Publications of Michaël Gillon
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See detailThe small binary asteroid (939) Isberga
Carry, B.; Matter, A.; Scheirich, P. et al

in Icarus (2015), 248

In understanding the composition and internal structure of asteroids, their density is perhaps the most diagnostic quantity. We aim here at characterizing the surface composition, mutual orbit, size, mass ... [more ▼]

In understanding the composition and internal structure of asteroids, their density is perhaps the most diagnostic quantity. We aim here at characterizing the surface composition, mutual orbit, size, mass, and density of the small main-belt binary asteroid (939) Isberga. For that, we conduct a suite of multi-technique observations, including optical lightcurves over many epochs, near-infrared spectroscopy, and interferometry in the thermal infrared. We develop a simple geometric model of binary systems to analyze the interferometric data in combination with the results of the lightcurve modeling. From spectroscopy, we classify Ibserga as a Sq-type asteroid, consistent with the albedo of 0.14<SUB>-0.06</SUB><SUP>+0.09</SUP> (all uncertainties are reported as 3-σ range) we determine (average albedo of S-types is 0.197 ± 0.153, see Pravec et al. (Pravec et al. [2012]. Icarus 221, 365-387). Lightcurve analysis reveals that the mutual orbit has a period of 26.6304 ± 0.0001 h, is close to circular (eccentricity lower than 0.1), and has pole coordinates within 7° of (225°, +86°) in Ecliptic J2000, implying a low obliquity of 1.5<SUB>-1.5</SUB><SUP>+6.0</SUP> deg . The combined analysis of lightcurves and interferometric data allows us to determine the dimension of the system and we find volume-equivalent diameters of 12.4<SUB>-1.2</SUB><SUP>+2.5</SUP> km and 3.6<SUB>-0.3</SUB><SUP>+0.7</SUP> km for Isberga and its satellite, circling each other on a 33 km wide orbit. Their density is assumed equal and found to be 2.91<SUB>-2.01</SUB><SUP>+1.72</SUP> gcm<SUP>-3</SUP> , lower than that of the associated ordinary chondrite meteorites, suggesting the presence of some macroporosity, but typical of S-types of the same size range (Carry [2012]. Planet. Space Sci. 73, 98-118). The present study is the first direct measurement of the size of a small main-belt binary. Although the interferometric observations of Isberga are at the edge of MIDI capabilities, the method described here is applicable to others suites of instruments (e.g., LBT, ALMA). [less ▲]

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See detailWASP-20b and WASP-28b: a hot Saturn and a hot Jupiter in near-aligned orbits around solar-type stars
Anderson, D. R.; Collier Cameron, A.; Hellier, C. et al

in Astronomy and Astrophysics (2015), 575

We report the discovery of the planets WASP-20b and WASP-28b along with measurements of their sky-projected orbital obliquities. WASP-20b is an inflated, Saturn-mass planet (0.31 M[SUB]Jup[/SUB]; 1.46 R ... [more ▼]

We report the discovery of the planets WASP-20b and WASP-28b along with measurements of their sky-projected orbital obliquities. WASP-20b is an inflated, Saturn-mass planet (0.31 M[SUB]Jup[/SUB]; 1.46 R[SUB]Jup[/SUB]) in a 4.9-day, near-aligned (λ = 12.7 ± 4.2°) orbit around CD-24 102 (V = 10.7; F9). Due to the low density of the planet and the apparent brightness of the host star, WASP-20 is a good target for atmospheric characterisation via transmission spectroscopy. WASP-28b is an inflated, Jupiter-mass planet (0.91 M[SUB]Jup[/SUB]; 1.21 R[SUB]Jup[/SUB]) in a 3.4-day, near-aligned (λ = 8 ± 18°) orbit around a V = 12, F8 star. As intermediate-mass planets in short orbits around aged, cool stars (7[SUP]+ 2[/SUP][SUB]-1[/SUB] Gyr and 6000 ± 100 K for WASP-20; 5[SUP]+ 3[/SUP][SUB]-2[/SUB] Gyr and 6100 ± 150 K for WASP-28), their orbital alignment is consistent with the hypothesis that close-in giant planets are scattered into eccentric orbits with random alignments, which are then circularised and aligned with their stars' spins via tidal dissipation. Based on observations made with: the WASP-South (South Africa) and SuperWASP-North (La Palma) photometric survey instruments; the C2 and EulerCam cameras and the CORALIE spectrograph, all mounted on the 1.2-m Euler-Swiss telescope (La Silla); the HARPS spectrograph on the ESO 3.6-m telescope (La Silla) under programs 072.C-0488, 082.C-0608, 084.C-0185, and 085.C-0393; and LCOGT's Faulkes Telescope North (Maui) and Faulkes Telescope South (Siding Spring).Full Tables 2 and 3 are only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A> (ftp://130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/575/A61">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/575/A61</A> [less ▲]

