A5033093476- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Adaptive optics and wavefront sensing
- Astrophysical Phenomena and Observations
- CCD and CMOS Imaging Sensors
- Galaxies: Formation, Evolution, Phenomena
- TiO2 Photocatalysis and Solar Cells
- Advanced oxidation water treatment
- Advanced Photocatalysis Techniques
- History and Developments in Astronomy
- Agricultural and Food Sciences
- Geophysics and Sensor Technology
- Photocathodes and Microchannel Plates
- Chemistry Education and Research
- High-pressure geophysics and materials
- Geophysics and Gravity Measurements
- Water Quality Monitoring and Analysis
- Environmental Sustainability and Education
- Medical Imaging and Pathology Studies
- Chemical Analysis and Environmental Impact
- Advanced optical system design
Laboratório Nacional de Astrofísica
2013-2024
Universidade Federal de Itajubá
2024
Universidade Federal de Sergipe
2013-2021
Universidade Federal Rural de Pernambuco
2017
Southern Astrophysical Research Telescope
2008-2014
Universidad Nacional Autónoma de México
2014
Universidade Estadual Paulista (Unesp)
2008-2013
Universidade Federal do Rio Grande do Sul
2012
Universidade Federal de Santa Catarina
2002-2009
Thüringer Landessternwarte Tautenburg
2006
To obtain better statistics on the occurrence of magnetism among white dwarfs, we searched spectra hydrogen atmosphere dwarf stars (DAs) in Data Release 7 Sloan Digital Sky Survey (SDSS) for Zeeman splittings and estimated magnetic fields. We found 521 DAs with detectable splittings, fields range from around 1 to 733 MG, which amounts 4 per cent all observed. As SDSS have low signal-to-noise ratios, carefully investigated by simulations theoretical how reliable our detection field was.
Abstract We present results from the characterization and optimization of Skipper charge-coupled devices (CCDs) for use in a focal plane prototype Southern Astrophysical Research Integral Field Spectrograph (SIFS). tested eight CCDs selected six SIFS based on performance results. The are 6k × 1k, 15 μ m pixels, thick, fully depleted, p -channel that have been thinned to ∼250 m, backside processed, treated with an anti-reflective coating. demonstrate single-sample readout noise <4.3 e −...
We report the discovery of 74 new pulsating DA white dwarf stars, or ZZ Cetis, from data obtained by Transiting Exoplanet Survey Satellite (TESS) mission, Sectors 1 to 39, corresponding first 3 cycles. This includes objects Southern Hemisphere (Sectors 1-13 and 27-39) Northern 14-26), observed with 120 s- 20 s-cadence. Our sample likely 13 low-mass one extremely candidate, considering mass determinations fitting Gaia magnitudes parallax. In addition, we present follow-up time series...
The structure of the Small Magellanic Cloud (SMC) is very complex, in particular periphery that suffers more from interactions with Large (LMC). A wealth observational evidence has been accumulated revealing tidal tails and bridges made up gas, stars star clusters. Nevertheless, a full picture SMC outskirts only recently starting to emerge 6D phase-space map plus age metallicity using clusters as tracers. In this work, we continue our analysis another outer region SMC, so-called West Halo,...
Context. The ESO public survey VISTA Variables in the Vía Láctea (VVV) surveyed inner Galactic bulge and adjacent southern disk from 2009–2015. Upon its conclusion, complementary VVV extended (VVVX) has expanded both temporal as well spatial coverage of original area, widening it 562 to 1700 sq. deg., providing additional epochs JHK s filters 2016–2023. Aims. With completion VVVX observations during first semester 2023, we present here observing strategy, a description data quality access,...
HR 1217 is one of the best-studied rapidly oscillating Ap (roAp) stars, with a frequency spectrum alternating even- and odd-ℓ modes that are distorted by presence strong, global magnetic field. Several recent theoretical studies have found within observable atmospheres roAp stars pulsation magneto-acoustic significant perturbations cyclic increasing frequency. To test these theories Whole Earth Telescope extended coverage campaign obtained 342 h Johnson B data at 10-s time resolution for...
BPM 37093 is the only hydrogen-atmosphere white dwarf currently known which has sufficient mass (~ 1.1 M_sun) to theoretically crystallize while still inside ZZ Ceti instability strip (T_eff ~ 12,000 K). As a consequence, this star represents our first opportunity test crystallization theory directly. If core substantially crystallized, then inner boundary for each pulsation mode will be located at top of solid rather than center star, affecting mainly average period spacing. This distinct...
We report on analysis of 308.3 hrs high speed photometry targeting the pulsating DA white dwarf EC14012-1446. The data were acquired with Whole Earth Telescope (WET) during 2008 international observing run XCOV26. Fourier transform light curve contains 19 independent frequencies and numerous combination frequencies. dominant peaks are 1633.907, 1887.404, 2504.897 microHz. Our amplitudes reveals that parent consistent modes spherical degree l=1. also provide m identifications for largest...
We present the first asteroseismological study for 42 massive ZZ Ceti stars based on a large set of fully evolutionary carbon$-$oxygen core DA white dwarf models characterized by detailed and consistent chemical inner profile envelope. Our sample comprise all with spectroscopic stellar masses between 0.72 $1.05M_{\odot}$ known to date. The analysis gives possibility ensemble properties pulsating cores, in particular thickness hydrogen envelope mass. A significant fraction our have mass high...
The VISCACHA (VIsible Soar photometry of star Clusters in tApii and Coxi HuguA) Survey is an ongoing project based on deep photometric observations Magellanic Cloud clusters, collected using the SOuthern Astrophysical Research (SOAR) telescope together with SOAR Adaptive Module Imager. Since 2015 more than 200 h time were used to observe about 130 stellar most them low mass (M < 104 M⊙) and/or located outermost regions Large Small Cloud. With this high-quality data set, we homogeneously...
