High-energy environment of super-Earth 55 Cnc e I: Far-UV chromospheric variability as a possible tracer of planet-induced coronal rain

The irradiation of close-in planets by their star influences their evolution and might be responsible for a population of ultra-short period planets eroded to their bare core. In orbit around a bright, nearby G-type star, the super-Earth 55 Cnc e offers the possibility to address these issues through UV transit observations. We used the Hubble Space Telescope to observe the transit in the FUV over 3 epochs in Apr. 2016, Jan. 2017, and Feb. 2017. These observations reveal significant short- and long-term variability in 55 Cnc chromospheric emission lines. In the last 2 epochs, we detected a larger flux in the C III, Si III, and Si IV lines after the planet passed the approaching quadrature, followed by a flux decrease in the Si IV doublet. In the second epoch these variations are contemporaneous with flux decreases in the Si II and C II doublet. All epochs show flux decreases in the N V doublet as well, albeit at different orbital phases. These flux decreases are consistent with absorption from optically thin clouds of gas, are mostly localized at low and redshifted radial velocities in the star rest frame, and occur preferentially before and during the transit. These 3 points make it unlikely that the variations are purely stellar, yet we show that the occulting material is also unlikely to originate from the planet. We tentatively propose that the motion of 55 Cnc e at the fringes of the stellar corona leads to the formation of a cool coronal rain. The inhomogeneity and temporal evolution of the stellar corona would be responsible for the differences between the visits. Additional variations are detected in the C II doublet in the first epoch and in the O I triplet in all epochs with a different behavior that points toward intrinsic stellar variability. Further observations at FUV wavelengths are required to disentangle between star-planet interactions and the activity of the star

[1]  E. Verwichte,et al.  ANALYSIS OF CORONAL RAIN OBSERVED BY IRIS, HINODE/SOT, AND SDO/AIA: TRANSVERSE OSCILLATIONS, KINEMATICS, AND THERMAL EVOLUTION , 2016 .

[2]  P. J. Wheatley,et al.  Temporal variations in the evaporating atmosphere of the exoplanet HD 189733b , 2012, 1206.6274.

[3]  D. O. Astronomy,et al.  Effects of mass loss for highly-irradiated giant planets , 2005, astro-ph/0508591.

[4]  N. Kaib,et al.  CoRoT-7b: SUPER-EARTH OR SUPER-Io? , 2009, 0912.1337.

[5]  S. Saar,et al.  On Stellar Activity Enhancement Due to Interactions with Extrasolar Giant Planets , 2000, The Astrophysical journal.

[6]  T. Louden,et al.  Reconstructing the high-energy irradiation of the evaporating hot Jupiter HD 209458b , 2016, 1605.07987.

[7]  Michael E. Brown,et al.  Observation of mass loading in the Io plasma torus , 1994 .

[8]  Kevin France,et al.  THE MUSCLES TREASURY SURVEY. I. MOTIVATION AND OVERVIEW , 2016, 1602.09142.

[9]  Lotfi Ben-Jaffel,et al.  Hubble Space Telescope detection of oxygen in the atmosphere of exoplanet HD 189733b , 2013, 1303.4232.

[10]  Lotfi Ben-Jaffel,et al.  TRANSIT OF EXOMOON PLASMA TORI: NEW DIAGNOSIS , 2014, 1404.1084.

[11]  R. Jayawardhana,et al.  A Search for Water in a Super-Earth Atmosphere: High-resolution Optical Spectroscopy of 55Cancri e , 2017, 1705.03022.

[12]  D. Queloz,et al.  Detection of a transit of the super-Earth 55 Cancri e with warm Spitzer , 2011, 1105.0415.

[13]  D. Roussel-Dupre,et al.  Skylab observations of H I Lyman-alpha , 1982 .

[14]  D. Sasselov,et al.  MOST detects variability on τ Bootis A possibly induced by its planetary companion , 2008, 0802.2732.

[15]  D. Ehrenreich,et al.  No hydrogen exosphere detected around the super-Earth HD 97658 b , 2016, 1609.04416.

[16]  V. Kashyap,et al.  XMM-NEWTON OBSERVATIONS OF HD 189733 DURING PLANETARY TRANSITS , 2010, 1008.3566.

