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Luca Malavolta

Publications and source records attributed to Luca Malavolta.

At least 19 recordsLinked to original sources
arXiv2026

HRMOS: A High-Resolution Multi-Object Spectrograph for the VLT

This White Paper presents the scientific rationale and instrument concept for HRMOS (High-Resolution Multi-Object Spectrograph), a next-generation instrument proposed for the ESO Very Large Telescope within the VLT 2030 roadmap. Current and planned facilities offer either multi-object spectroscopy or ultra-high spectral resolution, but not both. HRMOS fills this gap by combining very high spectral resolution, multi-object capability, and radial-velocity stability, enabling transformative studies in Galactic and extragalactic astrophysics. The baseline design provides a resolving power of R = 80000, radial-velocity precision of 10 m s-1 (goal: 5 m s-1), simultaneous observations of 50-60 targets, and broad optical coverage down to 385 nm. These capabilities enable precise measurements of elemental abundances, isotopic ratios, line profiles, and radial velocities for large stellar samples, including crowded fields, star clusters, the Galactic bulge, and nearby dwarf galaxies. HRMOS will address key questions on the age of the oldest stellar populations through nucleocosmochronology, the formation and survival of planetary systems, the assembly history of the Milky Way and satellites, the origin of the heaviest elements, stellar evolution, and the chemical and dynamical properties of the interstellar and circumgalactic medium. It will bridge large spectroscopic surveys and the next generation of extremely large telescopes, with strong synergies with 4MOST, Gaia, TESS, PLATO, the proposed Haydn mission, and future ELT instruments. Building on VLT/FLAMES heritage, HRMOS represents a strategic investment for European astronomy in the 2030s.

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arXiv2026

Understanding eccentric temperate giants: an in-depth study of the architecture and stellar obliquity of the TOI-2134 system

We revisit the TOI-2134 planetary system with three new high-cadence TESS sectors and 98 more spectra. This new analysis confirms the two orbiting planets by simultaneously modelling a total of eight sectors of corrected TESS photometry and 280 HARPS-N and SOPHIE radial velocities: an inner mini-Neptune in a near-circular $9.229198\pm0.000003$ days orbit, and an outer temperate sub-Saturn orbiting with a $95.852840\pm0.000042$ days period and eccentricity of $0.31\pm0.01$. The masses and radii of the planets were computed to be $9.37\pm0.54$ Me and $2.735\pm0.068$ Re for planet b, and $58.3\pm1.9$ Me and $7.35\pm0.18$ Re for planet c. The new data not only improves the detection significance and precisions on the planetary orbits, but also breaks the original multimodality in the eccentricity solution for the outer planet. We also detect a long-term trend in the radial velocity data, which we attribute to a stellar magnetic cycle. We investigate the spin-orbit alignment of the system via observations of the Rossiter-McLaughlin effect for TOI-2134~b with EXPRES and TOI-2134~c with PARAS-2. No RM effect was detected for planet b, but we find a 4.7$\sigma$ detection of a $59\pm31^{\circ}$ obliquity for planet c. Finally, we examine the architecture of the system, assess its completeness, investigate the planetary interior, and their suitability for follow-up atmospheric analysis.

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arXiv2026

Assessment of PLATO Science Performance

The PLATO mission is scheduled for launch early 2027. In this paper we present an overview of the performance drivers for the mission at the time where all flight models of the cameras have been tested and integrated on the optical bench. The PLATO consortium needs an estimate of the planet detection yield to dimension the ground-based radial velocity follow-up resources. We provide updated estimates on the yield of planet detections that can be expected from the mission under certain assumptions. As of today, large uncertainties remain on the planet occurrence rates, especially for small planets in long-period orbits, and on our ability to detect these planets in the presence of stellar variability and instrumental noise. To partially overcome these limitations, we compare results using different planet occurrence rates, detectability rates, and we include an estimate on the expected contribution of stellar variability to the noise budget. The final detection yield of PLATO will provide constraints to planet occurrence rates which in turn will help constraining planet formation models.

