2025-07-24 ミシガン大学
This composite shows a section of the interstellar medium scientists X-rayed for sulfur using the Japan-led XRISM (X-ray Imaging and Spectroscopy Mission). X-ray binary GX 340+0 is the blue dot in the center. The composite contains a blend of imagery in X-rays (represented in deep blue), infrared, and light. Image credit: DSS/DECaPS/eRosita/NASA’s Goddard Space Flight Center
＜関連情報＞
- https://news.umich.edu/xrism-satellite-takes-x-rays-of-milky-ways-sulfur/
- https://academic.oup.com/pasj/advance-article-abstract/doi/10.1093/pasj/psaf068/8176460
星間硫黄に関する XRISM の洞察 XRISM insights for interstellar sulfur
Lía Corrales , Elisa Costantini , Sascha Zeegers , Liyi Gu , Hiromitsu Takahashi , David Moutard , Megumi Shidatsu , Jon M Miller , Misaki Mizumoto , Randall K Smith …
Publications of the Astronomical Society of Japan Published:27 June 2025
DOI:https://doi.org/10.1093/pasj/psaf068
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 Kβ line centroid at 2470.8±1.1eV 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 3400. Absorption templates from three Fe-S compounds, troilite (FeS), pyrrhotite (Fe7S8) and pyrite (FeS2), 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 is40％±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.
