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CEMP Stars as Probes of First-Star Nucleosynthesis, the IMF, and Galactic Assembly

9–13 Sept 2019
University of Geneva A100 Sciences II
Europe/Zurich timezone

Georges Meynet

Contribution List

70 out of 70 displayed
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  1. 89. Welcome from the LOC & SOC
    Sylvia Ekström (Université de Genève), Prof. Raphael Hirschi (Keele University )
    09/09/2019, 09:00
  2. 45. CEMP Stars – Past Perspectives and Future Objectives
    Prof. Timothy Beers (University of Notre Dame)
    09/09/2019, 09:10

    It has been over a quarter century that the class of metal-poor stars known as carbon-enhanced metal-poor (CEMP) stars was first recognized. In that time, astronomers have recognized a number of sub-classes, apparently due to a variety of nucleosynthesis pathways. Most recently, the sub-class formerly referred to as CEMP-r/s has been shown to be due to the so-called intermediate...

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  3. 59. Observations of very iron-poor stars
    Dr Piercarlo Bonifacio (GEPI, Observatoire de Paris, Université PSL, CNRS)
    09/09/2019, 09:40

    At the time of writing there are fourteen stars known to have an iron content below 3.16 e-5 that of the Sun. Twelve out of fourteen of these stars are extremely enhanced in carbon, so that their total metal content Z is larger than 1e-3 that of the Sun, although their iron content may be lower than 1.e-7 that of the Sun. I will summarize extant observations of these very iron poor stars. New...

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  4. 44. 3D non-LTE chemical abundance measurements for CEMP stars
    anish amarsi
    09/09/2019, 10:10

    Stellar abundance measurements are heavily model dependent, and for late-type stars, the accuracy is often limited by the use of one-dimensional (1D) hydrostatic model atmospheres and the assumption of local thermodynamic equilibrium (LTE). Systematic errors imparted by the use of 1D LTE modelling tend to grow towards lower metallicities, and are thus especially significant for CEMP stars. ...

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  5. 35. Accurate abundances at the lowest detected iron abundance: SMSS 1605-1443
    Thomas Nordlander (Australian National University)
    09/09/2019, 11:00

    We recently announced the discovery of SMSS 1605-1443, which has the lowest detected iron abundance of any star at [Fe/H] = -6.2 (1D LTE). It is strongly carbon enhanced with [C/Fe] ~ 4, but otherwise exhibits a perfectly normal halo star abundance pattern with no detection of neutron capture elements. Assuming a single enrichment event, we find good matches to predictions for Population III...

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  6. 75. Looking for the most metal-poor stars with large surveys
    Dr David Aguado (University of Cambridge, UK)
    09/09/2019, 11:20

    In the Big Bang Nucleosynthesis (BBN), hydrogen, helium, and small traces of lithium and beryllium, were produced. A few million years after BBN, the first stars were born. Important questions about star formation, galactic evolution, and the yields of the first supernovae can be answered from the study of these first stars and their descendants. The most chemically primitive...

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  7. 80. CEMP Stars as Probes of First-Star Nucleosynthesis, the IMF, and Galactic Assembly
    Dr Starkenburg Else (Heidelberg)
    09/09/2019, 14:00

    The lowest metallicity stars that still exist today probably carry the imprint of very few supernova. As such, they represent our best observational approach to understand the First Stars. In this talk I will review the early (chemical) evolution of the Milky Way system from both modeling and observational perspectives. In particular, I will present results of the Pristine survey, a...

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  8. 50. Tracing the formation of the Milky Way through UMP and EMP stars
    Federico Sestito (Observatoire Astronomique de Strasbourg)
    09/09/2019, 14:30

    I will present the results of a Bayesian derivation of stellar parameters, distances, and orbits for all ultra metal-poor stars (UMPs, [Fe/H] $< -4$) available in the literature, as well as for the extremely metal-poor stars (EMPs, [Fe/H]$<-3$) observed by Pristine survey, a unique spectrophotometric survey based on a narrow-band Ca H$\&$K filter that aims to detect and analyse EMPs stars. The...