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See detailThe non-convex shape of (234) Barbara, the first Barbarian
Tanga, Paolo; Carry, B.; Colas, F. et al

in Monthly Notices of the Royal Astronomical Society (2015)

Asteroid (234) Barbara is the prototype of a category of asteroids that has been shown to be extremely rich in refractory inclusions, the oldest material ever found in the Solar System. It exhibits ... [more ▼]

Asteroid (234) Barbara is the prototype of a category of asteroids that has been shown to be extremely rich in refractory inclusions, the oldest material ever found in the Solar System. It exhibits several peculiar features, most notably its polarimetric behavior. In recent years other objects sharing the same property (collectively known as ”Barbarians”) have been discovered. Interferometric observations in the mid-infrared with the ESO VLTI suggested that (234) Barbara might have a bi-lobated shape or even a large companion satellite. We use a large set of 57 optical lightcurves acquired between 1979 and 2014, together with the timings of two stellar occultations in 2009, to determine the rotation period, spin-vector coordinates, and 3-D shape of (234) Barbara, using two different shape reconstruction algorithms. By using the lightcurves combined to the results obtained from stellar occultations, we are able to show that the shape of (234) Barbara exhibits large concave areas. Possible links of the shape to the polarimetric properties and the object evolution are discussed. We also show that VLTI data can be modeled without the presence of a satellite [less ▲]

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See detailThe Well-aligned Orbit of Wasp-84b: Evidence for Disk Migration of a Hot Jupiter
Anderson, D. R.; Triaud, A. H. M. J.; Turner, O. D. et al

in Astrophysical Journal. Letters (2015), 800

We report the sky-projected orbital obliquity (spin-orbit angle) of WASP-84 b, a 0.69{{M}[SUB]Jup[/SUB]} planet in an 8.52 day orbit around a G9V/K0V star, to be λ = -0.3 ± 1.7°. We obtain a true ... [more ▼]

We report the sky-projected orbital obliquity (spin-orbit angle) of WASP-84 b, a 0.69{{M}[SUB]Jup[/SUB]} planet in an 8.52 day orbit around a G9V/K0V star, to be λ = -0.3 ± 1.7°. We obtain a true obliquity of ψ = 17.3 ± 7.7° from a measurement of the inclination of the stellar spin axis with respect to the sky plane. Due to the young age and the weak tidal forcing of the system, we suggest that the orbit of WASP-84b is unlikely to have both realigned and circularized from the misaligned and/or eccentric orbit likely to have arisen from high-eccentricity migration. Therefore we conclude that the planet probably migrated via interaction with the protoplanetary disk. This would make it the first “hot Jupiter” (P\lt 10 d) to have been shown to have migrated via this pathway. Further, we argue that the distribution of obliquities for planets orbiting cool stars (T[SUB]eff[/SUB] < 6250 K) suggests that high-eccentricity migration is an important pathway for the formation of short-orbit, giant planets. Based on observations made with the HARPS-North spectrograph on the 3.6 m Telescopio Nazionale Galileo under OPTICON program 2013 B/069, the HARPS spectrograph on the ESO 3.6 m telescope under program 090.C-0540, and the RISE photometer on the 2.0 m Liverpool Telescope under programs PL12B13 and PL14A11. The photometric time-series and radial-velocity data used in this work are available at the CDS. [less ▲]

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See detailDust from Comet 209P/LINEAR during its 2014 Return: Parent Body of a New Meteor Shower, the May Camelopardalids
Ishiguro, Masateru; Kuroda, Daisuke; Hanayama, Hidekazu et al

in Astrophysical Journal. Letters (2015), 798

We report a new observation of the Jupiter family comet 209P/LINEAR during its 2014 return. The comet is recognized as a dust source of a new meteor shower, the May Camelopardalids. 209P/LINEAR was ... [more ▼]

