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Spectral Lines (spectral + line)
Selected AbstractsDetection and Analysis of Strong Oscillating Electric Fields in a Picosecond Laser Plasma with the Help of Plasma Satellites of X-ray Spectral LinesCONTRIBUTIONS TO PLASMA PHYSICS, Issue 3-4 2005V. S. Belyaev Abstract X-ray lines of ions in a solid target interacting with picosecond laser pulses of the intensity ,3 × 1017 W/cm2 were studied on the "Neodim" laser facility. We observed X-ray Ly, emission spectra of hydrogen-like fluorine ions. Satellite lines were also recorded, evidencing the presence of intense plasma oscillations with an amplitude of the electric field larger than 108 V/cm and a frequency of about 1015 s,1. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Laser-induced breakdown spectroscopy for soil diagnosticsEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 2 2001J. Bublitz Summary Laser-optical measurements and fibre optics are potentially attractive tools for applications in soil science because of their great sensitivity and selectivity and their capabilities for on-line and in situ analysis. We have investigated laser-induced breakdown spectroscopy (LIBS) for the quantitative detection of metal ions on the surface of natural soil samples from two sites (Hohenschulen and Oderbruch, Germany). The LIBS technique allows the spatially resolved investigation of adsorption and desorption effects of ions in soil. A frequency doubled (532 nm) and Q-switched Nd:YAG laser with a pulse duration of 8 ns is focused on the soil surface and induces a plasma. Typical power densities are 150 mJ mm,2. The plasma emission is recorded in time and spectrally resolved by a gateable optical multichannel analyser (OMA). A delay time of about 500 ns between laser pulse and OMA gate was used to resolve single atomic and ionic spectral lines from the intense and spectrally broad light that is emitted by the plasma itself. The dependency of the LIBS signal of a single spectral line on the amount of water in the sample is investigated in detail. The results indicate that quenching of water in the plasma plume reduces the line intensities, while the interaction with aquatic colloids increases the intensity. The two processes compete with each other, and a non-linear correlation between measured line intensities and the amount of water in the sample is obtained. This is verified by a simple computer simulation and has to be taken into account for the quantitative interpretation of LIBS signals, e.g. when absolute concentrations are estimated. In the present investigation natural calcium concentrations <,2 ,g kg,1 were measured with the LIBS technique in the samples for the two test sites. In addition, measurements were made with dry and water-saturated BaCl2 mixed soil samples, and no significant difference in the detection limit for barium was obtained. [source] OH-thermometry using laser polarization spectroscopy and laser-induced fluorescence spectroscopy in the OH A-X (1,0) bandJOURNAL OF RAMAN SPECTROSCOPY, Issue 7 2009J. Kiefer Abstract Laser-induced fluorescence (LIF) and polarization spectroscopy (PS) is used for OH-thermometry utilizing the off-diagonal A-X (1,0) band. Both techniques are used simultaneously in order to allow a comparison of the results. For deriving temperature information from the spectra, three methods are employed: (1) a contour fit method comparing experimental and calculated spectra, (2) spectral fitting of a single highly resolved spectral line and (3) a two-line intensity ratio approach. In general, both spectroscopic techniques gave similar results. The high-resolution approach (2) did not deliver reasonable results in our experiments. The most accurate but also most time consuming method was the contour fit (1). For future two-dimensional temperature measurements, the 2-line-method (3) was identified to be the method of choice. The present study contains, to the best of our knowledge, the first polarization spectroscopic study in the A-X (1,0) band of OH. Copyright © 2009 John Wiley & Sons, Ltd. [source] Discovery of rapid radial velocity variations in the roAp star 10 Aql and possible pulsations of , CrBMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2002O Kochukhov ABSTRACT We report discovery of radial velocity variations in rare earth spectral lines of the roAp star 10 Aql with amplitudes of between 30 and 130 m s,1 and periods of about 11 min. Radial velocity variations with amplitude 70 m s,1 may also have been detected in one spectral line of Fe i in , CrB. If confirmed, our results may indicate that all Ap stars in a certain temperature range pulsate, which means that roAp stars do not exist as a separate class but are only distinguished by higher pulsational amplitudes. [source] Quasi-localized low-frequency vibrational modes of disordered solids: Study by single-molecule spectroscopyPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 15 2004A. V. Naumov Editor's Choice of this issue of physica status solidi (b) is the article [1] by Andrei V. Naumov et al. This