Quiescent Emission From Transient Type I X-Ray Bursters

We propose precision spectroscopy for four quiescent neutron stars (NSs). The quiescent luminosities are due at least in part and perhaps entirely to thermal emission, powered by reactions in the deep crust, from the NS surface. Fits to previous observations with realistic H atmosphere spectralmodels find emission area radii consistent with that of a NS (10 km). We will use the unparalleled spectral capabilities of XMM to measure the radius/distance of these sources to 10 percent. Only if accretion occurs in quiescence can metals be present in the photosphere; for metalicities down to as low as Z0.03 Zsun, we will then measure the surface gravitational redshift, and constrain the NS equation of state. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]