Evolution and Final Fates of a Rotating 25 M⊙_{\odot} Pop III star

In this proceeding, we present the 1-dimensional stellar evolution of two rotating population III (Pop III) star models, each having a mass of 25 M$_{\odot}$ at the zero-age main-sequence (ZAMS). The slowly rotating model has an initial angular rotational velocity of 10 per cent of the critical angular rotational velocity. In contrast, the rapidly rotating model has an initial angular rotational velocity of 70 per cent of the critical angular rotational velocity. As an effect of rotationally enhanced mixing, we find that the rapidly rotating model suffers an enormous mass loss due to the deposition of a significant amount of CNO elements toward the surface after the main-sequence phase. We also display the simulated light curves as these models explode into core-collapse supernovae (CCSNe).Comment: Resubmitted after incorporating minor revision, Part of 3$^{rd}$ BINA conference proceeding

Revealing nature of GRB 210205A, ZTF21aaeyldq (AT2021any), and follow-up observations with the 4K×\times4K CCD Imager+3.6m DOT

Optical follow-up observations of optical afterglows of gamma-ray bursts are crucial to probe the geometry of outflows, emission mechanisms, energetics, and burst environments. We performed the follow-up observations of GRB 210205A and ZTF21aaeyldq (AT2021any) using the 3.6m Devasthal Optical Telescope (DOT) around one day after the burst to deeper limits due to the longitudinal advantage of the place. This paper presents our analysis of the two objects using data from other collaborative facilities, i.e., 2.2m Calar Alto Astronomical Observatory (CAHA) and other archival data. Our analysis suggests that GRB 210205A is a potential dark burst once compared with the X-ray afterglow data. Also, comparing results with other known and well-studied dark GRBs samples indicate that the reason for the optical darkness of GRB 210205A could either be intrinsic faintness or a high redshift event. Based on our analysis, we also found that ZTF21aaeyldq is the third known orphan afterglow with a measured redshift except for ZTF20aajnksq (AT2020blt) and ZTF19abvizsw (AT2019pim). The multiwavelength afterglow modelling of ZTF21aaeyldq using the afterglowpy package demands a forward shock model for an ISM-like ambient medium with a rather wider jet opening angle. We determine circumburst density of $n_{0}$ = 0.87 cm$^{-3}$, kinetic energy $E_{k}$ = 3.80 $\times 10^{52}$ erg and the afterglow modelling also indicates that ZTF21aaeyldq is observed on-axis ($\theta_{obs} < \theta_{core}$) and a gamma-ray counterpart was missed by GRBs satellites. Our results emphasize that the 3.6m DOT has a unique capability for deep follow-up observations of similar and other new transients for deeper observations as a part of time-domain astronomy in the future.Comment: Accepted for Special Issue of Journal of Astrophysics and Astronomy, 2022, Astrophysical jets and observational facilities: National perspective, 05 -09 April 2021, ARIES Nainita

DFT and Molecular Docking Studies of an Antiviral Drug: Molnupiravir

810-812This paper presents computational analysis of molnupiravir, the first orally administered antiviral drug approved by MHRA for the cure of COVID-19. Molnupiravir is the derivative of N4-hydroxycytidine with a ribose residue attached to an isobutyrate ester group. Method based on DFT has been employed to establish the optimised structure, electronic and optical parameters of the drug molecule. Further, molecular docking of molnupiravir on SARS-CoV-2 protein, glucocorticoid receptor (PDB ID: 1M2Z) has been performed so as to examine the preferred affinity and binding pattern of the drug

A Theoretical Study of Dye-DNA Interactions : Aminobenz (C) Acridine

Using quantum mechanical methods, binding of 7-aminobenz (c) acridine with DNA fragments has been examined. An all valence electron method, CNDO/2, has been employed to compute molecular charge distribution while perturbation theory valid for medium range has been used to obtain the preferred sites. Contribution of different components of intermolecular forces involved in stabilizing the stacked complexes has been analysed. All possible binding complexes have been taken into account and an attempt has been made to explain the activity of the dye

