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AAVSO Alert Notice 685: EM Cyg monitoring requested

November 8, 2019

AAVSO Forum threads (scroll to the bottom of a thread for latest posts):
 - Campaigns and Observation Reports: https://www.aavso.org/em-cyg-campaign-2019
 - Cataclysmic Variables: https://www.aavso.org/em-cyg-campaign-2019-01

Drs. Rob Fender (Oxford University) and Roque Ruiz-Carmona (Hebrew University of Jerusalem) have requested AAVSO assistance in nightly monitoring of the cataclysmic variable EM Cyg.

Dr. Ruiz-Carmona writes: “A number of cataclysmic variable stars are now known to exhibit radio emission, presumably due to jets as observed in other accreting systems with neutron stars and black holes rather than a white dwarf. Fender et al. (2019) have recently reported radio flares in SS Cyg both at early and late times in relation to the beginning of the outburst. We want to study how common these radio flares are in other systems, and analyse some of their properties. 

“Why do we need AAVSO observations?: The AAVSO monitoring of EM Cyg will trigger the observations in radio with the Arcminute Microkelvin Imager Large Array (AMI-LA). We would like the monitoring to continue until the system goes back into quiescence, so we can check whether or not there are optical rebrightenings associated with the radio flares. EM Cyg has a mean cycle of 19-33 days, so we are looking at a potentially month long [or longer] campaign. 

“Requested observations: EM Cyg is now visible at the beginning of the night and progressively becoming observable for a shorter window. It is a bright system (11.9-14.4 mag), so it should be  easy to observe. [Beginning immediately,] we request nightly coverage of this system with at least one observation per night, preferably in V filter.” Visual observations are also welcome. Notification of the conclusion of the campaign will be made via the forum threads given above.

Please submit observations to the AAVSO International Database as soon as possible. Visual observations are also welcome. If you see EM Cyg going into outburst, please also post to the forum threads above. The astronomers will be monitoring AAVSO data principally via MyNewsFlash but will also see posts in the forums.

Coordinates (J2000.0): R.A. 19 38 40.11  Dec. +30 30 28.4

AAVSO finder charts with comparison stars may be generated using the AAVSO Variable Star Plotter (VSP).

Please submit observations to the AAVSO International Database using the name EM CYG.

This AAVSO Alert Notice was compiled by Elizabeth O. Waagen using information supplied by Dr. Ruiz-Carmona.

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