Astrophys. J., 590, 846-857 (2003/June-3)
The physics of supernova remnant blast waves. II. Electron-ion equilibration in DEM L71 in the Large Magellanic Cloud.
RAKOWSKI C.E., GHAVAMIAN P. and HUGHES J.P.
Abstract (from CDS):
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 (g0≡Te/Tp) 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 (g0=me/mp), where the downstream electron and proton temperatures equilibrate through Coulomb collisions, (2) a planar, immediately equilibrated shock (g0=1), and (3) a spherical, equilibrated shock under Sedov evolution. Using independent measurements of T_e_and Tp, we find that the X-ray spectra from the fastest blast wave locations (Vs∼700-1000 km/s) 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 (Vs∼400-600 km/s) 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 g0. This model confirmed and strengthened the above results. Specifically, we found that X-ray spectra from an intermediate-velocity shock (Vs∼800 km/s) were consistent with intermediate equilibration, excluding both g0=me/mpand g0=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.
ISM: Individual: Alphanumeric: DEM L71 - ISM: Individual: Alphanumeric: SNR 0505-67.9 - Shock Waves - ISM: Supernova Remnants - X-Rays: ISM
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