Detection of Thermal Emission from an Extrasolar Planet

By D. Charbonneau, L. Allen, S. Megeath, G. Torres, R. Alonso, T. Brown, R. Gilliland, D. Latham, G. Mandushev, Francis T. O'Donovan and 1 more. 2005

609 citations recorded by the source corpus.

We present Spitzer Space Telescope infrared photometric time series of the transiting extrasolar planet system TrES-1. The data span a predicted time of secondary eclipse, corresponding to the passage of the planet behind the star. In both bands of our observations, we detect a flux decrement with a timing, amplitude, and duration as predicted by published parameters of the system. This signal represents the first direct detection of (i.e., the observation of photons emitted by) a planet orbiting another star. The observed eclipse depths (in units of relative flux) are 0.00066 ± 0.00013 at 4.5 μm and 0.00225 ± 0.00036 at 8.0 μm. These estimates provide the first observational constraints on models of the thermal emission of hot Jupiters. Assuming that the planet emits as a blackbody, we estimate an effective temperature of Tp = 1060 ± 50 K. Under the additional assumptions that the planet is in thermal equilibrium with the radiation from the star and emits isotropically, we find a Bond albedo of A = 0.31 ± 0.14. This would imply that the planet absorbs the majority of stellar radiation incident upon it, a conclusion of significant impact to atmospheric models of these objects. We also compare our data to a previously published model of the planetary thermal emission, which predicts prominent spectral features in our observational bands due to water and carbon monoxide. This model adequately reproduces the observed planet-to-star flux ratio at 8.0 μm; however, it significantly overpredicts the ratio at 4.5 μm. We also present an estimate of the timing of the secondary eclipse, which we use to place a strong constraint on the expression e cos ω, where e is the orbital eccentricity and ω is the longitude of periastron. The resulting upper limit on e is sufficiently small that we conclude that tidal dissipation is unlikely to provide a significant source of energy interior to the planet.

Subfields: Astronomy and Astrophysics, Instrumentation, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/934d12245a83ca58571198efccf5e1601c3deb22

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. Jon Fortney
2. N. Madhusudhan
3. D. Charbonneau
4. Sara Seager
5. A. Showman
6. J. Winn
7. J. Southworth
8. D. Deming

In Instrumentation

1. Jon Fortney
2. D. Charbonneau
3. N. Madhusudhan
4. J. Southworth
5. Sara Seager
6. A. Showman
7. J. Winn
8. H. Knutson

