Farhad Yusef-Zadeh
Dept. Astronomy Astroph., Northwestern Univ. (Evanston, Illinois, Etats-Unis d'Amérique)
Salle des séminaires Évry Schatzman, Institut d'Astrophysique de Paris
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| « The Black Hole and its flaring activity at the center of the Galaxy » |
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Farhad Yusef-Zadeh |
| Precise measurements taken at radio and infrared wavelengths over the past two decades have led to the conclusion that a 4.2 million solar mass black hole lies at the center of the Galaxy. These measurements are consistent with predictions of Einstein's general theory of relativity, including effects such as precession and gravitational redshift. After a brief introduction, I will present highlights of recent JWST observations aimed at studying the flaring activity of the black hole. The variability of the black hole probes the physics of the accretion flow at distances of just a few Schwarszchild radii. Observations indicate that the flux of Sgr A* fluctuates continuously, with multiple synchrotron flares occurring each day. I will argue that two distinct populations of particles are responsible for the bright and faint components of the variable synchrotron emission. Regarding the origin of the infrared flares, recent simulations suggest that they are ejected plasmoids from the accretion disk, produced by magnetic field line reconnection. Time permitting, I will also discuss the relationship between infrared flares and their counterparts at radio/Submillimeter and X-ray wavelengths. |
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vendredi 16 mai 2025 - 11:00 Salle des séminaires Évry Schatzman, Institut d'Astrophysique de Paris |
| Page web du séminaire / Seminar's webpage |