Expected signatures from hadronic emission processes in the TeV spectra of BL Lac objects

Abstract

The wealth of recent data from imaging air Cherenkov telescopes (IACTs), ultra-high energy cosmic-ray experiments and neutrino telescopes have fuelled a renewed interest in hadronic emission models for gamma-loud blazars. We explore physically plausible solutions for a lepto-hadronic interpretation of the stationary emission from high-frequency peaked BL Lac objects (HBLs). The modelled spectral energy distributions are then searched for specific signatures at very high energies that could help to distinguish the hadronic origin of the emission from a standard leptonic scenario. By introducing a few basic constraints on parameters of the model, such as assuming the co-acceleration of electrons and protons, we significantly reduced the number of free parameters. We then systematically explored the parameter space of the size of the emission region and its magnetic field for two bright gamma-loud HBLs, PKS 2155-304 and Mrk 421. For all solutions close to equipartition between the energy densities of protons and of the magnetic field, and with acceptable jet power and light-crossing timescales, we inspected the spectral hardening in the multi-TeV domain from proton-photon induced cascades and muon-synchrotron emission inside the source. Very-high-energy spectra simulated with the available instrument functions from the future Cherenkov Telescope Array (CTA) were evaluated for detectable features as a function of exposure time, source redshift, and flux level. Over a large range of model parameters, the spectral hardening due to internal synchrotron-pair cascades, the "cascade bump", should be detectable for acceptable exposure times with the future CTA for a few nearby and bright HBLs.

18 pages, 20 figures, plus appendix. A problem with formatting of the bibliography has been fixed and a few minor language revisions have been done

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Cited by in corpus (21)

• The blazar TXS 0506+056 associated with a high-energy neutrino: insights into extragalactic jets and cosmic ray acceleration
• Lepto-hadronic single-zone models for the electromagnetic and neutrino emission of TXS 0506+056
• Leptonic and Hadronic Radiative Processes in Supermassive-Black-Hole Jets
• Time-dependent lepto-hadronic modeling of the emission from blazar jets with SOPRANO: the case of TXS 0506+056, 3HSP J095507.9+355101 and 3C 279
• Electron-proton co-acceleration on relativistic shocks in extreme-TeV blazars
• Radio$-\gamma -$ray response in blazars as a signature of adiabatic blob expansion
• Luminous and high-frequency peaked blazars: the origin of the $\gamma$-ray emission from PKS 1424+240
• The relentless variability of Mrk 421 from the TeV to the radio
• Blazars at Very High Energies: Emission Modelling
• Probing an X-ray flare pattern in Mrk 421 induced by multiple stationary shocks: a solution to the bulk Lorentz factor crisis
• A self-consistent leptonic-hadronic interpretation of the electromagnetic and neutrino emissions from blazar TXS 0506+056
• Extragalactic Observatory Science with the ASTRI Mini-Array at the Observatorio del Teide
• Extreme HBL-like behavior of Markarian 421 and its two-zone photohadronic interpretation
• Putting the hadron beam scenario for extreme blazars to the test with the Cherenkov Telescope Array
• Long-term multi-band photometric monitoring of Mrk 501
• The Intrinsic Gamma-Ray Spectrum of TXS 0506+056: Intergalactic Propagation Effects
• TeV and keV-MeV Excesses as Probes for Hadronic Process in BL Lacertaes
• An Artificial Intelligence based approach for constraining the redshift of blazars using $\gamma$--ray observation
• A Systematic Search for Spectral Hardening in Blazar Flares with the Fermi-Large Area Telescope
• Very-high-energy gamma-ray detection and long-term multi-wavelength view of the flaring blazar B2 1811+31
• Analytical Constraints on the Radius and Bulk Lorentz Factor in the Lepto-Hadronic One-Zone Model of BL Lacs