A5074810206- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Solar and Space Plasma Dynamics
- Astronomical Observations and Instrumentation
- Astronomical and nuclear sciences
- Gamma-ray bursts and supernovae
- Atmospheric Ozone and Climate
- Galaxies: Formation, Evolution, Phenomena
- Calibration and Measurement Techniques
- History and Developments in Astronomy
- Space Science and Extraterrestrial Life
- Planetary Science and Exploration
- Adaptive optics and wavefront sensing
- Space Exploration and Technology
- solar cell performance optimization
- Inertial Sensor and Navigation
- Chemical Thermodynamics and Molecular Structure
- Graph theory and applications
- Geology and Paleoclimatology Research
- Advanced Mathematical Theories and Applications
- Analytic Number Theory Research
- Global Energy and Sustainability Research
- 14-3-3 protein interactions
Valongo Observatory
2015-2024
Universidade Federal do Rio de Janeiro
2014-2024
Laboratório Interinstitucional de e-Astronomia
2011-2018
Hospital Universitário Antônio Pedro
2012-2013
National Observatory
1991-1997
Building on the legacy of Sloan Digital Sky Survey (SDSS-I and II), SDSS-III is a program four spectroscopic surveys three scientific themes: dark energy cosmological parameters, history structure Milky Way, population giant planets around other stars. In keeping with SDSS tradition, will provide regular public releases all its data, beginning Data Release 8 (DR8), which was made in 2011 January includes SDSS-I SDSS-II images spectra reprocessed latest pipelines calibrations produced for...
ABSTRACT We report magnetic field measurements for κ 1 Cet, a proxy of the young Sun when life arose on Earth. carry out an analysis properties determined from spectropolarimetric observations and reconstruct large-scale surface to derive environment, stellar winds, particle flux permeating interplanetary medium around Cet. Our results show closer magnetosphere mass-loss rate , i.e., factor 50 times larger than current solar wind rate, resulting in interaction via space weather disturbances...
The detailed analysis of the optical spectrum and evolutionary state G2 Va star HR 6060 shows this object to have atmospheric parameters, mass, chromospheric activity, UBV colors indistinguishable from solar ones within observational uncertainties. Only its luminosity age are slightly higher than solar. Its abundance pattern is solar, with exception a slight excess Sc, V, elements heavier Sr. surpasses all previously claimed twins in likeness Sun, we recommend that it be considered for...
The early evolution of Earth's atmosphere and the origin life took place at a time when physical conditions Earth where radically different from its present state. radiative input Sun was much enhanced in high-energy spectral domain, order to model planetary atmospheres detail, knowledge solar is needed. We an investigation atmospheric parameters, state fluxes nearby star kap^1 Cet, previously thought have properties resembling those Sun. Atmospheric parameters were derived...
We analyze the non-standard mixing history of solar twins HIP 55459, 79672, 56948, 73815, and 100963, to determine as precisely possible their mass age. computed a grid evolutionary models with at several metallicities Toulouse-Geneva code for range stellar masses assuming an error bar +-50K in Teff. choose model that reproduces accurately observed low lithium abundances twins. Our best-fit each twin provides age solution constrained by Li content Teff determination. 56948 is most likely...
In several instances chemical abundances of dwarf and giant stars are used simultaneously under the assumption that they share same abundance scale. This might have implications in different astrophysical contexts. We aim to ascertain a methodology capable producing consistent metallicity scale for giants dwarfs. To achieve that, we analyzed dwarfs Hyades open cluster. All these archival high-resolution spectroscopic data obtained with HARPS UVES. addition, interferometric measurements...
Context. The α Centauri binary system, owing to its duplicity, proximity and brightness, components' likeness the Sun, is a fundamental calibrating object for theory of stellar structure evolution determination atmospheric parameters. This role, however, hindered by considerable disagreement in published analyses parameters abundances.
We report the abundances of C, Na, Mg, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, Zr, Ba, Ce, Nd, and Sm in 25 solar-type stars solar neighbourhood, their correlations with ages, kinematics, orbital parameters. The spectroscopic analysis, based high resolution S/N ratio data, was differential to Sun applied atomic line EWs C C2 spectral synthesis. performed a statistical study using tree clustering searching for groups sharing similar abundance patterns. derived Teff, log(g),...
We have analyzed new and previously published radial velocity (RV) observations of MARVELS-1, known to an ostensibly substellar companion in a ∼6 day orbit. find significant (∼100 m s−1) residuals the best-fit model for companion, these are naïvely consistent with interior giant planet P = 1.965 days nearly perfect 3:1 period commensurability (|Pb/Pc − 3| < 10−4). performed several tests reality such including dynamical analysis, search photometric variability, hunt contaminating stellar...