paper is Part II (Part I see [2]) of a study on elementary excitations in glasses, presented at the 11th International Conference on Phonon Scattering in Condensed Matter, St. Petersburg, 25,30 July 2004. For his outstanding talk, Naumov received the new physica status solidi Young Researcher Award which was bestowed for the first time at this conference. The cover picture is a sketch of a glass with a single impurity molecule and one hypothetical quasi-localized vibrational mode. The broadening and shift of the chromophore spectral line are caused by the interaction with this mode. Andrei V. Naumov is senior scientific researcher and deputy head of the Molecular Spectroscopy Department of the Institute of Spectroscopy, Troitsk. His main research interests are experimental and theoretical studies of low-temperature dynamics of amorphous solids (glasses, polymers etc.) via high resolution laser selective spectroscopy techniques. The second Editor's Choice is an article by E. A. Eliseev and M. D. Glinchuk [3]. Eugene A. Eliseev is scientific researcher at the Frantsevich Institute for Problems of Materials Science of the Ukrainian National Academy of Sciences, Kiev. His research areas are the theory of size and correlation effects in ferroelectric materials as well as modelling of disordered ferroelectrics properties. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Behavior of phonons in short period GaN-AlN superlatticesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2004C. Pinquier Abstract This work deals with short period GaN-AlN superlattices, studied by Raman spectroscopy using visible and ultraviolet excitations. The E2 (high) and E1(TO) phonons show a two-mode behavior. In contrast, we observed an unique spectral line in the A1(TO) spectrum: its dependence on the mean superlattice composition is in good agreement with recent theoretical results predicting its delocalized character. Two Raman lines strongly enhanced under ultraviolet excitations, were observed in the A1(LO) spectrum. Lattice dynamical simulations within the Rigid Ion Model have been performed to assign these Raman lines. The first one corresponds to an A1(LO) phonon confined in GaN wells. The second line is assigned to a dispersive B1 - like mode with an amplitude modulation similar to that of an interface mode. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Laser-induced breakdown spectroscopy for soil diagnosticsEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 2 2001J. Bublitz Summary Laser-optical measurements and fibre optics are potentially attractive tools for applications in soil science because of their great sensitivity and selectivity and their capabilities for on-line and in situ analysis. We have investigated laser-induced breakdown spectroscopy (LIBS) for the quantitative detection of metal ions on the surface of natural soil samples from two sites (Hohenschulen and Oderbruch, Germany). The LIBS technique allows the spatially resolved investigation of adsorption and desorption effects of ions in soil. A frequency doubled (532 nm) and Q-switched Nd:YAG laser with a pulse duration of 8 ns is focused on the soil surface and induces a plasma. Typical power densities are 150 mJ mm,2. The plasma emission is recorded in time and spectrally resolved by a gateable optical multichannel analyser (OMA). A delay time of about 500 ns between laser pulse and OMA gate was used to resolve single atomic and ionic spectral lines from the intense and spectrally broad light that is emitted by the plasma itself. The dependency of the LIBS signal of a single spectral line on the amount of water in the sample is investigated in detail. The results indicate that quenching of water in the plasma plume reduces the line intensities, while the interaction with aquatic colloids increases the intensity. The two processes compete with each other, and a non-linear correlation between measured line intensities and the amount of water in the sample is obtained. This is verified by a simple computer simulation and has to be taken into account for the quantitative interpretation of LIBS signals, e.g. when absolute concentrations are estimated. In the present investigation natural calcium concentrations <,2 ,g kg,1 were measured with the LIBS technique in the samples for the two test sites. In addition, measurements were made with dry and water-saturated BaCl2 mixed soil samples, and no significant difference in the detection limit for barium was obtained. [source] A new maximum entropy-based method for deconvolution of spectra with heteroscedastic noiseJOURNAL OF CHEMOMETRICS, Issue 12 2004Bård Buttingsrud Abstract Broadening of spectral lines combined with large and heteroscedastic noise contributions constitutes an important problem in analytical chemistry. Reduced interpretability and artefacts in further data analysis make deconvolution methods necessary. A new robust deconvolution method (RHEMEM) based on the principle of maximum entropy is proposed in order to effectively handle the presence of heteroscedastic noise. Other deconvolution methods