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GCN Circular 36177

GRB240418A: YAHPT Upper Limits
2024-04-19T11:15:10Z (3 months ago)
Tianrui Sun at Purple Mountain Obs,CAS <>
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Tian-Rui Sun, Jin-Jun Geng, Jian Chen, Yan-Long Hua  and Lei Hu report on behalf of the YAHPT team:

Following the detection of GRB 240418A by SWIFT (Siegel et al., GCN 36162; Evans et al., GCN 36166), 
we use the Yaoan High Precision Telescope at Yaoan Astronomy Observation Station (Yunnan province, China) to search and follow up its afterglow at XRT position.

We observed the target position with 180s exposure in V-band starting from 2024-04-18T20:32:14.600 about 486.6 seconds after the burst.
We took 25 images with total exposure time of 4500 seconds from 20:32:14 to 21:48:29.4. 
We did not detect any object up to V = 22.2 with the stacked images within the Enhanced Swift XRT position 
This non-detection results of the gamma-ray bursts is in agreement with the previous circulars 
(Lipunov et al., GCN 36163; Odeh et al., GCN 36165; Malesani et al., GCN 36167; Pozanenko et al. GCN 36168;).

We used the UCAC4 catalog (Vmag) as the magnitude reference for calibration.
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