arXiv subjects

Konstantinos Odysseas Xenos

Publications and source records attributed to Konstantinos Odysseas Xenos.

2 recordsLinked to original sources

arXiv2026

Rotation, spectral type, and albedo of the potentially hazardous asteroid (153814) 2001 WN$_{\text 5}$ Prior to the 2028 June close approach

The potentially hazardous asteroid (153814) 2001 WN$_5$ will pass inside the lunar distance on June 26, 2028, offering a rare opportunity to characterize a kilometer-scale near-Earth asteroid at high angular resolution. We aim to constrain the rotation state, shape, visible colors, geometric albedo, and taxonomy of 2001 WN$_5$ before its 2028 close approach. We combined new photometry from the 1.54 m Danish Telescope (DK154) with archival and survey observations from the Transiting Exoplanet Survey Satellite (TESS), Dark Energy Camera (DECam), Zwicky Transient Facility (ZTF), and the Asteroid Terrestrial-impact Last Alert System (ATLAS). These data were used to refine the rotation period, investigate the spin-shape solution space, derive visible colors, and estimate the geometric albedo from phase curve slopes. The available lightcurves do not uniquely constrain the sidereal rotation period, but the preferred pole solutions lie in the southern hemisphere in ecliptic coordinates. Visible colors from multiple independent datasets are consistent with the C-complex, while the TESS phase curve slopes give $p_{\rm V} = 0.13\pm0.04$, consistent with previous thermal-infrared albedo estimates. Combining the visible colors, albedo, and published near-infrared spectra, we classify 2001 WN$_5$ as most likely a B-type asteroid. The effective diameter is estimated to be $D = 0.81 \pm 0.13$ km using the $H$-$G$ model, while the linear model yields a slightly smaller value of $0.74 \pm 0.11$ km. During the 2028 encounter, 2001 WN$_5$ should reach an apparent diameter of about 0.5~arcsec, making it an excellent target for coordinated photometric, spectroscopic, and high-angular-resolution observations. Observations during the 2026-2027 apparition will be essential for improving its spin and shape model before its 2028 close approach.

astro-ph.EP↗

arXiv2025

How does the chemical composition of solids influence the formation of planetesimals?

The formation of planetesimals is a necessary step in the formation of planets. While several mechanisms have been proposed, a local dust-to-gas ratio above unity is a strong requirement to trigger the collapse of pebble clouds into planetesimals. A prime location for this is the water-ice line, where large water-rich pebbles evaporate and release their smaller silicate cores. This enhances the local dust-to-gas ratio due to the different inward drift speeds of large and small pebbles. Previous work suggested that planetesimal formation becomes difficult at overall dust-to-gas ratios below 0.6\%, consistent with the occurrence of close-in super Earths. However, the influence of disc composition on planetesimal formation remains unclear. Observations of stellar abundances show both a decrease and a wide spread in C/O ratios for low-metallicity stars. Using the C/O ratio as a proxy to determine water ice abundance in discs, we use the 1D disc evolution code chemcomp to simulate protoplanetary discs with varying C/O and dust-to-gas ratios over 3 Myr. Planetesimal formation is modeled using conditions based on dust-gas dynamics and pebble fragmentation. Our results confirm that planetesimal formation strongly depends on disc metallicity, with lower metallicity discs forming significantly fewer planetesimals. A lower carbon fraction generally promotes planetesimal formation by increasing water ice, while higher carbon fractions suppress it. The opposite is seen for oxygen: higher oxygen content leads to more efficient planetesimal formation at the same dust-to-gas ratio. We thus predict that planets around low-metallicity stars should be more common when their C/O ratio is low and oxygen is enhanced, a trend that can be tested observationally. Our simulations thus open a pathway to understand if the composition of the planet forming material influences the growth of planets.

astro-ph.EP↗