Atmospheric Characterization and Further Orbital Modeling of κ Andromeda b

Uyama, Taichi; Currie, Thayne; Hori, Yasunori; Rosa, Robert J. De; Mede, Kyle; Brandt, Timothy D.; Kwon, Jungmi; Guyon, Olivier; Lozi, Julien; Jovanović, Nemanja; Martinache, Frantz; Kudo, Tomoyuki; Tamura, Motohide; Kasdin, N. Jeremy; Groff, Tyler D.; Chilcote, Jeffrey; Hayashi, Masahiko; McElwain, Michael W.; Asensio-Torres, Rubén; Janson, Markus; Knapp, G. R.; Serabyn, Eugene

doi:10.3847/1538-3881/ab5afa

Cited by 8 publications

(19 citation statements)

References 101 publications

(163 reference statements)

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“…Since 2013, the high-contrast imagers and spectrographs such as GPI (Macintosh et al 2006), SPHERE (Beuzit et al 2019) or SCExAO/CHARIS (Groff et al 2015;Jovanovic et al 2015) have gathered low-resolution (R λ = 30-350) near-infrared (0.95-2.45 µm) spectra of exoplanets down to 100 mas from their host star. The spectra confirmed some of the results inferred earlier from photometric spectral energy distributions (e.g., Marois et al 2008;Bonnefoy et al 2013): the reduced surface gravity affects the vertical mixing and the gravitational settling of condensates, which leads to thicker cloud layers, upper atmosphere submicron hazes, and causes cloud opacities to remain down to T eff = 600 K at early ages (Bonnefoy et al 2016;Rajan et al 2017;Chauvin et al 2017Chauvin et al , 2018Samland et al 2017;Greenbaum et al 2018;Uyama et al 2020;Delorme et al 2017;Mesa et al 2020). These spectra, however had led to contradicting conclusions on the derivation of the atmospheric composition (Samland et al 2017;Rajan et al 2017), possibly owing to the limited resolution of the observations and uncertainties in the atmospheric models.…”

Section: Introductionsupporting

confidence: 82%

Medium-resolution spectrum of the exoplanet HIP 65426 b

Petrus

Bonnefoy

Chauvin

et al. 2021

A&A

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Medium-resolution integral-field spectrographs (IFS) coupled with adaptive-optics such as Keck/OSIRIS, VLT/MUSE, or SINFONI are appearing as a new avenue for enhancing the detection and characterization capabilities of young, gas giant exoplanets at large heliocentric distances (>5 au). We analyzed K-band VLT/SINFONI medium-resolution (Rλ ~5577) observations of the young giant exoplanet HIP 65426 b. Our dedicated IFS data analysis toolkit (TExTRIS) optimized the cube building, star registration, and allowed for the extraction of the planet spectrum. A Bayesian inference with the nested sampling algorithm coupled with the self-consistent forward atmospheric models BT-SETTL15 and Exo-REM using the ForMoSA tool yields Teff = 1560 ± 100 K, log(g) ≤ 4.40 dex, [M/H] = 0.05−0.22+0.24 dex, and an upper limit on the C/O (≤0.55). The object is also re-detected with the so-called “molecular mapping” technique. The technique yields consistent atmospheric parameters, but the loss of the planet pseudo-continuum in the process degrades or modifies the constraints on these parameters. The solar to sub-solar C/O ratio suggests an enrichment by solids at formation if the planet was formed beyond the water snowline (≥20 au) by core accretion (CA hereafter). However, a formation by gravitational instability (GI hereafter) cannot be ruled out. The metallicity is compatible with the bulk enrichment of massive Jovian planets from the Bern planet population models. Finally, we measure a radial velocity of 26 ± 15 km s−1 compatible with our revised measurement on the star. This is the fourth imaged exoplanet for which a radial velocity can be evaluated, illustrating the potential of such observations for assessing the coevolution of imaged systems belonging to star forming regions, such as HIP 65426.

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Section: Introductionsupporting

confidence: 82%

Medium-resolution spectrum of the exoplanet HIP 65426 b

Petrus

Bonnefoy

Chauvin

et al. 2021

A&A

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“…A recent analysis of the CHARIS data by Uyama et al (2020) found a slightly lower temperature using models from Allard et al (2012), Chabrier et al (2000, and Witte et al…”

Section: Temperature Gravity and Metallicitymentioning

confidence: 94%

“…In order to do this, we must construct a model grid that spans the expected values of these parameters. In a number of previous works on κ And b, the temperature was estimated to be ∼2000 K and the surface gravity ( g log )<5 (e.g., Hinkley et al 2013;Bonnefoy et al 2014;Todorov et al 2016;Currie et al 2018;Uyama et al 2020). The metallicity has not been constrained, but estimates from the host star suggest values near solar or slightly subsolar (Wu et al 2011;Jones et al 2016).…”

Section: Synthetic Spectramentioning

confidence: 99%

“…Bonnefoy et al (2014) derived a similar age to Carson et al (2013) of -+ 30 10 120 Myr based on the age of the Columba association and a lower mass limit of 10 M Jup based on "warm-start" evolutionary models, but did not constrain the surface gravity. More recent studies of κ And b by Currie et al (2018) and Uyama et al (2020) have concluded the object is low gravity ( g log ∼4-4.5) and resembles an L0-L1 dwarf. Other studies focusing on the host star found the system to be young (t∼30-40 Myr; Brandt & Huang 2015;David & Hillenbrand 2015).…”

