[vsnet-chat 610] Re: Stationary Asteroids and SN

["Wayne P. Johnson" <wpjohnson@anet.bna.boeing.com>]

     Bill,
     
     You make some valid points that should be incorporated into any SN 
     search program. We do not have an internet connection at our 
     observatory, but we are working to convince the board members that it 
     has become essential, no longer optional. That was the basic problem 
     with our N772 situation. We have a few club members who subscribe to 
     the IAU circulars, which I think is a great service. But I also think 
     that the ISN's webpage and notification service are invaluable. They 
     are not meant to be (nor do they pretend to be) the final authority on 
     the reality of a SN. It's nice to have an image to refer to when 
     following up a discovery or helping out on a potential one. One of the 
     big concerns in CBAT is the "request" for a spectroscopic check of the 
     candidate being interpreted as a "demand". As far as I'm concerned, if 
     it can be shown by looking at a reference image (from the DSS, Wray or 
     Vickers, say), another observation or calculation that the suspect is 
     not a SN then the question has been answered. There's no need to go 
     any further. 
     
     We did not have  access to the web at our observatory which caused a 
     lot of confusion for the CBAT when they received word of two SNe in 
     different locations in N772. We checked our planetarium program to see 
     if there were any asteroids near the galaxy. Two were located but they 
     were about 5' away, close but not that close to be of concern (or so 
     we thought). We also took a couple images separated by half an hour to 
     an hour to check for motion. We saw no motion. Of course, dawn light 
     was rapidly approaching which limited our ability to get a longer 
     baseline. Asteroid 1887 was of the expected brightness for a SN on the 
     rise in that galaxy and it was right along a spiral arm. I had a 
     previous image from the weekend before, which showed nothing there. We 
     did not think about an asteroid being at its stationary point. That 
     was a whole new trick.  
     
     As far as the reference image being "home-grown", that is the best of 
     all possible worlds. My other recent suspects point that out rather 
     well. I detected possible SNe very close to the nuclei of the 
     galaxies, N7727 and N379. I consulted the resources I had: the DSS, 
     Vickers and the Buil-Thouvenot atlas. I could not see any evidence for 
     stellar images near the nuclei of these two galaxies. I sent out a 
     request for help on the ISN, CBAT and Palomar Mt. A couple observers 
     from the ISN network sent images to me, but were not conclusive. The 
     observer using the 60-in telescope on Palomar was able to detect the 
     two stellar images that I imaged. I never heard back from CBAT. I 
     proved to my own satisfaction that the stellar image near the nucleus 
     of N7727 was indeed a foreground star by finding an earlier image I 
     had taken of the galaxy and locating the star. I notified CBAT (and 
     the others) of that fact to let them know that no follow-up work of 
     any sort was necessary. So much for a SN in N7727. I did not have a 
     reference image of N379 to work with and none of my fellow amateurs 
     who I had asked to observe this object were able to detect this 
     stellar image, though it was was clearly present in my images. It was 
     only after our report of a "SN" in N772 that I was told that 
     spectroscopy had been done on the two SN suspects in N7727 and N379. 
     Remember, I told them to cease and desist on the one in N7727. It was 
     only then that I found out that the N379 object was a foreground star, 
     too, which was all I wanted to know, but no one else in the world 
     could tell me that other than CBAT. 
     
     Needless to say, I'm in the doghouse at CBAT, but I hope that both 
     sides have a better understanding of what dynamics are involved with 
     making reports. I only contact CBAT when I have run out of references 
     or ideas. I definitely continue to make reference images and try to 
     ignore the originals until I have something solid to compare. 
     
     So many galaxies, so little time!
     
     Best regards,
     Wayne (aka Mr. Galaxy)   


______________________________ Reply Separator _________________________________
Subject: Stationary Asteroids and SN
Author:  Bill Dillon <bdillon@houston.geoquest.slb.com> at SMTPGTY
Date:    9/10/97 10:44 AM


I assume that most SN hunters subscribe to the IAU Circulars.  For about 
$72/year they can subscribe to the Computer Service offered by CBAT.  With 
that subscription, they can login and query the Minor Planet Center 
database for all known asteroids and comets within a certain radius of 
coordinates of interest.  This is your best source for up-to-date asteroid 
positions (the Lowell database is great too).
     
Perhaps if MPC asteroid positions were consulted, the new two-day 
rule could be relaxed.
     
Regarding the "lack of references", it seems to me that the best reference 
a SN hunter could have is an image of the target galaxy previously taken 
by the hunter.  That way you don't have problems introduced by different 
color sensitivities (e.g. comparing a blue-sensitive photograph with a 
red-sensitive CCD image) and resolutions.  The caution level should be
ten times higher if you are contemplating reporting a SN based on your 
first image of the galaxy.
     
Regards,
     
Bill Dillon
bdillon@houston.geoquest.slb.com
http://vsnet.geocities.com/CapeCanaveral/7477/

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