Santanu Mondal

Implementation of two-component advective flow solution in xspec

Spectral and Temporal properties of black hole candidates can be explained reasonably well using Chakrabarti-Titarchuk solution of two component advective flow (TCAF). This model requires two accretion rates, namely, the Keplerian disk accretion rate and the halo accretion rate, the latter being composed of a sub-Keplerian, low angular momentum flow which may or may not develop a shock. In this solution, the relevant parameter is the relative importance of the halo (which creates the Compton cloud region) rate with respect to the Keplerian disk rate (soft photon source). Though this model has been used earlier to manually fit data of several black hole candidates quite satisfactorily, for th e first time, we made it user friendly by implementing it into XSPEC software of GSFC/NASA. This enables any user to extract physical parameters of the accretion flows, such as two accre tion rates, the shock location, the shock strength etc. for any black hole candidate. We provide some examples of fitting a few cases using this model. Most importantly, unlike any other model, we show that TCAF is capable of predicting timing properties from the spectra l fits, since in TCAF, a shock is responsible for deciding spectral slopes as well as QPO frequencies.

Characterization of GX 339-4 outburst of 2010–11: analysis by xspec using two component advective flow model

We study spectral properties of GX 339-4 during its 2010-11 outburst with Two Component Advective Flow (TCAF) model after its inclusion in XSPEC as a table model. We compare results fitted by TCAF model with combined disk black body and power-law model. For a spectral fit, we use 2.5-25 keV spectral data of the PCA instrument onboard RXTE satellite. From our fit, accretion flow parameters such as Keplerian (disk) rate, sub-Keplerian (halo) rate, location and strength of shock are extracted. We quantify how the disk and the halo rates vary during the entire outburst. We study how the halo to disk accretion rate ratio (ARR), quasi-periodic oscillations (QPOs), shock locations and its strength vary when the system passes through hard, hard-intermediate, soft-intermediate, and soft states. We find pieces of evidence of monotonically increasing and decreasing nature of QPO frequencies depending on the variation of ARR during rising and declining phases. Interestingly, on days of transition from hard state to hard-intermediate spectral state (during the rising phase) or vice-versa (during decline phase), ARR is observed to be locally maximum. Non-constancy of ARR while obtaining reasonable fits points to the presence of two independent components in the flow.

ACCRETION FLOW PROPERTIES OF MAXI J1543–564 DURING 2011 OUTBURST FROM THE TCAF SOLUTION

We derive accretion flow properties of the transient black hole candidate (BHC) MAXI J1543–564 using the RXTE data. We use the two-component advective flow (TCAF) solution to fit the data of the initial rising phase of outburst (from 2011 May 10 to 15). The 2.5–25 keV spectra are fitted using the TCAF solution fits file as a local additive table model in XSPEC. We extract physical flow parameters such as the two-component (Keplerian disk and sub-Keplerian halo) accretion rates and size and the property of the Compton cloud (post-shock region close to a black hole). Similar to other classical transient BHCs, monotonic evolution of low-frequency quasi-periodic oscillations (QPOs) is observed during the rising phase of the outburst, which is fitted with the propagating oscillatory shock (POS) model, which describes how the Compton cloud properties change from day to day. From the nature of variations of TCAF model fitted physical flow parameters and QPOs, we only found hard-intermediate and soft-intermediate spectral states during this phase of the outburst under study. We also calculated the frequency of the dominating QPOs from the TCAF model fitted shock parameters and found that they roughly match with the observed and POS model fitted values. From our spectro-temporal study of the source with TCAF and POS models, the most probable mass of the BHC is found to be 12.6–14.0 M ⊙, or .

ACCRETION FLOW DYNAMICS OF MAXI J1836-194 DURING ITS 2011 OUTBURST FROM TCAF SOLUTION

The Galactic transient X-ray binary MAXI~J1836-194 was discovered on 29th August 2011. Here we make a detailed study of the spectral and timing properties of its 2011 outburst using archival data of RXTE Proportional Counter Array instrument. The evolution of accretion flow dynamics of the source during the outburst through spectral analysis with Chakrabarti-Titarchuks two-component advective flow (TCAF) solution as a local table model in XSPEC. We also fitted spectra with combined disk blackbody and power-law models and compared it with the TCAF model fitted results. The source is found to be in hard and hard-intermediate spectral states only during entire phase of this outburst. No soft or soft-intermediate spectral states are observed. This could be due to the fact that this object belongs to a special class of sources (e.g., MAXI~J1659-152, Swift~J1753.5-0127, etc.) that have very short orbital periods and that companion is profusely mass-losing or the disk is immersed inside an excretion disk. In these cases, flows in the accretion disk is primarily dominated by low viscous sub-Keplerian flow and the Keplerian rate is not high enough to initiate softer states. Low-frequency quasi-periodic oscillations (QPOs) are observed sporadically although as in normal outbursts of transient black holes, monotonic evolutions of QPO frequency during both rising and declining phases are observed. From the TCAF fits, we find mass of the black hole in the range of

Estimation of the mass of the black hole candidate MAXI J1659−152 using TCAF and POS models

7.5-11~M_\odot

ACCRETION FLOW DYNAMICS OF MAXI J1659-152 FROM THE SPECTRAL EVOLUTION STUDY OF ITS 2010 OUTBURST USING THE TCAF SOLUTION

and from time differences between peaks of the Keplerian and sub-Keplerian accretion rates we obtain viscous timescale for this particular outburst

Is Compton Cooling Sufficient to Explain Evolution of Observed Quasi-periodic Oscillations in Outburst Sources?

\sim 10

ESTIMATION OF MASS OF COMPACT OBJECT IN H 1743-322 FROM 2010 AND 2011 OUTBURSTS USING TCAF SOLUTION AND SPECTRAL INDEX–QPO FREQUENCY CORRELATION

~days.

Spectral signatures of dissipative standing shocks and mass outflow in presence of Comptonization around a black hole

The Galactic transient black hole candidate (BHC) MAXI~J1659-152 exhibited temporal and spectral evolution during its very first X-ray outburst (2010) after its discovery on 25th Sept. 2010. Our recent studies of a few transient BHCs including MAXI~J1659-152 using Chakrabarti-Titarchuk two-component advective flow (TCAF) solution as an additive table local model in XSPEC revealed details of accretion flow dynamics around the black hole (BH). The TCAF model fitted normalization (N) comes out to be almost constant throughout the entire outburst consisting of several spectral states. We introduce two independent methods to determine the mass (

Accretion Flow Properties of Swift J1753.5-0127 during Its 2005 Outburst

M_{BH}