9 research outputs found
TOI-1695 b:A Water World Orbiting an Early-M Dwarf in the Planet Radius Valley
Characterizing the bulk compositions of transiting exoplanets within the M dwarf radius valley offers a unique means to establish whether the radius valley emerges from an atmospheric mass-loss process or is imprinted by planet formation itself. We present the confirmation of such a planet orbiting an early-M dwarf (Tmag = 11.0294 ± 0.0074, Ms = 0.513 ± 0.012 Mâ, Rs = 0.515 ± 0.015 Râ, and Teff = 3690 ± 50 K): TOI-1695 b (P = 3.13 days and Rp = 1.90â0.14+0.16 Râ ). TOI-1695 bâs radius and orbital period situate the planet between model predictions from thermally driven mass loss versus gas depleted formation, offering an important test case for radius valley emergence models around early-M dwarfs. We confirm the planetary nature of TOI-1695 b based on five sectors of TESS data and a suite of follow-up observations including 49 precise radial velocity measurements taken with the HARPS-N spectrograph. We measure a planetary mass of 6.36 ± 1.00 Mâ, which reveals that TOI-1695 b is inconsistent with a purely terrestrial composition of iron and magnesium silicate, and instead is likely a water-rich planet. Our finding that TOI-1695 b is not terrestrial is inconsistent with the planetary system being sculpted by thermally driven mass loss. We present a statistical analysis of seven well-characterized planets within the M dwarf radius valley demonstrating that a thermally driven mass-loss scenario is unlikely to explain this population.</p
New Mass and Radius Constraints on the LHS 1140 Planets -- LHS 1140 b is Either a Temperate Mini-Neptune or a Water World
The two-planet transiting system LHS 1140 has been extensively observed since
its discovery in 2017, notably with , HST, TESS, and ESPRESSO, placing
strong constraints on the parameters of the M4.5 host star and its small
temperate exoplanets, LHS 1140 b and c. Here, we reanalyse the ESPRESSO
observations of LHS 1140 with the novel line-by-line framework designed to
fully exploit the radial velocity content of a stellar spectrum while being
resilient to outlier measurements. The improved radial velocities, combined
with updated stellar parameters, consolidate our knowledge on the mass of LHS
1140 b (5.600.19 M) and LHS 1140 c (1.910.06 M)
with unprecedented precision of 3%. Transits from , HST, and TESS are
jointly analysed for the first time, allowing us to refine the planetary radii
of b (1.7300.025 R) and c (1.2720.026 R).
Stellar abundance measurements of refractory elements (Fe, Mg and Si) obtained
with NIRPS are used to constrain the internal structure of LHS 1140 b. This
planet is unlikely to be a rocky super-Earth as previously reported, but rather
a mini-Neptune with a 0.1% H/He envelope by mass or a water world with a
water-mass fraction between 9 and 19% depending on the atmospheric composition
and relative abundance of Fe and Mg. While the mini-Neptune case would not be
habitable, a water-abundant LHS 1140 b potentially has habitable surface
conditions according to 3D global climate models, suggesting liquid water at
the substellar point for atmospheres with relatively low CO concentration,
from Earth-like to a few bars.Comment: 31 pages, 18 figures, accepted for publication in ApJ
RNA GâQuadruplex Invasion and Translation Inhibition by Antisense ÎłâPeptide Nucleic Acid Oligomers
We have examined the abilities of
three complementary Îł-peptide
nucleic acid (ÎłPNA) oligomers to invade an RNA G-quadruplex
and potently inhibit translation of a luciferase reporter transcript
containing the quadruplex-forming sequence (QFS) within its 5âČ-untranslated
region. All three ÎłPNA oligomers bind with low nanomolar affinities
to an RNA oligonucleotide containing the QFS. However, while all probes
inhibit translation with low to midnanomolar IC<sub>50</sub> values,
the ÎłPNA designed to hybridize to the first two G-tracts of
the QFS and adjacent 5âČ-overhanging nucleotides was 5â6
times more potent than probes directed to either the 3âČ-end
or internal regions of the target at 37 °C. This position-dependent
