979 research outputs found
Temporal features of LS I +61303 in hard X-rays from the Swift/BAT survey data
We study the long-term spectral and timing behaviour of LS I +61303
in hard X-rays (15--150 keV) using 10 years of survey data from the
Burst Alert Telescope (BAT) monitor. We focus on the detection of long
periodicities known to be present in this source in multiple wavelengths. We
clearly detect three periods: the shorter one at 26.48 days is compatible with
the orbital period of the system; the second, longer, periodicity at 26.93
days, is detected for the first time in X-rays and its value is consistent with
an analogous temporal feature recently detected in the radio and in the
gamma-ray waveband, and we associate it with a modulation caused by a
precessing jet in this system. Finally, we find also evidence of the long-term
periodicity at 1667 d, that results compatible with a beat frequency of
the two close, and shorter, periodicities. We discuss our results in the
context of the multi-band behaviour of the physical processes of this source.Comment: 5 pages, 8 figures. Published in MNRA
Advanced Ultrasonic Non-destructive Evaluation for Metrological Analysis and Quality Assessment of Impact Damaged Non-crimp Fabric Composites☆
Abstract Composite materials are nowadays massively utilized in a very large number of industrial applications. Thus, it has become essential to characterize the service behaviour they can provide depending on their working conditions. In this paper, the study of the influence of impact conditions on damage generation in high performance composite materials, consisting of non-crimp fabric composite laminates, is carried out through the application of an advanced ultrasonic non-destructive evaluation technique, known as full volume ultrasonic scanning. This technique is based on the pulse-echo immersion testing method and allows for the quantitative analysis of the internal material structure in the entire composite volume. The aim of the ultrasonic non-destructive evaluation analysis is the metrological characterization of the non-crimp fabric composite laminates in terms of actual thickness estimation and stacking sequence fiber orientation verification as well as their quality assessment in terms of impact damage development within the whole composite material volume
Evidence for a resonant cyclotron line in IGR J16493-4348 from the Swift-BAT hard X-ray survey
Resonant absorption cyclotron features are a key diagnostic tool to directly
measure the strength of the magnetic field of accreting neutron stars. However,
typical values for cyclotron features lie in the high-energy part of the
spectrum between 20 keV and 50 keV, where detection is often damped by the low
statistics from single pointed observations. We show that long-term monitoring
campaign performed with Swift-BAT of persistently, but faint, accreting
high-mass X-ray binaries is able to reveal in their spectra the presence of
cyclotron features. We extracted the average Swift-BAT 15-150 keV spectrum from
the 54 months long Swift-BAT survey of the high-mass X-ray source IGR
J16493-4348. To constrain the broadband spectrum we used soft X-ray spectra
from Swift-XRT and Suzaku pointed observations. We model the spectra using a
set of phenomenological models usually adopted to describe the energy spectrum
of accreting high-mass X-ray binaries; irrespective of the models we used, we
found significant improvements in the spectral fits adding to the models a
broad (10 keV width) absorption feature, with best-fitting energy estimate
between 30 and 33 keV, that we interpret as evidence for a resonant cyclotron
absorption feature. We also discuss instrumental issues related to the use of
Swift-BAT for this kind of studies and the statistical method to weight the
confidence level of this detection. Correcting for the gravitational redshift
of a 1.4 M_{\sun} neutron star, the inferred surface magnetic field is Bsurf
3.7 x 10^{12} Gauss. The spectral parameters of IGR J16493-4348 fit well with
empirical correlations observed when the whole sample of high-mass binaries
with detected cyclotron features is considered.Comment: Published in Astronomy & Astrophysics, 2011, 532, A7
- …