LOW-FREQUENCY QUASI-PERIODIC OSCILLATION FROM THE 11 Hz ACCRETING PULSAR IN TERZAN 5: NOT FRAME DRAGGING
نویسندگان
چکیده
We report on six RXTE observations taken during the 2010 outburst of the 11 Hz accreting pulsar IGR J17480−2446 located in the globular cluster Terzan 5. During these observations we find power spectra which resemble those seen in Z-type high-luminosity neutron star low-mass X-ray binaries, with a quasi-periodic oscillation (QPO) in the 35–50 Hz range simultaneous with a kHz QPO and broadband noise. Using well-known frequency–frequency correlations, we identify the 35–50 Hz QPOs as the horizontal branch oscillations, which were previously suggested to be due to Lense–Thirring (LT) precession. As IGR J17480−2446 spins more than an order of magnitude more slowly than any of the other neutron stars where these QPOs were found, this QPO cannot be explained by frame dragging. By extension, this casts doubt on the LT precession model for other low-frequency QPOs in neutron stars and perhaps even black hole systems.
منابع مشابه
Millihertz Quasi-periodic Oscillations and Thermonuclear Bursts from Terzan 5: a Showcase of Burning Regimes
We present a comprehensive study of the thermonuclear bursts and millihertz quasi-periodic oscillations (mHz QPOs) from the neutron star (NS) transient and 11 Hz X-ray pulsar IGR J17480–2446, located in the globular cluster Terzan 5. The increase in burst rate that we find during its 2010 outburst, when persistent luminosity rises from 0.1 to 0.5 times the Eddington limit, is in qualitative agr...
متن کاملThe MHD Alfven wave oscillation model of kHz Quasi Periodic Oscillations of Accreting X-ray Binaries
We ascribe the interpretation of the twin kilohertz Quasi Periodic Oscillations (kHz QPOs) of X-ray spectra of Low Mass X-Ray Binaries (LMXBs) to MHD Alfven wave oscillations in the different mass density regions of the accreted matter at the preferred radius, and the upper kHz QPO frequency coincides with the Keplerian frequency. The proposed model concludes that the kHz QPO frequencies depend...
متن کاملResonance in Forced Oscillations of an Accretion Disk and Kilohertz Quasi–Periodic Oscillations
We have performed numerical simulations of a radially perturbed “accretion” torus around a black hole or neutron star and find that the torus performs radial and vertical motions at the appropriate epicyclic frequencies. We find clear evidence that vertical motions are excited in a nonlinear resonance when the applied perturbation is periodic in time. The strongest resonant response occurs when...
متن کاملThe Stochastic X-ray Variability of the Accreting Millisecond Pulsar
In this work I report on the stochastic X-ray variability of the 340 Hz accreting millisecond pulsar MAXI J0911–655. Analyzing pointed observations of the XMM-Newton and NuSTAR observatories I find that the source shows broad band-limited stochastic variability in the 0.01− 10 Hz range, with a total fractional variability of ∼ 24% rms in the 0.4− 3 keV energy band, which increases to ∼ 40% rms ...
متن کاملLag of Low-Energy Photons in an X-ray Burst Oscillation: Doppler Delays
Numerous X-ray bursts show strong oscillations in their flux at several hundred Hz as revealed by RXTE. Analyzing one such oscillation from the X-ray binary Aql X-1, I find that low energy photons (3.5–5.7 keV) lag high energy photons (> 5.7 keV) by approximately 1 radian. The oscillations are thought to be produced by hot spots on the spinning neutron star. The lags can then be explained by a ...
متن کاملar X iv : a st ro - p h / 98 02 06 5 v 1 5 F eb 1 99 8 SIDEBANDS DUE TO QUASI - PERIODIC OSCILLATIONS IN 4 U 1626 − 67
The low-mass X-ray binary pulsar 4U 1626−67 shows 0.048 Hz quasi-periodic oscillations (QPOs) and red noise variability as well as coherent pulsations at the 0.130 Hz neutron star spin frequency. Power density spectra of observations made with the Rossi X-ray Timing Explorer show significant sidebands separated from the pulsar spin frequency (and its harmonics) by the QPO frequency. These show ...
متن کامل