Alert Notice 607: MASTER OT J132104.04+560957.8 photometry urgently needed for XMM observations

December 1, 2017: Dr. Mark Kennedy (Jodrell Bank Centre for Astrophysics, University of Manchester) requests AAVSO observers' assistance in providing optical coverage of the polar MASTER OT J132104.04+560957.8 in support of observations with the XMM-Newton satellite scheduled for this Sunday, 2017 December 3, 08:35:31 UT - 16:38:51 UT.

The XMM-Newton observations themselves will not include an optical component, so photometry provided by AAVSO observers is essential for the interpretation of the X-ray data.

Dr. Kennedy writes: "MASTER OT J132104.04+560957.8 is a fascinating polar which shows very dramatic optical variability. The most dramatic aspect of the object's light curve is the occasional disappearance of one of the optical maxima. The cause of these missing maxima is the focus of our XMM-Newton observations, and we require optical observations around the time of the X-ray observations to accurately construct an orbital ephemeris, and to allow us to relate any peculiar behavior seen in the X-ray light curve with the variations in the light curve produced by AAVSO volunteers."

He continues that MASTER OT J132104.04+560957.8 has a V range of 16.5 to 19.7, "depending heavily on whether the maxima are missing or not." The VSX range is given as V = 16.1 - 20.

Photometry is requested using Johnson V or Clear (unfiltered) with a V zero point; V is preferred to CV. Time series lasting as long as possible are requested, with as short a cadence as can be achieved with a S/N of at least 10. "Short exposures (<2 min) are encouraged so we can adequately sample variations during the orbit (the orbital period is 1.5 hours, so the better sampled this period is, the easier phasing the X-ray data will be)."

Coverage is requested beginning immediately and continuing at the same cadence through December 6 to enable the construction of the accurate orbital ephemeris needed to correctly phase the X-ray data.

Coordinates (2000.0): R.A. 13 21 04.04  Dec. +56 09 57.8

Finder charts with a comparison star sequence for MASTER OT J132104.04+560957.8 may be created using the AAVSO Variable Star Plotter (VSP). To see the sequence, an 'E' (30 arcmin) scale chart or one with smaller field of view must be selected.

Please submit observations to the AAVSO International Database using the name MASTER OT J132104.04+560957.8.

This observing campaign is being followed on the AAVSO Campaigns and Observing Reports online forum at

This AAVSO Alert Notice was compiled by Elizabeth O. Waagen


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