[17]  R. Gilliland,et al.  Hot super-Earths stripped by their host stars , 2016, Nature Communications.

[18]  V. Kashyap,et al.  Extrasolar Giant Planets and X-Ray Activity , 2008, 0807.1308.

[19]  David Ehrenreich,et al.  Mass-loss rates for transiting exoplanets , 2011, 1103.0011.

[20]  J. C. McConnell,et al.  Magnesium in the atmosphere of the planet HD 209458 b: observations of the thermosphere-exosphere transition region , 2013, 1310.8104.

[21]  A. Cameron,et al.  The On/Off Nature of Star-Planet Interactions , 2007, Proceedings of the International Astronomical Union.

[22]  L. Elkins‐Tanton.  Magma oceans in the inner solar system , 2012 .

[23]  Antonino Francesco Lanza.  Stellar coronal magnetic fields and star-planet interaction , 2009, 0906.1738.

[24]  J. Leroy.  Emissions ‘froides’ dans la couronne solaire , 1972 .

[25]  P. Judge,et al.  An Explanation of Remarkable Emission-line Profiles in Post-flare Coronal Rain , 2017, 1707.07069.

[26]  Tokyo Institute of Technology,et al.  MASS-LOSS EVOLUTION OF CLOSE-IN EXOPLANETS: EVAPORATION OF HOT JUPITERS AND THE EFFECT ON POPULATION , 2014, 1401.2511.

[27]  C. Schrijver.  Catastrophic cooling and high-speed downflow in quiescent solar coronal loops observed with TRACE , 2001 .

[28]  W. Cochran,et al.  REVISITING ρ1 CANCRI e: A NEW MASS DETERMINATION OF THE TRANSITING SUPER-EARTH , 2012, 1208.5709.

[29]  James E. Owen,et al.  The Evaporation Valley in the Kepler Planets , 2017, 1705.10810.

[30]  T. Barman,et al.  OPTICAL HYDROGEN ABSORPTION CONSISTENT WITH A THIN BOW SHOCK LEADING THE HOT JUPITER HD 189733B , 2015, 1507.05916.

[31]  C. Dorn,et al.  Bayesian analysis of interiors of HD 219134b, Kepler-10b, Kepler-93b, CoRoT-7b, 55 Cnc e, and HD 97658b using stellar abundance proxies , 2016, 1609.03909.

[32]  A. Kopp,et al.  MAGNETOHYDRODYNAMIC SIMULATIONS OF THE MAGNETIC INTERACTION OF HOT JUPITERS WITH THEIR HOST STARS: A NUMERICAL EXPERIMENT , 2011 .

[33]  D.Queloz,et al.  Reconnaissance of the TRAPPIST-1 exoplanet system in the Lyman-α line , 2017, 1702.07004.

[34]  J. J. Drake,et al.  THE CORONA OF HD 189733 AND ITS X-RAY ACTIVITY , 2014, 1403.1029.

[35]  Hot Jupiters and hot spots: The Short- and long-term chromospheric activity on stars with giant planets , 2004, astro-ph/0411655.

[36]  Xavier Bonfils,et al.  A giant comet-like cloud of hydrogen escaping the warm Neptune-mass exoplanet GJ 436b , 2015, Nature.

[37]  J. Linsky,et al.  ULTRAVIOLET SPECTROSCOPY OF RAPIDLY ROTATING SOLAR-MASS STARS: EMISSION-LINE REDSHIFTS AS A TEST OF THE SOLAR–STELLAR CONNECTION , 2012, 1205.6498.

[38]  Howard Isaacson,et al.  Five Planets Orbiting 55 Cancri , 2007, 0712.3917.

[39]  J. Fortney,et al.  THE ROLE OF CORE MASS IN CONTROLLING EVAPORATION: THE KEPLER RADIUS DISTRIBUTION AND THE KEPLER-36 DENSITY DICHOTOMY , 2013, 1305.0269.

[40]  G. Marcy,et al.  THE MASS–RADIUS RELATION FOR 65 EXOPLANETS SMALLER THAN 4 EARTH RADII , 2013, 1312.0936.

[41]  Alain Lecavelier des Etangs,et al.  Atmospheric escape from HD 189733b observed in H I Lyman-α: detailed analysis of HST/STIS September 2011 observations , 2013, 1301.6030.

