Line Blending Research Articles

XMM-Newton EPIC observations of 21 low-redshift PG quasars

We present an X-ray spectral analysis of 21 low redshift quasars observed with XMM-Newton EPIC. All the sources are Palomar Green quasars with redshifts between 0.05 and 0.4 and have low Galactic absorption along the line-of-sight. A large majority of quasars in the sample (19/21) exhibit a significant soft excess below ~1–1.5 keV, whilst two objects (PG 1114+445 and I Zw1) show a deficit of soft X-ray flux due to the presence of a strong warm absorber. Indeed, contrary to previous studies with ASCA and ROSAT, we find that the presence of absorption features near 0.6–1.0 keV is common in our sample. At least half of the objects appear to harbor a warm absorber, as found previously in Seyfert 1 galaxies. We find significant detections of Fe Kα emission lines in at least twelve objects, whilst there is evidence for some broadening of the line profile, compared to the EPIC-pn resolution, in five of these quasars. The determination of the nature of this broadening (e.g., Keplerian motion, a blend of lines, relativistic effects) is not possible with the present data and requires either higher S/N or higher resolution spectra. In seven objects the line is located between 6.7–7 keV, corresponding to highly ionized iron, whereas in the other five objects the line energy is consistent with 6.4 keV, i.e. corresponding to near neutral iron. The ionized lines tend to be found in the quasars with the steepest X-ray spectra. We also find a correlation between the continuum power law index Γ and the optical Hβ width, in both the soft and hard X-ray bands, whereby the steepest X-ray spectra are found in objects with narrow Hβ widths, which confirms previous ROSAT and ASCA results. The soft and hard band X-ray photon indices are also strongly correlated, i.e. the steepest soft X-ray spectra correspond the steepest hard X-ray spectra. We propose that a high accretion rate and a smaller black hole mass is likely to be the physical driver responsible for these trends, with the steep spectrum objects likely to have smaller black hole masses accreting near the Eddington rate.

A preliminary analysis of the sharp-lined A3V star 95 Leo

We have started an analysis of the sharp-lined superficially normal A3IVp star 95 Leo. We are using $2.4 \AA \mathrm {mm}^{-1}$ spectrograms covering $\lambda\lambda 3830-4934$ obtained with the 1.22-m telescope of the Dominion Astrophysical Observatory using CCD detectors. Their mean signal-to-noise ratios are $\ge\,200$ . The spectrograms are rectified and measured with the interactive computer graphics program REDUCE of Graham Hill and his associates. In measuring the spectrum with the VLINE routine, we use the fixed parameter feature to deconvolute metallic line blends and to measure weak lines. Effective temperature and surface gravity estimates based on spectrophotometry and H $\gamma$ profile fitting were given in the literature as 8300 K and 3.65, respectively. To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The Local Lyα Forest. IV. Space Telescope Imaging Spectrograph G140M Spectra and Results on the Distribution and Baryon Content of H i Absorbers

We present Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) G140M spectra of 15 extragalactic targets, which we combine with GHRS/G160M data to examine the statistical properties of the low-z Lyα forest. With STIS, we detect 109 Lyα absorbers at significance level (SL) of ≥4 σ over 0.002 240 mA) absorbers, the number density of low- absorbers at z = 0 is well above the extrapolation of d/dz from z > 2. However, log = 1.40 ± 0.08 for > 240 mA is 25% below the value obtained by the HST QSO Key Project, a difference that may arise from line blending. The slowing of the number density evolution of high- Lyα clouds is not as great as previously measured, and the break to slower evolution may occur later than previously suggested (z ~ 1.0 rather than 1.6). We find a 7.2 σ excess in the two-point correlation function (TPCF) of Lyα absorbers for velocity separations Δv ≤ 260 km s-1, which is exclusively due to the higher column density clouds. From our previous result that higher column density Lyα clouds cluster more strongly with galaxies, this TPCF suggests a physical difference between the higher and lower column density clouds in our sample. The systematic error produced by cosmic variance on these results increases the total errors on derived quantities by ~.

