312 research outputs found
IUE observations of cataclysmic variable
Twenty two approved International Ultraviolet Explorer (IUE) programs were studied over a 14 year period. These programs are listed. The observations and subsequent analysis centered on cataclysmic variables (close binaries with a late main sequence star transferring material to a primary white dwarf via an accretion disk). The early studies highlighted the flux distribution of the accretion disk at outburst and quiescence, while later studies accomplished time-resolved observations throughout the orbital cycles, the study of the outflowing winds present at outburst, the study of the white dwarf in those systems with low accretion rate. There are 39 publications resulting from this work which are listed. These results include those for individual systems (Stepanian's star, Lanning 10, AM Her, MV Lyr, TV Col, VW Hyi, T Leo, IR Gem, TT Ari, Z Cam, BV Pup, IP Peg, PG1030+590, V1315 Aql, SW UMa, V426 Oph, WZ Sge, BY Cam, and U Gem) as well as review articles in journals and publications from reviews at meetings that summarize the impact of IUE on the study of accretion disks, white dwarfs, and hot spots resulting from stream impact as well as magnetic accretion columns
XMM-Newton and Optical Observations of Cataclysmic Variables from SDSS
We report on XMM-Newton and optical results for 6 cataclysmic variables that
were selected from Sloan Digital Sky Survey spectra because they showed strong
HeII emission lines, indicative of being candidates for containing white dwarfs
with strong magnetic fields. While high X-ray background rates prevented
optimum results, we are able to confirm SDSSJ233325.92+152222.1 as an
intermediate polar from its strong pulse signature at 21 min and its obscured
hard X-ray spectrum. Ground-based circular polarization and photometric
observations were also able to confirm SDSSJ142256.31-022108.1 as a polar with
a period near 4 hr. Photometry of SDSSJ083751.00+383012.5 and
SDSSJ093214.82+495054.7 solidifies the orbital period of the former as 3.18 hrs
and confirms the latter as a high inclination system with deep eclipses.Comment: 31 pages, 14 figures. Accepted for publication in the Astronomical
Journa
The Recognition of Unusual Objects in the Sloan Digital Sky Survey Color System
We present 5 filter photometry of 21 carbon stars, 15 asteroids, 15
cataclysmic variables, 6 metal-poor stars, 5 Cepheids, 1775 field stars, blue
horizontal branch (BHB) stars and RR Lyrae stars in the globular clusters M 15
and M 2, two primary standards, and 19 secondary standards. The photometry was
carried out using a filter set identical to that which will be used for the
Sloan Digital Sky Survey. We find that carbon stars, CVs, R-type, J-type, and
V-type asteroids, BHB stars, and RR Lyr stars should be identifiable on the
basis of SDSS photometry alone, while Cepheids, metal-poor stars, and many
types of asteroids are indistinguishable from the stellar locus of field stars.Comment: 44 pages, 13 postscript figures. Accepted for publication in
Publications of the Astronomical Society of the Pacific, vol. 110, November
1998. Uses AAS Latex style file, version 4.
Quiescent photometric modulations of two low-inclination cataclysmic variables KZGem and TWVir
The quiescent periodic photometric modulations of two low-inclination
cataclysmic variables observed in Kepler K2 Campaigns 0 and 1, KZ Gem and TW
Vir, are investigated. A phase-correcting method was successfully used to
detect the orbital modulations of KZ Gem and TW Vir and improve their orbital
periods. The light curve morphologies of both CVs were further analyzed by
defining flux ratios and creating colormaps. KZ Gem shows ellipsoidal
modulations with an orbital period of 0.22242(1) day, twice the period listed
in the updated RK catalogue (Edition 7.24). With this newly determined period,
KZ Gem is no longer a CV in the period gap, but a long-period CV. A part of the
quiescent light curve of TW Vir that had the highest stability was used to
deduce its improved orbital period of 0.182682(3) day. The flat patterns shown
in the colormaps of the flux ratios for KZ Gem demonstrate the stability of
their orbital modulations, while TW Vir show variable orbital modulations
during the K2 datasets. In TW Vir, the single versus double-peaked nature of
the quiescent orbital variations before and after superoutburst may be related
to the effect of the superoutburst on the accretion disk.Comment: 10 pages, 12 figures, accepted by A&
A New Narrow-Line Seyfert 1 galaxy : RXJ1236.9+2656
We report identification of a narrow-line Seyfert 1 galaxy RXJ1236.9+2656.
X-ray emission from the NLS1 galaxy undergoes long-term variability with
0.1--2.0 keV flux changing by a factor of 2 within about 3 yr. The ROSAT PSPC
spectrum of RXJ1236.9+2656 is well represented by a power-law of Gamma = 3.7
absorbed by matter in our own Galaxy (N_H = 1.33X10^20 cm**-2). Intrinsic soft
X-ray luminosity of the NLS1 galaxy is estimated to be 1.5X10^43 erg/s in the
energy band of 0.1-2.0 keV. The optical spectrum of RXJ1236.9+2656 is typical
of NLS1 galaxies and shows narrow Balmer emission lines (1100 km/s < FWHM <
1700 km/s) of Hbeta, Halpha, and forbidden lines of [O III] and [N II]. Fe II
multiplets, usually present in optical spectra of NLS1 galaxies, are also
detected in RXJ1236.9+2656.Comment: 4 pages, A&A style Latex, To apear in A&A as a research not
The inter-outburst behavior of cataclysmic variables
Existing International Ultraviolet Explorer (IUE) and American Association of Variable Star Observers (AAVSO) archive data was used to accomplish a large scale study of what happens to the ultraviolet flux of accretion disk systems during the quiescent intervals between outbursts and how it relates to the preceding outburst characteristics of amplitude and width. The data sample involved multiple IUE observations for 16 dwarf novae and 8 novae along with existing optical coverage. Results indicate that most systems show correlated ultraviolet (UV) flux behavior with interoutburst phase, with 60 percent of the dwarf novae and 50 percent of the novae having decreasing flux trends while 33 percent of the dwarf novae and 38 percent of the novae show rising UV flux during the quiescent interval. All of the dwarf novae with decreasing UV fluxes at 1475A have orbital periods longer than 4.4 hours, while all (except BV Cen) with flat or rising fluxes at 1475A have orbital periods less than two hours. There are not widespread correlations of the UV fluxes with the amplitude of the preceding outburst and no correlations with the width of the outburst. From a small sample (7) that have relatively large quiescent V magnitude changes between the IUE observations, most show a strong correlation between the UV and optical continuum. Interpretation of the results is complicated by not being able to determine how much the white dwarf contributes to the ultraviolet flux. However, it is now evident that noticeable changes are occurring in the hot zones in accreting systems long after the outburst, and not only for systems that are dominated by the white dwarf. Whether these differences are due to different outburst mechanisms or to changes on white dwarfs which provide varying contributions to the UV flux remains to be determined
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