Showing papers by "Suzanne Aigrain published in 2017"
TL;DR: Dumusque et al. as mentioned in this paper proposed a method to solve the Suiza problem by using the Harvard-Smithsonian Center for Astrophysics (HSCA) data set.
Abstract: Fil: Dumusque, X.. Universidad de Ginebra; Suiza. Harvard-Smithsonian Center for Astrophysics; Estados Unidos
113 citations
University of Göttingen1, Max Planck Society2, Aarhus University3, University of Oxford4, Katholieke Universiteit Leuven5, Radboud University Nijmegen6, Georgia State University7, Ames Research Center8, Paris Diderot University9, University of Sydney10, Australian National University11, New York University Abu Dhabi12
TL;DR: In this paper, a new photometric technique, called Halo photometry, was developed to observe very bright stars using a limited number of pixels, which is simple, fast and does not require extensive pixel allocation, and will allow us to use K2 and other photometric missions, such as TESS, to observe the stars for asteroseismology and search for transiting exoplanets.
Abstract: The most powerful tests of stellar models come from the brightest stars in the sky, for which complementary techniques, such as astrometry, asteroseismology, spectroscopy and interferometry, can be combined. The K2 mission is providing a unique opportunity to obtain high-precision photometric time series for bright stars along the ecliptic. However, bright targets require a large number of pixels to capture the entirety of the stellar flux, and CCD saturation, as well as restrictions on data storage and bandwidth, limit the number and brightness of stars that can be observed. To overcome this, we have developed a new photometric technique, which we call halo photometry, to observe very bright stars using a limited number of pixels. Halo photometry is simple, fast and does not require extensive pixel allocation, and will allow us to use K2 and other photometric missions, such as TESS, to observe very bright stars for asteroseismology and to search for transiting exoplanets. We apply this method to the seven brightest stars in the Pleiades open cluster. Each star exhibits variability; six of the stars show what are most likely slowly pulsating B-star pulsations, with amplitudes ranging from 20 to 2000 ppm. For the star Maia, we demonstrate the utility of combining K2 photometry with spectroscopy and interferometry to show that it is not a 'Maia variable', and to establish that its variability is caused by rotational modulation of a large chemical spot on a 10 d time-scale.
82 citations
TL;DR: In this article, the discovery and characterization of four low-mass (M < 0.6 M) eclipsing binary (EB) systems in the sub-Gyr old Praesepe open cluster using Kepler/K2 time series photometry and Keck/HIRES spectroscopy was presented.
Abstract: We present the discovery and characterization of four low-mass (M < 0.6 M⊙) eclipsing binary (EB) systems in the sub-Gyr old Praesepe open cluster using Kepler/K2 time series photometry and Keck/HIRES spectroscopy. We present a new Gaussian process EB model, GP–EBOP, as well as a method of simultaneously determining effective temperatures and distances for EBs. Three of the reported systems (AD 3814, AD 2615 and AD 1508) are detached and double-lined, and precise solutions are presented for the first two. We determine masses and radii to 1%–3% precision for AD 3814 and to 5%–6% for AD 2615. Together with effective temperatures determined to ~50 K precision, we test the PARSEC v1.2 and BHAC15 stellar evolution models. Our EB parameters are more consistent with the PARSEC models, primarily because the BHAC15 temperature scale is hotter than our data over the mid-M-dwarf mass range probed. Both ADs 3814 and 2615, which have orbital periods of 6.0 and 11.6 days, are circularized but not synchronized. This suggests that either synchronization proceeds more slowly in fully convective stars than the theory of equilibrium tides predicts, or magnetic braking is currently playing a more important role than tidal forces in the spin evolution of these binaries. The fourth system (AD 3116) comprises a brown dwarf transiting a mid-M-dwarf, which is the first such system discovered in a sub-Gyr open cluster. Finally, these new discoveries increase the number of characterized EBs in sub-Gyr open clusters by 20% (40%) below M < 1.5 M⊙ (M < 0.6 M⊙).
