Online error compensation of magnetometer while drilling based on magnetic inertial planet optimization

Abstract The magnetic field configuration in the interior of neutron stars and its stability are open problems and may be impacted by the influence of a turbulent cascade within the star. Assessing the impact of turbulent flow with numerical simulations requires incredibly high resolution as well as long lived simulations covering multiple Alfven times. We present a series of simulations of magnetised neutron stars with resolution up to 29m and lasting at their longest 1.2s to assess this issue, the longest lasting and highest resolution such simulations to date. At the highest resolution we find evidence for a turbulent cascade absent in an unmagnetised star which cannot be captured with lower resolution simulations, consistent with Kolmogorov power law scaling. The presence of turbulence triggers an inverse cascade of helicity, while at late times the net helicity appears to vanish, suggesting that a twisted-torus is not formed in the magnetic field. We find that the presence of the magnetic field excites a characteristic quadrupolar oscillation of the density profile at 145Hz, consistent with Alfvenic modes proposed as the source of quasi-periodic oscillations observed in magnetars.

Abstract The recent detections of radio emission from the nearby exoplanet host, YZ Ceti, suggest that the star is possibly interacting with its rocky innermost planet. These radio emissions are characterized by strong circular polarization, and appear to repeat within consistent orbital phase windows dictated by the orbital position of YZ Ceti b. If confirmed, this interaction would provide a first means to concretely assess the magnetic field of a close-in rocky exoplanet. This kind of magnetic star–planet interaction (SPI) should depend on both the exoplanetary orbit and the geometry of the stellar magnetic field. In this article, we report measurements of the large-scale magnetic field topology of the star YZ Ceti for the first time, and interpret the cumulative radio data sets in that context to evaluate the plausibility of magnetic SPIs. We find evidence both against and in support of the SPI hypothesis, but crucially that the measured magnetic field does not rule out SPI scenarios. However, clear evaluation of these possibilities requires more accurate assessments of the magnetic field evolution across time. We additionally suggest that YZ Ceti may be exhibiting planet-induced flaring, potentially triggered by exoplanet crossings of the Alfvén surface as the planet’s orbit approaches the stellar magnetic equator, and YZ Ceti b experiences dramatic shifts in the ambient field, its polarity, and connectivity to the host star.

Abstract We present a refined phenomenological expression for the critical mass of a
neutron star (NS), meticulously incorporating the effects of both rotation
and magnetic helicity. This model is rigorously benchmarked against
established universal relations, observational constraints derived from
multi-messenger astronomy (including gravitational waves and electromagnetic
observations), surface deformation fits obtained from X-ray pulse profile
modeling, and correlations involving moment-of-inertia- compactness. Our
formulation extends the classical static Tolman- Oppenheimer- Volkoff (TOV)
limit by integrating key physical mechanisms: centrifugal support arising
from rapid rotation, complex magneto-superfluid interactions within the NS
core characterized by magnetic helicity, and relativistic shape deformation
(oblateness) induced by high spin rates. The model successfully reproduces
pivotal numerical results, such as the quasi-universal relation $M_{\max
}\approx (1.203\pm 0.022)M_{\mathrm{TOV}}$ for maximum rotating
configurations. This enhanced analytical framework provides a compact and
versatile tool for estimating critical masses and interpreting observational
data for rotating, magnetized compact stars, facilitating both analytical
studies and numerical simulations in relativistic astrophysics.

Abstract The observed spectra and light curves of the kilonova produced by the GW170817 binary neutron star merger provide complementary insights, but modeling both the spectral and time domains has proven challenging. Here, we model the optical–infrared light curves of the GW170817 kilonova, using the properties and physical conditions of the ejecta as inferred from detailed modeling of its spectra. Using our software tool Spectroscopic r -Process Abundance Retrieval for Kilonovae ( SPARK ), we first infer the r -process abundance pattern of the kilonova ejecta from spectra obtained at 1.4, 2.4, 3.4, and 4.4 days postmerger. From these abundances, we compute time-dependent radioactive heating rates and the wavelength-, time-, and velocity-dependent opacities of the ejecta. We use these inferred heating rates and opacities to inform a kilonova light-curve model, to reproduce the observed early time light curves and to infer a total ejecta mass of M ej = 0.11 M ⊙ , towards the higher end of those inferred from previous studies. The combination of a large ejecta mass from our light-curve modeling and the presence of both red and blue ejecta from our spectral modeling suggests the existence of a highly magnetized hypermassive neutron star remnant that survives for ∼0.01–0.5 s and launches a blue wind, followed by fast, red, neutron-rich winds launched from a magnetized accretion disk. By modeling both spectra and light curves together, we demonstrate how combining information from both the spectral and time domains can more robustly determine the physical origins of the ejected material.

