J/AJ/159/63 New AO obs. of exoplanets & brown dwarf companions (Bowler+, 2020)
Population-level eccentricity distributions of imaged exoplanets and brown dwarf
companions: dynamical evidence for distinct formation channels.
Bowler B.P., Blunt S.C., Nielsen E.L.
<Astron. J., 159, 63 (2020)>
=2020AJ....159...63B 2020AJ....159...63B
ADC_Keywords: Exoplanets; Stars, brown dwarf; Stars, masses; Spectral types;
Stars, ages; Infrared; References
Keywords: Exoplanet formation ; Brown dwarfs ; Extrasolar gas giants
Abstract:
The orbital eccentricities of directly imaged exoplanets and brown
dwarf companions provide clues about their formation and dynamical
histories. We combine new high-contrast imaging observations of
substellar companions obtained primarily with Keck/NIRC2 together with
astrometry from the literature to test for differences in the
population-level eccentricity distributions of 27 long-period giant
planets and brown dwarf companions between 5 and 100au using
hierarchical Bayesian modeling. Orbit fits are performed in a uniform
manner for companions with short orbital arcs; this typically results
in broad constraints for individual eccentricity distributions, but
together as an ensemble, these systems provide valuable insight into
their collective underlying orbital patterns. The shape of the
eccentricity distribution function for our full sample of substellar
companions is approximately flat from e=0-1. When subdivided by
companion mass and mass ratio, the underlying distributions for giant
planets and brown dwarfs show significant differences. Low mass ratio
companions preferentially have low eccentricities, similar to the
orbital properties of warm Jupiters found with radial velocities and
transits. We interpret this as evidence for in situ formation on
largely undisturbed orbits within massive extended disks. Brown dwarf
companions exhibit a broad peak at e∼0.6-0.9 with evidence for a
dependence on orbital period. This closely resembles the orbital
properties and period-eccentricity trends of wide (1-200au) stellar
binaries, suggesting that brown dwarfs in this separation range
predominantly form in a similar fashion. We also report evidence that
the "eccentricity dichotomy" observed at small separations extends to
planets on wide orbits: the mean eccentricity for the multi-planet
system HR8799 is lower than for systems with single planets. In the
future, larger samples and continued astrometric orbit monitoring will
help establish whether these eccentricity distributions correlate with
other parameters such as stellar host mass, multiplicity, and age.
Description:
HD49197 was targeted using the High Contrast Instrument for the Subaru
Next Generation Adaptive Optics (HiCIAO) near-infrared imager coupled
with the AO188 adaptive optic (AO) system at Subaru Telescope on UT
2011 December 28 (see Table 1 for details). A total of 60 frames was
acquired in Ks band, each with an integration time of 30s.
In total, we targeted 13 sources with substellar companions between
2014 and 2019 (see Table 1) with the NIRC2 camera behind natural guide
star AO at Keck Observatory. All observations were acquired with the
narrow camera mode, which provides a plate scale of ∼10mas/pix and a
field of view of 10.2"x10.2". Total on-source integration times ranged
from 3 to 81 minutes and the field-of-view rotation angle ranged from
3° to 119°.
