The mass of the white dwarf in the old nova BT Mon |
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Authors: | D. A. Smith,V. S. Dhillon,& T. R. Marsh |
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Affiliation: | Institute of Astronomy, Madingley Road, Cambridge CB3 0HA,;Royal Greenwich Observatory, Madingley Road, Cambridge CB3 0EZ,;Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH,;University of Southampton, Department of Physics and Astronomy, Highfield, Southampton SO17 1BJ |
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Abstract: | We present spectrophotometry of the eclipsing old nova BT Mon (Nova Mon 1939). By detecting weak absorption features from the secondary star, we find its radial velocity semi-amplitude to be K R = 205 ± 5 km s−1 and its rotational velocity to be v sin i = 138 ± 5 km s−1. We also measure the radial velocity semi-amplitude of the primary star to be K R = 170 ± 10 km s−1. From these parameters we obtain a mass of 1.04 ± 0.06 M⊙ for the white dwarf primary star and a mass of 0.87 ⊙ 0.06 M⊙ for the G8 V secondary star. The inclination of the system is found to be 82°.2 ± 32°.2 and we estimate that the system lies at a distance of 1700 ± 300 pc. The high mass of the white dwarf and our finding that BT Mon was probably a fast nova together constitute a new piece of evidence in favour of the thermonuclear runaway model of classical nova outbursts. The emission lines are single-peaked throughout the orbital cycle, showing absorption around phase 0.5, high-velocity S-wave components and large phase offsets in their radial velocity curves. In each of these respects, BT Mon is similar to the SW Sex stars. We also find quasi-periodic flaring in the trailed spectra, which makes BT Mon a candidate intermediate polar. |
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Keywords: | accretion accretion discs binaries: eclipsing binaries: spectroscopic stars: individual: BT Mon novae cataclysmic variables |
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