524 research outputs found
Discovery of a Quasi-Periodic Oscillation in the Ultraluminous X-ray Source IC 342 X-1: XMM-Newton Results
We report the discovery of a quasi-periodic oscillation (QPO) at 642 mHz in
an {\it XMM-Newton} observation of the ultraluminous X-ray source (ULX) IC 342
X-1. The QPO has a centroid at mHz, a coherence factor
of , and an amplitude (rms) of 4.1\% with significance of
. The energy dependence study shows that the QPO is stronger in the
energy range 0.3 - 5.0 keV. A subsequent observation (6 days later) does not
show any signature of the QPO in the power density spectrum. The broadband
energy spectra (0.3 - 40.0 keV) obtained by quasi-simultaneous observations of
{\it XMM-Newton} and {\it NuSTAR} can be well described by an absorbed {\it
diskbb} plus {\it cutoffpl} model. The best fitted spectral parameters are
power-law index () 1.1, cutoff energy () 7.9 keV and
disc temperature () 0.33 keV, where the QPO is detected. The
unabsorbed bolometric luminosity is 5.34 10 erg~s.
Comparing with the well known X-ray binary GRS 1915+105, our results are
consistent with the mass of the compact object in IC 342 X-1 being in the range
. We discuss the possible implications of our results.Comment: 7 pages, 3 figures (2 colour), in press (MNRAS
Estimation of mass outflow rates from dissipative accretion disc around rotating black holes
We study the properties of the dissipative accretion flow around rotating
black holes in presence of mass loss. We obtain the complete set of global
inflow-outflow solutions in the steady state by solving the underlying
conservation equations self-consistently. We observe that global inflow-outflow
solutions are not the isolated solution, instead such solutions are possible
for wide range of inflow parameters. Accordingly, we identify the boundary of
the parameter space for outflows, spanned by the angular momentum
() and the energy () at the inner sonic
point (), as function of the dissipation parameters and find that
parameter space gradually shrinks with the increase of dissipation rates.
Further, we examine the properties of the outflow rate (defined as
the ratio of outflow to inflow mass flux) and ascertain that dissipative
processes play the decisive role in determining the outflow rates. We calculate
the limits on the maximum outflow rate () in terms of
viscosity parameter () as well as black hole spin () and obtain
the limiting range as . Moreover, we
calculate the viable range of that admits the coupled inflow-outflow
solutions and find that for . Finally,
we discuss the observational implication of our formalism to infer the spin of
the black holes. Towards this, considering the highest observed QPO frequency
of black hole source GRO J1655-40 ( Hz), we constrain the spin value
of the source as .Comment: 15 pages, 14 Figures, To appear in MNRA
Fundamental States of Accretion/Jet Configuration and the Black Hole Candidate GRS1915+105
Advective disk paradigm of black hole accretion includes self-consistent
formation of shocks and outflows from post-shock region. We apply this paradigm
to understand rich variation of the light curve of the black hole candidate
GRS1915+105. We propose that out of five possible {\it fundamental states} the
black hole candidate GRS1915+105 moves around among three of them creating all
possible observed light curves.Comment: Latex file and four figures. Indian Journal of Physics (in press
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