Alert Notice 780: Observations needed for four YSO targets being observed with HST

June 14, 2022

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Dr. Frederick Walter (Stony Brook University) requests AAVSO observers' assistance in monitoring four T Tau stars in support of HST observations scheduled for June 16 - 19 -- THIS WEEK. As part of the HST ULLYSES program (which is part of the larger ODYSSEUS program), the HST is scheduled to obtain UV spectra of these accreting T Tauri stars. It would be helpful to have BVRI photometry for them in order to help interpret the UV spectra.

All four stars will be observed during this week, so coverage of them is needed beginning NOW; please see the table for exact dates and times.

Dr. Walter, who thanks AAVSO observers for their contributions to this program to date, provides the following information:

Name RA (2000.0) Dec (2000.0) Range (from VSX) MeanMag HST observations (UT) Coverage requested
IM Lup 15 56 09.16 -37 56 06.4 11.73 - 12.09 y 11.93 V 2022 Jun 16 02:00:37 - 12:19:52 Now - June 20
RX J1556.1-3655 (Lup) 15 56 02.10 -36 55 28.3 12.3 - 14.5 V 13.85 V 2022 Jun 17 01:50:18 - 13:44:59 Now - June 21
Sz 100  (Sco) 16 08 25.76 -39 06 01.2 15.4 - 16.9 V 15.54 V 2022 Jun 18 00:03:12 - 13:34:43 Now - June 22
Sz 104  (Sco) 16 08 30.81 -39 05 48.8 16.1 - 17.1 V 15.25 V 2022 Jun 18 14:25:51 - Jun 19 13:25:04 Now - June 23

If you can observe these targets, please obtain digital BVRI photometry on the dates specified. It is important to get single BVRI sequences each night, but longer sets of data would be useful if they can be obtained simultaneously with the HST observations. There will not be any TESS observations.

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

Please submit your observations to the AAVSO International Database using the names given in the table above.

Targets for this large campaign have been announced and discussed in numerous AAVSO Alert Notices, beginning with AAVSO Alert Notice 741.

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



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