(cba:news) UX UMa, and IGR J1955+00

Joe Patterson jop at astro.columbia.edu
Thu Jul 16 15:55:23 EDT 2015


Dear CBAers,

Some homework on these two stars!

UX UMa. I've drafted up a paper, minus the interpretation stuff, and 
with figures unlabelled and fragmentary (both attached), but I need some 
help from you.

1. Author list.  Can you check table 1 and supply, if you know it, how 
many nights/hours you contributed to this campaign.  Also, if possible 
and if consistent with some approximation to uniformity, tell me how 
you'd like your observatory/telescope described.  For actual authorship, 
I've usually used the criterion "at least 5% of the data", but since 
there are so many contributors, I might include everyone here.  For 
completeness you might also send your postal address, and if you like 
you can use your observatory name there, if you have one.

2. I was surprised, almost shocked, by the large-amplitude 3.7 day 
signal.  UX UMa has been very thoroughly studied for 60 years by some 
people (Walker, Krzeminski, Smak, etc.) who don't miss much.  They never 
had data like this, but I don't think they could have missed an effect 
this big.  Is the star unusually bright or faint this year?  It  would 
be nice if we knew!  Retroactively is fine.  If you have observed the 
star in this year's campaign, take some data exactly as you did and, 
more or less simultaneously, take some time series with calibrated V.

3.  And if you're so inclined, take another two weeks of time series, 
just to track this large-amplitude signal.

IGR J1955+00.  If you've observed this star, you know it's not like any 
other star we've ever discussed.  The 81 minute orbital (?) variations 
are huge, and the fast variations are huge and crazily fast.  We don't 
have the aperture and time resolution to explore the latter point... but 
the most likely interpretation at this point is that it's a radial 
accretor (AM Her star) and we're seeing cyclotron radiation from the 
accretion funnel.  That would imply an extremely red color for the 
variation - much redder than any (plausible) thermal process could 
manufacture.  We really need *simultaneous* time series in two colors - 
V and I would be an OK choice, and R and I would also be a good pair.
The more strictly simultaneous, the better.  Maybe you can use cba-chat 
to accomplish this: A does V, B does I, and we can thereby synthesize V-I.

Remarks on other stars tomorrow.

joe



(a)
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