V728 Herculis: an Active W Ursae Majoris System of F Spectral Type
Abstract
Observations made of the short-period eclipsing binary system V728 Her using a photoelectric telescope on four nights in June 1988 at Lowell Observatory are presented. Three times of minimum light were revealed by observations covering the eclipse portions of the light curves. A period study covering 80 years of observations indicates that a drastic period increase may have recently occurred, while indications such as a possible reversal of eclipse depths may suggest that V728 Her is magnetically active. Standard magnitudes derived for V728 Her and for comparison and check stars indicate that V728 Her is approximately of spectral type F3 while the comparison and check stars are K type. A preliminary light-curve solution indicates that the system consists of two nearly equal temperature components in the spectral class F3 to F4 in contact with a substantial fillout of near 20 percent and a mass ratio of about 0.4. This degree of contact is supported by the position of V728 Her on the period, color plane of Eggen. The period increase may indicate a mass exchange from the secondary to the primary component or a catastrophic angular-momentum loss due to an episode of massive stellar wind expulsion along lines of a corotating magnetic field.
- Publication:
-
Publications of the Astronomical Society of the Pacific
- Pub Date:
- September 1990
- DOI:
- 10.1086/132729
- Bibcode:
- 1990PASP..102..994S
- Keywords:
-
- Eclipsing Binary Stars;
- F Stars;
- Variable Stars;
- Light Curve;
- Magnetic Stars;
- Stellar Magnetic Fields;
- Stellar Magnitude;
- Astrophysics;
- STARS: W URSAE MAJORIS;
- STARS: INDIVIDUAL