AR Aur A+B is a close binary of astrophysical interest because dissimilar surface compositions are reported between similar late B-type dwarfs.A new spectroscopic study on this system was carried out based on the dise...AR Aur A+B is a close binary of astrophysical interest because dissimilar surface compositions are reported between similar late B-type dwarfs.A new spectroscopic study on this system was carried out based on the disentangled spectra,in order to determine their atmospheric parameters and elemental abundances.The effective temperature and microturbulence(determined from the equivalent widths of Fe II lines)turned out to be(11,150 K,0.9 km s^(-1))and(10,650 K,0.1 km s^(-1))for A and B,respectively.The chemical abundances of 28 elements were then derived while taking into account the non-LTE effect for Z≤15 elements(Z:atomic number).The following trends were elucidated for[X/H](abundance of X relative to the Sun):(1)Qualitatively,[X/H]shows a rough global tendency to increase with Z,with the gradient steeper for A than for B.(2)However,considerable dispersion is involved for A,since prominently large peculiarities are seen in specific elements reflecting the characteristics of HgMn stars(e.g.,very deficient N,Al,Sc,Ni;markedly overabundant P,Mn).(3)In contrast,the Z-dependence of[X/H]for B tends to be nearly linear with only a small dispersion.These observational facts may serve as a key to understanding the critical condition for the emergence of the chemical anomaly.展开更多
Gamma-ray spectrometer （GRS） is one of the main payloads on the Chang＇E-1 （CE-1） lunar probe, mainly aimed to detect the elemental abundances and distributions on the lunar surface. At 03：58 on 28 November 2007,...Gamma-ray spectrometer （GRS） is one of the main payloads on the Chang＇E-1 （CE-1） lunar probe, mainly aimed to detect the elemental abundances and distributions on the lunar surface. At 03：58 on 28 November 2007, it performed the first observation of the lunar gamma rays. As of 24 October 2008, 2105 h of effective gamma rays spectra had been acquired by CE-1 GRS, which covers the whole surface of the moon. This paper mainly describes the data processing procedures and methods of deriving the elemental abundances by using the CE-1 GRS time series corrected spectra： first, to bin data into pixels for mapping; then, to perform a background deduction of the cumulative spectra and obtain a peak area of the elements; and finally, to use the elemental abundances inversion model to produce the elemental abundances. Based on these processing methods, the global abundance maps of U, K, and Th at a 5°×5° equal-area pixel are acquired by CE-1 GRS data. The paper gives a preliminary analysis of the uncertainties of the elemental abundances.展开更多
Based on high resolution,high signal-to-noise(S/N)ratio spectra from Keck/HIRES,we have determined abundances of 20 elements for 18 Ba candidates.The parameter space of these stars is in the range of 4880≤Teff≤6050 ...Based on high resolution,high signal-to-noise(S/N)ratio spectra from Keck/HIRES,we have determined abundances of 20 elements for 18 Ba candidates.The parameter space of these stars is in the range of 4880≤Teff≤6050 K,2.56≤log g≤4.53 dex and-0.27≤[Fe/H]≤0.09 dex.It is found that four of them can be identified as Ba stars with[s/Fe]>0.25 dex(s:Sr,Y,Zr,Ba,La,Ce and Nd),and three of them are newly discovered,which include two Ba giants(HD 16178 and HD 22233)and one Ba subgiant(HD 2946).Our results show that the abundances ofα,odd and iron-peak elements(O,Na,Mg,Al,Si,Ca,Sc,Ti,Mn,Ni and Cu)for our program stars are similar to those of the thin disk,while the distribution of[hs/ls](hs:Ba,La,Ce and Nd,ls:Sr,Y and Zr)ratios of our Ba stars is similar to those of the known Ba objects.None of the four Ba stars show clear enhancement in carbon including the known CH subgiant HD 4395.It is found that three of the Ba stars present clear evidence of hosting stellar or sub-stellar companions from the radial velocity data.展开更多
The influence of radiative cooling on the unimolecular decay rates of free, hot clusters and molecules with unspecified excitation energies is quantified. Two different regimes, dedined by the magnitude of the energy ...The influence of radiative cooling on the unimolecular decay rates of free, hot clusters and molecules with unspecified excitation energies is quantified. Two different regimes, dedined by the magnitude of the energy of the photons emitted, are identified and the boundary between them is given. The boundary is determined in terms of the photon emission rate constants and thermal properties of the particles. Also the abundance spectra are calculated for the continuous cooling case, corresponding to small photon energies. The two regimes correspond to continuous cooling and single photon quenching of the unimolecular decay. The radiative effect can be parametrized by a redefinition of the time each individual cluster has available to undergo evaporation, expressed by an effective radiative time constant.展开更多
One-dimensional(1 D)model atmospheres are still the most commonly used tool for the determination of stellar chemical composition.Convection in the model is usually treated by mixing-length theory(MLT).The mixing-leng...One-dimensional(1 D)model atmospheres are still the most commonly used tool for the determination of stellar chemical composition.Convection in the model is usually treated by mixing-length theory(MLT).The mixing-length parameterαis generally calibrated from the Sun and applied to all other stars.The metal-poor giant,HD 122563,is an important benchmark star to test stellar atmosphere and interior physics.We investigate the influence of the convection mixing-length parameterαon the determination of chemical abundances of Na,Mg,Al,Si,Ca,Sc,Ti,Cr,Mn,Co,Ni,Sr,Y,Zr and Ba in the case of HD 122563,taking advantage of a high resolution and high signal-to-noise ratio HARPS spectrum.The abundance discrepanciesΔ[X/H]that occur due toαvariation rarely exceed 0.05 dex and most are less than 0.03 dex.We calculate the discrepancyΔ[X/H]using a line-by-line differential analysis.The abundance discrepancies do not have direct relation with either line strength or the excitation potential.For 1 D stellar atmospheric analysis of HD 122563,the accuracy of abundance determination does not strongly depend on the choice of mixing-length parameterα(causing average discrepancies of<0.03 dex),while the uncertainties in the effective temperature and surface gravity play a more important role.展开更多
