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YSO Bulletin
- May 2021 -

- Southern YSO Issue -

This brief issue is devoted entirely to the Southern YSO campaign that begins shortly after you receive the newsletter, and I have hurried it out for that very reason. Also, it's good to see that our Southern-hemisphere observers have something of their own to get involved with - us Northerners (for purely historical reasons I believe) have tended to observe a great many variable stars, not just YSOs... despite the fact that the antipodean skies are every bit as full of interest than the northern heavens - some would say even more so!
This is part of the Ulysses project run by Dr. Fred Walter (Stony Brook University) who requests AAVSO observers to monitor 17 Southern T Tau stars in support of a multi-site multiwavelength campaign, including observations by HST and TESS, being carried out in April - June 2021. An 18th star is included in this request and is being observed by TESS although not by HST. He provides the following information:
"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.
- 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 to 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 given below.

TargetRADECVHST planTESS
CHX18N11 11 46.32-76 20 09.211.9April 29 14:00-01:00 Apr 28 - Jun 24
HM Lup (Sz72)15 47 50.63-35 28 35.414.8May 3 13:00-01:30Apr 28 - Jun 25
GQ Lup (Sz75)15 49 12.10-35 39 05.111.4May 4 11:30-23:00Apr 28 - Jun 25
GW Lup (Sz71)15 46 44.73-34 30 35.513.5May 5 11:00-23:30Apr 28 - Jun 25
Sz7715 51 46.95-35 56 44.113.3May 7 10:30-22:30Apr 28 - Jun 25
Sz7615 49 30.74-35 49 51.415.2May 10 0900-20:00Apr 28 - Jun 25
Sz6615 39 28.28-34 46 18.015.0May 24 03:30-16:00Apr 28 - Jun 25
Sz4511 17 37.00-77 04 38.113.5May 25 03:00-14:00Apr 28 - Jun 24
XX Cha11 11 39.65-76 20 15.215.3May 29/30 0:00-11:30Apr 28 - Jun 24
GX Cha (HN 5)11 06 41.79-76 35 48.915.6May 31 0:00-09:30May 26 - Jun 24
IN Cha11 12 09.84-76 34 36.616.5June 5/6 21:00-07:00May 26 - Jun 24
T Cha11 57 13.44-79 21 31.711---Apr 28 - Jun 24
RU Lup15 56 42.31-37 49 15.51010 Aug - 2 Sep---
SZ Cha10 58 16.75-77 17 17.211.7 - 13.8 V---Apr 28 - Jun 24
TW Cha10 59 01.06-77 22 40.912.3 - 14.0 Vlate Apr-JunApr 28-Jun 24
SSTc2d J160000.6-42215816 00 00.60-42 21 56.816.4 - 16.7 VJun 19-23May 26-Jun 24
NSV 20468 (Sz 130)16 00 31.04-41 43 37.013.9 - 15.1 VJun 19-23May 26-Jun 24
NSV 20520 (Sz 111)16 08 54.68-39 37 43.114.1 - 14.6 VJun 18-23May 26-Jun 24
  • The TESS column indicates the dates that the target is in the TESS field. CHX 18N 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 in the forum threads given above 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 in the forum threads as it becomes available.