J/ApJ/903/L7 Planet parameters from IRAC measurements (Crossfield+, 2020)
Phase Curves of Hot Neptune LTT 9779b Suggest a High-metallicity Atmosphere.
Crossfield I.J.M., Dragomir D., Cowan N.B., Daylan T., Wong I.,
Kataria T., Deming D., Kreidberg L., Mikal-Evans T., Gorjian V.,
Jenkins J.S., Benneke B., Collins K.A., Burke C.J., Henze C.E.,
McDermott S., Mireles I., Watanabe D., Wohler B., Ricker G.,
Vanderspek R., Seager S., Jenkins J.M.
<Astrophys. J., 903, L7 (2020)>
=2020ApJ...903L...7C 2020ApJ...903L...7C
ADC_Keywords: Exoplanets; Photometry, infrared; Effective temperatures
Keywords: Exoplanet atmospheres
Abstract:
Phase-curve measurements provide a global view of the composition,
thermal structure, and dynamics of exoplanet atmospheres. Although
most of the dozens of phase-curve measurements made to date are of
large, massive hot Jupiters, there is considerable interest in probing
the atmospheres of the smaller planets that are the more typical
endproduct of the planet formation process. One such planet that is
favorable for these studies is the ultrahot Neptune LTT9779b, a rare
denizen of the Neptune desert. A companion paper presents the planet's
secondary eclipses and dayside thermal emission spectrum; in this work
we describe the planet's optical and infrared phase curves,
characterized using a combination of Spitzer and Transiting Exoplanet
Survey Satellite (TESS) photometry. We detect LTT9779b's thermal phase
variations at 4.5µm, finding a phase amplitude of 358±106ppm
and no significant phase offset, with a longitude of peak emission
occurring -10°±21° east of the substellar point. Combined
with our secondary eclipse observations, these phase-curve
measurements imply a 4.5µm dayside brightness temperature of
1800±120K, a nightside brightness temperature of 700±430K
(<1350K at 2σ confidence), and a day-night brightness
temperature contrast of 1110±460K. We compare our data to the
predictions of 3D general circulation models calculated at multiple
metallicity levels and to similar observations of hot Jupiters
experiencing similar levels of stellar irradiation. Though not
conclusive, our measurement of its small 4.5µm phase offset, the
relatively large amplitude of the phase variation, and the qualitative
differences between our target's dayside emission spectrum and those
of hot Jupiters of similar temperatures all suggest a supersolar
atmospheric metallicity for LTT9779b, as might be expected given its
size and mass. Finally, we measure the planet's transits at both
3.6µm and 4.5µm, providing a refined ephemeris
(P=0.79207022±0.00000069days, T0=2458783.51636±0.00027,
BJDTDB) that will enable efficient scheduling of future observations
to further characterize the atmosphere of this intriguing planet.
Description:
Our Spitzer observations provided near-continuous coverage of one full
orbital period of LTT 9779b in each of the 3.6µm and 4.5µm
channels of the InfraRed Array Camera (IRAC) instrument.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fig12.dat 261 19 Derived parameters from all IRAC 4.5m phase curve
measurements of planets on nearly-circular orbits
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See also:
II/328 : AllWISE Data Release (Cutri+ 2013)
J/ApJ/754/136 : Light curves of HD 149026b in 3.6-16um (Stevenson+, 2012)
J/ApJ/755/9 : Spitzer/IRAC light curves of GJ 436 system (Stevenson+, 2012)
J/A+A/552/A16 : Limb-darkening for CoRoT, Kepler, Spitzer. II. (Claret+, 2013)
J/ApJ/790/53 : Photometric data of HD 209458b (Zellem+, 2014)
J/A+A/619/A1 : 55 Cnc radial velocities and photometry (Bourrier+, 2018)
J/A+A/625/A136 : WASP-18b HST/WFC3 spectroscopic phase curves (Arcangeli+,2019)
Byte-by-byte Description of file: fig12.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- ID Planet identifier
15- 38 A24 --- Ref Reference (1)
40- 42 F3.1 um Mode [4.5] Wavelength at which observation were made
44- 52 F9.6 Mjup Mass [0.02/10.2]? Planetary mass
54- 58 F5.3 --- Sep [2.98/8.81] Planetary separation, stellar radii
60- 76 F17.15 --- Rad [0.02/0.17] Planetary radius in stellar radii
78- 82 I5 K Teff [3036/10170] Effective stellar temperature
84- 94 F11.9 --- DF/F [0.0001/0.005] Flux contrast in phase curve (2)
96-116 F21.19 --- e_DF/F [0.000001/0.06] Uncertainty in DF/F
118-134 F17.13 --- Offset [-23/57.6] Eastward phase offset
136-152 F17.14 --- e_Offset [0.1/21] Uncertainty in Offset
154-164 F11.6 ppm ecldep [0.0001/4140] Eclipse depth
166-184 F19.15 ppm e_ecldep [1e-6/220] Uncertainty in ecldep
186-189 I4 K TeqMax [1028/5176] Maximum equilibrium temperature
191-194 I4 K Tday [1031/5991] Planetary day side temperature
196-199 I4 K e_Tday [2/1458] Uncertainty in Tday
201-204 I4 K Tnight [481/4461] Planetary night side temperature
206-209 I4 K e_Tnight [2/1217] Uncertainty in Tnight
211-214 I4 --- DeltaT [270/2490] Day-night temperature contrast
216-219 I4 --- e_DeltaT [4/1395] Uncertainty in DeltaT
221-226 F6.4 --- aobs [0.18/0.76] Normalized day-night temperature
contrast (3)
228-233 F6.4 --- e_aobs [0.002/0.3] Uncertainty in aobs
235-240 F6.4 --- AB [0.02/0.88]? Bond albedo
242-247 F6.4 --- e_AB [0/0.3]? Uncertainty in AB
249-254 F6.4 --- epsilon [0.006/0.69]? Global heat recirculation
efficiency
256-261 F6.4 --- e_epsilon [0/0.3]? Uncertainty in epsilon
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Note (1): References as follows:
Bell et al. (2019) = 2019MNRAS.489.1995B 2019MNRAS.489.1995B
Crossfield et al. (2020) = This work
Dang et al. (2018) = 2018NatAs...2..220D 2018NatAs...2..220D
Demory et al. (2016) = 2016Natur.532..207D 2016Natur.532..207D
Keating et al. (2020) = 2020NatAs...3.1092K 2020NatAs...3.1092K
Knutson et al. (2012) = 2012ApJ...754...22K 2012ApJ...754...22K
Kreidberg et al. (2018) = 2018AJ....156...17K 2018AJ....156...17K
Kreidberg et al. (2019) = 2019Natur.573...87N 2019Natur.573...87N
Mansfield et al. (2020) = 2020ApJ...888L..15M 2020ApJ...888L..15M
Maxted et al. (2013) = 2013MNRAS.428.2645M 2013MNRAS.428.2645M
May and Stevenson (2020) = 2020AJ....160..140M 2020AJ....160..140M
Wong et al. (2015) = 2015ApJ...811..122W 2015ApJ...811..122W
Wong et al. (2016) = 2016ApJ...823..122W 2016ApJ...823..122W
Zellem et al. (2014) = J/ApJ/790/53
Zhang et al. (2018) = 2018AJ....155...83Z 2018AJ....155...83Z
Note (2): Relative to the mean flux level.
Note (3): (Tday-Tnight)/Tday.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 25-Feb-2022