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AR Pavonis

AR Pavonis is the second of the symbiotic light curves we're highlighting in this series of three.  AR Pav is one of the more interesting symbiotics in that it's one of the few that shows clear evidence of eclipses of the secondary.  In SY Mus we noted that the wave-like variations were caused by our changing viewing angle on the nebular emission region during the binary's orbital cycle.  We see the same wave-like variation in AR Pav with a period over 600 days, but here we also see a short, deep eclipse lasting about 75 days.  This eclipse is of the bright primary star which is accreting wind from the giant secondary in the system.  The inclination of the AR Pav binary system is high enough that the primary is eclipsed by the secondary. 

As in SY Mus, there's been no recent evidence of outbursts, although Skopal et al found evidence of increased activity in archival plate data from the early 20th century.  It has been suggested that the primary in AR Pav isn't a white dwarf but is instead a main sequence star.  That would make it harder for the star to have thermonuclear outbursts that characterize some symbiotics because the gravitational well around a main-sequence star isn't as steep as that around a white dwarf, and material falling onto the surface of a main-sequence star won't get as hot.  As the IBVS article linked below suggests, the nature of the primary remains unknown.

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