[vsnet-chat 912] (fwd) RE: comments NGC4462 (Filippenko)

[Taichi Kato <tkato>]

From alex@wormhole.berkeley.edu Wed May  6 01:47 JST 1998
Date: Tue, 5 May 1998 09:46:56 -0700
From: alex@wormhole.berkeley.edu (alex filippenko)
Subject: Please send this to vsnet-chat; I am unable to do so.


To all concerned:

  Regarding the circumstances of the discovery of SN 1998bn,
Dr. Michael Richmond's explanation (see below) is correct.  We were
very disappointed that our discovery was made 10 days after it might
have been.
  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.
  I certainly have always appreciated the efforts of the M1 group, and
am very grateful for their discovery of SN 1993J.
  Sincerely,

  Alex Filippenko

****

>From richmond@a188-l004.rit.edu Tue May  5 06:26:40 1998
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To: DRODRIG@santandersupernet.com
Subject: Re: [vsnet-chat 908] comments NGC4462 
Cc: alex@astron.Berkeley.EDU
Date: Tue, 05 May 1998 09:17:44 -0400
From: Stupendous Man <richmond@a188-l004.rit.edu>
Content-Length: 2506
Status: R

  I am no longer a member of the UC Berkeley SN Search team, 
but I think I can give you an explanation for the delay in their
announcement of SN 1998bn.  Please understand that I am merely
an interested bystander, and not speaking in any official capacity.

  The UCB group is expanding their search; they have a relatively
new telescope, and I believe may be changing their search strategy.
As a result, they are in the process of building up a set of 
"reference images" for galaxies in which they will look for SNe.

  The Apr 17 image of NGC 4462 was, in fact, intended to be a
reference image.  It was the first picture of the galaxy to be taken
under new circumstances.  The UCB search is set up to be conducted
automatically by software.  The software could not compare this
first "reference" image to any other, and so did not realize that
a new object appeared in it.

  If the UCB search was conducted by humans, who could compare each
and every image (even the "reference" image) to older photographs 
of each galaxy, then the object might have been found the next day.
But that's not the way it works.

  Note that SN 1998bn was very faint in this Apr 17 image -- not
very far at all about the detection threshold.  It would not have
been obvious, even to a human examining the image.

  The very next good image of NGC 4462 was taken 10 days later, on 
Apr 27.  The software compared this image to the Apr 17 reference
image, correctly noted that one source had brightened considerably
(about 3.7 mag), and alerted the UCB team.

  You will see that IAUC 6886 explains this set of circumstances,
as well as the abbreviated space allows.

  I believe that it is safe to say that this is one case in which
a dedicated set of human observers, such as the M1 Group, might have
beaten the automatic search to the punch ... if they had been 
looking carefully at NGC 4462 between Apr 17 and Apr 27.  It goes
to show that there is plenty of room in this business for automatic
AND human search teams; no single approach is always the best.

  I admire both the M1 Group and the UCB SN search team for their
hard work, and hope that everyone can focus on the new SN discoveries
that each will make.  I don't think that criticizing each other in 
public fora is good policy for any group of scientists.

-- 
-----                                      
Michael Richmond                   "This is the heart that broke my finger."
mwrsps@rit.edu                     http://a188-l004.rit.edu/richmond/




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