A HIGH BRAKING INDEX FOR A PULSAR

We present a phase-coherent timing solution for PSR J1640–4631, a young 206 ms pulsar using X-ray timing observations taken with NuSTAR. Over this timing campaign, we have measured the braking index of PSR J1640–4631 to be n = 3.15 ± 0.03. Using a series of simulations, we argue that this unusually high braking index is not due to timing noise, but is intrinsic to the pulsar's spin-down. We cannot, however, rule out contamination due to an unseen glitch recovery, although the recovery timescale would have to be longer than most yet observed. If this braking index is eventually proven to be stable, it demonstrates that pulsar braking indices greater than three are allowed in nature; hence, other physical mechanisms such as mass or magnetic quadrupoles are important in pulsar spin-down. We also present a 3σ upper limit on the pulsed flux at 1.4 GHz of 0.018 mJy.

[1]  N. Gehrels,et al.  ON THE BRAKING INDEX OF THE UNUSUAL HIGH-B ROTATION-POWERED PULSAR PSR J1846–0258 , 2015, 1506.06104.

[2]  Kristin K. Madsen,et al.  CALIBRATION OF THE NuSTAR HIGH-ENERGY FOCUSING X-RAY TELESCOPE , 2015, 1504.01672.

[3]  J. Pétri.  Multipolar electromagnetic fields around neutron stars: exact vacuum solutions and related properties , 2015, 1503.05307.

[4]  P. Lasky,et al.  Pulsar timing noise and the minimum observation time to detect gravitational waves with pulsar timing arrays , 2015, 1503.03298.

[5]  P. Weltevrede,et al.  The unusual glitch recoveries of the high-magnetic-field pulsar J1119−6127 , 2014, 1412.5853.

[6]  A. Lyne,et al.  45 years of rotation of the Crab pulsar , 2014, 1410.0886.

[7]  A. Cumming,et al.  Hall drift and the braking indices of young pulsars , 2014, 1406.3640.

[8]  V. M. Kaspi,et al.  NuSTAR DISCOVERY OF A YOUNG, ENERGETIC PULSAR ASSOCIATED WITH THE LUMINOUS GAMMA-RAY SOURCE HESS J1640−465 , 2014, 1405.0465.

[9]  P. Soffitta,et al.  Probing magnetar magnetosphere through X-ray polarization measurements , 2013, 1311.7500.

[10]  A. Lyne,et al.  Evolution of the Magnetic Field Structure of the Crab Pulsar , 2013, Science.

[11]  R. Perna,et al.  Unifying the observational diversity of isolated neutron stars via magneto-thermal evolution models. , 2013, 1306.2156.

[12]  William W. Zhang,et al.  THE NUCLEAR SPECTROSCOPIC TELESCOPE ARRAY (NuSTAR) HIGH-ENERGY X-RAY MISSION , 2013, Astronomical Telescopes and Instrumentation.

[13]  V. Kaspi,et al.  Detection of 107 glitches in 36 southern pulsars , 2012, 1211.2035.

[14]  A. Lyne,et al.  An analysis of the timing irregularities for 366 pulsars , 2009, 0912.4537.

[15]  S. Murray,et al.  HIGH-RESOLUTION X-RAY OBSERVATIONS OF THE PULSAR WIND NEBULA ASSOCIATED WITH THE GAMMA-RAY SOURCE HESS J1640−465 , 2009, 0910.2652.

[16]  S. Ransom,et al.  X-RAY AND RADIO TIMING OF THE PULSAR IN 3C 58 , 2009, 0901.2119.

[17]  D. Lai,et al.  Atmosphere models of magnetized neutron stars: QED effects, radiation spectra and polarization signals , 2006, astro-ph/0607168.

[18]  R. Manchester,et al.  TEMPO2, a new pulsar-timing package - I. An overview , 2006, astro-ph/0603381.

[19]  V. Kaspi,et al.  Birth and Evolution of Isolated Radio Pulsars , 2005, astro-ph/0512585.

[20]  B. Owen.  Maximum elastic deformations of compact stars with exotic equations of state. , 2005, Physical review letters.

[21]  A. Harding,et al.  Magnetar Spin-Down , 1999, The Astrophysical journal.

[22]  S. Johnston,et al.  Pulsar braking indices revisited , 1999, astro-ph/9905058.

[23]  California Institute of Technology,et al.  The Pulsar kick velocity distribution , 1997, astro-ph/9708071.

[24]  A. Melatos.  Spin-down of an oblique rotator with a current-starved outer magnetosphere , 1997 .

[25]  Z. Arzoumanian,et al.  Timing behavior of 96 radio pulsars , 1994 .

[26]  K. Postnov,et al.  Pulsar motion effect and Geminga's high braking index , 1993, Nature.

[27]  R. Blandford,et al.  On the interpretation of pulsar braking indices , 1988 .

[28]  F. Michel.  Relativistic stellar-wind torques , 1969 .

[29]  J. Gunn,et al.  Magnetic Dipole Radiation from Pulsars , 1969, Nature.

[30]  R. Manchester,et al.  A second measurement of a pulsar braking index , 1985, Nature.

[31]  R. B. Partridge,et al.  OPTICAL TIMING OF THE CRAB PULSAR, NP 0532. , 1972 .