Investigating the blazar TXS 0506+056 through sharp multi-wavelength eyes during 2017-2019

Abstract

The blazar TXS 0506+056 got into the spotlight of the astrophysical community in September 2017, when a high-energy neutrino detected by IceCube (IceCube-170922A) was associated at the 3 $\sigma$ level to a $\gamma$-ray flare from this source. This multi-messenger photon-neutrino association remains, as per today, the most significant one ever observed. TXS 0506+056 was a poorly studied object before the IceCube-170922A event. To better characterize its broad-band emission, we organized a multi-wavelength campaign lasting 16 months (November 2017 to February 2019), covering the radio-band (Metsähovi, OVRO), the optical/UV (ASAS-SN, KVA, REM, Swift/UVOT), the X-rays (Swift/XRT, NuSTAR), the high-energy $\gamma$ rays (Fermi/LAT) and the very-high-energy (VHE) $\gamma$ rays (MAGIC). In $\gamma$ rays, the behaviour of the source was significantly different from the 2017 one: MAGIC observations show the presence of flaring activity during December 2018, while the source only shows an excess at the 4$\sigma$ level during the rest of the campaign (74 hours of accumulated exposure); Fermi/LAT observations show several short (days-to-week timescale) flares, different from the long-term brightening of 2017. No significant flares are detected at lower energies. The radio light curve shows an increasing flux trend, not seen in other wavelengths. We model the multi-wavelength spectral energy distributions in a lepto-hadronic scenario, in which the hadronic emission emerges as Bethe-Heitler and pion-decay cascade in the X-rays and VHE $\gamma$ rays. According to the model presented here, the December 2018 $\gamma$-ray flare was connected to a neutrino emission that was too brief and not bright enough to be detected by current neutrino instruments.

18 pages, 6 figures; V2 to match published version, typo fixed

References in corpus (13)

• The All-Sky Automated Survey for Supernovae (ASAS-SN) Light Curve Server v1.0
• The major upgrade of the MAGIC telescopes, Part II: A performance study using observations of the Crab Nebula
• Time-integrated Neutrino Source Searches with 10 years of IceCube Data
• Energy spectra of gamma-rays, electrons and neutrinos produced at interactions of relativistic protons with low energy radiation
• The contribution of Fermi-2LAC blazars to the diffuse TeV-PeV neutrino flux
• A hadronic origin for ultra-high-frequency-peaked BL Lac objects
• TXS 0506+056, the first cosmic neutrino source, is not a BL Lac
• Association of IceCube neutrinos with radio sources observed at Owens Valley and Metsähovi Radio Observatories
• A Neutral Beam Model for High-Energy Neutrino Emission from the Blazar TXS 0506+056
• Apparent superluminal core expansion and limb brightening in the candidate neutrino blazar TXS 0506+056
• First broadband characterization and redshift determination of the VHE blazar MAGIC J2001+439
• ANTARES search for point-sources of neutrinos using astrophysical catalogs: a likelihood stacking analysis
• Medium-band observation of the neutrino emitting blazar, TXS 0506+056

Cited by in corpus (9)

• Implications of multiwavelength spectrum on cosmic-ray acceleration in blazar TXS 0506+056
• Long-term multi-wavelength study of 1ES 0647+250
• Implications of photon-ALP oscillations in the extragalactic neutrino source TXS 0506+056 at sub-PeV energies
• VERITAS and multiwavelength observations of the Blazar B3 2247+381 in response to an IceCube neutrino alert
• Proton Synchrotron, an explanation for possible extended VHE gamma-ray activity of TXS 0506+056 in 2017
• A Very-High-Energy Gamma-Ray View of the Transient Sky
• Cosmogenic Origin of KM3-230213A: Delayed Gamma-Ray Emission from A Cosmic-Ray Transient
• Selected results from IceCube
• Testing Weak Equivalence Principle with IceCube Event and Blazar