Evidence of vertical abundance stratification in the SB1 star HD 161660: a new HgMn

2020 ◽  
Vol 499 (3) ◽  
pp. 3720-3727
Author(s):  
G Catanzaro ◽  
M Giarrusso ◽  
M Munari ◽  
F Leone
Keyword(s):  
Chemical Composition ◽  
Rotational Velocity ◽  
Homogeneous Distribution ◽  
Atmospheric Parameters ◽  
Isotopic Mixture ◽  
Fundamental Parameters ◽  
Solar Composition ◽  
Chemical Pattern ◽  
Balmer Lines ◽  
Archive Data

ABSTRACT In this paper, we present a detailed spectroscopic study of the SB1 system HD 161660. New spectroscopic observations have been obtained by us with Catania Astrophysical Observatory Spectropolarimeter (CAOS@OAC). Combining these observations with archive data from [email protected], we derived atmospheric parameters as temperature and gravity (from the fit of Balmer lines), microturbulence and rotational velocity (from metal lines), and chemical composition. We found underabundances of helium, carbon, magnesium, sulphur and chromium, overabundances of neon, phosphorus, argon, manganese, xenon, and mercury. All other elements have solar composition. In particular, mercury abundance is derived taking into account an isotopic mixture different from the terrestrial one (essentially pure 202Hg). Considering this chemical pattern, we definitively confirm HD 161660 is an HgMn star. Further, variability of equivalent widths points out a non-homogeneous distribution of helium and magnesium over stellar surface. As to iron and phosphorus, we found a non-constant abundance with the optical depth, a result currently considered an evidence of vertical stratification. Finally, we improved the fundamental parameters characterizing the HD 161660 orbit.

scholarly journals Oxygen and silicon abundances in Cygnus OB2

2018 ◽  
Vol 620 ◽  
pp. A56 ◽  
Author(s):  
S. R. Berlanas ◽  
A. Herrero ◽  
F. Comerón ◽  
S. Simón-Díaz ◽  
M. Cerviño ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Rotational Velocity ◽  
Stellar Atmosphere ◽  
Homogeneous Distribution ◽  
Stellar Winds ◽  
Stellar Content ◽  
Galactocentric Distance ◽  
Fundamental Parameters ◽  
Chemical Enrichment ◽  
Galactic Longitude

Context. Cygnus OB2 is a rich OB association in the Galaxy located at only ∼1.4 kpc from us which has experienced intense star formation in the last 20–25 Myr. Its stellar population shows a correlation between age and Galactic longitude. Exploring the chemical composition of its stellar content we will be able to check the degree of homogeneity of the natal molecular cloud and possible effects of self-enrichment processes. Aims. Our aim is to determine silicon and oxygen abundances for a sample of eight early-type slow rotators (with rotational velocities below 80 km s−1) in Cygnus OB2 in order to check possible inhomogeneities across the whole association and whether there exists a correlation of chemical composition with Galactic longitude. Methods. We have performed a spectroscopic analysis of a sample of late O and early B stars with low rotational velocity in Cygnus OB2, which have been chosen so as to cover the whole association area. We have carried out an analysis based on equivalent widths of metal lines, the wings of the H Balmer lines and FASTWIND stellar atmosphere models to determine their stellar fundamental parameters (effective temperature and surface gravity) as well as the silicon and oxygen surface abundances. Results. We derive a rather homogeneous distribution of silicon and oxygen abundances across the region, with average values of 12 + log(Si/H) = 7.53 ± 0.08 dex and 12 + log(O/H) = 8.65 ± 0.12 dex. Conclusions. We find a homogeneous chemical composition in Cygnus OB2 with no clear evidence for significant chemical self-enrichment, despite indications of strong stellar winds and possible supernovae during the history of the region. Comparison with different scenarios of chemical enrichment by stellar winds and supernovae point to star forming efficiencies not significantly above 10%. The degree of homogeneity that we find is consistent with the observed Milky Way oxygen gradient based on H II regions. We also find that the oxygen scatter within Cygnus OB2 is at least of the same order than among H II regions at similar Galactocentric distance.

scholarly journals Influence of the precursor chemical composition on heavy metal adsorption properties of hemp (Cannabis Sativa) fibers based biocarbon

2017 ◽  
Vol 82 (12) ◽  
pp. 1417-1431 ◽  
Author(s):  
Marija Vukcevic ◽  
Biljana Pejic ◽  
Ivana Pajic-Lijakovic ◽  
Ana Kalijadis ◽  
Mirjana Kostic ◽  
...  
Keyword(s):  
Heavy Metal ◽  
Chemical Composition ◽  
Surface Area ◽  
Active Sites ◽  
Cannabis Sativa ◽  
Lignin Content ◽  
Area Measurement ◽  
Bet Surface Area ◽  
Homogeneous Distribution ◽  
Hemp Fibers

