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Sample records for microquasar xte j1550-564

  1. Moving relativistic large-scale X-ray jets in the microquasar XTE J1550-564

    NASA Astrophysics Data System (ADS)

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

    2003-10-01

    We have discovered large-scale moving X-ray and radio jets from the microquasar XTE J1550-564. Using X-ray and radio observations performed between 2000 and 2002, we showed that plasma ejected from XTE J1550-564 has been able to travel at relativistic velocities during many years, with evidence for gradual deceleration. The broadband spectrum of the jets is consistent with synchrotron emission from high energy particles accelerated in shocks. Full details can be found in Corbel et al. [Science 298 (2002a) 196], Karret et al. [ApJ 582 (2003) 933] and Tomsick et al. [ApJ (2003) 945].

  2. Moving relativistic large-scale X-ray jets in the microquasar XTE J1550-564

    NASA Astrophysics Data System (ADS)

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

    We have discovered large-scale moving X-ray and radio jets from the microquasar XTE J1550-564. Using X-ray observations from the Chandra Observatory performed between June 2000 (see also Tomsick et al., these proceedings) and June 2002, we showed that ejected plasma from XTE J1550-564 has been able to travel at relativistic velocities during many years, with evidence for gradual deceleration. The broadband spectrum of the jets is consistent with synchrotron emission from high energy particles accelerated in shocks. Full details can be found in Corbel et al. 2002, Kaaret et al. 2002, Tomsick et al. 2002.

  3. High-Frequency Quasi-Periodic Oscillations in the 2000 Outburst of the Galactic Microquasar XTE J1550-564

    NASA Technical Reports Server (NTRS)

    Miller, J. M.; Wijnands, R.; Homan, J.; Belloni, T.; Pooley, D.; Kouveliotou, C.; vanderKlis, M.; Lewin, W. H. G.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    We present an analysis of the high-frequency timing properties of the April-May 2000 outburst of the black hole candidate and Galactic microquasar XTE J1550-564, measured with the Rossi X-ray Timing Explorer, The rapid X-ray variability we measure is consistent with the source being in either the "very high" or "intermediate" canonical black hole state. A strong (5-8% RMS) quasi-periodic oscillation (QPO) is found between 249-278 Hz; this may represent the first recurrence of the same high-frequency QPO in subsequent outbursts of a transient black hole candidate. We also present possible evidence for a lower-frequency QPO at approximately 187 Hz, also reported previously and likely present simultaneously with the higher-frequency QPO. We discuss these findings within the context of the 1998 outburst of XTE J1550-564, and comment on implications for models of QPOs, accretion flows, and black hole spin.

  4. MODELING THE JET KINEMATICS OF THE BLACK HOLE MICROQUASAR XTE J1550-564: A CONSTRAINT ON SPIN-ORBIT ALIGNMENT

    SciTech Connect

    Steiner, James F.; McClintock, Jeffrey E.

    2012-02-01

    Measurements of black hole spin made using the continuum-fitting method rely on the assumption that the inclination of the black hole's spin axis to our line of sight is the same as the orbital inclination angle i of the host binary system. The X-ray and radio jet data available for the microquasar XTE J1550-564 offer a rare opportunity to test this assumption. Following the work of others, we have modeled these data and thereby determined the inclination angle {theta} of the jet axis, which is presumed to be aligned with the black hole's spin axis. We find {theta} Almost-Equal-To 71 Degree-Sign and place an upper limit on the difference between the spin and orbital inclinations of |{theta} - i| < 12 Degree-Sign (90% confidence). Our measurement tests for misalignment along the line of sight while providing no constraint perpendicular to this plane. Our constraint on the misalignment angle supports the prediction that the spinning black hole in XTE J1550-564 has aligned itself with the orbital plane and provides support for the measurement of its spin via the continuum-fitting method. Our conclusions are based on a simple and reasonable model of a pair of symmetric jets propagating into a low-density cavity whose western wall is Almost-Equal-To 20% closer to XTE J1550-564 than its eastern wall.

  5. The Large-Scale, Decelerating X-ray Jets from the Microquasar Xte J1550-564: Evidence for External Shocks Caused by the Jet-Ism Interaction?

    NASA Astrophysics Data System (ADS)

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

    2005-06-01

    Large-scale, decelerating, relativistic X-ray jets from microquasar XTE J1550-564 has been recently discovered with Chandra by Corbel et al. (2002). We find that the dynamical evolution of the approaching jet at the late time is consistent with the well-known Sedov evolutionary phase R∝ t 2/5. A trans-relativistic external shock dynamic model by analogy with the evolution of gamma-ray burst remnants, is shown to be able to fit the proper-motion data of the approaching jet reasonably well. The inferred interstellar medium density around the source is well below the canonical value n ISM˜1 cm-3. The rapidly fading X-ray emission can be interpreted as synchrotron radiation from the non-thermal electrons in the adiabatically expanding ejecta. These electrons were accelerated by the reverse shock (moving back into the ejecta) which becomes important when the inertia of the swept external matter leads to an appreciable slowing down of the original ejecta.

  6. External Shock Model for the Large-Scale, Relativistic X-Ray Jets from the Microquasar XTE J1550-564

    NASA Astrophysics Data System (ADS)

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

    2003-07-01

    Large-scale, decelerating, relativistic X-ray jets due to material ejected from the black-hole candidate X-ray transient and microquasar XTE J1550-564 have been recently discovered with Chandra by Corbel and coworkers. We find that the dynamical evolution of the eastern jet at the late time is consistent with the well-known Sedov evolutionary phase. A transrelativistic external shock dynamic model by analogy with the evolution of gamma-ray burst remnants is shown to be able to fit the observation data reasonably well. The inferred interstellar medium density around the source is well below the canonical value nISM~1cm-3. We find that the emission from the continuously shocked interstellar medium (forward shock region) decays too slowly to be a viable mechanism for the eastern X-ray jet. However, the rapidly fading X-ray emission can be interpreted as synchrotron radiation from the nonthermal electrons in the adiabatically expanding ejecta. These electrons were accelerated by the reverse shock (moving back into the ejecta), which becomes important when the inertia of the swept external matter leads to an appreciable slowing down of the original ejecta. To ensure the dominance of the emission from the shocked ejecta over that from the forward shock region during the period of the observations, the magnetic field and electron energy fractions in the forward shock region must be far below equipartition. Future continuous, follow-up multiwavelength observations of new ejection events from microquasars up to the significant deceleration phase should provide more valuable insight into the nature of the interaction between the jets and external medium.

  7. A Possible Optical Counterpart to XTE J1550--564

    NASA Astrophysics Data System (ADS)

    Orosz, Jerome; Bailyn, Charles; Jain, Raj

    1998-09-01

    We report YALO consortium observations using the Yale 1m telescope at Cerro Tololo Interamerican Observatory and the ANDICAM CCD camera. We have identified a possible optical counterpart to the recent X-ray transient XTE J1550-564 (IAUC 7008) in V-band images obtained September 8.99 UT. The J2000 coordinates of the candidate are R.A. = 15h51m04s, Decl. = -56o28'37.5", with errors on each value of about +/- 3 arcseconds.

  8. Phase Lag and Coherence Function of X-Ray Emission from Black Hole Candidate XTE J1550-564

    NASA Technical Reports Server (NTRS)

    Cui, Wei; Zhang, Shuang Nan; Chen, Wan

    2000-01-01

    We report the results from measuring the phase lag and coherence function of X-ray emission from black hole candidate XTE J1550-564. These temporal X-ray properties have been recognized to be increasingly important in providing important diagnostics of the dynamics of accretion flows around black holes. For XTE J1550-564, we found significant hard lag-the X-ray variability in high-energy bands lags behind that in low-energy bands-associated both with broadband variability and quasi-periodic oscillation (QPO) . However, the situation is more complicated for the QPO: while hard lag was measured for the first harmonic of the signal, the fundamental component showed significant soft lag. Such behavior is remarkably similar to what was observed of microquasar GRS 1915+105. The phase lag evolved during the initial rising phase of the 1998 outburst. The magnitude of both the soft and hard lags of the QPO increases with X-ray flux, while the Fourier spectrum of the broadband lag varies significantly in shape. The coherence function is relatively high and roughly constant at low frequencies and begins to drop almost right after the first harmonic of the QPO. It is near unity at the beginning and decreases rapidly during the rising phase. Also observed is that the more widely separated the two energy bands are, the less the coherence function between the two. It is interesting that the coherence function increases significantly at the frequencies of the QPO and its harmonics. We discuss the implications of the results on the models proposed for black hole candidates.

  9. Multiwavelength Observations of the Black Hole Candidate XTE J1550-564 during the 2000 Outburst

    NASA Astrophysics Data System (ADS)

    Jain, Raj K.; Bailyn, Charles D.; Orosz, Jerome A.; McClintock, Jeffrey E.; Remillard, Ronald A.

    2001-06-01

    We report optical, infrared, and X-ray light curves for the outburst, in 2000, of the black hole candidate XTE J1550-564. We find that the start of the outburst in the H and V bands precedes that seen in the Rossi X-Ray Timing Explorer All-Sky Monitor by 11.5+/-0.9 and 8.8+/-0.6 days, respectively; a similar delay has been observed in two other systems. About 50 days after the primary maxima in the VIH light curves, we find secondary maxima, most prominently in H. This secondary peak is absent in the X-ray light curve but coincides with a transition to the low/hard state. We suggest that this secondary peak may be due to nonthermal emission associated with the formation of a jet.

  10. Observational Signatures of Black Holes: Spectral and Temporal Features of XTE J1550-564

    NASA Technical Reports Server (NTRS)

    Titarchuk, Lev; Shrader, C. R.; White, Nicholas E. (Technical Monitor)

    2002-01-01

    The theoretical predictions of the converging inflow, or Bulk-Motion Comptonization model are discussed and some predictions are compared to X- and gamma-ray observations of the high-soft state of Galactic black hole candidate XTE J1550+564. The approx. 10(exp 2)-Hz QPO phenomenon tends to be detected in the high-state at times when the bolometric luminosity surges and the hard-powerlaw spectral component is dominant. Furthermore, the power in these features increases with energy. We offer interpretation of this phenomenon, as oscillations of the innermost part of the accretion disk, which in turn supplies the seed photons for the converging inflow where the hard power-law is formed through Bulk Motion Comptonization (BMC). We further argue that the noted lack of coherence between intensity variations of the high-soft-state low and high energy bands is a natural consequence of our model, and that a natural explanation for the observed hard and soft lag phenomenon is offered. In addition, we address some criticisms of the BMC model supporting our claims with observational results.

  11. XTE J1550-564: INTEGRAL Observations of a Failed Outburst

    NASA Technical Reports Server (NTRS)

    Sturner, S. J.; Shrader, C. R.

    2004-01-01

    The well known black-hole X-ray binary transient XTE J1550-564 underwent an outburst during the spring of 2003 which was substantially underluminous in comparison to previous periods of peak activity in that source. In addition, our analysis shows that it apparently remained in the hard spectral state over the duration of that outburst. This is again in sharp contrast to major out-bursts of that source in 1998/1999 during which it exhibited an irregular light curve, multiple state changes and collimated outflows. This leads us to classify it as a failed outburst. We present the results of our study of the spring 2003 event including light curves based on observations from both INTEGRAL and RXTE. In addition, we studied the evolution of the high-energy 3-300 keV continuum spectrum using data obtained with three main instruments on INTEGRAL. These spectra are consistent with typical low-hard-state thermal Comptonization emission. We also consider the 2003 event in the context of a multi-source, multi-event period-peak luminosity diagram in which it is a clear outlyer. We then consider the possibility that the 2003 event was due to a discrete accretion event rather than a limit-cycle instability. In that context, apply model fitting to derive the timescale for viscous propagation in the disk, and infer some physical characteristics.

  12. Implication of the Observable Spectral Cutoff Energy Evolution in XTE J1550-564

    NASA Technical Reports Server (NTRS)

    Titarchuk, Lev; Shaposhnikov, Nikolai

    2010-01-01

    The physical mechanisms responsible for production of the non-thermal emission in accreting black holes should be imprinted in the observational appearances of the power law tails in the X-ray spectra from these objects. Variety of spectral states observed from galactic black hole binaries by it Rossi X-ray Timing Explorer (RXTE) allow examination of the photon upscattering under different accretion regimes. We revisit of RXTE data collected from the black hole X-ray binary XTE J1550-564 during two periods of X-ray activity in 1998 and 2000 focusing on the behavior of the high energy cutoff of the power law part of the spectrum. For the 1998 outburst the Iran- sition from the low-hard state to the intermediate state was accompanied by a gradual decrease in the cutoff energy which then showed a sharp reversal to a clear increasing trend during the further evolution towards the very high and high-soft states. However, the 2000 outburst showed only the decreasing part of this pattern. Notably, the photon indexes corresponding to the cutoff increase for the 1998 event are much higher than the index values reached during the 2000 rise transition. We attribute this difference in the cutoff' energy behav- for to the different partial contributions of the thermal and non-thermal (bulk motion) Comptonization in photon upscattering. Namely, during the 1998 event the higher accretion rate presumably provided more cooling to the Comptonizing media and thus reducing the effectiveness of the thermal upscattering process. Under these conditions the bulk motion takes a leading role in boosting the input soft photons. Monte Carlo simulations of the The physical mechanisms responsible for production of the non-thermal emission in accreting black holes should be imprinted in the observational apperances of the power law tails in the X-ray spectra from these objects. Variety of spectral states observed from galactic black hole binaries by it Rossi X-ray Timing Explorer (RXTE) allow

  13. IMPLICATION OF THE OBSERVED SPECTRAL CUTOFF ENERGY EVOLUTION IN XTE J1550-564

    SciTech Connect

    Titarchuk, Lev; Shaposhnikov, Nikolai E-mail: lev.titarchuk@nrl.navy.mi

    2010-12-01

    The physical mechanisms responsible for the production of non-thermal emission in accreting black holes (BHs) should be imprinted in the observational appearances of the power-law tails in the X-ray spectra from these objects. Phenomenology of different spectral states exhibited by galactic BH binaries allows us to establish the physics of the photon upscattering under different accretion regimes. We revisit the data collected by the Rossi X-ray Timing Explorer from the BH X-ray binary XTE J1550-564 during two periods of X-ray activity in 1998 and 2000 focusing on the behavior of the high-energy cutoff of the power-law part of the spectrum. For the 1998 outburst, the transition from the low-hard state to the intermediate state was accompanied by a gradual decrease in the cutoff energy. This was followed by an extended minimum which then showed an abrupt reversal to a clear increasing trend as the source evolved to the very high and high-soft states. The 2000 outburst showed only the decreasing and extended minimum portions of this pattern. We attribute this difference in the cutoff energy behavior to the different partial contributions of the thermal and non-thermal (bulk motion) Comptonization. Namely, during the 1998 event the higher accretion rate presumably provided more cooling to the Comptonizing media and thus reducing the effectiveness of the thermal upscattering process. Under these conditions, the bulk motion takes a leading role in boosting the input soft photons. Recent Monte Carlo simulations by Laurent and Titarchuk strongly support this scenario.

  14. X-Ray Timing and Spectral Observations of Galactic Black Hole Candidate XTE J1550--564 During Outburst

    SciTech Connect

    Reilly, Kaice T

    2002-12-11

    Soft X-ray transients (SXTs), a sub-class of low-mass X-ray binaries (LMXBs), provide a unique opportunity to test General Relativity and to probe fundamental physics under conditions terrestrially unattainable. SXT outbursts are of great interest because they allow the study of LMXBs under a wide range of accretion rates. The majority of known SXTs contain black holes, therefore SXT outbursts are key to understanding accretion physics around black holes and in active galactic nuclei, which are thought to contain supermassive, M {approx} 10{sup 6} - 10{sup 10} M{circle_dot}, where M{circle_dot} is one solar mass, central compact objects. These compact objects are most likely black holes, which exhibit, on a much larger scale, accretion physics similar to that around black holes in SXTs. In this work, the timing and spectral properties of the SXT and microquasar XTE J1550-564 during outburst are studied. Observations made by the Unconventional Stellar Aspect (USA) Experiment on board the Advanced Research and Global Observation Satellite (ARGOS) are emphasized. USA data show a low-frequency quasi-periodic oscillation (LFQPO) with a centroid frequency that tends to increase with increasing USA flux and a fractional rms amplitude which is correlated with the USA hardness ratio (4-16 keV/1-4 keV). Several high-frequency quasi-periodic oscillations (HFQPOs) were detected by the Rossi X-ray Timing Explorer (RXTE), during periods where the LFQPO is seen to be weakening or not detectable at all. The evolution of the USA hardness ratio with time and source flux is examined. The hardness-intensity diagram shows counterclockwise cyclical evolution and possibly indicates the presence of two independent accretion flows: a geometrically thin, optically thick accretion disk and a hot sub-Keplerian flow.

  15. USA Observation of Spectral and Timing Evolution During the 2000 Outburst of XTE J1550--564

    SciTech Connect

    Reilly, Kaice T

    2002-12-06

    We report on timing and spectral observations of the 2000 outburst of XTE J1550--564 made by the Unconventional Stellar Aspect (USA) Experiment on board the Advanced Research and Global Observation Satellite (ARGOS). We observe a low-frequency quasi-periodic oscillation (LFQPO) with a centroid frequency that tends to increase with increasing flux and a fractional rms amplitude which is correlated with the hardness ratio. Several high-frequency quasi-periodic oscillations (HFQPO) were detected by RXTE, during periods where the LFQPO is seen to be weakening or not detectable at all. The evolution of the hardness ratio (4-16 keV/1-4 keV) with time and source flux is examined. The hardness-intensity diagram (HID) shows a cyclical movement in the counterclockwise direction and possibly indicates the presence of two independent accretion flows: a thin disk and a hot sub-Keplerian flow.

  16. Characterizing Intermittency of 4-Hz Quasi-periodic Oscillation in XTE J1550-564 Using Hilbert-Huang Transform

    NASA Astrophysics Data System (ADS)

    Su, Yi-Hao; Chou, Yi; Hu, Chin-Ping; Yang, Ting-Chang

    2015-12-01

    We present time-frequency analysis results based on the Hilbert-Huang transform (HHT) for the evolution of a 4-Hz low-frequency quasi-periodic oscillation (LFQPO) around the black hole X-ray binary XTE J1550-564. The origin of LFQPOs is still debated. To understand the cause of the peak broadening, we utilized a recently developed time-frequency analysis, HHT, for tracking the evolution of the 4-Hz LFQPO from XTE J1550-564. By adaptively decomposing the ˜4-Hz oscillatory component from the light curve and acquiring its instantaneous frequency, the Hilbert spectrum illustrates that the LFQPO is composed of a series of intermittent oscillations appearing occasionally between 3 and 5 Hz. We further characterized this intermittency by computing the confidence limits of the instantaneous amplitudes of the intermittent oscillations, and constructed both the distributions of the QPO’s high- and low-amplitude durations, which are the time intervals with and without significant ˜4-Hz oscillations, respectively. The mean high-amplitude duration is 1.45 s and 90% of the oscillation segments have lifetimes below 3.1 s. The mean low-amplitude duration is 0.42 s and 90% of these segments are shorter than 0.73 s. In addition, these intermittent oscillations exhibit a correlation between the oscillation’s rms amplitude and mean count rate. This correlation could be analogous to the linear rms-flux relation found in the 4-Hz LFQPO through Fourier analysis. We conclude that the LFQPO peak in the power spectrum is broadened owing to intermittent oscillations with varying frequencies, which could be explained by using the Lense-Thirring precession model.

  17. Near-infrared and optical observations of the failed outbursts of black hole binary XTE J1550-564

    NASA Astrophysics Data System (ADS)

    Curran, P. A.; Chaty, S.

    2013-09-01

    Context. A number of low mass X-ray binaries (LMXBs) undergo "failed outbursts" in which, instead of evolving through the canonical states, they remain in a hard state throughout the outburst. While the sources of X-ray and radio emission in the hard state are relatively well understood, the origin of the near-infrared (NIR) and optical emission is more complex though it likely stems from an amalgam of different emission processes, occurring as it does, at the intersecting wavelengths of those processes. Aims: We aim to identify the NIR/optical emission region(s) during a number of failed outbursts of one such LMXB and black hole candidate, XTE J1550-564, in order to confirm or refute their classification as hard-state, failed outbursts. Methods: We present unique NIR/optical images and spectra, obtained with the ESO-New Technology Telescope, during the failed outbursts of 2001 and 2000. We compare the NIR/optical photometric, timing, and spectral properties with those expected for the different emission mechanisms in the various LMXB states. Results: The NIR/optical data are consistent with having come from reprocessing of X-rays in the accretion disk, with no evidence of direct thermal emission from the disk itself. However, the observed variability in high-cadence NIR light curves suggest that the radio jet extends and contributes to the NIR wavelengths. Conclusions: We find that these failed outbursts did not transition to an intermediate state but remained in a true, hard state where there was no sign of jet quenching or deviation from the observed hard state correlations. Based on observations made with the European Southern Observatory telescopes obtained from the ESO/ST-ECF Science Archive Facility.

  18. X-ray jet emission from the black hole X-ray binary XTE J1550-564 with CHANDRA in 2000

    NASA Astrophysics Data System (ADS)

    Tomsick, J. A.; Corbel, S.; Fender, R. P.; Miller, J. M.; Orosz, J. A.; Tzioumis, T.; Wijnands, R.; Kaaret, P.

    We have discovered an X-ray jet due to material ejected from the black hole X-ray transient XTE J1550-564 (see also the Corbel et al. contribution to these proceedings). We present results from three Chandra observations made between 2000 June and 2000 September. For these observations, a source is present that moves in an eastward direction away from the point source associated with the compact object. The separation between the new source and the compact object changes from 21''.3 in June to 23''.4 in September, implying a proper motion of 21.2 ± 7.2 mas day-1, a projected separation of 0.31-0.85 pc and a jet velocity >0.22c for a source distance range of d = 2.8-7.6 kpc. These observations represent the first time that an X-ray jet proper motion measurement has been obtained for any accretion powered Galactic or extra-galactic source. Along with a 1998 VLBI proper motion measurement, the Chandra proper motion indicates that the jet decelerated between 1998 and 2000. Although we cannot definitively determine the X-ray emission mechanism, a synchrotron origin is viable and may provide the simplest explanation for the observations.

  19. X-Ray Jet Emission from the Black Hole X-Ray Binary XTE J1550-564 with Chandra in 2000

    NASA Astrophysics Data System (ADS)

    Tomsick, John A.; Corbel, Stéphane; Fender, Rob; Miller, Jon M.; Orosz, Jerome A.; Tzioumis, Tasso; Wijnands, Rudy; Kaaret, Philip

    2003-01-01

    We have discovered an X-ray jet due to material ejected from the black hole X-ray transient XTE J1550-564. The discovery was first reported in 2002 by Corbel and coworkers, and here we present an analysis of the three Chandra observations made between 2000 June and September. For these observations, a source is present that moves in an eastward direction away from the point source associated with the compact object. The separation between the new source and the compact object changes from 21.3" in June to 23.4" in September, implying a proper motion of 21.2+/-7.2 mas day-1, a projected separation of 0.31-0.85 pc, and an apparent jet velocity between 0.34+/-0.12 and 0.93+/-0.32 times the speed of light for a source distance range of d=2.8-7.6 kpc. These observations represent the first time that an X-ray jet proper-motion measurement has been obtained for any accretion-powered Galactic or extragalactic source. While this work deals with the jet to the east of the compact object, the western jet has also been detected in the X-ray and radio bands. The most likely scenario is that the eastern jet is the approaching jet and that the jet material was ejected from the black hole in 1998. Along with a 1998 VLBI proper-motion measurement, the Chandra proper motion indicates that the eastern jet decelerated between 1998 and 2000. There is evidence that the eastern jet is extended by +/-2"-3" in the direction of the proper motion. The upper limit on the source extension in the perpendicular direction is +/-1.5", which corresponds to a jet opening angle of less than 7.5d. The X-ray jet energy spectrum is well but not uniquely described by a power law with an energy index of α=-0.8+/-0.4 (Sν~να) and interstellar absorption. The eastern jet was also detected in the radio band during an observation made within 7.4 days of the June Chandra observation. The overall radio flux level is consistent with an extrapolation of the X-ray power law with α=-0.6. The 0.3-8 keV X-ray jet

  20. X-ray jets in microquasar

    NASA Astrophysics Data System (ADS)

    Corbel, S.

    2003-03-01

    Large scale moving relativistic X-ray jets have been recently discovered around the microquasar XTE J1550--564 (Corbel et al. 2002, Sci., 298, 196). They have been observed over a timescale of at least four years. The broadband spectra of the jets are consistent with synchrotron emission from high energy (up to 10 TeV) particles accelerated in shocks, possibly during the interaction of the jets with the interstellar medium. XTE J1550-564 offers 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 relativistic jets from Galactic x-ray binaries and active galactic nuclei. New results from the continuing multiwavelength campaign, as well as a comparison with other jet producing system, will be shown during this presentation.

  1. THE DISTANCE, INCLINATION, AND SPIN OF THE BLACK HOLE MICROQUASAR H1743-322

    SciTech Connect

    Steiner, James F.; McClintock, Jeffrey E.; Reid, Mark J.

    2012-01-20

    During its 2003 outburst, the black hole X-ray transient H1743-322 produced two-sided radio and X-ray jets. Applying a simple and symmetric kinematic model to the trajectories of these jets, we determine the source distance, 8.5 {+-} 0.8 kpc, and the inclination angle of the jets, 75 Degree-Sign {+-} 3 Degree-Sign . Using these values, we estimate the spin of the black hole by fitting its Rossi X-ray Timing Explorer spectra, obtained during the 2003 outburst, to a standard relativistic accretion-disk model. For its spin, we find a{sub *} = 0.2 {+-} 0.3 (68% limits), -0.3 < a{sub *} < 0.7 at 90% confidence. We strongly rule against an extreme value of spin: a{sub *} < 0.92 at 99.7% confidence. H1743-322 is the third known microquasar (after A0620-00 and XTE J1550-564) that displays large-scale ballistic jets and has a moderate value of spin. Our result, which depends on an empirical distribution of black hole masses, takes into account all known sources of measurement error.

  2. Relativistic Iron Emission and Disk Reflection in Galactic Microquasar XTE J1748-288

    NASA Technical Reports Server (NTRS)

    Miller, J. M.; Fox, D. W.; Matteo, T. DI; Wijnands, R.; Belloni, T.; Pooley, D.; Kouveliotou, C.; Lewin, W. H. G.

    2001-01-01

    We report evidence for an Fe K(alpha) fluorescence line feature and disk reflection in the very high, high-, and low-state X-ray spectra of the Galactic microquasar XTE J1748-288 during its 1998 June outburst. Spectral analyses are made on data gathered throughout the outburst by the Rossi X-Ray Timing Explorer Proportional Counter Array. Gaussian line, relativistic disk emission line, and ionized disk reflection models are fitted to the data. In the very high state the line profile appears strongly redshifted, consistent with disk emission from the innermost stable orbits around a maximally rotating Kerr black hole. In the high state the line profile is less redshifted and increasingly prominent. The low-state line profile is very strong (approx. 0.5 keV equivalent width) and centered at 6.7 +/- 0.10 keV; disk line emission model fits indicate that the inner edge of the disk fluctuates between approx. 20Rg and approx. 100Rg in this state. The disk reflection fraction is traced through the outburst; reflection from an ionized disk is preferred in the very high and high states, and reflection from a relatively neutral disk is preferred in the low state. We discuss the implications of our findings for the binary system dynamics and accretion flow geometry in XTE J1748-288.

  3. Relativistic Iron Emission and Disk Reflection in Galactic Microquasar XTE J1748-288

    NASA Technical Reports Server (NTRS)

    Miller, J. M.; Fox, D. W.; DiMatteo, T.; Wijnands, R.; Belloni, T.; Pooley, D.; Kouveliotou, C.; Lewin, W. H. G.

    2001-01-01

    We report evidence for an Fe K-alpha fluorescence line feature and disk reflection in the very high, high-, and low-state X-ray spectra of the Galactic microquasar XTE J1748 - 288 during its 1998 June outburst. Spectral analyses are made on data gathered throughout the outburst by the Rossi X-Ray Timing Explorer Proportional Counter Array. Gaussian line, relativistic disk emission line, and ionized disk reflection models are fitted to the data. In the very high state the line profile appears strongly redshifted, consistent with disk emission from the innermost stable orbits around a maximally rotating Kerr black hole. In the high state the line profile is less redshifted and increasingly prominent. The low-state line profile is very strong (approx. 0.5 keV equivalent width) and centered at 6.7 +/- 0.10 keV; disk line emission model fits indicate that the inner edge of the disk fluctuates between approx. 20R(sub g) and - approx. 100R(sub g) in this state. The disk reflection fraction is traced through the outburst; reflection from an ionized disk is preferred in the very high and high states, and reflection from a relatively neutral disk is preferred in the low state. We discuss the implications of our findings for the binary system dynamics and accretion flow geometry in XTE J1748 - 288.

  4. Relativistically Skewed Iron Emission and Disk Reflection in Galactic Microquasar XTE J1748-288

    NASA Technical Reports Server (NTRS)

    Miller, J. M.; Fox, D. W.; DiMatteo, T.; Wijnands, R.; Belloni, T.; Kouveliotou, C.; Lewin, W. H. G.

    2000-01-01

    We report evidence for an Fe K-alpha fluorescence line feature in the Very High, High, and Low state X-ray spectra of the galactic microquasar XTE JI748-288 during its June 1998 outburst. Spectral analyses were made on observations spread across the outburst, gathered with the Rossi X-ray Timing Explorer. Gaussian line. disk emission line, relativistic disk emission line, and disk reflection models are fit to the data. In the Very High State, the line profile is strongly redshifted and consistent with emission from the innermost radius of a maximally rotating Kerr black hole, 1.235 R(sub g). The line profile is less redshifted in the High State, but increasingly prominent. In the Low State, the line profile is very strong and centered af approx. 6.7 keV; disk line emission models constrain the inner edge of the disk to fluctuate between approx.20 and approx.59 R(sub g). We trace the disk reflection fraction across the full outburst of this source, and find well-constrained fractions below those observed in AGN in the Very High and High States, but consistent with other galactic sources in the Low State. We discuss the possible implications for black hole X-ray binary system dynamics and accretion flow geometry.

  5. Microquasars

    NASA Astrophysics Data System (ADS)

    Mirabel, I. Félix

    2007-01-01

    Microquasars are compact objects (stellar-mass black holes and neutron stars) in our Galaxy that mimic, on a smaller scale, many of the phenomena seen in quasars. Their discovery provided new insights into the physics of relativistic jets observed elsewhere in the universe, and the accretion jet coupling. Furthermore, microquasars are opening new horizons for the understanding of ultraluminous X-ray sources observed in external galaxies, gamma-ray bursts of long duration, and the origin of stellar black holes and neutron stars. Microquasars are one of the best laboratories to probe General Relativity in the limit of the strongest gravitational fields, and, as such, have become an area of topical interest for both high energy physics and astrophysics. To cite this article: I.F. Mirabel, C. R. Physique 8 (2007).

  6. On the Origin of Radio Emission in the X-Ray States of XTE J1650-500 during the 2001-2002 Outburst

    NASA Astrophysics Data System (ADS)

    Corbel, S.; Fender, R. P.; Tomsick, J. A.; Tzioumis, A. K.; Tingay, S.

    2004-12-01

    We report on simultaneous radio and X-ray observations of the black hole candidate XTE J1650-500 during the course of its 2001-2002 outburst. The scheduling of the observations allowed us to sample the properties of XTE J1650-500 in different X-ray spectral states, namely, the hard state, the steep power-law state, and the thermal dominant state, according to the recent spectral classification of McClintock & Remillard. The hard state is consistent with a compact jet dominating the spectral energy distribution at radio frequencies; however, the current data suggest that its contribution as direct synchrotron emission at higher energies may not be significant. In that case, XTE J1650-500 may be dominated by Compton processes (either inverse Comptonization of thermal disk photons and/or synchrotron self-Compton radiation from the base of the compact jet) in the X-ray regime. We surprisingly detect a faint level of radio emission in the thermal dominant state that may be consistent with the emission of previously ejected material interacting with the interstellar medium, similar (but on a smaller angular scale) to what was observed in XTE J1550-564 by Corbel and coworkers. Based on the properties of radio emission in the steep power-law state of XTE J1650-500 and taking into account the behavior of other black hole candidates (namely, GX 339-4, XTE J1550-564, and XTE J1859+226) while in the intermediate and steep power-law states, we are able to present a general pattern of behavior for the origin of radio emission in these two states that could be important for understanding the accretion-ejection coupling very close to the black hole event horizon.

  7. The Large-Scale, Decelerating X-Ray Jets from the Microquasar XTE J1550—564: Evidence for External Shocks Caused by the Jet-Ism Interaction?

    NASA Astrophysics Data System (ADS)

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

    Large-scale, decelerating, relativistic X-ray jets from microquasar XTE J1550—564 has been recently discovered with Chandra by Corbel et al. (2002). We find that the dynamical evolution of the approaching jet at the late time is consistent with the well-known Sedov evolutionary phase R ∝ t2/5. A trans-relativistic external shock dynamic model by analogy with the evolution of gammaray burst remnants, is shown to be able to fit the proper-motion data of the approaching jet reasonably well. The inferred interstellar medium density around the source is well below the canonical value nISM ˜ 1 cm-3. The rapidly fading X-ray emission can be interpreted as synchrotron radiation from the non-thermal electrons in the adiabatically expanding ejecta. These electrons were accelerated by the reverse shock (moving back into the ejecta) which becomes important when the inertia of the swept external matter leads to an appreciable slowing down of the original ejecta.

  8. Low-mass X-ray Binaries with RXTE

    NASA Technical Reports Server (NTRS)

    2004-01-01

    Below are the publications which directly and indirectly evolved from this very successful program: 1) 'Search for millisecond periodicities in type I X-ray bursts of the Rapid Burster'; 2) 'High-Frequency QPOs in the 2000 Outburst of the Galactic Microquasar XTE J1550-564'; 3) 'Chandra and RXTE Spectroscopy of Galactic Microquasar XTE 51550-564 in Outburst'; 4) 'GX 339-4: back to life'; 5) 'Evidence for black hole spin in GX 339-4: XMM-Newton EPIC-PN and RXTE spectroscopy of the very high state'.

  9. XTE Science Briefing from KSCNF

    NASA Technical Reports Server (NTRS)

    1995-01-01

    The X-ray Timing Explorer (XTE), launched on Dec. 30, 1995, is a Satellite that observes the fast-moving, high-energy worlds of black holes, neutron stars, x-ray pulsars and bursts of X-rays that light up the sky and then disappear forever. This videotape presents a pre-launch science briefing to the press by a few of the scientist and managers associated with the XTE satellite. The moderator for the press briefing is Jim Sahli, from the Public Affairs Office at Goddard Space Flight Center (GSFC). He introduces Alan Bunner, of the High Energy Astrophysics at NASA Headquarters; Fred Lamb, from the University of Illinois; Richard Mashotzky, X Ray Scientist at GSFC; Rick Rothschild, Principal Investigator from the University of California at San Diego; and Dale Schultz, the XTE project manager at GSFC. Dr. Bunner explains the electromagnetic spectrum, the placement of x-rays and the importance of the XTE observations to a better understanding of the Universe. Dr. Lamb, explains the difference between white dwarfs, neutron stars and black holes, and the type of observations that the XTE will give to a further understanding of these phenomena. Dr. Mashotzky expands the viewpoint to beyond the galaxy, and explains the interests of scientists who hope to use XTE to further study Quasars and Active Galactic Nuclei. Dr. Rothschild reviews some of the features of XTE, using a diagram to show the features of interest, such as the X ray Telescopes, and the collecting Proportional Counter Array (PCA.) Mr. Schultz presents a videotape tour of the XTE, in which he shows the scientific instruments and the other features of the satellite. In this tour, the source of each of the instruments is noted. Questions from the members of the press are then fielded. Many of the questions are about the cost of the XTE and any problems that are anticipated in regards to the launch.

  10. Black hole binaries and microquasars

    NASA Astrophysics Data System (ADS)

    Zhang, Shuang-Nan

    2013-12-01

    This is a general review on the observations and physics of black hole X-ray binaries and microquasars, with the emphasize on recent developments in the high energy regime. The focus is put on understanding the accretion flows and measuring the parameters of black holes in them. It includes mainly two parts: i) Brief review of several recent review article on this subject; ii) Further development on several topics, including black hole spin measurements, hot accretion flows, corona formation, state transitions and thermal stability of standard think disk. This is thus not a regular bottom-up approach, which I feel not necessary at this stage. Major effort is made in making and incorporating from many sources useful plots and illustrations, in order to make this article more comprehensible to non-expert readers. In the end I attempt to make a unification scheme on the accretion-outflow (wind/jet) connections of all types of accreting BHs of all accretion rates and all BH mass scales, and finally provide a brief outlook.

  11. "Microquasar" Discoveries Win Prize for Astronomers

    NASA Astrophysics Data System (ADS)

    The discovery of "microquasars" within our own Milky Way Galaxy has won two astronomers a prize from the High Energy Astrophysics Division of the American Astronomical Society. Felix Mirabel of the Center for Studies at Saclay, France, and Luis Rodriguez of the Institute of Astronomy at the National Autonomous University in Mexico City, were awarded the Bruno Rossi Prize at the American Astronomical Society meeting in Toronto, Ontario, today. The two researchers, who have collaborated for more than 15 years, used an orbiting X-Ray observatory and the National Science Foundation's Very Large Array (VLA) radio telescope to discover the extremely energetic microquasars. Microquasars are thought to be binary-star systems with one of the stars either a superdense neutron star or a black hole. They emit X-rays and eject jets of subatomic particles at speeds approaching that of light. Though the neutron stars or black holes in microquasars are only a few times the mass of the sun, the phenomena associated with them, such as the jets, are similar to those seen in active galaxies and quasars, believed to be powered by the gravitational energy of black holes with millions of times the mass of the sun. As such, the microquasars provide much closer "laboratories" for study of these phenomena, which remain poorly understood. The Rossi Prize is awarded for "a significant contribution to high energy astrophysics, with particular emphasis on recent work," according to the High Energy Astrophysics Division. Mirabel and Rodriguez began the research that led to the microquasar discoveries in 1990. Using the French-Russian SIGMA- GRANAT X-Ray satellite, they discovered a microquasar near the Milky Way's center in 1992. With the VLA, they found radio emission from this object. In 1992, using the same satellite, they discovered a similar object, called GRS 1915+105. In 1994, that object experienced an outburst that made it bright enough at radio wavelengths to observe with the VLA

  12. Prospects for Observations of Microquasars with GLAST

    SciTech Connect

    Dubois, Richard; /SLAC

    2007-10-09

    The Gamma-ray Large Area Space Telescope (GLAST) is a next generation high energy gamma-ray observatory due for launch in Fall 2007. The primary instrument is the Large Area Telescope (LAT), which will measure gamma-ray flux and spectra from 20 MeV to > 300 GeV and is a successor to the highly successful EGRET experiment on CGRO. The LAT will have better angular resolution, greater effective area, wider field of view and broader energy coverage than any previous experiment in this energy range. This poster will present performance estimates with particular emphasis on how these apply to studies of microquasars. The LAT's scanning mode will provide unprecedented uniformity of sky coverage and permit measurements of light curves for any source. We will show results from recent detailed simulations that illustrate the potential of the LAT to observe microquasar variability and spectra, including source sensitivity and ability to detect orbital modulation.

  13. An INTEGRAL Archival Search for Microquasar Candidates

    NASA Astrophysics Data System (ADS)

    Walker, L. M.; Larson, K. L.; Boone, L. M.

    2005-12-01

    We present the status of an ongoing effort to complete a systematic search of the INTEGRAL archive for possible microquasar candidates. Source screening follows the methodology of Motch et al. (1998), but employs current versions of the NRAO/VLA and X-ray catalogs for positional cross--correlation studies. Candidate source fluxes are evaluated with respect to the sensitivities of the the instruments on board the INTEGRAL satellite, and a preliminary analysis of ISGRI and JEM--X data for appropriate candidate sources is presented. This work was funded in part by The College of Wooster's NSF supported REU program (DMR-0243811).

  14. GLAST Status and Application to Microquasars

    SciTech Connect

    Dubois, Richard; /SLAC

    2006-11-15

    The Gamma-ray Large Area Space Telescope (GLAST) is a next generation high energy gamma-ray observatory due for launch in Fall 2007. The primary instrument is the Large Area Telescope (LAT), which will measure gamma-ray flux and spectra from 20 MeV to > 300 GeV and is a successor to the highly successful EGRET experiment on CGRO. The LAT will have better angular resolution, greater effective area, wider field of view and broader energy coverage than any previous experiment in this energy range. An overview of the LAT instrument design and construction is presented which includes performance estimates with particular emphasis on how these apply to studies of microquasars. The nature and quality of the data that will be provided by the LAT is described with results from recent detailed simulations that illustrate the potential of the LAT to observe gamma ray variability and spectra.

  15. From Cradle To Grave: Chandra Discovers The History Of Black Hole X-Ray Jets

    NASA Astrophysics Data System (ADS)

    2002-10-01

    For the first time, astronomers have tracked the life cycle of X-ray jets from a black hole. A series of images from NASA's Chandra X-ray Observatory has revealed that as the jets evolved, they traveled at near light speed for several years before slowing down and fading. "Watching these jets slow down and disappear is like watching a time-lapse movie of the rise and fall of the Bronze Age," said Stephane Corbel of the University of Paris VII and the French Atomic Energy Commission in Saclay, lead author of a paper in the October 4th issue of the journal Science. "Since the jets came from a stellar black hole in our galaxy, we watched in a few years developments that would have taken thousands of years to occur around a supermassive black hole in a distant galaxy." Astronomers have been using Chandra and radio telescopes to observe two opposing jets of high-energy particles emitted following an outburst, first detected in 1998 by NASA's Rossi X-ray Timing Explorer, from the double-star system XTE J1550-564. The X-ray jets, which require a continuous source of trillion-volt electrons to remain bright, were observed moving at about half the speed of light. Four years later, they are now more than three light years apart and slowing down. One of the jets has recently been observed to fade. XTE J1550-564 Time-Lapse Movie XTE J1550-564 Time-Lapse Movie "The ejection of jets from stellar and supermassive black holes is a common occurrence in the universe, so it is extremely important to understand the process," said John Tomsick of the University of California, San Diego, and author of an Astrophysical Journal paper scheduled for January 2003 publication describing the research. "For the first time, we have observed a jet from the initial explosion until it slowed and faded." The observations indicate that one jet, the eastern jet, is moving along a line tilted toward the Earth whereas the western jet is pointed away from the Earth. This alignment explains why the

  16. Chaotic and stochastic processes in the accretion flows of the black hole X-ray binaries revealed by recurrence analysis

    NASA Astrophysics Data System (ADS)

    Suková, Petra; Grzedzielski, Mikolaj; Janiuk, Agnieszka

    2016-02-01

    variability in the microquasars GRS 1915+105 and IGR J17091-3624. Furthermore, we also find significant traces of nonlinear dynamics in three other sources: GX 339-4, XTE J1550-564 and GRO J1655-40, particularly in the disk-dominated soft state, as well as in the intermediate states at the rising and declining phase of the outburst. Only for the source XTE J1650-500 no observation with such variability pattern was found. This is possibly due to the global accretion rate in this source being too small for the limit-cycle instability to develop.

  17. Prospects for High Energy Detection of Microquasars with the AGILE and GLAST Gamma-Ray Telescopes

    SciTech Connect

    Santolamazza, Patrizia; Pittori, Carlotta; Verrecchia, Francesco

    2007-08-21

    We estimate the sensitivities of the AGILE and GLAST {gamma}-ray experiments taking into account two cases for the galactic {gamma}-ray diffuse background (at high galactic latitude and toward the galactic center). Then we use sensitivities to estimate microquasar observability with the two experiments, assuming the {gamma}-ray emission above 100 MeV of a recent microquasar model.

  18. Gigantic Cosmic Corkscrew Reveals New Details About Mysterious Microquasar

    NASA Astrophysics Data System (ADS)

    2004-10-01

    Making an extra effort to image a faint, gigantic corkscrew traced by fast protons and electrons shot out from a mysterious microquasar paid off for a pair of astrophysicists who gained new insights into the beast's inner workings and also resolved a longstanding dispute over the object's distance. Microquasar SS 433 VLA Image of Microquasar SS 433 CREDIT: Blundell & Bowler, NRAO/AUI/NSF (Click on Image for Larger Version) The astrophysicists used the National Science Foundation's Very Large Array (VLA) radio telescope to capture the faintest details yet seen in the plasma jets emerging from the microquasar SS 433, an object once dubbed the "enigma of the century." As a result, they have changed scientists' understanding of the jets and settled the controversy over its distance "beyond all reasonable doubt," they said. SS 433 is a neutron star or black hole orbited by a "normal" companion star. The powerful gravity of the neutron star or black hole draws material from the stellar wind of its companion into an accretion disk of material tightly circling the dense central object prior to being pulled onto it. This disk propels jets of fast protons and electrons outward from its poles at about a quarter of the speed of light. The disk in SS 433 wobbles like a child's top, causing its jets to trace a corkscrew in the sky every 162 days. The new VLA study indicates that the speed of the ejected particles varies over time, contrary to the traditional model for SS 433. "We found that the actual speed varies between 24 percent to 28 percent of light speed, as opposed to staying constant," said Katherine Blundell, of the University of Oxford in the United Kingdom. "Amazingly, the jets going in both directions change their speeds simultaneously, producing identical speeds in both directions at any given time," Blundell added. Blundell worked with Michael Bowler, also of Oxford. The scientists' findings have been accepted by the Astrophysical Journal Letters. SS 433 New VLA

  19. Is XTE J1701-407 Extended?

    NASA Astrophysics Data System (ADS)

    Kaplan, David

    2007-09-01

    We recently observed the neutron star X-ray transient XTE J1701-407 with Chandra, using 1 ks of ACIS-S data for localization. However, the Chandra data do not show a point source. Instead the source appears extended over ~6 arcsec. We have investigated the data, consulting with experts both at MIT and SAO, and cannot ascribe the data to purely instrumental effects (aspect errors or pileup). The extended X-ray emission could come from an outflow or a dust scattering halo - both very interesting and rare phenomena. Jets allow detailed calorimetry of the outbursts, while scattering halos lead to geometric distances. We request a 5 ks ACIS-S subarray observation to definitively assess the morphology, trying to discriminate between these scenarios before the target fades into quiescence.

  20. Search for neutrino emission from microquasars with the ANTARES telescope

    NASA Astrophysics Data System (ADS)

    Galatà, S.

    2012-12-01

    Neutrino telescopes are nowadays exploring a new window of observation on the high energy universe and may shed light on the longstanding problem regarding the origin of cosmic rays. The ANTARES neutrino telescope is located underwater 40 km offshore from the Southern coast of France, on a plateau at 2475 m depth. Since 2007 it observes the high energy (>100 GeV) neutrino sky looking for cosmic neutrino sources. Among the candidate neutrino emitters are microquasars, i.e. galactic X-ray binaries exhibiting relativistic jets, which may accelerate hadrons thus producing neutrinos, under certain conditions. These sources are also variable in time and undergo X-ray or gamma ray outburst that can be related to the acceleration of relativistic particles witnessed by their radio emission. These events can provide a trigger to the neutrino search, with the advantage of drastically reducing the atmospheric neutrino background. A search for neutrino emission from microquasar during outbursts is presented based on the data collected by ANTARES between 2007 and 2010. Upper limits are shown and compared with the predictions.

  1. Discovery of a high-energy gamma-ray-emitting persistent microquasar

    PubMed

    Paredes; Marti; Ribo; Massi

    2000-06-30

    Microquasars are stellar x-ray binaries that behave as a scaled-down version of extragalactic quasars. The star LS 5039 is a new microquasar system with apparent persistent ejection of relativistic plasma at a 3-kiloparsec distance from the sun. It may also be associated with a gamma-ray source discovered by the Energetic Gamma Ray Experiment Telescope (EGRET) on board the COMPTON-Gamma Ray Observatory satellite. Before the discovery of LS 5039, merely a handful of microquasars had been identified in the Galaxy, and none of them was detected in high-energy gamma-rays.

  2. Veritas observations of the microquasar Cygnus X-3

    SciTech Connect

    Archambault, S.; Beilicke, M.; Buckley, J. H.; Bugaev, V.; Benbow, W.; Cerruti, M.; Berger, K.; Bird, R.; Bouvier, A.; Byrum, K.; Chen, X.; Federici, S.; Ciupik, L.; Connolly, M. P.; Cui, W.; Feng, Q.; Duke, C.; Dumm, J.; Errando, M.; Falcone, A. E-mail: cui@purdue.edu; Collaboration: VERITAS Collaboration) and; Smithsonian Astrophysical Observatory; and others

    2013-12-20

    We report results from TeV gamma-ray observations of the microquasar Cygnus X-3. The observations were made with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) over a time period from 2007 June 11 to 2011 November 28. VERITAS is most sensitive to gamma rays at energies between 85 GeV and 30 TeV. The effective exposure time amounts to a total of about 44 hr, with the observations covering six distinct radio/X-ray states of the object. No significant TeV gamma-ray emission was detected in any of the states, nor with all observations combined. The lack of a positive signal, especially in the states where GeV gamma rays were detected, places constraints on TeV gamma-ray production in Cygnus X-3. We discuss the implications of the results.

  3. Positron annihilation signatures associated with the outburst of the microquasar V404 Cygni.

    PubMed

    Siegert, Thomas; Diehl, Roland; Greiner, Jochen; Krause, Martin G H; Beloborodov, Andrei M; Bel, Marion Cadolle; Guglielmetti, Fabrizia; Rodriguez, Jerome; Strong, Andrew W; Zhang, Xiaoling

    2016-03-17

    Microquasars are stellar-mass black holes accreting matter from a companion star and ejecting plasma jets at almost the speed of light. They are analogues of quasars that contain supermassive black holes of 10(6) to 10(10) solar masses. Accretion in microquasars varies on much shorter timescales than in quasars and occasionally produces exceptionally bright X-ray flares. How the flares are produced is unclear, as is the mechanism for launching the relativistic jets and their composition. An emission line near 511 kiloelectronvolts has long been sought in the emission spectrum of microquasars as evidence for the expected electron-positron plasma. Transient high-energy spectral features have been reported in two objects, but their positron interpretation remains contentious. Here we report observations of γ-ray emission from the microquasar V404 Cygni during a recent period of strong flaring activity. The emission spectrum around 511 kiloelectronvolts shows clear signatures of variable positron annihilation, which implies a high rate of positron production. This supports the earlier conjecture that microquasars may be the main sources of the electron-positron plasma responsible for the bright diffuse emission of annihilation γ-rays in the bulge region of our Galaxy. Additionally, microquasars could be the origin of the observed megaelectronvolt continuum excess in the inner Galaxy.

  4. Positron annihilation signatures associated with the outburst of the microquasar V404 Cygni

    NASA Astrophysics Data System (ADS)

    Siegert, Thomas; Diehl, Roland; Greiner, Jochen; Krause, Martin G. H.; Beloborodov, Andrei M.; Bel, Marion Cadolle; Guglielmetti, Fabrizia; Rodriguez, Jerome; Strong, Andrew W.; Zhang, Xiaoling

    2016-03-01

    Microquasars are stellar-mass black holes accreting matter from a companion star and ejecting plasma jets at almost the speed of light. They are analogues of quasars that contain supermassive black holes of 106 to 1010 solar masses. Accretion in microquasars varies on much shorter timescales than in quasars and occasionally produces exceptionally bright X-ray flares. How the flares are produced is unclear, as is the mechanism for launching the relativistic jets and their composition. An emission line near 511 kiloelectronvolts has long been sought in the emission spectrum of microquasars as evidence for the expected electron-positron plasma. Transient high-energy spectral features have been reported in two objects, but their positron interpretation remains contentious. Here we report observations of γ-ray emission from the microquasar V404 Cygni during a recent period of strong flaring activity. The emission spectrum around 511 kiloelectronvolts shows clear signatures of variable positron annihilation, which implies a high rate of positron production. This supports the earlier conjecture that microquasars may be the main sources of the electron-positron plasma responsible for the bright diffuse emission of annihilation γ-rays in the bulge region of our Galaxy. Additionally, microquasars could be the origin of the observed megaelectronvolt continuum excess in the inner Galaxy.

  5. Delta XTE Lift and Mate at Complex 17A

    NASA Technical Reports Server (NTRS)

    1995-01-01

    This NASA Kennedy Space Center (KSC) video release presents footage of the lift and mate of NASA's X-ray Timing Explorer (XTE) to a McDonnell Douglas Delta II rocket at Launch Complex 17A, Cape Canaveral Air Station. The video includes shots of the workcrews as well as wide angle views of the spacecraft in its launching position. The XTE was launched into a circular orbit with an altitude of 600 km and an inclination of 23 degrees on Dec. 30, 1995.

  6. Delta XTE Spacecraft Arrives at CCAS Skid Strip

    NASA Technical Reports Server (NTRS)

    1995-01-01

    Footage shows the U.S Air Force Aircraft "Air Mobility Command" approaching, and landing at the Cape Canaveral Air Station Skid Strip (CCAS). The truck carrying the Delta XTE Spacecraft is also shown as it leaves the Air Mobility Command.

  7. Jet Formation and Dynamics: Comparison of Quasars and Microquasars

    NASA Astrophysics Data System (ADS)

    Kundt, Wolfgang

    Quasars and Microquasars share the following properties: (i) They have similar, elongated morphologies - reminiscent of being driven by supersonic beams - consisting of cores, knots, and heads, with jet-opening angles <~ 10^-2, and no beam branching; (ii) core/lobe power ratios of 10^2 +/- 2; (iii) fluctuating, broad and hard core spectra; (iv) (occasional) sidedness; (v) (occasional) superluminal growth. In all cases, the central engine is thought to be a rotating magnet whose reconnecting magnetic fields generate the relativistic pair plasma - of typical Lorentz factor 10^3 +/- 2 - which rams the jet channels and blows the cocoons (subsonically) after having been stalled in a head. The supersonic jets form on passing a central deLaval nozzle, first proposed by Blandford and Rees in 1974, which forms naturally due to the huge density contrast of 10^-8.3T_4 with respect to the ambient medium (of temperature T, T_4:=T/10^4 K). Beam stability and narrowness are likewise guaranteed by the density contrast (of jet fluid and CSM). Observed are both the (thermal) radiation of the rammed channel-wall material, and the synchrotron radiation of the deflected beam particles.

  8. Relativistic Jets in Active Galactic Nuclei and Microquasars

    NASA Astrophysics Data System (ADS)

    Romero, Gustavo E.; Boettcher, M.; Markoff, S.; Tavecchio, F.

    2017-01-01

    Collimated outflows (jets) appear to be a ubiquitous phenomenon associated with the accretion of material onto a compact object. Despite this ubiquity, many fundamental physics aspects of jets are still poorly understood and constrained. These include the mechanism of launching and accelerating jets, the connection between these processes and the nature of the accretion flow, and the role of magnetic fields; the physics responsible for the collimation of jets over tens of thousands to even millions of gravitational radii of the central accreting object; the matter content of jets; the location of the region(s) accelerating particles to TeV (possibly even PeV and EeV) energies (as evidenced by γ-ray emission observed from many jet sources) and the physical processes responsible for this particle acceleration; the radiative processes giving rise to the observed multi-wavelength emission; and the topology of magnetic fields and their role in the jet collimation and particle acceleration processes. This chapter reviews the main knowns and unknowns in our current understanding of relativistic jets, in the context of the main model ingredients for Galactic and extragalactic jet sources. It discusses aspects specific to active Galactic nuclei (especially blazars) and microquasars, and then presents a comparative discussion of similarities and differences between them.

  9. The Lukewarm Absorber in the Microquasar Cir X-1

    NASA Astrophysics Data System (ADS)

    Schulz, Norbert S.; Galloway, D. K.; Brandt, W. N.

    2006-09-01

    Through many observations in the last decades the extreme and violent X-ray binary Cir X-1 has been classified as a microquasar, Z-source, X-ray burster, and accreting neutron star exhibiting ultrarelativistic jets. Since the launch of Chandra the source underwent a dramatic change from a high flux (1.5 Crab) source to a rather low persistent flux ( 30 mCrab) in the last year. Spectra from Chandra High Energy Transmission Grating Spectrometer (HETGS) taken during this transformation have revealed many details besides the large overall flux change ranging from blue-shifted absorption lines indicating high-velocity (< 2000 km/s) outflows during high flux, persistently bright lines emission throughout all phases to some form of warm absorption in the low flux phase. Newly released atomic data allows us to analyse specifically the Fe K line region with unprecedented detail for all flux phases observed so far. We also compare these new results with recently released findings of warm absorbers and outflow signatures observed in other microqasars such as GX 339+4, GRS J1655-40, and GRS1915+115.

  10. Variable very-high-energy gamma-ray emission from the microquasar LS I +61 303.

    PubMed

    Albert, J; Aliu, E; Anderhub, H; Antoranz, P; Armada, A; Asensio, M; Baixeras, C; Barrio, J A; Bartelt, M; Bartko, H; Bastieri, D; Bavikadi, S R; Bednarek, W; Berger, K; Bigongiari, C; Biland, A; Bisesi, E; Bock, R K; Bordas, P; Bosch-Ramon, V; Bretz, T; Britvitch, I; Camara, M; Carmona, E; Chilingarian, A; Ciprini, S; Coarasa, J A; Commichau, S; Contreras, J L; Cortina, J; Curtef, V; Danielyan, V; Dazzi, F; De Angelis, A; de Los Reyes, R; De Lotto, B; Domingo-Santamaría, E; Dorner, D; Doro, M; Errando, M; Fagiolini, M; Ferenc, D; Fernández, E; Firpo, R; Flix, J; Fonseca, M V; Font, L; Fuchs, M; Galante, N; Garczarczyk, M; Gaug, M; Giller, M; Goebel, F; Hakobyan, D; Hayashida, M; Hengstebeck, T; Höhne, D; Hose, J; Hsu, C C; Isar, P G; Jacon, P; Kalekin, O; Kosyra, R; Kranich, D; Laatiaoui, M; Laille, A; Lenisa, T; Liebing, P; Lindfors, E; Lombardi, S; Longo, F; López, J; López, M; Lorenz, E; Lucarelli, F; Majumdar, P; Maneva, G; Mannheim, K; Mansutti, O; Mariotti, M; Martínez, M; Mase, K; Mazin, D; Merck, C; Meucci, M; Meyer, M; Miranda, J M; Mirzoyan, R; Mizobuchi, S; Moralejo, A; Nilsson, K; Oña-Wilhelmi, E; Orduña, R; Otte, N; Oya, I; Paneque, D; Paoletti, R; Paredes, J M; Pasanen, M; Pascoli, D; Pauss, F; Pavel, N; Pegna, R; Persic, M; Peruzzo, L; Piccioli, A; Poller, M; Pooley, G; Prandini, E; Raymers, A; Rhode, W; Ribó, M; Rico, J; Riegel, B; Rissi, M; Robert, A; Romero, G E; Rügamer, S; Saggion, A; Sánchez, A; Sartori, P; Scalzotto, V; Scapin, V; Schmitt, R; Schweizer, T; Shayduk, M; Shinozaki, K; Shore, S N; Sidro, N; Sillanpää, A; Sobczynska, D; Stamerra, A; Stark, L S; Takalo, L; Temnikov, P; Tescaro, D; Teshima, M; Tonello, N; Torres, A; Torres, D F; Turini, N; Vankov, H; Vitale, V; Wagner, R M; Wibig, T; Wittek, W; Zanin, R; Zapatero, J

    2006-06-23

    Microquasars are binary star systems with relativistic radio-emitting jets. They are potential sources of cosmic rays and can be used to elucidate the physics of relativistic jets. We report the detection of variable gamma-ray emission above 100 gigaelectron volts from the microquasar LS I 61 + 303. Six orbital cycles were recorded. Several detections occur at a similar orbital phase, which suggests that the emission is periodic. The strongest gamma-ray emission is not observed when the two stars are closest to one another, implying a strong orbital modulation of the emission or absorption processes.

  11. Theoretical overview on high-energy emission in microquasars

    NASA Astrophysics Data System (ADS)

    Bosch-Ramon, Valentí

    2007-06-01

    Microquasar (MQ) jets are sites of particle acceleration and synchrotron emission. Such synchrotron radiation has been detected coming from jet regions of different spatial scales, which for the instruments at work nowadays appear as compact radio cores, slightly resolvedradio jets, or (very) extended structures (e.g. Mirabel and Rodríguez, 1999; Fender, 2001; Corbel et al., 2002). Because of the presence of relativistic particles and dense photon, magnetic and matter fields, these outflows are also the best candidates to generate the very high-energy (VHE) gamma-rays detected coming from two of these objects, LS 5039 and LS I +61 303 (Aharonian, 2005; Aharonian et al., 2006a; and Albert, 2006, respectively), and may be contributing significantly to the X-rays emitted from the MQ core (e.g. Markoff et al., 2001; Bosch-Ramon et al., 2005a). In addition, beside electromagnetic radiation, jets at different scales are producing some amount of leptonic and hadronic cosmic rays (CR), and evidences of neutrino production in these objects may be eventually found. In this work, we review on the different physical processes that may be at work in or related to MQ jets. The jet regions capable to produce significant amounts of emission at different wavelengths have been reduced to the jet base, the jet at scales of the order of the size of the system orbital semi-major axis, the jet middle scales (the resolved radio jets), and the jet termination point. The surroundings of the jet could be sites of multiwavelength emission as well, deserving also an insight. We focus on those scenarios, either hadronic or leptonic, in which it seems more plausible to generate both photons from radio to VHE and high-energy neutrinos. We briefly comment as well on the relevance of MQ as possible contributors to the galactic CR in the GeV-PeV range.

  12. Probing the space-time geometry around black hole candidates with the resonance models for high-frequency QPOs and comparison with the continuum-fitting method

    SciTech Connect

    Bambi, Cosimo

    2012-09-01

    Astrophysical black hole candidates are thought to be the Kerr black hole predicted by General Relativity. However, in order to confirm the Kerr-nature of these objects, we need to probe the geometry of the space-time around them and check that observations are consistent with the predictions of the Kerr metric. That can be achieved, for instance, by studying the properties of the electromagnetic radiation emitted by the gas in the accretion disk. The high-frequency quasi-periodic oscillations observed in the X-ray flux of some stellar-mass black hole candidates might do the job. As the frequencies of these oscillations depend only very weakly on the observed X-ray flux, it is thought they are mainly determined by the metric of the space-time. In this paper, I consider the resonance models proposed by Abramowicz and Kluzniak and I extend previous results to the case of non-Kerr space-times. The emerging picture is more complicated than the one around a Kerr black hole and there is a larger number of possible combinations between different modes. I then compare the bounds inferred from the twin peak high-frequency quasi-periodic oscillations observed in three micro-quasars (GRO J1655-40, XTE J1550-564, and GRS 1915+105) with the measurements from the continuum-fitting method of the same objects. For Kerr black holes, the two approaches do not provide consistent results. In a non-Kerr geometry, this conflict may be solved if the observed quasi-periodic oscillations are produced by the resonance ν{sub θ}:ν{sub r} = 3:1, where ν{sub θ} and ν{sub r} are the two epicyclic frequencies. It is at least worth mentioning that the deformation from the Kerr solution required by observations would be consistent with the one suggested in another recent work discussing the possibility that steady jets are powered by the spin of these compact objects.

  13. Are 3C 120 and Other Active Galactic Nuclei Overweight Microquasars?

    NASA Astrophysics Data System (ADS)

    Marscher, Alan P.

    2005-11-01

    The appearance of superluminal radio knots follows drops in the X-ray flux in the FR1 radio galaxy 3C 120 and possibly the FR2 source 3C 111. This corresponds in a very general way to the behavior of the X-ray binary GRS 1915 + 105, but the light curves of the microquasar are much richer in detail. Starting in 2003.7, the character of the radio and X-ray light curves of 3C 120 changed, perhaps signaling a new stage of activity. I discuss here what one might expect when a microquasar is scaled up to AGN dimensions, and compare this with what we see in 3C 120. There is a mismatch between expectations and observations.

  14. Modulated High-Energy Gamma-Ray Emission from the Microquasar Cygnus X-3

    NASA Technical Reports Server (NTRS)

    Celik, O.; Harding, A. K.; Hays, E.; Johnson, T. J.; Pottschmidt, K.; Thompson, D. J.

    2009-01-01

    Microquasars are accreting black holes or neutron stars in binary systems with associated relativistic jets. Despite their frequent outburst activity, they have never been unambiguously detected emitting high-energy gamma rays. The Fermi Large Area Telescope (LAT) has detected a variable high-energy source coinciding with the position of the x-ray binary and microquasar Cygnus X-3. Its identification with Cygnus X-3 is secured by the detection of its orbital period in gamma rays, as well as the correlation of the LAT flux with radio emission from the relativistic jets of Cygnus X-3. The gamma-ray emission probably originates from within the binary system, opening new areas in which to study the formation of relativistic jets.

  15. Contribution due to clumpy winds to the non-thermal emission in microquasar jets

    NASA Astrophysics Data System (ADS)

    de la Cita, V. M.; del Palacio, S.; Bosch-Ramon, V.; Paredes-Fortuny, X.; Romero, G. E.; Khangulyan, D.

    2017-03-01

    Powerful jets in high-mass microquasars are likely to be crossed by dense inhomogeneities (clumps) from the stellar winds, which may lead to particle acceleration and thus nonthermal emission in X-rays and gamma-rays. We characterise a typical clump-jet interaction scenario and compute the contribution to the high-energy emission of these systems. We use hydrodynamical simulations of a single clump-jet interaction and we use this result to compute its non-thermal (synchrotron and inverse Compton) radiation. We present several radiative calculations for a number of clump states, as the clump is disrupted over time, letting different parameters vary (viewing angle, magnetic field). We obtain significant amounts of non-thermal radiation from jet-clump interactions in high-mass microquasars.

  16. Modulated high-energy gamma-ray emission from the microquasar Cygnus X-3.

    PubMed

    Abdo, A A; Ackermann, M; Ajello, M; Axelsson, M; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Baughman, B M; Bechtol, K; Bellazzini, R; Berenji, B; Blandford, R D; Bloom, E D; Bonamente, E; Borgland, A W; Brez, A; Brigida, M; Bruel, P; Burnett, T H; Buson, S; Caliandro, G A; Cameron, R A; Caraveo, P A; Casandjian, J M; Cecchi, C; Celik, O; Chaty, S; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Cominsky, L R; Conrad, J; Corbel, S; Corbet, R; Dermer, C D; de Palma, F; Digel, S W; do Couto e Silva, E; Drell, P S; Dubois, R; Dubus, G; Dumora, D; Farnier, C; Favuzzi, C; Fegan, S J; Focke, W B; Fortin, P; Frailis, M; Fusco, P; Gargano, F; Gehrels, N; Germani, S; Giavitto, G; Giebels, B; Giglietto, N; Giordano, F; Glanzman, T; Godfrey, G; Grenier, I A; Grondin, M-H; Grove, J E; Guillemot, L; Guiriec, S; Hanabata, Y; Harding, A K; Hayashida, M; Hays, E; Hill, A B; Hjalmarsdotter, L; Horan, D; Hughes, R E; Jackson, M S; Jóhannesson, G; Johnson, A S; Johnson, T J; Johnson, W N; Kamae, T; Katagiri, H; Kawai, N; Kerr, M; Knödlseder, J; Kocian, M L; Koerding, E; Kuss, M; Lande, J; Latronico, L; Lemoine-Goumard, M; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Madejski, G M; Makeev, A; Marchand, L; Marelli, M; Max-Moerbeck, W; Mazziotta, M N; McColl, N; McEnery, J E; Meurer, C; Michelson, P F; Migliari, S; Mitthumsiri, W; Mizuno, T; Monte, C; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nolan, P L; Norris, J P; Nuss, E; Ohsugi, T; Omodei, N; Ong, R A; Ormes, J F; Paneque, D; Parent, D; Pelassa, V; Pepe, M; Pesce-Rollins, M; Piron, F; Pooley, G; Porter, T A; Pottschmidt, K; Rainò, S; Rando, R; Ray, P S; Razzano, M; Rea, N; Readhead, A; Reimer, A; Reimer, O; Richards, J L; Rochester, L S; Rodriguez, J; Rodriguez, A Y; Romani, R W; Ryde, F; Sadrozinski, H F-W; Sander, A; Saz Parkinson, P M; Sgrò, C; Siskind, E J; Smith, D A; Smith, P D; Spinelli, P; Starck, J-L; Stevenson, M; Strickman, M S; Suson, D J; Takahashi, H; Tanaka, T; Thayer, J B; Thompson, D J; Tibaldo, L; Tomsick, J A; Torres, D F; Tosti, G; Tramacere, A; Uchiyama, Y; Usher, T L; Vasileiou, V; Vilchez, N; Vitale, V; Waite, A P; Wang, P; Wilms, J; Winer, B L; Wood, K S; Ylinen, T; Ziegler, M

    2009-12-11

    Microquasars are accreting black holes or neutron stars in binary systems with associated relativistic jets. Despite their frequent outburst activity, they have never been unambiguously detected emitting high-energy gamma rays. The Fermi Large Area Telescope (LAT) has detected a variable high-energy source coinciding with the position of the x-ray binary and microquasar Cygnus X-3. Its identification with Cygnus X-3 is secured by the detection of its orbital period in gamma rays, as well as the correlation of the LAT flux with radio emission from the relativistic jets of Cygnus X-3. The gamma-ray emission probably originates from within the binary system, opening new areas in which to study the formation of relativistic jets.

  17. Enhanced Gamma-Ray Emission from the Microquasar Cygnus X-3 Detected by AGILE

    NASA Astrophysics Data System (ADS)

    Piano, G.; Tavani, M.; Verrecchia, F.; Vercellone, S.; Munar-Adrover, P.; Bulgarelli, A.; Donnarumma, I.; Minervini, G.; Fioretti, V.; Pittori, C.; Lucarelli, F.; Striani, E.; Ursi, A.; Cardillo, M.; Gianotti, F.; Trifoglio, M.; Giuliani, A.; Mereghetti, S.; Caraveo, P.; Perotti, F.; Chen, A.; Argan, A.; Costa, E.; Del Monte, E.; Evangelista, Y.; Feroci, M.; Lazzarotto, F.; Lapshov, I.; Pacciani, L.; Soffitta, P.; Sabatini, S.; Vittorini, V.; Pucella, G.; Rapisarda, M.; Di Cocco, G.; Fuschino, F.; Galli, M.; Labanti, C.; Marisaldi, M.; Pellizzoni, A.; Pilia, M.; Trois, A.; Barbiellini, G.; Vallazza, E.; Longo, F.; Morselli, A.; Picozza, P.; Prest, M.; Lipari, P.; Zanello, D.; Cattaneo, P. W.; Rappoldi, A.; Colafrancesco, S.; Parmiggiani, N.; Ferrari, A.; Antonelli, A.; Giommi, P.; Salotti, L.; Valentini, G.; D'Amico, F.

    2017-03-01

    The AGILE-GRID detector is revealing gamma ray emission above 100 MeV from the microquasar Cygnus X-3. Integrating from 2017-03-15 UT 00:00:00 to 2017-03-16 UT 00:00:00, a preliminary multi-source likelihood analysis finds a gamma-ray flux F( > 100 MeV) = (4.2 +/- 1.7) x 10^-6 photons/cm^2/s with a detection significance near 4 sigma.

  18. JET TRAILS AND MACH CONES: THE INTERACTION OF MICROQUASARS WITH THE INTERSTELLAR MEDIUM

    SciTech Connect

    Yoon, D.; Morsony, B.; Heinz, S.; Wiersema, K.; Fender, R. P.; Russell, D. M.; Sunyaev, R.

    2011-11-20

    A subset of microquasars exhibits high peculiar velocity with respect to the local standard of rest due to the kicks they receive when being born in supernovae. The interaction between the radio plasma released by microquasar jets from such high-velocity binaries with the interstellar medium must lead to the production of trails and bow shocks similar to what is observed in narrow-angle tailed radio galaxies and pulsar wind nebulae. We present a set of numerical simulations of this interaction that illuminate the long-term dynamical evolution and the observational properties of these microquasar bow-shock nebulae and trails. We find that this interaction always produces a structure that consists of a bow shock, a trailing neck, and an expanding bubble. Using our simulations to model emission, we predict that the shock surrounding the bubble and the neck should be visible in H{sub {alpha}} emission, the interior of the bubble should be visible in synchrotron radio emission, and only the bow shock is likely to be detectable in X-ray emission. We construct an analytic model for the evolution of the neck and bubble shape and compare this model with observations of the X-ray binary SAX J1712.6-3739.

  19. Accretion disk winds as the jet suppression mechanism in the microquasar GRS 1915+105.

    PubMed

    Neilsen, Joseph; Lee, Julia C

    2009-03-26

    Stellar-mass black holes with relativistic jets, also known as microquasars, mimic the behaviour of quasars and active galactic nuclei. Because timescales around stellar-mass black holes are orders of magnitude smaller than those around more distant supermassive black holes, microquasars are ideal nearby 'laboratories' for studying the evolution of accretion disks and jet formation in black-hole systems. Whereas studies of black holes have revealed a complex array of accretion activity, the mechanisms that trigger and suppress jet formation remain a mystery. Here we report the presence of a broad emission line in the faint, hard states and narrow absorption lines in the bright, soft states of the microquasar GRS 1915+105. ('Hard' and 'soft' denote the character of the emitted X-rays.) Because the hard states exhibit prominent radio jets, we argue that the broad emission line arises when the jet illuminates the inner accretion disk. The jet is weak or absent during the soft states, and we show that the absorption lines originate when the powerful radiation field around the black hole drives a hot wind off the accretion disk. Our analysis shows that this wind carries enough mass away from the disk to halt the flow of matter into the radio jet.

  20. Delta XTE Spacecraft Solar Panel Deployment, Hangar AO at Cape Canaveral Air Station

    NASA Technical Reports Server (NTRS)

    1995-01-01

    The footage shows technicians in the clean room checking and adjusting the deployment mechanism of the solar panel for XTE spacecraft. Other scenes show several technicians making adjustments to software for deployment of the solar panels.

  1. Corrected Coordinates for the Possible OC to XTE J1550-56

    NASA Astrophysics Data System (ADS)

    Orosz, Jerome; Bailyn, Charles; Jain, Raj

    1998-09-01

    There was a slight error in the coordinates of the possible optical counterpart to XTE J1550-56 we reported in our previous telegram. The correct J2000 coordinates are RA = 15:50:58.78, DEC = -56:28:35.0. The coordinates printed on the finding chart available at http://www.astro.psu.edu/users/orosz/xte.html has been corrected (the arrow points to the correct object in any case). We regret this error.

  2. Discovery of a Transient Magnetar: XTE J1810-197

    NASA Technical Reports Server (NTRS)

    Ibrahim, Alaa I.; Markwardt, Craig B.; Swank, Jean H.; Ransom, Scott; Roberts, Mallory; Kaspi, Victoria; Woods, Peter M.; Safi-Harb, Samar; Balman, Solen; Parke, William C.

    2004-01-01

    We report the discovery of a new X-ray pulsar, XTE J1810-197, that was serendipitously discovered on 2003 July 15 by the Rossi X-Ray Timing Explorer (RXTE) while observing the soft gamma repeater SGR 1806-20. The pulsar has a 5.54 s spin period, a soft X-ray spectrum (with a photon index of approx. = 4). and is detectable in earlier RXTE observations back to 2003 January but not before. These show that a transient outburst began between 2002 November 17 and 2003 January 23 and that the source's persistent X-ray flux has been declining since then. The pulsar exhibits a high spin-down rate P approx.= l0(exp -11) s/s with no evidence of Doppler shifts due to a binary companion. The rapid spin-down rate and slow spin period imply a supercritical characteristic magnetic field B approx. = 3 x l0(exp 14) G and a young age tau less than or = 7600 yr. Follow-up Chandra observations provided an accurate position of the source. Within its error radius, the 1.5 m Russian-Turkish Optical Telescope found a limiting magnitude R(sub c) = 21.5. All such properties are strikingly similar to those of anomalous X-ray pulsars ad soft gamma repeaters, providing strong evidence that the source is a new magnetar. However, archival ASCA and ROSAT observations found the source nearly 2 orders of magnitude fainter. This transient behavior and the observed long-term flux variability of the source in absence of an observed SGR-like burst activity make it the first confirmed transient magnetar and suggest that other neutron stars that share the properties of XTE 51810- 197 during its inactive phase may be unidentified transient magnetars awaiting detection via a similar activity. This implies a larger population of magnetars than previously surmised and a possible evolutionary connection between magnetars and other neutron star families. Subject headings: pulsars: general -pulsars: individual (XTE 51810- 197) - stars: magnetic fields -

  3. Multiwavelength observations of XTE J1859+226

    NASA Astrophysics Data System (ADS)

    Haswell, C. A.; Chaty, S.; Cui, W.; Casares, J. V.; Hynes, R. I.

