Optical photometry of the black hole transient GS 1354-64 (BW Cir) in outburst

ATel #7620; J. Corral-Santana (U. Catolica de Chile), T. Munoz-Darias (IAC/ULL - Tenerife), J. A. Carballo-Bello (IFA-Valparaiso), F. E. Bauer (U. Catolica de Chile)
on 11 Jun 2015; 13:51 UT
Credential Certification: Teo Muñoz-Darias (tmd@brera.inaf.it)

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Following the recent outburst of GS 1354-64 (BW Cir) reported in ATel#7612 and ATel#7614, we have started an optical monitoring of this dynamically confirmed black hole. We obtained images in g', r' and i' SDSS bands on UT 20150610/11 with the SOAR Optical Imager (SOI) installed on the 4.1-m SOAR telescope at Cerro Pachon, Chile. The sky conditions were not stable, with poor seeing (1.5-1.8 arcsec) and some cirrus. In order to avoid contamination by nearby stars in the field, we performed PSF photometry using DAOPHOT II/ALLSTAR (Stetson 1987). The average magnitudes obtained are:

g'=19.76+-0.03
r'=18.49+-0.04
i'=18.34+-0.05

These values were calibrated against the stars A-C published in Casares et al. (2009) using the Jester et al. (2005) transformations. In agreement with X-ray observations (ATel#7612 and ATel#7614), the system is still fainter than observed in previous outbursts:

V=16.92 in 1987 (Kitamoto et al. 1990)
V=17.40 in 1997 (Brocksopp et al. 2001).


REFERENCES:
Brocksopp et al. 2001, MNRAS 323, 517
Casares et al. 2009, ApJS 181, 238
Jester et al. 2005, AJ, 130, 873, 895
Kitamoto et al. 1990, ApJ 361, 590
Stetson, 1987, PASP 99, 191

JMC-S acknowledges financial support to CONICYT through the FONDECYT project No. 3140310. Based on observations obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministerio da Ciencia, Tecnologia, e Inovacao (MCTI) da Republica Federativa do Brasil, the U.S. National Optical Astronomy Observatory (NOAO), the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU). These observations were granted by the Chilean TAC with the proposal number: CN2015A-88.