Finally, these new imaging observations of substellar companions were
combined with astrometry from the literature; see Table 8.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 108 18 Observations and astrometry of substellar
companions
table3.dat 230 22 Results from orbit fits
table4.dat 201 27 Sample of substellar companions between 2 and
75MJup and 5-100au exhibiting orbital motion
table5.dat 94 27 Summary of individual eccentricity distributions
companions
table8.dat 95 215 Literature astrometry
refs.dat 68 62 References for Table 4
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/ApJ/637/1067 : Near-IR spectral classification T dwarfs (Burgasser+,2006)
J/ApJ/703/1511 : Wide binaries in Taurus and Upper Sco (Kraus+, 2009)
J/ApJS/181/62 : Survey of young solar analogs (Metchev+, 2009)
J/ApJ/693/1084 : Ten new and updated multiplanet systems (Wright+, 2009)
J/ApJS/190/1 : A survey of stellar families (Raghavan+, 2010)
J/ApJ/725/331 : Astrometry in the Galactic Center (Yelda+, 2010)
J/AJ/144/62 : Tertiary companions spectroscopic binaries (Allen+, 2012)
J/ApJ/754/44 : The AstraLux Large M-dwarf Survey (Janson+ 2012)
J/ApJ/758/56 : Young M dwarfs within 25pc. II. (Shkolnik+, 2012)
J/ApJ/745/174 : Evolution models young gas-giant planets (Spiegel+, 2012)
J/ApJ/771/129 : Submillimetric Class II sources of Taurus (Andrews+, 2013)
J/ApJ/762/88 : Young stellar kinematic group candidate (Malo+, 2013)
J/A+A/551/A36 : Metallicity of M dwarfs. III. (Neves+, 2013)
J/A+A/562/A127 : Near-IR integral spectra of 15 M-L dwarfs (Bonnefoy+,2014)
J/ApJS/211/25 : Spitzer/IRS debris disk catalog. I. (Chen+, 2014)
J/ApJ/792/119 : Companions nearby stars from Pan-STARRS 1 (Deacon+, 2014)
J/ApJ/795/64 : Catalog exoplanet physical param. (Foreman-Mackey+, 2014)
J/ApJS/214/17 : Orbital monitoring of AstraLux binaries (Janson+, 2014)
J/ApJS/216/7 : Planets Around Low-Mass Stars (PALMS). IV. (Bowler+, 2015)
J/other/Sci/350.64 : 51 Eri b near-infrared spectrum (Macintosh+, 2015)
J/MNRAS/449/2618 : (MinMs) survey. I. (Ward-Duong+, 2015)
J/ApJS/225/32 : Extended abundance analysis of cool stars (Brewer+, 2016)
J/ApJ/821/89 : 12yrs radial velocity obs. exoplanet systems (Bryan+,2016)
J/A+A/594/A63 : International Deep Planet Survey results (Galicher+, 2016)
J/ApJS/224/2 : K2 EPIC stellar properties 138600 targets (Huber+, 2016)
J/MNRAS/456/2070 : Eccentricity distribution wide binaries (Tokovinin+, 2016)
J/ApJ/825/19 : Mass-rad. relation for planets with Rp<4 (Wolfgang+, 2016)
J/A+A/605/L9 : NIR spectrum of exoplanet HIP 65426b (Chauvin+, 2017)
J/A+A/604/A108 : UniDAM results (Mints+, 2017)
J/AJ/155/159 : RVs of the late-T dwarf GL 758 B host star (Bowler+, 2018)
J/AJ/155/180 : A catalog of cool dwarf targets TESS (Muirhead+, 2018)
J/AJ/156/286 : The LEECH exoplanet imaging survey (Stone+, 2018)
J/AJ/158/77 : Candidates & memb. Pisces-Eridanus stream (Curtis+, 2019)
J/A+A/623/A72 : Binarity of Hipparcos stars Gaia anomaly (Kervella+, 2019)
J/A+A/624/A118 : Fitted orbits and parameters of 51 Eridani b (Maire+,2019)
J/AJ/158/13 : The first 300 stars observed by the GPIES (Nielsen+, 2019)
J/AJ/157/71 : Keck/NIRC2 astrometry for GSC 6214-210 b (Pearce+, 2019)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- ID Target identification
17- 29 A13 --- Tel Telescope used (Keck/NIRC2, 17 occurrences or
Subaru/HiCIAO, 1 occurrence)
31- 34 I4 yr Obs.Y [2011/2019] UT year of observation
36- 38 A3 "month" Obs.M UT month of observation
40- 41 I2 d Obs.D UT day of observation
43- 50 F8.3 --- Epoch [2011/2020] Epoch of observation
52- 54 A3 --- Filt Filter used (H or KS)
56- 61 A6 --- Cor Coronograph used
63- 65 I3 --- Nf [3/160] Number of frames
67- 69 I3 --- Coadd [1/100] Coadds
71- 76 F6.3 s Exp [0.01/60] Exposition time
78- 80 I3 deg theta [3/119]? Rotation angle (θ)
