* Astronomy

Blobrana · L

RE: Supernova 2008in

Blobrana · L

Title: Type IIP supernova 2008in: the explosion of a normal red supergiant
Authors: V.P. Utrobin (1 and 2), N.N. Chugai (3) ((1) MPA, Garching, (2) ITEP, Moscow, (3) Institute of Astronomy, RAS, Moscow)

The explosion energy and the ejecta mass of a type IIP supernova make up the basis for the theory of explosion mechanism. So far, these parameters have only been determined for seven events. Type IIP supernova 2008in is another well-observed event for which a detailed hydrodynamic modelling can be used to derive the supernova parameters. Hydrodynamic modelling was employed to describe the bolometric light curve and the expansion velocities at the photosphere level. A time-dependent model for hydrogen ionisation and excitation was applied to model the Halpha and Hbeta line profiles. We found an ejecta mass of 13.6 solar masses, an explosion energy of 5.05x10^50 erg, a presupernova radius of 570 solar radii, and a radioactive Ni-56 mass of 0.015 solar masses. The estimated progenitor mass is 15.5 solar masses. We uncovered a problem of the Halpha and Hbeta description at the early phase, which cannot be resolved within a spherically symmetric model. The presupernova of SN 2008in was a normal red supergiant with the minimum mass of the progenitor among eight type IIP supernovae explored by means of the hydrodynamic modelling. The problem of the absence of type IIP supernovae with the progenitor masses <15 solar masses in this sample remains open.

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Blobrana · L

Title: Sn 2008in - bridging the gap between normal and faint supernovae of type IIP
Authors: Rupak Roy, Brijesh Kumar, Stefano Benetti, Andrea Pastorello, Fang Yuan, Peter J. Brown, Stefan Immler, Timur A. Fatkhullin, Alexander S. Moskvitin, Justyn Maund, Carl W. Akerlof, J. Craig Wheeler, Vladimir V. Sokolov, Rorbert M. Quimby, Filomena Bufano, Brajesh Kumar, Kuntal Misra, S. B. Pandey, Nancy Elias-Rosa, Peter W. A. Roming, Ram Sagar

We present optical photometric and low-resolution spectroscopic observations of the Type II plateau supernova (SN) 2008in, which occurred in the outskirts of the nearly face-on spiral galaxy M 61. Photometric data in the X-rays, ultraviolet and near-infrared bands have been used to characterise this event. The SN field was imaged with the ROTSE-IIIb optical telescope about seven days before the explosion. This allowed us to constrain the epoch of the shock breakout to JD = 2454825.6. The duration of the plateau phase, as derived from the photometric monitoring, was ~ 98 days. The spectra of SN 2008in show a striking resemblance to those of the archetypal low-luminosity IIP SNe 1997D and 1999br. A comparison of ejecta kinematics of SN 2008in with the hydrodynamical simulations of Type IIP SNe by Dessart et al. (2010) indicates that it is a less energetic event (~ 5 x 10^{50} erg). However, the light curve indicates that the production of radioactive ^{56}Ni is significantly higher than that in the low-luminosity SNe. Adopting an interstellar absorption along the SN direction of A_V ~ 0.3 mag and a distance of 13.2 Mpc, we estimated a synthesised Ni mass of ~ 0.015 solar masses. Employing semi-analytical formulae (Litvinova & Nadezhin 1985), we derived a pre-SN radius of ~ 126 solar radii, an explosion energy of ~ 5.4 x 10^{50} erg and a total ejected mass of ~ 16.7 solar masses. The latter indicates that the zero age main-sequence mass of the progenitor did not exceed 20 solar masses. Considering the above properties of SN 2008in, and its occurrence in a region of sub-solar metallicity ([O/H] ~ 8.44 dex), it is unlikely that fall-back of the ejecta onto a newly formed black hole occurred in SN 2008in. We therefore favour a low-energy explosion scenario of a relatively compact, moderate-mass progenitor star that generates a neutron star.

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Blobrana · L

A magnitude 15.1 Type II supernova, 2008in, has been discovered by D. Denisenko and S. Korotkiy on the 29th December, 2008, in the face-on spiral galaxy Messier 61 (NGC 4303) in the constellation Virgo.
The supernova is located 102" east and 22" north from the center of the galaxy.

Position(2000): RA = 12h22m01s.75, Dec. = +04°28'48".1.
Z = 0.005224

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