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Date: Thu, 1 Apr 93 17:05:38 +0900
From: Hitoshi Yamaoka <yamaoka@apsun1.astron.s.u-tokyo.ac.jp>
Subject: SN 1993J in M81
Dear Kato,
NEWS!! SN 1993J have discovered 3 days ago in NGC 3031=M81. It
would become about 8mag in few weeks, which will be the brightest
supernova in northern hemisphere since 1937C.
Could you make the photometry and spectroscopy (if possible) of
it? It makes very large help for SN study, UV or X-ray observation
(especially ASCA project), and distance estimation of extragalactic
SN, and so on.
Below, I put the informations from IAUC and other observers. The
article from Dr. Tsunebuka is in Japanese. Can you read it?? (If you
can, I will write e-mails in Japanese after this. ^_^)
This is NOT for an APRIL FOOL'S DAY (^_^)!
Regards,
Hitoshi Yamaoka, Dept. of Physics, Coll. of General Education,
Kyushu Univ., Japan
yamaoka@apsun1.astron.s.u-tokyo.ac.jp (I access this address every day)
g78261a@kyu-cc.cc.kyushu-u.ac.jp (This machine will wake up on 4/2)
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Circular No. 5731
SUPERNOVA 1993J IN NGC 3031
J. Ripero, Madrid, Spain, reports that F. Garcia, Lugo, Spain,
discovered a possible supernova on Mar. 28 as much as 5' southwest
of the nucleus of NGC 3031 = M81. The object was also recorded in an
ST-4 CCD image obtained by D. Rodriguez as some 30" northeast of a
mag 14 foreground star. Magnitude estimates: Mar. 26.9 UT, [14.0 (Garcia
and P. Pujol); 28.86, 12.0 (Garcia, visual), 29.1, 11.8 (Rodriguez, CCD
unfiltered); 29.88, 11.3 (Pujol); 29.88, 11.0 (Rodriguez).
A. V. Filippenko, University of California at Berkeley, reports:
"A CCD image of M81 obtained on Mar. 30.1 UT by R. R. Treffers
and Y. Paik (also of Berkeley) with the 0.8-m reflector at Leuschner
Observatory confirms the presence of a new stellar object roughly
45" west and 160" south of the nucleus. The visual magnitude is
approximately 11. Inspection of CCD spectra (range 356-731 nm)
obtained on Mar. 30.3 by M. Davis and D. Schlegel (also of Berkeley)
with the Lick 3-m Shane reflector reveals that the object is indeed
a supernova. The continuum is very blue and remarkably featureless.
The only clear absorption lines are narrow Na I D and Ca II H + K,
undoubtedly of interstellar origin. It is probable, but not yet
certain, that the object is a type II supernova observed only a few
days after the explosion. Note, however, that the type Ia SN 1991T
exhibited a relatively featureless spectrum well before maximum
brightness (Filippenko et al. 1992, Ap.J. 384, L15). Depending on its
spectral type, distance and extinction, SN 1993J may reach eighth
magnitude during the next two weeks. Aside from SN 1987A in the LMC,
it is therefore the brightest supernova since SN 1972E in NGC 5253.
Further observations throughout the electromagnetic spectrum are urged."
F. D. A. Hartwick, D. D. Balam, D. Zurek and R. M. Robb,
Climenhaga Observatory, University of Victoria, provide the following
precise position for the supernova, measured by Balam from a CCD image
obtained with the 0.5-m reflector on Mar. 30.25 UT: R.A. =
9h51m19s.27, Decl. = +69D15'25".7 (equinox 1950.0). Photometry
yields V = 10.2 +/- 0.1.
P. Garnavich and B. A. Hong, Dominion Astrophysical Observatory,
communicate: "Spectra (range 550-690 nm, resolution 0.6 nm) of the
supernova were taken with the DAO 1.8-m telescope on Mar. 30.25 UT.
The spectrum shows a strong, flat continuum with weak H alpha and He I
587.5 nm) features, consistent with that of a type II supernova."
