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GCN Circular 35093

Subject
GRB 231117A: Keck spectroscopy of afterglow candidate
Date
2023-11-18T06:10:57Z (3 months ago)
From
Tomas Ahumada Mena at Caltech <tahumada@caltech.edu>
Via
Web form
Tomas Ahumada, Yashvi Sharma(Caltech) on behalf of a larger collaboration: 

We report optical spectroscopic observations of the candidate counterpart of the short GRB 231117A (GCN 35083, 35071) with the Low Resolution Imaging Spectrometer (LRIS, Oke et al. 95) at the Keck I Observatory (C358, PI: Kasliwal). Observations started 2023-11-18 05:19:00 (~1.1 days after the burst), and consisted of 2x900 exposures with the 400/3400 grism and 400/8500 grating.

The spectrum shows narrow galaxy lines at redshift of z = 0.257 (H, [O II], [O III], N II). We also see narrow absorption lines consistent with MgII(2796,2803) doublet at this redshift. We note the spectrum shows a blue continuum. 

We thank Michael Lundquist and the Keck team for their support during this Target of Opportunity trigger.

The data presented herein were obtained at the W. M. Keck Observatory, 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.
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