[vsnet-grb-info 21154] GRB 180914B: DDOTI/OAN Detection and Confirmation of Fading

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23253
SUBJECT: GRB 180914B: DDOTI/OAN Detection and Confirmation of Fading 
DATE:    18/09/18 00:55:28 GMT
FROM:    Alan M. Watson at Instituto de Astronomia UNAM  <alan at astro.unam.mx>

Alan M. Watson (UNAM), Nat Butler (ASU), Eleonora Troja (GSFC), Rosa L.
Becerra (UNAM), William H. Lee (UNAM), and Alexander Kutyrev (GSFC)
report:

We observed the field of GRB 180914B (Ursi et al., GCN Circ. 23226) with
the DDOTI/OAN wide-field imager at the Observatorio Astronomico
Nacional on Sierra San Pedro Martir (http://ddoti.astroscu.unam.mx) from
2018-09-16 02:54 to 06:02 (32.5 to 35.7 hours after burst) and
2018-09-17 02:58 to 04:17 (56.6 to 57.9 after burst) obtaining 7200 and
3060 seconds exposure with no filter.

We detect the optical counterpart (Zheng & Filippenko, GCN Circ. 23237;
Troja, et al., GCN Circ. 23238) with the following magnitudes:

w = 19.45 +/- 0.10 (on 2018-09-16) 
w = 20.25 +/- 0.31 (on 2018-09-17)

These AB magnitudes are calibrated against the Pan-STARRS1 catalog and
are not corrected for Galactic extinction in the direction of the GRB.

We confirm the fading reported by de Ugarte Postigo et al. (GCN Circ.
23239), Troja et al. (GCN Circ. 23243), and Mazaeva et al. (GCN Circ.
23249).

DDOTI/OAN imaged the entire Fermi/LAT error region (Bissaldi et al., GCN
Circ. 23232). We confirm that there were no other uncatalogued sources
in the region on 2019-09-16 to a 10-sigma limit of w = 19.4.

We thank the staff of the Observatorio Astronomico Nacional in San Pedro
Martir.