X-Ray Study of Variable Gamma-Ray Pulsar PSR J2021+4026

Wang, Hui Hui; Takata, Jumpei; Hu, Chin-Ping; Lin, L.; Zhao, Jian

doi:10.3847/1538-4357/aab202

Cited by 7 publications

(10 citation statements)

References 45 publications

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“…This result, not found in previous works, implies that the mode change also affects the Xray emission, suggesting a modification in the magnetospheric regions connecting the dipole field with the inner components close to stellar surface. We have also reproduced the results of the previous X-ray timing analyses of the two XMM-Newton data sets by Lin et al (2013) and by Wang et al (2018), respectively. Given the implications of this result, we discuss all the validations that we performed to rule out possible systematic errors in our analysis.…”

Section: Introductionsupporting

confidence: 87%

“…Following this recovery, we triggered a target of opportunity (ToO) observation with XMM-Newton (PI: Razzano, Obs ID: 118 0763850101). Based on these data, Wang et al (2018) found no significant change in either the pulsar X-ray emission or in the relative phase shift between the γ-ray and X-ray pulse profiles taken around April 2012 (MJD 56027 (i.e. after the flux drop) and November 2015 (MJD 57376 (i.e.…”

Section: Introductionmentioning

confidence: 87%

“…In this analysis, we considered X-ray photons collected during two XMM-Newton observations. The first observation (Obs ID: 067059010, PI: Hui) was conducted with a 133 ks exposure on 2012 April 11 (MJD 56028), about 6 months after the first mode change, when the flux above 100 MeV, F 100 , was (1.10 ± 0.05) ×10 −6 ph cm −2 s −1 and the frequency spin-down, f 1 , was (-8.3 ± 0.2)×10 −13 Hz s −1 (Wang et al 2018). The MOS1/2 instruments were operated in full-window mode, while the pn was in small-window mode to enable a pulsation search.…”

Section: X-raysmentioning

confidence: 99%

“…The MOS1/2 instruments were operated in full-window mode, while the pn was in small-window mode to enable a pulsation search. The second observation (Obs ID: 0763850101, PI: Razzano) was taken with a similar exposure on 2015 December 20 (MJD 57376), about 3.7 years after the first observation, when the flux and spin-down of the pulsar had recovered to the initial state (F 100 = (1.30 ± 0.05) ×10 −6 ph cm −2 s −1 , f 1 = (-7.9 ± 0.2)×10 −13 Hz s −1 ) (Wang et al 2018), and the cameras were operated in the same modes. Following the prescription of the 3XMM catalogue, for the pn camera we selected events with pattern 0 for energies from 0.2 to 0.5 keV, and 0-4 for energies between 0.5 and 10 keV (Marelli et al 2016).…”

Section: X-raysmentioning

confidence: 99%

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Multiwavelength observations of PSR J2021+4026 across a mode change reveal a phase shift in its X-ray emission

Razzano¹,

Fiori²,

Parkinson³

et al. 2023

A&A

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Context. We have investigated the multiwavelength emission of PSR J2021+4026, the only isolated γ-ray pulsar known to be variable, which in October 2011 underwent a simultaneous change in γ-ray flux and spin-down rate, followed by a second mode change in February 2018. Multiwavelength monitoring is crucial to understand the physics behind these events and how they may have affected the structure of the magnetosphere. Aims. The monitoring of pulse profile alignment is a powerful diagnostic tool for constraining magnetospheric reconfiguration. We aim to investigate timing or flux changes related to the variability of PSR J2021+4026 via multiwavelength observations, including γ-ray observations from Fermi-LAT, X-ray observations from XMM-Newton, and a deep optical observation with the Gran Telescopio Canarias. Methods. We performed a detailed comparison of the timing features of the pulsar in γ and X-rays and searched for any change in phase lag between the phaseogram peaks in these two energy bands. Although previous observations did not detect a counterpart in visible light, we also searched for optical emission that might have increased due to the mode change, making this pulsar detectable in the optical. Results. We have found a change in the γ-to X-ray pulse profile alignment by 0.21 ± 0.02 in phase, which indicates that the first mode change affected different regions of the pulsar magnetosphere. No optical counterpart was detected down to g′ = 26.1 and r′ = 25.3. Conclusions. We suggest that the observed phase shift could be related to a reconfiguration of the connection between the quadrupole magnetic field near the stellar surface and the dipole field that dominates at larger distances. This is consistent with the picture of X-ray emission coming from the heated polar cap and with the simultaneous flux and frequency derivative change observed during the mode changes.

