Hard X-rays form U Geminorum.
Abstract
The A-2 experiment on HEAO 1 has discovered that the dwarf nova U Geminorum can be a weak source of hard X-rays at optical maximum. During the outburst in October 1977, when a strong soft X-ray flux was discovered, a 2-10-keV flux was also observed. Evidence is presented that this flux appeared with the rise to optical maximum, about half a day before the soft X-rays appeared, and persisted about 2 days. During these first 2 days of the outburst the average flux was 2.4 x 10 to the -11th erg/sq cm per sec, corresponding to a luminosity of 2.8 x 10 to the 31st erg/s for a distance of 100 pc and an absorbed thin thermal spectrum with kT of about 5 keV. During optical minimum an OSO 8 upper limit implies a luminosity less than 10 to the 31st erg/s. Restrictions on models of U Geminorum are discussed.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 1978
- DOI:
- 10.1086/182848
- Bibcode:
- 1978ApJ...226L.133S
- Keywords:
-
- Binary Stars;
- Novae;
- Satellite Observation;
- White Dwarf Stars;
- X Ray Sources;
- Heao 1;
- Oso-8;
- Stellar Luminosity;
- Time Response;
- Astrophysics;
- Dwarf Novae:X Rays;
- U Geminorum Stars:X Rays