 K over 15 rest-frame days, and is faster and brighter than any published core-collapse supernova, reaching 30% of the bolometric luminosity of the main peak. No physical (56)Ni-powered model can fit this initial peak. We show that a shock-cooling model followed by a magnetar driving the second phase of the light curve can adequately explain the entire light curve of DES14X3taz. Models involving the shock-cooling of extended circumstellar material at a distance of ≃400 R⊙ are preferred over the cooling of shock-heated surface layers of a stellar envelope. We compare DES14X3taz to the few double-peaked SLSN-I events in the literature. Although the rise times and characteristics of these initial peaks differ, there exists the tantalizing possibility that they can be explained by one physical interpretation.« less

  18. iShocks: X-ray binary jets with an internal shocks model

    NASA Astrophysics Data System (ADS)

    Jamil, O.; Fender, R. P.; Kaiser, C. R.

    2010-01-01

    In the following paper, we present an internal shocks model, iShocks, for simulating a variety of relativistic jet scenarios; these scenarios can range from a single ejection event to an almost continuous jet, and are highly user configurable. Although the primary focus in the following paper is black hole X-ray binary jets, the model is scale and source independent and could be used for supermassive black holes in active galactic nuclei or other flows such as jets from neutron stars. Discrete packets of plasma (or `shells') are used to simulate the jet volume. A two-shell collision gives rise to an internal shock, which acts as an electron re-energization mechanism. Using a pseudo-random distribution of the shell properties, the results show how for the first time it is possible to reproduce a flat/inverted spectrum (associated with compact radio jets) in a conical jet whilst taking the adiabatic energy losses into account. Previous models have shown that electron re-acceleration is essential in order to obtain a flat spectrum from an adiabatic conical jet: multiple internal shocks prove to be efficient in providing this re-energization. We also show how the high-frequency turnover/break in the spectrum is correlated with the jet power, νb ~ L~0.6W, and the flat-spectrum synchrotron flux is correlated with the total jet power, Fν ~ L~1.4W . Both the correlations are in agreement with previous analytical predictions.

  19. The Chandra Galactic Bulge Survey

    NASA Astrophysics Data System (ADS)

    Britt, C. T.; Hynes, R. I.; Jonker, P. G.; Maccarone, T.; Torres, M. A. P.; Steeghs, D.; Nelemans, G.; Johnson, C.; Greiss, S.

    2015-05-01

    The Chandra Galactic Bulge Survey (GBS) is a multi-wavelength survey of two 6×1 degree strips above and below the Galactic plane, including deep r' and i' imaging and time domain photometry from CTIO and shallow, wide-field X-ray imaging with Chandra. Targeting fields above |b|=1 avoids most of the copious extinction along the Galactic plane while maintaining high source density. This results in targets that are accessible to follow up in optical and NIR wavelengths. The X-ray observations are shallow to maximize the number of quiescent Low Mass X-ray Binaries (LMXBs) relative to Cataclysmic Variables (CVs). The goals of the GBS are to conduct a census of Low Mass X-ray Binaries in the Milky Way in order to constrain models of binary evolution, the common envelope phase in particular, and to expand the number of known LMXBs for optical follow up. Mass measurements in particular will help constrain the black hole (BH) mass distribution and the equation of state for neutron stars (NS). Constraining the BH mass distribution will constrain models of their formation in supernovae. The current population of Galactic BHs suffers from selection effects, which the GBS avoids by finding new objects while still in quiescence. We expect to find qLMXBs, magnetic CVs, RS CVn stars, and smaller numbers of other types of sources. After removing duplicates, there are 1640 unique X-ray sources in the 12 square degree survey area, which closely matches the predicted number of 1648. We are currently matching X-ray sources to counterparts in other wavelengths using new photometric and spectroscopic observations as well as in archival data where it exists, and searching for variability and periodicity in the counterparts in photometric data. So far, we have spectroscopically identified 27 interacting binaries including promising candidates for quiescent black holes.

  20. Wanted: Galactic Thief Who Steals Gas

    NASA Technical Reports Server (NTRS)

    2007-01-01

    [figure removed for brevity, see original site] Poster Version

    A big galaxy is stealing gas right off the 'back' of its smaller companion in this new image from NASA's Spitzer Space Telescope. The stolen gas is hot, but it might eventually cool down to make new stars and planets.

    The robber galaxy, called 3C 326 North, and its victim, 3C 326 South, are located about a billion light-years away from Earth in the Serpens constellation. They are both called radio galaxies, because the relativistic jets streaming out of their centers give off a great deal of radio waves. Other dots in the picture are foreground stars and background galaxies.

    When astronomers first collected data on the 3C 326 galaxies with Spitzer's infrared spectrometer, they were surprised to find that 3C 326 North is loaded with an enormous amount of hot gas, called molecular hydrogen gas, which is fuel for stars and planets. They then studied this archived picture taken with Spitzer's infrared array camera and noticed a tail of stars connecting 3C 326 North to 3C 326 South. This tail revealed that the galactic pair are gravitationally tangled and might eventually merge --and that 3C 326 North must be hoisting gas from its smaller companion.

    How is 3C 326 stealing the gas? The answer is gravity. The larger 3C 326 North, which is about the same mass as our Milky Way galaxy, has more gravity so the gas from 3C 326 South falls toward it in the same way that water rolls down hill on Earth. Even in space, it seems the bullies are bigger!

    This image shows infrared light of three wavelengths: 8-micron light is red; 4.5 microns is green; 3.6 microns is blue.

  1. A magnetically collimated jet from an evolved star.

    PubMed

    Vlemmings, Wouter H T; Diamond, Philip J; Imai, Hiroshi

    2006-03-01

    Planetary nebulae often have asymmetric shapes, even though their progenitor stars were symmetric; this structure could be the result of collimated jets from the evolved stars before they enter the planetary nebula phase. Theoretical models have shown that magnetic fields could be the dominant source of jet-collimation in evolved stars, just as these fields are thought to collimate outflows in other astrophysical sources, such as active galactic nuclei and proto-stars. But hitherto there have been no direct observations of both the magnetic field direction and strength in any collimated jet. Here we report measurements of the polarization of water vapour masers that trace the precessing jet emanating from the asymptotic giant branch star W43A (at a distance of 2.6 kpc from the Sun), which is undergoing rapid evolution into a planetary nebula. The masers occur in two clusters at opposing tips of the jets, approximately 1,000 au from the star. We conclude from the data that the magnetic field is indeed collimating the jet. PMID:16511488

  2. Jet Signatures in the Spectra of Accreting Black Holes

    NASA Astrophysics Data System (ADS)

    O' Riordan, Michael; Pe'er, Asaf; McKinney, Jonathan C.

    2016-03-01

    Jets are observed as radio emission in active galactic nuclei and during the low/hard state in X-ray binaries (XRBs), but their contribution at higher frequencies has been uncertain. We study the dynamics of jets in XRBs using the general-relativistic magnetohydrodynamic code HARM. We calculate the high-energy spectra and variability properties using a general-relativistic radiative transport code based on grmonty. We find the following signatures of jet emission: (i) a significant γ-ray peak above ˜1022 Hz, (ii) a break in the optical/UV spectrum, with a change from ν {L}ν ˜ {ν }0 to ν {L}ν ˜ ν , followed by another break at higher frequencies where the spectrum roughly returns to ν {L}ν ˜ {ν }0, and (iii) a pronounced synchrotron peak near or below ˜1014 Hz indicates that a significant fraction of any observed X-ray emission originates in the jet. We investigate the variability during a large-scale magnetic field inversion in which the Blandford-Znajek (BZ) jet is quenched and a new transient hot reconnecting plasmoid is launched by the reconnecting field. The ratio of the γ-rays to X-rays changes from {L}γ /{L}{{X}}\\gt 1 in the BZ jet to {L}γ /{L}{{X}}\\lt 1 during the launching of the transient plasmoid.

  3. Parsec-Scale Kinematic and Polarization Properties of MOJAVE AGN Jets

    NASA Astrophysics Data System (ADS)

    Lister, Matthew L.

    2013-12-01

    We describe the parsec-scale kinematics and statistical polarization properties of 200 AGN jets based on 15 GHz VLBA data obtained between 1994 Aug 31 and 2011 May 1. Nearly all of the 60 most heavily observed jets show significant changes in their innermost position angle over a 12 to 16 year interval, ranging from 10° to 150° on the sky, corresponding to intrinsic variations of ~ 0.5° to ~ 2°. The BL Lac jets show smaller variations than quasars. Roughly half of the heavily observed jets show systematic position angle trends with time, and 20 show indications of oscillatory behavior. The time spans of the data sets are too short compared to the fitted periods (5 to 12 y), however, to reliably establish periodicity. The rapid changes and large jumps in position angle seen in many cases suggest that the superluminal AGN jet features occupy only a portion of the entire jet cross section, and may be energized portions of thin instability structures within the jet. We have derived vector proper motions for 887 moving features in 200 jets having at least five VLBA epochs. For 557 well-sampled features, there are sufficient data to additionally study possible accelerations. The moving features are generally non-ballistic, with 70% of the well-sampled features showing either significant accelerations or non-radial motions. Inward motions are rare (2% of all features), are slow (< 0.1 mas per y), are more prevalent in BL Lac jets, and are typically found within 1 mas of the unresolved core feature. There is a general trend of increasing apparent speed with distance down the jet for both radio galaxies and BL Lac objects. In most jets, the speeds of the features cluster around a characteristic value, yet there is a considerable dispersion in the distribution. Orientation variations within the jet cannot fully account for the dispersion, implying that the features have a range of Lorentz factor and/or pattern speed. Very slow pattern speed features are rare, comprising

  4. Constraints on galactic wind models

    NASA Astrophysics Data System (ADS)

    Meiksin, Avery

    2016-09-01

    Observational implications are derived for two standard models of supernovae-driven galactic winds: a freely expanding steady-state wind and a wind sourced by a self-similarly expanding superbubble including thermal heat conduction. It is shown that, for the steady-state wind, matching the measured correlation between the soft X-ray luminosity and star formation rate of starburst galaxies is equivalent to producing a scaled wind mass-loading factor relative to the star formation rate of 0.5-3, in agreement with the amount inferred from metal absorption line measurements. The match requires the asymptotic wind velocity v∞ to scale with the star formation rate dot{M}_{ast } (in M⊙ yr-1) approximately as v_∞ ≃ (700-1000) {{km s^{-1}}} {dot{M}_{ast }}^{1/6}. The implied mass injection rate is close to the amount naturally provided by thermal evaporation from the wall of a superbubble in a galactic disc, suggesting that thermal evaporation may be a major source of mass loading. The predicted mass-loading factors from thermal evaporation within the galactic disc alone, however, are somewhat smaller, 0.2-2, so that a further contribution from cloud ablation or evaporation within the wind may be required. Both models may account for the 1.4 GHz luminosity of unresolved radio sources within starburst galaxies for plausible parameters describing the distribution of relativistic electrons. Further observational tests to distinguish the models are suggested.

  5. Relativistic 3D precessing jet simulations for the X-ray binary SS433

    NASA Astrophysics Data System (ADS)

    Monceau-Baroux, Rémi; Porth, Oliver; Meliani, Zakaria; Keppens, Rony

    2014-01-01

    Context. Modern high-resolution radio observations allow us a closer look into the objects that power relativistic jets. This is especially the case for SS433, an X-ray binary that emits a precessing jet that is observed down to the subparsec scale. Aims: We aim to study full 3D dynamics of relativistic jets associated with active galactic nuclei or X-ray binaries (XRB). In particular, we incorporate the precessing motion of a jet into a model for the jet associated with the XRB SS433. Our study of the jet dynamics in this system focuses on the subparsec scales. We investigate the impact of jet precession and the variation of the Lorentz factor of the injected matter on the general 3D jet dynamics and its energy transfer to the surrounding medium. After visualizing and quantifying jet dynamics, we aim to realize synthetic radio mapping of the data, to compare our results with observations. Methods: For our study we used a block-tree adaptive mesh refinement scheme and an inner time-dependent boundary prescription to inject precessing bipolar supersonic jets. Parameters extracted from observations were used. Different 3D jet realizations that match the kinetic flux of the SS433 jet were intercompared, which vary in density contrast and jet beam velocity. We tracked the energy content deposited in different regions of the domain affected by the jet. Our code allows us to follow the adiabatic cooling of a population of relativistic particles injected by the jet. This evolving energy spectrum of accelerated electrons, using a pressure-based proxy for the magnetic field, allowed us to obtain the radio emission from our simulation. Results: We find a higher energy transfer for a precessing jet than for standing jets with otherwise identical parameters as a result of the effectively increased interaction area. We obtain synthetic radio maps for all jets, from which one can see that dynamical flow features are clearly linked with enhanced emission sites. Conclusions: The

  6. Jets from young stars

    NASA Astrophysics Data System (ADS)

    Bally, John

    2007-10-01

    Most stars produce spectacular jets during their formation. There are thousands of young stars within 500 pc of the Sun and many power jets. Thus protostellar jets may be the most common type of collimated astrophysical outflow. Shocks powered by outflows excite many emission lines, exhibit a rich variety of structure, and motions with velocities ranging from 50 to over 500 km s-1. Due to their relative proximity, proper motions and structural changes can be observed in less than a year. I review the general properties of protostellar jets, summarize some results from recent narrow-band imaging surveys of entire clouds, discuss irradiated jets, and end with some comments concerning outflows from high-mass young stellar objects. Protostellar outflows are ideal laboratories for the exploration of the jet physics.

  7. Relativistic Jets in Collapsars

    NASA Astrophysics Data System (ADS)

    Zhang, Weiqun; Woosley, S. E.; MacFadyen, A. I.

    2003-04-01

    We examine the propagation of two-dimensional relativistic jets through the stellar progenitor in the collapsar model for gamma-ray bursts. In agreement with previous studies, we find that the jet is collimated by its passage. Moreover, interaction of the jet with the star causes mixing that sporadically decelerates the jet, leading to a highly variable Lorentz factor. The jet that finally emerges has a moderate Lorentz factor, but a very large internal energy loading. In a second series of calculations we follow the emergence of such enegy-loaded jets from the star. For the initial conditions chosen, conversion of the remaining internal energy gives a terminal Lorentz factor of approximately 150. Implications of our calculations for GRB light curves, the luminosity-variability relation, and the GRB-supernova association are discussed.

  8. What ignites optical jets?

    SciTech Connect

    Sebastian Jester

    2002-12-23

    The properties of radio galaxies and quasars with and without optical or X-ray jets are compared. The majority of jets from which high-frequency emission has been detected so far (13 with optical emission, 11 with X-rays, 13 with both) are associated with the most powerful radio sources at any given redshift. It is found that optical/X-ray jet sources are more strongly beamed than the average population of extragalactic radio sources. This suggests that the detection or non-detection of optical emission from jets has so far been dominated by surface brightness selection effects, not by jet physics. It implies that optical jets are much more common than is currently appreciated.

  9. New Developments in Galactic Archaeology

    NASA Astrophysics Data System (ADS)

    Freeman, Kenneth C.; HERMES/GALAH Team

    2014-01-01

    The goal of Galactic Archaeology is to unravel observationally the events that occurred during the assembly of the Milky Way. For example, how did the star formation rate and the mass spectrum of the star-forming clusters change with time since the Galaxy began to form, how much did minor mergers and accretion of satellite galaxies contribute to the stellar content of the Galactic components, and how did the chemical properties of the Galaxy evolve? The data for Galactic Archaeology include the phase space coordinates of stars (position and velocity) and the chemical space coordinates (abundances of up to about 30 chemical elements). Although we know that the distribution of individual elements contains important information about the star formation history and chemical evolution of the Galaxy, the available data for large samples of stars has so far restricted the use of chemical space data mainly to the overall metallicity and the alpha-element enhancement. We are entering an era of large high-resolution spectroscopic surveys in which the abundances of many elements from all of the major nucleosynthesis processes will be measured. It will be possible to use chemical tagging techniques to identify the debris of individual dispersed star forming aggregates. In combination with astrometry from the Gaia mission, it will be possible to derive ages for this recovered star formation debris, and build up the star formation history of the regions of the Milky Way accessible to these large surveys. The Galactic thick disk is of particular interest. Because almost all disk galaxies appear to have an old thick disk, thick disks are an important but as yet poorly understood part of the formation process for disk galaxies. Some theories of thick disk formation associate the thick disk with the large star-bursting complexes seen in proto-disk galaxies at high redshift. If the Galactic thick disk was built in this way, from a relatively small number of large aggregates, it will

  10. Relativistic Particle-In-Cell Simulations of Particle Accleration in Relativistic Jets

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.-I.; Hardee, P.; Mizuno, Y.; Medvedev, M.; Hartmann, D. H.; Fishman, J. F.

    2008-01-01

    Highly accelerated particles are observed in astrophysical systems containing relativistic jets and shocks, e.g., active galactic nuclei (AGNs), microquasars, and Gamma-Ray Bursts (GRBs). Particle-In-Cell (PIC) simulations of relativistic electron-ion and electron-positron jets injected into a stationary medium show that efficient acceleration occurs downstream in the jet. In collisionless relativistic shocks particle acceleration is due to plasma waves and their associated instabilities, e.g., the Buneman instability, other two-stream instabilities, and the Weibel (filamentation) instability. Simulations show that the Weibel instability is responsible for generating and amplifying highly non-uniform, small-scale magnetic fields. The instability depends on strength and direction of the magnetic field. Particles in relativistic jets may be accelerated in a complicated dynamics of relativistic jets with magnetic field. We present results of our recent PIC simulations.

