TITLE:   GCN CIRCULAR
NUMBER:  37818
SUBJECT: GRB 241018A: LCO/0.4m optical upper limits
DATE:    24/10/18 18:49:26 GMT
FROM:    Damien Turpin at CEA-Saclay <dturpin-astro@hotmail.com>

D. Turpin (CEA/Irfu), J. T. Palmerio (CEA/Irfu, GEPI/Obs. de Paris), A. Saccardi (GEPI/Obs. de Paris, CEA/Irfu), S. Vergani (GEPI/Obs. de Paris), S. Basa (UAR Pytheas, OHP, LAM), E. Le Floc'h (CEA Paris-Saclay, DAp/AIM) on behalf of a larger collaboration.

We observed the field of GRB 241018A detected by SVOM (Atteia et al., GCN 37812) with the LCO 0.4m telescope at the Haleakala Observatory equipped with the QHY600 CMOS camera . Our observation started at 2024-10-18 12:53:32 (T - TGRB ~ 1 h) with 2 series of 5 x 120s in sdss-g and r filter.

We did not detect any uncatalogued optical source in the error region of SVOM/ECLAIRs (Atteia et al., GCN 37812) and at the position of the SVOM/MXT afterglow candidate (Maggi et al., GCN 37814). We derived the following upper limit (5 sigma, AB system) calibrated with the PanSTARRS DR1 catalog and not corrected from the significant galactic extinction E(B-V) = 0.75:

Tmid-T0   | mag (AB)   | filter |
1.07h     |19.8 (U.L.) | sdssg  |
1.07h     |19.6 (U.L.) | sdssr  |

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 101004719.