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Register a new userOptical Observations of the Black Hole Candidate XTE J1550-564 During Re-Flare and Quiescence
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Authors
Raj K. Jain
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We report optical monitoring of the soft X-ray transient XTE J1550-564 during the 1999 season (4 January 1999 to 24 August 1999). The first optical observations available in 1999 show that the peak ``re-flare brightness had exceeded the peak brightness of the initial optical flare in September 1998 by over half a magnitude. We compare the optical re-flare light curves with the total X-ray flux, the power-law flux and disk flux light curves constructed from the spectral fits to RXTE/PCA data made by Sobczak et al. (1999, 2000). During the first 60 days of the observed optical re-flare, we find no correspondence between the thermal component of the X-rays often associated with a disk and the optical flux -- the former remains essentially flat whereas the latter declines exponentially and exhibits three substantial dips. However, the power law flux is anti-correlated with the optical dips, suggesting that the optical flux may by up-scattered into the X-ray by the hot corona. Periodic modulations were discovered during the final stage of the outburst (May to June), with P=1.546+/-0.038 days, and during quiescence (July and August), with P=1.540+/-0.008 days. The analysis of the combined data set reveals a strong signal for a unique period at P=1.541+/-0.009 days, which we believe to be the orbital period.
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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 RXTE 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 non-thermal emission associated with the formation of a jet.
We report the identification of the optical counterpart of the X-ray transient XTE J1550-564 described in two companion papers by Sobczak et al (1999) and Remillard et al (1999). We find that the optical source brightened by approximately 4 magnitudes over the quiescent counterpart seen at B~22 on a SERC survey plate, and then decayed by approximately 1.5 magnitudes over the 7 week long observation period. There was an optical response to the large X-ray flare described by Sobczak et al (1999), but it was much smaller and delayed by roughly 1 day.
We report on the analysis of new and previously published MMT optical spectra of the black hole binary XTE J1118+480 during the decline from the 2000 outburst to true quiescence. From cross-correlation with template stars, we measure the radial velocity of the secondary to derive a new spectroscopic ephemeris. The observations acquired during approach to quiescence confirm the earlier reported modulation in the centroid of the double-peaked Halpha emission line. Additionally, our data combined with the results presented by Zurita et al. (2002) provide support for a modulation with a periodicity in agreement with the expected precession period of the accretion disk of ~52 day. Doppler images during the decline phase of the Halpha emission line show evidence for a hotspot and emission from the gas stream: the hotspot is observed to vary its position, which may be due to the precession of the disk. The data available during quiescence show that the centroid of the Halpha emission line is offset by about -100 km/s from the systemic velocity which suggests that the disk continues to precess. A Halpha tomogram reveals emission from near the donor star after subtraction of the ring-like contribution from the accretion disk which we attribute to chromospheric emission. No hotspot is present suggesting that accretion from the secondary has stopped (or decreased significantly) during quiescence. Finally, a comparison is made with the black hole XRN GRO J0422+32: we show that the Halpha profile of this system also exhibits a behaviour consistent with a precessing disk.
Here we summarise the Swift broadband observations of the recently discovered X-ray transient and black hole candidate, XTE J1752-223,obtained over the period of outburst from October 2009 to June 2010. We offer a phenomenological treatment of the spectra as an indication of the canonical spectral state of the source during different periods of the outburst. We find that the high energy hardness-intensity diagrams over two separate bands follows the canonical behavior, confirming the spectral states. From Swift-UVOT data we confirm the presence of an optical counterpart which displays variability correlated, in the soft state, to the X-ray emission observed by Swift-XRT. The optical counterpart also displays hysteretical behaviour between the states not normally observed in the optical bands, suggesting a possible contribution from a synchrotron emitting jet to the optical emission in the rising hard state. Our XRT timing analysis shows that in the hard state there is significant variability below 10Hz which is more pronounced at low energies, while during the soft state the level of variability is consistent with being minimal.These properties of XTE J1752-223 support its candidacy as a black hole in the Galactic centre region.
In 1998 September, the X-ray transient XTE J1550-564 underwent a major outburst in soft and hard X-rays, followed by a radio flare. Australian Long Baseline Array images obtained shortly after the peak in the radio flare showed evolving structure. The components observed have an apparent separation velocity of >2c.
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