GCN Circular 44514
Subject
GRB 260509A: NOT spectroscopic redshift upper limit z < 1.95
Event
Date
2026-05-10T11:07:26Z (5 months ago)
From
Gregory Corcoran at University College Dublin <gregory.corcoran@ucdconnect.ie>
Via
Web form
G. Corcoran (UCD), A. Saccardi (CEA/Irfu), B. Schneider (LAM), D. B. Malesani (DAWN/NBI and Radboud), N. R. Tanvir (Univ. Leicester), Kostas Valeckas (NOT and NBI), V. Vuolteenaho (NOT and Oulu Univ.), report on behalf of a larger collaboration:
We observed the optical counterpart (O'Neill et al., GCN 44505; Saccardi et al. GCN 44506; Wu et al. GCN 44507; Sánchez Álvarez et al. GCN 44509; Zheng et al. GCN 44510; Lipunov et al. GCN 44512; Belkin GCN 44513) of the SVOM/ECLAIRs GRB 260509A (Götz et al., GCN 44504) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC spectrograph.
A spectrum consisting of 4x1200 s exposures was secured starting on 2026 May 10 at 00:22:16 UT (2.52 hr after the SVOM trigger), using grism #4 with the WG345 356_LP order blocker which covers the wavelength range 3400-9600 AA.
Based on a preliminary reduction of the spectra using PyLongslit (Valeckas et al. 2025 10.21105/joss.09264), a continuum is detected down to ~3600 AA, setting an upper limit to the redshift z < 1.95 based on the lack of HI absorption. We do not identify clear metal absorption features despite good S/N.
Further analysis is ongoing.