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V455 Andromedae

V455 Andromedae is a member of the WZ Sagittae subclass of dwarf novae.  These are stars that undergo very infrequent dwarf nova outbursts with very large amplitudes.  They have low masses and low accretion rates, and so in quiescence they're fainter than average dwarf nova progenitors; when they go into outburst, their bright disks make them as much as eight or more magnitudes brighter than their quiescent state, a factor of nearly a thousand.

V455 And had a major outburst in 2007, brightening from around V=16.5 all the way to magnitude 8.  The majority of the outburst ended quite quickly -- within a month or so, but the system took years to fade the last magnitude down to quiescence, and it still remains just above its historical quiescent level.  This is because the outburst heats up the white dwarf, and the white dwarf remains slightly brighter until it cools down.  This makes V455 And very interesting astrophysically because the white dwarf is pulsating, and changes in temperature modify the pulsation behavior.  Studying how pulsations change teaches us about the interior structure of white dwarfs, a field of science called asteroseismology.  Such observations were the purpose behind two observing campaigns requested by Dr. Paula Szkody in 2010 and 2011.

AAVSO 49 Bay State Rd. Cambridge, MA 02138 617-354-0484