TITLE: GCN CIRCULAR NUMBER: 30879 SUBJECT: GRB 210919A: Chandra rapid ToO upper limit DATE: 21/09/25 01:27:01 GMT FROM: Takanori Sakamoto at AGU <tsakamoto@phys.aoyama.ac.jp> T. Sakamoto (AGU), E. Troja (NASA/GSFC/ORAU), J. Norris (BSU), S. D. Barthelmy (GSFC), J. L. Racusin (GSFC), N. Kawai (Tokyo Tech), A. Fruchter (STScI), M. Im (SNU), B. Cenko (GSFC) A Chandra ToO observation of a short GRB 200919A (Tohuvavohu et al., GCN Circ. 30846) started on February 21 02:54 UT (~2.1 days after the GRB trigger) for a total of 19.8 ksec. We do not detect an X-ray afterglow at the location of the enhanced XRT position (Goad et al., GCN Circ. 30850). The calculated 3-sigma upper limit is 3.4 x 10^-4 c/s in the 0.3-8 keV band using aprates of the CIAO software package. Assuming N_H of 1.5 x 10^21 cm^-2 and photon index of 2, we estimated an 3-sigma unabsorbed flux upper limit of 6.9 x 10^-15 erg/cm2/s in the 0.3-8 keV band. We would like to thank Patrick Slane, Harvey Tananbaum, Andrea Prestwich, and the Chandra operation team for rapidly approving and making this observation.