The first broadband study of a NS transient in quiescence with XMM and NuSTAR

In quiescence, the soft Xray spectra of neutron star (NS) LowMass Xray Binary(LMXB) transients most often contain two components: one is due to thermalemission from the NS surface and is reasonably wellunderstood, while the otheris a hard (often very hard) powerlaw of unknown origin. The upcoming NuSTARmission will provide the first measurement of the >10 keV spectrum of quiescentNS LMXBs, which, along with XMMNewton observations, will allow us todiscriminate between accretion and pulsar rotation as the energy source for thepowerlaw component. We propose coordinated XMMNewton/NuSTAR observations ofthe closest and brightest quiescent system, Cen X4. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]