Uu-Cancri and Vz-Piscium Contact Systems Before the Common Envelope Phase
Abstract
We have analyzed the existing photoelectric light curves of twoK-type binary systems: UU Cnc, with a period of about 100 days, and VZ Psc, with a period of about 6 hours. Both show a large overcontact (38% for UU Cnc, 56% for VZ Psc) and a large temperature difference between components (ΔT≈1500 K and 1100 K, respectively). In the case of VZ Psc, the variability is due only to the non-spherical shape, i.e., no eclipse occurs, but the determination of the photometric solution is made possible by the existence of a spectroscopic mass ratio. We find that UU Cnc is now probably undergoing Case C mass transfer in a dynamical time-scale, with the mass ratio reversal having already occurred; the system is in contact, and is likely to evolve to a 100% filling factor, that is the so-called pre-common envelope phase, a unique case never observed before. The situation for VZ Psc is more uncertain, but a similar, although not identical, possibility exists.
- Publication:
-
Astrophysics and Space Science
- Pub Date:
- September 1989
- DOI:
- 10.1007/BF00640488
- Bibcode:
- 1989Ap&SS.159...67B
- Keywords:
-
- Binary Stars;
- Light Curve;
- Mass Transfer;
- Stellar Envelopes;
- Algorithms;
- Astronomical Photometry;
- Photoelectricity;
- Stellar Temperature;
- Temperature Distribution;
- Astrophysics