高能暂现源 · 每日文献综述

The Galactic center is a complex and crowded region hosting the supermassive black hole Sgr A*, numerous accreting compact objects, and diffuse X-ray emission. This paper presents the first in a series of studies analyzing the XRISM observation of the X-ray transient MAXI J1744-294/Swift J174540.2−290037, located ∼18″ from Sgr A*. The observation, conducted in 2025 March, along with XMM-Newton and NuSTAR coverage, aimed to investigate the Fe emission features of MAXI J1744-294 during its outburst. However, the region surrounding the source is heavily contaminated by X-ray emission from various diffuse and point sources, including strong line contributions from the supernova remnant Sgr A East and the Galactic center X-ray emission. Additionally, the nearby neutron star low-mass X-ray binary (NS-LMXB) AX J1745.6−2901 was also in outburst during the XRISM observation, further complicating the spectral analysis. This study focuses on disentangling the contributions of these overlapping sources by robustly modeling the background contamination and spatial─spectral mixing. We describe the methodologies, region selection, and data reduction techniques applied to the different instruments. Two complementary approaches—empirical and physical modeling—are employed to characterize diffuse emission and point-source contributions. The results provide a foundation for the detailed spectral analysis of MAXI J1744-294, AX J1745.6-2901, and the surrounding interstellar medium, which will be presented in subsequent papers. This study highlights the challenges and robust solutions for analyzing XRISM/Resolve data from crowded regions in conjunction with other X-ray telescope data.

Narrow, highly ionized X-ray emission lines in black hole low-mass X-ray binaries (BH-LMXBs) are rare and have been observed in only a few sources, during unusual, heavily obscured accretion states. We report on a detailed high-resolution spectral analysis of emission line features from the first XRISM observation of a BH-LMXB candidate in a bright soft state, MAXI J1744─294/Swift J174540.2-290037, in the central parsec region of our galaxy. The source was observed as part of an extensive, coordinated multiwavelength campaign on its recurring X-ray outburst in early 2025. Following the careful modeling of the contributions from multiple point sources and diffuse emission within the XRISM/Resolve field of view in M. Parra et al. (2026a; Paper I), and combining these data with broadband X-ray coverage from XMM-Newton and NuSTAR), we now identify a narrow (σ ∼ 500─1000 km s<SUP>−1</SUP>) static emission component intrinsic to the system. This component likely arises from a highly ionized (log ξ ≳ 5.5) photoionized plasma in the inner disk atmosphere and is accompanied by a weak, narrow Fe I Kα line at 6.4 keV. We also detect at least three narrow emission features at atypical energies between 6.7 and 7.1 keV. The lack of corresponding rest-frame atomic transitions points toward highly ionized blueshifted Fe lines with outflow velocities of −1300 to −6000 km s<SUP>−1</SUP>, which we model with multiple layers of photoionized or collisional plasma. We explore scenarios in which these unprecedented features are produced by multiple phases in a jet and/or a disk wind, and discuss potential similarities between MAXI J1744-294 and the exotic microquasar SS 433.