A spiral structure in the disk of EX Draconis on the rise to outburst maximum

Abstract

We report on the R-band eclipse mapping analysis of high-speed photometry of the dwarf nova EX Dra on the rise to the maximum of the November 1995 outburst. The eclipse map shows a one-armed spiral structure of ~180 degrees in azimuth, extending in radius from R ~0.2 to 0.43 R_{L1} (where R_{L1} is the distance from the disk center to the inner Lagrangian point), that contributes about 22 per cent of the total flux of the eclipse map. The spiral structure is stationary in a reference frame co-rotating with the binary and is stable for a timescale of at least 5 binary orbits. The comparison of the eclipse maps on the rise and in quiescence suggests that the outbursts of EX Dra may be driven by episodes of enhanced mass-transfer from the secondary star. Possible explanations for the nature of the spiral structure are discussed.

To appear in the Astrophysical Journal Letters; 8 pages, 2 figures; coded with AAS latex style

References in corpus (3)

• Eclipse studies of the dwarf-nova Ex Draconis
• Outbursts of EX Hydrae: mass-transfer events or disc instabilities?
• Eclipse maps of spiral shocks in the accretion disc of IP Pegasi in outburst

Cited by in corpus (6)

• Completion of a Survey and Detailed Study of Double-Peaked Emission Lines in Radio-Loud AGNs
• Evolution of the Nuclear Accretion Disk Emission in NGC 1097: Getting Closer to the Black Hole
• Long-Term Profile Variability of Double Peaked Emission Lines in Active Galactic Nuclei
• Variable Star Network: World Center for Transient Object Astronomy and Variable Stars
• Changes in the structure of the accretion disc of EX Draconis through the outburst cycle
• EX Draconis: Using Eclipses to Separate Outside-In and Inside-Out Outbursts