38 research outputs found
The mass determination of TOI-519 b: a close-in giant planet transiting a metal-rich mid-M dwarf
We report the mass determination of TOI-519 b, a transiting substellar object
around a mid-M dwarf. We carried out radial velocity measurements using Subaru
/ InfraRed Doppler (IRD), revealing that TOI-519 b is a planet with a mass of
. We also find that the host star is metal
rich ( dex) and has the lowest effective
temperature ( K) among all stars hosting known
close-in giant planets based on the IRD spectra and mid-resolution infrared
spectra obtained with NASA Infrared Telescope Facility / SpeX. The core mass of
TOI-519 b inferred from a thermal evolution model ranges from to
, which can be explained by both the core accretion and disk
instability models as the formation origins of this planet. However, TOI-519 is
in line with the emerging trend that M dwarfs with close-in giant planets tend
to have high metallicity, which may indicate that they formed in the core
accretion model. The system is also consistent with the potential trend that
close-in giant planets around M dwarfs tend to be less massive than those
around FGK dwarfs.Comment: 10 pages, 5 figures. Accepted for publication in PAS
An Earth-sized Planet around an M5 Dwarf Star at 22 pc
We report on the discovery of an Earth-sized transiting planet (R p = 1.015 ± 0.051 R ⊕) in a P = 4.02 day orbit around K2-415 (EPIC 211414619), an M5V star at 22 pc. The planet candidate was first identified by analyzing the light-curve data obtained by the K2 mission, and it is here shown to exist in the most recent data from TESS. Combining the light curves with the data secured by our follow-up observations, including high-resolution imaging and near-infrared spectroscopy with IRD, we rule out false-positive scenarios, finding a low false-positive probability of 2 × 10−4. Based on IRD’s radial velocities of K2-415, which were sparsely taken over three years, we obtain a planet mass of 3.0 ± 2.7 M ⊕ (M p < 7.5 M ⊕ at 95% confidence) for K2-415b. Being one of the lowest-mass stars (≈0.16 M ⊙) known to host an Earth-sized transiting planet, K2-415 will be an interesting target for further follow-up observations, including additional radial velocity monitoring and transit spectroscopy
Zodiacal Exoplanets in Time. X. The Orbit and Atmosphere of the Young "Neptune Desert"-Dwelling Planet K2-100b
We obtained high-resolution infrared spectroscopy and short-cadence
photometry of the 600-800 Myr Praesepe star K2-100 during transits of its
1.67-day planet. This Neptune-size object, discovered by the NASA K2 mission,
is an interloper in the "desert" of planets with similar radii on short period
orbits. Our observations can be used to understand its origin and evolution by
constraining the orbital eccentricity by transit fitting, measuring the
spin-orbit obliquity by the Rossiter-McLaughlin effect, and detecting any
extended, escaping hydrogen-helium envelope with the 10830A line of neutral
helium in the 2s3S triplet state. Transit photometry with 1-min cadence was
obtained by the K2 satellite during Campaign 18 and transit spectra were
obtained with the IRD spectrograph on the Subaru telescope. While the elevated
activity of K2-100 prevented us from detecting the Rossiter-McLaughlin effect,
the new photometry combined with revised stellar parameters allowed us to
constrain the eccentricity to e < 0.15/0.28 with 90%/99% confidence. We modeled
atmospheric escape as an isothermal, spherically symmetric Parker wind, with
photochemistry driven by UV radiation that we estimate by combining the
observed spectrum of the active Sun with calibrations from observations of
K2-100 and similar young stars in the nearby Hyades cluster. Our non-detection
(<5.7mA) of a transit-associated He I line limits mass loss of a
solar-composition atmosphere through a T<10000K wind to <0.3Me/Gyr. Either
K2-100b is an exceptional desert-dwelling planet, or its mass loss is occurring
at a lower rate over a longer interval, consistent with a core
accretion-powered scenario for escape.Comment: Accepted to MNRA
Mass and density of the transiting hot and rocky super-Earth LHS 1478 b (TOI-1640 b)
One of the main objectives of the Transiting Exoplanet Survey Satellite
({TESS}) mission is the discovery of small rocky planets around relatively
bright nearby stars. Here, we report the discovery and characterization of the
transiting super-Earth planet orbiting LHS~1478 (TOI-1640). The star is an
inactive red dwarf (\,mag and spectral type m3\,V) with mass and
radius estimates of \, and \,,
respectively, and an effective temperature of \,K.It was observed by
\tess in four sectors. These data revealed a transit-like feature with a period
of 1.949 days. We combined the TESS data with three ground-based transit
measurements, 57 radial velocity (RV) measurements from CARMENES, and 13 RV
measurements from IRD, determining that the signal is produced by a planet with
a mass of \, and a radius of
\,. The resulting bulk density of this planet
is 6.67\,g\,cm, which is consistent with a rocky planet with an Fe- and
MgSiO-dominated composition. Although the planet would be too hot to
sustain liquid water on its surface (its equilibrium temperature is about
595\,K, suggesting a Venus-like atmosphere), spectroscopic metrics based
on the capabilities of the forthcoming James Webb Space Telescope and the fact
that the host star is rather inactive indicate that this is one of the most
favorable known rocky exoplanets for atmospheric characterization.Comment: 14 pages, 10 figures, 6 tables, accepted for publication in A&
Sentiment-aware personalized tweet recommendation through multimodal FFM
For realizing quick and accurate access to desired information and ef- fective advertisements or election campaigns, personalized tweet recommendation is highly demanded. Since multimedia contents including tweets are tools for users to convey their sentiment, users’ interest in tweets is strongly influenced by sen- timent factors. Therefore, successful personalized tweet recommendation can be realized if sentiment in tweets can be estimated. However, sentiment factors were not taken into account in previous works and the performance of previous methods may be limited. To overcome the limitation, a method for sentiment-aware per- sonalized tweet recommendation through multimodal Field-aware Factorization Machines (FFM) is newly proposed in this paper. Successful personalized tweet recommendation becomes feasible through the following three contributions: (i) sentiment factors are newly introduced into personalized tweet recommendation, (ii) users’ interest is modeled by deriving multimodal FFM that enables collabora- tive use of multiple factors in a tweet, i.e., publisher, topic and sentiment factors, and (iii) the effectiveness of using sentiment factors as well as publisher and topic factors is clarified from results of experiments using real-world datasets related to worldwide hot topics, “#trump”, “#hillaryclinton” and “#ladygaga”. In addition to showing the effectiveness of the proposed method, the applicability of the pro- posed method to other tasks such as advertisement and social analysis is discussed as a conclusion and future work of this paper