effect was eliminated after the probes and target were preincubated
at an elevated temperature prior to translation, demonstrating that
kinetic effects exert significant control over quadruplex invasion
and translation inhibition. We also found that antisense ÎłPNAs
exhibited similarly potent effects against luciferase reporter transcripts
bearing QFS motifs having G<sub>2</sub>, G<sub>3</sub>, or G<sub>4</sub> tracts. Finally, our results indicate that ÎłPNA oligomers
exhibit selectivity and/or potency higher than those of other antisense
molecules such as standard PNA and 2âČ-OMe RNA previously reported
to target G-quadruplexes in RNA
Recommended from our members
Giant Outer Transiting Exoplanet Mass (GOT 'EM) Survey. II. Discovery of a Failed Hot Jupiter on a 2.7 Year, Highly Eccentric Orbit
Radial velocity (RV) surveys have discovered giant exoplanets on au-scale
orbits with a broad distribution of eccentricities. Those with the most
eccentric orbits are valuable laboratories for testing theories of high
eccentricity migration. However, few such exoplanets transit their host stars
thus removing the ability to apply constraints on formation from their bulk
internal compositions. We report the discovery of Kepler-1704 b, a transiting
4.15 giant planet on a 988.88 day orbit with the extreme
eccentricity of . Our decade-long RV baseline from the
Keck I telescope allows us to measure the orbit and bulk heavy element
composition of Kepler-1704 b and place limits on the existence of undiscovered
companions. Kepler-1704 b is a failed hot Jupiter that was likely excited to
high eccentricity by scattering events that possibly began during its gas
accretion phase. Its final periastron distance was too large to allow for tidal
circularization, so now it orbits it host from distances spanning 0.16 - 3.9
au. The maximum difference in planetary equilibrium temperature resulting from
this elongated orbit is over 700 K. A simulation of the thermal phase curve of
Kepler-1704 b during periastron passage demonstrates that it is a remarkable
target for atmospheric characterization from the James Webb Space Telescope,
which could potentially also measure the planet's rotational period as the hot
spot from periastron rotates in and out of view. Continued characterization of
the Kepler-1704 system promises to refine theories explaining the formation of
hot Jupiters and cool giant planets like those in the solar system
Recommended from our members
Giant Outer Transiting Exoplanet Mass (GOT 'EM) Survey. II. Discovery of a Failed Hot Jupiter on a 2.7 Yr, Highly Eccentric Orbit
Giant Outer Transiting Exoplanet Mass (GOT 'EM) Survey. II. Discovery of a Failed Hot Jupiter on a 2.7 Year, Highly Eccentric Orbit
Radial velocity (RV) surveys have discovered giant exoplanets on au-scale
orbits with a broad distribution of eccentricities. Those with the most
eccentric orbits are valuable laboratories for testing theories of high
eccentricity migration. However, few such exoplanets transit their host stars
thus removing the ability to apply constraints on formation from their bulk
internal compositions. We report the discovery of Kepler-1704 b, a transiting
4.15 giant planet on a 988.88 day orbit with the extreme
eccentricity of . Our decade-long RV baseline from the
Keck I telescope allows us to measure the orbit and bulk heavy element
composition of Kepler-1704 b and place limits on the existence of undiscovered
companions. Kepler-1704 b is a failed hot Jupiter that was likely excited to
high eccentricity by scattering events that possibly began during its gas
accretion phase. Its final periastron distance was too large to allow for tidal
circularization, so now it orbits it host from distances spanning 0.16 - 3.9
au. The maximum difference in planetary equilibrium temperature resulting from
this elongated orbit is over 700 K. A simulation of the thermal phase curve of
Kepler-1704 b during periastron passage demonstrates that it is a remarkable
target for atmospheric characterization from the James Webb Space Telescope,
which could potentially also measure the planet's rotational period as the hot
spot from periastron rotates in and out of view. Continued characterization of
