Position and Variability of 2A 1704+241

Citation
Wa. Morgan et Mr. Garcia, Position and Variability of 2A 1704+241, PUB AST S P, 113(789), 2001, pp. 1386-1392
Citations number
20
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Space Sciences
Journal title
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC
ISSN journal
0004-6280 → ACNP
Volume
113
Issue
789
Year of publication
2001
Pages
1386 - 1392
Database
ISI
SICI code
0004-6280(200111)113:789<1386:PAVO21>2.0.ZU;2-O
Abstract
We present results of analyses of observations of the X-ray source 2A 1704241 with the ROSAT Position Sensitive Proportional Counter (PSPC) and the H igh Resolution Imager (HRI). The source 2A 1704+241 was first associated wi th the M giant star HD 154791 based on observations with the HEAO 1 scannin g modulation collimator and the Einstein IPC and analysis of a spectrum of HD 154791 obtained with the International Ultraviolet Explorer. This identi fication was unusual because there are few bright X-ray binaries associated with an M giant star. We observed 2A 1704+241 with the PSPC and the HRI in order to determine more accurately the position of the X-ray source and in order to study the previously seen 900 s variability in the Einstein data. Based on the previous identification and determination of the position of MS 1703.7+2417, an active galactic nucleus in the field, and the position o f three previously unreported X-ray sources that we have associated with st ars in the USNO-A2.0 catalog, we have greatly reduced the X-ray positional error of 2A 1704+241. HD 154791 remains the prime candidate as the optical counterpart of the X-ray source. While the 50% modulation in the X-ray flux seen by the Einstein IPC is apparent in the ROSAT data, it appears to be a t a slightly different frequency.