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GCN Circular 24130

GRB 190406B: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 576241792)
2019-04-18T22:06:52Z (5 years ago)
Tomas Ahumada at U. of Maryland <>
Authors: Tomas Ahumada (UMD), S. Bradley Cenko (NASA GSFC), Michael W.
Coughlin (Caltech), Eric C. Bellm (UW), Leo P. Singer (NASA GSFC), Shaon
Ghosh (UWM), Mansi M. Kasliwal (Caltech), Shreya Anand (Caltech), Igor
Andreoni (Caltech), Scott Adams (Caltech), Matt Hankins (Caltech), Varun
Bhalerao (IITB), Harsh Kumar (IITB), V. Zach Golkhou (UW) on behalf of the
ZTF and GROWTH collaborations and the KPED team

We observed the localization region of the short GRB190406B (trigger
576241792) detected by the Gamma-Ray Burst Monitor (GBM) on the Fermi
satellite with the Palomar 48 inch telescope equipped with the 47 square
degree Zwicky Transient Facility (ZTF) camera. We obtained a series of r-
and g-band images covering 268 square degrees beginning at 08:01 UT on 2019
April 08 (44:52 hours after the burst trigger time). This corresponds to ~
44% of the probability enclosed in the intersection of the GBM and IPN
localization regions. We revisited the region on 2019 April 11, starting at
08:03 UT (116:54 hours after the burst trigger time) and we covered the
same ~ 44% of the probability region.

The images were processed through the ZTF reduction and image subtraction
pipelines at IPAC to search for potential counterparts. 240
high-significance transient and variable candidates were identified by our
pipeline in the area observed, 236 of which had previous detections with
ZTF in the days and weeks prior to the GRB trigger time (e.g., supernovae,
active galactic nuclei).

Further follow-up of 4 transients was obtained with the Kitt Peak EMCCD
Demonstrator (KPED) on the Kitt Peak 84-inch telescope on April 12.
Additionally, we obtained follow-up spectroscopy of 2 candidates with the
Double Spectrograph (DBSP) on Palomar 200��� the nights of April 12. The
candidates are listed below, however no photometric evolution or spectral
classification was consistent with an optical counterpart.


       ZTF ID            RA DEC         last non-detection discovery   KPED


                                 deg deg date in 2019       April 08 April

ZTF19aapgbri    275.504094 +55.964483    04-07 r<20.41    g = 21.36
  g=20.76        SN Ia
ZTF19aapgdcn  285.158686 +69.881810     04-04 r<19.49    g = 20.67   g=21.74
       SN Ia

ZTF19aapfxqv     276.915046 +65.626121    04-04 r<17.61    g=20.67
  g=20.67    SN*

ZTF19aapwbgo   278.519641 +57.057325    04-07 r<20.35    g=21.61   g=22.36


*Classification from photometric data points.

The median 5 sigma upper limit for an isolated point source in our images
was r > 21.5 and g > 21.8 mag for the observations made on April 8 26 and r
> 21.9 and g > 21.6 mag for the observations made on April 11.

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@UW. Alert filtering is being undertaken by the GROWTH marshal system,
supported by NSF PIRE grant 1545949.
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