Skip to main content
Testing. You are viewing the public testing version of GCN. For the production version, go to
Introducing Einstein Probe, Astro Flavored Markdown, and Notices Schema v4.0.0. See news and announcements

GCN Circular 24433

LIGO/Virgo S190426c: INT Observations of ZTF19aassfws
2019-05-09T15:13:58Z (5 years ago)
Mansi M. Kasliwal at Caltech/Carnegie <>
Christoffer Fremling (Caltech), Andrew Levan (Radboud),  Mansi Kasliwal
(Caltech) and Nial Tanvir (Leicester)

report on behalf of a larger collaboration

We imaged ZTF19aassfws (Perley et al. GCN 24331, Coughlin et al. GCN 24283)
with the INT on UT 2019-04-08. Difference imaging relative to PanSTARRS1
(Chambers et al. 2016) finds no detection in the r-band to r > 22.6 mag and
a bright detection in z-band at z ~ 20.8,corresponding to M_Z ~ -17.2 at
z=0.093 (Cenko et al. GCN24430). The z-band luminosity is higher than
GW170817 at this phase. The red color at this phase is plausible for a
kilonova but we cannot definitively rule out unrelated, nuclear activity.
We further caution that the INT and PS1 have different filter transmission
curves in z-band. We encourage follow-up to confirm or refute the
association of this source with the GW event S190426c (LVC et al. GCN
24237,  GCN 24411).

We thank the INT observers, Lord Dover and Tarik Zegmott for facilitating
these observations.
Looking for U.S. government information and services? Visit