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Sample records for microquasar xte j1550-564

  1. Evolution of relativistic jets from XTE J1550-564 and the environment of microquasars

    NASA Astrophysics Data System (ADS)

    Zhang, Shuang Nan; Hao, Jing Fang

    2008-10-01

    Two relativistic X-ray jets have been detected with the Chandra X-ray observatory in the black hole X-ray transient XTE J1550-564. We report a full analysis of the evolution of the two jets with a gamma-ray burst external shock model. A plausible scenario suggests a cavity outside the central source and the jets first travelled with constant velocity and then are slowed down by the interactions between the jets and the interstellar medium (ISM). The best fitted radius of the cavity is ~0.36 pc on the eastern side and ~0.46 pc on the western side, and the densities also show asymmetry, of ~0.015 cm-3 on the east to ~0.21 cm-3 on the west. Large scale low density region is also found in another microquasar system, H 1743-322. These results are consistent with previous suggestions that the environment of microquasars should be rather vacuous, compared to the normal Galactic environment. A generic scenario for microquasar jets is proposed, classifying the observed jets into three main categories, with different jet morphologies (and sizes) corresponding to different scales of vacuous environments surrounding them.

  2. Measuring Black-Hole Spin and Modeling the Jet Dynamics in Microquasar XTE J1550-564

    NASA Astrophysics Data System (ADS)

    Steiner, James F.; McClintock, J. E.

    2011-05-01

    The microquasar XTE J1550-564 produced the very first X-ray jets to be observed from a black-hole X-ray binary. Chandra imaging data obtained for these jets during 2000-2003 offer a near-unique opportunity to test whether the black hole's spin axis is tilted or aligned with respect to the plane of the binary orbit. To this end, we apply a kinematic relativistic blast-wave model to position measurements of the expanding jet. A comparison of the derived orientation of the jet to the optically measured binary inclination angle has important implications for the measurement of black hole spin. We present our results in the context of ongoing studies of the spins of several black holes, including XTE J1550-564.

  3. AN IMPROVED DYNAMICAL MODEL FOR THE MICROQUASAR XTE J1550-564

    SciTech Connect

    Orosz, Jerome A.; Steiner, James F.; McClintock, Jeffrey E.; Torres, Manuel A. P.; Remillard, Ronald A.; Bailyn, Charles D.; Miller, Jon M. E-mail: jsteiner@cfa.harvard.edu E-mail: mtorres@cfa.harvard.edu E-mail: charles.bailyn@yale.edu

    2011-04-01

    We present an improved dynamical model of the X-ray binary and microquasar XTE J1550-564 based on new moderate-resolution optical spectroscopy and near-infrared photometry obtained with the 6.5 m Magellan Telescopes at Las Campanas Observatory. Twelve spectra of the source were obtained using the Magellan Echellette Spectrograph between 2008 May 6 and August 4. In addition, several hundred images of the field were obtained between 2006 May and 2009 July in the J and K{sub S} filters using the PANIC camera. The agreement between the 2006/2007 and 2008 J and K{sub S} light curves is not perfect, and the differences can plausibly be attributed to a hot spot on the accretion disk during the 2006/2007 observations. By combining our new radial velocity measurements with previous measurements obtained in 2001 May at the 8.2 m Very Large Telescope and with light curves, we find an orbital period of P = 1.5420333 {+-} 0.0000024 days and a radial velocity semiamplitude of K{sub 2} = 363.14 {+-} 5.97 km s{sup -1}, which together imply an optical mass function of f(M) = 7.65 {+-} 0.38 M{sub sun}. We find that the projected rotational velocity of the secondary star is 55 {+-} 5 km s{sup -1}, which implies a very extreme mass ratio of Q {identical_to} M/M{sub 2} {approx} 30. Using a model of a Roche lobe-filling star and an azimuthally symmetric accretion disk, we fit simultaneously optical light curves from 2001, near-infrared light curves from 2008, and all of the radial velocity measurements to derive system parameters. We find an inclination of 74.{sup 0}7 {+-} 3.{sup 0}8 and component masses of M{sub 2} = 0.30 {+-} 0.07 M{sub sun} and M = 9.10 {+-} 0.61 M{sub sun} for the secondary star and black hole, respectively. We note that these results depend on the assumption that in 2008, the disk did not have a hot spot, and that the fraction of light contributed by the accretion disk did not change between the spectroscopic and photometric observations. By considering two

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. Colours of black holes: infrared flares from the hot accretion disc in XTE J1550-564

    NASA Astrophysics Data System (ADS)

    Poutanen, Juri; Veledina, Alexandra; Revnivtsev, Mikhail G.

    2014-12-01

    Outbursts of the black hole (BH) X-ray binaries are dramatic events occurring in our Galaxy approximately once a year. They are detected by the X-ray telescopes and often monitored at longer wavelengths. We analyse the X-ray and optical/infrared (OIR) light curves of the BH binary XTE J1550-564 during the 2000 outburst. By using the observed extreme colours as well as the characteristic decay time-scales of the OIR and X-ray light curves, we put strong constraints on the extinction towards the source. We accurately separate the contributions to the OIR flux of the irradiated accretion disc and a non-thermal component. We show that the OIR non-thermal component appears during the X-ray state transitions both during the rising and the decaying part of the outburst at nearly the same X-ray hardness but at luminosities differing by a factor of 3. The line marking the quenching/recovery of the non-thermal component at the X-ray hardness-flux diagram seems to coincide with the `jet line' that marks the presence of the compact radio jet. The inferred spectral shape and the evolution of the non-thermal component during the outburst, however, are not consistent with the jet origin, but are naturally explained in terms of the hybrid hot flow scenario, where non-thermal electrons emit synchrotron radiation in the OIR band. This implies a close, possibly causal connection between the presence of the hot flow and the compact jet. We find that the non-thermal component is hardening during the hard state at the decaying stage of the outburst, which indicates that the acceleration efficiency is a steep function of radius at low accretion rate.

  10. XTE J1550-564

    NASA Technical Reports Server (NTRS)

    Finger, Mark H.; Dieters, Stefan W.; Wilson, Robert B.

    1998-01-01

    A quasiperiodic oscillation (QPO) in the flux of this transient x-ray source is seen in power spectra of the BATSE 20-50-keV discriminator rates. On Sept. 9.0 UT, the QPO was centered on 271 +/- 2 mHz, and it had a FWHM of 30 +/- 5 mHz and a fractional rms of 19.2 +/- 2.5 percent. The QPO was first detected on Sept. 7.45 near 55 mHz and has been steadily increasing in frequency, reaching 350 mHz by Sept. 9.3. The QPO appears to have reached the Nyquist frequency (488 mHz) of our discriminator rates before the end of Sept. 9, and is no longer detectable in them.

  11. Ejection of the Corona at State Transitions: a Common Behavior in Microquasars?

    NASA Astrophysics Data System (ADS)

    Prat, L.; Rodriguez, J.

    2009-05-01

    The onset of most microquasar outbursts is characterized by a state transition between a Low/Hard State (LHS) and a High/Soft State (HSS). Besides drastic spectral and timing changes, this transition often shows a discrete ejection event detectable in the radio range. However, the exact nature of the ejected material and the mechanisms that give birth to these phenomena are yet to be unraveled. Recent simultaneous radio and X-ray observations on several sources point to a coronal nature of the ejected material. In the cases of GRS 1915+105, XTE J1550-564, and the 2002 outburst of GX 339-4, the flux of the Compton component decreases sharply just before an ejection is detected in the radio range. Finally, in the case of H1743-322, drastic physical changes occurred in the corona just before the state transition, compatible with the disappearance of part of this medium. Thus, the behavior of at least 4 microquasars points in the direction of an ejection of the corona at the state transition, feature that is yet to be confirmed (or infirmed) in the case of other available sources.

  12. 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.

  13. Spectrum of a jet-emitting disc: application to the microquasar XTE J1118+480

    NASA Astrophysics Data System (ADS)

    Zhang, Jian-Fu; Xie, Fu-Guo

    2013-10-01

    Under the framework of the magnetized accretion ejection structures, we analyse the energy balance properties, and study the spectral energy distributions (SEDs) of the jet-emitting disc (JED) model for black hole X-ray transients. Various radiative processes are considered, i.e. synchrotron, bremsstrahlung, and their Comptonizations, and external Comptonization of radiation from the outer thin disc. With these cooling terms taken into account, we solve the thermal equilibrium equation self-consistently and find three solutions, of which the cold and the hot solutions are stable. Subsequently, we investigate the theoretical SEDs for these two stable solutions. We find the hot JED model can naturally explain the spectra of the Galactic microquasars in their hard states. As an example, we apply this model to the case of XTE J1118+480.

  14. Microquasars

    NASA Astrophysics Data System (ADS)

    Castro-Tirado, Alberto J.; Greiner, Jochen; Paredes, Josep M.

    2001-06-01

    The study of microquasars, sources in our Galaxy displaying powerful relativistic jets, is a rapidly advancing field in astrophysics. New instrumentation on the ground (MERLIN, SCUBA, VLA, and VLT) and aboard satellites (ASCA, BSAX, ISO, IXAE and RXTE) has provided important results, and much more is expected to come from Chandra and XMM-Newton. In the future, powerful instrumentation will come online in sub-mm (ALMA) and gamma rays (INTEGRAL), extending our coverage to important regions for the study of microquasars. Energy transport via relativistic jets is one of the most important physical mechanisms taking place in compact objects, either in binary systems or in the nuclei of active galaxies. Large efforts have been devoted to proper understanding of the disk-jet connection, and even the effects of rotation or magnetic fields. Several important advances have been made recently, both from the point of view of the theoretical treatment of jets and the different new observational tests. All of them are reflected in this book, the first one devoted to the study of these enigmatic objects. Link: http://www.wkap.nl/book.htm/0-7923-6923-8

  15. VII Microquasar Workshop: Microquasars and Beyond

    NASA Astrophysics Data System (ADS)

    This workshop is the seventh of the series of conferences mainly devoted to Galactic black holes. The conference will cover all topics related to relativistic jet sources in the universe including microquasars, neutron stars, active galactic nuclei, and gamma-ray bursts. The results of the analysis of data from high energy missions (RXTE, Chandra, XMM-Newton, INTEGRAL, Swift, Suzaku, Agile) as well as from ground based observatories in the optical, infrared and radio bands will be presented. The emphasis will be on the formation and evolution of jets, and their relation to other accretion components. The broad context of the workshop will also allow researchers to present their results on the comparisons between microquasars, neutron stars, ultraluminous X-ray sources, active galactic nuclei and gamma-ray bursts. The workshop also intends to include presentations on recent missions (e.g. GLAST, ASTROSAT) and missions in preparation e.g. IXO concentrating on the prospects of black hole research with those missions. The program will be organized in sessions centered around a limited number of invited reviews, with contributed presentations and ample time for discussion. Young researchers will be encouraged to contribute.

  16. Black Hole Mass and Spin from the 2:3 Twin-peak QPOs in Microquasars

    NASA Astrophysics Data System (ADS)

    Mondal, Soumen

    2010-01-01

    In the Galactic microquasars with double peak kHz quasi-periodic oscillations (QPOs) detected in X-ray fluxes, the ratio of the twin-peak frequencies is exactly, or almost exactly 2:3. This rather strongly supports the fact that they originate a few gravitational radii away from its center due to two modes of accretion disk oscillations. Numerical investigations suggest that post-shock matter, before they settle down in a subsonic branch, execute oscillations in the neighborhood region of "shock transition". This shock may excite QPO mechanism. The radial and vertical epicyclic modes of oscillating matter exactly match with these twin-peak QPOs. In fully general relativistic transonic flows, we investigate that shocks may form very close to the horizon around highly spinning Kerr black holes and appear as extremum in the inviscid flows. The extreme shock location provides upper limit of QPOs and hence fixes "lower cutoff" of the spin. We conclude that the 2:3 ratio exactly occurs for spin parameters a >= 0.87 and almost exactly, for wide range of spin parameter, for example, XTE 1550-564, and GRO 1655-40 a>0.87, GRS 1915+105 a>0.83, XTE J1650-500 a>0.78, and H 1743-322 a>0.68. We also make an effort to measure unknown mass for XTE J1650-500(9.1 ~ 14.1 M sun) and H 1743-322(6.6 ~ 11.3 M sun).

  17. A search for new galactic microquasars

    NASA Astrophysics Data System (ADS)

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

    2002-01-01

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

  18. "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

  19. XTE J1908+094

    NASA Technical Reports Server (NTRS)

    Woods, P. M.; Kouveliotou, C.; Finger, M. H.; Gogus, E.; Swank, J.; Markwardt, C.; Strohmayer, T.; Six, N. Frank (Technical Monitor)

    2002-01-01

    Goddard Space Flight Center reports the serendipitous discovery of a new x-ray transient, XTE J1908+094, in RXTE (Rossi X-ray Timing Explorer) PCA (Proportional Counter Array) observations of the soft-gamma-ray repeater SGR 1900+14, triggered following the burst activity on Feb. 17-18 (GCN 1253). These observations failed to detect the 5.2-s SGR pulsations, pointing towards a possible new source as the origin of the high x-ray flux. An RXTE PCA scan of the region around SGR 1900+14 on Feb. 21 was consistent with emission only from known sources (and no new sources). However, the scans required SGR 1900+14 to be 20 times brighter than its quiescent flux level (GCN 1256). A Director's Discretionary Time Chandra observation on Mar. 11 showed that the SGR was quiescent and did not reveal any new source within the Chandra ACIS (Advanced CCD (charge coupled device) Imaging Spectrometer) field-of-view. A subsequent RXTE PCA scan on Mar. 17, taken in combination with the first scan, required that a new source be included in the fit. The best-fit position is R.A. 19h 08m 50s, Decl. = +9 22 deg .5 (equinox J2000.0; estimated 2 deg systematic error radius), or approximately 24 deg away from the SGR source. The source spectrum (2-30 kev) can be best fit with a power-law function including photoelectric absorption (column density N_h = 2.3 x 10(exp 22), photon index = 1.55). Iron line emission is present, but may be due to the Galactic ridge. Between Feb. 19 and Mar. 17, the source flux (2-10 keV) has risen from 26 to 64 mCrab. The power spectrum is flat between 1 mHz and 0.1 Hz, falling approximately as 1/f**0.5 up to 1 Hz. At 1 Hz is seen a broad quasiperiodic oscillation peak and a break to a 1/f**2 power law, which continues to 4 Hz. The fractional rms (root mean square) amplitude from 1 mHz to 4 Hz is 43 percent. No coherent pulsations are seen between 0.001 and 1024 Hz. The authors conclude that XTE J1908+094 is a new blackhole candidate.

  20. 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.

  1. Astronomers Trace Microquasar's Path Back in Time

    NASA Astrophysics Data System (ADS)

    2003-01-01

    Astronomers have traced the orbit through our Milky Way Galaxy of a voracious neutron star and a companion star it is cannibalizing, and conclude that the pair joined more than 30 million years ago and probably were catapulted out of a cluster of stars far from the Galaxy's center. Path of Microquasar and Sun Path of Microquasar (red) and Sun (yellow) through the Milky Way Galaxy for the past 230 million years. Animations: GIF Version MPEG Version CREDIT: Mirabel & Rodrigues, NRAO/AUI/NSF The pair of stars, called Scorpius X-1, form a "microquasar," in which material sucked from the "normal" star forms a rapidly-rotating disk around the superdense neutron star. The disk becomes so hot it emits X-rays, and also spits out "jets" of subatomic particles at nearly the speed of light. Using precise positional data from the National Science Foundation's Very Long Baseline Array (VLBA) and from optical telescopes, Felix Mirabel, an astrophysicist at the Institute for Astronomy and Space Physics of Argentina and French Atomic Energy Commission, and Irapuan Rodrigues, also of the French Atomic Energy Commission, calculated that Scorpius X-1 is not orbiting the Milky Way's center in step with most other stars, but instead follows an eccentric path far above and below the Galaxy's plane. Scorpius X-1, discovered with a rocket-borne X-ray telescope in 1962, is about 9,000 light-years from Earth. It is the brightest continuous source of X-rays beyond the Solar System. The 1962 discovery and associated work earned a share of the 2002 Nobel Prize in physics for Riccardo Giacconi. Mirabel and Rodrigues used a number of published observations to calculate the path of Scorpius X-1 over the past few million years. "This is the most accurate determination we have made of the path of an X-ray binary," said Mirabel. By tracing the object's path backward in time, the scientists were able to conclude that the neutron star and its companion have been traveling together for more than 30

  2. 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.

  3. Coordinated ASCA/EUVE/XTE Observations of Algol

    NASA Technical Reports Server (NTRS)

    Stern, Robert A.

    1997-01-01

    EUVE, Advanced Satellite for Cosmology and Astrophysics (ASCA), and X-ray Timing Explorer (XTE) observed the eclipsing binary Algol (Beta Per) from 1-7 Feb 1996. The coordinated observation covered approx. 2 binary orbits of the system, with a net exposure of approx. 160 ksec for EUVE, 40 ksec for ASCA (in 4 pointings), and 90 ksec for XTE (in 45 pointings). We discuss results of modeling the combined EUVE, ASCA, and XTE data using continuous differential emission measure distributions, and provide constraints on the abundance in the Algol system.

  4. Extreme particle acceleration in the microquasar Cygnus X-3.

    PubMed

    Tavani, M; Bulgarelli, A; Piano, G; Sabatini, S; Striani, E; Evangelista, Y; Trois, A; Pooley, G; Trushkin, S; Nizhelskij, N A; McCollough, M; Koljonen, K I I; Pucella, G; Giuliani, A; Chen, A W; Costa, E; Vittorini, V; Trifoglio, M; Gianotti, F; Argan, A; Barbiellini, G; Caraveo, P; Cattaneo, P W; Cocco, V; Contessi, T; D'Ammando, F; Del Monte, E; De Paris, G; Di Cocco, G; Di Persio, G; Donnarumma, I; Feroci, M; Ferrari, A; Fuschino, F; Galli, M; Labanti, C; Lapshov, I; Lazzarotto, F; Lipari, P; Longo, F; Mattaini, E; Marisaldi, M; Mastropietro, M; Mauri, A; Mereghetti, S; Morelli, E; Morselli, A; Pacciani, L; Pellizzoni, A; Perotti, F; Picozza, P; Pilia, M; Prest, M; Rapisarda, M; Rappoldi, A; Rossi, E; Rubini, A; Scalise, E; Soffitta, P; Vallazza, E; Vercellone, S; Zambra, A; Zanello, D; Pittori, C; Verrecchia, F; Giommi, P; Colafrancesco, S; Santolamazza, P; Antonelli, A; Salotti, L

    2009-12-01

    Super-massive black holes in active galaxies can accelerate particles to relativistic energies, producing jets with associated gamma-ray emission. Galactic 'microquasars', which are binary systems consisting of a neutron star or stellar-mass black hole accreting gas from a companion star, also produce relativistic jets, generally together with radio flares. Apart from an isolated event detected in Cygnus X-1, there has hitherto been no systematic evidence for the acceleration of particles to gigaelectronvolt or higher energies in a microquasar, with the consequence that we are as yet unsure about the mechanism of jet energization. Here we report four gamma-ray flares with energies above 100 MeV from the microquasar Cygnus X-3 (an exceptional X-ray binary that sporadically produces radio jets). There is a clear pattern of temporal correlations between the gamma-ray flares and transitional spectral states of the radio-frequency and X-ray emission. Particle acceleration occurred a few days before radio-jet ejections for two of the four flares, meaning that the process of jet formation implies the production of very energetic particles. In Cygnus X-3, particle energies during the flares can be thousands of times higher than during quiescent states. PMID:19935645

  5. 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.

  6. 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

  7. Accretion and Jets in Microquasars and Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Markoff, S.

    2006-09-01

    Black holes from stellar to galactic scales are observed to accrete material from their environments and, via an as yet unknown mechanism, produce jets of outflowing plasma. In X-ray binaries (XRBs), the systems display radically different radiative properties depending on the amount of captured gas reaching the event horizon. These modes of behavior (one of which includes ``microquasars'') correspond to actual physical changes in the environment near the black hole and can occur on timescales of days to weeks. Some of this behavior should hold true for active galactic nuclei (AGN) if the underlying physics scales with central mass and accretion power, as would be expected if black holes can be characterized mainly by their mass and local environment. However, the timescales on which changes occur should be inversely proportional to the mass. Recent studies support that this scaling applies in some cases, opening the way for comparisons of different stages of time-dependent behavior in microquasars to different classes of AGN zoology. In this distinctly jet-biased review, I will summarize our current understanding of accretion and outflow in these systems and present some of the newest progress addressing unanswered questions about the nature of the accretion flows, jet formation, and jet composition.

  8. 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.

  9. Black hole spin inferred from 3:2 epicyclic resonance model of high-frequency quasi-periodic oscillations

    NASA Astrophysics Data System (ADS)

    Šrámková, E.; Török, G.; Kotrlová, A.; Bakala, P.; Abramowicz, M. A.; Stuchlík, Z.; Goluchová, K.; Kluźniak, W.

    2015-06-01

    Estimations of black hole spin in the three Galactic microquasars GRS 1915+105, GRO J1655-40, and XTE J1550-564 have been carried out based on spectral and timing X-ray measurements and various theoretical concepts. Among others, a non-linear resonance between axisymmetric epicyclic oscillation modes of an accretion disc around a Kerr black hole has been considered as a model for the observed high-frequency quasi-periodic oscillations (HF QPOs). Estimates of spin predicted by this model have been derived based on the geodesic approximation of the accreted fluid motion. Here we assume accretion flow described by the model of a pressure-supported torus and carry out related corrections to the mass-spin estimates. We find that for dimensionless black hole spin a ≡ cJ/GM2 ≲ 0.9, the resonant eigenfrequencies are very close to those calculated for the geodesic motion. Their values slightly grow with increasing torus thickness. These findings agree well with results of a previous study carried out in the pseudo-Newtonian approximation. The situation becomes different for a ≳ 0.9, in which case the resonant eigenfrequencies rapidly decrease as the torus thickness increases. We conclude that the assumed non-geodesic effects shift the lower limit of the spin, implied for the three microquasars by the epicyclic model and independently measured masses, from a ~ 0.7 to a ~ 0.6. Their consideration furthermore confirms compatibility of the model with the rapid spin of GRS 1915+105 and provides highly testable predictions of the QPO frequencies. Individual sources with a moderate spin (a ≲ 0.9) should exhibit a smaller spread of the measured 3:2 QPO frequencies than sources with a near-extreme spin (a ~ 1). This should be further examined using the large amount of high-resolution data expected to become available with the next generation of X-ray instruments, such as the proposed Large Observatory for X-ray Timing (LOFT).

  10. VERITAS Observations of the Microquasar Cygnus X-3

    NASA Astrophysics Data System (ADS)

    Archambault, S.; Beilicke, M.; Benbow, W.; Berger, K.; Bird, R.; Bouvier, A.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cerruti, M.; Chen, X.; Ciupik, L.; Connolly, M. P.; Cui, W.; Duke, C.; Dumm, J.; Errando, M.; Falcone, A.; Federici, S.; Feng, Q.; Finley, J. P.; Fortson, L.; Furniss, A.; Galante, N.; Gillanders, G. H.; Griffin, S.; Griffiths, S. T.; Grube, J.; Gyuk, G.; Hanna, D.; Holder, J.; Hughes, G.; Humensky, T. B.; Kaaret, P.; Kertzman, M.; Khassen, Y.; Kieda, D.; Krawczynski, H.; Lang, M. J.; Madhavan, A. S.; Maier, G.; Majumdar, P.; McArthur, S.; McCann, A.; Moriarty, P.; Mukherjee, R.; Nieto, D.; O'Faoláin de Bhróithe, A.; Ong, R. A.; Otte, A. N.; Pandel, D.; Park, N.; Perkins, J. S.; Pohl, M.; Popkow, A.; Prokoph, H.; Quinn, J.; Ragan, K.; Rajotte, J.; Reyes, L. C.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Sembroski, G. H.; Sheidaei, F.; Smith, A. W.; Staszak, D.; Telezhinsky, I.; Theiling, M.; Tucci, J. V.; Tyler, J.; Varlotta, A.; Vincent, S.; Wakely, S. P.; Weekes, T. C.; Weinstein, A.; Williams, D. A.; Zitzer, B.; VERITAS Collaboration and; McCollough, M. L.; Astrophysical Observatory, Smithsonian

    2013-12-01

    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.

  11. 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.

  12. Nine Years of Observations of Hard X-Rays from Relativistic Jet Objects with BATSE

    NASA Technical Reports Server (NTRS)

    Fishman, G. J.; Harmon, B. A.; Fishman, G. J.; Six, N. Frank (Technical Monitor)

    2002-01-01

    The observed hard X-ray temporal and spectral characteristics will be displayed for over nine years of BATSE (Burst and Transient Source Experiment) data from the Compton Observatory. These observations were obtained using the Earth occultation technique, a technique that has become increasingly more sensitive and accurate as systematic effects are understood and corrected. The principal objects that are being presented in this study include: GRO J1655-40, GRS 1915+105, Cyg X-3, Cyg X-1, XTE J1550-564, XTE J1859+226, XTE J1748-288, and V4641 Sgr. Light curves and spectral will be presented and discussed in terms of relativistic jet production in these systems.

  13. 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. PMID:26934231

  14. 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.

  15. 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.

  16. 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.

  17. 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. PMID:16709745

  18. 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.

  19. 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.

  20. A broadband leptonic model for gamma-ray emitting microquasars

    NASA Astrophysics Data System (ADS)

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

    2006-02-01

    Observational and theoretical studies point to microquasars (MQs) as possible counterparts of a significant fraction of the unidentifiedgamma-ray sources detected so far. At present, a proper scenario to explain the emission beyond soft X-rays from these objects is not known, nor what the precise connection is between the radio and the high-energy radiation. We develop a new model where the MQ jet is dynamically dominated by cold protons and radiatively dominated by relativistic leptons. The matter content and power of the jet are both related with the accretion process. The magnetic field is assumed to be close to equipartition, although it is attached to and dominated by the jet matter. For the relativistic particles in the jet, their maximum energy depends on both the acceleration efficiency and the energy losses. The model takes into account the interaction of the relativistic jet particles with the magnetic field and all the photon and matter fields. Such interaction produces significant amounts of radiation from radio to very high energies through synchrotron, relativistic Bremsstrahlung, and inverse Compton (IC) processes. Variability of the emission produced by changes in the accretion process (e.g. via orbital eccentricity) is also expected. The effects of the gamma-ray absorption by the external photon fields on the gamma-ray spectrum have been taken into account, revealing clear spectral features that might be observed. This model is consistent to the accretion scenario, energy conservation laws, and current observational knowledge, and can provide deeper physical information of the source when tested against multiwavelength data.

  1. X-ray Variability of the Microquasar LS 5039 through its Eccentric Orbit

    NASA Technical Reports Server (NTRS)

    Swank, Jean (Technical Monitor); Miller, Jon

    2005-01-01

    Under this program, RXTE made a number of observations of the Galactic microquasar LS 5039, spaced through its binary orbital period. The results of an initial spectral and timing study have been published in a refereed journal. Work on integrating the RXTE data with simultaneous multi-wavelength data is presently underway.

  2. Stellar Pair Shot Out from Its Birthplace: Astronomers Link Moving Microquasar to Star Cluster

    NASA Astrophysics Data System (ADS)

    2004-07-01

    Astronomers studying data from the National Science Foundation's Very Long Baseline Array (VLBA) and other telescopes have concluded that a binary pair of stars forming an energetic microquasar was blasted out of the cluster in which it was born by a supernova explosion some 1.7 million years ago. This is the first time that a fast-moving stellar pair has been tracked back to a specific star cluster. Microquasar and Star Cluster The microquasar, circled in red, and stars of the cluster (yellow) in visible-light image. Green arrow indicates microquasar's motion in sky and yellow arrow indicates star cluster's motion. Red arrow indicates microquasar's motion relative to (away from) star cluster. CREDIT: NRAO/AUI/NSF (Click on Image for Larger Version) The scientists analyzed numerous observations of a microquasar called LSI +61 303, and concluded that it is moving away from a star cluster named IC 1805 at nearly 17 miles per second. A microquasar is a pair of stars, one of which is either a dense neutron star or a black hole, in which material sucked from a "normal" star forms a rapidly-rotating disk around the denser object. The disk becomes so hot it emits X-rays, and also spits out "jets" of subatomic particles at nearly the speed of light. "In this case, both the microquasar and the star cluster are about 7,500 light-years from Earth and the characteristics of the 'normal' star in the microquasar match those of the other stars in the cluster, so we feel confident that the microquasar was shot out from a birthplace in this cluster," said Felix Mirabel, an astrophysicist at the Institute for Astronomy and Space Physics of Argentina and French Atomic Energy Commission. Mirabel worked with Irapuan Rodrigues, of the Federal University of Rio Grande do Sul, Brazil, and Qingzhong Liu of the Purple Mountain Observatory in Nanjing, China. The astronomers reported their results in the August 1 issue of the scientific journal Astronomy & Astrophysics. Many neutron stars

  3. Radio Astronomical studies of microquasars with RATAN-600 radio telescope

    NASA Astrophysics Data System (ADS)

    Trushkin, Sergei; Nizhelskij, Nikolaj; Tsybulev, Peter; Bursov, Nikolaj

    Relativistic outflows of accreted matter in the collimated two opposite side jets, ejected from polar regions of accretion disks around black holes or neutron stars in microquasars, are the intensive sources of variable synchrotron radio emission and even TeV energy gamma-ray emission. The ballistic tracks of the clouds (blobs) are directly visible as radio jets in VLA and VLBI maps of SS433, GRS 1915+105, Cyg X-3. The temporal and frequency changes in the measured light curves are a key for deep understanding and a good probe test for physical models of of cosmic jets in mQSO and AGNs. A comparison the radio, optical, X-ray and now high energy gamma-ray intensities allows us to provide detailed studies. We have carried out the long-time monitoring (as a rule 200-250 daily measurements per year) Cyg X-3, GRS1915+10, SS433, Cyg X-1, LSI+61d303, LS5039 with RATAN-600 at 4.8, 7.7, 11.2, 21.7, and 30 GHz during last four years. While Cyg X-3 was in quiet state, we have detected clear radio-X-ray (RATAN-Swift) correlation. We have detected a lot of very bright flares (more than 1.5 Jy at 4.8 GHz) from SS433. In quiet state the radio emission of SS433 is modulated by a half of orbit period near 6.5d, probably being the geometric effect of precessing (164d) and nodding (6.1d) jets. GRS1915+105 have shown the clear correlation of flaring radio emission with X-ray flux from MAXI (Punsly et al., 2014 ApJ, in press). We have detected the enhanced absorption due to the rising hydrogen column density. We continue to study the super-orbital modulation (1666 days) of the flaring radio emission from LSI+61d303. The moments of maxima of the periodically flaring radio emission from it correlated with phase of this super-orbital period. The studies were supported by the grant 12-02-00812 from Russian Foundation of Basic Research.

  4. A new outburst of XTE J1739-285

    NASA Astrophysics Data System (ADS)

    Maccarone, Thomas J.; Bandyopadhyay, Reba; Kennea, Jamie

    2012-09-01

    With our program of Swift monitoring of the Galactic Bulge region (Atel #4109), we detect renewed activity of the X-ray binary XTE J1739-285. Using the pipeline of Phil Evans (Evans et al. 2007, A&A, 469, 379), we find that the source count rate is about 34 counts/sec in data taken on 4 September from 5:33 to 12:02 UT, with 372 seconds of exposure time on source. We note that the source is heavily piled up, since the data were taken in photon counting mode as part of an imaging survey and hence the count rate should be taken with caution.

  5. Additional Observations of XTE J1752-223

    NASA Astrophysics Data System (ADS)

    Markwardt, C. B.; Barthelmy, S. D.; Evans, P. A.; Swank, J. H.

    2009-10-01

    We report on additional observations of XTE J1752-223, a new transient recently reported active (ATEL #2258). Swift performed a dedicated follow-up observation at 2009-10-25 at 06:08 UT. A bright X-ray source was detected by the XRT instrument, heavily piled up. The best fit position from XRT is, R.A. = 268.06307 = 17:52:15.14 ; Dec. = -22.34274 = -22:20:33.8 (J2000) with estimated position error of about 5 arcsec.

  6. 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.

  7. 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. PMID:19965378

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

    NASA Astrophysics Data System (ADS)

    Fermi LAT Collaboration; 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.; Çelik, Ö.; 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, J.; 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. W.; Ylinen, T.; Ziegler, M.

    2009-12-01

    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.

  9. 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.

  10. 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.

  11. A search for time dependent neutrino emission from microquasars with the ANTARES telescope

    NASA Astrophysics Data System (ADS)

    Adrián-Martínez, S.; Albert, A.; André, M.; Anghinolfi, M.; Anton, G.; Ardid, M.; Astraatmadja, T.; Aubert, J.-J.; Baret, B.; Barrios, J.; Basa, S.; Bertin, V.; Biagi, S.; Bigongiari, C.; Bogazzi, C.; Bouhou, B.; Bouwhuis, M. C.; Brunner, J.; Busto, J.; Capone, A.; Caramete, L.; Cârloganu, C.; Carr, J.; Cecchini, S.; Charif, Z.; Charvis, P.; Chiarusi, T.; Circella, M.; Coniglione, R.; Core, L.; Costantini, H.; Coyle, P.; Creusot, A.; De Rosa, G.; Dekeyser, I.; Deschamps, A.; De Bonis, G.; Distefano, C.; Donzaud, C.; Dornic, D.; Dorosti, Q.; Drouhin, D.; Dumas, A.; Eberl, T.; Elsässer, D.; Emanuele, U.; Enzenhöfer, A.; Ernenwein, J.-P.; Escoffier, S.; Fehn, K.; Felis, I.; Fermani, P.; Folger, F.; Fusco, L. A.; Galatà, S.; Gay, P.; Geißelsöder, S.; Geyer, K.; Giordano, V.; Gleixner, A.; Gómez-González, J. P.; Graf, K.; Guillard, G.; van Haren, H.; Heijboer, A. J.; Hello, Y.; Hernández-Rey, J. J.; Herold, B.; Hößl, J.; Hofestädt, J.; James, C. W.; de Jong, M.; Kadler, M.; Kalekin, O.; Kappes, A.; Katz, U.; Kooijman, P.; Kouchner, A.; Kreykenbohm, I.; Kulikovskiy, V.; Lahmann, R.; Lambard, E.; Lambard, G.; Larosa, G.; Lattuada, D.; Lefèvre, D.; Leonora, E.; Loehner, H.; Loucatos, S.; Mangano, S.; Marcelin, M.; Margiotta, A.; Martínez-Mora, J. A.; Martini, S.; Mathieu, A.; Michael, T.; Migliozzi, P.; Montaruli, T.; Müller, C.; Neff, M.; Nezri, E.; Palioselitis, D.; Păvălaş, G. E.; Perrina, C.; Piattelli, P.; Popa, V.; Pradier, T.; Racca, C.; Riccobene, G.; Richter, R.; Rivière, C.; Robert, A.; Roensch, K.; Rostovtsev, A.; Saldaña, M.; Samtleben, D. F. E.; Sánchez-Losa, A.; Sanguineti, M.; Sapienza, P.; Schmid, J.; Schnabel, J.; Schulte, S.; Schüssler, F.; Seitz, T.; Sieger, C.; Spies, A.; Spurio, M.; Steijger, J. J. M.; Stolarczyk, T.; Taiuti, M.; Tamburini, C.; Tayalati, Y.; Trovato, A.; Vallage, B.; Vallée, C.; Van Elewyck, V.; Vernin, P.; Visser, E.; Vivolo, D.; Wagner, S.; Wilms, J.; de Wolf, E.; Yatkin, K.; Yepes, H.; Zornoza, J. D.; Zúñiga, J.

    2014-09-01

    Results are presented on a search for neutrino emission from a sample of six microquasars, based on the data collected by the ANTARES neutrino telescope between 2007 and 2010. By means of appropriate time cuts, the neutrino search has been restricted to the periods when the acceleration of relativistic jets was taking place at the microquasars under study. The time cuts have been chosen using the information from the X-ray telescopes RXTE/ASM and Swift/BAT, and, in one case, the gamma-ray telescope Fermi/LAT. No statistically significant excess has been observed, thus upper limits on the neutrino fluences have been derived and compared to the predictions by models. Constraints have been put on the ratio of proton to electron luminosity in the jets.

  12. 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 -

  13. 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.

  14. Looking for black-holes in X-ray binaries with XMM-Newton: XTE J1817-330 and XTE J1856+053

    SciTech Connect

    Sala, Gloria; Greiner, Jochen; Primak, Natalia

    2008-10-08

    The X-ray binary XTE J1817-330 was discovered in outburst on 26 January 2006 with RXTE/ASM. One year later, another X-ray transient discovered in 1996, XTE J1856+053, was detected by RXTE during a new outburst on 28 February 2007. We triggered XMM-Newton target of opportunity observationson these two objects to constrain their parameters and search for a stellar black holes. We summarize the properties of these two X-ray transients and show that the soft X-ray spectra indicate indeed the presence of an accreting stellar black hole in each of the two systems.

  15. 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.

  16. 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.

  17. 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.

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

    NASA Astrophysics Data System (ADS)

    Piano, G.; Tavani, M.; Bulgarelli, A.; Verrecchia, F.; Donnarumma, I.; Munar-Adrover, P.; Minervini, G.; Fioretti, V.; Zoli, A.; Pittori, C.; Lucarelli, F.; Vercellone, S.; Striani, E.; 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.

    2016-08-01

    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 2016-08-28 UT 09:00:00 to 2016-08-30 UT 09:00:00 (MJD: 57628.375 - 57630.375), a preliminary multi-source likelihood analysis detects a gamma-ray flux F( > 100 MeV) = (4.0 +/- 1.4) x 10^-6 photons/cm^2/s with a significance near 4 sigma.

  19. 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

  20. 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.

  1. Evolution of the X-Ray Properties of the Transient Magnetar XTE J1810-197

    NASA Astrophysics Data System (ADS)

    Alford, J. A. J.; Halpern, J. P.

    2016-02-01

    We report on X-ray observations of the 5.54 s transient magnetar XTE J1810-197 using the XMM-Newton and Chandra observatories, analyzing new data from 2008 through 2014, and re-analyzing data from 2003 through 2007 with the benefit of these six years of new data. From the discovery of XTE J1810-197 during its 2003 outburst to the most recent 2014 observations, its 0.3-10 keV X-ray flux has declined by a factor of about 50 from 4.1 × 10-11 to 8.1 × 10-13 erg cm-2 s-1. Its X-ray spectrum has now reached a steady state. Pulsations continue to be detected from a 0.3 keV thermal hot spot that remains on the neutron star (NS) surface. The luminosity of this hot spot exceeds XTE J1810-197’s spin-down luminosity, indicating continuing magnetar activity. We find that XTE J1810-197’s X-ray spectrum is best described by a multiple component blackbody model in which the coldest 0.14 keV component likely originates from the entire NS surface, and the thermal hot-spot is, at different epochs, well described by an either one- or two-component blackbody model. A 1.2 keV absorption line, possibly due to resonant proton scattering, is detected at all epochs. The X-ray flux of the hot spot decreased by ≈ 20% between 2008 and 2009 March, the same period during which XTE J1810-197 became radio quiet.

