TITLE:   GCN CIRCULAR
NUMBER:  23037
SUBJECT: GRB 180720B: AMI-LA 15.5 GHz observation
DATE:    18/07/25 09:12:00 GMT
FROM:    Itai Sfaradi at Hebrew U of Jerusalem  <itai.sfaradi@mail.huji.ac.il>

Itai Sfaradi (HUJI), Joe Bright (Oxford), Assaf Horesh (HUJI), Rob Fender
(Oxford) ,
Sara Motta (Oxford), David Titterington, Yvette Perrott (MRAO, Cambridge)
report:

We observed the position of GRB180720B (GCN CIRCULAR #22973) with the
Arcminute Microkelvin Imager Large Array (AMI-LA; Zwart et al. 2008; Hickish
et al. 2018) at 15.5 GHz on 2018-07-22.21 for 3.9 hours.
We clearly detect a source at the phase center, fitting the source with the
CASA task IMFIT
provides an integrated flux density of ~ 1 mJy and a position of RA:
00:02:07.02,
Dec: -02 55 02.224 with a synthesized beam major and minor FWHM of 93’’ and
27’’ respectively
(consistent with the position reported in GCN CIRCULAR #22973).

The custom pipeline REDUCE_DC (e.g. Perrott et al. 2015) was used to
calibrate
and flag the data, with 3C286 as the absolute flux calibrator and J2357-0152
as the interleaved phase calibrator.

We plan to continue monitoring this source, and would like to thank the
MRAO staff for carrying out these observations.