272 research outputs found
Optical Spectroscopy of GX 339-4 - Paper I: Orbital Modulation
Optical spectroscopic observations of GX 339-4 were carried out between 1998
May (X-ray high state) and 1999 May (X-ray low state) over 7 epochs. The
equivalent width of Halpha increased during the high state then decreased
during the low state. The equivalent width of HeII 4686 decreased over both
states. The full-width half-maximum of Halpha, Hbeta, HeII 4686 and the Bowen
Blend increased from 1998 to 1999 indicating that the emission line regions
moved closer to the compact object. Hbeta shows a redshifted absorption feature
at 4880 angstroms at all epochs. This line remains unidentified. Analysis of
individual spectra from 1998 May 28-31 show modulation of the radial
velocities, equivalent width and V/R ratios of Halpha on the 14.86 hour orbital
period. The equivalent width of HeII 4686 also varies on the orbital period.
This is the first time since the study of Calanan et al. (1992) that
spectroscopic data has confirmed the orbital period. The semi-amplitude of the
Halpha radial velocities is K_1 = 14 km/s. Hence the mass function = 2 x
10^(-4) Msun.Comment: 15 pages, 17 figures, accepted by MNRA
Low/hard state of microquasars at low luminosities
Galactic black hole transients (GBHTs) spend most of their time in the low/hard spectral state during the outburst decay. This state exhibits a hard X-ray spectrum with X-ray flux correlating with both the radio and the infrared flux. As the luminosity declines, the spectra of the GBHTs got harder. However, for a few sources at very low luminosity levels a softening of the spectrum has been observed. In this work we discuss the evolution of GBHTs at the very lowest luminosity levels using RXTE data and discuss the behavior of the X-ray spectrum, as well as the reported correlations
Complete Multiwavelength Evolution of Galactic Black Hole Transients During Outburst Decay II: Compact Jets and X-ray Variability Properties
We investigated the relation between compact jet emission and X-ray
variability properties of all black hole transients with multiwavelength
coverage during their outburst decays. We studied the evolution of all power
spectral components (including low frequency quasi-periodic oscillations), and
related this evolution to changes in jet properties tracked by radio and
infrared observations. We grouped sources according to their tracks in
radio/X-ray luminosity relation, and show that the standards show stronger
broadband X-ray variability than outliers at a given X-ray luminosity when the
compact jet turned on. This trend is consistent with the internal shock model
and can be important for the understanding of the presence of tracks in the
radio/X-ray luminosity relation. We also observed that the total and the QPO
rms amplitudes increase together during the earlier part of the outburst decay,
but after the compact jet turns either the QPO disappears or its rms amplitude
decreases significantly while the total rms amplitudes remain high. We discuss
these results with a scenario including a variable corona and a non-variable
disk with a mechanism for the QPO separate from the mechanism that create broad
components. Finally, we evaluated the timing predictions of the magnetically
dominated accretion flow model which can explain the presence of tracks in the
radio/X-ray luminosity relation.Comment: Accepted for publication by Ap
Connections between jet formation and multiwavelength spectral evolution in black hole transients
Multiwavelength observations are the key to understand conditions of jet formation in Galactic black hole transient (GBHT) systems. By studying radio and optical-infrared evolution of such systems during outburst decays, the compact jet formation can be traced. Comparing this with X-ray spectral and timing evolution we can obtain physical and geometrical conditions for jet formation, and study the contribution of jets to X-ray emission. In this work, first X-ray evolution - jet relation for XTE J1752-223 will be discussed. This source had very good coverage in X-rays, optical, infrared and radio. A long exposure with INTEGRAL also allowed us to study gamma-ray behavior after the jet turns on. We will also show results from the analysis of data from GX 339-4 in the hard state with SUZAKU at low flux levels. The fits to iron line fluorescence emission show that the inner disk radius increases by a factor of >27 with respect to radii in bright states. This result, along with other disk radius measurements in the hard state will be discussed within the context of conditions for launching and sustaining jets
Modeling the Optical-X-ray Accretion Lag in LMC X-3: Insights Into Black-Hole Accretion Physics
The X-ray persistence and characteristically soft spectrum of the black hole
X-ray binary LMC X-3 make this source a touchstone for penetrating studies of
accretion physics. We analyze a rich, 10-year collection of optical/infrared
(OIR) time-series data in conjunction with all available contemporaneous X-ray
data collected by the ASM and PCA detectors aboard the Rossi X-ray Timing
Explorer. A cross-correlation analysis reveals an X-ray lag of ~2 weeks.