  2. Evolution of the X-ray Properties of the Transient Magnetar XTE J1810-197

    NASA Astrophysics Data System (ADS)

    Alford, Jason

    2016-04-01

    We report on X-ray observations of the 5.54 s transient magnetar XTE J1810-197 using the XMM-Newton and Chandra observatories, analyzing new data from 2008 through 2014, and re-analyzing data from 2003 through 2007 with the benefit of these six years of new data. From the discovery of XTE J1810-197 during its 2003 outburst to the most recent 2014 observations, its 0.3-10 keV X-ray flux has declined by a factor of about 50 from 4.1E-11 to 8.1E-13 erg/cm^2/s. Its X-ray spectrum has now reached a steady state. Pulsations continue to be detected from a 0.3 keV thermal hot-spot that remains on the neutron star surface. The luminosity of this hot-spot exceeds XTE J1810-197's spin down luminosity, indicating continuing magnetar activity. We find that XTE J1810-197's X-ray spectrum is best described by a multiple component blackbody model in which the coldest 0.14 keV component likely originates from the entire neutron star surface, and the thermal hot-spot is, at different epochs, well described by an either one or two-component blackbody model. A 1.2 keV absorption line, possibly due to resonant proton scattering, is detected at all epochs. The X-ray flux of the hot spot decreased by approximately 20% between 2008 March and 2009 March, the same period during which XTE J1810-197 became radio quiet.

  3. 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.

  4. 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

  5. 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.

  6. The Anatomy Of A Magnetar: XMM Monitoring Of Transient AXP XTE J1810-197

    NASA Astrophysics Data System (ADS)

    Gotthelf, Eric V.; Halpern, J. P.; Perna, R.

    2006-09-01

    The transient anomalous X-ray pulsar (TAXP) XTE J1810-197 is a unique object whose remarkable properties offer great promise for deciphering the emission mechanism(s) of magnetars. This 5.54s pulsar was discovered in early 2003 during an outburst that has, as of 2006, faded near to quiescence, based on historic data. TAXP XTE J1810-197 is, most surprisingly, a highly variable radio pulsar with a unusual flat spectrum. This is the first confirmed example of radio flux from an AXP. Herein, we report on our semi-annual XMM monitoring campaign that has followed the pulsar for the last 3 years as its spectrum evolved. Fitting a double blackbody model we find that the component luminosities followed an exponential decay law with κ(BB1) = 870 days and κ(BB2) = 280 days, respectively. The temperatures of these components cooled at a rate of 22% per year from the nearly constant value recorded prior to 2004 March of kT(BB1) = 0.25 keV and kT(BB2) = 0.67 keV, respectively. The latest data show that the luminosity and temperature of the cooler component have effectively returned to their quiescent levels and that its pulsed fraction, which has steadily decreased with time, is now consistent with the previous lack of detected pulsations in quiescence. We use the energy dependence of the fading emission to decouple the pulsed components to solve for the viewing and emitting geometry of XTE J1810-197. Finally, we consider the emission mechanism(s) of XTE J1810-197 in the context of the coronal loop magnetar model of Beloborodov & Thompson (2006). This research is supported by XMM-Newton grant NNG05GJ61G and NASA ADP grant ADP04-0059-0024.

  7. 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.

  8. X-Ray Bursts from the Transient Magnetar Candidate XTE J1810-197

    NASA Technical Reports Server (NTRS)

    Kouveliotou, Chryssa; Woods, Peter M.; Gavriil, Fotis P.; Kaspi, Victoria M.; Roberts, Mallory S. E.; Ibrahim, Alaa; Markwardt, Craig B.; Swank, Jean H.; Finger, Mark H.

    2005-01-01

    We have discovered four X-ray bursts, recorded with the Rossi X-ray Timing Explorer Proportional Counter Array between 2003 September and 2004 April, that we show to originate from the transient magnetar candidate XTE 51810-197. The burst morphologies consist of a short spike or multiple spikes lasting approx. 1 s each followed by extended tails of emission where the pulsed flux from XTE 51810-197 is significantly higher. The burst spikes are likely correlated with the pulse maxima, having a chance probability of a random phase distribution of 0.4%. The burst spectra are best fit to a blackbody with temperatures 4-8 keV, considerably harder than the persistent X-ray emission. During the X-ray tails following these bursts, the temperature rapidly cools as the flux declines, maintaining a constant emitting radius after the initial burst peak. The temporal and spectral characteristics of these bursts closely resemble the bursts seen from 1E 1048.1-5937 and a subset of the bursts detected from 1E 2259+586, thus establishing XTE J1810-197 as a magnetar candidate. The bursts detected from these three objects are sufficiently similar to one another, yet si,g&cantly differe2t from those seen from soft gamma repeaters, that they likely represent a new class of bursts from magnetar candidates exclusive (thus far) to the anomalous X-ray pulsar-like sources.

  9. 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.; Kouveliotou, Chryssa

    2002-01-01

    The 89 s X-ray pulsar XTE J1906+09 was discovered during Rossi X-Ray Timing Explorer (RXTE) observations of SGR 1900+14 in 1996. Because 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 search for pulsations resulted in detections of only the two previously reported outbursts in 1996 September and 1998 August-September. Pulsed flux upper limits for the rest of the observations show that XTE J1906+09 is a transient X-ray pulsar and likely has a Be star companion. The RXTE all-sky monitor did not reveal XTE J1906+09. Pulse-timing analysis of the second outburst discovered a sinusoidal signature in the pulse frequencies that is likely produced by an orbital periastron passage. Fits to pulse phases using an orbital model and quadratic phase model have chi(exp 2) minima at orbital periods of 26-30 days for fixed mass functions of 5, 10, 15, and 20 solar masses. The pulse shape showed energy- and intensity-dependent variations. Pulse-phase spectroscopy quantified the energy-dependent variations. The phase-averaged spectrum used the pulse minimum spectrum as the background spectrum to eliminate effects from SGR 1900+14 and the Galactic ridge and 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)/sq cm, a photon index of 1.01 +/- 0.08, cutoff energy E(sub cut) = 11 +/- 1 keV, and e-folding energy E(sub fold) = 19 +/- 4 keV. Estimated 2-10 keV peak fluxes, corrected for contributions from the Galactic ridge and SGR 1900+14, are 6 x l0(exp -12) and 1.1 x 10(exp -10) ergs/sq cm/s for the 1996 and 1998 outbursts, respectively. XTE J1906+09 may be part of an unusual class of Be/X-ray binaries that do not lie on the general spin period versus orbital period correlation with the majority of Be/X-ray binaries.

  10. 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.

  11. Variable-Frequency QPOs from the Galactic Microquasar GRS 1915+105

    NASA Technical Reports Server (NTRS)

    Markwardt, Craig B.; Swank, Jean H.; Taam, Ronald E.

    1998-01-01

    We show that the galactic microquasar GRS 1915+105 exhibits quasi-periodic oscillations (QPOS) whose frequency varies continuously from 1-15 Hz, during spectrally hard dips when the source is in a flaring state. NN'e report here analyses of simultaneous energy spectra and power density spectra at 4 s intervals. The energy spectrum is well fit at each time step by an optically thick accretion disk plus power law model, while the power density spectrum consists of a varying red noise component plus the variable frequency QPO. The features of both spectra are strongly correlated with one another. The 1-15 Hz QPOs appear when the power law component becomes hard and intense, and themselves have an energy spectrum consistent with the power law component (with root mean square amplitudes as high as 10%). The frequency of the oscillations, however, is most strikingly correlated with the parameters of the thermal disk component. The tightest correlation is between QPO frequency and the disk X-ray flux. This fact indicates that the properties of the QPO are not determined by solely a disk or solely a corona.

  12. 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}).

  13. Discovery of photon index saturation in the black hole binaries

    NASA Astrophysics Data System (ADS)

    Titarchuk, Lev; Shaposhnikov, Nickolai; Seifina, Elena

    2010-03-01

    We present a study of the correlations between spectral, timing properties and mass accretion rate observed in X-rays from the eight Galactic Black Hole (BH) binaries during the transition between hard and soft states. We analyze all transition episodes from X-ray sources observed with Rossi X-ray Timing Explorer (RXTE). We show that broad-band energy spectra of Galactic sources during all these spectral states can be adequately presented by Bulk Motion Comptonization (BMC) model. We also present observable correlations between the index and the normalization of the disk ``seed'' component. The use of ``seed'' disk normalization, which is presumably proportional to mass accretion rate in the disk, is crucial to establish the index saturation effect during the transition to the soft state. We discovered the photon index saturation of the hard spectral components at values of 2.1-3. We present a physical model which explains the index-seed photon normalization correlations. We argue that the index saturation effect of the hard component (BMC1) is due to the soft photon Comptonization in the converging inflow close to BH. We apply our scaling technique to determine BH masses and distances for Cygnus X-1, GX 339-4, 4U 1543-47, XTE J1550-564, XTE J1650-500, H 1743-322 and XTE J1859-226. Good agreement of our results for sources with known values of BH masses and distance provides an independent verification for our scaling technique.

  14. Relevance of jet emitting disc physics to microquasars: application to Cygnus X-1

    NASA Astrophysics Data System (ADS)

    Petrucci, P. O.; Ferreira, J.; Henri, G.; Malzac, J.; Foellmi, C.

    2010-11-01

    Context. Interpretation of the X-ray spectra of X-ray binaries during their hard states requires a hot, optically thin medium. There are several accretion disc models that account for this aspect. However, none is designed to simultaneously explain powerful jets detected during these states. Aims: A new quasi-Keplerian hot accretion disc solution, a jet emitting disc (JED hereafter), which is part of a global disc-jet MHD structure producing stationary super-alfvénic ejection, is investigated here. Its radiative and energetic properties are then compared to the observational constraints found in Cygnus X-1. Methods: We solve the disc energy equation by balancing the local heating term with advection and cooling by synchrotron, bremsstrahlung, and Comptonization processes. The heating term, disc density, accretion velocity, and magnetic field amplitude were taken from published self-similar models of accretion-ejection structures. Both optically thin and thick regimes are considered in a one-temperature, gas-supported disc. Results: Three branches of solutions are found to be possible at a given radius, but we only investigate the hot, optically thin and geometrically slim solutions. These solutions give simultaneously and consistently the radiative and energetics properties of the disc-jet system. They are able to reproduce the global accretion-ejection properties of Cygnus X-1 very well, namely its X-ray spectral emission, jet power, and jet velocity. About half of the released accretion power is used to produce two mildly relativistic (v/c≃ 0.5) jets, and for a luminosity of about 1% of the Eddington luminosity, the JED temperature and optical depth are close to what is observed in the hard state of Cygnus X-1. Conclusions: The accretion and ejection properties of JEDs agree with the observations of the prototypical black hole binary Cygnus X-1. The JED solutions are likely to be relevant to the whole class of microquasars.

  15. A Deep XMM-Newton Observation of the Enigmatic Microquasar 1E 1740.7-2942

    NASA Astrophysics Data System (ADS)

    Miller, Jon

    1E 1740.7-2942 is a microquasar residing in the Galactic center. It is persistently bright at X-ray energies and has been shown to power large scale bi-polar jets, thus making it an ideal source to probe the jet generation/launching mechanism in accreting black holes. Analysis of archival data hinted at the presence of a relativistically broadened iron line, providing a means to constrain the spin of the black hole in this system for the first time. In AO-10 we were awarded a 130 ks XMM-Newton category B target of oppurtunity (ToO) observation, with the aim of observing this system in the low-hard state. This observation was triggered in April 2012 and the data have been obtained, where a preliminary analysis reveals the expected broad iron line. Modeling this iron line will allow us to constrain the spin of the black hole and probe its relation to the presence of large scale jets in this system. We request a total of $63.7k funding to support the analysis of this deep XMM-Newton observation, including the primary target (1E 1740.7-2942) and the serendipitous sources in the field of view (< 60). This proposal will enhance our understanding of the interaction of the accretion flow with the black hole and the generation of astrophysical jets, thus addressing NASA strategic objectives 2.4.1: Improve understanding of the origin and destiny of the universe, and the nature of black holes, dark energy, dark matter, and gravity. and 2.4.2: Improve understanding of the many phenomena and processes associated with galaxy, stellar, and planetary system formation and evolution from the earliest epochs to today.

  16. EPISODIC TRANSIENT GAMMA-RAY EMISSION FROM THE MICROQUASAR CYGNUS X-1

    SciTech Connect

    Sabatini, S.; Tavani, M.; Vittorini, V.; Piano, G.; Del Monte, E.; Feroci, M.; Argan, A.; D'Ammando, F.; Costa, E.; De Paris, G.; Bulgarelli, A.; Trifoglio, M.; Gianotti, F.; Di Cocco, G.; Barbiellini, G.; Caraveo, P.; Chen, A. W.

    2010-03-20

    Cygnus X-1 (Cyg X-1) is the archetypal black hole binary system in our Galaxy. We report the main results of an extensive search for transient gamma-ray emission from Cygnus X-1 carried out in the energy range 100 MeV-3 GeV by the AGILE satellite, during the period 2007 July-2009 October. The total exposure time is about 300 days, during which the source was in the 'hard' X-ray spectral state. We divided the observing intervals in 2-4 week periods, and searched for transient and persistent emission. We report an episode of significant transient gamma-ray emission detected on 2009 October 16 in a position compatible with Cyg X-1 optical position. This episode, which occurred during a hard spectral state of Cyg X-1, shows that a 1-2 day time variable emission above 100 MeV can be produced during hard spectral states, having important theoretical implications for current Comptonization models for Cyg X-1 and other microquasars. Except for this one short timescale episode, no significant gamma-ray emission was detected by AGILE. By integrating all available data, we obtain a 2{sigma} upper limit for the total integrated flux of F {sub {gamma}}{sub ,U.L.} = 3 x 10{sup -8} ph cm{sup -2} s{sup -1} in the energy range 100 MeV-3 GeV. We then clearly establish the existence of a spectral cutoff in the energy range 1-100 MeV that applies to the typical hard state outside the flaring period and that confirms the historically known spectral cutoff above 1 MeV.

  17. 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.

  18. 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.

  19. Optical re-brightening of the black hole binary XTE J1859+226

    NASA Astrophysics Data System (ADS)

    Corral-Santana, J. M.; Rodríguez-Gil, P.; Hurley, D.; Casares, J.

    2010-09-01

    Observations of the black hole binary XTE J1859+226 revealed an unexpected optical re-brightening. Images were taken with the Nordic Optical Telescope (NOT) using ALFOSC on Jul 13-14, the William Herschel Telescope (WHT) with ACAM on Aug 8 and the Isaac Newton Telescope (INT) with WFC on Aug 19 at the Observatorio del Roque de los Muchachos, La Palma, Spain. The target is found ~1 magnitude brighter than its quiescence level of R=22.48 +- 0.07 as reported in Zurita et al.

  20. A Survey of Variable Extragalactic Sources with XTE's All Sky Monitor (ASM)

    NASA Technical Reports Server (NTRS)

    Jernigan, Garrett

    1998-01-01

    The original goal of the project was the near real-time detection of AGN utilizing the SSC 3 of the ASM on XTE which does a deep integration on one 100 square degree region of the sky. While the SSC never performed sufficiently well to allow the success of this goal, the work on the project has led to the development of a new analysis method for coded aperture systems which has now been applied to ASM data for mapping regions near clusters of galaxies such as the Perseus Cluster and the Coma Cluster. Publications are in preparation that describe both the new method and the results from mapping clusters of galaxies.

  1. Corrected Name for 5.54 s Pulsar: XTE J1810-197

    NASA Astrophysics Data System (ADS)

    Swank, J. H.; Markwardt, C. B.; Ibrahim, A. I.

    2003-07-01

    In ATEL 167, we reported the position of a new source as R.A. = 18h10.9m, Decl. = -19o42' (equinox 2000.0) , with estimated 99% confidence semi-major axes of 5' in R.A. and 7' in Decl. We designated the new pulsar as XTE J1811-197. The same name appeared in CBET 36. It was brought to our attention by Dr. Marion Schmitz, head of the IAU Working Group on Designations, that the name did not follow the specifications of the IAU, which can be found at: http://cdsweb.u-strasbg.fr/iau-spec.html.

  2. 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)

  3. 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.

  4. Optical outburst of the B[e]/X-Ray system CI Cam/XTE J0421+560

    NASA Astrophysics Data System (ADS)

    Wijngaarden, M. J. P.; Gourdji, K.; Oostrum, L. C.; Henrichs, H. F.

    2016-10-01

    We report a very strong optical outburst of the B[e]/transient X-ray system CI Cam/XTE J0421+560. On 2016 Oct 09.064 we measured H alpha at 80 times the continuum flux level, similar to the previous reported outbursts in 1998 (Hynes et al., 2002) and 2005 (Yan et al., 2007).

  5. Doppler tomography of XTE J1118+480 revealing chromospheric emission from the secondary star

    NASA Astrophysics Data System (ADS)

    Zurita, C.; González Hernández, J. I.; Escorza, A.; Casares, J.

    2016-08-01

    Doppler tomography of emission lines in low-mass X-ray binaries allows us to investigate the structure and variability of the accretion discs as well as possible activity arising from the secondary stars. We present Doppler maps of the black hole binary XTE J1118+480 from spectra obtained using OSIRIS@GTC during quiescence on four different nights in 2011 and 2012. Doppler imaging of the Hα line shows, for the first time, a narrow component from the secondary star with observed equivalent widths varying in the range 1.2-2.9 Å but not correlated with the veiling of the accretion disc. The Hα flux of the secondary star is too large to be powered by X-ray irradiation, supporting chromospheric activity, possibly induced by rapid rotation, as the most likely origin of this feature in the black hole X-ray binary XTE J1118+480. In addition, we detect variations in the centroid of the Hα line on nightly basis. These are likely caused by a precessing accretion disc, although with a much lower amplitude (˜50 km s-1) than previously observed.

  6. 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.

  7. The variable spin-down rate of the transient magnetar XTE J1810-197

    NASA Astrophysics Data System (ADS)

    Pintore, Fabio; Bernardini, Federico; Mereghetti, Sandro; Esposito, Paolo; Turolla, Roberto; Rea, Nanda; Coti Zelati, Francesco; Israel, Gian Luca; Tiengo, Andrea; Zane, Silvia

    2016-05-01

    We have analysed XMM-Newton and Chandra observations of the transient magnetar XTE J1810-197 spanning more than 11 yr, from the initial phases of the 2003 outburst to the current quiescent level. We investigated the evolution of the pulsar spin period and we found evidence for two distinct regimes: during the outburst decay, dot{ν } was highly variable in the range -(2-4.5) × 10-13 Hz s-1, while during quiescence the spin-down rate was more stable at an average value of -1 × 10-13 Hz s-1. Only during ˜3000 d (from MJD 54165 to MJD 56908) in the quiescent stage it was possible to find a phase-connected timing solution, with dot{ν }=-4.9× 10^{-14} Hz s-1, and a positive second frequency derivative, ddot{ν }=1.8× 10^{-22} Hz s-2. These results are in agreement with the behaviour expected if the outburst of XTE J1810-197 was due to a strong magnetospheric twist.

  8. 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.

  9. CORRELATIONS IN HORIZONTAL BRANCH OSCILLATIONS AND BREAK COMPONENTS IN XTE J1701-462 AND GX 17+2

    SciTech Connect

    Bu, Qing-cui; Chen, Li; Zhang, Liang; Li, Zhao-sheng; Qu, Jin-lu; Belloni, T. M. E-mail: chenli@bnu.edu.cn E-mail: tomaso.belloni@brera.inaf.it

    2015-01-20

    We studied the horizontal branch oscillations (HBO) and the band-limited components observed in the power spectra of the transient neutron star low-mass X-ray binary XTE J1701-462 and the persistent ''Sco-like'' Z source GX 17+2. These two components were studied based on the state-resolved spectra. We found that the frequencies of XTE J1701-462 lie on the known correlations (WK and PBK), showing consistency with other types of X-ray binaries (black holes, atoll sources, and millisecond X-ray pulsars). However, GX 17+2 is shifted from the WK correlation like other typical Z sources. We suggest that the WK/PBK main track forms a boundary that separates persistent sources from transient sources. The characteristic frequencies of break and HBO are independent of accretion rate in both sources, though it depends on spectral models. We also report the energy dependence of the HBO and break frequencies in XTE J1701-462 and how the temporal properties change with spectral state in XTE J1701-462 and GX 17+2. We studied the correlation between rms at the break and the HBO frequency. We suggest that HBO and break components for both sources probably arise from a similar physical mechanism: Comptonization emission from the corona. These two components could be caused by the same kind of oscillation in a corona with uneven density, and they could be generated from different areas of the corona. We further suggest that different proportions of the Comptonization component in the total flux cause the different distribution between GX 17+2 and XTE J1701-462 in the rms{sub break}-rms{sub HBO} diagram.

  10. Tuning the composition of ternary Bi2Se3xTe3(1-x) nanoplates and their Raman scattering investigations

    NASA Astrophysics Data System (ADS)

    Wu, Peng; Chen, Haiping; Yang, Chao; Gan, Wei; Muhammad, Zahir; Song, Li

    2016-07-01

    We present the composition engineering and Raman scattering study of Bi2Se3xTe3(1-x) nanoplates that were synthesized by chemical vapor deposition method using different substrates, including fluorophlogopite mica, SiO2/Si. The characterizations revealed high crystallinity and layered-structure in the ternary Bi2Se3xTe3(1-x) products. Raman spectra of Bi2Se3xTe3(1-x) ranging from 80-200 cm-1 as a function of different Se-doping levels shows that intrinsic Raman peaks of Bi2Se3xTe3(1-x) nanoplates shift to higher frequency as the ratio of doped-Se increasing. The discontinuity of Raman peaks was found and discussed.

  11. Detection of a Relativistic Outflow from the Galactic Microquasar GRS 1758-258 in the Hard State

    NASA Astrophysics Data System (ADS)

    Reynolds, Mark; Miller, Jon; Cackett, Edward; King, Ashley

    2016-07-01

    Outflows in the form of collimated jets and wider angle winds are observed ubiquitously from accreting systems. Herein, we present the results of a Suzaku observation of the persistent Galactic microquasar GRS 1758-258 at a luminosity of ˜1% L_{Edd}. Spectral analysis reveals the presence of an absorption feature at an energy of ˜7.5 keV, consistent with the presence of a relativistic outflow (v ˜0.1c). Photo-ionization modeling with XSTAR finds this wind to be highly ionized consistent with absorption by Fe XXVI at a distance of ˜2700 R_g from the black hole. This is the highest velocity wind detected from a stellar mass black hole accretion flow to date, and represents the first detection of a photo-ionized outflow in the hard spectral state, demonstrating the persistent of the wind outflow mechanism down to luminosities of at least 1% L_{Edd}.

  12. 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.

  13. Infrared study of H 1743-322 in outburst: a radio-quiet and NIR-dim microquasar

    NASA Astrophysics Data System (ADS)

    Chaty, S.; Muñoz Arjonilla, A. J.; Dubus, G.

    2015-05-01

    Context. Microquasars are accreting Galactic sources that are commonly observed to launch relativistic jets. One of the most important issues regarding these sources is the energy budget of ejections relative to the accretion of matter. Aims: The X-ray binary, black hole candidate, and microquasar H 1743-322 exhibited a series of X-ray outbursts between 2003 and 2008. We took optical and near-infrared (OIR) observations with the ESO/NTT telescope during three of these outbursts (2003, 2004, and 2008). The goals of these observations were to investigate the presence of a jet, and to disentangle the various contributions constituting the spectral energy distribution (SED): accretion, ejection, and stellar emission. Methods: Photometric and spectroscopic OIR observations allowed us to produce a high time-resolution lightcurve in Ks-band, to analyze emission lines present in the IR spectra, to construct a multiwavelength SED including radio, IR, and X-ray data, and to complete the OIR vs. X-ray correlation of black hole binaries with H 1743-322 data points. Results: We detect rapid flares of duration ~5 min in the high time-resolution IR lightcurve. We identify hydrogen and helium emission lines in the IR spectra, coming from the accretion disk. The IR SED exhibits the spectral index typically associated with the X-ray high, soft state in our observations taken during the 2003 and 2004 outbursts, while the index changes to one that is typical of the X-ray low, hard state during the 2008 outburst. During this last outburst, we detected a change of slope in the NIR spectrum between the J and Ks bands, where the JH part is characteristic of an optically thick disk emission, while the HKs part is typical of optically thin synchrotron emission. Furthermore, the comparison of our IR data with radio and X-ray data shows that H 1743-322 exhibits a faint jet both in radio and NIR domains. Finally, we suggest that the companion star is a late-type main sequence star located in

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

    PubMed

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

    2010-07-01

    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. PMID:20613836

  15. 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.

  16. Multiwavelength observations of black hole and neutron star X-ray binaries

    NASA Astrophysics Data System (ADS)

    Jain, Raj Kumar

    X-ray novae (XNe) are binary systems in which matter is transferred from the companion star onto the compact object through an accretion flow. Besides providing the most compelling evidence for the existence of black holes, XNe present rare opportunities to test general relativity in the strong field limit. Multiwavelength observations, and in particular the correlated features of the multiwavelength light curves, lead to unique information about the accretion geometry, underlying radiative mechanisms, and relevant physical time-scales. The goal of this thesis is to provide extensive multiwavelength observations of XNe, covering entire outburst cycles, which present quantitative challenges to existing theories. By using instruments designed to conduct long term monitoring of XNe, namely the Rossi X ray Timing Explorer (RXTE) satellite and the Yale 1-m telescope (operated by the YALO consortium), we closely studied a black hole XN XTE J1550-564 and a neutron star XN Aquila X-1 in the optical/IR and X-ray wavelengths. We discovered the optical counterpart of XTE J1550 564, measured a preliminary value for its orbital period, detected several correlations and delays between features in the optical and X-ray light, and obtained the first extensive IR light curve from a black hole XN covering an entire outburst cycle. Similarly, we found delays and correlations in the light curves of Aquila X-1. Periodic signatures were found throughout the outburst. Contrary to prior knowledge, we find a ˜2% shorter period during the outburst rise, compared to the value during full outburst. We have also succeeded, for the first time, in triggering pointed RXTE observations of an XN based on the detection of the optical outburst, which typically precedes the X-ray outburst by a week or so. We proposed qualitative explanations for these observations, which, in the absence of detailed theoretical models, serves as a starting point for further theoretical endeavors. The outburst optical

  17. Gamma-ray polarization in accreting black holes: the case of XTE J1118+480

    NASA Astrophysics Data System (ADS)

    Vieyro, Florencia; Chaty, Sylvain; Romero, Gustavo E.

    2016-07-01

    Several black hole binaries (BHBs) present persistent soft gamma-ray emission (up to E ˜MeV). Although different models have been proposed to explain the origin of this component (non-thermal corona, relativistic jets), its nature still remains unknown. The detection of strong polarization at high-energies in the well-studied system Cygnus X-1 provides new constraints on the emitting region of the radiation. In this work we study the case of the BHB XTE J1118+480, a transient source that has been observed during two outbursts. In both cases multiwavelenght observations could be obtained because of the privileged location of the source, which implies low interstellar absorption. We apply a non-thermal lepto-hadronic coronal model to reproduce the X/γ-ray emission of this BHB during its outburts, and study the polarization of high-energy radiation expected for future episodes.

  18. 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.

  19. 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.

  20. Chemical analysis of anodic oxide layers based on Hg/sub 1-x/Cd/sub x/Te

    SciTech Connect

    Korsak, T.E.

    1987-02-01

    The goal of this work is to study the application of the photometric method in analyzing the composition of Hg/sub 1-x/Cd/sub x/Te solid solution anodic oxide with high accuracy and without preliminary separation of the elements. In order to determine cadmium content, a photometric measurement on a complex of this element with xylenol orange was used. Mercury concentration was determined using an extraction photometric method based on benzene extraction of chloride complexes of mercury anions with crystal violet. Tellurium content was determined by extraction with dichloroethane of bromide complexes of tellurium with diantipyrylpropylmethane. The authors synthesized diantipyrylpropylmethane as described. They studied single crystal Hg/sub 1-x/Cd/sub x/Te samples of random orientation with x = 0.2 and n-type conductivity.

  1. 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.

  2. 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.

  3. Optical second-harmonic imaging of Pb{sub x}Cd{sub 1-x}Te ternary alloys

    SciTech Connect

    Scheidt, T.; Rohwer, E.G.; Bergmann, H.M. von; Saucedo, E.; Dieguez, E.; Fornaro, L.; Stafast, H.

    2005-05-15

    We employ femtosecond laser pulses (80 fs, 1.59 eV, and 80 MHz) to study the optical second-harmonic (SH) response of Pb{sub x}Cd{sub 1-x}Te ternary alloys (x about 0.2) grown by the vertical Bridgman method. The alloy segregates into a Pb-rich and a Cd-rich phase, the latter dominating the SH response of the ternary alloy by at least two orders of magnitude. Several sample regions show a regular layer-by-layer accommodation of the Pb-rich and Cd-rich phases as seen by a periodic alternation of the alloy's SH response on a {approx}10-{mu}m length scale. Furthermore, we employ polarization-resolved SH imaging as well as SH imaging at different azimuthal angles to obtain spatially resolved mappings of the sample, which are sensitive to the composition as well as the growth orientation of the Pb{sub x}Cd{sub 1-x}Te material system. We observe an azimuthal phase shift of approximately 30 deg. between coherent macroscopic regions (several mm{sup 2}) in the Cd-rich phase of the ternary alloy. We interpret these regions as large area crystalline grains of (111) and (411) crystal orientations and approximately equal composition. Hence, SH imaging is shown to spatially resolve regions of different growth directions within the Pb{sub x}Cd{sub 1-x}Te sample.

  4. Structural and chemical analysis of grain boundaries and tellurium precipitates in commercial Cd{sub 1{minus}x}Zn{sub x}Te

    SciTech Connect

    Heffelfinger, J.R.; Medlin, D.L.; James, R.B.

    1998-06-01

    The structure and chemistry of grain boundaries in commercial Cd{sub 1{minus}x}Zn{sub x}Te, prepared by the high-pressure Bridgman technique, have been analyzed using transmission electron microscopy, scanning electron microscopy, infrared-light microscopy and visible-light microscopy. These analyses show that the grain boundaries inside the Cd{sub 1{minus}x}Zn{sub x}Te materials are decorated with tellurium precipitates. Analysis of a tellurium precipitate at a grain boundary by transmission electron microscopy and selected-area electron diffraction found the precipitate to consist of a single, saucer-shaped grain. Electron diffraction from the precipitate was consistent with the trigonal phase of tellurium (space group P3{sub 1}21), which is the equilibrium phase at room temperature and atmospheric pressure. This precipitate was found to be aligned with one of the adjacent CZT grains such that the tellurium (0{bar 1}11) planes were nearly parallel to the CZT (111) planes. High-resolution transmission electron microscopy of the Te/Cd{sub 1{minus}x}Zn{sub x}Te interface showed no tertiary phase at the interface. The structures of the grain boundaries and the Te/Cd{sub 1{minus}x}Zn{sub x}Te interface are discussed and related to their possible implications on Cd{sub 1{minus}x}Zn{sub x}Te gamma-ray detector performance.

  5. Fermi arc electronic structure and Chern numbers in the type-II Weyl semimetal candidate MoxW1 -xTe2

    NASA Astrophysics Data System (ADS)

    Belopolski, Ilya; Xu, Su-Yang; Ishida, Yukiaki; Pan, Xingchen; Yu, Peng; Sanchez, Daniel S.; Zheng, Hao; Neupane, Madhab; Alidoust, Nasser; Chang, Guoqing; Chang, Tay-Rong; Wu, Yun; Bian, Guang; Huang, Shin-Ming; Lee, Chi-Cheng; Mou, Daixiang; Huang, Lunan; Song, You; Wang, Baigeng; Wang, Guanghou; Yeh, Yao-Wen; Yao, Nan; Rault, Julien E.; Le Fèvre, Patrick; Bertran, François; Jeng, Horng-Tay; Kondo, Takeshi; Kaminski, Adam; Lin, Hsin; Liu, Zheng; Song, Fengqi; Shin, Shik; Hasan, M. Zahid

    2016-08-01

    It has recently been proposed that electronic band structures in crystals can give rise to a previously overlooked type of Weyl fermion, which violates Lorentz invariance and, consequently, is forbidden in particle physics. It was further predicted that MoxW1 -xTe2 may realize such a type-II Weyl fermion. Here, we first show theoretically that it is crucial to access the band structure above the Fermi level ɛF to show a Weyl semimetal in MoxW1 -xTe2 . Then, we study MoxW1 -xTe2 by pump-probe ARPES and we directly access the band structure >0.2 eV above ɛF in experiment. By comparing our results with ab initio calculations, we conclude that we directly observe the surface state containing the topological Fermi arc. We propose that a future study of MoxW1 -xTe2 by pump-probe ARPES may directly pinpoint the Fermi arc. Our work sets the stage for the experimental discovery of the first type-II Weyl semimetal in MoxW1 -xTe2 .

  6. Radio Disappearance of the Magnetar XTE J1810-197 and Continued X-ray Timing

    NASA Astrophysics Data System (ADS)

    Camilo, F.; Ransom, S. M.; Halpern, J. P.; Alford, J. A. J.; Cognard, I.; Reynolds, J. E.; Johnston, S.; Sarkissian, J.; van Straten, W.

    2016-04-01

    We report on timing, flux density, and polarimetric observations of the transient magnetar and 5.54 s radio pulsar XTE J1810-197 using the Green Bank, Nançay, and Parkes radio telescopes beginning in early 2006, until its sudden disappearance as a radio source in late 2008. Repeated observations through 2016 have not detected radio pulsations again. The torque on the neutron star, as inferred from its rotation frequency derivative \\dot{ν }, decreased in an unsteady manner by a factor of three in the first year of radio monitoring, until approximately mid-2007. By contrast, during its final year as a detectable radio source, the torque decreased steadily by only 9%. The period-averaged flux density, after decreasing by a factor of 20 during the first 10 months of radio monitoring, remained relatively steady in the next 22 months, at an average of 0.7 ± 0.3 mJy at 1.4 GHz, while still showing day-to-day fluctuations by factors of a few. There is evidence that during this last phase of radio activity the magnetar had a steep radio spectrum, in contrast to earlier flat-spectrum behavior. No secular decrease presaged its radio demise. During this time, the pulse profile continued to display large variations; polarimetry, including of a new profile component, indicates that the magnetic geometry remained consistent with that of earlier times. We supplement these results with X-ray timing of the pulsar from its outburst in 2003 up to 2014. For the first 4 years, XTE J1810-197 experienced non-monotonic excursions in frequency derivative by at least a factor of eight. But since 2007, its \\dot{ν } has remained relatively stable near its minimum observed value. The only apparent event in the X-ray record that is possibly contemporaneous with the radio shutdown is a decrease of ≈20% in the hot-spot flux in 2008-2009, to a stable, minimum value. However, the permanence of the high-amplitude, thermal X-ray pulse, even after the (unexplained) radio demise, implies

  7. 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.

  8. 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.

  9. RXTE Spectral Study of the New X-ray Transient XTE J1859+226

    NASA Astrophysics Data System (ADS)

    Focke, W. B.; Markwardt, C. B.; Swank, J. H.; Taam, R. E.

    1999-12-01

    The transient galactic black hole candidate XTE J1859+226 was discovered by the RXTE All Sky Monitor (ASM) on 1999 October 9, within a day after its outburst began. Pointed observations with RXTE began on 1999 October 10.57, and continued at a rate of about twice per day. Preliminary results of fits to PCA and HEXTE spectra for October 9--14 show that a simple absorbed powerlaw is insufficient to model the data. The fit is greatly improved by using an absorbed cutoff powerlaw with reflection. The photon index rose from 1.8 on October 9 to 3.2 on October 14. The cutoff energy started near 100 keV, dropped to 50 keV, then rose to an undetectable level between October 12.86 and October 13.11, potentially indicating a state change. We will present spectral analysis of these and later data, along with comparison of the spectral and timing properties. This work was funded by NASA.

  10. 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.

  11. Comparative study of Hg xCd 1-xTe films grown on CdTe thin films previously deposited from two different techniques

    NASA Astrophysics Data System (ADS)

    Ali, A.; Abbas Shah, N.; Maqsood, A.

    2009-04-01

    High quality cadmium telluride (CdTe) thin films were grown on glass substrates with two different techniques, two evaporation source (TES) and closed space sublimation (CSS). Further to the above mercury telluride (HgTe) was then deposited by using single source on both CdTe thin films for obtaining Hg xCd 1-xTe samples. The crystalline structure of the Hg xCd 1-xTe sample grown from CSS-CdTe showed the preferential (1 1 1) orientation with smoother and larger grain size than those of TES-CdTe. The optical transmission for TES-CdTe sample was above 90% in the 1000-1500 nm range whereas it was significantly below 80% for CSS-CdTe sample. The optical transmission for TES-Hg xCd 1-xTe and CSS-Hg xCd 1-xTe was ˜60%. The resistivity at room temperature of TES-CdTe and CSS-CdTe was ˜3.33×10 9 Ω cm and ˜2.20×10 8 Ω cm, respectively, while the resistivity of TES-Hg xCd 1-xTe and CSS-Hg xCd 1-xTe samples was ˜1.73 Ω cm and ˜5.34×10 5 Ω cm, respectively. The comparative study of ternary compound prepared with the above techniques has been carried out for the first time.

  12. First Principles Calculations of Structural, Electronic, Thermodynamic and Thermal Properties of BaxSr1-xTe Ternary Alloys

    NASA Astrophysics Data System (ADS)

    Chelli, S.; Meradji, H.; Amara Korba, S.; Ghemid, S.; El Haj Hassan, F.

    2014-12-01

    The structural, electronic thermodynamic and thermal properties of BaxSr1-xTe ternary mixed crystals have been studied using the ab initio full-potential linearized augmented plane wave (FP-LAPW) method within density functional theory (DFT). In this approach, the Perdew-Burke-Ernzerhof-generalized gradient approximation (PBE-GGA) was used for the exchange-correlation potential. Moreover, the recently proposed modified Becke Johnson (mBJ) potential approximation, which successfully corrects the band-gap problem was also used for band structure calculations. The ground-state properties are determined for the cubic bulk materials BaTe, SrTe and their mixed crystals at various concentrations (x = 0.25, 0.5 and 0.75). The effect of composition on lattice constant, bulk modulus and band gap was analyzed. Deviation of the lattice constant from Vegard's law and the bulk modulus from linear concentration dependence (LCD) were observed for the ternary BaxSr1-xTe alloys. The microscopic origins of the gap bowing were explained by using the approach of Zunger and co-workers. On the other hand, the thermodynamic stability of these alloys was investigated by calculating the excess enthalpy of mixing, ΔHm as well as the phase diagram. It was shown that these alloys are stable at high temperature. Thermal effects on some macroscopic properties of BaxSr1-xTe alloys were investigated using the quasi-harmonic Debye model, in which the phononic effects are considered.

