David Barrado (INTA-CSIC)
9/18/17, 5:15 PM
Different age-dating techniques can produce very different results. The main culprit for this state of affairs is the lack of a universal age scale and the absence of a systematic and robust cross-calibration of the various methods. This situation can change due to the availability of several massive database (Gaia, Cosmic-DANCe, Kepler, Gaia-ESO) and the development of state-of-the-art...
Emanuele Bertone (INAOE - Puebla)
9/18/17, 5:17 PM
The Kepler field has been entirely observed with the GALEX satellite, as part of the Complete All-Sky UV Survey Extension (CAUSE), in the NUV band (PI James Lloyd). For about 40 days in 2012, GALEX conducted a total of 17 visits, on average, of the whole field. In 2015, we published the GALEX CAUSE Kepler Catalog (GCK) of more than 660,000 NUV point-like sources with NUV≤22.6. We present the...
Roger Cohen (STScI)
9/18/17, 5:19 PM
The Galactic globular clusters (GGCs) located towards the bulge of the Milky Way suffer from severe total and differential extinction and high field star densities. They have therefore been systematically excluded from large-scale homogeneous GGC surveys, and will present a challenge for Gaia. Meanwhile, existing observations of bulge GGCs have revealed tantalizing hints they they hold clues...
Timothy Crundall (RSAA - Australian National University)
9/18/17, 5:21 PM
Current kinematic age techniques have been demonstrated to be unreliable despite being one of the best means to ascertain ages of young ensembles of stars. Three factors impact the success of traceback ages: (1) imprecise kinematic data introduce significant positional uncertainties when traced back millions of years, (2) incorporating errors in a classical way drives the convergence point to...
Jason Curtis (Columbia University)
9/18/17, 5:23 PM
We know chromospheric emission decays over time, and yet this empirical relation is still fundamentally an interpolation over 3.5 Gyr from the Hyades to the Sun despite 45 years of progress. Furthermore, its very existence was called into question by Pace et al. (2004, 2009, 2013), who argued that activity plummets and flatlines at 1 Gyr. I will present new HK data for NGC 752 (1.5 Gyr) and...
Anna Bárbara de Andrade Queiroz (Universidade Federal do Rio Grande do Sul)
9/18/17, 5:25 PM
Detailed studies of the Milky Way's stellar populations usually rely on indirect measurements of stellar distances, ages, masses and extinctions. Thanks to the availability of large stellar surveys, these parameters can be determined with unprecedented precision even for field stars. Using a Bayesian approach that can combine spectroscopic, photometric and astrometric data, we determine...
Andrea Dieball (University of Bonn)
9/18/17, 5:27 PM
Brown Dwarfs (BDs) present a link between stars and planets, and thus are important for our understanding of both star and planet formation and evolution. Large numbers of BDs have now been detected, but we still do not know much about OLD, METAL-POOR BDs. Globular clusters are the oldest, most metal-poor and most massive stellar aggregated in our Galaxy, and might have produced BDs in large...
57. Testing models for stellar angular momentum evolution with K2 observations of Praesepe and the Hyades
Stephanie Douglas (Harvard-Smithsonian CfA)
9/18/17, 5:29 PM
The oldest open clusters within 250 pc of the Sun, the Hyades and Praesepe, are important benchmarks for calibrating stellar properties such as rotation and magnetic activity. As they have the same age and roughly solar metallicity, these clusters serve as an ideal benchmark for stellar properties at ~600 Myr. We present rotation periods measured with the repurposed Kepler mission, K2, for 48...
Diane Feuillet (MPIA)
9/18/17, 5:31 PM
While detailed chemical abundances of stars are a very powerful tool for examining the evolutionary history of a galaxy, both simulations and observations are finding that abundances alone are not enough to break degeneracies in the proposed formation scenarios. To break these degeneracies, it is crucial that we also provide ages. By observing red giant stars in the near-IR, APOGEE has...
Adam Finley (University of Exeter)
9/18/17, 5:33 PM
Cool stars with outer convective envelopes are observed to have magnetic fields with a variety of geometries, which on large scales are dominated by a combination of the lowest order fields such as the dipole, quadrupole and octupole modes. Magnetised stellar wind outflows are primarily responsible for the loss of angular momentum from these objects during the main sequence. Previous works...
Clemence Fontanive (University of Edinburgh)
9/18/17, 5:35 PM
The binary properties of old brown dwarfs are observed to be substantially different than in young clusters, with fewer companions and closer separations seen around older objects. Measuring the initial brown dwarf binary frequency is necessary to allow more realistic modelling for formation theories. Similarly, constraining binary properties at field ages is essential to understand the...
50. Intracluster Age Gradients And Disk Longevities In Numerous MYStIX And SFiNCs Young Stellar Clusters
Konstantin Getman (Pennsylvania State University)
9/18/17, 5:37 PM
This study is based on YSO samples from the MYStIX and SFiNCs surveys, and a new estimator of pre-main sequence stellar ages, AgeJX, derived from X-ray and near-infrared photometric data. We present two main results here. First, the discovery of the core-halo age gradients (with younger cores and older halos) in numerous morphologically simple, isolated, and relatively rich stellar clusters....
