GCN 45016: EP260618a: Liverpool Telescope optical observations
2026-06-20T14:22:19.073Z | rev 0
A. Bochenek, D. A. Perley (LJMU), report:
We observed the field of EP260618a (Yang et al., GCN 44978; Jiang et al., GCN 44991) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 6x150s exposures in SDSS griz filters, starting at 2026-06-19 02:32:19 UT, approximately 17.96 hours after EP trigger.
Some z-band exposures had to be discarded prior to stacking. We detect a source in the images in all filters at the position reported by Becerra et al. (GCN 44988), also Malesani et al. (GCN 44990), Amram et al. (GCN 44994) and He et al. (GCN 45012). The photometry is:
| MJD (mid) | T_mid-T_0 | Filter | Mag. (AB) |
|---------------|-------------|-----------|---------------|
| 61210.11078 | 18.08 h | g | 22.47 ± 0.24 |
| 61210.12120 | 18.34 h | r | 22.03 ± 0.12 |
| 61210.13221 | 18.59 h | i | 21.62 ± 0.11 |
| 61210.14403 | 18.88 h | z | 21.48 ± 0.26 |
The photometry is in the AB magnitude system, was calibrated using nearby PanSTARRS secondary standards and was not corrected for extinction.
GCN 44994: EP260618a: OHP/T193 optical observations
2026-06-19T11:05:46.833Z | rev 0
P. Amram (LAM/Pytheas/AMU), C. Adami (LAM/Pytheas/AMU), D. Russeil (LAM/Pytheas/AMU) report on behalf of a larger collaboration:
We observed the field of EP260618a (Yang et al., GCN44978; see also Fermi GBM Team
, GCN44973 and Jiang et al., GCN44991) using the T193cm telescope at Observatoire de Haute-Provence (France) with the MISTRAL spectro-imager. We obtained 2x10 minutes of exposure in the r-band starting at 2026-06-18T21:12:40 UT (12.63 hr after the Yang et al. trigger).
In the stacked images, the optical counterpart detected by Becerra et al. (GCN44988) and Malesani et al. (GCN44990) is visible with preliminary magnitude of:
r = 21.86 +/- 0.09 mag
in good agreement with their measurements.
The photometric calibration was performed using nearby stars from the PanSTARRS catalog and the STDWeb/STDPipe tools (Karpov 2025), is in the AB system, and is not corrected for Galactic extinction.
We acknowledge the excellent support from Observatoire de Haute-Provence and in particular Stephane Favard. We acknowledge the excellent support of J. Schmitt and J.C. Brunel in the recent MISTRAL upgrade.