[vsnet-alert 15538] PU CMa

[Boris Gaensicke]

Dear All,

well ... if last week with V485 Cen was exciting, this week
was dramatic.

The target, PU CMa, a relatively poorly studied SU UMa
dwarf nova with a very short period (81.63min) decided
to go into outburst just 4 days before the scheduled HST
observation ... and, it is one of our brightest targets, so
not too much headroom to the bright object limit. No
need to tell you that this caused much tension at STScI,
as to (a) the object would fade fast enough to drop
below the safety limit of V~14.5, and (b) if there is any
chance that this is a pre-cursor of a superoutburst. The
scheduled time of the HST observations was tonight, UT00.

Well...

http://www.aavso.org/lcg/plot?auid=000-BCV-055&lastdays=8&obstotals=yes&calendar=calendar&grid=on&visual=on&uband=on&bband=on&v=on&pointsize=1&width=800&height=450

shows the last week of monitoring... it faded in a quite remarkably
linear way,  until this morning. I didn't sleep terribly well, and when
I woke up, the next few data points from Australia appeared, showing
an intermittent rise to ~14.5 - a pre-cursor? By that time, STScI
had to take a decision, and went with "go".

These were a few tense hours, as there was the small, but
non-zero chance that this would get brighter again. As  the
countdown ticked away, 2 images from South Africa,
and then the first image from Chile confirmed that PU CMa
had settled at V~15, and all went well... HST observed, and
we got a spectrum that seems to show the white dwarf,
heated by the outburst, and a still relatively bright
accretion disk.

Thanks the heroic effort that you have put in over the past
few days to make this happen!

Best wishes,

Boris

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For more information on this HST program, see

http://deneb.astro.warwick.ac.uk/phsdaj/public_html/12870/
http://deneb.astro.warwick.ac.uk/phsdaj/public_html/12870/Targets.html