A5029570243- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Astronomy and Astrophysical Research
- Astro and Planetary Science
- Gamma-ray bursts and supernovae
- Astronomical and nuclear sciences
- Astronomical Observations and Instrumentation
- Galaxies: Formation, Evolution, Phenomena
- History and Developments in Astronomy
- Nuclear physics research studies
- Astrophysical Phenomena and Observations
- Solar and Space Plasma Dynamics
- Adaptive optics and wavefront sensing
- Geological and Geophysical Studies
- Scientific Research and Discoveries
- Pulsars and Gravitational Waves Research
- High-pressure geophysics and materials
- Geophysics and Gravity Measurements
- Dental Radiography and Imaging
- Bone health and treatments
- Nuclear Physics and Applications
- Bone health and osteoporosis research
- Viral gastroenteritis research and epidemiology
- Historical Astronomy and Related Studies
- Metallurgy and Cultural Artifacts
Mount Stromlo Observatory
2013-2025
Australian National University
2016-2025
ARC Centre of Excellence for All-sky Astrophysics
2018-2025
Kolon Industries (South Korea)
2025
ASTRO-3D
2019-2024
ACT Government
2014-2024
Australian Research Council
2019-2023
National Heart Institute
2022-2023
Monash University
2013
University of North Carolina at Chapel Hill
2004-2008
The GALAH survey is a large high-resolution spectroscopic using the newly commissioned HERMES spectrograph on Anglo-Australian Telescope. provides (R ~28,000) spectra in four passbands for 392 stars simultaneously over 2 degree field of view. goal to unravel formation and evolutionary history Milky Way, fossil remnants ancient star events which have been disrupted are now dispersed throughout Galaxy. Chemical tagging seeks identify such solely from their common unique chemical signatures;...
We have conducted a differential elemental abundance analysis of unprecedented accuracy (∼0.01 dex) the Sun relative to 11 solar twins from Hipparcos catalog and 10 analogs planet searches. find that shows characteristic signature with ≈20% depletion refractory elements volatile in comparison twins. The differences correlate strongly condensation temperatures elements. This peculiarity also holds comparisons known close-in giant planets while majority found not such radial velocity...
We use high-precision photometry of red-giant-branch (RGB) stars in 57 Galactic globular clusters (GCs), mostly from the ‘Hubble Space Telescope (HST) UV Legacy Survey GCs’, to identify and characterize their multiple stellar populations. For each cluster pseudo-two-colour diagram (or ‘chromosome map’) is presented, built with a suitable combination magnitudes F275W, F336W, F438W, F814W filters that maximizes separation between In chromosome map most GCs (type-I clusters), separate two...
The Galactic Archaeology with HERMES (GALAH) survey is a large-scale stellar spectroscopic of the Milky Way and designed to deliver chemical information complementary large number stars covered by $Gaia$ mission. We present GALAH second public data release (GALAH DR2) containing 342,682 stars. For these stars, collaboration provides parameters abundances for up 23 elements community. Here we target selection, observation, reduction detailed explanation how spectra were analysed estimate...
We present a homogeneous chemical abundance analysis of 16 elements in 190 metal-poor Galactic halo stars (38 program and 152 literature objects). The sample includes 171 with [Fe/H] ⩽ −2.5, which 86 are extremely metal poor, −3.0. Our include 10 new objects −3.5. identify "normal" measure the trends between [X/Fe] [Fe/H], as well dispersion about mean trend for this sample. Using trend, we that chemically peculiar relative to at same metallicity. These unusual CEMP-no objects, one star high...
We present the metallicity results from ARGOS spectroscopic survey of Galactic bulge. Our aim is to understand formation bulge: did it form via mergers, as expected Lambda CDM theory, or disk instabilities, suggested by its boxy/peanut shape, both? have obtained spectra for 28,000 stars at a spectral resolution R = 11,000. From these spectra, we determined stellar parameters and distances an accuracy < 1.5 kpc. The in inner Galaxy span large range [Fe/H], -2.8 [Fe/H] +0.6. spatial...
Type Ia supernovae are key tools for measuring distances on a cosmic scale. They generally thought to be the thermonuclear explosion of an accreting white dwarf in close binary system. The nature mass donor is still uncertain. In single-degenerate model it main-sequence star or evolved star, whereas double-degenerate another dwarf. We show that velocity structure absorbing material along line sight 35 type tends blueshifted. These structures likely signatures gas outflows from supernova...
We summarize radial velocity studies of selected stars in the old, distant clusters Berkeley 20, 21, NGC 2141, 29, and 31. Cluster members are identified using optical infrared color-magnitude diagrams, as well velocities derived from high-resolution echelle spectra. Three M67 were observed similarly, those compare extremely with prior measures. Mean cluster determined. also employ highest quality spectra to analyze chemical compositions all six for [Fe/H], abundances α-elements, iron-peak...
... 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...
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.
Based on high-resolution spectra obtained with the MIKE spectrograph Magellan telescopes, we present detailed elemental abundances for 20 red giant stars in outer Galactic disk, located at Galactocentric distances between 9 and 13 kpc. The disk sample is complemented samples of giants from inner solar neighborhood, analyzed using identical methods. For beyond 10 kpc, only find chemical patterns associated local thin even far above plane. Our results show that relative densities thick disks...
