Shining tens to hundreds of times brighter than ordinary supernovae, superluminous supernovae provide an extreme view of power sources that may contribute to a range of cosmic explosions. Their high luminosities make them detectable throughout the high redshift universe where they may serve as tracers of their massive stellar progenitors and probes of the changes of gas in star-forming regions...
I will give an introduction of our studies on a recent type II supernova (SN 2023ixf) exploded in nearby galaxy M 101 at a distance of 6.85 Mpc. Such a close distance makes SN 2023ixf a nearby, bright stellar explosion that appears once in a decade, providing a rare apportunity to study the pre-explosion evolution of massive star and view the moment of shock breakout from the progenitor. Our...
Neutrinos are key players in core-collapse supernova explosion (CCSN) and binary neutron star mergers (BNSM) as the dominant courier of energy and lepton-number. The neutrino kinetics including transport, neutrino-matter interactions, and neutrino flavor conversions (or neutrino oscillations) would account for triggering CCSN explosion, driving disk-outflows in remnants BNSM, and having...
The development of hydrodynamical instabilities during the first second after core bounce is a key ingredient in the explosion mechanism of massive stars. It affects the birth properties of neutron stars and black holes and generates specific signatures in gravitational waves and neutrinos.
The advective-acoustic mechanism of the standing accretion shock instability (SASI) is well established...
Neutron stars and stellar-mass black holes are the remnants of massive star explosions. Most massive stars reside in close binary systems, and the interplay between the companion star and the newly formed compact object has been theoretically explored, but signatures for binarity or evidence for the formation of a compact object during a supernova explosion are still lacking. Here we report a...
While there is a broad consensus that Type Ia supernovae (SNe Ia) arise from explosions of carbon/oxygen (C/O) white dwarfs (WDs), the traditional scenario involving a Chandrasekhar-mass WD cannot account for the entire population. The detonation of a thin ($\sim$$0.01\,\mathrm{M_\odot}$) helium shell atop a $\sim$$1\,\mathrm{M_\odot}$ C/O core is a promising mechanism to explode...
Tidal disruption events (TDEs) provide unique laboratories to study the demographics, immediate stellar and gaseous environments, and accretion physics of the massive black hole population. Over the past few years, time domain sky surveys such as the optical Zwicky Transient Facility (ZTF) have led to a surge of TDE discoveries in galaxy centers. I will present how detailed X-ray studies of...
Supermassive black holes (SMBHs) lie at the centers of most galaxies, but the processes by which they grow and launch outflows that shape the galaxies around them remain poorly understood. In this talk, I will focus on tidal disruption events (TDEs) as probes of relativistic processes powered by SMBHs. A TDE occurs when a star passes too close to a SMBH and is torn apart by tidal forces from...
Tidal disruption event is a unique probe of quiescent massive black holes. In this talk, I will discuss how we can use tidal disruption events to constrain the demographics of massive black holes including intermediate mass black holes. I will also show our recent theoretical modelling results on the accretion, outflow and emission processes in tidal disruption events, which can be used to...
We propose that quasi-periodic eruptions (QPEs) in galactic nuclei are produced by a low-mass main-sequence star in a mildly eccentric (e ~ 0.5) orbit. We argue that the QPE emission is powered by circularization shocks, but not directly by black hole accretion. The stellar orbits needed to explain QPEs can be efficiently created by the Hills breakup of tight stellar binaries.
Sw 1644 was one of the most surprising tidal disruption events (TDEs). Its prompt emission in soft gamma-rays triggered Swift. Later this was followed by X-ray and Radio afterglows. The energy implied by the radio afterglow increased by a factor of 10 over a period of a few hundred days, reaching an ultimate value of a few times 1052 erg. This is much higher than in other TDEs. Recently...
ULTRASAT is a scientific satellite, that is planned to be launched to a geo-stationary orbit in 2026. It will carry a telescope with an unprecedentedly large field of view (200 squared degrees) and UV (230-290nm) sensitivity. These unique properties will enable us to detect and systematically study transient astronomical events within an extra-Galactic volume, that is hundreds of time larger...
We first discuss an off-axis jet model for the short gamma-ray burst (sGRB) 170817A associated with the gravitational wave event GW170817. We show that the origin of the off-axis emission arises from an off-center region of the jet, neither the jet core around the primary axis nor the line of sight at the viewing angle. This off-center location is generally created by the product of the...
In this presentation, I will delve into our recent research on Gamma-ray Bursts (GRBs) that deviate from standard classifications or progenitor models. These GRBs encompass a unique event originating from a magnetar giant flare, a distinct short-duration GRB not arising from a compact star merger, and a genuinely long-duration GRB resulting from a compact binary star merger. The discovery of...
Compact binary mergers serve as excellent astrophysical laboratories to explore a wide range of fundamental problems: from the formation of ultrafast outflows to the cosmic production of heavy metals, from the equation of state of cold ultra-dense matter to the expansion rate of the universe.
Our understanding of these systems was revolutionized in 2017 by the discovery of the first merger...
Many stripped envelope supernovae (SNe) present a signature of high-velocity material responsible for broad absorption lines in the observed spectrum. These include SNe that are associated with long gamma-ray bursts (LGRBs) and low-luminosity GRBs (llGRBs), and SNe that are not associated with GRBs. Recently it was suggested that this high-velocity material originates from a cocoon that is...
The study of intermediate-mass black holes (IMBHs) has recently drawn a lot of attention, since IMBHs can provide critical information on the seed formation process of supermassive black holes (SMBHs) along with the co-evolution of massive black holes (MBHs) and galaxies. However, detecting IMBHs is extremely difficult due to their small masses and dim luminosities. One of the most promising...
