The HARPS search for southern extra-solar planets. XXVI. Two giant planets around M0 dwarfs
Fewer giants planets are found around M dwarfs than around more massivestars, and this dependence of planetary characteristics on the mass ofthe central star is an important observational diagnostic of planetaryformation theories. In part to improve on those statistics, we aremonitoring the radial velocities of nearby M dwarfs with the HARPSspectrograph on the ESO 3.6 m telescope. We present here the detectionof giant planets around two nearby M0 dwarfs: planets, with minimummasses of respectively 5 Jupiter masses and 1 Saturn mass, orbit aroundGl 676A and HIP 12961. The latter is, by over a factor of two, the mostmassive planet found by radial velocity monitoring of an M dwarf, butits being found around an early M-dwarf is in approximate line with theupper envelope of the planetary vs stellar mass diagram. HIP 12961([Fe/H] = -0.07) is slightly more metal-rich than the average solarneighborhood ([Fe/H] = -0.17), and Gl 676A ([Fe/H] = 0.18) significantlyso. The two stars together therefore reinforce the growing trend forgiant planets being more frequent around more metal-rich M dwarfs, andthe 5 Jupiter mass Gl 676Ab being found around a metal-rich star isconsistent with the expectation that the most massive planetspreferentially form in disks with large condensate masses.Based on observations made with the HARPS instrument on the ESO 3.6-mtelescope at La Silla Observatory under program ID 072.C-0488Tables 3and 4 are also available in electronic form at the CDS via anonymous ftpto cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/cgi-bin/qcat?J/A+A/526/A141
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The Hill stability of the possible moons of extrasolar planets
The dynamical Hill stability has been derived for a full three-bodysystem composed of a binary moving on an inclined elliptical orbitrelative to a third body where the binary mass is very small comparedwith the mass of the third body. This physical situation arises in anumber of important astronomical contexts including extrasolar planetarysystems with a star-planet-moon configuration. The Hill stabilitycriterion against disruption and component exchange was applied to allthe known extrasolar planetary systems and the critical separation of apossible moon from the planet determined for moon/planet mass ratios of0.1, 0.01 and 0.001 assuming that the moon moves on a circular orbit. Itis clear that in those cases where the planet moves on a circular orbitabout the central star, the critical separation of the moon from theplanet does not change significantly as the value of the moon/planetmass ratio is reduced. In contrast, for eccentric systems there can bebig changes in the critical separation as the mass ratio decreases. Thevariation in size depends crucially on the size of the eccentricity ofthe planetary orbit.To determine the effect of an eccentrically orbiting moon, the Hillstability criterion was applied generally to the planet-moon binary fora range of moon/planet mass ratios assuming that the planet moved on acircular orbit around the central star. It was found that in all casesthe critical distance ratio increased, and hence the regions of Hillstability decreased as the binary eccentricity increased and also as theinclination of the third body to the binary was increased. The stabilityincreased slightly as the moon/planet ratio was decreased. Also as thebinary/third body mass ratio decreased the effects of the moon/planetmass ratio became less important and the stability curves tended tomerge. These types of changes make exchange or disruption of thecomponent masses more likely.
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UBV(RI)C JHK observations of Hipparcos-selected nearby stars
We present homogeneous, standardized UBV(RI)C photometry forover 700 nearby stars selected on the basis of Hipparcos parallaxes.Additionally, we list JHK photometry for about half of these stars, aswell as L photometry for 86 of the brightest. A number of stars withpeculiar colours or anomalous locations in various colour-magnitudediagrams are discussed.
