Return to Home Page
From DWest61506@aol.com Fri Mar 15 05:41:30 2002 Delivered-To: tkato@kusastro.kyoto-u.ac.jp Date: Thu, 14 Mar 2002 15:40:53 EST From: DWest61506@aol.com Subject: Nova V4740 Sgr Photometry To: <Brian.Skiff@lowell.edu>, <tkato@kusastro.kyoto-u.ac.jp>, <aavso@aavso.org>, <dgreen@cfa.harvard.edu>, <aah@nofs.navy.mil> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Virus-Scanned: by AMaViS perl-11 Content-Length: 1952 Seiichiro Kiyota's recent submission to VSNET caught my attention and I followed up with additional observations. The part that perplexed me was that usually for novae, V-Ic>0, in this case V-Ic = -0.7 mag. I had not seen a nova with this color in the past. 20020220.837 13.00Ic (Seiichiro Kiyota) 20020220.842 12.30V (Seiichiro Kiyota) My follow up measurements were taken with a 0.2m SCT + SBIG ST-8 CCD camera and V and Ic band filters. I stacked three 45 second exposures. The comparison stars were TYC 7392 3001 1 (V=10.53, Ic = 9.46) and TYC 7392 3006 1 (V=9.96, Ic = 8.72). The check star was HIP 89124 (V=9.91, Ic = 8.72). For the Tycho stars, the Ic magnitudes were inferred from the B-V color of the stars. My observations: 20020314.478 V = 12.8 +/- 0.1 and Ic = 15.9 +/- ~1.0 mag. The error bar of 1.0 mag on Ic may not be conservative enough, I only had a SNR of 2. The point is, V-Ic << 0. I used astrometry and images from previous observations during the outburst (IAUC 7708) for comparison. The V band image astrometry was within error limits of the published position and my previous observations. Due to the low SNR for the Ic band observation, I could not use the centroid feature of my software to verify the correct position. The Ic band observation position was determined based on the position! from previous images during outburst. There were no stars within the immediate vicinity of V4740 Sgr's position with Ic < 12.9. I did a quick search of the literature on novae photometry in ADS and couldn't find any examples where V-Ic<0. A possible progenitor star is GSC 2.2 S301213252784 which has position end figures of 45.302 s and 49.28" (J2000). The GSC 2.2 magnitudes for this star are V(green) = 16.09 and Red = 15.30. The color of this possible progenitor star is not consistent with my observations. I am confused, any comments, suggestions, and/or corrections would be welcomed. Thanks, Doug West
Return to the Daisaku Nogami
vsnet-adm@kusastro.kyoto-u.ac.jp
