29 research outputs found
Long-Term Optical Observations Of Two Lmxbs: Uw Crb (=Ms 1603+260) And V1408 Aql (=4U 1957+115)
We present new optical photometry of two low-mass X-ray binary stars, UW CrB (MS 1603+260) and V1408 Aql (4U 1957+115). UW CrB is an eclipsing binary and we refine its eclipse ephemeris and measure an upper limit to the rate of change of its orbital period, vertical bar P vertical bar < 4.2 x 10(-11) (unitless). The light curve of UW CrB shows optical counterparts of type I X-ray bursts. We tabulate the times, orbital phases, and fluences of 33 bursts and show that the optical flux in the bursts comes primarily from the accretion disk, not from the secondary star. The new observations are consistent with a model in which the accretion disk in UW CrB is asymmetric and precesses in the prograde direction with a period of similar to 5.5 days. The light curve of V1408 Aql has a low-amplitude modulation at its 9.33 hr orbital period. The modulation remained a nearly pure sine curve in the new data as it was in 1984 and 2008, but its mean amplitude was lower, 18% against 23% in the earlier data. A model in which the orbital modulation is caused by the varying aspect of the heated face of the secondary star continues to give an excellent fit to the light curve. We derive a much improved orbital ephemeris for the system.NSF 0958783Astronom
Bolometric and UV Light Curves of Core-Collapse Supernovae
The Swift UV-Optical Telescope (UVOT) has been observing Core-Collapse
Supernovae (CCSNe) of all subtypes in the UV and optical since 2005. We present
here 50 CCSNe observed with the Swift UVOT, analyzing their UV properties and
behavior. Where we have multiple UV detections in all three UV filters (\lambda
c = 1928 - 2600 \AA), we generate early time bolometric light curves, analyze
the properties of these light curves, the UV contribution to them, and derive
empirical corrections for the UV-flux contribution to optical-IR based
bolometric light curves
2MASS J05162881+2607387: A New Low-Mass Double-Lined Eclipsing Binary
We show that the star known as 2MASS J05162881+2607387 (hereafter J0516) is a
double-lined eclipsing binary with nearly identical low-mass components. The
spectroscopic elements derived from 18 spectra obtained with the High
Resolution Spectrograph on the Hobby-Eberly Telescope during the Fall of 2005
are K_1=88.45 +/- 0.48 km/s and K_2=90.43 +/- 0.60 km/s, resulting in a mass
ratio of$q=K_1/K_2 = 0.978 +/- 0.018 and minimum masses of M_1 sin^{3}i=0.775
+/- 0.016 solar masses and M_2 sin^{3}i=0.759 +/- 0.012 solar masses,
respectively. We have extensive differential photometry of J0516 obtained over
several nights between 2004 January-March (epoch 1) and 2004 October-2005
January plus 2006 January (epoch 2) using the 1m telescope at the Mount Laguna
Observatory. The source was roughly 0.1 mag brighter in all three bandpasses
during epoch 1 when compared to epoch 2. Also, phased light curves from epoch 1
show considerable out-of-eclipse variability, presumably due to bright spots on
one or both stars. In contrast, the phased light curves from epoch 2 show
little out-of-eclipse variability. The light curves from epoch 2 and the radial
velocity curves were analyzed using our ELC code with updated model atmospheres
for low-mass stars. We find the following: M_1=0.787 +/- 0.012 solar masses,
R_1=0.788 +/- 0.015 solar radii, M_2=0.770 +/- 0.009 solar masses, and
R_2=0.817 +/- 0.010 solar radii. The stars in J0516 have radii that are
significantly larger than model predictions for their masses, similar to what
is seen in a handful of other well-studied low-mass double-lined eclipsing
binaries. We compiled all recent mass and radius determinations from low-mass
binaries and determine an empirical mass-radius relation of the form R = 0.0324
+ 0.9343M + 0.0374M^2, where the quantities are in solar units.Comment: 16 pages, 10 figures (Figure 1 has degraded quality), to appear in
Ap
The Optical Orbital Light Curve of the Low-mass X-ray Binary V1408 Aquilae (= 4U 1957+115)
V1408 Aql (= 4U 1957+115) is a low-mass X-ray binary with an orbital period
near 9.3 hr, whose compact star is a black hole candidate. The system shows a
large-amplitude orbital photometric modulation at optical wavelengths. We have
obtained new optical photometry of V1408 Aql from which we derive the orbital
light curve and an improved orbital ephemeris. We show that the orbital light
curve can be reproduced by a model in which the accretion disk around the
compact star is thin, axisymmetric, and uneclipsed. The secondary star is
heated by X-rays from the compact star and the accretion disk. The orbital
modulation is produced entirely by the changing aspect of the irradiated
secondary star with orbital phase. Because the system does not eclipse, the
fits of the model light curves are insensitive to the orbital parameters,
allowing a wide range of orbital inclinations and mass ratios.Comment: 26 pages, 9 figures (3 in color), To appear as ApJ, 730, 43, 201
A Large Catalog of Homogeneous Ultra-Violet/Optical GRB Afterglows: Temporal and Spectral Evolution
