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Saul J. Adelman - One of the best experts on this subject based on the ideXlab platform.
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Elemental Abundance analyses with dao spectrograms xxxvii the normal a0 iv star γ geminorum
Publications of the Astronomical Society of the Pacific, 2015Co-Authors: Saul J. Adelman, A F Gulliver, Pongsakorn KaewkornmaungAbstract:We performed a fine analysis of the normal sharp-lined A0 IV star γ Geminorum with spectra having signal-to-noise ratios at the continuum of 500-1200 that were consistent with previous studies of this series. Our spectra have wavelength ranges of λλ3829-4730, 4873-4931, 4983-5042, and 5070-5210. The spectra measured with the program REDUCE have a two-pixel resolution of 0.072 A. We used ATLAS9 models and the program WIDTH9 to derive the Abundances of the metals. Most derived Abundances are close to solar with the Abundances of the heaviest elements Zr, Ba, La, Ce, and Nd showing greater than solar values. This suggests by comparison with the Abundances of other normal and Am stars that γ Gem might exhibit an incipient Am star phenomenon.
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Elemental Abundance analyses with dao spectrograms xxxvi the hot metallic line stars theta leonis and omicron pegasi
Publications of the Astronomical Society of the Pacific, 2015Co-Authors: Saul J. Adelman, A F Gulliver, Robert J HeatonAbstract:This series contains high-quality LTE Elemental Abundance analyses of sharp-lined and moderately rotating normal and peculiar Main Sequence Band B, A, and F stars. Their compositions were determined for comparison with analyses of somewhat similar stars and with theoretical predictions. Here we provide new and improved Elemental Abundances analyses for the well-studied hot metallic line stars θ Leonis and o Pegasi to better understand their relationship with other A stars. The analyses, which employ Kurucz's ATLAS9 model atmospheres and WIDTH9 codes and high signal-to-noise ratio (S/N) spectrograms obtained with Reticon and CCD detectors, are consistent with our previous analyses based upon coadded photographic plates. The spectral synthesis program STELLAR is used with the fluxes, the Hγ profiles, and the spectra to provide better estimates of the effective temperature, surface gravity, and metallicity. The agreement of the results for two species of the same element are usually improved. The errors have been slightly reduced compared to those of their previous analyses using DAO spectrograms. Abundances of additional elements have been determined. The very high S/N (≥500) spectra of o Peg (used previously for the stellar atlas of Gulliver et al.) were critical to finding the weakest lines and to defining the profiles of all lines. High-quality spectrograms of additional regions especially those longward of Hβ can be used to obtain some missing Elemental Abundances in both stars.
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Elemental Abundance analyses with dao spectrograms xxxv on the iron Abundances of b and a stars
Publications of the Astronomical Society of the Pacific, 2014Co-Authors: Saul J. AdelmanAbstract:I compared the results of LTE fine analyses for B and A stars based on the newer "precise and accurate" Fe II gf values of Melendez & Barbuy (MB) with those based on the relatively recent major critical compilation of Fuhr & Wiese (FW). Only nonblended Fe II lines with both FW and MB gf values for 34 B and A stars with equivalent widths derived from high dispersion, high (>200) signal-to-noise ratio Dominion Astrophysical Observatory spectra were used. For most stars the standard deviations of the Abundances derived from Fe II lines decrease slightly with the MB values, which is the signature of better consistency among the gf values. Then, for stars with many Fe I lines, I performed analyses using all lines with FW gf values and those with only A and B quality gf values and found minor improvements in the latter case. However, the Abundances and microturbulences derived from Fe I lines are in better agreement with the Fe II FW results. The discrepancy between the results for Fe I FW and Fe II MB values could be due to NLTE effects on Fe I. A more limited comparison is made with the recent theoretical values of Deb & Hibbert which, when used, show a greater scatter of the derived Fe II gf values and smaller Abundances than those obtained with the MB gf values.
