[vsnet-chat 4748] WZ Sge companion

[aah@nofs.navy.mil]

Continuing on my comments from yesterday, the coordinates
of WZ Sge and its companion are (my data using USNO-A2.0):
WZ Sge     20:07:36.53  +17:42:15.2  J2000
companion  20:07:35.77  +17:42:17.1  J2000

with typical errors of 100mas. This gives a separation of 10.9 arcsec.
This is not as bad as I mentioned earlier; the 7arcsec
value came directly from Robinson, Nather and Patterson
1978 ApJ 219, 168.  Based on my newly derived photometry
for the comparison:

  V     B-V    U-B    V-R    R-I
13.884  1.526  1.592  0.776  0.692

(0.03mag total errors except for U-B which has 0.07mag error),
you should not have problems with contamination as long
as your aperture is 15arcsec in diameter or smaller.
I'd suggest either using a small aperture or else one
large enough to encompass both stars; the inbetween ranges
will have some wierd results.  Remember, however, that the
contamination is highly dependent on your passband, worse at
red wavelengths or with unfiltered photometry.

Stan Walker mentions that he feels the companion is variable.
This is likely due to the redness of the companion.  However,
my data from 1995 plus this recent photometry match within 0.02mag,
though this is only over a total of 5 days in two closely spaced
sets and so is not definitive.

Note that HST visits WZ Sge again tonight (010822 UT) from
06:12 to 12:01 UT, and Chandra visits from 08:40 to 11:40;
time series monitoring is highly recommended!
Arne

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