1993 March 30 (5731) Brian G. Marsden
Circular No. 5733
SUPERNOVA 1993J IN NGC 3031
G. Gomez, Instituto de Astrofisica de Canarias; and R. Lopez,
University of Barcelona, report: "A spectrum (range 500-850 nm,
resolution 0.3 nm) taken on Mar. 30 by E. Perez with the 2.5-m Isaac
Newton Telescope shows some similarity to the premaximum spectrum
of the type II supernova 1990E. In particular, there is a very broad
(FWZI about 70 nm) emission band toward 650 nm that could correspond
to H alpha."
Corrigenda. On IAUC 5731, the names P. Pujol and B. A. Hong
should have been given as F. Pujol and H. B. Ann, respectively, and
the time of the first CCD image should have been Mar. 28.89, rather
than Mar. 29.1.
Further visual magnitude estimates: Mar. 29.95 UT, 11.1 (F.
Garcia, Lugo, Spain); 30.84, 10.3 (P. Schmeer, Bischmisheim, Germany).
1993 March 30 (5733) Brian G. Marsden
Circular No. 5736
SUPERNOVA 1993J in NGC 3031
Spectrograms obtained with the 1.93-m Observatoire de Haute Provence
telescope by Y. Andrillat on Mar. 30.95 UT showed no feature in the
region of the near-infrared Ca II triplet. On Mar. 31.00 H alpha was
detected in emission with an equivalent width of 0.03 nm and a FWHM of
190 km/s.
CCD photometry by P. Prugniel at the 0.8-m Observatoire de Haute
Provence telescope on Mar. 31.00 UT gave B = 11.05, B-R = +0.3.
J.-M. Perelmuter, Observatoire du Mont Megantic, Universite de
Montreal, notes the presence on Canada-France-Hawaii Telescope 1980
plates and Kitt Peak National Observatory 1990 CCD images of an object
within 0".2 of the position of SN 1993J quoted by Hartwick et al.
on IAUC 5731. The object appears stellar on images with FWHM as small
as 1".0 and had V = 20.0, B-V = +1.1, V-R = +0.7 (uncertainty 0.1 mag)
in Mar. 1990.
Visual magnitude estimates: Mar. 30.94 UT, 10.5 (J. D. Shanklin,
Cambridge, England); 31.1, 10 (R. Kohl, Lakewood, NY; independent
discovery); 31.13, 10.5 (F. Cianciolo, R. Gearhart and A. Dosaj,
Austin, TX).
1993 March 31 (5736) Brian G. Marsden
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Date: Thu, 1 Apr 93 12:32:19 +0900
From: nomoto
Message-ID: <vsnet-history570@hoge.baba.hajime.jp>
To: nomoto, shige, kumagai, yamaoka, tsuji, suzuki, wanajoh, iwamoto, ishimaru
Subject: 1993J
Status: R
From: alex%avf.hepnet@Lbl.Gov (ALEX FILIPPENKO, UC BERKELEY,
510-642-1813)
3-30-93
Dear Nova and Supernova Observers:
SN 1993J is the brightest supernova in the northern hemisphere
since SN 1937C. This is an unprecedented opportunity for us to really
observe it well. It is almost certainly a Type II caught extremely
early in its development.
As I mentioned last night, we need to get really good data on it
throughout the electromagnetic spectrum. I am willing to coordinate
ground-based photometry and spectroscopy. IUE is already on it, thanks
to George Sonneborn and gang. Bob Kirshner is looking into HST. I
think James Graham (Berkeley) will try to coordinate IR efforts. GRO
has been notified. Rob Petre is looking into X-ray observations. We
will see what EUVE can do here.
Regarding optical (and near-UV and near-IR) ground-based
observations: Low- or moderate-resolution spectroscopy and UVBRI
photometry during the next few months is important to do. The next two
weeks (bright run) are especially crucial, and will be difficult
because most of the larger telescopes will be equipped with IR
equipment or high-dispersion spectrographs (also very useful, of
course!). Some details:
Spectroscopy: Please try to get nightly spectra (even a few times
per night might be good during the next week) over as broad a
wavelength range as possible. Use a roughly 2" slit for good
resolution, and a 8-10" slit for good spectrophotometry. The wide slit
should be used even on non-photometric nights, to be sure that you are
not suffering differential light losses due to atmospheric dispersion.
