Further to AAVSO Alert Notice 345, the AAVSO requests continued observations of the bright dwarf novae U Geminorum (0749+22) and SS Cygni (2138+43) in support of radio observations of these objects by Dr. Christian Knigge (University of Southampton, UK). Knigge and collaborators will use the Very Large Array (New Mexico, USA) and MERLIN (Jodrell Bank, UK) radio telescopes to detect the brief spike in radio emission coincident with the onset of a dwarf nova outburst.

AAVSO light curves of SS Cyg (left) and U Gem (right).

AAVSO observers are requested to submit all observations -- including positive observations during quiescence, transition, and outburst, as well as "fainter-than" observations -- to the AAVSO via WebObs as rapidly as possible. Radio observations will only be made if they can be initiated within six hours of the onset of an outburst. Because of this constraint, we must know both that the star was in quiescence and that it is rising to outburst within the past six hours. If possible, please submit observations as they are made or immediately following your observing session.

AAVSO charts for these objects may be found at the following URLs:

• U Gem: http://www.aavso.org/cgi-bin/searchcharts3.pl?name=U%20Gem
• SS Cyg: http://www.aavso.org/cgi-bin/searchcharts3.pl?name=SS%20Cyg

This update was prepared by Dr. Matthew Templeton, AAVSO.