Diagnosing magnetars with transient cooling

Transient X-ray emission, with an approximate t^{-0.7} decay, was observed from SGR 1900+14 over 40 days following the the giant flare of 27 Aug 1998. We calculate in detail the diffusion of heat to the surface of a neutron star through an intense 10^{14}-10^{15} G magnetic field, following the release of magnetic energy in its outer layers. We show that the power law index, the fraction of burst energy in the afterglow, and the return to persistent emission can all be understood if the star is composed of normal baryonic material.Comment: 9 pages, 1 eps figur

The method of diffusion bonding in a vacuum without the application of external pressure.

Developed and experimentally confirmed a new technology of diffusion bonding in a vacuum without the application of external pressure for "bronzing" Surface axial piston pumps. Thus the pressure necessary for diffusion bonding is generated by the difference of thermal expansion of bronze and steel during heating and soaking at 750 ° C for 30 minutes. Thus, in cases where bronzing molding, welding, diffusion deposition difficult and the use of classical methods of diffusion bonding is not possible (can not attach an external mechanical pressure), the proposed method of diffusion bonding is effective.Разработана и экспериментально подтверждена новая технология диффузионной сварки в вакууме без приложения внешнего давления для «бронзирования» рабочих поверхностей аксиально-поршневых гидронасосов. При этом давление, необходимое для обеспечения диффузионной сварки, формируется за счет разности термического расширения бронзы и стали в процессе нагрева и выдержки при 750 °С, 30 минут. Таким образом для случаев, когда бронзирование методами литья, наплавки, диффузионного напыления затруднительно, а использование классических способов диффузионной сварки не представляется возможным (не удается приложить внешнее механическое давление), предложенный способ диффузионной сварки эффективен.Хозяйственный договор № 37/2005 от 24.01.2005 г., «Создание производственной технологии бронзирования цилиндрических отверстий блока цилиндров типа 310.4.56.260 СБ» заключенный между ОАО «ПСМ» - заказчик и УГЛТУ – исполнитель

White Dwarf Donors in Ultracompact Binaries: The Stellar Structure of Finite Entropy Objects

We discuss the mass-radius (M-R) relations for low-mass (M<0.1 Msun) white dwarfs (WDs) of arbitrary degeneracy and evolved (He, C, O) composition. We do so with both a simple analytical model and models calculated by integration of hydrostatic balance using a modern equation of state valid for fully ionized plasmas. The M-R plane is divided into three regions where either Coulomb physics, degenerate electrons or a classical gas dominate the WD structure. For a given M and central temperature, T_c, the M-R relation has two branches differentiated by the model's entropy content. We present the M-R relations for a sequence of constant entropy WDs of arbitrary degeneracy parameterized by M and T_c for pure He, C, and O. We discuss the applications of these models to the recently discovered accreting millisecond pulsars. We show the relationship between the orbital inclination for these binaries and the donor's composition and T_c. In particular we find from orbital inclination constraints that the probability XTE J1807-294 can accommodate a He donor is approximately 15% while for XTE J0929-304, it is approximately 35%. We argue that if the donors in ultracompact systems evolve adiabatically, there should be 60-160 more systems at orbital periods of 40 min than at orbital periods of 10 min, depending on the donor's composition.Comment: emulateapj style, 11 pages, 12 figures. Accepted to the Astrophysical Journal. Tables with interpolation routines of the M-R relations are available at http://www.physics.ucsb.edu/~cjdeloye/research.htm

The Neutron Star Crust: Nuclear Physics Input

A fully self-consistent model of the neutron star inner crust based upon models of the nucleonic equation of state at zero temperature is constructed. The results nearly match those of previous calculations of the inner crust given the same input equation of state. The extent to which the uncertainties in the symmetry energy, the compressibility, and the equation of state of low-density neutron matter affect the composition of the crust are examined. The composition and pressure of the crust is sensitive to the description of low-density neutron matter and the nuclear symmetry energy, and the latter dependence is non-monotonic, giving larger nuclei for moderate symmetry energies and smaller nuclei for more extreme symmetry energies. Future nuclear experiments may help constrain the crust and future astrophysical observations may constrain the nuclear physics input.Comment: 9 pages, 8 figures. Submitted to PR

