Constraints on the spin evolution of young planetary-mass companions

Surveys of young star-forming regions have discovered a growing population of planetary-mass (<13 MJup) companions around young stars1. There is an ongoing debate as to whether these companions formed like planets (that is, from the circumstellar disk)2, or if they represent the low-mass tail of the star-formation process3. In this study, we utilize high-resolution spectroscopy to measure rotation rates of three young (2–300 Myr) planetary-mass companions and combine these measurements with published rotation rates for two additional companions4,5 to provide a picture of the spin distribution of these objects. We compare this distribution to complementary rotation-rate measurements for six brown dwarfs with masses <20 MJup, and show that these distributions are indistinguishable. This suggests that either these two populations formed via the same mechanism, or that processes regulating rotation rates are independent of formation mechanism. We find that rotation rates for both populations are well below their break-up velocities and do not evolve significantly during the first few hundred million years after the end of accretion. This suggests that rotation rates are set during the late stages of accretion, possibly by interactions with a circumplanetary disk. This result has important implications for our understanding of the processes regulating the angular momentum evolution of young planetary-mass objects, and of the physics of gas accretion and disk coupling in the planetary-mass regime.Similar physical processes regulate the angular momentum of gas-giant planets and planetary-mass brown dwarfs. These processes are active mostly during the early phase of planetary evolution as rotation rates do not change after the first 2–300 Myr.

[1]  Coryn A. L. Bailer-Jones,et al.  Stellar rotation and variability in the Orion Nebula Cluster , 2002 .

[2]  Adam L. Kraus,et al.  THREE WIDE PLANETARY-MASS COMPANIONS TO FW TAU, ROXs 12, AND ROXs 42B , 2013, 1311.7664.

[3]  Bernhard Brandl,et al.  The fast spin-rotation of a young extra-solar planet , 2014 .

[4]  R. F. Jameson,et al.  Near‐infrared cross‐dispersed spectroscopy of brown dwarf candidates in the Upper Sco association★ , 2007, 0711.1109.

[5]  Spectroscopic Rotational Velocities of Brown Dwarfs , 2006, astro-ph/0603194.

[6]  Brendan P. Bowler,et al.  Imaging Extrasolar Giant Planets , 2016, 1605.02731.

[7]  Rotation and variability of very low mass stars and brown dwarfs near epsilon Ori , 2004, astro-ph/0410101.

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

[9]  A. Tielens,et al.  High-Resolution 4.7 Micron Keck/NIRSPEC Spectra of Protostars. II. Detection of the 13CO Isotope in Icy Grain Mantles , 2002, astro-ph/0206420.

[10]  E. Guenther,et al.  UVES spectra of young brown dwarfs in Cha I: Radial and rotational velocities ? , 2001, astro-ph/0110175.

[11]  K. Tsiganis,et al.  Explaining why the uranian satellites have equatorial prograde orbits despite the large planetary obliquity , 2012, 1208.4685.

[12]  Sara Seager,et al.  ATMOSPHERIC RETRIEVAL FOR SUPER-EARTHS: UNIQUELY CONSTRAINING THE ATMOSPHERIC COMPOSITION WITH TRANSMISSION SPECTROSCOPY , 2012, 1203.4018.

[13]  R. P. Butler,et al.  DETERMINING SPECTROMETER INSTRUMENTAL PROFILES USING FTS REFERENCE SPECTRA , 1995 .

[14]  Frantz Martinache,et al.  TWO WIDE PLANETARY-MASS COMPANIONS TO SOLAR-TYPE STARS IN UPPER SCORPIUS , 2010, 1011.2201.

[15]  Rafael Rebolo,et al.  DISCOVERY OF A YOUNG PLANETARY MASS COMPANION TO THE NEARBY M DWARF VHS J125601.92-125723.9 , 2015, Proceedings of the International Astronomical Union.

[16]  Michael C. Liu,et al.  THE RADIAL AND ROTATIONAL VELOCITIES OF PSO J318.5338-22.8603, A NEWLY CONFIRMED PLANETARY-MASS MEMBER OF THE β PICTORIS MOVING GROUP , 2016, 1601.04717.

[17]  Michael C. Liu,et al.  THE HAWAII INFRARED PARALLAX PROGRAM. II. YOUNG ULTRACOOL FIELD DWARFS , 2016, 1612.02426.

[18]  L. Hillenbrand,et al.  PRECISION PHOTOMETRIC MONITORING OF VERY LOW MASS σ ORIONIS CLUSTER MEMBERS: VARIABILITY AND ROTATION AT A FEW Myr , 2010, 1011.3539.

[19]  T. Barman,et al.  PHYSICAL PROPERTIES OF YOUNG BROWN DWARFS AND VERY LOW MASS STARS INFERRED FROM HIGH-RESOLUTION MODEL SPECTRA , 2009, 0911.3844.

