8 research outputs found
Revisiting K2-233 spectroscopic time-series with multidimensional Gaussian Processes
Detecting planetary signatures in radial velocity time-series of young stars
is challenging due to their inherently strong stellar activity. However, it is
possible to learn information about the properties of the stellar signal by
using activity indicators measured from the same stellar spectra used to
extract radial velocities. In this manuscript, we present a reanalysis of
spectroscopic HARPS data of the young star K2-233, which hosts three transiting
planets. We perform a multidimensional Gaussian Process regression on the
radial velocity and the activity indicators to characterise the planetary
Doppler signals. We demonstrate, for the first time on a real dataset, that the
use of a multidimensional Gaussian Process can boost the precision with which
we measure the planetary signals compared to a one-dimensional Gaussian Process
applied to the radial velocities alone. We measure the semi-amplitudes of
K2-233 b, c, and d as 1.31(-0.74)(+0.81), 1.81(-0.67)(+0.71), and
2.72(-0.70)(+0.66) m/s, which translates into planetary masses of
2.4(-1.3)(+1.5), 4.6(-1.7)(+1.8), and 10.3(-2.6)(+2.4), respectively. These new
mass measurements make K2-233 d a valuable target for transmission spectroscopy
observations with JWST. K2-233 is the only young system with two detected inner
planets below the radius valley and a third outer planet above it. This makes
it an excellent target to perform comparative studies, to inform our theories
of planet evolution, formation, migration, and atmospheric evolution.Comment: Accepted for publication in MNRA
The Multiplanet System TOI-421: A Warm Neptune and a Super Puffy Mini-Neptune Transiting a G9 V Star in a Visual Binary
We report the discovery of a warm Neptune and a hot sub-Neptune transiting TOI-421 (BD-14 1137, TIC 94986319), a bright (V = 9.9) G9 dwarf star in a visual binary system observed by the Transiting Exoplanet Survey Satellite (TESS) space mission in Sectors 5 and 6. We performed ground-based follow-up observationsâcomprised of Las Cumbres Observatory Global Telescope transit photometry, NIRC2 adaptive optics imaging, and FIbre-fed EchellĂ© Spectrograph, CORALIE, High Accuracy Radial velocity Planet Searcher, High Resolution Ăchelle Spectrometer, and Planet Finder Spectrograph high-precision Doppler measurementsâand confirmed the planetary nature of the 16 day transiting candidate announced by the TESS team. We discovered an additional radial velocity signal with a period of five days induced by the presence of a second planet in the system, which we also found to transit its host star. We found that the inner mini-Neptune, TOI-421 b, has an orbital period of P_b = 5.19672 ± 0.00049 days, a mass of M_b = 7.17 ± 0.66 Mâ, and a radius of R_b = 2.68^(+0.19)_(-0.18) Râ, whereas the outer warm Neptune, TOI-421 c, has a period of Pc = 16.06819 ± 0.00035 days, a mass of M_c = 16.42^(+1.06)_(-1.04) Mâ, a radius of R_c = 5.09^(+0.16)_(-0.15) Râ and a density of Ï_c = 0.685^(+0.080)_(-0.072) g cmâ»Âł. With its characteristics, the outer planet (Ï_c = 0.685^(+0.080)_(-0.072) g cmâ»Âł) is placed in the intriguing class of the super-puffy mini-Neptunes. TOI-421 b and TOI-421 c are found to be well-suited for atmospheric characterization. Our atmospheric simulations predict significant Lyα transit absorption, due to strong hydrogen escape in both planets, as well as the presence of detectable CH4 in the atmosphere of TOI-421 c if equilibrium chemistry is assumed
Density of Exoplanets
The internal structure of any planet is the result of its composition, radiation environment and age. Exoplanet interiors are hidden worlds that we are offered a glimpse into via the measurements of the most fundamental planet parameters; radius and mass. With this knowledge, we can distinguish rocky Earth-like planets from gaseous giants. We can look for new types of worlds, not represented in our own planetary neighbourhood, and we can ultimately link this diversity of planets to the underlying formation mechanisms. In this thesis, I summarise the exoplanet systems I have detected, confirmed and characterised with transit photometry and radial velocity measurements. They come from a whelm of ground and space-based transit surveys, all focusing on bright stars. I will describe the vetting and screening which lay the foundation for robust detections and stress the importance of identifying false positives
TESS Reveals a Short-period Sub-Neptune Sibling (HD 86226c) to a Known Long-period Giant Planet
The Transiting Exoplanet Survey Satellite mission was designed to find
transiting planets around bright, nearby stars. Here we present the detection
and mass measurement of a small, short-period (\,days) transiting
planet around the bright (), solar-type star HD 86226 (TOI-652, TIC
22221375), previously known to host a long-period (1600 days) giant
planet. HD 86226c (TOI-652.01) has a radius of and a
mass of 7.25 based on archival and new radial
velocity data. We also update the parameters of the longer-period,
not-known-to-transit planet, and find it to be less eccentric and less massive
than previously reported. The density of the transiting planet is g
cm, which is low enough to suggest that the planet has at least a small
volatile envelope, but the mass fractions of rock, iron, and water are not
well-constrained. Given the host star brightness, planet period, and location