    2000-03-01

    On March 2 06:00 UT the transient source XTE J1859+226 had faded considerably to R=18.0 in the optical (IAC) and to a flux of about 13 mCrab (RXTE ASM). However, it clearly remains active in the X-rays. From extrapolating the last spectrum obtained with HST on 2000, February 8th we predict the following approximate magnitude and colours: V~18.4, U-B=-0.5, B-V = V-R = R-I = +0.4. A final simultaneous HST/RXTE visit to this source (most likely a black hole) is scheduled for 2000, March 5th between 06:10 and 13:41 UT.

  4. Rapid variability as a probe of warped space-time around accreting black holes

    NASA Astrophysics Data System (ADS)

    Axelsson, Magnus

    2016-07-01

    The geometry of the inner accretion flow of X-ray binaries is complex, with multiple regions contributing to the observed emission. Frequency-resolved spectroscopy is a powerful tool in breaking this spectral degeneracy. We have extracted the spectra of the strong low-frequency quasi-periodic oscillation (QPO) and its harmonic in GX339-4 and XTE J1550-564, and compare these to the time-averaged spectrum and the spectrum of the rapid (<0.1 s) variability. Our results support the picture where the QPO arises from vertical (Lense-Thirring) precession of an inhomogeneous hot flow, softer at larger radii closer to the truncated disc and harder in the innermost parts where the rapid variability is produced. This coupling between variability and spectra allows us to constrain the soft Comptonization component, breaking the degeneracy plaguing the time-averaged spectrum and revealing the geometry of the accretion flow close to the black hole.

  5. AGILE Detection of Enhanced Gamma-Ray Emission from the Microquasar Cygnus X-3

    NASA Astrophysics Data System (ADS)

    Piano, G.; Tavani, M.; Munar-Adrover, P.; Bulgarelli, A.; Verrecchia, F.; Donnarumma, I.; Minervini, G.; Fioretti, V.; Pittori, C.; Lucarelli, F.; Vercellone, S.; Striani, E.; Ursi, A.; Cardillo, M.; Gianotti, F.; Trifoglio, M.; Giuliani, A.; Mereghetti, S.; Caraveo, P.; Perotti, F.; Chen, A.; Argan, A.; Costa, E.; Del Monte, E.; Evangelista, Y.; Feroci, M.; Lazzarotto, F.; Lapshov, I.; Pacciani, L.; Soffitta, P.; Sabatini, S.; Vittorini, V.; Pucella, G.; Rapisarda, M.; Di Cocco, G.; Fuschino, F.; Galli, M.; Labanti, C.; Marisaldi, M.; Pellizzoni, A.; Pilia, M.; Trois, A.; Barbiellini, G.; Vallazza, E.; Longo, F.; Morselli, A.; Picozza, P.; Prest, M.; Lipari, P.; Zanello, D.; Cattaneo, P. W.; Rappoldi, A.; Colafrancesco, S.; Parmiggiani, N.; Ferrari, A.; Paoletti, F.; Antonelli, A.; Giommi, P.; Salotti, L.; Valentini, G.; D'Amico, F.

    2017-03-01

    The AGILE-GRID detector is revealing gamma ray emission above 100 MeV from a source positionally consistent with the microquasar Cygnus X-3. Integrating from 2017-02-27 UT 03:00:00 to 2017-03-01 UT 03:00:00 (MJD 57811.125 - 57813.125), a preliminary multi-source likelihood analysis detects a gamma-ray flux F( > 100 MeV) = (3 +/- 1) x 10^-6 photons/cm^2/s with a detection significance near 4 sigma.

  6. Temporal Variability from the Two-Component Advective Flow Solution and Its Observational Evidence

    NASA Astrophysics Data System (ADS)

    Dutta, Broja G.; Chakrabarti, Sandip K.

    2016-09-01

    In the propagating oscillatory shock model, the oscillation of the post-shock region, i.e., the Compton cloud, causes the observed low-frequency quasi-periodic oscillations (QPOs). The evolution of QPO frequency is explained by the systematic variation of the Compton cloud size, i.e., the steady radial movement of the shock front, which is triggered by the cooling of the post-shock region. Thus, analysis of the energy-dependent temporal properties in different variability timescales can diagnose the dynamics and geometry of accretion flows around black holes. We study these properties for the high-inclination black hole source XTE J1550-564 during its 1998 outburst and the low-inclination black hole source GX 339-4 during its 2006-07 outburst using RXTE/PCA data, and we find that they can satisfactorily explain the time lags associated with the QPOs from these systems. We find a smooth decrease of the time lag as a function of time in the rising phase of both sources. In the declining phase, the time lag increases with time. We find a systematic evolution of QPO frequency and hard lags in these outbursts. In XTE J1550-564, the lag changes from hard to soft (i.e., from a positive to a negative value) at a crossing frequency (ν c) of ˜3.4 Hz. We present possible mechanisms to explain the lag behavior of high and low-inclination sources within the framework of a single two-component advective flow model.

  7. A LIKELY MICRO-QUASAR IN THE SHADOW OF M82 X-1

    SciTech Connect

    Xu, Xiao-jie; Liu, Jifeng; Liu, Jiren E-mail: jfliu@nao.cas.cn

    2015-02-01

    The ultra-luminous X-ray source M82 X-1 is one of the most promising intermediate mass black hole candidates in the local universe based on its high X-ray luminosities (10{sup 40}–10{sup 41} erg s{sup −1}) and quasi-periodic oscillations, and is possibly associated with a radio flare source. In this work, applying the sub-pixel technique to the 120 ks Chandra observation (ID: 10543) of M82 X-1, we split M82 X-1 into two sources separated by 1.″1. The secondary source is not detected in other M82 observations. The radio flare source is not found to associate with M82 X-1, but is instead associated with the nearby transient source S1 with an outburst luminosity of ∼10{sup 39} erg s{sup −1}. With X-ray outburst and radio flare activities analogous to the recently discovered micro-quasar in M31, S1 is likely to be a micro-quasar hidden in the shadow of M82 X-1.

  8. BeppoSAX observations of XTE J1946+274

    NASA Astrophysics Data System (ADS)

    Doroshenko, R.; Santangelo, A.; Doroshenko, V.; Piraino, S.

    2017-03-01

    We report on the BeppoSAX monitoring of a giant outburst of the transient X-ray pulsar XTE J1946+274 in 1998. The source was detected with a flux of 4 × 10-9 erg cm-2 s-1 (in 0.1-120 keV range). The broadband spectrum, typical for accreting pulsars, is well described by a cutoff power law with a cyclotron resonance scattering feature (CRSF) at 38 keV. This value is consistent with earlier reports based on the observations with Suzaku at factor of ten lower luminosity, which implies that the feature is formed close to the neutron star surface rather than in the accretion column. Pulsations with P 15.82 s were observed up to 70 keV. The pulse profile strongly depends on energy and is characterised by a "soft" and a "hard" peaks shifted by half period, which suggests a strong phase dependence of the spectrum, and that two components with roughly orthogonal beam patterns are responsible for the observed pulse shape. This conclusion is supported by the fact that the CRSF, despite its relatively high energy, is only detected in the spectrum of the soft peak of the pulse profile. Along with the absence of correlation of the line energy with luminosity, this could be explained in the framework of the recently proposed "reflection" model for CRSF formation. However more detailed modelling of both line and continuum formation are required to confirm this interpretation.

  9. Doppler Imaging of Black Hole SYSTEMS:XTE J1118+480.

    NASA Astrophysics Data System (ADS)

    Callanan, Paul; Perres-Torres, Manuel; Garcia, Michael

    We present time-resolved spectroscopy of the black-hole candidate XTE J1118+480 obtained during its approach to quiescence. Doppler imaging of the intense Hα line shows persistent emission with an origin in the gas stream/hotspot. In addition the Doppler maps show enhanced emission in the +Vx -Vy quadrant clearing incompatible with a stream/hotspot origin. We favour a non-uniform disk intensity distribution due to tidal effects as the origin of this emission. We compare our map with that of XTE J1118+480 in outburst as well as with those of other transient systems in quiescence

  10. Gemini H-band spectroscopy of the Galactic microquasar GRS 1915+105

    NASA Astrophysics Data System (ADS)

    McConnell, O.; Callanan, P.; Reynolds, M.

    2014-07-01

    Since its discovery in 1994 (Castro-Tirado 1994) GRS 1915+105 has become one of the most intensely studied of all the X-ray binaries in the Galaxy. This Galactic microquasar system is unique in that it has remained in outburst for the past 20 years: furthermore, initial measurements suggested a relatively high black hole mass of 14 ± 4 M_{⊙} (Greiner et al. 2001), outside the predicted mass range for such transients (Ozel et al. 2010). Here we present new Gemini H-band observations, and discuss the degree to which they can be used to refine the black hole mass in comparison to more recent estimates (Hurley et al 2013, Steeghs et al 2013). In addition, previous work found phase dependent emission of the CO bandheads in the K-band, and we present evidence of double peaked emission lines, indicative of ongoing mass transfer via the accretion disk.

  11. VLBA "Movie" Gives Scientists New Insights On Workings of Mysterious Microquasars

    NASA Astrophysics Data System (ADS)

    2004-01-01

    Astronomers have made a 42-day movie showing unprecedented detail of the inner workings of a strange star system that has puzzled scientists for more than two decades. Their work is providing new insights that are changing scientists' understanding of the enigmatic stellar pairs known as microquasars. SS 433 Frame from SS 433 Movie: End to end is some 200 billion miles. CREDIT: Mioduszewski et al., NRAO/AUI/NSF Image Files Single Frame Overall Jet View (above image) VLBA Movie (animated gif, 2.3 MB) Animated graphic of SS 433 System (18MB) (Created using software by Robert Hynes, U.Texas) Annotated brightening graphic Unannotated brightening Frame 1 Unannotated brightening Frame 2 "This once-a-day series of exquisitely-detailed images is the best look anyone has ever had at a microquasar, and already has made us change our thinking about how these things work," said Amy Mioduszewski, of the National Radio Astronomy Observatory (NRAO), in Socorro, New Mexico. The astronomers used the National Science Foundation's Very Long Baseline Array (VLBA), a system of radio telescopes stretching from Hawaii to the Caribbean, to follow daily changes in a binary-star system called SS 433, some 15,000 light-years from Earth in the constellation Aquila. Mioduszewski worked with Michael Rupen, Greg Taylor and Craig Walker, all of NRAO. They reported their findings to the American Astronomical Society's meeting in Atlanta, Georgia. SS 433 consists of a neutron star or black hole orbited by a "normal" companion star. The powerful gravity of the neutron star or black hole is drawing material from the stellar wind of its companion into an accretion disk of material tightly circling the dense, central object prior to being pulled onto that object. This disk propels jets of subatomic particles outward from its poles. In SS 433, the particles in the jets move at 26 percent of the speed of light; in other microquasars, the jet material moves at 90-95 percent of light speed. The disk in SS

  12. Origin of multi-band emission from the microquasar Cygnus X-1

    SciTech Connect

    Zhang, Jianfu; Lu, Jufu; Xu, Bing

    2014-06-20

    We study the origin of non-thermal emissions from the Galactic black hole X-ray binary Cygnus X-1, which is a confirmed high-mass microquasar. By analogy with the methods used in studies of active galactic nuclei, we propose a two-dimensional, time-dependent radiation model from the microquasar Cygnus X-1. In this model, the evolution equation for relativistic electrons in a conical jet are numerically solved by including escape, adiabatic, and various radiative losses. The radiative processes involved are synchrotron emission, its self-Compton scattering, and inverse Compton scatterings of an accretion disk and its surrounding stellar companion. This model also includes an electromagnetic cascade process of an anisotropic γ-γ interaction. We study the spectral properties of electron evolution and its emission spectral characteristic at different heights of the emission region located in the jet. We find that radio data from Cygnus X-1 are reproduced by the synchrotron emission, the Fermi Large Area Telescope measurements by the synchrotron emission and Comptonization of photons of the stellar companion, and the TeV band emission fluxes by the Comptonization of the stellar photons. Our results show the following. (1) The radio emission region extends from the binary system scales to the termination of the jet. (2) The GeV band emissions should originate from the distance close to the binary system scales. (3) The TeV band emissions could be inside the binary system, and these emissions could be probed by the upcoming Cherenkov Telescope Array. (4) The MeV tail emissions, which produce a strongly linearly polarized signal, are emitted inside the binary system. The location of the emissions is very close to the inner region of the jet.

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

    NASA Astrophysics Data System (ADS)

    Loh, Alan; Corbel, Stephane

    2017-02-01

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

  14. The Variability and Spectrum of NGC 4051 from Deep, Simultaneous EUVE and XTE Observations

    NASA Technical Reports Server (NTRS)

    Fruscione, Antonella; Cagnoni, Ilaria; Papadakis, Iossif; McHardy, Ian

    1998-01-01

    We present timing and spectral analysis of the data collected by the Extreme Ultraviolet Explorer Satellite (EUVE) for the Seyfert 1 galaxy NGC 4051 during 1996. NGC 4051 was observed twice in May 1996 and again in December 1996 for a total of more than 200 ksec. The observations were always simultaneous with hard X-ray observations conducted with the X-Ray Timing Explorer (XTE). The EUVE light curves are extremely variable during each observation, with the maximum variability during May 1996 when we registered changes by a factor of 21 over 8 hours and more than a factor of 24 variations from peak to minimum. We detected signal in the EUVE spectrograph in the 75-100 Arange which is well fitted by absorbed power law models. We will illustrate the results of our spectral and detailed power spectrum analysis for the simultaneous EUVE and XTE spectra and light curves and discuss the consequences on possible emission mechanisms.

  15. THE VARIABLE NEAR-INFRARED COUNTERPART OF THE MICROQUASAR GRS 1758–258

    SciTech Connect

    Luque-Escamilla, Pedro L.

    2014-12-10

    We present a new study of the microquasar system GRS 1758–258 in the near-infrared domain based on archival observations with the Hubble Space Telescope and the NICMOS camera. In addition to confirming the near-infrared counterpart pointed out by Muñoz-Arjonilla et al., we show that this object displays significant photometric variability. From its average magnitudes, we also find that GRS 1758–258 fits well within the correlation between the optical/near-infrared and X-ray luminosity known to exist for low-mass, black-hole candidate X-ray binaries in a hard state. Moreover, the spectral energy distribution built using all radio, near-infrared, and X-ray data available closest in time to the NICMOS observations can be reasonably interpreted in terms of a self-absorbed radio jet and an irradiated accretion disk model around a stellar-mass black hole. All these facts match the expected behavior of a compact binary system and strengthen our confidence in the counterpart identification.

  16. Inflow and outflow from the accretion disc of the microquasar SS433: UKIRT spectroscopy

    NASA Astrophysics Data System (ADS)

    Perez M., Sebastian; Blundell, Katherine M.

    2009-08-01

    A succession of near-infrared (near-IR) spectroscopic observations, taken nightly throughout an entire cycle of SS433's orbit, reveal (i) the persistent signature of SS433's accretion disc, having a rotation speed of ~500kms-1, (ii) the presence of circumbinary disc recently discovered at optical wavelengths by Blundell, Bowler & Schmidtobreick (2008) and (iii) a much faster outflow than has previously been measured for the disc wind, with a terminal velocity of ~1500kms-1. The increased wind terminal velocity results in a mass-loss rate of ~10-4Msolaryr-1. These, together with the newly (upwardly) determined masses for the components of the SS433 system, result in an accurate diagnosis of the extent to which SS433 has super-Eddington flows. Our observations imply that the size of the companion star is comparable with the semiminor axis of the orbit which is given by , where e is the eccentricity. Our relatively spectral resolution at these near-IR wavelengths has enabled us to deconstruct the different components that comprise the Brackett-γ (Brγ) line in this binary system, and their physical origins. With this line being dominated throughout our series of observations by the disc wind, and the accretion disc itself being only a minority (~15 per cent) contribution, we caution against use of the unresolved Brγ line intensity as an `accretion signature' in X-ray binaries or microquasars in any quantitative way.

  17. SUZAKU OBSERVATIONS OF THE GALACTIC CENTER MICROQUASAR 1E 1740.7-2942

    SciTech Connect

    Reynolds, Mark T.; Miller, Jon M.

    2010-06-20

    We present two Suzaku observations of the Galactic center microquasar 1E 1740.7-2942 separated by approximately 700 days. The source was observed on both occasions after a transition to the spectrally hard state. Significant emission from 1E 1740.7-2942 is detected out to an energy of 300 keV, with no spectral break or turnover evident in the data. We tentatively measure a lower limit to the cutoff energy of {approx}380 keV. The spectra are found to be consistent with a Comptonized corona on both occasions, where the high energy emission is consistent with a hard power-law ({Gamma} {approx} 1.8) with a significant contribution from an accretion disk with a temperature of {approx}0.4 keV at soft X-ray energies. The measured value for the inner radius of the accretion disk is found to be inconsistent with the picture whereby the disk is truncated at large radii in the low-hard state and instead favors a radius close to the ISCO (R{sub in} {approx} 10 - 20 R{sub g}).

  18. High-mass microquasars and low-latitude gamma-ray sources

    NASA Astrophysics Data System (ADS)

    Bosch-Ramon, V.; Romero, G. E.; Paredes, J. M.

    2005-01-01

    Population studies of unidentified EGRET sources suggest that there exist at least three different populations of galactic gamma-ray sources. One of these populations is formed by young objects distributed along the galactic plane with a strong concentration toward the inner spiral arms of the Galaxy. Variability, spectral and correlation analysis indicate that this population is not homogeneous. In particular, there is a subgroup of sources that display clear variability in their gamma-ray fluxes on timescales from days to months. Following the proposal by Kaufman Bernadó et al. (2002), we suggest that this group of sources might be high-mass microquasars, i.e. accreting black holes or neutron stars with relativistic jets and early-type stellar companions. We present detailed inhomogeneous models for the gamma-ray emission of these systems that include both external and synchrotron self-Compton interactions. We have included effects of interactions between the jet and all external photon fields to which it is exposed: companion star, accretion disk, and hot corona. We make broadband calculations to predict the spectral energy distribution of the emission produced in the inner jet of these objects up to GeV energies. The results and predictions can be tested by present and future gamma-ray instruments like INTEGRAL, AGILE, and GLAST.

  19. Multiwavelength observations of XTE J1859+226 on 1999, November 6th

    NASA Astrophysics Data System (ADS)

    Haswell, C. A.; Chaty, S.; Norton, A. J.; Chen, W.; Hynes, R. I.

    1999-11-01

    Further simultaneous HST and RXTE observations (visit #3) of the new X-ray transient XTE J1859+226 are scheduled for November 6th 1999 19:37 - 22:22 UT. Coordinated multi-wavelength observations (simultaneous, near-simultaneous, and following the evolution over days/weeks) would be extremely helpful. If you can observe simultaneously with HST and/or RXTE, high time-resolution data (< 10 seconds) will be particularly useful.

  20. Radio detection of XTE J1752-223 with the ATCA

    NASA Astrophysics Data System (ADS)

    Brocksopp, Catherine; Corbel, Stephane; Tzioumis, Tasso; Fender, Rob

    2009-11-01

    Following the detection of the new X-ray transient, XTE J1752-223, by RXTE and Swift (ATel. #2258; see also ATels. #2259, #2261, #2263, #2265, #2268, #2269), we have performed radio observations with the Australia Telescope Compact Array and the new CABB back-end. Data were obtained at 5.5 GHz and 9 GHz on October 30 and November 1. We detect a radio source at a position consistent with the X-ray coordinates.

  1. XTE J1752-223: Optical spectroscopy and infrared counterpart detection

    NASA Astrophysics Data System (ADS)

    Torres, M. A. P.; Steeghs, D.; Jonker, P. G.; Thompson, I.; Soderberg, A. M.

    2009-10-01

    Prompted by the discovery of its bright optical counterpart and the announcement of increased X-ray activity (ATels #2258, #2259, #2261, #2265, #2263), we have acquired additional observations of XTE J1752-223 at optical and near-infrared wavelengths. OPTICAL SPECTROSCOPY: An optical spectrum covering 3330-9165 Angstrom was obtained with the MIKE echelle spectrograph on the Magellan Clay telescope starting on 2009 Oct 26 UT 23:52.

  2. Development of the solar array deployment and drive system for the XTE spacecraft

    NASA Technical Reports Server (NTRS)

    Farley, Rodger; Ngo, Son

    1995-01-01

    The X-ray Timing Explorer (XTE) spacecraft is a NASA science low-earth orbit explorer-class satellite to be launched in 1995, and is an in-house Goddard Space Flight Center (GSFC) project. It has two deployable aluminum honeycomb solar array wings with each wing being articulated by a single axis solar array drive assembly. This paper will address the design, the qualification testing, and the development problems as they surfaced of the Solar Array Deployment and Drive System.

  3. Optical spectroscopy of the microquasar GRS 1758-258: a possible intermediate mass system?

    NASA Astrophysics Data System (ADS)

    Martí, Josep; Luque-Escamilla, Pedro L.; Muñoz-Arjonilla, Álvaro J.

    2016-11-01

    Context. GRS 1758-258 is one of two prototypical microquasars towards the Galactic center direction discovered almost a quarter of a century ago. The system remains poorly studied in the optical domain due to its counterpart being a very faint and absorbed target in a crowded region of the sky. Aims: Our aim is to investigate GRS 1758-258 in order to shed light on the nature of the stellar binary components. In particular, the main physical parameters of the donor star, such as the mass or the spectral type, are not yet well constrained. Methods: GRS 1758-258 has remained so far elusive to optical spectroscopy owing to its observational difficulties. Here, we use this traditional tool of stellar astronomy at low spectral resolution with a 10 m class telescope and a long slit spectrograph. Results: An improved spectrum is obtained as compared to previous work. The quality of the data does not allow the detection of emission or absorption features but, nevertheless, we manage to partially achieve our aims comparing the de-reddened continuum with the spectral energy distribution expected from an irradiated disc model and different donor star templates. Conclusions: We tentatively propose that GRS 1758-258 does not host a giant star companion. Instead, a main sequence star with mid-A spectral type appears to better agree with our data. The main impacts of this finding are the possibility that we are dealing with an intermediate mass system and, in this case, the prediction of an orbital period significantly shorter than previously proposed.

  4. High energy gamma rays from nebulae associated with extragalactic microquasars and ultra-luminous X-ray sources

    NASA Astrophysics Data System (ADS)

    Inoue, Yoshiyuki; Lee, Shiu-Hang; Tanaka, Yasuyuki T.; Kobayashi, Shogo B.

    2017-04-01

    In the extragalactic sky, microquasars and ultra-luminous X-ray sources (ULXs) are known as energetic compact objects locating at off-nucleus positions in galaxies. Some of these objects are associated with expanding bubbles with a velocity of 80-250 km s - 1. We investigate the shock acceleration of particles in those expanding nebulae. The nebulae having fast expansion velocity ≳ 120km s - 1 are able to accelerate cosmic rays up to ∼100 TeV. If 10% of the shock kinetic energy goes into particle acceleration, powerful nebulae such as the microquasar S26 in NGC 7793 would emit gamma rays up to several tens TeV with a photon index of ∼2. These nebulae will be good targets for future Cherenkov Telescope Array observations given its sensitivity and angular resolution. They would also contribute to ∼7% of the unresolved cosmic gamma-ray background radiation at ≥ 0.1 GeV. In contrast, particle acceleration in slowly expanding nebulae ≲ 120km s - 1 would be less efficient due to ion-neutral collisions and result in softer spectra at ≳ 10 GeV.

  5. Jet power and feedback from the newly-discovered radio/optical/X-ray microquasar S26 in NGC 7793

    NASA Astrophysics Data System (ADS)

    Soria, Roberto; Corbel, Stephane; Pakull, Manfred; Motch, Christian

    2009-07-01

    We have discovered an exceptional radio/optical/X-ray microquasar in the Sculptor galaxy NGC7793 (distance of 3.4 Mpc), with a large (300 x 150 pc) shock-ionized bubble, and X-ray hot spots where the collimated jet hits the interstellar medium. The radio nebula has an integrated flux of 1.2 mJy at 6 cm (more luminous than Cas A). The system resembles the famous Galactic microquasar SS433, but on an even grander scale. We propose deeper radio observations at higher spatial resolution with the ATCA: to identify the radio hot spots; to infer the jet power from the synchrotron luminosity of the hot spots; to determine the shape of the radio cocoon and compare it with the H-alpha, HeII 4686 and X-ray nebulae; to estimate the total (integrated) energy injected in the nebula by the jet/wind, and constrain its age; to search for the radio core. Our combined radio, X-ray and optical study of this source will help us model the radiative and mechanical power budget of accreting black holes, and their feedback onto the interstellar or intergalactic medium.

  6. Testing modified gravity and no-hair relations for the Kerr-Newman metric through quasiperiodic oscillations of galactic microquasars

    NASA Astrophysics Data System (ADS)

    Suvorov, Arthur George; Melatos, Andrew

    2016-01-01

    We construct multipole moments for stationary, asymptotically flat, spacetime solutions to higher-order curvature theories of gravity. The moments are defined using 3 +1 techniques involving timelike Killing vector constructions as in the classic papers by Geroch and Hansen. Using the fact that the Kerr-Newman metric is a vacuum solution to a particular class of f (R ) theories of gravity, we compute all its moments, and find that they admit recurrence relations similar to those for the Kerr solution in general relativity. It has been proposed previously that modeling the measured frequencies of quasiperiodic oscillations from galactic microquasars enables experimental tests of the no-hair theorem. We explore the possibility that, even if the no-hair relation is found to break down in the context of general relativity, there may be an f (R ) counterpart that is preserved. We apply the results to the microquasars GRS 1915 +105 and GRO J1655-40 using the diskoseismology and kinematic resonance models, and constrain the spins and "charges" of their black holes.

  7. A 300-parsec-long jet-inflated bubble around a powerful microquasar in the galaxy NGC 7793.

    PubMed

    Pakull, Manfred W; Soria, Roberto; Motch, Christian

    2010-07-08

    Black-hole accretion states near or above the Eddington luminosity (the point at which radiation force outwards overcomes gravity) are still poorly known because of the rarity of such sources. Ultraluminous X-ray sources are the most luminous class of black hole (L(X) approximately 10(40) erg s(-1)) located outside the nuclei of active galaxies. They are likely to be accreting at super-Eddington rates, if they are powered by black holes with masses less than 100 solar masses. They are often associated with shock-ionized nebulae, though with no evidence of collimated jets. Microquasars with steady jets are much less luminous. Here we report that the large nebula S26 (ref. 4) in the nearby galaxy NGC 7793 is powered by a black hole with a pair of collimated jets. It is similar to the famous Galactic source SS433 (ref. 5), but twice as large and a few times more powerful. We determine a mechanical power of around a few 10(40) erg s(-1). The jets therefore seem 10(4) times more energetic than the X-ray emission from the core. S26 has the structure of a Fanaroff-Riley type II (FRII-type) active galaxy: X-ray and optical core, X-ray hot spots, radio lobes and an optical and X-ray cocoon. It is a microquasar where most of the jet power is dissipated in thermal particles in the lobes rather than relativistic electrons.

  8. The Fading of Transient Anomalous X-Ray Pulsar XTE J1810-197

    NASA Astrophysics Data System (ADS)

    Halpern, J. P.; Gotthelf, E. V.

    2005-01-01

    Three observations of the 5.54 s transient anomalous X-ray pulsar XTE J1810-197 obtained over 6 months with the Newton X-ray Multi-Mirror (XMM-Newton) mission are used to study its spectrum and pulsed light curve as the source fades from outburst. The decay is consistent with an exponential of time constant ~300 days but not a power law as predicted in some models of sudden deep crustal heating events. All spectra are well fitted by a blackbody plus a steep power law, a problematic model that is commonly fitted to anomalous X-ray pulsars (AXPs). A two-temperature blackbody fit is also acceptable and better motivated physically in view of the faint optical/IR fluxes, the X-ray pulse shapes that weakly depend on energy in XTE J1810-197, and the inferred emitting areas that are less than or equal to the surface area of a neutron star. The fitted temperatures remained the same while the flux declined by 46%, which can be interpreted as a decrease in area of the emitting regions. The pulsar continues to spin down, albeit at a reduced rate of (5.1+/-1.6)×10-12 s s-1. The inferred characteristic age τc≡P/2P~17,000 yr, magnetic field strength Bs~1.7×1014 G, and outburst properties are consistent with both the outburst and quiescent X-ray luminosities being powered by magnetic field decay, i.e., XTE J1810-197 is a magnetar.

  9. System mass constraints for the accreting millisecond pulsar XTE J1814-338 using Bowen fluorescence

    NASA Astrophysics Data System (ADS)

    Wang, L.; Steeghs, D.; Casares, J.; Charles, P. A.; Muñoz-Darias, T.; Marsh, T. R.; Hynes, R. I.; O'Brien, K.

    2017-04-01

    We present phase-resolved spectroscopy of the millisecond X-ray pulsar XTE J1814-338 obtained during its 2003 outburst. The spectra are dominated by high-excitation emission lines of He II λ4686, Hβ, and the Bowen blend C III/N III 4630-50 Å. We exploit the proven Bowen fluorescence technique to establish a complete set of dynamical system parameter constraints using bootstrap Doppler tomography, a first for an accreting millisecond X-ray pulsar binary. The reconstructed Doppler map of the N III λ4640 Bowen transition exhibits a statistically significant (>4σ) spot feature at the expected position of the companion star. If this feature is driven by irradiation of the surface of the Roche lobe filling companion, we derive a strict lower limit to the true radial velocity semi-amplitude K2. Combining our donor constraint with the well-constrained orbit of the neutron star leads to a determination of the binary mass ratio: q = 0.123^{+0.012}_{-0.010}. The component masses are not tightly constrained given our lack of knowledge of the binary inclination. We cannot rule out a canonical neutron star mass of 1.4 M⊙ (1.1 M⊙ < M1 < 3.1 M⊙; 95 per cent). The 68/95 per cent confidence limits of M2 are consistent with the companion being a significantly bloated, M-type main-sequence star. Our findings, combined with results from studies of the quiescent optical counterpart of XTE J1814-338, suggest the presence of a rotation-powered millisecond pulsar in XTE J1814-338 during an X-ray quiescent state. The companion mass is typical of the so-called redback pulsar binary systems (M2 ∼ 0.2 M⊙).

  10. Serendipitous Detections of XTE J1906+09 with the Rossi X-ray Timing Explorer

    NASA Technical Reports Server (NTRS)

    Wilson, Colleen A.; Finger, Mark H.; Gogus, Ersin; Woods, Peter M.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    In 1996 during Rossi X-ray Timing Explorer (RXTE) observations of SCR 1900+14, the 89-second X-ray pulsar XTE J1906+09 was discovered. As a result of monitoring campaigns of SGR 1900+14, XTE J1906+09 was also monitored regularly in 1996 September, 1998 May-June, 1998 August-1999 July, and 2000 March-2001 January. A frequency grid search of these observations resulted in detections of only the two previously reported outbursts in 1996 September and 1998 August-September. The non-detection of XTE J1906+09 in most observations indicates that it is a transient X-ray pulsar and therefore likely has a Be star companion, Pulse timing analysis of the second outburst revealed a sinusoidal signature in the pulse frequencies that is likely produced by periastron passage in a long period, eccentric, orbit. During the second outburst, the pulse shape changed with increasing intensity, Low intensity pulse profiles from the second outburst are consistent with profiles from the fainter first outburst. Energy dependent pulse shape variations were seen in both outbursts. Pulse phase spectroscopy was used to quantify these variations. The phase averaged spectrum, using the pulse minimum spectrum as the background spectrum to eliminate effects from SGR 1900+14 and the galactic ridge, was well fitted by an absorbed power law with a high energy cutoff with column density N(sub H) = (6 +/- 1) x 10(exp 22) cm(sup -2), photon index = 1.01 +/- 0.08, cutoff energy E(sub cut) = 11 +/- 1 keV, and folding energy E(sub fold) = 19 +/- 4 keV.

  11. Black Hole Candidate XTE J1859+226 in the Low/Hard State

    NASA Astrophysics Data System (ADS)

    Miller, J. M.; Fox, D. W.; Pooley, D.; Lewin, W. H. G.

    2000-07-01

    Recent flaring activity of this source in the optical (Casares et al. 2000, IAUC #7451) has motivated a public RXTE TOO observation on 8 July 2000. XTE J1859+226 is a known X-ray nova that reached 1.4 Crab in the RXTE/ASM in October 1999 (Smith 1999, ATEL #47). During that outburst the source exhibited 150 and 187 Hz quasi-periodic oscillations (Cui et al. 2000, ApJ 535, L123) and radio emission (Pooley & Hjellming, IAUC #7278).

  12. Optical and near-IR observations of XTE J1859+226

    NASA Astrophysics Data System (ADS)

    Hynes, R. I.; Haswell, C. A.; Norton, A. J.; Chaty, S.; Rolfe, D. J.; Lott, D. A.; Solheim, J.-E.; Ostensen, R.; Garcia, R. A.; Fried, R.; O'Brien, K.; Horne, K.; Ioannou, Z.; Shafter, A.; Abbott, T. M. C.; Krisciunas, K.; Ivison, R. J.; Sano, Y.; Chen, W.; Shrader, C.; Livio, M.; Robinson, E. L.; Wagner, R. M.

    1999-10-01

    Following optical and near-infrared monitoring of XTE J1859+226 (IAUC #7279, #7284), HST/STIS observations were performed on Oct 18.10-18.38 spanning 112-1026nm. The UV spectrum shows broad (12000km/s FWZI) and deep Lyman alpha absorption, strong CIV 155nm emission (EW 1.1nm, 4000km/s FWZI) and weaker emission lines of CIII, NV, OIII, OIV, OV, SiIV and HeII. Sharp absorption lines of SiII, SiIII, MgII and other species also appear with possible interstellar origin.

  13. ATCA detection of increased radio emission from XTE J1752-223

    NASA Astrophysics Data System (ADS)

    Brocksopp, Catherine; Corbel, Stephane; Tzioumis, Tasso; Fender, Rob; Coriat, Mickael

    2010-01-01

    Following the announcement that the new X-ray transient source, XTE J1752-223 (ATel. 2258), is making a transition from the hard to the intermediate state (ATel. 2387, 2391, 2396), we have observed the radio counterpart with the Australia Telescope Compact Array and the new CABB back-end. The radio source has risen from the previous ~2 mJy plateau to 20 mJy at 1.2, 2.5, 5.5, 9, 17, 19 GHz on January 21.

  14. Radio lobes and X-ray hotspots in the microquasar S26

    NASA Astrophysics Data System (ADS)

    Soria, Roberto; Pakull, Manfred W.; Broderick, Jess W.; Corbel, Stephane; Motch, Christian

    2010-12-01

    We have studied the structure and energetics of the powerful microquasar/shock-ionized nebula S26 in NGC7793, with particular focus on its radio and X-ray properties. Using the Australia Telescope Compact Array, we have resolved for the first time the radio lobe structure and mapped the spectral index of the radio cocoon. The steep spectral index of the radio lobes is consistent with optically-thin synchrotron emission; outside the lobes, the spectral index is flatter, suggesting an additional contribution from free-free emission, and perhaps ongoing ejections near the core. The radio core is not detected, while the X-ray core has a 0.3-8 keV luminosity ~6 × 1036 erg s-1. The size of the radio cocoon matches that seen in the optical emission lines and diffuse soft X-ray emission. The total 5.5-GHz flux of cocoon and lobes is ~2.1 mJy, which at the assumed distance of 3.9 Mpc corresponds to about three times the luminosity of Cas A. The total 9.0-GHz flux is ~1.6 mJy. The X-ray hotspots (combined 0.3-8 keV luminosity ~2 × 1037 erg s-1) are located ~20 pc outwards of the radio hotspots (i.e. downstream along the jet direction), consistent with a different physical origin of X-ray and radio emission (thermal-plasma and synchrotron, respectively). The total particle energy in the bubble is ~1053 erg: from the observed radio flux, we estimate that only approximately a few times 1050 erg is stored in the relativistic electrons; the rest is stored in protons, nuclei and non-relativistic electrons. The X-ray-emitting component of the gas in the hotspots contains ~1051 erg, and ~1052 erg over the whole cocoon. We suggest that S26 provides a clue to understand how the ambient medium is heated by the mechanical power of a black hole near its Eddington accretion rate.

  15. Magnetoreflectivity of Pb{sub 1{minus}x}Eu{sub x}Te epilayers and PbTe/Pb{sub 1{minus}x}Eu{sub x}Te multiple quantum wells

    SciTech Connect

    Yuan, S.; Krenn, H.; Springholz, G.; Ueta, Y.; Bauer, G.; McCann, P.J.

    1997-02-01

    Molecular-beam epitaxy grown n-type Pb{sub 1{minus}x}Eu{sub x}Te epilayers (x{le}0.034) and PbTe/Pb{sub 1{minus}x}Eu{sub x}Te (x{le}0.039) multiple-quantum-well (MQW) samples were studied by magnetoreflectivity in the Faraday configuration (B{parallel}[111]) for magnetic fields up to 6T at 4.2 K. Since the IV-VI lead salt compounds are quite polar semiconductors, resonant electron-longitudinal-optic- (LO-) phonon coupling (Fr{umlt o}hlich coupling) modifies the cyclotron resonance (CR) energies in the Pb{sub 1{minus}x}Eu{sub x}Te single epilayers for the three-dimensional (3D) case. Due to the many-valley band structure {ital two} different Fr{umlt o}hlich coupling constants are relevant. However, the CR energies of quasi-two-dimensional (2D) carriers in PbTe wells [n{sup 2D}=(1.5{minus}3){times}10{sup 11}cm{sup {minus}2}] of PbTe/Pb{sub 1{minus}x}Eu{sub x}Te MQW samples do {ital not} exhibit a significant resonant electron-LO-phonon interaction. This observation is attributed to finite-electron concentration effects, in particular, to a partial filling of the lowest 2D Landau spin level. The static and dynamic screening of the polar interaction are considered as well, but are ruled out as an explanation for the absence of any remarkable polaron correction to the CR energies of electrons in the PbTe quantum wells for the range of carrier concentrations investigated. The magnetoreflectivity spectra of Pb{sub 1{minus}x}Eu{sub x}Te single layers and PbTe/Pb{sub 1{minus}x}Eu{sub x}Te quantum well samples are simulated numerically, using a model for the dielectric response of which also includes the electron-LO-phonon interaction. The transverse and longitudinal masses, and thus also the interband momentum matrix elements are determined for Pb{sub 1{minus}x}Eu{sub x}Te as a function of the composition up to x{lt}0.034. It is found that the transverse mass {ital increases} with Eu content, whereas the longitudinal one nearly stays constant. (Abstract Truncated)

  16. INTEGRAL Long-Term Monitoring of the Supergiant Fast X-Ray Transient XTE J1739-302

    NASA Technical Reports Server (NTRS)

    Blay, P.; Martinez-Nunez, S.; Negueruela, I.; Pottschmidt, K.; Smith, D. M.; Torrejon, J. M.; Reig, P.; Kretschmar, P.; Kreykenbohm, I.

    2008-01-01

    Context. In the past few years, a new class of High Mass X-Ray Binaries (HMXRB) has been claimed to exist, the Supergiant Fast X-ray Transients (SFXT). These are X-ray binary systems with a compact companion orbiting a supergiant star which show very short and bright outbursts in a series of activity periods overimposed on longer quiescent periods. Only very recently the first attempts to model the behaviour of these sources have been published, some of them within the framework of accretion from clumpy stellar winds. Aims. Our goal is to analyze the properties of XTE J1739-302/IGR J17391-3021 within the context of the clumpy structure of the supergiant wind. Methods. We have used INTEGRAL and RXTE/PCA observations in order to obtain broad band (1 - 200 keV) spectra and light curves of XTE J1739-302 and investigate its X-ray spectrum and temporal variability. Results. We have found that XTE J1739-302 follows a much more complex behaviour than expected. Far from presenting a regular variability pattern, XTE J1739-302 shows periods of high, intermediate, and low flaring activity.

  17. Discovery of a new type of topological Weyl fermion semimetal state in MoxW1-xTe2.

    PubMed

    Belopolski, Ilya; Sanchez, Daniel S; Ishida, Yukiaki; Pan, Xingchen; Yu, Peng; Xu, Su-Yang; Chang, Guoqing; Chang, Tay-Rong; Zheng, Hao; Alidoust, Nasser; Bian, Guang; Neupane, Madhab; Huang, Shin-Ming; Lee, Chi-Cheng; Song, You; Bu, Haijun; Wang, Guanghou; Li, Shisheng; Eda, Goki; Jeng, Horng-Tay; Kondo, Takeshi; Lin, Hsin; Liu, Zheng; Song, Fengqi; Shin, Shik; Hasan, M Zahid

    2016-12-05

    The recent discovery of a Weyl semimetal in TaAs offers the first Weyl fermion observed in nature and dramatically broadens the classification of topological phases. However, in TaAs it has proven challenging to study the rich transport phenomena arising from emergent Weyl fermions. The series MoxW1-xTe2 are inversion-breaking, layered, tunable semimetals already under study as a promising platform for new electronics and recently proposed to host Type II, or strongly Lorentz-violating, Weyl fermions. Here we report the discovery of a Weyl semimetal in MoxW1-xTe2 at x=25%. We use pump-probe angle-resolved photoemission spectroscopy (pump-probe ARPES) to directly observe a topological Fermi arc above the Fermi level, demonstrating a Weyl semimetal. The excellent agreement with calculation suggests that MoxW1-xTe2 is a Type II Weyl semimetal. We also find that certain Weyl points are at the Fermi level, making MoxW1-xTe2 a promising platform for transport and optics experiments on Weyl semimetals.

  18. Discovery of a Second Millisecond Accreting Pulsar: XTE J1751-305

    NASA Astrophysics Data System (ADS)

    Markwardt, C. B.; Swank, J. H.; Strohmayer, T. E.; in 't Zand, J. J. M.; Marshall, F. E.

    2002-08-01

    We report the discovery by the Rossi X-Ray Timing Explorer Proportional Counter Array of a second transient accreting millisecond pulsar, XTE J1751-305, during regular monitoring observations of the Galactic bulge region. The pulsar has a spin frequency of 435 Hz, making it one of the fastest pulsars. The pulsations contain the signature of orbital Doppler modulation, which implies an orbital period of 42 minutes, the shortest orbital period of any known radio or X-ray millisecond pulsar. The mass function, fX=(1.278+/-0.003)×10-6 Msolar, yields a minimum mass for the companion of between 0.013 and 0.017 Msolar, depending on the mass of the neutron star. No eclipses were detected. A previous X-ray outburst in 1998 June was discovered in archival All-Sky Monitor data. Assuming mass transfer in this binary system is driven by gravitational radiation, we constrain the orbital inclination to be in the range 30°-85° and the companion mass to be 0.013-0.035 Msolar. The companion is most likely a heated helium dwarf. We also present results from the Chandra High Resolution Camera-S observations, which provide the best-known position of XTE J1751-305.

  19. The Reawakening of the Sleeping X-ray Pulsar XTE J1946+274

    NASA Technical Reports Server (NTRS)

    Mueller, Sebastian; Mueller, Sebastian; Kuechnel, Matthias; Fuerst, Felix; Kreykenbohm, Ingo; Sagredo, Macarena; Obst, Maria; Wilms, Joern; Caballero, Isabel; Potttschmidt, Katja; Ferrigno, Carlo; Rothschild, Richard E.

    2012-01-01

    We report on a series of outbursts of the high mass X-ray binary XTE 11946+274 in 2010/2011 as observed with INTEGRAL, RXTE, and Swift. We discuss possible mechanisms resulting in the extraordinary outburst behavior of this source. The X-ray spectra can be described by standard phenomenological models, enhanced by an absorption feature of unknown origin at about 10 keV and a narrow iron K alpha fluorescence line at 6.4keV, which are variable in flux and pulse phase. We find possible evidence for the presence of a cyclotron resonance scattering feature at about 25 keV at the 93% level. The presence of a strong cyclotron line at 35 keV seen in data from the source's 1998 outburst and confirmed by a reanalysis of these data can be excluded. This result indicates that the cyclotron line feature in XTE 11946+274 is variable between individual outbursts.

  20. Discovery of a Second Millesecond Accreting Pulsar: XTE J1751-305

    NASA Technical Reports Server (NTRS)

    Markwardt, C. B.; Swank, J. H.; Strohmayer, T. E.; intZand, J. J. M.; Marshall, F. E.; White, Nicholas E. (Technical Monitor)

    2002-01-01

    We report the discovery by the RXTE PCA of a second transient accreting millisecond pulsar, XTE J1751-305, during regular monitoring observations of the galactic bulge region. The pulsar has a spin frequency of 435 Hz, making it one of the fastest pulsars. The pulsations contain the signature of orbital Doppler modulation, which implies an orbital period of 42 minutes, the shortest orbital period of any known radio or X-ray millisecond pulsar. The mass function, f(sub x) = (1.278 +/- 0.003) x 10 (exp -6) solar mass, yields a minimum mass for the companion of between 0.013 and 0.0017 solar mass depending on the mass of the neutron star. No eclipses were detected. A previous X-ray outburst in June, 1998, was discovered in archival All-Sky Monitor data. Assuming mass transfer in this binary system is driven by gravitational radiation, we constrain the orbital inclination to be in the range 30 deg-85 deg and the companion mass to be 0.013-0.035 solar mass. The companion is most likely a heated helium dwarf. We also present results from the Chandra HRC-S observations which provide the best known position of XTE J1751-305.

  1. XMM-Newton Spectroscopy of the Galactic Microquasar GRS 1758-258 in the Peculiar Off/Soft State

    NASA Technical Reports Server (NTRS)

    Miller, J. M.; Wunands, R.; Rodriguez-Pascual, P. M.; Ferrando, P.; Gaensler, B. M.; Goldwurm, A.; Lewin, W. H. G.; Pooley, D.

    2002-01-01

    We report on an XMM-Newton Reflection Grating Spectrometer observation of the black hole candidate and Galactic microquasar GRS 1758-258. The source entered a peculiar "off/soft" state in 2001 late February in which the spectrum softened while the X-ray flux-and the inferred mass accretion rate-steadily decreased. We find no clear evidence for emission or absorption lines in the dispersed spectra, indicating that most of the observed soft flux is likely from an accretion disk and not from a cool plasma. The accretion disk strongly dominates the spectrum in this lower luminosity state and is only mildly recessed from the marginally stable orbit. These findings may be di8licult to explain in terms of advection-dominated accretion flow (ADAF) models. We discuss these results within the context of ADAF models, simultaneous two-flow models, and observed correlations between hard X-ray flux and jet production.

  2. The effects of the stellar wind and orbital motion on the jets of high-mass microquasars

    NASA Astrophysics Data System (ADS)

    Bosch-Ramon, V.; Barkov, M. V.

    2016-05-01

    Context. High-mass microquasar jets propagate under the effect of the wind from the companion star, and the orbital motion of the binary system. The stellar wind and the orbit may be dominant factors determining the jet properties beyond the binary scales. Aims: This is an analytical study, performed to characterise the effects of the stellar wind and the orbital motion on the jet properties. Methods: Accounting for the wind thrust transferred to the jet, we derive analytical estimates to characterise the jet evolution under the impact of the stellar wind. We include the Coriolis force effect, induced by orbital motion and enhanced by the wind's presence. Large-scale evolution of the jet is sketched, accounting for wind-to-jet thrust transfer, total energy conservation, and wind-jet flow mixing. Results: If the angle of the wind-induced jet bending is larger than its half-opening angle, the following is expected: (i) a strong recollimation shock; (ii) bending against orbital motion, caused by Coriolis forces and enhanced by the wind presence; and (iii) non-ballistic helical propagation further away. Even if disrupted, the jet can re-accelerate due to ambient pressure gradients, but wind entrainment can weaken this acceleration. On large scales, the opening angle of the helical structure is determined by the wind-jet thrust relation, and the wind-loaded jet flow can be rather slow. Conclusions: The impact of stellar winds on high-mass microquasar jets can yield non-ballistic helical jet trajectories, jet partial disruption and wind mixing, shocks, and possibly non-thermal emission. Among other observational diagnostics, such as radiation variability at any band, the radio morphology on milliarcsecond scales can be informative on the wind-jet interaction.

  3. THE ROLE OF FAST MAGNETIC RECONNECTION ON THE RADIO AND GAMMA-RAY EMISSION FROM THE NUCLEAR REGIONS OF MICROQUASARS AND LOW LUMINOSITY AGNs

    SciTech Connect

    Kadowaki, L. H. S.; Pino, E. M. de Gouveia Dal; Singh, C. B. E-mail: dalpino@iag.usp.br

    2015-04-01

    Fast magnetic reconnection events can be a very powerful mechanism operating in the core region of microquasars and active galactic nuclei (AGNs). In earlier work, it has been suggested that the power released by fast reconnection events between the magnetic field lines lifting from the inner accretion disk region and the lines anchored into the central black hole could accelerate relativistic particles and produce the observed radio emission from microquasars and low luminosity AGNs (LLAGNs). Moreover, it has been proposed that the observed correlation between the radio emission and the mass of these sources, spanning 10{sup 10} orders of magnitude in mass, might be related to this process. In the present work, we revisit this model comparing two different fast magnetic reconnection mechanisms, namely, fast reconnection driven by anomalous resistivity (AR) and by turbulence. We apply the scenario above to a much larger sample of sources (including also blazars, and gamma-ray bursts—GRBs), and find that LLAGNs and microquasars do confirm the trend above. Furthermore, when driven by turbulence, not only their radio but also their gamma-ray emission can be due to magnetic power released by fast reconnection, which may accelerate particles to relativistic velocities in the core region of these sources. Thus the turbulent-driven fast reconnection model is able to reproduce verywell the observed emission. On the other hand, the emission from blazars and GRBs does not follow the same trend as that of the LLAGNs and microquasars, indicating that the radio and gamma-ray emission in these cases is produced beyond the core, along the jet, by another population of relativistic particles, as expected.

  4. The Role of Fast Magnetic Reconnection on the Radio and Gamma-ray Emission from the Nuclear Regions of Microquasars and Low Luminosity AGNs

    NASA Astrophysics Data System (ADS)

    Kadowaki, L. H. S.; de Gouveia Dal Pino, E. M.; Singh, C. B.

    2015-04-01

    Fast magnetic reconnection events can be a very powerful mechanism operating in the core region of microquasars and active galactic nuclei (AGNs). In earlier work, it has been suggested that the power released by fast reconnection events between the magnetic field lines lifting from the inner accretion disk region and the lines anchored into the central black hole could accelerate relativistic particles and produce the observed radio emission from microquasars and low luminosity AGNs (LLAGNs). Moreover, it has been proposed that the observed correlation between the radio emission and the mass of these sources, spanning 1010 orders of magnitude in mass, might be related to this process. In the present work, we revisit this model comparing two different fast magnetic reconnection mechanisms, namely, fast reconnection driven by anomalous resistivity (AR) and by turbulence. We apply the scenario above to a much larger sample of sources (including also blazars, and gamma-ray bursts—GRBs), and find that LLAGNs and microquasars do confirm the trend above. Furthermore, when driven by turbulence, not only their radio but also their gamma-ray emission can be due to magnetic power released by fast reconnection, which may accelerate particles to relativistic velocities in the core region of these sources. Thus the turbulent-driven fast reconnection model is able to reproduce verywell the observed emission. On the other hand, the emission from blazars and GRBs does not follow the same trend as that of the LLAGNs and microquasars, indicating that the radio and gamma-ray emission in these cases is produced beyond the core, along the jet, by another population of relativistic particles, as expected.

  5. A versatile 50 ft-lb-sec reaction wheel for TRMM and XTE missions

    NASA Astrophysics Data System (ADS)

    Bialke, Bill

    A 50 ft-lb-sec Reaction Wheel is being manufactured by ITHACO, Inc. for NASA's X-ray Timing Explorer (XTE) and Tropical Rainfall Measuring Mission (TRMM) missions, using the same mechanical assemblies as a similar Reaction Wheel developed by ITHACO for the Air Force's Advanced Research and Global Observation Satellite (ARGOS) (P91-1) mission. The versatile design allows variation in motor torque and speed capability with no mechanical modifications. State of the art ball bearing technology is combined with flight proven materials and conventional fabrication techniques to produce a relaible and manufacturable wheel assembly. An ironless armature brushless DC motor is incorporated for high efficiency and minimum weight. Comprehensive tradeoff analyses from the Reaction Wheel development are discussed for each component, and performance characteristics are presented for design variations from a high torque Reaction Wheel used in a three axis stabilized spacecraft to a low torque Momentum Wheel used in a momentum biased attitude Control System.

  6. The Rossi X-Ray Timing Explorer (XTE) Solar Array Anomaly

    NASA Technical Reports Server (NTRS)

    Gaddy, Edward M.; Kichak, Robert; Niemeyer, Lee; Stegeman, Richard

    2004-01-01

    The XTE was launched December 30, 1995. Shortly after launch, it become apparent that the solar array was not performing as expected. On leaving shadow, the array exhibited many discontinuous drops in current output. The size of each of these drops was consistent with the loss of a part of a sell. The current decreases could not be caused by the loss of an entire circuit. This meant that the array may have had numerous cracked solar cells that opened as array got warmer. Studies performed on the array's qualification panel suggest that the cell cracks may have been cased by extensive tap testing performed on the array and that these cracks were undetectable at room temperature using usual inspection method.

  7. SUBARCSECOND LOCATION OF IGR J17480-2446 WITH ROSSI XTE

    SciTech Connect

    Riggio, A.; Burderi, L.; Egron, E.; Di Salvo, T.; D'Ai, A.; Iaria, R.; Robba, N. R.; Papitto, A.; Belloni, T.; Motta, S.; Floris, M.; Testa, V.; Menna, M. T.

    2012-07-20

    On 2010 October 13, the X-ray astronomical satellite Rossi XTE, during the observation of the newly discovered accretion powered X-ray pulsar IGR J17480-2446, detected a lunar occultation of the source. From knowledge of the lunar topography and Earth, Moon, and spacecraft ephemerides at the epoch of the event, we determined the source position with an accuracy of 40 mas (1{sigma} c.l.), which is interesting, given the very poor imaging capabilities of RXTE ({approx}1 Degree-Sign ). For the first time, using a non-imaging X-ray observatory, the position of an X-ray source with a subarcsecond accuracy is derived, demonstrating the neat capabilities of a technique that can be fruitfully applied to current and future X-ray missions.

  8. THE MASS OF THE BLACK HOLE IN XTE J1118+480

    SciTech Connect

    Khargharia, Juthika; Froning, Cynthia S.; Robinson, Edward L.; Gelino, Dawn M. E-mail: cynthia.froning@colorado.edu E-mail: dawn@ipac.caltech.edu

    2013-01-01

    We present contemporaneous, broadband, near-infrared spectroscopy (0.9-2.45 {mu}m) and H-band photometry of the black hole X-ray binary, XTE J1118+480. We determined the fractional dilution of the NIR ellipsoidal light curves of the donor star from other emission sources in the system by comparing the absorption features in the spectrum with field stars of known spectral type. We constrained the donor star spectral type to K7 V-M1 V and determined that the donor star contributed 54% {+-} 27% of the H-band flux at the epoch of our observations. This result underscores the conclusion that the donor star cannot be assumed to be the only NIR emission source in quiescent X-ray binaries. The H-band light curve shows a double-humped asymmetric modulation with extra flux at orbital phase 0.75. The light curve was fitted with a donor star model light curve, taking into account a constant second flux component based on the dilution analysis. We also fitted models that included emission from the donor star, a constant component from the accretion disk, and a phase-variable component from the bright spot where the mass accretion stream impacts the disk. These simple models with reasonable estimates for the component physical parameters can fully account for the observed light curve, including the extra emission at phase 0.75. From our fits, we constrained the binary inclination to 68 Degree-Sign {<=} i {<=} 79 Degree-Sign . This leads to a black hole mass of 6.9 M{sub Sun} {<=} M{sub BH} {<=} 8.2 M{sub Sun }. Long-term variations in the NIR light curve shape in XTE J1118+480 are similar to those seen in other X-ray binaries and demonstrate the presence of continued activity and variability in these systems even when in full quiescence.

  9. Ion-implantation-induced damage and resonant levels in Pb/sub 1-x/Sn/sub x/Te

    SciTech Connect

    Gresslehner, K.H.; Palmetshofer, L.

    1980-09-01

    The dependence of the carrier concentration on the implantation dose and on the temperature was investigated in ion-implanted thin films of Pb/sub 1-x/Sn/sub x/Te (0< or =x<0.1). By assuming a twofold defect level in the conduction band we are able to fit the experimental results. With increasing tin content the energy of the defect level shifts towards the conduction-band edge. By extending the results to SnTe a general model for the understanding of the electrical properties of ion-implanted Pb/sub 1-x/Sn/sub x/Te (0< or =x< or =1) is suggested.

  10. Disentangling the NIR/optical emission of the black hole XTE J1650-500 during outburst

    NASA Astrophysics Data System (ADS)

    Curran, P. A.; Chaty, S.; Zurita Heras, J. A.

    2012-11-01

    Context. While the sources of X-ray and radio emission in the different states of low-mass X-ray binaries are relatively well understood, the origin of the near-infrared (NIR) and optical emission is more often debated. It is likely that the NIR/optical flux originates from an amalgam of different emission regions, because it occurs at the intersecting wavelengths of multiple processes. Aims: We aim to identify the NIR/optical emission region(s) of one such low-mass X-ray binary and black hole candidate, XTE J1650-500, via photometric, timing, and spectral analyses. Methods: We present unique NIR/optical images and spectra, obtained with the ESO-New Technology Telescope, during the peak of the 2001 outburst of XTE J1650-500. Results: The data suggest that the NIR/optical flux is due to a combination of emission mechanisms including a significant contribution from X-ray reprocessing and, at early times in the hard state, a relativistic jet that is NIR/radio dim compared to similar sources. Conclusions: The jet of XTE J1650-500 is relatively weak compared to that of other black hole low-mass X-ray binaries, possibly because we observe as it is being "turned off" or quenched at the state transition. While there are several outliers to the radio-X-ray correlation of the hard state of low-mass X-ray binaries, XTE J1650-500 is the first example of an outlier to the NIR/optical-X-ray correlation. Based on observations made with the European Southern Observatory telescopes obtained from the ESO/ST-ECF Science Archive Facility.

  11. The black hole candidate XTE J1752-223 towards and in quiescence: optical and simultaneous X-ray-radio observations

    NASA Astrophysics Data System (ADS)

    Ratti, E. M.; Jonker, P. G.; Miller-Jones, J. C. A.; Torres, M. A. P.; Homan, J.; Markoff, S.; Tomsick, J. A.; Kaaret, P.; Wijnands, R.; Gallo, E.; Özel, F.; Steeghs, D. T. H.; Fender, R. P.

    2012-07-01

    We present optical, X-ray and radio observations of the black hole transient (BHT) XTE J1752-223 towards and in quiescence. Optical photometry shows that the quiescent magnitude of XTE J1752-223 is fainter than 24.4 mag in the i' band. A comparison with measurements of the source during its 2009-2010 outburst shows that the outburst amplitude is more than 8 mag in the i' band. Known X-ray properties of the source combined with the faintness of the quiescence optical counterpart and the large outburst optical amplitude point towards a short orbital-period system (Porb≲ 6.8 h) with an M type (or later) mass donor, at a distance of 3.5 ≲d≲ 8 kpc. Simultaneous X-ray and radio data were collected with Chandra and the Expanded Very Large Array (EVLA), allowing constraints to be placed on the quiescent X-ray and radio flux of XTE J1752-223. Furthermore, using data covering the final stage of the outburst decay, we investigated the low-luminosity end of the X-ray-radio correlation for this source and compared it with other BHTs. We found that XTE J1752-223 adds to the number of outliers with respect to the 'standard' X-ray-radio luminosity relation. Furthermore, XTE J1752-223 is the second source, after the BHT H1743-322, that shows a transition from the region of the outliers towards the 'standard' correlation at low luminosity. Finally, we report on a faint, variable X-ray source we discovered with Chandra at an angular distance of ˜2.9 arcsec to XTE J1752-223 and at a position angle consistent with that of the radio jets previously observed from the BHT. We discuss the possibility that we detected X-ray emission associated with a jet from XTE J1752-223.

  12. Discovery and X-ray Monitoring of a New Black Hole Candidate XTE J1752-223

    NASA Astrophysics Data System (ADS)

    Shaposhnikov, Nikolai; Swank, J. H.; Markwardt, C. B.; Krimm, H.

    2010-03-01

    On October 23, 2009 a new X-ray transient source XTE J1752-223 was discovered by RXTE during observations scanning the Galactic Bulge region. Source identification in the optical, infra-red, and radio immediately followed. The first pointed RXTE observation, three days after the discovery, revealed a very hard non-thermal energy spectrum and strong iron line emission. After the initial rise the source flux leveled off and showed very stable properties for more than a month of monitoring observations until the Sun was too close for RXTE to observe. We analyzed RXTE data collected during this monitoring campaign. The aperiodic fast variability properties are strongly reminiscent of the extreme hard states shown by the well known black hole binary Cygnus X-1, as well as several other black hole candidates. The overall similarity of the source properties to those of other Galactic black holes classify XTE J1752-223 as a new stellar black hole candidate. We compare spectral and variability properties of XTE J1752-223 to Cygnus X-1 and discuss possible implications for various mechanisms of non-thermal emission.

  13. X-ray spectroscopic and timing studies of galactic black hole binaries

    NASA Astrophysics Data System (ADS)

    Miller, Jon Matthew

    In rare cases, optical observations of Galactic binary star systems which are bright in the X-ray portion of the electromagnetic spectrum dynamically constrain the mass of one component to be well above theoretical limits for a neutron star. These systems—and systems with similar X-ray properties—are classified as black hole binaries. In this thesis, I report on observations of black hole binaries made with satellite observatories in the X-ray band. The region closest to the black hole is revealed in X-rays due to the viscous heating of matter that is accreted from the companion star. X-ray observations of these systems may therefore reveal General Relativistic effects. A fundamental and testable prediction of General Relativity is that matter may orbit more closely around black holes with significant angular momentum. I have investigated the possibility of black hole “spin” and the geometry of accretion flows in these systems using X-ray continuum spectroscopy, fast variability studies, and the shape of iron fluorescent emission lines in this band. I present evidence for black hole spin in XTE J1550-564, XTE J1650- 500, and XTE J1748-248. Spin is not required by high- resolution spectral analysis of the archetypical Galactic black hole—Cygnus X-1—but a thermal accretion disk plus hot corona geometry is confirmed. Studies of XTE J1118+480 and GRS 1758-258 at low X-ray luminosity reveal that models for radiatively-inefficient accretion do not satisfactorily describe the geometry in these systems. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)/

  14. Modification of band gap in surface layer in Cd 1-xZn xTe by YAG:Nd +3 laser radiation

    NASA Astrophysics Data System (ADS)

    Medvid, Artur; Fedorenko, Leonid L.; Korbutjak, Dmytro V.; Kryluk, Sergiy G.; Yusupov, Mikola M.; Mychko, Aleksandr

    2007-02-01

    A mechanism of formation of graded band-gap based on Thermogradient Effect (TGE) is proposed in Cd 1-xZn xTe at irradiation by second harmonic of a Q-switched YAG:Nd laser. According to the effect, the interstitial atoms of Cd (Cd i) in Cd 1-xZn xTe move along the temperature gradient while the Cd vacancies (V Cd) and Zn atoms - in the opposite direction, into the bulk of the semiconductor where temperature is lower. Photoluminescence (PL) spectra studied at 5 K show that concentration of Zn atoms increases due to aggregation of VCd with Zn after laser irradiation. Formation of a graded band-gap in Cd 1-xZn xTe crystal at irradiation by second harmonica of YAG:Nd laser by is shown to be possible.

  15. GAMMA-RAY OBSERVATIONS OF THE MICROQUASARS CYGNUS X-1, CYGNUS X-3, GRS 1915+105, AND GX 339–4 WITH THE FERMI LARGE AREA TELESCOPE

    SciTech Connect

    Bodaghee, Arash; Tomsick, John A.; Pottschmidt, Katja; Rodriguez, Jérôme; Pooley, Guy G.

    2013-10-01

    Detecting gamma-rays from microquasars is a challenging but worthwhile endeavor for understanding particle acceleration and the jet mechanism and for constraining leptonic/hadronic emission models. We present results from a likelihood analysis on timescales of 1 day and 10 days of ∼4 yr worth of gamma-ray observations (0.1-10 GeV) by Fermi-LAT of Cyg X-1, Cyg X-3, GRS 1915+105, and GX 339–4. Our analysis reproduced all but one of the previous gamma-ray outbursts of Cyg X-3 as reported with Fermi or AGILE, plus five new days on which Cyg X-3 is detected at a significance of ∼5σ that are not reported in the literature. In addition, Cyg X-3 is significantly detected on 10 day timescales outside of known gamma-ray flaring epochs, which suggests that persistent gamma-ray emission from Cyg X-3 has been detected for the first time. For Cyg X-1 we find three low-significance excesses (∼3-4σ) on daily timescales that are contemporaneous with gamma-ray flares reported (also at low significance) by AGILE. Two other microquasars, GRS 1915+105 and GX 339–4, are not detected, and we derive 3σ upper limits of 2.3 × 10{sup –8} photons cm{sup –2} s{sup –1} and 1.6 × 10{sup –8} photons cm{sup –2} s{sup –1}, respectively, on the persistent flux in the 0.1-10 GeV range. These results enable us to define a list of the general conditions that are necessary for the detection of gamma-rays from microquasars.

  16. THE CROSS SPECTRAL TIME LAG EVOLUTION ALONG BRANCHES IN XTE J1701-462

    SciTech Connect

    Li Zhaosheng; Chen Li; Bu Qingcui; Wang Dehua; Qu Jinlu E-mail: chenli@bnu.edu.cn

    2013-04-20

    We investigate the cross spectrum of XTE J1701-462 in various types of neutron star low-mass X-ray binary subclasses during its 2006-2007 outburst. We analyze the relation between the time lags and temporal variabilities. We find that the hard time lags accompany horizontal branch oscillations (HBOs) and the soft time lags dominate the noise in the low frequency range 0.1-10 Hz on HB. In the Cyg-like phase, the time lags decrease on the middle normal branch (NB) from HB/NB vertex to NB/FB vertex, whereas the time lags are roughly invariant in the Sco-like source. We discuss the fact that the Compton upscattering by the corona introduces the soft lag in low-frequency noise. We suggest that the variation of the Comptonization component from the disk emission leads to the HBOs' time lag evolutions along the Z tracks. We also report the rms amplitude spectrum and phase lag spectrum for the normal branch oscillation (NBO). A {approx}160 Degree-Sign phase lag is found. We find that the rms amplitudes of both the Cyg-like and the Sco-like NBOs linearly increase with the photon energy in low energy bands, and drop in the highest energy band.

  17. Transient relativistic ejections and stationary core in XTE J1752-223

    NASA Astrophysics Data System (ADS)

    Yang, J.; Paragi, Z.; Corbel, S.; Gurvits, L. I.; Campbell, R. M.; Brocksopp, C.

    2011-11-01

    The Galactic X-ray transient XTE J1752-223 was shown to have properties of black hole binary candidates. As reported in our previous paper, we identified transient and decelerating ejecta in multi-epoch Very Long Baseline Interferometry (VLBI) observations with the European VLBI Network (EVN) and the NRAO Very Long Baseline Array (VLBA). Here we present new EVN and VLBA data in which a new transient ejection event and later a stationary component are identified. The latter is interpreted as a reappearance of the radio core/compact jet during the transition from soft to hard X-ray state. This component appears to be highly variable in brightness although effects of tropospheric instabilities might play a role too. We also re-analyse the earlier VLBI data and find that the transient ejecta closer to the core position has significantly higher proper motion, further strengthening the case for strongly decelerating ejecta on the scale of several hundred milliarcsecond, never observed in X-ray binaries before. Although the distance of the source is not well constrained, it is clear that these ejectas are at least mildly relativistic at the early stages. Moreover, we show the large scale environment of the transient from the Westerbork synthesis array data recorded in parallel during the EVN run.

  18. On the Nature of XTE J0421+560/CI Cam

    NASA Technical Reports Server (NTRS)

    Belloni, T.; vandenAncker, M.; Dieters, S.; Fender, R.; Fox, D. W.; Kommers, J. M.; Lewin, W. H. G.; VanParadijs, J.

    1999-01-01

    We present the results of the analysis of RXTE, BATSE and optical/IR data of the 1998 outburst of the x-ray transient system XTE J0421+650. The x-ray outburst shows a very fast decay initial e-folding time approximately 0.5 days, slowing down to about 2.3 days). The X ray spectrum in the 2-25 keV band is thermal, softening considerably during decay. Intrinsic absorption is observed, also strongly variable. A strong iron line at around 6.7 keV is observed. No fast time variability is observed (<0.1 rms in the 1-4906 Hz band at peak). The analysis of optical/IR data suggest that the secondary is a b[e] star and place the system at a distance of about 2 kpc. At this distance the 2-25 keV luminosity is about 5 x 10(exp 37) erg/seconds. We compare the properties of this system with those of the Be/NS LMC transient A 0538-66 and suggest that CI cam is of a similar nature. The presence of strong radio emission during outburst indicates that the compact object could be a black hole.

  19. Highly efficient functional GexPb1-xTe based thermoelectric alloys.

    PubMed

    Gelbstein, Yaniv; Davidow, Joseph

    2014-10-07

    Methods for enhancement of the direct thermal to electrical energy conversion efficiency, upon development of advanced thermoelectric materials, are constantly investigated mainly for efficient implementation of thermoelectric devices in automotive vehicles, for converting the waste heat generated in such engines into useful electrical power and thereby reduction of the fuel consumption and CO2 emission levels. It was recently shown that GeTe based compounds and specifically GeTe-PbTe rich alloys are efficient p-type thermoelectric compositions. In the current research, Bi2Te3 doping and PbTe alloying effects in GexPb1-xTe alloys, subjected to phase separation reactions, were investigated for identifying the phase separation potential for enhancement of the thermoelectric properties beyond a pure alloying effect. All of the investigated compositions exhibit maximal dimensionless figure of merit, ZT, values beyond 1, with the extraordinary value of 2.1 found for the 5% Bi2Te3 doped-Ge0.87Pb0.13Te composition, considered as among the highest ever reported.

  20. On the Nature of QPO Phase Lags in Black Hole Candidates

    NASA Technical Reports Server (NTRS)

    Shaposhnikov, Nikolai

    2012-01-01

    Observations of quasi-periodic oscillations (QPOs) in X-ray binaries hold a key to understanding many aspects of these enigmatic systems. Complex appearance of the Fourier phase lags related to QPOs is one of the most puzzling observational effects in accreting black holes. In this Letter we show that QPO properties, including phase lags, can be explained in a framework of a simple scenario, where the oscillating media provides a feedback on the emerging spectrum. We demonstrate that the QPO waveform is presented by the product of a perturbation and a time delayed response factors, where the response is energy dependent. The essential property of this effect is its non-linear and multiplicative nature. Our multiplicative reverberation model successfully describes the QPO components in energy dependent power spectra as well as the appearance of the phase lags between signal in different energy bands. We apply our model to QPOs observed by Rossi X-ray Timing Explorer in BH candidate XTE J1550-564. We briefly discuss the implications of the observed energy dependence of the QPO reverberation times and amplitudes to the nature of the power law spectral component and its variability.

  1. An empirical method for improving the quality of RXTE PCA spectra

    SciTech Connect

    García, Javier A.; McClintock, Jeffrey E.; Steiner, James F.; Remillard, Ronald A.; Grinberg, Victoria E-mail: jem@cfa.harvard.edu E-mail: rr@space.mit.edu

    2014-10-10

    We fitted all of the several hundred RXTE PCA spectra of the Crab individually to a simple power-law model; the total number of counts in the composite spectrum is >10{sup 9}. We then used the spectrum of residuals to derive a calibration tool, called pcacorr, that we apply to large samples of spectra for GX 339-4, H1743-322, and XTE J1550-564. Application of the tool improved the quality of all the fits, and the improvement is dramatic for spectra with ≳ 10{sup 7} counts. The Crab residual spectrum is somewhat different for each of the five Proportional Counter Array (PCA) detectors, but it was relatively stable over the course of the mission. We recommend that pcacorr be routinely applied to spectra with ≳ 10{sup 6} counts and that one include a systematic error of 0.1%, rather than the 0.5-1% value that has customarily been used. We expect that application of the tool will result in an increase in sensitivity of the PCA to faint spectral features by up to an order of magnitude.

  2. ON THE NATURE OF QUASI-PERIODIC OSCILLATION PHASE LAGS IN BLACK HOLE CANDIDATES

    SciTech Connect

    Shaposhnikov, Nikolai E-mail: lev@milkyway.gsfc.nasa.gov

    2012-06-20

    Observations of quasi-periodic oscillations (QPOs) in X-ray binaries hold a key to understanding many aspects of these enigmatic systems. Complex appearance of the Fourier phase lags related to QPOs is one of the most puzzling observational effects in accreting black holes (BHs). In this Letter we show that QPO properties, including phase lags, can be explained in a framework of a simple scenario, where the oscillating media provide feedback on the emerging spectrum. We demonstrate that the QPO waveform is presented by the product of a perturbation and time-delayed response factors, where the response is energy dependent. The essential property of this effect is its nonlinear and multiplicative nature. Our multiplicative reverberation model successfully describes the QPO components in energy-dependent power spectra as well as the appearance of the phase lags between signals in different energy bands. We apply our model to QPOs observed by the Rossi X-Ray Timing Explorer in BH candidate XTE J1550-564. We briefly discuss the implications of the observed energy dependence of the QPO reverberation times and amplitudes on the nature of the power-law spectral component and its variability.

  3. Revealing the inner accretion flow around black holes using rapid variability

    NASA Astrophysics Data System (ADS)

    Axelsson, Magnus

    2015-08-01

    The geometry of the inner accretion flow of X-ray binaries is complex, with multiple regions contributing to the observed emission. Frequency-resolved spectroscopy is a powerful tool in breaking this spectral degeneracy. We have extracted the spectra of the strong low-frequency quasi-periodic oscillation (QPO) and its harmonic in GX339-4 and XTE J1550-564. We compare these to the time-averaged spectrum and the spectrum of the rapid (< 0.1s) variability. Our results support the picture where the QPO arises from vertical (Lense-Thirring) precession of an inhomogeneous hot flow, so that it is softer at larger radii closer to the truncated disc, and harder in the innermost parts of the flow where the rapid variability is produced. This coupling between variability and spectra allows us to constrain the soft Comptonization component, breaking the degeneracy plaguing the time-averaged spectrum and revealing the geometry of the accretion flow close to the black hole. We further show how the upcoming launch of ASTRO-H will allow even more specific regions in the accretion flow to be probed.

  4. High-frequency quasi-periodic oscillations in black hole binaries

    NASA Astrophysics Data System (ADS)

    Belloni, T. M.; Sanna, A.; Méndez, M.

    2012-11-01

    We present the results of the analysis of a large data base of X-ray observations of 22 galactic black hole transients with the Rossi X-Ray Timing Explorer throughout its operative life for a total exposure time of ˜12 ms. We excluded persistent systems and the peculiar source GRS 1915+105, as well as the most recently discovered sources. The semi-automatic homogeneous analysis was aimed at the detection of high-frequency (100-1000 Hz) quasi-periodic oscillations (QPO), of which several cases were previously reported in the literature. After taking into account the number of independent trials, we obtained 11 detections from two sources only: XTE J1550-564 and GRO J1655-40. For the former, the detected frequencies are clustered around 180 and 280 Hz, as previously found. For the latter, the previously reported dichotomy 300-450 Hz is found to be less sharp. We discuss our results in comparison with kHz QPO in neutron-star X-ray binaries and the prospects for future timing X-ray missions.

  5. Growth and characterization of CdTe, Mn(x)Cd(1-x)Te, Zn(x)Cd(1-x)Te, and CdSe(y)Te(1-y) crystals

    NASA Astrophysics Data System (ADS)

    Lay, K. Y.; Giles-Taylor, N. C.; Schetzina, J. F.; Bachmann, K. J.