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Section: Introductionsupporting

confidence: 87%

Section: Introductionmentioning

confidence: 87%

Section: X-raysmentioning

confidence: 99%

Section: X-raysmentioning

confidence: 99%

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Multiwavelength observations of PSR J2021+4026 across a mode change reveal a phase shift in its X-ray emission

Razzano¹,

Fiori²,

Parkinson³

et al. 2023

A&A

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“…It is expected that if the abrupt state change of PSR J2021+4026 is caused by the twisting of the magnetosphere, the emission from the heated footprint contributes to the observed X-ray emission in a HSD state. In the previous studies of the X-ray emission from PSR J2021+4026 (Lin et al 2013;Wang et al 2018), there is no apparent difference between the X-ray emission properties in the HSD and LSD states. It is therefore that the twisted magnetosphere will not be the reason of the state change of PSR J2021+4026.…”

Section: Discussionmentioning

confidence: 81%

Repeated state change of variable gamma-ray pulsar, PSR J2021+4026

Takata,

Wang,

Lin

et al. 2020

Preprint

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PSR J2021+4026 is a radio-quiet gamma-ray pulsar and the first pulsar that shows state change of the gamma-ray emission and spin-down rate. The state change of PSR J2021+4026 was first observed at 2011 October, at which the pulsar changes the state from high gamma-ray flux/low spin-down rate state to low gamma-ray flux/high spin-down rate state. In December 2014, PSR J2021+4026 recovered the state before the 2011 state change over a timescale of a few months. We report that the long term evolution of the gamma-ray flux and timing behavior suggests that PSR J2021+4026 changed the state near 2018 February 1st and entered a new low gamma-ray flux/high spin-down rate state. At the 2018 state change, the averaged flux dropped from (1.29 ± 0.01) × 10 −6 cts cm −2 s −1 to (1.12 ± 0.01) × 10 −6 cts cm −2 s −1 , which is behavior similar to the case of the 2011 event. The spin-down rate has increased by ∼ 3% in the new state since the 2018 state change. The shapes of pulse profile and spectrum in GeV bands also changed at the 2018 event, and they are consistent with behavior at the 2011 state change. Our results probably suggest that PSR J2021+4026 is switching between different states with a timescale of several years, like some radio pulsars

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Strongly pulsed thermal X-rays from a single extended hot spot on PSR J2021+4026

Rigoselli

Mereghetti

Taverna

et al. 2021

A&A

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The radio-quiet pulsar PSR J2021+4026 is mostly known because it is the only rotation-powered pulsar that shows variability in its γ-ray emission. Using XMM-Newton archival data, we first confirmed that its flux is steady in the X-ray band, and then we showed that both the spectral and timing X-ray properties, that is to say the narrow pulse profile, the high pulsed fraction of 80–90%, and its dependence on the energy, can be better reproduced using a magnetized atmosphere model instead of simply a blackbody model. With a maximum likelihood analysis in the energy-phase space, we inferred that the pulsar has, in correspondence of one magnetic pole, a hot spot with a temperature of T ∼ 1 MK and colatitude extension of θ ∼ 20°. For the pulsar distance of 1.5 kpc, this corresponds to a cap of R ∼ 5 − 6 km, which is greater than the standard dimension of the dipolar polar caps. The large pulsed fraction further argues against emission from the entire star surface, as it would be expected in the case of secular cooling. An unpulsed (≲40% pulsed fraction), nonthermal component, probably originating in a wind nebula, is also detected. The pulsar geometry derived with our spectral fits in the X-ray is relatively well constrained (χ = 90° and ξ = 20°–25°) and consistent with what is deduced from γ-ray observations, provided that only one of the two hemispheres is active. The evidence for an extended hot spot in PSR J2021+4026, which was also found in other pulsars of a similar age but not in older objects, suggests a possible age dependence of the emitting size of thermal X-rays.

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X-Ray Study of Variable Gamma-Ray Pulsar PSR J2021+4026

Cited by 7 publications

References 45 publications

Multiwavelength observations of PSR J2021+4026 across a mode change reveal a phase shift in its X-ray emission

Multiwavelength observations of PSR J2021+4026 across a mode change reveal a phase shift in its X-ray emission

Repeated state change of variable gamma-ray pulsar, PSR J2021+4026

Strongly pulsed thermal X-rays from a single extended hot spot on PSR J2021+4026

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