The all-sky PLATO input catalogue Montalto, M.; Piotto, G.; Marrese, P. M. ...
Astronomy & astrophysics,
09/2021, Letnik:
653
Journal Article
Recenzirano
Odprti dostop
Context.
The ESA PLAnetary Transits and Oscillations of stars (PLATO) mission will search for terrestrial planets in the habitable zone of solar-type stars. Because of telemetry limitations, PLATO ...targets need to be pre-selected.
Aims.
In this paper, we present an all sky catalogue that will be fundamental to selecting the best PLATO fields and the most promising target stars, deriving their basic parameters, analysing the instrumental performances, and then planing and optimising follow-up observations. This catalogue also represents a valuable resource for the general definition of stellar samples optimised for the search of transiting planets.
Methods.
We used
Gaia
Data Release 2 astrometry and photometry and 3D maps of the local interstellar medium to isolate FGK (
V
≤ 13) and M (
V
≤ 16) dwarfs and subgiant stars.
Results.
We present the first public release of the all-sky PLATO input catalogue (asPIC1.1) containing a total of 2 675 539 stars including 2 378 177 FGK dwarfs and subgiants and 297 362 M dwarfs. The median distance in our sample is 428 pc for FGK stars and 146 pc for M dwarfs, respectively. We derived the reddening of our targets and developed an algorithm to estimate stellar fundamental parameters (
T
eff
, radius, mass) from astrometric and photometric measurements.
Conclusions.
We show that the overall (internal+external) uncertainties on the stellar parameter determined in the present study are ∼230 K (4%) for the effective temperatures, ∼0.1
R
⊙
(9%) for the stellar radii, and ∼0.1
M
⊙
(11%) for the stellar mass. We release a special target list containing all known planet hosts cross-matched with our catalogue.
ABSTRACT
The Milky Way Galaxy is literally teeming with exoplanets; thousands of planets have been discovered, with thousands more planet candidates identified. Terrestrial-like planets are quite ...common around other stars, and are expected to be detected in large numbers in the future. Such planets are the primary targets in the search for potentially habitable conditions outside the Solar system. Determining the atmospheric composition of exoplanets is mandatory to understand their origin and evolution, as atmospheric processes play crucial roles in many aspects of planetary architecture. In this work we construct and exploit a 1D radiative transfer model based on the discrete-ordinates method in plane-parallel geometry. Radiative results are linked to a convective flux that redistributes energy at any altitude producing atmospheric profiles in radiative–convective equilibrium. The model has been applied to a large number (6250) of closely dry synthetic CO2 atmospheres, and the resulting pressure and thermal profiles have been interpreted in terms of parameter variability. Although less accurate than 3D general circulation models, not properly accounting for e.g. clouds and atmospheric and ocean dynamics, 1D descriptions are computationally inexpensive and retain significant value by allowing multidimensional parameter sweeps with relative ease.
Context.
Temperate terrestrial exoplanets are likely to be common objects, but their discovery and characterization is very challenging because of the small intrinsic signal compared to that of their ...host star. Various concepts for optimized space missions to overcome these challenges are currently being studied. The Large Interferometer For Exoplanets (LIFE) initiative focuses on the development of a spacebased mid-infrared (MIR) nulling interferometer probing the thermal emission of a large sample of exoplanets.
Aims.
This study derives the minimum requirements for the signal-to-noise ratio (
S
/
N
), the spectral resolution (
R
), and the wavelength coverage for the LIFE mission concept. Using an Earth-twin exoplanet as a reference case, we quantify how well planetary and atmospheric properties can be derived from its MIR thermal emission spectrum as a function of the wavelength range,
S/N,
and
R
.
Methods.
We combined a cloud-free 1D atmospheric radiative transfer model, a noise model for observations with the LIFE interferometer, and the nested sampling algorithm for Bayesian parameter inference to retrieve planetary and atmospheric properties. We simulated observations of an Earth-twin exoplanet orbiting a G2V star at 10 pc from the Sun with different levels of exozodiacal dust emissions. We investigated a grid of wavelength ranges (3–20 μm, 4–18.5 μm, and 6–17 μm),
S/Ns
(5, 10, 15, and 20 determined at a wavelength of 11.2 μm), and
R
s (20, 35, 50, and 100).
