@article{0675722d03d24287b1112d3226dc1843,
title = "An archival search for neutron-star mergers in gravitational waves and very-high-energy gamma rays",
abstract = "The recent discovery of electromagnetic signals in coincidence with neutron-star mergers has solidified the importance of multimessenger campaigns in studying the most energetic astrophysical events. Pioneering multimessenger observatories, such as LIGO/Virgo and IceCube, record many candidate signals below the detection significance threshold. These sub-threshold event candidates are promising targets for multimessenger studies, as the information provided by them may, when combined with contemporaneous gamma-ray observations, lead to significant detections. Here we describe a new method that uses such candidates to search for transient events using archival very-high-energy gamma-ray data from imaging atmospheric Cherenkov telescopes (IACTs). We demonstrate the application of this method to sub-threshold binary neutron star (BNS) merger candidates identified in Advanced LIGO{\textquoteright}s first observing run. We identify eight hours of archival VERITAS observations coincident with seven BNS merger candidates and search them for TeV emission. No gamma-ray emission is detected; we calculate upper limits on the integral flux and compare them to a short gamma-ray burst model. We anticipate this search method to serve as a starting point for IACT searches with future LIGO/Virgo data releases as well as in other sub-threshold studies for multimessenger transients, such as IceCube neutrinos. Furthermore, it can be deployed immediately with other current-generation IACTs, and has the potential for real-time use that places a minimal burden on experimental operations. Lastly, this method may serve as a pilot for studies with the Cherenkov Telescope Array, which has the potential to observe even larger fields of view in its divergent pointing mode.",
author = "{Columbia Experimental Gravity Group (GECo)} and {VERITAS collaboration} and Adams, {C. B.} and W. Benbow and A. Brill and Buckley, {J. H.} and M. Capasso and Christiansen, {J. L.} and Chromey, {A. J.} and Daniel, {M. K.} and M. Errando and A. Falcone and Farrell, {K. A.} and Q. Feng and Finley, {J. P.} and L. Fortson and A. Furniss and A. Gent and C. Giuri and D. Hanna and T. Hassan and O. Hervet and J. Holder and G. Hughes and Humensky, {T. B.} and W. Jin and P. Kaaret and M. Kertzman and D. Kieda and S. Kumar and Lang, {M. J.} and M. Lundy and G. Maier and McGrath, {C. E.} and P. Moriarty and R. Mukherjee and D. Nieto and M. Nievas-Rosillo and S. O{\textquoteright}Brien and Ong, {R. A.} and Otte, {A. N.} and N. Park and S. Patel and K. Pfrang and M. Pohl and Prado, {R. R.} and E. Pueschel and J. Quinn and K. Ragan and Reynolds, {P. T.} and D. Ribeiro and E. Roache",
note = "Funding Information: This research is supported by grants from the U.S. Department of Energy Office of Science, the U.S. National Science Foundation and the Smithsonian Institution, by NSERC in Canada, and by the Helmholtz Association in Germany. This research used resources provided by the Open Science Grid, which is supported by the National Science Foundation and the U.S. Department of Energy{\textquoteright}s Office of Science, and resources of the National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science User Facility operated under Contract No. DE-AC02-05CH11231. We acknowledge the excellent work of the technical support staff at the Fred Lawrence Whipple Observatory and at the collaborating institutions in the construction and operation of the instrument. The Columbia and Barnard authors thank Columbia University in the City of New York and Barnard College for their support, and acknowledge the generous support of the National Science Foundation under grant PHY-1806554. Their Alabama colleagues thank the University of Alabama and acknowledge the support of the National Science Foundation under grant PHY-1914579. I. B. acknowledges the support of the National Science Foundation under grant PHY-1911796, the Alfred P. Sloan Foundation, and the University of Florida. The Columbia Experimental Gravity group is grateful for the generous support of the National Science Foundation under grant PHY-2012035. Publisher Copyright: {\textcopyright} 2021. The American Astronomical Society. All rights reserved.",
year = "2021",
month = sep,
day = "10",
doi = "10.3847/1538-4357/ac0623",
language = "English (US)",
volume = "918",
journal = "Astrophysical Journal",
issn = "0004-637X",
publisher = "IOP Publishing Ltd.",
number = "2",
}