arXiv subjects

M. K. Sharma

Publications and source records attributed to M. K. Sharma.

9 recordsLinked to original sources

arXiv2023

Influence of Dark Matter on the Magnetized Neutron Star

Over the past two decades, significant strides have been made in the study of Dark Matter (DM) admixed neutron stars and their associated properties. However, an intriguing facet regarding the effect of DM on magnetized neutron stars still remains unexplored. This study is carried out to analyze the properties of DM admixed magnetized neutron stars. The equation of state for the DM admixed neutron star is calculated using the relativistic mean-field model with the inclusion of a density-dependent magnetic field. Several macroscopic properties, such as mass, radius, particle fractions, tidal deformability, and the $f$-mode frequency, are calculated with different magnetic field strengths and DM configurations. The equation of state is softer with the presence of DM as well as for the parallel components of the magnetic field and vice-versa for the perpendicular one. Other macroscopic properties, such as mass, radius, tidal deformability, etc., are also affected by both DM and magnetic fields. The change in the magnitude of different neutron star observables is proportional to the amount of DM percentage and the strength of the magnetic field. We observe that the change is seen mainly in the core part of the star without affecting the crustal properties.

astro-ph.HE↗

arXiv2023

A Method to Load Tellurium in Liquid Scintillator for the Study of Neutrinoless Double Beta Decay

A method has been developed to load tellurium into liquid scintillator so as to permit searches for neutrinoless double beta decay with high sensitivity. The approach involves the synthesis of an oil-soluble tellurium compound from telluric acid and an organic diol. The process utilises distillable chemicals that can be safely handled underground and affords low radioactive backgrounds, low optical absorption and high light yields at loading levels of at least several percent Te by weight.

physics.ins-det↗

arXiv2023

Magnetised neutron star crust within effective relativistic mean-field model

Even though the crystallize nature of the neutron star crust plays a pivotal role in describing various fascinating astrophysical observations, its microscopic structure is not fully understood in the presence of a colossal magnetic field. In the present work, we study the crustal properties of a neutron star within an effective relativistic mean field framework in the presence of magnetic field strength $\sim 10^{17}$G. We calculate the equilibrium composition of the outer crust by minimizing the Gibbs free energy using the most recent atomic mass evaluations. The magnetic field significantly affects the equation of state (EoS) and the properties of the outer crust, such as neutron drip density, pressure, and melting temperature. For the inner crust, we use the compressible liquid drop model for the first time to study the crustal properties in a magnetic environment. The inner crust properties, such as mass and charge number distribution, isospin asymmetry, cluster density, etc., show typical quantum oscillations (De Haas-van Alphen effect) sensitive to the magnetic field's strength. The density-dependent symmetry energy influences the magnetic inner crust like the field-free case. We study the probable modifications in the pasta structures and it is observed that their mass and thickness changes by $\sim 10-15 \%$ depending upon the magnetic field strength. The fundamental torsional oscillation mode frequency is investigated for the magnetized crust in the context of quasiperiodic oscillations (QPO) in soft gamma repeaters. The magnetic field strengths considered in this work influences only the EoS of outer and shallow regions of the inner crust, which results in no significant change in global neutron star properties. However, the outer crust mass and its moment of inertia increase considerably with increase in magnetic field strength.

astro-ph.HE↗

arXiv2022

Pasta properties of the neutron star within effective relativistic mean-field model

We study the properties of pasta structures and their influence on the neutron star observables employing the effective relativistic mean-field (E-RMF) model. The compressible liquid drop model is used to incorporate the finite size effects, considering the possibility of nonspherical structures in the inner crust. The unified equation of states are constructed for several E-RMF parameters to study various properties such as pasta mass and thickness in the neutron star's crust. The majority of the pasta properties are sensitive to the symmetry energy in the subsaturation density region. Using the results from Monte Carlo simulations, we estimate the shear modulus of the crust in the context of quasiperiodic oscillations from soft gamma-ray repeaters and calculate the frequency of fundamental torsional oscillation mode in the inner crust. Global properties of the neutron star such as mass-radius profile, the moment of inertia, crustal mass, crustal thickness, and fractional crustal moment of inertia are worked out. The results are consistent with various observational and theoretical constraints.

nucl-th↗

arXiv2022

Crustal properties of a neutron star within an effective relativistic mean-field model