  11. Relativistic jet models for the BL Lacertae object Mrk 421 during three epochs of observation

    NASA Technical Reports Server (NTRS)

    Mufson, S. L.; Hutter, D. J.; Kondo, Y.; Wisniewski, W. Z.

    1988-01-01

    Coordinated observation of the nearby BL Lacertae object Mrk 421 obtained during May 1980, January 1984, and March 1984 are described. These observations give a time-frozen picture of the continuous spectrum of Mrk 421 at X-ray, ultraviolet, optical, and radio wavelengths. The observed spectra have been fitted to an inhomogeneous relativistic jet model. In general, the models reproduce the data well. Many of the observed differences during the three epochs can be attributed to variations in the opening angle of the jet and in the angle that the jet makes to the line of sight. The jet models obtained here are compared with the homogeneous, spherically symmetric, synchrotron self-Compton models for this source. The models are also compared with the relativistic jet models obtained for other active galactic nuclei.

  12. A Universal Scaling for the Energetics of Relativistic Jets From Black Hole Systems

    NASA Technical Reports Server (NTRS)

    Nemmen, R. S.; Georganopoulos, M.; Guiriec, S.; Meyer, E. T.; Gehrels, N.; Sambruna, R. M.

    2013-01-01

    Black holes generate collimated, relativistic jets which have been observed in gamma-ray bursts (GRBs), microquasars, and at the center of some galaxies (active galactic nuclei; AGN). How jet physics scales from stellar black holes in GRBs to the supermassive ones in AGNs is still unknown. Here we show that jets produced by AGNs and GRBs exhibit the same correlation between the kinetic power carried by accelerated particles and the gamma-ray luminosity, with AGNs and GRBs lying at the low and high-luminosity ends, respectively, of the correlation. This result implies that the efficiency of energy dissipation in jets produced in black hole systems is similar over 10 orders of magnitude in jet power, establishing a physical analogy between AGN and GRBs.

  13. Properties of gluon jets

    SciTech Connect

    Sugano, K.

    1986-09-01

    The properties of gluon jets are reviewed from an experimental point of view. The measured characteristics are compared to theoretical expectations. Although neither data nor models for the gluon jets are in the mature stage, there are remarkable agreements and also intriguing disagreements between experiment and theory. Since much interesting data have begun to emerge from various experiments and the properties of gluon jets are deeply rooted in the basic structure of non-Abelian gauge theory, the study of gluon jets casts further light on our understanding of QCD. Finally, the future prospects are discussed.

  14. Perspectives on jet noise

    NASA Technical Reports Server (NTRS)

    Ribner, H. S.

    1981-01-01

    Jet noise is a byproduct of turbulence. Until recently turbulence was assumed to be known statistically, and jet noise was computed therefrom. As a result of new findings though on the behavior of vortices and instability waves, a more integrated view of the problem has been accepted lately. After presenting a simple view of jet noise, the paper attempts to resolve the apparent differences between Lighthill's and Lilley's interpretations of mean-flow shear, and examines a number of ad hoc approaches to jet noise suppression.

  15. Interpretation of extragalactic jets

    SciTech Connect

    Norman, M.L.

    1985-01-01

    The nature of extragalatic radio jets is modeled. The basic hypothesis of these models is that extragalatic jets are outflows of matter which can be described within the framework of fluid dynamics and that the outflows are essentially continuous. The discussion is limited to the interpretation of large-scale (i.e., kiloparsec-scale) jets. The central problem is to infer the physical parameters of the jets from observed distributions of total and polarized intensity and angle of polarization as a function of frequency. 60 refs., 6 figs.

  16. SAS-2 galactic gamma ray results, 1

    NASA Technical Reports Server (NTRS)

    Thompson, D. J.; Fichtel, C. E.; Hartman, R. C.; Kniffen, D. A.; Bignami, G. F.; Lamb, R. C.; Oegelman, H.; Oezel, M. E.; Tuemer, T.

    1976-01-01

    Continuing analysis of the data from the SAS-2 high energy gamma-ray experiment has produced an improved picture of the sky at photon energies above 35 MeV. On a large scale, the diffuse emission from the galactic plane is the dominant feature observed by SAS-2. This galactic plane emission is most intense between galactic longitude 310 and 45 deg, corresponding to a region within 7kpc of the galactic center. Within the high-intensity region, SAS-2 observes peaks around galactic longitudes 315 deg, 330 deg, 345 deg, 0 deg, and 35 deg. These peaks appear to be correlated with such galactic features and components as molecular hydrogen, atomic hydrogen, magnetic fields, cosmic ray concentrations, and photon fields.

  17. The physics of galactic winds driven by active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Faucher-Giguère, Claude-André; Quataert, Eliot

    2012-09-01

    Active galactic nuclei (AGN) drive fast winds in the interstellar medium of their host galaxies. It is commonly assumed that the high ambient densities and intense radiation fields in galactic nuclei imply short cooling times, thus making the outflows momentum conserving. We show that cooling of high-velocity shocked winds in AGN is in fact inefficient in a wide range of circumstances, including conditions relevant to ultraluminous infrared galaxies (ULIRGs), resulting in energy-conserving outflows. We further show that fast energy-conserving outflows can tolerate a large amount of mixing with cooler gas before radiative losses become important. For winds with initial velocity vin ≳ 10 000 km s-1, as observed in ultraviolet and X-ray absorption, the shocked wind develops a two-temperature structure. While most of the thermal pressure support is provided by the protons, the cooling processes operate directly only on the electrons. This significantly slows down inverse Compton cooling, while free-free cooling is negligible. Slower winds with vin ˜ 1000 km s-1, such as may be driven by radiation pressure on dust, can also experience energy-conserving phases but under more restrictive conditions. During the energy-conserving phase, the momentum flux of an outflow is boosted by a factor ˜vin/2vs by work done by the hot post-shock gas, where vs is the velocity of the swept-up material. Energy-conserving outflows driven by fast AGN winds (vin ˜ 0.1c) may therefore explain the momentum fluxes Ṗ≫LAGN/c of galaxy-scale outflows recently measured in luminous quasars and ULIRGs. Shocked wind bubbles expanding normal to galactic discs may also explain the large-scale bipolar structures observed in some systems, including around the Galactic Centre, and can produce significant radio, X-ray and γ-ray emission. The analytic solutions presented here will inform implementations of AGN feedback in numerical simulations, which typically do not include all the important

  18. Detection of silicon in the Galactic center

    NASA Technical Reports Server (NTRS)

    Hertier, T.; Houck, J. R.; Graf, P.; Gull, G. E.

    1986-01-01

    The detection of the forbidden Si II 34.815 micron line in the Galactic center region is reported. It is demonstrated that, in the case of the Galactic center, the emission arises mainly from the photodissociation region and not the shocked molecular component seen via H2, CO, and OH lines. It is also shown that significant Si II emission is not expected from the ionized gas even though the Galactic center is a rather low excitation H II region.

  19. The precessing jets of 1E 1740.7-2942

    NASA Astrophysics Data System (ADS)

    Luque-Escamilla, Pedro L.; Martí, Josep; Martínez-Aroza, José

    2015-12-01

    Context. The source 1E 1740.7-2942 is believed to be one of the two prototypical microquasars towards the Galactic center region whose X-ray states strongly resemble those of Cygnus X-1. Yet, the bipolar radio jets of 1E 1740.7-2942 are very reminiscent of a radio galaxy. The true nature of the object has thus remained an open question for nearly a quarter of a century. Aims: Our main goal here is to confirm the Galactic membership of 1E 1740.7-2942 by searching for morphological changes of its extended radio jets in human timescales. This work was triggered as a result of recent positive detection of fast structural changes in the large-scale jets of the very similar source GRS 1758-258. Methods: We carried out an in-depth exploration of the Very Large Array public archives and fully recalibrated all 1E 1740.7-2942 extended data sets in the C configuration of the array. We obtained and analyzed matching beam radio maps for five epochs, covering years 1992, 1993, 1994, 1997 and 2000, with an angular resolution of a few arcseconds. Results: We clearly detected structural changes in the arc-minute jets of 1E 1740.7-2942 on timescales of roughly a year, which set a firm distance upper limit of 12 kpc. Moreover, a simple precessing twin-jet model was simultaneously fitted to the five observing epochs available. The observed changes in the jet flow are strongly suggestive of a precession period of ~1.3 yr. Conclusions: The fitting of the precession model to the data yields a distance of ~5 kpc. This value, and the observed changes, rule out any remaining doubts about the 1E 1740.7-2942 Galactic nature. To our knowledge, this microquasar is the second whose jet precession ephemeris become available after SS433. This kind of information is relevant to the physics of compact objects, since the genesis of the precession phenomenon occurs very close to the interplay region between the accretion disk and the compact object in the system. Appendix A and a movie associated to

  20. ATOMIC HYDROGEN IN A GALACTIC CENTER OUTFLOW

    SciTech Connect

    McClure-Griffiths, N. M.; Green, J. A.; Hill, A. S.; Lockman, F. J.; Dickey, J. M.; Gaensler, B. M.; Green, A. J.

    2013-06-10

    We describe a population of small, high-velocity, atomic hydrogen clouds, loops, and filaments found above and below the disk near the Galactic center. The objects have a mean radius of 15 pc, velocity widths of {approx}14 km s{sup -1}, and are observed at |z| heights up to 700 pc. The velocity distribution of the clouds shows no signature of Galactic rotation. We propose a scenario where the clouds are associated with an outflow from a central star-forming region at the Galactic center. We discuss the clouds as entrained material traveling at {approx}200 km s{sup -1} in a Galactic wind.

  1. Three-dimensional Magnetohydrodynamic Simulations of Relativistic Jets Injected into an Oblique Magnetic Field

    NASA Astrophysics Data System (ADS)

    Nishikawa, Ken-Ichi; Koide, Shinji; Sakai, Jun-ichi; Christodoulou, Dimitris M.; Sol, Hélène; Mutel, Robert L.

    1998-05-01

    We discuss the structure and relativistic kinematics that develop in three spatial dimensions when a moderately hot, supersonic jet propagates into a denser background medium and encounters resistance from an oblique magnetic field. Our simulations incorporate relativistic MHD in a four-dimensional spacetime and clearly show that (1) relatively weak, oblique fields (at 1/16 of the equipartition value) have only a negligible influence on the propagating jet and they are passively pushed away by the relativistically moving head; (2) oblique fields in equipartition with the ambient plasma provide more resistance and cause bending at the jet head but the magnitude of this deflection and the associated backflow are small compared to those identified by previous studies. The new results are understood as follows: Relativistic simulations have consistently shown that these jets are effectively heavy, and so they do not suffer substantial momentum losses and are not decelerated as efficiently as their nonrelativistic counterparts. In addition, the ambient magnetic field, however strong, can be pushed aside with relative ease by the beam, provided that the degrees of freedom associated with all three spatial dimensions are followed self-consistently during the simulations. The effect is analogous to pushing Japanese ``noren'' or vertical venetian blinds out of the way while the slats are allowed to bend in three-dimensional space rather than as a two-dimensional slab structure. Applied to relativistic extragalactic jets from blazars, the new results are encouraging, since superluminal outflows exhibit bending near their sources and their environments are profoundly magnetized--but observations do not provide support for irregular kinematics such as large-scale vortical motions and pronounced reverse flows near the points of origin.

  2. Inconsistency in super-luminal CERN-OPERA neutrino speed with the observed SN1987A burst and neutrino mixing for any imaginary neutrino mass

    NASA Astrophysics Data System (ADS)

    Fargion, Daniele; D'Armiento, Daniele

    2012-08-01

    We tried to fit in any way the recent OPERA-CERN claims of a neutrino super-luminal speed with the observed supernova SN1987A neutrino burst and all (or most) neutrino flavor oscillations. We considered three main frameworks: (1) tachyon imaginary neutrino mass, whose timing is nevertheless in conflict with the observed IMB-Kamiokande SN1987A burst by thousands of billion times longer. (2) An ad hoc anti-tachyon model whose timing shrinkage may accommodate the SN1987A burst but greatly disagrees with the energy-independent CERN-OPERA super-luminal speed. (3) A split neutrino flavor speed (among a common real mass relativistic νe component and a super-luminal νμ) in an ad hoc frozen speed scenario that leads to the prompt neutrino de-coherence and rapid flavor mixing (between νe and νμ, ντ) that are in conflict with most oscillation records. Therefore, we concluded that an error must be hidden in OPERA-CERN time calibration (as indeed recent rumors seem to confirm). We concluded recalling the relevance of the real guaranteed minimal atmospheric neutrino mass whose detection may be achieved by a millisecond graviton-neutrino split time delay among the gravity burst and neutronization neutrino peak in any future supernova explosion in Andromeda recordable in the Megaton neutrino detector.

  3. THE GALACTIC CENTER: NOT AN ACTIVE GALACTIC NUCLEUS

    SciTech Connect

    An, Deokkeun; Ramirez, Solange V.; Sellgren, Kris

    2013-06-01

    We present 10 {mu}m-35 {mu}m Spitzer spectra of the interstellar medium in the Central Molecular Zone (CMZ), the central 210 pc Multiplication-Sign 60 pc of the Galactic center (GC). We present maps of the CMZ in ionic and H{sub 2} emission, covering a more extensive area than earlier spectroscopic surveys in this region. The radial velocities and intensities of ionic lines and H{sub 2} suggest that most of the H{sub 2} 0-0 S(0) emission comes from gas along the line-of-sight, as found by previous work. We compare diagnostic line ratios measured in the Spitzer Infrared Nearby Galaxies Survey to our data. Previous work shows that forbidden line ratios can distinguish star-forming galaxies from low-ionization nuclear emission-line regions (LINERs) and active galactic nuclei (AGNs). Our GC line ratios agree with star-forming galaxies and not with LINERs or AGNs.

  4. Black holes in galactic centers

    SciTech Connect

    Rees, M.J. )

    1990-11-01

    For more than 25 years astronomers have known that some galaxies also have a bright, compact central nucleus whose emission does not come from normal stars. The most extreme instances of these so-called active galactic nuclei are quasars, objects no larger than the solar system whose total radiation exceeds that of 100 billion stars. Quasars seem to represent a particularly agitated stage in the development of some galaxies. Astronomers generally agree that gravity powers active galactic nuclei. The best candidate for the central engine of quasars is a black hole--a collapsed body whose gravity is so great that nothing, including light, can escape from it. The discovery of black holes in galactic centers, exciting in its own right, could affect current ideas about the evolution of the universe. Quasars appeared when the universe was less than one billion years old, indicting that some galaxies had already developed dense central regions. The early appearance of quasars rules out many cosmological models, which predict that the formation of galaxies should require billions of years, and even raises problems for the reigning cold dark matter model. Recent measurements of the cosmic background radiation intensify the puzzle. Most theorists think that galaxies formed from density variations in the newborn universe. Yet measurements of the background radiation indicate that any variations were so slight that it is difficult to understand how they could have produced the structures seen today. Apart from its cosmological significance, the detection of massive black holes also could elucidate predictions of Einstein's theory of general relativity.

  5. Galactic Sodium from AGB Stars

    NASA Astrophysics Data System (ADS)

    Izzard, R. G.; Gibson, B. K.; Stancliffe, R. J.

    2007-11-01

    Galactic chemical evolution (GCE) models which include sodium from type II supernovae (SNe) alone underestimate the abundance of sodium in the interstellar medium by a factor of 2 to 3 over about 3 ridex in metallicity and predict a flat behavior in the evolution of riNafe at super-solar metallicities. Conversely, recent observations of stars with rifeh ˜ +0.4 suggest that riNafe increases at high metallicity. We have combined stellar evolution models of asymptotic giant branch (AGB) and Wolf-Rayet (WR) stars with the latest SN yields in an attempt to resolve these problems dots and have created many more.

  6. Jet Lag in Athletes

    PubMed Central

    Lee, Aaron; Galvez, Juan Carlos

    2012-01-01

    Context: Prolonged transmeridian air travel can impart a physical and emotional burden on athletes in jet lag and travel fatigue. Jet lag may negatively affect the performance of athletes. Study Type: Descriptive review. Evidence Acquisition: A Medline search for articles relating to jet lag was performed (1990-present), as was a search relating to jet lag and athletes (1983-January, 2012). The results were reviewed for relevance. Eighty-nine sources were included in this descriptive review. Results: Behavioral strategies are recommended over pharmacological strategies when traveling with athletes; pharmacological aides may be used on an individual basis. Strategic sleeping, timed exposure to bright light, and the use of melatonin are encouraged. Conclusions: There is strong evidence that mood and cognition are adversely affected by jet lag. Some measures of individual and team performance are adversely affected as well. PMID:23016089

  7. Description of Jet Breakup

    NASA Technical Reports Server (NTRS)

    Papageorgiou, Demetrios T.

    1996-01-01

    In this article we review recent results on the breakup of cylindrical jets of a Newtonian fluid. Capillary forces provide the main driving mechanism and our interest is in the description of the flow as the jet pinches to form drops. The approach is to describe such topological singularities by constructing local (in time and space) similarity solutions from the governing equations. This is described for breakup according to the Euler, Stokes or Navier-Stokes equations. It is found that slender jet theories can be applied when viscosity is present, but for inviscid jets the local shape of the jet at breakup is most likely of a non-slender geometry. Systems of one-dimensional models of the governing equations are solved numerically in order to illustrate these differences.

  8. Multiple jet study

    NASA Technical Reports Server (NTRS)

    Walker, R. E.; Kors, D. L.

