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HST campaign on TCP J21040470+4631129 - Alert Notice 714

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weo
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HST campaign on TCP J21040470+4631129 - Alert Notice 714

AAVSO Alert Notice 714 announces an observing campaign on the WZ Sge-type variable TCP J21040470+4631129. Please see the notice for details and observing instructions.

Many thanks, and Good observing,

Elizabeth O. Waagen, AAVSO HQ

weo
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HST date/time set for TCP-J21040470+4631129 observations

The HST observations of TCP-J21040470+4631129 (AAVSO Alert Notice 714) have been scheduled for

Sep 12, 2020 07:16:37 to 13:07:28 UT

For the HST observations to take place, it is essential to have a positive observation 24 hours before this time showing the system in quiescence, so the night of September 10-11 UT is crucial.

Please continue nightly V snapshots through September 8, then more intensive monitoring September 9 through 12, then nightly snapshots through September 15. Please report observations promptly, especially from September 9 through 12.

Many thanks, and Good observing,

Elizabeth

weo
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Tonight critical for TCP J21040470+4631129 coverage

Tonight (2020 Sep 10-11) is critical for coverage of TCP J21040470+4631129 - please see Boris' post of Sep 4 in the Campaigns forum thread for this campaign; quoting from it: "We will have to report a detection of the system at its quiescent magnitude to STScI on noon (EDT) Friday Sept. 11th. Therefore observations Thursday night, pushing as far into Friday morning as visibility allows are particularly important (US observers will have an advantage here). And please report the data as soon as you get them."

Also, please continue your coverage through at least Sep 12 (see the Alert Notice).

Many thanks and Good observing,

Elizabeth

BorisGaensicke
Decision point: 9am EDT, Friday Sept. 11th

We have had an update from STScI that they need to anticipate the decision whether they consider it safe to observe TCP J21040470+4631129 with Hubble by three hours. That means the need to have the latest measurements of the brightness of the system by 9am EDT on Friday, Sept. 11th.

Thanks for your help with this, and clear skies!

Boris

BorisGaensicke
We are go for tomorrow's COS observations

STScI approved the COS observations for tomorrow. What happens next is that the flight engineers at NASA Goddard will send a tiny command to Hubble to swap the two sets of co-ordinates stored in the on-board observing program, so that TCP-J21040470+4631129 will go into the aperture of COS, rather than the blank sky position that was the safety default.

Thanks so much for all your observations, without which this HST program would not have been possible. 

BorisGaensicke
Success - almost!

First of all, thanks so much for your detailed observations of TCP J21040470+4631129 that were the key to get the HST observations through the final approval stage.

The HST ultraviolet observations of this CV went ahead, and the spectra we got reveal a fantastic amount of detail: the white dwarf totally dominates at ultraviolet wavelengths, and is still rather hot, in fact, hotter than any similar system a year into cooling from the outburst.  That is consistent with the outburst having been tremendously large and long, and we will be able to work, among a number of things, out how much energy was dumped into the white dwarf during the outburst. What is clear is that it will take the star many years to cool back into quiescence.

But, as mentioned, in the subject, there is a "but": during two of the six exposures, the COS shutter remained closed. It took a few days to figure out the reason - and to our relief, it wasn't the star misbehaving, or a mistake in the observing sequence: Hubble struggled for some time to acquire the guide stars it needs for the precision pointing, and for safety reasons the COS shutter remains closed in that case.

We're still establishing how much the loss of data affects the goals of this program, and there is a possiblity that the failed observations may be repeated. For that reason, it would be very helpful to continue  monitoring of TCP J21040470+4631129, though at a less intense level, maybe a few snapshots per week.

I'll get back in touch in a week or two.

Boris

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