Imagine the Universe!

Simulation of Aperiodic and Periodic Variabilities in X-RAY Sources


L. Burderi, M. Guainazzi, N. R. Robba

Istituto di Fisica, Universitá di Palermo, Via Archirafi 36, I- 90133 Palermo, Italy

Introduction

The Power Spectrum Density (PSD) has been extensively used to study the periodic (Harmonic Lines, HL) and the aperiodic (Red Noise, RN) features of the temporal variability of the High Mass X Ray Binaries (HMXRB). Some authors have proposed a very simple Shot Noise model (SN) in order to explain the RN feature (Terrel and Olsen 1970). In this scenario the plasma instabilities that can occur during the accretion process (Rayleigh-Taylor, Kelvin-Helmoltz, Alfvén zone instabilities above the accretion column) could clump the matter in blobs (Elsner and Lamb 1977,1984; Arons and Lea 1976); the shot emission associated with the accretion of these blobs is the cause of the aperiodic variability. The timescale associated with the instabilities mentioned above cover a very wide range (roughly from milliseconds to tens of seconds). Due to the casual occurrence of the blobs, as a consequence of the instability phenomena, these emissions are supposed to occur randomly (stochastically) in time.

This article was taken from http://www.astro.lsa.umich.edu/users/iotm/oct95/orion.html

The rest of the article can be viewed at that site.

If words seem to be missing from the articles, please read this.

Imagine the Universe! is a service of the High Energy Astrophysics Science Archive Research Center (HEASARC), Dr. Alan Smale (Director), within the Astrophysics Science Division (ASD) at NASA's Goddard Space Flight Center.

The Imagine Team
Project Leader: Dr. Barbara Mattson
Curator: Meredith Gibb
Responsible NASA Official: Phil Newman
All material on this site has been created and updated between 1997-2014.
This page last updated: Friday, 19-Nov-2004 15:08:44 EST