227 research outputs found
The Spin-Orbit Evolution of GJ 667C System: The Effect of Composition and Other Planet's Perturbations
Potentially habitable planets within the habitable zone of M-dwarfs are
affected by tidal interaction. We studied the tidal evolution in GJ 667C using
a numerical code we call TIDEV. We reviewed the problem of the dynamical
evolution focusing on the effects that a rheological treatment, different
compositions and the inclusion of orbital perturbations, have on the spin-down
time and the probability to be trapped in a low spin-orbit resonance.
Composition have a strong effect on the spin-down time, changing, in some
cases, by almost a factor of 2 with respect to the value estimated for a
reference Earth-like model. We calculated the time to reach a low resonance
value (3:2) for the configuration of 6 planets. Capture probabilities are
affected when assuming different compositions and eccentricities variations. We
chose planets b and c to evaluate the probabilities of capture in resonances
below 5:2 for two compositions: Earth-like and Waterworld planets. We found
that perturbations, although having a secular effect on eccentricities, have a
low impact on capture probabilities and noth- ing on spin-down times. The
implications of the eccentricity variations and actual habitability of the GJ
667C system are discussed.Comment: 15 pages, 9 figures, 4 tables. Accepted for publication in MNRAS - V
Quantum correlations between two distant cavity QED systems coupled by a mechanical resonator
Achieving quantum correlations between two distant systems is a desirable
feature for quantum networking. In this work, we study a system composed of two
quantum emitter-cavity subsystems spatially separated. A mechanical resonator
couples to either both quantum emitters or both cavities leading to quantum
correlations between both subsystems such as non-local light-matter dressed
states and cavity-cavity normal mode splitting. These indirect couplings can be
explained by an effective Hamiltonian for large energy detuning between the
mechanical resonator and the atoms/cavities. Moreover, it is found optimal
conditions for the physical parameters of the system in order to maximize the
entanglement of such phonon-mediated couplings
Location, orbit and energy of a meteoroid impacting the moon during the Lunar Eclipse of January 21, 2019
During lunar eclipse of January 21, 2019 a meteoroid impacted the Moon
producing a visible light flash. The impact was witnessed by casual observers
offering an opportunity to study the phenomenon from multiple geographical
locations. We use images and videos collected by observers in 7 countries to
estimate the location, impact parameters (speed and incoming direction) and
energy of the meteoroid. Using parallax, we achieve determining the impact
location at lat. , lon. and
geocentric distance as 356553 km. After devising and applying a photo-metric
procedure for measuring flash standard magnitudes in multiple RGB images having
different exposure times, we found that the flash, had an average G-magnitude
. We use gravitational ray tracing (GRT) to
estimate the orbital properties and likely radiant of the impactor. We find
that the meteoroid impacted the moon with a speed of km/s (70%
C.L.) and at a shallow angle, degrees. Assuming a normal error
for our estimated flash brightness, educated priors for the luminous efficiency
and object density, and using the GRT-computed probability distributions of
impact speed and incoming directions, we calculate posterior probability
distributions for the kinetic energy (median = 0.8 kton), body
mass ( = 27 kg) and diameter ( = 29 cm), and crater
size ( = 9 m). If our assumptions are correct, the crater left by
the impact could be detectable by prospecting lunar probes. These results arose
from a timely collaboration between professional and amateur astronomers which
highlight the potential importance of citizen science in astronomy.Comment: 19 pages, 11 figures, 4 tables. Data and scripts available in
https://github.com/seap-udea/MoonFlashes. Accepted for publication in MNRA
Ultrafast control of Rabi oscillations in a polariton condensate
We report the experimental observation and control of space and time-resolved
light-matter Rabi oscillations in a microcavity. Our setup precision and the
system coherence are so high that coherent control can be implemented with
amplification or switching off of the oscillations and even erasing of the
polariton density by optical pulses. The data is reproduced by a fundamental
quantum optical model with excellent accuracy, providing new insights on the
key components that rule the polariton dynamics.Comment: 5 pages, 3 figures, supplementary 7 pages, 4 figures. Supplementary
videos:
https://drive.google.com/folderview?id=0B0QCllnLqdyBNjlMLTdjZlNhbTQ&usp=sharin
Halo based reconstruction of the cosmic mass density field
We present the implementation of a halo based method for the reconstruction
of the cosmic mass density field. The method employs the mass density
distribution of dark matter haloes and its environments computed from
cosmological N-body simulations and convolves it with a halo catalog to
reconstruct the dark matter density field determined by the distribution of
haloes. We applied the method to the group catalog of Yang etal (2007) built
from the SDSS Data Release 4. As result we obtain reconstructions of the cosmic
mass density field that are independent on any explicit assumption of bias. We
describe in detail the implementation of the method, present a detailed
characterization of the reconstructed density field (mean mass density
distribution, correlation function and counts in cells) and the results of the
classification of large scale environments (filaments, voids, peaks and sheets)
in our reconstruction. Applications of the method include morphological studies
of the galaxy population on large scales and the realization of constrained
simulations.Comment: Accepted for publication in MNRA
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