D. Mékarnia
A5089369840- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astro and Planetary Science
- Astrophysics and Star Formation Studies
- Adaptive optics and wavefront sensing
- Astronomical Observations and Instrumentation
- Gamma-ray bursts and supernovae
- Calibration and Measurement Techniques
- Planetary Science and Exploration
- Space Exploration and Technology
- Plant Water Relations and Carbon Dynamics
- Astrophysics and Cosmic Phenomena
- Astrophysical Phenomena and Observations
- Geophysics and Gravity Measurements
- Remote Sensing in Agriculture
- Optical Wireless Communication Technologies
- Scientific Research and Discoveries
- Optical Polarization and Ellipsometry
- Atmospheric Ozone and Climate
- Advanced optical system design
- History and Developments in Astronomy
- Impact of Light on Environment and Health
- Geophysics and Sensor Technology
- High-pressure geophysics and materials
- Atmospheric aerosols and clouds
Observatoire de la Côte d’Azur
2015-2024
Université Côte d'Azur
2015-2024
Centre National de la Recherche Scientifique
2015-2024
Lagrange Laboratory
2014-2023
Max Planck Institute for Astronomy
2019
Max Planck Society
2019
Optica
2012
Astronomical Observatory of Rome
2009
European Southern Observatory
2008
Institut Fresnel
2001
Abstract Mature super-Earths and sub-Neptunes are predicted to be ≃ Jovian radius when younger than 10 Myr. Thus, we expect find 5–15 R ⊕ planets around young stars even if their older counterparts harbor none. We report the discovery validation of TOI 1227b, a 0.85 ± 0.05 J (9.5 ) planet transiting very-low-mass star (0.170 0.015 M ⊙ every 27.4 days. 1227's kinematics strong lithium absorption confirm that it is member previously discovered subgroup in Lower Centaurus Crux OB association,...
We report the discovery and characterisation of a pair sub-Neptunes transiting bright K-dwarf TOI-1064 (TIC 79748331), initially detected in TESS photometry. To characterise system, we performed retrieved CHEOPS, TESS, ground-based photometry, HARPS high-resolution spectroscopy, Gemini speckle imaging. host star determine $T_{\rm eff, \star}=4734\pm67$ K, $R_{\star}=0.726\pm0.007$ $R_{\odot}$, $M_{\star}=0.748\pm0.032$ $M_{\odot}$. present novel detrending method based on PSF shape-change...
Post-AGB stars are key objects for the study of dramatic morphological changes low- to intermediate-mass on their evolution from Asymptotic Giant Branch (AGB) towards Planetary Nebula stage. There is growing evidences that binary interaction processes may very well have a determining role in shaping process many objects, but so far direct evidence still weak. We aim at systematic dust distribution around large sample as probe symmetry breaking nebulae these systems. used imaging mid-infrared...
We report the discovery of TOI 837b and its validation as a transiting planet. characterize system using data from NASA TESS mission, ESA Gaia ground-based photometry El Sauce ASTEP400, spectroscopy CHIRON, FEROS, Veloce. find that 837 is $T=9.9$ mag G0/F9 dwarf in southern open cluster IC 2602. The star planet are therefore $35^{+11}_{-5}$ million years old. Combining transit with prior on stellar parameters derived color-magnitude diagram, we has an orbital period $8.3\,{\rm d}$ slightly...
Microlensing detections of cool planets are important for the construction an unbiased sample to estimate frequency beyond snow line, which is where giant thought form according core accretion theory planet formation. In this paper, we report discovery a detected from analysis light curve high-magnification microlensing event MOA 2010-BLG-477. The measured planet–star mass ratio q = (2.181 ± 0.004) × 10−3 and projected separation s 1.1228 0.0006 in units Einstein radius. angular radius...
The ASTEP (Antarctica Search for Transiting ExoPlanets) program was originally aimed at probing the quality of Dome C, Antarctica discovery and characterization exoplanets by photometry. In first year operation 40 cm 400 telescope (austral winter 2010), we targeted known transiting planet WASP-19b in order to try detect its secondary transits visible. This is made possible excellent sub-millimagnitude precision binned data. WASP-19 system observed during 24 nights May 2010. photometric...
