J/AJ/155/177 Obliquities of planetary & eclipsing binary systems (Dai+, 2018)
Stellar obliquity and magnetic activity of planet-hosting stars and eclipsing
binaries based on transit chord correlation.
Dai F., Winn J.N., Berta-Thompson Z., Sanchis-Ojeda R., Albrecht S.
<Astron. J., 155, 177-177 (2018)>
=2018AJ....155..177D 2018AJ....155..177D (SIMBAD/NED BibCode)
ADC_Keywords: Exoplanets ; Binaries, eclipsing ; Stars, masses ;
Stars, diameters ; Effective temperatures
Keywords: binaries: eclipsing - planetary systems -
planets and satellites: general - stars: activity - stars: rotation -
starspots
Abstract:
The light curve of an eclipsing system shows anomalies whenever the
eclipsing body passes in front of active regions on the eclipsed star.
In some cases, the pattern of anomalies can be used to determine the
obliquity Ψ of the eclipsed star. Here we present a method for
detecting and analyzing these patterns, based on a statistical test for
correlations between the anomalies observed in a sequence of eclipses.
Compared to previous methods, ours makes fewer assumptions and is easier
to automate. We apply it to a sample of 64 stars with transiting planets
and 24 eclipsing binaries for which precise space-based data are available,
and for which there was either some indication of flux anomalies or a
previously reported obliquity measurement. We were able to determine
obliquities for 10 stars with hot Jupiters. In particular we found
Ψ~<10° for Kepler-45, which is only the second M dwarf with a
measured obliquity. The other eight cases are G and K stars with low
obliquities. Among the eclipsing binaries, we were able to determine
obliquities in eight cases, all of which are consistent with zero. Our
results also reveal some common patterns of stellar activity for
magnetically active G and K stars, including persistently active
longitudes.
Description:
The motivation for our work was to develop a more objective method for
measuring obliquities that does not rely on explicit spot modeling and
can be more easily applied to a large sample of systems. Instead of
assuming that the active regions are discrete dark and bright spots, we
treat the transit light curve as a measure of the intensity distribution
of the stellar photosphere along the transit chord. For convenience, we
call this the transit chord correlation (TCC) method, although we do not
claim it is a completely new concept. It is closely related to eclipse
mapping (Horne 1985MNRAS.213..129H 1985MNRAS.213..129H), which has long been used to probe
the brightness distribution of stars and accretion disks.
In this paper, we explain the TCC method, validate it through application
to systems for which the stellar obliquity has been measured by independent
methods, and apply it to all the transiting planets for which the method is
currently feasible. We also apply the TCC method to a sample of eclipsing
binaries drawn from the Kepler survey.
We tried to assemble a collection of all the transit data sets for which
there seemed to be a reasonable chance of success for the TCC method.
The requirement for high S/N and a large number of consecutive transits
restricts us to data from the space missions CoRoT, Kepler, and K2.
Tables 1 and 2 summarize the results for the transiting planets and
eclipsing binaries, respectively.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 325 64 List of planetary systems searched
table2.dat 178 24 List of eclipsing binary systems searched
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See also:
V/133 : Kepler Input Catalog (Kepler Mission Team, 2009)
J/A+A/479/865 : CoRoT exoplanet candidates (Loeillet+, 2008)
J/ApJ/757/18 : Radial velocities for 16 hot Jupiter host stars
(Albrecht+, 2012)
J/MNRAS/443/2391 : Light curves of Qatar-2 transit events (Mancini+, 2014)
J/AJ/151/68 : Kepler Mission. VII. Eclipsing binaries in DR3 (Kirk+, 2016)
J/ApJ/824/15 : Orbital circularization of Kepler eclipsing bin.
(Van Eylen+, 2016)
J/AJ/154/105 : Parameters of 529 Kepler eclipsing binaries
(Kjurkchieva+, 2017)
http://exofop.ipac.caltech.edu : The Exoplanet Follow-up Observing Program
(ExoFOP) website
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Name Planetary system designation (1)
13 A1 --- n_Name [b] Note on Name (2)
15- 25 A11 --- Status Status of the planet (Confirmed or Brown Dwarf)
27- 40 F14.10 d Per [0.85353/125.63243] Orbital period
42- 53 F12.10 d e_Per [1.87e-08/0.0014]? Uncertainty in Per
55- 62 F8.4 --- a/R* [3.16/155.4] Scaled semimajor axis
64- 69 F6.4 --- e_a/R* [0.0039/3]? Lower limit uncertainty in a/R*
71- 76 F6.4 --- E_a/R* [0.0039/3]? Upper limit uncertainty in a/R*
78 A1 --- l_Mp [<] Limit flag on Mp
79- 87 F9.5 Mjup Mp [0.0149/120]? Planetary mass