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arXiv2026

Constraining Small Planet Compositions for Future Missions

Accurate mass and radius measurements of small transiting exoplanets are essential for probing their compositions, formation histories, and potential habitability. We present a uniform analysis of six planetary systems (each hosting at least one small transiting planet): K2-79, K2-106, K2-111, K2-222, K2-263, and TOI-1634. Our study combines new CHEOPS transit observations with archival photometry from K2, TESS, and ground-based facilities, alongside new and archival radial velocity data from HARPS-N, HIRES, ESPRESSO, and others. For each system, we perform joint transit and RV modelling, achieving typical precisions better than 15% and 5% for mass and radius, respectively, and thus enabling precise bulk density determinations. These reveal a range of compositions, including rocky planets near the radius valley (e.g. K2-106 b, TOI-1634 b), intermediate-density planets requiring steam-rich or mixed volatile envelopes (e.g. K2-111 b, K2-263 b), and low-density regimes, consistent with gas dwarfs or water-worlds (e.g. K2-79 b, K2-222 b). Several systems show evidence of additional companions detectable via RVs but not seen in transit. The results highlight the value of coordinated CHEOPS and HARPS-N observations in delivering some of the most precise bulk densities for small planets to date and support the preparation for future atmospheric characterisation missions.

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arXiv2025

The HD 60779 Planetary System: A Transiting Sub-Neptune on a 30-day Orbit and a More Massive Outer World

We present the discovery of the planetary system orbiting the bright (V = 7.2), nearby (35 pc), Sun-like star HD 60779, which has a mass of 1.050 +/- 0.044 solar masses and a radius of 1.129 +/- 0.013 solar radii. We report two TESS transits and a subsequent CHEOPS transit of HD 60779 b, a sub-Neptune with a radius of 3.250 (+0.100 / -0.098) Earth radii on a 29.986175 (+0.000030 / -0.000033) day orbit. Additionally, 286 HARPS-N radial velocity measurements reveal the mass of planet b (14.7 +1.1 / -1.0 Earth masses) and the presence of an outer planet, HD 60779 c, with an orbital period of 104.25 (+0.30 / -0.29) days and a minimum mass (m sin i) of 27.7 +/- 1.6 Earth masses. Both planets' orbits are consistent with being circular, suggesting that they have a dynamically quiet history. The data are not sufficient to determine whether planet c transits. HD 60779's uniquely high systemic radial velocity (129.75 +/- 0.12 km/s) allows its Lyman-alpha emission to avoid absorption by the interstellar medium, making it a prime candidate for probing atmospheric escape from HD 60779 b. HD 60779 is also the third-brightest host of a sub-Neptune with orbital period greater than 25 days and with both mass and radius measured, distinguishing it in terms of accessibility to spectroscopic characterization.

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arXiv2025

The mass of the exo-Venus Gliese 12 b, as revealed by HARPS-N, ESPRESSO, and CARMENES

Small temperate planets are prime targets for exoplanet studies due to their possible similarities with the rocky planets in the Solar System. M dwarfs are promising hosts since the planetary signals are within our current detection capabilities. Gliese 12 b is a Venus-sized temperate planet orbiting a quiet M dwarf. We present here the first precise mass measurement of this small exoplanet. We performed a detailed analysis using HARPS-N, ESPRESSO, and CARMENES radial velocities, along with new and archival \tess, \cheops, and MuSCAT2/3 photometry data. From fitting the available data, we find that the planet has a radius of $R_\mathrm{p} = 0.93\pm0.06 \,\mathrm{R_\oplus}$ and a mass of $M_\mathrm{p} = 0.95^{+0.29}_{-0.30} \,\mathrm{M_\oplus}$ (a $3.2\sigma$ measurement of the semi-amplitude $K=0.67\pm0.21\,\mathrm{m\,s^{-1}}$), and is on an orbit with a period of $12.761418^{+0.000060}_{-0.000055}\,\mathrm{d}$. A variety of techniques were utilised to attenuate stellar activity signals. Gliese 12 b has an equilibrium temperature of $T_\mathrm{eq}=317 \pm 8\,\mathrm{K}$, assuming an albedo of zero, and a density consistent with that of Earth and Venus ($\rho_\mathrm{p}=6.4\pm2.4\,\mathrm{g\,cm^{-3}}$). We find that Gliese 12 b has a predominantly rocky interior and simulations indicate that it is unlikely to have retained any of its primordial gaseous envelope. The bulk properties of Gliese 12 b place it in an extremely sparsely populated region of both mass--radius and density--$T_\mathrm{eq}$ parameter space, making it a prime target for follow-up observations, including Lyman-$\alpha$ studies.

