Glancing through the accretion column of EXO 2030+375

Ferrigno, C.; Pjanka, Patryk; Bozzo, E.; Klochkov, D.; Ducci, L.; Zdziarski, A. A.

doi:10.1051/0004-6361/201527837

Cited by 15 publications

(25 citation statements)

References 39 publications

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“…This was explained as due to the presence of additional dense matter (partial absorber) at certain phases of the pulsar. A peculiar narrow absorption dip was also detected in soft X-ray pulse profile obtained from XMM-Newton observation in May 2014 at a luminosity of ∼10 36 erg s −1 (Ferrigno et al 2016). This feature was interpreted as the effect of self absorption from accretion mount onto the neutron star surface.…”

Section: Introductionmentioning

confidence: 65%

“…Phase resolved spectroscopy confirmed the presence of additional dense matter at same phases of the profile. In addition to absorption dips, sometimes a narrow and sharp dip-like feature was detected in the pulse profiles at low luminosity (Ferrigno et al 2016). This feature was interpreted as due to self absorption from the accretion column.…”

Section: Pulse Profilesmentioning

confidence: 99%

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Decade long RXTE monitoring observations of Be/X-ray binary pulsar EXO 2030+375

Epili

Naik

Jaisawal

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We present a comprehensive timing and spectral studies of Be/X-ray binary pulsar EXO 2030+375 using extensive Rossi X-ray Timing Explorer observations from 1995 till 2011, covering numerous Type I and 2006 Type II outbursts. Pulse profiles of the pulsar were found to be strongly luminosity dependent. At low luminosity, the pulse profile consisted of a main peak and a minor peak that evolved into a broad structure at high luminosity with a significant phase shift. A narrow and sharp absorption dip, also dependent on energy and luminosity, was detected in the pulse profile. Comparison of pulse profiles showed that the features at a particular luminosity are independent of type of X-ray outbursts. This indicates that the emission geometry is solely a function of mass accretion rate. The broadband energy spectrum was described with a partial covering high energy cutoff model as well as a physical model based on thermal and bulk Comptonization in accretion column. We did not find any signature of cyclotron resonance scattering feature in the spectra obtained from all the observations. A detailed analysis of spectral parameters showed that, depending on source luminosity, the power-law photon index was distributed in three distinct regions. It suggests the phases of spectral transition from sub-critical to super-critical regimes in the pulsar as proposed theoretically. A region with constant photon index was also observed in ∼(2-4)×10 37 erg s −1 range, indicating critical luminosity regime in EXO 2030+375.

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Section: Introductionmentioning

confidence: 65%

Section: Pulse Profilesmentioning

confidence: 99%

Decade long RXTE monitoring observations of Be/X-ray binary pulsar EXO 2030+375

Epili

Naik

Jaisawal

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…However, also sharp features are sometimes observed, where the spectrum is changing dramatically over only a few percent of the rotational period of the NS. The most extreme example is probably EXO 2030+375, where the photon-index changes by ∆Γ > 1.2 and the absorption column also varies by over an order of magnitude (Ferrigno et al 2016b;Fürst et al 2017). This effect is interpreted as an accretion curtain moving through our line of sight, indicating a unique accretion geometry in EXO 2030+375.…”

