K2-19 is the second multiplanetary system discovered with K2 observations. The system is composed of two Neptune size planets close to the 3:2 mean-motion resonance. To better characterize the system ...we obtained two additional transit observations of K2-19b and five additional radial velocity observations. These were combined with K2 data and fitted simultaneously with the system dynamics (photodynamical model) which increases the precision of the transit time measurements. The higher transit time precision allows us to detect the chopping signal of the dynamic interaction of the planets that in turn permits to uniquely characterize the system. Although the reflex motion of the star was not detected, dynamic modelling of the system allowed us to derive planetary masses of M
b
= 44 ± 12 M⊕ and M
c
= 15.9 ± 7.0 M⊕ for the inner and the outer planets, respectively, leading to densities close to Uranus. We also show that our method allows the derivation of mass ratios using only the 80 d of observations during the first campaign of K2.
ABSTRACT
Small Solar system bodies serve as pristine records that have been minimally altered since their formation. Their observations provide valuable information regarding the formation and ...evolution of our Solar system. Interstellar objects can also provide insight on the formation of exoplanetary systems and planetary system evolution as a whole. In this work, we present the application of our framework to search for small Solar system bodies in exoplanet transit survey data collected by the Antarctic Search for Transiting ExoPlanets (ASTEP) project. We analysed data collected during the Austral winter of 2021 by the ASTEP 400 telescope located at the Concordia Station, at Dome C, Antarctica. We identified 20 known objects from dynamical classes ranging from Inner Main-belt asteroids to one comet. Our search recovered known objects down to a magnitude of V = 20.4 mag, with a retrieval rate of ∼80 per cent for objects with V ≤ 20 mag. Future work will apply the pipeline to archival ASTEP data that observed fields for periods of longer than a few hours to treat them as deep-drilling data sets and reach fainter limiting magnitudes for slow-moving objects, on the order of V ≈ 23–24 mag.
ABSTRACT
We present new speckle measurements of the position of Linus, the satellite of the asteroid (22) Kalliope, obtained at the 1 m Centre Pédagogique Planètes et Univers-Epsilon telescope on the ...Plateau de Calern, France. Observations were made in the visible domain with the speckle camera Pupil Interferometry Speckle camera and COronagraph. We obtained 122 measurements in February–March 2022 and April 2023, with a mean uncertainty close to 10 milliarcsec on the angular separation.
•Visible spectra of 65 asteroids members of Polana and Eulalia primitive families.•Spectral analyses show no significant differences among the spectra.•Continuum in spectral slopes from B- to ...C-types.•Spectral slope distribution shows no bimodality at 2-sigma level.•Family membership cannot be addressed from visible spectra.
The Polana–Eulalia family complex is located in the inner part of the asteroid belt, bounded by the ν6 and the 3:1 resonances, where we can find another three collisional families of primitive asteroids (Erigone, Clarissa, and Sulamitis), and a low-albedo population of background objects. This region of the belt is believed to be the most likely origin of the two primitive near-Earth asteroids that are the current targets of two sample return missions: NASA’s OSIRIS-REx and JAXA’s Hayabusa 2 to Asteroids (101955) Bennu and (162173) Ryugu (also known as 1999 JU3), respectively. Therefore, understanding these families will enhance the scientific return of these missions.
We present the results of a spectroscopic survey of asteroids in the region of the Polana–Eulalia family complex, and also asteroids from the background population of low-albedo, low-inclination objects. We obtained visible spectra of a total of 65 asteroids, using the 10.4m Gran Telescopio Canarias (GTC) and the 3.6m Telescopio Nazionale Galileo (TNG), both located at the El Roque de Los Muchachos Observatory, in the island of La Palma (Spain), and the 3.6m New Technology Telescope (NTT), located at the European Southern Observatory of La Silla, in Chile. From the spectral analysis of our sample we found that, in spite of the presence of distinct dynamical groups, the asteroids in this region present spectral homogeneity at visible wavelengths, showing a continuum of spectral slopes, from blue to moderately red, typical of primitive asteroids classified as B- and C-types. We conclude that visible spectra cannot be used to distinguish between members of the Polana and the Eulalia families, or members of the background population.