    1986-05-01

    Structures and growth characteristics of crystals based on the Cd-Te lattice, which are potentially useful in infrared radiation detectors, are described. Single crystals of CdTe, Mn(x)Cd(1-x)Te, and CdSe(y)Te(1-y) have been grown by the vertical Bridgman method and those of Zn(x)Cd(1-l)Te by zone leveling. Photoluminescence (PL) spectra were used to determine the quality and uniformity of composition. From the probing of small areas, allowed by this PL characterization technique, the uniform incorporation of Mn, Zn, and Se into the CdTe lattice was determined.

  6. Growth and characterization of CdTe, Mn(x)Cd(1-x)Te, Zn(x)Cd(1-x)Te, and CdSe(y)Te(1-y) crystals

    SciTech Connect

    Lay, K.Y.; Giles-Taylor, N.C.; Schetzina, J.F.; Bachmann, K.J.

    1986-05-01

    Structures and growth characteristics of crystals based on the Cd-Te lattice, which are potentially useful in infrared radiation detectors, are described. Single crystals of CdTe, Mn(x)Cd(1-x)Te, and CdSe(y)Te(1-y) have been grown by the vertical Bridgman method and those of Zn(x)Cd(1-l)Te by zone leveling. Photoluminescence (PL) spectra were used to determine the quality and uniformity of composition. From the probing of small areas, allowed by this PL characterization technique, the uniform incorporation of Mn, Zn, and Se into the CdTe lattice was determined. 15 references.

  7. A parallax distance to the microquasar GRS 1915+105 and a revised estimate of its black hole mass

    SciTech Connect

    Reid, M. J.; McClintock, J. E.; Steiner, J. F.; Narayan, R.; Steeghs, D.; Remillard, R. A.; Dhawan, V.

    2014-11-20

    Using the Very Long Baseline Array, we have measured a trigonometric parallax for the microquasar GRS 1915+105, which contains a black hole and a K-giant companion. This yields a direct distance estimate of 8.6{sub −1.6}{sup +2.0} kpc and a revised estimate for the mass of the black hole of 12.4{sub −1.8}{sup +2.0} M {sub ☉}. GRS 1915+105 is at about the same distance as some H II regions and water masers associated with high-mass star formation in the Sagittarius spiral arm of the Galaxy. The absolute proper motion of GRS 1915+105 is –3.19 ± 0.03 mas yr{sup –1} and –6.24 ± 0.05 mas yr{sup –1} toward the east and north, respectively, which corresponds to a modest peculiar speed of 22 ± 24 km s{sup –1} at the parallax distance, suggesting that the binary did not receive a large velocity kick when the black hole formed. On one observational epoch, GRS 1915+105 displayed superluminal motion along the direction of its approaching jet. Considering previous observations of jet motions, the jet in GRS 1915+105 can be modeled with a jet inclination to the line of sight of 60° ± 5° and a variable flow speed between 0.65c and 0.81c, which possibly indicates deceleration of the jet at distances from the black hole ≳ 2000 AU. Finally, using our measurements of distance and estimates of black hole mass and inclination, we provisionally confirm our earlier result that the black hole is spinning very rapidly.

  8. Searches for continuous gravitational waves from Scorpius X-1 and XTE J1751-305 in LIGO's sixth science run

    NASA Astrophysics Data System (ADS)

    Meadors, G. D.; Goetz, E.; Riles, K.; Creighton, T.; Robinet, F.

    2017-02-01

    Scorpius X-1 (Sco X-1) and x-ray transient XTE J1751-305 are low-mass x-ray binaries (LMXBs) that may emit continuous gravitational waves detectable in the band of ground-based interferometric observatories. Neutron stars in LMXBs could reach a torque-balance steady-state equilibrium in which angular momentum addition from infalling matter from the binary companion is balanced by angular momentum loss, conceivably due to gravitational-wave emission. Torque balance predicts a scale for detectable gravitational-wave strain based on observed x-ray flux. This paper describes a search for Sco X-1 and XTE J1751-305 in LIGO science run 6 data using the TwoSpect algorithm, based on searching for orbital modulations in the frequency domain. While no detections are claimed, upper limits on continuous gravitational-wave emission from Sco X-1 are obtained, spanning gravitational-wave frequencies from 40 to 2040 Hz and projected semimajor axes from 0.90 to 1.98 light-seconds. These upper limits are injection validated, equal any previous set in initial LIGO data, and extend over a broader parameter range. At optimal strain sensitivity, achieved at 165 Hz, the 95% confidence level random-polarization upper limit on dimensionless strain h0 is approximately 1.8 ×10-24. The closest approach to the torque-balance limit, within a factor of 27, is also at 165 Hz. Upper limits are set in particular narrow frequency bands of interest for J1751-305. These are the first upper limits known to date on r -mode emission from this XTE source. The TwoSpect method will be used in upcoming searches of Advanced LIGO and Virgo data.

  9. Thermal analysis of specific heat measurements in glassy Se80-xTe20Sbx alloys in glass transition region

    NASA Astrophysics Data System (ADS)

    Saraswat, S.; Mehta, N.; Sharma, S. D.

    2016-01-01

    In the present report, we have done specific heat measurements in glassy Se80-xTe20Sbx (0 ≤ x ≤ 15) alloys in glass transition region. Differential scanning calorimetry (DSC) technique is used for this purpose. We have observed a tremendously huge increase in the specific heat (Cp) values at the glass transition temperature. The thermal analysis shows that the values of Cp below glass transition temperature and the difference of Cp values before and after glass transition (∆Cp) are highly composition-dependent.

  10. Inclination dependence of QPO phase lags in black hole X-ray binaries

    NASA Astrophysics Data System (ADS)

    van den Eijnden, J.; Ingram, A.; Uttley, P.; Motta, S. E.; Belloni, T. M.; Gardenier, D. W.

    2017-01-01

    Quasi-periodic oscillations (QPOs) with frequencies from ˜0.05to30 Hz are a common feature in the X-ray emission of accreting black hole binaries. As the QPOs originate from the innermost accretion flow, they provide the opportunity to probe the behaviour of matter in extreme gravity. In this paper, we present a systematic analysis of the inclination dependence of phase lags associated with both type-B and type-C QPOs in a sample of 15 Galactic black hole binaries. We find that the phase lag at the type-C QPO frequency strongly depends on inclination, both in evolution with the QPO frequency and sign. Although we find that the type-B QPO soft lags are associated with high-inclination sources, the source sample is too small to confirm that this as a significant inclination dependence. These results are consistent with a geometrical origin of type-C QPOs and a different origin for type-B and type-C QPOs. We discuss the possibility that the phase lags originate from a pivoting spectral power law during each QPO cycle, while the inclination dependence arises from differences in dominant relativistic effects. We also search for energy dependences in the type-C QPO frequency. We confirm this effect in the three known sources (GRS 1915+105, H1743-322 and XTE J1550-564) and newly detect it in XTE J1859+226. Lastly, our results indicate that the unknown inclination sources XTE J1859+226 and MAXI J1543-564 are most consistent with a high inclination.

  11. Cd{sub 1−x}Mn{sub x}Te ultrasmall quantum dots growth in a silicate glass matrix by the fusion method

    SciTech Connect

    Dantas, Noelio Oliveira; Lima Fernandes, Guilherme de; Almeida Silva, Anielle Christine; Baffa, Oswaldo; Gómez, Jorge Antônio

    2014-09-29

    In this study, we synthesized Cd{sub 1−x}Mn{sub x}Te ultrasmall quantum dots (USQDs) in SiO{sub 2}-Na{sub 2}CO{sub 3}-Al{sub 2}O{sub 3}-B{sub 2}O{sub 3} glass system using the fusion method. Growth of these Cd{sub 1−x}Mn{sub x}Te USQDs was confirmed by optical absorption, atomic force microscopy (AFM), magnetic force microscopy (MFM), scanning transmission electron microscopy (TEM), and electron paramagnetic resonance (EPR) measurements. The blueshift of absorption transition with increasing manganese concentration gives evidence of incorporation of manganese ions (Mn{sup 2+}) in CdTe USQDs. AFM, TEM, and MFM confirmed, respectively, the formation of high quality Cd{sub 1−x}Mn{sub x}Te USQDs with uniformly distributed size and magnetic phases. Furthermore, EPR spectra showed six lines associated to the S = 5/2 spin half-filled d-state, characteristic of Mn{sup 2+}, and confirmed that Mn{sup 2+} are located in the sites core and surface of the CdTe USQD. Therefore, synthesis of high quality Cd{sub 1−x}Mn{sub x}Te USQDs may allow the control of optical and magnetic properties.

  12. In-Flight Observations of Long-Term Single-Event Effect (SEE) Performance on X-ray Timing Explorer (XTE) Solid-state Recorders (SSRs)

    NASA Technical Reports Server (NTRS)

    Poivey, Christian; Gee, George; LaBel, Kenneth A.; Barth, Janet L.

    2004-01-01

    We present multi-year Single Event Upset (SEU) flight data on Solid State Recorder (SSR) memories for the X-ray Timing Explorer (XTE) NASA mission. Actual SEU rates are compared to the predicted rates based on ground test data and environment models.

  13. Application of the Nonballistic Model to the Black Hole Candidate XTE J1752-223 and the Quasar NRAO 150

    NASA Astrophysics Data System (ADS)

    Zheng, T. Y.; Gong, B. P.

    2017-02-01

    Optical and radio observations of the black hole candidate XTE J1752-223 have exhibited a slightly curved motion of the jet components, which is associated with its radio light curve. In addition, observations of the quasar NRAO 150 have revealed a core–jet structure wobbling with a high angular speed. In this paper, the phenomena displayed in these two different sources are interpreted as the precession of a bent jet. In such a scenario, hot spots reproduced at different separations from the core precess on the same precession cone, in which different components correspond to different propagation times to the observer. By fitting the kinematics of the components of XTE J1752-223 and its light curve with a curved pattern of precession period 314 days, we find that the propagation time can make an earlier event appear later, and the jet axis can oscillate during its precession. Simulating the quasar NRAO 150 with the same scenario reveals that the knots at larger separation from the core precess at a slower speed than those closer in. A possible mechanism relating to the cooling time of a component is proposed. These three new results are of importance in understanding the physics underlying the curved jet as well as the activity of the central engine of different black hole systems.

  14. Prediction of an arc-tunable Weyl Fermion metallic state in Mo(x)W(1-x)Te2.

    PubMed

    Chang, Tay-Rong; Xu, Su-Yang; Chang, Guoqing; Lee, Chi-Cheng; Huang, Shin-Ming; Wang, BaoKai; Bian, Guang; Zheng, Hao; Sanchez, Daniel S; Belopolski, Ilya; Alidoust, Nasser; Neupane, Madhab; Bansil, Arun; Jeng, Horng-Tay; Lin, Hsin; Zahid Hasan, M

    2016-02-15

    A Weyl semimetal is a new state of matter that hosts Weyl fermions as emergent quasiparticles. The Weyl fermions correspond to isolated points of bulk band degeneracy, Weyl nodes, which are connected only through the crystal's boundary by exotic Fermi arcs. The length of the Fermi arc gives a measure of the topological strength, because the only way to destroy the Weyl nodes is to annihilate them in pairs in the reciprocal space. To date, Weyl semimetals are only realized in the TaAs class. Here, we propose a tunable Weyl state in Mo(x)W(1-x)Te2 where Weyl nodes are formed by touching points between metallic pockets. We show that the Fermi arc length can be changed as a function of Mo concentration, thus tuning the topological strength. Our results provide an experimentally feasible route to realizing Weyl physics in the layered compound Mo(x)W(1-x)Te2, where non-saturating magneto-resistance and pressure-driven superconductivity have been observed.

  15. RXTE and BeppoSAX Observations of the Transient X-ray Pulsar XTE J 18591+083

    NASA Technical Reports Server (NTRS)

    Corbet, R. H. D.; intZand, J. J. M.; Levine, A. M.; Marshall, F. E.

    2008-01-01

    We present observations of the 9.8 s X-ray pulsar XTE J159+083 made with the All-Sky Monitor (ASM) and Proportional Counter Array (PCA) on board the Rossi X-ray Timing Explorer (RXTE), and the Wide Field Cameras (WFC) on board BeppoSAX. The ASM data cover a 12 year time interval and show that an extended outburst occurred between approximately MJD50, 250, and 50, 460 (1996 June 16 to 1997 January 12). The ASM data excluding this outburst interval suggest a possible 61 day modulation. Eighteen sets of PCA observations were obtained over an approx. one month interval in 1999. The flux variability measured with the PCA appears consistent with the possible period found with the ASM. The PCA measurements of the pulse period showed it to decrease non-monotonically and then to increase significantly. Doppler shifts due to orbital motion rather than accretion torques appear to be better able to explain the pulse period changes. Observations with the WFC during the extended outburst give an error box which is consistent with a previously determined PCA error box but is significantly smaller. The transient nature of XTE J1859+083 and the length of its pulse period are consistent with it being a Be/neutral star binary. The possible 61 day orbital period would be of the expected length for a Be star system with a 9.8 s pulse period.

  16. XTE J2123-058: A New Neutron Star X-Ray Transient

    NASA Astrophysics Data System (ADS)

    Tomsick, John A.; Halpern, Jules P.; Kemp, Jonathan; Kaaret, Philip

    1999-08-01

    We report on optical and RXTE observations of a new high-latitude bursting X-ray transient, XTE J2123-058. We identified the optical counterpart and discovered a 5.9573+/-0.0016 hr periodic optical modulation, which was subsequently shown to be the same as the spectroscopic orbital period. From the absence of orbital X-ray modulation and the presence of partial optical eclipses we conclude that the binary inclination is between 55° and 73°. From the optical magnitude in quiescence and from the X-ray flux of type I X-ray bursts, we estimate that the source distance is between 4.5 and 15 kpc, which implies that the source is unusually far from the Galactic plane, since b=-36.2d. Optical bursts with properties consistent with being reprocessed X-ray bursts occurred. We detected a pair of high-frequency quasi-periodic oscillations (QPOs) at 847.1+/-5.5 Hz and 1102+/-13 Hz simultaneously. According to the beat-frequency model, this QPO separation implies a neutron star spin period of 3.92+/-0.22 ms. A change in the energy spectrum occurred during the decay of the outburst, which may have been due to the onset of the propeller mechanism. If so, then the neutron star magnetic field strength is between 2 and 8×108 G for an assumed distance of 10 kpc. However, the changes in the timing and spectral properties observed during the decay are typical of atoll sources, which may indicate that the changes are due solely to the dynamics of the accretion disk. As the phase-averaged V-band magnitude declined from 17.26 at the peak of the outburst to 19.24, and the X-ray flux decreased from 9.6×10-10 to 7.3×10-11 ergs cm-2 s-1, the peak-to-peak amplitude of the V-band modulation increased from 0.75 to 1.49 mag. This behavior can be explained if the size of the accretion disk decreases during the decay of the outburst.

  17. Study of CdTe/MgxCd1-xTe Double Heterostructures and Their Application in High Efficiency Solar Cells and in Luminescence Refrigeration

    NASA Astrophysics Data System (ADS)

    Zhao, Xinhao

    CdTe/MgxCd1-xTe double heterostructures (DHs) have been grown on lattice matched InSb (001) substrates using Molecular Beam Epitaxy. The MgxCd1-xTe layers, which have a wider bandgap and type-I band edge alignment with CdTe, provide sufficient carrier confinement to CdTe, so that the optical properties of CdTe can be studied. The DH samples show very strong Photoluminescence (PL) intensity, long carrier lifetimes (up to 3.6 micros) and low effective interface recombination velocity at the CdTe/MgxCd1-xTe heterointerface ( 1 cm/s), indicating the high material quality. Indium has been attempted as an n-type dopant in CdTe and it is found that the carriers are 100% ionized in the doping range of 1x1016 cm-3 to 1x1018 cm-3. With decent doping levels, long minority carrier lifetime, and almost perfect surface passivation by the MgxCd 1-xTe layer, the CdTe/MgxCd1-xTe DHs are applied to high efficiency CdTe solar cells. Monocrystalline CdTe solar cells with efficiency of 17.0% and a record breaking open circuit voltage of 1.096 V have been demonstrated in our group. Mg0.13Cd0.87Te (1.7 eV), also with high material quality, has been proposed as a current matching cell to Si (1.1 eV) solar cells, which could potentially enable a tandem solar cell with high efficiency and thus lower the electricity cost. The properties of Mg0.13Cd 0.87Te/Mg0.5Cd0.5Te DHs and solar cells have been investigated. Carrier lifetime as long as 0.56 ?s is observed and a solar cell with 11.2% efficiency and open circuit voltage of 1.176 V is demonstrated. The CdTe/MgxCd1-xTe DHs could also be potentially applied to luminescence refrigeration, which could be used in vibration-free space applications. Both external luminescence quantum efficiency and excitation-dependent PL measurement show that the best quality samples are almost 100% dominated by radiative recombination, and calculation shows that the internal quantum efficiency can be as high as 99.7% at the optimal injection level (10 17 cm-3

  18. The thermal diffusivity of Mn_xCd_1-xTe using the interferometric Mirage effect

    NASA Astrophysics Data System (ADS)

    Corona-Organiche, Edgar; Munoz-Aguirre, Narcizo; Morales-Toro, Juan Eduardo; Vazquez-Lopez, Carlos; Zelaya-Angel, Orlando; Lopez-Cruz, Elias

    2001-03-01

    Recently, N. Munoz-Aguirre et. al (N. Munoz-Aguirre, G. Gonzalez de la Cruz, Yu. G. Gurevich, G.N. Logvinov, and M.N. Kasyanchuk, Phys. Stat. Sol. (b), vol. 220, p. 781 (2000))reported a theoretical treatment of the heat diffusion in two-layer structures for application to photoacoustic experiments. They showed that the influence of the interface thermal contact between the layers plays an important role on the effective thermal parameters. In this work, the theory has been extended to the case of the Mirage effect detected by means of a Michelson-Morley interferometer, and applied to the system air-Mn_xCd_1-xTe, with x in the range 0.05 - 0.60.

  19. X-ray diffuse scattering study of local distortions in Fe1+xTe induced by excess Fe

    NASA Astrophysics Data System (ADS)

    Liu, X.; Lee, C.-C.; Xu, Z. J.; Wen, J. S.; Gu, G.; Ku, W.; Tranquada, J. M.; Hill, J. P.

    2011-05-01

    We report x-ray diffuse scattering studies of the iron chalcogenide Fe1+xTe as a function of doping and temperature for x=0.03, 0.08, and 0.12. In all cases, remarkably strong, characteristic diffuse scattering is observed. This scattering extends throughout the Brillouin zone and exhibits a nonmonotonic decay away from the fundamental Bragg peaks, with a peaklike structure at a reduced q≈(0.3,0,0.6). We interpret this scattering as Huang diffuse scattering resulting from distortions induced by the interaction between the excess Fe and the FeTe layers. The form of the scattering indicates that this interaction is strong and extends a number of unit cells away from the interstitial Fe site. Further, the diffuse scattering shows a sudden decrease on cooling through the structural and magnetic phase transition, reflecting the first-order change of the electronic structure of FeTe.

  20. High-Frequency Quasi-Periodic Oscillations in the Black Hole X-Ray Transient XTE J1650-500

    NASA Technical Reports Server (NTRS)

    Holman, Jeroen; Klein-Wolt, Marc; Rossi, Sabrina; Miller, Jon M.; Wijnands, Rudy; Belloni, Tomaso; VanDerKlis, Michiel; Lewin, Walter H. G.

    2003-01-01

    We report the detection of high-frequency variability in the black hole X-ray transient XTE 51650-500. A quasi-periodic oscillation (QPO) was found at 250 Hz during a transition from the hard to the soft state. We also detected less coherent variability around 50 Hz that disappeared when the 250 Hz QPO showed up. There are indications that when the energy spectrum hardened the QPO frequency increased from approx. 110 to approx. 270 Hz, although the observed frequencies are also consistent with being 1 : 2 : 3 harmonics of each other. Interpreting the 250 Hz as the orbital frequency at the innermost stable orbit around a Schwarzschild black hole leads to a mass estimate of 8.2 solar mass. The spectral results by Miller et al., which suggest considerable black hole spin, would imply a higher mass.

  1. THE FAST SPIRAL-IN OF THE COMPANION STAR TO THE BLACK HOLE XTE J1118+480

    SciTech Connect

    Gonzalez Hernandez, Jonay I.; Rebolo, Rafael; Casares, Jorge E-mail: rrl@iac.es

    2012-01-10

    We report the detection of an orbital period decay of P-dot =-1.83{+-}0.66 ms yr{sup -1} in the black hole X-ray binary XTE J1118+480. This corresponds to a period change of -0.85 {+-} 0.30 {mu}s per orbital cycle, which is {approx}150 times larger than expected from the emission of gravitational waves. These observations cannot be reproduced by conventional models of magnetic braking even when including significant mass loss from the system. The spiral-in of the star is either driven by magnetic braking under extremely high magnetic fields in the secondary star or by a currently unknown process, which will have an impact on the evolution and lifetime of black hole X-ray binaries.

  2. XTE J1752-223 in outburst: a persistent radio jet, dramatic flaring, multiple ejections and linear polarization

    NASA Astrophysics Data System (ADS)

    Brocksopp, C.; Corbel, S.; Tzioumis, A.; Broderick, J. W.; Rodriguez, J.; Yang, J.; Fender, R. P.; Paragi, Z.

    2013-06-01

    The black hole candidate, XTE J1752-223, was discovered in 2009 October when it entered an outburst. We obtained radio data from the Australia Telescope Compact Array for the duration of the ˜9 month event. The light curves show that the radio emission from the compact jet persisted for the duration of an extended hard state and through the transition to the intermediate state. The flux then rose rapidly by a factor of 10 and the radio source entered a series of at least seven maxima, the first of which was likely to be emission associated with the compact jet. The subsequent six flares were accompanied by variable behaviour in terms of radio spectrum, degree of linear polarization, morphology and associated X-ray behaviour. They were, however, remarkably similar in terms of the estimated minimum power required to launch such an ejection event. We compare the timing of radio peaks with the location of the ejecta, imaged by contemporaneous Very Long Baseline Interferometry experiments. We then discuss the mechanism behind the events, in terms of whether discrete ejections are the most likely description of the behaviour. One ejection, at least, appears to be travelling with apparent superluminal motion. The range of properties, however, suggests that multiple mechanisms may be relevant and that at least some of the emission is coming from shocked interactions amongst the ejecta and between the ejecta and the interstellar medium. We also compare the radio flux density with the X-ray source during the hard state and conclude that XTE J1752-223 is a radio-weak/X-ray-bright outlier on the universal correlation for black hole transient sources.

  3. MAXI GSC Observations of a Spectral State Transition in the Black Hole Candidate XTE J1752-223

    NASA Astrophysics Data System (ADS)

    Nakahira, Satoshi; Yamaoka, Kazutaka; Sugizaki, Mutsumi; Ueda, Yoshihiro; Negoro, Hitoshi; Ebisawa, Ken; Kawai, Nobuyuki; Matsuoka, Masaru; Tsunemi, Hiroshi; Daikyuji, Arata; Eguchi, Satoshi; Hiroi, Kazuo; Ishikawa, Masaki; Ishiwata, Ryoji; Isobe, Naoki; Kawasaki, Kazuyoshi; Kimura, Masashi; Kohama, Mitsuhiro; Mihara, Tatehiro; Miyoshi, Sho; Morii, Mikio; Nakagawa, Yujin E.; Nakajima, Motoki; Ozawa, Hiroshi; Sootome, Tetsuya; Sugimori, Kousuke; Suzuki, Motoko; Tomida, Hiroshi; Ueno, Shiro; Yamamoto, Takayuki; Yoshida, Atsumasa; Maxi Team

    2010-10-01

    We present the first results on the black-hole candidate XTE J1752-223 from the Gas Slit Camera (GSC) aboard the Monitor of All-sky X-ray Image (MAXI) on the International Space Station. Including the onset of an outburst reported by the Proportional Counter Array aboard the Rossi X-ray Timing Explorer on 2009 October 23, MAXI / GSC has been monitoring this source approximately 10 times per day with high sensitivity in the 2-20 keV band. XTE J1752-223 was initially in a low / hard state during the first 3 months. An anti-correlated behavior between the 2-4 keV and 4-20 keV bands was observed around 2010 January 20, indicating that the source exhibited a spectral transition to the high / soft state. A transient radio jet may have been ejected when the source was in the intermediate state where the spectrum was roughly explained by a power-law with a photon index of 2.5-3.0. The unusually long period in the initial low / hard state implies a slow variation in the mass-accretion rate, and a dramatic soft X-ray increase may be explained by a sudden appearance of the accretion disk component with a relatively low innermost temperature (0.4-0.7 keV). Such a low temperature might suggest that the maximum accretion rate was just above the critical gas-evaporation rate required for the state transition.

  4. CHARACTERIZING INTERMITTENCY OF 4-Hz QUASI-PERIODIC OSCILLATION IN XTE J1550–564 USING HILBERT–HUANG TRANSFORM

    SciTech Connect

    Su, Yi-Hao; Chou, Yi; Hu, Chin-Ping; Yang, Ting-Chang E-mail: yichou@astro.ncu.edu.tw

    2015-12-10

    We present time-frequency analysis results based on the Hilbert–Huang transform (HHT) for the evolution of a 4-Hz low-frequency quasi-periodic oscillation (LFQPO) around the black hole X-ray binary XTE J1550–564. The origin of LFQPOs is still debated. To understand the cause of the peak broadening, we utilized a recently developed time-frequency analysis, HHT, for tracking the evolution of the 4-Hz LFQPO from XTE J1550–564. By adaptively decomposing the ∼4-Hz oscillatory component from the light curve and acquiring its instantaneous frequency, the Hilbert spectrum illustrates that the LFQPO is composed of a series of intermittent oscillations appearing occasionally between 3 and 5 Hz. We further characterized this intermittency by computing the confidence limits of the instantaneous amplitudes of the intermittent oscillations, and constructed both the distributions of the QPO’s high- and low-amplitude durations, which are the time intervals with and without significant ∼4-Hz oscillations, respectively. The mean high-amplitude duration is 1.45 s and 90% of the oscillation segments have lifetimes below 3.1 s. The mean low-amplitude duration is 0.42 s and 90% of these segments are shorter than 0.73 s. In addition, these intermittent oscillations exhibit a correlation between the oscillation’s rms amplitude and mean count rate. This correlation could be analogous to the linear rms-flux relation found in the 4-Hz LFQPO through Fourier analysis. We conclude that the LFQPO peak in the power spectrum is broadened owing to intermittent oscillations with varying frequencies, which could be explained by using the Lense–Thirring precession model.

  5. Photovoltaic performances of Cu2-xTe sensitizer based on undoped and indium(3+)-doped TiO2 photoelectrodes and assembled counter electrodes.

    PubMed

    Srathongluan, Pornpimol; Kuhamaneechot, Rattanakorn; Sukthao, Prapatsawan; Vailikhit, Veeramol; Choopun, Supab; Tubtimtae, Auttasit

    2016-02-01

    Novel binary Cu2-xTe nanoparticles based on undoped and indium-doped TiO2 photoelectrodes were synthesized using a successive ionic layer adsorption and reaction (SILAR) technique as a sensitizer for liquid-junction solar cells. A larger diameter of TiO2 promoted a narrower energy band gap after indium doping, attributing to yield a broader absorption range of nanoparticle sensitizer due to the increasing amount of Cu2-xTe NPs on TiO2 surface. The atomic percentages showed the stoichiometric formation of Cu2Te incorporated in a Cu2-xTe structure. The best photovoltaic performance with the lower SILAR cycle, i.e., n=13 was performed after indium doping in both of carbon and Cu2S CEs and revealed that the efficiency of 0.73% under the radiant 100mW/cm(2) (AM 1.5G). The electrochemical impedance spectroscopy (EIS) was used to investigate the electrical properties via effect of material doping and counter electrodes with a lower charge-transfer resistance (Rct) and it was also found that the electron lifetime was improved after the sample doped with indium and assembled with carbon CE.

  6. VLBI OBSERVATION OF MICROQUASAR CYG X-3 DURING AN X-RAY STATE TRANSITION FROM SOFT TO HARD IN THE 2007 MAY-JUNE FLARE

    SciTech Connect

    Kim, Jeong-Sook; Kim, Sang Joon; Kim, Soon-Wook; Kurayama, Tomoharu; Honma, Mareki; Sasao, Tetsuo E-mail: skim@kasi.re.kr

    2013-07-20

    We present a radio observation of microquasar Cyg X-3 during an X-ray state transition from ultrasoft to hard state in the 2007 May-June flare using the VLBI Exploration of Radio Astrometry at 22 GHz. During the transition, a short-lived mini-flare of {approx}< 3 hr was detected prior to the major flare. In such a transition, a jet ejection is believed to occur, but there have been no direct observations to support it. An analysis of Gaussian fits to the observed visibility amplitudes shows a time variation of the source axis, or a structural change, during the mini-flare. Our model fits, together with other multiwavelength observations in the radio, soft, and hard X-rays, and the shock-in-jet models for other flaring activities at GHz wavebands, suggest a high possibility of synchrotron flares during the mini-flare, indicative of a predominant contribution from jet activity. Therefore, the mini-flare with an associated structural change is indicative of a jet ejection event in the state transition from ultrasoft to hard state.

  7. Optical properties of Ge xSb 20- xTe 80 thin films and their changes by light illumination

    NASA Astrophysics Data System (ADS)

    Pamukchieva, V.; Szekeres, A.

    2008-03-01

    The influence of light illumination on the optical constants of chalcogenide thin films with non-stoichiometric Ge xSb 20- xTe 80 ( x = 15, 17, 19) composition is studied by spectral ellipsometry in the visible range of light. The films were deposited onto glass substrates by vacuum thermal evaporation of parent glasses and were subjected to an 1-h illumination with a 500 W HBO mercury lamp. It has been established that illumination of the films leads to a decrease of the refractive index, n, in the whole spectral region studied and to an increase of the extinction coefficient, k, in the range of 600-800 nm. The optical bandgap energy Eg values are within 0.55-0.76 eV with a tendency to increase with increasing the Ge content. Illumination resulted in a sharp decrease of the Eg values indicating structural change in the films. Leaving the films at atmospheric conditions the optical parameters values change toward their initial values of unilluminated state.

  8. Multiwavelength Observations of the Black Hole Transient XTE J1752-223 during Its 2010 Outburst Decay

    NASA Astrophysics Data System (ADS)

    Chun, Y. Y.; Dinçer, T.; Kalemci, E.; Güver, T.; Tomsick, J. A.; Buxton, M. M.; Brocksopp, C.; Corbel, S.; Cabrera-Lavers, A.

    2013-06-01

    Galactic black hole transients show many interesting phenomena during outburst decays. We present simultaneous X-ray (RXTE, Swift, and INTEGRAL), and optical/near-infrared (O/NIR) observations (SMARTS) of the X-ray transient XTE J1752-223 during its outburst decay in 2010. The multiwavelength observations over 150 days in 2010 cover the transition from soft to hard spectral state. We discuss the evolution of radio emission with respect to the O/NIR light curve which shows several flares. One of those flares is bright and long, starting about 60 days after the transition in X-ray timing properties. During this flare, the radio spectral index becomes harder. Other smaller flares occur along with the X-ray timing transition, and also right after the detection of the radio core. We discuss the significances of these flares. Furthermore, using the simultaneous broadband X-ray spectra including INTEGRAL, we find that a high energy cut-off with a folding energy near 250 keV is necessary around the time that the compact jet is forming. The broadband spectrum can be fitted equally well with a Comptonization model. In addition, using photoelectric absorption edges in the XMM-Newton Reflection Grating Spectrometer X-ray spectra and the extinction of red clump giants in the direction of the source, we find a lower limit on the distance of >5 kpc.

  9. A decelerating jet observed by the EVN and VLBA in the X-ray transient XTE J1752-223

    NASA Astrophysics Data System (ADS)

    Yang, J.; Brocksopp, C.; Corbel, S.; Paragi, Z.; Tzioumis, T.; Fender, R. P.

    2010-11-01

    The recently discovered Galactic X-ray transient XTE J1752-223 entered its first known outburst in 2010, emitting from the X-ray to the radio regimes. Its general X-ray properties were consistent with those of a black hole candidate in various spectral states, when ejection of jet components is expected. To verify this, we carried out very long baseline interferometry (VLBI) observations. The measurements were carried out with the European VLBI Network (EVN) and the Very Long Baseline Array (VLBA) at four epochs in 2010 February. The images at the first three epochs show a moving jet component that is significantly decelerated by the last epoch, when a new jet component appears that is likely to be associated with the receding jet side. The overall picture is consistent with an initially mildly relativistic jet, interacting with the interstellar medium or with swept-up material along the jet. The brightening of the receding ejecta at the final epoch can be well explained by initial Doppler deboosting of the emission in the decelerating jet.

  10. NuSTAR AND SWIFT OBSERVATIONS OF THE BLACK HOLE CANDIDATE XTE J1908+094 DURING ITS 2013 OUTBURST

    SciTech Connect

    Tao, Lian; Walton, Dominic J.; Fürst, Felix; Grefenstette, Brian W.; Harrison, Fiona A.; Tendulkar, Shriharsh P.; Tomsick, John A.; Boggs, Steven E.; Craig, William W.; Kennea, Jamie; Miller, Jon M.; Christensen, Finn E.; Gandhi, Poshak; Hailey, Charles J.; Krimm, Hans A.; Pottschmidt, Katja; Zhang, William W.; Stern, Daniel

    2015-09-20

    The black hole (BH) candidate XTE J1908+094 went into outburst for the first time since 2003 in 2013 October. We report on an observation with the Nuclear Spectroscopic Telescope Array (NuSTAR) and monitoring observations with Swift during the outburst. NuSTAR caught the source in the soft state: the spectra show a broad relativistic iron line, and the light curves reveal a ∼40 ks flare, with the count rate peaking about 40% above the non-flare level and with significant spectral variation. A model combining a multi-temperature thermal component, a power law, and a reflection component with an iron line provides a good description of the NuSTAR spectrum. Although relativistic broadening of the iron line is observed, it is not possible to constrain the BH spin with these data. The variability of the power-law component, which can also be modeled as a Comptonization component, is responsible for the flux and spectral change during the flare, suggesting that changes in the corona (or possibly continued jet activity) are the likely cause of the flare.

  11. An optical study of vacuum evaporated Se 85-xTe 15Bi x chalcogenide thin films

    NASA Astrophysics Data System (ADS)

    Ambika; Barman, P. B.

    2010-02-01

    Thin films of Se 85-xTe 15Bi x ( x=0, 1, 2, 3, 4, 5) glassy alloys prepared by melt quenching technique, are deposited on glass substrate using thermal evaporation technique under vacuum. The analysis of transmission spectra, measured at normal incidence, in the spectral range 400-1500 nm helphelps us in the optical characterization of thin films under study. Well -known Swanepoel's method is employed to determine the refractive index ( n) and film thickness ( d). The increase in n with increasing Bi content over the entire spectral range is related to the increased polarizability of the larger Bi atom (atomic radius 1.46 Å) compared with the Se atom (atomic radius 1.16 Å). Dispersion energy ( E d), average energy gap ( E0) and static refractive index ( n0) isare calculated using Wemple-DiDomenico model (WDD). The value of absorption coefficient ( α) and hence extinction coefficient ( k) hashave been determined from transmission spectra. Optical band gap ( E g) is estimated using Tauc's extrapolation and is found to decrease from 1.46 to 1.24 eV with the Bi addition. This behavior of optical band gap is interpreted in terms of electronegativity difference of the atoms involved and cohesive energy of the system.

  12. MULTIWAVELENGTH OBSERVATIONS OF THE BLACK HOLE TRANSIENT XTE J1752-223 DURING ITS 2010 OUTBURST DECAY

    SciTech Connect

    Chun, Y. Y.; Dincer, T.; Kalemci, E.; Guever, T.; Tomsick, J. A.; Buxton, M. M.; Brocksopp, C.; Corbel, S.; Cabrera-Lavers, A.

    2013-06-10

    Galactic black hole transients show many interesting phenomena during outburst decays. We present simultaneous X-ray (RXTE, Swift, and INTEGRAL), and optical/near-infrared (O/NIR) observations (SMARTS) of the X-ray transient XTE J1752-223 during its outburst decay in 2010. The multiwavelength observations over 150 days in 2010 cover the transition from soft to hard spectral state. We discuss the evolution of radio emission with respect to the O/NIR light curve which shows several flares. One of those flares is bright and long, starting about 60 days after the transition in X-ray timing properties. During this flare, the radio spectral index becomes harder. Other smaller flares occur along with the X-ray timing transition, and also right after the detection of the radio core. We discuss the significances of these flares. Furthermore, using the simultaneous broadband X-ray spectra including INTEGRAL, we find that a high energy cut-off with a folding energy near 250 keV is necessary around the time that the compact jet is forming. The broadband spectrum can be fitted equally well with a Comptonization model. In addition, using photoelectric absorption edges in the XMM-Newton Reflection Grating Spectrometer X-ray spectra and the extinction of red clump giants in the direction of the source, we find a lower limit on the distance of >5 kpc.

  13. Study of band inversion in the PbxSn1-xTe class of topological crystalline insulators using x-ray absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Mitrofanov, K. V.; Kolobov, A. V.; Fons, P.; Krbal, M.; Tominaga, J.; Uruga, T.

    2014-11-01

    PbxSn1-xTe and PbxSn1-xSe crystals belong to the class of topological crystalline insulators where topological protection is achieved due to crystal symmetry rather than time-reversal symmetry. In this work, we make use of selection rules in the x-ray absorption process to experimentally detect band inversion along the PbTe(Se)-SnTe(Se) tie-lines. The observed significant change in the ratio of intensities of L1 and L3 transitions along the tie-line demonstrates that x-ray absorption can be a useful tool to study band inversion in topological insulators.

  14. X-ray photoelectron spectroscopy and atomic force microscopy characterization of the effects of etching Zn xCd 1- xTe surfaces

    NASA Astrophysics Data System (ADS)

    George, M. A.; Azoulay, M.; Jayatirtha, H. N.; Burger, A.; Collins, W. E.; Silberman, E.

    1993-10-01

    X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) was used for the first time to characterize the chemical composition of modified surfaces of Zn xCd 1- xTe single crystals. These surface treatments were selected for their relevance to device preparation procedures. The XPS peaks indicated an increase of the tellurium and a depletion of the cadmium concentrations upon etching in bromine methanol solution. AFM revealed the formation of pronounced Te inclusions. Higher x values correlated with a decrease in residual bromine left on the surface, while cut and polished samples had higher oxide concentrations and increased bromination of the surface than cleaved samples.

  15. An accurate position for the black hole candidate XTE J1752-223: re-interpretation of the VLBI data

    NASA Astrophysics Data System (ADS)

    Miller-Jones, J. C. A.; Jonker, P. G.; Ratti, E. M.; Torres, M. A. P.; Brocksopp, C.; Yang, J.; Morrell, N. I.

    2011-07-01

    Using high-precision astrometric optical observations from the Walter Baade Magellan Telescope in conjunction with high-resolution very long baseline interferometric (VLBI) radio imaging with the Very Long Baseline Array (VLBA), we have located the core of the X-ray binary system XTE J1752-223. Compact radio emission from the core was detected following the state transition from the soft to the hard X-ray state. Its position to the south-east of all previously detected jet components mandated a re-analysis of the existing VLBI data. Our analysis suggests that the outburst comprised at least two ejection events prior to 2010 February 26. No radio-emitting components were detected to the south-east of the core at any epoch, suggesting that the receding jets were Doppler-deboosted below our sensitivity limit. From the ratio of the brightness of the detected components to the measured upper limits for the receding ejecta, we constrain the jet speed β > 0.66 and the inclination angle to the line of sight θ < 49°. Assuming that the initial ejection event occurred at the transition from the hard intermediate state to the soft intermediate state, an initial period of ballistic motion followed by a Sedov phase (i.e. self-similar adiabatic expansion) appears to fit the motion of the ejecta better than a uniform deceleration model. The accurate core location can provide a long time baseline for a future proper motion determination should the system show a second outburst, providing insights into the formation mechanism of the compact object.

  16. Photoionization Modeling of Oxygen K Absorption in the Interstellar Medium: The Chandra Grating Spectra of XTE J1817-330

    NASA Astrophysics Data System (ADS)

    Gatuzz, E.; García, J.; Mendoza, C.; Kallman, T. R.; Witthoeft, M.; Lohfink, A.; Bautista, M. A.; Palmeri, P.; Quinet, P.

    2013-05-01

    We present detailed analyses of oxygen K absorption in the interstellar medium (ISM) using four high-resolution Chandra spectra toward the X-ray low-mass binary XTE J1817-330. The 11-25 Å broadband is described with a simple absorption model that takes into account the pile-up effect and results in an estimate of the hydrogen column density. The oxygen K-edge region (21-25 Å) is fitted with the physical warmabs model, which is based on a photoionization model grid generated with the XSTAR code with the most up-to-date atomic database. This approach allows a benchmark of the atomic data which involves wavelength shifts of both the K lines and photoionization cross sections in order to fit the observed spectra accurately. As a result we obtain a column density of N H = 1.38 ± 0.01 × 1021 cm-2 an ionization parameter of log ξ = -2.70 ± 0.023; an oxygen abundance of A_O= 0.689^{+0.015}_{-0.010}; and ionization fractions of O I/O = 0.911, O II/O = 0.077, and O III/O = 0.012 that are in good agreement with results from previous studies. Since the oxygen abundance in warmabs is given relative to the solar standard of Grevesse & Sauval, a rescaling with the revision by Asplund et al. yields A_O=0.952^{+0.020}_{-0.013}, a value close to solar that reinforces the new standard. We identify several atomic absorption lines—Kα, Kβ, and Kγ in O I and O II and Kα in O III, O VI, and O VII—the last two probably residing in the neighborhood of the source rather than in the ISM. This is the first firm detection of oxygen K resonances with principal quantum numbers n > 2 associated with ISM cold absorption.

  17. RAPID COOLING OF THE NEUTRON STAR IN THE QUIESCENT SUPER-EDDINGTON TRANSIENT XTE J1701-462

    SciTech Connect

    Fridriksson, Joel K.; Lewin, Walter H. G.; Homan, Jeroen; Wijnands, Rudy; Altamirano, Diego; Degenaar, Nathalie; Mendez, Mariano; Cackett, Edward M.; Brown, Edward F.; Belloni, Tomaso M.

    2010-05-01

    We present Rossi X-Ray Timing Explorer and Swift observations made during the final three weeks of the 2006-2007 outburst of the super-Eddington neutron star (NS) transient XTE J1701-462, as well as Chandra and XMM-Newton observations covering the first {approx_equal}800 days of the subsequent quiescent phase. The source transitioned quickly from active accretion to quiescence, with the luminosity dropping by over 3 orders of magnitude in {approx_equal}13 days. The spectra obtained during quiescence exhibit both a thermal component, presumed to originate in emission from the NS surface, and a non-thermal component of uncertain origin, which has shown large and irregular variability. We interpret the observed decay of the inferred effective surface temperature of the NS in quiescence as the cooling of the NS crust after having been heated and brought out of thermal equilibrium with the core during the outburst. The interpretation of the data is complicated by an apparent temporary increase in temperature {approx_equal}220 days into quiescence, possibly due to an additional spurt of accretion. We derive an exponential decay timescale of {approx_equal}120{sup +30}{sub -20} days for the inferred temperature (excluding observations affected by the temporary increase). This short timescale indicates a highly conductive NS crust. Further observations are needed to confirm whether the crust is still slowly cooling or has already reached thermal equilibrium with the core at a surface temperature of {approx_equal}125 eV. The latter would imply a high equilibrium bolometric thermal luminosity of {approx_equal}5 x 10{sup 33}ergs{sup -1} for an assumed distance of 8.8 kpc.

  18. Analysis of variability in the burst oscillations of the accreting millisecond pulsar XTE J1814-338

    NASA Technical Reports Server (NTRS)

    Watts, Anna L.; Strohmayer, Tod E.; Markwardt, Craig B.

    2005-01-01

    The accreting millisecond pulsar XTE J1814-338 exhibits oscillations at the known spin frequency during Type I X-ray bursts. The properties of the burst oscillations reflect the nature of the thermal asymmetry on the stellar surface. We present an analysis of the variability of the burst oscillations of this source, focusing on three characteristics: fractional amplitude, harmonic content and frequency. Fractional amplitude and harmonic content constrain the size, shape and position of the emitting region, whilst variations in frequency indicate motion of the emitting region on the neutron star surface. We examine both long-term variability over the course of the outburst, and short-term variability during the bursts. For most of the bursts, fractional amplitude is consistent with that of the accretion pulsations, implying a low degree of fuel spread. There is however a population of bursts whose fractional amplitudes are substantially lower, implying a higher degree of fuel spread, possibly forced by the explosive burning front of a precursor burst. For the first harmonic, substantial differences between the burst and accretion pulsations suggest that hotspot geometry is not the only mechanism giving rise to harmonic content in the latter. Fractional amplitude variability during the bursts is low; we can only rule out the hypothesis that the fractional amplitude remains constant at the l(sigma) level for bursts that do not exhibit photospheric radius expansion (PRE). There are no significant variations in frequency in any of the bursts except for the one burst that exhibits PRE. This burst exhibits a highly significant but small (= 0.1Hz) drop in frequency in the burst rise. The timescale of the frequency shift is slower than simple burning layer expansion models predict, suggesting that other mechanisms may be at work.

  19. Black Hole Mass Determination In the X-Ray Binary 4U 1630-47: Scaling of Spectral and Variability Characteristics

    NASA Technical Reports Server (NTRS)

    Seifina, Elena; Titarchuk, Lev; Shaposhnikov, Nikolai

    2014-01-01

    We present the results of a comprehensive investigation on the evolution of spectral and timing properties of the Galactic black hole candidate 4U 1630-47 during its spectral transitions. In particular, we show how a scaling of the correlation of the photon index of the Comptonized spectral component gamma with low-frequency quasi-periodic oscillations (QPOs), ?(sub L), and mass accretion rate, M, can be applied to the black hole mass and the inclination angle estimates.We analyze the transition episodes observed with the Rossi X-Ray Timing Explorer and BeppoSAX satellites.We find that the broadband X-ray energy spectra of 4U 1630-47 during all spectral states can be modeled by a combination of a thermal component, a Comptonized component, and a red-skewed iron-line component. We also establish that gamma monotonically increases during transition from the low-hard state to the high-soft state and then saturates for high mass accretion rates. The index saturation levels vary for different transition episodes. Correlations of gamma versus ?(sub L) also show saturation at gamma (is) approximately 3. Gamma -M and gamma -?(sub L) correlations with their index saturation revealed in 4U 1630-47 are similar to those established in a number of other black hole candidates and can be considered as an observational evidence for the presence of a black hole in these sources. The scaling technique, which relies on XTE J1550-564, GRO 1655-40, and H1743-322 as reference sources, allows us to evaluate a black hole mass in 4U 1630-47 yielding M(sub BH) (is) approximately 10 +/- 0.1 solar masses and to constrain the inclination angle of i (is) approximately less than 70 deg.

  20. Black hole mass determination in the X-ray binary 4U 1630-47: Scaling of spectral and variability characteristics

    SciTech Connect

    Seifina, Elena; Shaposhnikov, Nikolai E-mail: titarchuk@fe.infn.it E-mail: nikolai.v.shaposhnikov@nasa.gov

    2014-07-01

    We present the results of a comprehensive investigation on the evolution of spectral and timing properties of the Galactic black hole candidate 4U 1630-47 during its spectral transitions. In particular, we show how a scaling of the correlation of the photon index of the Comptonized spectral component Γ with low-frequency quasi-periodic oscillations (QPOs), ν {sub L}, and mass accretion rate, M-dot , can be applied to the black hole mass and the inclination angle estimates. We analyze the transition episodes observed with the Rossi X-Ray Timing Explorer and BeppoSAX satellites. We find that the broadband X-ray energy spectra of 4U 1630-47 during all spectral states can be modeled by a combination of a thermal component, a Comptonized component, and a red-skewed iron-line component. We also establish that Γ monotonically increases during transition from the low-hard state to the high-soft state and then saturates for high mass accretion rates. The index saturation levels vary for different transition episodes. Correlations of Γ versus ν {sub L} also show saturation at Γ ∼ 3. Γ-- M-dot and Γ-ν {sub L} correlations with their index saturation revealed in 4U 1630-47 are similar to those established in a number of other black hole candidates and can be considered as an observational evidence for the presence of a black hole in these sources. The scaling technique, which relies on XTE J1550-564, GRO 1655-40, and H1743-322 as reference sources, allows us to evaluate a black hole mass in 4U 1630-47 yielding M {sub BH} ∼ 10 ± 0.1 solar masses and to constrain the inclination angle of i ≲ 70°.

  1. Scaling of the photon index vs. mass accretion rate correlation and estimate of black hole mass in M101 ULX-1

    NASA Astrophysics Data System (ADS)

    Titarchuk, Lev; Seifina, Elena

    2016-01-01

    We report the results of Swift and Chandra observations of an ultraluminous X-ray source, ULX-1 in M101. We show strong observational evidence that M101 ULX-1 undergoes spectral transitions from the low/hard state to the high/soft state during these observations. The spectra of M101 ULX-1 are well fitted by the so-called bulk motion Comptonization (BMC) model for all spectral states. We have established the photon index (Γ) saturation level, Γsat = 2.8 ± 0.1, in the Γ versus mass accretion rate (Ṁ) correlation. This Γ-Ṁ correlation allows us to evaluate black hole (BH) mass in M101 ULX-1 to be MBH ~ (3.2-4.3) × 104 M⊙, assuming the spread in distance to M101 (from 6.4 ± 0.5 Mpc to 7.4 ± 0.6 Mpc). For this BH mass estimate we apply the scaling method, using Galactic BHs XTE J1550-564, H 1743-322 and 4U 1630-472 as reference sources. The Γ vs. Ṁ correlation revealed in M101 ULX-1 is similar to that in a number of Galactic BHs and clearly exhibits the correlation along with the strong Γ saturation at ≈ 2.8. This is robust observational evidence for the presence of a BH in M101 ULX-1. We also find that the seed (disk) photon temperatures are low, on the order of 40-100 eV, which is consistent with high BH mass in M101 ULX-1. Thus, we suggest that the central object in M101 ULX-1 has intermediate BH mass on the order of 104 solar masses.

  2. ESO 243-49 HLX-1: scaling of X-ray spectral properties and black hole mass determination

    NASA Astrophysics Data System (ADS)

    Titarchuk, Lev; Seifina, Elena

    2016-11-01

    We report the results of Swift/XRT observations (2008-2015) of a hyper-luminous X-ray source, ESO 243-49 HLX-1. We demonstrate a strong observational evidence that ESO 243-49 HLX-1 undergoes spectral transitions from the low/hard state to the high/soft state during these observations. The spectra of ESO 243-49 HLX-1 are well fitted by the so-called bulk motion Comptonization model for all spectral states. We have established the photon index (Γ) saturation level, Γsat = 3.0 ± 0.1, in the Γ versus mass accretion rate (Ṁ) correlation. This Γ-Ṁ correlation allows us to estimate black hole (BH) mass in ESO 243-49 HLX-1 to be MBH 7 × 104 M⊙ assuming the distance to ESO 243-49 of 95 Mpc. For the BH mass estimate we use the scaling method taking Galactic BHs XTE J1550-564, H 1743-322 and 4U 1630-472, and an extragalactic BH source, M101 ULX-1 as reference sources. The Γ versus Ṁ correlation revealed in ESO 243-49 HLX-1 is similar to those in a number of Galactic and extragalactic BHs and it clearly shows the correlation along with the strong Γ saturation at ≈3. This is a robust observational evidence for the presence of a BH in ESO 243-49 HLX-1. We also find that the seed (disk) photon temperatures are quite low, of order of 50-140 eV which are consistent with high BH mass in ESO 243-49 HLX-1.

  3. Erratum: "Photoionization Modeling of Oxygen K Absorption in the Interstellar Medium, the Chandra Grating Spectra of XTE J1817-330" (2013, Apj, 768, 60)

    NASA Technical Reports Server (NTRS)

    Gatuzz, E.; Garcia, J.; Mendoza, C.; Kallman, Timothy R.; Witthoeft, Michael C.; Lohfink, A.; Bautista, M. A.; Palmeri, P.; Quinet, P.

    2013-01-01

    In the published version of this paper, there are some minor inaccuracies in the absorption-line wavelengths listed in Table 4 as a result of a faulty reduction procedure of the Obs6615 spectrum. The shifts have been detected in a comparison with the wavelengths listed for this spectrum in the Chandra Transmission Grating Catalog and Archive (TGCat8). They are due to incorrect centroid positions of the zero-order image in both reductions as determined by the tgdetect utility which, when disentangled, yield the improved line positions of the amended Table 4 given below. It must also be pointed out that other quantitative findings of the original paper: 1. Table 5, p. 9: the column density (NH), ionization parameter, oxygen abundance of the warmabs model and the normalization and photon index of the power-law model; 2. Table 6, p. 9: the hydrogen column density of the warmabs fit; 3. Table 7, p. 9: the present oxygen equivalent widths of XTE J1817-330; and 4. Table 8, p. 10: the present oxygen column densities of XTE J1817-330 derived from both the curve of growth and warmabs model fit have been revised in the new light and are, within the estimated uncertainty ranges, in good accord with the new rendering.

  4. In-Flight Observations of Long-Term Single Event Effect(SEE)Performance on Orbview-2 and Xray Timing Explorer(XTE)Solid State Recorders (SSR)

    NASA Technical Reports Server (NTRS)

    Poivey, Christian; Barth, Janet L.; LaBel, Ken A.; Gee, George; Safren, Harvey

    2003-01-01

    This paper presents Single Event Effect (SEE) in-flight data on Solid State Recorders (SSR) that have been collected over a long period of time for two NASA spacecraft: Orbview-2 and XTE. SEE flight data on solid-state memories give an opportunity to study the behavior in space of SEE sensitive commercial devices. The actual Single Event Upset (SEU) rates can be compared with the calculated rates based on environment models and ground test data. The SEE mitigation schemes can also be evaluated in actual implementation. A significant amount of data has already been published concerning observed SEE effects on memories in space. However, most of the data presented cover either a short period of time or a small number of devices. The data presented here has been collected on a large number of devices during several years. This allows statistically significant information about the effect of space weather fluctuations on SEU rates, and the effectiveness of SEE countermeasures used to be analyzed. Only Orbview-2 data is presented in this summary. XTE data will be included in the final paper.

  5. Photoionization Modeling of Oxygen K Absorption in the Interstellar Medium: The Chandra Grating Spectra of XTE J1817-330

    NASA Technical Reports Server (NTRS)

    Gatuzz, E.; Garcia, J.; Menodza, C.; Kallman, T. R.; Witthoeft, M.; Lohfink, A.; Bautista, M. A.; Palmeri, P.; Quinet, P.

    2013-01-01

    We present detailed analyses of oxygen K absorption in the interstellar medium (ISM) using four high-resolution Chandra spectra towards the X-ray low-mass binary XTE J1817-330. The 11-25 A broadband is described with a simple absorption model that takes into account the pileup effect and results in an estimate of the hydrogen column density. The oxygen K-edge region (21-25 A) is fitted with the physical warmabs model, which is based on a photoionization model grid generated with the XSTAR code with the most up-to-date atomic database. This approach allows a benchmark of the atomic data which involves wavelength shifts of both the K lines and photoionization cross sections in order to fit the observed spectra accurately. As a result we obtain: a column density of N(sub H) = 1.38 +/- 0.01 x 10(exp 21) cm(exp -2); ionization parameter of log xi = .2.70 +/- 0.023; oxygen abundance of A(sub O) = 0.689(exp +0.015./-0.010); and ionization fractions of O I/O = 0.911, O II/O = 0.077, and O III/O = 0.012 that are in good agreement with previous studies. Since the oxygen abundance in warmabs is given relative to the solar standard of Grevesse and Sauval (1998), a rescaling with the revision by Asplund et al. (2009) yields A(sub O) = 0.952(exp +0.020/-0.013, a value close to solar that reinforces the new standard. We identify several atomic absorption lines.K-alpha , K-beta, and K-gamma in O I and O II; and K-alpha in O III, O VI, and O VII--last two probably residing in the neighborhood of the source rather than in the ISM. This is the first firm detection of oxygen K resonances with principal quantum numbers n greater than 2 associated to ISM cold absorption.

  6. Photoionization Modeling of Oxygen K Absorption in the Interstellar Medium:. [The Chandra Grating Spectra of XTE J1817-330

    NASA Technical Reports Server (NTRS)

    Gatuzz, E.; Garcia, J.; Mendoza, C.; Kallman, T. R.; Witthoeft, M.; Lohfink, A.; Bautista, M. A.; Palmeri, P.; Quinet, P.

    2013-01-01

    We present detailed analyses of oxygen K absorption in the interstellar medium (ISM) using four high-resolution Chandra spectra toward the X-ray low-mass binary XTE J1817-330. The 11-25 Angstrom broadband is described with a simple absorption model that takes into account the pile-up effect and results in an estimate of the hydrogen column density. The oxygen K-edge region (21-25 Angstroms) is fitted with the physical warmabs model, which is based on a photoionization model grid generated with the xstar code with the most up-to-date atomic database. This approach allows a benchmark of the atomic data which involves wavelength shifts of both the K lines and photoionization cross sections in order to fit the observed spectra accurately. As a result we obtain a column density of N(sub H) = 1.38 +/- 0.01 × 10(exp 21) cm(exp -2); an ionization parameter of log xi = -2.70 +/- 0.023; an oxygen abundance of A(sub O) = 0.689 (+0.015/-0.010); and ionization fractions of O(sub I)/O = 0.911, O(sub II)/O = 0.077, and O(sub III)/O = 0.012 that are in good agreement with results from previous studies. Since the oxygen abundance in warmabs is given relative to the solar standard of Grevesse & Sauval, a rescaling with the revision by Asplund et al. yields A(sub O) = 0.952(+0.020/-0.013), a value close to solar that reinforces the new standard.We identify several atomic absorption lines-K(alpha), K(beta), and K(gamma) in O(sub I) and O(sub II) and K(alpha) in O(sub III), O(sub VI), and O(sub VII)-the last two probably residing in the neighborhood of the source rather than in the ISM. This is the first firm detection of oxygen K resonances with principal quantum numbers n greater than 2 associated with ISM cold absorption.

  7. A late jet rebrightening revealed from multiwavelength monitoring of the black hole candidate XTE J1752-223

    NASA Astrophysics Data System (ADS)

    Russell, D. M.; Curran, P. A.; Muñoz-Darias, T.; Lewis, F.; Motta, S.; Stiele, H.; Belloni, T.; Miller-Jones, J. C. A.; Jonker, P. G.; O'Brien, K.; Homan, J.; Casella, P.; Gandhi, P.; Soleri, P.; Markoff, S.; Maitra, D.; Gallo, E.; Cadolle Bel, M.

    2012-01-01

    We present optical monitoring of the black hole candidate XTE J1752-223 during its 2009-10 outburst and decay to quiescence. The optical light curve can be described by an exponential decay followed by a plateau, then a more rapid fade towards quiescence. The plateau appears to be due to an extra component of optical emission that brightens and then fades over ˜40 days. We show evidence for the origin of this optical 'flare' to be the synchrotron jet during the decaying hard state, and we identify and isolate both disc and jet components in the spectral energy distributions. The optical flare has the same morphology and amplitude as a contemporaneous X-ray rebrightening. This suggests a common origin, but no firm conclusions can be made favouring or disfavouring the jet producing the X-ray flare. The quiescent optical magnitudes are B≥ 20.6, V≥ 21.1, R≥ 19.5, i'≥ 19.2. From the optical outburst amplitude we estimate a likely orbital period of <22 h. We also present near-infrared (NIR) photometry and polarimetry and rare mid-IR imaging (8-12 ?m) when the source is nearing quiescence. The fading jet component, and possibly the companion star, may contribute to the NIR flux. We derive deep mid-IR flux upper limits and NIR linear polarization upper limits. With the inclusion of radio data, we measure an almost flat jet spectral index between radio and optical; Fν∝ν˜+0.05. The data favour the jet break to optically thin emission to reside in the IR, but may shift to frequencies as high as the optical or UV during the peak of the flare. Based on observations collected at the European Southern Observatory, Chile, under ESO Programme ID 086.D-0610, the William Herschel Telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias and the Faulkes Telescopes at Haleakala, Maui, USA and Siding Spring, Australia.

  8. PHOTOIONIZATION MODELING OF OXYGEN K ABSORPTION IN THE INTERSTELLAR MEDIUM: THE CHANDRA GRATING SPECTRA OF XTE J1817-330

    SciTech Connect

    Gatuzz, E.; Mendoza, C.; Garcia, J.; Lohfink, A.; Kallman, T. R.; Witthoeft, M.; Bautista, M. A.; Palmeri, P.; Quinet, P. E-mail: claudio@ivic.gob.ve E-mail: alohfink@astro.umd.edu E-mail: michael.c.witthoeft@nasa.gov E-mail: palmeri@umons.ac.be

    2013-05-01

    We present detailed analyses of oxygen K absorption in the interstellar medium (ISM) using four high-resolution Chandra spectra toward the X-ray low-mass binary XTE J1817-330. The 11-25 A broadband is described with a simple absorption model that takes into account the pile-up effect and results in an estimate of the hydrogen column density. The oxygen K-edge region (21-25 A) is fitted with the physical warmabs model, which is based on a photoionization model grid generated with the XSTAR code with the most up-to-date atomic database. This approach allows a benchmark of the atomic data which involves wavelength shifts of both the K lines and photoionization cross sections in order to fit the observed spectra accurately. As a result we obtain a column density of N{sub H} = 1.38 {+-} 0.01 Multiplication-Sign 10{sup 21} cm{sup -2}; an ionization parameter of log {xi} = -2.70 {+-} 0.023; an oxygen abundance of A{sub O}= 0.689{sup +0.015}{sub -0.010}; and ionization fractions of O I/O = 0.911, O II/O = 0.077, and O III/O = 0.012 that are in good agreement with results from previous studies. Since the oxygen abundance in warmabs is given relative to the solar standard of Grevesse and Sauval, a rescaling with the revision by Asplund et al. yields A{sub O}=0.952{sup +0.020}{sub -0.013}, a value close to solar that reinforces the new standard. We identify several atomic absorption lines-K{alpha}, K{beta}, and K{gamma} in O I and O II and K{alpha} in O III, O VI, and O VII-the last two probably residing in the neighborhood of the source rather than in the ISM. This is the first firm detection of oxygen K resonances with principal quantum numbers n > 2 associated with ISM cold absorption.

  9. Evolution of the complicated decaying branch of the very long outburst in XTE J1701-462

    NASA Astrophysics Data System (ADS)

    Šimon, Vojtěch

    2015-05-01

    I analyze the evolution of the features which occurred on the timescale of weeks in the very long (∼600 d) X-ray outburst of the neutron star low-mass X-ray binary XTE J1701-462. I used RXTE/ASM (1.5-12 keV) and Swift/BAT (15-50 keV) observations for a time-series analysis of the long-term variations. I utilized the means (usually one-day) of intensity I to increase the signal-to-noise ratio. I applied weighted wavelet Z-transform to investigate the cyclic modulation of I. Using the combined data from both satellites, I also calculated the hardness ratio HR = I(15-50 keV)/I(1.5-12 keV) and investigated its evolution throughout the outburst. Despite the largely different profiles of the light curves in the ASM and the BAT bands especially in the first fourth of the outburst, the profiles of the measures of their scatter (the σresASM and the σresBAT curves) display mutual similarities. Both the σresASM and σresBAT curves achieved their maxima in the primary peak of the light curve which was present only in the ASM band. The formation of the quasi-periodic variations occurred and their approximate cycle-length PC was decided already in the surrounding of this peak when the bolometric luminosity was close to or even exceeding the Eddington limit. The modulation with PC is present in some time segments only in the ASM band, while the intensity variations are always chaotic in the BAT band. Using the results of spectroscopy of Lin et al., I suggests that only multicolor disk, dominant in the ASM band, was involved in this cycle. The existence of this cycle did not depend on the exact type of the Z, so it was independent of the exact conditions in the inner disk region. The length of PC displayed a large and gradual increase from ∼ 16 to ∼ 26 days with the progress of the outburst. Using models of Foulkes et al., I interpret these variations as a superorbital cycle, caused by tilting and warping of the irradiated disk.

  10. Identification of the optical counterpart of 1RXS J190141.0+012618 and a search for the optical counterpart of XTE J1901+014

    NASA Astrophysics Data System (ADS)

    Powell, C. R.; Norton, A. J.; Haswell, C. A.; Wolters, S. D.; Green, S. F.; Morales-Rueda, L.; Charles, P. A.; Worters, H.

    2002-05-01

    The RXTE error circle of X-ray transient XTE J1901+014, reported in IAUC #7880, includes the much smaller error circle of ROSAT source 1RXS J190141.0+012618, HRI position 19h01m40.1s, +1 26' 30" (J2000) uncertainty 10" (ATEL #89). We obtained Jacobus Kaptyn Telescope B, V, R, I images of the field on 2002 April 18 04:15 - 04:30, the same filters at the IAC80 Telescope (Instituto de Astrofísica de Canarias, Tenerife) on the same night 04:30 - 04:50, and R on the JKT on 2002 April 28 04:45.

  11. Optimal bandgap variants of Cd 1- xZn xTe for high-resolution X-ray and gamma-ray spectroscopy

    NASA Astrophysics Data System (ADS)

    Toney, J. E.; Schlesinger, T. E.; James, R. B.

    1999-06-01

    We show that the trade-off between noise and charge generation statistics in Cd 1- xZn xTe leads to an optimal band gap of approximately 2.0 eV at room temperature. This implies a ZnTe fraction of approximately 0.7-0.8. We show that for X-rays and relatively low energy gamma-rays Cd 0.2Zn 0.8Te theoretically offers a significant potential improvement in energy resolution over Cd 0.9Zn 0.1Te even if compensation of shallow levels is less complete and carrier lifetimes are an order of magnitude lower for the higher x variant. We also show that these calculations are consistent with observed detector performance reported by many workers over a large period of time.

  12. Enhanced thermoelectricity of three-dimensionally mesostructured BixSb2-xTe3 nanoassemblies: from micro-scaled open gaps to isolated sealed mesopores.

    PubMed

    Chen, Tsung-Han; Lin, Ping-Yu; Chang, Hsiu-Cheng; Chen, Chun-Hua

    2017-03-02

    We describe an innovative interfacial design concept and nanostructuring of novel BixSb2-xTe3 (BST) nanoassembled films comprising unique air-solid interfaces from micro-scaled open gaps to isolated sealed mesopores, and high-quality solid-solid ones including the coherent grain boundaries and specific twins, utilizing pulsed laser deposition (PLD), for potentially activating multiple thermoelectric enhancing mechanisms. The unusual mesopore embedded BST films exhibit the highest power factor of ∼33 μW cm(-1) K(-2), which is comparable to or higher than the previously reported values for BST, and the corresponding relatively low thermal diffusivity in contrast to that for dense pore-less BST films evidently reveals the crucial role of the three-dimensionally and densely arranged air-solid interfaces in significantly arising the phonon scattering.

  13. Spin-glass behavior and anomalous magnetoresistance in ferromagnetic Ge{sub 1-x}Fe{sub x}Te epilayer

    SciTech Connect

    Liu, Jindong; Cheng, Xiaomin Tong, Fei; Miao, Xiangshui

    2014-07-28

    We report that the Ge{sub 1-x}Fe{sub x}Te thin film exhibits spin-glass behavior when the Fe concentration increases to 0.08. A large bifurcation between the zero-field cooling and field cooling temperature-dependent magnetization was observed. The hysteresis loops after zero-field cooling and field cooling show an exchange bias effect. A time-dependent thermoremanent magnetization follows power-law decay, which confirms the existence of spin glass. The anomalous magnetotranport properties present a further evidence for spin-glass behavior and give a freezing temperature T{sub g} ∼ 5 K in the Ge{sub 0.92}Fe{sub 0.08}Te thin film.

  14. Surface photovoltage investigations of Cd 1-xMn xTe for x = 0.01 and 0.10

    NASA Astrophysics Data System (ADS)

    Kuźmiński, S.; Szaynok, A. T.

    1988-07-01

    Surface photovoltage investigations of Cd 1- xMn xTe monocrystals for x = 0.01 and 0.10 were performed in the temperature range between 100 and 300 K with a modified Kelvin method at a pressure of 10 -5 Pa. The surfaces with orientation (110) were ground, polished with "Gamal", and rinsed in acetone and alcohol. Three types of effects were observed on the surface spectroscopy curves: A sharp increase in photovoltage, connected with the electron band-to-band transitions for a photon energy equal to the energy gap. Photovoltage quenching attributed to the existence of surface states with energy just above the edge of the valence band. Increase in photovoltage in the range between 0.9 and 1.0 eV resulting from electron transitions between the valence band and energy states connected with manganese ions.

  15. Abundancias químicas de la compañera visible del agujero negro binario V4641 Sgr (XTE J1819-254)

    NASA Astrophysics Data System (ADS)

    Cúneo, V. A.; Jofré, E.; Pintado, O. I.; Gómez, M. N.

    2015-08-01

    In this work we expose an analysis of the chemical abundances of the optical companion of the confirmed black hole binary V4641 Sgr (XTE J1819-254) from GMOS spectra obtained with the Gemini North telescope. This analysis allowed to observe an enhancement of N, O, Mg and Si, attributed to the contamination of heavy elements generated during the supernova explosion that gave birth to the black hole. It was also observed that Cr and Fe were subabundant. The aim of this study is to test the formation scenario of a binary system containing a black hole as remnant of the supernova explosion of a massive star, and to provide information to better understand the final stages in the evolution of massive stars and black hole progenitors.

  16. Phase separation and exchange biasing in the ferromagnetic IV-VI semiconductor Ge{sub 1-x}Mn{sub x}Te

    SciTech Connect

    Lechner, R. T.; Springholz, G.; Hassan, M.; Groiss, H.; Kirchschlager, R.; Stangl, J.; Hrauda, N.; Bauer, G.

    2010-07-12

    Ferromagnetic Ge{sub 1-x}Mn{sub x}Te grown by molecular beam epitaxy with Mn content of x{sub Mn}approx =0.5 is shown to exhibit a strong tendency for phase separation. At higher growth temperatures apart from the cubic Ge{sub 0.5}Mn{sub 0.5}Te, a hexagonal MnTe and a rhombohedral distorted Ge{sub 0.83}Mn{sub 0.17}Te phase is formed. This coexistence of antiferromagnetic MnTe and ferromagnetic Ge{sub 0.5}Mn{sub 0.5}Te results in magnetic exchange-bias effects.

  17. Cross-correlations between soft and hard light curves depending on luminosity in the transient neutron star XTE J1701-462

    NASA Astrophysics Data System (ADS)

    Wang, Y. N.; Lei, Y. J.; Ding, G. Q.; Qu, J. L.; Ge, M. Y.; Zhang, C. M.; Chen, L.; Ma, X.

    2014-06-01

    Using all the observations from Rossi X-ray Timing Explorer for the accreting neutron star XTE J1701-462, we carry out a systematic study of the cross-correlation function between its soft and hard light curves. Over the entire outburst, XTE J1701-462 evolves from super-Eddington luminosities to quiescence and shows both Z and atoll behaviours. Following previous work, we divide the outburst into five intervals: one Cyg-like interval, three Sco-like intervals and one atoll interval, according to their different behaviours in the corresponding colour-colour diagrams (CCDs). With cross-correlation analyses, anti-correlation, positive and ambiguous correlations are found in the different intervals in this source. Both anti-correlated soft and hard time lags are detected, where hard lags mean that the hard photons lag behind the soft ones and soft lags mean the reverse. In the Cyg-like interval, anti-correlations are presented in the hard vertex and upper normal branch (NB) and positive correlations dominate the horizontal branch (HB) and lower NB. In the first two Sco-like intervals, anti-correlations are detected first and most of them are found in the HB and/or upper NB, while positive correlations are mostly detected in the lower NB and flaring branch (FB). In the following interval, i.e. the third Sco-like interval, anti-correlations occur on the upper FB and positive correlations are mainly distributed in the lower FB. The different intervals correspond to various luminosities; therefore, the position of anti-correlations in the CCD might depend on the luminosity. It is noted that, in the Cyg-like interval, positive correlations dominate the HB, which is not consistent with the behaviour of the Cyg-like Z sources GX 5-1 and Cyg X-2, the HBs of which host ambiguous correlations and anti-correlations. Hence, for comparison with GX 5-1, we analyse the spectra of the HB and the hard vertex of the Cyg-like interval. The fitting results show that, in contrast to GX 5

  18. Constraints on Braneworld Gravity Models from a Kinematic Limit on the Age of the Black Hole XTE J1118+480

    SciTech Connect

    Psaltis, Dimitrios

    2007-05-04

    In braneworld gravity models with a finite anti-de Sitter space (AdS) curvature in the extra dimension, the AdS/conformal field theory correspondence leads to a prediction for the lifetime of astrophysical black holes that is significantly smaller than the Hubble time, for asymptotic curvatures that are consistent with current experiments. Using the recent measurements of the position, three-dimensional spatial velocity, and mass of the black hole XTE J1118+480, I calculate a lower limit on its kinematic age of {>=}11 Myr (95% confidence). This translates into an upper limit for the asymptotic AdS curvature in the extra dimensions of <0.08 mm, which significantly improves the limit obtained by table top experiments of sub mm gravity.

  19. DISCOVERY AND MONITORING OF A NEW BLACK HOLE CANDIDATE XTE J1752-223 WITH RXTE: RMS SPECTRUM EVOLUTION, BLACK HOLE MASS, AND THE SOURCE DISTANCE

    SciTech Connect

    Shaposhnikov, Nikolai

    2010-11-10

    We report on the discovery and monitoring observations of a new galactic black hole (BH) candidate XTE J1752-223 by Rossi X-ray Timing Explorer (RXTE). The new source appeared on the X-ray sky on 2009 October 21 and was active for almost 8 months. Phenomenologically, the source exhibited the low-hard/high-soft spectral state bi-modality and the variability evolution during the state transition that matches standard behavior expected from a stellar mass BH binary. We model the energy spectrum throughout the outburst using a generic Comptonization model assuming that part of the input soft radiation in the form of a blackbody spectrum gets reprocessed in the Comptonizing medium. We follow the evolution of fractional root-mean-square (rms) variability in the RXTE/PCA energy band with the source spectral state and conclude that broadband variability is strongly correlated with the source hardness (or Comptonized fraction). We follow changes in the energy distribution of rms variability during the low-hard state and the state transition, and find further evidence that variable emission is strongly concentrated in the power-law spectral component. We discuss the implication of our results to the Comptonization regimes during different spectral states. Correlations of spectral and variability properties provide measurements of the BH mass and distance to the source. The spectral-timing correlation scaling technique applied to the RXTE observations during the hard-to-soft state transition indicates a mass of the BH in XTE J1752-223 between 8 and 11 solar masses and a distance to the source of about 3.5 kpc.

  20. A SPECTRAL STUDY OF THE RAPID TRANSITIONS OF TYPE-B QUASI-PERIODIC OSCILLATIONS IN THE BLACK HOLE TRANSIENT XTE J1859+226

    SciTech Connect

    Sriram, K.; Choi, C. S.; Rao, A. R.

    2013-09-20

    The fast transitions of type-B and type-A quasi-periodic oscillations (QPOs) are rarely found, and they are observed at the peak of the outburst in black hole transient (BHT) sources. The associated spectral variations during such events are crucial to understand the origin and location of such QPOs in the accretion disk. During the 1999 outburst of XTE J1859+226, on four occasions a rapid transition of type-B/A QPOs was noted. We performed broadband spectral analysis on these four observations to unveil the responsible spectral parameter causing the rapid transitions. After invoking simple spectral models, it was observed that disk parameters were consistently varying along with disk and power-law fluxes, and almost no change was noted in the power-law index parameter. Though using a complex physical model showed consistent results, the spectral parameter variations across the transitions were not significant. It was observed that the type-B QPO was always associated with an inner disk front which is closer to the BH. In one observation, a type-A QPO appeared as the source count rate suddenly dropped, and the power-law index as well as disk normalization parameter considerably changed during this transition. The spectral changes in this particular observation were similar to the changes observed in XTE J1817-330, indicating a common underlying mechanism. We have also examined a similar observation of BHT source GX 339-4, where a sudden transition of a type-A/B QPO was noted. Similar spectral study again revealed that the disk parameters were changing. We discuss the results in the framework of a truncated disk model and conclude that the movement of the coupled inner disk-corona region is responsible for such rapid transitions of type-B QPOs.

