[vsnet-alert 13880] Re: possible CV in Aur J055640.90+343846.8

[Denis Denisenko]

The possible CV in Auriga TCP J05564090+3438468 reported by Andrey
Samokhvalov in [vsnet-alert 13879] is actually identical to the star
USNO-A2.0 1200-04082601 (R.A.=05 56 40.89, Decl.=+34 38 47.5, R=18.9,
B=19.6) which is visible on the Palomar plates near the limit of
sensitivity.

I have measured the position of this star from color-combined POSS-II
BRI image and obtained exactly the same coordinates as from Astrotel
observations (05 56 40.90 +34 38 46.8). The crop of this color image
(200x200" FOV) with the variable star marked by dashes:
http://pics.livejournal.com/bigdenru/pic/000b20gy/ Note the unusual
violet color of the star which is the evidence of variability between
the epochs of Blue, Red and Infared Palomar plates.

The field of this variable was covered by Palomar-NEAT project on
three nights in 2001-2002. The star is obviously variable by more than
2 mags, with the maximum brightness detected on the images from 2002
Jan. 15. Using USNO-A2.0 1200-04083580 with R=16.0 as comparison star,
I have measured the following magnitudes from the nightly combined
images (unfiltered with the red zeropoint):

20011219.20  20.4C  (Palomar-NEAT)
20020104.40  19.6C  (Palomar-NEAT)
20020115.17  18.2C  (Palomar-NEAT)

Animation of combined NEAT images from three nights is available here:
http://pics.livejournal.com/bigdenru/pic/000b3pgp/

There is nothing in 2MASS at the position of the new var, so it is
likely a new cataclysmic variable indeed. The fast rise (by 1.5 mag in
11 days between two NEAT observations) is also rather incompatible
with the pulsating red variable.

Denis Denisenko