J 2021

Comparison of the Hartle-Thorne Model of Neutron Stars with its Kerr Approximation by using Resonant Switch Model

STUCHLÍK, Zdeněk, Kateřina KLIMOVIČOVÁ, Jan SCHEE, Gabriel TÖRÖK, Andrea KOTRLOVÁ et. al.

Basic information

Original name

Comparison of the Hartle-Thorne Model of Neutron Stars with its Kerr Approximation by using Resonant Switch Model

Authors

STUCHLÍK, Zdeněk (203 Czech Republic, belonging to the institution), Kateřina KLIMOVIČOVÁ (203 Czech Republic, belonging to the institution), Jan SCHEE (203 Czech Republic, belonging to the institution), Gabriel TÖRÖK (203 Czech Republic, belonging to the institution) and Andrea KOTRLOVÁ (203 Czech Republic, belonging to the institution)

Edition

Acta Astronomica, PL - Polská republika, 2021, 0001-5237

Other information

Language

English

Type of outcome

Článek v odborném periodiku

Field of Study

10308 Astronomy

Country of publisher

Poland

Confidentiality degree

není předmětem státního či obchodního tajemství

References:

RIV identification code

RIV/47813059:19630/21:A0000171

Organization unit

Institute of physics in Opava

UT WoS

000751812700004

Keywords in English

Stars: neutron;Stars: oscillations;Equation of state;X-rays: binaries

Tags

International impact, Reviewed

Links

LTT17003, research and development project.
Změněno: 13/9/2022 08:58, Mgr. Pavlína Jalůvková

Abstract

V originále

The Hartle-Thorne (H-T) models of slowly rotating neutron or quark stars, characterized by the mass M, dimensionless spin a, and reduced quadrupole moment q, are constructed for the observationally given rotational frequency frot = 580 Hz (290 Hz) of the compact star in the atoll source 4U 1636-53, and a wide range of equations of state (EoS) giving sequences of allowed states governed by the relations a(M), q(M). These sequences are used in the framework of the resonant switch (RS) model combining pairs of geodesic oscillation models to match the data of the twin high-frequency quasi-periodic oscillations observed in the 4U 1636-53 source. The results of the matching procedure using the H-T models are compared to those based on the Kerr approximation of the exterior of the neutron stars. The best H-T matches fix the only variant of the RS model combining particular modifications of the relativistic precession model, exclude the rotation frequency frot = 290 Hz, restrict the considered EoS to six of them, excluding the strange quark stars, and significantly improve precision of the matches given by any single geodesic oscillations model. The Kerr matching allows two variants of the RS model, thus, giving false information, and only three EoS, thus, giving insufficient information. Our results demonstrate that in the matching procedure, the Kerr approximation can be used only for neutron stars governed by the H-T models with q < 2, implying an important restriction on the applicability of the Kerr approximation for description of the oscillatory phenomena around neutron stars. On the other hand, the RS model is sufficiently discriminating for the spacetime metric to be largely determined by fitting to the data. The ranges of the external spacetime parameters of the neutron stars related to the best H-T matches are determined to be M approximate to 2.10-2.13 M-circle dot , a approximate to 0.21-0.25, q approximate to 1.8-2.3. Most compact neutron star is predicted by the Gandolfi EoS, when M approximate to 2.10 M-circle dot , a approximate to 0.21, q approximate to 1.8, with the equatorial radius R approximate to 10.83 km and eccentricity epsilon = 0.03.