Artem Burdanov
University of Liège
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Featured researches published by Artem Burdanov.
Nature | 2017
Michaël Gillon; A. H. M. J. Triaud; Brice-Olivier Demory; Emmanuel Jehin; Eric Agol; Katherine M. Deck; Susan M. Lederer; Julien de Wit; Artem Burdanov; James G. Ingalls; Emeline Bolmont; Jérémy Leconte; Sean N. Raymond; Franck Selsis; Martin Turbet; Khalid Barkaoui; Adam J. Burgasser; M. R. Burleigh; Sean J. Carey; Aleksander Chaushev; C. M. Copperwheat; Laetitia Delrez; Catarina S. Fernandes; Daniel L. Holdsworth; Enrico J. Kotze; Valérie Van Grootel; Yaseen Almleaky; Z. Benkhaldoun; Pierre Magain; D. Queloz
One aim of modern astronomy is to detect temperate, Earth-like exoplanets that are well suited for atmospheric characterization. Recently, three Earth-sized planets were detected that transit (that is, pass in front of) a star with a mass just eight per cent that of the Sun, located 12 parsecs away. The transiting configuration of these planets, combined with the Jupiter-like size of their host star—named TRAPPIST-1—makes possible in-depth studies of their atmospheric properties with present-day and future astronomical facilities. Here we report the results of a photometric monitoring campaign of that star from the ground and space. Our observations reveal that at least seven planets with sizes and masses similar to those of Earth revolve around TRAPPIST-1. The six inner planets form a near-resonant chain, such that their orbital periods (1.51, 2.42, 4.04, 6.06, 9.1 and 12.35 days) are near-ratios of small integers. This architecture suggests that the planets formed farther from the star and migrated inwards. Moreover, the seven planets have equilibrium temperatures low enough to make possible the presence of liquid water on their surfaces.
Nature | 2016
Michaël Gillon; Emmanuel Jehin; Susan M. Lederer; Laetitia Delrez; Julien de Wit; Artem Burdanov; Valérie Van Grootel; Adam J. Burgasser; A. H. M. J. Triaud; Cyrielle Opitom; Brice-Olivier Demory; D. K. Sahu; Daniella C. Bardalez Gagliuffi; Pierre Magain; D. Queloz
Star-like objects with effective temperatures of less than 2,700 kelvin are referred to as ‘ultracool dwarfs’. This heterogeneous group includes stars of extremely low mass as well as brown dwarfs (substellar objects not massive enough to sustain hydrogen fusion), and represents about 15 per cent of the population of astronomical objects near the Sun. Core-accretion theory predicts that, given the small masses of these ultracool dwarfs, and the small sizes of their protoplanetary disks, there should be a large but hitherto undetected population of terrestrial planets orbiting them—ranging from metal-rich Mercury-sized planets to more hospitable volatile-rich Earth-sized planets. Here we report observations of three short-period Earth-sized planets transiting an ultracool dwarf star only 12 parsecs away. The inner two planets receive four times and two times the irradiation of Earth, respectively, placing them close to the inner edge of the habitable zone of the star. Our data suggest that 11 orbits remain possible for the third planet, the most likely resulting in irradiation significantly less than that received by Earth. The infrared brightness of the host star, combined with its Jupiter-like size, offers the possibility of thoroughly characterizing the components of this nearby planetary system.
Nature | 2016
Julien de Wit; Hannah R. Wakeford; Michaël Gillon; Nikole K. Lewis; Jeff A. Valenti; Brice-Olivier Demory; Adam J. Burgasser; Artem Burdanov; Laetitia Delrez; Emmanuel Jehin; Susan M. Lederer; D. Queloz; A. H. M. J. Triaud; Valérie Van Grootel
Three Earth-sized exoplanets were recently discovered close to the habitable zone of the nearby ultracool dwarf star TRAPPIST-1 (ref. 3). The nature of these planets has yet to be determined, as their masses remain unmeasured and no observational constraint is available for the planetary population surrounding ultracool dwarfs, of which the TRAPPIST-1 planets are the first transiting example. Theoretical predictions span the entire atmospheric range, from depleted to extended hydrogen-dominated atmospheres. Here we report observations of the combined transmission spectrum of the two inner planets during their simultaneous transits on 4 May 2016. The lack of features in the combined spectrum rules out cloud-free hydrogen-dominated atmospheres for each planet at ≥10σ levels; TRAPPIST-1 b and c are therefore unlikely to have an extended gas envelope as they occupy a region of parameter space in which high-altitude cloud/haze formation is not expected to be significant for hydrogen-dominated atmospheres. Many denser atmospheres remain consistent with the featureless transmission spectrum—from a cloud-free water-vapour atmosphere to a Venus-like one.
