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| 3. |
- Eriksson, Mattias, et al.
(författare)
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Fluorescence Fe II lines as traces of fast outflows of white dwarf winds
- 2007
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Ingår i: Baltic Astronomy. - 1392-0049. ; 16:01, s. 95-97
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Tidskriftsartikel (refereegranskat)abstract
- A set of equations are put into a code forming a procedure to derive intensities of fluorescence lilies based on both physical properties of the fluorescent plasma and its location relative to the origin of the pumping emission. In a first test, the code is applied to symbiotic stars, and effort is made to explain the circumstances under which the two known Fell channels pumped by C IV are activated. For the channel at 1548.204 angstrom, which is most frequently observed to be active, there is a good agreement between the results of the calculations and the observed Fell line strengths. Fluorescence lines resulting from pumping through the other channel at 1548.411 angstrom can occur, according to the results of the calculations, only in the systems where a fast outflow from the white dwarf wind is present. The evidences of the white dwarf winds are found in the literature for all the symbiotic systems in which observation of the Fell fluorescence lines from the w(2)D(3/2) level is reported.
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| 4. |
- Eriksson, M, et al.
(författare)
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Modeling of C IV pumped fluorescence of Fe II in symbiotic stars
- 2008
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Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 477:1, s. 255-265
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Tidskriftsartikel (refereegranskat)abstract
- Aims. We describe how the C IV lambda 1548.18 line pumps the 1548.20 and 1548.41 angstrom channels of Fe II in symbiotic stars through the process known as photo-ionization by accidental resonance (PAR). We describe where and why Fe II fluorescence arises in symbiotic stars and whether the Fe II lambda 1548.41 channel can only be activated when there is a white-dwarf wind present in the system. Further, we aim to show how an analysis of the PAR-pumped lines helps to understand the phyisical conditions that they manifest. Methods. We calculate intensities of the C IV-pumped Fe II fluorescence lines in symbiotic stars, corresponding to the y(4)H(11/)2 and w(2)D(3/2) levels, based on a simple geometrical model of the emitting regions. We apply the model to seven symbiotic stars, known to have Fe II fluorescence lines pumped by C IV in their spectra. We compare the predicted intensities to the observed intensities of the selected symbiotic stars. Results. We find that we can reproduce the observed fluorescence intensities of the seven symbiotic stars in our sample, using parameters that are consistent with their known properties. We show that PAR-produced lines can be used as a diagnostic tool to derive important physical parameters of a stellar system. We suggest that the detection of Fe II lines corresponding to the w2D3/2 level in certain symbiotic stars provide evidence of hot shells expanding with velocities of at least hundreds km s(-1) in those systems.
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| 7. |
- Gurell, Jonas, 1981-, et al.
(författare)
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The FERRUM project : Transition probabilities for forbidden lines in [Fe II] and experimental metastable lifetimes
- 2009
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 508:1, s. 525-529
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Tidskriftsartikel (refereegranskat)abstract
- Context. Accurate transition probabilities for forbidden lines are important diagnostic parameters for low-density astrophysical plasmas. In this paper we present experimental atomic data for forbidden [Fe II] transitions that are observed as strong features in astrophysical spectra. Aims. We measure lifetimes for the 3d(6)((3)G)4s a (4)G(11/2) and 3d(6)((3)D)4s b (4)D(1/2) metastable levels in Fe II and experimental transition probabilities for the forbidden transitions 3d(7) a (4)F(7/2,9/2)-3d(6)((3)G)4s a (4)G(11/2). Methods. The lifetimes were measured at the ion storage ring facility CRYRING using a laser probing technique. Astrophysical branching fractions were obtained from spectra of Eta Carinae, obtained with the Space Telescope Imaging Spectrograph onboard the Hubble Space Telescope. The lifetimes and branching fractions were combined to yield absolute transition probabilities. Results. The lifetimes of the a (4)G(11/2) and the b (4)D(1/2) levels have been measured and have the following values, tau = 0.75 +/- 0.10 s and tau = 0.54 +/- 0.03 s respectively. Furthermore, we have determined the transition probabilities for two forbidden transitions of a (4)F(7/2,9/2)-a (4)G(11/2) at 4243.97 and 4346.85 angstrom. Both the lifetimes and the transition probabilities are compared to calculated values in the literature.
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| 10. |
- Liss, Per, et al.