We present the second Swift Ultra-Violet/Optical Telescope (UVOT) gamma-ray
burst (GRB) afterglow catalog, greatly expanding on the first Swift UVOT GRB
afterglow catalog. The second catalog is constructed from a database containing
over 120,000 independent UVOT observations of 538 GRBs first detected by Swift,
the High Energy Transient Explorer 2 (HETE2), the INTErnational Gamma-Ray
Astrophysics Laboratory (INTEGRAL), the Interplanetary Network (IPN), Fermi,
and Astro-rivelatore Gamma a Immagini Leggero (AGILE). The catalog covers GRBs
discovered from 2005 Jan 17 to 2010 Dec 25. Using photometric information in
three UV bands, three optical bands, and a `white' or open filter, the data are
optimally co-added to maximize the number of detections and normalized to one
band to provide a detailed light curve. The catalog provides positional,
temporal, and photometric information for each burst, as well as Swift Burst
Alert Telescope (BAT) and X-Ray Telescope (XRT) GRB parameters. Temporal slopes
are provided for each UVOT filter. The temporal slope per filter of almost half
the GRBs are fit with a single power-law, but one to three breaks are required
in the remaining bursts. Morphological comparisons with the X-ray reveal that
approximately 75% of the UVOT light curves are similar to one of the four
morphologies identified by Evans et al. (2009). The remaining approximately 25%
have a newly identified morphology. For many bursts, redshift and extinction
corrected UV/optical spectral slopes are also provided at 2000, 20,000, and
200,000 seconds.Comment: 44 pages, 14 figures, to be published in Astrophysical Journal
Supplementa
Supernovae Shock Breakout/Emergence Detection Predictions for a Wide-Field X-ray Survey
There are currently many large-field surveys operational and planned
including the powerful Vera C. Rubin Observatory Legacy Survey of Space and
Time. These surveys will increase the number and diversity of transients
dramatically. However, for some transients, like supernovae (SNe), we can gain
more understanding by directed observations (e.g. shock breakout, -ray
detections) than by simply increasing the sample size. For example, the initial
emission from these transients can be a powerful probe of these explosions.
Upcoming ground-based detectors are not ideally suited to observe the initial
emission (shock emergence) of these transients. These observations require a
large field-of-view X-ray mission with a UV follow up within the first hour of
shock breakout. The emission in the first one hour to even one day provides
strong constraints on the stellar radius and asymmetries in the outer layers of
stars, the properties of the circumstellar medium (e.g. inhomogeneities in the
wind for core-collapse SNe, accreting companion in thermonuclear SNe), and the
transition region between these two. This paper describes a simulation for the
number of SNe that could be seen by a large field of view lobster eye X-ray and
UV observatory.Comment: 13 pages, 7 figures, submitted to Ap
Optical and UV Light Curves of the Accretion Disk Corona Source 4U 1822-371
The eclipsing low-mass X-ray binary 4U is the prototypical accretion disk
corona (ADC) system. We have obtained new time-resolved UV spectrograms of 4U
with the Hubble Space Telescope and new V- and J-band light curves with the
1.3-m SMARTS telescope at CTIO. We present an updated ephemeris for the times
of the optical/UV eclipses. Model light curves do not give acceptable fits to
the UV eclipses unless the models include an optically-thick ADC.Comment: 3 pages, 2 figures, from A Population Explosion: The Nature and
Evolution of X-ray Binaries in Diverse Environment
The Structure of the Accretion Disk in the ADC X-Ray Binary 4U 1822-371 at Optical and Ultraviolet Wavelengths
The eclipsing low-mass X-ray binary 4U 1822-371 is the prototypical accretion
disk corona (ADC) system. We have obtained new time-resolved UV spectroscopy of
4U 1822-371 with the Advanced Camera for Surveys/Solar Blind Channel (ACS/SBC)
on the Hubble Space Telescope (HST) and new V- and J-band photometry with the
1.3-m SMARTS telescope at CTIO. We use the new data to construct its UV/optical
spectral energy distribution and its orbital light curve in the UV, V, and J
bands. We derive an improved ephemeris for the optical eclipses and confirm
that the orbital period is changing rapidly, indicating extremely high rates of
mass flow in the system; and we show that the accretion disk in the system has
a strong wind with projected velocities up to 4000 km/s.
We show that the disk has a vertically-extended, optically-thick component at
optical wavelengths.This component extends almost to the edge of the disk and
has a height equal to ~0.5 of the disk radius. As it has a low brightness
temperature, we identify it as the optically-thick base of a disk wind, not as
the optical counterpart of the ADC. Like previous models of 4U 1822-371, ours
needs a tall obscuring wall near the edge of the accretion disk, but we
interpret the wall as a layer of cooler material at the base of the disk wind,
not as a tall, luminous disk rim.Comment: 37 pages, 12 figures, submitted to Ap