82- 87 F6.1 mas Sep [361/5609] Separation (ρ)
89- 92 F4.1 mas e_Sep [1.7/15] Error on Sep
94- 99 F6.2 deg PA [19/354] Position angle
101-104 F4.2 deg e_PA [0.1/0.7] Error on PA
106-108 I3 --- S/N [9/816] Signal to noise ratio of the companion
detection
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- ID Target identification
17- 24 F8.3 yr Per [13/7460] Median period
27- 34 F8.3 yr e_Per [0.01/4800] 68.3% c.i. Negative error on Per
37- 43 F7.2 yr E_Per [0.02/3200] 68.3% c.i. Positive error on Per
45- 51 F7.2 yr b_Per [13/2360] 95.4% c.i. minimum period
53- 60 F8.2 yr B_Per [13/59800] 95.4% c.i. maximum period
62- 67 F6.2 au a [4/417] Median semi major axis
70- 77 F8.4 au e_a [0.009/160] 68.3% c.i. Negative error on a68
80- 87 F8.4 au E_a [0.009/100] 68.3% c.i. Positive error on a68
89- 94 F6.2 au b_a [4/201] 95.4% c.i minimum semi major axis
96-102 F7.2 au B_a [4/1320] 95.4% c.i. maximum semi major axis
104-109 F6.4 --- e [0.14/0.94] Median eccentricity
112-116 F5.3 --- e_e [0.001/0.5] 68.3% c.i. Negative error on e68
119-123 F5.3 --- E_e [0.001/0.42] 68.3% c.i. Positive error on e68
125-130 F6.4 --- b_e [0/0.86] 95.4% c.i. minimum eccentricity
132-136 F5.3 --- B_e [0.24/1] 95.4% c.i. maximum eccentricity
138-142 F5.1 deg inc [79/151] Median inclination
145-149 F5.2 deg e_inc [0.1/40] 68.3% c.i. Negative error on i68
152-156 F5.2 deg E_inc [0.1/38] 68.3% c.i. Positive error on i68
158-162 F5.1 deg b_inc [15/130] 95.4% c.i. minimum inclination
164-168 F5.1 deg B_inc [87/177] 95.4% c.i. minimum inclination
170-174 F5.1 deg omega [48/168] Argument of periastron (ω) (1)
177-181 F5.2 deg e_omega [0.3/87] Negative error on omega
184-188 F5.2 deg E_omega [0.4/74] Positive error on omega
190-194 F5.1 deg OMEGA [12/329] Ascending node (Ω) (1)
197-201 F5.2 deg e_OMEGA [0.1/76] Negative error on OMEGA
204-209 F6.2 deg E_OMEGA [0.1/100] Positive error on OMEGA
211-216 F6.4 --- Tau [0.04/0.99] Time of periastron passage (τ) (2)
219-223 F5.3 --- e_Tau [0.01/0.5] Negative error on Tau
226-230 F5.3 --- E_Tau [0.01/0.5] Positive error on Tau
--------------------------------------------------------------------------------
Note (1): Here ω amd Ω are defined on the interval [0,2π).
Note (2): Time of periastron passage is expressed as a fraction of the orbital
period after MJD=0.
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Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- ID Target identification (1)
17- 18 I2 h RAh [0/23] Hour of right ascension (J2000)
20- 21 I2 min RAm Minute of right ascension (J2000)
23- 27 F5.2 s RAs Second of right ascension (J2000)
29 A1 --- DE- [-+] Sign of declination (J2000)
30- 31 I2 deg DEd Degree of declination (J2000)
33- 34 I2 arcmin DEm Arcminute of declination (J2000)
36- 40 F5.2 arcsec DEs Arcsecond of declination (J2000)
42- 43 A2 --- SpT* Spectral type of the host star
45- 48 I4 Myr Agemin [30/6000]? Minimum estimated age
50- 54 I5 Myr Agemax [125/10000]? Maximum estimated age
56- 59 I4 Myr Age [5/5000]? Estimated age
62- 65 I4 Myr e_Age [1/1900]? Negative error on Age
67- 71 I5 Myr E_Age [1/2300]? Positive error on Age
73- 80 F8.4 mas plx [7/174] Parallaxe from Gaia DR2 (π)
82- 87 F6.4 mas e_plx [0.02/0.35] Error on plx
89- 92 F4.2 Msun M* [0.2/2.8] Stellar mass
95- 98 F4.2 Msun e_M* [0.02/0.2]? Negative error on M*
101-104 F4.2 Msun E_M* [0.02/0.2] Positive error on M*
106 A1 --- f_M* [a] Flag on M* (2)
108-109 I2 Mjup Mcmin [4/40]? Minimum companion mass (3)
111-112 I2 Mjup Mcmax [10/94]? Maximum companion mass (3)
114-117 F4.1 Mjup Mc [2/73]? Companion mass (3)
120-123 F4.1 Mjup e_Mc [0.8/21]? Negative error on Mc
126-129 F4.1 Mjup E_Mc [0.8/14]? Positive error on Mc
131-135 F5.2 10-2 M2/M1 [0.1/17] Mass ratio between the companion and
host star
138-141 F4.2 10-2 e_M2/M1 [0.05/5] Negative error on M2/M1