  13. 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.

  14. 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.

  15. 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.

  16. The Influence of Sublimated Aluminium Films on the Properties of Real Cdx Hg1-xTe Surface

    NASA Astrophysics Data System (ADS)

    Guseinov, Emil; Ismailov, Namýk; Tezer, Ateþ

    1996-05-01

    The electron properties of the Al-Cdx Hg1-x Te interface have been studied using conventional C-V, I-V measurements, spectral dependece of the photoconductivity, capacitor photolocomitive force and the photoelectromagnetic effect. A significant change of the spectral dependence of photoconductivity and the surface lifetime of charge carriers in Cdx Hg1-xTe samples covered by aluminium films has been revealed. The results obtained were interpreted by the influence of space charge region (SCR) on the photoconductivity.

  17. XTE J1752-223: a new RXTE and Swift detected X-ray transient in the galactic center region

    NASA Astrophysics Data System (ADS)

    Markwardt, C. B.; Swank, J. H.; Barthelmy, S. D.; Baumgartner, W. H.; Burrows, D. N.; Evans, P. A.; Holland, S. T.; Hoversten, E. A.; Page, K. L.

    2009-10-01

    On 2009-10-23 at 19:55 UT, RXTE discovered a new source while scanning the galactic bulge region, designated XTE J1752-223. Based on the existing PCA scan data, the best fit position is, R.A. = 268.05(16), Dec. = -22.31(4) (J2000), with estimated 95% uncertainty of the final digits shown in parentheses. The 2-10 keV flux of the source at that time was about 30 mCrab. In the past six months, no source has been detected at that position with 95% upper limit of about 1 mCrab.

  18. Terahertz radiation from Cd{sub x}Hg{sub 1-x}Te photoexcited by femtosecond laser pulses

    SciTech Connect

    Krotkus, A.; Adomavicius, R.; Molis, G.; Urbanowicz, A.; Eusebe, H.

    2004-10-01

    Terahertz radiation from Cd{sub x}Hg{sub 1-x}Te samples excited by femtosecond Ti:sapphire laser pulses were measured by using an ultrafast photoconductive antenna manufactured from low-temperature grown GaAs. Terahertz fields radiated by the samples of all three investigated alloy compositions with x=0, 0.2, and 0.3 were of the same order of magnitude. No azimuthal angle dependence of the radiated signal was detected, which evidences that linear current surge effect is dominating over nonlinear optical rectification.

  19. 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.

  20. 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.

  1. Black holes in GRBs, Binary X-ray sources and Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Ruffini, Remo; Patricelli, Barbara; Grazia Bernardini, Maria; Bianco, Carlo Luciano; Caito, Letizia; de Barros, Gustavo; Izzo, Luca

    Gamma Ray Bursts are possibly the most important tools to study the Physics of Black Holes (BHs), evidencing instantaneous BH formation occurring at the highest redshifts. Such pro-cesses of BH formation with distinctive processes of electron-positron pair creation by vacuum polarization are expected to be different from the ones observed in nearby binary X-ray sources (Cygnus X-1, GX 339-4, 4U 1543-47, XTE J1550-564, XTE J1650-500, H 1743-322 and XTE J1859-226). These last ones should in fact originate from precursors activity acting on much longer time scales, due to accretion mechanisms. We have studied high redshift GRB sources within the fireshell model to infer some of the properties of the BHs from which they originate. Here we present, as an example, the analysis of GRB 050904, characterized by a redshift z=6.3 and an isotropic energy release of Eiso = 1.04x1054 ergs, and of GRB090423, characterized by z = 8.1 and Eiso = 3.4x1053 ergs.We have searched for low redshift GRB sources having similar properties: same energetics, similar light curve structure, intense optical emission. The "twin sources" of these two bursts 0.937) and GRB090618 (z = 0.54) respectively. For both pairs of GRBs the numerical simulations that best repr positron plasma originating the GRB, as well as the same comoving spectral energy distribution. However, we h ncbm > .This could indicate that the two sources of each pair have a similar baryon ic progenitor, but occurred in d 109 sola rmasses. A viable approach based on the Dark Matter component versus the baryon ic component are being

  2. 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.

  3. 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.

  4. Influence of soft X-ray of a vacuum spark with laser initiation on the surface properties of solid solutions CdXHg1-XTe

    NASA Astrophysics Data System (ADS)

    Ananyin, O. B.; Bogdanov, G. S.; Vovchenko, E. D.; Gerasimov, I. A.; Melekhov, A. P.; Krapiva, P. S.; Novikov, I. K.; Ramakoti, R. S.; Sredin, V. G.

    2016-09-01

    At a certain form of broadband source soft X-ray spectrum is expected to achieve selective radiation exposure to one of the elements of a multi-component material CdXHg1-XTe. In this case we can talk about a change of the surface properties of the substance as a result of selective absorption of soft X-rays.

  5. Topological crystalline insulator Pb{sub x}Sn{sub 1-x}Te thin films on SrTiO{sub 3} (001) with tunable Fermi levels

    SciTech Connect

    Guo, Hua; Liu, Jun-Wei; Wang, Zhen-Yu; Wu, Rui; Ji, Shuai-Hua; Duan, Wen-Hui; Chen, Xi Xue, Qi-Kun; Yan, Chen-Hui; Zhang, Zhi-Dong; Wang, Li-Li; He, Ke; Ma, Xu-Cun

    2014-05-01

    In this letter, we report a systematic study of topological crystalline insulator Pb{sub x}Sn{sub 1-x}Te (0 < x < 1) thin films grown by molecular beam epitaxy on SrTiO{sub 3}(001). Two domains of Pb{sub x}Sn{sub 1-x}Te thin films with intersecting angle of α ≈ 45° were confirmed by reflection high energy diffraction, scanning tunneling microscopy, and angle-resolved photoemission spectroscopy (ARPES). ARPES study of Pb{sub x}Sn{sub 1-x}Te thin films demonstrated that the Fermi level of PbTe could be tuned by altering the temperature of substrate whereas SnTe cannot. An M-shaped valance band structure was observed only in SnTe but PbTe is in a topological trivial state with a large gap. In addition, co-evaporation of SnTe and PbTe results in an equivalent variation of Pb concentration as well as the Fermi level of Pb{sub x}Sn{sub 1-x}Te thin films.

  6. Ab initio calculations of structural, electronic, optical and thermodynamic properties of alkaline earth tellurides BaxSr1-XTe

    NASA Astrophysics Data System (ADS)

    Bahloul, B.; Bentabet, A.; Amirouche, L.; Bouhadda, Y.; Bounab, S.; Deghfel, B.; Fenineche, N.

    2014-03-01

    Structural, electronic and thermodynamic properties of SrTe and BaTe compounds and their ternary mixed crystals BaxSr1-xTe in the rock-salt structure have been studied with density functional theory (DFT), whereas the optical properties have been obtained by using empirical methods such as the modified Moss relation. The exchange-correlation potential was calculated using the generalized gradient approximation (GGA) of Perdew-Burke-Ernzerhof (PBE) and the local density approximation (LDA) of Teter-Pade (TP). In the present work, we used the virtual-crystal approximation (VCA) to study the effect of composition (x). The calculated lattice parameters at equilibrium volume and the bulk modulus for x=0 and x=1 are in good agreement with the literature data. Furthermore, the BaxSr1-xTe alloys are found to be an indirect band gap semiconductor. In addition, we have also predicted the heat capacities (CV), the entropy(S), the internal energy (U) and the Helmholtz free energy (F) of the parent compounds SrTe and BaTe.

  7. Investigation of InSb-In2XTe (X =Ge & Sn) pseudo binary alloys as potential thermoelectric materials

    NASA Astrophysics Data System (ADS)

    Ponnambalam, Vijayabarathi; Morelli, Donald T.

    2015-03-01

    Crystallizing in the zinc blende structure, InSb is known for promising thermoelectric properties with carrier mobility as high as ~ 104 cm2/V s at 300 K. However, the main drawback is its exceptionally high thermal conductivity ~ 20 W/m K at 300 K. In this regard, pseudo binaries InSb-In2XTe (X =Ge & Sn) hold the promise of offering reduced thermal conductivity while maintaining the other thermoelectric properties intact. A series of InSb-In2XTe type alloys has been synthesized. Thermal and electrical transport properties have been studied, and the results will be discussed with an emphasis on how the thermal conductivity is affected by the concentration of solute atoms. This work was supported as part of the Center for Revolutionary Materials for Solid State Energy Conversion, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001054.

  8. 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

    2016-01-01

    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. PMID:26875819

  9. 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.

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

    NASA Astrophysics Data System (ADS)

    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.

    2016-02-01

    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 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 MoxW1-xTe2, where non-saturating magneto-resistance and pressure-driven superconductivity have been observed.

  11. Long-Term Spectral and Timing Behavior of the Black Hole Candidate XTE J1908+094

    NASA Technical Reports Server (NTRS)

    Gogus, Ersin; Finger, Mark H.; Kouveliotou, Chryssa; Woods, Peter M.; Patel, Sandeep K.; Ruppen, Michael; Swank, Jean H.; Markwardt, Craig B.; VanDerKlis, Michiel

    2004-01-01

    We present the long-term X-ray light curves and detailed spectral and timing analyses of XTE J1908+094 using the Rossi X-Ray Timing Explorer Proportional Counter Array observations covering two outbursts in 2002 and early 2003. At the onset of the first outburst, the source was found in a spectrally low/hard state lasting for approx.40 days, followed by a 3 day long transition to the high/soft state. The source flux (in 2- 10 keV) reached approx.100 mcrab on 2002 April 6, then decayed rapidly. In power spectra, we detect strong band-limited noise and varying low- frequency quasi-periodic oscillations that evolved from approx.0.5 to approx.5 Hz during the initial low/hard state of the source. We find that the second outburst closely resembled the spectral evolution of the first. The X-ray transient s overall outburst characteristics led us to classify XTE J1908+094 as a black hole candidate. Here we also derive precise X-ray position of the source using Chandra observations that were performed during the decay phase of the first outburst and following the second outburst.

  12. Type I X-ray Bursts from the Neutron-star Transient XTE J1701-462

    NASA Astrophysics Data System (ADS)

    Lin, Dacheng; Altamirano, Diego; Homan, Jeroen; Remillard, Ronald A.; Wijnands, Rudy; Belloni, Tomaso

    2009-07-01

    The neutron-star X-ray transient XTE J1701-462 was observed for ~3 Ms with RXTE during its 2006-2007 outburst. Here we report on the discovery of three type-I X-ray bursts from XTE J1701-462. They occurred as the source was in transition from the typical Z-source behavior to the typical atoll-source behavior, at ~10% of the Eddington luminosity. The first burst was detected in the Z-source flaring branch (FB); the second in the vertex between the FB and normal branches; and the third in the atoll-source soft state. The detection of the burst in the FB cast doubts on earlier speculations that the FB is due to unstable nuclear burning of accreted matter. The last two of the three bursts show photospheric radius expansion, from which we estimate the distance to the source to be 8.8 kpc with a 15% uncertainty. No significant burst oscillations in the range 30-4000 Hz were found during these three bursts.

  13. Enhancement of the crystalline electric field by the conduction electrons in TmxLa1-xTe

    NASA Astrophysics Data System (ADS)

    Matsumura, T.; McEwen, K. A.; Eccleston, R. S.; Suzuki, T.

    2002-09-01

    The physical properties of TmxLa1-xTe for x=0.05 and 0.5 have been investigated by electrical resistivity, magnetic susceptibility, magnetization, and specific heat measurements and by inelastic neutron scattering. It is shown that the Tm ion experiences a large crystalline electric field (CEF) in a metallic environment at a low concentration of x=0.05. The level scheme for x=0.05 is determined to be Γ7-Γ8(10 meV)-Γ6(17.6 meV) by neutron scattering, which is consistent with the bulk properties. However, this scheme is completely opposite to the one predicted from the point charge model. Furthermore, since the Tm ions in an insulating system of TmxYb1-xTe do not show such a big CEF, the present result indicates that the conduction electrons play an important role in determining the strength of the CEF. The Γ7-->Γ8 excitation is split into some peaks. This is associated with the local structure around the Tm ions: when the number of other Tm ions in the first-nearest-neighbor rare-earth sites increases, the excitation energy decreases. At x=0.5, the CEF excitation disappears and only a broad quasielastic scattering is observed. The excitation spectrum is only reproduced by two Gaussian spectral functions both centered at zero energy.

  14. Reflection Spectroscopy of the Black Hole Binary XTE J1752-223 in the Bright Hard State

    NASA Astrophysics Data System (ADS)

    Garcia, Javier; Steiner, James F.; Grinberg, Victoria; McClintock, Jeffrey E.; Dauser, Thomas; Remillard, Ronald A.

    2016-04-01

    During its rise to maximum in 2009, XTE J1752-223 stalled for a full month in the bright hard state at about 30% of its peak (Eddington) luminosity. Along this extended period, 60 RXTE pointed observations showed the luminosity and hardness ratio of the source to be extraordinarily stable, resulting in a unique data set of exceptional quality. We combined all these 300 ks of RXTE data into a single PCA (3-45 keV) spectrum with 82 million counts and a single HEXTE spectrum (20-250 keV) with 10.4 million counts. Using our calibration tools PCACORR and HEXBCORR, we greatly enhanced the sensitivity of the detectors to faint spectral features, such as the Fe line and edge. Fitting the PCA+HEXTE spectrum using an advanced version of our reflection code, which includes a physical model of Comptonization, we constrained: the spin of the black hole (or alternatively the inner radius of the accretion disk); the inclination of the system; the ionization state and Fe abundance of the disk's atmosphere; and the temperature and optical depth of the corona. We compare these results with similar ones we reported earlier for GX 339-4 in the bright hard state. XTE J1752-223 and GX 339-4 are the first two of 29 black hole binaries we propose to study using recalibrated RXTE archival data and our reflection models.

  15. An XMM-Newton view of the dipping low-mass X-ray binary XTE J1710-281

    NASA Astrophysics Data System (ADS)

    Younes, G.; Boirin, L.; Sabra, B.

    2009-08-01

    Context: Studying the spectral changes during the dips exhibited by almost edge-on, low-mass X-ray binaries (LMXBs) is a powerful means of probing the structure of accretion disks. The XMM-Newton, Chandra, or Suzaku discovery of absorption lines from Fe xxv and other highly-ionized species in many dippers has revealed a highly-ionized atmosphere above the disk. A highly (but less strongly) ionized plasma is also present in the vertical structure causing the dips, together with neutral material. Aims: We aim to investigate the spectral changes during the dips of XTE J1710-281, a still poorly studied LMXB known to exhibit bursts, dips, and eclipses. Methods: We analyze the archived XMM-Newton observation of XTE J1710-281 performed in 2004 that covered one orbital period of the system (3.8 h). We modeled the spectral changes between persistent and dips in the framework of the partial covering model and the ionized absorber approach. Results: The persistent spectrum can be fit by a power law with a photon index of 1.94±0.02 affected by absorption from cool material with a hydrogen column density of (0.401±0.007)×1022 cm-2. The spectral changes from persistent to deep-dipping intervals are consistent with the partial covering of the power-law emission. Twenty-six percent of the continuum is covered during shallow dipping, and 78% during deep dipping. The column density decreases from 77_-38+67 × 1022 cm-2 during shallow dipping to (14 ± 2) × 1022 cm-2 during the deep-dipping interval. We do not detect any absorption line from highly ionized species such as Fe xxv. However, the upper-limits we derive on their equivalent width (EW) are not constraining. Despite not detecting any narrow spectral signatures of a warm absorber, we show that the spectral changes are consistent with an increase in column density and a decrease in ionization state of a highly-ionized absorber, associated with an increase in column density of a neutral absorber, in agreement with the

  16. Crystallographic properties of as grown CdxHg1- xTe epitaxial layers deposited by cathodic sputtering

    NASA Astrophysics Data System (ADS)

    Roussille, R.

    Large areas (up to 15 cm 2) CdxHg1- xTe epitaxial layers with Cd composition ( x value) from 0.14 to 0.4 (thickness < 15 μm) have been sputtered on to CdTe substrates with [111] orientations. The layers are grown on substrates heated up to 200°C with a deposition rate of 0.6 μm/h. Crystallographic characterization has been carried out, using different techniques such as: reflection high energy electron diffraction (RHEED), reflection X-ray topography and transmission electron microscopy (TEM). RHEED patterns reveal a good crystallographic quality. X-ray topographies show that the substructure of the layer is very similar to that of the substrate. These results are confirmed by TEM observations.

  17. 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.

  18. Ferromagnetism in Ge{sub 1-x}Cr{sub x}Te epilayers grown by molecular beam epitaxy

    SciTech Connect

    Fukuma, Y.; Asada, H.; Taya, T.; Irisa, T.; Koyanagi, T.

    2006-10-09

    IV-VI ferromagnetic semiconductor Ge{sub 1-x}Cr{sub x}Te has been grown on BaF{sub 2} (111) by molecular beam epitaxy. The ferromagnetism was clearly established by direct magnetization and Hall measurements. The experimental correlation between the anomalous Hall resistivity {rho}{sub xy} and the resistivity {rho}{sub xx}, {rho}{sub xy}{proportional_to}{rho}{sub xx}{sup 1.76}, is understood from the semiclassical nature of the charge carrier dynamics, suggesting that the ferromagnetism gives rise to p-d exchange interaction. The Curie temperature increases systematically from the substrate temperature T{sub S} of 300 to 250 to 200 deg. C and with increasing the Cr composition along with each T{sub S}.

  19. The Variable Quiescent X-Ray Emission of the Neutron Star Transient XTE J1701-462

    NASA Astrophysics Data System (ADS)

    Fridriksson, Joel K.; Homan, J.; Wijnands, R.; Cackett, E. M.; Degenaar, N.; Mendez, M.; Altamirano, D.; Brown, E. F.; Belloni, T. M.; Lewin, W. H. G.

    2011-01-01

    We have monitored the cooling of the neutron star in the transient low-mass X-ray binary XTE J1701-462 with Chandra and XMM-Newton since the source entered quiescence in 2007 after an exceptionally luminous 19-month outburst. A recent Chandra observation made almost 1200 days into quiescence indicates that the neutron star crust is likely still slowly cooling toward thermal equilibrium with the core. The current surface temperature is high compared to other quiescent neutron star transients, with an implied bolometric thermal flux of 5×1033 erg/s. The overall cooling curve seems to have followed a broken power-law shape as predicted by theoretical models, although the observed break is considerably earlier than what is expected from theory. After rapid cooling during the first 200 days of quiescence---strongly indicating a highly conductive neutron star crust---the source unexpectedly showed a large temporary increase in both thermal and non-thermal flux. Prompted by this we conducted a Swift monitoring program of the source during April-October 2010, with short observations taking place once every two weeks. During the program we detected short-term flares up to at least 1×1035 erg/s, a factor of 20 higher than the normal quiescent level. We compare this flaring---presumably arising from episodic low-level accretion---with the behavior observed from faint Galactic transients, and discuss whether flaring in XTE J1701-462 can significantly affect the cooling of the source and whether it can to some extent explain the high temperature of the neutron star core implied by our Chandra observations.

  20. 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.

  1. Charge Mediated Reversible Metal-Insulator Transition in Monolayer MoTe2 and WxMo1-xTe2 Alloy.

    PubMed

    Zhang, Chenxi; Kc, Santosh; Nie, Yifan; Liang, Chaoping; Vandenberghe, William G; Longo, Roberto C; Zheng, Yongping; Kong, Fantai; Hong, Suklyun; Wallace, Robert M; Cho, Kyeongjae

    2016-08-23

    Metal-insulator transitions in low-dimensional materials under ambient conditions are rare and worth pursuing due to their intriguing physics and rich device applications. Monolayer MoTe2 and WTe2 are distinguished from other TMDs by the existence of an exceptional semimetallic distorted octahedral structure (T') with a quite small energy difference from the semiconducting H phase. In the process of transition metal alloying, an equal stability point of the H and the T' phase is observed in the formation energy diagram of monolayer WxMo1-xTe2. This thermodynamically driven phase transition enables a controlled synthesis of the desired phase (H or T') of monolayer WxMo1-xTe2 using a growth method such as chemical vapor deposition (CVD) and molecular beam epitaxy (MBE). Furthermore, charge mediation, as a more feasible method, is found to make the T' phase more stable than the H phase and induce a phase transition from the H phase (semiconducting) to the T' phase (semimetallic) in monolayer WxMo1-xTe2 alloy. This suggests that a dynamic metal-insulator phase transition can be induced, which can be exploited for rich phase transition applications in two-dimensional nanoelectronics. PMID:27415610

  2. 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. PMID:26524258

  3. ACCRETION TORQUES AND MOTION OF THE HOT SPOT ON THE ACCRETING MILLISECOND PULSAR XTE J1807-294

    SciTech Connect

    Patruno, Alessandro; Wijnands, R.; Van der Klis, Michiel; Hartman, Jacob M.; Chakrabarty, Deepto

    2010-07-10

    We present a coherent timing analysis of the 2003 outburst of the accreting millisecond pulsar (AMXP) XTE J1807-294. We find a 95% confidence interval for the pulse frequency derivative of (+0.7, + 4.7) x 10{sup -14} Hz s{sup -1} and (-0.6, + 3.8) x 10{sup -14} Hz s{sup -1} for the fundamental and second harmonics, respectively. The sinusoidal fractional amplitudes of the pulsations are the highest observed among AMXPs and can reach values of up to 27% (2.5-30 keV). The pulse arrival time residuals of the fundamental frequency follow a linear anti-correlation with the fractional amplitudes that suggests hot spot motion both in longitude and latitude over the surface of the neutron star. An anti-correlation between residuals and X-ray flux suggests an influence of the accretion rate on pulse phase and casts doubts on the interpretation of pulse frequency derivatives in terms of changes of spin rates and torques on the neutron star.

  4. Optical and Infrared Observations of the Black Hole X-Ray Binary XTE J1118+480

    NASA Astrophysics Data System (ADS)

    Gelino, D. M.; Balman, S.; Kiziloglu, U.; Yilmaz, A.; Kalemci, E.; Tomsick, J. A.

    2003-12-01

    We present optical and near infrared observations of XTE J1118+480, a black hole X-ray transient. The data were obtained with the Kitt Peak National Observatory 2.1 m telescope and the Tubitak National Observatory 1.5 m Russian-Turkish telescope, and are modeled with the WD98 light curve modeling program to find the inclination of the system, and hence, the mass of the black hole. As the distorted companion orbits the black hole, the observed flux rises and falls in a predictable manner, giving rise to ``ellipsoidal variations.'' By modeling the variations observed during X-ray quiescence, we determine the orbital inclination of the system. Both optical and infrared data are needed to fully account for any source of flux that may contaminate the ellipsoidal variations, as a constant source of light will dilute the variations giving an artificially lower inclination angle and higher black hole mass. Once the inclination is known, it is combined with the observed mass function and mass ratio (q = (M2)/(M_1)) to find the mass of the black hole. This project is partially supported by a Center for Astrophysics and Space Sciences (CASS) Postdoctoral Fellowship.

  5. Long-Term Spectral and Temporal Evolution of Anomalous X-Ray Pulsar XTE J1810-197

    NASA Astrophysics Data System (ADS)

    Vurgun, Eda; Gogus, Ersin; Chakraborty, Manoneeta; Guver, Tolga

    2016-07-01

    We present spectral and timing studies of the first transient Anomalous X-ray Pulsar XTE J1810-197, a 5.54 s pulsar discovered in 2003, when its X-ray luminosity increased ~100 fold. We investigate the long-term behaviour of the surface temperature,emitting area, and the pulsed fraction. X-ray spectra are well fitted by a two-component blackbody model in which the cool component is most likely arising from the whole surface of star and the hot component is arising from a relatively small hot spot on it. The spectral analysis has also shown evidence for the presence of an absorbtion line feature around 1.2 keV in almost all observations. We fit this absorption feature with an asymmetric gaussian component since it shows an asymmetric structure. The pulse fraction exhibits slightly different temporal evolution in higher and lower energy bands. We will discuss correlative behaviour between the spectral and timing parameters in order to constrain magnetar cooling models.

  6. Constraints on the Emission and Viewing Geometry of the Transient Anomalous X-ray Pulsar XTE J1810-197

    NASA Technical Reports Server (NTRS)

    Perna, Rosalba; Gotthelf, E. V.

    2008-01-01

    The temporal decay of the flux components of the transient anomalous X-ray pulsar XTE J1 810-197 following its 2002 outburst presents a unique opportunity to probe the emission geometry of a magnetar. Toward this goal, we model the magnitude of the pulsar's modulation in narrow spectral bands over time. Following previous work, we assume that the postoutburst flux is produced in two distinct thermal components arising from a hot spot and a warm concentric ring. We include general relativistic effects on the blackbody spectra due to gravitational redshift and light bending near the stellar surface, which strongly depend on radius. This affects the model fits for the temperature and size of the emission regions. For the hot spot, the observed temporal and energy-dependent pulse modulation is found to require an anisotropic, pencil-beamed radiation pattern. We are able to constrain an allowed range for the angles that the line of sight (psi) and the hot spot pole (xi) make with respect to the spin axis. Within errors, this is defined by the locus of points in the xi-psi plane that lie along the line [xi + beta(R)] [psi + [beta(R)] = const, where beta(R) is a function of the radius R of the star. For a canonical value of R = 12 km, the viewing parameters range from psi = xi = 37deg to (psi, xi) = (85deg, 15deg). We discuss our results in the context of magnetar emission models.

  7. Correlated fast X-ray and optical variability in the black-hole candidate XTE J1118+480.

    PubMed

    Kanbach, G; Straubmeier, C; Spruit, H C; Belloni, T

    2001-11-01

    Black holes become visible when they accrete gas, a common source of which is a close stellar companion. The standard theory for this process (invoking a 'thin accretion disk') does not explain some spectacular phenomena associated with these systems, such as their X-ray variability and relativistic outflows, indicating some lack of understanding of the actual physical conditions. Simultaneous observations at multiple wavelengths can provide strong constraints on these conditions. Here we report simultaneous high-time-resolution X-ray and optical observations of the transient source XTE J1118+480, which show a strong but puzzling correlation between the emissions. The optical emission rises suddenly following an increase in the X-ray output, but with a dip 2-5 seconds in advance of the X-rays. This result is not easy to understand within the simplest model of the optical emission, where the light comes from reprocessed X-rays. It is probably more consistent with an earlier suggestion that the optical light is cyclosynchrotron emission that originates in a region about 20,000 km from the black hole. We propose that the time dependence is evidence for a relatively slow (<0.1c), magnetically controlled outflow. PMID:11700550

  8. The X-Ray Transient XTE J1118+480: Multiwavelength Observations of a Low-State Minioutburst

    NASA Astrophysics Data System (ADS)

    Hynes, R. I.; Mauche, C. W.; Haswell, C. A.; Shrader, C. R.; Cui, W.; Chaty, S.

    2000-08-01

    We present multiwavelength observations of the newly discovered X-ray transient XTE J1118+480 obtained in the rising phase of the 2000 April outburst. This source is located at unusually high Galactic latitude and in a very low absorption line of sight. This made the first Extreme Ultraviolet Explorer (EUVE) spectroscopy of an X-ray transient outburst possible. Together with our Hubble Space Telescope, Rossi X-Ray Timing Explorer, and United Kingdom Infrared Telescope data, this gives unprecedented spectral coverage. We find the source in the low hard state. The flat IR-UV continuum appears to be a combination of optically thick disk emission and possibly synchrotron, while at higher energies (including EUV), a typical low hard state power law is seen. EUVE observations reveal no periodic modulation, suggesting an inclination low enough that no obscuration by the disk rim occurs. We discuss the nature of the source and this outburst and conclude that it may be more akin to minioutbursts seen in GRO J0422+32 than to a normal X-ray transient outburst.

  9. 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.

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

    PubMed

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

    2014-11-26

    Pb(x)Sn(1-x)Te and Pb(x)Sn(1-x)Se 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.

  11. The kilohertz quasi-periodic oscillations during the Z and atoll phases of the unique transient XTE J1701-462

    NASA Astrophysics Data System (ADS)

    Sanna, Andrea; Méndez, Mariano; Altamirano, Diego; Homan, Jeroen; Casella, Piergiorgio; Belloni, Tomaso; Lin, Dacheng; van der Klis, Michiel; Wijnands, Rudy

    2010-10-01

    We analysed 866 observations of the neutron star low-mass X-ray binary XTE J1701-462 during its 2006-2007 outburst. XTE J1701-462 is the only example so far of a source that during an outburst showed, beyond any doubt, spectral and timing characteristics both of the Z and atoll type. There are 707 RXTE observations (~2.5 Ms) of the source in the Z phase and 159 in the atoll phase (~0.5 Ms). We found, respectively, pairs of kilohertz quasi-periodic oscillations (kHz QPOs) in eight observations during the Z phase and single kHz QPO in six observations during the atoll phase. Using the shift-and-add technique, we identified the QPO in the atoll phase as the lower kHz QPO. We found that the lower kHz QPO in the atoll phase has a significantly higher coherence and fractional rms amplitude than any of the kHz QPOs seen during the Z phase, and that in the same frequency range, atoll lower kHz QPOs show coherence and fractional rms amplitude, respectively, two and three times larger than the Z kHz QPOs. Out of the 707 observations in the Z phase, there is no single observation in which the kHz QPOs have a coherence or rms amplitude similar to those seen when XTE J1701-462 was in the atoll phase, even though the total exposure time was about five times longer in the Z than in the atoll phase. Since it is observed in the same source, the difference in QPO coherence and rms amplitude between the Z and atoll phase cannot be due to neutron star mass, magnetic field, spin, inclination of the accretion disc, etc. If the QPO frequency is a function of the radius in the accretion disc in which it is produced, our results suggest that in XTE J1701-462 the coherence and rms amplitude are not uniquely related to this radius. Here we argue that this difference is instead due to a change in the properties of the accretion flow around the neutron star. Regardless of the precise mechanism, our result shows that effects other than the geometry of space-time around the neutron star have a

  12. MAXI/GSC detection of renewed X-ray activity of the neutron star X-ray binary XTE J1709-267

    NASA Astrophysics Data System (ADS)

    Nakahira, S.; Matsuoka, T. Mihara M.; Negoro, H.; Ueno, S.; Tomida, H.; Ishikawa, M.; Nakagawa, Y. E.; Sugawara, Y.; Sugizaki, M.; Serino, M.; Iwakiri, W.; Shidatsu, M.; Sugimoto, J.; Takagi, T.; Kawai, N.; Isobe, N.; Sugita, S.; Yoshii, T.; Tachibana, Y.; Ono, Y.; Fujiwara, T.; Yoshida, A.; Sakamoto, T.; Kawakubo, Y.; Kitaoka, Y.; Tsunemi, H.; Shomura, R.; Nakajima, M.; Tanaka, K.; Masumitsu, T.; Kawase, T.; Ueda, Y.; Kawamuro, T.; Hori, T.; Tanimoto, A.; Tsuboi, Y.; Nakamura, Y.; Sasaki, R.; Yamauchi, M.; Furuya, K.; Yamaoka, K.

    2016-06-01

    We report on a detection of X-ray outburst from XTE J1709-267 triggered by the MAXI/GSC nova alert system at 12:25 on 2016 May 31. The MAXI/GSC 2-6 keV X-ray flux on May 31 is 210 mCrab, which is brighter than the peak flux of the previous outburst in July 2012 (160 mCrab in 2-6 keV; Atel #5319, Asai, K. et al, PASJ 67, 92, 2015).

  13. 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.

  14. 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.

  15. 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.

  16. Discovery and Photometric Observation of the Optical Counterpart of a Possible Galactic Halo X-Ray Transient, XTE J1118+480

    NASA Astrophysics Data System (ADS)

    Uemura, Makoto; Kato, Taichi; Matsumoto, Katsura; Yamaoka, Hitoshi; Takamizawa, Kesao; Sano, Yasuo; Haseda, Katsumi; Cook, Lewis M.; Buczynski, Denis; Masi, Gianluca

    2000-08-01

    We discovered an optical counterpart of about 13 mag of a soft X-ray transient, XTE J1118+480 on 2000 March 30. We performed astrometry and provided an accurate position of R.A. = 11h18m10.85s85, Decl. = +48deg02'12.9{' '}. The outbursting object has been identified with a 18.8 mag star in the USNO catalog. Our pre-discovery data shows another outburst during 2000 January, again coinciding with an outburst detected in X-rays. Through CCD time-series photometry, we found the presence of a periodic variation with an amplitude of 0.055 mag and a period of 0.17078 \\pm 0.00004 d$, which we consider to be a promising candidate of the orbital period. Because of the high galactic latitude and faint quiescence magnitude of 18.8, XTE J1118+480 is possibly the first firmly identified black hole candidate X-ray transient in the galactic halo.

  17. 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°.

  18. 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.

  19. 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.

  20. The Harmonic Structure of High-Frequency Quasi-periodic Oscillations in Accreting Black Holes

    NASA Astrophysics Data System (ADS)

    Schnittman, Jeremy D.; Bertschinger, Edmund

    2004-05-01

    Observations from the Rossi X-Ray Timing Explorer have shown the existence of high-frequency quasi-periodic oscillations (HFQPOs) in the X-ray flux from accreting black hole binary systems. In at least two systems, these HFQPOs come in pairs with a 2:3 frequency commensurability. We employ a simple ``hot spot'' model to explain the position and amplitude of the HFQPO peaks. Using the exact geodesic equations for the Kerr metric, we calculate the trajectories of massive test particles, which are treated as isotropic, monochromatic emitters in their rest frames. Photons are traced from the accretion disk to a distant observer to produce time- and frequency-dependent images of the orbiting hot spot and background disk. The power spectrum of the X-ray light curve consists of multiple peaks at integral combinations of the black hole coordinate frequencies. In particular, if the radial frequency is one-third of the azimuthal frequency (as is the case near the innermost stable circular orbit), beat frequencies appear in the power spectrum at two-thirds and four-thirds of the fundamental azimuthal orbital frequency, in agreement with observations. In addition, we model the effects of shearing the hot spot in the disk, producing an arc of emission that also follows a geodesic orbit, as well as the effects of nonplanar orbits that experience Lens-Thirring precession around the black hole axis. By varying the arc length, we are able to explain the relative amplitudes of the QPOs at either 2ν or 3ν in observations from XTE J1550-564 and GRO J1655-40. In the context of this model, the observed power spectra allow us to infer values for the black hole mass and angular momentum and also constrain the parameters of the model, such as the hot spot size and luminosity.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Influence of samarium on the thermoelectric figure of merit of Sm{sub x}Pb{sub 1-x}Te alloys

    SciTech Connect

    Aliev, F. F. Hasanov, H. A.

    2012-03-15

    The temperature and concentration dependences of the electrical (conductivity {sigma}, the Hall coefficient R), thermoelectric (thermovoltage {alpha}), and thermal (thermal conductivity K{sub tot}) characteristics of Sm{sub x}Pb{sub 1-x}Te alloys (x = 0, 0.02, 0.04, 0.08) are studied in the temperature range 100-500 K. Using the data for {sigma}, {alpha}, and K{sub tot}, the thermoelectric power {alpha}{sup 2}{sigma}, figure of merit Z, and efficiency {delta} are calculated. It is established that at room-temperature {alpha}{sup 2}{sigma} and Z peak at the hole concentration p Almost-Equal-To 1.2 Multiplication-Sign 10{sup 18} cm{sup -3}.

  7. Constraints on braneworld gravity models from a kinematic limit on the age of the black hole XTE J1118+480.

    PubMed

    Psaltis, Dimitrios

    2007-05-01

    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 > or =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. PMID:17501556

  8. 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.

  9. Low-temperature anomalies of the photoelectromagnetic effect in p-Cd{sub x}Hg{sub 1-x}Te due to recharging of surface states

    SciTech Connect

    Gassan-zade, S. G. Strikha, M. V.; Shepelsky, G. A.

    2008-04-15

    A number of anomalies inexplicable in the context of available theoretical models are observed in the photoelectromagnetic effect in p-Cd{sub x}Hg{sub 1-x}Te crystals. A general model of the photoelectromagnetic effect in semiconductors with a large ratio between the mobilities of electrons and holes is developed, taking into account the influence of space charge. The model allows the interpretation of all experimentally observed anomalies of the photoelectromagnetic effect, including the double sign inversion in magnetic field. Comparison of the theory with the experiment makes it possible to determine the parameters of the material. It is suggested that the space charge responsible for the anomalies of the photoelectromagnetic effect is associated with a high concentration of specific surface states ({approx}10{sup 13} cm{sup -3}) recharged when trapping nonequilibrium charge carriers.

  10. 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.

  11. 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

  12. 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.

  13. Stabilization of the fermi level by a resonant gallium level in Pb{sub 1-x}Sn{sub x}Te alloys

    SciTech Connect

    Skipetrov, E. P. Zvereva, E. A.; Dmitriev, N. N.; Golubev, A. V.; Slynko, V. E.

    2006-08-15

    Electrical properties of gallium-doped n-Pb{sub 1-x}Sn{sub x}Te alloys (x=0.09-0.21) are studied. Ahomalous temperature dependences of the Hall coefficient which indicate the Fermi level pinning by a resonant gallium level in the conduction band were detected. The dependences of the electron concentration and Fermi energy on the alloy composition and temperature are calculated from experimental data in terms of the two-band Kane dispersion relation. It is shown that the gallium resonant level position relative to the valence band top is almost independent of the matrix composition. The dependence of the thermal coefficient of the resonant level shift with respect to the midgap on the alloy composition is obtained.

  14. 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.

  15. Constraints on braneworld gravity models from a kinematic limit on the age of the black hole XTE J1118+480.

    PubMed

    Psaltis, Dimitrios

    2007-05-01

    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 > or =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.

  16. 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.

  17. 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.

  18. 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.

  19. Fast orbital decays of black hole X-ray binaries: XTE J1118+480 and A0620-00★

    NASA Astrophysics Data System (ADS)

    González Hernández, J. I.; Rebolo, R.; Casares, J.

