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BeppoSAX spectroscopy of the NGC7078 (M15) globular cluster X-ray source X2127+119

L. Sidoli·A. N. Parmar·T. Oosterbroek
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Abstract

Results of a 1999 November 16--17 BeppoSAX observation of the low-mass X-ray binary X2127+119 located in the globular cluster NGC7078 are presented. The system is believed to be one where the central neutron star is normally obscured by the accretion disk, and only X-rays scattered into our line of sight by an extended accretion disk corona (ADC) are observed. The 0.1--10 keV lightcurve is energy dependent and shows two partial eclipses separated by the 17.1 hr orbital period. The 0.1--100 keV spectrum is unusually complex, but can be successfully modeled using a partially covered power-law and disk-blackbody model. Together with a column consistent with the interstellar value to NGC7078, about 60% of the source is covered by an additional column of 1E22 atom/cm2. The absorbed component may be X-rays that pass through the outer layers of the accretion disk. The energy dependent intensity variations by a factor of ~2 may be modeled as due to a changing normalization of the disk-blackbody. None of the other spectral parameters appear to clearly depend on luminosity. The same spectral model is also able to fit an archival ASCA spectrum.

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L. Sidoli, A. N. Parmar, T. Oosterbroek. 2000-06-21. BeppoSAX spectroscopy of the NGC7078 (M15) globular cluster X-ray source X2127+119. https://arxiv.org/abs/astro-ph/0006307

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