TITLE:   GCN CIRCULAR
NUMBER:  36178
SUBJECT: EP240417a: YAHPT Optical Upper Limits
DATE:    24/04/19 11:17:05 GMT
FROM:    Tianrui Sun at Purple Mountain Obs,CAS <trsun@pmo.ac.cn>

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 EP240417a by Einstein Probe (Hu et al., GCN 36161), 
we use the Yaoan High Precision Telescope at Yaoan Astronomy Observation Station (Yunnan province, China) to search and follow up.

We observed the target position with 300s exposure in Rc-band starting from 2024-04-18T16:35:20.400 about.
We took 5 images with total exposure time of 1500 seconds from 16:35:20 to 16:55:30. 
We did not detect any possible optical counterpart up to Rc = 20.7 within the 3-arcmin radius.

We used the USNO B1.0 catalog (R2mag) as the magnitude reference for calibration.