77 citations
TL;DR: In this paper, the authors reported the discovery of a repeating photometric signal from a low-mass member of the Praesepe open cluster that they interpret as a Neptune-sized transiting planet.
Abstract: We report the discovery of a repeating photometric signal from a low-mass member of the Praesepe open cluster that we interpret as a Neptune-sized transiting planet. The star is JS 183 (HSHJ 163, EPIC 211916756), with T_(eff) = 3325 ± 100 K, M* = 0.44 ± 0.04 M⊙, R* = 0.44 ± 0.03 R⊙, and log g* = 4.82 ± 0.06. The planet has an orbital period of 10.134588 days and a radius of R_P = 0.32 ± 0.02 R_J. Since the star is faint at V = 16.5 and J = 13.3, we are unable to obtain a measured radial velocity orbit, but we can constrain the companion mass to below about 1.7 M J, and thus well below the planetary boundary. JS 183b (since designated as K2-95b) is the second transiting planet found with K2 that resides in a several-hundred-megayear open cluster; both planets orbit mid-M dwarf stars and are approximately Neptune sized. With a well-determined stellar density from the planetary transit, and with an independently known metallicity from its cluster membership, JS 183 provides a particularly valuable test of stellar models at the fully convective boundary. We find that JS 183 is the lowest-density transit host known at the fully convective boundary, and that its very low density is consistent with current models of stars just above the fully convective boundary but in tension with the models just below the fully convective boundary.
66 citations
TL;DR: In this paper, the authors reported the discovery of a repeating photometric signal from a low-mass member of the Praesepe open cluster that they interpret as a Neptune-sized transiting planet.
Abstract: We report the discovery of a repeating photometric signal from a low-mass member of the Praesepe open cluster that we interpret as a Neptune-sized transiting planet. The star is JS 183 (HSHJ 163, EPIC 211916756) with $T_{\rm eff} = 3325\pm100$ K, $M_{*} = 0.44\pm0.04$ $M_{\odot}$, $R_{*} = 0.44\pm0.03$ $R_{\odot}$, and $\log{g_*} = 4.82\pm0.06$. The planet has an orbital period of 10.134588 days and a radius of $R_{P}= 0.32\pm0.02$ $R_J$. Since the star is faint at $V=16.5$ and $J=13.3$, we are unable to obtain a measured radial-velocity orbit, but we can constrain the companion mass to below about 1.7 $M_J$, and thus well below the planetary boundary. JS 183b (since designated as K2-95b) is the second transiting planet found with ${\it K2}$ that resides in a several hundred Myr open cluster; both planets orbit mid-M dwarf stars and are approximately Neptune-sized. With a well-determined stellar density from the planetary transit, and with an independently known metallicity from its cluster membership, JS 183 provides a particularly valuable test of stellar models at the fully convective boundary. We find that JS 183 is the lowest-density transit host known at the fully convective boundary, and that its very low density is consistent with current models of stars just above the fully convective boundary but in tension with the models just below the fully convective boundary.
48 citations
TL;DR: In this article, the authors demonstrate how such discrepancies may readily arise from sub-optimal sampling and/or neglecting to model even a single coherent signal (stellar, planetary, or otherwise) that may be present in RVs.
Abstract: Initial RV characterisation of the enigmatic planet Kepler-10c suggested a mass of $\sim17$ M$_\oplus$, which was remarkably high for a planet with radius $2.32$ R$_\oplus$; further observations and subsequent analysis hinted at a (possibly much) lower mass, but masses derived using RVs from two different spectrographs (HARPS-N and HIRES) were incompatible at a $3\sigma$-level. We demonstrate here how such mass discrepancies may readily arise from sub-optimal sampling and/or neglecting to model even a single coherent signal (stellar, planetary, or otherwise) that may be present in RVs. We then present a plausible resolution of the mass discrepancy, and ultimately characterise Kepler-10c as having mass $7.37_{-1.19}^{+1.32}$ M$_\oplus$, and mean density $3.14^{+0.63}_{-0.55}$ g cm$^{-3}$.
