A Stable Analytic Magnetic Equilibrium

Duez et al. have verified that they can generate stable, non-force-free, equilibria for regions of stars. It is well known that purely poloidal or toroidal fields are unstable; however, mixed states are generally difficult to express analytically. Duez et al. generate a self-consistent mixed state and verify that it is stable. Such states will provide useful realistic models for stellar magnetic fields.

http://arxiv.org/abs/1009.5384 On the Stability of Non Force-Free Magnetic Equilibria in Stars

Black-Hole Inspiral Resonances

Flanagan and Hinderer have discovered a resonance phenomenon that ruins the adiabatic evolution of inspiral orbits around Kerr blackholes.   Orbits around Kerr black holes are characterized by a polar and azimuthal frequency, generally these two frequencies are not comeasureable.    This allows one to assume that the orbit completely fills the surface of a torus around the black hole, so one can average the various dissipative terms that cause the inspiral and accurately calculate the gravitational waveform.  However, when these two frequencies near the ratio of two small integers, this ergodic assumption fails and so does the averaging.   If the ratio is of two large integers, the duration of non-ergodicity is short so little phase error accumulates; however, for small integers the error in phase is of order unity.

http://arxiv.org/abs/1009.4923 Transient resonances in the inspirals of point particles into black holes

A Heavyweight Pulsar! Oh No, Maybe not!

The Black Widow millisecond pulsar is slowly vaporizing its companion star.  Van Kerkwijk obtained spectra of the companion and measured how much its velocity changes during its orbit about 325 km/s.  Because the star is illuminated by the pulsar the centre of light is closer to the centre of mass of the system than the centre of mass of the star does.  With atmospheric modelling and modelling the light curve, the authors address this issue and the question of the orbital inclination, yielding a really heavy pulsar at 2.4 +/- 0.1 solar masses.  Unfortunately once they account for the various systematic errors they get a quite modest and svelte neutron star whose mass is likely to be greater than 1.66 solar masses.  The observations are exquisite; unfortunately the models are not yet up to providing strong constraints.

http://arxiv.org/abs/1009.5427 Evidence for a Massive Neutron Star from a Radial-Velocity Study of the Companion to the Black Widow Pulsar PSR B1957+20

The Millisecond Pulsar Unveiling

Millisecond pulsars are believed to be form in binary systems comprised of a low-mass star and a neutron star, an LMXB.   As matter flows from the low-mass star onto the neutron star through an accretion disk, angular momentum flows as well.   Millisecond radio pulsars are especially common in globular clusters where such LMXBs are also common and the number of LMXBs in such systems agreed well with the numbers of millisecond pulsars in globular clusters and elsewhere.  Finally, several accreting neutron stars have been discovered with millisecond spin periods.   A final piece in the puzzle was the discovery of radio pulsations from PSR J102347.67+003841.2 in 2007.   This object spends sometime as an accreting neutron star from observations as late as 2000 and 2001 (from x-ray and optical measurement), and by 2007 the accretion disk had all but disappeared.   The first paper outlines a mechanism where gamma-rays produced near the light cylinder of the millisecond pulsar are sufficient to ablate the accretion disk entirely within such a short time.  The second paper provides a recent observational update on this really cool pulsar.

http://arxiv.org/abs/1009.4781 On the Transition from Accretion Powered to Rotation Powered Millisecond Pulsars

http://arxiv.org/abs/1008.1068 X-ray Variability and Evidence for Pulsations from the Unique Radio Pulsar/X-ray Binary Transition Object FIRST J102347.6+003841

The Fermi Pulsar Revolution

Arguably the most exciting result from the Fermi mission is the discovery of gamma-ray emission from many neutron stars.   A class of seven has grown to number nearly fifty in the first Fermi pulsar catalogue.  A large fraction of these objects are radio quiet and only a few lie in supernova remnants, so the identity of these objects would have remained unknown if it weren't for the outstanding sensitivity of Fermi and the development of blind search algorithms for the gamma-ray telescope.  Check out the following articles for more:

http://arxiv.org/abs/1009.2421 Fermi pulsar revolution by Patrizia A. Caraveo

http://arxiv.org/abs/1007.2183 Pulsar Results with the Fermi Large Area Telescope by Paul S. Ray, Pablo M. Saz Parkinson

http://arxiv.org/abs/1007.1381 New Neighbours: Modelling the Growing Population of Gamma-ray Millisecond Pulsars by C. Venter, A.K. Harding, T.J. Johnson