We report a new observation of the Jupiter family comet 209P/LINEAR during its 2014 return. The comet is recognized as a dust source of a new meteor shower, the May Camelopardalids. 209P/LINEAR was apparently inactive at a heliocentric distance r<SUB>h</SUB> = 1.6 AU and showed weak activity at r<SUB>h</SUB> <= 1.4 AU. We found an active region of <0.001% of the entire nuclear surface during the comet's dormant phase. An edge-on image suggests that particles up to 1 cm in size (with an uncertainty of factor 3-5) were ejected following a differential power-law size distribution with index q = –3.25 ± 0.10. We derived a mass-loss rate of 2-10 kg s<SUP>–1</SUP> during the active phase and a total mass of ≈5 × 10<SUP>7</SUP> kg during the 2014 return. The ejection terminal velocity of millimeter- to centimeter-sized particles was 1-4 m s<SUP>–1</SUP>, which is comparable to the escape velocity from the nucleus (1.4 m s<SUP>–1</SUP>). These results imply that such large meteoric particles marginally escaped from the highly dormant comet nucleus via the gas drag force only within a few months of the perihelion passage. [less ▲]

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See detailEvidence that Pluto's atmosphere does not collapse from occultations including the 2013 May 04 event
Olkin, C. B.; Young, L. A.; Borncamp, D. et al

in Icarus (2015), 246

Combining stellar occultation observations probing Pluto's atmosphere from 1988 to 2013, and models of energy balance between Pluto's surface and atmosphere, we find the preferred models are consistent ... [more ▼]

Combining stellar occultation observations probing Pluto's atmosphere from 1988 to 2013, and models of energy balance between Pluto's surface and atmosphere, we find the preferred models are consistent with Pluto retaining a collisional atmosphere throughout its 248-year orbit. The occultation results show an increasing atmospheric pressure with time in the current epoch, a trend present only in models with a high thermal inertia and a permanent N<SUB>2</SUB> ice cap at Pluto's north rotational pole. [less ▲]

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See detailThe binary near-Earth Asteroid (175706) 1996 FG3 - An observational constraint on its orbital evolution
Scheirich, P.; Pravec, P.; Jacobson, S. A. et al

in Icarus (2015), 245

Using our photometric observations taken between April 1996 and January 2013 and other published data, we derived properties of the binary near-Earth Asteroid (175706) 1996 FG<SUB>3</SUB> including new ... [more ▼]

Using our photometric observations taken between April 1996 and January 2013 and other published data, we derived properties of the binary near-Earth Asteroid (175706) 1996 FG<SUB>3</SUB> including new measurements constraining evolution of the mutual orbit with potential consequences for the entire binary asteroid population. We also refined previously determined values of parameters of both components, making 1996 FG<SUB>3</SUB> one of the most well understood binary asteroid systems. With our 17-year long dataset, we determined the orbital vector with a substantially greater accuracy than before and we also placed constraints on a stability of the orbit. Specifically, the ecliptic longitude and latitude of the orbital pole are 266 ° and - 83 ° , respectively, with the mean radius of the uncertainty area of 4 ° , and the orbital period is 16.1508 ± 0.0002 h (all quoted uncertainties correspond to 3σ). We looked for a quadratic drift of the mean anomaly of the satellite and obtained a value of 0.04 ± 0.20 deg /yr<SUP>2</SUP> , i.e., consistent with zero. The drift is substantially lower than predicted by the pure binary YORP (BYORP) theory of McMahon and Scheeres (McMahon, J., Scheeres, D. [2010]. Icarus 209, 494-509) and it is consistent with the tigidity and quality factor of μQ = 1.3 ×10<SUP>7</SUP> Pa using the theory that assumes an elastic response of the asteroid material to the tidal forces. This very low value indicates that the primary of 1996 FG<SUB>3</SUB> is a 'rubble pile', and it also calls for a re-thinking of the tidal energy dissipation in close asteroid binary systems. [less ▲]

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See detailVLT observations of giant exoplanet atmospheres: reliability and new results
Lendl, Monika; Delrez, Laetitia ULiege; Gillon, Michaël ULiege et al

in Twenty Years of Giant Exoplanets (2015)

