Tidal Love numbers of neutron stars

For a variety of fully relativistic polytropic neutron star models we calculate the star's tidal Love number k2. Most realistic equations of state for neutron stars can be approximated as a polytrope with an effective index n~0.5-1.0. The equilibrium stellar model is obtained by numerical integration of the Tolman-Oppenheimer-Volkhov equations. We calculate the linear l=2 static perturbations to the Schwarzschild spacetime following the method of Thorne and Campolattaro. Combining the perturbed Einstein equations into a single second order differential equation for the perturbation to the metric coefficient g_tt, and matching the exterior solution to the asymptotic expansion of the metric in the star's local asymptotic rest frame gives the Love number. Our results agree well with the Newtonian results in the weak field limit. The fully relativistic values differ from the Newtonian values by up to ~24%. The Love number is potentially measurable in gravitational wave signals from inspiralling binary neutron stars.Comment: corrected Eqs. (20) and (23) and entries in Table (1

Constraining neutron star tidal Love numbers with gravitational wave detectors

Ground-based gravitational wave detectors may be able to constrain the nuclear equation of state using the early, low frequency portion of the signal of detected neutron star - neutron star inspirals. In this early adiabatic regime, the influence of a neutron star's internal structure on the phase of the waveform depends only on a single parameter lambda of the star related to its tidal Love number, namely the ratio of the induced quadrupole moment to the perturbing tidal gravitational field. We analyze the information obtainable from gravitational wave frequencies smaller than a cutoff frequency of 400 Hz, where corrections to the internal-structure signal are less than 10 percent. For an inspiral of two non-spinning 1.4 solar mass neutron stars at a distance of 50 Mpc, LIGO II detectors will be able to constrain lambda to lambda < 2.0 10^{37} g cm^2 s^2 with 90% confidence. Fully relativistic stellar models show that the corresponding constraint on radius R for 1.4 solar mass neutron stars would be R < 13.6 km (15.3 km) for a n=0.5 (n=1.0) polytrope.Comment: 4 pages, 2 figures, minor correction

Habitat Selection by Chiricahua Leopard Frogs During Summer Monsoons

One-third of the described species of amphibians worldwide are threatened with extinction, including the Chiricahua leopard frog (Lithobates chiricahuensis).  This frog is highly aquatic, found in portions of Arizona and New Mexico, and listed as threatened under the Endangered Species Act.  Currently, the Chiricahua leopard frog is restricted to anthropogenic sources of water, including tanks maintained for livestock, throughout most of its range.  Movement habits of this frog and patterns of dispersal between disjunct water sources are not well understood.  We attached radio transmitters to 44 total frogs on the Ladder Ranch in southern New Mexico during summer 2014 and located each frog daily for up to 8 weeks (mean = 29 days).  We quantified habitat characteristics at each frog location and a random location 5 meters away.  We assessed fine-scale habitat selection using conditional logistic regression and also explored the degree of variation in selection among individual frogs.  Frogs chose areas with more low-lying cover (especially aquatic vegetation and woody debris), less overstory cover, and a mud substrate.  Whether the location was far from or close to water and the amount of overstory cover did not appear to be important for selection, suggesting that frogs are able to find areas that provide habitat away from water One-third of the described species of amphibians worldwide are threatened with extinction, including the Chiricahua leopard frog (Lithobates chiricahuensis).  This frog is highly aquatic, found in portions of Arizona and New Mexico, and listed as threatened under the Endangered Species Act.  Currently, the Chiricahua leopard frog is restricted to anthropogenic sources of water, including tanks maintained for livestock, throughout most of its range.  Movement habits of this frog and patterns of dispersal between disjunct water sources are not well understood.  We attached radio transmitters to 44 total frogs on the Ladder Ranch in southern New Mexico during summer 2014 and located each frog daily for up to 8 weeks (mean = 29 days).  We quantified habitat characteristics at each frog location and a random location 5 meters away.  We assessed fine-scale habitat selection using conditional logistic regression and also explored the degree of variation in selection among individual frogs.  Frogs chose areas with more low-lying cover (especially aquatic vegetation and woody debris), less overstory cover, and a mud substrate. Whether the location was far from or close to water and the amount of overstory cover did not appear to be important for selection, suggesting that frogs are able to find areas that provide habitat away from water bodies.  The variation among individuals was low, suggesting that tracked were selecting similar habitat characteristics. The findings of this study will inform active management of amphibians in anthropogenic settings, where managers can enhance amphibian habitat characteristics between occupied sites to improve population connectivity

Tidal deformability of neutron stars with realistic equations of state and their gravitational wave signatures in binary inspiral

The early part of the gravitational wave signal of binary neutron star inspirals can potentially yield robust information on the nuclear equation of state. The influence of a star's internal structure on the waveform is characterized by a single parameter: the tidal deformability lambda, which measures the star's quadrupole deformation in response to the companion's perturbing tidal field. We calculate lambda for a wide range of equations of state and find that the value of lambda spans an order of magnitude for the range of equation of state models considered. An analysis of the feasibility of discriminating between neutron star equations of state with gravitational wave observations of the early part of the inspiral reveals that the measurement error in lambda increases steeply with the total mass of the binary. Comparing the errors with the expected range of lambda, we find that Advanced LIGO observations of binaries at a distance of 100 Mpc will probe only unusually stiff equations of state, while the proposed Einstein Telescope is likely to see a clean tidal signature.Comment: 12 pages, submitted to PR

Understanding Movement Patterns of Chiricahua Leopard Frogs to Promote Species Persistence in Desert Ecosystems

