Hybrid stars in the light of GW170817

We have studied the effect of tidal deformability constraint given by the binary neutron star merger event GW170817 on the equations of state (EOS) of hybrid stars. The EOS are constructed by matching the hadronic EOS described by relativistic mean field (RMF) model and parameter sets NL3, TM1 and NL3$\omega\rho$ with the quark matter EOS described by modified MIT bag model, via Gibbs' construction. It is found that the tidal deformability constraints along with the lower bound on maximum mass ($M_{\rm max}=2.01\pm0.04M_\odot$) significantly limit the bag model parameter space ($B_{\rm eff}^{1/4}$, $a_4$). We also obtain upper limits on the radius of $1.4M_\odot$ and $1.6M_\odot$ stars as $R_{1.4}\leq13.2-13.5$ km and $R_{1.6}\leq13.2-13.4$ km, respectively for different hadronic EOS considered here.Comment: version accepted by Ap

Constraining the relativistic mean-field model equations of state with gravitational wave observations

The first detection of gravitational waves from the binary neutron star merger event GW170817 has started to provide important new constraints on the nuclear equation of state at high density. The tidal deformability bound of GW170817 combined with the observed two solar mass neutron star poses a serious challenge to theoretical formulations of realistic equations of state. We analyze a fully comprehensive set of relativistic nuclear mean-field theories by confronting them with the observational bounds and the measured neutron-skin thickness. We find that only a few models can withstand these bounds which predict a stiff overall equation of state but with a soft neutron-proton symmetry energy. Two possible indications are proposed: Circumstantial evidence of hadron-quark phase transition inside the star and new parametrizations that are consistent with ground state properties of finite nuclei and observational bounds. Based on extensive analysis of these sets, an upper limit on the radius of a $1.4M_\odot$ neutron star of $R_{1.4}\lesssim 12.9$ km is deduced.Comment: Matches with the published versio

Melting of antikaon condensate in protoneutron stars

We study the melting of a $K^-$ condensate in hot and neutrino-trapped protoneutron stars. In this connection, we adopt relativistic field theoretical models to describe the hadronic and condensed phases. It is observed that the critical temperature of antikaon condensation is enhanced as baryon density increases. For a fixed baryon density, the critical temperature of antikaon condensation in a protoneutron star is smaller than that of a neutron star. We also exhibit the phase diagram of a protoneutron star with a $K^-$ condensate.Comment: 17 pages including 7 figure

Nucleation of antikaon condensed matter in proto neutron stars

A first order phase transition from nuclear matter to antikaon condensed matter may proceed through thermal nucleation of a critical droplet of antikaon condensed matter during the early evolution of proto neutron stars (PNS). Droplets of new phase having radii larger than a critical radius would survive and grow, if the latent heat is transported from the droplet surface to the metastable phase. We investigate the effect of shear viscosity on the thermal nucleation time of the droplets of antikaon condensed matter. In this connection we particularly study the contribution of neutrinos in the shear viscosity and nucleation in PNS.Comment: Manuscript prepared based on the talk given at PANIC11 at MIT, Boston, USA during 24th-29th July, 201

Fluorescence modulation of an aggregation-induced emission active ligand via rigidification in a coordination polymer and its application in singlet oxygen sensing

A new Zn(II)-based coordination polymer (CP) having the formula [Zn(L)(2,2'-bpy)] (1) was synthesized using ZnCl2, 3,3'-(anthracene-9,10-diyl)diacrylic acid ligand (H2L), and 2,2'-bipyridine (2,2'-bpy) in DMF under solvothermal conditions. Here, the anthracene-based dicarboxylic acid ligand shows aggregation-induced emission (AIE) activity in an ethanol/hexane medium. Single-crystal X-diffraction analysis reveals that the one-dimensional (1D) zigzag chainlike structure of 1 is assembled from tetrahedrally coordinated Zn2+ ions interconnected by 2,2'-bpy and ditopic anthracene-based ligand molecules. The crystal structure analysis reveals that the ditopic anthracene-based flexible ligand adopts a twisted conformation in the CP crystal compared to its free state. Because of the twisted conformation of the ATE active ligand in the CP crystal, a large (similar to 80 nm) hypsochromic shift was observed in the emission spectrum with a drastic color change compared to the free state of ligand. The origin of these rare fluorescence properties is ascribed to the twisted diacrylic acid ligand conformation and rigidity in the CP crystal. An unprecedented response was observed toward singlet oxygen (O-1(2)) by 1 via a fluorescence turn-off mechanism. The presence of the anthracene moiety is the main influential factor for O-1(2) sensing, which undergoes [4 + 2] cycloaddition reaction with O-1(2), producing a nonemissive 9,10-endoperoxide product. The unique photoluminescence properties along with tunable fluorescence responses indicate that incorporating an AIE active anthracene core into the CP crystal is a beneficial strategy to develop new fluorescent materials with significant sensing ability

Glitch Behavior of Pulsars and Contribution from Neutron Star Crust

Pulsars are highly magnetized rotating neutron stars with a very stable rotation speed. Irrespective of their stable rotation rate, many pulsars have been observed with the sudden jump in the rotation rate, which is known as pulsar glitch. The glitch phenomena are considered to be an exhibit of superfluidity of neutron matter inside the neutron star's crustal region. The magnitude of such rapid change in rotation rate relative to their stable rotation frequency can quantify the moment of inertia of the crustal region to the total moment of inertia of the star called as the fractional moment of inertia (FMI). In this paper, we have calculated FMI for different masses of the star using six different representative unified equations of state (EoS) constructed under Relativistic Mean Field (RMF) framework. We have performed an event-wise comparison of FMI obtained from data with that of theoretically calculated values with and without considering the entrainment effect. It is found that larger glitches can't be explained by crustal FMI alone, even without the entrainment.Comment: 9 pages, 3 figures, 1 table, revised, accepted for publication in Ap