[vsnet-grb-info 25699] ZTF Discovery of ZTF20abbiixp: The Likely Optical Afterglow to GRB 200524A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  27799
SUBJECT: ZTF Discovery of ZTF20abbiixp: The Likely Optical Afterglow to GRB 200524A
DATE:    20/05/24 18:47:58 GMT
FROM:    Anna Ho at Caltech  <annayqho at gmail.com>

Anna Y. Q. Ho, Yuhan Yao (Caltech), Daniel A. Perley (LJMU) report on
behalf of the Zwicky Transient Facility collaboration:

The Zwicky Transient Facility (ZTF, Bellm et al. 2019, Graham et al. 2019)
discovered ZTF20abbiixp, a fast transient at
14h12m10.33s +60d54m19.0s (J2000)
213.043037 +60.905288 (J2000)
as part of the ZTF Uniform Depth Survey (Goldstein et al. in prep).

ZTF20abbiixp was first detected at r~17.4 mag on UT 2020-05-24T06:52:07 and
faded by 0.3 mag over the next 30 minutes, with a total of four
observations showing continuous fading. The last non-detection was 24 hours
prior (2020-05-23T06:43:03) with a limiting magnitude of r>20.4 mag. There
is no counterpart in ZTF reference images down to a limiting magnitude of
r>22.90.

We searched the GCN archive and determined that ZTF20abbiixp is in the
error circle of GRB 200524A, which was detected by Fermi-GBM and Fermi-LAT
(GCN 27797). The position of ZTF20abbiixp is 0.151 degrees offset from the
LAT position, within the 0.2 degree error radius (90% containment).

The time of GRB 200524A was 1.802 hours prior to the first detection of
ZTF20abbiixp. We conclude that ZTF20abbiixp is very likely to be the GRB
afterglow.

Follow-up observations are highly encouraged.

ZTF is a project led by PI S. R. Kulkarni at Caltech (see ATEL #11266), and
includes IPAC; WIS, Israel; OKC, Sweden; JSI/UMd, USA; UW,USA; DESY,
Germany; NRC, Taiwan; UW Milwaukee, USA and LANL USA. ZTF acknowledges the
generous support of the NSF under AST MSIP Grant No 1440341. Alert
distribution service provided by DIRAC at UW. Alert filtering is being
undertaken by the GROWTH marshal system, supported by NSF PIRE grant
1545949.