Multi-frequency study of DEM L299 in the Large Magellanic Cloud

Aims. We have studied the H ii region DEM L299 in the Large Magellanic Cloud (LMC) to understand its physical characteristics and morphology in different wavelengths. Methods. We performed a spectral analysis of archived XMM-Newton EPIC data and studied the morphology of DEM L299 in X-ray, optical, and radio wavelengths. We used Hα, [S ii], and [O iii] data from the Magellanic Cloud Emission Line Survey (MCELS) and radio 21 cm line data from the Australia Telescope Compact Array (ATCA) and the Parkes Telescope as well as radio continuum data (3 cm, 6 cm, 20 cm, 36 cm) from ATCA and from the Molonglo Synthesis Telescope (MOST). Results. Our morphological studies imply that, in addition to the supernova remnant SNR B0543-68.9 reported in previous studies, a superbubble also overlaps the SNR in projection. The position of the SNR is clearly defined through the [S ii]/Hα flux ratio image. Moreover, the optical images show a shell-like structure that is located farther to the north and is filled with diffuse X-ray emission, which again indicates the superbubble. Radio 21 cm line data show a shell around both objects. Radio continuum data show diffuse emission at the position of DEM L299, which appears clearly distinguished from the H ii region LHA 120-N 164 that lies south-west of it. We determined the spectral index of SNR B0543-68.9 to be α = -0.34, which indicates the dominance of thermal emission and therefore a rather mature remnant. We determined the basic properties of the diffuse X-ray emission for the SNR, the superbubble, and a possible blowout region of the bubble, as suggested by the optical and X-ray data. We obtained an age of (8.9 +9.2 -5.4) kyr for the SNR and a temperature of (0.64 +0.73 -0.20) keV for the hot gas inside the SNR, as well as a thermal energy content and temperature of the hot gas inside the superbubble of (4.3+8.1 -2.6) x 1050 φ0.5 erg and (0.74+0.36 -0.30) keV, with φ being the gas-filling factor. Conclusions. We conclude that DEM L299 consists of a superposition of SNR B0543-68.9 and a superbubble, which we identified based on optical data. Note: Some of the scientific symbols cannot be represented correctly in the abstract. Please read with caution and refer to the original publication