1999/04/12 by Helen Johnston, H. M. Johnston, Rob Fender +2 · 4 citations
Physics and Astronomy · #Astrophysical Phenomena and Observations #Pulsars and Gravitational Waves Research #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1046/j.1365-8711.1999.02702.x
published as Mon.Not.Roy.Astron.Soc. 308 (1999) 415 · 9 pages including 9 figures; accepted for publication in MNRAS; references fixed
arxiv created 1999/04/12 · openalex publication_date 1999/09/19 · arxiv updated 2009/12/01 · openalex created_date 2021/02/01 · openalex updated_date 2026/08/01
We present new optical and infrared (IR) observations of Cir X-1 taken near apastron. Both sets of spectra show asymmetric emission lines. Archival optical observations show that an asymmetric Hα emission line has been in evidence for the past 20 years, although the shape of the line has changed significantly. We present an eccentric (e∼0.7–0.9) low-mass binary model, where the system consists of a neutron star orbiting around a (sub)giant companion star of 3–5 M⊙. We suggest that the broad components of the emission lines arise in a high-velocity, optically thick flow near the neutron star, while the narrow components of the optical and the IR lines arise near the companion star and a heated ejecta shell surrounding the binary respectively. In this model, the velocity of the narrow component reflects the space velocity of the binary; the implied radial velocity (+430 km s−1 after correcting for Galactic rotation) is the highest velocity known for an X-ray binary.