TITLE:   GCN CIRCULAR
NUMBER:  39229
SUBJECT: LIGO/Virgo/KAGRA S250206dm: Spectroscopic Classification of AT2025bay and AT2025baz with Keck I/LRIS
DATE:    25/02/08 07:55:32 GMT
FROM:    Viraj Karambelkar at Indian Inst of Tech,Bombay <karambelkarvraj21197@gmail.com>

Viraj Karambelkar (Caltech), Tomás Ahumada (Caltech), Mansi Kasliwal
(Caltech) report on behalf of the ZTF and GROWTH collaborations:


We report optical spectroscopy of two counterpart candidates reported by
the Zwicky Transient Facility, AT 2025bay, AT 2025baz (GCN #39228) in the
localization region of LIGO/Virgo S200206dm (LVC, GCN #39175,39184). We
used the Low Resolution Imaging Spectrometer (Oke et al. 1995) on the Keck
I telescope, reduced  data using the idl package lpipe (Perley 2019) and
find:


ZTF25aaffyzc  / AT2025bay shows broad features matching a Type Ia supernova
before maximum at z = 0.19


ZTF25aaffzpx / AT2025baz matches a Cataclysmic Variable in the Milky Way
and shows Balmer emission lines at z = 0.0


Thus, AT2025bay and AT2025baz are not related to the gravitational wave
event.


We are grateful to the Keck Observatory staff, Sherry Yeh and Matthew Wahl,
as well as observers, Andrew Howard and Howard Isaacson, for swiftly
co-operating with these Target-of-Opportunity observations for rapidly
setting targets.