    2014-02-01

    We present new 10.4 m-GTC/OSIRIS spectroscopic observations of the black hole X-ray binary XTE J1118+480 that confirm the orbital period decay at dot{P}=-1.90± 0.57 ms yr-1. This corresponds to a period change of -0.88 ± 0.27 μs per orbital cycle. We have also collected observations of the black hole X-ray binary A0620-00 to derive an orbital period derivative of dot{P}=-0.60± 0.08 ms yr-1 (-0.53 ± 0.07 μs/cycle). Angular momentum losses due to gravitational radiation are unable to explain these large orbital decays in these two short-period black hole binaries. The orbital period decay measured in A0620-00 is very marginally consistent with the predictions of conventional models including magnetic braking, although significant mass-loss (dot{M}_BH / dot{M}_2 ≤ 20 per cent) from the system is required. The fast spiral-in of the star in XTE J1118+480, however, does not fit any standard model and may be driven by magnetic braking under extremely high magnetic fields and/or may require an unknown process or non-standard theories of gravity. This result may suggest an evolutionary sequence in which the orbital period decay begins to speed up as the orbital period decreases. This scenario may have an impact on the evolution and lifetime of black hole X-ray binaries.

  20. Microquasar Monitoring with the GBI

    NASA Astrophysics Data System (ADS)

    Waltman, E. B.; Ghigo, F. D.; Hjellming, R. M.; Johnston, K. J.

    1999-05-01

    Monitoring of the X-ray binaries GRS 1915+105, Cygnus X-3 (2030+407), LSI +61(deg) 303 (0236+610), and SS 433 (1909+048) at 2 and 8 GHz with the Green Bank Interferometer (GBI) is available on the website of the GBI. In addition to the 1997-1999 fluxes which have been available as public domain data, the archival data on these sources prior to 1996 are now included in the archives directory on the GBI website. The GBI is a facility of the NSF, operated by the NRAO with support for the Monitoring Program provided by the US Naval Observatory, the Naval Research Laboratory, and NASA, which should be acknowledged with the requested funding credit statement.

  1. Lithium synthesis in microquasar accretion.

    PubMed

    Iocco, Fabio; Pato, Miguel

    2012-07-13

    We study the synthesis of lithium isotopes in the hot tori formed around stellar mass black holes by accretion of the companion star. We find that sizable amounts of both stable isotopes 6Li and 7Li can be produced, the exact figures varying with the characteristics of the torus and reaching as much as 10(-2) M⊙ for each isotope. This mass output is enough to contaminate the entire Galaxy at a level comparable with the original, pregalactic amount of lithium and to overcome other sources such as cosmic-ray spallation or stellar nucleosynthesis. PMID:23030150

  2. Lithium synthesis in microquasar accretion.

    PubMed

    Iocco, Fabio; Pato, Miguel

    2012-07-13

    We study the synthesis of lithium isotopes in the hot tori formed around stellar mass black holes by accretion of the companion star. We find that sizable amounts of both stable isotopes 6Li and 7Li can be produced, the exact figures varying with the characteristics of the torus and reaching as much as 10(-2) M⊙ for each isotope. This mass output is enough to contaminate the entire Galaxy at a level comparable with the original, pregalactic amount of lithium and to overcome other sources such as cosmic-ray spallation or stellar nucleosynthesis.

  3. Imaging X-Ray, Optical, and Infrared Observations of the Transient Anomalous X-Ray Pulsar XTE J1810-197

    NASA Astrophysics Data System (ADS)

    Gotthelf, E. V.; Halpern, J. P.; Buxton, M.; Bailyn, C.

    2004-04-01

    We report X-ray imaging, timing, and spectral studies of XTE J1810-197, a 5.54 s pulsar discovered by Ibrahim and coworkers in recent Rossi X-Ray Timing Explorer (RXTE) observations. In a set of short exposures with the High Resolution Camera on board the Chandra X-Ray Observatory, we detect a strongly modulated signal (55%+/-4% pulsed fraction) with the expected period located at (J2000) 18h09m51s08, -19deg43'51.7", with a uncertainty radius of 0.6" (90% confidence level). Spectra obtained with XMM-Newton are well fitted by a two-component model that typically describes anomalous X-ray pulsars (AXPs), an absorbed blackbody plus power law with parameters kT=0.67+/-0.01 keV, Γ=3.7+/-0.2, NH=(1.05+/-0.05)×1022 cm-2, and FX(0.5-10keV)=3.98×10-11 ergs cm-2 s-1. Alternatively, a two-temperature blackbody fit is just as acceptable. The location of CXOU J180951.0-194351 is consistent with a point source seen in archival Einstein, ROSAT, and ASCA images, when its flux was nearly 2 orders of magnitude fainter, and from which no pulsations are found. The spectrum changed dramatically between the ``quiescent'' and ``active'' states; the former can be modeled as a softer blackbody. Using XMM-Newton timing data, we place an upper limit of 0.03 lt-s on any orbital motion in the period range 10 minutes-8 hr. Optical and infrared images obtained on the SMARTS 1.3 m telescope at the Cerro Tololo Inter-American Observatory (CTIO) show no object in the Chandra error circle to limits V=22.5, I=21.3, J=18.9, and K=17.5. Together, these results argue that CXOU J180951.0-194351 is an isolated neutron star, one most similar to the transient AXP AX J1844.8-0256. Continuing study of XTE J1810-197 in various states of luminosity is important for understanding and possibly unifying a growing class of isolated, young neutron stars that are not powered by rotation.

  4. 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.

  5. Material inhomogeneities in Cd{sub 1-x}Zn{sub x}Te and their effects on large volume gamma-ray detectors

    SciTech Connect

    Scyoc, J.M. van; Lund, J.C.; Morse, D.H.

    1996-08-01

    Cadmium zinc telluride (Cd{sub 1-x}Zn{sub x}Te or CZT) has shown great promise as a material for room temperature x-ray and gamma-ray detectors. There has been a push for the development of CZT detectors with a volume greater than 1 cm{sup 3}. However, nonuniformities in the material over this scale degrade the performance of the detectors. Variations in the zinc fraction, and thus the bandgap, and changes in the impurity distributions, both of which arise from the selective segregation of elements during crystal growth, result in spectral distortions. In this work, several materials characterization techniques were combined with detector evaluations to determine the materials properties limiting detector performance. Materials measurements were performed on detectors found to have differing performance. Measurements conducted include infrared transmission, particle induced x-ray emission, photoluminescence, and triaxial x-ray diffraction. To varying degrees, these measurements reveal that `poor-performance` detectors exhibit higher nonuniformities than `spectrometer-grade` detectors. This is reasonable, as regions of CZT material with different properties will give different localized spectral responses, which combine to result in a degraded spectrum for the total device. 7 refs., 6 figs.

  6. Growth of ferromagnetic semiconductor Ge{sub 1-x}Mn{sub x}Te films on BaF{sub 2} (111) by ionized cluster beam deposition

    SciTech Connect

    Fukuma, Y.; Arifuku, M.; Asada, H.; Koyanagi, T.

    2005-04-01

    IV-VI ferromagnetic semiconductor Ge{sub 1-x}Mn{sub x}Te (x{approx_equal}0.4) films were grown on BaF{sub 2} (111) substrates by an ionized cluster beam method. In neutral cluster beam deposition, Ge{sub 0.64}Mn{sub 0.36}Te films grown at substrate temperatures in the range from 250 to 300 deg. C show an epitaxial relationship Ge{sub 0.64}Mn{sub 0.36}Te/GeTe(111)parallel BaF{sub 2}(111). The crystallinity of the Ge{sub 0.64}Mn{sub 0.36}Te layer is improved with increasing substrate temperature. Further improvements of the crystal properties such as the crystallinity and the surface smoothness are accomplished by the proper acceleration of the ionized GeTe cluster, although the acceleration of the ionized MnTe cluster hardly gives rise to any noticeable improvement of the crystalline quality. The crystalline quality significantly affects the ferromagnetism: the enhancement of the spontaneous magnetization and the decrease of the coercive field are observed for the film grown using the ionized GeTe cluster at the acceleration voltage of 1 kV due to the decreases of magnetic disorder caused by inhomogeneities in Mn distribution and pinning sites of domain-wall motion.

  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. The use of pulse processing techniques to improve the performance of Cd{sub 1{minus}x}Zn{sub x}Te gamma-ray spectrometers

    SciTech Connect

    Lund, J.C.; Olsen, R.; Van Scyoc, J.M.; James, R.B.

    1996-06-01

    Cd{sub 1{minus}x}Zn{sub x}Te (CZT) has recently shown great promise for use as a room temperature gamma-ray detector material. The availability of large volume (>1 cm{sup 3}) high resistivity CZT crystals has allowed the demonstration of detectors much larger than can be built with the similar material CdTe. However, CZT--like many other room-temperature materials--suffers from the poor transport properties of holes. The poor hole drift properties of CZT cause the characteristic hole tailing in gamma-ray pulse height spectra. The authors have applied pulse processing methods to reduce the hole tailing effects and improve the energy resolution of CZT detectors. They have used two signal processing methods to reduce hole tailing in CZT detectors: digital rise-time compensation and dual time-constant sampling. They discuss the implementation of these techniques, demonstrate results obtained in the laboratory, and compare the performance obtained with other detector systems.

  9. Relativistic Astrophysics in Black Hole and Low-Mass Neutron Star Binaries LTSA98

    NASA Technical Reports Server (NTRS)

    Cui, Wei

    2000-01-01

    My group, in close collaboration with Dr. Zhang's group at University of Alabama-Huntsville, have been systematically analyzing and re-analyzing a substantial amount of archival data from previous and ongoing X-ray missions, in order to study possible relativistic effects around stellar-mass black holes and neutron stars. Our effort has been focused primarily on the data from the Rossi X-ray Timing Explorer. We carefully studied interesting quasi-periodic X-ray variability in newly discovered black hole candidates (XTE J1859+226 and XTE J1550-564), which, as we had proposed earlier, could be caused by general relativistic process (e.g., frame dragging) around the central black hole. We also discovered an intriguing temporal correlation between X-ray photons at different energies that is associated with the quasi-periodic signals of interest. The results provided new insights into the physical origin of the phenomena. Furthermore, we studied the spectral lines of black hole candidates which provide another avenue for studying general relativistic processes around black holes. The lines-may originate in the relativistic jets (which could be powered by the spin of the black hole) or in the disk around the black hole, as in the cases of 4U 1630-47 and GX 339-4 (two well-known black hole candidates), and may thus be distorted or shifted due to relativistic effects. Of course, neutron star systems were not forgotten either. After examining the properties of newly discovered fast quasi-periodic variability (at kiloHertz) associated with such systems, we proposed a relativistic model to explain the origin of the signals. We have also started to use new great observatories in orbit (such as Chandra and XMM-Newton) to observe the sources that are of interest to us. Finally, interesting results were also been obtained from our collaborations with other groups who are interested in some of the same objects. Such collaborative efforts have greatly enhanced the project and will

  10. Dependence of the electrical parameters of MBE-grown Cd{sub x}Hg{sub 1} {sub -} {sub x}Te films on the level of doping with indium

    SciTech Connect

    Varavin, V. S. Dvoretskii, S. A.; Ikusov, D. G.; Mikhailov, N. N.; Sidorov, Yu. G.; Sidorov, G. Yu.; Yakushev, M. V.

    2008-06-15

    Dependences of the minority-carrier lifetime and electron mobility in Cd{sub x}Hg{sub 1-x}Te films on their indium-doping level are studied. Films with x {approx} 0.22 grown by molecular-beam epitaxy on GaAs substrates were in situ doped with indium across their entire thickness. The temperature dependences of the lifetime were studied in the temperature range 77-300 K. The decrease in the lifetime, observed as the doping level increases, is governed by the mechanism of Auger recombination. As the doping level becomes higher, the mobility decreases in qualitative agreement with theoretical calculations.

  11. The 2013-2014 Outburst of XTE J1908+094 Observed with Swift and NuSTAR: Spectral Evolution and Black Hole Spin Constraint

    NASA Astrophysics Data System (ADS)

    Zhang, Liang; Chen, Li; Qu, Jin-lu; Bu, Qing-cui; Zhang, Wei

    2015-11-01

    We present a spectral study of the black hole candidate XTE J1908+094 during its 2013-2014 outburst. We analyzed 36 Swift/XRT observations together with a NuSTAR observation taken along this period. The outburst evolution is similar to what is previously observed in other black hole transients. The source transited from an initial low/hard state to a high/soft state and then went back to the low/hard state. The low/hard-state spectra are dominated by a hard component, while the high/soft-state spectra are dominated by a soft component. In the high/soft state, we find that the disk bolometric luminosity deviates weakly from the standard {T}{{in}}4 dependence, exhibiting a flatter dependence as {L}{{disk}}\\propto {T}{{in}}2. The radial temperature profile is found to be flatter than that of the standard accretion disk. These results suggest an advection-dominated slim disk. During the NuSTAR observation, the source was in the high/soft state. A flare is seen in the NuSTAR light curves. During the flare, a spectral softening occurs with an increase in power-law flux. We suggest that the flare may be associated with the relativistic jets. A broad Fe Kα line and a disk reflection component are observed in the spectra, providing an opportunity to measure the black hole spin via the Fe-line method. We have fitted the NuSTAR spectra with different relativistically blurred disk reflection models. However, the data do not allow us to constrain the spin of the black hole.

  12. Material inhomogeneities in Cd{sub 1{minus}x}Zn{sub x}Te and their effects on large volume gamma-ray detectors

    SciTech Connect

    Scyoc, J.M. Van; Lund, J.C.; Morse, D.H.

    1997-09-01

    Cadmium zinc telluride (Cd{sub 1{minus}x}Zn{sub x}Te or CZT) has shown great promise as a material for room-temperature x-ray and gamma-ray detectors. In particular, polycrystalline material grown by the High Pressure Bridgman method with nominal Zn fraction (x) from 0.1 to 0.2 has been used to fabricate high resolution gamma-ray spectrometers with resolution approaching that of cooled high-purity Ge. For increased sensitivity, large areas (> 1 cm{sup 2}) are required, and for good sensitivity to high energy gamma photons, thick detectors (on the order of 1 cm) are required. Thus there has been a push for the development of CZT detectors with a volume greater than 1 cm{sup 3}. However, nonuniformities in the material over this scale degrade the performance of the detectors. Variations in the zinc fraction, and thus the bandgap, and changes in the impurity distributions, both of which arise from the selective segregation of elements during crystal growth, result in spectral distortions. In this work several materials characterization techniques were combined with detector evaluations to determine the materials properties limiting detector performance. Materials measurements were performed on detectors found to have differing performance. Measurements conducted include infrared transmission (IR), particle induced x-ray emission (PIXE), photoluminescence (PL), and triaxial x-ray diffraction (TAXRD). To varying degrees, these measurements reveal that poor-performance detectors exhibit higher nonuniformities than spectrometer-grade detectors. This is reasonable, as regions of CZT material with different properties will give different localized spectral responses, which combine to result in a degraded spectrum for the total device.

  13. The Rapid X-Ray Variability of V4641 Sagittarii (SAX J1819.3-2525 = XTE J1819-254).

    PubMed

    Wijnands; van Der Klis M

    2000-01-10

    We report on the rapid X-ray variability of the variable star and X-ray transient V4641 Sagittarii (SAX J1819.3-2525 = XTE J1819-254) as observed on 1999 September 15 by the proportional counter array (PCA) on board the Rossi X-Ray Timing Explorer. During the first approximately 900 s of the first PCA observation, V4641 Sgr showed very strong X-ray fluctuations by a factor of 4 on timescales of seconds to about 500 on timescales of minutes. The spectrum of the source during this flaring episode became harder when the count rate decreased. After this flaring episode, V4641 Sgr entered a quiescent state in which it remained for the rest of this and subsequent PCA observations. The X-ray spectrum was considerably softer in this quiescent state than during the flaring episode. The intrinsic X-ray luminosity (during both the flaring episode and the quiescent state) and the rapid X-ray variability do not strongly constrain the nature of the compact object (neutron star or black hole) in the system, although a black hole seems to be more likely. The very short duration of the bright X-ray phase of V4641 Sgr and its likely close proximity suggest that many similar objects could be present in our Galaxy, most of which are not noticed when they are in outburst because of the short duration of these outbursts. A considerable number of the black holes present in our Galaxy might be contained in systems similar to V4641 Sgr. PMID:10600626

  14. 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.

  15. 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.

  16. Metal Nitrides Grown from Ca/Li Flux: Ca6Te3N2 and New Nitridoferrate(I) Ca6(LixFe1-x)Te2N3.

    PubMed

    Dickman, Matthew J; Latturner, Susan E

    2016-08-24

    Two new tellurium-containing nitrides were grown from reactions in molten calcium and lithium. The compound Ca6Te3N2 crystallizes in space group R3̅c (a = 12.000(3)Å, c = 13.147(4)Å; Z = 6); its structure is an anti-type of rinneite (K3NaFeCl6) and 2H perovskite related oxides such as Sr3Co2O6. The compound Ca6(LixFe1-x)Te2N3 where x ≈ 0.48 forms in space group P42/m (a = 8.718(3)Å, c = 6.719(2)Å; Z = 2) with a new stuffed anti-type variant of the Tl3BiCl6 structure. Band structure calculations and easily observable red/green dichroic behavior indicate that Ca6Te3N2 is a highly anisotropic direct band gap semiconductor (Eg = 2.5 eV). Ca6(LixFe1-x)Te2N3 features isolated linear N-Fe-N units with iron in the rare Fe(1+) state. The magnetic behavior of the iron site was characterized by magnetic susceptibility measurements, which indicate a very high magnetic moment (5.16μB) likely due to a high degree of spin-orbit coupling. Inherent disorder at the Fe/Li mixed site frustrates long-range communication between magnetic centers. PMID:27479366

  17. 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

  18. Disc-corona energetics in the very high state of Galactic black holes

    NASA Astrophysics Data System (ADS)

    Done, Chris; Kubota, Aya

    2006-09-01

    The X-ray spectra of Galactic binary systems dominated by a quasi-thermal component (disc dominated or high/soft state) are well described by a standard Shakura-Sunyaev disc structure down to the last stable orbit around the black hole. This is not the case in the very high (or steep power-law) state, where the X-ray spectra show both a strong disc component and strong, steep tail to higher energies. We use two such spectra from the black hole transient XTE J1550-564 as specific examples of this state, where the power emitted in the tail is more than 50 per cent of the bolometric luminosity. The simultaneous ASCA and RXTE data show that these have disc spectra which are significantly lower in temperature than those seen from the same source at the same luminosity in the high/soft state. If these give a true picture of the disc, then either the disc emissivity has reduced, and/or the disc truncates above the last stable orbit. However, it is often assumed that the tail is produced by Compton scattering, in which case its shape in these spectra requires that the Comptonizing region is marginally optically thick (τ ~ 2-3), and covers a large fraction of the inner disc. This will distort our view of the disc, especially of the hottest-temperature material. We build a theoretical model of a Comptonizing corona over an inner disc, and fit this to the data, but find that it still requires a large increase in inner disc radius for a standard disc emissivity. Instead, it seems more probable that the disc emissivity changes in the presence of the corona. We implement the specific inner disc-corona coupling model of Svensson & Zdziarski, in which some fraction f of the accretion power is dissipated in the corona, leaving only a fraction 1 - f to be dissipated in the optically thick disc. We show that this can explain the low-temperature/high-luminosity disc emission seen in the very high state with only a small increase in radius of the disc. While this inferred disc

  19. 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

  20. 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.

  1. 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.

  2. Analysis of the Influence of Thermal Treatment on the Stability of Ag1-xSb1+xTe2+x and Se-Doped AgSbTe2

    NASA Astrophysics Data System (ADS)

    Wyzga, P. M.; Wojciechowski, K. T.

    2016-03-01

    In order to systematize the knowledge on thermodynamic stability and thermoelectric properties of AgSbTe2-based alloys, several experiments examining the influence of thermal treatment on their structural and thermoelectric properties were performed. Samples with a nominal composition of AgSbTe2 and AgSbTe1.98Se0.02 were prepared and then annealed in various temperature conditions. It was confirmed that Ag1-xSb1+xTe2+x ( β phase) is the only thermodynamically stable ternary compound in the Ag2Te-Sb2Te3 pseudobinary system. It was also proved that thermal stability of β phase is limited—it slowly decomposes below 633 K. In contrast to some reports, it was also indicated that a small amount of Se does not lead to stabilisation of AgSbTe2 crystal structure. Despite slow kinetics of the decomposition processes, thermoelectric properties of the material are notably affected by thermal treatment and amount of Ag2Te precipitations. Maximal ZT value of prepared materials varies from 0.65 at 575 K to 1.07 at 563 K.

  3. Thermoelectric and microstructural properties of Pb{sub 0.9-x}Sn{sub 0.1}Ge{sub x}Te compounds prepared by spinodal decomposition

    SciTech Connect

    Sondergaard, M.; Christensen, M.; Johnsen, S.; Stiewe, C.; Dasgupta, T.; Mueller, E.; Iversen, B.B.

    2011-05-15

    Three samples of Pb{sub 0.9-x}Sn{sub 0.1}Ge{sub x}Te with x=0.25, 0.35, 0.6 were prepared by heating the mixtures above the melting point of the constituent elements followed by quenching in water. The x=0.6 sample is close to the center of the immiscibility region, while the x=0.25 and 0.35 samples are in the Pb rich region inside the spinodal miscibility gap. Microstructural investigations using Powder X-ray Diffraction, Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy revealed both GeTe-rich and PbTe-rich phases. The samples were uniaxially hot pressed and the thermoelectric properties were characterized in the temperature range 2-400 K using a commercial apparatus and from 300 to 650 K with a custom designed setup. The best sample (x=0.6) reached zT{approx}0.6 at 650 K, while the x=0.25 and 0.35 samples showed thermal instability at elevated temperatures. -- Graphical abstract: Spinodal decomposition in the GeTe-SnTe-PbTe system demonstrated by SEM and EXS images. Display Omitted Highlights: {yields} Investigation of Pb-rich part of the spinodal miscibility gap in PbTe-SnTe-GeTe. {yields} zT=0.6 at 650 K reproduced for Pb{sub 0.3}Sn{sub 0.1}Ge{sub 0.6}Te. {yields} Pb-rich phases shown to be thermally instable. {yields} Thermoelectric property characterization at low and high temperature. {yields} Microstructural investigations using PXRD, SEM, EDX and PSM.

  4. 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

  5. XTE Observations of Intermediate Polars: RXTE TOO Observations of Supernovae

    NASA Technical Reports Server (NTRS)

    Schlegel, E.; Swank, Jean (Technical Monitor)

    2002-01-01

    Two intermediate polar cataclysmic variables, PQ Gem and AO Psc, were observed jointly with the Rossi X-ray Timing Explorer (RXTE) and ground-based photometry. The analysis of intermediate polars (IPs) is complex because these objects exhibit light curves that behave differently as a function of energy and that behave differently when phased on the orbital or on the spin periods. The presence of two periods in one system is essentially equivalent to analyzing two different X-ray sources. A preliminary analysis of the PQ Gem data was carried out and presented at the Annapolis Workshop on Magnetic Cataclysmic Variables. The final analysis of the data were held up by problems with the background estimation. The RXTE PCA team has released a new version of the background estimator. The PQ Gem must be reanalyzed using the new background. We have also installed a spectral model that calculates the expected emission from an accretion column. That model is undergoing final testing before we apply it to the data.

  6. 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.

  7. Etchant for HgxCd1-xTe Crystals

    NASA Technical Reports Server (NTRS)

    Irene, E. A.

    1983-01-01

    Preferential etching by mixture of nitric and hydrochloric acids reveals crystal dislocation defects (type D) and impurity-dislocation defects (type S) in these crystals, which have optical and electrical applications.

  8. 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.

  9. INTEGRAL serendipitous detection of the gamma-ray microquasar LS 5039

    NASA Astrophysics Data System (ADS)

    Goldoni, P.; Ribó, M.; di Salvo, T.; Paredes, J. M.; Bosch-Ramon, V.; Rupen, M.

    2007-06-01

    LS 5039 is the only X-ray binary persistently detected at TeV energies by the Cherenkov HESS telescope. It is moreover a γ-ray emitter in the GeV and possibly MeV energy ranges. To understand important aspects of jet physics, like the magnetic field content or particle acceleration, and emission processes, such as synchrotron and inverse Compton (IC), a complete modeling of the multiwavelength data is necessary. LS 5039 has been detected along almost all the electromagnetic spectrum thanks to several radio, infrared, optical and soft X-ray detections. However, hard X-ray detections above 20 keV have been so far elusive and/or doubtful, partly due to source confusion for the poor spatial resolution of hard X-ray instruments. We report here on deep (˜300 ks) serendipitous INTEGRAL hard X-ray observations of LS 5039, coupled with simultaneous VLA radio observations. We obtain a 20 40 keV flux of 1.1±0.3 mCrab (5.9 (±1.6) ×10-12 erg cm-2 s-1), a 40 100 keV upper limit of 1.5 mCrab (9.5×10-12 erg cm-2 s-1), and typical radio flux densities of ˜25 mJy at 5 GHz. These hard X-ray fluxes are significantly lower than previous estimates obtained with BATSE in the same energy range but, in the lower interval, agree with extrapolation of previous RXTE measurements. The INTEGRAL observations also hint to a break in the spectral behavior at hard X-rays. A more sensitive characterization of the hard X-ray spectrum of LS 5039 from 20 to 100 keV could therefore constrain key aspects of the jet physics, like the relativistic particle spectrum and the magnetic field strength. Future multiwavelength observations would allow to establish whether such hard X-ray synchrotron emission is produced by the same population of relativistic electrons as those presumably producing TeV emission through IC.

  10. 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

  11. Enhanced gamma-ray emission from the microquasar Cygnus X-3 detected by AGILE

    NASA Astrophysics Data System (ADS)

    Piano, G.; Pittori, C.; Verrecchia, F.; Tavani, M.; Bulgarelli, A.; Fioretti, V.; Zoli, A.; Munar-Adrover, P.; Lucarelli, F.; Donnarumma, I.; Vercellone, S.; Striani, E.; 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.

    2016-04-01

    Integrating from 2016-04-16 00:00 UT to 2016-04-19 00:00 UT, the AGILE-GRID detector is revealing gamma-ray emission above 100 MeV from a source positionally consistent with Cygnus X-3 at Galactic coordinates (l, b) = (79.4, 0.2) +/- 0.6 (stat.) +/- 0.1 (syst.) deg, with flux F( > 100 MeV) = (2.0 +/- 0.8) x 10^-6 photons/cm^2/s, as determined by a multi-source likelihood analysis.

  12. 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.

  13. 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

  14. Bright radio emission from an ultraluminous stellar-mass microquasar in M 31.

    PubMed

    Middleton, Matthew J; Miller-Jones, James C A; Markoff, Sera; Fender, Rob; Henze, Martin; Hurley-Walker, Natasha; Scaife, Anna M M; Roberts, Timothy P; Walton, Dominic; Carpenter, John; Macquart, Jean-Pierre; Bower, Geoffrey C; Gurwell, Mark; Pietsch, Wolfgang; Haberl, Frank; Harris, Jonathan; Daniel, Michael; Miah, Junayd; Done, Chris; Morgan, John S; Dickinson, Hugh; Charles, Phil; Burwitz, Vadim; Della Valle, Massimo; Freyberg, Michael; Greiner, Jochen; Hernanz, Margarita; Hartmann, Dieter H; Hatzidimitriou, Despina; Riffeser, Arno; Sala, Gloria; Seitz, Stella; Reig, Pablo; Rau, Arne; Orio, Marina; Titterington, David; Grainge, Keith

    2013-01-10

    A subset of ultraluminous X-ray sources (those with luminosities of less than 10(40) erg s(-1); ref. 1) are thought to be powered by the accretion of gas onto black holes with masses of ∼5-20M cicled dot, probably by means of an accretion disk. The X-ray and radio emission are coupled in such Galactic sources; the radio emission originates in a relativistic jet thought to be launched from the innermost regions near the black hole, with the most powerful emission occurring when the rate of infalling matter approaches a theoretical maximum (the Eddington limit). Only four such maximal sources are known in the Milky Way, and the absorption of soft X-rays in the interstellar medium hinders the determination of the causal sequence of events that leads to the ejection of the jet. Here we report radio and X-ray observations of a bright new X-ray source in the nearby galaxy M 31, whose peak luminosity exceeded 10(39) erg s(-1). The radio luminosity is extremely high and shows variability on a timescale of tens of minutes, arguing that the source is highly compact and powered by accretion close to the Eddington limit onto a black hole of stellar mass. Continued radio and X-ray monitoring of such sources should reveal the causal relationship between the accretion flow and the powerful jet emission. PMID:23235823

  15. CI Cam/XTE J0421+560 resides in optical active state since 2013

    NASA Astrophysics Data System (ADS)

    Goranskij, V. P.; Metlova, N. V.; Metlov, V. G.; Barsukova, E. A.

    2016-10-01

    We perform regular spectral and photometric monitoring of CI Cam since its large outburst in 1998. The last spectrum of the H alpha region was taken on 2016 Oct 09.025 UT very close to the time reported in ATel #9634.

  16. 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. .

  17. Using XTE as Part of the IPN to Derive Accurate GRB Locations

    NASA Technical Reports Server (NTRS)

    Barthelmy, S.

    1998-01-01

    The objective of this final report was to integrate the Rossi X-Ray Timing Explorer PCA into the 3rd Interplanetary Network of gamma-ray burst detectors, to allow more bursts to be detected and accurately localized. Although the necessary software was implemented to do this at Goddard and at UC Berkeley, several factors made a full integration impossible or impractical.

  18. Global Simulations of the Interaction of Microquasar Jets with a Stellar Wind in High-mass X-ray Binaries

    NASA Astrophysics Data System (ADS)

    Yoon, D.; Heinz, S.

    2015-03-01

    Jets powered by high-mass X-ray binaries must traverse the powerful wind of the companion star. We present the first global three-dimensional simulations of jet-wind interaction in high-mass X-ray binaries. We show that the wind momentum flux intercepted by the jet can lead to significant bending of the jet and that jets propagating through a spherical wind will be bent to an asymptotic angle {{\\psi }∞ }. We derive simple expressions for {{\\psi }∞ } as a function of jet power and wind thrust. For known wind parameters, measurements of {{\\psi }∞ } can be used to constrain the jet power. In the case of Cygnus X-1, the lack of jet precession as a function of orbital phase observed by the Very Long Baseline Array can be used to put a lower limit on the jet power of {{L}jet}≳ {{10}36} ergs {{s}-1}. We further discuss the case where the initial jet is inclined relative to the binary orbital axis. We also analyze the case of Cygnus X-3 and show that jet bending is likely negligible unless the jet is significantly less powerful or much wider than currently thought. Our numerical investigation is limited to isotropic stellar winds. We discuss the possible effects of wind clumping on jet-wind interaction, which are likely significant, but argue that our limits on jet power for Cygnus X-1 are likely unaffected by clumping unless the global wind mass-loss rate is orders of magnitude below the commonly assumed range for Cyg X-1.

  19. 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.

  20. 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.

  1. Origin of in-plane anisotropic resistivity in the antiferromagnetic phase of Fe1 +xTe

    NASA Astrophysics Data System (ADS)

    Kaneshita, Eiji; Tohyama, Takami

    2016-07-01

    Motivated by a recent experimental report on in-plane anisotropic resistivity in the double-striped antiferromagnetic phase of FeTe, we theoretically calculate in-plane resistivity by applying a memory function approach to the ordered phase. We find that the resistivity is larger along an antiferromagnetically ordered direction than along a ferromagnetically ordered one, consistent with experimental observation. The anisotropic results are mainly contributed from Drude weight, whose behavior is attributed to Fermi surface topology of the ordered phase.

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

    DOE PAGESBeta

    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; et al

    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

  3. XTE Observations of the Intraday Variable BL LAC S5 0716+714 in a coordinated Multiwavelength Study

    NASA Technical Reports Server (NTRS)

    Worrall, D. M.; Swank, Jean (Technical Monitor)

    2001-01-01

    S5 0716+714 was observed with the Rossi X-ray Timing Explorer (RXTE) between 6 and 22 April 1996 as part of a multifrequency monitoring campaign for this source observed to show extreme intra-day variability (IDV) at a number of frequencies. There were 24 distinct epochs of observation ('views') with the RXTE Proportional Counter Array (PCA), each lasting on average 3-4 ks. There were a number of technical problems with the data. During view 10 no Proportional Counter Unit (PCU) was on. A gain change (from gain epoch 2 to gain epoch 3) took place during view 11, on 15 April 1996. No data were received for view 18. Views 10, 11 and 18 have been omitted from our analysis. There were two distinct pointings of the telescope in views 4 and 17 (all the other observations have only one pointing), and in many of the pointings the data are broken by periods where the high voltage was turned off during South Atlantic Anomaly (SAA) passages and Earth occultations. Originally no filter file was available for views 21 and 22, and for the second pointing of view 17, because housekeeping data were missing, but these data were supplied when the observations were reprocessed in early 1998. For most of the remaining observations only three PCUs were on; the exceptions are views 23, 24 (four PCUs) and 17, 19, 20, 21 and 22 (five PCUs). All working PCUs have been analyzed. The third part of the first pointing of view 17 was found to be very short and is discarded from our analysis. The second part of observation 2 is pointed far off-axis and is discarded.

  4. 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

  5. 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.

  6. 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.

  7. Structural, electronic, and magnetic investigation of magnetic ordering in MBE-grown CrxSb2-xTe3 thin films

    NASA Astrophysics Data System (ADS)

    Collins-McIntyre, L. J.; Duffy, L. B.; Singh, A.; Steinke, N.-J.; Kinane, C. J.; Charlton, T. R.; Pushp, A.; Kellock, A. J.; Parkin, S. S. P.; Holmes, S. N.; Barnes, C. H. W.; van der Laan, G.; Langridge, S.; Hesjedal, T.

    2016-07-01

    We report the structural, electronic, and magnetic study of Cr-doped Sb2Te3 thin films grown by a two-step deposition process using molecular-beam epitaxy (MBE). The samples were investigated using a variety of complementary techniques, namely, x-ray diffraction (XRD), atomic force microscopy, SQUID magnetometry, magneto-transport, and polarized neutron reflectometry (PNR). It is found that the samples retain good crystalline order up to a doping level of x=0.42 (in Cr x Sb2-x Te3), above which degradation of the crystal structure is observed by XRD. Fits to the recorded XRD spectra indicate a general reduction in the c-axis lattice parameter as a function of doping, consistent with substitutional doping with an ion of smaller ionic radius. The samples show soft ferromagnetic behavior with the easy axis of magnetization being out-of-plane. The saturation magnetization is dependent on the doping level, and reaches from ˜2 μ_\\text{B} to almost 3 μ_\\text{B} per Cr ion. The transition temperature (T{c}) depends strongly on the Cr concentration and is found to increase with doping concentration. For the highest achievable doping level for phase-pure films of x=0.42 , a T{c} of 125 K was determined. Electric transport measurements find surface-dominated transport below ˜10 K. The magnetic properties extracted from anomalous Hall effect data are in excellent agreement with the magnetometry data. PNR studies indicate a uniform magnetization profile throughout the film, with no indication of enhanced magnetic order towards the sample surface.

  8. 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.).

  9. The influence of the magnetic field on the effect of drag of electrons by phonons in n-Cd{sub x}Hg{sub 1-x}Te

    SciTech Connect

    Aliyev, S. A.; Zulfigarov, E. I.; Selim-Zade, R. I.; Agayev, Z. F.

    2009-09-15

    Thermopower in n-Cd{sub 0.2}Hg{sub 0.8}Te (6-100 K) is studied. A large effect of drag of the charge carriers by phonons {alpha}{sub ph} is found. The influence of the magnetic field H on the drag thermopower is considered. It is established that the magnetic field exerts the effect mainly on the electron component of {alpha}{sub ph}. The data are interpreted in the context of the theory taking into account the effect of H on thermopower {alpha}{sub ph}, in which parameter A({epsilon}) proportional to the static force of the drag effect is introduced. By the experimental data {alpha}{sub ph}(T, H), T, and H dependences A({epsilon}) are determined. It is shown that, as H increases, A({epsilon}) sharply decreases. This explains a decrease in {alpha}{sub ph} in the magnetic field, power index k in dependence {alpha}{sub ph} {proportional_to} T{sup -}{kappa}, and narrowing the region of manifestation of the drag effect. It is established that at classically high fields, the drag effect in n-Cd{sub 0.2}Hg{sub 0.8}Te does not vanish.

  10. Ion distribution preferences in ternary crystals ZnxCd1-xTe, Zn1-xHgxTe and Cd1-xHgxTe

    NASA Astrophysics Data System (ADS)

    Robouch, B. V.; Kutcherenko, I. V.; Cestelli Guidi, M.; Kisiel, A.; Marcelli, A.; Robouch, P.; Piccinini, M.; Nucara, A.; Triboulet, R.; Burattini, E.; Cebulski, J.; Sheregii, E. M.; Polit, J.

    2011-11-01

    Similar ternary semiconductors are sometimes associated with widely different structures characterized by different site occupation preferences. We have used far-infrared (FIR) spectra to determine the site occupation preference coefficients for three ternary semiconductor alloys: ZnCdTe, ZnHgTe and CdHgTe and, in the case of ZnHgTe, have validated it by X-ray absorption fine structure (EXAFS) analysis. While ZnCdTe spectra exhibit the canonical configuration with eight phonon lines free of vibrational defect lines and only a slight departure from a random ion distribution, CdHgTe spectra show the eight canonical phonon modes plus an additional vibrational defect line and constant preference coefficients. In contrast, two defect lines and only four modes characterize ZnHgTe spectra, as extreme preferences prevent the formation of two of the five expected tetrahedral configuration arrangements. Moreover, for this system, comparison with EXAFS data points out the vibrational nature of both the extra lines. The analysis clearly shows that assuming a Bernoulli distribution of the component configurations of semiconductors may lead to wrong assessments of the evolution of its properties with relative content.

  11. 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.

  12. X-ray irradiation effects on the trapping properties of Cd{sub 1-x}Zn{sub x}Te detectors

    SciTech Connect

    Fraboni, B.; Pasquini, L.; Castaldini, A.; Cavallini, A.

    2009-11-01

    CdZnTe-based detectors possess unique properties as room-temperature x- and gamma-ray detectors. We report on the effects of x-ray irradiation on CdZnTe and CdTe:Cl detectors with increasing x-ray doses. We correlate the 'macroscopic' performance of the detectors, investigated by gamma-ray spectroscopy to the 'microscopic' effects induced by the impinging radiation, i.e., the defective states introduced in the crystal lattice. The electrical activity of the defects and their activation energy have been investigated by photo induced current transient spectroscopy and by space charge limited current analyses. We identify the x-ray dose that induces a significant degradation in the detector performance, and by cross-correlating the results obtained, we achieve a reliable estimate of the actual concentration of electrically active deep states and assess the potentiality of these experimental methods as tools for quantitative analyses of high resistivity materials.

  13. Photoluminescence of Hg{sub 1-x}Cd{sub x}Te based heterostructures grown by molecular-beam epitaxy

    SciTech Connect

    Mynbaev, K. D. Bazhenov, N. L.; Ivanov-Omskii, V. I.; Mikhailov, N. N.; Yakushev, M. V.; Sorochkin, A. V.; Remesnik, V. G.; Dvoretsky, S. A.; Varavin, V. S.; Sidorov, Yu. G.

