TITLE:   GCN CIRCULAR
NUMBER:  46174
SUBJECT: EP261015a/SN 2026ahoa: spectroscopic redshift confirmation z=0.310
DATE:    26/11/06 16:28:50 GMT
FROM:    Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo@ucd.ie>

G. Corcoran (UCD), A. Martin-Carrillo (UCD), A. J. Levan (Radboud and Warwick), D. B. Malesani (DAWN/NBI and Radboud), M. De Pasquale (U. of Messina), report on behalf of the Stargate collaboration:

We observed the optical counterpart SN 2026ahoa (Corcoran et al., GCN 46131; Kumnurdmanee et al., GCN 46153) to the Einstein Probe Fast X-ray transient EP261015a (Li et al., GCN 45956) using the ESO VLT UT1 (Antu) equipped with the FORS2 instrument. A spectroscopic sequence of 4x600 s were obtained using the 1200R grating with the GG435 order blocker, covering the wavelength range of 5870-7150 AA, starting at 01:29:30 UT on 2026-11-06 (21.5 days after EP trigger). The position angle of the slit was set to cover both the position of the transient and that of the host galaxy nucleus.

In a preliminary reduction, we clearly identify H-beta and [OIII] 5007 at a redshift consistent with that mentioned in Corcoran et al.  (GCN 46131), with a refined redshift z = 0.310. We note that the emission lines are present at both the location of the supernova as well as over the galaxy itself with a slight velocity difference between the two.

We acknowledge the excellent support from the ESO observing staff in Paranal, in particular Martina Baratella and Juan Carlos Olivares.