Recent X-ray Observations of Strongly Magnetized Neuton Stars, Magnetars

Teruaki Enoto
Kavli Institute for Particle Astrophysics and Cosmology, Stanford University


Soft gamma repeaters (SGRs) and Anomalous X-ray Pulsars (AXPs) are strange X-ray pulsars showing slow rotations, bright soft X-rays, and recurrent burst activities. Based on accumulating observational evidence, these pulsars are now thought to be magnetically powered neutron stars, or ``magnetars" with an extremely strong magnetic field of 1e+14-15 G. Such a field is by 2-3 orders of magnitudes higher than those of normal neutron stars, and well above the quantum critical field, 4.4e+13 G. Although such a strong field is considered to induce characteristic burst activities and particular X-ray spectra, little is known about how the magnetic energy is dissipated and converted into the radiation.

In order to provide an unified characterization of this class, we performed a comprehensive study of broad-band X-ray spectra for 9 magnetars, using the Japanese-US Suzaku satellite. The soft thermal component (kT~0.5 keV) was detected from all of them, and the enigmatic (newly discovered) hard X-ray tail was successfully detected from 7 of them. It was revealed that the two-component spectrum is correlated with their characteristic age and their magnetic field, in such a way that the hard X-ray component becomes weaker (relative to the soft component), yet harder, for sources with older characteristic ages. This spectral evolution can become a new key feature of magnetars. I will introduce recent progress of X-ray observation of magnetars.The standard model of cosmology has been remarkably successful in explaining the detailed evolution of galaxies and large-scale structure beginning from primordial density perturbations.  Supermassive black holes, however, seem to present a more difficult challenge.  The standard cosmological model, as currently understood, cannot explain how supermassive black holes are born, how they grow, and why or how they die.  This talk will present a novel approach for analyzing data from  quasar surveys that reveals new information about the luminosity and evolution of black holes. Instead of resolving these problems, the results suggest even deeper puzzles that may require new ideas in astrophysics or fundamental physics to resolve.