Three-body force effect on P-3 F-2 neutron superfluidity in neutron matter, neutron star matter, and neutron stars

We investigate the effect of microscopic three-body forces on the P-3 F-2 neutron superfluidity in neutron matter, beta-stable neutron star matter, and neutron stars by using the BCS theory and the Brueckner-Hartree-Fock approach. We adopt the Argonne V18 potential supplemented with a microscopic three-body force as the realistic nucleon-nucleon interaction. We have concentrated on studying the three-body force effect on the P-3 F-2 neutron pairing gap. It is found that the three-body force effect considerably enhances the P-3 F-2 neutron superfluidity in neutron star matter and neutron stars.

(PF2)-P-3 neutron superfluidity in neutron stars and three-body force effect

We investigate the (PF2)-P-3 neutron superfluidity in beta-stable neutron star matter and neutron stars by using the BCS theory and the Brueckner-Hartree-Fock approach. We adopt the Argonne V-18 potential supplemented with a microscopic three-body force as the realistic nucleon-nucleon interaction. We have concentrated on studying the three-body force effect on the (PF2)-P-3 neutron pairing gap. It is found that the three-body force effect is to enhance remarkably the (PF2)-P-3 neutron superfluidity in neutron star matter and neutron stars.

Antikaon condensation and in-medium kaon and antikaon production in protoneutron stars

Antikaon condensation and kaon and antikaon production in protoneutron stars are investigated in a chiral hadronic model (also referred to as the FST model in this paper). The effects of neutrino trapping on protoneutron stars are analyzed systematically. It is shown that neutrino trapping makes the critical density of K- condensation delay to higher density and (K) over bar (0) condensation not occur. The equation of state (EOS) of (proto)neutron star matter with neutrino trapping is stiffer than that without neutrino trapping, As a result, the maximum masses of (proto)neutron stars with neutrino trapping are larger than those without neutrino trapping. If hyperons are taken into account, antikaon does not form a condensate in (Proto)neutron stars. Meanwhile, the corresponding EOS becomes much softer, and the maximum masses of (proto)neutron stars are smaller than those without hyprons. Finally, our results illustrate that the Q values for K+ and K- production in (proto)neutron stars are not sensitive to neutrino trapping and inclusion of hyperons.

Antikaon condensation and deconfinement phase transition in neutron stars

Antikaon condensation and deconfinement phase transition in neutron stars are investigated in a chiral hadronic model (also referred as to the FST model) for the hadronic phase and in the MIT bag model for the deconfined quark matter phase. It is shown that the existence of quark matter phase makes antikaon condensation impossible in neutron stars. The properties of neutron stars are sensitive to the bag constant. For the small values of the bag constant, the pure quark matter core appears and hyperons are strongly suppressed in neutron stars, whereas for the large bag constant, the hadron-quark mixed phase exists in the center of neutron stars. The maximum masses of neutron stars with the quark matter phase are lower than those without the quark matter phase; meanwhile, the maximum masses of neutron stars with the quark matter phase increase with the bag constant.

Transport parameters in neutron stars from in-medium N N cross sections

We present a numerical study of shear viscosity and thermal conductivity of symmetric nuclear matter, pure neutron matter, and beta-stable nuclear matter, in the framework of the Brueckner theory. The calculation of in-medium cross sections and nucleon effective masses is performed with a consistent two- and three-body interaction. The investigation covers a wide baryon density range as needed in the applications to neutron stars. The results for the transport coefficients in beta-stable nuclear matter are used to make preliminary predictions on the damping time scales of nonradial modes in neutron stars.

Searching the Sky with CONFIGR-STARS

SyNAPSE program of the Defense Advanced Projects Research Agency (HRL Laboratories LLC, subcontract #801881-BS under DARPA prime contract HR0011-09-C-0001); CELEST, a National Science Foundation Science of Learning Center (SBE-0354378)

High-resolution Keck I spectroscopy of Galactic halo post-asymptotic giant branch stars

Absolute and differential abundance analyses have been performed from high-resolution, high signal-to-noise ratio optical (Keck I) spectra for three evolved Galactic halo stars, namely PG 1704 + 222, HD 341617 and LSIV -0401. Their derived atmospheric parameters indicate that all three objects are undergoing a post-asymptotic giant branch (post-AGB) phase of evolution. A differential abundance analysis reveals HD 341617 as having a mild carbon deficiency of 0.74 dex, possibly due to the star having evolved off the AGB before the onset of the third dredge-up. Although such carbon underabundances are typical of hot post-AGB objects, the same trend is not observed in PG 1704 + 222, where the carbon abundance is found to be consistent with those derived for nitrogen and oxygen. Hence, a dredge-up scenario need not be invoked to explain the chemical composition of PG 1704 + 222. For LSIV -0401 no iron deficiency is apparent relative to magnesium and silicon, and hence a gas- dust separation event in the AGB progenitor need not be invoked for this star.