of the planet near both the ``radius gap'' and the ``hot Neptune desert'', HD
86226c is an interesting candidate for transmission spectroscopy to further
refine its composition.Comment: Accepted in AJ on 22 June 202
The multiplanet system TOI-421: A sarm Neptune and a super puffy mini-Neptune Ttransiting a G9 V Star in a visual binary
We report the discovery of a warm Neptune and a hot sub-Neptune transiting TOI-421 (BD-14 1137, TIC 94986319), a bright (V = 9.9) G9 dwarf star in a visual binary system observed by the Transiting Exoplanet Survey Satellite (TESS) space mission in Sectors 5 and 6. We performed ground-based follow-up observations-comprised of Las Cumbres Observatory Global Telescope transit photometry, NIRC2 adaptive optics imaging, and FIbre-fed Echelle Spectrograph, CORALIE, High Accuracy Radial velocity Planet Searcher, High Resolution echelle Spectrometer, and Planet Finder Spectrograph high-precision Doppler measurements-and confirmed the planetary nature of the 16 day transiting candidate announced by the TESS team. We discovered an additional radial velocity signal with a period of five days induced by the presence of a second planet in the system, which we also found to transit its host star. We found that the inner mini-Neptune, TOI-421 b, has an orbital period of P-b = 5.19672 +/- 0.00049 days, a mass of M-b = 7.17 +/- 0.66 M-circle plus, and a radius of R-b = R-circle plus, whereas the outer warm Neptune, TOI-421 c, has a period of P-c = 16.06819 +/- 0.00035 days, a mass of M-c = 16.42(-1.04)(+1.06)M(circle plus), a radius of R-c = 5.09(-0.15)(+0.16)R(circle plus), and a density of rho(c) = 0.685(-0.072)(+0.080) cm(-3). With its characteristics, the outer planet (rho(c) = 0.685(-0.0072)(+0.080) cm(-3)) is placed in the intriguing class of the super-puffy mini-Neptunes. TOI-421 b and TOI-421 c are found to be well-suited for atmospheric characterization. Our atmospheric simulations predict significant Ly alpha transit absorption, due to strong hydrogen escape in both planets, as well as the presence of detectable CH4 in the atmosphere of TOI-421 c if equilibrium chemistry is assumed.KESPRINT collaboration, an international consortium devoted to the characterization and research of exoplanets discovered with space-based missions
NASA's Science Mission directorate
NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center
National Aeronautics & Space Administration (NASA)
European Research Council (ERC)
817540
European Research Council under the European Union's Horizon 2020 research and innovation program
832428
CRT foundation
2018.2323
Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT)
CONICYT FONDECYT
3180246
Millennium Science Initiative, Chilean Ministry of Economy
IC120009
Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT)
CONICYT FONDECYT
1171208
Irish Research Council for Science, Engineering and Technology
GOIPD/2018/659
Swedish National Space Agency
DNR 65/19
136/13
Australian Research Council
170100521
NASA through Caltech/JPL grant
RSA-1006130
NASA through TESS Guest Investigator Program
80NSSC19K1727
Alfred P. Sloan Foundation
National Aeronautics & Space Administration (NASA)
80NSSC18K1585
80NSSC19K0379
National Science Foundation (NSF)
AST1717000
Spanish Government
RYC-2015-17697
FPI-SO from the Spanish Ministry of Economy and Competitiveness (MINECO)
SEV-2015-0548-17-2
BES-2017-082610
National Aeronautics & Space Administration (NASA)
NNX17AF27G
HeisingSimons foundation
PLATO grant
GOLF CNES grant
CONICYT-PFCHA/Doctorado Nacional, Chile
21140646
German Research Foundation (DFG)
PA525/18-1
PA525/19-1
PA525/20-1
HA3279/12-1
RA714/14-1
National Aeronautics & Space Administration (NASA
The Multiplanet System TOI-421*
We report the discovery of a warm Neptune and a hot sub-Neptune transiting TOI-421 (BD-14 1137, TIC 94986319), a bright (V = 9.9) G9 dwarf star in a visual binary system observed by the Transiting Exoplanet Survey Satellite (TESS) space mission in Sectors 5 and 6. We performed ground-based follow-up observations-comprised of Las Cumbres Observatory Global Telescope transit photometry, NIRC2 adaptive optics imaging, and FIbre-fed Echelle Spectrograph, CORALIE, High Accuracy Radial velocity Planet Searcher, High Resolution echelle Spectrometer, and Planet Finder Spectrograph high-precision Doppler measurements-and confirmed the planetary nature of the 16 day transiting candidate announced by the TESS team. We discovered an additional radial velocity signal with a period of five days induced by the presence of a second planet in the system, which we also found to transit its host star. We found that the inner mini-Neptune, TOI-421 b, has an orbital period of P-b = 5.19672 +/- 0.00049 days, a mass of M-b = 7.17 +/- 0.66 M-circle plus, and a radius of R-b = R-circle plus, whereas the outer warm Neptune, TOI-421 c, has a period of P-c = 16.06819 +/- 0.00035 days, a mass of M-c = 16.42(-1.04)(+1.06)M(circle plus), a radius of R-c = 5.09(-0.15)(+0.16)R(circle plus), and a density of rho(c) = 0.685(-0.072)(+0.080) cm(-3). With its characteristics, the outer planet (rho(c) = 0.685(-0.0072)(+0.080) cm(-3)) is placed in the intriguing class of the super-puffy mini-Neptunes. TOI-421 b and TOI-421 c are found to be well-suited for atmospheric characterization. Our atmospheric simulations predict significant Ly alpha transit absorption, due to strong hydrogen escape in both planets, as well as the presence of detectable CH4 in the atmosphere of TOI-421 c if equilibrium chemistry is assumed