4,305 research outputs found
Descobreixen un nou sistema binari de raigs-gamma a la nostra galàxia
L'equip de col∙laboració del telescopi espacial Fermi-LAT, integrat entre altres pels científics de l'Institut de Ciències de l'Espai (CSIC-IEEC), amb seu a la UAB, Andrea Caliandro, Daniela Hadasch i Diego Torres, ha descobert un nou sistema binari de raigs gamma en els voltants del centre Galàctic. El descobriment ha merescut la publicació de l'estudi a la prestigiosa revista Science ja que a dia d'avui, només es coneixen uns quants sistemes que emeten en raigs gamma.El equipo de colaboración del telescopio espacial Fermi-LAT, integrado entre otros por los científicos del Instituto de Ciencias del Espacio (CSIC-IEEC), ubicado en el campus de la UAB, Andrea Caliandro, Daniela Hadasch y Diego Torres, han descubierto un nuevo sistema binario de rayos gamma en los inmediaciones del Centro Galáctico tal descubrimiento ha merecido la publicación del estudio en la prestigiosa revista Science ya que a día de hoy, solo se conocen un puñado de sistemas que emiten en rayos gamma
Multi-wavelength observations of the transitional millisecond pulsar binary XSSJ12270-4859
We present an analysis of X-ray, Ultraviolet and optical/near-IR photometric
data of the transitional millisecond pulsar binary XSSJ12270-4859, obtained at
different epochs after the transition to a rotation-powered radio pulsar state.
The observations, while confirming the large-amplitude orbital modulation found
in previous studies after the state change, also reveal an energy dependence of
the amplitudes as well as variations on time scale of months. The amplitude
variations are anti-correlated in the X-ray and the UV/optical bands. The
average X-ray spectrum is described by a power law with \Gamma index of 1.07(8)
without requiring an additional thermal component. The power law index \Gamma
varies from 1.2 to 1.0 between superior and inferior conjunction of the neutron
star. We interpret the observed X-ray behaviour in terms of synchrotron
radiation emitted in an extended intrabinary shock, located between the pulsar
and the donor star, which is eclipsed due to the companion orbital motion. The
G5 type donor dominates the UV/optical and near-IR emission and is similarly
found to be heated up to ? 6500K as in the disc state. The analysis of optical
light curves gives a binary inclination 46 < i < 65deg and a mass ratio 0.11 <
q <0.26. The donor mass is found to be 0.15 < M2 < 0.36Msun for a neutron star
mass of 1.4Msun. The variations in the amplitude of the orbital modulation are
interpreted in terms of small changes in the mass flow rate from the donor
star. The spectral energy distribution from radio to gamma-rays is composed by
multiple contributions that are different from those observed during the
accretion-powered state.Comment: 10 pages, 8 figures, 1 table Accepted for publication in Monthly
Notices Royal Astronomical Society, Main Journa
Cosmic rays in the surroundings of SNR G35.6-0.4
HESS J1858+020 is a TeV gamma-ray source that was reported not to have any
clear cataloged counterpart at any wavelength. However, it has been recently
proposed that this source is indirectly associated with the radio source,
re-identified as a supernova remnant (SNR), G35.6-0.4. The latter is found to
be middle-aged ( kyr) and to have nearby molecular clouds (MCs). HESS
J1858+020 was proposed to be the result of the interaction of protons
accelerated in the SNR shell with target ions residing in the clouds. The Fermi
Large Area Telescope (LAT) First Source Catalog does not list any source
coincident with the position of HESS J1858+020, but some lie close. Here, we
analyse more than 2 years of data obtained with the Fermi-LAT for the region of
interest, and consider whether it is indeed possible that the closest LAT
source, 1FGL J1857.1+0212c, is related to HESS J1858+020. We conclude it is
not, and we impose upper limits on the GeV emission originating from HESS
J1858+020. Using a simplified 3D model for the cosmic-ray propagation out from
the shell of the SNR, we consider whether the interaction between SNR G35.6-0.4