Estimating ages for a large number of giants is of great importance for studying Galactic evolution.In this work,we determine stellar ages and masses for 556007 giants from LAMOST Data Release 5(DR5)with empirical rel...Estimating ages for a large number of giants is of great importance for studying Galactic evolution.In this work,we determine stellar ages and masses for 556007 giants from LAMOST Data Release 5(DR5)with empirical relations estimated from chemical[C/N]abundance ratios.Our sample reveals the two wellknown sequences in the age-[α/M]relation.The high-αsequence is composed of stars older than 8 Gyr and low-αsequence is composed of stars with age ranging from 0 Gyr to 13.8 Gyr.Our sample also shows a flat age-[M/H]relation up until 12 Gyr.We compare these distributions with Galactic Chemical Evolution models for reference.When looking at the spatial distribution of stars in 2 Gyr age bins,we find that young stars are concentrated towards the Galactic plane and older stars extend to higher height above and below the disk.We find a smooth transition of median Galactic height for different age bins,which suggests a strong age-dependence on Galactic scale height.展开更多
Elemental abundance patterns of globular cluster stars can provide important clues for understanding cluster formation and early chemical evolution.The origin of the abundance patterns,however,still remains poorly und...Elemental abundance patterns of globular cluster stars can provide important clues for understanding cluster formation and early chemical evolution.The origin of the abundance patterns,however,still remains poorly understood.We have studied the impact of p-capture reaction cycles on the abundances of oxygen,sodium and aluminium considering nuclear reaction cycles of carbon-nitrogenoxygen-fluorine,neon-sodium and magnesium-aluminium in massive stars in stellar conditions of temperature range 2×107to 10×107K and typical density of 102gm cc-1.We have estimated abundances of oxygen,sodium and aluminium with respect to Fe,which are then assumed to be ejected from those stars because of rotation reaching a critical limit.These ejected abundances of elements are then compared with their counterparts that have been observed in some metal-poor evolved stars,mainly giants and red giants,of globular clusters M3,M4,M13 and NGC 6752.We observe an excellent agreement with[O/Fe]between the estimated and observed abundance values for globular clusters M3 and M4 with a correlation coefficient above 0.9 and a strong linear correlation for the remaining two clusters with a correlation coefficient above 0.7.The estimated[Na/Fe]is found to have a correlation coefficient above 0.7,thus implying a strong correlation for all four globular clusters.As far as[Al/Fe]is concerned,it also shows a strong correlation between the estimated abundance and the observed abundance for globular clusters M13 and NGC 6752,since here also the correlation coefficient is above 0.7 whereas for globular cluster M4 there is a moderate correlation found with a correlation coefficient above 0.6.Possible sources of these discrepancies are discussed.展开更多
Chemical composition of very metal-poor(VMP)stars can provide observational constraints on current models of nucleosynthesis and the chemical evolution of the Galaxy.It has been found that the scatter of[Na/Fe]versus[...Chemical composition of very metal-poor(VMP)stars can provide observational constraints on current models of nucleosynthesis and the chemical evolution of the Galaxy.It has been found that the scatter of[Na/Fe]versus[Fe/H]in VMP stars is very large in contrast with most other elements.Moreover,a negative slope in[Na/Fe]versus[Fe/H]was found for giants,which is very unlikely according to the theory of nucleosynthesis.For the sample of93 VMP stars in the metallicity range-4.25<[Fe/H]<-1.64 we obtained NLTE sodium abundances using the line profile fitting method by employing accurate atmospheric parameters determined when taking into account NLTE line formation for both FeⅠand FeⅡ.Originally selected from the LAMOST low-resolution spectral database,the spectra of stars were obtained with the High Dispersion Spectrograph of the Subaru Telescope.For 57turn-off stars in metallicity domain-3.04<[Fe/H]<-1.64,we obtained mean[Na/Fe]=-0.29±0.14 and positive slope 0.09±0.06.For 21 giants distributed over metallicity-3.59<[Fe/H]<-2.19,we found mean[Na/Fe]=-0.35±0.1 and positive slope 0.07±0.07.Our[Na/Fe]trend is lower by~0.2 dex,compared to the modern GCE model.We believe the GCE model should be adjusted,by considering the associated scatter.Twelve stars in our sample are found to be outliers,with too low or too high Na abundances.展开更多
We present the dependence of electron temperature fluctuations of O++ and H+ by the chemical abundances of oxygen and nitrogen. Models assume that hydrogen density is uniform in one case and non uniform in the second ...We present the dependence of electron temperature fluctuations of O++ and H+ by the chemical abundances of oxygen and nitrogen. Models assume that hydrogen density is uniform in one case and non uniform in the second case, which vary with the distance from the central star. The abundances of oxygen and nitrogen change by scale factor 5 and 1/5. Our analysis suggests that temperature fluctuations are consistent with photoionization. Using the cloudy photoionization code, we found a reasonable close agreement of the computed value with the one that was done before this work. Our simulation also shows that how change of abundances affects temperature fluctuations and its value is less than 0.01.展开更多
We present stellar parameters and abundances of 15 elements （Na, Mg, A1, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Ni, Cu, Y and Ba） for 23 field RR Lyrae variables based on high-resolution （R ~ 60 000） and high signal-to-no...We present stellar parameters and abundances of 15 elements （Na, Mg, A1, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Ni, Cu, Y and Ba） for 23 field RR Lyrae variables based on high-resolution （R ~ 60 000） and high signal-to-noise （S/N~ 200） spectra obtained using the High Dispersion Spectrograph on the Subaru Telescope. Six stars in the sample have more than one spectrum observed at different pulsation phases. The derived abundance ratios of [X/Fe] for 14 elements （except for Ba） do not vary during the pulsation cycle. An interesting curve of [Ba/Fe] versus phase is detected for the first time and it shows decreasing [Ba/Fe] with increasing temperature at a given metallicity. Combining with data in the literature, abundances of most RR Lyrae stars as a function of [Fe/H] follow the same trends as those of dwarf stars, but [Sc/Fe] and [Y/Fe] ratios of RR Lyrae stars at solar metallicity are lower than those of dwarf stars. The kinematics of RR Lyrae stars indicate that three comparatively metal-rich RR Lyrae stars might originate from the thick disk and they show higher [a/Fe] ratios than RR Lyrae stars with thin disk kinematics. Among 23 RR Lyrae stars, two special objects are found with abnormal abundances; TV Lib has high [a/Fe], [Sc/Fe], [Y/Fe] and [Ba/Fe] ratios while TW Her has solar [a/Fe] but significantly lower [Sc/Fe], [Y/Fe] and [Ba/Fe] ratios as compared with other RR Lyrae stars.展开更多
