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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 ULg; Gillon, Michaël ULg; Demory, B.-O. et al

in Astronomy and Astrophysics (in press)

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 detailTRAPPIST detection of the light from a bloated hot Jupiter at the edge of tidal disruption
Delrez, Laetitia ULg; Gillon, Michaël ULg; Lendl, Monika ULg et al

Poster (2014, April 30)

Abstract : We present here the discovery by the WASP-­South survey, in close collaboration with the Euler and TRAPPIST telescopes, of the transiting planet WASP-­121b as well as the measurement of its ... [more ▼]

Abstract : We present here the discovery by the WASP-­South survey, in close collaboration with the Euler and TRAPPIST telescopes, of the transiting planet WASP-­121b as well as the measurement of its thermal emission at 0.9 microns. WASP-­121b is a very inflated (1.76 RJup) Jupiter-­mass (1.02 MJup) planet that transits every 1.27 days a bright F6V star. It is remarkable as its orbital radius is only ~10% larger than its Roche limit, suggesting that it might experience mass loss through Roche-­lobe overflow. Thanks to its large size and extreme irradiation (~7 10^9 erg s-1 cm-­2), it was predicted to display a thermal emission of ~0.1% of the stellar flux in the near-­infrared. Using the TRAPPIST robotic telescope, we could detect this thermal emission signal at ~5 sigma in the z'-­band. This measurement, a first for a ground-­based 60cm telescope, allows to place preliminary constraints on the atmospheric properties of this very special hot Jupiter. [less ▲]

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See detailTRAPPIST monitoring of comet C/2012 F6 (Lemmon)
Opitom, Cyrielle ULg; Jehin, Emmanuel ULg; Manfroid, Jean ULg et al

Poster (2014, April)

C/2012 F6 (Lemmon) is a long period comet discovered by the Mount Lemmon Survey on 2012 March 23 at 5 AU from the sun. C/2012 F6 (Lemmon) reached perihelion on March 23, 2013 at 0.73 AU from the sun. In ... [more ▼]

C/2012 F6 (Lemmon) is a long period comet discovered by the Mount Lemmon Survey on 2012 March 23 at 5 AU from the sun. C/2012 F6 (Lemmon) reached perihelion on March 23, 2013 at 0.73 AU from the sun. In December 2012 the comet was unexpectedly bright, allowing us to make an extensive monitoring during several months with both broadband and narrowband filters to follow the evolution of the comet chemical composition. The monitoring was made with TRAPPIST robotic telescope installed at La Silla observatory [1]. TRAPPIST is a 60-cm telescope dedicated to the study of exoplanets and small bodies in the solar system. The telescope is equipped with a 2Kx2K FLI Proline CCD camera very sensitive in the blue and the red. A set of narrowband cometary filters designed by the NASA for the Hale-Bopp Observing Campaign [2] is permanently mounted on the telescope along with classic Johnson-Cousins B, V, Rc, and Ic filters. We observed the comet from December 11, 2012 to March 4, 2013 (pre-perihelion) and from April 29, 2013 to June 11, 2013 (post-perihelion). At least 2 or 3 observing runs per week were programmed during this period. We collected 1358 images on 52 nights. In January and February the comet visibility allowed us to make several long runs and to detect the comet rotational variability. From the comet images in narrowband filters we studied the gaseous coma chemical composition and activity by deriving OH, NH, CN, C2 and C3 production rates using a classical Haser model [3]. The production and properties of the dust component were studied through the observation of C/2012 F6 (Lemmon) with narrowband continuum filters at 344.2 nm (UC), 444.9 nm (BC), 525.7 nm (GC) and 713.0 nm (RC). We used A(θ)fρ [4] parameter as a proxy for the dust production. [less ▲]

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See detailHerschel observations of nebulae ejected by massive evolved stars
Vamvatira-Nakou, Chloi ULg; Hutsemekers, Damien ULg; Royer, P. et al

Poster (2013, October)

