TY - JOUR

T1 - Polarization of reflected X-ray emission from the Sgr A molecular complex: Multiple flares, multiple sources?

AU - Khabibullin, I

AU - Churazov, E

AU - Ferrazzoli, R

AU - Kaaret, P

AU - Kolodziejczak, JJ

AU - Marin, F

AU - Sunyaev, R

AU - Svoboda, J

AU - Vikhlinin, A

AU - Chen, CT

AU - Barnouin, T

AU - Costa, E

AU - Di Gesu, L

AU - Di Marco, A

AU - Ehlert, SR

AU - Forman, W

AU - Kim, DE

AU - Kraft, R

AU - Maksym, WP

AU - Matt, G

AU - Poutanen, J

AU - Soffitta, P

AU - Swartz, DA

AU - Agudo, I

AU - Antonelli, LA

AU - Baldini, L

AU - Baumgartner, WH

AU - Bellazzini, R

AU - Bianchi, S

AU - Bongiorno, SD

AU - Bonino, R

AU - Brez, A

AU - Bucciantini, N

AU - Capitanio, F

AU - Castellano, S

AU - Cavazzuti, E

AU - Ciprini, S

AU - De Rosa, A

AU - Del Monte, E

AU - Di Lalla, N

AU - Donnarumma, I

AU - Doroshenko, V

AU - Dovciak, M

AU - Enoto, T

AU - Evangelista, Y

AU - Fabiani, S

AU - Garcia, JA

AU - Gunji, S

AU - Hayashida, K

AU - Heyl, J

AU - Iwakiri, W

AU - Jorstad, SG

AU - Karas, V

AU - Kislat, F

AU - Kitaguchi, T

AU - Krawczynski, H

AU - La Monaca, F

AU - Latronico, L

AU - Liodakis, I

AU - Maldera, S

AU - Manfreda, A

AU - Marscher, AP

AU - Marshall, HL

AU - Massaro, F

AU - Mitsuishi, I

AU - Mizuno, T

AU - Muleri, F

AU - Negro, M

AU - Ng, CY

AU - O'Dell, SL

AU - Omodei, N

AU - Oppedisano, C

AU - Papitto, A

AU - Pavlov, GG

AU - Peirson, AL

AU - Pesce-Rollins, M

AU - Petrucci, PO

AU - Pilia, M

AU - Possenti, A

AU - Puccetti, S

AU - Ramsey, BD

AU - Rankin, J

AU - Ratheesh, A

AU - Roberts, OJ

AU - Romani, RW

AU - Sgro, C

AU - Slane, P

AU - Spandre, G

AU - Tamagawa, T

AU - Tavecchio, F

AU - Taverna, R

AU - Tawara, Y

AU - Tennant, AF

AU - Thomas, NE

AU - Tombesi, F

AU - Trois, A

AU - Tsygankov, SS

AU - Turolla, R

AU - Vink, J

AU - Weisskopf, MC

AU - Wu, KW

AU - Xie, F

AU - Zane, S

N1 - Times Cited in Web of Science Core Collection: 0 Total Times Cited: 0 Cited Reference Count: 68

PY - 2026/3/1

Y1 - 2026/3/1

N2 - The extended X-ray emission observed in the direction of several molecular clouds in the central molecular zone (CMZ) of our Galaxy exhibits spectral and temporal properties consistent with the X-ray echo scenario. This concept postulates that the observed signal is a light-travel-time delayed reflection of a short (delta t 10(39) erg s(-1)) flare that was most probably produced a few hundred years ago by Sgr A*. This scenario also predicts a distinct polarization signature for the reflected X-ray continuum, with the polarization vector being perpendicular to the direction toward the primary source and the polarization degree being determined by the scattering angle. We report the results of two deep observations of the currently brightest (in reflected emission) molecular complex Sgr A taken with the Imaging X-ray Polarimetry Explorer (IXPE) in 2022 and 2023. We confirm the previous polarization measurement for a large region encompassing the Sgr A complex with high significance. We also reveal an inconsistent polarization pattern for the brightest reflection region in its center. Specifically, the X-ray polarization from this region is almost perpendicular to the expected direction in the case of Sgr A* illumination, and it shows a smaller degree of polarization compared to the large region. Taken at face value, this could indicate the simultaneous propagation of several illumination fronts throughout the CMZ, with the origin of one of them not being Sgr A*. The primary source could be associated with the Arches stellar cluster or a currently unknown source located closer to the illuminated cloud, potentially lowering the required luminosity of the primary source. Although significantly deeper observations with IXPE would be required to unequivocally distinguish between the scenarios, a combination of high-resolution imaging and micro-calorimetric spectroscopy offers an additional promising path forward.

AB - The extended X-ray emission observed in the direction of several molecular clouds in the central molecular zone (CMZ) of our Galaxy exhibits spectral and temporal properties consistent with the X-ray echo scenario. This concept postulates that the observed signal is a light-travel-time delayed reflection of a short (delta t 10(39) erg s(-1)) flare that was most probably produced a few hundred years ago by Sgr A*. This scenario also predicts a distinct polarization signature for the reflected X-ray continuum, with the polarization vector being perpendicular to the direction toward the primary source and the polarization degree being determined by the scattering angle. We report the results of two deep observations of the currently brightest (in reflected emission) molecular complex Sgr A taken with the Imaging X-ray Polarimetry Explorer (IXPE) in 2022 and 2023. We confirm the previous polarization measurement for a large region encompassing the Sgr A complex with high significance. We also reveal an inconsistent polarization pattern for the brightest reflection region in its center. Specifically, the X-ray polarization from this region is almost perpendicular to the expected direction in the case of Sgr A* illumination, and it shows a smaller degree of polarization compared to the large region. Taken at face value, this could indicate the simultaneous propagation of several illumination fronts throughout the CMZ, with the origin of one of them not being Sgr A*. The primary source could be associated with the Arches stellar cluster or a currently unknown source located closer to the illuminated cloud, potentially lowering the required luminosity of the primary source. Although significantly deeper observations with IXPE would be required to unequivocally distinguish between the scenarios, a combination of high-resolution imaging and micro-calorimetric spectroscopy offers an additional promising path forward.

KW - Galaxy: center

KW - Galaxy: nucleus

KW - X-rays: ISM

KW - XMM-NEWTON OBSERVATIONS

KW - SAGITTARIUS A-ASTERISK

KW - GALACTIC-CENTER

KW - NONTHERMAL EMISSION

KW - ARCHES CLUSTER

KW - PAST ACTIVITY

KW - A(STAR)

KW - VIEW

KW - DISCOVERY

KW - ECHOES

UR - https://www.mendeley.com/catalogue/25c1da17-8896-3baf-8aab-c197b150bf06/

U2 - 10.1051/0004-6361/202556768

DO - 10.1051/0004-6361/202556768

M3 - Article

VL - 707

JO - ASTRONOMY & ASTROPHYSICS

JF - ASTRONOMY & ASTROPHYSICS

SN - 0004-6361

ER -