Kilohertz quasi-periodic oscillation and atoll source states in 4U 0614+09

M. Méndez, M. Van Der Klis, J. Van Paradijs, W. H G Lewin, F. K. Lamb, B. A. Vaughan, E. Kuulkers, Dimitrios Psaltis

Research output: Contribution to journalArticle

44 Citations (Scopus)

Abstract

We report three RXTE/PCA observations of the low-mass X-ray binary 4U 0614+09. They show strong (∼30% rms) band-limited noise with a cutoff frequency varying between 0.7 and 15 Hz in correlation with the X-ray flux, fx. We observe two nonsimultaneous 11%-15% (rms) kHz peaks near 728 and 629 Hz in the power spectra of two of our observations when fx ∼ 10-9 ergs cm-2 s-1 (2-10 keV) but find no quasi-periodic oscillations (QPOs; <6% rms) when fx is half that. We suggest that count rate may not be a good measure for Ṁ even in sources as intrinsically weak as 4U 0614+09 and that QPO frequency and noise cutoff frequency track Ṁ more closely than count rate. The QPO increases in rms amplitude from 11% ±1.3% at 3 keV to 37% ± 12% at 23 keV; the fractional amplitude of the band-limited noise is energy independent. This suggests different sites of origin for these two phenomena. The spectrum of the oscillating flux roughly corresponds to a black body with temperature 1.56 ± 0.2 keV and radius 500 ± 200 m (other models fit as well), which might indicate that the oscillations originate at a small region on the neutron star surface.

Original languageEnglish (US)
JournalAstrophysical Journal
Volume485
Issue number1 PART II
StatePublished - 1997
Externally publishedYes

Fingerprint

atoll
oscillation
oscillations
cut-off
X Ray Timing Explorer
erg
neutron stars
power spectra
x rays
radii
energy
temperature
rate

Keywords

  • Accretion, accretion disks
  • Stars: neutron
  • X-rays: stars

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Méndez, M., Van Der Klis, M., Van Paradijs, J., Lewin, W. H. G., Lamb, F. K., Vaughan, B. A., ... Psaltis, D. (1997). Kilohertz quasi-periodic oscillation and atoll source states in 4U 0614+09. Astrophysical Journal, 485(1 PART II).

Kilohertz quasi-periodic oscillation and atoll source states in 4U 0614+09. / Méndez, M.; Van Der Klis, M.; Van Paradijs, J.; Lewin, W. H G; Lamb, F. K.; Vaughan, B. A.; Kuulkers, E.; Psaltis, Dimitrios.

In: Astrophysical Journal, Vol. 485, No. 1 PART II, 1997.

Research output: Contribution to journalArticle

Méndez, M, Van Der Klis, M, Van Paradijs, J, Lewin, WHG, Lamb, FK, Vaughan, BA, Kuulkers, E & Psaltis, D 1997, 'Kilohertz quasi-periodic oscillation and atoll source states in 4U 0614+09', Astrophysical Journal, vol. 485, no. 1 PART II.
Méndez M, Van Der Klis M, Van Paradijs J, Lewin WHG, Lamb FK, Vaughan BA et al. Kilohertz quasi-periodic oscillation and atoll source states in 4U 0614+09. Astrophysical Journal. 1997;485(1 PART II).
Méndez, M. ; Van Der Klis, M. ; Van Paradijs, J. ; Lewin, W. H G ; Lamb, F. K. ; Vaughan, B. A. ; Kuulkers, E. ; Psaltis, Dimitrios. / Kilohertz quasi-periodic oscillation and atoll source states in 4U 0614+09. In: Astrophysical Journal. 1997 ; Vol. 485, No. 1 PART II.
@article{3541811eadfa4969b374669377fda22c,
title = "Kilohertz quasi-periodic oscillation and atoll source states in 4U 0614+09",
abstract = "We report three RXTE/PCA observations of the low-mass X-ray binary 4U 0614+09. They show strong (∼30{\%} rms) band-limited noise with a cutoff frequency varying between 0.7 and 15 Hz in correlation with the X-ray flux, fx. We observe two nonsimultaneous 11{\%}-15{\%} (rms) kHz peaks near 728 and 629 Hz in the power spectra of two of our observations when fx ∼ 10-9 ergs cm-2 s-1 (2-10 keV) but find no quasi-periodic oscillations (QPOs; <6{\%} rms) when fx is half that. We suggest that count rate may not be a good measure for Ṁ even in sources as intrinsically weak as 4U 0614+09 and that QPO frequency and noise cutoff frequency track Ṁ more closely than count rate. The QPO increases in rms amplitude from 11{\%} ±1.3{\%} at 3 keV to 37{\%} ± 12{\%} at 23 keV; the fractional amplitude of the band-limited noise is energy independent. This suggests different sites of origin for these two phenomena. The spectrum of the oscillating flux roughly corresponds to a black body with temperature 1.56 ± 0.2 keV and radius 500 ± 200 m (other models fit as well), which might indicate that the oscillations originate at a small region on the neutron star surface.",
keywords = "Accretion, accretion disks, Stars: neutron, X-rays: stars",
author = "M. M{\'e}ndez and {Van Der Klis}, M. and {Van Paradijs}, J. and Lewin, {W. H G} and Lamb, {F. K.} and Vaughan, {B. A.} and E. Kuulkers and Dimitrios Psaltis",
year = "1997",
language = "English (US)",
volume = "485",
journal = "Astrophysical Journal",
issn = "0004-637X",
publisher = "IOP Publishing Ltd.",
number = "1 PART II",