In Statistical and Nonlinear Physics

1. Jon Fortney
2. N. Madhusudhan
3. Sara Seager
4. A. Showman
5. M. Marley
6. M. Line
7. C. Mordasini
8. D. Charbonneau

Citations in the corpus

• Design Considerations for a Ground-Based Transit Search for Habitable Planets Orbiting M Dwarfs (2007, background): “…et al. 2007), while infrared monitoring during secondary eclipse has led to the detection of broadband thermal emission from HD 209458b, TrES-1, HD 189733b, HD 149026b, and GJ 436b (Deming et al. 2005; Charbonneau et al. 2005; Deming et al. 2006; Harrington et al. 2007; Deming et al. 2007).”
• KEPLER-18b, c, AND d: A SYSTEM OF THREE PLANETS CONFIRMED BY TRANSIT TIMING VARIATIONS, LIGHT CURVE VALIDATION, WARM-SPITZER PHOTOMETRY, AND RADIAL VELOCITY MEASUREMENTS (2011, background): “The Spitzer/IRAC photometry is known to be systematically affected by the so-called pixel-phase effect (see e.g., Charbonneau et al. 2005; Knutson et al. 2008).”
• A Gaussian process framework for modelling instrumental systematics: application to transmission spectroscopy (2011, methodology): “…spectra, in particular using the Hubble Space Telescope (HST) and Spitzer Space Telescope (SST) have provided some of the most detailed observations of exoplanet atmospheres to date (see e.g. Charbonneau et al. 2002; Vidal-Madjar et al. 2003; Charbonneau et al. 2005; Deming et al. 2005).”
• A Transiting Planet of a Sun-like Star (2006, background): “…brighter stars provide adequate flux to enable interesting follow-up observations, including observations of atmospheric composition (Charbonneau et al. 2002; Vidal-Madjar et al. 2004), exosphere extent (Vidal-Madjar et al. 2003), and infrared emission (Charbonneau et al. 2005; Deming et al. 2005).”
• THERMAL PHASE VARIATIONS OF WASP-12b: DEFYING PREDICTIONS (2011, neutral): “IRAC channels 1 and 2 exhibit well-known IPSVs: photons hitting certain parts of a pixel lead to more electron counts than photons hitting other parts of the same pixel (e.g., Charbonneau et al. 2005; Morales-Calder´on et al. 2006).”
• DISEQUILIBRIUM CARBON, OXYGEN, AND NITROGEN CHEMISTRY IN THE ATMOSPHERES OF HD 189733b AND HD 209458b (2011, background): “…atmospheres, transit and eclipse observations have proven to be invaluable for inferring properties of both the planet and its host star (e.g., Charbonneau et al. 2000, 2002, 2005; Henry et al. 2000; Seager & Sasselov 2000; Brown 2001; Brown et al. 2001; Burrows et al. 2001; Hubbard et al.…”
• A CORRELATION BETWEEN STELLAR ACTIVITY AND HOT JUPITER EMISSION SPECTRA (2010, background): “Table 1 Ca II H & K Line Strengths Star Teff b (K) v sin ib B−V SHK f log(R′HK) f HD 17156 5980 4.3 0.64 0.155 -5.022 HD 147506 6260 20.7 0.41 0.191e -4.780 HD 149026 6150c 6.2 0.61 0.152 -5.030 HD 179949 6170 7.0 0.50 0.232 -4.622 HD 189733 5090 2.7 0.93 0.508 -4.501 HD 209458 6070 4.0 0.59 0.160 -”
• 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).”
• SPITZER SECONDARY ECLIPSES OF THE DENSE, MODESTLY-IRRADIATED, GIANT EXOPLANET HAT-P- 20 b ?> USING PIXEL-LEVEL DECORRELATION (2014, background): “The earliest such decorrelations (e.g., Charbonneau et al. 2005; Knutson et al. 2008; Machalek et al. 2008) modeled the intensity fluctuations as polynomial (typically quadratic) functions of the Y-coordinate, sometimes with a weaker (e.g., linear) dependence on the X-coordinate.”
• 3.6 AND 4.5 μm PHASE CURVES AND EVIDENCE FOR NON-EQUILIBRIUM CHEMISTRY IN THE ATMOSPHERE OF EXTRASOLAR PLANET HD 189733b (2012, background): “This effect is due to a well-documented intra-pixel sensitivity variation (e.g., Reach et al. 2005; Charbonneau et al. 2005, 2008; Morales-Calderon et al. 2006; Knutson et al. 2008), in which the sensitivity of an individual pixel varies between the center and the edge.”
• Rejecting Astrophysical False Positives from the TrES Transiting Planet Survey: The Example of GSC 03885–00829 (2006, background): “Examples of detailed follow– up observations include the measurement of several chemical abundances in the atmosphere of HD209458b (Charbonneau et al. 2002; Vidal-Madjar et al. 2003) and the first direct detections of emitted planetary radiation (Charbonneau et al. 2005; Deming et al. 2005).”
• LOW FALSE POSITIVE RATE OF KEPLER CANDIDATES ESTIMATED FROM A COMBINATION OF SPITZER AND FOLLOW-UP OBSERVATIONS (2015, background): “The Spitzer/IRAC photometry is known to be systematically affected by the so-called pixel-phase effect (see e.g., Charbonneau et al. 2005).”
• Planet formation and migration (2005, background): “The direct detections of the transiting planets HD 209458 b (Deming et al. 2005) and TrES–1 (Charbonneau et al 2005) were reported simultaneously in March 2005.”
• Exoplanet Atmospheres: Physical Processes (2010, background): “Although the first secondary eclipse detections (Charbonneau et al. 2005; Deming et al. 2005a) were statistically robust at the just under 6-σ level, they again were not absolutely convincing to the entire astronomy community.”