(författare)
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Renal effects of CO2 and iodinated contrast media in patients undergoing renovascular intervention : a prospective, randomized study
- 2005
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Ingår i: Journal of Vascular and Interventional Radiology. - 1051-0443 .- 1535-7732. ; 16:1, s. 57-65
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: CO2 gas has been proposed for use instead of iodinated contrast media in angiographic examinations in patients at risk of developing renal failure from contrast media. The influence of intraarterial injection of CO2 with small added amounts of ioxaglate (200 mgI/mL) or ioxaglate alone on renal function in patients with suspected renal artery stenosis was studied in a prospective, randomized study. MATERIALS AND METHODS: One hundred twenty-three patients underwent renovascular intervention (n = 83) and/or renal angiography (n = 40) for suspected renal artery stenosis. Patients with a serum creatinine concentration less than 200 micromol/L (n = 82) were randomized prospectively to receive CO2 with small added amounts of ioxaglate (n = 37) or only ioxaglate (n = 45). Patients with serum creatinine levels greater than 200 micromol/L (n = 41) were not randomized and initially received CO2. Serum creatinine concentrations were measured within 1 day before and 1 day, 2 days, and 2-3 weeks after the procedure. RESULTS: The amount of injected CO2 did not relate to an increase in serum creatinine level. In the randomized groups, and also when the whole patient sample was considered, the amount of injected iodine was significantly correlated (P = .011) with an increase in serum creatinine level and a decrease in estimated creatinine clearance after 2 days. Among the randomized patients, one in the CO2 group and three in the ioxaglate group had a more than 25% increase in serum creatinine level within the first 2 days after the intervention. CONCLUSION: The risk of impairment of renal function is lower after injection of CO2 with small amounts of added ioxaglate compared with injection of a larger amount of ioxaglate alone. The larger the amount of administered iodinated contrast medium, the greater the risk of development of renal failure.
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| 11. |
- Ljung, Gunilla, et al.
(författare)
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New and improved experimental oscillator strengths in ZrII and the solar abundance of zirconium
- 2006
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Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 456:3, s. 167-1181
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 12. |
- Lundqvist, Martin, et al.
(författare)
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Improved oscillator strengths and wavelengths in Hf II, with applications to stellar elemental abundances
- 2006
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Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 450:1, s. 115-407
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Tidskriftsartikel (refereegranskat)abstract
- Aims. We present new and improved radiative lifetimes for eight levels in HfI and 18 levels in HfII, along with oscillator strengths and wavelengths for 195 transitions in HfII. With these data we determine the abundance of hafnium in two chemically peculiar stars: the hot-Am star HR 3383 and the HgMn star chi Lupi, and discuss the implications of the new data to the hafnium abundance for the Sun and the metal-poor galactic halo stars CS 22892-052 and CS 31082-001. Methods. The oscillator strengths are derived by combining radiative lifetimes measured with the laser induced fluorescence technique and branching fractions determined from intensity calibrated Fourier transform spectra. The hafnium abundance in the two sharp-lined peculair stars is determined by comparison of spectra obtained from instruments onboard the Hubble Space Telescope with synthetic spectra, while the abundance of hafnium in the solar photosphere and the metal-poor halo stars is discussed in terms of rescaling previous investigations using the new g f values. Results. The abundance enhancement of hafnium has been determined in HR 3383 to be +1.7 dex and that for chi Lupi A is +1.3 dex. In the course of the analysis we have also determined an abundance enhancement for molybdenum in HR 3383 to be +1.2 dex, which is similar to that known for. Lupi A. The abundances in the metal-poor halo stars CS 31082-001 and CS 22892-052 were rescaled to log epsilon(Hf) = -0.75 and -0.82 respectively, with smaller 1 sigma uncertainty. This has the effect of improving the theoretical fits of r-process nucleosynthesis to abundance data for heavy elements. The change of g f values also implies that the hafnium abundance in the solar photosphere should be reduced by up to 0.2 dex, thereby inducing a discrepancy with the meteoritic hafnium abundance.
