Why soft X-ray transients can remain in the low/hard state during outburst

Meyer-Hofmeister, E.

doi:10.1051/0004-6361:20040369

Cited by 31 publications

(38 citation statements)

References 26 publications

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“…Thus the luminosity at which the soft-to-hard transition occurs is consistent between the two major outbursts. They are also consistent with theoretical predictions of state transitions at luminosities near 0.02 − 0.05L EDD if one accounts for the hysteresis effect (Meyer-Hofmeister 2004;Meyer et al 2000). For the 2003 outburst, we find that the 2 -200 keV flux during revolution 57 was 9.33 × 10 −9 ergs cm −2 s −1 if we use the ISGRI normalization for the COMPTT model.…”

Section: Spectral Analysissupporting

confidence: 86%

XTE J1550−564:INTEGRALObservations of a Failed Outburst

Sturner

Shrader

2005

ApJ

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The well known black-hole X-ray binary transient XTE J1550-564 underwent an outburst during the spring of 2003 which was substantially underluminous in comparison to previous periods of peak activity in that source. In addition, our analysis shows that it apparently remained in the hard spectral state over the duration of that outburst. This is again in sharp contrast to major outbursts of that source in 1998/1999 during which it exhibited an irregular light curve, multiple state changes and collimated outflows. This leads us to classify it as a "failed outburst." We present the results of our study of the spring 2003 event including light curves based on observations from both INTEGRAL and RXTE. In addition, we studied the evolution of the high-energy 3-300 keV continuum spectrum using data obtained with three main instruments on INTEGRAL. These spectra are consistent with typical low-hard-state thermal Comptonization emission. We also consider the 2003 event in the context of a multi-source, multi-event period-peak luminosity diagram in which it is a clear outlyer. We then consider the possibility that the 2003 event was due to a discrete accretion event rather than a limit-cycle instablility. In that context, we apply model fitting to derive the timescale for viscous propagation in the disk, and infer some physical characteristics.

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Section: Spectral Analysissupporting

confidence: 86%

XTE J1550−564:INTEGRALObservations of a Failed Outburst

Sturner

Shrader

2005

ApJ

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“…These observed contradictory features can be explained if we assume that the inner hot flow (ADAF) condenses back onto the inner disk, relatively increasing the size of the disk, steepens the power-law index, and increases the hard flux. The IM state is the most probable phase of accretion where the condensation of the inner hot matter can transform into an inner disk (Meyer-Hofmeister 2004;Meyer et al 2007;Liu et al 2007). More studies are required to understand this phenomenon (if it is true), especially in order to understand the properties of the new disk (which formed from the condensation of hot matter) and the indigenous disk (standard Keplerian disk).…”

Section: Discussionmentioning

confidence: 99%

Anti-Correlated Soft Lags in the Intermediate State of Black Hole Source Gx 339–4

Sriram

Rao

Choi

2010

ApJ

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We report the few hundred second anti-correlated soft lags between soft and hard energy bands in the source GX 3394 using RXTE observations. In one observation, anti-correlated soft lags were observed using the ISGRI/INTEGRAL hard energy band and the PCA/RXTE soft energy band light curves. The lags were observed when the source was in hard and soft intermediate states, i.e., in a steep power-law state.We found that the temporal and spectral properties were changed during the lag timescale.The anti-correlated soft lags are associated with spectral variability during which the geometry of the accretion disk is changed. The observed temporal and spectral variations are explained using the framework of truncated disk geometry. We found that during the lag timescale, the centroid frequency of quasi-periodic oscillation is decreased, the soft flux is decreased along with an increase in the hard flux, and the power-law index steepens together with a decrease in the disk normalization parameter. We argue that these changes could be explained if we assume that the hot corona condenses and forms a disk in the inner region of the accretion disk. The overall spectral and temporal changes support the truncated geometry of the accretion disk in the steep power-law state or in the intermediate state.

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“…to form a so-called high/soft state. Otherwise the source stays in a low/hard state for the whole life of the outburst (Meyer-Hofmeister 2004).…”

Section: Discussionmentioning

confidence: 99%

Outbursts from IGR J17473-2721

Zhang

Chen

Wang³

et al. 2009

A&A

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Aims. IGR J17473-2721 was discovered by INTEGRAL as a neutron star low mass X-ray binary. To date, two outbursts have been detected in X-rays by RXTE/ASM and SWIFT: the one occurring in 2005 was weak and was characterized by a low/hard state spectrum; the one of March 2008 was strong and showed a 6-step evolution in its flux. We investigate their evolution, emphasizing the later outburst. Methods. We analyzed all available observations carried out by RXTE on IGR J17473-2721 during its later outburst. We analyzed as well all the available SWIFT/BAT data on this source. Results. The flux of the latter outburst rose in ∼one month and then kept roughly constant for the following ∼two months. During this time period, the source was in a low/hard state. The source moved to a high/soft state within the following three days, accompanied by the occurrence of an additional outburst at soft X-rays and the end of the preceding outburst in hard X-rays. During the decay of this soft outburst, the source went back to a low/hard state within 6 days, with a luminosity 4 times lower than the first transition. This shows a full cycle of the hysteresis in transition between the hard and the soft states. The fact that the flux remained roughly constant for ∼two months at times prior to the spectral transition to a high/soft state might be regarded as the result of balancing the evaporation of the inner disk and the inward accretion flow, in a model in which the state transition is determined by the mass flow rate. Such a balance might be broken via an additional mass flow accreting onto the inner disk, which lightens the extra soft outburst and causes the state transition. However, the possibility of an origin of the emission from the jet during this time period cannot be excluded. The spectral analysis suggests an inclined XRB system for IGR J17473-2721. Such a long-lived preceding low/hard state makes IGR J17473-2721 resemble the behavior of outbursts seen in black hole X-ray binaries like GX 339-4.

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Why soft X-ray transients can remain in the low/hard state during outburst

Cited by 31 publications

References 26 publications

XTE J1550−564:INTEGRALObservations of a Failed Outburst

XTE J1550−564:INTEGRALObservations of a Failed Outburst

Anti-Correlated Soft Lags in the Intermediate State of Black Hole Source Gx 339–4

Outbursts from IGR J17473-2721

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