SPECTRAL AND PHOTOMETRIC DIAGNOSTICS OF GIANT PLANET FORMATION SCENARIOS

By D. Spiegel, Adam Burrows. 2011

271 citations recorded by the source corpus.

Gas-giant planets that form via core accretion might have very different characteristics from those that form via disk instability. Disk-instability objects are typically thought to have higher entropies, larger radii, and (generally) higher effective temperatures than core-accretion objects. In this paper, we provide a large set of models exploring the observational consequences of high-entropy (hot) and low-entropy (cold) initial conditions, in the hope that this will ultimately help to distinguish between different physical mechanisms of planet formation. However, the exact entropies and radii of newly formed planets due to these two modes of formation cannot, at present, be precisely predicted. It is possible that the distribution of properties of core-accretion-formed planets and the distribution of properties of disk-instability-formed planets overlap. We, therefore, introduce a broad range of “warm-start” gas-giant planet models. Between the hottest and the coldest models that we consider, differences in radii, temperatures, luminosities, and spectra persist for only a few million to a few tens of millions of years for planets that are a few times Jupiter's mass or less. For planets that are ∼five times Jupiter's mass or more, significant differences between hottest-start and coldest-start models persist for on the order of 100 Myr. We find that out of the standard infrared bands (J, H, K, L′, M, N) the K and H bands are the most diagnostic of the initial conditions. A hottest-start model can be from ∼4.5 mag brighter (at Jupiter's mass) to ∼9 mag brighter (at 10 times Jupiter's mass) than a coldest-start model in the first few million years. In more massive objects, these large differences in luminosity and spectrum persist for much longer than in less massive objects. Finally, we consider the influence of atmospheric conditions on spectra, and find that the presence or absence of clouds, and the metallicity of an atmosphere, can affect an object's apparent brightness in different bands by up to several magnitudes.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/56ee45c92bdeb9a9defc62b3bf07e8c170ff37a1

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. B. Bowler
2. Jon Fortney
3. M. Marley
4. Michael C. Liu
5. C. Mordasini
6. N. Madhusudhan
7. Th. Henning
8. A. Burgasser

Citations in the corpus

• DIRECT IMAGING OF A COLD JOVIAN EXOPLANET IN ORBIT AROUND THE SUN-LIKE STAR GJ 504 (2013, background): “Since GJ 504 is older than 100 Myr, its inferred mass is less sensitive to the uncertainty in initial conditions for the employed model (Marley et al. 2007; Spiegel & Burrows 2012) than the previously imaged planets which have younger age than GJ 504 b.”
• THE GEMINI/NICI PLANET-FINDING CAMPAIGN: THE FREQUENCY OF PLANETS AROUND YOUNG MOVING GROUP STARS (2013, methodology): “Additionally, we have adopted hot-start models here, which predict considerably brighter planets at these young ages compared to cold-start or warm-start models (for instance Spiegel & Burrows 2012 and Marleau & Cumming 2013).”
• First light of the VLT planet finder SPHERE - III. New spectrophotometry and astrometry of the HR 8799 exoplanetary system (2015, background): “We caution that the tracks do not explore the impact of the initial conditions on the mass predictions due to the lack of “cold-start” and “warm-start” evolutionary models (e.g., Marley et al. 2007; Spiegel & Burrows 2012) in the brown-dwarf mass range.”
• Imaging Extrasolar Giant Planets (2016, background): “This motivated a class of warm-start models with intermediate initial entropies that probably better reflect dissipative accretion shocks that occur in nature (Spiegel & Burrows 2012; Marleau & Cumming 2013).”
• MASSES, RADII, AND CLOUD PROPERTIES OF THE HR 8799 PLANETS (2012, background): “Intermediate cases, such as explored by Spiegel & Burrows (2012), are possible, but we set those aside for now.”
• THE IMPRINT OF EXOPLANET FORMATION HISTORY ON OBSERVABLE PRESENT-DAY SPECTRA OF HOT JUPITERS (2016, background): “…lower entropy is likely due to the lower gas accretion rate in the disk-limited phase: in Mordasini (2013), a rate of 10−2 M⊕/yr was assumed, while here the typical gas accretion rate is only of order 2 × 10−4 M⊕/yr, which is known to lead to lower post-formation entropies (Spiegel & Burrows 2012).”
• A YOUNG PROTOPLANET CANDIDATE EMBEDDED IN THE CIRCUMSTELLAR DISK OF HD 100546 (2013, background): “Models with lower specific entropy in the initial conditions for the formation process predict even higher masses (cf. Spiegel & Burrows 2012).”
• Discovery of a planetary-mass companion within the gap of the transition disk around PDS 70 (2018, unknown): “We also compared the H-band photometry to the warm-start models from Spiegel & Burrows (2012), as well as the hot-start COND models from Baraffe et al. (2003), resulting in a similar finding (5–10 MJup for the former, and 4–5 MJup for the latter).”
• Characterization of exoplanets from their formation - II. The planetary mass-radius relationship (2012, background): “High gas accretion rates in the runway phase for example make the “cold start” scenario become more similar to the “hot start” scenario (see Spiegel & Burrows 2012).”
• PLANETS AROUND LOW-MASS STARS (PALMS). IV. THE OUTER ARCHITECTURE OF M DWARF PLANETARY SYSTEMS (2014, background): “On the other hand, “cold start” and “warm start” models (e.g., Marley et al. 2007; Spiegel & Burrows 2012; Mollière & Mordasini 2012; Bodenheimer et al. 2013) follow a core accretion prescription, which assumes significant loss of initial entropy at formation through punctuated energy dissipation…”
• DISCOVERY OF A PROBABLE 4–5 JUPITER-MASS EXOPLANET TO HD 95086 BY DIRECT IMAGING (2013, methodology): “Moreover, we attempted a comparison of the L’ band magnitude of HD95086 b to ”warm-start” evolutionary models predictions (Spiegel & Burrows 2012) with different initial conditions (see Fig.”
• Characterization of exoplanets from their formation - I. Models of combined planet formation and evolution (2012, background): “The results for “cold starts” can be compared with Marley et al. (2007) or Spiegel & Burrows (2012).”
• Retrieving scattering clouds and disequilibrium chemistry in the atmosphere of HR 8799e (2020, background): “It was found by Spiegel & Burrows (2012); Marley et al. (2012); Marleau & Cumming (2014), however, that at least a classical cold start assumption (Marley et al. 2007) is ruled out for these planets.”