[vsnet-image 11] GSC 3712 00317 : a 2MASS selected red variable

[no name <crawl@zoom.co.uk>]

In vsnet-id-2mass 27 it states that GSC 3712 00317, suggested as
variable from 2MASS indications by Taichi Kato in vsnet-id-2mass 19, is
variable, based on red plate images derived from the USNO Flagstaff
Station Finder Chart Service at :

http://www.nofs.navy.mil/data/FchPix/cfra.html

[see
http://www.kusastro.kyoto-u.ac.jp/vsnet/Mail/vsnet-id-2mass/msg00027.html]

The attached [32kb] JPEG file shows 4 red plate and red filter fields
for this star taken at different times, each field being very roughly an
arcmin across and plate limit about red mag 20 or so.

Although slightly different emulsions and filters are used in each
image, which can cause some brightness variation due to colour effects
in such a red star, it can be seen that relative to all the other stars
in the field, this star varies in brightness over and above effects like
variant exposure times etc.

The image contains 4 clips derived from plates of the following surveys,
clipped from the original 3' requested USNOFS pixel plots, with GSC 3712
00317 near centre in each case...

Plate Details:

Top Left:     POSSI  plate; date 1952.7077; emuls: 103aE; filter: RP2444

Top Right:    POSSII plate; date 1989.9671; emuls: IIIaF; filter:
RG610-4

Bottom Left:  POSSII plate; date 1993.7262; emuls: IIIaJ; filter:
GG385-2

Bottom Right: POSSII palte; date 1994.8241; emuls: IVN;   filter  RG9-8


Although only 4 plates were found in this instance, as many as 10 can be
found.  Keep images down to 3 arcmin or less for smaller files, and
follow the USNOFS instructions.  Select "yes" in the pixel dialogue.
BEWARE: ensure you only use red or blue plates that are _also_
*filtered*, as nonfiltered plates behave different and give the
impression of variability in comparison to the filtered plates, whilst
only really showing colour effects.

See
http://www.kusastro.kyoto-u.ac.jp/vsnet/Mail/vsnet-id-2mass/maillist.html
for more candidates, some people discover comets in SOHO LASCO images on
cloudy nights, now new variable stars can be identified from survey
archive images on cloudy nights...

Cheers

John

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