DW Ursae Majoris
Abstract
F. V. Hessman, Max-Planck-Institut fur Astronomie, Heidelberg, reports: "The eclipsing cataclysmic variable DW UMa (PG 1030+590) has entered a previously-unseen low state. Rough brightness estimates indicate B and R magnitudes of 17 and 18, roughly 2-3 mag lower than normal (Shafter, Hessman, and Zhang 1988, Ap.J. 327, 248). H-alpha is still singly peaked and has an equivalent width similar to that during the normal state but has become much narrower. He II 468.6 nm, previously as strong as H-beta, has disappeared altogether. High-resolution, time-resolved spectroscopy made with the Cassegrain Twin-Spectrograph on the Calar Alto 3.5-m reflector shows line profiles reminiscent of the low-state of TT Ari (Shafter et al. 1985, Ap.J. 290, 707). Crude relative photometry made with a slit star shows the system to be highly variable, enough to mask whatever eclipses are still present in the spectra. Very low photometric excursions and the faintness of the system in the near-infrared indicate that neither the white dwarf nor the secondary star contribute significantly to the optical spectrum. Unlike TT Ari, DW UMa normally has 20- min 1.5-mag eclipses, so high-speed photometry and polarimetry may be able to shed considerable light on the structure of the inner disk during a period of substantially smaller (though not negligible) accretion rates."
- Publication:
-
International Astronomical Union Circular
- Pub Date:
- February 1990
- Bibcode:
- 1990IAUC.4971....1H