We discuss the carbon-normal and carbon-rich populations of Galactic halo stars having [Fe/H] ≲ −3.0, utilizing chemical abundances from high-resolution, high signal-to-noise model-atmosphere analyses. The C-rich population represents ∼28% below = −3.1, with present sample comprising 16 CEMP-no stars, two others ∼ −5.5 uncertain classification. is O-rich ([O/Fe] ≳ +1.5); light elements Na, Mg, Al are enhanced relative to Fe in half sample; for Z > 20 (Ca) there little evidence enhancements...
We present the kinematic results from our ARGOS spectroscopic survey of Galactic bulge Milky Way. Our aim is to understand formation bulge. examine kinematics about 17,400 stars in located within 3.5 kpc centre, identified 28,000 star survey. determine if has been internally driven disk instabilities as suggested by its boxy shape, or mergers have played a significant role expected Lambda CDM simulations. From velocity measurements across latitudes b = -5 deg, -7.5 deg and -10 we find be...
Multi-band Hubble Space Telescope photometry reveals that the main sequence, sub-giant, and red-giant branch of globular cluster NGC 6752 splits into three components in close analogy with distinct segments along its horizontal stars. These triple sequences are consistent stellar groups: a population chemical composition similar to field-halo stars (Population a), Population (c) enhanced sodium nitrogen, depleted carbon oxygen, an helium abundance (ΔY ∼ 0.03), (b) intermediate (between...
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...
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...
We present radial velocities and chemical abundances for nine stars in the old, distant open clusters Be 18, 21, 22, 32, PWM 4. For 18 4, these are first abundance measurements. Combining our data with literature results produces a compilation of some 68 measurements 49 unique clusters. this combined sample, we study as function distance, age, metallicity. confirm that metallicity gradient outer disk is flatter than vicinity solar neighborhood. also metal-poor enhancements ratios [alpha/Fe]...
We present an AAOmega spectroscopic study of red giant stars in Bootes I, which is ultra-faint dwarf galaxy, and Segue 1, suggested to be either extremely low-luminosity galaxy or a star cluster. Our focus quantifying the mean abundance dispersion iron carbon, searching for distant radial-velocity members, these systems. The primary conclusion our investigation that spread carbon both I 1 large. For 4 16 velocity members have [C/H] < ~-3.1, while 2 > ~-2.3, suggesting range Delta[C/H] ~ 0.8....
Near the minor axis of Galactic bulge, at latitudes b < -5 degrees, red giant clump stars are split into two components along line sight. We investigate this using three fields from ARGOS survey that lie on (l,b) = (0,-5), (0,-7.5), (0,-10) degrees. The separation is evident for with [Fe/H] > -0.5 in higher-latitude fields, but not field Stars do show split. compare spatial distribution and kinematics predictions an evolutionary N-body model a bulge grew disk via bar-related instabilities....
We present a high resolution spectroscopic analysis of 62 red giants in the Milky Way globular cluster NGC5286. have determined abundances representative light proton-capture, alpha, Fe-peak and neutron-capture element groups, combined them with photometry multiple sequences observed along colour-magnitude diagram. Our principal results are: (i) broad, bimodal distribution s-process abundance ratios, two main s-poor s-rich groups; (ii) substantial star-to-star Fe variations, stars having...
We present the chemical compositions for eight bright giants in globular cluster NGC 1851. Our analysis reveals large star-to-star abundance variations and correlations of light elements O, Na, Al, a feature found every well-studied cluster. However, 1851 also exhibits s-process Zr La. These are correlated with Al anticorrelated O. Furthermore, La abundances appear to around two distinct values. A recent study revealed double subgiant branch data reinforce notion that there stellar...
We present CN and CH indices CaII triplet metallicities for 34 giant stars chemical abundances 33 elements in 14 giants the globular cluster M2. Assuming program are members, our analysis reveals (i) an extreme variation line strengths, (ii) a metallicity dispersion with dominant peak at [Fe/H] = -1.7 smaller peaks -1.5 -1.0, (iii) star-to-star abundance variations correlations light O, Na, Al Si (iv) large (and possibly bimodal) distribution of all produced mainly via s-process solar system...
We describe the motivation, field locations and stellar selection for ARGOS spectroscopic survey of 28,000 stars in bulge inner disk Milky Way galaxy across latitudes b = -5 deg to -10 deg. The primary goal this is constrain formation processes establish whether it predominantly a merger or instability remnant. From spectra (R 11,000), we have measured radial velocities determined parameters, including metallicities [alpha/Fe] ratios. Distances were estimated from derived parameters about...
We present high-precision multi-band photometry for the globular cluster (GC) M2. combine analysis of photometric data obtained from Hubble Space Telescope UV Legacy Survey Galactic GCs GO-13297, with chemical abundances by Yong et al.(2014), and compare models in order to analyze multiple stellar sequences we identified color-magnitude diagram (CMD). find three main components, composed metal-poor, metal-intermediate, metal-rich stars (hereafter referred as population A, B, C,...