such as Jansson's method, Fourier self-deconvolution and LOMEP are also studied with respect to their ability to handle heteroscedastic noise. A systematic simulation study is used to compare the performance of the new method with the reference methods. They are evaluated according to reconstruction performance, robustness and the ability to work without manual input. Copyright © 2005 John Wiley & Sons, Ltd. [source] Study of electronic spectra of free-base porphin and Mg-porphin: Comprehensive comparison of variety of ab initio, DFT, and semiempirical methodsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 3 2005Josef Abstract SAC (symmetry adapted cluster)/SAC-CI and CASPT2 (multiconfigurational second-order perturbation theory) electron excitation spectra of free-base porphin and magnesium-porphin were determined using basis set functions augmented by both the polarization and diffuse functions,6-31+G(d). Such basis is recommended for correct description of the spectra because diffuse functions play fundamental roles in the formation of Rydberg MOs. The obtained results indicated that already the lowest roots in Au, B1u, B2g, and B3g irreducible representations display Rydberg character. The calculated spectra are in a good agreement with both experimental and recently calculated electronic transitions. It is concluded that the SAC/SAC-CI level spectral lines are significantly affected by configuration selection when energy thresholds 5.0 × 10,6 and 5.0 × 10,7 a.u. are used for the determination of ground and excited state properties. © 2004 Wiley Periodicals, Inc. J Comput Chem 26: 294,303, 2005 [source] Improvement of rotational CARS thermometry in fuel-rich hydrocarbon flames by inclusion of N2 -H2 Raman line widthsJOURNAL OF RAMAN SPECTROSCOPY, Issue 7 2009Alexis Bohlin Abstract In rotational coherent anti-Stokes Raman spectroscopy (CARS) thermometry applied to air-fed flames, the temperature sensitivity mainly depends on the intensity distribution of the nitrogen spectral lines. Temperatures are estimated by numerical fitting of theoretical spectra to experimental ones, and one uncertainty in the calculation of theoretical CARS spectra for specific flame conditions is the accuracy in utilized line-broadening coefficients. In a previous article, self-broadened N2 -N2 line widths were considered in the spectral calculations as well as those of N2 -CO, N2 -CO2, N2 -H2O, and N2 -O2. In the present article, we also include N2 -H2 line widths calculated from a newly developed model, and it is shown that the evaluated temperature from flame spectra increases with increasing mole fractions of hydrogen. For example, in a very rich flame at , = 2.5, the use of available line-width data for all major species gives a temperature raise of 72 K at a temperature of ,1700 K, in comparison with using self-broadened N2 -N2 line widths only. Half of this temperature raise is related to the inclusion of N2 -H2 line widths. This article emphasizes the importance of using adequate line-broadening models for rotational CARS thermometry in flames. Copyright © 2009 John Wiley & Sons, Ltd. [source] Fourier transform Raman and Fourier transform infrared spectra of cross-linked polyurethaneurea films synthesized from solutionsJOURNAL OF RAMAN SPECTROSCOPY, Issue 10 2002Valentina Romanova Cross-linked polyurethaneurea films based on polyoxytetramethylene glycol and polyoxypropylene glycol with toluene diisocyanate and 3,3,-dichloro-4,4,-diaminodiphenylmethane were synthesized in a solution where the solvent evaporates during the polymerization. FT-Raman and FTIR spectra were analysed and intermolecular force constants of hydrogen bonds were calculated. On the basis of the intensity of the Raman and IR spectral lines, which reflects hydrogen bond formation, the optimum structure of hydrogen bonds and the conformations of macromolecules of polyurethaneurea were observed for the solvent ethyl acetate. Copyright © 2002 John Wiley & Sons, Ltd. [source] The oxygen vacancy in Ga2O3: a double resonance investigation,MAGNETIC RESONANCE IN CHEMISTRY, Issue S1 2005H. J. Kümmerer Abstract When produced under reducing conditions, ,-Ga2O3 is transformed into an n -type semiconductor with delocalized conduction electrons that exhibit a very strong electron spin resonance (ESR) and a strong hyperfine coupling to the gallium nuclei of the host lattice. We apply the Overhauser-shift technique to investigate single crystals of this compound. With extension to the high magnetic field of a W-band spectrometer, we were able to resolve all spectral lines that were recorded and to assign them to their corresponding electronic and nuclear states. This separate analysis was the basis to access additional sample characteristics: the hyperfine coupling that is actually averaged out in the ESR signal, as well as the nuclear relaxation rates could be analyzed. Systematic measurements by varying the microwave power revealed the Overhauser shift in thermal equilibrium. The signal could be tracked to very small microwave saturation parameters, at which the deviation