Abstract
Date & Time: 3 July 2023, 10:00 to 11:00
Speaker: Dr. Tianqi Zhao
Title: Constraining Nuclear Models and Equation of State with Parity-violating Asymmetry of 208Pb and 48Ca
Abstract: Neutron skin of 48Ca and 208Pb have been known to provide important information about the symmetry energy of nuclear matter. Previous skin measurements involving strong integration probes might be subject to various systematic errors. Purely electro-weak probes such as parity-violating asymmetry of 48Ca (CREX) and 208Pb (PREX) in elastic electron scattering are particularly valuable. We generate a few hundred thousand energy density functional and calculate finite nuclear properties, infinite nuclear matter properties as well as neutron star properties. Our joint analysis of PREX and CREX data flavor energy density functional with a large bulk symmetry energy 𝑆𝑣 and a small slope 𝐿, which is in 2-𝑠𝑖𝑔𝑚𝑎 (95\%) tension with nuclei masses and charge radii. This tension leads to a strong constraint on symmetry energy slope 𝐿=42+15−17 MeV. The posterior distribution is dominated by CREX data since CREX ruled out large 𝐿 while PREX likelihood has a big tail which is compatible with small 𝐿. Joint analyses with astronomical constraints including maximum mass, tidal deformability, and radius observation slightly tighten the lower bound 𝐿=43+15−11 MeV. Furthermore, we found the result agree nicely with previous neutron skin experiment, dipole probabilities as well as ab-initial calculation.
Date & Time: 3 July 2023, 11:00 to 12:00
Speaker: Prof. Takashi Nakatsukasa
Title: Transport properties of neutrons in neutron-star crust
Abstract: Structure and dynamics of inhomogeneous asymmetric nuclear matter may influence a number of observed phenomena of neutron stars, such as cooling and dissipation of magnetic fields. Especially, the pulsar glitch phenomena are supposed to occur in the inner crust region. Since the mobility of free neutrons is a key issue, we study transport properties of free neutrons in the inner crust. We discuss effect of Bragg scattering and neutron superfluidity.
Date & Time: 3 July 2023, 12:30 to 13:30
Speaker: Prof. Kazuyuki Sekizawa
Title: Time-Dependent Density Functional Theory for Superfluid Dynamics in the Inner Crust of Neutron Stars
Abstract: Superfluidity is one of the fundamental properties of neutron star matter. For instance, the so-called neutron star "glitch", a sudden increase of the rotational frequency of pulsars, has been considered to be related to dynamics of a huge number of vortices of superfluid neutrons in the inner crust of the neutron star. Although many macroscopic models have been developed so far, precise values of model parameters, like vortex-nucleus interaction, vortex tension, effective mass of nuclear clusters, and so on, are not at all obvious. An important mission for nuclear physicists is to derive such physical ingredients of macroscopic models from microscopic many-body theories taking full account of nucleonic degrees of freedom. The most sophisticated description to date can be achieved by a local formulation of superfluid time-dependent density functional theory (TDDFT), which we call TDSLDA (Time-Dependent Superfluid Local Density Approximation). In this talk, I will briefly introduce TDSLDA and present our recent studies of superfluid dynamics in the inner crust of neutron stars, achieved with state-of-the-art computational tools and top-tier supercomputers.
Date & Time: 3 July 2023, 16:00 to 17:00
Speaker: Prof. S K Patra
Title: Probing the Surface Characteristics of Finite Nuclei and Neutron Stars using the Coherent Density Fluctuation Model
Abstract: The intriguing similarities in structure and composition between finite nuclei and neutron stars suggest that we can explore the physics of compact objects by extending our knowledge from terrestrial experiments and theoretical formulations of dense matter systems. Understanding the equation of state of nuclear matter and pure neutron matter establishes a significant connection between finite nuclei and dense celestial bodies. In our recent study, we propose a method to investigate the nuclear and structural properties of nuclei and neutron stars using a coherent density fluctuation model with the main component being the relativistic mean-field (RMF) equation of state. We derive a density-dependent analytical expression for the binding energy per nucleon in dense matter with varying neutron-proton asymmetry, which reflects the outcomes of the RMF model driven by effective field theory. By applying the obtained energy per nucleon expression, along with the RMF density weight function, within the coherent density fluctuation model, we calculate surface properties such as incompressibility, neutron pressure, symmetry energy, and its derivatives for closed/semi-closed-shell even-even nuclei like 16O, 40Ca, 48Ca, 56Ni, 90Zr, 116Sn, and 208Pb. Furthermore, we adapt this formalism to accurately determine the magnitude range of various structural and isospin compositional properties of a neutron star. The modified functional for the stellar matter is convoluted with a density-dependent weight function specific to the neutron star, which we obtain using the NL3, G3, and IU-FSU parameter sets. This calculation provides numerical values for the incompressibility and symmetry energy of the star. By approaching neutron star properties through a finite nuclei perspective, we establish a multidimensional and strongly correlated link between these two objects of unequal size. The theoretical approach employed in this study opens up new opportunities for nuclear and astrophysicists to uncover a wealth of information about dense astronomical objects and exotic finite nuclei.
