ABSTRACT
In this work, we present the analysis of 976 814 FGKM dwarf and subgiant stars in the Transiting Exoplanet Survey Telescope (TESS) full frame images (FFIs) of the Southern ecliptic ...hemisphere. We present a new pipeline, DIAmante, developed to extract optimized, multisector photometry from TESS FFIs and a classifier, based on the Random Forest technique, trained to discriminate plausible transiting planetary candidates from common false positives. A new statistical model was developed to provide the probability of correct identification of the source of variability. We restricted the planet search to the stars located in the least crowded regions of the sky and identified 396 transiting planetary candidates among which 252 are new detections. The candidates’ radius distribution ranges between 1 R⊕ and 2.6 RJ with median value of 1 RJ and the period distribution ranges between 0.25 and 105 d with median value of 3.8 d. The sample contains four long period candidates (P > 50 d), one of which is new, and 64 candidates with periods between 10 and 50 d (42 new ones). In the small planet radius domain (4R < R⊕), we found 39 candidates among which 15 are new detections. Additionally, we present 15 single transit events (14 new ones), a new candidate multiplanetary system, and a novel candidate around a known TOI. By using Gaia dynamical constraints, we found that 70 objects show evidence of binarity. We release a catalogue of the objects we analysed and the corresponding light curves and diagnostic figures through the MAST and ExoFOP portals.
ABSTRACT
The scope of the project ‘A PSF-based Approach to TESS High Quality data Of Stellar clusters’ (PATHOS) is the extraction and analysis of high-precision light curves of stars in stellar ...clusters and young associations for the identification of candidate exoplanets and variable stars. The cutting-edge tools used in this project allow us to measure the real flux of stars in dense fields, minimizing the effects due to contamination by neighbour sources. We extracted about 200 000 light curves of stars in 645 open clusters located in the Southern ecliptic hemisphere and observed by TESS during the first year of its mission. We searched for transiting signals and we found 33 objects of interest, 11 of which are strong candidate exoplanets. Because of the limited SNR, we did not find any Earth or super-Earth. We identified two Neptune-size planets orbiting stars with $R_{\star }\lt 1.5\, \mathrm{\it R}_{\odot }$, implying a frequency $f_{\star }=1.34 \pm 0.95\, {{\ \rm per\ cent}}$, consistent with the frequency around field stars. The seven Jupiter candidates around stars with $R_{\star }\lt \, 1.5\, \mathrm{\it R}_{\odot }$ imply a frequency $f_{\star }=0.19\pm 0.07\, {{\ \rm per\ cent}}$, which is smaller than in the field. A more complete estimate of the survey completeness and false positive rate is needed to confirm these results. Light curves used in this work will be made available to the astronomical community on the Mikulski Archive for Space Telescope under the project PATHOS.
ABSTRACT
The TESS mission will survey ∼85 per cent of the sky, giving us the opportunity of extracting high-precision light curves of millions of stars, including stellar cluster members. In this ...work, we present our project ‘A PSF-based Approach to TESS High quality data Of Stellar clusters’ (PATHOS), aimed at searching and characterize candidate exoplanets and variable stars in stellar clusters using our innovative method for the extraction of high-precision light curves of stars located in crowded environments. Our technique of light-curve extraction involves the use of empirical point spread functions (PSFs), an input catalogue and neighbour-subtraction. The PSF-based approach allows us to minimize the dilution effects in crowded environments and to extract high-precision photometry for stars in the faint regime (G > 13). For this pilot project, we extracted, corrected, and analysed the light curves of 16 641 stars located in a dense region centred on the globular cluster 47 Tuc. We were able to reach the TESS magnitude T ∼ 16.5 with a photometric precision of ${\sim} 1{{\ \rm per\ cent}}$ on the 6.5-h time-scale; in the bright regime we were able to detect transits with depth of ∼34 parts per million. We searched for variables and candidate transiting exoplanets. Our pipeline detected one planetary candidate orbiting a main-sequence star in the Galactic field. We analysed the period–luminosity distribution for red-giant stars of 47 Tuc and the eclipsing binaries in the field. Light curves are uploaded on the Mikulski Archive for Space Telescopes under the project PATHOS.
