text: 370,15,1209747112042409984,96253726,Navin Sridhar,"Holiday special! New paper out – <LINK>! This is a paper that I started working on during my undergrad @CaltechSURF project with @jaj_garcia, which later grew on to become a wonderful collaboration with @vicgrinberg, Jack Steiner, Riley Connors among others (1/8) In this paper, we investigate the evolution of certain properties of black hole accretion disk/corona viz., inner disk radius, ionization parameter, temperatures of—inner disk, corona, and its optical depth, etc., across the bright hard to soft state transition of GX 339–4 (2/8) By employing a set of relativistic reflection models, we deduce that the inner disk truncation radius approaches R_in~ISCO during the early onset of bright hard state, and the disk inner edge remains small (&lt;9 Gravitational radii) throughout the hard to soft state transition(3/8) We compare the disk properties (mentioned in 2/8) between outbursts with state transitions occurring at *different luminosities*, and find identical evolutionary trends in the disk properties (including R_in~ISCO), with differences seen only in the temp. and optical depth (4/8) By applying a self-consistent Comptonized accretion disk model accounting for the scatter of disk photons by corona, we find R_in~ISCO, using the temperature dependent values of spectral hardening factor—thereby independently confirming our results from reflection analysis (5/8) With the inner disk barely moving towards the black hole during the bright hard to soft state transition, the changes seen in the disk/coronal properties can be attributed to factors like coronal compactification, increase in accretion rate, spectral hardening factor, etc. (6/8) In the end, we also establish that for ~Kerr black holes, data from RXTE/PCA along with relxill family of relativistic reflection models is capable of discerning Fe K fluorescent features, narrow enough to being able to constrain disk inner radius as large as R_in~120*ISCO (7/8) For a broader discussion of even more model parameters, and for a detailed analysis procedure with the underlying statistical footing (MCMC), please go through our paper: <LINK>. Feel free to share this work, and your questions/comments if any :) (8/8)",https://arxiv.org/abs/1912.11447,"We present the analysis of several observations of the black hole binary GX 339--4 during its bright intermediate states from two different outbursts (2002 and 2004), as observed by RXTE/PCA. We perform a consistent study of its reflection spectrum by employing the relxill family of relativistic reflection models to probe the evolutionary properties of the accretion disk including the inner disk radius ($R_{\rm in}$), ionization parameter ($\xi$), temperatures of the inner disk ($T_{\rm in}$), corona ($kT_{\rm e}$), and its optical depth ($\tau$). Our analysis indicates that the disk inner edge approaches the inner-most stable circular orbit (ISCO) during the early onset of bright hard state, and that the truncation radius of the disk remains low ($\lesssim 14 R_{\rm g}$) throughout the transition from hard to soft state. This suggests that the changes observed in the accretion disk properties during the state transition are driven by variation in accretion rate, and not necessarily due to changes in the inner disk's radius. We compare the aforementioned disk properties in two different outbursts, with state transitions occurring at dissimilar luminosities, and find identical evolutionary trends in the disk properties, with differences only seen in corona's $kT_{\rm e}$ and $\tau$. We also perform an analysis by employing a self-consistent Comptonized accretion disk model accounting for the scatter of disk photons by the corona, and measure low inner disk truncation radius across the bright intermediate states, using the temperature dependent values of spectral hardening factor, thereby independently confirming our results from the reflection spectrum analysis. ","Evolution of the accretion disk-corona during bright hard-to-soft state