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Deep and rapid observations of strong-lensing galaxy clusters within the sky localization of GW170814

Smith, G.P.; Bianconi, M.; Jauzac, M.; Richard, J.; Robertson, A.; Berry, C.P.L.; Massey, R.; Sharon, K.; Farr, W.M.; Veitch, J.

Deep and rapid observations of strong-lensing galaxy clusters within the sky localization of GW170814 Thumbnail


G.P. Smith

M. Bianconi

J. Richard

A. Robertson

C.P.L. Berry

K. Sharon

W.M. Farr

J. Veitch


We present observations of two strong-lensing galaxy clusters located within the 90 per cent credible sky localization maps released following LIGO-Virgo’s discovery of the binary black hole (BH-BH) gravitational wave (GW) source GW170814. Our objectives were (1) to search for candidate electromagnetic (EM) counterparts to GW170814 under the hypothesis that it was strongly-lensed, and thus more distant and less massive than inferred by LIGO-Virgo, and (2) to demonstrate the feasibility of rapid target of opportunity observations to search for faint lensed transient point sources in crowded cluster cores located within GW sky localizations. Commencing 20 hours after discovery, and continuing over 12 nights, we observed Abell 3084 (z = 0.22) and SMACS J0304.3−4401 (z = 0.46) with GMOS on the Gemini-South telescope, and Abell 3084 with MUSE on ESO’s Very Large Telescope. We detect no candidate EM counterparts in these data. Calibration of our photometric analysis methods using simulations yield 5σ detection limits for transients in difference images of the cores of these clusters of i = 25. This is the most sensitive photometric search to date for counterparts to GW sources, and rules out the possibility that GW170814 was lensed by these clusters with a kilonova-like EM counterpart. Based on the detector frame masses of the compact objects, and assuming that at least one Neutron Star (NS) is required in the merging system to produce a kilonova-like counterpart, implies that GW170814 was neither a NS-NS nor NS-BH merger at z > 8 lensed by either of these clusters. Also, in the first ever emission line search for counterparts to GW sources, we detected no lines down to a 5σ detection limit of 5 × 10−17erg s−1 cm−2.


Smith, G., Bianconi, M., Jauzac, M., Richard, J., Robertson, A., Berry, C., …Veitch, J. (2019). Deep and rapid observations of strong-lensing galaxy clusters within the sky localization of GW170814. Monthly Notices of the Royal Astronomical Society, 485(4), 5180-5191.

Journal Article Type Article
Acceptance Date Feb 13, 2019
Online Publication Date Mar 8, 2019
Publication Date Jun 30, 2019
Deposit Date Mar 18, 2019
Publicly Available Date Mar 20, 2019
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 485
Issue 4
Article Number 5180-5191
Pages 5180-5191
Related Public URLs


Accepted Journal Article (2.3 Mb)

Copyright Statement
© 2019 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society.

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