Contents
Images
Upload your image
DSS Images Other Images
Related articles
Structure and Evolution of Nearby Stars with Planets. II. Physical Properties of ~1000 Cool Stars from the SPOCS Catalog
We derive detailed theoretical models for 1074 nearby stars from theSPOCS (Spectroscopic Properties of Cool Stars) Catalog. The Californiaand Carnegie Planet Search has obtained high-quality (R~=70,000-90,000,S/N~=300-500) echelle spectra of over 1000 nearby stars taken with theHamilton spectrograph at Lick Observatory, the HIRES spectrograph atKeck, and UCLES at the Anglo Australian Observatory. A uniform analysisof the high-resolution spectra has yielded precise stellar parameters(Teff, logg, vsini, [M/H], and individual elementalabundances for Fe, Ni, Si, Na, and Ti), enabling systematic erroranalyses and accurate theoretical stellar modeling. We have created alarge database of theoretical stellar evolution tracks using the YaleStellar Evolution Code (YREC) to match the observed parameters of theSPOCS stars. Our very dense grids of evolutionary tracks eliminate theneed for interpolation between stellar evolutionary tracks and allowprecise determinations of physical stellar parameters (mass, age,radius, size and mass of the convective zone, surface gravity, etc.).Combining our stellar models with the observed stellar atmosphericparameters and uncertainties, we compute the likelihood for each set ofstellar model parameters separated by uniform time steps along thestellar evolutionary tracks. The computed likelihoods are used for aBayesian analysis to derive posterior probability distribution functionsfor the physical stellar parameters of interest. We provide a catalog ofphysical parameters for 1074 stars that are based on a uniform set ofhigh-quality spectral observations, a uniform spectral reductionprocedure, and a uniform set of stellar evolutionary models. We explorethis catalog for various possible correlations between stellar andplanetary properties, which may help constrain the formation anddynamical histories of other planetary systems.
| Spectroscopic Properties of Cool Stars (SPOCS). I. 1040 F, G, and K Dwarfs from Keck, Lick, and AAT Planet Search Programs
We present a uniform catalog of stellar properties for 1040 nearby F, G,and K stars that have been observed by the Keck, Lick, and AAT planetsearch programs. Fitting observed echelle spectra with synthetic spectrayielded effective temperature, surface gravity, metallicity, projectedrotational velocity, and abundances of the elements Na, Si, Ti, Fe, andNi, for every star in the catalog. Combining V-band photometry andHipparcos parallaxes with a bolometric correction based on thespectroscopic results yielded stellar luminosity, radius, and mass.Interpolating Yonsei-Yale isochrones to the luminosity, effectivetemperature, metallicity, and α-element enhancement of each staryielded a theoretical mass, radius, gravity, and age range for moststars in the catalog. Automated tools provide uniform results and makeanalysis of such a large sample practical. Our analysis method differsfrom traditional abundance analyses in that we fit the observed spectrumdirectly, rather than trying to match equivalent widths, and wedetermine effective temperature and surface gravity from the spectrumitself, rather than adopting values based on measured photometry orparallax. As part of our analysis, we determined a new relationshipbetween macroturbulence and effective temperature on the main sequence.Detailed error analysis revealed small systematic offsets with respectto the Sun and spurious abundance trends as a function of effectivetemperature that would be inobvious in smaller samples. We attempted toremove these errors by applying empirical corrections, achieving aprecision per spectrum of 44 K in effective temperature, 0.03 dex inmetallicity, 0.06 dex in the logarithm of gravity, and 0.5 kms-1 in projected rotational velocity. Comparisons withprevious studies show only small discrepancies. Our spectroscopicallydetermined masses have a median fractional precision of 15%, but theyare systematically 10% higher than masses obtained by interpolatingisochrones. Our spectroscopic radii have a median fractional precisionof 3%. Our ages from isochrones have a precision that variesdramatically with location in the Hertzsprung-Russell diagram. We planto extend the catalog by applying our automated analysis technique toother large stellar samples.