Date & Time: 4 July 2023, 9:30 to 10:30
Speaker: Prof. Ang Li
Title: Neutron star inner structure: from the equation of state to the phase state
Abstract: The study of neutron star equation of state (EOS) has entered a quantitative age, with a growing body of robust data to clarify the basic facts of these mysterious objects. And it could be the first big scientific problem (related to QCD in the non-perturbative low energy region) resolved in the era of gravitational wave astronomy, after their first proposition in 1932 (by Landau) and the first discovery in 1967 (by Hewish & Bell). Constraints on EOS mainly come from theoretical many-body calculations, laboratory measurements of nuclear properties & reactions, and observations in astronomy. I will introduce our recent works on constraining the exotic phases of neutron stars by connecting consistently (hyper)nuclear physics and GW+EM observations, including dark matter mixed neutron stars.
Date & Time: 4 July 2023, 11:00 to 12:00
Speaker: Prof. Sarira Sahu
Title: Deciphering the 18 TeV photons from the Gamma-Ray Burst GRB221009A
Abstract: On 9 October, 2022, an extremely powerful gamma-ray burst, GRB 221009A, was detected by several instruments. Despite being obstructed by the Milky Way galaxy, its afterglow outburst outshone all other GRBs seen before. LHAASO detected several thousands very high energy photons extending up to 18 TeV. Detection of such energetic photons are unexpected due to the large opacity of the Universe. It is possible that in the afterglow epoch the intrinsic very high energy photon flux from the source might have increased manifolds, which could compensate the attenuation by pair-production with the extragalactic background light. We propose such a scenario and show that very high energy photons can be observed on the Earth from the interaction of very high energy protons with the seed synchrotron photons in the external forward shock region of the GRB jet.
Date & Time: 4 July 2023, 12:30 to 13:30
Speaker: Mr. Naresh K Patra
Title: Nearly model-independent constraints on dense matter equation of state in a Bayesian approach
Abstract: In this talk, I will discuss the construction of minimally constrained EoSs using a Bayesian approach. Our minimal constraints include a few basic properties of saturated nuclear matter and low-density pure neutron matter EoS obtained from a precise next-to-next-to-next-to-leading-order (N$^{3}$LO) calculation in chiral effective field theory. Then I will show how we found the tidal deformability and radius of NS with mass $1-2 M_\odot$ are strongly correlated with the pressure of $\beta$-equilibrated matter at densities higher than the saturation density ($\rho_0 = 0.16$ fm$^{-3}$) in a nearly model-independent manner. Then I will discuss a parametrized form of pressure for $\beta$-equilibrated matter, around 2$\rho_0$, as a function of neutron star mass and the corresponding tidal deformability.
Date & Time: 4 July 2023, 14:30 to 15:30
Speaker: Prof. Luciano Rezzolla
Title: Binary Neutron Stars: from macroscopic collisions to microphysics
Abstract: I will argue that if black holes represent one the most fascinating implications of Einstein's theory of gravity, neutron stars in binary system are arguably its richest laboratory, where gravity blends with astrophysics and particle physics. I will discuss the rapid recent progress made in modelling these systems and show how the gravitational signal can provide tight constraints on the equation of state and sound speed for matter at nuclear densities, as well as on one of the most important consequences of general relativity for compact stars: the existence of a maximum mass. Finally, I will discuss how the merger may lead to a phase transition from hadronic to quark matter. Such a process would lead to a signature in the post-merger gravitational-wave signal and open an observational window on the production of quark matter in the present Universe.