}

TY - JOUR

T1 - Kilohertz quasi-periodic oscillation and atoll source states in 4U 0614+09

AU - Méndez, M.

AU - Van Der Klis, M.

AU - Van Paradijs, J.

AU - Lewin, W. H G

AU - Lamb, F. K.

AU - Vaughan, B. A.

AU - Kuulkers, E.

AU - Psaltis, Dimitrios

PY - 1997

Y1 - 1997

N2 - We report three RXTE/PCA observations of the low-mass X-ray binary 4U 0614+09. They show strong (∼30% rms) band-limited noise with a cutoff frequency varying between 0.7 and 15 Hz in correlation with the X-ray flux, fx. We observe two nonsimultaneous 11%-15% (rms) kHz peaks near 728 and 629 Hz in the power spectra of two of our observations when fx ∼ 10-9 ergs cm-2 s-1 (2-10 keV) but find no quasi-periodic oscillations (QPOs; <6% rms) when fx is half that. We suggest that count rate may not be a good measure for Ṁ even in sources as intrinsically weak as 4U 0614+09 and that QPO frequency and noise cutoff frequency track Ṁ more closely than count rate. The QPO increases in rms amplitude from 11% ±1.3% at 3 keV to 37% ± 12% at 23 keV; the fractional amplitude of the band-limited noise is energy independent. This suggests different sites of origin for these two phenomena. The spectrum of the oscillating flux roughly corresponds to a black body with temperature 1.56 ± 0.2 keV and radius 500 ± 200 m (other models fit as well), which might indicate that the oscillations originate at a small region on the neutron star surface.

AB - We report three RXTE/PCA observations of the low-mass X-ray binary 4U 0614+09. They show strong (∼30% rms) band-limited noise with a cutoff frequency varying between 0.7 and 15 Hz in correlation with the X-ray flux, fx. We observe two nonsimultaneous 11%-15% (rms) kHz peaks near 728 and 629 Hz in the power spectra of two of our observations when fx ∼ 10-9 ergs cm-2 s-1 (2-10 keV) but find no quasi-periodic oscillations (QPOs; <6% rms) when fx is half that. We suggest that count rate may not be a good measure for Ṁ even in sources as intrinsically weak as 4U 0614+09 and that QPO frequency and noise cutoff frequency track Ṁ more closely than count rate. The QPO increases in rms amplitude from 11% ±1.3% at 3 keV to 37% ± 12% at 23 keV; the fractional amplitude of the band-limited noise is energy independent. This suggests different sites of origin for these two phenomena. The spectrum of the oscillating flux roughly corresponds to a black body with temperature 1.56 ± 0.2 keV and radius 500 ± 200 m (other models fit as well), which might indicate that the oscillations originate at a small region on the neutron star surface.

KW - Accretion, accretion disks

KW - Stars: neutron

KW - X-rays: stars

UR - http://www.scopus.com/inward/record.url?scp=21744461712&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=21744461712&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:21744461712

VL - 485

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 1 PART II

ER -