X and UV radiation from accreting non-magnetic degenerate dwarfs
type: CreativeWork
description: "X radiation from degenerate stars is produced by the impact of accreting matter with the stellar surface. The resulting X-ray and UV spectrum gives vital clues about the nature of the underlying star and the extreme conditions of temperature and magnetic field strength that may exist in the emission region. While the X-ray spectra of many sources have been extensively observed, the lack of systematic theoretical studies of X-ray emission from degenerate stars has so far prevented the exploitation of these observations. I have therefore carried out a comprehensive study of X-ray emission from non-magnetic degenerate dwarfs. I report the results of detailed numerical calculations that span the entire range of accretion rates and stellar masses, and that include the important, but previously unexplored, regime at moderate and high accretion rates. My calculations show that the characteristics of X radiation from non-magnetic degenerate dwarfs are qualitatively different than heretofore stated. I find: (1) Stars undergoing spherical accretion can produce a maximum hard X-ray luminosity Lhmax = 4.5 x 10^36 erg s-1 which is a factor of 4 larger, and occurs [or an electron scattering optical depth more than an order of magnitude larger, than earlier estimates suggested. (2) Contrary to previous reports, even high mass stars can produce low temperature (s 10 keY) X-ray spectra. (3) It has been stated that the temperature of the X-ray spectra produced by such stars is independent of X-ray intensity, and depends only on the stellar mass. I find, however, that at moderate and high accretion rates the spectral temperature varies dramatically and the star exhibits a pronounced-correlation between X-ray spectral temperature and luminosity. Such a correlation is not expected for neutron stars, and may be an important signature of degenerate dwarf X-ray sources. (4) At moderate and high accretion rates, the spectra have a power law high energy tail and, if the mass is high (M ~ 1.…
abstract: "X radiation from degenerate stars is produced by the impact of accreting matter with the stellar surface. The resulting X-ray and UV spectrum gives vital clues about the nature of the underlying star and the extreme conditions of temperature and magnetic field strength that may exist in the emission region. While the X-ray spectra of many sources have been extensively observed, the lack of systematic theoretical studies of X-ray emission from degenerate stars has so far prevented the exploitation of these observations. I have therefore carried out a comprehensive study of X-ray emission from non-magnetic degenerate dwarfs. I report the results of detailed numerical calculations that span the entire range of accretion rates and stellar masses, and that include the important, but previously unexplored, regime at moderate and high accretion rates. My calculations show that the characteristics of X radiation from non-magnetic degenerate dwarfs are qualitatively different than heretofore stated. I find: (1) Stars undergoing spherical accretion can produce a maximum hard X-ray luminosity Lhmax = 4.5 x 10^36 erg s-1 which is a factor of 4 larger, and occurs [or an electron scattering optical depth more than an order of magnitude larger, than earlier estimates suggested. (2) Contrary to previous reports, even high mass stars can produce low temperature (s 10 keY) X-ray spectra. (3) It has been stated that the temperature of the X-ray spectra produced by such stars is independent of X-ray intensity, and depends only on the stellar mass. I find, however, that at moderate and high accretion rates the spectral temperature varies dramatically and the star exhibits a pronounced-correlation between X-ray spectral temperature and luminosity. Such a correlation is not expected for neutron stars, and may be an important signature of degenerate dwarf X-ray sources. (4) At moderate and high accretion rates, the spectra have a power law high energy tail and, if the mass is high (M ~ 1.…
author: Kylafis, Nikolaos Dimitrios
language: en
keywords: x radiation, UV radiation, accreting non-magnetic degenerate dwarfs, degenerate stars, stellar surface
date published: 2011-06-30T16:16:33Z
date modified: 2026-07-22T22:25:24Z
provider: University of Illinois - Urbana-Champaign
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Illinois at Urbana-Champaign

PropertyValue
property ID: Handle
value: http://hdl.handle.net/2142/25601