    1973-01-01

    Test data is presented which allows determination of jet penetration and mixing of multiple cold air jets into a ducted subsonic heated mainstream flow. Jet-to-mainstream momentum flux ratios ranged from 6 to 60. Temperature profile data is presented at various duct locations up to 24 orifice diameters downstream of the plane of jet injection. Except for two configurations, all geometries investigated had a single row of constant diameter orifices located transverse to the main flow direction. Orifice size and spacing between orifices were varied. Both of these were found to have a significant effect on jet penetration and mixing. The best mixing of the hot and cold streams was achieved with duct height.

  9. Jet physics at CDF

    SciTech Connect

    Melese, P.

    1997-05-01

    We present high E{sub T} jet measurements from CDF at the Fermilab Tevatron Collider. The incfilusive jet cross section at {radical}s = 1800 GeV with {approximately} 5 times more data is compared to the published CDF results, preliminary D0 results, and next-to-leading order QCD predictions. The {summation}E{sub T} cross section is also compared to QCD predictions and the dijet angular distribution is used to place a limit on quark compositeness. The inclusive jet cross section at {radical}s = 630 GeV is compared with that at 1800 GeV to test the QCD predictions for the scaling of jet cross sections with {radical}s. Finally, we present momentum distributions of charged particles in jets and compare them to Modified Leading Log Approximation predictions.

  10. Centrifugally driven MHD-winds in active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Camenzind, M.

    1986-02-01

    When the prime mover in quasars is a supermassive magnetized and rapidly rotating object, the centrifugal instability can drive strong MHD-winds away from the equatorial region and extract angular momentum and rotational energy from the central object. The author shows that the necessary magnetic fields are produced, when this central object has been formed from the central part of a galactic disc. The position of the light cylinder for these objects requires a relativistic description for the corresponding MHD-winds. The author discusses the relevant equations for any stationary and axisymmetric spacetime and derives explicitly the position of the Alfvén point in the flow. He finds that centrifugally driven winds from supermassive objects carry a Poynting flux comparable with the kinetic energy flux. In addition, the magnetic field structure in the open wind zone requires the existence of a global current topology, which might explain the necessary magnetic collimation for escaping jet material. As a result, centrifugally driven winds from rapidly rotating supermassive objects carry the energy necessary to power the non-thermal emission of BLR AGNs and the material required to fuel the broad emission line clouds and the thermal jets.

  11. Implosive accretion and outbursts of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Lovelace, R. V. E.; Romanova, M. M.; Newman, W. I.

    1994-01-01

    A model and simulation code have been developed for time-dependent axisymmetric disk accretion onto a compact object including for the first time the influence of an ordered magnetic field. The accretion rate and radiative luminosity of the disk are naturally coupled to the rate of outflow of energy and angular momentum in magnetically driven (+/- z) winds. The magnetic field of the wind is treated in a phenomenological way suggested by self-consistent wind solutions. The radial accretion speed u(r, t) of the disk matter is shown to be the sum of the usual viscous contribution and a magnetic contribution proportional to r(exp 3/2)(B(sub p exp 2))/sigma, where B(sub p)(r,t) is the poloidal field threading the disk and sigma(r,t) is the disk's surface mass density. An enhancement or variation in B(sub p) at a large radial distance leads to the formation of a soliton-like structure in the disk density, temperature, and B-field which propagates implosively inward. The implosion gives a burst in the power output in winds or jets and a simultaneous burst in the disk radiation. The model is pertinent to the formation of discrete fast-moving components in jets observed by very long baseline interferometry. These components appear to originate at times of optical outbursts of the active galactic nucleus.

  12. Diffuse γ-Ray Emission from Misaligned Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Di Mauro, M.; Calore, F.; Donato, F.; Ajello, M.; Latronico, L.

    2014-01-01

    Active galactic nuclei (AGNs) with jets seen at small viewing angles are the most luminous and abundant objects in the γ-ray sky. AGNs with jets misaligned along the line of sight appear fainter in the sky but are more numerous than the brighter blazars. We calculate the diffuse γ-ray emission due to the population of misaligned AGNs (MAGNs) unresolved by the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope (Fermi). A correlation between the γ-ray luminosity and the radio-core luminosity is established and demonstrated to be physical by statistical tests, as well as compatible with upper limits based on Fermi-LAT data for a large sample of radio-loud MAGNs. We constrain the derived γ-ray luminosity function by means of the source-count distribution of the radio galaxies detected by the Fermi-LAT. We finally calculate the diffuse γ-ray flux due to the whole MAGN population. Our results demonstrate that MAGNs can contribute from 10% up to nearly the entire measured isotropic gamma-ray background. We evaluate a theoretical uncertainty on the flux of almost an order of magnitude.

  13. Diffuse γ-ray emission from misaligned active galactic nuclei

    SciTech Connect

    Di Mauro, M.; Donato, F.; Calore, F.; Ajello, M.; Latronico, L.

    2014-01-10

    Active galactic nuclei (AGNs) with jets seen at small viewing angles are the most luminous and abundant objects in the γ-ray sky. AGNs with jets misaligned along the line of sight appear fainter in the sky but are more numerous than the brighter blazars. We calculate the diffuse γ-ray emission due to the population of misaligned AGNs (MAGNs) unresolved by the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope (Fermi). A correlation between the γ-ray luminosity and the radio-core luminosity is established and demonstrated to be physical by statistical tests, as well as compatible with upper limits based on Fermi-LAT data for a large sample of radio-loud MAGNs. We constrain the derived γ-ray luminosity function by means of the source-count distribution of the radio galaxies detected by the Fermi-LAT. We finally calculate the diffuse γ-ray flux due to the whole MAGN population. Our results demonstrate that MAGNs can contribute from 10% up to nearly the entire measured isotropic gamma-ray background. We evaluate a theoretical uncertainty on the flux of almost an order of magnitude.

  14. The Outburst of the Blazar S5 0716+71 in 2011 October: Shock in a Helical Jet

    NASA Astrophysics Data System (ADS)

    Larionov, V. M.; Jorstad, S. G.; Marscher, A. P.; Morozova, D. A.; Blinov, D. A.; Hagen-Thorn, V. A.; Konstantinova, T. S.; Kopatskaya, E. N.; Larionova, L. V.; Larionova, E. G.; Troitsky, I. S.

    2013-05-01

    We present the results of optical (R band) photometric and polarimetric monitoring and Very Long Baseline Array (VLBA) imaging of the blazar S5 0716+714 along with Fermi γ-ray data during a multi-waveband outburst in 2011 October. We analyze total and polarized intensity images of the blazar obtained with the VLBA at 43 GHz during and after the outburst. Monotonic rotation of the linear polarization vector at a rate of >~ 50° per night coincided with a sharp maximum in γ-ray and optical flux. At the same time, within the uncertainties, a new superluminal knot appeared with an apparent speed of 21 ± 2c. The general multi-frequency behavior of the outburst can be explained within the framework of a shock wave propagating along a helical path in the blazar's jet.

  15. 3-D RPIC simulations of relativistic jets: Particle acceleration, magnetic field generation, and emission

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.-I.

    2006-01-01

    Nonthermal radiation observed from astrophysical systems containing (relativistic) jets and shocks, e.g., supernova remnants, active galactic nuclei (AGNs), gamma-ray bursts (GRBs), and Galactic microquasar systems usually have power-law emission spectra. Fermi acceleration is the mechanism usually assumed for the acceleration of particles in astrophysical environments. Recent PIC simulations using injected relativistic electron-ion (electro-positron) jets show that acceleration occurs within the downstream jet, rather than by the scattering of particles back and forth across the shock as in Fermi acceleration. Shock acceleration is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, other two-streaming instability, and the Weibel instability) created in the .shocks are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the jet head. The "jitter" radiation from deflected electrons has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants. We will review recent PIC simulations which show particle acceleration in jets.

  16. Supernova Nucleosynthesis and Galactic Evolution

    NASA Astrophysics Data System (ADS)

    Thielemann, F.-K.; Argast, D.; Brachwitz, F.; Hix, W. R.; Höflich, P.; Liebendörfer, M.; Martinez-Pinedo, G.; Mezzacappa, A.; Nomoto, K.; Panov, I.

    The understanding of the abundance evolution in the interstellar medium, and especially the enrichment of heavy elements, as a function of space and time reflects the history of star formation and the lifetimes of the diverse contributing stellar objects. Therefore, the understanding of the endpoints of stellar evolution is essential. These are mainly planetary nebulae and type II/Ib/Ic supernovae as evolutionary endpoints of single stars, but also events in binary systems can contribute, like e.g. supernovae of type Ia, novae and possibly X-ray bursts and neutron star or neutron star - black hole mergers. Despite many efforts, a full and self-consistent understanding of supernovae (the main contributors to nucleosynthesis in galaxies) is not existing, yet. However, observed spectra, light curves, radioactivities/decay gamma-rays and galactic evolution witness the composition of their ejecta and constrain model uncertainties. We focus on (i) neutrino-induced explosions for type II supernovae and the innermost ejected layers, (ii) electron captures in type Ia supernovae and neutron-rich Fe-group nuclei and finally (iii) galactic chemical evolution and possible r-process sites.

  17. Introduction to Galactic Chemical Evolution

    NASA Astrophysics Data System (ADS)

    Matteucci, Francesca

    2016-04-01

    In this lecture I will introduce the concept of galactic chemical evolution, namely the study of how and where the chemical elements formed and how they were distributed in the stars and gas in galaxies. The main ingredients to build models of galactic chemical evolution will be described. They include: initial conditions, star formation history, stellar nucleosynthesis and gas flows in and out of galaxies. Then some simple analytical models and their solutions will be discussed together with the main criticisms associated to them. The yield per stellar generation will be defined and the hypothesis of instantaneous recycling approximation will be critically discussed. Detailed numerical models of chemical evolution of galaxies of different morphological type, able to follow the time evolution of the abundances of single elements, will be discussed and their predictions will be compared to observational data. The comparisons will include stellar abundances as well as interstellar medium ones, measured in galaxies. I will show how, from these comparisons, one can derive important constraints on stellar nucleosynthesis and galaxy formation mechanisms. Most of the concepts described in this lecture can be found in the monograph by Matteucci (2012).

  18. Chemical complexity in galactic nuclei

    NASA Astrophysics Data System (ADS)

    Martin-Pintado, Jesus

    2007-12-01

    In recent years our knowledge of the chemical complexity in the nuclei of galaxies has dramatically changed. Recent observations of the nucleus of the Milky Way, of the starburst galaxy NGC253 and of the ultraluminous infrared galaxy (ULIRG) Arp220 have shown large abundance of complex organic molecules believed to be formed on grains. The Galactic center appears to be the largest repository of complex organic molecule like aldehydes and alcohols in the galaxy. We also measure large abundance of methanol in starburst galaxies and in ULIRGs suggesting that complex organic molecules are also efficiently produced in the central region of galaxies with strong star formation activity. From the systematic observational studies of molecular abundance in regions dominated by different heating processes like shocks, UV radiation, X-rays and cosmic rays in the center of the Milky Way, we are opening the possibility of using chemistry as a diagnostic tool to study the highly obscured regions of galactic centers. The templates found in the nucleus of the Milky Way will be used to establish the main mechanisms driving the heating and the chemistry of the molecular clouds in galaxies with different type of activity. The role of grain chemistry in the chemical complexity observed in the center of galaxies will be also briefly discussed.

  19. The Chandra Galactic Bulge Survey

    NASA Astrophysics Data System (ADS)

    Hynes, Robert I.; Jonker, P. G.; Bassa, C. G.; Nelemans, G.; Steeghs, D.; Torres, M. A. P.; Maccarone, T. J.; Greiss, S.; Clem, J.; Dieball, A.; Mikles, V. J.; Britt, C. T.; Gossen, L.; Collazzi, A. C.; Wijnands, R.; In't Zand, J. J. M.; Mendez, M.; Rea, N.; Kuulkers, E.; Ratti, E. M.; van Haaften, L. M.; Heinke, C.; Ozel, F.; Groot, P. J.; Verbunt, F.

    2012-01-01

    The Chandra Galactic Bulge Survey (GBS) is a shallow but wide survey of two approximately 6x1 degree strips of the Galactic Bulge about a degree above and below the plane. The survey by design targets regions where extinction and crowding are manageable and optical counterparts are accessible to detailed follow-up. Our strategy is based on going deep enough to detect quiescent low-mass X-ray binaries (LMXBs), but no deeper in order to avoid an excess of cataclysmic variables (CVs), while covering a large area to maximize the numbers of recovered objects. The primary goals of the GBS are to test predictions of binary evolutionary models through number counts and period distributions of detected sources, and to greatly expand the sample of LMXBs suitable for detailed optical follow-up including mass determination. We have identified 1234 X-ray sources most with optical counterparts, and expect these to be divided evenly between quiescent LMXBs, magnetic CVs, and R CVn stars, with smaller numbers of other source types. We are actively pursuing multiwavelength follow-up including searches for optical, infrared, and ultraviolet counterparts, measurement of variability, and optical spectroscopy. I will summarize the goals of the project and highlight some of the results obtained so far. This work is supported by the National Science Foundation under Grant No. AST-0908789.

  20. Galactic evolution of 7Li

    NASA Astrophysics Data System (ADS)

    Matteucci, Francesca

    2010-04-01

    Lithium represents a key element in cosmology, as it is one of the few nuclei synthesized during the Big Bang. The primordial abundance of 7Li allows us to impose constraints on the primordial nucleosynthesis and on the baryon density of the universe. However, 7Li is not only produced during the Big Bang but also during galactic evolution: measures of stellar Li in our Galaxy suggest an almost constant Li abundance (the so-called Spite plateau) at low metallicities and a subsequent increase in the disk stars, leading to a Li abundance in Population I stars higher by a factor of ten than in Population II stars. This means that there must exist several possible stellar sources of 7Li: asymptotic giant branch stars, supernovae, novae, red giant stars. 7Li is also partly produced in spallation processes while 6Li is entirely produced by such processes. All of these sources have been included in galactic chemical evolution models and constraints have been derived on the primordial 7Li and its evolution, as well on stellar models. I will review these models and their results and what we have learned about 7Li evolution. Some still open problems, such as the disagreement between the primordial 7Li abundance as derived by WMAP and as measured in Population II stars, and the uncertainties about the main sources of stellar 7Li will be discussed.

  1. The Bolocam Galactic Plane Survey

    NASA Technical Reports Server (NTRS)

    Glenn, Jason; Aguirre, James; Bally, John; Battersby, Cara; Bradley, Eric Todd; Cyganowski, Claudia; Dowell, Darren; Drosback, Meredith; Dunham, Miranda K.; Evans, Neal J., II; Ginsburg, Adam; Harvey, Paul; Rosolowsky, Erik; Schlingman, Wayne; Shirley, Yancy L.; Stringfellow, Guy S.; Walawender, Josh; Williams, Jonathan

    2009-01-01

    The Bolocam Galactic Plane Survey (BGPS) is a 1.1 millimeter continuum survey of the northern Galactic Plane made with Bolocam and the Caltech Submillimeter Observatory. The coverage totals 170 square degrees, comprised of a contiguous range from -10.5 deg is less than or equal to 90.5 deg, 0.5 deg is less than or equal to b is less than or equal to 0.5 deg, with extended coverage in b in selected regions, and four targeted regions in the outer Galaxy, including: IC1396, toward the Perseus arm at l is approximately 111 deg, W3/4/5, and Gem OB1. Depths of the maps range from 30 to 60 mJy beam (sup 1). Approximately 8,400 sources were detected and the maps and source catalog have been made publicly available. Millimeter-wave thermal dust emission reveals dense regions within molecular clouds, thus the BGPS serves as a database for studies of the dense interstellar medium and star formation within the Milky Way.

  2. Special Features of Galactic Dynamics

    NASA Astrophysics Data System (ADS)

    Efthymiopoulos, Christos; Voglis, Nikos; Kalapotharakos, Constantinos

    This is an introductory article to some basic notions and currently open problems of galactic dynamics. The focus is on topics mostly relevant to the so-called `new methods' of celestial mechanics or Hamiltonian dynamics, as applied to the ellipsoidal components of galaxies, i.e., to the elliptical galaxies and to the dark halos and bulges of disk galaxies. Traditional topics such as Jeans theorem, the role of a `third integral' of motion, Nekhoroshev theory, violent relaxation, and the statistical mechanics of collisionless stellar systems are first discussed. The emphasis is on modern extrapolations of these old topics. Recent results from orbital and global dynamical studies of galaxies are then shortly reviewed. The role of various families of orbits in supporting self-consistency, as well as the role of chaos in galaxies, are stressed. A description is then given of the main numerical techniques of integration of the N-body problem in the framework of stellar dynamics and of the results obtained via N-Body experiments. A final topic is the secular evolution and self-organization of galactic systems.

  3. Star formation in Galactic flows

    NASA Astrophysics Data System (ADS)

    Smilgys, Romas; Bonnell, Ian A.

    2016-06-01

    We investigate the triggering of star formation in clouds that form in Galactic scale flows as the interstellar medium passes through spiral shocks. We use the Lagrangian nature of smoothed particle hydrodynamics simulations to trace how the star-forming gas is gathered into self-gravitating cores that collapse to form stars. Large-scale flows that arise due to Galactic dynamics create shocks of the order of 30 km s-1 that compress the gas and form dense clouds (n > several × 102 cm-3) in which self-gravity becomes relevant. These large-scale flows are necessary for creating the dense physical conditions for gravitational collapse and star formation. Local gravitational collapse requires densities in excess of n > 103 cm-3 which occur on size scales of ≈1 pc for low-mass star-forming regions (M < 100 M⊙), and up to sizes approaching 10 pc for higher mass regions (M > 103 M⊙). Star formation in the 250 pc region lasts throughout the 5 Myr time-scale of the simulation with a star formation rate of ≈10-1 M⊙ yr-1 kpc-2. In the absence of feedback, the efficiency of the star formation per free-fall time varies from our assumed 100 per cent at our sink accretion radius to values of <10-3 at low densities.

