Browsing by Author "Reisenegger, A"

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    Rotochemical heating in millisecond pulsars
    (2005) Fernández, R; Reisenegger, A
    Rotochemical heating originates in a departure from beta equilibrium due to spin-down compression in a rotating neutron star. The main consequence is that the star eventually arrives at a quasi-equilibrium state in which the thermal photon luminosity depends only on the current value of the spin-down power, which is directly measurable. Only in millisecond pulsars does the spin-down power remain high long enough for this state to be reached with a substantial luminosity. We report an extensive study of the effect of this heating mechanism on the thermal evolution of millisecond pulsars, developing a general formalism in the slow-rotation approximation of general relativity that takes the spatial structure of the star fully into account, and using a sample of realistic equations of state to solve the nonsuperfluid case numerically. We show that nearly all observed millisecond pulsars are very likely to be in the quasi-equilibrium state. Our predicted quasi-equilibrium temperatures for PSR J0437-4715 are only 20% lower than inferred from observations. Accounting for superfluidity should increase the predicted value.
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    The Shapley Supercluster. II. Spectroscopic observations in a wide area and general morphology
    (2000) Quintana, H; Carrasco, ER; Reisenegger, A
    We report 2868 new multiobject spectroscopic measurements of galaxy redshifts in an area roughly 12 degrees x 6 degrees (right ascension x declination) centered on the Shapley Supercluster (SSC). These correspond to 2627 different galaxies. Including other measurements reported in the literature, the total number of galaxies with measured redshifts in a 19 degrees x 16 degrees area centered on the supercluster now reaches 5090. Of these, 949 lie in the redshift range 9000-18,000 km s(-1), which we tentatively identify with the SSC. This unprecedented sample allows a quite detailed qualitative morphological study of the SSC. Based on the three-dimensional distribution of galaxies and clusters of galaxies, we identify several subcondensations of the supercluster, as well as walls and filaments connecting them. We also iind another supercluster in the background, at redshift similar to 23,000 km s(-1).
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    The shapley supercluster. III. Collapse dynamics and mass of the central concentration
    (2000) Reisenegger, A; Quintana, H; Carrasco, ER; Maze, J
    We present the first application of a spherical collapse model to a supercluster of galaxies. Positions and redshifts of similar to 3000 galaxies in the Shapley supercluster (SSC) are used to define velocity caustics that limit the gravitationally collapsing structure in its central part. This is found to extend at least to 8 h(-1) Mpc of the central cluster, A3558, enclosing 11 ACO clusters. Infall velocities reach similar to 2000 km s(-1). Dynamical models of the collapsing region are used to estimate its mass profile. An upper bound on the mass, based on a pure spherical infall model, gives M(<8 h(-1) Mpc) less than or similar to 1.3 x 10(16) h(-1) M. for an Einstein-de Sitter (critical) universe and M(<8 h(-1) Mpc) less than or similar to 8.5 x 10(15) h(-1) M. for an empty universe. The Diaferio & Geller model, based on estimating the escape velocity, gives a significantly lower value, M(<8 h(-1) Mpc) approximate to 2.1 x 10(15) h(-1) M., very similar to the mass Geller et al. found around the Coma cluster by the same method and comparable to or slightly lower than the dynamical mass in the vriialized regions of clusters enclosed in the same region of the SSC. In both models, the overdensity in this region is substantial, but it is far from the value required to account for the peculiar motion of the Local Group with respect to the cosmic microwave background.