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Update on Gaensicke HST campaign

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Matthew Templeton
Update on Gaensicke HST campaign

Hello everyone,

Boris Gaensicke sent the following to several people and mailing lists of the BAAVSS and CBA regarding recent happenings with his HST campaign to observe dwarf novae in quiescence.  I'm reposting it so that those engaged in the campaign have a chance to see feedback from the PI.

Thanks to all AAVSO observers participating in this and all of our other campaigns!


Subject: (cba:chat) PU CMa

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.


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,


AAVSO 49 Bay State Rd. Cambridge, MA 02138 617-354-0484