HD 74194, a new binary supergiant fast X-ray transient?, possible optical counterpart of INTEGRAL hard X-ray source IGR J08408-4503
ATel #819; Rodolfo Barba, Roberto Gamen (Universidad de La Serena, Chile), Nidia Morrell (Las Campanas Observatory, Chile)
on 23 May 2006; 10:28 UT
Credential Certification: Rodolfo Barba (firstname.lastname@example.org)
Subjects: Optical, X-ray, Binary, Star, Variables
HD 74194 is an O-type supergiant, classified as O8.5 Ib (f) (Walborn 1973, AJ 78, 1067), also suspected as single-lined binary (see Maiz Apellaniz et al. 2004, ApJS 151, 103). This star is being spectroscopically monitored as part of our program of study of massive binaries. We have obtained high-resolution spectra of HD 74194 with the Echelle spectrograph attached to the du Pont 2.5-m telescope at Las Campanas Observatory in 2006 May 18.00, 20.96, 22.00, and 22.97. The Halpha profile changed from a double-peaked emission (in May 18.0 and May 22.00), with similar strength in both emission components, to a P Cyg-like profile (in May 20.96 and 22.97), meaning the complete absence of the blue emission peak which was replaced by an extended blue absorption wing. We also detected radial velocity variations in the HeI and HeII absorption lines with an amplitude of about 35 km/s. Recently, Pellizza et al. (astro-ph/0605559) reported the discovery of IGR J17544-2619 as a high mass X-ray binary with an O9 Ib secondary. The optical spectrum of HD 74194 strongly resembles that of the optical counterpart of IGR J17544-2619. Thus, we propose that HD 74194 is associated with the hard X-ray source IGR J08408-4503 (Gotz et al., ATel #813; Mereghetti et al., ATel #814, Masetti et al. ATel #815, Brandt et al. ATel #817, Kennea & Campana ATel #818) and that it is a high-mass binary that belongs to the same kind of fast X-ray transient sources as IGR J17544-2619.