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GCN Circular 24302

Subject

LIGO/Virgo S190425z: ZTF photometry of the UVOT transient candidate hours before discovery

Date

2019-04-27T21:06:42Z (5 years ago)

From

Igor Andreoni at Caltech <igor.andreoni@gmail.com>

Igor Andreoni (Caltech), S. Bradley Cenko (NASA GSFC), F. Masci (IPAC), M. Graham (Caltech)

On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations

We report pre-detection forced photometry upper limits for the Swift/UVOT transient candidate (Breeveld et al., GCN 24296Not found
 
 
) from recent observations with the Zwicky Transient Facility (ZTF). Forced photometry was performed on images processed through the ZTF reduction and image subtraction pipelines at IPAC (Masci et al. 2019).

------------------------------------
date (UT) | filter | maglim
------------------------------------
2019-04-25T10:05:01.746 | r | 20.51
2019-04-25T10:07:12.096 | g | 20.48
2019-04-25T11:26:44.153 | r | 20.47
2019-04-26T07:49:33.277 | g | 21.58	
2019-04-26T09:36:47.686 | r | 20.42
------------------------------------

The candidate was detected with Swift/UVOT on 2019-04-26 at 18:49:22 UT (Breeveld et al., GCN 24296Not found
 
 
).  Thus, if associated with the gravitational wave event, the ZTF non-detections may constrain the rise time and temperature during the rise of the transient. 

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 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.