On the Geometry of the X-ray emission from pulsars a consistent inclination and beaming solution for the Be/X-ray pulsar SXP 1062

Cappallo, R.; Laycock, S.; Christodoulou, Dimitris M.; Roy, Ankur; Bhattacharya, Sayantan; Coe, M. J.; Zezas, A.

doi:10.1093/mnras/staa1320

Cited by 3 publications

(2 citation statements)

References 37 publications

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“…The vertical dotted lines drawn in Figure 9 signify the estimated Coulomb luminosity (L X,Coul ∼ 8 × 10 36 erg s −1 ) and critical luminosity (L X,crit ∼ 5 × 10 37 erg s −1 ) of the pulsar. Indication of correlation between the separation of the peaks in the pulse profiles and the X-ray luminosity has been observed in another Be X-ray binary pulsar SXP 1062 by Cappallo et al (2020). We note this trend is opposite to what is noticed in XTE J1946 +274.…”

Section: Exploring Dependence Of Peak Separation On X-ray Luminositycontrasting

confidence: 39%

AstroSat Observations of the Be/X-Ray Binary XTE J1946+274 During 2018 and 2021 Outbursts

Chandra

Roy

Agrawal³

2023

Res. Astron. Astrophys.

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We present the timing and spectral studies of the Be/X-ray binary XTE J1946+274 during its 2018 and 2021 giant outbursts using observations with the SXT and the LAXPC instruments on the AstroSat satellite. Unlike the 1998 and 2010 outbursts, where a giant outburst was followed by several low intensity periodic outbursts, the 2018 and 2021 outbursts were single outbursts. The X-ray pulsations are detected over a broad energy band covering 0.5-80 keV from the compact object. We construct the spin evolution history of the pulsar over two decades and find that the pulsar spins-up during the outbursts but switches to spin-down state in the quiescent periods between the outbursts. Energy resolved pulse profiles generatedin several bands in 0.5-80 keV show that the pulse shape varies with the energy. The energy spectrum of the pulsar is determined for the 2018 and 2021 outbursts. The best fit spectral models require presence of Cyclotron Reson ant Scattering Feature (CRSF) at about 43 keV in the energy spectra of both the outbursts. We find indication of possible reversal in the correlation between the cyclotron line energy and luminosity which needs to be ascertained from future observations. Using the best fit spectra the X-ray luminosity of XTE J1946+274 is inferred to be 2.7 × 10^37 erg/s for the 2018 observations and 2.3 × 10^37 erg/s for the 2021 observations. We discuss possible mechanisms which can drive outbursts in this transient Be X-ray binary.

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Section: Exploring Dependence Of Peak Separation On X-ray Luminositycontrasting

confidence: 39%

AstroSat Observations of the Be/X-Ray Binary XTE J1946+274 During 2018 and 2021 Outbursts

Chandra

Roy

Agrawal³

2023

Res. Astron. Astrophys.

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“…Through modeling the features of pulse profiles, it attempts to constrain the inclination and magnetic dipole axis angle of a given XRP. Polestar has been previously applied to two other pulsars in the SMC, namely, SXP 348 (Cappallo et al 2019) and SXP 1062 (Cappallo et al 2020). Here we apply the same geometric model for the first time on profiles observed during a type II outburst.…”

Section: Motivation For the Following Analysismentioning

confidence: 99%

Modeling the Luminosity-dependent Pulse Profile and Emission Geometry of SMC X-2 during a Giant Outburst

Roy

Cappallo

Laycock

et al. 2022

ApJ

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One of the brightest X-ray pulsars in the Small Magellanic Cloud is SMC X-2. During its most recent major outburst in 2015, this transient pulsar displayed significant changes in both its accretion state and magnetosphere, particularly when it entered the low-luminosity regime of subcritical accretion. Polestar is a pulse-profile modeling code that helps in delineating the geometry of the emission as the source evolves past outburst and toward lower-luminosity states. Applying Polestar to XMM-Newton and NuSTAR pulse profiles, we constrained the most likely inclination of the spin axis of the pulsar to be i = 87° ± 4°. As the X-ray luminosity declined, an increase in the pulsed fraction was detected from Swift observations, which suggests a transition from fan- to pencil-beam emission during the later stages of the outburst. Additionally, we also performed analysis of the OGLE IV light curves, which showed strong modulation in the optical profiles during the outburst.

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The giant outburst of EXO 2030+375

Thalhammer,

Ballhausen,

Sokolova-Lapa

et al. 2024

A&A

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The Be X-ray binary EXO 2030+375 went through its third recorded giant outburst from June 2021 to early 2022. We present the results of both spectral and timing analysis based on NICER monitoring, covering the 2−10 keV flux range from 20 to 310 mCrab. Dense monitoring with observations carried out about every second day and a total exposure time of ∼160 ks allowed us to closely track the source evolution over the outburst. Changes in the spectral shape and pulse profiles showed a stable luminosity dependence during the rise and decline. The same type of dependence has been seen in past outbursts. The pulse profile is characterized by several distinct peaks and dips. The profiles show a clear dependence on luminosity with a stark transition at a luminosity of ∼2 × 1036 erg s−1, indicating a change in the emission pattern. Using relativistic raytracing, we demonstrate how anisotropic beaming of emission from an accretion channel with a constant geometrical configuration can give rise to the observed pulse profiles over a range of luminosities.

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On the Geometry of the X-ray emission from pulsars a consistent inclination and beaming solution for the Be/X-ray pulsar SXP 1062

Cited by 3 publications

References 37 publications

AstroSat Observations of the Be/X-Ray Binary XTE J1946+274 During 2018 and 2021 Outbursts

AstroSat Observations of the Be/X-Ray Binary XTE J1946+274 During 2018 and 2021 Outbursts

Modeling the Luminosity-dependent Pulse Profile and Emission Geometry of SMC X-2 during a Giant Outburst

The giant outburst of EXO 2030+375

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