GCN Circular 25526
Subject
LIGO/Virgo S190814bv: no variation of DESGW candidates AT 2019onj and AT 2019okr from ENGRAVE VLT/HAWK-I observations, and archival detection
Date
2019-08-28T19:26:10Z (5 years ago)
From
Susanna Vergani at INAF/Brera <susilandia@gmail.com>
J. Japelj (Univ. of Amsterdam), E. Kankare (Univ. Turku), E. Kool
(OKC), A. J. Levan (Radboud Univ.), K. Maguire (Trinity College
Dublin), D. B. Malesani (DTU Space), S. Mattila (Univ. Turku), B.
Milvang-Jensen (DAWN/NBI), T. Reynolds (Univ. Turku), N.B. Sabha
(Univ. Innsbruck), S. D. Vergani (Paris Observatory-CNRS) report on
behalf of the ENGRAVE collaboration:
ENGRAVE targeted 9 fields containing 17 high-probability host galaxies
for S190814bv, based on the LALInference skymap (LIGO Scientific
Collaboration and Virgo Collaboration, GCN 25333), with deep
VLT/HAWK-I imaging over two epochs in a search for intrinsically
faint, near-infrared transient sources. As part of this search, we
observed the field of two candidates, AT 2019onj and AT 2019okr,
reported by Soares-Santos et al. (GCN 25486).
The observations were conducted between 06:55 and 07:14 UT on
2019-08-16 and a second epoch between 04:32 and 04:50 UT on
2019-08-21, approximately 1.4 and 6.3 d after S190814bv, respectively
(600 s exposure per epoch in the Ks filter). The sources are detected
in both epochs with magnitudes:
Name dT Ks mag
AT 2019onj 1.4 d 19.20 +- 0.03
AT 2019onj 6.3 d 19.15 +- 0.02
AT 2019okr 1.4 d 19.55 +- 0.03
AT 2019okr 6.3 d 19.54 +- 0.03
The magnitudes (in the Vega system, not corrected for extinction) are
based on preliminary photometry calibrated against a single 2MASS
star, and the absolute calibration has an extra error by 0.05 mag.
No significant variability can be measured between our HAWK-I observations.
This field was also covered serendipitously by the ESO/VISTA survey
telescope in the Ks band during its science verification program. Both
objects are detected in images from 2009-10-23 and 2009-10-30, and
both are fainter than in the HAWK-I images (by 0.68+-0.18 and 0.83 +-
0.26 mag for AT 2019onj and AT 2019okr, respectively). The large
uncertainty is entirely due to the low S/N of the archival VISTA data.
The lack of variability between the VLT/HAWK-I epochs and especially
the archival detections suggest that AT2019onj and AT2019okr are
unrelated to S190814bv.
We acknowledge the ESO observing staff at Paranal, in particular S.
Brillant, J. Corral-Santana, B. Haussler, C. Opitom, F. J. Selman, and
T. Szeifert. Based on observations collected by the ENGRAVE
collaboration at the European Southern Observatory under ESO program
0103.D-0722 (for further information on ENGRAVE see
http://www.engrave-eso.org/). The VISTA data were secured under
science verification program 60.A-9285(A). We acknowledge valuable
help with the archival VISTA data by Carlos Gonzalez-Fernandez (CASU /
IoA Cambridge).