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מאמרים קשורים
Directly Determined Linear Radii and Effective Temperatures of Exoplanet Host Stars
We present interferometric angular sizes for 12 stars with knownplanetary companions, for comparison with 28 additional main-sequencestars not known to host planets. For all objects we estimate bolometricfluxes and reddenings through spectral-energy distribution (SED) fits,and in conjunction with the angular sizes, measurements of effectivetemperature. The angular sizes of these stars are sufficiently smallthat the fundamental resolution limits of our primary instrument, thePalomar Testbed Interferometer, are investigated at thesub-milliarcsecond level and empirically established based upon knownperformance limits. We demonstrate that the effective temperature scaleas a function of dereddened (V – K)0 color isstatistically identical for stars with and without planets. A usefulbyproduct of this investigation is a direct calibration of the TEFF scale for solarlike stars, as a function of both spectraltype and (V – K)0 color, with an precision of\overline{\Delta T}_{\it {(V-K)}_0} = 138\,K over the range (V –K)0 = 0.0-4.0 and \overline{\Delta T}_{SpType} = 105\,K forthe range F6V-G5V. Additionally, in an Appendix we provide SED fits forthe 166 stars with known planets which have sufficient photometryavailable in the literature for such fits; this derived "XO-Rad"database includes homogeneous estimates of bolometric flux, reddening,and angular size.
| The HARPS search for southern extra-solar planets. X. A m sin i = 11 M_⊕ planet around the nearby spotted M dwarf GJ 674
Context: How planet properties depend on stellar mass is a keydiagnostic of planetary formation mechanisms. Aims: This motivatesplanet searches around stars that are significantly more massive or lessmassive than the Sun, and in particular our radial velocity search forplanets around very low-mass stars. Methods: As part of that program,we obtained measurements of GJ 674, an M 2.5 dwarf atd = 4.5 pc. These measurements have dispersion much in excess of theirinternal errors. An intensive observing campaign demonstrates that theexcess dispersion is due to two superimposed coherent signals, withperiods of 4.69 and 35 days. Results: These data are described well bya 2-planet Keplerian model where each planet has a ~11 M_⊕ minimummass. A careful analysis of the (low-level) magnetic activity ofGJ 674, however, demonstrates that the 35-day periodcoincides with the stellar rotation period. This signal thereforeoriginates in a spot inhomogeneity modulated by stellar rotation. The4.69-day signal, on the other hand, is caused by a bona-fide planet,GJ 674b. Conclusions: Its detection adds to thegrowing number of Neptune-mass planets around M-dwarfs and reinforcesthe emerging conclusion that this mass domain is much more populatedthan the Jovian mass range. We discuss the metallicity distributions ofM dwarf with and without planets and find a low 11% probability thatthey are drawn from the same parent distribution. Moreover, we findtentative evidence that the host star metallicity correlates with thetotal mass of their planetary system.Based on observations made with the HARPS instrument on the ESO 3.6 mtelescope under the GTO program ID 072.C-0488 at Cerro La Silla (Chile).Radial-velocity, photometric and Ca II H+K index time series are onlyavailable in electronic format the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strabg.fr/cgi-bin/qcat?J/A+A/474/293
| Dynamical Evidence for a Black Hole in the Microquasar XTE J1550-564
Optical spectroscopic observations of the companion star (type G8 IV toK4 III) in the microquasar system XTE J1550-564 reveal a radial velocitycurve with a best-fitting spectroscopic period ofPsp=1.552+/-0.010 days and a semiamplitude ofK2=349+/-12 km s-1. The optical mass function isf(M)=6.86+/-0.71Msolar (1 σ). We tentatively measurethe rotational velocity of the companion star to beVrotsini=90+/-10 km s-1, which when taken at facevalue implies a mass ratio ofQ≡M1/M2=6.6+2.5-1.6 (1σ), using the above value of K2. We derive constraintson the binary parameters from simultaneous modeling of the ellipsoidallight and radial velocity curves. We find 1 σ ranges for thephotometric period (1.5430days<=Pph<=1.5440days),K-velocity (350.2<=K2<=368.6 km s-1),inclination (67.0d<=i<=77.4d), mass ratio (Q>=12.0), andorbital separation(11.55Rsolar<=a<=12.50Rsolar). Given thesegeometrical constraints, we find that the most likely value of the massof the compact object is 9.41 Msolar with a 1 σ rangeof 8.36Msolar<=M1<=10.76Msolar.If we apply our tentative value of Vrotsini=90+/-10 kms-1 as an additional constraint in the ellipsoidal modeling,we find 1 σ ranges of 1.5432days<=Pph<=1.5441daysfor the photometric period, 352.2<=K2<=370.1 kms-1 for the K-velocity, 70.8d<=i<=75.4d for theinclination, 6.7<=Q<=11.0 for the mass ratio, and12.35Rsolar<=a<=13.22Rsolar for the orbitalseparation. These geometrical constraints imply the most likely value ofthe mass of the compact object of 10.56 Msolar with a 1σ range of9.68Msolar<=M1<=11.58Msolar. Ineither case the mass of the compact object is well above the maximummass of a stable neutron star, and we therefore conclude that XTEJ1550-564 contains a black hole. Based on observations collected at theEuropean Southern Observatory, Chile (program 67.D-0229), at theMagellan Walter Baade Telescope at the Las Campanas Observatory, Chile,and the William Herschel Telescope operated on the island of La Palma bythe Isaac Newton Group in the Spanish Observatorio del Roque de losMuchachos of the Instituto de Astrofisica de Canarias.
| A homogeneous catalog of new UBV and H-beta photometry of B- and A-type stars in and around the Scorpius-Centaurus OB association
B- and A-type stars in and near the Sco-Cen OB association areinvestigated with UBV and H-beta photometry to acquire data relevant tothe luminosity function of Sco-Cen. The measurements generally consistof two 10-s integrations of U, B, V, (W, N) filters, and theobservations are corrected iteratively for atmospheric extinction andinstrumental response. The data presented give the mean V magnitude,mean B-V, mean U-B, and the estimated uncertainties for these values.The catalog provides a homogeneous catalog of data for a large fieldwith stellar objects delineating membership to the association Sco-Cenand that affect the luminosity function of the aggregate.
| UBV photometry of E region standard stars of intermediate brightness
Photometry data are given for 335 stars in the nine E regions.Observations were made using a photometer and filters on the 47 cmreflector at Cape Town. The stellar dispersions are summarized. Data arepresented in tabular form.
| Photoelectric standards of intermediate brightness in the E-regions. I. UBV photometry.
Not Available
| Fainter Standards for VRI Photometry in the E Regions
Not Available
| VRI Photometry of E and F Region Stars [errata: 1978MNSSA..37...35C & 1980MNSSA..39...32C]
Not Available
| Lichtelektrische UBV-Photometrie von Standardsternen und in vier Sternfeldern am Äquator
Not Available
| Standard magnitudes in the E regions.
Not Available
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | מזבח |
| התרוממות ימנית: | 17h28m31.06s |
| סירוב: | -46°52'21.1" |
| גודל גלוי: | 8.532 |
| מרחק: | 112.108 פארסק |
| תנועה נכונה: | -3.1 |
| תנועה נכונה: | -47.4 |
| B-T magnitude: | 9.584 |
| V-T magnitude: | 8.619 |
קטלוגים וכינוים:
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