2,168 research outputs found
Statistical Properties of Multiple Optical Emission Components in Gamma-Ray Bursts and Implications
Well-sampled optical lightcurves of 146 gamma-ray bursts (GRBs) are complied
from the literature. Multiple optical emission components are extracted with
power-law function fits to these lightcurves. We present a systematical
analysis for statistical properties and their relations to prompt gamma-ray
emission and X-ray afterglow for each component. We show that peak luminosity
in the prompt and late flares are correlated and the evolution of the peak
luminosity may signal the evolution of the accretion rate. No tight correlation
between the shallow decay phase/plateau and prompt gamma-ray emission is found.
Assuming that they are due to a long-lasting wind injected by a compact object,
we show that the injected behavior favors the scenarios of a long-lasting wind
after the main burst episode. The peak luminosity of the afterglow onset is
tightly correlated with Eiso, and it is dimmer as peaking later. Assuming that
the onset bump is due to the fireball deceleration by the external medium, we
examine the Gamma_0-Eiso relation and find that it is confirmed with the
current sample. Optical re-brightening is observed in 30 GRBs in our sample. It
shares the same relation between the width and the peak time as found in the
onset bump, but no clear correlation between the peak luminosity and Eiso as
observed in the onset bumps is found. Although its peak luminosity also decays
with time, the slope is much shallower than that of the onset peak. We get L
t^{-1}_{p}$, being consistent with off-axis observations to an expanding
external fireball in a wind-like circum medium. The late re-brightening may
signal another jet component. Mixing of different emission components may be
the reason for the observed chromatic breaks in different energy bands.Comment: 10 pages, 5 figures, to be published by IJMPD (Proceedings of "The
Third Galileo - Xu Guangqi meeting", Beijing, October 11-15, 2011
Triangle singularity in the decays
We study the reaction and
find that the mechanism to produce this decay develops a triangle singularity
around ~MeV. The differential width
shows a rapid growth around the
invariant mass being 1515~MeV as a consequence of the triangle singularity of
this mechanism, which is directly tied to the nature of the and
as dynamically generated resonances from the interaction of
pseudoscalar mesons. The branching ratios obtained for the decays are of the order of , accessible in
present facilities, and we argue that their observation should provide relevant
information concerning the nature of the low-lying scalar mesons.Comment: 12 pages, 8 figures, published in EPJ
Radioactive Decay of Specific Heavy Elements as an Energy Source for Late-Time Kilonovae and Potential JWST Observations
Revealing the temporal evolution of individual heavy elements synthesized in
the merger ejecta from binary neutron star mergers not only improves our
understanding of the origin of heavy elements beyond iron but also clarifies
the energy sources of kilonovae. In this work, we present a comprehensive
analysis of the temporal evolution of the energy fraction of each nuclide based
on the -process nucleosynthesis simulations. The heavy elements dominating
the kilonova emission within ~days are identified, including
Sb, Sb, Sb, Sb, Te, I,
Rn, Ra, Ra, and Ac. It is found that the
late-time kilonova light curve (~days) is highly sensitive to the
presence of the heavy element Ac (with a half-life of 10.0~days). Our
analysis shows that the James Webb Space Telescope (JWST), with its high
sensitivity in the near-infrared band, is a powerful instrument for the
identification of these specific heavy elements.Comment: 7 pages, 8 figures, accepted by MNRA
Female media use behavior and agreement with publicly promoted agenda-specific health messages.
This study set out to explore the relationship between female media use behavior and agreement with agenda-specific publicly promoted health messages. A random digit dial telephone cross-sectional survey was conducted using a nationally representative sample of female residents aged 25 and over. Respondents' agreement with health messages was measured by a six-item Health Information Scale (HIS). Data were analyzed using chi-square tests and multiple logistic regression. This survey achieved a response rate of 86% (n = 1074). In this study the longest duration of daily television news watching (OR = 2.32), high self-efficacy (OR = 1.56), and greater attention to medical and health news (OR = 5.41) were all correlates of greater agreement with the selected health messages. Surprisingly, Internet use was not significant in the final model. Many women that public health interventions need to be targeting are not receptive to health information that can be accessed through Internet searches. However, they may be more readily targeted by television campaigns. Agenda-specific public health campaigns aiming to empower women to serve as nodes of information transmission and achieve efficient trickle down through the family unit might do better to invest more heavily in television promotion
Event Rate of Fast Radio Burst from Binary Neutron-star Mergers
It is proposed that one-off fast radio burst (FRB) with periodic structures
may be produced during the inspiral phase of a binary neutron-star (BNS)
merger. In this paper, we study the event rate of such kind of FRB. We first
investigate the properties of two one-off FRBs with periodic structures (i.e.,
FRB~20191221A and FRB~20210213A) in this scenario, by assuming the fast
magnetosonic wave is responsible for their radio emission. For the luminosities
and periods of these bursts, it is found that the pre-merger BNS with magnetic
field strength is required. This is relatively
high compared with that of the most of the BNSs observed in our Galaxy, of
which the magnetic field is around . Since the observed BNSs
in our Galaxy are the binaries without suffering merger, a credited event rate
of BNS-merger originated FRBs should be estimated by considering the evolution
of both the BNS systems and their magnetic fields. Based on the population
synthesis and adopting a decaying magnetic field of NSs, we estimate the event
rate of BNS-mergers relative to their final magnetic fields. We find that the
rapid merged BNSs tend to merge with high magnetization, and the event rate of
BNS-merger originated FRBs, i.e., the BNS-mergers with both NSs' magnetic field
being higher than is ( of the total BNS-mergers) in redshift .Comment: 11 pages, 2 figures, accepted for publication in Astrophysical
Journa
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