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Haoxiang Lin

Publications and source records attributed to Haoxiang Lin.

9 recordsLinked to original sources
arXiv2024

Implication of Jet Physics from MeV Line Emission of GRB 221009A

Ultrarelativistic jets are believed to play an important role in producing prompt emission and afterglow of gamma-ray bursts (GRBs), but the nature of the jet is poorly known owing to the lack of decisive features observed in the prompt emission. The discovery of an emission line evolving from about 37 to 6 MeV in the brightest-of-all-time GRB 221009A provides an unprecedented opportunity to probe GRB jet physics. The time evolution of the central energy of the line with power-law index $-1$ is naturally explained by the high-latitude curvature effect. Under the assumption that the line emission is generated in the prompt emission by $e^\pm$ pair production, cooling, and annihilation in the jet, we can strictly constrain jet physics with observed line emission properties. We find that the radius of the emission region is $r\gtrsim10^{16}$ cm. The narrow line width of $\sim10\%$ requires that the line emission occurs within $\sim10\%$ of the dynamical time, which further implies short timescales of pair cooling to the nonrelativistic state and pair annihilation, as well as a slightly clumpy emission region. If the jet's Lorentz factor is $\Gamma\gtrsim400$, the fast cooling requirement needs an energy density of magnetic field in the jet much larger than that of prompt gamma rays, i.e., a magnetically dominated jet. The temporal behavior of line flux suggests some angle dependence of line emission. We also discuss the difficulties of other scenarios for the observed emission line.

astro-ph.HE↗
arXiv2021

On the use of CHIME to Detect Long-Duration Radio Transients from Neutron Star Mergers

Short gamma-ray burst (SGRB) GRB 170817A was found to be related to a binary neutron star (BNS) merger. It is uncertain whether all SGRBs are caused by BNS mergers, and also under what conditions a BNS merger can cause a SGRB. As BNS mergers can cause SGRBs, afterglow observations will also provide an alternative measurement of the BNS merger rate independent of gravitational-wave observations. In previous work by Feng et al. (2014), the feasibility of the detection of afterglows was considered using a variety of radio observatories and a simple flux threshold detection algorithm. Here, we consider a more sophisticated detection algorithm for SGRB afterglows, and provide an estimate of the trials factors for a realistic search to obtain an updated estimate of the possibility of observing afterglows with the Canadian Hydrogen Intensity Mapping Experiment (CHIME). We estimate 893 and 312 afterglows per year can be detected using a $3 \sigma$ confidence level threshold with two jet models, one with half opening angle uniformly distributed in $6^\circ$ to $30^\circ$ and the other uniformly distributed in $3^\circ$ to $8^\circ$ with the median $6^\circ$. We also find 88% and 98%, respectively, of the detectable afterglows for each jet opening distribution are off-axis, which are candidates for orphan afterglows. Our result predicts fewer detectable sources per year than the earlier analysis, but confirms the essential conclusion that using CHIME to search for afterglows will be effective at constraining the astrophysical merger rate.

astro-ph.HE↗
arXiv2021

Tensor Network for Supervised Learning at Finite Temperature

The large variation of datasets is a huge barrier for image classification tasks. In this paper, we embraced this observation and introduce the finite temperature tensor network (FTTN), which imports the thermal perturbation into the matrix product states framework by placing all images in an environment with constant temperature, in analog to energy-based learning. Tensor network is chosen since it is the best platform to introduce thermal fluctuation. Different from traditional network structure which directly takes the summation of individual losses as its loss function, FTTN regards it as thermal average loss computed from the entanglement with the environment. The temperature-like parameter can be automatically optimized, which gives each database an individual temperature. FTTN obtains improvement in both test accuracy and convergence speed in several datasets. The non-zero temperature automatically separates similar features, avoiding the wrong classification in previous architecture. The thermal fluctuation may give a better improvement in other frameworks, and we may also implement the temperature of database to improve the training effect.

cs.LG↗
arXiv2020

Detectability of radio afterglows from binary neutron star mergers and implications for fast radio bursts

