IKT 16: the first X-ray confirmed composite SNR in the SMC

Abstract

Aims. IKT 16 is an X-ray and radio-faint supernova remnant (SNR) in the Small Magellanic Cloud (SMC). A detailed X-ray study of this SNR with XMM-Newton confirmed the presence of a hard X-ray source near its centre, indicating the detection of the first composite SNR in the SMC. With a dedicated Chandra observation we aim to resolve the point source and confirm its nature. We also acquire new ATCA observations of the source at 2.1 GHz with improved flux density estimates and resolution. Methods. We perform detailed spatial and spectral analysis of the source. With the highest resolution X-ray and radio image of the centre of the SNR available today, we resolve the source and confirm its pulsar wind nebula (PWN) nature. Further, we constrain the geometrical parameters of the PWN and perform spectral analysis for the point source and the PWN separately. We also test for the radial variations of the PWN spectrum and its possible east west asymmetry. Results. The X-ray source at the centre of IKT 16 can be resolved into a symmetrical elongated feature centring a point source, the putative pulsar. Spatial modelling indicates an extent of 5.2 of the feature with its axis inclined at 82• east from north, aligned with a larger radio feature consisting of two lobes almost symmetrical about the X-ray source. The picture is consistent with a PWN which has not yet collided with the reverse shock. The point source is about three times brighter than the PWN and has a hard spectrum of spectral index 1.1 compared to a value 2.2 for the PWN. This points to the presence of a pulsar dominated by non-thermal emission. The expectedĖ is ∼10 37 erg s −1 and spin period <100 ms. However, the presence of a compact nebula unresolved by Chandra at the distance of the SMC cannot completely be ruled out.

Discovery of a pulsar-powered bow shock nebula in the Small Magellanic Cloud supernova remnant DEM S5

“…Such a TeV flux level is within the reach of the forthcom-ingČerenkov Telescope Array (CTA) (Martin et al 2019;Cherenkov Telescope Array Consortium et al 2019). A similar X-ray to TeV flux scaling may apply to the other PWN in the SMC, IKT 16 (Maitra et al 2015), bringing it within the reach of the CTA. ).…”

“…There are only two known young SMC pulsars: an 8.02 s anomalous X-ray pulsar, CXOU J010043.1-721134, with a characteristic age of ∼6700 yr (Tiengo et al 2008); The second one powers the only confirmed pulsar wind nebula (PWN) in the SMC, inside the large (74.5 pc diameter) SNR IKT 16. IKT 16 hosts a suspected pulsar with a spin-down luminosity ( E) ∼10 37 erg s −1 and an age of ∼14.7 kyr (Owen et al 2011;Maitra et al 2015). The PWN within IKT 16 was discovered with a dedicated Chandra observation, which resolved the hard (2-4.5 keV) X-ray point source seen with XMM-Newton into a faint and soft symmetric nebula surrounding a bright and hard point source.…”

The supernova remnant population of the Small Magellanic Cloud

“…MCSNR J0058−7217 / IKT 16 : This SNR is atypical in the SMC because of the hard extended source near its centre, suggested as the first PWN of the SMC (Owen et al 2011) and then confirmed with high-resolution Chandra observations (Maitra et al 2015). To characterise the extended soft X-ray emission from the underlying SNR, we included the pulsar and PWN components obtained in the Chandra analysis with fixed parameters in our analysis of the integrated emission.…”

“…In a similar manner as in B17 where the LMC radio continuum sample were investigated, we used all available radio continuum data described in various surveys to date (Filipovic et al 1997(Filipovic et al , 1998Filipović et al 2002;Payne et al 2004b;Filipović et al 2005;Reid et al 2006;Payne et al 2007;Wong et al 2011a;Crawford et al 2011;Wong et al 2011bWong et al , 2012a. Some earlier radio continuum studies of selected SMC SNRs were shown in Filipović et al (2008); Owen et al (2011);Haberl et al (2012c); Crawford et al (2014); Maitra et al (2015). Where possible, our study improves upon these previous SMC SNR studies.…”

Measurement of the Core-collapse Progenitor Mass Distribution of the Small Magellanic Cloud

“…The progenitor masses implied by the SFHs associated with these remnants is consistent with theoretical work by e.g., Sukhbold et al (2016) who suggested that neutron stars are produced in SNe of stars < 30M . These four remnants have been suggested to harbour either a PWN/CCO or is associated with a Be/X-ray pulsar system (Yokogawa et al 2000;Williams et al 2006;Owen et al 2011;Haberl et al 2012b;Maitra et al 2015;Vogt et al 2018).…”