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Looking back to two late summer maxima

The Mira type variables Chi Cygni and R Ursae Majoris passed through their 2016 maxima during the late summer.

This report is based on observations reported by Don Matthews, Jonathan Shanklin, Matthew Barrett, Tracie Heywood, Tony Markham and Bob Steele.

Chi Cygni

The years 2013-2015 had produced three very contrasting maxima. The maxima of May 2013 and August 2015 had been considerably brighter than the average peak value, while that of late June 2014 had only reached around mag 6.5, making it one of the faintest ever seen.

We had no way of knowing in advance how bright (or faint) the maximum of 2016 would be. We could only say that it would happen in mid September (give or take a week or two).

In the event, it turned out to be a pretty "average" maximum, peaking near mag 5.0. As can be seen, the maximum was rather "flat-topped", with little change in brightness being seen between late August and late September, before the fade eventually set in.

The next maximum of Chi Cygni is expected to occur around late October 2017.

R Ursae Majoris

Whereas Chi Cygni will (usually) reach naked eye visibility at maximum, observation of the maxima of R Ursae Majoris requires the use of binoculars. The brightest maxima can reach mag 6.7, but the average peak is about half a magnitude fainter.

At the start of 2016, R Ursae Majoris was still fading from its late 2015 maximum. It remained well below binocular visibility throughout most of first half of the year, but telescopic observations by Don Matthews showed it passing through minimum in April. Poor weather and mid-year twilight meant that most of the subsequent rise back to maximum went unobserved, but by early August it was closing in on maximum once again. Maximum was reached by late August and little change was then seen in brightness for a few weeks. By October, the fade was clearly underway and by late November R UMa had once more dropped below binocular visibility.

The next maximum of R Ursae Majoris is due to occur in July 2017.

Added by:  Tracie Heywood