5,583 research outputs found
Properties of the redback millisecond pulsar binary 3FGL J0212.1+5320
Linares et al. (2016) obtained quasi-simultaneous g', r' and i-band light
curves and an absorption line radial velocity curve of the secondary star in
the redback system 3FGL J0212.1+5320. The light curves showed two maxima and
minima primarily due to the secondary star's ellipsoidal modulation, but with
unequal maxima and minima. We fit these light curves and radial velocities with
our X-ray binary model including either a dark solar-type star spot or a hot
spot due to off-centre heating from an intrabinary shock, to account for the
unequal maxima. Both models give a radial velocity semi-amplitude and
rotational broadening that agree with the observations. The observed secondary
star's effective temperature is best matched with the value obtained using the
hot spot model, which gives a neutron star and secondary star mass of =1.85 and =0.50
, respectively.Comment: 10 pages, 8 figues, accepted by MNRA
A 5 Meps $100 USB2.0 Address-Event Monitor-Sequencer Interface
This paper describes a high-speed USB2.0 Address-
Event Representation (AER) interface that allows simultaneous
monitoring and sequencing of precisely timed AER data. This
low-cost (<$100), two chip, bus powered interface can achieve
sustained AER event rates of 5 megaevents per second (Meps).
Several boards can be electrically synchronized, allowing simultaneous
synchronized capture from multiple devices. It has three
AER ports, one for sequencing, one for monitoring and one for
passing through the monitored events. This paper also describes
the host software infrastructure that makes the board usable for a
heterogeneous mixture of AER devices and that allows recording
and playback of recorded data
Hierarchy of inequalities for quantitative duality
We derive different relations quantifying duality in a generic two-way
interferometer. These relations set different upper bounds to the visibility V
of the fringes measured at the output port of the interferometer. A hierarchy
of inequalities is presented which exhibits the influence of the availability
to the experimenter of different sources of which-way information contributing
to the total distinguishability D of the ways. For mixed states and unbalanced
interferometers an inequality is derived, V^2+ Xi^2 \leq 1, which can be more
stringent than the one associated with the distinguishability (V^2+ D^2 \leq
1).Comment: 7 pages, 4 figure
Las maravillas ocultas en la tabla periódica
Este trabajo constituye un enfoque holista de la Tabla Periódica (TP). Basados en el origen de los nombres de los elementos como punto de partida, es posible recorrer distintos campos del conocimiento, no sólo química, sino historia, geografía, mitología, biografías de personajes famosos, etc. Así, a medida que se aprende sobre los elementos químicos, su comportamiento y sus propiedades, se tiene la oportunidad de aprender y repasar sobre otras disciplinas. Es como si la (TP), a través de cada casilla, abriera una puerta hacia el maravilloso mundo del saber. La aplicación de esta propuesta en un curso electivo en la Universidad del Valle (Cali, Colombia) usando la TP como eje central ha permitido identificar nuevos caminos para enseñar química y caracterizar los aspectos que aumentan las competencias transversales de los alumnos de diversas carreras en la Universidad
Low-frequency QPO from the 11 Hz accreting pulsar in Terzan 5: not frame dragging
We report on 6 RXTE observations taken during the 2010 outburst of the 11 Hz
accreting pulsar IGR J17480-2446 located in the globular cluster Terzan 5.
