Multi-frequency study of the newly confirmed supernova remnant MCSNR J0512−6707 in the Large Magellanic Cloud^⋆

¹ Institut für Astronomie und Astrophysik, Kepler Center for Astro and Particle Physics, Eberhard Karls Universität Tübingen, Sand 1, Tübingen 72076, Germany
e-mail: kavanagh@astro.uni-tuebingen.de
² Western Sydney University, Locked Bag 1791, Penrith, NSW 2751, Australia
³ Cerro Tololo Inter-American Observatory, Casilla 603, La Serena, Chile
⁴ Laboratoire AIM, CEA-IRFU/CNRS/Université Paris Diderot, Service d’Astrophysique, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France
⁵ Max-Planck-Institut für extraterrestrische Physik, Giessenbachstraße, 85748 Garching, Germany

Received: 17 July 2015
Accepted: 22 September 2015

Abstract

Aims. We present a multi-frequency study of the supernova remnant MCSNR J0512−6707 in the Large Magellanic Cloud.

Methods. We used new data from XMM-Newton to characterise the X-ray emission and data from the Australian Telescope Compact Array, the Magellanic Cloud Emission Line Survey, and Spitzer to gain a picture of the environment into which the remnant is expanding. We performed a morphological study, determined radio polarisation and magnetic field orientation, and performed an X-ray spectral analysis.

Results. We estimated the remnant’s size to be 24.9 ( ± 1.5) × 21.9 ( ± 1.5) pc, with the major axis rotated ~29° east of north. Radio polarisation images at 3 cm and 6 cm indicate a higher degree of polarisation in the northwest and southeast tangentially oriented to the SNR shock front, indicative of an SNR compressing the magnetic field threading the interstellar medium. The X-ray spectrum is unusual as it requires a soft (~0.2 keV) collisional ionisation equilibrium thermal plasma of interstellar medium abundance, in addition to a harder component. Using our fit results and the Sedov dynamical model, we showed that the thermal emission is not consistent with a Sedov remnant. We suggested that the thermal X-rays can be explained by MCSNR J0512−6707 having initially evolved into a wind-blown cavity and is now interacting with the surrounding dense shell. The origin of the hard component remains unclear. We could not determine the supernova type from the X-ray spectrum. Indirect evidence for the type is found in the study of the local stellar population and star formation history in the literature, which suggests a core-collapse origin.

Conclusions. MCSNR J0512−6707 likely resulted from the core-collapse of high mass progenitor which carved a low density cavity into its surrounding medium, with the soft X-rays resulting from the impact of the blast wave with the surrounding shell. The unusual hard X-ray component requires deeper and higher spatial resolution radio and X-ray observations to confirm its origin.