21 research outputs found
A pair of sub-Neptunes transiting the bright K-dwarf TOI-1064 characterized with CHEOPS
We report the discovery and characterization of a pair of sub-Neptunes transiting the bright K-dwarf TOI-1064 (TIC 79748331), initially detected in the Transiting Exoplanet Survey Satellite (TESS) photometry. To characterize the system, we performed and retrieved the CHaracterising ExOPlanets Satellite (CHEOPS), TESS, and ground-based photometry, the High Accuracy Radial velocity Planet Searcher (HARPS) high-resolution spectroscopy, and Gemini speckle imaging. We characterize the host star and determine Teff,â=4734±67Kâ , Râ=0.726±0.007Rââ , and Mâ=0.748±0.032Mââ . We present a novel detrending method based on point spread function shape-change modelling and demonstrate its suitability to correct flux variations in CHEOPS data. We confirm the planetary nature of both bodies and find that TOI-1064 b has an orbital period of Pb = 6.44387 ± 0.00003 d, a radius of Rb = 2.59 ± 0.04 Râ, and a mass of Mb=13.5+1.7â1.8 Mâ, whilst TOI-1064 c has an orbital period of Pc=12.22657+0.00005â0.00004 d, a radius of Rc = 2.65 ± 0.04 Râ, and a 3Ï upper mass limit of 8.5 Mâ. From the high-precision photometry we obtain radius uncertainties of âŒ1.6 per cent, allowing us to conduct internal structure and atmospheric escape modelling. TOI-1064 b is one of the densest, well-characterized sub-Neptunes, with a tenuous atmosphere that can be explained by the loss of a primordial envelope following migration through the protoplanetary disc. It is likely that TOI-1064 c has an extended atmosphere due to the tentative low density, however further radial velocities are needed to confirm this scenario and the similar radii, different masses nature of this system. The high-precision data and modelling of TOI-1064 b are important for planets in this region of massâradius space, and it allow us to identify a trend in bulk densityâstellar metallicity for massive sub-Neptunes that may hint at the formation of this population of planets
The low density, hot Jupiter TOI-640 b is on a polar orbit
TOI-640 b is a hot, puffy Jupiter with a mass of M
and radius of R, orbiting a slightly evolved F-type
star with a separation of R. Through
spectroscopic in-transit observations made with the HARPS spectrograph, we
measured the Rossiter-McLaughlin effect, analysing both in-transit radial
velocities and the distortion of the stellar spectral lines. From these
observations, we find the host star to have a projected obliquity of
. From the TESS light curve, we measured the stellar
rotation period, allowing us to determine the stellar inclination,
, meaning we are viewing the star pole-on. Combining
this with the orbital inclination allowed us to calculate the host star
obliquity, . TOI-640 b joins a group of planets orbiting
over stellar poles within the range . The origin of this
orbital configuration is not well understood.Comment: 15 pages, 12 figures, accepted for publication in A&A, in pres
A Radial Velocity Study of the Planetary System of pi Mensae: Improved Planet Parameters for pi Mensae c and a Third Planet on a 125 Day Orbit
Ï Men hosts a transiting planet detected by the Transiting Exoplanet Survey Satellite space mission and an outer planet in a 5.7 yr orbit discovered by radial velocity (RV) surveys. We studied this system using new RV measurements taken with the HARPS spectrograph on ESO's 3.6 m telescope, as well as archival data. We constrain the stellar RV semiamplitude due to the transiting planet, Ï Men c, as Kc = 1.21 ± 0.12 m s^{â1}, resulting in a planet mass of M_{c} = 3.63 ± 0.38 M_{â}. A planet radius of R_{c} = 2.145 ± 0.015 R_{â} yields a bulk density of Ïc = 2.03 ± 0.22 g cm^{â3}. The precisely determined density of this planet and the brightness of the host star make Ï Men c an excellent laboratory for internal structure and atmospheric characterization studies. Our HARPS RV measurements also reveal compelling evidence for a third body, Ï Men d, with a minimum mass M_{d} sin i_{d} = 13.38 ± 1.35 M_{â} orbiting with a period of Porb,d = 125 days on an eccentric orbit (e_{d} = 0.22). A simple dynamical analysis indicates that the orbit of Ï Men d is stable on timescales of at least 20 Myr. Given the mutual inclination between the outer gaseous giant and the inner rocky planet and the presence of a third body at 125 days, Ï Men is an important planetary system for dynamical and formation studies
TOI-733 b -- a planet in the small-planet radius valley orbiting a Sun-like star
We report the discovery of a hot ( 1055 K) planet in
the small planet radius valley transiting the Sun-like star TOI-733, as part of
the KESPRINT follow-up program of TESS planets carried out with the HARPS
spectrograph. TESS photometry from sectors 9 and 36 yields an orbital period of
= days and a radius of
= .