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  9. 41. The Metallicity Gradient in the Outer Halo of the Milky Way
    Sarah Dietz
    09/09/2019, 14:50

    We present a study of the metallicity gradient in the outer halo component of the Milky Way's dual halo system, using metallicities from SDSS DR15 and several other datasets along with high-precision astrometry from Gaia DR2. It has previously been recognized that the outer halo has one of the most metal-poor stellar populations in our Galaxy (peaking around [Fe/H] = -2.2). In this work, we...

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  10. 60. Observations of 200 New CEMP Stars from the South African Large Telescope
    Kaitlin Rasmussen (University of Notre Dame)
    09/09/2019, 15:10

    Carbon-enhanced metal-poor stars belong to the second generation of stars to form in the Universe; as such, they are a valuable insight into nuclear processes and stellar environments that predate the formation of the Milky Way. At present, approximately one hundred and fifty CEMP stars have been studied via high-resolution spectroscopy. We have observed over 200 new CEMP stars at the South...

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  11. 90. CEMP-no and the early chemical enrichment of the Milky Way
    Dr Cristina Chiappini (Leibniz-Institut für Astrophysik Potsdam (AIP))
    09/09/2019, 16:00
  12. 70. 3D carbon and oxygen abundances in CEMP stars from molecular lines
    Dr A. Kučinskas (Vilnius University, Lithuania)
    09/09/2019, 16:30

    Molecular lines are frequently the only available carbon and oxygen abundance indicators in CEMP stars. However, formation of molecular lines in the atmospheres of CEMP stars is prone to the influence of convection and NLTE. These effects have to be properly taken into account when aiming at reliable abundance estimates. In this contribution we present an overview of the current status in the...

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  13. 21. Short poster presentations
    09/09/2019, 16:50
    Oral contribution
  14. 76. Very Iron-poor Stars and an Update of the SkyMapper Extremely Metal-Poor Star Program
    Prof. David Yong (Australia)
    10/09/2019, 09:00

    The atmospheres of low-mass stars preserve information on the chemical and physical conditions of their birth gas clouds. Studying chemical abundances in the oldest, most metal-poor stars provides an observational window into the early Universe through which we can infer the properties and details of the earliest chemical enrichment events (e.g., supernovae, AGB stars).

    The most metal-poor...

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  15. 72. CEMP stars in dwarf galaxies
    Dr Asa Skuladottir (Heidelberg, Germany)
    10/09/2019, 09:30

    Dwarf galaxies are the most common type of galaxy in the Universe. The Local Group is the only place where we are able to obtain an unobscured view of early star formation and chemical enrichment in galaxies from abundance measurements in individual stars by using moderate- to highresolution spectroscopy. Recent measurements of [Ce/Fe] in different dwarf spheroidal galaxies, suggest possible...

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  16. 64. Abundances and Kinematics of CEMP stars - A new classification
    Camilla Juul Hansen
    10/09/2019, 10:00

    The elements locked up in old, metal-poor stars carry a wealth of information on the properties of the early Universe and how it evolved. Stellar abundances are fossil records of the physical conditions in the interstellar medium and of the progenitors that created the material the low-mass stars formed from. All heavy elements show a large star-to-star abundance scatter at low metallicities,...

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  17. 26. Binarity among CEMP-no stars: an indication of multiple formation pathways?
    Ms Anke Arentsen
    10/09/2019, 10:50

    Understanding the origin of CEMP-no stars is crucial for our understanding of physical processes in the early universe. CEMP-no stars do not show any s-process enhancement and therefore cannot easily be explained by transfer of carbon and s-process elements from a binary AGB companion like the CEMP-s stars. This has been supported by the large radial velocity program by Hansen et al. (2016),...

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  18. 85. Seeking the origin of CEMP-r/s stars
    Prof. Birgitta Nordström (Niels Bohr Institute, Copenhagen, denmark)
    10/09/2019, 11:10

    The elemental abundances in many metal-poor stars show enhancements of carbon and as well neutron-capture elements: CEMP-s, CEMP-r and CEMP-r/s stars. In several radial velocity (RV) projects we have tried to uncover the origin of CEMP stars with enhancements of s- and/or r-process elements. The orbital elements of those that are binaries seem to give hints about the origin of the...

