Sveneric Johansson

A new multiplet table for Fe I

We have recorded spectra of iron-neon and iron-argon hollow cathode lamps in the region 1700A -- 5um (59000 -- 2000cm-1), with Fourier transform (FT) spectrometers at the National Solar Observatory, Tucson, Arizona, U.S.A. and Imperial College, London, U.K., and with a high resolution grating spectrograph at the National Institute of Standards and Technology, Gaithersburg, U.S.A. The uncertainty of the strongest lines in the FT spectra is <0.002cm-1 (0.2mA at 3000A; 8mA at 2um). Pressure and current-dependent shifts are <0.001cm-1 for transitions between low lying levels, increasing to 0.006 cm-1 for transitions between the most highly excited levels. We report 28 new energy levels of Fe I and revised values of another 818 levels. We have identified 9501 lines as due to 9759 transitions in Fe I, and these are presented in the form of a new multiplet table and finding list. This compares with the 5500 lines due to 467 energy levels in the multiplet tables of Moore (1950, 1959). The biggest increase is in the near ultraviolet and near infra-red, and many of the new lines are present in the solar spectrum. Experimental log(gf) values are included where available. A further 125 unidentified lines due to Fe I are given.

The Spectrum and Term System of Fe II

The spectrum of singly ionized iron, Fe II, has been recorded in the wavelength regions 900-2200 A and 4800-11200 A by means of a pulsed hollow-cathode discharge. In the vacuum-ultraviolet region identifications are given for 1358 lines. The list for the region above 4800 A contains 1564 observed lines, 1341 of which are identified. In the 2200-4800 A range about 350 lines in the line list published by Dobbie in 1938 have been newly identified. On the basis of interferometric measurements made by G. Norlen of 350 lines a recalculation of the whole term system has been performed. Altogether 576 energy levels are now known in Fe II, some 250 of which are the results of the present analysis. The levels belong to the configurations (3d6)4s, 5s, 6s, 4p, 5p, 3d, 4d, 5d, 4f and (3d54s)4s, 5s, 4p, 4d and 3d54p2. Theoretical predictions of the structure of the (3d64p + 3d65p + 3d54s4p) complex by J. Sinzelle and J. F. Wyart are in good agreement with the observations. The ionization energy has been determined to 130 563 ± 10 cm-1.

Experimental f-Value and Isotopic Structure for the Ni I Line Blended with [O I] at 6300 Å

We have measured the oscillator strength of the Ni I line at 6300.34A, which is known to be blended with the forbidden line [O I]lambda6300 used for the determination of the oxygen abundance in coolstars. We also give wavelengths of the two isotopic line components of 58 Ni and 60 Ni derived from the asymmetriclaboratory line profile. These two line components of Ni I have to beconsidered when calculating a line profile of the 6300 A featureobserved in stellar and solar spectra. We also discuss the labeling ofthe energy levels involved in the Ni I line since level mixing makes thetheoretical predictions uncertain.

New and improved experimental oscillator strengths in Zr II and the solar abundance of zirconium

Using the Fourier Transform Spectrometer at Lund Observatory, intensity calibrated spectra of singly ionized zirconium have been recorded and analyzed. Oscillator strengths for 263 Zr II spectral lines in the region 2500-5400 angstrom have been derived by combining new experimental branching fractions with previously measured radiative lifetimes. The transitions combine 34 odd parity levels with 29 low metastable levels between 0 and 2.4 eV. The experimental branching fractions have been compared with theoretical values and the oscillator strengths with previously published data when available. The oscillator strengths have been employed to derive the solar photospheric Zr abundance based on both 1D and 3D model atmospheres. Based on the seven best and least perturbed Zr II lines in the solar disk-center spectrum, we determine the solar Zr abundance to log epsilon(Zr) = 2.58 +/- 0.02 when using a 3D hydrodynamical solar model atmosphere. The new value is in excellent agreement with the meteoritic Zr abundance. (Less)

Very high resolution ultraviolet spectroscopy of a chemically peculiar star: Results of the chi Lupi Pathfinder project

We summarize here the results of a major eight-year investigation of the extraordinarily detailed UV spectrum of the sharp-lined, nonmagnetic, main-sequence, chemically peculiar star chi Lupi (B9.5p HgMn + A2 Vm). The UV observations are composed of 345 Angstrom of the spectrum acquired with the Goddard High Resolution Spectrograph (GHRS) on board the Hubble Space Telescope at an average resolution of 0.023 Angstrom. The complete set of echelle spectrograms is presented as an atlas in a companion paper. These data were supplemented by optical-wavelength spectra obtained at the Angle-Australian Telescope. Quantitatively accurate analysis and theoretical interpretation of these data required major improvements in the accuracy and completeness of available atomic data-wavelengths, transition probabilities, hyperfine structure, and isotope shifts-for the lowest ionization states of many elements. A large, international group of theoretical and experimental atomic physicists has collaborated in this investigation, and their results are summarized or referenced in this paper. In turn, the GHRS observations of chi Lupi have become a useful source of data for atomic spectroscopy, displaying many transitions that are difficult to observe in a laboratory setting. Measured abundances or upper limits are presented for 72 ions of 51 chemical elements, spanning the periodic table. We have confirmed and refined previously identified isotopic abundance anomalies in mercury and platinum and have discovered similar isotopic anomalies in thallium and, tentatively, in lead. Large discrepancies among the LTE abundances derived, using a chemically homogeneous model atmosphere, from two or three ionization states of the same element are found to be common. In some cases these are due to departures from LTE in the ionization equilibria, but the largest such discrepancies probably result from chemical stratification within the photosphere. We find qualitative trends in the abundances of the elements that clearly signify radiatively driven diffusion and gravitational settling as the primary mechanism producing abundance anomalies. However, detailed non-LTE diffusion calculations for mercury and thallium show that there is insufficient unsaturated radiative force within the chemically enriched atmosphere to sustain the observed huge overabundances of these elements in equilibrium with gravity. Either other hydrodynamic processes, such as slow mass motions or unexpectedly strong stellar winds must assist radiation pressure in supporting the enriched material, or the observed abundance patterns simply provide a snapshot in time of a nonequilibrium, time-variable phenomenon. (Less)

