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Joint X-ray and EHT Probe of Sgr A*: Flares, Black Hole Shadows and a New Source

Presentation #307.04 in the session The Event Horizon Telescope in Light of High-Energy Emission.

Published onJul 01, 2023
Joint X-ray and EHT Probe of Sgr A*: Flares, Black Hole Shadows and a New Source

Located in the nucleus of the Milky Way galaxy, Sgr A* is one of the best studied supermassive black hole. Given its large apparent angular size, Sgr A* is an ideal target for the EHT to image the dark shadow caused by gravitational light bending and photon capture close to the event horizon. One challenge in the EHT Sgr A* data analysis is that its emission level changes on a 10-30 minute time scale. Sgr A* undergoes hour-long flares 3-4 times a day in the NIR band and roughly once per day in the X-ray band. During X-ray flares, Sgr A*’s luminosity increases by a factor of 10-400 over the quiescent luminosity. Fast X-ray variability on timescale of <100 s suggests a compact emission region located within a few gravitational radii from the black hole. The EHT multi-wavelength science working group has overseen successful EHT Sgr A* observation campaign jointly with a range of observatories during 2017-2022. In this talk, I will feature X-ray flares detected during the joint Sgr A* observation campaign with the EHT and an unexpected new X-ray source detected merely at 1 parsec from the black hole.

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