Letter to the Editor

3HSP J095507.9+355101: A flaring extreme blazar coincident in space and time with IceCube-200107A

¹ Institute for Advanced Study, Technische Universität München, Lichtenbergstrasse 2a, 85748 Garching bei München, Germany
e-mail: giommipaolo@gmail.com
² Associated to Agenzia Spaziale Italiana, ASI, Via del Politecnico s.n.c., 00133 Roma, Italy
³ ICRANet, Piazzale della Repubblica 10, 65122 Pescara, Italy
⁴ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
⁵ Associated to INAF – Osservatorio Astronomico di Roma, Via Frascati 33, 00040 Monteporzio Catone, Italy
⁶ Technische Universität München, Physik-Department, James-Frank-Str. 1, 85748 Garching bei München, Germany
⁷ Institutt for fysikk, NTNU, Trondheim, Norway
⁸ INAF – Osservatorio Astronomico di Roma, Via Frascati 33, 00040 Monteporzio Catone, Italy
⁹ INAF – IASF Milano, Via Corti 12, 20133 Milano, Italy

Received: 15 May 2020
Accepted: 5 July 2020

Abstract

The uncertainty region of the highly energetic neutrino IceCube200107A includes 3HSP J095507.9+355101 (z = 0.557), an extreme blazar, which was detected in a high, very hard, and variable X-ray state shortly after the neutrino arrival. Following a detailed multiwavelength investigation, we confirm that the source is a genuine BL Lac. This new detection differs from TXS 0506+056, which is thus far the first source associated with IceCube neutrinos, and is considered a “masquerading” BL Lac. As in the case of TXS 0506+056, 3HSP J095507.9+355101 is also way off the so-called blazar sequence. We consider 3HSP J095507.9+355101 a possible counterpart to the IceCube neutrino. Finally, we discuss some theoretical implications in terms of neutrino production.