Synchronous extreme spectral variability of BE UMa.
Abstract
Observations of the variable star BE Ursae Majoris (period 2.29 days) are reported which demonstrate dramatic spectral variability on a time scale of hours and days in synchrony with the periodic light variations. Spectrophotometric observations were made on three consecutive nights in March 1981 and four consecutive nights in April 1981 in the range 3400-6800 A. The observations are observed to correspond to one of three spectral states: (1) a blue continuum with strong, narrow Balmer, He I, He II and C III 4650 A emission; (2) a featureless UV-excess continuum; or (3) a blue continuum with He II 4686 A and an unidentified 4050 A absorption feature, with transitions between these states taking place on a time scale of hours. Results are interpreted in terms of a model of a detached binary consisting of an extremely hot (approximately 100,000 K) white dwarf and a cool M star, the upper layers of which are irradiated by the intense ionizing flux of its hot companion.
- Publication:
-
Nature
- Pub Date:
- September 1981
- DOI:
- 10.1038/293200a0
- Bibcode:
- 1981Natur.293..200M
- Keywords:
-
- Binary Stars;
- M Stars;
- Stellar Models;
- Stellar Spectrophotometry;
- Variable Stars;
- White Dwarf Stars;
- Absorption Spectra;
- Balmer Series;
- Emission Spectra;
- Spectrum Analysis;
- Stellar Spectra;
- Astrophysics;
- BINARY STARS;
- M STARS;
- STELLAR MODELS;
- STELLAR SPECTROPHOTOMETRY;
- VARIABLE STARS;
- WHITE DWARF STARS;
- ABSORPTION SPECTRA;
- BALMER SERIES;
- EMISSION SPECTRA;
- SPECTRUM ANALYSIS;
- STELLAR SPECTRA