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Emission from the secondary star in the old cataclysmic variable WZ Sagittae

Emission from the secondary star in the old cataclysmic variable WZ Sagittae
Emission from the secondary star in the old cataclysmic variable WZ Sagittae
We present the first detection of the mass donor star in the cataclysmic variable WZ Sagittae. 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-1 and an apparent velocity amplitude of K'2=493+/-10 km s-1. Doppler tomography reveals a highly asymmetric accretion disk including a significant bright spot contribution 20 days into the outburst. We estimate the apparent primary radial velocity using the Halpha tomogram and find K'1=37+/-5 km s-1. Accounting for the likely systematic errors affecting both K1 and K2 measurements, we conservatively derive 493 km s-1<K2<585 km s-1 and K1<37 km s-1. The measured phase offset between bright spot eclipse and inferior conjunction of the secondary star brackets the allowed mass ratio (q=M2/M1) to lie between 0.040 and 0.075. These constraints imply a white dwarf with M1>0.70 Msolar and a low-mass secondary with M2<0.11 Msolar. A nondegenerate mass donor, implying WZ Sge has not yet evolved through its minimum period, is therefore not ruled out by our observations. This would require an improved estimate of K1.
accretion, accretion disks, stars, novae, cataclysmic variables, WZ Sagittae
0004-637X
L145-L148
Steeghs, D.
ab1118c0-944a-427a-bfbf-6b82e1320280
Marsh, T.R.
85d03859-70b1-4f83-958e-e743e1e0c59a
Knigge, C.
ac320eec-631a-426e-b2db-717c8bf7857e
Maxted, P.F.L.
19af6be6-d8f8-4560-867b-7c5ab6095ed5
Kuulkers, E.
bbe4b980-0d14-46c7-92a4-7bc8149a1947
Skidmore, W.
6e7ecce6-4ffc-41ff-8734-379a31807317
Steeghs, D.
ab1118c0-944a-427a-bfbf-6b82e1320280
Marsh, T.R.
85d03859-70b1-4f83-958e-e743e1e0c59a
Knigge, C.
ac320eec-631a-426e-b2db-717c8bf7857e
Maxted, P.F.L.
19af6be6-d8f8-4560-867b-7c5ab6095ed5
Kuulkers, E.
bbe4b980-0d14-46c7-92a4-7bc8149a1947
Skidmore, W.
6e7ecce6-4ffc-41ff-8734-379a31807317

Steeghs, D., Marsh, T.R., Knigge, C., Maxted, P.F.L., Kuulkers, E. and Skidmore, W. (2001) Emission from the secondary star in the old cataclysmic variable WZ Sagittae. Astrophysical Journal, 562 (2), L145-L148. (doi:10.1086/338107).

Record type: Article

Abstract

We present the first detection of the mass donor star in the cataclysmic variable WZ Sagittae. 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-1 and an apparent velocity amplitude of K'2=493+/-10 km s-1. Doppler tomography reveals a highly asymmetric accretion disk including a significant bright spot contribution 20 days into the outburst. We estimate the apparent primary radial velocity using the Halpha tomogram and find K'1=37+/-5 km s-1. Accounting for the likely systematic errors affecting both K1 and K2 measurements, we conservatively derive 493 km s-1<K2<585 km s-1 and K1<37 km s-1. The measured phase offset between bright spot eclipse and inferior conjunction of the secondary star brackets the allowed mass ratio (q=M2/M1) to lie between 0.040 and 0.075. These constraints imply a white dwarf with M1>0.70 Msolar and a low-mass secondary with M2<0.11 Msolar. A nondegenerate mass donor, implying WZ Sge has not yet evolved through its minimum period, is therefore not ruled out by our observations. This would require an improved estimate of K1.

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More information

Published date: 20 November 2001
Keywords: accretion, accretion disks, stars, novae, cataclysmic variables, WZ Sagittae

Identifiers

Local EPrints ID: 26875
URI: http://eprints.soton.ac.uk/id/eprint/26875
ISSN: 0004-637X
PURE UUID: 0cb182cc-5aa2-4647-8541-ede4ca6b5b8f

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Date deposited: 24 Apr 2006
Last modified: 09 Nov 2021 07:33

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Contributors

Author: D. Steeghs
Author: T.R. Marsh
Author: C. Knigge
Author: P.F.L. Maxted
Author: E. Kuulkers
Author: W. Skidmore

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