arXiv subjects

Isabella Pagano

Publications and source records attributed to Isabella Pagano.

At least 19 recordsLinked to original sources

arXiv2026

The Longest-period Young Transiting Exoplanets. A Duo of Puffy Giants inside a Debris Disk

We identify two large-radius planets around the F-type star HD 114082 as the longest-period young transiting exoplanets known. From the first transit, detected by NASA's Transiting Exoplanet Survey Satellite (TESS), and a second dip, spotted by the Next-Generation Transit Survey (NGTS), we predicted mid-transit times for HD 114082 b (planet b). We pinpoint its orbit (period Pb= 225.5504$\pm$0.0004 days) from a third transit captured with the ESA's CHaracterising ExOplanet Satellite and the upgraded Antarctic Search for Transiting ExoPlanets telescope (ASTEP+), alongside orbit-discriminating observations. Another dimming partly covered by ASTEP+ completes the four-transit series. We support with dynamical evidence the planetary nature of a deeper transit detected with TESS and NGTS, identifying planet c. Additionally, we reexamine the debris disk, fitting its excess emission with two dust components. Fundamental stellar parameters are inferred from stellar evolution models, while a joint modeling of photometric and radial-velocity time series yields the planetary parameters, with masses further constrained using an N-body code. For planet b, the semimajor axis a$_b$= 0.791$\pm$0.008 au, eccentricity eb$\approx$ 0, inclination ib= 89.791$\pm$0.014 degrees, radius Rb= 1.046$\pm$0.014 R$_J$, and 95 % confidence upper limit on its mass M$_{95\%,b}$= 1.6 M$_J$. For planet c, a$_c$= 0.99$^{+0.03}_{-0.04}$ au, ec$\approx$ 0, i$_c$= 89.701$\pm$0.011 degrees, R$_c$= 1.36$\pm$0.03 R$_J$, and M$_{95\%,c}$= 2.0 M$_J$ (0.24 M$_J$ if adding transit timing variation constrains). They seem to be moderate-to-low-mass giants in nearly resonant, coplanar, circular orbits that formed in situ, or beyond the snowline, and migrated inwards, shaping the disk.

astro-ph.EP↗

arXiv2026

An Ultra-Short Period Super-Earth and a Sub-Neptune Orbiting the K dwarf TOI-4311

We report the discovery and characterisation of the multi-planetary system around TOI-4311, a K dwarf kinematically between the Galactic thick disk and Hercules stream. TOI-4311 hosts an ultra-short-period super-Earth (P$\sim$0.99 d, $1.376\substack{+0.077\\-0.080}$ R$_\oplus$) and a longer period sub-Neptune (P$\sim$15 d, $2.47\substack{+0.12\\-0.11}$ R$_\oplus$) that was first detected in the TESS photometry. Using follow-up observations with CHEOPS and HARPS, we refine the planetary radius of both planets, derive the mass of planet b ($4.5\substack{+1.5\\-1.4}$ M$_\oplus$) and confirm the planetary nature of planet c. Intriguingly, a third periodic signal is clearly detected in our HARPS RVs that we cannot link to stellar activity. This signal could be attributed to a third planet (P$\sim$38 d, Msin(i)=$26.4\substack{+6.3\\-6.8}$ M$_\oplus$) in the system, however with the current photometric dataset we do not find a transit. Our dynamical analysis highlights that this potential outer planet would remain stable. Using the precise radius and mass for TOI-4311 b we model its interior structure and find that it is very dense given the host star's galactic kinematics and chemistry. Hence this system could challenge current formation theories and provide insights into planet formation across the galaxy.

astro-ph.EP↗

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.

astro-ph.EP↗

arXiv2026

The PLATO Science Calibration and Validation Plan: Targets for the First Long-pointing Field

