Alert Notice 802: HST observing BP Tau this week - photometry needed

December 12, 2022

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Further to AAVSO Alert Notice 801, Dr. Frederick Walter (Stony Brook University) informs us that HST observations of the classical T Tau star BP Tau  have been scheduled for:

Start time: 13 Dec 2022 03:23:07               End time: 13 Dec 2022 04:13:57
Start time: 15 Dec 2022 10:54:38               End time: 15 Dec 2022 11:45:28
Start time: 17 Dec 2022 00:59:04               End time: 17 Dec 2022 01:49:54

Times are UT. Photometry leading up to, or during the HST observations, will be particularly useful. Additional observations with HST will be scheduled for before 2023 January 7.

Dr. Walter provides the following information and instructions:

"ODYSSEUS is an international collaborative campaign to understand the processes involved in the formation of low mass stars, their circumstellar disks, and their planets, via the time-variability of these systems. Please read other Alert Notices (starting from AAVSO Alert Notice 725) and forum notes on this program for more details.

Observations of the final HST/ULLYSES/ODYSSEUS target, BP Tau, are underway. "This is a monitoring target, so the HST will obtain 4 sets of UV spectra over an interval of about 3 weeks (3 rotation periods). In addition, BP Tau is in TESS sector 59, which will be observed continuously through 23 December.

Target Details:
Target        RA  (J2000)  Dec               <V>      Range           HST  observation dates
BP Tau     04 19 15.83 +29 06 26.9    12.1     11.5-12.7 V    2022 13 December - 2023  7 January (see exact times above)

"I ask that those of you who can to obtain CCD filter photometry (BVRI preferred, and U if you can) at least nightly for BP Tau through January 7.

"Please try to obtain 1% S/N (0.01 mag), so that colors are accurate to about 2% (0.02 mag).

"Additional exact times of the HST observations will be announced in an Alert Notice and in the above forum threads when available, the hopes of obtaining exact simultaneity on occasion. But the important thing is to establish the trends in the color variability. Typical variability timescales are a few hours. TESS will catch the flares. Note that there will be no TESS coverage of BP Tau for the second half of the HST observations (23 December - 7 January); during this interval your photometry will be even more important.

"Thanks again for contributing to a very successful and productive program."

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

Please submit observations to the AAVSO International Database using the name BP TAU.

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


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


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