Thank you for all the observations you have contributed to the ODYSSEUS program. The high cadence photometry and colors are instrumental for understanding the changes in accretion and extinction in these rapidly-accreting T Tauri stars, and in interpreting the variability in the TESS photometry. Now, after a long sojourn to the southern hemisphere, we return to the north.
The final 2 HST/ULLYSES/ODYSSEUS targets, GM Aur and BP Tau, will be observed starting later this month. These are monitoring targets, so the HST will obtain
4 sets of UV spectra of each star over an interval of about 3 weeks (3 rotation periods). In addition, both targets are in TESS sector 59, which will be observed continuously for 27 days, 26 November through 23 December.
Target Details:
target RA (J2000) Dec <V> Range HST observation dates
1. GM Aur 4 55 10.98 +30 21 59.1 12.2 11.8-12.6 26 November - 13 December
2. BP Tau 4 19 15.86 +29 06 27.2 12.1 11.5-12.7 12 December - 7 January
I ask that those of you who can obtain CCD filter photometry (BVRI preferred, and U if you can) at least nightly for these targets:
1 GM Aur: 25 November through 23 December
2. BP Tau: 25 November through 7 January
Please try to obtain 1% S/N (0.01 mag), so that colors are accurate to about 2% (0.02 mag).
I will amend this notice with exact times of the HST observations when available, in the hopes of obtaining exact simultaneity on occasion. But the important thing is to establish the trends in the color variability. Typical variability timescales are a few hours. TESS will catch the flares. Note that there will be no TESS coverage of BP Tau for the second half of the HST observations (23 December - 7 January); during this interval your photometry will be even more important.
Thanks again for contributing to a very successful and productive program.
UPDATE 11/28 with HST observation times for the first 6 (of 12) HST observations of GM Aur
UPDATE 12/09 with HST observation times for all HST observations of GM Aur
1. Start time: 26 Nov 2022 20:57:24 End time: 26 Nov 2022 21:49:53
2. Start time: 28 Nov 2022 09:28:09 End time: 28 Nov 2022 10:20:38
3. Start time: 29 Nov 2022 18:47:44 End time: 29 Nov 2022 19:40:13
4. Start time: 01 Dec 2022 08:54:28 End time: 01 Dec 2022 09:46:57
5. Start time: 02 Dec 2022 18:15:05 End time: 02 Dec 2022 19:07:34
6. Start time: 04 Dec 2022 06:45:49 End time: 04 Dec 2022 07:38:18
7. Start time: 06 Dec 2022 06:22:58 End time: 06 Dec 2022 07:15:27
8. Start time: 07 Dec 2022 07:48:19 End time: 07 Dec 2022 08:40:48
9. Start time: 09 Dec 2022 07:28:00 End time: 09 Dec 2022 09:11:19
10. Start time: 10 Dec 2022 11:56:02 End time: 10 Dec 2022 12:48:31
11. Start time: 12 Dec 2022 03:35:49 End time: 12 Dec 2022 04:28:18
12. Start time: 13 Dec 2022 14:29:55 End time: 13 Dec 2022 15:22:24
UPDATE 12/12 with HST observation times for the first 7 (of 12) HST observations of BP Tau
1. Start time: 13 Dec 2022 03:23:07 End time: 13 Dec 2022 04:13:57
2. Start time: 15 Dec 2022 10:54:38 End time: 15 Dec 2022 11:45:28
3. Start time: 17 Dec 2022 00:59:04 End time: 17 Dec 2022 01:49:54
4. Start time: 19 Dec 2022 13:15:51 End time: 19 Dec 2022 14:06:41
5. Start time: 21 Dec 2022 12:51:34 End time: 21 Dec 2022 13:42:24
6. Start time: 23 Dec 2022 12:26:56 End time: 23 Dec 2022 13:17:46
7. Start time: 25 Dec 2022 12:02:30 End time: 25 Dec 2022 12:53:20
8. Start time: 27 Dec 2022 16:23:54 End time: 27 Dec 2022 17:14:44
9. Start time: 29 Dec 2022 12:48:22 End time: 29 Dec 2022 13:39:12
10. Start time: 31 Dec 2022 15:34:08 End time: 31 Dec 2022 16:24:58
UPDATE 12/28 with final HST observation times of BP Tau
11. Start time: 02 Jan 2023 13:34:05 End time: 02 Jan 2023 14:24:55
12. Start time: 04 Jan 2023 14:44:26 End time: 04 Jan 2023 15:35:16
13. Start time: 06 Jan 2023 11:09:12 End time: 06 Jan 2023 12:00:02
-
(there are 13 scheduled visits because one failed)
Times are UT. Photometry leading up to, or during the HST observations, will be particularly useful.
This will be the final request for observations for this program. Thanks for contributing. Any further updates will be focused on scientific resuts.
