77 research outputs found
Black hole mass determination in the X-ray binary 4U 1630--47: Scaling of spectral and variability characteristics
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 of quasi-periodic oscillations (QPO), nu_L and mass
accretion rate, can be applied to the black hole mass and the
inclination angle estimates. We analyze the transition episodes observed with
the {\it Rossi} X-ray Timing Explorer (RXTE) 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 nu_L also shows saturation at Gamma ~ 3. Gamma-Mdot and Gamma-nu_L
correlations with their index saturation revealed in 4U~1630--47 are similar to
those established in a number of other BHCs 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 H 1743-322
as reference sources, allows us to evaluate a black hole mass in 4U~1630--47
yielding M_{BH}~10+/- 0.1 solar masses, and to constrain the inclination angle
of i< 70 degrees.Comment: 33 pages, 13 Figures. The paper is accepted and scheduled for
publication in The Astrophysical Journal, July 1, 2014, v 789, 1 issu
On the Nature of the Compact Object in SS~433. Observational Evidence of X-ray Photon Index Saturation
We present an analysis of the X-ray spectral properties observed from black
hole candidate (BHC) binary SS~433. We have analyzed RXTE data from this
source, coordinated with Green Bank Interferometer/RATAN-600. We show that
SS~433 undergoes a X-ray spectral transition from the low hard state (LHS) to
the intermediate state (IS). We show that the X-ray broad-band energy spectra
during all spectral states are well fit by a sum of so called ``Bulk Motion
Comptonization (BMC) component'' and by two (broad and narrow) Gaussians for
the continuum and line emissions respectively. In addition to these spectral
model components we also find a strong feature that we identify as a
"blackbody-like (BB)" component which color temperature is in the range of 4-5
keV in 24 IS spectra during the radio outburst decay in SS~433. Our
observational results on the "high temperature BB" bump leads us to suggest the
presence of gravitationally redshifted annihilation line emission in this
source. I\ We have also established the photon index saturation at about 2.3 in
index vs mass accretion correlation. This index-mass accretion correlation
allows us to evaluate the low limit of black hole (BH) mass of compact object
in SS~433, M_{bh}> 2 solar masses, using the scaling method using BHC GX 339-4
as a reference source. Our estimate of the BH mass in SS 433 is consistent with
recent BH mass measurement using the radial-velocity measurements of the binary
system by Hillwig & Gies who find that M_{x}=(4.3+/-0.8 solar masses. This is
the smallest BH mass found up to now among all BH sources. Moreover, the index
saturation effect versus mass accretion rate revealed in SS~433, like in a
number of other BH candidates, is the strong observational evidence for the
presence of a BH in SS~433.Comment: 29 pages, 14 figures. Accepted for the ApJ, 2010, October 1, v. 721
(2
ESO 243-49 HLX-1: scaling of X-ray spectral properties and black hole mass determination
We report the results of Swift/XRT observations (2008-2015) of a
hyper-luminous X-ray source, ESO 243-49 HLX-1. We found a strong observational
evidence that ESO 243-49 HLX-1 underwent spectral transitions from the low/hard
state to the high/soft state during these observations. The spectra of ESO
243-49 HLX-1 are well fitted by the so-{called} bulk motion Comptonization
model for all spectral states. We have established the photon index Gamma
saturation level, Gamma_{sat}$=3.0+/-0.1, in the correlation of Gamma versus
mass accretion rate dot M. This Gamma-dot M correlation allows us to estimate
the black hole (BH) mass in ESO 243-49 HLX-1 to be M_{BH}~ 7x 10^4 solar
masses, assuming the distance to ESO 243-49 of 95 Mpc. For the BH mass estimate
we used the scaling method, taking Galactic BHs XTE~J1550-564, H~1743-322 and
4U~1630-472, and an extragalactic BH source, M101 ULX-1 as reference sources.
The Gamma-dot M correlation revealed in ESO 243-49 HLX-1 is similar to those in
a number of Galactic and extragalactic BHs and it clearly shows the correlation
along with the strong Gamma saturation at ~ 3. This is a reliable observational
evidence of a BH in ESO 243-49 HLX-1. We also found that the seed (disk) photon
temperatures are quite low, of order of 50-140 eV which are consistent with a
high BH mass in ESO 243-49 HLX-1.Comment: 21 pages, 8 figures, accepted by Astronomy and Astrophysics on August
29, 201
Scaling of the photon index vs mass accretion rate correlation and estimate of black hole mass in M101 ULX-1
We report the results of Swift and Chandra observations of an ultra-luminous
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 (\Gamma) saturation level,
\Gamma_{sat}=2.8 +/- 0.1, in the \Gamma vs. mass accretion rate (\dot M)
correlation. This \Gamma-\dot M correlation allows us to evaluate black hole
(BH) mass in M101 ULX-1 to be M_{BH}~(3.2 - 4.3)x10^4 solar masses 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 use the scaling method taking Galactic BHs XTE~J1550-564,
H~1743-322 and 4U~1630-472 as reference sources. The Gamma vs. \dot M
correlation revealed in M101~ULX-1 is similar to that in a number of Galactic
BHs and exhibits clearly the correlation along with the strong \Gamma
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
quite low, of 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 of order 10^{4} solar massesComment: 12 pages, 9 figures, accepted by Astronomy & Astrophysic
Active galaxy nuclei: current state of the problem
This review presents the main points of current advances in the field of
active galactic nuclei (AGN). A brief historical excursion about the search for
the nature of AGN is given. The problem of close binary systems consisting of
supermassive black holes located in the centers of galaxies is discussed in
details. The main characteristics, as well as new methods for studying and
``weighing'' these new objects, are described. This paper is based on a
presentation made in the astrophysical seminar, which dedicated to the memory
of the outstanding astrophysicist N.G. Bochkarev (took place on May 19, 2023 at
the Sternberg Astronomical Institute of Moscow State University).Comment: 20 pages, 10 figure
How to distinguish white dwarf and neutron star X-ray binaries during their X-ray outbursts?
Neutron stars (NSs) and white dwarfs (WDs) are characterized by different
geometric and physical properties, but their observed properties are often
similar, making them difficult to distinguish. Therefore, it is desirable to
search for their spectral features that could be easily identified from
observations. We present spectral and timing signatures of NSs and WDs hosted
in accreting X-ray binaries that can be easily identified from X-ray
observations. We perform spectral and timing analysis of 4U~1636--53 and
SS~Cygni, as typical representatives of such NS and WD binaries, based on their
X-ray observations by RXTE, ASCA, Suzaku and BeppoSAX uising {\it
Comptonization} spectral model. As a result, we formulate a criterion that
makes it easy to distinguish NS from WD in such binaries: NS X-rays exhibits
clear quasi-stable behavior with the index and is characterized by
quasi periodic oscillations (QPOs) at ~Hz, although WD X-rays
is stable with and is accompanied by QPOs at
~Hz during source outbursts. In addition, we revealed that in
4U~1636--53 the mHz QPOs anti-correlate with the plasma temperature, of
Compton cloud (or the corona around a NS. This allowed us to associate mHz-QPOs
with the corona dynamics during outburst cycle. The above index effect, now
well established for 4U~1636--53 and SS~Cygni using extensive observations, has
previously been found in other low-mass X-ray NS and WD binaries and agrees
well with the criterion for distinguishing NSs and WDs presented here.Comment: 14 figures, 9 table
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