A descriptive title

ATel #14211; Simona Paiano (INAF/OA Roma - IASF Milano - IASF Palermo ), Renato Falomo (INAF/OAPD), Aldo Treves (Università dell'Insubria, INAF/OA Brera), Riccardo Scarpa (IAC, Universidad de la Laguna), Paolo Padovani (ESO), Paolo Giommi (ASI)
on 24 Nov 2020; 18:45 UT
Credential Certification: Simona Paiano (simona.paiano@inaf.it)

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IceCube 201114A is a high energy neutrino event of potential astrophysical interest (GCN 28887). A plausible association inside the neutrino error box is with the gamma-ray BL Lac source 4FGLJ0658.6+0636 (3HSPJ065845.6+063711, NVSSJ065844+063711), that is a very high energy (E > 100 GeV; Atel 14200) emitter . The X-ray counterpart at the epoch of the event was in a moderate high state (GCN 28895, Atel 14199, 14201). On 2020 November 17, we obtained an optical spectrum in the range 4100 - 7700 Ang (S/N ~ 60) of the target (g = 19.9) at the Gran Telescopio Canarias (10.4 m), using the spectrograph OSIRIS with grism R1000B (exposure time = 4500 sec). The optical spectrum is characterized by a featureless continuum that is well described by power-law shape, with a spectral index of -1.3 ( using E(B-V)=0.22 ). We set an upper limit for any emission or absorption lines to equivalent width EW < 0.45 Ang. From the absence of the absorption lines of the host galaxy we obtain a lower limit (see Paiano et al 2017) of the redshift z > 0.5. From the above properties this source is classified as a BL Lac object. The spectrum can be retrieved in the spectroscopic database ZBLLAC (https://web.oapd.inaf.it/zbllac/ ; Landoni et al 2020).