GCN 44117: EP260321a: JinShan near-infrared observations

2026-03-26T07:29:39.155Z | rev 2 | event: EP260321a
Lin. B. He, X. Liu (NAOC), S.Y. Fu, A.D. Zhu, L. Lei, H.Z. Wu, W.H. Lei, Y.C. Zou (HUST), J. An, S.Q. Jiang, Z.P. Zhu, D. Xu (NAOC), J.Z. Liu (XAO), Zhong-Nan Dong, Bin Ma (Sun Yat-sen University)

We observed the field of EP260321a (Huang et. al, GCN 44068) using the JinShan 100C telescope, equipped with the INS Mars640 SWIR Camera, located at Altay, Xinjiang, China. Observation started at 2026-03-25 15:12:02 UT, i.e., 4.11 days post-burst, and a series of J-band frames were obtained.

The optical counterpart (Lee et al., GCN 44070; Tanvir et al., GCN 44082; Moran et al., GCN 44083; Ahumada et al., GCN 44084; Liu et al., GCN 44087; de Ugarte Postigo et al., GCN 44091; Xu et al., GCN 44092; Pankov et al. GCN 44103; Corcoran et al., GCN 44105; Rastinejad et al., GCN 44107; Gao et al., GCN 44110) was detected in our stacked J-band frame with magnitude J ~ 17.2 (Vega) at a mid-time 99.3 hrs post-burst. The magnitude was calibrated with the nearby 2MASS catalog and without the Galactic extinction correction.

We acknowledge the excellent support from T.Q. Chen and J.F. Zhang for enabling these observations.