The visible spectra of the two targets of sample return missions, Asteroids Bennu and Ryugu, are compatible with the spectra of the asteroids in this region, supporting previous studies that suggested either the Polana family or the background population as the most likely origins of these NEAs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Context. VX Sgr is a cool, evolved, and luminous red star whose stellar parameters are difficult to determine, which affects its classification.
Aims. We aim to spatially resolve the photospheric ...extent as well as the circumstellar environment.
Methods. We used interferometric observations obtained with the MATISSE instrument in the L (3–4 μm), M (4.5–5 μm), and N (8–13 μm) bands. We reconstructed monochromatic images using the MIRA software. We used 3D radiation-hydrodynamics simulations carried out with CO5BOLD and a uniform disc model to estimate the apparent diameter and interpret the stellar surface structures. Moreover, we employed the radiative transfer codes OPTIM3D and RADMC3D to compute the spectral energy distribution for the L, M, and N bands, respectively.
Results. MATISSE observations unveil, for the first time, the morphology of VX Sgr across the L, M, and N bands. The reconstructed images show a complex morphology with brighter areas whose characteristics depend on the wavelength probed. We measured the angular diameter as a function of the wavelength and showed that the photospheric extent in the L and M bands depends on the opacity through the atmosphere. In addition to this, we also concluded that the observed photospheric inhomogeneities can be interpreted as convection-related surface structures. The comparison in the N band yielded a qualitative agreement between the N-band spectrum and simple dust radiative transfer simulations. However, it is not possible to firmly conclude on the interpretation of the current data because of the difficulty in constraing the model parameters using the limited accuracy of our absolute flux calibration.
Conclusions. MATISSE observations and the derived reconstructed images unveil the appearance of VX Sgr’s stellar surface and circumstellar environment across a very large spectral domain for the first time.
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Context.
Since July 2014, the
Gaia
mission of the European Space Agency has been surveying the entire sky down to magnitude 20.7 in the visible. In addition to the millions of daily observations of ...stars, thousands of Solar System objects (SSOs) are observed. By comparing their positions, as measured by
Gaia
, to those of known objects, a daily processing pipeline filters known objects from potential discoveries. However, owing to
Gaia
’s specific observing mode, which follows a predetermined scanning law designed for stars as “fixed” objects on the celestial sphere, potential newly discovered moving objects are characterized by very few observations, which are acquired over a limited time. Furthermore, these objects cannot be specifically targeted by
Gaia
itself after their first detection. This aspect was recognized early on in the design of the
Gaia
data processing.
Aims.
A daily processing pipeline dedicated to these candidate discoveries was set up to release calls for observations to a network of ground-based telescopes. Their aim is to acquire follow-up astrometry and to characterize these objects.
Methods.
From the astrometry measured by
Gaia
, preliminary orbital solutions are determined, allowing us to predict the position of these potentially newly discovered objects in the sky while accounting for the large parallax between
Gaia
and the Earth (separated by 0.01 au). A specific task within the
Gaia
Data Processing and Analysis Consortium has been responsible for the distribution of requests for follow-up observations of potential
Gaia
SSO discoveries. Since late 2016, these calls for observations (nicknamed “alerts”) have been published via a Web interface with a quasi-daily frequency, together with observing guides, which is freely available to anyone worldwide.
Results.
Between November 2016 and the end of the first year of the extended mission (July 2020), over 1700 alerts were published, leading to the successful recovery of more than 200 objects. Among them, six have a provisional designation assigned with the
Gaia
observations; the others were previously known objects with poorly characterized orbits, precluding identification at the time of
Gaia
observations. There is a clear trend for objects with a high inclination to be unidentified, revealing a clear bias in the current census of SSOs against high-inclination populations.
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A new polarimeter based on the wedged double Wollaston concept has been built at the Torino Observatory and installed on a 1-m telescope at the Calern observing station of the Observatoire de la Cote ...d'Azur, France. Its main purpose is to carry out a polarimetric survey of minor Solar system objects, which is called the Calern Asteroid Polarimetric Survey. In this paper, we describe the new Torino polarimeter and the results of preliminary scientific validation tests. A number of standard stars with known polarization states, as well as a number of asteroids for which the polarimetric properties are known, have been observed in order to assess the instrument's accuracy. The instrumental polarization has been found to be stable within a few 10 super( -4) units. A total of 124 new polarimetric observation of 78 asteroids are presented. In the case of asteroids already observed in the past, the new data are in agreement with available phase-polarization curves with error bars smaller than most previously published data. We also present data for 21 asteroids that have never been observed before in polarimetry.