from the usual linear relation between power and shift becomes evident and the shift clearly approaches a constant value. This value in equilibrium was determined directly from a fit to a sequence of measurements, whereas standard X-band experiments only provided indirect conclusions. The probability densities of the electrons at the nuclei in the two nonequivalent crystallographic positions,the lattice sites with octahedral and tetrahedral coordination,could also be determined directly. The enhanced resolution revealed an otherwise hidden substructure in the nuclear resonance signals. On the basis of a microscopic model, this structure could be used to probe the environment of the oxygen vacancy more precisely and to determine the extension of the electronic wave function of the donor electrons. Copyright © 2005 John Wiley & Sons, Ltd. [source] Non-contrast-enhanced perfusion and ventilation assessment of the human lung by means of fourier decomposition in proton MRIMAGNETIC RESONANCE IN MEDICINE, Issue 3 2009Grzegorz Bauman Abstract Assessment of regional lung perfusion and ventilation has significant clinical value for the diagnosis and follow-up of pulmonary diseases. In this work a new method of non-contrast-enhanced functional lung MRI (not dependent on intravenous or inhalative contrast agents) is proposed. A two-dimensional (2D) true fast imaging with steady precession (TrueFISP) pulse sequence (TR/TE = 1.9 ms/0.8 ms, acquisition time [TA] = 112 ms/image) was implemented on a 1.5T whole-body MR scanner. The imaging protocol comprised sets of 198 lung images acquired with an imaging rate of 3.33 images/s in coronal and sagittal view. No electrocardiogram (ECG) or respiratory triggering was used. A nonrigid image registration algorithm was applied to compensate for respiratory motion. Rapid data acquisition allowed observing intensity changes in corresponding lung areas with respect to the cardiac and respiratory frequencies. After a Fourier analysis along the time domain, two spectral lines corresponding to both frequencies were used to calculate the perfusion- and ventilation-weighted images. The described method was applied in preliminary studies on volunteers and patients showing clinical relevance to obtain non-contrast-enhanced perfusion and ventilation data. Magn Reson Med, 2009. © 2009 Wiley-Liss, Inc. [source] Observation and modelling of main-sequence star chromospheres , X. Radiative budgets on Gl 867A and AU Mic (dM1e), and a two-component model chromosphere for Gl 205 (dM1),MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2010E. R. Houdebine ABSTRACT We report on high-resolution observations of two dM1 stars: Gl 867A, an active dM1e star, and Gl 205, a less active dM1 star. The wavelength coverage is from 3890 to 6820 Å with a resolving power of about 45 000. The difference spectrum of these two stars allows us to make a survey of spectral lines sensitive to magnetic activity. We chose these two stars because, to within measurement errors, they have very close properties: Gl 867A has R= 0.726 R,, [M/H]= 0.080 dex and Teff= 3416 K, and Gl 205 has R= 0.758 R,, [M/H]= 0.101 dex and Teff= 3493 K. We find that besides traditional chromospheric lines, many photospheric lines are ,filled-in' in the active star spectrum. These differences are, most of the time, weak in absolute fluxes but can be large in terms of differences in the spectral-line equivalent widths. We calculate the differences in surface fluxes between these two stars for many spectral lines. We derive the radiative budgets for two dM1e stars: Gl 867A and AU Mic. We show that the sum of the numerous spectral lines represents a significant fraction of the radiative cooling of the outer atmosphere. We also re-investigate the cooling from the continuum from the visible to the extreme ultraviolet; we find that earlier predictions of the calculations of Houdebine et al. (Paper V) are in good agreement with observations. We emphasize that if this radiative cooling is chromospheric in character, then in chromospheric model calculations, we should include the radiative losses in Ca i, Cr i, V i, Ti i and Fe i. From simple constraints, we derive model chromospheres for quiescent and active regions on Gl 205. We show that the quiescent regions have a strong absorption H, profile. The plage regions show a filled-in intermediate activity H, profile. We also present possible spectral line profiles of quiescent and active regions on Gl 867A. [source] Discovery of large-scale methanol and hydroxyl maser filaments in W3(OH)MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006L. Harvey-Smith ABSTRACT Images of the 6.7-GHz methanol maser emission from W3(OH) made at 50- and 100-mas angular resolution with the Multi-Element Radio-Linked Interferometer Network (MERLIN) are presented. The masers lie across the western face of the ultracompact H ii region in extended filaments which may trace large-scale shocks. There is a complex interrelation between the 6.7-GHz methanol masers and hydroxyl (OH) masers at 1.7 and 4.7 GHz. Together the two species trace an