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[vsnet-campaign-dn 1318] Re: WZ Sge companion
Hi Arne,
A very interesting point here, particularly when you're using an ST6 in the
low-res mode to keep the download time short. I'd been wondering how the
data reduction would go once WZ was fainter and I found out last night -
with
about 5% of the
measures displaced by half a magnitude or so on the bright side.
Earlier I asked about the possibility of variability in the companion but I
see by the colours that it would be trivial. You've also confirmed this. I
was just going on appearance and I've experienced this in the past - with
stars appearing much brighter on very clear nights. But the photometer says
they're still the same!
I've been wondering about the earlier measures. From here WZ Sagittae moves
from around 3 air masses to 1.8 at the meridian. Consequently the focus is
never much good and the seeing wouldn't normally be tolerated. So the
companion star is a problem. I had no idea of the distance of this star but
I see you now have a good value so that I can now reset the software
apertures and
rework the data better. The thing that impresses me is that there are a
couple of guys in NZ measuring this from 41.5S - 6.5 degrees worse off than
here!
Regards,
Stan
----- Original Message -----
From: <aah@nofs.navy.mil>
To: <vsnet-campaign-dn@kusastro.kyoto-u.ac.jp>
Cc: <news@cba.phys.columbia.edu>
Sent: Tuesday, August 21, 2001 3:53 PM
Subject: WZ Sge companion
> For those interested, here are the UBVRI magnitudes
> for the companion (zero points from the Henden/Sumner sequence,
> which in turn was from only one photometric night, so
> the zero points on these can move a couple of hundredths):
>
> V B-V U-B V-R R-I
> 13.884 1.526 1.592 0.776 0.692
>
> photometric error is also about 0.02mag for each magnitude/color
> except for U-B, which has a 0.06mag error. I'll adjust
> these values in a few days when I get more photometric data
> on the field.
>
> The companion is about 7arcsec west of the variable, so if
> you are using apertures larger than about 15arcsec diameter,
> you will be including the much of the companion in the aperture.
> For unfiltered or reddish filters, the companion currently
> contributes about half of the light in apertures that include
> both stars. For apertures smaller than 15arcsec, you will be
> just measuring the variable. It is those apertures near 15arcsec
> that will have the most problem, as you may or may not include
> the companion depending on the seeing and the quality of your
> centroiding when two equal-magnitude stars are near each other.
> Arne
>
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