2-6 September 2024
CJD Bonn Castell
Europe/Berlin timezone
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Contribution

PKS 1424-418: A best case of the blazar radio/gamma-ray connection

Speakers

  • Dr. Daewon KIM

Primary authors

Co-authors

Content

Blazars, a subclass of radio-loud AGN are among the best laboratories for high-energy astrophysics in the Universe. The relativistic jets in blazars are prominent gamma-ray emitters with rapid variablity down to minute scales. The underlying physical mechanisms and origin of the gamma-ray emission, however, are not yet fully understood. One of the key diagnoses for the relevant studies is to explore statistically significant correlations between gamma-ray and lower-energy band (e.g., radio-to-optical) light curves in the sources. In this work, we analyzed the correlation with millimeter (> 90GHz) radio light curves in the blazar PKS 1424-418 and found a long-term, tight radio/gamma-ray connection which is atypical compared to the cases of other blazars. The correlation spans ~8.5 years with a small amount of time lag (i.e., less than three days). Given the well-known blazar jet model with the core-shift theory, the results indicate that the gamma-ray production site is spatially connected to the location of the millimeter radio core at e.g., (sub)parsec scales in the jet of PKS 1424-418. Additional analysis of the evolution of radio spectral index (95GHz vs. 345GHz) clearly shows us the coincidence between the spectral hardenings and gamma-ray flares. This further implies that a small displacement between the gamma-ray origin and the radio core may occurs when the source flares at gamma-rays, perhaps due to the passage of a strong moving shock/blob. We suggest that this particular blazar might be a persistent source of the radio/gamma-ray connection.