No anticorrelation between cyclotron line energy and X-ray flux in 4U 0115+634

Müller, Sebastian; Ferrigno, C.; Kühnel, Matthias; Schönherr, G.; Becker, Peter A.; Wolff, M. T.; Hertel, D.; Schwarm, Fritz-Walter; Grinberg, V.; Obst, Maria; Caballero, I.; Pottschmidt, K.; Fürst, Felix; Kreykenbohm, I.; Rothschild, R. E.; Hemphill, Paul; Martínez-Núñez, Silvia; Torrejón, José M.; Klochkov, D.; Staubert, R.; Wilms, J.

doi:10.1051/0004-6361/201220359

Cited by 73 publications

(81 citation statements)

References 43 publications

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“…Later this effect was confirmed using the RXTE and INTEGRAL data (Nakajima et al, 2006;Tsygankov et al, 2007;Klochkov et al, 2011;Boldin et al, 2013). Such a behaviour can be explained either by the modification of the emitting regions in the vicinity of the neutron star or by artificial effects due to poor knowledge of the spectral continuum Müller et al, 2013;Boldin et al, 2013).…”

Section: Discussionmentioning

confidence: 76%

“…An important result of INTEGRAL is the discovery of an anti-correlation between the cyclotron energy and the X-ray luminosity in the transient Xray pulsars V 0332+53 (Tsygankov et al, 2006;Mowlavi et al, 2006) and 4U 0115+63 (Nakajima et al (2006); Tsygankov et al (2007); but see Müller et al (2013) and Boldin et al (2013) for the influence of the continuum spectral shape). This result initiated a systematic study of the cyclotron energy properties as a function of the source luminosity.…”

Section: Be Systems X-ray Pulsars and Properties Of Cyclotron Absorpmentioning

confidence: 99%

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High-mass X-ray binaries in the Milky Way

Walter

Lutovinov

Bozzo

et al. 2015

Astron Astrophys Rev

228

234

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High-mass X-ray binaries are fundamental in the study of stellar evolution, nucleosynthesis, structure and evolution of galaxies and accretion processes. Hard X-rays observations by INTEGRAL and Swift have broadened significantly our understanding in particular for the super-giant systems in the Milky Way, which number has increased by almost a factor of three. INTEGRAL played a crucial role in the discovery, study and understanding of heavily obscured systems and of fast X-ray transients. Most super-giant systems can now be classified in three categories: classical/obscured, eccentric and fast transient.The classical systems feature low eccentricity and variability factor of ∼ 10 3 , mostly driven by hydrodynamic phenomena occurring on scales larger than the accretion radius. Among them, systems with short orbital periods and close to Roche-Lobe overflow or with slow winds, appear highly obscured. In eccentric systems, the variability amplitude can reach even higher factors, because of the contrast of the wind density along the orbit. Four super-giant systems, featuring fast outbursts, very short orbital periods and anomalously low accretion rates, are not yet understood.Simulations of the accretion processes on relatively large scales have progressed and reproduce parts of the observations. The combined effects of wind

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Section: Discussionmentioning

confidence: 76%

Section: Be Systems X-ray Pulsars and Properties Of Cyclotron Absorpmentioning

confidence: 99%

High-mass X-ray binaries in the Milky Way

Walter

Lutovinov

Bozzo

et al. 2015

Astron Astrophys Rev

228

234

View full text Add to dashboard Cite

show abstract

“…Both lines are well localised and do not dominate the continuum, in contrast to the case of 4U 0115+63, for example, where inadequately modelled cyclotron lines could fully distort the continuum, as illustrated in Fig. 8 of Müller et al (2013b) for instance.…”

Section: Pulse-averaged Spectrummentioning

confidence: 95%

“…There are also X-ray pulsars in which an indication for a correlation between the CRSF energy and luminosity is reported but so far not unambiguously confirmed, such as 4U 0115+63 (Müller et al 2013b;Iyer et al 2015) and 4U 1538-522 (Hemphill et al 2014). Here, we focus on the accreting pulsar Cep X-4 discovered in 1972 with the Orbiting Solar Observatory-7 (Ulmer et al 1973) and re-discovered in 1988 with Ginga as GS 2138+56 during a one-month-long X-ray outburst (Makino & GINGA Team 1988).…”

Section: Arxiv:170206361v1 [Astro-phhe] 21 Feb 2017mentioning

confidence: 99%

Luminosity-dependent changes of the cyclotron line energy and spectral hardness in Cepheus X-4

Vybornov

Klochkov

Gornostaev

et al. 2017

A&A

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Context. X-ray spectra of accreting pulsars are generally observed to vary with their X-ray luminosity. In particular, the hardness of the X-ray continuum is found to depend on luminosity. In a few sources, the correlation between the energy of the cyclotron resonance scattering feature (CRSF) and the luminosity is clear. Different types (signs) of the correlation are believed to reflect different accretion modes. Aims. We analyse two NuSTAR observations of the transient accreting pulsar Cep X-4 during its 2014 outburst. Our analysis is focused on a detailed investigation of the dependence of the CRSF energy and of the spectral hardness on X-ray luminosity, especially on short timescales. Methods. To investigate the spectral changes as a function of luminosity within each of the two observations, we used the intrinsic variability of the source on the timescale of individual pulse cycles (tens of seconds) , the so-called pulse-to-pulse variability. Results. We find that the NuSTAR spectrum of Cep X-4 contains two CRSFs: the fundamental line at~30 keV and its harmonic at~55 keV. We find for the first time that the energy of the fundamental CRSF increases and the continuum becomes harder with increasing X-ray luminosity not only between the two observations, that is, on the long timescale, but also within an individual observation, on the timescale of a few tens of seconds. We investigate these dependencies in detail including their non-linearity. We discuss a possible physical interpretation of the observed behaviour in the frame of a simple one-dimensional model of the polar emitting region with a collisionless shock formed in the infalling plasma near the neutron star surface. With this model, we are able to reproduce the observed variations of the continuum hardness ratio and of the CRSF energy with luminosity.

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“…For this reason, empirical models are typically used (see Müller et al 2013;and DeCesar et al 2013 for recent summaries).…”

Section: Continuum Of Gro J1008−57mentioning

confidence: 99%

GRO J1008−57: an (almost) predictable transient X-ray binary

Kühnel

Müller

Kreykenbohm

et al. 2013

A&A

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A study of archival RXTE, Swift, and Suzaku pointed observations of the transient high-mass X-ray binary GRO J1008−57 is presented. A new orbital ephemeris based on pulse arrival-timing shows the times of maximum luminosities during outbursts of GRO J1008−57 to be close to periastron at orbital phase −0.03. This makes the source one of a few for which outburst dates can be predicted with very high precision. Spectra of the source in 2005, 2007, and 2011 can be well described by a simple power law with high-energy cutoff and an additional black body at lower energies. The photon index of the power law and the black-body flux only depend on the 15-50 keV source flux. No apparent hysteresis effects are seen. These correlations allow us to predict the evolution of the pulsar's X-ray spectral shape over all outbursts as a function of just one parameter, the source's flux. If modified by an additional soft component, this prediction even holds during GRO J1008−57's 2012 type II outburst.

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No anticorrelation between cyclotron line energy and X-ray flux in 4U 0115+634

Cited by 73 publications

References 43 publications

High-mass X-ray binaries in the Milky Way

High-mass X-ray binaries in the Milky Way

Luminosity-dependent changes of the cyclotron line energy and spectral hardness in Cepheus X-4

GRO J1008−57: an (almost) predictable transient X-ray binary

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