This paper proposes to exploit gravitational lensing effects to improve the sensitivity of neutrino telescopes to the intrinsic neutrino emission of distant blazar populations. This strategy is illustrated with a search for cosmic neutrinos in the direction of four distant and gravitationally lensed Flat-Spectrum Radio Quasars. The magnification factor is estimated for each system assuming a singular isothermal profile for the lens. Based on data collected from 2007 to 2012 by the ANTARES neutrino telescope, the strongest constraint is obtained from the lensed quasar B0218+357, providing a limit on the total neutrino luminosity of this source of 1.08× 1046 erg s-1. This limit is about one order of magnitude lower than those previously obtained in the ANTARES standard point source searches with non-lensed Flat-Spectrum Radio Quasars.
Adrián-Martínez, S., Albert, A., André, M., Anton, G., Ardid, M., Aubert, J. J., … Falco, E. E. (2014). Constraining the neutrino emission of gravitationally lensed Flat-Spectrum Radio Quasars with ANTARES data. Journal of Cosmology and Astroparticle Physics, 2014(11). https://doi.org/10.1088/1475-7516/2014/11/017