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Elemental Abundance analyses with dao spectrograms xxxii hr 6455 a3 iii δ aqr a3 v η lep f2 v and 1 boo a1 v
Astronomische Nachrichten, 2011Co-Authors: K. Yüce, Saul J. Adelman, A F Gulliver, G HillAbstract:We examine the sharp-lined stars HR 6455 (A3 III, v sin i = 8.7 km s–1) and η Lep (F2 V, v sin i = 13.5 km s–1) as well as δ Aqr (A3 V, v sin i = 81 km s–1) and 1 Boo (A1 V, v sin i = 59 km s–1) to increase the number consistently analyzed A and F stars using high dispersion and high S/N (≥200) spectrograms obtained with CCD detectors at the long Coude camera of the 1.22-m telescope of the Dominion Astrophysical Observatory. Such studies contribute to understanding systematic Abundance differences between normal and non-magnetic main-sequence band chemically peculiar A and early F stars. LTE fine analyses of HR 6455, δ Aqr, and 1 Boo using Kurucz's ATLAS suite programs show the same general Elemental Abundance trends with differences in the metal richness. Light and iron-peak element Abundances are generally solar or overabundant while heavy element and rare earth element Abundances are overabundant. HR 6455 is an evolved Am star while δ Aqr and 1 Boo show the phenomenon to different extents. Most derived Abundances of η Lep are solar (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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Elemental Abundance analyses with DAO spectrograms. XXVIII. Comparisons with two series of automated Elemental Abundance analyses
New Astronomy, 2011Co-Authors: K. Yüce, Saul J. Adelman, Austin F. GulliverAbstract:Abstract We compare the results of our series of fine analyses based on Dominion Astrophysical Observatory long camera coude spectra with those of the same stars from the series of automated Elemental Abundance analyses by Hill (1995) and by Erspamer and North (2003) . We usually find good agreement with the results of the first paper for those elements with well-determined Abundances and somewhat poorer agreement with results of the second paper.
Z Lopezgarcia - One of the best experts on this subject based on the ideXlab platform.
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Elemental Abundance studies of cp stars the helium weak stars hd 19400 hd 34797 and hd 35456
Astronomy and Astrophysics, 2003Co-Authors: M S Alonso, Z Lopezgarcia, Stella Malaroda, F LeoneAbstract:An analysis of the Abundances of the helium-weak CP stars HD 19400, HD 34797 and HD 35456, is presented using ATLAS9 model atmospheres and observational material taken with a REOSC echelle spectrograph attached to the Jorge Sahade 2.15 m telescope at CASLEO. The light elements are deficient except silicon which is overabundant in HD 19400 and HD 34797. The iron peak elements are all overabundant by factors between 5 and 60. The heavy elements show an overAbundance in the three stars studied.
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Elemental Abundance study of the cp star hd 206653
Astronomy and Astrophysics, 2002Co-Authors: J F Albacetecolombo, Z Lopezgarcia, H Levato, Stella Malaroda, M GrossoAbstract:An analysis of the Abundances of the Silicon star HD 206653 is presented using an ATLAS9 model atmosphere and observational material taken with a REOSC echelle spectrograph attached to the Jorge Sahade 2.15 m telescope at CASLEO. The light elements are solar or deficient except silicon which is overabundant by a factor of 5. The iron peak elements are all overabundant by factors between 10 and 50. Sr and Y are around 1000 times the solar values. Among the Rare Earths only Ce and Eu are identified; both are overabundant by large factors.
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Elemental Abundance studies of cp stars iii the magnetic cp stars alpha scl and hd 170973
Astronomy and Astrophysics, 2001Co-Authors: Saul J. Adelman, Z Lopezgarcia, O I PintadoAbstract:Fine analyses of the magnetic CP stars α Scl and HD 170973 are presented using ATLAS9 model atmospheres which have same bulk metallicity as the deduced Abundances. The light elements are mostly solar except for silicon, and all the heavier elements except nickel in HD 170973, which is solar, are greatly overabundant. The iron peak elements are typically 10 times overabundant, Sr is of order of 1000 times solar, Y and Zr are of order of 100 times solar. The rare earths are 1000 or more times overabundant.
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Elemental Abundance studies of cp stars ii the silicon stars hd 133029 and hd 192913
Astronomy & Astrophysics Supplement Series, 1999Co-Authors: Z Lopezgarcia, Saul J. AdelmanAbstract:Fine analyses of the silicon stars HD 133029 and HD 192913 are presented using ATLAS9 model atmospheres whose predictions fit the optical region spectrophotometry and H γ profiles and have the same bulk metallicity as the deduced Abundances. Both are very He poor stars. The light elements are mostly solar except for silicon, and all the heavier elements, except nickel in HD 133029 which is solar, are greatly overabundant. The iron peak elements are typically 10 times overabundant. SrYZr are of order of 100 times solar. The rare earths are 1000 or more times overabundant.
