[vsnet-chat 589] Nova Confirmations

["STAN WALKER" <astroman@voyager.co.nz>]

Greetings,

One has to agree in part with Taichi Kato's comments in respect of IAU
Circular 6737 - nova discoveries are relatively infrequent and even the odd
mistake can be tolerated in an attempt to obtain more observations of
these. Or are novae not of interest any more? Surely a possible nova is of
more importance than some of the material published in these Circulars at
some expense. If any criticism is to be levelled it is of the considerable
amount of "non-telegraphic" material in the Circulars which lessens their
impact and appeal.

Rather than attempt spectroscopic measures why not get a UBV confirmation
of the object? Comparison of the B-V and U-B colours will almost always
confirm that the object is a CV and this is probably easier to arrange than
spectroscopy. A half metre telescope will get acceptable CV colours at V =
14 in about 5 minutes, including reductions, and at fainter magnitudes
there are probably not a great number of observational possibilities in a
nova discovery. 

Most nova suspects (regretfully there have been few recently) in the
Southern Hemisphere are checked out within hours and we could probably
offer to try objects south of about 30N.

The other answer is, of course, to use filters for the CCD images. Anyone
using CCDs for any VS discovery work should be using at least a V filter
and preferably B, R and I as well. The other comments in the circular were
sensible - in New Zealand we had a group of photographers who were turning
up new "variables" at an alarming rate. The simple process of taking two
frames eliminated 99% of these and saved a lot of fruitless pe measures.
The use of crude yellow and blue filters allowed some idea of whether any
real discovery was "just another faint red variable" or a possible nova.

If it would help the Photometry Section of the RASNZ can offer to do UBV
photometry of any suspects accessible to us. We have a number of members in
NZ and Australia who can produce reliable UBV measures down to about V = 14
if the object is a strong UV emitter such as a nova. The limit may be a
little less if it turns out to be a red variable of some type. Our CCD
photometry is presently limited to BVRI which is not as conclusive but we
have hopes of obtaining U sensitive detectors in the near future.

Regards,
Stan Walker
Director Photometry Section, RASNZ

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