Astronomy and Astrophysics – Astrophysics
Scientific paper
2002-02-05
Astronomy and Astrophysics
Astrophysics
4 pages, 4 figures, to appear in Proc. Symp. `New Visions of the X-ray Universe in the XMM-Newton and Chandra Era', 26-30 Nov
Scientific paper
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. Plasma diagnostics with the Ne IX, O VII and N VI He-alpha lines and the radiative recombination continua of O VII and N VII, indicate the gas is heated by photoionization. We use spectral models to measure the element abundance ratios N/O, C/O, and Ne/O, which quantify CNO processing in HZ Her. Photoexcitation and high-density effects are not differentiated by the measured He-alpha lines. We set limits on the location, temperature and density of the line emission region. 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 O VII He-alpha emission lines with sigma = 3200 +- 700 km/s and complex profiles. Other broad lines may be present. The broad lines may originate in a region near the pulsar magnetosphere. Fe L lines are not detected.
den Herder Jan Willem
Hailey Charles J.
Jimenez-Garate Mario A.
Ramsay Gavin
Zane Silvia
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