bluuebunny/crossref_metadata_2025_split huggingface dataset:
The RAVE harvest: from the relation between abundances and kinematic of the Milky Way stars to tools for the abundance analysis of the spectra
Authors: Boeche Corrado ,   the RAVE collaboration
Published: January 2014

AbstractRAVE is a spectroscopic survey of the Milky Way which collected more than 500,000 stellar spectra of nearby stars in the Galaxy. The RAVE consortium analysed these spectra to obtain radial velocities, stellar parameters and chemical abundances. These data, together with spatial and kinematic information like positions, proper motions, and distance estimations, make the RAVE database a rich source for galactic archaeology. I present recent investigations on the chemo-kinematic relations and chemical gradients in the Milky Way disk using RAVE data and compare our results with the Besançon models. I also present the code SPACE, an evolution of the RAVE chemical pipeline, which integrates the measurements of stellar parameters and chemical abundances in one single process.
Chromospherically Active Stars in the RAVE Survey
Authors: Žerjal M. , Zwitter T. , Matijevič G. , Strassmeier K. G. ,   RAVE Collaboration
Published: January 2014

AbstractWe present a qualitative characterization of activity levels of a large database of ~44,000 candidate RAVE stars (unbiased, magnitude limited medium resolution survey) that show chromospheric emission in the Ca II infrared triplet and this vastly enlarges previously known samples. Our main motivation to study these stars is the anti-correlation of chromospheric activity and stellar ages that could be calibrated using stellar clusters with known ages. Locally linear embedding used for a morphological classification of spectra revealed 53,347 cases with a suggested emission component in the calcium lines. We analyzed a subsample of ~44,000 stars with S/N>20 using a spectral subtraction technique where observed reference spectra of inactive stars were used as templates instead of synthetic ones. Both the equivalent width of the excess emission for each calcium line and their sum is derived for all candidate active stars with no respect to the origin of their emission flux. ~17,800 spectra show a detectable chromospheric flux with at least 2 σ confidence level. The overall distribution of activity levels shows a bimodal shape, with the first peak coinciding with inactive stars and the second with the pre-main-sequence cases.
Properties of abundance gradient along the Galactic disk and the role of LAMOST
Authors: Hou J.L. , Chen L. , Yu J.C. , Sellwood J. , Pryor C. 
Published: January 2014

AbstractIn this paper, we present our recent work on the evolution of abundance gradients along the Milky Way disk based on the Geneva Copenhagen Survey (GCS) and Radial Velocity Experiment (RAVE) data. We will also discuss the role of the LAMOST Milky Way disk survey in clarifying the properties of metallicity breaks observed through open clusters and young tracers along the Milky Way disk. It is believed that the Galactic disk forms inside-out, in which the stellar population at increasing radii is younger and more metal poor. This picture is consistent with most Galactic Chemical Evolution (GCE) models which also predict a tight correlation between the metallicity and age of stars at a given radius. However, it is only a result of “steady state" and no dynamical evolution effects were taken into account. We have selected two stellar samples from GCS and RAVE, each sample contains about 10,000 local thin-disk, main-sequence stars. We use the guiding radius which is determined by the conservation of z-direction angular momentum, to eliminate the blurring effects. And also use the effective temperature of the main sequence stars as a proxy of stellar age. It is shown that the metallicity gradient flattens as the age increases. This is not consistent with our previous GCE prediction, but can be explained by radial mixing effects. In order to further demonstrate the abundance breaks observed in the Galactic disk we have proposed, and have been carrying out, an open cluster survey project based on LAMOST. We plan to observe at least 400 open clusters in the northern Galactic sky. From the observations, we will get uniform parameters for those clusters with radial velocity and metallicities. We anticipate that this uniform open cluster sample could clarify the observed abundance break around the Milky Way disk corotation radius and also give a more robust result concerning the evolution of the abundance gradient.
Strömgren-Crawford uvbyβ all sky survey - towards understanding of the Galaxy
Authors: Wang Wei , Zhao Gang , Chen Yuqin , Liu Yujuan 
Published: January 2014

