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Near-infrared integral-field spectroscopy of the companion to GQ Lupi
Context: The first substellar companion of possibly planetary massaround a normal star, GQ Lup, has been directly imaged (Neuhäuseret al. 2005, A&A, 435, L13). Besides the unknown formation history,the mass of such an object is a criterion to decide about its truenature. Aims: We aim to determine the physical properties of the GQ Lupcompanion - effective temperate (T_eff) and surface gravity (log{g}),and thus its mass independently from evolutionary models. Methods: Weuse the adaptive optics integral-field spectrograph SINFONI at the VLTfor near-infrared spectroscopy from 1.1 to 2.5 μm with a resolutionof R = 2500-4000. We compare these spectra with synthetic atmosphericmodels (GAIA v2.0 cond). Results: From the complete set of spectra wefind a consistent effective temperature and surface gravity of T_eff =2650 ± 100 K and log{g} = 3.7 ± 0.5 dex. Combined with aslightly revised luminosity of log{L/Lȯ} = -2.25± 0.24 dex for the companion, we determine a radius of R =3.50+1.50-1.03 {R_Jup} and thus a mass of 25{M_Jup}. The uncertainty of this value is rather high. Due to the largeuncertainty of the surface gravity, the mass could range from 4 to 155{M_Jup}. By comparing the paramaters of the companion of GQ Lup to theones of 2MASS J05352184-0546085, published by Stassunet al. (2006, Nature, 440, 311), we conclude that the companion to GQLup A has a mass lower than 36 ± 3 {M_Jup}.Based on observations collected at the European Southern Observatory,Chile, in programmes 275.C-5033(A) and 077.C-0264(A).
| New Estimates of the Solar-Neighborhood Massive Star Birthrate and the Galactic Supernova Rate
The birthrate of stars of masses >=10 Msolar is estimatedfrom a sample of just over 400 O3-B2 dwarfs within 1.5 kpc of the Sunand the result extrapolated to estimate the Galactic supernova ratecontributed by such stars. The solar-neighborhood Galactic-plane massivestar birthrate is estimated at ~176 stars kpc-3Myr-1. On the basis of a model in which the Galactic stellardensity distribution comprises a ``disk+central hole'' like that of thedust infrared emission (as proposed by Drimmel and Spergel), theGalactic supernova rate is estimated at probably not less than ~1 normore than ~2 per century and the number of O3-B2 dwarfs within the solarcircle at ~200,000.
| Catalog of Galactic OB Stars
An all-sky catalog of Galactic OB stars has been created by extendingthe Case-Hamburg Galactic plane luminous-stars surveys to include 5500additional objects drawn from the literature. This work brings the totalnumber of known or reasonably suspected OB stars to over 16,000.Companion databases of UBVβ photometry and MK classifications forthese objects include nearly 30,000 and 20,000 entries, respectively.
| Extinction law survey based on UV ANS photometry
The paper presents an extensive survey of interstellar extinction curvesderived from the ANS photometric measurements of early type starsbelonging to our Galaxy. This survey is more extensive and deeper thanany other one, based on spectral data. The UV color excesses aredetermined with the aid of 'artificial standards', a new techniqueproposed by the authors which allows the special check of Sp/L match ofa target and the selected standard. The results indicate that extinctionlaw changes from place to place.
| A study of SCO 0B1 and NGC 6231. II - A new analysis
A new analysis of the Sco 0B1 association, and the two open clusters NGC6231 and Tr 24 was undertaken, making use of the extensive amount ofpublished data for this region of the southern sky. The averageinterstellar reddening, due mostly to foreground particulate matter, isE(b - y) = 0.326 mag or E(B - V) = 0.44 mag, with a pronouncednorth-to-south variation across the association. The distance moduli ofthe three aggregates are indistinguishable from one another; their meandistance from the sun is 2.0 kpc. A logarithmic age of 6.9 +/- 0.2 yearswas derived for the systems. Photometric criteria were used to assigndifferent degrees of membership to the B-type stars. Potential variablestar candidates were noted. Contrary to previous suggestions, NGC 6231retains its role as the nucleus of Sco 0B1 and, finally, the physicalreality of Tr 24 itself is questioned and briefly discussed.
| The fundamental physical parameters of main-sequence and near main-sequence B type stars as derived from uvby,beta photometry
From spectrophotometric measurements of hydrogen line intensities, uvbyphotometry and photoelectrically determined H-beta and H-gamma indicesof 75 B2-B6 main-sequence stars, effective temperature and surfacegravity are derived by using the model atmospheres computed by Kurucz(1974). Comparisons between the g values and the MK luminosityclassification show good agreement for the MK standard stars but ratherserious disagreement for the average stars in such a way that most ofthe stars classified in luminosity class V really belong to class IV.Using the evolutionary model sequences calculated by Hejlesen et al.(1972) the stellar mass, age and luminosity are determined from the uvbyand beta data through effective temperature and surface gravity. Thetheoretically derived luminosities are in excellent agreement with theluminosities derived by calibrations.
| Prediction of spectral classification from photometric observations - Application of the UVBY beta photometry and the MK spectra classification. II - General case
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&A....85...93M&db_key=AST
| Prediction of spectral classification from photometric observations-application to the UVBY beta photometry and the MK spectral classification. I - Prediction assuming a luminosity class
An algorithm based on multiple stepwise and isotonic regressions isdeveloped for the prediction of spectral classification from photometricdata. The prediction assumes a luminosity class with reference touvbybeta photometry and the MK spectral classification. The precisionattained is about 90 percent and 80 percent probability of being withinone spectral subtype respectively for luminosity groups I and V and forluminosity groups III and IV. A list of stars for which discrepanciesappear between photometry and spectral classification is given.
| Interstellar absorption and color excess in SCO OB1
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971AJ.....76..237S&db_key=AST
| Determination of proper motions in the region of the association Scorpius OB1
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