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| 18. |
- Nilsson, Hampus
(författare)
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Infrared laboratory spectroscopy with astrophysical applications
- 2009
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Ingår i: Physica Scripta. - : Institute of Physics Publishing (IOPP). - 0031-8949 .- 1402-4896. ; T134, s. 014009-014009
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Tidskriftsartikel (refereegranskat)abstract
- The infrared (IR) atomic spectral lines that can be observed in laboratory and astrophysical spectra depend both on the atomic structure and the physical conditions in which the atoms reside. This is a brief review of IR laboratory spectroscopy, discussing which lines in the wavelength interval 1–5 μm can be expected to be seen in different astrophysical sources.
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| 19. |
- Nilsson, Hampus, et al.
(författare)
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Lifetime measurements and transition probability calculations in singly ionized tungsten (W II)
- 2008
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Ingår i: European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 49:1, s. 13-19
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Tidskriftsartikel (refereegranskat)abstract
- New measurements of radiative lifetimes for 9 levels in singly ionized tungsten (W II) have been performed with the time-resolved laser-induced-fluorescence technique. Transition probabilities have been obtained from a combination of experimental lifetimes and theoretical branching fractions. The reliability of the present results is assessed through the good agreement observed between the calculated lifetimes and the experimental values from this work and from previous publications. These new results fill in a gap in the available data for this atomic species particularly important for fusion reactors.
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| 20. |
- Nilsson, Hampus, et al.
(författare)
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The FERRUM project: improved experimental oscillator strengths in CrII
- 2006
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Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 445:3, s. 1165-1168
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Tidskriftsartikel (refereegranskat)abstract
- We report absolute oscillator strengths for 119 Cr II transitions in the wavelength region 2050-4850 angstrom. The transition probabilities have been derived by combining radiative lifetimes, measured with time- resolved laser induced fluorescence, and branching fractions from intensity calibrated Fouirer transform spectrometer data. New radiative lifetimes for the 3d(4)(D-5)4p F-4, D-4 and P-6 terms are reported, adding up to a total of 25 energy levels with measured lifetimes used to derive this improved set of atomic data.
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| 21. |
- Palmeri, P., et al.
(författare)
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Lifetime measurements and calculated transition probabilities in W III
- 2008
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Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 78:1
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Tidskriftsartikel (refereegranskat)abstract
- New experimental lifetimes for two levels in doubly ionized tungsten, W III, have been obtained using the time-resolved laser-induced-fluorescence technique. Theoretical oscillator strengths obtained from a HFR calculation including the effects of core-polarization are reported for all transitions from levels below E < 70000 cm(-1) and with log g f >= -2, thus greatly extending our knowledge of the radiative data in W III. Good agreement is found between the calculated lifetimes and the experimental values from this and previous works. These new results fill a gap in the available data for this ion which is expected to play an important role in fusion reactors.
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| 24. |
- Quinet, P., et al.
(författare)
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Laser-induced-fluorescence lifetime measurements and relativistic Hartree-Fock oscillator strength calculations in singly ionized platinum
- 2008
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Ingår i: Physical Review A. ; 77, s. 1-022501
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Tidskriftsartikel (refereegranskat)abstract
- Radiative lifetimes of eight odd-parity states of Pt II, in the energy range from 51 408 to 64 388 cm−1, have been measured by means of the time-resolved laser-induced-fluorescence technique. Free, singly ionized platinum ions were obtained in a laser-produced plasma and a tunable laser with 1.5 ns duration pulse was used to selectively excite the Pt+ ions. The comparison of the experimental results with relativistic Hartree-Fock calculations emphasizes the importance of valence-valence correlation and of core-polarization effects in this complex ion. A new and extensive set of calculated oscillator strengths and transition probabilities is reported in the present paper.
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| 25. |
- Quinet, Pascal, et al.
(författare)
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Laser-induced-fluorescence lifetime measurements and relativistic Hartree-Fock oscillator strength calculations in singly ionized platinum
- 2008
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 77:2
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Tidskriftsartikel (refereegranskat)abstract
- Radiative lifetimes of eight odd-parity states of Pt II, in the energy range from 51 408 to 64 388 cm−1, have been measured by means of the time-resolved laser-induced-fluorescence technique. Free, singly ionized platinum ions were obtained in a laser-produced plasma and a tunable laser with 1.5 ns duration pulse was used to selectively excite the Pt+ ions. The comparison of the experimental results with relativistic Hartree-Fock calculations emphasizes the importance of valence-valence correlation and of core-polarization effects in this complex ion. A new and extensive set of calculated oscillator strengths and transition probabilities is reported in the present paper.
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