The quiescent emission of the first low-B soft gamma repeater

Soft gamma repeaters (SGRs) are part of a rapidly increasing group of Xraysources exhibiting sporadic and powerful emission of short bursts and outbursts,believed to be magnetars, i.e. neutron stars powered by extreme magnetic fields( Bsim10^{14}10^{15} G). We have recently discovered the first SGR with a lowmagnetic field (Rea et al. 2010, Science, 330, 944; Rea et al. 2013, ApJ 770,65), SGR 0418+5729 discovered in outburst after it emitted bursts similar tothose of magnetars. We ask for a 120,ks XMM observation to measure SGR 0418+5729.s quiescent flux and surface temperature, crucial for tuning the magnetar modelas well as predict how many hidden magnetars there might be within the pulsarpopulation (abridged). truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]