Results.
We find that H
2
O, CO
2
, and O
3
are detectable if
S/N ≥
10 (uncertainty ≤ ± 1.0 dex). We find upper limits for N
2
O (abundance ≲10
−3
). In conrtrast, CO, N
2
, and O
2
are unconstrained. The lower limits for a CH
4
detection are
R
= 50 and
S
/
N
= 10. Our retrieval framework correctly determines the exoplanet’s radius (uncertainty ≤ ± 10%), surface temperature (uncertainty ≤ ± 20 K), and surface pressure (uncertainty ≤ ± 0.5 dex) in all cloud-free retrieval analyses. Based on our current assumptions, the observation time required to reach the specified
S/N
for an Earth-twin at 10 pc when conservatively assuming a total instrument throughput of 5% amounts to ≈6−7 weeks with four 2m apertures.
Conclusions.
We provide first order estimates for the minimum technical requirements for LIFE via the retrieval study of an Earth-twin exoplanet. We conclude that a minimum wavelength coverage of 4–18.5 μm, an
R
of 50, and an
S/N
of at least 10 is required. With the current assumptions, the atmospheric characterization of several Earth-like exoplanets at a distance of 10 pc and within a reasonable amount of observing time will require apertures ≥ 2m.
Following the recommendations to NASA (in the Astro2020 Decadal survey) and ESA (through the Voyage2050 process), the search for life on exoplanets will be a priority in the next decades. Two ...concepts for direct imaging space missions are being developed for this purpose: the Habitable Worlds Observatory (HWO) and the Large Interferometer for Exoplanets (LIFE). These two concepts operate in different spectral regimes: HWO is focused on reflected light spectra in the ultraviolet, visible, and near-infrared ( while LIFE will operate in the mid-infrared ( to capture the thermal emission of temperate exoplanets. In this study, we aim to assess the potential of HWO and LIFE to characterize a cloud-free Earth twin orbiting a Sun-like star at a distance of 10 pc, both as separate missions and in synergy with each other. We aim to quantify the increase in information that can be gathered by joint atmospheric retrievals on a habitable planet. We performed Bayesian retrievals on simulated data obtained by an mission and a one separately, then jointly. We considered the baseline spectral resolutions currently assumed for these concepts and used two increasingly complex noise simulations, obtained using state-of-the-art noise simulators. An concept would allow one to strongly constrain H2O O2 and O3 in the atmosphere of a cloud-free Earth twin, while the atmospheric temperature profile is not well constrained (with an average uncertainty approx 100 K). observations would strongly constrain CO2 H2O and O3 and provide stronger constraints on the thermal atmospheric structure and surface temperature (down to approx 10 K uncertainty). For all the investigated scenarios, both missions would provide an upper limit on CH4 . A joint retrieval on and data would accurately define the atmospheric thermal profile and planetary parameters. It would decisively constrain CO2 H2O O2 and O3 and find weak constraints on CO and CH4 . The significance of the detection is in all cases greater than or equal to the single-instrument retrievals. Both missions provide specific information that is relevant for the characterization of a terrestrial habitable exoplanet, but the scientific yield can be maximized by considering synergistic studies of observations. The use of and together will provide stronger constraints on biosignatures and life indicators, with the potential to be transformative for the search for life in the Universe.
Large Interferometer For Exoplanets (LIFE) Quanz, S. P.; Ottiger, M.; Fontanet, E. ...
Astronomy and astrophysics (Berlin),
08/2022, Letnik:
664
Journal Article, Web Resource
Recenzirano
Odprti dostop
Context.
One of the long-term goals of exoplanet science is the atmospheric characterization of dozens of small exoplanets in order to understand their diversity and search for habitable worlds and ...potential biosignatures. Achieving this goal requires a space mission of sufficient scale that can spatially separate the signals from exoplanets and their host stars and thus directly scrutinize the exoplanets and their atmospheres.
Aims.
