127 research outputs found
Appearance of Saturn's F ring azimuthal channels for the anti-alignment configuration between the ring and Prometheus
In this article we explore the aspect of the F ring with respect to the
anti-alignment configuration between the ring and Prometheus. We focus our
attention on the shape of the F ring's azimuthal channels which were first
reported by Porco et al. (2005) and numerically explored by Murray et al.
(2005), who found excellent agreement between Cassini's ISS reprojected images
and their numerical model via a direct comparison. We find that for
anti-alignment the channels are wider and go deeper inside the ring material.
From our numerical model we find a new feature, an island in the middle of
the channel. This island is made up of the particles that have been perturbed
the most by Prometheus and only appears when this satellite is close to
apoapsis. In addition, plots of the anti-alignment configuration for different
orbital stages of Prometheus are obtained and discussed here.Comment: Number of pages: 12, number of tables: 1, number of figures:
The TWA 3 Young Triple System: Orbits, Disks, Evolution
We have characterized the spectroscopic orbit of the TWA 3A binary and
provide preliminary families of probable solutions for the TWA 3A visual orbit
as well as for the wide TWA 3A--B orbit. TWA 3 is a hierarchical triple located
at 34 pc in the 10 Myr old TW Hya association. The wide component
separation is 1."55; the close pair was first identified as a possible binary
almost 20 years ago. We initially identified the 35-day period orbital solution
using high-resolution infrared spectroscopy which angularly resolved the A and
B components. We then refined the preliminary orbit by combining the infrared
data with a re-analysis of our high-resolution optical spectroscopy. The
orbital period from the combined spectroscopic solution is 35 days, the
eccentricity is 0.63, and the mass ratio is 0.84; although this
high mass ratio would suggest that optical spectroscopy alone should be
sufficient to identify the orbital solution, the presence of the tertiary B
component likely introduced confusion in the blended optical spectra. Using
millimeter imaging from the literature, we also estimate the inclinations of
the stellar orbital planes with respect to the TWA 3A circumbinary disk
inclination and find that all three planes are likely misaligned by at least
30 degrees. The TWA 3A spectroscopic binary components have spectral
types of M4.0 and M4.5; TWA 3B is an M3. We speculate that the system formed as
a triple, is bound, and that its properties were shaped by dynamical
interactions between the inclined orbits and disk.Comment: Accepted to Ap
JWST observations of stellar occultations by solar system bodies and rings
In this paper we investigate the opportunities provided by the James Webb
Space Telescope (JWST) for significant scientific advances in the study of
solar system bodies and rings using stellar occultations. The strengths and
weaknesses of the stellar occultation technique are evaluated in light of
JWST's unique capabilities. We identify several possible JWST occultation
events by minor bodies and rings, and evaluate their potential scientific
value. These predictions depend critically on accurate a priori knowledge of
the orbit of JWST near the Sun-Earth Lagrange-point 2 (L2). We also explore the
possibility of serendipitous stellar occultations by very small minor bodies as
a by-product of other JWST observing programs. Finally, to optimize the
potential scientific return of stellar occultation observations, we identify
several characteristics of JWST's orbit and instrumentation that should be
taken into account during JWST's development.Comment: This paper is one of a series for a special issue on Solar System
observations with JWST in PASP. Accepted 2-Oct-2015. Preprint 30 pages, 5
tables, 8 figure
Material Around the Centaur (2060) Chiron from the 2018 November 28 UT Stellar Occultation
A stellar occultation of Gaia DR3 2646598228351156352 by the Centaur (2060)
Chiron was observed from the South African Astronomical Observatory on 2018
November 28 UT. Here we present a positive detection of material surrounding
Chiron from the 74-in telescope for this event. Additionally, a global
atmosphere is ruled out at the tens of mircobar level for several possible
atmospheric compositions. There are multiple 3-sigma drops in the 74-in light
curve: three during immersion and two during emersion. Occulting material is
located between 242-270 km from the center of the nucleus in the sky plane.
Assuming the ring-plane orientation proposed for Chiron from the 2011
occultation, the flux drops are located at 352, 344, and 316 km (immersion),
and 357, and 364 km (emersion) from the center, with normal optical depths of
0.26, 0.36, and 0.22 (immersion) and 0.26 and 0.18 (emersion), and equivalent
widths between 0.7-1.3 km. This detection is similar to the previously proposed
two-ring system and is located within the error bars of that ring-pole plane;
however, the normal optical depths are less than half of the previous values,
and three features are detected on immersion. These results suggest that the
properties of the surrounding material have evolved between the 2011, 2018, and
2022 observations.Comment: Accepted by the Planetary Science Journal 21 Oct. 2023; 13 pages, 9
figures, 4 table
Detección de Leucoptera sinuella (Reutti) (Lepidoptera: Lyonetiidae) en Chile, con la identificación de algunos parasitoides asociados
En marzo del 2015 el Servicio Agrícola y Ganadero (SAG), a través de actividades de vigilancia forestal, detectó por primera vez en Chile la presencia de Leucoptera sinuella (Reutti), atacando follaje de álamos (Populus spp., Salicaceae), en la comuna de Talagante (Región Metropolitana de Santiago).
Actividades de prospección desarrolladas por el SAG han determinado que este microlepidóptero se encuentra distribuido en diversas comunas de las regiones de Valparaíso, Metropolitana de Santiago, Libertador General Bernardo O’Higgins, Maule, Ñuble y Biobío. Adicionalmente, fueron
identificadas siete especies de microhimenópteros parasitoides asociados a L. sinuella, pertenecientes a las familias Eulophidae (6 especies) y Chalcididae (1 especie)
- …