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See detailThe EChO science case
Tinetti, Giovanna; Drossart, Pierre; Eccleston, Paul et al

in Experimental Astronomy (2015), 1502

The discovery of almost 2000 exoplanets has revealed an unexpectedly diverse planet population. Observations to date have shown that our Solar System is certainly not representative of the general ... [more ▼]

The discovery of almost 2000 exoplanets has revealed an unexpectedly diverse planet population. Observations to date have shown that our Solar System is certainly not representative of the general population of planets in our Milky Way. The key science questions that urgently need addressing are therefore: What are exoplanets made of? Why are planets as they are? What causes the exceptional diversity observed as compared to the Solar System? EChO (Exoplanet Characterisation Observatory) has been designed as a dedicated survey mission for transit and eclipse spectroscopy capable of observing a large and diverse planet sample within its four-year mission lifetime. EChO can target the atmospheres of super-Earths, Neptune-like, and Jupiter-like planets, in the very hot to temperate zones (planet temperatures of 300K-3000K) of F to M-type host stars. Over the next ten years, several new ground- and space-based transit surveys will come on-line (e.g. NGTS, CHEOPS, TESS, PLATO), which will specifically focus on finding bright, nearby systems. The current rapid rate of discovery would allow the target list to be further optimised in the years prior to EChO's launch and enable the atmospheric characterisation of hundreds of planets. Placing the satellite at L2 provides a cold and stable thermal environment, as well as a large field of regard to allow efficient time-critical observation of targets randomly distributed over the sky. A 1m class telescope is sufficiently large to achieve the necessary spectro-photometric precision. The spectral coverage (0.5-11 micron, goal 16 micron) and SNR to be achieved by EChO, thanks to its high stability and dedicated design, would enable a very accurate measurement of the atmospheric composition and structure of hundreds of exoplanets. [less ▲]

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See detailWASP-94 A and B planets: hot-Jupiter cousins in a twin-star system
Neveu-VanMalle, M.; Queloz, D.; Anderson, D. R. et al

in Astronomy and Astrophysics (2014), 572

We report the discovery of two hot-Jupiter planets, each orbiting one of the stars of a wide binary system. <ASTROBJ>WASP-94A</ASTROBJ> (<ASTROBJ>2MASS 20550794-3408079</ASTROBJ>) is an F8 type star ... [more ▼]

We report the discovery of two hot-Jupiter planets, each orbiting one of the stars of a wide binary system. <ASTROBJ>WASP-94A</ASTROBJ> (<ASTROBJ>2MASS 20550794-3408079</ASTROBJ>) is an F8 type star hosting a transiting planet with a radius of 1.72 ± 0.06 R<SUB>Jup</SUB>, a mass of 0.452 ± 0.034 M<SUB>Jup</SUB>, and an orbital period of 3.95 days. The Rossiter-McLaughlin effect is clearly detected, and the measured projected spin-orbit angle indicates that the planet occupies a retrograde orbit. <ASTROBJ>WASP-94B</ASTROBJ> (<ASTROBJ>2MASS 20550915-3408078</ASTROBJ>) is an F9 stellar companion at an angular separation of 15'' (projected separation 2700 au), hosting a gas giant with a minimum mass of 0.618 ± 0.028 M<SUB>Jup</SUB> with a period of 2.008 days, detected by Doppler measurements. The orbital planes of the two planets are inclined relative to each other, indicating that at least one of them is inclined relative to the plane of the stellar binary. These hot Jupiters in a binary system bring new insights into the formation of close-in giant planets and the role of stellar multiplicity. The radial-velocity and photometric data used for this work are only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A> (ftp://130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/572/A49">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/572/A49</A> [less ▲]

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See detailDiscovery of WASP-85Ab: a hot Jupiter in a visual binary system
Brown, D. J. A.; Anderson, D. R.; Armstrong, D. J. et al

E-print/Working paper (2014)

We report the discovery of the transiting hot Jupiter exoplanet WASP-85Ab. Using a combined analysis of spectroscopic and photometric data, we determine that the planet orbits its host star every 2.66 ... [more ▼]