Planet searches using the radial velocity technique show a paucity of companions to solar-type stars within ~5 AU in mass range ~10 - 80 M$_{\text{Jup}}$. This deficit, known as brown dwarf desert, currently has no conclusive explanation. New substellar this region help asses reality desert and provide insight formation evolution these objects. Here we present 10 new two low-mass stellar companion candidates around from Multi-object APO Radial-Velocity Exoplanet Large-Area Survey (MARVELS)...
Solar twins and analogs are fundamental in the characterization of Sun's place context stellar measurements, as they understanding how typical solar properties its neighborhood. They also important for representing sunlight observable night sky diverse photometric spectroscopic tasks, besides being natural candidates harboring planetary systems similar to ours possibly even life-bearing environments. We report a survey twin stars within 50 pc Sun. Hipparcos absolute magnitudes (B-V)_Tycho...
The Mount Wilson Ca II index log$(R'_{\rm HK})$ is the accepted standard metric of calibration for chromospheric activity versus age relation FGK stars. Recent results claim its inability to discern levels, and thus ages, stars older than $\sim$2 Gyr, which would severely hamper application date disk Sun. We present a new activity-age Mt. explicitly taking into account mass $[$Fe/H$]$ biases, implicit in samples selected have precise that so far gone unappreciated. show these selection...
Context. To date, the CoRoT space mission has produced more than 124 471 light curves. Classifying these curves in terms of unambiguous variability behavior is mandatory for obtaining an unbiased statistical view on their controlling root-causes.
Combining stellar atmospheric parameters, such as effective temperature, surface gravity, and metallicity, with barycentric radial velocity data provides insight into the chemo-dynamics of Milky Way our local Galactic environment. We analyse 3075 stars spectroscopic from Sloan Digital Sky Survey III MARVELS survey present parameters for 2343 dwarf using spectral indices method, a modified version equivalent width method. velocities sample 2610 median uncertainty 0.3 km s−1. determine ages...
A calibration of Hα as both a chromospheric diagnostic and an age indicator is presented, complementing the works previously done on this subject (Herbig 1985;Pasquini & Pallavicini 1991).The was built with statistically significant sample, covering nine years observations, including 175 solar neighborhood stars.Regarding indicator, presence stars for which very accurate ages are determined, such those belonging to clusters kinematic groups, lends confidence our analysis.We also investigate...
We report the discovery of a candidate brown dwarf or very low mass stellar companion (MARVELS-5b) to star HIP 67526 from Multi-object APO Radial Velocity Exoplanet Large-area Survey (MARVELS). The radial velocity curve for this object contains 31 epochs spread over 2.5 years. Our Keplerian fit using Markov Chain Monte Carlo approach, reveals that has an orbital period $90.2695^{+0.0188}_{-0.0187}$ days, eccentricity $0.4375 \pm 0.0040$ and semi-amplitude $2948.14^{+16.65}_{-16.55}$ m...
We report the discovery of a highly eccentric, double-lined spectroscopic binary star system (TYC 3010-1494-1), comprising two solar-type stars that we had initially identified as single with brown dwarf companion. At moderate resolving power MARVELS spectrograph and spectrographs used for subsequent radial-velocity (RV) measurements (R ~ <30,000), this particular stellar mimics single-lined an RV signal would be induced by companion (Msin(i)~50 M_Jup) to primary. least three properties...
The first determination of the age Galactic thin disk from Th/Eu nucleocosmochronology was accomplished by us in Papers I and II. present work aimed at reducing uncertainty expanding stellar sample with inclusion seven new objects – an increase 37%. A set [Th/Eu] abundance ratios determined spectral synthesis merged results Paper I. Abundances for new, extended were analyzed aid a chemical evolution (GDCE) model developed is result averaged estimate obtained II conjunction literature data...
The fact that most extrasolar planets found to date are orbiting metal-rich stars lends credence the core accretion mechanism of gas giant planet formation over its competitor, disc instability mechanism. However, is not refined point explaining orbital parameters such as unexpected semimajor axes and eccentricities. We propose a model correlates metallicity host star with original axis massive planet, prior migration, assuming scenario governs formation. predicts optimum regions for...
Aims.We compare and discuss abundances trends in normal giants, mild barium, barium stars, searching for differences similarities between stars that could help shed some light on the origin of these similar objects. Also, we search nucleosynthetic effects possibly related to s-process were observed literature elements like Cu other types enriched stars.
We present a new short-period brown dwarf (BD) candidate around the star TYC 1240-00945-1. This was discovered in first year of Multi-object APO Radial Velocity Exoplanets Large-area Survey (MARVELS), which is part Sloan Digital Sky (SDSS) III, and we designate BD as MARVELS-1b. MARVELS uses technique dispersed fixed-delay interferometery to simultaneously obtain radial velocity (RV) measurements for 60 objects per field using single, custom-built instrument that fiber fed from SDSS 2.5 m...