    2011-07-15

    Photoluminescence (PL) of Hg{sub 1-x}Cd{sub x}Te-based heterostructures grown by molecular-beam epitaxy (MBE) on GaAs and Si substrates has been studied. It is shown that a pronounced disruption of the long-range order in the crystal lattice is characteristic of structures of this kind. It is demonstrated that the observed disordering is mostly due to the nonequilibrium nature of MBE and can be partly eliminated by postgrowth thermal annealing. Low-temperature spectra of epitaxial layers and structures with wide potential wells are dominated by the recombination peak of an exciton localized in density-of-states tails; the energy of this peak is substantially lower than the energy gap. In quantum-well (QW) structures at low temperatures, the main PL peak is due to carrier recombination between QW levels and the energy of the emitted photon is strictly determined by the effective (with the QW levels taken into account) energy gap.

  14. Defects in the crystal structure of Cd{sub x}Hg{sub 1-x}Te layers grown on the Si (310) substrates

    SciTech Connect

    Yakushev, M. V. Gutakovsky, A. K.; Sabinina, I. V.; Sidorov, Yu. G.

    2011-07-15

    Microstructure of the CdTe (310) and CdHgTe (310) layers grown by molecular-beam epitaxy on Si substrates has been studied by the methods of transmission electron microscopy and selective etching. It is established that formation of antiphase domains in the CdHgTe/CdTe/ZnTe/Si(310) is determined by the conditions of formation of the ZnTe/Si interface. Monodomain layers can be obtained by providing conditions that enhance zinc adsorption. An increase in the growth temperature and in the pressure of Te{sub 2} vapors gives rise to antiphase domains and induces an increase in their density to the extent of the growth of poly-crystals. It is found that stacking faults exist in a CdHgTe/Si(310) heterostructure; these defects are anisotropically distributed in the bulk of grown layers. The stacking faults are predominantly located in one (111) plane, which intersects the (310) surface at an angle of 68 Degree-Sign . The stacking faults originate at the ZnTe/Si(310) interface. The causes of origination of stacking faults and of their anisotropic distribution are discussed.

  15. 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

  16. 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

  17. 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

    This thesis focuses on High-Mass X-ray Binaries (HMXBs) 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. Often, they 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, namely 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 a 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 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

  18. Target of Opportunity Positioning of Transient X-Ray Pulsars

    NASA Technical Reports Server (NTRS)

    Chakrabarty, Deepto

    2003-01-01

    Our program successfully localized three newly-identified transient X-ray pulsars. XTE J1858+034 is a 221 s pulsar (Takeshima et al. 1998, IAUC 6826), XTE J1946+274 is a 15.8 s pulsar (Takeshima and Chakrabarty 1998, IAUC 7016), and XTE J0111.2-7317 is a 31 s pulsar in the Small Magellanic Cloud (Chakrabarty et al. 1998, IAUC 7048). This last pulsar was a particularly interesting source, and our XTE observations enabled prompt follow-up observations with the ASCA mission (Yokogawa et al. 2000, ApJ. 539, 191).

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

    DOE PAGESBeta

    Lee, Inhee; Kim, Chung Koo; Lee, Jinho; Billinge, Simon J. L.; Zhong, Ruidan D.; Schneeloch, John A.; Liu, Tiansheng S.; Valla, Tonica; Tranquada, John M.; Gu, Genda D.; et al

    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

  20. 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

    2015-02-01

    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 [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.

  1. Characterisation of dark current in novel Hg 1- xCd xTe mid-wavelength infrared photovoltaic detectors based on n-on-p junctions formed by plasma-induced type conversion

    NASA Astrophysics Data System (ADS)

    Rais, M. H.; Musca, C. A.; Antoszewski, J.; Dell, J. M.; Nener, B. D.; Faraone, L.

    2000-06-01

    This paper reports initial characterisation results for planar mid-wavelength infrared (MWIR) photodiodes fabricated using a novel reactive ion plasma-induced n-on-p junction formation technology on vacancy-doped p-type HgCdTe grown by LPE on CdZnTe substrates. The junction is formed without the need for post-implant annealing typically required by ion implantation junction formation techniques to repair damage or to move the junction away from damaged regions. The dark current and dynamic resistance, Rd, of the fabricated photodiodes have been characterised as a function of temperature. At 80 K, the zero-bias dynamic resistance-junction area product ( R0A) of the diodes is 4.6×10 7 Ω cm 2, with the devices being diffusion limited down to ˜135 K. Dynamic resistance has been measured for temperatures between 80 and 195 K and biases between -200 and +150 mV. Modelling of the observed dark current has been undertaken using three distinct mechanisms, diffusion, generation-recombination, and trap-assisted tunnelling. The results show that the plasma-induced junction formation technique can produce high-performance planar HgCdTe photodiodes. The dark current mechanisms found in these devices are similar to those found in diodes formed using conventional ion implantation techniques.

  2. Influence of Surface Mobility of Charge Carriers on Cdx Hg1-x Te (x=0,2-0,3) Photoconductivity

    NASA Astrophysics Data System (ADS)

    Salaev, Eldar; Guseýnov, Emil; Ýsmaýlov, Namýk; Tezer, Ateþ

    1997-10-01

    Experimental data on the photoconductivity of CdxHg1-xTe with different surface states are presented. The results are interpreted by he influence of surface mobility of charge carriers on photoeffect phenomena and the value of surface mobility for chemically treated, for polished surface and for aluminium covered surfaces of CdxHg1-xTe crystals are given.

  3. Comparative study of black hole transients XTEJ1652-453 and XTEJ1752-223

    NASA Astrophysics Data System (ADS)

    Radhika, D.; Ramadevi, M. C.; Seetha, S.

    Transient sources are seen to undergo a sudden increase in flux to achieve its peak within very few days and then slowly decay over several days or months to the quiescent level. These are binary systems which can be either a LMXB or HMXB. Here we explain the characteristics of two transient sources XTE J1652-453 and XTE 1752-223, both first discovered by PCA on-board RXTE (Rossi X-ray Timing Explorer). XTE J1652-453 was detected during two PCA scans on 28th June, 2009 and 1st July 2009 and is located at an R.A of 16h52m20.33s and Dec of -45°20'39.6'' in the galactic centre region; while XTE J1752-223 was detected on 23-10-2009 in the galactic bulge region at R.A = 17h52m13.2s and Dec = -22°18'30''. XTE J1652-453 is observed to have a faster rise to the peak, while XTE J1752-223 had a very slow rise along with a precursor. The spectral study suggests that both the sources do have thermal and non-thermal emissions and show different characteristic spectral state transitions. From the data analyzed, it is understood that XTE J1752-223 rises from its quiescence to the Low/Hard state, then into the High/Soft state via the intermediate state. Both XTE J1652-453 and XTE J1752-223 remain in the High/Soft state while in the peak, and during decay exhibit intermediate state for a long period of 2 months and enter the Low/Hard state before reaching the quiescence. Spectral study of both the sources also shows the presence of a relativistic Fe Kα emission line. Type C QPO's are seen in the case of XTE J1752-223 while in the intermediate state, but no characteristic features or QPO's are seen in XTE J1652-453. An estimation of the innermost radius of the accretion disc and equivalent mass proves that both the sources are LMXB's and black hole candidates. We would like to present a comparison of both these sources by spectral and timing analysis.

  4. ASCA Observations of the Dwarf Novae SS Cyg and VW Hyi And Observations of the Precessing Disk Cataclysmic Variable TV Col

    NASA Technical Reports Server (NTRS)

    Schlegel, E.; Swank, Jean (Technical Monitor)

    2001-01-01

    The observations for both SS Cyg and VW Hyi were to be scheduled as Targets of Opportunity jointly with other satellites. The VW Hyi observation was obtained jointly with EUVE during a superoutburst. The XTE data were initially processed, revealing no detection. However, the XTE team improved the instrumental background model and distributed it in July 1998. A further improvement was made in August 1999. The improved models allow a better background subtraction, thereby detecting previously un-detected sources.

  5. Circinus X-1: A Neutron Star Doing Its Best Impression Of A Black Hole?

    NASA Astrophysics Data System (ADS)

    Heinz, Sebastian; Sell, P.; Schulz, N.; Brandt, N.; Calvelo, D.; Jonker, P.

    2011-09-01

    The X-ray binary Circinus X-1 is a trailblazer in many ways: (a) It is one of only two neutron star X-ray binaries with a resolved radio jet, making it a prototype and defining member of the class of neutron star microquasars. (b) It is one of only two microquasars with well established large scale, diffuse radio lobes. (c) Its jet has been clocked at a Lorentz factor of Gamma=16, potentially making it the fastest microquasar to date. (d) Finally, Circinus X-1 has become the first and only neutron star XRB with a resolved X-ray jet: Recent Chandra and radio observations show the source in glorious detail, revealing parsec scale shocks and arcsecon scale extended X-ray emission. I will discuss the constraints we can put on the jet power from this neutron star and their implications for our understanding of relativistic jets from compact objects as a whole.

  6. 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.

  7. 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.

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

    NASA Astrophysics Data System (ADS)

    Choudhary, Abdur Rahim

    1994-11-01

    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.

  9. L'astronomie dans le monde

    NASA Astrophysics Data System (ADS)

    Manfroid, J.

    2010-01-01

    Galaxie cannibale; Archéologie cosmique; Trumpler 14; Etoile vampire; Trou noir errant; Micro-quasar gamma; Métaux intergalactiques; V838 Mon; Supernova particulière; Titan; Mars; Vie martienne; Variations des étoiles semblables au Soleil; GJ758B

  10. 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

  11. The predicted giant flare of Cyg X-3 occurs

    NASA Astrophysics Data System (ADS)

    Trushkin, S. A.; Nizhelskij, N. A.; Tsybulev, P. G.; Zhekanis, G. V.

    2016-09-01

    Three weeks ago we predicted (ATel #9416) that Cyg X-3 entered in the ''ultra-soft'' X-ray state and a giant flare are very probable. Later Cyg X-3 has indeed shown the relatively bright flare (ATel #9444), maximal fluxes were lower 700 mJy at 4-22 GHz and then the microquasar had again quenched.

  12. 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.

  13. 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.

  14. Diluted magnetic semiconductor superlattices and heterostructures

    NASA Astrophysics Data System (ADS)

    Datta, S.; Furdyna, J. K.; Gunshor, R. L.

    Diluted magnetic semiconductors (DMS) are mixed semiconducting crystals whose lattice is made up in part of substitutional magnetic ions. Cd 1-xMn xTe and Hg 1-xMn xTe are examples of such materials. Their structural and band parameters can be "tuned" by composition over a wide range. They can thus be exploited in situations completely similar to those involving Ga 1-xAl xAs. Using molecular beam epitaxy, we have grown Cd 1-xMn xTe superlattices with alternating Mn content, having up to 150 layers, with layer thickness ranging from 50 to 100 Å. The superlattice structure is clearly revealed by transmission electron microscopy and by zone-folding of the phonon spectrum observed in Raman scattering. Photoluminescence observed on Cd 1-xMn xTe superlattices is several orders of magnitude greater than that from a Cd 1-xMn xTe film with uniform Mn content, or from bulk Cd 1-xMn xTe specimens. The presence of localized magnetic moments in DMS results in a strong exchange interaction between these moments and band electrons. This in turn leads to gigantic Zeeman splittings of impurity states, exciton levels, Landau levels, and the bands themselves. Zeeman splittings as large as 20 meV (which in non-magnetic semiconductors would require unrealistic megagauss fields) are easily achieved in DMS in fields of several kilogauss. Since the magnitude of this exchange-induced splitting in DMS can be comparable to the binding energies and to the minigaps encountered in multiple quantum wells, DMS superlattices hold promise of a host of novel effects of both fundamental and applied interest.

  15. 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.

  16. 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.

  17. 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.

  18. Low-cost CdZnTe devices for cascade cell application

    SciTech Connect

    Basol, B.M.; Kapur, V.K. )

    1990-11-01

    This report describes a research program to develop a low-cost technique for producing Cd{sub 1-x}Zn{sub x}Te devices for cascade solar cell applications. The technique involves a two-stage process for fabricating such devices with a band gap of about 1.7 eV and a transparent contact layer of low-resistivity ZnTe. In the first stage, thin films of Cd, Zn, and Te are deposited in stacked layers as Cd{sub 1-x}An{sub x}Te. The second stage involves hearing and reacting the layers to form the compound. At first, electrodeposition was used for depositing the layers to successfully fabricate Dc{sub 1-x}Zn{sub x}Te thin-film devices. These films were also intrinsically doped with copper. For the first time, transparent ZnTe films of low resistivity were obtained in a two-stage process; preliminary solar cells using films with low Zn content were demonstrated. A second phase of the project involved growing films with higher Zn content (>15%). Such films were grown on CdS-coated substrates for fabricating devices. The effects of the solar-cell processing steps on the Cd{sub 1-x}Zn{sub x}Te and CdS/Cd{sub 1-x}Zn{sub x}Te interfaces were studied; results showed that the nature of the interface depended on the stoichiometry of the Cd{sub 1-x}Zn{sub x}Te thin film. A sharp interface was observed for the CdS/CdTe structures, but the interface became highly diffused as the Zn content in the absorber layer increased above 15%. The interaction between the CdS window layer and the Cd{sub 1-x}Zn{sub x}Te absorber layer was found to result from an exchange reaction between Zn in the absorber layer and the thin CdS film. 14 refs., 10 figs.

  19. Appropriate materials and preparation techniques for polycrystalline-thin-film thermophotovoltaic cells

    SciTech Connect

    Dhere, N.G.

    1997-03-01

    Polycrystalline-thin-film thermophotovoltaic (TPV) cells have excellent potential for reducing the cost of TPV generators so as to address the hitherto inaccessible and highly competitive markets such as self-powered gas-fired residential warm air furnaces and energy-efficient electric cars, etc. Recent progress in polycrystalline-thin-film solar cells have made it possible to satisfy the diffusion length and intrinsic junction rectification criteria for TPV cells operating at high fluences. Continuous ranges of direct bandgaps of the ternary and pseudoternary compounds such as Hg{sub 1{minus}x}Cd{sub x}Te, Pb{sub 1{minus}x}Cd{sub x}Te, Hg{sub 1{minus}x}Zn{sub x}Te, and Pb{sub 1{minus}x}Zn{sub x}S cover the region of interest of 0.50{endash}0.75 eV for efficient TPV conversion. Other ternary and pseudoternary compounds which show direct bandgaps in most of or all of the 0.50{endash}0.75 eV range are Pb{sub 1{minus}x}Zn{sub x}Te, Sn{sub 1{minus}x}Cd{sub 2x}Te{sub 2}, Pb{sub 1{minus}x}Cd{sub x}Se, Pb{sub 1{minus}x}Zn{sub x}Se, and Pb{sub 1{minus}x}Cd{sub x}S. Hg{sub 1{minus}x}Cd{sub x}Te (with x{approx}0.21) has been studied extensively for infrared detectors. PbTe and Pb{sub 1{minus}x}Sn{sub x}Te have also been studied for infrared detectors. Not much work has been carried out on Hg{sub 1{minus}x}Zn{sub x}Te thin films. Hg{sub 1{minus}x}Cd{sub x}Te and Pb{sub 1{minus}x}Cd{sub x}Te alloys cover a wide range of cut-off wavelengths from the far infrared to the near visible. Acceptors and donors are introduced in these materials by excess non-metal (Te) and excess metal (Hg and Pb) respectively. Extrinsic acceptor impurities are Cu, Au, and As while and In and Al are donor impurities. Hg{sub 1{minus}x}Cd{sub x}Te thin films have been deposited by isothermal vapor-phase epitaxy (VPE), liquid phase epitaxy (LPE), hot-wall metalorganic chemical vapor deposition (MOCVD), electrodeposition, sputtering, molecular beam epitaxy (MBE), laser-assisted evaporation, and vacuum

  20. Jet-induced star formation by accreting black holes: impact on stellar, galaxy, and cosmic evolution

    NASA Astrophysics Data System (ADS)

    Mirabel, Igor Felix

    2016-07-01

    Evidence that relativistic jets trigger star formation along their axis has been found associated to low redshift and high redshift accreting supermassive black holes. However, the physical processes by which jet-cloud interaction may trigger star formation has so far not been elucidated. To gain insight into this potentially important star formation mechanism during reionization, when microquasars were form prolifically before AGN, our international team is carrying out a muliwavelength study of a microquasar jet-induced star formation region in the Milky Way using data from space missions (Chandra, Integral, ISO, Herschel) and from the ground (at cm and mm wavelengths with the VLA and IRAM, and IR with Gemini and VLT). I will show that this relative nearby star forming region is an ideal laboratory to test models of jet-induced star formation elsewhere in the universe.

  1. 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.

  2. A Toy Model for 3:2 Ratio of kHz QPO Frequency in Black Hole X-ray Binaries

    NASA Astrophysics Data System (ADS)

    Wang, Ding-Xiong; Ye, Yong-Chun; Ma, Ren-Yi; Gong, Xiao-Long

    2005-06-01

    Production of pairs of high frequency quasi-periodic oscillations (QPOs) in black hole X-ray binaries is discussed based on a model of non-axisymmetric magnetic coupling of a rotating black hole (BH) with its surrounding accretion disk, in which a puzzling 3:2 ratio of the upper frequency to the lower frequency is explained. In addition, the correlation of the pairs of high frequency QPOs with the jets from microquasars is discussed.

  3. Multi-wavelength observations of Cygnus X-3

    NASA Astrophysics Data System (ADS)

    Varlotta, Angelo

    2012-07-01

    Cygnus X-3 is a X-ray binary consisting of an accreting compact object orbiting a Wolf-Rayet star with collimated relativistic jets, placing it firmly in the category of microquasars. It has been detected at radio frequencies and up to the high-energy gamma rays (>100 MeV) by the Fermi LAT. Many theoretical models envision very-high-energy (VHE) emission (>100 GeV) when the source manifests relativistic persistent jets or transient ejections. In light of our multi-wavelength studies of Cygnus X-3 in the radio, infra-red, soft x-ray, hard x-ray and gamma-ray (<100 GeV) bands and with the aid of VERITAS, we believe we can cast light on the particular conditions which could trigger VHE emission. We argue this can help us understand the mechanisms that may trigger VHE gamma-ray emission, thus improving our knowledge of particle acceleration and radiative processes in the jets. The implications have far reaching consequences on the understanding of other microquasars and also of active galactic nuclei, which are in many ways similar to microquasars and are prominent VHE gamma-ray sources.

  4. XMM-Newton observations of two transient millisecond X-ray pulsars in quiescence

    NASA Astrophysics Data System (ADS)

    Campana, S.; Ferrari, N.; Stella, L.; Israel, G. L.

    2005-05-01

    We report on XMM-Newton observations of two X-ray transient millisecond pulsars (XRTMSPs). We detected XTE J0929-314 with an unabsorbed luminosity of ˜ 7× 1031 erg s-1 (0.5-10 keV) at a fiducial distance of 10 kpc. The quiescent spectrum is consistent with a simple power law spectrum. The upper limit on the flux from a cooling neutron star atmosphere is about 20% of the total flux. XTE J1807-294 instead was not detected. We can put an upper limit on the source quiescent 0.5-10 keV unabsorbed luminosity ⪉ 4×1031 erg s-1 at 8 kpc. These observations strenghten the idea that XRTMSPs have quiescent luminosities significantly lower than classical neutron star transients.

  5. 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.

  6. 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.

  7. 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.

  8. Rheological characterization of O/W emulsions incorporated with neutral and charged polysaccharides.

    PubMed

    Vianna-Filho, Ricardo Padilha; Petkowicz, Carmen Lúcia Oliveira; Silveira, Joana Léa Meira

    2013-03-01

    The effects of polysaccharides, including xyloglucan from Hymenaea courbaril (XG), galactomannans from Schizolobium parahybae (GMSP) and Mimosa scabrella (GMMS), xanthan gum (XT), sodium hyaluronate (HNa) and Fucogel(®) (FG), on the rheological behavior of cosmetic emulsions were evaluated. These incorporations gave rise to six emulsified systems, denoted XGE, GMSPE, GMMSE, XTE, HNaE and FGE, respectively. The emulsion consistency was found to follow the trend GMSPE>XGE>HNaE>FGE>XTE>GMMSE. In general, the addition of polysaccharides increased the viscoelastic properties of the emulsions and decreased the creep compliance. The neutral polysaccharides (GMSPE, GMMSE) led to better stability of the emulsions after storing for 20 days relative to charged polymers. It was found that polysaccharides XG, GMSP and GMMS, which come from the seeds of native Brazilian plant species, might be used to modify the flow properties and stabilities of oil-water emulsions.

  9. 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.

  10. Magnetoabsorption in narrow-gap HgCdTe epitaxial layers in the terahertz range

    SciTech Connect

    Ikonnikov, A. V. Zholudev, M. S.; Gavrilenko, V. I.; Mikhailov, N. N.; Dvoretskii, S. A.

    2013-12-15

    The magnetoabsorption and photoconductivity spectra are investigated in the terahertz (THz) range at a temperature of T = 4.2 K for n-Hg{sub 1−x}Cd{sub x}Te bulk epitaxial layers of various compositions (both semiconductor and semimetallic) grown by molecular-beam epitaxy. Within the framework of the Kane 8 · 8 model, the electron and hole Landau levels are calculated. It is shown that, in contrast to the results of previous investigations, all observed resonance lines are related to transitions between the Landau levels of free carriers (the cyclotron resonance in the conduction band and the transitions between heavy-hole and electron Landau levels), which is evidence of the high purity and structural perfection of the samples. The possibility of using zero-gap Hg{sub 1−x}Cd{sub x}Te solid solutions as THz photodetectors tunable by magnetic field is shown.

  11. Equilibrium composition in II?VI telluride MOCVD systems

    NASA Astrophysics Data System (ADS)

    Ben-Dor, L.; Greenberg, J. H.

    1999-03-01

    Thermodynamic calculations, or computer simulation of the equilibrium composition, offer an excellent possibility to reduce drastically the elaborate trial-and-error experimental efforts of finding the optimal preparation conditions for MOCVD processes (temperature T, pressure P, initial composition of the vapors X), to limit them only to the P- T- X field of existence of the solid to be prepared and an acceptable yield of the product. In this communication equilibrium composition was investigated for MOCVD processes of CdTe, ZnTe, HgTe and solid solutions Cd xZn 1- xTe and Hg xCd 1- xTe. A number of volatile organometallic compounds have been used as precursors for MOCVD growth. These are dimethylcadmium (CH 3) 2Cd, DMCd; diethylzinc (C 2H 5) 2Zn, DEZn; diisopropylzinc [CH(CH 3) 2] 2Zn, DiPZn; diethyltellurium (C 2H 5) 2Te, DETe; diisopropyltellurium [CH(CH 3) 2] 2Te, DiPTe; methylallyltellurium CH 3TeCH 2CHCH 2, MATe. A choice of the particular combination of the precursors largely depends on the desired composition of the film to be prepared, especially in cases of solid solutions Cd xZn 1- xTe and Hg xCd 1- xTe where the vapor pressure of the precursors is instrumental for the composition of the vapor in the reaction zone and, ultimately, for the composition x of the solid solution. Equilibrium composition for II-VI telluride MOCVD systems was investigated at temperatures up to 873 K in hydrogen and inert gas atmospheres at pressures up to 1 atm. P- T- X regions of existence were outlined for each of the five materials.

  12. 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.

  13. 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

  14. 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.

  15. 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.

  16. 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

  17. 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.

  18. Infrared Photodiodes Made by Low Energy Ion Etching of Molecular Beam Epitaxy Grown Mercury-Cadmium Alloy

    NASA Astrophysics Data System (ADS)

    Yoo, Sung-Shik

    Ion etching was used to form junctions on the p-type (111)B Hg_{1-x}Cd_ {x}Te grown by Molecular Beam Epitaxy(MBE). When Hg_{1-x}Cd_{x}Te layers are etched by Ar ions at energies ranging between 300 and 450eV, the top Hg_{1 -x}Cd_{x}Te layer is converted to n-type. The converted region is electrically characterized as a defective n^+-region near the surface, and a low doped n^--region exist below the damaged region. The total thickness of the converted n-type layer was found to be considerable. These results suggest that the creation of the n-type layer is due to the filling of mercury vacancies by mercury atoms displaced by the Ar ion irradiation on the surface. For the performance of the resulting photodiodes on MBE grown (111)B Hg_{1-x}Cd _{x}Te using this technique, the dynamic resistances at 80K are one order of magnitude less than those of junctions made on Liquid Phase Epitaxially and Bulk grown Hg_{1 -x}Cd_{x}Te. The ion etching technique was compared with ion implantation technique by fabricating diodes on the same MBE grown (111)B Hg _{1-x}Cd_{x}Te layers. The result of the comparison illustrates that ion etching technique is as good as ion implantation technique for the fabrication of Hg_{1-x}Cd _{x}Te photodiodes. Also it is believed that the performance of the diodes is limited by a relatively large density of twin defects usually found in MBE grown (111)B Hg_{1-x}Cd _{x}Te.

  19. Effective performance for undoped and boron-doped double-layered nanoparticles-copper telluride and manganese telluride on tungsten oxide photoelectrodes for solar cell devices.

    PubMed

    Srathongluan, Pornpimol; Vailikhit, Veeramol; Teesetsopon, Pichanan; Choopun, Supab; Tubtimtae, Auttasit

    2016-11-01

    This work demonstrates the synthesis of a novel double-layered Cu2-xTe/MnTe structure on a WO3 photoelectrode as a solar absorber for photovoltaic devices. Each material absorber is synthesized using a successive ionic layer adsorption and reaction (SILAR) method. The synthesized individual particle sizes are Cu2-xTe(17) ∼5-10nm and MnTe(3) ∼2nm, whereas, the aggregated particle sizes of undoped and boron-doped Cu2-xTe(17)/MnTe(11) are ∼50 and 150nm, respectively. The larger size after doping is due to the interconnecting of nanoparticles as a network-like structure. A new alignment of the energy band is constructed after boron/MnTe(11) is coated on boron/Cu2-xTe nanoparticles (NPs), leading to a narrower Eg equal to 0.58eV. Then, the valence band maximum (VBM) and conduction band minimum (CBM) with a trap state are also up-shifted to near the CBM of WO3, leading to the shift of a Fermi level for ease of electron injection. The best efficiency of 1.41% was yielded for the WO3/boron-doped [Cu2-xTe(17)/MnTe(11)] structure with a photocurrent density (Jsc)=16.43mA/cm(2), an open-circuit voltage (Voc)=0.305V and a fill factor (FF)=28.1%. This work demonstrates the feasibility of this double-layered structure with doping material as a solar absorber material. PMID:27451035

  20. Required composition uniformity of Hg1-xCdxTe substrate for focal plane arrays

    NASA Astrophysics Data System (ADS)

    Gopal, Vishnu

    1996-10-01

    This paper presents a comparison of theoretically predicted spatial NETD and mean temporal NETD as a function of the composition uniformity of Hg(subscript 1-x)Cd(subscript x)Te substrate used in the fabrication of IR detector arrays. The prediction of the spatial NETD is based on the residual spatial noise left behind in the FPA after implementing a linear two point nonuniformity compensation algorithm. The effect of using an optical filter on the spatial NETD is also included to show that the specifications on the composition uniformity of the Hg(subscript 1-x)Cd(subscript x)Te substrate can be partially relaxed by using an optical filter whose cut-off wavelength is less than the cutoff wavelength of the photodiodes of mean response. The composition uniformity leading to temporal noise rather than the spatial noise limited performances are suggested to be indicating the required composition uniformity of Hg(subscript 1-x)Cd(subscript x)Te substrate for focal plane arrays (FPA). The results are presented for both MWIR and LWIR HgCdTe hybrid FPAs.

  1. 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. PMID:16929292

  2. 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.

  3. 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.

  4. 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.

  5. 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

    2015-04-01

    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.

  6. 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.

  7. 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.

  8. The beginning of a giant radio flare from Cygnus X-3

    NASA Astrophysics Data System (ADS)

    Trushkin, S. A.; Nizhelskij, N. A.; Tsybulev, P. G.; Zhekanis, G. V.

    2016-09-01

    As we suggested in ATel #9416, galactic microquasar Cygnus X-3 is currently undergoing a flaring activity. If on 30 August 2016 (MJD 57630.798) its fluxes were 120-128 mJy at 4.6, 8.2, 11.2 GHz in the RATAN-600 radio telescope observations, then on 31 August (MJD 57631.795) the fluxes became 60, 300, 570, 740, 800 mJy at 2.3, 4.6, 8.2, 11.2 and 21.7 GHz with typical errors about 3-7%.

  9. 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.

  10. Large-scale Jets in GRS 1915+105

    NASA Astrophysics Data System (ADS)

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

    2005-05-01

    Observations with the Very Large Array (VLA), originally intended to support the HERO balloon flight, show multiple arcsecond-scale components moving out from the core of the black hole X-ray binary GRS 1915+105. Data taken at 8.46 GHz on May 11 and May 23 show extended emission along the known jet axis of this microquasar (e.g., Mirabel & Rodriguez 1994 [MR94], Nature, 371, 46-48). The beam was roughly round in both observations, with a full-width at half-maximum of about 0.67 arcseconds.

  11. Search for new stellar sources of gamma-rays

    NASA Astrophysics Data System (ADS)

    Martí, Josep; Sánchez-Ayaso, Estrella; Luque-Escamilla, Pedro L.; Sánchez-Sutil, Juan R.

    2013-12-01

    We review and report about the present status of our search for gamma-ray binaries, microquasars, and new kinds of gamma-ray source associated with star forming regions in the Galaxy. The search is being carried out using cross-identification techniques applied to public databases and archives. A few promising candidates have been so far identified. These include the emission line star VES 737 and the central cluster of the Monoceros R2 star forming region. The observational data supporting the proposed associations is shortly presented and discussed.

  12. 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

  13. 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.

  14. 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.

  15. Spectral energy distribution, radio maps and polarization of Cygnus X-1: a lepto-hadronic model

    NASA Astrophysics Data System (ADS)

    Vila, G. S.; Pepe, C.; Romero, G. E.

    2016-08-01

    The microquasar Cygnus X-1 is one of the most studied astrophysical sources. Several radiative models for the non-thermal broadband emission of Cygnus X-1 are available. For the jet emission in particular, only leptonic models have been considered despite the observational evidence of the presence of hadrons in the jets of other microquasars. In this work, we present an inhomogeneous, lepto-hadronic jet model for the non-thermal broadband emission of Cygnus X-1. We calculate the contribution to the spectrum of both relativistic electrons and protons, taking into account their interaction with the magnetic field, matter and photon fields internal and external to the jet. We obtain best-fit models for the spectrum that reproduce the observations from radio to gamma rays, including the MeV tail whose origin is still disputed. We also produce synthetic radio maps of the jet and compare them to actual interferometric observations of the source. Finally, we present preliminary results for the degree of polarization of the jet radiation in the MeV band.

  16. 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.

  17. On the reprocessing of gamma-rays produced by jets

    NASA Astrophysics Data System (ADS)

    Orellana, M.; Pellizza, L. J.; Romero, G. E.

    2011-02-01

    Systems of two very different sizescales are known to produce very high-energy (VHE) radiation in their jets: AGNs and microquasars. The produced VHE photons (Eγ ~ 1 TeV) can be absorbed by the intense environmental soft photon fields, coming from the companion star (in high mass binaries) or from the accreting material (disk+corona in AGNs), as these are the dominant sources at energies around ~(mec2)2/Eγ. Energetic pairs are created by the photon-photon annihilation, and, depending on how efficient are the competing cooling channels, the absorption can lead to a reprocessing by Inverse Compton pair-cascade development. A self-consistent modeling of these systems as gamma-ray sources should then include, along with the emission and absorption processes, a thorough treatment of the pair cascades. We discuss here on this issue, focusing on our (preliminary) results of numerical simulations devoted to a study case similar to the high-mass microquasar candidate LS 5039.

  18. Feasibility study of Lense-Thirring precession in LS I +61°303

    NASA Astrophysics Data System (ADS)

    Massi, M.; Zimmermann, L.

    2010-06-01

    Context. Very recent analysis of the radio spectral index and high energy observations have shown that the two-peak accretion/ejection microquasar model applies for LS I +61°303. Aims: The fast variations of the position angle observed with MERLIN and confirmed by consecutive VLBA images must therefore be explained in the context of the microquasar scenario. Methods: We calculate what could be the precessional period for the accretion disk in LS I +61°303 under tidal forces of the Be star (Ptidal-forces) or under the effect of frame dragging produced by the rotation of the compact object (PLense-Thirring). Results: Ptidal-forces is more than one year. PLense-Thirring depends on the truncated radius of the accretion disk, Rtr. We determined Rtr = 300 rg for observed QPO at 2 Hz. This value is much above the few rg, where the Bardeen-Petterson effect should align the midplane of the disk. For this truncated radius of the accretion disk PLense-Thirring for a slow rotator results in a few days. Conclusions: Lense-Thirring precession induced by a slowly rotating compact object could be compatible with the daily variations of the ejecta angle observed in LS I +61°303.

  19. The puzzling varying radio structure of LS I +61°303

    NASA Astrophysics Data System (ADS)

    Zimmermann, L.; Massi, M.

    Recent analysis of the radio spectral index and high energy observations have shown that the two-peak accretion/ejection microquasar model applies for LS I +61°303. Aim of this work is therefore, to find in the context of the microquasar scenario a possible explanation for the fast (daily) variations of the position angle observed with MERLIN and confirmed by consecutive VLBA images. We calculate what could be the precessional period for the accretion disk under tidal forces of the Be star (PTF) or under the effect of frame dragging produced by rotation of the compact object (PLT). Our results are that PTF is at least one year, while PLT strongly depends on the truncated radius of the accretion disk (Rtr). We determine Rtr = 300 r_g for observed QPO at 2 Hz. This value is much above the few r_g, where the Bardeen-Petterson effect should align the midplane of the disk, and agrees well with the expectation of the truncated radius for the very low/hard state of LS I +61°303 (>100 r_g). For Rtr = 300 r_g, PLT results in a few days for a slow rotator. Therefore we conclude that Lense-Thirring precession could explain the daily variations of the ejecta angle observed in LS I +61°303.

  20. 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.

  1. 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

    2015-12-01

    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. PMID:26605521

  2. 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

    2015-12-01

    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.

  3. A positron annihilation radiation telescope using Laue diffraction in a crystal lens

    SciTech Connect

    Smither, R.K. ); von Ballmoos, P. . Centre d'Etude Spatiale des Rayonnements)

    1993-03-01

    We present a new type of gamma-ray telescope featuring a Laue diffraction lens, a detector module with a 3-by-3 germanium array, and a balloon gondola stabilized to 5 arc sec pointing accuracy. The instrument's lens is designed to collect 511 keV photons on its 150 CM[sup 2] effective area and focus them onto a small detector having only [approx]14 CM[sup 3] of equivalent volume for background noise. As a result, this telescope overcomes the mass-sensitivity impasse of present detectors in which the collection areas are identical to the detection area. The sensitivity of our instrument is anticipated to be 3 [times] 10[sup [minus]5] ph cm[sup [minus]2] S[sup [minus]1] at 511 key with an angular resolution of 15 arc sec and an energy resolution of 2 keV. These features will allow the resolve of a possible energetically narrow 511 keV positron annihilation line both energy-wise and spatially within a Galactic Center microquasar'' as 1El740.7-2942 or GRS1758-258. In addition to the galactic microquasars,'' other prime objectives include Cyg X-1, X-ray binaries, pulsars, and AGNS.

  4. A positron annihilation radiation telescope using Laue diffraction in a crystal lens

    SciTech Connect

    Smither, R.K.; von Ballmoos, P.

    1993-03-01

    We present a new type of gamma-ray telescope featuring a Laue diffraction lens, a detector module with a 3-by-3 germanium array, and a balloon gondola stabilized to 5 arc sec pointing accuracy. The instrument`s lens is designed to collect 511 keV photons on its 150 CM{sup 2} effective area and focus them onto a small detector having only {approx}14 CM{sup 3} of equivalent volume for background noise. As a result, this telescope overcomes the mass-sensitivity impasse of present detectors in which the collection areas are identical to the detection area. The sensitivity of our instrument is anticipated to be 3 {times} 10{sup {minus}5} ph cm{sup {minus}2} S{sup {minus}1} at 511 key with an angular resolution of 15 arc sec and an energy resolution of 2 keV. These features will allow the resolve of a possible energetically narrow 511 keV positron annihilation line both energy-wise and spatially within a Galactic Center ``microquasar`` as 1El740.7-2942 or GRS1758-258. In addition to the galactic ``microquasars,`` other prime objectives include Cyg X-1, X-ray binaries, pulsars, and AGNS.

  5. Multi-wavelength study of the first γ-ray emitting LMXB XSS J12270-4859

    NASA Astrophysics Data System (ADS)

    Saitou, Kei; Tsujimoto, Masahiro; Ebisawa, Ken; Ishida, Manabu; Mukai, Koji; Nagayama, Takahiro; Nishiyama, Shogo; Gandhi, Poshak

    2012-03-01

    Fermi is discovering many new γ-ray sources, and 1FGL J1227.9-4852 is one of them. Recent studies suggest that this source is associated with the X-ray source XSS J12270-4859 (hereafter J12270), of which nature is poorly understood. In this paper, we show results of our Suzaku and RXTE X-ray observations which are partly simultaneous with near-infrared (NIR) observations using Infra Red Survey Facility (IRSF). We found that J12270 shows (1) no emission lines in the X-ray spectra, (2) unique rapid temporal variations in X-rays, and (3) almost simultaneous X-ray and NIR flares. To investigate its nature, we constructed a spectral energy distribution (SED) from radio to γ-rays. Because of the similarity of its SED with those of other microquasars, we propose that J12270 is a microquasar with a synchrotron jet, and also the first γ-ray emitting low-mass X-ray binary.

  6. COMMON PATTERNS IN THE EVOLUTION BETWEEN THE LUMINOUS NEUTRON STAR LOW-MASS X-RAY BINARY SUBCLASSES

    SciTech Connect

    Fridriksson, Joel K.; Homan, Jeroen; Remillard, Ronald A.

