TITLE: GCN CIRCULAR NUMBER: 21895 SUBJECT: LIGO/Virgo G298048: TOROS photometry of SSS17a DATE: 17/09/18 16:22:27 GMT FROM: Mario Diaz at U of Texas M. Diaz, L. Macri, J.L. Nilo Castellon, B. Sanchez, C. Mendes, C. Colazo, M. Schneitter, C. Girardini, D. Garcia Lambas, M. Beroiz, A. Zadrozny, R. Camuccio, M. Castillo. J. Garcia for the TOROS collaboration We have completed the PSF photometry of the observations of GW170817 carried out at the T80S telescope and the EABA telescope on 08/18/2017 and 08/19/2017 (GCN 21619, GCN, 21620). We calibrated our measurements using the Pan-STARRS1 catalog available at STScI, using their reported PSF magnitudes and uncertainties. The mid-point of our observations was 1.467d after the GW trigger - LIGO/Virgo G298048- (Julian Date of 2457984.495). At that time, we measured magnitudes of g=18.60, r=17.99, i=17.80 with uncertainties of +-0.02 mag. Additionally with our observations utilizing the EABA telescope we obtained r=18.78+-0.03 at 2.456d after the GW trigger -LIGO/Virgo G298048-. _______________________________________ Mario C. Díaz Director Center for Gravitational Wave Astronomy and Professor Department of Physics and Astronomy The University of Texas Rio Grande Valley (956) 882-6690 FAX: (956) 882-6726 mario.diaz@utrgv.edu http://www.mariodiaz.org/ ______________________________________ No ceder Carhue al huinca. Calfucura (1873)