AbstractThe Strömgren-Crawford (SC) intermediate-band photometric system is a very powerful and efficient one for the detailed study of stars, and therefore the Milky Way and local universe. However, due to the narrow bandwidth, low efficiency of detectors and serious atmospheric extinction in u band, and high photometric accuracy required, there was only one all sky survey in this system finished a decade ago, which is restricted to stars brighter than 8.3 mag in y (equal to V) in the solar neighborhood. In this context, it is the right time to carry out an all sky survey to a completeness depth of ~19 mag, equivalent to a volume-completed distance 4 kpc for solar-type stars. For stars brighter than 15 mag in V, the expected photometric accuracies are ~0.01mag. With these stars, high precision 3D extinction map can be obtained thanks to the β index. Stellar atmospheric parameters can be determined with accuracies comparable to those from high-resolution spectroscopy. Fundamental parameters like stellar luminosities and distances can be reliably estimated as well. We propose to use the Nanshan 1m telescope to start the survey in early 2014 in the Northern sky. There are several 1-m class telescopes in Chile which can be used to perform the Southern sky survey. This entire survey, when finished, will greatly improve our knowledge on stars and the Galaxy, and will provide us the first 6D map of the Milky Way together with the LAMOST survey and the Gaia mission.
Automated stellar abundance analysis
Authors: Recio-Blanco Alejandra 
Published: January 2014

AbstractThe advent of Milky Way high-resolution spectroscopic surveys has brought our attention to the importance of precise chemical abundance measurements to disentangle the stellar population puzzle of the Galaxy. Moreover, automated stellar parameters are the bedrock of Galactic spectroscopic surveys science. They allow a rapid and homogeneous processing of extensive data sets, necessary for an efficient scientific return. In this review, I discuss the different parametrization techniques, focusing on the automated determination of individual element abundances. Each of them has its optimal application conditions that mainly depend on the computation time constraints, the spectral resolution, the wavelength domain, the data signal-to-noise ratio and parameter degeneracy problems. The main algorithms in the literature are also reviewed.
Constraints on the Galactic bar with RAVE
Authors: Antoja T. , Helmi A. ,   the RAVE collaboration
Published: January 2014

AbstractWe derive the pattern speed of the Galactic bar from the analysis of the kinematics of the Hercules stream at different Galactocentric radii with RAVE, assuming that Hercules is caused by the bar. We find a well constrained pattern speed of Ωb=1.98+0.04−0.08 Ωo, where Ω0 is the local circular frequency.
A systematic study of NLTE abundances of nearby stars
Authors: Chen Y. Q. , Zhao G. , Mashonkina L. , Shi J. R. , Zhang H. W. , Tan K. F. 
Published: January 2014

AbstractApproximately 80 stars from the thin disk, the thick disk and the halo of the Galaxy, in the range of −3.0 < [Fe/H] < +0.5, surface gravity of 3.0 < logg < 4.7 and temperature of 4500 K < Teff < 6500 K, have been observed with the Shane/Hamilton and CFHT/Espadons spectrographs in order to carry out a systematic NLTE study of nearby stars in a consistent way. We will determine reliably stellar parameters and determine precise elemental abundances via a comprehensive NLTE analysis of the spectral lines of Li, Na, Mg, Al, Si, K, Ca, Sc, Mn, Fe, Sr, Zr, Ba, Nd, and Eu elements. Finally, we aim to investigate the chemical evolution of the Galaxy through different stellar populations based on the NLTE abundances for total 15 elements.
3D Galactic extinction modelling
Authors: Hanson Richard J. , Bailer-Jones Coryn A. L. 
Published: January 2014

AbstractUsing multi-band photometry we train a forward model to emulate the colour-change due to temperature and extinction for stars. We simultaneously solve for the astrophysical parameters (APs) extinction A0, temperature Teff and distance modulus μr in a Bayesian framework for individual stars. We introduce an HRD prior to account for previous knowledge about the distribution of stars in the temperature- absolute magnitude plane (see also Bailer-Jones 2011). This allows us to infer distance information. We obtain the full three dimensional PDFs of all the stars in a field, allowing us to determine extinction-distance profiles for a given line of sight.
Velocity distributions of surviving companion stars of type Ia supernovae in the Milky Way
Authors: Jia S. , Wang B. , Han Z. 
Published: January 2014

AbstractThe companion stars of type Ia supernovae (SNe Ia) would survive the explosions and show peculiar properties in the single-degenerate (SD) scenario. Whit different SD SN Ia channels, we obtained the velocity distributions of the surviving companion stars in the Milky Way. All properties presented may be verified by future observations.
Estimation of Galactic Model Parameters In High Latitude With SDSS and SCUSS
Authors: Jia Yunpeng , Du Cuihua 
Published: January 2014

