A5031353884- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astronomical Observations and Instrumentation
- Solar and Space Plasma Dynamics
- Gamma-ray bursts and supernovae
- Astronomical and nuclear sciences
- Calibration and Measurement Techniques
- Atmospheric Ozone and Climate
- Organic Electronics and Photovoltaics
- Thin-Film Transistor Technologies
- Geophysics and Gravity Measurements
- Adaptive optics and wavefront sensing
- Silicon and Solar Cell Technologies
- High-pressure geophysics and materials
- History and Developments in Astronomy
- Scientific Research and Discoveries
- Astrophysics and Cosmic Phenomena
- Rock Mechanics and Modeling
- Drilling and Well Engineering
- Space Science and Extraterrestrial Life
- Regional Economic and Spatial Analysis
- Astrophysical Phenomena and Observations
- Plant and soil sciences
Heliatek (Germany)
2023-2024
Tacoma Community College
2017-2021
Carnegie Observatories
2010-2019
Carnegie Institution for Science
2010-2019
Technological University of Pereira
2019
The University of Texas at Austin
2007-2017
Universidad Nacional Autónoma de México
2014
University of Wisconsin–Madison
2012
Max Planck Society
2008-2011
Max Planck Institute for Astrophysics
2008-2011
We present a re-analysis of the Geneva-Copenhagen survey, which benefits from infrared flux method to improve accuracy derived stellar effective temperatures and uses latter build consistent improved metallicity scale. Metallicities are calibrated on high-resolution spectroscopy checked against four open clusters moving group, showing excellent consistency. The new temperature scales provide better match theoretical isochrones, used for Bayesian analysis ages. With respect previous analyses,...
Various effective temperature scales have been proposed over the years. Despite much work and high internal precision usually achieved, systematic differences of order 100 K (or more) among various are still present. We present an investigation based on Infrared Flux Method aimed at assessing source such discrepancies pin down their origin. break impasse different by using a large set solar twins, stars which spectroscopically photometrically identical to Sun, absolute zero point scale...
We present up-to-date metallicity-dependent temperature vs. color calibrations for main sequence and giant stars based on temperatures derived with the infrared flux method (IRFM). Seventeen colors in following photometric systems: UBV, uvby, Vilnius, Geneva, RI(Cousins), DDO, Hipparcos-Tycho, 2MASS, have been calibrated. The spectral types covered range from F0 to K5 (7000 K<Teff<4000 K) some relations extending below 4000 K or up 8000 K. Most of are valid metallicity -3.5<[Fe/H]<0.4,...
We derive the abundance of 19 elements in a sample 64 stars with fundamental parameters very similar to solar, which minimizes impact systematic errors our spectroscopic 1D-LTE differential analysis, using high-resolution (), high signal-to-noise ratio () spectra. The estimated elemental abundances relative solar are as small 0.025 dex. ratios [X/Fe] function agree closely previously established patterns Galactic thin-disk chemical evolution. Interestingly, majority show significant...
The infrared flux method (IRFM) has been applied to a sample of 135 dwarf and 36 giant stars covering the following regions atmospheric parameters space: 1) metal-rich ([Fe/H]>0) end (consisting mostly planet-hosting stars), 2) cool (Teff<5000 K) metal-poor (-1
... We confirm the well-established differences for [$\alpha$/Fe] at a given metallicity between local thin and thick disks. For all elements investigated, we find no chemical distinction bulge disk, in agreement with our previous study of C, N O but contrast to other groups relying on literature values nearby disk dwarf stars. -1.5 < [Fe/H] -0.3 exactly same trend is followed by both stars, star-to-star scatter only 0.03 dex. Furthermore, populations share location knee [alpha/Fe] vs...
We derive a self-consistent set of atmospheric parameters and abundances 17 elements for the red giant star Arcturus: Teff = 4286+/-30 K, logg 1.66+/-0.05, [Fe/H] -0.52+/-0.04. The effective temperature was determined using model atmosphere fits to observed spectral energy distribution from blue mid-infrared (0.44 10 um). surface gravity calculated trigonometric parallax stellar evolution models. A differential abundance analysis relative solar spectrum allowed us iron equivalent width...
Context. The evolution of the Milky Way bulge and its relationship with other Galactic populations is still poorly understood. has been suggested to be either a merger-driven classical or product dynamical instability inner disk.
We study HIP 56948, the best solar twin known to date, determine with an unparalleled precision how similar is Sun in its physical properties, chemical composition and planet architecture. explore whether abundances anomalies may be due pollution from stellar ejecta or terrestrial formation. perform a differential abundance analysis (both LTE NLTE) using high resolution (R = 100,000) S/N (600) Keck HIRES spectra of 56948. use precise radial velocity data McDonald observatories search for...