The continental crustobody of China is composed of three regional crustobodies, i. e., the Cathaysian crustobody, the West China crustobody and the South Tibet crustobody. This paper gives their mass models and elemen...The continental crustobody of China is composed of three regional crustobodies, i. e., the Cathaysian crustobody, the West China crustobody and the South Tibet crustobody. This paper gives their mass models and element abundance values and discusses their regional abundance characteristics from metallogenic elernents, heat source elements and lanthanide elements. The conclusion is that their geochemical backgrounds are quite different from each other.展开更多
Spectral indices from OMEGA hyperspectral data show that there are two main phyllosilicates exposed in and around Mawrth Vallis:Al phyllosilicates and Fe/Mg phyllosilicates.Detailed analysis of CRISM spectra shows tha...Spectral indices from OMEGA hyperspectral data show that there are two main phyllosilicates exposed in and around Mawrth Vallis:Al phyllosilicates and Fe/Mg phyllosilicates.Detailed analysis of CRISM spectra shows that Al phyllosilicates such as montmorillonite,hydrated silica,kaolinite;Fe/Mg phyllosilicates such as nontronite,saponite,serpentine are widespread on the light-toned outcrops.Though similar stratigraphical sequences,morphologies and textures are observed on both sides of Mawrth Vallis from HiRISE images,suggesting that the geological processes that formed these units must have operated at a regional scale;the multiple endmember spectral mixture analysis(MESMA) derived mineral abundance indicates that there is a higher level of alteration in the western side relative to the eastern side.We suggest that the observed phyllosilicates,stratigraphical sequences and different levels of alteration might have been caused by sedimentary deposition processes in which the composition of the external source sediment or the local solution was different,or by a pedogenic process closely related to the leaching of abundant liquid water with different chemical properties.展开更多
The relative conformer energies of glycine are evaluated by using a focal point analysis expressed as（HF→MP2→MP3→CCSD→CCSD（T））.The conformer abundances at various temperatures（298–500 K） are calculated base...The relative conformer energies of glycine are evaluated by using a focal point analysis expressed as（HF→MP2→MP3→CCSD→CCSD（T））.The conformer abundances at various temperatures（298–500 K） are calculated based on the relative energies and Boltzmann statistical thermostatistical analysis with and without considering internal hindered rotations.A comparison between the available Raman spectrum and the electron momentum spectrum confirms that the influence of rigid-rotor hindered rotation on the conformational proportions of glycine is considerable,especially for the IIIp structure.The conformational interconversions are discussed.It is found that with increasing temperature,the mole fraction of IIn keeps constant and Ip structure can convert into IVn and IIIp,leading to the decrease in the weight of Ip and the increase in the weights of IVn and IIIp conformers,which is in accordance with experimental observations.展开更多
Based on the LC-ESI/MSn technique, the four pairs of isomers of psoralen and isopsoralen, imperatorin and isoimperatorin, neohesperidin and hesperidin, naringin and narirutin were distinguished mainly by comparison of...Based on the LC-ESI/MSn technique, the four pairs of isomers of psoralen and isopsoralen, imperatorin and isoimperatorin, neohesperidin and hesperidin, naringin and narirutin were distinguished mainly by comparison of the relative abundances of their major fragment ions. Because of the effect of the hydrogen on the C8 of psoralen, the intensity of the fragment ion formed by the loss of CO2 was relatively increased. By comparing the abundance of the product ions formed by the loss of CO and 2CO, the isomers of psoralen and isopsoralen could be distinguished. This method can also be used to distinguish the isomers of imperatorin and isoimperatorin. Because of the different con- nected position between glucose and rhamnose, in the mass spectrum of neohesperidin, the relative abundances of ions at m/z 489 and 343 generated by the ring-cross cleavage of glycan were more than 10%, while in the mass spec- trum of hesperidin, they were all less than 1%. This approach can also be used to distinguish the isomers ofnaringin and narirutin. Although the fragmentation pathways were similar, according to the tiny difference of structure, the change of relative intensity of main fragment ions could be observed and it could be used to distinguish some isomers more accurately and quickly.展开更多
Through a detailed study of the abundances and spatial-temporal distribution patterns of Te,Bi,As,Se,Cu,Pb,Zn,Au,and Ag in the rock types of different geological epochs in the Dashuigou independent tellurium deposit,a...Through a detailed study of the abundances and spatial-temporal distribution patterns of Te,Bi,As,Se,Cu,Pb,Zn,Au,and Ag in the rock types of different geological epochs in the Dashuigou independent tellurium deposit,and in combination with other research findings of previous researchers in this area,the authors conclude as follows:Abundances of the main ore-forming elements Te,Bi,As,Se,Au,and Ag are not high in the regional geological background,generally lower or close to their respective crustal Clark values,but almost all altered country rocks contain high levels of ore-forming elements.This indicates that the deposit’s ore-forming elements do not come from the country rocks.This also indicates that the geological thermal events that cause alteration and mineralization originate from depths and may be related to mantle plumes.Considering the distribution pattern of these ore-forming elements in the ore bodies’hanging wall and footwall,the metallogenic mechanism may be as follows:Mineralization is not achieved through lateral secretion in the horizontal or near horizontal direction,but rather through the upward movement and emplacement of deep ore-forming elements driven by geological processes such as mantle plumes.In addition,the migration of deep ore-forming elements is not achieved through dispersed infiltration between overlying rock particles,but through non widespread concentrated penetrating channels.This type of channel is likely to be the expansion structures where faults from different directions intersect,or where linear faults intersect with circular structures.展开更多