In order to meet the science goals of the PLATO space mission, an extensive science calibration and validation plan has been designed. This paper describes this plan, as well as the methodology adopted to select the science calibration and validation stars that have entered its input catalogue. This is the so-called {\tt scvPIC}, which is part of the general PLATO Input Catalogue (PIC) for the first selected long pointing field in the Southern Hemisphere known as LOPS2. While many of PLATO's science requirements needed dedicated stars as calibrators as discussed here, its most stringent requirement is the delivery of the age of the host stars of exoplanetary systems with an accuracy better than 10\% for a G0V star of {\it V} = 10 mag, i.e. a nearby Sun-like star. This is presently not within reach for large populations of dwarfs and subgiants in the Milky Way as it requires the models of their stellar interiors to be improved. We discuss how this ambitious age requirement led to the selection of tens of thousands of red giants, and of thousands of main-sequence early F-type gravity-mode pulsators in order to deduce their internal rotation profile across stellar evolution. This asteroseismic observable will then be imported as key information into improved models of dwarfs and subgiants in the Milky Way as optimal modelling tools for ever better age-dating of the exoplanet hosts as the PLATO mission moves along. Additional calibrators and validators included in the {\tt scvPIC} are a few thousands of binaries, a few hundreds of legacy and benchmark stars, a few hundred photometrically stable stars, and six transiting brown dwarfs.

astro-ph.SR↗

arXiv2025

Searching for Exoplanets Born Outside the Milky Way: VOYAGERS Survey Design

Observations over the past few decades have found that planets are common around nearby stars in our Galaxy, but little is known about planets that formed outside the Milky Way. We describe the design and early implementation of a survey to test whether planets also exist orbiting the remnant stars of ancient dwarf galaxies that merged with the Milky Way, and if so, how they differ from their Milky Way counterparts. VOYAGERS (Views Of Yore - Ancient Gaia-enceladus Exoplanet Revealing Survey) is a radial velocity (RV) search using precision spectrographs to discover exoplanets orbiting very low metallicity ($-2.8 < [\mathrm{Fe/H}] \leq -0.8$) stars born in the dwarf galaxy Enceladus, which merged with the Milky Way galaxy about 10 Gyr ago. A sample of 22 candidates have been screened from a catalog of Gaia-Enceladus-Sausage (GES) members using a combination of stellar properties and reconnaissance observations from the TRES spectrograph. Precision RV measurements have been initiated using the NEID, HARPS-N, and CARMENES spectrographs. We plan to focus most upcoming observations on 10 main sequence targets. Data collection is well underway, with 778 observations on 22 candidates (385 of which are 10 focus targets), but far from complete. This survey is designed to be sensitive to sub-Neptune mass planets with periods up to hundreds of days. We note that the RV analysis gives mass multiplied by $\sin (inclination)$ or the minimum mass for exoplanets. The expected survey yield is three planets, assuming that occurrence rates are similar to those in the Milky Way and taking into account the degeneracy with inclination in our yield models. Our survey is designed to detect at least one exoplanet if occurrence rates are similar to known Milky Way exoplanets or, if no exoplanets are discovered, to rule out a Milky Way-like planet population in GES with 95% confidence level.

astro-ph.EP↗

arXiv2025

An Ultra-Short Period Super-Earth and Sub-Neptune Spanning the Radius Valley Orbiting the Kinematic Thick Disk Star TOI-2345

A crucial chemical link between stars and their orbiting exoplanets is thought to exist. If universal, this connection could affect the formation and evolution of all planets. Therefore, this potential vital link needs testing by characterising exoplanets around chemically-diverse stars. We present the discovery of two planets orbiting the metal-poor, kinematic thick-disk K-dwarf TOI-2345. TOI-2345 b is a super-Earth with a period of 1.05 days and TOI-2345 c is a sub-Neptune with a period of 21 days. In addition to the target being observed in 4 TESS sectors, we obtained 5 CHEOPS visits and 26 radial velocities from HARPS. By conducting a joint analysis of all the data, we find TOI-2345 b to have a radius of $1.504\substack{+0.047\\-0.044}$ R$_\oplus$ and a mass of $3.49\pm0.85$ M$_\oplus$; and TOI-2345 c to have a radius of $2.451\substack{+0.045\\-0.046}$ R$_\oplus$ and a mass of $7.27\substack{+2.27\\-2.45}$ M$_\oplus$. To explore chemical links between these planets and their host star, we model their interior structures newly accounting for devolatised stellar abundances. TOI-2345 adds to the limited sample of well characterised planetary systems around thick disk stars. This system challenges theories of formation and populations of planets around thick disk stars with its Ultra-Short Period super-Earth and the wide period distribution of these two planets spanning the radius valley.

