[vsnet-chat 5261] Re: V4740 Sgr Photometry

[aah@nofs.navy.mil]

Doug presented a compilation of the photometry
available for V4740 Sgr.

Assuming that the photometry is properly calibrated (and
you should really check this, since the 2001 datasets
must obviously have different comparison stars than the
2002 ones, based on the brightness of the nova), then
the problem probably resides in the fact that you are
using broad-band filters on a non-blackbody object.
Usually novae go into what is called the nebular phase
about this time period past the peak, and that is dominated
by emission lines.  You really need to get a spectrum
and see what is going on.  While the continuum is probably
too faint for your spectrograph, the emission lines might
peak high enough for you to detect with a long exposure.
You might give it a try, or find some kind professional
that will let you look over his/her shoulder.  The Asiago
observers follow novae quite a bit; perhaps someone like
Rosino could be contacted.
  Of course, if you think broadband filters are giving
you problems, just try to calibrate unfiltered photometry
of nebular-phase novae...
Arne

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