AbstractUsing star counts method, we estimated the Galactic structure parameters in high latitude field (50° ≤ l ≤ 55°, −46° ≤ b ≤ −44°), 10 deg2 field with Sloan Digital Sky Survey (SDSS) and South Galactic Cap of U-band Sky Survey (SCUSS), to explore their possible variations with absolute magnitude. Here we just considered three components: double exponential thin disk and thick disk and a de Vaucouleurs halo. And these parameters were obtained by minimising χ2.
The abundance distribution of [α/Fe] in the Galactic disk stars
Authors: Li Ji , Fu Ruijuan 
Published: January 2014

AbstractThe abundance ratio [α/Fe] is a useful tracer to probe the history of star formation and the chemical evolution of the Galaxy. We present a statistical analysis of [α/Fe] in 953 dwarf stars to investigate the distributions of [α/Fe] in the the thin- and thick-disk stars.
The 3-D extinction law in the 2nd quadrant of the Galactic disk
Authors: Liu Chao , Fang Min , Wu Yue , Carrell Kenneth , Xue Xiangxiang , van de Ven Glenn 
Published: January 2014

AbstractWe estimate the 3D extinction law in the optical–NIR bands for a line of sight in the 2nd quadrant of the Galactic disk. Two dust lanes are identified at ~9 and ~10.25 kpc in both AV and RV, indicating that the size of the dust grains in the spiral arms is larger than that in the inter-arm regions.
The identification of K giant stars in LAMOST pilot survey
Authors: Liu Chao , Yang Fan , Deng Licai , Xu Yan , Cui Wenyuan , Xue Xiangxiang , Gao Shuang , Zhang Yueyang , Xin Yu 
Published: January 2014

AbstractA support vector machine (SVM) method is applied to select K giant stars directly from the spectral features of LAMOST spectra. The performance of the algorithm is assessed using the MILES library. It shows that the completeness of the K giant stars is 87% with only about 6% dwarf contamination. This allows us to select 18,013 K giant stars at |b|>20° and 38,108 at |b|<20° from LAMOST pilot survey data.
Near-infrared spectroscopy of Cepheids in the Galactic nuclear disk
Authors: Matsunaga Noriyuki , Fukue Kei , Kobayashi Naoto , Ikeda Yuji , Yamamoto Ryo , Kyu Shiori , Hamano Satoshi , Yasui Chikako , Tsujimoto Takuji , Aoki Wako , Nishiyama Shogo , Nagata Tetsuya , Genovali Katia , Inno Laura , Bono Giuseppe 
Published: January 2014

AbstractWe are carrying out near-infrared spectroscopy of Cepheids in the Galactic nuclear disk. The H-band spectra taken with SUBARU/IRCS indicate that their kinematics are consistent with the rotation of the nuclear disk.
Helium double-detonation explosions for the progenitors of type Ia supernovae
Authors: Wang B. , Liu D. , Jia S. , Han Z. 
Published: January 2014

AbstractThermonuclear explosions from helium double-detonation sub-Chandrasekhar mass model have been considered as an alternative way for the production of type Ia supernovae (SNe Ia). In this work, we systematically studied the helium double-detonation model, in which a carbon–oxygen white dwarf (CO WD) accumulates a helium layer from a non-degenerate helium star.
Exploration of Galactic Structures beyond the Sun toward the anti-center of the Milky Way
Authors: Xu Yan , Newberg Heidi 
Published: January 2014

AbstractWe map the stellar distribution on Hess diagram in the Anti-Center roughly in the boxes 130<l<230, −30<b<−10 and 10<b<30. There are ‘extra components’ associated with the anti-center structures of figure 1 of Newberg et al. (2002). The turnoff point of the structure in the North sky is at 16m.5 and the turnoff point in the South is at 17m.5. In our work, these structures can be found in all of the longitude in our box that can't be explained by standard thin or thick disk models. The distance of the North structure is about 2 kpc (we call it the North near structure) and the galactic height is about 0.7 kpc, the distance of the South structure is about 4 – 6 kpc (we call it the South middle structure). The Vgsr distribution of stars selected along the North near structure has a kinematic distribution similar to that of thick disk stars. But the metallicities of these stars are quite similar to the metallicity distribution of thin disk stars. We try to explain these structures with wave structure of the Galactic plane.
Abundance analysis of barium stars
Authors: Yang Guochao , Liang Yanchun , Cui Wenyuan , Zhang Bo 
Published: January 2014

