The GAPS Programme at TNG Damasso, M.; Lanza, A. F.; Benatti, S. ...
Astronomy and astrophysics (Berlin),
10/2020, Volume:
642
Journal Article
Peer reviewed
Open access
Context.
Detecting and characterising exoworlds around very young stars (age ≤10 Myr) are key aspects of exoplanet demographic studies, especially for understanding the mechanisms and timescales of ...planet formation and migration. Any reliable theory for such physical phenomena requires a robust observational database to be tested. However, detection using the radial velocity method alone can be very challenging because the amplitude of the signals caused by the magnetic activity of such stars can be orders of magnitude larger than those induced even by massive planets.
Aims.
We observed the very young (~2 Myr) and very active star V830 Tau with the HARPS-N spectrograph between October 2017 and March 2020 to independently confirm and characterise the previously reported hot Jupiter V830 Tau b (
K
b
= 68 ± 11 m s
−1
;
m
b
sin
i
b
= 0.57 ± 0.10
M
Jup
;
P
b
= 4.927 ± 0.008 d).
Methods.
Because of the observed ~1 km s
−1
radial velocity scatter that can clearly be attributed to the magnetic activity of V830 Tau, we analysed radial velocities extracted with different pipelines and modelled them using several state-of-the-art tools. We devised injection-recovery simulations to support our results and characterise our detection limits. The analysis of the radial velocities was aided by a characterisation of the stellar activity using simultaneous photometric and spectroscopic diagnostics.
Results.
Despite the high quality of our HARPS-N data and the diversity of tests we performed, we were unable to detect the planet V830 Tau b in our data and cannot confirm its existence. Our simulations show that a statistically significant detection of the claimed planetary Doppler signal is very challenging.
Conclusions.
It is important to continue Doppler searches for planets around young stars, but utmost care must be taken in the attempt to overcome the technical difficulties to be faced in order to achieve their detection and characterisation. This point must be kept in mind when assessing their occurrence rate, formation mechanisms, and migration pathways, especially without evidence of their existence from photometric transits.
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The GAPS Programme at TNG Biazzo, K.; D’Orazi, V.; Desidera, S. ...
Astronomy and astrophysics (Berlin),
08/2022, Volume:
664
Journal Article
Peer reviewed
Open access
Context.
Exoplanetary properties strongly depend on stellar properties: to know the planet with accuracy and precision it is necessary to know the star as accurately and precisely as possible.
Aims.
...Our immediate aim is to characterize in a homogeneous and accurate way a sample of 27 transiting planet-hosting stars observed within the Global Architecture of Planetary System program. For the wide visual binary XO-2, we considered both components (N: hosting a transiting planet; S: without a known transiting planet). Our final goal is to widely analyze the sample by deriving several stellar properties, abundances of many elements, kinematic parameters, and discuss them in the context of planetary formation.
Methods.
We determined the stellar parameters (effective temperature, surface gravity, rotational velocity) and abundances of 26 elements (Li, C, N, O, Na, Mg, Al, Si, S, Ca, Sc, Ti, V, Cr, Fe, Mn, Co, Ni, Cu, Zn, Y, Zr, Ba, La, Nd, Eu). Our study is based on high-resolution HARPS-N at TNG and FEROS at ESO spectra and uniform techniques. Depending on stellar parameters and chemical elements, we used line equivalent widths or spectral synthesis methods. We derived kinematic properties taking advantage of
Gaia
data and for the first time in exoplanet host stars we estimated ages using elemental ratios as chemical clocks.
Results.
