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Special Notice #168: Outburst of the symbiotic star Z Andromedae

AAVSO Special Notice #168

Outburst of the symbiotic star Z Andromedae
September 25, 2009

The bright symbiotic star Z Andromedae is currently in outburst, having risen from magnitude 10.3 to 9.3 over the past 30 days.  Rapid brightening from approximately magnitude 10 to its current brightness occurred over the past 10-15 days.  Both visual and instrumental photometry of Z And are requested at this time.

Z And is an interacting binary system, where mass is transferred from an M giant secondary star to a white dwarf primary, where it can undergo thermonuclear burning on the white dwarf's surface.  The star undergoes outbursts peaking at magnitude 8.5 to 9.5 and typically separated by about 630 days.  Larger outbursts occur much less frequently, with recurrence times of 10-20 years.  Observations are requested at this time to assess whether Z And will brighten significantly beyond the more common outburst range.  Both visual observers and instrumental observers are strongly encouraged to observe; instrumental observers are asked to make filtered observations, with Johnson V being the primary filter, and Johnson B being secondary; other filters may also be used if available, but V and B are preferred.

Z And is located at the following (J2000) coordinates:

RA: 23:33:40.00 ,  Dec: +48:49:06.0

Charts for Z And may be plotted with the AAVSO Variable Star Plotter: http://www.aavso.org/observing/charts/vsp/index.html?pickname=Z%20Ando

Please submit all observations to the AAVSO using the name "Z AND".

This AAVSO Special Notice was prepared by M. Templeton.
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