Section: Cyclotron Line Parameters As Function Of Pulse Phasementioning

confidence: 99%

Cyclotron lines in highly magnetized neutron stars

Staubert

Trümper

Kendziorra

et al. 2019

A&A

234

221

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Cyclotron lines, also called cyclotron resonant scattering features (CRSF) are spectral features, generally appearing in absorption, in the X-ray spectra of objects containing highly magnetized neutron stars, allowing the direct measurement of the magnetic field strength in these objects. Cyclotron features are thought to be due to resonant scattering of photons by electrons in the strong magnetic fields. The main content of this contribution focusses on electron cyclotron lines as found in accreting X-ray binary pulsars (XRBP) with magnetic fields on the order of several 10 12 Gauss. Also, possible proton cyclotron lines from single neutron stars with even stronger magnetic fields are briefly discussed. With regard to electron cyclotron lines, we present an updated list of XRBPs that show evidence of such absorption lines. The first such line was discovered in a 1976 balloon observation of the accreting binary pulsar Hercules X-1, it is considered to be the first direct measurement of the magnetic field of a neutron star. As of today (mid 2018), we list 36 XRBPs showing evidence of one ore more electron cyclotron absorption line(s). A few have been measured only once and must be confirmed (several more objects are listed as candidates). In addition to the Tables of objects, we summarize the evidence of variability of the cyclotron line as a function of various parameters (especially pulse phase, luminosity and time), and add a discussion of the different observed phenomena and associated attempts of theoretical modeling. We also discuss our understanding of the underlying physics of accretion onto highly magnetized neutron stars. For proton cyclotron lines, we present tables with seven neutron stars and discuss their nature and the physics in these objects.

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“…Furthermore we searched for a neutral Fe Kα line, modeled by a narrow Gaussian at 6.4 keV, that has often been observed in this source (e.g., Reig & Coe 1999;Naik et al 2013;Ferrigno et al 2016). We do not find clear evidence of the presence of this line, with a 90% upper limit on the equivalent width around 25-30 eV, independent of the choice of the continuum model (Table 1).…”

Section: Phase-averaged Spectramentioning

confidence: 99%

“…They interpret this feature as part of the accretion column passing through our line of sight towards the main X-ray producing region, resulting in a higher absorption column and in a more reprocessed spectrum. Ferrigno et al (2016) argue that the accretion column grows in size with increasing Xray luminosity and therefore the duration of the feature should also increase. However, due to the limited phase-space resolution possible with Suzaku, they could not confirm this theory using a brighter Suzaku observation.…”

Section: Introductionmentioning

confidence: 99%

Studying the accretion geometry of EXO 2030+375 at luminosities close to the propeller regime

Fürst¹,

Kretschmar²,

Kajava³

et al. 2017

A&A

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The Be X-ray binary EXO 2030+375 was in an extended low-luminosity state during most of 2016. We observed this state with NuSTAR and Swift, supported by INTEGRAL observations and optical spectroscopy with the Nordic Optical Telescope (NOT). We present a comprehensive spectral and timing analysis of these data here to study the accretion geometry and investigate a possible onset of the propeller effect. The Hα data show that the circumstellar disk of the Be-star is still present. We measure equivalent widths similar to values found during more active phases in the past, indicating that the low-luminosity state is not simply triggered by a smaller Be disk. The NuSTAR data, taken at a 3-78 keV luminosity of ∼6.8 × 10 35 erg s −1 (for a distance of 7.1 kpc), are nicely described by standard accreting pulsar models such as an absorbed power law with a high-energy cutoff. We find that pulsations are still clearly visible at these luminosities, indicating that accretion is continuing despite the very low mass transfer rate. In phaseresolved spectroscopy we find a peculiar variation of the photon index from ∼1.5 to ∼2.5 over only about 3% of the rotational period. This variation is similar to that observed with XMM-Newton at much higher luminosities. It may be connected to the accretion column passing through our line of sight. With Swift/XRT we observe luminosities as low as 10 34 erg s −1 where the data quality did not allow us to search for pulsations, but the spectrum is much softer and well described by either a blackbody or soft power-law continuum. This softer spectrum might be due to the accretion being stopped by the propeller effect and we only observe the neutron star surface cooling.

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Glancing through the accretion column of EXO 2030+375

Cited by 15 publications

References 39 publications

Decade long RXTE monitoring observations of Be/X-ray binary pulsar EXO 2030+375

Decade long RXTE monitoring observations of Be/X-ray binary pulsar EXO 2030+375

Cyclotron lines in highly magnetized neutron stars

Studying the accretion geometry of EXO 2030+375 at luminosities close to the propeller regime

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