Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userTOI-269 b: An eccentric sub-Neptune transiting a M2 dwarf revisited with ExTrA
211
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We present the confirmation of a new sub-Neptune close to the transition between super-Earths and sub-Neptunes transiting the M2 dwarf TOI- 269 (TIC 220479565, V = 14.4 mag, J = 10.9 mag, Rstar = 0.40 Rsun, Mstar = 0.39 Msun, d = 57 pc). The exoplanet candidate has been identified in multiple TESS sectors, and validated with high-precision spectroscopy from HARPS and ground-based photometric follow-up from ExTrA and LCO-CTIO. We determined mass, radius, and bulk density of the exoplanet by jointly modeling both photometry and radial velocities with juliet. The transiting exoplanet has an orbital period of P = 3.6977104 +- 0.0000037 days, a radius of 2.77 +- 0.12 Rearth, and a mass of 8.8 +- 1.4 Mearth. Since TOI-269 b lies among the best targets of its category for atmospheric characterization, it would be interesting to probe the atmosphere of this exoplanet with transmission spectroscopy in order to compare it to other sub-Neptunes. With an eccentricity e = 0.425+0.082-0.086, TOI-269 b has one of the highest eccentricities of the exoplanets with periods less than 10 days. The star being likely a few Gyr old, this system does not appear to be dynamically young. We surmise TOI-269 b may have acquired its high eccentricity as it migrated inward through planet-planet interactions.
rate research
Read More
We report the discovery of a transiting, temperate, Neptune-sized exoplanet orbiting the nearby ($d$ = 27.5 pc), M3V star TOI-1231 (NLTT 24399, L 248-27, 2MASS J10265947-5228099). The planet was detected using photometric data from the Transiting Exoplanet Survey Satellite and followed up with observations from the Las Cumbres Observatory and the Antarctica Search for Transiting ExoPlanets program. Combining the photometric data sets, we find that the newly discovered planet has a radius of 3.65$^{+0.16}_{-0.15}$ R$_{oplus}$, and an orbital period of 24.246 days. Radial velocity measurements obtained with the Planet Finder Spectrograph on the Magellan Clay telescope confirm the existence of the planet and lead to a mass measurement of 15.5$pm$3.3 M$_{oplus}$. With an equilibrium temperature of just 330K TOI-1231 b is one of the coolest small planets accessible for atmospheric studies thus far, and its host stars bright NIR brightness (J=8.88, K$_{s}$=8.07) make it an exciting target for HST and JWST. Future atmospheric observations would enable the first comparative planetology efforts in the 250-350 K temperature regime via comparisons with K2-18 b. Furthermore, TOI-1231s high systemic radial velocity (70.5 kms) may allow for the detection of low-velocity hydrogen atoms escaping the planet by Doppler shifting the H I Ly-alpha stellar emission away from the geocoronal and ISM absorption features.
Large sub-Neptunes are uncommon around the coolest stars in the Galaxy and are rarer still around those that are metal-poor. However, owing to the large planet-to-star radius ratio, these planets are highly suitable for atmospheric study via transmission spectroscopy in the infrared, such as with JWST. Here we report the discovery and validation of a sub-Neptune orbiting the thick-disk, mid-M dwarf star TOI-2406. We first infer properties of the host star by analysing the stars near-infrared spectrum, spectral energy distribution, and Gaia parallax. We use multi-band photometry to confirm that the transit event is on-target and achromatic, and we statistically validate the TESS signal as a transiting exoplanet. We then determine physical properties of the planet through global transit modelling of the TESS and ground-based time-series data. We determine the host to be a metal-poor M4V star, located at a distance of 56 pc, with a sub-solar metallicity $(mathrm{[Fe/H] = -0.38 pm 0.07})$, and a member of the thick disk. The planet is a relatively large sub-Neptune for the M-dwarf planet population, with $mathrm{R_p = 2.94 pm 0.17} mathrm{R_oplus}$ and $mathrm{P = 3.077}$ d, producing transits of 2% depth. We note the orbit has a non-zero eccentricity to 3$mathrm{sigma}$, prompting questions about the dynamical history of the system. This system is an interesting outcome of planet formation and presents a benchmark for large-planet formation around metal-poor, low-mass stars. The system warrants further study, in particular radial velocity follow-up to determine the planet mass and constrain possible bound companions. Furthermore, TOI-2406 b is a good target for future atmospheric study through transmission spectroscopy, particularly in the category of warm sub-Neptunes.
