4U 0115 + 63: phase lags and cyclotron resonant scattering

Ferrigno, C.; Falanga, M.; Bozzo, E.; Becker, Peter A.; Klochkov, D.; Santangelo, A.

doi:10.1051/0004-6361/201116826

Cited by 57 publications

(49 citation statements)

References 56 publications

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“…The pulse map shows that the secondary peak starts to form at ∼6 keV and is of comparable strength to the main peak above ∼15 keV. Interestingly, we do not find any significant phase shifts around the cyclotron line energy as predicted by theory (Schönherr et al 2014) and as observed in 4U 0115+634 by Ferrigno et al (2011).…”

Section: Timing Analysissupporting

confidence: 68%

Suzakuobservations of the 2013 outburst of KS 1947+300

Ballhausen

Kühnel

Pottschmidt

et al. 2016

A&A

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We report on the timing and spectral analysis of two Suzaku observations with different flux levels of the high-mass X-ray binary KS 1947+300 during its 2013 outburst. In agreement with simultaneous NuSTAR observations, the continuum is well described by an absorbed power law with a cutoff and an additional blackbody component. In addition, we find fluorescent emission from neutral, Helike, and even H-like iron. We determine a pulse period of ∼18.8 s with the source showing a spin-up between the two observations. Both Suzaku observations show very similar behavior of the pulse profile, which is strongly energy dependent. This profile has an evolution from a profile with one peak at low energies to a profile with two peaks of different widths toward higher energies seen in both the Suzaku and NuSTAR data. Such an evolution to a more complex profile at higher energies is rarely seen in X-ray pulsars, most cases show the opposite behavior. Pulse phase-resolved spectral analysis shows a variation in the absorbing column density, N H , over pulse phase. Spectra taken during the pulse profile minima are intrinsically softer compared to the pulse phase-averaged spectrum.

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Section: Timing Analysissupporting

confidence: 68%

Suzakuobservations of the 2013 outburst of KS 1947+300

Ballhausen

Kühnel

Pottschmidt

et al. 2016

A&A

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“…Such type of effects e.g. phase-shifts (lags) or significant variations in pulse profiles close to the cyclotron absorption line energy are also seen in two other Be/X-ray binary pulsars such as V 0332+53 (Tsygankov et al 2006) and 4U 0115+63 (Ferrigno et al 2011). Using a numerical study on the effect of cyclotron resonant scattering in highly magnetized accretion powered X-ray pulsars, Schönherr et al (2014) showed that a strong change in the pulse profile is expected at the cyclotron absorption line energy.…”

Section: Pulse Profilesmentioning

confidence: 71%

Suzakuview of the Be/X-ray binary pulsar GX 304-1 during Type I X-ray outbursts

Jaisawal

Naik

Epili

2016

Mon. Not. R. Astron. Soc.

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We report the timing and spectral properties of Be/X-ray binary pulsar GX 304-1 by using two Suzaku observations during its 2010 August and 2012 January X-ray outbursts. Pulsations at ∼275 s were clearly detected in the light curves from both the observations. Pulse profiles were found to be strongly energy-dependent. During 2010 observation, prominent dips seen in soft X-ray ( 10 keV) pulse profiles were found to be absent at higher energies. However, during 2012 observation, the pulse profiles were complex due to the presence of several dips. Significant changes in the shape of the pulse profiles were detected at high energies (>35 keV). A phase shift of ∼0.3 was detected while comparing the phase of main dip in pulse profiles below and above ∼35 keV. Broad-band energy spectrum of pulsar was well described by a partially absorbed Negative and Positive power-law with Exponential cutoff (NPEX) model with 6.4 keV iron line and a cyclotron absorption feature. Energy of cyclotron absorption line was found to be ∼53 and 50 keV for 2010 and 2012 observations, respectively, indicating a marginal positive dependence on source luminosity. Based on the results obtained from phase-resolved spectroscopy, the absorption dips in the pulse profiles can be interpreted as due to the presence of additional matter at same phases. Observed positive correlation between cyclotron line energy and luminosity, and significant pulse-phase variation of cyclotron parameters are discussed in the perspective of theoretical models on cyclotron absorption line in X-ray pulsars.

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“…Moreover, this mechanism coupled with a reflecting disk, would produce a complex lag-spectrum, with a dimple (also defined by Kotov et al 2001, antilags, as they anticipate the softer band) at the energies of the fluorescent iron line very similarly to what observed in the GRO J1744-28. Finally, we also mention the possibility that the lag discontinuity might be caused by an abrupt change in the energydependent scattering cross-section at the cyclotron resonant energy (as suggested for the accreting pulsar 4U 0115+63 by Ferrigno et al 2011), though the results from spectral analysis in D' Aì et al (2015) indicated the presence of a moderately broad absorption feature at lower energy ∼ 4.7 keV.…”

Section: Discussionmentioning

confidence: 89%

“…Recently Miyasaka et al (2013) reported an energy dependent hard phase lag for the slowly spinning (Pspin = 12.29 s), X-ray pulsar GS 0834-430, and an energy-modulated phase-lag has been reported for 4U 0115+63 (Ferrigno et al 2011). The fractional delay for AMXPs is of the order of 5% and soft photons lag harder ones, whereas the hard phase lag in GS 0834-430 shows a monotonic rise with energy attaining a 30% of the pulse period above 50 keV.…”

Section: Discussionmentioning

confidence: 99%

Discovery of hard phase lags in the pulsed emission of GRO J1744−28

D’Aí¹,

Burderi

Salvo

et al. 2016

Monthly Notices of the Royal Astronomical Society: Letters

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We report on the discovery and energy dependence of hard phase lags in the 2.14 Hz pulsed profiles of GRO J1744-28. We used data from XMM-Newton and NuSTAR. We were able to well constrain the lag spectrum with respect to the softest (0.3-2.3 keV) band: the delay shows increasing lag values reaching a maximum delay of ∼ 12 ms, between 6 and 6.4 keV. After this maximum, the value of the hard lag drops to ∼ 7 ms, followed by a recovery to a plateau at ∼ 9 ms for energies above 8 keV. N uST AR data confirm this trend up to 30 keV, but the measurements are statistically poorer, and therefore, less constraining. The lag-energy pattern up to the discontinuity is well described by a logarithmic function. Assuming this is due to a Compton reverberation mechanism, we derive a size for the Compton cloud R cc ∼ 120 R g , consistent with previous estimates on the magnetospheric radius. In this scenario, the sharp discontinuity at ∼ 6.5 keV appears difficult to interpret and suggests the possible influence of the reflected component in this energy range. We therefore propose the possible coexistence of both Compton and disc reverberation to explain the scale of the lags and its energy dependence.

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4U 0115 + 63: phase lags and cyclotron resonant scattering

Cited by 57 publications

References 56 publications

Suzakuobservations of the 2013 outburst of KS 1947+300

Suzakuobservations of the 2013 outburst of KS 1947+300

Suzakuview of the Be/X-ray binary pulsar GX 304-1 during Type I X-ray outbursts

Discovery of hard phase lags in the pulsed emission of GRO J1744−28

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