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  19. 29. Multiplicity of the first stars from machine learning-based classification of stellar fossils
    Tilman Hartwig (University of Tokyo)
    10/09/2019, 11:30

    We derive for the first time the multiplicity of the first stars from the abundance patterns of extremely metal-poor (EMP) stars in the Milky Way. Based on theoretical models of the chemical yields of the first supernovae, we train decision trees to classify EMP stars. This machine learning-based approach predicts if a certain abundance pattern is consistent with supernova enrichment by one or...

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  20. 40. The binarity of dwarf carbon stars and their possible role as main sequence counterparts to CEMP stars
    Mr Lewis Whitehouse (University College London)
    10/09/2019, 11:50

    Contrary to expectations, the most abundant carbon stars in the Galaxy are long-lived,
    main-sequence stars. The origin of these dwarf carbon (dC) stars is an astrophysical
    curiosity that is 40 years(!) old, and the mechanisms for enhancing their observed C/O
    above unity are poorly constrained. Intriguingly, a significant fraction of the dC stars
    have clear halo kinematics, and are thus...

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  21. 61. Origin of CEMP-no morphology in the Milky Way halo
    Jinmi Yoon
    10/09/2019, 14:00

    The last 30 years of galactic archaeological studies have provided many lines of evidence that CEMP-no stars are direct descendants of the very first stars. In particular, the last few years have been very thrilling because the recent observational studies have shown that there are likely multiple pathways to form CEMP-no stars based on distinctly different CEMP-no groups exhibited in the...

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  22. 38. Dynamical Relics with Chemically Peculiar Stars from Ancient Small Dwarf Galaxies
    Dr Zhen Yuan (Shanghai Astronomical Observatory, CAS)
    10/09/2019, 14:20

    Stellar halo of the Milky Way is believed to have formed through hierarchical mergers of small stellar systems such as dwarf galaxies. By studying the orbits and chemistry of very metal-poor halo stars, we can decipher the merger events of ancient galaxies, as well as their chemical properties. We applied a novel clustering method, StarGO, to the largest bright very metal-poor star catalog...

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  23. 23. Chemodynamical Analysis of Six Low-Metallicity Stars in the Halo System of the Milky Way
    Mr Mohammad Mardini (National Astronomical Observatories of China)
    10/09/2019, 14:40

    In this work, we study the chemical compositions and kinematics of six metal-poor stars in the Galactic Halo. These stars were selected from the LAMOST survey and were followed up with high-resolution (R $\sim$~110,000) with the Lick/APF. By investigating the chemical compositions and kinematics of this sample, we identified two carbon-enhanced metal-poor stars (J1630+0953 and J2216+0246)...

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  24. 28. Constraining nucleosynthesis in CEMP-s progenitors using Fluorine
    Aldo Mura Guzman (Australian National University)
    10/09/2019, 15:00

    Carbon-Enhanced Metal-Poor (CEMP) stars are among the most important objects for constraining the formation and evolution of the first stellar populations in the Galaxy. CEMP stars with enhancements in slow neutron-capture process (s-process) elements (CEMP-s stars, objects with [Fe/H] < -2, [C/Fe] > 0.7 and [Ba/Fe] > 1) are a significant fraction (as high as 25%) of all metal-poor stars. Of...

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  25. 53. Chemical enrichment and ionizing escape fraction from observations of GRBs
    Prof. Nial Tanvir (University of Leicester)
    10/09/2019, 15:50

    Gamma-ray bursts can be seen to very high redshifts, and the bright power-law continua of their afterglows provide ideal backlights for absorption lines studies. I will review what we have learnt from GRBs about evolving chemical abundances in the early universe; and consider the implications of the high HI column densities seen on the sight lines to GRBs for the escape fraction of ionizing...

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  26. 77. The First Stars: Our Emerging Theoretical Framework
    Prof. Volker Bromm (USA)
    10/09/2019, 16:20

    I will review the current standard model of how the first stars formed at the end of the cosmic dark ages, and how they impacted the subsequent history of the universe. The Population III formation process is intricately linked to the particle physics nature of dark matter, and can thus serve as an astrophysical laboratory to probe this elusive component of the cosmic matter-energy content. I...

