Context.
Ultra-short-period (USP) planets are defined as planets with orbital periods shorter than one day. This type of planets is rare, highly irradiated, and interesting because their formation ...history is unknown.
Aims.
We aim to obtain precise mass and radius measurements to confirm the planetary nature of a USP candidate found by the Transiting Exoplanet Survey Satellite (TESS). These parameters can provide insights into the bulk composition of the planet candidate and help to place constraints on its formation history.
Methods.
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.
Results.
We confirm and characterize HD 20329b, a USP planet transiting a solar-type star. The host star (HD 20329,
V
= 8.74 mag,
J
= 7.5 mag) is characterized by its G5 spectral type with
M
*
= 0.90 ± 0.05
M
⊙
,
R
*
= 1.13 ± 0.02
R
⊙
, and
T
eff
= 5596 ± 50 K; it is located at a distance
d
= 63.68 ± 0.29 pc. By jointly fitting the available TESS transit light curves and follow-up radial velocity measurements, we find an orbital period of 0.9261 ± (0.5 × 10
−4
) days, a planetary radius of 1.72 ± 0.07
R
⊗
, and a mass of 7.42 ± 1.09
M
⊗
, implying a mean density of
ρ
p
= 8.06 ± 1.53 g cm
−3
. HD 20329b joins the ~30 currently known USP planets with radius and Doppler mass measurements.
Temperature inversion layers are predicted to be present in ultra-hot giant planet atmospheres. Although such inversion layers have recently been observed in several ultra-hot Jupiters, the chemical ...species responsible for creating the inversion remain unidentified. Here, we present observations of the thermal emission spectrum of an ultra-hot Jupiter, WASP-189b, at high spectral resolution using the HARPS-N spectrograph. Using the cross-correlation technique, we detect a strong Fe
I
signal. The detected Fe
I
spectral lines are found in emission, which is direct evidence of a temperature inversion in the planetary atmosphere. We further performed a retrieval on the observed spectrum using a forward model with an MCMC approach. When assuming a solar metallicity, the best-fit result returns a temperature of 4320
−100
+120
K at the top of the inversion, which is significantly hotter than the planetary equilibrium temperature (2641 K). The temperature at the bottom of the inversion is determined as 2200
−800
+1000
K. Such a strong temperature inversion is probably created by the absorption of atomic species like Fe
I
.
We present the discovery and characterization of WASP-148, a new extrasolar system that includes at least two giant planets. The host star is a slowly rotating inactive late-G dwarf with a
V
= 12 ...magnitude. The planet WASP-148b is a hot Jupiter of 0.72
R
Jup
and 0.29
M
Jup
that transits its host with an orbital period of 8.80 days. We found the planetary candidate with the SuperWASP photometric survey, then characterized it with the SOPHIE spectrograph. Our radial velocity measurements subsequently revealed a second planet in the system, WASP-148c, with an orbital period of 34.5 days and a minimum mass of 0.40
M
Jup
. No transits of this outer planet were detected. The orbits of both planets are eccentric and fall near the 4:1 mean-motion resonances. This configuration is stable on long timescales, but induces dynamical interactions so that the orbits differ slightly from purely Keplerian orbits. In particular, WASP-148b shows transit-timing variations of typically 15 min, making it the first interacting system with transit-timing variations that is detected on ground-based light curves. We establish that the mutual inclination of the orbital plane of the two planets cannot be higher than 35°, and the true mass of WASP-148c is below 0.60
M
Jup
. We present photometric and spectroscopic observations of this system that cover a time span of ten years. We also provide their Keplerian and Newtonian analyses; these analyses should be significantly improved through future TESS observations.
