arXiv subjects

Ye Feng

Publications and source records attributed to Ye Feng.

21 records · Page 2Linked to original sources

arXiv2021

Estimating the black hole spin for the X-ray binary MAXI J1820+070

MAXI J1820+070 is a newly-discovered black hole X-ray binary, whose dynamical parameters, namely the black hole mass, the inclination angle and the source distance, have been estimated recently. \emph{Insight}-HXMT have observed its entire outburst from March 14th, 2018. In this work, we attempted to estimate the spin parameter~$a_*$, using the continuum-fitting method and applying a fully-relativistic thin disk model to the soft-state spectra obtained by \emph{Insight}-HXMT. It is well know that $a_*$ is strongly dependent on three dynamical parameters in this method, and we have examined two sets of parameters. Adopting our preferred parameters: $M$ = $8.48^{+0.79}_{-0.72}~M_\odot$, $i=63^\circ\pm3^\circ$ and $D=2.96\pm0.33$ kpc, we found a slowly-spinning black hole of $a_*=0.14 \pm 0.09$ ($1σ$), which give a prograde spin parameter as majority of other systems show. While it is also possible for the black hole to have a retrograde spin (less than 0) if different dynamical parameters are taken.

astro-ph.HE↗

arXiv2021

Re-estimating the Spin Parameter of the Black Hole in Cygnus X-1

Cygnus X-1 is a well-studied persistent black hole X-ray binary. Recently, the three parameters needed to estimate the black hole spin of this system, namely the black hole mass $M$, the orbital inclination $i$ and the source distance $D$, have been updated. In this work we redetermine the spin parameter using the continuum-fitting technique for those updated parameter values. Based on the assumption that the spin axis of the black hole is aligned with the orbital plane, we fit the thermal disk component to a fully relativistic thin accretion disk model. The error in the spin estimate arising from the combined observational uncertainties is obtained via Monte Carlo (MC) simulations. We demonstrate that, without considering the counteracting torque effect, the new spin parameter is constrained to be a$_* > 0.9985$ (3$σ$), which confirms that the spin of the black hole in Cygnus X-1 is extreme.

astro-ph.HE↗

arXiv2020

Reductive Clustering: An Efficient Linear-time Graph-based Divisive Cluster Analysis Approach

We propose an efficient linear-time graph-based divisive cluster analysis approach called Reductive Clustering. The approach tries to reveal the hierarchical structural information through reducing the graph into a more concise one repeatedly. With the reductions, the original graph can be divided into subgraphs recursively, and a lite informative dendrogram is constructed based on the divisions. The reduction consists of three steps: selection, connection, and partition. First a subset of vertices of the graph are selected as representatives to build a concise graph. The representatives are re-connected to maintain a consistent structure with the previous graph. If possible, the concise graph is divided into subgraphs, and each subgraph is further reduced recursively until the termination condition is met. We discuss the approach, along with several selection and connection methods, in detail both theoretically and experimentally in this paper. Our implementations run in linear time and achieve outstanding performance on various types of datasets. Experimental results show that they outperform state-of-the-art clustering algorithms with significantly less computing resource requirements.

cs.AI↗