Rapid Cooling of the Neutron Star in Cassiopeia A Triggered by Neutron Superfluidity in Dense Matter

We propose that the observed cooling of the neutron star in Cassiopeia A is due to enhanced neutrino emission from the recent onset of the breaking and formation of neutron Cooper pairs in the 3P2 channel. We find that the critical temperature for this superfluid transition is ~0.5x10^9 K. The observed rapidity of the cooling implies that protons were already in a superconducting state with a larger critical temperature. Our prediction that this cooling will continue for several decades at the present rate can be tested by continuous monitoring of this neutron star.Comment: Revised version, to be published in Phys. Rev. Let

Theoretical Examination of the Lithium Depletion Boundary

We explore the sensitivity in open cluster ages obtained by the lithium depletion boundary (LDB) technique to the stellar model input physics. The LDB age technique is limited to open clusters with ages ranging from 20 to 200 Myr. Effective 1-sig errors in the LDB technique due to uncertain input physics are roughly 3% at the oldest age increasing to 8% at the youngest age. Bolometric correction uncertainties add an additional 10 to 6% error to the LDB age technique for old and young clusters, respectively. Rotation rates matching the observed fastest rotators in the Pleiades affect LDB ages by less than 2%. The range of rotation rates in an open cluster are expected to ``smear'' the LDB location by only 0.02 mag for a Pleiades age cluster increasing to 0.06 mag for a 20 Myr cluster. Thus, the observational error of locating the LDB (~7-10%) and the bolometric correction uncertainty currently dominate the error in LDB ages. For our base case, we formally derive a LDB age of 148 +- 19 Myr for the Pleiades, where the error includes 8, 3, and 9% contributions from observational, theoretical, and bolometric correction sources, respectively. A maximally plausible 0.3 magnitude shift in the I-band bolometric correction to reconcile main sequence isochrone fits with the observed (V-I) color for the low mass Pleiades members results in an age of 126 +- 11 Myr, where the error includes observational and theoretical errors only. Upper main-sequence-fitting ages that do not include convective core overshoot for the Pleiades (~75 Myr) are ruled out by the LDB age technique.Comment: 35 pages, 9 figures, accepted Ap

Ion structure factors and electron transport in dense Coulomb plasmas

The dynamical structure factor of a Coulomb crystal of ions is calculated at arbitrary temperature below the melting point taking into account multi-phonon processes in the harmonic approximation. In a strongly coupled Coulomb ion liquid, the static structure factor is split into two parts, a Bragg-diffraction-like one, describing incipient long-range order structures, and an inelastic part corresponding to thermal ion density fluctuations. It is assumed that the diffractionlike scattering does not lead to the electron relaxation in the liquid phase. This assumption, together with the inclusion of multi-phonon processes in the crystalline phase, eliminates large discontinuities of the transport coefficients (jumps of the thermal and electric conductivities, as well as shear viscosity, reported previously) at a melting point.Comment: 4 pages, 2 figures, REVTeX using epsf.sty. Phys. Rev. Lett., in pres

Electron thermal conductivity owing to collisions between degenerate electrons

We calculate the thermal conductivity of electrons produced by electron-electron Coulomb scattering in a strongly degenerate electron gas taking into account the Landau damping of transverse plasmons. The Landau damping strongly reduces this conductivity in the domain of ultrarelativistic electrons at temperatures below the electron plasma temperature. In the inner crust of a neutron star at temperatures T < 1e7 K this thermal conductivity completely dominates over the electron conductivity due to electron-ion (electron-phonon) scattering and becomes competitive with the the electron conductivity due to scattering of electrons by impurity ions.Comment: 8 pages, 3 figure