9 August update: All HST observations are now scheduled.
16 August update: Two new HST observations have been added, on August 23 and 24, because 2 of the earlier observations failed. Please keep RU Lup on your target list through August 25. It will be valuable to have observations even on the nights that HST is not observing to ensure continuity, and to enable us to place any large variations in context.
The last part of the 2-year long HST/ULYSSES/ODYSSEUS pre-main sequence star campaign continues this month with the second epoch monitoring of the second monitoring target, RU Lupi. 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. The first monitoring target, TW Hya, was observed in March (with your help); the last 2 targets, BP Tau and GM Aur, are likely to be scheduled in November/December.
This month the HST will reprise its monitoring of the pre-main sequence star RU Lup, obtaining 12 sets of ultra-violet spectra spread over roughly three stellar rotation periods. The window for RU Lup is August 10-20. It will be not be observed with TESS, so ground-based observations are critical if we are to place the HST observations in a long-term context.
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 database. Thanks in advance for your contributions to this campaign.
The target: RU Lupi
Position: 15 56 42.31 -37 49 15.5 (J2000).
Magnitude: V~9.6
RU Lup is a bright, highly active classical T Tauri star in the Lupus star formation region. The rotation period is about 3.7 days. The system is almost pole-on, so stochastic variability dominates over rotational modulation. The VSX catalog reports it as faint as V=12.9, but it is generally closer to its brightest level. The TESS data from 2019 shown peak-to-peak variations of 0.8 mag.
Please try to get 1% BVRI CCD photometry (0.01 mag precision), we we can determine colors to 2% or better.
The current HST schedule is (all times are UT):
Start time: 10 Aug 2022 05:54:46 End time: 10 Aug 2022 06:48:32
Start time: 11 Aug 2022 05:44:11 End time: 11 Aug 2022 06:37:57
Start time: 12 Aug 2022 05:33:57 End time: 12 Aug 2022 06:27:43
Start time: 13 Aug 2022 00:38:00 End time: 13 Aug 2022 01:31:46
Start time: 14 Aug 2022 02:03:39 End time: 14 Aug 2022 03:20:27
Start time: 14 Aug 2022 21:07:59 End time: 14 Aug 2022 22:01:45
Start time: 15 Aug 2022 16:12:29 End time: 15 Aug 2022 17:06:15
Start time: 16 Aug 2022 14:27:25 End time: 16 Aug 2022 15:21:11
Start time: 17 Aug 2022 12:42:08 End time: 17 Aug 2022 13:35:54
Start time: 18 Aug 2022 12:31:54 End time: 18 Aug 2022 13:25:40
Start time: 19 Aug 2022 09:10:48 End time: 19 Aug 2022 10:04:34
Start time: 20 Aug 2022 09:00:05 End time: 20 Aug 2022 09:53:51
Start time: 23 Aug 2022 10:01:42 End time: 23 Aug 2022 10:55:28
Start time: 24 Aug 2022 09:50:15 End time: 24 Aug 2022 10:47:36
(Note that all scheduled HST times are subject to change.)
While you should try to get CCD photometry while HST is observing, it is also important to get as complete coverage as possible during this time period. Any observations August 5 through August 21 UT are valuable. The HST observations will last about 1 hour/day; in August RU Lup is observable from the ground for only about 3-4 hours/night.