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

Abstract

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.

Long-term evolution of the neutron-star spin period of SXP 1062

“…(iii) A rapid spin-down of the NS oḟ P s = 0.26 s d −1 (Haberl et al 2012) that was observed over the interval between 2010 Mar. 25 and Apr.…”

“…We used the same model, as described in Haberl et al (2012), i.e. an absorbed power law where we assume Galactic photoelectric absorption with a column density of N H,gal = 6 × 10 20 cm −2 with solar abundances according to Wilms et al (2000), and a free column density, N H,smc , with abundances set to 0.2 solar accounting for absorption by the interstellar medium of the SMC or within the BeXRB system.…”

“…Suggested scenarios include an initially slow spin period (Haberl et al 2012), an initially and/or presently strong magnetic field (Popov & Turolla 2012;Fu & Li 2012), and the accretion of magnetised matter (Ikhsanov 2012).…”

Discovery of SXP 265, a Be/X-ray binary pulsar in the Wing of the Small Magellanic Cloud★

“…These systems enable a wealth of possible physical studies. Prominent examples are the recently discovered pulsar LXP 169 (Maggi et al 2013), which shows optical transits likely caused by material captured by the NS, and SXP 1062 (Hénault-Brunet et al 2012;Haberl et al 2012;Sturm et al 2013a), which is associated to a supernova remnant allowing a robust age determination. Both systems can be used to constrain accretion physics.…”

HFPK 334: An Unusual Supernova Remnant in the Small Magellanic Cloud

“…There is one confirmed PWN in the SMC, IKT 16 (Owen et al 2011), and at least three other candidate PWNs, HFPK 334, DEM S5 and IKT 4. The other 20 SNRs range from the very young 1E0102 at 1400 years old to the very old HFPK 419 at 50000 years old (Haberl et al 2012a), giving an unparalleled insight into the evolution of of SNRs and their environment. Kahabka et al (1999) first detected HFPK 334 with Röntgensatellit (ROSAT ), and list it as source 179 in their catalogue.…”