GCN Circular 45920
Subject
GRB 261011A: VLT/X-shooter redshift constraints
Event
Date
2026-10-12T07:37:55Z (a month ago)
From
Nicolas Monsalves <n.m.monsalvesgonzalez@gmail.com>
Via
Web form
Nicolas Monsalves, Yu-Han Yang and Eleonora Troja (U Rome) report on behalf of the ERC BHianca team:
We observed the field of GRB 261011A (Huang et al., GCN 45895; Cenko et al., GCN 45896) with the X-Shooter spectrograph on the ESO VLT UT3 (Melipal). Observations began at T+13.4 hours and obtained a total of 4 x 600 s spectra at an average airmass of about 1.1.
At the position of the optical counterpart (Cenko et al., GCN 45896; O'Neill et al., GCN 45897; Fu et al., GCN 45898; Izzo et al., GCN 45899; Wu et al., GCN 45900; Yin et al., GCN 45901; Shi et al., GCN 45903; Aryan et al., GCN 45904; Arya et al., GCN 45907; Izzo et al., GCN 45909; Huang et al., GCN 45913; Bochenek et al., GCN 45914; Li et al., GCN 45915; Zhao et al., GCN 45916; Takahashi et al., GCN 45917) we detect a faint continuum in all three arms.
In the UVB arm we detect continuum emission down to ~4270 Angstrom, which sets a robust upper limit to the redshift z<3.7. The flux remains consistent with zero between ~4000 and ~4270 Angstrom,with a weak signal reappearing blueward of ~4000 Angstrom. Interpreting this broad feature as a damped Lyman-alpha absorption trough, we infer a tentative redshift of z=2.405.
We thank the staff at the VLT, for the rapid execution of these observations.