J/ApJ/755/9 Spitzer/IRAC light curves of GJ 436 system (Stevenson+, 2012)
Two nearby sub-Earth-sized exoplanet candidates in the GJ 436 system.
Stevenson K.B., Harrington J., Lust N.B., Lewis N.K., Montagnier G.,
Moses J.I., Visscher C., Blecic J., Hardy R.A., Cubillos P., Campo C.J.
<Astrophys. J., 755, 9 (2012)>
=2012ApJ...755....9S 2012ApJ...755....9S
ADC_Keywords: Photometry, infrared ; Planets ; Stars, double and multiple
Keywords: planets and satellites: detection; stars: individual: GJ 436;
techniques: photometric
Abstract:
We report the detection of UCF-1.01, a strong exoplanet candidate with
a radius 0.66±0.04 times that of Earth (R⊕). This sub-Earth
sized planet transits the nearby M-dwarf star GJ 436 with a period of
1.365862±8x10-6 days. We also report evidence of a
0.65±0.06R⊕ exoplanet candidate (labeled UCF-1.02) orbiting
the same star with an undetermined period. Using the Spitzer Space
Telescope, we measure the dimming of light as the planets pass in
front of their parent star to assess their sizes and orbital
parameters. If confirmed today, UCF-1.01 and UCF-1.02 would be
designated GJ 436c and GJ 436d, respectively, and would be part of the
first multiple-transiting-planet system outside of the Kepler field.
Assuming Earth-like densities of 5.515g/cm3, we predict both
candidates to have similar masses (∼0.28M⊕, 2.6 Mars-masses)
and surface gravities of ∼0.65g (where g is the gravity on Earth).
UCF-1.01's equilibrium temperature (Teq, where emitted and absorbed
radiation balance for an equivalent blackbody) is 860K, making the
planet unlikely to harbor life as on Earth. Its weak gravitational
field and close proximity to its host star imply that UCF-1.01 is
unlikely to have retained its original atmosphere; however, a
transient atmosphere is possible if recent impacts or tidal heating
were to supply volatiles to the surface. We also present additional
observations of GJ 436b during secondary eclipse. The 3.6µm light
curve shows indications of stellar activity, making a reliable
secondary eclipse measurement impossible. A second non-detection at
4.5µm supports our previous work in which we find a
methane-deficient and carbon monoxide-rich dayside atmosphere.
Description:
We observed GJ 436 at 3.6 and 4.5um using Spitzer's InfraRed Array
Camera (IRAC). Including the two previously analyzed data sets listed
in Table 1, we present six Spitzer observations spanning just over
three years (2008 Jul 14 to 2011 Jul 30).
Objects:
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RA (2000) DE Designation(s) (Period)
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11 42 11.18 +26 42 22.6 GJ 436 = TYC 1984-2613-1 (P=1.365862)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 105 6 Observation information
fits/* . 4 Light curves of GJ 436, in FITS format,
in Spitzer/IRAC 4.5um
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See also:
J/MNRAS/414/1278 : Eccentricities of transiting planets (Pont+, 2011)
J/MNRAS/411/L46 : Exoplanet magnetic fields (Vidotto+, 2011)
J/A+A/527/A140 : Mass limits on substellar companions (Reffert+, 2011)
J/ApJ/733/68 : Exoplanet masses derived from RVs (Brown+, 2011)
J/ApJ/716/1336 : Stability analysis of single-planet (Kopparapu+, 2010)
J/ApJ/709/168 : Eccentric orbits in exoplanets (Anglada-Escude+, 2010)
J/A+A/507/481 : GJ 436b and XO-1b transits (Caceres+, 2009)
J/ApJ/705/1226 : Planet-bearing stars in Spitzer (Bryden+, 2009)
J/ApJ/701/1922 : Radio interferometric planet search. I. (Bower+, 2009)
J/ApJ/700/L73 : Photospheric fluxes at 24 and 70µm (Kospal+, 2009)
J/ApJ/694/1559 : Photometric follow-up obs. of GJ 436b (Shporer+, 2009)
J/ApJ/692/L9 : Tidal evolution of transiting exoplanets (Levrard+, 2009)
J/ApJ/689/L149 : Gliese 436b transits parameter variations (Coughlin+, 2008)
J/A+A/486/1039 : HST transit light curve for GJ436b (Bean+, 2008)
J/A+A/475/1125 : Characterization of the hot Neptune GJ 436b (Demory+, 2007)
J/A+A/471/L51 : Spitzer obs. of the hot Neptune GJ 436b (Gillon+, 2007)
J/ApJ/666/475 : Extrasolar planet taxonomy (Marchi+, 2007)
J/ApJ/649/1010 : Habitability of known exoplanetary systems (Jones+, 2006)
J/ApJ/646/505 : Catalog of nearby exoplanets (Butler+, 2006)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Date Observation date
13- 16 I4 min Dur [258/4207] Duration time
18- 20 F3.1 s Exp [0.1/0.4] Frame exposure time
22- 27 I6 --- NFr [36160/588480] Total number of frames
29- 36 A8 --- Pipeline [S18.18.0] Spitzer pipeline
38- 40 F3.1 um lambda [3.6/8] Observation wavelength
42- 44 A3 --- Ref Previous publications (1)
46- 58 F13.7 d MJD ? MJD date of observation at DCE start
(JD-2400000.5) (2)
60-105 A46 --- FileName Name of FITS file in subdirectory fits (2)
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Note (1): Reference as follows:
K10 = parts were published by Knutson et al. (2010ApJ...720.1569K 2010ApJ...720.1569K);
B10 = Ballard et al. (2010PASP..122.1341B 2010PASP..122.1341B).
Note (2): Columns added by CDS.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 06-Mar-2014