Related papers: Optically observable zero-age main-sequence O star…

The last decade has witnessed significant advances in our observational understanding of the earliest stages of low-mass star formation. The advent of sensitive receivers on large radio telescopes such as the JCMT and IRAM 30m MRT has led…

Old neutron stars (ONSs) which have radiated away their internal and rotational energy may still shine if accreting the interstellar medium. Despite their large number, only two promising candidates have been detected so far and rather…

The ESO Supernova Progenitor Survey (SPY) has identified 58 (mostly helium-rich) subluminous O stars. We use the Balmer line strength to distinguish sdO from He-sdO (no Balmer lines) and present the results of the analyses of high…

We report on the identification of the old stellar population galaxy candidates at z > 5. We developed a new infrared color selection scheme to isolate galaxies with the strong Balmer breaks at z > 5, and applied it to the ultra-deep and…

Age determination is undertaken for nearby early-type (BAF) stars, which constitute attractive targets for high-contrast debris disk and planet imaging surveys. Our analysis sequence consists of: acquisition of uvby{\beta} photometry from…

We present a new spectroscopic classification for OB stars based on H-band (1.5 micron to 1.8 micron) observations of a sample of stars with optical spectral types. Our initial sample of nine stars demonstrates that the combination of He I…

Whether massive stars can occasionally form in relative isolation or if they require a large cluster of lower-mass stars around them is a key test in the differentiation of star formation theories as well as how the initial mass function of…

We use synthetic model spectra to investigate the potential of near-ultraviolet (3000-4050 \r{A}) observations of massive O-type stars. We highlight the He I $\lambda$3188 and He II $\lambda$3203 pair as a potential temperature diagnostic…

We have obtained high resolution (R = 10,000) K-band spectra of candidate young massive stars deeply embedded in high-mass star-forming regions. These objects were selected from a near-infrared survey of 44 regions of high-mass…

Context. The first magnetic fields in O- and B-type stars that do not belong to the Bp-star class, have been discovered. The cyclic UV wind-line variability, which has been observed in a significant fraction of early-type stars, is likely…

Our current understanding of the chemical evolution of the Universe is that a first generation of stars was formed out of primordial material, completely devoid of metals (Pop III stars). This first population of stars comprised massive…

Strong, globally-organized magnetic fields are found for a small fraction of O, B, and A stars. At the same time, many theoretical and indirect observational studies suggested ubiquitous presence of weak localized magnetic fields at the…

We have obtained spectroscopic redshifts for 24 red galaxies from a sample with median Ks=18.7 and F814W - Ks > 4, using the Keck telescope. These EROshave high resolution morphologies from HST (Yan & Thompson 2003). Among the 24 redshifts,…

The Milky Way's most luminous, young and massive (M > 10^4 Msun) star clusters and OB associations have largely evaded detection despite knowledge of their surrounding H II regions. We search for these clusters and associations within the…

We present results using 2-D spectral imagery and photometry obtained with the Hubble Space Telescope (HST) for the starburst H II region, NGC 604, in nearby galaxy M33. The spectral imagery was acquired with the Space Telescope Imaging…

We analyze a set of optical-to-near-infrared long-slit nuclear spectra of 16 infrared-luminous spiral galaxies. All of the studied sources present H$_2$ emission, which reflects the star-forming nature of our sample, and they clearly…

The evolution of massive stars is still partly unconstrained. Mass, metallicity, mass loss and rotation are the main drivers of stellar evolution. Binarity and magnetic field may also significantly affect the fate of massive stars. Our goal…

This work presents the first large-scale photometric variability survey of the intermediate age (~200 Myr) open cluster M11. Thirteen nights of data over two observing seasons were analyzed (using crowded field and ensemble photometry…

The Magnetism in Massive Stars (MiMeS) survey represents a high precision systematic search for magnetic fields in hot, massive OB stars. To date, MiMeS Large Programs (ESPaDOnS@CFHT, Narval@TBL, [email protected]) and associated PI programs…

Massive stars typically undergo short-lived post-main sequence evolutionary phases with strong mass loss and occasional mass eruptions. Many of such massive stars in transition phases have been identified based on their dusty envelopes. The…