ABSTRACT
We report the discovery of TOI-530b, a transiting Saturn-like planet around an M0.5V dwarf, delivered by the Transiting Exoplanet Survey Satellite (TESS). The host star is located at a ...distance of 147.7 ± 0.6 pc with a radius of R* = 0.54 ± 0.03 R⊙ and a mass of M* = 0.53 ± 0.02 M⊙. We verify the planetary nature of the transit signals by combining ground-based multiwavelength photometry, high-resolution spectroscopy from SPIRou as well as high-angular-resolution imaging. With V = 15.4 mag, TOI-530b is orbiting one of the faintest stars accessible by ground-based spectroscopy. Our model reveals that TOI-530b has a radius of 0.83 ± 0.05 RJ and a mass of 0.37 ± 0.08 MJ on a 6.39-d orbit. TOI-530b is the sixth transiting giant planet hosted by an M-type star, which is predicted to be infrequent according to core accretion theory, making it a valuable object to further study the formation and migration history of similar planets. Furthermore, we identify a potential dearth of hot massive giant planets around M-dwarfs with separation distance smaller than 0.1 au and planet-to-star mass ratio between 2 × 10−3 and 10−2. We also find a possible correlation between hot giant planet formation and the metallicity of its parent M-dwarf. We discuss the potential formation channel of such systems.
We report the discovery of an ultrahot Jupiter with an extremely short orbital period of 0.67247414 ± 0.00000028 days (∼16 hr). The 1.347 ± 0.047 RJup planet, initially identified by the Transiting ...Exoplanet Survey Satellite (TESS) mission, orbits TOI-2109 (TIC 392476080)—a T(eff) ∼ 6500 K F-type star with a mass of 1.447 ± 0.077 Mꙩ, a radius of 1.698 ± 0.060 Rꙩ, and a rotational velocity of v sin i =81.9 ± 1.7 km/s. The planetary nature of TOI-2109b was confirmed through radial-velocity measurements, which yielded a planet mass of 5.02 ± 0.75 M(Jup). Analysis of the Doppler shadow in spectroscopic transit observations indicates a well-aligned system, with a sky-projected obliquity of λ = 1.°7± 1.°7. From the TESS full-orbit light curve, we measured a secondary eclipse depth of 731 ± 46 ppm, as well as phase-curve variations from the planet's longitudinal brightness modulation and ellipsoidal distortion of the host star. Combining the TESS-band occultation measurement with a K(s)-band secondary eclipse depth (2012 ± 80 ppm) derived from ground-based observations, we find that the dayside emission of TOI-2109b is consistent with a brightness temperature of 3631 ± 69 K, making it the second hottest exoplanet hitherto discovered. By virtue of its extreme irradiation and strong planet–star gravitational interaction, TOI-2109b is an exceptionally promising target for intensive follow-up studies using current and near-future telescope facilities to probe for orbital decay, detect tidally driven atmospheric escape, and assess the impacts of H2 dissociation and recombination on the global heat transport.
Abstract
We present observations of two bright M dwarfs (TOI-1634 and TOI-1685:
J
= 9.5–9.6) hosting ultra-short-period (USP) planets identified by the TESS mission. The two stars are similar in ...temperature, mass, and radius (
T
eff
≈ 3500 K,
M
⋆
≈ 0.45–0.46
M
⊙
, and
R
⋆
≈ 0.45–0.46
R
⊙
), and the planets are both super-Earth size (1.25
R
⊕
<
R
p
< 2.0
R
⊕
). For both systems, light curves from ground-based photometry exhibit planetary transits, whose depths are consistent with those from the TESS photometry. We also refine the transit ephemerides based on the ground-based photometry, finding the orbital periods of
P
= 0.9893436 ± 0.0000020 days and
P
= 0.6691416 ± 0.0000019 days for TOI-1634b and TOI-1685b, respectively. Through intensive radial velocity (RV) observations using the InfraRed Doppler (IRD) instrument on the Subaru 8.2 m telescope, we confirm the planetary nature of the TOIs and measure their masses: 10.14 ± 0.95
M
⊕
and 3.43 ± 0.93
M
⊕
for TOI-1634b and TOI-1685b, respectively, when the observed RVs are fitted with a single-planet circular-orbit model. Combining those with the planet radii of
R
p
= 1.749 ± 0.079
R
⊕
(TOI-1634b) and 1.459 ± 0.065
R
⊕
(TOI-1685b), we find that both USP planets have mean densities consistent with an Earth-like internal composition, which is typical for small USP planets. TOI-1634b is currently the most massive USP planet in this category, and it resides near the radius valley, which makes it a benchmark planet in the context of discussing the size limit of rocky planet cores as well as testing the formation scenarios for USP planets. Excess scatter in the RV residuals for TOI-1685 suggests the presence of a possible secondary planet or unknown activity/instrumental noise in the RV data, but further observations are required to check those possibilities.
