[vsnet-alert 15663] Re: Next HST observations: SDSS1544+2553 and 1RXSJ105010.3-140431

Boris Gaensicke Boris.Gaensicke at warwick.ac.uk
Mon Apr 29 06:22:07 JST 2013

Dear All,

thanks so much for your help with the HST observations of QZ Lib! The
moon made it tough to get measurements during the critical 24 hours
before HST would slew to the star, but it all worked out well. The COS
spectrum shows a very cool white dwarf, exactly what we were
after ... and it has a so far unique set of emission lines that will
have us scratching our head for a while.

On to the next two:

* SDSS1544+2553 May 1, 2013 04:06:20 to  08:17:24

a long-period (6h) dwarf nova discovered
by SDSS, which is eclipsing, and has reasonably
frequent outbursts (CRTS light
We already
go quite good of coverage over the last ~2 weeks,
and the star shows fairly large-amplitude activity,
V=16.6 +/- 0.4 mag. It is eclipsing, with the following

HJD(phi=0) = 2454878.0062(15)+0.251282(2)E

(see Skinner et al.
We will
need quite dense (every 30min or so) monitoring in
the last ~48h leading up to the HST observations to
distinguish this regular variability from any upwards
trend that would flag the beginning of an outburst...

* 1RXSJ105010.3-140431 May 10, 2013 07:51:01to 12:01:57

this is a short-period WZ Sge candidate, identified from
X-ray emission (2001A&A...376..448M<http://adsabs.harvard.edu/abs/2001A%26A...376..448M>),
that to my knowledge
has not yet had an observed outburst. Let's make sure we know
if the first one happens on May 10th!

Best wishes,


For more information on this HST program, see


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