AbstractWe obtained the chemical abundances of more than 20 Barium (Ba) stars by analysing high resolution echelle spectra. They show obvious overabundances of neutron capture process elements, such as Y, Zr, Ba, La and Eu. Their abundance pattern can be explained by binary accretion through stellar wind, where the Ba stars have accreted the ejecta from the companion stars which were in AGB stages at that time and now evolve as white dwarfs.
Chromospheric activities of late-type stars based on Guoshoujing Telescope
Authors: Zhang L. Y. , Zhang G. Y. , Shi J. R. , Luo A. L. , Zhao J. K. , Zhao Y. H. , Wu H. , Zhou A. Y. , Pi Q. F. ,   LAMOST Collaboration
Published: January 2014

AbstractWe present chromospheric activities of late-type stars based on stellar spectrum survey of LAMOST (also called GuoShouJing telescope) in 2010-2013. Using the equivalent widths of the Hα line (larger than 1 Å), we have found 6391 active stars from 99741 M stars.
Visible AO Observations at Halpha for Accreting Young Planets
Authors: Close L.M. , Follette K. , Males J.R. , Morzinski K. , Rodigas T.J. , Hinz P. , Wu Y-L. , Apai D. , Najita J. , Puglisi A. , Esposito S. , Riccardi A. , Bailey V. , Xompero M. , Briguglio R. , Weinberger A. 
Published: January 2014

AbstractWe utilized the new high-order (250-378 mode) Magellan Adaptive Optics system (MagAO) to obtain very high-resolution science in the visible with MagAO's VisAO CCD camera. In the good-median seeing conditions of Magellan (0.5–0.7″) we find MagAO delivers individual short exposure images as good as 19 mas optical resolution. Due to telescope vibrations, long exposure (60s) r' (0.63μm) images are slightly coarser at FWHM = 23-29 mas (Strehl ~ 28%) with bright (R < 9 mag) guide stars. These are the highest resolution filled-aperture images published to date. Images of the young (~ 1 Myr) Orion Trapezium θ1 Ori A, B, and C cluster members were obtained with VisAO. In particular, the 32 mas binary θ1 Ori C1C2 was easily resolved in non-interferometric images for the first time. Relative positions of the bright trapezium binary stars were measured with ~ 0.6–5 mas accuracy. In the second commissioning run we were able to correct 378 modes and achieved good contrasts (Strehl>20% on young transition disks at Hα). We discuss the contrasts achieved at Hα and the possibility of detecting low mass (~ 1–5 Mjup) planets (past 5AU) with our new SAPPHIRES survey with MagAO at Hα.
SCExAO: First Results and On-Sky Performance
Authors: Currie Thayne , Guyon Olivier , Martinache Frantz , Clergeon Christophe , McElwain Michael , Thalmann Christian , Jovanovic Nemanja , Singh Garima , Kudo Tomoyuki 
Published: January 2014

AbstractWe present new on-sky results for the Subaru Coronagraphic Extreme Adaptive Optics imager (SCExAO) verifying and quantifying the contrast gain enabled by key components: the closed-loop coronagraphic low-order wavefront sensor (CLOWFS) and focal plane wavefront control (“speckle nulling”). SCExAO will soon be coupled with a high-order, Pyramid wavefront sensor which will yield > 90% Strehl ratio and enable 106–107 contrast at small angular separations allowing us to image gas giant planets at solar system scales. Upcoming instruments like VAMPIRES, FIRST, and CHARIS will expand SCExAO's science capabilities.
Young Brown Dwarfs as Giant Exoplanet Analogs
Authors: Faherty Jacqueline K. , Cruz Kelle L. , Rice Emily L. , Riedel Adric 
Published: January 2014

AbstractYoung brown dwarfs and directly-imaged exoplanets have enticingly similar photometric and spectroscopic characteristics, indicating that their cool, low gravity atmospheres should be studied in concert. Similarities between the peculiar shaped H band, near and mid-IR photometry as well as location on color magnitude diagrams provide important clues about how to extract physical properties of planets from current brown dwarf observations. In this proceeding we discuss systems newly assigned to 10-150 Myr nearby moving groups, highlight the diversity of this uniform age-calibrated brown dwarf sample, and reflect on their implication for understanding current and future planetary data.
Estimation of Contaminants for Direct Imaging of Exoplanets: Constraint on the Stellar Distribution Model with both NIR and Deep Imaging Data
Authors: Konishi Mihoko , Shibai Hiroshi , Matsuo Taro , Yamamoto Kodai , Sudo Jun , Samland Matthias S. , Fukagawa Misato , Sumi Takahiro ,   SEEDS team
Published: January 2014

