MODELING THE OXYGEN K ABSORPTION IN THE INTERSTELLAR MEDIUM: AN XMM-NEWTON VIEW OF Sco X-1
- Department of Physics, Western Michigan University, Kalamazoo, MI 49008 (United States)
- Astrophysikalisches Institut Potsdam, An der Sternwarte 16 D-14482 Potsdam (Germany)
- NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
- Centro de Fisica, IVIC, Caracas 1020 (Venezuela, Bolivarian Republic of)
- Astrophysique et Spectroscopie, Universite de Mons-UMONS, B-7000 Mons (Belgium)
We investigate the X-ray absorption structure of oxygen in the interstellar medium by analyzing XMM - Newton observations of the low-mass X-ray binary Sco X-1. Simple models based on the O I atomic photoabsorption cross section from different sources are used to fit the data and evaluate the impact of the atomic data on the interpretation of the observations. We show that relatively small differences in the atomic calculations can yield spurious results, and that the most complete and accurate set of atomic cross sections successfully reproduce the observed data in the 21.0-24.5 A wavelength region of the spectrum. Our fits indicate that the absorption is mainly due to neutral gas with an ionization parameter of {xi} = 10{sup -4} erg cm s{sup -1} and an oxygen column density of N{sub O} {approx} (8-10) x 10{sup 17} cm{sup -2}. The models are able to reproduce both the K edge and the K{alpha} absorption line from O I which are the two main features in this region. We find no conclusive evidence for absorption by anything other than atomic oxygen.
- OSTI ID:
- 21562742
- Journal Information:
- Astrophysical Journal Letters, Vol. 731, Issue 1; Other Information: DOI: 10.1088/2041-8205/731/1/L15; ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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