X-RAY-SPECTRA FROM NEUTRON-STARS ACCRETING AT LOW RATES

The spectral properties of X-ray radiation produced in a static atmosp here around a neutron star accreting at very low rates are investigate d. Previous results by Alme & Wilson are extended to the range 10(-7) less than or equal to L/L(Edd) less than or equal to 10(-3) to include the typical luminosities, L similar to 10(31)-10(32) ergs s(-1), expe cted from isolated neutron stars accreting the interstellar medium. Th e emergent spectra show an overall hardening with respect to the black body at the neutron star effective temperature in addition to a signif icant excess over the Wien tail. The relevance of present results in c onnectin with the observability of low-luminosity X-ray sources is bri efly discussed.