Related papers: Screening the Hipparcos-based astrometric orbits o…
We perform a search for faint, common proper motion companions of Hipparcos stars using the recently published LSPM-north catalog of stars with proper motion mu>0.15 arcsec/yr. Our survey uncovers a total of 521 systems with angular…
The formation scenarios for single low-mass (M < 0.45 Msol) white dwarfs include enhanced mass loss from a metal-rich progenitor star or a common envelope phase of a solar-like star with a close-in massive planet or a brown dwarf. Both…
The last decade of direct imaging (DI) searches for sub-stellar companions has uncovered a widely diverse sample that challenges the current formation models, while highlighting the intrinsically low occurrence rate of wide companions,…
Recent studies have shown that close-in brown dwarfs in the mass range 35-55 M$_{\rm Jup}$ are almost depleted as companions to stars, suggesting that objects with masses above and below this gap might have different formation mechanisms.…
Exoplanets which are detected using the radial velocity technique have a well-known ambiguity of their true mass, caused by the unknown inclination of the planetary orbit with respect to the plane of the sky. Constraints on the inclination…
Aims: Completing the poorly known substellar census of the solar neighbourhood, especially with respect to the coolest brown dwarfs, will lead to a better understanding of failed star formation processes and binary statistics with different…
Among the 120 000 objects in the Hipparcos catalogue, only 235 were fitted with an orbital model. Besides these 235 original astrometric binaries, most Hipparcos entries with a known spectroscopic orbit (extrasolar planet or stellar…
Massive stars are recognized for their high degree of multiplicity, yet the mass ratio regime below 0.1 remains insufficiently explored. It is therefore unknown whether extremely low-mass (possibly substellar) companions can form and…
Results are presented for a Hubble Space Telescope Advanced Camera for Surveys high-resolution imaging campaign of 90 white dwarfs with known or suspected low mass stellar and substellar companions. Of the 72 targets which remain candidate…
The masses of compact objects like white dwarfs, neutron stars and black holes are fundamental to astrophysics, but very difficult to measure. We present the results of an analysis of subluminous B (sdB) stars in close binary systems with…
We have undertaken a series of hydrodynamic + N-body simulations in order to explore the properties of young stars. Our results suggest that the IMF may be sensitive to environment in its substellar region, with more brown dwarfs being…
Brown dwarfs, stars with insufficient mass to burn hydrogen, could contribute to the dark matter in the Galactic disk, galactic halos or even a background critical density. We consider the detectability of such brown dwarfs in various…
The difference in formation process between binary stars and planetary systems is reflected in their composition as well as their orbital architecture, particularly orbital eccentricity as a function of orbital period. It is suggested here…
The masses of compact objects like white dwarfs, neutron stars and black holes are fundamental to astrophysics, but very difficult to measure. We present the results of an analysis of subluminous B (sdB) stars in close binary systems with…
We are conducting a planet search survey with HARPS since seven years. The volume-limited stellar sample includes all F2 to M0 main-sequence stars within 57.5 pc, where extrasolar planetary signatures are systematically searched for with…
We present the first results of a large imaging survey to identify wide brown dwarf companions to stars within 10 pc. We have performed a deep (H-band limit ~ 19.0 mag), wide field (up to 16x16 arcmin) astrometric imaging campaign in two…
We present four newly validated transiting brown dwarfs identified through TESS photometry and confirmed with high-precision radial velocity measurements obtained from the FEROS and PLATOSpec spectrographs. Notably, three of these…
I report the results of a survey for low-mass (0.030 <~ M <~ 0.013 M_solar) brown dwarfs in the direction of the TW Hya association using 2MASS. Two late-M dwarfs show signs of low surface gravity and are strong candidates to be young,…
We present constraints on the presence of substellar companions to the nearby ($d\sim7.6$ pc), young ($440\pm40$ Myr) K4Ve star TW Piscis Austrini, the wide ($\sim$0.3 pc) companion to the A4V star Fomalhaut. We combined absolute astrometry…
The Intermediate Astrometric Data (IAD) and Transit Data (TD) made available by ESA after the Hipparcos mission make it possible to re-process the observations of any Hipparcos entry. This paper illustrates how TD and IAD may be used in…