We report the discovery of the transiting hot Jupiter exoplanet WASP-85Ab. Using a combined analysis of spectroscopic and photometric data, we determine that the planet orbits its host star every 2.66 days, and has a mass of 1.09+/-0.03 M_Jup and a radius of 1.44+/-0.02 R_Jup. The host star is of G5 spectral type, with magnitude V=11.2, and lies 125+/-80 pc distant. We find stellar parameters of T_eff=5685+/-65 K, super-solar metallicity ([Fe/H]=0.08+/-0.10), M_star=1.04+/-0.07 M_sun and R_star=0.96+/-0.13 R_sun. The system has a K-dwarf binary companion, WASP-85B, at a separation of approximately 1.5". The close proximity of this companion leads to contamination of our photometry, decreasing the apparent transit depth that we account for during our analysis. Without this correction, we find the depth to be 50 percent smaller, the stellar density to be 32 percent smaller, and the planet radius to be 18 percent smaller than the true value. Many of our radial velocity observations are also contaminated; these are disregarded when analysing the system in favour of the uncontaminated HARPS observations, as they have reduced semi-amplitudes that lead to underestimated planetary masses. We find a long-term trend in the binary position angle, indicating a misalignment between the binary and orbital planes. WASP observations of the system show variability with a period of 14.64 days, indicative of rotational modulation caused by stellar activity. Analysis of the Ca ii H+K lines shows strong emission that implies that both binary components are strongly active. We find that the system is likely to be less than a few Gyr old. WASP-85 lies in the field of view of K2 Campaign 1. Long cadence observations of the planet clearly show the planetary transits, along with the signature of stellar variability. Analysis of the K2 data, both long and short cadence, is ongoing. [less ▲]

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See detailA global analysis of Spitzer and new HARPS data confirms the loneliness and metal-richness of GJ 436 b
Lanotte, Audrey ULiege; Gillon, Michaël ULiege; Demory, B.-O. et al

in Astronomy and Astrophysics (2014), 572

Context. GJ 436b is one of the few transiting warm Neptunes for which a detailed characterisation of the atmosphere is possible, whereas its non-negligible orbital eccentricity calls for further ... [more ▼]

Context. GJ 436b is one of the few transiting warm Neptunes for which a detailed characterisation of the atmosphere is possible, whereas its non-negligible orbital eccentricity calls for further investigation. Independent analyses of several individual datasets obtained with Spitzer have led to contradicting results attributed to the different techniques used to treat the instrumental effects. Aims. We aim at investigating these previous controversial results and developing our knowledge of the system based on the full Spitzer photometry dataset combined with new Doppler measurements obtained with the HARPS spectrograph. We also want to search for additional planets. Methods. We optimise aperture photometry techniques and the photometric deconvolution algorithm DECPHOT to improve the data reduction of the Spitzer photometry spanning wavelengths from 3-24 {\mu}m. Adding the high precision HARPS radial velocity data, we undertake a Bayesian global analysis of the system considering both instrumental and stellar effects on the flux variation. Results. We present a refined radius estimate of RP=4.10 +/- 0.16 R_Earth, mass MP=25.4 +/- 2.1 M_Earth and eccentricity e= 0.162 +/- 0.004 for GJ 436b. Our measured transit depths remain constant in time and wavelength, in disagreement with the results of previous studies. In addition, we find that the post-occultation flare-like structure at 3.6 {\mu}m that led to divergent results on the occultation depth measurement is spurious. We obtain occultation depths at 3.6, 5.8, and 8.0 {\mu}m that are shallower than in previous works, in particular at 3.6 {\mu}m. However, these depths still appear consistent with a metal-rich atmosphere depleted in methane and enhanced in CO/CO2, although perhaps less than previously thought. We find no evidence for a potential planetary companion, stellar activity, nor for a stellar spin-orbit misalignment. [ABRIDGED] [less ▲]

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See detailThree sub-Jupiter-mass planets: WASP-69b & WASP-84b transit active K dwarfs and WASP-70Ab transits the evolved primary of a G4+K3 binary
Anderson, D. R.; Collier Cameron, A.; Delrez, Laetitia ULiege et al

in Monthly Notices of the Royal Astronomical Society (2014), 445(2),

We report the discovery of the transiting exoplanets WASP-69b, WASP-70Ab and WASP-84b, each of which orbits a bright star (V ˜ 10). WASP-69b is a bloated Saturn-mass planet (0.26 MJup, 1.06 RJup) in a 3 ... [more ▼]

