Steeghs, D., Howell, Steve B., Knigge, Christian, Gaensicke, B. T., Sion, Edward M. and Welsh, William F.. (2007) Dynamical constraints on the component masses of the cataclysmic variable WZ Sagittae. Astrophysical Journal, Vol.667 (No.1). pp. 442-447. ISSN 0004-637X

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Abstract

We present phase-resolved spectroscopy of the short-period cataclysmic variable WZ Sge obtained with the Hubble Space Telescope. We were able to resolve the orbital motion of a number of absorption lines that likely probe the environment near the accreting white dwarf. The radial velocities derived from simultaneous fits to 13 absorption lines indicate an orbital velocity semi-amplitude of K-UV (47 +/- 3) km s(-1). However, we find that the phase zero is offset from the white dwarf ephemeris by +0.1. Our offset and velocity amplitude are very similar to constraints derived from optical emission lines from the quiescent accretion disk, despite the fact that we are probing material much closer to the primary. If we associate the UV amplitude with K-1, our dynamical constraints together with the published K-2 estimates and the known binary inclination of i = 77 +/- 2 imply 0.88 M-circle dot < M-1 < 1.53 M-circle dot, 0: 078 M-circle dot < M-2 < 0.13 M-circle dot, and 0.075 < q = M-2/M-1 < 0.101. If we interpret the mean velocity of the UV lines [-(16 +/- 4) km s(-1)] as being due to the gravitational redshift caused in the high-g environment near the white dwarf, we find v(grav) (56 +/- 5) km s(-1), which provides an independent estimate on the mass of the primary of M-1 (0.85 +/- 0.04) M-circle dot when coupled with a mass-radius relation. Our primary mass estimates are in excellent agreement and are also self-consistent with spectrophotometric fits to the UV fluxes despite the observed phase offset. It is at this point unclear what causes the observed phase offset in the UV spectra and by how much it distorts the radial velocity signature from the underlying white dwarf.

Item Type:	Journal Article
Subjects:	Q Science > QB Astronomy
Divisions:	Faculty of Science > Physics
Journal or Publication Title:	Astrophysical Journal
Publisher:	IOP Publishing
ISSN:	0004-637X
Official Date:	20 September 2007
Dates:	Date Event 20 September 2007 Published
Volume:	Vol.667
Number:	No.1
Number of Pages:	6
Page Range:	pp. 442-447
Identification Number:	10.1086/520702
Status:	Not Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
URI:	http://wrap.warwick.ac.uk/id/eprint/31384

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