We have obtained far-infrared Herschel PACS imaging and spectroscopic observations of nebulae associated to massive evolved stars. The study of these nebulae is crucial to understand the evolution of ... [more ▼]

We have obtained far-infrared Herschel PACS imaging and spectroscopic observations of nebulae associated to massive evolved stars. The study of these nebulae is crucial to understand the evolution of these stars as it can reveal the mass-loss history. The infrared images along with available data at other wavelengths give a complete view of their morphology. The dust modeling provides the dust parameters, such as the temperature, the mass and the composition of dust. The spectroscopic analysis provides the gas C,N,O abundances and mass. Based on these observations, the evolutionary status of the star at the time of the nebula ejection can be constrained. We present here selected results of an ongoing exhaustive study of nebulae around low- and high-luminosity LBVs (AG Car, HR Car, WRAY 15-751, G79.29+0.46, HD168625), WN stars (NGC6888, M1-67, He3-519) and Of stars (NGC6164/5). [less ▲]

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See detailTRAPPIST (TRAnsiting Planets and PlanetesImals Small Telescope)
Jehin, Emmanuel ULg; Gillon, Michaël ULg; Opitom, Cyrielle ULg et al

in EPSC Abstract 2013 (2013, September 13), 8

TRAPPIST is a 60-cm robotic telescope that has been installed in June 2010 at the ESO La Silla Observatory [1]. Operated from Liège (Belgium) it is devoted to the detection and characterisation of ... [more ▼]

TRAPPIST is a 60-cm robotic telescope that has been installed in June 2010 at the ESO La Silla Observatory [1]. Operated from Liège (Belgium) it is devoted to the detection and characterisation of exoplanets and to the study of comets and other small bodies in the Solar System. We describe here the hardware and the goals of the project and give an overview of the comet production rates monitoring after three years of operations. [less ▲]

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See detailTRAPPIST monitoring of comet C/2012 F6 (Lemmon)
Opitom, Cyrielle ULg; Jehin, Emmanuel ULg; Manfroid, Jean ULg et al

Poster (2013, September 12)

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See detailTRAPPIST monitoring of comet C/2012 F6 (Lemmon)
Opitom, Cyrielle ULg; Jehin, Emmanuel ULg; Manfroid, Jean ULg et al

in EPSC Abstract 2013 (2013, September 12), 8

Comet C/2012 F6 is a long-period comet that reached perihelion on March 23, 2012. The unexpected brightness of this comet since December 2012 allowed us to obtain narrowband photometry and to study its ... [more ▼]

Comet C/2012 F6 is a long-period comet that reached perihelion on March 23, 2012. The unexpected brightness of this comet since December 2012 allowed us to obtain narrowband photometry and to study its chemical composition as well as its rotation. [less ▲]

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See detailCOSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses: XIV. Time delay of the doubly lensed quasar SDSS~J1001+5027
Rathna Kumar, S.; Tewes, M.; Stalin, C.S. et al

in Astronomy and Astrophysics (2013), 557

This paper presents optical R-band light curves and the time delay of the doubly imaged gravitationally lensed quasar SDSS J1001+5027 at a redshift of 1.838. We have observed this target for more than six ... [more ▼]

This paper presents optical R-band light curves and the time delay of the doubly imaged gravitationally lensed quasar SDSS J1001+5027 at a redshift of 1.838. We have observed this target for more than six years, between March 2005 and July 2011, using the 1.2-m Mercator Telescope, the 1.5-m telescope of the Maidanak Observatory and the 2-m Himalayan Chandra Telescope. Our resulting light curves are composed of 443 independent epochs, and show strong intrinsic quasar variability, with an amplitude of the order of 0.2 magnitudes. From this data, we measure the time delay using five different methods, all relying on distinct approaches. One of these techniques is a new development presented in this paper. All our time-delay measurements are perfectly compatible. By combining them, we conclude that image A is leading B by 119.3 ± 3.3 days (1σ, 2.8%), including systematic errors. It has been shown recently that such accurate time-delay measurements offer a highly complementary probe of dark energy and spatial curvature, as they independently constrain the Hubble constant. The next mandatory step towards using SDSS J1001+5027 in this context will be the measurement of the redshift of the lensing galaxy, in combination with deep HST imaging. [less ▲]

