Transmission spectroscopy is an important technique to probe the atmospheres of exoplanets. With the advent of the Transiting Exoplanet Survey Satellite (TESS) and, in the future, of the PLAnetary ...Transits and Oscillations of stars (PLATO), more and more transiting planets around bright stars will be found and the observing time of current large telescopes used to apply these techniques will not suffice. We demonstrate here that 2-m class telescopes equipped with spectrographs with high resolving power may be used for a certain number of potential targets. We obtained a timeseries of high-resolution Fiber-fed Extended Range Optical Spectrograph (FEROS) spectra at the 2.2-m telescope at La Silla of the very hot-Jupiter hosting planet, WASP-18b, and show that our upper limit is consistent with the expectations. This is the first analysis of its kind using 2-m class telescopes, and it serves to highlight their potential. In this context, we then proceed to discuss the suitability of this class of telescopes for the upcoming flood of scientifically interesting targets from the TESS space mission, and propose a methodology to select the most promising targets. This is of particular significance given that observing time on 2-m class telescopes is more readily available than on large 8-m class facilities.
Context.
In the time of large space surveys that provide tremendous amounts of precise data, it is highly desirable to have a commonly accepted methodology and system for the classification of ...variable stars. This is especially important for A-F stars, which can show intrinsic brightness variations due to both rotation and pulsations.
Aims.
The goal of our study is to provide a reliable classification of the variability of A-F stars brighter than 11 mag located in the northern TESS continuous viewing zone. We also aim to provide a thorough discussion about issues in the classification related to data characteristics and the issues arising from the similar light-curve shape generated by different physical mechanisms.
Methods.
We used TESS long- and short-cadence photometric data and corresponding Fourier transform to classify the variability type of the stars. We also used spectroscopic observations to determine the projected rotational velocity of a few stars.
Results.
We present a clear and concise classification system that is demonstrated on many examples. We find clear signs of variability in 3025 of 5923 studied stars (51%). For 1813 of these 3025 stars, we provide a classification; the rest cannot be unambiguously classified. Of the classified stars, 64.5% are pulsating stars of
g
-mode γ Doradus (GDOR) and
p
-mode
δ
Scuti types and their hybrids. We realised that the long- and short-cadence pre-search data conditioning simple aperture photometry data can differ significantly not only in amplitude but also in the content of instrumental and data-reduction artefacts, making the long-cadence data less reliable. We identified a new group of stars that show stable light curves and characteristic frequency spectrum patterns (8.5% of the classified stars). According to the position in the Hertzsprung-Russell diagram, these stars are likely GDOR stars but are on average about 200 K cooler than GDORs and have smaller amplitudes and longer periods. With the help of spectroscopic measurements of
v
sin
i
, we show that the variability of stars with unresolved groups of peaks located close to the positions of the harmonics in their frequency spectra (16% of the classified stars) can be caused by rotation rather than by pulsations. We show that without spectroscopic observations it can be impossible to unambiguously distinguish between ellipsoidal variability and rotational variability. We also applied our methodology to three previous studies and find significant discrepancies in the classification.
Conclusions.
We demonstrate how difficult the classification of variable A-F stars can be when using only photometric data, how the residual artefacts can produce false positives, and that some types cannot actually be distinguished without spectroscopic observations. Our analysis provides collections that can be used as training samples for automatic classification.
HD 191939 (TOI-1339) is a nearby (
d
= 54 pc), bright (
V
= 9 mag), and inactive Sun-like star (G9 V) known to host a multi-planet transiting system. Ground-based spectroscopic observations confirmed ...the planetary nature of the three transiting sub-Neptunes (HD 191939 b, c, and d) originally detected by TESS and were used to measure the masses for planets b and c with 3σ precision. These previous observations also reported the discovery of an additional Saturn-mass planet (HD 191939 e) and evidence for a further, very long-period companion (HD 191939 f). Here, we report the discovery of a new non-transiting planet in the system and a refined mass determination of HD 191939 d. The new planet, HD 191939 g, has a minimum mass of 13.5±2.0
M
⊕
and a period of about 280 days. This period places the planet within the conservative habitable zone of the host star, and near a 1:3 resonance with HD 191939 e. The compilation of 362 radial velocity measurements with a baseline of 677 days from four different high-resolution spectrographs also allowed us to refine the properties of the previously known planets, including a 4.6
σ
mass determination for planet d, for which only a 2
σ
upper limit had been set until now. We confirm the previously suspected low density of HD 191939 d, which makes it an attractive target for attempting atmospheric characterisation. Overall, the planetary system consists of three sub-Neptunes interior to a Saturn-mass and a Uranus-mass planet plus a high-mass long-period companion. This particular configuration has no counterpart in the literature and makes HD 191939 an exceptional multi-planet transiting system with an unusual planet demographic worthy of future observation.
