arXiv subjects

Gabriele Columba

Publications and source records attributed to Gabriele Columba.

5 recordsLinked to original sources

arXiv2026

Analysis of the young disk around WRAY 15-1880: does it contain a primitive planetary system?

Observations of (giant) planets accreting material within their natal environment are crucial to constrain models for their formation. WRAY 15-1880 (aka RX J1842.9-3532) in the Corona Australis (CrA) complex has a prominent pre-transitional disk, and an age of ~2.8+-0.7 Myr, computed by comparison with isochrones using the accurate dynamical mass derived from disk kinematics. Hence, this star is in the late phases of disk evolution and might host accreting planets. We acquire new polarimetric imaging data with VLT-SPHERE and analyze archive observations taken with VLT-SPHERE, VLT-MUSE, and ALMA, finding a candidate Jupiter-like companion within the disk gap from high-contrast imaging. The mass estimates of the candidate companion, derived from various methods, are consistent with an object in the range of 0.3-7.6 MJup. The spectrum of the candidate companion is consistent with a T3 spectral type, in agreement with expectations of an object of a few Jupiter masses. We find an emission blob North-West of the star in the ALMA data rotating solidly with the candidate companion, that can be interpreted as a vortex/dust trap at the m=1 Lindblad resonance of the planet. Accretion on the candidate planet is not detected from the VLT-MUSE archival data. This may be due to insufficient contrast, an observational geometry that is unfavorable for viewing the planet's surface, or it could indicate that we are merely observing irregularities within the disk. Finally, we identify a microjet extending from the star perpendicular to the disk in these data.

astro-ph.SR↗

arXiv2025

Disk Evolution Study Through Imaging of Nearby Young Stars (DESTINYS): V721 CrA and BN CrA have wide and structured disks in polarised IR

We present near-infrared scattered-light observations of the disks around two stars of the Corona Australis star-forming region, V721 CrA, and BN CrA, obtained with VLT/SPHERE, in the H band, as part of the DESTINYS large programme. Our objective is to analyse the morphology of these disks, and highlight their main properties. We adopt an analytical axisymmetric disk model to fit the observations and perform a regression on key disk parameters, namely the dust mass, the height profile, and the inclination. We use RADMC-3D code to produce synthetic observations of the analytical models, with full polarised scattering treatment. Both stars show resolved and extended disks with substructures in the near-IR. The disk of V721 CrA is vertically thicker, radially smaller (120 au), and brighter than BN CrA (190 au). It also shows spiral arms in the inner regions. The disk of BN CrA shows a dark circular lane, which could be either an intrinsic dust gap or a self-cast shadow. Both disks are compatible with the evolutionary stage of their parent subgroup within the CrA region: V721 CrA belongs to the "on-cloud" part of CrA, which is dustier, denser and younger, whereas BN CrA is found on the outskirts of the older "off-cloud" group.

astro-ph.SR↗

arXiv2025

Shape and spin state model of contact binary (388188) 2006 DP14 using combined radar and optical observations

Contact binaries are found throughout the solar system. The recent discovery of Selam, the satellite of MBA (152830) Dinkinesh, by the NASA LUCY mission has made it clear that the term `contact binary' covers a variety of different types of bi-modal mass distributions and formation mechanisms. Only by modelling more contact binaries can this population be properly understood. We determined a spin state and shape model for the Apollo group contact binary asteroid (388188) 2006 DP14 using ground-based optical and radar observations collected between 2014 and 2023. Radar delay-Doppler images and continuous wave spectra were collected over two days in February 2014, while 16 lightcurves in the Cousins R and SDSS-r filters were collected in 2014, 2022 and 2023. We modelled the spin state using convex inversion before using the SHAPE modelling software to include the radar observations in modelling concavities and the distinctive neck structure connecting the two lobes. We find a spin state with a period of $(5.7860\pm0.0001)$ hours and pole solution of $\lambda = (180\pm121)^\circ$ and $\beta = (-80\pm7)^\circ$ with morphology indicating a 520 m long bi-lobed shape. The model's asymmetrical bi-modal mass distribution resembles other small NEA contact binaries such as (85990) 1999 JV6 or (8567) 1996 HW1, which also feature a smaller `head' attached to a larger `body'. The final model features a crater on the larger lobe, similar to several other modelled contact binaries. The model's resolution is 25 m, comparable to that of the radar images used.

