J/ApJ/747/35 HST/WFC3 transit observation of GJ1214b (Berta+, 2012)
The flat transmission spectrum of the super-Earth GJ1214b from Wide Field
Camera 3 on the Hubble Space Telescope.
Berta Z.K., Charbonneau D., Desert J.-M., Miller-Ricci Kempton E.,
McCullough P.R., Burke C.J., Fortney J.J., Irwin J., Nutzman P., Homeier D.
<Astrophys. J., 747, 35 (2012)>
=2012ApJ...747...35B 2012ApJ...747...35B
ADC_Keywords: Planets ; Stars, double and multiple ; Spectrophotometry
Keywords: eclipses - planets and satellites: atmospheres -
planets and satellites: individual (GJ1214b) - stars: low-mass -
techniques: spectroscopic
Abstract:
Capitalizing on the observational advantage offered by its tiny M
dwarf host, we present Hubble Space Telescope/Wide Field Camera 3
(WFC3) grism measurements of the transmission spectrum of the
super-Earth exoplanet GJ1214b. These are the first published WFC3
observations of a transiting exoplanet atmosphere. After correcting
for a ramp-like instrumental systematic, we achieve nearly
photon-limited precision in these observations, finding the
transmission spectrum of GJ1214b to be flat between 1.1 and 1.7µm.
Inconsistent with a cloud-free solar composition atmosphere at
8.2σ, the measured achromatic transit depth most likely implies
a large mean molecular weight for GJ1214b's outer envelope. A dense
atmosphere rules out bulk compositions for GJ1214b that explain its
large radius by the presence of a very low density gas layer
surrounding the planet. High-altitude clouds can alternatively explain
the flat transmission spectrum, but they would need to be optically
thick up to 10 mbar or consist of particles with a range of sizes
approaching 1 µm in diameter.
Description:
We observed three transits of GJ1214b on UT 2010 October 8, 2011 March
28, and 2011 July 23 with the G141 grism on WFC3's infrared channel
(HST Proposal GO-12251, PI: Z. Berta), obtaining simultaneous
multiwavelength spectrophotometry of each transit between 1.1 and 1.7um.
Objects:
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RA (2000) DE Designation(s) (Period)
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17 15 18.94 +04 57 49.7 GJ 1214b = GJ 1214 b (P=1.58040481)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 89 576 White light curves from WFC3/G141
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See also:
B/hst : HST Archived Exposures Catalog (STScI, 2007)
J/A+A/549/A10 : Transits of GJ 1214 (Harpsoe+, 2013)
J/A+A/538/A46 : Transit observations of GJ1214b (de Mooij+, 2012)
J/ApJ/731/123 : APOSTLE light curve of GJ 1214b (Kundurthy+, 2011)
J/ApJ/736/12 : Transit light curves of GJ1214 (Berta+, 2011)
J/ApJ/716/1336 : Stability analysis of single-planet (Kopparapu+, 2010)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 14 F14.6 d BJD Barycentric Julian Date at mid-exposure
16- 22 F7.5 --- RFlux [0.98/1.01] Relative flux (1)
24- 30 F7.5 --- e_RFlux Uncertainty in RFlux
32- 37 F6.4 ct/s Sky Sky background in electrons/s
39- 46 F8.3 pix X0 The 0th order X position (2)
48- 53 F6.3 pix Y0 The 0th order Y position (2)
55- 59 F5.3 pix A0 Gaussian width of 0th order spectrum in the
horizontal direction
61- 65 F5.3 pix B0 Gaussian width of 0th order spectrum in the
vertical direction
67- 72 F6.3 pix Y1 The 1st order Y position (2)
74- 79 F6.4 pix B1 Gaussian width of 1st order spectrum in the
vertical direction
81- 87 F7.5 --- Slope Slope of 1st order spectrum
89 I1 --- Visit [1/3] Visit number
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Note (1): Normalized to the median flux level of the out-of-transit
observations in each visit.
Note (2): Position measured relative to the Gaussian center of each visit's
direct image.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 25-Sep-2013