{
  "eventId": "EP260610b",
  "subject": "EP260610b: GTC likely spectroscopic redshift z = 1.10",
  "createdOn": 1781189564968,
  "circularId": 44915,
  "submittedHow": "web",
  "body": "A. P. C. van Hoof (Radboud), D. Mata Sanchez (IAC and ULL), G. Corcoran (UCD), A. J. Levan (Radboud and Warwick), P. G. Jonker (Radboud), D. B. Malesani (DAWN/NBI and Radboud), David Garcia Alvarez (GTC), report on behalf of a larger collaboration:\n\nWe observed the optical counterpart (Levan et al., GCN 44897; Xin et al., GCN 44900; Zhu et al., GCN 44902; Burkhonov et al., GCN 44904; Moreno Mendez et al., GCN 44906) of the fast X-ray transient EP260610b (Wu et al., GCN 44895; Guo et al., GCN 44912) using the Gran Telescopio Canarias (GTC) located in the island of La Palma (Canary Islands, Spain), equipped with the OSIRIS+ spectrograph. A sequence of 3x1200 s observations was secured using grism R1000B, which covers the wavelength range 3600-7790 AA. The observation mid time was 2026 Jun 11.183 UT (15.58 hr after the EP/WXT trigger).\n\nIn the acquisition image (taken 14.96 hr after trigger), we measure an AB magnitude r = 23.38 +- 0.11, calibrated against the Pan-STARRS catalog, and not corrected for Galactic extinction. The delivered seeing was 0.8\".\n\nWeak continuum is detected across the entire wavelength range. From the lack of hydrogen absorption, we can set a firm upper limit to the redshift z < 2.1. Weak absorption features can also be identified matching Mg II and Fe II at z = 1.10. Line-stacking analysis confirms a significant absorption system at this redshift, which we suggest to be the likely redshift of EP260610b.\n",
  "format": "text/plain",
  "submitter": "Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani@nbi.ku.dk>"
}