TITLE:   GCN CIRCULAR
NUMBER:  26039
SUBJECT: GRB 191019A: NOT optical observations
DATE:    19/10/19 21:30:22 GMT
FROM:    Daniel Perley at Liverpool JMU  <d.a.perley@ljmu.ac.uk>

D. A. Perley (LJMU), D. B. Malesani (DTU Space), A. de Ugarte Postigo 
(HETH, IAA/CSIC; DARK/NBI), D. Xu (NAO/CAS), J. P. U. Fynbo (DAWN/NBI), 
K. E. Heintz (Univ. Iceland), and N. E. Jannsen (NOT) report on behalf 
of a larger collaboration:

We observed the field of GRB 191019A (Simpson et al., GCN 26031) with 
the Nordic Optical Telescope (NOT) equipped with the ALFOSC imaging 
camera. Observations started on 2019 Oct 19.822 UT (4.52 hr after the 
trigger).

In a single 120 s image taken in the SDSS i band, we detect the object 
mentioned by Reva et al. (GCN 26036), which is also visible in the 
Pan-STARRS archival images and is consistent with the X-ray position 
(Evans et al., GCN 26034). The target is clearly extended (FWHM 1.4" 
with a seeing of 1.1").

The object centroid has coordinates (J2000, calibrated against the Gaia 
catalog):

RA  =  22:40:05.89
Dec = -17:19:42.7

Measuring its magnitude over an aperture of 1.7" radius, we obtain i = 
18.66 +/- 0.01 AB (statistical error), compared to i = 18.71 +/- 0.01 
from the Pan-STARRS catalog (Chambers et al. 2015, arXiv:1612.05560), 
confirmed by our own measurement on the i-band Pan-STARRS image. The 
small flux difference may be due to calibration, color effects, or 
variable aperture correction, so we do not claim any afterglow 
detection.  A conservative limit on the afterglow magnitude at the time 
of our observation would be i > 21.

We note the elevated column density measured in a preliminary analysis 
of the X-ray spectra (Evans et al., GCN 26034). This may suggest a 
dust-obscured event.









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