Aligning the slit along the parallactic angle also helps (see
Filippenko 1982, PASP, 94, 715). Take spectra of standard stars
through the same slit widths (roughly 2" and 8-10" slits). I suggest
Feige 34 for the UV part (since it does not contain strong Balmer
lines and is therefore easier to calibrate).
Photometry: Be sure to get as many bands (primarily UBVRI) as
possible. Do standard stars, especially if the nights are
photometric. Even if they are not photometric, differential photometry
will be useful from stars on the same field.
Nick Suntzeff of CTIO has contacted me, and offers very valuable
advice (based on their experience with SN 1987A). To implement it, we
will need some help, as outlined below.
(1) We should consider defining a local star of neutral color as
the standard star for use, especially by people with photoelectric
photometers. Since the SN might reach mag 8-9, we should probably
find an A star or F star in this mag range as our standard. Also,
let's pick another star 2-3 mag fainter. As the SN fades these two
stars will allow a uniform set of photometric calibrations.
This will reduce the errror in the photometry due to the
extinction, which can easily dominate the overall errors. Observers
with photoelectric photometers on small telescopes can often get
really good phtometry even in non-photometic conditions if we provide
a local standard.
ACTION ITEM: WE NEED THE COLORS OF STARS NEAR SN 1993J TO CHOOSE
GOOD LOCAL STANDARDS. Can anyone get this? OTHERWISE, LET'S USE THE
STARS CLOSEST TO THE SUPERNOVA (SEE BELOW).
(2) Much more importantly, we need to define a local
spectrophotometric standard. EVERYONE reduces spectrophotometry
differently, and if there are no stars in common, we will have a hell
of a time getting out the 5% wiggles in the data, which I am sure will
turn out to be interesting to a large number of theorists. (The
"Bochum" event comes to mind for SN 1987A.) With the local standard,
we will not have to worry about extinction and a host of other
problems. ANY star will do, but if we choose an early-type star, we
can at least see the errors in the continuum (away from the H-lines at
least). We need to verify that both the spectroscopic and photometric
standards are not variable.
It is extremeley important to always observe this local
spectrophotometric standard! Observe it in the same way that you
observe the supernova. Also observe one of the normal KPNO standards,
of course. (I recommend Feige 34
UNTIL FURTHER INFORMATION ABOUT THE COLORS AND NON-VARIABILITY OF
NEARBY STARS BECOMES AVAILABLE, I SUGGEST THAT WE CHOOSE THE 11.4 MAG
(HST GSC "V") STAR SOMEWHAT TO THE SOUTHEAST OF THE SUPERNOVA AS OUR
"BRIGHT" STANDARD STAR (CALL IS "STAR B"), AND THE 14.6 MAG (HST GSC
"V") STAR IMMEDIATELY TO THE SOUTH OF THE SUPERNOVA AS OUR "FAINT"
STANDARD STAR (CALL IT "STAR C").
THE BRIGHT STAR'S J2000 POSITION IS (STAR B):
ALPHA = 09 55 41.5, DELTA = 69 00 30.
THE FAINT STAR'S J2000 POSITION IS (STAR C):
ALPHA = 09 55 23.6, DELTA = 69 00 49.
THE SUPERNOVA'S J2000 POSITION IS APPROXIMATELY
ALPHA = 09 55 25.0, DELTA = 69 01 13.
NOTE THAT THE BRIGHT STAR (HST GSC "V" = 12.3) TO THE NORTHEAST OF
THE SN (CALL IT "STAR A") IS SURROUNDED BY A BRIGHTER BACKGROUND.
THUS, ALL OTHER THINGS BEING EQUAL, IT IS NOT AS FAVORABLE. HOWEVER,
IF IT TURNS OUT TO HAVE MORE NEUTRAL COLORS THAN STAR B MENTIONED
ABOVE, WE MIGHT WANT TO USE IT.
(Note that the above naming convention follows that established by
Michael Richmond a few hours ago. His e-mail address is
richmond@astro.princeton.edu, in case you want an e-mail version
of a finder chart for the SN.)
Stay tuned for more information.....
