TITLE:   GCN CIRCULAR
NUMBER:  35944
SUBJECT: X-ray transient EP240315a: Montarrenti Observatory optical upper limit
DATE:    24/03/17 14:48:52 GMT
FROM:    Simone Leonini at Montarrenti Observatory (Siena, Italy) <s.leonini@iol.it>

S. Leonini, M. Conti, P. Rosi, L.M. Tinjaca Ramirez (Montarrenti Observatory, Siena, Italy, part of UAI/SSV-GRB section), M.G. Dainotti (National Astronomical Observatory of Japan), Y. Niino (Tokyo University, Institute of Astronomy), K. Kalinowski (Aarhus University, Department of Physics and Astronomy) and B. De Simone (Universita' degli Studi Di Salerno) report:

We observed the field of the possible optical countepart of the X-ray transient EP240315a (Einstein Probe, GCN 35931, Zhang et al.; GCN 35932, GCN 35933, Srivastav et al.; GCN 35935, Jiang et al.; GCN 35937, Rau; GCN 35938, Chen et al.)  with the automated and remoted 0.53m Ritchey-Chretien telescope at Montarrenti Observatory (Siena, Italy, IAU code C88).

The observations were started at 2024-03-16 20:10:21 UT (approximately 24 hours after the discovery of the X-ray transient) stacking 32x40s V and Rc-band CCD images.
 
We have not found any optical transient candidate within the error-box of the EP mission position with the following upper limit: 

   MJD      Filter      Limit     SNR
60385.8572    V        > 20.43    6.9
60385.8578    Rc       > 20.90    5.4

Magnitude was calibrated with the nearby PanSTAR stars converted using Lupton (2005) equations. No correction for galactic dust extinction was applied.