An ATCA radio-continuum study of the Small Magellanic Cloud -- III. Supernova remnants and their environments

Ballet

et al. 2011

A&A

Self Cite

Aims. IKT 16 is an X-ray and radio-faint supernova remnant (SNR) in the Small Magellanic Cloud (SMC). A previous X-ray study of this SNR found a hard X-ray source near its centre. Using all available archival and proprietary XMM-Newton data, alongside new multi-frequency radio-continuum surveys and optical observations at Hα and forbidden [SII] and [OIII] lines, we aim to constrain the properties of the SNR and discover the nature of the hard source within. Methods. We combine XMM-Newton datasets to produce the highest quality X-ray image of IKT 16 to date. We use this, in combination with radio and optical images, to conduct a multi-wavelength morphological analysis of the remnant. We extract separate spectra from the SNR and the bright source near its centre, and conduct spectral fitting of both regions. Results. We find IKT 16 to have a radius of 37 ± 3 pc, with the bright source located 8 ± 2 pc from the centre. This is the largest known SNR in the SMC. The large size of the remnant suggests it is likely in the Sedov-adiabatic phase of evolution. Using a Sedov model to fit the SNR spectrum, we find an electron temperature kT of 1.03 ± 0.12 keV and an age of ≈14700 yr. The absorption found requires the remnant to be located deep within the SMC. The bright source is fit with a power law with index Γ = 1.58 ± 0.07, and is associated with diffuse radio emission extending towards the centre of the SNR. We argue that this source is likely to be the neutron star remnant of the supernova explosion, and infer its transverse kick velocity to be 580 ± 100 km s −1 . The X-ray and radio properties of this source strongly favour a pulsar wind nebula (PWN) origin.

Section: Radiosupporting

confidence: 68%

“…23 sources classified as SNRs have been discovered in the SMC (Filipović et al 2005;Payne et al 2007). Most of these have been found with associated soft X-ray emission, exhibiting a variety of morphological structures.…”

Section: Introductionmentioning

confidence: 99%

IKT 16: a composite supernova remnant in the Small Magellanic Cloud

Owen

Ballet

et al. 2011

A&A

Self Cite

“…We estimate that the surface brightness of this SNR is 1.6 × 10 −22 W m −2 Hz −1 Sr −1 with a luminosity of 3.4 × 10 15 W Hz −1 , assuming a distance of 60 kpc and diameter of 166 . This makes it the faintest known radio SNR in the SMC (Filipović et al 2005(Filipović et al , 2008Owen et al 2011). …”

Section: Radio-continuummentioning

confidence: 99%

SXP 1062, a young Be X-ray binary pulsar with long spin period

Haberl

Sturm

et al. 2011

A&A

Context. The Small Magellanic Cloud (SMC) is ideally suited to investigating the recent star formation history from X-ray source population studies. It harbours a large number of Be/X-ray binaries (Be stars with an accreting neutron star as companion), and the supernova remnants can be easily resolved with imaging X-ray instruments. Aims. We search for new supernova remnants in the SMC and in particular for composite remnants with a central X-ray source. Methods. We study the morphology of newly found candidate supernova remnants using radio, optical and X-ray images and investigate their X-ray spectra.Results. Here we report on the discovery of the new supernova remnant around the recently discovered Be/X-ray binary pulsar CXO J012745.97−733256.5 = SXP 1062 in radio and X-ray images. The Be/X-ray binary system is found near the centre of the supernova remnant, which is located at the outer edge of the eastern wing of the SMC. The remnant is oxygen-rich, indicating that it developed from a type Ib event. From XMM-Newton observations we find that the neutron star with a spin period of 1062 s (the second longest known in the SMC) shows a very high average spin-down rate of 0.26 s per day over the observing period of 18 days. Conclusions. From the currently accepted models, our estimated age of around 10 000−25 000 years for the supernova remnant is not long enough to spin down the neutron star from a few 10 ms to its current value. Assuming an upper limit of 25 000 years for the age of the neutron star and the extreme case that the neutron star was spun down by the accretion torque that we have measured during the XMM-Newton observations since its birth, a lower limit of 0.5 s for the birth spin period is inferred. For more realistic, smaller long-term average accretion torques our results suggest that the neutron star was born with a correspondingly longer spin period. This implies that neutron stars in Be/X-ray binaries with long spin periods can be much younger than currently anticipated.

“…Typical limiting point-source luminosities of a few 10 33 erg s −1 are reached with XMM-Newton and extended objects like SNRs can be easily resolved 1 . Today a total number of eighteen classified SNRs are known in the SMC, which are listed in Table 1 (Filipović et al 2005; Table 1. SNRs and SNR candidates in the SMC.…”

Section: Introductionmentioning

confidence: 99%

“…SNRs and SNR candidates in the SMC. The radio spectral index (α) is taken from Filipović et al (2005) Payne et al 2007;van der Heyden et al 2004;Dickel et al 2001;Mathewson et al 1984;Mills et al 1982;Hughes & Smith 1994;Nazé et al 2004, and references therein). Thirteen of the remnants were covered by early XMM-Newton observations and a comprehensive study was presented by van der Heyden et al (2004).…”

Section: Introductionmentioning

confidence: 99%

New XMM-Newton observations of supernova remnants in the Small Magellanic Cloud

Haberl

Winkler³

et al. 2008

A&A

Self Cite

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 α , [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.