During these observations we find power spectra which resemble those seen in
Z-type high-luminosity neutron star low-mass X-ray binaries, with a
quasi-periodic oscillation (QPO) in the 35-50 Hz range simultaneous with a kHz
QPO and broad band noise. Using well known frequency-frequency correlations, we
identify the 35-50 Hz QPOs as the horizontal branch oscillations (HBO), which
were previously suggested to be due to Lense-Thirring precession. As IGR
J17480-2446 spins more than an order of magnitude more slowly than any of the
other neutron stars where these QPOs were found, this QPO can not be explained
by frame dragging. By extension, this casts doubt on the Lense-Thirring
precession model for other low-frequency QPOs in neutron-star and perhaps even
black-hole systems.Comment: 6 pages, 5 figures, Accepted for publication in ApJ
Spike-based control monitoring and analysis with Address Event Representation
Neuromorphic engineering tries to mimic biological
information processing. Address-Event Representation (AER) is
a neuromorphic communication protocol for spiking neurons
between different chips. We present a new way to drive robotic
platforms using spiking neurons. We have simulated spiking
control models for DC motors, and developed a mobile robot
(Eddie) controlled only by spikes. We apply AER to the robot
control, monitoring and measuring the spike activity inside the
robot. The mobile robot is controlled by the AER-Robot tool,
and the AER information is sent to a PC using the
USBAERmini2 interface.Junta de Andalucía P06-TIC-01417Ministerio de Educación y Ciencia TEC2006-11730-C03-0
Human vs. Computer Slot Car Racing using an Event and Frame-Based DAVIS Vision Sensor
This paper describes an open-source
implementation of an event-based dynamic and
active pixel vision sensor (DAVIS) for racing
human vs. computer on a slot car track. The
DAVIS is mounted in "eye-of-god" view. The
DAVIS image frames are only used for setup and
are subsequently turned off because they are not
needed. The dynamic vision sensor (DVS) events
are then used to track both the human and
computer controlled cars. The precise control of
throttle and braking afforded by the low latency of
the sensor output enables consistent outperformance
of human drivers at a laptop CPU
load of <3% and update rate of 666Hz. The sparse
output of the DVS event stream results in a data
rate that is about 1000 times smaller than from a
frame-based camera with the same resolution and
update rate. The scaled average lap speed of the
1/64 scale cars is about 450km/h which is twice as
fast as the fastest Formula 1 lap speed. A feedbackcontroller
mode allows competitive racing by
slowing the computer controlled car when it is
ahead of the human. In tests of human vs.
computer racing the computer still won more than
80% of the races.Unión Europea FP7-ICT-270324Unión Europea FP7-ICT-60095
Convocation
The origins of phenotypic variation within mimetic Heliconius butterflies have long fascinated biologists and naturalists. However, the evolutionary processes that have generated this extraordinary diversity remain puzzling. Here we examine intraspecific variation across Heliconius cydno diversification and compare this variation to that within the closely related H. melpomene and H. timareta radiations. Our data, which consist of both mtDNA and genome scan from nearly 2250 AFLP loci, reveal a complex history of differentiation and admixture at different geographic scales. Both mtDNA and AFLP phylogenies suggest that H. timareta and H. cydno are probably geographic extremes of the same radiation that likely diverged from H. melpomene during the Pliocene-Pleistocene boundary. MtDNA suggest that this radiation originated in Central America or the Northwestern region of South America, with a subsequent colonization of the eastern and western slopes of the Andes. Our genome-scan data indicate significant admixture among sympatric H. cydno/H.timareta and H. melpomene populations across the extensive geographic ranges of the two radiations. Within H. cydno, both mtDNA and AFLP data indicate significant population structure at local scales, with strong genetic differences even among adjacent H. cydno color pattern races. These genetic patterns highlight the importance of past geoclimatic events, intraspecific gene flow, and local population differentiation in the origin and establishment of new adaptive forms
Constraining the properties of neutron star crusts with the transient low-mass X-ray binary Aql X-1
Aql X-1 is a prolific transient neutron star low-mass X-ray binary that
exhibits an accretion outburst approximately once every year. Whether the
thermal X-rays detected in intervening quiescent episodes are the result of
cooling of the neutron star or due to continued low-level accretion remains
unclear. In this work we use Swift data obtained after the long and bright 2011
and 2013 outbursts, as well as the short and faint 2015 outburst, to
investigate the hypothesis that cooling of the accretion-heated neutron star
crust dominates the quiescent thermal emission in Aql X-1. We demonstrate that
the X-ray light curves and measured neutron star surface temperatures are
consistent with the expectations of the crust cooling paradigm. By using a
thermal evolution code, we find that ~1.2-3.2 MeV/nucleon of shallow heat
release describes the observational data well, depending on the assumed
mass-accretion rate and temperature of the stellar core. We find no evidence
for varying strengths of this shallow heating after different outbursts, but
this could be due to limitations of the data. We argue that monitoring Aql X-1
for up to ~1 year after future outbursts can be a powerful tool to break model
degeneracies and solve open questions about the magnitude, depth and origin of
shallow heating in neutron star crusts.Comment: 14 pages, 5 figures, 3 tables, accepted to MNRA
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