Monthly Notices of the Royal Astronomical Society | 2017
Kirill V. Sokolovsky; P. Gavras; A. Karampelas; S. V. Antipin; I. Bellas-Velidis; P. Benni; A. Z. Bonanos; Artem Burdanov; S. Derlopa; D. Hatzidimitriou; A. D. Khokhryakova; D. M. Kolesnikova; S. A. Korotkiy; E. G. Lapukhin; M. I. Moretti; A. Popov; E. Pouliasis; N. N. Samus; Z. Spetsieri; S. A. Veselkov; K. V. Volkov; M. Yang; A. M. Zubareva
Photometric measurements are prone to systematic errors presenting a challenge to low-amplitude variability detection. In search for a general-purpose variability detection technique able to recover a broad range of variability types including currently unknown ones, we test 18 statistical characteristics quantifying scatter and/or correlation between brightness measurements. We compare their performance in identifying variable objects in seven time series data sets obtained with telescopes ranging in size from a telephoto lens to 1m-class and probing variability on time-scales from minutes to decades. The test data sets together include lightcurves of 127539 objects, among them 1251 variable stars of various types and represent a range of observing conditions often found in ground-based variability surveys. The real data are complemented by simulations. We propose a combination of two indices that together recover a broad range of variability types from photometric data characterized by a wide variety of sampling patterns, photometric accuracies, and percentages of outlier measurements. The first index is the interquartile range (IQR) of magnitude measurements, sensitive to variability irrespective of a time-scale and resistant to outliers. It can be complemented by the ratio of the lightcurve variance to the mean square successive difference, 1/h, which is efficient in detecting variability on time-scales longer than the typical time interval between observations. Variable objects have larger 1/h and/or IQR values than non-variable objects of similar brightness. Another approach to variability detection is to combine many variability indices using principal component analysis. We present 124 previously unknown variable stars found in the test data.
Astronomy and Astrophysics | 2018
Simon L. Grimm; Brice-Olivier Demory; Michaël Gillon; Caroline Dorn; Eric Agol; Artem Burdanov; Laetitia Delrez; Marko Sestovic; A. H. M. J. Triaud; Martin Turbet; Emeline Bolmont; Anthony Caldas; Julien de Wit; Emmanuel Jehin; Jérémy Leconte; Sean N. Raymond; Valérie Van Grootel; Adam J. Burgasser; Sean J. Carey; Daniel C. Fabrycky; Kevin Heng; David M. Hernandez; James G. Ingalls; Susan M. Lederer; Franck Selsis; D. Queloz
Context. The TRAPPIST-1 system hosts seven Earth-sized, temperate exoplanets orbiting an ultra-cool dwarf star. As such, it represents a remarkable setting to study the formation and evolution of terrestrial planets that formed in the same protoplanetary disk. While the sizes of the TRAPPIST-1 planets are all known to better than 5% precision, their densities have significant uncertainties (between 28% and 95%) because of poor constraints on the planets masses. Aims.The goal of this paper is to improve our knowledge of the TRAPPIST-1 planetary masses and densities using transit-timing variations (TTV). The complexity of the TTV inversion problem is known to be particularly acute in multi-planetary systems (convergence issues, degeneracies and size of the parameter space), especially for resonant chain systems such as TRAPPIST-1. Methods. To overcome these challenges, we have used a novel method that employs a genetic algorithm coupled to a full N-body integrator that we applied to a set of 284 individual transit timings. This approach enables us to efficiently explore the parameter space and to derive reliable masses and densities from TTVs for all seven planets. Results. Our new masses result in a five- to eight-fold improvement on the planetary density uncertainties, with precisions ranging from 5% to 12%. These updated values provide new insights into the bulk structure of the TRAPPIST-1 planets. We find that TRAPPIST-1\,c and e likely have largely rocky interiors, while planets b, d, f, g, and h require envelopes of volatiles in the form of thick atmospheres, oceans, or ice, in most cases with water mass fractions less than 5%.
Monthly Notices of the Royal Astronomical Society | 2018
L. Delrez; Michaël Gillon; A. H. M. J. Triaud; Brice-Olivier Demory; J. de Wit; J. Ingalls; Eric Agol; Emeline Bolmont; Artem Burdanov; Adam J. Burgasser; Sean J. Carey; Emmanuel Jehin; Jérémy Leconte; Susan Maria Lederer; D. Queloz; Franck Selsis; Valérie Van Grootel
The recently detected TRAPPIST-1 planetary system, with its seven planets transiting a nearby ultracool dwarf star, offers the first opportunity to perform comparative exoplanetology of temperate Earth-sized worlds. To further advance our understanding of these planets’ compositions, energy budgets, and dynamics, we are carrying out an intensive photometric monitoring campaign of their transits with the Spitzer Space Telescope. In this context, we present 60 new transits of the TRAPPIST-1 planets observed with Spitzer/Infrared Array Camera (IRAC) in 2017 February and March. We combine these observations with previously published Spitzer transit photometry and perform a global analysis of the resulting extensive data set. This analysis refines the transit parameters and provides revised values for the planets’ physical parameters, notably their radii, using updated properties for the star. As part of our study, we also measure precise transit timings that will be used in a companion paper to refine the planets’ masses and compositions using the transit timing variations method. TRAPPIST-1 shows a very low level of low-frequency variability in the IRAC 4.5-μm band, with a photometric RMS of only 0.11 per cent at a 123-s cadence. We do not detect any evidence of a (quasi-)periodic signal related to stellar rotation. We also analyse the transit light curves individually, to search for possible variations in the transit parameters of each planet due to stellar variability, and find that the Spitzer transits of the planets are mostly immune to the effects of stellar variations. These results are encouraging for forthcoming transmission spectroscopy observations of the TRAPPIST-1 planets with the James Webb Space Telescope.
