Study of the long-term evolution of the accretion dynamics of GX 339-4

We study the dynamical behaviour of the galactic black hole source GX 339-4 during 2002-2011 outbursts using RXTE, Swift(XRT), XMM-Newton(PN) archival data. We present the spectral evolution of the source using four outbursts data and discuss their similarities/differences between outbursts. We infer that the second peak in 2002/03 and 2004/05 outbursts can be due to a second instant of triggered instability in the accretion disc due to irradiation from the central X-ray source after peak-I. This propagates in viscous time scale and takes ~80-90 days after peak-I to produce peak-II. This unifies all four outbursts having a long rising time of ~90 days. The dynamical evolution of accretion parameters have been studied by modeling the individual observed spectrum with two-component accretion disc model where a Keplerian accretion disc produces the soft photons and the hard part of the spectrum originates from a hot sub-Keplerian central corona. A generic mathematical model has been proposed to understand the evolution of accretion parameters for sources like GX 339-4 which have longer rising time. Also, the possible differences of physical scenario for outbursts with shorter rising time are also discussed.Comment: Accepted for publication in mnra

Broadband X-ray properties of black holes GRS 1758-258 and 1E 1740.7-2942: AstroSat and NuSTAR results

We present the results on broadband X-ray properties of persistent black hole binaries GRS 1758$-$258 and 1E 1740.7$-$2942 using AstroSat, NuSTAR and Swift-XRT observations carried out during 2016$-$2022. We perform spectral modeling of both sources after eliminating the contamination in their \textit{LAXPC} spectra from nearby X-ray sources. Preliminary spectral modelling using Comptonization and line emission ($\sim$ 6.4 keV) models suggest that GRS 1758$-$258 occupies both dim-soft state ($kT_{bb}=0.37\pm0.01$ keV, $\Gamma\sim5.9$, $L_{bol}=1$ of Eddington luminosity L$_{Edd}$) and hard state ($\Gamma=1.64-2.22$, $kT_{e}$=4$-$45 keV, $L_{bol}$=1$-$5 % L$_{Edd}$) that requires a multi-colour disc blackbody model ($kT_{in}=0.54\pm0.01$ keV) occasionally. 1E 1740.7$-$2942 instead is found only in hard state ($\Gamma$=1.67$-$2.32, $kT_{e}$=5$-$16 keV, $L_{bol}$=1$-$2 % L$_{Edd}$). Reflection properties of both sources are studied by applying relativistic reflection model RELXILL to the broadband spectra. Our results from \textit{AstroSat} and \textit{NuSTAR} consistently unveiled the presence of a Comptonizing region along with an ionized reflection region (ionization parameter $log\xi$=2.7$-$3.8 and 2.7$-$4.7 erg cm s$^{-1}$ in GRS 1758$-$258 and 1E 1740.7$-$2942 respectively) in both sources. Reflection modeling revealed GRS 1758$-$258 to have a high metal abundance ($A_{fe}=3.9^{+0.4}_{-0.3}$ times solar metal abundance) and inclination angle ($i$) of $61\pm2^{\circ}$. In case of 1E 1740.7$-$2942, $i$ is constrained to be $55\pm1^{\circ}$. Finally, we discuss the implication of our findings in the context of accretion dynamics by comparing our results with the previous studies.Comment: Accepted for publication in MNRA

Spectral and accretion evolution of H1743−322 during outbursts in RXTE era

Aims. We study the spectral evolution of the H1743−322 during outbursts in the RXTE era. We aim to connect the variation of the spectral parameters with the accretion parameters along with the progress of the outbursts. We understand the evolution of the accretion parameters and hence the dynamics of the accretion process in light of the irradiated disc instability model. Methods. We provide a comprehensive study of all the outbursts of H1743−322 between 2003 and 2011. We performed spectral modelling of all the RXTE/PCA observations using phenomenological models. Also, we carried out spectral modelling by a hydrodynamic accretion flow model and estimated the accretion parameters. We applied the irradiated disc instability scenario in the presence of both Keplerian and sub-Keplerain accretion components to understand the evolution of accretion parameters. For this purpose, we propose a toy model for the time variation of the accretion rates following a powerlaw during outbursts. Results. All of the outbursts show spectral state transitions in the hardness-intensity diagram. The 2003 and 2004 outbursts are long-duration outbursts and relatively softer than the other outbursts. The 2008b and 2011 outbursts provide a unique opportunity to estimate the critical accretion rate (ṁdc) for triggering an outburst in this system within a narrow range of 0.076 < ṁdc < 0.086 (in Eddington units). In the absence of any dynamical measurement, we attempt to constrain a few orbital parameters of the system using an assumed mass and ṁdc in the range

Effect of seed treatments, spacing and season of sowing on yield and quality of coriander (Coriandrum sativum L.) under rain shelter: Yield and quality of coriander under rain shelter

Coriander is an important herb &amp; seed spice. The yield of coriander is influenced by the agronomic practices adopted during cultivation. This study was carried out in the Department of Plantation Crops and Spices, College of Horticulture, Vellanikkara, Kerala Agricultural University from July 2019 to March 2020 to analyse the effect of seed treatments, spacing and growing season on yield and quality of coriander leaves under rain shelter. The experiment was laid out in factorial completely randomized design (FCRD) with three replications. The study revealed that, presowing seed treatments improved the growth and yield of coriander than untreated seeds. The impact of seed treatments was conspicuous at the time of harvest on growth, yield and quality parameters. Hydropriming for 24 h was found to be the best presowing seed treatment followed by seed treatment with GA3 50 ppm for 8 h. A closer spacing of 10 x 10 cm which accommodated more plants per unit area recorded the highest biomass and herbage yield plot-1. October – December season was found to be the best for obtaining better growth and yield in leaf coriander. Hence, the study concluded that, hydropriming for 24 h or seed treatment with GA3 50 ppm for 8 h, a closer spacing of 10 x 10 cm and October – December season are the ideal combination for the best performance of variety CO-4 for leaf purpose under rain shelter in the tropical moist humid climate