Abstract Astronomers do not have a complete picture of the effects wide-binary companions (semimajor axes greater than 100 au) on formation and evolution exoplanets. We investigate these using new data from Gaia Early Data Release 3 Transiting Exoplanet Survey Satellite mission to characterize systems with transiting identify sample 67 exoplanet candidates (with well-determined, edge-on orbital inclinations) that reside in wide visual binary systems. derive limits parameters for measure...
TOI-2525 is a K-type star with an estimated mass of M = 0.849$_{-0.033}^{+0.024}$ M$_\odot$ and radius R 0.785$_{-0.007}^{+0.007}$ R$_\odot$ observed by the TESS mission in 22 sectors (within 1 39). The light curves yield significant transit events two companions, which show strong timing variations (TTVs) semi-amplitude $\sim$6 hours. We performed TTV dynamical, photo-dynamical curve analysis data, combined radial velocity (RV) measurements from FEROS PFS, we confirmed planetary nature...
We present the discovery of two exoplanets transiting TOI-836 (TIC 440887364) using data from TESS Sector 11 and 38. is a bright ($T = 8.5$ mag), high proper motion ($\sim\,200$ mas yr$^{-1}$), low metallicity ([Fe/H]$\approx\,-0.28$) K-dwarf with mass $0.68\pm0.05$ M$_{\odot}$ radius $0.67\pm0.01$ R$_{\odot}$. obtain photometric follow-up observations variety facilities, we use these data-sets to determine that inner planet, b, $1.70\pm0.07$ R$_{\oplus}$ super-Earth in 3.82 day orbit,...
Abstract AU Mic is a young (22 Myr), nearby exoplanetary system that exhibits excess transit timing variations (TTVs) cannot be accounted for by the two known transiting planets nor stellar activity. We present statistical “validation” of tentative planet d (even though there are examples “confirmed” with ambiguous orbital periods). add 18 new transits and nine midpoint times in an updated TTV analysis to prior work. perform joint modeling light curves using EXOFASTv2 extract times. Next, we...
Aims.Analysis of the innermost regions carbon-rich star IRC+10216 and outer layers its circumstellar envelope have been performed in order to constrain mass-loss history.
This paper analyses 3.5 years of site testing data obtained at Dome C, Antarctica, based on measurements with three DIMMs located different elevations. Basic statistics the seeing and isoplanatic angle are given, as well characteristic time temporal fluctuations these two parameters, which we found to around 30 minutes 8 m. The 3 exploited a profiler surface layer, provide robust estimation its statistical properties. It appears have very sharp upper limit (less than 1 m). fraction spent by...
The optical turbulence above Dome C in winter is mainly concentrated the first tens of metres ground. Properties this so-called surface layer (SL) were investigated during period 2007–2012 by a set sonic anemometers placed on 45 m high tower. We present results long-term monitoring refractive index structure constant |$C_n^2$| within SL, and confirm its thickness 35 m. give statistics contribution SL to seeing coherence time. also investigate properties large-scale functions temperature show...
We report the discovery of five transiting companions near hydrogen-burning mass limit in close orbits around main sequence stars originally identified by Transiting Exoplanet Survey Satellite (TESS) as TESS Objects Interest (TOIs): TOI-148, TOI-587, TOI-681, TOI-746, and TOI-1213. Using ground-based photometry well radial velocities from CORALIE, CHIRON, TRES, FEROS spectrographs, we found have orbital periods between 4.8 27.2 days, masses 77 98 $\mathrm{M_{Jup}}$, radii 0.81 1.66...
Abstract High-eccentricity tidal migration is a possible way for giant planets to be placed in short-period orbits. If this happens often, one would expect catch proto hot Jupiters on highly elliptical orbits undergoing high-eccentricity migration. As of yet, few such systems have been discovered. Here, we introduce TOI-3362b (TIC-464300749b), an 18.1 day, 5 M Jup planet orbiting main-sequence F-type star that likely The orbital eccentricity 0.815 <mml:math...