the Kepler-1704 system promises to refine theories explaining the formation of
hot Jupiters and cool giant planets like those in the solar system
Masses, revised radii, and a third planet candidate in the âInvertedâ planetary system around TOI-1266
Funding: RC acknowledges support from the Natural Sciences and Engineering Council of Canada (NSERC) and the Banting Postdoctoral Fellowship Program administered by the Government of Canada. MP acknowledges the financial support from the Agenzia Spaziale Italiana-Istituto Nazionale di Astrofisica (ASI-INAF) Addendum no. 2018-24-HH.1-2022 âPartecipazione italiana al Gaia DPAC â Operazioni e attivitĂ analisi datiâ. FR is funded by the University of Exeterâs College of Engineering, Maths and Physical Sciences, UK.Is the population of close-in planets orbiting M dwarfs sculpted by thermally driven escape or is it a direct outcome of the planet formation process? A number of recent empirical results strongly suggest the latter. However, the unique architecture of the TOI-1266 system presents a challenge to models of planet formation and atmospheric escape given its seemingly âinvertedâ architecture of a large sub-Neptune (Pb = 10.9 d, Rp,b = 2.62 ± 0.11 Râ) orbiting interior to that of the systemâs smaller planet (Pc = 18.8 d, Rp,c = 2.13 ± 0.12 Râ). Here, we present revised planetary radii based on new TESS and diffuser-assisted ground-based transit observations, and characterize both planetary masses using a set of 145 radial velocity measurements from HARPS-N (Mp,b = 4.23 ± 0.69 Mâ, Mp,c = 2.88 ± 0.80 Mâ). Our analysis also reveals a third planet candidate (Pd = 32.3 d, Mp,d sin i = 4.59+0.96-0.94, Mâ), which if real, would form a chain of near 5:3 period ratios, although the system is likely not in a mean motion resonance. Our results indicate that TOI-1266 b and c are among the lowest density sub-Neptunes around M dwarfs and likely exhibit distinct bulk compositions of a gas-enveloped terrestrial (Xenv,b = 5.5 ± 0.7 per cent) and a water-rich world (WMFc = 59 ± 14 per cent), which is supported by hydrodynamic escape models. If distinct bulk compositions are confirmed through atmospheric characterization, the systemâs unique architecture would represent an interesting test case of inside-out sub-Neptune formation at pebble traps.Publisher PDFPeer reviewe
New Mass and Radius Constraints on the LHS 1140 Planets -- LHS 1140 b is Either a Temperate Mini-Neptune or a Water World
LHS 1140 b and c are two small temperate exoplanets transiting a nearby M4.5 dwarf. The planetary system was observed with multiple facilities since its discovery in 2017, including MEarth, , HARPS, ESPRESSO, HST, and TESS, placing strong constraints on the physical parameters of the planets and star. Here, we reanalyse the publicly available ESPRESSO observations of LHS 1140 with the novel line-by-line framework designed to fully exploit the radial velocity content of a stellar spectrum while being resilient to outlier measurements. This analysis reduces radial velocity uncertainties by 60% compared with published values derived from the cross-correlation function method. This improvement, combined with updated stellar parameters, consolidates our knowledge on the mass of LHS 1140 b (5.600.19 M) and LHS 1140 c (1.910.06 M) with unprecedented precision (3%). A joint analysis of transit data obtained with , HST, and TESS allows us to refine the planetary radius for b (1.7300.025 R) and c (1.2720.026 R). Stellar abundance measurements of refractory elements (Fe, Mg and Si) obtained with NIRPS are used to constrain the internal structure of LHS 1140 b. This habitable zone planet is unlikely to be a rocky super-Earth, but rather a mini-Neptune with a 0.1% H/He-rich mass envelope or a water world with a water-mass fraction between 9 and 19% depending on the atmospheric composition and relative abundance of Fe and Mg. Although LHS 1140 c remains consistent with a rocky planet, we detect a 4 discrepancy in the transit depths measured by and TESS. Finally, we find no evidence of the candidate LHS 1140 d and attribute this 80-day signal to stellar activity