Peter Wurz - One of the best experts on this subject based on the ideXlab platform.
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Solar wind Elemental Abundances related to the Sun's open magnetic flux
Astronomy & Astrophysics, 2009Co-Authors: X. Wang, Berndt Klecker, Peter WurzAbstract:Context. We present an investigation of the effects of solar magnetic field on the Elemental Abundance ratios of heavy ions in the solar wind. Aims. We compare the Elemental Abundance ratios Fe/O, Si/O, Mg/O, Ne/O, and C/O over the 23rd solar cycle, attention being given to the varying fraction of open magnetic flux on the visible side of the solar disc. Methods. We use ACE solar wind data, the current sheet source surface (CSSS) model of the corona, and SoHO/MDI data to relate solar wind compositional properties with the fraction of open magnetic flux on the Sun. We include both a quasi-stationary and intermittent solar wind. Results. For the six investigated solar wind speed ranges, the Elemental composition shows a similar FIP-bias of the quasi-stationary solar wind composition with respect to the photosphere but with three plateaus separating low-, mid-, and high-FIP elements. The average enrichment factor for the low-FIP element group (Mg, Fe, Si) with respect to the photospheric values is between 1.67 and 2.47 when the fraction of open magnetic flux on the visible side of the solar disc is above 14%, and it ranges from 2.78 to 4.15 when this fraction is less than 7%. They are close to the enrichment of low-FIP elements with respect to the photospheric values in quasi-stationary fast- and slow- solar wind, which implies similar fractionation mechanisms for the stationary solar wind and the intermittent solar wind. In the low alpha ( alpha is the fraction of open magnetic flux on the visible side of the solar disc), the enrichment of heavy elements for the fast solar wind is well correlated with the high fraction of CMEs. In addition, both the charge state ratios and the Elemental Abundance ratios exhibit a lower dependence on alpha in a slow solar wind than in a fast solar wind. The dependence of the charge state ratios on alpha is correlated with FIP, which implies that solar magnetic effects play a non-negligible role in the Elemental fractionation of the solar wind. We suggest that lower hybrid waves play an important role in the possible linkage between solar magnetic field and Elemental fractionation.
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the fe o Elemental Abundance ratio in the solar wind as observed with soho celias ctof
Journal of Geophysical Research, 1999Co-Authors: M. R. Aellig, Peter Bochsler, Peter Wurz, H. Grünwaldt, S. Hefti, F. M. Ipavich, D. HovestadtAbstract:Using data of the Charge Time-of-Flight (CTOF) mass spectrometer of the Charge, Element, and Isotope Analysis System (CELIAS) on board the Solar and Heliospheric Observatory (SOHO) from ∼80 days of observation around solar minimum we derive a value for the Fe/O Abundance ratio for the inecliptic solar wind of 0.11 ± 0.03. Since Fe has a low first ionization potential (FIP) and O is a high-FIP element, their relative Abundance is diagnostic for the FIP fractionation process. The unprecedented time resolution of the CELIAS CTOF sensor allows a fine-scaled study of the Fe/O ratio as a function of the solar wind bulk speed. On average, the Fe/O Abundance ratio shows a continuous decrease by a factor of 2 with increasing solar wind speed between 350 and 500 km/s. This corresponds to the well-known FIP effect dependence. Our value at ∼500 km/s agrees with the previously observed Fe/O ratio in the fast solar wind emerging from polar coronal holes whereas the value for speeds below 350 km/s is consistent with a remote Abundance determination in the leg of a coronal streamer. The variability of the Fe/O Abundance ratio is much larger in the slow than in the fast solar wind.
