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Alert Notice 639: CH Cyg coverage requested

July 3, 2018: The symbiotic variable CH Cyg is undergoing a fade that began on June 25. Multicolor photometry is requested; V and particularly B should take priority over Rc and Ic. Observations made two to three times a week are sufficient; time series observations are not needed. Visual observations are also requested and encouraged. Spectroscopy would be very welcome and appreciated. Coverage should continue throughout the observing season.

The AAVSO has had an ongoing campaign on CH Cyg for Dr. Margarita Karovska (Harvard-Smithosonian Center for Astrophysics) underway for the past several years (links below). These fading events are of particular interest when the system fades most in B, as is currently happening. There is not a long history of B observations of CH Cyg, so it is essential to have good coverage in B throughout the fading episode and afterwards.

Information on the CH Cyg campaign may be found in: AAVSO Alert Notice 454 and AAVSO Special Notices #267, #268, #294, #320, and #417.

Coordinates:  RA 19 24 33.07   Dec. +50 14 29.1  (J2000.0)

Charts: Charts with a comparison star sequence for CH Cyg may be created using the AAVSO Variable Star Plotter (VSP).

Submit observations: Please submit observations to the AAVSO International Database using the name CH CYG.

AAVSO Forums: CH Cyg is the topic of the AAVSO Campaigns and Observation Reports forum thread https://www.aavso.org/ch-cyg-fading

and the AAVSO Cataclysmic Variables forum thread https://www.aavso.org/ch-cygni-precipitous-fading

 

This AAVSO Alert Notice was compiled by Elizabeth O. Waagen.
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