Challenges in reconciling observations and theory of the brightest high-energy flare ever of 3C 279

TL;DR

This paper analyzes the brightest gamma-ray flare of blazar 3C 279 observed in 2015, comparing observational data with theoretical models, and highlights challenges in reconciling observations with existing jet emission theories.

Contribution

It provides a detailed spectral energy distribution of the flare and tests one-zone leptonic and lepto-hadronic models against the data, revealing challenges in current jet physics models.

Findings

Models challenge the physical conditions in the jet.

Lepto-hadronic model aligns with recent VHE data.

Spectral modeling constrains emission region parameters.

Abstract

Recent high-energy missions have allowed keeping watch over blazars in flaring states, which provide deep insights into the engine powered by supermassive black holes. However, having a quasar caught in a very bright flaring state is not easy requiring long surveys. Therefore, the observation of such flaring events represents a goldmine for theoretical studies. Such a flaring event was captured by the INTEGRAL mission in June 2015 while performing its (as of today) deepest extragalactic survey when it caught the prominent blazar 3C~279 in its brightest flare ever recorded at gamma-ray energies. The flare was simultaneously recorded by the Fermi gamma-ray mission, by the Swift mission, by the INTEGRAL mission and by observations ranging from UV, through optical to the near-IR bands. The derived snapshot of this broad spectral energy distribution of the flare has been modeled in the context of a one-zone radiation transfer leptonic and lepto-hadronic models constraining the single emission components. The derived parameters of both models challenge the physical conditions in the jet. However, very recently published very-high-energy (VHE) data at TeV energies are very close to our lepto-hadronic model.