scholarly journals The large amplitude X-ray variability in NGC 7589: possible evidence for accretion mode transition

2019 ◽  
Vol 492 (2) ◽  
pp. 2335-2346 ◽  
Author(s):  
Zhu Liu ◽  
He-Yang Liu ◽  
Huaqing Cheng ◽  
Erlin Qiao ◽  
Weimin Yuan
Keyword(s):  
Large Amplitude ◽  
Mode Transition ◽  
High Luminosity ◽  
X Ray ◽  
Accretion Flow ◽  
Thin Disc ◽  
Inner Region ◽  
X Ray Binaries ◽  
Term Monitoring

ABSTRACT We report the discovery of large amplitude X-ray variability in the low-luminosity active galactic nucleus NGC 7589, and present possible observational evidence for accretion mode transition in this source. Long-term X-ray flux variations by a factor of more than 50 are found using X-ray data obtained by Swift/X-Ray Telescope and XMM–Newton over 17 yr. Results of long-term monitoring data in the UV, optical, and infrared bands over ∼20 yr are also presented. The Eddington ratio λEdd increased from 10−3 to ∼0.13, suggesting a transition of the accretion flow from an advection dominated accretion flow to a standard thin accretion disc. Further evidence supporting the thin disc in the high-luminosity state is found by the detection of a significant soft X-ray component in the X-ray spectrum. The temperature of this component ($\sim 19^{+15}_{-7}$ eV, fitted with a blackbody model) is in agreement with the predicted temperature of the inner region for a thin disc around a black hole (BH) with mass of ∼107M⊙. These results may indicate that NGC 7589 had experienced accretion mode transition over a time-scale of a few years, suggesting the idea that similar accretion processes are at work for massive BH and BH X-ray binaries.

scholarly journals Magnetically Driven Warping and Precession of Accretion Disks: Implications for Exotic Stellar Variabilities

2002 ◽  
Vol 187 ◽  
pp. 215-220
Author(s):  
Dong Lai
Keyword(s):  
Accretion Disks ◽  
Low Frequency ◽  
Disk Accretion ◽  
X Ray ◽  
T Tauri ◽  
Magnetic Stars ◽  
Low Mass ◽  
Inner Region ◽  
X Ray Binaries

AbstractThe inner region of the accretion disk around a magnetized star is subjected to magnetic torques that induce warping and precession of the disk. These torques arise from interactions between the stellar field and the induced electric currents in the disk. These novel magnetic effects give rise to some “exotic” stellar variabilities, and may play an important role in explaining a number of puzzling behaviors related to disk accretion onto magnetic stars, such as mHz QPOs in X-ray pulsars, long-term periodicities of X-ray binaries (including precession of jets), low-Frequency (10-50 Hz) QPO’s in low-mass X-ray binaries, and photometric variabilities of T Tauri stars.

The Extremes of AGN Variability

2016 ◽  
Vol 12 (S324) ◽  
pp. 168-171 ◽  
Author(s):  
S. Komossa ◽  
D. Grupe ◽  
N. Schartel ◽  
L. Gallo ◽  
J. L. Gomez ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
X Ray ◽  
Accretion Flow ◽  
Multi Wavelength ◽  
Long Term Monitoring ◽  
Term Monitoring ◽  
Spectral States ◽  
Ongoing Monitoring

AbstractWe present results from our ongoing monitoring programs aimed at identifying and understanding Active Galactic Nuclei (AGN) in extreme flux and spectral states. Observations of AGN in extreme states can reveal the nature of the inner accretion flow, the physics of matter under strong gravity, and they provide insight on the properties of ionized absorbers and outflows launched near supermassive black holes (SMBHs). We present new results from our long-term monitoring of IC 3599, WPVS007, and Mrk 335, multi-wavelength follow-ups of the newly identified changing-look AGN HE 1136–2304, and UV–X-ray follow-ups of the binary SMBH candidate OJ 287 after its 2015 optical maximum, now in a new optical-X-ray–high-state.

scholarly journals The coupling of a disk corona and a jet for the radio/X-ray correlation in black hole X-ray binaries

