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Discovery of the Optical Afterglow and Host Galaxy of Short GRB 181123B at z = 1.754: Implications for Delay Time Distributions

Paterson, K. and Fong, W. and Nugent, A. and Rouco Escorial, A. and Leja, J. and Laskar, T. and Chornock, R. and Miller, A. A. and Scharwächter, J. and Cenko, S. B. and Perley, D. and Tanvir, N. R. and Levan, A. and Cucchiara, A. and Cobb, B. E. and De, K. and Berger, E. and Terreran, G. and Alexander, K. D. and Nicholl, M. and Blanchard, P. K. and Cornish, D. (2020) Discovery of the Optical Afterglow and Host Galaxy of Short GRB 181123B at z = 1.754: Implications for Delay Time Distributions. Astrophysical Journal Letters, 898 (2). Art. No. L32. ISSN 2041-8213.

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We present the discovery of the optical afterglow and host galaxy of the Swift short-duration gamma-ray burst (SGRB) GRB 181123B. Observations with Gemini-North starting ≈9.1 hr after the burst reveal a faint optical afterglow with i ≈ 25.1 mag at an angular offset of 0.”59 ± 0.”16 from its host galaxy. Using grizYJHK observations, we measure a photometric redshift of the host galaxy of z = 1.77^(+0.30)_(−0.17). From a combination of Gemini and Keck spectroscopy of the host galaxy spanning 4500–18000 Å, we detect a single emission line at 13390 Å, inferred as Hβ at z = 1.754 ± 0.001 and corroborating the photometric redshift. The host galaxy properties of GRB 181123B are typical of those of other SGRB hosts, with an inferred stellar mass of ≈9.1 × 10⁹ M⊙, a mass-weighted age of ≈0.9 Gyr, and an optical luminosity of ≈0.9L*. At z = 1.754, GRB 181123B is the most distant secure SGRB with an optical afterglow detection and one of only three at z > 1.5. Motivated by a growing number of high-z SGRBs, we explore the effects of a missing z > 1.5 SGRB population among the current Swift sample on delay time distribution (DTD) models. We find that lognormal models with mean delay times of ≈4–6 Gyr are consistent with the observed distribution but can be ruled out to 95% confidence, with an additional ≈one to five Swift SGRBs recovered at z > 1.5. In contrast, power-law models with ∝t⁻¹ are consistent with the redshift distribution and can accommodate up to ≈30 SGRBs at these redshifts. Under this model, we predict that ≈1/3 of the current Swift population of SGRBs is at z > 1. The future discovery or recovery of existing high-z SGRBs will provide significant discriminating power on their DTDs and thus their formation channels.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Paterson, K.0000-0001-8340-3486
Fong, W.0000-0002-7374-935X
Nugent, A.0000-0002-2028-9329
Rouco Escorial, A.0000-0003-3937-0618
Leja, J.0000-0001-6755-1315
Laskar, T.0000-0003-1792-2338
Chornock, R.0000-0002-7706-5668
Miller, A. A.0000-0001-9515-478X
Scharwächter, J.0000-0003-1585-9486
Cenko, S. B.0000-0003-1673-970X
Perley, D.0000-0001-8472-1996
Tanvir, N. R.0000-0003-3274-6336
Levan, A.0000-0001-7821-9369
Cucchiara, A.0000-0001-6455-5660
Cobb, B. E.0000-0002-9118-9448
De, K.0000-0002-8989-0542
Berger, E.0000-0002-9392-9681
Terreran, G.0000-0003-0794-5982
Alexander, K. D.0000-0002-8297-2473
Nicholl, M.0000-0002-2555-3192
Blanchard, P. K.0000-0003-0526-2248
Cornish, D.0000-0002-1533-9037
Additional Information:© 2020 The American Astronomical Society. Received 2020 May 25; revised 2020 July 7; accepted 2020 July 8; published 2020 July 28. We acknowledge Sarah Wellons, Allison Strom, and David Sand for helpful discussions that aided this work and Mansi Kasliwal for facilitating Keck observations. The Fong Group at Northwestern acknowledges support by the National Science Foundation under grant Nos. AST-1814782 and AST-1909358. This work was also supported in part by the National Aeronautics and Space Administration through grant HST-GO-15606.001-A from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555, and Chandra Award No. DD7-18095X, issued by the Chandra X-ray Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of NASA under contract NAS8-03060. M.N. is supported by a Royal Astronomical Society Research Fellowship. A.J.L has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement No. 725246, TEDE; PI: Levan). A.A.M. is funded by the Large Synoptic Survey Telescope Corporation, the Brinson Foundation, and the Moore Foundation in support of the LSSTC Data Science Fellowship Program; he also receives support as a CIERA Fellow from the CIERA Postdoctoral Fellowship Program (Center for Interdisciplinary Exploration and Research in Astrophysics, Northwestern University). J.L. is supported by an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-1701487. K.D.A. acknowledges support provided by NASA through the NASA Hubble Fellowship grant HST-HF2-51403.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. Based on observations obtained at the international Gemini Observatory (PIs: Paterson, Fong; Program IDs GS-2018B-Q-112, GN-2018B-Q-117, GS-2019A-FT-107), a program of NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation on behalf of the Gemini Observatory partnership: the National Science Foundation (United States), National Research Council (Canada), Agencia Nacional de Investigación y Desarrollo (Chile), Ministerio de Ciencia, Tecnología e Innovación (Argentina), Ministério da Ciência, Tecnologia, Inovações e Comunicações (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea). W. M. Keck Observatory and MMT Observatory access was supported by Northwestern University and the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA). Some of the data presented herein were obtained at the W. M. Keck Observatory (PIs: Miller, Fong, Paterson; Programs 2018B_NW254, 2018B_NW249, 2019A_O329), which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Observations reported here were obtained at the MMT Observatory, a joint facility of the University of Arizona and the Smithsonian Institution (PI: Fong; Programs 2018C-UAO-G4, 2019A-UAO-G7, 2020A-UAO-G212-20A). This research was supported in part through the computational resources and staff contributions provided for the Quest high-performance computing facility at Northwestern University, which is jointly supported by the Office of the Provost, the Office for Research, and Northwestern University Information Technology. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester. Facilities: Swift (XRT and UVOT) - Swift Gamma-Ray Burst Mission, Gemini-North (GMOS) - , Gemini-South (GMOS - , FLAMINGOS-2) - , Keck:I (MOSFIRE) - , Keck:II (DEIMOS) - , MMT (MMIRS). -
Funding AgencyGrant Number
NASA ChandraDD7-18095X
Royal Astronomical SocietyUNSPECIFIED
European Research Council (ERC)725246
Large Synoptic Survey Telescope CorporationUNSPECIFIED
Brinson FoundationUNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA)UNSPECIFIED
Northwestern UniversityUNSPECIFIED
NSF Astronomy and Astrophysics FellowshipAST-1701487
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:Gamma-ray bursts
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Gamma-ray bursts (629)
Record Number:CaltechAUTHORS:20200728-095149443
Persistent URL:
Official Citation:K. Paterson et al 2020 ApJL 898 L32
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:104603
Deposited By: Tony Diaz
Deposited On:28 Jul 2020 20:03
Last Modified:28 Jul 2020 20:03

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