Stellar atmospheric parameters and elemental abundances are traditionally determined using template matching techniques based on high-resolution spectra.However,these methods are sensitive to noise and unsuitable for ...Stellar atmospheric parameters and elemental abundances are traditionally determined using template matching techniques based on high-resolution spectra.However,these methods are sensitive to noise and unsuitable for ultra-low-resolution data.Given that the Chinese Space Station Telescope(CSST)will acquire large volumes of ultra-low-resolution spectra,developing effective methods for ultra-low-resolution spectral analysis is crucial.In this work,we investigated the Fully Connected Residual Network(FCResNet)for simultaneously estimating atmospheric parameters(T_(eff),log g,[Fe/H])and elemental abundances([C/Fe],[N/Fe],[Mg/Fe]).We trained and evaluated FCResNet using CSST-like spectra(R~200)generated by degrading LAMOST spectra(R~1800),with reference labels from APOGEE.FCResNet significantly outperforms traditional machine learning methods(KNN,XGBoost,S VR)and CNN in prediction precision.For spectra with the g-band signal-tonoise ratio greater than 20,FCResNet achieves precisions of 78 K,0.15 dex,0.08 dex,0.05 dex,0.10 dex,and0.05 dex for T_(eff),log g,[Fe/H],[C/Fe],[N/Fe]and[Mg/Fe],respectively,on the test set.FCResNet processes one million spectra in only 42 s while maintaining a simple architecture with only 348 KB model size.These results suggest that FCResNet is a practical and promising tool for processing the large volume of ultra-lowresolution spectra that will be obtained by CSST in the future.展开更多
The protein elicitor from the mycelium of Alternaria tenuissima has been isolated.The elicitor triggered resistance to the tobacco mosaic virus in tobacco by inducing relative oxygen species,but without causing hypers...The protein elicitor from the mycelium of Alternaria tenuissima has been isolated.The elicitor triggered resistance to the tobacco mosaic virus in tobacco by inducing relative oxygen species,but without causing hypersensitive necrosis.The elicitor is reported to impart resistance against Verticillium dahliae and to increase yield in cotton,but its mechanism is not yet clear.In this study,the stable isotope labelled mass spectrometry method was used to quantify the relative abundances of protein expression induced by PeaT1 in Arabidopsis.A significant difference in the relative abundances for the expression of different proteins related to metabolism,modification,regulatory,defense,stress and antioxidation was found in Arabidopsis.展开更多
Following the researches of helium isotopic compositions in mantle-derived xenoliths in eastern China, this study reported noble gas abundances and isotopic compositions of mantle-derived xenoliths from Kuandian of Li...Following the researches of helium isotopic compositions in mantle-derived xenoliths in eastern China, this study reported noble gas abundances and isotopic compositions of mantle-derived xenoliths from Kuandian of Liaoning Province, Huinan of Jilin Province and Hannuoba of Hebei Province. Compared with the middle ocean ridge basalt (MORB) and other continental areas, mantle-derived xenoliths in NE China are characterized by slightly low noble gas abundances, 3He/4He equivalent to or lower than that of MORB, 40Ar/36Ar lower than that of MORB, 38Ar/36Ar and Ne-Kr-Xe isotopic ratios equivalent to those of atmosphere. These results indicate the heterogeneity of subcontinental lithospheric mantle beneath northeastern China, that is, a MORB reservoir-like mantle beneath Kuandian and an enriched/metasomatized mantle beneath Huinan. Low 40Ar/ 36Ar ratios in the three studied areas may imply that a subducted atmospheric component has been preserved in the subcontinental lithospheric mantle.展开更多
Object LAMOST J020623.21+494127.9(program star) in the thin disk of the Milky Way is reported as a highly r-process-enhanced r-II star with [Eu/Fe] = +1.32 and [Fe/H] =-0.54. The chemical profile of the star reflects ...Object LAMOST J020623.21+494127.9(program star) in the thin disk of the Milky Way is reported as a highly r-process-enhanced r-II star with [Eu/Fe] = +1.32 and [Fe/H] =-0.54. The chemical profile of the star reflects the intrinsic composition of the gas cloud present at its birth. Using an abundance decomposition method, we fit25 elements from the abundance data set, including 10 heavy neutron-capture elements. We explore the astrophysical origin of the elements in this star through its abundance ratios and component ratios. We find that the contributions from the massive stars played a significant role in the production of light elements in the program star. Our analysis reveals that the heavy neutron-capture elements are produced purely by the main r-process. However, the adopted main r-process model does not adequately fit the observed data, suggesting another main r-process pattern may exist.展开更多
Accurate determinations of metallicity for large,complete stellar samples are essential for advancing various studies of the Milky Way.In this paper,we present a data-driven algorithm that leverages photometric data f...Accurate determinations of metallicity for large,complete stellar samples are essential for advancing various studies of the Milky Way.In this paper,we present a data-driven algorithm that leverages photometric data from the KiDS and the VIKING surveys to estimate stellar absolute magnitudes,effective temperatures,and metallicities.The algorithm is trained and validated using spectroscopic data from LAMOST,SEGUE,APOGEE,and GALAH,as well as a catalog of very metal-poor stars from the literature,and Gaia EDR3 data.This approach enables us to estimate metallicities,effective temperatures,and g-band absolute magnitudes for approximately 0.8 million stars in the KiDS data set.The photometric metallicity estimates exhibit an uncertainty of around 0.28 dex when compared to spectroscopic studies,within the metallicity range of−2 dex to 0.5 dex.The photometric effective temperature estimates have an uncertainty of around 149 K,while the uncertainty in the absolute magnitudes is approximately 0.36 mag.The metallicity estimates are reliable for values down to about−2 dex.This catalog represents a valuable resource for studying the structure and chemical properties of the Milky Way,offering an extensive data set for future investigations into Galactic formation and evolution.展开更多
文摘AR Aur A+B is a close binary of astrophysical interest because dissimilar surface compositions are reported between similar late B-type dwarfs.A new spectroscopic study on this system was carried out based on the disentangled spectra,in order to determine their atmospheric parameters and elemental abundances.The effective temperature and microturbulence(determined from the equivalent widths of Fe II lines)turned out to be(11,150 K,0.9 km s^(-1))and(10,650 K,0.1 km s^(-1))for A and B,respectively.The chemical abundances of 28 elements were then derived while taking into account the non-LTE effect for Z≤15 elements(Z:atomic number).The following trends were elucidated for[X/H](abundance of X relative to the Sun):(1)Qualitatively,[X/H]shows a rough global tendency to increase with Z,with the gradient steeper for A than for B.(2)However,considerable dispersion is involved for A,since prominently large peculiarities are seen in specific elements reflecting the characteristics of HgMn stars(e.g.,very deficient N,Al,Sc,Ni;markedly overabundant P,Mn).(3)In contrast,the Z-dependence of[X/H]for B tends to be nearly linear with only a small dispersion.These observational facts may serve as a key to understanding the critical condition for the emergence of the chemical anomaly.
