Evidence for a Circumplanetary Disk around Protoplanet PDS 70 b

We present the first observational evidence for a circumplanetary disc around the protoplanet PDS~70~b, based on a new spectrum in the $K$ band acquired with VLT/SINFONI. We tested three hypotheses to explain the spectrum: Atmospheric emission from the planet with either (1) a single value of extinction or (2) variable extinction, and (3) a combined atmospheric and circumplanetary disc model. Goodness-of-fit indicators favour the third option, suggesting circumplanetary material contributing excess thermal emission --- most prominent at $\lambda \gtrsim 2.3 \mu$m. Inferred accretion rates ($\sim 10^{-7.8}$--$10^{-7.3} M_J$ yr$^{-1}$) are compatible with observational constraints based on the H$\alpha$ and Br$\gamma$ lines. For the planet, we derive an effective temperature of 1500--1600 K, surface gravity $\log(g)\sim 4.0$, radius $\sim 1.6 R_J$, mass $\sim 10 M_J$, and possible thick clouds. Models with variable extinction lead to slightly worse fits. However, the amplitude ($\Delta A_V \gtrsim 3$mag) and timescale of variation ($\lesssim$~years) required for the extinction would also suggest circumplanetary material.

[1]  J. Burns,et al.  Gas drag in primordial circumplanetary envelopes: A mechanism for satellite capture , 1979 .

[2]  J. A. Eisner,et al.  SPECTRAL ENERGY DISTRIBUTIONS OF ACCRETING PROTOPLANETS , 2015, 1502.05412.

[3]  T. Ray,et al.  VLT integral field spectroscopy of embedded protostars: using near-infrared emission lines as tracers of accretion and outflow , 2011 .

[4]  A. Scholz,et al.  Variability in young very low mass stars: two surprises from spectrophotometric monitoring , 2016, 1602.07925.

[5]  C. Baruteau,et al.  PROTOPLANETARY DISKS INCLUDING RADIATIVE FEEDBACK FROM ACCRETING PLANETS , 2015, 1505.03392.

[6]  Johns Hopkins University,et al.  Disk Accretion onto High-Mass Planets , 1999 .

[7]  L. Mayer,et al.  Circumplanetary discs around young giant planets: a comparison between core-accretion and disc instability , 2016, 1610.01791.

[8]  Martin G. Cohen,et al.  THE WIDE-FIELD INFRARED SURVEY EXPLORER (WISE): MISSION DESCRIPTION AND INITIAL ON-ORBIT PERFORMANCE , 2010, 1008.0031.

[9]  J. Wisniewski,et al.  Differences in the Gas and Dust Distribution in the Transitional Disk of a Sun-like Young Star, PDS 70 , 2018, 1804.00529.

[10]  D. Mouillet,et al.  Direct exoplanet detection and characterization using the ANDROMEDA method: Performance on VLT/NaCo data , 2015, 1508.06406.

[11]  L. Close,et al.  An Explanation of the Very Low Radio Flux of Young Planet-mass Companions , 2017, 1710.07489.

[12]  E. Mamajek,et al.  The star formation history and accretion-disc fraction among the K-type members of the Scorpius–Centaurus OB association , 2016, 1605.08789.

[13]  Marc Van Droogenbroeck,et al.  VIP: Vortex Image Processing Package for High-contrast Direct Imaging , 2017, 1705.06184.

[14]  M. Bate,et al.  Circumplanetary disc properties obtained from radiation hydrodynamical simulations of gas accretion by protoplanets , 2009, 0904.4884.

[15]  P. Rojo,et al.  A library of near-infrared integral field spectra of young M–L dwarfs , 2013, 1306.3709.

[16]  Floris van Liere.  Planet Formation , 2009 .

[17]  J. Szulágyi,et al.  Observability of forming planets and their circumplanetary discs II. – SEDs and near-infrared fluxes , 2019, Monthly Notices of the Royal Astronomical Society.

[18]  N. Madhusudhan.  Exoplanetary Atmospheres: Key Insights, Challenges, and Prospects , 2019, Annual Review of Astronomy and Astrophysics.

[19]  F. Allard,et al.  Models of very-low-mass stars, brown dwarfs and exoplanets , 2011, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences.

[20]  T. Fusco,et al.  Orbital and atmospheric characterization of the planet within the gap of the PDS 70 transition disk , 2018, Astronomy & Astrophysics.

[21]  Andrew S. Ackerman,et al.  Precipitating Condensation Clouds in Substellar Atmospheres , 2001, astro-ph/0103423.

[22]  S. E. Persson,et al.  Emission from CO Band Heads in Young Stellar Objects , 1987 .