89- 95 F7.5 Mjup e_Mp [0.0009/8.8]? Lower limit uncertainty in Mp
97-104 F8.5 Mjup E_Mp [0.0009/14]? Upper limit uncertainty in Mp
106-111 F6.4 Rjup Rp [0.149/1.614] Planetary radius
113-118 F6.4 Rjup e_Rp [0.0054/0.79] Lower limit uncertainty in Rp
120-125 F6.4 Rjup E_Rp [0.0054/0.79] Upper limit uncertainty in Rp
127-131 F5.3 Msun M* [0.59/1.54] Mass of the host star
133-137 F5.3 Msun e_M* [0.01/0.62] Lower limit uncertainty in M*
139-143 F5.3 Msun E_M* [0.01/0.62] Upper limit uncertainty in M*
145-149 F5.3 Rsun R* [0.55/2.02] Radius of the host star
151-155 F5.3 Rsun e_R* [0.018/0.927] Lower limit uncertainty in R*
157-161 F5.3 Rsun E_R* [0.018/0.927] Upper limit uncertainty in R*
163-166 I4 K Teff [3820/8500] Effective temperature of the host
star
168-170 I3 K e_Teff [32/400] Uncertainty in Teff
172-177 F6.3 d Pphot [1.245/31.6]? Stellar rotation period measured
from rotational modulation in the light curve
179-183 F5.3 d e_Pphot [0.014/3.6]? Uncertainty in Pphot
185-190 F6.2 d Ptcc [0.8/115] Stellar rotation period that gives
the strongest transit chord correlation (TCC)
192-195 F4.2 d e_Ptcc [0.1/4] Uncertainty in Ptcc
197-200 F4.1 --- Nsigma [0.7/59.6] Statistical significance of
correlation compared to the results of
scrambling test Nσ
202-206 F5.2 --- Ptcc/Per [0.13/25.82] Ratio between the stellar rotation
and orbital periods
208 A1 --- l_PsiUp [<] Limit flag on PsiUp
209-210 I2 deg PsiUp [4/16]? Upper limit on the true obliquity
ΨUpper (G1)
212 A1 --- l_lambda [<] Limit flag on lambda
213-217 F5.1 deg lambda [-52/155]? Obliquity constraint from the
literature λlit
219-223 F5.1 deg e_lambda [2/140]? Lower limit uncertainty in lambda
225-228 F4.1 deg E_lambda [2/37]? Upper limit uncertainty in lambda
231-238 A8 --- n_lambda System with prograde obliquity
240-284 A45 --- Ref Reference(s)
286-325 A40 --- Bibcode Bibcode of the reference(s)
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Note (1): The systems are sorted by the significance of correlation in the
residual flux.
Note (2): Note as follows:
b = Systems whose stellar obliquity was previously reported to be low yet did
not show strong transit chord correlation (TCC). These systems are likely
magnetically inactive: the host stars are above the Kraft break; the
light curve lacks rotational modulation. Alternatively, the high impact
parameter of the planet indicates that the transit chord might have missed
the active latitude.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 I7 --- KIC [2438502/8230809] Kepler Input Catalog number
(Cat. V/133)
9- 31 A23 --- Status Status of the eclipsing binary system
33- 44 F12.9 d Per [2.02558/53.2204218] Orbital period
46- 56 F11.9 d e_Per [1.75e-07/0.0083] Uncertainty in Per
58- 64 F7.4 --- ecosw [-0.0873/0.0155]? Eccentricity constraint from
Van Eylen et al. (2016, J/ApJ/824/15)
e*cos(ω)
66- 71 F6.4 --- e_ecosw [0.0008/0.0118]? Uncertainty in ecosw
73- 78 F6.3 --- a/R* [1.96/22.96] Scaled semimajor axis
80- 87 F8.6 --- R1/R2 [0.0909/0.416822] Primary to secondary star
radius ratio
89- 96 F8.6 --- e_R1/R2 [1e-06/0.00162] Uncertainty in R1/R2
98-102 F5.3 Msun M* [0.526/1.431] Mass of the host star
104-108 F5.3 Msun e_M* [0.03/0.305] Uncertainty in M*
110-114 F5.3 Rsun R* [0.512/6.447] Radius of the host star
116-120 F5.3 Rsun e_R* [0.026/1.781] Uncertainty in R*
122-125 I4 K Teff [4648/6348] Effective temperature of the host
star
127-129 I3 K e_Teff [62/296] Uncertainty in Teff
131-136 F6.3 d Pphot [2.47/78]? Stellar rotation period measured
from rotational modulation in the light curve
138-142 F5.3 d e_Pphot [0.01/3]? Uncertainty in Pphot
144-146 A3 --- n_Pphot [ELV ] Note on Pphot (1)
148-152 F5.2 d Ptcc [0.6/80.4] Stellar rotation period that gives
the strongest transit chord correlation (TCC)
154-157 F4.2 d e_Ptcc [0.1/4] Uncertainty in Ptcc
159-162 F4.1 --- Nsigma [1.9/12.6] Statistical significance of
correlation compared to the results of
scrambling test Nσ
164-167 F4.2 --- Ptcc/Per [0.16/6.62] Ratio between the stellar rotation
and orbital periods
169 A1 --- l_PsiUp [<] Limit flag on PsiUp
170-171 I2 deg PsiUp [3/22]? Upper limit on the true obliquity
ΨUpper (G1)
173-178 A6 --- Ref [ExoFOP] Reference
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Note (1): Note as follows:
ELV = Unable to measure Pphot because ellipsoidal light variation dominates
the flux variation.
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Global notes:
Note (G1): The upper limit on the true obliquity is only calculated when a low
stellar obliquity is detected.
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History:
From electronic version of the journal
(End) Tiphaine Pouvreau [CDS] 19-Nov-2018