Cheers,
Alex Filippenko
-----------------------------------------------------------
From: alex%avf.hepnet@Lbl.Gov (ALEX FILIPPENKO, UC BERKELEY,
510-642-1813)
3-30-93
SN 1993J observers:
One or two more things before I have to leave my office for the
afternoon:
(1) Please try to get the widest spectral coverage, even if it
means a loss of spectral resolution. 3100-10000 Ang is great for
"optical" observers. We need to overlap with the space-UV and also
the IR.
(2) This is a great "cloudy night" project --- spectra can be
smoothed, etc. The more coverage we have, the better. We can weed
out the worst spectra later, if there is an overabundance of data.
You can actually observe tenth mag stars through VERY THICK CLOUDS!
Just try to get the SN and the local standard.
Let me know what's happening, especially in the ground-based optical
effort.
Best of luck!
Alex Filippenko
-----------------------------------------------------
From: alex%avf.hepnet@Lbl.Gov (ALEX FILIPPENKO, UC BERKELEY,
510-642-1813)
3-31-93
Dear Nova and Supernova observers,
Several items concerning SN 1993J in M81:
(1) We have some information about the stars near SN 1993J, which will
be used for calibration purposes. I append a note from Michael
Richmond (with apologies to those of you who have already seen it). We
agree that for photometry, we should use as many comparison stars as
possible for the time being. Any stars that are found to be variable
can be thrown out later on.
(2) Regarding the local spectroscopic standard that should be observed
whenever you observe the supernova: Spectroscopy by Jim Liebert and
Jay Holberg at the Steward 90" shows that Star B is a late F star with
pretty strong Balmer lines. Star C may be a bit later, perhaps a G.
Until further notice, then, let's adopt Star B as our spectroscopic
comparison star. As already noted, Star B is better than Star A
anyway, in terms of having smaller background starlight contamination.
I will try to find a nearby star with an even earlier spectral
type, but I don't have any observing time with a spectrograph until
April 12. Late F (Star B) should be pretty good, though --- we'll be
able to see continuum deviations from what it SHOULD look like, except
near the strong Balmer lines.
The basic idea is as follows: observe and reduce this star in the
same way that you do SN 1993J (using normal KPNO or Oke/Gunn
standards). Then e-mail me the reduced spectra of SN 1993J AND Star
B. I'll then carefully check all the spectra when systematically
looking at the complete data set. Any deviations of Star B's spectrum
from the adopted one (which defines what it SHOULD look like) will
then be used to correct the spectrum of SN 1993J. Be sure to send me
BOTH the narrow-slit and wide-slit spectra, if you are able to take
data through two slit widths. (The extraction window should be large
for the wide-slit spectrum, of course.)
I emphasize once again that you should try to go as far down to
the near-UV as possible, to connect up with the IUE spectra.
By the way, I would prefer that any spectra that you wish to
contribute to the collaboration be e-mailed to me in 2-column format
(e.g., MONGO PL format), with the first column being wavelength
and the second being f-nu or f-lambda.
(3) Brian Schmidt and Pilar Ruiz-lapuente (CfA) have sent me the
following messages for distribution. I'm sorry if some of you have
already received them.
(4) If you would like to be taken OFF my distribution list, please let
me know by e-mail. Similarly, if you want to be put on it, send me a
message.
Best of luck with your observations! Remember --- keep at it even if
skies are cloudy!
Alex Filippenko
***
From Brian Schmidt:
A PostScript Finding chart of SN 1993J is available through
anonymous ftp at cfa0.harvard.edu (128.103.40.1). It is in
the directory pub/brian/ and you can get the compressed
version 93J.finder.ps.Z (use UNIX uncompress), or the full
PostScript File "93J.finder.ps". Print it out on a PostScript
printer with 1 Mbyte of memory or more.
This SN~II - because it is in a galaxy in which a Cepheid
distance will be shortly forthcoming from HST observations (Mould et
al) - is especially interesting for application of the Expanding
Photosphere Method to determine its distance (Schmidt Eastman and
Kirshner 1992 ApJ). To do the best job on this SN, spectroscopic and
photometric observations through the bright-time are strongly
encouraged, as are all other observations.
This SN has probably nearly reached its B-maximum, which at
m_B = 10.5 - 11 is typical for a SN II (Distance Modulus for M81 is
27.5 Freedman 1990 - average Sn~II have M_B = -16 to -18). We can
expect it to brighten in the near-IR for several more weeks, and it
will probably remain more-or-less steady in VR and I for the next
hundred days.
