Current X-ray missions are providing high-quality X-ray spectra from neutron stars ( NSs ) in quiescent low-mass X-ray binaries ( qLMXBs ) .
This has motivated us to calculate new hydrogen-atmosphere models , including opacity due to free-free absorption and Thomson scattering , thermal electron conduction , and self-irradiation by photons from the compact object .
We have constructed a self-consistent grid of neutron star models covering a wide range of surface gravities as well as effective temperatures , which we make available to the scientific community .

We present multi-epoch { \it Chandra } Â X-ray observations of the qLMXB X7 in the globular cluster 47 Tuc , which is remarkably nonvariable on timescales from minutes to years .
Its high-quality X-ray spectrum is adequately fit by our hydrogen-atmosphere model without any hard power-law component or narrow spectral features .
If a mass of 1.4 { M _ { \odot } } Â is assumed , our spectral fits require that its radius be in the range R _ { ns } = 14.5 ^ { +1.8 } _ { -1.6 } km ( 90 % confidence ) , larger than expected from currently preferred models of NS interiors .
If its radius is assumed to be 10 km , then a mass of M _ { ns } = 2.20 ^ { +0.03 } _ { -0.16 } { M _ { \odot } } Â is required .
Using models with the appropriate surface gravity for each value of the mass and radius becomes important for interpretation of the highest quality data .