AAVSO: American Association of Variable Star Observers

Proposal #163

Proposer (43151) Stewart Bean (sjbeanmail@aol.com) obscode: BENS
Assigned To(3663) Dirk Terrell
Date SubmittedNov. 16, 2020

Proposal to AAVSOnet

Monitoring UGER stars to determine their supercycle period

Otulakowska-Hypka and Olech (MNRAS 433, 1338–1343 (2013) presented results suggesting that for SU Uma stars there is evidence that the time between successive superoutbursts ( the supercycle period) is increasing. A subset of the stars (UGER) they studied have short supercycle periods of less than 60 days permitting changes to be recognised relatively quickly. The following are discussed in their paper: ER Uma, RZ Lmi and IX Dra. In project 154, the IX Dra superoutburst for mid November has been timed within about +-0.5 days determining the supercycle period (over the most recent eight cycles including earlier TESS measurements) to be 59.5 days. This is slightly longer than the 58.5 days found in 2010 by Otulakowska-Hypka and Olech.

Analysis of the AAVSO data for RZ Lmi over the most recent 5000 days suggests that its period is increasing ( but not smoothly) by one third of a day per year to the current value of 24 days.
For ER Uma the current period seems to be about 44 days whilst the above publication suggests 44 days around 2450000 increasing to 55 days around 2456000. In “Detection of Change in Supercycles in ER Ursae Majoris” Publications of the Astronomical Society of Japan 65(3), 54-1-8, 2013 supercycle length changes are analysed. Their data ran for about 20 years up to 2012 and showed variations from 43 to 55 days in a O-C analysis.

It is proposed that ER Uma and RZ Lmi are monitored during this observing season to determine their supercycle lengths using V filter photometry.


Stewart Bean

Target RA (H.HH) Dec (D.DD) Magnitude Telescope Observation Frequency Expiration Date Proprietary Term
ER Uma 9.786636 51.90242 15.0–12.0 BSM_NH2 May 16, 2021 No


(43151) Stewart Bean — Nov. 16, 2020, 2:53 p.m.

RZ Lmi 09 51 48.91 +34 07 23.8 14 to 16 mag

(3663) Dirk Terrell — Nov. 17, 2020, 3:39 p.m.

From Arne:
These are both relatively bright and are in uncrowded fields. I don't see any technical problems with this proposal. I would just use the V filter, both since Stewart is only interested in outburst timing and because CVs flicker, making accurate colors difficult to measure. I would put them on all of the northern sites at once/night cadence and let weather and Scheduler priority determine how many observations per night actually occur.

(43151) Stewart Bean — Nov. 17, 2020, 4:01 p.m.

Thank you very much. That sounds fine to me.
I will raise awareness within the BAA VSS to follow these two stars as well.

(4726) Kenneth Menzies — Nov. 17, 2020, 5:05 p.m.

Committed on NM. Will run daily.

(43151) Stewart Bean — Nov. 27, 2020, 12:10 p.m.

Kato san (Kyoto Uni, Japan) in vsnet-alert 25015 Nov 25th asks for photometry of RZ Lmi in line with my project proposal.

"Observations are needed to see whether durations of
superoutburst have increased. If the change is
confirmed, it would be a suggestion of an increased
mass-transfer rate (may be leading to a standstill?).
Please keep watching. Time-resolved photometry would be
also desired."

Seems RZ Lmi may be rather special.

All images fine.

(43151) Stewart Bean — Dec. 19, 2020, 5:30 a.m.

Ive not received an image since 10 Dec. Is everything OK ?

(43151) Stewart Bean — Dec. 26, 2020, 12:08 p.m.

Some images received now . thanks

(43151) Stewart Bean — Jan. 23, 2021, 12:06 p.m.

Last nights images (22 jan 2021) for both ER Uma and RZ Lmi are about 1/2 degree out with both targets just outside the field of view.
Strangely those for IX Dra taken a bit earlier are fine.

(43151) Stewart Bean — June 12, 2021, 6:51 a.m.

There is now enough data to write up on RZ Lmi to answer the original call by Kato.
If there is another quality project requiring NM2 time, I am content to give way on RZ Lmi.



(43151) Stewart Bean — June 28, 2021, 5:50 p.m.

Ken and Dirk,
Looking at the historical data, we are now at the end of the observing season for RZ Lmi.
I think we can say that the RZ Lmi task has been completed and I will write up for the next BAA VSS circular.

Comments on this proposal are closed.