877 research outputs found
Hydrodynamics of circumbinary accretion: Angular momentum transfer and binary orbital evolution
We carry out 2D viscous hydrodynamical simulations of circumbinary accretion
using the AREPO code. We self-consistently compute the accretion flow over a
wide range of spatial scales, from the circumbinary disk (CBD) far from the
central binary, through accretion streamers, to the disks around individual
binary components, resolving the flow down to 2% of the binary separation. We
focus on equal-mass binaries with arbitrary eccentricities. We evolve the flow
over long (viscous) timescales until a quasi-steady is reached, in which the
mass supply rate at large distances (assumed constant) equals the
time-averaged mass transfer rate across the disk and the total mass accretion
rate onto the binary components. This quasi-steady state allows us to compute
the secular angular momentum transfer rate onto the binary,
, and the resulting orbital evolution. Through direct
computation of the gravitational and accretion torques on the binary, we find
that is consistently positive (i.e., the binary gains
angular momentum), with in the
range of , depending on the binary eccentricity (where
are the binary semi-major axis and angular frequency); we also
find that this is equal to the net angular momentum
current across the CBD, indicating that global angular momentum balance is
achieved in our simulations. We compute the time-averaged rate of change of the
binary orbital energy for eccentric binaries, and thus obtain the secular rates
and . In all cases,
is positive, i.e., the binary expands while
accreting. We discuss the implications of our results for the merger of
supermassive binary black holes and for the formation of close stellar
binaries.Comment: 18 pages, 13 figures, 1 table. Accepted for publication in Ap
Suppression of extreme orbital evolution in triple systems with short range forces
The Lidov-Kozai (LK) mechanism plays an important role in the secular
evolution of many hierarchical triple systems. The standard LK mechanism
consists of large-amplitude oscillations in eccentricity and inclination of a
binary subject to the quadrupole potential from an outer perturber. Recent work
has shown that when the octupole terms are included in the potential, the inner
binary can reach more extreme eccentricities as well as undergo orientation
flips. It is known that pericenter precessions due to short-range effects, such
as General Relativity and tidal and rotational distortions, can limit the
growth of eccentricity and even suppress standard (quadrupolar) LK
oscillations, but their effect on the octupole-level LK mechanism has not been
fully explored. In this paper, we systematically study how these short-range
forces affect the extreme orbital behaviour found in octupole LK cycles. In
general, the influence of the octupole potential is confined to a range of
initial mutual inclinations Itot centered around 90deg (when the inner binary
mass ratio is <<1), with this range expanding with increasing octupole
strength. We find that, while the short-range forces do not change the width
and location of this "window of influence", they impose a strict upper limit on
the maximum achievable eccentricity. This limiting eccentricity can be
calculated analytically, and its value holds even for strong octupole potential
and for the general case of three comparable masses. Short-range forces also
affect orbital flips, progressively reducing the range of Itot within which
flips are possible as the intensity of these forces increases.Comment: 20 pages,15 figures, updated to match version published on MNRA
Global controllability tests for geometric hybrid control systems
Hybrid systems are characterized by having an interaction between continuous
dynamics and discrete events. The contribution of this paper is to provide
hybrid systems with a novel geometric formulation so that controls can be
added. Using this framework we describe some new global controllability tests
for hybrid control systems exploiting the geometry and the topology of the set
of jump points, where the instantaneous change of dynamics take place.
Controllability is understood as the existence of a feasible trajectory for the
system joining any two given points. As a result we describe examples where
none of the continuous control systems are controllable, but the associated
hybrid system is controllable because of the characteristics of the jump set.Comment: 27 pages, 5 figure
Inferencia del origen del bovino Criollo Cubano a través del análisis de patri- y matrilinajes
Antes de descubrimiento, no existÃan bovinos en América. Los primeros, fueron introducidos en la Antillas Mayores (La Española, Puerto Rico, Jamaica y Cuba), y desde allà trasladados al resto de Latinoamérica. Actualmente, existen en Cuba alrededor de 1300 bovinos Criollos, concentrados principalmente en la región oriental. Con el objetivo de analizar el origen materno de esta raza y detectar eventos contemporáneos de flujo génico por vÃa paterna, se analizó un fragmento de 240 pb del D-loop mitocondrial (mtADN) y 5 microsatélites del cromosoma Y (BTY), en 36 hembras y 21 machos respectivamente. La diversidad genética se estimó mediante el número de haplotipos, el número de sitios polimórficos, el número de diferencias nucleotÃdicas entre pares de secuencias y el Ãndice de diversidad nucleotÃdica, mientras que el análisis filogenético se realizó utilizando el método de median joining network. Dicho