相关论文: Relics of ancient post-AGB stars in a primitive me…

Among presolar materials recovered in meteorites, abundant SiC and Al$_{2}$O$_{3}$ grains of AGB origins were found. They showed records of C, N, O, $^{26}$Al and s-element isotopic ratios that proved invaluable in constraining the…

We report isotopic data for a total of 96 presolar oxide grains found in residues of several unequilibrated ordinary chondrite meteorites. Identified grain types include Al2O3, MgAl2O4, hibonite (CaAl12O19) and Ti oxide. This work greatly…

Mainstream presolar SiC grains from primitive meteorites show a clear s-process signature in the isotopic composition of heavy trace elements. These grains most likely condensed in the winds of a variety of AGB stars. However, the non-solar…

Although mainstream SiC grains, the major group of presolar SiC grains found in meteorites, are believed to have originated in the expanding envelope of asymptotic giant branch (AGB) stars during their late carbon-rich phases, their Si…

We report on the results of NanoSIMS isotope imaging of low-density supernova graphite grains from the Orgueil meteorite. 70 nm thick microtomed sections of three supernova graphite grains were deposited on Si wafers and isotopically imaged…

Presolar grains constitute remnants of stars that existed before the formation of the solar system. In addition to providing direct information on the materials from which the solar system formed, these grains provide ground-truth…

We compare literature data for the isotopic ratios of Zr, Sr, and Ba from analysis of single meteoritic stardust silicon carbide (SiC) grains to new predictions for the slow neutron-capture process (the s process) in metal-rich asymptotic…

About a year after core collapse supernova, dust starts to condense in the ejecta. In meteorites, a fraction of C-rich presolar grains (e.g., silicon carbide (SiC) grains of Type-X and low density graphites) are identified as relics of…

We report Mo isotopic compositions of 37 presolar SiC grains of types Y (19) and Z (18), rare types commonly argued to have formed in lower-than-solar metallicity asymptotic giant branch (AGB) stars. Direct comparison of the Y and Z grain…

We report O, Mg-Al, Si, Ca, and Ti isotopic data for an unusual presolar oxide/silicate aggregate grain, M526-69, previously reported in the primitive ordinary chondrite Meteorite Hills 00526. The $\approx 1\mu$m aggregate consists of a Mg-…

Recent models for evolved Low Mass Stars (with $M \lesssim 3M_\odot$), undergoing the AGB phase assume that magnetic flux-tube buoyancy drives the formation of $^{13}$C reservoirs in He-rich layers. We illustrate their crucial properties,…

Microscopic presolar grains extracted from primitive meteorites have extremely anomalous isotopic compositions revealing the stellar origin of these grains. The composition of presolar spinel grain OC2 is different from that of all other…

The photospheres of low-mass red giants show CNO isotopic abundances that are not satisfactorily accounted for by canonical stellar models. The same is true for the measurements of these isotopes and of the $^{26}$Al/$^{27}$Al ratio in…

Isotopic ratios of C, N, Si, and trace heavy elements in presolar SiC grains from meteorites provide crucial constraints to nucleosynthesis. A long-debated issue is the origin of the so-called A+B grains, as for them no stellar progenitor…

Bulk meteoritic data show isotopic variability of $slow$-neutron-capture ($s$-process) origin in a several elements heavier than Fe. One peculiar feature is that the lighter $s$-process elements (e.g., Zr and Mo) present larger anomalies…

A new formation scenario for TiC and Fe,Ni-metal inclusions in presolar graphite grains of supernova origin is described. The mineralogy and chemistry require condensation of (Fe,Ni)-titanides from Fe, Ni, and Ti-rich gaseous ejecta,…

We study the effects of neutron captures in AGB stars on \oq Fe-group\cqb elements, with an emphasis on Cr, Fe, and Ni. These elements show anomalies in $^{54}$Cr, $^{58}$Fe, and $^{64}$Ni in solar-system materials, which are commonly…

Certain types of silicon carbide (SiC) grains, e.g., SiC-X grains, and low density (LD) graphites are C-rich presolar grains that are thought to have condensed in the ejecta of core-collapse supernovae (CCSNe). In this work we compare C, N,…

We report the discovery of five SiC grains and one graphite grain isolated from the Murchison carbonaceous meteorite whose major-element isotopic compositions indicate an origin in nova explosions. The grains are characterized by low…

Presolar grains in meteorites formed in a sample of AGB stars that ended their lives within ~1 Gyr of the origin of the Solar System 4.6 Gyr ago. The O-isotopic compositions of presolar O-rich stardust reflect the masses and metallicities…