[vsnet-chat 3828] Re: [vsnet-alert 5399] Re: Nova suspect in Tau

[aah@nofs.navy.mil]

This is a likely variable for at least two reasons:  it is
very red, probably intrinsic since other stars in the
region do not exhibit the same redness, and almost every
intrinsically red star is variable;  and Brian Skiff mentioned
the object was barely visible on three POSS plates, yet my
B frame easily detects the object.  (note: there is another
faint red star in the grouping of three just to the southeast of
the object in question.  The URL for my 4-filter composite,
in case it didn't get copied to vsnet-chat, is
http://ftp.nofs.navy.mil/pub/outgoing/aah/misc/nova.jpg)
  Most extreme red objects are long period variables, so
to get a good period, you may need to monitor the star for
a year or more.  Since Miras/SR are pretty common, IBVS will
probably require that you do get a decent estimate of the
period and a light curve before they will accept the object
for publication.  However, I bet that this object is in
both the ROTSE and LOTIS databases, so you might contact
them to see if you can get such data prior to their formal
release.  Just go to
http://vsnet.stsci.edu/astroweb/astronomy.html
and search.
  Note that accurate photometry of red objects is quite
difficult.  Different types of unfiltered CCDs will have
very different red responses, so combining data from
multiple sites will usually have systematic errors.  Even
filtered observations will need to be transformed onto the
standard system by taking data in at least two standard filters.
You will need to use comparison stars that are considerably
bluer than the variable since using similar-colored stars means
that they too will be variable.  This color difference will also
yield systematic differences between sites.
Arne

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