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Date: Fri, 9 Apr 93 07:35:48 PDT
From: alex%bkyim.hepnet@Lbl.Gov (ALEX FILIPPENKO, UC BERKELEY, 510-642-1813)
Subject: a few odds and ends
4-9-93
SN 1993J fans,
Here are just a few tidbits. My computer was down last night, and I have
to go catch a flight soon, so I'll send more information tomorrow.
Cheers,
Alex
******
From Stan Woosley:
From: SMTP%"woosley@lick.UCSC.EDU" 8-APR-1993 10:28:11.22
The shape Brian Schmidt gives in his Christmas Card is, except
for the precursor that has dominated the first two weeks, similar to
what Eastman (and Weaver and Pinto) and I are submitting and
what others have talked about for II-p for years. Circumstellar interaction
and a possible early false photospere is a possibility that has occurred
to many of us, but Roger thinks the circumstellar density was not
high enough for that. One has to get the x-rays and radio emission
out. Maybe the pre-SN burped before the explosion and the mass loss was
irregular. There is evidence for time variability in the precursor.
Right now it is impossible to say how far up the light curve will
go and how long it will last. We are in a state similar
to SN 1987A at the same age when we did
not know the mass of the hydrogen envelope or the amount of 56Ni
ejected. I'm sure everyone would like to be the first to say
they knew all along what was happening, but I claim that
is physically impossible right now. If, for example the star
was almost a WR with say a few tenths of a solar mass of H
still hanging on and if it ejected a few tenths Msun of 56Ni
it could get much brighter soon, like a Ib. If all the Ni fell back
and the envelope was low in mass, it could go out in two weeks.
If the envelope mass was large, we are beginning an enduring plateau
of 3 months. If it was an AGB star we could get a combination
of the above effects (depending on envelope mass) and an exceptionally
bright tail. I'm sure others will think of still other possibilities.
The next two weeks should be critical in deciding and I'm sure
I don't need to encourage the observers to keep observing.
****
From Robert Cumming:
From: rjc@mail.ast.cam.ac.uk (Robert Cumming)
I keep expecting someone in your messages to point out the similarity
between the '93J light curve and the V curve of SN 1988A. I found it
in Patat et al (Arcetri preprint), and also Ruiz-Lapuente et al (1991,
ApJ, 378, L41) and Benetti et al (1991, A&A, 247, 410). SN 1988A was
caught before maximum, showed a ~2-mag drop over the first few days,
like '93J, then stayed almost constant till about d120.
My vote's for a II-P too then!
***
From Gerard de Vaucouleurs:
From: SMTP%"gav@astro.as.utexas.edu" 8-APR-1993 15:31:56.30
Here are a few results from a preliminary analysis of the V light curve.
\documentstyle[12pt]{article}
\oddsidemargin 0pt
\topmargin -1.0in
\textheight 9.5in
\textwidth 6.5in
\begin{document}
\begin{center}
{\bf SN1993J: Note no. 2 (4/8/93)}
\end{center}
Including the pre-discovery CCD observation by A. Neely on March 28.3
= JD 074.80 (13.8 corrected to 13.2 for zero point), a cubic fit of the
visual light curve reduced to the TB (SSC) V scale [*A = 11.4, *B = 11.9,
*C = 14.0], with 70 data points (67 after 2$\sigma$ rejection of 3 residuals
larger than 0.5 mag) from March 28.30 to April 7.55, gives\\
\begin{center}
$v = 32.403 - 6.9561 x + 0.70548 x^{2} - 0.022395 x^{3}$\\
\end{center}
where x = JD - 2449070.0.\\ \par
Extrapolation to m $\simeq$ 20.0 suggests an onset date of JD 072.3 = March
25.8 with an initial slope dm/dt $\simeq$ + 3 mag/day.
The onset date is consistent with the non-detection (R $>$ 17.0) on March
25.6 by van Driel and with v $>$ 14.0 on March 26.9 (x = 3.4, v = 16.0) by
Pujol and Ripero.\\
The visual maximum remains unchanged at v = 10.5 $\pm$ 0.1 on or about
JD 078.2 = March 31.7 (previous estimate JD 077.7).\\
The negative photographic observation by Merlin (m $>$ 16.0 on March 27.91
= JD 074.41) - when the calculated magnitude was v = 13.5 - remains a puzzle.
The limiting magnitude of the original film should be re-determined using
the SSC comparison stars.\\
The 'unfiltered' CCD observations are in general agreement with the visual
magnitudes but with a larger scatter ($\sigma$ = 0.27 mag). As previously
reported, however, the V-band CCD observations, corrected for zero point,
depart from the visual curve by up to 0.5 mag during the early decline phase.
There is better agreement now. \\
The reality or otherwise of the suspected pre-maximum 'jump' from
v $\simeq$ 11.2 on March 29 to 10.4 on March 30 depends critically on
the (mainly unreported) magnitudes adopted on these two dates for the
comparison stars. Given the standard deviation of 0.2 mag of the visual
observations from the cubic fit above, the observations of March 29 and
30 are all well within $\pm 2\sigma$ of the mean curve. These early
observations need to be carefully re-examined by the original observers
and re-reduced to the scale of the T-B Atlas (or to a revised scale still
to come).\\
The B-V color has been increasing at a steady (linear) rate of + 0.015
mag/day since JD 078.0 March 31.5. The two initial observations by Unger
on JD 077, suggesting a much more rapid initial reddening should be checked.
I am not aware of any previous supernova having shown such a discontinuity
in its rate of reddening.\\
Grateful acknowlegement is made to Dr. T. Kato for his many communications
and valuable 'photometric history' of SN1993J. \\
G. de Vaucouleurs (gav@astro.as.utexas.edu)
***
From Geoff Lawrence:
From: SMTP%"gfl@ast1.spa.umn.edu" 8-APR-1993 14:28:41.17
G.F. Lawrence and A. Paulson obtained J,H and K photometry of SN1993J on
April 3.39 1993 at the University of Minnesota 0.76 m telescope using an
InSb photometer. Standard IR photometric techniques were employed with a
27 arcsec beamsize and a 44 arcsec north/south throw. Calibration was
against the IRTF standard stars HR 3888 and HR 5447. The magnitudes,
corrected for air mass, are:
April 3.39 1993 J 10.91 +/- 0.05
H 10.66 +/- 0.05
K 10.48 +/- 0.08
******
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