We present the discovery and characterization of two sub-Neptunes in close orbits, as well as a tentative outer planet of a similar size, orbiting TOI-1260 – a low metallicity K6 V dwarf star. ...Photometry from Transiting Exoplanet Survey Satellite(TESS) yields radii of R(b) = 2.33 ± 0.10 and R(c) = 2.82 ± 0.15 Rꚛ, and periods of 3.13 and 7.49 d for TOI-1260 b and TOI-1260 c, respectively. We combined the TESS data with a series of ground-based follow-up observations to characterize the planetary system. From HARPS-N high-precision radial velocities we obtain M(b) = 8.6(+1.4,−1.5) and M(c) = 11.8(+3.4,−3.2) Mꚛ. The star is moderately active with a complex activity pattern, which necessitated the use of Gaussian process regression for both the light-curve detrending and the radial velocity modelling, in the latter case guided by suitable activity indicators. We successfully disentangle the stellar-induced signal from the planetary signals, underlining the importance and usefulness of the Gaussian process approach. We test the system’s stability against atmospheric photoevaporation and find that the TOI-1260 planets are classic examples of the structure and composition ambiguity typical for the 2–3 Rꚛ range.
The GAPS programme at TNG Mantovan, G.; Malavolta, L.; Desidera, S. ...
Astronomy and astrophysics (Berlin),
02/2024, Letnik:
682
Journal Article
Recenzirano
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.
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.
We report the discovery of TOI-1268b, a transiting Saturn-mass planet from the TESS space mission. With an age of less than 1 Gyr, derived from various age indicators, TOI-1268b is the youngest ...Saturn-mass planet known to date; it contributes to the small sample of well-characterised young planets. It has an orbital period of
P
= 8.1577080 ± 0.0000044 days, and transits an early K-dwarf star with a mass of
M
*
= 0.96 ± 0.04
M
⊙
, a radius of
R
*
= 0.92 ± 0.06
R
⊙
, an effective temperature of
T
eff
= 5300 ± 100 K, and a metallicity of 0.36 ± 0.06 dex. By combining TESS photometry with high-resolution spectra acquired with the Tull spectrograph at the McDonald Observatory, and the high-resolution spectrographs at the Tautenburg and Ondřejov Observatories, we measured a planetary mass of
M
p
= 96.4 ± 8.3
M
⊕
and a radius of
R
p
= 9.1 ± 0.6
R
⊕
. TOI-1268 is an ideal system for studying the role of star-planet tidal interactions for non-inflated Saturn-mass planets. We used system parameters derived in this paper to constrain the planet’s tidal quality factor to the range of 10
4.5–5.3
. When compared with the sample of other non-inflated Saturn-mass planets, TOI-1268b is one of the best candidates for transmission spectroscopy studies.
The TOI-1130 is a known planetary system around a K-dwarf consisting of a gas giant planet, TOI-1130 c on an 8.4-day orbit that is accompanied by an inner Neptune-sized planet, TOI-1130 b, with an ...orbital period of 4.1 days. We collected precise radial velocity (RV) measurements of TOI-1130 with the HARPS and PFS spectrographs as part of our ongoing RV follow-up program. We performed a photodynamical modeling of the HARPS and PFS RVs, along with transit photometry from the Transiting Exoplanet Survey Satellite (TESS) and the TESS Follow-up Observing Program (TFOP). We determined the planet masses and radii of TOI-1130 b and TOI-1130 c to be
M
b
= 19.28 ± 0.97
M
⊕
and
R
b
= 3.56 ± 0.13
R
⊕
, and
M
c
=
325.59 ± 5.59
M
⊕
and
R
c
= 13.32
−1.41
+1.55
R
⊕
, respectively. We have spectroscopically confirmed the existence of TOI-1130 b, which had previously only been validated. We find that the two planets have orbits with small eccentricities in a 2:1 resonant configuration. This is the first known system with a hot Jupiter and an inner lower mass planet locked in a mean-motion resonance. TOI-1130 belongs to the small, yet growing population of hot Jupiters with an inner low-mass planet that poses a challenge to the pathway scenario for hot Jupiter formation. We also detected a linear RV trend that is possibly due to the presence of an outer massive companion.
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