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arXiv2025

The Magnetically Induced Radial Velocity Variation of Gliese 341 and an Upper Limit to the Mass of Its Transiting Earth-sized Planet

The Transiting Exoplanet Survey Satellite (TESS) mission identified a potential 0.88 REarth planet with a period of 7.577 days, orbiting the nearby M1V star GJ 341 (TOI 741.01). This system has already been observed by the James Webb Space Telescope (JWST) to search for presence of an atmosphere on this planet. Here, we present an in-depth analysis of the GJ 341 system using all available public data. We provide improved parameters for the host star, an updated value of the planet radius, and support the planetary nature of the object (now GJ 341 b). We use 57 HARPS radial velocities to model the magnetic cycle and activity of the host star, and constrain the mass of GJ 341 b to upper limits of 4.0 MEarth (3 sigma) and 2.9 MEarth (1 sigma). We also rule out the presence of additional companions with M sin i > 15.1 MEarth, and P < 1750 days, and the presence of contaminating background objects during the TESS and JWST observations. These results provide key information to aid the interpretation of the recent JWST atmospheric observations and other future observations of this planet.

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arXiv2024

The TESS-Keck Survey. XII. A Dense 1.8 R$_\oplus$ Ultra-Short-Period Planet Possibly Clinging to a High-Mean-Molecular-Weight Atmosphere After the First Gyr

The extreme environments of ultra-short-period planets (USPs) make excellent laboratories to study how exoplanets obtain, lose, retain, and/or regain gaseous atmospheres. We present the confirmation and characterization of the USP TOI-1347 b, a $1.8 \pm 0.1$ R$_\oplus$ planet on a 0.85 day orbit that was detected with photometry from the TESS mission. We measured radial velocities of the TOI-1347 system using Keck/HIRES and HARPS-N and found the USP to be unusually massive at $11.1 \pm 1.2$ M$_\oplus$. The measured mass and radius of TOI-1347 b imply an Earth-like bulk composition. A thin H/He envelope (>0.01% by mass) can be ruled out at high confidence. The system is between 1 and 1.8 Gyr old; therefore, intensive photoevaporation should have concluded. We detected a tentative phase curve variation (3$\sigma$) and a secondary eclipse (2$\sigma$) in TESS photometry, which if confirmed could indicate the presence of a high-mean-molecular-weight atmosphere. We recommend additional optical and infrared observations to confirm the presence of an atmosphere and investigate its composition.

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arXiv2024

Characterization of K2-167 b and CALM, a new stellar activity mitigation method

We report precise radial velocity (RV) observations of HD 212657 (= K2-167), a star shown by K2 to host a transiting sub-Neptune-sized planet in a 10 day orbit. Using Transiting Exoplanet Survey Satellite (TESS) photometry, we refined the planet parameters, especially the orbital period. We collected 74 precise RVs with the HARPS-N spectrograph between August 2015 and October 2016. Although this planet was first found to transit in 2015 and validated in 2018, excess RV scatter originally limited mass measurements. Here, we measure a mass by taking advantage of reductions in scatter from updates to the HARPS-N Data Reduction System (2.3.5) and our new activity mitigation method called CCF Activity Linear Model (CALM), which uses activity-induced line shape changes in the spectra without requiring timing information. Using the CALM framework, we performed a joint fit with RVs and transits using EXOFASTv2 and find $M_p = 6.3_{-1.4}^{+1.4}$ $M_{\oplus}$ and $R_p = 2.33^{+0.17}_{-0.15}$ $R_{\oplus}$, which places K2-167 b at the upper edge of the radius valley. We also find hints of a secondary companion at a $\sim$ 22 day period, but confirmation requires additional RVs. Although characterizing lower-mass planets like K2-167 b is often impeded by stellar variability, these systems especially help probe the formation physics (i.e. photoevaporation, core-powered mass loss) of the radius valley. In the future, CALM or similar techniques could be widely applied to FGK-type stars, help characterize a population of exoplanets surrounding the radius valley, and further our understanding of their formation.