Marina Giarrusso (Università di Catania)
9/18/17, 5:39 PM
In principle the surface lithium abundance (A(Li)) of PMSlate-type stars can be used to derive stellar ages by means of evolutionary models. Unfortunately,the disagreement between predictions and observations does not confirm the method. Note that uncertainty on different input physics (eq.of state, nuclear cross sections.,.) and physics mechanisms (external convection,diffusion,..) lead to...
Christopher Johnson (Space Telescope Science Institute)
9/18/17, 5:41 PM
We present preliminary results of an HST photometric and astrometric campaign aimed at probing the unexplored population of low and intermediate-mass binaries (P = ~2 days - ~200 years) in the young, massive cluster Westerlund 2 (Wd2). Over the next 3 years, we have a total of 45 orbits using the HST WFC3 instrument. We will be able to measure, for the first time, the separation, flux ratio...
Jeremy Jones (Georgia State University)
9/18/17, 5:43 PM
The rapid rotation of A-stars introduces two major difficulties when isochrone dating them. The oblateness and gravity darkening induced by rapid rotation affects the shape and temperature profile of the star. This rotation also changes how the star evolves and must be accounted for when choosing evolution models for comparison. Interferometric observations can address this first concern and...
Vera KOZHURINA-PLATAIS (STScI)
9/18/17, 5:45 PM
The advent of precision Hubble Space Telescope photometry has fundamentally changed the old concept of massive star clusters as simple stellar populations. It is now proven that essentially all old clusters (older than 9 Gyr) host multiple populations. Our efforts are currently shifted toward younger clusters which show the onset of multiple populations in the Red Giant Branch and other...
54. Searching for Be Stars in the Open Clusters with PTF/iPTF: I. Cluster Sample and Be Star Candidates
CHIEN-DE LEE (National Central University-Taiwan)
9/18/17, 5:47 PM
We conducted a search for Be stars in open clusters using Hα imaging photometry of the Palomar Transient Factory Survey, to investigate the connections between Be star phenomena and ages and environments of clusters. With carefully member identification, we discovered 96 Be star candidates in 32 clusters from 104 open clusters. These selected candidates and those known Be stars show a...
CHIEN-DE LEE (National Central University-Taiwan)
9/18/17, 5:49 PM
B[e] stars are the hot stars with forbidden lines in their spectra, which can be found in a wide range of stellar ages, from pre-main sequence objects to evolved stars. However, the evolution of most objects with B[e] phenomena are yet to be classified. We study a sample of eight B[e] stars with uncertain evolutionary status to shed light on the origin of their circumstellar dust. We...
Diego Lorenzo-Oliveira (Universidade de São Paulo)
9/18/17, 5:51 PM
It is well known that the magnetic activity of solar type stars decreases with age, but it is widely debated in the literature whether there is a smooth decline or if there is an early sharp drop until 1-2 Gyr followed by a relatively inactive and constant phase. We revisited the activity-age (AC) relation through Mount Wilson (MW) Ca II H & K activity indices. We measure the activity indices...
90. Time evolution of high-energy emissions of low-mass stars: Fundamental parameters and Halpha & Ca II IRT age-activity relations
Diego Lorenzo-Oliveira (Universidade Federal do Rio de Janeiro)
9/18/17, 5:53 PM
The age-magnetic activity relations are an efficient alternative way of age-dating low mass dwarfs. Our goal is to establish new age-chromospheric activity relations for KM dwarfs. We secured high-resolution spectra for 100 stars, including a subsample of wide binary stars with well-known ages and members of young kinematic groups. We selected a subsample of M dwarfs with interferometric Teff...
Eduardo Martin (CSIC-INTA Centro de Astrobiología)
9/18/17, 5:55 PM
The lithium depletion boundary (LDB) is a reliable method to obtain ages for open clusters and stellar associations. So far it has been applied to clusters and associations younger than 150 Myr where the LDB takes place among the late-M type population. In older clusters the LDB is expected to move toward fainter luminosities and cooler temperatures, i.e. the realm of the L dwarfs. Using...
Thomas Masseron (IAC)
9/18/17, 5:57 PM
I will present the results concerning the collaboration between the Gaia-ESO spectroscopic survey and the CoRoT mission. This collaboration allow to obtain spectroscopic and seismic parameters for ~1600 Galactic giant stars. I will discuss the procedure we used to derive the parameters with an excellent accuracy.
83. Ages of Six Bulge Globular Clusters and their Multiple Stellar Populations from the HST Large Legacy Treasury Program
Raphael Oliveira (Universidade de São Paulo (IAG/USP))
9/18/17, 5:59 PM
The HST Large Legacy Treasury Program (GO-13297, PI Piotto) is a UV-initiative proposal (WFC3/UVIS) to complement the existing optical database of the ACS Globular Cluster (GC) Treasury (GO-10775, PI Sarajedini). This unprecedented photometric database allows accurate and self-consistent determinations of ages, metallicities, distances and reddening values (by the analysis of optical CMDs), as...
