AR-2019-2020

the Poisson distributions, and that the straight fil- aments in the SDSS galaxy distribution can extend only up to a length-scale of 30h1Mpc. Our results indicate that the environment of a galaxy exhibits a gradual transition towards a higher local dimen- sion with increasing length-scales, finally approach- ing a nearly homogeneous network on large scales. We compare our findings with a semi-analytical galaxy catalogue from the Millennium Run simula- tion, and these are in fairly good agreement with the observations. We also test the effects of the number density of the sample and the cut-off in the goodness of fit, which shows that the results are nearly independent of these factors. Finally, we apply the method to a set of simulations of the segment Cox process and we find that it can char- acterize such distributions. This anyalysis has been done in collaboration with Suman Sarkar. Sanjay Kumar Pandey Software to compute the energy dependent time-lag and r.m.s from a thermal Comptonized medium Understanding various observed phenomena in X- ray binaries involves some very challenging and interesting phenomena of astrophysics. Quasi- periodic oscillations (QPO) in low-mass X-ray bi- naries (LMXB) is one such problem. It is be- lieved that X-ray luminosity of X-ray binaries is due to accretion disc formed by material accreted from a companion star on the copact star such as a netron star. X-ray emission from these binary system vary on wide range of time scales. This variability is in general quantified by computing power density spectra (PDS). Peaked feature of PDS are QPOs. Several models have been pro- posed to explain the observed kHz QPOs. One such model is proposed by Kumar and Misra in 2014. Using the linearized time-dependent Kom- paneets equation, they proposed a method to cal- culate shape of the r.m.s. as well as time-lag as a function of energy. We have developed a soft- ware “COMPT-Time-Lag-RMS” which consists of numerical codes to compute the energy dependent time-lag and r.m.s from a thermal Comptonized medium. The software computes the time and en- ergy dependent time-lag when (a) the seed photon temperature is varied and (b) the coronal heating rate is varied. The energy dependent time-lags are due to light travel timing affects due to Compton scattering in a medium. The results can be com- pared with observed values, provided the time-lags are interpreted as such. This softwar has been up- loaded to http : //astrosat − ssc.iucaa.in/ ? q = data a nd a nalysis . This work has been doen in col- laboration with Ranjeev Misra. Amit Pathak DFT study on interstellar PAH molecules with aliphatic side groups Polycyclic aromatic hydrocarbon (PAH) molecules have been long adjudged to contribute to the frequently detected distinct emission features at 3 . 3 , 6 . 2 , 7 . 7 , 8 . 6 , 11 . 2 , and 12 . 7 μ m with weaker and blended features distributed in the 3 − 20 μ m re- gion. The comparatively weaker 3 . 4 μ m emission feature has been attributed to have an aliphatic origin as carrier. PAH with an aliphatic functional group attached to it is one of the proposed poten- tial candidate carriers for the 3 . 4 μ m emission band, however, the assignment of carrier is still enig- matic. In this work, we employ density functional theory calculation on a symmetric and compact PAH molecule; coronene (C24H12) with aliphatic side group to investigate any spectral similarities with observed features at 3 − 4 micronμm . The side groups considered in this study are -H (hydro- genated), -CH3 (methyl), -CH2-CH3 (ethyl), and -CH=CH2 (vinyl) functional groups. Considering the possible presence of deuterium (D) in PAHs, we also include D in the aliphatic side group to study the spectral behaviour. We present a detailed anal- ysis of the IR spectra of these molecules and discuss possible astrophysical implications. This work has been in collaboration with Mridusmita Buragohain, Itsuki Sakon, and Takashi Onaka. Bikash Chandra Paul Anisotropic compact objects in f ( T ) gravity with FinchSkea geometry We study the relativistic solutions of anisotropic compact stars with FinchSkea (FS) metric in f ( T ) gravity framework. The modified FS geometry is considered to obtain the equation of state (EoS) for different known stellar objects with given mass and radius. The modified Chaplygin gas (MCG) EoS is also considered to obtain stellar objects, as the EoS inside the star is not yet known. The results ob- tained here are important in the two cases to under- stand properties of known stars, which are however