An improved orbital ephemeris for Cygnus X-1
Abstract
By accumulating all available radial velocity data and combining it with our own spectroscopy we present a new and improved ephemeris for Cygnus X-1 (V1357 Cygni/HDE226868). We initially calculate an orbital period of 5.599847+/-0.000018 days and then, by including the more recent radial velocities of LaSala et al. (1998) and Sowers et al. (1998) we refine this to 5.599829+/-0.000016 days. Using 27 years' worth of photometry, we also calculate a photometric period of 5.599836+/-0.000024 - remarkably similar to the spectroscopic one.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- March 1999
- DOI:
- 10.48550/arXiv.astro-ph/9812077
- arXiv:
- arXiv:astro-ph/9812077
- Bibcode:
- 1999A&A...343..861B
- Keywords:
-
- X-RAYS: STARS;
- STARS: INDIVIDUAL: CYGNUS X-1;
- STARS: BINARIES: SPECTROSCOPIC;
- EPHEMERIDES;
- Astrophysics
- E-Print:
- Accepted for publication in A&