J/AJ/156/292 Effect of close companions on exoplanetary radii (Teske+, 2018)
The effects of stellar companions on the observed transiting exoplanet radius
distribution.
Teske J.K., Ciardi D.R., Howell S.B., Hirsch L.A., Johnson R.A.
<Astron. J., 156, 292 (2018)>
=2018AJ....156..292T 2018AJ....156..292T (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets
Keywords: binaries: close - planets and satellites: detection -
techniques: high angular resolution
Abstract:
Understanding the distribution and occurrence rate of small planets was
a fundamental goal of the Kepler transiting exoplanet mission, and could
be improved with K2 and Transiting Exoplanet Survey Satellite (TESS).
Deriving accurate exoplanetary radii requires accurate measurements of
the host star radii and the planetary transit depths, including accounting
for any "third light" in the system due to nearby bound companions or
background stars. High-resolution imaging of Kepler and K2 planet
candidate hosts to detect very close (within ∼0.5") background or bound
stellar companions has been crucial for both confirming the planetary
nature of candidates, and the determination of accurate planetary radii
and mean densities. Here we present an investigation of the effect of close
companions, both detected and undetected, on the observed (raw count)
exoplanet radius distribution. We demonstrate that the recently detected
"gap" in the observed radius distribution (also seen in the
completeness-corrected distribution) is fairly robust to undetected stellar
companions, given that all of the systems in the sample have undergone
some kind of vetting with high-resolution imaging. However, while the gap
in the observed sample is not erased or shifted, it is partially filled
in after accounting for possible undetected stellar companions. These
findings have implications for the most likely core composition, and thus
formation location, of super-Earth and sub-Neptune planets. Furthermore,
we show that without high-resolution imaging of planet candidate host
stars, the shape of the observed exoplanet radius distribution will be
incorrectly inferred, for both Kepler- and TESS-detected systems.
Description:
Fulton et al. (2017, J/AJ/154/109, hereafter F17) compared their sample
to the Furlan et al. (2017, J/AJ/153/71) high-resolution imaging catalog,
and found no significant change to their observed planet radius
distribution by removing KOI hosts with known companions or large dilution
corrections. Ultimately they chose not to filter their catalog using
high-resolution imaging results. We want to answer the question, how do
stellar companions affect the bimodal observed exoplanet radius
distribution found in F17? For completeness, we investigate the effect of
both detected and undetected companions. To account for the effect of
detected companions, we cross-matched the Kepler host star sample with
high-resolution imaging observations cataloged by Furlan et al. (2017,
J/AJ/153/71) and Ziegler et al. (2018AJ....156...83Z 2018AJ....156...83Z) and applied average
radius correction factors calculated as in Furlan et al. (2017,
J/AJ/153/71). To account for the effect of undetected companions, we use
a prescription modified from Ciardi et al. (2015ApJ...805...16C 2015ApJ...805...16C) to
calculate updated radius correction factors, and applied these values.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 19 107 Average radius correction factors
table2.dat 73 577 Modified radius correction factors
--------------------------------------------------------------------------------
See also:
J/ApJ/646/523 : Exoplanet systems with stellar companions (Raghavan+, 2006)
J/A+A/546/A10 : Multiplicity in transiting planet-host stars
(Lillo-Box+, 2012)
J/MNRAS/421/2498 : Stellar companions of exoplanet host stars (Ginski+, 2012)
J/ApJ/763/41 : Kepler multiple-candidate systems radii (Ciardi+, 2013)
J/ApJ/809/77 : Transiting Exoplanet Survey Satellite (TESS)
(Sullivan+, 2015)
J/ApJ/813/130 : Kepler multiple transiting planet systems (Wang+, 2015)
J/AJ/152/8 : Impact of stellar multiplicity on planetary systems I.
(Kraus+, 2016)
J/AJ/153/71 : Kepler follow-up observation program. I. Imaging
(Furlan+, 2017)
J/AJ/153/117 : KOIs companions from high-resolution imaging (Hirsch+, 2017)
J/AJ/154/109 : California-Kepler Survey (CKS). III. Planet radii
(Fulton+, 2017)
J/AJ/155/48 : California-Kepler Survey (CKS). V. Masses and radii
(Weiss+, 2018)
J/AJ/156/83 : Effect of stellar companions on planetary systems
(Ziegler+, 2018)
J/AJ/156/264 : California-Kepler Survey. VII. Planet radius gap
(Fulton+, 2018)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- KOI [18/4653] Planet host (KOI -NNNN)
6- 11 F6.4 --- XR-pri [0/1.547] Mean radius correction factor assuming
the planet orbits the primary star
13- 19 F7.4 --- XR-sec [0/12.5094] Mean radius correction factor assuming
the planet orbits the secondary star
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- KOI [2/4864] Planet host (KOI -NNNN)
6- 13 F8.6 --- f [0.060878/0.584358] Fraction of multiples not
removed by the assumed vetted in the case of
typical Kepler distances (1)
15- 22 F8.6 --- f-TESS [0/0.342363] Fraction of multiples not removed
by the assumed vetted in the case of TESS
distances (1)
24- 30 F7.5 --- XR-5050 [1.08904/2.48514] Mean companion only correction
in the 50/50 primary/secondary case (2)
32- 39 F8.6 --- e_XR-5050 [0.248748/1.66623] rms uncertainty in XR-5050
41- 47 F7.5 --- XR-7030 [1.0338/1.85229] Mean companion only correction
in the 70/30 primary/secondary case (2)
49- 56 F8.6 --- e_XR-7030 [0.159162/0.924759] rms uncertainty in XR-7030
58- 64 F7.5 --- XR-9010 [1.02115/1.38421] Mean companion only correction
in the 90/10 primary/secondary case (2)
66- 73 F8.6 --- e_XR-9010 [0.085909/0.385081] rms uncertainty in XR-9010
--------------------------------------------------------------------------------
Note (1): The assumed vetted, ground-based RV and high-resolution imaging
follow up.
Note (2): We list the different radius correction factors we calculated for each
KOI, given different oprob values (50/50, 70/30, or 90/10). We modify the
original Ciardi et al. (2015ApJ...805...16C 2015ApJ...805...16C) XR factors to reflect only the
multi-star scenarios, and choose to test three different scenarios for the
probability that the primary versus a companion star hosts the planet,
oprob - 90/10, 70/30, and the original 50/50.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 26-Apr-2019