44 citations
Max Planck Society1, University of Tokyo2, New York University Abu Dhabi3, University of Sydney4, University of Birmingham5, Paris Diderot University6, University of Oxford7, Tata Institute of Fundamental Research8, Centre national de la recherche scientifique9, New Mexico State University10, Apache Corporation11, Search for extraterrestrial intelligence12, Aarhus University13, Pierre-and-Marie-Curie University14, Space Science Institute15, Tel Aviv University16, University of La Laguna17, Spanish National Research Council18
TL;DR: In this article, the power spectrum of a binary star system was analyzed to measure individual mode frequencies, adapting their methods where necessary to accommodate the fact that both stars oscillate in a similar frequency range.
Abstract: Binary star systems are important for understanding stellar structure and evolution, and are especially useful when oscillations can be detected and analysed with asteroseismology. However, only four systems are known in which solar-like oscillations are detected in both components. Here, we analyse the fifth such system, HD 176465, which was observed by Kepler . We carefully analysed the system’s power spectrum to measure individual mode frequencies, adapting our methods where necessary to accommodate the fact that both stars oscillate in a similar frequency range. We also modelled the two stars independently by fitting stellar models to the frequencies and complementaryparameters. We are able to cleanly separate the oscillation modes in both systems. The stellar models produce compatible ages and initial compositions for the stars, as is expected from their common and contemporaneous origin. Combining the individual ages, the system is about 3.0 ± 0.5 Gyr old. The two components of HD 176465 are young physically-similar oscillating solar analogues, the first such system to be found, and provide important constraints for stellar evolution and asteroseismology.
37 citations
TL;DR: The ARC2 pipeline as discussed by the authors identifies and corrects any isolated discontinuities in the light curves, then removes trends common to many light curves using the publicly available co-trending basis vectors, within an approximate Bayesian framework.
Abstract: We present ARC2 (Astrophysically Robust Correction 2), an open-source Python-based systematics-correction pipeline to correct for the Kepler prime mission long cadence light curves. The ARC2 pipeline identifies and corrects any isolated discontinuities in the light curves, then removes trends common to many light curves. These trends are modelled using the publicly available co-trending basis vectors, within an (approximate) Bayesian framework with `shrinkage' priors to minimise the risk of over-fitting and the injection of any additional noise into the corrected light curves, while keeping any astrophysical signals intact. We show that the ARC2 pipeline's performance matches that of the standard Kepler PDC-MAP data products using standard noise metrics, and demonstrate its ability to preserve astrophysical signals using injection tests with simulated stellar rotation and planetary transit signals. Although it is not identical, the ARC2 pipeline can thus be used as an open source alternative to PDC-MAP, whenever the ability to model the impact of the systematics removal process on other kinds of signal is important.
27 citations
TL;DR: In this paper, the discovery of four low-mass eclipsing binary (EB) systems in the sub-Gyr old Praesepe open cluster using Kepler/K2 time-series photometry and Keck/HIRES spectroscopy was presented.
Abstract: We present the discovery of four low-mass ($M<0.6$ $M_\odot$) eclipsing binary (EB) systems in the sub-Gyr old Praesepe open cluster using Kepler/K2 time-series photometry and Keck/HIRES spectroscopy. We present a new Gaussian process eclipsing binary model, GP-EBOP, as well as a method of simultaneously determining effective temperatures and distances for EBs. Three of the reported systems (AD 3814, AD 2615 and AD 1508) are detached and double-lined, and precise solutions are presented for the first two. We determine masses and radii to 1-3% precision for AD 3814 and to 5-6% for AD 2615. Together with effective temperatures determined to $\sim$50 K precision, we test the PARSEC v1.2 and BHAC15 stellar evolution models. Our EB parameters are more consistent with the PARSEC models, primarily because the BHAC15 temperature scale is hotter than our data over the mid M-dwarf mass range probed. Both ADs 3814 and 2615, which have orbital periods of 6.0 and 11.6 days, are circularized but not synchronized. This suggests that either synchronization proceeds more slowly in fully convective stars than the theory of equilibrium tides predicts or magnetic braking is currently playing a more important role than tidal forces in the spin evolution of these binaries. The fourth system (AD 3116) comprises a brown dwarf transiting a mid M-dwarf, which is the first such system discovered in a sub-Gyr open cluster. Finally, these new discoveries increase the number of characterized EBs in sub-Gyr open clusters by 20% (40%) below $M<1.5$ $M_{\odot}$ ($M<0.6$ $M_{\odot}$).