CaII K interstellar observations towards early-type disc and halo stars

We present high-resolution (R = lambda/Deltalambda similar to 40 000) Ca II K interstellar observations (lambda(air) = 3933.66Angstrom) towards 88 mainly B-type stars, of which 74 are taken from the Edinburgh-Cape or Palomar-Green surveys, and 81 have > 25degrees. The majority of the data come from previously existing spectroscopy, although also included are 18 new observations of stars with echelle spectra taken with UVES on the Very Large Telescope UT2 (Kueyen). Some 49 of the sample stars have distance estimates above the Galactic plane (z) greater than or equal to 1 kpc, and are thus good probes of the halo interstellar medium. Of the 362 interstellar Ca K components that we detect, 75 (21 per cent) have absolute values of their LSR velocity values exceeding 40 km s(-1). In terms of the deviation velocity for the sightlines with distance estimates, 46/273 (17 per cent) of components have velocity values exceeding those predicted by standard Galactic rotation by more than 40 km s(-1). Combining this data set with previous observations, we find that the median value of the reduced equivalent width (REW) of stars with z greater than or equal to 1 kpc (EW x sin ) is similar to 115 mAngstrom (n = 80), similar to that observed in extragalactic sightlines by Bowen. Using data of all z distances, the REW at infinity is found to be similar to 130 mAngstrom, with the scaleheight (1) of the Ca II K column density distribution being;z 800 pc (n = 196) and reduced column density at infinity of log[N(Ca II K) cm(-2)] similar to 12.24. This implies that similar to30 per cent of Ca II K absorption occurs at distances exceeding similar to1 kpc. For nine sightlines, with distance exceeding 1 kpc and with a companion object within 5degrees, we find that all but two have values of Ca II reduced equivalent width the same to within similar to20 per cent, when the REW of the nearest object is extrapolated to the distance of the further of the pair, and assuming 1 = 800 pc. For 29 of our sightlines with z greater than or equal to 1 kpc and a H I detection from the Leiden-Dwingeloo survey (beamsize of 0.5degrees), we find log(N(Ca II K)IN(H I)) ranging from -7.4 to - 8.4. Values of the Ca II K abundance relative to neutral hydrogen (log[N(Ca II K) cm(-2)] - log[N(H I) cm(-2)]) are found to be more than similar to0.5 dex higher in stars with distances exceeding approximate to100 pc, when compared with the (log[N(Ca II K) cm(-2)] -log[N(H-tot) cm(-2)]) values found in nearby sightlines such as those in Wakker & Mathis (2000). Finally, stellar Ca II K equivalent widths of the sample are determined for 26 objects.

CaII K interstellar observations towards early-type disc and halo stars - distances to intermediate- and high-velocity clouds

We compare existing high spectral resolution (R = lambda/Deltalambda similar to 40 000) Ca II Kobservations (lambda(air) = 3933.66 Angstrom) towards 88 mainly B-type stars, and new observations taken using the Intermediate dispersion Spectrograph and Imaging System (ISIS) on the William Herschel Telescope at R similar to 10 000 towards three stars taken from the Palomar-Green Survey, with 21-cm HI emission-line profiles, in order to search for optical absorption towards known intermediate- and high-velocity cloud complexes. Given certain assumptions, limits to the gas phase abundance of Ca II are estimated for the cloud components. We use the data to derive the following distances from the Galactic plane (z). (i) Tentative lower z-height limits of 2800 and 4100 pc towards complex C using lack of absorption in the spectra of HD341617 and PG 0855 + 294, respectively. (ii) A weak lower z-height of 1400 pc towards complex WA-WB using lack of absorption in EC 09470-1433 and a weak lower limit of 2470 pc using lack of absorption in EC 09452-1403. (iii) An upper z- height of 2470 pc towards a southern intermediate- velocity cloud (IVC) with v(LSR) = -55 km s(-1) using PG 2351 + 198. (iv) Detection of a possible IVC in Ca II absorption at v(LSR) = +52 km s(-1) using EC 20104-2944. No associated HI in emission is detected. At this position, normal Galactic rotation predicts velocities of up to similar to+ 25 km s(-1). The detection puts an upper z-height of 1860 pc to the cloud. (v) Tentative HI and Ca II K detections towards an IVC at similar to+70 km s(-1) in the direction of high-velocity cloud (HVC) complex WE, sightline EC 06387-8045, indicating that the IVC may be at a z-height lower than 1770 pc. (vi) Detection of Ca II K absorption in the spectrum of PG 0855 + 294 in the direction of IV20, indicating that this IVC has a z-height smaller than 4100 pc. (vii) A weak lower z-height of 4300 pc towards a small HVC with v(LSR) = +115 km s(-1) at l, b = 200degrees, + 52degrees, using lack of absorption in the Ca II K spectrum of PG 0955 + 291.