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arXiv · 1112.4602

A time-variable, phase-dependent emission line in the X-ray spectrum of the isolated neutron star RX J0822-4300

A. De Luca·D. Salvetti·A. Sartori·P. Esposito·A. Tiengo·S. Zane·R. Turolla·F. Pizzolato·R. P. Mignani·P. A. Caraveo·S. Mereghetti·G. F. Bignami
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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--2010. 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 disk. 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.

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A. De Luca, D. Salvetti, A. Sartori, P. Esposito, A. Tiengo, S. Zane, R. Turolla, F. Pizzolato, R. P. Mignani, P. A. Caraveo, S. Mereghetti, G. F. Bignami. 2011-12-20. A time-variable, phase-dependent emission line in the X-ray spectrum of the isolated neutron star RX J0822-4300. https://doi.org/10.1111/j.1745-3933.2011.01209.x

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