On the complex X-ray structure tracing the motion of Geminga

Abstract

A deep (100 ks) XMM-Newton observation of Geminga has shown two faint tails of diffuse X-ray emission, extending for ∼2' behind the pulsar, well aligned with the proper motion (PM) direction. We report here on a recent ∼20 ks Chandra observation, which unveils a new structure, ∼25" long and ∼5" thick, starting at the pulsar position and perfectly aligned with the PM direction, with a surface brightness ∼40 times higher than that of the XMM Tails. The Chandra comet-like feature has a remarkably hard spectrum (photon index ∼0.9-1.4) and a luminosity of ∼5.5 × 1028 erg s-1, comparable to the energetics of the larger XMM one. Geminga is thus the first neutron star to show a clear X-ray evidence of a large-scale, outer bow-shock as well as a short, inner cometary trail. © ESO 2005.