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arXiv2023

TESS Spots a Super-Puff: The Remarkably Low Density of TOI-1420b

We present the discovery of TOI-1420b, an exceptionally low-density ($ρ= 0.08\pm0.02$ g cm$^{-3}$) transiting planet in a $P = 6.96$ day orbit around a late G dwarf star. Using transit observations from TESS, LCOGT, OPM, Whitin, Wendelstein, OAUV, Ca l'Ou, and KeplerCam along with radial velocity observations from HARPS-N and NEID, we find that the planet has a radius of $R_p$ = 11.9 $\pm$ 0.3 $R_\Earth$ and a mass of $M_p$ = 25.1 $\pm$ 3.8 $M_\Earth$. TOI-1420b is the largest-known planet with a mass less than $50M_\Earth$, indicating that it contains a sizeable envelope of hydrogen and helium. We determine TOI-1420b's envelope mass fraction to be $f_{env} = 82^{+7}_{-6}\%$, suggesting that runaway gas accretion occurred when its core was at most $4-5\times$ the mass of the Earth. TOI-1420b is similar to the planet WASP-107b in mass, radius, density, and orbital period, so a comparison of these two systems may help reveal the origins of close-in low-density planets. With an atmospheric scale height of 1950 km, a transmission spectroscopy metric of 580, and a predicted Rossiter-McLaughlin amplitude of about $17$ m s$^{-1}$, TOI-1420b is an excellent target for future atmospheric and dynamical characterization.

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arXiv2023

Hyades Member K2-136c: The Smallest Planet in an Open Cluster with a Precisely Measured Mass

K2-136 is a late-K dwarf ($0.742\pm0.039$ M$_\odot$) in the Hyades open cluster with three known, transiting planets and an age of $650\pm70$ Myr. Analyzing K2 photometry, we found that planets K2-136b, c, and d have periods of $8.0$, $17.3$, and $25.6$ days and radii of $1.014\pm0.050$ R$_\oplus$, $3.00\pm0.13$ R$_\oplus$, and $1.565\pm0.077$ R$_\oplus$, respectively. We collected 93 radial velocity measurements (RVs) with the HARPS-N spectrograph (TNG) and 22 RVs with the ESPRESSO spectrograph (VLT). Analyzing HARPS-N and ESPRESSO data jointly, we found K2-136c induced a semi-amplitude of $5.49\pm0.53$ m s$^{-1}$, corresponding to a mass of $18.1\pm1.9$ M$_\oplus$. We also placed $95$% upper mass limits on K2-136b and d of $4.3$ and $3.0$ M$_\oplus$, respectively. Further, we analyzed HST and XMM-Newton observations to establish the planetary high-energy environment and investigate possible atmospheric loss. K2-136c is now the smallest planet to have a measured mass in an open cluster and one of the youngest planets ever with a mass measurement. K2-136c has $\sim$75% the radius of Neptune but is similar in mass, yielding a density of $3.69^{+0.67}_{-0.56}$ g cm$^{-3}$ ($\sim$2-3 times denser than Neptune). Mass estimates for K2-136b (and possibly d) may be feasible with more RV observations, and insights into all three planets' atmospheres through transmission spectroscopy would be challenging but potentially fruitful. This research and future mass measurements of young planets are critical for investigating the compositions and characteristics of small exoplanets at very early stages of their lives and providing insights into how exoplanets evolve with time.

