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(1993 May 26)
subject: SN1993J circular
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% V-band Light Curve of SN 1993J during the first 50 days
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% Okyudo, M., Kato, T., Ishida, T. and Yamaoka, H.
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% (Submitted to the Publ. Astron. Soc. Japan. Letters Section)
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\documentstyle[twoside]{article}
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\markboth{Okyudo et al.}{Light Curve of SN 1993J}
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% Version 0.0 on 21 May 1993.
% Version 0.5 on 24 May 1993.
% Version 0.8 on 25 May 1993.
% Version 1.0 on 25 May 1993. Submitted to PASJ
% Version 1.0C on 26 May 1993. for Circulation using with E-mail
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\title{
{\bf V-band Light Curve of SN 1993J \\
during the first 50 days }
}
\author{
Masami {\sc Okyudo} \\
\medskip
{\it Nishi-Harima Astronomical Observatory, Sayo-cyo, Hyogo 679-53 } \\
Taichi {\sc Kato} \\
\medskip
{\it Department of Astronomy of Kyoto University, Sakyo-ku, Kyoto, 606-01 } \\
Toshihito {\sc Ishida} and Noritaka {\sc Tokimasa} \\
\medskip
{\it Nishi-Harima Astronomical Observatory, Sayo-cyo, Hyogo 679-53 } \\
Hitoshi {\sc Yamaoka} \\
{\it Department of Physics, College of General Education,} \\
\bigskip
{\it Kyushu University, Ropponmatsu, Fukuoka, 810 } \\
{\it Submitted to the Publ. Astron. Soc. Japan. Letters Section} \\
}
\date{}
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\begin{document}
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\maketitle
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\begin{abstract}
We present here the V-band light curve of type II supernova 1993J
during the first 50 days. SN 1993J seems to be peculiar as a
type II supernova, because already two light maxima exist
during our observation period.
This type of light curve is observed for the first time.
\end{abstract}
\noindent
{\bf Key words}:
M 81 ( NGC 3031); SN 1993J; Star; Supernovae; CCD-Photometry
\section{Introduction}
Supernova (SN) 1993J was discovered in M81 (NGC3031)
on March 28 (Garcia 1993) and was spectroscopically confirmed as a
type II SN (Garnavich and Hong 1993).
Because it is the brightest supernova
in the northen hemisphere since SN 1954A, extensive observations
using various instruments at many wavelength bands from
the hard X-ray to the radio are going on.
Because of the peculiarity of the light curve
and the spectroscopic developement of SN1993J,
quick publication of the earliest results may help to
construct the model fitted to SN 1993J.
Therefore, we present in this letter the V-band light curve of SN 1993J
during the first 50 days.
\section{Observations}
We have been performing CCD photometric observations since April 1
at Nishi-Harima Astronomical Observatory (NHAO) and Ouda Station,
Department of Astronomy of Kyoto University (OSDAK).
V- and BVIc-band photometries have been carried out using 60-cm
reflectors of NHAO and OSDAK, respectively.
The filter systems approximate the standard Johnson ( B and V )
and Kron-Cousins ( I ) systems.
After the images are de-biased and flat-fielded,
aperture photometries were carried out using APPHOT package of
IRAF\footnote{IRAF is distributed by the National Optical Astronomy
Observatories, U.S.A.} routine at NHAO
and original automatic photometric program
developed by one of the authors (T.K) at OSDAK, respectively.
A CCD image of the field obtained at NHAO is shown in figure 1.
Several comparison stars are
contained simultaneously in the same field with SN 1993J.
The local comparison stars A and B are marked in the figure 1.
\section{Results}
Photometric results in the V-band are listed in table 1.
V-magnitudes of SN 1993J are calculated assuming V = 11.90
for star B (Corwin 1993).
The typical error in the V magnitude is 0.01 mag.
No color corrections were made.
The light curve in the V-band is presented in figure 2.
Although differences between stars A and B are nearly identical
at both sites, there exist systematic difference between two sites
in V-magnitudes of SN 1993J.