and the MCs nearby could give rise to the TeV emission of HESS J1858+020
without producing a GeV counterpart. If so, the pair of SNR/TeV source with no
GeV detection would be reminiscent of other similarly-aged SNRs, such as some
of the TeV hotspots near W28, for which cosmic-ray diffusion may be used to
explain their multi-frequency phenomenology. However, for HESS J1858+020, we
found that although the phase space in principle allows for such GeV--TeV
non-correlation to appear, usual and/or observationally constrained values of
the parameters (e.g., diffusion coefficients and cloud-SNR likely distances)
would disfavor it.Comment: In press in MNRA
New Insight into the FS CMa System MWC 645 from Near-Infrared and Optical Spectroscopy
The B[e] phenomenon is manifested by a heterogeneous group of stars
surrounded by gaseous and dusty circumstellar envelopes with similar physical
conditions. Among these stars, the FS CMa-type objects are suspected to be
binary systems, which could be experiencing or have undergone a mass-transfer
process that could explain the large amount of material surrounding them. We
aim to contribute to the knowledge of a recently confirmed binary, MWC 645,
which could be undergoing an active mass-transfer process. We present
near-infrared and optical spectra, identify atomic and molecular spectral
features, and derive different quantitative properties of line profiles. Based
on publicly available photometric data, we search for periodicity in the light
curve and model the spectral energy distribution. We have detected molecular
bands of CO in absorption at 1.62 m and 2.3 m for the first time. We
derive an upper limit for the effective temperature of the cool binary
component. We found a correlation between the enhancement of the H
emission and the decrease in optical brightness that could be associated with
mass-ejection events or an increase in mass loss. We outline the global
properties of the envelope, possibly responsible for brightness variations due
to a variable extinction, and briefly speculate on different possible
scenarios.Comment: 20 pages, 11 figures, 2 tables, published in Galaxie
INTEGRAL observations of the gamma-ray binary 1FGL J1018.6-5856
The Fermi-LAT collaboration has recently reported that one of their detected
sources, namely, 1FGL J1018.6-5856, is a new gamma-ray binary similar to LS
5039. This has prompted efforts to study its multi-frequency behavior. In this
report, we present the results from 5.78-Ms INTEGRAL IBIS/ISGRI observations on
the source 1FGL J1018.6-5856.
By combining all the available INTEGRAL data, a detection is made at a
significance level of 5.4 sigma in the 18-40 keV band, with an average
intensity of 0.074 counts/s . However, we find that, there is non-statistical
noise in the image that effectively reduces the significance to about 4 sigma
and a significant part of the signal appears to be located in a 0.2-wide phase
region, at phases 0.4-0.6 (where even the corrected significance amounts to 90%
of the total signal found). Given the scarcity of counts, a variability is
hinted at about 3 sigma at the hard X-rays, with an anti-correlation with the
Fermi-LAT periodicity. Should this behavior be true, it would be similar to
that found in LS 5039, and prompt observations with TeV telescopes at phases
anti-correlated with the GeV maximum.Comment: Accepted for publication in Astrophysical Journal Letters; 6 pages, 1
figur
Dynamical Masses for Pre-Main Sequence Stars: A Preliminary Physical Orbit for V773 Tau A
We report on interferometric and radial-velocity observations of the
double-lined 51-d period binary (A) component of the quadruple pre-main
sequence (PMS) system V773 Tau. With these observations we have estimated
preliminary visual and physical orbits of the V773 Tau A subsystem. Among other
parameters, our orbit model includes an inclination of 66.0 2.4 deg, and
allows us to infer the component dynamical masses and system distance. In
particular we find component masses of 1.54 0.14 and 1.332 0.097
M_{\sun} for the Aa (primary) and Ab (secondary) components respectively.