  1. THE TRANSIENT ACCRETING X-RAY PULSAR XTE J1946+274: STABILITY OF X-RAY PROPERTIES AT LOW FLUX AND UPDATED ORBITAL SOLUTION

    SciTech Connect

    Marcu-Cheatham, Diana M.; Pottschmidt, Katja; Kühnel, Matthias; Müller, Sebastian; Falkner, Sebastian; Kreykenbohm, Ingo; Caballero, Isabel; Jenke, Peter J.; Wilson-Hodge, Colleen A.; Fürst, Felix; Grinberg, Victoria; Hemphill, Paul B.; Rothschild, Richard E.; Klochkov, Dmitry; Terada, Yukikatsu; and others

    2015-12-10

    We present a timing and spectral analysis of the X-ray pulsar XTE J1946+274 observed with Suzaku during an outburst decline in 2010 October and compare with previous results. XTE J1946+274 is a transient X-ray binary consisting of a Be-type star and a neutron star with a 15.75 s pulse period in a 172 days orbit with 2–3 outbursts per orbit during phases of activity. We improve the orbital solution using data from multiple instruments. The X-ray spectrum can be described by an absorbed Fermi–Dirac cut-off power-law model along with a narrow Fe Kα line at 6.4 keV and a weak Cyclotron Resonance Scattering Feature (CRSF) at ∼35 keV. The Suzaku data are consistent with the previously observed continuum flux versus iron line flux correlation expected from fluorescence emission along the line of sight. However, the observed iron line flux is slightly higher, indicating the possibility of a higher iron abundance or the presence of non-uniform material. We argue that the source most likely has only been observed in the subcritical (non-radiation dominated) state since its pulse profile is stable over all observed luminosities and the energy of the CRSF is approximately the same at the highest (∼5 × 10{sup 37} erg s{sup −1}) and lowest (∼5 × 10{sup 36} erg s{sup −1}) observed 3–60 keV luminosities.

  2. Discovery and Monitoring of a New Black Hole Candidate XTE J1752-223 with RXTE: RMS Spectrum Evolution, BH Mass and the Source Distance

    NASA Technical Reports Server (NTRS)

    Shaposhinikov, Nikolai; Markwardt, Craig; Swank, Jean; Krimm, Hans

    2010-01-01

    We report on the discovery and monitoring observations of a new galactic black hole candidate XTE J1752-223 by Rossi X-ray Timing Explorer (RXTE). The new source appeared on the X-ray sky on October 21 2009 and was active for almost 8 months. Phenomenologically, the source exhibited the low-hard/highsoft spectral state bi-modality and the variability evolution during the state transition that matches standard behavior expected from a stellar mass black hole binary. We model the energy spectrum throughout the outburst using a generic Comptonization model assuming that part of the input soft radiation in the form of a black body spectrum gets reprocessed in the Comptonizing medium. We follow the evolution of fractional root-mean-square (RMS) variability in the RXTE/PCA energy band with the source spectral state and conclude that broad band variability is strongly correlated with the source hardness (or Comptonized fraction). We follow changes in the energy distribution of rms variability during the low-hard state and the state transition and find further evidence that variable emission is strongly concentrated in the power-law spectral component. We discuss the implication of our results to the Comptonization regimes during different spectral states. Correlations of spectral and variability properties provide measurements of the BH mass and distance to the source. The spectral-timing correlation scaling technique applied to the RXTE observations during the hardto- soft state transition indicates a mass of the BH in XTE J1752-223 between 8 and 11 solar masses and a distance to the source about 3.5 kiloparsec.

  3. Chevrel-phase solid solution Mo 6Se 8- xTe x. Study of its superconducting, magnetic and NMR properties

    NASA Astrophysics Data System (ADS)

    Hamard1a, C.; Auffret, V.; Peña, O.; Le Floch, M.; Nowak, B.; Wojakowski, A.

    2000-09-01

    The Chevrel-phase solid solution Mo 6Se 8-Mo 6Te 8 was studied by X-ray diffraction, AC and DC magnetic susceptibility and 77Se and 125Te NMR spectroscopy. From the smooth evolution of the lattice parameters and superconducting critical temperatures, a progressive substitution of selenium atoms by tellurium is shown, on the whole range of composition 0⩽ x⩽8, in the formulation Mo 6Se 8- xTe x: the unit-cell volume increases linearly because of the larger ionic size of tellurium, while Tc decreases rapidly (from 6.45 down to 0 K) because of the different formal oxidation states of the anions and a probable evolution of the Fermi level in the density of states. Results of magnetic susceptibility support this model and suggest the inhibition of the intrinsic metallic behavior with increasing x. The NMR spectra of the binaries Mo 6Se 8 and Mo 6Te 8 reveal two significant features, attributed to two different chalcogen positions in the R 3¯ symmetry. At low Se contents in Mo 6Se 8- xTe x ( x=7.5, 7 and 6), selenium first fills the two X(2) sites along the three-fold axis (2c positions), and then it becomes statistically distributed over the general 6f positions, leading to broad 77Se NMR lines. On the other hand, substitution of Te atoms in Mo 6Se 8 seems to occur in a random way, creating large perturbations on the 125Te NMR spectra, over the whole range of x. Theoretical analysis based on the presence of two anisotropic lines (of axial and non-axial symmetries, respectively) allowed us to estimate their anisotropy factors and to perfectly simulate the frequency response of both Mo 6Se 8 and Mo 6Te 8 binaries. Analysis of the Knight shift anisotropy leads us to conclude about the importance of the molybdenum z 2 molecular orbital contribution which controls the Mo-X dipolar interactions.

  4. A Spectral Study of the Black Hole Candidate XTE J1752-223 in the High/Soft State with MAXI, Suzaku, and Swift

    NASA Astrophysics Data System (ADS)

    Nakahira, Satoshi; Koyama, Shu; Ueda, Yoshihiro; Yamaoka, Kazutaka; Sugizaki, Mutsumi; Mihara, Tatehiro; Matsuoka, Masaru; Yoshida, Atsumasa; Makishima, Kazuo; Ebisawa, Ken; Kubota, Aya; Yamada, Shin'ya; Negoro, Hitoshi; Hiroi, Kazuo; Ishikawa, Masaki; Kawai, Nobuyuki; Kimura, Masashi; Kitayama, Hiroki; Kohama, Mitsuhiro; Matsumura, Takanori; Morii, Mikio; Nakajima, Motoki; Serino, Motoko; Shidatsu, Megumi; Sootome, Tetsuya; Sugimori, Kousuke; Suwa, Fumitoshi; Tomida, Hiroshi; Tsuboi, Yoko; Tsunemi, Hiroshi; Ueno, Shiro; Usui, Ryuichi; Yamamoto, Takayuki; Yamazaki, Kyohei; Tashiro, Makoto S.; Terada, Yukikatsu; Seta, Hiromi

    2012-02-01

    We report on an X-ray spectral analysis of the black hole candidate XTE J1752-223 in the 2009-2010 outburst, utilizing data obtained with the MAXI/Gas Slit Camera (GSC), the Swift/XRT, and Suzaku, which work complementarily. As already reported by Nakahira et al. (2010, PASJ, 62, L27), MAXI monitored the source continuously throughout the entire outburst for about eight months. All of the MAXI/GSC energy spectra in the high/soft state, lasting for 2 months, are well represented by a multi-color disk plus power-law model. The innermost disk temperature changed from ˜0.7 keV to ˜0.4 keV and the disk flux decreased by an order of magnitude. Nevertheless, the innermost radius is constant at ˜41 D3.5(cos i)-1/2km, where D3.5 is the source distance in units of 3.5 kpc and i the inclination. The multi-color disk parameters obtained with the MAXI/GSC are consistent with those with the Swift/XRT and Suzaku. The Suzaku data also suggest a possibility that the disk emission is slightly Comptonized, which could account for broad iron-K features reported previously. Assuming that the obtained innermost radius represents the innermost stable circular orbit for a non-rotating black hole, we estimate the mass of the black hole to be 5.51 ± 0.28 M⊙ D3.5(cos i)-1/2, where the correction for the stress-free inner boundary condition and color hardening factor of 1.7 are taken into account. If the inclination is less than 49°, as suggested from radio monitoring of transient jets, and the soft-to-hard transition in 2010 April occurred at 1%-4% of Eddignton luminosity, the fitting of the Suzaku spectra with a relativistic accretion-disk model derives constraints on the mass and the distance to be 3.1-55M⊙ and 2.3-22 kpc, respectively. This confirms that the compact object in XTE J1752-223 is a black hole.

  5. Evidence of Spin and Energy Extraction in a Galactic Black Hole Candidate: The XMM-NEWTON/EPIC SPECTRUM of XTE 11650-500

    NASA Technical Reports Server (NTRS)

    Miller, J. M.; Fabian, A. C.; Wunands, R.; Reynolds, C. S.; Ehle, M.; Freyberg, M. J.; VanDerKlis, M.; Lewin, W. H. G.; Sanchez-Fernandez, C.; Castro-Tirado, A. J.

    2002-01-01

    We observed the Galactic black hole candidate XTE J1650-500 early in its fall of 2001 outburst with the XMM-Newton European Photon Imaging pn Camera (EPIC-pn). The observed spectrum is consistent with the source having been in the very high state. We h d a broad, skewed Fe Kar emission line that suggests the primary in this system may be a Kerr black hole and that indicates a steep disk emissivity profile that is hard to explain in terms of a standard accretion disk model. These results are quantitatively and qualitatively similar to those from an XMM-Newton observation of the Seyfert galaxy MCG -6-30-15. The steep emissivity in MCG -6-30-15 may be explained by the extraction and dissipation of rotational energy from a black hole with nearly maximal angular momentum or from material in the plunging region via magnetic connections to the inner accretion disk. If this process is at work in both sources, an exotic but fundamental general relativistic prediction may be confirmed across a factor of l0(exp 6) in black hole mass. We discuss these results in terms of the accretion flow geometry in stellar-mass black holes and the variety of enigmatic phenomena often observed in the very high state.

  6. Energy states in the surface layer of Cd 1-xMn xTe monocrystals for x = 0.22, 0.30 and 0.40

    NASA Astrophysics Data System (ADS)

    Szaynok, A. T.

    1989-04-01

    Investigations of the spectral dependence of the surface photovoltage of Cd 1- xMn xTe monocrystals for x = 0.22, 0.30 and 0.40 were carried out in the temperature range between 80 and 300 K with a modified Kelvin method at an ambient atmosphere pressure of 10 -5 Pa. The surfaces with (110) orientation were ground, polished with "Gamal" powder, and rinsed in acetone and alcohol. Four types of effects on the surface spectroscopy curves have been observed. A sharp increase in photovoltage, connected with electron band-to-band transitions for a photon energy equal to the energy gap. Photovoltage quenching attributed to the existence of surface states with energy just above the edge of the valence band. An increase in photovoltage in the range between 1.0 and 1.3 eV resulting from electron transitions between the valence band and energy states connected with manganese ions. An inversion effect, occurring at rather lower temperature which can be joined with electron transitions from the acceptor levels to the conduction band.

  7. ON THE NATURE OF THE FIRST TRANSIENT Z SOURCE XTE J1701-462: ITS ACCRETION DISK STRUCTURE, NEUTRON STAR MAGNETIC FIELD STRENGTH, AND HARD TAIL

    SciTech Connect

    Ding, G. Q.; Wang, N.; Yan, S. P.; Zhang, S. N.; Qu, J. L. E-mail: dinggq@gmail.com

    2011-08-15

    Using data from the Rossi X-Ray Timing Explorer, we investigate the spectral evolution along a 'Z' track and a '{nu}' track on the hardness-intensity diagrams of the first transient Z source XTE J1701-462. The spectral analyses suggest that the inner disk radius depends on the mass accretion rate, in agreement with the model prediction, R{sub in}{proportional_to}M-dot{sup 2/7}{sub disk}, for a radiation-pressure-dominated accretion disk interacting with the magnetosphere of a neutron star (NS). The changes in the disk mass accretion rate M-dot{sub disk} are responsible for the evolution of the 'Z' or '{nu}' track. Radiation pressure thickens the disk considerably and also produces significant outflows. The NS surface magnetic field strength, derived from the interaction between the magnetosphere and the radiation-pressure-dominated accretion disk, is {approx}(1-3) x 10{sup 9} G, which is possibly between normal atoll and Z sources. A significant hard tail is detected in the horizontal branches and we discuss several possible origins of the hard tail.

  8. Modeling of electron energy spectra and mobilities in semi-metallic Hg{sub 1−x}Cd{sub x}Te quantum wells

    SciTech Connect

    Melezhik, E. O. Gumenjuk-Sichevska, J. V.; Sizov, F. F.

    2015-11-21

    Electron mobility, energy spectra, and intrinsic carrier concentrations in the n-type Hg{sub 0.32}Cd{sub 0.68}Te/Hg{sub 1−x}Cd{sub x}Te/Hg{sub 0.32}Cd{sub 0.68}Te quantum well (QW) in semi-metallic state are numerically modeled. Energy spectra and wave functions were calculated in the framework of the 8-band k-p Hamiltonian. In our model, electron scattering on longitudinal optical phonons, charged impurities, and holes has been taken into account, and the mobility has been calculated by an iterative solution of the Boltzmann transport equation. Our results show that the increase of the electron concentration in the well enhances the screening of the 2D electron gas, decreases the hole concentration, and can ultimately lead to a high electron mobility at liquid nitrogen temperatures. The increase of the electron concentration in the QW could be achieved in situ by delta-doping of barriers or by applying the top-gate potential. Our modeling has shown that for low molar composition x the concentration of holes in the well is high in a wide range of electron concentrations; in this case, the purity of samples does not significantly influence the electron mobility. These results are important in the context of establishing optimal parameters for the fabrication of high-mobility Hg{sub 1−x}Cd{sub x}Te quantum wells able to operate at liquid nitrogen temperature and thus suitable for applications in terahertz detectors.

  9. XTE J1701-462 AND ITS IMPLICATIONS FOR THE NATURE OF SUBCLASSES IN LOW-MAGNETIC-FIELD NEUTRON STAR LOW-MASS X-RAY BINARIES

    SciTech Connect

    Homan, Jeroen; Fridriksson, Joel K.; Remillard, Ronald A.; Lewin, Walter H. G.; Van der Klis, Michiel; Wijnands, Rudy; Altamirano, Diego; Mendez, Mariano; Lin Dacheng; Casella, Piergiorgio; Belloni, Tomaso M.

    2010-08-10

    We report on an analysis of Rossi X-Ray Timing Explorer data of the transient neutron star low-mass X-ray binary (NS-LMXB) XTE J1701-462, obtained during its 2006-2007 outburst. The X-ray properties of the source changed between those of various types of NS-LMXB subclasses. At high luminosities, the source switched between two types of Z source behavior and at low luminosities we observed a transition from Z source to atoll source behavior. These transitions between subclasses primarily manifest themselves as changes in the shapes of the tracks in X-ray color-color (CD) and hardness-intensity diagrams (HID), but they are accompanied by changes in the kHz quasi-periodic oscillations, broadband variability, burst behavior, and/or X-ray spectra. We find that for most of the outburst the low-energy X-ray flux is a good parameter to track the gradual evolution of the tracks in CD and HID, allowing us to resolve the evolution of the source in greater detail than before and relate the observed properties to other NS-LMXBs. We further find that during the transition from Z to atoll, characteristic behavior known as the atoll upper banana can equivalently be described as the final stage of a weakening Z source flaring branch, thereby blurring the line between the two subclasses. Our findings strongly suggest that the wide variety in behavior observed in NS-LXMBs with different luminosities can be linked through changes in a single variable parameter, namely the mass accretion rate, without the need for additional differences in the neutron star parameters or viewing angle. We briefly discuss the implications of our findings for the spectral changes observed in NS-LMXBs and suggest that, contrary to what is often assumed, the position along the color-color tracks of Z sources is not determined by the instantaneous mass accretion rate.

  10. Relativistic Disk Reflection in the Neutron Star X-Ray BinaryXTE J1709-267 with NuSTAR

    NASA Astrophysics Data System (ADS)

    Ludlam, R. M.; Miller, J. M.; Cackett, E. M.; Degenaar, N.; Bostrom, A. C.

    2017-04-01

    We perform the first reflection study of the soft X-ray transient and Type 1 burst source XTE J1709-267 using NuSTAR observations during its 2016 June outburst. There was an increase in flux near the end of the observations, which corresponds to an increase from ∼0.04 L Edd to ∼0.06 L Edd assuming a distance of 8.5 kpc. We have separately examined spectra from the low- and high-flux intervals, which are soft and show evidence of a broad Fe K line. Fits to these intervals with relativistic disk reflection models have revealed an inner-disk radius of {13.8}-1.8+3.0 {R}g (where {R}g={GM}/{c}2) for the low-flux spectrum and {23.4}-5.4+15.6 {R}g for the high-flux spectrum at the 90% confidence level. The disk is likely truncated by a boundary layer surrounding the neutron star (NS) or the magnetosphere. Based on the measured luminosity and the accretion efficiency for a disk around an NS, we estimate that the theoretically expected size for the boundary layer would be ∼ 0.9{--}1.1 {R}g from the NS’s surface, which can be increased by spin or viscosity effects. Another plausible scenario is that the disk could be truncated by the magnetosphere. We place a conservative upper limit on the strength of the magnetic field at the poles (assuming {a}* =0 and {M}{NS}=1.4{M}ȯ ) of B≤slant 0.75-3.70× {10}9 G, though X-ray pulsations have not been detected from this source.

  11. Lattice dynamical investigations for Raman and infrared frequencies of Te doped Bi1-xTa1-xTe2xO4; 0

    PubMed

    Garg, Shaveen; Sinha, M M; Gupta, H C

    2014-09-15

    We have applied short range force constant model and used normal coordinate analysis based on G-F matrix method in investigating for Raman and infrared modes in Te doped Bi1-xTa1-xTe2xO4; 0xTe2xO4 (0

  12. A DIRECT MEASUREMENT OF THE HEAT RELEASE IN THE OUTER CRUST OF THE TRANSIENTLY ACCRETING NEUTRON STAR XTE J1709-267

    SciTech Connect

    Degenaar, N.; Miller, J. M.; Wijnands, R.

    2013-04-20

    The heating and cooling of transiently accreting neutron stars provides a powerful probe of the structure and composition of their crust. Observations of superbursts and cooling of accretion-heated neutron stars require more heat release than is accounted for in current models. Obtaining firm constraints on the depth and magnitude of this extra heat is challenging and therefore its origin remains uncertain. We report on Swift and XMM-Newton observations of the transient neutron star low-mass X-ray binary XTE J1709-267, which were made in 2012 September-October when it transitioned to quiescence after a {approx_equal}10 week long accretion outburst. The source is detected with XMM-Newton at a 0.5-10 keV luminosity of L{sub X} {approx_equal} 2 Multiplication-Sign 10{sup 34}(D/8.5 kpc){sup 2} erg s{sup -1}. The X-ray spectrum consists of a thermal component that fits to a neutron star atmosphere model and a non-thermal emission tail, each of which contribute {approx_equal}50% to the total flux. The neutron star temperature decreases from {approx_equal}158 to {approx_equal}152 eV during the {approx_equal}8 hr long observation. This can be interpreted as cooling of a crustal layer located at a column density of y {approx_equal} 5 Multiplication-Sign 10{sup 12} g cm{sup -2} ({approx_equal}50 m inside the neutron star), which is just below the ignition depth of superbursts. The required heat generation in the layers on top would be {approx_equal}0.06-0.13 MeV per accreted nucleon. The magnitude and depth rule out electron captures and nuclear fusion reactions as the heat source, but it may be accounted for by chemical separation of light and heavy nuclei. Low-level accretion offers an alternative explanation for the observed variability.

  13. Studying X-Ray Binaries with High Energy Frequency Quasi-Periodic Oscillations

    NASA Technical Reports Server (NTRS)

    Kaaret, P.; West, Donald K. (Technical Monitor)

    2002-01-01

    The goal of this investigation is to further our understanding of the dynamics of secreting neutron stars and black holes in the hope of using these systems as probes of the physics of strong gravitational fetus. The main focus of this work has been a multi-year program of simultaneous millisecond X-ray timing and spectral observations carried out with the Rossi X-Ray Timing Explorer (RXTE) to perform the X-ray timing and one of the satellites Asca, BeppoSAX, or Chandra to perform X-ray spectral measurements. With the advent of Chandra, we have extended our work to incLude extragalactic X-ray binaries. We conducted a comprehensive study of the X-ray and radio behavior of the Black Hole Candidate (BHC) X-ray transient XTE J1550-564 using RXTE, Chandra, and the Australian Telescope Compact Array (ATCA). We showed that strong radio emission is associated with major X-ray outbursts involving an X-ray state transition, while a compact radio jet is seen in the low/hard X-ray state found in the outburst decay. Interesting, the total energy required to produce the compact jet may be a substantial fraction of the total accretion energy of the system in that state. We also performed a detailed study of the spectral and timing properties of the decay. In joint RXTE/BeppoSAX observations of the neutron-star X-ray binary Cyg X-2, we discovered a correlation between the timing properties (the frequency of the horizontal branch oscillations) and the properties of a soft, thermal component of the X-ray spectrum. d e showed that more det

  14. X-RAY OBSERVATIONS OF THE BLACK HOLE TRANSIENT 4U 1630-47 DURING 2 YEARS OF X-RAY ACTIVITY

    NASA Technical Reports Server (NTRS)

    Tomsick, John A.; Corbel, Stephane; Goldwurm, Andrea; Kaaret, Philip

    2005-01-01

    The black hole candidate (BHC) X-ray transient 4U 1630-47 continuously produced strong X-ray emission for more than 2 years during its 2002-2004 outburst, which is one of the brightest and longest outbursts ever seen from this source. We use more than 300 observations made with the Rossi X-Ray Timing Explorer (RXTE) to study the source throughout the outburst, along with hard X-ray images from the International Gamma-Ray Astrophysics Laboratory (INTEGRAL), which are critical for interpreting the RXTE data in this crowded field. The source exhibits extreme behaviors, which can be interpreted as an indication that the system luminosity approaches the Eddington limit. For 15 observations, fitting the spectral continuum with a disk-blackbody plus power-law model results in measured inner disk temperatures between 2.7 and 3.8 keV, and such temperatures are only rivaled by the brightest BHC systems, such as GRS 1915+105 and XTE J1550-564. If the high temperatures are caused by the dominance of electron scattering opacity in the inner regions of the accretion disk, it is theoretically required that the source luminosity be considerably higher than 20% of the Eddington limit. We detect a variety of high-amplitude variability, including hard 10-100 s flares, which peak at levels as much as 2-3 times higher than nonflare levels. The X-ray properties in 2002-2004 are significantly different from those seen during the 1998 outburst, which is the only outburst with detected radio jet emission. Our results support the "jet line" concept recently advanced by Fender and coworkers. Our study allows for a test of the quantitative McClintock & Remillard spectral state definitions, and we find that these definitions alone do not provide a complete description of the outburst. Finally, for several of the observations, the high-energy emission is dominated by the nearby sources IGR J16320-4751 and IGR J16358-4726, and we provide information on when these sources were bright and on the

  15. Imaging Dirac-Mass Disorder from Magnetic Dopant-Atoms in the Ferromagnetic Topological Insulator Crx(Bi0.1Sb0.9)2-xTe3 - Part II

    NASA Astrophysics Data System (ADS)

    Lee, Inhee; Kim, Chung Koo; Lee, Jinho; Billinge, Simon; Zhong, Ruidan; Schneeloch, John; Liu, Tiansheng; Tranquada, John; Gu, Genda; Davis, J. C.

    2015-03-01

    We present Part II of the spectroscopic imaging - scanning tunneling microscopy (SI-STM) study of ferromagnetic Crx(Bi0.1Sb0.9)2-xTe3 single crystals measured at 4.5 K. As Part II we show how both spectroscopic analysis in real and momentum space demonstrate the coincident Dirac mass gap identified. Distribution of gap width, gap center, and gap anisotropy will be discussed. The anticipated relationship Δ (r) ~ n (r) is confirmed throughout, and exhibits an electron-dopant interaction energy J* = 145 meV .nm2. These observations reveal how magnetic dopant atoms actually generate the TI mass gap and that, to achieve the novel physics expected of time-reversal-symmetry breaking TI materials, control of the resulting Dirac-mass gap disorder will be essential.

  16. Phase Diagram of HgTe -ZnTe Pseudobinary and Density, Heat Capacity, and Enthalphy of Mixing of Hg(sub 1-x)Zn(sub x)Te Pseudobinary Melts

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua; Sha, Yi-Gao; Mazuruk, K.; Lehoczky, S. L.

    1996-01-01

    In this article, the solidus temperatures of the Hg(sub 1-x) Zn(sub x)Te pseudobinary phase diagram for several compositions in the low x region were measured by differential thermal analysis and the HgTe-ZnTe pseudobinary phase diagram was constructed. The densities of two HgZnTe melts, x = 0.10 and 0.16, were determined by an in situ pycnometric technique in a transparent furnace over, respectively, 110 and 50 C ranges of temperature. The thermodynamic properties of the melts, such as the heat capacity and enthalpy of mixing, were calculated for temperatures between the liquidus and 1500 C by assuming an associated solution model for the liquid phase.

  17. A PROPELLER-EFFECT INTERPRETATION OF MAXI/GSC LIGHT CURVES OF 4U 1608-52 AND Aql X-1 AND APPLICATION TO XTE J1701-462

    SciTech Connect

    Asai, K.; Matsuoka, M.; Mihara, T.; Sugizaki, M.; Serino, M.; Nakahira, S.; Negoro, H.; Ueda, Y.; Yamaoka, K.

    2013-08-20

    We present the luminosity dwell-time distributions during the hard states of two low-mass X-ray binaries containing a neutron star (NS), 4U 1608-52 and Aql X-1, observed with MAXI/GSC. The luminosity distributions show a steep cutoff on the low-luminosity side at {approx}1.0 Multiplication-Sign 10{sup 36} erg s{sup -1} in both sources. The cutoff implies a rapid luminosity decrease in their outburst decay phases and this decrease can be interpreted as being due to the propeller effect. We estimate the surface magnetic field of 4U 1608-52 to be (0.5-1.6) Multiplication-Sign 10{sup 8} G and Aql X-1 to be (0.6-1.9) Multiplication-Sign 10{sup 8} G from the cutoff luminosity and apply the same propeller mechanism to the similar rapid luminosity decrease observed in the transient Z source, XTE J1701-462, with RXTE/ASM. Assuming that the spin period of the NS is on the order of milliseconds, the observed cutoff luminosity implies a surface magnetic field on the order of 10{sup 9} G.

  18. A Propeller-effect Interpretation of MAXI/GSC Light Curves of 4U 1608-52 and Aql X-1 and Application to XTE J1701-462

    NASA Astrophysics Data System (ADS)

    Asai, K.; Matsuoka, M.; Mihara, T.; Sugizaki, M.; Serino, M.; Nakahira, S.; Negoro, H.; Ueda, Y.; Yamaoka, K.

    2013-08-01

    We present the luminosity dwell-time distributions during the hard states of two low-mass X-ray binaries containing a neutron star (NS), 4U 1608-52 and Aql X-1, observed with MAXI/GSC. The luminosity distributions show a steep cutoff on the low-luminosity side at ~1.0 × 1036 erg s-1 in both sources. The cutoff implies a rapid luminosity decrease in their outburst decay phases and this decrease can be interpreted as being due to the propeller effect. We estimate the surface magnetic field of 4U 1608-52 to be (0.5-1.6) × 108 G and Aql X-1 to be (0.6-1.9) × 108 G from the cutoff luminosity and apply the same propeller mechanism to the similar rapid luminosity decrease observed in the transient Z source, XTE J1701-462, with RXTE/ASM. Assuming that the spin period of the NS is on the order of milliseconds, the observed cutoff luminosity implies a surface magnetic field on the order of 109 G.

  19. FP-LAPW methodology based theoretical investigation of structural, electronic and optical properties of MgxPb1-xS, MgxPb1-xSe and MgxPb1-xTe ternary alloys

    NASA Astrophysics Data System (ADS)

    Chattopadhyaya, Surya; Bhattacharjee, Rahul

    2017-01-01

    The structural, electronic and optical properties of MgxPb1-xS, MgxPb1-xSe and MgxPb1-xTe alloys for 0≤ x≤1 in their rock-salt (B1) crystallographic phase have been calculated using the full-potential linearized augmented plane wave (FP-LAPW) method under the framework of density functional theory (DFT). Using the Wu-Cohen generalized-gradient approximation (WC-GGA) induced exchange-correlation potential scheme, the ground state structural parameters such as equilibrium lattice constants, bulk modulus and its pressure derivatives are calculated and deviations of the lattice constants from Vegard's law and the bulk modulus from linear concentration dependence have been observed for the alloys. Electronic band structures and density of states have been calculated using Tran-Blaha modified Becke-Johnsoexit3b2tex.batn (TB-mBJ) parameterization scheme to study the electronic properties of the binary compounds and their ternary alloys. Using the approach of Zunger and co-workers, the microscopic origins of band gap bowing have been discussed in term of volume deformation, charge exchange and structural relaxation. Optical properties of the binary compounds and their ternary alloys have been calculated in terms of their respective dielectric function, refractive index, reflectivity and optical conductivity. Few calculated results are compared with available experimental and other theoretical data.

  20. The Microquasar Cyg X-1: A Short Review

    NASA Technical Reports Server (NTRS)

    Nowak, M. A.; Wilms, J.; Hanke, M.; Pottschmidt, K.; Markoff, S.

    2011-01-01

    We review the spectral properties of the black hole candidate Cygnus X-I. Specifically, we discuss two recent sets of multi-satellite observations. One comprises a 0.5-500 keY spectrum, obtained with eve!)' flying X-ray satellite at that time, that is among the hardest Cyg X-I spectra observed to date. The second set is comprised of 0.5-40 keV Chandra-HETG plus RXTE-PCA spectra from a radio-quiet, spectrally soft state. We first discuss the "messy astrophysics" often neglected in the study of Cyg X-I, i.e., ionized absorption from the wind of the secondary and the foreground dust scattering halo. We then discuss components common to both state extremes: a low temperature accretion disk, and a relativistically broadened Fe line and reflection. Hard state spectral models indicate that the disk inner edge does not extend beyond > or approx.= 40 GM/sq c , and may even approach as close as approx. = 6GM/sq c. The soft state exhibits a much more prominent disk component; however, its very low normalization plausibly indicates a spinning black hole in the Cyg X-I system. Key words. accretion, accretion disks - black hole physics - X-rays:binaries

  1. Structure change via partial Se/Te substitution: crystal structure and physical properties of the telluride Ba(2)Cu(4-x)Te(5) in contrast to the selenide-telluride Ba(2)Cu(4-x)Se(y)Te(5-y).

    PubMed

    Mayasree, Oottil; Cui, Yanjie; Assoud, Abdeljalil; Kleinke, Holger

    2010-07-19

    The chalcogenides Ba(2)Cu(4-x)Se(y)Te(5-y) were synthesized from the elements in stoichiometric ratios at 700 degrees C, followed by annealing at 600 degrees C. The ternary telluride Ba(2)Cu(4-x)Te(5) crystallizes in a new structure type, space group C2/c, with lattice dimensions of a = 9.4428(6) A, b = 9.3289(6) A, c = 13.3028(8) A, beta = 101.635(1) degrees , V = 1147.8(1) A(3), for x = 0.75(1) (Z = 4). The corresponding selenide-telluride adopts another new, but strongly related, structure type, space group P4(1)2(1)2, with a = 6.5418(3) A, c = 25.782(2) A, V = 1103.3(1) A(3), for Ba(2)Cu(3.26(2))Se(0.729(8))Te(4.271) (Z = 4). Between 0.13 and 1.0 Te per formula unit can be replaced with Se, while the Cu content appears to vary only within 0.67

  2. XTE Proposal #20102--"SS 433's High Energy Spectrum"

    NASA Technical Reports Server (NTRS)

    Band, David L.; Blanco, P.; Rothschild, R.; Kawai, N.; Kotani, T.; Oka, T.; Wagner, R. M.; Hjellming, R.; Rupen, M.; Brinkmann, W.

    1999-01-01

    We observed the jet-producing compact binary system SS 433 with RXTE during three multiwavelength campaigns, the first in conjunction with ASCA observations, the second simultaneous with a VLA-VLBA-MERLIN campaign, and the third associated with a Nobeyama millimeter-band campaign. All these campaigns included optical observations. Occurring at different jet precession and binary phases, the observations also monitored the system during a radio flare. The data provide SS 433's X-ray spectrum over more than an energy decade, and track the spectral variations as the X-ray source was partially eclipsed. The continuum can be modeled as a power law with an exponential cutoff, which can be detected to approximately 50 keV. Strong line emission is evident in the 5-10 keV range which can be modeled as a broad line whose energy is precession independent and a narrow line whose energy does vary with jet precession phase; this line model is clearly an over simplification since the PCA does not have sufficient energy resolution to detect the lines ASCA observed. The eclipses are deeper at high energy and at jet precession phases when the jets are more inclined towards and away from us. A large radio flare occurred between two sets of X-ray monitoring observations; an X-ray observation at the peak of the flare found a softer spectrum with a flux approximately 1/3 that of the quiescent level.

  3. JTDE I XTE34 Materials Research and Development Report,

    DTIC Science & Technology

    1988-01-15

    excess of the design level. In Figure 11 the microstructure of the single-crystal MAR - M247 blades is shown in the area adjacent to the fracture face...from the tip shroud rupture failure. The metallographic structures shown in these photos is indicative of acceptably processed MAR - M247 mate- rial. As...treatments, they would be expected in MAR - M247 material which is limited by incipient melting to solution treatments of approximately 2250F. This

  4. Black Hole X Ray Nova Outburst with XTE and HST

    NASA Technical Reports Server (NTRS)

    Patterson, Joseph; Haswell, Carole

    1998-01-01

    We obtained multiwavelength coverage of the soft X-ray transient. GRO J1655-40 during its 1996 outburst, using HST (Hubble Space Telescope), RXTE (Rossi X Ray Timing Explorer), CGRO (Compton Gamma Ray Observatory), and ground-based facilities. This outburst was qualitatively different from other SXT (Soft X Ray Telescope) outbursts and from previous outbursts of this source. The onset of hard X-ray activity occurred very slowly, over several months, and was delayed relative to the soft X-ray rise. During this period, the optical fluxes declined steadily. This apparent anticorrelation is not consistent with with the standard disk instability model of SXT outbursts, nor is it expected if the optical output is dominated by reprocessed X-rays, as in persistent low-mass X-ray binaries. Based on the strength of the 2175-A interstellar absorption feature, we constrain the reddening to be E(B - V) = 1.2 plus or minus 0.1, a result which is consistent with the known properties of the source and with the strength of other interstellar absorption lines. After this dereddening we find that the spectra are dominated by a component peaking in the optical, with the expected v (sup l/3) disk spectrum seen only in the ultraviolet. Bowen fluorescence lines of NIII and OIII are also seen, as well as possible P Cyg profiles in the ultraviolet resonance lines. These features suggest an accretion-disk wind. The X-ray spectra broadly resemble the high/soft state commonly seen in black hole candidates, but evolve through two substates.

  5. Chandra Discovers the X-ray Signature of a Powerful Wind from a Galactic Microquasar

    NASA Astrophysics Data System (ADS)

    2000-11-01

    NASA's Chandra X-ray Observatory has detected, for the first time in X rays, a stellar fingerprint known as a P Cygni profile--the distinctive spectral signature of a powerful wind produced by an object in space. The discovery reveals a 4.5-million-mile-per-hour wind coming from a highly compact pair of stars in our galaxy, report researchers from Penn State and the Massachusetts Institute of Technology in a paper they will present on 8 November 2000 during a meeting of the High-Energy Astrophysics Division of the American Astronomical Society in Honolulu, Hawaii. The paper also has been accepted for publication in The Astrophysical Journal Letters. "To our knowledge, these are the first P Cygni profiles reported in X rays," say researchers Niel Brandt, assistant professor of astronomy and astrophysics at Penn State, and Norbert S. Schulz, research scientist at the Massachusetts Institute of Technology. The team made the discovery during their first observation of a binary-star system with the Chandra X-ray Observatory, which was launched into space in July 1999. The system, known as Circinus X-1, is located about 20,000 light years from Earth in the constellation Circinus near the Southern Cross. It contains a super-dense neutron star in orbit around a normal fusion-burning star like our Sun. Although Circinus X-1 was discovered in 1971, many properties of this system remain mysterious because Circinus X-1 lies in the galactic plane where obscuring dust and gas have blocked its effective study in many wavelengths. The P Cygni spectral profile, previously detected primarily at ultraviolet and optical wavelengths but never before in X rays, is the textbook tool astronomers rely on for probing stellar winds. The profile looks like the outline of a roller coaster, with one really big hill and valley in the middle, on a data plot with velocity on one axis and the flow rate of photons per second on the other. It is named after the famous star P Cygni, in which such profiles have been observed for over one hundred years. "When you see a P Cygni profile, you immediately know the object you are observing is producing a powerful outflow," Brandt says. Chandra is the first X-ray observatory capable of capturing data of sufficiently high resolution to reveal an X-ray P Cygni profile. Brandt and Schulz say their discovery occurred because they were able to use Chandra continuously for one-third of a day to observe Circinus X-1, plus its signal in X rays is generally very bright, partly because it is relatively nearby in our own Galaxy. P Cygni lines at ultraviolet or optical wavelengths had not been previously seen from Circinus X-1 because a large amount of dust in the galactic plane lies between Earth and this system and this dust is an efficient absorber of ultraviolet and optical light. However, the energetic X rays created by Circinus X-1 could easily penetrate through the obscuring dust and gas--similar to the way medical X-rays on Earth can penetrate through people's bodies. "We were hoping to detect some kind of X-ray line emission from the accreting neutron star in Circinus X-1, but it caught us totally by surprise to observe a complex emission structure like a P Cygni profile in high-energy X rays." schulz says. "This detection clearly marks a new area in X-ray astrophysics, where we will be able to study dynamical structures in the universe like we currently do at ultraviolet or optical wavelengths." Brandt and Schulz used two of Chandra's instruments, known together as the High-Energy Transmission Grating Spectrometer (HETGS), to detect the X rays and produce a high-resolution X-ray spectrum of Circinus X-1. This spectrum is analogous to the rainbow we can see at optical wavelengths. "Chandra's X-ray spectrum is 50 times more detailed than previous X-ray observatories could obtain," Schulz says. First, the super-fine transmission gratings acted like a prism to separate the X-rays into discrete energy bands. Then, the Advanced CCD Imaging Spectrometer (ACIS) was used as a camera to record the X-ray spectral data, which computers processed and plotted onto a graph, revealing the P Cygni signature. Specific elements, such as silicon or iron, emit specific X-ray wavelengths, revealing their presence in the emitting material to astronomers. Before the observation with Chandra, astronomers knew the force of gravity in an X-ray binary system strips material off the surface of the normal star and then pulls this material toward the surface of the super-dense neutron star, forming a relatively flat spiraling cloud of gas called an accretion disk. The detailed Chandra data revealed, in addition, that the radiation and rotational forces in the Circinus X-1 disk are blasting some of the inward-spiraling gas back out into space in a powerful wind, which creates the P Cygni lines in the object's spectrum. P Cygni profiles carry much diagnostic information that is hard to obtain in other ways--such as how fast the wind is moving, how much material it contains, how dense it is, and its chemical composition. "The wind coming out of Circinus X-1 is composed of gas that contains highly ionized atoms of silicon, neon, iron, magnesium, and sulfur, and its peak observed velocity is about 4.5 million miles per hour--so fast it would cross the entire radius of the Earth in about three seconds," Brandt reports. The astronomers used Doppler techniques that detect positive velocities from material moving away from Earth, with signals shifted toward the red end of the spectrum, and negative velocities from material that is coming toward Earth, with signals shifted toward the blue end of the spectrum. "We learned these two stars clearly interact dramatically with each other while this wind is blowing outward at high velocity, which appears to be causing certain properties of the wind to change over time," Schulz says. The researchers produced a time-lapse movie of one of their spectra, which is available on the World Wide Web, along with other information about the discovery, at http://www.astro.psu.edu/users/niel/cirx1/cirx1.html. A binary-star system 20,000 light years from Earth in the constellation of Circinus. Animation showing the strong variability over time of one of the P Cygni spectral lines seen by Chandra from Circinus X-1 (Click Image to View Animation) Credit: Niel Brandt and Norbert Schulz (Note: This animation is the same as the one referred to in the above paragraph) Atoms irradiated with energetic X-rays can emit as well as absorb them at specific wavelengths. Whether astronomers observe emission or absorption depends on the state and environment of the irradiated atoms, so these processes carry vital information about the emitting and absorbing material. Regarding the time-lapse movie, Schulz commented "You can see this profile flipping up and down between a strong emission line on the red side and a strong absorption line on the blue side. We don't yet fully understand what this means, but it does indicate the dynamic nature of this system. We see indications that sometimes either the emitting or the absorbing region gets obscured by matter so thick that not even X rays can penetrate it." The researchers say one reason their discovery that Circinus X-1 has a high-velocity wind is important is that this small two-star system now has striking similarities with a type of luminous active galaxy known as a broad-absorption-line quasar. Broad-absorption-line quasars are galaxies containing a violent centers powered by supermassive black holes. "This type of galaxy has an accretion disk circling its black hole plus very powerful winds created when radiation pushes material off of the disk and out into space," Brandt says. "The disk winds from broad-absorption-line quasars create P Cygni lines in the spectra of these objects. Circinus X-1, with the newly detected X-ray P Cygni profiles, appears in many ways to be a microscopic version of a broad-absorption-line quasar." "Although a typical AGN has a roughly ten-million-solar-mass black hole at its center while the Circinus X-1 system has a neutron star only slightly more massive than our Sun, both systems must obey the same laws of physics," Brandt says. "Gas is gas and gravity is gravity and that's all there is to it--you put gas and gravity together and they make a disk and often, apparently, a disk-generated wind." The researchers hope X-ray P Cygni profiles will be found to be a fairly common property of X-ray binaries containing neutron stars and black holes. "If we can find X-ray P Cygni profiles in more systems, we can learn a great deal about the geometry and the dynamics of the winds these systems emit," Schulz says. "Due to the penetrating nature of X rays, X-ray P Cygni lines have the significant advantage that they can be used to probe winds even from systems that are heavily obscured by dust along the line of sight." The High-Energy Transmission Grating Spectrometer was built by the Massachusetts Institute of Technology with Bruno Rossi Professor Claude Canizares as Principal Investigator. The ACIS X-ray camera was conceived and developed for NASA by Penn State and the Massachusetts Institute of Technology under the leadership of Gordon Garmire, Evan Pugh Professor of Astronomy and Astrophysics at Penn State. The observation of Circinus X-1 was part of the first round of Chandra's guest observer program. The guest observer program is a competitive one open to the World science community. NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program. TRW Inc., Redondo Beach, California, is the prime contractor for the spacecraft. The Smithsonian's Chandra X-ray Center controls science and flight operations from Cambridge, Massachusetts. Circinus X-1 Handout Constellation Circinus To follow Chandra's progress, visit the Chandra site at: http://chandra.harvard.edu AND http://chandra.nasa.gov This research was supported by the Chandra X-ray Center, the Alfred P. Sloan Foundation, and the Smithsonian Astrophysical Observatory. This is a joint press release from Penn State and the Massachusetts Institute of Technology Digital images and movies are available on the World Wide Web at http://www.astro.psu.edu/users/niel/cirx1/cirx1.html Science Contacts: Niel Brandt: 814-865-3509 Norbert S. Schulz: 617-258-5767 Barbara K. Kennedy (PIO at Penn State): 814-863-4682 Deborah Halber (PIO at MIT): 617-253-2700 or 617-258-9276

  6. Recent Results of VLBA Imaging of X-Ray Binaries: the Newest and Oldest Microquasars

    NASA Astrophysics Data System (ADS)

    Mioduszewski, A. J.; Dhawan, V.; Rupen, M. P.

    2005-12-01

    X-ray binaries are stellar systems in which X-ray emission results from accretion from a normal star onto a compact object, i.e., a neutron star or black hole. Radio emission is associated both with X-ray outbursts, and with more stable conditions when the X-rays are dominated by a persistent hard power-law component. The VLBA has played a crucial role in studying these systems, by allowing detailed AU-scale imaging. This has allowed direct measurements of morphologies, orientations, expansion speeds, and scattering sizes, as well as detailed astrometric and proper motion studies. We review results from our group in this area, namely observations of H1743-322 and SS433.

  7. THE NOT-SO-MASSIVE BLACK HOLE IN THE MICROQUASAR GRS1915+105

    SciTech Connect

    Steeghs, D.; Parsons, S. G.; McClintock, J. E.; Reid, M. J.; Littlefair, S.; Dhillon, V. S.

    2013-05-10

    We present a new dynamical study of the black hole X-ray transient GRS1915+105 making use of near-infrared spectroscopy obtained with X-shooter at the Very Large Telescope. We detect a large number of donor star absorption features across a wide range of wavelengths spanning the H and K bands. Our 24 epochs covering a baseline of over 1 yr permit us to determine a new binary ephemeris including a refined orbital period of P = 33.85 {+-} 0.16 days. The donor star radial velocity curves deliver a significantly improved determination of the donor semi-amplitude which is both accurate (K{sub 2} = 126 {+-} 1 km s{sup -1}) and robust against choice of donor star template and spectral features used. We furthermore constrain the donor star's rotational broadening to vsin i = 21 {+-} 4 km s{sup -1}, delivering a binary mass ratio of q = 0.042 {+-} 0.024. If we combine these new constraints with distance and inclination estimates derived from modeling the radio emission, a black hole mass of M{sub BH} = 10.1 {+-} 0.6 M{sub Sun} is inferred, paired with an evolved mass donor of M{sub 2} = 0.47 {+-} 0.27 M{sub Sun }. Our analysis suggests a more typical black hole mass for GRS1915+105 rather than the unusually high values derived in the pioneering dynamical study by Greiner et al. Our data demonstrate that high-resolution infrared spectroscopy of obscured accreting binaries can deliver dynamical mass determinations with a precision on par with optical studies.

  8. High-Energy Polarization from Jets in AGN and Microquasars (Solicited)

    NASA Astrophysics Data System (ADS)

    Boettcher, Markus

    2016-07-01

    This talk will give an overview of recent advances in theoretical predictions of X-ray and gamma-ray polarization of the emission from relativistic jet sources. The high-energy emission from such sources is either synchrotron radiation from ultrarelativistic particles or Compton emission, either synchrotron self-Compton or Comptonization of external radiation. I will present model calculations of the resulting high-energy polarization in various model scenarios, with high-energy emission dominated both by leptonic and hadronic emission processes. The results demonstrate the prospect of diagnosing the topology of magnetic fields in relativistic astrophysical jets and distinguishing between leptonic and hadronic high-energy emission models, with important implications concerning the origin of ultra-high-energy cosmic-rays and high-energy neutrinos.

  9. Fermi-LAT Observation of Increased Gamma-ray Emission from the Microquasar Cygnus X-3

    NASA Astrophysics Data System (ADS)

    Loh, Alan; Corbel, Stephane; Dubus, Guillaume; Corbet, Robin

    2016-01-01

    Recently, the hard X-ray emission from the high-mass X-ray binary Cygnus X-3 has drastically dropped since 2016 Jan 11 (MJD 57398, as observed by Swift/BAT http://swift.gsfc.nasa.gov/results/transients/CygX-3/, Krimm et al. 2013, ApJS 209, 14) indicating a possible transition to the soft state.

  10. A SEYFERT-2-LIKE SPECTRUM IN THE HIGH-MASS X-RAY BINARY MICROQUASAR V4641 SGR

    SciTech Connect

    Morningstar, Warren R.; Miller, Jon M.; Reynolds, M. T.; Maitra, Dipankar E-mail: jonmm@umich.edu

    2014-05-10

    We present an analysis of three archival Chandra observations of the black hole V4641 Sgr, performed during a decline into quiescence. The last two observations in the sequence can be modeled with a simple power law. The first spectrum, however, is remarkably similar to spectra observed in Seyfert-2 active galactic nuclei, which arise through a combination of obscuration and reflection from distant material. This spectrum of V4641 Sgr can be fit extremely well with a model including partial-covering absorption and distant reflection. This model recovers a Γ ≅ 2.0 power-law incident spectrum, typical of black holes at low Eddington fractions. The implied geometry is plausible in a high-mass X-ray binary like V4641 Sgr, and may be as compelling as explanations invoking Doppler-split line pairs in a jet, and/or unusual Comptonization. We discuss potential implications and means of testing these models.

  11. Comparing the ρ and χ class spectra of the microquasar GRS 1915+105 observed with BeppoSAX

    NASA Astrophysics Data System (ADS)

    Mineo, T.; Del Santo, M.; Massaro, E.; Massa, F.; D'Aì, A.

    2017-02-01

    Context. BeppoSAX observed GRS 1915+105 during two variability classes at the same 2-10 keV flux level. The ρ class is characterized by quasi-periodic flares recurring on a time-scale of 1 to 2 min, namely heartbeat, while the χ class is characterized by no strong temporal variability. Aims: The aim of this work is to coherently analyze the source spectrum in these two classes and to gain insight into the source conditions that inset the heartbeats. Methods: A single χ spectrum was accumulated, while ρ data were split in runs where five phase-resolved spectra were selected. In addition to the multicolor disc black body, the fitting model includes a hybrid Comptonization plus a Compton reflection component. Results: Our results show that the emission in the ρ class is dominated by the multi-temperature disk, while in the χ class the Comptonised component is dominant. The disk temperature varies between a maximum of 1.95 ± 0.11 keV reached at the peak and a minimum of 0.95 keV in the χ class. In both classes we detect a significant contribution from a non-thermal electron population to the total Comptonized emission. A broadened iron emission line is detected in the χ spectrum. We interpret the line shape as being due to reflection from an accretion disk extremely close to the black-hole ( gravitational radii), with an equivalent width of 200 ± 20 eV. Concomitantly, upper limits of 150 eV can be derived from the ρ spectra. Conclusions: In the framework of coupled disc-corona models, these results point out that the source emission is strongly affected by the fractions of accretion energy distributed between the disk, the corona, and possibly the wind, with no indication on the conditions that inset the heartbeats.

  12. NMR in Chevrel-phase solid solution Mo 6Se 8- xTe x

    NASA Astrophysics Data System (ADS)

    Hamard, C.; Le Floch, M.; Peña, O.; Wojakowski, A.

    1999-01-01

    The Mo 6Se 8-Mo 6Te 8 solid solution was studied by X-ray diffraction, magnetic susceptibility and 77Se and 125Te NMR. Dynamic studies show that substitution occurs differently when Se replaces Te in Mo 6Te 8 than when Te replaces Se in Mo 6Se 8. Selenium first fills the high-symmetry sites and then it becomes statistically distributed on the 6f positions of the R3¯ symmetry. In the second case, Te occupies randomly the 8 X sites of the Mo 6X 8 structure, creating large perturbations of the 125Te NMR spectra over the whole range of x.

  13. Thermoelectric properties of n-type polycrystalline BixSb2-xTe3 alloys

    NASA Technical Reports Server (NTRS)

    Snyder, J.; Gerovac, N.; Caillat, T.

    2002-01-01

    (BixSbl-x)2Te3(.5 = x = .7) polycrystalline samples were synthesized using a combination of melting and powder metallurgy techniques. The samples were hot pressed in graphite dies and cut perpendicular and parallel to the pressing direction. Samples were examined by microprobe analysis to determine their atomic composition. The thermoelectric properties were measured at room temperature in both directions. These properties include Seebeck coefficient, thermal conductivity, electrical resistivity, and Hall effect. The thermoelectric figure-of-merit, ZT, was calculated fiom these properties.

  14. Black Hole X-Ray Nova Outburst with XTE and HST

    NASA Technical Reports Server (NTRS)

    Patterson, Joseph; Haswell, Carole

    1999-01-01

    We obtained multiwavelength coverage of the soft X-ray transient GRO J1655-40 during its 1996 outburst, using HST, RXTE, CGRO, and ground-based facilities. This outburst was qualitatively different from other SXT outbursts and from previous outbursts of this source. The onset of hard X-ray activity occurred very slowly, over several months, and was delayed relative to the soft X-ray rise. During this period, the optical fluxes declined steadily. This apparent anticorrelation is not consistent with with the standard disk instability model of SXT outbursts, nor is it expected if the optical output is dominated by reprocessed X-rays, as in persistent low-mass X-ray binaries. .

  15. Improvement in crystalline quality of Cd 1- xZn xTe( x=4%) crystals grown in graphite crucible

    NASA Astrophysics Data System (ADS)

    Garg, Arun Kumar; Srivastava, Meenakshi; Narula, R. C.; Bagai, R. K.; Kumar, Vikram

    2004-01-01

    In this paper, we report improvement in the crystalline quality of CdZnTe (Zn=4%) crystals, with respect to etch pit density and full-width half-maximum (FWHM) of the X-ray rocking curve, grown in graphite crucible as compared to crystals grown in carbon-coated quartz ampoule. Uniform dislocation density distribution of the order of 2-3×10 4 cm -2 with no cellular structure and improvement in FWHM value (18-30 arcsec) with reduced splitting of peaks in X-ray rocking curves have been observed in the complete cadmium zinc telluride (CZT) wafers (30 mm×50 mm). We have used a larger X-ray beam (10 mm×1 mm) to study the crystalline quality of the complete CZT ingot. The effect of variation of beam size on X-ray rocking curve and its FWHM value indicates that the use of large beam size gives the true assessment of the spatial crystalline perfection of the grown CZT crystals. Although improvement in terms of crystalline perfection has been achieved in CZT material, the fall in optical transmission in the longer wave length spectral region and measured electrical properties in the annealed CZT samples point towards the incorporation of impurities in CZT during growth from the graphite crucible. Our results clearly indicate that overall improvement in the quality of CZT crystal is achievable with the use of ultra-high-purity graphite as the crucible.

  16. Deep electronic levels in high-pressure Bridgman Cd{sub 1-x}Zn{sub x}Te

    SciTech Connect

    Szeles, C.; Shan, Y.Y.; Lynn, K.G.; Eissler, E.E.

    1995-12-01

    The behavior of deep electronic levels was studied as a function of Zn concentration in CdZnTe crystals grown by the high-pressure Bridgman technique using thermoelectric effect spectroscopy. A significant increase of the thermal ionization energies of hole traps was observed with the increasing Zn content of the ternary compound. The effect explains the stronger hole trapping and the resulting much shorter hole lifetime usually observed in CdZnTe as compared to CdTe. The behavior also suggests increased carrier recombination and explains the strong deterioration of electron collection in detectors fabricated from CdZnTe of high Zn concentration.

  17. Optical studies of the X-ray transient XTE J2123-058 - II. Phase-resolved spectroscopy

    NASA Astrophysics Data System (ADS)

    Hynes, R. I.; Charles, P. A.; Haswell, C. A.; Casares, J.; Zurita, C.; Serra-Ricart, M.

    2001-06-01

    We present time-resolved spectroscopy of the soft X-ray transient XTEJ2123-058 in outburst. A useful spectral coverage of 3700-6700Å was achieved spanning two orbits of the binary, with single-epoch coverage extending to ~9000Å. The optical spectrum approximates a steep blue power law, consistent with emission on the Rayleigh-Jeans tail of a hot blackbody spectrum. The strongest spectral lines are Heii 4686Å and Ciii/Niii 4640Å (Bowen blend) in emission. Their relative strengths suggest that XTEJ2123-058 was formed in the Galactic plane, not in the halo. Other weak emission lines of Heii and Civ are present, and Balmer lines show a complex structure, blended with Heii. Heii 4686-Å profiles show a complex multiple S-wave structure, with the strongest component appearing at low velocities in the lower-left quadrant of a Doppler tomogram. Hα shows transient absorption between phases 0.35 and 0.55. Both of these effects appear to be analogous to similar behaviour in SW Sex type cataclysmic variables. We therefore consider whether the spectral line behaviour of XTEJ2123-058 can be explained by the same models invoked for those systems.

  18. Prediction of an arc-tunable Weyl Fermion metallic state in MoxW1-xTe2

    DOE PAGES

    Chang, Tay-Rong; Xu, Su-Yang; Chang, Guoqing; ...

    2016-02-15

    A Weyl semimetal is a new state of matter that hosts Weyl fermions as emergent quasiparticles. The Weyl fermions correspond to isolated points of bulk band degeneracy, Weyl nodes, which are connected only through the crystal’s boundary by exotic Fermi arcs. The length of the Fermi arc gives a measure of the topological strength, because the only way to destroy the Weyl nodes is to annihilate them in pairs in the reciprocal space. To date, Weyl semimetals are only realized in the TaAs class. Here, we propose a tunable Weyl state in MoxW1₋xTe2 where Weyl nodes are formed by touchingmore » points between metallic pockets. We show that the Fermi arc length can be changed as a function of Mo concentration, thus tuning the topological strength. Lastly,our results provide an experimentally feasible route to realizing Weyl physics in the layered compound MoxW1₋xTe2, where non-saturating magneto-resistance and pressure-driven superconductivity have been observed.« less

  19. The broad-band radio spectrum of LS I +61°303 in outburst

    NASA Astrophysics Data System (ADS)

    Zimmermann, L.; Fuhrmann, L.; Massi, M.

    2015-08-01

    Aims: Our aim is to explore the broad-band radio continuum spectrum of LS I +61°303 during its outbursts by employing the available set of secondary focus receivers of the Effelsberg 100 m telescope. Methods: The clear periodicity of the system LS I +61°303 allowed observations to be scheduled covering the large radio outburst in March-April 2012. We observed LS I +61°303 on 14 consecutive days at 2.6, 4.85, 8.35, 10.45, 14.3, 23, and 32 GHz with a cadence of about 12 h followed by two additional observations several days later. Based on these observations we obtained a total of 24 quasi-simultaneous broad-band radio spectra. Results: During onset, the main flare shows an almost flat broad-band spectrum, most prominently seen on March 27, 2012, where - for the first time - a flat spectrum (α = 0.00 ± 0.07, S ∝ να) is observed up to 32 GHz (9 mm wavelength). The flare decay phase shows superimposed "sub-flares" with the spectral index oscillating between -0.4 and -0.1 in a quasi-regular fashion. Finally, the spectral index steepens during the decay phase, showing optically thin emission with values α ~ -0.5 to -0.7. Conclusions: The radio characteristics of LS I +61°303 compare well with those of the microquasars XTE J1752-223 and Cygnus X-3. In these systems the flaring phase is actually also composed of a sequence of outbursts with clearly different spectral characteristics: a first outburst with a flat/inverted spectrum followed by a bursting phase of optically thin emission.

  20. Ancient Black Hole Speeds Through Sun's Galactic Neighborhood, Devouring Companion Star

    NASA Astrophysics Data System (ADS)

    2001-09-01

    Astronomers using the National Science Foundation's Very Long Baseline Array (VLBA) radio telescope have found an ancient black hole speeding through the Sun's Galactic neighborhood, devouring a small companion star as the pair travels in an eccentric orbit looping to the outer reaches of our Milky Way Galaxy. The scientists believe the black hole is the remnant of a massive star that lived out its brief life billions of years ago and later was gravitationally kicked from its home star cluster to wander the Galaxy with its companion. "This discovery is the first step toward filling in a missing chapter in the history of our Galaxy," said Felix Mirabel, an astrophysicist at the Institute for Astronomy and Space Physics of Argentina and French Atomic Energy Commission. "We believe that hundreds of thousands of very massive stars formed early in the history of our Galaxy, but this is the first black hole remnant of one of those huge primeval stars that we've found." "This also is the first time that a black hole's motion through space has been measured," Mirabel added. A black hole is a dense concentration of mass with a gravitational pull so strong that not even light can escape it. The research is reported in the Sept. 13 issue of the scientific journal Nature. XTE J1118+480 The object is called XTE J1118+480 and was discovered by the Rossi X-Ray satellite on March 29, 2000. Later observations with optical and radio telescopes showed that it is about 6,000 light-years from Earth and that it is a "microquasar" in which material sucked by the black hole from its companion star forms a hot, spinning disk that spits out "jets" of subatomic particles that emit radio waves. Most of the stars in our Milky Way Galaxy are within a thin disk, called the plane of the Galaxy. However, there also are globular clusters, each containing hundreds of thousands of the oldest stars in the Galaxy which orbit the Galaxy's center in paths that take them far from the Galaxy's plane. XTE J

  1. Two XTE A01 Projects: A Multifrequency Study of Circinus X-1 and a Search for Microsecond Variability From Bright Galactic X-Ray Source

    NASA Technical Reports Server (NTRS)

    Jernigan, Garrett

    1998-01-01

    This final report describes the research of a single common portion of the above-named two projects, conducted by G. Jernigan, i.e., the theory for a new method, a variation of a Kolmogorov-Smirnov test, for determining the fastest variability present in an X-ray source. The current phase involves testing the newly developed code on real example sources (CYG X1). Unfortunately, there are no calibration sources for testing the code, which therefore required the development of an X-ray source simulation code. The goal is to evaluate the sensitivity of the code for the detection of a range of different types of variability (bursts, pulsations, etc.).

  2. Theoretical Study of Role of Sb in Se_0.85-xTe_0.15Sbx Chalcogenide Glass in Influencing Glass Transition Temperature

    NASA Astrophysics Data System (ADS)

    Maharjan, N. B.; Paudyal, D. D.; Jeong, J.; Scheicher, R. H.; Das, T. P.

    2001-03-01

    The influence of Sb impurity on glass transition temperature (Tg) has recently been studied using Differential Scanning Calorimetry(N. B. Maharjan et al., Phy. Stat. Sol. (a) 178, 663 (2000)). The results indicate that Tg initially increases with Sb concentration (x), reaching a maximum at 0.04, subsequently decreasing till x=0.06 and then becoming constant. Qualitative explanation of this behavior for Tg has been suggested^1 using earlier ideas in the literature regarding the role of Sb in the interaction between chains in the Se_1-xTex system and bond energy strength considerations involving Se-Se and Sb-Se bonds. These ideas are being tested quantitatively using Hartree-Fock Cluster procedures, previously utilized by our group for study(H. S. Cho et al., (to be published); H. S. Cho et al., Hyperfine Interactions 96, 213 (1995)) of nuclear quadrupole interactions including that of ^125Te in Selenium and Tellurium(P. Boolchand et al., Phys. Rev. Lett. 30, 1292 (1973)).

  3. Electrical properties of Pb{sub 1-x}Mn{sub x}Te single crystals with an excess of tellurium

    SciTech Connect

    Bagieva, G. Z. Abdinova, G. D.; Mustafayev, N. B.; Abdinov, D. Sh.

    2013-03-15

    The effect of excess Te atoms (as high as 0.5 at %) and thermal treatment at 473 K for 120 h on the electrical conductivity {sigma}, the thermopower coefficient {alpha}, and the Hall coefficient R of Pb{sub 0.96}Mn{sub 0.04}Te single crystals in the temperature range {approx}77-300 K is investigated. It is shown that excess atoms of tellurium predominantly act as acceptor impurity centers at low concentrations in unannealed samples and form antisite defects at relatively high concentrations (0.05 at % or higher) being located mainly in vacancies of the lead sublattice, and decrease the hole concentration. As a result of annealing, certain lattice defects (for example, deformational) are healed, and the accommodation process for Te atoms at lead-sublattice vacancies is intensified. These processes substantially affect the values of the electrical parameters, their temperature dependences, as well as the sign of the thermopower and Hall coefficients of the samples.

  4. High hydrostatic pressure effects on the exciton spin states in CdTe/Cd{sub 1-x}Mn{sub x}Te single quantum wells

    SciTech Connect

    Yokoi, H.; Kakudate, Y.; Schmiedel, T.; Tozer, S.; Jones, E.D.; Takeyama, S.; Wojtowicz, T.; Karczewski, G.; Kossut, J.

    1996-10-01

    Photoluminescence (PL) was measured in a CdTe/Cd{sub 0.76}Mn{sub 0. 24}Te single quantum well structure under hydrostatic pressure up to 2.68 GPa and magnetic fields up to 30 T at 4.2 K. Pressure coefficients of exciton energies were found to be well width dependent. Magneto-PL experiments revealed negative pressure dependence of N{sub 0}({alpha}-{beta}) in barriers and saturation of T{sub 0} by the pressure.

  5. The H(sub infinity) optimal controller design and reduction for the inertial hold mode of the attitude control system of the XTE spacecraft

    NASA Technical Reports Server (NTRS)

    Xu, Zhong Ling; Zhou, Gui AN

    1994-01-01

    The Inertial Hold Mode (IHM) is one mode of the attitude control system of the X-ray Timing Explorer spacecraft that is disturbed by both parametric uncertainties and external torque disturbance. The IHM model is modified into a typical H-infinity mixed-sensitivity problem through choosing suitable weighting functions W(sub 1)(s) and W(sub 3)(s). The controller is designed by the H-infinity optimization technique with the transformation of shifting the imaginary axis. It can stabilize the plant with uncertainties from the natural frequencies of the flexible body. The gain margin and phase margin of the system are 24.03 db and 55.04 deg, respectively. The step response attenuates to zero within 150 seconds. These show that the controller satisfies the specified requirements. Since the order of the controller appears high, it is reduced to fourth order one. The results show that the stability and the performance of the system with the reduced controller are retained perfectly.

  6. Studies of boron implantation through photochemically deposited SiO/sub 2/ films on Hg/sub 1-x/Cd/sub x/Te. Technical report

    SciTech Connect

    Bowman, R.C.; Robertson, R.E.; Knudsen, J.F.; Downing, R.G.

    1987-05-22

    Variable-temperature Hall and resistivity measurements were used to monitor the changes in carrier behavior in p-type Hg(1-x)Cd(x)Te when boron ions are implanted through photochemically deposited SiO/sub 2/. The formation of an n-type layer is demonstrated. Quantitative and nondestructive determination of the absolute /sup 10/B concentration and distribution were obtained by the novel method of neutron-depth profiling. As expected, the boron distributions in the SiO/sub 2/ films and Hg(1-x)Cd(x)Te are strongly dependent upon the ion implant energy. However, negligible changes in the boron depth profiles were found after 200 C anneals. The present results are briefly related to the performance behavior of mid-wavelength infrared (MWIR) sensors produced via generic ion-implantation procedures.

  7. Neutron Scattering Investigation of Phonon Scattering Rates in Ag1-xSb1+xTe2+x (x = 0, 0.1, and 0.2)

    SciTech Connect

    Abernathy, Douglas L; Budai, John D; Delaire, Olivier A; Ehlers, Georg; Hong, Tao; Karapetrova, Evguenia A.; Ma, Jie; May, Andrew F; McGuire, Michael A; Specht, Eliot D

    2014-01-01

    The phonon dispersions and scattering rates of the thermoelectric material AgSbTe$_{2}$ were measured as a function of temperature with inelastic neutron scattering. The results show that phonon scattering rates are large and weakly dependent on temperature. The lattice thermal conductivity was calculated from the measured phonon lifetimes and group velocities, providing good agreement with bulk transport measurements. The measured phonon scattering rates and their temperature dependence are compared with models of phonon scattering by anharmonicity and point defect. We find that these processes cannot account for the large total phonon scattering rates observed, and their lack of temperature dependence. Neutron and synchrotron diffraction measurements on single crystals revealed an extensive nanostructure from cation ordering, which is likely responsible for the strong phonon scattering.

  8. Reproducing the Correlations of Type C Low-frequency Quasi-periodic Oscillation Parameters in XTE J1550–564 with a Spiral Structure

    NASA Astrophysics Data System (ADS)

    Varniere, Peggy; Vincent, Frederic H.

    2017-01-01

    While it has been observed that the parameters intrinsic to the type C low-frequency quasi-periodic oscillations are related in a nonlinear manner among themselves, there has been, up to now, no model to explain or reproduce how the frequency, the FWHM, and the rms amplitude of the type C low-frequency quasi-periodic oscillations behave with respect to one another. Here we are using a simple toy model representing the emission from a standard disk and a spiral such as that caused by the accretion–ejection instability to reproduce the overall observed behavior and shed some light on its origin. This allows us to prove the ability of such a spiral structure to be at the origin of flux modulation over more than an order of magnitude in frequency.

  9. Magnetic jets from accretion disks : field structure and X-ray emission

    NASA Astrophysics Data System (ADS)

    Memola, Elisabetta

    2002-06-01

    . We also calculate the X-ray emission in the energy range 0.2--10.1,keV from a microquasar relativistic jet close to its source of 5 solar masses. In order to do it, we apply the jet flow parameters (densities, velocities, temperatures of each volume element along the collimating jet) derived in the literature from the relativistic magnetohydrodynamic equations. We obtain theoretical thermal X-ray spectra of the innermost jet as composition of the spectral contributions of the single volume elements along the jet. Since relativistic effects as Doppler shift and Doppler boosting due to the motion of jets toward us might be important, we investigate how the spectra are affected by them considering different inclinations of the line of sight to the jet axis. Emission lines of highly ionized iron are clearly visible in our spectra, probably also observed in the Galactic microquasars GRS 1915+105 and XTE J1748-288. The Doppler shift of the emission lines is always evident. Due to the chosen geometry of the magnetohydrodynamic jet, the inner X-ray emitting part is not yet collimated. Ergo, depending on the viewing angle, the Doppler boosting does not play a major role in the total spectra. This is the first time that X-ray spectra have been calculated from the numerical solution of a magnetohydrodynamic jet. Astrophysikalische Jets sind stark kollimierte Materieströmungen hoher Geschwindigkeit. Sie stehen im Zusammenhang mit einer Fülle verschiedener astrophysikalischer Objekte wie jungen Sternen, stellaren schwarzen Löchern ('Mikro-Quasare'), Galaxien mit aktivem Kern (AGN) und wahrscheinlich auch mit dem beobachteten intensiven Aufblitzen von Gamma-Strahlung (Gamma Ray Bursts). Insbesondere hat sich gezeigt, dass die Jets der Mikro-Quasare wahrscheinlich als kleinskalige Version der Jets der AGN anzusehen sind. Neben den Beobachtungen haben vor allem auch theoretische Überlegungen gezeigt, dass Magnetfelder bei der Jetentstehung, -beschleunigung und -kollimation eine

  10. 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

  11. Probing the Structure and Morphology of X-ray and Gamma-ray Binaries Using a Multi-Wavelength, Multi-MIssion Approach

    NASA Astrophysics Data System (ADS)

    Coley, Joel Barry

    2016-01-01

    This thesis focuses on High-Mass X-ray Binaries and their gamma-ray precursors, consisting of a compact object and an optical companion. Matter lost from the companion is accreted by the compact object where the gravitational potential energy is converted into X-ray radiation. The predominant high-energy emissions in gamma-ray binaries are in the MeV to TeV bandpasses. These are attributed to relativistic jets in microquasars or shocks from winds of the donor star and pulsar powered by rapid rotation of the neutron star.I use multi-wavelength observations with RXTE, MAXI, Swift, Suzaku, Fermi and ATCA to provide detailed temporal and spectral information on several X-ray binaries and one gamma-ray binary, 1FGL J1018.6-5856.My survey of the eclipsing HMXBs IGR J16393-4643, IGR J16418-4532, IGR J16479-4514, IGR J18027-2016 and XTE J1855-026 demonstrates that the physical parameters of both stellar components can be constrained. In IGR J16393-4643, spectral types of B0 V or B0-5 III are found to be consistent with the eclipse duration and Roche-lobe size, but the previously proposed spectral types in IGR J16418- 4532 and IGR J16479-4514 were not. Also found to be consistent with the eclipse half-angle and Roche-lobe size were the mass donor spectral types of IGR J18027-2016 and XTE J1855-026.4U 1210-64 was postulated to be an HMXB powered by the Be mechanism. Long-term observations show distinct high and low states and a 6.7101±0.0005 day modulation. A sharp dip interpreted to be an eclipse is found in the folded light curves. The eclipse half-angle is not consistent with the previously proposed spectral type B5 V, pointing to possible spectral types of B0 V or B0-5 III.The gamma-ray binary 1FGL J1018.6-5856, discovered by the Fermi Large Area Telescope, consists of an O6 V((f)) star and a suspected rapidly spinning pulsar. I exploit the 6.5 yr gamma-ray data to search for long-term changes in the properties of the 16.531±0.006 day orbital modulation. The best

  12. Low Temperature Thermoelectric Properties and Aging Phenomena of Nanostructured p-TYPE Bi2-XSbXTe3 (x = 1.46, 1.48, 1.52 and 1.55)

    NASA Astrophysics Data System (ADS)

    Hitchcock, Dale; Liu, Yen-Liang; Liu, Yufei; Tritt, Terry M.; He, Jian; Liu, Chia-Jyi

    2013-08-01

    Over the past decade the widely used p-type (Bi2-xSbx)Te3 bulk thermoelectric materials have been subject to various nanostructuring processes for higher thermoelectric performance. However, these nanostructuring processing were conducted on compositions optimized for bulk materials (x 1.52-1.55). This leads to the question of whether the optimal composition for bulk materials is the same for their nanoscale counterparts. In this work we hydrothermally grew Bi2-xSbxTe3 nanopowders (nominally, x = 1.46, 1.48, 1.52 and 1.55) and measured their thermoelectric properties on cold-pressed vacuum-sintered pellets (74-78% of the theoretical density) below 300 K. The measurements were conducted 18 months apart to probe the aging phenomena, with the samples stored in ambient conditions. We have found that (i) the peak of thermopower shifts to lower temperatures upon nanostructuring but it shifts back to higher temperatures upon aging; (ii) the electrical conductivity degrades by a factor of 1.5-2.3 upon aging while the temperature dependence is largely retained; and (iii) the ZT of freshly made samples is sensitive to the x value, a maximum ZT 1.25( 0.62) at 270 K ( 255 K) was attained in the freshly made sample x = 1.55(x = 1.46), respectively; while the ZT of aged samples is significantly lowered by a factor of 2-4 but lesser x-dependent. These observations have been discussed in the context of charge buildup and compensation at grain boundaries.

  13. Imaging Dirac-mass disorder from magnetic dopant atoms in the ferromagnetic topological insulator Crx(Bi0.1Sb0.9)2-xTe3.

    PubMed

    Lee, Inhee; Kim, Chung Koo; Lee, Jinho; Billinge, Simon J L; Zhong, Ruidan; Schneeloch, John A; Liu, Tiansheng; Valla, Tonica; Tranquada, John M; Gu, Genda; Davis, J C Séamus

    2015-02-03

    To achieve and use the most exotic electronic phenomena predicted for the surface states of 3D topological insulators (TIs), it is necessary to open a "Dirac-mass gap" in their spectrum by breaking time-reversal symmetry. Use of magnetic dopant atoms to generate a ferromagnetic state is the most widely applied approach. However, it is unknown how the spatial arrangements of the magnetic dopant atoms influence the Dirac-mass gap at the atomic scale or, conversely, whether the ferromagnetic interactions between dopant atoms are influenced by the topological surface states. Here we image the locations of the magnetic (Cr) dopant atoms in the ferromagnetic TI Cr0.08(Bi0.1Sb0.9)1.92Te3. Simultaneous visualization of the Dirac-mass gap Δ(r) reveals its intense disorder, which we demonstrate is directly related to fluctuations in n(r), the Cr atom areal density in the termination layer. We find the relationship of surface-state Fermi wavevectors to the anisotropic structure of Δ(r) not inconsistent with predictions for surface ferromagnetism mediated by those states. Moreover, despite the intense Dirac-mass disorder, the anticipated relationship [Formula: see text] is confirmed throughout and exhibits an electron-dopant interaction energy J* = 145 meV·nm(2). These observations reveal how magnetic dopant atoms actually generate the TI mass gap locally and that, to achieve the novel physics expected of time-reversal symmetry breaking TI materials, control of the resulting Dirac-mass gap disorder will be essential.

  14. Imaging Dirac-mass disorder from magnetic dopant atoms in the ferromagnetic topological insulator Crx(Bi0.1Sb0.9)2-xTe3

    DOE PAGES

    Lee, Inhee; Kim, Chung Koo; Lee, Jinho; ...

