Constraints on Cosmic-ray Acceleration Efficiency in Balmer Shocks of Two Young Type Ia Supernova Remnants in the Large Magellanic Cloud

We present results from an optical study of two young Balmer-dominated remnants of SNIa in the Large Magellanic Cloud, 0509−67.5 and 0519−69.0, in an attempt to search for signatures of efficient cosmic-ray (CR) acceleration. We combine proper motion measurements with corresponding optical spectrosc...

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Bibliographic Details
Published in:The Astrophysical journal 2018-08, Vol.862 (2), p.148
Main Authors: Hovey, Luke, Hughes, John P., McCully, Curtis, Pandya, Viraj, Eriksen, Kristoffer
Format: Article
Language:English
Subjects:
Acceleration
Accelerators
ASTRONOMY AND ASTROPHYSICS
Astrophysics
Cosmic rays
Data points
Efficiency
Filaments
H alpha line
Ionization
ISM: individual objects (SNR 0509-67.5, SNR 0519-69.0)
ISM: kinematics and dynamics
ISM: supernova remnants
Magellanic clouds
shock waves
Supernova
Supernova remnants
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Summary:We present results from an optical study of two young Balmer-dominated remnants of SNIa in the Large Magellanic Cloud, 0509−67.5 and 0519−69.0, in an attempt to search for signatures of efficient cosmic-ray (CR) acceleration. We combine proper motion measurements with corresponding optical spectroscopic measurements of the H line at multiple rim positions from VLT/FORS2 and SALT/RSS and compare our results to published Balmer shock models. Analyses of the optical spectra result in broad H widths in the range of 1800-4000 km s−1 for 12 separate Balmer-dominated filaments that show no evidence for forbidden line emission; the corresponding shock speeds from proper motion measurements from HST span a range of 1700-8500 km s−1. Our measured values of shock speeds and broad H widths in 0509−67.5 and 0519−69.0 are fit well with a Balmer shock model that does not include effects of efficient CR acceleration. We determine an upper limit of 7%/χ (95% confidence) on the CR acceleration efficiency for our ensemble of data points, where χ is the ionization fraction of the pre-shock gas. The upper limits on the individual remnants are 6%/χ (0509−67.5) and 11%/χ (0519−69.0). These upper limits are below the integrated CR acceleration efficiency in the Tycho supernova remnant, where the shocks predominantly show little H emission, indicating that Balmer-dominated shocks are not efficient CR accelerators.
ISSN:0004-637X
1538-4357
1538-4357
DOI:10.3847/1538-4357/aac94b