This paper presents the Sixth Catalogue of galactic Wolf-Rayet stars (Pop. I), a short history on the five earlier WR catalogues, improved spectral classification, finding charts, a discussion on related objects, and a review of the current status of Wolf-Rayet star research. The appendix presents a bibliography on most of the Wolf-Rayet literature published since 1867.

The Sixth Catalogue of galactic Wolf-Rayet stars, their past and present

New observational facilities are becoming increasingly capable of observing reflected light from transiting and directly imaged extrasolar planets. In this study, we provide an analytic framework to interpret observed phase curves, geometric albedos, and polarization of giant planet atmospheres. We compute the observables for non-conservative Rayleigh scattering in homogeneous semi-infinite atmospheres using both scalar and vector formalisms. In addition, we compute phase curves and albedos for Lambertian, isotropic, and anisotropic scattering phase functions. We provide analytic expressions for geometric albedos and spherical albedos as a function of the scattering albedo for Rayleigh scattering in semi-infinite atmospheres. Given an observed geometric albedo our prescriptions can be used to estimate the underlying scattering albedo of the atmosphere, which in turn is indicative of the scattering and absorptive properties of the atmosphere. We also study the dependence of polarization in Rayleigh scattering atmospheres on the orbital parameters of the planet-star system, particularly on the orbital inclination. We show how the orbital inclination of non-transiting exoplanets can be constrained from their observed polarization parameters. We consolidate the formalism, solution techniques, and results from analytic models available in the literature, often scattered in various sources, and present a systematic procedure to compute albedos, phase curves, and polarization of reflected light.

https://iopscience.iop.org/article/10.1088/0004-637X/747/1/25/pdf

Analytic models for albedos, phase curves, and polarization of reflected light from exoplanets

Analytic models for albedos, phase curves and polarization of reflected light from exoplanets

Algol (β Persei) is the prototypical semidetached eclipsing binary and a hierarchical triple system. From 2006 to 2010 we obtained 121 high-resolution and high signal-to-noise ratio echelle spectra of this object. Spectral disentangling yields the individual spectra of all three stars, and greatly improved elements both the inner and outer orbits. We find masses of M_A = 3.39 ± 0.06 M⊙, M_B = 0.770 ± 0.009 M⊙ and M_C = 1.58 ± 0.09 M⊙. The disentangled spectra also give the light ratios between the components in the B and V bands. Atmospheric parameters for the three stars are determined, including detailed elemental abundances for Algol A and Algol C. We find the following effective temperatures: T_A = 12 550 ± 120 K, T_B = 4900 ± 300 K and T_C = 7550 ± 250 K. The projected rotational velocities are v_A sin i_A = 50.8 ± 0.8  km/s, v_B sin i_B = 62 ± 2 km/s and v_C sin i_C = 12.4 ± 0.6 km/s. This is the first measurement of the rotational velocity for Algol B, and confirms that it is synchronous with the orbital motion. The abundance patterns of components A and C are identical to within the measurement errors, and are basically solar. They can be summarized as mean metal abundances: [M/H]_A = −0.03 ± 0.08 and [M/H]_C = 0.04 ± 0.09. A carbon deficiency is confirmed for Algol A, with tentative indications for a slight overabundance of nitrogen. The ratio of their abundances is (C/N)_A = 2.0 ± 0.4, half of the solar value of (C/N)⊙ = 4.0 ± 0.7. The new results derived in this study, including detailed abundances and metallicities, will enable tight constraints on theoretical evolutionary models for this complex system.

/pdf/spectroscopically-resolving-the-algol-triple-system-3b5w4wfvvt.pdf

Spectroscopically resolving the Algol triple system

We present numerical simulations of the polarimetric variations produced by a binary star placed at the center of an empty spherical cavity inside a circumbinary ellipsoidal and optically thin envelope. Thomson single-scattering is considered along with pre- and postscattering extinction factors which produce a time-varying optical depth. The orbits are circular or eccentric. The mass ratio (and luminosity ratio) is in general equal to 1.0. As a function of the orbital (and envelope) inclination, the polarization follows a sin2 (i) law. High polarization levels will result from a high inclination, a high optical depth, a flat envelope, or a big central cavity. Polarimetric variations are more apparent for a low inclination, a high optical depth, a flat envelope, a small cavity, or an orbit that brings the stars close to the inner edge of the cavity. It is then shown that the 1978 BME (Brown, McLean, & Emslie) model can be used to find the orbital inclination if it is 45°, even though this model does not include variable absorption effects as in our simulations. The geometry (flatness of the envelope, size of the central cavity) and size of the orbit have no significant influence on the inclination found by the BME model. For eccentric orbits, single-periodic variations (variations seen once per orbit) appear for eccentricities as low as 0.10. As the eccentricity increases, these single-periodic variations dominate over the double-periodic (seen twice per orbit) ones. The inclinations found by the BME model with the first-order coefficients are then more reliable than those found with the second-order coefficients, especially for the highest eccentricities. For low eccentricities, e 0.3, the inclinations can be found with the first or second-order coefficients, if i > 20° and i > 45°, respectively. For the high eccentricities, 0.3 10°. Since with polarimetric observations the true inclination is not known a priori, we discuss how to use the BME model in that context.

J. C. Kemp

Papers

A polarimetric determination of binary inclinations: results for five systems.