Possible constraints on the density dependence of the nuclear symmetry energy from quasi-periodic oscillations in soft gamma repeaters

Hajime Sotani, Ken'ichiro Nakazato, Kei Iida, Kazuhiro Oyamatsu

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32 Citations (Scopus)

Abstract

We systematically examine the fundamental frequencies of shear torsional oscillations in neutron star crusts in a manner that is dependent on the parameter L characterizing the poorly known density dependence of the symmetry energy. The identification of the lowest quasiperiodic oscillation (QPO) among the observedQPOs from giant flares in soft-gamma repeaters as the l = 2 fundamental torsional oscillations enables us to constrain the parameter L as L ≤ 47.4MeV, which is the most conservative restriction on L obtained in the present work that assumes that the mass and radius of the flaring neutron stars range 1.4-1.8M⊙ and 10-14 km. Next, we identify one by one a set of the low-lying frequencies observed in giant flares as the fundamental torsional oscillations. The values of L that can reproduce all the observed frequencies in terms of the torsional oscillations coupled with a part of dripped neutrons via entrainment effects are then constrained as 101.1 ≤ L ≤ 131.0MeV. Alternatively, if only the second lowest frequency observed in SGR 1806-20 has a different origin, one obtains relatively low L values ranging 58.0 ≤ L ≤ 85.3MeV, which seem more consistent with other empirical constraints despite large uncertainties.

Original languageEnglish
Pages (from-to)2060-2068
Number of pages9
JournalMonthly Notices of the Royal Astronomical Society
Volume434
Issue number3
DOIs
Publication statusPublished - Sep 1 2013
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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