    2015-01-20

    To achieve and use the most exotic electronic phenomena predicted for the surface states of 3D topological insulators (TIs), it is necessary to open a “Dirac-mass gap” in their spectrum by breaking time-reversal symmetry. Use of magnetic dopant atoms to generate a ferromagnetic state is the most widely applied approach. However, it is unknown how the spatial arrangements of the magnetic dopant atoms influence the Dirac-mass gap at the atomic scale or, conversely, whether the ferromagnetic interactions between dopant atoms are influenced by the topological surface states. Here we image the locations of the magnetic (Cr) dopant atoms in themore » ferromagnetic TI Cr₀.₀₈(Bi₀.₁Sb₀.₉)₁.₉₂Te₃. Simultaneous visualization of the Dirac-mass gap Δ(r) reveals its intense disorder, which we demonstrate is directly related to fluctuations in n(r), the Cr atom areal density in the termination layer. We find the relationship of surface-state Fermi wavevectors to the anisotropic structure of Δ(r) not inconsistent with predictions for surface ferromagnetism mediated by those states. Moreover, despite the intense Dirac-mass disorder, the anticipated relationship Δ(r)∝n(r) is confirmed throughout and exhibits an electron–dopant interaction energy J* = 145 meV·nm². In addition, these observations reveal how magnetic dopant atoms actually generate the TI mass gap locally and that, to achieve the novel physics expected of time-reversal symmetry breaking TI materials, control of the resulting Dirac-mass gap disorder will be essential.« less

  15. Imaging Dirac-mass disorder from magnetic dopant atoms in the ferromagnetic topological insulator Crx(Bi0.1Sb0.9)2-xTe3

    PubMed Central

    Lee, Inhee; Kim, Chung Koo; Lee, Jinho; Billinge, Simon J. L.; Zhong, Ruidan; Schneeloch, John A.; Liu, Tiansheng; Valla, Tonica; Tranquada, John M.; Gu, Genda; Davis, J. C. Séamus

    2015-01-01

    To achieve and use the most exotic electronic phenomena predicted for the surface states of 3D topological insulators (TIs), it is necessary to open a “Dirac-mass gap” in their spectrum by breaking time-reversal symmetry. Use of magnetic dopant atoms to generate a ferromagnetic state is the most widely applied approach. However, it is unknown how the spatial arrangements of the magnetic dopant atoms influence the Dirac-mass gap at the atomic scale or, conversely, whether the ferromagnetic interactions between dopant atoms are influenced by the topological surface states. Here we image the locations of the magnetic (Cr) dopant atoms in the ferromagnetic TI Cr0.08(Bi0.1Sb0.9)1.92Te3. Simultaneous visualization of the Dirac-mass gap Δ(r) reveals its intense disorder, which we demonstrate is directly related to fluctuations in n(r), the Cr atom areal density in the termination layer. We find the relationship of surface-state Fermi wavevectors to the anisotropic structure of Δ(r) not inconsistent with predictions for surface ferromagnetism mediated by those states. Moreover, despite the intense Dirac-mass disorder, the anticipated relationship Δ(r)∝n(r) is confirmed throughout and exhibits an electron–dopant interaction energy J* = 145 meV·nm2. These observations reveal how magnetic dopant atoms actually generate the TI mass gap locally and that, to achieve the novel physics expected of time-reversal symmetry breaking TI materials, control of the resulting Dirac-mass gap disorder will be essential. PMID:25605947

  16. AN APPARENTLY EXTENDED INFRARED COUNTERPART TO 1E 1740.7-2942

    SciTech Connect

    MartI, J.; Sanchez-Sutil, J. R.; Munoz-Arjonilla, A. J.; Sanchez-Ayaso, E.; Garcia-Hernandez, M. T.

    2010-10-01

    We present the results of a revised search for the near-infrared counterpart to the microquasar 1E 1740.7-2942, which has eluded identification despite the many years elapsed since its discovery. By taking into account new astrometric information, we have been successful to identify a single near-infrared source, with apparent non-stellar morphology, whose position agrees well with that of the microquasar X-ray and radio-emitting core at the subarcsecond level. The possible implications of this finding with respect to the nature of 1E 1740.7-2942 are discussed.

  17. OOD/OOP experience in the Science Operations Center part of the ground system for X ray Timing Explorer mission

    NASA Technical Reports Server (NTRS)

    Choudhary, Abdur Rahim

    1994-01-01

    The Science Operations Center (SOC) for the X-ray Timing Explorer (XTE) mission is an important component of the XTE ground system. Its mandate includes: (1) command and telemetry for the three XTE instruments, using CCSDS standards; (2) monitoring of the real-time science operations, reconfiguration of the experiment and the instruments, and real-time commanding to address the targets of opportunity (TOO) and alternate observations; and (3) analysis, processing, and archival of the XTE telemetry, and the timely delivery of the data products to the principal investigator (PI) teams and the guest observers (GO). The SOC has two major components: the science operations facility (SOF) that addresses the first two objectives stated above and the guest observer facility (GOF) that addresses the third. The SOF has subscribed to the object oriented design and implementation; while the GOF uses the traditional approach in order to take advantage of the existing software developed in support of previous missions. This paper details the SOF development using the object oriented design (OOD), and its implementation using the object oriented programming (OOP) in C++ under Unix environment on client-server architecture using Sun workstations. It also illustrates how the object oriented (OO) and the traditional approaches coexist in SOF and GOF, the lessons learned, and how the OOD facilitated the distributed software development collaboratively by four different teams. Details are presented for the SOF system, its major subsystems, its interfaces with the rest of the XTE ground data system, and its design and implementation approaches.

  18. Black holes

    PubMed Central

    Brügmann, B.; Ghez, A. M.; Greiner, J.

    2001-01-01

    Recent progress in black hole research is illustrated by three examples. We discuss the observational challenges that were met to show that a supermassive black hole exists at the center of our galaxy. Stellar-size black holes have been studied in x-ray binaries and microquasars. Finally, numerical simulations have become possible for the merger of black hole binaries. PMID:11553801

  19. 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.

  20. No Radio Flaring Detected from Cygnus X-3 at 3 GHz by Allen Telescope Array

    NASA Astrophysics Data System (ADS)

    Williams, P. K. G.; Bower, G. C.; Tomsick, J. A.; Bodaghee, A.; Corbet, R. H. D.

    2011-01-01

    Following the announcement of a 98 GHz flare from the microquasar Cygnus X-3 (ATel #3130), we observed it with the Allen Telescope Array (Welch et al., 2009 Proc. IEEE 97 1438 for 2.5 hours beginning at 2011 January 28.848 UT (MJD 55589.848), about 4.0 hours after the 98 GHz observations concluded.

  1. Black holes.

    PubMed

    Brügmann, B; Ghez, A M; Greiner, J

    2001-09-11

    Recent progress in black hole research is illustrated by three examples. We discuss the observational challenges that were met to show that a supermassive black hole exists at the center of our galaxy. Stellar-size black holes have been studied in x-ray binaries and microquasars. Finally, numerical simulations have become possible for the merger of black hole binaries.

  2. Observations of some X-ray transients with RXTE

    NASA Astrophysics Data System (ADS)

    Borozdin, Konstantin N.; Priedhorsky, William C.; Revnivtsev, Mikhail G.; Emelyanov, Artem N.; Trudolyubov, Sergey P.; Titarchuk, Lev G.; Vikhlinin, Alexey A.

    2000-04-01

    We present results of observations of several X-ray transients with RXTE in 1996-1998, namely, GRS 1739-278, XTE J1748-288, GS 1354-64. 2S1803-245 and XTE J0421+560 (CI Cam). We studied light curves and spectra of their outbursts and compared them with observations of other X-ray transients. We discuss fits of high state spectra with BMC model, and similarities and differences between black holes and neutron stars in their low state. Special attention is paid to CI Cam as possible legate for new class of X-ray transients. .

  3. Observations of some x-ray transients with RXTE

    NASA Astrophysics Data System (ADS)

    Borozdin, K.; Priedhorsky, W.

    1999-11-01

    We present results of observations of several X-ray transients with RXTE in 1996-1998, namely, GRS 1739-278, XTE J1748-288, GS 1354-64, 2S1803-245 and XTE J0421+560 (CI Cam). We studied light curves and spectra of their outbursts and compared them with observations of other X-ray transients. We discuss fits of high state spectra with BMC model, and similarities and differences between black holes and neutron stars in their low state. Special attention is paid to CI Cam as possible legate for new class of X-ray transients.

  4. Zone leveling and solution growth of complex compound semiconductors in space

    NASA Technical Reports Server (NTRS)

    Bachmann, K. J.

    1986-01-01

    A research program on complex semiconducting compounds and alloys was completed that addressed the growth of single crystals of CdSe(y)Te(1-y), Zn(x)Cd(1-x)Te, Mn(x)Cd(1-x)Te, InP(y)As(1-y) and CuInSe2 and the measurement of fundamental physico-chemical properties characterizing the above materials. The purpose of this ground based research program was to lay the foundations for further research concerning the growth of complex ternary compound semiconductors in a microgravity environment.

  5. OBSERVATIONS OF SOME X-RAY TRANSIENTS WITH RXTE

    SciTech Connect

    K. BOROZDIN; W. PRIEDHORSKY; ET AL

    1999-11-01

    We present results of observations of several X-ray transients with RXTE in 1996-1998, namely, GRS 1739-278, XTE J1748-288, GS 1354-64, 2S1803-245 and XTE J0421+560 (CI Cam). We studied light curves and spectra of their outbursts and compared them with observations of other X-ray transients. We discuss fits of high state spectra with BMC model, and similarities and differences between black holes and neutron stars in their low state. Special attention is paid to CI Cam as possible legate for new class of X-ray transients.

  6. Design, development and testing of the x-ray timing explorer High Gain Antenna System

    NASA Technical Reports Server (NTRS)

    Lecha, Javier; Woods, Claudia; Phan, Minh

    1995-01-01

    The High Gain Antenna System (HGAS), consisting of two High Gain Antenna Deployment Systems (HGADS) and two Antenna Pointing Systems (APS), is used to position two High Gain Antennas (HGA) on the X-Ray Timing Explorer (XTE). A similar APS will be used on the upcoming Tropical Rainfall Measuring Mission (TRMM). Both XTE and TRMM are NASA in-house satellites. The salient features of the system include the two-axis gimbal and control electronics of the APS and the spring deployment and latch/release mechanisms of the HGADS. This paper describes some of the challenges faced in the design and testing of this system and their resolutions.

  7. High efficiency cadmium and zinc telluride-based thin film solar cells

    SciTech Connect

    Rohatgi, A.; Summers, C.J.; Erbil, A.; Sudharsanan, R.; Ringel, S. . School of Electrical Engineering)

    1990-10-01

    Polycrystalline Cd{sub 1-x}Zn{sub x}Te and Cd{sub 1-x}Mn{sub x}Te films with a band gap of 1.7 eV were successfully grown on glass/SnO{sub 2}/CdS substrates by molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD), respectively. Polycrystalline Cd{sub 1-x}Zn{sub x}Te films grown by MBE resulted in uniform composition and sharp interfaces. However, polycrystalline Cd{sub 1-x}Mn{sub x}Te films grown by MOCVD showed nonuniform compositions and evidence of manganese accumulation at the Cd{sub 1-x}Mn{sub x}Te/CdS interface. We found that manganese interdiffuses and replaces cadmium in the CdS film. By improving the CdTe/CdS interface and, thus, reducing the collection function effects, the efficiency of the MOCVD CdTe cell can be improved to about 13.5%. MBE-grown CdTe cells also produced 8%--9% efficiencies. The standard CdTe process was not optimum for ternary films and resulted in a decrease in the band gap. Recent results indicate that CdCl{sub 2} + ZnCl{sub 2} chemical treatment may prevent the band-gap reduction, and that chromate etch (rather than bromine etch) may provide the solution to contact resistance in the ternary cells.

  8. The optical counterparts of accreting millisecond X-ray pulsars during quiescence

    NASA Astrophysics Data System (ADS)

    D'Avanzo, P.; Campana, S.; Casares, J.; Covino, S.; Israel, G. L.; Stella, L.

    2009-12-01

    Context: Eight accreting millisecond X-ray pulsars (AMXPs) are known to date. Although these systems are well studied at high energies, very little information is available for their optical/NIR counterparts. Up to now, only two of them, SAX J1808.4-3658 and IGR J00291+5934, have a secure multi-band detection of their optical counterparts in quiescence. Aims: All these systems are transient low-mass X-ray binaries. Optical and NIR observations carried out during quiescence give a unique opportunity to constrain the nature of the donor star and to investigate the origin of the observed quiescent luminosity at long wavelengths. In addition, optical observations can be fundamental as they ultimately allow us to estimate the compact object mass through mass function measurements. Methods: Using data obtained with the ESO-Very Large Telescope, we performed a deep optical and NIR photometric study of the fields of XTE J1814-338 and of the ultracompact systems XTE J0929-314 and XTE J1807-294 during quiescence in order to look for the presence of a variable counterpart. If suitable candidates were found, we also carried out optical spectroscopy. Results: We present here the first multi-band (VR) detection of the optical counterpart of XTE J1814-338 in quiescence together with its optical spectrum. The optical light curve shows variability in both bands consistent with a sinusoidal modulation at the known 4.3 h orbital period and presents a puzzling decrease of the V-band flux around superior conjunction that may be interpreted as a partial eclipse. The marginal detection of the very faint counterpart of XTE J0929-314 and deep upper limits for the optical/NIR counterpart of XTE J1807-294 are also reported. We also briefly discuss the results reported in the literature for the optical/NIR counterpart of XTE J1751-305. Conclusions: Our findings are consistent with AMXPs being systems containing an old, weakly magnetized neutron star, reactivated as a millisecond radio pulsar

  9. Estimating the contribution of Galactic sources to the diffuse neutrino flux

    NASA Astrophysics Data System (ADS)

    Anchordoqui, Luis A.; Goldberg, Haim; Paul, Thomas C.; da Silva, Luiz H. M.; Vlcek, Brian J.

    2014-12-01

    Motivated by recent IceCube observations we reexamine the idea that microquasars are high energy neutrino emitters. By stretching to the maximum the parameters of the Fermi engine we show that the nearby high-mass x-ray binary LS 5039 could accelerate protons up to above about 20 PeV. These highly relativistic protons could subsequently interact with the plasma producing neutrinos up to the maximum observed energies. After that we adopt the spatial density distribution of high-mass x-ray binaries obtained from the deep INTEGRAL Galactic plane survey, and we assume LS 5039 typifies the microquasar population to demonstrate that these powerful compact sources could provide a dominant contribution to the diffuse neutrino flux recently observed by IceCube.

  10. A method to detect positron anisotropies with Pamela data

    NASA Astrophysics Data System (ADS)

    Panico, B.; Adriani, O.; Barbarino, G. C.; Bazilevskaya, G. A.; Bellotti, R.; Boezio, M.; Bogomolov, E. A.; Bongi, M.; Bonvicini, V.; Bottai, S.; Bruno, A.; Cafagna, F.; Campana, D.; Carbone, R.; Carlson, P.; Casolino, M.; Castellini, G.; De Donato, C.; De Santis, C.; De Simone, N.; Di Felice, V.; Formato, V.; Galper, A. M.; Giaccari, U.; Karelin, A. V.; Koldashov, S. V.; Koldobskiy, S.; Krutkov, S. Y.; Kvashnin, A. N.; Leonov, A.; Malakhov, V.; Marcelli, L.; Martucci, M.; Mayorov, A. G.; Menn, W.; Merge, M.; Mikhailov, V. V.; Mocchiutti, E.; Monaco, A.; Mori, N.; Munini, R.; Osteria, G.; Palma, F.; Papini, P.; Pearce, M.; Picozza, P.; Pizzolotto, C.; Ricci, M.; Ricciarini, S. B.; Sarkar, R.; Scotti, V.; Simon, M.; Sparvoli, R.; Spillantini, P.; Stozhkov, Y. I.; Vacchi, A.; Vannuccini, E.; Vasilyev, G. I.; Voronov, S. A.; Yurkin, Y. T.; Zampa, G.; Zampa, N.; Zverev, V. G.

    2014-11-01

    The PAMELA experiment is collecting data since 2006; its results indicate the presence of a large flux of positron with respect to electrons in the CR spectrum above 10 GeV. This excess might also be originated in objects such as pulsars and microquasars or through dark matter annihilation. Here the electrons and positrons events collected by PAMELA have been analized searching for anisotropies. The analysis is performed at different angular scales and results will be presented at the conference.

  11. FERMI-LAT Observations of Galatic Transients

    NASA Technical Reports Server (NTRS)

    Hays, Elizabeth

    2010-01-01

    This slide presentation reviews the use of the Large Area Telescope on the Fermi Observatory observations of Galactic Transients. LAT all-sky monitoring is producing spectacular results for the GeV transient sky: (1) New blazars and unidentified transients (2) Probing the jet of the Cygnus X-3 microquasar (3) Discovery of gamma rays from V407 Cygni nova (4) Fast high-energy gamma-ray flares from the Crab Nebula.

  12. Search of the Galactic sources of the cosmic ray triplet with energies above 1020 eV

    NASA Astrophysics Data System (ADS)

    Gnatyk, R.; Zhdanov, V.

    2016-06-01

    Among the registered extremely high energy cosmic rays (EHECR, E > 1020 eV) there is a triplet of events in a circle with radius of 40 in the Galactic center region. With the use of the backtracking method for the calculation of EHECR trajectories in the Galactic magnetic it is shown that potential sources of galactic triplet can be microquasars SS433, GRS1915+105, magnetar SGR1900+14 and globular star cluster NGC6760.

  13. 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.

  14. The role of magnetic reconnection on jet/accretion disk systems

    NASA Astrophysics Data System (ADS)

    de Gouveia Dal Pino, E. M.; Piovezan, P. P.; Kadowaki, L. H. S.

    2010-07-01

    Context. It was proposed earlier that the relativistic ejections observed in microquasars could be produced by violent magnetic reconnection episodes at the inner disk coronal region (de Gouveia Dal Pino & Lazarian 2005). Aims: Here we revisit this model, which employs a standard accretion disk description and fast magnetic reconnection theory, and discuss the role of magnetic reconnection and associated heating and particle acceleration in different jet/disk accretion systems, namely young stellar objects (YSOs), microquasars, and active galactic nuclei (AGNs). Methods: In microquasars and AGNs, violent reconnection episodes between the magnetic field lines of the inner disk region and those that are anchored in the black hole are able to heat the coronal/disk gas and accelerate the plasma to relativistic velocities through a diffusive first-order Fermi-like process within the reconnection site that will produce intermittent relativistic ejections or plasmons. Results: The resulting power-law electron distribution is compatible with the synchrotron radio spectrum observed during the outbursts of these sources. A diagram of the magnetic energy rate released by violent reconnection as a function of the black hole (BH) mass spanning 109 orders of magnitude shows that the magnetic reconnection power is more than sufficient to explain the observed radio luminosities of the outbursts from microquasars to low luminous AGNs. In addition, the magnetic reconnection events cause the heating of the coronal gas, which can be conducted back to the disk to enhance its thermal soft X-ray emission as observed during outbursts in microquasars. The decay of the hard X-ray emission right after a radio flare could also be explained in this model due to the escape of relativistic electrons with the evolving jet outburst. In the case of YSOs a similar magnetic configuration can be reached that could possibly produce observed X-ray flares in some sources and provide the heating at the

  15. Explorer Program: X-ray Timing Explorer

    NASA Technical Reports Server (NTRS)

    1995-01-01

    This booklet describes the X-ray Timing Explorer (XTE), one in a series of Explorer missions administered by the National Aeronautics and Space Administration's (NASA) Office of Space Science and managed by the NASA Goddard Space Flight Center (GSFC). The X-ray astronomy observatory is scheduled for launch into low-Earth orbit by Delta 2 expendable launch vehicle in late summer of 1995. The mission is expected to operate for at least 2 years and will carry out in-depth timing and spectral studies of the X-ray sources in the 2 to 200 kilo-electron Volt (keV) range. XTE is intended to study the temporal and broad-band spectral phenomena associated with stellar and galactic systems containing compact objects, including neutron stars, white dwarfs, and black holes.

  16. Coordinated Millisecond X-RAY+OPTICAL too for Black Hole Transients

    NASA Astrophysics Data System (ADS)

    Spruit, Hendrik

    This is a target of opportunity proposal for simultaneous X-ray +optical observations of new soft X-ray transients or new outbursts from known transient sources. Strong X-ray/optical correlations at 0.03--5 s time scales were observed in XTE J1118+480. These turn out to be difficult to fit into a disk reprocessing model. Cyclo-synchrotron emission in the inner accretion regions and/or an outflow may be involved. The high quality of the data obtained on XTE J1118, combined with the puzzling properties of the correlation suggest that observations of this kind provide unique new diagnostics of the accretion proicess in black hole transients. This is a resubmission of a cycle 8 TOO.

  17. Coordinated Millisecond X-RAY+OPTICAL too for Black Hole Transients

    NASA Astrophysics Data System (ADS)

    Spruit, Hendrik

    This is a target of opportunity proposal for simultaneous X-ray +optical observations of new soft X-ray transients. Strong X- ray/optical correlations at 0.03--5 s time scales were observed in XTE J1118+480. These turn out to be difficult to fit into a disk reprocessing model. Cyclo-synchrotron emission in the inner accretion regions and/or an outflow may be involved. The high quality of the data obtained on XTE J1118, combined with the puzzling properties of the correlation suggest that observations of this kind provide unique new diagnostics of the accretion proicess in black hole transients. This is a resubmission of a cycle 7 TOO (not triggered).

  18. Magnetic anisotropy induced by crystal distortion in Ge{sub 1−x}Mn{sub x}Te/PbTe//KCl (001) ferromagnetic semiconductor layers

    SciTech Connect

    Knoff, W. Łusakowski, A.; Domagała, J. Z.; Minikayev, R.; Taliashvili, B.; Łusakowska, E.; Pieniążek, A.; Szczerbakow, A.; Story, T.

    2015-09-21

    Ferromagnetic resonance (FMR) study of magnetic anisotropy is presented for thin layers of IV-VI diluted magnetic semiconductor Ge{sub 1−x}Mn{sub x}Te with x = 0.14 grown by molecular beam epitaxy on KCl (001) substrate with a thin PbTe buffer. Analysis of the angular dependence of the FMR resonant field reveals that an easy magnetization axis is located near to the normal to the layer plane and is controlled by two crystal distortions present in these rhombohedral Ge{sub 1−x}Mn{sub x}Te layers: the ferroelectric distortion with the relative shift of cation and anion sub-lattices along the [111] crystal direction and the biaxial in-plane, compressive strain due to thermal mismatch.

  19. Distribution of the surface potential of epitaxial HgCdTe

    SciTech Connect

    Novikov, V. A. Grigoryev, D. V.; Bezrodnyy, D. A.; Dvoretsky, S. A.

    2014-09-08

    We studied the distribution of surface potential of the Hg{sub 1−x}Cd{sub x}Te epitaxial films grown by molecular beam epitaxy. The studies showed that the variation of the spatial distribution of surface potential in the region of the V-defect can be related to the variation of the material composition of epitaxial film. The V-defect is characterized by increased of Hg content with respect to the composition of the solid solution of Hg{sub 1−x}Cd{sub x}Te epitaxial film. In this paper, it was demonstrated that the unformed V-defects can be observed together with the macroscopic V-defects on the epitaxial film surface. These unformed V-defects can allow the creation of a complex surface potential distribution profile due to the redistribution of the solid solution composition.

  20. Effect of the microstructure on the thermoelectric properties of polycrystalline lanthanum chalcogenides

    NASA Technical Reports Server (NTRS)

    Lockwood, A.; Wood, C.; Vandersande, J.; Zoltan, A.; Parker, J.; Danielson, L.; Alexander, M.; Whittenberger, D.

    1987-01-01

    Small amounts of second phase materials can have important effects on the thermoelectric properties of polycrystalline gamma-La(3-x)X4 (X-S, Te; X in the range of 0 to 1/3). Microscopic examination by SEM of hot pressed La(3-x)Te4 samples has revealed from 1-5 vol. pct of La2O2Te, an amount which is not detected by X-ray powder diffraction measurements. This amount of La2O2Te resulting from oxygen contamination can reduce the concentration of electrons by as much as 10 to 75 percent below the electron concentration calculated for single phase La(3-x)Te4 in the composition range of greatest interest. Small amounts of second phase materials can also lower the lattice thermal conductivity by scattering low frequency phonons. These results indicate that microstructural effects should be considered when electrical and thermal properties of polycrystalline materials are analyzed.

  1. Temperature and frequency dependence of AC conductivity of new quaternary Se-Te-Bi-Pb chalcogenide glasses

    NASA Astrophysics Data System (ADS)

    Yadav, Preeti; Sharma, Ambika

    2016-05-01

    The aim of the present work is to study the temperature and frequency dependence of ac conductivity of new quaternary Se84-xTe15Bi1.0Pbx chalcogenide glasses. The Se84-xTe15Bi1.0Pbx (x = 2, 6) glassy alloys are prepared by using melt quenching technique. The temperature and frequency dependent behavior of ac conductivity σac(ω) has been carried out in the frequency range 42 Hz to 5 MHz and in the temperature range of 298-323 K below glass transition temperature. The behavior of ac conductivity is described in terms of the power law ωs. The obtained temperature dependence behavior of ac conductivity and frequency component (s) are explained by means of correlated barrier hopping model recommended by Elliot.

  2. Magnetoimpedance and magnetocapacitance of anion-substituted manganese chalcogenides

    NASA Astrophysics Data System (ADS)

    Aplesnin, S. S.; Romanova, O. B.; Korolev, V. V.; Sitnikov, M. N.; Yanushkevich, K. I.

    2017-02-01

    The magnetoresistive effect in MnSe1-XTeX manganese chalcogenides with a substitute concentration of X = 0.1 is studied by impedance spectroscopy. The magnetoimpedance above the Neel temperature is found. The obtained experimental data are explained in the framework of the model of existence of magnetic nanoareas of two types. Two activation energies in the low- and high-frequency regions are determined from the frequency and temperature dependences of the permittivity described in the Debye model. The extrema found in the temperature dependence of the pyroelectric current are consistent with the maxima in the temperature dependence of magnetization. Temperature dependence of the carrier relaxation time is established. The magnetocapacitance of the MnSe1-XTeX solid solutions is found. The change in the carrier type above the Neel temperature and the temperature of the transition to the magnetically ordered state in the MnTe nanoarea is established.

  3. Multifunctional Cu2−xTe Nanocubes Mediated Combination Therapy for Multi-Drug Resistant MDA MB 453

    PubMed Central

    Poulose, Aby Cheruvathoor; Veeranarayanan, Srivani; Mohamed, M. Sheikh; Aburto, Rebeca Romero; Mitcham, Trevor; Bouchard, Richard R.; Ajayan, Pulickel M.; Sakamoto, Yasushi; Maekawa, Toru; Kumar, D. Sakthi

    2016-01-01

    Hypermethylated cancer populations are hard to treat due to their enhanced chemo-resistance, characterized by aberrant methylated DNA subunits. Herein, we report on invoking response from such a cancer lineage to chemotherapy utilizing multifunctional copper telluride (Cu2−XTe) nanocubes (NCs) as photothermal and photodynamic agents, leading to significant anticancer activity. The NCs additionally possessed photoacoustic and X-ray contrast imaging abilities that could serve in image-guided therapeutic studies. PMID:27775048

  4. Segregation during directional melting and its implications on seeded crystal growth: A theoretical analysis

    NASA Technical Reports Server (NTRS)

    Bourret, E. D.; Favier, J. J.; Witt, A. F.

    1982-01-01

    Directional melting of binary systems, as encountered during seeding in melt growth, is analyzed for concurrent compositional changes at the crystal-melt interface. It is shown that steady state conditions cannot normally be reached during seeding and that the growth interface temperature at the initial stages of seeded growth is a function of backmelt conditions. The theoretical treatment is numerically applied to Hg1-xCdXTe and Ga-doped Ge.

  5. Distribution of zinc, resistivity, and photosensitivity in a Vertical Bridgman grown Cd1-xZnxTe ingot.

    SciTech Connect

    Babentsov,V.; Franc, J.; Fauler, A.; Fiederle, M.; James, R.B.

    2008-05-01

    We present the results of a comprehensive study of distribution of zinc, resistivity, and photosensitivity in a Cd{sub 1-x}Zn{sub x}Te ingot grown by the Vertical Bridgman method. We used several complementary methods, viz., glow discharge mass spectroscopy, photoluminescence-, resistivity-, and photosensitivity-mapping, along with photo-induced current transient spectroscopy to characterize the material. We identified electronic levels in the band-gap responsible for compensation, recombination, and photosensitivity.

  6. Thin film cadmium telluride, zinc telluride, and mercury zinc telluride solar cells. Final subcontract report, 1 July 1988--31 December 1991

    SciTech Connect

    Chu, T.L.

    1992-04-01

    This report describes research to demonstrate (1) thin film cadmium telluride solar cells with a quantum efficiency of 75% or higher at 0. 44 {mu}m and a photovoltaic efficiency of 11.5% or greater, and (2) thin film zinc telluride and mercury zinc telluride solar cells with a transparency to sub-band-gap radiation of 65% and a photovoltaic conversion efficiency of 5% and 8%, respectively. Work was directed at (1) depositing transparent conducting semiconductor films by solution growth and metal-organic chemical vapor deposition (MOCVD) technique, (2) depositing CdTe films by close-spaced sublimation (CSS) and MOCVD techniques, (3) preparing and evaluating thin film CdTe solar cells, and (4) preparing and characterizing thin film ZnTe, CD{sub 1-x}Zn{sub 1-x}Te, and Hg{sub 1-x}Zn{sub x}Te solar cells. The deposition of CdS films from aqueous solutions was investigated in detail, and their crystallographic, optical, and electrical properties were characterized. CdTe films were deposited from DMCd and DIPTe at 400{degrees}C using TEGa and AsH{sub 3} as dopants. CdTe films deposited by CSS had significantly better microstructures than those deposited by MOCVD. Deep energy states in CdTe films deposited by CSS and MOCVD were investigated. Thin films of ZnTe, Cd{sub 1- x}Zn{sub x}Te, and Hg{sub 1-x}Zn{sub x}Te were deposited by MOCVD, and their crystallographic, optical, and electrical properties were characterized. 67 refs.

  7. Effects of Ge replacement in GeTe by Ag or Sb on the Seebeck coefficient and carrier concentration modified by local electron imbalance

    NASA Astrophysics Data System (ADS)

    Levin, E. M.; Howard, A.; Straszheim, W. E.

    2015-03-01

    XRD, SEM, EDS, 125Te NMR, Seebeck coefficient, and electrical resistivity of AgxGe50-xTe50 and SbxGe50-xTe50 alloys have been studied. Replacement of Ge in GeTe by Sb significantly increases the Seebeck coefficient, while replacement by Ag decreases it. These effects can be attributed to a change in carrier concentration observed via 125Te NMR spin-lattice relaxation measurements and NMR signal position, which mostly depends on the Knight shift. Variation in carrier concentration in AgxGe50-xTe50 and SbxGe50-xTe50 can be attributed to different electron configurations of valence electrons of Ag (4d105s1) and Sb (5s25p3) compared to that of Ge (4s24p2) resulting in local electron imbalances and changing the concentration of charge carrier (holes) generated by Ge vacancies. In contrast, our 125Te NMR and Seebeck coefficient data for Ag2Sb2Ge46Te50 are similar to those observed for GeTe. This shows that effects from Ag and Sb compensate each other and indicates the existence of [Ag +Sb] pairs. The effects of Ge replacement in GeTe by Ag, Sb, or [Ag +Sb] on rhombohedral lattice distortion also have been analyzed. Interplay between the Seebeck coefficient and electrical resistivity in these alloys results in variation of power factor; the value of 45 mW/cm K2, the highest among known tellurides, was found for Sb2Ge48Te50.

  8. Multifunctional Cu2‑xTe Nanocubes Mediated Combination Therapy for Multi-Drug Resistant MDA MB 453

    NASA Astrophysics Data System (ADS)

    Poulose, Aby Cheruvathoor; Veeranarayanan, Srivani; Mohamed, M. Sheikh; Aburto, Rebeca Romero; Mitcham, Trevor; Bouchard, Richard R.; Ajayan, Pulickel M.; Sakamoto, Yasushi; Maekawa, Toru; Kumar, D. Sakthi

    2016-10-01

    Hypermethylated cancer populations are hard to treat due to their enhanced chemo-resistance, characterized by aberrant methylated DNA subunits. Herein, we report on invoking response from such a cancer lineage to chemotherapy utilizing multifunctional copper telluride (Cu2‑XTe) nanocubes (NCs) as photothermal and photodynamic agents, leading to significant anticancer activity. The NCs additionally possessed photoacoustic and X-ray contrast imaging abilities that could serve in image-guided therapeutic studies.

  9. L'astronomie dans le monde

    NASA Astrophysics Data System (ADS)

    Manfroid, J.

    2002-06-01

    Loi tchèque sur la pollution lumineuse; XTE J0929-314; Futurs amas de galaxies; Palomar 5; La météo des naines brunes; Trous noirs et galaxies elliptiques; Europe; 2MASS; Mars; Io; Matière sombre; Un objet très froid; Les oscillations stellaires; Un système lanétaire en formation; Binaire serrée; Satellites de Jupiter; Mars sous la loupe; Le Hubble nouveau

  10. Thin film cadmium telluride, zinc telluride, and mercury zinc telluride solar cells

    SciTech Connect

    Chu, T.L. )

    1992-04-01

    This report describes research to demonstrate (1) thin film cadmium telluride solar cells with a quantum efficiency of 75% or higher at 0. 44 {mu}m and a photovoltaic efficiency of 11.5% or greater, and (2) thin film zinc telluride and mercury zinc telluride solar cells with a transparency to sub-band-gap radiation of 65% and a photovoltaic conversion efficiency of 5% and 8%, respectively. Work was directed at (1) depositing transparent conducting semiconductor films by solution growth and metal-organic chemical vapor deposition (MOCVD) technique, (2) depositing CdTe films by close-spaced sublimation (CSS) and MOCVD techniques, (3) preparing and evaluating thin film CdTe solar cells, and (4) preparing and characterizing thin film ZnTe, CD{sub 1-x}Zn{sub 1-x}Te, and Hg{sub 1-x}Zn{sub x}Te solar cells. The deposition of CdS films from aqueous solutions was investigated in detail, and their crystallographic, optical, and electrical properties were characterized. CdTe films were deposited from DMCd and DIPTe at 400{degrees}C using TEGa and AsH{sub 3} as dopants. CdTe films deposited by CSS had significantly better microstructures than those deposited by MOCVD. Deep energy states in CdTe films deposited by CSS and MOCVD were investigated. Thin films of ZnTe, Cd{sub 1- x}Zn{sub x}Te, and Hg{sub 1-x}Zn{sub x}Te were deposited by MOCVD, and their crystallographic, optical, and electrical properties were characterized. 67 refs.

  11. Endothelial nitric oxide synthase in the amphibian, Xenopus tropicalis.

    PubMed

    Trajanovska, Sofie; Donald, John A

    2011-04-01

    Nitric oxide (NO) is generated by NO synthase (NOS) of which there are three isoforms: neuronal NOS (nNOS, nos1), inducible NOS (iNOS, nos2), and endothelial NOS (eNOS, nos3). This study utilised the genome of Xenopus tropicalis to sequence a nos3 cDNA and determine if eNOS protein is expressed in blood vessels. A nos3 cDNA was sequenced that encoded a 1177 amino acid protein called XteNOS, which showed closest sequence identity to mammalian eNOS protein. The X. tropicalis nos3 gene and eNOS protein were determined to be an orthologue of mammalian nos3 and eNOS using gene synteny and phylogenetic analyses, respectively. In X. tropicalis, nos3 mRNA expression was highest in lung and skeletal muscle and lower in the liver, gut, kidney, heart and brain. Western analysis of kidney protein using an affinity-purified anti-XteNOS produced a single band at 140kDa. Immunohistochemistry showed XteNOS immunoreactivity in the proximal tubule of the kidney and endocardium of the heart, but not in the endothelium of blood vessels. Thus, X. tropicalis has a nos3 gene that appears not to be expressed in the vascular endothelium.

  12. Weak antilocalization effect of topological crystalline insulator Pb(1-x)Sn(x)Te nanowires with tunable composition and distinct {100} facets.

    PubMed

    Safdar, Muhammad; Wang, Qisheng; Wang, Zhenxing; Zhan, Xueying; Xu, Kai; Wang, Fengmei; Mirza, Misbah; He, Jun

    2015-04-08

    Pb(1-x)Sn(x)Te is a unique topological crystalline insulator (TCI) that undergoes a topological phase transition from topological trivial insulator to TCI with the change of Sn content and temperature. Meanwhile, the surface states properties of Pb(1-x)Sn(x)Te are strongly dependent on crystallographic plane orientation. In this work, we first reported controllable synthesis of rectangular prismatic Pb(x)Sn(1-x)Te nanowires by vapor deposition method. Rectangular prismatic Pb(x)Sn(1-x)Te nanowires exhibits distinct {100} surfaces. Furthermore, The Sn composition of Pb(1-x)Sn(x)Te nanowires can be continuously controlled from 0 to 1. Low temperature magnetotransport shows that PbTe nanowire exhibits weak localization (WL) effect, whereas Pb0.5Sn0.5Te and Pb0.2Sn0.8Te nanowires display pronounced weak antilocalization (WAL) effect. This transition is explained by the topological phase transform of Pb(1-x)Sn(x)Te from trivial to nontrivial insulator with Sn content (x) exceeding 0.38. Pb(x)Sn(1-x)Te nanowires synthesized in this work lay a foundation for probing spin-correlated electron transport and show great potentials for future applications of tunable spintronic devices.

  13. Transient pulsed radio emission from a magnetar

    NASA Astrophysics Data System (ADS)

    Camilo, Fernando; Ransom, Scott M.; Halpern, Jules P.; Reynolds, John; Helfand, David J.; Zimmerman, Neil; Sarkissian, John

    2006-08-01

    Anomalous X-ray pulsars (AXPs) are slowly rotating neutron stars with very bright and highly variable X-ray emission that are believed to be powered by ultra-strong magnetic fields of >1014 G, according to the `magnetar' model. The radio pulsations that have been observed from more than 1,700 neutron stars with weaker magnetic fields have never been detected from any of the dozen known magnetars. The X-ray pulsar XTE J1810 - 197 was revealed (in 2003) as the first AXP with transient emission when its luminosity increased 100-fold from the quiescent level; a coincident radio source of unknown origin was detected one year later. Here we show that XTE J1810 - 197 emits bright, narrow, highly linearly polarized radio pulses, observed at every rotation, thereby establishing that magnetars can be radio pulsars. There is no evidence of radio emission before the 2003 X-ray outburst (unlike ordinary pulsars, which emit radio pulses all the time), and the flux varies from day to day. The flux at all radio frequencies is approximately equal-and at >20GHz XTE J1810 - 197 is currently the brightest neutron star known. These observations link magnetars to ordinary radio pulsars, rule out alternative accretion models for AXPs, and provide a new window into the coronae of magnetars.

  14. Revealing Surface States in In-Doped SnTe Nanoplates with Low Bulk Mobility.

    PubMed

    Shen, Jie; Xie, Yujun; Cha, Judy J

    2015-06-10

    Indium (In) doping in topological crystalline insulator SnTe induces superconductivity, making In-doped SnTe a candidate for a topological superconductor. SnTe nanostructures offer well-defined nanoscale morphology and high surface-to-volume ratios to enhance surface effects. Here, we study In-doped SnTe nanoplates, In(x)Sn(1-x)Te, with x ranging from 0 to 0.1 and show they superconduct. More importantly, we show that In doping reduces the bulk mobility of In(x)Sn(1-x)Te such that the surface states are revealed in magnetotransport despite the high bulk carrier density. This is manifested by two-dimensional linear magnetoresistance in high magnetic fields, which is independent of temperature up to 10 K. Aging experiments show that the linear magnetoresistance is sensitive to ambient conditions, further confirming its surface origin. We also show that the weak antilocalization observed in In(x)Sn(1-x)Te nanoplates is a bulk effect. Thus, we show that nanostructures and reducing the bulk mobility are effective strategies to reveal the surface states and test for topological superconductors.

  15. Preparation and physical properties of MgxFeTe with tetragonal phase

    NASA Astrophysics Data System (ADS)

    Lee, W. H.; Chuang, M. C.; Syu, K. J.; Chen, S. C.; Chen, Y. Y.

    2014-03-01

    Unlike Fe1.01Se, which has a superconducting Tc near 8 K, Fe1+xTe shows no superconductivity though it forms the same tetragonal structure with 0.06 < x <0.17. The excess Fe (2) in Fe1+xTe not only stabilizes the PbO-type crystal structure with space group P4/nmm but also is strongly magnetic as an electron donor. According to the spin fluctuation driven scenario of superconductivity the results indicate that FeTe with doping is a likely higher-temperature superconductor. In order to reduce the magnetic strength and keep the same tetragonal structure in Fe1+xTe, in this work, we have prepared single phase samples MgxFeTe with x around 0.1. Magnetic and electrical properties, the magnesium positions in the crystal structure as well as the possibility of high-Tc superconductivity in the MgxFeTe system investigated will be discussed. Supported by the National Science Council of Republic of China under Contract Number NSC-102-2112-M-194-005-MY3.

  16. Transient pulsed radio emission from a magnetar.

    PubMed

    Camilo, Fernando; Ransom, Scott M; Halpern, Jules P; Reynolds, John; Helfand, David J; Zimmerman, Neil; Sarkissian, John

    2006-08-24

    Anomalous X-ray pulsars (AXPs) are slowly rotating neutron stars with very bright and highly variable X-ray emission that are believed to be powered by ultra-strong magnetic fields of >10(14) G, according to the 'magnetar' model. The radio pulsations that have been observed from more than 1,700 neutron stars with weaker magnetic fields have never been detected from any of the dozen known magnetars. The X-ray pulsar XTE J1810-197 was revealed (in 2003) as the first AXP with transient emission when its luminosity increased 100-fold from the quiescent level; a coincident radio source of unknown origin was detected one year later. Here we show that XTE J1810-197 emits bright, narrow, highly linearly polarized radio pulses, observed at every rotation, thereby establishing that magnetars can be radio pulsars. There is no evidence of radio emission before the 2003 X-ray outburst (unlike ordinary pulsars, which emit radio pulses all the time), and the flux varies from day to day. The flux at all radio frequencies is approximately equal--and at >20 GHz XTE J1810-197 is currently the brightest neutron star known. These observations link magnetars to ordinary radio pulsars, rule out alternative accretion models for AXPs, and provide a new window into the coronae of magnetars.

  17. Probing the Masses and Radii of Donor Stars in Eclipsing X-Ray Binaries with the Swift Burst Alert Telescope

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

    Physical parameters of both the mass donor and compact object can be constrained in X-ray binaries with well-defined eclipses, as our survey of wind-fed supergiant X-ray binaries IGR J16393-4643, IGR J16418-4532, IGR J16479-4514, IGR J18027-2016, and XTE J1855-026 reveals. Using the orbital period and Kepler’s third law, we express the eclipse half-angle in terms of radius, inclination angle, and the sum of the masses. Pulse-timing and radial velocity curves can give masses of both the donor and compact object as in the case of the “double-lined” binaries IGR J18027-2016 and XTE J1855-026. The eclipse half angles are {15}-2+3, {31.7}-0.8+0.7, 32 ± 2,34 ± 2, and 33.6+/- 0.7 degrees for IGR J16393-4643, IGR J16418-4532, IGR J16479-4514, IGR J18027-2016, and XTE 1855-026, respectively. In wind-fed systems, the primary not exceeding the Roche-lobe size provides an upper limit on system parameters. In IGR J16393-4643, spectral types of B0 V or B0-5 III are found to be consistent with the eclipse duration and Roche-lobe, but the previously proposed donor stars in IGR J16418-4532 and IGR J16479-4514 were found to be inconsistent with the Roche-lobe size. Stars with spectral types O7.5 I and earlier are possible. For IGR J18027-2016, the mass and radius of the donor star lie between 18.6-19.4 {M}⊙ and 17.4-19.5 {R}⊙ . We constrain the neutron star mass between 1.37 and 1.43 {M}⊙ .We find the mass and radius of the donor star in XTE J1855-026 to lie between 19.6-20.2 {M}⊙ and 21.5-23.0 {R}⊙ . The neutron star mass was constrained to 1.77-1.82 {M}⊙ . Eclipse profiles are asymmetric in IGR J18027-2016 and XTE J1855-026, which we attribute to accretion wakes.

  18. The jet and arc molecular clouds toward Westerlund 2, RCW 49, and HESS J1023–575; {sup 12}CO and {sup 13}CO (J = 2-1 and J = 1-0) observations with NANTEN2 and Mopra telescope

    SciTech Connect

    Furukawa, N.; Ohama, A.; Fukuda, T.; Torii, K.; Hayakawa, T.; Sano, H.; Okuda, T.; Yamamoto, H.; Moribe, N.; Mizuno, A.; Maezawa, H.; Onishi, T.; Kawamura, A.; Mizuno, N.; Dawson, J. R.; Dame, T. M.; Yonekura, Y.; Aharonian, F.; De Oña Wilhelmi, E.; Rowell, G. P. E-mail: fukui@a.phys.nagoya-u.ac.jp; and others

    2014-02-01

    We have made new CO observations of two molecular clouds, which we call 'jet' and 'arc' clouds, toward the stellar cluster Westerlund 2 and the TeV γ-ray source HESS J1023–575. The jet cloud shows a linear structure from the position of Westerlund 2 on the east. In addition, we have found a new counter jet cloud on the west. The arc cloud shows a crescent shape in the west of HESS J1023–575. A sign of star formation is found at the edge of the jet cloud and gives a constraint on the age of the jet cloud to be ∼Myr. An analysis with the multi CO transitions gives temperature as high as 20 K in a few places of the jet cloud, suggesting that some additional heating may be operating locally. The new TeV γ-ray images by H.E.S.S. correspond to the jet and arc clouds spatially better than the giant molecular clouds associated with Westerlund 2. We suggest that the jet and arc clouds are not physically linked with Westerlund 2 but are located at a greater distance around 7.5 kpc. A microquasar with long-term activity may be able to offer a possible engine to form the jet and arc clouds and to produce the TeV γ-rays, although none of the known microquasars have a Myr age or steady TeV γ-rays. Alternatively, an anisotropic supernova explosion which occurred ∼Myr ago may be able to form the jet and arc clouds, whereas the TeV γ-ray emission requires a microquasar formed after the explosion.

  19. Magnetic reconnection process in accretion disk systems

    NASA Astrophysics Data System (ADS)

    Piovezan, P.; de Gouveia Dal Pino, E. M.

    2009-08-01

    At the present study, we investigate the role of magnetic reconnection in three different astrophysical systems, namely young stellar objects (YSO's), microquasars, and active galactic nuclei (AGN's). In the case of microquasars and AGN's, violent reconnection episodes between the magnetic field lines of the inner disk region (which are established by a turbulent dynamo) and those anchored into the black hole are able to heat the coronal/disk gas and accelerate particles to relativistic velocities through a diffusive first-order Fermi-like process within the reconnection site that will produce relativistic blobs. The heating of the coronal/disk gas is able to produce a steep X-ray spectrum with a luminosity that is consistent with the observations and we argue that it is being produced mainly at the foot of the reconnection zone, while the Fermi-like acceleration process within the reconnection site results a power-law electron distribution with N(E) ∝ E-α, with α=5/2, and a corresponding synchrotron radio power-law spectrum with a spectral index that is compatible with that observed during the radio flares in microquasars (Sν ∝ ν-0.75). The scaling laws that we derive for AGN's indicate that the same mechanism may be occurring there. Finally, in the case of the YSO's, a similar magnetic configuration can be reached. The amount of magnetic energy that can be extracted from the inner disk region can heat the coronal gas to temperatures of the order of 10^8 K and could explain the observed X-ray flaring emission.

  20. The Jet and Arc Molecular Clouds toward Westerlund 2, RCW 49, and HESS J1023-575 12CO and 13CO (J = 2-1 and J = 1-0) observations with NANTEN2 and Mopra Telescope

    NASA Astrophysics Data System (ADS)

    Furukawa, N.; Ohama, A.; Fukuda, T.; Torii, K.; Hayakawa, T.; Sano, H.; Okuda, T.; Yamamoto, H.; Moribe, N.; Mizuno, A.; Maezawa, H.; Onishi, T.; Kawamura, A.; Mizuno, N.; Dawson, J. R.; Dame, T. M.; Yonekura, Y.; Aharonian, F.; de Oña Wilhelmi, E.; Rowell, G. P.; Matsumoto, R.; Asahina, Y.; Fukui, Y.

    2014-02-01

    We have made new CO observations of two molecular clouds, which we call "jet" and "arc" clouds, toward the stellar cluster Westerlund 2 and the TeV γ-ray source HESS J1023-575. The jet cloud shows a linear structure from the position of Westerlund 2 on the east. In addition, we have found a new counter jet cloud on the west. The arc cloud shows a crescent shape in the west of HESS J1023-575. A sign of star formation is found at the edge of the jet cloud and gives a constraint on the age of the jet cloud to be ~Myr. An analysis with the multi CO transitions gives temperature as high as 20 K in a few places of the jet cloud, suggesting that some additional heating may be operating locally. The new TeV γ-ray images by H.E.S.S. correspond to the jet and arc clouds spatially better than the giant molecular clouds associated with Westerlund 2. We suggest that the jet and arc clouds are not physically linked with Westerlund 2 but are located at a greater distance around 7.5 kpc. A microquasar with long-term activity may be able to offer a possible engine to form the jet and arc clouds and to produce the TeV γ-rays, although none of the known microquasars have a Myr age or steady TeV γ-rays. Alternatively, an anisotropic supernova explosion which occurred ~Myr ago may be able to form the jet and arc clouds, whereas the TeV γ-ray emission requires a microquasar formed after the explosion.

  1. Science of Compact X- and Gamma-ray Sources: MAXI and GLAST

    NASA Technical Reports Server (NTRS)

    Thompson, Dave

    2008-01-01

    MAXI and GLAST will be surveying the sky simultaneously. Compact objects that may show variability will be excellent targets for coordinated multiwavelength studies. Gamma-ray bursts (and afterglows), pulsars, high-mass X-ray binaries, microquasars, and active galactic nuclei are all objects whose X- and gamma-ray relationship can be explored by such observations. Of particular interest will be variable unidentified gamma-ray sources, whose contemporaneous observations by MAXI may prove decisive in identifying the source of the high-energy emission.

  2. Compton scattering of blackbody photons by relativistic electrons

    NASA Astrophysics Data System (ADS)

    Zdziarski, Andrzej A.; Pjanka, Patryk

    2013-12-01

    We present simple and accurate analytical formulas for the rates of Compton scattering by relativistic electrons integrated over the energy distribution of blackbody seed photons. Both anisotropic scattering, in which blackbody photons arriving from one direction are scattered by an anisotropic electron distribution into another direction, and scattering of isotropic seed photons are considered. Compton scattering by relativistic electrons off blackbody photons from either stars or cosmic microwave background takes place, in particular, in microquasars, colliding-wind binaries, supernova remnants, interstellar medium and the vicinity of the Sun.

  3. 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

  4. The Ballerina Experiment on the Rømer Mission

    NASA Astrophysics Data System (ADS)

    Brandt, Soren

    The Rømer mission has recently been approved as the next mission within the Danish Small Satellite Program. The scientific payload will consist of two separate experiments, the MONS and the Ballerina payloads. The primary objective of Ballerina is to provide accurate, real-time positions relayed to ground for ~ 70 Gamma Ray Bursts (GRBs) per year, and to study the temporal and spectral evolution of the early GRB X-ray afterglow. As an additional goal, Ballerina will detect and study bright X-ray transients, in particular X-ray novae and micro-quasar systems. R{\\o}mer is currently scheduled for launch in late 2003.

  5. INDUCED MAXIMUM MAGNETIC FIELD IN COSMIC OUTFLOW SYSTEM BY A RELATIVISTIC CURRENT FILAMENTATION INSTABILITY: EXACT ANALYTICAL MODEL

    SciTech Connect

    Mehdian, H.; Hajisharifi, K.; Hasanbeigi, A.

    2015-03-10

    We present an analytical study of current filamentation instability (CFI) in a fully relativistic cold plasma system, including arbitrary currents. For our purposes, we employ the cold fluid equations, together with Maxwell's equations as well as the plasma shell concept and boost frame method, to obtain an exact solution of the instability growth rate. A simple relation is found for the maximum growth rate of the CFI (for any arbitrary current system), which remarkably is used to calculate the large magnitude of an induced magnetic field in astrophysical environments such as active galactic nuclei (AGNs), microquasars, supernova remnants (SNRs), and stellar winds. We find that the magnetic field is amplified in the SNR up to the level required to justify the recent discovery of the year-scale variability in the X-ray emission of SNRs. Also, the maximum magnetic field of two and three orders higher (or two orders lower) than that of the SNR has been derived for microquasars and AGNs (or stellar winds), respectively. Moreover, making use of the exact analytical solution of the CFI, it is shown that the maximum magnetic field up to around 10{sup 8} G can be detected from a classical cold counterstreaming system after a saturation time.

  6. DETECTION OF PERSISTENT GAMMA-RAY EMISSION TOWARD SS433/W50

    SciTech Connect

    Bordas, P.; Yang, R.; Kafexhiu, E.; Aharonian, F. E-mail: ryang@mpi-hd.mpg.de

    2015-07-01

    The microquasar SS433 features the most energetic jets known in our Galaxy. A large fraction of the jet kinetic power is delivered to the surrounding W50 nebula at the jet termination shock, from which high-energy emission and cosmic-ray production have been anticipated. Here, we report on the detection of a persistent gamma-ray signal obtained with the Fermi Large Area Telescope from an unidentified source that we tentatively associate, given its 99.9% confidence level position accuracy and the lack of any other high-energy emitter counterpart in the studied region, with SS433. The obtained spectral energy distribution displays a distinct maximum at ∼250 MeV and only extends up to ∼800 MeV. We discuss the possibility that the observed gamma-ray emission is produced through proton–proton collisions at the SS433/W50 interaction regions. If the same mechanism is operating in other baryon-loaded microquasar jets, their collective contribution could represent a significant fraction of the total galactic cosmic-ray flux at GeV energies.

  7. Hard X-ray component in the Sco X-1 spectrum: Synchrotron emission from a nono-quasar

    NASA Astrophysics Data System (ADS)

    Manchanda, R. K.

    Sco X-1 is a low mass X-ray binary system and is the very first X-ray source to be discovered in 1962. From the recent observation of a resolved radio jet the souce has been included in the list of galactic microquasars. The observed spectral data in the 2-20 keV energy band fits a Free-free emission from a hot plasma. Above 20 keV, a hard tail has been reported on occasions. During our continuuing balloon borne X-ray survey in the 20-200 keV region using high sensitivity Large Area Scintillation counter Experiment, Sco X-1 was observed on two different occasions. Eventhough the total X-ray luminosity of the source different, the spectral nature of the source did not show any variation. The presence of hard X-ray flux is unmistakable. We present the spectra data in the hard X-ray band and discuss the results in terms of geometrical characteristics of the X-ray source and the observed temporal variations. It is proposed that while a core activity is similar to the micro-quasars, the absence of abrupt changes similar to GRS 1915+105, in the CGRO and RXTE data suggest a with much reduced magnitude.

  8. X-ray, Optical and Radio Observations of the Extragalactic Superbubble N7793-S26

    NASA Astrophysics Data System (ADS)

    Pannuti, Thomas; Schlegel, E. M.; Filipovic, M. D.; Crawford, E.; Payne, J.; Grimes, C. K.

    2012-01-01

    We present a multi-wavelength (X-ray, optical and radio) spatial and spectral analysis of the extragalactic superbubble N7793-S26. Prior observations and analysis of this source had revealed extended emission spanning nearly 400 parsecs at all three wavelength domains: the extended morphology of this object suggests a superbubble classification, prompting the argument that N7793-S26 is actually a microquasar. We investigate the microquasar interpretation of this source based on analysis of its spatial and spectral properties and compare N7793-S26 to another known extragalactic superbubble located in the Local Group Galaxy IC 10. We investigate the scenario that the soft X-ray sources seen at the northern and southern edges of N7793-S26 are actually supernova remnants and that the central hard X-ray source is an X-ray binary serendipitously located to give the appearance of a central engine with two jets. This scenario will be presented and discussed.

  9. What if a black hole devours too much?

    NASA Astrophysics Data System (ADS)

    Liu, Jifeng

    2016-01-01

    The formation of relativistic jets by an accreting compact object is one of the fundamental mysteries of astrophysics. While the theory is poorly understood, observations of relativistic jets from systems known as microquasars have led to a well-established phenomenology. Relativistic jets are not expected from sources with soft or supersoft X-ray spectra, although two such systems are known to produce relatively low-velocity bipolar outflows. Here we report optical spectra of an ultraluminous supersoft X-ray source (ULS) in the nearby galaxy M81 (M81 ULS-1) showing blueshifted broad Hα emission lines, characteristic of baryonic jets with relativistic speeds. The time variable jets have projected velocities ~17 per cent of the speed of light, and seem similar to those in the prototype microquasar SS 433. Such relativistic jets are not expected to be launched from white dwarfs, but an origin from a black hole or neutron star in M81 ULS-1 is hard to reconcile with its constant soft X-rays. The completely unexpected presence of relativistic jets in a ULS challenges the canonical theories for jet formation, but can be explained by a long speculated super-critically accreting black hole with optically thick outflows.

  10. Cruise Science with the Compact X-ray Spectrometer (D-CIXS) of SMART-1

    NASA Astrophysics Data System (ADS)

    Vilhu, O.; Muhli, P.; Huovelin, J.; Hakala, P.; Hannikainen, D. C.; Grande, M.; Kellett, B.

    2000-10-01

    The primary objective of the SMART-1 (ESA) mission is to test solar electric propulsion and to orbit the Moon for a nominal period of six months. The science payload includes e.g. the Demonstration of a Compact Imaging X-ray Spectrometer D-CIXS (pronounced Dee-Kicks!). Its main goal is to observe fluorescence X-rays with high spectral and spatial resolution from the Moon's surface. During the escape phase leaving Earth (15 - 17 months), D-CIXS can observe X-ray sources. Solar flares will also be monitored with the X-ray Solar Monitor (XSM). We present a potential cruise science program for selected X-ray binaries and microquasars. The long journey to the Moon provides us with an unique opportunity to study long-term variability of XRBs on a regular basis using X-ray spectroscopy. The accumulated data can be used to probe the geometry and physical properties of accretion disks of about a dozen persistently bright XRBs, and, in particular, to search for and verify the presence and stability of superorbital periods (tilted and warped disks). Further, we present simulations with D-CIXS on the long time scale behaviour of the disk-corona structure in a selected microquasar. This work is supported by the Finnish Technology Development Agency TEKES, Academy of Finland and PPARC of UK.

  11. MAGIC CONSTRAINTS ON {gamma}-RAY EMISSION FROM CYGNUS X-3

    SciTech Connect

    Aleksic, J.; Blanch, O.; Antonelli, L. A.; Bonnoli, G.; Antoranz, P.; Backes, M.; Baixeras, C.; Barrio, J. A.; Bastieri, D.; Gonzalez, J. Becerra; Bednarek, W.; Berdyugin, A.; Berger, K.; Bernardini, E.; Biland, A.; Boller, A.; Bock, R. K.; Tridon, D. Borla; Bordas, P.; Bosch-Ramon, V. E-mail: tysaito@mpp.mpg.d

    2010-09-20

    Cygnus X-3 is a microquasar consisting of an accreting compact object orbiting around a Wolf-Rayet star. It has been detected at radio frequencies and up to high-energy {gamma} rays (above 100 MeV). However, many models also predict a very high energy (VHE) emission (above hundreds of GeV) when the source displays relativistic persistent jets or transient ejections. Therefore, detecting such emission would improve the understanding of the jet physics. The imaging atmospheric Cherenkov telescope MAGIC observed Cygnus X-3 for about 70 hr between 2006 March and 2009 August in different X-ray/radio spectral states and also during a period of enhanced {gamma}-ray emission. MAGIC found no evidence for a VHE signal from the direction of the microquasar. An upper limit to the integral flux for energies higher than 250 GeV has been set to 2.2 x 10{sup -12} photons cm{sup -2} s{sup -1} (95% confidence level). This is the best limit so far to the VHE emission from this source. The non-detection of a VHE signal during the period of activity in the high-energy band sheds light on the location of the possible VHE radiation favoring the emission from the innermost region of the jets, where absorption is significant. The current and future generations of Cherenkov telescopes may detect a signal under precise spectral conditions.

  12. Relativistic baryonic jets from an ultraluminous supersoft X-ray source

    NASA Astrophysics Data System (ADS)

    Liu, Ji-Feng; Bai, Yu; Wang, Song; Justham, Stephen; Lu, You-Jun; Gu, Wei-Min; Liu, Qing-Zhong; di Stefano, Rosanne; Guo, Jin-Cheng; Cabrera-Lavers, Antonio; Álvarez, Pedro; Cao, Yi; Kulkarni, Shri

    2015-12-01

    The formation of relativistic jets by an accreting compact object is one of the fundamental mysteries of astrophysics. Although the theory is poorly understood, observations of relativistic jets from systems known as microquasars (compact binary stars) have led to a well established phenomenology. Relativistic jets are not expected to be produced by sources with soft or supersoft X-ray spectra, although two such systems are known to produce relatively low-velocity bipolar outflows. Here we report the optical spectra of an ultraluminous supersoft X-ray source (ULS) in the nearby galaxy M81 (M81 ULS-1; refs 9, 10). Unexpectedly, the spectra show blueshifted, broad Hα emission lines, characteristic of baryonic jets with relativistic speeds. These time-variable emission lines have projected velocities of about 17 per cent of the speed of light, and seem to be similar to those from the prototype microquasar SS 433 (refs 11, 12). Such relativistic jets are not expected to be launched from white dwarfs, and an origin from a black hole or a neutron star is hard to reconcile with the persistence of M81 ULS-1’s soft X-rays. Thus the unexpected presence of relativistic jets in a ULS challenges canonical theories of jet formation, but might be explained by a long-speculated, supercritically accreting black hole with optically thick outflows.

  13. Relativistic baryonic jets from an ultraluminous supersoft X-ray source.

    PubMed

    Liu, Ji-Feng; Bai, Yu; Wang, Song; Justham, Stephen; Lu, You-Jun; Gu, Wei-Min; Liu, Qing-Zhong; Di Stefano, Rosanne; Guo, Jin-Cheng; Cabrera-Lavers, Antonio; Álvarez, Pedro; Cao, Yi; Kulkarni, Shri

    2015-12-03

    The formation of relativistic jets by an accreting compact object is one of the fundamental mysteries of astrophysics. Although the theory is poorly understood, observations of relativistic jets from systems known as microquasars (compact binary stars) have led to a well established phenomenology. Relativistic jets are not expected to be produced by sources with soft or supersoft X-ray spectra, although two such systems are known to produce relatively low-velocity bipolar outflows. Here we report the optical spectra of an ultraluminous supersoft X-ray source (ULS) in the nearby galaxy M81 (M81 ULS-1; refs 9, 10). Unexpectedly, the spectra show blueshifted, broad Hα emission lines, characteristic of baryonic jets with relativistic speeds. These time-variable emission lines have projected velocities of about 17 per cent of the speed of light, and seem to be similar to those from the prototype microquasar SS 433 (refs 11, 12). Such relativistic jets are not expected to be launched from white dwarfs, and an origin from a black hole or a neutron star is hard to reconcile with the persistence of M81 ULS-1's soft X-rays. Thus the unexpected presence of relativistic jets in a ULS challenges canonical theories of jet formation, but might be explained by a long-speculated, supercritically accreting black hole with optically thick outflows.

  14. Heartbeat Oscillation detected in IGR J17091-3624

    NASA Astrophysics Data System (ADS)

    Reynolds, Mark; Miller, Jon; King, Askley

    2016-04-01

    We report on the results of ongoing monitoring observation of the Galactic micro-quasar IGR J17091-3624 with Swift/XRT in windowed timing mode. In an ~860s observation on 2016-04-13T13:05:46 UT (obsid: 00031921133), clear oscillations are detected consistent with the re-emergence of the so-called heartbeat oscillation (ATel #3230, #3418) in the accretion flow of this micro-quasar with a frequency of approximately 0.027 Hz. The source spectrum is well characterized by model consisting of the emission from an accretion disk and a hot optically thin Comptonizing corona, e.g., kT_disk ~ 0.9 keV, kT0_corona ~ 0.6 keV, tau_corona ~ 0.6, kT_e == 100 keV (chi^2/dof = 496/462), with a flux of f_x ~ 1.4e-09 erg/s/cm^2 corresponding to a luminosity of ~ 1e37 (d/8kpc)^2 erg/s in the 0.3-10.0 keV band.

  15. Influence of copper to indium atomic ratio on the properties of Cu-In-Te based thin-film solar cells prepared by low-temperature co-evaporation

    SciTech Connect

    Mise, Takahiro; Nakada, Tokio

    2012-09-15

    The influence of copper to indium atomic ratio (Cu/In) on the properties of Cu-In-Te based thin films and solar cells was investigated. The films (Cu/In = 0.38-1.17) were grown on both bare and Mo-coated soda-lime glass substrates at 250 Degree-Sign C by single-step co-evaporation using a molecular beam epitaxy system. Highly (112)-oriented CuInTe{sub 2} films were obtained at Cu/In ratios of 0.84-0.99. However, stoichiometric and Cu-rich films showed a poor film structure with high surface roughness. The films consist of polyhedron-shaped grains, which are related to the coexistence of a Cu{sub 2-x}Te phase, and significant evidence for the coexistence of the Cu{sub 2-x}Te phase in the stoichiometric and Cu-rich films is presented. KCN treatment was performed for the films in order to remove the Cu{sub 2-x}Te phase. The stoichiometric CuInTe{sub 2} thin films exhibited a high mobility above 50 cm{sup 2}/V s at room temperature after the KCN treatment. A preliminary solar cell fabricated using a 1.4-{mu}m-thick Cu-poor CuInTe{sub 2} thin film (Cu/In = 0.84, E{sub g} = 0.988 eV) yielded a total-area efficiency of 2.10%. The photovoltaic performance of the cell was improved after long-term ambient aging in dark conditions.

  16. Electronic structure of ruthenium-doped iron chalcogenides

    NASA Astrophysics Data System (ADS)

    Winiarski, M. J.; Samsel-Czekała, M.; Ciechan, A.

    2014-12-01

    The structural and electronic properties of hypothetical RuxFe1-xSe and RuxFe1-xTe systems have been investigated from first principles within the density functional theory (DFT). Reasonable values of lattice parameters and chalcogen atomic positions in the tetragonal unit cell of iron chalcogenides have been obtained with the use of norm-conserving pseudopotentials. The well known discrepancies between experimental data and DFT-calculated results for structural parameters of iron chalcogenides are related to the semicore atomic states which were frozen in the used here approach. Such an approach yields valid results of the electronic structures of the investigated compounds. The Ru-based chalcogenides exhibit the same topology of the Fermi surface (FS) as that of FeSe, differing only in subtle FS nesting features. Our calculations predict that the ground states of RuSe and RuTe are nonmagnetic, whereas those of the solid solutions RuxFe1-xSe and RuxFe1-xTe become the single- and double-stripe antiferromagnetic, respectively. However, the calculated stabilization energy values are comparable for each system. The phase transitions between these magnetic arrangements may be induced by slight changes of the chalcogen atom positions and the lattice parameters a in the unit cell of iron selenides and tellurides. Since the superconductivity in iron chalcogenides is believed to be mediated by the spin fluctuations in single-stripe magnetic phase, the RuxFe1-xSe and RuxFe1-xTe systems are good candidates for new superconducting iron-based materials.

  17. EVIDENCE OF LIGHT-BENDING EFFECTS AND ITS IMPLICATION FOR SPECTRAL STATE TRANSITIONS

    SciTech Connect

    Reis, R. C.; Miller, J. M.; Reynolds, M. T.; Fabian, A. C.; Walton, D. J.; Steiner, J. F.; Cackett, E.

    2013-01-20

    It has long been speculated that the nature of the hard X-ray corona may be an important second driver of black hole state transitions, in addition to the mass accretion rate through the disk. However, a clear physical picture of coronal changes has not yet emerged. We present results from a systematic analysis of Rossi X-Ray Timing Explorer observations of the stellar-mass black hole binary XTE J1650-500. All spectra with significant hard X-ray detections were fit using a self-consistent, relativistically blurred disk reflection model suited to high ionization regimes. Importantly, we find evidence that both the spectral and timing properties of black hole states may be partially driven by the height of the X-ray corona above the disk, and related changes in how gravitational light bending affects the corona-disk interaction. Specifically, the evolution of the power-law, thermal disk, and relativistically convolved reflection components in our spectral analysis indicates that: (1) the disk inner radius remains constant at r {sub in} =1.65 {+-} 0.08 GM/c {sup 2} (consistent with values found for the ISCO of XTE J1650-500 in other works) throughout the transition from the brighter phases of the low-hard state to the intermediate states (both the hard-intermediate and soft-intermediate), through to the soft state and back; (2) the ratio between the observed reflected X-ray flux and power-law continuum (the 'reflection fraction', R) increases sharply at the transition between the hard-intermediate and soft-intermediate states ('ballistic' jets are sometimes launched at this transition); (3) both the frequency and coherence of the high-frequency quasi-periodic oscillations observed in XTE J1650-500 increase with R. We discuss our results in terms of black hole states and the nature of black hole accretion flows across the mass scale.

  18. Raman, infrared, photoluminescence and theoretical studies of the II-VI-VI ternary CdSeTe

    NASA Astrophysics Data System (ADS)

    Feng, Z. C.; Becla, P.; Kim, L. S.; Perkowitz, S.; Feng, Y. P.; Poon, H. C.; Williams, K. P.; Pitt, G. D.

    1994-04-01

    We have examined Bridgman-grown zincblende CdSe xTe 1- x ( x < 0.36) by Raman scattering, Fourier transform infrared reflectivity, photoluminescence and theoretical analysis. The Raman data showed evidence of surface structural improvement by long-term room temperature annealing. The combined Raman and infrared data confirmed the interpretation that a third infrared mode besides the CdTe- and CdSe-like transverse optical phonon modes, arose from non-random atomic clustering. Room temperature photoluminescence spectra were obtained and compared with pseudopotential calculations.

  19. Coordinated Millisecond RXTE+OPTICAL Observations of Persistent LMXB

    NASA Astrophysics Data System (ADS)

    Spruit, Hendrik

    We propose to search for correlated X-ray/optical emission from black hole candidates and neutron star accreters. The unexpectedly fast and complex correlations between visible light and X-rays seen in our previous observations of XTE J1118+480 indicate that the visible light may be be an important source of information on the nature of the accretion flow in the inner regions of the accretion flow, and its relation with outfl;ows. Targets to be observed are the persistent black hole candidates GX 339-4 and Cyg X-1, and the neutron star accreters Cyg X-2 and the jet-source Cir X-1.

  20. Outburst of the X-ray transient in NGC 6440 and identification of the optical and quiescent X-ray counterparts

    NASA Astrophysics Data System (ADS)

    in't Zand, Jean; Pooley, Dave; Lewin, Walter; van Kerkwijk, Marten; Verbunt, Frank

    2001-08-01

    We have obtained observations with ESO NTT SUSI2 in B and R and with Chandra ACIS-S of the transient in NGC6440, which is in outburst again since before 2001 Aug 14, as discovered with RXTE ASM (http://xte.mit.edu/asmlc/ASM.html). The Chandra position of the transient coincides with the brightest source (of some 20 detected sources) in our 2000 July 4 Chandra observation, obtained when the transient was not active, and with the optical variable V2 which was active during 1998 August outburst of the transient.

  1. Ab-initio study of structural, electronic and magnetic properties of CdTe doped transition metal Co

    NASA Astrophysics Data System (ADS)

    Zitouni, A.; Bentata, Samir; Benstaali, W.; Abbar, B.

    2014-07-01

    The full potential linear augmented plane wave (FPLAPW) based on density-functional theory (DFT) is employed to study the structural, electronic and magnetic properties of transition metal Co doped CdTe. We have analyzed the structural parameters, charge and spin densities, total and partial densities of states within the generalized gradient approximation (GGA). The results show a Half-Metallic Dilute Magnetic Semiconductors (HM-DMS) character with an important magnetic moment. The results obtained, make the CoxCd1-xTe a potential promising candidate for application in spintronics.

  2. Analytical Electron Diffraction from Iii-V and II-Vi Semiconductors

    NASA Astrophysics Data System (ADS)

    Spellward, Paul

    Available from UMI in association with The British Library. This thesis describes the development and evaluation of a number of new TEM-based techniques for the measurement of composition in ternary III-V and II-VI semiconductors. New methods of polarity determination in binary and ternary compounds are also presented. The theory of high energy electron diffraction is outlined, with particular emphasis on zone axis diffraction from well-defined strings. An account of TEM microstructural studies of Cd_{rm x}Hg _{rm 1-x}Te and CdTe epitaxial layers, which provided the impetus for developing the diffraction-based analytical techniques, is given. The wide range of TEM-based compositional determination techniques is described. The use of HOLZ deficiency lines to infer composition from a lattice parameter measurement is evaluated. In the case of Cd_{ rm x}Hg_{rm 1-x}Te, it is found to be inferior to other techniques developed. Studies of dynamical aspects of HOLZ diffraction can yield information about the dispersion surface from which a measure of composition may be obtained. This technique is evaluated for Al_{rm x}Ga_{rm 1-x} As, in which it is found to be of some use, and for Cd_{rm x}Hg _{rm 1-x}Te, in which the large Debye-Waller factor associated with mercury in discovered to render the method of little value. A number of critical voltages may be measured in medium voltage TEMs. The (111) zone axis critical voltage of Cd_{rm x}Hg _{rm 1-x}Te is found to vary significantly with x and forms the basis of an accurate technique for composition measurement in that ternary compound. Other critical voltage phenomena are investigated. In Al _{rm x}Ga_ {rm 1-x}As and other light ternaries, a non-systematic critical voltage is found to vary with x, providing a good indicator of composition. Critical voltage measurements may be made by conventional CBED or by various other techniques, which may also simultaneously yield information on the spatial variation of composition. The

  3. New class of topological superconductors protected by magnetic group symmetries.

    PubMed

    Fang, Chen; Gilbert, Matthew J; Bernevig, B Andrei

    2014-03-14

    We study a new type of three-dimensional topological superconductor that exhibits Majorana zero modes (MZM) protected by a magnetic group symmetry, a combined antiunitary symmetry composed of a mirror reflection and time reversal. This new symmetry enhances the noninteracting topological classification of a superconducting vortex from Z2 to Z, indicating that multiple MZMs can coexist at the end of one magnetic vortex of unit flux. Especially, we show that a vortex binding two MZMs can be realized on the (001) surface of a topological crystalline insulator SnTe with proximity induced BCS Cooper pairing, or in bulk superconductor InxSn1-xTe.

  4. Atomic-Scale Visualization of Quasiparticle Interference on a Type-II Weyl Semimetal Surface

    NASA Astrophysics Data System (ADS)

    Zheng, Hao; Bian, Guang; Chang, Guoqing; Lu, Hong; Xu, Su-Yang; Wang, Guangqiang; Chang, Tay-Rong; Zhang, Songtian; Belopolski, Ilya; Alidoust, Nasser; Sanchez, Daniel S.; Song, Fengqi; Jeng, Horng-Tay; Yao, Nan; Bansil, Arun; Jia, Shuang; Lin, Hsin; Hasan, M. Zahid

    2016-12-01

    We combine quasiparticle interference simulation (theory) and atomic resolution scanning tunneling spectromicroscopy (experiment) to visualize the interference patterns on a type-II Weyl semimetal Mox W1 -xTe2 for the first time. Our simulation based on first-principles band topology theoretically reveals the surface electron scattering behavior. We identify the topological Fermi arc states and reveal the scattering properties of the surface states in Mo0.66 W0.34 Te2 . In addition, our result reveals an experimental signature of the topology via the interconnectivity of bulk and surface states, which is essential for understanding the unusual nature of this material.

  5. Upper limit on the radio emission from the soft gamma-ray repeater SGR 1833-0832

    NASA Astrophysics Data System (ADS)

    Burgay, M.; Possenti, A.; Esposito, P.; Israel, G. L.; Rea, N.; Sarkissian, J.; Tiengo, A.; Turolla, R.; Zane, S.; Gotz, D.; Stella, L.; Mereghetti, S.

