Constraints on the Obliquities of Kepler Planet-hosting Stars

Stars with hot Jupiters have obliquities ranging from 0° to 180°, but relatively little is known about the obliquities of stars with smaller planets. Using data from the California-Kepler Survey, we investigate the obliquities of stars with planets spanning a wide range of sizes, most of which are smaller than Neptune. First, we identify 156 planet hosts for which measurements of the projected rotation velocity ( ) and rotation period are both available. By combining estimates of v and , we find nearly all the stars to be compatible with high inclination, and hence, low obliquity (≲20°). Second, we focus on a sample of 159 hot stars ( K) for which is available but not necessarily the rotation period. We find six stars for which is anomalously low, an indicator of high obliquity. Half of these have hot Jupiters, even though only 3% of the stars that were searched have hot Jupiters. We also compare the distribution of the hot stars with planets to that of 83 control stars selected without prior knowledge of planets. The mean of the control stars is lower than that of the planet hosts by a factor of approximately , as one would expect if the planet hosts have low obliquities. All these findings suggest that the Kepler planet-hosting stars generally have low obliquities, with the exception of hot stars with hot Jupiters.

[1]  P. Cargile,et al.  The California-Kepler Survey. I. High-resolution Spectroscopy of 1305 Stars Hosting Kepler Transiting Planets , 2017, 1703.10400.

[2]  P. Cargile,et al.  The California-Kepler Survey. II. Precise Physical Properties of 2025 Kepler Planets and Their Host Stars , 2017, 1703.10402.

[3]  A. Dupree,et al.  THE KEPLER FOLLOW-UP OBSERVATION PROGRAM. I. A CATALOG OF COMPANIONS TO KEPLER STARS FROM HIGH-RESOLUTION IMAGING , 2016, 1612.02392.

[4]  S. Udry,et al.  THE ORBIT AND MASS OF THE THIRD PLANET IN THE KEPLER-56 SYSTEM , 2016, 1608.03627.

[5]  D. Fabrycky,et al.  Outer-planet scattering can gently tilt an inner planetary system , 2016, 1607.08630.

[6]  J. Valenti,et al.  SPECTRAL PROPERTIES OF COOL STARS: EXTENDED ABUNDANCE ANALYSIS OF 1,617 PLANET-SEARCH STARS , 2016, 1606.07929.

[7]  M. R. Haas,et al.  FALSE POSITIVE PROBABILITIES FOR ALL KEPLER OBJECTS OF INTEREST: 1284 NEWLY VALIDATED PLANETS AND 428 LIKELY FALSE POSITIVES , 2016, 1605.02825.

[8]  Tsevi Mazeh,et al.  Dearth of short-period Neptunian exoplanets - a desert in period-mass and period-radius planes , 2016, 1602.07843.

[9]  Bruce D. Clarke,et al.  Identifying False Alarms in the Kepler Planet Candidate Catalog , 2016, 1602.03204.

[10]  T. Bedding,et al.  SPIN–ORBIT ALIGNMENT OF EXOPLANET SYSTEMS: ENSEMBLE ANALYSIS USING ASTEROSEISMOLOGY , 2016, 1601.06052.

[11]  K. Batygin,et al.  MAGNETIC ORIGINS OF THE STELLAR MASS-OBLIQUITY CORRELATION IN PLANETARY SYSTEMS , 2015, 1508.02365.

[12]  T. Matsakos,et al.  A HOT JUPITER FOR BREAKFAST? EARLY STELLAR INGESTION OF PLANETS MAY BE COMMON , 2015, 1507.07967.

[13]  T. Mazeh,et al.  PHOTOMETRIC AMPLITUDE DISTRIBUTION OF STELLAR ROTATION OF KOIs—INDICATION FOR SPIN–ORBIT ALIGNMENT OF COOL STARS AND HIGH OBLIQUITY FOR HOT STARS , 2015, 1501.01288.

[14]  Joshua N. Winn,et al.  The Occurrence and Architecture of Exoplanetary Systems , 2014, 1410.4199.

[15]  T. Morton,et al.  OBLIQUITIES OF KEPLER STARS: COMPARISON OF SINGLE- AND MULTIPLE-TRANSIT SYSTEMS , 2014, 1408.6606.

[16]  H. Kjeldsen,et al.  Asteroseismic inference on the spin-orbit misalignment and stellar parameters of HAT-P-7 , 2014, 1407.7516.

[17]  Y. Suto,et al.  Determination of Three-dimensional Spin-orbit Angle with Joint Analysis of Asteroseismology, Transit Lightcurve, and the Rossiter-McLaughlin Effect: Cases of HAT-P-7 and Kepler-25 , 2014, 1407.7332.

[18]  K. Batygin,et al.  EARLY EXCITATION OF SPIN–ORBIT MISALIGNMENTS IN CLOSE-IN PLANETARY SYSTEMS , 2014, 1406.4183.

[19]  P. McCullough,et al.  Transiting Exoplanet Survey Satellite (TESS) , 2014, Astronomical Telescopes and Instrumentation.

[20]  R. Dawson.  ON THE TIDAL ORIGIN OF HOT JUPITER STELLAR OBLIQUITY TRENDS , 2014, 1405.1735.

[21]  T. Mazeh,et al.  ROTATION PERIODS OF 34,030 KEPLER MAIN-SEQUENCE STARS: THE FULL AUTOCORRELATION SAMPLE , 2014, 1402.5694.

[22]  M. Barbieri,et al.  Stellar Spin-Orbit Misalignment in a Multiplanet System , 2013, Science.

