Variable Stars - BB Dor
Type VY Scl subtype of nova-like variables Nova-like stars. Cataclysmic variables where the mass transfer rate is above a certain limit and their accretion disks are stable because they are nearly fully ionized to their outer (tidal cut off) boundary and this condition suppresses dwarf nova outbursts. Also known as UX (UX Ursae Majoris stars). VY Scl subtype of the nova-like variables. They are cataclysmic binary systems with a hot (35,000-65,000 K) and luminous white dwarf that occasionally undergo fadings of more than 1 magnitude (up to several magnitudes) due to a low rate of mass transfer. These fadings might last from days to years. At maximum they vary up to 1 magnitude. They show no outbursts even though at minimum they fall into the dwarf novae instability strip. This could be caused by the possible magnetic nature of the white dwarf. Orbital periods usually range between 0.12 and 0.18 d. AAVSO Alert 323: January 14, 2013  Dr. Boris Gaensicke (Warwick University), who is the coordinating PI on the large observing campaign underway to observe cataclysmic variables with the HST Cosmic Origins Spectrograph (see AAVSO Alert Notice 471 and follow-up AAVSO Special Notices as listed on the AAVSO Observing Campaigns page), is requesting observations tonight and over the next few nights of the novalike variable BB Dor. He writes: "it appears that the SW Sex star BB Dor is in a deep low state, and that would make it a very interesting target for HST ultraviolet observations: during the normal high state, it is impossible to see the white dwarf in the system, as it is shielded by the accretion disk - however, in a low state, there is a good probability that most of the disk is gone...
Hills Observatory: 1 January 2013 to 6 May 2018
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