A. Hourihane
A5082180004- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astronomical Observations and Instrumentation
- Gamma-ray bursts and supernovae
- Astro and Planetary Science
- Galaxies: Formation, Evolution, Phenomena
- Astrophysical Phenomena and Observations
- Astronomical and nuclear sciences
- Atmospheric Ozone and Climate
- Scientific Research and Discoveries
- History and Developments in Astronomy
- Vitamin D Research Studies
- Bone health and osteoporosis research
- Archaeology and ancient environmental studies
- Geophysics and Gravity Measurements
- SAS software applications and methods
- Adaptive optics and wavefront sensing
- Solar and Space Plasma Dynamics
- Leaf Properties and Growth Measurement
- Blind Source Separation Techniques
- Pulsars and Gravitational Waves Research
- Pacific and Southeast Asian Studies
- Australian Indigenous Culture and History
- Nutrition, Genetics, and Disease
University of Cambridge
2014-2024
Osservatorio Astrofisico di Catania
2018
Institute of Astronomy
2017
Universidad Complutense de Madrid
2014
University College Cork
2005-2011
(Abridged) We have used the atmospheric parameters, [alpha/Fe] abundances and radial velocities, determined from Gaia-ESO Survey GIRAFFE spectra of FGK-type stars (iDR1), to provide a chemo-kinematical characterisation disc stellar populations. focuss on subsample 1016 with high quality covering volume |Z|<4.5kpc R in range 2-13kpc. identified thin thick separation vs [M/H] plane, thanks presence low-density region number density distribution. The seem lie progressively thinner layers...
The Gaia-ESO Survey is obtaining high-quality spectroscopic data for about 10^5 stars using FLAMES at the VLT. UVES high-resolution spectra are being collected 5000 FGK-type stars. These analyzed in parallel by several state-of-the-art methodologies. Our aim to present how these analyses were implemented, discuss their results, and describe a final recommended parameter scale defined. We also precision (method-to-method dispersion) accuracy (biases with respect reference values) of...
In the last 15 years different ground-based spectroscopic surveys have been started (and completed) with general aim of delivering stellar parameters and elemental abundances for large samples Galactic stars, complementing Gaia astrometry. Among those surveys, Gaia-ESO Public Spectroscopic Survey (GES), only one performed on a 8m class telescope, was designed to target 100,000 stars using FLAMES ESO VLT (both Giraffe UVES spectrographs), covering all Milky Way populations, special focus open...
Context. The Gaia-ESO Public Spectroscopic Survey is an ambitious project designed to obtain astrophysical parameters and elemental abundances for 100 000 stars, including large representative samples of the stellar populations in Galaxy, a well-defined sample 60 (plus 20 archive) open clusters. We provide internally consistent results calibrated on benchmark stars star clusters, extending across very wide range ages. This provides legacy data set intrinsic value, equally wide-ranging...
We study the relationship between age, metallicity, and alpha-enhancement of FGK stars in Galactic disk. The results are based upon analysis high-resolution UVES spectra from Gaia-ESO large stellar survey. explore limitations observed dataset, i.e. accuracy parameters selection effects that caused by photometric target preselection. find colour magnitude cuts survey suppress old metal-rich young metal-poor stars. This suppression may be as high 97% some regions age-metallicity relationship....
In the current era of large spectroscopic surveys Milky Way, reference stars for calibrating astrophysical parameters and chemical abundances are paramount importance. We determine elemental Mg, Si, Ca, Sc, Ti, V, Cr, Mn, Co Ni our predefined set Gaia FGK benchmark stars. By analysing high-resolution high-signal to noise spectra taken from several archive datasets, we combined results eight different methods on a line-by-line basis. perform detailed homogeneous analysis systematic...
(Abridged) We analyzed the stellar parameters and radial velocities of ~1200 stars in five bulge fields as determined from Gaia-ESO survey data (iDR1). use VISTA Variables The Via Lactea (VVV) photometry to obtain reddening values by using a semi-empirical T_eff-color calibration. From Gaussian decomposition metallicity distribution functions, we unveil clear bimodality all fields, with relative size components depending specific position on sky. In agreement some previous studies, find mild...
Aims. Until recently, most high-resolution spectroscopic studies of the Galactic thin and thick discs were mostly confined to objects in solar vicinity. Here we aim at enlarging volume which individual chemical abundances are used characterise discs, using first internal data release Gaia-ESO survey (GES iDR1).
The spatial distribution of elemental abundances in the disc our Galaxy gives insights both on its assembly process and subsequent evolution, stellar nucleogenesis different elements. Gradients can be traced using several types objects as, for instance, (young old) stars, open clusters, HII regions, planetary nebulae. We aim at tracing radial distributions elements produced through nucleosynthetic channels -the alpha-elements O, Mg, Si, Ca Ti, iron-peak Fe, Cr, Ni Sc - by Gaia-ESO idr4...
Photometry alone is not sufficient to unambiguously distinguish between ultra-faint star clusters and dwarf galaxies because of their overlap in morphological properties. Here we report on VLT/GIRAFFE spectra candidate member stars two recently discovered satellites Reticulum 2 Horologium 1, obtained as part the ongoing Gaia-ESO Survey. We identify 18 members 5 1. find have a velocity dispersion ~3.22 km/s, implying M/L ratio ~ 500. inferred stellar parameters for all candidates mean...
The radial metallicity distribution in the Galactic thin disc represents a crucial constraint for modelling formation and evolution. Open clusters allow us to derive both its evolution over time. In this paper we perform first investigation of present-day based on [Fe/H] determinations late type members pre-main-sequence clusters. Because their youth, these are therefore essential tracing current inter-stellar medium metallicity. We used products Gaia-ESO Survey analysis 12 young regions...
