TITLE:   GCN CIRCULAR
NUMBER:  25461
SUBJECT: LIGO/Virgo S190814bv: Keck NIRES spectroscopy of DG19wxnjc/AT2019npv
DATE:    19/08/24 13:57:14 GMT
FROM:    Mansi M. Kasliwal at Caltech/Carnegie  <mansikasliwal@gmail.com>

K. De, M. M. Kasliwal, I. Andreoni, V. Karambelkar, Y. Sharma (Caltech)

report on behalf of the GROWTH (Global Relay of Observatories Watching
Transients Happen) collaboration

We observed DG19wxnjc/AT2019npv (Goldstein et al. GCN 25393)  with NIRES
(Wilson et al. 2004) on the Keck II telescope starting 2019-08-24 11:41 UT.
The host galaxy redshift (Jonker et al. GCN 25454) and light curve (Annis
et al. GCN 25458, Smartt et al. GCN 25455, Chen et al. GCN 25457) hinted at
a possible association with the neutron star black hole merger S190814bv
(LVC et al. GCN 25324, GCN 25333). Our on-source integration time with
Keck/NIRES was 40min. We see a mostly featureless continuum from the
transient from 0.94 to 2.45 microns. There is possibly a Helium feature
around 10830A, however, it could be an artifact due to proximity to a
telluric feature. Given the lack of obvious identifiable features, we
encourage deep optical spectroscopy to distinguish between a kilonova
origin or supernova origin.

We are grateful to the W. M. Keck Observatory staff, especially Greg
Doppmann and Terry Stickel, for facilitating this partnership target of
opportunity observation. We thank the observer Leslie Young for her kind
co-operation.