ABSTRACT
The knowledge of the ages of stars hosting exoplanets allows us to obtain an overview on the evolution of exoplanets and understand the mechanisms affecting their life. The measurement of ...the ages of stars in the Galaxy is usually affected by large uncertainties. An exception are the stellar clusters: For their coeval members, born from the same molecular cloud, ages can be measured with extreme accuracy. In this context, the project PATHOS is providing candidate exoplanets orbiting members of stellar clusters and associations through the analysis of high-precision light curves obtained with cutting-edge tools. In this work, we exploited the data collected during the second year of the Transiting Exoplanet Survey Satellite mission. We extracted, analysed, and modelled the light curves of $\sim 90\, 000$ stars in open clusters located in the Northern ecliptic hemisphere in order to find candidate exoplanets. We measured the frequencies of candidate exoplanets in open clusters for different orbital periods and planetary radii, taking into account the detection efficiency of our pipeline and the false positive probabilities of our candidates. We analysed the age–RP distribution of candidate and confirmed exoplanets with periods <100 d and well constrained ages. While no peculiar trends are observed for Jupiter-size and (super-)Earth-size planets, we found that objects with $4 \lesssim R_{\rm P} \lesssim 13R_{\rm Earth}$ are concentrated at ages ≲200 Myr; different scenarios (atmospheric losses, migration, etc.) are considered to explain the observed age–RP distribution.
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
Materials with strongly correlated electrons often exhibit interesting physical properties. An example of these materials is the layered oxide perovskite Sr
2
RuO
4
, which has been ...intensively investigated due to its unusual properties. Whilst the debate on the symmetry of the superconducting state in Sr
2
RuO
4
is still ongoing, a deeper understanding of the Sr
2
RuO
4
normal state appears crucial as this is the background in which electron pairing occurs. Here, by using low-energy muon spin spectroscopy we discover the existence of surface magnetism in Sr
2
RuO
4
in its normal state. We detect static weak dipolar fields yet manifesting at an onset temperature higher than 50 K. We ascribe this unconventional magnetism to orbital loop currents forming at the reconstructed Sr
2
RuO
4
surface. Our observations set a reference for the discovery of the same magnetic phase in other materials and unveil an electronic ordering mechanism that can influence electron pairing with broken time reversal symmetry.
NbRe-based superconducting thin films recently received relevant interest in the field of low-temperature electronics. However, for these materials the electrical conduction mechanisms, in particular ...in the normal state, still need to be investigated in more detail. Here, NbRe and NbReN films of different thicknesses have been deposited on two different substrates, namely monocrystalline Si and Formula: see text buffered Si. The films were characterized by DC electrical transport measurements. Moreover, a connection with the charge carriers fluctuation processes has been made by analyzing the electrical noise generated in the normal state region. Despite the films morphology seems not to be affected by the substrate used, a lower noise level has been found for the ones grown on Formula: see text, in particular for NbReN. From this study it emerges that both NbRe and NbReN ultrathin films are of very good quality, as far as the low-temperature electrical noise and conduction are concerned, with noise levels competitive with NbN. These results may further support the proposal of using these materials in a nanowire form in the field of superconducting electronics.
ABSTRACT
We present a detailed analysis of HARPS-N radial velocity observations of K2-100, a young and active star in the Praesepe cluster, which hosts a transiting planet with a period of 1.7 d. We ...model the activity-induced radial velocity variations of the host star with a multidimensional Gaussian Process framework and detect a planetary signal of 10.6 ± 3.0 ${\rm m\, s^{-1}}$, which matches the transit ephemeris, and translates to a planet mass of 21.8 ± 6.2 M⊕. We perform a suite of validation tests to confirm that our detected signal is genuine. This is the first mass measurement for a transiting planet in a young open cluster. The relatively low density of the planet, $2.04 _{ - 0.61 } ^ { + 0.66 }$ ${\rm g\, cm^{-3}}$, implies that K2-100b retains a significant volatile envelope. We estimate that the planet is losing its atmosphere at a rate of $10^{11}\!-\!10^{12}\, {\rm g\, s^{-1}}$ due to the high level of radiation it receives from its host star.
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