Mercury in the HgMn stars chi Lupi and HR 7775

Observations of mercury lines in the HgMn stars chi Lupi and HR 7775 made with the Hubble Space Telescope Goddard High Resolution Spectrograph are presented and analyzed. In chi Lupi we find that all observed lines are consistent with the same isotopic mixture (essentially pure (204)Hg). Strong ionization anomalies are present, with UV Hg I lines being too weak and Hg III lines too strong for the abundance derived from lines of the majority ionization state, Hg rr. Observations of mercury in I;IR 7775 show less extreme isotope and ionization anomalies. We find that the ionization anomaly in the Hg I resonance lines can be plausibly explained as a non-LTE effect, but the same non-LTE calculations show that the Hg III ionization anomaly in chi Lupi cannot be explained in this way. Radiative force calculations show that the observed mercury abundance cannot be supported in the atmosphere by the radiative forces alone. We suggest that weak mixing brings mercury into the line-forming region from below the photosphere, while a wind of order 10(-14) M. yr(-1) supports a cloud of Hg III at very small optical depths. (Less)

Experimental oscillator strengths in Th II

We have measured radiative lifetimes of ten Th II levels by using thelaser-induced fluorescence technique and branching fractions withFourier transform spectroscopy. By combining the new branching fractionswith a total of 23 lifetimes, from the present work and frommeasurements by Simonsen et al. (cite{Simonsen}), absolute oscillatorstrengths for 180 lines have been derived. Some of these new f-valuesreported are relevant for radioactive dating of stars.

The Spectrum and Term System of Singly Ionized Titanium, Ti II

The TiII spectrum has been recorded in the region 1100-11 000 A. 1240 lines have been classified as transitions between 204 levels of the configurations (3d + 4s)3, 3d2 nl (nl = 5, 6s; 4, 5p; 4, 5d; 4f) and 3d4s4p. Parametric studies including configuration interaction have been carried out for a number of configurations. The ionization energy has been determined to 109 494 ± 20 cm-1.

The spectrum and term analysis of Co II

High-resolution spectra of singly ionized cobalt have been recorded by Fourier transform spectrometry in the region 1420-33333 A (70422-3000 cm-1) with cobalt-neon and cobalt-argon hollow cathode lamps as sources. Most of the Co II lines exhibit broadening due to hyperfine structure, but the wavenumber uncertainty for the center of gravity of the strongest lines is less than 0.002 cm-1. Of the previously listed energy levels of Co II, 215 have been revised and six have been discarded. In addition, 171 new levels have been found of which 125 are reported here for the first time. The number of classified lines has doubled with wavenumbers and classifications being presented for 2373 Co II lines, of which 1242 involve the new levels.

The Origin of Fe II and [Fe II] Emission Lines in the 4000-10000 Å Range in the BD Weigelt Blobs of η Carinae*

We present numerical simulations that reproduce the salient features of the amazingly strong (Fe ii) and Fe ii emission spectra in the B and D Weigelt blobs ofCarinae. For our studies we have used spectra obtained during the 1998 epoch observations with the Hubble Space Telescope (HST). The spectrum of the B and D Weigelt blobs dominates in (Fe ii) and Fe ii emission lines. The same observations show no Fe i or Fe iii. We have compared our measurements of the strongest (� 200) (Fe ii) and Fe ii lines and blends in the spectrum with theoretical predictions. Our predictions are based on non-LTE modeling of the Fe ii atom, which includes the lowest 371 energy levels (all levels up to 11.6 eV). We have investigated the dependence of the spectrum on electron density, pumping by the blackbody-like stellar continuum, and intense Ly� emission. We find that radiative pumping is essential in explaining the observed spectrum. We have identified the main pumping routes responsible for the observed Fe ii emission. Comparison between the model and observations reveals details of the radiation field. Pumping by the blackbody-like stellar radiation field from � Carinae explains the numerous strong (Fe ii) and Fe ii lines in the range of 4000-6500 A ˚ . The strongest Fe ii lines in a range of 8000-10000 Aare pumped by intense Lyradiation. Subject headings: H ii regions — ISM: individual (� Carinae) — line: formation — line: identification On-line material: machine-readable table