The effective temperature of our stars is ~4400–6700 K, while the iron abundance Fe/H is within −0.3 and 0.4 dex. Lithium is present in seven stars. The X/H and X/Fe abundances versus Fe/H are consistent with the Galactic chemical evolution. The dependence of X/Fe with the condensation temperature is critically analyzed with respect to stellar and kinematic properties. All targets with measured C and O abundances show C/O < 0.8, compatible with Si present in rock-forming minerals. Mean C/O and C/O values are slightly lower than for the Sun. Most of targets show 1.0 < Mg/Si < 1.5, compatible with Mg distributed between olivine and pyroxene, and mean Mg/Si lower than for the Sun. HAT-P-26, the target hosting the lowest-mass planet, shows the highest Mg/Si ratio. From our chemodynamical analysis we find agreement between ages and position within the Galactic disk. Finally, we note a tendency for higher-density planets to be around metal-rich stars and hints of higher stellar abundances of some volatiles (e.g., O) for lower-mass planets. We cannot exclude that part of our results could be also related to the location of the stars within the Galactic disk.
Conclusions.
We try to trace the planetary migration scenario from the composition of the planets related to the chemical composition of the hosting stars. This kind of study will be useful for upcoming space mission data to get more insights into the formation-migration mechanisms.
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43.
The GAPS Programme at TNG Borsa, F.; Lanza, A. F.; Raspantini, I. ...
Astronomy and astrophysics (Berlin),
09/2021, Volume:
653
Journal Article
Peer reviewed
Open access
Context.
Giant planets in short-period orbits around bright stars represent optimal candidates for atmospheric and dynamical studies of exoplanetary systems.
Aims.
We aim to analyse four transits of ...WASP-33b observed with the optical high-resolution HARPS-N spectrograph to confirm its nodal precession, study its atmosphere, and investigate the presence of star-planet interactions.
Methods.
We extracted the mean line profiles of the spectra using the least-squares deconvolution method, and we analysed the Doppler shadow and the radial velocities. We also derived the transmission spectrum of the planet, correcting it for the stellar contamination due to rotation, centre-to-limb variations, and pulsations.
Results.
We confirm the previously discovered nodal precession of WASP-33b, almost doubling the time coverage of the inclination and projected spin-orbit angle variation. We find that the projected obliquity reached a minimum in 2011, and we used this constraint to derive the geometry of the system, and in particular its obliquity at that epoch (
ϵ
= 113.99° ± 0.22°) and the inclination of the stellar spin axis (
i
s
= 90.11° ± 0.12°). We also derived the gravitational quadrupole moment of the star
J
2
= (6.73 ± 0.22) × 10
−5
, which we find to be in close agreement with the theoretically predicted value. Small systematics errors are computed by shifting the date of the minimum projected obliquity. We present detections of H
α
and H
β
absorption in the atmosphere of the planet, with a contrast almost twice as small as that previously detected in the literature. We also find evidence for the presence of a pre-transit signal, which repeats in all four analysed transits and should thus be related to the planet. The most likely explanation lies in a possible excitation of a stellar pulsation mode by the presence of the planetary companion.
Conclusions.
A future common analysis of all available datasets in the literature will help shed light on the possibility that the observed Balmer lines’ transit depth variations are related to stellar activity and pulsation, and to set constraints on the planetary temperature–pressure structure and thus on the energetics possibly driving atmospheric escape. A complete orbital phase coverage of WASP-33b with high-resolution spectroscopic (and spectro-polarimetric) observations could help us to understand the nature of the pre-transit signal.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
45.
The GAPS Programme at TNG Claudi, R.; Bruno, G.; Fossati, L. ...