***
From Pilar Ruiz-lapuente:
An account with images of the SN in M81 taken at Mount Hopkins
Observatory has been set up for those interested in getting an
accurate position to the object. The way to access to this account is
making an anonymous ftp to
cfa0.harvard.edu.
The images have the names *.SN_M81 and are located in
the subdirectory /incoming/pilar.
***
From Michael Richmond:
Astrometry and Photometry of SN 1993J
------------------------------------------------------------
I've gone through the Leuschner images from last night
(Mar30 UT) and derived a position based on the values for
nearby stars given in the Guide Star Catalog. Here is the
position I derived, together with the one from the IAU
Circular 5731:
RA (2000.0) Dec (2000.0) RA (1950.0) Dec (1950.0)
================================================================
me 09:55:25.0 +69:01:13.3 09:51:19.25 +69:15:26.4
IAU 09:55:25.02 +69:01:12.6 09:51:19.27 +69:15:25.7
You can take your pick. They're pretty close.
The offsets of the SN may be of more use to observers.
The best object to use is star C (from my previous chart: if
you don't already have it, you can get it via anonymous FTP
from "spiff.princeton.edu"; cd to "richmond" and get the file
"chart"), which is very close to the SN; however, some observers
may want to use the nucleus of the galaxy. Since the nucleus is
very extended, however, it may not be as easy to measure an offset
precisely.
SN offset from RA (arcsec) Dec (arcsec)
==============================================================
star C 7.4 E 24.3 N
nucleus 44.7 W +/- 0.05 161.1 S +/- 0.3
Note that the offset from the nucleus in declination may be off by
up to 0.3 arcsec or so, due to the large distance and a slight
uncertainty in our plate scale. The offsets from star C
should be good to less than 0.05 arcsec, since they are
so small.
Now, let me GUESS at the colors of the stars in the field.
Our images showed four possible comparison stars, called
A,B,C and F in the finding chart I mailed out earlier.
As Alex has mentioned, star A is immersed in a brighter
portion of M81 than either B or C; and star F is likewise
in a bright region. Nonetheless, I measured the RELATIVE
magnitudes of the stars and the SN in our images (2 each
of VRI), NOT making any color corrections, and came up with
the following uncalibrated relative colors:
Uncalibrated magnitudes and colors relative to star A
star V (V-R) (R-I) GSC "V"
==========================================================
B 0.51 -0.09 +0.06 -0.9
C 3.10 +0.01 +0.04 +2.3
F 3.27 +0.16 +0.04
SN -0.69 -0.31 -0.22
From which I conclude that
a) the SN is blue (no surprise)
b) stars A, B, C all have pretty similar colors,
with star F being slightly redder.
Let me point out, however, that the Guide Star Catalog's
magnitude values for stars A, B, and C are VERY different
from the ones I expected from our images. It's possible
that one of stars A or B is a variable, with quite a large
amplitude. We should be careful to make photometric measurements
relative to as many stars as possible in every frame!
Alex has already suggested that we use stars "B" and "C" as our
photometric comparisons - I suggest that we use all three
of A, B and C, at least until enough time passes that we
can get better photometry and assure ourselves that some
stars are non-varying.
Finally, a request: the Hubble Atlas picture of M81 shows
several very faint point sources near the location of the SN,
in the midst of the spiral arm. It is POSSIBLE that one of
them might be a supergiant progenitor. If anyone knows of
high-resolution images of this section of the galaxy that might
already exist in the literature, please let us know. This
COULD be the second SN progenitor to be identified!
(actually third, if you include SN 1961V --- Alex).
ADDENDUM BY ALEX: IAUC 5736 notes the presence of a possible
progenitor (or tight cluster containing the progenitor) on CFHT plates
obtained in 1980 and on KPNO images obtained in 1990. The object
appears stellar to 1". At V = 20.0, this object would have an absolute
V magnitude of -7.5 (adopting a distance modulus of 27.5 from Freedman
1990) --- not totally outrageous for a supergiant. Any other CCD
images or plates should also be examined, as suggested by Michael
Richmond above.
----------------------------------------------------------
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