144-147 F4.2 10-2 E_M2/M1 [0.05/5] Positive error on M2/M1
149-156 A8 --- SpTc Companion spectral type
159-161 F3.1 --- e_SpTc [0.5/1.5]? Negative error on SpTc
164-166 F3.1 --- E_SpTc [0.5/1.5]? Positive error on SpTc
168-171 F4.2 arcsec Sep [0.2/6.8] Separation in arcsec
173-175 I3 au Sepau [9/100] Separation in au
177-180 F4.2 --- IWA/a [0.08/1.6] Ratio between inner working angle
and semi-major axis (4)
182-186 F5.3 --- dt/Per [0.002/0.53] Fractional orbital coverage
(Δt/P) (5)
188-201 A14 --- Ref Reference(s) (see refs.dat file)
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Note (1): In the case of GJ504B, Bonnefoy+ (2018A&A...618A..63B 2018A&A...618A..63B)
find two degenerate solutions for the host age (21±2Myr or
4.0±1.8Gyr), which results in two solutions for the companion mass
1.3-0.3+0.6 or 23-9+10MJup) and mass ratio
(0.11±0.04x10-2 or 1.8±0.8x10-2). For this study we adopt
the older age and correspondingly higher companion mass.
Note (2): Flag as follows:
a = Uncertainty in the host mass is approximated from multiple
assessments in the literature (Meshkat+, 2013ApJ...775L..40M 2013ApJ...775L..40M ;
Chen+, 2014, J/ApJS/211/25).
Note (3): Assumes hot-start cooling history.
Note (4): IWA/a refers to the inner working angle at the contrast of
the companion and at the time of discovery, divided by the maximum a
posteriori of the semimajor axis distribution. The IWA was visually
estimated based on the discovery papers. This value (IWA/a) represents
a useful metric to assess the potential impact of discovery bias on
the inferred population-level eccentricity distribution (see Dupuy &
Liu, 2011ApJ...733..122D 2011ApJ...733..122D and Section 4.4). Values above 1.0, between
0.5 and 1.0, and below 0.5 indicate strong, moderate, and minimal
discovery bias, respectively.
Note (5): Computed from the time baseline over which this companion has been
imaged (Δt) and the best-fit orbital period (P).
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Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- ID Target identification
17- 21 F5.3 --- e-med [0.08/0.94] Median eccentricity
23- 27 F5.3 --- e-MAP [0.02/0.98] Maximum a posteriori probability
eccentricity
29- 33 F5.3 --- e68min [0/0.91] 68% c.i. minimum eccentricity
35- 38 F4.2 --- e68max [0.13/0.99] 68% c.i. maximum eccentricity
40- 45 F6.4 --- e95min [0/0.86] 95% c.i. minimum eccentricity
47- 50 F4.2 --- e95max [0.16/0.99] 95% c.i. maximum eccentricity
52- 62 A11 --- Data Code associates to data (1)
64- 92 A29 --- Ref2 Orbit fit references
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Note (1): Code as follows:
DI = relative astrometry from direct imaging (27 occurrences)
Ast = absolute astrometry from HGCA, Brandt, 2018ApJS..239...31B 2018ApJS..239...31B
(5 occurrences)
RV = relative radial velocities (6 occurrences)
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Byte-by-byte Description of file: table8.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- ID Target identification
17- 24 F8.3 yr Epoch [1998.31/2018.72] Epoch in decimal years
26- 32 F7.2 mas Sep [177/5670] Separation
34- 39 F6.2 mas e_Sep [0.2/100] Uncertainty in Sep
41- 47 F7.3 deg PA [1.8/359.16] Position angle
49- 53 F5.3 deg e_PA [0.01/8.5] Uncetainty in P
55- 75 A21 --- Auth First author's name(s) of the reference
77- 95 A19 --- BibCode Bibcode of the reference
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Byte-by-byte Description of file: refs.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Ref Reference code
4- 22 A19 --- BibCode Bibcode of the reference
24- 44 A21 --- Auth First author's name(s)
46- 68 A23 --- Comm Comment
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History:
From electronic version of the journal
(End) Prepared by Coralie Fix [CDS], 20-Mar-2020