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

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