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SN 2012aw in M95 - 16 marzo 2012

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SN 2012aw (A.R. 10 43 53.72, Dec. +11 40 17.7) scoperta il 16 marzo 2012 nella galassia M95 - NGC3351 (offset 60W 115N), magnitudine 15.4, tipo IIP.

SN scoperta da Paolo Fagotti e Jure Skvarc. Prima individuazione indipendente di Alessandro Dimai con il telescopio Vittore Maioni dell'Osservatorio del Col Drusciè (S.C. 0,28 m f/6,3) il 16.8493 di marzo.

La SN2012aw, al momento della scoperta, distava poco meno di un grado dal pianeta Marte, nella costellazione del Leone. A questo link si può scaricare l'immagine del 24 marzo 2012, con Marte e la SN2012aw nello stesso campo di ripresa.

                                                  Electronic Telegram No. 3054
Central Bureau for Astronomical Telegrams
CBAT Director:  Daniel W. E. Green; Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
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SUPERNOVA 2012aw IN M95 = PSN J10435372+1140177
     Paolo Fagotti, Bastia Umbra, Italy, reports his discovery of a possible
supernova (magnitude R = 15) near M95 = NGC 3351 on CCD images taken on Mar.
16.86 UT with a 0.5-m reflector (+ MX916 camera) at Porziano d'Assisi, Italy,
the object measured to be located at R.A. = 10h43m53s.76, Decl. = +11d40'17".9
(equinox 2000.0 presumed).  Additional CCD magnitudes for the variable as
reported to the Central Bureau:  Mar. 13.96, [19.5 (Alessandro Dimai, Cortina
d'Ampezzo, Italy; 51-cm Ullrich telescope); 14.89, [17.3 (U. Quadri, L.
Strabla, R. Girelli, and A. Quadri, 25-cm f/5 robotic telescope, Bassano
Bresciano, Italy; V band noted); 16.849, 15.4 (Dimai; 28-cm telescope;
limiting mag 17.0; position end figures 53s.78, 17".0; independent discovery
in the course of the Italian Supernovae Search Project; image posted at URL
17.04, 13-14 (Luigi Fiorentino, Bari, Italy, 8-cm refractor + DSLR camera;
no position given, possible independent detection); 17.90, R = 13 (Jure
Skvarc, Crni Vrh Observatory, Slovenia, 0.60-m f/3.3 Cichocki telescope;
independent discovery on four 60-s images; position end figures 53s.72,
17".7; offset 60" west, 115" south of the center of M95; image posted at URL
note that Mars' presence only about a half degree from the variable caused
the four diffraction spikes on the composite image); 19.985, 13.3 (Gianluca
Masi, 43-cm f/6.8 robotic telescope, Ceccano, Italy; position end figures
53s.73, 17".8; 24 reference stars from NOMAD catalogue).  Skvarc notes that
nothing is visible at the position of the variable in seven archive images
taken during 2005 Apr. 25-2012 Feb. 15; he adds that the variable is only
3".3 from an x-ray source noted by Swartz et al. (2006, Ap.J. 647, 1030;
object s8).  The designation PSN J10435372+1140177 was assigned when Skvarc
posted his discovery at the Central Bureau's TOCP webpage, and the
designation SN 2012aw is assigned here based on the spectroscopic reports

     R. Itoh, T. Ui, and Masayuki Yamanaka, Hiroshima University, report that
they obtained a low-resolution (R = 400) optical spectrum of PSN
J10435372+1140177 = SN 2012aw on Mar. 19.5 UT at the Higashi-Hiroshima
Observatory of Hiroshima University.  After the recession velocity of the
host galaxy is corrected for, the spectra show a broad P-Cyg profile of the
H-alpha feature with a strong blue continuum, similar to profiles of the
type-IIP supernova 2006bp at two days after maximum light.

     Ulisse Munari, Istituto Nazionale di Astrofisica, Padova Astronomical
Observatory, obtained an under-exposed spectrum (peak S/N = 28; range
330-740 nm; dispersion 0.23 nm/pixel) of PSN J10435372+1140177 in a very
short break (5 min) in the thick cloud cover over Asiago Observatory on
Mar. 17.77 UT with the 1.22-m reflector (+ Boller & Chivens spectrograph).
The spectrum tracing corresponds to a very blue (hot) continuum, essentially
featureless, with no absorption bands and no detectable emission lines,
resembling a black-body energy distribution, similar to what is seen in a
cataclysmic variable close to maximum brightness.  Munari adds that Antonio
Vagnozzi and Flavio Castellani (ANS Collaboration) measured magnitudes B =
13.71 and V = 13.81 on Mar. 17.94, and B = 13.58 and V = 13.63 on Mar. 18.85.

     A. Siviero, L. Tomasella, A. Pastorello, S. Benetti, and U. Munari,
Istituto Nazionale di Astrofisica, Osservatorio Astronomico di Padova; M.
Ergon, J. Sollerman, and F. Taddia, Department of Astronomy, Stockholm
University; and G. Barisevicius, Nordic Optical Telescope, report that two
spectra of PSN J10435372+1140177 = SN 2012aw were obtained on Mar. 19.85 UT
with the 1.22-m Galileo telescope (+ Boller & Chivens spectrograph; range
320-780 nm, resolution 0.7 nm) and on Mar. 19.92 with the 2.5-m Nordic Optical
Telescope (+ ALFOSC; range 320-910 nm, resolution 1.6 nm).  They suggest that
the object is a very young type-II supernova.  Cross-correlation with a
library of supernova spectra via GELATO (Harutyuyan et al. 2008, A.Ap. 488,
383) gives an excellent fit with the type-IIP supernova 1999gi (Leonard et al.
2002, A.J. 124, 2490) about 4-5 days after the core-collapse.  The spectra of
2012aw show a very blue continuum and very prominent, broad hydrogen and He
I 587.6-nm lines with a P-Cyg profile.  The ejecta velocity, as deduced from
the minimum of H_alpha, is about 15000 km/s.  There is a clear evolution if
these spectra are compared with that obtained on Mar. 18.77 at the 1.22-m
Galileo telescope, which showed a blue, featureless continuum.

NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2012 CBAT
2012 March 20                    (CBET 3054)              Daniel W. E. Green