[42]  D. Ehrenreich,et al.  Strong H i Lyman-α variations from an 11 Gyr-old host star: a planetary origin? , 2017, 1703.00504.

[43]  D. Müller,et al.  Dynamics of solar coronal loops I. Condensation in cool loops and its effect on transition region lines , 2003 .

[44]  N. Madhusudhan,et al.  A POSSIBLE CARBON-RICH INTERIOR IN SUPER-EARTH 55 Cancri e , 2012, 1210.2720.

[45]  Sijie Yu,et al.  SOLAR LIMB PROMINENCE CATCHER AND TRACKER (SLIPCAT): AN AUTOMATED SYSTEM AND ITS PRELIMINARY STATISTICAL RESULTS , 2010, 1004.4553.

[46]  Xavier Bonfils,et al.  Hint of a transiting extended atmosphere on 55 Cancri b , 2012, 1210.0531.

[47]  D. Ehrenreich,et al.  High-energy environment of super-Earth 55 Cancri e , 2018, Astronomy & Astrophysics.

[48]  Kevin France,et al.  LYα TRANSIT SPECTROSCOPY AND THE NEUTRAL HYDROGEN TAIL OF THE HOT NEPTUNE GJ 436b , 2014, 1403.6834.

[49]  N. Santos,et al.  CHEMICAL CLUES ON THE FORMATION OF PLANETARY SYSTEMS: C/O VERSUS Mg/Si FOR HARPS GTO SAMPLE , 2010, Proceedings of the International Astronomical Union.

[50]  Patrick Antolin,et al.  On-Disk Coronal Rain , 2012, 1203.2077.

[51]  F. Tian.  THERMAL ESCAPE FROM SUPER EARTH ATMOSPHERES IN THE HABITABLE ZONES OF M STARS , 2009 .

[52]  U. Maryland,et al.  Improved precision on the radius of the nearby super-Earth 55 Cnc e , 2011, 1110.4783.

[53]  E. Chiang,et al.  Catastrophic evaporation of rocky planets , 2013, 1302.2147.

[54]  Tidal heating of terrestrial extrasolar planets and implications for their habitability , 2008, 0808.2770.

[55]  Canada.,et al.  Atmospheric escape from hot Jupiters , 2004, astro-ph/0403369.

[56]  D. Nesvorný,et al.  EMERGING TRENDS IN A PERIOD–RADIUS DISTRIBUTION OF CLOSE-IN PLANETS , 2012, 1211.4533.

[57]  H. Mason,et al.  CHIANTI—AN ATOMIC DATABASE FOR EMISSION LINES. XII. VERSION 7 OF THE DATABASE , 2012 .

[58]  R. G. West,et al.  Near-UV Absorption , Chromospheric Activity , and Star-Planet Interactions in the WASP-12 system . 1 , 2022 .

[59]  T. Davis,et al.  Evidence for a lost population of close-in exoplanets , 2009, 0903.1782.

[60]  Juan M. Fontenla,et al.  Energy Balance in the Solar Transition Region. II. Effects of Pressure and Energy Input on Hydrostatic Models , 1991 .

[61]  Antonino Francesco Lanza.  Star-planet magnetic interaction and activity in late-type stars with close-in planets , 2012, 1206.5893.

[62]  Howard Isaacson,et al.  The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets , 2017, 1703.10375.

[63]  M. Mayor,et al.  An extended upper atmosphere around the extrasolar planet HD209458b , 2003, Nature.

[64]  Antonino Francesco Lanza,et al.  Photospheric activity, rotation, and star-planet interaction of the planet-hosting star CoRoT-6 , 2010, 1007.3647.

[65]  K. Shibata,et al.  CORONAL RAIN AS A MARKER FOR CORONAL HEATING MECHANISMS , 2009, 0910.2383.

[66]  High-speed coronal rain , 2005 .

[67]  Christoph Mordasini,et al.  PLANETARY POPULATION SYNTHESIS COUPLED WITH ATMOSPHERIC ESCAPE: A STATISTICAL VIEW OF EVAPORATION , 2014, 1409.2879.

[68]  K. France,et al.  WARM CORONAL RAIN ON YOUNG SOLAR ANALOG EK DRACONIS? , 2010 .

