We perform axisymmetric two-dimensional magnetohydrodynamic simulations (MHD) to investigate accretion flows around spinning supermassive black holes (SMBHs). To mimic the space-time geometry of black holes, we consider effective Kerr potential (Dihingia et al., 2018), and the mass of the black holes is $10^8 M_{\odot}$. We initialize the accretion disc with a magnetized torus by adopting the...
The radiation reprocessing model, in which an optically-thick layer or outflow absorbs the high-energy emission from a central source and re-emits in longer wavelengths, has been frequently invoked to explain some optically bright transients such as tidal disruption events (TDEs) and fast blue optical transients (FBOTs).Previous studies on this model did not take into account either the time...
Our study introduces a new algorithm for black hole feedback in the Numerical Investigation of a Hundred Astrophysical Objects (NIHAO) project of galaxy simulations. We present two modes of black hole feedback based on both theoretical models and observational evidence highlighting the importance of kinetic AGN outflows in massive galaxies. To account for high Eddington accretion rates, we...
We perform general-relativistic magnetohydrodynamic (GRMHD) simulations around the Kerr black hole in a two-temperature paradigm. The goal is to understand the physics around them and extract more accurate physical information from astrophysical observations. Keeping that in mind, we developed a self-consistent numerical formalism to study electron thermodynamics in GRMHD by incorporating...
The accretion of dark matter (DM) into astrophysical black holes slowly increases their mass, and this mass accretion depends on DM models and model parameters. If this mass accretion effect can be measured accurately enough, it is possible to rule out some DM models, and, with the sufficient technology and the help of other DM constraints, possibly confirm one model. We propose a DM probe...
In this talk, i will discuss the detection of high frequency quasi-periodic oscillation (QPO) in the black hole x-ray binary MAXI J1348-630 in its hard spectral state. MAXI J1348-630 went through a reflare during MJD 58634 to MJD 58674 after a 104 days long outburst which began on MJD 58509. During the reflare the binary system evolved through a series of hard states of varying luminosity. We...
Primordial Black Holes (PBHs), proposed to be formed during gravitational collapses of matter in the very beginning of the universe, are one of the many candidates that have been proposed to be a constituent of Dark Matter (DM). They are especially interesting in the fact that they do not need to invoke an unknown particle, and therefore new physics. Postulated to span a wide range of masses...
Accretion is the energy source for many high-energy astrophysical phenomena. Since 1970s four basic solutions describing the accretion processes have been established with specific assumptions, i.e., the standard thin disk (SSD), the Shapiro-Lightman-Eardley (SLE) solution, the slim disk and the advection-dominated accretion flow (ADAF). We present a generalized self-similar solution based...
Multiphase outflows driven by active galactic nuclei (AGN) have a profound impact on the evolution of their host galaxies. The effects of AGN feedback are especially prominent in the brightest cluster galaxies (BCGs) of cool-core clusters, where there is a concentration of gas in all phases, ranging from cold molecular gas to hot, $>10^7\,$K ionized plasma. In this talk I describe recent...
In tidal disruption events the stellar disrupted by massive black hole results in
an elongated stream of gas that partly falls back to pericenter. If the black hole
rotates around an axis misaligned with the initial stellar orbit, the first stream
crossing may occur at periapse if the returing stream fail to collide itself near
apocenter due to Lense-Thirring effect. In our work we study...
By performing two-dimensional general relativistic radiation magnetohydrodynamics (GRRMHD) simulations with various spin parameters, $a^*$, we investigate the supercritical disks in the standard and normal evolution (SANE) and magnetically arrested disk (MAD) states. As a result, it is revealed that the energy outflow efficiency increases with $|a^*|$ in the SANE state. For example, it is 5%...
The hot wind captured by the black hole can naturally form an advection dominated accretion flow (ADAF), which, as it flows toward the black hole, partially condensates into a cold disk as a consequence of efficient radiative cooling at small distances, and then accretes to the black hole via a disk-corona configuration. We present our detailed study of such accretion flows possibly exist in...
Tidal disruption events (TDEs), apart from producing luminous electromagnetic (EM) flares, can generate potentially detectable gravitational wave (GW) burst signals by future space-borne GW detectors. We propose the first methodology to constrain the Hubble constant $H_0$ with TDEs by incorporating the EM-observable parameters (e.g., stellar mass, black hole (BH) mass, and spin) into fitting...
Pulsar-black hole (BH) binary systems, which have not been found yet, are unique celestial laboratories for testing relativistic theories of gravity and understanding the formation of gravitational wave sources. We study the self gravitational lensing effect in a Pulsar-BH system. Because this effect from the BH magnifies the pulsar signal once per orbital period, we find that it may generate...
Extreme-mass-ratio inspirals are important sources for space-borne gravitational-wave detectors. Such a source normally consists of a stellar-mass black hole (BH) and a Kerr supermassive BH (SMBH), but recent astrophysical models predict that the small body could also be a stellar-mass binary BH (BBH).
A BBH reaching several gravitational radii of a SMBH will induce rich observable...
