اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدOn the non-Poissonian repetition pattern of FRB121102
48
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
Rhe Fast Radio Burst FRB121102 has been observed to repeat in an irregular fashion. Using published timing data of the observed bursts, we show that Poissonian statistics are not a good description of this random process. As an alternative we suggest to describe the intervals between bursts with a Weibull distribution with a shape parameter smaller than one, which allows for the clustered nature of the bursts. We quantify the amount of clustering using the parameters of the Weibull distribution and discuss the consequences that it has for the detection probabilities of future observations and for the optimization of observing strategies. ew{Allowing for this generalization, we find a mean repetition rate of r=5.7^{+3.0}_{-2.0} per day and index k=0.34^{+0.06}_{-0.05} for a correlation function xi(t)=(t/t_0)^{k-1}.
قيم البحث
اقرأ أيضاً
Fast radio bursts (FRBs) are bright, millisecond-duration radio pulses whose origins are unknown. To date, only one (FRB 121102) out of several dozen has been seen to repeat, though the extent to which it is exceptional remains unclear. We discuss de
tecting repetition from FRBs, which will be very important for understanding their physical origin, and which also allows for host galaxy localisation. We show how the combination of instrument sensitivity, beamshapes, and individual FRB luminosity functions affect the detection of sources whose repetition is not necessarily described by a homogeneous Poisson process. We demonstrate that the Canadian Hydrogen Intensity Mapping Experiment (CHIME) could detect many new repeating FRBs for which host galaxies could be subsequently localised using other interferometers, but it will not be an ideal instrument for monitoring FRB 121102. If the luminosity distributions of repeating FRBs are given by power-laws with significantly more dim than bright bursts, CHIMEs repetition discoveries could preferentially come not from its own discoveries, but from sources first detected with lower-sensitivity instruments like the Australian Square Kilometer Array Pathfinder (ASKAP) in flys eye mode. We then discuss observing strategies for upcoming surveys, and advocate following up sources at approximately regular intervalsand with telescopes of higher sensitivity, when possible. Finally, we discuss doing pulsar-like periodicity searching on FRB follow-up data, based on the idea that while most pulses are undetectable, folding on an underlying rotation period could reveal the hidden signal.
We present a detailed study of the complex time-frequency structure of a sample of previously reported bursts of FRB 121102 detected with the MeerKAT telescope in September 2019. The wide contiguous bandwidth of these observations have revealed a com
plex bifurcating structure in some bursts at $1250$ MHz. When de-dispersed to their structure-optimised dispersion measures, two of the bursts show a clear deviation from the cold plasma dispersion relationship below $1250$ MHz. We find a differential dispersion measure of ${sim}1{-}2$ pc cm$^{-3}$ between the lower and higher frequency regions of each burst. We investigate the possibility of plasma lensing by Gaussian lenses of ${sim}10$ AU in the host galaxy, and demonstrate that they can qualitatively produce some of the observed burst morphologies. Other possible causes for the observed frequency dependence, such as Faraday delay, are also discussed. Unresolved sub-components in the bursts, however, may have led to an incorrect DM determination. We hence advise exercising caution when considering bursts in isolation. We analyse the presence of two apparent burst pairs. One of these pairs is a potential example of upward frequency drift. The possibility that burst pairs are echoes is also discussed. The average structure-optimised dispersion measure is found to be $563.5pm 0.2 (text{sys}) pm 0.8 (text{stat})$ pc cm$^{-3}$ $-$ consistent with the values reported in 2018. We use two independent methods to determine the structure-optimised dispersion measure of the bursts: the DM_phase algorithm and autocorrelation functions. The latter $-$ originally developed for pulsar analysis $-$ is applied to FRBs for the first time in this paper.
We study the connection of matter density and its tracers from the PDF perspective. One aspect of this connection is the conditional expectation value $langle delta_{mathrm{tracer}}|delta_mrangle$ when averaging both tracer and matter density over so
me scale. We present a new way to incorporate a Lagrangian bias expansion of this expectation value into standard frameworks for modelling the PDF of density fluctuations and counts-in-cells statistics. Using N-body simulations and mock galaxy catalogs we confirm the accuracy of this expansion and compare it to the more commonly used Eulerian parametrization. For halos hosting typical luminous red galaxies, the Lagrangian model provides a significantly better description of $langle delta_{mathrm{tracer}}|delta_mrangle$ at second order in perturbations. A second aspect of the matter-tracer connection is shot-noise, ie the scatter of tracer density around $langle delta_{mathrm{tracer}}|delta_mrangle$. It is well known that this noise can be significantly non-Poissonian and we validate the performance of a more general, two-parameter shot-noise model for different tracers and simulations. Both parts of our analysis are meant to pave the way for forthcoming applications to survey data.
The usual development of the continuous-time random walk (CTRW) proceeds by assuming that the present is one of the jumping times. Under this restrictive assumption integral equations for the propagator and mean escape times have been derived. We gen
eralize these results to the case when the present is an arbitrary time by recourse to renewal theory. The case of Erlang distributed times is analyzed in detail. Several concrete examples are considered.
Interevent times in temporal contact data from humans and animals typically obey heavy-tailed distributions, and this property impacts contagion and other dynamical processes on networks. We theoretically show that distributions of interevent times h
eavier-tailed than exponential distributions are a consequence of the most basic metapopulation model used in epidemiology and ecology, in which individuals move from a patch to another according to the simple random walk. Our results hold true irrespectively of the network structure and also for more realistic mobility rules such as high-order random walks and the recurrent mobility patterns used for modeling human dynamics.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