We think that strong emission or absorption lines of the SN emphasize
the difference of photometric systems.
\begin{table}[h]
\caption{Photometric results of SN 1993J.}
\begin{center}
\begin{tabular}{rrrrl}\hline
UT & V-mag. & Star B - A & Sites & Remarks \\
\hline\hline
April 1.660 & 11.22 & 0.50 & NHAO \\
2.494 & 11.50 & 0.50 & OSDAK \\
3.555 & 11.76 & 0.47 & OSDAK \\
5.489 & 11.88 & 0.48 & OSDAK \\
5.614 & 11.89 & 0.47 & OSDAK \\
5.660 & 11.98 & 0.49 & NHAO \\
6.485 & 11.84 & 0.45 & OSDAK \\
6.685 & 11.79 & 0.49 & OSDAK \\
7.496 & 11.70 & 0.50 & OSDAK \\
7.610 & 11.69 & 0.49 & NHAO \\
8.576 & 11.68 & 0.50 & NHAO \\
9.541 & 11.46 & 0.49 & OSDAK \\
9.659 & 11.52 & 0.49 & NHAO \\
10.471 & 11.33 & 0.49 & OSDAK \\
10.608 & 11.46 & 0.49 & NHAO \\
11.659 & 11.30 & 0.49 & NHAO \\
12.476 & 11.11 & 0.48 & OSDAK \\
12.557 & 11.24 & 0.49 & NHAO \\
13.577 & 11.17 & 0.49 & NHAO \\
14.628 & 11.03 & 0.50 & NHAO \\
16.601 & 10.88 & 0.49 & NHAO \\
17.612 & 11.00 & 0.49 & NHAO \\
18.644 & 10.97 & 0.48 & NHAO \\
19.634 & 10.85 & 0.48 & NHAO \\
20.605 & 11.04 & 0.49 & NHAO \\
23.510 & 11.27 & 0.47 & NHAO & Bad condition, only single frame \\
25.620 & 11.27 & 0.45 & OSDAK \\
25.719 & 11.40 & 0.48 & NHAO \\
26.583 & 11.55 & 0.46 & NHAO \\
26.740 & 11.46 & 0.47 & NHAO \\
27.609 & 11.64 & 0.46 & NHAO \\
May 4.663 & 12.04 & 0.47 & NHAO \\
5.611 & 12.05 & 0.47 & NHAO \\
6.749 & 12.10 & 0.47 & NHAO & Low altitude \\
7.701 & 12.07 & 0.48 & NHAO \\
11.689 & 12.21 & 0.51 & NHAO \\
12.469 & 12.25 & 0.52 & NHAO \\
14.618 & 12.37 & 0.50 & NHAO \\
15.646 & 12.35 & 0.51 & NHAO \\
16.487 & 12.38 & 0.46 & OSDAK \\
\hline
\end{tabular}
\end{center}
\end{table}
\section{Discussion}
Characteristics of the light curve are as follows.
Initially, the beightness of the SN decayed rapidly at a rate of 0.3 mag/day.
According to other observations,
the first maximum was on March 30 and its magnitude in the V-band was about
10.7 (e.g., Hartwick et al. 1993).
The brightness of SN 1993J gradually rose
again at a rate of 0.1 mag/day after April 5 and
the second maximum was reached on around April 18.
After the second maximum, the SN entered into a decay phase
with a rate of 0.1 mag/day.
Since the first of May, the decay rate becomes to 0.03 mag/day.
Type II supernovae have been subclassified by the shapes of
their light curves; (1) type II-P supernovae ( SNe II-P ),
which have the extended plateau phase, of which duration is
about 100 days (Patat et al. 1993),
and (2) type II-L supernovae ( SNe II-L ),
which have no plateau but dim linearly in magnitude
after single maximum.
SN 1993J clearly fits to none of above two types.
Very early first maximum and the following rapid decay are similar
to those observed in SN 1988A ( Ruiz-Lapuente et al. 1990 ),
but the following long plateau of SN 1988A is far
from the property observed in SN 1993J.
Such a rapid variation at the early phase is not predicted
from explosion models of a red supergiant star
without any circumstellar matter.
