- Abbasi, R;
- Ackermann, M;
- Adams, J;
- Agarwalla, SK;
- Aguilar, JA;
- Ahlers, M;
- Alameddine, JM;
- Amin, NM;
- Andeen, K;
- Argüelles, C;
- Ashida, Y;
- Athanasiadou, S;
- Ausborm, L;
- Axani, SN;
- Bai, X;
- Balagopal, AV;
- Baricevic, M;
- Barwick, SW;
- Bash, S;
- Basu, V;
- Bay, R;
- Beatty, JJ;
- Becker Tjus, J;
- Beise, J;
- Bellenghi, C;
- Benning, C;
- BenZvi, S;
- Berley, D;
- Bernardini, E;
- Besson, DZ;
- Blaufuss, E;
- Bloom, L;
- Blot, S;
- Bontempo, F;
- Book Motzkin, JY;
- Boscolo Meneguolo, C;
- Böser, S;
- Botner, O;
- Böttcher, J;
- Braun, J;
- Brinson, B;
- Brostean-Kaiser, J;
- Brusa, L;
- Burley, RT;
- Butterfield, D;
- Campana, MA;
- Caracas, I;
- Carloni, K;
- Carpio, J;
- Chattopadhyay, S;
- Chau, N;
- Chen, Z;
- Chirkin, D;
- Choi, S;
- Clark, BA;
- Coleman, A;
- Collin, GH;
- Connolly, A;
- Conrad, JM;
- Coppin, P;
- Corley, R;
- Correa, P;
- Cowen, DF;
- Dave, P;
- De Clercq, C;
- DeLaunay, JJ;
- Delgado, D;
- Deng, S;
- Desai, A;
- Desiati, P;
- de Vries, KD;
- de Wasseige, G;
- DeYoung, T;
- Diaz, A;
- Díaz-Vélez, JC;
- Dierichs, P;
- Dittmer, M;
- Domi, A;
- Draper, L;
- Dujmovic, H;
- Dutta, K;
- DuVernois, MA;
- Ehrhardt, T;
- Eidenschink, L;
- Eimer, A;
- Eller, P;
- Ellinger, E;
- El Mentawi, S;
- Elsässer, D;
- Engel, R;
- Erpenbeck, H;
- Evans, J;
- Evenson, PA;
- Fan, KL;
- Fang, K;
- Farrag, K;
- Fazely, AR;
- Fedynitch, A;
- Feigl, N;
- Fiedlschuster, S
Active galactic nuclei (AGN) are promising candidate sources of high-energy astrophysical neutrinos, since they provide environments rich in matter and photon targets where cosmic-ray interactions may lead to the production of gamma rays and neutrinos. We searched for high-energy neutrino emission from AGN using the Swift-BAT Spectroscopic Survey catalog of hard X-ray sources and 12 yr of IceCube muon track data. First, upon performing a stacked search, no significant emission was found. Second, we searched for neutrinos from a list of 43 candidate sources and found an excess from the direction of two sources, the Seyfert galaxies NGC 1068 and NGC 4151. We observed NGC 1068 at flux ϕνμ+ν¯μ = 4.02-+1.521.58 × 10-11 TeV−1 cm−2 s−1 normalized at 1 TeV, with a power-law spectral index γ = 3.10-+0.220.26, consistent with previous IceCube results. The observation of a neutrino excess from the direction of NGC 4151 is at a posttrial significance of 2.9σ. If interpreted as an astrophysical signal, the excess observed from NGC 4151 corresponds to a flux ϕνμ+ν¯μ = 1.51-+0.810.99 × 10-11 TeV−1 cm−2 s−1 normalized at 1 TeV and γ = 2.83-+0.280.35