    2010-03-01

    The soft gamma-ray repeater J1833-0832 has been discovered on 2010 March 19 thanks to the detection of a short burst by Swift (GCN #10526). Prompted by the detection of a radio outburst following the X-ray transient activity of two other magnetars, the anomalous X-ray pulsars XTE J1810-197 and 1E 1547.0-5408 (Camilo et al. 2006, Nature, 442, 892; 2007, ApJ, 666, L93), we observed the source with the 64-m Parkes radio telescope.

  6. Magnetic field effect on the Coulomb interaction of acceptors in semimagnetic quantum dot

    SciTech Connect

    Kalpana, P.; Merwyn, A.; Nithiananthi, P.; Jayakumar, K.; Reuben, Jasper D.

    2015-06-24

    The Coulomb interaction of holes in a Semimagnetic Cd{sub 1-x}Mn{sub x}Te / CdTe Spherical and Cubical Quantum Dot (SMQD) in a magnetic field is studied using variational approach in the effective mass approximation. Since these holes in QD show a pronounced collective behavior, while distinct single particle phenomena is suppressed, their interaction in confined potential becomes very significant. It has been observed that acceptor-acceptor interaction is more in cubical QD than in spherical QD which can be controlled by the magnetic field. The results are presented and discussed.

  7. High Energy Astrophysics Program (HEAP)

    NASA Technical Reports Server (NTRS)

    Angelini, Lorella; Corcoran, Michael; Drake, Stephen; McGlynn, Thomas A.; Snowden, Stephen; Mukai, Koji; Cannizzo, John; Lochner, James; Rots, Arnold; Christian, Eric; Barthelmy, Scott; Palmer, David; Mitchell, John; Esposito, Joseph; Sreekumar, P.; Hua, Xin-Min; Mandzhavidze, Natalie; Chan, Kai-Wing; Soong, Yang; Barrett, Paul

    1998-01-01

    This report reviews activities performed by the members of the USRA contract team during the 6 months of the reporting period and projected activities during the coming 6 months. Activities take place at the Goddard Space Flight Center, within the Laboratory for High Energy Astrophysics. Developments concern instrumentation, observation, data analysis, and theoretical work in astrophysics. Supported missions include advanced Satellite for Cosmology and Astrophysics (ASCA), X-Ray Timing Experiment (XTE), X-Ray Spectrometer (XRS), Astro-E, High Energy Astrophysics Science Archive Research Center (HEASARC) and others.

  8. High Energy Astrophysics Program (HEAP)

    NASA Technical Reports Server (NTRS)

    Angelini, L.

    1998-01-01

    This report reviews activities performed by members of the USRA contract team during the six months of the reporting period and projected activities during the coming six months. Activities take place at the Goddard Space Flight Center, within the Laboratory for High Energy Astrophysics. Developments concern instrumentation, observation, data analysis, and theoretical work in Astrophysics Missions supported include: Advanced Satellite for Cosmology and Astrophysics (ASCA), X-ray Timing Experiment (XTE), X-ray Spectrometer (XRS), Astro-E, High Energy Astrophysics Science Archive Research Center (HEASARC), and others.

  9. High Energy Astrophysics Research and Programmatic Support

    NASA Technical Reports Server (NTRS)

    Angelini, Lorella

    1998-01-01

    This report reviews activities performed by members of the USRA contract team during the six months of the reporting period and projected activities during the coming six months. Activities take place at the Goddard Space Flight Center, within the Laboratory for High Energy Astrophysics. Developments concern instrumentation, observation, data analysis, and theoretical work in Astrophysics. Missions supported include: Advanced Satellite for Cosmology and Astrophysics (ASCA), X-ray Timing Experiment (XTE), X-ray Spectrometer (XRS), Astro-E, High Energy Astrophysics Science Archive Research Center (HEASARC), and others.

  10. High Energy Astrophysics Research and Programmatic Support

    NASA Technical Reports Server (NTRS)

    Angelini, L. (Editor)

    1997-01-01

    This report reviews activities performed by members of the USRA contract team during the six months of the reporting period and projected activities during the coming six months. Activities take place at the Goddard Space Flight Center, within the Laboratory for High Energy Astrophysics. Developments concern instrumentation, observation, data analysis, and theoretical work in Astrophysics. Missions supported include: Advanced Satellite for Cosmology and Astrophysics (ASCA), X-ray Timing Experiment (XTE), X-ray Spectrometer (XRS), Astro-E, High Energy Astrophysics Science Archive Research Center (HEASARC), and others.

  11. High Energy Astrophysics Program

    NASA Technical Reports Server (NTRS)

    1996-01-01

    This report reviews activities performed by members of the USRA (Universities Space Research Association) contract team during the six months during the reporting period (10/95 - 3/96) and projected activities during the coming six months. Activities take place at the Goddard Space Flight Center, within the Laboratory for High Energy Astrophysics. Developments concern instrumentation, observation, data analysis, and theoretical work in Astrophysics. Missions supported include: Advanced Satellite for Cosmology and Astrophysics (ASCA), X-ray Timing Experiment (XTE), X-ray Spectrometer (XRS), Astro-E, High Energy Astrophysics Science, Archive Research Center (HEASARC), and others.

  12. High Energy Astrophysics Program

    NASA Technical Reports Server (NTRS)

    1996-01-01

    This report reviews activities performed-by members of the USRA contract team during the six months of the reporting period and projected activities during the coming six months. Activities take place at the Goddard Space Flight Center, visiting the Laboratory for High Energy Astrophysics. Developments concern instrumentation, observation, data analysis, and theoretical work in Astrophysics. Missions supported include: Advanced Satellite for Cosmology and Astrophysics (ASCA); X-ray Timing Experiment (XTE); X-ray Spectrometer (XRS); Astro-E; High Energy Astrophysics Science Archive Research Center (HEASARC), and others.

  13. ’MODESRCH’, An Improved Computer Program for Obtaining ELF/VLF/LF Mode Constants in an Earth-Ionosphere Waveguide

    DTIC Science & Technology

    1976-10-01

    0 RHO = O*C i TA-LT=iu.0 RAt T 3. Gt"AX = 50 SEP = 091 TVSt-=-1 .0 LUB=-Io0 C NUFLAG = 0 COEFi’U(1L .) b1 C UL FPU ( 21 *5UF C OEf! U ( 3 te= 4E F)’PNU...Lt20 Ili ITI TLE(K)=I BCD ( K) 11. READ 904vJITtENS(1),ENS(1) 904t FC2RMAT IF7,295XtE9.2tEIO.2) IF (H7 .LT, 0.0) GO TO 15 HTS(J) =E 1T ANC, HTS(J

  14. X-ray Astronomy at SLAC

    SciTech Connect

    Saz Parkinson, P

    2005-04-06

    The USA (Unconventional Stellar Aspect) experiment was launched in February of 1999 and operated for approximately 18 months. Group K at SLAC (Stanford Linear Accelerator Center) participated in this experiment along with the Naval Research Laboratory (NRL). The author discusses the USA experiment and the data accumulated, along with some of the results obtained from the observations of such objects as the extragalactic BL Lac object 1ES1959+65, the Black Hole Candidate (BHC) XTE J1118+480, and the eccentric X-ray binary system Circinus X-1.

  15. Integration of Externally Carried Weapon Systems with Military Helicopters (L’Integration des Systemes d’Armes Transportes en Charge Externe sur les Helicopteres Militaires)

    DTIC Science & Technology

    1990-04-01

    structurales. Le rapport traite 6galement de questions op ~ rationnelles et de certains probl~mes spicifiques. Le teXte eat compiti par trois annexes: - Annexe I...origines modestes pendant la deuxiinme guerre mondiale o6 it~ a k6e deploye principalement conime plateforme d’observation et v~hicule de recherche et de...appropries de Ia communaute de I’OTAN. Des efforts considirables ont iti faits lors des recherches dc donneies pour assurer l’exhaustivit. Alors it eat

  16. Electrophysical properties of solid solutions of silver in PbTe

    SciTech Connect

    Sharov, M. K.

    2012-05-15

    The thermopower coefficient {alpha}{sub 0} and the electrical conductivity {sigma} of Pb{sub 1-x}Ag{sub x}Te solid solutions, where x = (0-0.007), are measured at T = 300 K. The hole concentration p is calculated. All samples are of the p type. With increasing silver content, {alpha}{sub 0} decreases, while p and {sigma} increase. For undoped crystals, {alpha}{sub 0} = 251.0 {mu}V/K, p = 1.1 Multiplication-Sign 10{sup 18} cm{sup -3}, and {sigma} = 165 {Omega}{sup -1} cm{sup -1}. At the silver-solubility limit for x = 0.007, {alpha}{sub 0} = 193.8 {mu}V/K, p = 2.3 Multiplication-Sign 10{sup 18} cm{sup -3}, and {sigma} = 216 {Omega}{sup -1} cm{sup -1}. The hole concentration in all samples is much lower than the concentration of introduced silver atoms. The hole gas in Pb{sub 1-x}Ag{sub x}Te solid solutions is weakly degenerate in the entire silver-concentration range.

  17. Orbital period decay of compact black hole X-ray binaries: the influence of circumbinary disks?

    NASA Astrophysics Data System (ADS)

    Chen, Wen-Cong; Li, Xiang-Dong

    2015-11-01

    Context. Recently, compact black hole X-ray binaries XTE J 1118+480 and A0620-00 have been reported to be experiencing a fast orbital period decay, which is two orders of magnitude higher than expected with gravitational wave radiation. Magnetic braking of an Ap/Bp star has been suggested to account for the period change when the surface magnetic field of the companion star Bs ≳ 104 G. However, our calculation indicates that anomalous magnetic braking cannot significantly contribute to the large orbital period decay rates observed in these two sources even if Bs ≳ 104 G. Aims: Observations have provided evidence that circumbinary disks around two compact black hole X-ray binaries may exist. Our analysis shows that, for some reasonable parameters, tidal torque between the circumbinary disk and the binary can efficiently extract the orbital angular momentum from the binary, and result in a large orbital period change rate. Methods: Based on the circumbinary disk model, we simulate the evolution of XTE J 1118+480 via a stellar evolution code. Results: Our computations are approximatively in agreement with the observed data (the masses of two components, donor star radius, orbital period, and orbital period derivative). Conclusions: The mass transfer rate and circumbinary disk mass are obviously far greater than the inferred values from observations. Therefore, it seems that the circumbinary disk is unlikely to be the main cause of the rapid orbital decay observed in some compact black hole X-ray binaries.

  18. Hot White Dwarf Donors in Ultracompact X-Ray Binaries

    NASA Astrophysics Data System (ADS)

    Bildsten, Lars

    2002-09-01

    The discovery of two accreting millisecond X-ray pulsars in binaries with ~43 minute orbital periods allows for a new probe of the donor's structure. For XTE J1751-305, only a hot white dwarf (WD) can fill the Roche lobe. A cold He WD is a possible solution for XTE J0929-314, although I will show that evolutionary arguments make a hot WD more likely. In addition to being larger than the T=0 models, these finite entropy, low-mass (Mc<0.03 Msolar) WDs have a minimum mass for a fixed core temperature. If they remain hot as they lose mass and expand, they can ``evaporate'' to leave an isolated millisecond radio pulsar. They also adiabatically expand upon mass loss at a rate faster than the growth of the Roche radius if the angular momentum deposited in the disk is not returned to the donor. If the timescale of the resulting runaway mass transfer is shorter than the viscous timescale in the outer disk, then the mass transfer instability of Ruderman & Shaham for He WDs would be realized. However, my estimates of these timescales still make the instability unlikely for adiabatic responses. I close by noting the possible impact of finite temperature WDs on our understanding of AM CVn binaries.

  19. New data of radio emission from three AXPs

    NASA Astrophysics Data System (ADS)

    Teplykh, Daria

    2011-07-01

    Anomalous X-ray pulsars (AXPs) are a group of 9 X-ray sources showing periodical pulsation at periods in the 2-12 s range. The main problem is the source of energy, because their X-ray luminosities much higher than can be provided by the rotational kinetic-energy losses. Many attempts have been made to detect radio emission. The first detection of periodical pulsations from the AXP 1E 2259+586 have been made at the frequency 111 MHz by Malofeev (Malofeev et al., 2001, 2005). The second transient AXP XTE J1810-197 and the third AXP candidate 1E1547.0-5408 (Camilo et al., 2006, 2007) have been detected in the large frequency band 0.69-42 GHz. In this report we present new data for three AXPs 1E 2259+586, 4U 0142+61 and XTE J1810-197 at low frequencies. The observations were carried out on two sensitive transit radio telescopes in the range 42-112 MHz. The flux densities and mean pulse profiles, the estimation of the distances and integrated radio luminosities are presented. We used new digital receivers to obtain pulse profiles and dynamic spectra. Comparison with X-ray data shows large differences in the mean pulse widths and luminosities.

  20. NASA's spacecraft data system

    NASA Technical Reports Server (NTRS)

    Cudmore, Alan; Flanegan, Mark

    1993-01-01

    The NASA Small Explorer Data System (SEDS), a space flight data system developed to support the Small Explorer (SMEX) project, is addressed. The system was flown on the Solar Anomalous Magnetospheric Particle Explorer (SAMPEX) SMEX mission, and with reconfiguration for different requirements will fly on the X-ray Timing Explorer (XTE) and the Tropical Rainfall Measuring Mission (TRMM). SEDS is also foreseen for the Hubble repair mission. Its name was changed to Spacecraft Data System (SDS) in view of expansions. Objectives, SDS hardware, and software are described. Each SDS box contains two computers, data storage memory, uplink (command) reception circuitry, downlink (telemetry) encoding circuitry, Instrument Telemetry Controller (ITC), and spacecraft timing circuitry. The SDS communicates with other subsystems over the MIL-STD-1773 data bus. The SDS software uses a real time Operating System (OS) and the C language. The OS layer, communications and scheduling layer, application task layer, and diagnostic software, are described. Decisions on the use of advanced technologies, such as ASIC's (Application Specific Integrated Circuits) and fiber optics, led to technical improvements, such as lower power and weight, without increasing the risk associated with the data system. The result was a successful SAMPEX development, integration and test, and mission using SEDS, and the upgrading of that system to SDS for TRMM and XTE.

  1. Interaction of pulsed Nd:YAG laser radiation with the (001) surface of ZnCdTe crystals

    SciTech Connect

    Majchrzak, T; Rozniakowski, K; Wojtatowicz, T W

    1999-10-31

    An investigation was made of the interaction of pulsed Nd:YAG laser radiation with mixed Zn{sub x}Cd{sub 1-x}Te (x=0.47) crystals. These crystals were grown by the directional solidification method. Various physical phenomena occurring during the interaction of the laser radiation with the crystal surface were observed. Melted regions (craters) appeared as a result of the interaction. Surface microtopography and microsegregation of the elements were investigated with a scanning electron microscope and an x-ray microanalyser. The experimentally determined crater diameters were less than 1 mm, whereas our calculation (based on the one-photon absorption model) predicted the maximum temperature in the irradiated zone to be less than the melting point of Zn{sub x}Cd{sub 1-x}Te. The two-photon absorption must therefore be taken into account. There were no changes in the chemical composition in the irradiated zone. Soliton-like waves originated on the melted and solidified surface of a crater. A ring-like distribution of granules was attributed to the diffraction in the optical system. (laser applications and other topics in quantum electronics)

  2. Studying Low Mass X-Ray Binaries: Revealing the Optical Counterpart in 1747-214 and Measuring the Masses of the Black Holes in 1859+226 and 1009-45

    NASA Astrophysics Data System (ADS)

    Gelino, Dawn M.; Tomsick, John A.

    2003-02-01

    Low mass x-ray binaries (LMXBs) contain compact, black hole (BH) or neutron star (NS) primaries, and cool, low-mass secondary stars. A limited number of BHs and NSs have accurate mass measurements. It is important to determine the primary mass of the LMXBs to better understand how BH masses influence their outburst behavior, and to better constrain the NS equations of state. To determine the mass of the primary object we need to measure the orbital inclination, i. We propose to determine i for two BH LMXBs, XTE J1859+226 and GRS 1009-45 (=N Vel 93) through modeling of their ellipsoidal variations. Because most LMXBs are not eclipsing, modeling their light curves is currently the only feasible method for determining the inclination. We will model the light curves with WD98. We also propose to identify the optical counterpart to the NS system EXO 1747-214, in order to begin the process of measuring the NS mass. We have successfully used NOAO facilities and this modeling technique to find accurate BH masses in four LMXBs. In order to expand the sample of known BH and NS systems, we request seven nights on the KPNO and CTIO 4m to obtain optical and infrared data on XTE J1859+226, GRS 1009-45, and EXO 1747-214.

  3. Dynamic thermo-mechanical properties of various flowable resin composites

    PubMed Central

    Balthazard, Rémy; Vincent, Marin; Dahoun, Abdessellam; Mortier, Eric

    2016-01-01

    Background This study compared the storage modulus (E’), the loss modulus (E’’) and the loss tangent (tan δ) of various flowable resin composites. Material and Methods Grandio Flow (GRF), GrandioSo Heavy Flow (GHF), Filtek Supreme XTE (XTE) and Filtek Bulk Fill (BUL) flowable resins and Clinpro Sealant (CLI) ultra-flowable pit and fissure sealant resin were used. 25 samples were tested using a dynamical mechanical thermal analysis system in bending mode. Measurements were taken within a temperature range of 10 to 55°C. The results were statistically analyzed using mixed-effect and repeated-measure analysis of variance followed by paired multiple comparisons. Results For all the materials, the E’ values decrease with temperature, whereas the tan δ values increase. Irrespective of the temperature, GHF and GRF present E’ and E’’ values significantly higher than all the other materials and CLI presents values significantly lower than all the other materials. Observation of the values for all the materials reveals a linear progression of the tan δ values with temperature. Conclusions A variation in temperature within a physiological range generates modifications in mechanical properties without damaging the material, however. Filler content in volume terms appears to be the crucial parameter in the mechanical behavior of tested materials. Key words:Dynamic mechanical thermal analysis, elastic modulus, filler content, flowable resin composites, loss modulus, loss tangent. PMID:27957266

  4. Structural and optoelectronic properties of Mg substituted ZTe (Z=Zn, Cd and Hg)

    NASA Astrophysics Data System (ADS)

    Khan, Imad; Subhan, Fazle; Ahmad, Iftikhar; Ali, Zahid

    2015-08-01

    Wide band gap semiconductor alloys, MgxZ1-xTe (Z=Zn, Cd and Hg), are investigated over a full range of Mg compositions (0≤x≤1) using density functional theory (DFT). The variation in the lattice constant of MgxZ1-xTe is linear with the composition x, and all these alloys obey Vegrd's law. The CdTe (6.50 Å) and MgTe (6.44 Å) are lattice matched compounds, therefore the lattice constant of MgCdTe decreases slightly with the concentration x, whereas the lattice constant also decreases for MgHgTe but increases for MgZnTe. It is due to the fact that Mg has larger size than Zn and smaller size than Cd and Hg. The band gap of these compounds are calculated using the modified Becke-Johnson (mBJ) exchange potential as LDA and GGA are not effective in producing the experimental band gap of a strongly correlated electron system. The calculated band gaps of these compounds cover the range 0-3.5 eV and are consistent with the experimental band gaps. The band gaps exhibit nonlinear behavior or bowing effect with the change in concentration. The frequency dependent optical properties like dielectric functions, and indices of refraction of these ternary systems are also calculated and discussed.

  5. Structural and optical properties of In doped Se-Te phase-change thin films: A material for optical data storage

    NASA Astrophysics Data System (ADS)

    Pathak, H. P.; Shukla, Nitesh; Kumar, Vipin; Dwivedi, D. K.

    2016-02-01

    Se75-xTe25Inx (x = 0, 3, 6, & 9) bulk glasses were obtained by melt quench technique. Thin films of thickness 400 nm were prepared by thermal evaporation technique at a base pressure of 10-6 Torr onto well cleaned glass substrate. a-Se75-xTe25Inx thin films were annealed at different temperatures for 2 h. As prepared and annealed films were characterized by X-ray diffraction and UV-Vis spectroscopy. The X-ray diffraction results show that the as-prepared films are of amorphous nature while it shows some poly-crystalline structure in amorphous phases after annealing. The optical absorption spectra of these films were measured in the wavelength range 400-1100 nm in order to derive the extinction and absorption coefficient of these films. It was found that the mechanism of optical absorption follows the rule of allowed non-direct transition. The optical band gap of as prepared and annealed films as a function of photon energy has been studied. The optical band gap is found to decrease with increase in annealing temperature in the present glassy system. It happens due to crystallization of amorphous films. The decrease in optical band gap due to annealing is an interesting behavior for a material to be used in optical storage. The optical band gap has been observed to decrease with the increase of In content in Se-Te glassy system.

  6. Anomalous Hall effect sensors based on magnetic element doped topological insulator thin films

    NASA Astrophysics Data System (ADS)

    Ni, Yan; Zhang, Zhen; Nlebedim, Ikenna; Jiles, David

    Anomalous Hall effect (AHE) is recently discovered in magnetic element doped topological insulators (TIs), which promises low power consumption highly efficient spintronics and electronics. This discovery broaden the family of Hall effect (HE) sensors. In this work, both HE and AHE sensor based on Mn and Cr doped Bi2Te3 TI thin films will be systematically studied. The influence of Mn concentration on sensitivity of MnxBi2-xTe3 HE sensors will be discussed. The Hall sensitivity increase 8 times caused by quantum AHE will be reported. AHE senor based on Cr-doped Bi2Te3 TI thin films will also be studied and compared with Mn doped Bi2Te3 AHE sensor. The influence of thickness on sensitivity of CrxBi2-xTe3 AHE sensors will be discussed. Ultrahigh Hall sensitivity is obtained in Cr doped Bi2Te3. The largest Hall sensitivity can reach 2620 Ω/T in sensor which is almost twice higher than that of the normal semiconductor HE sensor. Our work indicates that magnetic element doped topological insulator with AHE are good candidates for ultra-sensitive Hall effect sensors.

  7. Low Frequency Radio Transients in the Galactic Center

    NASA Astrophysics Data System (ADS)

    Hyman, S. D.; Bartleson, A. L.; Lazio, T. J. W.; Kassim, N. E.

    2001-12-01

    We report the detection of a new radio transient source, GCRT J1746-2757, located only 1.1 degrees north of the Galactic center. Consistent with other radio transients toward the Galactic center, this source brightened and faded on a time scale of a few months. No X-ray counterpart was detected, but upper limits suggest that GCRT J1746-2757 may have been a "fast" transient, with a time scale of days. We also report new 0.33 GHz measurements of the radio counterpart to the X-ray transient source, XTE J1748-288, previously detected and monitored at higher radio frequencies. We show that the spectrum of XTE J1748-288 steepened considerably during a period of a few months after its peak. We also discuss the need for a more efficient means of finding additional radio transients. This research is supported by funding from the Jeffress Memorial Trust, Research Corporation, and the Sweet Briar College Faculty Grants program. Basic research in radio astronomy at NRL is supported by the Office of Naval Research.

  8. 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.

  9. How to Determine The Precession of the Inner Accretion Disk in Cygnus X-1

    SciTech Connect

    Torres, D F; Romero, G E; Barcons, X; Lu, Y

    2005-01-05

    We show that changes in the orientation of the inner accretion disk of Cygnus X-1 affect the shape of the broad Fe K{alpha} emission line emitted from this object, in such a way that eV-level spectral resolution observations (such as those that will be carried out by the ASTRO-E2 satellite) can be used to analyze the dynamics of the disk. We here present a new diagnosis tool, supported by numerical simulations, by which short observations of Cygnus X-1, separated in time, can determine whether its accretion disk actually processes, and if so, determine its period and precession angle. Knowing the precession parameters of Cygnus X-1 would result in a clarification of the origin of such precession, distinguishing between tidal and spin-spin coupling. This approach could also be used for similar studies in other microquasar systems.

  10. Design and Tests of the Hard X-Ray Polarimeter X-Calibur

    NASA Technical Reports Server (NTRS)

    Beilicke, M.; Baring, M. G.; Barthelmy, S.; Binns, W. R.; Buckley, J.; Cowsik, R.; Dowkontt, P.; Garson, A.; Guo, Q.; Haba, Y.; Israel, M. H.; Kunieda, H.; Lee, K.; Matsumoto, H.; Miyazawa, T.; Okajima, T.; Schnittman, J.; Tamura, K.; Tueller, J.; Krawczynski, H.

    2012-01-01

    X-ray polarimetry promises to give qualitatively new information about high-energy astrophysical sources, such as binary black hole systems, micro-quasars, active galactic nuclei, and gamma-ray bursts. We designed, built and tested a hard X-ray polarimeter X-Calibur to be used in the focal plane of the InFOC(mu)S grazing incidence hard X-ray telescope. X-Calibur combines a low-Z Compton scatterer with a CZT detector assembly to measure the polarization of 10 - 80 keY X-rays making use of the fact that polarized photons Compton scatter preferentially perpendicular to the electric field orientation. X-Calibur achieves a high detection efficiency of order unity.

  11. The role of Magnetic Reconnection in Compact Sources and Jet Acceleration

    NASA Astrophysics Data System (ADS)

    Singh, Chandra Bahadur; De Gouveia Dal Pino, Elisabete; Kadowaki, Luis H. S.

    Almost a decade ago de Gouveia Dal Pino and Lazarian (2005) proposed a model for producing jet plasmons and particle acceleration by magnetic reconnection events in the surrounds of accretion disks around black holes with magnetospheres. Although this model predicts that the amount of magnetic power released by reconnection is more than sufficient to explain observed flares from black hole mass sources in different scales (from microquasars to low luminous active galactic nuclei; see de Gouveia Dal Pino et al. 2010), it still requires refinement and numerical testing. In this work, we take into account relativistic effects by introducing a Pseudo Newtonian approach to the model and also present the results of 2D MHD numerical simulations under this approach.

  12. Modelling a Simultaneous Radio/X-Ray Flare from Cyg X-1

    NASA Technical Reports Server (NTRS)

    Leventis, Konstantinos; Markoff, Sera; Wilsm, Joern; Nowak, Michael A.; Maitra, Dipankar; Pottschmidt, Katja; Pooley, Guy G.; Kreykenbohm, Ingo; Rotschild, Richard E.

    2008-01-01

    The long-term monitoring campaign of Cyg X-1 has provided the detection of the first simultaneous radio/X-ray flare seen from that source. We investigate the physical characteristics of the event in terms of emission from a homogeneous, expanding blob of pair-plasma, superimposed on a baseline flux in both bands. We find that while the radio flare can be reconstructed under various configurations of a cooling blob, continuous (re)acceleration of particles inside the jet is necessary to sustain X-ray emission at the levels implied by the data, for the observed duration. We present major results of the modelling and discuss implications for the role of microquasar jets.

  13. Winds of Change: The Physics of Accretion, Ejection, and X-ray Variability in GRS1915+105

    NASA Astrophysics Data System (ADS)

    Neilsen, Joseph

    2013-04-01

    In the last twenty years, even as multiwavelength observations of black hole X-ray binaries have led to major advances, the microquasar GRS 1915+105 has continually challenged our understanding of the physics of accretion and ejection. With its relativistic jets, ionized winds, and myriad states of rapid, extreme variability, this remarkable black hole has been alternately seen as the black sheep of X-ray binaries and a Rosetta stone for black hole astrophysics. In this talk, I will present our efforts to use a decade of high-resolution X-ray spectroscopy of GRS 1915+105 to shed light on the processes that regulate its erratic behavior. I will highlight in particular the role of accretion disk winds on time scales ranging from seconds to years. Drawing on recent results, I will discuss the broader implications of these massive winds for the physics of inflows and outflows around black holes.

  14. HESS-II reconstruction strategy and performance in the low-energy (20-150 GeV) domain

    SciTech Connect

    Becherini, Y.; Djannati-Atai, A.; Punch, M.; Bernloehr, K.; Ehlert, S.; Masbou, J.; Moulin, E.

    2008-12-24

    In mid-2009 a notable upgrade of the H.E.S.S. telescope system will take place: a new telescope with a 600 m{sup 2} mirror area and very-high-resolution camera (0.07 deg.) will be positioned at the centre of the present configuration, with the aim of lowering the threshold and enhance its sensitivity in the 100 GeV to several TeV energy range. HESS-II will permit the investigation of the lower energy {gamma}-ray spectra in various cosmic accelerators, giving information on the origin of the {gamma}-rays observed, and will detect AGNs with a redshift greater than 0.2 (being less affected by absorption by Extragalactic Background Light--EBL--in this energy range) and will search for new classes of very high energy {gamma}-ray emitters (pulsars, microquasars, GRB, and dark matter candidates)

  15. The X-ray spectral and timing properties of a major radio flare episode in Cygnus X-3

    NASA Astrophysics Data System (ADS)

    Koljonen, Karri I. I.; Hannikainen, Diana C.; McCollough, Michael L.; Pooley, Guy G.; Trushkin, Sergei A.; Droulans, Robert

    2013-02-01

    The microquasar Cygnus X-3 is known for massive outbursts that emit radiation from radio to γ-rays associated with jet ejection events. Using Principal Component Analysis to probe fast (~1 min) X-ray spectral evolution followed by subsequent spectral fits to the time-averaged spectra (~3 ks), we find that the overall X-ray variability during major outbursts can be attributed to two components. The spectral evolution of these components are best fitted with hybrid Comptonization and thermal bremsstrahlung components. Most of the X-ray variability is attributed to the hybrid Comptonization component. However, the spectral evolution of the thermal component is linked to a change in the X-ray spectral state. Phase-folding the fit results shows that the thermal component is restricted to two orbital phase regions opposite to each other, possibly indicating a flattened stellar wind from the Wolf-Rayet companion.

  16. A universal scaling for the energetics of relativistic jets from black hole systems.

    PubMed

    Nemmen, R S; Georganopoulos, M; Guiriec, S; Meyer, E T; Gehrels, N; Sambruna, R M

    2012-12-14

    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 AGN is still unknown. Here, we show that jets produced by AGN and GRBs exhibit the same correlation between the kinetic power carried by accelerated particles and the gamma-ray luminosity, with AGN 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.

  17. Design and Tests of the Hard X-Ray Polarimeter X-Calibur

    NASA Technical Reports Server (NTRS)

    Beilicke, M.; Binns, W. R.; Buckley, J.; Cowsik, R.; Dowkontt, P.; Garson, A.; Guo, Q.; Israel, M. H.; Lee, K.; Krawczynski, H.; Baring, M. G.; Barthelmy, S.; Okajima, T.; Schnittman, J.; Tueller, J.; Haba, Y.; Kunieda, H.; Matsumoto, H.; Miyazawa, T.; Tamura, K.

    2011-01-01

    X-ray polarimetry promises to give new information about high-energy astrophysical sources, such as binary black hole systems, micro-quasars, active galactic nuclei, and gamma-ray bursts. We designed, built and tested a hard X-ray polarimeter X-Calibur to be used in the focal plane of the InFOC(mu)S grazing incidence hard X-ray telescope. X-Calibur combines a low-Z Compton scatterer with a CZT detector assembly to measure the polarization of 10-80 keV X-rays making use of the fact that polarized photons Compton scatter preferentially perpendicular to the electric field orientation. X-Calibur achieves a high detection efficiency of order unity.

  18. 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.

  19. An unusually massive stellar black hole in the Galaxy.

    PubMed

    Greiner, J; Cuby, J G; McCaughrean, M J

    2001-11-29

    The X-ray source known as GRS1915+105 belongs to a group dubbed 'microquasars'. These objects are binary systems which sporadically eject matter at speeds that appear superluminal, as is the case for some quasars. GRS1915+105 is also one of only two known binary sources thought to contain a maximally spinning black hole. Determining the basic parameters of GRS195+105, such as the masses of the components, will help us to understand jet formation in this system, as well as providing links to other objects which exhibit jets. Using X-ray data, indirect methods have previously been used to infer a variety of masses for the accreting compact object in the range 10-30 solar masses (M middle dot in circle). Here we report a direct measurement of the orbital period and mass function of GRS1915+105, which allow us to deduce a mass of 14 +/- 4 M middle dot in circle for the black hole. Black holes with masses >5-7 M middle dot in circle challenge the conventional picture of black-hole formation in binary systems. Based on the mass estimate, we interpret the distinct X-ray variability of GRS1915+105 as arising from instabilities in an accretion disk that is dominated by radiation pressure, and radiating near the Eddington limit (the point where radiation pressure supports matter against gravity). Also, the mass estimate constrains most models which relate observable X-ray properties to the spin of black holes in microquasars.

  20. Great enhancements in the thermoelectric power factor of BiSbTe nanostructured films with well-ordered interfaces

    NASA Astrophysics Data System (ADS)

    Chang, Hsiu-Cheng; Chen, Chun-Hua; Kuo, Yung-Kang

    2013-07-01

    An innovative concept of twin-enhanced thermoelectricity was proposed to fundamentally resolve the high electrical resistance while not degrading the phonon scattering of the thermoelectric nanoassemblies. Under this frame, a variety of highly oriented and twinned bismuth antimony telluride (BixSb2-xTe3) nanocrystals were successfully fabricated by a large-area pulsed-laser deposition (PLD) technique on insulated silicon substrates at various deposition temperatures. The significant presence of the nonbasal- and basal-plane twins across the hexagonal BiSbTe nanocrystals, which were experimentally and systematically observed for the first time, evidently contributes to the unusually high electrical conductivity of ~2700 S cm-1 and the power factor of ~25 μW cm-1 K-2 as well as the relatively low thermal conductivity of ~1.1 W m-1 K-1 found in these nanostructured films.An innovative concept of twin-enhanced thermoelectricity was proposed to fundamentally resolve the high electrical resistance while not degrading the phonon scattering of the thermoelectric nanoassemblies. Under this frame, a variety of highly oriented and twinned bismuth antimony telluride (BixSb2-xTe3) nanocrystals were successfully fabricated by a large-area pulsed-laser deposition (PLD) technique on insulated silicon substrates at various deposition temperatures. The significant presence of the nonbasal- and basal-plane twins across the hexagonal BiSbTe nanocrystals, which were experimentally and systematically observed for the first time, evidently contributes to the unusually high electrical conductivity of ~2700 S cm-1 and the power factor of ~25 μW cm-1 K-2 as well as the relatively low thermal conductivity of ~1.1 W m-1 K-1 found in these nanostructured films. Electronic supplementary information (ESI) available: Morphologies, XRD patterns, SEM compositions and room-temperature thermoelectric properties of the series of (015) oriented Bi0.4Sb1.6Te3 nanocolumns (Fig. S1-S3), (00l) oriented

  1. The effects of dust scattering on high-resolution X-ray absorption edge structure

    NASA Astrophysics Data System (ADS)

    Corrales, Lia; Garcia, Javier; Wilms, Joern; Baganoff, Frederick K.

    2016-04-01

    In high resolution X-ray spectroscopy, dust scattering significantly enhances the total extinction optical depth and alters the shape of photoelectric absorption edges. This effect is modulated by the dust grain size distribution, spatial location along the line of sight, and the imaging resolution of the X-ray telescope. We focus in particular on the Fe L-edge at 0.7 keV, fitting a template for the total extinction to the high resolution spectrum of three X-ray binaries from the Chandra archive: GX 9+9, XTE J1817-330, and Cyg X-1. In cases where dust is intrinsic to the source, a covering factor based on the angular extent of the dusty material must be applied to the extinction curve, regardless of imaging resolution. We discuss the various astrophysical cases in which scattering effects need to be taken into account.

  2. Coordinated Millisecond RXTE+OPTICAL Observations of Persistent LMXB

    NASA Astrophysics Data System (ADS)

    Spruit, Hendrik

    In RXTE+optical observatipons of XTE J1118+480 we found the visible light to be strongly correlated with the X-rays on time scales of 0.03 - 5s. The short time scales, and a `premonition dip' in the visible preceding the X-rays, turn out to be difficult to understand in existing models. Simultaneous fast X-ray+optical obervations thus may give new clues on the poorly understood inner regions of the accretion flow in XRB, and their relation to outflows. We propose to observe for this purpose the brightest persistent low-mass black hole accreters, and two well studied neutron star accreters. (Cyg X-1, GX 339-4, Cyg X- 2 and the neutron star jet source Cir X-1).

  3. Contribution of the n-side to the R 0A product of long wavelength n+n-pHg1- xCdxTe photodiodes in the diffusion controlled regime

    NASA Astrophysics Data System (ADS)

    Gonzalez, C.; Centeno, J. M.; Sangrador, J.

    The contribution of the n-side to the total differential resistance by area product in the dark (R 0A) of longwavelength n+n-p photodiodes made in Hg 1- xCd xTe (MCT) is analyzed in the diffusion controlled regime based on a model of an abrupt junction. The results of the modeling indicate that the p-side contribution determines an upper limit to R 0A whose actual value is decreased by the n-side contribution. In many practical diodes, the n-side contribution is negligible, but it can be important under some particular conditions that can occur, as is discussed in this study.

  4. Singularity free charged anisotropic solutions of Einstein-Maxwell field equations in general relativity

    NASA Astrophysics Data System (ADS)

    Singh, K. N.; Pant, N.

    2016-07-01

    In this paper, we present generalization of anisotropic analogue of charged Heintzmann's solution of the general relativistic field equations in curvature coordinates. These exact solutions are stable and well behaved in all respect for a wide range of anisotropy parameter and charge parameter. We have found that these new solutions are suitable for the modeling of super dense stars like neutron stars and quark stars because they yield a wide range of masses and radii with simple mathematical expressions. By tuning different values of the few parameters, we can model various neutron stars and quark stars which are compatible with the experimentally observed values of masses and radii. Therefore, we have synchronized our solution with the observed values of some of the compact stars XTE J1739 - 217, EXO 0748 - 676, PSR J1614 - 2230, PSR J0348 + 0432 and PSR B0943 + 10.

  5. Design and simulated performance of a CARS spectrometer for dynamic temperature measurements using electronic heterodyning

    NASA Technical Reports Server (NTRS)

    Deen, M. Jamal; Thompson, E. D.

    1989-01-01

    A new design for generating CARS signals and for the detection and processing of these signals is presented and evaluated. The design is based on electronic heterodyning of the CARS spectrum of nitrogen at two selected narrowband frequencies, ratioing the resulting signal strengths, and comparing this ratio with a theoretically derived temperature scale. A reference cell is incorporated into the design for system calibration and for accurate temperature measurements. The spectrometer is found capable of measuring temperature in the submillisecond time scale with an accuracy of 10 percent in the 1000-2000 K temperature range. A typical result using the Hg(x)Cd(1-x)Te photomixer for T = 1500 K, Delta T = 50 K is a SNR of 21 dB and a data collection rate of 300 Hz.

  6. Anisotropic compact stars in Karmarkar spacetime

    NASA Astrophysics Data System (ADS)

    Newton Singh, Ksh.; Pant, Neeraj; Govender, M.

    2017-01-01

    We present a new class of solutions to the Einstein field equations for an anisotropic matter distribution in which the interior space-time obeys the Karmarkar condition. The necessary and sufficient condition required for a spherically symmetric space-time to be of Class One reduces the gravitational behavior of the model to a single metric function. By assuming a physically viable form for the grr metric potential we obtain an exact solution of the Einstein field equations which is free from any singularities and satisfies all the physical criteria. We use this solution to predict the masses and radii of well-known compact objects such as Cen X-3, PSR J0348+0432, PSR B0943+10 and XTE J1739-285.

  7. Great enhancements in the thermoelectric power factor of BiSbTe nanostructured films with well-ordered interfaces.

    PubMed

    Chang, Hsiu-Cheng; Chen, Chun-Hua; Kuo, Yung-Kang

    2013-08-07

    An innovative concept of twin-enhanced thermoelectricity was proposed to fundamentally resolve the high electrical resistance while not degrading the phonon scattering of the thermoelectric nanoassemblies. Under this frame, a variety of highly oriented and twinned bismuth antimony telluride (BixSb2-xTe3) nanocrystals were successfully fabricated by a large-area pulsed-laser deposition (PLD) technique on insulated silicon substrates at various deposition temperatures. The significant presence of the nonbasal- and basal-plane twins across the hexagonal BiSbTe nanocrystals, which were experimentally and systematically observed for the first time, evidently contributes to the unusually high electrical conductivity of ~2700 S cm(-1) and the power factor of ~25 μW cm(-1) K(-2) as well as the relatively low thermal conductivity of ~1.1 W m(-1) K(-1) found in these nanostructured films.

  8. Effect of the arsenic cracking zone temperature on the efficiency of arsenic incorporation in CdHgTe films in molecular-beam epitaxy

    SciTech Connect

    Sidorov, G. Yu. Mikhailov, N. N.; Varavin, V. S.; Ikusov, D. G.; Sidorov, Yu. G.; Dvoretskii, S. A.

    2008-06-15

    Cd{sub x}Hg{sub 1-x}Te films with x {approx} 0.22 and thickness of {approx}10 {mu}m have been grown by molecular-beam epitaxy on gallium arsenide substrates and doped in situ with arsenic. Activation annealing of doped films provided p-type conduction with a hole density of up to 10{sup 17} cm{sup -3}. The influence exerted by the arsenic cracking zone temperature on the efficiency of arsenic incorporation into the CdHgTe film was studied. A model describing the dependence of the arsenic concentration in the films on the arsenic cracking zone temperature was suggested. A comparison of the model and the experimental data demonstrated that the incorporation efficiency of diatomic arsenic is approximately two orders of magnitude higher than that of tetratomic arsenic.

  9. Accreting Millisecond Pulsars: Neutron Star Masses and Radii

    NASA Technical Reports Server (NTRS)

    Strohmayer, Tod

    2004-01-01

    High amplitude X-ray brightness oscillations during thermonuclear X-ray bursts were discovered with the Rossi X-ray Timing Explorer (RXTE) in early 1996. Spectral and timing evidence strongly supports the conclusion that these oscillations are caused by rotational modulation of the burst emission and that they reveal the spin frequency of neutron stars in low mass X-ray binaries. The recent discovery of X-ray burst oscillations from two accreting millisecond pulsars has confirmed this basic picture and provided a new route to measuring neutron star properties and constraining the dense matter equation of state. I will briefly summarize the current observational understanding of accreting millisecond pulsars, and describe recent attempts to determine the mass and radius of the neutron star in XTE J1814-338.

  10. THE PROPER MOTION OF PSR J1550-5418 MEASURED WITH VLBI: A SECOND MAGNETAR VELOCITY MEASUREMENT

    SciTech Connect

    Deller, A. T.; Camilo, F.; Halpern, J. P.; Reynolds, J. E.

    2012-03-20

    The formation mechanism of neutron stars with extremely large magnetic field strengths (magnetars) remains unclear. Some formation scenarios predict that magnetars should be born with extremely high space velocities, >1000 km s{sup -1}. Using the Long Baseline Array in Australia, we have measured the proper motion of the intermittently radio-bright magnetar PSR J1550-5418 (1E 1547.0-5408): {mu} = 9.2 {+-} 0.6 mas yr{sup -1}. For a likely distance of 6 {+-} 2 kpc, the implied transverse velocity is 280{sup +130}{sub -120} km s{sup -1} after correcting for Galactic rotation. Along with the Almost-Equal-To 200 km s{sup -1} transverse velocity measured for the magnetar XTE J1810-197, this result suggests that formation pathways producing large magnetic fields do not require very large birth kicks.

  11. RXTE Observation of Cygnus X-1: Spectra and Timing

    NASA Technical Reports Server (NTRS)

    Wilms, J.; Dove, J.; Nowak, M.; Vaughan, B. A.

    1997-01-01

    We present preliminary results from the analysis of an R.XTE observation of Cyg X-1 in the hard state. We show that the observed X-ray spectrum can be explained with a model for an accretion disk corona (ADC), in which a hot sphere is situated inside of a cold accretion disk (similar to an advection dominated model). ADC Models with a slab-geometry do not successfully fit the data. In addition to the spectral results we present the observed temporal properties of Cyg X-1, i.e. the coherence-function and the time-lags, and discuss the constraints the. temporal properties imply for the accretion geometry in Cyg X-1.

  12. The Goodness of Simultaneous Fits in ISIS

    NASA Astrophysics Data System (ADS)

    Kühnel, Matthias; Falkner, Sebastian; Grossberger, Christoph; Ballhausen, Ralf; Dauser, Thomas; Schwarm, Fritz-Walter; Kreykenbohm, Ingo; Nowak, Michael A.; Pottschmidt, Katja; Ferrigno, Carlo; Rothschild, Richard E.; Martínez-Núñez, Silvia; Torrejón, José Miguel; Fürst, Felix; Klochkov, Dmitry; Staubert, Rüdiger; Kretschmar, Peter; Wilms, Jörn

    2016-02-01

    In a previous work, we introduced a tool for analyzing multiple datasets simultaneously, which has been implemented into ISIS. This tool was used to fit many spectra of X-ray binaries. However, the large number of degrees of freedom and individual datasets raise an issue about a good measure for a simultaneous fit quality. We present three ways to check the goodness of these fits: we investigate the goodness of each fit in all datasets, we define a combined goodness exploiting the logical structure of a simultaneous fit, and we stack the fit residuals of all datasets to detect weak features. These tools are applied to all RXTE-spectra from GRO 1008-57, revealing calibration features that are not detected significantly in any single spectrum. Stacking the residuals from the best-fit model for the Vela X-1 and XTE J1859+083 data evidences fluorescent emission lines that would have gone undetected otherwise.

  13. Outbursts and State Transitions in Black Hole Candidates observed by MAXI

    NASA Astrophysics Data System (ADS)

    Negoro, H.; Maxi Team

    2010-12-01

    MAXI continuously observes several black hole candidates in our Galaxy and LMC. MAXI already detected various state transitions in Cyg X-1, GX 339-4, Swift J1752.5-127, and black hole transients, H 1743-332, 4U 1630, XTE J1752-223, and MAXI J1659-125. From these observations, we try to clarify what happens during the transitions, and what triggers the transitions. In any case, fast alerts just before the transitions and soon after the outbursts are crucial to detect, for instance, radio and high energy gamma-ray jets or emission. We also present some successful examples of alerts from our MAXI transient alert system.

  14. Improving the method of calculating electronic properties of narrow bandgap semiconductors

    NASA Technical Reports Server (NTRS)

    Patterson, James D.

    1987-01-01

    A previously developed code for calculating the mobility of charge carriers in narrow bandgap semiconductors does not predict the correct temperature dependence in all cases. It is thought that this is due to the way the electronic screening of the carriers is treated in the model. The objective of this research is to improve the handling of the screening by going beyond the current first Born approximation. Much of this work is directly related to the alloy semiconductor Hg sub 1-xCd sub xTe which is important for infrared detectors and is a good candidate for microgravity crystal growth. The principal conclusion, so far, is that the major difficulty is probably the treatment of short range screening at higher temperatures.

  15. Study of optical nonlinearities in Se-Te-Bi thin films

    NASA Astrophysics Data System (ADS)

    Sharma, Ambika; Yadav, Preeti; Kumari, Anshu

    2014-04-01

    The present work reports the nonlinear refractive index of Se85-xTe15Bix thin films calculated by Ticha and Tichy relation. The nonlinear refractive index of Chalcogenide amorphous semiconductor is well correlated with the linear refractive index and WDD parameters which in turn depend on the density and molar volume of the system. The density of the system is calculated theoretical as well as experimentally by using Archimedes principle. The linear refractive index and WDD parameters are calculated using single transmission spectra in the spectral range of 400-1500 nm. It is observed that linear as well as nonlinear refractive index increases with Bi content. The results are analyzed on the basis of increasing polarizability due to larger radii of Bi.

  16. High energy from space

    NASA Technical Reports Server (NTRS)

    Margon, Bruce; Canizares, Claude; Catura, Richard C.; Clark, George W.; Fichtel, Carl E.; Friedman, Herbert; Giacconi, Riccardo; Grindlay, Jonathan E.; Helfand, David J.; Holt, Stephen S.

    1991-01-01

    The following subject areas are covered: (1) important scientific problems for high energy astrophysics (stellar activity, the interstellar medium in galaxies, supernovae and endpoints of stellar evolution, nucleosynthesis, relativistic plasmas and matter under extreme conditions, nature of gamma-bursts, identification of black holes, active nuclei, accretion physics, large-scale structures, intracluster medium, nature of dark matter, and the X- and gamma-ray background); (2) the existing experimental programs (Advanced X-Ray Astrophysics Facility (AXAF), Gamma Ray Observatory (GRO), X-Ray Timing Explorer (XTE), High Energy Transient Experiment (HETE), U.S. participation in foreign missions, and attached Shuttle and Space Station Freedom payloads); (3) major missions for the 1990's; (4) a new program of moderate missions; (5) new opportunities for small missions; (6) technology development issues; and (7) policy issues.

  17. Mise au point dans le ternaire TlBiTe. Existence de deux phases nonstoechiometriques de type TlBiTe 2

    NASA Astrophysics Data System (ADS)

    Pradel, A.; Tedenac, J. C.; Brun, G.; Maurin, M.

    1982-11-01

    The cross section BiTeTlTe of the phase diagram TlBiTe was constructed by X-ray, microstructure, and DTA methods. Two phases were emphasized: Tl 1- xBi 1+ xTe 2 with x = 0.06, and Tl 1- yBi 1+ yTe 2 with y = 0.2. The first one is a nonstoichiometric representation of what so many authors studied as TlBiTe 2. The latter is a high-temperature phase which decomposes in eutectoïd reaction (415°C): 1.18{ Tl0.8Bi1.2Te2} ⇄ Tl0.94Bi1.06Te2 + 0.36 { BiTe} . The high-temperature form undergoes a phase transformation by quenching, giving a metastable low-temperature form. The discussion includes electrical resistivity and thermoelectric measurements of each of them.

  18. Structural analysis of Cr aggregation in ferromagnetic semiconductor (Zn,Cr)Te

    SciTech Connect

    Kobayashi, H.; Yamawaki, K.; Nishio, Y.; Kanazawa, K.; Kuroda, S.; Mitome, M.; Bando, Y.

    2013-12-04

    The Cr aggregation in a ferromagnetic semiconductor (Zn,Cr)Te was studied by performing precise analyses using TEM and XRD of microscopic structure of the Cr-aggregated regions formed in iodine-doped Zn{sub 1−x}Cr{sub x}Te films with a relatively high Cr composition x ∼ 0.2. It was found that the Cr-aggregated regions are composed of Cr{sub 1−δ}Te nanocrystals of the hexagonal structure and these hexagonal precipitates are stacked preferentially on the (111)A plane of the zinc-blende (ZB) structure of the host ZnTe crystal with its c-axis nearly parallel to the (111){sub ZB} plane.

  19. General sacrificial template method for the synthesis of cadmium chalcogenide hollow structures.

    PubMed

    Miao, Jian-Jun; Jiang, Li-Ping; Liu, Chang; Zhu, Jian-Min; Zhu, Jun-Jie

    2007-07-09

    Semiconductor CdX (X=Te, Se, S) hollow structures have been successfully prepared by using Cd(OH)Cl precursors as a sacrificial template. The hollow structures can be hollow spheres or tubes by controlling the shape of the sacrificial template. The products were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and energy-dispersive spectrometry. The obtained results showed that the hollow structures had complementary shapes and sizes of the original sacrificial templates. This is a general method for the synthesis of cadmium chalcogenide hollow structures, and the method is simpler and more practical than direct synthesis of certain hollow structures, which further widens the avenue to using those materials that have been synthesized with various shapes to fabricate specific hollow structures.

  20. Improving the method of calculating electronic properties of narrow bandgap semiconductors

    NASA Astrophysics Data System (ADS)

    Patterson, James D.

    1987-11-01

    A previously developed code for calculating the mobility of charge carriers in narrow bandgap semiconductors does not predict the correct temperature dependence in all cases. It is thought that this is due to the way the electronic screening of the carriers is treated in the model. The objective of this research is to improve the handling of the screening by going beyond the current first Born approximation. Much of this work is directly related to the alloy semiconductor Hg sub 1-xCd sub xTe which is important for infrared detectors and is a good candidate for microgravity crystal growth. The principal conclusion, so far, is that the major difficulty is probably the treatment of short range screening at higher temperatures.

  1. New Layered Structures of Cuprous Chalcogenides as Thin Film Solar Cell Materials: Cu2Te and Cu2Se

    NASA Astrophysics Data System (ADS)

    Nguyen, Manh Cuong; Choi, Jin-Ho; Zhao, Xin; Wang, Cai-Zhuang; Zhang, Zhenyu; Ho, Kai-Ming

    2013-10-01

    The stable crystal structures of two cuprous chalcogenides of Cu2X (X=Te or Se) are predicted using an adaptive genetic algorithm in combination with first-principles density functional theory calculations. Both systems are found to prefer a unique and previously unrecognized layered structure, with the total energies much lower than all structures proposed in the literature so far. The newly discovered structures are further shown to be dynamically and mechanically stable, and possess electronic properties consistent with existing experimental observations. In particular, their layered nature is expected to prevail over other structural forms at the interfaces of thin-film solar cells, and knowledge about the precise atomic structures of the interfaces is a prerequisite for achieving long-term stability and high efficiency of CdTe and Cu(In,Ga)Se2 solar cells.

  2. New layered structures of cuprous chalcogenides as thin film solar cell materials: Cu2Te and Cu2Se.

    PubMed

    Nguyen, Manh Cuong; Choi, Jin-Ho; Zhao, Xin; Wang, Cai-Zhuang; Zhang, Zhenyu; Ho, Kai-Ming

    2013-10-18

    The stable crystal structures of two cuprous chalcogenides of Cu2X (X=Te or Se) are predicted using an adaptive genetic algorithm in combination with first-principles density functional theory calculations. Both systems are found to prefer a unique and previously unrecognized layered structure, with the total energies much lower than all structures proposed in the literature so far. The newly discovered structures are further shown to be dynamically and mechanically stable, and possess electronic properties consistent with existing experimental observations. In particular, their layered nature is expected to prevail over other structural forms at the interfaces of thin-film solar cells, and knowledge about the precise atomic structures of the interfaces is a prerequisite for achieving long-term stability and high efficiency of CdTe and Cu(In,Ga)Se2 solar cells.

  3. Monitoring MRK 509: the Origin of the Reflection

    NASA Astrophysics Data System (ADS)

    Leighly, Karen

    Ginga and ASCA observations of Mrk 509 show evidence for a strong Compton refl tion component and a strong, broad iron K(alpha) line which may originate in a elativistic disk. However, there is no direct evidence to physically link thes two components. We will combine 10 ksec coordinated XTE and ASCA observations order to obtain sufficient bandwidth and signal to simultaneously constrain th continuum, iron line and reflection components. We request 16 such observatio to determine if the components vary together and to estimate the lag in order constrain the geometry. Its high flux, strong reflection component and strong ut moderate time scale variability make Mrk 509 the ideal target for this key st. Simultaneous IUE observations will allow the determination of the X-ray/UV

  4. Wavelength Dependence on the Space Charge Collection

    SciTech Connect

    Washington, A.; Teague, L.; Duff, M.; Burger, A.; Groza, M.; Buliga, V.

    2012-05-31

    The distribution of the internal electric field in Cd{sub 1-x}Zn{sub x}Te (CZT) materials has significant effects on the charge collection ability. Light exposure at various wavelengths is a relatively unexplored process that alters charge collection at the anode contact. The use of multiple wavelengths can target charge carriers at various trap energies and positions throughout the crystal. The controlled illumination increases charge collection by releasing trapped electron and hole carriers in the crystal despite differences in light energy. Our study presents the results from our investigation of the effect of external illumination of CZT on the internal electric field via the Pockels effect. The space charge collection is further analyzed based on location and intensity relative to the specific wavelength of illumination.

  5. An Integral Study of Galactic Black Hole States

    NASA Technical Reports Server (NTRS)

    2005-01-01

    XTE 51550-564 was clearly detected with INTEGRAL out to 600 keV with the SPI, and is one of only two sources detected with IBISPICSIT. Software difficulties in analyzing the data prevented us from progressing with the analysis past the most elementary stages (see last year's report). The support from the INTEGRAL help desk has been very disappointing. People affiliated with INTEGRAL published a paper on the results of our data before we could master the reduction and analysis software. We are not the only group that got stuck with the analysis without adequate support from the INTEGRAL help desk. This was a rather disappointing experience as we lost many months of valuable time and efforts.

  6. Bibliography of Soviet Laser Developments Number 53, May-June 1981.

    DTIC Science & Technology

    1982-07-20

    PISETSKAYA S F 53 PROSYIRINA G D 10 *PANCHENKO M V 62 PISKAREVA M V 87 PROVAZNIK J 66 PANCHENKO V A 98 PISKUNOV V N 71 PRUCLO V 1 117 PANCHENKO V B3 98...82 UNCLASSIFIED OTA-OS T270OZ-004-8 F/ 22 N 1.0 MICROCOPY RESOLUTION TEST CHART NATIONAL BUREAU OF STANDARDS-1963A III., II~ U. *38 *m c3n DEFENSE I I...Gel’mont, B.L., V.I. Ivanov-Omskiy, V.A. Mal’tseva, and V.A. Smirnov (4). Radiative impurity recombination in n -Cdxal1 xTe. FTP, no. 6, 1981, 1109

  7. Bayesian timing analysis of giant flare of SGR 180620 by RXTE PCA

    NASA Astrophysics Data System (ADS)

    Hambaryan, V.; Neuhäuser, R.; Kokkotas, K. D.

    2011-04-01

    Aims: By detecting high-frequency quasi-periodic oscillations (QPOs) and estimating their frequencies during the decaying tail of giant flares from soft gamma-ray repeaters (SGRs) useful constraints for the equation of state (EoS) of superdense matter may be obtained via comparison with theoretical predictions of eigenfrequencies. Methods: We used the data collected by the Rossi X-Ray Timing Explorer (RXTE/XTE) Proportional Counter Array (PCA) of a giant flare of SGR 1806-20 on 2004 Dec. 27 and applied an existing Bayesian periodicity detection method to search for oscillations of a transient nature. Results: In addition to the already detected frequencies, we found a few new frequencies (fQPOs ~ 16.9,21.4,36.4,59.0,116.3 Hz) of predicted oscillations based on the APR14 EoS for SGR 1806-20.

  8. Electronic properties of surfaces, subsurface layers and interfaces for semiconductor and semimetal solid solutions

    NASA Astrophysics Data System (ADS)

    Romanov, O. V.; Belygh, A. M.; Krasnov, E. L.; Kalenik, V. I.

    1992-05-01

    The electronic and physical-chemical properties of restorded (dDX≤0.5-1.0 nm) surfaces at the depth of the space-charge region and of semiconductor(semimetal)-native anodic oxide (dDX=1.0-100 nm) interfaces have been investigated by the combined field effect in electrolytes (CFEE) method at T = 273-305 K and in metal-oxide-semiconductor (MOS) systems at T = 77-305 K for monocrystalline solid solutions CdxHg1-xTe (0≤x≤0.4) and MnxHg1-xTe (0≤x≤0.24). The interpretation of experimental capacitance-potential and current-potential characteristics has been effectuated allowing for the degeneracy of the electron-hole gas and conduction band non-parabolicity (considered in the Kane approximation). The electronic properties of the surface and subsurface regions have been determined: the forbidden zone (Eg), the thermodynamic equilibrium (ni) and non-equilibrium (nix) carrier concentrations for intrinsic material or the doping level (NA,D) for extrinsic material, the density-of- states effective masses (mcx, mhx), the equilibrium semiconductor(semimetal) surface potential (Vs0) and total electric charge captured at the interface defects (Qtot0), the fast surface states (FSS) density (NSS). The FSS density and the total electric charge at the interface (Qtotox) increase drastically (0.5-2 orders) as a function of the anodic oxide thickness at dOX < 8-12 nm.

  9. Enough Is Enough

    NASA Technical Reports Server (NTRS)

    Barrowman, James

    2003-01-01

    The spacecraft was nearly integrated and had passed some of its early mechanical and electrical testing. One of its instruments, the Proportional Counter Array (PCA), had a gas leak in one of the five proportional counter modules that made up the array. The science division where the instrument was being developed wanted a gas replenishment system added to assure the PCA would last for the entire mission. Adding a gas replenishment system would mean interrupting spacecraft integration and testing; developing a new subsystem and integrating it onto the spacecraft; modifying all the PCA modules; including a complex integration of the instrument onto the spacecraft; and implementing a more complex performance and environmental test process. It was the wrong answer because it made a simple design more complex and added little value to the mission at a major cost in time and dollars. Our mission couldn't afford the additional budget and schedule risks. XTE was the latest of a long line of projects being managed by my Explorer Program Office, but it was unique in being the first project we had agreed to do for a fixed price. NASA HQ agreed, in return, to provide us with the funding profile we needed to make it happen. We were both trying to break the unhealthy spiral in the Explorer program that saw current missions overrunning and pushing subsequent missions downstream to the point where their science was becoming marginal. The science community was upset and wanted better performance from NASA. I summarized my arguments to the director. The Engineering Directorate had taken responsibility for the spacecraft development when we established XTE as an in-house project at Goddard Space Flight Center, and also was supporting the PCA development. "It adds complexity," I reiterated. "It's a significant cost impact for only a marginal reliability increase". His response was music to my ears, "Jim, I won't stand in your way, but you'll have to convince the scientists and

  10. Supermagnetic Neutron Star Surprises Scientists, Forces Revision of Theories

    NASA Astrophysics Data System (ADS)

    2006-08-01

    Astronomers using radio telescopes from around the world have discovered a spinning neutron star with a superpowerful magnetic field -- called a magnetar -- doing things no magnetar has been seen to do before. The strange behavior has forced them to scrap previous theories about radio pulsars and promises to give new insights on the physics behind these extreme objects. Magnetar Artist's Conception of Magnetar With Radio Beams ALL IMAGES AND ANIMATIONS CREDIT: Bill Saxton, NRAO/AUI/NSF Image and Animation Files Magnetar Graphic (above image, JPEG, 32K) Animation With Sound From GBT Detection of XTE J1810-197 (8.6M) Animation With Sound From GBT Detection of XTE J1810-197 (Full Size, 29M) The magnetar, approximately 10,000 light-years from Earth in the direction of the constellation Sagittarius, is emitting powerful, regularly-timed pulses of radio waves just like radio pulsars, which are neutron stars with far less intense magnetic fields. Usually, magnetars are visible only in X-rays and sometimes very weakly in optical and infrared light. "No one has ever found radio pulses coming from a magnetar before. We thought that magnetars didn't do this," said Fernando Camilo of Columbia University. "This object is going to teach us new things about magnetar physics that we would never have learned otherwise," Camilo added. Neutron stars are the remnants of massive stars that have exploded as supernovae. Containing more mass than the Sun, they are compressed to a diameter of only about 15 miles, making them as dense as atomic nuclei. Ordinary pulsars are neutron stars that emit "lighthouse beams" of radio waves along the poles of their magnetic fields. As the star spins, the beam of radio waves is flung around, and when it passes the direction of Earth, astronomers can detect it with radio telescopes. Scientists have found about 1700 pulsars since their first discovery in 1967. While pulsars have strong magnetic fields, about a dozen neutron stars have been dubbed

  11. Dramatic Outburst Reveals Nearest Black Hole

    NASA Astrophysics Data System (ADS)

    2000-01-01

    Sgr. The radio observations revealed the presence of a jet escaping from the system at mind-boggling speeds. Only three other galactic X-ray stellar systems have been found to eject material at such speeds. They have been dubbed "microquasars" because, on a smaller scale, they resemble quasars, which lie at the hearts of distant galaxies and also spew out high-velocity jets of particles. In galaxy-core quasars, the black holes are millions of times more massive than the Sun; in the more nearby microquasars the black holes are roughly three to twenty times more massive than the Sun. The extremely high velocity of the jets suggests that their origin lies close to the event horizon of a black hole. Microquasar activity is thought to arise when the black hole in the binary system draws material away from its companion star. The material surrounding the black hole forms a rapidly spinning disk called an accretion disk. This disk is heated by friction to millions of degrees, causing it to emit X-rays. As spiralling gas moves into the gravity well of the black hole, it moves faster and faster. Magnetic fields in the disk are believed to expel the charged subatomic particles at speeds close to that of light. As the charged particles interact with the magnetic fields, they emit radio waves. If some of the material escapes by being magnetically expelled into space, the matter may continue moving at the tremendous speed it had attained near the black hole. After their ejection, the jets of particles expand and cool, fading from astronomers' view. V4641 Sgr excites astronomers because it is close and because it acted so differently from other microquasars. In other microquasars, outbursts have dimmed more slowly over weeks or months rather than hours. "There's something fundamentally different about this one; it's more extreme than any other example," Hjellming said. "And because this system happens to be so close to us, `it is very likely that there are more objects like V4641

  12. Implications of the radio spectral index transition in LS I +61°303 for its INTEGRAL data analysis

    NASA Astrophysics Data System (ADS)

    Zimmermann, L.; Massi, M.

    2012-01-01

    Context. The TeV emitting X-ray binary LS I +61°303 has two radio periodicities that correspond to a large periodic outburst with the same period as the orbit, 26.5 days (phase Φ), and a second periodicity of 1667 days (phase Θ), which modulates the orbital phase and amplitude of the large outburst. Analyses of the radio spectral index revealed in LS I +61°303 the presence of the critical transition typical for microquasars from optically thick emission (related to a steady jet) to an optically thin outburst (related to a transient jet), and found that it occurs at Φcrit, which is modulated by Θ: Φcrit = f(Θ). Aims: We examine the possible implications of averaging high energy data over large Θ and Φ intervals in the light of puzzling published INTEGRAL results, which differ for different averaging of the data. Methods: In microquasars, a simultaneous transition between two X-ray states occurs at the switch from optically thick radio emission to an optically thin radio outburst, from the low/hard to the steep power-law state. Assuming that the same transition occurs in LS I +61°303 at Φcrit, we can show qualitatively the effect of averaging high energy data on Θ, by analysing the effects of averaging radio spectral index data across the same Θ interval. We then model the two X-ray states, low/hard and steep power-law state, and show quantitatively how their mixing can affect the results. Results: When folded over too large a Θ interval, spectral data from INTEGRAL can yield a false picture of the emission behaviour of the source along the orbit because it may be mixing two spectral states. Furthermore, averaging the data along the orbit may result in a dominant low/hard spectral state, which, for insufficiently extended sampling, might appear without a cut-off. Conclusions: The INTEGRAL results can be interpreted as two X-ray states that alternate with each other along the orbit. The implications of this analysis for HE/VHE data from LS I +61°303

  13. INTRINSIC ELECTROMAGNETIC VARIABILITY IN CELESTIAL OBJECTS CONTAINING RAPIDLY SPINNING BLACK HOLES

    SciTech Connect

    Zhang, Fan

    2016-02-10

    Analytical studies have raised the concern that a mysterious expulsion of magnetic field lines by a rapidly spinning black hole (dubbed the black hole Meissner effect) would shut down the Blandford–Znajek process and quench the jets of active galactic nuclei and microquasars. This effect is, however, not seen observationally or in numerical simulations. Previous attempts at reconciling the predictions with observations have proposed several mechanisms to evade the Meissner effect. In this paper, we identify a new evasion mechanism and discuss its observational significance. Specifically, we show that the breakdown of stationarity is sufficient to remove the expulsion of the magnetic field at all multipole orders, and that the associated temporal variation is likely turbulent because of the existence of efficient mechanisms for sharing energy across different modes. Such an intrinsic (as opposed to being driven externally by, e.g., changes in the accretion rate) variability of the electromagnetic field can produce the recorded linear correlation between microvariability amplitudes and mean fluxes, help create magnetic randomness and seed sheared magnetic loops in jets, and lead to a better theoretical fit to the X-ray microvariability power spectral density.

  14. ON THE ROLE OF FAST MAGNETIC RECONNECTION IN ACCRETING BLACK HOLE SOURCES

    SciTech Connect

    Singh, C. B.; De Gouveia Dal Pino, E. M.; Kadowaki, L. H. S. E-mail: dalpino@iag.usp.br

    2015-01-30

    We attempt to explain the observed radio and gamma-ray emission produced in the surroundings of black holes by employing a magnetically dominated accretion flow model and fast magnetic reconnection triggered by turbulence. In earlier work, a standard disk model was used and we refine the model by focusing on the sub-Eddington regime to address the fundamental plane of black hole activity. The results do not change substantially with regard to previous work, ensuring that the details of accretion physics are not relevant in the magnetic reconnection process occurring in the corona. Rather, our work puts fast magnetic reconnection events as a powerful mechanism operating in the core region near the jet base of black hole sources on more solid ground. For microquasars and low-luminosity active galactic nuclei, the observed correlation between radio emission and the mass of the sources can be explained by this process. The corresponding gamma-ray emission also seems to be produced in the same core region. On the other hand, emission from blazars and gamma-ray bursts cannot be correlated to core emission based on fast reconnection.

  15. The Universal Book of Astronomy: From the Andromeda Galaxy to the Zone of Avoidance

    NASA Astrophysics Data System (ADS)

    Darling, David

    2003-10-01

    The ultimate guide to the final frontier This alphabetical tour of the universe provides all the history, science, and up-to-the-minute facts needed to explore the skies with authority. Packed with more than 3,000 entries that cover everything from major observatories and space telescopes to biographies of astronomers throughout the ages, it showcases an extraordinary array of newfound wonders, including microquasars, brown dwarfs, and dark energy, as well as a host of individual comets, asteroids, moons, planets, stars, nebulas, and galaxies. Featuring nearly 200 illustrations and eight pages of color photographs, this comprehensive guide provides easy lookup of topics and offers more in-depth information than can be found in existing star guides or astronomy dictionaries. It's an ideal resource for the amateur astronomer or anyone with an interest in the mysteries of the cosmos. David Darling, PhD (Brainerd, MN), is the author of The Complete Book of Spaceflight (0-471-05649-9) and Equations of Eternity, a New York Times Notable Book.

  16. Black Hole Blows Big Bubble

    NASA Astrophysics Data System (ADS)

    2010-07-01

    Combining observations made with ESO's Very Large Telescope and NASA's Chandra X-ray telescope, astronomers have uncovered the most powerful pair of jets ever seen from a stellar black hole. This object, also known as a microquasar, blows a huge bubble of hot gas, 1000 light-years across, twice as large and tens of times more powerful than other known microquasars. The discovery is reported this week in the journal Nature. "We have been astonished by how much energy is injected into the gas by the black hole," says lead author Manfred Pakull. "This black hole is just a few solar masses, but is a real miniature version of the most powerful quasars and radio galaxies, which contain black holes with masses of a few million times that of the Sun." Black holes are known to release a prodigious amount of energy when they swallow matter. It was thought that most of the energy came out in the form of radiation, predominantly X-rays. However, the new findings show that some black holes can release at least as much energy, and perhaps much more, in the form of collimated jets of fast moving particles. The fast jets slam into the surrounding interstellar gas, heating it and triggering an expansion. The inflating bubble contains a mixture of hot gas and ultra-fast particles at different temperatures. Observations in several energy bands (optical, radio, X-rays) help astronomers calculate the total rate at which the black hole is heating its surroundings. The astronomers could observe the spots where the jets smash into the interstellar gas located around the black hole, and reveal that the bubble of hot gas is inflating at a speed of almost one million kilometres per hour. "The length of the jets in NGC 7793 is amazing, compared to the size of the black hole from which they are launched," says co-author Robert Soria [1]. "If the black hole were shrunk to the size of a soccer ball, each jet would extend from the Earth to beyond the orbit of Pluto." This research will help

  17. Black Hole Blows Big Bubble

    NASA Astrophysics Data System (ADS)

    2010-07-01

    Combining observations made with ESO's Very Large Telescope and NASA's Chandra X-ray telescope, astronomers have uncovered the most powerful pair of jets ever seen from a stellar black hole. This object, also known as a microquasar, blows a huge bubble of hot gas, 1000 light-years across, twice as large and tens of times more powerful than other known microquasars. The discovery is reported this week in the journal Nature. "We have been astonished by how much energy is injected into the gas by the black hole," says lead author Manfred Pakull. "This black hole is just a few solar masses, but is a real miniature version of the most powerful quasars and radio galaxies, which contain black holes with masses of a few million times that of the Sun." Black holes are known to release a prodigious amount of energy when they swallow matter. It was thought that most of the energy came out in the form of radiation, predominantly X-rays. However, the new findings show that some black holes can release at least as much energy, and perhaps much more, in the form of collimated jets of fast moving particles. The fast jets slam into the surrounding interstellar gas, heating it and triggering an expansion. The inflating bubble contains a mixture of hot gas and ultra-fast particles at different temperatures. Observations in several energy bands (optical, radio, X-rays) help astronomers calculate the total rate at which the black hole is heating its surroundings. The astronomers could observe the spots where the jets smash into the interstellar gas located around the black hole, and reveal that the bubble of hot gas is inflating at a speed of almost one million kilometres per hour. "The length of the jets in NGC 7793 is amazing, compared to the size of the black hole from which they are launched," says co-author Robert Soria [1]. "If the black hole were shrunk to the size of a soccer ball, each jet would extend from the Earth to beyond the orbit of Pluto." This research will help

  18. The Cosmic Ray Electron Excess

    NASA Technical Reports Server (NTRS)

    Chang, J.; Adams, J. H.; Ahn, H. S.; Bashindzhagyan, G. L.; Christl, M.; Ganel, O.; Guzik, T. G.; Isbert, J.; Kim, K. C.; Kuznetsov, E. N.; Panasyuk, M. I.; Panov, A. D.; Schmidt, W. K. H.; Seo, E. S.; Sokolskaya, N. V.; Watts, J. W.; Wefel, J. P.; Wu, J.; Zatsepin, V. I.

    2008-01-01

    This slide presentation reviews the possible sources for the apparent excess of Cosmic Ray Electrons. The presentation reviews the Advanced Thin Ionization Calorimeter (ATIC) instrument, the various parts, how cosmic ray electrons are measured, and shows graphs that review the results of the ATIC instrument measurement. A review of Cosmic Ray Electrons models is explored, along with the source candidates. Scenarios for the excess are reviewed: Supernova remnants (SNR) Pulsar Wind nebulae, or Microquasars. Each of these has some problem that mitigates the argument. The last possibility discussed is Dark Matter. The Anti-Matter Exploration and Light-nuclei Astrophysics (PAMELA) mission is to search for evidence of annihilations of dark matter particles, to search for anti-nuclei, to test cosmic-ray propagation models, and to measure electron and positron spectra. There are slides explaining the results of Pamela and how to compare these with those of the ATIC experiment. Dark matter annihilation is then reviewed, which represent two types of dark matter: Neutralinos, and kaluza-Kline (KK) particles, which are next explained. The future astrophysical measurements, those from GLAST LAT, the Alpha Magnetic Spectrometer (AMS), and HEPCAT are reviewed, in light of assisting in finding an explanation for the observed excess. Also the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC) could help by revealing if there are extra dimensions.

  19. MAX-a gamma-ray lense for nuclear astrophysics.

    SciTech Connect

    von Ballmoos, P.; Halloin, H.; Skinner, G.; Smither, B.; Paul, J.; Abrosimov, N.; Alvarez, J.; Astier , P.; Bastie, P.; Barrett, D.; Bazzano, A.; Blanchard, A.; Boutonnet, A.; Brousse, P.; Cordier, B.; Courvoisier, T.; DiCocco, G.; Giuliani, A.; Hamelin, B.; Hernanz, M.; Jean, P.; Isern, J.; Knodlseder, J.; Laurent, P.; Lebrun, F.; Experimental Facilities Division; CESR; CEA-Saclay; Inst. fur Kristallzuchtung; IEEC; LPNHE; Inst. Laue-Langevin; IAS; LA-OMP; Alcatel Space Industries; ISDC; TESRE; Univ. Insurbia

    2004-01-01

    The mission concept MAX is a space borne crystal diffraction telescope, featuring a broad-band Laue lens optimized for the observation of compact sources in two wide energy bands of high astrophysical relevance. For the first time in this domain, gamma-rays will be focused from the large collecting area of a crystal diffraction lens onto a very small detector volume. As a consequence, the background noise is extremely low, making possible unprecedented sensitivities. The primary scientific objective of MAX is the study of type Ia supernovae by measuring intensities, shifts and shapes of their nuclear gamma-ray lines. When finally understood and calibrated, these profoundly radioactive events will be crucial in measuring the size, shape, and age of the Universe. Observing the radioactivities from a substantial sample of supernovae and novae will significantly improve our understanding of explosive nucleosynthesis. Moreover, the sensitive gamma-ray line spectroscopy performed with MAX is expected to clarify the nature of galactic microquasars (e{sup +}e{sup -} annihilation radiation from the jets), neutrons stars and pulsars, X-ray Binaries, AGN, solar flares and, last but not least, gamma-ray afterglow from gamma-burst counterparts.

