Search results for "Open clusters"
showing 10 items of 22 documents
Abundances of Be Stars in Very Young Open Clusters
2000
The Be Phenomenon in Early-Type Stars, IAU Colloquium 175, ASP Conference Proceedings, Vol. 214, edited by Myron A. Smith and Huib F. Henrichs. Astronomical Society of the Pacific, ISBN 1-58381-045-5, 2000, p.59 We present here standard uvbyβ CCD photometry for five open clusters of the Galaxy in order to determine abundances of Be stars, as a function of age.
The Gaia-ESO Survey: Catalogue of Hα emission stars
2015
We discuss the properties of Hα emission stars across the sample of 22035 spectra from the Gaia-ESO Survey internal data release, observed with the GIRAFFE instrument and largely belonging to stars in young open clusters. Automated fits using two independent Gaussian profiles and a third component that accounts for the nebular emission allow us to discern distinct morphological types of Hα line profiles with the introduction of a simplified classification scheme. All in all, we find 3765 stars with intrinsic emission and sort their spectra into eight distinct morphological categories: single-component emission, emission blend, sharp emission peaks, double emission, P-Cygni, inverted P-Cygni…
X-ray spectral and timing characteristics of the stars in the young open cluster IC 2391
2005
We present X-ray spectral and timing analysis of members of the young open cluster IC 2391 observed with the XMM-Newton observatory. We detected 99 X-ray sources by analysing the summed data obtained from MOS1, MOS2 and pn detectors of the EPIC camera; 24 of them are members, or probable members, of the cluster. Stars of all spectral types have been detected, from the early-types to the late-M dwarfs. Despite the capability of the instrument to recognize up to 3 thermal components, the X-ray spectra of the G, K and M members of the cluster are well described with two thermal components (at kT$_1 \sim$ 0.3-0.5 keV and kT$_2 \sim$ 1.0-1.2 keV respectively) while the X-ray spectra of F members…
Optical spectroscopy of X-ray sources in the Taurus molecular cloud: discovery of ten new pre-main sequence stars
2008
We have analyzed optical spectra of 25 X-ray sources identified as potential new members of the Taurus molecular cloud (TMC), in order to confirm their membership in this SFR. Fifty-seven candidates were previously selected among the X-ray sources in the XEST survey, having a 2MASS counterpart compatible with a PMS star based on color-magnitude and color-color diagrams. We obtained high-resolution optical spectra for 7 of these candidates with the SARG spectrograph at the TNG telescope, which were used to search for Li absorption and to measure the Ha line and the radial and rotational velocities; 18 low-resolution optical spectra obtained with DOLORES for other candidate members were used …
The gaia-eso survey: dynamical analysis of the l1688 region in ophiuchus
2016
The Gaia ESO Public Spectroscopic Survey (GES) is providing the astronomical community with high-precision measurements of many stellar parameters including radial velocities (RVs) of stars belonging to several young clusters and star-forming regions. One of the main goals of the young cluster observations is to study of their dynamical evolution and provide insight into their future, revealing if they will eventually disperse to populate the field, rather than evolve into bound open clusters. In this paper we report the analysis of the dynamical state of L1688 in the $\rho$~Ophiuchi molecular cloud using the dataset provided by the GES consortium. We performed the membership selection of t…
Mapping accretion and its variability in the young open cluster NGC 2264: A study based on u-band photometry
2014
We aim at characterizing the accretion properties of several hundred members of the star-forming cluster NGC 2264 (3 Myr). We performed a deep u,g,r,i mapping and a simultaneous u+r monitoring of the region with CFHT/MegaCam in order to directly probe the accretion process from UV excess measurements. Photometric properties and stellar parameters are determined homogeneously for about 750 monitored young objects, spanning the mass range 0.1-2 Mo. About 40% are classical (accreting) T Tauri stars, based on various diagnostics (H_alpha, UV and IR excesses). The remaining non-accreting members define the (photospheric+chromospheric) reference UV emission level over which flux excess is detecte…
The Gaia-ESO survey: Discovery of a spatially extended low-mass population in the Vela OB2 association
2015
The nearby (distance~350-400 pc), rich Vela OB2 association, includes $\gamma^2$ Velorum, one of the most massive binaries in the solar neighbourhood and an excellent laboratory for investigating the formation and early evolution of young clusters. Recent Gaia-ESO survey observations have led to the discovery of two kinematically distinct populations in the young (10-15 Myr) cluster immediately surrounding $\gamma^2$ Velorum. Here we analyse the results of Gaia-ESO survey observations of NGC 2547, a 35 Myr cluster located two degrees south of $\gamma^2$ Velorum. The radial velocity distribution of lithium-rich pre-main sequence stars shows a secondary population that is kinematically distin…
The Second APOKASC Catalog: The Empirical Approach
2018
We present a catalog of stellar properties for a large sample of 6676 evolved stars with APOGEE spectroscopic parameters and \textit{Kepler} asteroseismic data analyzed using five independent techniques. Our data includes evolutionary state, surface gravity, mean density, mass, radius, age, and the spectroscopic and asteroseismic measurements used to derive them. We employ a new empirical approach for combining asteroseismic measurements from different methods, calibrating the inferred stellar parameters, and estimating uncertainties. With high statistical significance, we find that asteroseismic parameters inferred from the different pipelines have systematic offsets that are not removed b…
The Gaia-ESO Survey: The origin and evolution of s-process elements
2018
Context. Several works have found an increase of the abundances of the s-process neutron-capture elements in the youngest Galactic stellar populations. These trends provide important constraints on stellar and Galactic evolution and they need to be confirmed with large and statistically significant samples of stars spanning wide age and distance intervals. Aims. We aim to trace the abundance patterns and the time evolution of five s-process elements - two belonging to the first peak, Y and Zr, and three belonging to the second peak, Ba, La, and Ce - using the Gaia-ESO IDR5 results for open clusters and disc stars. Methods. From the UVES spectra of cluster member stars, we determined the ave…
Gaia-ESO Survey: Global properties of clusters Trumpler 14 and 16 in the Carina nebula
2017
Aims: We present the first extensive spectroscopic study of the global population in star clusters Trumpler 16, Trumpler 14, and Collinder 232 in the Carina nebula, using data from the Gaia-ESO Survey, down to solar-mass stars. Methods: In addition to the standard homogeneous survey data reduction, a special processing was applied here because of the bright nebulosity surrounding Carina stars. Results: We find about 400 good candidate members ranging from OB types down to slightly subsolar masses. About 100 heavily reddened early-type Carina members found here were previously unrecognized or poorly classified, including two candidate O stars and several candidate Herbig Ae/Be stars. Their l…