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

TL;DR

This paper reports on the first observed outburst of the black hole candidate MAXI J1836-194, analyzing multi-instrument data to characterize its spectral states and classify it as a 'failed' outburst with specific state transitions.

Contribution

It provides the first detailed multi-instrument spectral and timing analysis of MAXI J1836-194's outburst, highlighting its 'failed' outburst nature and state transition behavior.

Findings

The outburst was a 'failed' type with incomplete state transition.

The source transitioned from low/hard to hard intermediate state.

Spectral hardening and flux decrease occurred during the decay phase.

Abstract

MAXI J1836-194 is a transient black-hole candidate discovered in outburst by MAXI 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 of the X-ray flux, thus it entered again the low/hard state and began its return to quiescence.