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TOPIC: Sandage-96

Blobrana

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Posts: 131433

Date: Jun 21 01:19 2012

Supernova 2004dj	Permalink

Title: X-Ray emission from SN 2004dj: A Tale of Two Shocks Authors: Sayan Chakraborti, Naveen Yadav, Alak Ray, Randall Smith, Poonam Chandra Type IIP (Plateau) Supernovae are the most commonly observed variety of core collapse events. They have been detected in a wide range of wavelengths from radio, through optical to X-rays. The standard picture of a type IIP supernova has the blastwave interacting with the progenitor's circumstellar matter to produce a hot region bounded by a forward and a reverse shock. This region is thought to be responsible for most of the X-ray and radio emission from these objects. Yet the origin of X-rays from these supernovae is not well understood quantitatively. The relative contributions of particle acceleration and magnetic field amplification in generating the X-ray and radio emission need to be determined. In this work we analyse archival Chandra observations of SN 2004dj, the nearest supernova since SN 1987A, along with published radio and optical information. We determine the pre-explosion mass loss rate, blastwave velocity, electron acceleration and magnetic field amplification efficiencies. We find that a greater fraction of the thermal energy goes into accelerating electrons than into amplifying magnetic fields. We conclude that the X-ray emission arises out of a combination of inverse Compton scattering by non-thermal electrons accelerated in the forward shock and thermal emission from supernova ejecta heated by the reverse shock. Read more (225kb, PDF) __________________

Blobrana

L

Posts: 131433

Date: Dec 10 17:26 2008

Sandage-96	Permalink

Title: The Young, Massive, Star Cluster Sandage-96 After the Explosion of SN 2004dj in NGC 2403 Authors: J.Vinko, K.Sarneczky, Z.Balog, S.Immler, B.E.K.Sugerman, P.J. Brown, K.Misselt, Gy.M.Szabo, Sz.Csizmadia, M.Kun, P.Klagyivik, R.J.Foley, A.V.Filippenko, B.Csak, L.L.Kiss The bright Type II-plateau supernova (SN) 2004dj occurred within the young, massive stellar cluster Sandage-96 in a spiral arm of NGC 2403. New multi-wavelength observations obtained with several ground-based and space-based telescopes are combined to study the radiation from Sandage-96 after SN 2004dj faded away. Sandage-96 started to dominate the flux in the optical bands starting September 2006 (~800 d after explosion). The optical fluxes are equal to the pre-explosion ones within the observational uncertainties. An optical Keck spectrum obtained ~900 d after explosion shows the dominant blue continuum from the cluster stars shortward of 6000 \AA as well as strong SN nebular emission lines redward. The integrated spectral energy distribution (SED) of the cluster has been extended into the ultraviolet region by archival XMM-Newton and new Swift observations, and compared with theoretical models. The outer parts of the cluster have been resolved by the Hubble Space Telescope, allowing the construction of a colour-magnitude diagram. The fitting of the cluster SED with theoretical isochrones results in cluster ages between 10--40 Myr, depending on metallicity and the model family. The isochrone fitting indicates that the resolved part of the cluster has a bimodal age distribution: a younger population at ~10--16 Myr, and an older one at ~32--100 Myr which is similar to the age distribution of the nearby field stars. These stars may have been captured from the field during the cluster formation. The young age of Sandage-96 suggest 12 < M_prog < 20 M_\odot as the most probable mass range for the progenitor of SN 2004dj. This is consistent with, but perhaps slightly higher than, most of the other Type II-plateau SN progenitor masses determined so far. Read more (3323kb, PDF) __________________

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