astro-ph.EP↗

arXiv2024

Disk Evolution Study Through Imaging of Nearby Young Stars (DESTINYS): PDS 111, an old T Tauri star with a young-looking disk

The interplay between T Tauri stars and their circumstellar disks, and how this impacts the onset of planet formation has yet to be established. We studied a seemingly old T Tauri star, PDS 111, and its disk. We analyzed optical, infrared, and sub-millimeter observations obtained with VLT/X-shooter, Mercator/HERMES, TESS, VLT/SPHERE, and ALMA, providing a new view on PDS 111 and its protoplanetary disk. The multi-epoch spectroscopy yields photospheric lines to classify the star, and emission lines to study variability in the hot inner disk and to determine the mass-accretion rate. The SPHERE and ALMA observations are used to characterize the dust distribution of the small and large grains, respectively. PDS 111 is a weak-line T Tauri star with spectral type G2, exhibits strong H$α$ variability and with a low mass-accretion rate of $1-5\times10^{-10}$\,M$_{\odot}$\,yr$^{-1}$. We measured an age of the system of 15.9$^{+1.7}_{-3.7}$ Myr using pre-main sequence tracks. The SPHERE observations show a strongly flaring disk with an asymmetric substructure. The ALMA observations reveal a 30 au cavity in the dust continuum emission with a low contrast asymmetry in the South-West of the disk and a dust disk mass of 45.8\,$M_\oplus$. The $^{12}$CO radial extension is at least three times larger than that of the dust emission. Although the measured age is younger than suggested in literature, PDS 111 still seems relatively old; this provides insight into disk properties at an advanced stage of pre-main sequence evolution. The characteristics of this disk are very similar to its younger counterparts: strongly flaring, an average disk mass, a typical radial extent of the disk gas and dust, and the presence of common substructures. This suggests that disk evolution has not significantly changed the disk properties. These results show similarities with the "Peter Pan disks" around M-dwarfs.

astro-ph.EP↗

arXiv2023

Statistics of Magrathea exoplanets beyond the Main Sequence. Simulating the long-term evolution of circumbinary giant planets with TRES

Notwithstanding the tremendous growth of the exoplanetary field in the last decade, limited attention has been paid to the planets around binary stars. Circumbinary planets (CBPs) have been discovered primarily around Main Sequence (MS) stars. No exoplanet has been found orbiting double white dwarf (DWD) binaries yet. We modelled the long-term evolution of CBPs, throughout the life stages of their hosts, from MS to white dwarf (WD). Our goal is to provide the community with both theoretical constraints on CBPs evolution beyond the MS and the occurrence rates of planet survival. We further developed the publicly available Triple Evolution Simulation (TRES) code, implementing a variety of physical processes affecting substellar bodies. We then used this code to simulate the evolution, up to one Hubble time, of two synthetic populations of circumbinary giant planets. Each population has been generated using different priors for the planetary orbital parameters. In our simulated populations we identified several evolutionary categories, such as survived, merged, and destabilised systems. Our primary focus is those systems where the planet survived the entire system evolution and orbits a DWD binary, which we call "Magrathea" planets. We found that a significant fraction of simulated CBPs survive and become Magratheas. In the absence of multi-planet migration mechanisms, this category of planets is characterised by long orbital periods. Magrathea planets are a natural outcome of triple systems evolution, and they could be relatively common in the Galaxy. They can survive the death of their binary hosts if they orbit far enough to avoid engulfment and instabilities. Our results can ultimately be a reference to orient future observations of this uncharted class of planets and to compare different theoretical models.

astro-ph.EP↗