Universal detection of high-temperature emission in X-ray isolated neutron stars

Yoneyama, T.; Hayashida, Kentaro; Nakajima, Hiroshi; Matsumoto, Hironori

doi:10.1093/pasj/psy135

Cited by 17 publications

(13 citation statements)

References 43 publications

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“…As it is illustrated in Fig. 8, not only the line properties, but also the best fit parameters of the continuum model are very similar to those recently reported in a systematic analysis of all the XDINS spectra with the G2BB model (Yoneyama et al 2019). face (the inclusion of the hot component would not significantly change the result, adding only about 3% to the total luminosity, well within the uncertainties).…”

Section: Connections With the Xdinsssupporting

confidence: 86%

“…A real improvement in the fit was obtained by adding to the blackbody a broad absorption line modelled with a Gaussian (GBB) centered at E = 1.09 ± 0.09 keV and width σ = 0.28 ± 0.08 keV (χ 2 ν = 1.12 for 210 dof). Following the recent results of Yoneyama et al (2019), we explored the possibility to adopt a two blackbody component model plus a Gaussian line in absorption (G2BB). With this model we found a good fit with the line placed at E = 0.39 +0.02 −0.03 keV and with a broadening of σ = 0.08 +0.03 −0.02 keV (χ 2 ν = 1.00 for 208 dof).…”

Section: Spectral Analysismentioning

confidence: 99%

“…Comparison between PSR J0726−2612 and the XDINSs B p and B cyc are the magnetic field at the poles evaluated from the timing parameter and from the cyclotron energy, respectively. E cyc values are taken fromYoneyama et al (2019), while L X values fromViganò et al (2013).…”

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confidence: 99%

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XMM-Newton observations of PSR J0726−2612, a radio-loud XDINS

Rigoselli

Mereghetti

Suleimanov

et al. 2019

A&A

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We present the results of an XMM-Newton observation of the slowly rotating (P = 3.4 s), highly magnetized (B ≈ 3×10 13 G) radio pulsar PSR J0726−2612. A previous X-ray observation with the Chandra satellite showed that some of the properties of PSR J0726−2612 are similar to those of the X-ray Dim Isolated Neutron Stars (XDINSs), a small class of nearby slow pulsars characterized by purely thermal X-ray spectra and undetected in the radio band. We confirm the thermal nature of the X-ray emission of PSR J0726−2612, which can be fit by the sum of two blackbodies with temperatures kT 1 = 0.074 +0.006 −0.011 keV and kT 2 = 0.14 +0.04 −0.02 keV and emitting radii R 1 = 10.4 +10.8 −2.8 km and R 2 = 0.5 +0.9 −0.3 km, respectively (assuming a distance of 1 kpc). A broad absorption line modeled with a Gaussian profile centred at 0.39 +0.02 −0.03 keV is required in the fit. The pulse profile of PSR J0726−2612 is characterized by two peaks with similar intensity separated by two unequal minima, a shape and pulsed fraction that cannot be reproduced without invoking magnetic beaming of the X-ray emission. The presence of a single radio pulse suggests that in PSR J0726−2612 the angles that the dipole axis and the line of sight make with the rotation axis, ξ and χ respectively, are similar. This geometry differs from that of the two radio-silent XDINSs with a double peaked pulse profile similar to that of PSR J0726−2612, for which ξ ∼ 90 • and χ ∼ 45 • have been recently estimated. These results strengthen the similarity between PSR J0726−2612 and the XDINSs and support the possibility that the lack of radio emission from the latter might simply be due to an unfavourable viewing geometry.

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Section: Connections With the Xdinsssupporting

confidence: 86%

Section: Spectral Analysismentioning

confidence: 99%

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XMM-Newton observations of PSR J0726−2612, a radio-loud XDINS

Rigoselli

Mereghetti

Suleimanov

et al. 2019

A&A

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“…In addition, these NSs exhibit X-ray pulsations [183], which indicate that the temperature distribution on their surface is inhomogeneous. It is indeed found that a spectrum analysis based on a two-temperature blackbody model gives a larger radius and a lower surface temperature for these XDINSs [198], with which the discrepancy between the prediction and observation is signi cantly reduced. Another potential explanation for the discrepancy is that the XDINSs have undergone the magnetic eld decay, which makes the spin-down age di er from the actual age.…”

Section: Ordinary Pulsars and Xdinssmentioning

confidence: 81%

Thermal Evolution of Neutron Stars as a Probe of Physics beyond the Standard Model

