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In this paper, I review how optical spectro-interferometry has become a particularly well suited technique to study the close environment of young stars, by spatially resolving both their IR continuum and line emission regions. I summarize…
Young massive stars play an important role in the evolution of the interstellar medium (ISM) and the self-regulation of star formation in giant molecular clouds (GMCs) by injecting energy, momentum, and radiation (stellar feedback) into…
Recent observations and simulations have suggested that HII regions around massive stars may vary in their size and emitted flux on timescales short enough to be observed. This variability can have a number of causes, ranging from…
We present a new model of the optical nebular emission from HII regions by combin- ing the results of the Binary Population and Spectral Synthesis (bpass) code with the photoion- ization code cloudy (Ferland et al. 1998). We explore a…
In the light of the recent results of the stellar interferometry, we examine the nature of the extra molecular layer outside the photosphere of red super- giant stars, so far studied mostly with the use of the infrared spectra. Although the…
With the recent discoveries of interstellar objects `Oumuamua and Borisov traversing the solar system, understanding the dynamics of interstellar objects is more pressing than ever. These detections have highlighted the possibility that…
Following on from ideas presented in a recent paper by Schneider et al. (2010) on "The Far Future of Exoplanet Direct Characterization", I argue that they have exaggerated the technical obstacles to performing such 'direct characterization'…
We present some results of an on-going project aimed at studying a sample of Galactic HII regions ionized by a single massive star to test the predictions of modern generation stellar atmosphere codes in the H Lyman continuum. The…
Interstellar bubbles are structures in the interstellar medium with diameters of a few to tens of parsecs. Their progenitors are stellar winds, intense radiation of massive stars, or supernova explosions. Star formation and young stellar…
We derive the distribution of interferometric visibility for a source exhibiting strong diffractive scintillation, with particular attention to spectral resolution at or near the Nyquist limit. We also account for arbitrary temporal…
The search for extraterrestrial communication has mainly focused on microwave photons since the 1950s. We compare other high speed information carriers to photons, such as electrons, protons, and neutrinos, gravitational waves, inscribed…
Using data from the Southern Galactic Plane Survey we have measured the spatial power spectrum of the interstellar neutral atomic hydrogen in the fourth Galactic quadrant. This function shows the same power law behavior that has been found…
Kuiper belt objects smaller than a few kilometers are difficult to observe directly. They can be detected when they randomly occult a background star. Close to the ecliptic plane, each star is occulted once every tens of thousands of hours,…
Intense neutrino beams that accompany muon colliders can be used for interstellar communications. The presence of multi-TeV extraterrestrial muon collider at several light-years distance can be detected after one year run of IceCube type…
If massive stars form by disk accretion, then bipolar outflows should be generated as in the case of low-mass star formation. High accretion rates lead to high outflow rates and make the wind density very large near the protostar. We…
Observations of stellar surfaces - except for the Sun - are hampered by their tiny angular extent, while observed spectral lines are smeared by averaging over the stellar surface, and by stellar rotation. Exoplanet transits can be used to…
We search for an infrared signature of the transiting extrasolar planet HD 209458b during secondary eclipse. Our method, which we call `occultation spectroscopy,' searches for the disappearance and reappearance of weak spectral features due…
The observation of small bodies in the Space Environment is an ongoing important task in astronomy. While nowadays new objects are mostly detected in larger sky surveys, several follow-up observations are usually needed for each object to…
So far, high resolution techniques on the one hand provide morphological information on bright nearby objects. On the other hand, telescopes with large collecting areas allow us to detect very faint and distant objects, but not to obtain a…
[Full abstract in the paper] We aim to better constrain the atmospheric properties of the directly imaged exoplanet 51~Eri~b by using a retrieval approach on higher signal-to-noise data than previously reported. In this context, we also…