相关论文: A Strontium-rich Ultra Metal-poor Star in the Atar…

We present an elemental abundance analysis for four newly discovered ultra metal-poor stars from the Hamburg/ESO survey, with $\mathrm{[Fe/H]}\leq-4$. Based on high-resolution, high signal-to-noise spectra, we derive abundances for 17…

The element abundance ratios of four low-mass stars with extremely low metallicities indicate that the gas out of which the stars formed was enriched in each case by at most a few, and potentially only one low-energy, supernova. Such…

Context. The first generation of stars formed in the Galaxy left behind the chemical signatures of their nucleosynthesis in the interstellar medium, visible today in the atmospheres of low-mass stars formed afterwards. Sampling the…

In this work, we present high-resolution spectroscopic observations for six metal-poor stars with [Fe/H]<-3 (including one with [Fe/H]<-4), selected using narrow-band Ca II HK photometry from the DECam MAGIC Survey. The spectroscopic data…

Stars formed with initial mass over 50 Msun are very rare today, but they are thought to be more common in the early universe. The fates of those early, metal-poor, massive stars are highly uncertain. Most are expected to directly collapse…

Compilations of abundances of Strontium and Barium in extremely metal-poor stars show that an apparent cutoff is observed for [Sr/Ba] at [Fe/H]$<$-3.6 and large fluctuations for [Fe/H]$>$-3.6 with a clear upper bound depending on…

We report Zn abundances for 18 very metal-poor stars studied in our previous work, covering the metallicity range -3.2 < [Fe/H] < -2.5. The [Zn/Fe] values of most stars show an increasing trend with decreasing [Fe/H] in this metallicity…

We present a Magellan/MIKE high-resolution (R ~ 35,000) spectrum of the ancient star SD 1313-0019 which has an iron abundance of [Fe/H] = -5.0, paired with a carbon enhancement of [C/Fe] ~ 3.0. The star was initially identified by Allende…

We report the discovery of RAVE J203843.2-002333, a bright (V = 12.73), very metal-poor ([Fe/H] = -2.91), r-process-enhanced ([Eu/Fe] = +1.64 and [Ba/Eu] = -0.81) star selected from the RAVE survey. This star was identified as a metal-poor…

The early F dwarf star ``J37'' in the open cluster NGC6633 shows an unusual pattern of photospheric abundances, including an order of magnitude enhancement of lithium and iron-peak elements, but an under-abundance of carbon. As a…

We discuss the current status of the sample of Lithium abundances in extremely metal poor (EMP) turn-off (TO) stars collected by our group, and compare it with the available literature results. In the last years, evidences have accumulated…

Measurable amounts of Be could have been synthesised primordially if the Universe were non-homogeneous or in the presence of late decaying relic particles. We investigate the Be abundance in the extremely metal-poor star 2MASS J1808-5104…

Low-metallicity very massive stars with an initial mass of $\sim 140$--$260\, {\rm M_\odot}$ are expected to end their lives as pair-instability supernovae (PISNe). The abundance pattern resulting from a PISN differs drastically from…

Signature from Pop III massive stars of $140$--$260\,{\rm M_\odot}$ that end their lives as pair-instability supernovae (PISNe) are expected to be seen in very metal-poor (VMP) stars of ${\rm [Fe/H]}\leq -2$. Although thousands of VMP stars…

SMSS J031300.36-670839.3 (hereafter SM0313-6708) is a sub-giant halo star, with no detectable Fe lines and large overabundances of C and Mg relative to Ca. We obtained VLT-UVES spectra extending to 3060 Angstroms showing strong OH A-X band…

We present a detailed chemical-abundance analysis of a highly $r$-process enhanced (RPE) star, 2MASS J00512646-1053170, using high-resolution spectroscopic observations with $Hubble\ Space\ Telescope$/STIS in the UV and Magellan/MIKE in the…

We have been exploring large spectroscopic databases such as SDSS to search for unique stars with extremely low iron content with the goal of extracting detailed information from the early phases of the Galaxy. We recently identified two…

We present Keck/HIRES observations of six metal-poor stars in two of the ultra-faint dwarf galaxies orbiting the Milky Way, Ursa Major II and Coma Berenices. These observations include the first high-resolution spectroscopic observations of…

We present the measurement of 26 elemental abundances of SMSS J022423.27$-$573705.1 (SMSS 0224$-$5737), an extremely metal-poor (EMP) star with a weak $r$-process signature. We report the measurements of N, O, V, Zn, and Ba, and the upper…

We report on the spectroscopic analysis of RAVE J183013.5-455510, an extremely metal-poor star, highly enhanced in CNO, and with discernible contributions from the rapid neutron-capture process. There is no evidence of binarity for this…