[69]  R. Paul Butler,et al.  Radial Velocities for 889 Late-Type Stars , 2001, astro-ph/0112477.

[70]  S. Parenti,et al.  Solar Prominences: Observations , 2014 .

[71]  James E. Owen,et al.  KEPLER PLANETS: A TALE OF EVAPORATION , 2013, 1303.3899.

[72]  E. Gallo,et al.  A COMPREHENSIVE STATISTICAL ASSESSMENT OF STAR–PLANET INTERACTION , 2014, 1411.3348.

[73]  G. H'ebrard,et al.  First Detection of Hydrogen in the \beta\ Pictoris Gas Disk , 2016, 1612.00848.

[74]  Jonathan J. Fortney,et al.  HOW THERMAL EVOLUTION AND MASS-LOSS SCULPT POPULATIONS OF SUPER-EARTHS AND SUB-NEPTUNES: APPLICATION TO THE KEPLER-11 SYSTEM AND BEYOND , 2012, 1205.0010.

[75]  W. Ip,et al.  On the Star-Magnetosphere Interaction of Close-in Exoplanets , 2004 .

[76]  D. A. Verner,et al.  Atomic data for astrophysics. II. New analytic fits for photoionization cross sections of atoms and ions , 1996 .

[77]  Drake Deming,et al.  DETECTION OF THERMAL EMISSION FROM A SUPER-EARTH , 2012, 1205.1766.

[78]  A.H.M.J.Triaud,et al.  Temporal Evolution of the High-energy Irradiation and Water Content of TRAPPIST-1 Exoplanets , 2017, 1708.09484.

[79]  Brice-Olivier Demory,et al.  Variability in the super-Earth 55 Cnc e , 2015, 1505.00269.

[80]  Ch. Helling,et al.  EARLY UV INGRESS IN WASP-12b: MEASURING PLANETARY MAGNETIC FIELDS , 2010, 1009.5947.

[81]  F. Adams.  MAGNETICALLY CONTROLLED OUTFLOWS FROM HOT JUPITERS , 2011, 1101.4234.

[82]  H. Lammer,et al.  THE EVOLUTION OF STELLAR ROTATION AND THE HYDROGEN ATMOSPHERES OF HABITABLE-ZONE TERRESTRIAL PLANETS , 2015, 1511.03647.

[83]  J. Owen,et al.  Planetary evaporation by UV and X‐ray radiation: basic hydrodynamics , 2012, 1206.2367.

[84]  S. Matt,et al.  MAGNETIC GAMES BETWEEN A PLANET AND ITS HOST STAR: THE KEY ROLE OF TOPOLOGY , 2015, 1511.02837.

[85]  E. Shkolnik.  AN ULTRAVIOLET INVESTIGATION OF ACTIVITY ON EXOPLANET HOST STARS , 2013, 1301.6192.

[86]  E. Guinan,et al.  The effect of tidal locking on the magnetospheric and atmospheric evolution of ``Hot Jupiters'' , 2004 .

[87]  L. Fossati,et al.  On the ultraviolet anomalies of the WASP-12 and HD 189733 systems: Trojan satellites as a plasma source , 2016, 1605.02507.

[88]  Jaymie M. Matthews,et al.  A SUPER-EARTH TRANSITING A NAKED-EYE STAR , 2011, 1104.5230.

[89]  Eugene H. Avrett,et al.  Structure of the solar chromosphere. III. Models of the EUV brightness components of the quiet sun , 1981 .

[90]  T. Matsakos,et al.  Classification of magnetized star--planet interactions: bow shocks, tails, and inspiraling flows , 2015, 1503.03551.

[91]  U. Motschmann,et al.  A magnetic communication scenario for hot Jupiters , 2006 .

[92]  H. Peter,et al.  Dynamics of solar coronal loops II. Catastrophic cooling and high-speed downflows , 2004, astro-ph/0405538.

[93]  L. Rogers.  MOST 1.6 EARTH-RADIUS PLANETS ARE NOT ROCKY , 2014, 1407.4457.

[94]  R. Jayawardhana,et al.  GROUND-BASED TRANSIT OBSERVATIONS OF THE SUPER-EARTH 55 Cnc e , 2014, 1411.7660.

