A continuous flaring- to normal-branch transition in
 Scorpius X-1

Casella, P.; Belloni, T.; Stella, L.

doi:10.1051/0004-6361:20052912

Cited by 20 publications

(19 citation statements)

References 15 publications

(14 reference statements)

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“…1-2ks in the case of Sco X-1. 6 This is a known characteristic of NBOs in Sco X-1, and such a behaviour has been reported by, e.g., Casella et al 2006. an association between X-ray power spectra which combine NBO and HBO and the launch of the URF, and for an association between the hard apex and the corresponding flat-topped noise PDS and the launch of the lobes. We note, however, that the association between the launch of the URFs and the appearance of a NBO+HBO in the X-ray PDS is based on one single event for which both X-ray and radio data are available.…”

Section: Launch Of Urf #2mentioning

confidence: 67%

A connection between accretion states and the formation of ultrarelativistic outflows in a neutron star X-ray binary

Motta

Fender

2018

Monthly Notices of the Royal Astronomical Society

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The nearby accreting neutron star binary Sco X-1 is the closest example of ongoing relativistic jet production at high Eddington ratios. Previous radio studies have revealed that alongside mildly relativistic, radio-emitting ejecta, there is at times a much faster transfer of energy from the region of the accretion flow along the jet. The nature of this ultrarelativistic flow remains unclear and while there is some evidence for a similar phenomenon in other systems which might contain neutron stars, it has never been observed in a confirmed black hole system. We have compared these previous radio observations with a new analysis of simultaneous X-ray observations which were performed with the RXTE mission. We find that the ejection of the ultra-relativistic flow seems to be associated with the simultaneous appearance of two particular types of quasi-periodic oscillations in the X-ray power spectrum. In contrast, the mildly relativistic, radio-emitting outflows may be associated with flat-topped broad band noise in the X-ray power spectrum. This is the first time a link, albeit tentative, has been found between these mysterious unseen flows and the accretion flow from which they are launched.

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Section: Launch Of Urf #2mentioning

confidence: 67%

A connection between accretion states and the formation of ultrarelativistic outflows in a neutron star X-ray binary

Motta

Fender

2018

Monthly Notices of the Royal Astronomical Society

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“…Therefore, these three regions partially overlap, allowing type-B QPOs and type-A QPOs to ap-pear at different luminosity levels. This possibility is supported by the fact that while type-B QPOs are sometimes found in correspondence to peaks in the source flux for the case of GX 339-4 and Motta et al 2012 for GRO J16550-40), some other times it is type-A QPOs that are observed in correspondence to flux peaks (Casella et al 2004), similarly to what is seen for FBOs in NSs (Casella et al 2006).…”

Section: Nbos and Type-b Qposmentioning

confidence: 79%

Links between quasi-periodic oscillations and accretion states in neutron star low-mass X-ray binaries

Motta

Escorial

Kuulkers

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We analysed the Rossi X-ray Timing Explorer (RXTE) data from a sample of bright accreting neutron star (NS) low-mass X-ray binaries (LMXBs). With the aim of studying the quasiperiodic variability as a function of the accretion regime, we carried out a systematic search of the quasi-periodic oscillations (QPOs) in the X-ray time series of these systems, using the integrated fractional variability as a tracker for the accretion states. We found that the three QPO types originally identified in the '80s for the brightest LMXBs, the so-called Z-sources, i.e., horizontal, normal and flaring branch oscillations (HBOs, NBOs and FBOs, respectively), are also identified in the slightly less bright NS LMXBs, the so-called Atoll sources, where we see QPOs with a behaviour consistent with the HBOs and FBOs. We compared the quasiperiodic variability properties of our NS sample with those of a sample of black hole (BH) LMXBs. We confirm the association between HBOs, NBOs and FBOs observed in Z-sources, with the type-C, type-B and type-A QPOs, respectively, observed in BH systems, and we extended the comparison to the HBO-like and FBO-like QPOs seen in Atoll sources. We conclude that the variability properties of BH and weakly-magnetized NS LMXBs show strong similarities, with QPOs only weakly sensitive to the nature of the central compact object in both classes of systems. We find that the historical association between kHz QPOs and highfrequency QPOs, seen around NSs and BHs, respectively, is not obvious when comparing similar accretion states in the two kinds of systems.

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“…arc length S along the track. However, in recent years authors have found several properties that do not A35, page 2 of 16 correlate (Wijnands et al 1996;Homan et al 2002;Casella et al 2006;Dieters & van der Klis 2000) so that S is not a measure ofṀ.…”

Section: A Monotonic Variation Of Mass Accretion Rate?mentioning

confidence: 99%

Spectral investigations of the nature of the Scorpius X-1 like sources

Church

Gibiec

Bałucińska‐Church

et al. 2012

A&A

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We present results of spectral investigations of the Sco X-1 like Z-track sources Sco X-1, GX 349+2, and GX 17+2 based on Rossi-XTE (RXTE) observations determining spectral evolution along the Z-track. Results are obtained for a spectral model describing an extended accretion disk corona. The results are compared with previous results for the Cyg X-2 like group: Cyg X-2, GX 340+0, and GX 5-1 and a general model for the Z-track sources proposed. On the normal branch, the Sco-like and Cyg-like sources are similar, the results indicating an increase of mass accretion rateṀ between soft and hard apex, not as in the standard view that this increases monotonically around the Z. In the Cyg-like sources, increasingṀ causes the neutron star temperature kT to increase from ∼1 to ∼2 keV. At the lower temperature, the radiation pressure is small, but at the higher kT , the emitted flux of the neutron star is several times super-Eddington and the high radiation pressure disrupts the inner disk and launches the relativistic jets observed on the upper normal and horizontal branches. In the Sco-like sources, the main physical difference is the high kT of more than 2 keV on all parts of the Z-track suggesting jets are always possible, even on the flaring branch. The flaring branch in the Cyg-like sources is associated with a release of energy on the neutron star consistent with unstable nuclear burning. The Sco-like sources are very different as flaring appears to be a combination of unstable burning and an increase ofṀ which makes flaring much stronger. Analysis of 15 years of RXTE ASM data on all 6 classic Z-track sources shows the high rate and strength of flaring in the Sco-like sources suggesting that the continual release of energy heats the neutron star causing the high kT . Analysis of a Sco X-1 observation with unusually little flaring supports this. GX 17+2 appears to be transitional between the Cyg and Sco-like types. Our results do not support the suggestion that Cyg or Sco-like nature is determined by the luminosity.

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A continuous flaring- to normal-branch transition in Scorpius X-1

Cited by 20 publications

References 15 publications

A connection between accretion states and the formation of ultrarelativistic outflows in a neutron star X-ray binary

A connection between accretion states and the formation of ultrarelativistic outflows in a neutron star X-ray binary

Links between quasi-periodic oscillations and accretion states in neutron star low-mass X-ray binaries

Spectral investigations of the nature of the Scorpius X-1 like sources

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