17 citations
University of Oxford1, University of Cambridge2, University of Grenoble3, Universidade Federal de Minas Gerais4, University of Turin5, Heidelberg University6, California Institute of Technology7, Ames Research Center8, INAF9, European Space Agency10, University of La Laguna11, Spanish National Research Council12
TL;DR: In this article, the authors used two optical CoRoT runs from 2008 and 2011/2012 (spanning 23 and 39 days), along with infrared Spitzer 3.6 and 4.5 μm observations (covering 21 and 29 days) to model the out-of-eclipse light curves, finding that the large scale structure in both CoRoTs light curves is consistent with the constructive and destructive interference of starspot signals at two slightly different periods.
Abstract: CoRoT 223992193 is the only known low-mass, pre-main sequence eclipsing binary that shows evidence of a circumbinary disk. The system displays complex photometric and spectroscopic variability over a range of timescales and wavelengths. Using two optical CoRoT runs from 2008 and 2011/2012 (spanning 23 and 39 days), along with infrared Spitzer 3.6 and 4.5 μm observations (spanning 21 and 29 days, and simultaneous with the second CoRoT run), we model the out-of-eclipse light curves, finding that the large scale structure in both CoRoT light curves is consistent with the constructive and destructive interference of starspot signals at two slightly different periods. Using the vsini of both stars, we interpret this as the two stars having slightly different rotation periods: the primary is consistent with synchronisation and the secondary rotates slightly supersynchronously. Comparison of the raw 2011/2012 light curve data to the residuals of our spot model in colour-magnitude space indicates additional contributions consistent with a combination of variable dust emission and obscuration. There appears to be a tentative correlation between this additional variability and the binary orbital phase, with the system displaying increases in its infrared flux around primary and secondary eclipse. We also identify short-duration flux dips preceding secondary eclipse in all three CoRoT and Spitzer bands. We construct a model of the inner regions of the binary and propose that these dips could be caused by partial occultation of the central binary by the accretion stream onto the primary star. Analysis of 15 Hα profiles obtained with the FLAMES instrument on the Very Large Telescope reveal an emission profile associated with each star. The majority of this is consistent with chromospheric emission but additional higher velocity emission is also seen, which could be due to prominences. However, half of the secondary star’s emission profiles display full widths at 10% intensity that could also be interpreted as having an accretion-related origin. In addition, simultaneous u and r-band observations obtained with the MEGACam instrument on the Canada France Hawaii Telescope reveal a short-lived u-band excess consistent with either an accretion hot spot or stellar flare. The photometric and spectroscopic variations are very complex but are consistent with the picture of two active stars possibly undergoing non-steady, low-level accretion; the system’s very high inclination provides a new view of such variability.
17 citations
TL;DR: In this article, the authors used ground-based transmission spectroscopy to study the atmosphere of WASP-80b, a warm inflated gas giant with an equilibrium temperature of ∼$800~K, covering the spectral range from 520~to~910~nm.
Abstract: We set out to study the atmosphere of WASP-80b, a warm inflated gas giant with an equilibrium temperature of $\sim$800~K, using ground-based transmission spectroscopy covering the spectral range from 520~to~910~nm. The observations allow us to probe the existence and abundance of K and Na in WASP-80b's atmosphere, existence of high-altitude clouds, and Rayleigh-scattering in the blue end of the spectrum.
We observed two spectroscopic time series of WASP-80b transits with the OSIRIS spectrograph installed in the Gran Telescopio CANARIAS, and use the observations to estimate the planet's transmission spectrum between 520~nm and 910~nm in 20~nm-wide passbands, and around the K~I and Na~I resonance doublets in 6~nm-wide passbands. We model three previously published broadband datasets consisting of 27 light curves jointly prior to the transmission spectroscopy analysis in order to obtain improved prior estimates for the planet's orbital parameters, average radius ratio, and stellar density.
