185 research outputs found
Optical and X-ray Studies of Ten X-ray Selected Cataclysmic Binaries
We report on ground-based optical observations of ten cataclysmic binaries
that were discovered through their X-ray emission. Time-resolved radial
velocity spectroscopy yields unambiguous orbital periods for eight objects and
ambiguous results for the remaining two. The orbital periods range from 87 min
to 9.38 hr. We also obtained time-series optical photometry for six targets,
four of which have coherent pulsations. These periods are 1218 s for 1RXS
J045707.4+452751, 628 s for AX J1740.2-2903, 477 s for AX J1853.3-0128, and 935
s for IGR J19267+1325. A total of seven of the sources have coherent
oscillations in X-rays or optical, indicating that they are intermediate polars
(DQ Herculis stars). Time-resolved spectroscopy of one object, Swift
J2218.4+1925, shows that it is an AM Herculis star, or polar, and IGR
J19552+0044 may also be in that class. For another object, Swift J0476.2-1611,
we find an orbital period of 9.384 hr and detect the spectrum of the secondary
star. The secondary's spectral contribution implies a distance of 900 (+190,
-150) pc, where the error bars are estimated using a Monte Carlo technique to
account for correlated uncertainties.Comment: Accepted for publication in The Astronomical Journal. 38 pages, 16
figures Revised to include a correct finding chart for RX J0457+4
Spectroscopy and Photometry of Cataclysmic Variable Candidates from the Catalina Real Time Survey
The Catalina Real Time Survey (CRTS) has found over 500 cataclysmic variable
(CV) candidates, most of which were previously unknown. We report here on
followup spectroscopy of 36 of the brighter objects. Nearly all the spectra are
typical of CVs at minimum light. One object appears to be a flare star, while
another has a spectrum consistent with a CV but lies, intriguingly, at the
center of a small nebulosity. We measured orbital periods for eight of the CVs,
and estimated distances for two based on the spectra of their secondary stars.
In addition to the spectra, we obtained direct imaging for an overlapping
sample of 37 objects, for which we give magnitudes and colors. Most of our new
orbital periods are shortward of the so-called period gap from roughly 2 to 3
hours. By considering the cross-identifications between the Catalina objects
and other catalogs such as the Sloan Digital Sky Survey, we argue that a large
number of cataclysmic variables remain uncatalogued. By comparing the CRTS
sample to lists of previously-known CVs that CRTS does not recover, we find
that the CRTS is biased toward large outburst amplitudes (and hence shorter
orbital periods). We speculate that this is a consequence of the survey
cadence.Comment: Accepted for publication in The Astronomical Journal. 35 pages,
including 7 figure
Optical Counterparts of Two Fermi Millisecond Pulsars: PSR J1301+0833 and PSR J1628-3205
Using the 1.3m and 2.4m telescopes of the MDM Observatory, we identified the
close companions of two eclipsing millisecond radio pulsars discovered by the
Green Bank Telescope in searches of Fermi Gamma-ray Space Telescope sources,
and measured their light curves. PSR J1301+0833 is a black widow pulsar in a
6.5 hr orbit whose companion star is strongly heated on the side facing the
pulsar. It varies from R = 21.8 to R > 24 around the orbit. PSR J1628-3205 is a
"redback," a nearly Roche-lobe filling system in a 5.0 hr orbit whose optical
modulation in the range 19.0 < R < 19.4 is dominated by strong ellipsoidal
variations, indicating a large orbital inclination angle. PSR J1628-3205 also
shows evidence for a long-term variation of about 0.2 mag, and an asymmetric
temperature distribution possibly due to either off-center heating by the
pulsar wind, or large starspots. Modelling of its light curve restricts the
inclination angle to i > 55 degrees, the mass of the companion to 0.16 < M_c <
0.30 M_sun, and the effective temperature to 3560 < T_eff < 4670 K. As is the
case for several redbacks, the companion of PSR J1628-3205 is less dense and
hotter than a main-sequence star of the same mass.Comment: 9 pages, 5 figures, accepted for publication in Ap
Cataclysmic Variables in the SUPERBLINK Proper Motion Survey
We have discovered a new high proper motion cataclysmic variable (CV) in the
SUPERBLINK proper motion survey, which is sensitive to stars with proper
motions greater than 40 mas/yr. This CV was selected for follow-up observations
as part of a larger search for CVs selected based on proper motions and their
NUV-V and V-K colors. We present spectroscopic observations from the 2.4m
Hiltner Telescope at MDM Observatory. The new CV's orbital period is near 96
minutes, its spectrum shows the double-peaked Balmer emission lines
characteristic of quiescent dwarf novae, and its V magnitude is near 18.2.
Additionally, we present a full list of known CVs in the SUPERBLINK catalog.Comment: Accepted for publication in The Astronomical Journal, 22 pages, 6
figure
Spectroscopy of Four Cataclysmic Variables with Periods above 7 Hours
We present spectroscopy of four cataclysmic variables. Using radial velocity
measurements, we find orbital periods for the first time. The stars and their
periods are GY Hya, 0.347230(9) d; SDSS J204448-045929, 1.68(1) d; V392 Hya,
0.324952(5) d; and RX J1951.7+3716, 0.492(1) d. We also detect the spectra of
the secondary stars, estimate their spectral types, and derive distances based
on surface brightness and Roche lobe constraints.Comment: 22 pages, 3 figures, 5 tables, to be published in December 2006 PAS
An Optical Study of Two VY Sculptoris-Type Cataclysmic Binary Stars: V704 And and RX J2338+431
We report observations of the known cataclysmic variable star (CV) V704 And,
and also confirm that the optical counterpart of the ROSAT Galactic Plane
Survey source RX J2338+431 is a heretofore-neglected CV. Photometric and
spectroscopic observations from MDM Observatory show both systems to be
novalike variables that exhibit dips of 4-5 magnitudes from their mean
brightnesses, establishing them as members of the VY~Scl subclass. From
high-state emission-line radial velocities, we determine orbital periods of
0.151424(3) d (3.63 hr) for V704 And and 0.130400(1) d (3.13 hr) for RX
J2338+431. In V704 And, we find that the H-alpha emission-line measures cluster
into distinct regions on a plot of equivalent width versus full width at
half-maximum, which evidently correspond to high, intermediate, and low
photometric states. This allows us to assign spectra to photometric states when
contemporaneous photometry is not available, an apparently novel method that
may be useful in studies of other novalikes. Our low-state spectra of RX
J2338+431 show features of an M-type secondary star, from which we estimate a
distance of 890 +- 200 pc, in good agreement with the Gaia DR2 parallax.Comment: Accepted for Astronomical Journa
- …