Sökresultat

We report on experimental branching fractions (BFs) for 19 transitions from the three 3d 5( 6S)4s4p( 3P) y6P levels in Fe II, measured in Fourier transform spectra of a Penning discharge lamp and a hollow cathode lamp. The transition wavelengths span the interval between 1600 and 2850 Å. Absolute oscillator strengths ( f-values) have been derived by combining the BFs with experimental radiative li

The conceptual design of the Large Earth-based Solar Telescope (LEST)has evolved through the years. In 1995-97 it was discussed whether atechnology demonstration telescope could be built at a lower cost thanthe LEST originally proposed. In 1997, a de-scoped LEST design, theso-called "Mini-LEST", was conceived and proposed to the LEST community.The telescope has an innovative design with a small fi

Parity forbidden radiative transitions from metastable levels are observed in spectra of low-density astrophysical plasmas. These lines are used as probes of the physical conditions, made possible due to the long lifetime of their upper level. In a joint effort, the FERRUM project aims to obtain new and accurate atomic data for the iron-group elements, and part of this project concerns forbidden l

First results from a study into the abundance trends of oxygen in the Galactic thin and thick disks are presented. Oxygen abundances for 63nearby F and G dwarf stars, based on very high resolution spectra (R∼215 000) and high signal-to-noise (S/N>400) of the faint forbidden oxygen line at 6300Å, have been determined. Our findings can be summarized as follows: 1) at [Fe/H]<0 the oxygen trends in th

Titanium spectra recorded in the infrared wavelength region with a Fourier Transform Spectrometer have been analysed, and 572 lines have been identified as transitions of the types 3d-4f, 4d-4f and 4-5g. 11 lines in the UV region around 2400 angstrom have been identified as belonging to the 3d(3)4s a(5)F-3d(2)4s(F-4)4f transition array. 113 levels of the 3d(2)4s(F-4)4f, 3d(3)(F-4)4f and 3d(2)4s(F-

Tantalum spectra, emitted from a hollow cathode, have been recorded with a Fourier transform spectrometer in the region 2000–5000 Ů The observed hyperfine patterns of Ta II have been analyzed, yielding center-of-gravity wavelengths for 199 lines and hyperfine constants for 38 even and 97 odd levels of Ta II. Improved energy level values have been derived. The laboratory data have been used for a s

In spectra obtained from foil-excited and laser-produced plasmas, we have identified 70 new lines as belonging to the spectra of fluorine-like scandium and vanadium ions, Sc XIII and V XV The new lines in the wavelength region from 70 to 600 Angstrom represent 2p(4)3s-3p, 3p-3d and 3d-4f transition arrays. The spectra have been interpreted with the aid of theoretical calculations, and the consiste

From a detailed elemental abundance analysis of 102 F and G dwarf starswe present abundance trends in the Galactic thin and thick disks for 14elements (O, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Zn, Y, Ba, and Eu).Stellar parameters and elemental abundances (except for Y, Ba and Eu)for 66 of the 102 stars were presented in our previous studies (Bensbyet al. 2003, 2004a). The 36 stars that are new in t

Chemical abundances for 15 elements (C, N, O, Na, Mg, Al, Si, K, Ca, Ti, V, Cr, Mn, Fe, and Ni) are presented for 83 stellar members of the 4 Gyr old solar-metallicity open cluster M67. The sample contains stars spanning a wide range of evolutionary phases, from G dwarfs to red clump stars. The abundances were derived from near-IR (λ1.5-1.7 μm) high-resolution spectra (R ,F= ,F22,500) from the SD

We map the trends of elemental abundance ratios across the Galactic disk, spanning R = 3-15 kpc and midplane distance |Z| = 0-2 kpc, for 15 elements in a sample of 20,485 stars measured by the SDSS/APOGEE survey (O, Na, Mg, Al, Si, P, S, K, Ca, V, Cr, Mn, Fe, Co, Ni). Adopting Mg rather than Fe as our reference element, and separating stars into two populations based on [Fe/Mg], we find that the m