Direct-Impact Algol Binaries in Kepler Fields: Light Curves
Abstract
We propose FUV and NUV GALEX observations of two Algol-type interacting binaries (UZ Lyr and BR Cyg) located in the field of view of the Kepler spacecraft in order to obtain their UV light curves for a study of the physics of mass transfer in the systems. Both binaries are direct-impact systems where the gas stream from the mass loser impacts the photosphere of the mass gainer at a steep angle. Based upon FUSE spectroscopy of a similar system U Cep, we expect to find evidence for an accretion hot spot centered on the impact site. Since the temperature in the hot spot is 2-3 times that of the late B-type mass gainer's photosphere, its presence is seen more prominently in the FUV. The proposed GALEX observations will be taken with a cadence of 300 s during the target's visibility and cover one orbital period (1.89 d and 1.33 d). The GALEX photometry will be combined with ground-based and Kepler photometry to determine the temperature and azimuthal location of the hot spot and the systemic parameters for the binaries. We will look for evidence of flaring activity at the impact site that would show more prominently in the UV. The GALEX observations will support Kepler observations of these systems that will be carried through by D. Gies (co-I on this proposal). Since the GALEX field-of-view is 1.2 degrees, as a bonus we will also obtain information on short-term and flare activity on many other stars in the Kepler field that might lead to a targeted Kepler proposal in future GO cycles.
- Publication:
-
GALEX Proposal
- Pub Date:
- 2009
- Bibcode:
- 2009galx.prop...79P