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Detection of flaring very-high-energy gamma-ray emission from BL Lacertae with the MAGIC telescopes

ATel #14826; Oscar Blanch (Institut de Fisica d'Altes Energies, IFAE-BIST), Giacomo Bonnoli (IAA-CSIC - Granada), Hiromu Iwasaki, Jelena Striskovic, and Ryo Imazawa, on behalf of the MAGIC collaboration
on 4 Aug 2021; 11:13 UT
Credential Certification: David Paneque (dpaneque@slac.stanford.edu)

Subjects: Gamma Ray, TeV, VHE, AGN, Blazar

Referred to by ATel #: 14839

The MAGIC telescopes have observed an increase in the very-high-energy (VHE; >100 GeV) gamma-ray flux from BL Lacertae. The preliminary analysis of the MAGIC data taken on 2021/08/02 (MJD 59428.9) indicates a flux corresponding to about 1.3C.U. at E> 100GeV, which is about one order of magnitude higher than typical non-flaring flux values. BL Lacertae is very variable in the VHE gamma-ray range, and shows VHE gamma-ray fluxes as high as 3 C.U. (ATel #14032).

BL Lacertae is a blazar located at redshift 0.0686, and it has shown several bright VHE gamma-ray flares in the past (http://tevcat.uchicago.edu/?mode=1&showsrc=118). The MAGIC observations were triggered by the detection of the all-time highest flux at optical wavelengths (ATel #14820). BL Lac is undergoing a high state in gamma rays (Fermi-LAT: https://fermi.gsfc.nasa.gov/FTP/glast/data/lat/catalogs/asp/current/lightcurves/BLLac_86400_1yr.png) and in X-rays as well (Swift: https://www.swift.psu.edu/monitoring/source.php?source=BLLacertae). The current outbreak began in early July 2021 (ATel #14751, ATel #14773) and has been reported in many occasions (ATel #14774, ATel #14777, ATel #14782, ATel #14783).

MAGIC observations on BL Lac will continue during the next days and multiwavelength observations are encouraged. The MAGIC contact persons for these observations are O.Blanch (blanch@ifae.es) and Giacomo Bonnoli (bonnoli@iaa.es)

The preliminary analysis has been performed by Hiromu Iwasaki (iwasaki.hiromu.47n@st.kyoto-u.ac.jp) and Jelena Striskovic (jelena.striskovic@gmail.com).

MAGIC is a system of two 17m-diameter Imaging Atmospheric Cherenkov Telescopes located at the Canary island of La Palma, Spain, and designed to perform gamma-ray astronomy in the energy range from 50 GeV to greater than 50 TeV.