[vsnet-chat 4620] Re: V589 Her

[aah@nofs.navy.mil]

I just realized that I observed this field Sunday night
during a flurry of photometric calibration activity
(a break in the monsoon).  The variable's position and
magnitude from this recent BV image pair:

16:22:07.16  +19:22:37.1  J2000  +/- 0.1arcsec internal
  V   = 18.25 +/- 0.04
  B-V = +0.35 +/- 0.06
  
So again, the position agrees with the ones posted earlier.
The magnitude of the variable is somewhat fainter than
the quoted USNO-A magnitudes, but that is common.  I wasn't
trying to get photometry on the CV itself which is why the
photometric errors are so large.

Yamaoka-san mentions:
>>Since Yamaoka-san notes a fainter companion,
>>you should be careful on your photometry as the CV fades.

>But every DSS image shows the USNO star far brighter than a dim star I
>noted.  I guess this dim star will not affect large for the photometry
>even on quietience.

The dim star is fainter, but not that much fainter than the
quiescent CV.  If an included companion star is 5 magnitudes fainter,
it will make a 0.01mag difference in the photometry.  In this case,
the magnitude difference between the two stars is much less, and since
the angular separation is only 2arcsec, the fainter star will be
included in any aperture photometry. In particular, for CVs the
intrinsic color tends to be quite blue and faint companions tend
to be quite red.  Therefore the measured color of a quiescent CV
with a close angular companion will often be considerably redder
than in reality.

Arne

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