Light element production in the circumstellar matter of Type Ic supernovae at low metallicity

Ko Nakamura, Susumu Inoue, Shinya Wanajo, Toshikazu Shigeyama

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

We investigate energetic Type Ic supernovae as production sites for 6Li and Be in the early stages of the Milky Way. Recent observations have revealed that some very metal-poor stars with [Fe/H]< -2.5 possess unexpectedly high abundances of 6Li. Some also exhibit enhanced abundances of Be as well as N. From a theoretical point of view, recent studies of the evolution of metal-poor massive stars show that rotation-induced mixing can enrich the outer H and He layers with C, N, and O (CNO) elements, particularly N, and at the same time cause the intense mass loss of these layers. Here we consider energetic supernova explosions occurring after the progenitor star has lost all but a small fraction of the He layer. The fastest portion of the supernova ejecta and the circumstellar matter (CSM), both of which are composed of He and CNO, can interact directly and induce light-element production through spallation and He-He fusion reactions. The CSM should be sufficiently thick to energetic particles so that the interactions terminate within its innermost regions. We calculate the resulting 6Li/O and 9Be/O ratios in the ejecta+CSMmaterial out of which the very metal-poor stars may form. We find that they are consistent with the observed values if the mass of the He layer remaining on the pre-explosion core is ∼0.01-0.1 Ṁand if the mass fraction of N mixed in the He layer is ∼0.01. Further observations of 6Li, Be, and N at low metallicity should provide us with critical tests of this production scenario.

Original languageEnglish
Title of host publicationProceedings of Science
Publication statusPublished - 2006
Externally publishedYes
Event9th International Symposium on Nuclear Astrophysics - Nuclei in the Cosmos, NIC 2006 - Geneva, Switzerland
Duration: 2006 Jun 252006 Jun 30

Other

Other9th International Symposium on Nuclear Astrophysics - Nuclei in the Cosmos, NIC 2006
CountrySwitzerland
CityGeneva
Period06/6/2506/6/30

Fingerprint

stellar envelopes
light elements
metallicity
supernovae
ejecta
stars
explosions
metals
spallation
energetic particles
massive stars
fusion
causes
interactions

ASJC Scopus subject areas

  • General

Cite this

Nakamura, K., Inoue, S., Wanajo, S., & Shigeyama, T. (2006). Light element production in the circumstellar matter of Type Ic supernovae at low metallicity. In Proceedings of Science

Light element production in the circumstellar matter of Type Ic supernovae at low metallicity. / Nakamura, Ko; Inoue, Susumu; Wanajo, Shinya; Shigeyama, Toshikazu.

Proceedings of Science. 2006.

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Nakamura, K, Inoue, S, Wanajo, S & Shigeyama, T 2006, Light element production in the circumstellar matter of Type Ic supernovae at low metallicity. in Proceedings of Science. 9th International Symposium on Nuclear Astrophysics - Nuclei in the Cosmos, NIC 2006, Geneva, Switzerland, 06/6/25.
Nakamura K, Inoue S, Wanajo S, Shigeyama T. Light element production in the circumstellar matter of Type Ic supernovae at low metallicity. In Proceedings of Science. 2006
Nakamura, Ko ; Inoue, Susumu ; Wanajo, Shinya ; Shigeyama, Toshikazu. / Light element production in the circumstellar matter of Type Ic supernovae at low metallicity. Proceedings of Science. 2006.
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N2 - We investigate energetic Type Ic supernovae as production sites for 6Li and Be in the early stages of the Milky Way. Recent observations have revealed that some very metal-poor stars with [Fe/H]< -2.5 possess unexpectedly high abundances of 6Li. Some also exhibit enhanced abundances of Be as well as N. From a theoretical point of view, recent studies of the evolution of metal-poor massive stars show that rotation-induced mixing can enrich the outer H and He layers with C, N, and O (CNO) elements, particularly N, and at the same time cause the intense mass loss of these layers. Here we consider energetic supernova explosions occurring after the progenitor star has lost all but a small fraction of the He layer. The fastest portion of the supernova ejecta and the circumstellar matter (CSM), both of which are composed of He and CNO, can interact directly and induce light-element production through spallation and He-He fusion reactions. The CSM should be sufficiently thick to energetic particles so that the interactions terminate within its innermost regions. We calculate the resulting 6Li/O and 9Be/O ratios in the ejecta+CSMmaterial out of which the very metal-poor stars may form. We find that they are consistent with the observed values if the mass of the He layer remaining on the pre-explosion core is ∼0.01-0.1 Ṁand if the mass fraction of N mixed in the He layer is ∼0.01. Further observations of 6Li, Be, and N at low metallicity should provide us with critical tests of this production scenario.

AB - We investigate energetic Type Ic supernovae as production sites for 6Li and Be in the early stages of the Milky Way. Recent observations have revealed that some very metal-poor stars with [Fe/H]< -2.5 possess unexpectedly high abundances of 6Li. Some also exhibit enhanced abundances of Be as well as N. From a theoretical point of view, recent studies of the evolution of metal-poor massive stars show that rotation-induced mixing can enrich the outer H and He layers with C, N, and O (CNO) elements, particularly N, and at the same time cause the intense mass loss of these layers. Here we consider energetic supernova explosions occurring after the progenitor star has lost all but a small fraction of the He layer. The fastest portion of the supernova ejecta and the circumstellar matter (CSM), both of which are composed of He and CNO, can interact directly and induce light-element production through spallation and He-He fusion reactions. The CSM should be sufficiently thick to energetic particles so that the interactions terminate within its innermost regions. We calculate the resulting 6Li/O and 9Be/O ratios in the ejecta+CSMmaterial out of which the very metal-poor stars may form. We find that they are consistent with the observed values if the mass of the He layer remaining on the pre-explosion core is ∼0.01-0.1 Ṁand if the mass fraction of N mixed in the He layer is ∼0.01. Further observations of 6Li, Be, and N at low metallicity should provide us with critical tests of this production scenario.

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