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The effect of activity on stellar temperatures and radii
Context: Recent analyses of low-mass eclipsing binary stars haveunveiled a significant disagreement between the observations andpredictions of stellar structure models. Results show that theoreticalmodels underestimate the radii and overestimate the effectivetemperatures of low-mass stars but yield luminosities that accord withobservations. A hypothesis based upon the effects of stellar activitywas put forward to explain the discrepancies. Aims: In this paper westudy the existence of the same trend in single active stars and providea consistent scenario to explain systematic differences between activeand inactive stars in the H-R diagram reported earlier. Methods: Theanalysis is done using single field stars of spectral types late-K and Mand computing their bolometric magnitudes and temperatures throughinfrared colours and spectral indices. The properties of the stars insamples of active and inactive stars are compared statistically toreveal systematic differences. Results: After accounting for a numberof possible bias effects, active stars are shown to be cooler thaninactive stars of similar luminosity therefore implying a larger radiusas well, in proportions that are in excellent agreement with those foundfrom eclipsing binaries. Conclusions: The present results generalisethe existence of strong radius and temperature dependences on stellaractivity to the entire population of low-mass stars, regardless of theirmembership in close binary systems.Tables 1 and 2 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/478/507
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Further observations of Hipparcos red stars and standards for UBV(RI)C photometry
We present homogeneous and standardized UBV(RI)C JHKphotometry for over 100 M stars selected from an earlier paper on thebasis of apparent photometric constancy. L photometry has been obtainedfor stars brighter than about L = 6. Most of the stars have asubstantial number of UBV(RI)C observations and, it is hoped,will prove useful as red supplementary standards. Additionally, we listJHK photometry for nearly 300 Hipparcos red stars not selected asstandards, as well as L photometry for the brightest stars.
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Improved Astrometry and Photometry for the Luyten Catalog. II. Faint Stars and the Revised Catalog
We complete construction of a catalog containing improved astrometry andnew optical/infrared photometry for the vast majority of NLTT starslying in the overlap of regions covered by POSS I and by the secondincremental Two Micron All Sky Survey (2MASS) release, approximately 44%of the sky. The epoch 2000 positions are typically accurate to 130 mas,the proper motions to 5.5 mas yr-1, and the V-J colors to0.25 mag. Relative proper motions of binary components are measured to 3mas yr-1. The false-identification rate is ~1% for11<~V<~18 and substantially less at brighter magnitudes. Theseimprovements permit the construction of a reduced proper-motion diagramthat, for the first time, allows one to classify NLTT stars intomain-sequence (MS) stars, subdwarfs (SDs), and white dwarfs (WDs). We inturn use this diagram to analyze the properties of both our catalog andthe NLTT catalog on which it is based. In sharp contrast to popularbelief, we find that NLTT incompleteness in the plane is almostcompletely concentrated in MS stars, and that SDs and WDs are detectedalmost uniformly over the sky δ>-33deg. Our catalogwill therefore provide a powerful tool to probe these populationsstatistically, as well as to reliably identify individual SDs and WDs.
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Hipparcos red stars in the HpV_T2 and V I_C systems
For Hipparcos M, S, and C spectral type stars, we provide calibratedinstantaneous (epoch) Cousins V - I color indices using newly derivedHpV_T2 photometry. Three new sets of ground-based Cousins V I data havebeen obtained for more than 170 carbon and red M giants. These datasetsin combination with the published sources of V I photometry served toobtain the calibration curves linking Hipparcos/Tycho Hp-V_T2 with theCousins V - I index. In total, 321 carbon stars and 4464 M- and S-typestars have new V - I indices. The standard error of the mean V - I isabout 0.1 mag or better down to Hp~9 although it deteriorates rapidly atfainter magnitudes. These V - I indices can be used to verify thepublished Hipparcos V - I color indices. Thus, we have identified ahandful of new cases where, instead of the real target, a random fieldstar has been observed. A considerable fraction of the DMSA/C and DMSA/Vsolutions for red stars appear not to be warranted. Most likely suchspurious solutions may originate from usage of a heavily biased color inthe astrometric processing.Based on observations from the Hipparcos astrometric satellite operatedby the European Space Agency (ESA 1997).}\fnmsep\thanks{Table 7 is onlyavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/397/997
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UBV(RI)C photometry of Hipparcos red stars
We present homogeneous and standardized UBV(RI)C photometryfor nearly 550 M stars selected from the Hipparcos satellite data baseusing the following selection criteria: lack of obvious variability (noHipparcos variability flag); δ<+10°(V-I)>1.7 and Vmagnitude fainter than about 7.6. Comparisons are made between thecurrent photometry, other ground-based data sets and Hipparcosphotometry. We use linear discriminant analysis to determine aluminosity segregation criterion for late-type stars, and principalcomponent analysis to study the statistical structure of the colourindices and to calibrate absolute magnitude in terms of (V-I) for thedwarf stars. Various methods are used to determine the mean absolutemagnitude of the giant stars. We find 10 dwarf stars, apparentlypreviously unrecognized (prior to Hipparcos) as being within 25pc,including five within 20pc.
