The first outburst of the black-hole candidate MAXI J1836−194 observed by INTEGRAL, Swift, and RXTE

¹ ISDC Data Centre for Astrophysics, Chemin d’Écogia 16, 1290 Versoix, Switzerland
e-mail: Carlo.Ferrigno@unige.ch
² IASF-Roma, INAF, via Fosso del Cavaliere 100, 00152 Rome, Italy

Received: 17 November 2011
Accepted: 22 December 2011

Abstract

MAXI J1836−194 is a transient black-hole candidate discovered in outburst on 30 August 2011. We report on the available INTEGRAL, Swift, and RXTE observations performed in the direction of the source during this event before 55 864 MJD. Combining the broad band (0.6–200 keV) spectral and timing information obtained from these data with the results of radio observations, we show that the event displayed by MAXI J1836−194 is another example of “failed” outburst. During the first  ~20 days after the onset of the event, the source underwent a transition from the canonical low/hard to the hard intermediate state, while reaching the highest X-ray flux. In the  ~40 days following the peak of the outburst, the source displayed a progressive spectral hardening and a decrease in the X-ray flux, thus it entered again the low/hard state and began its return to quiescence.