Following on from the IX Dra observations ( which continue at AAVSOnet), I am now monitoring ER Uma and RZ Lmi in order to time their superoutbursts. The supercycle period, P(sc), for these two are relatively short and apparently increasing as shown below from M. Otulakowska-Hypka‹ and A. Olech MNRAS 433, 1338–1343 (2013).
My estimate from the AAVSO, ASAS-SN and Lasair records suggests that their P(sc) values are around 44 and 24 days. The interest is to determine P(sc) for this observing season and check the above graphs. Fortunately, the AAVSOnet committee have agreed to a request to contribute one of their robotic telescopes to the task.
ER Uma may be starting a superoutburst now. RZ Lmi could be next week although both dates are long extrapolations.
I would appreciate help with these observations although both are really morning stars at present: only 35 deg above the horizon at midnight but overhead at 06:00. Ideal for robotic telescopes.
Thanks in advance
Stewart Bean
RZ Lmi was 14.26 at 2020/11/24 11:06:56 UT
ER Uma was at 12.8 at 2020/11/24 11:13:38 UT
Both were measured using AAVSOnet.
ER Uma was at 14.7 last night down from 12.8 at maximum 13 days ago. So that superoutburst has been completed. The superoutburst period is around 40-50 days so about this time next month could be the next one.
RZ Lmi is in quiescence following a normal outburst on 3 Dec. The next superoutburst is due shortly as its super period is only about 20 days.
Last night's result from AAVSOnet gave a V Mag of 13.5. Er Uma has displayed a series of gradually more intense normal outbursts. It is now 40 days since the start of the last superoutburst.
With a supercycle length of around 45-50 days in the present epoch the next superoutburst may occur shortly. The graph below shows how the supercycle period has varied over the last 200 cycles (27 years).
Previous superoutbursts have reached Mag 12.5.
Stewart
04-01-2021 0340-0421UT: ER UMa Mag. 14.8-15.0 (TG)
Was this also with your 80mm frac, Graeme? Really shows what’s possible with a small scope plus CCD.
Yes - it needs much longer exposures than with my 350mm newt at home(!) and there's greater uncertainty, but definitely can determine that it's not in outburst
Clear skies offer some definite advantage, and it's much darker there as well than my garden here in the UK!
Unfortunately, not possible last night.
That could be the last minimum before the superoutburst begins.
I also got Mag 15 on Jan4 from New Mexico AAVSO BSM NM2.
The only TESS record happens to show the approach to a superoutburst. The normal outbursts are 'peaky' or 'trianglular' at least compared to IX Da and RZ Lmi.
2021-01-07 2154-2208UT ER UMa Mag 13.6V
2021-01-07 2218-2234UT RZ LMi Mag 17.1V
(350mm Newt, ST2000XM)
I got ER Uma at 13.44 at 2021/01/06 05:06:59 from AAVSOnet
ER Uma is showing increasing bright normal outbursts. Should be in a superoutburst during the next 10 days based upon a 45-50 day period.
RZ Lmi at 16.7 at 2021/01/06 05:18:54 again from AAVSOnet. Will be in superoutburst shortly as its period is only ~ 20 days.
AAVSOnet BSM_NM gave 14.25 V Mag at UTC 2021/01/12 04:58:12 which is similar to the previous two superoutbursts.
ER Uma probably in superoutburst at mag 12.6 V at 2021/01/17 04:44:36.
In the next two weeks ER Uma will probably start a new superoutburst. This is based upon a superoutburst period of 55+/-5 days.
A graph of the superoutburst period against supercycle number is further up the thread - which shows this star "wanders" around 50 or 55 days for the super cycle period.
ER Uma is a good target in the spring. Observations are encouraged.
Stewart
ER UMa was last reported to be at a low state at 14.8 visual from Hungary. So a superoutburst should happen soon, but, unlike IX Dra , each period varies by upto +_ 7 days from the last. Observations would be most welcome in the next week - howling gales permitting.
The stream of AAVSOnet images I have relied upon for ER Uma, IX Dra and RZ Lmi ( all UGER stars) has paused for some reason.
