A time-variable, phase-dependent emission line in the X-ray spectrum of the isolated neutron star RX J0822-4300
Abstract
RX J0822-4300 is the central compact object associated with the Puppis A supernova remnant. Previous X-ray observations suggested RX J0822-4300 to be a young neutron star with a weak dipole field and a peculiar surface temperature distribution dominated by two antipodal spots with different temperatures and sizes. An emission line at 0.8 keV was also detected. We performed a very deep (130-ks) observation with XMM-Newton, which allowed us to study in detail the phase-resolved properties of RX J0822-4300. Our new data confirm the existence of a narrow spectral feature, best modelled as an emission line, only seen in the 'soft'-phase interval - when the cooler region is best aligned to the line of sight. Surprisingly, comparison of our recent observations to the older ones yields evidence for a variation in the emission-line component, which can be modelled as a decrease in the central energy from ∼0.80 keV in 2001 to ∼0.73 keV in 2009-10. The line could be generated via cyclotron scattering of thermal photons in an optically-thin layer of gas, or, alternatively, it could originate in low-rate accretion by a debris disc. In any case, a variation in energy, pointing to a variation of the magnetic field in the line-emitting region, cannot be easily accounted for.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- March 2012
- DOI:
- 10.1111/j.1745-3933.2011.01209.x
- arXiv:
- arXiv:1112.4602
- Bibcode:
- 2012MNRAS.421L..72D
- Keywords:
-
- stars: neutron;
- pulsars: general;
- X-rays: individual: RX J0822-4300;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- Accepted for publication in MNRAS Letters. 5 pages, 4 figures