Hubble Space Telescope and Ground-Based Observations of V455 Andromedae Post-Outburst

Abstract

Hubble Space Telescope spectra obtained in 2010 and 2011, three and four years after the large amplitude dwarf nova outburst of V455 And, were combined with optical photometry and spectra to study the cooling of the white dwarf, its spin, and possible pulsation periods after the outburst. The modeling of the ultraviolet (UV) spectra show that the white dwarf temperature remains ~600 K hotter than its quiescent value at three years post outburst, and still a few hundred degrees hotter at four years post outburst. The white dwarf spin at 67.6 s and its second harmonic at 33.8 s are visible in the optical within a month of outburst and are obvious in the later UV observations in the shortest wavelength continuum and the UV emission lines, indicating an origin in high temperature regions near the accretion curtains. The UV light curves folded on the spin period show a double-humped modulation consistent with two-pole accretion. The optical photometry two years after outburst shows a group of frequencies present at shorter periods (250-263 s) than the periods ascribed to pulsation at quiescence, and these gradually shift toward the quiescent frequencies (300-360 s) as time progresses past outburst. The most surprising result is that the frequencies near this period in the UV data are only prominent in the emission lines, not the UV continuum, implying an origin away from the white dwarf photosphere. Thus, the connection of this group of periods with non-radial pulsations of the white dwarf remains elusive.

18 pages, 14 figs; accepted for ApJ

References in corpus (6)

• Pulsational Instabilities in Accreting White Dwarfs
• HST/STIS Spectroscopy and Modeling of the Long Term Cooling of WZ Sagittae following the July 2001 Outburst
• HST and Optical Observations of Three Pulsating Accreting White Dwarfs in Cataclysmic Variables
• HST and Optical Data Reveal White Dwarf Cooling, Spin and Periodicities in GW Librae 3-4 Years after Outburst
• Remarkable spectral variability on the spin period of the accreting white dwarf in V455 And
• Multiwavelength Photometry and Hubble Space Telescope Spectroscopy of the Old Nova V842 Centaurus

Cited by in corpus (6)

• Ideas for Citizen Science in Astronomy
• TESS light curves of cataclysmic variables -- II: Superhumps in old novae and novalike variables
• R-mode oscillations in accreting white dwarfs in cataclysmic variables
• The post-outburst pulsations of the accreting white dwarf in the cataclysmic variable GW Librae
• Spectroscopic Observations of V455 Andromedae Superoutburst in 2007: the Most Exotic Spectral Features in Dwarf Nova Outbursts
• Miscellaneous photometric variations in cataclysmic variables: V455 And, SS Cyg, AQ Men, LQ Peg, RW Tri and UX UMa