{
  "bibcode": "2024GCN.38293....1Z",
  "subject": "EP trigger ID 01709065118: Keck/LRIS spectroscopic observations",
  "createdOn": 1732246663271,
  "submitter": "Weikang Zheng at UC Berkeley <weikang@berkeley.edu>",
  "body": "WeiKang Zheng, Thomas G. Brink, Alexei V. Filippenko (UC Berkeley), and Yi\nYang (Tsinghua Univ., Beijing), report on behalf of the KAIT GRB team:\n\n\nWe observed the M-type star 1RXS J225817.2-110434, the optical counterpart\nof an EP flare event (trigger ID 01709065118; Zhou et al., GCN 37715; Zheng\net al., GCN 37733), with the Low Resolution Imaging Spectrometer (LRIS; Oke\net al. 1995) on the Keck I 10 m telescope. Observations were performed on\nOct. 5, 2024 UTC, with the 600/4000 grism and 400/8500 grating. Two spectra\nwith exposure times of 60 s and 80 s were obtained at 07:26 and 09:46 UTC,\ncorresponding to 1.72 and 4.05 hr (respectively) after the EP/WXT trigger\ntime. The spectra exhibit a red continuum flux with strong superposed\nhydrogen Balmer emission lines as well as Ca II H&K and TiO emission lines,\nconsistent with a typical dMe star spectrum. Moreover, the flux of the\nBalmer emission lines dropped by nearly half between the two epochs. The\ncontinuum below 3500 Ang also dropped significantly. This is consistent\nwith the light-curve behavior reported by Lick/KAIT (Zheng et al., GCN\n37733), where the star brightness decreased after the EP/WXT trigger.\n\n\nThe data presented herein were obtained at the W. M. Keck Observatory,\nwhich is operated as a scientific partnership among the California\nInstitute of Technology, the University of California, and the National\nAeronautics and Space Administration. The Observatory was made possible by\nthe generous financial support of the W. M. Keck Foundation. The authors\nwish to recognize and acknowledge the very significant cultural role and\nreverence that the summit of Maunakea has always had within the indigenous\nHawaiian community. We are most fortunate to have the opportunity to\nconduct observations from this mountain.\n",
  "circularId": 38293,
  "submittedHow": "email"
}