Date & Time: 4 July 2023, 16:00 to 17:00
Speaker: Mr. SK MD ADIL IMAM
Title: Neutron stars to finite nuclei : A direct mapping
Abstract: The iso-scalar and iso-vector nuclear matter parameters (NMPs) are frequently used to characterise the equations of state (EoSs) that govern the properties of neutron stars (NSs). Recent attempts to relate the radius and tidal deformability of a NS to the individual NMPs have been inconclusive. These properties display strong correlations with the pressure of NS matter which depends on several NMPs. We systematically analyze to isolate the NMPs that predominantly determine the tidal deformability, over a wide range of NS mass. The tidal deformability of the NS with mass 1.2-1.8 M can be determined within 10% directly in terms of four nuclear matter parameters, namely, the incompressibility (K0)and skewness (Q0) of symmetric nuclear matter, and the slope (L0) and curvature parameter (Ksym,0) of symmetry energy.
Date & Time: 5 July 2023, 9:30 to 10:30
Speaker: Prof. B. K. Agrawal
Title: On the relation of tidal deformability of neutron stars with nuclear matter parameters
Abstract: The equations of state which determine the properties of neutron stars are often characterized by the iso-scalar and iso-vector nuclear matter parameters. Recent attempts to relate the tidal deformability of a neutron stars to the individual nuclear matter parameters have been inconclusive. We have performed a systematic analysis to isolate nuclear matter parameters which predominantly determine the tidal deformability over a wide range of neutron stars mass. The tidal deformability of the neutron stars with mass 1.2-1.8 M_sun can be determined within 10% directly in terms of four nuclear matter parameters, namely, the incompressibility K0 and skewness Q0 of symmetric nuclear matter, and the slope L0 and curvature parameter Ksym,0 of symmetry energy.
Date & Time: 5 July 2023, 11:00 to 12:00
Speaker: Dr. Chiranjib Mondal
Title: Detectability of a phase transition in neutron star matter with third-generation gravitational wave interferometers
Abstract: Possible strong first-order hadron-quark phase transitions in neutron star interiors leave an imprint on gravitational waves, which could be detected with planned third-generation interferometers. Given a signal from the late inspiral of a binary neutron star (BNS) coalescence, assessing the presence of such a phase transition depends on the precision that can be attained in the determination of the tidal deformability parameter, as well as on the model used to describe the hybrid star equation of state. I will present a general modelling of the hybrid equation of state spanning the whole parameter space which is consistent with present experimental and observational constraints. Using such modelling I will demonstrate possible identification of hadron-quark phase transition signal from a single loud BNS event in the upcoming network of third generation detectors.
Date & Time: 5 July 2023, 14:30 to 15:30
Speaker: Dr. Bhaskar Biswas
Title: Probing nuclear physics and cosmology with neutron stars
Abstract: Neutron Stars are the densest known objects in the visible universe. They have been observed in several electromagnetic bands and have also been detected in gravitational waves as the binary neutron star merger event GW170817. These observations have led to a better understanding of their interiors, environments, and evolution. In this lecture, I will discuss the current understanding of the neutron star equation of state as it is derived from all available astrophysical observations. At the end of my talk, I will also present a method for inferring the Hubble constant solely from gravitational wave signals from a binary neutron star merger, even when the associated electromagnetic counterparts are missing.