We seek to quantify the exoplanet detection performance of a space-based mid-infrared (MIR) nulling interferometer that measures the thermal emission of exoplanets. We study the impact of various parameters and compare the performance with that of large single-aperture mission concepts that detect exoplanets in reflected light.
Methods.
We have developed an instrument simulator that considers all major astrophysical noise sources and coupled it with Monte Carlo simulations of a synthetic exoplanet population around main-sequence stars within 20 pc of the Sun. This allows us to quantify the number (and types) of exoplanets that our mission concept could detect. Considering single visits only, we discuss two different scenarios for distributing 2.5 yr of an initial search phase among the stellar targets. Different apertures sizes and wavelength ranges are investigated.
Results.
An interferometer consisting of four 2 m apertures working in the 4–18.5 μ.m wavelength range with a total instrument throughput of 5% could detect up to ≈550 exoplanets with radii between 0.5 and 6
R
⊕
with an integrated
S
/
N
≥ 7. At least ≈160 of the detected exoplanets have radii ≤1.5
R
⊕
. Depending on the observing scenario, ≈25–45 rocky exoplanets (objects with radii between 0.5 and 1.5
R
⊕
) orbiting within the empirical habitable zone (eHZ) of their host stars are among the detections. With four 3.5 m apertures, the total number of detections can increase to up to ≈770, including ≈60–80 rocky eHZ planets. With four times 1 m apertures, the maximum detection yield is ≈315 exoplanets, including ≤20 rocky eHZ planets. The vast majority of small, temperate exoplanets are detected around M dwarfs. The impact of changing the wavelength range to 3–20 μm or 6–17 μm on the detection yield is negligible.
Conclusions.
A large space-based MIR nulling interferometer will be able to directly detect hundreds of small, nearby exoplanets, tens of which would be habitable world candidates. This shows that such a mission can compete with large single-aperture reflected light missions. Further increasing the number of habitable world candidates, in particular around solar-type stars, appears possible via the implementation of a multi-visit strategy during the search phase. The high median S/N of most of the detected planets will allow for first estimates of their radii and effective temperatures and will help prioritize the targets for a second mission phase to obtain high-S/N thermal emission spectra, leveraging the superior diagnostic power of the MIR regime compared to shorter wavelengths.
Context.
Terrestrial exoplanets in the habitable zone are likely a common occurrence. The long-term goal is to characterize the atmospheres of dozens of such objects. The Large Interferometer For ...Exoplanets (LIFE) initiative aims to develop a space-based mid-infrared (MIR) nulling interferometer to measure the thermal emission spectra of such exoplanets.
Aims.
We investigate how well LIFE could characterize a cloudy Venus-twin exoplanet. This allows us to: (1) test our atmospheric retrieval routine on a realistic non-Earth-like MIR emission spectrum of a known planet, (2) investigate how clouds impact retrievals, and (3) further refine the LIFE requirements derived in previous Earth-centered studies.
Methods.
We ran Bayesian atmospheric retrievals for simulated LIFE observations of a Venus-twin exoplanet orbiting a Sun-like star located 10 pc from the observer. The LIFE
SIM
noise model accounted for all major astrophysical noise sources. We ran retrievals using different models (cloudy and cloud-free) and analyzed the performance as a function of the quality of the LIFE observation. This allowed us to determine how well the atmosphere and clouds are characterizable depending on the quality of the spectrum.
Results.
At the current minimal resolution (
R
= 50) and signal-to-noise (
S
/
N
= 10 at 11.2 μ m) requirements for LIFE, all tested models suggest a CO
2
-rich atmosphere (≥30% in mass fraction). Further, we successfully constrain the atmospheric pressure-temperature (
P–T
) structure above the cloud deck (
P–T
uncertainty ≤ ± 15 K). However, we struggle to infer the main cloud properties. Further, the retrieved planetary radius (
R
pl
), equilibrium temperature (
T
eq
), and Bond albedo (
A
B
) depend on the model. Generally, a cloud-free model performs best at the current minimal quality and accurately estimates
R
pl
,
T
eq
, and
A
B
. If we consider higher quality spectra (especially
S
/
N
= 20), we can infer the presence of clouds and pose first constraints on their structure.
