Kinematics and binaries in young stellar aggregates. II. NGC 6913 ≡ M 29

Astronomy and Astrophysics (Impact Factor: 4.38). 02/2004; 415(1):145-154. DOI: 10.1051/0004-6361:20034067
Source: arXiv


Between 1996 and 2003 we obtained 226 high resolution spectra of 16 stars in the field of the young open cluster NGC 6913, to constrain its main properties and study its internal kinematics. Twelve of the program stars turned out to be members, one of them probably unbound. Nine are binaries (one eclipsing and another double lined) and for seven of them the observations allowed us to derive the orbital elements. All but two of the nine discovered binaries are cluster members. In spite of the young age (a few Myr), the cluster already shows signs that could be interpreted as evidence of dynamical relaxation and mass segregation. However, they may be also the result of an unconventional formation scenario. The dynamical (virial) mass as estimated from the radial velocity dispersion is larger than the cluster luminous mass, which may be explained by a combination of the optically thick interstellar cloud that occults part of the cluster, the unbound state or undetected very wide binary orbit of some of the members that inflate the velocity dispersion and a high inclination for the axis of possible cluster angular momentum. All the discovered binaries are hard enough to survive average close encounters within the cluster and do not yet show signs of relaxation of the orbital elements to values typical of field binaries. Table 2 is only available in electronic form at Table 4 is only available in electronic form at the CDS via anonymous ftp to ( or via

Download full-text


Available from: Lina Tomasella, Jan 22, 2015
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Context: The distance to the wellknown bipolar nebula S106 and its associated molecular cloud is highly uncertain. Values between 0.5 and 2 kpc are given in the literature, favoring a view of S106 as an isolated object at a distance of 600 pc as part of the “Great Cygnus Rift”. However, there is evidence that S106 is physically associated with the Cygnus X complex at a distance of 1.7 kpc (Schneider et al. 2006, A&A, 458, 855). In this case, S106 is a more massive and more luminous star forming site than previously thought. Aims: We aim to understand the large-scale distribution of molecular gas in the S106 region, its possible association with other clouds in the Cygnus X south region, and the impact of UV radiation on the gas. This will constrain the distance to S106. Methods: We employ a part of an extended 13CO and C18O 1to0 survey, performed with the FCRAO, and data from the MSX and Spitzer satellites to study the spatial distribution and correlation of molecular cloud/PDR interfaces in Cygnus X south. The 2MASS survey is used to obtain a stellar density map of the region. Results: We find evidence that several molecular clouds including S106 are directly shaped by the UV radiation from members of several Cygnus OB clusters, mainly NGC 6913, and are thus located at a distance of 1.7 kpc in the Cygnus X complex. The definition of OB associations in terms of spatial extent and stellar content in the Cygnus X south region is revised.
    Full-text · Article · Oct 2007 · Astronomy and Astrophysics
  • [Show abstract] [Hide abstract]
    ABSTRACT: This is a study of the population of B and Be stars in the young, relatively poor, diffuse stellar clusters NGC 6871 and NGC 6913. High resolution spectra are used to study the Hα line of eleven stars in order to detect emission. Emission profiles were found for three stars in the cluster NGC 6871; one of these is a known WR-star and the Be-star BD +35°3956 demonstrates the transition from the B to the Be phase. Spectra of seven of the B stars revealed no traces of emission in the Hα line. During the time of our observations, the Be star V1322 Cyg in the cluster NGC 6913 had a strong emission Hα line profile with substantial variability in intensity and equivalent width. Moderate resolution spectra of seven stars in the cluster NGC 6871 over wavelengths of 4420-4960 Å and ten stars in the cluster NGC 6913 over wavelengths of 4050-5100 Å are used to classify the series of B and Be stars spectrally and to estimate their T eff and log g. It was found that three of the stars are not members of the clusters NGC 6871 or NGC 6913.
    No preview · Article · Apr 2009 · Astrophysics
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present V- and I-passband photometry of massive stars in the Cyg OB1 and Cyg OB2 associations, based on about 80 observing nights spanning 300 days in the 2011 season. The variability of 22 supergiants and 48 OB-stars with luminosity classes III--V is analyzed. We report two new variable OB stars and 15 variable supergiants of which four are new discoveries. The light variations of Schulte 12 are interpreted as microvariability. We also present light curves of the red supergiants BC Cyg and BI Cyg which exhibit brightness drop of more than 0.4 mag during the season.
    Preview · Article · Jan 2012
Show more