scholarly journals Signatures of Einstein-Maxwell dilaton-axion gravity from the observed jet power and the radiative efficiency

2021 ◽  
Vol 103 (4) ◽  
Author(s):  
Indrani Banerjee ◽  
Bhaswati Mandal ◽  
Soumitra SenGupta
Keyword(s):  
Radiative Efficiency ◽  
Jet Power

scholarly journals The Origin of Radio Emission in Black Hole X-ray Binaries

Galaxies ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 78
Author(s):  
Xiang Liu ◽  
Ning Chang ◽  
Xin Wang ◽  
Qi Yuan
Keyword(s):  
Black Hole ◽  
Radio Emission ◽  
Thin Disk ◽  
Quiescent State ◽  
X Ray ◽  
Radiative Efficiency ◽  
Accretion Flows ◽  
X Ray Binaries ◽  
Jet Power ◽  
Disk Component

We studied the relation of accretion-jet power and disk luminosity, especially the jet efficiencies and disk radiative efficiencies for different accretion disks as well as black hole (BH) spin, in order to explore the origin of radio emission in black hole X-ray binaries (BHXBs). We found that jet efficiency increases more rapidly (efficient) than the nearly constant disk radiative efficiency for thin disk component in high accretion regime, which could account for the steep track (μ>1) in the observed radio and X-ray luminosity relations (LR∝LXμ), but the thin disk component may not be able to explain the standard track (μ≈0.6) in the BHXBs. For hot accretion flows (HAF), the resulting jet efficiency changes along with the large range of accretions from quiescent state to nearly Eddington state, which could account for the standard track in the BHXBs. The BH spin-jet is discussed for the magnetic arrested disk (MAD) state; in this state, the spin-jet power might contribute to a linear correlation between jet power and mass accretion rate for a given source. More accurate observations are required to test the results.

scholarly journals Cosmological Evolution of Supermassive Black Holes: Mass Functions and Spins

2012 ◽  
Vol 8 (S290) ◽  
pp. 259-260 ◽  
Author(s):  
Yan-Rong Li ◽  
Jian-Min Wang ◽  
Luis C. Ho
Keyword(s):  
Black Holes ◽  
Mass Function ◽  
Supermassive Black Holes ◽  
Cosmological Evolution ◽  
Radiative Efficiency ◽  
Bolometric Luminosity ◽  
History Of ◽  
Minor Mergers ◽  
Mass Dependent ◽  
Mass Functions

AbstractWe derive the mass function of supermassive black holes (SMBHs) over the redshift range 0 > z ≲ 2, using the latest deep luminosity and mass functions of field galaxies. Applying this mass function, combined with the bolometric luminosity function of active galactic nuclei (AGNs), into the the continuity equation of SMBH number density, we explicitly obtain the mass-dependent cosmological evolution of the radiative efficiency for accretion. We suggest that the accretion history of SMBHs and their spins evolve in two distinct regimes: an early phase of prolonged accretion, plausibly driven by major mergers, during which the black hole spins up, then switching to a period of random, episodic accretion, governed by minor mergers and internal secular processes, during which the hole spins down. The transition epoch depends on mass, mirroring other evidence for “cosmic downsizing” in the AGN population.

scholarly journals Interpreting the X-ray afterglows of gamma-ray bursts with radiative losses and millisecond magnetars

2020 ◽  
Vol 499 (4) ◽  
pp. 5986-5992
Author(s):  
Nikhil Sarin ◽  
Paul D Lasky ◽  
Gregory Ashton
Keyword(s):  
Gravitational Wave ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Dipole Radiation ◽  
X Ray ◽  
Radiative Efficiency ◽  
Central Engine ◽  
Radiative Losses ◽  
Wave Emission ◽  
Prompt Emission

ABSTRACT The spin-down energy of millisecond magnetars has been invoked to explain X-ray afterglow observations of a significant fraction of short and long gamma-ray bursts. Here, we extend models previously introduced in the literature, incorporating radiative losses with the spin-down of a magnetar central engine through an arbitrary braking index. Combining this with a model for the tail of the prompt emission, we show that our model can better explain the data than millisecond-magnetar models without radiative losses or those that invoke spin-down solely through vacuum dipole radiation. We find that our model predicts a subset of X-ray flares seen in some gamma-ray bursts. We can further explain the diversity of X-ray plateaus by altering the radiative efficiency and measure the braking index of newly born millisecond magnetars. We measure the braking index of GRB061121 as $n=4.85^{+0.11}_{-0.15}$ suggesting the millisecond-magnetar born in this gamma-ray burst spins down predominantly through gravitational-wave emission.

Enhanced Radiative Efficiency in GaN Nanowires Grown on Sputtered TiNx: Effects of Surface Electric Fields

ACS Photonics ◽  
2021 ◽  
Author(s):  
Thomas Auzelle ◽  
Mani Azadmand ◽  
Timur Flissikowski ◽  
Manfred Ramsteiner ◽  
Katrin Morgenroth ◽  
...  
Keyword(s):  
Electric Fields ◽  
Radiative Efficiency ◽  
Gan Nanowires

scholarly journals No correlation between disc scale height and jet power in GRMHD simulations

2012 ◽  
Vol 424 (1) ◽  
pp. 524-531 ◽  
Author(s):  
P. Chris Fragile ◽  
Julia Wilson ◽  
Marco Rodriguez
Keyword(s):  
Scale Height ◽  
Jet Power

The Spectral Dependence of the Non-Radiative Efficiency in Hydrogenated Amorphous Silicon

1992 ◽  
Vol 258 ◽  
Author(s):  
J. Fan ◽  
J. Kakalios
Keyword(s):  
Amorphous Silicon ◽  
Room Temperature ◽  
Hydrogenated Amorphous Silicon ◽  
Free Carrier ◽  
Radiative Efficiency ◽  
Sharp Minimum ◽  
Carrier Thermalization ◽  
Hydrogenated Amorphous ◽  
Kinetics Of ◽  
Heat Released

ABSTRACTThe room temperature non-radiative efficiency, defined as the ratio of the heat released per absorbed photon for doped and undoped hydrogenated amorphous silicon (a-Si:H) has been measured using photo-pyroelectric spectroscopy (PPES) for photon energies ranging from 2.5 to 1.6 eV. There is a fairly sharp minimum in the non-radiative efficiency when the a-Si:H is illuminated with near bandgap photons. We describe a model wherein this minimum arises from the variation in the amount of heat generated by free carrier thermalization as the incident photon energy is varied, and report measurements of the excitation kinetics of the non-radiative efficiency which support this proposal.

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