Context. Polarimetry is a powerful remote sensing tool to characterise solar system planets and, potentially, to detect and characterise exoplanets. The linear polarisation of a planet as a function ...of wavelength and phase angle is sensitive to the cloud and haze particle properties in planetary atmospheres, as well as to their altitudes and optical thicknesses. Aims. We present for the first time polarimetric signals of Jupiter mapped over the entire disk, showing features such as contrasts between the belts and zones, the polar regions, and the Great Red Spot. We investigate the use of these maps for atmospheric characterisation and discuss the potential application of polarimetry to the study of the atmospheres of exoplanets. Methods. We have obtained polarimetric images of Jupiter, in the B, V, and R filters, over a phase angle range of α = 4°–10.5°. In addition, we have obtained two spectropolarimetric datasets, over the wavelength range 500–850 nm. An atmospheric model was sought for all of the datasets, which was consistent with the observed behaviour over the wavelength and phase angle range. Results. The polarimetric maps show clear latitudinal structure, with increasing polarisation towards the polar regions, in all filters. The spectropolarimetric datasets show a decrease in polarisation as a function of wavelength along with changes in the polarisation in methane absorption bands. A model fit was achieved by varying the cloud height and haze optical thickness; this can roughly produce the variation across latitude for the V and R filters, but not for the B filter data. The same model particles are also able to produce a close fit to the spectropolarimetric data. The atmosphere of Jupiter is known to be complex in structure, and data taken at intermediate phase angles (unreachable for Earth-based telescopes) seems essential for a complete characterisation of the atmospheric constituents. Because exoplanets orbit other stars, they are observable at intermediate phase angles and thus promise to be better targets for Earth-based polarimetry.
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Rotation significantly impacts on the structure and life of stars. In phases of high rotation velocity (close to critical), the photospheric structure can be highly modified, and present in ...particular geometrical deformation (rotation flattening) and latitudinal-dependent flux (gravity darkening). The fastest known rotators among the nondegenerate stars close to the main sequence, Be stars, are key targets for studying the effects of fast rotation on stellar photospheres. We seek to determine the purely photospheric parameters of Achernar based on observations recorded during an emission-free phase (normal B phase). The analysis did not reveal any important circumstellar contribution, so that Achernar was essentially in a normal B phase at least from mid-2009 to end-2012, and the model parameters derived in this work provide a fair description of its photosphere. This model offers a promising explanation to the fact that the measured Beta parameter decreases with flattening and shows significantly lower values than the classical prediction of von Zeipel.
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Aims. Several studies suggest that the activity level of a planet-host star can be influenced by the presence of a close-by orbiting planet. Moreover, the interaction mechanisms that have been ...proposed, magnetic interaction and tidal interaction, exhibit a very different dependence on the orbital separation between the star and the planet. A detection of activity enhancement and characterization of its dependence on planetary orbital distance can, in principle, allow us to characterize the physical mechanism behind the activity enhancement. Methods. We used the HARPS-N spectrograph to measure the stellar activity level of HD80606 during the planetary periastron passage and compared the activity measured to that close to apastron. Being characterized by an eccentricity of 0.93 and an orbital period of 111days, the system's extreme variation in orbital separation makes it a perfect target to test our hypothesis. Results. We find no evidence for a variation in the activity level of the star as a function of planetary orbital distance, as measured by all activity indicators employed: log(R'HK), H sub(alpha), NaI, and HeI. None of the models employed, whether magnetic interaction or tidal interaction, provides a good description of the data. The photometry revealed no variation either, but it was strongly affected by poor weather conditions. Conclusions. We find no evidence for star-planet interaction in HD80606 at the moment of the periastron passage of its very eccentric planet. The straightforward explanation for the non-detection is the absence of interaction as a result of a low magnetic field strength on either the planet or the star and of the low level of tidal interaction between the two. However, we cannot exclude two scenarios: i) the interaction can be instantaneous and of magnetic origin, being concentrated on the substellar point and its surrounding area; and ii) the interaction can lead to a delayed activity enhancement. In either scenario, a star-planet interaction would not be detectable with the dataset described in this paper.
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