Date & Time: 5 July 2023, 16:00 to 17:00
Speaker: Prof. Ritam Mallick
Title: Machine Learning and universal relations: new tools to Probe the Matter in Neutron Stars
Abstract: The quest to understand the properties of matter at high density has intrigued physicists for more than a few decades. The problem is complicated, as having a proper theory describing it is challenging. Also, earth-based experiments to probe them have yet to materialize. One of the naturally occurring laboratories where such matter exists is the cores of a neutron star. Recent precise mass and radius measurement of quite a few pulsars, along with gravitational wave detection of binary mergers, has thrown some light towards constraining matter properties that can reside inside neutron stars. Out of the few tools which have been used to constrain the matter properties are Machine learning and universal relations. Maschine learning techniques can be used to find the speed of sound inside a neutron star which depends strongly on the equation of state describing the matter. Moreover, few parameters of neutron stars are seen to be insensitive towards the microscopic description of matter and follow almost universal relations with each other. In this talk, we will discuss how both can be used as a tool, their limitations and future prospects of understanding the matter properties at high density
Date & Time: 6 July 2023, 9:30 to 10:30
Speaker: Prof. Bedangadas Mohanty
Title: Rare event searches in Super CDMS experiment
Abstract: Dark matter makes up approximately 27% of the total mass-energy budget of the Universe. However, the identities of the particles that make up dark matter are unknown and remain one of the biggest challenges in Physics. In the first part of the talk, I will discuss the status of the dark matter search from the Super CDMS experiment. In the second part of the talk, I will discuss the search for lightly ionizing particles (LIPs) in the Super CDMS experiment. The standard model (SM) does not include free fractionally charged particles since the quarks are bound within hadrons. However, extensions of SM allow for unbound quarks, non-integer-charged bound states of quarks, or new leptons with fractional charge. Often, they are called LIPs as they would lose energy in detectors at a slower rate than known minimum ionizing particles. Direct searches are exciting because energetic cosmic rays may produce LIPs with masses inaccessible to collider experiments. A clear observation of fractional charge would be important since, depending on the type of particle observed, it might mean that confinement breaks down under some circumstances or that entirely new classes of particles exist. Using the CDMSlite detectors of SuperCDMS, we have explored and excluded a large area in the charge, mass, and velocity parameter space of LIPs. The results will be discussed in the talk.
Date & Time: 6 July 2023, 11:00 to 12:00
Speaker: Dr. Davood Rafiei
Title: X-ray pulse profile as a novel probe for the bosonic dark matter halo around neutron stars
Abstract: We consider the presence of self-interacting bosonic dark matter (DM) within neutron stars (NSs) as a mixed compact object, it is shown that depending on the DM model parameters, i.e. mass, self-coupling constant and its fraction, DM could reside as a dense core inside NS or form an extended halo around it. In this regard, the formation of a DM halo around the NS can potentially change the geometry outside the surface of the star and also the light propagation characteristics in this region. Therefore, as a new observable, we extensively consider the variation of the EM pulse profile in the presence of the DM halo around NSs for different DM model parameters. It is seen that depending on the compactness of the mixed object, minimum fluxes of the pulse profiles would be altered. Our results show that the DM admixed NSs should be considered as a novel possibility to interpret X-ray observations of compact objects during the analysis of NICER and STROBE-X telescopes.
Date & Time: 6 July 2023, 12:30 to 13:30
Speaker: Mr Suprovo Ghosh
Title: Multi-physics constraints at different densities to probe nuclear symmetry energy in Neutron stars
Abstract: Neutron stars provide us the unique opportunity to study cold and dense nuclear matter under extreme conditions far beyond the reach of terrestrial experiments, such as nuclear or heavy-ion collisions. We recently explored the parameter space of both nucleonic and hyperonic stars within the framework of the Relativistic Mean Field model, allowed by present uncertainties in state-of-the-art nuclear and hypernuclear experimental data. We imposed multi-physics constraints at different density regimes to restrict the parameter space: Chiral effective field theory, heavy-ion collision data as well as multi-messenger astrophysical observations of neutron stars. We investigated possible correlations between empirical nuclear and hypernuclear parameters, particularly the symmetry energy and its slope, with observable properties of neutron stars. We found that the most important nuclear parameters to consider for astrophysical data are the effective nucleon mass and the nuclear saturation density. We also concluded that the inclusion of hyperons generates a tension between the astrophysical and heavy ion data constraining considerably the available parameter space.
