Optical follow-up of IceCube-190730A with ZTF
ATel #12974; R. Stein (DESY), A. Franckowiak (DESY), M. M. Kasliwal (Caltech), I. Andreoni (Caltech), M. Coughlin (Caltech), L. P. Singer (NASA GSFC), F. Masci (IPAC), S. van Velzen (UMD)
on 31 Jul 2019; 23:18 UT
Credential Certification: Anna Franckowiak (anna.franckowiak@desy.de)
Subjects: Optical, Neutrinos
On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations:
We observed the localization region of the high-energy neutrino event IceCube-190730A (#12967) with the Palomar 48-inch telescope equipped with the 47-square-degree ZTF camera (Bellm et al. 2019, Graham et al. 2019).
We obtained target-of-opportunity observations for two field covering the 90% confidence region, beginning at UT 2019-07-31 04:32 in the r-band filter and UT 2019-07-31 05:02 in the g-band filter (8 hours after the neutrino detection), each with an exposure length of 300s.
The neutrino was reported in #12967 to be in coincidence with the FSRQ source PKS 1502+106. Forced photometry was performed on images processed through the ZTF reduction and image subtraction pipelines at IPAC (Masci et al. 2019) at the position of this source. We detect the blazar in g-band at a magnitude of 18.48+/-0.02, but not in r-band due to poor observing conditions. The median 5 sigma upper limit for an isolated point source in our images was r > 18.19 and g > 20.78 mag for the observations made on July 31.
The g-band detection is consistent with previous quiescent detections of this source, and there is no evidence of flaring activity either in these observations or in many previous detections over the past six months. The source has previously been detected as part of the public ZTF alert stream (#11685), under the name ZTF18aaqnqzx. The apparent lack of flaring activity is consistent with observations reported in other wavelengths (e.g #12972).
A search for other potential counterparts in the neutrino error region is ongoing. The area will continue to be imaged as part of regular survey observations.
The ZTF forced-photometry service was funded under the Heising-Simons Foundation grant #12540303 (PI: Graham). ZTF and GROWTH are worldwide collaborations comprising Caltech, USA; IPAC, USA, WIS, Israel; OKC, Sweden; JSI/UMd, USA; U Washington, USA; DESY, Germany; MOST, Taiwan; UW Milwaukee, USA; LANL USA; Tokyo Tech, Japan; IIT-B, India; IIA, India; LJMU, UK; TTU, USA; and USyd, Australia. ZTF acknowledges the generous support of the NSF under AST MSIP Grant No 1440341. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert filtering and follow-up coordination is being undertaken by the GROWTH marshal system (Kasliwal et al. 2019).