Conclusions.
Our study shows that the minimal R and S/N requirements for LIFE suffice to characterize the structure and composition of a Venus-like atmosphere above the cloud deck if an adequate model is chosen. Crucially, the cloud-free model is preferred by the retrieval for low spectral qualities. We thus find no direct evidence for clouds at the minimal
R
and
S
/
N
requirements and cannot infer the thickness of the atmosphere. Clouds are only constrainable in MIR retrievals of spectra with
S
/
N
≥ 20. The model dependence of our retrieval results emphasizes the importance of developing a community-wide best-practice for atmospheric retrieval studies.
The GAPS Programme at TNG Carleo, I.; Malavolta, L.; Lanza, A. F. ...
Astronomy and astrophysics (Berlin),
06/2020, Letnik:
638
Journal Article
Recenzirano
Context.
The existence of hot Jupiters is still not well understood. Two main channels are thought to be responsible for their current location: a smooth planet migration through the protoplanetary ...disk or the circularization of an initial highly eccentric orbit by tidal dissipation leading to a strong decrease in the semimajor axis. Different formation scenarios result in different observable effects, such as orbital parameters (obliquity and eccentricity) or frequency of planets at different stellar ages.
Aims.
In the context of the GAPS Young Objects project, we are carrying out a radial velocity survey with the aim of searching and characterizing young hot-Jupiter planets. Our purpose is to put constraints on evolutionary models and establish statistical properties, such as the frequency of these planets from a homogeneous sample.
Methods.
Since young stars are in general magnetically very active, we performed multi-band (visible and near-infrared) spectroscopy with simultaneous GIANO-B + HARPS-N (GIARPS) observing mode at TNG. This helps in dealing with stellar activity and distinguishing the nature of radial velocity variations: stellar activity will introduce a wavelength-dependent radial velocity amplitude, whereas a Keplerian signal is achromatic. As a pilot study, we present here the cases of two known hot Jupiters orbiting young stars: HD 285507 b and AD Leo b.
Results.
Our analysis of simultaneous high-precision GIARPS spectroscopic data confirms the Keplerian nature of the variation in the HD 285507 radial velocities and refines the orbital parameters of the hot Jupiter, obtaining an eccentricity consistent with a circular orbit. Instead, our analysis does not confirm the signal previously attributed to a planet orbiting AD Leo. This demonstrates the power of the multi-band spectroscopic technique when observing active stars.
The GAPS Programme at TNG Carleo, I.; Desidera, S.; Nardiello, D. ...
Astronomy and astrophysics (Berlin),
01/2021, Letnik:
645
Journal Article
Recenzirano
Odprti dostop
Context.
Young stars and multi-planet systems are two types of primary objects that allow us to study, understand, and constrain planetary formation and evolution theories.
Aims.
We validate the ...physical nature of two Neptune-sized planets transiting TOI-942 (TYC 5909-319-1), a previously unacknowledged young star (50
−20
+30
Myr) observed by the TESS space mission in Sector 5.
Methods.
Thanks to a comprehensive stellar characterization, TESS light curve modeling and precise radial-velocity measurements, we validated the planetary nature of the TESS candidate and detected an additional transiting planet in the system on a larger orbit.
Results.
From photometric and spectroscopic observations we performed an exhaustive stellar characterization and derived the main stellar parameters. TOI-942 is a relatively active K2.5V star (log
R
′
HK
= −4.17 ± 0.01) with rotation period
P
rot
= 3.39 ± 0.01 days, a projected rotation velocity
v
sin
i
⋆
= 13.8 ± 0.5 km s
−1
, and a radius of ~0.9
R
⊙
. We found that the inner planet, TOI-942 b, has an orbital period
P
b
= 4.3263 ± 0.0011 days, a radius
R
b
= 4.242
−0.313
+0.376
R
⊕
, and a mass upper limit of 16
M
⊕
at 1
σ
confidence level. The outer planet, TOI-942 c, has an orbital period
P
c
= 10.1605
−0.0053
+0.0056
days, a radius
R
c
= 4.793
−0.351
+0.410
R
⊕
, and a mass upper limit of 37
M
⊕
at 1
σ
confidence level.