  4. Observationally constraining the jet power extracted from spinning black holes

    NASA Astrophysics Data System (ADS)

    Markoff, Sera

    2014-03-01

    Black holes of all sizes, from stellar to supermassive, launch relativistic jets of magnetized plasma that can radiate across the entire electromagnetic spectrum. These flows originate from near-event horizon scales, where ordered magnetic fields threading the plasma likely play a defining role in their collimation and source of power. Depending on where the power is extracted from in the system, e.g., the inner accretion flow or the ergosphere of the black hole, there can be a markedly different dependence of observed power on black hole spin. Further complicating our ability to derive the spin from observations is the fact that the exact relationship between jet emission properties and spin will be very model dependent, and the fact that jets themselves evolve depending on the state of the accretion flow. I will present an overview of the current state of the art in understanding black hole jet observations and their relation to spin, as well as discuss some special cases like our Galactic center's supermassive black hole Sgr A*, and the evolving jets observed in X-ray binary systems.

  5. Galactic Variable Sky with EGRET and GLAST

    SciTech Connect

    Digel, S.W.; /SLAC

    2006-11-28

    The characteristics of the largely-unidentified Galactic sources of gamma rays that were detected by EGRET are reviewed. Proposed source populations that may have the correct spatial, spectral, luminosity, and variability properties to be the origins of the EGRET sources are also presented. Finally, the prospects for studying Galactic gamma-ray sources with the GLAST LAT are reviewed.

  6. A CATALOG OF GALACTIC INFRARED CARBON STARS

    SciTech Connect

    Chen, P. S.

    2012-02-15

    We collected almost all of the Galactic infrared carbon stars (IRCSs) from literature published up to the present to organize a catalog of 974 Galactic IRCSs in this paper. Some of their photometric properties in the near-, mid-, and far-infrared are discussed.

  7. Chemical and dynamical evolution of galactic discs

    NASA Technical Reports Server (NTRS)

    Clarke, Catherine J.

    1989-01-01

    The relative roles of star formation and viscously-induced radial flows in galactic disks are discussed. It is shown that the present-day distributions of stars, gas, and metals in galactic spirals need not reflect initial conditions but may instead indicate a cooperation between star forming and viscous processes over the disk lifetime.

  8. Tunable THz Generation by the Interaction of a Super-luminous Laser Pulse with Biased Semiconductor Plasma

    SciTech Connect

    Papadopoulos, K.; Zigler, A.

    2006-01-03

    Terahertz (THz) radiation is electromagnetic radiation in the range between several hundred and a few thousand GHz. It covers the gap between fast-wave electronics (millimeter waves) and optics (infrared). This spectral region offers enormous potential for detection of explosives and chemical/biological agents, non-destructive testing of non-metallic structural materials and coatings of aircraft structures, medical imaging, bio-sensing of DNA stretching modes and high-altitude secure communications. The development of these applications has been hindered by the lack of powerful, tunable THz sources with controlled waveform. The need for such sources is accentuated by the strong, but selective absorption of THz radiation during transmission through air with high vapor content. The majority of the current experimental work relies on time-domain spectroscopy using fast electrically biased photoconductive sources in conjunction with femto-second mode-locked Ti:Sapphire lasers. These sources known as Large Aperture Photoconductive Antennas (LAPA) have very limited tunability, relatively low upper bound of power and no bandwidth control. The paper presents a novel source of THz radiation known as Miniature Photoconductive Capacitor Array (MPCA). Experiments demonstrated tunability between .1 - 2 THz, control of the relative bandwidth {delta}f/f between .5-.01, and controlled pulse length and pulse waveform (temporal shape, chirp, pulse-to-pulse modulation etc.). Direct scaling from the current device indicates efficiency in excess of 30% at 1 THz with 1/f2 scaling at higher frequencies, peak power of 100 kW and average power between .1-1 W. The physics underlying the MPCA is the interaction of a super-luminous ionization front generated by the oblique incidence of a Ti:Sapphire laser pulse on a semiconductor crystal (ZnSe) biased with an alternating electrostatic field, similar to that of a frozen wave generator. It is shown theoretically and experimentally that the

  9. Jet Noise Suppression

    NASA Technical Reports Server (NTRS)

    Gliebe, P. R.; Brausch, J. F.; Majjigi, R. K.; Lee, R.

    1991-01-01

    The objectives of this chapter are to review and summarize the jet noise suppression technology, to provide a physical and theoretical model to explain the measured jet noise suppression characteristics of different concepts, and to provide a set of guidelines for evolving jet noise suppression designs. The underlying principle for all jet noise suppression devices is to enhance rapid mixing (i.e., diffusion) of the jet plume by geometric and aerothermodynamic means. In the case of supersonic jets, the shock-cell broadband noise reduction is effectively accomplished by the elimination or mitigation of the shock-cell structure. So far, the diffusion concepts have predominantly concentrated on jet momentum and energy (kinetic and thermal) diffusion, in that order, and have yielded better noise reduction than the simple conical nozzles. A critical technology issue that needs resolution is the effect of flight on the noise suppression potential of mechanical suppressor nozzles. A more thorough investigation of this mechanism is necessary for the successful development and design of an acceptable noise suppression device for future high-speed civil transports.

  10. Anisotropy and corotation of galactic cosmic rays.

    PubMed

    Amenomori, M; Ayabe, S; Bi, X J; Chen, D; Cui, S W; Danzengluobu; Ding, L K; Ding, X H; Feng, C F; Feng, Zhaoyang; Feng, Z Y; Gao, X Y; Geng, Q X; Guo, H W; He, H H; He, M; Hibino, K; Hotta, N; Hu, Haibing; Hu, H B; Huang, J; Huang, Q; Jia, H Y; Kajino, F; Kasahara, K; Katayose, Y; Kato, C; Kawata, K; Labaciren; Le, G M; Li, A F; Li, J Y; Lou, Y-Q; Lu, H; Lu, S L; Meng, X R; Mizutani, K; Mu, J; Munakata, K; Nagai, A; Nanjo, H; Nishizawa, M; Ohnishi, M; Ohta, I; Onuma, H; Ouchi, T; Ozawa, S; Ren, J R; Saito, T; Saito, T Y; Sakata, M; Sako, T K; Sasaki, T; Shibata, M; Shiomi, A; Shirai, T; Sugimoto, H; Takita, M; Tan, Y H; Tateyama, N; Torii, S; Tsuchiya, H; Udo, S; Wang, B; Wang, H; Wang, X; Wang, Y G; Wu, H R; Xue, L; Yamamoto, Y; Yan, C T; Yang, X C; Yasue, S; Ye, Z H; Yu, G C; Yuan, A F; Yuda, T; Zhang, H M; Zhang, J L; Zhang, N J; Zhang, X Y; Zhang, Y; Zhang, Yi; Zhaxisangzhu; Zhou, X X

    2006-10-20

    The intensity of Galactic cosmic rays is nearly isotropic because of the influence of magnetic fields in the Milky Way. Here, we present two-dimensional high-precision anisotropy measurement for energies from a few to several hundred teraelectronvolts (TeV), using the large data sample of the Tibet Air Shower Arrays. Besides revealing finer details of the known anisotropies, a new component of Galactic cosmic ray anisotropy in sidereal time is uncovered around the Cygnus region direction. For cosmic-ray energies up to a few hundred TeV, all components of anisotropies fade away, showing a corotation of Galactic cosmic rays with the local Galactic magnetic environment. These results have broad implications for a comprehensive understanding of cosmic rays, supernovae, magnetic fields, and heliospheric and Galactic dynamic environments. PMID:17053141

  11. Research Opportunities on board Virgin Galactic's SpaceShipTwo

    NASA Astrophysics Data System (ADS)

    Attenborough, S.; Pomerantz, W.; Stephens, K.

    2013-09-01

    Virgin Galactic is building the world's first commercial spaceline. Our suborbital spaceflight system, pictured in Figure 1, consists of two vehicles: WhiteKnightTwo (WK2) and SpaceShipTwo (SS2). WhiteKnightTwo is a four-engine, dual-fuselage jet aircraft capable of high-altitude heavy lift missions, including, but not limited to fulfilling its role as a mothership for SpaceShipTwo, an air-launched, suborbital spaceplane capable of routinely reaching an apogee up to 110 kilometers. In conjunction, these two vehicles allow access to space and to regions of the atmosphere ranging from the troposphere to the thermosphere; additionally, they provide extended periods of microgravity in a reliable and affordable way. SpaceShipTwo, with a payload capacity of up to 1,300 lbs. (~600 kg), features payload mounting interfaces that are compatible with standard architectures such as NASA Space Shuttle Middeck Lockers, Cargo Transfer Bags, and server racks, in addition to custom structures. With the standard interface, payloads are allowed access to the large 17 inch diameter cabin windows for external observations. Each dedicated research flight will be accompanied by a Virgin Galactic Flight Test Engineer, providing an opportunity for limited in-flight interaction. In addition, tended payloads - a flight that includes the researcher and his or her payload - are also an option. At a price point that is highly competitive with parabolic aircraft and sounding rockets and significantly cheaper than orbital flights, SpaceShipTwo is a unique platform that can provide frequent and repeatable research opportunities. Suborbital flights on SpaceShipTwo offer researchers several minutes of microgravity time and views of the external environment in the upper atmosphere and in outer space. In addition to serving as an important research platform in and of itself, SpaceShipTwo also offers researchers a means to test, iterate, and calibrate experiments designed for orbital platforms

  12. Efficient acceleration of relativistic magnetohydrodynamic jets

    NASA Astrophysics Data System (ADS)

    Toma, Kenji; Takahara, Fumio

    2013-08-01

    Relativistic jets in active galactic nuclei, galactic microquasars, and gamma-ray bursts are widely considered to be magnetohydrodynamically driven by black hole accretion systems, although the conversion mechanism from the Poynting into the particle kinetic energy flux is still open. Recent detailed numerical and analytical studies of global structures of steady, axisymmetric magnetohydrodynamic (MHD) flows with specific boundary conditions have not reproduced as rapid an energy conversion as required by observations. In order to find more suitable boundary conditions, we focus on the flow along a poloidal magnetic field line just inside the external boundary, without treating the transfield force balance in detail. We find some examples of the poloidal field structure and corresponding external pressure profile for an efficient and rapid energy conversion as required by observations, and that the rapid acceleration requires a rapid decrease of the external pressure above the accretion disk. We also clarify the differences between the fast magnetosonic point of the MHD flow and the sonic point of the de Laval nozzle.

  13. The Connection between the Radio Jet and the Gamma-ray Emission in the Radio Galaxy 3C 120

    NASA Astrophysics Data System (ADS)

    Casadio, Carolina; Gómez, José L.; Grandi, Paola; Jorstad, Svetlana G.; Marscher, Alan P.; Lister, Matthew L.; Kovalev, Yuri Y.; Savolainen, Tuomas; Pushkarev, Alexander B.

    2015-08-01

    We present the analysis of the radio jet evolution of the radio galaxy 3C 120 during a period of prolonged γ-ray activity detected by the Fermi satellite between 2012 December and 2014 October. We find a clear connection between the γ-ray and radio emission, such that every period of γ-ray activity is accompanied by the flaring of the millimeter very long baseline interferometry (VLBI) core and subsequent ejection of a new superluminal component. However, not all ejections of components are associated with γ-ray events detectable by Fermi. Clear γ-ray detections are obtained only when components are moving in a direction closer to our line of sight. This suggests that the observed γ-ray emission depends not only on the interaction of moving components with the millimeter VLBI core, but also on their orientation with respect to the observer. Timing of the γ-ray detections and ejection of superluminal components locate the γ-ray production to within ∼0.13 pc from the millimeter VLBI core, which was previously estimated to lie about 0.24 pc from the central black hole. This corresponds to about twice the estimated extension of the broad line region, limiting the external photon field and therefore suggesting synchrotron self Compton as the most probable mechanism for the production of the γ-ray emission. Alternatively, the interaction of components with the jet sheath can provide the necessary photon field to produced the observed γ-rays by Compton scattering.

  14. Quasi-static model of collimated jets and radio lobes. I. Accretion disk and jets

    SciTech Connect

    Colgate, Stirling A.; Li, Hui; Fowler, T. Kenneth; Pino, Jesse

    2014-07-10

    This is the first of a series of papers showing that when an efficient dynamo can be maintained by accretion disks around supermassive black holes in active galactic nuclei, it can lead to the formation of a powerful, magnetic helix that could explain both the observed radio jet/lobe structures on very large scales and ultimately the enormous power inferred from the observed ultra-high-energy cosmic rays. In this work, we solve a set of one-dimensional equations similar to the steady-state standard accretion disk model, but now including the large-scale magnetic fields giving rises to jets. We find that the frequently made assumption that large-scale fields are frozen into the disk is fundamentally incorrect, due to the necessity for current and the accreting mass to flow perpendicular to magnetic flux surfaces. A correct treatment greatly simplifies the calculations, yielding fields that leave the disk nearly vertically with magnetic profiles uniquely determined by disk angular momentum conservation. Representative solutions of the magnetic fields in different radial regions of the disk surface are given, and they determine the overall key features in the jet structure and its dissipation, which will be the subjects of later papers.

  15. Surprise Discovery of an X-Ray Jet

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-02-01

    Accreting, supermassive black holes that reside at galactic centers can power enormous jets, bright enough to be observed from vast distances away. The recent discovery of such a jet in X-ray wavelengths, without an apparent radio counterpart, has interesting implications for our understanding of how these distant behemoths shine.An Excess of X-RaysQuasar B3 0727+409 was serendipitously discovered to host an X-ray jet when a group of scientists, led by Aurora Simionescu (Institute of Space and Astronautical Sciences of the Japan Aerospace Exploration Agency), was examining Chandra observations of another object.The Chandra data reveal bright, compact, extended emission from the core of quasar B3 0727+409, with a projected length of ~100 kpc. There also appears to be further X-ray emission at a distance of ~280 kpc, which Simionescu and collaborators speculate may be the terminal hotspot of the jet.The quasar is located at a redshift of z=2.5 which makes this jet one of only a few high-redshift X-ray jets known to date. But what makes it especially intriguing is that, though the authors searched through both recent and archival radio observations of the quasar, the only radio counterpart they could find was a small feature close to the quasar core (which may be a knot in the jet). Unlike what is typical of quasar jets, there was no significant additional radio emission coinciding with the rest of the X-ray jet.Making Jets ShineX-ray-to-radio flux ratio vs. redshift, for X-ray quasar jets detected with Chandra. B3 0727+409 is shown in red (with and without the radio knot). The curves represent inverse-Compton scattering models with different magnetic field strengths. [Simionescu et al. 2016]What does this mean? To answer this, we must consider one of the outstanding questions about quasar jets: what radiation processes dominate their emission? One process possibly contributing to the X-ray emission is inverse-Compton scattering of low-energy cosmic microwave

  16. Angular Scaling In Jets

    SciTech Connect

    Jankowiak, Martin; Larkoski, Andrew J.; /SLAC

    2012-02-17

    We introduce a jet shape observable defined for an ensemble of jets in terms of two-particle angular correlations and a resolution parameter R. This quantity is infrared and collinear safe and can be interpreted as a scaling exponent for the angular distribution of mass inside the jet. For small R it is close to the value 2 as a consequence of the approximately scale invariant QCD dynamics. For large R it is sensitive to non-perturbative effects. We describe the use of this correlation function for tests of QCD, for studying underlying event and pile-up effects, and for tuning Monte Carlo event generators.

  17. A Temporal Analysis Indicates a Mildly Relativistic Compact Jet in GRS 1915+105

    NASA Astrophysics Data System (ADS)

    Punsly, Brian; Rodriguez, Jérôme

    2016-05-01

    Most of our knowledge of the radio morphology and kinematics of X-ray binary partially synchrotron self-absorbed compact jets (hereafter, compact jets) is based on the observations of GRS 1915+105, which has the most prominent compact jet. Yet, the compact jet bulk velocity, v, is poorly constrained in the literature, 0.07\\lt v/c\\lt 0.98. In spite of this uncertainty, compact jets are often unified with relativistic jets in active galactic nuclei. We estimated v as part of a temporal analysis of GRS 1915+105 jets in “high plateau states” (HPS). We define HPS as a state showing a hard X-ray spectrum and low level of long-term (\\gt 10 s) X-ray activity associated with 15 GHz flux density \\gt 70 mJy for \\gt 7 consecutive days. The radio emission is associated with compact jet emission. Two HPS were monitored at 15 GHz during their termination with e-folding times of 3.8 and 8.6 hr. We combine this timescale with the scale of the spatial variation of the linear source of a Very Large Baseline Array image preceding the fade of one of these HPS in order to estimate the jet speed. Our assumption that the reduction in radio emissivity propagates as an approximate discontinuity down the HPS jet (leaving a weak jet in its wake) indicates 0.17\\lt v/c\\lt 0.43. This agrees closely with the only other existing v estimates that are derived directly from radio images, jet asymmetry produced by Doppler enhancement.

