TITLE:   GCN CIRCULAR
NUMBER:  24684
SUBJECT: GRB 190530A: Bright afterglow confirmed by OSN
DATE:    19/05/30 21:58:06 GMT
FROM:    Alexander Kann at IAA-CSIC  <kann@iaa.es>

D. A. Kann, L. Izzo (both HETH/IAA-CSIC), A. de Ugarte Postigo 
(HETH/IAA-CSIC, DARK/NBI), M. Blazek, C. C. Thoene, K. Bensch (all 
HETH/IAA-CSIC), and V. Casanova (IAA-CSIC) report:

We observed the afterglow position (Lipunov et al., GCN 24680) of the 
extremely bright GRB 190530A (GBM detection and localization: Fermi GBM 
team, GCN 24676, Biltzinger et al., GCN 24677; Fermi-LAT localization: 
Longo et al., GCN 24679; Agile-MCAL/GRID detections: Lucarelli et al., 
GCN 24678, Verecchia et al., GCN 24683) with the 1.5-m telescope of the 
Sierra Nevada Observatory (OSN), Spain. The afterglow is well-detected.

We measure the following AB magnitude:

Rc = 17.63  +- 0.10 mag at 0.437314 days after the GRB.

The magnitude were derived against 1 nearby star from the SDSS catalog, 
using the transformation equations of Lupton (2005), and transformed 
back into AB mag.

We note this is an exceedingly bright afterglow, further follow-up is 
encouraged despite the bad visibility.