Browsing by Author "Henden, Arne"
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Item HST and Optical Data Reveal White Dwarf Cooling, Spin, and Periodicities in GW Librae 3-4 Years After Outburst(2012-07-10) Szkody, Paula; Mukadam, Anjum S.; Gänsicke, Boris T.; Henden, Arne; Sion, Edward M.; Townsley, Dean M.; Chote, Paul; Harmer, Diane; Harpe, Eric J.; Hermes, J. J.; Sullivan, Denis J.; Winget, D. E.; University of Alabama TuscaloosaItem Hubble Space Telescope and Ground-Based Observations of V455 Andromedae Post-Outburst(2013-09-20) Szkody, Paula; Mukadam, Anjum S.; Gänsicke, Boris T.; Henden, Arne; Sion, Edward M.; Townsley, Dean M.; Christian, Damian; Falcon, Ross E.; Pyrzas, Stylianos; Brown, Justin; Funkhouser, Kelsey; University of Alabama TuscaloosaHubble Space Telescope spectra obtained in 2010 and 2011, 3 and 4 yr 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 shows that the white dwarf temperature remains ∼600 K hotter than its quiescent value at 3 yr post-outburst, and still a few hundred degrees hotter at 4 yr 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 2 yr 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.Item Hubble Space Telescope and Optical Data on SDSSJ0804+5103 (EZ Lyn) One Year After Outburst(2013-05) Szkody, Paula; Mukadam, Anjum S.; Sion, Edward M.; Gänsicke, Boris T.; Henden, Arne; Townsley, Dean M.; University of Alabama TuscaloosaWe present an ultraviolet (UV) spectrum and light curve of the short orbital period cataclysmic variable EZ Lyn obtained with the Cosmic Origins Spectrograph on the Hubble Space Telescope 14 months after its dwarf nova outburst, along with ground-based optical photometry. The UV spectrum can be fit with a 13,100 K, log g = 8 white dwarf using 0.5 solar composition, while fits to the individual lines are consistent with solar abundance for Si and Al, but only 0.3 solar for C. The Discrete Fourier Transforms of the UV and optical light curves at 14 months following outburst show a prominent period at 256 s. This is the same period reported by Pavlenko in optical data obtained seven months and one year after outburst, indicating its long-term stability over several months, but this period is not evident in the pre-outburst data and is much shorter than the 12.6 minute period that was seen in observations obtained during an interval from 8 months to 2.5 yr after the 2006 outburst. In some respects, the long and short periods are similar to the behavior seen in GW Lib after its outburst but the detailed explanation for the appearance and disappearance of these periods and their relation to non-radial pulsation modes remain to be explored with theoretical models.