ORCID Profile
0000-0002-6506-1985
Current Organisation
Purple Mountain Observatory
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Publisher: EDP Sciences
Date: 10-2022
DOI: 10.1051/0004-6361/202243134
Abstract: Context. The Gaia-ESO Public Spectroscopic Survey is an ambitious project designed to obtain astrophysical parameters and elemental abundances for 100 000 stars, including large representative s les of the stellar populations in the Galaxy, and a well-defined s le of 60 (plus 20 archive) open clusters. We provide internally consistent results calibrated on benchmark stars and star clusters, extending across a very wide range of abundances and ages. This provides a legacy data set of intrinsic value, and equally a large wide-ranging dataset that is of value for the homogenisation of other and future stellar surveys and Gaia's astrophysical parameters. Aims. This article provides an overview of the survey methodology, the scientific aims, and the implementation, including a description of the data processing for the GIRAFFE spectra. A companion paper introduces the survey results. Methods. Gaia-ESO aspires to quantify both random and systematic contributions to measurement uncertainties. Thus, all available spectroscopic analysis techniques are utilised, each spectrum being analysed by up to several different analysis pipelines, with considerable effort being made to homogenise and calibrate the resulting parameters. We describe here the sequence of activities up to delivery of processed data products to the ESO Science Archive Facility for open use. Results. The Gaia-ESO Survey obtained 202 000 spectra of 115 000 stars using 340 allocated VLT nights between December 2011 and January 2018 from GIRAFFE and UVES. Conclusions. The full consistently reduced final data set of spectra was released through the ESO Science Archive Facility in late 2020, with the full astrophysical parameters sets following in 2022. A companion article reviews the survey implementation, scientific highlights, the open cluster survey, and data products.
Publisher: EDP Sciences
Date: 09-2018
DOI: 10.1051/0004-6361/201833027
Abstract: A ims. We report 20 new lithium-rich giants discovered within the Gaia -ESO Survey, including the first Li-rich giant with an evolutionary stage confirmed by CoRoT (Convection, Rotation and planetary Transits) data. We present a detailed overview of the properties of these 20 stars. M ethods. Atmospheric parameters and abundances were derived in model atmosphere analyses using medium-resolution GIRAFFE or high-resolution UVES (Ultraviolet and Visual Echelle Spectrograph) spectra. These results are part of the fifth internal data release of the Gaia -ESO Survey. The Li abundances were corrected for non-local thermodynamical equilibrium effects. Other stellar properties were investigated for additional peculiarities (the core of strong lines for signs of magnetic activity, infrared magnitudes, rotational velocities, chemical abundances, and Galactic velocities). We used Gaia DR2 parallaxes to estimate distances and luminosities. R esults. The giants have A (Li) 2.2 dex. The majority of them (14 of 20 stars) are in the CoRoT fields. Four giants are located in the field of three open clusters, but are not members. Two giants were observed in fields towards the Galactic bulge, but likely lie in the inner disc. One of the bulge field giants is super Li-rich with A (Li) = 4.0 dex. Conclusions . We identified one giant with infrared excess at 22 μ m. Two other giants, with large v sin i , might be Li-rich because of planet engulfment. Another giant is found to be barium enhanced and thus could have accreted material from a former asymptotic giant branch companion. Otherwise, in addition to the Li enrichment, the evolutionary stages are the only other connection between these new Li-rich giants. The CoRoT data confirm that one Li-rich giant is at the core-He burning stage. The other giants are concentrated in close proximity to the red giant branch luminosity bump, the core-He burning stages, or the early-asymptotic giant branch. This is very clear from the Gaia -based luminosities of the Li-rich giants. This is also seen when the CoRoT Li-rich giants are compared to a larger s le of 2252 giants observed in the CoRoT fields by the Gaia -ESO Survey, which are distributed throughout the red giant branch in the T eff -log g diagram. These observations show that the evolutionary stage is a major factor for the Li enrichment in giants. Other processes, such as planet accretion, contribute at a smaller scale.
Publisher: EDP Sciences
Date: 02-2018
DOI: 10.1051/0004-6361/201731677
Abstract: Lithium abundance in most of the warm metal-poor main sequence stars shows a constarnt plateau ( A (Li) ~ 2.2 dex) and then the upper envelope of the lithium vs. metallicity distribution increases as we approach solar metallicity. Meteorites, which carry information about the chemical composition of the interstellar medium (ISM) at the solar system formation time, show a lithium abundance A (Li) ~ 3.26 dex. This pattern reflects the Li enrichment history of the ISM during the Galaxy lifetime. After the initial Li production in big bang nucleosynthesis, the sources of the enrichment include asymptotic giant branch (AGB) stars, low-mass red giants, novae, type II supernovae, and Galactic cosmic rays. The total amount of enriched Li is sensitive to the relative contribution of these sources. Thus different Li enrichment histories are expected in the Galactic thick and thin disc. We investigate the main sequence stars observed with UVES in Gaia -ESO Survey iDR4 catalogue and find a Li- [ α /Fe] anticorrelation independent of [Fe/H], T eff , and log ( g ). Since in stellar evolution different α enhancements at the same metallicity do not lead to a measurable Li abundance change, the anticorrelation indicates that more Li is produced during the Galactic thin disc phase than during the Galactic thick disc phase. We also find a correlation between the abundance of Li and s-process elements Ba and Y, and they both decrease above the solar metallicity, which can be explained in the framework of the adopted Galactic chemical evolution models.
