VY Scl Research Articles

Feedback Mass Transfer in Cataclysmic Variables: An Explanation of the Behaviour of VY Scl Stars

Abstract We investigate irradiation-driven mass transfer in cataclysmic variables in the presence of shielding of the radiation by an accretion disk. We have shown that the shielding can cause a temporal drop of 3–5 magnitudes in the brightness of systems with orbital periods shorter than about 4 hr. This provides a possible explanation for the brightness variations in the VY Scl stars.

Star spots and the period gap in cataclysmic variables

view Abstract Citations (164) References (40) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Star Spots and the Period Gap in Cataclysmic Variables Livio, M. ; Pringle, J. E. Abstract We propose a model for the occasional drops in brightness in the VY Scl stars, and we show that the apparent absence of dwarf novae in the 3-4 hr period range is a plausible consequence of the proposed model. We also propose a new model for the formation of the period gap in the distribution of cataclysmic variables, in the context of which, the period gap and the behavior of dwarf novae, nova-like variables, VY Scl stars, and AM Her systems are all self-consistent. Publication: The Astrophysical Journal Pub Date: June 1994 DOI: 10.1086/174202 Bibcode: 1994ApJ...427..956L Keywords: Brightness; Cataclysmic Variables; Dwarf Novae; Periodic Variations; Starspots; Stellar Models; Stellar Oscillations; Accretion Disks; Mass Transfer; Stellar Luminosity; Stellar Mass Accretion; Stellar Mass Ejection; Astrophysics; STARS: BINARIES: CLOSE; STARS: NOVAE; CATACLYSMIC VARIABLES; STARS: OSCILLATIONS full text sources ADS | data products SIMBAD (1)

OBSERVED LOW STATES IN DQ HERCULIS SYSTEMS

ABSTRACT The Harvard Plate Collection was used to search for the existence of low accretion rate states in three DQ Her-type cataclysmic variables. The search shows that DQ Her systems may show the typical low-state behavior of AM Her or VY Scl systems. However, there are also DQ Her systems which show little or no reduction in accretion rate over long periods of time. In plotting the amplitude range of the low- to high-state behavior as a function of the orbital period, it is apparent that the AM Her systems below the period gap follow a decreasing trend of activity as the period gap is approached. If this behavior is interpreted as a measure of the accretion rate, this trend is opposite to the relationships calculated for gravitational radiation and magnetic braking below the gap by Hameury et al. (1988). Above the gap the amplitude generally increases with orbital period of VY Scl systems, with a steeper relationship than for magnetic braking.

Photometry and spectroscopy of short-period cataclysmic variables

Broad-band UBVJHK photometric measurements on 20 dwarf novae and nine nova-like systems and 10 A resolution spectrophotometry from 3500 to 5400 A of 15 cataclysmic variables are presented, with emphasis on the quiescent values of the dwarf novae and on the normal states of the nova-like systems. These data are used together with values from the literature to make a comparison of the colors and line strengths of the systems with orbital periods below the 2-3 hr period gap (mostly SU UMa stars) with those systems in the 3-4 hr period group (including VY Scl stars, dwarf novae, and nova-like systems). The results show the largest difference in the mean and spread of equivalent width between the two sides of the period gap, and linear trends are apparent in bluer V J and U - B colors and increasing strength of He II lambda 4686 as the period gap is approached from the ultrashort-period end.

TT ARIETIS - The low state

A comprehensive photometric and spectroscopic study of the low state of the novalike variable TT Ari has been made with observations spanning the UV to IR spectral regions. The roughly 5 mag drop in the system's luminosity from the high state indicates that the mass-transfer rate decreased by more than two orders of magnitude. The drastic reduction in the luminosity of the accretion disk between the high and low states enabled the white dwarf component to be directly observed for the first time. The broad absorption profiles at various lines and the UV energy distribution are best fitted by a hot white dwarf. A lower limit of 200 pc for the distance to TT Ari is derived, and the behavior of TT Ari is compared to that of another novalike variable, MV Lyr. The long-term photometric behavior of TT Ari makes it a typical member of the VY Scl subclass of novalike variables.

THE ORBIT OF VY SCULPTORIS DETERMINED NEAR MINIMUM LIGHT.

ABSTRACT Spectroscopic data are presented for the cataclysmic variable VY Scl taken during the rise from the low state of 1983 when the spectrum still showed strong emission lines. The period is not definitely established but is probably 0.1662 days. No strong phase-related spectral changes are seen, but there are night-to-night changes in the line intensities. The system appears to be viewed at a low inclination, with a white dwarf mass of 0.8 solar mass or more. The emission-line profiles have a narrow peak whose velocity variation is small but in phase with the broad-line base.

Lanning 10 and 33 - The X-ray, UV, and optical fluxes

UV spectra from IUE, optical spectroscopy, broad band photometry, and upper limits on the X-ray flux from Einstein are used to specify the characteristics of Lanning 10 and 33. Data on Lanning 33 are consistent with a 22,000 K Be star at a distance of 5 to 7 kpc, and Lanning 10 appears to include a F5-G0 star plus a hot component greater than 35,000 K at a distance of 0.9 to 1.3 kpc. The optical eclipsed fluxes are subtracted from the uneclipsed, and the observed fluxed distribution of the eclipsed light does not follow a simple power law, but is closer to a 12,000 K + or - 1000 K blackbody. Lanning 10 is placed in the category of VY Scl variables.

THE NATURE OF V751 CYGNI

ABSTRACT High-speed photometry of the peculiar variable V751 Cyg shows it to display rapid variations, or flickering, similar to that of the cataclysmic variables. V751 Cyg is similar in every respect to vY Scl, and belongs to a very small group of cataclysmic variables which now includes VY Scl, UX UMa, and CO -42 14462. These stars appear to be dwarf novae which are continuously or nearly continuously erupting. Key words: variable star - dwarf nova

VY SCL, A NEW RAPID BLUE VARIABLE.

ABSTRACT Rapid variations with an underlying 500-second periodicity are reported for VY Scl, a blue star at the south galactic pole. Broad absorption lines are visible beneath the bright line spectrum. It is suggested that the star is a dwarf nova, not the R CrB-type star previously proposed. Key words: variable star - photometry - spectrum