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See detailHerschel imaging and spectroscopy of the nebula around the luminous blue variable star WRAY 15-751
Vamvatira-Nakou, Chloi ULg; Hutsemekers, Damien ULg; Royer, P. et al

in Astronomy and Astrophysics (2013), 557

We have obtained far-infrared Herschel-PACS imaging and spectroscopic observations of the nebular environment of the luminous blue variable (LBV) WRAY 15-751. The far-infrared images clearly show that the ... [more ▼]

We have obtained far-infrared Herschel-PACS imaging and spectroscopic observations of the nebular environment of the luminous blue variable (LBV) WRAY 15-751. The far-infrared images clearly show that the main, dusty nebula is a shell of radius 0.5 pc and width 0.35 pc extending outside the Hα nebula. Furthermore, these images reveal a second, bigger and fainter dust nebula that is observed for the first time. Both nebulae lie in an empty cavity, very likely the remnant of the O-star wind bubble formed when the star was on the main sequence. The kinematic ages of the nebulae are calculated to be about 2 × 10^4 and 8 × 10^4 years, and we estimated that each nebula contains ~0.05 Msun of dust. Modeling of the inner nebula indicates a Fe-rich dust. The far-infrared spectrum of the main nebula revealed forbidden emission lines coming from ionized and neutral gas. Our study shows that the main nebula consists of a shell of ionized gas surrounded by a thin photodissociation region illuminated by an “average” early-B star. We derive the abundance ratios N/O = 1.0 ± 0.4 and C/O = 0.4 ± 0.2, which indicate a mild N/O enrichment. From both the ionized and neutral gas components we estimate that the inner shell contains 1.7 ± 0.6 Msun of gas. Assuming a similar dust-to-gas ratio for the outer nebula, the total mass ejected by WRAY 15-751 amounts to 4± 2 Msun. The measured abundances, masses and kinematic ages of the nebulae were used to constrain the evolution of the star and the epoch at which the nebulae were ejected. Our results point to an ejection of the nebulae during the red super-giant (RSG) evolutionary phase of an ~40 Msun star. The multiple shells around the star suggest that the mass-loss was not a continuous ejection but rather a series of episodes of extreme mass-loss. Our measurements are compatible with the recent evolutionary tracks computed for an ~40 Msun star with little rotation. They support the O–BSG–RSG–YSG–LBV filiation and the idea that high-luminosity and low-luminosity LBVs follow different evolutionary paths. [less ▲]

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See detailSPECULOOS: Search for habitable Planets EClipsing ULtra-cOOl Stars
Gillon, Michaël ULg; Jehin, Emmanuel ULg; Delrez, Laetitia ULg et al

Poster (2013, July 01)

The 1000 nearest ultra-cool stars (spectral type M6 and latter) represent a unique opportunity for the search for life outside our solar system. Due to their small luminosity, their habitable zone is 30 ... [more ▼]

The 1000 nearest ultra-cool stars (spectral type M6 and latter) represent a unique opportunity for the search for life outside our solar system. Due to their small luminosity, their habitable zone is 30-100 times closer than for the Sun, the corresponding orbital periods ranging from one to a few days. Thanks to this proximity, the transits of a habitable planet are much more probable and frequent than for an Earth-Sun analog, while their tiny size (about 1 Jupiter radius) leads to transits deep enough for a ground-based detection, even for sub-Earth size planets. Furthermore, a habitable planet transiting one of these nearby ultra-cool stars would be amenable for a thorough atmospheric characterization, including the detection of possible biosignatures, notably with the near-to-come JWST. Motivated by these reasons, we have set up the concept of a ground-based survey optimized for detecting planets of Earth-size and below transiting the nearest Southern ultra-cool stars. We present here this concept and its status. [less ▲]

