EF Peg – tricky photometry

[Mr Ian David Sharp]

Hi all,

Having seen a VSS alert about EF Peg in outburst (this is the first outburst detected of this UGSU star since January 2022), I was intrigued to observe it, especially in light of the fact that there is another star only 5 arc-seconds away.

I managed to arrange the star annulus to cover EF Peg and the Gap annulus to contain the near-by star with a clear background annulus. See attached screen shot. Also attached are the 6 measurements which averaged at Vmag = 11.80 (2025-08-28 21:21:43 UTC)

Cheers
Ian.

Attachments:

1. 

   EF-Peg-Photometry.png
   

2. 

   20250828_EF-Peg_V_PixelSkies-C11_IDS_plot_lines.png
   

[Gary Poyner]

Hi Ian,

Yep, it’s very tricky to measure. It’s easier visually. Unscrew your camera…;-)

Gary

[Mr Ian David Sharp]

Gary Poyner wrote:

Yep, it’s very tricky to measure. It’s easier visually. Unscrew your camera…;-)

How about this, Gary…this from last night – just over an hour.

Cheers
Ian.

Attachments:

1. 

   20250829_EF-Peg_V_PixelSkies-C11_IDS_plot_lines_check.png
   

[Tony Vale]

Isn’t this object likely to show superhumps during a superoutburst ? VSX lists an orbital period of 2.01 hours

[Mr Ian David Sharp]

Tony Vale wrote:

<p class=”wp-dark-mode-bg-image”>Isn’t this object likely to show superhumps during a superoutburst ? VSX lists an orbital period of 2.01 hours

Hi Tony,

Thanks. Just to prove your point here’s a long run of nearly 7 hours on EF Peg from last night in Spain. (2025-08-30 19:46 to 2025-08-31 02:28 UTC). The superhumps are very clear and you can see the Lomb-Scargle period analysis gave 2.0988 hours!

Cheers
Ian.

Attachments:

1. 

   EF-Peg-Period.png
   

[Tony Vale]

Hi Ian,
Excellent photometry and analysis as ever.
I thought (perhaps wrongly !) that the superhump period would be a bit longer than the orbital period not identical to it. I wonder if the VSX period is actually the superhump period not the orbital period. I notice that there is a smaller peak in the Lomb-Scargle chart at just over 1 hour. Could that be the orbital period I wonder ?

Tony

[Mr Ian David Sharp]

Tony Vale wrote:

Excellent photometry and analysis as ever

Many thanks Tony,

The best paper I can find is this one from 1993 and there does not seem to be a modern analysis as far as I can see.

Photometry of EF Pegasi during Superoutburst

The authors say the following in the abstract:

EF Pegasi was observed photometrically during a superoutburst in 1991 October. Superhumps seen during these observations were best fit with a period of 2h .09. This period is used to determine a likely orbital period of 2h .05 and a mass ratio (M_2/M_1) of 0.26. Distance estimates for EF Peg give values of 250 to 600 pc.

Cheers
Ian.

[Gary Poyner]

Hi Ian, Tony,

There hasn’t been a whole lot of t/s on EF Peg over the years – probably because of the difficulties with the close comparison star.

Taichi Kato measured the superhump period during the 1991 superoutburst as 0.08705d (Publications of the Astronomical Society of Japan, Volume 54, Issue 1, 25 February 2002). The Porb is 0.0837d, so yes, the superhump period is longer than the orbital – as expected.

Ian Miller obtained a good run during the 2009 superoutburst (the first observed since 2001). I’m trying to find Ian Millers Psh in my files, but I don’t seem to have it for some reason. If you have Peranso, then you could get Ian’s data from the VSS database and look at it to see if the Psh has changed.

Every time my PC updated the Bios I required a new code from Tonny, so I gave up with Peranso.

Gary

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