Motivated by this result, we develop a model that reproduces the complex OIR
light curves of LMC X-3. The model is comprised of three components of
emission: stellar light; accretion luminosity from the outer disk inferred from
the time-lagged X-ray emission; and light from the X-ray-heated star and outer
disk. Using the model, we filter a strong noise component out of the
ellipsoidal light curves and derive an improved orbital period for the system.
Concerning accretion physics, we find that the local viscous timescale in the
disk increases with the local mass accretion rate; this in turn implies that
the viscosity parameter alpha decreases with increasing luminosity. Finally, we
find that X-ray heating is a strong function of X-ray luminosity below ~50% of
the Eddington limit, while above this limit X-ray heating is heavily
suppressed. We ascribe this behavior to the strong dependence of the flaring in
the disk upon X-ray luminosity, concluding that for luminosities above ~50% of
Eddington, the star lies fully in the shadow of the disk.Comment: Accepted in ApJ (12 pages long in emulateapj format
The Mass of the Black Hole in LMC X-3
We analyze a large set of new and archival photometric and spectroscopic
observations of LMC X-3 to arrive at a self-consistent dynamical model for the
system. Using echelle spectra obtained with the MIKE instrument on the 6.5m
Magellan Clay telescope and the UVES instrument on the second 8.2m Very Large
Telescope we find a velocity semiamplitude for the secondary star of
km s, where the uncertainty includes an estimate of
the systematic error caused by X-ray heating. Using the spectra, we also find a
projected rotational velocity of km s.
From an analysis of archival and light curves as well as new and
light curves from the SMARTS 1.3m telescope, we find an inclination of
for models that do not include X-ray heating and an
inclination of for models that incorporate X-ray
heating. Adopting the latter inclination measurement, we find masses of
and for the companion star
and the black hole, respectively. We briefly compare our results with earlier
work and discuss some of their implications.Comment: 31 pages, 15 figures, substantial revisions, ApJ, accepte
PROPERTIES OF THE 24 DAY MODULATION IN GX 13+1 FROM NEAR-INFRARED AND X-RAY OBSERVATIONS
A 24 day period for the low-mass X-ray binary (LMXB) GX 13+1 was previously proposed on the basis of seven years of RXTE All-Sky Monitor (ASM) observations and it was suggested that this was the orbital period of the system. This would make it one of the longest known orbital periods for a Galactic LMXB powered by Roche lobe overflow. We present here the results of (1) K-band photometry obtained with the SMARTS Consortium CTIO 1.3 m telescope on 68 nights over a 10 month interval; (2) continued monitoring with the RXTE ASM, analyzed using a semi-weighted power spectrum instead of the data filtering technique previously used; and (3) Swift Burst Alert Telescope (BAT) hard X-ray observations. Modulation near 24 days is seen in both the K band and additional statistically independent ASM X-ray observations. However, the modulation in the ASM is not strictly periodic. The periodicity is also not detected in the Swift BAT observations, but modulation at the same relative level as seen with the ASM cannot be ruled out. If the 24 day period is the orbital period of system, this implies that the X-ray modulation is caused by structure that is not fixed in location. A possible mechanism for the X-ray modulation is the dipping behavior recently reported from XMM-Newton observations
Multiwavelength observations of the black hole transient XTE J1752-223 during its 2010 outburst decay
Galactic black hole transients show many interesting phenomena during outburst decays. We present simultaneous X-ray (RXTE, Swift, and INTEGRAL), and optical/near-infrared (O/NIR) observations (SMARTS), of the X-ray transient, XTE J1752-223 during its outburst decay in 2010. The multi- wavelength observations of 150 days in 2010 cover the transition from soft to hard spectral state. The evolution of ATCA/VLBI radio observations are shown to confirm the compact jet appearance. The source shows flares in O/NIR during changes in X-ray and radio properties. One of those flares is bright and long, and starts about 20 days after the transition in timing. Other, smaller flares occur along with the transition in timing and increase in power-law flux, and also right after the detection of the core with VLBI. Furthermore, using the simultaneous broadband X-ray spectra including IN- TEGRAL, we found that a high energy cut-off is necessary with a folding energy at around 250 keV around the time that the compact jet is forming. The broad band spectrum can also be fitted equally well with a Comptonization model. In addition, using photoelectric absorption edges in the XMM– Newton RGS X-ray spectra and the extinction of red clump giants in the direction of the source, we found a lower limit on the distance of > 5 kpc
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