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Date: Wed, 7 Apr 93 23:30:33 PDT
From: alex%bkyim.hepnet@Lbl.Gov (ALEX FILIPPENKO, UC BERKELEY, 510-642-1813)
Subject: SN 1993J daily update
4-7-93
SN 1993J enthusiasts:
A lot has happened today, and I could not put much of it in here
due to lack of time. Most of it has appeared (or will soon appear)
in the IAU Circulars. Here are a few tidbits from various people:
***
From Rob Fesen (fesen@oak.dartmouth.edu)
Do not yet have reduced data yet from low dispersion spectra taken
April 1 thru 6 but observer G. Darling (MDM 2.4m) reports a weakening of the
SN's blue continuum strength with H-alpha now `readily' apparent in spectra
from nites of 4/4 thru 4/6.
***
From George Sonneborn
From: SMTP%"SONNEBORN@FORNAX.GSFC.NASA.GOV" 7-APR-1993 13:42:42.88
(IAU Circular which you've all seen by now.) Then:
On a related subject, what is the heliocentric velocity of the SN? Does anybody
know for certain? Accuracy of <10 km/sec would be helpful. Interpretation of
the N V emission profiles may depend on its value.
***
Could you please circulate this cry for help. There is too much
disagreement between the CCD and visual observations, near and
immediately past maximum. Thanks.
GV(gav@astro.as.utexas.edu)
V-BAND LIGHT CURVE: the V (CCD) and mv (visual) observations, all
reduced as far as possible to the same zero point (*B = 11.90),
give different epochs for maximum light. Polynomial fits (4 terms)
give the following epochs and magnitude at maximum:
____________________________________________________________________
Data n JD-2449000 Maximum V(max) rms residual
V (CCD) 22 077 to 083 076.0 10.6 0.04 mag
mv 62 075 to 083 077.7 10.5 0.21
____________________________________________________________________
The two curves agree near JD 077 and JD 083, but diverge by up to
0.5 mag near JD 079-080. The V(CCD) curve is inconsistent with the
early visual observations (mv = 11 12, JD 075-077). Could the visual
observers please identify their comparison stars and adopted magnitudes?
If the maximum did in fact take place on March 29-30 as suggested by
the CCD data, the rise from onset (JD 072.0?) would be incredibly fast.
The visual data fit in much more smoothly with the discovery and
pre-discovery data.
Has anyone done bona fide UBVRI photometry of the supernova and comparison
stars with a real photoelectric photometer with a 1P21 or S20 cathode?
G. de Vaucouleurs (gav@astro.as.utexas.edu)
***
From Brian Schmidt (brian@cfaleavitt.harvard.edu)
SN 1993J is amsot certainly a classic SN-II~P. Although
the initial maximum is a little strange - is strikes me that it was
caused by the reprocessing of the UV flash by the Circumstellar
Medium. Now that the SN Has moved through this - evidenced by the
sudden upsurge in Radio emissions and appearance of P-Cygni profiles,
I think we can guess that the SN will reach a 2nd maximum in
most of the optical bands - the IR bands maximum being much more
extended in time than the blue bands, with the entire
plateau period lasting about 120 days... Here it is in a picture
| ----------------------120 days ------------------|
A guess at the "V" lightcurve
x
x x
x x xxxxxxxxxxxxxxxx
x x xxxxxx xxxxxx
x x xxxxxxxxx
x x
x x
x x
x x
x x
x x
x
x
x
x
x
x
My guess is that the JHK bands may keep rising for a couple of months -
it all depends on how fast the photosphere moves inward.
Good Luck in observing 93J.
Brian Schmidt
P.S.
I have put a fits file on cfa0.harvard.edu (128.103.40.1) that
shows a nice CCD picture of M81 11'x11' showing the SN, with
inserts at the bottom showing the SN "Before" (yes you can saee the
progenitor) and after. If you would like it, anonymous ftp to cfa0,
and "cd pub/brian", then type "binary", and finally "get 93J.BandA.F"
or "get 93J.BandA.F.Z" if you want the smaller UNIX compressed
version.
****
From Craig Wheeler:
From: SMTP%"wheel@astro.as.utexas.edu" 7-APR-1993 10:08:26.73
I am pretty convinced, and speculated thusly in a seminar on Monday, that we
have only seen some kind of precursor, a shock going through a
dense atmosphere or circumstellar nebula. If this is right
then it should climb to true maximum in the next week, just in
time for the next dark time. As it stands, I don't think we
have any idea yet what it is going to be. Standard Type II plateau
is still the best bet, but we can't rule out Type II linear, or
even some variety of Type I. Maybe another 87K Alex? Alejandro
Clocchiatti reports from McDonald that he is starting to see
P Cygni profiles.