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See detailSearch for a habitable terrestrial planet transiting the nearby red dwarf GJ 1214
Gillon, Michaël ULg; Demory, B.-O.; Madhusudhan, N. et al

in Astronomy and Astrophysics (2013)

High-precision eclipse spectrophotometry of transiting terrestrial exoplanets represents a promising path for the first atmospheric characterizations of habitable worlds and the search for life outside ... [more ▼]

High-precision eclipse spectrophotometry of transiting terrestrial exoplanets represents a promising path for the first atmospheric characterizations of habitable worlds and the search for life outside our solar system. The detection of terrestrial planets transiting nearby late-type M-dwarfs could make this approach applicable within the next decade, with soon-to-come general facilities. In this context, we previously identified GJ 1214 as a high-priority target for a transit search, as the transit probability of a habitable planet orbiting this nearby M4.5 dwarf would be significantly enhanced by the transiting nature of GJ 1214 b, the super-Earth already known to orbit the star. Based on this observation, we have set up an ambitious high-precision photometric monitoring of GJ 1214 with the Spitzer Space Telescope to probe the inner part of its habitable zone in search of a transiting planet as small as Mars. We present here the results of this transit search. Unfortunately, we did not detect any other transiting planets. Assuming that GJ 1214 hosts a habitable planet larger than Mars that has an orbital period smaller than 20.9 days, our global analysis of the whole Spitzer dataset leads to an a posteriori no-transit probability of ~98%. Our analysis allows us to significantly improve the characterization of GJ 1214 b, to measure its occultation depth to be 70 ± 35 ppm at 4.5 mum, and to constrain it to be smaller than 205 ppm (3sigma upper limit) at 3.6 mum. In agreement with the many transmission measurements published so far for GJ 1214 b, these emission measurements are consistent with both a metal-rich and a cloudy hydrogen-rich atmosphere. [less ▲]

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See detailFast-evolving weather for the coolest of our two new substellar neighbours
Gillon, Michaël ULg; Triaud, A. H. M. J.; Jehin, Emmanuel ULg et al

in Astronomy and Astrophysics (2013), 555

We present the results of an intense photometric monitoring in the near-infrared (~0.9 microns) with the TRAPPIST robotic telescope of the newly discovered binary brown dwarf WISE J104915.57-531906.1, the ... [more ▼]

We present the results of an intense photometric monitoring in the near-infrared (~0.9 microns) with the TRAPPIST robotic telescope of the newly discovered binary brown dwarf WISE J104915.57-531906.1, the third closest system to the Sun at a distance of only 2 pc. Our twelve nights of photometric time-series reveal a quasi-periodic (P = 4.87+-0.01 h) variability with a maximal peak-peak amplitude of ~11% and strong night-to-night evolution. We attribute this variability to the rotational modulation of fast-evolving weather patterns in the atmosphere of the coolest component (~T1-type) of the binary. No periodic signal is detected for the hottest component (~L8-type). For both brown dwarfs, our data allow us to firmly discard any unique transit during our observations for planets >= 2 Rearth. For orbital periods smaller than ~9.5 h, transiting planets are excluded down to an Earth-size. [less ▲]

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See detailTime Delays in Gravitationally Lensed Quasars
Eulaers, Eva ULg; Magain, Pierre ULg; Sohy, Sandrine ULg

Poster (2013, June 25)

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See detailThe Nebula around the Luminous Blue Variable WRAY 15-751 as seen by Herschel
Vamvatira-Nakou, Chloi ULg; Hutsemekers, Damien ULg; Royer, P. et al

in Massive Stars: From alpha to Omega (2013, June 01)

To understand the evolution of massive stars it is crucial to study the nebulae associated to Luminous Blue Variables which can reveal the star mass-loss history. We obtained far-infrared Herschel PACS ... [more ▼]

