of 26
Letters
https://doi.org/10.1038/s41550-019-0800-5
A sub-Neptune exoplanet with a low-metallicity
methane-depleted atmosphere and Mie-scattering
clouds
Björn Benneke
1
*, Heather A. Knutson
2
, Joshua Lothringer
3
, Ian J.M. Crossfield
4
, Julianne I. Moses
5
,
Caroline Morley
6
, Laura Kreidberg
7
, Benjamin J. Fulton
2
, Diana Dragomir
4
, Andrew W. Howard
8
,
Ian Wong
9
, Jean-Michel Désert
10
, Peter R. McCullough
11
, Eliza M.-R. Kempton
12,13
, Jonathan Fortney
14
,
Ronald Gilliland
15
, Drake Deming
12
and Joshua Kammer
16
1
Department of Physics and Institute for Research on Exoplanets, Université de Montréal, Montréal, Quebec, Canada.
2
Division of Geological and Planetary
Sciences, California Institute of Technology, Pasadena, CA, USA.
3
Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA.
4
Department
of Physics and Kavli Institute of Astronomy, Massachusetts Institute of Technology, Cambridge, MA, USA.
5
Space Science Institute, Boulder, CO, USA.
6
Department of Astronomy, University of Texas, Austin, TX, USA.
7
Department of Astronomy, Harvard University, Cambridge, MA, USA.
8
Department of
Astronomy, California Institute of Technology, Pasadena, CA, USA.
9
Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute
of Technology, Cambridge, MA, USA.
10
Anton Pannekoek Institute for Astronomy, University of Amsterdam, Amsterdam, The Netherlands.
11
Department
of Physics and Astronomy, Johns Hopkins University, Baltimore, MD, USA.
12
Department of Astronomy, University of Maryland, College Park, MD, USA.
13
Department of Physics, Grinnell College, Grinnell, IA, USA.
14
Department of Astronomy, University of California, Santa Cruz, CA, USA.
15
Space Telescope
Science Institute, Baltimore, MD, USA.
16
Southwest Research Institute, San Antonio, TX, USA. *e-mail: bbenneke@astro.umontreal.ca
SUPPLEMENTARY INFORMATION
In the format provided by the authors and unedited.
NA
tuRE AstR
oNoM
y
|
www.nature.com/natureastronomy
Supplementary Information
742
743
A Su
b
-
Neptune Exoplanet with a Low
-
Metallicity Methane
-
Depleted Atmosphere
744
and Mie
-
Scattering
Cloud
s
745
B
JÖRN
B
ENNEKE
1
,
H
EATHER
A.
K
NUTSON
2
,
J
OSHUA
L
OTHRINGER
3
,
I
AN
C
ROSSFIELD
4
,
J
ULIANNE
746
M
OSES
5
,
C
AROLINE
M
ORLEY
6
,
L
AURA
K
REIDBERG
7
,
BJ
F
ULTON
2
,
D
IANA
D
RAGOMIR
4,17
,
A
NDREW
747
H
OWARD
8
,
I
AN
W
ONG
9
,
J
EAN
-
M
ICHEL
D
ÉSERT
10
,
P.R.
M
C
C
ULLOUGH
11
,
E
LIZA
M.
-
R.
748
K
EMPTON
12,13,
,
J
ONATHAN
F
ORTNEY
14
,
R
ONALD
G
ILLILAND
15
,
D
RAKE
D
EMING
12
,
J
OSHUA
749
K
AMMER
16
750
[18]
Department of Physics
a
n
d
Institute for Research on Exoplanet
s
, Université de Montréal
, Montréal, QC, Canada
751
[19]
Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA
752
[20]
Lunar & Planetary Laboratory, University of Arizona, 1629 E. University Boulevard., Tucson, AZ, USA
753
[21]
Department of Physics and
Kavli Institute of Astronomy, Massachusetts Institute of Technology, 77 Massachusetts Ave,
754
Cambridge, MA, 02139, USA
755
[22]
Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301, USA
756
[23]
Department of Astronomy, University of Texas, Austin, TX 787
12, USA
757
[24]
Department of Astronomy, Harvard University, 60 Garden Street, Cambridge, MA 02138, USA
758
[25]
Department of Astronomy, California Institute of Technology, Pasadena, CA 91125, USA
759
[26]
Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Ins
titute of Technology, 77 Massachusetts
760
Ave, Cambridge, MA, 02139, USA
761
[27]
Anton Pannekoek Institute for Astronomy, University of Amsterdam, 1090 GE Amsterdam, The Netherlands
762
[28]
Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, U
SA
763
[29]
Department of Astronomy, University of Maryland, College Park, MD 20742, USA
764
[30]
Department of Physics, Grinnell College, 1116 8th Avenue, Grinnell, IA 50112, USA
765
[31]
Department of Astronomy, University of California, Santa Cruz, CA 95064, USA
766
[32]
Space Telescope S
cience Institute, 3700 San Martin Dr., Baltimore, MD 21218, USA
767
[33]
Southwest Research Institute, San Antonio TX, USA
768
[34]
NASA Hubble Fellow
769
770
771
Instrument
Filter/Grism
Transit/Eclipse
Wavelength [
μ
m]
UT Start Date
HST/STIS
G750L
Transits
0.55
1.0
2015 Feb 07
20
15 May 12
2016 Apr 03
HST/WFC3
G141
Transits
1.1
1.7
2015 Jan 28
2015 Mar 13
2015 Oct 22
Spitzer/IRAC
Channel 1
Transits
3.0
4.0
2012 Dec 22
2017 Jan 25
2017 Feb 20
Spitzer/IRAC
Channel 2
Transits
4.0
5.0
2012 Jun 11
2012 Jun 15
2013 Jan 01
Spitz
er/IRAC
Channel 1
Eclipse
3.0
4.0
2014 Jan 15
2014 Jan 28
2014 Jun 14
2014 Jun 24
2015 Jan 30
2015 Feb 06
2015 Feb 09
2015 Feb 12
2015 Jun 19
2015 Jul 19
Spitzer/IRAC
Channel 2
Eclipse
4.0
5.0
2014 Jan 21
2014 Feb 4
2014 Jun 21
2014 Jul 10
2015 Jan 10
2015 Jan 13
2015 Jan 17
2015 Jan 20
2015 Jan 23
2015 Jan 27
Supplementary
Table
1
: Summary of presented transit and eclipse observation of GJ
3470b.
772
773
774
Supplementary
Figure
1
: White light curve fit (left) and a typical spectral light curve fit (right) from the
775
joint analysis of the three WFC3 transit observations of GJ
3470b. The top panel shows the best fitting
776
model light curves (black curve), overlaid with the systemat
ics
-
corrected data (circles). Residuals from the
777
light curve fits are shown in the middle panels. All corrected WFC3 light curve fits are free of obvious
778
systematics. The bottom panels shows a histogram of the residuals normalized by the fitted photometric
779
scatter parameter for each respective transit. The residuals follow the expected Gaussian distribution for
780
photon noise limited observations.
781
782
783
Supplementary
Figure
2
: White light curve fit (left) and a typic
al spectral light curve fit (right) from the
784
joint analysis of the three STIS transit observations of GJ
3470b. The top panel shows the best fitting model
785
light curves (black curve), overlaid with the systematics
-
corrected data (circles). Residuals from th
e light
786
curve fits are shown in the middle panels. The bottom panels shows a histogram of the residuals normalized
787
by the fitted photometric scatter parameter for each respective transit.
788
789
790