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We combine pulsar population synthesis with simulation-based inference (SBI) to constrain the magnetorotational properties of isolated Galactic radio pulsars. We first develop a framework to model neutron star birth properties and their dynamical and magnetorotational evolution. We specifically sample initial magnetic field strengths, B, and spin periods, P, from lognormal distributions and capture the late-time magnetic field decay with a power law. Each lognormal is described by a mean, μlogB,μlogP , and standard deviation, σlogB,σlogP , while the power law is characterized by the index, a late. We subsequently model the stars’ radio emission and observational biases to mimic detections with three radio surveys, and we produce a large database of synthetic P– Ṗ diagrams by varying our five magnetorotational input parameters. We then follow an SBI approach that focuses on neural posterior estimation and train deep neural networks to infer the parameters’ posterior distributions. After successfully validating these individual neural density estimators on simulated data, we use an ensemble of networks to infer the posterior distributions for the observed pulsar population. We obtain μlogB=13.10−0.10+0.08 , σlogB=0.45−0.05+0.05 and μlogP=−1.00−0.21+0.26 , σlogP=0.38−0.18+0.33 for the lognormal distributions and alate=−1.80−0.61+0.65 for the power law at the 95% credible interval. We contrast our results with previous studies and highlight uncertainties of the inferred a late value. Our approach represents a crucial step toward robust statistical inference for complex population synthesis frameworks and forms the basis for future multiwavelength analyses of Galactic pulsars.

The X-ray spectrum of the soft-γ-ray repeater SGR 0418+5729 is found to exhibit an absorption line, the properties of which depend strongly on the star’s rotational phase; this line is interpreted as a proton cyclotron feature and its energy implies a magnetic field ranging from 2 × 10 14 gauss to more than 10 15 gauss. Spectral analysis of a rotating magnetar The Milky Way object SGR 0418+5729, first observed in June 2009 as a soft-γ-ray repeater, is thought to be a magnetar, a type of neutron star with a powerful magnetic field. This paper reports the analysis of the X-ray spectrum of this exotic object. The spectrum has an absorption line that varies dramatically in magnitude according to the star's rotational phase. The authors interpret this line as a cyclotron absorption feature generated near the surface, and its energy implies a magnetic field in the region of 10 15 gauss. Soft-γ-ray repeaters (SGRs) and anomalous X-ray pulsars (AXPs) are slowly rotating, isolated neutron stars that sporadically undergo episodes of long-term flux enhancement (outbursts) generally accompanied by the emission of short bursts of hard X-rays 1 , 2 . This behaviour can be understood in the magnetar model 3 , 4 , 5 , according to which these sources are mainly powered by their own magnetic energy. This is supported by the fact that the magnetic fields inferred from several observed properties 6 , 7 , 8 of SGRs and AXPs are greater than—or at the high end of the range of—those of radio pulsars. In the peculiar case of SGR 0418+5729, a weak dipole magnetic moment is derived from its timing parameters 9 , whereas a strong field has been proposed to reside in the stellar interior 10 , 11 and in multipole components on the surface 12 . Here we show that the X-ray spectrum of SGR 0418+5729 has an absorption line, the properties of which depend strongly on the star’s rotational phase. This line is interpreted as a proton cyclotron feature and its energy implies a magnetic field ranging from 2 × 10 14  gauss to more than 10 15  gauss.

The Imaging X-ray Polarimetry Explorer (IXPE) observed for the first time highly polarized X-ray emission from the magnetar 1E 1841−045, targeted after a burst-active phase in 2024 August. To date, IXPE has observed four other magnetars during quiescent periods, highlighting substantially different polarization properties. 1E 1841−045 exhibits a high, energy-dependent polarization degree, which increases monotonically from ≈15% at 2–3 keV up to ≈55% at 5.5–8 keV, while the polarization angle, aligned with the celestial north, remains fairly constant. The broadband spectrum (2–79 keV) obtained by combining simultaneous IXPE and NuSTAR data is well modeled by a blackbody and two power-law components. The unabsorbed 2–8 keV flux (≈2 × 10−11 erg cm−2 s−1) is about 10% higher than that obtained from archival XMM-Newton and NuSTAR observations. The polarization of the soft, thermal component does not exceed ≈25%, and may be produced by a condensed surface or a bombarded atmosphere. The intermediate power law is polarized at around 30%, consistent with predictions for resonant Compton scattering in the star magnetosphere; meanwhile, the hard power law exhibits a polarization degree exceeding 65%, pointing to a synchrotron/curvature origin.

IAU Symposium 337 was held at Jodrell Bank Observatory in September 2017 to celebrate the past fifty years of pulsar astrophysics and to look forward to the next fifty.

The magnetar 1E 1841–045 exhibited a new active episode starting on 2024 August 20, marked by X-ray bursts and enhanced persistent emission. Using data from the Einstein Probe (EP), we report on the timing and spectral results following the onset of this outburst. The pulse profile displays a multipeaked structure, with notable phase shifts in the secondary peak. Energy-resolved pulse profile analysis indicates a transition in the dominant peak of the pulse profile above 5.8 keV. The 0.5–10 keV X-ray spectrum is well modeled by a combined blackbody and power-law (BB+PL) model, showing a ∼20% flux increase following the outburst. Phase-resolved spectroscopy indicates a correlation between BB temperature and pulse profile intensity, along with spectral hardening at a specific pulse phase. The high spatial resolution of EP enables effective separation of the supernova remnant emission, which is crucial for measuring the intrinsic pulse emission of the source. These findings underscore the intricate relationship between magnetar outbursts, pulse profile evolution, and spectral characteristics.