Neutron-capture elements in halo, thick-disk, and thin-disk stars: Neodymium

We have derived the LTE neodymium abundances in 60 cool stars with metallicities [Fe/H] from 0.25 to −1.71 by applying a synthetic-spectrum analysis to spectroscopic observations of NdII lines with a resolution of λ/Δλ⋍60 000 and signal-to-noise ratios of 100–200. We have improved the atomic parameters of NdII and blending lines by analyzing the corresponding line pro files in the solar spectrum. Neodymium is overabundant with respect to iron in halo stars, [Nd/Fe]=0.33±0.09, with the [Nd/Fe] ratio decreasing systematically with metallicity when [Fe/H]>−1. This reflects an onset of efficient iron production in type I supernovae during the formation of the thick disk. The [Nd/Ba] and [Nd/Eu] abundance ratios behave differently in halo, thick-disk, and thin-disk stars. The observed abundance ratios in halo stars, [Nd/Ba]=0.34±0.08 and [Nd/Eu]=−0.27±0.05, agree within the errors with the ratios of the elemental yields for the r-process. These results support the conclusion of other authors based on analyses of other elements that the r-process played the dominant role in the synthesis of heavy elements during the formation of the halo. The [Nd/Ba] and [Nd/Eu] ratios for thick-disk stars are almost independent of metallicity ([Nd/Ba]=0.28(±0.03)−0.01(±0.04) [Fe/H] and [Nd/Eu]=−0.13(±0.03)+0.05(±0.04) [Fe/H]) but are smaller in absolute value than the corresponding ratios for halo stars, suggesting that the synthesis of s-process nuclei started during the formation of the thick disk. The s-process is estimated to have contributed ⋍30% of the neodymium produced during this stage of the evolution of the Galaxy. The [Nd/Ba] ratio decreases abruptly by 0.17 dex in the transition from the thick to the thin disk. The systematic decrease of [Nd/Ba] and increase of [Nd/Eu] with increasing metallicity of thin-disk stars point toward a dominant role of the s-process in the synthesis of heavy elements during this epoch.

A long hard look at MCG-6-30-15 withXMM-Newton- II. Detailed EPIC analysis and modelling

The bright Seyfert 1 galaxy MCG‐6-30-15 has provided some of the best evidence to date for the existence of supermassive black holes in active galactic nuclei. Observations with ASCA revealed an X-ray iron line profile shaped by strong Doppler and gravitational effects. In this paper the shape of the iron line, its variability characteristics and the robustness of this spectral interpretation are examined using the long XMM‐Newton observation taken in 2001. A variety of spectral models, both including and excluding the effects of strong gravity, are compared to the data in a uniform fashion. The results strongly favour models in which the spectrum is shaped by emission from a relativistic accretion disc. It is far more difficult to explain the 3‐10 keV spectrum using models dominated by absorption (by either warm or partially covering cold matter), emission line blends, curved continua or additional continuum components. These provide a substantially worse fit to the data and fail to explain other observations (such as the simultaneous BeppoSAX spectrum). This reaffirms the veracity of the relativistic ‘disc line’ interpretation. The short term variability in the shape of the energy spectrum is investigated and explained in terms of a two-component emission model. Using a combination of spectral variability analyses, the spectrum is successfully decomposed into a variable power-law component (PLC) and a reflection-dominated component (RDC). The former is highly variable while the latter is approximately constant throughout the observation, leading to the well-known spectral variability patterns. Consideration of the long term X-ray monitoring of MCG‐6-30-15 by RXTE demonstrates that the long XMM‐Newton observation sampled the ‘typical’ state of the source. These results and those of other analyses of the large XMM‐Newton data set are summarized and their implications for understanding this enigmatic source are discussed.