extended filamentary structure that stretches at least 3100 au across the face of the ultracompact H ii region. The dominant 6.7-GHz methanol emission coincides with the radio continuum peak and is populated by masers with broad spectral lines. The 6.7-GHz methanol emission is elongated at position angle 50° with a strong velocity gradient, and bears many similarities to the methanol maser disc structure reported in NGC 7538. It is surrounded by arcs of ground state OH masers at 1.7 GHz and highly excited OH masers at 13.44 GHz, some of which have the brightest methanol masers at their focus. We suggest that this region hosts the excitation centre for the ultracompact H ii region. [source] Discovery of rapid radial velocity variations in the roAp star 10 Aql and possible pulsations of , CrBMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2002O Kochukhov ABSTRACT We report discovery of radial velocity variations in rare earth spectral lines of the roAp star 10 Aql with amplitudes of between 30 and 130 m s,1 and periods of about 11 min. Radial velocity variations with amplitude 70 m s,1 may also have been detected in one spectral line of Fe i in , CrB. If confirmed, our results may indicate that all Ap stars in a certain temperature range pulsate, which means that roAp stars do not exist as a separate class but are only distinguished by higher pulsational amplitudes. [source] Development of portable CdZnTe spectrometers for remote sensing of signatures from nuclear materialsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2005Arnold Burger Abstract Room temperature cadmium zinc telluride (CZT) gamma-ray spectrometers are being developed for a number for years for medical, space and national security applications where high sensitivity, low operating power and compactness are indispensable. The technology has matured now to the point where large volume (several cubic centimeters) and high energy resolution (approximately 1% at 660 eV) of gamma photons, are becoming available for their incorporation into portable systems for remote sensing of signatures from nuclear materials. The straightforward approach of utilizing a planar CZT device has been excluded due to the incomplete collection arising from the trapping of holes and causing broadening of spectral lines at energies above 80 keV, to unacceptable levels of performance. Solutions are being pursued by developing devices aimed at processing the signal produced primarily by electrons and practically insensitive to the contribution of holes, and recent progress has been made in the areas of material growth as well as electrode and electronics design. Present materials challenges are in the growth of CZT boules from which large, oriented single crystal pieces can be cut to fabricate such sizable detectors. Since virtually all the detector grade CZT boules consist of several grains, the cost of a large, single crystal section is still high. Co-planar detectors, capacitive Frisch-grid detectors and devices taking advantage of the small pixel effect, are configurations with a range of requirements in crystallinity and defect content and involve variable degrees of complexity in the fabrication, surface passivation and signal processing. These devices have been demonstrated by several research groups and will be discussed in terms of their sensitivity and availability. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Cover Picture: Plasma Process.PLASMA PROCESSES AND POLYMERS, Issue 1 2006Polym. Cover: The picture on the cover shows axial, time-dependent distributions of (a) total light emission intensity, and [(b) to (d)] those of spectral lines at (b) 380.5 nm (N2), (c) 391.4 nm (N2+), and (d) 706.5 nm (He I), during the positive voltage half-cycle of an atmospheric-pressure He discharge across a needle-plane gap. Needle position at 3.0 mm, alumina dielectric plane at 0 mm. Further details can be found in the Full Paper by V. Poenariu, M. R. Wertheimer,* and R. Bartnikas on page 17. [source] A chromospheric dark-cored fibril in Ca II IR spectraASTRONOMISCHE NACHRICHTEN, Issue 6 2010C. Beck Abstract We investigate the thermodynamical and magnetic properties of a "dark-cored" fibril seen in the chromospheric Ca II IR line at 854.2 nm to determine the physical process behind its appearance. We analyse a time series of spectropolarimetric observations obtained in the Ca II IR line at 854.2 nm and the photospheric Fe I line at 630.25 nm. We simultaneously invert the spectra in both wavelength ranges with the SIR code to obtain the temperature and velocity stratification with height in the solar atmosphere and the magnetic field properties in the photosphere. The structure can be clearly traced in the line-of-sight (LOS) velocity and the temperature maps. It connects from a small pore with kG fields to a region with lower field strength. The flow velocity and the temperature indicate that the height of the structure increases with increasing distance from the inner footpoint. The Stokes V signal of 854.2 nm shows a Doppler-shifted polarization signal with the same