Astronomy and astrophysics (Berlin),
02/2024, Volume:
682
Journal Article
Peer reviewed
Context . Stellar activity is the most relevant types of astrophysical noise that affect the discovery and characterization of extrasolar planets. On the other hand, the amplitude of stellar activity ...could hint at an interaction between the star and a close-in giant planet. Progress has been made in recent years in understanding how to deal with stellar activity and search for observational evidence of star-planet interactions. Aims . The aim of this work is to characterize the chromospheric activity of stars hosting short-period exoplanets by studying the correlations between the chromospheric emission (CE) in the Ca II H&K and the planetary parameters. Methods . We measured CE in the Ca II H&K lines using more than 1900 high-resolution spectra of a sample composed of 76 targets, observed with the HARPS-N spectrograph between 2012 and 2020. We transformed the fluxes into bolometric- and photospheric-corrected chromospheric emission ratios, R ′ HK . Furthermore, we completed the sample of hosts digging for data in previous works. Stellar parameters T eff , B – V , and V were retrieved homogeneously from the Gaia DR3. Then, M ★ , R ★ , and ages were determined from isochrone fitting. We retrieved planetary data from the literature and catalogs. The search for correlations between the log( R ′ HK ) and planetary parameters have been performed through both Spearman’s rank and its statistics as well as the more sophisticated Gaussian mixture model method. Results . We found that the distribution of log( R ′ HK ) for the transiting planet hosts is different from the distribution of field main-sequence and sub-giant stars. The log( R ′ HK ) of planetary hosts is correlated with planetary parameters proportional to the planetary radius to the power of n ( R P n , indicating a common origin for the correlations. The statistical analysis has also highlighted four clusters of host stars with different behavior in terms of their stellar activity with respect to the planetary surface gravity. Some of the host stars have a value of log( R ′ HK ) that is lower than the basal level of activity for main sequence stars. The planets of these systems are very close to filling their Roche lobe, suggesting that they evaporate through hydrodynamic escape under the strong irradiation of the host star, creating shrouds that absorb the core of the chromospheric resonance lines.
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46.
The GAPS programme with HARPS-N at TNG Covino, E; Esposito, M; Barbieri, M ...
Astronomy and astrophysics (Berlin),
06/2013, Volume:
554
Journal Article
Peer reviewed
Open access
Our understanding of the formation and evolution of planetary systems is still fragmentary because most of the current data provide limited information about the orbital structure and dynamics of ...these systems. The knowledge of the orbital properties for a variety of systems and at different ages yields information on planet migration and on star-planet tidal interaction mechanisms. In this context, a long-term, multi-purpose, observational programme has started with HARPS-N at TNG and aims to characterise the global architectural properties of exoplanetary systems. The goal of this first paper is to fully characterise the orbital properties of the transiting system Qatar-1 as well as the physical properties of the star and the planet. We find that the system is well aligned and fits well within the general lambda versus Tsubeff trend. We can definitely rule out any significant orbital eccentricity. The evolutionary status of the system is inferred based on gyrochronology, and the present orbital configuration and timescale for orbital decay are discussed in terms of star-planet tidal interactions.
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The GAPS Programme at TNG Basilicata, M.; Giacobbe, P.; Bonomo, A. S. ...
Astronomy and astrophysics (Berlin),
6/2024, Volume:
686
Journal Article
Peer reviewed
Context. The atmospheric characterisation of hot and warm Neptune-size exoplanets is challenging mainly due to their relatively small radius and atmospheric scale height, which reduce the amplitude ...of atmospheric spectral features. The warm-Neptune HAT-P-11 b is a remarkable target for atmospheric characterisation because of the large brightness of its host star ( V = 9.46 mag; H = 7.13 mag). Aims. The aims of this work are to review the main physical and architectural properties of the HAT-P-11 planetary system, and to probe the presence of eight molecular species in the atmosphere of HAT-P-11 b through near-infrared (NIR) high-resolution transmission spectroscopy. Methods. We reviewed the physical and architectural properties of the HAT-P-11 planetary system by analysing transits and occultations of HAT-P-11 b from the Kepler data set as well as HIRES at Keck archival radial-velocity data. We modelled the latter with Gaussian-process regression and a combined quasi-periodic and squared-exponential kernel to account for stellar variations on both (short-term) rotation and (long-term) activity-cycle timescales. In order to probe the atmospheric composition of HAT-P-11 b, we observed four transits of this target with the NIR GIANO-B at TNG spectrograph and cross-correlated the data with template atmospheric transmission spectra. Results. We find that the long-period radial-velocity signal previously attributed to the HAT-P-11 c planet ( P ~ 9.3 yr; M p sin i ~ 1.6 M J ; e ~ 0.6) is more likely due to the stellar magnetic activity cycle. Nonetheless, the H IPPARCOS - Gaia difference in the proper-motion anomaly suggests that an outer-bound companion might still exist. For HAT-P-11 b, we measure a radius of R p = 0.4466 ± 0.0059 R J , a mass of M p = 0.0787 ± 0.0048 M J , a bulk density of ρ p = 1.172 ± 0.085 g cm −3 , and an orbital eccentricity of e = 0.2577 −0.0025 +0.0033 . These values are compatible with those from the literature. Probing its atmosphere, we detect the presence of two molecular species, H 2 O and NH 3 , with a S/N of 5.1 and 5.3, and a significance of 3.4 σ and 5.0 σ , respectively. We also tentatively detect the presence of CO 2 and CH 4 , with a S/N of 3.0 and 4.8, and a significance of 3.2 σ and 2.6 σ , respectively. Conclusions. We revisit the HAT-P-11 planetary system, confirm the presence of H 2 O, and report the detection of NH 3 in the atmosphere of HAT-P-11 b, also finding hints for the presence of CO 2 and CH 4 that need to be confirmed by further observations.
