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I have included Y UMI in my CCD observing program since January. This star has only few observations in its light curve. Looking at its light curve it seems to me that it has recently displayed a hump in the descending light curve at B and V while at Ic the light curve appears to be very flat at around maximum. I am aware that it is probably too early to jump to any conclusion but perhaps this star can be added to the humper list (I don't recall having seen it there but I maybe wrong) as suspected humper.


Gianluca (RGN)

sfra's picture


Your work with Y UMI certainly shows a very interesting light curve.  I have never seen a "stall" on the decending light curve unless it's part of a Dual-Maxima event. Dual-Maxima events appears to be closely related to the "stalling" or "hump" behavior seen on many Mira stars.  The RASNZ has been doing a long project on stars that show Dual-Maxima behavior.  The following is a link to their project page that explains a lot about this behavior: This website is in the process of being update.

W. S. G. Walker published a paper in 2009 in the JAAVSO on one star, BH CRU, that shows this behavior.  He may have more updates available but I couldn't find them today.

It's shame that Y UMI has so few observations in the AID, only 269 as of this afternoon.  I'm going to add it to my observing list and start tracking it too if the skies here ever clear!

I'm going to add it to the "Humps" page as a potential Dual-Maxima star and a star to be watched over it's next few cycles if not longer.  I'm glad you are getting obseration with B, V and Ic filters as this may be important on it's next Maxima or Dual-Maxima.

This may be a very interesting star to watch! 






Hi Frank,

thank you for adding Y UMi in your list of targets. It is an interesting star but observing for me will be getting harder over the next period of time, particularly at B, as it is approaching mimimum. I am observing it with a small refractor (90 mm) as it is the only scope I can actually place on my small balcony.  To obtaing a decent SNR I have to take quite a long exposures but I feel this star will be out of reach for me when it is approaching 18th magnitude. If you have a bigger scope it would be probably an easier target to follow at B.


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