## The eccentric short-period orbit of the supergiant fast X-ray transient HD 74194 (=LM Vel)

Gamen, R.; Barbá, R. H.; Walborn, N. R.; Morrell, N. I.; Arias, J. I.; Maíz Apellániz, J.; Sota, A.; Alfaro, E. J.
Astronomy & Astrophysics, Volume 583, id.L4, 5 pp. (2015).
11/2015

#### ABSTRACT

Aims. We present the first orbital solution for the O-type supergiant star HD 74194, which is the optical counterpart of the supergiant fast X-ray transient IGR J08408-4503. Methods. We measured the radial velocities in the optical spectrum of HD 74194, and we determined the orbital solution for the first time. We also analysed the complex H{\alpha} profile. Results. HD 74194 is a binary system composed of an O-type supergiant and a compact object in a short-period ($P=9.5436\pm0.0002$ d) and high-eccentricity ($e=0.63\pm0.03$) orbit. The equivalent width of the H{\alpha} line is not modulated entirely with the orbital period, but seems to vary in a superorbital period ($P=285\pm10$ d) nearly 30 times longer than the orbital one.

Aims. We present the first orbital solution for the O-type supergiant star HD 74194, which is the optical counterpart of the supergiant fast X-ray transient IGR J08408-4503. Methods. We measured the radial velocities in the optical spectrum of HD 74194, and we determined the orbital solution for the first time. We also analysed the complex Hα profle. Results. HD 74194 is a binary system composed of an O-type supergiant and a compact object in a short-period (P=9.5436 ± 0.0002 d) and high-eccentricity (e=0.63 ± 0.03) orbit. The equivalent width of the Hα line is not modulated entirely with the orbital period, but seems to vary in a superorbital period (P=285 ± 10 d) nearly 30 times longer than the orbital one.

Table 3 is available in electronic form at http://www.aanda.org/10.1051/0004-6361/201527140/olm