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

Astronomy and Astrophysics (Impact Factor: 4.38). 12/2011; 537(0004-6361). DOI: 10.1051/0004-6361/201118369
Source: arXiv


(shortened) The 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, and the supernova remnants can be easily resolved
with imaging X-ray instruments. We search for new supernova remnants in the SMC
and in particular for composite remnants with a central X-ray source. We study
the morphology of newly found candidate supernova remnants using radio, optical
and X-ray images and investigate their X-ray spectra. Here we report on the
discovery of the new supernova remnant around the recently discovered Be/X-ray
binary pulsar 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 shows a very high average
spin-down rate of 0.26 s per day over the observing period of 18 days. From the
currently accepted models, our estimated age of around 10000-25000 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 25000 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.

Download full-text


Available from: Evan J. Crawford
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The newly discovered Be/X-ray binary in the Small Magellanic Cloud, SXP 1062, provides the first example of a robust association with a supernova remnant (SNR). The short age estimated for the SNR qualifies SXP 1062 as the youngest known source in its class, tau ~ 1e4 yr. As such, it allows to test current models of magneto-rotational evolution of neutron stars ina still unexplored regime. Here we discuss possible evolutionary scenarios for SXP 1062 in the attempt to reconcile its long spin period, P=1062 s, and short age. Although several options can be considered, like an anomalously long initial period or the presence of a fossil disc, our results indicate that SXP 1062 may host a neutron star born with a large initial magnetic field, typically in excess of ~ 1e14 G, which then decayed to ~ 1e13 G.
    Full-text · Article · Dec 2011 · Monthly Notices of the Royal Astronomical Society
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present two new catalogues of radio-continuum sources in the field of the Small Magellanic Cloud (SMC). These catalogues contain sources found at 4800 MHz (lambda=6 cm) and 8640 MHz (lambda=3 cm). Some 457 sources have been detected at 3 cm with 601 sources at 6 cm created from new high-sensitivity and resolution radio-continuum images of the SMC from Crawford et al. (2011).
    Full-text · Article · Mar 2012 · Serbian Astronomical Journal
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The spin behaviour of the neutron star in the newly discovered young Be/X-ray long-period pulsar SXP 1062 is discussed. The star is observed to rotate with the period of 1062s, and spin-down at the rate ~ - 2.6 \times 10^{-12} Hz s^{-1}. I show that all of the conventional accretion scenarios encounter major difficulties explaining the rapid spin-down of the pulsar. These difficulties can be, however, avoided within the magnetic accretion scenario in which the neutron star is assumed to accrete from a magnetized wind. The spin-down rate of the pulsar can be explained within this scenario provided the surface magnetic field of the neutron star is B_* ~ 4 \times 10^{13} G. I show that the age of the pulsar in this case lies in the rage (2-4) \times 10^4 yr, which is consistent with observations. The spin evolution of the pulsar is briefly discussed.
    Preview · Article · May 2012 · Monthly Notices of the Royal Astronomical Society
Show more