LIGO/Virgo S190814bv: no variation of DESGW candidates AT 2019onj and AT 2019okr from ENGRAVE VLT/HAWK-I observations, and archival detection
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).
GRB Coordinates Network
- Pub Date:
- August 2019