Mark Pecaut (Rockhurst University)
9/18/17, 6:01 PM
The TW Hya Association (TWA) is the youngest of the nearby moving groups. In order to better constrain the age of this benchmark stellar association, we reexamine the Lithium depletion age for TWA. We adopt Lithium equivalent width measurements from the literature along with improved luminosity estimates based on newly available trigonometric distances. We correlate the observed Li depletion...
5. The Power of Combined Infrared and X-ray Data: Probing Stellar Ages in Obscured Massive Galactic Star-Forming Regions
Matthew Povich (California State Polytechnic University, Pomona)
9/18/17, 6:03 PM
I will present two new techniques for constraining the evolutionary ages of intermediate-mass (2-8 Msun), pre-main-sequence stars (IMPS) in obscured, massive Galactic star-forming regions using combined infrared (IR) and X-ray photometry catalogs containing thousands of objects. High-spatial-resolution X-ray images identify IMPS that lack IR excess emission from circumstellar dusk disks. IMPS...
Loredana Prisinzano (INAF-Osservatorio Astronomico di Palermo)
9/18/17, 6:05 PM
Accurate knowledge of the amount of interstellar extinction and its properties are crucial to determine stellar masses and ages and to understand the star formation mechanisms. This can be challenging for young clusters such as NGC6530, hosted by the Lagoon Nebula, a very complex HII region illuminated by many O and B-type massive stars of the cluster. A detailed study on the complex dynamics...
Elena Sacchi (Bologna University / INAF)
9/18/17, 6:07 PM
The synthetic Color-Magnitude Diagram technique is a great tool to explore the detailed star formation history (SFH) of nearby galaxies and refine stellar evolution models by comparing them with the data. Within this framework, I will discuss the results obtained for galaxies of different morphological type which are part of the HST Legacy ExtraGalactic UV Survey (LEGUS), whose aim is to...
Hannah Schunker (Max Planck Institute for Solar System Research)
9/18/17, 6:09 PM
Gyrochronology is an empirical relationship that describes the spin down of a star as it ages.This spin-down may occur through angular momentum loss via the stellar wind. Stellar dynamos drive this wind, and in Sun-like stars the rotational shear at the base of the convection zone is a candidate for the driver of the dynamo. We show that the asteroseismic signatures of rotation and rotation...
Aldo Serenelli (Institute of Space Sciences- CSIC IEEC)
9/18/17, 6:11 PM
Experimental results on radiative opacities (Bailey et al. 2015) suggest that commonly used radiative opacity calculations underestimate the true opacity at conditions similar to the base of the solar convective envelope. This hints at a solution to the solar abundance problem. New calculations of radiative opacities have become available: the new OPLIB opacities (Colgan et al. 2016) for...
Lawrence Short (Astrophysics Research Institute, Liverpool John Moores University)
9/18/17, 6:13 PM
Stellar evolution theory shows that massive stars evolve more rapidly than low mass stars reaching the instability strip at a younger age. The relatively low density of more massive stars also means that they will experience longer pulsation periods. Therefore long period Cepheids are of higher stellar mass than their short period counterparts hence they are younger. This mean that a...
Giovanni Maria Strampelli (STScI)
9/18/17, 6:15 PM
Young binary stars provide us with perfectly coeval pairs of stars, born in the same environment and with the same metallicity. Comparing their properties may thus provide key information on the early stages of stellar evolution, and constrain theoretical models developed to predict isochrones and evolutionary tracks during the Pre-Main-Sequence. We present new results relative to the...
Frédéric Thévenin (OCA)
9/18/17, 6:17 PM
HD122563 is a metal-poor ([M/H] = -2.5) old Population II star. It is one of the few nearby metal-poor stars that can be studied in detail. Such a benchmark star is important for understanding the physics of stellar atmospheres in the not-so-solar metallicity regime, understanding oscillations and stellar interiors in the context of metallicities, and providing a reference point for...
Mark Veyette (Boston University)
9/18/17, 6:19 PM
For M dwarf stars, stellar age is perhaps the most difficult fundamental parameter to measure. With main-sequence lifetimes much greater than the age of the universe, M dwarf ages cannot be derived by matching observables to model grids. M dwarfs can also maintain rapid rotation for several gigayears, complicating efforts to derive ages through gyrochonology. We present a novel approach to...
Marusa Zerjal (Australian National University)
9/18/17, 6:21 PM
An empirical age-activity relation is one of the most straightforward dating techniques for individual Solar-like and cooler dwarfs. While precise dating is not possible, an age estimate with typical 0.2 dex uncertainty is easily attainable from a single spectral measurement in the range from a few tens of millions of years up to a few gigayears. A model free and data-driven approach has been...