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Evidence for r-process Delay in Very Metal-poor Stars

Tarumi, Yuta and Hotokezaka, Kenta and Beniamini, Paz (2021) Evidence for r-process Delay in Very Metal-poor Stars. Astrophysical Journal Letters, 913 (2). Art. No. L30. ISSN 2041-8205. doi:10.3847/2041-8213/abfe13.

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The abundances of r-process elements of very metal-poor stars capture the history of the r-process enrichment in the early stage of star formation in a galaxy. Currently, various types of astrophysical sites including neutron star mergers (NSMs), magneto-rotational supernovae, and collapsars, are suggested as the origin of r-process elements. The time delay between the star formation and the production of r-process elements is the key to distinguish these scenarios, with the caveat that the diffusion of r-process elements in the interstellar medium may induce the delay in r-process enrichment because r-process events are rare. Here we study the observed Ba abundance data of very metal-poor stars as the tracer of the early enrichment history of r-process elements. We find that the gradual increase of [Ba/Mg] with [Fe/H], which is remarkably similar among the Milky Way and classical dwarfs, Requires a significant time delay (100 Myr–1 Gyr) of r-process events from star formation rather than the diffusion-induced delay. We stress that this conclusion is robust to the assumption regarding s-process contamination in the Ba abundances because the sources with no delay would overproduce Ba at very low metallicities, even without the contribution from the s-process. Therefore, we conclude that sources with a delay, possibly NSMs, are the origins of r-process elements.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Hotokezaka, Kenta0000-0002-2502-3730
Beniamini, Paz0000-0001-7833-1043
Additional Information:© 2021. The American Astronomical Society. Received 2021 February 5; revised 2021 April 24; accepted 2021 May 5; published 2021 June 2. We thank the anonymous referee for useful comments. We also thank Yutaka Hirai, Tadafumi Matsuno, Naoki Yoshida, Brian Metzger, and Daniel Siegel for insightful comments. Y.T. is supported by JSPS KAKENHI grant No. 20J21795. K.H. is supported by JSPS Early-Career Scientists grant No. 20K14513. The research of P.B. was funded by the Gordon and Betty Moore Foundation through grant GBMF5076.
Funding AgencyGrant Number
Japan Society for the Promotion of Science (JSPS)20J21795
Japan Society for the Promotion of Science (JSPS)20K14513
Gordon and Betty Moore FoundationGBMF5076
Subject Keywords: Galaxy abundances; Chemical abundances; Stellar abundances; R-process; Nuclear astrophysics
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Galaxy abundances (574); Chemical abundances (224); Stellar abundances (1577); R-process (1324); Nuclear astrophysics (1129)
Record Number:CaltechAUTHORS:20210604-111534333
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Official Citation:Yuta Tarumi et al 2021 ApJL 913 L30
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:109380
Deposited By: George Porter
Deposited On:07 Jun 2021 14:55
Last Modified:16 Nov 2021 19:35

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