New optically identified supernova remnants in the Large Magellanic Cloud
Maitra, Chandreyee; Sasaki, Manami; Alsaberi, Rami Z. E.; Haberl, Frank; Maggi, Pierre; Parker, Quentin A.; Stupar, Milorad; Sano, Hidetoshi; Filipović, Miroslav D.; Crawford, Evan J.; Kavanagh, Patrick J.; Leahy, Denis; Payne, Jeffrey L.; Seitenzahl, Ivo R.; Pannuti, Thomas G.; Rowell, Gavin; Points, Sean D.; Yew, Miranda; Vukotić, Branislav; Urošević, Dejan; Bozzetto, Luke M.; Leverenz, Howard; Park, Laurence A. F.
Australia, Chile, Germany, France, Ireland, Hong Kong SAR, Serbia, Japan, Canada, United States
Abstract
We present a new optical sample of three Supernova Remnants (SNRs) and 16 Supernova Remnant (SNR) candidates in the Large Magellanic Cloud (LMC). These objects were originally selected using deep H α, [S II], and [O III] narrow-band imaging. Most of the newly found objects are located in less dense regions, near or around the edges of the LMC's main body. Together with previously suggested MCSNR J0541-6659, we confirm the SNR nature for two additional new objects: MCSNR J0522-6740 and MCSNR J0542-7104. Spectroscopic follow-up observations for 12 of the LMC objects confirm high [S II]/H α emission-line ratios ranging from 0.5 to 1.1. We consider the candidate J0509-6402 to be a special example of the remnant of a possible type Ia Supernova (SN) which is situated some 2° (~1.75 kpc) north from the main body of the LMC. We also find that the SNR candidates in our sample are significantly larger in size than the currently known LMC SNRs by a factor of ~2. This could potentially imply that we are discovering a previously unknown but predicted, older class of large LMC SNRs that are only visible optically. Finally, we suggest that most of these LMC SNRs are residing in a very rarefied environment towards the end of their evolutionary span where they become less visible to radio and X-ray telescopes.