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  • 1.
    Edvardsson, Sverker
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Karlsson, KG
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Spin axis variations of Mars: numerical limitations and model dependences2008In: Astronomical Journal, ISSN 0004-6256, E-ISSN 1538-3881, Vol. 135, no 4, p. 1151-1160Article in journal (Refereed)
    Abstract [en]

    Celestial mechanical integrations for the whole solar system are carried out over four billion years before and after the present. The orbital solution of the solar system is stable during this whole time period. An instantaneous spin axis model including triaxiality is developed. In particular, spin axis precession, the Martian obliquity, solar torques, and the orbital eccentricity/inclination of Mars are studied. Model dependences from general relativity, solar oblateness, the Martian moons, solar mass loss, etc. are tested. Although the obliquity of Mars sometimes shows dramatic variations, some structures are robust and seem insensitive to the initial spin precession rate. A full integration is carried out during a total of 8000 Myr resulting in a Martian obliquity that is restricted between 10 and 60 degrees. The problems with numerical noise due to limited machine precision, integration step sizes, and the chaotic sensitivity of the solutions are studied and discussed. The limited machine precision (15-16 figures) alone is found to limit the duration of exact obliquity solutions to about 80 Myr.

  • 2. Fogle, M
    et al.
    Badnell, N.R.
    Glans, Peter
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Loch, S.D.
    Madzunkov, S
    Abdel-Naby, Sh.A.
    Pindzola, M.S.
    Schuch, R
    Electron-ion recombination of Be-like C, N, and O2005In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 442, no 2, p. 757-766Article in journal (Refereed)
    Abstract [en]

    The absolute total recombination reaction rate coefficients for Be-like C, N, and O have been measured using the CRYRING storage ring and compared with the results from distorted-wave theory. For the theory results, it is found that shifts to NIST energy values for the core excited energies of the recombining system are not sufficient to accurately match all of the resonance positions and heights at lower energies. These theory results represent the quality of most archived theory DR data. The accurate calculation of these low energy resonances still presents a significant challenge to theory. In addition, trielectronic recombination resonances, associated with the formation of triply excited states during recombination, have been observed in the total recombination reaction rate coefficient spectra of N3+ and O4+. Finally, we construct a dielectronic recombination Maxwellian rate coefficient from the experimental results for low n resonances, and from the theoretical results for high n resonances. In the case of O4+, the trielectronic recombination resonances have a strong influence on the low temperature Maxwellian rate coefficient. Our best hybrid Maxwellian rate coefficient is compared with archived distorted-wave theory data, and is found to be in reasonable agreement, even at the low temperatures.

  • 3. Sordo, R
    et al.
    Vallenari, A
    Tantalo, R
    Alalrd, F
    Blomme, R
    Bouret, J-C
    Brott, I
    Fremat, Y
    Martayan, C
    Damerdji, Y
    Edvardsson, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Josselin, E
    Plez, B
    Kochukhov, O
    Kontizas, M
    Munari, U
    Saguner, T
    Zorec, J
    Schweitzer, A
    Tsalmantza, P
    Synthetic stellar and SSP libraries as templates for Gaia simulations2010In: Astrophysics and Space Science, ISSN 0004-640X, E-ISSN 1572-946X, Vol. 328, no 1-2, p. 331-335Article in journal (Refereed)
    Abstract [en]

    ESA's Gaia mission will collect low resolution spectroscopy in the optical range for ∼109 objects. Complete and up-to-date libraries of synthetic stellar spectra are needed to built algorithms aimed to automatically derive the classification and the parametrization of this huge amount of data. In addition, libraries of stellar spectra are one of the main ingredients of stellar population synthesis models, aiming to derive the properties of unresolved stellar populations from their integrated light. We present (a) the newly computed libraries of synthetic spectra built by the Gaia community, covering the whole optical range (300-1100 nm) at medium-high resolution of (0.3 nm) for stars spanning the most different types, from M to O, from A-peculiar to Emission lines to White Dwarfs, and (b) the implementation of those libraries in our SSP code (Tantalo in The Initial Mass Function 50 Years Later, 327:235 2005), exploring different stellar evolution models.

  • 4. Vallenari, A.
    et al.
    Sordo, R.
    Tantalo, R.
    Allard, F.
    Blomme, R.
    Bouret, J. -C
    Brott, I.
    Fremat, Y.
    Martayan, C.
    Damerdji, Y.
    Edvardsson, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Josselin, E.
    Plez, B.
    Kochukhov, O.
    Kontizas, M.
    Schweitzer, A.
    Zorec, J.
    Tsalmantza, P.
    Munari, U.
    Saguner, T.
    Synthetic stellar libraries and SSP simulations in the Gaia Era2009In: Proceedings of the International Astronomical Union, 2009, no S262, p. 444-445Conference paper (Refereed)
    Abstract [en]

    The Gaia mission will obtain accurate positions, parallaxes and proper motions for 109 object all over the sky. In addition, it will collect low resolution spectroscopy in the optical range for ∼ 109 objects, stars, galaxies, and QSOs. Parameters of those objects are expected to be part of the final Catalog. Complete and up-to-date libraries of synthetic stellar spectra are needed to train the algorithms to classify this huge amount of data. Here we focus on the use of the synthetic libraries of spectra calculated by the Gaia community to derive grids of Single Stellar Populations as building blocks of population synthesis models. © International Astronomical Union 2010.

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