The Hamburg/ESO R-process Enhanced Star survey (HERES)

Ren, Juchao; Christlieb, N.; Zhao, Gang

doi:10.1051/0004-6361/201118241

Cited by 22 publications

(17 citation statements)

References 41 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It is also necessary to point out the possibility of different abundance ratios in the outputs of different r-and s-process events, which was realized in the last decade. Some of the most recent observational evidence for the nonuniversality of the r process was discussed by Ren et al (2012).…”

Section: Discussionmentioning

confidence: 99%

THE CHEMICAL COMPOSITION OFρPUPPIS AND THE SIGNS OF ACCRETION IN THE ATMOSPHERES OF B–F-TYPE STARS

Yushchenko

Gopka

Kang

et al. 2015

View full text Add to dashboard Cite

We investigated the chemical composition of ρ Pup using high-resolution spectral observations taken from the Very Large Telescope and the IUE archives and also spectra obtained at the 1.8 m telescope of the Bohyunsan observatory in Korea. The abundances of 56 chemical elements and the upper limits of Li and Be abundances were determined. The abundance pattern of ρ Pup was found to be similar to that of Am-type stars. The possibility of the influence of the accretion of interstellar gas and dust on the abundance patterns of B-F-type stars is discussed. The plots of the relative abundances of chemical elements in the atmospheres of ρ Pup and δ Sct versus the second ionization potentials of these elements show the correlations. The discontinuities at 13.6 and 24.6 eV-the ionization potentials of hydrogen and helium, respectively, are also exhibited in these plots. These discontinuities can be explained by interaction of the atoms of interstellar gas, mainly hydrogen and helium atoms, with the atoms of stellar photospheres (so-called charge-exchange reactions). Note that only the jumps near 13.6 and 24.6 eV were pointed out in previous investigations of relative abundances versus the second ionization potentials for Am-type stars. The dependencies of the relative abundances of chemical elements on the second ionization potentials of these elements were investigated using the published abundance patterns of B-F-type stars. The correlations of relative and absolute abundances of chemical elements, second ionization potentials, and projected rotational velocities are clearly detected for stars with effective temperatures between 7,000 and 12,000 K. If the correlation of relative abundances and second ionization potentials can be explained by the accretion of interstellar gas on the stellar surfaces, the investigation of these correlations can provide valuable information on the density and velocities of interstellar gas in different regions of the Galaxy and also on the influence of this phenomenon on stellar evolution. The dependencies of the relative abundances of chemical elements on the condensation temperatures of these elements were also found in the atmospheres of ρ Pup, δ Sct, and other B-F-type stars. Ten possible λ Boo-type stars were detected. The effective temperatures of these objects are between 10,900 and 14,000 K.

show abstract

Section: Discussionmentioning

confidence: 99%

THE CHEMICAL COMPOSITION OFρPUPPIS AND THE SIGNS OF ACCRETION IN THE ATMOSPHERES OF B–F-TYPE STARS

Yushchenko

Gopka

Kang

et al. 2015

View full text Add to dashboard Cite

show abstract

“…Given the overall small number of Th measurements, it might be possible that there is also a separate population of "actinide deficient" stars, of which DES J033523−540407 is the first example. Since Th is hard to detect, it would not be surprising if lower-Th stars were mostly not identified (e.g., the two stars in Ren et al 2012 with low Th/Eu are only 1σ detections and often would not be reported). Of course, given the large uncertainty, DES J033523−540407 is also only ∼1σ away from having a normal Th/Eu ratio.…”

Section: Comparison To Other Metal-poor Starsmentioning

confidence: 99%

“…Note that only eight r-II stars in our halo sample have Th abundances. We thus also plot the Th/Eu ratios from the sample compiled byRen et al (2012) (dashed blue histogram). The Th/Eu ratio of DES J033523−540407 falls at the lower end of the halo star distribution.…”

mentioning

confidence: 99%

From Actinides to Zinc: Using the Full Abundance Pattern of the Brightest Star in Reticulum II to Distinguish between Different r-process Sites^*

