Derek L. Buzasi
A5077606112- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astro and Planetary Science
- Astronomical Observations and Instrumentation
- Astrophysics and Star Formation Studies
- Gamma-ray bursts and supernovae
- Solar and Space Plasma Dynamics
- Adaptive optics and wavefront sensing
- History and Developments in Astronomy
- Geophysics and Gravity Measurements
- Atmospheric Ozone and Climate
- Geological and Geophysical Studies
- Scientific Computing and Data Management
- Space Exploration and Technology
- Distributed and Parallel Computing Systems
- Superconducting Materials and Applications
- Calibration and Measurement Techniques
- Astrophysical Phenomena and Observations
- Spacecraft Design and Technology
- Pulsars and Gravitational Waves Research
- Advanced Optical Sensing Technologies
- Optical Systems and Laser Technology
- Economic and Technological Innovation
- Space Science and Extraterrestrial Life
- Nuclear physics research studies
Florida Gulf Coast University
2014-2024
Florida State University
2013
Eureka Scientific
2009-2011
University of Washington
2009
United States Air Force Academy
2002-2008
Pennsylvania State University
1987-2008
The University of Sydney
2007
University of Warwick
2007
University of California, Berkeley
2000-2002
Valdosta State University
1997
The Kepler mission was designed to determine the frequency of Earth-sized planets in and near habitable zone Sun-like stars. is region where planetary temperatures are suitable for water exist on a planet's surface. During first 6 weeks observations, monitored 156,000 stars, five new exoplanets with sizes between 0.37 1.6 Jupiter radii orbital periods from 3.2 4.9 days were discovered. density Neptune-sized Kepler-4b similar that Neptune GJ 436b, even though irradiation level 800,000 times...
We report the detection of a planet whose orbit surrounds pair low-mass stars. Data from Kepler spacecraft reveal transits across both stars, in addition to mutual eclipses giving precise constraints on absolute dimensions all three bodies. The is comparable Saturn mass and size, nearly circular 229-day around its two parent eclipsing stars are 20% 69% as massive sun, have an eccentric 41-day orbit. motions bodies confined within 0.5 degree single plane, suggesting that formed circumbinary disk.
We have analyzed solar-like oscillations in ~1700 stars observed by the Kepler Mission, spanning from main-sequence to red clump. Using evolutionary models, we test asteroseismic scaling relations for frequency of maximum power (nu_max), large separation (Delta_nu) and oscillation amplitudes. show that difference Delta_nu-nu_max relation unevolved evolved can be explained different distributions effective temperature stellar mass, agreement with what is expected relations. For amplitudes,...
We have measured solar-like oscillations in red giants using time-series photometry from the first 34 days of science operations Kepler Mission. The light curves, obtained with 30 minute sampling, reveal clear a large sample G and K giants, extending luminosity clump down to bottom giant branch. confirm strong correlation between separation (Δν) frequency maximum power (νmax). focus on 50 low-luminosity stars (νmax > 100 μHz, L ≲ L☉) having high signal-to-noise ratios showing unambiguous...
The granulation pattern that we observe on the surface of Sun is due to hot plasma from interior rising photosphere where it cools down, and descends back into at edges granules. This visible manifestation convection taking place in outer part solar zone. Because red giants have deeper zones more extended atmospheres than Sun, cannot a priori assume scaled version granulation. Until now, neither observations nor 1D analytical models could put constraints giants. However, thanks...
Kepler Mission results are rapidly contributing to fundamentally new discoveries in both the exoplanet and asteroseismology fields. The data returned from unique terms of number stars observed, precision photometry for time series observations, temporal extent high duty cycle observations. As first mission provide extensive measurements on thousands over months years at a level hitherto possible only Sun, will vastly increase our knowledge stellar variability quiet solar-type stars. Here we...
We have studied solar-like oscillations in ~800 red-giant stars using Kepler long-cadence photometry. The sample includes ranging evolution from the lower part of branch to Helium main sequence. investigate relation between large frequency separation (Delta nu) and maximum power (nu_max) show that it is different for red giants than main-sequence stars, which consistent with evolutionary models scaling relations. distributions nu_max Delta nu are qualitative agreement a simple stellar...
Recently the number of main-sequence and subgiant stars exhibiting solar-like oscillations that are resolved into individual mode frequencies has increased dramatically. While only a few such data sets were available for detailed modeling just decade ago, Kepler mission produced suitable observations hundreds new targets. This rapid expansion in observational capacity been accompanied by shift analysis strategies to yield uniform derived stellar properties more quickly easily. We use...
We present preliminary asteroseismic results from Kepler on three G-type stars. The observations, made at one-minute cadence during the first 33.5d of science operations, reveal high signal-to-noise solar-like oscillation spectra in all stars: About 20 modes may be clearly distinguished each star. discuss appearance spectra, use frequencies and frequency separations to provide radii, masses ages stars, comment light these prospects for inference other solar-type stars that will observe.
ABSTRACT We examine the repeatability, reliability, and accuracy of differential exoplanet eclipse depth measurements made using InfraRed Array Camera (IRAC) on Spitzer Space Telescope during post-cryogenic mission. have re-analyzed an existing 4.5 μ m data set, consisting 10 observations XO-3b system secondary eclipse, seven different techniques for removing correlated noise. find that, average, a given technique, estimate is repeatable from epoch to within 156 parts per million (ppm). Most...
