THE CLIMATE OF HD 189733b FROM FOURTEEN TRANSITS AND ECLIPSES MEASURED BY SPITZER

By E. Agol, N. Cowan, H. Knutson, D. Deming, J. Steffen, G. Henry, D. Charbonneau. 2010

227 citations recorded by the source corpus.

We present observations of six transits and six eclipses of the transiting planet system HD 189733 taken with the Spitzer Space Telescope's Infrared Array Camera (IRAC) at 8 μm, as well as a re-analysis of previously published data. We use several novel techniques in our data analysis, the most important of which is a new correction for the detector “ramp” variation with a double-exponential function, which performs better and is a better physical model for this detector variation. Our main scientific findings are (1) an upper limit on the variability of the dayside planet flux of 2.7% (68% confidence); (2) the most precise set of transit times measured for a transiting planet, with an average accuracy of 3 s; (3) a lack of transit-timing variations, excluding the presence of second planets in this system above 20% of the mass of Mars in low-order mean-motion resonance at 95% confidence; (4) a confirmation of the planet's phase variation, finding the night side is 64% as bright as the day side, as well as an upper limit on the nightside variability of 17% (68% confidence); (5) a better correction for stellar variability at 8 μm causing the phase function to peak 3.5 hr before secondary eclipse, confirming that the advection and radiation timescales are comparable at the 8 μm photosphere; (6) variation in the depth of transit, which possibly implies variations in the surface brightness of the portion of the star occulted by the planet, posing a fundamental limit on non-simultaneous multi-wavelength transit absorption measurements of planet atmospheres; (7) a measurement of the infrared limb darkening of the star, which is in good agreement with stellar atmosphere models; (8) an offset in the times of secondary eclipse of 69 s, which is mostly accounted for by a 31 s light-travel time delay and 33 s delay due to the shift of ingress and egress by the planet hot spot; this confirms that the phase variation is due to an offset hot spot on the planet; (9) a retraction of the claimed eccentricity of this system due to the offset of secondary eclipse, which is now just an upper limit; and (10) high-precision measurements of the parameters of this system. These results were enabled by the exquisite photometric precision of Spitzer IRAC; for repeat observations the scatter is less than 0.35 mmag over the 590 day timescale of our observations after decorrelating with detector parameters.

