[vsnet-grb-info 22250] LIGO/Virgo S190426c: PS1 historical detections and ZTF photometry of Gaia19boq AT2019egk

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  24349
SUBJECT: LIGO/Virgo S190426c: PS1 historical detections and ZTF photometry of Gaia19boq AT2019egk
DATE:    19/04/30 04:46:24 GMT
FROM:    Igor Andreoni at Caltech  <igor.andreoni at gmail.com>

Igor Andreoni (Caltech), Shreya Anand (Caltech), Mansi Kasliwal (Caltech)

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

We report photometry and historical detections of the transient candidate Gaia19boq AT2019egk (Kostrzewa-Rutkowska et al., GCN 24344).  

Previous detections are reported in the Pan-STARRS1 Data Release 2 database (Chambers et al., 2016) at coordinates consistent with Gaia19boq, suggesting outburst history. 

The following table summarizes the ZTF photometry of the source on the days near the gravitational wave event S190426c (LIGO and Virgo Collaboration, GCN 24237). 
----------------------------------------------------
Date (UTC) | filter |  mag  | err
----------------------------------------------------
2019-04-24 10:41:57.120 |  r  | >20.02 |  -
2019-04-27 08:29:28.320 |  g  | 18.88 | 0.04
2019-04-27 09:54:51.840 |  r  | 18.51 | 0.04
2019-04-28 08:28:10.560 |  g | 19.02 | 0.04

The Gaia19boq transient, dubbed also ZTF19aaslxmg, shows red color and rapid evolution within 2 days after the gravitational wave event S190426c (LIGO and Virgo Collaboration, GCN 24237).  The red color could be due to high Galactic extinction E(B-V) = 0.9733 magnitudes (Schlafly & Finkbeiner, 2011).  

We conclude that Gaia19boq AT2019egk is a Galactic variable source unrelated with the gravitational wave event S190426c (LIGO and Virgo Collaboration, GCN 24237).

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 at UW (Patterson et al. 2019). Alert filtering and follow-up co-ordination is being undertaken by the GROWTH marshal system (Kasliwal et al. 2019).