Context. Since July 2014, the Gaia mission has been engaged in a high-spatial-resolution, time-resolved, precise, accurate astrometric, and photometric survey of entire sky. Aims. We present Science Alerts project, which operation since 1 June 2016. describe system developed to enable discovery publication transient events as seen by . Methods. outline data handling, timings, performances, we detection algorithms filtering procedures needed manage high false alarm rate. identify two classes...
The discovery of lithium-rich giants contradicts expectations from canonical stellar evolution. Here we report on the serendipitous 20 Li-rich observed during Gaia-ESO Survey, which includes first nine giant stars known towards CoRoT fields. Most our have near-solar metallicities and parameters consistent with being before luminosity bump. This is difficult to reconcile deep mixing models proposed explain lithium enrichment, because these can only operate at later evolutionary stages: or...
The Gaia-ESO Survey is a large public spectroscopic survey that aims to derive radial velocities and fundamental parameters of about 10^5 Milky Way stars in the field clusters. Observations are carried out with multi-object optical spectrograph FLAMES, using simultaneously medium resolution (R~20,000) GIRAFFE high (R~47,000) UVES spectrograph. In this paper, we describe methods software used for data reduction, derivation velocities, quality control FLAMES-UVES spectra. Data reduction has...
Context. Chemically inhomogeneous populations are observed in most globular clusters, but not open clusters. Cluster mass seems to play a key role the existence of multiple populations.
Abridged: We used the fourth internal data release of Gaia-ESO survey to characterize bulge chemistry, spatial distribution, kinematics, and compare it chemically with thin thick disks. The sample consist on ~2500 red clump stars in 11 fields ($-10^\circ\leq l\leq+8^\circ$ $-10^\circ\leq b\leq-4^\circ$), a set ~6300 disk selected for comparison. MDF is confirmed be bimodal across whole sampled area, metal-poor dominating at high latitudes. metal-rich exhibit bar-like kinematics display...
Context. The nature of the metallicity gradient inside solar circle (RGC < 8 kpc) is poorly understood, but studies Cepheids and a small sample open clusters suggest that it steepens in inner disk.
Stellar evolution models predict that internal mixing should cause some sodium overabundance at the surface of red giants more massive than ~ 1.5--2.0 Msun. The aluminium abundance not be affected. Nevertheless, observational results disagree about presence and/or degree Na and Al overabundances. In addition, Galactic chemical adopting different stellar yields lead to quite predictions for behavior [Na/Fe] [Al/Fe] versus [Fe/H]. Overall, observed trends these abundances with metallicity are...
Gaia and its complementary spectroscopic surveys combined will yield the most comprehensive database of kinematic chemical information stars in Milky Way. The FGK benchmark play a central role this matter as they are calibration pillars for atmospheric parameters abundances various surveys. analyses done by combining different methods, results be affected systematic uncertainties inherent each method. In paper we explore some these uncertainties. We determined line Ca, Cr, Mn Co four using...
We show that non-magnetic models for the evolution of pre-main-sequence (PMS) stars *cannot* simultaneously describe colour-magnitude diagram (CMD) and pattern lithium depletion seen in cluster young, low-mass surrounding $\gamma^2$ Velorum. The age 7.5+/-1 Myr inferred from CMD is much younger than implied by strong Li M-dwarfs occurs at redder colours predicted. epoch which a star given mass depletes its surface temperature are both dependent on radius. demonstrate if have radii ~10 per...
Context. Open clusters are recognised as excellent tracers of Galactic thin-disc properties. At variance with intermediate-age and old open clusters, for which a significant number studies is now available, younger than ≲150 Myr have been mostly overlooked in terms their chemical composition until recently (with few exceptions). On the other hand, previous investigations seem to indicate an anomalous behaviour young includes (but not limited to) slightly sub-solar iron (Fe) abundances...
The Gaia-ESO survey (GES) is now in its fifth and last year of observations, has already produced tens thousands high-quality spectra stars all Milky Way components. This paper presents the strategy behind selection astrophysical calibration targets, ensuring that GES results on radial velocities, atmospheric parameters, chemical abundance ratios will be both internally consistent easily comparable with other literature results, especially from large spectroscopic surveys Gaia. particularly...
The spatial distribution of elemental abundances and their time evolution are among the major constraints to disentangle scenarios formation Galaxy. We used sample open clusters available in final release Gaia-ESO survey trace Galactic radial abundance iron ratio gradients, evolution. selected member stars 62 clusters, with ages from 0.1 about 7~Gyr, located thin disc at Galactocentric radii 6 21~kpc. analysed shape resulting [Fe/H] gradient, average gradients [El/H] [El/Fe] combining...
The last decade has seen a revolution in our knowledge of the Galaxy thanks to Gaia and asteroseismic space missions ground-based spectroscopic surveys. To complete this picture, it is necessary map ages its stellar populations. During recent years, dependence on time abundance ratios involving slow (s) neutron-capture $\alpha$ elements (called chemical-clocks) been used provide estimates ages, usually limited volume close Sun. We aim analyse relations chemical clocks Galactic disc extending...
We present the first results of EMBLA survey (Extremely Metal-poor BuLge stars with AAOmega), aimed at finding metal-poor in Milky Way bulge, where oldest should now preferentially reside. utilizes SkyMapper photometry to pre-select candidates, which are subsequently confirmed using AAOmega spectroscopy. describe discovery and analysis four bulge giants −2.72 ≤ [Fe/H] −2.48, lowest metallicity studied high-resolution spectroscopy date. Using FLAMES/UVES spectra through Gaia-ESO Survey we...