Because radio, ultraviolet and X-ray observations in the early phase
( Pooley and Green 1993; Sonneborn et al. 1993; Zimmermann et al. 1993 )
show that there would be considerable amounts of circumstellar matter,
the first maximum would be related with this circumstellar matter.
Light curve of SN 1993J around the second maximum resembles
to the maximum of type Ib supernovae ( SNe Ib ),
as pointed out by Nomoto et al. ( 1993 ).
On the other hand, Filippenko and Matheson ( 1993 )
observed that the spectra of SN 1993J is changing
from those of SN II to SN Ib.
SN 1987K is the only one example whose spectra changed in this manner,
and is classified as a type IIb supernova ( Filippenko 1988 ).
SN 1993J would be classified as this type.
Shigeyama et al. ( 1993 ) gives a theoretical light curve
with the explosion of the evolved star whose hydrogen envelope is
almost lost, which is probably caused by binary interation.
Their light curve show two maxima which well explains
the light curve of SN 1993J.
\section{Conclusion}
In this letter,
we have presented the V-band light curve of SN 1993J
during the first 50 days.
Type II supernova which has two maxima during the first 50 days is
observed for the first time.
New explosion models are urged and being constructed for interpretation
of the light curve of SN 1993J.
We hope that this letter will be of help in the future studies.
We are continuing these photometric programs till SN becomes undetected
by our systems.
%\medskip
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\bigskip
\begin{thebibliography}{99}
%
\bibitem{C93}
Corwin, H. G. 1993, {\it IAU Circular} No. 5742.
%
\bibitem{F88}
Filippenko, A. V. 1988, {\it Astron. J.}, {\bf 96}, 1941.
%
\bibitem{FM93}
Filippenko, A. V. and Matheson, T. 1993, {\it IAU Circular}, No. 5787.
%
\bibitem{G93}
Garcia, F. 1993, {\it IAU Circular} No. 5731.
%
\bibitem{GH93}
Garnavich, P. and Hong, B. A. 1993, {\it IAU Circular} No. 5731.
%
\bibitem{HBZR93}
Hartwick, F. D. A., Balam, D. D., Zurek, D., and Robb, R. M. 1993, {\it IAU Circular} No. 5731.
%
\bibitem{NSSKYS93}
Nomoto, K., Suzuki, T., Shigeyama, T., Kumagai, S., Yamaoka, H., and Saio, H.
1993, {\it Nature}, submitted.
%
\bibitem{PBCT93}
Patat, F., Barbon, R., Cappellaro, E., and Turatto, M. 1993,
{\it Astron. Astrophys. Suppl.}, {\bf 98}, 443.
%
\bibitem{PG93}
Pooley, G. G. and Green, D. A. 1993, {\it IAU Circular}, No. 5751.
%
\bibitem{RKLC90}
Ruiz-Lapuente, P., Kidger, M., Lopez, R., and Canal, R. 1990, {\it Astron. J.}, {\bf 100}, 782.
%
\bibitem{SSKNSY93}
Shigeyama, T., Suzuki, T., Kumagai, S., Nomoto, K., Saio, H., and Yamaoka, H.
1993 {\it Astrophys. J. (Letters)}, submitted.
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\bibitem{S93}
Sonneborn, G., Rodriguez, P. M., Wamsteker, W., Fransson, C., and Kirshner, R. P. 1993, {\it IAU Circular}, No. 5754.
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\bibitem{ZLMPHPATFPLP93}
Zimmermann, H. U., Lewin, W., Magnier, E., Predehl, P., Hasinger, G., Pietsch, W., Aschenbach, B., Trumper, J., Fabbiano, G., van Paradijs, J., Lubin, L., and Petre, R. 1993, {\it IAU Circular}, No. 5748 and 5750.
\end{thebibliography}
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\begin{flushleft}
{\large\bf Figure Captions}
\end{flushleft}
\noindent
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Fig. 1. Finding chart (a CCD image) of SN 1993J,
the comparison star (B),
and the check stars (A) and (C).
The field of view is $6' \times 4'$.
\bigskip
\noindent
Fig. 2.
V-band light curve of SN 1993J.
Initial rapid decline and broader second maximum are clearly seen.
\end{document}
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