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  27. 37. Fragmentation Condition in a Primordial Accretion Disk
    Ms Wei-Ting Liao (University of Illinois at Urbana-Champaign)
    10/09/2019, 16:50

    The accretion disks around Population III (PopIII) stars are known to fragment under fast H$_2$ cooling.
    Based on the vertical disk structure, we study the optical depth for H$_2$ line cooling under an accretion disk geometry. With the physically motivated optical depth, we find that cooling in the inner disk with $r < 10 {\rm\ AU}$ is attenuated significantly due to the large surface...

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  28. 56. Thermodynamics of H2 in the context of the First Stars
    Piyush Sharda (Australian National University)
    10/09/2019, 17:10

    It is well known that the adiabatic index of H2 varies as its rovibrational modes are excited as a function of temperature. For the formation of the first stars at redshifts 20 and above, this variation can be significant because the primordial molecular clouds where the first stars form and the material present in accretion shocks near the first protostars can reach high temperatures where...

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  29. 27. Surviving Pristine Stars and the Implications of their Non-detection Paper Number
    Mattis Magg (Universität Heidelberg)
    10/09/2019, 17:30

    As of now, the initial mass function (IMF) of metal-free stars is one of the key unsolved problems in the early Universe. Of particular interest is whether there are low-mass population III (Pop III) stars that survive until today. To determine how many such stars we should find in the Milky Way, we model Pop III star formation and feedback in the progenitors of Milky Way-like haloes. Assuming...

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  30. 73. The variety of CEMP-no abundances: back-and-forth mixing between H- and He-burning
    Prof. André Maeder (Geneva University)
    11/09/2019, 09:00

    Stellar nucleosynthesis defines a sequence of abundances: - pure products of H-burning; - pure products of He-burning; - products of He-burning mixed into the H-burning region (class 2); - products of class 2 mixed in He-burning (class 3); - products of class 3 again mixed in H-burning zone (class 4). CEMP-no stars with enough observed data are distributed in classes 2, 3 and 4. Spinstars...

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  31. 25. Probing the rotation of early massive stars from the abundances of metal-poor stars
    Arthur Choplin (Konan University)
    11/09/2019, 09:30

    The study of the long-dead early generations of massive stars is crucial in order to obtain a complete picture of the chemical evolution of the Universe. The nature of these stars can be inferred indirectly by investigating the origin of the low-mass extremely metal-poor stars observed in our neighborhood, some of which are almost as old as the Universe. The material forming these low-mass...

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  32. 69. Mechanical mass loss in very metal poor massive stars
    Mr Sébastien Martinet (Geneva University)
    11/09/2019, 09:50

    Mass loss is expected to be very low at very low metallicities, even more for the first generations of stars. A lower mass loss induces a lower angular momentum lost during the main sequence, resulting in faster rotators. As the surface velocity increases, due to internal angular momentum transport from the core to the surface, the first stars reach critical velocity at their surface way...

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  33. 43. An Alternative Progenitor Scenario for the Most Iron-poor CEMP-no Stars.
    Ondrea Clarkson
    11/09/2019, 10:10

    Understanding the nature of the first stars is essential to decipher the chemical abundance patterns in the most iron-poor CEMP stars. Due to their zero-metallicity nature, Pop III stars were structurally quite different than stars of higher metallicity. Namely, interactions between H- and He-burning layers have been recorded in the literature for both rotating and non-rotating stellar models....

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  34. 49. The origin of CEMP-i stars - Results from a comprehensive multi-method simulations approach
    Falk Herwig (University of Victoria)
    11/09/2019, 11:00

    Most C-enhanced metal poor stars show substantial enhancements of heavy n-capture elements, mostly of second-peak elements such as Ba, La and Eu. We report on a comprehensive simulation program involving 3D hydrodynamic simulations, 1D stellar evolution and nucleosynthesis simulations, galactic chemical evolution simulations as well as novel approaches to neutron-capture nucleosynthesis...