We report on the discovery and validation of Kepler-452b, a transiting planet identified by search through 4 years data collected NASA's Kepler Mission. This possibly rocky orbits its G2 host star every days, longest orbital period for small ( ) exoplanet to date. The likelihood that this has composition lies between 49% 62%. an effective temperature 5757 ± 85 K 4.32 0.09. At mean separation AU, is well within optimistic habitable zone (recent Venus/early Mars), experiencing only 10% more...
The abundances of iron and oxygen are homogeneously determined in a sample 523 nearby (d<150 pc) FGK disk halo stars with metallicities the range -1.5-0.3, we find no obvious indication sudden decrease (i.e., 'knee') [O/Fe] vs. [Fe/H] pattern thick-disk that would connect thick thin trends at high metallicity. We conclude Type Ia supernovae (SN Ia) did not contribute significantly to chemical enrichment disk. [Abridged]
Abstract The compositions of stars are a critical diagnostic tool for many topics in astronomy such as the evolution our Galaxy, formation planets, and uniqueness Sun. Previous spectroscopic measurements indicate large intrinsic variation elemental abundance patterns with similar overall metal content. However, systematic errors arising from inaccuracies stellar models known to be limiting factor studies, thus it is uncertain what extent observed diversity real. Here we report abundances 30...
Context. We are carrying out a search for planets around sample of solar twin stars using the HARPS spectrograph. The goal this project is to exploit advantage offered by twins obtain chemical abundances unmatched precision. This survey will enable new studies stellar composition – planet connection.
The atmospheric parameters of the components 16Cygni binary system, in which secondary has a gas giant planet detected, are measured accurately using high quality observational data. Abundances relative to solar obtained for 25 elements with mean error 0.023 dex. fact that 16CygA about four times more lithium than 16CygB is normal considering slightly different masses stars. abundance patterns and B, iron, typical observed most so-called twin stars, exception heavy (Z>30), can, however, be...
[ABRIDGED] Based on high-resolution (R~42000 to 48000) and high signal-to-noise (S/N~50 150) spectra obtained with UVES/VLT, we present detailed elemental abundances (O, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Zn, Y, Ba) stellar ages for 26 microlensed dwarf subgiant stars in the Galactic bulge. The analysis is based equivalent width measurements standard 1-D LTE MARCS model atmospheres. We also NLTE Li line synthesis of 7Li at 670.8 nm. show that bulge metallicity distribution (MDF)...
We study the stars of binary system 16 Cygni to determine with high precision their chemical composition. Knowing that component B has a detected planet at least 1.5 Jupiter masses, we investigate if there are peculiarities could be attributed formation around this star. perform differential abundance analysis using resolution (R = 81,000) and S/N (∼700) CFHT/ESPaDOnS spectra Sun; latter was obtained from light reflected asteroids. abundances components relative Sun between A as well....
We have determined precise stellar parameters and lithium abundances in a sample of 117 stars with basic properties very similar to the Sun. This selection reduces biasing effects systematic errors analysis. estimate ages our mainly from isochrone fitting but also measurements rotation period X-ray luminosity test connection between abundance, age, parameters. find strong evidence for increasing depletion age. Our includes 14 that are known host planets it does not support recent claims...
We derive atmospheric parameters and lithium abundances for 671 stars include our measurements in a literature compilation of 1381 dwarf subgiant stars. First, "lithium desert" the effective temperature (Teff) versus abundance (A_Li) plane is observed such that no with Teff~6075 K A_Li~1.8 are found. speculate most on low A_Li side desert have experienced short-lived period severe surface destruction as main-sequence or Next, we search differences content thin-disk thick-disk stars, but find...
Important insights into the formation and evolution of Galactic disc(s) are contained in chemical compositions stars. We analysed high-resolution high signal to noise HARPS spectra 79 solar twin stars order obtain precise determinations their atmospheric parameters, ages ($\sigma$$\sim$0.4 Gyr) abundances ($\sigma$$<$0.01~dex) 12 neutron-capture elements (Sr, Y, Zr, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy). This valuable dataset allows us study [X/Fe]-age relations over a time interval $\sim$10...
We study with unprecedented detail the chemical composition and stellar parameters of solar twin 18 Sco in a strictly differential sense relative to Sun. Our is mainly based on high-resolution (R ∼ 110,000), high signal-to-noise ratio (800–1,000) Very Large Telescope UVES spectra, which allow us achieve precision about 0.005 dex abundances. The effective temperature surface gravity are Teff = 5823 ± 6 K log g 4.45 0.02 dex, i.e., 46 hotter than Sun 0.01 higher. Its metallicity [Fe/H] 0.054...