Our modeling of the subsystem component spectral energy distributions finds
temperatures and luminosities consistent with previous studies, and coupled
with the component mass estimates allows for comparison with PMS stellar models
in the intermediate-mass range. We compare V773 Tau A component properties with
several popular solar-composition models for intermediate-mass PMS stars. All
models predict masses consistent to within 2-sigma of the dynamically
determined values, though some models predict values that are more consistent
than others.Comment: ApJ in press; 25 pages, 6 figures; data tables available in journal
versio
Phylodynamics of vampire bat-transmitted rabies in Argentina
Common vampire bat populations distributed from Mexico to Argentina are important rabies reservoir hosts in Latin America. The aim of this work was to analyse the population structure of the rabies virus (RABV) variants associated with vampire bats in the Americas and to study their phylodynamic pattern within Argentina. The phylogenetic analysis based on all available vampire bat-related N gene sequences showed both a geographical and a temporal structure. The two largest groups of RABV variants from Argentina were isolated from northwestern Argentina and from the central western zone of northeastern Argentina, corresponding to livestock areas with different climatic, topographic and biogeographical conditions, which determined their dissemination and evolutionary patterns. In addition, multiple introductions of the infection into Argentina, possibly from Brazil, were detected. The phylodynamic analysis suggests that RABV transmission dynamics is characterized by initial epizootic waves followed by local enzootic cycles with variable persistence. Anthropogenic interventions in the ecosystem should be assessed taking into account not only the environmental impact but also the potential risk of disease spreading through dissemination of current RABV lineages or the emergence of novel ones associated with vampire bats.Fil: Torres, Carolina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Microbiología, Inmunología y Biotecnología. Cátedra de Virología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Lema, C.. Dirección Nacional de Instituto de Investigación. Administración Nacional de Laboratorio e Instituto de Salud; ArgentinaFil: Gury Dohmen, F.. Instituto de Zoonosis “Dr. Luis Pasteur”; ArgentinaFil: Beltran, F.. Instituto de Zoonosis “Dr. Luis Pasteur”; ArgentinaFil: Novaro, L.. Ministerio de Agricultura, Ganadería, Pesca y Alimento. Servicio Nacional de Sanidad y Calidad Agroalimentaria; ArgentinaFil: Russo, S.. Ministerio de Agricultura, Ganadería, Pesca y Alimento. Servicio Nacional de Sanidad y Calidad Agroalimentaria; ArgentinaFil: Freire, M. C.. Dirección Nacional de Instituto de Investigación. Administración Nacional de Laboratorio e Instituto de Salud; ArgentinaFil: Velasco Villa, A.. Centers for Disease Control and Prevention; Estados UnidosFil: Mbayed, Viviana Andrea. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Microbiología, Inmunología y Biotecnología. Cátedra de Virología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Cisterna , D. M.. Ministerio de Agricultura, Ganadería, Pesca y Alimento. Servicio Nacional de Sanidad y Calidad Agroalimentaria; Argentin
Predicting and Characterizing Neurodegenerative Subtypes with Multimodal Neurocognitive Signatures of Social and Cognitive Processes
Background: Social cognition is critically compromised across neurodegenerative diseases, including the behavioral variant frontotemporal dementia (bvFTD), Alzheimer's disease (AD), and Parkinson's disease (PD). However, no previous study has used social cognition and other cognitive tasks to predict diagnoses of these conditions, let alone reporting the brain correlates of prediction outcomes. Objective: We performed a diagnostic classification analysis using social cognition, cognitive screening (CS), and executive function (EF) measures, and explored which anatomical and functional networks were associated with main predictors. Methods: Multiple group discriminant function analyses (MDAs) and ROC analyses of social cognition (facial emotional recognition, theory of mind), CS, and EF were implemented in 223 participants (bvFTD, AD, PD, controls). Gray matter volume and functional connectivity correlates of top discriminant scores were investigated. Results: Although all patient groups revealed deficits in social cognition, CS, and EF, our classification approach provided robust discriminatory characterizations. Regarding controls, probabilistic social cognition outcomes provided the best characterization for bvFTD (together with CS) and PD, but not AD (for which CS alone was the best predictor). Within patient groups, the best MDA probabilities scores yielded high classification rates for bvFTD versus PD (98.3%, social cognition), AD versus PD (98.6%, social cognition+CS), and bvFTD versus AD (71.7%, social cognition+CS). Top MDA scores were associated with specific patterns of atrophy and functional networks across neurodegenerative conditions. Conclusion: Standardized validated measures of social cognition, in combination with CS, can provide a dimensional classification with specific pathophysiological markers of neurodegeneration diagnoses.Fil: Ibanez Barassi, Agustin Mariano. Universidad de San Andrés; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Adolfo Ibañez; Chile. Universidad de Dublin; Irlanda. University of California; Estados UnidosFil: Fittipaldi, Sol. Universidad Nacional de Córdoba; Argentina. Universidad de San Andrés; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Trujillo, Catalina. Universidad del Valle; ColombiaFil: Jaramillo, Tania. Universidad del Valle; ColombiaFil: Torres, Alejandra. Universidad del Valle; ColombiaFil: Cardona, Juan F.. Universidad del Valle; ColombiaFil: Rivera, Rodrigo. Universidad de Chile; ChileFil: Slachevsky, Andrea. Universidad de Chile; ChileFil: Garciá, Adolfo. Universidad de San Andrés; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Santiago de Chile; Chile. University of California; Estados UnidosFil: Bertoux, Maxime. Universidad Adolfo Ibañez; ChileFil: Baez, Sandra. Universidad de los Andes; Colombi
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