Open AccessHigh‐resolution optical and infrared spectroscopic observations of Cir X‐1
Author(s) -
Johnston Helen M.,
Fender Robert,
Wu Kinwah
Publication year - 1999
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.1999.02702.x
Subject(s) - physics , astrophysics , radial velocity , ejecta , line (geometry) , infrared , neutron star , binary number , emission spectrum , x ray binary , spectral line , astronomy , supernova , stars , geometry , mathematics , arithmetic
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 H α 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.