The spectrum of the roAp star HD 101065 (Przybylski's star) in the Li I 6708 Å spectral region

We carried out a detailed analysis of spectra of the unique roAp star HD 101065 (Przybylski's star) near the resonance doublet Li I 6708 A, using a most complete line list including all possible transitions between REE levels of the NIST database. Our model calculations were performed under two assumptions: a blend of Li and REE lines, and a blend of REE lines only. They prove that Li lines are present in the range 6707.72−6708.02 A and that the resulting Li abundance is 3.1 dex (in the scale log N(H) = 12.0), while the isotopic ratio 6 Li/ 7 Li is near to 0.3.

Further evidence for a variable fine-structure constant from Keck/HIRES QSO absorption spectra

We have previously presented evidence for a varying fine-str ucture constant, α, in two independent samples of Keck/HIRES QSO absorption spectra. Here we present a detailed manymultiplet analysis of a third Keck/HIRES sample containing 78 absorption systems. We also re-analyse the previous samples, providing a total of 128 absorption systems over the redshift range 0.2 < zabs < 3.7. The results, with raw statistical errors, indicate a small er weighted mean α in the absorption clouds: �α/α = ( 0.574 ± 0.102) × 10 5 . All three samples separately yield consistent and significant values of �α/α. The analyses of low-z (i.e. zabs < 1.8) and high-z systems rely on different ions and transitions with very different dependencies on α, yet they also give consistent results. We identify an addit ional source of random error in 22 high-z systems characterized by transitions with a large dynamic range in apparent optical depth. Increasing the statistical erro rs on �α/α for these systems gives our fiducial result, a weighted mean �α/α = ( 0.543 ± 0.116) × 10 5 , representing 4.7 σ evidence for a varying α. Assuming that �α/α = 0 at zabs = 0, the data marginally prefer a linear increase in α with time rather than a constant offset from the laboratory value: u α/α = (6.40 ± 1.35) × 10 16 yr 1 . The two-point correlation function for α is consistent with zero over 0.2‐13 Gpc comoving scales and the angular distribution of �α/α shows no significant dipolar anisotropy. We therefore have no eviden ce for spatial variations in �α/α. We extend our previous searches for possible systematic errors, giving detailed analyses of potential kinematic effects, line blending, wavelength miscalibration, spectrograph temperature variations, atmospheric dispersion and isotopic /hyperfine structure effects. The latter two are potentially the most significant. However, overall, known systematic errors do not explain the results. Future many-multiplet analyses of indep endent QSO spectra from different telescopes and spectrographs will provide a now crucial check on our Keck/HIRES results.

Measuring stellar magnetic fields from high resolution spectroscopy of near-infrared lines

Zeeman splitting of otherwise degenerate levels provides a straight-forward method of measuring stellar magnetic fields. In the optical, the relative displacements of the Zeeman components are quite small compared to the rotational line broad- ening, and therefore observations of Zeeman splitting are usually possible only for rather strong magnetic fields in very slowly rotating stars. However, the magnitude of the Zeeman splitting is proportional to the square of the wavelength, whereas rota- tional line broadening mechanisms are linear in wavelength; therefore, there is a clear advantage in using near-infrared spectral lines to measure surface stellar magnetic fields. We have obtained high resolution ( R 25 000) spectra in the 15 625-15 665 A region for two magnetic chemically peculiar stars, viz. HD 176232 and HD 201601, and for the suspected magnetic chemi- cally peculiar star HD 180583, as part of a pilot study aimed at determining the accuracy with which we can measure stellar magnetic fields using the Zeeman splitting of near-infrared lines. We confirm that in principle the magnetic field strength can be estimated from the magnetic intensification of spectral lines, i.e. the increase in equivalent width of a line over the zero- field value. However, due to line blending as well as the dependence of this intensification on abundance and field geometry, accurate estimates of the magnetic field strengths can be obtained only by modelling the line profiles by means of spectral synthesis techniques. Using this approach, we find a 1.4 kG magnetic field modulus in HD 176132 and an upper limit of 0.2 kG in HD 180583. The very weak infrared lines in the spectrum of HD 201601 are consistent with a 3.9 kG field modulus estimated from the splitting of the Feii 6149.258 A line seen in an optical spectrum. Finally, we would like to draw attention to the fact that there are no suciently detailed and reliable atomic line lists available for the near-infrared region that can be used in high resolution work; a large fraction of the features observed in our spectra remains to be identified.

