Alert Notice 796: Monitoring requested for 12 dwarf novae in support of HST observations in 2022-2023

The target table below is being updated as each target is completed or rescheduled.  -  Elizabeth O. Waagen

Notes:  LL Lyr was not able to be observed due to issues with HST. It has been rescheduled for the 2023-2024 year of this campaign.   -  Elizabeth O. Waagen, October 24, 2023

Please observe LL Lyr nightly in anticipation of upcoming HST observations in September. An Alert Notice will be issued when it has been scheduled.  -  Elizabeth O. Waagen, September 5, 2023

V479 And was successfully observed in December 2022.  -  Elizabeth O. Waagen, February 3, 2023

HST observations of ZTF18acxhphf were successfully carried out. V479 And has been rescheduled for December 2022. Please continue nightly snapshots of it and CH UMa, the other December target, as well as beginning coverage of ASASSN-18dg, the January 2023 target.  -  Elizabeth O. Waagen, December 6, 2022

HST observations of ZTF18acxhphf have been postponed to November 2022. Please continue with nightly snapshots.  -  Elizabeth O. Waagen, October 24, 2022

October 19, 2022

AAVSO Forum threads (scroll to the bottom of a thread for latest posts):
 - Campaigns and Observing Reports:
 - Cataclysmic Variables:

Please subscribe to these threads if you are participating in the campaign so you can be updated by the astronomers and by HQ. Join in the discussion or ask questions there!

Drs. Anna Francesca Pala (European Space Agency, ESAC, Spain) and Thomas Kupfer (Texas Tech University), on behalf of a large consortium of astronomers, have requested AAVSO observers' assistance in monitoring 12 dwarf nova cataclysmic variables in support of observations with the Hubble Space Telescope.

Coverage is requested to begin immediately and continue through September 2023. The month each star is scheduled to be observed by HST is given in the table below. When specific HST dates are announced, they will be posted in the forum threads (above) related to this campaign. The webpage for this Alert Notice will also be updated.

This 2022-2023 campaign on dwarf novae is the third part of a larger campaign which includes additional dwarf novae to be observed in 2023-2024 (to be announced later), 11 dwarf novae observed in 2021-2022 (AAVSO Alert Notice 758), and 15 VY Scl stars for which coverage (2021-2024) was requested in AAVSO Alert Notice 754.

Dr. Pala writes: "In the last 20 years, the study of compact interacting binaries has led to two major breakthroughs in astrophysics: the discovery of dark energy and the first detection of gravitational waves. Although binaries are critically important to probe the properties of the Universe and to test fundamental physical theories, our understanding of their evolution and final fate is still far from being complete.

"Accreting white dwarfs are ideal laboratories in which to test the models of compact binary evolution. We are carrying out a large program with the Cosmic Origin Spectrograph (COS), onboard the Hubble Space Telescope (HST), to obtain ultraviolet spectroscopy of 43 accreting white dwarfs, with the aim to accurately measure their effective temperatures, masses and accretion rates. These fundamental parameters will provide firm observational constraints on the angular momentum loss mechanisms driving the evolution of all types of binaries, and on the formation channel of the brightest gravitational wave sources. Moreover, we will unveil the intimate connection between accreting white dwarfs and Type Ia Supernova explosions.  
"Because of the extremely variable nature of accreting white dwarfs, we have to make absolutely sure that the HST observations are obtained during quiescence, as the detectors of the Cosmic Origin Spectrograph can be damaged by exposure to too much light. The outstanding support from the AAVSO observers is crucial to ensure the success of this program, which entirely relies on ground-based observers who can monitor the targets in the weeks prior to the HST observations."

INSTRUCTIONS: To assess the quiescent state of each target, nightly observations in V starting at least three weeks before the HST observations are requested, then a more intensive monitoring the week before the observations, and then nightly monitoring again for two/three weeks after the observations. As with all targets for HST, it will be crucial to have a positive V measurement 24 hours before the scheduled HST time so the HST team can make a go-nogo decision.