Multi-dimensional Gaussian process modelling of the radial velocity
measurements from HARPS and activity indicators, gives a semi-amplitude of
= m s, translating into a planet mass of
= . These
parameters imply that the planet is of moderate density ( =
g cm) and place it in the transition
region between rocky and volatile-rich planets with H/He-dominated envelopes on
the mass-radius diagram. Combining these with stellar parameters and
abundances, we calculate planet interior and atmosphere models, which in turn
suggest that TOI-733 b has a volatile-enriched, most likely secondary outer
envelope, and may represent a highly irradiated ocean world - one of only a few
such planets around G-type stars that are well-characterised.Comment: Accepted for publication in A&
Company for the ultra-high density, ultra-short period sub-Earth GJ 367 b: discovery of two additional low-mass planets at 11.5 and 34 days
GJ 367 is a bright (V 10.2) M1 V star that has been recently found
to host a transiting ultra-short period sub-Earth on a 7.7 hr orbit. With the
aim of improving the planetary mass and radius and unveiling the inner
architecture of the system, we performed an intensive radial velocity follow-up
campaign with the HARPS spectrograph -- collecting 371 high-precision
measurements over a baseline of nearly 3 years -- and combined our Doppler
measurements with new TESS observations from sectors 35 and 36. We found that
GJ 367 b has a mass of = 0.633 0.050 M and a
radius of = 0.699 0.024 R, corresponding to
precisions of 8% and 3.4%, respectively. This implies a planetary bulk density
of = 10.2 1.3 g cm, i.e., 85% higher than
Earth's density. We revealed the presence of two additional non transiting
low-mass companions with orbital periods of 11.5 and 34 days and minimum
masses of = 4.13 0.36 M and
= 6.03 0.49 M, respectively,
which lie close to the 3:1 mean motion commensurability. GJ 367 b joins the
small class of high-density planets, namely the class of super-Mercuries, being
the densest ultra-short period small planet known to date. Thanks to our
precise mass and radius estimates, we explored the potential internal
composition and structure of GJ 367 b, and found that it is expected to have an
iron core with a mass fraction of 0.91. How this iron core is
formed and how such a high density is reached is still not clear, and we
discuss the possible pathways of formation of such a small ultra-dense planet.Comment: 28 pages, 11 figures. Accepted for publication in ApJ
HD 20329b: An ultra-short-period planet around a solar-type star found by TESS
We used TESS light curves and HARPS-N spectrograph radial velocity
measurements to establish the physical properties of the transiting exoplanet
candidate found around the star HD 20329 (TOI-4524). We performed a joint fit
of the light curves and radial velocity time series to measure the mass,
radius, and orbital parameters of the candidate. We confirm and characterize HD
20329b, an ultra-short-period (USP) planet transiting a solar-type star. The
host star (HD 20329, mag, mag) is characterized by its G5
spectral type with M,
R, and K; it is located at a distance pc. By jointly
fitting the available TESS transit light curves and follow-up radial velocity
measurements, we find an orbital period of
days, a planetary radius of , and a mass of
, implying a mean density of
g cm. HD 20329b joins the 30
currently known USP planets with radius and Doppler mass measurements.Comment: Accepted for publication in A&A, 26 page
A low-eccentricity migration pathway for a 13-h-period Earth analogue in a four-planet system
It is commonly accepted that exoplanets with orbital periods shorter than one day, also known as ultra-short-period (USP) planets, formed further out within their natal protoplanetary disks before migrating to their current-day orbits via dynamical interactions. One of the most accepted theories suggests a violent scenario involving high-eccentricity migration followed by tidal circularization. Here we present the discovery of a four-planet system orbiting the bright (V = 10.5) K6 dwarf star TOI-500. The innermost planet is a transiting, Earth-sized USP planet with an orbital period of ~13 hours, a mass of 1.42 ± 0.18 Mâ, a radius of 1.166â0.058+0.061Râ and a mean density of 4.89â0.88+1.03gcmâ3. Via Doppler spectroscopy, we discovered that the system hosts 3 outer planets on nearly circular orbits with periods of 6.6, 26.2 and 61.3 days and minimum masses of 5.03 ± 0.41 Mâ, 33.12 ± 0.88 Mâ and 15.05â1.11+1.12Mâ, respectively. The presence of both a USP planet and a low-mass object on a 6.6-day orbit indicates that the architecture of this system can be explained via a scenario in which the planets started on low-eccentricity orbits then moved inwards through a quasi-static secular migration. Our numerical simulations show that this migration channel can bring TOI-500 b to its current location in 2 Gyr, starting from an initial orbit of 0.02 au. TOI-500 is the first four-planet system known to host a USP Earth analogue whose current architecture can be explained via a non-violent migration scenario
