1,720 research outputs found
The syntax of slavic predicate case
In this article I provide a syntactic framework for case patterns found in Slavic secondary predicates
Possible Optical/Infrared Jet Emission in 4U 1543-47
We have taken optical and infrared observations during the 2002 outburst of
the soft X-ray transient, 4U 1543-47. A secondary maximum occurs in the
lightcurves during the outburst decline. This feature is much stronger at
infrared wavelengths than optical. We have applied single blackbody, multicolor
blackbody and broken-power law models to the optical/infrared spectral energy
distribution of the secondary maximum and find that the broken power-law
provides the best fit. We therefore conclude that the secondary maximum
emission originates from a jet. We also show the most recent lightcurves of the
2002/2003 outburst of GX 339-4 in which a secondary maximum appears. This leads
us to the conclusion that secondary maxima may be a common occurrence in soft
X-ray transients during outburst decline which appear after the object
transitions into the low-hard state. Infrared observations of such phenomena
will give reliable triggers for multiwavelength observations, allowing us to
greatly improve our knowledge of jet formation and behavior, and how this
relates to the accretion geometry.Comment: 4 pages, to appear in ``X-Ray Timing 2003: Rossi and Beyond''
conference proceedings, references now visibl
Outburst Morphology in the Soft X-ray Transient Aquila X-1
We present optical and near-IR (OIR) observations of the major outbursts of
the neutron star soft X-ray transient binary system Aquila X-1, from summer
1998 -- fall 2007. The major outbursts of the source over the observed timespan
seem to exhibit two main types of light curve morphologies, (a) the classical
Fast-Rise and Exponential-Decay (FRED) type outburst seen in many soft X-ray
transients and (b) the Low-Intensity State (LIS) where the
optical-to-soft-X-ray flux ratio is much higher than that seen during a FRED.
Thus there is no single correlation between the optical (R-band) and soft X-ray
(1.5-12 keV, as seen by the ASM onboard RXTE) fluxes even within the hard state
for Aquila X-1, suggesting that LISs and FREDs have fundamentally different
accretion flow properties. Time evolution of the OIR fluxes during the major
LIS and FRED outbursts is compatible with thermal heating of the irradiated
outer accretion disk. No signature of X-ray spectral state changes or any
compact jet are seen in the OIR, showing that the OIR color-magnitude diagram
(CMD) can be used as a diagnostic tool to separate thermal and non-thermal
radiation from X-ray binaries where orbital and physical parameters of the
system are reasonably well known. We suggest that the LIS may be caused by
truncation of the inner disk in a relatively high mass accretion state,
possibly due to matter being diverted into a weak outflow.Comment: Accepted for publication in ApJ. Uses aastex. 27 pages and 10 figure
Connecting GRBs and galaxies: the probability of chance coincidence
Studies of GRB host galaxies are crucial to understanding GRBs. However,
since they are identified by the superposition in the plane of the sky of a GRB
afterglow and a galaxy there is always a possibility that an association
represents a chance alignment, rather than a physical connection. We examine a
uniform sample of 72 GRB fields to explore the probability of chance
superpositions. There is typically a ~1% chance that an optical afterglow will
coincide with a galaxy by chance. While spurious host galaxy detections will,
therefore, be rare, the possibility must be considered when examining
individual GRB/host galaxy examples. It is also tempting to use the large and
uniform collection of X-ray afterglow positions to search for GRB-associated
galaxies. However, we find that approximately half of the 14 superpositions in
our sample are likely to occur by chance, so in the case of GRBs localized only
by an X-ray afterglow, even statistical studies are suspect.Comment: edited, accepted by Ap
IR Monitoring of the Microquasar GRS 1915+105: Detection of Orbital and Superhump Signatures
We present the results of seven years of K-band monitoring of the low-mass
X-ray binary GRS 1915+105. Positive correlations between the infrared flux and
the X-ray flux and X-ray hardness are demonstrated. Analysis of the frequency
spectrum shows that the orbital period of the system is
days. The phase and amplitude of the orbital modulation suggests that the
modulation is due to the heating of the face of the secondary star. We also
report another periodic signature between 31.2 and 31.6 days, most likely due
to a superhump resonance. From the superhump period we then obtain a range on
the mass ratio of the system, .Comment: 16 pages, 6 figures; v2: minor change
M51 ULX-7: superorbital periodicity and constraints on the neutron star magnetic field
In this work, we explore the applicability of standard theoretical models of accretion to the observed properties of M51 ULX-7. The spin-up rate and observed X-ray luminosity are evidence of a neutron star with a surface magnetic field of 2-7 x 10(13) G, rotating near equilibrium. Analysis of the X-ray light curve of the system (Swift/XRT data) reveals the presence of a similar to 39 d superorbital period. We argue that the superorbital periodicity is due to disc precession, and that material is accreted on to the neutron star at a constant rate throughout it. Moreover, by attributing this modulation to the free precession of the neutron star we estimate a surface magnetic field strength of 3-4 x 10(13) G. The agreement of these two independent estimates provide strong constraints on the surface polar magnetic field strength of the NS
Period derivative of the M15 X-ray Binary AC211/X2127+119
We have combined Rossi X-ray Timing Explorer observations of X2127+119, the
low-mass X-ray binary in the globular cluster M15, with archival X-ray
lightcurves to study the stability of the 17.1 hr orbital period. We find that
the data cannot be fit by the Ilovaisky (1993) ephemeris, and requires either a
7sigma change to the period or a period derivative Pdot/P~9x10e-7 per year.
Given its remarkably low L_X/L_opt such a Pdot lends support to models that
require super-Eddington mass transfer in a q~1 binary.Comment: 11 pages, 3 figures, to be published in New Astronom
- …