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The Fe/O Elemental Abundance ratio in the solar wind
AIP Conference Proceedings, 1999Co-Authors: M. R. Aellig, H. Holweger, Peter Bochsler, Peter Wurz, H. Grünwaldt, S. Hefti, F. M. Ipavich, Berndt KleckerAbstract:We analyze the Fe/O Elemental Abundance ratio in the solar wind from SOHO/CELIAS/CTOF data. Analyzed in different solar wind regimes this ratio is indicative of the strength of the FIP fractionation process because iron is a low FIP element and oxygen is a high FIP element. It is investigated whether there is a significant fractionation of the Fe/O ratio in the coronal hole solar wind. For the first time, to our knowledge, we attempt to eliminate the influence of model-dependent parameters on the derivation of the photospheric Fe/O ratio thereby increasing the accuracy of its determination. The Fe/O ratio in coronal hole solar wind is slightly higher than in the photosphere. Even with our optimistic estimates of the uncertainties of the photospheric Fe/O ratio the observed fractionation is only marginally significant.
David Yong - One of the best experts on this subject based on the ideXlab platform.
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Elemental Abundance ratios in stars of the outer galactic disk iv a new sample of open clusters
The Astronomical Journal, 2012Co-Authors: David Yong, Bruce W Carney, Eileen D FrielAbstract:We present radial velocities and chemical Abundances for nine stars in the old, distant open clusters Be18, Be21, Be22, Be32, and PWM4. For Be18 and PWM4, these are the first chemical Abundance measurements. Combining our data with literature results produces a compilation of some 68 chemical Abundance measurements in 49 unique clusters. For this combined sample, we study the chemical Abundances of open clusters as a function of distance, age, and metallicity. We confirm that the metallicity gradient in the outer disk is flatter than the gradient in the vicinity of the solar neighborhood. We also confirm that the open clusters in the outer disk are metal-poor with enhancements in the ratios [{alpha}/Fe] and perhaps [Eu/Fe]. All elements show negligible or small trends between [X/Fe] and distance ( 13 kpc) samples may have different trends with distance. There is no evidence for significant Abundance trends versus age (<0.04 dex Gyr{sup -1}). We measure the linear relation between [X/Fe] and metallicity, [Fe/H], and find that the scatter about the mean trend is comparable to the measurement uncertainties.more » Comparison with solar neighborhood field giants shows that the open clusters share similar Abundance ratios [X/Fe] at a given metallicity. While the flattening of the metallicity gradient and enhanced [{alpha}/Fe] ratios in the outer disk suggest a chemical enrichment history different from that of the solar neighborhood, we echo the sentiments expressed by Friel et al. that definitive conclusions await homogeneous analyses of larger samples of stars in larger numbers of clusters. Arguably, our understanding of the evolution of the outer disk from open clusters is currently limited by systematic Abundance differences between various studies.« less
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Elemental Abundance ratios in stars of the outer galactic disk iv a new sample of open clusters
arXiv: Astrophysics of Galaxies, 2012Co-Authors: David Yong, Bruce W Carney, Eileen D FrielAbstract:We present radial velocities and chemical Abundances for nine stars in the old, distant open clusters Be 18, Be 21, Be 22, Be 32, and PWM 4. For Be 18 and PWM 4, these are the first chemical Abundance measurements. Combining our data with literature results produces a compilation of some 68 chemical Abundance measurements in 49 unique clusters. For this combined sample, we study the chemical Abundances of open clusters as a function of distance, age, and metallicity. We confirm that the metallicity gradient in the outer disk is flatter than the gradient in the vicinity of the solar neighborhood. We also confirm that the open clusters in the outer disk are metal-poor with enhancements in the ratios [alpha/Fe] and perhaps [Eu/Fe]. All elements show negligible or small trends between [X/Fe] and distance ( 13 kpc) samples may have different trends with distance. There is no evidence for significant Abundance trends versus age (< 0.04 dex/Gyr). We measure the linear relation between [X/Fe] and metallicity, [Fe/H], and find that the scatter about the mean trend is comparable to the measurement uncertainties. Comparison with solar neighborhood field giants shows that the open clusters share similar Abundance ratios [X/Fe] at a given metallicity. While the flattening of the metallicity gradient and enhanced [alpha/Fe] ratios in the outer disk suggest a different chemical enrichment history to the solar neighborhood, we echo the sentiments expressed by Friel et al. that definitive conclusions await homogeneous analyses of larger samples of stars in larger numbers of clusters. Arguably, our understanding of the evolution of the outer disk from open clusters is currently limited by systematic Abundance differences between various studies.