Binary neutron star (BNS) mergers are one of the proposed origins for both repeating and non-repeating fast radio bursts (FRBs), which associates FRBs with gravitational waves and short gamma-ray bursts (GRBs). In this work, we explore detectability of radio afterglows from BNS mergers and compare it to the observed radio limits on FRB afterglows. We calculate the afterglow flux powered by the two components: a relativistic jet and a slower isotropic ejecta, and quantify the detection probability as a function of the source redshift, observing time, and flux sensitivity. The model parameter distributions inferred from short GRB afterglows are adopted, and viewing angle distributions (uniform spherical, gravitational-wave, on-axis biased) are assumed to reflect different searching scenario. Assuming that FRBs are not strongly beamed, we make comparison to FRBs detected with reported radio limits and find the detection probabilities are 1--10% in general, and hence not a strong constraint on the BNS progenitor model considering the small sample number (<10). In particular for some nearby FRBs (e.g. 180916.J0158+65, 190608), we find a high chance of detection (>20% at 10$\mu$Jy sensitivity) for the isotropic component that would peak around $\sim$1--10 years after the merger. Therefore a long term radio monitoring of persistent radio emission for these objects is important.

astro-ph.HE↗
arXiv2018

Nonthermal afterglow of the binary neutron star merger GW170817: a more natural modeling of electron energy distribution leads to a qualitatively different new solution

The observed nonthermal afterglow spectrum of the binary neutron star (BNS) merger GW170817 from radio to X-ray are consistent with synchrotron radiation by shock-accelerated electrons. However, previous afterglow modeling studies were based on a simplified assumption that the acceleration efficiency is extremely high, i.e. all electrons in the shock are accelerated as a nonthermal population. This affects the estimate of the minimum electron energy and hence $\nu_m$, the peak frequency of the afterglow spectrum. Here we present Bayesian fitting to the observed data with a more natural electron energy distribution, in which the acceleration efficiency is a free parameter. Interestingly, the maximum likelihood solutions are found with radio flux below $\nu_m$ in the early phase, in contrast to previous studies that found the radio frequency always above $\nu_m$. Therefore the $\nu_m$ passage through the radio band could have been clearly detected for GW170817, if sufficient low-frequency radio data had been taken in early time. In the new solutions, the lowest energy of electrons is found close to equipartition with the post shock protons, but only a small fraction ($<$10\%) of electrons are accelerated as nonthermal particles. The jet energy and interstellar medium density are increased by 1--2 orders of magnitude from the conventional modeling, though these are still consistent with other constraints. We encourage to take densely sampled low-frequency radio data in the early phase for future BNS merger events, which would potentially detect $\nu_m$ passage and give a strong constraint on electron energy distribution and particle acceleration efficiency.

astro-ph.HE↗
arXiv2015

On the Well Extension of Partial Well Orderings

In this paper, we study the well extension of strict(irreflective) partial well orderings. We first prove that any partially well-ordered structure can be extended to a well-ordered one. Then we prove that every linear extension of is well-ordered if and only if A has no infinite totally unordered subset under R.

cs.LO↗
arXiv2014

A Constructive Proof on the Compositionality of Linearizability

Linearizability is the strongest correctness property for both shared memory and message passing systems. One of its useful features is the compositionality: a history (execution) is linearizable if and only if each object (component) subhistory is linearizable. In this paper, we propose a new hierarchical system model to address challenges in modular development of cloud systems. Object are defined by induction from the most fundamental atomic Boolean registers, and histories are represented as countable well-ordered structures of events to deal with both finite and infinite executions. Then, we present a new constructive proof on the compositionality theorem of linearizability inspired by Multiway Merge. This proof deduces a theoretically efficient algorithm which generates linearization in O(N*logP) running time with O(N) space, where P and N are process/event numbers respectively.

cs.DC↗
arXiv2013

SOAP3-dp: Fast, Accurate and Sensitive GPU-based Short Read Aligner

To tackle the exponentially increasing throughput of Next-Generation Sequencing (NGS), most of the existing short-read aligners can be configured to favor speed in trade of accuracy and sensitivity. SOAP3-dp, through leveraging the computational power of both CPU and GPU with optimized algorithms, delivers high speed and sensitivity simultaneously. Compared with widely adopted aligners including BWA, Bowtie2, SeqAlto, GEM and GPU-based aligners including BarraCUDA and CUSHAW, SOAP3-dp is two to tens of times faster, while maintaining the highest sensitivity and lowest false discovery rate (FDR) on Illumina reads with different lengths. Transcending its predecessor SOAP3, which does not allow gapped alignment, SOAP3-dp by default tolerates alignment similarity as low as 60 percent. Real data evaluation using human genome demonstrates SOAP3-dp's power to enable more authentic variants and longer Indels to be discovered. Fosmid sequencing shows a 9.1 percent FDR on newly discovered deletions. SOAP3-dp natively supports BAM file format and provides a scoring scheme same as BWA, which enables it to be integrated into existing analysis pipelines. SOAP3-dp has been deployed on Amazon-EC2, NIH-Biowulf and Tianhe-1A.

q-bio.GN↗