    2015-08-10

    The X-ray transient XTE J1701–462 was the first source observed to evolve through all known subclasses of low-magnetic-field neutron star low-mass X-ray binaries (NS-LMXBs), as a result of large changes in its mass accretion rate. To investigate to what extent similar evolution is seen in other NS-LMXBs we have performed a detailed study of the color–color and hardness–intensity diagrams (CDs and HIDs) of Cyg X-2, Cir X-1, and GX 13+1—three luminous X-ray binaries, containing weakly magnetized neutron stars, known to exhibit strong secular changes in their CD/HID tracks. Using the full set of Rossi X-ray Timing Explorer Proportional Counter Array data collected for the sources over the 16 year duration of the mission, we show that Cyg X-2 and Cir X-1 display CD/HID evolution with close similarities to XTE J1701–462. Although GX 13+1 shows behavior that is in some ways unique, it also exhibits similarities to XTE J1701–462, and we conclude that its overall CD/HID properties strongly indicate that it should be classified as a Z source, rather than as an atoll source. We conjecture that the secular evolution of Cyg X-2, Cir X-1, and GX 13+1—illustrated by sequences of CD/HID tracks we construct—arises from changes in the mass accretion rate. Our results strengthen previous suggestions that within single sources Cyg-like Z source behavior takes place at higher luminosities and mass accretion rates than Sco-like Z behavior, and lend support to the notion that the mass accretion rate is the primary physical parameter distinguishing the various NS-LMXB subclasses.

  7. 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.

  8. High-Temperature Transport in Lanthanum Telluride and Other Modern Thermoelectric Materials

    NASA Astrophysics Data System (ADS)

    May, Andrew F.

    This manuscript discusses the materials physics of thermal and electrical transport in the solid state. In particular, the focus is on thermoelectric materials, which enable the direct conversion between thermal and electrical energy. The ability of simple approximations and semiclassical models to describe transport is explored in a variety of systems. In some cases, the traditional models provide a very accurate description of the transport for the compositions of interest to thermoelectric applications. This is the case for n-type Ba8Ga16-xGe30+x, where a single, parabolic band model captures the electrical transport and thus allows the accurate prediction of optimal composition for energy conversion. This is not found to be true in La3-xTe4, and more than one parabolic conduction band is required to describe the electrical transport. In this case, the use of ab initio electronic band structure calculations provided critical knowledge for physical models to be developed. The influence of structure on thermal transport is also examined in detail. The compounds considered typically possess low lattice thermal conductivity, with values often being less than or equal to 1 W/m/K at 300 K. This can generally be associated with large unit cells, where the high number of atoms per unit cell results in a large number of optical modes, which carry little heat due to their low group velocities. Phonon scattering is also considered, and the cation vacancies in La3-xTe 4 are found to reduce the lattice thermal conductivity by over 100% at room temperature. Finally, the resulting thermoelectric efficiency is discussed, where leg efficiencies near 20% of the Carnot efficiency are predicted in segmented legs. The work detailed here has led to the continued development of La3-xTe4 by the Jet Propulsion Laboratory, where it is a top candidate for future use in deep-space power-generation systems.

  9. 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.

  10. 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.

  11. Common Patterns in the Evolution between the Luminous Neutron Star Low-Mass X-ray Binary Subclasses

    NASA Astrophysics Data System (ADS)

    Fridriksson, Joel K.; Homan, Jeroen; Remillard, Ronald A.

    2015-08-01

    The X-ray transient XTE J1701-462 was the first source observed to evolve through all known subclasses of low-magnetic-field neutron star low-mass X-ray binaries (NS-LMXBs), as a result of large changes in its mass accretion rate. To investigate to what extent similar evolution is seen in other NS-LMXBs we have performed a detailed study of the color-color and hardness-intensity diagrams (CDs and HIDs) of Cyg X-2, Cir X-1, and GX 13+1—three luminous X-ray binaries, containing weakly magnetized neutron stars, known to exhibit strong secular changes in their CD/HID tracks. Using the full set of Rossi X-ray Timing Explorer Proportional Counter Array data collected for the sources over the 16 year duration of the mission, we show that Cyg X-2 and Cir X-1 display CD/HID evolution with close similarities to XTE J1701-462. Although GX 13+1 shows behavior that is in some ways unique, it also exhibits similarities to XTE J1701-462, and we conclude that its overall CD/HID properties strongly indicate that it should be classified as a Z source, rather than as an atoll source. We conjecture that the secular evolution of Cyg X-2, Cir X-1, and GX 13+1—illustrated by sequences of CD/HID tracks we construct—arises from changes in the mass accretion rate. Our results strengthen previous suggestions that within single sources Cyg-like Z source behavior takes place at higher luminosities and mass accretion rates than Sco-like Z behavior, and lend support to the notion that the mass accretion rate is the primary physical parameter distinguishing the various NS-LMXB subclasses.

  12. Influence of the Ion Coordination Number on Cation Exchange Reactions with Copper Telluride Nanocrystals.

    PubMed

    Tu, Renyong; Xie, Yi; Bertoni, Giovanni; Lak, Aidin; Gaspari, Roberto; Rapallo, Arnaldo; Cavalli, Andrea; Trizio, Luca De; Manna, Liberato

    2016-06-01

    Cu2-xTe nanocubes were used as starting seeds to access metal telluride nanocrystals by cation exchanges at room temperature. The coordination number of the entering cations was found to play an important role in dictating the reaction pathways. The exchanges with tetrahedrally coordinated cations (i.e., with coordination number 4), such as Cd(2+) or Hg(2+), yielded monocrystalline CdTe or HgTe nanocrystals with Cu2-xTe/CdTe or Cu2-xTe/HgTe Janus-like heterostructures as intermediates. The formation of Janus-like architectures was attributed to the high diffusion rate of the relatively small tetrahedrally coordinated cations, which could rapidly diffuse in the Cu2-xTe NCs and nucleate the CdTe (or HgTe) phase in a preferred region of the host structure. Also, with both Cd(2+) and Hg(2+) ions the exchange led to wurtzite CdTe and HgTe phases rather than the more stable zinc-blende ones, indicating that the anion framework of the starting Cu2-xTe particles could be more easily deformed to match the anion framework of the metastable wurtzite structures. As hexagonal HgTe had never been reported to date, this represents another case of metastable new phases that can only be accessed by cation exchange. On the other hand, the exchanges involving octahedrally coordinated ions (i.e., with coordination number 6), such as Pb(2+) or Sn(2+), yielded rock-salt polycrystalline PbTe or SnTe nanocrystals with Cu2-xTe@PbTe or Cu2-xTe@SnTe core@shell architectures at the early stages of the exchange process. In this case, the octahedrally coordinated ions are probably too large to diffuse easily through the Cu2-xTe structure: their limited diffusion rate restricts their initial reaction to the surface of the nanocrystals, where cation exchange is initiated unselectively, leading to core@shell architectures. Interestingly, these heterostructures were found to be metastable as they evolved to stable Janus-like architectures if annealed at 200 °C under vacuum. PMID:27177274

  13. 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

  14. 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.

  15. 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.

  16. Influence of the Ion Coordination Number on Cation Exchange Reactions with Copper Telluride Nanocrystals.

    PubMed

    Tu, Renyong; Xie, Yi; Bertoni, Giovanni; Lak, Aidin; Gaspari, Roberto; Rapallo, Arnaldo; Cavalli, Andrea; Trizio, Luca De; Manna, Liberato

    2016-06-01

    Cu2-xTe nanocubes were used as starting seeds to access metal telluride nanocrystals by cation exchanges at room temperature. The coordination number of the entering cations was found to play an important role in dictating the reaction pathways. The exchanges with tetrahedrally coordinated cations (i.e., with coordination number 4), such as Cd(2+) or Hg(2+), yielded monocrystalline CdTe or HgTe nanocrystals with Cu2-xTe/CdTe or Cu2-xTe/HgTe Janus-like heterostructures as intermediates. The formation of Janus-like architectures was attributed to the high diffusion rate of the relatively small tetrahedrally coordinated cations, which could rapidly diffuse in the Cu2-xTe NCs and nucleate the CdTe (or HgTe) phase in a preferred region of the host structure. Also, with both Cd(2+) and Hg(2+) ions the exchange led to wurtzite CdTe and HgTe phases rather than the more stable zinc-blende ones, indicating that the anion framework of the starting Cu2-xTe particles could be more easily deformed to match the anion framework of the metastable wurtzite structures. As hexagonal HgTe had never been reported to date, this represents another case of metastable new phases that can only be accessed by cation exchange. On the other hand, the exchanges involving octahedrally coordinated ions (i.e., with coordination number 6), such as Pb(2+) or Sn(2+), yielded rock-salt polycrystalline PbTe or SnTe nanocrystals with Cu2-xTe@PbTe or Cu2-xTe@SnTe core@shell architectures at the early stages of the exchange process. In this case, the octahedrally coordinated ions are probably too large to diffuse easily through the Cu2-xTe structure: their limited diffusion rate restricts their initial reaction to the surface of the nanocrystals, where cation exchange is initiated unselectively, leading to core@shell architectures. Interestingly, these heterostructures were found to be metastable as they evolved to stable Janus-like architectures if annealed at 200 °C under vacuum.

  17. Local structure and electrical switching in chalcogenide glasses

    NASA Astrophysics Data System (ADS)

    Murugavel, S.; Asokan, S.

    1998-08-01

    Bulk AlxAs40Te60-x and AlxAs40-xTe60 glasses (5<=x<=20) are found to exhibit memory and threshold switching. 27Al solid-state NMR measurements reveal that in both series of glasses, Al resides in tetrahedrally (fourfold) as well as octahedrally (sixfold) coordinated environments, with the fraction of fourfold coordinated Al atoms in the glasses decreasing with Al content. Fourfold coordinated Al atoms provide structural flexibility, and promote memory switching at low Al content (x<15). At higher Al content, the growth in the fraction of sixfold coordinated atoms leads to increased network connectivity, which promotes threshold switching.

  18. High Energy Astrophysics Program (HEAP)

    NASA Technical Reports Server (NTRS)

    Angelini, L.; Holdridge, David V.; Norris, J. (Technical Monitor)

    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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Stark spectroscopy of CdTe and CdMnTe quantum dots embedded in n-i-p diodes

    SciTech Connect

    Kłopotowski, Ł. Fronc, K.; Wojnar, P.; Wiater, M.; Wojtowicz, T.; Karczewski, G.

    2014-05-28

    We investigate charging effects in CdTe and Cd{sub 1−x}Mn{sub x}Te quantum dots embedded in n-i-p diodes. The tunneling of holes out of the dots at reverse bias and hole injection at forward bias control the dot charge state and allow for its electric field tuning. Furthermore, we analyze the Stark shifts of the photoluminescence transitions and evaluate the effect of the electric field on the binding of the observed excitonic complexes. We find that the binding can be strengthened or weakened depending on the zero-field alignment of the electron and hole wavefunctions.

  4. 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.

  5. Molecular beam epitaxy of CdTe on GaAs substrates and HgCdTe on CdTe/GaAs alternate substrates

    SciTech Connect

    Lange, M.D.

    1993-12-31

    Two aspects of molecular-beam epitaxy (MBE) of the infrared sensitive semiconductor Hg{sub 1-x}Cd{sub x}Te were investigated: control of the substrate temperature by infrared pyrometer in addition to rear thermocouple, and improvement of CdTe/GaAs alternate substrates. Pyrometer behavior was recorded while controlling the temperatures of growing Hg{sub 1-x}Cd{sub x}Te with a frontal thermocoupled that contacted their surfaces. These recordings were interpreted in terms of emission and absorption, transmission and reflection, and thin-film interference. Based on these results, temperature control by rear thermocouple was reexamined, resulting in improved technique of that temperature control method as well. A temperature control technique combining both the pyrometer and the rear thermocoupled was developed; and evidence is presented and the rear thermocouple was developed; and evidence is presented for the resulting improvement in crystalline and electrical quality of MBE Hg{sub 1-x}Cd{sub x}Te. Investigations of Hg{sub 1-x}Cd{sub x}Te MBE onto more afforadable, larger, and more rugged CdTe/GaAs alternate substrates focused chiefly on improving the MBE of CdTe onto GaAs. This heteroepitaxy was studied primarily in terms of the influences on CdTe crystalline quality of the mismatches in bonding character, lattice spacing, thermal expansion, and charge imbalance between these two zincblende crystals. A novel dual epitaxial relationship, CdTe(331)B/GaAs(112)B and CdTe (112)B/GaAs(112)B, was discovered in these investigations; and the nonparellel orientation proves superior to the parallel orientation and to both orientations of the previously known CdTe(111)B/GaAs(001) and CdTe(001)/GaAs(001) dual epitaxial relationship. A charge imbalance model, applied to these four heterointerfaces, predicts the balancing of that charge by movement of electrons into or out of the heterointerfacial dangling bonds, which exist due to the lattice mismatch.

  6. Quiescent thermal emission from neutron stars in low-mass X-ray binaries

    NASA Astrophysics Data System (ADS)

    Turlione, A.; Aguilera, D. N.; Pons, J. A.

    2015-05-01

    Context. We monitored the quiescent thermal emission from neutron stars in low-mass X-ray binaries after active periods of intense activity in X-rays (outbursts). Aims: The theoretical modeling of the thermal relaxation of the neutron star crust may be used to establish constraints on the crust composition and transport properties, depending on the astrophysical scenarios assumed. Methods: We numerically simulated the thermal evolution of the neutron star crust and compared them with inferred surface temperatures for five sources: MXB 1659-29, KS 1731-260, XTE J1701-462, EXO 0748-676 and IGR J17480-2446. Results: We find that the evolution of MXB 1659-29, KS 1731-260 and EXO 0748-676 can be well described within a deep crustal cooling scenario. Conversely, we find that the other two sources can only be explained with models beyond crustal cooling. For the peculiar emission of XTE J1701-462 we propose alternative scenarios such as residual accretion during quiescence, additional heat sources in the outer crust, and/or thermal isolation of the inner crust due to a buried magnetic field. We also explain the very recent reported temperature of IGR J17480-2446 with an additional heat deposition in the outer crust from shallow sources.

  7. 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.

  8. 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.

  9. 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.

  10. On the detectability of CO molecules in the interstellar medium via X-ray spectroscopy

    NASA Astrophysics Data System (ADS)

    Joachimi, Katerine; Gatuzz, Efraín; García, Javier A.; Kallman, Timothy R.

    2016-09-01

    We present a study of the detectability of CO molecules in the Galactic interstellar medium using high-resolution X-ray spectra obtained with the XMM-Newton Reflection Grating Spectrometer. We analysed 10 bright low mass X-ray binaries (LMXBs) to study the CO contribution in their line of sights. A total of 25 observations were fitted with the ISMabs X-ray absorption model which includes photoabsorption cross-sections for O I, O II, O III and CO. We performed a Monte Carlo (MC) simulation analysis of the goodness of fit in order to estimate the significance of the CO detection. We determine that the statistical analysis prevents a significant detection of CO molecular X-ray absorption features, except for the lines of sight towards XTE J1718-330 and 4U 1636-53. In the case of XTE J1817-330, this is the first report of the presence of CO along its line of sight. Our results reinforce the conclusion that molecules have a minor contribution to the absorption features in the O K-edge spectral region. We estimate a CO column density lower limit to perform a significant detection with XMM-Newton of N(CO) > 6 × 1016 cm-2 for typical exposure times.

  11. Studies on the diffusion of zinc in cadmium telluride at 800°C

    NASA Astrophysics Data System (ADS)

    Jones, E. D.; Clark, J. C.; Mullin, J. B.; Brinkman, A. W.

    1994-04-01

    The diffusion of zinc into bulk grown cadmium telluride has been studied at 800°C as a function of anneal time and mass of the diffusion source. The diffusions were carried out in evacuated silica ampoules and the diffusion profiles were measured using a radiotracer sectioning technique, although some measurements were obtained using scanning electron microscopy with an EDAX attachment. When the mass of zinc placed in the ampoule exceeded 2 mg, a ternary compound of Zn xCd 1- xTe, with x = 0.8, was formed on the surface of the slice early on in the diffusion and the diffusion profiles consisted of two components. Two values of the diffusivity were obtained, Dslow → 2 × 10 -11 cm 2 s -1 and Dfast → 2 × 10 -10 cm 2 s -1, for anneal times exceeding 6 h and a mass of zinc of 8 mg placed in the ampoule. This contrasted with the results when the mass of zinc was less than 2 mg when no effective surface layer of the ternary compound was formed and diffusion profiles consisting of a single component were obtained. It is proposed that two diffusion mechanisms are operating, one due to zinc atoms diffusing from the vapour into the Zn xCd 1- xTe layer and the second an interdiffusion between the ternary compound in the surface of the slice and the CdTe in the bulk.

  12. 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.

  13. High Resolution Spectroscopy of AGN in Outburst: The Gaseous Nuclear Environment and the WIGM

    NASA Technical Reports Server (NTRS)

    Mushotzky, Richard (Technical Monitor); Nicastro, Fabrizio

    2004-01-01

    This grant is associated to a successful XMM-A02 proposal to observe blazars in outburst states, to X-ray the intergalactic medium, searching for intervening ionized absorption. The observation was triggered on August 31 2003, on the blazar 1H 0414+009 (2=0.287), when the target was showing a level of activity of about 20 mCrab in the total XTE-ASM band. The observation was performed 1 day later (on September 1, 2003) and lasted for 79 ks (79 % of the requested time). Unfortunately, assuming that the XTE-ASM notification was real, the target had recovered his quiescent level of approx. 0.35 mCrab, when the XMM RGS observed it. This, combined with the lower-than-requested exposure, produced an XMM-RGS spectrum containing only - 40 counts per resolution element in the 24.1 less than lambda(A) less than 30 range, insufficient to detect even the strongest predicted lines from the OVII WHIM. However, we do detect the Local Group WHIM OVII system in the spectrum of this blazar.

  14. Synthesis and evaluation of lead telluride/bismuth antimony telluride nanocomposites for thermoelectric applications

    NASA Astrophysics Data System (ADS)

    Ganguly, Shreyashi; Zhou, Chen; Morelli, Donald; Sakamoto, Jeffrey; Uher, Ctirad; Brock, Stephanie L.

    2011-12-01

    Heterogeneous nanocomposites of p-type bismuth antimony telluride (Bi 2- xSb xTe 3) with lead telluride (PbTe) nanoinclusions have been prepared by an incipient wetness impregnation approach. The Seebeck coefficient, electrical resistivity, thermal conductivity and Hall coefficient were measured from 80 to 380 K in order to investigate the influence of PbTe nanoparticles on the thermoelectric performance of nanocomposites. The Seebeck coefficients and electrical resistivities of nanocomposites decrease with increasing PbTe nanoparticle concentration due to an increased hole concentration. The lattice thermal conductivity decreases with the addition of PbTe nanoparticles but the total thermal conductivity increases due to the increased electronic thermal conductivity. We conclude that the presence of nanosized PbTe in the bulk Bi 2- xSb xTe 3 matrix results in a collateral doping effect, which dominates transport properties. This study underscores the need for immiscible systems to achieve the decreased thermal transport properties possible from nanostructuring without compromising the electronic properties.

  15. Short and long term effects of additional post curing and polishing systems on the color change of dental nano-composites.

    PubMed

    Egilmez, Ferhan; Ergun, Gulfem; Cekic-Nagas, Isil; Vallittu, Pekka K; Lassila, Lippo V J

    2013-01-01

    The purpose was to determine the short and long term effects of polishing systems and post-heat-light curing on the color stability of nano-composites. The disc shaped samples (ø=10 mm, h=3 mm) were prepared. Forty subgroups (n=5) were designed according to two different curing conditions and five different polishing methods. Color change measurements were performed on the day of specimen preparation (base) and repeated after 1 and 7 months of water storage. MANOVA and Tukey's post hoc tests were applied (p<0.05). While the color difference values of resin composites were ranked as EXP2>EXP1>CME≥XTE after 1 month (p<0.05), after 7 months the ranking was EXP2≥EXP1>XTE>CME (p<0.05). Type and compositions of nano-composites may be important on the long-term color stability of the restoration. Additional post-heat-light curing of nano-composites may produce higher color change than the hand-light curing protocol. Consequently, the polishing procedures should be applied to obtain more resistant composite surface to discoloration. PMID:23370878

  16. Numerical Simulations of Viscous Accretion Flow around Black Holes

    NASA Astrophysics Data System (ADS)

    Lee, Seong-Jae; Chattopadhyay, Indranil; Kumar, Rajiv; Hyung, Siek; Ryu, Dongsu

    2016-06-01

    We present shocked viscous accretion flow onto a black hole in a two dimensional cylindrical geometry, where initial conditions were chosen from analytical solutions. The simulation code used the Lagrangian Total Variation Diminishing (LTVD) and remap routine, which enabled us to attain high accuracy in capturing shocks and to handle the angular momentum distribution correctly. The steady state shocked solution in the inviscid, as well as in the viscous regime, matched theoretical predictions well, but increasing viscosity renders the accretion shock unstable. Large amplitude shock oscillation is accompanied by intermittent, transient inner multiple shocks. Such oscillation of the inner part of disk is interpreted as the source of QPO in hard X-rays observed in microquasars; and strong shock oscillation induces strong episodic jet emission. The periodicity of jets and shock oscillation are similar. Our simulation shows that the jets for higher viscosity parameter are evidently stronger and faster than that for lower viscosity.

  17. 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.

  18. 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)

  19. Search for TeV Gamma Rays from Cygnus X-3

    NASA Astrophysics Data System (ADS)

    Cui, Wei; VERITAS Collaboration

    2013-06-01

    We report results from a systematic search for gamma-ray emission from Cygnus X-3 at TeV energies with VERITAS. The source is an enigmatic X-ray binary that has defied classification. Its short orbital period is typical of low-mass X-ray binaries, yet signatures of a Wolf-Rayet star are evident. Powerful jets seen are indicative of microquasar, but arguments for the existence of a neutron star are also compelling. Recently, Cygnus X-3 was detected at GeV gamma-ray energies with AGILE and Fermi LAT. There is strong evidence that GeV gamma-ray production is correlated with the radio/X-ray properties of the source. To this end, we have also carried out more focused searches for TeV gamma rays in the radio/X-ray states of interest.

  20. Jet-Environment Interactions as Diagnostics of Jet Physics

    NASA Astrophysics Data System (ADS)

    Heinz, Sebastian

    2014-09-01

    In this chapter, we will explore the interaction of jets with their environments. Jets can transport a sizable fraction of accretion energy away from black holes and neutron stars. Because they are collimated, they can travel to distances far beyond the gravitational sphere of influence of the black hole. Yet, their interaction with the interstellar and intergalactic medium must eventually halt their advance and dissipate the energy they carry. The termination of the jet, and the inflation of large scale cavities of relativistic plasma offers one of the most powerful ways to constrain the physics of jets. In this chapter, we will review the inflation of radio lobes, the propagation of hot spots, the creation of shells and cavities, and the bending of jet by proper motion through their environment, both in the context of AGN jets and microquasars.

  1. 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.

  2. 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.

  3. 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.

  4. Design and tests of the hard x-ray polarimeter X-Calibur

    NASA Astrophysics Data System (ADS)

    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.

    2011-09-01

    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 InFOCμS 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.

  5. Design and tests of the hard x-ray polarimeter X-Calibur

    NASA Astrophysics Data System (ADS)

    Beilicke, M. G.; Baring, M.; Barthelmy, S.; Binns, W. R.; Buckley, J.; Cowsik, R.; Dowkontt, P.; Garson, A.; Guo, Q.; Haba, Y.; Israel, M. H.; Kislat, F.; Kunieda, H.; Lee, K.; Martin, J.; Matsumoto, H.; Miyazawa, T.; Okajima, T.; Schnittman, J.; Tamura, K.; Tueller, J.; Krawczynski, H.

    2012-10-01

    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 InFOCμS grazing incidence hard X-ray telescope. X-Calibur combines a low-Z Compton scatterer with a CZT detector assembly to measure the polarization of 20-60 keV X-rays making use of the fact that polarized photons Compton scatter preferentially perpendicular to the electric field orientation; in principal, a similar space-borne experiment could be operated in the 5 - 100 keV regime. X-Calibur achieves a high detection efficiency of order unity.

  6. The hard X-ray polarimeter X-Calibur

    NASA Astrophysics Data System (ADS)

    Beilicke, M.; Baring, M. G.; Barthelmy, S.; Binns, W. R.; Buckley, J.; Cowsik, R.; Dowkontt, P.; Guo, Q.; Haba, Y.; Israel, M. H.; Kunieda, H.; Lee, K.; Martin, J.; Matsumoto, H.; Miyazawa, T.; Okajima, T.; Schnittman, J.; Tamura, K.; Tueller, J.; Krawczynski, H.

    2012-12-01

    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 In FOCμS grazing incidence hard X-ray telescope. X-Calibur combines a low-Z Compton scatterer with a CZT detector assembly to measure the polarization of 20-60keV X-rays making use of the fact that polarized photons Compton scatter preferentially perpendicular to the electric field orientation; in principal, a similar space-borne experiment could be operated in the 5-100keV regime. X-Calibur achieves a high detection efficiency of order unity.

  7. 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.

  8. The beaming pattern of external Compton emission from relativistic outflows: The case of anisotropic distribution of electrons

    SciTech Connect

    Kelner, S. R.; Lefa, E.; Rieger, F. M.; Aharonian, F. A.

    2014-04-20

    The beaming pattern of radiation emitted by a relativistically moving source, such as jets in microquasars, active galactic nuclei, and gamma-ray bursts, is a key issue for understanding acceleration and radiation processes in these objects. In this paper, we introduce a formalism based on a solution of the photon transfer equation to study the beaming patterns for emission produced by electrons accelerated in the jet and the upscattering photons of low-energy radiation fields of external origin (the so-called external Compton scenario). The formalism allows us to treat non-stationary, non-homogeneous, and anisotropic distributions of electrons, but assuming homogeneous/isotropic and non-variable target photon fields. We demonstrate the non-negligible impact of the anisotropy in the electron distribution on angular and spectral characteristics of the EC radiation.

  9. Spectrum and timing phenomena in IGR J17091-3624 2011 outburst

    NASA Astrophysics Data System (ADS)

    Zhang, Z.; Qu, J. L.; Gao, H. Q.; Zhou, J. N.

    2013-02-01

    X-ray source IGR J17091-3624 was discovered by INTEGRAL observatory on 2003 April (Kuulkers 2003). A outburst was detected with Swift/Burst Alert Telescope (BAT) in late January 2011 (Krimm 2011). IGR J17091-3624 has a similar timing phenomena to microquasar GRS 1915+105(Belloni 2000; Altamirano 2011). We have analyzed the evolution of temporal and spectral characteristic of IGR J17091-3624 during the 2011 outburst. We find that (1) all the QPOs can be divided into two types, QPO-AB and QPO-C, (2) a small outburst tracks clockwise in the HID, (3) the relationship between hardness and disk color temperature forms a V-shape. Those results will give a strong constraint on the disk radiative process.

  10. 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.

  11. Contrasting distances using Type Ia supernovae and gamma ray events in the local universe

    NASA Astrophysics Data System (ADS)

    Girola, R.

    2014-10-01

    In the year 1998, it is discovered -through Type Ia supernova observation- that the universe is expanding at an accelerating rate. One interpretation, which is not contrary to General Relativity, accepts the existence of a cosmological constant other than zero and of Quintessence, a repulsive force. These supernovae are used as standard candles to measure both distances and the accelerating expansion rate of the universe. Although this is based on well-known and proven facts, it was found that the method employed contains systematic errors. The purpose of this study is to present an alternative method to reduce the errors through the measurement of galactic distances, using gamma-ray events from gamma-ray binaries and microquasars. As the actual supernova population is rather small to be statistically reliable, it is supported with numerical simulations to provide a contrast between Type Ia supernovae and gamma-ray events. To this end, we apply the measurement of Type Ia supernovae to nearby galaxies where is possible to measure the accelerating expansion of the universe. Afterwards, assuming that the observations and instrumentations would enable this possibility, we perform the measurements of a group of microquasars, taking on account their approximate equitable distribution of energy which is contrary to the results of supernovae. Our study remains open to further exploration on whether there is a difference between the distances measured or they are compatible and they manage to minimize the systematic error of Type Ia supernova method. In this way, we estimate if the distances are consistent in each case as well as we calculate the measurement of the universe's expansion.

  12. 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.

  13. 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

  14. 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

    2013-08-01

    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. PMID:23803956

  15. LPE growth and characterization of 1.3 μm (Hg, Cd)Te layers

    NASA Astrophysics Data System (ADS)

    Janik, E.; Ferah, M.; Legros, R.; Triboulet, R.; Brossat, T.; Riant, Y.

    1985-08-01

    The growth of epitaxial layers of Cd xHg 1- xTe with x=0.7, suitable for optoelectronic applications, is obtained. The growth is performed by LPE from a Te-rich solution in a closed tube tipping system, on hydroplane polished CdTe or Cd 1- yZn yTe substrates. The growth apparatus and procedure are described. Layers of thickness 10-40 μm, grown at 500-600°C, were obtained. Attention was paid mainly to the surface morphological quality and good decantation from the layers. The surface morphology was observed by Nomarski contrast photography, the profile concentration measured by electron microprobe, and back reflection Laue patterns are presented also. We report, also, the results of measurements of the optical and electrical parameters of grown layers and the characteristics of photodiodes made from them.

  16. Discovery of the acceleration in the wind emission lines of CI Cam

    NASA Astrophysics Data System (ADS)

    Barsukova, E. A.; Klochkova, V. G.; Panchuk, V. E.; Yushkin, M. V.; Goranskij, V. P.; Miroshnichenko, A. S.; Bjorkman, K. S.; Manset, N.

    2007-03-01

    CI Cam (XTE J0421+560) is an X-ray transient and a binary system with the optical companion, which shows the B[e] phenomenon. Its strong all-wavelength outburst occured in 1998 April. The system consists of a B4 III-V star and a possible white dwarf on an eccentric (e = 0.62) orbit with the period of 19.407 day (ATel #416; Astronomy Reports, 2006, V.50, 664). We analysed seventeen echelle spectra (resolution FWHM=0.08-0.21A) taken with Russian 6-m telescope BTA (LYNX and NES spectrographs), CFHT (ESPaDOnS spectrograph), and McDonald 2.1-m (Sandiford spectrograph) and 2.7-m (cs2 spectrograph) telescopes.

  17. 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.

  18. Half-metallic ferromagnetism in Cr-doped semiconducting Ge-chalcogenide: Density functional approach

    SciTech Connect

    Saini, Hardev S.; Singh, Mukhtiyar; Thakur, Jyoti; Kashyap, Manish K.

    2014-04-24

    A supercell approach has been used to calculate the electronic and magnetic properties of Cr-doped Ge chalcogenide, Ge{sub 1−x}Cr{sub x}Te (x = 0.25 and 0.125). The calculations have been performed using full potential Linear Augmented Plane Wave (FPLAPW) method within generalized gradient approximation (GGA) as exchange-correlation (XC) potential. The calculated results show that the doping of Cr induces the 100% spin polarization at Fermi level (EF) and showed the robust half metallic ferromagnetism in this compound. Thus, the compound at both dopant concentrations behave as dilute magnetic semiconductor (DMS) showing metallic property in majority and semiconducting for minority spin channels which is best suited for spintronic applications. The total magnetic moments of this compound are mainly due to Cr-d states present at E{sup F} with negligible contribution from electronic states of other atoms.

  19. 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.

  20. Effect of the bias electric field on the spectral distribution of the photodielectric effect in the Schottky-barrier structures based on the cadmium-zinc telluride crystals

    SciTech Connect

    Komar', V. K.; Puzikov, V. M.; Chugai, O. N. Nalivaiko, D. P.; Sulima, S. V.; Abashin, S. L.

    2007-06-15

    Spectral dependences of effective values of the real and imaginary parts of the low-frequency permittivity of the Cd{sub 1-x}Zn{sub x}Te crystals (x=0.12-0.16) with the Schottky barrier fabricated on the surface are measured. It is found that the boundary wavelengths of the characteristic portions of the measured dependences represented in the complex plane correspond to energies of photons, which cause the radical variations in the state of negatively charged and electrically neutral localized acceptor states. The variations in the energy spectrum of the localized states, which are determined by the magnitude and polarity of the electric bias applied to the Shottky barrier, are found.

  1. 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.

  2. Physical Interpretation of the UV/X-Ray Variability Behavior of NGC 7469

    NASA Astrophysics Data System (ADS)

    Petrucci, P.; Maraschi, L.; Haardt, F.; Nandra, K.

    We present a re-analysis of the simultaneous 30 day IUE/XTE observation of NGC 7469 done in 1996 using a detailed Comptonization model. Our results are completely consistent with a slab geometry where all the observed UV emission is supposed to cross the corona. The UV seed photon emission appears to be dominated by the reprocessing of the X-rays. We found a strong anticorrelation between the corona temperature and the UV flux. Such an anticorrelation is clearly inconsistent with a fixed disc-corona configuration and suggests a variation of the geometry of the system. We also find a correlation between the corona optical depth and the X-ray flux which may reflect processes linked to the corona formation. During the observations, NGC 7469 appears to accrete near its Eddington limit. This source could then be an example of magnetically dominated disc-corona system.

  3. Negative luminescence from In1 - xAlxSb and Cdx Hg1 - x Te diodes

    NASA Astrophysics Data System (ADS)

    Ashley, T.; Elliott, C. T.; Gordon, N. T.; Hall, R. S.; Johnson, A. D.; Pryce, G. J.

    1995-12-01

    Indium aluminium antimonide (In 1- xAl xSb) and cadmium mercury telluride (Cd xHg 1- xTe) heterostructure diodes, which comprise a near intrinsic active region bounded by more highly doped contact regions, exhibit positive or negative luminescence at medium to long infrared wavelengths when forward or reverse biased respectively at room temperature. In reverse bias, the carrier densities in the near intrinsic region are reduced below their equilibrium values by the effects of exclusion and extraction. In consequence, the radiative recombination is reduced and the devices emit less infrared radiation than the thermal equilibrium value. The observed intensity of the negative luminescence is in general agreement with expected values.

  4. 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.

  5. Photoresponse asymmetry of CdZnTe crystals

    SciTech Connect

    But, A. V. Mygal, V. P.; Phomin, A. S.

    2011-02-15

    It is shown that transformation of photoelectric characteristics of sensors based on Cd{sub 1-x}Zn{sub x}Te (x = 0.05-0.15) crystals into parametric spectral I({lambda})-dI/d{lambda}, kinetic I(t)-dI/dt, and dynamic U-I({Delta}y){sub f,{lambda}} signatures (I({lambda}) is the photocurrent, U is the voltage, f is the frequency, t is the time, and y is the coordinate) makes it possible to reveal integrative photoresponse features caused by the photoresponse asymmetry and nonlinearity. Indices of asymmetry and balance of dynamic and energy photoinduced states are suggested; these indices represent systematically the effect of multiscale fields on photoelectronic processes. Using these indices, the ranges of external effects at which systematic features of photoresponse of sensors are minimal or maximal are determined, which makes it possible to increase the efficiency of purposeful selection and treatment of sensors.

  6. Large external ΔT and cooling power densities in thin-film Bi2Te3-superlattice thermoelectric cooling devices

    NASA Astrophysics Data System (ADS)

    Bulman, G. E.; Siivola, E.; Shen, B.; Venkatasubramanian, R.

    2006-09-01

    Experimental I-V-Tc-ΔT data of thin-film superlattice thermoelectric modules is used to determine the internal ΔT, cross-plane Seebeck coefficient, effective thermal interface resistance, device ZT, and Qmax. We demonstrate 55K of external cooling at 300K (Tc_min=244.8K), with an estimated heat pumping capacity of 128W /cm2. The average ZT300 for the best superlattice devices is 0.75, compared to 0.66 for a bulk BixSb2-xTe3/Bi2SexTe3-x device. Our model indicates a significantly higher internal ΔT occurs across the active thermoelectric element, which was verified using buried thermocouples.

  7. Black Hole Formation in Galactic X-Ray Binaries

    NASA Astrophysics Data System (ADS)

    Willems, Bart; Fragos, T.; Kalogera, V.

    2006-12-01

    In recent years, an increasing number of proper motions have been measured for Galactic black hole X-ray binaries. When supplemented with accurate determinations of other system parameters, these kinematical constraints harbor a wealth of information on compact object formation, such as wether or not black holes receive kicks at birth. In this presentation, we present constraints on the formation of the black hole X-ray binaries GRO J1655-40 and XTE J1118+480. We particularly explore the origin of the compact objects in these X-ray binaries by modeling the ongoing mass transfer phase, tracing the motion in the Galaxy back to the birth site of the black hole, and examining the dynamics of core-collapses of the black hole progenitor.

  8. 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.

  9. 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.

  10. Growth and structure of photosensitive Pb{sub 1-x}Mn{sub x}Te(Ga) epitaxial films

    SciTech Connect

    Nuriev, I. R.; Sadygov, R. M.; Nazarov, A. M.

    2008-05-15

    The growth and structure of (1-1.5)-{mu}m-thick Pb{sub 1-x}Mn{sub x}Te(Ga)(x = 0.06) films with 0.4-0.9 at % of gallium, grown on BaF{sub 2}(111) and Pb{sub 1-x}Sn{sub x}Te (x = 0.2) (100) substrates by molecular beam epitaxy, have been investigated. It is established that the films are crystallized into an fcc structure, and their growth planes are (111) and (100), according to the substrate orientation. The optimal conditions for obtaining high-resistivity photosensitive p-and n-type films with a perfect crystal structure (W{sub 1/2} = 80''-100'') have been determined.

  11. Locating and Determining the Nature of a Persistent Hard X-Ray Source GROJ1814-12

    NASA Technical Reports Server (NTRS)

    Tavani, Marco

    1998-01-01

    The nature of the persistent hard X-ray source GROJ1814-12 discovered by BATSE a year ago is puzzling. Several potential X-ray sources are in the approximately 25 ft radius error box. Our XTE scanning observation attempted to determine the exact position of the hard X-ray source with respect with other sources. No obvious candidate is emerging from the analysis. A report is being prepared by the observing group. The persistent hard X-ray source GROJ1814-12 might be an example of a low-mass X-ray binary producing a strong flux of hard X-rays, and therefore be of the greatest importance for the theory of neutron star emission.

  12. Multifractal spectrums for volumes of spatial forms on surface of ZnxCd1-xTe-Si (111) heterostructures and estimation of the fractal surface energy

    NASA Astrophysics Data System (ADS)

    Moskvin, Pavel; Kryzhanivskyy, Vyacheslav; Lytvyn, Petro; Rashkovetskyi, Liubomyr

    2016-09-01

    Multifractal (MF) analysis is used to describe volumes of spatial forms that are formed on the surface of thin layers of ZnxCd1-xTe solid solution grown on the Si (111) substrate. MF analysis is performed on the basis of AFM images of the solid solution surface. The parameters of the MF spectrums for the distribution of volumes of the spatial forms, which formed the surface relief, were found. On the basis of a formal approach and data on the multifractal parameters for the volume and the area of the surface spatial forms the mathematic expression which takes into account the contribution of the fractal surface structure in its surface energy were proposed. The behavior of the surface energy of the system depending on the fractal parameters that describe the volume and the area of the spatial forms on the fractal surface were discussed.