Doppler Imaging of the Ap starϵUrsae Majoris: Ca, Cr, Fe, Mg, Mn, Ti, Sr

The surface abundance structure of seven elements of the brightest chemically peculiar A-type star, Ursae Majoris ( UMa, HD 112185, HR 4905) has been determined. Cr, Fe and, Mn are enhanced at the magnetic polar region of UMa while they avoid the magnetic equator. Sr seems to behave like Cr, Fe, and Mn, but is concentrated only at one of the two magnetic poles. Ti, in contrast, is accumulated at the magnetic equator and is depleted where Cr and Fe are accumulated, in accordance with theoretical predictions. Mg and Ca do not correlate with the distribution of Cr, Fe, Mn, and Sr or with Ti. The surface distribution of Mn, Sr, Ti, and Mg was determined for the first time for this star. A Doppler Imaging code was used that allows to analyse elements present in complex spectral line blends and thus to increase significantly the potential to map more elements. We compare our Cr and Fe distributions to already published maps. The high consistency of our results, based on dierent observations and Doppler Imaging codes, proves the reliability of the dierent methods.

Spectral Analyses of 4 Lacertae and ν Cephei

Supergiants are the most luminous stars in galaxies that are currently forming many stars. Reliable abundance determinations, for the most part, reflect the values of the interstellar material out of which they formed. Thus, they can be used to trace the chemical history of their parent galaxies. This study derived the stellar atmospheric parameters and elemental abundances of the early spectral type supergiants 4 Lac (B9 Iab) (HR 8541, HD 212593) and n Cep (A2 Ia) (HR 8334, HD 207260) from Reticon and CCD exposures obtained with the long camera of the 1.22 m telescope of the Dominion Astrophysical Observatory in Victoria, British Columbia. They cover 3830–4950 A with signal-to-noise ratios of at least 200 and a 2 pixel resolution of 0.072 A. The spectra were measured with the graphics spectroscopic analysis program REDUCE (G. Hill & W. A. Fisher 1986, Publ. Dominion Astrophys. Obs., 16, 193). The tailored analyses were performed using the LTE plane-parallel model atmospheres code ATLAS9 (R. L. Kurucz 1993, Kurucz CD-ROM 13 [Cambridge: Smithsonian Astrophys. Obs.]). They are similar to those performed by K. A. Venn (1995, ApJS, 99, 659) and B. Albayrak (2000, A&A, 364, 237), who studied supergiants with similar and cooler effective temperatures. The study of 4 Lac extends this type of analysis to a slightly hotter effective temperature. For weak features, the lines were measured using profiles whose width was found from medium-strength unblended lines to aid the process of trying to deconvolve blended lines. For each spectrogram, I identified the cleanest spectral features and found the radial velocity using the laboratory wavelengths. The remaining lines were identified with A Multiplet Table of Astrophysical Interest (C. E. Moore 1945, Princeton: Princeton Univ. Obs.) and more recent references. The adopted values Teff p 10,250 K and log g p 1.85 for 4 Lac and Teff p 8400 K and log g p 1.10 for n Cep were determined using the wings of Hb, and Fe i/ii and Si ii/iii ionization equilibria for 4 Lac and the wings of Hb and Fe i/ii and Cr i/ii ionization equilibria for n Cep. A microturbulence of 2.8 km s for 4 Lac was found from Fe ii lines using WIDTH9 1

