2003/03/04 by Cara E. Rakowski, Parviz Ghavamian, John P. Hughes · 2 citations
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics and Cosmic Phenomena #Gamma-ray bursts and supernovae #astro-ph
paper · pdf · doi:10.1086/375162
published as Astrophys.J. 590 (2003) 846-857 · 22 pages, including 11 postscript figs, LaTeX, accepted to ApJ, see companion paper
arxiv created 2003/03/04 · openalex publication_date 2003/06/20 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
We present analysis and modeling of X-ray spectra from the blast wave shock of DEM L71 in the Large Magellanic Cloud. This remnant exhibits widespread Balmer-dominated emission characteristic of nonradiative shocks in partially neutral gas. We have used Chandra ACIS-S data and optical Fabry-Pérot spectra of the blast wave to measure the electron and proton temperatures, respectively. In principle, when combined, these measurements can determine the degree of electron-ion temperature equilibration ( g 0 ≡ T e / T p ) immediately behind the shock front. In our X-ray analysis we fit Chandra spectra of three nested regions behind the blast wave under three different scenarios: (1) a planar, initially unequilibrated shock ( g 0 = m e / m p ), where the downstream electron and proton temperatures equilibrate through Coulomb collisions, (2) a planar, immediately equilibrated shock ( g 0 = 1), and (3) a spherical, equilibrated shock under Sedov evolution. Using independent measurements of T e and T p , we find that the X-ray spectra from the fastest blast wave locations ( V s ~ 700-1000 km s -1 ) are consistent with little or no equilibration at the shock front and are inconsistent with full equilibration. In contrast, spectra from regions showing slower blast wave speeds ( V s ~ 400-600 km s -1 ) allow full equilibration but exclude zero equilibration. In order to directly constrain the initial equilibration, we incorporated our knowledge of the proton temperatures into our X-ray models to build planar shock models that allow for a variable g 0 . This model confirmed and strengthened the above results. Specifically, we found that X-ray spectra from an intermediate-velocity shock ( V s ~ 800 km s -1 ) were consistent with intermediate equilibration, excluding both g 0 = m e / m p and g 0 = 1 at greater than 1 σ. Overall, our results support the picture of decreasing electron-ion equilibration with increasing shock speed found from previous studies of optical spectra in other Balmer-dominated supernova remnants.