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The redshift of 3FGLJ0627.9-1517: a possible counterpart of the Icecube neutrino event IC-170321

ATel #12269; Simona Paiano (INAF-OA Padova), Renato Falomo (INAF-OA Padova), Aldo Treves (Universita' dell'Insubria), Marco Landoni (INAF-OA Brera), Riccardo Scarpa (IAC)
on 5 Dec 2018; 08:57 UT
Credential Certification: Simona Paiano (simona.paiano@inaf.it)

Subjects: Optical, Gamma Ray, Neutrinos, AGN, Blazar

Since April 2016, some 10 neutrino Icecube events have been made public (see https://gcn.gsfc.nasa.gov/amon_hese_events.html and https://gcn.gsfc.nasa.gov/amon_ehe_events.html ). The AGILE team embarked in a search for transient gamma-ray sources (>100 MeV) temporally and spatially coincident with these neutrino events and found 3 gamma-ray sources coincident with them (Lucarelli et al., 2018). For one of these sources (B), we recently (March 2018) obtained an optical spectrum of the most interesting counterpart, the HSP blazar 2WHSP J062753.2-151956 (Chang et al., 2017) which is associated to the Fermi gamma-ray source 3FGLJ0627.9-1517. The spectrum of this object (g = 19.4) was obtained at the 10.4m Gran Telescopio Canarias using OSIRIS (exposure time = 6000 sec and spectral range = 4100-7700 Ang). The spectrum is characterized by the combination of a power-law emission and starlight from host galaxy typical of BL Lac object of low nucleus-to-host ratio. We clearly detect absorption features due to CaII doublet, G-band, and H_beta at z= 0.3102. The spectrum is reported in our online ZBLLac database (http://archive.oapd.inaf.it/zbllac/). At this redshift the AGILE gamma-ray luminosity is ~2x10^46 erg s-1, comparable to that of TXS0506+056 (AGILE source C).

ZBLLAC: A spectroscopic library of BL Lac objects