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arXiv2023

The PEPSI Exoplanet Transit Survey (PETS). II. A Deep Search for Thermal Inversion Agents in KELT-20 b/MASCARA-2 b with Emission and Transmission Spectroscopy

Recent observations have shown that the atmospheres of ultra hot Jupiters (UHJs) commonly possess temperature inversions, where the temperature increases with increasing altitude. Nonetheless, which opacity sources are responsible for the presence of these inversions remains largely observationally unconstrained. We used LBT/PEPSI to observe the atmosphere of the UHJ KELT-20 b in both transmission and emission in order to search for molecular agents which could be responsible for the temperature inversion. We validate our methodology by confirming previous detections of Fe I in emission at $16.9σ$. Our search for the inversion agents TiO, VO, FeH, and CaH results in non-detections. Using injection-recovery testing we set $4σ$ upper limits upon the volume mixing ratios for these constituents as low as $\sim1\times10^{-9}$ for TiO. For TiO, VO, and CaH, our limits are much lower than expectations from an equilibrium chemical model, while we cannot set constraining limits on FeH with our data. We thus rule out TiO and CaH as the source of the temperature inversion in KELT-20 b, and VO only if the line lists are sufficiently accurate.

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arXiv2022

Kepler-102: Masses and Compositions for a Super-Earth and Sub-Neptune Orbiting an Active Star

Radial velocity (RV) measurements of transiting multiplanet systems allow us to understand the densities and compositions of planets unlike those in the Solar System. Kepler-102, which consists of 5 tightly packed transiting planets, is a particularly interesting system since it includes a super-Earth (Kepler-102d) and a sub-Neptune-sized planet (Kepler-102e) for which masses can be measured using radial velocities. Previous work found a high density for Kepler-102d, suggesting a composition similar to that of Mercury, while Kepler-102e was found to have a density typical of sub-Neptune size planets; however, Kepler-102 is an active star, which can interfere with RV mass measurements. To better measure the mass of these two planets, we obtained 111 new RVs using Keck/HIRES and TNG/HARPS-N and modeled Kepler-102's activity using quasi-periodic Gaussian Process Regression. For Kepler-102d, we report a mass upper limit of M$_{d} < $5.3 M$_{\oplus}$ [95\% confidence], a best-fit mass of M$_{d}$=2.5 $\pm$ 1.4 M$_{\oplus}$, and a density of $ρ_{d}$=5.6 $\pm$ 3.2 g/cm$^{3}$ which is consistent with a rocky composition similar in density to the Earth. For Kepler-102e we report a mass of M$_{e}$=4.7 $\pm$ 1.7 M$_{\oplus}$ and a density of $ρ_{e}$=1.8 $\pm$ 0.7 g/cm$^{3}$. These measurements suggest that Kepler-102e has a rocky core with a thick gaseous envelope comprising 2-4% of the planet mass and 16-50% of its radius. Our study is yet another demonstration that accounting for stellar activity in stars with clear rotation signals can yield more accurate planet masses, enabling a more realistic interpretation of planet interiors.

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arXiv2022

Independent validation of the temperate Super-Earth HD79211 b using HARPS-N

We present high-precision radial velocities (RVs) from the HARPS-N spectrograph for HD79210 and HD79211, two M0V members of a gravitationally-bound binary system. We detect a planet candidate with a period of $24.421^{+0.016}_{-0.017}$ days around HD79211 in these HARPS-N RVs, validating the planet candidate originally identified in CARMENES RV data alone. Using HARPS-N, CARMENES and HIRES RVs spanning a total of 25 years, we further refine the planet candidate parameters to $P=24.422\pm0.014$ days, $K=3.19\pm0.27$ m/s, $M$ sin $i = 10.6 \pm 1.2 M_\oplus$, and $a = 0.142 \pm0.005$ au. We do not find any additional planet candidate signals in the data of HD79211 nor do we find any planet candidate signals in HD79210. This system adds to the number of exoplanets detected in binaries with M dwarf members, and serves as a case study for planet formation in stellar binaries.

