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ER Uma and RZ Lmi: Observations requested.

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ER Uma and RZ Lmi: Observations requested.

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

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RZ Lmi and ER Uma both seem to have started a superoutburst

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.

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ER Uma completes a superoutburst; RZ Lmi about to start one.

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.

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ER Uma is close to the next superoutburst.

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

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04-01-2021

04-01-2021 0340-0421UT: ER UMa Mag. 14.8-15.0 (TG)

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Was this also with your 80mm

Was this also with your 80mm frac, Graeme? Really shows what’s possible with a small scope plus CCD.

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Yes - it needs much longer

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.

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Last minimum before super?

That could be the last minimum before the superoutburst begins.

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ER Uma and TESS record

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.

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2021-01-07 2154-2208UT

2021-01-07 2154-2208UT  ER UMa Mag 13.6V 
2021-01-07 2218-2234UT RZ LMi Mag 17.1V

(350mm Newt, ST2000XM)

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Jan 7th

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.

 

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RZ Lmi probably in superoutburst

AAVSOnet BSM_NM gave 14.25 V Mag at UTC 2021/01/12 04:58:12 which is similar to the previous two superoutbursts.

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ER Uma very bright

ER Uma probably in superoutburst at mag 12.6 V at 2021/01/17 04:44:36.