We report the discovery of the transiting exoplanets WASP-69b, WASP-70Ab and WASP-84b, each of which orbits a bright star (V ˜ 10). WASP-69b is a bloated Saturn-mass planet (0.26 MJup, 1.06 RJup) in a 3.868-d period around an active, ˜1-Gyr, mid-K dwarf. ROSAT detected X-rays 60±27 arcsec from WASP-69. If the star is the source then the planet could be undergoing mass-loss at a rate of ˜1012 g s-1. This is one to two orders of magnitude higher than the evaporation rate estimated for HD 209458b and HD 189733b, both of which have exhibited anomalously large Lyman alpha absorption during transit. WASP-70Ab is a sub-Jupiter-mass planet (0.59 MJup, 1.16 RJup) in a 3.713-d orbit around the primary of a spatially resolved, 9-10-Gyr, G4+K3 binary, with a separation of 3.3 arcsec (>=800 au). WASP-84b is a sub-Jupiter-mass planet (0.69 MJup, 0.94 RJup) in an 8.523-d orbit around an active, ˜1-Gyr, early-K dwarf. Of the transiting planets discovered from the ground to date, WASP-84b has the third-longest period. For the active stars WASP-69 and WASP-84, we pre-whitened the radial velocities using a low-order harmonic series. We found that this reduced the residual scatter more than did the oft-used method of pre-whitening with a fit between residual radial velocity and bisector span. The system parameters were essentially unaffected by pre-whitening. [less ▲]

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See detailWASP-104b and WASP-106b: two transiting hot Jupiters in 1.75-day and 9.3-day orbits
Smith, A. M. S.; Anderson, D. R.; Armstrong, D. J. et al

in Astronomy and Astrophysics (2014)

We report the discovery from the WASP survey of two exoplanetary systems, each consisting of a Jupiter-sized planet transiting an 11th magnitude (V) main-sequence star. WASP-104b orbits its star in 1.75 d ... [more ▼]

We report the discovery from the WASP survey of two exoplanetary systems, each consisting of a Jupiter-sized planet transiting an 11th magnitude (V) main-sequence star. WASP-104b orbits its star in 1.75 d, whereas WASP-106b has the fourth-longest orbital period of any planet discovered by means of transits observed from the ground, orbiting every 9.29 d. Each planet is more massive than Jupiter (WASP-104b has a mass of 1.27±0.05 MJup, while WASP-106b has a mass of 1.93±0.08 MJup). Both planets are just slightly larger than Jupiter, with radii of 1.14±0.04 and 1.09±0.04 RJup for WASP-104 and WASP-106 respectively. No significant orbital eccentricity is detected in either system, and while this is not surprising in the case of the short-period WASP-104b, it is interesting in the case of WASP-106b, because many otherwise similar planets are known to have eccentric orbits. [less ▲]

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See detailPlanets and Stellar Activity: Hide and Seek in the CoRoT-7 system
Haywood, R. D.; Cameron, A. C.; Queloz, D. et al

in Monthly Notices of the Royal Astronomical Society (2014), 443(3), 2517-2531

Since the discovery of the transiting Super-Earth CoRoT-7b, several investigations have been made of the number and precise masses of planets present in the system, but they all yield different results ... [more ▼]

Since the discovery of the transiting Super-Earth CoRoT-7b, several investigations have been made of the number and precise masses of planets present in the system, but they all yield different results, owing to the star's high level of activity. Radial velocity (RV) variations induced by stellar activity therefore need to be modelled and removed to allow a reliable detection of all planets in the system. We re-observed CoRoT-7 in January 2012 with both HARPS and the CoRoT satellite, so that we now have the benefit of simultaneous RV and photometric data. We fitted the off-transit variations in the CoRoT lightcurve using a harmonic decomposition similar to that implemented in Queloz et al. (2009). This fit was then used to model the stellar RV contribution, according to the methods described by Aigrain et al. (2011). This model was incorporated into a Monte Carlo Markov Chain in order to make a precise determination of the orbits of CoRoT-7b and CoRoT-7c. We also assess the evidence for the presence of one or two additional planetary companions. [less ▲]

