158 research outputs found
Observational evidence for mass ejection during soft X-ray dips in GRS1915+105
We investigate the connection between the X-ray and radio properties of the
Galactic microquasar GRS1915+105, by analyzing the X-ray data observed with
RXTE, during the presence of a huge radio flare (~450 mJy). The X-ray
lightcurve shows two dips of ~100 second duration. Detailed time resolved
spectral analysis shows the existence of three spectral components: a
multicolor disk-blackbody, a Comptonized component due to hot plasma and a
power-law. We find that the Comptonized component is very weak during the dip.
This is further confirmed by the PHA ratio of the raw data and ratio of the
lightcurves in different energy bands. These results, combined with the fact
that the 0.5 -- 10 Hz QPO disappears during the dip and that the Comptonized
component is responsible for the QPO lead to the conclusion that during the
dips the matter emitting Comptonized spectrum is ejected away. This establishes
a direct connection between the X-ray and radio properties of the source.Comment: Replaced with some minor changes, corrected typos. Added Journal Re
A Retrograde Spin of the Black Hole in MAXI J1659–152
We present the results of spectral analysis of the galactic black-hole binary
MAXI J1659--152 in the rising phase of the outburst that lasted for about 65
days starting on 2010 September 25. The presence of a broad Fe line, verified
by Monte-Carlo simulations, and coverage of a wide energy band by utilizing the
combined spectral capabilities of XMM-Newton/EPIC-pn and RXTE/PCA allowed us to
use a combination of reflection spectroscopy and continuum fitting methods to
estimate the spin of the black hole. We explored the entire parameter range
allowed by the present uncertainties on black-hole mass, inclination, and
distance as well as the accretion rate. We show that for about 95 percentage of
parameter space and very reasonable upper limits on mass accretion rate, the
spin of the black hole has to be negative. This is the first clear detection of
negative spin in a galactic black-hole binary.Comment: Published in ApJL. 9 pages, 4 figure
Disk-Jet Connection in Cygnus X-3
We present the results of a detailed correlation study between the soft
X-ray, hard X-ray, and radio emission (obtained from RXTE ASM, BATSE, and GBI
observations, respectively) of the bright radio emitting Galactic X-ray binary
Cygnus X-3. We detect a very strong positive correlation between the soft X-ray
and radio emission during the low-hard and minor flaring periods of the source,
and an anti-correlation between the soft and hard X-ray emissions. We present
statistical arguments to suggest that the anti-correlation between the radio
and hard X-ray emission, reported earlier, is primarily due to their
correlation and anti-correlation, respectively, with the soft X-ray emission.
We make a wide band X-ray spectral study using the pointed RXTE observations
and detect a pivotal behaviour in the X-ray spectrum. We argue that this X-ray
spectral pivoting is responsible for the anti-correlation between the soft and
hard X-ray emissions. The strong correlation between the soft X-ray and radio
emission suggests a close link between the accreting mechanism, plasma cloud
surrounding the compact object and the radio emission.Comment: Accepted in A&A Letters. Major revioson of discussion, minor revision
of tables and figure
X-ray spectral components in the hard state of GRS 1915+105: origin of the 0.5 - 10 Hz QPO
We investigate the origin of the ubiquitous 0.5 - 10 Hz QPO in the Galactic microquasar GRS 1915+105. Using the archival X-ray data from RXTE, we make a wide band X-ray spectral fitting to the source during a low-hard state observed in 1999 June. We resolve the X-ray spectra into three components, namely a multi-color disk component, a Comptonised component and a power-law at higher energies. This spectral description is favored compared to other normally used spectra like a cut-off power law, hard components with reflection etc. We find that the 0.5 - 10 Hz QPO is predominantly due to variations in the Comptonised component. We use this result to constrain the location of the various spectral components in the source
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