Authors

Citation

Mc. Miller et al., Effects of rapid stellar rotation on equation-of-state constraints derivedfrom quasi-periodic brightness oscillations, ASTROPHYS J, 509(2), 1998, pp. 793-801

Citations number

44

Language

INGLESE

art.tipo

Article

Categorie Soggetti

Space Sciences

Journal title

ASTROPHYSICAL JOURNAL

ISSN journal

0004-637X
→ ACNP

Volume

509

Issue

2

Year of publication

1998

Part

1

Pages

793 - 801

Database

ISI

SICI code

0004-637X(199812)509:2<793:EORSRO>2.0.ZU;2-M

Abstract

Quasi-periodic X-ray brightness oscillations (QPOs) with frequencies greate
r than or similar to 1 kHz have now been discovered in more than a dozen ne
utron stars in low-mass X-ray binary systems using the Rossi X-Ray Timing E
xplorer. There is strong evidence that the frequencies of some kilohertz os
cillations are the orbital frequencies of accreting gas in nearly circular
orbits around these stars. Some stars that produce kilohertz QPOs may have
spin frequencies greater than or similar to 400 Hz. For spin rates this hig
h, first-order analytic treatments of the effects of the star's rotation on
its structure and the spacetime are inaccurate. Here we use the results of
a large number of fully relativistic, self-consistent numerical calculatio
ns of the stellar structure of rapidly rotating neutron stars and their int
erior and exterior spacetimes to investigate the constraints on the propert
ies of such stars that can be derived if stable circular orbits of various
frequencies are observed. We have computed the equatorial radius of the sta
r, the radius of the innermost stable circular orbit, and the frequency of
the highest frequency stable circular orbit as functions of the stellar spi
n rate for spin rates up to the maximum possible and for several illustrati
ve equations of state. Our calculations show that the upper bounds on the s
tiffness of neutron star matter implied by a given orbital frequency are ty
pically significantly stricter for stars with spin frequencies greater than
or similar to 400 Hz than for slowly rotating stars.