Realtime supernova

Blob · #1 (**permalink**) 31-August-2006, 12:58 AM

Astronomers say they have witnessed a stellar explosion - or supernova - unfolding in real time.

Their observations, outlined in the journal Nature, offer the most detailed picture yet of these cosmic explosions.

An initial release of energy from the star was picked up by the US Swift satellite in February, allowing experts to train their telescopes on the event.
This short, sharp outburst, known as an X-ray flash, is effectively an early warning signal that the star was going to turn supernova.

Source

Quote:

A link between long gamma-ray bursts (GRBs) and supernovae has been established, but whether there is a similar relationship between the weaker and softer X-ray flashes and supernovae is unclear. GRB/XRF 060218, spotted by the Swift satellite on 18 February this year, may supply that missing link. In the first of four papers on this novel burster, Campana et al. report the sighting of the X-ray signature of a shock break-out, possible evidence of a supernova in progress. Pian et al. report the optical discovery of a type Ic supernova 2006aj associated with GRB/XRF 060218. Soderberg et al. report radio and X-ray observations that show that XRF 060218 is 100 times less energetic than, but of a type that is ten times more common than cosmological GRBs. Mazzali et al. modelled the spectra and light curve of SN 2006aj to show that it had a much smaller explosion energy and ejected much less mass than other GRB-supernovae, suggesting that it was produced by a star with a mass was only about 20 times that of the Sun, leaving behind a neutron star, rather than a black hole.

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Title: Supernova 2006aj and the associated X-Ray Flash 060218
Authors: Sollerman, J.; Jaunsen, A. O.; Fynbo, J. P. U.; Hjorth, J.; Jakobsson, P.; Stritzinger, M.; Feron, C.; Laursen, P.; Ovaldsen, J. -E.; Selj, J.; Thöne, C. C.; Xu, D.; Davis, T.; Gorosabel, J.; Watson, D.; Duro, R.; Ilyin, I.; Jensen, B. L.; Lysfjord, N.; Marquart, T.; Nielsen, T. B.; Näränen, J.; Schwarz, H. E.; Walch, S.; Wold, M.; Östlin, G.

We have studied the afterglow of the gamma-ray burst (GRB) of February 18, 2006. This is a nearby long GRB, with a very low peak energy, and is therefore classified as an X-ray Flash (XRF). XRF 060218 is clearly associated with a supernova -- dubbed SN 2006aj. We present early spectra for SN 2006aj as well as optical lightcurves reaching out to 50 days past explosion. Our optical lightcurves define the rise times, the lightcurve shapes and the absolute magnitudes in the U, V and R bands, and we compare these data with data for other relevant supernovae. SN 2006aj evolved quite fast, somewhat similarly to SN 2002ap, but not as fast as SN 1994I. Our spectra show the evolution of the supernova over the peak, when the U-band portion of the spectrum rapidly fades due to extensive line blanketing. We compare to similar spectra of very energetic Type Ic supernovae. Our first spectra are earlier than spectra for any other GRB-SN. The spectrum taken 12 days after burst in the rest frame is similar to somewhat later spectra of both SN 1998bw and SN 2003dh, implying a rapid early evolution. This is consistent with the fast lightcurve. From the narrow emission lines from the host galaxy we derive a redshift of z=0.0331±0.0007. This makes XRF 060218 the second closest gamma-ray burst detected. The flux of these emission lines indicate a high-excitation state, and a modest metallicity and star formation rate of the host galaxy.

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Blob · #2 (**permalink**) 31-August-2006, 01:16 AM

See Strange GRB

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