[vsnet-alert 2640] Extremely rare outburst of CI Gem

[Patrick Schmeer <extpasc@rz.uni-sb.de>]

EXTREMELY RARE OUTBURST OF CI GEM

Last evening I found on a CCD image taken upon my request by Mark Parker with
the UC Santa Barbara ROT (Celestron-14 telescope) on Feb. 18.185 UT a 'new'
object of mag 15-16 slightly south of the cataloged position of CI Gem.
As comparison image I used one taken with the same instrument on Feb. 11.161
UT.

Shortly after my detection I made a phone call to the Isaac Newton Group (ING)
at La Palma. Few hours later Pepe Vilchez and Peter Sorensen took three 150 sec
images with the Wide Field Camera (WFC) attached to the Issac Newton Telescope
(INT). The 'new' object is clearly visible on these images.

A candidate object for CI Gem in quiescence is marked both in Duerbeck's nova
catalog and in the CV catalog by Downes and Shara. The coordinates according
to D/S are:
R.A. 06h30m05.75s   Decl. +22d18'57.7"   (J2000.0)
The USNO-A2.0 catalog gives the following coordinates for this star:
R.A. 06h30m05.745s  Decl. +22d18'58.18"  (J2000.0)   r= 18.4, b= 19.0
Vilchez and Sorensen mention the very blue color of the 'new' object and a
magnitude difference of R= -2.6 and B= -3.9 between the 'new' object and
Duerbeck's CI Gem candidate. Using the USNO magnitudes I get R= 15.8 and
B= 15.1 for the 'new' object.
Using the first INT image I computed the following coordinates for the 'new'
object:
R.A. 06h30m05.90s   Decl. +22d18'50.8"   (J2000.0)
Nothing is visible at this position on the POSS image reproduced in Duerbeck's
catalog. So I would suggest a magnitude range for ('the true') CI Gem of 15 -
[21.

CI Gem = 101.1943 Gem = S 3428 was discovered in 1943 by C. Hoffmeister on
Sonneberg plates taken in 1940 January (MVS 30). The star reached a maximum
of mpg= 14.7 on JD 2429632.5 (Jan. 4) and was brighter than mpg= 16.0 between
JD 2429630.5 (Jan. 2) and JD 2429646.6 (Jan. 18) (P. Ahnert et al., VSS 1,
107).
W. Wenzel (IBVS 3440) found three additional outbursts on Sonneberg plates:
1963 Oct. 15 = JD 2438318.5: mpg= 16.5 (2 plates)
1966 Feb. 23 = JD 2439180.4: mpg= 16.5
1986 Dec.  3 = JD 2446768.6: mpg= 14.5

Spectroscopy and high-speed photometry are strongly recommended for the current
rare outburst of CI Gem (a SU UMa-type dwarf nova candidate).

My warmest thanks to Mark Parker and Tom Fuller (both UCSB) and Pepe Vilchez
and Peter Sorensen (both ING).

Regards,
Patrick

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