[vsnet-grb-info 23386] LIGO/VirgoS190814bv: CFHTphotometryof AT2019npv

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  25485
SUBJECT: LIGO/VirgoS190814bv: CFHTphotometryof AT2019npv
DATE:    19/08/27 08:05:00 GMT
FROM:    Xiaofeng Wang at Tsinghua University  <wang_xf at mail.tsinghua.edu.cn>

X. Wang (THU), S. Antier (APC), M. Coughlin (Caltech),  W. Li (THU), X. Zhang (THU), 
J. Mo (THU), G. Xi (THU), J. Bai (Yunnan Obs), S. Basa (LAM),  E. Bertin (IAP), 
M. Blazek (HETH/IAA-CSIC), Michel Boer (Artemis), A. Coleiro (APC), N. Christensen (Artemis), 
S. Ehgamberdiev (UBAI), D. A. Kann (HETH/IAA-CSIC), A. Klotz (IRAP), D. Coward (OzGrav-UWA), 
J.G. Ducoin (LAL), B. Gendre (OzGrav-UWA), P. Hello (LAL),  L. Hu (PMO), C. Lachaud (APC), 
X. Jiang (NAOC), N. Leroy (LAL), B. Li (PMO),  W. Lin (THU),  D. Mirzaqulov (UBAI), 
T. Sun (PMO), C. Thoene (HETH/IAA-CSIC), D. Turpin (NAOC), L. Wang (Texas University/PMO), 
A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), X.  Wu (PMO), H. Zhao (PMO), X. Zeng (XAO),
J. J. Zhang (YNAO), J. C. Zhang (THU):

Report on behalf of AOGOT (All-sky Observations of Gravitational Optical Transients) and Grandma joint collaborations:

Using the MegaPrime/MegaCam instrument (1x1 deg FOV) at the
Canada-France-Hawaii Telescope, we observed the candidate AT2019npv
reported by Goldstein et al (GCN 25393) close to a galaxy at z=0.056
(Jonker et al, GCN 25454), which was a candidate electromagnetic
counterpart of the GW event S190814bv (LIGO/Virgo Collaboration,
GCN 25324, GCN. 25333).

Multiple images were obtained with the CFHT for this object
in g(210sx2), r(240sx2) and i(300sx2) bands beginning at 2019-08-24 13:08
UTC. Using references from the DECam Legacy Survey (DECaLS), we performed
image differencing in g and r-bands, with a low significance detection in
g-band and an r-band estimate of r_AB = 23.0+-0.05 mag (i-band has a
significant detection, but the reference is not available and therefore the
numbers are unreliable).

This object has been ruled out by different spectroscopic observations
and photometric archival analysis as being related to the LIGO/Virgo
GW candidate (GCN25468, GCN25475, GCN5478).