LL And rare outburst

A spectrum (R~500)

Robin

Hi Robin,

I think it probably was LL And.  I have a pre-print of a paper written by Taichi Kato in 1993 and printed in PASJ, which suggests that the 1979 Nova was indeed LL And (there were positional issues with the 1979 report).   In it Kato-san writes (about the 1979 event)…

This supposed identification, which was later confirmed by the detection of a new outburst in 1993, of a relatively bright (19 mag) quiescent counterpart naturally suggested the dwarf nova-type classification.  This information was quickly relayed to observers through the international alert networks (e.g. VSNET) and the object has been continuously monitored since then. The long-awaited next outburst finally occurred in 1993

I know I was observing it for a long time before the 1993 outburst, and was thrilled to see it for the first time then, confirming Tonny VanMunsters original detection.   Indeed Tonny (in Belgium) and I were discussing the outburst on the telephone whilst looking at it through our telescopes!   We did this several times in the 1990’s during rare outburst detections.   Sadly those days are now gone – as has some of the fun of it.

Gary

Another low resolution R~500 spectrum last night (low SNR due to bright full moon) continues to show no evidence of H alpha (in emission or absorption) but the higher Balmer absorption lines have increase in depth. V mag for  the two spectra were ~12.8/13.7 (AAVSO)

Robin

Certainly looked a lot fainter from here…..

 While between OTAs, I have been using my 114mm guidescope and an unfiltered Lodestar to occasionally take some measurements of LL And. Because they were mainly taken on moonlit or partially cloudy nights (and I am a deep sky observer) I just let the camera run a series of 30s frames in the hope it might drive down the errors that would be present with such a small light grasp instrument. Its not the best way to do this sort of thing, but it was simple to do and fun.

To analyse the data, I wrote Python code to plate solve all the frames, locate all the stars, compare the catalogue stars to those on my frames, established the Zp for each frame and thus derive the mag of LL And. I then took the median result (mag1).

To make things more interesting, I also looked at 4 comparison stars from the AAVSO chart and derived mags (mag2) for those using the sums of the fluxes measured from all the frames. I may extend the number of comparison stars.

The results are these:

Date      Mag1   Mag2   Magerr  Frames

210917  13.15   13.32    0.15      122

210918  13.39   13.60    0.4        212

210921  13.71   13.90    0.25      307

210922  13.77   13.98    0.25      277

210929  14.58   14.71    0.35      156

211010  17.41   17.26    0.8        179

Usable results could have been obtained with far fewer frames, but I had hoped to see some evidence of superhump activity (yeah I know) so I just let it run.   

What I am noticing from this – apart from how interesting LL And is – is that the Mag1 value seems consistently brighter than the Mag2 value. I won’t be submitting any observations formally until I figure out what causes that. Has anyone any thoughts on what I might be doing wrong?

EDIT: Andy worked out the problem and I am ashamed that I didn’t myself. One approach used the Gaia g catalogue mag values and the other used the AAVSO sequence mags ie V.