To understand the evolution of massive stars it is crucial to study the nebulae associated to Luminous Blue Variables which can reveal the star mass-loss history. We obtained far-infrared Herschel PACS imaging and spectroscopic observations of the nebula associated with the Luminous Blue Variable star WRAY 15-751. These images revealed a second nebula, bigger and cooler, lying in an empty cavity that probably delineates the remnant of the O-star bubble formed when the star was on the Main Sequence. The dust mass and temperature were derived from the modeling of the far-infrared SED. The analysis of the emission line spectrum revealed that the main nebula consists of a region of photoionised gas surrounded by a thin photodissociation region. Both regions are mixed with dust. The calculated C, N, O abundances, together with the estimated mass-loss rate, show that the nebula was ejected from the star during a Red Supergiant phase. This is compatible with the latest evolutionary tracks for a ~40 Mo star with little rotation. [less ▲]

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See detailCOSMOGRAIL: the COSmological MOnitoring of
GRAvItational Lenses: XIII. Time delays and 9-yr optical monitoring of the lensed quasar RX J1131-1231

Tewes, M.; Courbin, F.; Meylan, G. et al

in Astronomy and Astrophysics (2013)

We present the results from 9 years of optically monitoring the gravitationally lensed z=0.658 quasar RX J1131-1231. The R band light curves of the 4 individual images of the quasar are obtained using ... [more ▼]

We present the results from 9 years of optically monitoring the gravitationally lensed z=0.658 quasar RX J1131-1231. The R band light curves of the 4 individual images of the quasar are obtained using deconvolution photometry, for a total of 707 epochs. Several sharp quasar variability features strongly constrain the time delays between the quasar images. Using three different numerical techniques, we measure these delays for all possible pairs of quasar images, while always processing the 4 light curves simultaneously. For all three methods, the delays between the 3 close images A, B and C are compatible with being 0, while we measure the delay of image D to be 91 days, with a fractional uncertainty of 1.5% (1 sigma), including systematic errors. Our analysis of random and systematic errors accounts in a realistic way for the observed quasar variability, fluctuating microlensing magnification over a broad range of temporal scales, noise properties, and seasonal gaps. Finally, we find that our time delay measurement methods yield compatible results when applied to subsets of the data. [less ▲]

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See detailCOSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses: XII. Time delays of the doubly lensed quasars SDSS~J1206+4332 and HS~2209+1914
Eulaers, Eva ULg; Tewes, Malte; Magain, Pierre ULg et al

in Astronomy and Astrophysics (2013)

Aims. Within the framework of the COSMOGRAIL collaboration we present 7- and 8.5-year-long light curves and time-delay esti- mates for two gravitationally lensed quasars: SDSS J1206+4332 and HS 2209+1914 ... [more ▼]

Aims. Within the framework of the COSMOGRAIL collaboration we present 7- and 8.5-year-long light curves and time-delay esti- mates for two gravitationally lensed quasars: SDSS J1206+4332 and HS 2209+1914. Methods. We monitored these doubly lensed quasars in the R-band using four telescopes: the Mercator, Maidanak, Himalayan Chandra, and Euler Telescopes, together spanning a period of 7 to 8.5 observing seasons from mid-2004 to mid-2011. The pho- tometry of the quasar images was obtained through simultaneous deconvolution of these data. The time delays were determined from these resulting light curves using four very different techniques: a dispersion method, a spline fit, a regression difference technique, and a numerical model fit. This minimizes the bias that might be introduced by the use of a single method. Results. The time delay for SDSS J1206+4332 is ∆tAB = 111.3 ± 3 days with A leading B, confirming a previously published result within the error bars. For HS 2209+1914 we present a new time delay of ∆tBA = 20.0 ± 5 days with B leading A. Conclusions. The combination of data from up to four telescopes have led to well-sampled and nearly 9-season-long light curves, which were necessary to obtain these results, especially for the compact doubly lensed quasar HS 2209+1914. [less ▲]

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See detailThe TRAPPIST survey of southern transiting planets – Physical properties of the WASP-36 planetary system
Delrez, Laetitia ULg; Gillon, Michaël ULg; Jehin, Emmanuel ULg et al

Poster (2013, April 29)

