Wagner J. B. Corradi

Characterization and photometric membership of the open cluster NGC 1981

Open clusters belonging to star-forming complexes are the leftovers from the initial stellar generations. The study of these young systems provides constraints to models of star formation and evolution as well as to the properties of the Galactic disc. We aimed at investigating NGC 1981, a young open cluster in the Orion nebula region, using near-IR and BV(RI) c photometric data. We devised a method that accounts for the field contamination and allows to derive photometric membership for the cluster stars. A new cluster centre was determined by Gaussian fittings to the 2D stellar distribution on the sky, and has been used to obtain the radial stellar density profile and the structural parameters. Mass functions were computed for stars inside the cluster limiting radius and total mass estimated from them. Although more easily distinguished by its grouping of six relatively bright stars, an underlying population of faint pre-main-sequence stars is evident in the cluster area. We showed that this population is related to the cluster itself rather than to the nearby Orion nebula cluster. Additionally, a fraction of the cluster low mass stars may have been evaporated from the region in its early evolution leading to the present sparse, loose structure. The estimated parameters of NGC 1981 are core radius R c = 0.09 ± 0.04 pc, limiting radius R lim = 1.21 ± 0.11 pc, age t = 5 ± 1 Myr, distance modulus (m - M) o = 7.9 ± 0.1(380 ± 17 pc), reddening E(B - V) = 0.07 ± 0.03 and total mass m = 137 ± 14 M⊙.

Investigation of Galactic open cluster remnants: the case of NGC 7193*

Galactic open clusters (OCs) that survive the early gas-expulsion phase are gradually destroyed over time by the action of disruptive dynamical processes. Their final evolutionary stages are characterized by a poorly populated concentration of stars called open cluster remnant (OCR). This study is devoted to assess the real physical nature of the OCR candidate NGC 7193. GMOS/Gemini spectroscopy of 53 stars in the inner target region were obtained to derive radial velocities and atmospheric parameters. We also employed photometric and proper motion data. The analysis method consists of the following steps: (i) analysis of the statistical resemblance between the cluster and a set of field samples with respect to the sequences defined in colour-magnitude diagrams (CMDs); (ii) a 5-dimensional iteractive exclusion routine was employed to identify outliers from kinematical and positional data; (iii) isochrone fitting to the

Open cluster characterization via cross-correlation with a spectral library

K_{s}\times(J-K_{s})

Membership probability via control-field colour–magnitude decontamination †

CMD of the remaining stars and the dispersion of spectral types along empirical sequences in the

Chemical Composition Study of an Accretion Episode in the Herbig Candidate Star PDS080

(J-H)\times(H-K_{s})

Stellar parameters and evidence of circumstellar activity for a sample of Herbig Ae/Be stars

diagram was checked. A group of stars was identified for which the mean heliocentric distance is compatible with that obtained via isochrone fitting and whose metallicities are compatible with each other. Fifteen member stars observed spectroscopically were identified together with other 19 probable members. Our results indicate that NGC 7193 is a genuine OCR, of an once very populous OC, for which the following parameters were derived:

OPTICAL POLARIZATION MAPPING TOWARD THE INTERFACE BETWEEN THE LOCAL CAVITY AND LOOP I

d=501\,\pm\,46\,

INTERSTELLAR REDDENING IN THE LOCAL BUBBLE AND LOOP I REGION: INSIGHT FROM STRÖMGREN PHOTOMETRY ANALYSIS AND THREE-DIMENSIONAL MODELING

pc,

Basis for a SOAR Optical Imager Pipeline

t=2.5\,\pm\,1.2\,

Aproxime-se: Programa de Extensão Universitária em EaD

Gyr,