A Search for Kilonovae in the Dark Energy Survey

Doctor, Z and Kessler, R and Chen, H Y and Farr, B and Finley, D A and Foley, R J and Goldstein, D A and Holz, D E and Kim, A G and Morganson, E and Sako, M and Scolnic, D and Smith, M and Soares-Santos, M and Spinka, H and Abbott, T M C and Abdalla, F B and Allam, S and Annis, J and Bechtol, K and Benoit-Lévy, A and Bertin, E and Brooks, D and Buckley-Geer, E and Burke, D L and Rosell, A C and Kind, M C and Carretero, J and Cunha, C E and D’Andrea, C B and Costa, L N da and DePoy, D L and Desai, Shantanu and Diehl, H T and Drlica-Wagner, A and Eifler, T F and Frieman, J and García-Bellido, J and Gaztanaga, E and Gerdes, D W and Gruendl, R A and Gschwend, J and Gutierrez, G and James, D J and Krause, E and Kuehn, K and Kuropatkin, N and Lahav, O and Li, T S and Lima, M and Maia, M A G and March, M and Marshall, J L and Menanteau, F and Miquel, R and Neilsen, E and Nichol, R C and Nord, B and Plazas, A A and Romer, A K and Sanchez, E and Scarpine, V and Schubnell, M and Sevilla-Noarbe, I and Smith, R C and Sobreira, F and Suchyta, E and Swanson, M E C and Tarle, G and Walker, A R and Wester, W (2017) A Search for Kilonovae in the Dark Energy Survey. Astrophysical Journal, 837 (1). p. 57. ISSN 1538-4357

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Abstract

The coalescence of a binary neutron star pair is expected to produce gravitational waves (GW) and electromagnetic radiation, both of which may be detectable with currently available instruments. We describe a search for a predicted r-process optical transient from these mergers, dubbed the "kilonova" (KN), using griz broadband data from the Dark Energy Survey Supernova Program (DES-SN). Some models predict KNe to be redder, shorter-lived, and dimmer than supernovae (SNe), but the event rate of KNe is poorly constrained. We simulate KN and SN light curves with the Monte-Carlo simulation code SNANA to optimize selection requirements, determine search efficiency, and predict SN backgrounds. Our analysis of the first two seasons of DES-SN data results in 0 events, and is consistent with our prediction of 1.1 +/- 0.2 background events based on simulations of SNe. From our prediction, there is a 33% chance of finding 0 events in the data. Assuming no underlying galaxy flux, our search sets 90% upper limits on the KN volumetric rate of 1.0 x 10(7) Gpc(-3) yr(-1) for the dimmest KN model we consider (peak i-band absolute magnitude M-i = -11.4 mag) and 2.4 x 10(4) Gpc-3 yr-1 for the brightest (Mi = -16.2 mag). Accounting for anomalous subtraction artifacts on bright galaxies, these limits are similar to 3 times higher. This analysis is the first untriggered optical KN search and informs selection requirements and strategies for future KN searches. Our upper limits on the KN rate are consistent with those measured by GW and gamma-ray burst searches.

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