2014 ◽  
Vol 10 (S312) ◽  
pp. 247-248
Author(s):  
Erlin Qiao
Keyword(s):  
Black Hole ◽  
General Idea ◽  
High Luminosity ◽  
X Ray ◽  
Accretion Flow ◽  
X Ray Binaries

AbstractWe interpret the radio/X-ray correlation of LR ∝ LX~1.4 for LX/LEdd ≳ 10−3 with a detailed disk corona-jet model, in which the accretion flow and the jet are connected by a parameter, η, describing the fraction of the matter in the accretion flow ejected outward to form the jet. We calculate LR and LX at different Ṁ, adjusting η to fit the observed radio/X-ray correlation of the black hole X-ray transient H1743-322 for LX/LEdd > 10−3. It is found that the value of η for this radio/X-ray correlation for LX/LEdd > 10−3, is systematically less than that of the case for LX/LEdd < 10−3, which is consistent with the general idea that the jet is often relatively suppressed at the high luminosity phase in black hole X-ray binaries.

scholarly journals The radiative efficiency of neutron stars at low-level accretion

2021 ◽  
Vol 502 (3) ◽  
pp. 3870-3878
Author(s):  
Erlin Qiao ◽  
B F Liu
Keyword(s):  
Black Hole ◽  
Model Parameters ◽  
X Ray ◽  
The Real ◽  
Radiative Efficiency ◽  
Accretion Flow ◽  
Low Level ◽  
Low Mass ◽  
Inner Region ◽  
X Ray Binaries

ABSTRACT When neutron star low-mass X-ray binaries (NS-LMXBs) are in the low-level accretion regime (i.e. $L_{\rm X}\lesssim 10^{36}\ \rm erg\ s^{-1}$), the accretion flow in the inner region around the NS is expected to exist in the form of the hot accretion flow, e.g. the advection-dominated accretion flow (ADAF) as that in black hole X-ray binaries. Following our previous studies in Qiao & Liu (2020a, b) on the ADAF accretion around NSs, in this paper, we investigate the radiative efficiency of NSs with an ADAF accretion in detail, showing that the radiative efficiency of NSs with an ADAF accretion is much lower than that of $\epsilon \sim {\dot{M} GM\over R_{*}}/{\dot{M} c^2}\sim 0.2$ despite the existence of the hard surface. As a result, given an X-ray luminosity LX (e.g. between 0.5 and 10 keV), $\dot{M}$ calculated by $\dot{M}=L_{\rm X}{R_{*}\over {GM}}$ is lower than the real $\dot{M}$ calculated within the framework of the ADAF accretion. The real $\dot{M}$ can be more than two orders of magnitude higher than that calculated by $\dot{M}=L_{\rm X}{R_{*}\over {GM}}$ with appropriate model parameters. Finally, we discuss that if applicable, the model of ADAF accretion around a NS can be applied to explain the observed millisecond X-ray pulsation in some NS-LMXBs (such as PSR J1023+0038, XSS J12270−4859, and IGR J17379−3747) at a lower X-ray luminosity of a few times of $10^{33}\ \rm erg\ s^{-1}$, since at this X-ray luminosity the calculated $\dot{M}$ with the model of ADAF accretion can be high enough to drive a fraction of the matter in the accretion flow to be channelled on to the surface of the NS forming the X-ray pulsation.

scholarly journals IUE Studies of Luminous X-Ray Binaries

1983 ◽  
Vol 6 ◽  
pp. 648-648
Author(s):  
J.B. Hutchings
Keyword(s):  
Magellanic Clouds ◽  
Thick Shell ◽  
High Luminosity ◽  
Uv Spectrum ◽  
X Ray ◽  
Unique Object ◽  
The Future ◽  
Orbit Inclination ◽  
Supercritical Accretion ◽  
X Ray Binaries

IUE has been used to study 11 high luminosity X-ray binaries, of which 3 are in the Magellanic Clouds. In the supergiant systems, X-ray ionisation bubbles have been found in most cases, leading to a greater understanding of the winds and accretion processes. Further studies of precessing objects such as LMC X-4 with IUE and ST are clearly of considerable interest, relating to X-ray heating and blanketing. Detailed studies of the Cyg X-l ionisation bubble may resolve the long standing puzzle of its orbit inclination and masses. UV continua have furnished valuable information on extinction, temperatures and luminosities, and the presence of non-stellar (i.e. disk) luminosity. Here too, more detailed studies are clearly indicated for the future. A unique object of interest is the LMC transient 0538-66 whose UV spectrum has quasarlike lines and luminosity which varies oppositely to the visible. This may be a case of supercritical accretion generating an optically thick shell (“disk”) about the pulsar.

