{
  "bibcode": "2024GCN.36839....1L",
  "circularId": 36839,
  "submittedHow": "web",
  "eventId": "EP240708a",
  "body": "C.-H. Lai, A. Aryan, T.-W. Chen, Y. J. Yang (all NCU), Y.-L. Wu (NTNU), C.-S. Lin (NCU), S. Yang (HNAS), W.-J. Hou, H.-Y. Hsiao, C.-C. Ngeow, A. Sankar.K, M.-H. Lee, Y.-C. Pan, H.-C. Lin, J.-K. Guo (all NCU), S. J. Smartt (Oxford/QUB), H.-W. Lin (UMich), H. F. Stevance, S. Srivastav, J. Gillanders (Oxford), A. K. H. Kong (NTHU), M. Fulton, T. Moore, C. Angus and A. Aamer (all QUB) report: \n\nWe observed the field of the fast X-ray transient EP240708a (Chen et al., GCN 36838) using the One-meter Telescope (LOT) at Lulin Observatory in Taiwan as part of the Kinder collaboration (Chen & Yang et al., 2024arXiv240609270C). The first LOT epoch of observations started at 16:38 UT on 09th of July 2024 (MJD = 60500.693), 17.16 hrs after the EP trigger. \n\nWe utilized the astroalign (Beroiz et al., 2020, A&C, 32, 100384) and astropy (Astropy Collaboration et al., 2022, ApJ, 935, 167) packages to align and stack the individual frames. We  subtracted the stacked images with the Pan-STARRS1 template image using hotpants (Becker A., 2015, ascl.soft. ascl:1504.004). The subtracted image did not provide any evidence of a new source. Moreover, we utilized the python based package, AutoPhOT (Brennan & Fraser, 2022, A&A, 667, A62) to perform the PSF photometry on our stacked frame. \n\nWe did not detect any optical counterpart in the errorbox of 3 arcminute around the reported position of the EP240708a in the stacked and subtracted frames. The details of the observations and measured 3-sigma upper limit (in the AB system) are as follow:\n\nTelescope | Filter | MJD (start) | t-t0 | Exposure | Magnitude | avg. Seeing | med. Airmass\nLOT | r | 60500.693 | 17.16 hrs | 300 sec * 6 | > 22.6 | 1\".86 | 2.16\nLOT | g | 60500.719 | 17.78 hrs | 300 sec * 6 | > 22.4 | 1\".67| 1.82\n\nThe presented magnitudes are calibrated using the field stars from the Pan-STARRS1 catalog and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V) = 0.03 mag in the direction of the transient (Schlafly & Finkbeiner 2011).\n\n",
  "createdOn": 1720555985856,
  "format": "text/plain",
  "subject": "EP240708a: Optical upper limits with Kinder observations",
  "submitter": "Amar Aryan at National Central University, Institute of Astronomy (NCUIA) <amararyan941@gmail.com>"
}