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Neutrino-heated winds from millisecond protomagnetars as sources of the weak r-process

Vlasov, Andrey D. and Metzger, Brian D. and Lippuner, Jonas and Roberts, Luke F. and Thompson, Todd A. (2017) Neutrino-heated winds from millisecond protomagnetars as sources of the weak r-process. Monthly Notices of the Royal Astronomical Society, 468 (2). pp. 1522-1533. ISSN 0035-8711.

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We explore heavy element nucleosynthesis in neutrino-driven winds from rapidly rotating, stronglymagnetized protoneutron stars (‘millisecond protomagnetars’) forwhich themagnetic dipole is aligned with the rotation axis, and the field is assumed to be a static force-free configuration. We process the protomagnetar wind trajectories calculated by Vlasov, Metzger & Thompson through the r-process nuclear reaction network SkyNet using contemporary models for the evolution of the wind electron fraction during the protoneutron star cooling phase. Although we do not find a successful second or third-peak r-process for any rotation period P, we show that protomagnetars with P ∼ 1–5 ms produce heavy element abundance distributions that extend to higher nuclear mass number than from otherwise equivalent spherical winds (with the mass fractions of some elements enhanced by factors of �100–1000). The heaviest elements are synthesized by outflows emerging along flux tubes that graze the closed zone and pass near the equatorial plane outside the light cylinder. Due to dependence of the nucleosynthesis pattern on the magnetic field strength and rotation rate of the protoneutron star, natural variations in these quantities between core collapse events could contribute to the observed diversity of the abundances of weak r-process nuclei in metal-poor stars. Further diversity, including possibly even a successful third-peak r-process, could be achieved for misaligned rotators with non-zero magnetic inclination with respect to the rotation axis. If protomagnetars are central engines for GRBs, their relativistic jets should contain a high-mass fraction of heavy nuclei of characteristic mass number ¯A ≈ 100, providing a possible source for ultrahigh energy cosmic rays comprised of heavy nuclei with an energy spectrum that extends beyond the nominal Grezin–Zatsepin–Kuzmin cut-off for protons or iron nuclei.

Item Type:Article
Related URLs:
URLURL TypeDescription
Metzger, Brian D.0000-0002-4670-7509
Lippuner, Jonas0000-0002-5936-3485
Roberts, Luke F.0000-0001-7364-7946
Additional Information:© 2017 The Authors. Accepted 2017 February 20. Received 2017 February 20; in original form 2017 January 11. ADV and BDM gratefully acknowledge support from the National Science Foundation (AST-1410950, AST-1615084), NASA, through the Astrophysics Theory Program (NNX16AB30G) and the Fermi Guest Investigator Program (NNX15AU77G, NNX16AR73G), the Research Corporation for Science Advancement Scialog Program (RCSA 23810), and the Alfred P. Sloan Foundation.
Funding AgencyGrant Number
Research Corporation23810
Alfred P. Sloan FoundationUNSPECIFIED
Issue or Number:2
Record Number:CaltechAUTHORS:20170525-123433997
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:77762
Deposited By: Joy Painter
Deposited On:25 May 2017 20:30
Last Modified:09 Mar 2020 13:19

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