The Colloquium takes place every Wednesday at 11:15 AM - Warsaw Copernicus Astronomical Centre online by means of Zoom platform. The Colloquium is given in English and chaired by dr Stanisław Bajtlik (contact mail seminar@camk.edu.pl). People from outside of the Copernicus Center are very welcome to participate. For technical detailes please contact Dr. Stanislaw Bajtlik (bajtlik@camk.edu.pl).
Rameshan Thimmappa (Department of Physics, Villanova University)
Relativistic jets in radio galaxies provide unique laboratories for investigating particle acceleration and shock physics. Here, I present high-resolution X-ray and optical studies of two nearby radio galaxies, Pictor A and M87. In Pictor A, using Chandra observations, the western hotspot was resolved into a thin shock-front structure, revealing energy-dependent offsets between the X-ray/optical and radio emission. The hotspot also exhibits long-term flux variability and spectral steepening downstream of the shock. In addition, an X-ray filament has been detected in the eastern lobe of Pictor A. For M87, multi-epoch Chandra and Hubble observations of knot HST-1 in the jet reveal a correlation between flux and positional offset during its flare around 2005, along with substantial long-term flux variability and apparent superluminal motion. These observations further suggest that the X-ray and UV/optical emission may originate from physically distinct regions. Together, these studies demonstrate how spatially resolved imaging and multi-epoch variability analyses can probe the internal structure, dynamics, and high-energy synchrotron emission of relativistic jets in active galactic nuclei.
Journal Club takes place on Mondays at 11:15 AM in the Seminar Room. The presentation is given in English and is chaired by Journal Club Coordinators. Anyone interested in giving a Journal Club talk is encouraged to contact the email: journalclub(@camk.edu.pl).
Miljenko Cemeljic (NCAC, Warsaw)
https://www.nature.com/articles/s41586-025-09912-0
