We find line emission from the hydrogen- and/or helium-like ions of Ne , O , N and C in the low and short-on states of Her X-1 , using the XMM-Newton Reflection Grating Spectrometer .
The emission line velocity broadening is 200 < \sigma < 500 km s ^ { -1 } .
Plasma diagnostics with the \ion NeIX , \ion OVII and \ion NVI He \alpha lines and the radiative recombination continua of \ion OVII and \ion NVII , indicate the gas is heated by photoionization , with an electron temperature of T = 6 \pm 2 eV .
We use spectral models to measure element abundance ratios of [ { N } / { O } ] = 9.5 \pm 1.3 , [ { C } / { O } ] = 0.68 \pm 0.16 , and [ { Ne } / { O } ] = 2.4 \pm 1.2 times solar , which quantify CNO processing in HZ Her .
Photoexcitation and high-density effects are not differentiated by the measured He \alpha lines , as shown by calculations that use previous UV photometry .
We set limits on the location of the line emission region , and find an electron density n _ { e } > 10 ^ { 11 } cm ^ { -3 } .
The narrow emission lines can be attributed to reprocessing in either an accretion disk atmosphere and corona or on the X-ray illuminated face of HZ Her .
In the main-on state , the bright continuum only allows the detection of interstellar absorption , plus \ion OVII He \alpha emission lines with \sigma = 3200 \pm 700 km s ^ { -1 } and complex profiles .
Other broad lines may be present .
The broad lines may originate in a region near the pulsar magnetosphere .
In such a case , periodic occultations of the Her X-1 magnetosphere must occur with 35 d phase , consistent with the precession of the accretion disk .
Fe L lines are not detected .