XRISM insights for interstellar sulfur

Publications of the Astronomical Society of Japan, vol. 77, pp. S107–S116

Abstract

Abstract The X-ray Imaging Spectroscopy Mission (XRISM) provides the best spectral resolution with which to study sulfur (S) K-shell photoabsorption features from the interstellar medium (ISM). For the first time, we demonstrate the high-signal detection of interstellar atomic S ii K-beta absorption in the spectrum of X-ray binaries (XRBs) 4U 1630-472 and GX 340$+$0. The persistence of this feature across multiple instruments, targets, and flux states implies that it is interstellar in nature. We measure the S ii K$\beta$ line centroid at $2470.8 \pm 1.1$ eV after including systematic uncertainties. We also find that the most recently published high-resolution S ii absorption template requires a systematic energy scale shift of $+7\!-\!8$ eV, which is comparable to the level of disagreement among various atomic modeling procedures. The XRISM 300 ks observation of GX 340$+$0 provides unprecedented signal-to-noise in the S K region, and we find evidence of residual absorption from solid S in the spectra of GX 340$+$0. Absorption templates from three Fe-S compounds, troilite (FeS), pyrrhotite (Fe$_7$S$_8$) and pyrite (FeS$_2$), provide equally good fits to the residuals. Even though we are not able to distinguish among these three compounds, they provide equal estimates for the abundance of S locked in dust grains. Having accounted for both the gaseous and solid S in the GX 340$+$0 sightline provides us with a direct measurement of S depletion, which is $40{\%} \pm 15\%$. Our depletion measurement provides an upper limit to the fraction of interstellar Fe bound in Fe-S compounds of ${<}25\%$, which is consistent with prior studies of Fe-S compounds via Fe L-shell absorption. Both XRBs in this study are at a distance of approximately 11 kpc and on the opposite side of the Galactic disk, suggesting that this value could represent the average S depletion of the Milky Way when integrated across all phases of the ISM.

Authors 18

1. Lía Corrales corresponding

   University of Michigan

   Affiliation as printed

   University of Michigan Department of Astronomy, , 323 West Hall, 1085 S University Ave, Ann Arbor, MI 48109 ,

2. E. Costantini Aachen Netherlands Institute for Space Research

   Space Research Organisation Netherlands · University of Amsterdam

   Affiliation as printed

   Netherlands Institute for Space Research (SRON) , Niels Bohrweg 4, 2333 CA Leiden ,

   University of Amsterdam Anton Pannekoek Institute for Astronomy, , Science Park 904, 1098 XH Amsterdam ,

3. Sascha Tamara Zeegers

   European Space Agency · European Space Research and Technology Centre

   Affiliation as printed

   European Space Agency European Space Research and Technology Centre, , 2201 AZ Noordwijk ,

   European Space Research and Technology Centre, European Space Agency , 2201 AZ Noordwijk ,

4. Liyi Gu Aachen Netherlands Institute for Space Research

   Space Research Organisation Netherlands

   Affiliation as printed

   Netherlands Institute for Space Research (SRON) , Niels Bohrweg 4, 2333 CA Leiden ,

5. Hiromitsu TAKAHASHI

   Hiroshima University

   Affiliation as printed

   Hiroshima University Department of Physical Science, , 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526 ,

6. D. L. Moutard

   University of Michigan

   Affiliation as printed

   University of Michigan Department of Astronomy, , 323 West Hall, 1085 S University Ave, Ann Arbor, MI 48109 ,

7. M. Shidatsu

   Ehime University

   Affiliation as printed

   Ehime University Department of Physics, , 2-5 Bunkyo-cho, Matsuyama, Ehime 790-8577 ,

8. Jon M. Miller

   University of Michigan

   Affiliation as printed

   University of Michigan Department of Astronomy, , 323 West Hall, 1085 S University Ave, Ann Arbor, MI 48109 ,

9. Misaki Mizumoto

   University of Teacher Education Fukuoka

   Affiliation as printed

   University of Teacher Education Fukuoka Science Research Education Unit, , 1-1 Akamabunkyo-machi, Munakata, Fukuoka 811-4192 ,

10. Randall K. Smith

    Center for Astrophysics Harvard & Smithsonian

    Affiliation as printed

    Center for Astrophysics Harvard & Smithsonian , 60 Garden St., Cambridge, MA 02138 ,

11. Ralf Ballhausen

    Goddard Space Flight Center · University of Maryland, College Park

    Affiliation as printed

    NASA Goddard Space Flight Center , Greenbelt, MD 20771 ,

    University of Maryland College Park , 4296 Stadium Dr., College Park, MD 20742 ,

12. Priyanka Chakraborty

    Center for Astrophysics Harvard & Smithsonian

    Affiliation as printed

    Center for Astrophysics Harvard & Smithsonian , 60 Garden St., Cambridge, MA 02138 ,

13. María Díaz Trigo

    European Southern Observatory

    Affiliation as printed

    European Southern Observatory , Karl-Schwarzschild-Strasse 2, 85748, Garching bei München ,

14. R. M. Ludlam

    Wayne State University

    Affiliation as printed

    Wayne State University Department of Physics, , 666 W. Hancock, Detroit, MI 48201 ,

15. Takao Nakagawa

    Tokyo City University · Japan Aerospace Exploration Agency · Institute of Space and Astronautical Science

    Affiliation as printed

    Japan Aerospace Exploration Agency Institute of Space & Astronautical Science, , 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 ,

    Tokyo City University Advanced Research Laboratories, , 1-28-1 Tamazutsumi, Setagaya-ku, Tokyo 158-8557 ,

16. I. Psaradaki

    Massachusetts Institute of Technology

    Affiliation as printed

    Massachusetts Institute of Technology Kavli Institute for Astrophysics and Space Research, , 70 Vassar St, Cambridge, MA 02139 ,

17. Shinya Yamada

    Rikkyo University

    Affiliation as printed

    Rikkyo University Department of Physics, , 3-34-1 Nishi-Ikebukuro, Toshima-ku, Tokyo 171-8501 ,

18. Caroline Anne Kilbourne

    Goddard Space Flight Center

    Affiliation as printed

    NASA Goddard Space Flight Center , Greenbelt, MD 20771 ,