arXiv subjects

Y. -L. Wang

Publications and source records attributed to Y. -L. Wang.

2 recordsLinked to original sources

arXiv2025

An Intermediate-mass Black Hole Lurking in A Galactic Halo Caught Alive during Outburst

Stellar-mass and supermassive black holes abound in the Universe, whereas intermediate-mass black holes (IMBHs) of ~10^2-10^5 solar masses in between are largely missing observationally, with few cases found only. Here we report the real-time discovery of a long-duration X-ray transient, EP240222a, accompanied by an optical flare with prominent H and He emission lines revealed by prompt follow-up observations. Its observed properties evidence an IMBH located unambiguously in the halo of a nearby galaxy and flaring by tidally disrupting a star -- the only confirmed off-nucleus IMBH-tidal disruption event so far. This work demonstrates the potential of sensitive time-domain X-ray surveys, complemented by timely multi-wavelength follow-ups, in probing IMBHs, their environments, demographics, origins and connections to stellar-mass and supermassive black holes.

astro-ph.HE↗

arXiv2017

Three-component fermions with surface Fermi arcs in topological semimetal tungsten carbide

Topological Dirac and Weyl semimetals not only host quasiparticles analogous to the elementary fermionic particles in high-energy physics, but also have nontrivial band topology manifested by exotic Fermi arcs on the surface. Recent advances suggest new types of topological semimetals, in which spatial symmetries protect gapless electronic excitations without high-energy analogy. Here we observe triply-degenerate nodal points (TPs) near the Fermi level of WC, in which the low-energy quasiparticles are described as three-component fermions distinct from Dirac and Weyl fermions. We further observe the surface states whose constant energy contours are pairs of Fermi arcs connecting the surface projection of the TPs, proving the nontrivial topology of the newly identified semimetal state.

cond-mat.mtrl-sci↗