Search Publications
The local density of matter mapped by Hipparcos
Flynn, Chris; Holmberg, Johan
We determine the velocity distribution and space density of a volume-complete sample of A and F stars, using parallaxes and proper motions from the Hipparcos satellite. We use these data to solve for the gravitational potential vertically in the local Galactic disc, by comparing the Hipparcos measured space density with predictions from various di…
Infrared colours for Mira-like long-period variables found in the (M⊙<~10-7 Msolar yr-1) Hipparcos Catalogue
Feast, Michael; Whitelock, Patricia; Marang, Freddy
Near-infrared, JHKL, photometry is presented for 193 Mira and semi-regular variables that were observed by Hipparcos; periods, bolometric magnitudes and amplitudes are derived for 92 of them. Because of the way in which the Hipparcos targets were selected, this group of stars provides a useful data base of Miras with low mass-loss rates (M⊙
The age of the solar neighbourhood
Binney, James; Dehnen, Walter; Bertelli, Gianpaolo
High-quality Hipparcos data for a complete sample of nearly 12000 main-sequence and subgiant stars, together with Padua isochrones, are used to constrain the star formation history of the solar neigbourhood and the processes that stochastically accelerate disc stars. The velocity dispersion of a coeval group of stars is found to increase with time…
The recent star formation history of the Hipparcos solar neighbourhood
Gilmore, Gerard; Valls-Gabaud, David; Hernandez, X.
We use data from the Hipparcos catalogue to construct colour-magnitude diagrams for the solar neighbourhood, which are then treated using advanced Bayesian analysis techniques to derive the star formation rate history, SFR(t), of this region over the last 3Gyr. The method we use allows the recovery of the underlying SFR(t) without the need of assu…
Hipparcos parallaxes for Mira-like long-period variables
Feast, Michael; Whitelock, Patricia
This paper concerns the calibration of the K period-luminosity relation for Mira variables using Hipparcos parallaxes. K magnitudes are available for 255 Mira-like variables which were observed by Hipparcos. Period-luminosity zero-points are evaluated for various subgroups of data. The best solution for oxygen-rich Miras, which uses 180 stars, omi…
Mira kinematics from Hipparcos data: a Galactic bar to beyond the Solar circle
Whitelock, Patricia A.; Feast, Michael W.
The space motions of Mira variables are derived from radial velocities, Hipparcos proper motions and a period-luminosity relation. The previously known dependence of Mira kinematics on the period of pulsation is confirmed and refined. In addition, it is found that Miras with periods in the range 145-200d in the general Solar neighbourhood have a n…
The distribution of bright OB stars in the Canis Major-Puppis-Vela region of the Milky Way
Kaltcheva, N. T.; Hilditch, R. W.
The picture of the young stellar groups in the Canis Major-Puppis-Vela (215 deg<l<275 deg) section of the Milky Way is studied and updated utilizing uvbyβ photometry of intrinsically luminous OB stars. We use all data from the literature to create a sample with 98per cent completeness to 9.5mag. The very dense low reddened OB association CMa…
The discovery of a low-mass, pre-main-sequence stellar association around γ Velorum
Jeffries, R. D.; Naylor, T.; Pozzo, M. +3 more
We report the serendipitous discovery of a population of low-mass, pre-main-sequence (PMS) stars in the direction of the Wolf-Rayet/O-star binary system γ2Vel and the Vela OB2 association. We argue that γ2Vel and the low-mass stars are truly associated and approximately coeval, and that both are at distances between 360 and 4…
A moving group of young stars in Carina-Vela
Makarov, Valeri V.; Urban, Sean
Accurate two-colour photometry and proper motions of 7096 young X-ray stars in the ROSAT All-Sky Survey Bright Star Catalogue, version 1RXS, are extracted from the Tycho-2 Catalogue. The sample is dominated by red main-sequence and possibly pre-main-sequence stars. On a global proper motion convergence map, two features are very prominent: the nea…
Absolute magnitudes of OB and Be stars based on Hipparcos parallaxes
Wegner, W.
Absolute visual magnitudes of OB stars are determined from Hipparcos parallaxes using a sample of 1207 unreddened and 441 reddened stars of luminosity classes V-IV, III, Ia and Iab-Ib-II. The value of total-to-selective extinction R for reddened stars was calculated from near-infrared photometry. The new MV calibration is compared with …