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  35. 48. A new grid of Geneva stellar evolution models for Population-III stars
    Laura Murphy (Trinity College Dublin)
    11/09/2019, 11:20

    Understanding the nature of the first stars and their explosive deaths is key to understanding the early universe and the evolution of high-redshift galaxies. With new facilities such as JWST we may soon have the first observations of the earliest stellar populations, but to understand these observations we will require detailed theoretical models. Using the Geneva stellar evolution code, we...

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  36. 31. Low-mass primordial stars: i-process nucleosynthesis during core-flash proton ingestion episodes?
    Dr Simon Campbell (Monash University)
    11/09/2019, 11:40

    Models of zero metallicity and extremely metal-poor stars show that they evolve differently to their more metal-rich counterparts. In particular they suffer violent proton-ingestion episodes (PIEs) that lead to extreme carbon enrichment at the surface. The fresh carbon has a fundamental effect on their further evolution, and can be transferred to binary companions, producing CEMP stars. As...

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  37. 52. Observational Evidence for Aspherical Jet-Like Population III Supernova Explosion
    Rana Ezzeddine (Massachusetts Institute of Technology)
    11/09/2019, 12:00

    Theoretical investigations have long indicated that supernovae of the first stars would explode in an asymmetric fashion, mainly driven by their fast rotations. However, insufficient observational evidence has prevented in-depth studies. Ultra metal-poor stars ([Fe/H]<-5) encode information about their First progenitor star, such as the explosion mechanism, through the relative...

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  38. 57. CEMP star formation from faint supernova explosions
    Gen Chiaki
    11/09/2019, 12:20

    Large observation campaigns of metal-poor stars in Galactic halo and dwarf galaxies have revealed that there are stars with higher carbon abundance relative to the solar one ([C/Fe] > 0.7; carbon-enhanced metal-poor [CEMP] stars). It has been considered that long-lived or low-mass CEMP stars form through fragmentation of their parent clouds induced by gas cooling of carbon grains. Carbon...

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  39. 42. Simulating and Observing the First Galaxies
    Prof. John Wise (Georgia Institute of Technology)
    12/09/2019, 09:00

    JWST will uncover a vast population of low-luminosity galaxies at Cosmic Dawn that is responsible for most of reionization. We present predictions on this high-redshift population, focusing on their physical properties and role during reionization. We use two suites of high-resolution cosmological simulations -- the Renaissance Simulations and the Tempest Simulations -- that sample different...

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  40. 91. Building-up Pop III IMF in the Milky Way-like galaxies
    Dr Shingo Hirano (Kyushu University)
    12/09/2019, 09:30
  41. 82. First star mass distribution: empirical constraints
    Prof. Salvadori Stefania (University of Florence, Italy)
    12/09/2019, 10:00

    The Local Group holds the living fossils of the first stars and galaxies. Still, these precious relics are extremely rare, and hence very difficult to catch. In this talk I will discuss the most recent observational findings and theoretical predictions for present-day metal-poor stars, underlying the links with the properties of the first stars. In particular, I will show that chemical...

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  42. 81. Connecting the first galaxies with ultra faint dwarfs in the Local Group
    Prof. Jeon Myoungwon (Korea)
    12/09/2019, 11:00

    We investigate the star formation histories and chemical evolution of isolated analogs of Local Group untra-faint dwarf galaxies (UFDs) and gas-rich, low-mass dwarfs. We perform a suite of cosmological hydrodynamic zoom-in simulations to follow their evolution from the era of the first generation of stars down to z = 0. We confirm that reionization, combined with supernova (SN) feedback, is...

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  43. 86. Exploring the stellar ionising continuum of galaxies in the context of cosmic reionisation
    Prof. Anne Verhamme (UNIGE)
    12/09/2019, 11:30

    Cosmic reionization corresponds to the period in the history of the Universe during which the predominantly neutral intergalactic medium was ionised by the emergence of the first luminous sources. I will first briefly describe what we know about cosmic reionisation from observations, and explain the actual limitations/challenges of state-of-the art simulations of this phenomenon.
    In...