Subfields: Astronomy and Astrophysics, Instrumentation

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Citations in the corpus

 ?> -REx. II. RETRIEVAL OF EMISSION SPECTRA (2015, methodology): “We have compiled data sets ranging from the NIR (1.4µm) to the MIR (24µm), namely: HST/NICMOS (Swain et al. 2009), Spitzer/IRAC 3.6, 4.5 µm (Knutson et al. 2012), 8.0 µm (Agol et al. 2010), Spitzer/IRS spectroscopy (Grillmair et al. 2008), Spitzer/IRS 16 & 24 µm photometry (Charbonneau et al. 2008).”
THE FLAT TRANSMISSION SPECTRUM OF THE SUPER-EARTH GJ1214b FROM WIDE FIELD CAMERA 3 ON THE HUBBLE SPACE TELESCOPE (2011, background): “These ramps are reminiscent of those seen in highcadence Spitzer light curves at 8 and 16 µm (e.g. Deming et al. 2006; Knutson et al. 2007a; Charbonneau et al. 2008) which Agol et al. (2010) recently proposed may be due to “charge trapping” within the detector pixels.”
THERMAL PHASE VARIATIONS OF WASP-12b: DEFYING PREDICTIONS (2011, unknown): “This means that we do not look for eclipse depth variability (searches for such variability have so far only resulted in upper limits: Agol et al. 2010; Knutson et al. 2011).”
Optimal estimation retrievals of the atmospheric structure and composition of HD 189733b from secondary eclipse spectroscopy (2011, background): “If we consider the eff ct of varying the radius ratio over the range 0.147<Rp/R∗<0.160 (Agol et al. 2010), then we find that the best-fitting molecular abundances vary over the ranges: H2O (6.5–6.7×10−4), CO2 (2.0– 2.2×10−3), CO (2.5–3.3×10−3), and CH4 (1–10×10−7), respectively (Fig.”
ORBITAL PHASE VARIATIONS OF THE ECCENTRIC GIANT PLANET HAT-P-2b (2013, methodology): “This ramp in the flux values has been previously noted for IRAC 8.0 µm observations (e.g. Knutson et al. (2007, 2009a); Agol et al. (2010)) as well as 3.6 and 4.5 µm observations (e.g. Beerer et al. (2011); Todorov et al. (2012)).”
starry: Analytic Occultation Light Curves (2018, methodology): “…map corresponding to the maximum likelihood model is plotted at the top right, showing a statistically significant eastward offset in the location of the hotspot in agreement with previous studies (Knutson et al. 2007; Agol et al. 2010; de Wit et al. 2012; Majeau et al. 2012; Rauscher et al. 2018).”
The prevalence of dust on the exoplanet HD 189733b from Hubble and Spitzer observations (2012, methodology): “We use Désert et al. (2009), Désert et al. (2011) and Knutson et al. (2012) for measurements in the 3.6-µm, 4.5-µm and 5.8 µm channels of IRAC on Spitzer, and Agol et al. (2010) for the 8-micron channel. c© 2012 RAS, MNRAS 000, 1–31”
Hubble Space Telescope transmission spectroscopy of the exoplanet HD 189733b: high‐altitude atmospheric haze in the optical and near‐ultraviolet with STIS (2011, methodology): “The system parameters have been very accurately measured from the high S/N transit light curves of HST and Spitzer (Pont et al. 2007; Sing et al. 2009; Agol et al. 2010; Désert et al. 2011), and we used those of Agol et al. (2010) for this study, taken at the longest wavelength.”
Temperature–pressure profile of the hot Jupiter HD 189733b from HST sodium observations: detection of upper atmospheric heating (2012, methodology): “We compared our sodium absorption depth with the radius observed at 8 µm by Agol et al. (2010), assuming that this feature is due to absorption from atmospheric water.”
3.6 AND 4.5 μm PHASE CURVES AND EVIDENCE FOR NON-EQUILIBRIUM CHEMISTRY IN THE ATMOSPHERE OF EXTRASOLAR PLANET HD 189733b (2012, methodology): “For the secondary eclipse we approximate the planet as a uniform disk (for more on this see Agol et al. 2010) where the depth is measured relative to the average of the phase curve function over the duration of the eclipse.”
EQUATORIAL SUPERROTATION ON TIDALLY LOCKED EXOPLANETS (2011, background): “Their HD 189733b models in particular compare favorably with a variety of observational constraints (Showman et al. 2009; Agol et al. 2010), and here we focus on their solarmetallicity, synchronously rotating HD 189733b case.”
Kepler-22b: A 2.4 EARTH-RADIUS PLANET IN THE HABITABLE ZONE OF A SUN-LIKE STAR (2011, methodology): “We employed the techniques described in Agol et al. (2010) for the treatment of the images before photometry.”
A chemical model for the atmosphere of hot Jupiters (2012, background): “…et al. 2009b, for emission spectrum) and (Knutson et al. 2007, 2009; Swain et al. 2008b; Beaulieu et al. 2008; Sing et al. 2009; Désert et al. 2009; Agol et al. 2010, for transmission spectrum), but we do not discuss the agreement between observations and synthetic spectra, as we did not attempt…”
SPITZER PHASE CURVE CONSTRAINTS FOR WASP-43b AT 3.6 AND 4.5 μm (2016, background): “Light-Curve Systematics and Fits After a decade of work, Spitzer’s systematics are generally considered to be well understood (e.g. Charbonneau et al. 2005; Agol et al. 2010; Knutson et al. 2011; Ingalls et al. 2012; Stevenson et al. 2012; Lewis et al. 2013; Deming et al. 2015).”