TOI-2196 b : Rare planet in the hot Neptune desert transiting a G-type star
Funding: C.M.P., M.F., I.G., and J.K. gratefully acknowledge the support of the Swedish National Space Agency (DNR 65/19, 174/18, 177/19, 2020-00104). L.M.S and D.G. gratefully acknowledge financial support from the CRT foundation under Grant No. 2018.2323 âGaseous or rocky? Unveiling the nature of small worldsâ. P.K. acknowledges support from grant LTT-20015. E.G. acknowledge the support of the ThĂŒringer Ministerium fĂŒr Wirtschaft, Wissenschaft und Digitale Gesellschaft. J.S.J. gratefully acknowledges support by FONDECYT grant 1201371 and from the ANID BASAL projects ACE210002 and FB210003. H.J.D. acknowledges support from the Spanish Research Agency of the Ministry of Science and Innovation (AEI-MICINN) under grant PID2019-107061GBC66, DOI: 10.13039/501100011033. D.D. acknowledges support from the TESS Guest Investigator Program grants 80NSSC21K0108 and 80NSSC22K0185. M.E. acknowledges the support of the DFG priority program SPP 1992 "Exploring the Diversity of Extrasolar Planets" (HA 3279/12-1). K.W.F.L. was supported by Deutsche Forschungsgemeinschaft grants RA714/14-1 within the DFG Schwerpunkt SPP 1992, Exploring the Diversity of Extrasolar Planets. N.N. acknowledges support from JSPS KAKENHI Grant Number JP18H05439, JST CREST Grant Number JPMJCR1761. M.S.I.P. is funded by NSF.The hot Neptune desert is a region hosting a small number of short-period Neptunes in the radius-instellation diagram. Highly irradiated planets are usually either small (R âČ 2 Râ) and rocky or they are gas giants with radii of âł1 RJ. Here, we report on the intermediate-sized planet TOI-2196 b (TIC 372172128.01) on a 1.2 day orbit around a G-type star (V = 12.0, [Fe/H] = 0.14 dex) discovered by the Transiting Exoplanet Survey Satellite in sector 27. We collected 41 radial velocity measurements with the HARPS spectrograph to confirm the planetary nature of the transit signal and to determine the mass. The radius of TOI-2196 b is 3.51 ± 0.15 Râ, which, combined with the mass of 26.0 ± 1.3 Mâ, results in a bulk density of 3.31â0.43+0.51 g cmâ3. Hence, the radius implies that this planet is a sub-Neptune, although the density is twice than that of Neptune. A significant trend in the HARPS radial velocity measurements points to the presence of a distant companion with a lower limit on the period and mass of 220 days and 0.65 MJ, respectively, assuming zero eccentricity. The short period of planet b implies a high equilibrium temperature of 1860 ± 20 K, for zero albedo and isotropic emission. This places the planet in the hot Neptune desert, joining a group of very few planets in this parameter space discovered in recent years. These planets suggest that the hot Neptune desert may be divided in two parts for planets with equilibrium temperatures of âł1800 K: a hot sub-Neptune desert devoid of planets with radii of â 1.8â3 Râ and a sub-Jovian desert for radii of â5â12 Râ. More planets in this parameter space are needed to further investigate this finding. Planetary interior structure models of TOI-2196 b are consistent with a H/He atmosphere mass fraction between 0.4% and 3%, with a mean value of 0.7% on top of a rocky interior. We estimated the amount of mass this planet might have lost at a young age and we find that while the mass loss could have been significant, the planet had not changed in terms of character: it was born as a small volatile-rich planet and it remains one at present.Publisher PDFPeer reviewe
TOI-2046b, TOI-1181b, and TOI-1516b, three new hot Jupiters from TESS: planets orbiting a young star, a subgiant, and a normal star
We present the confirmation and characterization of three hot Jupiters, TOI-1181b, TOI-1516b, and TOI-2046b, discovered by the TESS space mission. The reported hot Jupiters have orbital periods between 1.4 and 2.05 d. The masses of the three planets are 1.18 ± 0.14 MJ, 3.16 ± 0.12âMJ, and 2.30 ± 0.28 MJ, for TOI-1181b, TOI-1516b, and TOI-2046b, respectively. The stellar host of TOI-1181b is a F9IV star, whereas TOI-1516b and TOI-2046b orbit F main sequence host stars. The ages of the first two systems are in the range of 2â5 Gyrs. However, TOI-2046 is among the few youngest known planetary systems hosting a hot Jupiter, with an age estimate of 100â400 Myrs. The main instruments used for the radial velocity follow-up of these three planets are located at OndĆejov, Tautenburg, and McDonald Observatory, and all three are mounted on 2â3 m aperture telescopes, demonstrating that mid-aperture telescope networks can play a substantial role in the follow-up of gas giants discovered by TESS and in the future by PLATO