Waste hemp (Cannabis sativa) fibers were used as sustainable and renewable raw materials for production of low-cost biocarbon sorbent for heavy metals removal. Carbon precursors of different chemical composition were obtained by oxidative and alkaline treatments of hemp fibers. Influence of lignocellulosic precursor chemical composition on hemp fibers-based biocarbon (HFB) characteristics was examined by BET surface area measurement, scanning electron microscopy and mass titration. It was found that lignin content and polymorphic transformation of cellulose increase the SBET of microporous HFBs, while hemicelluloses induce more homogeneous distribution of adsorption active sites. Heavy metal ions adsorption onto HFBs is primarily influenced by the amount of surface oxygen groups, while specific surface area plays a secondary role. Equilibrium data obtained for lead ions adsorption were analyzed by different nonlinear adsorption isotherms, and the best fitting model was chosen using standard deviation and Akaike information criterion (AICC). The maximum adsorption capacities of HFBs ranged from 103.1 to 116.3 mg Pb/g. Thermodynamic parameters showed that Pb2+ adsorption onto HFBs is a spontaneous and complex endothermic process, suggesting the coexistence of physisorption and chemisorption mechanisms.

scholarly journals Tests of Evolution Models Using Eclipsing Binaries

1995 ◽  
Vol 10 ◽  
pp. 419-422
Author(s):  
J. Andersen
Keyword(s):  
Chemical Composition ◽  
Star Clusters ◽  
Stellar Model ◽  
Eclipsing Binaries ◽  
Fundamental Parameter ◽  
Fundamental Parameters ◽  
Stellar Models ◽  
Absolute Age ◽  
Cluster Sequence ◽  
Hr Diagram

Stellar models are the means by which we describe and understand the distribution of stars in the HR diagram. A stellar model is, in principle, completely specified by the three fundamental parameters mass, chemical composition, and age. Comparing the properties of models and real stars with the same parameters will tell us if our recipe for constructing stellar models is realistic. Unfortunately, the only star for which all three are known independently of stellar models is the Sun. For stars of other masses and ages we must devise observational tests in which at least one fundamental parameter is unknown. Two such popular test objects are double-lined eclipsing binaries and star clusters.In suitable eclipsing binaries we can determine both masses and chemical composition; the absolute age is unknown, but the same for both stars. Since evolution depends most sensitively on the mass, eclipsing binaries provide a very direct test of the models, but only for two points on a single isochrone. In star clusters, neither ages nor individual masses are known, but the detailed shape and population of a well-observed cluster sequence in the HR diagram provide a number of additional probes into the models.

Chemical Composition of a Young Star HD 377

2012 ◽  
Vol 21 (4) ◽  
Author(s):  
Tõnu Kipper
Keyword(s):  
Chemical Composition ◽  
High Resolution ◽  
Main Sequence ◽  
Young Star ◽  
Main Sequence Star ◽  
High Resolution Spectrum ◽  
Atmospheric Parameters

AbstractA high resolution spectrum of a pre-main sequence star HD 377 is analyzed. The atmospheric parameters are found to be: T

scholarly journals EUVE J0825-16.3 and EUVE J1501-43.6: Two dMe Double–Lined Spectroscopic Binaries

2006 ◽  
Vol 2 (S240) ◽  
pp. 690-696
Author(s):  
D. Montes ◽  
I. Crespo-Chacón ◽  
M.C. Gálvez ◽  
M.J. Fernández-Figueroa
Keyword(s):  
High Resolution ◽  
Orbital Period ◽  
Binary Systems ◽  
Cross Correlation ◽  
Rotational Velocity ◽  
Spectroscopic Binaries ◽  
Balmer Lines ◽  
First Time ◽  
Orbital Solution ◽  
Similar Intensity

AbstractHigh-resolution echelle spectroscopic observations taken with the FEROS spectrograph at the ESO 2.2-m telescope confirm the binary nature of the dMe stars EUVE J0825−16.3 and EUVE J1501−43.6, previously reported by Christian & Mathioudakis (2002). In these binary systems, emission of similar intensity from both components is detected in the Na i D1 & D2, He i D3, Ca II H&K, Ca II IRT and Balmer lines. We have determined precise radial velocities by cross-correlation with radial velocity standard stars, which have allowed us to obtain for the first time the orbital solution of these systems. Both binaries consist of two nearly equal M0V components with an orbital period shorter than 3.5 days. We have analyzed the behaviour of the chromospheric activity indicators (variability and possible flares). In addition, we have determined its rotational velocity and kinematics.

scholarly journals Investigation of the Double-mode Cepheid TU Cas: Atmospheric Parameters and Chemical Composition

1993 ◽  
Vol 139 ◽  
pp. 382-382
Author(s):  
S. M. Andrievsky ◽  
V. V. Kovtyukh ◽  
E. N. Makarenko ◽  
I. A. Usenko
Keyword(s):  
Chemical Composition ◽  
Southern Hemisphere ◽  
Open Cluster ◽  
Atmospheric Parameters

