Searching supernovae

by Alain Klotz

up to now : 2 supernovae discovered

1. Instrumental design

I observed about 300 galaxies by clear night since 1 feb 2000 with a fully automatized LX200 telescope (8" diameter). Telescope is placed on a home made "tripod roll table" which is designed to be very easy transportable and for a fast polar alignment.

The CCD is an Audine equiped by an Kaf-401E chip (grade 0 quality). The camera has no shutter. An "unsmearing" algorithm is used after the dark correction. The flat correction is not performed. Each image is integrated 60 seconds with a binning 2x2 (sampling is 3.3 arcsec/pixel).

About 300 to 400 fields are recorded each night. A quick visu software, named SNVisu, was created with the AudeLA platform. It allows to see the night image (at left) and the reference image (at right) on the same screen.

2. Software design

I use the open source AudeLA software to acquire, process and visualize images. That software, used also by Robin Chassagne, allowed him to find many supernovae. At the beginning of the night, simple pointing model is computed to be sure the telescop will center the targets best than 3 arcmin.

3. Confirmation procedure

What to do if a new object is detected ?

At time T+0h, one must confirm that the candidate is not a known star neither an asteroïd.

Step1 : Digital Sky Survey : http://skyview.gsfc.nasa.gov
or enter here the coordinates or the source name:
Step2 : List of Recent Supernovae : http://cfa-www.harvard.edu/cfa/ps/lists/RecentSupernovae.html
Step3 : Check your (super)nova suspects for known minor planets : http://scully.harvard.edu/~cgi/CheckSN
Step4 : Search to the nearest archive image own database where the candidate not appear.
Step5 : Measure the offset (arcsec) of the candidates from the nucleus
Step6 : Measure the magnitude

At T+24h, the goal is to confirm the candidate is really as star, not a ghost (cosmic, etc.).

Step 7 : Try to make another image of the field of the candidate.

If the first steps are good, repport the discovery :

Step 8 : How to Report Discovery of a Supernova : http://cfa-www.harvard.edu/cfa/ps/HowToReportDiscovery.html
Step 9 : Mail to cbat@cfa.harvard.edu and copies to dgreen@cfa.harvard.edu & green@cfa.harvard.edu .

Exemple of such a mail :

SN in NGC 7678

A. Klotz, Guitalens, France, reports the discovery of an apparent
supernova (mag about 15.1 +/- 0.4) on images (limiting mag about 17.0)
taken on 2002 Jun. 18.09 UT and 19.02 UT with a 0.20-m reflector
(+ CCD camera).

SN is located at about R.A. = 23h28m30s.4, Decl. = +22o25'44"
(equinox 2000.0), which is 30" east and 22" north of the nucleus of
NGC 7678. The new object is not present on Palomar Sky
Survey images, neither on an image taken on 2001 Sep. 11.94 UT.

You can see images in the following URL :

http://alain.klotz.free.fr/snalert/n7678-020617.html

Best Regards,

Alain KLOTZ

4. Discoveries

4.1. SN2002dp in NGC7678

A big observation effort was made to find my first supernova : 82 complete nights, 19700 images of 2660 differents fields. Details of this SN available here. Hereafter, the copy of the screen of the discovery :

4.2. SN2002gd in NGC7537

Details of this SN available here. Hereafter, the copy of the screen of the discovery :

5. Examples of false candidates

NGC 684 (Night 2001-08-26)

Hard copy of the "discovery screen"

Image taken by René ROY on 2001-08-26.9 did not confirm the SN