Alert Notice 852: AB Aur coverage needed now for HST observations this week

February 20, 2024

AAVSO Forum threads (scroll to the bottom of a thread for latest posts):
- Campaigns & Observation Reports:
- Young Stellar Objects:

Please subscribe to these threads if you are observing this star so you can be updated by the astronomers and by HQ. Join in the discussion or ask questions there!

Further to AAVSO Alert Notice 848 (and Alert Notices 809, 811, 814, 842), Dr. Lauren Biddle (University of Texas) informs us that observations of the the bright (6.9-8.4V) young, accreting A0 Herbig Ae star, AB Aur, have been scheduled with the Hubble Space Telescope on:

2024 February 21 - 22:

Feb 21  10:55:11 - 11:54:38 UT
Feb 21  21:59:26 - 22:58:53
Feb 21  23:34:20 - Feb 22  00:33:47
Feb 22  01:09:13 - 02:08:40

Photometry is requested, and observers are asked to focus especially on February 20 - 23 (and continue coverage through at least mid-March). As with all HST observations, a positive V magnitude is required 24 hours before the scheduled time of observations for final approval of the observations.

Dr. Biddle writes: "[This is a] short reminder that the optimal observing cadence will depend on the filters you plan to use.

"Observers with B, V, and/or Rc filters: 3 – 5 observations spread out roughly equally in time over the course of the night.

"Observers with HA filters: As many observations as you are willing and able to acquire. If you are observing with an HA filter, please prioritize only the HA filter.

"In this context, a single observation is comprised of the full sequence of exposures that will be stacked to create a final image. The comp and check stars for this campaign are several magnitudes fainter than AB Aur, and so we ask observers to take multiple exposures in each filter and stack the exposures to attain a comp star S/N of 100 or more while not overexposing AB Aur."

All observers are requested to use GSC 02387-00489 (the 104 in the AAVSO AB Aur sequence, Rc = 10.071) as their single comp star and GSC 2387-0935 (the 120 in the sequence, Rc = 11.382) as their check star. Single comp star photometry is strongly preferred for this campaign. 

There has been considerable discussion about this campaign in the forum threads above. Observers are urged to read these posts (scroll to the end of the thread to see the most recent posts). Observers are also reminded of the very interesting webinar on AB Aur and this campaign that took place on November 19, 2023. View the video on the AAVSO's YouTube channel here:

Coordinates (2000.0):  R.A. 04 55 45.84  Dec. +30 33 04.3  (from VSX page for AB Aur)

Charts with comparison stars for AB Aur may be created using the AAVSO Variable Star Plotter (VSP). It is recommended that observers use the 'E' scale when creating charts for AB Aur. Observers should be aware that the 116 comp star appeared in earlier versions of the AB Aur sequence, but is not the recommended comp star to use for these observations.

Please submit observations to the AAVSO International Database using the name AB AUR.

This AAVSO Alert Notice was compiled by Elizabeth O. Waagen using information provided by Lauren Biddle and Walt Cooney.



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