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chemical inhomogeneity in red giant branch stars and rr lyrae variables in ngc 1851 two subpopulations in red giant branch
The Astrophysical Journal, 2009Co-Authors: Jae Woo Lee, Jina Lee, Young Woon Kang, Youngwook Lee, Sangil Han, Seok Joo Joo, Soochang Rey, David YongAbstract:We investigate the red giant branch (RGB) subpopulations of NGC 1851 using Ca uvby photometry. Our color-magnitude diagrams show that the RGB stars have two subpopulations and the RGB stars in NGC 1851 appear to have distinct Elemental Abundance patterns with the [Ca/H] Abundance. We discuss that the Elemental Abundance patterns can be explained by the contributions from the asymptotic giant stars, confirming the previous studies by others. The RR Lyrae variables in NGC 1851 appear to have a large metallicity spread and, perhaps, a bimodal metallicity distribution. Our period shift analysis of the RR Lyrae variables shows that the helium enhancement appears to be insignificant in the NGC 1851 RR Lyrae population. However, the helium enrichment scenario in the blue or the red parts of horizontal branch (HB) cannot be completely ruled out. Our results show that about 18% of the bright RGB stars have enhanced CNO Abundances, sharply in contrast to previous estimates by others (38%), making it difficult to explain the double subgiant, RGB sequences, and the bimodal HB distribution by their number ratios.
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Elemental Abundance ratios in stars of the outer galactic disk iii cepheids
The Astronomical Journal, 2006Co-Authors: David Yong, Bruce W Carney, Maria Luisa Teixera De Almeida, Brian L PohlAbstract:We present metallicities, [Fe/H], and Elemental Abundance ratios, [X/Fe], for a sample of 24 Cepheids in the outer Galactic disk based on high-resolution echelle spectra. The sample members have galactocentric distances covering 12 kpc ≤ RGC ≤ 17.2 kpc, making them the most distant Galactic Cepheids upon which detailed Abundance analyses have been performed. We find subsolar ratios of [Fe/H] and overAbundances of [α/Fe], [La/Fe], and [Eu/Fe] in the program stars. All Abundance ratios exhibit a dispersion that exceeds the measurement uncertainties. As seen in our previous studies of old open clusters and field giants, enhanced ratios of [α/Fe] and [Eu/Fe] reveal that recent star formation has taken place in the outer disk with Type II supernovae preferentially contributing ejecta to the interstellar medium and with Type Ia supernovae playing only a minor role. The enhancements for La suggest that asymptotic giant branch stars have contributed to the chemical evolution of the outer Galactic disk. Some of the young Cepheids are more metal-poor than the older open clusters and field stars at comparable galactocentric distances. This demonstrates that the outer disk is not the end result of the isolated evolution of an ensemble of gas and stars. We showed previously that the older open clusters and field stars reached a basement metallicity at about 10-11 kpc. The younger Cepheids reach the same metallicity but at larger galactocentric distances, roughly 14 kpc. This suggests that the Galactic disk has been growing with time, as predicted from numerical simulations. The outer disk Cepheids appear to exhibit a bimodal distribution for [Fe/H] and [α/Fe]. Most of the Cepheids continue the trends with galactocentric distance exhibited by S. M. Andrievsky's larger Cepheid sample, and we refer to these stars as the Galactic Cepheids. A minority of the Cepheids show considerably lower [Fe/H] and higher [α/Fe], and we refer to these stars as the Merger Cepheids. One signature of a merger event would be composition differences between the Galactic and Merger Cepheids. The Cepheids satisfy this requirement, and we speculate that the distinct compositions suggest that the Merger Cepheids may have formed under the influence of significant merger or accretion events. The short lifetimes of the Cepheids reveal that the merger event may be ongoing, with the Monoceros Ring and Canis Major galaxy being possible merger candidates.