We report the discovery of a multiplanetary system transiting the M0 V dwarf HD 260655 (GJ 239, TOI-4599). The system consists of at least two transiting planets, namely HD 260655 b, with a period of ...2.77 d, a radius of
R
b
= 1.240 ± 0.023
R
⊕
, a mass of
M
b
= 2.14 ± 0.34
M
⊕
, and a bulk density of
ρ
b
= 6.2 ± 1.0 g cm
−3
, and HD 260655 c, with a period of 5.71 d, a radius of ${R_c} = 1.533_{ - 0.046}^{ + 0.051}{R_ \oplus }$, a mass of
M
c
= 3.09 ± 0.48
M
⊕
, and a bulk density of ${\rho _c} = 4.7_{ - 0.8}^{ + 0.9}{\rm{g}}$ g cm
−3
. The planets have been detected in transit by the Transiting Exoplanet Survey Satellite (TESS) mission and confirmed independently with archival and new precise radial velocities obtained with the HIRES and CARMENES instruments since 1998 and 2016, respectively. At a distance of 10 pc, HD 260655 has become the fourth closest known multitransiting planet system after HD 219134, LTT 1445 A, and AU Mic. Due to the apparent brightness of the host star (
J
= 6.7 mag), both planets are among the most suitable rocky worlds known today for atmospheric studies with the
James Webb
Space Telescope, both in transmission and emission.
CARMENES input catalog of M dwarfs Shan, Y.; Revilla, D.; Skrzypinski, S. L. ...
Astronomy and astrophysics (Berlin),
04/2024, Volume:
684
Journal Article
Peer reviewed
Open access
Aims. Knowledge of rotation periods ( P rot ) is important for understanding the magnetic activity and angular momentum evolution of late-type stars, as well as for evaluating radial velocity signals ...of potential exoplanets and identifying false positives. We measured photometric and spectroscopic P rot for a large sample of nearby bright M dwarfs with spectral types from M0 to M9, as part of our continual effort to fully characterize the Guaranteed Time Observation programme stars of the CARMENES survey. Methods. We analyse light curves chiefly from the SuperWASP survey and TESS data. We supplemented these with our own follow-up photometric monitoring programme from ground-based facilities, as well as spectroscopic indicator time series derived directly from the CARMENES spectra. Results. From our own analysis, we determined P rot for 129 stars. Combined with the literature, we tabulated P rot for 261 stars, or 75% of our sample. We developed a framework to evaluate the plausibility of all periods available for this sample by comparing them with activity signatures and checking for consistency between multiple measurements. We find that 166 of these stars have independent evidence that confirmed their P rot . There are inconsistencies in 27 periods, which we classify as debated. A further 68 periods are identified as provisional detections that could benefit from independent verification. We provide an empirical relation for the P rot uncertainty as a function of the P rot value, based on the dispersion of the measurements. We show that published formal errors seem to be often underestimated for periods longwards of ∼10 d. We examined rotation–activity relations with emission in X-rays, H α , Ca II H&K, and surface magnetic field strengths for this sample of M dwarfs. We find overall agreement with previous works, as well as tentative differences in the partially versus fully convective subsamples. We show P rot as a function of stellar mass, age, and galactic kinematics. With the notable exception of three transiting planet systems and TZ Ari, all known planet hosts in this sample have P rot ≳ 15 d. Conclusions. Inherent challenges in determining accurate and precise stellar P rot means independent verification is important, especially for inactive M dwarfs. Evidence of potential mass dependence in activity–rotation relations would suggest physical changes in the magnetic dynamo that warrants further investigation using larger samples of M dwarfs on both sides of the fully convective boundary. Important limitations need to be overcome before the radial velocity technique can be routinely used to detect and study planets around young and active stars.
The GAPS programme at TNG Mantovan, G.; Malavolta, L.; Desidera, S. ...