displacement as in the intensity profile, indicating that the supersonic flow seen in the LOS velocity is located within magnetized plasma. We conclude that the chromospheric dark-cored fibril traces a siphon flow along magnetic field lines, driven by the gas pressure difference caused by the higher magnetic field strength at the inner footpoint. We suggest that fast flows guided by the magnetic field lead to the appearance of "dark-cored" fibrils in intensity images. Although the observations included the determination of the polarization signal in the chromospheric Ca II IR line, the signal could not be analysed quantitatively due to the low S/N. Chromospheric polarimetry will thus require telescopes of larger aperture able to collect a sufficient number of photons for a reliable determination of polarization in deep and only weakly polarized spectral lines (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] High-fidelity spectroscopy at the highest resolutionsASTRONOMISCHE NACHRICHTEN, Issue 5 2010D. Dravins Abstract High-fidelity spectroscopy presents challenges for both observations and in designing instruments. High-resolution and high-accuracy spectra are required for verifying hydrodynamic stellar atmospheres and for resolving intergalactic absorption-line structures in quasars. Even with great photon fluxes from large telescopes with matching spectrometers, precise measurements of line profiles and wavelength positions encounter various physical, observational, and instrumental limits. The analysis may be limited by astrophysical and telluric blends, lack of suitable lines, imprecise laboratory wavelengths, or instrumental imperfections. To some extent, such limits can be pushed by forming averages over many similar spectral lines, thus averaging away small random blends and wavelength errors. In situations where theoretical predictions of lineshapes and shifts can be accurately made (e.g., hydrodynamic models of solar-type stars), the consistency between noisy observations and theoretical predictions may be verified; however this is not feasible for, e.g., the complex of intergalactic metal lines in spectra of distant quasars, where the primary data must come from observations. To more fully resolve lineshapes and interpret wavelength shifts in stars and quasars alike, spectral resolutions on order R = 300 000 or more are required; a level that is becoming (but is not yet) available. A grand challenge remains to design efficient spectrometers with resolutions approaching R = 1 000 000 for the forthcoming generation of extremely large telescopes (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The exceptional Herbig Ae star HD 101412: The first detection of resolved magnetically split lines and the presence of chemical spots in a Herbig star,ASTRONOMISCHE NACHRICHTEN, Issue 4 2010S. Hubrig Abstract In our previous search for magnetic fields in Herbig Ae stars, we pointed out that HD 101412 possesses the strongest magnetic field among the Herbig Ae stars and hence is of special interest for follow-up studies of magnetism among young pre-main-sequence stars. We obtained high-resolution, high signal-to-noise UVES and a few lower quality HARPS spectra revealing the presence of resolved magnetically split lines. HD 101412 is the first Herbig Ae star for which the rotational Doppler effect was found to be small in comparison to the magnetic splitting and several spectral lines observed in unpolarized light at high dispersion are resolved into magnetically split components. The measured mean magnetic field modulus varies from 2.5 to 3.5kG, while the mean quadratic field was found to vary in the range of 3.5 to 4.8 kG. To determine the period of variations, we used radial velocity, equivalent width, line width, and line asymmetry measurements of variable spectral lines of several elements, as well as magnetic field measurements. The period determination was done using the Lomb-Scargle method. The most pronounced variability was detected for spectral lines of He I and the iron peak elements, whereas the spectral lines of CNO elements are only slightly variable. From spectral variations and magnetic field measurements we derived a potential rotation period Prot = 13.86 d, which has to be proven in future studies with a larger number of observations. It is the first time that the presence of element spots is detected on the surface of a Herbig Ae/Be star. Our previous study of Herbig Ae stars revealed a trend towards stronger magnetic fields for younger Herbig Ae stars, confirmed by statistical tests. This is in contrast to a few other (non-statistical) studies claiming that magnetic Herbig Ae stars are progenitors of the magnetic Ap stars. New developments in MHD theory show that the measured magnetic field strengths are compatible with a current-driven instability of toroidal fields generated by differential rotation in the stellar interior. This explanation for magnetic intermediate-mass stars could be an alternative to a frozen-in fossil field (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||||||||||||||