2009/11/02 by M. Cocchi, R. Farinelli, A. Paizis +2 · 1 citation
Earth and Planetary Sciences · Physics and Astronomy · #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Black-body radiation #Context (archaeology) #High-pressure geophysics and materials #Luminosity #Neutron star #Nuclear physics #Observatory #Optics #Photon #Physics #Pulsars and Gravitational Waves Research #Radiation #Spectral line #astro-ph.HE
paper · pdf · doi:10.1051/0004-6361/200912796
6 pages, 2 figures. Accepted for publication in A&A
arxiv created 2009/11/02 · openalex publication_date 2009/11/04 · arxiv updated 2015/05/14 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
<i>Context. <i/>GS 1826-238is a well-studied X-ray bursting neutron star in a low mass binary system. Thermal Comptonisation by a hot electron cloud ( keV) is a widely accepted mechanism accounting for its high energy emission, while the nature of most of its soft X-ray output is not completely understood. A further low energy component is typically needed to model the observed spectra: pure blackbody and Comptonisation-modified blackbody radiation by a lower temperature (a few keV) electron plasma were suggested to explain the low energy data. <i>Aims. <i/>In order to better characterise the nature of the low energy emission and the bolometric output of the source, the steady emission of GS 1826-238is studied by means of sensitive, broad band (X to soft Gamma-rays) measurements obtained by the <i>INTEGRAL<i/> observatory. <i>Methods. <i/>In this data analysis, the newly developed, up-to-date Comptonisation model comptb is applied for the first time to study effectively the low-hard state variability of a low-luminosity neutron star in a low-mass X-ray binary system. Three joint ISGRI/JEM-X data sets (two from observations performed in 2003 and one from 2006) were analysed. <i>Results. <i/>We confirm that the 3-200 keV emission of GS 1826-238is characterised by Comptonisation of soft seed photons by a hot electron plasma. A single spectral component is sufficient to model the observed spectra. At lower energies, no direct blackbody emission is observed and there is no need to postulate a low temperature Compton region. Compared to the 2003 measurements, the plasma temperature decreased from ~<i>20<i/> to ~<i>14<i/> keV in 2006, together with the seed photons temperature. The source intensity was also found to be ~ lower in 2006, whilst the average recurrence frequency of the X-ray bursts significantly increased. Possible explanations for this apparent deviation from the typical limit-cycle behaviour of this burster are discussed.