| 11. |
- Romeo, Alessandro, 1961
(författare)
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Modelling gravity in N-body simulations of disc galaxies. Optimal types of softening for given dynamical requirements
- 1998
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 335, s. 922-928
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Tidskriftsartikel (refereegranskat)abstract
- Modelling gravity is a fundamental problem that must be tackled in N-body simulations of stellar systems, and satisfactory solutions require a deep understanding of the dynamical effects of softening. In a previous paper (Romeo 1997), we have devised a method for exploring such effects, and we have focused on two applications that reveal the dynamical differences between the most representative types of softened gravity. In the present paper we show that our method can be applied in another, more fruitful, way: for developing new ideas about softening. Indeed, it opens a direct route to the discovery of optimal types of softened gravity for given dynamical requirements, and thus to the accomplishment of a physically consistent modelling of disc galaxies, even in the presence of a cold interstellar gaseous component and in situations that demand anisotropic resolution.
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| 12. |
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| 13. |
- Alvarez, R, et al.
(författare)
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Near-infrared narrow-band photometry of M-giant and Mira stars: models meet observations
- 1998
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Ingår i: ASTRONOMY AND ASTROPHYSICS. - : SPRINGER VERLAG. - 0004-6361. ; 330:3, s. 1109-1119
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Tidskriftsartikel (refereegranskat)abstract
- From near-infrared, narrow-band photometry of 256 oxygen-rich Mira variables we obtain evidence about the loops that these stars follow in colour-colour diagrams. We also find a phase lag between indices related to molecular band-strength of titanium oxid
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| 14. |
- Andersen, AC, et al.
(författare)
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Optical properties of carbon grains: Influence on dynamical models of AGB stars
- 1999
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Ingår i: ASTRONOMY AND ASTROPHYSICS. - : SPRINGER VERLAG. - 0004-6361. ; 349:1, s. 243-252
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Tidskriftsartikel (refereegranskat)abstract
- For amorphous carbon several laboratory extinction data are available, which show quite a wide range of differences due to the structural complexity of this material. We have calculated self-consistent dynamic models of circumstellar dust-shells around ca
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| 15. |
- Ardeberg, Arne, et al.
(författare)
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On the history of star formation in the bar of the Large Magellanic Cloud
- 1997
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Ingår i: ASTRONOMY AND ASTROPHYSICS. - : SPRINGER VERLAG. - 0004-6361. ; 322:2, s. L13-L16
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Tidskriftsartikel (refereegranskat)abstract
- With the HST PC and uvby photometry, we investigate evolutionary signatures in a field in the centre of the LMC Bar. Field stars close to the turn off point in the HR diagram are used for a study of ages and evolution of the stellar popu lations dominatin
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| 16. |
- Asplund, Martin, et al.
(författare)
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A stellar endgame - The born-again Sakurai's object
- 1997
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Ingår i: ASTRONOMY AND ASTROPHYSICS. - : SPRINGER VERLAG. - 0004-6361. ; 321:2, s. L17-L20
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Tidskriftsartikel (refereegranskat)abstract
- The surface chemical composition of this remarkable star shows that it is hydrogen-deficient, carbon-rich and enriched in the light s-process elements. Spectra taken in May and October 1996 indicate a decrease in the surface hydrogen abundance by 0.7 dex
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| 17. |
- Asplund, Martin, et al.
(författare)
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Abundance similarities between the R CrB star V854 Cen and the born-again Sakurai's object
- 1998
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Ingår i: ASTRONOMY AND ASTROPHYSICS. - : SPRINGER VERLAG. - 0004-6361. ; 332:2, s. 651-660
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Tidskriftsartikel (refereegranskat)abstract
- The elemental abundances of the mildly hydrogen-deficient R Coronae Borealis (R CrB) star V854 Cen have been estimated. The R CrB stars have been divided into majority and minority classes judging by their abundance patterns. Class assignment has previous
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| 18. |
- Asplund, Martin, et al.
(författare)
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Line-blanketed model atmospheres for R Coronae Borealis stars and hydrogen-deficient carbon stars
- 1997
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Ingår i: ASTRONOMY AND ASTROPHYSICS. - : SPRINGER VERLAG. - 0004-6361. ; 318:2, s. 521-534
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Tidskriftsartikel (refereegranskat)abstract
- We have constructed line-blanketed model atmospheres for the hydrogen-deficient and carbon-rich R Coronae Borealis (RCrB) stars, as well as for the similar hydrogen-deficient carbon (HdC) stars and the cool extreme helium (EHe) stars. Improved continuum o
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| 19. |
- ASPLUND, M
(författare)
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SPECTROSCOPY OF RY-SAGITTARII DURING THE 1993 MINIMUM
- 1995
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Ingår i: ASTRONOMY AND ASTROPHYSICS. - : SPRINGER VERLAG. - 0004-6361. ; 294:3, s. 763-772
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The R Coronae Borealis (RCB) star RY Sgr underwent a deep minimum (DELTAV approximately 7.m5) in 1993. Here medium and low resolution observations from approximately 35 days into the decline are presented together with photometry from the early phases unt
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| 20. |
- Asplund, M
(författare)
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The stability of late-type stars close to the Eddington limit
- 1998
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Ingår i: ASTRONOMY AND ASTROPHYSICS. - : SPRINGER VERLAG. - 0004-6361. ; 330:2, s. 641-650
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The opacity-modified Eddington limit has been computed for hydrogen-deficient model atmospheres. The R Coronae Borealis (R CrB) stars are found to be located strikingly close to the limit, which suggests that the unknown trigger mechanism for their visual
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