arXiv subjects

O. Schreurs

Publications and source records attributed to O. Schreurs.

4 recordsLinked to original sources

arXiv2026

The trans-Neptunian object (119951) 2002 KX14 revealed via multiple stellar occultations

(119951) 2002 KX14 is a large classical TNO with limited previous observations and unresolved questions regarding its physical properties. Five stellar occultations by 2002 KX14 were observed from 2020 to 2023, involving multiple telescopes across different locations in Europe and the Americas. The five occultations resulted in 15 positive chords, accurately measuring the 2002 KX14's shape and size. The projected ellipse has semi-major and semi-minor axes of $241.0 \pm 7.2$ km and $157.1 \pm 5.2$ km, respectively, corresponding to an average area-equivalent diameter of $389.2 \pm 8.7$ km. The geometric albedo was estimated at $11.9 \pm 0.7\%$.

astro-ph.EP↗

arXiv2025

A high geometric albedo and small size of the Haumea cluster member (24835) 1995 SM55 from a stellar occultation and photometric observations

Trans-Neptunian objects (TNOs) are among the most ancient bodies of the solar system. Understanding their physical properties is key to constraining their origin and the evolution of the outer regions beyond Neptune. Stellar occultations provide highly accurate size and shape information. (24835) 1995 SM55 is one of the few members of the Haumea cluster and thus of particular interest. We aimed to determine its projected size, absolute magnitude, and geometric albedo, and to compare these with Haumea. A stellar occultation on 25 February 2024 was observed from five sites, with seven positive detections and 33 negative chords. An elliptical fit to the occultation chords yields semi-axes of $(104.3 \pm 0.4) \times (83.5 \pm 0.5)$ km, giving an area-equivalent diameter of $186.7 \pm 1.8$ km, smaller than the 250 km upper limit from Herschel thermal data. Photometry provides an absolute magnitude $H_V = 4.55 \pm 0.03$, a phase slope of $0.04 \pm 0.02$ mag/deg, and a $V-R = 0.37 \pm 0.05$. The rotational variability has an amplitude $Δm = 0.05$ mag, but the period remains uncertain. Combining occultation and photometry, we derive a geometric albedo $p_V = 0.80 \pm 0.04$, one of the highest values measured for a TNO. This value is slightly higher than that of Haumea, consistent with the interpretation that 1995 SM55 belongs to the Haumea cluster.

astro-ph.EP↗

arXiv2024

A study of centaur (54598) Bienor from multiple stellar occultations and rotational light curves

Centaurs, distinguished by their volatile-rich compositions, play a pivotal role in understanding the formation and evolution of the early solar system, as they represent remnants of the primordial material that populated the outer regions. Stellar occultations offer a means to investigate their physical properties, including shape, rotational state, or the potential presence of satellites and rings. This work aims to conduct a detailed study of the centaur (54598) Bienor through stellar occultations and rotational light curves from photometric data collected during recent years. We successfully predicted three stellar occultations by Bienor, which were observed from Japan, Eastern Europe, and the USA. In addition, we organized observational campaigns from Spain to obtain rotational light curves. At the same time, we develop software to generate synthetic light curves from three-dimensional shape models, enabling us to validate the outcomes through computer simulations. We resolve Bienor's projected ellipse for December 26, 2022, determine a prograde sense of rotation, and confirm an asymmetric rotational light curve. We also retrieve the axes of its triaxial ellipsoid shape as a = (127 $\pm$ 5) km, b = (55 $\pm$ 4) km, and c = (45 $\pm$ 4) km. Moreover, we refine the rotation period to 9.1736 $\pm$ 0.0002 hours and determine a geometric albedo of (6.5 $\pm$ 0.5) %, higher than previously determined by other methods. Finally, by comparing our findings with previous results and simulated rotational light curves, we analyze whether an irregular or contact-binary shape, the presence of an additional element such as a satellite, or significant albedo variations on Bienor's surface, may be present.

astro-ph.EP↗

arXiv2023

Constraints on (2060) Chiron's size, shape, and surrounding material from the November 2018 and September 2019 stellar occultations

After the discovery of rings around the largest known Centaur object, (10199) Chariklo, we carried out observation campaigns of stellar occultations produced by the second-largest known Centaur object, (2060) Chiron, to better characterize its physical properties and presence of material on its surroundings. We predicted and successfully observed two stellar occultations by Chiron. These observations were used to constrain its size and shape by fitting elliptical limbs with equivalent surface radii in agreement with radiometric measurements. Constraints on the (2060) Chiron shape are reported for the first time. Assuming an equivalent radius of R$_{equiv}$ = 105$^{+6}_{-7}$ km, we obtained a semi-major axis of a = 126 $\pm$ 22 km. Considering Chiron's true rotational light curve amplitude and assuming it has a Jacobi equilibrium shape, we were able to derive a 3D shape with a semi-axis of a = 126 $\pm$ 22 km, b = 109 $\pm$ 19 km, and c = 68 $\pm$ 13 km, implying in a volume-equivalent radius of R$_{vol}$ = 98 $\pm$ 17 km, implying a density of 1119 $\pm$ 4 kg m$^{-3}$. We determined the physical properties of the 2011 secondary events around Chiron, which may then be directly compared with those of Chariklo rings, as the same method was used. Data obtained from SAAO in 2018 do not show unambiguous evidence of the proposed rings, mainly due to the large sampling time. Meanwhile, we discarded the possible presence of a permanent ring similar to (10199) Chariklo's C1R in optical depth and extension. Using the first multi-chord stellar occultation by (2060) Chiron and considering it to have a Jacobi equilibrium shape, we derived its 3D shape. New observations of a stellar occultation by (2060) Chiron are needed to further investigate the material's properties around Chiron, such as the occultation predicted for September 10, 2023.

astro-ph.EP↗