Search

Context. A complete overview of the supernova remnant (SNR) population is required to investigate their evolution and interaction with the surrounding interstellar medium in the Small Magellanic Cloud (SMC).Aims. Recent XMM-Newton observations of the SMC cover three known SNRs (DEM?S5, SNR?B0050-72.8, and SNR?B0058-71.8), which are poorly studied and are X-ray faint. We used new multi-frequency radio-continuum surveys and new optical observations at?H?, [S?ii], and [O?iii]?wavelengths, in combination with the X-ray data, to investigate their properties and to search for new SNRs in the SMC.Methods. We used X-ray source selection criteria and found one SMC object with typical SNR characteristics (HFPK?334), that was initially detected by ROSAT. We analysed the X-ray spectra and present multi-wavelength morphological studies of the three SNRs and the new candidate.Results. Using a non-equilibrium ionisation collisional plasma model, we find temperatures kT around 0.18?keV for the three known remnants and 0.69?keV for the candidate. The low temperature, low surface brightness, and large extent of the three remnants indicates relatively large ages. The emission from the new candidate (HFPK?334) is more centrally peaked and the higher temperature suggests a younger remnant. Our new radio images indicate that a pulsar wind nebulae (PWN) is possibly associated with this object.Conclusions. The SNRs known in the SMC show a variety of morphological structures that are relatively uncorrelated in the different wavelength bands, probably caused by the different conditions in the surrounding medium with which the remnant interacts.

Many of the high mass X-ray binaries (HMXRBs) discovered in recent years in our Galaxy are characterized by a high absorption, most likely intrinsic to the system, that can impede their detection at the softest X-ray energies. Exploiting the good coverage obtained with sensitive XMM-Newtonobservations, we have undertaken a search for highly absorbed X-ray sources in the Small Magellanic Cloud (SMC), which is known to contain a large number of HMXRBs. After a systematic analysis of 62 XMM-NewtonSMC observations, we obtained a sample of 30 sources with evidence of an equivalent hydrogen column density larger than 3 × 1023cm-2. Five of these sources are clearly identified as HMXRBs, four being previously known (including three X-ray pulsars) and one, XMMU J005605.8–720012, being reported here for the first time. For the latter, we present optical spectroscopy confirming the association with a Be star in the SMC. The other sources in our sample have optical counterparts fainter than magnitude  ~16 in the Vband, and many have possible NIR counterparts consistent with highly reddened early-type stars in the SMC. While their number is broadly consistent with the expected population of background highly absorbed active galactic nuclei, a few of them could be HMXRBs in which an early-type companion is severely reddened by local material.