Time-dependent search for neutrino emission from Mrk 421 and Mrk 501 observed by the HAWC gamma-ray observatory

Abstract

on behalf of the ANTARES CollaborationThe principles of a search for high energy neutrino emission in coincidence with very high energy (VHE; 0.1-100 TeV) gamma-ray flares from two bright extragalactic sources, based on the data collected in 2012-2016 by the ANTARES neutrino detector and High Altitude Water Cherenkov (HAWC) gamma-ray observatory, are presented. The ANTARES telescope observes with high duty cycle an instantaneous field of view of 2π. To study variable sources like blazars, it is crucial to achieve unbiased monitoring and an instrument like HAWC is capable of long term and continuous monitoring of the source with nearly 100% duty cycle. Markarian 421 (Mrk 421) and Markarian 501 (Mrk 501) are the brightest and the closest BL Lac objects known. In contrast to other types of active galactic nuclei (AGN), BL Lacs are characterized by rapid and largeamplitude flux variability. Such radio-loud AGNs with collimated jets aligned to the line of sight, are candidate sources of the observed high energy cosmic rays and of accompanying neutrinos and gamma rays produced in hadronic interactions with the surrounding medium.

ANTARES search for high-energy neutrinos from TeV-emitting blazars, Markarian 421 and 501, in coincidence with HAWC gamma-ray flares

“…A search for ν candidades in coincidence with γ-rays from astrophysical sources is performed using an unbinned likelihood-ratio maximization method [13,14,10,11]. The goal is to determine the relative contribution of background and signal components for a given direction in the sky and at a given time.…”

“…Additionally, N S and N B are unknown signal events and known background rate (a priori when building L) respectively [9]. The N S is fitted by maximizing the likelihood L. The background PDFs are all computed using data only [10,11].…”

“…Cuts on these parameters are used to improve the signal-to-noise ratio [9]. Atmospheric ν-s are the main source of background; an additional source of background is due to the mis-reconstructed atmospheric µ-s [10,11].…”

“…The latest results of a search which extends previously presented results [9] to a longer period that covers ANTARES data collected between November 2014 and December 2017 are discussed. As the nearest blazars to Earth, both are excellent sources to test the blazar-neutrino connection scenario, especially during flares where time-dependent ν searches may have a higher detection probability because of a reduced background [9,10,11].…”

Search for high-energy neutrino emission from Mrk 421 and Mrk 501 with the ANTARES neutrino telescope

“…A search for neutrino candidades in coincidence with γ-rays from astrophysical sources is performed using an unbinned likelihood-ratio maximization method [5,6,7]. The goal is to determine the relative contribution of background and signal components for a given direction in the sky and at a given time.…”