Evidence for a Dense, Inhomogeneous Circumstellar Medium in the Type Ia SNR 0519-69.0

TL;DR

This study uses long-term HST imagery to measure shock velocities in SNR 0519-69.0, revealing a dense, inhomogeneous circumstellar medium that influences shock dynamics and brightness variations.

Contribution

It provides the first high-accuracy proper motion measurements of the remnant's shocks, demonstrating the impact of a dense, uneven circumstellar environment on shock velocities and emission properties.

Findings

Shock velocities range from 1670 km/s to 5280 km/s.

Bright knots correlate with denser regions, indicating inhomogeneous circumstellar medium.

No X-ray emission detected from the fastest shocks, consistent with lower ambient density.

Abstract

We perform an expansion study of the Balmer dominated outer shock of the SNR 0519$-$69.0 in the LMC by using a combination of new HST WFC3 imagery obtained in 2020 and archival ACS images from 2010 and 2011. Thanks to the very long time baseline, our proper motion measurements are of unprecedented accuracy. We find a wide range of shock velocities, with the fastest shocks averaging 5280 km/s and the slowest grouping of shocks averaging just 1670 km/s. We compare the H_alpha images from HST with X-ray images from Chandra and mid-IR images from Spitzer, finding a clear anti-correlation between the brightness of the remnant in a particular location and the velocity of the blast wave at that location, supporting the idea that the bright knots of X-ray and IR emission result from an interaction with a dense inhomogeneous circumstellar medium. We find no evidence for X-ray emission, thermal or nonthermal, associated with the fastest shocks, as expected if the fastest velocities are the result of the blast wave encountering the lower density ambient medium of the LMC. We derive an age of the remnant of 670 +/- 70 yr, consistent with results derived from previous investigations.