[23]  L. Walkowicz,et al.  Rotation periods, variability properties and ages for Kepler exoplanet candidate host stars , 2013, 1309.2159.

[24]  R. Gilliland,et al.  KEPLER-63b: A GIANT PLANET IN A POLAR ORBIT AROUND A YOUNG SUN-LIKE STAR , 2013, 1307.8128.

[25]  G. Marcy,et al.  LOW STELLAR OBLIQUITIES IN COMPACT MULTIPLANET SYSTEMS , 2013, 1302.4443.

[26]  W. D. Cochran,et al.  ASTEROSEISMIC DETERMINATION OF OBLIQUITIES OF THE EXOPLANET SYSTEMS KEPLER-50 AND KEPLER-65 , 2013, 1302.3728.

[27]  K. Batygin.  A primordial origin for misalignments between stellar spin axes and planetary orbits , 2012, Nature.

[28]  Kento Masuda,et al.  PLANET–PLANET ECLIPSE AND THE ROSSITER–McLAUGHLIN EFFECT OF A MULTIPLE TRANSITING SYSTEM: JOINT ANALYSIS OF THE SUBARU SPECTROSCOPY AND THE KEPLER PHOTOMETRY , 2012, 1209.4362.

[29]  D. Lin,et al.  INTERNAL GRAVITY WAVES MODULATE THE APPARENT MISALIGNMENT OF EXOPLANETS AROUND HOT STARS , 2012, 1209.2435.

[30]  John C. Geary,et al.  Alignment of the stellar spin with the orbits of a three-planet system , 2012, Nature.

[31]  R. P. Butler,et al.  OBLIQUITIES OF HOT JUPITER HOST STARS: EVIDENCE FOR TIDAL INTERACTIONS AND PRIMORDIAL MISALIGNMENTS , 2012, 1206.6105.

[32]  J. Winn,et al.  MEASUREMENTS OF STELLAR INCLINATIONS FOR KEPLER PLANET CANDIDATES , 2012, 1401.1229.

[33]  M. R. Haas,et al.  PLANET OCCURRENCE WITHIN 0.25 AU OF SOLAR-TYPE STARS FROM KEPLER , 2011, 1103.2541.

[34]  Avi Shporer,et al.  A Possible Tilted Orbit of the Super-Neptune HAT-P-11b , 2010, 1009.5677.

[35]  Avi Shporer,et al.  THE OBLIQUE ORBIT OF THE SUPER-NEPTUNE HAT-P-11b , 2010, 1009.5671.

[36]  John Asher Johnson,et al.  HOT STARS WITH HOT JUPITERS HAVE HIGH OBLIQUITIES , 2010, 1006.4161.

[37]  K. Schlaufman,et al.  EVIDENCE OF POSSIBLE SPIN–ORBIT MISALIGNMENT ALONG THE LINE OF SIGHT IN TRANSITING EXOPLANET SYSTEMS , 2010, 1006.2851.

[38]  C. Moutou,et al.  Observation of the full 12-hour-long transit of the exoplanet HD80606b. Warm-Spitzer photometry and SOPHIE spectroscopy , 2010, 1004.0790.

[39]  D. A. Caldwell,et al.  SELECTION, PRIORITIZATION, AND CHARACTERISTICS OF KEPLER TARGET STARS , 2010, 1001.0349.

[40]  Motohide Tamura,et al.  First Evidence of a Retrograde Orbit of a Transiting Exoplanet HAT-P-7b , 2009, 0908.1673.

[41]  M. Holman,et al.  HAT-P-7: A RETROGRADE OR POLAR ORBIT, AND A THIRD BODY , 2009, 0908.1672.

[42]  E. Ford,et al.  Dynamical Outcomes of Planet-Planet Scattering , 2007, astro-ph/0703166.

[43]  J. Valenti,et al.  Spectroscopic Properties of Cool Stars (SPOCS). I. 1040 F, G, and K Dwarfs from Keck, Lick, and AAT Planet Search Programs , 2005 .

[44]  R. Schiavon,et al.  A library of high resolution synthetic stellar spectra from 300 nm to 1.8 μm with solar and α-enhanced composition , 2005, astro-ph/0505511.

[45]  S. Barnes.  On the Rotational Evolution of Solar- and Late-Type Stars, Its Magnetic Origins, and the Possibility of Stellar Gyrochronology , 2003, astro-ph/0303631.

[46]  E. Schatzman.  A theory of the role of magnetic activity during star formation , 1960 .

[47]  O. Struve.  On the axial rotation of stars. , 1930 .

[48]  R. P. Kraft,et al.  STUDIES OF STELLAR ROTATION. V. THE DEPENDENCE OF ROTATION ON AGE AMONG SOLAR-TYPE STARS. , 1967 .

[49]  S. Chandrasekhar,et al.  On the Integral Equation Governing the Distribution of the True and the Apparent Rotational Velocities of Stars. , 1950 .

[50]  S. Tremaine,et al.  Submitted to ApJ Preprint typeset using L ATEX style emulateapj v. 10/09/06 SHRINKING BINARY AND PLANETARY ORBITS BY KOZAI CYCLES WITH TIDAL FRICTION , 2022 .

[51]  ACCEPTED FOR PUBLICATION IN THE ASTROPHYSICAL JOURNAL (2009 AUGUST 18) Preprint typeset using LATEX style emulateapj v. 10/09/06 THE TRANSIT INGRESS AND THE TILTED ORBIT OF THE EXTRAORDINARILY ECCENTRIC EXOPLANET HD 80606b , 2022 .