Designing an optimal kilonova search using DECam for gravitational-wave events

C. R. Bom*, J. Annis, A. Garcia, A. Palmese, N. Sherman, M. Soares-Santos, L. Santana-Silva, R. Morgan, K. Bechtol, T. Davis, H. T. Diehl, S. S. Allam, T. G. Bachmann, B. M. O. Fraga, J. García-Bellido, M. S. S. Gill, K. Herner, C. D. Kilpatrick, M. Makler, F. Olivares E.M. E. S. Pereira, J. Pineda, A. Santos, D. L. Tucker, M. P. Wiesner, M. Aguena, O. Alves, D. Bacon, P. H. Bernardinelli, E. Bertin, S. Bocquet, D. Brooks, M. Carrasco Kind, J. Carretero, C. Conselice, M. Costanzi, L. N. da Costa, J. De Vicente, S. Desai, P. Doel, S. Everett, I. Ferrero, J. Frieman, M. Gatti, D. W. Gerdes, D. Gruen, R. A. Gruendl, G. Gutierrez, S. R. Hinton, D. L. Hollowood, K. Honscheid, D. J. James, K. Kuehn, N. Kuropatkin, P. Melchior, J. Mena-Fernández, F. Menanteau, A. Pieres, A. A. Plazas Malagón, M. Raveri, M. Rodriguez-Monroy, E. Sanchez, B. Santiago, I. Sevilla-Noarbe, M. Smith, E. Suchyta, M. E. C. Swanson, G. Tarle, C. To, N. Weaverdyck

*Corresponding author for this work

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We address the problem of optimally identifying all kilonovae detected via gravitational-wave emission in the upcoming LIGO/Virgo/KAGRA observing run, O4, which is expected to be sensitive to a factor of ∼7 more binary neutron star (BNS) alerts than previously. Electromagnetic follow-up of all but the brightest of these new events will require >1 m telescopes, for which limited time is available. We present an optimized observing strategy for the DECam during O4. We base our study on simulations of gravitational-wave events expected for O4 and wide-prior kilonova simulations. We derive the detectabilities of events for realistic observing conditions. We optimize our strategy for confirming a kilonova while minimizing telescope time. For a wide range of kilonova parameters, corresponding to a fainter kilonova compared to GW170817/AT 2017gfo, we find that, with this optimal strategy, the discovery probability for electromagnetic counterparts with the DECam is ∼80% at the nominal BNS gravitational-wave detection limit for O4 (190 Mpc), which corresponds to an ∼30% improvement compared to the strategy adopted during the previous observing run. For more distant events (∼330 Mpc), we reach an ∼60% probability of detection, a factor of ∼2 increase. For a brighter kilonova model dominated by the blue component that reproduces the observations of GW170817/AT 2017gfo, we find that we can reach ∼90% probability of detection out to 330 Mpc, representing an increase of ∼20%, while also reducing the total telescope time required to follow up events by ∼20%.

Original languageEnglish
Article number122
Number of pages21
JournalAstrophysical Journal
Issue number2
Publication statusPublished - 8 Jan 2024


  • UKRI
  • STFC

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