Spectral monitoring of RX J1856.5-3754 with XMM-Newton. Analysis of EPIC-pn data

Understand

Using a large set of XMM-Newton observations we searched for long term spectral and flux variability of the isolated neutron star RX J1856.5-3754 in the time interval from April 2002 to October 2011.

• This is the brightest and most extensively observed source of a small group of nearby, thermally emitting isolated neutron stars, of which at least one member (RX J0720.4-3125, Hohle et al., 2010) has shown long term variability.
• A detailed analysis of the data obtained with the EPIC-pn camera in the 0.15-1.2 keV energy range reveals small variations in the temperature derived with a single blackbody fit (of the order of 1% around kT^inf \sim 61 eV).
• Such variations are correlated with the position of the source on the detector and can be ascribed to an instrumental effect, most likely a spatial dependence of the channel to energy relation.