Most Galactic metal-poor stars exhibit enhanced α-abundances（e.g.[Mg/Fe] ～ ＋0.4） according to previous studies of stellar chemical compositions.However, a handful of metal-poor stars with large deficiencies in Mg...Most Galactic metal-poor stars exhibit enhanced α-abundances（e.g.[Mg/Fe] ～ ＋0.4） according to previous studies of stellar chemical compositions.However, a handful of metal-poor stars with large deficiencies in Mg（e.g. [Mg/Fe]～-0.2） show severe departures from this α-enhancement trend. The sub-solar[Mg/Fe] ratios of these anomalous stars indicate that they possess different chemical enrichment histories than the majority of Galactic metal-poor stars. In previous work,we presented a method to select Mg-poor metal-poor stars from low-resolution SDSS spectra based on a spectral matching technique. In this paper, a similar method is applied to low-resolution（R ～ 1800） LAMOST spectra. Stellar [Mg/Fe] abundances are determined by using stellar parameters delivered by the LAMOST Data Release2 catalog. From a sample of ～ 60 000 stars with atmospheric parameters in the range Teff = [5500, 6500] K and [Fe/H] = [-2.4, ＋0.5], we select 15 candidate Mg-poor metal-poor stars.展开更多
One of the essential controls on the microwave thermal emissions(MTE) of the lunar regolith is the abundance of Fe O and TiO_2, known as the(Fe O+Ti O_2) abundance(FTA). In this paper, a radiative transfer simulation ...One of the essential controls on the microwave thermal emissions(MTE) of the lunar regolith is the abundance of Fe O and TiO_2, known as the(Fe O+Ti O_2) abundance(FTA). In this paper, a radiative transfer simulation is employed first to study the change in the brightness temperature(T_B) with FTA under a range of frequencies and surface temperatures. Then, we analyze the influence of FTA on the MTE of the lunar regolith using microwave sounder(CELMS) data from the Chang'E-2 lunar orbiter, Clementine UV-VIS data, and lunar samples recovered from the Apollo and Surveyor projects. We conclude that:(1) FTA strongly influences the MTE of the lunar regolith, but it is not the decisive control, and(2) FTA decreases slightly with depth. This research plays an essential role in appropriately inverting CELMS data to obtain lunar regolith parameters.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 11390371, 11233004, 11303040 and U1431106)
文摘Most Galactic metal-poor stars exhibit enhanced α-abundances（e.g.[Mg/Fe] ～ ＋0.4） according to previous studies of stellar chemical compositions.However, a handful of metal-poor stars with large deficiencies in Mg（e.g. [Mg/Fe]～-0.2） show severe departures from this α-enhancement trend. The sub-solar[Mg/Fe] ratios of these anomalous stars indicate that they possess different chemical enrichment histories than the majority of Galactic metal-poor stars. In previous work,we presented a method to select Mg-poor metal-poor stars from low-resolution SDSS spectra based on a spectral matching technique. In this paper, a similar method is applied to low-resolution（R ～ 1800） LAMOST spectra. Stellar [Mg/Fe] abundances are determined by using stellar parameters delivered by the LAMOST Data Release2 catalog. From a sample of ～ 60 000 stars with atmospheric parameters in the range Teff = [5500, 6500] K and [Fe/H] = [-2.4, ＋0.5], we select 15 candidate Mg-poor metal-poor stars.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41371332 & 41590851)the Fundamental Research Funds for the Central Universities (Grant No. JCKY-QKJC23)the Science and Technology Development Fund of Macao (Grant No. 110/2014/A3)
文摘One of the essential controls on the microwave thermal emissions(MTE) of the lunar regolith is the abundance of Fe O and TiO_2, known as the(Fe O+Ti O_2) abundance(FTA). In this paper, a radiative transfer simulation is employed first to study the change in the brightness temperature(T_B) with FTA under a range of frequencies and surface temperatures. Then, we analyze the influence of FTA on the MTE of the lunar regolith using microwave sounder(CELMS) data from the Chang'E-2 lunar orbiter, Clementine UV-VIS data, and lunar samples recovered from the Apollo and Surveyor projects. We conclude that:(1) FTA strongly influences the MTE of the lunar regolith, but it is not the decisive control, and(2) FTA decreases slightly with depth. This research plays an essential role in appropriately inverting CELMS data to obtain lunar regolith parameters.