CROCODILE Hayoz, J.; Cugno, G.; Quanz, S. P. ...
Astronomy and astrophysics (Berlin),
10/2023, Letnik:
678
Journal Article
Recenzirano
Context.
The investigation of the atmospheres of closely separated, directly imaged gas giant exoplanets is challenging due to the presence of stellar speckles that pollute their spectrum. To remedy ...this, the analysis of medium- to high-resolution spectroscopic data via cross-correlation with spectral templates (cross-correlation spectroscopy) is emerging as a leading technique.
Aims.
We aim to define a robust Bayesian framework combining, for the first time, three widespread direct-imaging techniques, namely photometry, low-resolution spectroscopy, and medium-resolution cross-correlation spectroscopy in order to derive the atmospheric properties of close-in directly imaged exoplanets. Current atmospheric characterisation frameworks are indeed either not compatible with all three observing techniques or they lack the commitment to efficient sampling strategies that allow high-dimensional forward models.
Methods.
Our framework
CROCODILE
(cross-correlation retrievals of directly imaged self-luminous exoplanets) naturally combines the three techniques by adopting adequate likelihood functions. To validate our routine, we simulated observations of gas giants similar to the well-studied
β
Pictoris b planet and we explored the parameter space of their atmospheres to search for potential biases.
Results.
We obtain more accurate measurements of atmospheric properties when combining photometry, low- and medium-resolution spectroscopy into atmospheric retrievals than when using the techniques separately as is usually done in the literature. Indeed, the combined fit is, on average, 20% more accurate than fitting only medium-resolution cross-correlation spectroscopy. We find that medium-resolution (
R
≈ 4000)
K
-band cross-correlation spectroscopy alone is not suitable to constrain the atmospheric properties of our synthetic datasets; however, this problem disappears when simultaneously fitting photometry throughout the
Y
and
M
bands and low-resolution (
R
≈ 60) spectroscopy between the
Y
and
H
bands. Our thorough testing demonstrates that free chemistry is a suitable forward model to retrieve the atmospheric thermal and chemical properties of cloudless gas giants at chemical equilibrium.
Conclusions.
CROCODILE
provides a robust statistical framework to interpret medium-resolution spectroscopic data of close-in directly imaged exoplanets, where speckles originating from stellar stray light render the extraction of the continuum difficult. Our framework allows the atmospheric characterisation of directly imaged exoplanets using the high-quality spectral data that will be provided by the new generation of instruments such as the Enhanced Resolution Imager and Spectrograph (ERIS) at the Very Large Telescope, the Mid-Infrared Instrument (MIRI) aboard the
James Webb
Space Telescope, and in the future the Mid-infrared ELT Imager and Spectrograph (METIS) at the Extremely Large Telescope.
The heterogeneity of papers dealing with the discovery and characterization of exoplanets makes every attempt to maintain a uniform exoplanet catalog almost impossible. Four sources currently ...available online (NASA Exoplanet Archive, Exoplanet Orbit Database, Exoplanet Encyclopaedia, and Open Exoplanet Catalogue) are commonly used by the community, but they can hardly be compared, due to discrepancies in notations and selection criteria. Exo-MerCat is a Python code that collects and selects the most precise measurement for all interesting planetary and orbital parameters contained in the four databases, accounting for the presence of multiple aliases for the same target. It can download information about the host star as well by the use of Virtual Observatory ConeSearch connections to the major archives such as SIMBAD and those available in VizieR. A Graphical User Interface is provided to filter data based on the user’s constraints and generate automatic plots that are commonly used in the exoplanetary community. With Exo-MerCat, we retrieved a unique catalog that merges information from the four main databases, standardizing the output and handling notation differences issues. Exo-MerCat can correct as many issues that prevent a direct correspondence between multiple items in the four databases as possible, with the available data. The catalog is available as a VO resource for everyone to use and it is periodically updated, according to the update rates of the source catalogs.
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