AbstractThere are faint contaminants near primary stars in the direct imaging of exoplanets. Our goal is to estimate statistically the ratio of exoplanets in the detected batch of point sources by calculating the fraction of contamination. In this study, we compared the detected number of stars with the number of contaminants predicted by our model. We found that the observed number of faint stars were fewer than the predicted results towards the Pleiades and GOODS-South field when the parameters of the conventional stellar distribution models were employed. We thus estimated new model parameters in correspondence to the results of the observations.
High-fidelity photometry and astrometry of high-contrast imaged companions using LOCI processing.
Authors: Maire Jérôme , Gagné Jonathan , Lafrenière David , Graham James R. , Doyon René 
Published: January 2014

RésuméDirect imaging and spectroscopy of exoplanets is a key element for understanding planet formation and migration. Such direct detections and characterizations remains technologically challenging, since a very high contrast ratio and small angular separation are involved, and futhermore speckle noise limits the high-contrast imaging performance. We further discuss a speckle subtraction and suppression technique that fully takes advantage of spectral and time-domain information on quasi-static speckles to measure the highest-fidelity photometry as well as accurate astrometry of detected companions.
Testing Optimized Principal Component Analysis on Coronagraphic Images of the Fomalhaut System
Authors: Meshkat Tiffany , Kenworthy Matthew , Quanz Sascha P. , Amara Adam 
Published: January 2014

AbstractWe present the results of a study to optimize the principal component analysis (PCA) algorithm for planet detection, a new algorithm complementing ADI and LOCI for increasing the contrast achievable next to a bright star. We apply PCA to our Fomalhaut VLT NACO Apodizing Phase Plate NB4.05 data.
The Gemini NICI Planet-Finding Campaign: The Frequency of Giant Planets around Young B and A Stars
Authors: Nielsen Eric L. , Liu Michael C. , Wahhaj Zahed , Biller Beth A. , Hayward Thomas L. ,   The Gemini NICI Planet-Finding Campaign Team
Published: January 2014

AbstractWe have carried out high contrast imaging of 70 young, nearby B and A stars to search for brown dwarf and planetary companions as part of the Gemini NICI Planet-Finding Campaign. Our survey represents the largest, deepest survey for planets around high-mass stars (≈1.5–2.5 M⊙) conducted to date and includes the planet hosts β Pic and Fomalhaut. Despite detecting two new brown dwarfs, our observations did not detect new planets around our target stars, and we present upper limits on the fraction of high-mass stars that can host giant planets that are consistent with our null result.
Direct Imaging Of Long Period Radial Velocity Targets With NICI
Authors: Salter Graeme S. , Tinney Chris G. , Wittenmyer Robert A. , Jenkins James S. , Jones Hugh R.A. , O'Toole Simon J. 
Published: January 2014

AbstractWe are finally entering an era where radial velocity and direct imaging parameter spaces are starting to overlap. Radial velocity measurements provide us with a minimum mass for an orbiting companion (the mass as a function of the inclination of the system). By following up these long period radial velocity detections with direct imaging we can determine whether a trend seen is due to an orbiting planet at low inclination or an orbiting brown dwarf at high inclination. In the event of a non-detection we are still able to put a limit on the maximum mass of the orbiting body. The Anglo-Australian Planet Search is one of the longest baseline radial velocity planet searches in existence, amongst its targets are many that show long period trends in the data. Here we present our direct imaging survey of these objects with our results to date. ADI Observations have been made using NICI (Near Infrared Coronagraphic Imager) on Gemini South and analysed using an in house, LOCI-like, post processing.
A Direct Imaging Study to Search for and to Characterize Planetary Mass Companions
Authors: Ward-Duong K. , Patience J. , De Rosa R. J. , Rajan A. , Hinz P. , Skemer A. , Morzinski K. , Males J. , Close L. M. , McCarthy D. W. , Kulesa C. 
Published: January 2014

AbstractWe present preliminary results from two parallel programs to search for new substellar companions to nearby, young M-stars and to characterize the atmospheres of known planetary mass and temperature substellar companions. For the M-star survey, we are analyzing high angular resolution archival data on systems within 15pc, complementing a subset with well-determined young ages based on measurements of several age indicators. The results include stellar and substellar companion candidates, which we are currently pursuing with follow-up second epoch images. The characterization component of the project involves using LBT LMIRCam and MMT ARIES direct imaging and spectroscopy data to investigate the atmospheres of known young substellar companions with masses overlapping the planetary regime. These atmospheric studies will represent an analogous comparison to the atmospheres of young imaged planets, and provide a means to fundamentally test evolutionary models, enhancing our understanding of the overall substellar population.