CLOUDS AND CHEMISTRY IN THE ATMOSPHERE OF EXTRASOLAR PLANET HR8799b

By Travis S. Barman, B. Macintosh, Q. Konopacky, C. Marois. 2011

250 citations recorded by the source corpus.

Using the integral field spectrograph OSIRIS, on the Keck II telescope, broad near-infrared H- and K-band spectra of the young exoplanet HR8799b have been obtained. In addition, six new narrowband photometric measurements have been taken across the H and K bands. These data are combined with previously published photometry for an analysis of the planet's atmospheric properties. Thick photospheric dust cloud opacity is invoked to explain the planet's red near-IR colors and relatively smooth near-IR spectrum. Strong water absorption is detected, indicating a hydrogen-rich atmosphere. Only weak CH4 absorption is detected at K band, indicating efficient vertical mixing and a disequilibrium CO/CH4 ratio at photospheric depths. The H-band spectrum has a distinct triangular shape consistent with low surface gravity. New giant planet atmosphere models are compared to these data with best-fitting bulk parameters, Teff = 1100 K ±100 and log (g) = 3.5 ± 0.5 (for solar composition). Given the observed luminosity (log Lobs/L☉ ∼ − 5.1), these values correspond to a radius of 0.75 RJup+0.17− 0.12 and a mass of ∼0.72 MJup+2.6 − 0.6—strikingly inconsistent with interior/evolution models. Enhanced metallicity (up to ∼10× that of the Sun) along with thick clouds and non-equilibrium chemistry are likely required to reproduce the complete ensemble of spectroscopic and photometric data and the low effective temperatures (<1000 K) required by the evolution models.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/1d5c4606fca49fea2459a847a091b9923f051b12

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In Astronomy and Astrophysics

