http://arxiv.org/abs/2304.06967
The center of the Milky Way Galaxy hosts a $\sim$4 million solar mass black hole (Sgr A$^$) that is currently very quiescent with a luminosity many orders of magnitude below those of active galactic nuclei. Reflection of X-rays from Sgr A$^$ by dense gas in the Galactic Center region offers a means to study its past flaring activity on times scales of hundreds and thousands of years. The shape of the X-ray continuum and the strong fluorescent iron line observed from giant molecular clouds in the vicinity of Sgr A$^$ are consistent with the reflection scenario. If this interpretation is correct, the reflected continuum emission should be polarized. Here we report observations of polarized X-ray emission in the direction of the Galactic center molecular clouds using the Imaging X-ray Polarimetry Explorer (IXPE). We measure a polarization degree of 31\% $\pm$ 11\%, and a polarization angle of $-$48$^\circ$ $\pm$ 11$^\circ$. The polarization angle is consistent with Sgr A$^$ being the primary source of the emission, while the polarization degree implies that some 200 years ago the X-ray luminosity of Sgr A$^*$ was briefly comparable to a Seyfert galaxy.
F. Marin, E. Churazov, I. Khabibullin, et. al.
Mon, 17 Apr 23
20/51
Comments: 24 pages, 5 figures, 4 tables, author’s version of the paper accepted for publication in Nature