Abstract
We present the discovery and validation of a temperate sub-Neptune around the nearby mid-M dwarf TIC 470381900 (TOI-1696), with a radius of 3.09 ± 0.11
R
⊕
and an orbital period of 2.5 days, ...using a combination of Transiting Exoplanets Survey Satellite (TESS) and follow-up observations using ground-based telescopes. Joint analysis of multiband photometry from TESS, Multicolor Simultaneous Camera for studying Atmospheres of Transiting exoplanets (MuSCAT), MuSCAT3, Sinistro, and KeplerCam confirmed the transit signal to be achromatic as well as refined the orbital ephemeris. High-resolution imaging with Gemini/’Alopeke and high-resolution spectroscopy with the Subaru InfraRed Doppler (IRD) confirmed that there are no stellar companions or background sources to the star. The spectroscopic observations with IRD and Infrared Telescope Facility SpeX were used to determine the stellar parameters, and it was found that the host star is an M4 dwarf with an effective temperature of
T
eff
= 3185 ± 76 K and a metallicity of Fe/H = 0.336 ± 0.060 dex. The radial velocities measured from IRD set a 2
σ
upper limit on the planetary mass to be 48.8
M
⊕
. The large radius ratio (
R
p
/
R
⋆
∼ 0.1) and the relatively bright near-infrared magnitude (
J
= 12.2 mag) make this planet an attractive target for further follow-up observations. TOI-1696 b is one of the planets belonging to the Neptunian desert with the highest transmission spectroscopy metric discovered to date, making it an interesting candidate for atmospheric characterizations with JWST.
Abstract
We report the discovery of TOI-2285b, a sub-Neptune-sized planet transiting a nearby (42 pc) M dwarf with a period of 27.3 d. We identified the transit signal from the Transiting Exoplanet ...Survey Satellite photometric data, which we confirmed with ground-based photometric observations using the multiband imagers MuSCAT2 and MuSCAT3. Combining these data with other follow-up observations including high-resolution spectroscopy with the Tillinghast Reflector Echelle Spectrograph, high-resolution imaging with the SPeckle Polarimeter, and radial velocity (RV) measurements with the InfraRed Doppler instrument, we find that the planet has a radius of $1.74 \pm 0.08\, R_\oplus$, a mass of $\lt \!\!19.5\,M_\oplus$ ($95\%$ c.l.), and an insolation flux of 1.54 ± 0.14 times that of the Earth. Although the planet resides just outside the habitable zone for a rocky planet, if the planet harbors an H2O layer under a hydrogen-rich atmosphere, then liquid water could exist on the surface of the H2O layer depending on the planetary mass and water mass fraction. The bright host star in the near-infrared (Ks = 9.0) makes this planet an excellent target for further RV and atmospheric observations to improve our understanding of the composition, formation, and habitability of sub-Neptune-sized planets.
We present the discovery and validation of a temperate sub-Neptune around the
nearby mid-M dwarf TIC 470381900 (TOI-1696), with a radius of $3.09 \pm 0.11
\,R_\oplus$ and an orbital period of $2.5 ...\,\rm{days}$, using a combination of
TESS and follow-up observations using ground-based telescopes. Joint analysis
of multi-band photometry from TESS, MuSCAT, MuSCAT3, Sinistro, and KeplerCam
confirmed the transit signal to be achromatic as well as refined the orbital
ephemeris. High-resolution imaging with Gemini/'Alopeke and high-resolution
spectroscopy with the Subaru/IRD confirmed that there are no stellar companions
or background sources to the star. The spectroscopic observations with IRD and
IRTF/SpeX were used to determine the stellar parameters, and found the host
star is an M4 dwarf with an effective temperature of $T_{eff} = 3185 \pm
76\,\rm{K}$ and a metallicity of Fe/H $=0.336 \pm 0.060 \,\rm{dex}$. The
radial velocities measured from IRD set a $2$-$\sigma$ upper limit on the
planetary mass to be $48.8 \,M_\oplus$. The large radius ratio ($R_p/R_\star
\sim 0.1$) and the relatively bright NIR magnitude ($J=12.2 \,\rm{mag}$) make
this planet an attractive target for further followup observations. TOI-1696b
is one of the planets belonging to the Neptunian desert with the highest
transmission spectroscopy metric discovered to date, making it an interesting
candidate for atmospheric characterizations with JWST.