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  44. 24. CEMP stars: their origin and connection with stars that reionized the Universe
    Dr Mahavir Sharma
    12/09/2019, 12:00

    The carbon enhanced metal poor (CEMP) stars are of immense importance as they likely carry signatures of first few generations of stars in the Universe. At the observational front there has been a tremendous advance in our ours understanding of CEMP stars, and recently theoretical studies have provided new insights. Nevertheless, the origin of CEMP stars, and in particular that of their...

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  45. 51. Multi-dimensional modelling of stellar interiors
    Prof. Raphael Hirschi (Keele University )
    12/09/2019, 14:00

    Stars are complex three-dimensional (3D) objects involving many physical processes: convection, rotation, magnetic fields. In this talk, I will review the efforts to constrain the physical ingredients of 1D stellar evolution models of the first stars using multi-D (magneto-)hydrodynamic simulations.

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  46. 78. Asteroseismology and transport processes in stellar interiors
    Dr Patrick Eggenberger (Geneva University)
    12/09/2019, 14:30

    Thanks to space missions, measurements of solar-like oscillations are now available for a large sample of stars. This has led to the precise characterization of the global and internal properties of these stars, and in particular of their internal rotation. In this talk, we will first discuss how these asteroseismic measurements can help us progress in the modelling of angular momentum...

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  47. 36. Asteroseismology and high-resolution spectroscopy of halo stars
    Tadafumi Matsuno
    12/09/2019, 15:00

    We derive stellar masses and precise chemical abundances for 26 halo red giants, among which 5 and 17 turned out to be [Fe/H]<-2 and <-1, respectively, by combining high-resolution spectroscopy and asteroseismology. We selected the 26 stars in the Kepler field based on radial velocity and metallicity estimated from spectroscopic surveys and confirmed that they show halo-like kinematics using...

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  48. 54. New light on the Sun: Updates on helioseismology and the Solar modelling problem
    Gaël Buldgen (Université de Genève)
    12/09/2019, 15:20

    The Sun holds a special place in stellar astrophysics, we use it as reference for the determination of the chemical abundances of all stars in the Milky Way. Since 1962, the field of helioseismology has provided unprecedented ways of testing the internal structure of solar models. Soon after the discovery of neutrino-oscillation and the end of the solar neutrino problem, the revision of the...

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  49. 95. Probing the early Universe with black hole binaries
    Tassos Fragos
    12/09/2019, 16:10

    Binary stellar systems are unique astrophysical laboratories for the study of black holes (BHs). Accretion of matter from a binary companion gives rise to X-ray emission, bringing them to the X-ray binary phase and making them visible on Gpc scales, while the recent gravitational wave observations enabled us to witness the last few seconds of the lives of coalescing binary BHs. X-ray binaries...

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  50. 55. Life and death of supermassive stars
    Dr Lionel Haemmerlé (Université de Genève)
    12/09/2019, 16:40

    Supermassive stars (SMSs) are candidates for being the progenitors of the most massive quasars discovered recently at high redshift. The viability of this formation channel (direct collapse) depends on the properties of the progenitor, whose evolution is dominated by rapid accretion. I will present the most recent models of SMSs, that include accretion and rotation, and discuss their...

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  51. 92. General discussion
    12/09/2019, 17:00

    Possible themes:
    - The hunt for EMP stars: new strategies, new methods of analysis
    - What is the helium content of EMP? How to know? What to expect?
    - Multi-messenger astrophysics for the study of the first stars
    - Possible links and differences between EMP and stars in globular clusters?

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  52. 87. Modeling the first stages of galaxy formation
    Pascale Jablonka (EPFL - EPF Lausanne)
    13/09/2019, 09:00

    I will review (some of) the latest developments in chemo-dynamical numerical simulations of galaxies, particularly focusing on the early formation stages.

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  53. 65. Formation and Evolution of Milky Way Galaxy: Abundance trends of stable and short-lived nuclides
    Ms Tejpreet Kaur (Department of Physics, Panjab University, Chandigarh)
    13/09/2019, 09:30

    To understand the formation and evolution of Milky Way galaxy, Galactic Chemical Evolution (GCE) simulations are performed using N-body Monte Carlo technique. Our GCE models predict the elemental abundance gradients of C, N, O, Mg, Si, Ca, Ti, Fe, and Zn using the revised solar abundance of value 0.0143. The galaxy is radially divided into eight annular rings of 2 kpc width each at a distance...

