Alert Notice 756: GM Aur being observed by HST and TESS

The final set of HST observations for GM Aur have been scheduled:

AAVSO Forum threads (scroll to the bottom of a thread for latest posts):
- Campaigns and Observation Reports: https://www.aavso.org/odysseus-v-photometry-gm-aur-support-hst-and-tess-01
- Young Stellar Objects: https://www.aavso.org/odysseus-v-photometry-gm-aur-support-hst-and-tess
Note that these forum threads are NOT the same as for other Alert Notices related to the ODYSSEUS program.

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

Dr. Frederick Walter (Stony Brook University) requests AAVSO observers' assistance in monitoring the classical T Tau star GM Aur in support of observations with HST and TESS scheduled for October-November 2021.

Dr. Walter provides the following information and instructions:

"Part V of the ODYSSEUS pre-main sequence star program starts this month. 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 forum notes on this program for more details.

"The HST will monitor the pre-main sequence star GM Aur for 3 stellar rotation periods (about 18 days) starting 13 October. It is being observed simultaneously with TESS.

"If you can, please obtain CCD BVRI observations of this star at least nightly during this campaign (Oct 13-Nov 1). If you can observe during the HST windows, please do so." Filters in order of priority are B and V, then Ic, then Rc.

"Because we will have TESS photometry, your primary contribution will be the photometric colors. Please try to obtain 1% photometry (0.01 mag uncertainty) so we can compute colors to better than 2%. It is the color changes that will help us determine the cause for any changes in the UV line fluxes, or in the overall brightness.

"Thank you for your contributions to the earlier parts of the ODYSSEUS campaign. Your participation in this campaign is a big part of its success.

"Please upload any data you get to the AAVSO International Database. Thanks in advance for your contributions to this campaign.

The current HST schedule is:
Date        Start  (UT)      End
13 Oct 2021 11:54:10        12:46:38
15 Oct 2021 06:46:59        07:39:27
16 Oct 2021 16:08:03        17:00:31
17 Oct 2021 20:46:03        21:38:31
19 Oct 2021 14:23:24        16:05:31
20 Oct 2021 21:48:12        22:40:40
22 Oct 2021 15:03:54        15:56:22
23 Oct 2021 22:49:33        23:42:01

"The other 4 observations will be scheduled next week, and should occur between October 21 and November 1.

GM Aur particulars:
Position: 04 55 10.97 +30 21 59.7 (J2000, from VSX page for GM Aur).
Magnitude: V~12.2
Spectral type: K7

Note: In 2019 TESS observations [showed] GM Aur varied by about 0.05 mag on timescales of a few days.

Note also that GM Aur is within 28 arcsec of 2MASS J04551015+3021333, a star of comparable brightness (G=11.3), of which little is known. Since this star will be blended with GM Aur in the TESS images (21 arcsec pixels), please also extract photometry for this star. We will need to know how it is varying (if it is) in order to assess GM Aur's variability. The near-IR colors and the GAIA parallax suggest that this star is a background giant.

2MASS J04551015+3021333 particulars:
Position: 04 55 10.16 +30 21 33.2  (J2000) 
Magnitude: G=11.3

Note: this star is not in VSX as of October 14 but will be added. If you are not able to submit observations of 2MASS J04551015+3021333 to the AAVSO International Database, please hold on to the observations until it is added to VSX; a note will be put in the forum thread above when that happens.

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

Submit observations: Please submit observations using the name GM AUR to the AAVSO International Database.

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

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SUBMIT OBSERVATIONS TO THE AAVSO

Information on submitting observations to the AAVSO may be found at:
 - Photometry/visual observations: https://www.aavso.org/webobs
 - Spectroscopy: https://www.aavso.org/apps/avspec/

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