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48.
The GAPS Programme at TNG Basilicata, M; Giacobbe, P; Bonomo, A S ...
Astronomy and astrophysics (Berlin),
06/2024, Volume:
686
Journal Article
Peer reviewed
Context. The atmospheric characterisation of hot and warm Neptune-size exoplanets is challenging mainly due to their relatively small radius and atmospheric scale height, which reduce the amplitude ...of atmospheric spectral features. The warm-Neptune HAT-P-11 b is a remarkable target for atmospheric characterisation because of the large brightness of its host star (V = 9.46 mag; H = 7.13 mag). Aims. The aims of this work are to review the main physical and architectural properties of the HAT-P-11 planetary system, and to probe the presence of eight molecular species in the atmosphere of HAT-P-11 b through near-infrared (NIR) high-resolution transmission spectroscopy. Methods. We reviewed the physical and architectural properties of the HAT-P-11 planetary system by analysing transits and occultations of HAT-P-11 b from the Kepler data set as well as HIRES at Keck archival radial-velocity data. We modelled the latter with Gaussian-process regression and a combined quasi-periodic and squared-exponential kernel to account for stellar variations on both (short-term) rotation and (long-term) activity-cycle timescales. In order to probe the atmospheric composition of HAT-P-11 b, we observed four transits of this target with the NIR GIANO-B at TNG spectrograph and cross-correlated the data with template atmospheric transmission spectra. Results. We find that the long-period radial-velocity signal previously attributed to the HAT-P-11 c planet (P ~ 9.3 yr; Mp sin i ~ 1.6 MJ; e ~ 0.6) is more likely due to the stellar magnetic activity cycle. Nonetheless, the HIPPARCOS-Gaia difference in the proper-motion anomaly suggests that an outer-bound companion might still exist. For HAT-P-11 b, we measure a radius of Rp = 0.4466 ± 0.0059 RJ, a mass of Mp = 0.0787 ± 0.0048 MJ, a bulk density of ρp = 1.172 ± 0.085 g cm−3, and an orbital eccentricity of e = 0.2577−0.0025+0.0033. These values are compatible with those from the literature. Probing its atmosphere, we detect the presence of two molecular species, H2O and NH3, with a S/N of 5.1 and 5.3, and a significance of 3.4 σ and 5.0 σ, respectively. We also tentatively detect the presence of CO2 and CH4, with a S/N of 3.0 and 4.8, and a significance of 3.2 σ and 2.6 σ, respectively. Conclusions. We revisit the HAT-P-11 planetary system, confirm the presence of H2O, and report the detection of NH3 in the atmosphere of HAT-P-11 b, also finding hints for the presence of CO2 and CH4 that need to be confirmed by further observations.
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49.
The GAPS Programme at TNG Sozzetti, A.; Pinamonti, M.; Damasso, M. ...
