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 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:
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RA (2000) DE Designation(s)
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21 35 19.1 +28 11 51 HR 8257 = WDS J21353+2812AB
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 86 349 HR 8257 PTI V2 data, predictions and residuals
from "Joint" orbit model
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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
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Bytes Format Units Label Explanations
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1- 10 F10.4 d MJD Modified Julian Date of the Observation
12- 21 A10 "YYYY/MM/DD" Obs.date 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
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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 1999PASP..111..111C).
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 29-Apr-2011