J/ApJ/761/57 CHARA array angular diameters of HR 8799 (Baines+, 2012)
The CHARA array angular diameter of HR 8799 favors planetary masses for
its imaged companions.
Baines E.K., White R.J., Huber D., Jones J., Boyajian T., McAlister H.A.,
ten Brummelaar T.A., Turner N.H., Sturmann J., Sturmann L.,
Goldfinger P.J., Farrington C.D., Riedel A.R., Ireland M., von Braun K.,
Ridgway S.T.
<Astrophys. J., 761, 57 (2012)>
=2012ApJ...761...57B 2012ApJ...761...57B
ADC_Keywords: Stars, nearby ; Interferometry ; Stars, diameters
Keywords: planetary systems; stars: fundamental parameters;
stars: individual: HR 8799; techniques: high angular resolution;
techniques: interferometric
Abstract:
HR 8799 is an hF0 mA5 γ Doradus-, λ Bootis-, Vega-type
star best known for hosting four directly imaged candidate planetary
companions. Using the CHARA Array interferometer, we measure HR 8799's
limb-darkened angular diameter to be 0.342±0.008mas (an error of
only 2%). By combining our measurement with the star's parallax and
photometry from the literature, we greatly improve upon previous
estimates of its fundamental parameters, including stellar radius
(1.44±0.06R☉), effective temperature (7193±87K, consistent
with F0), luminosity (5.05±0.29L☉), and the extent of the
habitable zone (HZ; 1.62-3.32AU). These improved stellar properties
permit much more precise comparisons with stellar evolutionary models,
from which a mass and age can be determined, once the metallicity of
the star is known. Considering the observational properties of other
λ Bootis stars and the indirect evidence for youth of HR 8799,
we argue that the internal abundance, and what we refer to as the
effective abundance, is most likely near solar. Finally, using the
Yonsei-Yale evolutionary models with uniformly scaled solar-like
abundances, we estimate HR 8799's mass and age considering two
possibilities: 1.516+0.038-0.024M☉ and 33+7-13.2Myr if
the star is contracting toward the zero-age main sequence or
1.513+0.023-0.024M☉ and 90+381-50Myr if it is expanding
from it. This improved estimate of HR 8799's age with realistic
uncertainties provides the best constraints to date on the masses of
its orbiting companions, and strongly suggests they are indeed
planets. They nevertheless all appear to orbit well outside the HZ of
this young star.
Description:
Observations were obtained using the Center for High Angular
Resolution Astronomy (CHARA) Array, a six element optical-infrared
interferometer located on Mount Wilson, California. All data were
taken using the S2-W2 baseline (177m) in 2010-2011 (see table 3).
Objects:
-------------------------------------------------
RA (ICRS) DE Designation(s)
-------------------------------------------------
23 07 28.72 +21 08 03.3 HR 8799 = HD 218396
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 39 1587 Calibrated visibilities
table4.dat 53 29 HR 8799 angular diameter measurements
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See also:
III/213 : General Catalog of mean radial velocities (Barbier-Brossat+, 2000)
J/ApJ/745/147 : Binaries among debris disk stars (Rodriguez+, 2012)
J/A+A/529/A75 : Limb-darkening coefficients (Claret+, 2011)
J/A+A/499/967 : Long-term monitoring of γ Dor stars (Cuypers+, 2009)
J/A+A/472/241 : UV Flux distributions of gamma Dor stars (Gerbaldi+, 2007)
J/A+A/463/671 : Rotational velocities of A-type stars. III. (Royer+, 2007)
J/AJ/133/1421 : BV differential phot. of 11 gamma Dor stars (Henry+, 2007)
J/ApJ/660/1556 : Characterization of dusty debris disks (Rhee+, 2007)
J/A+A/352/555 : Fundamental parameters of stars (Allende Prieto+, 1999)
J/A+AS/106/257 : Stroemgren photometry of F and G stars (Olsen 1994)
J/A+AS/102/89 : uvby-beta Photometry of G5 stars (Olsen 1993)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 "YYYY/MMM/DD" Date Date of the observation
13- 14 A2 --- --- [HD]
16- 21 I6 --- Cal Calibrator used (HD 213617,
HD 214698 or HD 219487) (1)
23- 27 F5.3 10+8/rad SFreq [2.1/2.8] Spatial frequency (in units of
108cycles/radian)
29- 33 F5.3 --- V2 [0.3/1.2] Calibrated visibility
35- 39 F5.3 --- e_V2 [0.02/0.4] The 1σ error in V2
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Note (1): HD 214617 and HD 218487 in table3 of the paper are misprints for
HD 213617 and HD 219487, respectively; table corrected at CDS.
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Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 20 A20 --- Date Observation date(s) (1)
22- 27 I6 --- Cal ? HD calibrator
29 A1 --- f_Cal [A] A: All calibrators
31- 35 F5.3 mas thetUD [0.2/0.4] Apparent uniform disk (UD) angular
diameter of the star (θUD)
37- 41 F5.3 mas e_thetUD [0.007/0.03] thetUD uncertainty
43- 47 F5.3 mas thetLD [0.3/0.4] Limb-darkening angular diameter
(θLD)
49- 53 F5.3 mas e_thetLD [0.007/0.03] thetLD uncertainty
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Note (1): Dates between 2010-Aug and 2011-Sep; data were obtained using the
S2-W2 baseline at 177m for all nights except for 2011 Sep 30, which
were obtained using the S1-E1 baseline at 331m.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 07-Aug-2014