(cba:news) ER UMa and BK Lyn (Joe Patterson) [2012-05-04T21:16:28Z]

Dear CBAers,

Here's a message from Enrique, which I heartily endorse.  The delicate 
issues of period-finding are accomplished now, due to all the diligent 
and global coverage.  But when we want to study *stability* of these 
periods, we do need *some* coverage late and early in observing seasons 
(when the length of the time series is necessarily short).  So if you're 
an ER UMa soldier, you can take some breaks, but squeeze in a few more 
runs before twilight shuts you down.  Runs >2 hr, that is; below 2 hrs, 
the information is just too slim.

Exactly the same situation applies to BK Lyn. This one is a touch more 
critical, though, for two reasons:

1. BK Lyn has not maintained equal popularity among CBAers; some of you 
are getting tired.  Summon just a little more energy for the gun lap.

2. BK Lyn did a most amazing thing this year.  It turned into a dwarf 
nova!  While we have plenty of data documenting (and proving) this, a 
key question is: when a novalike turns into a dwarf nova, does it do so 
just once (and then smoothly evolve), or does it *stagger* its way? 
Because I believe this star to be the remnant of a 2000 year old nova, 
the former possibility (if true) would set the timescale for old novae 
to turn into dwarf novae.  That number has never been known... but is it 
known now?

Keep the faith on other targets, which are much more seasonal.  And if 
you're covering CR Boo or V803 Cen, can you loudly announce it when 
these stars go into superoutburst (signified when they reach V~13 and 
show big superhumps)?  The supers only last a couple of days, and we 
need to get global coverage in order to confidently parse the period 
structure.

joe



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Return-Path: <edmiguel63@xxxxxxxxx>


Hi Joe

 The latest data on ER UMa show that the latest superoutburst is over
(the third well-covered this season),
with ER UMa returning to quiescence ...... still flashing negative
superhumps. After ~150 days of intensive coverage during 2012 it's
probably time to stop our thorough follow-up on ER UMa and concentrate
on other targets. Next super is expected for 5-6  June, and in the
meantime, time series will get unavoidably shorter. However, I'm still
interested in registering when the next super exactly starts - just to
have another value of the recurrence time, so as to have further proof
of the likely lengthening of the supercycle in ER UMa. For this, I
would suggest stopping ER UMa coverage now, but carrying out ~2 hour
early-evening time series starting by the end of May until the
expected June superoutburst is
observed.

 Enrique