* Astronomy

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RE: Supernova 2008D

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Title: Supernova 2008D associated with the Luminous X-ray Transient 080109: An Energetic Explosion of a Massive Helium Star
Authors: Masaomi Tanaka, Nozomu Tominaga, Ken'ichi Nomoto, S. Valenti, D.K. Sahu, T. Minezaki, Y. Yoshii, M. Yoshida, G.C. Anupama, S. Benetti, G. Chincarini, M. Della Valle, P. A. Mazzali, E. Pian

We present a theoretical model for supernova (SN) 2008D associated with the luminous X-ray transient 080109. The optical light curve and spectra of the SN are modelled based on realistic progenitor models and the explosion models are obtained from hydrodynamic/nucleosynthetic calculations. We find that SN 2008D is a more energetic explosion than normal core-collapse supernovae, with an ejecta mass of Mej = 5.3 ± 1.0 Msun and a kinetic energy of KE = 6.0 ± 2.5 x 10^{51} erg. The mass of the progenitor is estimated to be Mms = 20-25 Msun. These properties are intermediate between those of normal SNe and hypernovae associated with gamma-ray bursts. The mass of the central remnant is estimated as 1.6 - 1.8 Msun, which is near the boundary between neutron star and black hole formation.

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Title: The metamorphosis of Supernova SN2008D/XRF080109: a link between Supernovae and GRBs/Hypernovae
Authors: Paolo A. Mazzali, Stefano Valenti, Massimo Della Valle, Guido Chincarini, Daniel N. Sauer, Stefano Benetti, Elena Pian, Tsvi Piran, Valerio D'Elia, Nancy Elias-Rosa, Raffaella Margutti, Francesco Pasotti, L. Angelo Antonelli, Filomena Bufano, Sergio Campana, Enrico Cappellaro, Stefano Covino, Paolo D'Avanzo, Fabrizio Fiore, Dino Fugazza, Roberto Gilmozzi, Deborah Hunter, Kate Maguire, Elisabetta Maiorano, Paola Marziani, Nicola Masetti, Felix Mirabel, Hripsime Navasardyan, Ken'ichi Nomoto, Eliana Palazzi, Andrea Pastorello, Nino Panagia, Leonardo J. Pellizza, Re'em Sari, Stephen Smartt, Gianpiero Tagliaferri, Masaomi Tanaka, Stefan Taubenberger, Nozomu Tominaga, Carrie Trundle, Massimo Turatto

The only supernovae (SNe) to have shown early gamma-ray or X-ray emission thus far are overenergetic, broad-lined Type Ic SNe (Hypernovae - HNe). Recently, SN 2008D shows several novel features: (i) weak XRF, (ii) an early, narrow optical peak, (iii) disappearance of the broad lines typical of SNIc HNe, (iv) development of He lines as in SNeIb. Detailed analysis shows that SN 2008D was not a normal SN: its explosion energy (KE ~ 6*10^{51} erg) and ejected mass (~7 Msun) are intermediate between normal SNeIbc and HNe. We derive that SN 2008D was originally a ~30Msun star. When it collapsed a black hole formed and a weak, mildly relativistic jet was produced, which caused the XRF. SN 2008D is probably among the weakest explosions that produce relativistic jets. Inner engine activity appears to be present whenever massive stars collapse to black holes.

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Scientists have for the first time witnessed the flash of light produced inside a dying star just before it explodes, according to a study on Thursday that provides a unique glimpse into how a supernova forms.
The red supergiant, more than 500 times more massive than the Earth`s own sun, was destroyed after its core collapsed and a deadly shock wave of energy completely blew it up.

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In the latest in a series of supernova firsts, scientists report in Science that they pinpointed a star that flared in the ultraviolet portion of the spectrum for several hours before blowing itself apart in a supernova. The researchers believe the finding represents the earliest visible sign of an imminent supernovaa surge in temperature as the expanding internal shock wave strains to break free of the star but has yet to shred it apart.

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Astronomers have observed the aftermath of spectacular stellar explosions known as supernovae before, but until now no one has witnessed a star dying in real time. While observing supernova 2007uy with the Swift X-ray Telescope, Alicia Soderberg and Edo Berger (Princeton University) discovered a mysterious X-ray flash elsewhere in the galaxy NGC 2770 located about 90 million light years away .

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Princeton Scientists' Rendering of the Birth of a Supernova

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Credit: NASA/Swift Science Team/Stefan Immler.

Supernova 2008D.kmz
Google Sky file (1kb, kmz)

Position(2000): RA 09 09 30.72, Dec 33 08 08.54

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Credit: NASA/Swift Science Team/Stefan Immler.

On January 9, 2008, Swift caught a bright X-ray burst from an exploding star. A few days later, SN 2008D appeared in visible light.

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Thanks to a fortunate observation with NASA's Swift satellite, astronomers, for the first time, have caught a normal supernova at the moment of its birth -- the first instant when an exploding star begins spewing its energy into space,

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