AN EMPIRICAL TORQUE NOISE AND SPIN-UP MODEL FOR ACCRETION-POWERED X-RAY PULSARS

Date

1993-01-01

Author

Baykal, Altan

Metadata

Show full item record

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Item Usage Stats

179
views

0
downloads

By using the first order autoregressive time series model, rotation histories of accretion-powered X-ray pulsars are modeled yielding a torque noise strength S(in) and the average secular spin-up term [OMEGA]. We find that Her X-1, Cen X-3, A0535 + 26, and Vela X-1 can be modeled with white torque-noise leading to random walks in pulse frequency; for the remaining sources the random walk model is also acceptable. Using this model we calculate the noise strengths in the frequency derivative and estimate the remaining secular angular accelerations. Subsequently we compare noise strength parameters with the X-ray luminosities L(x) and the secular angular accelerations. We do not see any distinction in these correlations that separate wind accreting sources from disk accreting sources. In the absence of any clear evidence for the two types of accretion, we suggest a simple scenario for the pulse frequency fluctuations in terms of episodes of mass transfer with positive and negative torques. The data shows that sources with L(x) > 10(37) erg s-1, spin-up on the average even though they experience a large amount of reverse torques. We do not see any significant secular spin-up/down behaviour for most of the sources with L(x) < 10(37) erg s-1.

Subject Keywords

X-ray binaries, Autoregressive process, Timing noise

URI

https://hdl.handle.net/11511/55264

Journal

ASTRONOMY & ASTROPHYSICS

Collections

Department of Physics, Article

Suggestions

OpenMETU
Core

A SHOT NOISE MODEL FOR A 2-COMPONENT NEUTRON-STAR Baykal, Altan; KIZILOGLU, U (1991-12-01) The two component neutron star model and the response of the neutron star under the influence of external white torque noise are reviewed. A new simulation technique is developed for estimating the crust core coupling time and the moment of inertia of the superfluid in the neutron star from the irregularly sampled data. The model is applied to Vela X-1, since this source has a long period P = 283 s and theoretical estimates of crust-core coupling time which are proportional to P lie in the observable region...
An investigation of the dynamics of coherent structures in a turbulent channel flow with a vertical sidewall obstruction Köken, Mete (2009-08-01) The physics of the flow around a vertical-wall obstruction attached to one of the sidewalls of a straight channel is numerically investigated using detached eddy simulation (DES) at a high channel Reynolds number, Re=5 x 10(5) (case HR). In particular, the study investigates the role played by the large-scale coherent structures in the sediment entrainment processes at the bed for conditions close to the initiation of scour (flat bed) in a loose-bed channel. Scale effects are investigated by comparing the r...
A numerically efficient frequency domain method for analysis of non Linear multi degree of freedom systems Özer, Mehmet Bülent (2012-08-15) Linear structural models contain mass, stiffness and damping matrices as well as a forcing vector. Once these matrices and the forcing vector are known, the response can be calculated through the methods of linear algebra. The system matrices of the linear model do not contain any terms that depend on the system response vector, therefore the calculation of the system response do not require an iterative procedure. On the other hand, frequency domain analysis of non-linear structural models generally contai...
A non-linear mathematical model for dynamic analysis of spur gears including shaft and bearing dynamics Özgüven, Hasan Nevzat (Elsevier BV, 1991-3) A six-degree-of-freedom non-linear semi-definite model with time varying mesh stiffness has been developed for the dynamic analysis of spur gears. The model includes a spur gear pair, two shafts, two inertias representing load and prime mover, and bearings. As the shaft and bearing dynamics have also been considered in the model, the effect of lateral-torsional vibration coupling on the dynamics of gears can be studied. In the non-linear model developed several factors such as time varying mesh stiffness an...
A study on uncertainty-based flood analysis Akpınar, Mustafa Berkay; Akyürek, Sevda Zuhal; Yanmaz, Ali Melih; Department of Civil Engineering (2023-1) A hydraulic model is a collection of mathematical equations that give a simple representation of reality with the inputs obtained from hydrological assessments to estimate flow, flow depth and velocity in channels. Basically, hydraulic models require digital elevation models, Intensity-Duration-Frequency curves, maximum flows from hydrographs, and roughness coefficients from field studies and/or satellite images. Inherently, these major inputs have uncertainties due to the complex nature of the evalua...

Citation Formats

A. Baykal, “AN EMPIRICAL TORQUE NOISE AND SPIN-UP MODEL FOR ACCRETION-POWERED X-RAY PULSARS,” ASTRONOMY & ASTROPHYSICS, pp. 119–125, 1993, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/55264.