Core-collapse supernova from a possible progenitor star of 100 M⊙_{\odot}

In this work, we study the synthetic explosions of a massive star. We take a 100 M$_{\odot}$ zero--age main--sequence (ZAMS) star and evolve it until the onset of core-collapse using {\tt MESA}. Then, the resulting star model is exploded using the publicly available stellar explosion code, {\tt STELLA}. The outputs of {\tt STELLA} calculations provide us the bolometric light curve and photospheric velocity evolution along with other physical properties of the underlying supernova. In this paper, the effects of having large Hydrogen-envelope on the supernova light curve have been explored. We also explore the effects of the presence of different amounts of nickel mass and the effect of changing the explosion energy of the resulting supernovae from such heavy progenitors, on their bolometric light curves and photospheric velocities.Comment: Published as a Special Issue of Journal of Astrophysics and Astronomy, 2022, Astrophysical jets and observational facilities: National perspective, 05 -09 April 2021, ARIES Nainita

Analyses of Hydrogen-stripped core-collapse supernovae using MOSFiT and MESA based tools

In this work, we employ two publicly available analysis tools to study four hydrogen(H)--stripped core--collapse supernovae (CCSNe) namely, SN 2009jf, iPTF13bvn, SN 2015ap, and SN 2016bau. We use the Modular Open-Source Fitter for Transients ({\tt MOSFiT}) to model the multi band light curves. {\tt MOSFiT} analyses show ejecta masses (log M$_{ej}$) of $0.80_{-0.13}^{+0.18}$ M$_{\odot}$, $0.15_{-0.09}^{+0.13}$ M$_{\odot}$, $0.19_{-0.03}^{+0.03}$ M$_{\odot}$, and $0.19_{+0.02}^{-0.01}$ M$_{\odot}$ for SN 2009jf, iPTF13vn, SN 2015ap, and SN 2016au, respectively. Later, Modules for Experiments in Stellar Astrophysics ({\tt MESA}), is used to construct models of stars from pre-main sequence upto core collapse which serve as the possible progenitors of these H-stripped CCSNe. Based on literature, we model a 12 M$_{\odot}$ ZAMS star as the possible progenitor for iPTF13vn, SN 2015ap, and SN 2016bau while a 20 M$_{\odot}$ ZAMS star is modeled as the possible progenitor for SN 2009jf. Glimpses of stellar engineering and the physical properties of models at various stages of their lifetime have been presented to demonstrate the usefulness of these analysis threads to understand the observed properties of several classes of transients in detail.Comment: Accepted for Special Issue of Journal of Astrophysics and Astronomy, 2022, Astrophysical jets and observational facilities: National perspective, 05 -09 April 2021, ARIES Nainita

Photometric studies on the host galaxies of gamma-ray bursts using 3.6m Devasthal Optical Telescope

In this article, we present multi-band photometric observations and analysis of the host galaxies for a sample of five interesting gamma-ray bursts (GRBs) observed using the 3.6m Devasthal Optical Telescope (DOT) and the back-end instruments. The host galaxy observations of GRBs provide unique opportunities to estimate the stellar mass, ages, star-formation rates, and other vital properties of the burst environments and hence progenitors. We performed a detailed spectral energy distribution modelling of the five host galaxies using an advanced tool called Prospector, a stellar population synthesis model. Furthermore, we compared the results with a larger sample of well-studied host galaxies of GRBs, supernovae, and normal star-forming galaxies. Our SED modelling suggests that GRB 130603B, GRB 140102A, GRB 190829A, and GRB 200826A have massive host galaxies with high star formation rates (SFRs). On the other hand, a supernovae-connected GRB 030329 has a rare low-mass galaxy with a low star formation rate. We also find that GRB 190829A has the highest (in our sample) amount of visual dust extinction and gas in its local environment of the host, suggesting that the observed high energy emission from this burst might have a unique local environment. Broadly, the five GRBs in our sample satisfy the typical correlations between host galaxies parameters and these physical parameters are more common to normal star-forming galaxies at the high-redshift Universe. Our results also demonstrate the capabilities of 3.6m DOT and the back-end instruments for the deeper photometric studies of the host galaxies of energetic transients such as GRBs, supernovae, and other transients in the long run.Comment: Accepted for Special Issue of Journal of Astrophysics and Astronomy, 2022, Astrophysical jets and observational facilities: National perspective, 05 -09 April 2021, ARIES Nainita