13,190 research outputs found
Constraining fast radio burst progenitors with gravitational lensing
Fast Radio Bursts (FRBs) are new transient radio sources discovered recently.
Because of the angular resolution restriction in radio surveys, no optical
counter part has been identified yet so it is hard to determine the progenitor
of FRBs. In this paper we propose to use radio lensing survey to constrain FRB
progenitors. We show that, different types of progenitors lead to different
probabilities for a FRB to be gravitationally lensed by dark matter halos in
foreground galaxies, since different type progenitors result in different
redshift distributions of FRBs. For example, the redshift distribution of FRBs
arising from double stars shifts toward lower redshift than of the FRBs arising
from single stars, because double stars and single stars have different
evolution timescales. With detailed calculations, we predict that the FRB
sample size for producing one lensing event varies significantly for different
FRB progenitor models. We argue that this fact can be used to distinguish
different FRB models and also discuss the practical possibility of using
lensing observation in radio surveys to constrain FRB progenitors.Comment: 14 pages, including 6 figures and 1 tabl
Search for strong gravitational lensing effect in the current GRB data of BATSE
Because gamma-ray bursts (GRBs) trace the high-z Universe, there is an
appreciable probability for a GRB to be gravitational lensed by galaxies in the
universe. Herein we consider the gravitational lensing effect of GRBs
contributed by the dark matter halos in galaxies. Assuming that all halos have
the singular isothermal sphere (SIS) mass profile in the mass range and all GRB samples follow
the intrinsic redshift distribution and luminosity function derived from the
Swift LGRBs sample, we calculated the gravitational lensing probability in
BATSE, Swift/BAT and Fermi/GBM GRBs, respectively. With an derived probability
result in BATSE GRBs, we searched for lensed GRB pairs in the BATSE 5B GRB
Spectral catalog. The search did not find any convincing gravitationally lensed
events. We discuss our result and future observations for GRB lensing
observation.Comment: 18 pages, 8 figure
Teachers' recognition of school bullying according to background variables and type of bullying
How teachers identify and judge school bullying may affect their willingness to intervene in bullying situations and influence their strategies for doing so. This study aimed to investigate whether there were significant differences in teachers' identification of bullying incidents according to background variables (gender, teaching experience, and education level). The participants of this study were 150 primary school and middle school teachers in Taiwan, A 24-item Recognition of Bullying incidents Questionnaire (RBIQ) was used in this study to explore whether teachers can identify physical, verbal, and relational scenarios as bullying or non-bullying incidents. A mixed-model two way ANOVA was used to analyze this data. Results revealed that teachers' teaching experiences significantly interacted with behavioral types, and teachers' education levels also sigm candy interacted with behavioral types. In addition, no gender differences in the identification of bullying were observed. Overall, teachers were more likely to identifi physical bullying incidents than relational ones. The results of this study suggest that teachers should participate in training to help them identify bullying incidents, particularly when these involve relational bullying
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