Detection of a Hot Subdwarf Companion to the Be Star FY Canis Majoris

Abstract

The rapid rotation of Be stars may be caused in some cases by past mass and angular momentum accretion in an interacting binary in which the mass donor is currently viewed as a small, hot subdwarf stripped of its outer envelope. Here we report on the spectroscopic detection of such a subdwarf in the Be binary system FY Canis Majoris from the analysis of data acquired by the IUE spacecraft and KPNO Coude Feed Telescope over the course of 16 and 21 years, respectively. We present a double-lined spectroscopic orbit for the binary based upon radial velocities from the IUE spectra and use the orbital solutions with a Doppler tomography algorithm to reconstruct the components' UV spectra. The subdwarf is hot (T_eff = 45+/-5 kK) and has a mass of about 1.3 M_sun and a radius of about 0.6 R_sun. It contributes about 4% as much flux as the Be star does in the FUV. We also present observations of the H-alpha and He I 6678 emission features that are formed in the circumstellar disk of the Be star. Orbital flux and velocity variations in the He I 6678 profile indicate that much of the emission forms along the disk rim facing the hot subdwarf where the disk is probably heated by the incident radiation from the subdwarf. A study of the FUV infall shell lines discovered in the 1980s confirms their episodic presence but reveals that they tend to be found around both quadrature phases, unlike the pattern in Algol binaries. Phase-dependent variations in the UV N V doublet suggest the presence of a N-enhanced wind from the subdwarf and a possible shock-interaction region between the stars where the subdwarf's wind collides with the disk of the Be star.

arXiv comment46 pages, 15 figures, ApJ in press

References in corpus (10)

• A Grid of NLTE Line-Blanketed Model Atmospheres of O-type Stars
• A natural explanation for periodic X-ray outbursts in Be/X-ray binaries
• Effects of gravitational darkening on the determination of fundamental parameters in fast rotating B-type stars
• Formation of contact in massive close binaries
• Binary star progenitors of long gamma-ray bursts
• Constraining the mass transfer in massive binaries through progenitor evolution models of Wolf-Rayet+O binaries
• Viscous Effects on the Interaction between the Coplanar Decretion Disc and the Neutron Star in Be/X-Ray Binaries
• Cross-Correlation and Maximum Likelihood Analysis: A New Approach to Combine Cross-Correlation Functions
• Estimating Be Star Disk Radii using H-alpha Emission Equivalent Widths
• On Rejuvenation in Massive Binary Systems

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