Related papers: A New Dynamical Model for the Black Hole Binary LM…
NGC300 X-1 and IC10 X-1 are currently the only two robust extragalactic candidates for being Wolf-Rayet/black hole X-ray binaries, the Galactic analogue being Cyg X-3. These systems are believed to be a late product of high-mass X-ray…
Details of simultaneous photometric and spectroscopic observations of the optical counterpart of the `supersoft' X-ray source 1E 0035.4-7230 (SMC 13) are presented. Although the spectrum is dominated by emission lines of He II, the Balmer…
BG Gem is an eclipsing binary with a 91.6-day orbital period. The more massive primary component does not seem to show absorption lines in the spectrum, while the less massive secondary is thought to be a K-type star, possibly a supergiant.…
The formation of close massive black-hole binaries is a challenge for binary evolutionary models, especially the intriguing system M33 X-7 which harbours one of the most massive stellar-mass black holes (16 solar masses) orbiting a 70 solar…
We report the discovery of 1RXH J082623.6-505741, a 10.4 hr orbital period compact binary. Modeling extensive optical photometry and spectroscopy reveals a $\sim 0.4 M_{\odot}$ K-type secondary transferring mass through a low-state…
The optical light curves of quiescent black hole low-mass X-ray binaries often exhibit significant non-ellipsoidal variabilities, showing the photospheric radiation of the companion star is veiled by other source of optical emission.…
The binary parameters of the microquasar GRS 1915+105 have been determined by the detection of Doppler-shifted 12CO and 13CO lines in its K-band spectrum (Greiner et al., 2001, Nature, 414, 522). Here, we present further analysis of the…
We detected a possible quasi-periodic oscillation (QPO) of ~ 71 days in the 0.1 -- 300 GeV gamma-ray Fermi-LAT light curve of the high redshift flat spectrum radio quasar B2 1520+31. We identify and confirm that quasi-period by Lomb Scargle…
We present the results of timing and spectral analysis of X-ray high state observations of the high-mass X-ray pulsar SMC X-1 with Chandra, XMM-Newton, and ROSAT, taken between 1991 and 2001. The source has L_X ~ 3-5 x 10^38 ergs/s, and the…
We obtained 16 VLT/X-shooter observations of GX 339-4 in quiescence in the period May - September 2016 and detected absorption lines from the donor star in its NIR spectrum. This allows us to measure the radial velocity curve and projected…
We present the results of a 140 ks XMM-Newton observation of the B2 star $\rho$ Ophiuchi A. The star has exhibited strong X-ray variability: a cusp-shaped increase of rate, similar to that which we partially observed in 2013, and a bright…
We revisit various sets of published results from X-ray and optical studies of the Galactic black hole (BH) candidate MAXI J0637-430, which went into outburst in 2019. Combining the previously reported values of peak outburst luminosity,…
Soft X-ray Transients (SXTs) are binary systems that are believed to consist of a black hole and a normal late type dwarf star which fills its Roche Lobe. We have used GRIM II on the ARC 3.5 meter telescope at Apache Point Observatory to…
We offer a brief description of the bulk-motion Comptonization (BMC) model for accretion onto black holes, illustrated by its application to observational data for LMC X-1, and Nova Muscae 1991. We then extract some physical parameters of…
One of the plausible unification schemes in physics considers the observable universe to be a 4-dimensional surface (the "brane") embedded in a higher-dimensional curved spacetime (the "bulk"). In such braneworld gravity models with…
Context. Recent astrometric and spectroscopic surveys of OB stars have revealed a few stellar-mass black holes (BHs) with orbital periods as low as 10 days. No X-ray counterpart has been detected, due to the absence of a radiatively…
Her X-1 has been monitored nearly continuously in soft X-rays (2-12 keV) since February 1996 by the ASM on board RXTE. We present analysis of these observations which include 23 contiguous 35-day cycles. We present the best yet average…
We model the dynamical structure of M87 (NGC4486) using high spatial resolution long-slit observations of stellar light in the central regions, two-dimensional stellar light kinematics out to half of the effective radius, and globular…
The bright soft X-ray transient Nova Muscae 1991 was intensively observed during its entire 8-month outburst using the Large Area Counter (LAC) onboard the Ginga satellite. Recently, we obtained accurate estimates of the mass of the black…
A search for recoiling supermassive black hole candidates recently yielded the best candidate thus far, SDSS J092712.65+294344.0 reported by Komossa et al. Here we propose the alternative hypothesis that this object is a supermassive black…