FUSE Observations of the Dwarf Nova SW UMa During Quiescence

Abstract

We present spectroscopic observations of the short-period cataclysmic variable SW Ursa Majoris, obtained by the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite while the system was in quiescence. The data include the resonance lines of O VI at 1031.91 and 1037.61 A. These lines are present in emission, and they exhibit both narrow (~ 150 km/s) and broad (~ 2000 km/s) components. The narrow O VI emission lines exhibit unusual double-peaked and redshifted profiles. We attribute the source of this emission to a cooling flow onto the surface of the white dwarf primary. The broad O VI emission most likely originates in a thin, photoionized surface layer on the accretion disk. We searched for emission from H_2 at 1050 and 1100 A, motivated by the expectation that the bulk of the quiescent accretion disk is in the form of cool, molecular gas. If H_2 is present, then our limits on the fluxes of the H_2 lines are consistent with the presence of a surface layer of atomic H that shields the interior of the disk. These results may indicate that accretion operates primarily in the surface layers of the disk in SW UMa. We also investigate the far-UV continuum of SW UMa and place an upper limit of 15,000 K on the effective temperature of the white dwarf.

arXiv comment21 Pages, 3 figures, to be published in ApJ

References in corpus (17)

• The disc instability model of dwarf-novae and low-mass X-ray binary transients
• Overview of the Far Ultraviolet Spectroscopic Explorer Mission
• On-Orbit Performance of the Far Ultraviolet Spectroscopic Explorer (FUSE) Satellite
• The Effect of Resistivity on the Nonlinear Stage of the Magnetorotational Instability in Accretion Disks
• The FUV spectrum of TW Hya. I. Observations of H${}_2$ Fluorescence
• On the origin of episodic accretion in Dwarf Novae
• Two Types of X-ray Spectra in Cataclysmic Variables
• Viscosity Mechanisms in Accretion Disks
• Ultraviolet Emission Line Ratios of Cataclysmic Variables
• The Spatial Distribution of Fluorescent H${}_2$ Near T Tau
• Analysis of H2 Emission from Mira B in UV Spectra from HST
• WZ Sge: HST Spectroscopy of the Cooling of the White Dwarf after the 2001 Outburst
• WZ Sge: FUSE Spectroscopy of the 2001 Outburst
• Chandra Observations of the Dwarf Nova WX Hyi in Quiescence
• Keck IR Spectroscopy of WZ Sge: Detection of Molecular Emission from the Accretion Disk
• Chandra Observation of V426 Oph: Weighing the Evidence for a Magnetic White Dwarf
• A Local One-Zone Model of MHD Turbulence in Dwarf Nova Disks

Cited by in corpus (1)

• A Survey of Far Ultraviolet Spectroscopic Explorer Observations of Cataclysmic Variables