A combined very large telescope and Gemini study of the atmosphere of the directly imaged planet, β Pictoris b

Thayne Currie, Adam Burrows, Nikku Madhusudhan, Misato Fukagawa, Julien H. Girard, Rebekah Dawson, Ruth Murray-Clay, Scott Kenyon, Marc Kuchner, Soko Matsumura, Ray Jayawardhana, John Chambers, Ben Bromley

Research output: Contribution to journalArticlepeer-review

67 Scopus citations

Abstract

We analyze new/archival VLT/NaCo and Gemini/NICI high-contrast imaging of the young, self-luminous planet β Pictoris b in seven near-to-mid IR photometric filters, using advanced image processing methods to achieve high signal-to-noise, high precision measurements. While β Pic b's near-IR colors mimic those of a standard, cloudy early-to-mid L dwarf, it is overluminous in the mid-infrared compared to the field L/T dwarf sequence. Few substellar/planet-mass objects - i.e., κ And b and 1RXJ 1609B - match β Pic b's JHKsL' photometry and its 3.1 μm and 5 μm photometry are particularly difficult to reproduce. Atmosphere models adopting cloud prescriptions and large (∼60 μm) dust grains fail to reproduce the β Pic b spectrum. However, models incorporating thick clouds similar to those found for HR 8799 bcde, but also with small (a few microns) modal particle sizes, yield fits consistent with the data within the uncertainties. Assuming solar abundance models, thick clouds, and small dust particles (〈a〉 = 4 μm), we derive atmosphere parameters of log (g) = 3.8 ± 0.2 and T eff = 1575-1650 K, an inferred mass of 7 MJ , and a luminosity of log(L/L̇) ∼-3.80 ± 0.02. The best-estimated planet radius, ≈1.65 ± 0.06 RJ , is near the upper end of allowable planet radii for hot-start models given the host star's age and likely reflects challenges constructing accurate atmospheric models. Alternatively, these radii are comfortably consistent with hot-start model predictions if β Pic b is younger than ≈7 Myr, consistent with a late formation well after its host star's birth ∼12 Myr ago.

Original languageEnglish (US)
Article number15
JournalAstrophysical Journal
Volume776
Issue number1
DOIs
StatePublished - Oct 10 2013

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • planetary systems
  • stars: early-type
  • stars: individual (beta Pictoris)

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