Origin of the low-temperature plasma in the Galactic center X-ray emission

TL;DR

This study investigates the low-temperature plasma in the Galactic Center X-ray emission, revealing clumpy structures near Sagittarius A* with specific spectral properties, suggesting a distinct origin from known point sources.

Contribution

It provides detailed spectral and spatial analysis of the low-temperature plasma, proposing a new understanding of its origin near the Galactic Center.

Findings

Identified symmetric soft diffuse sources near Sagittarius A*

Spectral properties indicate a plasma temperature of 0.6-0.7 keV

Abundances are higher than those of typical point sources

Abstract

The Galactic Center X-ray Emission (GCXE) is composed of high temperature (7 keV) and low temperature (1 keV) plasmas (HTP and LTP, respectively). The global structure of the HTP is roughly uniform over the Galactic center (GC) region, and the origin of the HTP has been extensively studied. On the other hand, the LTP is more clumpy, and the origin has not been studied in detail. In the S XV He alpha line map, a pair of horn-like soft diffuse sources are seen at the symmetric positions with respect to Sagittarius A^{star}. The X-ray spectra of the pair are well represented by an absorbed thin thermal plasma model of a temperature and N_H of 0.6-0.7 keV and 4x10^{22} cm^{-2}, respectively. The N_H values indicate that the pair are located near at the GC. Then the dynamical time scales of the pair are 10^{5} yr. The Si and S abundances and the surface brightnesses in the S XV He alpha line band are 0.7-1.2 and 0.6-1.3 solar, and (2.0-2.4)x10^{-15} erg s^{-1} cm^{-2} arcmin^{-2}, respectively. The temperature, abundances, and surface brightness are similar to those of the LTP in the GCXE, while the abundances are far larger than those of known point sources, typically coronal active stars and RS CVn-type active binaries. Based on these results, possible origin of the LTP is discussed.