  13. Evidence for charge Kondo effect in superconducting Tl-doped PbTe

    SciTech Connect

    Fisher, I

    2010-01-11

    We report results of low-temperature thermodynamic and transport measurements of Pb{sub 1-x}Tl{sub x}Te single crystals for Tl concentrations up to the solubility limit of approximately x = 1.5%. For all doped samples, we observe a low-temperature resistivity upturn that scales in magnitude with the Tl concentration. The temperature and field dependence of this upturn are consistent with a charge Kondo effect involving degenerate Tl valence states differing by two electrons, with a characteristic Kondo temperature T{sub K} {approx} 6 K. The observation of such an effect supports an electronic pairing mechanism for superconductivity in this material and may account for the anomalously high T{sub c} values.

  14. Binary Inspiral in Quadratic Gravity

    NASA Astrophysics Data System (ADS)

    Yagi, Kent

    2015-01-01

    Quadratic gravity is a general class of quantum-gravity-inspired theories, where the Einstein-Hilbert action is extended through the addition of all terms quadratic in the curvature tensor coupled to a scalar field. In this article, we focus on the scalar Gauss- Bonnet (sGB) theory and consider the black hole binary inspiral in this theory. By applying the post-Newtonian (PN) formalism, we found that there is a scalar dipole radiation which leads to -1PN correction in the energy flux relative to gravitational radiation in general relativity. From the orbital decay rate of a low-mass X-ray binary A0600-20, we obtain the bound that is six orders of magnitude stronger than the current solar system bound. Furthermore, we show that the excess in the orbital decay rate of XTE J1118+480 can be explained by the scalar radiation in sGB theory.

  15. 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.

  16. 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.

  17. 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.

  18. Acidic Ultrafine Tungsten Oxide Molecular Wires for Cellulosic Biomass Conversion.

    PubMed

    Zhang, Zhenxin; Sadakane, Masahiro; Hiyoshi, Norihito; Yoshida, Akihiro; Hara, Michikazu; Ueda, Wataru

    2016-08-22

    The application of nanocatalysis based on metal oxides for biomass conversion is of considerable interest in fundamental research and practical applications. New acidic transition-metal oxide molecular wires were synthesized for the conversion of cellulosic biomass. The ultrafine molecular wires were constructed by repeating (NH4 )2 [XW6 O21 ] (X=Te or Se) along the length, exhibiting diameters of only 1.2 nm. The nanowires dispersed in water and were observed using high-angle annular dark-field scanning transmission electron microscopy. Acid sites were created by calcination without collapse of the molecular wire structure. The acidic molecular wire exhibited high activity and stability and promoted the hydrolysis of the glycosidic bond. Various biomasses including cellulose were able to be converted to hexoses as main products. PMID:27482857

  19. 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.

  20. MAXI/GSC: Instrument and Early Results

    NASA Astrophysics Data System (ADS)

    Mihara, Tatehiro; MAXI Team

    2010-03-01

    The MAXI/GSC is slit-camera system using large-area proportional counters. The GSC continues observation since August 10, 2009. So far we issued 4 ATELs and 3 GCNs. Although the instant FOV of GSC is 2.4% of the sky, two gamma-ray bursts occurred in it. One (GRB090831A) of them was localized by MAXI circle and narrow IPN annulus. The 4 TELs are on three known Be transient binary pulsars (4U2206+54, A0535+26, GX304-1) and one new blackhole binary (XTE J1752-223). The 2.5-month all-sky image contains about 200 sources. We are preparing for a public web site (http://maxi.riken.jp) containing light curves, images, and spectra of the listed sources.

  1. Using anodic aluminum oxide templates and electrochemical method to deposit BiSbTe-based thermoelectric nanowires

    PubMed Central

    2014-01-01

    In this study, the cyclic voltammetry method was first used to find the reduced voltages and anodic peaks of Bi3+, Sb3+, and Te4+ ions as the judgments for the growth of the (Bi,Sb)2 - x Te3 + x-based materials. Ethylene glycol (C2H6O2) was used as a solvent, and 0.3 M potassium iodide (KI) was used to improve the conductivity of the solution. Two different electrolyte formulas were first used: (a) 0.01 M Bi(NO3)3-5H2O, 0.01 M SbCl3, and 0.01 M TeCl4 and (b) 0.015 M Bi(NO3)3-5H2O, 0.005 M SbCl3, and 0.0075 M TeCl4. The potentiostatic deposition process was first used to find the effect of reduced voltage on the variation of compositions of the (Bi,Sb)2 - xTe3 + x-based materials. After finding the better reduced voltage, 0.01 M Bi(NO3)3-5H2O, 0.01 M SbCl3, and 0.01 M TeCl4 were used as the electrolyte formula. The pulse deposition process was successfully used to control the composition of the (Bi,Sb)2 - xTe3 + x-based materials and grow the nanowires in anodic aluminum oxide (AAO) templates. PMID:24502697

  2. Exciton binding energies and the valence-band offset in mixed type-I--type-II strained-layer superlattices

    SciTech Connect

    Peyla, P.; Merle d'Aubigne, Y.; Wasiela, A.; Romestain, R.; Mariette, H. ); Sturge, M.D. ); Magnea, N.; Tuffigo, H. )

    1992-07-15

    Strained CdTe-Cd{sub 1{minus}{ital x}}Zn{sub {ital x}}Te superlattices are of mixed type: electrons and heavy holes are confined to the CdTe layers (type I) while light holes are confined to the Cd{sub 1{minus}{ital x}}Zn{sub {ital x}}Te layers (type II). In this paper we calculate the exciton binding energy (EBE) as a function of superlattice period for both type-I (spatially direct) and type-II (spatially indirect) excitons. For the heavy-hole (type-I) exciton the binding energy is larger than the bulk value, and varies only slowly with the period down to small periods, where the exciton acquires a three-dimensional character and our calculation breaks down. For the light-hole (type-II) exciton the binding energy at large period is much smaller, due to the spatial separation of electron and hole. As the period decreases, the binding energy increases steadily to reach its bulk value for vanishingly small period. Given the EBE's, we can fit the already published data on the exciton transition energies with a single adjustable parameter, the average valence-band offset'' (averaged over the heavy and light holes). This is the algebraic sum of the chemical-offset and the hydrostatic-strain contribution, and is found to be (2{plus minus}4)% of the difference in band gap between the barrier and well. This value lies in the range predicted theoretically.

  3. 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

  4. Multiwavelength study of the northeastern outskirts of the extended TeV source HESS J1809–193

    SciTech Connect

    Rangelov, Blagoy; Kargaltsev, Oleg; Hare, Jeremy; Volkov, Igor; Posselt, Bettina; Pavlov, George G.

    2014-11-20

    HESS J1809–193 is an extended TeV γ-ray source in the Galactic plane. Multiwavelength observations of the HESS J1809–193 field reveal a complex picture. We present results from three Chandra X-Ray Observatory and two Suzaku observations of a region in the northeastern outskirts of HESS J1809-193, where enhanced TeV emission has been reported. Our analysis also includes GeV γ-ray and radio data. One of the X-ray sources in the field is the X-ray binary XTE J1810-189, for which we present the outburst history from multiple observatories and confirm that XTE J1810-189 is a strongly variable type I X-ray burster, which can hardly produce TeV emission. We investigate whether there is any connection between the possible TeV extension of HESS J1809–193 and the sources seen at lower energies. We find that another X-ray binary candidate, Suzaku J1811-1900, and a radio supernova remnant, SNR G11.4–0.1, can hardly be responsible for the putative TeV emission. Our multiwavelength classification of fainter X-ray point sources also does not produce a plausible candidate. We conclude that the northeast extension of HESS J1809–193, if confirmed by deeper observations, can be considered a dark accelerator—a TeV source without a visible counterpart at lower energies.

  5. Mass Ratio Determination from H α Lines in Black Hole X-Ray Transients

    NASA Astrophysics Data System (ADS)

    Casares, J.

    2016-05-01

    We find that the mass ratio q in quiescent black hole (BH) X-ray transients is tightly correlated with the ratio of the double-peak separation (DP) to the full width half maximum (FWHM) of the H α emission line, {log}q=-6.88-23.2\\quad {log}({DP}/{FWHM}). This correlation is explained through the efficient truncation of the outer disk radius by the 3:1 resonance with the companion star. This is the dominant tidal interaction for extreme mass ratios q={M}2/{M}1≲ 0.25, the realm of BH (and some neutron star) X-ray transients. Mass ratios can thus be estimated with a typical uncertainty of ≈32%, provided that the H α profile used to measure DP/FWHM is an orbital phase average. We apply the DP/FWHM–q relation to the three faint BH transients XTE J1650–500, XTE J1859+226, and Swift J1357–0933 and predict q={0.026}-0.007+0.038, {0.049}-0.012+0.023 and {0.040}-0.005+0.003, respectively. This new relation, together with the {FWHM}{--}{K}2 correlation presented in Paper I, allows the extraction of fundamental parameters from very faint targets and, therefore, the extension of dynamical BH studies to much deeper limits than was previously possible. As an example, we combine our mass ratio determination for Swift J1357–0933 with previous reported values to yield a BH mass of 12.4 ± 3.6 M ⊙. This confirms Swift J1357–0933 as one of the most massive BH low-mass X-ray binaries in the Galaxy.

  6. The detection of terahertz waves by semimetallic and by semiconducting materials

    NASA Astrophysics Data System (ADS)

    Gouider, F.; Nachtwei, G.; Brüne, C.; Buhmann, H.; Vasilyev, Yu. B.; Salman, M.; Könemann, J.; Buckle, P. D.

    2011-01-01

    We present a survey of photoresponse (PR) measurements of various devices containing quantum wells (QWs) of HgTe of various widths dQW and of InSb. By varying dQW for HgTe, the material properties of the QW material change from semiconducting to semimetallic as dQW is increased above a value of about 6nm. We have studied the PR of devices made from CdxHg1-xTe/HgTe/CdxHg1-xTe wafers with values of the QW width in the range of 6 nm≤dQW≤21 nm. Only for samples with semimetallic HgTe QWs, a measurable PR could be detected. However, our investigations of samples made from AlxIn1-xSb/InSb/AlxIn1-xSb wafers gave evidence that a measurable PR also can appear from devices with a semiconducting QW. Both cyclotron-resonant (CR) and nonresonant (bolometric, BO) interaction mechanisms can contribute to the PR signal. Whereas the CR contribution is dominant in AlxIn1-xSb/InSb/AlxIn1-xSb samples, in CdxHg1-xTe/HgTe/CdxHg1-xTe samples the behavior is more complex. In a sample with dQW=8 nm, the PR is clearly dominated by the BO contribution. In the PR of another sample of dQW=12 nm, both contributions (BO and CR) are present. The sample of dQW=21 nm shows a PR with not clearly separable BO and CR contributions.

  7. 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

  8. The precessing jets of 1E 1740.7-2942

    NASA Astrophysics Data System (ADS)

    Luque-Escamilla, Pedro L.; Martí, Josep; Martínez-Aroza, José

    2015-12-01

    Context. The source 1E 1740.7-2942 is believed to be one of the two prototypical microquasars towards the Galactic center region whose X-ray states strongly resemble those of Cygnus X-1. Yet, the bipolar radio jets of 1E 1740.7-2942 are very reminiscent of a radio galaxy. The true nature of the object has thus remained an open question for nearly a quarter of a century. Aims: Our main goal here is to confirm the Galactic membership of 1E 1740.7-2942 by searching for morphological changes of its extended radio jets in human timescales. This work was triggered as a result of recent positive detection of fast structural changes in the large-scale jets of the very similar source GRS 1758-258. Methods: We carried out an in-depth exploration of the Very Large Array public archives and fully recalibrated all 1E 1740.7-2942 extended data sets in the C configuration of the array. We obtained and analyzed matching beam radio maps for five epochs, covering years 1992, 1993, 1994, 1997 and 2000, with an angular resolution of a few arcseconds. Results: We clearly detected structural changes in the arc-minute jets of 1E 1740.7-2942 on timescales of roughly a year, which set a firm distance upper limit of 12 kpc. Moreover, a simple precessing twin-jet model was simultaneously fitted to the five observing epochs available. The observed changes in the jet flow are strongly suggestive of a precession period of ~1.3 yr. Conclusions: The fitting of the precession model to the data yields a distance of ~5 kpc. This value, and the observed changes, rule out any remaining doubts about the 1E 1740.7-2942 Galactic nature. To our knowledge, this microquasar is the second whose jet precession ephemeris become available after SS433. This kind of information is relevant to the physics of compact objects, since the genesis of the precession phenomenon occurs very close to the interplay region between the accretion disk and the compact object in the system. Appendix A and a movie associated to

  9. 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.

  10. 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.

  11. 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.

  12. Intrinsic Electromagnetic Variability in Celestial Objects Containing Rapidly Spinning Black Holes

    NASA Astrophysics Data System (ADS)

    Zhang, Fan

    2016-02-01

    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.

  13. THE 2010 MAY FLARING EPISODE OF CYGNUS X-3 IN RADIO, X-RAYS, AND {gamma}-RAYS

    SciTech Connect

    Williams, Peter K. G.; Bower, Geoffrey C.; Tomsick, John A.; Bodaghee, Arash; Pooley, Guy G.; Pottschmidt, Katja; Rodriguez, Jerome; Migliari, Simone; Trushkin, Sergei A.

    2011-06-01

    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 data set 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 day softening and recovery of the X-ray emission, followed almost immediately by a {approx}1 Jy radio flare at 15 GHz, followed by a 4.3{sigma} {gamma}-ray flare (E > 100 MeV) {approx}1.5 days 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.

  14. Spectral lags of flaring events in LS I+61°303 from RXTE Observations

    NASA Astrophysics Data System (ADS)

    Sarkar, Tamal; Sarkar, Samir; Bhadra, Arunava

    2016-07-01

    This work reports the first discovery of (negative) spectral lags in X-ray emission below 10keV from the gamma ray binary LS I+61° 303 during large flaring episodes using Rossi X-ray Timing Explorer (RXTE) observations. It is found from the RXTE data that during the flares, low energy (3–5 keV) variations lead the higher energy (8–10 keV) variations by a few tens of seconds whereas no significant time lag is observed during the non-flaring states. The observed spectral lag features for flaring events suggest that inverse Compton scattering may be operating, at least in some part of the system. Another possibility is that the sites of particle acceleration may be different for flaring and non-flaring events such as in the microquasar model, in which the flaring radiation may come from hot spots sitting above the black hole while steady state emissions are due to the jets.

  15. 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.

  16. 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.

  17. 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.

  18. Simulations of Viscous Accretion Flow around Black Holes in a Two-dimensional Cylindrical Geometry

    NASA Astrophysics Data System (ADS)

    Lee, Seong-Jae; Chattopadhyay, Indranil; Kumar, Rajiv; Hyung, Siek; Ryu, Dongsu

    2016-11-01

    We simulate shock-free and shocked viscous accretion flows onto a black hole in a two-dimensional cylindrical geometry, where initial conditions were chosen from analytical solutions. The simulation code used the Lagrangian total variation diminishing plus remap routine, which enabled us to attain high accuracy in capturing shocks and to handle the angular momentum distribution correctly. The inviscid shock-free accretion disk solution produced a thick disk structure, while the viscous shock-free solution attained a Bondi-like structure, but in either case, no jet activity nor any quasi-periodic oscillation (QPO)-like activity developed. The steady-state shocked solution in the inviscid as well as in the viscous regime matched theoretical predictions well. However, increasing viscosity renders the accretion shock unstable. Large-amplitude shock oscillation is accompanied by intermittent, transient inner multiple shocks. This oscillation of the inner part of the disk is interpreted as the source of QPO in hard X-rays observed in micro-quasars. Strong shock oscillation induces strong episodic jet emission. The jets also show the existence of shocks, which are produced as one shell hits the preceding one. The periodicities of the jets and shock oscillation are similar; the jets for the higher viscosity parameter appear to be stronger and faster.

  19. 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

    NASA Astrophysics Data System (ADS)

    Xue, Li; Sądowski, Aleksander; Abramowicz, Marek A.; Lu, Ju-Fu

    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.

  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. 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

  2. Jets and Accretion Disks in X-ray Binaries

    NASA Astrophysics Data System (ADS)

    Tomsick, John

    The outflow of material in the form of jets is a common phenomenon in astronomical sources with accretion disks. Even though jets are seen coming from the cores of galaxies, Galactic compact objects in X-ray binaries, and stars as they are forming, we do not understand in detail what accretion disk conditions are necessary to support a relativistic jet. This proposal focuses on multi-wavelength studies of X-ray binaries in order to improve our understanding of the connection between the disk and the jet. Specifically, this proposal includes work on two approved cycle 14 Rossi X-ray Timing Explorer (RXTE) programs, an approved XMM-Newton program, as well as a synthesis study of transient black hole X-ray binaries using archival RXTE and radio data. We plan to use X-ray spectral and timing properties to determine the disk properties during the re-activation of the compact jet (as seen in the radio and infrared) during the decays of black hole transient outbursts, to determine how the inner disk properties change at low mass accretion rates, and to use RXTE along with multi-wavelength observations to constrain the jet properties required for the microquasar Cygnus~X-3 to produce high- energy emission. Due to the ubiquity of jets in astrophysical settings, these science topics are relevant to NASA programs dealing with the origin, structure, evolution, and destiny of the Universe, and especially to understanding phenomena near black holes.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Decoding the Heartbeat of GRS1915+105 with NuSTAR and Chandra

    NASA Astrophysics Data System (ADS)

    Zoghbi, Abderahmen; Miller, Jon; Harrison, Fiona A.

    2016-07-01

    GRS 1915+105 is a microquasar that shows extreme variability in X-ray, IR and radio bands. It shows disk emission, relativistic jets and strong winds during its different states. We observed this source simultaneously with NuSTAR and Chandra during the heartbeat state, characterized a 50 seconds strong oscillations. The oscillations are likely due to thermal/viscous instability in the inner disk when it deviates significantly from the standard Shakura & Sunyaev disk. Combining the high sensitivity of NuSTAR and the high resolution of Chandra, we use phase spectroscopy to study the details of these oscillation, revealing changes in the inner accretion disk as well as the launching of powerful winds during the oscillations. This is the first time we are able to study the detailed changes in the reflection spectrum from the inner accretion disk, providing unprecedented insights into the geometry and physical processes in action during the oscillations. I will discuss the implications of these results on accretion physics, the thermal instability and the launching mechanism of the wind.

  9. Spectral lags of flaring events in LS I+61°303 from RXTE Observations

    NASA Astrophysics Data System (ADS)

    Sarkar, Tamal; Sarkar, Samir; Bhadra, Arunava

    2016-07-01

    This work reports the first discovery of (negative) spectral lags in X-ray emission below 10keV from the gamma ray binary LS I+61° 303 during large flaring episodes using Rossi X-ray Timing Explorer (RXTE) observations. It is found from the RXTE data that during the flares, low energy (3-5 keV) variations lead the higher energy (8-10 keV) variations by a few tens of seconds whereas no significant time lag is observed during the non-flaring states. The observed spectral lag features for flaring events suggest that inverse Compton scattering may be operating, at least in some part of the system. Another possibility is that the sites of particle acceleration may be different for flaring and non-flaring events such as in the microquasar model, in which the flaring radiation may come from hot spots sitting above the black hole while steady state emissions are due to the jets.

  10. On the magnetization of jet-launching discs

    NASA Astrophysics Data System (ADS)

    Tzeferacos, P.; Ferrari, A.; Mignone, A.; Zanni, C.; Bodo, G.; Massaglia, S.

    2009-12-01

    Magnetohydrodynamic models of collimated outflows produced by accretion discs around compact objects can be used for interpreting the phenomenology of active astrophysical objects as young stellar objects, microquasars, X-ray binaries, gamma-ray bursts, extended radio galaxies and active galactic nuclei. In the present work, we discuss how the strength of magnetic fields determines the characteristics of solutions in models where the collimated outflow and the accretion disc are treated consistently. We perform an extensive analysis of the magnetic field's strength by non-relativistic axisymmetric numerical simulations using the PLUTO code. We discuss in detail the characteristics of the numerical solutions with specific reference to the efficiency of transforming accretion inflows into collimated superfast magnetosonic outflows. The relevance of the resistivity parameter used in numerical simulations is analysed. The main results are that magnetic fields around and below equipartition with plasma pressure allow for steady superfast magnetosonic collimated jet solutions; for even lower magnetization, the solutions found are unsteady, with small velocities and matter-dominated magnetic field lines that behave kinematically; magnetic fields above equipartition lead to unsteady sub-Alfvénic winds. These results allow to conclude that stationary super-Alfvénic and superfast magnetosonic outflow solutions are found only for equipartition and weaker magnetic fields, for the range studied in this article.

  11. A Gamma-Ray Burst/Pulsar for Cosmic Ray Positrons with a Dark Matter-Like Spectrum

    NASA Astrophysics Data System (ADS)

    Ioka, K.

    2010-04-01

    We propose that a nearby gamma-ray burst (GRB) or GRB-like (old, single, and short-lived) pulsar, supernova remnant, or microquasar about 10^{5-6} years ago may be responsible for the excesses of cosmic ray positrons and electrons recently observed in the PAMELA, ATIC/PPB-BETS, Fermi, and HESS experiments. We can reproduce the smooth Fermi/HESS spectra as well as the spiky ATIC/PPB-BETS spectra. The spectra have a sharp cutoff that is similar to the dark matter predictions, sometimes together with a line (not similar), since high-energy cosmic rays cool fast where the cutoff/line energy marks the source age. A GRB-like astrophysical source is expected to have a small but finite spread in the cutoff/line as well as anisotropy in the cosmic ray and diffuse gamma-ray flux, providing a method for the Fermi and future CALET experiments to discriminate between dark matter and astrophysical origins.

  12. 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.

  13. The Multi-wavelength Characteristics of the TeV Binary LS I +61°303

    NASA Astrophysics Data System (ADS)

    Saha, L.; Chitnis, V. R.; Shukla, A.; Rao, A. R.; Acharya, B. S.

    2016-06-01

    We study the characteristics of the TeV binary LS I+61°303 in radio, soft X-ray, hard X-ray, and gamma-ray (GeV and TeV) energies. The long-term variability characteristics are examined as a function of the phase of the binary period of 26.496 days as well as the phase of the superorbital period of 1626 days, dividing the observations into a matrix of 10 × 10 phases of these two periods. We find that the long-term variability can be described by a sine function of the superorbital period, with the phase and amplitude systematically varying with the binary period phase. We also find a definite wavelength-dependent change in this variability description. To understand the radiation mechanism, we define three states in the orbital/superorbital phase matrix and examine the wideband spectral energy distribution. The derived source parameters indicate that the emission geometry is dominated by a jet structure showing a systematic variation with the orbital/superorbital period. We suggest that LS I+61°303 is likely a microquasar with a steady jet.

  14. Arrhenius reconsidered: astrophysical jets and the spread of spores

    NASA Astrophysics Data System (ADS)

    Sheldon, Malkah I.; Sheldon, Robert B.

    2015-09-01

    In 1871, Lord Kelvin suggested that the fossil record could be an account of bacterial arrivals on comets. In 1903, Svante Arrhenius suggested that spores could be transported on stellar winds without comets. In 1984, Sir Fred Hoyle claimed to see the infrared signature of vast clouds of dried bacteria and diatoms. In 2012, the Polonnaruwa carbonaceous chondrite revealed fossilized diatoms apparently living on a comet. However, Arrhenius' spores were thought to perish in the long transit between stars. Those calculations, however, assume that maximum velocities are limited by solar winds to ~5 km/s. Herbig-Haro objects and T-Tauri stars, however, are young stars with jets of several 100 km/s that might provide the necessary propulsion. The central engine of bipolar astrophysical jets is not presently understood, but we argue it is a kinetic plasma instability of a charged central magnetic body. We show how to make a bipolar jet in a belljar. The instability is non-linear, and thus very robust to scaling laws that map from microquasars to active galactic nuclei. We scale up to stellar sizes and recalculate the viability/transit-time for spores carried by supersonic jets, to show the viability of the Arrhenius mechanism.

  15. 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. 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.

  17. ESTIMATION OF THE NEUTRINO FLUX AND RESULTING CONSTRAINTS ON HADRONIC EMISSION MODELS FOR Cyg X-3 USING AGILE DATA

    SciTech Connect

    Baerwald, P.; Guetta, D.

    2013-08-20

    In this work, we give an estimate of the neutrino flux that can be expected from the microquasar Cyg X-3. We calculate the muon neutrino flux expected here on Earth as well as the corresponding number of neutrino events in the IceCube telescope based on the so-called hypersoft X-ray state of Cyg X-3. If the average emission from Cyg X-3 over a period of 5 yr were as high as during the used X-ray state, a total of 0.8 events should be observed by the full IceCube telescope. We also show that this conclusion holds by a factor of a few when we consider the other measured X-ray states. Using the correlation of AGILE data on the flaring episodes in 2009 June and July to the hypersoft X-ray state, we calculate that the upper limits on the neutrino flux given by IceCube are starting to constrain the hadronic models, which have been introduced to interpret the high-energy emission detected by AGILE.

  18. 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.

  19. Observation of binary systems at very-high energies with VERITAS

    NASA Astrophysics Data System (ADS)

    Maier, G.; VERITAS Collaboration

    2012-12-01

    Non-thermal variable emission from radio to very-high energy gamma rays (VHE; >100 GeV) are the prime characteristics of gamma-ray binaries. The underlying physical processes leading to the observed VHE emission are not well understood, as even the most basic features of these systems are under dispute (microquasar model vs shocked pulsar wind model). VHE binaries can be difficult to observe, some have orbital periods of the order of years (e.g. HESS J0632+057 or PSR B1259-69) or show irregular emission patterns as observed in LS I +61 303. We present here new VERITAS observations of the binary systems LS I +61 303 and HESS J0632+057 carried out with higher sensitivity and more dense temporal coverage than previous observations. The gamma-ray results and their astrophysical implications are discussed in the context of contemporaneous observations with Swift XRT and Fermi LAT at X-ray and gamma-ray energies.

  20. 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.

  1. 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.

  2. Dips in X-Ray Flux Associated with Superluminal Ejections in the Radio Galaxy 3C 120

    NASA Technical Reports Server (NTRS)

    Marscher, A. P.; Jorstad, S. G.; Gomez, J. L.; Aller, M. F.

    2001-01-01

    We compare the RXTE X-ray light curve of 3C 120 from our late 1997 to early 2000 observations, plus early 1997 archival data, with both the cm-wave light curves (University of Michigan Radio Astronomy Observatory) and the times of ejections of apparent superluminal components (from VLBA observations). There is no correlation between the X-ray and radio light curves. However, the epochs of all four observed superluminal ejections correspond, to within the errors, with pronounced dips in the X-ray light curves (photon energies in the range 2-20 keV). This behavior is similar to that of the binary-system 'microquasar' GRS1915+105 in the Milky Way galaxy, although in 3C 120 there is no evidence for rapid, quasi-periodic fluctuations in X-ray flux. These observations therefore support the notion that in active galactic nuclei eruptions of energetic outflow are related to excess accretion onto a supermassive black hole.

  3. 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

  4. 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.

  5. 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

  6. 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

  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. 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.

  9. Recent results from the ANTARES neutrino telescope

    NASA Astrophysics Data System (ADS)

    Van Elewyck, Véronique

    2014-04-01

    The ANTARES neutrino telescope is currently the largest operating water Cherenkov detector and the largest neutrino detector in the Northern Hemisphere. Its main scientific target is the detection of high-energy (TeV and beyond) neutrinos from cosmic accelerators, as predicted by hadronic interaction models, and the measurement of the diffuse neutrino flux. Its location allows for surveying a large part of the Galactic Plane, including the Galactic Centre. In addition to the standalone searches for point-like and diffuse high-energy neutrino signals, ANTARES has developed a range of multi-messenger strategies to exploit the close connection between neutrinos and other cosmic messengers such as gamma-rays, charged cosmic rays and gravitational waves. This contribution provides an overview of the recently conducted analyses, including a search for neutrinos from the Fermi bubbles region, searches for optical counterparts with the TAToO program, and searches for neutrinos in correlation with gamma-ray bursts, blazars, and microquasars. Further topics of investigation, covering e.g. the search for neutrinos from dark matter annihilation, searches for exotic particles and the measurement of neutrino oscillations, are also reviewed.

  10. Status and Performance of the Hard X-Ray Polarimeter X-Calibur

    NASA Astrophysics Data System (ADS)

    Kislat, Fabian; Beilicke, M.; Guo, Q.; Krawczynski, H.

    2013-01-01

    X-ray polarimetry promises unique information about astrophysical objects such as binary black hole systems, neutron stars, microquasars, active galactic nuclei, and gamma-ray bursts. X-Calibur is a hard x-ray polarimeter to be flown in the focal plane of the InFOCµS grazing incidence mirror in the fall of 2013 from Fort Sumner (NM). During the one-day flight X-Calibur will measure spectrum and polarization of x-rays in the 20-80keV range from up to five selected sources. X-Calibur exploits the fact that polarized photons Compton scatter preferentially in a direction orthogonal to the orientation of their electric field vector. By combining a low-Z Compton scatterer with high-Z Cadmium Zinc Telluride (CZT) detectors to photo-absorb the scattered x-rays, X-Calibur achieves a high detection efficiency of almost unity and a large modulation factor close to the theoretical limit given by the physics of Compton scattering. We report on the design of X-Calibur, as well as results of laboratory calibration measurements characterizing the performance of the instrument. We also present the sensitivity of the polarimeter for the upcoming balloon flight.

  11. The Hard X-ray Polarimeter X-Calibur - Astrophysical Motivation and Performance

    NASA Astrophysics Data System (ADS)

    Beilicke, Matthias; Baring, M. G.; Tueller, J.; Krawczynski, H.; Barthelmy, S. D.; Binns, W.; Buckley, J. H.; Cowsik, R.; Guo, Q.; Israel, M. H.; Kislat, F.; Matsumoto, H.; Okajima, T.; Schnittman, J.

    2013-04-01

    X-ray polarimetry promises to give qualitatively new information about high-energy sources, such as binary black hole systems, rotation and accretion powered neutron stars, microquasars, active galactic nuclei and gamma-ray bursts. We designed, built and tested a hard X-ray polarimeter X-Calibur to be flown in the focal plane of the InFOCuS grazing incidence hard X-ray telescope in fall 2013. The polarimeter combines a low-Z Compton scatterer with a high-Z Cadmium Zinc Telluride (CZT) detector assembly to measure the polarization of 20-80 keV X-rays. X-Calibur makes use of the fact that polarized photons Compton scatter preferentially perpendicular to the electric field orientation. In contrast to competing designs, which use only a small fraction of the incoming X-rays, X-Calibur achieves a high detection efficiency of order unity. We report on the technical design of X-Calibur, the X-Calibur and InFOCuS sensitivity on short and long duration balloon flights, and present detailed laboratory calibration measurements characterizing the performance of the instrument.

  12. Simulation and Laboratory results of the Hard X-ray Polarimeter: X-Calibur

    NASA Astrophysics Data System (ADS)

    Guo, Qingzhen; Beilicke, M.; Kislat, F.; Krawczynski, H.

    2014-01-01

    X-ray polarimetry promises to give qualitatively new information about high-energy sources, such as binary black hole (BH) systems, Microquasars, active galactic nuclei (AGN), GRBs, etc. We designed, built and tested a hard X-ray polarimeter 'X-Calibur' to be flown in the focal plane of the InFOCuS grazing incidence hard X-ray telescope in 2014. X-Calibur combines a low-Z Compton scatterer with a CZT detector assembly to measure the polarization of 20- 80 keV X-rays making use of the fact that polarized photons Compton scatter preferentially perpendicular to the E field orientation. X-Calibur achieves a high detection efficiency of order unity. We optimized of the design of the instrument based on Monte Carlo simulations of polarized and unpolarized X-ray beams and of the most important background components. We have calibrated and tested X-Calibur extensively in the laboratory at Washington University and at the Cornell High-Energy Synchrotron Source (CHESS). Measurements using the highly polarized synchrotron beam at CHESS confirm the polarization sensitivity of the instrument. In this talk we report on the optimization of the design of the instrument based on Monte Carlo simulations, as well as results of laboratory calibration measurements characterizing the performance of the instrument.

  13. The hard X-ray polarimeter X-Calibur

    NASA Astrophysics Data System (ADS)

    Beilicke, Matthias

    2014-08-01

    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 balloon-borne InFOCuS grazing incidence hard X-ray telescope. X-Calibur combines a low-Z Compton scatterer with a CZT detector assembly to measure the polarization of 20-60 keV X-rays making use of the fact that polarized photons Compton scatter preferentially perpendicular to the electric field orientation. The X-Calibur detector assembly is completed, tested, and calibrated. X-Calibur achieves a high detection efficiency of order unity. The results of the performance studies will be presented. A first flight is scheduled from Ft.Sumner, NM, in fall 2014. In principal, a similar space-borne experiment could be operated in the 5-100 keV regime.

  14. Experimental results obtained with the positron-annihilation- radiation telescope of the Toulouse-Argonne collaboration

    SciTech Connect

    Naya, J.E.; von Ballmoos, P.; Albernhe, F.; Vedrenne, G.; Smither, R.K.; Faiz, M.; Fernandez, P.B.; Graber, T.

    1995-10-01

    We present laboratory measurements obtained with a ground-based prototype of a focusing positron-annihilation-radiation telescope developed by the Toulouse-Argonne collaboration. This balloon-borne telescope has been designed to collect 511-keV photons with an extremely low instrumental background. The telescope features a Laue diffraction lens and a detector module containing a small array of germanium detectors. It will provide a combination of high spatial and energy resolution (15 arc sec and 2 keV, respectively) with a sensitivity of {approximately}3{times}10{sup {minus}5} photons cm{sup {minus}2}s{sup {minus}1}. These features will allow us to resolve a possible narrow 511-keV line both energetically and spatially within a Galactic center ``microquasar`` or in other broad-class annihilators. The ground-based prototype consists of a crystal lens holding small cubes of diffracting germanium crystals and a 3{times}3 germanium array that detects the concentrated beam in the focal plane. Measured performances of the instrument at different line energies (511 keV and 662 keV) are presented and compared with Monte-Carlo simulations. The advantages of a 3{times}3 Ge-detector array with respect to a standard-monoblock detector have been confirmed. The results obtained in the laboratory have strengthened interest in a crystal-diffraction telescope, offering new perspectives for die future of experimental gamma-ray astronomy.

  15. Near-Infrared and X-Ray Observations of XSS J12270-4859

    NASA Astrophysics Data System (ADS)

    Saitou, Kei; Tsujimoto, Masahiro; Ebisawa, Ken; Ishida, Manabu; Mukai, Koji; Nagayama, Takahiro; Nishiyama, Shogo; Gandhi, Poshak

    2011-11-01

    XSS J12270-4859 (J12270) is an enigmatic source of unknown nature. Previous studies revealed that the source has unusual X-ray temporal characteristics, including repetitive short-term flares, followed by spectral hardening, non-periodic dips, and dichotomy in activity; i.e., intervals filled with flares and those without. Together with a power-law X-ray spectrum, it is suggested to be a low-mass X-ray binary. In order to better understand the object, we present the results of our near-infrared (NIR) photometry and linear polarimetry observations as well as X-ray spectroscopy observations, which overlap with each other partially in time, taken respectively with the InfraRed Survey Facility (IRSF) and the Rossi X-ray Timing Explorer (RXTE). We detected several simultaneous NIR and X-ray flares for the first time. No significant NIR polarization was obtained. We assembled data taken with IRSF, RXTE, Suzaku, Swift, and other missions in the literature and compared the flare profile and the spectral energy distribution (SED) with some representative high-energy sources. Based on some similarities of the repetitive NIR and X-ray flaring characteristics and the broad SED, we argue that J12270 is reminiscent of microquasars with a synchrotron jet, which is at a very low-luminosity state of ≈ 10-4 Eddington luminosity for a stellar mass black hole or neutron star at a reference distance of 1 kpc.

  16. The peculiar source XSS J12270-4859: a LMXB detected by FERMI?

    NASA Astrophysics Data System (ADS)

    Bonnet-Bidaud, J. M.; de Martino, D.; Mouchet, M.; Falanga, M.; Belloni, T.; Masetti, N.; Mukai, K.; Matt, G.

    The X-ray source XSS J12270-4859 has been first suggested to be a magnetic cataclysmic variable of Intermediate Polar type on the basis of its optical spectrum and a possible 860 s X-ray periodicity. However further X-ray observations by the Suzaku and XMM-Newton satellites did not confirm this periodicity but show a very peculiar variability, including moderate repetitive flares and numerous absorption dips. These characteristics together with a suspected 4.3 h orbital period would suggest a possible link with the so-called "dipping sources", a sub-class of Low-Mass X-ray Binaries (LMXB). Based on the released FERMI catalogues, the source was also found coincident with a very high energy (0.1-300 GeV) VHE source 2FGL J1227.7-4853. The good positional coincidence, together with the lack of any other bright X-ray sources in the field, makes this identification highly probable. However, none of the other standard LMXB have been so far detected by FERMI. Most galactic HE sources are associated with rotation-powered pulsars. We present here new results obtained from a 30 ksec high-time resolution XMM observations in January 2011 that confirm the flaring-dipping behaviour and provide upper limits on fast X-ray pulsations. We discuss the possible association of the source with either a microquasar or an accreting rotation powered pulsar.

  17. The Relationship Between X-Rays and Relativistic Jets

    NASA Technical Reports Server (NTRS)

    Marscher, A. P.; Jorstad, S. G.; McHardy, I. M.; Aller, M. F.; Balonek, T. J.; Villata, M.; Raiteri, C. M.; Ostorero, L.; Tosti, G.; Terasranta, H.

    2002-01-01

    We present recent multiwaveband observations centered on X-ray monitoring of blazars and the radio galaxy 3C 120 with the RXTE satellite, In 3C 120, we observed four X-ray dips, each followed by ejections of superluminal radio knots down the jet. This behavior, similar to that of the microquasar GRS 1915+105, is interpreted as infall of a piece of the inner accretion disk causing ejection of energy into the relativistic jet. The X-ray emission from the quasars PKS 1510-089, 3C 279, and 3C 273 is highly variable on timescales as short as approximately 1 day. Over 2 years, X-ray flares in PKS 1510-089 occurred about 2 weeks after radio outbursts, which can be explained by light-travel delays. In 3C 279 the X-ray and optical variations are usually well correlated, with very little, if any, time delay. We conclude that the X-ray and optical emission from blazars occurs near the radio core rather than close to the black hole.

  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 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. The Nançay Radio Telescope Archive

    NASA Astrophysics Data System (ADS)

    Theureau, G.; Martin, J.-M.; Cognard, I.; Borsenberger, J.

