Search results for "Open cluster"
showing 10 items of 53 documents
The Gaia-ESO Survey: The present-day radial metallicity distribution of the Galactic disc probed by pre-main-sequence clusters
2017
Full list of authors: Spina, L.; Randich, S.; Magrini, L.; Jeffries, R. D.; Friel, E. D.; Sacco, G. G.; Pancino, E.; Bonito, R.; Bravi, L.; Franciosini, E.; Klutsch, A.; Montes, D.; Gilmore, G.; Vallenari, A.; Bensby, T.; Bragaglia, A.; Flaccomio, E.; Koposov, S. E.; Korn, A. J.; Lanzafame, A. C. Smiljanic, R.; Bayo, A.; Carraro, G.; Casey, A. R.; Costado, M. T.; Damiani, F.; Donati, P.; Frasca, A.; Hourihane, A.; Jofré, P.; Lewis, J.; Lind, K.; Monaco, L.; Morbidelli, L.; Prisinzano, L.; Sousa, S. G.; Worley, C. C.; Zaggia, S.
Spectroscopy of red giants in the open clusters NGC 1545 and Tr2
2011
The results of local thermodynamic equilibrium (LTE) abundance analysis are presented for four red giants in the fields of open clusters NGC 1545 and Tr2. The membership of HD 27276, HD 27292 and HD 16068 was confirmed and the age of NGC 1545 was updated: log age(yr) = 7.95. A mild deficiency of iron-group elements was found on average for NGC 1545 and Tr2, [Fe/H]=−0.13 and −0.07 with an uncertainty of about 0.08 dex. Oxygen and carbon are moderately depleted in all cluster giants, [O/Fe]=−0.23 ± 0.05 dex and [C/Fe]=−0.56 ± 0.07 dex on average. Nitrogen is enhanced, [N/Fe] values in range +0.4 to +1.2 dex, and lithium depleted. Sodium is slightly enhanced, [Na/Fe]=+0.26 ± 0.04 dex on avera…
Correlation between the spatial distribution of circumstellar disks and massive stars in the young open cluster NGC 6611
2009
Context: the observations of the proplyds in the Orion Nebula Cluster, showing clear evidence of ongoing photoevaporation, have provided a clear proof about the role of the externally induced photoevaporation in the evolution of circumstellar disks. NGC 6611 is an open cluster suitable to study disk photoevaporation, thanks to its large population of massive members and of stars with disk. In a previous work, we obtained evidence of the influence of the strong UV field generated by the massive cluster members on the evolution of disks around low-mass Pre-Main Sequence members. That work was based on a multi-band BVIJHK and X-ray catalog purposely compiled to select the cluster members with …
Luminosity and Mass Function of the Galactic open cluster NGC 2422
2003
We present UBVRI photometry of the open cluster NGC 2422 (age $\sim 10^8$ yr) down to a limiting magnitude $V\simeq19$. These data are used to derive the Luminosity and Mass Functions and to study the cluster spatial distribution. By considering the color-magnitude diagram data and adopting a representative cluster main sequence, we obtained a list of candidate cluster members based on a photometric criterion. Using a reference field region and an iterative procedure, a correction for contaminating field stars has been derived in order to obtain the Luminosity and the Mass Functions in the $M=0.4-3.5 M_\odot$ range. By fitting the spatial distribution, we infer that a non-negligible number …
XMM-Newton observations of the young open cluster Blanco 1. II. X-ray time variability and flares.
2005
We study the X-ray variability of the young open cluster Blanco 1 observed with the EPIC camera on board the XMM-Newton X-ray observatory. The time coverage of EPIC observations has allowed us to address short time scale (hours) variability, while the comparison with previous ROSAT observations has allowed us to investigate the variability on time scale of six years. On the time scale of hours, dM stars of the cluster are more variable than solar-mass stars. The main features of X-ray light curves in dM stars appear to be essentially flare-like events with a typical duration of the order of a few ks, while dF-dG stars show smooth variations. Two intense flares were observed in the ZS76 clus…
XMM-Newton observation of the classical T Tauri star SU Aurigae and the surrounding field
2007
Aims. We investigate the properties of the X-ray emitting plasma of the classical T Tauri star SU Aurigae and of other sources in the field of view. Methods. We use XMM-Newton to obtain a high-resolution RGS spectrum of SU Aur as well as EPIC imaging data and lowresolution spectra of the star and of other X-ray sources in the surrounding field. We reconstruct the emission measure distribution of SU Aur from the RGS spectrum using a line-based method, and we perform multi-temperature fits of the MOS spectra of the strongest sources both for the full observation and for selected time intervals to study their spectral variability. Results. The emission from SU Aur is highly variable, showing t…
Be stars in open clusters. I. uvby $ ^{\bf \beta}$ photometry
1996
We present uvby β photometry for Be stars in eight open clusters and two OB associations. It is shown that Be stars occupy anomalous positions in the photometric diagrams, which can be explained in terms of the circumstellar continuum radiation contribution to the photometric indices. In the - M V plane Be stars appear redder than the non emission B stars, due to the additional reddening caused by the hydrogen free-bound and free-free recombination in the circumstellar envelope. In the c 0 - M V plane the earlier Be stars present lower c 0 values than absorption-line B stars, which is caused by emission in the Balmer discontinuity, while the later Be stars deviate towards higher c 0 values,…
XMM-Newton observations of the young open cluster Blanco 1
2004
We present an X-ray study of the high metallicity young open cluster Blanco 1 based on XMM--Newton data. X-ray spectroscopy of cluster members is presented for the first time as well as new X-ray distribution functions of late-type stars. We detected all known dF and dG stars in the EPIC field and 80% and 90% of dK and dM stars, respectively. The X-ray spectral analysis of the X-ray brightest cluster stars and X-ray color analysis of a larger sample show that a model with two temperatures (at about 0.3 and 1 keV) explains the quiescent activity phase spectra. We discuss also the nature of unidentified X-ray sources in the observed region and their X-ray spectral properties.
Simultaneous uvbyβ Photometry and Hα Spectroscopy of Be Stars in Open Clusters
1994
The usual methods of spectral clasification, equivalent widths of Balmer lines or photometric calibrations are not suitable for the determination of the astrophysical parameters of the underlying star in Be-type objects. The spectrum is distorted by the circumstellar envelope lines, while the contribution of the envelope continuum radiation contaminates the photometric indices.
Be stars in open clusters
1997
We present Hα line profiles (, at continuum level, for some objects) for 58 stars in 8 northern open clusters and associations, complemented with Hβ and Hγ profiles for 36 of them as well as Hδ and Hϵ for 16 programme stars. Our observations, though lower in resolution, yield results which are in good agreement with those obtained in earlier works based mainly on field Be stars. Our data suggest a similar spectroscopic behavior for both field and cluster Be stars. The line parameters (EW, FWHM , ) have been obtained for each line. Nearly the whole set of stars have previously published quasi-simultaneous photometry, so a study of reliable correlations between photometric and spectroscopic d…