AbstractAtmospheric parameters and abundances of 25 elements were determined from two spectrograms of TU Cas (with dispersion 9 Å/mm) obtained in 1977 and 1990. We find Teff= 5860 - 6000K; logg = 1.0 - 1.5; and vt = 2.9 - 5.3 km/s.The value of [Fe/H] ∼ -0.5 testifies to the fact that TU Cas is deficient in metals compared with other double-mode Cepheids. More exact values of [Fe/H] for 9 double-mode Cepheids in the Southern Hemisphere (Barrell 1982), V367 Set (a member of the open cluster NGC 6649) and our value for TU Cas all show a good correlation with P1/P0. As the atmospheric Fe abundance increases, the ratio P1/P0 decreases.Our measured values for abundances (in brackets) of various elements in the atmosphere of TU Cas are: C (8.26), Na (6.32), Mg (7.07), Si (6.85), S (6.96), Ca (5.88), Sc (2.71), Ti (4.34), V (3.35), Cr (5.29), Mn (4.92), Fe (6.94), Co (4.47), Ni (5.70), Zn (3.63), Sr (2.00), Y (2.17), Zr (2.21), Ba (1.41), La (1.08), Ce (0.96), Nd (0.82), Sm (0.42), Eu (1.04), and Gd (0.92).

Biosensing Surfaces Based on Quantum Dots Array

2014 ◽  
Vol 490-491 ◽  
pp. 1602-1606 ◽  
Author(s):  
Jana Drbohlavová ◽  
Jana Chomoucka ◽  
Radim Hrdý ◽  
Vojtech Svatos ◽  
Jaromir Hubalek
Keyword(s):  
Quantum Dots ◽  
Chemical Composition ◽  
Fluorescence Spectroscopy ◽  
Surface Topography ◽  
Electrochemical Detection ◽  
Physical Adsorption ◽  
Homogeneous Distribution ◽  
Alumina Template ◽  
Detection Of Biomolecules

The fabrication of self-ordered semiconductor (TiO2) and noble metal (Au) QDs arrays was successfully achieved by advanced nonlithographic template based method, namely using nanoporous alumina template. The emphasis was placed on the successful preparation of QDs arrays with the desired size, homogeneous distribution and optical (especially fluorescence) properties. Titania and gold QDs characterization by SEM, EDX and fluorescence spectroscopy was performed in order to verify their surface topography, chemical composition and emission properties in UV/VIS range of spectra, respectively. The surface biofunctionalization of QDs was realized via simple physical adsorption of glutathione tripeptide, which makes these arrays suitable for potential biosensing application, mainly in optical and electrochemical detection of biomoleculesin vitro.

scholarly journals Chemical Composition of European Propolis: Expected and Unexpected Results

2002 ◽  
Vol 57 (5-6) ◽  
pp. 530-533 ◽  
Author(s):  
Vassya Bankova ◽  
Milena Popova ◽  
Stefan Bogdanov ◽  
Anna-Gloria Sabatini
Keyword(s):  
Chemical Composition ◽  
Alpine Region ◽  
Two Samples ◽  
Chemical Pattern ◽  
Ferulic Acids

Ten propolis samples from Bulgaria, Italy and Switzerland were analyzed by GC-MS. As expected, most samples displayed the typical chemical pattern of “poplar” propolis: they contained pinocembrin, pinobanksin and its 3-O-acetate, chrysin, galangin, prenyl esters of caffeic and ferulic acids. Two samples differed significantly: one from the Graubünden Alpine region, Switzerland, rich in phenolic glycerides, and one from Sicily which contained only a limited number of phenolics and was rich in diterpenic acids.

scholarly journals An investigation of the double-mode Cepheid TU Cassiopeiae - I. Atmospheric parameters and chemical composition

1993 ◽  
Vol 265 (2) ◽  
pp. 257-260 ◽  
Author(s):  
S. M. Andrievsky ◽  
V. V. Kovtjukh ◽  
E. N. Makarenko ◽  
I. A. Usenko
Keyword(s):  
Chemical Composition ◽  
Atmospheric Parameters

scholarly journals Where do Be stars stand in the picture of rotational mixing?

2010 ◽  
Vol 6 (S272) ◽  
pp. 85-86
Author(s):  
Paul R. Dunstall ◽  
Ines Brott ◽  
Philip L. Dufton ◽  
Chris J. Evans
Keyword(s):  
Critical Velocity ◽  
Rotational Velocity ◽  
Magellanic Clouds ◽  
Evolutionary Status ◽  
Evolutionary Models ◽  
Be Stars ◽  
Atmospheric Parameters ◽  
B Stars ◽  
The Absolute ◽  
Fast Rotating

AbstractAtmospheric parameters and photospheric abundances have been estimated for 60 Be-type stars located in 4 fields over the Magellanic Clouds. Particular attention has been given to the absolute nitrogen abundances to test theories of rotational mixing, an important factor in the evolutionary status of B-type stars, Hunter et al. (2008). The analysis used the non-LTE atmospheric code TLUSTY and required the implementation of a procedure to compensate for possible contamination due to the presence of a circumstellar disc. Through comparison with evolutionary models of fast rotating B-type stars and projected rotational velocity distributions our results support the theory that Be-type stars are typically faster rotators than B stars, but the measured nitrogen enhancements appear to be significantly less than expected for Be stars rotating with velocities greater than 70% of their critical velocity

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