[vsnet-chat 584] Comment on IAUC 6737

[Taichi Kato <tkato@kusastro.kyoto-u.ac.jp>]

(cc: of mail to Marsden, not sent to the list)
Dr. Brian Marsden,

  You wrote in IAUC No. 6737:

>      In the specific case of a CCD or photographic detection of an apparent
> supernova and nova, observers are henceforth requested, before
> making a report, to perform at least three of the following four tasks,
> if credit is expected for a discovery.  Firstly, they should make a
> precise astrometric measurement of the object's position, specifying
> date and time (and magnitude); secondly, they should also
> observe on a second night to verify that the object is in precisely
> the same location; thirdly, they should show that the object was
> not present on comparable images on some other occasion;
> fourthly, they should clearly demonstrate the object's nature from its
> spectrum.

  These task criteria may hold in solar system objects, but I completely
disagree the second (and in many cases, fourth) point particularly in the
cases of novae and possibly supernovae.  Waiting for a second night for
fast novae (and supernovae) in early stages is simply a waste of the
"first day of the golden time".  Novae in fireball stage will in less than
a day change themselves by cooling and veiling the hot source.  The same
may be true for early supernovae.  The second night may be in some cases
already too late.  This is the point quite different from in minor planet
discoveries.  We have learned the case of Nova Sgr 1996, which was left
unnotified to potential nova observers for more than two weeks (!) since
the discovery report reached the CBAT.  The only plausible reason for
such a treatment was the fourth point -- the object was not spectroscopically
confirmed.  The light from the nova passed in vain the earth in the meantime,
and the information was lost forever.  I have heard from Sakurai-san (the
discoverer) himself that he also felt regretful of the astronomical loss,
and the waste of human opportunity of witnessing the early evolvement of
that nova.  Even without spectroscopic confirmation, we can still do useful
photometry (and maybe some spectroscopy) and astrometry, and a search for
quiescent counterpart.  Some false alarms may arise if any of criteria
is not fulfilled, but many experienced field astronomers usually quickly
know which is false and which is true.  This usually minimizes the
expense of the telescope time.  I personally feel the reasoning mentioned
in the IAUCs 6736, 6737 are only justified in the point of the proper
assignment of credit to the discoverer.

Regards,
Taichi Kato

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