Astronomy and astrophysics (Berlin),
02/2024, Volume:
682
Journal Article
Peer reviewed
Open access
Context . Short-period giant planets ( P ≲ 10 days, M p >0.1 M J ) are frequently found to be solitary compared to other classes of exo-planets. Small inner companions to giant planets with P ≲ 15 ...days are known only in five compact systems: WASP-47, Kepler-730, WASP-132, TOI-1130, and TOI-2000. Here, we report the confirmation of TOI-5398, the youngest known compact multi-planet system composed of a hot sub-Neptune (TOI-5398 c, P c = 4.77271 days) orbiting interior to a short-period Saturn (TOI-5398 b, P b = 10.590547 days) planet, both transiting around a 650 ± 150 Myr G-type star. Aims . As part of the Global Architecture of Planetary Systems (GAPS) Young Object project, we confirmed and characterised this compact system, measuring the radius and mass of both planets, thus constraining their bulk composition. Methods . Using multi-dimensional Gaussian processes, we simultaneously modelled stellar activity and planetary signals from the Transiting Exoplanet Survey Satellite (TESS) Sector 48 light curve and our High Accuracy Radial velocity Planet Searcher (HARPS-N) radial velocity (RV) time series. We confirmed the planetary nature of both planets, TOI-5398 b and TOI-5398 c, and obtained a precise estimation of their stellar parameters. Results . Through the use of astrometric, photometric, and spectroscopic observations, our findings indicate that TOI-5398 is a young, active G dwarf star (650 ± 150 Myr) with a rotational period of P rot = 7.34 days. The transit photometry and RV measurements enabled us to measure both the radius and mass of planets b, R b = 10.30 ± 0.40 R ⊕ , M b = 58.7 ± 5.7 M ⊕ , and c, R c = 3.52 ± 0.19 R ⊕ , M c = 11.8 ± 4.8 M ⊕ . TESS observed TOI-5398 during sector 48 and no further observations are planned in the current Extended Mission, making our ground-based light curves crucial for improvement of the ephemeris. With a transmission spectroscopy metric (TSM) value of around 300, TOI-5398 b is the most amenable warm giant (10 < P < 100 days) for JWST atmospheric characterisation.
Context.
M dwarfs are ideal targets for the search of Earth-size planets in the habitable zone using the radial velocity method, and are attracting the attention of many ongoing surveys. One of the ...expected results of these surveys is that new multiple-star systems have also been found. This is the case also for the CARMENES survey, thanks to which nine new double-line spectroscopic binary systems have already been announced.
Aims.
Throughout the five years of the survey the accumulation of new observations has resulted in the detection of several new multiple-stellar systems with long periods and low radial-velocity amplitudes. Here we newly characterise the spectroscopic orbits and constrain the masses of eight systems and update the properties of a system that we had reported earlier.
Methods.
We derived the radial velocities of the stars using two-dimensional cross-correlation techniques and template matching. The measurements were modelled to determine the orbital parameters of the systems. We combined CARMENES spectroscopic observations with archival high-resolution spectra from other instruments to increase the time span of the observations and improve our analysis. When available, we also added archival photometric, astrometric, and adaptive optics imaging data to constrain the rotation periods and absolute masses of the components.
Results.
We determined the spectroscopic orbits of nine multiple systems, eight of which are presented for the first time. The sample is composed of five single-line binaries, two double-line binaries, and two triple-line spectroscopic triple systems. The companions of two of the single-line binaries, GJ 3626 and GJ 912, have minimum masses below the stellar boundary, and thus could be brown dwarfs. We found a new white dwarf in a close binary orbit around the M star GJ 207.1, located at a distance of 15.79 pc. From a global fit to radial velocities and astrometric measurements, we were able to determine the absolute masses of the components of GJ 282 C, which is one of the youngest systems with measured dynamical masses.
Two sub-Neptunes around the M dwarf TOI-1470 González-Álvarez, E.; Zapatero Osorio, M. R.; Caballero, J. A. ...
Astronomy and astrophysics (Berlin),
07/2023, Volume:
675
Journal Article
Peer reviewed
Open access
Aims.
A transiting planet candidate with a sub-Neptune radius orbiting the nearby (
d
= 51.9 ± 0.07 pc) M1.5 V star TOI-1470 with a period of ~2.5 d was announced by the NASA Transiting Exoplanet ...Survey Satellite (TESS), which observed the field of TOI-1470 in four different sectors. We aim to validate its planetary nature using precise radial velocities (RVs) taken with the CARMENES spectrograph.