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  54. 68. The Galactic bulge and old stellar populations
    Prof. Beatriz Barbuy
    13/09/2019, 10:20

    We present observations and theoretical models regarding the formation of the Galactic bulge. Our main interest concerns the blue horizontal branch and moderately metal-poor globular clusters, that might be among the oldest objects in the Galaxy. We also present abundances, in particular of heavy elements, that could provide evidence for early s-process nucleosynthesis in early rotating massive stars.

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  55. 74. Extremely metal-poor stars in the next generation large surveys
    Dr Vanessa Hill (France)
    13/09/2019, 10:50

    TBD

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  56. 94. Concluding discussion
    13/09/2019, 11:20

    Each participant will be asked to answer in a few written lines the two following questions:
    1) What is the most interesting thing she/he has learnt during the conference?
    2)What non-answered question(s) she/he would like to study in the coming years about CEMP stars?

    The answers will be collected and a SOC member will prepare a small presentation to share the results with the audience.

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  57. 33. A new stellar cluster Gaia 2
    Dr şeyma çalışkan (Ankara University)
    posters

    Stellar clusters are the key for understanding of galaxy formation and evolution because they host number of old stars. We determine the atmospheric parameters of two members of a new stellar cluster Gaia 2. The low resolution spectra of the stars were obtained at TÜBİTAK National Observatory, using the RTT150 telescope (with 1.5 m). We announce the first results in the present study.

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  58. 47. An Extended Empirical Library for Metal-Poor Stars Recognition and Parameterization
    Dr Bing Du (NAOC)
    posters

    We present an extended empirical stellar spectra library created using spectra from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) DR5 and the Sloan Digital Sky Survey’s extended Baryon Oscillation Spectroscopic Survey (eBOSS). Using more spectra of Metal-poor stars observed by both LAMOST and SDSS, we generated denser low-metallicity templates to fill in data...

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  59. 30. Chemical signatures of rotating massive stars dying in faint explosions
    Gabriele Cescutti (National Institute for Astrophysics - INAF)

    We have recently investigated the origin of chemical signatures observed in the oldest star of our Galaxy by means of a stochastic chemical evolution model. The elements we have studied are carbon, nitrogen and oxygen and furthermore neutron-capture elements. We have found that rotating massive stars are a promising way to explain several signatures observed in these fossil stars.
    Analysing...

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  60. 32. CNO abundances in the early Galaxy
    Dr Susmitha Rani Antony (Tata Institute of Fundamental Research Mumbai)

    Carbon-enhanced metal-poor (CEMP) stars contribute to about 20% of the metal-poor stars below [Fe/H] < -2.0. The origin of carbon in these stars could be due to AGB mass transfer in a binary system. These class of objects (CEMP-s) also show enhancement of s-process elements, and most of them show radial velocity variations indicating the presence of a companion. However, the class of CEMP...

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  61. 58. Current Results of the New Metallicity Calibration Method for EMP Stars
    Dr Dogus Ozuyar (Ankara University)
    posters

    The aim of the proposed study is to present the current results of a freshly developed photometric metallicity calibration method for the discovery of new EMP stars ([Fe/H] < -2.5). Different from others, this system is theoretically formed by a narrow band filter (CaK) centered on Ca II K line (3933Å) together with the broad band SDSS (Sloan Digital Sky Survey) filters (ugr). Our calibration...

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  62. 39. Detailed abundance analysis of new CEMP stars from HESP-GOMPA survey
    Mr Bandyopadhyay Avrajit (Indian Institute of Astrophysics, Bangalore)

    The aim of this work is to study the chemical abundances of Milky Way halo stars which belong to the oldest stellar population of the Galaxy and detailed Chemical analysis of these populations can address several intriguing problems in the area of galaxy formation. For our present study, we have carried out high resolution spectroscopic survey using the Hanle Echelle Spectrograph (HESP) at 2m...

