Elemental Abundances in the Diffuse Interstellar Medium from Joint Far-ultraviolet and X-Ray Spectroscopy: Iron, Oxygen, Carbon, and Sulfur
The Astronomical Journal, vol. 167, pp. 217
Abstract
Abstract In this study, we investigate interstellar absorption lines along the line of sight toward the galactic low-mass X-ray binary Cygnus X-2. We combine absorption line data obtained from high-resolution X-ray spectra collected with the Chandra and XMM-Newton satellites, along with far-UV absorption lines observed by the Hubble Space Telescope’s (HST) Cosmic Origins Spectrograph (COS) instrument. Our primary objective is to understand the abundance and depletion of oxygen, iron, sulfur, and carbon. To achieve this, we have developed an analysis pipeline that simultaneously fits both the UV and X-ray data sets. This novel approach takes into account the line-spread function of HST/COS, enhancing the precision of our results. We examine the absorption lines of Fe ii, S ii, C ii, and C i present in the far-UV spectrum of Cygnus X-2, revealing the presence of at least two distinct absorbers characterized by different velocities. Additionally, we employ Cloudy simulations to compare our findings concerning the ionic ratios for the studied elements. We find that gaseous iron and sulfur exist in their singly ionized forms, Fe ii and S ii, respectively, while the abundances of C ii and C i do not agree with the Cloudy simulations of the neutral ISM. Finally, we explore discrepancies in the X-ray atomic data of iron and discuss their impact on the overall abundance and depletion of iron.
Authors 12
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University of Michigan · Space Research Organisation Netherlands · Massachusetts Institute of Technology
Affiliation as printed
LSA, University of Michigan, 1085 South University Avenue, Ann Arbor, MI 48109, USA
MIT Kavli Institute for Astrophysics and Space Research, 70 Vassar Street, Cambridge, MA 02139, USA
SRON Netherlands Institute for Space Research, Niels Bohrweg 4, 2333 CA Leiden, The Netherlands
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Affiliation as printed
LSA, University of Michigan, 1085 South University Avenue, Ann Arbor, MI 48109, USA
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Affiliation as printed
University of Washington, Seattle, WA 98195, USA
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University of Nebraska at Kearney
Affiliation as printed
University of Nebraska at Kearney, Department of Physics and Astronomy, 2502 19th Avenue, Kearney, NE 68849, USA
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Space Research Organisation Netherlands
Affiliation as printed
SRON Netherlands Institute for Space Research, Niels Bohrweg 4, 2333 CA Leiden, The Netherlands
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Space Telescope Science Institute
Affiliation as printed
Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
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Massachusetts Institute of Technology
Affiliation as printed
MIT Kavli Institute for Astrophysics and Space Research, 70 Vassar Street, Cambridge, MA 02139, USA
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Space Research Organisation Netherlands
Affiliation as printed
SRON Netherlands Institute for Space Research, Niels Bohrweg 4, 2333 CA Leiden, The Netherlands
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California Institute of Technology · Goddard Space Flight Center
Affiliation as printed
Cahill Center for Astrophysics, California Institute of Technology, Pasadena, CA 91125, USA
X-ray Astrophysics Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
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Affiliation as printed
Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA
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Affiliation as printed
X-ray Astrophysics Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
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Affiliation as printed
Columbia Astrophysics Laboratory and Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027, USA
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