Please begin observing ZTF18acxhphf immediately. Because the specific HST dates of the other targets are not known, it would be prudent to begin nightly coverage of each of them the month before the HST window given in the table. For example, begin observing CH UMa (scheduled for December) on November 1. Please focus your efforts on the next upcoming target, but if you have time, it would be good also to make observations of the later targets in order to give good long-term coverage for the HST planners.

A minimum SNR~20 is requested. If the target is too faint to obtain the minimum SNR in V, switch to CV. If a target is observed going into outburst, please submit your observation(s) as soon as possible and begin obtaining multiple observations per night.

Dr. Pala adds: "We know that some observers carry out time-series observations and also spectroscopy, and we welcome any additional contributions. Nonetheless the monitoring to assess quiescence should have the highest priority since, without it, there is the risk to lose the allocated orbits.

"In case of time-series observations, an uninterrupted light curve in a single filter (preferably B or V) would be better than alternating with different filters. CV observations can still be useful but V-filter observations should be the priority (whenever possible).

"DSLR observations, particularly if they are transformed to V, will be useful and are welcome. Visual observations will also be very valuable."

Dr. Pala further informs us that a website that includes all the information on the progam is in preparation. When it is ready, the link will be posted in the forum threads given above.

Targets: October 2022 – September 2023

Name (primary VSX name) R.A. (2000) Dec (2000) Range CV type HST window

Scheduled for/Completed

ZTF18acxhphf (Aqr) 22 52 37.05 -05 19 17.0 18.4-21.3 g IBWD+E October 2022

October 28 Nov 17 17:32:14 UT -  Nov 18 00:50:55 UT completed

V479 And 00 18 56.93 +34 54 44.2 16.7-17.9 V AM: November 2022

December 22-23 2022 completed

CH UMa 10 07 00.72 +67 32 47.5 10.7-15.3 V UG December 2022 completed
ASASSN-18dg (Eri) 04 07 49.30 -00 07 16.7 15.5-21.3 g UGSU/IBWD+E January 2023

February 10-11 completed

SDSS J080449.49+161624.8 (Cnc) 08 04 49.49 +16 16 24.9 17.8-19.1 CV IBWD February 2023 February 16 completed
SSS 100511:061754-362655 (Col) 06 17 53.83 -36 26 54.5 14.2-18 CV UG March 2023 March 24 completed
GP Com 13 05 42.40 +18 01 03.8 15.7-16.2 V IBWD April 2023 May 25
SDSS J161909.10+135145.5 (Her) 16 19 09.10 +13 51 45.6 15.2-17.9 g UGZ May 2023 May 5 completed
HP Lib 15 35 53.07 -14 13 12.2 13.55-13.8 V IBWD+ZZB: June 2023 June 23 completed
V1082 Sgr 19 07 21.87 -20 46 50.5 13.4-15.6 V DQ: July 2023 August 11 - no, too risky to observe
V584 Lyr 19 10 59.42 +28 56 38.7 14.3-19.6 V UG August 2023

August 24-25 completed

LL Lyr 18 35 12.82 +38 20 04.3 12.9-18.5 V UG September 2023 not observable-added to 2024

Charts with comparison stars for the targets may be created using the AAVSO Variable Star Plotter (VSP).

Please submit observations in a timely manner, and as soon as possible if a star is seen going into outburst. Use the primary name given in the above table.
  - Photometry and visual observations: AAVSO International Database
  - Spectroscopy: AAVSO Spectroscopy Database
(links at the end of this Alert Notice)

Observers are encouraged to subscribe to the forum threads above and use them to report any interesting observations and post questions or comments for Dr. Pala and Dr. Kupfer.

Dr. Pala writes that "Our team deeply values the support from AAVSO observers and significant contributors will be invited to join the papers as co-authors."

This AAVSO Alert Notice was compiled by Elizabeth O. Waagen using material provided by Dr. Pala.


Information on submitting observations to the AAVSO may be found at:
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 - Spectroscopy:


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