IRAS 01005+7910 is a cold IRAS source. We present its optical identification, photometric and spectroscopic observation results. Its optical counterpart is classified as a B2Ie star with V magnitude 10.85. Its Hα lin...IRAS 01005+7910 is a cold IRAS source. We present its optical identification, photometric and spectroscopic observation results. Its optical counterpart is classified as a B2Ie star with V magnitude 10.85. Its Hα line shows the P Cygni profile. According to its location in the Galaxy (b = 16.6), we consider it to be a post-AGB star or a proto-planetary nebula.展开更多
The discovery of silicate carbon star poses a challenge to the theory of stellar evolution in the late stage, hence it is important to look for more silicate carbon stars. To this end we have carried out cross-identif...The discovery of silicate carbon star poses a challenge to the theory of stellar evolution in the late stage, hence it is important to look for more silicate carbon stars. To this end we have carried out cross-identifications between the new IRAS Low-Resolution Spectrum （LRS） database and the new carbon star catalog, CGCS3. We have found nine new silicate carbon stars with silicate features around 10μm and/or 18 μm. These newly identified stars are located in the Regions Ilia and VII in the IRAS two-color diagram, which means they indeed have typical far infrared colors of silicate carbon stars. The infrared properties of each of these sources are discussed.展开更多
Based on the s-process nucleosynthesis model with the 13C（α, n）16O reaction occurring under radiative conditions in the interpulse phases, we investigate the characteristics of the distribution of neutron exposure ...Based on the s-process nucleosynthesis model with the 13C（α, n）16O reaction occurring under radiative conditions in the interpulse phases, we investigate the characteristics of the distribution of neutron exposure in low-mass Asymptotic Giant Branch （AGB） stars. We introduce a new concept, the distribution of neutron exposures of the Galaxy （NEG）, to study the chemical evolution characteristics of the Galaxy for s-process elements. Using a chemical evolution model of the Galaxy, we develop a model for the NEG and obtain the evolution results of the NEG in different epochs. The present results appear to reasonably reproduce the distribution of neutron exposures of the solar system （hereafter NES）. The main component and the strong component in the NES are built up in different epochs. The strong component of the s-process is mainly synthesised in the low-mass and metal-poor AGB stars, and the main component is produced by the s-process in the low-mass AGB stars with higher metallicities.展开更多
Energetic outflows from main sequence stars accreting mass at very high rates might account for the powering of some eruptive objects, such as merging main sequence stars, major eruptions of luminous blue variables, e...Energetic outflows from main sequence stars accreting mass at very high rates might account for the powering of some eruptive objects, such as merging main sequence stars, major eruptions of luminous blue variables, e.g., the Great Eruption of Eta Carinae, and other intermediate luminosity optical transients（ILOTs; red novae; red transients）. These powerful outflows could potentially also supply the extra energy required in the common envelope process and in the grazing envelope evolution of binary systems. We propose that a massive outflow/jets mediated by magnetic fields might remove energy and angular momentum from the accretion disk to allow such high accretion rate flows. By examining the possible activity of the magnetic fields of accretion disks, we conclude that indeed main sequence stars might accrete mass at very high rates, up to≈10^-2M⊙yr^-1for solar type stars, and up toion≈1 M⊙yr^-1for very massive stars. We speculate that magnetic fields amplified in such extreme condits might lead to the formation of massive bipolar outflows that can remove most of the disk＇s energy and angular momentum. It is this energy and angular momentum removal that allows the very high mass accretion rate onto main sequence stars.展开更多
Observations of the ^12CO（3–2） emission from the circumstellar envelope（CSE） of the variable star π1Gru using the compact array of the ALMA observatory have been recently made accessible to the public. An analys...Observations of the ^12CO（3–2） emission from the circumstellar envelope（CSE） of the variable star π1Gru using the compact array of the ALMA observatory have been recently made accessible to the public. An analysis of the morphology and kinematics of the CSE is presented with a result very similar to that obtained earlier for ^12CO（2–1） emission using the Submillimeter Array. A quantitative comparison is made using their flared disk model. A new model is presented that provides a significantly better description of the data, using radial winds and smooth evolutions of the radio emission and wind velocity from the stellar equator to the poles.展开更多