Section: Introductionmentioning

confidence: 98%

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Moderate-resolution K-band Spectroscopy of Substellar Companion κ Andromedae b

Wilcomb

Konopacky

Barman

et al. 2020

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We present moderate-resolution (R∼4000) K-band spectra of the "super-Jupiter," κ Andromedae b. The data were taken with the OSIRIS integral field spectrograph at Keck Observatory. The spectra reveal resolved molecular lines from H 2 O and CO, and are compared to a custom PHOENIX atmosphere model grid appropriate for young planetary-mass objects. We fit the data using a Markov chain Monte Carlo forward-modeling method. Using a combination of our moderate-resolution spectrum and low-resolution, broadband data from the literature, we derive an effective temperature of T eff =1950-2150 K, a surface gravity of = g log 3.5 4.5 -, and a metallicity of [M/ H]=−0.2-0.0. These values are consistent with previous estimates from atmospheric modeling and the currently favored young age of the system (<50 Myr). We derive a C/O ratio of -+ 0.70 0.24 0.09 for the source, broadly consistent with the solar C/O ratio. This, coupled with the slightly subsolar metallicity, implies a composition consistent with that of the host star, and is suggestive of formation by a rapid process. The subsolar metallicity of κ Andromedae b is also consistent with predictions of formation via gravitational instability. Further constraints on formation of the companion will require measurement of the C/O ratio of κ Andromedae A. We also measure the radial velocity of κ Andromedae b for the first time, with a value of −1.4±0.9 km s −1 relative to the host star. We find that the derived radial velocity is consistent with the estimated high eccentricity of κ Andromedae b.

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“…The IFS further plays a key role in studying the atmosphere of the planets by providing a spectrum with low spectral resolution (R = λ/δλ ∼ 20 − 75) of each de-tection. At this resolution, broad molecular absorption bands can be identified, and the pseudo-continuum holds information about the pressure-temperature profile and clouds (e.g., De Rosa et al 2016;Bonnefoy et al 2016;Chilcote et al 2017;Rajan et al 2017;Delorme et al 2017;Samland et al 2017;Bonnefoy et al 2018;Greenbaum et al 2018;Müller et al 2018;Chauvin et al 2018;Currie et al 2018;Uyama et al 2020;Stone et al 2020;Ward-Duong et al 2021).…”

Section: Introductionmentioning

confidence: 99%

Spectral unmixing for exoplanet direct detection in hyperspectral data

Rameau

Chanussot

Carlotti

et al. 2021

A&A

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Context. The direct detection of faint exoplanets with high-contrast instruments can be boosted by combining it with high spectral resolution. For integral field spectrographs yielding hyperspectral data, this means that the majority of the field of view consists of diffracted starlight spectra and a spatially localized planet. Observation analysis usually relies on classic cross-correlation with theoretical spectra, maximized at the position and with the properties of the planet. In a purely blind-search context, this supervised strategy can be biased with model mismatch and/or be computationally inefficient. Aims. Using an approach that is inspired by the analysis of hyperspectral data within the remote-sensing community, we aim to propose an alternative to cross-correlation that is fully data-driven, which decomposes the data into a set of individual spectra and their corresponding spatial distributions. This strategy is called spectral unmixing. Methods. We used an orthogonal subspace projection to identify the most distinct spectra in the field of view. Their spatial distribution maps were then obtained by inverting the data. These spectra were then used to break the original hyperspectral images into their corresponding spatial distribution maps via non-negative least squares. A matched filter with the instrument point-spread function (or visual inspection) was then used to detect the planet on one of the maps. The performance of our method was evaluated and compared with a cross-correlation using simulated hyperspectral data with medium resolution from the ELT/HARMONI integral field spectrograph. Results. We show that spectral unmixing effectively leads to a planet detection solely based on spectral dissimilarities at significantly reduced computational cost. The extracted spectrum holds significant signatures of the planet while being not perfectly separated from residual starlight. The sensitivity of the supervised cross-correlation is three to four times higher than with unsupervised spectral unmixing, the gap is biased toward the former because the injected and correlated spectrum match perfectly. The algorithm was furthermore vetted on real data obtained with VLT/SINFONI of the β Pictoris system. This led to the detection of β Pictoris b with a signal-to-noise ratio of 28.5. Conclusions. Spectral unmixing is a viable alternative strategy to a cross-correlation to search for and characterize exoplanets in hyperspectral data in a purely data-driven approach. The advent of large data from the forthcoming IFS on board JWST and future ELTs motivates further algorithm development along this path.

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Atmospheric Characterization and Further Orbital Modeling of κ Andromeda b

Cited by 8 publications

References 101 publications

Medium-resolution spectrum of the exoplanet HIP 65426 b

Medium-resolution spectrum of the exoplanet HIP 65426 b

Moderate-resolution K-band Spectroscopy of Substellar Companion κ Andromedae b

Spectral unmixing for exoplanet direct detection in hyperspectral data

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