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Coronal emission from the shocked circumstellar ring of SN 1987A
Stockholm University, Faculty of Science, Department of Astronomy.
Stockholm University, Faculty of Science, Department of Astronomy.
Stockholm University, Faculty of Science, Department of Astronomy.
Stockholm University, Faculty of Science, Department of Astronomy.
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2006 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 456, no 2, 581-589 p.Article in journal (Refereed) Published
Abstract [en]

High resolution spectra with UVES/VLT of SN 1987A from December 2000 until November 2005 show a number of high ionization lines from gas with velocities of ± 350 km s-1, emerging from the shocked gas formed by the ejecta-ring collision. These include coronal lines from [Fe X], [Fe XI] and [Fe XIV] which have increased by a factor of 20 during the observed period. The evolution of the lines is similar to that of the soft X-rays, indicating that they arise in the same component. The line ratios are consistent with those expected from radiative shocks with velocity 310{-}390 km s-1, corresponding to a shock temperature of (1.6{-}2.5)× 106 K. A fraction of the coronal emission may, however, originate in higher velocity adiabatic shocks.

Place, publisher, year, edition, pages
2006. Vol. 456, no 2, 581-589 p.
Keyword [en]
supernovae: individual: SN 1987A, circumstellar matter, shock waves
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:su:diva-20166DOI: 10.1051/0004-6361:20065325OAI: oai:DiVA.org:su-20166DiVA: diva2:186691
Available from: 2007-02-27 Created: 2007-02-27 Last updated: 2017-12-13Bibliographically approved
In thesis
1. X-ray emission from supernova shock waves
Open this publication in new window or tab >>X-ray emission from supernova shock waves
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A theoretical study of the interaction between supernovae and their surroundings is presented.

Supernovae are the endpoint of the life of massive stars, and are the dominant contributors to the chemical evolution of the Universe. During its life a massive star greatly modifies its environment. During and after the explosion of the star it interacts with its surroundings in a number of ways. A study of this interaction yields invaluable information about the late stages of stellar evolution and the physics of supernova explosions. Recent advances in observational facilities have given a wealth of observational data on interacting supernovae, and it is therefore essential to have good theoretical models for interpreting the data.

This thesis presents an overview of the physics of supernovae and of their interaction with a circumstellar medium. In particular the reverse shock created by the interaction is investigated. In most Type IIL and Type IIn supernovae this shock is radiative, and due to the high temperature most of the radiation comes out as X-rays. A numerical model is presented which calculates the emission from the cooling region behind the reverse shock in a self-consistent way, by combining a hydrodynamic model with a time-dependent ionization balance and multilevel calculations. This has been applied to some of the best cases of circumstellar interaction.

As a further application of the model the radio and X-ray emission from Type IIP supernovae is discussed. We estimate the mass loss rate of the progenitors of Type IIP supernovae, and find that a superwind phase is not required.

VLT observations of the ring of SN 1987A show broad optical emission lines coming from a range of ionization stages, in particular optical coronal lines of Fe X-XIV. Models of the line emission indicate that the lines are formed by cooling shocks with shock velocities in the range 310-390 km/s, confirming the picture of shocks striking the protrusions from the ring obliquely.

X-ray observations of the Type IIb SN 1993J and Type IIn SN 1998S are analyzed. For SN 1993J we find that the spectrum is best fit with a CNO-enriched composition. For SN 1998S we find that the high metal overabundance that has previously been claimed, is not necessary when a self-consistent model of the cooling region is applied.

Place, publisher, year, edition, pages
Stockholm: Institutionen för astronomi, 2007. 62 p.
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
urn:nbn:se:su:diva-6671 (URN)91-7155-377-0 (ISBN)
Public defence
2007-03-20, sal FB53, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 10:00
Opponent
Supervisors
Available from: 2007-02-27 Created: 2007-02-20 Last updated: 2012-08-27Bibliographically approved
2. The rebirth of Supernova 1987A: a study of the ejecta-ring collision
Open this publication in new window or tab >>The rebirth of Supernova 1987A: a study of the ejecta-ring collision
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Supernovae are some of the most energetic phenomena in the Universe and they have throughout history fascinated people as they appeared as new stars in the sky. Supernova (SN) 1987A exploded in the nearby satellite galaxy, the Large Magellanic Cloud (LMC), at a distance of only 168,000 light years. The proximity of SN 1987A offers a unique opportunity to study the medium surrounding the supernova in great detail. Powered by the dynamical interaction of the ejecta with the inner circumstellar ring, SN 1987A is dramatically evolving at all wavelengths on time scales less than a year. This makes SN 1987A a great ``laboratory'' for studies of shock physics. Repeated observations of the ejecta-ring collision have been carried out using the UVES echelle spectrograph at VLT. This thesis covers seven epochs of high resolution spectra taken between October 1999 and November 2007. Three different emission line components are identified from the spectra. A narrow (~10 km/s) velocity component emerges from the unshocked ring. An intermediate (~250 km/s) component arises in the shocked ring, and a broad component extending to ~15,000 km/s comes from the reverse shock. Thanks to the high spectral resolution of UVES, it has been possible to separate the shocked from the unshocked ring emission. For the unshocked gas, ionization stages from neutral up to Ne V and Fe VII were found. The line fluxes of the low-ionization lines decline during the period of the observations. However, the fluxes of the [O III] and [Ne III] lines appear to increase and this is found to be consistent with the heating of the pre-shock gas by X-rays from the shock interactions. The line emission from the ejecta-ring collision increases rapidly as more gas is swept up by the shocks. This emission comes from ions with a range of ionization stages (e.g., Fe II-XIV). The low-ionization lines show an increase in their line widths which is consistent with that these lines originate from radiative shocks. The high-ionization line profiles (Fe X-XIV) initially show larger spectral widths, which indicates that at least a fraction of the emission comes from non-radiative shocks.

Place, publisher, year, edition, pages
Stockholm: Institutionen för astronomi, 2008. 70 p.
Keyword
supernovae, SN 1987A, circumstellar matter, shock waves
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
urn:nbn:se:su:diva-8290 (URN)978-91-7155-771-1 (ISBN)
Public defence
2008-12-04, sal FA32, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 10:30
Opponent
Supervisors
Available from: 2008-11-13 Created: 2008-11-13 Last updated: 2012-08-27Bibliographically approved

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