# Evolution of spectral and temporal properties of MAXI J1836-194 during 2011 outburst

## TL;DR

This study analyzes the 2011 outburst of MAXI J1836-194 using spectral and timing data, revealing accretion dynamics, spectral state transitions, and the outburst's classification as 'failed' due to the absence of soft states.

## Contribution

First detailed spectral and timing analysis of MAXI J1836-194's 2011 outburst using TCAF model to extract physical accretion parameters and classify spectral states.

## Key findings

- Observed QPO frequency evolution during the outburst.
- Identified spectral state transitions from hard to hard-intermediate.
- Classified the outburst as 'failed' due to lack of soft states.

## Abstract

We study transient Galatic black hole candidate MAXI~J1836-194 during its 2011 outburst using RXTE/PCA archival data. 2.5-25~keV spectra are fitted with Two Component Advective Flow (TCAF) model fits file as an additive table local model in XSPEC. From TCAF model spectral fits, physical parameters such as Keplerian disk rate, sub-Keplerian halo rate, shock location and compression ratio are extracted directly for better understanding of accretion processes around the BHC during this outburst. Low frequency quasi-periodic oscillation (QPO) are observed sporadically during the entire epoch of the outburst, with a general trend of increasing frequency during rising and decreasing frequency during declining phases of the outburst, as in other transient BHCs. The nature of the variation of the accretion rate ratio (ratio of halo and disk rates) and QPOs (if observed), allows us to properly classify entire epoch of the outburst into following two spectral state, such as hard (HS), hard-intermediate (HIMS). These states are observed in the sequence of HS (Ris.) $\rightarrow$ HIMS (Ris.) $\rightarrow$ HIMS (Dec.) $\rightarrow$ HS (Dec.). This outburst of MAXI~J1836-194 could be termed as `failed' outburst, since no observation of soft (SS) and soft-intermediate (SIMS) spectral state are found during the entire outburst.