TITLE: GCN CIRCULAR NUMBER: 44351 SUBJECT: EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring DATE: 26/04/20 04:03:59 GMT FROM: Alberto Castro-Tirado at Inst.de Astro. de Andalucia <ajct@iaa.es> S. Guziy, F. J. Aceituno, A. J. Castro-Tirado, M.D. Caballero-García, M. Gritsevich, I. Pérez-García, R. Sánchez-Ramírez, S.-Y. Wu (IAA-CSIC) and A. Fernández-Martin and M. M. Sánchez-Andújar (CAHA), on behalf of a larger collaboration,report: We observed EP260416a (Hu et al., GCN 44307) with both the 1.5m telescope at Observatorio de Sierra Nevada (OSN) and the 2.2m telescope at Calar Alto Observatory (CAHA), in Southern Spain. A series of 300 s BVRI exposures were obtained at the 1.5m OSN starting on Apr 17, 21:04 UT, complemented by one 100s i-band image at the 2.2m CAHA, on Apr 18, 01:04 UT., i.e. 39.6 h and 43.6 h respectively, after the initial trigger. The optical counterpart (Ducoin et al., GCN 44310; Li et al., GCN 44315; Hua et al., GCN 44318; Lee et al., GCN 44319; Zheng et al., GCN 44321; Martin-Carrillo et al., GCN 44328; Li et al., GCN 44334, He et al. GCN 44336, An et al. GCN 44339, Jelinek et al. GCN 44341) is well detected in our images. We measure B = 21.08 +/- 0.14 and R = 20.99 +/- 0.07 on Apr 17, 21:15 UT and I = 19.82 +/-0.18 on Apr 18, 01:04 UT (none corrected for Galactic extinction). The night after, a second epoch BVRI observation was conducted at the 1.5m OSN, for which measure R = 21.59 +/- 0.10 on Apr 18, 20:14 UT. Our measurement is consistent with the continued fading of the afterglow. Further optical monitoring is being carried out. View this GCN Circular online at https://gcn.nasa.gov/circulars/44351. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...