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arXiv2022

Characterization of exoplanetary atmospheres with SLOPpy

Transmission spectroscopy is among the most fruitful techniques to infer the main opacity sources present in the upper atmosphere of a transiting planet and to constrain the composition of the thermosphere and of the unbound exosphere. Not having a public tool able to automatically extract a high-resolution transmission spectrum creates a problem of reproducibility for scientific results. As a consequence, it is very difficult to compare the results obtained by different research groups and to carry out a homogeneous characterization of the exoplanetary atmospheres. In this work, we present a standard, publicly available, user-friendly tool, named SLOPpy (Spectral Lines Of Planets with python), to automatically extract and analyze the optical transmission spectrum of exoplanets as accurately as possible. Several data reduction steps are first performed by SLOPpy to correct the input spectra for sky emission, atmospheric dispersion, the presence of telluric features and interstellar lines, center-to-limb variation, and Rossiter-McLaughlin effect, thus making it a state-of-the-art tool. The pipeline has successfully been applied to HARPS and HARPS-N data of ideal targets for atmospheric characterization. To first assess the code's performance and to validate its suitability, here we present a comparison with the results obtained from the previous analyses of other works on HD 189733 b, WASP-76 b, WASP-127 b, and KELT-20 b. Comparing our results with other works that have analyzed the same datasets, we conclude that this tool gives results in agreement with the published results within 1$σ$ most of the time, while extracting, with SLOPpy, the planetary signal with a similar or higher statistical significance.

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arXiv2022

The GAPS Programme at TNG XXXIX -- Multiple molecular species in the atmosphere of the warm giant planet WASP-80 b unveiled at high resolution with GIANO-B

Detections of molecules in the atmosphere of gas giant exoplanets allow us to investigate the physico-chemical properties of the atmospheres. Their inferred chemical composition is used as tracer of planet formation and evolution mechanisms. Currently, an increasing number of detections is showing a possible rich chemistry of the hotter gaseous planets, but whether this extends to cooler giants is still unknown. We observed four transits of WASP-80 b, a warm transiting giant planet orbiting a late-K dwarf star with the near-infrared GIANO-B spectrograph installed at the Telescopio Nazionale Galileo and performed high resolution transmission spectroscopy analysis. We report the detection of several molecular species in its atmosphere. Combining the four nights and comparing our transmission spectrum to planetary atmosphere models containing the signature of individual molecules within the cross-correlation framework, we find the presence of H2O, CH4, NH3 and HCN with high significance, tentative detection of CO2, and inconclusive results for C2H2 and CO. A qualitative interpretation of these results, using physically motivated models, suggests an atmosphere consistent with solar composition and the presence of disequilibrium chemistry and we therefore recommend the inclusion of the latter in future modelling of sub-1000K planets.

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arXiv2022

The Interferometric Binary Epsilon Cancri in Praesepe: Precise Masses and Age

We observe the brightest member of the Praesepe cluster, Epsilon Cancri, to precisely measure the characteristics of the stars in this binary system, en route to a new measurement of the cluster's age. We present spectroscopic radial velocity measurements and interferometric observations of the sky-projected orbit to derive the masses, which we find to be M_1/M_sun = 2.420 +/- 0.008 and M_2/M_sun = 2.226 +/- 0.004. We place limits on the color-magnitude positions of the stars by using spectroscopic and interferometric luminosity ratios while trying to reproduce the spectral energy distribution of Epsilon Cancri. We re-examine the cluster membership of stars at the bright end of the color-magnitude diagram using Gaia data and literature radial velocity information. The binary star data are consistent with an age of 637 +/- 19 Myr, as determined from MIST model isochrones. The masses and luminosities of the stars appear to select models with the most commonly used amount of convective core overshooting.

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arXiv2022

The PEPSI Exoplanet Transit Survey (PETS) I: Investigating the presence of a silicate atmosphere on the super-Earth 55 Cnc e

The study of exoplanets and especially their atmospheres can reveal key insights on their evolution by identifying specific atmospheric species. For such atmospheric investigations, high-resolution transmission spectroscopy has shown great success, especially for Jupiter-type planets. Towards the atmospheric characterization of smaller planets, the super-Earth exoplanet 55 Cnc e is one of the most promising terrestrial exoplanets studied to date. Here, we present a high-resolution spectroscopic transit observation of this planet, acquired with the PEPSI instrument at the Large Binocular Telescope. Assuming the presence of Earth-like crust species on the surface of 55 Cnc e, from which a possible silicate-vapor atmosphere could have originated, we search in its transmission spectrum for absorption of various atomic and ionized species such as Fe , Fe+, Ca , Ca+, Mg and K , among others. Not finding absorption for any of the investigated species, we are able to set absorption limits with a median value of 1.9 x RP. In conclusion, we do not find evidence of a widely extended silicate envelope on this super-Earth reaching several planetary radii.

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