Water vapor line parameters in the 13 000– [formula omitted] region

Line parameters of water vapor have been obtained in the 13 000– 9250 cm −1 spectral region. The measurements were performed with a high resolution Fourier transform spectrometer coupled to long-path multiple reflection cells. Emphasis was put on the determination of accurate parameters for the weak lines, most of which have not been previously reported in the literature. A total of 7061 lines have been studied. Their positions and intensities have been determined, and for many of analyzed lines, self- and air-broadening coefficients, as well as pressure-induced shifts were obtained. A preliminary analysis of the dependence of the broadenings and shifts, with vibrational and rotational quantum numbers is given. The discussion is focused on the comparison between our measured parameters and those listed in the HITRAN database. A very good agreement is reported for the positions and intensities. It is suggested that the construction of a comprehensive and complete dataset for water vapor in this spectral region requires the merging of independent measurements, and of calculated values of broadenings and shifts for weak and blended lines.

Synthetic High‐Resolution Line Spectra of Star‐forming Galaxies below 1200 A

We have generated a set of far-ultraviolet stellar libraries using spectra of OB and Wolf-Rayet stars in the Galaxy and the Large and Small Magellanic Cloud. The spectra were collected with the Far Ultraviolet Spectroscopic Explorer and cover a wavelength range from 1003.1 to 1182.7 ? at a resolution of 0.127 ?. The libraries extend from the earliest O to late-O and early-B stars for the Magellanic Cloud and Galactic libraries, respectively. Attention is paid to the complex blending of stellar and interstellar lines, which can be significant, especially in models using Galactic stars. The most severe contamination is due to molecular hydrogen. Using a simple model for the H2 line strength, we were able to remove the molecular hydrogen lines in a subset of Magellanic Cloud stars. Variations of the photospheric and wind features of C III ?1176, O VI ??1032, 1038, P V ??1118, 1128, and S IV ??1063, 1073, 1074 are discussed as a function of temperature and luminosity class. The spectral libraries were implemented into the LavalSB and Starburst99 packages and used to compute a standard set of synthetic spectra of star-forming galaxies. Representative spectra are presented for various initial mass functions and star formation histories. The valid parameter space is confined to the youngest ages of less than 10 Myr for an instantaneous burst, prior to the age when incompleteness of spectral types in the libraries sets in. For a continuous burst at solar metallicity, the parameter space is not limited. The suite of models is useful for interpreting the rest-frame far-ultraviolet in local and high-redshift galaxies.

A critical comparison of spectroscopic and evolutionary masses for O-type binary systems

We have embarked on a program to directly compare spectroscopic and evolutionary masses with those obtained from a combination of spectroscopic and photometric orbital solutions for O-type binary systems. The ability to directly determine the spectroscopic masses of the individual components of O-type binary systems has been difficult, because of the severe line blending that is present in these systems. Doppler tomography is an iterative scheme, that uses an ensemble of spectra to reconstruct the individual component spectra. These individual spectra can then be analyzed.

Far Ultraviolet Spectrum of Mars

A spectrum of Mars of unprecedented quality was obtained in the range of 904–1183 Å with a spectral resolution of 0.2 Å using the Far Ultraviolet Spectroscopic Explorer. Besides marking the first detection of molecular hydrogen on Mars (Krasnopolsky and Feldman, Science 2001 294, 1914–1917), the spectrum also revealed many emission lines of H, O, N, C, Ar, He, N +, C +, and Ar + and the bands of N 2 and CO. The spectrum makes it possible to study the emission multiplet structures and the component ratios and to separate many of the blended lines. From the argon lines, we retrieved Ar mixing ratios of 1.5 and 1.3% at 150 and 130 km, respectively, in excellent agreement with the Viking mass spectrometric measurements of 1.6% in the lower atmosphere. The He 584-Å emission observed in second order also agrees with the Extreme Ultraviolet Explorer detection of He on Mars. The observed spectrum may be used as a database to study specific problems such as the dayglow excitation, radiative transfer, and composition in Mars' upper atmosphere.

