[vsnet-chat 527] Re: Variable near M27 (Jahn)

[bas@lowell.Lowell.Edu (Brian Skiff)]

     The B-R color of 3.5 is actually quite typical for mid-M giants, such
as semiregulars or Miras, especially for such stars right on the galactic
plane.  I have been identifying many hundreds of IRAS sources with stars
appearing in photographic-infrared spectral surveys, and their colors in the
A1.0 catalogue are typically ~3.5 or higher (5.0 is not uncommon because
of the sometimes heavy reddening).  Mainly what the color information tells
us is that the star is another of the ubiquitous cool variables.  If we make
the naive assumption that Gianluca's images show something like the full
amplitude (no more than about 1.5 magnitudes at R), then the star is more
likely to be an ordinary semiregular rather than a Mira.  The period (better
as "cycle length") is thus probably more likely to be ~100 days rather than
the ~300 days typical of Miras.
     Observations about once per week with V and I filters should readily
reveal the lightcurve.  As mentioned previously, there are other known
variables in the field (the Masi variable _is_not_ Ondra's variable), and
certainly plenty more to be found, so CCD frames covering the field near
M27 on a consistent basis will provide data on more than just this star.
     By the way, the Masi variable is not otherwise catalogued, does not
appear in IRAS, etc.

\Brian

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