First Orbital Solution for the Non-thermal Emitter Cyg OB2 No. 9
English
Nazé, Yaël[Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique observationnelle (sol et espace) >]
Damerdji, Yassine[Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Astroph. extragalactique et observations spatiales (AEOS) >]
Rauw, Grégor[Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Sciences spatiales >]
Kiminki, D. C.[Department of Physics & Astronomy, University of Wyoming, Laramie, WY 82070, USA]
Mahy, Laurent[Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique observationnelle (sol et espace) >]
Kobulnicky, H. A.[Department of Physics & Astronomy, University of Wyoming, Laramie, WY 82070, USA]
Morel, Thierry[Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Groupe d'astrophysique des hautes énergies (GAPHE) >]
De Becker, Michaël[Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Département d'astrophys., géophysique et océanographie (AGO) >]
Eenens, P.[Departamento de Astronomia, Universidad de Guanajuato, Apartado 144, 36000 Guanajuato, GTO, Mexico]
Barbieri, C.[Dipartimento di Astronomia, Universitá degli studi di Padova, vicolo Osservatorio 2, 35122 Padova, Italy]
[en] After the first detection of its binary nature, the spectroscopic monitoring of the non-thermal radio emitter Cyg OB2 No. 9 (P = 2.4 yr) has continued, doubling the number of available spectra of the star. Since the discovery paper of 2008, a second periastron passage has occurred in 2009 February. Using a variety of techniques, the radial velocities could be estimated and a first, preliminary orbital solution was derived from the He I 5876 line. The mass ratio appears close to unity and the eccentricity is large, i.e., 0.7-0.75. X-ray data from 2004 and 2007 are also analyzed in quest of peculiarities linked to binarity. The observations reveal neither large overluminosity nor strong hardness, but it must be noted that the high-energy data were taken after the periastron passage, at a time where colliding wind emission may be low. Some unusual X-ray variability is however detected, with a 10% flux decrease between 2004 and 2007. To clarify their origin and find a more obvious signature of the wind-wind collision, additional data, taken at periastron and close to it, are needed. Based on observations collected at the Haute-Provence Observatory and with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and the USA (NASA).
[Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique observationnelle (sol et espace) >]