The Astrophysical Journal | 2018
Valérie Van Grootel; Catarina S. Fernandes; Michaël Gillon; Emmanuel Jehin; Jean Manfroid; Richard Scuflaire; Adam J. Burgasser; Khalid Barkaoui; Z. Benkhaldoun; Artem Burdanov; Laetitia Delrez; Brice-Olivier Demory; Julien de Wit; D. Queloz; A. H. M. J. Triaud
TRAPPIST-1 is an ultracool dwarf star transited by seven Earth-sized planets, for which thorough characterization of atmospheric properties, surface conditions encompassing habitability, and internal compositions is possible with current and next-generation telescopes. Accurate modeling of the star is essential to achieve this goal. We aim to obtain updated stellar parameters for TRAPPIST-1 based on new measurements and evolutionary models, compared to those used in discovery studies. We present a new measurement for the parallax of TRAPPIST-1, 82.4 ± 0.8 mas, based on 188 epochs of observations with the TRAPPIST and Liverpool Telescopes from 2013 to 2016. This revised parallax yields an updated luminosity of L =(5.22 ± 0.19) x 10⁻⁴ Lʘ, which is very close to the previous estimate but almost two times more precise. We next present an updated estimate for TRAPPIST-1 stellar mass, based on two approaches: mass from stellar evolution modeling, and empirical mass derived from dynamical masses of equivalently classified ultracool dwarfs in astrometric binaries. We combine them using a Monte-Carlo approach to derive a semi-empirical estimate for the mass of TRAPPIST-1. We also derive estimate for the radius by combining this mass with stellar density inferred from transits, as well as an estimate for the effective temperature from our revised luminosity and radius. Our final results are M = 0.089 ± 0.006 Mʘ, R =0.121 ± 0.003 Rʘ , and Teff= 2516 ± 41 K. Considering the degree to which the TRAPPIST-1 system will be scrutinized in coming years, these revised and more precise stellar parameters should be considered when assessing the properties of TRAPPIST-1 planets.
Monthly Notices of the Royal Astronomical Society | 2019
M. Lendl; D. R. Anderson; A. Bonfanti; F. Bouchy; Artem Burdanov; A. Collier Cameron; Laetitia Delrez; Michaël Gillon; C. Hellier; Emmanuel Jehin; P. F. L. Maxted; L. Dyregaard Nielsen; F. Pepe; Don Pollacco; D. Queloz; D. Ségransan; J. Southworth; B. Smalley; Samantha Thompson; O. D. Turner; A. H. M. J. Triaud; S. Udry; Richard G. West
We report the discovery of four transiting hot Jupiters, WASP-147, WASP-160B, WASP-164 and WASP-165 from the WASP survey. WASP-147b is a near Saturn-mass (
arXiv: Instrumentation and Methods for Astrophysics | 2018
Michaël Gillon; Emmanuel Jehin; D. Queloz; Yaseen Almleaky; Laetitia Delrez; Artem Burdanov; Elsa Ducrot; Sandrine Sohy; Sam Thompson; Julien de Wit; Brice-Olivier Demory; Valérie Van Grootel; Catarina S. Fernandes; Catriona Murray; Adam J. Burgasser; A. H. M. J. Triaud; Khalid Barkaoui; Z. Benkhaldoun; James McCormac; Roi Alonso; R. Rebolo
M_P = 0.28 M_{J}
Monthly Notices of the Royal Astronomical Society | 2018
L. Y. Temple; C. Hellier; Yaseen Almleaky; D. R. Anderson; F. Bouchy; D. J. A. Brown; Artem Burdanov; Collier Cameron; L. Delrez; Michaël Gillon; Richard Hall; Emmanuel Jehin; M. Lendl; P. F. L. Maxted; L. D. Nielsen; F. Pepe; Don Pollacco; D. Queloz; D. Ségransan; B. Smalley; Sandrine Sohy; Samantha Thompson; A. H. M. J. Triaud; O. D. Turner; S. Udry; Richard G. West
) object with a radius of