Observations made by the Unconventional Stellar Aspect (USA) Experiment on board the Advanced Research and Global Observation Satellite (ARGOS) are emphasized. In this work, the timing and spectral properties of the SXT and microquasar XTE J 1550-564 during outburst are studied. These compact objects are most likely black holes, which exhibit, on a much larger scale, accretion physics similar to that around black holes in SXTs. The majority of known SXTs contain black holes, therefore SXT outbursts are key to understanding accretion physics around black holes and in active galactic nuclei, which are thought to contain supermassive, M is one solar mass, central compact objects. SXT outbursts are of great interest because they allow the study of LMXBs under a wide range of accretion rates. Soft X-ray transients (SXTs), a sub-class of low-mass X-ray binaries (LMXBs), provide a unique opportunity to test General Relativity and to probe fundamental physics under conditions terrestrially unattainable. X-Ray Timing and Spectral Observations of Galactic Black Hole Candidate XTE J 1550-564 During Outburst The hardness-intensity diagram (HID) shows a cyclical movement in the counterclockwise direction and possibly indicates the presence of two independent accretion flows: a thin disk and a hot sub-Keplerian flow. The evolution of the hardness ratio (4-16 keV/1-4 keV) with time and source flux is examined. Several high-frequency quasi-periodic oscillations (HFQPO) were detected by RXTE, during periods where the LFQPO is seen to be weakening or not detectable at all. We observe a low-frequency quasi-periodic oscillation (LFQPO) with a centroid frequency that tends to increase with increasing flux and a fractional rms amplitude which is correlated with the hardness ratio. We report on timing and spectral observations of the 2000 outburst of XTE J 1550-564 made by the Unconventional Stellar Aspect (USA) Experiment on board the Advanced Research and Global Observation Satellite (ARGOS). USA Observation of Spectral and Timing Evolution During the 2000 Outburst of XTE J 1550-564Įnergy Technology Data Exchange (ETDEWEB) In this source, the transition between the low/hard state and the hard-intermediate state appears to be a smooth process. An interplay between these two components was also observed as a function of their characteristic frequency. At low energies, the lowest-frequency component dominates, while at high energies the higher-frequency one has a higher fractional rms. We also studied the energy dependence of the timing features and conclude that the two continuum components observed in the power spectrum, although both more intense at high energies, show a different dependence on energy. From this, we argue that the peak observed at half the QPO frequency, usually referred to as 'sub-harmonic', could be the fundamental frequency, leading to the sequence 1:2:3:4. This component is broad, with a quality factor of âˆ❀.6. In addition to the QPO and its harmonic peaks, a new 1.5ν component was detected in the power spectra. In all observations, the quality factors (ν 0 /FWHM) of the fundamental and second harmonic peaks were observed to be consistent, suggesting that the quasi-periodic nature of the oscillation is due to frequency modulation. The QPO frequency is observed to vary on timescales between âˆ❁00 s and days, correlated with the count rate contribution from the optically thick accretion disk: we studied this correlation and discuss its influence on the QPO width. We present the results of a timing analysis of the low-frequency quasi-periodic oscillation (QPO) in the Rossi X-Ray Timing Explorer data of the black hole binary XTE J 1550-564 during its 1998 outburst. ![]() Rao Fengyun Belloni, Tomaso Stella, Luigi Zhang Shuangnan Li Tipei International Nuclear Information System (INIS) LOW-FREQUENCY OSCILLATIONS IN XTE J 1550-564 ![]() Radio flux density upper limits (3σ) of 26 μJy (at 5.5 GHz), 47 μJy (at 9 GHz) for GRO J1655−40 and We present the results of radio observations of the black hole binaries GRO J1655−40 and XTE J 1550− 564 in quiescence, with the upgraded Australia Telescope Compact Array. Limits on the quiescent radio emission from the black hole binaries GRO J1655−40 and XTE J 1550− 564Ĭalvelo, D.E.
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