We present ten new transit light curves obtained with the TRAPPIST (TRAnsiting Planets and PlanetesImals Small Telescope) and Euler telescopes for the recently discovered planetary system WASP-36 (Smith ... [more ▼]

We present ten new transit light curves obtained with the TRAPPIST (TRAnsiting Planets and PlanetesImals Small Telescope) and Euler telescopes for the recently discovered planetary system WASP-36 (Smith et al. 2012). Thanks to this extensive data set, we are able to confirm and improve the parameters of the system. WASP-36 is a solar-mass G2 dwarf which hosts a giant planet on a 1.54 d orbit. With a mass of ~2.3 MJup and a radius of ~1.3 RJup, this planet is slightly denser than Jupiter. One of the most interesting properties of the system is its low stellar metallicity ([Fe/H] =-0.26+-0.10), as giant planets are actually known to be rare around such stars (e.g. Fischer & Valenti 2005). Furthermore, due to its small orbital distance and large radius, WASP-36b is an exquisite target for spectrophotometric emission measurements able to constrain the thermal and chemical properties of its atmosphere. [less ▲]

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See detailTRAPPIST-UCDTS: A prototype search for habitable planets transiting ultra-cool stars
Gillon, Michaël ULg; Jehin, Emmanuel ULg; Fumel, A. et al

in Saglia, Roberto (Ed.) European Physical Journal Web of Conferences (2013, April 01)

The ˜1000 nearest ultra-cool stars (spectral type M6 and latter) represent a unique opportunity for the search for life outside solar system. Due to their small luminosity, their habitable zone is 30-100 ... [more ▼]

The ˜1000 nearest ultra-cool stars (spectral type M6 and latter) represent a unique opportunity for the search for life outside solar system. Due to their small luminosity, their habitable zone is 30-100 times closer than for the Sun, the corresponding orbital periods ranging from one to a few days. Thanks to this proximity, the transits of a habitable planet are much more probable and frequent than for an Earth-Sun analog, while their tiny size (˜1 Jupiter radius) leads to transits deep enough for a ground-based detection, even for sub-Earth size planets. Furthermore, a habitable planet transiting one of these nearby ultra-cool star would be amenable for a thorough atmospheric characterization, including the detection of possible biosignatures, notably with the near-to-come JWST. Motivated by these reasons, we have set up the concept of a ground-based survey optimized for detecting planets of Earth-size and below transiting the nearest Southern ultra-cool stars. To assess thoroughly the actual potential of this future survey, we are currently conducting a prototype mini-survey using the TRAPPIST robotic 60cm telescope located at La Silla ESO Observatory (Chile). We summarize here the preliminary results of this mini-survey that fully validate our concept. [less ▲]

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See detailGravitationall lensing evidence against extended dark matter halos
Magain, Pierre ULg; Chantry, Virginie ULg

E-print/Working paper (2013)

It is generally thought that galaxies are embedded in dark matter halos extending well beyond their luminous matter. The existence of these galactic halos is mainly derived from the larger than expected ... [more ▼]

It is generally thought that galaxies are embedded in dark matter halos extending well beyond their luminous matter. The existence of these galactic halos is mainly derived from the larger than expected velocities of stars and gas in the outskirts of spiral galaxies. Much less is known about dark matter around early-type (elliptical or lenticular) galaxies. We use gravitational lensing to derive the masses of early-type galaxies deflecting light of background quasars. This provides a robust measurement of the total mass within the Einstein ring, a circle whose diameter is comparable to the separation of the different quasar images. We find that the mass-to-light ratio of the lensing galaxies does not depend on radius, from inner galactic regions out to several half-light radii. Moreover, its value does not exceed the value predicted by stellar population models by more than a factor two, which may be explained by baryonic dark matter alone, without any need for exotic matter. Our results thus suggest that, if dark matter is present in early-type galaxies, its amount does not exceed the amount of luminous matter and its density follows that of luminous matter, in sharp contrast to what is found from rotation curves of spiral galaxies. [less ▲]

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