AB Aur monitoring requested for HST observations
Abstract:
Drs. Lauren Biddle, Brendan Bowler (University of Texas), Yifan Zhou (University of Virginia), and Mr. Walt Cooney (Madrona Peak Observatory) request AAVSO observers' assistance in monitoring the bright (6.9-8.4V) young, accreting A0 Herbig Ae star, AB Aur, in support of HST observations planned for December 2023 - January 2024. They provide the following information: Two epochs of HST observations have been completed, and the final 2 sets of HST observations will take place in late December and January, but observers are asked to observe AB Aur beginning immediately and continuing through February. Building the light curve in the weeks leading up to the HST observations [and afterwards] is essential so that, Dr. Biddle writes: "we have a complete and accurate understanding of the star’s accretion activity and the behavior of its variability, including bright massive accretion events and rare dimming events. Observers will be notified about the exact HST dates as soon as the information becomes available."
Justification:
"Recently, a point-like source has been detected with direct imaging of the circumstellar disk of AB Aur, indicating the potential existence of an accreting protoplanet at an orbital distance of ~100 AU (Currie et al. 2022; Zhou et al. 2022). However, unresolved features of protoplanetary disks can mimic planets by scattering light from the central star, causing false-positive signals — a major challenge in validating candidate protoplanets. Additional evidence is required to validate the existence of the protoplanet candidate, AB Aur b. Our team has an approved HST program that will confirm or refute the existence of the candidate protoplanet with accretion light echoes. We seek to answer the question: Is emission from this point-like feature a bona fide accreting protoplanet, or is it an unresolved compact disk structure seen in scattered light? If flux from the companion source varies synchronously with the host star, that would point to the disk scattering scenario, whereas uncorrelated behavior would support the planet interpretation. The nature of this experiment relies heavily on the variability signature of the central star, and so it is essential that we understand the nature of its variability to the fullest extent during the weeks leading up to, and overlapping with the HST observations. This monitoring campaign will provide critical support for the success of our HST program by enabling us to recover the characteristics of AB Aur’s variability. New science resulting from this campaign will be published in the Astrophysical Journal alongside the HST results as a multi-part series."
Requested Data Types:
Photometry
Targets
| Name | Magnitude | Variability Type | Photometry Notes | Spectroscopy Notes |
|---|---|---|---|---|
| AB Aur | 6.90 | UXOR/ROT |
Cadence: Not Specified Precision: 100 |
Not Requested |
Spectroscopy Lines:
H-alpha (6563.0 Å)
Photometry Filters:
B (Johnson), V (Johnson)
Comparison Stars:
No comparison stars provided
Co-Authorship
Observers are not eligible for co-authorship.
Additional Observer Input:
Not provided
Additional Submission Location:
Not provided
Forum URL
N/A
Notes:
Principal Investigator: Lauren Biddle, Brendan Bowler, Yifan Zhou, Walt Cooney; Imported Campaign (Alert Notice #842)