Steeghs, D, Marsh, T, Knigge, C, Maxted, PFL, Kuulkers, E and Skidmore, W (2001) Emission from the secondary star in the old CV WZ Sge. The Astrophysical Journal Letters, 562 (2). pp. 145-148. ISSN 1538-4357

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We present the first detection of the mass donor star in the cataclysmic variable WZ Sge. Phase resolved spectroscopy reveals narrow Balmer emission components from the irradiated secondary star during the 2001 outburst. Its radial velocity curve indicates a systemic velocity of -72 +/- 3 km/s and an apparent velocity amplitude of K_2_app=493 +/- 10 km/s. Doppler tomography reveals a highly asymmetric accretion disc including a significant bright spot contribution 20 days into the outburst. We estimate the primary radial velocity K_1 using a center of symmetry method and find K_1_app=37 +/- 5 km/s. Accounting for the likely systematic errors affecting both K_1 and K_2 measurements, we conservatively derive 508 < K_2 < 585 km/s and K_1 < 37 km/s. This implies a massive white dwarf with M_1 > 0.77 M_sun. A non-degenerate mass donor, implying WZ Sge has not yet evolved through its minimum orbital period, is not ruled out by our observations. This would require an improved estimate of K_1. Together with the measured phase offset between bright spot eclipse and inferior conjuction of the secondary star, we can bracket the allowed mass ratio (q=M_2/M_1) to lie between 0.040 and 0.073. This provides a firm upper limit to the mass of the secondary of M_2 < 0.10 M_sun.

Item Type: Article
Additional Information: This is the accepted author manuscript (AAM). The final published version (version of record) is available online via IOP at Please refer to any applicable terms of use of the publisher.
Uncontrolled Keywords: accretion, accretion disks; novae, cataclysmic variables; stars: individual (WZ Sagittae)
Subjects: Q Science > QB Astronomy
Divisions: Faculty of Natural Sciences > School of Physical and Geographical Sciences
Related URLs:
Depositing User: Symplectic
Date Deposited: 20 Aug 2015 14:13
Last Modified: 14 Jun 2018 09:16

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