[vsnet-newvar 1742] re New Bernhard variable (BrhV126)

[jg@jgws.freeisp.co.uk]

Now that USNO B1.0 is available via ViZieR I impore new variable
searchers to use the B1 and R1 magnitudes in it instead of USNO A2.0 red
and blue.

Why?

Well, it seems that R1 and B1 are predominantly same date observations
from POSS I = DSS1 images, so for example in this case we get B1-R1 of
around +1.7, whereas the USNO A2.0 red - blue is +2.2

In this case it isn't too crucial, but sometimes GSC2.2 and/or USNO A2.0
seem to use a mix of plates from DSS1 and DSS2, ie plates of different
dates, which means some of the apparent colour difference can actually
be a result of the variability of the object.  Things can then appear to
be very red when they are not.  Most DSS2 plates are not same date, so
if the red and blue magnitudes are from those, there is the same
problem.

There is also some improvement in photometry in B1.0 apparently, or at
least a better calibration source is used.  I have seen no appraisal of
this as yet, however.


Anyway, having said that:

I downloaded the plates from the NOFS server,
www.nofs.navy.mil/data/fchpix , and found that there are only DSS1 and
DSS2 plates available, ie one each of red and blue for DSS1 and DSS2
(and one DSS2 IVN incidentally).

The star is overexposed on the red plates, and nearly so on the blue.

However, little variation can be seen on these plates, which from past
experience suggests that the star is most likely variable at less than
two magnitudes in amplitude.

So, it is more likely a SemiRegular variable if an LPV, it being a
likely LPV from the photometry and colour, as Klaus noted.


A BrhV126 MISCELLANY :-

BT-VT from Tycho2 is +1.0

Also StM 543 of spectrum M6.5, helping confirm its LPVhood

Brightest in IRAS in the 12 micron band, possibly suggestive of silicate
emission, again helping to confirm LPVhood.

In 2MASS, but no photometry given, so probably only included as a
'marker' object


Cheers

John Greaves

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