    2006-07-01

    The Nançay radio telescope (NRT) is a national facility, the fourth single-dish instrument in the world for its collecting area. It provides spectral and/or continuum data in the frequency range 1.06 to 3.5 GHz, and covers various scientific fields in solar system astronomy (comets, planets...), galactic astronomy (pulsars, late type stars, star forming regions, microquasars...) and extragalactic astronomy (HI in galaxies, large scale structure of the universe, quasars...). Two on-line databases {http://klun.obs-nancay.fr} and a general archive are being designed to fullfill the VO standards: HIG (HI profiles of Galaxies) contains reduced 1-D 21-cm spectra for ˜4500 galaxies; NAP (Nançay Archive of Pulsars) provides a few thousand pulse profiles from regular timing observations of ˜40 pulsars; NRTA (Nançay Radio Telescope Archive) will host all NRT data from the backends (correlator, digital spectrometer and pulsar dedispersors). Most of the data consist of dynamical spectra (time-frequency domain). The package which is used for the database management and for the data-processing pipeline is the Pleinpot software, which has been developed for the hyperleda database {http://leda.univ-lyon1.fr/install/mirror.html}.

  6. Searching for the Physical Drivers of Eigenvector 1: From Quasars to Nanoquasars

    NASA Astrophysics Data System (ADS)

    Zamanov, R.; Marziani, P.

    2002-06-01

    We point out an analogy between two accreting white dwarfs (CH Cyg and MWC 560) with jets and powerful quasars. In spite of the enormous difference in the mass of the central object (a factor ~107), the emission lines are strikingly similar to those of I Zw 1 (the prototype ``narrow-line Seyfert 1'' nucleus whose spectrum is widely used as an Fe II template for almost all quasars). The spectral similarities give us the unique possibility to consider the optical Eigenvector 1 diagram using objects less massive by a factor of millions. Our results reinforce the interpretation of the ``Eigenvector 1 correlations'' found for low-redshift quasars as driven mainly by the source luminosity-to-central compact object mass ratio. The accreting white dwarfs CH Cyg and MWC 560, their jets and emission lines, may well represent the low-energy, nonrelativistic end of the accretion phenomena, which encompass the most powerful quasars and microquasars. The remarkable similarities suggest that they may be legitimately considered ``nanoquasars.''

  7. A RADIO PULSAR SEARCH OF THE {gamma}-RAY BINARIES LS I +61 303 AND LS 5039

    SciTech Connect

    Virginia McSwain, M.; Ray, Paul S.; Ransom, Scott M.; Roberts, Mallory S. E.; Dougherty, Sean M.; Pooley, Guy G. E-mail: paul.ray@nrl.navy.mil E-mail: malloryr@gmail.com E-mail: guy@mrao.cam.ac.uk

    2011-09-01

    LS I +61 303 and LS 5039 are exceptionally rare examples of high-mass X-ray binaries with MeV-TeV emission, making them two of only five known '{gamma}-ray binaries'. There has been disagreement within the literature over whether these systems are microquasars, with stellar winds accreting onto a compact object to produce high energy emission and relativistic jets, or whether their emission properties might be better explained by a relativistic pulsar wind colliding with the stellar wind. Here we present an attempt to detect radio pulsars in both systems with the Green Bank Telescope. The upper limits of flux density are between 4.1 and 14.5 {mu}Jy, and we discuss the null results of the search. Our spherically symmetric model of the wind of LS 5039 demonstrates that any pulsar emission will be strongly absorbed by the dense wind unless there is an evacuated region formed by a relativistic colliding wind shock. LS I +61 303 contains a rapidly rotating Be star whose wind is concentrated near the stellar equator. As long as the pulsar is not eclipsed by the circumstellar disk or viewed through the densest wind regions, detecting pulsed emission may be possible during part of the orbit.

  8. Supernovae, hypernovae and gamma ray bursts

    NASA Astrophysics Data System (ADS)

    Dar, Arnon

    2001-05-01

    Recent observations suggest that gamma ray bursts (GRBs) and their afterglows are produced by highly relativistic jets emitted in core collapse supernova explosions (SNe). The result of the event, probably, is not just a compact object plus a spherical ejecta: within a day, a fraction of the parent star falls back to produce a thick accretion disk around the compact object. Instabilities in the disk induce a sudden collapse with ejection of jets of highly relativistic ``cannonballs'' of plasma in opposite directions, similar to those ejected by microquasars. The jet of cannonballs exit the supernova shell/ejecta reheated by their collision with it, emitting highly forward-collimated radiation which is Doppler shifted to γ-ray energy. Each cannonball corresponds to an individual pulse in a GRB. They decelerate by sweeping up the ionized interstellar matter in front of them, part of which is accelerated to cosmic-ray energies and emits synchrotron radiation: the afterglow. The Cannonball Model cannot predict the timing sequence of these pulses, but it fares very well in describing the total energy, energy spectrum, and time-dependence of the individual γ-ray pulses and afterglows. It also predicts that GRB pulses are accompanied by detectable short pulses of TeV neutrinos and sub TeV γ-rays, that are much more energetic and begin and peak a little earlier. .

  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. 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.

  11. Study of the Local Structure of II-Vi Ternary Alloys by Extended X-Ray Absorption Fine Structure

    NASA Astrophysics Data System (ADS)

    Pong, Way-Faung

    Bondlengths, Debye-Waller factors, and site occupancy in the diluted magnetic semiconductors Zn_ {rm 1 - x}Mn_{ rm x}Se and Hg_{ rm 1 - x}Mn_{rm x}Te, and the narrow-gap semiconductor Hg _{rm 1 - x}Cd _{rm x}Te have been measured using extended x-ray absorption fine structure (EXAFS). The nearest-neighbor bond lengths in all of these alloys are found to be constant as a function of alloy composition within the experimental uncertainty of 0.01A. Because the average cation-cation distance changes with Mn composition, these results necessarily imply distortion of the tetrahedral bond angles. In the case of Zn_{rm 1 - x}Mn_{rm x} Se, the anion sublattice is shown to suffer the largest distortion, but the cation sublattice also exhibits some relaxation. The repercussions of these results are discussed, in terms of the amount of cation and anion sublattice distortion at low temperature and its connection to the superexchange mechanism occurring between the Mn ^{+2} ions and mediated by the intervening anion in Zn_{rm 1 - x}Mn_{rm x} Se. From the NN bond length relaxation results shown in this study and those reported elsewhere for the III -V-based and II-VI-based ternary compounds and DMS alloys, it appears that substitution of Mn^{+2 } ions into II-VI-based compounds causes greater local distortion, in general, than otherwise observed when group II cations are substituted for one another. We believe that the tetrahedral bond weakening in DMS is due to MN 3d-orbital (t_2) and anion p-orbital hybridization in DMS, leaving fewer p-orbitals available for tetrahedral bonding. This leads to the weakening of the bond force constants alpha, beta, as well as the bond becoming more ionic as Mn^{+2} is substituted into the II-VI-based compounds. Finally, the experimentally extended electron energy loss fine structure (EXELFS) technique, with modulations in the differential inelastic electron scattering cross -section above an absorption core edge, has been used in recent years to

  12. 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.

  13. Spectral Modeling of the Comptonized Continua of Accreting X-Ray Pulsars

    NASA Astrophysics Data System (ADS)

    Wolff, Michael Thomas; Pottschmidt, Katja; Becker, Peter A.; Marcu, Diana; Wilms, Jörn; Wood, Kent S.

    2015-01-01

    We are undertaking a program to analyze the X-ray spectra of the accretion flows onto strongly magnetic neutron stars in high mass binary systems such as Cen X-3, and XTE J1946+274. These accreting pulsars typically have X-ray spectra consisting of broad Comptonized cutoff power-laws. Current theory suggests these X-ray spectra result from radiation-dominated shocks that develop in the high-velocity magnetically channeled plasma accretion flows onto the surfaces of the neutron stars. These X-ray pulsars often, but not always, show cyclotron resonant scattering features implying neutron star surface magnetic field strengths above 1012 G. Proper fitting of cyclotron line centroids (for example, to investigate how the line centroid varies with X-ray luminosity) requires a robust model for the Comptonized X-ray continuum upon which the cyclotron lines are superposed, and this can be provided by a continuum model based on the physics of the accretion column.We discuss in this presentation our ongoing program for the analysis of the X-ray spectra formed in these systems. Our program consists of two parts. First, we are modeling the X-ray spectra from the Suzaku X-ray satellite of accreting X-ray pulsars Cen X-3 and XTE J1946+274 utilizing the best currently existing empirical models. The second part of our program is building a new analysis tool based on the analytical model of Becker and Wolff (2007). In the high temperature optically thick plasma flows, the processes of bremsstrahlung emission from the hot plasma, black body emission from a thermal mound near the neutron star surface, and cyclotron emission from electrons in the first Landau excited state, all contribute to the total observed X-ray spectrum. We show recent results from our new implementation and its comparison with the Suzaku data for these X-ray pulsars.This research is supported by the NASA Astrophysics Data Analysis Program.

  14. Near-infrared survey of high mass X-ray binary candidates

    NASA Astrophysics Data System (ADS)

    Torrejón, J. M.; Negueruela, I.; Smith, D. M.; Harrison, T. E.

    2010-02-01

    Context. The INTEGRAL satellite is detecting a large population of new X-ray sources that were missed by previous missions because of high obscuration and, in some cases, very short duty cycles. The nature of these sources must be addressed by characterizing their optical and/or infrared counterparts. Aims: We investigate the nature of the optical counterparts to five of these newly discovered X-ray sources. Methods: We combine infrared spectra in the I, J,H, and K bands with JHK photometry to characterize the spectral type, luminosity class, and distance to the infrared counterparts to these systems. For IGR J19140+0951, we present spectroscopy from the red to the K band and new red and infrared photometry. For SAX J18186-1703 and IGR J18483-0311, we present the first intermediate-resolution spectroscopy to be published. Finally, for IGR J18027-2016, we present new I and K band spectra. Results: We find that four systems harbour early-type B supergiants. All of them are heavily obscured, with E(B-V) ranging between 3 and 5, implying visual extinctions of ~ 9 to 15 mag. We refine the published classifications of IGR J18027-2016 and IGR J19140+0951 by constraining their luminosity class. In the first case, we confirm the supergiant nature but exclude a class III. In the second case, we propose a slightly higher luminosity class (Ia instead of Iab) and provide an improved value of the distance based on new optical photometry. Two other systems, SAX J18186-1703 and IGR J18483-0311 are classified as supergiant fast X-ray transients (SFXTs). XTE J1901+014, on the other hand, contains no bright infrared source in its error circle. Conclusions: Owing to their infrared and X-ray characteristics, IGR J18027-2016 and IGR J19140+0951, emerge as supergiant X-ray binaries with X-ray luminosities of the order of L_X˜ [1-2]× 1036 erg s-1, while SAX J1818.6-1703 and IGR J18483-0311, are found to be SFXTs at 2 and 3 kpc, respectively. Finally, XTE J1901+014 emerges as a puzzling

  15. Two to six compound thin films by MOCVD for tandem solar cells

    NASA Astrophysics Data System (ADS)

    Britt, Jeffrey Scott

    Polycrystalline Cd(1-x)Zn(x)S and Hg(x)Zn(1-x)Te films have been deposited on a variety of substrates by MOCVD. Deposition conditions have been adjusted based on measurements of the material properties. Heterojunction solar cells have been formed from these materials and their potential application as the upper member of a tandem solar cell has been examined. The evaluation and optimization of a high efficiency CdTe/CdS solar cell has also been accomplished. Polycrystalline Cd(1-x)Zn(x)S films were deposited at 350-425 C by the reaction between DMCd, DEZn, and the novel source, propanethiol (PM) in a H2 flow. The growth rate and bandgap energy are strongly dependent on the growth temperature, DMCd/DEZn molar ratio, and the II/VI molar ratio. TMAl and octyl-chloride have been introduced into the reaction mixture to lower resistivities to values suitable for device operation. Polycrystalline ZnTe films have been deposited at 270-400 C by the reaction between DIPTe and DMZn or DEZn in a H2 flow. ZnTe films have been deposited by photoenhanced and conventional MOCVD. Polycrystalline Hg(x)Zn(1-x)Te films have been deposited at 350-410 C by the reaction between elemental Hg, DIPTe, and DMZn in a H2 flow. AsH3 was introduced to the reaction mixture to control the resistivity. Heterojunctions have been formed with Cd(1-x)Zn(x)S and ZnSe. The films and junctions have been characterized by x-ray, optical transmission, low temperature photoluminescence, SEM, and electrical measurements. The evaluation and optimization of a CSS CdTe/CdS solar cell has been formed. A technique for the formation of low-resistance contacts to CdTe with HgTe has also been developed. A pre-deposition heat treatment of CdS in H2 has been demonstrated beneficial to the photovoltaic characteristics of the junction. A post-deposition CdCl2 treatment has been shown to have a profound influence on the electrical characteristics of CSS CdTe/CdS junctions. The identification of optical losses in CSS Cd

  16. 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

  17. Chemical trends of the luminescence in wide band gap II 1-xMn xVI semimagnetic semiconductors

    NASA Astrophysics Data System (ADS)

    Benecke, C.; Busse, W.; Gumlich, H.-E.

    1990-04-01

    Time resolved emission and excitation spectroscopy is used to investigate the Mn correlated luminescence in wide band gap II-VI compounds, i.e. Zn 1-xMn xS, Cd 1-xMn xSe, Zn 1-xMn xTe and Cd 1-xMn xTe. Additional Information has been obtained with CdxZnyMnzTe( x+ y+ z=1) in checking the luminescence by variation of the ratio of the cations Cd and Zn. Generally speaking, at least two distinct emissions bands can be observed for each II 1- xMn xVI compound. One emissions band is attributed to the internal transition 4T 1(G)→ 6A 1(S) of the 3d 5 electron of the Mn 2+ on regular metal sites with energies of about ≈2 eV. The other emission band is found to occur in the near infrared range of about ≈1.3 eV. This emission band is tentatively interpreted as a transition of Mn 2+ ions on interstitial sites or in small Mn chalcogenide clusters, both interpretations assuming cubic symmetry. This model is supported by the existence of low energy excitation bands and by the great similarity of the shape of the two emission bands which lead to comparable Huang-Rhys factors and effective phonon energies. Also the established trend in the experimental data of the II-VI compounds under consideration confirm this interpretation. For both the IR and the yellow Mn 2+ center, the Racah parameters B and C and the crystal field parameter Dq are determined on the basis of experimental data. As a result, the energy of both the emission and the excitation bands is predominantly determined by the sorrounding anions. These bands shift to higher energies when the anions are changed in the fixed order: Te→Se→S. Regularly, there is also a spectral shift when Zn is replaced by Cd, which is smaller than the shift due to the variation of onions.

  18. 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.

  19. Phase correlations in the CuAlSe2-CuAlTe2 system

    NASA Astrophysics Data System (ADS)

    Korzun, B. V.; Fadzeyeva, A. A.; Bente, K.; Schmitz, W.; Kommichau, G.

    2005-07-01

    Alloys in the CuAlSe2-CuAlTe2 system were synthesized in BN-crucibles in silica tubes under vacuum to obtain the corresponding phase equilibria. X-ray powder diffraction and thermal analytic data of the T-x phase diagram revealed a complete solid solutions series in the subsolidus region. Within the CuAlSe2xTe2(1-x) system the refined lattice parameters a and c approximately obey the Vegard rule and also the cell volume and the heat of fusion confirm linear correlations with the composition of the mixed crystals. The anion position parameter calculated after S. C. Abrahams & J. L. Bernstein (uAB) and J. E Jaffe & A. Zunger (uJZ) is greater than 0.25 and reveals a linear dependence on composition. The liquidus part of the CuAlSe2xTe2(1-x) system with x < 0.35 exhibits vertical section behaviour with a ternary peritectic followed up by a ternary monotectic whereas the region with x > 0.35 shows quasibinary equilibria.

  20. Bridgman crystal growth

    NASA Technical Reports Server (NTRS)

    Carlson, Frederick

    1990-01-01

    The objective of this theoretical research effort was to improve the understanding of the growth of Pb(x)Sn(1-x)Te and especially how crystal quality could be improved utilizing the microgravity environment of space. All theoretical growths are done using the vertical Bridgman method. It is believed that improved single crystal yields can be achieved by systematically identifying and studying system parameters both theoretically and experimentally. A computational model was developed to study and eventually optimize the growth process. The model is primarily concerned with the prediction of the thermal field, although mass transfer in the melt and the state of stress in the crystal were of considerable interest. The evolution is presented of the computer simulation and some of the important results obtained. Diffusion controlled growth was first studied since it represented a relatively simple, but nontheless realistic situation. In fact, results from this analysis prompted a study of the triple junction region where the melt, crystal, and ampoule wall meet. Since microgravity applications were sought because of the low level of fluid movement, the effect of gravitational field strength on the thermal and concentration field was also of interest. A study of the strength of coriolis acceleration on the growth process during space flight was deemed necessary since it would surely produce asymmetries in the flow field if strong enough. Finally, thermosolutal convection in a steady microgravity field for thermally stable conditions and both stable and unstable solutal conditions was simulated.

  1. Numerical Simulations of a Prompt Hard X-ray Emission During its Bright Outburst

    NASA Astrophysics Data System (ADS)

    Filippova, Ekaterina V.; Revnivtsev, M.; Lutovinov, A.

    2007-08-01

    We present a simple numerical model of the X-ray emission of the system XTE J0421+560/CI Cam during its bright outburst on 31 March 1998. Basing on the spectral and timing behavior of the object we argue that this outburst is a prompt X-ray/hard X-ray emission of a classical nova-type explosion (thermonuclear runaway on the surface of the white dwarf) unlike many other outbursts of X-ray binary systems. The thermonuclear runaway on the surface of the white dwarf leads to the formation of fast ejecta which moves through the dense stellar wind of the optical companion (B giant). Shock waves, which are formed in the material of the wind and that of the ejecta heats the matter up to X-ray temperatures. We use the spherically symmetric Lagrangian hydro- simulation to follow the evolution of the explosion. Up to now we have extensively simulated early phases of the outburst and showed that using of physically motivated simulations one can put constrains on the velocity of the ejecta and the stellar companion mass loss rate. In order to follow X-ray evolution throughout the whole outburst we develop a fully adaptive code.

  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. WISE detection of the galactic low-mass X-ray binaries

    SciTech Connect

    Wang, Xuebing; Wang, Zhongxiang

    2014-06-20

    We report on the results from our search for the Wide-field Infrared Survey Explorer (WISE) detection of the Galactic low-mass X-ray binaries (LMXBs). Among 187 binaries cataloged in Liu et al., we find 13 counterparts and 2 candidate counterparts. For the 13 counterparts, 2 (4U 0614+091 and GX 339–4) have already been confirmed by previous studies to have a jet and 1 (GRS 1915+105) to have a candidate circumbinary disk, from which the detected infrared emission arose. Having collected the broadband optical and near-infrared data in the literature and constructed flux density spectra for the other 10 binaries, we identify that 3 (A0620–00, XTE J1118+480, and GX 1+4) are candidate circumbinary disk systems, 4 (Cen X-4, 4U 1700+24, 3A 1954+319, and Cyg X-2) had thermal emission from their companion stars, and 3 (Sco X-1, Her X-1, and Swift J1753.5–0127) are peculiar systems with the origin of their infrared emission rather uncertain. We discuss the results and WISE counterparts' brightness distribution among the known LMXBs, and suggest that more than half of the LMXBs would have a jet, a circumbinary disk, or both.

  4. 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.

  5. Mission Operations Centers (MOCs): Integrating key spacecraft ground data system components

    NASA Technical Reports Server (NTRS)

    Harbaugh, Randy; Szakal, Donna

    1994-01-01

    In an environment characterized by decreasing budgets, limited system development time, and user needs for increased capabilities, the Mission Operations Division (MOD) at the National Aeronautics and Space Administration Goddard Space Flight Center initiated a new, cost-effective concept in developing its spacecraft ground data systems: the Mission Operations Center (MOC). In the MOC approach, key components are integrated into a comprehensive and cohesive spacecraft planning, monitoring, command, and control system with a single, state-of-the-art graphical user interface. The MOD is currently implementing MOC's, which feature a common, reusable, and extendable system architecture, to support the X-Ray Timing Explorer (XTE), Tropical Rainfall Measuring Mission (TRMM), and Advanced Composition Explorer (ACE) missions. As a result of the MOC approach, mission operations are integrated, and users can, with a single system, perform real-time health and safety monitoring, real-time command and control, real-time attitude processing, real-time and predictive graphical spacecraft monitoring, trend analysis, mission planning and scheduling, command generation and management, network scheduling, guide star selection, and (using an expert system) spacecraft monitoring and fault isolation. The MOD is also implementing its test and training simulators under the new MOC management structure. This paper describes the MOC concept, the management approaches used in developing MOC systems, the technologies employed and the development process improvement initiatives applied in implementing MOC systems, and the expected benefits to both the user and the mission project in using the MOC approach.

  6. Structural semiconductor-to-semimetal phase transition in two-dimensional materials induced by electrostatic gating.

    PubMed

    Li, Yao; Duerloo, Karel-Alexander N; Wauson, Kerry; Reed, Evan J

    2016-01-01

    Dynamic control of conductivity and optical properties via atomic structure changes is of technological importance in information storage. Energy consumption considerations provide a driving force towards employing thin materials in devices. Monolayer transition metal dichalcogenides are nearly atomically thin materials that can exist in multiple crystal structures, each with distinct electrical properties. By developing new density functional-based methods, we discover that electrostatic gating device configurations have the potential to drive structural semiconductor-to-semimetal phase transitions in some monolayer transition metal dichalcogenides. Here we show that the semiconductor-to-semimetal phase transition in monolayer MoTe2 can be driven by a gate voltage of several volts with appropriate choice of dielectric. We find that the transition gate voltage can be reduced arbitrarily by alloying, for example, for Mo(x)W(1-x)Te2 monolayers. Our findings identify a new physical mechanism, not existing in bulk materials, to dynamically control structural phase transitions in two-dimensional materials, enabling potential applications in phase-change electronic devices. PMID:26868916

  7. Structural semiconductor-to-semimetal phase transition in two-dimensional materials induced by electrostatic gating

    NASA Astrophysics Data System (ADS)

    Li, Yao; Duerloo, Karel-Alexander N.; Wauson, Kerry; Reed, Evan J.

    2016-02-01

    Dynamic control of conductivity and optical properties via atomic structure changes is of technological importance in information storage. Energy consumption considerations provide a driving force towards employing thin materials in devices. Monolayer transition metal dichalcogenides are nearly atomically thin materials that can exist in multiple crystal structures, each with distinct electrical properties. By developing new density functional-based methods, we discover that electrostatic gating device configurations have the potential to drive structural semiconductor-to-semimetal phase transitions in some monolayer transition metal dichalcogenides. Here we show that the semiconductor-to-semimetal phase transition in monolayer MoTe2 can be driven by a gate voltage of several volts with appropriate choice of dielectric. We find that the transition gate voltage can be reduced arbitrarily by alloying, for example, for MoxW1-xTe2 monolayers. Our findings identify a new physical mechanism, not existing in bulk materials, to dynamically control structural phase transitions in two-dimensional materials, enabling potential applications in phase-change electronic devices.

  8. 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.

  9. 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.

  10. 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.

  11. Towards defect-free epitaxial CdTe and MgCdTe layers grown on InSb (001) substrates

    NASA Astrophysics Data System (ADS)

    Lu, Jing; DiNezza, Michael J.; Zhao, Xin-Hao; Liu, Shi; Zhang, Yong-Hang; Kovacs, Andras; Dunin-Borkowski, Rafal E.; Smith, David J.

    2016-04-01

    A series of three CdTe/MgxCd1-xTe (x~0.24) double heterostructures grown by molecular beam epitaxy on InSb (001) substrates at temperatures in the range of 235-295 °C have been studied using conventional and advanced electron microscopy techniques. Defect analysis based on bright-field electron micrographs indicates that the structure grown at 265 °C has the best structural quality of the series, while structures grown at 30 °C lower or higher temperature show highly defective morphology. Geometric phase analysis of the CdTe/InSb interface for the sample grown at 265 °C reveals minimal interfacial elastic strain, and there is no visible evidence of interfacial defect formation in aberration-corrected electron micrographs of this particular sample. Such high quality CdTe epitaxial layers should provide the basis for applications such as photo-detectors and multi-junction solar cells.

  12. 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.

  13. INTEGRAL study of temporal properties of bright flares in Supergiant Fast X-ray Transients

    NASA Astrophysics Data System (ADS)

    Sidoli, L.; Paizis, A.; Postnov, K.

    2016-04-01

    We have characterized the typical temporal behaviour of the bright X-ray flares detected from the three Supergiant Fast X-ray Transients (SFXTs) showing the most extreme transient behaviour (XTE J1739-302, IGR J17544-2619, SAX J1818.6-1703). We focus here on the cumulative distributions of the waiting-time (time interval between two consecutive X-ray flares), and the duration of the hard X-ray activity (duration of the brightest phase of an SFXT outburst), as observed by INTEGRAL/IBIS in the energy band 17-50 keV. Adopting the cumulative distribution of waiting-times, it is possible to identify the typical time-scale that clearly separates different outbursts, each composed by several single flares at ˜ks time-scale. This allowed us to measure the duration of the brightest phase of the outbursts from these three targets, finding that they show heavy-tailed cumulative distributions. We observe a correlation between the total energy emitted during SFXT outbursts and the time interval covered by the outbursts (defined as the elapsed time between the first and the last flare belonging to the same outburst as observed by INTEGRAL). We show that temporal properties of flares and outbursts of the sources, which share common properties regardless different orbital parameters, can be interpreted in the model of magnetized stellar winds with fractal structure from the OB-supergiant stars.

  14. Properties of MIS structures based on graded-gap HgCdTe grown by molecular beam epitaxy

    SciTech Connect

    Voitsekhovskii, A. V. Nesmelov, S. N.; Dzyadookh, S. M.; Varavin, V. S.; Dvoretskii, S. A.; Mikhailov, N. N.; Sidorov, Yu. G.; Vasiliev, V. V.

    2008-11-15

    The effect of near-surface graded-gap layers on the electrical characteristics of MIS structures fabricated based on heteroepitaxial Hg{sub 1-x} Cd{sub x}Te films grown by molecular beam epitaxy with a two-layer SiO{sub 2}/Si{sub 3}N{sub 4} insulator and anodic oxide film is studied experimentally. It is shown that a larger modulation of capacitance (depth and width of the valley) is observed compared with the structures without the graded-gap layer. The field dependences of photovoltage of MIS structures with the graded-gap layers had a classical form and were characterized by a drop only in the enrichment region. For the structures without the graded-gap layer with x = 0.22, a drop in the voltage dependence of the photocurrent is observed in the region of pronounced inversion. This drop is governed by limitation of the space charge region by processes of tunneling generation via deep levels. The properties of the HgCdTe-insulator interfaces are studied.

  15. 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.

  16. PASSIVATION OF SEMICONDUCTOR SURFACES FOR IMPROVED RADIATION DETECTORS: X-RAY PHOTOEMISSION ANALYSIS

    SciTech Connect

    Nelson, A; Conway, A; Reinhardt, C; Ferreira, J; Nikolic, R; Payne, S

    2007-12-10

    Surface passivation of device-grade radiation detector materials was investigated using x-ray photoelectron spectroscopy in combination with transport property measurements before and after various chemical treatments. Specifically Br-MeOH (2% Br), KOH with NH{sub 4}F/H{sub 2}O{sub 2} and NH{sub 4}OH solutions were used to etch, reduce and oxidize the surface of Cd{sub (1-x)}Zn{sub x}Te semiconductor crystals. Scanning electron microscopy was used to evaluate the resultant microscopic surface morphology. Angle-resolved high-resolution photoemission measurements on the valence band electronic structure and core lines were used to evaluate the surface chemistry of the chemically treated surfaces. Metal overlayers were then deposited on these chemically treated surfaces and the I-V characteristics measured. The measurements were correlated to understand the effect of interface chemistry on the electronic structure at these interfaces with the goal of optimizing the Schottky barrier height for improved radiation detector devices.

  17. 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.

  18. 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.

  19. 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.

  20. Inter-band optoelectronic properties in quantum dot structure of low band gap III-V semiconductors

    SciTech Connect

    Dey, Anup; Maiti, Biswajit; Chanda, Debasree

    2014-04-14

    A generalized theory is developed to study inter-band optical absorption coefficient (IOAC) and material gain (MG) in quantum dot structures of narrow gap III-V compound semiconductor considering the wave-vector (k{sup →}) dependence of the optical transition matrix element. The band structures of these low band gap semiconducting materials with sufficiently separated split-off valance band are frequently described by the three energy band model of Kane. This has been adopted for analysis of the IOAC and MG taking InAs, InSb, Hg{sub 1−x}Cd{sub x}Te, and In{sub 1−x}Ga{sub x}As{sub y}P{sub 1−y} lattice matched to InP, as example of III–V compound semiconductors, having varied split-off energy band compared to their bulk band gap energy. It has been found that magnitude of the IOAC for quantum dots increases with increasing incident photon energy and the lines of absorption are more closely spaced in the three band model of Kane than those with parabolic energy band approximations reflecting the direct the influence of energy band parameters. The results show a significant deviation to the MG spectrum of narrow-gap materials having band nonparabolicity compared to the parabolic band model approximations. The results reflect the important role of valence band split-off energies in these narrow gap semiconductors.

  1. High Compositional Homogeneity of CdTexSe1-x Crystals Grown by the Bridgman Method

    DOE PAGESBeta

    Roy, U. N.; Bolotnikov, A. E.; Camarda, G. S.; Cui, Y.; Hossain, A.; Lee, K.; Lee, W.; Tappero, R.; Yang, G.; Gul, R.; et al

    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

  2. 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.

  3. ANOMALOUS X-RAY PULSARS AND SOFT GAMMA-RAY REPEATERS IN THE OUTER GAP MODEL: CONFRONTING FERMI OBSERVATIONS

    SciTech Connect

    Tong, H.; Song, L. M.; Xu, R. X.

    2011-09-01

    Anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs) are magnetar candidates, i.e., neutron stars powered by a strong magnetic field. If they are indeed magnetars, they will emit high-energy gamma rays that are detectable by the Fermi Large Area Telescope (LAT), according to the outer gap model. However, no significant detection is reported in recent Fermi-LAT observations of all known AXPs and SGRs. Considering the discrepancy between theory and observations, we calculate the theoretical spectra for all AXPs and SGRs with sufficient observational parameters. Our results show that most AXPs and SGRs are high-energy gamma-ray emitters if they are really magnetars. The four AXPs 1E 1547.0-5408, XTE J1810-197, 1E 1048.1-5937, and 4U 0142+61 should have been detected by Fermi-LAT. There is therefore a conflict between the outer gap model in the case of magnetars and Fermi observations. Possible explanations in the magnetar model are discussed. On the other hand, if AXPs and SGRs are fallback disk systems, i.e., accretion-powered for the persistent emissions, most of them are not high-energy gamma-ray emitters. Future deep Fermi-LAT observations of AXPs and SGRs will help us make clear whether they are magnetars or fallback disk systems.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  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. X-Ray Continua of Broad Absorption Line Quasars

    NASA Technical Reports Server (NTRS)

    Mathur, S.

    1999-01-01

    The targets for this program, PG1416-129 and LBQS 2212-1759 were known to be Broad Absorption Line Quasars (BALQSOs). BALQSOs are highly absorbed in soft X-rays. Good high energy response of Rossi-XTE made them ideal targets for observation. We observed LBQS 2212-1759 with PCA. We have now analyzed the data and found that the source was not detected. Since our target was expected to be faint, reliable estimate of background was very important. With the release of new FTOOLS (version 4.1) we were able to do so. We also analyzed a well known bright object and verified our results with the published data. This gave us confidence in the non-detection of our target LBQS 2212-1759. We are currently investigating the implications of this non-detection. Due to some scheduling problems, our second target PG1416-129 was not observed in A01. It was observed on 06/26/98. This target was detected with RXTE. We are now working on the spectral analysis with XSPEC.

  10. 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.

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

    NASA Technical Reports Server (NTRS)

    Tavani, Marco

    1998-01-01

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

  12. Confinement effects in semimagnetic semiconductors

    NASA Astrophysics Data System (ADS)

    Dietl, Tomasz

    1998-02-01

    An overview is given of selected novel effects observed recently by various groups in modulated structures of Cd 1- xMn xTe. Millikelvin studies of submicron wires doped with either indium or iodine have demonstrated the existence of a new mechanism, by which the universal conductance fluctuations can be generated in mesoscopic systems containing magnetic ions. Moreover, 1/ f conductance noise as well as thermal and magnetic irreversibilities have been observed, providing important information on spin-glass dynamics. Finite size effects in magnetic properties have been probed by direct static and dynamic SQUID measurements on superlattices consisting of few-monolayer spin-glass films separated by nonmagnetic barriers. The confined holes have been found to exert a strong influence upon the magnetic ions and to induce a ferromagnetic phase transition above 1 K in quantum wells modulation doped by nitrogen. Finally, it has been shown also that the giant spin-splitting of the bands offers a tool to tune the coupling between confined photon and exciton modes in photonic structures.

  13. 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.

  14. The X-Ray Spectral Evolution of Galactic Black Hole X-Ray Binaries toward Quiescence

    NASA Astrophysics Data System (ADS)

    Plotkin, Richard. M.; Gallo, Elena; Jonker, Peter G.

    2013-08-01

    Most transient black hole X-ray binaries (BHXBs) spend the bulk of their time in a quiescent state, where they accrete matter from their companion star at highly sub-Eddington luminosities (we define quiescence here as a normalized Eddington ratio lx = L 0.5-10 keV/L Edd < 10-5). Here, we present Chandra X-ray imaging spectroscopy for three BHXB systems (H 1743-322, MAXI J1659-152, and XTE J1752-223) as they fade into quiescence following an outburst. Multiple X-ray observations were taken within one month of each other, allowing us to track each individual system's X-ray spectral evolution during its decay. We compare these three systems to other BHXB systems. We confirm that quiescent BHXBs have softer X-ray spectra than low-hard-state BHXBs, and that quiescent BHXB spectral properties show no dependence on the binary system's orbital parameters. However, the observed anti-correlation between X-ray photon index (Γ) and lx in the low-hard state does not continue once a BHXB enters quiescence. Instead, Γ plateaus to an average langΓrang = 2.08 ± 0.07 by the time lx reaches ~10-5. lx ~ 10-5 is thus an observationally motivated upper limit for the beginning of the quiescent spectral state. Our results are discussed in the context of different accretion flow models and across the black hole mass scale.

  15. 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.

  16. 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.}

  17. The role of localized junction leakage in the temperature-dependent laser-beam-induced current spectra for HgCdTe infrared focal plane array photodiodes

    SciTech Connect

    Feng, A. L.; Li, G. E-mail: xschen@mail.sitp.ac.cn; He, G.; Sun, Z. Q.; Hu, W. D.; Chen, X. S. E-mail: xschen@mail.sitp.ac.cn; Yin, F.; Zhang, B.; Lu, W.

    2013-11-07

    We have performed the study on the dependence of laser beam induced current (LBIC) spectra on the temperature for the vacancy-doped molecular beam epitaxy grown Hg{sub 1−x}Cd{sub x}Te (x = 0.31) photodiodes by both experiment and numerical simulations. It is found that the measured LBIC signal has different distributions for different temperature extents. The LBIC profile tends to be more asymmetric with increasing temperature below 170 K. But the LBIC profile becomes more symmetric with increasing temperature above 170 K. Based on a localized leakage model, it is indicated that the localized junction leakage can lead to asymmetric LBIC signal, in good agreement with the experimental data. The reason is that the trap-assisted tunneling current is the dominant leakage current at the cryogenic temperature below 170 K while the diffusion current component becomes dominant above the temperature of 170 K. The results are helpful for us to better clarify the mechanism of the dependence of LBIC spectra on temperature for the applications of HgCdTe infrared photodiodes.

  18. Specific features of the spectra and relaxation kinetics of long-wavelength photoconductivity in narrow-gap HgCdTe epitaxial films and heterostructures with quantum wells

    SciTech Connect

    Rumyantsev, V. V. Ikonnikov, A. V.; Antonov, A. V.; Morozov, S. V.; Zholudev, M. S.; Spirin, K. E.; Gavrilenko, V. I.; Dvoretskii, S. A.; Mikhailov, N. N.

    2013-11-15

    The spectra and relaxation kinetics of interband photoconductivity are investigated in narrow-gap Hg{sub 1-x}Cd{sub x}Te epitaxial films with x = 0.19-0.23 and in structures with HgCdTe-based quantum wells (QWs), having an interband-transition energy in the range of 30-90 meV, grown by molecular-beam epitaxy on GaAs (013) substrates. A long-wavelength sensitivity band caused by impurities or defects is found in the spectra of the structures with quantum wells in addition to the interband photoconductivity. It is shown that the lifetimes of nonequilibrium carriers in the structures with QWs is less than in bulk samples at the same optical-transition energy. From the measured carrier lifetimes, the ampere-watt responsivity and the equivalent noise power for a film with x = 0.19 at a wavelength of 19 {mu}m are estimated. When investigating the relaxation kinetics of the photoconductivity at 4.2 K in high excitation regime, it is revealed that radiative recombination is dominant over other mechanisms of nonequilibrium-carrier recombination.

  19. 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.

  20. Superhumps in Cataclysmic Binaries. XXV. qcrit, ɛ(q), and Mass-Radius

    NASA Astrophysics Data System (ADS)

    Patterson, Joseph; Kemp, Jonathan; Harvey, David A.; Fried, Robert E.; Rea, Robert; Monard, Berto; Cook, Lewis M.; Skillman, David R.; Vanmunster, Tonny; Bolt, Greg; Armstrong, Eve; McCormick, Jennie; Krajci, Thomas; Jensen, Lasse; Gunn, Jerry; Butterworth, Neil; Foote, Jerry; Bos, Marc; Masi, Gianluca; Warhurst, Paul

    2005-11-01

    We report on successes and failures in searching for positive superhumps in cataclysmic variables, and show the superhumping fraction as a function of orbital period. Basically, all short-period system do, all long-period systems do not, and a 50% success rate is found at Porb=3.1+/-0.2 hr. We can use this to measure the critical mass ratio for the creation of superhumps. With a mass-radius relation appropriate for cataclysmic variables, and an assumed mean white-dwarf mass of 0.75 Msolar, we find a mass ratio qcrit=0.35+/-0.02. We also report superhump studies of several stars of independently known mass ratio: OU Vir, XZ Eri, UU Aqr, and KV UMa (=XTE J1118+480). The latter two are of special interest, because they represent the most extreme mass ratios for which accurate superhump measurements have been made. We use these to improve the ɛ(q) calibration, by which we can infer the elusive q from the easy-to-measure ɛ (the fractional period excess of Psuperhump over Porb). This relation allows mass and radius estimates for the secondary star in any cataclysmic variable (CV) showing superhumps. The consequent mass-radius law shows an apparent discontinuity in radius near 0.2 Msolar, as predicted by the disrupted magnetic braking model for the 2.1-2.7 hr period gap. This is effectively the ``empirical main sequence'' for CV secondaries.