Non-thermal emission from standing relativistic shocks: an application to red giant winds interacting with AGN jets

Abstract

Galactic and extragalactic relativistic jets have rich environments that are full of moving objects, such as stars and dense clumps. These objects can enter into the jets and generate shocks and non-thermal emission. We characterize the emitting properties of the downstream region of a standing shock formed due to the interaction of a relativistic jet with an obstacle. We focus on the case of red giants interacting with an extragalactic jet. We perform relativistic axisymmetric hydrodynamical simulations of a relativistic jet meeting an obstacle of very large inertia. The results are interpreted in the framework of a red giant whose dense and slow wind interacts with the jet of an active galactic nucleus. Assuming that particles are accelerated in the standing shock generated in the jet as it impacts the red giant wind, we compute the non-thermal particle distribution, the Doppler boosting enhancement, and the non-thermal luminosity in gamma rays. The available non-thermal energy from jet-obstacle interactions is potentially enhanced by a factor of $\sim 100$ when accounting for the whole surface of the shock induced by the obstacle, instead of just the obstacle section. The observer gamma-ray luminosity, including the flow velocity and Doppler boosting effects, can be ~300(g/10)^2 times higher than when the emitting flow is assumed at rest and only the obstacle section is considered, where g is the jet Lorentz factor. For a whole population of red giants inside the jet of an AGN, the predicted persistent gamma-ray luminosities may be potentially detectable for a jet pointing to the observer. Obstacles interacting with relativistic outflows, for instance clouds and populations of stars for extragalactic jets, or stellar wind inhomogeneities in microquasar jets and in winds of pulsars in binaries, should be taken into account when investigating the non-thermal emission from these sources.

7 pages, 6 figures, version after proofs to appear in Astronomy & Astrophysics

References in corpus (6)

• The Black Hole Mass, Stellar M/L, and Dark Halo in M87
• Gamma-ray flares from red giant/jet interactions in AGN
• TANAMI monitoring of Centaurus A: The complex dynamics in the inner parsec of an extragalactic jet
• AGN Jet Mass Loading and Truncation by Stellar Winds
• MAGIC observations of the giant radio galaxy M87 in a low-emission state between 2005 and 2007
• Simulations of an inhomogeneous stellar wind interacting with a pulsar wind in a binary system

Cited by in corpus (7)

• Cloud ablation by a relativistic jet and the extended flare in CTA 102 in 2016 and 2017
• Non-thermal radiation from collisions of compact objects with intermediate scale jets in active galaxies
• The impact of red giant/AGB winds on AGN jet propagation
• Orphan γ-ray flares from relativistic blobs encountering luminous stars
• Gamma rays from red giant wind bubbles entering the jets of elliptical host blazars
• Non-thermal emission resulting from a supernova explosion inside an extragalactic jet
• Absorption effects in the blazar's gamma-ray spectra due to luminous stars crossing the jet