J/A+A/625/A59 tau Boo Radial velocities & astrometric data (Justesen+, 2019)
Constraining the orbit of the planet-hosting binary τ Bootis:
Clues about planetary formation and migration.
Justesen A.B., Albrecht S.
<Astron. Astrophys. 625, A59 (2019)>
=2019A&A...625A..59J 2019A&A...625A..59J (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets ; Radial velocities ;
Positional data
Keywords: stars: individual: tau Bootis - planetary systems -
planet-disk interactions - astrometry -
techniques: radial velocities -
planets and satellites: dynamical evolution and stability
Abstract:
The formation of planets in compact or highly eccentric binaries and
the migration of hot Jupiters are two outstanding problems in planet
formation. Detailed characterisation of known systems is important for
informing and testing models. The hot Jupiter τ Boo Ab orbits the
primary star in the long-period (P≳1000yr), highly eccentric (e∼0.9)
double star system τ Bootis. Due to the long orbital period, the
orbit of the stellar binary is poorly constrained.
Here we aim to constrain the orbit of the stellar binary τ Boo AB
in order to investigate the formation and migration history of the
system. The mutual orbital inclination of the stellar companion and
the hot Jupiter has important implications for planet migration. The
binary eccentricity and periastron distance are important for
understanding the conditions under which τ Boo formed.
We combine more than 150 years of astrometric data with twenty-five
years of high-precision radial velocities. The combination of
sky-projected and line-of-sight measurements places tight constraints
on the orbital inclination, eccentricity, and periastron distance of
τ Boo AB. We determine the orbit of τ Boo B and find an
orbital inclination of 47.2+2.7-3.7°, a periastron
distance of 28.3+2.3-3.0au, and an eccentricity of
0.87+0.04-0.03. We find that the orbital inclinations of
τ Boo Ab and τ Boo B, as well as the stellar spin-axis of
τ Boo A coincide at ∼45 degrees, a result
consistent with the assumption of a well-aligned, coplanar system.
The likely aligned, coplanar configuration suggests planetary
migration within a well-aligned protoplanetary disc. Due to the high
eccentricity and small periastron distance of τ Boo B, the
protoplanetary disc was tidally truncated at ∼6au. We suggest that
τ Boo Ab formed near the edge of the truncated disc and migrated
inwards with high eccentricity due to spiral waves generated by the
stellar companion.
Description:
The astrometric data is downloaded from the Washington Double Star
Catalog (WDS) and the Gaia DR2 Archive. The radial velocities are
downloaded from The Twenty-Five Year Lick Planet Search and from
observations of tau Boo using the HARPS-N spectrograph at the
Telescopio Nazionale Galileo (TNG).
Objects:
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RA (2000) DE Designation(s)
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13 47 15.74 +17 27 24.9 tau Boo = HR 5185
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
astrodat.dat 50 61 Astrometric measurements of tau Boo
rvdat1.dat 40 147 Radial velocities of tau Boo
(Lick Dewar 6, 8, 13)
rvdat2.dat 40 25 Radial velocities of tau Boo (HARPS)
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See also:
J/A+A/578/A64 : Velocity curve of τ Boo A (Borsa+, 2015)
Byte-by-byte Description of file: astrodat.dat
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Bytes Format Units Label Explanations
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1- 11 F11.6 yr Obs.date Date of observation in decimal years
13- 21 F9.6 arcsec rho Sky-projected separation
23- 30 F8.6 arcsec e_rho ?=0 Formal uncertainty of rho (1)
32- 41 F10.6 deg theta Position angle
43- 50 F8.6 deg e_theta ?=0 Formal uncertainty of theta (1)
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Note (1): Missing formal uncertainties are given as zeroes.
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Byte-by-byte Description of file: rvdat1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 F14.6 d BJD Barycentric Julian date of observation
16- 28 F13.6 m/s RV Relative radial velocity
30- 38 F9.6 m/s e_RV Formal uncertainty on radial velocity
40 I1 --- Setup [1/3] Setup used for observation (1)
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Note (1): Setup code as follows:
1 = Lick Dewar 13
2 = Lick Dewar 6
3 = Lick Dewar 8
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Byte-by-byte Description of file: rvdat2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 F14.6 d BJD Barycentric Julian date of observation
16- 28 F13.6 m/s RV Radial velocity
30- 38 F9.6 m/s e_RV Formal uncertainty on radial velocity
40 I1 --- Setup [4] Setup used for observation (1)
--------------------------------------------------------------------------------
Note (1): Setup code as follows:
4 = HARPS-N
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History:
From Anders Bo Justesen, justesen(at)phys.au.dk
Acknowledgements:
Based on observations made as part of the observing programs OPT17A_64
and A35TAC_26 with the Italian Telescopio Nazionale Galileo (TNG)
operated on the island of La Palma by the Fundacion Galileo Galilei of
the INAF (Istituto Nazionale di Astrofisica) at the Spanish
Observatorio del Roque de los Muchachos of the Instituto de
Astrofisica de Canarias. This research has made use of the Washington
Double Star Catalog maintained at the U.S. Naval Observatory. This
work has made use of data from the European Space Agency (ESA) mission
Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data
Processing and Analysis Consortium (DPAC,
https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the
DPAC has been provided by national institutions, in particular the
institutions participating in the Gaia Multilateral Agreement.
(End) Patricia Vannier [CDS] 08-Apr-2019