X-ray polarization evidence for a 200 years-old flare of Sgr A$^*$
Creators: name: Marin, Frédéric
name: Churazov, Eugene
name: Khabibullin, Ildar
name: Ferrazzoli, Riccardo
name: Di Gesu, Laura
name: Barnouin, Thibault
name: Di Marco, Alessandro
name: Middei, Riccardo
name: Vikhlinin, Alexey
name: Costa, Enrico
name: Soffitta, Paolo
name: Muleri, Fabio
name: Sunyaev, Rashid
name: Forman, William
name: Kraft, Ralph
name: Bianchi, Stefano
name: Donnarumma, Immacolata
name: Petrucci, Pierre-Olivier
name: Enoto, Teruaki
name: Agudo, Iván
name: Antonelli, Lucio A.
name: Bachetti, Matteo
name: Baldini, Luca
name: Baumgartner, Wayne H.
name: Bellazzini, Ronaldo
name: Bongiorno, Stephen D.
name: Bonino, Raffaella
name: Brez, Alessandro
name: Bucciantini, Niccolò
name: Capitanio, Fiamma
name: Castellano, Simone
name: Cavazzuti, Elisabetta
name: Chen, Chien-Ting
name: Ciprini, Stefano
name: De Rosa, Alessandra
name: Del Monte, Ettore
name: Di Lalla, Niccolò
name: Doroshenko, Victor
name: Dovciak, Michal
name: Ehlert, Steven R.
name: Evangelista, Yuri
name: Fabiani, Sergio
name: Garcia, Javier A.
name: Gunji, Shuichi
name: Hayashida, Kiyoshi
name: Heyl, Jeremy
name: Ingram, Adam
name: Iwakiri, Wataru
name: Jorstad, Svetlana G.
name: Kaaret, Philip
name: Karas, Vladimir
name: Kitaguchi, Takao
name: Kolodziejczak, Jeffery J.
name: Krawczynski, Henric
name: La Monaca, Fabio
name: Latronico, Luca
name: Liodakis, Ioannis
name: Maldera, Simone
name: Manfreda, Alberto
name: Marinucci, Andrea
name: Marscher, Alan P.
name: Marshall, Herman L.
name: Massaro, Francesco
name: Matt, Giorgio
name: Mitsuishi, Ikuyuki
name: Mizuno, Tsunefumi
name: Negro, Michela
name: Ng, C. -Y.
name: O'Dell, Stephen L.
name: Omodei, Nicola
name: Oppedisano, Chiara
name: Papitto, Alessandro
name: Pavlov, George G.
name: Peirson, Abel L.
name: Perri, Matteo
name: Pesce-Rollins, Melissa
name: Pilia, Maura
name: Possenti, Andrea
name: Poutanen, Juri
name: Puccetti, Simonetta
name: Ramsey, Brian D.
name: Rankin, John
name: Ratheesh, Ajay
name: Roberts, Oliver J.
name: Romani, Roger W.
name: Sgrò, Carmelo
name: Slane, Patrick
name: Spandre, Gloria
name: Swartz, Doug
name: Tamagawa, Toru
name: Tavecchio, Fabrizio
name: Taverna, Roberto
name: Tawara, Yuzuru
name: Tennant, Allyn F.
name: Thomas, Nicholas E.
name: Tombesi, Francesco
name: Trois, Alessio
name: Tsygankov, Sergey S.
name: Turolla, Roberto
name: Vink, Jacco
name: Weisskopf, Martin C.
name: Wu, Kinwah
name: Xie, Fei
name: Zane, Silvia
Publisher: name: arXiv
Year: 2023
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences
subject: FOS: Physical sciences
subject: J.2.3; J.2.9
subject: 85-06

description: 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.
description: 24 pages, 5 figures, 4 tables, author's version of the paper accepted for publication in Nature