R.-Z. Li, B.-T. Wang, J. Mao, and J.-M. Bai (YNAO, CAS) report:
We observed the field of GRB 240411B (Li et al., GCN 36063, T0 at 15:32:54 UT) using the GMG-2.4m telescope at the Lijiang Observatory. The observation began at 2024-04-11T21:55:31, approximately 6.4 hours after the trigger.
The optical counterpart of GRB 240411B, not visible in the Pan-STARRS1 r-band image, was (marginally/clearly) detected at the coordinates (J2000):
RA = 15h 26m 10.15s
DEC = -02d 08' 47.0"
, with a positional uncertainty of 0.5" or better.
The preliminary analysis results are shown as follows:
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Tmid-T0 [s] filter mag 5-sigma UL
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23257 ± 300 R 21.16 ± 0.15 22.64
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The given magnitudes are derived based on calibration against Pan-STARRS1 field stars and are not corrected for the expected Galactic foreground extinction, corresponding to a reddening of E(B-V) = 0.138 mag in the direction of the optical counterpart (Schlafly & Finkbeiner 2011).
We acknowledge the staff at the Lijiang Observatory for conducting the observation.
GRB 240411B: GMG optical upper limit
R.-Z. Li, B.-T. Wang, J. Mao, and J.-M. Bai (YNAO, CAS) report:
We observed the field of GRB 240411B (Li et al., GCN 36063, T0 at 15:32:54 UT) using the GMG-2.4m telescope at the Lijiang Observatory. The observation began at 2024-04-11T21:55:31, approximately 6.4 hours after the trigger.
No any optical counterpart of GRB 240411B was detected within the XRT/EP-WXT/EP-FXT/VT error circle (GCN XXX).
The preliminary analysis results are shown as follows:
----------------------------------
Tmid-T0 [s] filter 5-sigma UL
----------------------------------
23257 ± 300 R 22.64
----------------------------------
The given magnitudes are derived based on calibrating against Pan-STARRS1 field stars.
We acknowledge the staff at the Lijiang Observatory for conducting the observation.
GRB 240411B: GMG optical observation
GRB 240411B: GMG optical upper limit