[vsnet-grb-info 23011] GRB 190719C: NOT candidate optical afterglow and host

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  25110
SUBJECT: GRB 190719C: NOT candidate optical afterglow and host
DATE:    19/07/19 23:23:34 GMT
FROM:    Kasper Elm Heintz at Univ. of Iceland and DAWN/NBI  <keh14 at hi.is>

Daniele B. Malesani (DTU Space), Kasper E. Heintz (Univ. Iceland), Daniel A. Perley (LJMU), Bo Milvang-Jensen (DAWN/NBI), Shane Moran (NOT and Univ. Turku) report on behalf of a larger collaboration:

We observed the field of the Fermi and Swift GRB 190719C (Fermi GBM Team, GCN 25104; Ambrosi et al., GCN 25106) using the Nordic Optical Telescope equipped with the ALFOSC camera. A set of 3 exposures by 300 s each was secured in the r band.

At the edge of the currently available XRT error circle (3.6" error radius), a single object is detected at approximate coordinates (J2000):

RA = 16:00:49.59
Dec = +13:00:04.3

This object is clearly extended, and we measure r = 22.01 +- 0.05 AB using a wide aperture, calibrated against nearby Pan-STARRS objects.

We notice that the object is also detected in the Pan-STARRS r-band image, for which we measure a slightly fainter magnitude r = 22.50 +- 0.16 AB. Visual comparison of the NOT and Pan-STARRS images indicated a shift in the centroid between the two epochs, with excess light in the NOT images to the West of the archival object.

We thus suggest that we are seeing a faint afterglow superimposed on its host galaxy. Further imaging at later epochs is required to carry out image subtraction and provide accurate position and magnitude for the afterglow.

New observations with the NOT will be requested as soon as the telescope is available.