Date & Time: 6 July 2023, 15:00 to 16:00
Speaker: Mr. Bikram Pradhan
Title: Constraining nuclear parameters using f-modes from glitching pulsars
Abstract: Gravitational waves (GW) emanating from unstable quasi-normal modes in Neutron Stars (NS) could be accessible with the improved sensitivity of the current gravitational wave (GW) detectors or with the next-generation GW detectors and therefore employed to study the NS interior. By considering potential GW candidates detectable by A+ and Einstein Telescope (ET) originating from f-modes excited by glitches in isolated pulsars, we demonstrate the inverse problem of NS asteroseismology in a Bayesian formalism to constrain the nuclear parameters within a relativistic mean field (RMF) description of NS interior. For a single detected GW event from the Vela pulsar in A+ and ET, within a 90\% symmetric credible interval (SCI), the nucleon effective mass ($m^*$) can be restricted within $10\%$ and $5\%$, respectively, while the incompressibility ($K$) and the slope of the symmetry energy ($L$) are only loosely constrained. A single event can constrain the f-mode frequency of a $1.4M_{\odot}$ ($f_{1.4M_{\odot}}$) within 100 Hz and 50 Hz in A+ and ET, respectively. Additionally, we consider multiple GW candidates in our analysis. For multiple (ten) events detected with A+ and ET, $m^*$ can be constrained to 3\% and 2\%, respectively. All the other nuclear saturation parameters get well constrained. The $f_{1.4M_{\odot}}$ can be estimated within 50 Hz and 20 Hz in A+ and ET, respectively. Uncertainty in other NS properties such as radius of a $1.4M_{\odot}$ ($R_{1.4M_{\odot}}$), f-mode damping time of a $1.4M_{\odot}$ ($\tau_{1.4M_{\odot}}$) and few equations of state (EOS) properties including squared speed of sound ($c_s^2$) are also estimated.
Date & Time: 6 July 2023, 16:30 to 17:30
Speaker: Prof. Tanja Hinderer
Title: Probing subatomic physics with gravitational waves from neutron star binary inspirals
Abstract: The gravitational waves from neutron star binary systems carry unique information about their interiors, where matter is compressed by strong gravity to several times nuclear density and novel phases emerge. Measuring this information in the data relies on accurate models of the interplay of matter with strong-field, dynamical gravity. I will discuss recent advances in our understanding of matter signatures in gravitational waves generated during the relatively clean binary inspiral epoch that is accessible with current detectors, with particular focus on different aspects of dynamical tidal effects. I will also summarize what we have learned from recent measurements, and conclude with an outlook onto the prospects and challenges for the next years as gravitational-wave science continues to move towards an era of precision physics.
Date & Time: 6 July 2023, 19:00 to 20:00
Speaker: Prof. Grigoris Panotopoulos
Title: Properties of spherical configurations made of dark matter and dark energy
Abstract:In the halo of a Galaxy a configuration made of Dark matter may be form. At the same time, since Dark energy is everywhere, one can imagine a configuration made of both dark components. Assuming a polytropic equation of state for dark matter, and an extended chaplygin gas EoS for dark energy, we compute the mass-to-radius profiles, the tidal Love numbers as well as the spectra of radial oscillation modes for such Dark stars.
Date & Time: 7 July 2023, 9:30 to 10:30
Speaker: Prof. Debarati Chatterjee
Title: R-modes to probe the presence of Dark Matter in Neutron Stars
Abstract:The recent direct detection of Gravitational Waves from mergers of Neutron Stars has opened up the possibility to explore the properties of dense matter in their interior. Isolated neutron stars can also emit gravitational waves when perturbed, and the wave characteristics if detected may contain signatures of their composition. It is conjectured that dark matter may also exist within neutron stars, and their presence could affect their observable properties. In this talk, I will present the first systematic investigation of effects of the presence of dark matter on r-mode oscillations in neutron stars (NS). Employing a dark matter (DM) model based on the neutron decay anomaly, we imposed constraints on the model using recent multi-messenger astrophysical observations. We then estimated shear and bulk viscosities in presence of DM in comparison with hadronic models. We investigated the effect of DM on the r-mode instability window and also tested their compatibility with current X-ray and pulsar observational data.
Date & Time: 7 July 2023, 11:00 to 12:00
Speaker: Prof. Sophia Han
Title: Challenges in identifying novel phases of dense matter in neutron stars
Abstract: Of great interest for nuclear and particle physics, neutron stars are at the heart of multimessenger astronomy to address long-standing puzzles about how strongly-interacting matter behaves under the most extreme conditions in our Universe. In this talk, I will briefly review what we have learned about the high-density equation of state using astronomical and terrestrial probes, and advances in theory and modeling efforts needed to interpret these observations. In particular I will focus on recent developments in constraining viable scenarios of possible phase transitions in the dense interior of neutron stars, as well as prospects and challenges to identify them in the near future.