We recover a flat transmission spectrum with no evidence of Rayleigh scattering or K~I or Na~I absorption, and obtain an improved system characterisation as a by-product of the broadband- and GTC-dataset modelling. The transmission spectra estimated separately from the two observing runs are consistent with each other, as are the transmission spectra estimated using either a parametric or nonparametric systematics models. The flat transmission spectrum favours an atmosphere model with high-altitude clouds over cloud-free models with stellar or sub-stellar metallicities.
INAF1, Aix-Marseille University2, Institut d'Astrophysique de Paris3, University of Bordeaux4, University of Geneva5, Spanish National Research Council6, University of La Laguna7, German Aerospace Center8, Université Paris-Saclay9, Facultad de Ciencias Exactas y Naturales10, University of Buenos Aires11, Leiden University12, Chalmers University of Technology13, University of Turin14, Sao Paulo State University15, Centre national de la recherche scientifique16, Janssen Pharmaceutica17, University of Cologne18, Technical University of Berlin19, Paris Diderot University20
TL;DR: In this article, a new analysis of the CoRoT-9 system based on five years of radial-velocity (RV) monitoring with HARPS and three new space-based transits observed with coRoT and Spitzer is presented.
Abstract: CoRoT-9b is one of the rare long-period (P=95.3 days) transiting giant planets with a measured mass known to date. We present a new analysis of the CoRoT-9 system based on five years of radial-velocity (RV) monitoring with HARPS and three new space-based transits observed with CoRoT and Spitzer. Combining our new data with already-published measurements we redetermine the CoRoT-9 system parameters and find good agreement with the published values. We uncover a higher significance for CoRoT-9b's small but non-zero eccentricity ($e=0.133^{+0.042}_{-0.037}$) and find no evidence for additional planets in the system. We use simulations of planet-planet scattering to show that CoRoT-9b's eccentricity may have been generated by an instability in which a $\sim 50~M_\oplus$ planet was ejected from the system. This scattering would not have produced a spin-orbit misalignment, so we predict that CoRoT-9b's orbit should lie within a few degrees of the initial plane of the protoplanetary disk. As a consequence, any significant stellar obliquity would indicate that the disk was primordially tilted.
INAF1, Aix-Marseille University2, Institut d'Astrophysique de Paris3, University of Bordeaux4, University of Geneva5, Spanish National Research Council6, University of La Laguna7, German Aerospace Center8, Université Paris-Saclay9, University of Buenos Aires10, Facultad de Ciencias Exactas y Naturales11, Leiden University12, Chalmers University of Technology13, University of Turin14, Sao Paulo State University15, Centre national de la recherche scientifique16, Janssen Pharmaceutica17, University of Cologne18, Technical University of Berlin19, Paris Diderot University20
TL;DR: In this article, a new analysis of the CoRoT-9 system based on five years of radial-velocity (RV) monitoring with HARPS and three new space-based transits observed with coRoT and Spitzer is presented.
Abstract: CoRoT-9b is one of the rare long-period (P=95.3 days) transiting giant planets with a measured mass known to date. We present a new analysis of the CoRoT-9 system based on five years of radial-velocity (RV) monitoring with HARPS and three new space-based transits observed with CoRoT and Spitzer. Combining our new data with already published measurements we redetermine the CoRoT-9 system parameters and find good agreement with the published values. We uncover a higher significance for the small but non-zero eccentricity of CoRoT-9b ($e=0.133^{+0.042}_{-0.037}$) and find no evidence for additional planets in the system. We use simulations of planet-planet scattering to show that the eccentricity of CoRoT-9b may have been generated by an instability in which a $\sim 50~M_\oplus$ planet was ejected from the system. This scattering would not have produced a spin-orbit misalignment, so we predict that CoRoT-9b orbit should lie within a few degrees of the initial plane of the protoplanetary disk. As a consequence, any significant stellar obliquity would indicate that the disk was primordially tilted.