Tue, 11/26/2013 - 14:25


CT Lac is a star I stumbled over several weeks ago while looking for examples of long-period pulsating variables.  It's a semiregular (SRa) and carbon star with very long period of 562 days.  If you look at the last ten years or so of data, you'll find that the amplitude has appeared to decrease and, more strikingly, the maximum magnitude has also appeared to decline.  The AAVSO light curve only goes back to the late 1960s, but in that time at least there's no evidence of similar behavior.

It's possible the star is doing something similar to the Miras and semiregulars with long secondary periods (like RU Vir), but there's no way to tell that without additional multiwavelength observations and/or spectra.

This star isn't well observed and observations appear to be very sparse even though Lacerta is well placed right now.  If you are looking for interesting objects to mix up your observing program, this might be a good one to add to your list (both visual and CCD).


American Association of Variable Star Observers (AAVSO)

Thanks Matthew,

I've been looking for some LPV's for long term ob's, CT 's now on my programme. (no idea how I missed this post  !)


CT Lac


Thanks for calling CT Lac to our attention. I will try to get on this star as soon as possible. It looks like a great on e for visual observers. There is even a 6.3 magnitude star right by CT. Those of you with the AAVSO Variable Star Atlas can find the 6.3 star marked 6.3. There is no Flamstead #. You can use the Atlas chart as a good finder. CT is not marked on the first version of the Atlas, I don't know about the second. Make sure you print off a new VSP chart. I had a 2011 one and I found a few comp star differences!!!


Chris Stephan  SET

Wooster, OH

American Association of Variable Star Observers (AAVSO)
v778 cyg

V778 Cyg is another red star like this; apparently Carbon star, well north too, and right next to that galaxy on the Cyg-Cep border (NGC 6939 I think) that is a good source of supernovae! V778 Cyg isn't faint - around 10-12mv.