Methods.
We obtained 44 RV measurements with CARMENES spanning eight months between 3 June 2020 and 17 January 2021. For a better characterization of the parent star activity, we also collected contemporaneous optical photometric observations at the
Joan Oró
and Sierra Nevada Observatories, and we retrieved archival photometry from the literature. We used ground-based photometric observations from MuSCAT and also from MuSCAT2 and MuSCAT3 to confirm the planetary transit signals. We performed a combined photometric and spectroscopic analysis by including Gaussian processes and Keplerian orbits to simultaneously account for the stellar activity and planetary signals.
Results.
We estimate that TOI-1470 has a rotation period of 29 ± 3d based on photometric and spectroscopic data. The combined analysis confirms the discovery of the announced transiting planet, TOI-1470 b, with an orbital period of 2.527093 ± 0.000003 d, a mass of 7.32
-1.24
+1.21
M
⊕
, and a radius of 2.18
-0.04
+0.04
R
⊕
. We also discover a second transiting planet that was not announced previously by TESS, TOI-1470 c, with an orbital period of 18.08816 ± 0.00006 d, a mass of 7.24
-2.77
+2.87
M
⊕
, and a radius of 2.47
-0.02
+0.02
R
⊕
. The two planets are placed on the same side of the radius valley of M dwarfs and lie between TOI-1470 and the inner border of its habitable zone.
Aims
.
We report the discovery and validation of two TESS exoplanets orbiting faint M dwarfs: TOI-4479b and TOI-2081b.
Methods
.
We jointly analyzed space (TESS mission) and ground-based (MuSCAT2, ...MuSCAT3 and SINISTRO instruments) light curves using our multicolor photometry transit analysis pipeline. This allowed us to compute contamination limits for both candidates and validate them as planet-sized companions.
Results
.
We found TOI-4479b to be a sub-Neptune-sized planet (
R
p
= 2.82
−0.63
+0.65
R
⊕
) and TOI-2081b to be a super-Earth-sized planet (
R
p
= 2.04
−0.54
+0.50
R
⊕
). Furthermore, we obtained that TOI-4479b, with a short orbital period of 1.15890
−0.00001
+0.00002
days, lies within the Neptune desert and is in fact the largest nearly ultra-short period planet around an M dwarf known to date.
Conclusions
.
These results make TOI-4479b rare among the currently known exoplanet population of M dwarf stars and an especially interesting target for spectroscopic follow-up and future studies of planet formation and evolution.
ABSTRACT
We report the discovery of two mini-Neptunes in near 2:1 resonance orbits (P = 7.610303 d for HIP 113103 b and P = 14.245651 d for HIP 113103 c) around the adolescent K-star HIP 113103 (TIC ...121490076). The planet system was first identified from the TESS mission, and was confirmed via additional photometric and spectroscopic observations, including a ∼17.5 h observation for the transits of both planets using ESA CHEOPS. We place ≤4.5 min and ≤2.5 min limits on the absence of transit timing variations over the 3 yr photometric baseline, allowing further constraints on the orbital eccentricities of the system beyond that available from the photometric transit duration alone. With a planetary radius of Rp = $1.829_{-0.067}^{+0.096}$ R⊕, HIP 113103 b resides within the radius gap, and this might provide invaluable information on the formation disparities between super-Earths and mini-Neptunes. Given the larger radius Rp = $2.40_{-0.08}^{+0.10}$ R⊕ for HIP 113103 c, and close proximity of both planets to HIP 113103, it is likely that HIP 113103 b might have lost (or is still losing) its primordial atmosphere. We therefore present simulated atmospheric transmission spectra of both planets using JWST, HST, and Twinkle. It demonstrates a potential metallicity difference (due to differences in their evolution) would be a challenge to detect if the atmospheres are in chemical equilibrium. As one of the brightest multi sub-Neptune planet systems suitable for atmosphere follow up, HIP 113103 b and HIP 113103 c could provide insight on planetary evolution for the sub-Neptune K-star population.
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