Swift J045106.8−694803: a highly magnetized neutron star in the Large Magellanic Cloud

Abstract

We report the analysis of a highly magnetised neutron star in the Large Magellanic Cloud (LMC). The high mass X-ray binary pulsar Swift J045106.8-694803 has been observed with Swift X-ray telescope (XRT) in 2008, The Rossi X-ray Timing Explorer (RXTE) in 2011 and the X-ray Multi-Mirror Mission -Newton (XMM-Newton) in 2012. The change in spin period over these four years indicates a spin-up rate of −5.01 ± 0.06 s/yr, amongst the highest observed for an accreting pulsar. This spin-up rate can be accounted for using Ghosh and Lamb's (1979) accretion theory assuming it has a magnetic field of (1.2± 0.2 0.7 )×10 14 Gauss. This is over the quantum critical field value. There are very few accreting pulsars with such high surface magnetic fields and this is the first of which to be discovered in the LMC. The large spin-up rate is consistent with Swift Burst Alert Telescope (BAT) observations which show that Swift J045106.8-694803 has had a consistently high X-ray luminosity for at least five years. Optical spectra have been used to classify the optical counterpart of Swift J045106.8-694803 as a B0-1 III-V star and a possible orbital period of 21.631±0.005 days has been found from MACHO optical photometry.

XMM–Newton observation of the highly magnetized accreting pulsar Swift J045106.8−694803: evidence of a hot thermal excess

“…This is an order of magnitude larger than the statistical error derived in the source detection, and as such is the dominant error on the position. This position is consistent with the Swift positions reported by Beardmore et al (2009) and Klus et al (2013) confirming that these three detections are the same source. Figure 1 shows a V-band image with the location of the Swift and XMM positions with radii equal to the 1σ errors.…”

“…This source was detected in the Large Magellanic Cloud (LMC) by the Swift/BAT hard X-ray survey (Beardmore et al 2009) and was followed by a 15.5 ks observation with the Swift XRT instrument. This confirmed the position of the source and revealed a periodic signal at 187 s. From the accretion model of Ghosh & Lamb (1979), Klus et al (2013) derived a magnetic field B ∼ 1.2 × 10 14 G from the spin-up rate, indicating that Swift J045106.8-694803 is a highly magnetised accreting pulsar (i.e., neutron star with a super strong magnetic field B 10 14 G). However, there are several interpretations of the high spin down rates observed in these sources which do not require super strong magnetic fields, such as accretion of magnetised material (e.g.…”

“…Detailed modelling of deeper observations, with better signal-to-noise, could provide an independent measurement of the magnetic field; furthermore, future polarization studies could even break the degeneracy between α and ζ. Klus et al (2013) use the pulse period determined in this work along with data from Swift and RXTE to show that Swift J045106.8-694803 has a magnetic field above the quantum critical value. Two other accreting pulsars are known with Ṗ values consistent with a super stong magnetic field, 4U2206+54 (Reig et al 2012) and SXP 1062 (Popov & Turolla 2012;Hénault-Brunet et al 2012).…”

How to make a mature accreting magnetar

“…Fu & Li (2012) • Swift J045106.8-694803. Klus et al (2013). Also a large list of possible candidates can be found in Klus et al (2014); Ho et al (2014) (see also Shi et al 2015).…”

Discovery of a 168.8 s X-ray pulsar transiting in front of its Be companion star in the Large Magellanic Cloud

“…About 45 candidates have also been identified during the XMM-Newton survey of the SMC (Sturm et al 2013). While the LMC is about ten times as massive as the SMC, it contains only A&A 554, A1 (2013) 14 confirmed BeXRBs so far (Liu et al 2005;Masetti et al 2006;Sturm et al 2012;Klus et al 2013). This discrepancy is possibly explained by different star formation histories (SFHs).…”