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Alert Notice #480: MR UMa superoutburst coverage requested for HST observations

March 8, 2013:  Dr. Boris Gaensicke (Warwick University) has requested observations of the currently-outbursting SU UMa-type cataclysmic variable MR UMa in preparation for and support of HST observations scheduled for the week 2013 April 4-7.

Dr. Gaensicke says that, since MR UMa appears to be in superoutburst, the HST observations scheduled for next month "might offer an unplanned opportunity to measure the post-outburst cooling of the WD in this system." Observations in the AAVSO International Database show MR UMa at magnitude 13.662 V on 2013 March 8.35944 UT (JD 2456359.85944, J. Roe, Bourbon, MO), down from 13.3 visual on March 2.841 (2456354.341, P. Dubovsky, Kolonica, Slovakia). The outburst may have begun earlier - MR UMa is around 13 V at maximum, and the most recent observation prior to the one on March 2 was 9 days earlier (February 21.41667, 2456344.91667, C. Chiselbrook, Marietta, GA) and showed MR UMa at <13.9 visual. The previous outburst, also a superoutburst, occurred in June 2012.

Nightly observations are requested now through at least April 10. As the HST observations draw closer, the cadence of observations may be revised. For obtaining magnitudes, V observations are preferred; visual observations are also welcome.

Coordinates:  R.A. 11 31 22.39  Dec. +43 22 38.4  (2000.0)

Charts for MR UMa made be created using the AAVSO Variable Star Plotter (

Please submit observations to the AAVSO International Database as MR UMA.

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


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