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A metallicity study of 1987A-like supernova host galaxies
Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
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2013 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 558, UNSP A143Article in journal (Refereed) Published
Abstract [en]

Context. The origin of the blue supergiant (BSG) progenitor of Supernova (SN) 1987A has long been debated, along with the role that its sub-solar metallicity played. We now have a sample of SN 1987A-like events that arise from the rare core collapse (CC) of massive (similar to 20 M-circle dot) and compact (less than or similar to 100 R-circle dot) BSGs. Aims. The metallicity of the explosion sites of the known BSG SNe is investigated, as well as the association of BSG SNe to star-forming regions. Methods. Both indirect and direct metallicity measurements of 13 BSG SN host galaxies are presented, and compared to those of other CC SN types. Indirect measurements are based on the known luminosity-metallicity relation and on published metallicity gradients of spiral galaxies. In order to provide direct metallicity measurements based on strong line diagnostics, we obtained spectra of each BSG SN host galaxy both at the exact SN explosion sites and at the positions of other H II regions. We also observed these hosts with narrow H alpha and broad R-band filters in order to produce continuum-subtracted H alpha images. This allows us to measure the degree of association between BSG SNe and star-forming regions, and to compare it to that of other SN types. Results. BSG SNe are found to explode either in low-luminosity galaxies or at large distances from the nuclei of luminous hosts. Therefore, their indirectly measured metallicities are typically lower than those of SNe IIP and Ibc. This result is confirmed by the direct metallicity estimates, which show slightly sub-solar oxygen abundances (12 + log (O/H) similar to 8.3-8.4 dex) for the local environments of BSG SNe, similar to that of the Large Magellanic Cloud (LMC), where SN 1987A exploded. However, we also note that two objects of our sample (SNe 1998A and 2004em) were found at near solar metallicity. SNe IIb have a metallicity distribution similar to that of our BSG SNe. Finally, we find that the degree of association to star-forming regions is similar among BSG SNe, SNe IIP and IIn. Conclusions. Our results suggest that LMC metal abundances play a role in the formation of some 1987A-like SNe. This would naturally fit in a single star scenario for the progenitors. However, the existence of two events at nearly solar metallicity suggests that also other channels, e.g. binarity, contribute to produce BSG SNe.

Place, publisher, year, edition, pages
2013. Vol. 558, UNSP A143
Keyword [en]
supernovae: general, stars: evolution, galaxies: abundances
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
URN: urn:nbn:se:su:diva-98317DOI: 10.1051/0004-6361/201322276ISI: 000326574000143OAI: oai:DiVA.org:su-98317DiVA: diva2:683421
Note

AuthorCount:9;

Available from: 2014-01-03 Created: 2014-01-03 Last updated: 2017-12-06Bibliographically approved
In thesis
1. Observations of rare supernovae and their environments
Open this publication in new window or tab >>Observations of rare supernovae and their environments
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Supernovae (SNe) are the final stage in the life of massive stars. Their explosion unbinds the progenitor star revealing its inner layers. The SN ejecta interact with the circumstellar material (CSM), providing further information on the progenitor star.

In this work we present the study of rare SN subtypes, aiming to investigate their observational and physical properties and those of their progenitor stars.These studies include the analysis of SN samples as well as that of single objects.Two main SN classes are discussed: radioactively-powered events and SNe interacting with their CSM.

Within the first group, we investigated the rare (~1% of core-collapse SNe) family of SN 1987A-like events. These SNe are found to be the explosion of compact, hydrogen-rich blue supergiant (BSG) stars, and to occur mainly in moderately low metallicity environs. We also studied a sample of 20 stripped-envelope (SE) SNe, which are also powered by the decay of radioactive 56Ni. These SNe are the result of the core-collapse of massive, hydrogen or even helium-poor stars stripped of their outer envelopes by line-driven winds and/or by the accretion onto companion stars.We investigated the differences among the early-time light curves of the subtypes forming the SE SN group (IIb, Ib, Ic, Ic-BL) and found that in all of them the 56Ni is strongly mixed out in the ejecta. This result suggests that the difference between helium-poor and helium-rich SNe is due to an actual lack of helium in SNe Ic and Ic-BL rather than to a different degree of 56Ni mixing.

Our work on CSM-interacting SNe include the study of a sample of SNe IIn, i.e. core-collapse SNe interacting with hydrogen-rich CSM, and the analysis of SN 2008J, a particularly rare event which we interpreted as the interaction of a thermonuclear SN Ia with a thick hydrogen-rich CSM. Spectral analysis of the SN IIn sample suggests that these SNe are likely to be the explosion of luminous blue variable stars (LBVs), although other channels are not excluded.

Place, publisher, year, edition, pages
Stockholm: Department of Astronomy, Stockholm University, 2014. 80 p.
Keyword
Supernova, stellar evolution, metallicity, circumstellar interaction
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
urn:nbn:se:su:diva-108286 (URN)978-91-7649-030-3 (ISBN)
Public defence
2014-12-19, sal FB52, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:00 (English)
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Supervisors
Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 5: Submitted.

Available from: 2014-11-27 Created: 2014-10-17 Last updated: 2014-11-20Bibliographically approved

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Taddia, FrancescoSollerman, JesperGafton, EmanuelFransson, ClaesLeloudas, GeorgiosErgon, Mattias
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