Periodic variability during the X-ray decline of 4U 1636-53

Shih, I. C.; Bird, A. J.; Charles, P. A.; Cornelisse, R.; Tiramani, D.

doi:10.1111/j.1365-2966.2005.09224.x

Cited by 33 publications

(65 citation statements)

References 27 publications

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“…Similar behaviour has been observed since 2002 (Shih et al 2005(Shih et al , 2011Belloni et al 2007;Lyu et al 2014). 4U 1705−44: Mini-outburst occurred repeatedly during the periods of no normal outbursts.…”

Section: Mini-outburst and Normal Outburstsupporting

confidence: 78%

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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Section: Mini-outburst and Normal Outburstsupporting

confidence: 78%

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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“…It belongs to the class of atoll sources (Hasinger & van der Klis 1989). 4U 1636−53 shows intensity variations up to a factor of 10 on a ∼40 d cycle (Shih et al 2005;Belloni et al 2007), following a narrow track in the color-color diagram and hardness-intensity diagram (Belloni et al 2007;Altamirano et al 2008a). 4U 1636−53 was first observed as a strong continuous X-ray source with Copernicus (Willmore et al 1974) and Uhuru (Giacconi et al 1974).…”

Section: U 1636−53mentioning

confidence: 99%

Millihertz Quasi-Periodic Oscillations in 4u 1636–536: Putting Possible Constraints on the Neutron Star Size

Stiele

Kong

2016

ApJ

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Based on previous studies of quasi-periodic oscillations in neutron star LMXBs, mHz quasiperiodic oscillations (QPO) are believed to be related to 'marginally stable' burning on the neutron star (NS) surface. Our study of phase resolved energy spectra of these oscillations in 4U 1636−53 shows that the oscillations are not caused by variations in the blackbody temperature of the neutron star, but reveals a correlation between the change of the count rate during the mHz QPO pulse and the spatial extend of a region emitting blackbody emission. The maximum size of the emission area R 2 BB = 216.7 +93.2 −86.4 km 2 , provides the direct evidence that the oscillations originate from a variable surface area constrained on the NS and are therefore not related to instabilities in the accretion disk. The obtained lower limit on the size of the neutron star (11.0 km) rules out equations of state that prefer small NS radii. Observations of mHz QPOs in NS LMXBs with NICER and eXTP will reduce the statistical uncertainty in the lower limit on the NS radius, which together with better estimates of the hardening factor and distance, will allow improving discrimination between different equations of state and compact star models. Furthermore, future missions will allow us to measure the peak blackbody emission area for a single mHz QPO pulse, which will push the lower limit to larger radii.

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“…4U 1636-53 is a persistent X-ray source, although it shows variations in intensity up to a factor of 10, following a narrow track in the colour-colour diagram (CD) and hardness-intensity diagram (HID; Belloni et al 2007;Altamirano et al 2008) with a ∼40-d cycle (Shih et al 2005;Belloni et al 2007). The transition through the CD (or HID) is thought to be driven by changes in the mass accretion rate.…”

Section: U 1636-53mentioning

confidence: 99%

Broad iron line in the fast spinning neutron-star system 4U 1636−53

Sanna

Hiemstra

Méndez

et al. 2013

Monthly Notices of the Royal Astronomical Society

111

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We analysed the X-ray spectra of six observations, simultaneously taken with XMMNewton and Rossi X-ray Timing Explorer (RXTE), of the neutron star low-mass X-ray binary 4U 1636-53. The observations cover several states of the source, and therefore a large range of inferred mass accretion rate. These six observations show a broad emission line in the spectrum at around 6.5 keV, likely due to iron. We fitted this line with a set of phenomenological models of a relativistically broadened line, plus a model that accounts for relativistically smeared and ionised reflection from the accretion disc. The latter model includes the incident emission from both the neutronstar surface or boundary layer and the corona that is responsible for the high-energy emission in these systems. From the fits with the reflection model we found that in four out of the six observations the main contribution to the reflected spectrum comes from the neutron-star surface or boundary layer, whereas in the other two observations the main contribution to the reflected spectrum comes from the corona. We found that the relative contribution of these two components is not correlated to the state of the source. From the phenomenological models we found that the iron line profile is better described by a symmetric, albeit broad, profile. The width of the line cannot be explained only by Compton broadening, and we therefore explored the case of relativistic broadening. We further found that the direct emission from the disc, boundary layer, and corona generally evolved in a manner consistent with the standard accretion disc model, with the disc and boundary layer becoming hotter and the disc moving inwards as the source changed from the hard in to the soft state. The iron line, however, did not appear to follow the same trend.

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Periodic variability during the X-ray decline of 4U 1636-53

Cited by 33 publications

References 27 publications

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

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

Millihertz Quasi-Periodic Oscillations in 4u 1636–536: Putting Possible Constraints on the Neutron Star Size

Broad iron line in the fast spinning neutron-star system 4U 1636−53

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