Yanagi

2020

Preprint

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The physics beyond the standard model (BSM) has not appeared in extensive experimental and observational searches. Although the problems in the standard model strongly suggest the existence of a more fundamental theory, its detail is still unclear. In such a situation, it becomes more and more important to further extend the area of new physics search beyond the conventional ones. In this dissertation, we study the thermal evolution of neutron stars (NSs) as a probe of new physics.The NS cooling is well studied and the current standard theory is successful in explaining many of the observed surface temperatures of NSs. If a new particle is light enough to be created in NSs, and has small interactions with ordinary matter, its emission can be an extra cooling source. If this enhancement of cooling spoils the success of the standard cooling, the model should be excluded. An important candidate of such a new particle is axion, which dynamically solves the strong CP problem of the standard model. The axion-nucleon coupling induces the axion emission from the NS core, and it a ects the cooling of young NSs. The stringent constraint is obtained by comparing the predicted cooling curve to the observed surface temperature of the NS in the supernova remnant of Cassiopeia A (Cas A). We constrain the axion models by taking account of the temperature evolution in the whole life of the Cas A NS. The resultant limit on the axion decay constant is ≳ 10 8 GeV, which is comparable to the existing limit from SN1987A.The NS heating provides yet another example of probing new physics in NSs. In particular, it is known that the dark matter (DM) accretion leads to the heating of old NSs. It occurs through the DM accumulation in NSs by the scattering with nucleons, and their subsequent annihilation inside the star. The surface temperatures of old NSs ( ≳ 10 7 yr) are predicted to be = (2 − 3) × 10 3 K, which is stark contrast to the standard cooling theory. Thus the measurement of the surface temperatures of old NSs can provide a hint/constraint for DM models. This conclusion is, however, drawn with the assumption that there is no other heating source. In fact, it is known that the non-equilibrium beta process induces the late-time heating through the imbalance of chemical potentials among nucleons and leptons: this is called rotochemical heating and is inevitable for pulsars. The rotochemical heating typically predicts ∼ 10 5−6 K for old NSs, and hence can be much stronger than the DM heating. This possibility has been overlooked in the studies of DM heating. In this dissertation, we address the condition in which DM heating dominates the rotochemical heating. For that purpose, we rst perform detailed analysis of the rotochemical heating; extending the previous studies, we perform numerical calculation with both the proton and neutron pairing gaps, and compare the predictions to the observations. Then we include the DM heating, and investigate whether the DM heating is visible or not, varying the NS parameters. We nd that the DM heati...

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“…In this paper, we do not describe the data reduction and details of analysis because of limited pages. See Yoneyama et al (; hereafter Y18) for details.…”

Section: Introductionmentioning

confidence: 99%

Unification of strongly magnetized neutron stars with regard to X‐ray emission from hot spots

et al. 2019

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Strongly magnetized isolated neutron stars (NSs) are categorized into two families according, mainly, to their magnetic field strength. The one with a higher magnetic field of 10 14 -10 15 Gauss is called "magnetar," and the other is the X-ray isolated neutron star (XINS) with 10 13 Gauss. Both magnetars and XINSs show thermal emission in X-rays, whose spectra are different. The soft X-ray spectrum (below 10 keV) of a magnetar is reproduced with a two-temperature blackbody (2BB), whereas that of an XINS shows only a single-temperature blackbody (1BB), and its temperature is even lower than that of magnetars. On the basis of the magnetic field and temperature, it is often speculated that XINSs may be old and cooled magnetars. However, no other strong observational evidence has yet been reported to support the speculation. Here, we report that all the seven known XINSs show high-temperature emission, which should have a similar origin to that of magnetars. Analyzing all the XMM-Newton data of the XINSs with the highest statistics ever achieved, we find that their X-ray spectra are all reproduced with a 2BB model, similar to magnetars, as opposed to the traditional 1BB model. Their emission radii and temperature ratios are also similar to those of magnetars except for two XINSs, which show significantly smaller radii than the others. The remarkable similarity in the X-ray spectra between XINSs and magnetars suggests that the origins of their emitting regions are also the same. The lower temperature in XINSs can be explained if XINSs are older than magnetars. Therefore, this result is another observational indication that supports the standard hypothesis of classification of highly magnetized NSs. This article is based on our paper Yoneyama et al. (2019; accepted to PASJ).

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Universal detection of high-temperature emission in X-ray isolated neutron stars

Cited by 17 publications

References 43 publications

XMM-Newton observations of PSR J0726−2612, a radio-loud XDINS

XMM-Newton observations of PSR J0726−2612, a radio-loud XDINS

Thermal Evolution of Neutron Stars as a Probe of Physics beyond the Standard Model

Unification of strongly magnetized neutron stars with regard to X‐ray emission from hot spots

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