Return to Home Page
Date: Sun, 16 May 93 10:17:18 CDT From: gav@astro.as.utexas.edu (Gerard de Vaucouleurs) Subject: SN93J Note 3 >From G. de Vaucouleurs (gav@astro.as.utexas.edu) (5.15.93) Note 3 on SN1993J compilations: 1. On 93/05/04.3 (JD111.8) correct first Richmond observations to read U = 14.30 (NOT 13.30). 2. Johnson or Cousins system? The Appleton+Eitter R and I observations are recorded in the Kato, Granslo, and other compilations as being on the J system, but the run of their V-R, V-I colors fit much better with the C system. Could the observers and/or compilers please verify their filters or records? Also are the the published data raw (instrumental) colors, or are they properly reduced to the adopted standard system (that is, including color terms)? 3. With the increase in the color index of the star large systematic differences have appeared between different sources, particularly in U-B, B-V. This is evidently due to the neglect of the color terms in some or all of the published provisional values. Could the observers please notify the compilers (and all of us) whether their UBVRI magnitudes are in the raw (instrumental) color systems of their instruments or have already (at least in some cases) been reduced to some standard system (which?). 4. Bad News. Brian Skiff, Lowell Observatory, reports that the 14th mag. star nearest to the SN (*C of Richmond = GSC 0340) is definitely variable with an uncomfortably large amplitude as follows: ..................... [quoted by permssion] ........................ JD102.65 V=14.95, 103.65: 14.65, 114.66:14.41, 115.66: 14.84, 116.68: 14.67, 117.68: 14.67, 118.68: 14.58. <V> = 14.68 +/- 0.06 (s.d.: 0.17). ..................................................................... This is unfortunate because Neely's important prediscovery observation was referred to it, namely SN(0.8)C on JD074.8. It is most important, therefore, to monitor *C regularly (at least UBV and spectroscopically) to establish whether it is a regular, predictable variable (cepheid? eclipsing binary?) or an irregular variable. In the first case the early observation may be salvaged, in the second only a rough estimate is all that may be possible (unless other stars could be used as standards on the original CCD frame). Measurements of *C on pre-discovery, archival pictures of M 81 will be also valuable. A convenient comparison star (which could be used as a test of constancy) could be GSC 1037 (7 s W, 10' N of 0340 = 14.1 on the TB chart). B. Skiff found it constant to +/- 0.01 on 3 nights (May 9-11) at <V> = 14.44, but ~0.3-0.4 mag fainter than indicated on the TB chart from two previous measurements at McDonald observatory (sources JN and BH, ApJS, 24, 421, 1972). New observations are needed. 5. Onset time. From a consideration of the light and color curves I derive for the time of onset to = JD074.0 +/- 0.1 (or less) = March 27.5. The initial flash peaked at JD077.0, V = 10.72; the following minimum was on JD082.8, V = 12.87; the main maximum was on JD095.6, V = 10.86. The initial rise rate of the flash was 1.0 mag/day, of the main maximum ~0.1 mag/day. The two components can be neatly separated, but more information on the early visual and unfiltered CCD observations is needed for a definitive solution. Bets are still open on whether it will turn out to be a plateau Type II or something else.
Return to the Daisaku Nogami
vsnet-adm@kusastro.kyoto-u.ac.jp
