ER UMa stars: V1159 Orion update

[Stewart John Bean]

With the clocks changing, its time to review the behaviour of some of the ER Uma stars. First up: V1159 Ori.

VSSC 193 covered V1159 Ori in detail suggesting a irregular trend towards longer superoutburst periods ( 45 days to upto 70 days). The nominal definition of ER Uma is that they have superoutbursts between 20 and 90 days apart. Recent V1159 Ori observations support the trend but also make a definitive statement difficult.

This trend appears to be strengthening with only two superoutbursts ( JD 2460611 and 2460741) in the most recent complete observing season – 130 days apart. Interestingly the frequent normal outbursts continue which are perhaps a better definition for this group of stars.
The difficulty of interpreting the light curve is compounded as two superoutbursts may have occurred either side of the observing season. The good news is that a superoutburst was observed in early 2025 September meaning that we a have a chance to observe the next superoutburst over this winter. After the next superoutburst I will prepare an update for the VSSC.

Regards

Stewart Bean

[Jeremy Shears]

Thanks for the timely update, Stewart.
One to keep an eye on over the next few months.

[Stewart John Bean]

How do I look up the ZTF code for ER Uma? It will be something like ZTF******* Stewart

[Stewart John Bean]

For V1159 Ori an observer on the equator would be able to fill in, to some extent, the summer gap in observations.

[Jeremy Shears]

Stewart John Bean wrote:

How do I look up the ZTF code for ER Uma? It will be something like ZTF******* Stewart

VSX lists synonyms, but not for ER UMa it seems. In the case of V1159 Ori it is ZTF22abhvjny

If you need ZTF photometry on ER UMa, you can access it from the the VSX entry on ER UMa, using the “External Links” drop down and selecting “ZTF”.

• This reply was modified 2 weeks, 5 days ago by Jeremy Shears.
• This reply was modified 2 weeks, 5 days ago by Jeremy Shears.

[Mr Ian David Sharp]

Hi all,

Here’s a run I did on V1159 Ori the night before last from my C11 in Spain (2025-10-27). Interesting short term variability. The SNR of the target star was around 100. The average V mag was 14.89 over the 21 frames.

I will carry on monitoring it…

Cheers
Ian.

Attachments:

1. 

   V1159-ORI.png
   

[Stewart John Bean]

Ian,
Interesting that you are in Spain. One of the challenges is to observe V1159 Ori ( Declination only -3 degrees) around conjunction. The best place would be from the Equator. All my reported observations have been via an AAVSOnet project.
I forgot to use the Slooh Canary 2 (27 deg latitude) instrument this summer for the job – especially as it now has a V filter.

VSX gives a period of 90min for V1159 Ori.

Stewart

[Mr Ian David Sharp]

Stewart John Bean wrote:

VSX gives a period of 90min for V1159 Ori.

Hi Stewart,

Well, I’m not in Spain but my kit is. I’ll try and get a really long run on it to see if I can pick up the period. The weather in Spain is not cooperating!

Cheers
Ian.

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