We use the effective relativistic mean-field (E-RMF) model to study the crustal properties of the neutron star. The unified equations of state (EoS) are constructed using recently developed E-RMF parameter sets, such as FSUGarnet, IOPB-I, and G3. The outer crust composition is determined using the atomic mass evaluation 2020 data [Chinese Physics C {\bf 45}, 030002 (2021)] along with the available Hartree-Fock-Bogoliubov mass models [Phys. Rev. C {\bf 88}, 024308 (2013)] for neutron-rich nuclei. The structure of the inner crust is estimated by performing the compressible liquid drop model calculations using the same E-RMF functional as that for the uniform nuclear matter in the liquid core. Various neutron star properties such as mass-radius ($M-R$) relation, the moment of inertia ($I$), the fractional crustal moment of inertia ($I_{crust}/I$), mass ($M_{crust})$ and thickness ($l_{crust}$) of the crust are calculated with three unified EoSs. The crustal properties are found to be sensitive to the density-dependent symmetry energy and slope parameter advocating the importance of the unified treatment of neutron star EoS. The three unified EoSs, IOPB-I-U, FSUGarnet-U, and G3-U, reproduced the observational data obtained with different pulsars, NICER, and glitch activity and are found suitable for further description of the structure of the neutron star.

nucl-th↗

arXiv2021

Optical calibration of the SNO+ detector in the water phase with deployed sources

SNO+ is a large-scale liquid scintillator experiment with the primary goal of searching for neutrinoless double beta decay, and is located approximately 2 km underground in SNOLAB, Sudbury, Canada. The detector acquired data for two years as a pure water Cherenkov detector, starting in May 2017. During this period, the optical properties of the detector were measured in situ using a deployed light diffusing sphere, with the goal of improving the detector model and the energy response systematic uncertainties. The measured parameters included the water attenuation coefficients, effective attenuation coefficients for the acrylic vessel, and the angular response of the photomultiplier tubes and their surrounding light concentrators, all across different wavelengths. The calibrated detector model was validated using a deployed tagged gamma source, which showed a 0.6% variation in energy scale across the primary target volume.

physics.ins-det↗

arXiv2015

On partition function in Astronomy \& Astrophysics

In order to analyze spectrum from the interstellar medium (ISM), spectrum of the molecule of interest is recorded in a laboratory, and accurate rotational and centrifugal distortion constants are derived. By using these constants, one can calculate accurate partition function. However, in the same paper, where these constants are derived, the partition function is calculated by using a semi-empirical expression. We have looked into the details of this semi-empirical expression and compared the values, obtained from it, with the accurate ones. As an example, we have considered the case of Methanimine (CH$_2$NH) which is detected in a number of cosmic objects. It is found that for the kinetic temperature $T > 120$ K, the semi-empirical expression gives large value as compared to the accurate one. The deviation becomes about 25\% larger than the accurate one at the kinetic temperature of 400 K.

astro-ph.GA↗

arXiv2015

Some observations about the MOLSCAT

For calculation of cross sections for collisional transitions between rotational levels in a molecule, a computer code, MOLSCAT has been developed by Hutson \& Green (1994). For the transitions between rotational levels in H$_2$CS due to collisions with He atom, we have calculated cross sections under the CS approximation. In the MOLSCAT, there is provision to input more than one values of total energies. Here, for example, we are interested in the cross sections for total energy 11 cm$^{-1}$. The calculations have been done for the single energy 11 cm$^{-1}$ and for eight combinations, having energies (11, 12), (12, 11), (10, 11), (11, 10), (11, 12, 13), (9, 10, 11), (10, 11, 12), (9, 10, 11, 12, 13) cm$^{-1}$. We have found that the cross sections for 11 cm$^{-1}$, in general, differ from one another in all the 9 calculations. The reason for the difference in the results appears that the MOLSCAT uses the intermediate data of calculations for one energy, in the calculations for other energies. Under such circumstances, the possible suggestion can be to run the MOLSCAT for a single energy at a time.

astro-ph.IM↗

arXiv1997

Fission and cluster decay of $^{76}$Sr nucleus in the ground-state and formed in heavy-ion reactions

Calculations for fission and cluster decay of $^{76}Sr$ are presented for this nucleus to be in its ground-state or formed as an excited compound system in heavy-ion reactions. The predicted mass distribution, for the dynamical collective mass transfer process assumed for fission of $^{76}Sr$, is clearly asymmetric, favouring $α$-nuclei. Cluster decay is studied within a preformed cluster model, both for ground-state to ground-state decays and from excited compound system to the ground-state(s) or excited states(s) of the fragments.

nucl-th↗