One-third of the described species of amphibians worldwide are threatened with extinction, including the Chiricahua leopard frog (Lithobates chiricahuensis). This frog is highly aquatic, found in portions of Arizona and New Mexico, and listed as threatened under the Endangered Species Act. Currently, habitat for the Chiricahua leopard frog generally is restricted to anthropogenic sources of water, including tanks maintained for livestock. Movement habits of this frog and patterns of dispersal between disjunct water sources are not well understood. On the Ladder Ranch, a working bison ranch in southern New Mexico, we constructed pitfall traps to capture frogs leaving stock tanks. We attached radio transmitters to 14 individuals during the summer of 2013 to study the potential for movement between widely-spaced tanks. Individuals captured in stock tanks (n = 11) showed very high site fidelity, never leaving their source location while carrying transmitters up to 18 days. Individuals captured in a nearby creek (n = 3) moved as much as 2800 m over a 17-day period. Daily movements of these individuals varied greatly (mean = 121 m, SD = 249) and do not appear to be related to temperature or precipitation. During the 2014 field season, we will attempt to track a larger number of animals moving along the creek corridor and to nearby tanks. Quantifying movement abilities of native amphibians will allow biologists to manage anthropogenic water sources to support movement between habitat patches and maintain functioning metapopulations, while preserving important features of the Ranch for livestock use

Post-1-Newtonian tidal effects in the gravitational waveform from binary inspirals

The gravitational wave signal from an inspiralling binary neutron star system will contain detailed information about tidal coupling in the system, and thus, about the internal physics of the neutron stars. To extract this information will require highly accurate models for the gravitational waveform. We present here a calculation of the gravitational wave signal from a binary with quadrupolar tidal interactions which includes all post-1-Newtonian-order effects in both the conservative dynamics and wave generation. We consider stars with adiabatically induced quadrupoles moving in circular orbits, and work to linear in the stars' quadrupole moments. We find that post-1-Newtonian corrections increase the tidal signal by approximately 20% at gravitational wave frequencies of 400 Hz.Comment: 7 page

Localized versus itinerant magnetic moments in Na0.72CoO2

Based on experimental 59Co-NMR data in the temperature range between 0.1 and 300 K, we address the problem of the character of the Co 3d-electron based magnetism in Na0.7CoO2. Temperature dependent 59Co-NMR spectra reveal different Co environments below 300 K and their differentiation increases with decreasing temperature. We show that the 23Na- and 59Co-NMR data may consistently be interpreted by assuming that below room temperature the Co 3d-electrons are itinerant. Their magnetic interaction appears to favor an antiferromagnetic coupling, and we identify a substantial orbital contribution corb to the d-electron susceptibility. At low temperatures corb seems to acquire some temperature dependence, suggesting an increasing influence of spin-orbit coupling. The temperature dependence of the spin-lattice relaxation rate T1-1(T) confirms significant variations in the dynamics of this electronic subsystem between 200 and 300K, as previously suggested. Below 200 K, Na0.7CoO2 may be viewed as a weak antiferromagnet with TN below 1 K but this scenario still leaves a number of open questions.Comment: 8.7 pages, 6 Figures, submitted to Phys. Rev.

Unconventional Charge Ordering in Na0.70CoO2 below 300 K

We present the results of measurements of the dc-magnetic susceptibility chi(T) and the 23Na-NMR response of Na_{0.70}CoO_{2} at temperatures between 50 and 340 K. The chi(T) data suggest that for T > 75 K, the Co ions adopt an effective configuration of Co^{3.4+}. The 23Na-NMR response reveals pronounced anomalies near 250 and 295 K, but no evidence for magnetic phase transitions is found in chi(T). Our data suggest the onset of a dramatic change in the Co 3d-electron spin dynamics at 295 K. This process is completed at 230 K. Our results maybe interpreted as evidence for either a tendency to electron localization or an unconventional charge-density wave phenomenon within the cobalt oxide layer, CoO_2, 3d electron system near room temperature.Comment: 4 pages, 4 figures, re-submitted to Physical Review Letters. The manuscript has been revised following the recommendations of the referees. The discussion section contains substantial change

Constraints on the Dense Matter Equation of State and Neutron Star Properties from NICER's Mass-Radius Estimate of PSR J0740+6620 and Multimessenger Observations

In recent years our understanding of the dense matter equation of state (EOS) of neutron stars has significantly improved by analyzing multimessenger data from radio/X-ray pulsars, gravitational wave events, and from nuclear physics constraints. Here we study the additional impact on the EOS from the jointly estimated mass and radius of PSR J0740+6620, presented in Riley et al. (2021) by analyzing a combined dataset from X-ray telescopes NICER and XMM-Newton. We employ two different high-density EOS parameterizations: a piecewise-polytropic (PP) model and a model based on the speed of sound in a neutron star (CS). At nuclear densities these are connected to microscopic calculations of neutron matter based on chiral effective field theory interactions. In addition to the new NICER data for this heavy neutron star, we separately study constraints from the radio timing mass measurement of PSR J0740+6620, the gravitational wave events of binary neutron stars GW190425 and GW170817, and for the latter the associated kilonova AT2017gfo. By combining all these, and the NICER mass-radius estimate of PSR J0030+0451 we find the radius of a 1.4 solar mass neutron star to be constrained to the 95% credible ranges 12.33^{+0.76}_{-0.81} km (PP model) and 12.18^{+0.56}_{-0.79} km (CS model). In addition, we explore different chiral effective field theory calculations and show that the new NICER results provide tight constraints for the pressure of neutron star matter at around twice saturation density, which shows the power of these observations to constrain dense matter interactions at intermediate densities