[20]  Discovery of Rotational Modulations in the Planetary-Mass Companion 2M1207b: Intermediate Rotation Period and Heterogeneous Clouds in a Low Gravity Atmosphere , 2015, 1512.02706.

[21]  P. H. Hauschildt,et al.  Evolutionary models for cool brown dwarfs and extrasolar giant planets. The case of HD 209458 , 2003 .

[22]  Subhanjoy Mohanty,et al.  The T Tauri Phase Down to Nearly Planetary Masses: Echelle Spectra of 82 Very Low Mass Stars and Brown Dwarfs , 2005, astro-ph/0502155.

[23]  K. Mužić,et al.  ROTATION PERIODS OF YOUNG BROWN DWARFS: K2 SURVEY IN UPPER SCORPIUS , 2015, 1506.06771.

[24]  S. R. Kulkarni,et al.  Dynamical Masses of the Binary Brown Dwarf GJ 569 Bab , 2004, astro-ph/0407334.

[25]  A. Burrows,et al.  SEARCH FOR VERY LOW-MASS BROWN DWARFS AND FREE-FLOATING PLANETARY-MASS OBJECTS IN TAURUS , 2009, 0911.1925.

[26]  S. Littlefair,et al.  Radial and rotational velocities of young brown dwarfs and very low-mass stars in the Upper Scorpius OB association and the ρ Ophiuchi cloud core , 2006, astro-ph/0609053.

[27]  Caltech,et al.  Very Low Mass Stars and Brown Dwarfs in Taurus-Auriga , 2002, astro-ph/0209164.

[28]  H. Bouy,et al.  Spectroscopy of new brown dwarf members of ρ Ophiuchi and an updated initial mass function , 2012, 1201.1912.

[29]  Jonathan Tennyson,et al.  HITEMP, the high-temperature molecular spectroscopic database , 2010 .

[30]  Photometric variability of a young, low-mass brown dwarf , 2003, astro-ph/0306398.

[31]  Ansgar Reiners,et al.  A new extensive library of PHOENIX stellar atmospheres and synthetic spectra , 2013, 1303.5632.

[32]  U. O. O. Astrophysics,et al.  The slow spin of the young sub-stellar companion GQ Lupi b and its orbital configuration , 2016, 1607.00012.

[33]  T. Guillot,et al.  A Nongray Theory of Extrasolar Giant Planets and Brown Dwarfs , 1997, astro-ph/9705201.

[34]  Sergei N. Yurchenko,et al.  ExoMol: molecular line lists for exoplanet and other atmospheres , 2012 .

[35]  C. A. Grady,et al.  A STATISTICAL ANALYSIS OF SEEDS AND OTHER HIGH-CONTRAST EXOPLANET SURVEYS: MASSIVE PLANETS OR LOW-MASS BROWN DWARFS? , 2014, 1404.5335.

[36]  D. Stevenson,et al.  Despin Mechanism for Protogiant Planets and Ionization State of Protogiant Planetary Disks , 1996 .

[37]  Russel J. White,et al.  THE NIRSPEC ULTRACOOL DWARF RADIAL VELOCITY SURVEY , 2010, 1008.3874.

[38]  Ian J. M. Crossfield,et al.  Doppler Imaging of Exoplanets and Brown Dwarfs , 2014, 1404.7853.

[39]  Peter Plavchan,et al.  WEATHER ON OTHER WORLDS. II. SURVEY RESULTS: SPOTS ARE UBIQUITOUS ON L AND T DWARFS , 2014, 1411.3051.

[40]  William R. Ward,et al.  A common mass scaling for satellite systems of gaseous planets , 2006, Nature.

[41]  J. Eastman,et al.  Barycentric Corrections at 1 cm s-1 for Precise Doppler Velocities , 2014, 1409.4774.

[42]  F. Gallet,et al.  Improved angular momentum evolution model for solar-like stars , 2013, 1306.2130.

[43]  K. Cruz,et al.  FUNDAMENTAL PARAMETERS AND SPECTRAL ENERGY DISTRIBUTIONS OF YOUNG AND FIELD AGE OBJECTS WITH MASSES SPANNING THE STELLAR TO PLANETARY REGIME , 2015, 1508.01767.

[44]  R. J. Wainscoat,et al.  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, 1310.0457.

[45]  F. Shu,et al.  Magnetocentrifugally Driven Flows from Young Stars and Disks. VI. Accretion with a Multipole Stellar Field , 2008, 0806.4769.

[46]  Bernhard R. Brandl,et al.  Fast spin of the young extrasolar planet β Pictoris b , 2014, Nature.

[47]  J. Laskar,et al.  The four final rotation states of Venus , 2001, Nature.