Date & Time: 7 July 2023, 12:30 to 13:30
Speaker: Dr. Prasad Ravichandran
Title: Neutron Star to Quark Star Conversion: The Catastrophic and Gradual Mechanism
Abstract: The existence of quark stars is an open problem in astrophysics, and the quest to find such stars has attained a lot of focus in recent years. According to a conjecture of QCD, at extreme densities found in neutron star interior, the normal nuclear matter is no longer the stable ground state, and it is prone to convert to 3-flavor quark matter (u, d, s quark matter), which is the ground state at such densities. Such conversions are possible at the pro-neutron star stage after the core collapse, in isolated neutron stars during their lifetime, or in hyper-massive neutron stars formed in the binary merger. We addressed the shock-induced phase transition scenario by performing simulations in general relativistic hydrodynamics code (GR1D). The simulation reveals the conversion time to be 30-50 microseconds, which indicates a rapid process. This time scale differs from previous studies involving simple analytical estimates. The obtained gravitational wave signal is short-lived (burst-type) with a frequency of about 100 kilohertz and may be observed in future high-frequency GW detectors. The aftermath of deconfinement is 2-flavor quark matter (u,d) to 3-flavor quark matter (u,d,s) conversion, and distinct emissions can originate from it. The time scale and energy budget available indicate that short gamma-ray bursts and fast radio bursts could arise in phase transition events. Further, we have addressed the spin-down driven phase transition scenario, wherein magnetic braking drives neutron stars from their birth (Keplerian rotation) to later stages of life (slow spin). The density rise during spin-down can lead to the formation of a quark core or the growth of an existing quark core (from birth). Such progressive phase transitions differ from catastrophic ones and can produce persistent or multiple transient signals (braking index changes, GWs from excited oscillation modes, neutrino bursts). Detecting these multi-messenger signals and their sky localization may help find the quark/hybrid stars formed via phase transition.
Date & Time: 7 July 2023, 14:30 to 15:30
Speaker: Dr. Tuhin Malik
Title: Unraveling neutron stars' properties: Exploring the Nuclear Equation of State, Hyperons, and Compatibility with pQCD
Abstract:The behavior of the nuclear equation of state (EOS), a crucial factor in describing neutron stars (NSs), is extensively investigated using a Bayesian approach applied to various classes of relativistic mean field models. These models encompass density-dependent meson couplings (DDH), and interactions with non-linear characteristics. Through Bayesian analysis, we explore the parameter space of these models and assess their compatibility with observational data. The study incorporates essential nuclear saturation properties and constraints from neutron stars with masses exceeding 2M⊙. Additionally, a precise N3LO calculation within chiral effective field theory is employed to include the equation of state at low densities, specifically the pure neutron matter EOS. A key aspect examined in this investigation is the possible presence of hyperons within neutron stars and how different model sets account for their onset. Hyperons, exotic particles containing strange quarks, may appear at high densities. By comparing predictions from various models, we can determine the likelihood of hyperon existence within neutron stars and evaluate their influence on the EOS.
Our approach, based on microscopic models of hadronic matter, allows us to discuss neutron star composition and establish a reference in relation to agnostic descriptions of the equation of state connecting the low density EOS to perturbative quantum chromodynamics (pQCD) results, which aim to identify deconfinement signatures. The compatibility of the considered models with pQCD, a framework for understanding the strong nuclear force at high energies, is analyzed. The agreement between the hadronic models and pQCD serves as a measure of their alignment with fundamental particle physics principles. Additionally, measures of conformality and the normalized trace anomaly are calculated for the model sets under consideration. The findings indicate that pQCD favors models exhibiting a substantial contribution from the nonlinear vector field term or incorporating hyperons. This suggests that the inclusion of these features in the models leads to better agreement with fundamental principles and observations. A thorough discussion of the hadronic EOS is considered crucial for identifying a deconfinement phase transition.
Date & Time: 7 July 2023, 16:00 to 17:00
Speaker: Dr. H C Das
Title: Universal Relations for the Anisotropic Neutron Stars
Abstract:Universal relationships play a crucial role in investigating star properties that remain challenging to probe with existing detectors. In this presentation, we explore the characteristics of anisotropic neutron stars using a simplified model. By calculating and analyzing the relationships between certain properties, we discover universal patterns specific to anisotropic stars. Leveraging these equation-of-state-insensitive relationships and employing diverse observational data, we establish constraints on the degree of anisotropy within neutron stars. This talk aims to shed light on the intriguing nature of anisotropic neutron stars and their observable features.