Polarization and long-term variability of Sgr A* X-ray echo

Abstract

We use a model of the molecular gas distribution within ~100 pc from the center of the Milky Way (Kruijssen, Dale & Longmore) to simulate time evolution and polarization properties of the reflected X-ray emission, associated with the past outbursts from Sgr A*. While this model is too simple to describe the complexity of the true gas distribution, it illustrates the importance and power of long-term observations of the reflected emission. We show that the variable part of X-ray emission observed by Chandra and XMM from prominent molecular clouds is well described by a pure reflection model, providing strong support of the reflection scenario. While the identification of Sgr A* as a primary source for this reflected emission is already a very appealing hypothesis, a decisive test of this model can be provided by future X-ray polarimetric observations, that will allow placing constraints on the location of the primary source. In addition, X-ray polarimeters (like, e.g., XIPE) have sufficient sensitivity to constrain the line-of-sight positions of molecular complexes, removing major uncertainty in the model.

17 pages, 10 figures, accepted for publication in MNRAS

References in corpus (6)

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• Discrete sources as the origin of the Galactic X-ray ridge emission
• Variable accretion and emission from the stellar winds in the Galactic centre
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• Revisiting the complex nuclear region of NGC 6240 with Chandra
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• SRG/eROSITA view of X-ray reflection in the Central Molecular Zone: a snapshot in September-October 2019
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• New Constraints on Cosmic Particle Populations at the Galactic Center using X-ray Observations of the Molecular Cloud Sagittarius B2
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• 25 years of XMM-Newton observations of the Sgr A complex: 3D distribution and internal structure of the clouds
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• Constraints on the collimated X-ray emission of SS 433 from the reflection on molecular clouds
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