1E1207.4-5209
Cyclotron LinesTo "view" the surface of hot young neutron stars requires observations of their X-ray emission: the emission peaks in the "soft" X-ray band with photon energies of 0.1 - 1 keV. Most of the X-ray spectra of such stars indeed showed the expected characteristic of thermal emission from their surfaces.Recently XMM-Newton observations of 1E1207.4-5209 gave convincing proof of additional cyclotron spectral features: charged particles in a magnetic field oscillate at a particular resonant frequency - this is called "cyclotron resonance". Cyclotron line features in the spectra of neutron stars hence can be used to estimate the strength of their magnetic fields: For a magnetic field strength of e.g. about 6 1010 Gauss, the resonant frequency of electron oscillations corresponds to an absorbed-photon energy of 0.7 keV; absorption will also occur at multiples of this fundamental energy. Protons can resonantly absorb radiation in a magnetic field, but, for a given resonant frequency, the corresponding magnetic field would be 2000 times higher than in the case of cyclotron resonance of electrons (because a proton is 2000 times heavier than an electron). Cyclotron resonances have been seen before in a handful of neutron stars in binary systems, the first one being Hercules X-1. [Refs 11 & 12] |
| 1E1207.4-5209 |