We report the discovery of TOI-2285b, a sub-Neptune-sized planet transiting a nearby (42 pc) M dwarf with a period of 27.3 days. We identified the transit signal from the Transiting Exoplanet Survey ...Satellite photometric data, which we confirmed with ground-based photometric observations using the multiband imagers MuSCAT2 and MuSCAT3. Combining these data with other follow-up observations including high resolution spectroscopy with the Tillinghast Reflector Echelle Spectrograph, high resolution imaging with the SPeckle Polarimeter, and radial velocity (RV) measurements with the InfraRed Doppler instrument, we find that the planet has a radius of 1.74 \(\pm\) 0.08 \(R_\oplus\), a mass of \(<\) 19.5 \(M_\oplus\) (95\% c.l.), and an insolation flux of 1.54 \(\pm\) 0.14 times that of the Earth. Although the planet resides just outside the habitable zone for a rocky planet, if the planet harbors an H\(_2\)O layer under a hydrogen-rich atmosphere, then liquid water could exist on the surface of the H\(_2\)O layer depending on the planetary mass and water mass fraction. The bright host star in the near infrared (\(K_s=9.0\)) makes this planet an excellent target for further RV and atmospheric observations to improve our understanding on the composition, formation, and habitability of sub-Neptune-sized planets.
We report the discovery of an ultrahot Jupiter with an extremely short orbital period of \(0.67247414\,\pm\,0.00000028\) days (\(\sim\)16 hr). The \(1.347 \pm 0.047\) \(R_{\rm Jup}\) planet, ...initially identified by the Transiting Exoplanet Survey Satellite (TESS) mission, orbits TOI-2109 (TIC 392476080): a \(T_{\rm eff} \sim 6500\) K F-type star with a mass of \(1.447 \pm 0.077\) \(M_{\rm Sun}\), a radius of \(1.698 \pm 0.060\) \(R_{\rm Sun}\), and a rotational velocity of \(v\sin i_* = 81.9 \pm 1.7\) km s\(^{-1}\). The planetary nature of TOI-2109b was confirmed through radial velocity measurements, which yielded a planet mass of \(5.02 \pm 0.75\) \(M_{\rm Jup}\). Analysis of the Doppler shadow in spectroscopic transit observations indicates a well-aligned system, with a sky-projected obliquity of \(\lambda = 1\overset{\circ}{.}7 \pm 1\overset{\circ}{.}7\). From the TESS full-orbit light curve, we measured a secondary eclipse depth of \(731 \pm 46\) ppm, as well as phase-curve variations from the planet's longitudinal brightness modulation and ellipsoidal distortion of the host star. Combining the TESS-band occultation measurement with a \(K_s\)-band secondary eclipse depth (\(2012 \pm 80\) ppm) derived from ground-based observations, we find that the dayside emission of TOI-2109b is consistent with a brightness temperature of \(3631 \pm 69\) K, making it the second hottest exoplanet hitherto discovered. By virtue of its extreme irradiation and strong planet-star gravitational interaction, TOI-2109b is an exceptionally promising target for intensive follow-up studies using current and near-future telescope facilities to probe for orbital decay, detect tidally driven atmospheric escape, and assess the impacts of H\(_2\) dissociation and recombination on the global heat transport.
We report the discovery of TOI-530b, a transiting giant planet around an M0.5V dwarf, delivered by the Transiting Exoplanet Survey Satellite (TESS). The host star is located at a distance of ...\(147.7\pm0.6\) pc with a radius of \(R_{\ast}=0.54\pm0.03\ R_{\odot}\) and a mass of \(M_{\ast}=0.53\pm0.02\ M_{\odot}\). We verify the planetary nature of the transit signals by combining ground-based multi-wavelength photometry, high resolution spectroscopy from SPIRou as well as high-angular-resolution imaging. With \(V=15.4\) mag, TOI-530b is orbiting one of the faintest stars accessible by ground-based spectroscopy. Our model reveals that TOI-530b has a radius of \(0.83\pm0.05\ R_{J}\) and a mass of \(0.4\pm0.1\ M_{J}\) on a 6.39-d orbit. TOI-530b is the sixth transiting giant planet hosted by an M-type star, which is predicted to be infrequent according to core accretion theory, making it a valuable object to further study the formation and migration history of similar planets. We discuss the potential formation channel of such systems.
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