[vsnet-chat 913] Re: comments NGC4462 (Filippenko)

[Taichi Kato <tkato>]

Alex Filippenko wrote:

>   My comments in the Sky & Telescope article were not meant to be a
> criticism of the M1 group. Rather, they reflect the unfortunate fact
> that there was no simple way to rapidly communicate results to large
> groups of astronomers back in 1993. With e-mail communications much
> more extensive these days (for example, through this nova network),
> such delays are generally minimized.

   On the SN 1993J occasion, there was already "nova network", from which
I was first informed of this rare event.  The network was already actually
in operation, and the M1 group informed to the most appropriate astronomical
communities, but the news was issued nearly a day after.  Further to comment
on, my log on SN 1998J clearly shows the first news was from the AAVSO.

   On the contrary to the Filippenko's above comment, the CBAT seems to be
more enthusiastic in introducing addotional constraints to discoverers,
which, if strictly followed by an observer, may result in an unrecoverable
delay of a day or even more.  The observer may be requested to take a second
night image in order to verify the suspect supernova is not a foreground
asteroid.  The CBAT's statement is outlined in IAUC 6737, and I made the
following comment in vsnet-chat 584.

(http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/Mail/vsnet-chat/msg00584.html)

    The vsnet-chat thread can be followed from the above URL.  Some relevant
parts extraced below:

---------------------------------------------------------------------------
from [vsnet-chat 584]

  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

---------------------------------------------------------------------------

also from [vsnet-chat 595], in response to Marsden's reply:

    Additional comments:

(1) The positional problem of SN 1993J was quite minute.  It may be actually
that that very observer missed the chance of getting the earliest spectrum,
but many others actually managed to take the spectrum even before any accurate
positional measurement was issued.  Our Okayama Astrophysical Observatory
colleagues were not an exception.  The position was revised by the first-aid
volunteer astronomers.  It sounds to me only an excuse to give that very
specific case (unsuccessful attempts are quite often attributed to inadequate
information -- of course, I am not intending to referring to that
observation).  I certainly believe a great majority of supernova researchers
welcomed the initial SN 1993J discovery alert, though it was at that time
too rough to meet your suggested standard, being distributed timely through
internet.

---------------------------------------------------------------------------

also from [vsnet-chat 631]

Dear ISN people, the CBAT members, and vsnet-chat members,

    Just for the record.  I have successfully retrieved articles from my
log file of SN 1993J showing how efficiently the network worked at the
very earliest stage of discovery confirmation and observations.  Hope
this actual time sequence would help the discussion of SN discovery and
confirmation matters.

Best regards,
Taichi Kato
--------------------------------------------------------------------------

    The first alert of SN 1993J reached me via Novanet, just before noon
of 1993 Mar. 30, local time.  J. Mattei of the AAVSO sent this alert
at around 01h 56m UT (Mar. 30), addressing the discovery of a possible
supernova in M81 by Francisco Garcia Diaz.  This article stated that
the object was detected visually by him on Mar. 28.86 UT, and confirmed
using a CCD by Diego Rodriguez on Mar. 29.1 UT.  So it took nearly a day
this first alert to be known by world-wide observers after Rodriguez's
confirmation.  This alert described the position of the object as "200
arcsec south and 210 arcsec west of the nucleus, and is about 25 arcsec
to the northeast of a 14.0 magnitude star shown on finder charts of this
galaxy by the AAVSO and those by G. D. Thompson and J. T. Bryan".

   About three hours after this alert, S. Starrfield forwarded a message
to Novanet that the supernova was "confirmed" visually by an ASU student.
He also relayed an updated relative position to the galaxy.

   At about 06h 02m UT, P. Garnavich posted to Novanet the first spectro-
scopic observation of the supernova, taken at 06h 00m UT, suggesting a
very early type-II.  This spectroscopic observation was also reported
(at the bottom lines) in IAUC No. 5731.

   A. Filippenko sent almost simultaneously (06h 03m UT) an alert article
calling special attention to this object, and suggested how to make
useful spectrophotometric and multiwavelength photometry.  He noted that
the chance of initial infrared observations at the Palomer 5-m was missed
due to the large positional error in the initial report [if only there
was WWW and a displayed image, this misfortune would not have occurred..]

   Thanks to these alert messages and adequate suggestions, many observers
could follow the earliest development of this supernova, and western
observers were given enough time to optimize their observations:
BVRI-photometry started on Mar. 30.19 UT (Richmond), well before the
discovery was announced in IAUC issues, and U-measurement on Mar. 30.89 UT
(Penny at La Palma) when the ultraviolet flux was dramatically decreasing.
The earliest (to my knowledge) visual observation outside the discoverer's
group was apparently done by T. McGrath on Mar. 30.17 UT, and a number of
experienced variable star observers just followed.

---------------------------------------------------------------------------

PS. Dr. Filippenko, and interested, please feel free to (temporarily)
    subscribe to vsnet-chat.

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