  20. The Formation of Relativistic Jets from Kerr Black Holes

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.-I.; Richardson, G.; Preece, R.; Hardee, P.; Koide, S.; Shibata, K.; Kudoh, T.; Sol, H.; Fishman, G. J.

    2003-01-01

    We have performed the first fully three-dimensional general relativistic magnetohydrodynamics (GRMHD) simulation for Schwarzschild and Kerr black holes with a free falling corona and thin accretion disk. The initial simulation results with a Schwarzschild metric show that a jet is created as in the previous axisymmetric simulations with mirror symmetry at the equator. However, the time to form the jet is slightly longer than in the 2-D axisymmetric simulation. We expect that the dynamics of jet formation are modified due to the additional freedom in the azimuth dimension without axisymmetry with respect to the Z axis and reflection symmetry respect to the equatorial plane. The jet which is initially formed due to the twisted magnetic fields and shocks becomes a wind at the later time. The wind flows out with a much wider angle than the initial jet. The twisted magnetic fields at the earlier time were untwisted and less pinched. The accretion disk became thicker than the initial condition. Further simulations with initial perturbations will provide insights for accretion dynamics with instabilities such as magneto-rotational instability (MRI) and accretion-eject instability (AEI). These instabilities may contribute to variabilities observed in microquasars and AGN jets.

  1. Spectropolarimetry Emission from SS433

    NASA Astrophysics Data System (ADS)

    Llorens, Miguel Charcos; Eikenberry, Stephen S.

    2008-05-01

    In the last few years, spectropolarimetry has become an important tool in the study of AGN. Their geometry is obtained by comparing synthetic Stokes spectra with the observed spectropolarimetry. Similar techniques can be applied to the study of the scattering regions in the jets and disk of X-ray binary systems. We introduce a new code DESPEJO (Dynamical Evolution of Spectropolarimetry Emission of Jet Objects) that has been developed to analyze line intensity and polarization components in the emission from scattering regions on microquasars. In particular, the heating mechanisms and ejection of the gas in the jets of SS433 remain a mystery. Previous work on its polarized emission tried in vain to answer questions about the physical origin of its jets. Because SS433 has unique geometrical and dynamical configurations the study of synthetic polarimetric spectra and their evolution will give an important insight into the jet mechanism. We present our initial results with DESPEJO using the first spectropolarimetry data of this target. This method will give clues on the formation, acceleration, collimation and state of the gas bullets in its jets as well as on other properties of the system concerning the nature of the donor star and disk geometry.

  2. The Accretion Flow-Discrete Ejection Connection in GRS 1915+105

    NASA Astrophysics Data System (ADS)

    Punsly, Brian; Rodriguez, Jérôme; Trushkin, Sergei A.

    2016-07-01

    The microquasar GRS 1915+105 is known for its spectacular discrete ejections. They occur unexpectedly, thus their inception has escaped direct observation. It has been shown that the X-ray flux increases in the hours leading up to a major ejection. In this article, we consider the serendipitous interferometric monitoring of a modest version of a discrete ejection described in Reid et al. that would have otherwise escaped detection in daily radio light curves. The observation begins ˜1 hr after the onset of the ejection, providing unprecedented accuracy on the estimate of the ejection time. The astrometric measurements allow us to determine the time of ejection as {{MJD}} {56436.274}-0.013+0.016, i.e., within a precision of 41 minutes (95% confidence). Just like larger flares, we find that the X-ray luminosity increases in last 2-4 hr preceding ejection. Our finite temporal resolution indicates that this elevated X-ray flux persists within {21.8}-19.1+22.6 minutes of the ejection with 95% confidence, the highest temporal precision of the X-ray-superluminal ejection connection to date. This observation provides direct evidence that the physics that launches major flares occurs on smaller scales as well (lower radio flux and shorter ejection episodes). The observation of a X-ray spike prior to a discrete ejection, although of very modest amplitude, suggests that the process linking accretion behavior to ejection is general from the smallest scales to high luminosity major superluminal flares.

  3. 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.

  4. Production and Collimation of Astrophysical Jets or Accretion: M87 and SN 1987A Scenarios

    NASA Astrophysics Data System (ADS)

    Bernal, C. G.; Page, D.

    2006-06-01

    Jets and outflows of various degrees of collimation and energetics are an ubiquitous phenomenon in astrophysics. They are present at all length scales, ranging from those found in young stellar objects (YSOs, Reipurth & Bally1991) and the galactic microquasars (Mirabel & Rodriguez 1994, Fender & Belloni 2004), to kpc-scale relativistic jets in AGNs. In many cases these appear to be symmetrical, with two oppositely directed lines of flow, and almost always they seem to be directly connected with accretion onto a central object at the base of the collimated outflow. The energy in the outflow itself ultimately comes from the gravitational potential well created by the central object. The structure and evolution of jet-like structures under a variety of physical conditions is a problem that generally requires numerical modelling. However, in certain cases valuable insight can be gained from purely hydrodynamical analytical solutions which exhibit outflows (or accretion) of varying characteristics. We show here several solutions of this type, applicable to various accretion scenarios. Assuming that our solutions are Jets, we applied the model to M87 scenario and to SN1987A scenario, assuming that our solutions are like accretion.

  5. A STUDY OF RADIO POLARIZATION IN PROTOSTELLAR JETS

    SciTech Connect

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

    2016-01-10

    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{sup −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.

  6. Plasma phenomenology in astrophysical systems: Radio-sources and jets

    SciTech Connect

    Montani, Giovanni; Petitta, Jacopo

    2014-06-15

    We review the plasma phenomenology in the astrophysical sources which show appreciable radio emissions, namely Radio-Jets from Pulsars, Microquasars, Quasars, and Radio-Active Galaxies. A description of their basic features is presented, then we discuss in some details the links between their morphology and the mechanisms that lead to the different radio-emissions, investigating especially the role played by the plasma configurations surrounding compact objects (Neutron Stars, Black Holes). For the sake of completeness, we briefly mention observational techniques and detectors, whose structure set them apart from other astrophysical instruments. The fundamental ideas concerning angular momentum transport across plasma accretion disks—together with the disk-source-jet coupling problem—are discussed, by stressing their successes and their shortcomings. An alternative scenario is then inferred, based on a parallelism between astrophysical and laboratory plasma configurations, where small-scale structures can be found. We will focus our attention on the morphology of the radio-jets, on their coupling with the accretion disks and on the possible triggering phenomena, viewed as profiles of plasma instabilities.

  7. SPECTRAL ANALYSIS IN ORBITAL/SUPERORBITAL PHASE SPACE AND HINTS OF SUPERORBITAL VARIABILITY IN THE HARD X-RAYS OF LS I +61°303

    SciTech Connect

    Li, Jian; Torres, Diego F.; Zhang, Shu

    2014-04-10

    We present an INTEGRAL spectral analysis in the orbital/superorbital phase space of LS I +61°303. A hard X-ray spectrum with no cutoff is observed at all orbital/superorbital phases. The hard X-ray index is found to be uncorrelated with the radio index (non-simultaneously) measured at the same orbital and superorbital phases. In particular, the absence of an X-ray spectrum softening during periods of negative radio index does not favor a simple interpretation of the radio index variations in terms of a microquasar's changes of state. We uncover hints of superorbital variability in the hard X-ray flux, in phase with the superorbital modulation in soft X-rays. An orbital phase drift of the radio peak flux and index along the superorbital period is observed in the radio data. We explore its influence on a previously reported double-peak structure of a radio orbital light curve, and present it as a plausible explanation.

  8. Monitoring the Black Hole Binary GRS 1758-258 with INTEGRAL and RXTE

    NASA Technical Reports Server (NTRS)

    Pottschmidt, Katja; Chernyakova, Masha; Lubinski, Piotr; Migliari, Simone; Smith, David M.; Zdziarski, Andrzej A.; Tomsick, John A.; Bezayiff, N.; Kreykenbohm, Ingo; Kretschmar, Peter; Kalemci, Emrah

    2008-01-01

    The microquasar GRS 1758-258 is one of only three persistent black hole binaries that spend most of their time in the hard spectral state, the other two being Cyg X-l and 1E 1741.7-2942. It therefore provides the rare opportunity for an extensive long term study of this important black hole state which is associated with strong variability and radio jet emission. INTEGRAL has been monitoring the source since the first Galactic Center Deep Exposure season in spring 2003 during two 2-3 months long Galactic Center viewing epochs each year, amounting to 11 epochs including spring of 2008. With the exception of the last epoch quasi-simultaneous RXTE monitoring observations are available as well. Here we present an analysis of the epoch averaged broad band spectra which display considerable long term variability, most notably the occurrence of two soft/off states, extreme examples for the hysteretic behavior of black hole binaries. The hard source spectrum and long exposures allow us to extend the analysis for several epochs to approximately 800 keV using PICsIT data and address the question of the presence of a non-thermal Comptonization component.

  9. The evolution of radio-loud active galactic nuclei as a function of black hole spin

    NASA Astrophysics Data System (ADS)

    Garofalo, D.; Evans, D. A.; Sambruna, R. M.

    2010-08-01

    Recent work on the engines of active galactic nuclei jets suggests that their power depends strongly and perhaps counter-intuitively on black hole spin. We explore the consequences of this on the radio-loud population of active galactic nuclei and find that the time evolution of the most powerful radio galaxies and radio-loud quasars fits into a picture in which black hole spin varies from retrograde to prograde with respect to the accreting material. Unlike the current view, according to which jet powers decrease in tandem with a global downsizing effect, we argue for a drop in jet power resulting directly from the paucity of retrograde accretion systems at lower redshift z caused by a continuous history of accretion dating back to higher z. In addition, the model provides simple interpretations for the basic spectral features differentiating radio-loud and radio-quiet objects, such as the presence or absence of disc reflection, broadened iron lines and signatures of disc winds. We also briefly describe our models' interpretation of microquasar state transitions. We highlight our result that the most radio-loud and most radio-quiet objects both harbour highly spinning black holes but in retrograde and prograde configurations, respectively.

  10. Polarization Radiation with Turbulent Magnetic Fields from X-Ray Binaries

    NASA Astrophysics Data System (ADS)

    Zhang, Jian-Fu; Xiang, Fu-Yuan; Lu, Ju-Fu

    2017-02-01

    We study the properties of polarized radiation in turbulent magnetic fields from X-ray binary jets. These turbulent magnetic fields are composed of large- and small-scale configurations, which result in the polarized jitter radiation when the characteristic length of turbulence is less than the non-relativistic Larmor radius. On the contrary, the polarized synchrotron emission occurs, corresponding to a large-scale turbulent environment. We calculate the spectral energy distributions and the degree of polarization for a general microquasar. Numerical results show that turbulent magnetic field configurations can indeed provide a high degree of polarization, which does not mean that a uniform, large-scale magnetic field structure exists. The model is applied to investigate the properties of polarized radiation of the black-hole X-ray binary Cygnus X-1. Under the constraint of multiband observations of this source, our studies demonstrate that the model can explain the high polarization degree at the MeV tail and predict the highly polarized properties at the high-energy γ-ray region, and that the dominant small-scale turbulent magnetic field plays an important role for explaining the highly polarized observation at hard X-ray/soft γ-ray bands. This model can be tested by polarization observations of upcoming polarimeters at high-energy γ-ray bands.

  11. Coordinated Radio and High-Energy Observations of Cygnus X-3 with the Allen Telescope Array

    NASA Astrophysics Data System (ADS)

    Williams, Peter K. G.; Bower, G. C.; Tomsick, J. A.; Allen Telescope Array Team

    2011-01-01

    The microquasar Cygnus X-3 is one of the few Galactic sources known to produce relativistic jets and can be one of the brightest radio sources in the Galaxy when flaring. In late 2009 it became the first such system to be seen in the gamma-ray regime with detections by both AGILE and Fermi. We have observed Cyg X-3 at 3 GHz every 5 days for the past six months with the Allen Telescope Array in conjunction with space-based X-ray (INTEGRAL, RXTE) and gamma-ray (Fermi) observations. We present results from both the long-term dataset and intensive observing sessions in which we obtain the radio lightcurve of Cyg X-3 on 10-minute timescales. We focus particularly on a May 2010 minor flare event for which we have coverage in all three bands.The first phase of the ATA was funded through generous grants from the Paul G. Allen Family Foundation. UC Berkeley, the SETI Institute, the National Science Foundation (Grant No. 0540599), Sun Microsystems, Xilinx, Nathan Myhrvold, Greg Papadopoulos, and other corporations and individual donors contributed additional funding.

  12. New Class of Self-Consistent Current Sheets and Filaments in Collisionless Plasma

    NASA Astrophysics Data System (ADS)

    Derishev, E. V.; Kocharovsky, V. V.; Kocharovsky, Vl. V.; Martyanov, V. Yu.

    2006-08-01

    A continuous set of stationary current sheets and filaments in collisionless multi-component plasma is found analytically using integrals of two-dimensional motion of particles in the self-consistent magnetic field. In our solutions, which are relativistic in general, the magnetic energy density can be comparable to that of particles, and the spatial scale can be arbitrary compared to typical gyroradius of the particles. We consider the properties of newly found stationary solutions and their possible applications to analysis of magnetic field configurations emerging in various astrophysical plasmas, including coronal structures, shocks and jets. The results are used for interpretation of recent observations and numerical simulations. By choosing particular dependence of particle distribution function on the integrals of motion we are able to obtain various profiles of magnetic field and self-consistent current, including non-monotone. The obtained solutions describe much more general class of equilibrium configurations as compared to known generalizations of Harris current sheets. On this basis, we suggest a way to describe slow dynamics and filamentation of collisionless current configurations in coronal plasma and in Active Galactic Nuclei, Gamma-Ray Bursts, and microquasars.

  13. Looking into the heart of a beast: The black hole binary LS 5039

    NASA Astrophysics Data System (ADS)

    Szalai, Tamas; Kiss, Laszlo L.; Sarty, Gordon E.

    2010-03-01

    LS 5039 is a relatively close microquasar consisting of a late O-type star and a compact object (very possibly a black hole) on a highly eccentric orbit with a period of 3.9 days. The high X-ray, gamma-ray and radio luminosity indicate light-matter interaction, which arise from the stellar wind of the primary star accreting toward the black hole. Former examinations suggest that LS 5039 could be a prototype of wind-fed high mass X-ray binaries (WXBs) with diskless main sequence O primaries. Now there is a great chance to better understand the configuration and the physical processes in the exotic system. In July 2009 LS 5039 was followed by the Canadian MOST space telescope to get ultraprecise photometric data in a month-long semi-continuous time series. Parallel to this, we have taken simultaneous high-resolution optical spectra using the 2.3m ANU telescope of the Siding Spring Observatory, supplemented with further data obtained in early August 2009 with the same instrument. Here we present the first results from the new echelle spectra, which represent the best optical spectroscopy ever obtained for this intriguing system. We determined fundamental orbital and physical parameters of LS 5039 and examined the configuration and the circumstellar environment of the system via radial velocity measurements and detailed line-profile analysis of H-Balmer, He I and He II lines.

  14. SEARCHES FOR TIME-DEPENDENT NEUTRINO SOURCES WITH ICECUBE DATA FROM 2008 TO 2012

    SciTech Connect

    Aartsen, M. G.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Arguelles, C.; Baker, M.; Ahrens, M.; Altmann, D.; Anderson, T.; Arlen, T. C.; Archinger, M.; Baum, V.; Auffenberg, J.; Bai, X.; Barwick, S. W.; Bay, R.; Beatty, J. J.; Tjus, J. Becker; Becker, K.-H.; Collaboration: IceCube Collaboration; and others

    2015-07-01

    In this paper searches for flaring astrophysical neutrino sources and sources with periodic emission with the IceCube neutrino telescope are presented. In contrast to time-integrated searches, where steady emission is assumed, the analyses presented here look for a time-dependent signal of neutrinos using the information from the neutrino arrival times to enhance the discovery potential. A search was performed for correlations between neutrino arrival times and directions, as well as neutrino emission following time-dependent light curves, sporadic emission, or periodicities of candidate sources. These include active galactic nuclei, soft γ-ray repeaters, supernova remnants hosting pulsars, microquasars, and X-ray binaries. The work presented here updates and extends previously published results to a longer period that covers 4 years of data from 2008 April 5 to 2012 May 16, including the first year of operation of the completed 86 string detector. The analyses did not find any significant time-dependent point sources of neutrinos, and the results were used to set upper limits on the neutrino flux from source candidates.

  15. NuSTAR and integral observations of a low/hard state of 1E1740.7-2942

    SciTech Connect

    Natalucci, Lorenzo; Bazzano, Angela; Fiocchi, Mariateresa; Ubertini, Pietro; Tomsick, John A.; Boggs, Steven E.; Craig, William W.; Krivonos, Roman; Smith, David M.; Bachetti, Matteo; Barret, Didier; Christensen, Finn E.; Fürst, Felix; Grefenstette, Brian W.; Harrison, Fiona A.; Hailey, Charles J.; Kuulkers, Erik; Miller, Jon M.; Pottschmidt, Katja; Stern, Daniel; and others

    2014-01-01

    The microquasar 1E1740.7-2942, also known as the 'Great Annihilator,' was observed by NuSTAR in the summer of 2012. We have analyzed in detail two observations taken ∼2 weeks apart, for which we measure hard and smooth spectra typical of the low/hard state. A few weeks later the source flux declined significantly. Nearly simultaneous coverage by INTEGRAL is available from its Galactic Center monitoring campaign lasting ∼2.5 months. These data probe the hard state spectrum from 1E1740.7-2942 before the flux decline. We find good agreement between the spectra taken with IBIS/ISGRI and NuSTAR, with the measurements being compatible with a change in flux with no spectral variability. We present a detailed analysis of the NuSTAR spectral and timing data and upper limits for reflection of the high energy emission. We show that the high energy spectrum of this X-ray binary is well described by thermal Comptonization.

  16. 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.

  17. The GlobalJetWatch spectrographs: a fibre-fed spectrograph for small telescopes

    NASA Astrophysics Data System (ADS)

    Clarke, Fraser J.; Gosling, Andrew J.; Doolin, Sam; Goodall, Paul; Perez, Sebastian; Pattinson, Paul; Makin, Rick; Blundell, Katherine M.

    2008-07-01

    The GlobalJetWatch project (www.globaljetwatch.net) will place small (0.5-metre) commerical telescopes in four schools around the world. Each telescope will be equipped with a custom designed spectrograph, currently being built by the Astrophysics sub-department of the University of Oxford. The scientific goal of the project is to provide continual monitoring of a rosetta stone object, the micro-quasar SS433. In addition, the project has a significant out-reach element, aiming to involve school children on four-continents in front-line astronomical research. The spectrograph is a fibre-fed fixed format cross-dispersed echellete design providing R~6000 spectra from 4300-8500 in a single exposure. The spectrograph is built almost entirely from off-the-shelf components. The four GlobalJetWatch sites (Australia, India, South Africa, Chile) will be commissioned in 2008/09. Here we present the baseline design of the spectrograph, and initial results from the prototype on-sky commissioning in Oxford.

  18. ASGARD: A LARGE SURVEY FOR SLOW GALACTIC RADIO TRANSIENTS. I. OVERVIEW AND FIRST RESULTS

    SciTech Connect

    Williams, Peter K. G.; Bower, Geoffrey C.; Croft, Steve; Keating, Garrett K.; Law, Casey J.; Wright, Melvyn C. H.

    2013-01-10

    Searches for slow radio transients and variables have generally focused on extragalactic populations, and the basic parameters of Galactic populations remain poorly characterized. We present a large 3 GHz survey performed with the Allen Telescope Array (ATA) that aims to improve this situation: ASGARD, the ATA Survey of Galactic Radio Dynamism. ASGARD observations spanned two years with weekly visits to 23 deg{sup 2} in two fields in the Galactic plane, totaling 900 hr of integration time on science fields and making it significantly larger than previous efforts. The typical blind unresolved source detection limit was 10 mJy. We describe the observations and data analysis techniques in detail, demonstrating our ability to create accurate wide-field images while effectively modeling and subtracting large-scale radio emission, allowing standard transient-and-variability analysis techniques to be used. We present early results from the analysis of two pointings: one centered on the microquasar Cygnus X-3 and one overlapping the Kepler field of view (l = 76 Degree-Sign , b = +13. Degree-Sign 5). Our results include images, catalog statistics, completeness functions, variability measurements, and a transient search. Out of 134 sources detected in these pointings, the only compellingly variable one is Cygnus X-3, and no transients are detected. We estimate number counts for potential Galactic radio transients and compare our current limits to previous work and our projection for the fully analyzed ASGARD data set.

  19. Evidence of elevated X-ray absorption before and during major flare ejections in GRS 1915+105

    SciTech Connect

    Punsly, Brian; Rodriguez, Jérôme

    2014-03-10

    We present time-resolved X-ray spectroscopy of the microquasar GRS 1915+105 with the MAXI observatory in order to study the accretion state just before and during the ejections associated with its major flares. Radio monitoring with the RATAN-600 radio telescope from 4.8-11.2 GHz has revealed two large, steep-spectrum major flares in the first eight months of 2013. Since the RATAN has received one measurement per day, we cannot determine the jet-forming time without more information. Fortunately, this is possible since a distinct X-ray light curve signature that occurs preceding and during major ejections has been determined in an earlier study. The X-ray luminosity spikes to very high levels in the hours before ejection, then becomes variable (with a nearly equal X-ray luminosity when averaged over the duration of the ejection) during a brief 3-8 hr ejection process. By comparing this X-ray behavior with MAXI light curves, we can estimate the beginning and end of the ejection episode of the strong 2013 flares to within ∼3 hr. Using this estimate in conjunction with time-resolved spectroscopy from the data in the MAXI archives allows us to deduce that the X-ray absorbing hydrogen column density increases significantly in the hours preceding the ejections and remains elevated during the ejections responsible for the major flares. This finding is consistent with an outflowing wind or enhanced accretion at high latitudes.

  20. GRS 1915+105 AS A GALACTIC ANALOG OF A FANAROFF-RILEY II QUASAR

    SciTech Connect

    Punsly, Brian; Rodriguez, Jerome E-mail: brian.punsly@comdev-usa.com

    2013-06-20

    We study the long-term time-averaged kinetic luminosity, Q-bar , of the major flares of the Galactic microquasar GRS 1915+105 and the relationship to the intrinsic X-ray (bolometric) luminosity, L{sub bol}, and scale it to that of a complete sample of SDSS/FIRST Fanaroff-Riley (FR) II quasars. If the scale invariance hypothesis for black holes (BHs) holds then we show that the expected distribution in the Q-bar -L{sub bol} scatter plane of GRS 1915+105 is consistent with FR II quasars for distances D = 10.7-11 kpc. We compare the specific values of kinetic luminosity and L{sub bol} during flares of GRS 1915+105 to that predicted by several three-dimensional MHD simulations of BH accretion flows with relativistic ejections. If FR II quasars are a scaled up version of GRS 1915+105, the data are consistent with numerical models when they contain an ergospheric disk jet and the BH spin is a/M = 0.99 or a/M = 0.998 (we estimate a/M > 0.984). In the framework of scale invariance of BHs, our results may imply that FR II quasars also hold rapidly rotating BHs.

  1. Revisiting Evidence of Chaos in X-Ray Light Curves: The Case of GRS 1915+105

    NASA Astrophysics Data System (ADS)

    Mannattil, Manu; Gupta, Himanshu; Chakraborty, Sagar

    2016-12-01

    Nonlinear time series analysis has been widely used to search for signatures of low-dimensional chaos in light curves emanating from astrophysical bodies. A particularly popular example is the microquasar GRS 1915+105, whose irregular but systematic X-ray variability has been well studied using data acquired by the Rossi X-ray Timing Explorer. With a view to building simpler models of X-ray variability, attempts have been made to classify the light curves of GRS 1915+105 as chaotic or stochastic. Contrary to some of the earlier suggestions, after careful analysis, we find no evidence for chaos or determinism in any of the GRS 1915+105 classes. The dearth of long and stationary data sets representing all the different variability classes of GRS 1915+105 makes it a poor candidate for analysis using nonlinear time series techniques. We conclude that either very exhaustive data analysis with sufficiently long and stationary light curves should be performed, keeping all the pitfalls of nonlinear time series analysis in mind, or alternative schemes of classifying the light curves should be adopted. The generic limitations of the techniques that we point out in the context of GRS 1915+105 affect all similar investigations of light curves from other astrophysical sources.

  2. Supermassive Black Hole Mimics Smaller Cousins

    NASA Astrophysics Data System (ADS)

    2002-06-01

    Scientists have caught a supermassive black hole in a distant galaxy in the act of spurting energy into a jet of electrons and magnetic fields four distinct times in the past three years, a celestial take on a Yellowstone geyser. This quasar-like "active" galaxy is essentially a scaled-up model of the so-called microquasars within our Milky Way Galaxy, which are smaller black holes with as much as ten times the mass of the sun. This means that scientists can now use their close-up view of microquasars to develop working models of the most massive and powerful black holes in the universe. Artist's Conception of 3C 120. Scene from an animation of 3C 120. CREDIT: Cosmovision These results -- published in the June 6 issue of Nature -- are the fruit of a three-year monitoring campaign with the National Science Foundation's Very Long Baseline Array (VLBA), a continent-wide radio-telescope system, and NASA's Rossi X-ray Timing Explorer. "This is the first direct, observational evidence of what we had suspected: The jets in active galaxies are powered by disks of hot gas orbiting around supermassive black holes," said Alan Marscher of the Institute for Astrophysical Research at Boston University, who led this international team of astronomers. Active galaxies are distant celestial objects with exceedingly bright cores, often radiating with the brilliance of thousands of ordinary galaxies, fueled by the gravity of a central million- to billion-solar-mass black hole pulling in copious amounts of interstellar gas. Marscher and his colleagues have established the first direct observational link between a supermassive black hole and its jet. The source is an active galaxy named 3C120 about 450 million light-years from Earth. This link has been observed in microquasars, several of which are scattered across the Milky Way Galaxy, but never before in active galaxies, because the scale (distance and time) is so much greater. The jets in galaxy 3C120 are streams of particles

  3. Searches for Time-dependent Neutrino Sources with IceCube Data from 2008 to 2012

    NASA Astrophysics Data System (ADS)

    Aartsen, M. G.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Ahrens, M.; Altmann, D.; Anderson, T.; Archinger, M.; Arguelles, C.; Arlen, T. C.; Auffenberg, J.; Bai, X.; Barwick, S. W.; Baum, V.; Bay, R.; Baker, M.; Beatty, J. J.; Becker Tjus, J.; Becker, K.-H.; BenZvi, S.; Berghaus, P.; Berley, D.; Bernardini, E.; Bernhard, A.; Besson, D. Z.; Binder, G.; Bindig, D.; Bissok, M.; Blaufuss, E.; Blumenthal, J.; Boersma, D. J.; Bohm, C.; Bos, F.; Bose, D.; Böser, S.; Botner, O.; Brayeur, L.; Bretz, H.-P.; Brown, A. M.; Buzinsky, N.; Casey, J.; Casier, M.; Cheung, E.; Chirkin, D.; Christov, A.; Christy, B.; Clark, K.; Classen, L.; Clevermann, F.; Coenders, S.; Cowen, D. F.; Cruz Silva, A. H.; Daughhetee, J.; Davis, J. C.; Day, M.; de André, J. P. A. M.; De Clercq, C.; Dembinski, H.; De Ridder, S.; Desiati, P.; de Vries, K. D.; de Wasseige, G.; de With, M.; DeYoung, T.; Díaz-Vélez, J. C.; Dumm, J. P.; Dunkman, M.; Eagan, R.; Eberhardt, B.; Ehrhardt, T.; Eichmann, B.; Eisch, J.; Euler, S.; Evenson, P. A.; Fadiran, O.; Fazely, A. R.; Fedynitch, A.; Feintzeig, J.; Felde, J.; Filimonov, K.; Finley, C.; Fischer-Wasels, T.; Flis, S.; Frantzen, K.; Fuchs, T.; Gaisser, T. K.; Gaior, R.; Gallagher, J.; Gerhardt, L.; Gier, D.; Gladstone, L.; Glüsenkamp, T.; Goldschmidt, A.; Golup, G.; Gonzalez, J. G.; Goodman, J. A.; Góra, D.; Grant, D.; Gretskov, P.; Groh, J. C.; Groß, A.; Ha, C.; Haack, C.; Haj Ismail, A.; Hallen, P.; Hallgren, A.; Halzen, F.; Hanson, K.; Hebecker, D.; Heereman, D.; Heinen, D.; Helbing, K.; Hellauer, R.; Hellwig, D.; Hickford, S.; Hignight, J.; Hill, G. C.; Hoffman, K. D.; Hoffmann, R.; Homeier, A.; Hoshina, K.; Huang, F.; Huelsnitz, W.; Hulth, P. O.; Hultqvist, K.; In, S.; Ishihara, A.; Jacobi, E.; Jacobsen, J.; Japaridze, G. S.; Jero, K.; Jurkovic, M.; Kaminsky, B.; Kappes, A.; Karg, T.; Karle, A.; Kauer, M.; Keivani, A.; Kelley, J. L.; Kheirandish, A.; Kiryluk, J.; Kläs, J.; Klein, S. R.; Köhne, J.-H.; Kohnen, G.; Kolanoski, H.; Koob, A.; Köpke, L.; Kopper, C.; Kopper, S.; Koskinen, D. J.; Kowalski, M.; Krings, K.; Kroll, G.; Kroll, M.; Kunnen, J.; Kurahashi, N.; Kuwabara, T.; Labare, M.; Lanfranchi, J. L.; Larsen, D. T.; Larson, M. J.; Lesiak-Bzdak, M.; Leuermann, M.; Lünemann, J.; Madsen, J.; Maggi, G.; Mahn, K. B. M.; Maruyama, R.; Mase, K.; Matis, H. S.; Maunu, R.; McNally, F.; Meagher, K.; Medici, M.; Meli, A.; Meures, T.; Miarecki, S.; Middell, E.; Middlemas, E.; Milke, N.; Miller, J.; Mohrmann, L.; Montaruli, T.; Morse, R.; Nahnhauer, R.; Naumann, U.; Niederhausen, H.; Nowicki, S. C.; Nygren, D. R.; Obertacke, A.; Olivas, A.; Omairat, A.; O'Murchadha, A.; Palczewski, T.; Paul, L.; Pepper, J. A.; Pérez de los Heros, C.; Pfendner, C.; Pieloth, D.; Pinat, E.; Posselt, J.; Price, P. B.; Przybylski, G. T.; Pütz, J.; Quinnan, M.; Rädel, L.; Rameez, M.; Rawlins, K.; Redl, P.; Rees, I.; Reimann, R.; Relich, M.; Resconi, E.; Rhode, W.; Richman, M.; Riedel, B.; Robertson, S.; Rodrigues, J. P.; Rongen, M.; Rott, C.; Ruhe, T.; Ruzybayev, B.; Ryckbosch, D.; Saba, S. M.; Sander, H.-G.; Sandroos, J.; Santander, M.; Sarkar, S.; Schatto, K.; Scheriau, F.; Schmidt, T.; Schmitz, M.; Schoenen, S.; Schöneberg, S.; Schönwald, A.; Schukraft, A.; Schulte, L.; Schulz, O.; Seckel, D.; Sestayo, Y.; Seunarine, S.; Shanidze, R.; Smith, M. W. E.; Soldin, D.; Spiczak, G. M.; Spiering, C.; Stamatikos, M.; Stanev, T.; Stanisha, N. A.; Stasik, A.; Stezelberger, T.; Stokstad, R. G.; Stößl, A.; Strahler, E. A.; Ström, R.; Strotjohann, N. L.; Sullivan, G. W.; Sutherland, M.; Taavola, H.; Taboada, I.; Tamburro, A.; Ter-Antonyan, S.; Terliuk, A.; Tešić, G.; Tilav, S.; Toale, P. A.; Tobin, M. N.; Tosi, D.; Tselengidou, M.; Unger, E.; Usner, M.; Vallecorsa, S.; van Eijndhoven, N.; Vandenbroucke, J.; van Santen, J.; Vanheule, S.; Vehring, M.; Voge, M.; Vraeghe, M.; Walck, C.; Wallraff, M.; Weaver, Ch.; Wellons, M.; Wendt, C.; Westerhoff, S.; Whelan, B. J.; Whitehorn, N.; Wichary, C.; Wiebe, K.; Wiebusch, C. H.; Williams, D. R.; Wissing, H.; Wolf, M.; Wood, T. R.; Woschnagg, K.; Xu, D. L.; Xu, X. W.; Xu, Y.; Yanez, J. P.; Yodh, G.; Yoshida, S.; Zarzhitsky, P.; Ziemann, J.; Zoll, M.; IceCube Collaboration

    2015-07-01

    In this paper searches for flaring astrophysical neutrino sources and sources with periodic emission with the IceCube neutrino telescope are presented. In contrast to time-integrated searches, where steady emission is assumed, the analyses presented here look for a time-dependent signal of neutrinos using the information from the neutrino arrival times to enhance the discovery potential. A search was performed for correlations between neutrino arrival times and directions, as well as neutrino emission following time-dependent light curves, sporadic emission, or periodicities of candidate sources. These include active galactic nuclei, soft γ-ray repeaters, supernova remnants hosting pulsars, microquasars, and X-ray binaries. The work presented here updates and extends previously published results to a longer period that covers 4 years of data from 2008 April 5 to 2012 May 16, including the first year of operation of the completed 86 string detector. The analyses did not find any significant time-dependent point sources of neutrinos, and the results were used to set upper limits on the neutrino flux from source candidates.

  4. The 2010 May Flaring Episode of Cygnus X-3 in Radio, X-Rays, and gamma-Rays

    NASA Technical Reports Server (NTRS)

    Williams, Peter K. G.; Tomsick, John A.; Bodaghee, Arash; Bower, Geoffrey C.; Pooley, Guy G.; Pottschmidt, Katja; Rodriguez, Jerome; Wilms, Joern; Migliari, Simone; Trushkin, Sergei A.

    2011-01-01

    In 2009, Cygnus X-3 (Cyg X-3) became the first microquasar to be detected in the GeV gamma-ray regime, via the satellites Fermi and AGILE. The addition of this new band to the observational toolbox holds promise for building a more detailed understanding of the relativistic jets of this and other systems. We present a rich dataset of radio, hard and soft X-ray, and gamma-ray observations of Cyg X-3 made during a flaring episode in 2010 May. We detect a approx.3-d softening and recovery of the X-ray emission, followed almost immediately by a approx.1-Jy radio flare at 15 GHz, followed by a 4.3sigma gamma-ray flare (E > 100 MeV) approx.1.5 d later. The radio sampling is sparse, but we use archival data to argue that it is unlikely the gamma-ray flare was followed by any significant unobserved radio flares. In this case, the sequencing of the observed events is difficult to explain in a model in which the gamma-ray emission is due to inverse Compton scattering of the companion star's radiation field. Our observations suggest that other mechanisms may also be responsible for gamma-ray emission from Cyg X-3.

  5. 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.

  6. 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.

  7. Particle Acceleration, Magnetic Field Generation and Emission from Relativistic Jets and Supernova Remnants

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.-I.; Hartmann, D. H.; Hardee, P.; Hededal, C.; Mizunno, Y.; Fishman, G. J.

    2006-01-01

    We performed numerical simulations of particle acceleration, magnetic field generation, and emission from shocks in order to understand the observed emission from relativistic jets and supernova remnants. The investigation involves the study of collisionless shocks, where the Weibel instability is responsible for particle acceleration as well as magnetic field generation. A 3-D relativistic particle-in-cell (RPIC) code has been used to investigate the shock processes in electron-positron plasmas. The evolution of theWeibe1 instability and its associated magnetic field generation and particle acceleration are studied with two different jet velocities (0 = 2,5 - slow, fast) corresponding to either outflows in supernova remnants or relativistic jets, such as those found in AGNs and microquasars. Slow jets have intrinsically different structures in both the generated magnetic fields and the accelerated particle spectrum. In particular, the jet head has a very weak magnetic field and the ambient electrons are strongly accelerated and dragged by the jet particles. The simulation results exhibit jitter radiation from inhomogeneous magnetic fields, generated by the Weibel instability, which has different spectral properties than standard synchrotron emission in a homogeneous magnetic field.

  8. Emission of gravitational waves by precession of slim accretion disks dynamically driven by the Bardeen-Petterson effect

    NASA Astrophysics Data System (ADS)

    Alfonso, W. D.; Sánchez, L. A.; Mosquera, H. J.

    2015-11-01

    The electromagnetic radiation emitted from some astrophysical objects such as active galactic nuclei (AGN), micro-quasars (M-QSRs), and central engines of gamma-ray burst (GRBs), seems to have a similar physical origin: a powerful jet of plasma ejected from a localized system, presumably composed of an accretion disk encircling a compact object. This radiation is generally beamed in the polar directions and in some cases, it appears to have a spiral-like structure that could be explained if the central system itself precesses. In this work, we use the slim disk accretion model, presented by Popham et al. (1999), to studying the gravitational waves (GWs) emitted by the precession of the accretion disk around a solar-mass Kerr black hole (KBH). For practical purposes, this model describes the central engine of a class of GRBs when some astrophysical constrains are fulfilled. The induced precession considered here is driven by the Bardeen-Petterson effect, which results from the combination of viscous effects in such disks and the relativistic frame-dragging effect. We evaluate the feasibility of direct detection of the GWs computed for such a model and show that the precession of this kind of systems could be detected by gravitational wave observatories like DECIGO, ultimate-DECIGO, and BBO, with higher probability if such a class of sources are placed at distances less than 1 Mpc.

  9. STUDIES OF THERMALLY UNSTABLE ACCRETION DISKS AROUND BLACK HOLES WITH ADAPTIVE PSEUDOSPECTRAL DOMAIN DECOMPOSITION METHOD. II. LIMIT-CYCLE BEHAVIOR IN ACCRETION DISKS AROUND KERR BLACK HOLES

    SciTech Connect

    Xue Li; Lu Jufu; Sadowski, Aleksander; Abramowicz, Marek A. E-mail: lujf@xmu.edu.cn

    2011-07-01

    For the first time ever, we derive equations governing the time evolution of fully relativistic slim accretion disks in the Kerr metric and numerically construct their detailed non-stationary models. We discuss applications of these general results to a possible limit-cycle behavior of thermally unstable disks. Our equations and numerical method are applicable in a wide class of possible viscosity prescriptions, but in this paper we use a diffusive form of the 'standard alpha prescription' that assumes that the viscous torque is proportional to the total pressure. In this particular case, we find that the parameters that dominate the limit-cycle properties are the mass-supply rate and the value of the alpha-viscosity parameter. Although the duration of the cycle (or the outburst) does not exhibit any clear dependence on the black hole spin, the maximal outburst luminosity (in the Eddington units) is positively correlated with the spin value. We suggest a simple method for a rough estimate of the black hole spin based on the maximal luminosity and the ratio of outburst to cycle durations. We also discuss a temperature-luminosity relation for the Kerr black hole accretion disk limit cycle. Based on these results, we discuss the limit-cycle behavior observed in microquasar GRS 1915+105. We also extend this study to several non-standard viscosity prescriptions, including a 'delayed heating' prescription recently addressed by the MHD simulations of accretion disks.

  10. Identifying Galactic Cosmic Ray Origins With Super-TIGER

    NASA Technical Reports Server (NTRS)

    deNolfo, Georgia; Binns, W. R.; Israel, M. H.; Christian, E. R.; Mitchell, J. W.; Hams, T.; Link, J. T.; Sasaki, M.; Labrador, A. W.; Mewaldt, R. A.; Stone, E. C.; Waddington, C. J.; Wiedenbeck, M. E.

    2009-01-01

    Super-TIGER (Super Trans-Iron Galactic Element Recorder) is a new long-duration balloon-borne instrument designed to test and clarify an emerging model of cosmic-ray origins and models for atomic processes by which nuclei are selected for acceleration. A sensitive test of the origin of cosmic rays is the measurement of ultra heavy elemental abundances (Z > or equal 30). Super-TIGER is a large-area (5 sq m) instrument designed to measure the elements in the interval 30 < or equal Z < or equal 42 with individual-element resolution and high statistical precision, and make exploratory measurements through Z = 60. It will also measure with high statistical accuracy the energy spectra of the more abundant elements in the interval 14 < or equal Z < or equal 30 at energies 0.8 < or equal E < or equal 10 GeV/nucleon. These spectra will give a sensitive test of the hypothesis that microquasars or other sources could superpose spectral features on the otherwise smooth energy spectra previously measured with less statistical accuracy. Super-TIGER builds on the heritage of the smaller TIGER, which produced the first well-resolved measurements of elemental abundances of the elements Ga-31, Ge-32, and Se-34. We present the Super-TIGER design, schedule, and progress to date, and discuss the relevance of UH measurements to cosmic-ray origins.

  11. Observations of High Energy Cosmic Ray Electrons by the ATIC Balloon Experiment

    NASA Technical Reports Server (NTRS)

    Guzik, T. G.; Chang, J.; Adams, J. H., Jr.; Ahn, H. S.; Bashindzhagyan, G. L.; Christl, M.; Isbert, J.; Kim, K. C.; Kuznetsov, E. N.; Panasyuk, M. I.; Panov, A. D.; Schmidt, W. K. H.; Seo, E. S.; Sokolskaya N. V.; Watts, J. W.; Wefel, J. P.; Wu, J.; Zatsepin, V. I.

    2009-01-01

    Recently the Advanced Thin Ionization Calorimeter (ATIC) balloon experiment reported observations of high energy cosmic ray electrons over the energy range 300 to 800 GeV, indicating a feature or "bump" in the otherwise smoothly decreasing energy spectrum. The severe energy losses that occur as these high energy particles traverse the galaxy render the cosmic ray electron spectrum sensitive to local (a few kiloparsecs) sources and hence very interesting. The ATIC results are the first time that such a cosmic ray spectrum anomaly has been observed at high energy. Potential sources of this electron excess include pulsars, microquasars, supernovae remnants as well as the annihilation of exotic dark matter candidate particles. ATIC has had three successful high altitude flights over the continent of Antarctica 2000-2001, 2002-2003 and 2007-2008. Only results from the first two flights have been reported so far. During this talk we will discuss the ATIC experiment, the electron observations (including preliminary results from the most recent ATIC flight), examine the merits of the various source models and compare the ATIC observations with other recent measurements.

  12. IXPE: The Imaging X-ray Polarimetry Explorer, Implementing a Dedicated Polarimetry Mission

    NASA Technical Reports Server (NTRS)

    Ramsey, Brian

    2014-01-01

    Only a few experiments have conducted x-ray polarimetry of cosmic sources since Weisskopf et al confirmed the 19% polarization of the Crab Nebula with the Orbiting Solar Observatory (OSO-8) in the 70's center dot The challenge is to measure a faint polarized component against a background of non-polarized signal (as well as the other, typical background components) center dot Typically, for a few % minimum detectable polarization, 106 photons are required. center dot So, a dedicated mission is vital with instruments that are designed specifically to measure polarization (with minimal systematic effects) Over the proposed mission life (2- 3 years), IXPE will first survey representative samples of several categories of targets: magnetars, isolated pulsars, pulsar wind nebula and supernova remnants, microquasars, active galaxies etc. The survey results will guide detailed follow-up observations. Precise calibration of IXPE is vital to ensuring sensitivity goals are met. The detectors will be characterized in Italy, and then a full calibration of the complete instrument will be performed at MSFC's stray light facility. Polarized flux at different energies Heritage: X-ray Optics at MSFC polarimetry mission.

  13. THE MISSING GOLIATH'S SLINGSHOT: MASSIVE BLACK HOLE RECOIL AT M83

    SciTech Connect

    Dottori, Horacio; Diaz, Ruben J.; Facundo Albacete-Colombo, Juan

    2010-07-01

    The Fanaroff-Riley II radio source J133658.3-295105, which is also an X-ray source, appears to be projected onto the disk of the barred-spiral galaxy M83 at about 60'' from the galaxy's optical nucleus. J133658.3-295105 and its radio lobes are aligned with the optical nucleus of M 83 and two other radio sources, neither of which are supernova remnants or H II regions. Due to this peculiar on-the-sky projection, J133658.3-295105 was previously studied by Gemini+GMOS optical spectroscopy, which marginally revealed the presence of H{alpha} in emission receding at 130 km s{sup -1} with respect to the optical nucleus. In this Letter, we reanalyze the Chandra spectroscopy carried out in 2000. We show that J133658.3-295105 presents an Fe K{alpha} emission line at a redshift of z = 0.018. This redshift is compatible with a black hole at the distance of M 83. We discuss similarities to the recently reported micro-quasar in NGC 5408. This finding reinforces the kicked-off black hole scenario for J133658.3-295105.

  14. STOCHASTIC VARIABILITY IN X-RAY EMISSION FROM THE BLACK HOLE BINARY GRS 1915+105

    SciTech Connect

    Polyakov, Yuriy S.; Neilsen, Joseph; Timashev, Serge F.

    2012-06-15

    We examine stochastic variability in the dynamics of X-ray emission from the black hole system GRS 1915+105, a strongly variable microquasar commonly used for studying relativistic jets and the physics of black hole accretion. The analysis of sample observations for 13 different states in both soft (low) and hard (high) energy bands is performed by flicker-noise spectroscopy (FNS), a phenomenological time series analysis method operating on structure functions and power spectrum estimates. We find the values of FNS parameters, including the Hurst exponent, flicker-noise parameter, and characteristic timescales, for each observation based on multiple 2500 s continuous data segments. We identify four modes of stochastic variability driven by dissipative processes that may be related to viscosity fluctuations in the accretion disk around the black hole: random (RN), power-law (1F), one-scale (1S), and two-scale (2S). The variability modes are generally the same in soft and hard energy bands of the same observation. We discuss the potential for future FNS studies of accreting black holes.

  15. Erratic Black Hole Regulates Itself

    NASA Astrophysics Data System (ADS)

    2009-03-01

    New results from NASA's Chandra X-ray Observatory have made a major advance in explaining how a special class of black holes may shut off the high-speed jets they produce. These results suggest that these black holes have a mechanism for regulating the rate at which they grow. Black holes come in many sizes: the supermassive ones, including those in quasars, which weigh in at millions to billions of times the mass of the Sun, and the much smaller stellar-mass black holes which have measured masses in the range of about 7 to 25 times the Sun's mass. Some stellar-mass black holes launch powerful jets of particles and radiation, like seen in quasars, and are called "micro-quasars". The new study looks at a famous micro-quasar in our own Galaxy, and regions close to its event horizon, or point of no return. This system, GRS 1915+105 (GRS 1915 for short), contains a black hole about 14 times the mass of the Sun that is feeding off material from a nearby companion star. As the material swirls toward the black hole, an accretion disk forms. This system shows remarkably unpredictable and complicated variability ranging from timescales of seconds to months, including 14 different patterns of variation. These variations are caused by a poorly understood connection between the disk and the radio jet seen in GRS 1915. Chandra, with its spectrograph, has observed GRS 1915 eleven times since its launch in 1999. These studies reveal that the jet in GRS 1915 may be periodically choked off when a hot wind, seen in X-rays, is driven off the accretion disk around the black hole. The wind is believed to shut down the jet by depriving it of matter that would have otherwise fueled it. Conversely, once the wind dies down, the jet can re-emerge. "We think the jet and wind around this black hole are in a sort of tug of war," said Joseph Neilsen, Harvard graduate student and lead author of the paper appearing in the journal Nature. "Sometimes one is winning and then, for reasons we don

  16. 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.

  17. Relativistic Particle-In-Cell Simulation Studies of Prompt and Early Afterglows from GRBs

    NASA Technical Reports Server (NTRS)

    Nishikawa, Ken-Ichi; Hardee, Philip; Mizuno, Yosuke; Fishman, Gerald

    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 (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 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.-/

  18. 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.

  19. 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.

  20. Microscopic Processes in Relativistic Jets

    NASA Technical Reports Server (NTRS)

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

    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 (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.

  1. New Relativistic Particle-In-Cell Simulation Studies of Prompt and Early Afterglows from GRBs

    NASA Technical Reports Server (NTRS)

    Nishikawa, Ken-ichi; Hardee, P.; Mizuno, Y.; Zhang, B.; Medvedev, M.; Hartmann, D.; Fishman, J. F.; 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 (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.

  2. 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.

  3. Relativistic Particle-in-Cell Simulation Studies of Prompt and Early Afterglows Observed by GLAST

    NASA Technical Reports Server (NTRS)

    Mizuno, Y.; Nishikawa, K.-I.; Hardee, P.; Fishman, G. J.; Preece, R.

    2007-01-01

    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 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.

  4. Resolving The Sky - Radio Interferometry: Past, Present and Future

    NASA Astrophysics Data System (ADS)

    For more than half a century, radio interferometry has revolutionised our view of the Universe. New phenomena, such as relativistic motion in AGN have been discovered, and a wealth of detail has been revealed about a wide variety of astronomical sources, from nearby stars to the most distant galaxies. These discoveries have been enabled by radio interferometry's routine capability to deliver images with sub-milliarcsecond resolution and micro-arcsecond precision astrometry. Major new advances in both the interferometric technique and the science it delivers are expected over the coming decade. This conference will take a look at the past, present and future of radio interferometry, as the astronomical community prepares for the next big step forward, the Square Kilometre Array (SKA). The meeting coincides with the retirement of Prof. Richard T. Schilizzi, Director of the SKA Project Development Office (SPDO) and past director of the Joint Institute for VLBI in Europe (JIVE). We celebrate the major contribution Richard has made to the field with a scientific programme that will address the following topics: key historical developments in interferometry, the study of micro-quasars and AGN, the development of advanced interferometry techniques and new calibration algorithms, future interferometers (incl. ALMA, SKA and the SKA pathfinders & precursors), mm and sub-mm interferometry, precision spacecraft navigation, geodetic VLBI and Space VLBI.

  5. An AGN or a Be star as possible counterparts of 3FGL J0133.3+5930

    NASA Astrophysics Data System (ADS)

    Martí, J.; Luque-Escamilla, P. L.; Paredes, J. M.; Iwasawa, K.; Galindo, D.; Ribó, M.; Marín-Felip, V.

    2017-03-01

    We present recent results from our program for cross-identification of unassociated gamma-ray sources at low galactic latitudes. The main motivation for this work is the search for new members of the scarce class of gamma-ray binaries and microquasars. Here we report the case of the Fermi LAT source 3FGL J0133.3+5930. Two peculiar objects have been found inside the 95% confidence contour of this unassociated gamma-ray source. One of them is the optically bright Be star TYC 3683-985-1, also consistent with the ROSAT X-ray source 1RXS J013326.9+592946. In this work, we have discovered it to be a new eclipsing binary system. The other is the Swift X-ray source SWIFT J0132.9+ 5932 whose radio, infrared and optical counterpart are still under study. Based on the observational evidence available, SWIFT J0132.9+5932 stands as the most likely counterpart to 3FGL J0133.3+5930. Although its spectral energy distribution appears to be consistent with a stellar system, a possible Active Galactic Nuclei nature cannot be yet ruled out.

  6. Fast launch speeds in radio flares, from a new determination of the intrinsic motions of SS 433's jet bolides

    NASA Astrophysics Data System (ADS)

    Jeffrey, Robert M.; Blundell, Katherine M.; Trushkin, Sergei A.; Mioduszewski, Amy J.

    2016-09-01

    We present new high-resolution, multi-epoch, Very Long Baseline Array (VLBA) radio images of the Galactic microquasar SS 433. We are able to observe plasma knots in the milliarcsecond-scale jets more than 50 d after their launch. This unprecedented baseline in time allows us to determine the bulk launch speed of the radio-emitting plasma during a radio flare, using a new method which we present here, and which is completely independent of optical spectroscopy. We also apply this method to an earlier sequence of 39 short daily VLBA observations, which cover a period in which SS 433 moved from quiescence into a flare. In both data sets we find, for the first time at radio wavebands, clear evidence that the launch speeds of the milliarcsecond-scale jets rise as high as 0.32c during flaring episodes. By comparing these images of SS 433 with photometric radio monitoring from the RATAN-600 telescope, we explore further properties of these radio flares.

  7. On the radio properties of the intermediate-mass black hole candidate ESO 243-49 HLX-1

    NASA Astrophysics Data System (ADS)

    Cseh, D.; Webb, N. A.; Godet, O.; Barret, D.; Corbel, S.; Coriat, M.; Falcke, H.; Farrell, S. A.; Körding, E.; Lenc, E.; Wrobel, J. M.

    2015-02-01

    We present follow-up radio observations of ESO 243-49 HLX-1 from 2012 using the Australia Telescope Compact Array (ATCA) and the Karl G. Jansky Very Large Array (VLA). We report the detection of radio emission at the location of HLX-1 during its hard X-ray state using the ATCA. Assuming that the `Fundamental Plane' of accreting black holes is applicable, we provide an independent estimate of the black hole mass of M_{BH}≤ 2.8^{+7.5}_{-2.1} × 106 M⊙ at 90 per cent confidence. However, we argue that the detected radio emission is likely to be Doppler-boosted and our mass estimate is an upper limit. We discuss other possible origins of the radio emission such as being due to a radio nebula, star formation, or later interaction of the flares with the large-scale environment. None of these were found adequate. The VLA observations were carried out during the X-ray outburst. However, no new radio flare was detected, possibly due to a sparse time sampling. The deepest, combined VLA data suggest a variable radio source and we briefly discuss the properties of the previously detected flares and compare them with microquasars and active galactic nuclei.

  8. A Multi-Wavelength Study of the Gamma-Ray Binary 1FGL J1018.6-5856

    NASA Astrophysics Data System (ADS)

    Coley, Joel Barry; Corbet, Robin; Cheung, Chi C.; Dubus, Guillaume; Edwards, Philip; McBride, Vanessa; Stevens, Jamie

    2016-04-01

    1FGL J1018.6-5856, the first gamma-ray binary discovered by the Fermi Large Area Telescope (LAT), consists of an O6 V((f)) star and suspected rapidly spinning pulsar. While 1FGL J1018.6-5856 has been postulated to be powered by the interaction between a relativistic pulsar wind and the stellar wind of the companion, a microquasar scenario where the compact object is a black hole cannot be ruled out. We present the first extensive multi-wavelength analysis of 1FGL J1018.6-5856 with the Australia Telescope Compact Array (ATCA), Fermi LAT and the Swift X-ray Telescope (XRT) to better determine the properties of the 16.531$\\pm$0.006 day orbital modulation. The radio amplitude modulation is found to decline with increasing frequency, which is a possible indication of the presence of free-free absorption. This is further supported by the absence of clear modulation in the 33.0 and 35.0\\,GHz bands, which were not previously reported. The best-fit spectral model of the Swift XRT data consists of a featureless power law with index $\\Gamma\\sim$1.3--1.7 modified by an absorber that fully covers the source. This is possible evidence that 1FGL J1018.6-5856 is a non-accreting system.

  9. The Ferroelectric Transition in GERMANIUM(X)LEAD(1 - EXAFS Investigation of the Germanium and Lead Sites.

    NASA Astrophysics Data System (ADS)

    Islam, Quazi Towhidul

    Ge_{rm x}Pb _{rm 1-x}Te alloys undergo a ferroelectric phase transition from a high temperature cubic phase to a low temperature trigonal phase. The phase transition is second order and is caused by softening of a zone-center transverse optical phonon. This alloy system exhibits several experimental results not found in other IV-VI alloys. For small x, the transition temperature is a strong non-linear function of temperature, the resistivity has a logarithmic dependence on temperature, and there is a Schottky-type specific heat. These results suggest that Ge plays an important role in the phase transition in Ge_{rm x}Pb _{rm 1-x}Te alloys. EXAFS studies on the Ge K-edge in alloys from x = 0.01 to 0.30 and in the trigonal and cubic phases have been performed. The EXAFS results show that Ge is displaced from the Pb site by 0.73 +/- 0.03 A at all temperatures in the cubic phase, and by 0.60 +/- 0.04 A for x = 0.18 to 0.71 +/- 0.03 A for x = 0.01 at 10K in the trigonal phase. Since Ge atom is always off-site, the phase transition implies a long-range ordering of local dipoles along the trigonal c-axis below the transition. The displacive character of the phase transition is established by direct determination of the sublattice shift by Pb L_3-edge EXAFS studies. At 6K, the magnitude of the shift is 0.12 +/- 0.02 A for x = 0.10 alloy and 0.13 +/- 0.02 A for x = 0.18 alloy, which have transition temperatures 243 +/- 16K and 314 +/- 4K respectively. Several short-range anharmonic potentials in which the Ge atom moves have been considered. A symmetric one -dimensional double-well potential along the < 111> direction with a barrier height ~80 meV at the center of the cell adequately describes the room temperature data. The low-temperature behavior cannot be explained by this potential nor by a triple-well potential with three possible Ge sites along <111 >, nor by a distribution of Ge between two symmetric double-well potentials, one along <111> and the other along <100

  10. Reducing On-Board Computer Propagation Errors Due to Omitted Geopotential Terms by Judicious Selection of Uploaded State Vector

    NASA Technical Reports Server (NTRS)

    Greatorex, Scott (Editor); Beckman, Mark

    1996-01-01

    Several future, and some current missions, use an on-board computer (OBC) force model that is very limited. The OBC geopotential force model typically includes only the J(2), J(3), J(4), C(2,2) and S(2,2) terms to model non-spherical Earth gravitational effects. The Tropical Rainfall Measuring Mission (TRMM), Wide-field Infrared Explorer (WIRE), Transition Region and Coronal Explorer (TRACE), Submillimeter Wave Astronomy Satellite (SWAS), and X-ray Timing Explorer (XTE) all plan to use this geopotential force model on-board. The Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) is already flying this geopotential force model. Past analysis has shown that one of the leading sources of error in the OBC propagated ephemeris is the omission of the higher order geopotential terms. However, these same analyses have shown a wide range of accuracies for the OBC ephemerides. Analysis was performed using EUVE state vectors that showed the EUVE four day OBC propagated ephemerides varied in accuracy from 200 m. to 45 km. depending on the initial vector used to start the propagation. The vectors used in the study were from a single EUVE orbit at one minute intervals in the ephemeris. Since each vector propagated practically the same path as the others, the differences seen had to be due to differences in the inital state vector only. An algorithm was developed that will optimize the epoch of the uploaded state vector. Proper selection can reduce the previous errors of anywhere from 200 m. to 45 km. to generally less than one km. over four days of propagation. This would enable flight projects to minimize state vector uploads to the spacecraft. Additionally, this method is superior to other methods in that no additional orbit estimates need be done. The definitive ephemeris generated on the ground can be used as long as the proper epoch is chosen. This algorithm can be easily coded in software that would pick the epoch within a specified time range that would

  11. Outburst of the 2 s Anomalous X-ray Pulsar 1E 1547.0-5408

    NASA Technical Reports Server (NTRS)

    Halpern, J. P.; Gotthelf, E. V.; Camilo, F.; Reynolds, J.; Ransom, S. M.

    2008-01-01

    Following our discovery of radio pulsations from the newly recognized anomalous X-ray pulsar (AXP) 1E 1547.0-5408, we initiated X-ray monitoring with the Swift X-ray telescope and obtained a single target-of-opportunity observation with the Newton X-ray Multi-Mirror Mission (XMM-Newton). In comparison with its historic minimum flux of 3 x 10(exp -l3)ergs/sq cm/s, the source was found to be in a record high state, f(sub x)(1-8 keV) = 5 x 10(exp -12)ergs/sq cm/s, or L(sub x) = 1.7 x 10(exp 35)(d/9 kpc )(sup 2)ergs/s, and declining by 25% in 1 month. Extrapolating the decay, we bound the total energy in this outburst to 1042 ergs < E < ergs. The spectra (fitted with a Comptonized blackbody) show that an increase in the temperature and area of a hot region, to 0.5 keV and -16% of the surface area of the neutron star, respectively, are primarily responsible for its increase in luminosity. The energy, spectrum, and timescale of decay are consistent with a deep crustal heating event, similar to an interpretation of the X-ray turn-on of the transient AXP XTE J18 10- 197. Simultaneous with the 4.6 hr ATdA4-Newton observation, we observed at 6.4 GHz with the Parkes telescope, measuring the phase relationship of the radio and X-ray pulse. The X-ray pulsed fraction of 1E 1547.0-5408 is only approx. 7 %, while its radio pulse is relatively broad for such a slow pulsar, which may indicate a nearly aligned rotator. As also inferred from the transient behavior of XTE J18 10-197, the only other AXP known to emit in the radio, the magnetic field rearrangement responsible for this X-ray outburst of 1E 1547.0-5408 is probably the cause of its radio turn-on.

  12. Connections Between Jet Formation and Multiwavelength Spectral Evolution in Black Hole Transients

    NASA Technical Reports Server (NTRS)

    Kakemci, Emrah; Chun, Yoon-Young; Dincer, Tolga; Buxton, Michelle; Tomsick, John A.; Corbel, Stephane; Kaaret, Philip

    2011-01-01

    Multiwavelength observations are the key to understand conditions of jet formation in Galactic black hole transient (GBHT) systems. By studying radio and optical-infrared evolution of such systems during outburst decays, the compact jet formation can be traced. Comparing this with X-ray spectral and timing evolution we can obtain physical and geometrical conditions for jet formation, and study the contribution of jets to X-ray emission. In this work, first X-ray evolution - jet relation for XTE J1752-223 will be discussed. This source had very good coverage in X-rays, optical, infrared and radio. A long exposure with INTEGRAL also allowed us to study gamma-ray behavior after the jet turns on. We will also show results from the analysis of data from GX 339-4 in the hard state with SUZAKU at low flux levels. The fits to iron line fluorescence emission show that the inner disk radius increases by a factor of greater than 27 with respect to radii in bright states. This result, along with other disk radius measurements in the hard state will be discussed within the context of conditions for launching and sustaining jets.

  13. Effect of Sn doping on nonlinear optical properties of quaternary Se-Sn-(Bi,Te) chalcogenide thin films

    NASA Astrophysics Data System (ADS)

    Yadav, Preeti; Sharma, Ambika

    2015-08-01

    The aim of this work is to report the effect of Sn doping on the third order nonlinear optical properties of chalcogenide Se84-xTe15Bi1.0Snx thin films. Melt quenching technique has been used for the preparation of bulk chalcogenide glasses. Thin films of the studied composition are deposited on cleaned glass substrate by thermal evaporation technique. Optical band gap (Eg) is calculated by using Tauc extrapolation method and is found to increase from 1.27 eV to 1.64 eV with the incorporation of Sn content. Stryland approach is utilized for the calculation of two photon absorption coefficient (β2). The nonlinear refractive index (n2) and third order susceptibility (χ(3) are calculated using Tichy and Ticha approach. The result shows that nonlinear refractive index (n2) follows the same trend as that of linear refractive index (n). The values of n2 of studied composition as compared to pure silica are 1000-5000 times higher.

  14. HPVB AND HPVZM SHAPED GROWTH OF CDZNTE, CDSE AND ZNSE CRYSTALS.

    SciTech Connect

    KOLESNIKOV,N.N.; JAMES,R.B.; BERZIGIAROVA,N.S.; KULAKOV,M.P.

    2002-07-07

    High-pressure Bridgman (HPVB) and vertical zone melting (HPVZM) growth processes have been applied for the manufacturing of Cd{sub 1-x}Zn{sub x}Te (x = 0.04-0.2), CdSe and ZnSe crystal tapes with sizes up to 120 x 120 x 12 mm. The influences of the technological parameters describing the growth processes on the crystal quality and some selected material properties are discussed. The dependence of the inclusion (bubbles) content on the deviation from melt stoichiometry is determined. A method for growing plates with low content of inclusions is described. High-resistivity crystal tapes of undoped CdZnTe (10{sup 10} Ohm x cm), CdSe (10{sup 11} Ohm x cm) and ZnSe (>10{sup 11} Ohm x cm) were prepared. The possibility of tape growth on oriented seeds is shown for the example of CdSe. The primary differences between HPVB and HPVZM results are described. The main HPVZM advantage for II-VI compound crystal growth is the possibility of obtaining crystals with more stoichiometric composition or with a controlled deviation from stoichiometry. Hence, HPVZM is preferable for growing high-resistivity II-VI crystals with low inclusion content and possibly with better transport properties. Keywords for this report are: Crystal growth, shaped crystal growth, ZnSe, CdSe, CdZnTe, CZT, HPVB, Bridgman, HPVZM, zone melting, radiation detectors.

  15. Influence of Mn concentration on magnetic topological insulator MnxBi2−xTe3 thin-film Hall-effect sensor

    DOE PAGES

    Ni, Y.; Zhang, Z.; Nlebedim, I. C.; ...

    2015-06-11

    Hall-effect (HE) sensors based on high-quality Mn-doped Bi2Te3 topological insulator (TI) thin films have been systematically studied in this paper. Improvement of Hall sensitivity is found after doping the magnetic element Mn into Bi2Te3. The sensors with low Mn concentrations, MnxBi2-xTe3, x = 0.01 and 0.08 show the linear behavior of Hall resistance with sensitivity about 5 Ω/T. And their Hall sensitivity shows weak dependence on temperature. For sensors with high Mn concentration (x = 0.23), the Hall resistance with respect to magnetic field shows a hysteretic behavior. Moreover, its sensitivity shows almost eight times as high as that ofmore » the HE sensors with low Mn concentration. The highest sensitivity can reach 43 Ω/T at very low magnetic field. This increase of Hall sensitivity is caused by the occurrence of anomalous HE (AHE) after ferromagnetic phase transition. Our work indicates that the magnetic-element-doped TIs with AHE are good candidates for HE sensors.« less

  16. 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.

  17. Search for Nonthermal X-Rays from Supernova Remnant Shells

    NASA Astrophysics Data System (ADS)

    Petre, R.; Keohane, J.; Hwang, U.; Allen, G.; Gotthelf, E.

    The demonstration by ASCA that the nonthermal X-ray emission from the rim of SN1006 is synchrotron emission from TeV electrons, produced in the same environment responsible for cosmic ray protons and nuclei (Koyama et al. 1995, Nature 378, 255), has stimulated a search for nonthermal X-rays from other remnants. Nonthermal emission has subsequently been found to arise in the shells of at least two other remnants, Cas A and IC 443. In Cas A, a hard tail is detected using ASCA, XTE, and OSSE to energies exceeding 100 keV; the shape of the spectrum rules out all mechanisms except synchrotron radiation. In IC 443, the previously known hard emission has been shown using ASCA to be isolated to a small region along the rim of the remnant, where the shock is interacting most strongly with a molecular cloud. Nonthermal X-ray emission is thought to arise here by enhanced cosmic ray production associated with the shock/cloud interaction (Keohane et al. 1997, ApJ in press). We describe the properties of the nonthermal emission in SN1006, Cas A, and IC 443, and discuss the status of our search for nonthermal emission associated with the shocks of other Galactic and LMC SNR's.

  18. The Magnetar Nature and the Outburst Mechanism of a Transient Anomalous X-ray Pulsar

    NASA Technical Reports Server (NTRS)

    Guver, Tolga; Ozel, Feryal; Gogus, Ersin; Kouveliotou, Chryssa

    2007-01-01

    Anomalous X-ray Pulsars (AXPs) belong to a class of neutron stars believed to harbor the strongest magnetic fields in the universe, as indicated by their energetic bursts and their rapid spindowns. However, a direct measurement of their surface field strengths has not been made to date. It is also not known whether AXP outbursts result from changes in the neutron star magnetic field or crust properties. Here we report the first, spectroscopic measurement of the surface magnetic field strength of an AXP, XTE J1810-197, and solidify its magnetar nature. The field strength obtained from detailed spectral analysis and modeling is remarkably close to the value inferred from the rate of spindown of this source and remains nearly constant during numerous observations spanning over two orders of magnitude in source flux. The surface temperature, on the other hand, declines steadily and dramatically following the 2003 outburst of this source. Our findings demonstrate that heating occurs in the upper neutron star crust during an outburst and sheds light on the transient behaviour of AXPs.

  19. Detailed Physical Modeling Reveals the Magnetar Nature of a Transient Anomalous X-ray Pulsar

    NASA Technical Reports Server (NTRS)

    Guever, T.; Oezel, F.; Goegues, E.; Kouveliotou, C.

    2007-01-01

    Anomalous X-ray Pulsars (AXPs) belong to a class of neutron stars believed to harbor the strongest magnetic fields in the universe, as indicated by their energetic bursts and their rapid spindowns. However, a direct measurement of their surface field strengths has not been made to date. It is also not known whether AXP outbursts result from changes in the neutron star magnetic field or crust properties. Here we report the first, spectroscopic measurement of the surface magnetic field strength of an AXP, XTE J1810-197, and solidify its magnetar nature. The field strength obtained from detailed spectral analysis and modeling is remarkably close to the value inferred from the rate of spindown of this source and remains nearly constant during numerous observations spanning over two orders of magnitude in source flux. The surface temperature, on the other hand, declines steadily and dramatically following the 2003 outburst of this source. Our findings demonstrate that heating occurs in the upper neutron star crust during an outburst and sheds light on the transient behaviour of AXPs.

  20. Influence of substrate materials on the properties of CdTe thin films grown by hot-wall epitaxy

    NASA Astrophysics Data System (ADS)

    Bilevych, Ye.; Soshnikov, A.; Darchuk, L.; Apatskaya, M.; Tsybrii, Z.; Vuychik, M.; Boka, A.; Sizov, F.; Boelling, O.; Sulkio-Cleff, B.

    2005-02-01

    Growth of high-quality CdTe thin films by hot-wall epitaxy (HWE) under different temperature conditions and the control of their physical, electrical and structural properties have been examined by various ways. CdTe (1 1 0), Zn 0.04Cd 0.96Te (1 1 1), Hg 0.2Cd 0.8Te (1 1 1), Si (1 1 1) and BaF 2 (1 1 1) were used as substrates. The obtained films have the cut-off wavelength at 0.84-0.85 μm and the transmission of about 55-60% out of the fundamental absorption domain. The current-voltage investigations have shown that the contact properties strongly depend on the contact material and contact fabrication method and less depend on substrate materials. The film-specific resistances (4-7)×10 4 Ω cm were determined. The CdTe deposition (layer thickness about 1000 Å) on Cd xHg 1-xTe resulted in significant increase in photodiodes electrical parameters. All samples showed the crystalline structure according to the XRD data with strong influence on lattice mismatch between CdTe and substrate materials. Atomic force microscope (AFM) investigations have shown a smooth and defect-free surface with a roughness range of 15-100 nm for 50 μm of basic length.

  1. Vortex pinning properties in Fe-chalcogenides

    NASA Astrophysics Data System (ADS)

    Leo, A.; Grimaldi, G.; Guarino, A.; Avitabile, F.; Nigro, A.; Galluzzi, A.; Mancusi, D.; Polichetti, M.; Pace, S.; Buchkov, K.; Nazarova, E.; Kawale, S.; Bellingeri, E.; Ferdeghini, C.

    2015-12-01

    Among the families of iron-based superconductors, the 11-family is one of the most attractive for high field applications at low temperatures. Optimization of the fabrication processes for bulk, crystalline and/or thin film samples is the first step in producing wires and/or tapes for practical high power conductors. Here we present the results of a comparative study of pinning properties in iron-chalcogenides, investigating the flux pinning mechanisms in optimized Fe(Se{}1-xTe x ) and FeSe samples by current-voltage characterization, magneto-resistance and magnetization measurements. In particular, from Arrhenius plots in magnetic fields up to 9 T, the activation energy is derived as a function of the magnetic field, {U}0(H), whereas the activation energy as a function of temperature, U(T), is derived from relaxation magnetization curves. The high pinning energies, high upper critical field versus temperature slopes near critical temperatures, and highly isotropic pinning properties make iron-chalcogenide superconductors a technological material which could be a real competitor to cuprate high temperature superconductors for high field applications.

  2. Structure and thermoelectric properties of CoSb3-3XGe1.5X Te1.5X (X = 0 ~ 1)

    NASA Astrophysics Data System (ADS)

    Su, Xianli; Tang, Xinfeng; Uher, Ctirad; Wuhan University of Technology Team; University of Michigan Team

    2014-03-01

    Changes in the phonon vibration spectra created by substitutions on the rings or by deforming the rings decrease the lattice thermal conductivity. In this research we focused the Ge and Te co-doped and fully compensated CoSb3-3xGe1.5xTe1.5x skutterudite compounds for the first time. A single-phase skutterudite can be obtained with x smaller than 0.50. In comparison with a ternary skutterudite of the form CoGe1.5Te1.5, the order-disorder transition can be observed due to the different configuration of four-member pnicogen rings. Rietveld refinement result shows that the bond distance of Sb-Sb decreases with the increase of the Ge and Te content. With x smaller than 0.5, Ge/Te distribute randomly on the four-member near-square Sb rings. For the CoGe1.5Te1.5 sample, Ge Te distribute in a staggered pattern. Due to the different bonding distance and bonding angle, the near-square ring turns into a parallelogram ring, the essence of the order-disorder transition. The thermal conductivity decreases dramatically with the increasing content of Ge/Te double-doping due to the enhanced alloy scattering.

  3. Surface Plasmons in 3D Topological Insulators

    NASA Astrophysics Data System (ADS)

    Kogar, Anshul; Vig, Sean; Cho, Gil; Thaler, Alexander; Xiao, Yiran; Hughes, Taylor; Wong, Man-Hong; Chiang, Tai-Chang; MacDougall, Greg; Abbamonte, Peter

    2015-03-01

    Most studies of three-dimensional (3D) topological insulators have concentrated on their one-electron properties as exhibited by angle-resolved photoemission spectroscopy (ARPES) or by scanning tunneling microscopy (STM). Many-body interactions are often neglected in the treatment of models of topological insulators, such as in the Kane-Mele and Bernevig-Hughes-Zhang models. Using angle-resolved inelastic electron scattering from the surface, I will present data on the collective mode that owes its existence to the presence of many-body interactions, the surface plasmon (SP), in two known 3D topological insulators, Bi2Se3 and Bi0.5Sb1.5Se1 . 5 + xTe1 . 5 - x. Surprisingly, the SP was prominent even after depressing the Fermi energy into the bulk band gap. Having studied the SP as a function of doping, momentum transfer and its aging properties, I will present evidence to suggest that bulk-surface coupling is crucial in explaining many of its properties. A simple model with dynamic bulk screening will be presented showing qualitative agreement with the observations. Lastly, the relation of the observed surface plasmon to the predicted spin-plasmon mode and to the kinks seen in the electronic dispersion as measured by ARPES will be discussed. The work was supported as part of the Center for Emergent Superconductivity, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science.

  4. The UCSD high energy X-ray timing experiment cosmic ray particle anticoincidence detector

    NASA Technical Reports Server (NTRS)

    Hink, P. L.; Rothschild, R. E.; Pelling, M. R.; Macdonald, D. R.; Gruber, D. E.

    1991-01-01

    The HEXTE, part of the X-Ray Timing Explorer (XTE), is designed to make high sensitivity temporal and spectral measurements of X-rays with energies between 15 and 250 keV using NaI/CsI phoswich scintillation counters. To achieve the required sensitivity it is necessary to provide anticoincidence of charged cosmic ray particles incident upon the instrument, some of which interact to produce background X-rays. The proposed cosmic ray particle anticoincidence shield detector for HEXTE uses a novel design based on plastic scintillators and wavelength-shifter bars. It consists of five segments, each with a 7 mm thick plastic scintillator, roughly 50 cm x 50 cm in size, coupled to two wavelength-shifter bars viewed by 1/2 inch photomultiplier tubes. These segments are configured into a five-sided, box-like structure around the main detector system. Results of laboratory testing of a model segment, and calculations of the expected performance of the flight segments and particle anticoincidence detector system are presented to demonstrate that the above anticoincidence detector system satisfies its scientific requirements.

  5. The behaviour of Gd in lead and tin tellurides and its effect on their physical properties

    NASA Astrophysics Data System (ADS)

    Zayachuk, D. M.; Matulenis, E. L.; Mikityuk, V. I.

    1992-06-01

    The behaviour of gadolinium in Pb 1- xSn xTe (0 ⩽ x ⩽ 0.3) introduced during Bridgman growth and its effect on the composition profiles and free carrier concentration is investigated. The Gd, Pb, Sn and Te contents in crystals were determined by electron microprobe analysis, and the free carrier concentration was obtained by Hall measurements. The results indicate that Gd behaves like an impurity with a segregation coefficient larger than unity, which strongly depends on the Gd concentration N( L) Gd in the melt and is given by KS = 1 + Aexp( - BN( L) Gd), where A takes values of 8 or 9 and B a value of about 10 -20 cm 3. The effect of such a strong KS( N( L) Gd) dependence is that all the Gd impurity concentrates in the first-to-freeze section, leaving the rest of the ingot free from the impurity. Thus, by introducing Gd during melt growth of lead-tin telluride crystals, one can obtain high quality crystals of the solid solutions studied.