基金supported by the National High Technology Research and Development Program of China(Nos2008AA12A212 and 2010AA122202)the National Natural Science Foundation of China(Nos41040031 and 40904024)
文摘Gamma-ray spectrometer （GRS） is one of the main payloads on the Chang＇E-1 （CE-1） lunar probe, mainly aimed to detect the elemental abundances and distributions on the lunar surface. At 03：58 on 28 November 2007, it performed the first observation of the lunar gamma rays. As of 24 October 2008, 2105 h of effective gamma rays spectra had been acquired by CE-1 GRS, which covers the whole surface of the moon. This paper mainly describes the data processing procedures and methods of deriving the elemental abundances by using the CE-1 GRS time series corrected spectra： first, to bin data into pixels for mapping; then, to perform a background deduction of the cumulative spectra and obtain a peak area of the elements; and finally, to use the elemental abundances inversion model to produce the elemental abundances. Based on these processing methods, the global abundance maps of U, K, and Th at a 5°×5° equal-area pixel are acquired by CE-1 GRS data. The paper gives a preliminary analysis of the uncertainties of the elemental abundances.
基金supported by the National Key R&D Program of China (No. 2019YFA0405502)the National Natural Science Foundation of China (Grant Nos. 12090040, 12090044, 11833006, 12022304, 11973052, 11973042, U2031144 and U1931102)+1 种基金supported by the Astronomical Big Data Joint Research Center, co-founded by the National Astronomical Observatories, Chinese Academy of Sciences (CAS)support from the Youth Innovation Promotion Association of the CAS (id. 2019060)
文摘Based on high resolution,high signal-to-noise(S/N)ratio spectra from Keck/HIRES,we have determined abundances of 20 elements for 18 Ba candidates.The parameter space of these stars is in the range of 4880≤Teff≤6050 K,2.56≤log g≤4.53 dex and-0.27≤[Fe/H]≤0.09 dex.It is found that four of them can be identified as Ba stars with[s/Fe]>0.25 dex(s:Sr,Y,Zr,Ba,La,Ce and Nd),and three of them are newly discovered,which include two Ba giants(HD 16178 and HD 22233)and one Ba subgiant(HD 2946).Our results show that the abundances ofα,odd and iron-peak elements(O,Na,Mg,Al,Si,Ca,Sc,Ti,Mn,Ni and Cu)for our program stars are similar to those of the thin disk,while the distribution of[hs/ls](hs:Ba,La,Ce and Nd,ls:Sr,Y and Zr)ratios of our Ba stars is similar to those of the known Ba objects.None of the four Ba stars show clear enhancement in carbon including the known CH subgiant HD 4395.It is found that three of the Ba stars present clear evidence of hosting stellar or sub-stellar companions from the radial velocity data.
文摘The influence of radiative cooling on the unimolecular decay rates of free, hot clusters and molecules with unspecified excitation energies is quantified. Two different regimes, dedined by the magnitude of the energy of the photons emitted, are identified and the boundary between them is given. The boundary is determined in terms of the photon emission rate constants and thermal properties of the particles. Also the abundance spectra are calculated for the continuous cooling case, corresponding to small photon energies. The two regimes correspond to continuous cooling and single photon quenching of the unimolecular decay. The radiative effect can be parametrized by a redefinition of the time each individual cluster has available to undergo evaporation, expressed by an effective radiative time constant.
基金the National Natural Science Foundation of China(Grant Nos.11988101,11890694,11773033)the National Key R&D Program of China(No.2019YFA0405502)。
文摘One-dimensional(1 D)model atmospheres are still the most commonly used tool for the determination of stellar chemical composition.Convection in the model is usually treated by mixing-length theory(MLT).The mixing-length parameterαis generally calibrated from the Sun and applied to all other stars.The metal-poor giant,HD 122563,is an important benchmark star to test stellar atmosphere and interior physics.We investigate the influence of the convection mixing-length parameterαon the determination of chemical abundances of Na,Mg,Al,Si,Ca,Sc,Ti,Cr,Mn,Co,Ni,Sr,Y,Zr and Ba in the case of HD 122563,taking advantage of a high resolution and high signal-to-noise ratio HARPS spectrum.The abundance discrepanciesΔ[X/H]that occur due toαvariation rarely exceed 0.05 dex and most are less than 0.03 dex.We calculate the discrepancyΔ[X/H]using a line-by-line differential analysis.The abundance discrepancies do not have direct relation with either line strength or the excitation potential.For 1 D stellar atmospheric analysis of HD 122563,the accuracy of abundance determination does not strongly depend on the choice of mixing-length parameterα(causing average discrepancies of<0.03 dex),while the uncertainties in the effective temperature and surface gravity play a more important role.