I get both stars quasi-nightly in V (only) at Lowell with our 1.1-m telescope. I can understand wanting U (or Sloan u) to look at the accretion variability, but what does having BVRI tell you that V alone does not? I see in the T Tauri literature people going to great efforts to get all the filters, yet the lightcurves are completely parallel to each other apart from having smaller amplitude at the longer wavelengths, very much as expected. Can you give some science rationale for needing all four filters in this case?
\Brian
Hi Brian,
Very basically, we want to know if the star changes color. Both increased accretion and decreased absorption on the line of sight make the star bluer as it brightens, but the slopes of the color-color relations differ (they are close, but not exactly parallel). Absorption by large grains has a different reddening curve (large R_V) than by "normal" small grains (R_V=3.1). Interpretation of color-magnitude relations in multiple colors is more secure than interpretations of a single color; you cannot make a color0color diagram in a single color.
U is most sensitive to changes in accretion or reddening, but is harder to get. B-V, or B-I are good to have, the latter having more leverage. If you want to drop a filter, R (or r') can be hard to interpret because of variable H-alpha emission.
TESS will be observing with a continuous 10 minute cadence, so occasional V magnitudes alone do not add much. TESS is a single channel broadband (600-1000 nm) photometer; we need colors to interpret the inevitable changes in brightness.
Fred
I have added both stars in BVI filters for nightly observations although weather conditions might change in the coming weeks in Chile.
Josch
I will add both stars to my scheduler today also - Hopefully our weather down here in Australia might finally be improving - Poor dome has only opened about 2 nights over the last 3 months.
AAVSO Alert Notice 801 reports on the campaign underway on the T Tau stars GM Aur and BP Tau. Please see the notice for details and observing instructions.
There are threads for this campaign under the following AAVSO forums:
- Campaigns and Observing Reports: https://www.aavso.org/odysseus-xii-final-targets-update-2-1130-more-hst-observation-times-01
- Young Stellar Objects (YSO): https://www.aavso.org/odysseus-xii-final-targets-update-4-1212-even-more-hst-observation-times-bp-tau
Please subscribe to these threads if you are participating in the campaign so you can be updated. Join in the discussion or ask questions there!
Many thanks, and Good observing,
Elizabeth O. Waagen, AAVSO HQ
AAVSO Alert Notice 802 gives this week's (2022 December 13-17) HST observing schedule for the T Tau star BP Tau. Please see the notice for details and observing instructions.
There are threads for this campaign under the following AAVSO forums:
- Campaigns and Observing Reports: https://www.aavso.org/odysseus-xii-final-targets-update-2-1130-more-hst-observation-times-01
- Young Stellar Objects (YSO): https://www.aavso.org/odysseus-xii-final-targets-update-4-1212-even-more-hst-observation-times-bp-tau
Please subscribe to these threads if you are participating in the campaign so you can be updated. Join in the discussion or ask questions there!
Many thanks, and Good observing,
Elizabeth O. Waagen, AAVSO HQ
Just wondering : do you want 1 observation per night, or a time series, as if it were an exoplanet ?
While TESS is…
Hi Pieter,
While TESS is observing these stars (through Dec 23) where is little need for time series. 1 (or a few) observations per night will be useful for getting colors while TESS will provide a 10 minute cadence light curve. If you want to do time series, concentrate on B (the TESS band is 600-1000 nm) .
BP Tau observations will run through about January 7; from Dec 23-Jan 7 time series on BP Tau will be useful.
Thanks for your contributions,
Fred
AAVSO Alert Notice 806 reports on the campaign underway on the T Tau star BP Tau. Please see the notice for details and observing instructions.
There are threads for this campaign under the following AAVSO forums:
- Campaigns and Observing Reports: https://www.aavso.org/odysseus-xii-final-targets-update-2-1130-more-hst-observation-times-01
- Young Stellar Objects (YSO): https://www.aavso.org/odysseus-xii-final-targets-update-4-1212-even-more-hst-observation-times-bp-tau
Please subscribe to these threads if you are participating in the campaign so you can be updated. Join in the discussion or ask questions there!
Many thanks, and Good observing,
Elizabeth O. Waagen, AAVSO HQ
AAVSO Alert Notice 806 reports on the campaign underway on the T Tau star BP Tau. Please see the notice for details and observing instructions.
There are threads for this campaign under the following AAVSO forums:
- Campaigns and Observing Reports: https://www.aavso.org/odysseus-xii-final-targets-update-2-1130-more-hst-observation-times-01
- Young Stellar Objects (YSO): https://www.aavso.org/odysseus-xii-final-targets-update-4-1212-even-more-hst-observation-times-bp-tau
Please subscribe to these threads if you are participating in the campaign so you can be updated. Join in the discussion or ask questions there!
Many thanks, and Good observing,
Elizabeth O. Waagen, AAVSO HQ