1. Michael C. Liu
2. B. Bowler
3. T. Dupuy
4. M. Marley
5. A. Burgasser
6. K. Luhman
7. Jon Fortney
8. J. D. Kirkpatrick

Citations in the corpus

• THE EXTREMELY RED, YOUNG L DWARF PSO J318.5338−22.8603: A FREE-FLOATING PLANETARY-MASS ANALOG TO DIRECTLY IMAGED YOUNG GAS-GIANT PLANETS (2013, background): “2Note that 2MASS J1207−39b can be described as “underluminous,” as its luminosity (log(Lbol/L⊙) = −4.73 ± 0.12 dex; Barman et al. 2011b) is somewhat low relative to field L dwarfs.”
• SIMULTANEOUS DETECTION OF WATER, METHANE, AND CARBON MONOXIDE IN THE ATMOSPHERE OF EXOPLANET HR 8799 b (2015, methodology): “Evidence for quenching of CO and CH4 in the atmospheres of the HR8799 planets has been established elsewhere (Hinz et al. 2010; Barman et al. 2011a; Skemer et al. 2012; Marley et al. 2012).”
• THE HAWAII INFRARED PARALLAX PROGRAM. II. YOUNG ULTRACOOL FIELD DWARFS (2016, background): “Theoretical work (e.g., Barman et al. 2011b; Madhusudhan et al. 2011; Marley et al. 2012; Lee et al. 2013; Zahnle & Marley 2014) has helped provide physical context for direct imaging observations.”
• THE GEMINI/NICI PLANET-FINDING CAMPAIGN: THE FREQUENCY OF PLANETS AROUND YOUNG MOVING GROUP STARS (2013, background): “…HR 8799 planets; Chauvin et al. 2005a; Marois et al. 2008, 2010) have lacked methane absorption and show extremely red colors, likely due to dust clouds and/or non-equilibrium chemistry in their atmospheres (Bowler et al. 2010; Skemer et al. 2011; Barman et al. 2011a, 2011b; Currie et al. 2011).”
• FUNDAMENTAL PARAMETERS AND SPECTRAL ENERGY DISTRIBUTIONS OF YOUNG AND FIELD AGE OBJECTS WITH MASSES SPANNING THE STELLAR TO PLANETARY REGIME (2015, background): “…poorly reproduced regions such as the H-band peak and λ< 0.9 μm result in sometimes highly discrepant best fit parameters (e.g., Teff and surface gravity) and consequently unreliable or unphysical radii estimates (e.g., Bowler et al. 2010; Barman et al. 2011; Dupuy & Kraus 2013; Liu et al. 2013).”
• First light of the VLT planet finder SPHERE - III. New spectrophotometry and astrometry of the HR 8799 exoplanetary system (2015, methodology): “…data used in the fit (R ∼ 30), a good indicator for the surface gravity of substellar objects is the spectral shape in the ∼1.5−1.8 µm range (see, e.g., Barman et al. 2011; Chilcote et al. 2015), but 6 The flux values corresponding to the first and last two channels of IFS were removed from the…”
• DIRECT IMAGING OF A COLD JOVIAN EXOPLANET IN ORBIT AROUND THE SUN-LIKE STAR GJ 504 (2013, background): “It has been proposed that planetary candidates with hot atmospheres (Teff ∼ 1000 K) around HR 8799 or 2M 1207 may have thick clouds (Barman et al. 2011a; Madhusudhan et al. 2011; Skemer et al. 2011; Marley et al. 2012) although their cloud properties are under discussion (Barman et al. 2011a,b).”
• NEGLECTED CLOUDS IN T AND Y DWARF ATMOSPHERES (2012, background): “Several studies of the HR 8799 planets have shown that the iron and silicate clouds play a significant role in their atmospheres (Marois et al. 2008; Barman et al. 2011; Galicher et al. 2011; Bowler et al. 2010; Currie et al. 2011; Madhusudhan et al. 2011; Marley et al. 2012).”
• LARGE-AMPLITUDE VARIATIONS OF AN L/T TRANSITION BROWN DWARF: MULTI-WAVELENGTH OBSERVATIONS OF PATCHY, HIGH-CONTRAST CLOUD FEATURES (2012, background): “…of low gravity atmospheres to retain a thicker and higher cloud layer, high metallicity, and/or non-equilibrium chemistry may be responsible (e.g. Barman et al. 2011), and highlights that significant interdependencies between effective temperature, condensate properties, surface gravity, and…”
• THE BROWN DWARF KINEMATICS PROJECT (BDKP). III. PARALLAXES FOR 70 ULTRACOOL DWARFS (2012, background): “The latest-type L dwarfs in our sample may be higher mass analogs to HR 8799b (Barman et al. 2011).”
• The Formation and Early Evolution of Low-Mass Stars and Brown Dwarfs (2012, background): “However, the onset of methane absorption (i.e., a type of T0) may occur at lower temperatures for young brown dwarfs than for older objects in the field (Barman et al. 2011b, Section 4.4).”
• On the Cool Side: Modeling the Atmospheres of Brown Dwarfs and Giant Planets (2014, methodology): “Barman et al. (2011), for example, utilize the abundances of Asplund et al. (2009) which are very similar to the Lodders (2003) abundances utilized by the Marley/Saumon group.”
• ORBITAL MOTION OF HR 8799 b, c, d USING HUBBLE SPACE TELESCOPE DATA FROM 1998: CONSTRAINTS ON INCLINATION, ECCENTRICITY, AND STABILITY (2011, background): “Models using thick cloud layers that are not present in brown dwarfs tend to reproduce the planets’ SEDs with higher fidelity (Marois et al. 2008; Currie et al. 2011a; Barman et al. 2011; Madhusudhan et al. 2011).”
• A STUDY OF THE DIVERSE T DWARF POPULATION REVEALED BY WISE (2013, background): “37+113343.7 (Faherty et al. 2013), 2MASS 1207b (Patience et al. 2010; Barman et al. 2011a) and the HR 8799 planets (Bowler et al. 2010; Barman et al. 2011b; Marley et al. 2012) have low surface gravity, appear to be dusty, resemble the L dwarf standards, and lack the methane features of T dwarfs.”
• THE HAWAII INFRARED PARALLAX PROGRAM. I. ULTRACOOL BINARIES AND THE L/T TRANSITION, (2012, background): “…is which present in at least some objects (Enoch et al. 2003; Clarke et al. 2008; Artigau et al. 2009) and the age/gravity-dependence of the L/T transition (e.g., Metchev & Hillenbrand 2006; Luhman et al. 2007; Dupuy et al. 2009c; Stephens et al. 2009; Bowler et al. 2010b; Barman et al. 2011).”
• Retrieving scattering clouds and disequilibrium chemistry in the atmosphere of HR 8799e (2020, background): “Using OSIRIS H and K band spectra at low resolution, Barman et al. (2011) report on HR 8799b exhibiting weaker CH4 absorption than expected, and that disequilibrium chemistry may be at play in order to decrease the CH4 abundance.”