| A Comparison of Observationally Determined Radii with Theoretical Radius Predictions for Short-Period Transiting Extrasolar Planets
Two extrasolar planets, HD 209458b and TrES-1, are currently known totransit bright parent stars for which physical properties can beaccurately determined. The two transiting planets have very similarmasses and periods and hence invite detailed comparisons between theirobserved and theoretically predicted properties. In this paper, we carryout these comparisons. We first report photometric and spectroscopicfollow-up observations of TrES-1, and we use these observations toobtain improved estimates for the planetary radius,Rpl=(1.08+/-0.05)RJ, and the planetary mass,Mpl=(0.729+/-0.036)MJ. We also confirm that theinclination estimate of the planetary orbit as i=88.2d. These valuesagree with those obtained by Alonso et al. in their discovery paper, butthe uncertainty in the planet radius has been improved as a result ofboth high-cadence photometry of two full transits and from independentradius determinations for the V=11.8 K0 V parent star. We deriveestimates for the TrES-1 stellar parameters ofR*/Rsolar=0.83+/-0.03 (by combining independentestimates from stellar models, high-resolution spectra, and transitlight curve fitting) M*/Msolar=0.87+/-0.05 (viafitting to evolutionary tracks), Teff=5214+/-23K,[Me/H]=0.001+/-0.04, rotational velocityVsin(i)=1.08+/-0.3kms-1, logg=4.52+/-0.05dex,logL*/Lsolar=-0.32, d=157+/-6pc, and an age ofτ=4+/-2Gyr. These estimates of the physical properties of the systemallow us to compute evolutionary models for the planet that result in apredicted radius of Rpl=1.05RJ for a model thatcontains an incompressible 20 M⊕ core and a radiusRpl=1.09RJ for a model without a core. We use ourgrids of planetary evolution models to show that, with standardassumptions, our code also obtains good agreement with the observedradii of the other recently discovered transiting planets, includingOGLE-TR-56b, OGLE-TR-111b, OGLE-TR-113b, and OGLE-TR-132b. We report anupdated radius for HD 209458b ofRpl=(1.32+/-0.05)RJ, based on a new radiusestimate of R*=1.12Rsolar for the parent star. Ourtheoretical predictions for the radius of HD 209458b areRpl=1.05RJ and 1.09RJ for models withand without cores. HD 209458b is therefore the only transiting planetwhose radius does not agree well with our theoretical models. We arguethat tidal heating stemming from dynamical interaction with a secondplanet is currently the most viable explanation for its inflated size.
| Chromospheric Ca II Emission in Nearby F, G, K, and M Stars
We present chromospheric Ca II H and K activity measurements, rotationperiods, and ages for ~1200 F, G, K, and M type main-sequence stars from~18,000 archival spectra taken at Keck and Lick Observatories as a partof the California and Carnegie Planet Search Project. We have calibratedour chromospheric S-values against the Mount Wilson chromosphericactivity data. From these measurements we have calculated medianactivity levels and derived R'HK, stellar ages,and rotation periods from general parameterizations for 1228 stars,~1000 of which have no previously published S-values. We also presentprecise time series of activity measurements for these stars.Based on observations obtained at Lick Observatory, which is operated bythe University of California, and on observations obtained at the W. M.Keck Observatory, which is operated jointly by the University ofCalifornia and the California Institute of Technology. The KeckObservatory was made possible by the generous financial support of theW. M. Keck Foundation.
| Detection of moving clusters by a method of cinematic pairs
The algorithm of revealing of pairs stars with common movement isoffered and is realized. The basic source is the catalogue HIPPARCOS. Onconcentration of kinematic pairs it is revealed three unknown earliermoving clusters in constellations: 1) Phe, 2) Cae, 3) Hor and, wellknown, in 4) UMa are revealed. On an original technique the members ofclusters -- all 87 stars are allocated. Coordinates of the clustersconvergent point α, delta; (in degrees), spatial speed (in km/s)and age (in 106 yr) from isochrone fitting have made: 1) 51,-29, 19.0, 500, 5/6; 2) 104, -32, 23.7, 300, 9/12; 3) 119, -27, 22.3,100, 9/22; 4) 303, -31, 16.7, 500, 16/8 accordingly. Numerator offraction -- number of stars identified as the members of clusters,denominator -- number of the probable members (with unknown radialspeeds). The preliminary qualitative analysis of clusters spatialstructure is carried in view of their dynamic evolution.
|
Submit a new article
Related links
Submit a new link
Member of following groups:
|
Observation and Astrometry data
| Constellation: | Hydre |
| Right ascension: | 09h17m55.38s |
| Declination: | -03°23'14.1" |
| Apparent magnitude: | 7.777 |
| Distance: | 32.787 parsecs |
| Proper motion RA: | 26.7 |
| Proper motion Dec: | -65.7 |
| B-T magnitude: | 8.84 |
| V-T magnitude: | 7.865 |
Catalogs and designations:
|