We should also be careful about the progenitor. Granted that there
is something there within 0.25", that is a few parsecs at 3 - 4 Mpc. It
could be a cluster (reddened HII region?). The progenitor could
be fainter, which leaves open a host of possibilities from AGB
stars to CV's.
Onward and UPWARD!
Craig
****
From Dave Arnett:
From: SMTP%"dave@neutrino.physics.arizona.edu" 7-APR-1993 14:06:59.00
Regarding J. C. Wheeler's comments on the maximum in SN1993J:
It does resemble the shock breakout that Syd Falk examined
back in the 1970's. If so the rise time should be short (hours).
Shock breakout must happen, so it would be nice if we do
have another rather different example.
To sort this out, we will need to contruct a continuum
spectrum around "maximum" to derive a bolometric luminosity
and (at least) a mean photon energy (color temperature).
Besides the heat, the other part of the hydrodynamics is
the velocity field. We can try to fill in the velocity
information from the development of spectral lines. What are
the earliest reliable data on lines from the supernova's
photosphere? It is worth expending some effort to get high
quality, wide coverage spectra of the developing lines because
that will allow us to determine the shock strength (and
the distance of the supernova).
What happens next depends upon parameters like mass, initial
radius, Ni56 ejected, etc., and hopefully things we have not
yet thought of. I agree with Craig that the
progenitor question is still unclear, but it surely is important!
Dave
****
more from Craig Wheeler:
Here is the text of a circular we just submitted. Alejandro and
I were editing it while he exposed tonight, 10 minutes ago, and
the H-alpha emission is still there!
Any bets on a II linear?
Craig
J. C. Wheeler and A. Clocchiatti report that spectra from 500 to 850 nm
obtained with the Imaging Grism Instrument on the 0.76 m telescope
of McDonald Observatory on April 6.3 and 7.3 with a dispersion of
0.7 nm/pixel show the onset of strong H-alpha and distinct P-Cygni
profiles. Crude reduction by division by a polynomial fit
to a continuum of a DA dwarf (GRW+705824=EG102)
reveals that the spectrum on April 7.3
has an emission peak at 654.5 nm of 29 nm FWHM with a broad minimum
at 616.3 nm. The emission is roughly 6 times stronger than the absorption,
appears to have sharp blue and red edges at 637 and 781 nm,
respectively, and is asymmetric with a stronger red wing.
This emission is most readily identified with H-alpha.
The lack of deep absorption may indicate fluorescence from
circumstellar material which may affect the location of the minimum.
Another feature shows a P-Cygni profile with a maximum
at 588.4 nm and a well-defined minimum at
566.5 nm. This feature could be either He I lambda 5876 or Na D.
For He I, the minimum represents a velocity of 10,760 km/s.
The emission is approximately as strong as the absorption.
The peak also shows a narrow absorption line of interstellar Na D.
Another broad mimimum appears at about 500 nm. Pending more accurate
reduction, the spectrum resembles that of the Type II linear
SN 1979C on May 28, 1979 (Branch et al. Ap. J. 244, 780, 1981)
although identification of the nature of the event at this time is premature.
*****
From Andrew Pickles:
From: SMTP%"@cmsa.Berkeley.EDU:pickles@UHIFA.bitnet" 7-APR-1993 16:45:58.21
J,K photometry of the supernova in M81 (and nearby ref. stars) was
obtained with the UH 2.2-m telescope and NICMOS HgCdTe camera on UT
april 2.44 (photometric) and april 6.30 (through clouds). Other ir
photometry and one red optical spectrum should be reported separately.
UT april 1993 SN A B C
2.44 J 10.72 10.41 10.96 13.49 +/- .03
2.44 K 10.38 10.02 10.52 13.13 +/- .05
2.44 J-K 0.34
6.30 J 10.83+/-.06
6.30 K 10.23+/-.10 by comparison with stars A,B
6.30 J-K 0.60
Aloha, Andrew Pickles, Univ. Hawaii.
pickles@galileo.ifa.hawaii.edu
***
From Tashi Kato:
From: SMTP%"tkato@kusastro.kyoto-u.ac.jp" 7-APR-1993 12:22:28.13
M. Okyudo and T. Ishida (Nishi-Harima Observatory, Hyogo, Japan)
obtained following differential photometry of SN1993J using 0.6-m
reflector + CCD. The supernova was confirmed to be on the rise.
The color band is Johnson V (uncalibrated, but the color system
is very close to the standard V).
1993 Apr. 7.610 UT SN1993J V=11.69 (assuming star B as V=11.90)
star B - star A = +0.49
Regards,
Taichi Kato (Kyoto University)
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