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  63. 84. IMF of the first enrichment sources and their contribution to galaxy evolution
    Prof. Chiaki Kobayashi (University of Hertfordshire, UK)
    Invited presentation

    First I will show the initial mass function (IMF) of the first enrichment sources obtained with our abundance fitting analysis. We compare the elemental abundance patterns of about 200 extremely metal-poor (EMP) stars to our nucleosynthesis yields of primordial supernovae. As a result, the IMF spans 13-100 Msun with a peak at 25 Msun with a large fraction of hypernovae. The majority of the...

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  64. 88. Iron-peak elements Sc, V, Mn, Cu, and Zn in Galactic bulge globular clusters
    Heitor Ernandes
    posters

    Globular clusters are tracers of the history of star formation and chemical enrichment in the early Galaxy. Their abundance pattern can help understanding their chemical enrichment processes. In particular, the iron-peak elements have been relatively little studied so far in the Galactic bulge.
    Methods. The main aim of this work is to verify the strength of abundances of iron-peak elements...

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  65. 34. Metal poor stars in Gaia
    Ms Theodora Xylakis-Dornbusch (ZAH/LSW, University of Heidelberg )
    posters

    The study of the oldest and most metal-poor stars in our Galaxy promotes our
    understanding of the cosmic chemical evolution and the beginning of Galaxy and
    star formation. However, they are notoriously difficult to find, with only 5
    stars of [Fe/H]<-5 having been detected to date. Thus, the spectrophotometric
    data of ~1 billion stars which will become available with the third Gaia...

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  66. 66. Putting CEMP-s stars into context: the swan songs of stars as recorded by their binary companions
    Dr Pierre North (Ecole Polytechnique Fédérale de Lausanne (EPFL))

    CEMP-s stars are thought to be the EMP equivalents of Pop. I barium stars or of Pop. ii CH stars, owing their chemical peculiarities to binary evolution. Their present-day companion is a CO white dwarf that had been the core of an AGB stars. We review the observations of different types of chemically peculiar stars originating from binary evolution, including those presumably polluted by a...

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  67. 46. r-Process Sites, their Ejecta Composition, and their Imprint in Galactic Chemical Evolution
    Prof. Friedrich-K. Thielemann (University of Basel and GSI Darmstadt)

    From low metallicity stars and the presence of radioactive isotopes in deep-sea sediments we know that the main r-process, producing the heaviest elements, is a rare event. The question remains whether neutron star mergers, via GW170817 the only proven r-process site, are the only contributors or also (a rare class of) supernovae, hypernovae/collapsars, as well as neutron star - black hole...

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  68. 63. SALT CEMP Stars Survey
    Mr Joseph Zepeda (University of Notre Dame)
    posters

    CEMP stars have increasingly been shown to be important for understanding Pop III stars, early chemical enrichment, and many neutron capture nucleosynthetic processes. However, currently there are only approximately 150 CEMP stars that have been studied in high resolution. While this number is sufficient for statistic of a single population of stars, CEMP stars exist in many varied subgroups...

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  69. 67. Searching the Metal-poor Star with Deep Learning Method
    Dr Jiannan Zhang (National Astronomical Observatories, CAS)
    posters

    Searching for the rare metal-poor stars requires fast and effective analysis methods on the vast spectral survey data. Here, we develop a deep learning network to search for metal-poor and carbon-enhanced metal-poor (CEMP) stars in low-resolution spectra. We train a deep convolutional neural network (CNN) on a synthesized stellar spectra grid with Teff ranging from 5000K to 7500K, log g...

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  70. 62. The Pristine Survey: High-resolution spectroscopy and kinematics of new extremely metal-poor stars
    Collin Kielty (University of Victoria)

    Extremely metal-poor stars (EMPs, [Fe/H] < -3) are excellent tools for Galactic archaeologists to study the first stars and the early formation history of the Milky Way. A great diversity has been seen in the EMP stars, both in the medley of their chemical abundance ratios, as well as in their kinematics; a diversity suggestive of the variety of their nucleosynthetic origins and formation...

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