An improved orbital ephemeris for Cygnus X-1

Authors
Brocksopp, C Tarasov, AE Lyuty, VM Roche, P
Citation
C. Brocksopp et al., An improved orbital ephemeris for Cygnus X-1, ASTRON ASTR, 343(3), 1999, pp. 861-864
Citations number
33
Categorie Soggetti
Space Sciences
Journal title
ASTRONOMY AND ASTROPHYSICS
ISSN journal
00046361 → ACNP
Volume
343
Issue
3
Year of publication
1999
Pages
861 - 864
Database
ISI
SICI code
0004-6361(199903)343:3<861:AIOEFC>2.0.ZU;2-I
Abstract
By accumulating all available radial velocity data and combining it with ou r own spectroscopy we present a new and improved ephemeris for Cygnus X-l ( V1357 Cygni/HDE226868). We initially calculate an orbital period of 5.59984 7 +/- 0.000018 days and then, by including the,more recent radial velocitie s of LaSala et al. (1998) and Sowers et al. (1998) we refine this to 5.5998 29 +/- 0.000016 days. Using 27 years' worth of photometry, we also calculat e a photometric period of 5.599836 +/- 0.000024 -remarkably similar to the spectroscopic one.