Frebel

2018

ApJ

View full text Add to dashboard Cite

The ultra-faint dwarf galaxy Reticulum II was enriched by a rare and prolific r-process event, such as a neutron star merger. To investigate the nature of this event, we present high-resolution Magellan/MIKE spectroscopy of the brightest star in this galaxy. The high signal-to-noise allows us to determine the abundances of 41 elements, including the radioactive actinide element Th and first ever detections of third r-process peak elements (Os and Ir) in a star outside the Milky Way. The observed neutron-capture element abundances closely match the solar r-process component, except for the first r-process peak which is significantly lower than solar but matches other r-process enhanced stars. The ratio of first peak to heavier r-process elements implies the r-process site produces roughly equal masses of high and low electron fraction ejecta, within a factor of 2. We compare the detailed abundance pattern to predictions from nucleosynthesis calculations of neutron star mergers and magneto-rotationally driven jet supernovae, finding that nuclear physics uncertainties dominate over astrophysical uncertainties. We measure log Th/Eu = −0.84 ± 0.06 (stat) ± 0.22 (sys), somewhat lower than all previous Th/Eu observations. The youngest age we derive from this ratio is 21.7±2.8 (stat)±10.3 (sys) Gyr, indicating that current initial production ratios do not well describe the r-process event in Reticulum II. The abundance of light elements up to Zn are consistent with extremely metal-poor Milky Way halo stars. They may eventually provide a way to distinguish between neutron star mergers and magneto-rotationally driven jet supernovae, but this would require more detailed knowledge of the chemical evolution of Reticulum II.

show abstract

“…2, this comparison can constrain the coalescence timescale. The [21,22,23,24]. Upper limits coming from [21] and [25] are not included in these figures.…”

Section: Pos(nic Xiii)172mentioning

confidence: 99%

Cosmic Star Formation, Gamma-Ray Burst Rate at high redshift and Cosmic Chemical Evolution

Vangioni¹,

Goriely²,

Daigne³

2015

Proceedings of XIII Nuclei in the Cosmos — PoS(NIC XIII)

View full text Add to dashboard Cite

Recent optical/IR/UV observations and Gamma-ray burst rate determinations have led to significant progress in constraining the star formation rate (SFR) at high redshift. The SFR is a fundamental quantity since it is used to predict, among others, the ionization history of the Universe, the evolution of the cosmic chemical abundances and the supernova rates as a function of the redshift. Such predictions are made here using a hierarchical model for structure formation. In this context, we focus our attention on the origin and evolution of a typical r process element, Europium, in two possible scenarios for the main astrophysical production site, namely core collapse supernovae (CCSN) and neutron star mergers (NSM). We find that this model favours NSM as the main r process site, specifically at low metallicity, and in addition, constrains the NSM time delay to ∼ 0.1-0.2 Gyr. On the other hand, the evolution of Eu abundances puts also a constraint on the merger rate, which allows an independent prediction of the expected merger rate in the horizon of the gravitational wave detectors advanced Virgo/ad LIGO, as well as a prediction for the expected rate of electromagnetic counterparts to mergers in large NIR surveys. Finally, while this model favors NSM as the main r-process site, more observations at very low metallicity and improved predictions from the nucleosynthetic evolution of massive stars are needed to confirm this result.

show abstract

The Hamburg/ESO R-process Enhanced Star survey (HERES)

Cited by 22 publications

References 41 publications

THE CHEMICAL COMPOSITION OFρPUPPIS AND THE SIGNS OF ACCRETION IN THE ATMOSPHERES OF B–F-TYPE STARS

THE CHEMICAL COMPOSITION OFρPUPPIS AND THE SIGNS OF ACCRETION IN THE ATMOSPHERES OF B–F-TYPE STARS

From Actinides to Zinc: Using the Full Abundance Pattern of the Brightest Star in Reticulum II to Distinguish between Different r-process Sites^*

Cosmic Star Formation, Gamma-Ray Burst Rate at high redshift and Cosmic Chemical Evolution

Contact Info

Product

Resources

About

The Hamburg/ESO R-process Enhanced Star survey (HERES)

Cited by 22 publications

References 41 publications

THE CHEMICAL COMPOSITION OFρPUPPIS AND THE SIGNS OF ACCRETION IN THE ATMOSPHERES OF B–F-TYPE STARS

THE CHEMICAL COMPOSITION OFρPUPPIS AND THE SIGNS OF ACCRETION IN THE ATMOSPHERES OF B–F-TYPE STARS

From Actinides to Zinc: Using the Full Abundance Pattern of the Brightest Star in Reticulum II to Distinguish between Different r-process Sites*

Cosmic Star Formation, Gamma-Ray Burst Rate at high redshift and Cosmic Chemical Evolution

Contact Info

Product

Resources

About

From Actinides to Zinc: Using the Full Abundance Pattern of the Brightest Star in Reticulum II to Distinguish between Different r-process Sites^*