In the Wide-field Infrared Survey Explorer （WISE） all-sky source catalog there are 76 million mid-infrared point sources that were detected in the first three WISE bands and have association with only one 2MASS near...In the Wide-field Infrared Survey Explorer （WISE） all-sky source catalog there are 76 million mid-infrared point sources that were detected in the first three WISE bands and have association with only one 2MASS near-IR source within 3. We search for their identifications in the SIMBAD database and find 3.2 million identified sources. Based on these known sources, we establish three criteria for selecting candidate asymptotic giant branch （AGB） stars in the Galaxy, which are three defined zones in a color-color diagram, Galactic latitude ｜b｜ 〈 20°, and ＂corrected＂ WISE third-band W3c≤ 11. Applying these criteria to the WISE＋2MASS sources, 1.37 million of them are selected. We analyze the WISE third-band W3 distribution of the selected sources, and further establish that W3〈8 is required in order to exclude a large fraction of normal stars from them. We therefore find 0.47 million candidate AGB stars in our Galaxy from the WISE source catalog. Using W3c, we estimate their distances and derive their Galactic distributions. The candidates are generally distributed around the Galactic center uniformly, with 68% （1-σ） of them within approximately 8 kpc. We discuss the idea that optical spectroscopy can be used to verify the C-rich AGB stars in our candidates, and thus a fraction of them （-10%） will be good targets for the Large Sky Area Multi-Object Fiber Spectroscopic Telescope （LAMOST） survey that is planned to start in fall of 2012.展开更多
We investigate the spectral variations of seven carbon stars in the infrared using ISO SWS spectral data. Continuum variations of those carbon stars show that during the central star pulsations when carbon stars becom...We investigate the spectral variations of seven carbon stars in the infrared using ISO SWS spectral data. Continuum variations of those carbon stars show that during the central star pulsations when carbon stars become fainter in the infrared, their ISO SWS spectra become redder and the near-IR temperature （Tnir） decreases. When carbon stars become brighter in the infrared, their ISO SWS spectra become bluer and Tnir increases. Furthermore, it is found that the shorter 1abe wavelength of spectral features, such as the 2.48＋2.58 （C2H2＋HCN＋CO＋C2）, 3.05 （C2H2＋HCN） and 3.90 （C2H2） μm features, is, the better the correlation of their relative integrated fluxes with the fluxes of the continuum is. The changes of the 5.2 （C3）, 11.30 （SIC） and 13.70 （C2H2）μm features do not obviously correlate with the fluxes of the continuum.展开更多
The properties and classification of IRAS 19111+2555 have so far not been well determined. We collect all the available information and data of this star, and take the data obtained by IRAS LRS and ISO SWS to discuss ...The properties and classification of IRAS 19111+2555 have so far not been well determined. We collect all the available information and data of this star, and take the data obtained by IRAS LRS and ISO SWS to discuss its properties and classification. The star is found to have a 3.1μm feature in absorption and a 10μm feature in emission, so it is possibly a new silicate carbon star.展开更多
文摘IRAS 01005+7910 is a cold IRAS source. We present its optical identification, photometric and spectroscopic observation results. Its optical counterpart is classified as a B2Ie star with V magnitude 10.85. Its Hα line shows the P Cygni profile. According to its location in the Galaxy (b = 16.6), we consider it to be a post-AGB star or a proto-planetary nebula.
基金Supported by the National Natural Science Foundation of China.
文摘The discovery of silicate carbon star poses a challenge to the theory of stellar evolution in the late stage, hence it is important to look for more silicate carbon stars. To this end we have carried out cross-identifications between the new IRAS Low-Resolution Spectrum （LRS） database and the new carbon star catalog, CGCS3. We have found nine new silicate carbon stars with silicate features around 10μm and/or 18 μm. These newly identified stars are located in the Regions Ilia and VII in the IRAS two-color diagram, which means they indeed have typical far infrared colors of silicate carbon stars. The infrared properties of each of these sources are discussed.
基金Supported by the National Natural Science Foundation of China.
文摘Based on the s-process nucleosynthesis model with the 13C（α, n）16O reaction occurring under radiative conditions in the interpulse phases, we investigate the characteristics of the distribution of neutron exposure in low-mass Asymptotic Giant Branch （AGB） stars. We introduce a new concept, the distribution of neutron exposures of the Galaxy （NEG）, to study the chemical evolution characteristics of the Galaxy for s-process elements. Using a chemical evolution model of the Galaxy, we develop a model for the NEG and obtain the evolution results of the NEG in different epochs. The present results appear to reasonably reproduce the distribution of neutron exposures of the solar system （hereafter NES）. The main component and the strong component in the NES are built up in different epochs. The strong component of the s-process is mainly synthesised in the low-mass and metal-poor AGB stars, and the main component is produced by the s-process in the low-mass AGB stars with higher metallicities.
