[vsnet-chat 5265] Re: V4740 Sgr Photometry

["Stan Walker" <astroman@xtra.co.nz>]

Hi Arne,

On this topic I remember making UBV measures of a nova many years ago from
Auckland where the B-V came out at -0.65 or similar. Quite nonsensical. The
guys at Mt John said that this nova had the highest H beta emission they'd
ever seen. But it illustrates your point about broadband photometry.

Regards,
Stan

PS. The earlier message had a brief attachment - should have put this in the
text. Apologies to all.


----- Original Message -----
From: <aah@nofs.navy.mil>
To: <vsnet-chat@kusastro.kyoto-u.ac.jp>
Sent: Tuesday, March 26, 2002 3:37 PM
Subject: [vsnet-chat 5261] Re: V4740 Sgr Photometry


> 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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