* Astronomy

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RE: Supernova 2007gr

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An astronomer at Hatfield's University of Hertfordshire has helped discover that exploding stars produce material travelling at more than half the speed of light.
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Astronomers in the Netherlands catch supernova, observe relativistic expansion

An international team of scientists, including several astronomers from the Joint Institute for VLBI in Europe (JIVE) and the Netherlands Institute for Radio Astronomy (ASTRON), both located in Dwingeloo, have observed a supernova with peculiar radio emission. In a paper to be published in the 28 January 2010 issue of Nature, the team led by JIVE's Zsolt Paragi reports, for the first time ever, detection of a relativistic outflow in a Type Ic supernova, thus supporting the link with the even more energetic Gamma Ray Bursts, some of the most energetic explosions in the Universe.
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Doctor Who and the Silver Spiral

Far across the universe, something big was about to happen. The explosion would outshine an entire galaxy and be visible billions of kilometres away. Its light would travel across the universe for millions of years but, aside from a few astronomers, it would go unnoticed on the Earth.
With a grating, wheezing noise, a small blue box flickered into existence.
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Title: The carbon-rich type Ic SN 2007gr: the photospheric phase
Authors: S. Valenti, N. Elias-Rosa, S.Taubenberger, V. Stanishev, I. Agnoletto, D. Sauer, E. Cappellaro, A. Pastorello, S.Benetti, A. Riffeser, U. Hopp, H. Navasardyan, D.Tsvetkov, V. Lorenzi, F. Patat, M. Turatto, R. Barbon, S. Ciroi, F. Di Mille, S. Frandsen, J.P.U. Fynbo, P. Laursen, P.A. Mazzali

The first two months of spectroscopic and photometric monitoring of the nearby type Ic SN 2007gr are presented. The very early discovery (less than 5 days after the explosion) and the relatively short distance of the host galaxy motivated an extensive observational campaign. SN 2007gr shows an average peak luminosity but unusually narrow spectral lines and an almost flat photospheric velocity profile. The detection of prominent carbon features in the spectra is shown and suggest a wide range in carbon abundance in stripped-envelope supernovae. SN 2007gr may be an important piece in the puzzle of the observed diversity of CC SNe.

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Title: The birth place of the type Ic Supernova 2007gr
Authors: R. Mark Crockett, Justyn R. Maund, Stephen J. Smartt, Seppo Mattila, Andrea Pastorello, Jonathan Smoker, Andrew W. Stephens, Johan Fynbo, John J. Eldridge, I. John Danziger, Christopher R. Benn
(Version v3)

We report our attempts to locate the progenitor of the peculiar type Ic SN 2007gr in HST pre-explosion images of the host galaxy, NGC 1058. Aligning adaptive optics Altair/NIRI imaging of SN 2007gr from the Gemini (North) Telescope with the pre-explosion HST WFPC2 images, we identify the SN position on the HST frames with an accuracy of 20 mas. Although nothing is detected at the SN position we show that it lies on the edge of a bright source, 134 ±23 mas (6.9 pc) from its nominal centre. Based on its luminosity we suggest that this object is possibly an unresolved, compact and coeval cluster and that the SN progenitor was a cluster member, although we note that model profile fitting favours a single bright star. We find two solutions for the age of this assumed cluster; 7 ±0.5 Myrs and 20-30 Myrs, with turn-off masses of 28 ±4 Msun and 12-9 Msun respectively. Pre-explosion ground-based K-band images marginally favour the younger cluster age/higher turn-off mass. Assuming the SN progenitor was a cluster member, the turn-off mass provides the best estimate for its initial mass. More detailed observations, after the SN has faded, should determine if the progenitor was indeed part of a cluster, and if so allow an age estimate to within ~2 Myrs thereby favouring either a high mass single star or lower mass interacting binary progenitor.

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Date: 04:45 UT, 8 September 2007
Exposure: 10 seconds

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Supernova identified as Type Ib/c

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SN 2007gr in NGC 1058

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Supernova 2007gr