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[vsnet-chat 6223] Re: [vsnet-campaign-v4641sgr 169] Re: V4641 Sgr, recent data

In a message dated 4/11/2003 7:19:46 PM Central Standard Time, tkato@kusastro.kyoto-u.ac.jp writes:


Re: [vsnet-campaign-v4641sgr 168] Re: V4641 Sgr, recent data

> > # I wonder what is the reason for a 1-mag difference between visual and
> > # CCV V-band observations.
> >
>
> I am guessing the difference is due to emission lines.  This is similar to
> what is observed in novae during the nebular phase.

    Less likely.  V4641 Sgr lacks strong emission lines in quiescence,
which was the reason why the object was disregarded by most of CV observers.
The spectrum strongly resembles that of an A0 star, indicating that
there is little chance for an error arising from transformation/response
function problems.

Regards,
Taichi Kato


Taichi:
To make sure I was measuring the correct star, I measured the position on one of my images to be 18 19 21.6 -25 24 24.9 +/- 0.4 arcsec (based on GSC 1.1).  IBVS 5068 gives a position of 18 19 21.7 -25 24 25.  I also checked some other images on the web and IBVS and I feel I am measuring the correct star.  There is a star at 18 19 22.66 -25 24 10.0 (my astrometry).  I measured this star at V=13.8 using AAVSO chart photometry.  This star is 20.7" (PA=316 degree) from V4641 Sgr.  Maybe this is the star others are observing??
Regards,
Doug West

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