In this paper we report the discovery of TOI-220 $b$, a new sub-Neptune detected by the Transiting Exoplanet Survey Satellite (TESS) and confirmed by radial velocity follow-up observations with the HARPS spectrograph. Based on the combined analysis of TESS transit photometry and high precision radial velocity measurements we estimate a planetary mass of 13.8 $pm$ 1.0 M$_{Earth}$ and radius of 3.03 $pm$ 0.15 R$_{Earth}$, implying a bulk density of 2.73 $pm$ 0.47 $textrm{g cm}^{-3}$. TOI-220 $b$ orbits a relative bright (V=10.4) and old (10.1$pm$1.4 Gyr) K dwarf star with a period of $sim$10.69 d. Thus, TOI-220 $b$ is a new warm sub-Neptune with very precise mass and radius determinations. A Bayesian analysis of the TOI-220 $b$ internal structure indicates that due to the strong irradiation it receives, the low density of this planet could be explained with a steam atmosphere in radiative-convective equilibrium and a supercritical water layer on top of a differentiated interior made of a silicate mantle and a small iron core.
We present the bright (V$_{mag} = 9.12$), multi-planet system TOI-431, characterised with photometry and radial velocities. We estimate the stellar rotation period to be $30.5 pm 0.7$ days using archival photometry and radial velocities. TOI-431b is a super-Earth with a period of 0.49 days, a radius of 1.28 $pm$ 0.04 R$_{oplus}$, a mass of $3.07 pm 0.35$ M$_{oplus}$, and a density of $8.0 pm 1.0$ g cm$^{-3}$; TOI-431d is a sub-Neptune with a period of 12.46 days, a radius of $3.29 pm 0.09$ R$_{oplus}$, a mass of $9.90^{+1.53}_{-1.49}$ M$_{oplus}$, and a density of $1.36 pm 0.25$ g cm$^{-3}$. We find a third planet, TOI-431c, in the HARPS radial velocity data, but it is not seen to transit in the TESS light curves. It has an $M sin i$ of $2.83^{+0.41}_{-0.34}$ M$_{oplus}$, and a period of 4.85 days. TOI-431d likely has an extended atmosphere and is one of the most well-suited TESS discoveries for atmospheric characterisation, while the super-Earth TOI-431b may be a stripped core. These planets straddle the radius gap, presenting an interesting case-study for atmospheric evolution, and TOI-431b is a prime TESS discovery for the study of rocky planet phase curves.
[Abridged] We exploit the extreme radial velocity (RV) precision of the ultra-stable echelle spectrograph ESPRESSO on the VLT to unveil the physical properties of the transiting sub-Neptune TOI-130 b, uncovered by TESS orbiting the nearby, bright, late F-type star HD 5278 (TOI-130) with a period $P_{rm b}=14.3$. We use 43 ESPRESSO high-resolution spectra and broad-band photometry information to derive accurate stellar atmospheric and physical parameters of HD 5278. We exploit the TESS light curve (LC) and spectroscopic diagnostics to gauge the impact of stellar activity on the ESPRESSO RVs. We perform a joint ESPRESSO RVs + TESS LC analysis using fully Bayesian frameworks to determine the system parameters. The updated stellar parameters of HD 5278 are T$_mathrm{eff}=6203pm64$ K, $log g =4.50pm0.11$ dex, [Fe/H]=$-0.12pm0.04$ dex, M$_star=1.126_{-0.035}^{+0.036}$ M$_odot$ and R$_star=1.194_{-0.016}^{+0.017}$ R$_odot$. We determine HD 5278 bs mass and radius to be $M_{rm b} = 7.8_{-1.4}^{+1.5}$ M$_oplus$ and $R_{rm b} = 2.45pm0.05$ R$_oplus$. The derived mean density, $varrho_{rm b} = 2.9_{-0.5}^{+0.6}$ g cm$^{-3}$, is consistent with a bulk composition with a substantial ($sim30%$) water mass fraction and a gas envelope comprising $sim17%$ of the measured radius. Given the host brightness and irradiation levels, HD 5278 b is one of the best targets orbiting G-F primaries for follow-up atmospheric characterization measurements with HST and JWST. We discover a second, non-transiting companion in the system, with a period $P_{rm c}=40.87_{-0.17}^{+0.18}$ days and a minimum mass $M_{rm c}sin i_{rm c} =18.4_{-1.9}^{+1.8}$ M$_oplus$. We study emerging trends in the growing population of transiting sub-Neptunes, and provide statistical evidence for a low occurrence of close-in, $10-15$ M$_oplus$ companions around G-F primaries with $T_mathrm{eff}gtrsim5500$ K.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