scholarly journals Radiative efficiency of hot accretion flow and the radio/X-ray correlation in X-ray binaries

2014 ◽  
Vol 10 (S312) ◽  
pp. 139-140
Author(s):  
Fu-Guo Xie
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Accretion Rate ◽  
Galactic Nuclei ◽  
X Ray ◽  
Radiative Efficiency ◽  
Accretion Flow ◽  
Accretion Rates ◽  
Distinctive Property ◽  
X Ray Binaries

AbstractSignificant progresses have been made since the discovery of hot accretion flow, a theory successfully applied to the low-luminosity active galactic nuclei (LLAGNs) and black hole (BH) X-ray binaries (BHBs) in their hard states. Motivated by these updates, we re-investigate the radiative efficiency of hot accretion flow. We find that, the brightest regime of hot accretion flow shows a distinctive property, i.e. it has a constant efficiency independent of accretion rates, similar to the standard thin disk. For less bright regime, the efficiency has a steep positive correlation with the accretion rate, while for faint regime typical of advection-dominated accretion flow, the correlation is shadower. This result can naturally explain the observed two distinctive correlations between radio and X-ray luminosities in black hole X-ray binaries. The key difference in systems with distinctive correlations could be the viscous parameter, which determines the critical luminosity of different accretion modes.

Long term multiwavelength monitoring of high mass x-ray binaries

1994 ◽  
Author(s):  
Paul Roche ◽  
Malcolm Coe ◽  
Chris Everall ◽  
Juan Fabregat ◽  
Victor Reglero ◽  
...  
Keyword(s):  
High Mass ◽  
X Ray ◽  
X Ray Binaries

scholarly journals Accretion Disc Formation in Intermediate Polars

1996 ◽  
Vol 158 ◽  
pp. 161-164
Author(s):  
G. A. Wynn ◽  
A. R. King
Keyword(s):  
Magnetic Field ◽  
Accretion Disc ◽  
Local Magnetic Field ◽  
Magnetic Systems ◽  
X Ray ◽  
Accretion Flow ◽  
Intermediate Polars ◽  
X Ray Binaries ◽  
The Magnetic Field ◽  
Disc Formation

The large-scale accretion flow in the intermediate polars (IPs) is still a matter of vigorous debate. It is known that the magnetic field of the white dwarf (WD) controls the accretion flow close to the surface, channeling the plasma onto the polecaps and giving rise to X-ray emission modulated at the WD spin period (Pspin). After their discovery it was assumed that IPs were the WD analogues of the pulsing X-ray binaries, where a magnetic neutron star accretes from a disrupted accretion disc. However, a number of authors have pointed out that the criteria for disc formation in IPs are less certain than those for the X-ray binaries.The simplest possible criterion for disc formation in a binary is that the accretion flow should be able to orbit freely about the primary star (see Frank, King & Raine 1991 for a review). In non-magnetic systems this is merely the condition that the minimum approach distance of the free stream (Rmin) should exceed the radius of the primary. The situation in magnetic systems is more complex, as the magnetic field of the primary presents an obstacle to the infalling accretion stream. In many treatments of IPs it is assumed that the plasma stream is able to orbit freely about the WD until the ram pressure of the stream is of the same order as the magnetic pressureρv2~B2/8π, whereρis the stream density,vthe stream velocity andBthe local magnetic field strength. This condition fixes the magnetospheric radius,Rmag, inside which the magnetic field is assumed to thread the stream material and direct the accretion flow along the fieldlines.

scholarly journals Long-term variability of low-mass X-ray binaries

2014 ◽  
Vol 64 ◽  
pp. 02008
Author(s):  
E. Filippova ◽  
M. Revnivtsev ◽  
E. R. Parkin
Keyword(s):  
X Ray ◽  
Low Mass ◽  
X Ray Binaries
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