Multi-frequency study of Local Group supernova remnants

Abstract

Context. The SNRs known in the Local Group show a variety of morphological structures that are relatively uncorrelated in the different wavelength bands. This variety is probably caused by the different conditions in the surrounding medium with which the remnant interacts. Aims. Recent ATCA, XMM-Newton and MCELS observations of the Magellanic Clouds (MCs) cover a number of new and known SNRs which are poorly studied, such as SNR J0528-6714. This particular SNR exhibits luminous radio-continuum emission, but is one of the unusual and rare cases without detectable optical and very faint X-ray emission (initially detected by ROSAT and listed as object [HP99] 498). We used new multi-frequency radio-continuum surveys and new optical observations at Hα, [S ii] and [O iii]wavelengths, in combination with XMM-Newton X-ray data, to investigate the SNR properties and to search for a physical explanation for the unusual appearance of this SNR. Methods. We analysed the X-ray and Radio-Continuum spectra and present multi-wavelength morphological studies of this SNR. Results. We present the results of new moderate resolution ATCA observations of SNR J0528-6714. We found that this object is a typical older SNR with a radio spectral index of α = −0.36 ± 0.09 and a diameter of D = 52.4 ± 1.0 pc. Regions of moderate and somewhat irregular polarisation were detected which are also indicative of an older SNR. Using a non-equilibrium ionisation collisional plasma model to describe the X-ray spectrum, we find temperatures kT of 0.26 keV for the remnant. The low temperature, low surface brightness, and large extent of the remnant all indicate a relatively advanced age. The near circular morphology indicates a type Ia event. Conclusions. Our study revealed one of the most unusual cases of SNRs in the Local Group of galaxies -a luminous radio SNR without optical counterpart and, at the same time, very faint X-ray emission. While it is not unusual to not detect an SNR in the optical, the combination of faint X-ray and no optical detection makes this SNR very unique.

Multifrequency study of the Large Magellanic Cloud supernova remnant J0529−6653 near pulsar B0529-66

“…The absence of detectable optical emission (Fig. 2) from this SNR is not unique as other well‐studied SNRs, such as LMC SNR J0528–6714 (Crawford et al 2010) or the Galactic Vela Jr (Stupar et al 2005), also do not exhibit optical emission. The ISM in the interior of SGS LMC‐4 must have very low density and hence the lack of optical emission.…”

Four new X-ray-selected supernova remnants in the Large Magellanic Cloud

“…In particular, SNRs lacking one or two of the conventional signatures are harder to identify. Examples of such SNRs can be found in Klimek et al (2010), Crawford et al (2010), Grondin et al (2012), and Bozzetto et al (2013a).…”

XMMU J0541.8-6659, a new supernova remnant in the Large Magellanic Cloud

“…Several SNRs in the LMC have been investigated using observations with ROSAT (Filipović et al 1998;Williams et al 1999), Chandra X-ray Observatory (Hughes et al 2006;Seward et al 2010) and XMM-Newton (Williams et al 2004;Klimek et al 2010;Crawford et al 2010) satellites, allowing a more detailed view of their morphologies and spectra. Badenes et al (2010) have studied the size distribution of the SNRs in the Magellanic Clouds (MCs), which has a maximum at ∼40 pc and may extend up to sizes of ∼100 pc.…”