astro-ph.EP↗

arXiv2024

In-situ observations of resident space objects with the CHEOPS space telescope

The CHaracterising ExOPlanet Satellite (CHEOPS) is a partnership between the European Space Agency and Switzerland with important contributions by 10 additional ESA member States. It is the first S-class mission in the ESA Science Programme. CHEOPS has been flying on a Sun-synchronous low Earth orbit since December 2019, collecting millions of short-exposure images in the visible domain to study exoplanet properties. A small yet increasing fraction of CHEOPS images show linear trails caused by resident space objects crossing the instrument field of view. To characterize the population of satellites and orbital debris observed by CHEOPS, all and every science images acquired over the past 3 years have been scanned with a Hough transform algorithm to identify the characteristic linear features that these objects cause on the images. Thousands of trails have been detected. This statistically significant sample shows interesting trends and features such as an increased occurrence rate over the past years as well as the fingerprint of the Starlink constellation. The cross-matching of individual trails with catalogued objects is underway as we aim to measure their distance at the time of observation and deduce the apparent magnitude of the detected objects. As space agencies and private companies are developing new space-based surveillance and tracking activities to catalogue and characterize the distribution of small debris, the CHEOPS experience is timely and relevant. With the first CHEOPS mission extension currently running until the end of 2026, and a possible second extension until the end of 2029, the longer time coverage will make our dataset even more valuable to the community, especially for characterizing objects with recurrent crossings.

astro-ph.EP↗

arXiv2024

Revisiting the conundrum of the sub-Jovian and Neptune desert. A new approach that incorporates stellar properties

The search for exoplanets has led to the identification of intriguing patterns in their distributions, one of which is the so-called sub-Jovian and Neptune desert. The occurrence rate of Neptunian exoplanets with an orbital period $P\lesssim 4$ days sharply decreases in this region in period-radius and period-mass space. We present a novel approach to delineating the sub-Jovian and Neptune desert by considering the incident stellar flux $F$ on the planetary surface as a key parameter instead of the traditional orbital period of the planets. Through this change of perspective, we demonstrate that the incident flux still exhibits a paucity of highly irradiated Neptunes, but also captures the proximity to the host star and the intensity of stellar radiation. Leveraging a dataset of confirmed exoplanets, we performed a systematic analysis to map the boundaries of the sub-Jovian and Neptune desert in the $(F,R_p)$ and $(F,M_p)$ diagrams, with $R_p$ and $M_p$ corresponding to the planetary radius and mass, respectively. By using statistical techniques and fitting procedures, we derived analytical expressions for these boundaries that offer valuable insights into the underlying physical mechanisms governing the dearth of Neptunian planets in close proximity to their host stars. We find that the upper and lower bounds of the desert are well described by a power-law model in the $(F,R_p)$ and $(F,M_p)$ planes. We also obtain the planetary mass-radius relations for each boundary by combining the retrieved analytic expressions in the two planes. This work contributes to advancing our knowledge of exoplanet demographics and to refining theoretical models of planetary formation and evolution within the context of the sub-Jovian and Neptune desert.

astro-ph.EP↗

arXiv2024

PLATO's signal and noise budget

ESA's PLATO mission aims the detection and characterization of terrestrial planets around solar-type stars as well as the study of host star properties. The noise-to-signal ratio (NSR) is the main performance parameter of the PLATO instrument, which consists of 24 Normal Cameras and 2 Fast Cameras. In order to justify, verify and breakdown NSR-relevant requirements the software simulator PINE was developed. PINE models the signal pathway from a target star to the digital output of a camera based on physical models and considers the major noise contributors. In this paper, the simulator's coarse mode is introduced which allows fast performance analyses on instrument level. The added value of PINE is illustrated by exemplary applications.

