Related papers: Pre-main Sequence stars in LH91
We use a robust sample of 11 z~7 galaxies (z-dropouts) to estimate the stellar mass density of the universe when it was only ~750 Myr old. We combine the very deep optical to near-Infrared photometry from the HST ACS and NICMOS cameras with…
Chemical abundances of eight O- and B-type stars are determined from high-resolution spectra obtained with the MIKE instrument on the Magellan 6.5m Clay telescope. The sample is selected from 42 candidates of membership in the Leading Arm…
Young populations at Z<Zo are being examined to understand the role of metallicity in the first phases of stellar evolution. For the analysis it is necessary to assign mass and age to Pre--Main Sequence (PMS) stars. While it is well known…
We present optical spectra of 45 intermediate mass Herbig Ae/Be stars. Together with the multi-epoch spectroscopic and photometric data compiled for a large sample of these stars and ages estimated for individual stars by using pre-main…
In an ongoing effort to identify and study high-mass protostellar candidates we have observed in various tracers a sample of 235 sources selected from the IRAS Point Source Catalog, mostly with dec < -30 deg, with the SEST antenna at…
We report on the results of an optical spectroscopic survey designed to confirm the youth and determine the spectral types among a sample of young stellar object (YSO) candidates in the Serpens Molecular Cloud. We observed 150 infrared…
We present low-, medium-, and high-resolution optical spectra of LS-RCrA~1. We confirm both pre-main sequence status and membership, through the detection of lithium, presence of narrow potassium indicative of low gravity, and measurement…
The 30 Doradus region in the Large Magellanic Cloud (LMC) is the most energetic star-forming region in the Local Group. It is powered by the feedback from the massive stars in R136, the 1-2 Myr old central massive cluster. 30 Doradus has…
During an analysis of optical spectra of 80 young star clusters in several nearby spiral galaxies, [O III] and [N II] emission lines were noted in some cases. Three of these emission line sources are identified as likely planetary nebula…
Context. The properties of variable stars can give independent constraints on the star formation history of the host galaxy, by determining the age and metallicity of the parent population. Aims. We investigate the pulsation properties of…
Directly imaged exoplanets in wide orbits challenge current gas giant formation theories. They need to form quickly and acquire enough material before the disk dissipates, which cannot be accommodated by in-situ formation by core accretion.…
Berkeley 59 is a nearby ($\sim$1 kpc) young cluster associated with the Sh2-171 H{\sc ii} region. We present deep optical observations of the central $\sim$2.5$\times$2.5 pc$^2$ area of the cluster, obtained with the 3.58-m Telescopio…
We present maps of the 850 micron and 450 micron continuum emission seen towards a sample of 68 high-mass protostellar candidates with luminosities ranging from 10^2.5 to 10^5 solar luminosity. Most of these candidate high-mass stars are in…
A high number of embedded clusters is found in the Galaxy. Depending on the formation scenario, most of them can evolve to unbounded groups that are dissolved within a few tens of Myr. A systematic study of young stellar clusters showing…
We present the results from our time-series imaging data taken with the 1.3m Devasthal fast optical telescope and 0.81m Tenagara telescope in $V$, $R_{c}$, $I_{c}$ bands covering an area of $\sim18^\prime.4\times 18^\prime.4$ towards the…
HD 142527 is a young pre-main sequence star with properties indicative of the presence of a giant planet or/and a low-mass stellar companion. We have analyzed an X-Shooter/Very Large Telescope spectrum to provide accurate stellar parameters…
Using Hubble Space Telescope (HST) photometry, we characterize the age of the stellar association in the vicinity of supernova (SN) 2011dh and use it to infer the zero-age main sequence mass (M_{ZAMS}) of the progenitor star. We find two…
We present photometric and spectroscopic results for the low mass pre-main sequence (PMS) stars with spectral types K - M in the cometary globule (CG) 30/31/38 complex. We obtained multi-object high resolution spectra for the targets…
We report the discovery of low-mass PMS stars in the younger subgroup of the Cepheus OB3 association, Cep OB3b, using {\it UBVI} CCD photometry and spectroscopy. The location of a PMS is well defined in a V versus (V-I) colour-magnitude…
Accretion from protoplanetary or debris disks can contaminate the stellar photosphere, which is detectable in stars with radiative envelopes due to relatively slower photospheric mixing. The contaminated photosphere reflects ongoing disk…