Investigating the Blazar TXS 0506+056 through Sharp Multiwavelength Eyes During 2017–2019

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