Early-Phase Spectra of “Hypernova” SN 2002[CLC]ap[/CLC

The spectral evolution of the peculiar Type Ic supernova (SN) 2002ap during the first 40 days is presented. The spectra display very broad absorption features, which are typical of The maximum expansion velocity measured on the earliest spectra exceeds 3 × 104 km s-1. The spectrum of SN 2002ap at the epoch of maximum brightness resembles that of SN 1997ef more than that of SN 1998bw. The spectral evolution of SN 2002ap proceeds at about 1.5 times the rate of SN 1997ef. The parameterized supernova spectrum synthesis code SYNOW was used to perform line identification and deduce velocity information from the early-phase spectra, which are heavily affected by line blending. The photospheric velocity, as deduced from the fitting results and from the blueshift of the Si II λ6355 absorption minimum, is lower than in previously studied hypernovae. At advanced epochs, the Si II λ6355 absorption minimum becomes difficult to distinguish. This may be caused by the growth of [O I] λλ6300, 6364 emission. Together with the rapid spectral evolution, this suggests that SN 2002ap should enter the nebular phase sooner than previously studied hypernovae.

Pulse Phase Variations of the X‐Ray Spectral Features in the Radio‐quiet Neutron Star 1E 1207−5209

We present the results of an XMM-Newton observation of the radio-quiet X-ray pulsar 1E 1207� 5209 located at the center of the shell-like supernova remnant G296.5+10.0. The X-ray spectrum is characterized by the presence of two phase-dependent absorption lines at energies of � 0.7 and � 1.4 keV. Moreover, these broad spectral features have significant substructure, suggesting that they are caused by the blending of several narrower lines. We interpret such features as evidence for an atmosphere containing metals and a magnetic field value of a few 10 12 G, consistent with the observed spin-down rate _ P ¼ð 1:98 � 0:83 Þ� 10 � 14 s s � 1 . Since 1E 1207� 5209 is the only X-ray–emitting pulsar showing evidence of such features, we tentatively link them to the unique combination of age and energetics that characterize this object. We suggest that a young age and a low level of magnetospheric activity are favorable conditions for the detection of atomic spectral features from Z > 1 elements in neutron star atmospheres, which would be either blanketed by a thin layer of accreted hydrogen in older objects or masked by nonthermal processes in young energetic pulsars. Subject headings: pulsars: individual (1E 1207� 5209) — stars: neutron — X-rays: stars

Observations of high-ntransitions in the spectra of near-neon-like copper ions fromlaser-produced plasmas

Spectra in the 7.50-8.70 Å range from highly chargedcopper ions are analysed, and line identifications are made forthe Na-, Ne-, F- and O-like charge states. The spectra arerecorded with a spherically bent crystal spectrometer usingeither a mica or quartz crystal for moderate (λ/Δλ = 3000) and high (λ/Δλ = 8000) energy resolution,respectively. The plasmas from which the spectra are emittedare formed with either a Nd:glass (15 ns pulse) or a XeCl(12 ns pulse) laser. Systematic variations in the observedspectra with pulse energy are studied. Using different laserenergies, and defocusing of the laser to reduce the intensity,we create plasmas with different ionization statedistributions, which allows us to deconvolve blended lines fromdifferent copper ions. Line identifications are made based onrelativistic atomic structure calculations that account forconfiguration interaction in level energies and transitionrates. We use full kinetics simulations of ion emissivities,not just calculations of theoretical transition energies, toidentify the strong and weak lines in crowded spectral regions.We identify 2p-nℓ transitions for Ne-like Cu19+for 4⩽n⩽8 and 2s-np transitions for 4⩽n⩽6. We offer the first identification of high-n(n⩽8) Na-like satellites to Ne-like Rydberg resonancelines. The first and second ionization energies for Cu19+are found, at 1689.02 and 1709.16 eV, respectively, based on ourobservations.

