Pre-Outburst Gemini Images of the Location of SN2008S in NGC6946

The position for SN2008S reported in CBET 1234, dated 2008 February 2, is shown with a yellow circle. The positions of USNO-B1.0 stars are shown with green circles. Note that north is 9.9 deg CCW from the vertical.

Images of the field containing SN2008S were obtained during programs GS-2004B-C-3, GN-2004B-DD-6, GN-2005B-Q-54, and GN-2006A-Q-52.

Please see the paper at this link for discussion of the programs and a finder chart and tables of tertiary standards for the field.

Text submitted to CBAT on Sunday, April 6, 2008

PRE-OUTBURST IMAGING OF THE FIELD OF SN2008S IN NGC 6946

D.L. Welch (McMaster University), G.C. Clayton (Lousiana State University),
and B. Sugerman (Goucher College) report six epochs of pre-outburst g', r',
and i' imaging of SN 2008S in NGC 6946 obtained with Gemini GMOS-N.
Exposures of length 60 seconds were obtained in each of the filters on
UT 2004 August 20, 2004 October 8, 2004 December 11, 2005 August 4,
2005 October 4, and 2006 July 18. Image FWHM ranged from 0.58 to 0.88
arcsec. Based on the photometric transformations between g'r'i' and VRI
reported in Welch et al. 2007, Ap.J., 669, 525 we conclude no object
brighter than V=24.0, R=24.5, and I=22.9 mag was detected at the 3-sigma
level at the position of SN2008S in any of these images. Reduced and
WCS-registered images of the field may be downloaded from
http://crocus.physics.mcmaster.ca/SN2008S/.


Image                     FWHM  FWHM   X   Fil Exp
	                   (px)  (")           (s)
--------------------------------------------------
chip2rgN20040820S0056.fits  4.1  0.60 1.310  r' 60
chip2rgN20040820S0057.fits  4.8  0.70 1.310  g' 60
chip2rgN20040820S0058.fits  4.1  0.60 1.310  i' 60
chip2rgN20041008S0062.fits  6.0  0.88 1.322  r' 60
chip2rgN20041008S0063.fits  5.6  0.82 1.321  g' 60
chip2rgN20041008S0064.fits  4.9  0.72 1.320  i' 60
chip2rgN20041211S0010.fits  4.5  0.66 1.650  r' 60
chip2rgN20041211S0011.fits  4.9  0.72 1.658  g' 60
chip2rgN20041211S0012.fits  4.3  0.63 1.667  i' 60
chip2rgN20050804S0168.fits  4.6  0.67 1.404  r' 60
chip2rgN20050804S0169.fits  5.3  0.77 1.400  g' 60
chip2rgN20050804S0170.fits  4.5  0.66 1.396  i' 60
chip2rgN20051004S0124.fits  4.4  0.64 1.311  r' 60
chip2rgN20051004S0125.fits  4.5  0.66 1.311  g' 60
chip2rgN20051004S0126.fits  4.0  0.58 1.311  i' 60
chip2rgN20060718S0114.fits  5.7  0.83 1.360  r' 60
chip2rgN20060718S0115.fits  6.0  0.88 1.362  g' 60
chip2rgN20060718S0116.fits  5.8  0.85 1.365  i' 60
The following images have a WCS system which has been fit to USNO-B1.0 positions in the field. This new WCS is to be preferred to the automatically-generated WCS in the original GMOS-N image headers.
Doug Welch, welch@physics.mcmaster.ca
Last updated: 2008 Apr 10