  18. DOUBLE-PEAKED NARROW-LINE ACTIVE GALACTIC NUCLEI. II. THE CASE OF EQUAL PEAKS

    SciTech Connect

    Smith, K. L.; Shields, G. A.; Salviander, S.; Stevens, A. C.; Rosario, D. J. E-mail: shields@astro.as.utexas.edu E-mail: acs0196@mail.utexas.edu

    2012-06-10

    Active galactic nuclei (AGNs) with double-peaked narrow lines (DPAGNs) may be caused by kiloparsec-scale binary AGNs, bipolar outflows, or rotating gaseous disks. We examine the class of DPAGNs in which the two narrow-line components have closely similar intensity as being especially likely to involve disks or jets. Two spectroscopic indicators support this likelihood. For DPAGNs from Smith et al., the 'equal-peaked' objects (EPAGNs) have [Ne V]/[O III]ratios lower than for a control sample of non-double-peaked AGNs. This is unexpected for a pair of normal AGNs in a galactic merger, but may be consistent with [O III] emission from a rotating ring with relatively little gas at small radii. Also, [O III]/H{beta} ratios of the redshifted and blueshifted systems in the EPAGN are more similar to each other than in a control sample, suggestive of a single ionizing source and inconsistent with the binary interpretation.

  19. Is the `disappearance' of low-frequency QPOs in the power spectra a general phenomenon for Disk-Jet symbiosis ?

    NASA Astrophysics Data System (ADS)

    Nandi, A.; Radhika, D.; Seetha, S.

    One of the best possible ways to look for disk-Jet symbiosis in galactic Black Holes is to study the correlation between X-ray and radio emissions. Beyond this study, is there any alternative way to trace the symbiosis? To answer, we investigated the X-ray features of few black hole candidates based on the archival data of PCA/RXTE. We found evidences of `disappearance' of QPOs in the power density spectra and subsequent spectral softening of the energy spectra during the radio flares (i.e., `transient' jets). We delve deep into the nature of the accretion dynamics to understand the disk-jet symbiosis.

  20. Quark-novae Occurring in Massive Binaries : A Universal Energy Source in Superluminous Supernovae with Double-peaked Light Curves

    NASA Astrophysics Data System (ADS)

    Ouyed, Rachid; Leahy, Denis; Koning, Nico

    2016-02-01

    A quark-nova (QN; the sudden transition from a neutron star into a quark star), which occurs in the second common envelope (CE) phase of a massive binary, gives excellent fits to superluminous, hydrogen-poor, supernovae (SLSNe) with double-peaked light curves, including DES13S2cmm, SN 2006oz, and LSQ14bdq (http://www.quarknova.ca/LCGallery.html). In our model, the H envelope of the less massive companion is ejected during the first CE phase, while the QN occurs deep inside the second, He-rich, CE phase after the CE has expanded in size to a radius of a few tens to a few thousands of solar radii; this yields the first peak in our model. The ensuing merging of the quark star with the CO core leads to black hole formation and accretion, explaining the second long-lasting peak. We study a sample of eight SLSNe Ic with double-humped light curves. Our model provides good fits to all of these, with a universal explosive energy of 2 × 1052 erg (which is the kinetic energy of the QN ejecta) for the first hump. The late-time emissions seen in iPTF13ehe and LSQ14bdq are fit with a shock interaction between the outgoing He-rich (i.e., second) CE and the previously ejected H-rich (i.e., first) CE.

  1. The tendency analytical equations of stable nuclides and the superluminal velocity motion laws of matter in geospace

    NASA Astrophysics Data System (ADS)

    Yan, Kun

    In this paper, by discussing the existent distribution trend of relation for the proton number and the neutron number to be included by the stable nuclides in geospace, the tendency analytical method and it's periodic distribution equation forms of the stable nuclides are expressed at first. Then the comparison result between the curve of the theoretical equation analysis and the points of the experimental distribution data of the stable nuclides in geospace are given. Further more, the stable nuclide limit and the chemical element limit for the chemical element periodic table are given, and the possible corresponding relation equation with the positron-particle annihilation is expressed, which includes the estimation of the order of the static mass to be situated nearby at the electron neutrino structural dimension. Subsequently, by forming two hypotheses about the energy state of vacuum matter, and basing on the equivalent Binet equation, the mass equations and the energy equations of the partial moving with light-velocity or superluminal-velocity motion fusing with the results of Einstein special relativity are expressed. As inference, the possible corresponding relations between the mass equations and energy equations with the dark matter and dark energy are discussed tentatively.

  2. Galactic Center Fly-in

    NASA Astrophysics Data System (ADS)

    Hanson, A.; Fu, C.-W.; Li, Y.; Frisch, P. C.

    2006-06-01

    Beginning with the familiar constellations of the night sky, we present a multispectral zoom into the core of the Milky Way Galaxy. After traveling over seven orders of magnitude in spatial scale, we discover the violent phenomena occurring within one light year of the Black Hole at the Galactic Core. This animated zoom includes data with wavelengths from radio to X-ray, and is based entirely on data or models that have been aligned at all spatial scales in order to provide a single continuous visual trip into the Center of the Milky Way Galaxy. The visualization challenge has been to align and choreograph data acquired over a wide range of wavelength and spatial scales, and obtain a new scientific as well as educational perspective of the dense core of our Galaxy.

  3. Galactic Interactions and Dark Matter

    NASA Astrophysics Data System (ADS)

    Willig, T.; Storrs, A.

    2005-12-01

    In studying galactic interactions is it possible with present instrumentation to find evidence of dark matter within these interactions? The present theory is that dark matter and its gravitational force is what accounts for much of spiral galaxy rotation curves. If this is true, we should be able to find evidence of dark matter when two galaxies (one being a spiral galaxy) interact. Several pairs of interacting galaxies in various stages of interaction will be studied. In addition, several non interacting spiral galaxies will be studied for comparisons. We present analysis of a variety of archival imaging data from radio maps through x-ray images in an attempt to observe the effects of dark matter in galaxy interactions.

  4. Star formation across galactic environments

    NASA Astrophysics Data System (ADS)

    Young, Jason

    I present here parallel investigations of star formation in typical and extreme galaxies. The typical galaxies are selected to be free of active galactic nuclei (AGN), while the extreme galaxies host quasars (the most luminous class of AGN). These two environments are each insightful in their own way; quasars are among the most violent objects in the universe, literally reshaping their host galaxies, while my sample of AGN-free star-forming galaxies ranges from systems larger than the Milky Way to small galaxies which are forming stars at unsustainably high rates. The current paradigm of galaxy formation and evolution suggests that extreme circumstances are key stepping stones in the assembly of galaxies like our Milky Way. To test this paradigm and fully explore its ramifications, this dual approach is needed. My sample of AGN-free galaxies is drawn from the KPNO International Spectroscopic Survey. This Halpha-selected, volume-limited survey was designed to detect star-forming galaxies without a bias toward continuum luminosity. This type of selection ensures that this sample is not biased toward galaxies that are large or nearby. My work studies the KISS galaxies in the mid- and far-infrared using photometry from the IRAC and MIPS instruments aboard the Spitzer Space Telescope. These infrared bands are particularly interesting for star formation studies because the ultraviolet light from young stars is reprocessed into thermal emission in the far-infrared (24mum MIPS) by dust and into vibrational transitions features in the mid-infrared (8.0mum IRAC) by polycyclic aromatic hydrocarbons (PAHs). The work I present here examines the efficiencies of PAH and thermal dust emission as tracers of star-formation rates over a wide range of galactic stellar masses. I find that the efficiency of PAH as a star-formation tracer varies with galactic stellar mass, while thermal dust has a highly variable efficiency that does not systematically depend on galactic stellar mass

  5. The galactic model of GRBs

    SciTech Connect

    Colgate, S.A.; Li, H.

    1997-09-01

    The galactic model of gamma ray bursts (GRBs) is based upon the observed production of soft gamma ray repeaters (SGRs) in the galaxy and the consequences of a reasonable model to explain them. In this view GRBs are the long term result of the burn-out conditions of the SGRs in this and in other galaxies. A delay of {approximately} 30 million years before GRBs are being actively produced can be understood as the time required for the ejected matter during the SGR phase to cool, condense, and form planetesimals that are eventually captured by the central neutron star. The amount of disk matter and the interaction between each GRB and the disk determine the rate of burst production and turn-off time of GRBs. The x-ray afterglow as well as optical emission is derived from x-ray fluorescence and ionization of previously ablated matter.

  6. Carbon and Oxygen Galactic Gradients

    NASA Astrophysics Data System (ADS)

    Carigi, L.; Peimbert, M.; Esteban, C.; García-Rojas, J.

    2006-06-01

    A chemical evolution model of the Galaxy has been computed to reproduce the O/H gradients from Galactic HII regions. This model solves the C enrichment problem because it fits the C/H and C/O gradients and the C and O histories of the solar vicinity. The model is based on C yields dependent on metallicity (Z) owing to stellar winds. The C yields of massive stars (MS) increase with Z and those of low and intermediate mass stars (LIMS) decrease with Z. An important result is that the fraction of carbon in the interstellar medium (ISM) due to MS and LIMS is strongly dependent on Z of the ISM, therefore, that fraction depends on time and on the Galactocentric distance. At present and in the solar vicinity about half of the C in the interstellar medium has been produced by MS and half by LIMS.

  7. Theory of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Shields, G. A.

    1986-01-01

    The involvement of accretion disks around supermassive black holes in the theory of active galactic nuclei (AGN) is discussed. The physics of thin and thick accretion disks is discussed and the partition between thermal and nonthermal energy production in supermassive disks is seen as uncertain. The thermal limit cycle may operate in supermassive disks (Shields, 1985), with accumulation of gas in the disk for periods of 10 to the 4th to 10 to the 7th years, punctuated by briefer outbursts during which the mass is rapidly transferred to smaller radii. An extended X-ray source in AGN is consistent with observations (Tennant and Mushotsky, 1983), and a large wind mass loss rate exceeding the central accretion rate means that only a fraction of the mass entering the disk will reach the central object; the rest being lost to the wind. Controversy in the relationship between the broad lines and the disk is also discussed.

  8. Detecting galactic binaries with LISA

    NASA Astrophysics Data System (ADS)

    Cornish, Neil J.; Porter, Edward K.

    2005-09-01

    One of the main sources of gravitational waves for the LISA space-borne interferometer is galactic binary systems. The waveforms for these sources are represented by eight parameters of which four are intrinsic and four are extrinsic to the system. Geometrically, these signals exist in an 8D parameter space. By calculating the metric tensor on this space, we calculate the number of templates needed to search for such sources. We show in this study that below a particular monochromatic frequency of f0 ~ 1.6 × 10-3 Hz we can ignore one of the intrinsic parameters and search over a 7D space. Beyond this frequency, we have a change in dimensionality of the parameter space from 7 to 8 dimensions. This sudden change in dimensionality results in a change in the scaling of template number as a function of the monochromatic frequency from ~f1.250 to ~f5.880.

  9. Solar modulation of galactic antiprotons

    NASA Technical Reports Server (NTRS)

    Perko, J. S.

    1987-01-01

    Galactic antiproton data of current interest lie in an energy regime heavily influenced by solar modulation. Correcting for it needs to be done more carefully than it has been in the past. The well-known force-field analytic approximation of the spherically-symmetric, steady-state, cosmic-ray transport equation is applied in order to account for modulation down to at least 100 MeV. A sample solution which applies to the currently available antiproton data set (1979-80), and can be used to accurately modulate any possible interstellar antiproton spectrum, is given. The solution is easily adapted for comparison to future measurements. It also shows that boosting the low-energy (less than 600 MeV) side of the interstellar antiproton spectrum will not affect the low-energy spectrum at 1 AU, due to strong adiabatic deceleration during that time.

  10. Dilution jet mixing program

    NASA Technical Reports Server (NTRS)

    Srinivasan, R.; Coleman, E.; Johnson, K.

    1984-01-01

    Parametric tests were conducted to quantify the mixing of opposed rows of jets (two-sided injection) in a confined cross flow. Results show that jet penetrations for two sided injections are less than that for single-sided injections, but the jet spreading rates are faster for a given momentum ratio and orifice plate. Flow area convergence generally enhances mixing. Mixing characteristics with asymmetric and symmetric convergence are similar. For constant momentum ratio, the optimum S/H(0) with in-line injections is one half the optimum value for single sided injections. For staggered injections, the optimum S/H(0) is twice the optimum value for single-sided injection. The correlations developed predicted the temperature distributions within first order accuracy and provide a useful tool for predicting jet trajectory and temperature profiles in the dilution zone with two-sided injections.

  11. Jet lag prevention

    MedlinePlus

    ... your internal clock before you travel. While in flight: DO NOT sleep unless it matches the bedtime ... decrease jet lag. If you will be in flight during the bedtime of your destination, take some ...

  12. Counterflowing Jet Subsystem Design

    NASA Technical Reports Server (NTRS)

    Farr, Rebecca; Daso, Endwell; Pritchett, Victor; Wang, Ten-See

    2010-01-01

    A counterflowing jet design (a spacecraft and trans-atmospheric subsystem) employs centrally located, supersonic cold gas jets on the face of the vehicle, ejecting into the oncoming free stream. Depending on the supersonic free-stream conditions and the ejected mass flow rate of the counterflowing jets, the bow shock of the vehicle is moved upstream, further away from the vehicle. This results in an increasing shock standoff distance of the bow shock with a progressively weaker shock. At a critical jet mass flow rate, the bow shock becomes so weak that it is transformed into a series of compression waves spread out in a much wider region, thus significantly modifying the flow that wets the outer surfaces, with an attendant reduction in wave and skin friction drag and aerothermal loads.

  13. Microlensing by the galactic bar

    NASA Technical Reports Server (NTRS)

    Zhao, Hongsheng; Spergel, David N.; Rich, R. Michael

    1995-01-01

    We compute the optical depth and duration distribution of microlensing events towrd Baade's window in a model composed of a Galactic disk and a bar. The bar model is a self-consistent dynamical model built out of individual orbits that has been populated to be consistent with the COBE maps of the Galaxy and kinematic observations of the Galactic bulge. We find that most of the lenses are in the bulge with a line-of-sight distance 6.25 kpc (adopting R(sub 0) = 8 kpc). The microlensing optical depth of a 2 x 10(exp 10) solar mass bar plus a truncated disk is (2.2 +/- 0.45) x 10(exp -6), consistent with the large optical depth (3.2 +/- 1.2) x 10(exp -6) found by Udalski et al. (1994). This model optical depth is enhanced over the predictions of axisymmetric models by Kiraga & Paczynski (1994) by slightly more than a factor of 2, since the bar is elongated along the line of sight. The large Einstein radius and small transverse velocity dispersion also predict a longer event duration in the self-consistent bar model than in the Kiraga-Paczynski model. The event rate and duration distribution also depend on the lower mass cutoff of the lens mass function. With a 0.1 solar mass cutoff, five to seven events (depending on the contribution of disk lenses) with a logarithmic mean duration of 20 days are expected for the Optical Gravitational Lensing Experiment (OGLE) according to our model, while Udalski et al. (1994) observed nine events with durations from 8 to 62 days. On the other hand, if most of the lenses are brown dwarfs, our model predicts too many short-duration events. A Kolmogorov-Smirnov test finds only 7% probability for the model with 0.01 solar mass cutoff to be consistent with current data.

  14. PREFACE: Galactic Center Workshop 2006

    NASA Astrophysics Data System (ADS)

    Schödel, Rainer; Bower, Geoffrey C.; Muno, Michael P.; Nayakshin, Sergei; Ott, Thomas

    2006-12-01

    We are pleased to present the proceedings from the Galactic Center Workshop 2006—From the Center of the Milky Way to Nearby Low-Luminosity Galactic Nuclei. The conference took place in the Physikzentrum, Bad Honnef, Germany, on 18 to 22 April 2006. It is the third workshop of this kind, following the Galactic Center Workshops held 1998 in Tucson, Arizona, and 2002 in Kona, Hawaii. The center of the Milky Way is the only galactic nucleus of a fairly common spiral galaxy that can be observed in great detail. With a distance of roughly 8 kpc, the resolution that can currently be achieved is of the order 40 mpc/8000 AU in the X-ray domain, 2 mpc/400 AU in the near-infrared, and 0.01 mpc/1 AU with VLBI in the millimeter domain. This is two to three orders of magnitude better than for any comparable nearby galaxy, making thus the center of the Milky Way thetemplate object for the general physical interpretation of the phenomena that can be observed in galactic nuclei. We recommend the summary article News from the year 2006 Galactic Centre workshopby Mark Morris and Sergei Nayakshin—who also gave the summary talk of the conference—to the reader in order to obtain a first, concise overview of the results presented at the workshop and some of the currently most exciting—and debated—developments in recent GC research. While the workshops held in 1998 and 2002 were dedicated solely to the center of the Milky Way, the field of view was widened in Bad Honnef to include nearby low-luminosity nuclei. This new feature followed the realization that not only the GC serves as a template for understanding extragalactic nuclei, but that the latter can also provide the context and broader statistical base for understanding the center of our Milky Way. This concerns especially the accretion and emission processes related to the Sagittarius A*, the manifestation of the super massive black hole in the GC, but also the surprising observation of great numbers of massive, young

  15. The Galactic evolution of phosphorus

    NASA Astrophysics Data System (ADS)

    Caffau, E.; Bonifacio, P.; Faraggiana, R.; Steffen, M.

