A metallicity lower limit in the be URSAE majoris sdO/DAO atmosphere from EUVE observations.
Abstract
Observations of the post-common envelope binary system BE UMa are presented and analyzed. Neutral hydrogen absorption precluded any chance of detection except over the wavelength range δδ 80-120. We observed BE Ursae Majoris for 55 875 s with the short-wave spectrometer aboard the Extreme Ultraviolet Explorer satellite and failed to detect the object. Comparison of our null measurement with the pure H/He best-fit sdO/DAO models of Liebert et al. (1995, ApJ, 441, 424) and new mixed-metallicity models indicates that at the minimum a detectable deficit in continuum strength in this wavelength region does indeed exist, even after allowing for worst-case neutral hydrogen absorption along the line of sight. We attribute this quenching to the presence of metals and estimate nmetals/nH>O.O1, where nmetals/nH is the ratio of metals to hydrogen number densities. Further, the He/H ratio is consistent with the solar value.
- Publication:
-
The Astronomical Journal
- Pub Date:
- September 1997
- DOI:
- 10.1086/118555
- Bibcode:
- 1997AJ....114.1227F
- Keywords:
-
- ULTRAVIOLET: STARS;
- STARS: ATMOSPHERES