A5028961446- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Astronomical Observations and Instrumentation
- Gamma-ray bursts and supernovae
- Atomic and Molecular Physics
- Inorganic Fluorides and Related Compounds
- Galaxies: Formation, Evolution, Phenomena
- Astrophysical Phenomena and Observations
- Historical Studies on Spain
- History and Developments in Astronomy
- X-ray Spectroscopy and Fluorescence Analysis
- demographic modeling and climate adaptation
- Molecular Spectroscopy and Structure
- Nuclear physics research studies
- Bee Products Chemical Analysis
- Extraction and Separation Processes
- Electron and X-Ray Spectroscopy Techniques
- Inorganic Chemistry and Materials
- Atmospheric Ozone and Climate
- Adaptive optics and wavefront sensing
- Quantum Dots Synthesis And Properties
- Advancements in Battery Materials
- Solar and Space Plasma Dynamics
SUNY Geneseo
2007-2024
Kitt Peak National Observatory
2010
Indiana University Bloomington
2002-2009
Vanderbilt University
2009
École Polytechnique Fédérale de Lausanne
2009
University of Hawaii at Hilo
2009
Johns Hopkins University
2009
University of Baltimore
2009
University of Florida
2004-2006
We present the elemental abundances of HE1327-2326, most iron-deficient star known, determined from a comprehensive analysis spectra obtained with Subaru Telescope High Dispersion Spectrograph.
WIYN/Hydra spectroscopy (at R~15,000) of the moderately metal-rich Praesepe and Hyades open clusters was used to study their main sequence (MS) iron ([Fe/H]) lithium (A(Li)) abundances. Self-consistent [Fe/H] Li analyses these consistent age, which we re-evaluate, confirms they have provides a foundation investigate poorly understood G-dwarf F-dwarf Li-depletions. Neither phenomenon agrees with standard stellar evolution theory, but possible explanations abound. We supplement our A(Li)...
The early F dwarf star ``J37'' in the open cluster NGC6633 shows an unusual pattern of photospheric abundances, including order magnitude enhancement lithium and iron-peak elements, but under-abundance carbon. As a consequence its thin convection zone these anomalies have been attributed to either radiative diffusion or accretion hydrogen-depleted material. By comparing high resolution VLT/UVES spectra J37 (and other stars NGC 6633) with syntheses Be ii doublet region at 3131 Ang, we...
<i>Aims. <i/>Employing photometric rotation periods for solar-type stars in NGC 1039 [M 34], a young, nearby open cluster, we use its mass-dependent period distribution to derive the cluster's age distance independent way, i.e., so-called gyrochronology method.<i>Methods. <i/>We present an analysis of 55 new periods, using light curves derived from differential photometry, solar type cluster 34]. We also exploit results recently-completed, standardized, homogeneous <i>BVI<i/>c CCD survey...
We present WIYN/Hydra spectra of 34 red giant candidate members NGC 188, which, together with WOCS and Gaia data yield 23 single members, 6 binary 4 nonmembers, 1 nonmember. report [Fe/H] for 29 derive [Fe/H]$_{\rm{NGC188}}$ = +0.064 $\pm$ 0.018 dex ($\sigma_{\mu}$) (sky A(Fe)$_{\odot}$ 7.520 0.015 ($\sigma_{\mu}$)). discuss effects on the derived parameters varying Yale-Yonsei isochrones to fit turnoff. take advantage coolest, lowest-gravity giants refine line list near Li 6707.8 \AA. Using...
Abstract We consider WIYN/Hydra spectra of 329 photometric candidate members the 420 Myr old open cluster M48 and report lithium detections or upper limits for 234 likely members. The 171 single define a number notable Li-mass trends, some delineated even more clearly than in Hyades/Praesepe: giants are consistent with subgiant Li dilution prior MS depletion due to rotational mixing. A dwarfs (8600–7700 K) have higher presumed initial abundance. Two five late (7700–7200 Li-rich, possibly...
We report the discovery of significant depletion Li on surfaces F dwarf stars in 150 Myr old open cluster M35, analagous to a feature 700 Hyades that has been referred as "Li gap." have caught gap act forming: using high-resolution, high signal-to-noise ratio WIYN/Hydra observations, we detect all but few M35 stars; maximum lies at least 0.6-0.8 dex below minimally depleted (or undepleted) stars. The region (1) is quite wide, with clear seen from 6000 6700 K or hotter, (2) shows dispersion...
We present results from a near-infrared spectroscopic study of candidate brown dwarfs and low mass stars in the young cluster NGC 2024. Using FLAMINGOS on KPNO 2.1m 4m telescopes, we have obtained spectra ~70 new members classified them via prominent J H band water absorption features. Derived spectral types range ~M1 to later than M8 with typical classification errors 0.5-1 subclasses. By combining these JHK photometry, place objects H-R diagram use pre-main sequence evolutionary models...
Hydra spectra of 85 G-K dwarfs in the young cluster, M35, near Li 6708 Angstrom line region are analyzed. From velocities and Gaia astrometry, 78 likely single-star members which, combined with previous work, produces 108 T_eff ranging from 6150 to 4000 K as defined by multicolor, broad-band photometry, E(B-V ) = 0.20 [Fe/H] -0.15, though there indications metallicity may be closer solar. A(Li) follows a well-delineated decline 3.15 for hottest stars upper limits <= 1.0 among coolest dwarfs....