    2011-08-01

    Context. As a galaxy evolves, its chemical composition changes and the abundance ratios of different elements are powerful probes of the underlying evolutionary processes. Phosphorous is an element whose evolution has remained quite elusive until now, because it is difficult to detect in cool stars. The infrared weak P i lines of the multiplet 1, at 1050-1082 nm, are the most reliable indicators of the presence of phosphorus. The availability of CRIRES at VLT has permitted access to this wavelength range in stellar spectra. Aims: We attempt to measure the phosphorus abundance of twenty cool stars in the Galactic disk. Methods: The spectra are analysed with one-dimensional model-atmospheres computed in local thermodynamic equilibrium (LTE). The line formation computations are performed assuming LTE. Results: The ratio of phosphorus to iron behaves similarly to sulphur, increasing towards lower metallicity stars. Its ratio with respect to sulphur is roughly constant and slightly larger than solar, [P/S] = 0.10 ± 0.10. Conclusions: We succeed in taking an important step towards the understanding of the chemical evolution of phosphorus in the Galaxy. However, the observed rise in the P/Fe abundance ratio is steeper than predicted by Galactic chemical evolution model developed by Kobayashi and collaborators. Phosphorus appears to evolve differently from the light odd-Z elements sodium and aluminium. The constant value of [P/S] with metallicity implies that P production is insensitive to the neutron excess, thus processes other than neutron captures operate. We suggest that proton captures on 30Si and α captures on 27Al are possibilities to investigate. We see no clear distinction between our results for stars with planets and stars without any detected planet. Based on observations obtained with the CRIRES spectrograph at ESO-VLT Antu 8.2 m telescope at Paranal, Programme 386.D-0130, P.I. E. Caffau.

  16. Jets in hadronic reactions

    SciTech Connect

    Paige, F.E.

    1983-01-01

    Recent experimental data on the properties of jets in hadronic reactions are reviewed and compared with theoretical expectations. Jets are clearly established as the dominant process for high E/sub T/ events in hadronic reactions. The cross section and the other properties of these events are in qualitative and even semiquantitative agreement with expectations based on perturbative QCD. However, we can not yet make precise tests of QCD, primarily because there are substantial uncertainties in the theoretical calculations. 45 references. (WHK)

  17. Clouds Dominate the Galactic Halo

    NASA Astrophysics Data System (ADS)

    2003-01-01

    Using the exquisite sensitivity of the National Science Foundation's Robert C. Byrd Green Bank Telescope (GBT), astronomer Jay Lockman of the National Radio Astronomy Observatory (NRAO) in Green Bank, W. Va., has produced the best cross-section ever of the Milky Way Galaxy's diffuse halo of hydrogen gas. This image confirms the presence of discrete hydrogen clouds in the halo, and could help astronomers understand the origin and evolution of the rarefied atmosphere that surrounds our Galaxy. Lockman presented his findings at the American Astronomical Society meeting in Seattle, WA. Hydrogen Clouds Graphic Artist's Rendering of the Milky Way (background) with insert showing GBT image of cross-section of neutral atomic Hydrogen Credit: Kirk Woellert/National Science Foundation Patricia Smiley, NRAO. "The first observations with the Green Bank Telescope suggested that the hydrogen in the lower halo, the transition zone between the Milky Way and intergalactic space, is very clumpy," said Lockman. "The latest data confirm these results and show that instead of trailing away smoothly from the Galactic plane, a significant fraction of the hydrogen gas in the halo is concentrated in discrete clouds. There are even some filaments." Beyond the star-filled disk of the Milky Way, there exists an extensive yet diffuse halo of hydrogen gas. For years, astronomers have speculated about the origin and structure of this gas. "Even the existence of neutral hydrogen in the halo has been somewhat of a puzzle," Lockman remarked. "Unlike the Earth's atmosphere, which is hot enough to hold itself up against the force of gravity, the hydrogen in the halo is too cool to support itself against the gravitational pull of the Milky Way." Lockman points out that some additional factor has to be involved to get neutral hydrogen to such large distances from the Galactic plane. "This force could be cosmic rays, a supersonic wind, the blast waves from supernovae, or something we have not thought of

  18. PREFACE: Galactic Center Workshop 2006

    NASA Astrophysics Data System (ADS)

    Schödel, Rainer; Bower, Geoffrey C.; Muno, Michael P.; Nayakshin, Sergei; Ott, Thomas

    2006-12-01

    We are pleased to present the proceedings from the Galactic Center Workshop 2006—From the Center of the Milky Way to Nearby Low-Luminosity Galactic Nuclei. The conference took place in the Physikzentrum, Bad Honnef, Germany, on 18 to 22 April 2006. It is the third workshop of this kind, following the Galactic Center Workshops held 1998 in Tucson, Arizona, and 2002 in Kona, Hawaii. The center of the Milky Way is the only galactic nucleus of a fairly common spiral galaxy that can be observed in great detail. With a distance of roughly 8 kpc, the resolution that can currently be achieved is of the order 40 mpc/8000 AU in the X-ray domain, 2 mpc/400 AU in the near-infrared, and 0.01 mpc/1 AU with VLBI in the millimeter domain. This is two to three orders of magnitude better than for any comparable nearby galaxy, making thus the center of the Milky Way thetemplate object for the general physical interpretation of the phenomena that can be observed in galactic nuclei. We recommend the summary article News from the year 2006 Galactic Centre workshopby Mark Morris and Sergei Nayakshin—who also gave the summary talk of the conference—to the reader in order to obtain a first, concise overview of the results presented at the workshop and some of the currently most exciting—and debated—developments in recent GC research. While the workshops held in 1998 and 2002 were dedicated solely to the center of the Milky Way, the field of view was widened in Bad Honnef to include nearby low-luminosity nuclei. This new feature followed the realization that not only the GC serves as a template for understanding extragalactic nuclei, but that the latter can also provide the context and broader statistical base for understanding the center of our Milky Way. This concerns especially the accretion and emission processes related to the Sagittarius A*, the manifestation of the super massive black hole in the GC, but also the surprising observation of great numbers of massive, young

  19. Horizon-scale Lepton Acceleration in Jets: Explaining the Compact Radio Emission in M87

    NASA Astrophysics Data System (ADS)

    Broderick, Avery E.; Tchekhovskoy, Alexander

    2015-08-01

    It has now become clear that the radio jet in the giant elliptical galaxy M87 must turn on very close to the black hole. This implies the efficient acceleration of leptons within the jet at scales much smaller than feasible by the typical dissipative events usually invoked to explain jet synchrotron emission. Here we show that the stagnation surface, the separatrix between material that falls back into the black hole and material that is accelerated outward forming the jet, is a natural site of pair formation and particle acceleration. This occurs via an inverse Compton pair catastrophe driven by unscreened electric fields within the charge-starved region about the stagnation surface and substantially amplified by a post-gap cascade. For typical estimates of the jet properties in M87, we find excellent quantitive agreement between the predicted relativistic lepton densities and those required by recent high-frequency radio observations of M87. This mechanism fails to adequately fill a putative jet from Sagittarius A* with relativistic leptons, which may explain the lack of an obvious radio jet in the Galactic center. Finally, this process implies a relationship between the kinetic jet power and the gamma-ray luminosity of blazars, produced during the post-gap cascade.

  20. Jets at lowest mass accretion rates

    NASA Astrophysics Data System (ADS)

    Maitra, Dipankar; Cantrell, Andrew; Markoff, Sera; Falcke, Heino; Miller, Jon; Bailyn, Charles

    2011-02-01

    We present results of recent observations and theoretical modeling of data from black holes accreting at very low luminosities (L/LEdd <~ 10-8). We discuss our newly developed time-dependent model for episodic ejection of relativistic plasma within a jet framework, and a successful application of this model to describe the origin of radio flares seen in Sgr A*, the Galactic center black hole. Both the observed time lags and size-frequency relationships are reproduced well by the model. We also discuss results from new Spitzer data of the stellar black hole X-ray binary system A0620-00. Complemented by long term SMARTS monitoring, these observations indicate that once the contribution from the accretion disk and the donor star are properly included, the residual mid-IR spectral energy distribution of A0620-00 is quite flat and consistent with a non-thermal origin. The results above suggest that a significant fraction of the observed spectral energy distribution originating near black holes accreting at low luminosities could result from a mildly relativistic outflow. The fact that these outflows are seen in both stellar-mass black holes as well as in supermassive black holes at the heart of AGNs strengthens our expectation that accretion and jet physics scales with mass.

  1. VLBA Reveals Formation Region of Giant Cosmic Jet

    NASA Astrophysics Data System (ADS)

    1999-10-01

    , Italy, Finland, Sweden and Spain. The signals from all the telescopes were combined to produce an image with extremely great resolution, or ability to discern fine detail. The combination of radio telescopes formed, in effect, a telescope the size of the Earth. In addition to using NSF's VLBA, Junor received financial support for his research from the NSF. Biretta and Livio received support from NASA. Both radio observations with the VLBA and optical observations with the Hubble Space Telescope have measured the motions of concentrations of material in M87's jets, and have shown the material to be moving at apparent speeds greater than that of light. This "superluminal" motion is a geometric illusion created by material moving nearly, but under, the speed of light, but in a direction somewhat toward the Earth. M87 also is known by radio astronomers as Virgo A, the strongest emitter of radio waves in the constellation Virgo. The galaxy was discovered by the French astronomer Charles Messier in 1781. The jet was first seen in 1918 by Lick Observatory astronomer Heber Curtis, who described it as "a curious straight ray." The galaxy's radio emission was first observed by Australian astronomers in 1948/49. M87 is the largest of thousands of galaxies in the Virgo Cluster of galaxies. The Local Group of galaxies, of which our own Milky Way is a member, is in the outskirts of the Virgo Cluster. The VLA and VLBA are instruments of the National Radio Astronomy Observatory, a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc. The Space Telescope Science Institute is operated by the Association of Universities for Research in Astronomy, Inc. for NASA, under contract with NASA's Goddard Space Flight Center, Greenbelt, MD. ### CAPTION for Radio Images: Radio images of the galaxy M87 at different scales show, top left, giant, bubble-like structures where radio emission is thought to be powered by the jets from the galaxy

  2. Pitch angle of galactic spiral arms

    SciTech Connect

    Michikoshi, Shugo; Kokubo, Eiichiro E-mail: kokubo@th.nao.ac.jp

    2014-06-01

    One of the key parameters that characterizes spiral arms in disk galaxies is a pitch angle that measures the inclination of a spiral arm to the direction of galactic rotation. The pitch angle differs from galaxy to galaxy, which suggests that the rotation law of galactic disks determines it. In order to investigate the relation between the pitch angle of spiral arms and the shear rate of galactic differential rotation, we perform local N-body simulations of pure stellar disks. We find that the pitch angle increases with the epicycle frequency and decreases with the shear rate and obtain the fitting formula. This dependence is explained by the swing amplification mechanism.

  3. DETERMINING THE OPTIMAL LOCATIONS FOR SHOCK ACCELERATION IN MAGNETOHYDRODYNAMICAL JETS

    SciTech Connect

    Polko, Peter; Markoff, Sera; Meier, David L.

    2010-11-10

    Observations of relativistic jets from black hole systems suggest that particle acceleration often occurs at fixed locations within the flow. These sites could be associated with critical points that allow the formation of standing shock regions, such as the magnetosonic modified fast point (MFP). Using the self-similar formulation of special relativistic magnetohydrodynamics by Vlahakis and Koenigl, we derive a new class of flow solutions that are both relativistic and cross the MFP at a finite height. Our solutions span a range of Lorentz factors up to at least 10, appropriate for most jets in X-ray binaries and active galactic nuclei, and a range in injected particle internal energy. A broad range of solutions exists, which will allow the eventual matching of these scale-free models to physical boundary conditions in the analysis of observed sources.

  4. Hydrodynamic stability of jets produced by mass accreting systems

    NASA Technical Reports Server (NTRS)

    Hardee, P. E.

    1982-01-01

    The existing model for pulsed X-ray emission from the source Hercules X-1 is reviewed. A necessary part of this model is a processing accretion disk which turns the source on and off with 35 day cycle. It is usually assumed that precession of the primary star in this binary system, Hz Hercules, slaves the disk to its precession rate. This model can account for the system behavior in a qualitative manner. Precession of Hz Hercules with 35 day period requires precession of the binary orbit. Pulse arrival times from Herc X-1 have been analyzed for orbital precession. The inclusion of precession does not significantly improve the results obtained assuming a non-precessing orbit. The fluid dynamical stability of extra-galactic jets and the possible consequences of Kelvin-Helmholtz instability at the jet surface external medium interface are considered.

  5. General relativistic magnetohydrodynamical simulations of the jet in M 87

    NASA Astrophysics Data System (ADS)

    Mościbrodzka, Monika; Falcke, Heino; Shiokawa, Hotaka

    2016-02-01

    Context. The connection between black hole, accretion disk, and radio jet can be constrained best by fitting models to observations of nearby low-luminosity galactic nuclei, in particular the well-studied sources Sgr A* and M 87. There has been considerable progress in modeling the central engine of active galactic nuclei by an accreting supermassive black hole coupled to a relativistic plasma jet. However, can a single model be applied to a range of black hole masses and accretion rates? Aims: Here we want to compare the latest three-dimensional numerical model, originally developed for Sgr A* in the center of the Milky Way, to radio observations of the much more powerful and more massive black hole in M 87. Methods: We postprocess three-dimensional GRMHD models of a jet-producing radiatively inefficient accretion flow around a spinning black hole using relativistic radiative transfer and ray-tracing to produce model spectra and images. As a key new ingredient in these models, we allow the proton-electron coupling in these simulations depend on the magnetic properties of the plasma. Results: We find that the radio emission in M 87 is described well by a combination of a two-temperature accretion flow and a hot single-temperature jet. Most of the radio emission in our simulations comes from the jet sheath. The model fits the basic observed characteristics of the M 87 radio core: it is "edge-brightened", starts subluminally, has a flat spectrum, and increases in size with wavelength. The best fit model has a mass-accretion rate of Ṁ ~ 9 × 10-3M⊙ yr-1 and a total jet power of Pj ~ 1043 erg s-1. Emission at λ = 1.3 mm is produced by the counter-jet close to the event horizon. Its characteristic crescent shape surrounding the black hole shadow could be resolved by future millimeter-wave VLBI experiments. Conclusions: The model was successfully derived from one for the supermassive black hole in the center of the Milky Way by appropriately scaling mass and

  6. Baryon Loading Efficiency and Particle Acceleration Efficiency of Relativistic Jets: Cases for Low Luminosity BL Lacs

    NASA Astrophysics Data System (ADS)

    Inoue, Yoshiyuki; Tanaka, Yasuyuki T.

    2016-09-01

    Relativistic jets launched by supermassive black holes, so-called active galactic nuclei (AGNs), are known as the most energetic particle accelerators in the universe. However, the baryon loading efficiency onto the jets from the accretion flows and their particle acceleration efficiencies have been veiled in mystery. With the latest data sets, we perform multi-wavelength spectral analysis of quiescent spectra of 13 TeV gamma-ray detected high-frequency-peaked BL Lacs (HBLs) following one-zone static synchrotron self-Compton (SSC) model. We determine the minimum, cooling break, and maximum electron Lorentz factors following the diffusive shock acceleration (DSA) theory. We find that HBLs have {P}B/{P}e∼ 6.3× {10}-3 and the radiative efficiency {ε }{{rad,jet}}∼ 6.7× {10}-4, where P B and P e is the Poynting and electron power, respectively. By assuming 10 leptons per one proton, the jet power relates to the black hole mass as {P}{{jet}}/{L}{{Edd}}∼ 0.18, where {P}{{jet}} and {L}{{Edd}} is the jet power and the Eddington luminosity, respectively. Under our model assumptions, we further find that HBLs have a jet production efficiency of {η }{{jet}}∼ 1.5 and a mass loading efficiency of {ξ }{{jet}}≳ 5× {10}-2. We also investigate the particle acceleration efficiency in the blazar zone by including the most recent Swift/BAT data. Our samples ubiquitously have particle acceleration efficiencies of {η }g∼ {10}4.5, which is inefficient to accelerate particles up to the ultra-high-energy-cosmic-ray (UHECR) regime. This implies that the UHECR acceleration sites should not be the blazar zones of quiescent low power AGN jets, if one assumes the one-zone SSC model based on the DSA theory.

  7. Baryon Loading Efficiency and Particle Acceleration Efficiency of Relativistic Jets: Cases for Low Luminosity BL Lacs

    NASA Astrophysics Data System (ADS)

    Inoue, Yoshiyuki; Tanaka, Yasuyuki T.

    2016-09-01

    Relativistic jets launched by supermassive black holes, so-called active galactic nuclei (AGNs), are known as the most energetic particle accelerators in the universe. However, the baryon loading efficiency onto the jets from the accretion flows and their particle acceleration efficiencies have been veiled in mystery. With the latest data sets, we perform multi-wavelength spectral analysis of quiescent spectra of 13 TeV gamma-ray detected high-frequency-peaked BL Lacs (HBLs) following one-zone static synchrotron self-Compton (SSC) model. We determine the minimum, cooling break, and maximum electron Lorentz factors following the diffusive shock acceleration (DSA) theory. We find that HBLs have {P}B/{P}e˜ 6.3× {10}-3 and the radiative efficiency {ɛ }{{rad,jet}}˜ 6.7× {10}-4, where P B and P e is the Poynting and electron power, respectively. By assuming 10 leptons per one proton, the jet power relates to the black hole mass as {P}{{jet}}/{L}{{Edd}}˜ 0.18, where {P}{{jet}} and {L}{{Edd}} is the jet power and the Eddington luminosity, respectively. Under our model assumptions, we further find that HBLs have a jet production efficiency of {η }{{jet}}˜ 1.5 and a mass loading efficiency of {ξ }{{jet}}≳ 5× {10}-2. We also investigate the particle acceleration efficiency in the blazar zone by including the most recent Swift/BAT data. Our samples ubiquitously have particle acceleration efficiencies of {η }g˜ {10}4.5, which is inefficient to accelerate particles up to the ultra-high-energy-cosmic-ray (UHECR) regime. This implies that the UHECR acceleration sites should not be the blazar zones of quiescent low power AGN jets, if one assumes the one-zone SSC model based on the DSA theory.

