[vsnet-newvar 1683] CMC12 190729.2-013610 is a Mira variable

[jg@jgws.freeisp.co.uk]

CMC12 190729.2-013610   -   Mira variable

RA 19 07 29.2807 sd 0.019"  Dec -01 36 10.242 sd 0.056"  (ICRS)  [REF1]

has r'_CMT_ mag 13.798 with standard deviation (sd) 0.862 from 6
photometric observatoins [see note2]

(see REF1 for details of r'_CMT_ magnitudes, which are meant to be
similar to SDSS r', itself a modification/extension/rederivation of the
'red' passband gunn r)

Examination of archival survey plate images of 1' square [REF2] confirms
this to be a large amplitude object on both sets of four red and four
blue plates dated 1950.5448, 1951.6427, 1988.4668, 1995.5797 (red
plates) and 1950.5448, 1951.6427, 1984.4175, 1988.6119 (blue plates)
respectively. Marked variation of the object relative to adjacent stars
is evident in both sets of plates, independently.

Despite being apparently quite faint visually (it is not in the GSC, but
that is not conclusive), the object is overexposed on a 1992.4011 'far
red' IVN plate and has 2MASS photometry of:-

J  6.495 +/- 0.014 ;  H  5.475 +/- 0.010  ;  Ks  4.937 +/- 0.012

showing the object to be bright in the near infrared.

It is solely detected at and shows a point source function in Band A of
the MSX5C infrared catalogue, suggestive of silicate emission from a
late type star.  (It lies within the 3" error margin of the MSX5C
position in terms of declination, but 1" outside of that in terms of RA.
However there is no other prospective candidate evident within an
arcminute).

It is also an IRAS source.

Marked variation randomly sampled over several survey plates is usually
consistant with a large amplitude regularly varying object (an erratic
object is likely to be at non-active brightness most of the time).

Red stars undergoing large amplitude change over time are invariably
Mira variables.


IDENTIFICATIONS :

USNOB1.0 0833-0472210 19 07 29.26 err .08" -01 36 10.1 err .09"
[REF2] [note1]

GSC2.2 S300232233258 19 07 29.26 err .26" -01 36 10.0 err .25"

2MASS 1907292-013610

MSX5C_G033.3351-04.3029

IRAS 19048-0140

---------------------------------------------------------



John Greaves



Acknowledgements: This research made strong use of Guide 8 by Bill J
Gray; the CDS online services of SIMBAD, VizieR and Aladin; and NOFS
archive server [REF2].  The CMC12 V1.0 (Carlsberg Meridian Catalogue 12
Version 1.0) was sourced via CDS ftp services from subdirectory
.../I/282, where an explanatory readme file and copy of [REF1] can also
be found.


[REF1] Evans D.W., Irwin M.J., Helmer L.  Astron. Astrophys. 395, 347
(2002)

[REF2] This examination made use of the USNOFS Image and Catalogue
server at www.nofs.navy.mil/data/FchPix


[note1] (USNOB1.0 identifiers' reality/meaning unsure at this time)

[note2]
A guesstimatory feel for the meaning of the r'_CMT_ standard deviations
was made by comparison of handfuls common objects from the CMC12 and
MISAO variables, and also of FASTT variables thought to be LPVs.  The
latter was also useful in having an instrumental magnitude passband not
too dissimilar to CMC12, indeed mean magnitudes from CMC12 and FASTT
often compared well to within a tenth or two of a magnitude.  From this
a cut off standard deviation on r'_CMT_ was guesstimated to give an
extremely small subset of the whole that possibility contained long
period variables.

Each is examined individually through many catalogue searches, which
often revealed that variability of the object was already known in the
GCVS, NSV, MISAO project, ASAS survey or FASTT.

Objects without a known and/or suspect variable star catalogue entry
were then examined via the NOFS archive images.  In some cases these
images revealed that the standard deviation values were the result of
duplicity induced variability (two or more _very_ close similar stars),
or revealed that the object just wasn't variable, at least to a large
enough amplitude to be noted on the images, such that the standard
deviation was likely to be caused by unknown experiment specific
factors.

The remaining, smallest number, of objects show evidence of being
unknown Miras.

This is from a subset of roughly 4100 objects in CMC12 with standard
deviation >0.75 (out of 6.3 million objects, but single observations
perforce have no standard deviation) preliminary results suggest
somewhere between 1 to 5 percent will be unknown Miras.

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