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ATEL # 2845; J. M. Corral-Santana (IAC, ULL), P. Rodríguez-Gil (ING, IAC, ULL), D. Hurley (ING, UCC), J. Casares (IAC, ULL)
on 17 Sep 2010; 17:17 UT
Distributed as an Instant Email Notice (Transients)
Password Certification: P. Rodriguez-Gil (email@example.com)
Subjects: Optical, Binaries, Black Holes, Transients
Observations of the black hole binary XTE J1859+226 revealed an unexpected optical re-brightening. Images were taken with the Nordic Optical Telescope (NOT) using ALFOSC on Jul 13-14, the William Herschel Telescope (WHT) with ACAM on Aug 8 and the Isaac Newton Telescope (INT) with WFC on Aug 19 at the Observatorio del Roque de los Muchachos, La Palma, Spain. The target is found ~1 magnitude brighter than its quiescence level of R=22.48 +- 0.07 as reported in Zurita et al. MNRAS 334, 999 (2002).
Instead of the ellipsoidal modulation seen at quiescence, the light curves are dominated by the presence of flares and dips with amplitudes up to 0.4 mag and typical timescales of minutes (see link below). This behaviour does not seem to be associated to an increase in X-ray activity. Follow-up observations in the optical and other wavelengths are highly encouraged.
The WHT and the INT are operated on the island of La Palma by the Isaac Newton Group (ING) in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias (IAC). The NOT is operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias (IAC).