Publisher: Oxford University Press (OUP)
Date: 24-04-2018
Publisher: EDP Sciences
Date: 09-2023
Publisher: American Astronomical Society
Date: 28-07-2022
Abstract: We report the discovery of a new 5.78 ms period millisecond pulsar (MSP), PSR J1740−5340B (NGC 6397B), in an eclipsing binary system discovered with the Parkes radio telescope (now also known as Murriyang) in Australia and confirmed with the MeerKAT radio telescope in South Africa. The measured orbital period, 1.97 days, is the longest among all eclipsing binaries in globular clusters (GCs) and consistent with that of the coincident X-ray source U18, previously suggested to be a “hidden MSP.” Our XMM-Newton observations during NGC 6397B’s radio-quiescent epochs detected no X-ray flares. NGC 6397B is either a transitional MSP or an eclipsing binary in its initial stage of mass transfer after the companion star left the main sequence. The discovery of NGC 6397B potentially reveals a subgroup of extremely faint and heavily obscured binary pulsars, thus providing a plausible explanation for the apparent dearth of binary neutron stars in core-collapsed GCs as well as a critical constraint on the evolution of GCs.
Publisher: EDP Sciences
Date: 10-2022
DOI: 10.1051/0004-6361/202243141
Abstract: Context. In the last 15 years different ground-based spectroscopic surveys have been started (and completed) with the general aim of delivering stellar parameters and elemental abundances for large s les of Galactic stars, complementing Gaia astrometry. Among those surveys, the Gaia -ESO Public Spectroscopic Survey, the only one performed on a 8m class telescope, was designed to target 100 000 stars using FLAMES on the ESO VLT (both Giraffe and UVES spectrographs), covering all the Milky Way populations, with a special focus on open star clusters. Aims. This article provides an overview of the survey implementation (observations, data quality, analysis and its success, data products, and releases), of the open cluster survey, of the science results and potential, and of the survey legacy. A companion article reviews the overall survey motivation, strategy, Giraffe pipeline data reduction, organisation, and workflow. Methods. We made use of the information recorded and archived in the observing blocks during the observing runs in a number of relevant documents in the spectra and master catalogue of spectra in the parameters delivered by the analysis nodes and the working groups in the final catalogue and in the science papers. Based on these sources, we critically analyse and discuss the output and products of the Survey, including science highlights. We also determined the average metallicities of the open clusters observed as science targets and of a s le of clusters whose spectra were retrieved from the ESO archive. Results. The Gaia-ESO Survey has determined homogeneous good-quality radial velocities and stellar parameters for a large fraction of its more than 110 000 unique target stars. Elemental abundances were derived for up to 31 elements for targets observed with UVES. Lithium abundances are delivered for about 1/3 of the s le. The analysis and homogenisation strategies have proven to be successful several science topics have been addressed by the Gaia -ESO consortium and the community, with many highlight results achieved. Conclusions. The final catalogue will be released through the ESO archive in the first half of 2022, including the complete set of advanced data products. In addition to these results, the Gaia -ESO Survey will leave a very important legacy, for several aspects and for many years to come.
Publisher: EDP Sciences
Date: 09-2021
DOI: 10.1051/0004-6361/202141340
Abstract: Context. After more than 50 years, astronomical research still struggles to reconstruct the history of lithium enrichment in the Galaxy and to establish the relative importance of the various 7 Li sources in enriching the interstellar medium (ISM) with this fragile element. Aims. To better trace the evolution of lithium in the Milky Way discs, we exploit the unique characteristics of a s le of open clusters (OCs) and field stars for which high-precision 7 Li abundances and stellar parameters are homogeneously derived by the Gaia -ESO Survey (GES). Methods. We derive possibly un-depleted 7 Li abundances for 26 OCs and star forming regions with ages from young (∼3 Myr) to old (∼4.5 Gyr), spanning a large range of galactocentric distances, 5 R GC /kpc 15, which allows us to reconstruct the local late Galactic evolution of lithium as well as its current abundance gradient along the disc. Field stars are added to look further back in time and to constrain 7 Li evolution in other Galactic components. The data are then compared to theoretical tracks from chemical evolution models that implement different 7 Li forges. Results. Thanks to the homogeneity of the GES analysis, we can combine the maximum average 7 Li abundances derived for the clusters with 7 Li measurements in field stars. We find that the upper envelope of the 7 Li abundances measured in field stars of nearly solar metallicities (−0.3 [Fe/H]/dex +0.3) traces very well the level of lithium enrichment attained by the ISM as inferred from observations of cluster stars in the same metallicity range. We confirm previous findings that the abundance of 7 Li in the solar neighbourhood does not decrease at super-solar metallicity. The comparison of the data with the chemical evolution model predictions favours a scenario in which the majority of the 7 Li abundance in meteorites comes from novae. Current data also seem to suggest that the nova rate flattens out at later times. This requirement might have implications for the masses of the white dwarf nova progenitors and deserves further investigation. Neutrino-induced reactions taking place in core-collapse supernovae also produce some fresh lithium. This likely makes a negligible contribution to the meteoritic abundance, but could be responsible for a mild increase in the 7 Li abundance in the ISM of low-metallicity systems that would counterbalance the astration processes.
Location: China
Location: China
Location: Italy
No related grants have been discovered for Xiaoting Fu.