Abstract SPARC4 is a new astronomical instrument developed entirely by Brazilian institutions, currently installed on the 1.6 m Perkin-Elmer telescope of Pico dos Dias Observatory. It allows user to perform photometric or polarimetric observations simultaneously in four SDSS bands ( g , r i and z ). In this paper, we describe control system for SPARC4. This composed S4ACS, S4ICS, S4GUI softwares associated hardware. S4ACS responsible controlling EMCCD scientific cameras (one each band)....
The periodic spectroscopic events in η Carinae are now well established and occur near the periastron passage of two massive stars a very eccentric orbit. Several mechanisms have been proposed to explain variations different spectral features, such as an eclipse by wind–wind collision (WWC) boundary, shell ejection from primary star or accretion its wind onto secondary. All them problems explaining all observed phenomena. To better understand nature cyclic events, we performed dense...
Using the SOuthern Astrophysical Research telescope (SOAR) Optical Imager at SOAR 4.1 m telescope, we report on discovery of five new massive pulsating white dwarf stars. Our results represent an increase about 20 per cent in number pulsators. We have detected both short and long periods, low high amplitude pulsation modes, covering whole range ZZ Ceti instability strip.
Variations in the pulsation arrival time of five independent frequencies DB white dwarf EC 20058-5234 individually imitate effects reflex motion induced by a planet or companion but are inconsistent when considered unison. The vary periodically 12.9 year cycle and undergo secular changes that with simple neutrino plus photon-cooling models. magnitude periodic variations increases period pulsations, possibly hinting corresponding physical mechanism is located near surface star. phase appears...
The spectral classification 'subdwarf A' (sdA) is given to stars showing H-rich spectra and sub-main-sequence surface gravities, but effective temperature lower than the zero-age horizontal branch. Their evolutionary origin an enigma. In this work, we discuss results of follow-up observations selected sdAs. We obtained time-resolved spectroscopy for 24 objects time-series photometry another 19 objects. For two targets, report both observations. confirm seven be new extremely low-mass white...
Abstract Trojan asteroids are small bodies orbiting around the L 4 or 5 Lagrangian points of a Sun-planet system. Due to their peculiar orbits, they provide key constraints Solar System evolution models. Despite numerous dedicated observational efforts in last decade, asteroid 2010 TK 7 has been only known Earth thus far. Here we confirm that recently discovered 2020 XL is second transient known. To study its orbit, used archival data from 2012 2019 and observed object 2021 three...
Using the The SOuthern Astrophysical Research (SOAR) 4.1-m telescope, we report on discovery of low amplitude pulsations for three stars previously reported as not-observed-to-vary (NOV) by Mukadam et al. and Mullally al., which are inside ZZ Ceti instability strip. With two pulsators discovered Castanheira have now found variability in a total five NOVs. We also eight new pulsating stars, not observed, bringing number known to 148. In addition, lowered detection limit 10 NOVs located near...
We provide a homogeneous set of structural parameters 83 star clusters located at the periphery Small Magellanic Cloud (SMC) and Large (LMC). The clusters' stellar density surface brightness profiles were built from deep, AO assisted optical images, uniform analysis techniques. obtained King Elson et al. model fittings. Integrated magnitudes masses (for subsample) are also provided. sample contains mostly low with distances between 4.5 6.5 kpc 1 LMC SMC centres, respectively. analysed their...
HR 1217 is a prototypical rapidly oscillating Ap star that has presented test to the theory of non-radial stellar pulsation. Prior observations showed clear pattern five modes with alternating frequency spacings 33.3 and 34.6 μHz, sixth mode at problematic spacing 50.0 μHz (which equals 1.5×33.3 μHz) high-frequency side. Asymptotic pulsation allowed for 34 but Hipparcos rule out such spacing. Theoretical calculations magnetoacoustic in stars by Cunha predicted there should be previously...
We report on the analysis of 436.1 hrs nearly continuous high-speed photometry pulsating DB white dwarf GD358 acquired with Whole Earth Telescope (WET) during 2006 international observing run, designated XCOV25. The Fourier transform (FT) light curve contains power between 1000 to 4000 microHz, dominant peak at 1234 microHz. find 27 independent frequencies distributed in 10 modes, as well numerous combination frequencies. Our discussion focuses a new asteroseismological GD358, incorporating...
The formation scenario of the Magellanic Bridge during an encounter between Large and Small Clouds $\sim200\,$Myr ago, as proposed by $N$-body models, would be imprinted in chemical enrichment kinematics its stars, sites ongoing star along extension. We present analysis 33 clusters using photometry obtained with SOAR 4-m telescope equipped adaptive optics for VISCACHA survey. performed a membership selection derived self-consistent ages, metallicities, distances reddening values via...
We report our analysis of the stability pulsation periods in DAV star (pulsating hydrogen atmosphere white dwarf) ZZ Ceti, also called R548. On basis observations that span 31 years, we conclude period 213.13 s observed Ceti drifts at a rate dP/dt ≤ (5.5 ± 1.9) × 10-15 s-1, after correcting for proper motion. Our results are consistent with previous values this mode and an improvement over them because larger time base. The characteristic timescale implied is ∣ P/ ≥ 1.2 Gyr, comparable to...
This paper analyses the Whole Earth Telescope observations of HL Tau 76, first discovered pulsating DA white dwarf. The star was observed during two campaigns. It a second priority target XCOV13 campaign in 1996 and one XCOV18 1999. 1999 reached 66.5% duty cycle. With total duration 18 days, frequency resolution achieved is 0.68 μHz. such resolution, we were able to find as many 78 significant frequencies power spectrum, which 34 are independent after removal all linear combinations. In...