文摘Energetic outflows from main sequence stars accreting mass at very high rates might account for the powering of some eruptive objects, such as merging main sequence stars, major eruptions of luminous blue variables, e.g., the Great Eruption of Eta Carinae, and other intermediate luminosity optical transients（ILOTs; red novae; red transients）. These powerful outflows could potentially also supply the extra energy required in the common envelope process and in the grazing envelope evolution of binary systems. We propose that a massive outflow/jets mediated by magnetic fields might remove energy and angular momentum from the accretion disk to allow such high accretion rate flows. By examining the possible activity of the magnetic fields of accretion disks, we conclude that indeed main sequence stars might accrete mass at very high rates, up to≈10^-2M⊙yr^-1for solar type stars, and up toion≈1 M⊙yr^-1for very massive stars. We speculate that magnetic fields amplified in such extreme condits might lead to the formation of massive bipolar outflows that can remove most of the disk＇s energy and angular momentum. It is this energy and angular momentum removal that allows the very high mass accretion rate onto main sequence stars.
基金support from the staff of the ALMA Helpdeskthe Vietnam National Satellite Center(VNSC/VAST)the NAFOSTED funding agency,the World Laboratory,the Odon Vallet Foundation and the Rencontres du Viet Nam
文摘Observations of the ^12CO（3–2） emission from the circumstellar envelope（CSE） of the variable star π1Gru using the compact array of the ALMA observatory have been recently made accessible to the public. An analysis of the morphology and kinematics of the CSE is presented with a result very similar to that obtained earlier for ^12CO（2–1） emission using the Submillimeter Array. A quantitative comparison is made using their flared disk model. A new model is presented that provides a significantly better description of the data, using radial winds and smooth evolutions of the radio emission and wind velocity from the stellar equator to the poles.
基金supported in part by the Pre-phase Studies of Space Science Projects of the Chinese Academy of Sciences,National Basic Research Program of China(973 Project, 2009CB824800)the National Natural Science Foundation of China (Grant No.11073042)funded by the National Aeronautics and Space Administration
文摘In the Wide-field Infrared Survey Explorer （WISE） all-sky source catalog there are 76 million mid-infrared point sources that were detected in the first three WISE bands and have association with only one 2MASS near-IR source within 3. We search for their identifications in the SIMBAD database and find 3.2 million identified sources. Based on these known sources, we establish three criteria for selecting candidate asymptotic giant branch （AGB） stars in the Galaxy, which are three defined zones in a color-color diagram, Galactic latitude ｜b｜ 〈 20°, and ＂corrected＂ WISE third-band W3c≤ 11. Applying these criteria to the WISE＋2MASS sources, 1.37 million of them are selected. We analyze the WISE third-band W3 distribution of the selected sources, and further establish that W3〈8 is required in order to exclude a large fraction of normal stars from them. We therefore find 0.47 million candidate AGB stars in our Galaxy from the WISE source catalog. Using W3c, we estimate their distances and derive their Galactic distributions. The candidates are generally distributed around the Galactic center uniformly, with 68% （1-σ） of them within approximately 8 kpc. We discuss the idea that optical spectroscopy can be used to verify the C-rich AGB stars in our candidates, and thus a fraction of them （-10%） will be good targets for the Large Sky Area Multi-Object Fiber Spectroscopic Telescope （LAMOST） survey that is planned to start in fall of 2012.
基金supported by the National Natural Science Foundation of China(Grant No.10803023)supported by the Natural Science Foundation Project of CQ CSTC(No.2008BB0153)
文摘We investigate the spectral variations of seven carbon stars in the infrared using ISO SWS spectral data. Continuum variations of those carbon stars show that during the central star pulsations when carbon stars become fainter in the infrared, their ISO SWS spectra become redder and the near-IR temperature （Tnir） decreases. When carbon stars become brighter in the infrared, their ISO SWS spectra become bluer and Tnir increases. Furthermore, it is found that the shorter 1abe wavelength of spectral features, such as the 2.48＋2.58 （C2H2＋HCN＋CO＋C2）, 3.05 （C2H2＋HCN） and 3.90 （C2H2） μm features, is, the better the correlation of their relative integrated fluxes with the fluxes of the continuum is. The changes of the 5.2 （C3）, 11.30 （SIC） and 13.70 （C2H2）μm features do not obviously correlate with the fluxes of the continuum.
文摘The properties and classification of IRAS 19111+2555 have so far not been well determined. We collect all the available information and data of this star, and take the data obtained by IRAS LRS and ISO SWS to discuss its properties and classification. The star is found to have a 3.1μm feature in absorption and a 10μm feature in emission, so it is possibly a new silicate carbon star.
