Superspinning Quark Stars Limited by Twin High-Frequency Quasiperiodic Oscillations

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F47813059%3A19240%2F17%3AA0000030" target="_blank" >RIV/47813059:19240/17:A0000030 - isvavai.cz</a>

Result on the web

<a href="http://acta.astrouw.edu.pl/Vol67/n2/a_67_2_6.html" target="_blank" >http://acta.astrouw.edu.pl/Vol67/n2/a_67_2_6.html</a>

DOI - Digital Object Identifier

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Result language

angličtina

Original language name

Superspinning Quark Stars Limited by Twin High-Frequency Quasiperiodic Oscillations

Original language description

We study properties of Keplerian disks and their high-frequency quasi-periodic oscillations (HF QPOs) in the field of quark stars with dimensionless spin a breaking the black-hole spin limit of a = 1 up to a approximate to 1.3. Using the external geometry of the superspinning quark stars approximated by the Kerr geometry, we show that the Keplerian disks have to touch the surface of such quark stars and their accretion efficiency eta approximate to 18% significantly exceeds the efficiency related to the Schwarzschild black holes. Using the geodesic oscillation models, we test possible existence of the superspinning quark stars in atoll sources demonstrating the twin HF QPOs with resonant frequency ratios 3:2, 4:3, 5:4. For explanation of the twin HF QPOs we consider the standard relativistic precession model and its modifications, the tidal distortion model, the resonance epicyclic and the warped disk model. In a given model, we assume occurrence of the twin oscillatory modes at a common resonant dimensionless radius x = r/M determined by the frequency ratio and the quark star spin a. The theoretical limit R &gt; 3M on the quark star surface radius puts strong restrictions on the relations between the resonant radii x and the quark star spin a. These restrictions imply that all the considered geodesic oscillation models can be excluded, except for one variant of the relativistic precession model, or alternatively the tidal distortion and warped disk models, that allow for appearance of the twin HF QPOs with frequency ratio 3 : 2 at radii slightly above the theoretical limit on the radius of the quark star surface, but exclude the smaller frequency ratios (4:3, 5:4).

Czech name

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Czech description

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Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

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OECD FORD branch

10308 - Astronomy (including astrophysics,space science)

Project

Result was created during the realization of more than one project. More information in the Projects tab.

Continuities

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)<br>I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2017

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

Acta Astronomica

ISSN

0001-5237

e-ISSN

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Volume of the periodical

67

Issue of the periodical within the volume

2

Country of publishing house

PL - POLAND

Number of pages

21

Pages from-to

181-201

UT code for WoS article

000407362400006

EID of the result in the Scopus database

2-s2.0-85026386567