Boron provides a special probe below the stellar surface since it survives to greater depths than do Li and Be. To search for B depletions we have observed in 13 F G dwarfs with large Be depletions; comparison also obtained spectra of five stars that are undepleted We used HST STIS obtain I resonance line at 2497 Å. The spectral resolution is 30,000 or 114,000, median signal-to-noise ratio 70 pixel-1. New been Keck HIRES four standard ~48,000 resolution. Abundances determined by spectrum...
We present deep BVI observations of the core M35 and a nearby comparison field obtained at WIYN 3.5 m telescope under excellent seeing conditions. These probe to V > 26 display lower main sequence in BV VI CMDs down = 23.3 24.6, respectively. At these faint magnitudes background Galactic stars are far more numerous than cluster stars, yet by using smoothing technique CMD density distribution subtraction we able recover fiducial luminosity function 24.6. find location be consistent with...
Using WIYN/Hydra observations, we report the first discovery of a super-Li-rich dwarf, star J37 Hyades-aged cluster NGC 6633. This star's gargantuan surface Li abundance A(Li) = 4.29 ± 0.07 [A(X) ≡ 12 + log(NX/NH)] is factor 10 larger than abundances observed in meteorites and minimally depleted young open stars. may be smoking gun for action diffusion, models which predict existence striking overabundances due to radiative acceleration (the "Li peak") extremely narrow Teff range 6900-7100...
We obtained JHK images and low-resolution JH spectra in the embedded young cluster Serpens cloud Main core (also known as North). determined spectral types for 15 previously identified members (for 5 of them first time), 1 new candidate, 11 stars that appear to be field interlopers. Extinction, which we derived an analytical expression, was by taking SpT near-IR excess into account. The location on Hertzsprung-Russell diagram indicates probed a low-mass population (0.05 - 1.5 Msol),...
WIYN/Hydra spectra (R $\sim$ 13,500, signal-to-noise pixel$^{-1}$ = 50-1000) of a 400 $\unicode{x212B}$ region around Li 6708 are used to determine radial and rotational velocities for 287 photometrically selected candidate members the open cluster M48. The sample ranges from turnoff A stars late-K dwarfs eight giants. We combine our $V_{\rm{RAD}}$ measurements power spectrum analysis with parallax proper motion data Gaia DR2 evaluate membership multiplicity. classify 152 as single members,...
We present $UBVRI$ photometry of 8702 stars in a $0.5 ^\circ\times0.5 ^\circ$ field the direction NGC 7142, taken with Half Degree Imager (HDI) at WIYN 0.9-meter telescope, to improve knowledge this cluster's basic parameters. Our spans ranges 10.6 - 20.4 mag $U$, 22.0 $B$, 10.0 21.8 $V$, 9.2 20.7 $R$, and 8.5 19.9 $I$. Using color-color diagrams that employ all four color combinations include versus $B-V$, we derive reddening-metallicity relation for cluster, preferred values $E(B-V$) =...
Open clusters (OC) of 1-3 Gyr age contain intermediate-to-low-mass stars in evolutionary phases multiple relevance to understanding Li evolution. Stars leaving the main sequence (MS) from hot side Lithium dip (LD) at a fixed can include range mass, varying degrees core degeneracy, and helium ignition under quiescent or flash conditions. An ongoing survey significant sample giant branch below LD key open has revealed patterns that supply critical clues underlying source variation among...
Abstract We have analyzed high-dispersion spectra in the Li 6708 Å region for 167 stars within anticenter cluster NGC 2204. From 105 probable members, abundance analysis of 45 evolved produces [Fe/H] = −0.40 ± 0.12, [Si/Fe] 0.14 [Ca/Fe] 0.29 0.07, and [Ni/Fe] −0.12 0.10, where quoted errors are standard deviations. With E ( B − V ) 0.07 m M 0 13.12, appropriate isochrones provide an excellent match from main sequence through tip giant branch age 1.85 0.05 Gyr. spectrum synthesis A (Li) below...
We have analyzed high-dispersion spectra in the Li 6708 Angstrom region for 167 stars within anticenter cluster, NGC 2204. From 105 probable members, abundance analysis of 45 evolved produces [Fe/H] = -0.40 +/- 0.12, [Si/Fe] 0.14 [Ca/Fe] 0.29 0.07, and [Ni/Fe] -0.12 0.10, where quoted errors are standard deviations. With E(B-V) 0.07 (m-M)_0 13.12, appropriate isochrones provide an excellent match from main sequence through tip giant branch age 1.85 0.05 Gyr. spectrum synthesis A(Li) below...
Abstract We present a spectroscopic analysis of 7774 Å O i triplet abundances, 8498–8662 Ca ii chromospheric activity, and rotation in the Pleiades open cluster, with objective thoroughly examining overabundance trends observed cool cluster dwarfs, to thereby make clear cause that trend. High-dispersion, contemporaneous spectra triplet, H α spectral regions 41 dwarfs were acquired using Hydra on WIYN 3.5 m telescope. Our emission equivalent-width data exhibit strong positive correlation...
We consider WIYN/Hydra spectra of 329 photometric candidate members the 420-Myr-old open cluster M48, and report Lithium detections or upper limits for 234 likely members. The 171 single define a number notable Li-mass trends, some delineated even more clearly than in Hyades/Praesepe: giants are consistent with subgiant Li dilution prior MS depletion due to rotational mixing. A dwarfs (8600-7700K) have higher presumed initial abundance. Two five late (7700- 7200K) Li-rich, possibly...