Search Publications
Elemental abundance survey of the Galactic thick disc
Lambert, David L.; Allende Prieto, Carlos; Reddy, Bacham E.
We have performed an abundance analysis for F- and G- dwarfs of the Galactic thick-disc component. A sample of 176 nearby (d<= 150pc) thick-disc candidate stars was chosen from the Hipparcos catalogue and subjected to a high-resolution spectroscopic analysis. Using accurate radial velocities combined with the Hipparcos astrometry, kinematics (U…
The colours of the Sun
Flynn, Chris; Holmberg, Johan; Portinari, Laura
We compile a sample of Sun-like stars with accurate effective temperatures, metallicities and colours (from the ultraviolet to the near-infrared). A crucial improvement is that the effective temperature scale of the stars has recently been established as both accurate and precise through direct measurement of angular diameters obtained with stella…
A maximum-likelihood method for fitting colour-magnitude diagrams
Naylor, Tim; Jeffries, R. D.
We present a maximum-likelihood method for fitting two-dimensional model distributions to stellar data in colour-magnitude space. This allows one to include (for example) binary stars in an isochronal population. The method also allows one to derive formal uncertainties for fitted parameters, and assess the likelihood that a good fit has been foun…
Finding benchmark brown dwarfs to probe the substellar initial mass function as a function of time
Steele, I. A.; Pinfield, D. J.; Kendall, T. R. +5 more
Using a simulated disc brown dwarf (BD) population, we find that new large area infrared surveys are expected to identify enough BDs covering wide enough mass-age ranges to potentially measure the present day mass function down to ~0.03Msolar, and the BD formation history out to 10Gyr, at a level that will be capable of establishing if …
A catalogue of close binaries located in the δ Scuti region of the Cepheid instability strip
Demircan, O.; Soydugan, F.; Soydugan, E. +1 more
A catalogue of close eclipsing binary systems (detached and semidetached) with at least one of the components located in the δ Scuti region of the Cepheid instability strip is presented. The positions of the stars in the instability strip are determined by their accurate temperatures and luminosities. Observationally detected binaries (20 semideta…
HD3651B: the first directly imaged brown dwarf companion of an exoplanet host star
Mazeh, T.; Neuhäuser, R.; Mugrauer, M. +1 more
In the course of our ongoing multiplicity study of exoplanet host stars we detected a faint companion located at ~43arcsec (480au physical projected separation) north-west of its primary - the exoplanet host star HD3651 at 11pc. The companion, HD3651B, clearly shares the proper motion of the exoplanet host star in our four images, obtained with th…
Absolute magnitudes of OB and Be stars based on Hipparcos parallaxes - II
Wegner, W.
A new method of determining absolute visual magnitudes of early-type stars, based on averaging Hipparcos parallaxes (ESA 1997) inside samples of the same spectrum and luminosity (Sp/L) classes, is proposed. The used sample consists of 6262 unreddened and reddened OB stars as well as 430 Be stars of luminosity classes Ia, Iab, Ib, II, III, IV and V…
Luminosity function of contact binaries based on the All Sky Automated Survey (ASAS)
Rucinski, Slavek M.
The luminosity function for contact binary stars of the W UMa type is evaluated on the basis of the All Sky Automated Survey (ASAS) photometric project covering all stars south of δ=+ 28° within a magnitude range 8 < V < 13. Lack of colour indices enforced a limitation to 3374 systems with P < 0.562 d (i.e. 73 per cent of all systems with…
New members in the Upper Scorpius association from the UKIRT Infrared Deep Sky Survey Early Data Release†
Hambly, N. C.; Jameson, R. F.; Lodieu, N.
We present the results of a 9.3-deg2 infrared (ZYJHK) survey in the Upper Scorpius association extracted from the UKIRT Infrared Deep Sky Survey (UKIDSS) Galactic Cluster Survey Early Data Release. We have selected a total of 112 candidates from the (Z-J, Z) colour-magnitude diagram over the Z= 12.5-20.5 magnitude range, corresponding t…
Metallicity and absolute magnitude calibrations for UBV photometry
Karataş, Y.; Schuster, W. J.
Calibrations are presented here for metallicity ([Fe/H]) in terms of the ultraviolet excess, [δ(U - B) at B - V = 0.6, hereafter δ0.6], and also for the absolute visual magnitude (MV) and its difference with respect to the Hyades (ΔMHV) in terms of δ0.6 and (B - V), making use of high-resoluti…