Optical Spectroscopy of X-Mega targets in the Carina Nebula - VI. FO 15: a new O-Type double-lined eclipsing binary

Abstract

We report the discovery of a new O-type double-lined spectroscopic binary with a short orbital period of 1.4 days. We find the primary component of this binary, FO 15, to have an approximate spectral type O5.5Vz, i.e. a Zero-Age-Main-Sequence star. The secondary appears to be of spectral type O9.5V. We have performed a numerical model fit to the public ASAS photometry, which shows that FO 15 is also an eclipsing binary. We find an orbital inclination of ~ 80 deg. From a simultaneous light-curve and radial velocity solution we find the masses and radii of the two components to be 30 +/- 1 and 16 +/- 1 solar masses and 7.5 +/- 0.5 and 5.3 +/- 0.5 solar radii. These radii, and hence also the luminosities, are smaller than those of normal O-type stars, but similar to recently born ZAMS O-type stars. The absolute magnitudes derived from our analysis locate FO 15 at the same distance as Eta Carinae. From Chandra and XMM X-ray images we also find that there are two close X-ray sources, one coincident with FO 15 and another one without optical counterpart. This latter seems to be a highly variable source, presumably due to a pre-main-sequence stellar neighbour of FO 15.

arXiv comment11 pages, 9 figures, 3 tables. Accepted for publication in MNRAS. Higher resolution version available at http://lilen.fcaglp.unlp.edu.ar/papers2006.html

References in corpus (7)

• A new calibration of stellar parameters of Galactic O stars
• A Computational Guide to Physics of Eclipsing Binaries. Paper I. Demonstrations and Perspectives
• A Grid of NLTE Line-Blanketed Model Atmospheres of O-type Stars
• O stars with weak winds: the Galactic case
• CHORIZOS: a CHi-square cOde for parameteRized modelIng and characteriZation of phOtometry and Spectrophotometry
• Chandra Observations of Associates of $\eta$ Car: I. Luminosities
• Classification of O Stars in the Yellow-Green: The Exciting Star VES 735

Cited by in corpus (19)

• Binary interaction dominates the evolution of massive stars
• The Galactic O-Star Spectroscopic Survey (GOSSS). II. Bright Southern Stars
• UBVJHK synthetic photometry of Galactic O stars
• The relation between the most-massive star and its parental star cluster mass
• The masses, and the mass discrepancy of O-type stars
• Carina OB Stars: X-ray Signatures of Wind Shocks and Magnetic Fields
• Photometric and Spectroscopic Studies of Massive Binaries in the Large Magellanic Cloud. I. Introduction and Orbits for Two Detached Systems: Evidence for a Mass Discrepancy?
• XMM-Newton X-ray study of early type stars in the Carina OB1 association
• Towards an Accurate Determination of Parameters for Very Massive Stars: the Eclipsing Binary LMC-SC1-105
• Optical spectroscopy of X-Mega targets in the Carina nebula - VII On the multiplicity of Tr 16-112, HD 93343 and HD 93250
• Gaia-ESO Survey: global properties of clusters Trumpler 14 and 16 in the Carina Nebula
• An X-ray survey of low-mass stars in Trumpler 16 with Chandra
• MY Camelopardalis, a very massive merger progenitor
• A radial velocity survey of the Carina Nebula's O-type stars
• Spectroscopic study of the extremely young O-type triple system Herschel 36 A in the Hourglass Nebula. I. Orbital properties
• A Survey for High-Mass Eclipsing Binaries
• Gaia-ESO Survey: massive stars in the Carina Nebula. A new census of OB stars
• Eclipsing high-mass binaries I. Light curves and system parameters for CPD-518946, PISMIS24-1 and HD319702
• Detection of new O-type stars in the obscured stellar cluster Tr 16-SE in the Carina Nebula with KMOS