{
  "bibcode": "2023GCN.33521....1P",
  "body": "Danielle Pieterse (Radboud Univ.), Johan P. U. Fynbo (DAWN/NBI), Luca \nIzzo (DARK/NBI), Jesse Palmerio (GEPI, Obs. Paris and IAP), Andrea \nSaccardi (GEPI, Obs. Paris), Nial R. Tanvir (Leicester), Dong Xu \n(NAO/CAS), Zi-Pei Zhu (NAOC, HUST), Daniele B. Malesani (Radboud univ. \nand DAWN/NBI) and Pall Jakobsson (Univ. Iceland), report on behalf of \nthe Stargate collabaration:\n\nWe observed the field of GRB 230325A (Moss et al., GCN 33516) using the \nESO VLT UT3 (Melipal) equipped with the X-shooter spectrograph. Images \nwere also taken with the acquisition camera. An object is visible \nconsistent with the UVOT-enhanced XRT position (Goad et al., GCN 33518), \nat coordinates (0.5\" error):\n\nRA = 19:47:23.98�� (J2000)\nDec = -46:04:33.3�� (J2000)\n\nFor this object, we measure the following magnitudes (calibrated against \nnearby objects from the Legacy Survey; Dey et al. 2019, AJ, 157, 168):\n\nFilter Mean date�������������� Time since GRB�� Exptime�� Magnitude\n �������������� (UT)������������������������ (days)������������������ (s)���������� (AB)\n--------------------------------------------------------------\nr���������� 2023 Mar 25.371�� 0.235�������������������� 45������������ 22.70 +- 0.08\nz���������� 2023 Mar 25.372�� 0.236�������������������� 60������������ 22.35 +- 0.08\ng���������� 2023 Mar 25.374�� 0.237�������������������� 45������������ 22.16 +- 0.23\n\nAn object is present at a consistent location in the Legacy Survey, but \nsignificantly fainter, and it is the likely GRB host galaxy. The \nconsistency with the XRT position and the flux increase compared to the \nLegacy Survey confirm that the object we see in the X-shooter images is \nthe optical afterglow of GRB 230325A.\n\n\nSpectroscopy was carried out, covering the wavelength range 3000-21000 \nAA, and consisting of 2 exposures by 600 s each. The observation mid \ntime was 2023 Mar 25.383 UT (0.247 days after the GRB).\n\nOnly a faint continuum is detected from this source, which allows us to \nset a redshift upper limit z <~ 3. In addition, two emission lines are \nvisible, which are consistent with Halpha and [O III] 5008 at a common \nredshift z = 1.664, which we suggest to be the GRB redshift.\n\nWe acknowledge excellent support from the ESO observing staff in \nParanal, in particular Fuyan Bian and Konrad Tristram.",
  "circularId": 33521,
  "createdOn": 1679777767000,
  "email": "d.malesani@astro.ru.nl",
  "subject": "GRB 230325A: X-shooter optical afterglow and redshift",
  "submitter": "Daniele B Malesani at Radboud U  <d.malesani@astro.ru.nl>",
  "eventId": "GRB 230325A"
}