análisis permitió detectar 15 haplotipos mitocondriales (10 del haplogrupo europeo T3, 3 del africano T1, 1 del cercano oriente T2 y 1 ambiguo T1-T3) y 3 haplotipos en el BTY, ambos del haplogrupo cebuÃno Y3. En el mtADN se detectaron 23 sitios polimórficos con una diversidad nucleotÃdica de 0,014 y 3,36 diferencias medias entre pares de secuencias. En conclusión, la población de bovinos Criollos Cubanos presentó una composición haplotÃpica mitocondrial comparable a la de otras razas criollas y mediterráneas, hecho que concuerda con su origen histórico. El BTY evidenció altos niveles de introgresion paterna de genes del zebú.Cattle was absent from America before the discovery. Initially, bovine were brought to Greater Antilles (La Española, Puerto Rico, Jamaica and Cuba islands), and in the course of a few years, they were taken from Caribbean islands to the rest of Latin America. Nowadays, Cuban Creole cattle population is about 1300 heads, mainly located in the eastern region of the island. With the aim of analyzing the maternal origin of Cuban Creole cattle and detect possible contemporaneous, male mediated, gene flow, a 240 pb fragment of mitochondrial D-loop (mtDNA) and five microsatellites of Y chromosome (BTY) were studied in 36 dams and 21 sires, respectively. Genetic diversity was evaluated through number of haplotypes, mean number of pairwise differences and nucleotide diversity. The phylogenetic analysis was performed using a median joining. A total of 15 mtDNA haplotypes were detected in the studied population (10 from the European haplogroup T3, 3 from the African T1, 1 from the Nearern East T2, and 1 ambiguous T1-T3). The number of polymorphic sites, the mean nucleotide diversity, and the mean number of pairwise differences were 23, 0.014 and 3.36, respectively. Two patrilinages were detected, both belonging to the Y3 Zebu haplogroup. In conclusion, Cuban Creole cattle population had a mtDNA haplotypic composition similar to the observed in Creole and Mediterranean breeds, what is in concordance with its historical origin. Y chromosome analysis evidenced a male mediated process of zebu introgression.Fil: Liron, Juan Pedro. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico CONICET- La Plata. Instituto de Genética Veterinaria "Ing. Fernando Noel Dulout". Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias. Instituto de Genética Veterinaria; ArgentinaFil: Acosta, A.. Centro Nacional de Sanidad Agropecuaria. Laboratorio de Genética Molecular; CubaFil: Rogberg Muñoz, Andres. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico CONICET- La Plata. Instituto de Genética Veterinaria "Ing. Fernando Noel Dulout". Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias. Instituto de Genética Veterinaria; ArgentinaFil: Uffo, O.. Centro Nacional de Sanidad Agropecuaria. Laboratorio de Genética Molecular; CubaFil: Posik, Diego Manuel. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico CONICET- La Plata. Instituto de Genética Veterinaria "Ing. Fernando Noel Dulout". Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias. Instituto de Genética Veterinaria; ArgentinaFil: Garcia, J.. Ministerio de la Agricultura. Dirección Nacional de Genética; CubaFil: Peral Garcia, Pilar. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico CONICET- La Plata. Instituto de Genética Veterinaria "Ing. Fernando Noel Dulout". Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias. Instituto de Genética Veterinaria; ArgentinaFil: Giovambattista, Guillermo. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico CONICET- La Plata. Instituto de Genética Veterinaria "Ing. Fernando Noel Dulout". Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias. Instituto de Genética Veterinaria; Argentin
Orbital alignment of the eccentric warm Jupiter TOI-677 b
Warm Jupiters lay out an excellent laboratory for testing models of planet
formation and migration. Their separation from the host star makes tidal
reprocessing of their orbits ineffective, which preserves the orbital
architectures that result from the planet-forming process. Among the measurable
properties, the orbital inclination with respect to the stellar rotational
axis, stands out as a crucial diagnostic for understanding the migration
mechanisms behind the origin of close-in planets. Observational limitations
have made the procurement of spin-orbit measurements heavily biased toward hot
Jupiter systems. In recent years, however, high-precision spectroscopy has
begun to provide obliquity measurements for planets well into the warm Jupiter
regime. In this study, we present Rossiter-McLaughlin (RM) measurements of the
projected obliquity angle for the warm Jupiter TOI-677 b using ESPRESSO at the
VLT. TOI-677 b exhibits an extreme degree of alignment (
deg), which is particularly puzzling given its significant eccentricity (). TOI-677 b thus joins a growing class of close-in giants that
exhibit large eccentricities and low spin-orbit angles, which is a
configuration not predicted by existing models. We also present the detection
of a candidate outer brown dwarf companion on an eccentric, wide orbit ( and yr). Using simple estimates, we show that this
companion is unlikely to be the cause of the unusual orbit of TOI-677 b.
Therefore, it is essential that future efforts prioritize the acquisition of RM
measurements for warm Jupiters.Comment: 15 pages, 6 figures, 5 tables. Accepted for publication in the
Astronomical Journa
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