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Wed, 07 Dec 2016 - The decreasing amplitude of R Scuti

Observations by section members show that R Scuti has had a relatively quiet year in 2016, compared with recent years.

There was a deep minimum in the early spring and what appear to be three shallow minima later in the year (June, early Sep, early Nov).

Maybe, if we want to keep to the "rule" that R Scuti should show alternate deep and shallow minima, the second shallow minima could be interpreted as just a rather shallow "deep minimum"). In reality, though, R Scuti doesn't always follow the "rules".

Although the overall brightness range seen during 2016 has still been over two magnitudes, this has been less than that seen in recent years.

If we look at SPA observations as far back as 2013 ,we can see that the deep minima were somewhat deeper

Indeed, the deep minima of 2013 were so prolonged that R Scuti didn't brighten all the way back to maximum before the fade into the next deep minimum started - there was certainly no sign of an intervening shallow minimum. The most impressive rate of brightness change occurred in late Oct/early Nov, with R Scuti brightening by nearly four magnitudes in little more than a couple of weeks!

2014 and 2015 then showed the deep minima becoming less deep.

This behaviour of R Scuti is not that new, however. If we look at the BAA VSS light curve going back to 1982, we can see that there have been years in which the deep minima have been very deep and other years in which the overall brightness range of R Scuti has been rather small - somewhat smaller in some years than that of 2016.

Is there some long term periodicity that affects the depth of the deep minima? There is certainly a hint of some wave effect in the depths of the deep minima, but there is no clear sign of any period (e.g. looking at the deeper minima in 1996, 2006 and 2013, we see that 1996 to 2006 was 10 years, but 2006 to 2013 was only 7 years)

 

Added by: Tracie Heywood