Structure and evolution of irradiated accretion disks. I - Static thermal equilibrium structure. II - Dynamical evolution of a thermally unstable torus

Tuchman, Y.; Mineshige, Shin; Wheeler, J. C.

doi:10.1086/169045

Cited by 51 publications

(71 citation statements)

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“…The critical temperature discussed in Section 2.2.2 and C are degenerate parameters. The results of our earlier work on the X-ray and IR data of AXPs constrain the value of C to the range 10 −4 -7 × 10 −4 (Ertan &Çalışkan 2006), which remains in the range of the estimated irradiation efficiencies of SXTs (10 −4 -10 −3 ; de Jong et al 1996;Dubus et al 1999;Tuchman et al 1990). …”

Section: X-ray Irradiationmentioning

confidence: 79%

On the X-Ray Outbursts of Transient Anomalous X-Ray Pulsars and Soft Gamma-Ray Repeaters

Çalışkan¹,

Ertan²

2012

ApJ

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We show that the X-ray outburst light curves of four transient anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs), namely, XTE J1810−197, SGR 0501+4516, SGR 1627−41, and CXOU J164710.2−455216, can be produced by the fallback disk model that was also applied to the outburst light curves of persistent AXPs and SGRs in our earlier work. The model solves the diffusion equation for the relaxation of a disk that has been pushed back by a soft gamma-ray burst. The sets of main disk parameters used for these transient sources are very similar to each other and to those employed in our earlier models of persistent AXPs and SGRs. There is a characteristic difference between the X-ray outburst light curves of transient and persistent sources. This can be explained by the differences in the disk surface density profiles of the transient and persistent sources in quiescence indicated by their quiescent X-ray luminosities. Our results imply that a viscous disk instability operating at a critical temperature in the range of ∼1300-2800 K is a common property of all fallback disks around AXPs and SGRs. The effect of the instability is more pronounced and starts earlier for the sources with lower quiescent luminosities, which leads to the observable differences in the X-ray enhancement light curves of transient and persistent sources. A single active disk model with the same basic disk parameters can account for the enhancement phases of both transient and persistent AXPs and SGRs. We also present a detailed parameter study to show the effects of disk parameters on the evolution of the X-ray luminosity of AXPs and SGRs in the X-ray enhancement phases.

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Section: X-ray Irradiationmentioning

confidence: 79%

On the X-Ray Outbursts of Transient Anomalous X-Ray Pulsars and Soft Gamma-Ray Repeaters

Çalışkan¹,

Ertan²

2012

ApJ

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“…Open circles and filled triangles represent data of soft and hard states, respectively. Theoretical lines of (a), (b), and (c) are calculated by equation (2) with C = 10 −4 (Tuchman et al 1990). The irradiation temperatures of (a), (b), and (c) are T irr = 10000 K, 5000 K, and 3000 K, respectively.…”

Section: Mini-outburst and Disk Instability Modelmentioning

confidence: 99%

“…In other words, instability is determined by not only the mass accretion rate, but also the X-ray luminosity. Tuchman, Mineshige, and Wheeler (1990) calculated the instability in consideration of the effect of irradiation, and generated the S-shaped curves at different irradiation temperatures. They concluded that for sufficiently strong irradiation (irradiation temperature above 10000 K), the hydrogen and helium atoms are completely ionized, thus, the thermal instability is suppressed.…”

Section: Introductionmentioning

confidence: 99%

X-ray variability with spectral state transitions in NS-LMXBs observed with MAXI/GSC and Swift/BAT

Asai¹,

Mihara²,

Matsuoka³

et al. 2015

Publications of the Astronomical Society of Japan

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X-ray variabilities with spectral state transitions in bright low mass X-ray binaries containing a neutron star are investigated by using the one-day bin light curves of MAXI/GSC (Gas Slit Camera) and Swift/BAT (Burst Alert Telescope). Four sources (4U 1636−536, 4U 1705−44, 4U 1608−52, and GS 1826−238) exhibited small-amplitude X-ray variabilities with spectral state transitions. Such "mini-outbursts" were characterized by smaller amplitudes (several times) and shorter duration (less than several tens of days) than those of "normal outbursts." Theoretical model of disk instability by Mineshige and Osaki (PASJ, 37, 1, 1985) predicts both large-amplitude outbursts and small-amplitude variabilities. We interpret the normal outbursts as the former prediction of this model, and the mini-outbursts as the latter. Here, we can also call the mini-outburst as "purr-type outburst" referring to theoretical work. We suggest that similar variabilities lasting for several tens of days without spectral state transitions, which are often observed in the hard state, may be a repeat of mini-outbursts.

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“…Examples of such irradiated S -curves can be found in Tuchman et al (1990) and Dubus et al (1999). The low, cold branch corresponds to a layer of neutral hydrogen while in the upper, hot branch hydrogen is ionized.…”

Section: Vertical Structurementioning

confidence: 99%

The disc instability model for X-ray transients: Evidence for truncation and irradiation

Dubus

Hameury

Lasota

2001

A&A

342

549

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Abstract.We study the prospect of explaining the outbursts of Soft X-ray Transients (SXTs) by the thermalviscous instability in a thin disc. This instability is linked to hydrogen ionization and is significantly changed when irradiation of the disc by X-rays from the inner regions is included. We present the first numerically reliable, physically consistent calculations of the outburst cycles which include the effects of accretion disc irradiation. The decay from outburst is governed by irradiation, as pointed out by King & Ritter (1998), leading to slow exponential decays. At the end of the outburst, the disc is severely depleted, which lengthens the time needed to rebuild mass to the critical density for an outburst. Despite this, the long recurrence times and quiescent X-ray luminosities of SXTs still require the inner disc to be replaced by another type of flow in quiescence, presumably a hot advection dominated accretion flow (ADAF). We include the effects of such truncation and show that the resulting lightcurves are conclusively similar to those of SXTs like A0620-00. We conclude that the two-α disc instability model provides an adequate description of the outbursts of SXTs when both truncation and irradiation are included. The values for the viscosities in outburst and in quiescence are comparable to those used in CVs. We discuss the model in the context of present observations.

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Structure and evolution of irradiated accretion disks. I - Static thermal equilibrium structure. II - Dynamical evolution of a thermally unstable torus

Cited by 51 publications

References 0 publications

On the X-Ray Outbursts of Transient Anomalous X-Ray Pulsars and Soft Gamma-Ray Repeaters

On the X-Ray Outbursts of Transient Anomalous X-Ray Pulsars and Soft Gamma-Ray Repeaters

X-ray variability with spectral state transitions in NS-LMXBs observed with MAXI/GSC and Swift/BAT

The disc instability model for X-ray transients: Evidence for truncation and irradiation

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