HST/FOC observations confirm the presence of a spectral feature in the optical spectrum of Geminga
Mignani, R. P. ; Caraveo, P. A. ; Bignami, G. F.
Feb - 1998

journal : Astronomy and Astrophysics Letters
type: Article Journal

Abstract
New optical and near-UV HST observations of Geminga are presented. When compared with previous ground-based and HST imaging, the data confirm and better define the presence of an emission feature centered at 6,000 Angstrom and superimposed on the thermal continuum best fitting the extreme-UV/soft X-ray data. This feature may be interpreted in terms of cyclotron emission originated from a mixture of H/He ions in the neutron stars atmosphere. In the case of pure Hydrogen, the feature wavelength would imply a magnetic field of order 3-5 10d11 G, consistent with the value deduced from the dynamical parameters of the pulsar. If due to a cyclotron emission, the observation of this feature would represent the first case of an in situ measurement of the surface magnetic field of an isolated neutron star.

keywords : G. F. Bignami: ASI authors