Date: Mon, 14 Jun 93 18:50:22 PDT From: alex%bkyim.hepnet@Lbl.Gov (ALEX FILIPPENKO, UC BERKELEY, 510-642-1813) Subject: SN 1993J update 6-14-93 Dear SN 1993J fans: It has been quite some time since I last sent you an update on the supernova; I've been away at several meetings, etc. The supernova is doing interesting things, though, and we need to keep observing it. In particular, there seems to be a shortage of infrared measurements. JHK photometry (and at longer wavelengths, if possible) should be done soon, since much of the bolometric luminosity of SN 1993J is now coming out in the infrared. It is conceivable that SN 1993J will form dust sometime during its first year, making infrared measurements even more important. JHK photometry should be easy for anyone who has access to the right equipment and telescopes. Infrared spectroscopy is also very desireable, but is considerably more difficult. Let me emphasize, however, that even the photometry would be of enormous value. Optical photometry should be continued, of course. There are indications that the U and B light curves have flattened out (but V, R, and I seem to still be dropping). Many of the smaller telescopes that I know of have CCDs that are not very sensitive in U, so data from other telescopes is badly needed. I urge anyone with the capability of doing UB photometry to get measurements as often as possible. Of critical importance to understanding the radio data is the velocity of the circumstellar wind. This can be obtained through high-dispersion data taken at early times. There are already some indications that the narrow H-alpha emission line had FWHM around 200-300 km/s in the very earliest spectra, but that within a few days it had become much narrower and fainter. I urge anyone with access to high-dispersion spectra taken during the first few days after explosion to publish them soon, or at least to make the results known to modelers and the radio observers. The most recent photometry table that I have from Taichi Kato is dated June 4. I will wait until he sends me an update before e-mailing it out, unless I receive no update within a few days. Cheers, Alex Filippenko
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