Astronomy and astrophysics (Berlin),
09/2023, Volume:
677
Journal Article
Peer reviewed
Open access
The nearby mid-K dwarf HIP 66074 was recently identified as host to a candidate super-Jupiter companion on a ∼300 day, almost edge-on, orbit, based on
Gaia
Data Release 3 (DR3) astrometry. Initial ...attempts at confirming the planetary nature of the signal based on publicly available radial-velocity (RV) observations uncovered an intriguing conundrum: the inferred RV semi-amplitude appears to be a factor of 15 smaller than the one predicted based on the
Gaia
solution (corresponding to a 7-
M
Jup
companion on a close to edge-on orbit). We present the results of intensive RV monitoring of HIP 66074 with the HARPS-N spectrograph. We detected the companion at the
Gaia
period, but with an extremely eccentric orbit (
e
= 0.948 ± 0.004), a semi-amplitude
K
= 93.9
−7.0
+9.4
m s
−1
, and a minimum mass
m
b
sin
i
b
= 0.79 ± 0.05
M
Jup
. We used detailed simulations of
Gaia
astrometry with the DR3 time-span to show that the conundrum can be fully resolved by taking into account the combination of the initially sub-optimal RV sampling and systematic biases in the
Gaia
astrometric solution, which include an underestimation of the eccentricity and incorrect identification of orbital inclination, which has turned out to correspond to a close to face-on configuration (
i
≲ 13°). With an estimated mass in the approximate range of 3 − 7
M
Jup
, we find that HIP 66074b (≡Gaia-3b) is the first exoplanet candidate astrometrically detected by
Gaia
to be successfully confirmed based on RV follow-up observations.
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Context. M-dwarf stars are promising targets for identifying and characterizing potentially habitable planets. K2-3 is a nearby (45 pc), early-type M dwarf hosting three small transiting planets, the ...outermost of which orbits close to the inner edge of the stellar (optimistic) habitable zone. The K2-3 system is well suited for follow-up characterization studies aimed at determining accurate masses and bulk densities of the three planets. Aims. Using a total of 329 radial velocity measurements collected over 2.5 years with the HARPS-N and HARPS spectrographs and a proper treatment of the stellar activity signal, we aim to improve measurements of the masses and bulk densities of the K2-3 planets. We use our results to investigate the physical structure of the planets. Methods. We analysed radial velocity time series extracted with two independent pipelines using Gaussian process regression. We adopted a quasi-periodic kernel to model the stellar magnetic activity jointly with the planetary signals. We used Monte Carlo simulations to investigate the robustness of our mass measurements of K2-3 c and K2-3 d, and to explore how additional high-cadence radial velocity observations might improve these values. Results. Even though the stellar activity component is the strongest signal present in the radial velocity time series, we are able to derive masses for both planet b (Mb = 6.6 ± 1.1 M⊕) and planet c (Mc = 3.1−1.2+1.3 M⊕) $M_{\textrm{c}}=3.1^{+1.3}_{-1.2}$Mc=3.1−1.2+1.3. The Doppler signal from K2-3 d remains undetected, likely because of its low amplitude compared to the radial velocity signal induced by the stellar activity. The closeness of the orbital period of K2-3 d to the stellar rotation period could also make the detection of the planetary signal complicated. Based on our ability to recover injected signals in simulated data, we tentatively estimate the mass of K2-3 d to be Md = 2.7 −0.8+1.2 M⊕ $_{\textrm{-0.8}}^{\textrm{+1.2}}$-0.8+1.2 M⊕. These mass measurements imply that the bulk densities and therefore the interior structures of the three planets may be similar. In particular, the planets may either have small H/He envelopes (<1%) or massive water layers, with a water content ≥50% of their total mass, on top of rocky cores. Placing further constraints on the bulk densities of K2-3 c and d is difficult; in particular, we would not have been able to detect the Doppler signal of K2-3 d even by adopting a semester of intense, high-cadence radial velocity observations with HARPS-N and HARPS.
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