Alert Notice 720: Photometry requested for SS Cyg

September 13, 2020

AAVSO Forum threads (scroll to the bottom of a thread for latest posts):
- Campaigns and Observation Reports:
- Cataclysmic Variables:

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Dr. Mariko Kimura (RIKEN, Japan) requests AAVSO assistance in obtaining V and Rc photometry of the cataclysmic variable SS Cyg in support of an orbital period study.

Dr. Kimura writes: "The X-ray flux of SS Cyg is now increasing and 10-times larger than usual.  This object is brightest at X-ray wavelengths in these 25 years.  The quiescent level of the optical luminosity is also rising.  I consider that this increase of the optical baseline may be caused by the X-ray irradiation of the outer accretion disk and/or the secondary star.  In this case, we could see the irradiation component of the secondary star becomes dominant in the orbital light curve.  I would like to confirm this hypothesis by intensive filtered optical photometry during the quiescent state.  

"I tried to derive the orbital profile from the data taken by the AAVSO observers during the recent 1 yr, but the data was not enough.  More observations are necessary and V-band or R-band photometry is preferable."

Multiple V and Rc CCD and PEP observations per night are requested beginning now. Visual observations (not more than one per night for this campaign) are welcome. The campaign will continue until the SS Cyg X-ray flux has returned to usual levels. The end of the campaign will be announced in the AAVSO forum threads given above; please be sure to subscribe to be kept informed.

As Dr. Kimura mentioned, SS Cyg has also been behaving atypically in the optical over the past several months. Observations in the AAVSO International Database indicate that SS Cyg was at visual magnitude 10.8 on 2020 Sep. 13.28120 UT (G. Sarty, Saskatoon, SK, Canada). SS Cyg has a V range of 7.7-12.4.

Coordinates (J2000): R.A. 21 42 42.79  Dec. +43 35 09.9 (from VSX entry for SS Cyg)

Charts with comparison stars for SS Cyg may be created using the AAVSO Variable Star Plotter (VSP).

Please report all observations to the AAVSO International Database using the name SS CYG.

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


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