[23]  Laird M. Close,et al.  Magellan Adaptive Optics Imaging of PDS 70: Measuring the Mass Accretion Rate of a Young Giant Planet within a Gapped Disk , 2018, The Astrophysical Journal Letters.

[24]  G. Rieke,et al.  A TREND BETWEEN COLD DEBRIS DISK TEMPERATURE AND STELLAR TYPE: IMPLICATIONS FOR THE FORMATION AND EVOLUTION OF WIDE-ORBIT PLANETS , 2013, Proceedings of the International Astronomical Union.

[25]  R. Nelson,et al.  GLOBAL HYDROMAGNETIC SIMULATIONS OF A PLANET EMBEDDED IN A DEAD ZONE: GAP OPENING, GAS ACCRETION, AND FORMATION OF A PROTOPLANETARY JET , 2013, 1309.2871.

[26]  A. Scholz,et al.  Clumpy dust rings around non-accreting young stars , 2019, Monthly Notices of the Royal Astronomical Society.

[27]  Adam Burrows,et al.  MODEL ATMOSPHERES FOR MASSIVE GAS GIANTS WITH THICK CLOUDS: APPLICATION TO THE HR 8799 PLANETS AND PREDICTIONS FOR FUTURE DETECTIONS , 2011, 1102.5089.

[28]  Zhaohuan Zhu,et al.  ACCRETING CIRCUMPLANETARY DISKS: OBSERVATIONAL SIGNATURES , 2014, 1408.6554.

[29]  J. H. V. Girard,et al.  The near-infrared spectral energy distribution of β Pictoris b , 2013, 1302.1160.

[30]  A. Savitzky,et al.  Smoothing and Differentiation of Data by Simplified Least Squares Procedures. , 1964 .

[31]  Julien H. Girard,et al.  Separating extended disc features from the protoplanet in PDS 70 using VLT/SINFONI , 2019, Monthly Notices of the Royal Astronomical Society.

[32]  Timothy D. Brandt,et al.  THE STRUCTURE OF PRE-TRANSITIONAL PROTOPLANETARY DISKS. I. RADIATIVE TRANSFER MODELING OF THE DISK+CAVITY IN THE PDS 70 SYSTEM , 2012, 1209.3772.

[33]  Olivier Guyon,et al.  POLARIMETRIC IMAGING OF LARGE CAVITY STRUCTURES IN THE PRE-TRANSITIONAL PROTOPLANETARY DISK AROUND PDS 70: OBSERVATIONS OF THE DISK , 2012, 1208.2075.

[34]  William R. Ward,et al.  Formation of the Galilean Satellites: Conditions of Accretion , 2002 .

[35]  R. West,et al.  Long-term variability of T Tauri stars using WASP , 2016, 1611.03013.

[36]  Michael C. Liu,et al.  A NEAR-INFRARED SPECTROSCOPIC STUDY OF YOUNG FIELD ULTRACOOL DWARFS , 2013, 1305.4418.

[37]  M. Bonnefoy,et al.  An Upper Limit on the Mass of the Circumplanetary Disk for DH Tau b , 2017, 1705.08470.

[38]  Julien H. Girard,et al.  In-depth study of moderately young but extremely red, very dusty substellar companion HD206893B , 2017, 1709.00349.

[39]  Luca Ricci,et al.  SEARCHING FOR CIRCUMPLANETARY DISKS AROUND LkCa 15 , 2014, 1404.5627.

[40]  J. R. Houck,et al.  Infrared Spectroscopy In Astronomy , 1981, Other Conferences.

[41]  T. A. Lister,et al.  Gaia Data Release 2. Summary of the contents and survey properties , 2018, 1804.09365.

[42]  D. Fantinel,et al.  Discovery of a planetary-mass companion within the gap of the transition disk around PDS 70 , 2018, Astronomy & Astrophysics.

[43]  R. Smart,et al.  The extremely red L dwarf ULAS J222711 004547 - dominated by dust. , 2014, 1401.0420.

[44]  J. Szulágyi,et al.  Effects of the Planetary Temperature on the Circumplanetary Disk and on the Gap , 2017, 1705.08444.

[45]  Timothy D. Brandt,et al.  Recovery of the Candidate Protoplanet HD 100546 b with Gemini/NICI and Detection of Additional (Planet-Induced?) Disk Structure at Small Separations , 2014, 1411.0315.

[46]  Models of accreting gas giant protoplanets in protostellar disks , 2004, astro-ph/0412377.

[47]  F. Allard,et al.  New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit , 2015, 1503.04107.