The Large Synoptic Survey Telescope is designed to provide an unprecedented optical imaging dataset that will support investigations of our Solar System, Galaxy and Universe, across half the sky over ten years repeated observation. However, exactly how LSST observations be taken (the observing strategy or "cadence") not yet finalized. In this dynamically-evolving community white paper, we explore detailed performance anticipated science expected depend on small changes strategy. Using...
NASA's re-purposed Kepler mission—dubbed K2—has brought new scientific opportunities that were not anticipated for the original mission. One science goal makes optimal use of K2's capabilities, in particular its 360° ecliptic field view, is galactic archaeology—the study evolution Galaxy from fossil stellar record. The thrust this research to exploit high-precision, time-resolved photometry K2 order detect oscillations red giant stars. This asteroseismic information can provide estimates...
We present the discovery of TOI-197.01, first transiting planet identified by Transiting Exoplanet Survey Satellite (TESS) for which asteroseismology host star is possible. TOI-197 (HIP116158) a bright (V=8.2 mag), spectroscopically classified subgiant oscillates with an average frequency about 430 muHz and displays clear signature mixed modes. The oscillation amplitude confirms that redder TESS bandpass compared to Kepler has small effect on oscillations, supporting expected yield thousands...
Aims.We present the most precise light curve ever obtained of a detached eclipsing binary star and use it investigate inclusion non-linear limb darkening laws in models binaries. This curve, bright system β Aurigae, was using tracker aboard wire satellite contains 30 000 datapoints with point-to-point scatter 0.3 mmag.
We present the first results from Transiting Exoplanet Survey Satellite (TESS) on rotational and pulsational variability of magnetic chemically peculiar A-type stars. analyse TESS 2-min cadence data sectors 1 2 a sample 83 Five new rapidly oscillating Ap (roAp) stars are announced. One these pulsates with periods around 4.7 min, making it shortest period roAp star known to date. Four out five multiperiodic. Three singly periodic one show presence mode splitting. Individual frequencies...
We present an analysis of the first 20-second cadence light curves obtained by TESS space telescope during its extended mission. find a precision improvement data compared to 2-minute for bright stars when binned same (~10-25% better T<~8 mag, reaching equal at T~13 mag), consistent with pre-flight expectations based on differences in cosmic ray mitigation algorithms. two results enabled this improvement. First, we use detect oscillations three solar analogs (gamma Pav, zeta Tuc and pi Men)...
Abstract The consistently low activity level of the old solar analog 51 Peg not only facilitated discovery first hot Jupiter, but also led to suggestion that star could be experiencing a magnetic grand minimum. However, 50 yr time series showing minimal chromospheric variability associated with onset weakened braking (WMB), where sufficiently slow rotation disrupts cycling and production large-scale fields by stellar dynamo, thereby shrinking Alfvén radius inhibiting efficient loss angular...
The large number of stars for which uninterrupted high-precision photometric timeseries data are being collected with \textit{Kepler} and CoRoT initiated the development automated methods to analyse stochastically excited oscillations in main-sequence, subgiant red-giant stars. Aims: We investigate differences results global oscillation parameters G K due different definitions. also uncertainties originating from stochastic nature oscillations. Methods: For this investigation we use Kepler...
Mass estimates of K giants are generally very uncertain. Traditionally, stellar masses single field stars determined by comparing their location in the Hertzsprung-Russell diagram with evolutionary models. Applying an additional method to determine mass is therefore significant interest for understanding evolution. We present time series analysis 11 recently observed WIRE satellite. With this comprehensive sample, we report first confirmation that characteristic acoustic frequency, νmax, can...
Since the onset of `space revolution' high-precision high-cadence photometry, asteroseismology has been demonstrated as a powerful tool for informing Galactic archaeology investigations. The launch NASA TESS mission enabled seismic-based inferences to go full sky -- providing clear advantage large ensemble studies different Milky Way components. Here we demonstrate its potential investigating Galaxy by carrying out first asteroseismic study red giant stars observed TESS. We use sample 25...
We report the discovery of a warm sub-Saturn, TOI-257b (HD 19916b), based on data from NASA's Transiting Exoplanet Survey Satellite (TESS). The transit signal was detected by TESS and confirmed to be planetary origin radial velocity observations. An analysis photometry, Minerva-Australis, FEROS, HARPS velocities, asteroseismic stellar oscillations reveals that has mass $M_P=0.138\pm0.023$\,$\rm{M_J}$ ($43.9\pm7.3$\,$M_{\rm \oplus}$), radius $R_P=0.639\pm0.013$\,$\rm{R_J}$...
There is an intricate relationship between the organization of large-scale magnetic fields by a stellar dynamo and rate angular momentum loss due to magnetized winds. An essential ingredient for operation Coriolis force, which imprints organizing flows on global convective patterns inhibits complete cancellation bipolar regions. Consequently, it natural expect rotational threshold action efficient that mediates through braking. Here we present new observational constraints braking...