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See detailWASP-117b: a 10-day-period Saturn in an eccentric and misaligned orbit
Lendl, Monika ULiege; Triaud, A. H. M. J.; Anderson, D. R. et al

in Astronomy and Astrophysics (2014), 568

We report the discovery of WASP-117b, the first planet with a period beyond 10 days found by the WASP survey. The planet has a mass of M_p = 0.2755 (+/-0.0090) M_jup, a radius of R_p = 1.021 (-0.065 +0 ... [more ▼]

We report the discovery of WASP-117b, the first planet with a period beyond 10 days found by the WASP survey. The planet has a mass of M_p = 0.2755 (+/-0.0090) M_jup, a radius of R_p = 1.021 (-0.065 +0.076) R_jup and is in an eccentric (e = 0.302 +/-0.023), 10.02165 +/- 0.00055 d orbit around a main-sequence F9 star. The host star's brightness (V=10.15 mag) makes WASP-117 a good target for follow-up observations, and with a planetary equilibrium temperature of T_eq = 1024 (-26 +30) K and a low planetary density (rho_p = 0.259 (-0.048 +0.054) rho_jup) it is one of the best targets for transmission spectroscopy among planets with periods around 10 days. From a measurement of the Rossiter-McLaughlin effect, we infer a projected angle between the planetary orbit and stellar spin axes of beta = -44 (+/-11) deg, and we further derive an orbital obliquity of psi = 69.5 (+3.6 -3.1) deg. Owing to the large orbital separation, tidal forces causing orbital circularization and realignment of the planetary orbit with the stellar plane are weak, having had little impact on the planetary orbit over the system lifetime. WASP-117b joins a small sample of transiting giant planets with well characterized orbits at periods above ~8 days. [less ▲]

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See detailColour-magnitude diagrams of transiting Exoplanets - II. A larger sample from photometric distances
Triaud, Amaury H. M. J.; Lanotte, Audrey ULiege; Smalley, Barry et al

in Monthly Notices of the Royal Astronomical Society (2014), 444(1), 711-728

CColour-magnitude diagrams form a traditional way of presenting luminous objects in the Universe and compare them to each other. Here, we estimate the photometric distance of 44 transiting exoplanetary ... [more ▼]

CColour-magnitude diagrams form a traditional way of presenting luminous objects in the Universe and compare them to each other. Here, we estimate the photometric distance of 44 transiting exoplanetary systems. Parallaxes for seven systems confirm our methodology. Combining those measurements with fluxes obtained while planets were occulted by their host stars, we compose colour-magnitude diagrams in the near and mid-infrared. When possible, planets are plotted alongside very low mass stars and field brown dwarfs, who often share similar sizes and equilibrium temperatures. They offer a natural, empirical, comparison sample. We also include directly imaged exoplanets and the expected loci of pure blackbodies. Irradiated planets do not match blackbodies; their emission spectra are not featureless. For a given luminosity, hot Jupiters' daysides show a larger variety in colour than brown dwarfs do and display an increasing diversity in colour with decreasing intrinsic luminosity. The presence of an extra absorbent within the 4.5 μm band would reconcile outlying hot Jupiters with ultra-cool dwarfs' atmospheres. Measuring the emission of gas giants cooler than 1000 K would disentangle whether planets' atmospheres behave more similarly to brown dwarfs' atmospheres than to blackbodies, whether they are akin to the young directly imaged planets, or if irradiated gas giants form their own sequence. [less ▲]

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See detailThe shape and rotation of the tumbling asteroid (99942) Apophis
Scheirich, P.; Pravec, P.; Durech, J. et al

in Muinonen, Karri (Ed.) Asteroids, Comets, Meteors 2014 (2014, July 01)

Photometric observations of the asteroid (99942) Apophis taken from December 2012 to April 2013 revealed that it is in a non-principal axis rotation state. We constructed a numerical model of the asteroid ... [more ▼]

Photometric observations of the asteroid (99942) Apophis taken from December 2012 to April 2013 revealed that it is in a non-principal axis rotation state. We constructed a numerical model of the asteroid's shape and rotation. The asteroid is in a short-axis mode (SAM) of excited rotation. The precession and rotation periods are P_φ = 27.38 ± 0.07 h and P_ψ = 263 ± 6 h, respectively. The rotation is retrograde with the angular momentum vector's ecliptic longitude and latitude of 250° and -75° (the uncertainty area is approximately an ellipse with the major and minor semiaxes of 27° and 14°, respectively). The shape of the asteroid is dynamically close to a prolate ellipsoid, with the lengths of largest and intermediate axes of 1.64 ± 0.09 and 1.14^{+0.04}_{-0.08}, respectively (the shortest axis is normalized to unity); the largest and intermediate moments of inertia differ by 3-4 [less ▲]

