GRANDMA follow-up observations of the EP X-ray transient (EP240305a)

ATel #16531; S. Antier (OCA), X. Wang (Tsinghua Uni), W.-M. Yuan (NAOC), H-B Eggenstein (KNC), M. Freeberg (KNC), F. Navarete (LNA/MCTI), L. Fraga (SOAR), Y. Jongen (KNC), M. Masek (FZU), S. Karpov (FZU), B. Gendre (UWA), J. Hambsch (KNC), J-P Vignes (KNC), S. Vanaverke (KNC), J-L Virlichie (KNC), J. Cazard (KNC), P. Traverse (KNC), H. Roy (KNC), A. Taylor (KNC), I. Tosta e Melo (UniCT-DFA), P. Hello (IJCLAB), D. Turpin (CEA-Saclay/Irfu), T. Pradier (Unistra/IPHC), M. Coughlin (UMN), C. Andrade (UMN), P-A Duverne (APC), T. Eposito (Unistellar), A. Perrocheau (Unistellar)
on 15 Mar 2024; 09:15 UT
Credential Certification: Antier Sarah (sarah.antier@oca.eu)

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We performed a target of opportunity observations with GRANDMA and its science Kilonova-catcher (KNC) on the X-ray flare EP240305a detected by Einstein Probe (EP) WXT on March 5 2024 (ATel #16509) and followed by Swift XRT (Atel #16514). GRANDMA began observations at 2024-03-08T10:28:49 and stops observation two days after. We do not detect any significant evolution in terms of brightness in B,V,R at the location RA (J2000) = 122.921, Dec(J2000) =-54.652. We reported below a subset on the observations (Mjd, filter, system, detection, error, name of the telescope) as follow and using STDpipe (Karpov, 2020) to calibrate our images: *** B-band *** (calibrated with gaia) --> (60377.62829861, B, Vega, 19.2, 0.1, iTel) (60378.17844103, B, Vega, 19.6, 0.2, PW17'') (60379.17844103, B, Vega, 19.6, 0.2, PW17'') (60379.41216435185, B, Vega, 19.3, 0.1, iTel). In *** V-band *** (calibrated with gaia) --> (60377.436686458335,V, Vega, 18.47, 0.1, iTel) (60377.54403935185, V, Vega, 18.71, 0.1, iTel) (60377.99979167, V, Vega, 18.1, 0.2, XO3)(60378.17844103, V, Vega, 18.6, 0.2, PW17'')(60379.15374421296, V, Vega, 18.5, 0.1, FRAM) (60379.17844103, V, Vega, 18.6, 0.2, PW17''). In *** R-band *** (calibrated with gaia) : (60378.17844103, Rc, Vega, 18.2, 0.2, PW17'') (60378.44021990741, Rc, Vega, 18.22, 0.03, iTel) (60379.15374652778, Rc, Vega, 18.43, 0.15, FRAM) (60379.17844103, Rc, Vega, 18.2, 0.2, PW17'')(60379.473912037036,Rc, Vega, 18.15, 0.03, iTel). In *** sdssr-band *** (calibrated with Skymapper) --> (60379.09986111, sdssr, AB, 18.61, 0.0, SOAR). In *** sdssi-band *** (calibrated with Skymapper) --> (60379.09987268, sdssi, AB, 18.37, 0.0, SOAR) We thank the Einstein Probe team for useful communication. We thank all Kilonova-catcher participants and Unistellar. We are happy to provide further analysis on demand, as we have many more images taken at various epoch in different filters. GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/).