  6. FTOOLS: A FITS Data Processing and Analysis Software Package

    NASA Astrophysics Data System (ADS)

    Blackburn, J. K.

    FTOOLS, a highly modular collection of over 110 utilities for processing and analyzing data in the FITS (Flexible Image Transport System) format, has been developed in support of the HEASARC (High Energy Astrophysics Science Archive Research Center) at NASA's Goddard Space Flight Center. Each utility performs a single simple task such as presentation of file contents, extraction of specific rows or columns, appending or merging tables, binning values in a column or selecting subsets of rows based on a boolean expression. Individual utilities can easily be chained together in scripts to achieve more complex operations such as the generation and displaying of spectra or light curves. The collection of utilities provides both generic processing and analysis utilities and utilities specific to high energy astrophysics data sets used for the ASCA, ROSAT, GRO, and XTE missions. A core set of FTOOLS providing support for generic FITS data processing, FITS image analysis and timing analysis can easily be split out of the full software package for users not needing the high energy astrophysics mission utilities. The FTOOLS software package is designed to be both compatible with IRAF and completely stand alone in a UNIX or VMS environment. The user interface is controlled by standard IRAF parameter files. The package is self documenting through the IRAF help facility and a stand alone help task. Software is written in ANSI C and \\fortran to provide portability across most computer systems. The data format dependencies between hardware platforms are isolated through the FITSIO library package.

  7. Einstein-Maxwell Field Equation in Isotropic Coordinates: An Application to Modeling Superdense Star

    NASA Astrophysics Data System (ADS)

    Pant, Neeraj; Ahmad, Mohammad; Pradhan, N.

    2016-03-01

    We present a charged analogue of Pant et al. (2010, Astrophys. Space Sci., 330, 353) solution of the general relativistic field equations in isotropic coordinates by using simple form of electric intensity E that involve charge parameter K. Our solution is well behaved in all respects for all values of X lying in the range 0 < X≤ 0.11, K lying in the range 4 < K≤ 6.2 and Schwarzschild compactness parameter u lying in the range 0 < u≤ 0.247. Since our solution is well behaved for wide ranges of the parameters, we can model many different types of ultra-cold compact stars like quark stars and neutron stars. We have shown that corresponding to X = 0.077 and K = 6.13 for which u = 0.2051 and by assuming surface density ρ b =4.6888×1014 g cm -3 the mass and radius are found to be 1.509 M ⊙, 10.906 km respectively which match with the observed values of mass 1.51 M ⊙ and radius 10.90 km of the quark star XTE J1739-217. The well behaved class of relativistic stellar models obtained in this work might have astrophysical significance in the study of more realistic internal structures of compact stars.

  8. Preparation of dilute magnetic semiconductor films by metalorganic chemical vapor deposition

    NASA Technical Reports Server (NTRS)

    Nouhi, Akbar (Inventor); Stirn, Richard J. (Inventor)

    1988-01-01

    A method for preparation of a dilute magnetic semiconductor (DMS) film is provided, in which a Group II metal source, a Group VI metal source and a transition metal magnetic ion source are pyrolyzed in the reactor of a metalorganic chemical vapor deposition (MOCVD) system by contact with a heated substrate. As an example, the preparation of films of Cd(sub 1-x)Mn(sub x)Te, in which 0 is less than or equal to x less than or equal to 0.7, on suitable substrates (e.g., GaAs) is described. As a source of manganese, tricarbonyl (methylcyclopentadienyl) manganese (TCPMn) is employed. To prevent TCPMn condensation during its introduction into the reactor, the gas lines, valves and reactor tubes are heated. A thin-film solar cell of n-i-p structure, in which the i-type layer comprises a DMS, is also described; the i-type layer is suitably prepared by MOCVD.

  9. Li3Gd3Te2O12:Eu3+- an intense red phosphor for solid state lighting applications

    NASA Astrophysics Data System (ADS)

    Tiwari, Hansnath; Asiri Naidu, S.; Varadaraju, U. V.

    2017-02-01

    Li3Gd3-3xEu3xTe2O12 (x=0.05-1.0) phases with garnet structure were synthesized by high temperature solid state reaction and the photoluminescence properties were investigated. The appearance of bands due to intra 4 f transitions of Gd3+ in the excitation spectra recorded by monitoring the 612 nm emission line of the activator indicates Gd3+→Eu3+ energy transfer in this host lattice. Under 395 nm excitation, the electric dipole transition is predominant in the emission spectrum of Eu3+ and is in agreement with the C2 point group (noncentrosymmetric) of the EuO8 polyhedron. The critical concentration of the Eu3+ activator in this series was found to be 0.6 (x=0.2) above which, concentration quenching occurs. The emission intensity of the phosphor composition, Li3Gd2.4Eu0.6Te2O12 is 4 times that of the commercial sample of Y2O3:Eu3+ phosphor.

  10. Strong-field Gravitational Effects in the Timing and Spectroscopy of X-Ray Binaries

    NASA Technical Reports Server (NTRS)

    Bertschinger, Edmund

    2005-01-01

    Using the ray-tracing code described, we developed additional features to the hot spot model to explain the broadening of the quasi-periodic oscillation (QPO) peaks as well as the damping of higher frequency harmonics in the power spectrum. We derived a number of analytic results that agree closely with more detailed numerical calculations. Three primary pieces are developed: the superposition of multiple hot spots with finite lifetimes and random phases, a width in the radial distribution of geodesic orbits, and the scattering of photons from the hot spot through a corona around the black hole. The complete model is used to fit the observed power spectra of both type A and type B QPOs seen in XTE 51550-564, giving confidence limits on each of the model parameters. These results were presented in a conference paper and in a refereed publication. We also explored the possibility of using higher-order statistics, particularly the bispectrum and bicoherence, to distinguish between competing QPO models. These methods were applied to the hot spot model and a method was proposed to map out the spacetime metric around Kerr black holes in Ref. 3 below.

  11. Interference as an Origin of the Peaked Noise in Accreting X-Ray Binaries

    NASA Astrophysics Data System (ADS)

    Veledina, Alexandra

    2016-12-01

    We propose a physical model for the peaked noise in the X-ray power density spectra of accreting X-ray binaries. We interpret its appearance as an interference of two Comptonization continua: one coming from the upscattering of seed photons from the cold thin disk and the other fed by the synchrotron emission of the hot flow. Variations of both X-ray components are caused by fluctuations in mass accretion rate, but there is a delay between them corresponding to the propagation timescale from the disk Comptonization radius to the region of synchrotron Comptonization. If the disk and synchrotron Comptonization are correlated, the humps in the power spectra are harmonically related and the dips between them appear at frequencies related as odd numbers 1:3:5. If they are anti-correlated, the humps are related as 1:3:5, but the dips are harmonically related. Similar structures are expected to be observed in accreting neutron star binaries and supermassive black holes. The delay can be easily recovered from the frequency of peaked noise and further used to constrain the combination of the viscosity parameter and disk height-to-radius ratio α(H/R)2 of the accretion flow. We model multi-peak power spectra of black hole X-ray binaries GX 339-4 and XTE J1748-288 to constrain these parameters.

  12. Monitoring The Crab Pulsar

    NASA Technical Reports Server (NTRS)

    Rots, Arnold H.; Swank, Jean (Technical Monitor)

    2001-01-01

    The monitoring of the X-ray pulses from the Crab pulsar is still ongoing at the time of this writing, and we hope to be able to continue the campaign for the life of the XTE mission. We have established beyond all doubt that: (1) the X-ray main pulse leads the radio pulse by approximately 300 microseconds, (2) this phase lag is constant and not influenced by glitches, (3) this lag does not depend on X-ray energy, (4) the relative phase of the two X-ray pulses does not vary, and (5) the spectral indices of primary, secondary, and inter-pulse are distinct and constant. At this time we are investigating whether the radio timing ephemeris can be replaced by an x-ray ephemeris and whether any long-time timing ephemeris can be established. If so, it would enable use to study variations in pulse arrival times at a longer time scales. Such a study is easier in x-rays than at radio wavelengths since the dispersion measure plays no role. These results were reported at the 2000 HEAD Meeting in Honolulu, HI. Travel was paid partly out of this grant. The remainder was applied toward the acquisition of a laptop computer that allows independent and fast analysis of all monitoring observations.

  13. Connections between jet formation and multiwavelength spectral evolution in black hole transients

    NASA Astrophysics Data System (ADS)

    Kalemci, Emrah; Chun, Yoon-Young; Dinçer, Tolga; Buxton, Michelle; Tomsick, John A.; Corbel, Stephane; Kaaret, Philip

    2011-02-01

    Multiwavelength observations are the key to understand conditions of jet formation in Galactic black hole transient (GBHT) systems. By studying radio and optical-infrared evolution of such systems during outburst decays, the compact jet formation can be traced. Comparing this with X-ray spectral and timing evolution we can obtain physical and geometrical conditions for jet formation, and study the contribution of jets to X-ray emission. In this work, first X-ray evolution - jet relation for XTE J1752-223 will be discussed. This source had very good coverage in X-rays, optical, infrared and radio. A long exposure with INTEGRAL also allowed us to study gamma-ray behavior after the jet turns on. We will also show results from the analysis of data from GX 339-4 in the hard state with SUZAKU at low flux levels. The fits to iron line fluorescence emission show that the inner disk radius increases by a factor of >27 with respect to radii in bright states. This result, along with other disk radius measurements in the hard state will be discussed within the context of conditions for launching and sustaining jets.

  14. Spin texture on the Fermi surface of tensile-strained HgTe

    NASA Astrophysics Data System (ADS)

    Zaheer, Saad; Young, S. M.; Cellucci, D.; Teo, J. C. Y.; Kane, C. L.; Mele, E. J.; Rappe, Andrew M.

    2013-01-01

    We present ab initio and k·p calculations of the spin texture on the Fermi surface of tensile-strained HgTe, which is obtained by stretching the zinc-blende lattice along the (111) axis. Tensile-strained HgTe is a semimetal with pointlike accidental degeneracies between a mirror symmetry protected twofold degenerate band and two nondegenerate bands near the Fermi level. The Fermi surface consists of two ellipsoids which contact at the point where the Fermi level crosses the twofold degenerate band along the (111) axis. However, the spin texture of occupied states indicates that neither ellipsoid carries a compensating Chern number. Consequently, the spin texture is locked in the plane perpendicular to the (111) axis, exhibits a nonzero winding number in that plane, and changes winding number from one end of the Fermi ellipsoids to the other. The change in the winding of the spin texture suggests the existence of singular points. An ordered alloy of HgTe with ZnTe has the same effect as stretching the zinc-blende lattice in the (111) direction. We present ab initio calculations of ordered HgxZn1-xTe that confirm the existence of a spin texture locked in a 2D plane on the Fermi surface with different winding numbers on either end.

  15. A numerical investigation of wind accretion in persistent Supergiant X-ray Binaries I - Structure of the flow at the orbital scale

    NASA Astrophysics Data System (ADS)

    El Mellah, I.; Casse, F.

    2017-01-01

    Classical Supergiant X-ray Binaries host a neutron star orbiting a supergiant OB star and display persistent X-ray luminosities of 1035 to 1037 erg· s-1. The stellar wind from the massive companion is believed to be the main source of matter accreted by the compact object. With this first paper, we introduce a ballistic model to evaluate the influence of the orbital effects on the structure of the accelerating winds which participate to the accretion process. Thanks to the parametrization we retained and the numerical pipeline we designed, we can investigate the supersonic flow and the subsequent observables as a function of a reduced set of characteristic numbers and scales. We show that the shape of the permanent flow is entirely determined by the mass ratio, the filling factor, the Eddington factor and the α-force multiplier which drives the stellar wind acceleration. Provided scales such as the orbital period are known, we can trace back the observables to evaluate the mass accretion rates, the accretion mechanism, the shearing of the inflow and the stellar parameters. We discuss the likelihood of wind-formed accretion discs around the accretors in each case and confront our model to three persistent Supergiant X-ray Binaries (Vela X-1, IGR J18027-2016, XTE J1855-026).

  16. Mössbauer studies of the peculiar magnetism in parent compounds of the iron-based superconductors

    NASA Astrophysics Data System (ADS)

    Jasek, A. K.; Komędera, K.; Błachowski, A.; Ruebenbauer, K.; Żukrowski, J.; Bukowski, Z.; Karpinski, J.

    2015-02-01

    A review of the magnetism in the parent compounds of the iron-based superconductors is given based on the transmission Mössbauer spectroscopy of 57Fe and 151Eu. It was found that the 3d magnetism is of the itinerant character with varying admixture of the spin-polarized covalent bonds. For the '122' compounds, a longitudinal spin density wave (SDW) develops. In the case of the EuFe2As2, a divalent europium arranges in an anti-ferromagnetical order at a much lower temperature as compared with the onset of SDW. These two magnetic systems remain almost uncoupled one to another. For the non-stoichiometric Fe1+xTe parent of the '11' family, one has a transversal SDW and magnetic order of the interstitial iron with relatively high and localized magnetic moments. These two systems are strongly coupled one to another. For the 'grand parent' of the iron-based superconductors FeAs, one observes two mutually orthogonal phase-related transversal SDW on the iron sites. There are two sets of such spin arrangements due to two crystallographic iron sites. The FeAs exhibits the highest covalency among the compounds studied, but it has still a metallic character. A contribution to XVI National Conference on Superconductivity, Zakopane, Poland, 7-12 October 2013.

  17. Extremely fast orbital decay of the black hole X-ray binary Nova Muscae 1991

    NASA Astrophysics Data System (ADS)

    González Hernández, J. I.; Suárez-Andrés, L.; Rebolo, R.; Casares, J.

    2017-02-01

    We present new medium-resolution spectroscopic observations of the black hole X-ray binary Nova Muscae 1991 taken with X-Shooter spectrograph installed at the 8.2-m VLT telescope. These observations allow us to measure the time of inferior conjunction of the secondary star with the black hole in this system that, together with previous measurements, yield an orbital period decay of dot{P}=-20.7± 12.7 ms yr-1 (-24.5 ± 15.1 μs per orbital cycle). This is significantly faster than those previously measured in the other black hole X-ray binaries A0620-00 and XTE J1118+480. No standard black hole X-ray binary evolutionary model is able to explain this extremely fast orbital decay. At this rate, the secondary star would reach the event horizon (as given by the Schwarzschild radius of about 32 km) in roughly 2.7 Myr. This result has dramatic implications on the evolution and lifetime of black hole X-ray binaries.

  18. Giant anisotropic magnetoresistance in a quantum anomalous Hall insulator

    NASA Astrophysics Data System (ADS)

    Kandala, Abhinav; Richardella, Anthony; Kempinger, Susan; Liu, Chao-Xing; Samarth, Nitin

    2015-07-01

    When a three-dimensional ferromagnetic topological insulator thin film is magnetized out-of-plane, conduction ideally occurs through dissipationless, one-dimensional (1D) chiral states that are characterized by a quantized, zero-field Hall conductance. The recent realization of this phenomenon, the quantum anomalous Hall effect, provides a conceptually new platform for studies of 1D transport, distinct from the traditionally studied quantum Hall effects that arise from Landau level formation. An important question arises in this context: how do these 1D edge states evolve as the magnetization is changed from out-of-plane to in-plane? We examine this question by studying the field-tilt-driven crossover from predominantly edge-state transport to diffusive transport in Crx(Bi,Sb)2-xTe3 thin films. This crossover manifests itself in a giant, electrically tunable anisotropic magnetoresistance that we explain by employing a Landauer-Büttiker formalism. Our methodology provides a powerful means of quantifying dissipative effects in temperature and chemical potential regimes far from perfect quantization.

  19. Giant anisotropic magnetoresistance in a quantum anomalous Hall insulator.

    PubMed

    Kandala, Abhinav; Richardella, Anthony; Kempinger, Susan; Liu, Chao-Xing; Samarth, Nitin

    2015-07-07

    When a three-dimensional ferromagnetic topological insulator thin film is magnetized out-of-plane, conduction ideally occurs through dissipationless, one-dimensional (1D) chiral states that are characterized by a quantized, zero-field Hall conductance. The recent realization of this phenomenon, the quantum anomalous Hall effect, provides a conceptually new platform for studies of 1D transport, distinct from the traditionally studied quantum Hall effects that arise from Landau level formation. An important question arises in this context: how do these 1D edge states evolve as the magnetization is changed from out-of-plane to in-plane? We examine this question by studying the field-tilt-driven crossover from predominantly edge-state transport to diffusive transport in Crx(Bi,Sb)(2-x)Te3 thin films. This crossover manifests itself in a giant, electrically tunable anisotropic magnetoresistance that we explain by employing a Landauer-Büttiker formalism. Our methodology provides a powerful means of quantifying dissipative effects in temperature and chemical potential regimes far from perfect quantization.

  20. The GRB coordinates network (GCN): A status report

    NASA Astrophysics Data System (ADS)

    Barthelmy, S. D.; Butterworth, P.; Cline, T. L.; Gehrels, N.; Marshall, F.; Takeshima, T.; Connaughton, V.; Kippen, R. M.; Kouveliotou, C.; Robinson, C. R.

    1998-05-01

    A review of the GRB Coordinates Network (GCN) will be given. The GCN has recently replaced the BATSE Coordinates Distribution Network (BACODINE), maintaining all of BACODINE's original capabilities and services, but also providing new sources of GRB location information. These are: (1) source locations using the MSFC LOCBURST algorithm, (2) the Rossi-XTE detections (PCA and ASM), (3) the Interplanetary Network (IPN) locations, and (4) CGRO-COMPTEL locations. These new sources of locations are available for distribution in the minutes-to-hours-to-days time delay ranges, and they also have increasingly and significantly reduced error boxes, thus providing a broad range of time delays and error box sizes to fit within the observing capabilities of a broad range of follow-up instruments in the radio, optical, and TeV gamma-ray bands. Extreme-UV transients from ALEXIS are also now distributed. For all sources of location information, all the distribution methods are available (Internet Socket, E-mail, Alpha-numeric and Numeric Pagers, and Phone/modem) and several filters. Sites can choose which sources to receive and what filters to be applied. The GCN web site has been expanded to include a globally inclusive table of locations, light-curves, and fluence information which is automatically updated in real-time.

  1. Current Perspectives in High Energy Astrophysics

    NASA Technical Reports Server (NTRS)

    Ormes, Jonathan F. (Editor)

    1996-01-01

    High energy astrophysics is a space-age discipline that has taken a quantum leap forward in the 1990s. The observables are photons and particles that are unable to penetrate the atmosphere and can only be observed from space or very high altitude balloons. The lectures presented as chapters of this book are based on the results from the Compton Gamma-Ray Observatory (CGRO) and Advanced Satellite for Cosmology and Astrophysics (ASCA) missions to which the Laboratory for High Energy Astrophysics at NASA's Goddard Space Flight Center made significant hardware contributions. These missions study emissions from very hot plasmas, nuclear processes, and high energy particle interactions in space. Results to be discussed include gamma-ray beaming from active galactic nuclei (AGN), gamma-ray emission from pulsars, radioactive elements in the interstellar medium, X-ray emission from clusters of galaxies, and the progress being made to unravel the gamma-ray burst mystery. The recently launched X-ray Timing Explorer (XTE) and prospects for upcoming Astro-E and Advanced X-ray Astronomy Satellite (AXAF) missions are also discussed.

  2. SEXTANT: A Demonstration of X-ray Pulsar-Based Navigation Using NICER

    NASA Astrophysics Data System (ADS)

    Ray, Paul S.; Mitchell, Jason W; Winternitz, Luke M; Hasouneh, Monther A; Price, Samuel R; Valdez, Jennifer; Yu, Wayne H; Semper, Sean R; Wood, Kent S.; Wolff, Michael Thomas; Arzoumanian, Zaven; Litchford, Ronald J; Gendreau, Keith

    2014-08-01

    The Station Explorer for X-ray Timing and Navigation Technology (SEXTANT) is a technology-demonstration enhancement to the Neutron-star Interior Composition Explorer (NICER) mission. NICER is a NASA Explorer Mission of Opportunity that will be hosted on the International Space Station (ISS). SEXTANT will, for the first time, demonstrate real-time, on-board X-ray pulsar-based navigation (XNAV), a significant milestone in the quest to establish a GPS-like navigation capability available throughout our Solar System and beyond. The SEXTANT XNAV demonstration will exploit the large collecting area (>1800 cm^2), low background (<0.2 counts/s), and precise timing (<300 ns) of the NICER X-ray Timing Instrument (XTE). Taking advantage of NICER’s science observations of X-ray emitting millisecond pulsars, which are nature’s most stable clocks, the SEXTANT flight software will demonstrate real-time orbit determination with error less than 10 km in any direction, through measurements made over 2 weeks or less in the highly dynamic low-Earth ISS orbit. The completed technology demonstration will bring the XNAV concept and algorithms to a Technology Readiness Level of 8 and will inform the design and configuration of future practical XNAV implementations.

  3. The Magnetohydrodynamical Model of Kilohertz Quasi-periodic Oscillations in Neutron Star Low-mass X-Ray Binaries (II)

    NASA Astrophysics Data System (ADS)

    Shi, Chang-Sheng; Zhang, Shuang-Nan; Li, Xiang-Dong

    2014-08-01

    We study the kilohertz quasi-periodic oscillations (kHz QPOs) in neutron star low-mass X-ray binaries (LMXBs) with a new magnetohydrodynamics (MHD) model, in which the compressed magnetosphere is considered. The previous MHD model is reexamined and the relation between the frequencies of the kHz QPOs and the accretion rate in LMXBs is obtained. Our result agrees with the observations of six sources (4U 0614+09, 4U 1636-53, 4U 1608-52, 4U 1915-15, 4U 1728-34, and XTE 1807-294) with measured spins. In this model, the kHz QPOs originate from the MHD waves in the compressed magnetosphere. The single kHz QPOs and twin kHz QPOs are produced in two different parts of the accretion disk and the boundary is close to the corotation radius. The lower QPO frequency in a frequency-accretion rate diagram is cut off at a low accretion rate and the twin kHz QPOs encounter a top ceiling at a high accretion rate due to the restriction of the innermost stable circular orbit.

  4. ELECTROMAGNETIC SPINDOWN OF A TRANSIENT ACCRETING MILLISECOND PULSAR DURING QUIESCENCE

    SciTech Connect

    Melatos, A.; Mastrano, A. E-mail: alpham@unimelb.edu.au

    2016-02-10

    The measured spindown rates in quiescence of the transient accreting millisecond pulsars IGR J00291+5934, XTE J1751–305, SAX J1808.4–3658, and Swift J1756.9–2508 have been used to estimate the magnetic moments of these objects assuming standard magnetic dipole braking. It is shown that this approach leads to an overestimate if the amount of residual accretion is enough to distort the magnetosphere away from a force-free configuration through magnetospheric mass loading or crushing, so that the lever arm of the braking torque migrates inside the light cylinder. We derive an alternative spindown formula and calculate the residual accretion rates where the formula is applicable. As a demonstration we apply the alternative spindown formula to produce updated magnetic moment estimates for the four objects above. We note that based on current uncertain observations of quiescent accretion rates, magnetospheric mass loading and crushing are neither firmly indicated nor ruled out in these four objects. Because quiescent accretion rates are not measured directly (only upper limits are placed), without more data it is impossible to be confident about whether the thresholds for magnetospheric mass loading or crushing are reached or not.

  5. The Appearance of Non-Spherical Systems. Application to LMXB

    NASA Astrophysics Data System (ADS)

    Różańska, A.; Bełdycki, B.; Madej, J.; Adhikari, T. P.; You, B.

    2017-03-01

    We study the appearance of the neutron star-accretion disk system as seen by a distant observer in the UV/X-ray domain. The observed intensity spectra are computed assuming non-spherical geometry of the whole system, in which outgoing spectrum is not represented by the flux spectrum, the latter being valid for spherically symmetric objects. Intensity spectra of our model display double bumps in UV/X-ray energy domains. Such structure is caused by the fact that the the source is not spherically symmetric, and the proper integration of intensity over emitted area is needed to reproduce observed spectral shape. Relative normalization of double bump is self consistently computed by our model. X-ray spectra of such a type were often observed in LMXB with accretion disk, ultra luminous X-ray sources, and accreting black hole systems with hot inner compact corona. Our model naturally explains high energy broadening of the disk spectrum observed in some binaries. We attempted to fit our model to X-ray data of XTE J1709-267 from XMM-Newton. Unfortunately, the double intensity bump predicted by our model for LMXB is located in soft X-ray domain, uncovered by existing data for this source.

  6. High Compositional Homogeneity of CdTexSe1-x Crystals Grown by the Bridgman Method

    DOE PAGES

    Roy, U. N.; Bolotnikov, A. E.; Camarda, G. S.; ...

    2015-02-03

    We obtained high-quality CdTexSe1-x (CdTeSe) crystals from ingots grown by the vertical Bridgman technique. The compositional uniformity of the ingots was evaluated by X-ray fluorescence at BNL’s National Synchrotron Light Source X27A beam line. The resulting compositional homogeneity was highly uniform throughout the ingot, and the effective segregation coefficient of Se was ~1.0. This uniformity offers potential opportunity to enhance the yield of the materials for both infrared substrate and radiation-detector applications, so greatly lowering the cost of production and also offering us the prospect to grow large-diameter ingots for use as large-area substrates and for producing higher efficiency gamma-raymore » detectors. The concentration of secondary phases was found to be much lower, by eight- to ten fold compared to that of conventional CdxZn1-xTe (CdZnTe or CZT).« less

  7. The growth of a cubic, single phase, Cd 0.6Mn 0.4Te single crystal by the vertical gradient freeze method

    NASA Astrophysics Data System (ADS)

    Azoulay, M.; Raizman, A.; Weingarten, R.; Shacham, H.; Feldstein, H.

    1993-03-01

    The growth of CdMnTe single crystals faces some difficulties due to the phase transition in the solid state at high temperatures, just after solidification. To overcome this problem, it has been suggested to grow the crystals from a Te-rich solution by the traveling heater method at a lower temperature than that of growth from the melt, or alternatively to grow the crystal from the melt at high axial thermal gradient near the interface. In this paper, we present for the first time the growth of cubic, single phase, CdxMn1-xTe single crystals by the vertical gradient freeze technique under a very low axial thermal gradient in the melt (3°C/cm) and high manganese content (x ≈ 40%). The solidification stage is characterized by a rapid cooling of the crystal through the phase transition temperature region, followed by annealing at about 800°C. The crystal exhibits a very high crystalline perfection, as measured by the double-crystal X-ray rocking curves with a full width at half maximum of 30 arc sec and low optical losses of about 1 dB/mm between 650 and 820 nm with λ-cutoff at 630 nm. Further magneto-optical properties are currently examined for a possible application in devices.

  8. Space and Earth Sciences, Computer Systems, and Scientific Data Analysis Support, Volume 1

    NASA Technical Reports Server (NTRS)

    Estes, Ronald H. (Editor)

    1993-01-01

    This Final Progress Report covers the specific technical activities of Hughes STX Corporation for the last contract triannual period of 1 June through 30 Sep. 1993, in support of assigned task activities at Goddard Space Flight Center (GSFC). It also provides a brief summary of work throughout the contract period of performance on each active task. Technical activity is presented in Volume 1, while financial and level-of-effort data is presented in Volume 2. Technical support was provided to all Division and Laboratories of Goddard's Space Sciences and Earth Sciences Directorates. Types of support include: scientific programming, systems programming, computer management, mission planning, scientific investigation, data analysis, data processing, data base creation and maintenance, instrumentation development, and management services. Mission and instruments supported include: ROSAT, Astro-D, BBXRT, XTE, AXAF, GRO, COBE, WIND, UIT, SMM, STIS, HEIDI, DE, URAP, CRRES, Voyagers, ISEE, San Marco, LAGEOS, TOPEX/Poseidon, Pioneer-Venus, Galileo, Cassini, Nimbus-7/TOMS, Meteor-3/TOMS, FIFE, BOREAS, TRMM, AVHRR, and Landsat. Accomplishments include: development of computing programs for mission science and data analysis, supercomputer applications support, computer network support, computational upgrades for data archival and analysis centers, end-to-end management for mission data flow, scientific modeling and results in the fields of space and Earth physics, planning and design of GSFC VO DAAC and VO IMS, fabrication, assembly, and testing of mission instrumentation, and design of mission operations center.

  9. The effects of dust scattering on high-resolution X-ray absorption edge structure

    NASA Astrophysics Data System (ADS)

    Corrales, L.; García, J.; Wilms, J.; Baganoff, F.

    2016-06-01

    High energy studies of astrophysical dust complement observations of dusty interstellar gas at other wavelengths. With high resolution X-ray spectroscopy, dust scattering significantly enhances the total extinction optical depth and alters the shape of photoelectric absorption edges. This effect is modulated by the dust grain size distribution, spatial location along the line of sight, and the imaging resolution of the X-ray telescope. At soft energies, the spectrum of scattered light is likely to have significant features at the 0.3 keV (C-K), 0.5 keV (O-K), and 0.7 keV (Fe-L) photoelectric absorption edges. This direct probe of ISM dust grain elements will be important for (i) understanding the relative abundances of graphitic grains or PAHs versus silicates, and (ii) measuring the depletion of gas phase elements into solid form. We focus in particular on the Fe-L edge, fitting a template for the total extinction to the high resolution spectrum of three X-ray binaries from the Chandra archive: GX 9+9, XTE J1817-330, and Cyg X-1. We discuss ways in which spectroscopy with XMM can yield insight into dust obscured objects such as stars, binaries, AGN, and foreground quasar absorption line systems.

  10. A new X-ray outburst in the globular cluster NGC 6440: SAX J1748.9-2021

    NASA Astrophysics Data System (ADS)

    in 't Zand, J. J. M.; Verbunt, F.; Strohmayer, T. E.; Bazzano, A.; Cocchi, M.; Heise, J.; van Kerkwijk, M. H.; Muller, J. M.; Natalucci, L.; Smith, M. J. S.; Ubertini, P.

    1999-05-01

    For the second time in 27 years a bright transient X-ray source has been detected coincident with the globular cluster NGC 6440. It was found to be active in August, 1998, with the Wide Field Camera and the narrow field instruments on the BeppoSAX spacecraft, and with the All-Sky Monitor and the Proportional Counter Array on the RossiXTE spacecraft. Four X-ray bursts were detected, at least one of which shows the characteristics of a thermonuclear flash on a neutron star, in analogy with some ~ 20 optically identified low-mass X-ray binaries. The broad-band spectrum is hard as is common among low-mass X-ray binaries of lower luminosity (la10 (37) erg s(-1) ) and can be explained by a Comptonized model. During the burst the >30 keV emission brightened, consistent with part of the burst emission being Compton up scattered within ~ 10(11) cm.

  11. Synthesis of monoclinic IrTe2 under high pressure and its physical properties

    DOE PAGES

    Li, X.; Yan, J. -Q.; Singh, D. J.; ...

    2015-10-12

    In a pressure-temperature (P-T) diagram for synthesizing IrTe2 compounds, the well-studied trigonal (H) phase with the CdI2-type structure is stable at low pressures. The superconducting cubic (C) phase can be synthesized under higher temperatures and pressures. A rhombohedral phase with the crystal structure similar to the C phase can be made at ambient pressure; but the phase contains a high concentration of Ir deficiency. Here, we report that a rarely studied monoclinic (M) phase can be stabilized in narrow ranges of pressure and temperature in this P-T diagram. Moreover, the peculiar crystal structure of the M-IrTe2 eliminates the tendency tomore » form Ir-Ir dimers found in the H phase. The M phase has been fully characterized by structural determination and measurements of electrical resistivity, thermoelectric power, DC magnetization, and specific heat. These physical properties have been compared with those in the H and C phases of Ir1-xTe2. Finally, we present magnetic and transport properties and specific heat of the M-IrTe2 can be fully justified by calculations with the density-functional theory.« less

  12. Study of damage induced by room-temperature Al ion implantation in Hg{sub 0.8}Cd{sub 0.2}Te by x-ray diffuse scattering

    SciTech Connect

    Renault, P.O.; Declemy, A.; Leveque, P.; Fayoux, C.; Bessiere, M.; Lefebvre, S.; Corbel, C.; Baroux, L.

    1997-07-01

    Ion-implantation is a widely used doping technique in II{endash}VI semiconductors. Nevertheless, ion-implantation damage has to be better understood to properly control this process. In order to investigate the implantation-induced defects in such compounds, room-temperature implantations of 320 keV Al ions have been performed on crystalline samples of [111] Hg{sub 1{minus}x}Cd{sub x}Te (x{approx}20{percent}) for doses ranging from 10{sup 13} to 10{sup 15}cm{sup {minus}2}. We report the first measurements of x-ray diffuse scattering close to different Bragg reflections on such as-implanted samples. The evolution of the diffuse intensity as a function of the dose has been observed. The defect-induced diffuse intensity arises mainly from interstitial dislocation loops. Nevertheless, vacancy loops are observed above 3{times}10{sup 14}Al/cm{sup 2}. The mean radius of the dislocation loops increases in size by three to four times when the dose rises from 10{sup 13} to 10{sup 15}cm{sup {minus}2}. Finally, the saturation of point defects has been observed independently of their clustering at about 5{times}10{sup 13}Al/cm{sup 2}, that is in the same range as the saturation dose of the sheet electron concentration. {copyright} {ital 1997 American Institute of Physics.}

  13. The magnetohydrodynamical model of kilohertz quasi-periodic oscillations in neutron star low-mass X-ray binaries (II)

    SciTech Connect

    Shi, Chang-Sheng; Zhang, Shuang-Nan; Li, Xiang-Dong

    2014-08-10

    We study the kilohertz quasi-periodic oscillations (kHz QPOs) in neutron star low-mass X-ray binaries (LMXBs) with a new magnetohydrodynamics (MHD) model, in which the compressed magnetosphere is considered. The previous MHD model is reexamined and the relation between the frequencies of the kHz QPOs and the accretion rate in LMXBs is obtained. Our result agrees with the observations of six sources (4U 0614+09, 4U 1636-53, 4U 1608-52, 4U 1915-15, 4U 1728-34, and XTE 1807-294) with measured spins. In this model, the kHz QPOs originate from the MHD waves in the compressed magnetosphere. The single kHz QPOs and twin kHz QPOs are produced in two different parts of the accretion disk and the boundary is close to the corotation radius. The lower QPO frequency in a frequency-accretion rate diagram is cut off at a low accretion rate and the twin kHz QPOs encounter a top ceiling at a high accretion rate due to the restriction of the innermost stable circular orbit.

  14. A family of well-behaved Karmarkar spacetimes describing interior of relativistic stars

    NASA Astrophysics Data System (ADS)

    Singh, Ksh. Newton; Pant, Neeraj

    2016-10-01

    We present a family of new exact solutions for relativistic anisotropic stellar objects by considering a four-dimensional spacetime embedded in a five-dimensional pseudo Euclidean space, known as Class I solutions. These solutions are well behaved in all respects, satisfy all energy conditions, and the resulting compactness parameter is also within Buchdahl limit. The well-behaved nature of the solutions for a particular star solely depends on the index n. We have discussed the solutions in detail for the neutron star XTE J1739-285 (M=1.51M_⊙, ~R=10.9 km). For this particular star, the solution is well behaved in all respects for 8 ≤ n ≤ 20. However, the solutions with n<8 possess an increasing trend of the sound speed and the solutions belonging to n>20 disobey the causality condition. Further, the well-behaved nature of the solutions for PSR J0348+0432 (2.01M_⊙, ~11 km), EXO 1785-248 (1.3M_⊙, 8.85 km), and Her X-1 (0.85M_⊙, 8.1 km) are specified by the index n with limits 24 ≤ n ≤ 54, 1.5 ≤ n ≤ 4, and 0.8 ≤ n ≤ 2.7, respectively.

  15. Effect of tellurium addition on the physical properties of germanium selenide glassy semiconductors

    NASA Astrophysics Data System (ADS)

    Sharma, Pankaj; Katyal, S. C.

    2008-10-01

    Effect of tellurium (Te) addition on the physical properties, density ( ρ), molar volume ( Vm), compactness ( δ), cohesive energy (CE), coordination number ( m), lone pair electrons ( L) and glass transition temperature ( Tg) of Ge 10Se 90-xTe x ( x=0, 10, 20, 30, 40, 50) bulk glassy alloy has been investigated. The density of the glassy alloys has been found to increase with the increasing Te content. The molar volume and compactness of the structure of the glass, determined from measured density of the glass, have been found to increase with the increase of Te content. The CE of the investigated samples has been calculated using the chemical bond approach (CBA) and is correlated with decrease in optical band gap with the increase of Te content. The glass transition temperature has been estimated using Tichy-Ticha approach and found to increase with the increase of Te content. This has been observed that the estimated glass transition temperature using Tichy-Ticha approach is not consistent with experimental results.

  16. Wear properties of a novel resin composite compared to human enamel and other restorative materials.

    PubMed

    D'Arcangelo, C; Vanini, L; Rondoni, G D; Pirani, M; Vadini, M; Gattone, M; De Angelis, F

    2014-01-01

    The purpose of this in vitro study was to compare the two-body wear resistance of human enamel, a pressable glass-ceramic (Imagine PressX), a type 3 gold alloy (Aurocast8), three resins composites currently available on the market (Enamel plus HRi, Filtek Supreme XTE, Ceram.X duo), and one recently introduced resin composite (Enamel plus HRi-Function). Resin composites were tested after simple light curing and after a further heat polymerization cycle. Ten cylindrical specimens (7 mm in diameter) were manufactured with each dental material according to standard laboratory procedures. Ten flat enamel specimens were obtained from freshly extracted human molars and included in the control group. All samples were subjected to a two-body wear test in a dual-axis chewing simulator over up to 120,000 loading cycles, against yttria stabilized tetragonal zirconia polycrystal cusps. Wear resistance was analyzed by measuring the vertical substance loss (mm) and the volume loss (mm(3)). Antagonist wear (mm) was also recorded. Data were statistically analyzed using one-way analysis of variance (ANOVA) (wear depth and volume loss) and Kruskal-Wallis one-way ANOVA on ranks (antagonist wear). Heat-cured HRi function and Aurocast8 showed similar mean values for wear depth and volumetric loss, and their results did not statistically differ in comparison with the human enamel.

  17. Development of Novel Two-dimensional Layers, Alloys and Heterostructures

    NASA Astrophysics Data System (ADS)

    Liu, Zheng

    2015-03-01

    The one-atom-think graphene has fantastic properties and attracted tremendous interests in these years, which opens a window towards various two-dimensional (2D) atomic layers. However, making large-size and high-quality 2D layers is still a great challenge. Using chemical vapor deposition (CVD) method, we have successfully synthesized a wide varieties of highly crystalline and large scale 2D atomic layers, including h-BN, metal dichalcogenides e.g. MoS2, WS2, CdS, GaSe and MoSe2 which belong to the family of binary 2D materials. Ternary 2D alloys including BCN and MoS2xSe2 (1 - x) are also prepared and characterized. In addition, synthesis of 2D heterostructures such as vertical and lateral graphene/h-BN, vertical and lateral TMDs are also demonstrated. Complementary to CVD grown 2D layers, 2D single-crystal (bulk) such as Phosphorene (P), WTe2, SnSe2, PtS2, PtSe2, PdSe2, WSe2xTe2 (1 - x), Ta2NiS5andTa2NiSe5 are also prepared by solid reactions. There work provide a better understanding of the atomic layered materials in terms of the synthesis, atomic structure, alloying and their physical properties. Potential applications of these 2D layers e.g. optoelectronic devices, energy device and smart coating have been explored.

  18. Electromagnetic Spindown of a Transient Accreting Millisecond Pulsar During Quiescence

    NASA Astrophysics Data System (ADS)

    Melatos, A.; Mastrano, A.

    2016-02-01

    The measured spindown rates in quiescence of the transient accreting millisecond pulsars IGR J00291+5934, XTE J1751-305, SAX J1808.4-3658, and Swift J1756.9-2508 have been used to estimate the magnetic moments of these objects assuming standard magnetic dipole braking. It is shown that this approach leads to an overestimate if the amount of residual accretion is enough to distort the magnetosphere away from a force-free configuration through magnetospheric mass loading or crushing, so that the lever arm of the braking torque migrates inside the light cylinder. We derive an alternative spindown formula and calculate the residual accretion rates where the formula is applicable. As a demonstration we apply the alternative spindown formula to produce updated magnetic moment estimates for the four objects above. We note that based on current uncertain observations of quiescent accretion rates, magnetospheric mass loading and crushing are neither firmly indicated nor ruled out in these four objects. Because quiescent accretion rates are not measured directly (only upper limits are placed), without more data it is impossible to be confident about whether the thresholds for magnetospheric mass loading or crushing are reached or not.

  19. The Swift/BAT Hard X-ray Survey

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

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

  20. Peculiar objects towards 3FGL J0133.3+5930: an eclipsing Be star and an active galactic nucleus

    NASA Astrophysics Data System (ADS)

    Martí, Josep; Luque-Escamilla, Pedro L.; Paredes, Josep M.; Iwasawa, Kazushi; Galindo, Daniel; Ribó, Marc; Marín-Felip, Víctor

    2017-02-01

    Aims: We aim to contribute to the identification of unassociated gamma-ray sources in the galactic plane to enlarge the currently known population of gamma-ray binaries and related systems, such as radio-emitting X-ray binaries and microquasars. These objects are currently regarded as excellent test beds for the understanding of high-energy phenomena in stellar systems. Methods: Potential targets of study are selected based on cross-identification of the third Fermi Large Area Telescope catalogue with historical catalogues of luminous stars that have often been found as optical counterparts in known cases. Follow-up observations and analysis of multi-wavelength archival data are later used to seek further proofs of association beyond the simple positional agreement. Results: Current results enable us to present here the case of the Fermi source 3FGL J0133.3+5930 where two peculiar objects have been discovered inside its region of uncertainty. One of them is the star TYC 3683-985-1 (LS I +59 79) whose eclipsing binary nature is reported in this work. The other is the X-ray source Swift J0132.9+5932, which we found to be a likely low-power active galactic nucleus at z = 0.1143 ± 0.0002. If this second object is of blazar type, it could easily account for the observed gamma-ray photon flux. However, this is not confirmed at present, thus rendering the star system TYC 3683-985-1 as a still possible alternative counterpart candidate to the Fermi source.

  1. News from Cosmic Gamma-ray Line Observations

    NASA Astrophysics Data System (ADS)

    Diehl, Roland

    The measurement of gamma rays at MeV energies from cosmic radioactivities is one of the key tools for nuclear astrophysics, in its study of nuclear reactions and how they shape objects such as massive stars and supernova explosions. Additionally, the unique gamma-ray signature from the annihilation of positrons falls into this same astronomical window, and positrons are often produced from radioactive beta decays. Nuclear gamma-ray telescopes face instrumental challenges from penetrating gamma rays and cosmic-ray induced backgrounds. But the astrophysical benefits of such efforts are underlined by the discoveries of nuclear gamma rays from the brightest of the expected sources. In recent years, both thermonuclear and core-collapse supernova radioactivity gamma rays have been measured in spectral detail, and complement conventional supernova observations with measurements of origins in deep supernova interiors, from the decay of 56Ni, 56Co, and 44Ti . The diffuse afterglow in gamma rays of radioactivity from massive-star nucleosynthesis is analysed on the large (galactic) scale, with findings important for recycling of matter between successive stellar generations: From 26Al gamma-ray line spectroscopy, interstellar cavities and superbubbles have been recognised in their importance for ejecta transport and recycling. Diffuse galactic emissions from radioactivity and positron-annihilation γ rays should be connected to nucleosynthesis sources: Recently new light has been shed on this connection, among others though different measurements of radioactive 60Fe, and through spectroscopy of positron annihilation gamma rays from a flaring microquasar and from different parts of our Galaxy.

  2. A Giant Radio Flare from Cygnus X-3 with Associated Gamma-Ray Emission

    NASA Technical Reports Server (NTRS)

    Corbel, S.; Dubus, G.; Tomsick, J. A.; Szostek, A.; Corbet, R. H. D.; Miller-Jones, J. C. A.; Richards, J. L.; Pooley, G.; Trushkin, S.; Dubois, R.; Hill, A. B.; Kerr, M.; Max-Moerbeck, W.; Readhead, A. C. S.; Bodaghee, A.; Tudose, V.; Parent, D.; Wilms, J.; Pottschmidt, K.

    2012-01-01

    With frequent flaring activity of its relativistic jets, Cygnus X-3 (Cyg X-3) is one of the most active microquasars and is the only Galactic black hole candidate with confirmed high energy gamma-ray emission, thanks to detections by Fermi/LAT and AGILE. In 2011, Cyg X-3 was observed to transit to a soft X-ray state, which is known to be associated with high-energy gamma-ray emission. We present the results of a multiwavelength campaign covering a quenched state, when radio emission from Cyg X-3 is at its weakest and the X-ray spectrum is very soft. A giant (approx 20 Jy) optically thin radio flare marks the end of the quenched state, accompanied by rising non-thermal hard X-rays. Fermi/LAT observations (E greater than or equal 100 MeV) reveal renewed gamma-ray activity associated with this giant radio flare, suggesting a common origin for all non-thermal components. In addition, current observations unambiguously show that the gamma-ray emission is not exclusively related to the rare giant radio flares. A 3-week period of gamma-ray emission is also detected when Cyg X-3 was weakly flaring in radio, right before transition to the radio quenched state. No gamma rays are observed during the one-month long quenched state, when the radio flux is weakest. Our results suggest transitions into and out of the ultrasoft X-ray (radio quenched) state trigger gamma-ray emission, implying a connection to the accretion process, and also that the gamma-ray activity is related to the level of radio flux (and possibly shock formation), strengthening the connection to the relativistic jets.

  3. RADIATION PRESSURE AND MASS EJECTION IN {rho}-LIKE STATES OF GRS 1915+105

    SciTech Connect

    Neilsen, Joseph; Remillard, Ronald A.; Lee, Julia C.

    2012-05-01

    We present a unifying scenario to address the physical origin of the diversity of X-ray light curves within the {rho} variability class of the microquasar GRS 1915+105. This 'heartbeat' state is characterized by a bright flare that recurs every {approx}50-100 s, but the profile and duration of the flares vary significantly from observation to observation. Based on a comprehensive, phase-resolved study of heartbeats in the Rossi X-ray Timing Explorer archive, we demonstrate that very different X-ray light curves do not require origins in different accretion processes. Indeed, our detailed comparison of the phase-resolved spectra of a double-peaked oscillation and a single-peaked oscillation shows that different cycles can have basically similar X-ray spectral evolution. We argue that all heartbeat oscillations can be understood as the result of a combination of a thermal-viscous radiation pressure instability, a local Eddington limit in the disk, and a sudden, radiation-pressure-driven evaporation or ejection event in the inner accretion disk. This ejection appears to be a universal, fundamental part of the {rho} state, and is largely responsible for a hard X-ray pulse seen in the light curve of all cycles. We suggest that the detailed shape of oscillations in the mass accretion rate through the disk is responsible for the phenomenological differences between different {rho}-type light curves, and we discuss how future time-dependent simulations of disk instabilities may provide new insights into the role of radiation pressure in the accretion flow.

  4. The Mysterious Galactic Center Radio Source N3

    NASA Astrophysics Data System (ADS)

    Ludovici, Dominic; Lang, Cornelia C.; Morris, Mark; Mutel, Robert Lucien; Mills, Elisabeth A. C.; Toomey, James E.; Ott, Juergen

    2017-01-01

    Here we report on multi-wavelength radio observations of the mysterious point source "N3" that appears to be located in the vicinity of the Galactic Center. VLA observations between 2 and 50 GHz reveal that N3 is a compact and bright non-thermal source (56 mJy at 10 GHz) which is superimposed upon the non-thermal radio filaments (NTFs) of the Radio Arc. Our highest frequency observations place a strict upper limit of 65x28 milli-arcseconds on the size of this source. We compare our observations to those of Yusef-Zadeh (1987) and Lang (1997) and conclude that N3 is variable over long time scales. Additionally, we present the detection of a compact molecular cloud located adjacent to N3 in projection. CH3CN, CH3OH, CS, HC3N, HNCO, SiO, SO, and NH3 are detected in the cloud and most transitions have FWHM line widths of ~20 km s-1. The rotational temperature determined from the metastable NH3 transitions ranges from 79 K to 183 K depending on the transitions used and the location in the cloud. We present evidence that this molecular cloud is interacting with N3. After exploring the relationship between the NTFs, molecular cloud, and N3, we conclude that N3 likely lies within the Galactic Center. We are able to rule out many possible physical counterparts, including an active star, HII region, young supernova, AGN, and micro-quasar. To further constrain the nature of N3, we also discuss new extremely high resolution observations of N3 taken with the VLBA, and what these observations reveal about the true nature of this mysterious source.

  5. Canadian Led X-ray Polarimeter Mission CXP

    NASA Technical Reports Server (NTRS)

    Kaspi, V.; Hanna, D.; Weisskopf, M.; Ramsey, B.; Ragan, K.; Vachon, B.; Elsner, R.; Heyl, J.; Pavlov, G.; Cumming, A.; Sutton, M.; Rowlands, N.

    2006-01-01

    We propose a Canadian-led X-ray Polarimetry Mission (CXP), to include a scattering X-ray Polarimeter and sensitive All-Sky X-ray Monitor (ASXM). Polarimetry would provide a new observational window on black holes, neutron stars, accretion disks and jets, and the ASXM would offer sensitive monitoring of the volatile X-ray sky. The envisioned polarimeter consists of a hollow scattering beryllium cone surrounded by an annular proportional counter, in a simple and elegant design that is reliable and low-risk. It would be sensitive in the 6-30 keV band to approx. 3% polarization in approx. 30 Galactic sources and 2 AGN in a baseline 1-yr mission, and have sensitivity greater than 10 times that of the previous X-ray polarimeter flown (NASA's OSO-8, 1975-78) for most sources. This X-ray polarimeter would tackle questions like, Do black holes spin?, How do pulsars pulse?, What is the geometry of the magnetic field in accreting neutron stars? Where and how are jets produced in microquasars and AGN?, What are the geometries of many of the most famous accretion-disk systems in the sky? This will be done using a novel and until-now unexploited technique that will greatly broaden the available observational phase space of compact objects by adding to timing and spectroscopy observations of polarization fraction and position angle as a function of energy. The All-Sky X-ray Monitor would scan for transients, both as potential targets for the polarimeter but also as a service to the worldwide astronomical community. The entire CXP mission could be flown for $40- 60M CDN, according to estimates by ComDev International, and could be built entirely in Canada. It would fall well within the CSA's SmallSat envelope and would empower the growing and dynamic Canadian High-Energy Astrophysics community with world leadership in a potentially high impact niche area.

  6. Prospects for Fermi Particle Acceleration at Coronal Magnetic Reconnection Sites

    NASA Astrophysics Data System (ADS)

    Provornikova, E.; Laming, J. M.; Lukin, V.

    2015-12-01

    The mechanism of first order Fermi acceleration of particles interacting with the converging magnetized flows at a reconnection site was introduced recently in an attempt to predict the energy distribution of particles resulting from violent reconnection in galactic microquasars. More careful consideration of this mechanism showed that the spectral index of accelerated particles is related to the total plasma compression within a reconnection region, similar to that in the formulation for diffusive shock acceleration. In the solar context, reconnection regions producing strong compression could be the source of suprathermal "seed particles". A hard spectrum of such suprathermal particles is believed to be necessary to initiate the particle acceleration process at low Mach number coronal mass ejection shocks close to the Sun where the gradual solar energetic particle events originate. As a first step to investigate the efficiency of Fermi acceleration, we explore the degree of plasma compression that can be achieved at reconnection sites in the solar corona. This work presents a set of 2D two-temperature resistive MHD simulations of the dynamics of several magnetic configurations within a range of lower corona plasma parameters. Energy transport processes in the MHD model include anisotropic thermal conduction for electrons and ions and radiative cooling. Magnetic configurations considered are a Harris current sheet, a force-free current sheet, a flux rope sitting above an arcade of magnetic loops, and two merging flux ropes. We demonstrate that only for some magnetic topologies, corresponding in particular to 3D magnetic nulls, the compression ratio, sufficient for first order Fermi acceleration in the reconnection region, can be achieved. These represent the potential sites in the solar corona where a hard seed particle energetic spectrum could be produced.

  7. A Multiwavelength Study of Cygnus X-1: The First Mid-infrared Spectroscopic Detection of Compact Jets

    NASA Astrophysics Data System (ADS)

    Rahoui, Farid; Lee, Julia C.; Heinz, Sebastian; Hines, Dean C.; Pottschmidt, Katja; Wilms, Jörn; Grinberg, Victoria

    2011-07-01

    We report on a Spitzer/InfraRed Spectrograph (mid-infrared), RXTE/PCA+HEXTE (X-ray), and Ryle (radio) simultaneous multiwavelength study of the microquasar Cygnus X-1, which aimed at an investigation of the origin of its mid-infrared emission. Compact jets were present in two out of three observations, and we show that they strongly contribute to the mid-infrared continuum. During the first observation, we detect the spectral break—where the transition from the optically thick to the optically thin regime takes place—at about 2.9 × 1013 Hz. We then show that the jet's optically thin synchrotron emission accounts for Cygnus X-1's emission beyond 400 keV, although it cannot alone explain its 3-200 keV continuum. A compact jet was also present during the second observation, but we do not detect the break, since it has likely shifted to higher frequencies. In contrast, the compact jet was absent during the last observation, and we show that the 5-30 μm mid-infrared continuum of Cygnus X-1 stems from the blue supergiant companion star HD 226868. Indeed, the emission can then be understood as the combination of the photospheric Rayleigh-Jeans tail and the bremsstrahlung from the expanding stellar wind. Moreover, the stellar wind is found to be clumpy, with a filling factor f ∞ ≈ 0.09-0.10. Its bremsstrahlung emission is likely anti-correlated to the soft X-ray emission, suggesting an anti-correlation between the mass-loss and mass-accretion rates. Nevertheless, we do not detect any mid-infrared spectroscopic evidence of interaction between the jets and Cygnus X-1's environment and/or the companion star's stellar wind.

  8. The Cosmic Battery Revisited

    NASA Technical Reports Server (NTRS)

    Contopoulos, Ioannis; Kazanas, Demosthenes; Christodoulos, Dimistris M.

    2007-01-01

    We reinvestigate the generation and accumulation of magnetic flux in optically thin accretion flows around active gravitating objects. The source of the magnetic field is the azimuthal electric current associated with the Poynting-Robertson drag on the electrons of the accreting plasma. This current generates magnetic field loops which open up because of the differential rotation of the flow. We show through simple numerical simulations that what regulates the generation and accumulation of magnetic flux near the center is the value of the plasma conductivity. Although the conductivity is usually considered to be effectively infinite for the fully ionized plasmas expected near the inner edge of accretion disks, the turbulence of those plasmas may actually render them much less conducting due to the presence of anomalous resistivity. We have discovered that if the resistivity is sufficiently high throughout the turbulent disk while it is suppressed interior to its inner edge, an interesting steady-state process is established: accretion carries and accumulates magnetic flux of one polarity inside the inner edge of the disk, whereas magnetic diffusion releases magnetic flux of the opposite polarity to large distances. In this scenario, magnetic flux of one polarity grows and accumulates at a steady rate in the region inside the inner edge and up to the point of equipartition when it becomes dynamically important. We argue that this inward growth and outward expulsion of oppositely-directed magnetic fields that we propose may account for the approx. 30 min cyclic variability observed in the galactic microquasar GRS1915+105.

  9. PERIODIC STRUCTURE IN THE MEGAPARSEC-SCALE JET OF PKS 0637-752

    SciTech Connect

    Godfrey, L. E. H.; Ekers, R.; Lovell, J. E. J.; Burke-Spolaor, S.; Bicknell, G. V.; Jauncey, D. L.; Birkinshaw, M.; Worrall, D. M.; Schwartz, D. A.; Marshall, H. L.; Gelbord, J.; Perlman, E. S.; Georganopoulos, M.

    2012-10-20

    We present 18 GHz Australia Telescope Compact Array imaging of the megaparsec-scale quasar jet PKS 0637-752 with angular resolution {approx}0.''58. We draw attention to a spectacular train of quasi-periodic knots along the inner 11'' of the jet, with average separation {approx}1.1 arcsec (7.6 kpc projected). We consider two classes of model to explain the periodic knots: those that involve a static pattern through which the jet plasma travels (e.g., stationary shocks) and those that involve modulation of the jet engine. Interpreting the knots as re-confinement shocks implies the jet kinetic power Q{sub jet} {approx} 10{sup 46} erg s{sup -1}, but the constant knot separation along the jet is not expected in a realistic external density profile. For models involving modulation of the jet engine, we find that the required modulation period is 2 Multiplication-Sign 10{sup 3} yr < {tau} < 3 Multiplication-Sign 10{sup 5} yr. The lower end of this range is applicable if the jet remains highly relativistic on kiloparsec scales, as implied by the IC/CMB model of jet X-ray emission. We suggest that the periodic jet structure in PKS 0637-752 may be analogous to the quasi-periodic jet modulation seen in the microquasar GRS 1915+105, believed to result from limit cycle behavior in an unstable accretion disk. If variations in the accretion rate are driven by a binary black hole, the predicted orbital radius is 0.7 pc {approx}< a {approx}< 30 pc, which corresponds to a maximum angular separation of {approx}0.1-5 mas.

  10. Multi-colour optical photometry of V404 Cygni in outburst

    NASA Astrophysics Data System (ADS)

    Martí, Josep; Luque-Escamilla, Pedro L.; García-Hernández, María T.

    2016-02-01

    Context. This observational paper has been prepared in the context of the large multi-wavelength effort by many observers with the aim of following up the transient flaring event of V404 Cygni that took place for several weeks in 2015 June. Aims: Our main original aim was to contribute to the study of this transient source by acquiring broad-band photometric observations during its most active flaring phases. Nevertheless, after a detailed analysis of the data, several interesting results were obtained that encouraged a dedicated publication. Methods: The methodology used was based on broad-band differential CCD photometry. This outburst of V404 Cygni rendered the source a very bright target easily within reach of small educational telescopes. Therefore, the 41 cm telescope available at the Astronomical Observatory of the University of Jaén was used in this work. Results: We detected variability at different time scales, both in amplitude and colour. Individual optical flares appear every half hour on average during our 3 h long observation, although large-amplitude (~1 mag) variations are also observed to occur on intervals as short as 10 min. Also, colour variations appear to be highly correlated in a colour-colour diagram. Another remarkable finding is the detection of time lag, from about one to a fraction of a minute between light curves in different filters (VRcIc). Conclusions: The observed behaviour is tentatively interpreted in an scenario based on the ejection of non-thermal emitting, relativistic plasmons, with their synchrotron spectra extending up to optical wavelengths. This would render some of the V404 Cygni flares very similar to those of the well-know microquasar GRS 1915+105

  11. New insights from cosmic gamma rays

    NASA Astrophysics Data System (ADS)

    Roland, Diehl

    2016-04-01

    The measurement of gamma rays from cosmic sources at ~MeV energies is one of the key tools for nuclear astrophysics, in its study of nuclear reactions and their impacts on objects and phenomena throughout the universe. Gamma rays trace nuclear processes most directly, as they originate from nuclear transitions following radioactive decays or high-energy collisions with excitation of nuclei. Additionally, the unique gamma-ray signature from the annihilation of positrons falls into this astronomical window and is discussed here: Cosmic positrons are often produced from β-decays, thus also of nuclear physics origins. The nuclear reactions leading to radioactive isotopes occur inside stars and stellar explosions, which therefore constitute the main objects of such studies. In recent years, both thermonuclear and core-collapse supernova radioactivities have been measured though 56Ni, 56Co, and 44Ti lines, and a beginning has thus been made to complement conventional supernova observations with such measurements of the prime energy sources of supernova light created in their deep interiors. The diffuse radioactive afterglow of massive-star nucleosynthesis in gamma rays is now being exploited towards astrophysical studies on how massive stars feed back their energy and ejecta into interstellar gas, as part of the cosmic cycle of matter through generations of stars enriching the interstellar gas and stars with metals. Large interstellar cavities and superbubbles have been recognised to be the dominating structures where new massive-star ejecta are injected, from 26Al gamma-ray spectroscopy. Also, constraints on the complex interiors of stars derive from the ratio of 60Fe/26Al gamma rays. Finally, the puzzling bulge-dominated intensity distribution of positron annihilation gamma rays is measured in greater detail, but still not understood; a recent microquasar flare provided evidence that such objects may be prime sources for positrons in interstellar space, rather than

  12. The 511 keV emission from positron annihilation in the Galaxy

    SciTech Connect

    Prantzos, N.; Boehm, C.; Bykov, A. M.; Diehl, R.; Ferriere, K.; Guessoum, N.; Jean, P.; Knoedlseder, J.; Marcowith, A.; Moskalenko, I. V.; Strong, A.; Weidenspointner, G.

    2011-07-01

    The first {gamma}-ray line originating from outside the Solar System that was ever detected is the 511 keV emission from positron annihilation in the Galaxy. Despite 30 years of intense theoretical and observational investigation, the main sources of positrons have not been identified up to now. Observations in the 1990s with OSSE/CGRO (Oriented Scintillation Spectrometer Experiment on GRO satellite/Compton Gamma Ray Observatory) showed that the emission is strongly concentrated toward the Galactic bulge. In the 2000s, the spectrometer SPI aboard the European Space Agency's (ESA) International Gamma Ray Astrophysics Laboratory (INTEGRAL) allowed scientists to measure that emission across the entire Galaxy, revealing that the bulge-to-disk luminosity ratio is larger than observed at any other wavelength. This mapping prompted a number of novel explanations, including rather ''exotic'' ones (e.g., dark matter annihilation). However, conventional astrophysical sources, such as type Ia supernovae, microquasars, or x-ray binaries, are still plausible candidates for a large fraction of the observed total 511 keV emission of the bulge. A closer study of the subject reveals new layers of complexity, since positrons may propagate far away from their production sites, making it difficult to infer the underlying source distribution from the observed map of 511 keV emission. However, in contrast to the rather well-understood propagation of high-energy (>GeV) particles of Galactic cosmic rays, understanding the propagation of low-energy ({approx}MeV) positrons in the turbulent, magnetized interstellar medium still remains a formidable challenge. The spectral and imaging properties of the observed 511 keV emission are reviewed and candidate positron sources and models of positron propagation in the Galaxy are critically discussed.

  13. The youngest known X-ray binary: Circinus X-1 and its natal supernova remnant

    SciTech Connect

    Heinz, S.; Sell, P.; Fender, R. P.; Jonker, P. G.; Brandt, W. N.; Calvelo-Santos, D. E.; Tzioumis, A. K.; Nowak, M. A.; Schulz, N. S.; Wijnands, R.; Van der Klis, M.

    2013-12-20

    Because supernova remnants are short-lived, studies of neutron star X-ray binaries within supernova remnants probe the earliest stages in the life of accreting neutron stars. However, such objects are exceedingly rare: none were known to exist in our Galaxy. We report the discovery of the natal supernova remnant of the accreting neutron star Circinus X-1, which places an upper limit of t < 4600 yr on its age, making it the youngest known X-ray binary and a unique tool to study accretion, neutron star evolution, and core-collapse supernovae. This discovery is based on a deep 2009 Chandra X-ray observation and new radio observations of Circinus X-1. Circinus X-1 produces type I X-ray bursts on the surface of the neutron star, indicating that the magnetic field of the neutron star is small. Thus, the young age implies either that neutron stars can be born with low magnetic fields or that they can rapidly become de-magnetized by accretion. Circinus X-1 is a microquasar, creating relativistic jets that were thought to power the arcminute-scale radio nebula surrounding the source. Instead, this nebula can now be attributed to non-thermal synchrotron emission from the forward shock of the supernova remnant. The young age is consistent with the observed rapid orbital evolution and the highly eccentric orbit of the system and offers the chance to test the physics of post-supernova orbital evolution in X-ray binaries in detail for the first time.

  14. A MULTIWAVELENGTH STUDY OF CYGNUS X-1: THE FIRST MID-INFRARED SPECTROSCOPIC DETECTION OF COMPACT JETS

    SciTech Connect

    Rahoui, Farid; Lee, Julia C.; Heinz, Sebastian; Hines, Dean C.; Pottschmidt, Katja; Wilms, Joern; Grinberg, Victoria E-mail: jclee@cfa.harvard.edu E-mail: hines@stsci.edu E-mail: joern.wilms@sternwarte.uni-erlangen.de

    2011-07-20

    We report on a Spitzer/InfraRed Spectrograph (mid-infrared), RXTE/PCA+HEXTE (X-ray), and Ryle (radio) simultaneous multiwavelength study of the microquasar Cygnus X-1, which aimed at an investigation of the origin of its mid-infrared emission. Compact jets were present in two out of three observations, and we show that they strongly contribute to the mid-infrared continuum. During the first observation, we detect the spectral break-where the transition from the optically thick to the optically thin regime takes place-at about 2.9 x 10{sup 13} Hz. We then show that the jet's optically thin synchrotron emission accounts for Cygnus X-1's emission beyond 400 keV, although it cannot alone explain its 3-200 keV continuum. A compact jet was also present during the second observation, but we do not detect the break, since it has likely shifted to higher frequencies. In contrast, the compact jet was absent during the last observation, and we show that the 5-30 {mu}m mid-infrared continuum of Cygnus X-1 stems from the blue supergiant companion star HD 226868. Indeed, the emission can then be understood as the combination of the photospheric Rayleigh-Jeans tail and the bremsstrahlung from the expanding stellar wind. Moreover, the stellar wind is found to be clumpy, with a filling factor f{sub {infinity}} {approx} 0.09-0.10. Its bremsstrahlung emission is likely anti-correlated to the soft X-ray emission, suggesting an anti-correlation between the mass-loss and mass-accretion rates. Nevertheless, we do not detect any mid-infrared spectroscopic evidence of interaction between the jets and Cygnus X-1's environment and/or the companion star's stellar wind.

  15. The Youngest Known X-Ray Binary: Circinus X-1 and Its Natal Supernova Remnant

    NASA Astrophysics Data System (ADS)

    Heinz, S.; Sell, P.; Fender, R. P.; Jonker, P. G.; Brandt, W. N.; Calvelo-Santos, D. E.; Tzioumis, A. K.; Nowak, M. A.; Schulz, N. S.; Wijnands, R.; van der Klis, M.

    2013-12-01

    Because supernova remnants are short-lived, studies of neutron star X-ray binaries within supernova remnants probe the earliest stages in the life of accreting neutron stars. However, such objects are exceedingly rare: none were known to exist in our Galaxy. We report the discovery of the natal supernova remnant of the accreting neutron star Circinus X-1, which places an upper limit of t < 4600 yr on its age, making it the youngest known X-ray binary and a unique tool to study accretion, neutron star evolution, and core-collapse supernovae. This discovery is based on a deep 2009 Chandra X-ray observation and new radio observations of Circinus X-1. Circinus X-1 produces type I X-ray bursts on the surface of the neutron star, indicating that the magnetic field of the neutron star is small. Thus, the young age implies either that neutron stars can be born with low magnetic fields or that they can rapidly become de-magnetized by accretion. Circinus X-1 is a microquasar, creating relativistic jets that were thought to power the arcminute-scale radio nebula surrounding the source. Instead, this nebula can now be attributed to non-thermal synchrotron emission from the forward shock of the supernova remnant. The young age is consistent with the observed rapid orbital evolution and the highly eccentric orbit of the system and offers the chance to test the physics of post-supernova orbital evolution in X-ray binaries in detail for the first time.

  16. Deep and Monitoring Observations of the Black Hole Candidates 1E 1740.7-2942 and GRS 1758-258

    NASA Technical Reports Server (NTRS)

    Heindl, William A.

    1998-01-01

    The purpose of this effort was to obtain detailed information on the long term variability of the power spectra and energy spectra of the two Black Hole Candidates (BHCs) and so-called "micro-quasars", 1E 1740.7-2942 and GRS 1758-258. Observations with the pointed instruments on the Rossi X-ray Timing Explorer (RXTE) were carried out on a weekly basis for an entire year, in order to observe the extent to which these sources changed on long timescales. The observations also served as a trigger for longer observations carried out under a sister proposal "Target of Opportunity Observations of the Black Hole Candidates 1E 1740.7-2942 and GRS 1758-258". The work done at UCSD by W. Heindl consisted first of monitoring the data from the High Energy X-ray Timing Experiment (HEXTE) to determine when the sources were bright enough to trigger our Target of Opportunity observations. He was then responsible for the reduction and interpretation of the HEXTE data and for contributing to the publication of results of this work. Historically, these objects have been highly variable on long timescales. Observations between 1988 and 1995 found that they tend to spend periods of several months in high and low flux states which differ in luminosity by more than an order of magnitude. In more than 2 years of RXTE observations to date, we have found variability only on the level of tens of percent. Both sources have remained near their historical maximum luminosities during this time. This is a significant change from previous behavior, and indicates that their accretion rates have stabilized in recent years. In addition, their observed spectra have been quite stable.

  17. An HST proper-motion study of the optical jet in 3C 264: Direct Evidence for the Internal Shock Model

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    Some of the most energetic phenomena in the Universe involve highly relativistic flows, in which particles are accelerated up to TeV energies. In the case of relativistic jets from Active Galactic Nuclei (AGN), these flows can carry enough energy to significantly influence both galactic and cluster evolution. While the exact physical mechanism that accelerates the radiating particles within the jet is not known, a widely adopted framework is the internal shock model, invoked to explain high-energy, non-thermal radiation from objects as diverse as microquasars, gamma-ray bursts, and relativistic jets in AGN. This model posits an unsteady relativistic flow that gives rise to components in the jet with different speeds. Faster components catch up to and collide with slower ones, leading to internal shocks. Despite its wide popularity as a theoretical framework, however, no occurance of this mechanism has ever been directly observed. We will present evidence of such a collision in a relativistic jet observed with the Hubble Space Telescope (HST) in the nearby radio galaxy 3C 264 (Meyer et al., 2015, Nature). Using images taken over 20 years, we show that a bright ‘knot’ in the jet is moving at an apparent speed of 7.0 +/- 0.8c and is in the incipient stages of a collision with a slow-moving knot (1.8 +/- 0.5c) just downstream. In the most recent epoch of imaging, we see evidence of brightening of the two knots as they commence their kiloparsec-scale collision. This is the behaviour expected in the internal shock scenario and the first direct evidence that internal shocks are a valid description of particle acceleration in relativistic jets.

  18. Very High Energy Observations of the Binaries V 404 Cyg and 4U 0115+634 during Giant X-Ray Outbursts

    NASA Astrophysics Data System (ADS)

    Archer, A.; Benbow, W.; Bird, R.; Bourbeau, E.; Buchovecky, M.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cerruti, M.; Connolly, M. P.; Cui, W.; Errando, M.; Falcone, A.; Feng, Q.; Fernandez-Alonso, M.; Finley, J. P.; Fleischhack, H.; Flinders, A.; Fortson, L.; Furniss, A.; Griffin, S.; Grube, J.; Hütten, M.; Hanna, D.; Hervet, O.; Holder, J.; Humensky, T. B.; Johnson, C. A.; Kaaret, P.; Kar, P.; Kelley-Hoskins, N.; Kertzman, M.; Kieda, D.; Krause, M.; Kumar, S.; Lang, M. J.; Lin, T. T. Y.; Maier, G.; Moriarty, P.; Mukherjee, R.; Nieto, D.; O'Brien, S.; Ong, R. A.; Park, N.; Pohl, M.; Popkow, A.; Pueschel, E.; Quinn, J.; Ragan, K.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Rousselle, J.; Rovero, A. C.; Sadeh, I.; Schlenstedt, S.; Sembroski, G. H.; Shahinyan, K.; Staszak, D.; Telezhinsky, I.; Tyler, J.; Wakely, S. P.; Wilcox, P.; Wilhelm, A.; Williams, D. A.

    2016-11-01

    Transient X-ray binaries produce major outbursts in which the X-ray flux can increase over the quiescent level by factors as large as 107. The low-mass X-ray binary V 404 Cyg and the high-mass system 4U 0115+634 underwent such major outbursts in 2015 June and October, respectively. We present here observations at energies above hundreds of GeV with the VERITAS observatory taken during some of the brightest X-ray activity ever observed from these systems. No gamma-ray emission has been detected by VERITAS in 2.5 hr of observations of the microquasar V 404 Cyg from 2015, June 20-21. The upper flux limits derived from these observations on the gamma-ray flux above 200 GeV of F \\lt 4.4× {10}-12 cm-2 s-1 correspond to a tiny fraction (about 10-6) of the Eddington luminosity of the system, in stark contrast to that seen in the X-ray band. No gamma-rays have been detected during observations of 4U 0115+634 in the period of major X-ray activity in 2015 October. The flux upper limit derived from our observations is F \\lt 2.1× {10}-12 cm-2 s-1 for gamma-rays above 300 GeV, setting an upper limit on the ratio of gamma-ray to X-ray luminosity of less than 4%.

  19. A timing view of the heartbeat state of GRS 1915+105

    NASA Astrophysics Data System (ADS)

    Yan, Shu-Ping; Ji, Li; Méndez, Mariano; Liu, Si-Ming; Wang, Na; Li, Xiang-Dong; Ge, Ming-Yu; Liao, Jin-Yuan; Niu, Shu; Qu, Jin-Lu; Ding, Guo-Qiang; Liu, Qing-Zhong; Sun, Wei

    2017-02-01

    We present a timing analysis of two Rossi X-ray Timing Explorer observations of the microquasar GRS 1915+105 during the heartbeat state. The phase-frequency-power maps show that the intermediate-frequency aperiodic X-ray variability weakens as the source softens in the slow rise phase, and when the quasi-periodic oscillation disappears in the rise phase of the pulse of the double-peaked class, its sub-harmonic is still present with a hard phase lag. In the slow rise phase, the energy-frequency-power maps show that most of the aperiodic variability is produced in the corona, and may also induce the aperiodic variability observed at low energies from an accretion disc, which is further supported by the soft phase lag especially in the intermediate-frequency range (with a time delay up to 20 ms). In the rise phase of the pulse, the low-frequency aperiodic variability is enhanced significantly and there is a prominent hard lag (with a time delay up to 50 ms), indicating that the variability is induced by extension of the disc towards small radii as implied by the increase in flux and propagates into the corona. However, during the hard pulse of the double-peaked class, the variability shows no significant lag, which may be attributed to an optically thick corona. These timing results are generally consistent with the spectral results presented by Neilsen, Remillard & Lee which indicated that the slow rise phase corresponds to a local Eddington limit and the rise phase of the pulse corresponds to a radiation pressure instability in the disc.

  20. Properties of unique hard X-ray dips observed from GRS 1915+105 and IGR J17091–3624 and their implications

    SciTech Connect

    Pahari, Mayukh; Yadav, J. S.; Bhattacharyya, Sudip; Rodriguez, Jérôme; Pandey, S. K.

    2013-11-20

    We report a comprehensive study on spectral and timing properties of hard X-ray dips uniquely observed in some so-called variability classes of the micro-quasars GRS 1915+105 and IGR J17091–3624. These dips are characterized by a sudden decline in the 2.0-60.0 keV X-ray intensity by a factor of 4-12 simultaneous with the increase in hardness ratio by a factor of 2-4. Using 31 observations of GRS 1915+105 with RXTE/PCA, we show that different behaviors are observed in different types of variability classes, and we find that a dichotomy is observed between classes with abrupt transitions versus those with smoother evolution. For example, both energy-lag spectra and frequency-lag spectra of hard X-ray dips in classes with abrupt transitions and shorter dip intervals show hard-lag (hard photons lag soft photons), while both lag spectra during hard dips in classes with smoother evolution and longer dip intervals show soft-lag. Both lag time-scales are of the order of 100-600 mS. We also show that timing and spectral properties of hard X-ray dips observed in light curves of IGR J17091–3624 during its 2011 outburst are consistent with the properties of the abrupt transitions in GRS 1915+105 rather than smooth evolutions. A global correlation between the X-ray intensity cycle time and hard dip time is observed for both abrupt and smooth transition which may be due to two distinct physical processes whose time-scales are eventually correlated. We discuss implications of our results in the light of some generic models.