Alert Notice 733: HST observing schedule for TW Hya

March 8, 2021

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Further to AAVSO Alert Notice 731, Dr. Fred Walter (Stony Brook University) informs us that the HST observations of the T Tau star TW Hya will take place as follows:

09 Mar 2021 00:41:22 UT - 01:34:24 UT
09 Mar 2021 18:07:33 - 19:00:35
10 Mar 2021 14:46:11 - 15:39:13
11 Mar 2021 13:00:06 - 14:20:17
12 Mar 2021 12:49:28 - 14:08:40
13 Mar 2021 14:14:23 - 15:07:25
14 Mar 2021 12:28:39 - 13:44:45
15 Mar 2021 12:18:09 - 13:32:35
15 Mar 2021 23:25:14 - 00:18:16
16 Mar 2021 21:39:22 - 22:32:24
17 Mar 2021 19:53:29 - 20:46:31
18 Mar 2021 18:07:36 - 19:00:38

Dr. Walter says that "the important thing is to get dense-enough establish trends and periodicities."

Observations are requested in four bands (B,V and either Cousins RI (preferred) or Sloan ri). Once the HST observations are completed, please continue to monitor TW Hya through April 5, but at a lower cadence, with one observation per night. The satellite TESS is also observing TW Hya and will continue to do so through March 27.

"TW Hya is fairly bright, with a mean V ~ 11, and a historical range from 10.6 to 11.3 (from VSX). The typical day-to-day range of variability is +/- 0.1 mag. I seek to extract colors accurate to better than 2% (0.02 mag), which requires CCD photometry accurate to better than 0.01 mag."

TW Hya is being observed as part of the ODYSSEUS pre-main sequence star program that is underway. As noted in Alert Notice 731, 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.

Coordinates (2000.0): 11 01 51.91 -34 42 17.0 (from VSX page for TW Hya)

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

Please submit observations to the AAVSO International Database using the name TW HYA.

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



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