Related papers: Main-Seqence Fitting Distance to the sigma Ori Clu…
We present results of a 90 ksec Chandra X-ray observation of the young sigma Orionis cluster (age ~3 Myr) obtained with the High Energy Transmission Grating Spectrometer. We use the high resolution grating spectrum and moderate resolution…
We use Gaia DR2 to hunt for runaway stars from the Orion Nebula Cluster (ONC). We search a region extending 45{\deg} around the ONC and out to 1 kpc to find sources that overlapped in angular position with the cluster in the last ~10 Myr.…
Free-floating substellar candidates with estimated theoretical masses of as low as ~5 Jupiter masses have been found in the ~3 Myr old sigma Orionis open cluster. As the overlap with the planetary mass domain increases, the question of how…
The young open star cluster M25 (IC 4725) is located in the direction of the galactic center in a crowded region, near much irregular absorption features on Sagittarius arm. This cluster has some difficult observing problems due to its…
One of the results of the Milky Way Star Clusters (MWSC) survey by Kharchenko et al. (2013) was the detection of a slight under-density of old (ca. 1 Gyr) clusters within the nearest kilo-parsec from the Sun. This under-density may be due…
We present the results of a H- and K-band multi-object and long-slit spectroscopic survey of substellar mass candidates in the outer regions of the Orion Nebula Cluster. The spectra were obtained using MOIRCS on the 8.2-m Subaru telescope…
We report very intense and variable Halpha emission (pseudo-equivalent widths of ~180, 410 A) of S Ori 55, a probable free-floating, M9-type substellar member of the young sigma Orionis open star cluster. After comparison with…
The Galactic globular cluster system is incomplete, especially in the low latitude regions of the Galactic bulge and disk. We report the physical characterization of twelve star clusters in the Milky Way, most of which are explored here for…
We investigate the nature of 4 young and low-mass open clusters (OCs) located in the $2^{nd}$ and $3^{rd}$ quadrants with near-IR 2MASS photometry (errors $<0.1$ mag). After field decontamination, the colour-magnitude diagrams (CMDs)…
The Ophiuchus molecular cloud complex has produced in Lynds 1688 the richest known embedded cluster within ~300 pc of the Sun. Unfortunately, distance estimates to the Oph complex vary by nearly ~40% (~120-165 pc). Here I calculate a new…
Determining the distance to the open cluster M29 (NGC 6913) has proven difficult, with distances determined by various authors differing by a factor of two or more. To solve this problem, we have initiated a new photometric investigation of…
(abridged) A scenario for the formation of multiple co-eval populations separated in age by about 1 Myr in very young clusters (VYCs, ages less than 10 Myr) and with masses in the range 600-20000 Msun is outlined. It rests upon a converging…
The giant molecular cloud Orion A is the closest massive star-forming region to earth ($d\sim400$ pc). It contains the rich Orion Nebula Cluster (ONC) in the North, and low-mass star-forming regions (L1641, L1647) to the South. To get a…
The distance of the Virgo cluster is derived in the B band from the 21 cm-line width-absolute magnitude relation. The latter is calibrated using 18 spirals with Cepheid distances mainly from HST. The calibration is applied to a complete…
We present further arguments that the Hipparcos parallaxes for some of the clusters and associations represented in the Hipparcos catalog should be used with caution in the study of the Galactic structure. It has been already shown that the…
In this Letter, we report Very Long Baseline Array observations of 22 GHz water masers toward the protostar CARMA-6, located at the center of the Serpens South young cluster. From the astrometric fits to maser spots, we derive a distance of…
As part of an investigation into the high mass end of the initial mass-final mass relation we performed a search for new white dwarf members of the nearby (172.4 pc), young (80-90 Myr) $\alpha$ Persei open star cluster. The photometric and…
We present the sub-mm/mm SED for a sample of eight young circumstellar disks in the outer regions of the Orion Nebula Cluster. New observations were carried out at 2.9 mm with the CARMA array and for one disk, 216-0939, at 3.3 and 6.8 mm…
We use masses, radii, and luminosities of the detached eclipsing binary OGLEGC17 derived from photometric and spectroscopic observations to calculate the age and distance of the globular cluster omega Cen. Age versus turnoff mass and age…
UBVRI CCD photometry of a $2.^{\prime}1 \times 3.^{\prime}3$ field centered on the young open cluster Haffner~18 is presented and discussed. Spectroscopic classification of seven stars is also provided. 44 clusters members are identified,…