基金supported by the National Natural Science Foundation of China(Grant Nos.11988101,11890694)National Key R&D Program of China(No.2019YFA0405502)China Scholarship Council。
文摘Estimating ages for a large number of giants is of great importance for studying Galactic evolution.In this work,we determine stellar ages and masses for 556007 giants from LAMOST Data Release 5(DR5)with empirical relations estimated from chemical[C/N]abundance ratios.Our sample reveals the two wellknown sequences in the age-[α/M]relation.The high-αsequence is composed of stars older than 8 Gyr and low-αsequence is composed of stars with age ranging from 0 Gyr to 13.8 Gyr.Our sample also shows a flat age-[M/H]relation up until 12 Gyr.We compare these distributions with Galactic Chemical Evolution models for reference.When looking at the spatial distribution of stars in 2 Gyr age bins,we find that young stars are concentrated towards the Galactic plane and older stars extend to higher height above and below the disk.We find a smooth transition of median Galactic height for different age bins,which suggests a strong age-dependence on Galactic scale height.
文摘Elemental abundance patterns of globular cluster stars can provide important clues for understanding cluster formation and early chemical evolution.The origin of the abundance patterns,however,still remains poorly understood.We have studied the impact of p-capture reaction cycles on the abundances of oxygen,sodium and aluminium considering nuclear reaction cycles of carbon-nitrogenoxygen-fluorine,neon-sodium and magnesium-aluminium in massive stars in stellar conditions of temperature range 2×107to 10×107K and typical density of 102gm cc-1.We have estimated abundances of oxygen,sodium and aluminium with respect to Fe,which are then assumed to be ejected from those stars because of rotation reaching a critical limit.These ejected abundances of elements are then compared with their counterparts that have been observed in some metal-poor evolved stars,mainly giants and red giants,of globular clusters M3,M4,M13 and NGC 6752.We observe an excellent agreement with[O/Fe]between the estimated and observed abundance values for globular clusters M3 and M4 with a correlation coefficient above 0.9 and a strong linear correlation for the remaining two clusters with a correlation coefficient above 0.7.The estimated[Na/Fe]is found to have a correlation coefficient above 0.7,thus implying a strong correlation for all four globular clusters.As far as[Al/Fe]is concerned,it also shows a strong correlation between the estimated abundance and the observed abundance for globular clusters M13 and NGC 6752,since here also the correlation coefficient is above 0.7 whereas for globular cluster M4 there is a moderate correlation found with a correlation coefficient above 0.6.Possible sources of these discrepancies are discussed.
基金funded by the National Natural Science Foundation of China(NSFC,Grant Nos.11988101 and 11890694)the National Key R&D Program of China No.2019YFA0405502。
文摘Chemical composition of very metal-poor(VMP)stars can provide observational constraints on current models of nucleosynthesis and the chemical evolution of the Galaxy.It has been found that the scatter of[Na/Fe]versus[Fe/H]in VMP stars is very large in contrast with most other elements.Moreover,a negative slope in[Na/Fe]versus[Fe/H]was found for giants,which is very unlikely according to the theory of nucleosynthesis.For the sample of93 VMP stars in the metallicity range-4.25<[Fe/H]<-1.64 we obtained NLTE sodium abundances using the line profile fitting method by employing accurate atmospheric parameters determined when taking into account NLTE line formation for both FeⅠand FeⅡ.Originally selected from the LAMOST low-resolution spectral database,the spectra of stars were obtained with the High Dispersion Spectrograph of the Subaru Telescope.For 57turn-off stars in metallicity domain-3.04<[Fe/H]<-1.64,we obtained mean[Na/Fe]=-0.29±0.14 and positive slope 0.09±0.06.For 21 giants distributed over metallicity-3.59<[Fe/H]<-2.19,we found mean[Na/Fe]=-0.35±0.1 and positive slope 0.07±0.07.Our[Na/Fe]trend is lower by~0.2 dex,compared to the modern GCE model.We believe the GCE model should be adjusted,by considering the associated scatter.Twelve stars in our sample are found to be outliers,with too low or too high Na abundances.
文摘We present the dependence of electron temperature fluctuations of O++ and H+ by the chemical abundances of oxygen and nitrogen. Models assume that hydrogen density is uniform in one case and non uniform in the second case, which vary with the distance from the central star. The abundances of oxygen and nitrogen change by scale factor 5 and 1/5. Our analysis suggests that temperature fluctuations are consistent with photoionization. Using the cloudy photoionization code, we found a reasonable close agreement of the computed value with the one that was done before this work. Our simulation also shows that how change of abundances affects temperature fluctuations and its value is less than 0.01.
基金Supported by the National Natural Science Foundation of China
文摘We present stellar parameters and abundances of 15 elements （Na, Mg, A1, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Ni, Cu, Y and Ba） for 23 field RR Lyrae variables based on high-resolution （R ~ 60 000） and high signal-to-noise （S/N~ 200） spectra obtained using the High Dispersion Spectrograph on the Subaru Telescope. Six stars in the sample have more than one spectrum observed at different pulsation phases. The derived abundance ratios of [X/Fe] for 14 elements （except for Ba） do not vary during the pulsation cycle. An interesting curve of [Ba/Fe] versus phase is detected for the first time and it shows decreasing [Ba/Fe] with increasing temperature at a given metallicity. Combining with data in the literature, abundances of most RR Lyrae stars as a function of [Fe/H] follow the same trends as those of dwarf stars, but [Sc/Fe] and [Y/Fe] ratios of RR Lyrae stars at solar metallicity are lower than those of dwarf stars. The kinematics of RR Lyrae stars indicate that three comparatively metal-rich RR Lyrae stars might originate from the thick disk and they show higher [a/Fe] ratios than RR Lyrae stars with thin disk kinematics. Among 23 RR Lyrae stars, two special objects are found with abnormal abundances; TV Lib has high [a/Fe], [Sc/Fe], [Y/Fe] and [Ba/Fe] ratios while TW Her has solar [a/Fe] but significantly lower [Sc/Fe], [Y/Fe] and [Ba/Fe] ratios as compared with other RR Lyrae stars.