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The Palomar/MSU Nearby Star Spectroscopic Survey.II.The Southern M Dwarfs and Investigation of Magnetic Activity
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996AJ....112.2799H&db_key=AST
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The initial mass function and the dynamical evolution of open clusters. III. With primordial binaries.
This paper presents the results of several direct N-body calculations ofstar cluster models, containing a fraction of initial binary population,without mass loss due to stellar evolution. These primordial binariesare generated with several initial mass functions for checking theirinfluence on the dynamical evolution of clusters. Our results show thatprimordial binaries dominate completely the evolution of poor clustersand control it until they are ejected or disrupted; their effect issmaller for rich clusters. The quantitative behaviour seems to bedependent on the mass spectrum. Evolution of primordial binaries isexamined in detail. The binary escape rate is studied and someconclusions are presented. The final product of cluster evolution, thestar cluster remnant, is also discussed.
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Dynamics of nearby multiple stars. The alpha Centauri system
The triple star system alpha Cen AB and Proxima Cen - the component C -is the nearest to the Sun. The study of its dynamics has shown that thissystem is probably not a chance one. The motion of the component C(Proxima) with respect to the center of mass of the pair AB ishyperbolic with the probability P = 1.0. We observe, therefore, a slowpassage of C close to the pair AB. We propose the hypothesis that thissystem is a part of a stellar moving group. We list the probable membersof this group amongst the nearby stars. Amongst them we have thebinaries Gliese 140.1 and 676, the triple system ADS 10288 (Gliese649.1), and six single stars. The probability to find these stars bychance inside the velocity space cube with a side of 20 km/s aroundalpha Cen is equal to about 2%.
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Statistical studies of visual double and multiple stars. II. A catalogue of nearby wide binary and multiple systems.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1994RMxAA..28...43P&db_key=AST
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Improved Position of Southern NSV Stars. I.
Not Available
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Catalogue of Variable or Suspected Stars Nearby the Sun
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1990A&AS...85..971P&db_key=AST
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UBV (RI)c photometry of faint nearby stars.
Not Available
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Predicted infrared brightness of stars within 25 parsecs of the sun
Procedures are given for transforming selected optical data intoinfrared flux densities or irradiances. The results provide R, T(eff)blackbody approximations for about 2000 of the stars in Woolley et al.'sCatalog of Stars (1970) within 25 pc of the sun, and additional whitedwarfs, with infrared flux densities predicted for them at ninewavelengths from 2.2 to 101 microns including the Infrared AstronomySatellite bands.
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New light on faint stars. I - The luminosity function in the solar neighbourhood
From photoelectric photometry of red dwarf stars identified in anobjective prism survey, a magnitude-limited complete sample has beendefined. Applying photometric parallaxes, calibrated for theKron-Cousins system by observations of trigonometric parallax stars,this sample is used to determine the space densities of stars withabsolute magnitudes between + 7 and + 12. The resultant luminosityfunction is consistent with the Luyten and Wielen functions for thesolar neighbourhood. An analysis of the stellar kinematics shows littlesignificant evidence of a substantial local population of low spacemotion M-dwarfs.
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UBV Photometry of 500 Southern Stars [erratum: 1973MNSSA..32...48C]
Not Available
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