Related papers: Be Stars in the Open Cluster NGC 6830
Be stars are rapidly rotating B-type stars that exhibit Balmer emission lines in their optical spectra. These stars play an important role in studies of stellar evolution and disk structures. In this work, we carried out a systematic search…
Be objects are stars of B spectral type showing lines of the Balmer series in emission. The presence of these lines is attributed to the existence of an extended envelope, disk type, around them. Some stars are observed in both the Be and…
Star clusters are privileged laboratories for studying the evolution of massive stars (OB stars). One particularly interesting question concerns the phases, during which the classical Be stars occur, which unlike HAe/Be stars, are not…
In this study, we analyze the emission lines of different species present in 118 Galactic field classical Be stars in the wavelength range of 3800 - 9000 \AA. We re-estimated the extinction parameter (A$_V$) for our sample stars using the…
This paper checks on the roles of metallicity and evolutionary age in the appearance of the so-called Be phenomenon. Slitless CCD spectra were obtained covering the bulk of the Small Magellanic Cloud. For Halpha line emission twice as…
We present an analysis of high dispersion spectra (R~40000) of three red clump stars in the old open cluster NGC 6819. The spectra were obtained with SARG, the high dispersion spectrograph of the Telescopio Nazionale Galileo. The spectra…
The open cluster NGC 7419 is known to contain five red supergiants and a very high number of Be stars. However, there are conflicting reports about its age and distance that prevent a useful comparison with other clusters. We intend to…
Emission-line stars in young open clusters are identified to study their properties, as a function of age, spectral type and their evolutionary state. 207 open star clusters were observed using slitless spectroscopy method and 157 emission…
Aims: To measure the beryllium abundance in two TO stars of the Globular Cluster NGC 6752, one oxygen rich and sodium poor, the other presumably oxygen poor and sodium rich. Be abundances in these stars are used to put on firmer grounds the…
We used a dataset of archival Hubble Space Telescope images obtained through the F555W, F814W and F656N filters, to perform a complete search for objects showing $H\alpha$ emission in the globular cluster NGC 6397. As photometric…
At low metallicity, B-type stars show lower loss of mass and, therefore, angular momentum so that it is expected that there are more Be stars in the Magellanic Clouds than in the Milky Way. However, till now, searches for Be stars were only…
We describe a variability study of the moderately old open cluster NGC 6819. We have detected 4 new detached eclipsing binaries near the cluster turnoff (one of which may be in a triple system). Several of these systems should be able to…
H$\alpha$ emission is a clear indicator of circumstellar activity in Be stars, historically employed to assess the classical Be star (CBe) population in young open clusters (YOCs). The YOC NGC330 in the Small Magellanic Cloud exhibits a…
We present uvby-beta CCD photometry of the field of the open cluster NGC 1893. Our photometry is deep enough to cover the complete main sequence B spectral type. We identify ~50 very likely members of the cluster down to spectral type…
We present the results from a three night, time-series study of the open cluster NGC 6791 using the Megacam wide-field mosaic CCD camera on the 6.5m MMT telescope. The aim of this study was to demonstrate the ability to obtain very high…
We present the results of a spectroscopic investigation of two Large Magellanic Cloud globular clusters, NGC 1953 and NGC 1856. Both clusters have similar ages (250 and 300 Myr, respectively). Spectra were recorded with the…
Through the modelling of near-infrared photometry of star plus disk systems with the codes BEDISK/BERAY, we successfully describe the WISE photometric characteristics of Be stars in five young open clusters, NGC 663, NGC 869, NGC 884, NGC…
We present multiple epochs of H-alpha spectroscopy for 47 members of the open cluster NGC 3766 to investigate the long term variability of its Be stars. Sixteen of the stars in this sample are Be stars, including one new discovery. Of…
We present Balmer lines spectroscopy for a sample of 48 Be stars. For most of them, H$\alpha$ and H$\beta$ have been observed more than two times, in a total period spanning almost two years between 2008 and 2009. Spectral synthesis of the…
The precise measurement of stellar abundances plays a pivotal role in providing constraints on the chemical evolution of the Galaxy. However, before spectral lines can be employed as reliable abundance indicators, particularly for…