Abstract We present the detection and characterization of TOI-4994b (TIC 277128619b), a warm Saturn-sized planet discovered by NASA Transiting Exoplanet Survey Satellite. transits G-type star ( V = 12.6 mag) with mass, radius, effective temperature <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mo>⋆</mml:mo> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>1.00</mml:mn> <mml:msubsup> <mml:mn>5</mml:mn>...
Visibility observations at 11 μm of o Ceti have been made with the University California (Berkeley) Infrared Spatial Interferometer during time period 1988-1995. The observed visibilities change dramatically from one epoch to another and are not consistent simple heating or cooling dust in luminosity as a function stellar phase. Instead, large temporal variations density within few radii photosphere occurred. Spherically symmetric models distribution two shells, three star, other...
The Concordia Base in Dome C, Antarctica, is an extremely promising site for photometric astronomy due to the 3- month long night during Antarctic winter, favorable weather conditions, and low scintillation. ASTEP project (Antarctic Search Transiting ExoPlanets) a pilot which seeks identify transiting planets understand limits of visible photometry from this site. 400 optical 40cm telescope with field view 1° x 1°. expected sensitivity 1E-3, per hour at least 1,000 stars. design guarantees...
TOI-216 hosts a pair of warm, large exoplanets discovered by the TESS Mission. These planets were found to be in or near 2:1 resonance, and both them exhibit transit timing variations (TTVs). Precise characterization planets' masses radii, orbital properties, resonant behavior can test theories for origins orbiting close their stars. Previous system using first six sectors data suffered from degeneracy between planet mass eccentricity. Radial velocity measurements HARPS, FEROS, PFS break...
Abstract We present the discovery and characterization of HIP 33609 b, a transiting warm brown dwarf orbiting late B star, discovered by NASA's Transiting Exoplanet Survey Satellite as TOI-588 b. b is large ( R = <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>1.580</mml:mn> </mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.070</mml:mn> <mml:mo>+</mml:mo> <mml:mn>0.074</mml:mn> </mml:msubsup> </mml:math> J ) on highly eccentric e...
Abstract The impact of the Double Asteroid Redirection Test spacecraft into Dimorphos, moon asteroid Didymos, changed Dimorphos’s orbit substantially, largely from ejection material. We present results 12 Earth-based facilities involved in a world-wide campaign to monitor brightness and morphology ejecta first 35 days after impact. After an initial brightening ∼1.4 mag, we find consistent dimming rates 0.11–0.12 mag day −1 week, 0.08–0.09 over entire study period. system returned its...
Abstract We present the spectroscopic confirmation and precise mass measurement of warm giant planet TOI-199 b. This was first identified in TESS photometry confirmed using ground-based from ASTEP Antarctica including a full 6.5 hr long transit, PEST, Hazelwood, LCO; space NEOSSat; radial velocities (RVs) FEROS, HARPS, CORALIE, CHIRON. Orbiting late G-type star, b has <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>104.854</mml:mn>...
We present the discovery and characterization of two warm mini-Neptunes transiting K3V star TOI-815 in a K–M binary system. Analysis its spectra rotation period reveal to be young, with an age 200 −200 +400 Myr. TOI-8l5b has 11.2-day radius 2.94 ± 0.05 R ⊕ transits observed by TESS, CHEOPS, ASTEP, LCOGT. The outer planet, TOI-8l5c, 2.62 0.10 , based on observations three nonconsecutive TESS; targeted CHEOPS photometry radial velocity follow-up ESPRESSO were required confirm 35-day period....
Abstract We present three-dimensional (3D) maps of Jupiter’s atmospheric circulation at cloud-top level from Doppler-imaging data obtained in the visible domain with JIVE, second node JOVIAL network, which is mounted on Dunn Solar Telescope Sunspot, New Mexico. report 12 nights observations between 2018 May 4 and 30, representing a total about 80 hr. First, average zonal wind profile derived our compatible that cloud-tracking measurements performed Hubble Space images April Outer Planet...