AAVSO: American Association of Variable Star Observers

Proposal #267

Proposer (36547) Lauren Herrington (lherrington@aavso.org) obscode: HLAA
Assigned To(3663) Dirk Terrell
Date SubmittedJune 6, 2022

Recurrent nova U Scorpii went into outburst a few hours ago, and was last reported at magnitude 9.2. In vsnet alert #26801, issued today, Patrick Schmeer reported that spectroscopy of U Sco is "urgently required". At its current magnitude, U Sco is well within reach of the Star Analyzer gratings on BSM-Berry and BSM-TX.

This proposal requests to monitor U Sco spectroscopically until it becomes too faint for the AAVSOnet Star Analyzers. All spectra will be reduced and uploaded to AVSpec.

The use of the eShel on OC-61 is also highly encouraged, as its dramatically higher resolution will likely make the resulting spectra much more valuable to researchers than Star Analyzer spectra; however, I understand that there may be technical difficulties involved, since the procedure for remote control has not yet been determined. Total exposure times will likely need to be long (>1hr) in order to achieve an acceptable S/N with the OC-61 eShel.

U Sco is an extremely fast nova, and will therefore probably fade out of reach of the OC-61 eShel within a few days, and the AAVSOnet Star Analyzers within two weeks.

Target RA (H.HH) Dec (D.DD) Magnitude Telescope Observation Frequency Expiration Date Proprietary Term
U Sco 16.375217 -17.87856 7.5–19.3 BSM_Berry Dec. 5, 2022 No


(36547) Lauren Herrington — June 7, 2022, 2:17 p.m.

Thank you for accepting my proposal!

I noticed that this is marked "Priority - Normal". I have another currently active proposal for Star Analyzer spectra which is marked "Priority - Normal", and it took about ~10 days for the first images to be taken. I understand that there are weather- and technical-related delays (and that the Priority flag on this page may not have much meaning), but I wanted to re-emphasize the importance of speed for these observations, given that U Sco is an *extremely* fast nova. It reached its peak 12 hours ago, and as of 4 hours ago, it had already faded by 0.6 magnitudes. If it's possible to treat these as priority observations, I would recommend that; otherwise, much of the useful data may be missed.

(4726) Kenneth Menzies — June 8, 2022, 12:06 a.m.

Committed to Berry. 5s exposure initially. You will need to keep track of this and make exposure recommendations.

(36547) Lauren Herrington — June 8, 2022, 7:41 p.m.

Excellent, thank you! Will do.

(36547) Lauren Herrington — June 9, 2022, 4:01 p.m.

I did some math based on the exposure times from the test proposal and the current magnitude of U Scorpii, and it looks like long exposure times in excess of 1 minute are more likely to yield useable spectra. Somewhere around 3-5 minutes would probably be best. (Truly "optimum" exposure occurs at somewhere around 1hr, but of course the spectrum does not need to span the whole histogram in order to be useful, and skyglow would probably thwart any exposure much longer than 5 minutes.)

(4726) Kenneth Menzies — June 9, 2022, 4:28 p.m.

Exposure now 180s. Focus=-100

(36547) Lauren Herrington — June 21, 2022, 5:32 p.m.

I haven't received any images yet, but U Sco is now down to 14th magnitude, so unfortunately I think that it has probably passed out of the useful range BSM-Berry. (An hour+ of long subexposures might still be able to detect the spectrum, but in the dense starfields of Scorpius, it would be quite contaminated by faint background stars.) As a result, this plan should probably be cancelled.

(4726) Kenneth Menzies — June 22, 2022, 7:27 p.m.

Plan archived

Comments on this proposal are closed.