Penumbral structure and kinematics from high-spatial-resolution observations of $\ion{Ca}{II}$ K

High-spatial-resolution spectra of the Ca ii K line obtained with the Swedish Vacuum Solar Telescope (SVST) on La Palma are used to study the penumbra of a sunspot. The observed radiation tem- peratures in the Ca ii K wing are used to derive the temperature stratication of ne-structure elements in the penumbra. It is found that in general, over the observed atmospheric depth range, penumbral structures keep their relative brightness identity with respect to their local surroundings, i.e., bright (dark) structures in the lower photosphere remain bright (dark) in the upper photosphere. Hot structures have a larger temperature dif- ference between the bottom and the top of the photosphere than cool structures. Three semi-empirical atmosphere models, a cool, hot and mean model, are presented as being representative for the temperature stratication of penumbral ne structure. The mean temperature distribution of the centre-side penumbra is found to be up to 50 K hotter in the higher photosphere as compared to the limb-side penumbra. Hot structures being more numerous in the centre-side penumbra can account for this dierence. These are primarily found near the outer penumbral boundary. It is suggested that the asymmetry can be explained by a dierential line-of-sight eect that is caused by isotherms in bright structures having in the higher photosphere a tilt angle of approximately 7 with the horizontal, pointing downward towards the outer boundary. Line blends in the extended Ca ii Kw ing are selected to study the Evershed eect and its height dependence. At a number of locations, the Evershed eect is found to be concentrated in channels which have a tendency to coincide with dark laments. A weak corre- lation between brightness and velocity signal is found but also a number of bright structures with a signicant Evershed signal. Simple numerical tests of flow channels in the penumbral atmosphere are performed to confront existing theoretical models with the observations. From these experiments it is found that the bulk of the flow must be concentrated in the lower atmospheric layers, i.e., below 200 km, and must have a velocity not higher than 6 km s 1 . A channel width of 200 km is found to give the best reproduction of the observed velocities, so that the flow is either concentrated in a single channel or in a bundle of narrower channels. No direct indication is found of the Evershed channels being elevated above the continuum, and it is estimated that the flow channels reach down to at least 50 km above the continuum.

Measurements of hyperfine structure in Ta II

We report the first extensive measurements of hyperfine structure in Ta II. Spectra of Ta II were recorded by high-resolution Fourier transform spectrometry in the region 10 000-53 000 cm - 1 (1886-10 000 A) and the majority of observed lines show significant hyperfine structure. Computer fits to several hundred of these line profiles have yielded values of the magnetic dipole hyperfine interaction constant A for 88 energy levels with an uncertainty of between 0.5 and 10 per cent for the majority of A factors. The A factors range from - 0.078 to +0.065 cm - 1 for the even levels and from -0.064 to +0.083 cm - 1 for the odd levels. For the majority of these A factors no previous measurements are known. Approximate values of the electric quadrupole hyperfine interaction constant B were found for 73 levels. These measurements of A and B factors allow, for the first time, the effects of hyperfine structure in Ta II lines to be correctly accounted for both in abundance analysis and in the resolution of blended lines in astrophysical spectra.

Time evolution of Lyman-alpha fine-structure components for Al XIII.

We present a comparison of measured and theoretically modeled Lyman-alpha intensity ratios of hydrogenlike Al XIII impurity ions in a deuterium base plasma in the COMPASS-D tokamak. The time evolution of the intensity ratios is computed from a collisional-radiative model using measured plasma parameters and compared with line-of-sight integral values measured using a high-resolution crystal spectrometer. The variations in the modeled values follow the experimental data in the case of the L-mode plasma, taking into account variations in the electron parameters during the discharges. Apparent discrepancies between the observed and calculated ratios in the case of the H-mode plasma are attributed to line blending due to satellites of nearby Fe emission.