Open AccessRotational broadening and Doppler tomography of the quiescent X‐ray nova Centaurus X‐4
Author(s) -
Torres M. A. P.,
Casares J.,
MartínezPais I. G.,
Charles P. A.
Publication year - 2002
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.1365-8711.2002.05521.x
Subject(s) - physics , astrophysics , x ray binary , spectroscopy , doppler effect , emission spectrum , astronomy , spectral line , x ray , radial velocity , binary star , stars , optics , neutron star
We present high‐ and intermediate‐resolution spectroscopy of the X‐ray nova Centaurus X‐4 during its quiescent phase. Our analysis of the absorption features supports a K3–K5 V spectral classification for the companion star, which contributes ≃75 per cent of the total flux at H α . Using the high‐resolution spectra we have measured the rotational broadening of the secondary star to be v sin i =43±6 km s ‐1 and determined a binary mass ratio of q =0.17±0.06 . Combining our results for K 2 and q with the published limits for the binary inclination, we constrain the mass of the compact object and the secondary star to the ranges 0.49< M 1 <2.49 M ⊙ and 0.04< M 2 <0.58 M ⊙ . A Doppler image of the H α line shows emission coming from the secondary star, but no hotspot is present. We discuss the possible origins of this emission.