  8. Spitzer Digs Up Galactic Fossil

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site] Figure 1

    [figure removed for brevity, see original site] Figure 2

    This false-color image taken by NASA's Spitzer Space Telescope shows a globular cluster previously hidden in the dusty plane of our Milky Way galaxy. Globular clusters are compact bundles of old stars that date back to the birth of our galaxy, 13 or so billion years ago. Astronomers use these galactic 'fossils' as tools for studying the age and formation of the Milky Way.

    Most clusters orbit around the center of the galaxy well above its dust-enshrouded disc, or plane, while making brief, repeated passes through the plane that each last about a million years. Spitzer, with infrared eyes that can see into the dusty galactic plane, first spotted the newfound cluster during its current pass. A visible-light image (inset of Figure 1) shows only a dark patch of sky.

    The red streak behind the core of the cluster is a dust cloud, which may indicate the cluster's interaction with the Milky Way. Alternatively, this cloud may lie coincidentally along Spitzer's line of sight.

    Follow-up observations with the University of Wyoming Infrared Observatory helped set the distance of the new cluster at about 9,000 light-years from Earth - closer than most clusters - and set the mass at the equivalent of 300,000 Suns. The cluster's apparent size, as viewed from Earth, is comparable to a grain of rice held at arm's length. It is located in the constellation Aquila.

    Astronomers believe that this cluster may be one of the last in our galaxy to be uncovered.

    This image composite was taken on April 21, 2004, by Spitzer's infrared array camera. It is composed of images obtained at four wavelengths: 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange) and 8 microns (red).

    Galactic Fossil Found Behind Curtain of Dust In Figure 2, the image mosaic shows the same patch of sky in various wavelengths of light. While the

  9. Observational aspects of AGN jets at high energy

    NASA Astrophysics Data System (ADS)

    Kataoka, Jun

    2015-03-01

    For the last two decades, significant and dramatic progress has been made in understanding astrophysical jet sources, particularly in the X-ray and gamma-ray energy bands. For example, the Chandra X-ray observatory reveals a number of AGN jets extending from kpc to Mpc scales. More recently, the Fermi Gamma-ray Space Telescopes launched in 2008 started monitoring the gamma-ray sky with excellent sensitivity of about ten times greater than that of EGRET onboard CGRO, and has detected more than 2,000 sources (mostly AGNs) as of 2014. Moreover, Fermi-LAT has discovered gamma-ray emissions not only from blazars but from a dozen radio galaxies not previously known to emit gamma-rays. Closer to home, the Fermi-bubbles were discovered to extend 50 degrees above and below the Galactic center. These large scale diffuse gamma-ray structures are similar in structure to AGN lobes such as those seen in Cen A and provide evidence for past activity in our Galactic center. In this review, I will first summarize recent highlights of large scale jets in radio galaxies, specifically resolved by the Chandra X-ray observatory. Next I will move on to the gamma-ray sky to present some highlights from Fermi-LAT observations of ``misaligned'' blazars, namely radio galaxies. I will discuss a unification scheme connecting blazars and misaligned radio galaxies. In the last part, I will also briefly comment on recent multiband observations of the Fermi-bubble and possible impacts on the AGN jet physics in the near future.

  10. H II REGION DRIVEN GALACTIC BUBBLES AND THEIR RELATIONSHIP TO THE GALACTIC MAGNETIC FIELD

    SciTech Connect

    Pavel, Michael D.; Clemens, D. P. E-mail: clemens@bu.edu

    2012-12-01

    The relative alignments of mid-infrared traced Galactic bubbles are compared to the orientation of the mean Galactic magnetic field in the disk. The orientations of bubbles in the northern Galactic plane were measured and are consistent with random orientations-no preferential alignment with respect to the Galactic disk was found. A subsample of H II region driven Galactic bubbles was identified, and as a single population they show random orientations. When this subsample was further divided into subthermal and suprathermal H II regions, based on hydrogen radio recombination linewidths, the subthermal H II regions showed a marginal deviation from random orientations, but the suprathermal H II regions showed significant alignment with the Galactic plane. The mean orientation of the Galactic disk magnetic field was characterized using new near-infrared starlight polarimetry and the suprathermal H II regions were found to preferentially align with the disk magnetic field. If suprathermal linewidths are associated with younger H II regions, then the evolution of young H II regions is significantly affected by the Galactic magnetic field. As H II regions age, they cease to be strongly linked to the Galactic magnetic field, as surrounding density variations come to dominate their morphological evolution. From the new observations, the ratios of magnetic-to-ram pressures in the expanding ionization fronts were estimated for younger H II regions.

  11. Particle Acceleration, Magnetic Field Generation, and Associated Emission in Collisionless Relativistic Jets

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.-I.

    2007-01-01

    Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., active galactic nuclei (AGNs), gamma-ray bursts (GRBs), and Galactic microquasar systems usually have power-law emission spectra. Recent PIC simulations using injected relativistic electron-ion (electro-positron)jets show that acceleration occurs within the downstream jet. Shock acceleration is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, other two-streaming instability, and the Weibel instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the jet head. The "jitter" radiation from deflected electrons has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.

  12. Particle Acceleration, Magnetic Field Generation and Associated Emission in Collisionless Relativistic Jets

    NASA Technical Reports Server (NTRS)

    Nishikawa, K. I.; Ramirez-Ruiz, E.; Hardee, P.; Mizuno, Y.; Fishman. G. J.

    2007-01-01

    Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., active galactic nuclei (AGNs), gamma-ray bursts (GRBs), and Galactic microquasar systems usually have power-law emission spectra. Recent PIC simulations using injected relativistic electron-ion (electro-positron) jets show that acceleration occurs within the downstream jet. Shock acceleration is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, other two-streaming instability, and the Weibel instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the jet head. The "jitter" radiation from deflected electrons has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.

  13. PAGaN I: Multi-Frequency Polarimetry of AGN Jets with KVN

    NASA Astrophysics Data System (ADS)

    Kim, Jae-Young; Trippe, Sascha; Sohn, Bong Won; Oh, Junghwan; Park, Jong-Ho; Lee, Sang-Sung; Lee, Taeseok; Kim, Daewon

    2015-10-01

    Active Galactic Nuclei (AGN) with bright radio jets offer the opportunity to study the structure of and physical conditions in relativistic outflows. For such studies, multi-frequency polarimetric very long baseline interferometric (VLBI) observations are important as they directly probe particle densities, magnetic field geometries, and several other parameters. We present results from first-epoch data obtained by the Korean VLBI Network (KVN) within the frame of the Plasma Physics of Active Galactic Nuclei (PAGaN) project. We observed seven radio-bright nearby AGN at frequencies of 22, 43, 86, and 129 GHz in dual polarization mode. Our observations constrain apparent brightness temperatures of jet components and radio cores in our sample to >10^{8.01} K and >10^{9.86} K, respectively. Degrees of linear polarization m_{L} are relatively low overall: less than 10%. This indicates suppression of polarization by strong turbulence in the jets. We found an exceptionally high degree of polarization in a jet component of BL Lac at 43 GHz, with m_{L} ˜ 40%. Assuming a transverse shock front propagating downstream along the jet, the shock front being almost parallel to the line of sight can explain the high degree of polarization.

  14. Dark matter particles in the galactic halo

    SciTech Connect

    Bernabei, R. Belli, P.; Montecchia, F.; Nozzoli, F.; Cappella, F.; D'Angelo, A.; Incicchitti, A.; Prosperi, D.; Cerulli, R.; Dai, C. J.; He, H. L.; Kuang, H. H.; Ma, J. M.; Sheng, X. D.; Ye, Z. P.

    2009-12-15

    Arguments on the investigation of the DarkMatter particles in the galactic halo are addressed. Recent results obtained by exploiting the annual modulation signature are summarized and the perspectives are discussed.

  15. Dark matter particles in the galactic halo

    NASA Astrophysics Data System (ADS)

    Bernabei, R.; Belli, P.; Montecchia, F.; Nozzoli, F.; Cappella, F.; D'Angelo, A.; Incicchitti, A.; Prosperi, D.; Cerulli, R.; Dai, C. J.; He, H. L.; Kuang, H. H.; Ma, J. M.; Sheng, X. D.; Ye, Z. P.

    2009-12-01

    Arguments on the investigation of the DarkMatter particles in the galactic halo are addressed. Recent results obtained by exploiting the annual modulation signature are summarized and the perspectives are discussed.

  16. The source and distribution of Galactic positrons

    NASA Technical Reports Server (NTRS)

    Purcell, W. R.; Dixon, D. D.; Cheng, L.-X.; Leventhal, M.; Kinzer, R. L.; Kurfess, J. D.; Skibo, J. G.; Smith, D. M.; Tueller, J.

    1997-01-01

    The oriented scintillation spectrometer experiment (OSSE) observations of the Galactic plane and the Galactic center region were combined with observations acquired with other instruments in order to produce a map of the Galactic 511 keV annihilation radiation. Two mapping techniques were applied to the data: the maximum entropy method, and the basis pursuit inversion method. The resulting maps are qualitatively similar and show evidence for a central bulge and a weak galactic disk component. The weak disk is consistent with that expected from positrons produced by the decay of radioactive Al-26 in the interstellar medium. Both maps suggest an enhanced region of emission near l = -4 deg, b = 7 deg, with a flux of approximately 50 percent of that of the bulge. The existence of this emission appears significant, although the location is not well determined. The source of this enhanced emission is presently unknown.

  17. Evaluation of Galactic Cosmic Ray Models

    NASA Technical Reports Server (NTRS)

    Adams, James H., Jr.; Heiblim, Samuel; Malott, Christopher

    2009-01-01

    Models of the galactic cosmic ray spectra have been tested by comparing their predictions to an evaluated database containing more than 380 measured cosmic ray spectra extending from 1960 to the present.

  18. The Heliosphere and the Galactic Environment

    NASA Video Gallery

    The boundaries surrounding our heliosphere can change both due to changes in our galactic environment and through changes in the solar wind emitted by the Sun. We see here an animation of the bound...

  19. UNBOUND GEODESICS FROM THE ERGOSPHERE AND THE MESSIER 87 JET PROFILE

    SciTech Connect

    Gariel, J.; Marcilhacy, G.; Santos, N. O. E-mail: gmarcilhacy@hotmail.com

    2013-09-10

    Assuming that the spin a of the black hole presumably located at the core of the active galactic nucleus Messier 87 takes the value which maximizes the ergospheric volume of the Kerr spacetime, we find the results compatible with the recent observations obtained by high-resolution interferometry on the origin of the jet, which would be located inside the innermost stable circular orbit diameter. Moreover, we find that a flow of unbound geodesics issued from the ergoregion is able to frame the best fits at large scales recently obtained for describing the observed profile of the relativistic jet launched from this central engine.

  20. The Disk-Jet Connection in Radio-Loud AGN: The X-Ray Perspective

    NASA Technical Reports Server (NTRS)

    Sambruna, Rita

    2008-01-01

    Unification schemes assume that radio-loud active galactic nuclei (AGN) contain an accretion disk and a relativistic jet perpendicular to the disk, and an obscuring molecular torus. The jet dominance decreases with larger viewing angles from blazars to Broad-Line and Narrow-Line Radio Galaxies. A fundamental question is how accretion and ejecta are related. The X-rays provide a convenient window to study these issues, as they originate in the innermost nuclear regions and penetrate large obscuring columns. I review the data, using observations by Chandra but also from other currently operating high-energy experiments. Synergy with the upcoming GLAST mission will also be highlighted.

  1. Impulsively started incompressible turbulent jet

    SciTech Connect

    Witze, P O

    1980-10-01

    Hot-film anemometer measurements are presented for the centerline velocity of a suddenly started jet of air. The tip penetration of the jet is shown to be proportional to the square-root of time. A theoretical model is developed that assumes the transient jet can be characterized as a spherical vortex interacting with a steady-state jet. The model demonstrates that the ratio of nozzle radius to jet velocity defines a time constant that uniquely characterizes the behavior and similarity of impulsively started incompressible turbulent jets.

  2. Ram-jet Performance

    NASA Technical Reports Server (NTRS)

    Cervenko, A. J.; Friedman, R.

    1956-01-01

    The ram jet is basically one of the most dimple types of aircraft engine. It consists only of an inlet diffuser, a combustion system, and an exit nozzle. A typical ram-jet configuration is shown in figure 128. The engine operates on the Brayton cycle, and ideal cycle efficiency depends only on the ratio of engine to ambient pressure. The increased, engine pressures are obtained by ram action alone, and for this reason the ram jet has zero thrust at zero speed. Therefore, ram-jet-powered aircraft must be boosted to flight speeds close to a Mach number of 1.0 before appreciable thrust is generated by the engine. Since pressure increases are obtained by ram action alone, combustor-inlet pressures and temperatures are controlled by the flight speed, the ambient atmospheric condition, and by the efficiency of the inlet diffuser. These pressures and temperatures, as functions of flight speed and altitude, are shown in figure 129 for the NACA standard atmosphere and for practical values of diffuser efficiency. It can be seen that very wide ranges of combustor-inlet temperatures and pressures may be encountered over the ranges of flight velocity and altitude at which ram jets may be operated. Combustor-inlet temperatures from 500 degrees to 1500 degrees R and inlet pressures from 5 to 100 pounds per square inch absolute represent the approximate ranges of interest in current combustor development work. Since the ram jet has no moving parts in the combustor outlet, higher exhaust-gas temperatures than those used in current turbojets are permissible. Therefore, fuel-air ratios equivalent to maximum rates of air specific impulse or heat release can be used, and, for hydrocarbon fuels, this weight ratio is about 0.070. Lower fuel-air ratios down to about 0.015 may also be required to permit efficient cruise operation. This fuel-air-ratio range of 0.015 to 0.070 used in ram jets can be compared with the fuel-air ratios up to 0.025 encountered in current turbojets. Ram-jet

  3. Relativistic Dark Matter at the Galactic Center

    SciTech Connect

    Amin, Mustafa A.; Wizansky, Tommer; /SLAC

    2007-11-16

    In a large region of the supersymmetry parameter space, the annihilation cross section for neutralino dark matter is strongly dependent on the relative velocity of the incoming particles. We explore the consequences of this velocity dependence in the context of indirect detection of dark matter from the galactic center. We find that the increase in the annihilation cross section at high velocities leads to a flattening of the halo density profile near the galactic center and an enhancement of the annihilation signal.

  4. GLIMPSE360: Completing the Spitzer Galactic Plane Survey

    NASA Astrophysics Data System (ADS)

    Whitney, Barbara; GLIMPSE360 Team

    2009-05-01

    GLIMPSE360 will map the remaining 187 degrees of the Galactic Plane that have not been previously observed with the Spitzer Space Telescope. Thus the survey will cover longitude l=65-265.5 degrees excluding l 102-109 and l 76-82. The latitude range will be 3.1 degrees, wider than the previous GLIMPSE surveys (2 degrees) because the disk flares more in the Outer Galaxy. The latitude center will follow the CO/HI warp at a Galactocentric radius of 13 kpc. Three visits on each sky position with 0.6&12s HDR frames will provide a high dynamic range of sensitivity that exceeds GLIMPSE at both ends. This will allow us to determine the edge of the Galactic stellar disk, study low- and high-mass star formation in both the nearby Perseus arm and the Far Outer Galaxy, and study evolved stars throughout the Galaxy. Following the tradition of the previous GLIMPSE Legacy programs, we will deliver enhanced data products for the survey --- source lists and cleaned mosaics --- to the community. The science goals are as encompassing as the survey and include: determining the star formation rate of the Galaxy, the stellar disk scale heights and lengths across the Galaxy, how the dust extinction law varies with location in the disk; and cataloging stars, star clusters, PAH bubbles, supernova remnants, infrared dark clouds, outflows from massive protostars, planetary nebulae, external galaxies in the Zone of Avoidance, and many other types of objects. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech

  5. Unwrapping the X-ray spectra of active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Reynolds, C. S.

    2016-05-01

    Active galactic nuclei (AGN) are complex phenomena. At the heart of an AGN is a relativistic accretion disk around a spinning supermassive black hole (SMBH) with an X-ray emitting corona and, sometimes, a relativistic jet. On larger scales, the outer accretion disk and molecular torus act as the reservoirs of gas for the continuing AGN activity. And on all scales from the black hole outwards, powerful winds are seen that probably affect the evolution of the host galaxy as well as regulate the feeding of the AGN itself. In this review article, we discuss how X-ray spectroscopy can be used to study each of these components. We highlight how recent measurements of the high-energy cutoff in the X-ray continuum by NuSTAR are pushing us to conclude that X-ray coronae are radiatively-compact and have electron temperatures regulated by electron-positron pair production. We show that the predominance of rapidly-rotating objects in current surveys of SMBH spin is entirely unsurprising once one accounts for the observational selection bias resulting from the spin-dependence of the radiative efficiency. We review recent progress in our understanding of fast (v˜ (0.1-0.3)c, highly-ionized (mainly visible in Fe XXV and Fe XXVI lines), high-column density winds that may dominate quasar-mode galactic feedback. Finally, we end with a brief look forward to the promise of Astro-H and future X-ray spectropolarimeters.