astro-ph.EP↗

arXiv2024

The PLATO Mission

PLATO (PLAnetary Transits and Oscillations of stars) is ESA's M3 mission designed to detect and characterise extrasolar planets and perform asteroseismic monitoring of a large number of stars. PLATO will detect small planets (down to <2 R_(Earth)) around bright stars (<11 mag), including terrestrial planets in the habitable zone of solar-like stars. With the complement of radial velocity observations from the ground, planets will be characterised for their radius, mass, and age with high accuracy (5 %, 10 %, 10 % for an Earth-Sun combination respectively). PLATO will provide us with a large-scale catalogue of well-characterised small planets up to intermediate orbital periods, relevant for a meaningful comparison to planet formation theories and to better understand planet evolution. It will make possible comparative exoplanetology to place our Solar System planets in a broader context. In parallel, PLATO will study (host) stars using asteroseismology, allowing us to determine the stellar properties with high accuracy, substantially enhancing our knowledge of stellar structure and evolution. The payload instrument consists of 26 cameras with 12cm aperture each. For at least four years, the mission will perform high-precision photometric measurements. Here we review the science objectives, present PLATO's target samples and fields, provide an overview of expected core science performance as well as a description of the instrument and the mission profile at the beginning of the serial production of the flight cameras. PLATO is scheduled for a launch date end 2026. This overview therefore provides a summary of the mission to the community in preparation of the upcoming operational phases.

astro-ph.IM↗

arXiv2024

PLATO on the shoulders of TESS: analyzing mono-transit planet candidates in TESS data as a prior knowledge for PLATO observations

The Transiting Exoplanet Survey Satellite (TESS) and the upcoming PLATO mission (PLAnetary Transits and Oscillations of stars) represent two space-based missions with complementary objectives in the field of exoplanet science. While TESS aims at detecting and characterizing exoplanets around bright and nearby stars on a relative short-period orbit, PLATO will discover a wide range of exoplanets including rocky planets within the habitable zones of their stars. We analyze mono-transit events in TESS data around stars that will or could be monitored by the PLATO mission, offering a unique opportunity to bridge the knowledge gap between the two missions and gain deeper insights into exoplanet demographics and system architectures. We found $48$ TESS mono-transit events around stars contained in the all-sky PLATO Input Catalog; of these, at least four will be imaged on the first long-pointing PLATO field, LOPS2. We uniformly vetted this sample to rule out possible false positive detections thus removing $10$ signals from the original sample. We developed an analytic method which allows us to estimate both the orbital period and inclination of a mono-transit planet candidate using only the shape of the transit. We derived the orbital period and inclination estimates for $30$ TESS mono-transit planet candidates. Finally, we investigated whether these candidates are amenable targets for a CHEOPS observing campaign.

astro-ph.EP↗

arXiv2023

Measuring stellar rotation and activity with PLATO

Due to be launched late 2026, the PLATO mission will bring the study of main-sequence solar-type and low-mass stars into a new era. In particular, PLATO will provide the community with a stellar sample with solar-type oscillations and activity-induced brightness modulation of unequalled size. We present here the main features of the analysis module that will be dedicated to measure stellar surface rotation and activity in the PLATO Stellar Analysis System.

astro-ph.IM↗

arXiv2023

High-charge 10 GeV electron acceleration in a 10 cm nanoparticle-assisted hybrid wakefield accelerator

In an electron wakefield accelerator, an intense laser pulse or charged particle beam excites plasma waves. Under proper conditions, electrons from the background plasma are trapped in the plasma wave and accelerated to ultra-relativistic velocities. We present recent results from a proof-of-principle wakefield acceleration experiment that reveal a unique synergy between a laser-driven and particle-driven accelerator: a high-charge laser-wakefield accelerated electron bunch can drive its own wakefield while simultaneously drawing energy from the laser pulse via direct laser acceleration. This process continues to accelerate electrons beyond the usual decelerating phase of the wakefield, thus reaching much higher energies. We find that the 10-centimeter-long nanoparticle-assisted wakefield accelerator can generate 340 pC, 10.4+-0.6 GeV electron bunches with 3.4 GeV RMS convolved energy spread and 0.9 mrad RMS divergence. It can also produce bunches with lower energy, a few percent energy spread, and a higher charge. This synergistic mechanism and the simplicity of the experimental setup represent a step closer to compact tabletop particle accelerators suitable for applications requiring high charge at high energies, such as free electron lasers or radiation sources producing muon beams.