文摘The continental crustobody of China is composed of three regional crustobodies, i. e., the Cathaysian crustobody, the West China crustobody and the South Tibet crustobody. This paper gives their mass models and element abundance values and discusses their regional abundance characteristics from metallogenic elernents, heat source elements and lanthanide elements. The conclusion is that their geochemical backgrounds are quite different from each other.
基金supported by the National Natural Science Foundation of China(Grant No.41002120)Opening Fund of Geomathematics Key Laboratory of Sichuan Province(Grant No.SCSXDZ2013005)
文摘Spectral indices from OMEGA hyperspectral data show that there are two main phyllosilicates exposed in and around Mawrth Vallis:Al phyllosilicates and Fe/Mg phyllosilicates.Detailed analysis of CRISM spectra shows that Al phyllosilicates such as montmorillonite,hydrated silica,kaolinite;Fe/Mg phyllosilicates such as nontronite,saponite,serpentine are widespread on the light-toned outcrops.Though similar stratigraphical sequences,morphologies and textures are observed on both sides of Mawrth Vallis from HiRISE images,suggesting that the geological processes that formed these units must have operated at a regional scale;the multiple endmember spectral mixture analysis(MESMA) derived mineral abundance indicates that there is a higher level of alteration in the western side relative to the eastern side.We suggest that the observed phyllosilicates,stratigraphical sequences and different levels of alteration might have been caused by sedimentary deposition processes in which the composition of the external source sediment or the local solution was different,or by a pedogenic process closely related to the leaching of abundant liquid water with different chemical properties.
基金Project supported by the Young Scientists Funds of the National Natural Science Foundation of China(Grant Nos.11404154 and 11304136)
文摘The relative conformer energies of glycine are evaluated by using a focal point analysis expressed as（HF→MP2→MP3→CCSD→CCSD（T））.The conformer abundances at various temperatures（298–500 K） are calculated based on the relative energies and Boltzmann statistical thermostatistical analysis with and without considering internal hindered rotations.A comparison between the available Raman spectrum and the electron momentum spectrum confirms that the influence of rigid-rotor hindered rotation on the conformational proportions of glycine is considerable,especially for the IIIp structure.The conformational interconversions are discussed.It is found that with increasing temperature,the mole fraction of IIn keeps constant and Ip structure can convert into IVn and IIIp,leading to the decrease in the weight of Ip and the increase in the weights of IVn and IIIp conformers,which is in accordance with experimental observations.
基金Supported by the National Natural Science Foundation of China(Nos.30670212 and 30870262)
文摘Based on the LC-ESI/MSn technique, the four pairs of isomers of psoralen and isopsoralen, imperatorin and isoimperatorin, neohesperidin and hesperidin, naringin and narirutin were distinguished mainly by comparison of the relative abundances of their major fragment ions. Because of the effect of the hydrogen on the C8 of psoralen, the intensity of the fragment ion formed by the loss of CO2 was relatively increased. By comparing the abundance of the product ions formed by the loss of CO and 2CO, the isomers of psoralen and isopsoralen could be distinguished. This method can also be used to distinguish the isomers of imperatorin and isoimperatorin. Because of the different con- nected position between glucose and rhamnose, in the mass spectrum of neohesperidin, the relative abundances of ions at m/z 489 and 343 generated by the ring-cross cleavage of glycan were more than 10%, while in the mass spec- trum of hesperidin, they were all less than 1%. This approach can also be used to distinguish the isomers ofnaringin and narirutin. Although the fragmentation pathways were similar, according to the tiny difference of structure, the change of relative intensity of main fragment ions could be observed and it could be used to distinguish some isomers more accurately and quickly.
文摘Through a detailed study of the abundances and spatial-temporal distribution patterns of Te,Bi,As,Se,Cu,Pb,Zn,Au,and Ag in the rock types of different geological epochs in the Dashuigou independent tellurium deposit,and in combination with other research findings of previous researchers in this area,the authors conclude as follows:Abundances of the main ore-forming elements Te,Bi,As,Se,Au,and Ag are not high in the regional geological background,generally lower or close to their respective crustal Clark values,but almost all altered country rocks contain high levels of ore-forming elements.This indicates that the deposit’s ore-forming elements do not come from the country rocks.This also indicates that the geological thermal events that cause alteration and mineralization originate from depths and may be related to mantle plumes.Considering the distribution pattern of these ore-forming elements in the ore bodies’hanging wall and footwall,the metallogenic mechanism may be as follows:Mineralization is not achieved through lateral secretion in the horizontal or near horizontal direction,but rather through the upward movement and emplacement of deep ore-forming elements driven by geological processes such as mantle plumes.In addition,the migration of deep ore-forming elements is not achieved through dispersed infiltration between overlying rock particles,but through non widespread concentrated penetrating channels.This type of channel is likely to be the expansion structures where faults from different directions intersect,or where linear faults intersect with circular structures.
