TITLE:   GCN CIRCULAR
NUMBER:  25798
SUBJECT: GRB 190919B: BOOTES-5/JGT and BOOTES-3/YA optical observations
DATE:    19/09/21 15:04:32 GMT
FROM:    Alberto J. Castro-Tirado at IAA-CSIC  <ajct@iaa.es>

Y.-D. Hu, E. Fernandez-Garcia and A. J. Castro-Tirado (IAA-CSIC), D. 
Hiriart and W. H. Lee (UNAM), S. Jeong and I. H. Park (SKKU) and M. D. 
Caballero-Garcia (ASU-CAS, CZ), I. Carrasco, C. Perez del Pulgar (Univ. 
de Malaga) and R. Querel (NIWA) on behalf of a larger collaboration, 
report:

The 60cm BOOTES-5/JGT robotic telescope at Observatorio Astronomico 
Nacional in San Pedro Martir (Mexico) automatically responded in 3.33 
hrs to the INTEGRAL trigger of GRB190919B (Mereghetti et al., GCNC 
25788). A series of unfiltered images were taken (60s exposure time). 
The optical source is detected at the position reported by Bolmer et al. 
(GCNC 25789) and Tyurina et al. (GCNC 25791) in the co-added image from 
which we derive a magnitude of 19.56 +/- 0.15 at median time of 4.41 h 
after the trigger.

Few hours later, the 60cm BOOTES-3/YA robotic telescope at NIWA Lauder 
in Otago (New Zealand) also automatically responded to this trigger and 
gathered a serie of unfiltered images (60s exposure time). The optical 
source still can be detected in the co-added image with a magnitude of f 
21.2 +/- 0.4 at a median time of 9.54 hrs after trigger.

These results confirm the fading of the afterglow. The magnitude is 
calibrated against the USNO-B1 catalog and is not corrected for Galactic 
extinction in the direction of the GRB. Further observations are 
ongoing.

We thank the staff at both the Observatorio Astronomico Nacional in San 
Pedro Martir and NIWA Lauder for their excellent support.