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J/ApJ/695/1527       HR 8257: orbit and basic properties          (Fekel+, 2009)

HR 8257: a three-dimensional orbit and basic properties. Fekel F.C., Boden A.F., Tomkin J., Torres G. <Astrophys. J., 695, 1527-1536 (2009)> =2009ApJ...695.1527F
ADC_Keywords: Binaries, spectroscopic ; Interferometry ; Spectroscopy Keywords: binaries: spectroscopic - stars: fundamental parameters - stars: individual (HR 8257) Abstract: We have used interferometric and spectroscopic observations of HR 8257 to determine a three-dimensional orbit of the system. The orbit has a period of 12.21345 days and an eccentricity of 0.2895. The masses of the F0 and F2 dwarf components are 1.56 and 1.38M, respectively, with fractional errors of 1.4%. Our orbital parallax of 13.632±0.095mas, corresponding to a distance of 73.4±0.6pc, differs from the Hipparcos result by just 2% and has a significantly smaller uncertainty. From our spectroscopic observations and spectral energy distribution modeling we determine the component effective temperatures and luminosities to be Teff(A)=7030±200K and Teff(B)=6560±200K and LA=9.4±0.3L and LB=4.7±0.2L. The primary rotates pseudosynchronously, while the secondary is not far from its pseudosynchronous rotational velocity. Although both early-F stars are slowly rotating, neither component of this close binary is an Am star. A comparison with evolutionary tracks indicates that the stars are slightly metal poor, and although the components have evolved away from the zero-age main sequence, they are both still dwarfs. Description: Our K-band observations of HR 8257 and the objects in our calibrator list were obtained with the PTI (interferometer located at the Palomar Observatory) on 58 nights between 2000 June 25 and 2005 October 14, a data set spanning roughly 5.3yr and 159 orbital periods. From 2000 July to 2006 December, observations from several spectrographs have been collected. Objects: -------------------------------------------------- RA (2000) DE Designation(s) -------------------------------------------------- 21 35 19.1 +28 11 51 HR 8257 = WDS J21353+2812AB -------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 86 349 HR 8257 PTI V2 data, predictions and residuals from "Joint" orbit model
See also: V/89 : Ages, Metallicities, Galactic Orbit of F stars (Marsakov+ 1995) B/sb9 : SB9: 9th Catalogue of Spectroscopic Binary Orbits (Pourbaix+ 2004-2011) V/130 : Geneva-Copenhagen Survey of Solar neighbourhood III (Holmberg+, 2009) J/ApJS/176/276 : PTI calibrator catalog (van Belle+, 2008) J/A+A/450/681 : Companions to close spectroscopic binaries (Tokovinin+, 2006) Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 10 F10.4 d MJD Modified Julian Date of the Observation 12- 21 A10 "YYYY/MM/DD" Date of the Observation 23- 30 A8 "h:m:s" Obs.time Time of the Observation 32- 36 F5.3 um lambda Effective center-band wavelength (1) 38- 42 F5.3 --- MV2 Measured visibility squared (2) 44- 48 F5.3 --- e_MV2 Error in MV2 50- 54 F5.3 --- PV2 Predicted visibility squared 56- 61 F6.3 --- Resid Residual; data-model 63- 70 F8.4 m u The u baseline length 72- 80 F9.4 m v The v baseline length 82- 86 F5.3 --- Phase Orbital phase
Note (1): Wavelengths are SNR-weighted across the channels in the PTI spectrometer (at Palomar). Note (2): From PTI synthetic wide-band reductions (Colavita, 1999PASP..111..111C).
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 29-Apr-2011
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