physics.plasm-ph↗

arXiv2023

TESS and CHEOPS Discover Two Warm Sub-Neptunes Transiting the Bright K-dwarf HD 15906

We report the discovery of two warm sub-Neptunes transiting the bright (G = 9.5 mag) K-dwarf HD 15906 (TOI 461, TIC 4646810). This star was observed by the Transiting Exoplanet Survey Satellite (TESS) in sectors 4 and 31, revealing two small transiting planets. The inner planet, HD 15906 b, was detected with an unambiguous period but the outer planet, HD 15906 c, showed only two transits separated by $\sim$ 734 days, leading to 36 possible values of its period. We performed follow-up observations with the CHaracterising ExOPlanet Satellite (CHEOPS) to confirm the true period of HD 15906 c and improve the radius precision of the two planets. From TESS, CHEOPS and additional ground-based photometry, we find that HD 15906 b has a radius of 2.24 $\pm$ 0.08 R$_\oplus$ and a period of 10.924709 $\pm$ 0.000032 days, whilst HD 15906 c has a radius of 2.93$^{+0.07}_{-0.06}$ R$_\oplus$ and a period of 21.583298$^{+0.000052}_{-0.000055}$ days. Assuming zero bond albedo and full day-night heat redistribution, the inner and outer planet have equilibrium temperatures of 668 $\pm$ 13 K and 532 $\pm$ 10 K, respectively. The HD 15906 system has become one of only six multiplanet systems with two warm ($\lesssim$ 700 K) sub-Neptune sized planets transiting a bright star (G $\leq$ 10 mag). It is an excellent target for detailed characterisation studies to constrain the composition of sub-Neptune planets and test theories of planet formation and evolution.

astro-ph.EP↗

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.

astro-ph.EP↗

arXiv2023

The TESS Triple-9 Catalog II: a new set of 999 uniformly-vetted exoplanet candidates

The Transiting Exoplanet Survey Satellite (TESS) mission is providing the scientific community with millions of light curves of stars spread across the whole sky. Since 2018 the telescope has detected thousands of planet candidates that need to be meticulously scrutinized before being considered amenable targets for follow-up programs. We present the second catalog of the Plant Patrol citizen science project containing 999 uniformly-vetted exoplanet candidates within the TESS ExoFOP archive. The catalog was produced by fully exploiting the power of the Citizen Science Planet Patrol project. We vetted TESS Objects of Interest (TOIs) based on the results of Discovery And Vetting of Exoplanets DAVE pipeline. We also implemented the Automatic Disposition Generator, a custom procedure aimed at generating the final classification for each TOI that was vetted by at least three vetters. The majority of the candidates in our catalog, $752$ TOIs, passed the vetting process and were labelled as planet candidates. We ruled out $142$ candidates as false positives and flagged $105$ as potential false positives. Our final dispositions and comments for all the planet candidates are provided as a publicly available supplementary table.

astro-ph.EP↗

arXiv2022

A systematic validation of hot Neptunes in TESS data

We statistically validated a sample of hot Neptune candidates applying a two-step vetting technique using DAVE and TRICERATOPS. We performed a systematic validation of 250 transit-like events in the Transiting Exoplanet Survey Satellite (TESS) archive in the parameter region defined by $P\leq 4$ d and $3R_\oplus\leq R\leq 5R_\oplus$. Through our analysis, we identified 18 hot Neptune-sized candidates, with a false positive probability $<50\%$. Nine of these planet candidates still need to be confirmed. For each of the nine targets we retrieved the stellar parameters using ARIADNE and derived constraints on the planetary parameters by fitting the lightcurves with the juliet package. Within this sample of nine candidates, we statistically validated (i.e, with false positive probability < $0.3\%$) two systems (TOI-277 b and TOI-1288 b) by re-processing the candidates with TRICERATOPS along with follow-up observations. These new validated exoplanets expand the known hot Neptunes population and are high-priority targets for future radial velocities follow-up.

astro-ph.EP↗

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.

astro-ph.EP↗