HST ULYSSES Southern T Tauri campaign

REVISED TARGET INFO (as of April 23) IS IN POST BELOW THAT ANNOUNCES ALERT NOTICE 741

UPDATED April 18. June 17, July 17, July 30

JUNE 17 UPDATE: Due to an HST safing event, the observations of Sz 111, Sz 130, and STc2d J160000.6-4221582, scheduled for this weekend, are unlikely to be done. The targets are still in the TESS observing window, so please keep observing. Details on rescheduling will be posted when available.

July 17 UPDATE: HST observations have resumed. Two targets are re-scheduled for next week:

 - Sz 130:  22 Jul 2021 13:17:02 - 22 Jul 2021 21:32:41
 - STc2dJ 160000.6-422158: 23 Jul 2021 04:28:52 - 23 Jul 2021 16:19:45

Please add these two targets to your observing queue if practical, through July 22 (Sz 130) or July 23 (SSTC2DJ160000.6-422158).

July 30 UPDATE: HST will observe Sz 76 on August 8 from 11:27:38 through 18:56:12 UT. Please add this target to your observing queue if practical. There will be no TESS data, so frequent (at least nightly) BVRI observations will be helpful for setting the context for the HST spectra.

12 nights of monitoring observations of RU Lup are scheduled Aug 10-21. Details will be forthcoming soon.

Part III of the ODYSSEUS pre-main sequence star program starts later 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.

Thanks to all of you who participated in and obtained data for parts I (13 northern T Tauri stars) and II (monitoring of TW Hya) of this program.

The HST will obtain snapshots of a number of  pre-main sequence (T Tauri) stars in the south over the coming months. The 17 targets for his campaign are all brighter than V~16. Most of these observations will take place while the targets are in the TESS field, yielding about 27 days of continuous 600-1000nm photometry with a 10 minute cadence.

TESS data, both in terms of length of coverage and data quality, cannot be matched from the ground, but TESS is a single channel photometer operating in the red. We need ground-based optical photometry to place the TESS magnitudes in context, and determine what the stars may have been doing when HST was observing them.
- Pre-main sequence stars may experience enhanced accretion events or long-lived flares, either of which cause the star to become bluer, and
- they may experience variable circumstellar extinction, which may cause the star will become redder, or
- if the variable extinction is caused by optically-thick (opaque) irregularities in the circumstellar disk, their colors may not change as they fade.
Clearly, changes in extinction in particular are important for interpreting the UV spectra, which are very sensitive to the absorption.

The targets scheduled for late April through early June are:
Target                       RA   (2000)   DEC     <V>         HST plan                    TESS         
CHX18N            11 11 46.32    -76 20 09.2  11.9     April 29 14:30-23:37    4/28 - 6/24
GQ Lup (Sz75)  15 49 12.10    -35 39 05.1  11.4    May 3 13:00-01:30       4/28 - 5/25

HM Lup (Sz72)  15 47 50.63    -35 28 35.4  14.8    May 4 11:30-23:00       4/28 - 5/25

GW Lup (Sz71)  15 46 44.73   -34 30 35.5  13.5    May 5 11:00-23:30       4/28 - 5/25

Sz77                  15 51 46.95    -35 56 44.1  13.3    May 7 10:30-22:30       4/28 - 5/25

Sz76                  15 49 30.74    -35 49 51.4  15.2    May 10 0900-20:00      4/28 - 5/25
Sz76   revisit     15 49 30.74    -35 49 51.4  15.2    June 29                                            see note for June 17
Sz76   revisit 2  15 49 30.74    -35 49 51.4  15.2    August 8 11:27 - 18:56                       
Sz66                  15  39  28.28  -34 46 18.0  15.0    May 24 03:30-16:00     4/28 - 5/25   see note
Sz45                  11  17  37.00   -77 04 38.1  13.5   May 25 03:00-14:00     4/28 - 6/24
XX Cha              11  11  39.65   -76 20 15.2  15.3   May 29/30 0:00-11:30  4/28 - 6/24
GX Cha (HN 5)  11  06  41.79   -76 35 48.9  15.6   May 31 0:00-09:30       5/26 - 6/24
IN Cha               11  12  09.84   -76 34 36.6  16.5   June 5/6 21:00-07:00   5/26 - 6/24

Sz 130                16 00 31.25    -41 43 37.2  14.7   July 22 13:17 - 21:32  5/26 - 6/24  See note for July 17

SZ 111                 16 08 54.69    -39 37 43.1 14.0   June 20 18:12 - 22:19  5/26 - 6/24 

STc2d J160000.6-4221582   16 00 00.60  -42 21 56.8  July 23 04:29 - 16:19  5/26 - 6/24   See note for July 17

T Cha                 11 57 13.44   -79 21 31.7  11       ---                                 4/28 - 6/24

RU Lup              15 56 42.31   -37 49 15.5  10     10 Aug - 21 Aug               ---      

Target Notes:

- The TESS column indicates the dates that the target is in the TESS field. CHX18N and T Cha are near the ecliptic pole, and will be viewed for 54 days.

- Note that the HST times are preliminary and may yet change, but it is likely they will fall within the posted window.. The final schedule will be posted here when available.

- T Cha is not an HST target; please obtain occasional observations while the target is in the TESS window to let us correlate colors with TESS magnitudes.

- RU Lup will be monitored by the HST for 12 days during its plan window. It will not be observed with TESS.

- Information on the other targets in this campaign will be posted as it becomes available.

- ADDED 4/26: Please note that Sz66 is located 6" from a brighter star (Sz 65; delta-mag ~ 3 at V). Please do not waste time on this star if the seeing is bad, or unless you have a good plate scale. Also, please check the mean V magnitudes - some of these targets are on the faint side.

- Added 4/28: The dates for GQ Lup  and HM Lup have been swapped. The Table has been updated.

- Added 5/21: Sz 111 and Sz 130 are now scheduled for June 20. The table has been updated.

- Added 6/15: STc2d J160000.6-4221582 is now scheduled for June 21. The table has been updated.

                        The first HST observation of Sz 76 failed, and has been rescheduled for June 29. There will be no TESS coverage, so ground-based photometry is crucial.

- Added 7/17: HST observations of Sz 130 and STc2d J160000.6-4221582 have been re-scheduled for July 22 and July 23, respectively. There will be no TESS coverage, so ground-based photometry is crucial.

Timing Requirements: CCD filter photometry on the 3 nights surrounding the HST observation. Observe during the time of the HST observation, if possible.
If not possible (2/3 of the HST observations will take place while the target is below the horizon or in daylight from any particular observatory), please get CCD filter photometry before and after the HST observations. There is no need to obtain long time series: TESS will provide that.

Filter Requirements: It is important to use standard broadband filters. Concentrate on B and V, which TESS does not observe, and on Rc and Ic, which will enable cross-calibration with TESS. T Tauri stars tend to be more variable at shorter wavelengths.

TESS color calibration: Two or more sets of BVRcIc observations during the 27 day TESS window will help us “calibrate” the TESS photometry, and correlate color changes with brightness changes.

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