Re: Tycho 992-1443-1

[jg <jg@jgws.freeisp.co.uk>]

Michael Koppelman wrote:
> 
> This one seems slightly suspicious. It's star 12525 in the July data set.
> It's not a huge variation, but the average V mag goes form 10.95 to 11 in
> 4 days and I goes from 8.84 to 9.01. That's almost 0.2 mag. This is after
> I delete all the lines with a flag that is non-zero. Tycho has it at 11.1
> in V. B-R is 2.7, so it's pretty red. A linear trend line in Excel says it
> is dimming by 0.044 mag per day in I.
> 
> Michael K.

This "faint" IRAS source is gonna turn out to be an LPV if ought.

That means month's to years to tie down a period, if any, as there'd be
no periodicity if it turns out to be an Irregular variable of low
amplitude, or ill defined (multi)periodicity if a semiregular of low
amplitude.

Tycho has it at 11.1 in VJ or 11.1 in VT????  Red stars get problematic
in Tycho especially when it comes to derivation of VJ if it turns out to
be VJ that you're quoting.  If VT you're quoting, that's meaningless in
this context.

Just looked it up.  VJ is 11.04 according to Tycho, so it don't look
high amplitude.  BT-VT about 2.3, not very red.

Summary: yep, probable variable, but highly likely to necessitate _long_
term CCD work to characterize, with no necessity of any periodicity
being found even then, though magnitude range would be so evinced.

Cheers

John G.