[95]  A. F. Lanza,et al.  On the correlation between stellar chromospheric flux and the surface gravity of close-in planets , 2014, 1410.8363.

[96]  H. Mason,et al.  CHIANTI - an atomic database for emission lines - I. Wavelengths greater than 50 Å , 1997 .

[97]  H. Rauer,et al.  Comet-like tail-formation of exospheres of hot rocky exoplanets: Possible implications for CoRoT-7b , 2011 .

[98]  Antonino Francesco Lanza,et al.  A BIMODAL CORRELATION BETWEEN HOST STAR CHROMOSPHERIC EMISSION AND THE SURFACE GRAVITY OF HOT JUPITERS , 2015, 1510.04691.

[99]  M. Fridlund,et al.  Search for an exosphere in sodium and calcium in the transmission spectrum of exoplanet 55 Cancri e , 2016, 1606.08447.

[100]  S. Udry,et al.  ROSSITER–MCLAUGHLIN OBSERVATIONS OF 55 Cnc e , 2014, 1408.2007.

[101]  G. H'ebrard,et al.  Detecting the spin-orbit misalignment of the super-Earth 55 Cancri e , 2014, 1406.6813.

[102]  G. Hebrard,et al.  Evaporation of the planet HD 189733b observed in H I Lyman-α , 2010, 1003.2206.

[103]  S. Seager,et al.  EFFECTS OF STELLAR FLUX ON TIDALLY LOCKED TERRESTRIAL PLANETS: DEGREE-1 MANTLE CONVECTION AND LOCAL MAGMA PONDS , 2011 .

[104]  T. Ayres.  THE FLARE-ONA OF EK DRACONIS , 2015, 1505.02320.

[105]  J. Rowe,et al.  KOI-2700b—A PLANET CANDIDATE WITH DUSTY EFFLUENTS ON A 22 hr ORBIT , 2013, 1312.2054.

[106]  K. Cunha,et al.  CARBON AND OXYGEN ABUNDANCES IN COOL METAL-RICH EXOPLANET HOSTS: A CASE STUDY OF THE C/O RATIO OF 55 CANCRI , 2013, 1309.6032.

[107]  Björn Benneke,et al.  A map of the large day–night temperature gradient of a super-Earth exoplanet , 2016, Nature.

[108]  G. H'ebrard,et al.  Detection of Oxygen and Carbon in the Hydrodynamically Escaping Atmosphere of the Extrasolar Planet HD 209458b , 2004, astro-ph/0401457.

[109]  A. D. Etangs,et al.  A diagram to determine the evaporation status of extrasolar planets , 2006, astro-ph/0609744.

[110]  P. Petit,et al.  The effects of stellar winds on the magnetospheres and potential habitability of exoplanets , 2014, 1409.1237.

[111]  G. Walker,et al.  Evidence for Planet-induced Chromospheric Activity on HD 179949 , 2003 .

[112]  CHEMISTRY OF SILICATE ATMOSPHERES OF EVAPORATING SUPER-EARTHS , 2009, 0906.1204.

[113]  L. Kiss,et al.  A SHORT-PERIOD CENSOR OF SUB-JUPITER MASS EXOPLANETS WITH LOW DENSITY , 2010, 1012.4791.

[114]  R. Hu,et al.  A Case for an Atmosphere on Super-Earth 55 Cancri e , 2017, 1710.03342.

[115]  J. Tennyson,et al.  DETECTION OF AN ATMOSPHERE AROUND THE SUPER-EARTH 55 CANCRI E , 2015, 1511.08901.

[116]  R. G. West,et al.  METALS IN THE EXOSPHERE OF THE HIGHLY IRRADIATED PLANET WASP-12b , 2010, 1005.3656.

[117]  Daniel C. Fabrycky,et al.  RADIAL VELOCITY PLANETS DE-ALIASED: A NEW, SHORT PERIOD FOR SUPER-EARTH 55 Cnc e , 2010, 1005.4050.

[118]  K. Wood,et al.  Exoplanet transit variability: bow shocks and winds around HD 189733b , 2013, 1309.2938.

[119]  H. F. Astrophysics,et al.  FUV VARIABILITY OF HD 189733. IS THE STAR ACCRETING MATERIAL FROM ITS HOT JUPITER? , 2015, 1503.05590.