Transitional millisecond pulsars (tMSPs) bridge the evolutionary gap between accreting neutron stars in low-mass X-ray binaries and millisecond radio pulsars. These systems exhibit a unique subluminous X-ray state characterized by the presence of an accretion disk and rapid switches between high and low X-ray emission modes. The high mode features coherent millisecond pulsations spanning from the X-ray to the optical band. We present multiwavelength polarimetric observations of the tMSP PSR J1023+0038 aimed at conclusively identifying the physical mechanism powering its emission in the subluminous X-ray state. During the high mode, we report a probable detection of polarized emission in the 2–6 keV energy range, with a polarization degree of (12 ± 3)% and a polarization angle of −2∘ ± 9∘measured counterclockwise from the north celestial pole toward the east (99.7% confidence level, c.l.; uncertainties are quoted at 1σ). At optical wavelengths, we find a polarization degree of (1.41 ± 0.04)% and a polarization angle aligned with that in the X-rays, suggesting a common physical mechanism operating across these bands. Remarkably, the polarized flux spectrum matches the pulsed emission spectrum from optical to X-rays. The polarization properties differ markedly from those observed in other accreting neutron stars and isolated rotation-powered pulsars and are also inconsistent with an origin in a compact jet. Our results provide direct evidence that the polarized and pulsed emissions both originate from synchrotron radiation at the boundary region formed where the pulsar wind interacts with the inner regions of the accretion disk.

We report the discovery of PSR J1646−4545, a 431 ms isolated pulsar, in the direction of the young massive cluster Westerlund 1. The pulsar was found in data taken between the years 2005 and 2010 with the “Murriyang” Parkes radio telescope in Australia. Thanks to the numerous detections of the pulsar, we were able to derive a phase-connected timing solution spanning the whole data set. This allowed us to precisely locate the pulsar at the border of the cluster and to measure its spin-down rate. The latter implies a characteristic age of ∼25 Myr, about twice as large as the estimated age of Westerlund 1. The age of PSR J1646−4545, together with its dispersion measure of ∼1029 pc cm−3, more than twice the value predicted by the two main galactic electron density models for Westerlund 1, makes the association of the pulsar with the cluster highly unlikely. We also report on ramifications from the presence of a magnetar in Westerlund 1 and the apparent lack of ordinary radio pulsars.

These two types of compact objects share several similarities, despite their different compositions. A short workshop in Spain brought communities together to share understanding of dense matter under extreme conditions.

Large X-ray observatories such as Chandra and XMM-Newton have been delivering scientific breakthroughs in research fields as diverse as our Solar System, the astrophysics of stars, stellar explosions and compact objects, accreting supermassive black holes, and large-scale structures traced by the hot plasma permeating and surrounding galaxy groups and clusters. The recently launched X-Ray Imaging and Spectroscopy Mission observatory is opening in earnest the new observational window of non-dispersive high-resolution spectroscopy. However, several questions remain open, such as the effect of the stellar radiation field on the habitability of nearby planets, the equation of state regulating matter in neutron stars, the origin and distribution of metals in the Universe, the processes driving the cosmological evolution of the baryons locked in the gravitational potential of dark matter and the impact of supermassive black hole growth on galaxy evolution, to mention just a few. Furthermore, X-ray astronomy has a key part to play in multimessenger astrophysics. Addressing these questions experimentally requires an order-of-magnitude leap in sensitivity, spectroscopy and survey capabilities with respect to existing X-ray observatories. This article succinctly summarizes the main areas where high-energy astrophysics is expected to contribute to our understanding of the Universe in the next decade and describes a new mission concept under study by the European Space Agency, the scientific community worldwide and two international partners (JAXA and NASA), designed to enable transformational discoveries: NewAthena. This concept inherits its basic payload design from a previous study carried out until 2022, Athena. This Perspective looks forwards to the next decade of X-ray astronomy, explaining how it will contribute to better understanding of the high-energy Universe. In this context, the authors describe the NewAthena mission, a concept led by the European Space Agency.

The lack of isolated X-ray pulsars with spin periods longer than 12 s raises the question of where the population of evolved high-magnetic-field neutron stars has gone. Unlike canonical radiopulsars, X-ray pulsars are not subject to physical limits to the emission mechanism nor observational biases against the detection of sources with longer periods. Here we show that a highly resistive layer in the innermost part of the crust of neutron stars naturally limits the spin period to a maximum value of about 10–20 s. This highly resistive layer is expected if the inner crust is amorphous and heterogeneous in nuclear charge, possibly owing to the existence of a nuclear ‘pasta’ phase. Our findings suggest that the maximum period of isolated X-ray pulsars may be the first observational evidence for an amorphous inner crust, whose properties can be further constrained by future X-ray timing missions combined with more detailed models. A pulsar is a rotating neutron star that beams out electromagnetic waves. The absence of isolated X-ray pulsars with periods longer than 12 s could be a clue to the structural composition of a neutron star’s crust, as simulations show that an amorphous layer would prevent a pulsar from spinning down.