基金supported by the National Astronomical Observatories of Chinese Academy of Sciences(No.E4ZR0516)the National Natural Science Foundation of China(12273078,12273075 and 12411530071)+2 种基金support from Royal Society IECNSFC233140 exchange grantFunding for the Project has been provided by the National Development and Reform CommissionFunding for the Sloan Digital Sky Survey IV has been provided by the Alfred P.Sloan Foundation,the U.S.Department of Energy Office of Science,and the Participating Institutions。
文摘Stellar atmospheric parameters and elemental abundances are traditionally determined using template matching techniques based on high-resolution spectra.However,these methods are sensitive to noise and unsuitable for ultra-low-resolution data.Given that the Chinese Space Station Telescope(CSST)will acquire large volumes of ultra-low-resolution spectra,developing effective methods for ultra-low-resolution spectral analysis is crucial.In this work,we investigated the Fully Connected Residual Network(FCResNet)for simultaneously estimating atmospheric parameters(T_(eff),log g,[Fe/H])and elemental abundances([C/Fe],[N/Fe],[Mg/Fe]).We trained and evaluated FCResNet using CSST-like spectra(R~200)generated by degrading LAMOST spectra(R~1800),with reference labels from APOGEE.FCResNet significantly outperforms traditional machine learning methods(KNN,XGBoost,S VR)and CNN in prediction precision.For spectra with the g-band signal-tonoise ratio greater than 20,FCResNet achieves precisions of 78 K,0.15 dex,0.08 dex,0.05 dex,0.10 dex,and0.05 dex for T_(eff),log g,[Fe/H],[C/Fe],[N/Fe]and[Mg/Fe],respectively,on the test set.FCResNet processes one million spectra in only 42 s while maintaining a simple architecture with only 348 KB model size.These results suggest that FCResNet is a practical and promising tool for processing the large volume of ultra-lowresolution spectra that will be obtained by CSST in the future.
基金supported by the Hi-Tech Research and Development Program of China (Grant No. 2006AA10A210)
文摘The protein elicitor from the mycelium of Alternaria tenuissima has been isolated.The elicitor triggered resistance to the tobacco mosaic virus in tobacco by inducing relative oxygen species,but without causing hypersensitive necrosis.The elicitor is reported to impart resistance against Verticillium dahliae and to increase yield in cotton,but its mechanism is not yet clear.In this study,the stable isotope labelled mass spectrometry method was used to quantify the relative abundances of protein expression induced by PeaT1 in Arabidopsis.A significant difference in the relative abundances for the expression of different proteins related to metabolism,modification,regulatory,defense,stress and antioxidation was found in Arabidopsis.
基金This work was supported by the National Climbing Program (Grant No. 95-P-39).
文摘Following the researches of helium isotopic compositions in mantle-derived xenoliths in eastern China, this study reported noble gas abundances and isotopic compositions of mantle-derived xenoliths from Kuandian of Liaoning Province, Huinan of Jilin Province and Hannuoba of Hebei Province. Compared with the middle ocean ridge basalt (MORB) and other continental areas, mantle-derived xenoliths in NE China are characterized by slightly low noble gas abundances, 3He/4He equivalent to or lower than that of MORB, 40Ar/36Ar lower than that of MORB, 38Ar/36Ar and Ne-Kr-Xe isotopic ratios equivalent to those of atmosphere. These results indicate the heterogeneity of subcontinental lithospheric mantle beneath northeastern China, that is, a MORB reservoir-like mantle beneath Kuandian and an enriched/metasomatized mantle beneath Huinan. Low 40Ar/ 36Ar ratios in the three studied areas may imply that a subducted atmospheric component has been preserved in the subcontinental lithospheric mantle.
基金supported by the National Key Basic R&D Program of China No. 2024YFA1611903the National Natural Science Foundation of China (NSFC, Grant No. 12173013)+2 种基金the project of Hebei provincial department of science and technology under the grant No. 226Z7604Gthe Hebei NSF (No. A2021205006)the China Manned Space Project for funding support of this study
文摘Object LAMOST J020623.21+494127.9(program star) in the thin disk of the Milky Way is reported as a highly r-process-enhanced r-II star with [Eu/Fe] = +1.32 and [Fe/H] =-0.54. The chemical profile of the star reflects the intrinsic composition of the gas cloud present at its birth. Using an abundance decomposition method, we fit25 elements from the abundance data set, including 10 heavy neutron-capture elements. We explore the astrophysical origin of the elements in this star through its abundance ratios and component ratios. We find that the contributions from the massive stars played a significant role in the production of light elements in the program star. Our analysis reveals that the heavy neutron-capture elements are produced purely by the main r-process. However, the adopted main r-process model does not adequately fit the observed data, suggesting another main r-process pattern may exist.
基金partially supported by the National Natural Science Foundation of China 12173034 and 12322304he National Natural Science Foundation of Yunnan Province202301AV070002+1 种基金the Xingdian talent support program of Yunnan Provincethe science research grants from the China Manned Space Project with NO.CMS-CSST-2021-A09,CMS-CSST-2021-A08 and CMS-CSST-2021-B03。
文摘Accurate determinations of metallicity for large,complete stellar samples are essential for advancing various studies of the Milky Way.In this paper,we present a data-driven algorithm that leverages photometric data from the KiDS and the VIKING surveys to estimate stellar absolute magnitudes,effective temperatures,and metallicities.The algorithm is trained and validated using spectroscopic data from LAMOST,SEGUE,APOGEE,and GALAH,as well as a catalog of very metal-poor stars from the literature,and Gaia EDR3 data.This approach enables us to estimate metallicities,effective temperatures,and g-band absolute magnitudes for approximately 0.8 million stars in the KiDS data set.The photometric metallicity estimates exhibit an uncertainty of around 0.28 dex when compared to spectroscopic studies,within the metallicity range of−2 dex to 0.5 dex.The photometric effective temperature estimates have an uncertainty of around 149 K,while the uncertainty in the absolute magnitudes is approximately 0.36 mag.The metallicity estimates are reliable for values down to about−2 dex.This catalog represents a valuable resource for studying the structure and chemical properties of the Milky Way,offering an extensive data set for future investigations into Galactic formation and evolution.
