Proposal #306

Proposer (1546) Walt Cooney ( obscode: CWT
Assigned To(3663) Dirk Terrell
Date SubmittedDec. 26, 2022

Target: AB Aur
Spectral Type: A0 Herbig Ae
Coordinates (J2000): 04:55:45.846 +30:33:04.292
Vmag: 7.05
Rmag: 6.96
Variability Type: UXOR/ROT
Purpose of Campaign:
The purpose of the AAVSO monitoring campaign is to provide critical observational support in the months leading up to, and coinciding with, HST observations of the young, accreting, A0 Herbig Ae star, AB Aur, so that we have a complete and accurate understanding of the star’s accretion activity and the behavior of its variability.
Members of our team have 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 variability of the central star, and so it is essential that we understand the nature of its variability to the fullest extent during the months 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.
Duration of Campaign:
The campaign should begin as soon as possible and extend over the course of several months until the completion of the HST observations in early–mid February.
Observation Type:
Filtered CCD photometry.
B, V, R
The filter pattern for a single observing sequence is as follows: 1 x B, 1 x V, 1 x R
Observing Cadence:
Beginning immediately – Jan 6, 2023: A few (2-5) observing sequences per night.
**HST observations scheduled for Jan 7 – 8 **: As many sequences as possible.
Jan 9 – Feb 5 (at the earliest): Return to a few (2-5) observing sequences per night.

HST plan windows provided by the Space Telescope Science Institute ( indicate that **the second round of HST observations will most likely occur between Feb 6 – March 6**. The exact dates will become available in late January and we will update AAVSOnet as soon as the second round of HST dates are known. As with the first found of HST dates, as many sequences as possible should be observed on these nights.
Additional Observation Details:
Please include comp star "76" (000-BJX-825) at 04:55:48.48 +30:2016.5 in the field of view to use as a comp star, although this comp star is actually slightly variable. A field center that would include AB Aur and this comp star approximately equidistant from center would be 04 55 47.7 +30 26 23.3

Target RA (H.HH) Dec (D.DD) Magnitude Telescope Observation Frequency Expiration Date Proprietary Term
AB Aur 4.929402 30.55119 8.4–6.9 BSM_NH2 1 March 15, 2023 No


(3663) Dirk Terrell — Dec. 29, 2022, 9:58 p.m.

The TAC suggests using a better comp star. See TESS data plots at:

(1546) Walt Cooney — Dec. 29, 2022, 10:10 p.m.

In addition to BVR data for this system, H-alpha data would be extremely helpful. That filter isn't normally available in AAVSOnet filter wheels, but Arne and Gary Walker have installed one in BSM-NH to help out on this request. Could the AAVSOnet plan that is submitted to BSM-NH please also include HA images? We would appreciate it if the plan ran as 1xB-1xV-1xR-10xHA. We are also running HA images separately at MPO61 (not via the AAVSOnet system). I am also gathering HA data at my Starry Night Observatory in Columbus, TX.


(4726) Kenneth Menzies — Dec. 29, 2022, 10:58 p.m.

What exposures are you using for HA at MPO61? I suspect 10xHA will suck up a lot of available time? (It is quite bright.) Do you really need that many? Any alternatives that meet our other proposers' needs?

(1546) Walt Cooney — Dec. 29, 2022, 11:12 p.m.

We are using 30 second exposures in H-alpha at MPO. I don't know how long that might translate to for BSM-NH. The benefit of running more exposures would be to get a better look at the true precision in the H-alpha data but ten isn't a magic number for that. H-alpha is actually the filter that is most helpful for this project, and so putting some emphasis on that filter with the one BSM scope that can do H-alpha has value.

(4726) Kenneth Menzies — Dec. 29, 2022, 11:18 p.m.

You have listed two different HST observing periods. Which is correct/desired?

(4726) Kenneth Menzies — Dec. 29, 2022, 11:33 p.m.

Committed to NH. Await comments from Walt per questions above.

(1546) Walt Cooney — Dec. 30, 2022, 12:10 a.m.

Ken, there will be several sets of observations of AB Aur by HST. We would like to image AB Aur with AAVSOnet frequently both times HST observes it. We only know the date of the first set of HST observations with good certainty. That's the Jan 7-8 slot. HST will return to the field sometime after Feb 5. We will update the proposal when that date is known better.

(1546) Walt Cooney — Dec. 30, 2022, 9:25 p.m.

Thank you for the images from BSM_NH2 last night. The BVR exposure times look right on. The HA images are all donuts. Maybe the HA filter that Arne put in the wheel is not the same thickness as the other filters and so needs a focus offset?

(1546) Walt Cooney — Jan. 1, 2023, 9:43 p.m.

The first HST observing run is approaching (Jan 7-8). Would it be possible to assign more than one BSM to this project to increase the chance of getting data as weather interferes at different stations? Thanks.

(1546) Walt Cooney — Jan. 20, 2023, 2:45 a.m.

Thank you for the AB Aur images coming in from BS-NH2. Because the comp stars are 4 or 5 magnitudes fainter than the target, could you please increase the number of B, V, and Rc images to 5 as is being done for Ha so that the B, V, and Rc images can be stacked for better accuracy? Stacking exposures is the current request in the active AAVSO campaign as well. Thanks. -Walt

(4726) Kenneth Menzies — Jan. 21, 2023, 4:19 p.m.

#exp increased to 5.

(4726) Kenneth Menzies — Jan. 21, 2023, 4:21 p.m.

Are HA images focused now? I assume so.

(2108) Arne Henden — Feb. 12, 2023, 12:38 p.m.

Now that the HST observations have been made, should we disable this project, or do you want additional monitoring? At least, I think the extra monitoring set up at BSM_NM and BSM_TX should be disabled.

(1546) Walt Cooney — Nov. 29, 2023, 11:04 p.m.

Please re-up this plan now that the next AB Aur observations for HST are planned. I'll alert AAVSOnet when the exact dates of the HST observations are identified so that we can run a long time series to coincide. In the mean time, I'd like to request 5 consecutive 60 second Ha images at BSM_NH2 as often as the AAVSOnet folks think is acceptable per night and as many nights as acceptable given the fact this is a shared resource with competing priorities. In a perfect world, I'd ask for sets of 5 Ha images every hour every clear night, but realize that isn't reasonable.

I will sum the five 60 second image sets to get a single image with adequate S/N of the comp and check stars. That data point will be submitted to the AAVSO for the campaign.

I do not request filters other than Ha.


Comments on this proposal are closed.