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See detailTransiting exoplanets from the CoRoT space mission. XXVI. CoRoT-24: a transiting multiplanet system
Alonso, R.; Moutou, C.; Endl, M. et al

in Astronomy and Astrophysics (2014), 567

We present the discovery of a candidate multiply transiting system, the first one found in the CoRoT mission. Two transit-like features with periods of 5.11 and 11.76 d are detected in the CoRoT light ... [more ▼]

We present the discovery of a candidate multiply transiting system, the first one found in the CoRoT mission. Two transit-like features with periods of 5.11 and 11.76 d are detected in the CoRoT light curve around a main sequence K1V star of r = 15.1. If the features are due to transiting planets around the same star, these would correspond to objects of 3.7 ± 0.4 and 5.0 ± 0.5 R[SUB]⊕[/SUB] , respectively. Several radial velocities serve to provide an upper limit of 5.7 M[SUB]⊕[/SUB] for the 5.11 d signal and to tentatively measure a mass of 28[SUP]+11[/SUP][SUB]-11[/SUB] M[SUB]⊕[/SUB] for the object transiting with a 11.76 d period. These measurements imply low density objects, with a significant gaseous envelope. The detailed analysis of the photometric and spectroscopic data serves to estimate the probability that the observations are caused by transiting Neptune-sized planets as much as over 26 times higher than a blend scenario involving only one transiting planet and as much as over 900 times higher than a scenario involving two blends and no planets. The radial velocities show a long-term modulation that might be attributed to a 1.5 M[SUB]Jup[/SUB] planet orbiting at 1.8 AU from the host, but more data are required to determine the precise orbital parameters of this companion. The CoRoT space mission, launched on 27 December 2006, has been developed and is operated by the CNES, with the contribution of Austria, Belgium, Brazil, ESA (RSSD and Science Program), Germany, and Spain. Some of the observations were made with the HARPS spectrograph at ESO La Silla Observatory (184.C-0639) and with the HIRES spectrograph at the Keck Telescope (N035Hr, N143Hr 260 and N095Hr). Partly based on observations obtained at ESO Paranal Observatory, Chile (086.C-0235(A) and B).Tables 2-4 and Fig. 12 are available in electronic form at <A href="http://www.aanda.org/10.1051/0004-6361/201118662/olm">http://www.aanda.org</A> [less ▲]

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See detailHD 97658 and its super-Earth. Spitzer & MOST transit analysis and modeling of the host star
Van Grootel, Valérie ULiege; Gillon, Michaël ULiege; Valencia, D. et al

Conference (2014, July)

Super-Earths transiting nearby bright stars are key objects that simultaneously allow for accurate measurements of both their mass and radius, providing essential constraints on their internal composition ... [more ▼]

Super-Earths transiting nearby bright stars are key objects that simultaneously allow for accurate measurements of both their mass and radius, providing essential constraints on their internal composition. We present here the confirmation, based on Spitzer transit observations, that the super-Earth HD 97658 b transits its host star. HD 97658 is a low-mass ($M_*=0.77\pm0.05\,M_{\odot}$) K1 dwarf, as determined from the Hipparcos parallax and stellar evolution modeling. To constrain the planet parameters, we carry out Bayesian global analyses of Keck-HIRES radial velocities, and MOST and Spitzer photometry. HD 97658 b is a massive ($M_P=7.55^{+0.83}_{-0.79} M_{\oplus}$) and large ($R_{P} = 2.247^{+0.098}_{-0.095} R_{\oplus}$ at 4.5 $\mu$m) super-Earth. We investigate the possible internal compositions for HD 97658 b. Our results indicate a large rocky component, by at least 60% by mass, and very little H-He components, at most 2% by mass. We also discuss how future asteroseismic observations can improve the knowledge of the HD 97658 system, in particular by constraining its age. Orbiting a bright host star, HD 97658 b will be a key target for coming space missions TESS, CHEOPS, PLATO, and also JWST, to characterize thoroughly its structure and atmosphere. [less ▲]

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