Browsing by Author "Fabregat, J."

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    First results of an H alpha based search of classical Be stars in the Perseus Arm and beyond
    (OXFORD UNIV PRESS, 2013) Raddi, R.; Drew, J. E.; Fabregat, J.; Steeghs, D.; Wright, N. J.; Sale, S. E.; Farnhill, H. J.; Barlow, M. J.; Greimel, R.; Sabin, L.; Corradi, R. M. L.; Drake, J. J.
    We investigate a region of the Galactic plane, between 120 degrees <= l <= 140 degrees and -1 degrees <= b <= +4 degrees, and uncover a population of moderately reddened (E(B - V) similar to 1) classical Be stars within and beyond the Perseus and Outer Arms. 370 candidate emission-line stars (13 less than or similar to r less than or similar to 16) selected from the Isaac Newton Telescope Photometric H alpha Survey of the Northern Galactic plane have been followed up spectroscopically. A subset of these, 67 stars with properties consistent with those of classical Be stars, have been observed at sufficient spectral resolution (Delta lambda approximate to 2-4 angstrom) at blue wavelengths to narrow down their spectral types. We determine these to a precision estimated to be +/-1 subtype and then we measure reddenings via spectral energy distribution fitting with reference to appropriate model atmospheres. Corrections for contribution to colour excess from circumstellar discs are made using an established scaling to H alpha emission equivalent width. Spectroscopic parallaxes are obtained after luminosity class has been constrained via estimates of distances to neighbouring A/F stars with similar reddenings. Overwhelmingly, the stars in the sample are confirmed as luminous classical Be stars at heliocentric distances ranging from 2 kpc up to similar to 2 kpc. However, the errors are presently too large to enable the cumulative distribution function with respect to distance to distinguish between models placing the stars exclusively in spiral arms, or in a smooth exponentially declining distribution.
  • Thumbnail Image
    Item
    VISTA Milky Way Public Survey
    (2009) Minniti, D.; Lucas, P.; Ahumada, A. V.; Zoccali, M.; Catelan, Marcio; Morelli, L.; Tappert, C.; Pignata, G.; Toledo, I.; Ruiz, M. T.; Carraro, G.; Casassus, S.; Bronfman, L.; Barbá, R. H.; Gamen, R.; Gieren, W.; Geisler, D.; Pietrzynski, G.; Mennickent, R. E.; Kurtev, R.; Borissova, J.; Mirabel, F.; Ivanov, V. D.; Saviane, I.; Vanzi, L.; Monaco, L.; Rejkuba, M.; Messineo, M.; Bedin, L.; Stephens, A.; Barbuy, B.; Bica, E.; Clariá, J. J.; CASU (VDFS) Team; WFAU (VDFS) Team; Emerson, J.; Drew, J.; López-Correidora, M.; Martin, E.; Goldman, B.; Gianinni, T.; Eisloeffel, J.; Groot, P.; Fabregat, J.; Hambly, N.; Longmore, A.; Walton, N.; de Grijs, R.; Hoare, M.; Schroeder, A.; Naylor, T.; Barlow, M.; Zijlstra, A.; White, G.; Gosling, A.; McGowan, K.; Adamson, A.; Bandyopadhyay, R.; Thompson, M.; Cropper, M.; Lucey, J.; Kerins, E.; Hodgkin, S.; Pinfield, D.
    We propose a public IR variability survey, named ``Vista Variables in the Vía Láctea'' (VVV), of the Milky Way bulge and an adjacent section of the mid-plane where star formation activity is high. This would take 1920 hours, covering ∼ 10^9 point sources within an area of 520 sq deg, including 33 known globular clusters and ∼ 350 open clusters. The final products will be a deep IR atlas in 5 passbands and a catalogue of ∼ 10^6 variable point sources. These will produce a 3-D map of the surveyed region (unlike single-epoch surveys that only give 2-D maps) using well-understood primary distance indicators such as RR Lyrae stars. It will yield important information on the ages of the populations. The observations will be combined with data from MACHO, OGLE, EROS, VST, SPITZER, HST, CHANDRA, INTEGRAL, and ALMA for a complete understanding of the variable sources in the inner Milky Way. Several important implications for the history of the Milky Way, for globular cluster evolution, for the population census of the bulge and center, and for pulsation theory would follow from this survey....