Optical spectroscopy of X-Mega targets – I. CPD −59° 2635: a new double-lined O-type binary in the Carina Nebula |
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| Authors: | JF Albacete Colombo †‡ NI Morrell †§¶ VS Niemela †&#; MF Corcoran |
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| Institution: | 1Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque S/N, 1900 La Plata, Argentina;2Universities Space Research Association, 7501 Forbes Blvd, Ste 206, Seabrook, MD 20706, USA;3Laboratory for High Energy Astrophysics, Goddard Space Flight Center, Greenbelt, MD 20771, USA |
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| Abstract: | Optical spectroscopy of CPD −59° 2635, one of the O-type stars in the open cluster Trumpler 16 in the Carina Nebula, reveals this star to be a double-lined binary system. We have obtained the first radial velocity orbit for this system, consisting of a circular solution with a period of 2.2999 d and semi-amplitudes of 208 and 273 km s−1. This results in minimum masses of 15 and 11 M⊙ for the binary components of CPD −59° 2635, which we classified as O8V and O9.5V, although spectral type variations of the order of 1 subclass, which we identify as the Struve–Sahade effect , seem to be present in both components. From ROSAT HRI observations of CPD −59° 2635 we determine a luminosity ratio log( L x/ L bol)≈−7 , which is similar to that observed for other O-type stars in the Carina Nebula region. No evidence of light variations is present in the available optical or X-ray data sets. |
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| Keywords: | binaries: general stars: early-type stars: individual: CPD −59° 2635 open clusters and associations: individual: Trumpler 16 X-rays: stars |
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