Thanks in advance
Stewart
James DeYoung (USA) has uploaded three days of results - including superhumps starting at JD 2459285.5. So the outburst seems to have started at JD 2459285 giving a superoutburst period of 55.3 days since the last. This compares to 54.7 days for the previous period. So 55 days seems a good number to use for the next outburst although there may be an increasing trend as shown in the graph.
The next superoutburst may be around May 5th give or take a week.
ER Uma is expected to start a superoutburst shortly (due date May 5th) so if anyone can help with observations that would be great. ER Uma is a reasonably bright target when in outburst, at about V mag 13, and is high in the sky in the evenings during May. Yesterday it was down at Vmag 15 so that may have been the minimum before a rise to superoutburst.
Stewart
ER UMa, V = 12.88 ± 0.04 on May 5.
Stewart,
ER UMa at 12.4 visual on May 05.063UT. My previous observation was 14.6 visual on May 01.965UT
Gary
V mag 12.4 and 12.88 would suggest a superoutburst has started about 53 days from the previous start.
Jose Ripero Osorio (AAVSO) also reports 12.2 on May 4th.
If anyone can collect time resolved photometry to record super humps that would be good.
Stewart
Forecast looks OK for me this evening - I'll have a go if OK.
Continues to look like a superoutburst. Stewart
Currently 13.0-13.1CV (21:40-22:20UT on 6th May 2021). Answers on a postcard for this intruder...
Appears to show superhumps with period similar to the published 91.67min (going from the minima). Data in BAA VSS database for analysis. Got hindered by next door's greengage tree, and software hang at the end...
(Clear filter with V comparison stars used. 40sec each, ST2000XM+350mm Newt @ f4.52)
They look good to me. Variation of about 0.15 mag is about right for superhumps, i think. So it all fits.
Thanks , Stewart
ER UMa May 7.2837 2021 V = 13.08 ± 0.03
ER Uma was at quite dim last night at 15.0 V mag. It is also approaching time for the next superoutburst as the last one started around JD 2459338. With a super outburst period of 55 +_ 5 days, this minimum may be the last before a normal outburst triggers the superoutburst. A few extra observations in the next 5 days could capture the event nicely.
Thanks in advance.
Stewart
ER UMa appears in outburst this evening:
Jun 23.907UT - 12.83CV
I also find the variable bright at r 12.88 +/-0.05 (Unfiltered CCD, GaiaDR2/Astrometrica). Poor conditions of drifting high cloud in Moonlight Measurement were from start, mid and end of a frame sequence at 5s intervals for 20min.
Definitely in outburst and possibly this will trigger the superoutburst. The last superoutburst was recorded, at its brightest at 12.2 visual, by OJR (AAVSO) on 2459339. So we are ~50 days later right now. Could well brighten over the next day or two.
Stewart
Its a difficult target right now!
I used iTEL 18 last night to get a time series. VPhot reports the V filter magnitude dropping from 13.15 to 13.3 over 13 minutes. The variation may be related to the orbital period of 90 min or the change in skyglow in the dusk sky. Going to repeat tonight but starting a bit later. Stewart
The present superoutburst seems to have been recorded first by Graeme Coates and Tim Haymes on the evening of the 23rd June. This translates to a superoutburst period of 51 +-1 day which is right in the middle of the range of values from 45 to 55 days discussed in VSSC188.
Thanks again to Graeme and Tim and all other contributors.
This target is now really difficult and June has previously marked the end of the observing season. In October the whole cycle begins again with a possible superoutburst around Oct 1. Can this one be observed?
Stewart
AAVSOnet telescopes in New Mexico have made two observations of ER UMa this week marking the start of this star's observing season. As noted above, the next superoutburst may be around Oct 1 but could be later by a week or so as ER Uma does appear to vary its super cycle period between 45 and 55 days.
For UK observers, the star is very low in the north by north west sky in the evening. In the unsociable early morning, it does rise about 30 degrees above the horizon before dawn.
More details on ER UMa were presented in VSS Circular 188.