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Elemental Abundance ratios in stars of the outer galactic disk iii cepheids
arXiv: Astrophysics, 2005Co-Authors: David Yong, Bruce W Carney, Luisa De Almeida, Brian L PohlAbstract:We present metallicities, [Fe/H], and Elemental Abundance ratios, [X/Fe], for a sample of 24 Cepheids in the outer Galactic disk. The sample have Galactocentric distances covering 12 < R_GC (kpc) < 17.2 making them the most distant Galactic Cepheids upon which detailed Abundance analyses have been performed. We find sub-solar ratios of [Fe/H] and overAbundances of [alpha/Fe], [La/Fe], and [Eu/Fe]. All Abundance ratios exhibit a dispersion that exceeds the measurement uncertainties. As seen in our previous studies of old open clusters and field giants, enhanced ratios of [alpha/Fe] and [Eu/Fe] reveal that recent star formation has taken place in the outer disk. The outer disk Cepheids appear to exhibit a bimodal distribution for [Fe/H] and [alpha/Fe]. Most of the Cepheids continue the trends with Galactocentric distance exhibited by Andrievsky's larger Cepheid sample and we refer to these stars as the "Galactic Cepheids". A minority of the Cepheids show considerably lower [Fe/H] and higher [alpha/Fe] and we refer to these stars as the "Merger Cepheids". One signature of a merger event would be composition differences between the "Galactic" and "Merger" Cepheids. The Cepheids satisfy this requirement and we speculate that the distinct compositions suggest that the "Merger Cepheids" may have formed under the influence of significant merger or accretion events. The short lifetimes of the Cepheids reveal that the merger event may be on-going with the Monoceros ring and Canis Major galaxy being possible merger candidates. [Abridged]
K A Arnaud - One of the best experts on this subject based on the ideXlab platform.
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central Elemental Abundance ratios in the perseus cluster resonant scattering or sn ia enrichment
The Astrophysical Journal, 2001Co-Authors: Renato A Dupke, K A ArnaudAbstract:We have determined Abundance ratios in the core of the Perseus Cluster for several elements. These ratios indicate a central dominance of Type 1a supernova (SN Ia) ejecta similar to that found for A496, A2199, and A3571. Simultaneous analysis of ASCA spectra from SIS1, GIS2, and GIS3 shows that the ratio of Ni to Fe Abundances is ~3.4 ± 1.1 times solar within the central 4'. This ratio is consistent with (and more precise than) that observed in other clusters whose central regions are dominated by SN Ia ejecta. Such a large Ni overAbundance is predicted by "convective deflagration" explosion models for SNe Ia such as W7 but is inconsistent with delayed detonation models. We note that with current instrumentation the Ni Kα line is confused with Fe Kβ and that the Ni overAbundance we observe has been interpreted by others as an anomalously large ratio of Fe Kβ to Fe Kα caused by resonant scattering in the Fe Kα line. We argue that a central enhancement of SN Ia ejecta and hence a high ratio of Ni to Fe Abundances are naturally explained by scenarios that include the generation of chemical gradients by suppressed SN Ia winds or ram pressure stripping of cluster galaxies. It is not necessary to suppose that the intracluster gas is optically thick to resonant scattering of the Fe Kα line.
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central Elemental Abundance ratios in the perseus cluster resonant scattering or sn ia enrichment
arXiv: Astrophysics, 2000Co-Authors: Renato A Dupke, K A ArnaudAbstract:We have determined Elemental Abundance ratios in the core of the Perseus cluster for several elements. These ratios indicate a central dominance of SN Ia ejecta similar to that found for A496, A2199 and A3571 (Dupke & White 2000). Simultaneous analysis of ASCA spectra from SIS1, GIS 2&3 shows that the ratio of Ni to Fe Abundances is ~ (3.4 +- 1.1) times Solar within the central 4'. This ratio is consistent with (and more precise than) that observed in other clusters whose central regions are dominated by SN Ia ejecta. Such a large Ni over-Abundance is predicted by "Convective Deflagration" explosion models for SN Ia such as "W7" but is inconsistent with delayed detonation models. We note that with current instrumentation the NiK(alpha) line is confused with FeK(beta) and that the Ni over-Abundance we observe has been interpreted by others as an anomalously large ratio of FeK(beta) to FeK(alpha) caused by resonant scattering in the FeK(alpha) line. We argue that a central enhancement of SN Ia ejecta and hence a high ratio of Ni to Fe is naturally explained by scenarios that include the generation of chemical gradients by suppressed SN Ia winds or ram-pressure stripping of cluster galaxies. It is not necessary to suppose that the intracluster gas is optically thick to resonant scattering of the FeK(alpha) line.