  6. Silicate features in Galactic and extragalactic post-AGB discs

    NASA Astrophysics Data System (ADS)

    Gielen, C.; Bouwman, J.; van Winckel, H.; Lloyd Evans, T.; Woods, P. M.; Kemper, F.; Marengo, M.; Meixner, M.; Sloan, G. C.; Tielens, A. G. G. M.

    2011-09-01

    Aims: In this paper we study the Spitzer and TIMMI2 infrared spectra of post-AGB disc sources, both in the Galaxy and the LMC. Using the observed infrared spectra we determine the mineralogy and dust parameters of the discs, and look for possible differences between the Galactic and extragalactic sources. Methods: Modelling the full spectral range observed allows us to determine the dust species present in the disc and different physical parameters such as grain sizes, dust abundance ratios, and the dust and continuum temperatures. Results: We find that all the discs are dominated by emission features of crystalline and amorphous silicate dust. Only a few sample sources show features due to CO2 gas or carbonaceous molecules such as PAHs and C60 fullerenes. Our analysis shows that dust grain processing in these discs is strong, resulting in large average grain sizes and a very high crystallinity fraction. However, we do not find any correlations between the derived dust parameters and properties of the central source. There also does not seem to be a noticeable difference between the mineralogy of the Galactic and LMC sources. Even though the observed spectra are very similar to those of protoplanetary discs around young stars, showing similar mineralogy and strong grain processing, we do find evidence for differences in the physical and chemical processes of the dust processing. Based on observations obtained at the European Southern Observatory (ESO), La Silla, observing program 072.D-0263 and 077.D-0555, and on observations made with the Spitzer Space Telescope (program id 3274 and 50092), which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA.Appendix A is available in electronic form at http://www.aanda.org

  7. Transient Events in Archival VLA Observations of the Galactic Center

    NASA Astrophysics Data System (ADS)

    Chiti, Anirudh; Chatterjee, S.; Wharton, R.; Cordes, J. M.; Lazio, J.; Kaplan, D. L.; Bower, G. C.; Croft, S.

    2014-01-01

    A number of different classes of stars, sub-stellar objects, and stellar remnants exhibit variability at radio wavelengths on time scales ranging from sub-seconds to hours. The direction toward the Galactic center not only has the highest stellar densities in the Galaxy, but also appears to have a range of interstellar scattering properties that may aid in the detection of new, radio-selected transient events. We have examined all archival VLA observations of the Galactic center field from 1985 to 2005 at 5 GHz and 8.4 GHz for a total of 214 hours of integration time, spanning 99 observations at 5 GHz with a typical area of 4.41E-4 square degrees and 116 observations at 8.4 GHz with a typical area of 8E-4 square degrees. We used a pipeline to search for transient events down to the shortest time scales allowed by the data (typically 10 seconds) by generating model-subtracted visibility data for each observation and then imaging the residual visibilities over short time intervals to search for outlier events. We present one radio transient event and at least 7 other promising candidates with significances ranging from 5.6 to 10.2 sigma that have passed all our tests, and discuss the possible source classes for these candidates and the event rate implications. We acknowledge support from the National Science Foundation for this work. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

  8. The Twin Jet Nebula

    NASA Technical Reports Server (NTRS)

    1997-01-01

    M2-9 is a striking example of a 'butterfly' or a bipolar planetary nebula. Another more revealing name might be the 'Twin Jet Nebula.' If the nebula is sliced across the star, each side of it appears much like a pair of exhausts from jet engines. Indeed, because of the nebula's shape and the measured velocity of the gas, in excess of 200 miles per second, astronomers believe that the description as a super-super-sonic jet exhaust is quite apt. This is much the same process that takes place in a jet engine: The burning and expanding gases are deflected by the engine walls through a nozzle to form long, collimated jets of hot air at high speeds. M2-9 is 2,100 light-years away in the constellation Ophiucus. The observation was taken Aug. 2, 1997 by the Hubble telescope's Wide Field and Planetary Camera 2. In this image, neutral oxygen is shown in red, once-ionized nitrogen in green, and twice-ionized oxygen in blue.

  9. Jet penetration in glass

    SciTech Connect

    Moran, B.; Glenn, L.A.; Kusubov, A.

    1991-05-01

    We describe a phenomenological model which accounts for the mechanical response of glass to intense impulsive loading. An important aspect of this response is the dilatancy accompanying fracture. We have also conducted a number of experiments with 38.1-mm diameter precision shaped charges to establish the performance against various targets and to allow evaluation of our model. At 3 charge diameters standoff, the data indicate that both virgin and damaged glass offer better (Bernoulli-scaled) resistance to penetration than either of 4340 steel, or 6061-T6 aluminum alloy. Time-resolved measurements indicate two distinct phases of jet penetration in glass: An initial hydrodynamic phase, and a second phase characterized by a slower penetration velocity. Our calculations show that at early time, a crater is formed around the jet and only the tip of the undisturbed jet interacts with the glass. At late time the glass has collapsed on the jet and degraded penetration continues via a disturbed and fragmented jet.

  10. Sweeping Jet Optimization Studies

    NASA Technical Reports Server (NTRS)

    Melton, LaTunia Pack; Koklu, Mehti; Andino, Marlyn; Lin, John C.; Edelman, Louis

    2016-01-01

    Progress on experimental efforts to optimize sweeping jet actuators for active flow control (AFC) applications with large adverse pressure gradients is reported. Three sweeping jet actuator configurations, with the same orifice size but di?erent internal geometries, were installed on the flap shoulder of an unswept, NACA 0015 semi-span wing to investigate how the output produced by a sweeping jet interacts with the separated flow and the mechanisms by which the flow separation is controlled. For this experiment, the flow separation was generated by deflecting the wing's 30% chord trailing edge flap to produce an adverse pressure gradient. Steady and unsteady pressure data, Particle Image Velocimetry data, and force and moment data were acquired to assess the performance of the three actuator configurations. The actuator with the largest jet deflection angle, at the pressure ratios investigated, was the most efficient at controlling flow separation on the flap of the model. Oil flow visualization studies revealed that the flow field controlled by the sweeping jets was more three-dimensional than expected. The results presented also show that the actuator spacing was appropriate for the pressure ratios examined.

  11. Non-thermal emission from standing relativistic shocks: an application to red giant winds interacting with AGN jets

    NASA Astrophysics Data System (ADS)

    Bosch-Ramon, V.

    2015-03-01

    Context. Galactic and extragalactic relativistic jets are surrounded by rich environments that are full of moving objects, such as stars and dense medium inhomogeneities. These objects can enter into the jets and generate shocks and non-thermal emission. Aims: We characterize the emitting properties of the downstream region of a standing shock formed due to the interaction of a relativistic jet with an obstacle. We focus on the case of red giants interacting with an extragalactic jet. Methods: We perform relativistic axisymmetric hydrodynamical simulations of a relativistic jet meeting an obstacle of very large inertia. The results are interpreted in the framework of a red giant whose dense and slow wind interacts with the jet of an active galactic nucleus. Assuming that particles are accelerated in the standing shock generated in the jet as it impacts the red giant wind, we compute the non-thermal particle distribution, the Doppler boosting enhancement, and the non-thermal luminosity in gamma rays. Results: The available non-thermal energy from jet-obstacle interactions is potentially enhanced by a factor of ~100 when accounting for the whole surface of the shock induced by the obstacle, instead of just the obstacle section. The observer gamma-ray luminosity, including the effective obstacle size, the flow velocity and Doppler boosting effects, can be ~300 (γj/10)2 times higher than when the emitting flow is assumed at rest and only the obstacle section is considered, where γj is the jet Lorentz factor. For a whole population of red giants inside the jet of an active galactic nucleus, the predicted persistent gamma-ray luminosities may be potentially detectable for a jet pointing approximately to the observer. Conclusions: Obstacles interacting with relativistic outflows, for instance clouds and populations of stars for extragalactic jets, or stellar wind inhomogeneities in microquasar jets and in winds of pulsars in binaries, should be taken into account when

  12. B-jets and z + b-jets at CDF

    SciTech Connect

    Jeans, Daniel; /Rome U.

    2006-06-01

    The authors present CDF cross-section measurements for the inclusive production of b jets and the production of b jets in association with a Z{sup 0} boson. Both measurements are in reasonable agreement with NLO QCD predictions.

  13. Jet Feedback on the Hosts of Radio Galaxies

    NASA Astrophysics Data System (ADS)

    Lanz, L.; Ogle, P. M.; Alatalo, K.; Appleton, P. N.

    2016-06-01

    Feedback due to active galactic nuclei is one of the key components of the current paradigm of galaxy evolution; however our understanding of the process remains incomplete. Radio galaxies with strong rotational H_2 emission provide an interesting window into the effect of radio jet feedback on their host galaxies, since the large masses of warm (>100 K) H_2 cannot solely be heated by star formation, instead requiring jet-driven ISM turbulence to power the molecular emission. I will discuss the insights multiwavelength (X-ray to submm) observations of 22 H_2 luminous radio galaxies yield on the process of jet feedback in these galaxies and the impact on star formation activity. Specifically, I find that the diffuse X-ray and warm H_2 emission are consistent with both being powered by dissipation of the jet's mechanical energy into the interstellar medium (ISM) and that the resulting turbulence injected into the ISM by this process results in the suppression of star formation activity by a factor of 3--6. The hosts of these galaxies show a wide range of star formation activity and optical and IR colors, indicating a diversity of evolutionary states in which this process may be active.

  14. Arrhenius reconsidered: astrophysical jets and the spread of spores

    NASA Astrophysics Data System (ADS)

    Sheldon, Malkah I.; Sheldon, Robert B.

    2015-09-01

    In 1871, Lord Kelvin suggested that the fossil record could be an account of bacterial arrivals on comets. In 1903, Svante Arrhenius suggested that spores could be transported on stellar winds without comets. In 1984, Sir Fred Hoyle claimed to see the infrared signature of vast clouds of dried bacteria and diatoms. In 2012, the Polonnaruwa carbonaceous chondrite revealed fossilized diatoms apparently living on a comet. However, Arrhenius' spores were thought to perish in the long transit between stars. Those calculations, however, assume that maximum velocities are limited by solar winds to ~5 km/s. Herbig-Haro objects and T-Tauri stars, however, are young stars with jets of several 100 km/s that might provide the necessary propulsion. The central engine of bipolar astrophysical jets is not presently understood, but we argue it is a kinetic plasma instability of a charged central magnetic body. We show how to make a bipolar jet in a belljar. The instability is non-linear, and thus very robust to scaling laws that map from microquasars to active galactic nuclei. We scale up to stellar sizes and recalculate the viability/transit-time for spores carried by supersonic jets, to show the viability of the Arrhenius mechanism.

  15. WIMPs at the galactic center

    SciTech Connect

    Agrawal, Prateek; Batell, Brian; Fox, Patrick J.; Harnik, Roni

    2015-05-07

    Simple models of weakly interacting massive particles (WIMPs) predict dark matter annihilations into pairs of electroweak gauge bosons, Higgses or tops, which through their subsequent cascade decays produce a spectrum of gamma rays. Intriguingly, an excess in gamma rays coming from near the Galactic center has been consistently observed in Fermi data. A recent analysis by the Fermi collaboration confirms these earlier results. Taking into account the systematic uncertainties in the modelling of the gamma ray backgrounds, we show for the first time that this excess can be well fit by these final states. In particular, for annihilations to (WW, ZZ, hh, tt{sup -bar}), dark matter with mass between threshold and approximately (165, 190, 280, 310) GeV gives an acceptable fit. The fit range for bb{sup -bar} is also enlarged to 35 GeV≲m{sub χ}≲165 GeV. These are to be compared to previous fits that concluded only much lighter dark matter annihilating into b, τ, and light quark final states could describe the excess. We demonstrate that simple, well-motivated models of WIMP dark matter including a thermal-relic neutralino of the MSSM, Higgs portal models, as well as other simplified models can explain the excess.

  16. WIMPs at the galactic center

    DOE PAGESBeta

    Agrawal, Prateek; Batell, Brian; Fox, Patrick J.; Harnik, Roni

    2015-05-07

    Simple models of weakly interacting massive particles (WIMPs) predict dark matter annihilations into pairs of electroweak gauge bosons, Higgses or tops, which through their subsequent cascade decays produce a spectrum of gamma rays. Intriguingly, an excess in gamma rays coming from near the Galactic center has been consistently observed in Fermi data. A recent analysis by the Fermi collaboration confirms these earlier results. Taking into account the systematic uncertainties in the modelling of the gamma ray backgrounds, we show for the first time that this excess can be well fit by these final states. In particular, for annihilations to (WW,more » ZZ, hh, tt¯), dark matter with mass between threshold and approximately (165, 190, 280, 310) GeV gives an acceptable fit. The fit range for bb¯ is also enlarged to 35 GeV ≲ mχ ≲ 165 GeV. These are to be compared to previous fits that concluded only much lighter dark matter annihilating into b, τ, and light quark final states could describe the excess. We demonstrate that simple, well-motivated models of WIMP dark matter including a thermal-relic neutralino of the MSSM, Higgs portal models, as well as other simplified models can explain the excess.« less

  17. WIMPs at the galactic center

    SciTech Connect

    Agrawal, Prateek; Batell, Brian; Fox, Patrick J.; Harnik, Roni

    2015-05-07

    Simple models of weakly interacting massive particles (WIMPs) predict dark matter annihilations into pairs of electroweak gauge bosons, Higgses or tops, which through their subsequent cascade decays produce a spectrum of gamma rays. Intriguingly, an excess in gamma rays coming from near the Galactic center has been consistently observed in Fermi data. A recent analysis by the Fermi collaboration confirms these earlier results. Taking into account the systematic uncertainties in the modelling of the gamma ray backgrounds, we show for the first time that this excess can be well fit by these final states. In particular, for annihilations to (WW, ZZ, hh, tt¯), dark matter with mass between threshold and approximately (165, 190, 280, 310) GeV gives an acceptable fit. The fit range for bb¯ is also enlarged to 35 GeV ≲ mχ ≲ 165 GeV. These are to be compared to previous fits that concluded only much lighter dark matter annihilating into b, τ, and light quark final states could describe the excess. We demonstrate that simple, well-motivated models of WIMP dark matter including a thermal-relic neutralino of the MSSM, Higgs portal models, as well as other simplified models can explain the excess.

  18. A Galactic Binary Detection Pipeline

    NASA Technical Reports Server (NTRS)

    Littenberg, Tyson B.

    2011-01-01

    The Galaxy is suspected to contain hundreds of millions of binary white dwarf systems, a large fraction of which will have sufficiently small orbital period to emit gravitational radiation in band for space-based gravitational wave detectors such as the Laser Interferometer Space Antenna (LISA). LISA's main science goal is the detection of cosmological events (supermassive black hole mergers, etc.) however the gravitational signal from the galaxy will be the dominant contribution to the data - including instrumental noise over approximately two decades in frequency. The catalogue of detectable binary systems will serve as an unparalleled means of studying the Galaxy. Furthermore, to maximize the scientific return from the mission, the data must be "cleansed" of the galactic foreground. We will present an algorithm that can accurately resolve and subtract 2:: 10000 of these sources from simulated data supplied by the Mock LISA Data Challenge Task Force. Using the time evolution of the gravitational wave frequency, we will reconstruct the position of the recovered binaries and show how LISA will sample the entire compact binary population in the Galaxy.

  19. Radioactivity in the galactic plane

    NASA Technical Reports Server (NTRS)

    Walraven, G. D.; Haymes, R. C.

    1976-01-01

    The paper reports the detection of a large concentration of interstellar radioactivity during balloon-altitude measurements of gamma-ray energy spectra in the band between 0.02 and 12.27 MeV from galactic and extragalactic sources. Enhanced counting rates were observed in three directions towards the plane of the Galaxy; a power-law energy spectrum is computed for one of these directions (designated B 10). A large statistical deviation from the power law in a 1.0-FWHM interval centered near 1.16 MeV is discussed, and the existence of a nuclear gamma-ray line at 1.15 MeV in B 10 is postulated. It is suggested that Ca-44, which emits gamma radiation at 1.156 MeV following the decay of radioactive Sc-44, is a likely candidate for this line, noting that Sc-44 arises from Ti-44 according to explosive models of supernova nucleosynthesis. The 1.16-MeV line flux inferred from the present data is shown to equal the predicted flux for a supernova at a distance of approximately 3 kpc and an age not exceeding about 100 years.

  20. Aeroacoustic Experiments with Twin Jets

    NASA Technical Reports Server (NTRS)

    Bozak, Richard F.; Henderson, Brenda S.

    2012-01-01

    While the noise produced by a single jet is azimuthally symmetric, multiple jets produce azimuthally varying far-field noise. The ability of one jet to shield another reduces the noise radiated in the plane of the jets, while often increasing the noise radiated out of the plane containing the jets. The present study investigates the shielding potential of twin jet configurations over subsonic and over-expanded supersonic jet conditions with simulated forward flight. The experiments were conducted with 2 in. throat diameter nozzles at four jet spacings from 2.6d to 5.5d in center-to-center distance, where d is the nozzle throat diameter. The current study found a maximum of 3 dB reduction in overall sound pressure level relative to two incoherent jets in the peak jet noise direction in the plane containing the jets. However, an increase of 3 dB was found perpendicular to the plane containing the jets. In the sideline direction, shielding is observed for all jet spacings in this study.