Abstract The rotational evolution of a strongly magnetized neutron star (NS), accreting or isolated, is driven by external torques of different nature. In addition to the torques, even the tiniest deformations of the NS crust can affect its rotation through asymmetries in its inertia tensor. Several factors may be responsible for the deformations, including strong magnetic fields, internal stresses, or local heating. The main effect produced by the deformations is the so-called free precession: the motion of the rotational axis with respect to the crust. We consider the evolution of a triaxially deformed isolated NS with a strong dipolar magnetic field for a broad range of parameters, taking into account the magnetic field decay. We show that the combination of pulsar torques and free precession results in a considerable broadening of the distribution of magnetic obliquity angles (the angle between the magnetic and rotational axes) and creates a population of objects where the rotational axis does not align with the magnetic axis at all but enters a limit-cycle regime. The combination of free precession and magnetic torques can also explain the observed distribution in pulsar braking indices by creating a periodic oscillation in the magnetic obliquity.

Abstract In this work, we investigate the impact of nonlinear Born-Infeld (BI) electrodynamics on the internal structure and macroscopic properties of cold and magnetized neutron stars (NSs). By incorporating the Born-Infeld field into a relativistic quantum hadrodynamics framework (QHD-II), we derive modified equations of state (EoS) and analyze their influence through the Tolman–Oppenheimer–Volkoff (TOV) equations. We utilize the GM1 and GM3 parameterizations to explore different hardness regimes of nuclear matter under strong magnetic fields. Our results are compared with observational data from massive pulsars like PSR J0740+6620 and the compact object HESS J1731-347, providing constraints on the BI parameter β. We find that for the Born-Infeld parameter β < 10 20 G, nonlinear effects soften the EoS, reducing the maximum NS masses by up to 10% compared to Maxwellian predictions. For β >> 10 20 G, BI electrodynamics converges to the classical limit, with GM1 (stiff EoS) supporting M max ≈ 2.0M ⊙ and GM3 (soft EoS) yielding M max ≈ 1.8M ⊙ . These results constrain BI modifications in magnetars with B ≥ 10 15 G. Our astrophysical constraints on the parameter β, particularly the stability threshold β ≥ 10 20 G for B ∼ 10 15 G, provide a valuable link to fundamental physics, potentially informing models of nonlinear QED and effective string theories where such a parameter naturally emerges.

Cyclotron resonance between electromagnetic waves and plasmas may be a universal acceleration phenomenon of charged particles in magnetized planets. Coherent fine structures of whistler-mode waves serve as a signature of nonlinear resonance. However, the fine wave structures at Mercury have remained unknown due to limited spacecraft observations. Here we show that plasma wave observations by the third BepiColombo mission Mercury flyby (2023) have identified discrete whistler-mode emission waves similar to those observed in Earth’s magnetosphere. The frequency sweep rates of Mercury’s wave chirping tones correspond to those at Earth, based on the scaling law for planetary magnetospheric size. Furthermore, although the spatial coverage on the dayside and dusk sectors is insufficient, the spatial characteristics of Mercury’s whistler-mode waves during all the Mercury flybys (2021 to 2025) reveal an asymmetric dawn-to-night sector, which suggests nonlinear growth characterized by the distorted magnetospheric shape. These spatiotemporal features strongly indicate that electron precipitation events occur primarily in the active wave (dawn-side) region through nonlinear resonant mechanisms similar to those in Earth’s magnetosphere. This study highlights the potential significance of nonlinear resonant processes in shaping Mercury’s unique plasma environment within its small magnetosphere.

Abstract In this work, we explore the vacuum and plasma magnetosphere of a slowly rotating, magnetized neutron star in a conformally coupled scalar field, so-called Bocharova–Bronnikov-Melnikov–Bekenstein (BBMB) geometry. Starting from the vacuum solutions to Maxwell’s equations in a curved spacetime, we derive modified magnetic and electric field structures in the BBMB geometry. We then investigate the behavior of the Goldreich–Julian (GJ) charge density, accelerating electric fields parallel to magnetic field lines, pair production thresholds, and the rate of energy loss through dipolar radiation in the magnetized star. The coupled scalar field significantly enhances magnetic field strength, charge separation, and parallel acceleration, as well as particle acceleration. We also study the deathline conditions that are responsible for secondary pair formation in the BBMB geometry. All results are compared with the general relativistic (GR) limit. As a result, deathline in the $$P-\dot{P}$$ P - P ˙ diagram is located above in the spacetime compared with GR frame, implying extended pulsar activity compared to GR. Radiative luminosities from the magnetodipolar radiation process are also increased compared to GR predictions. These findings suggest that BBMB gravity could play a crucial role in shaping the high-energy phenomena of neutron stars and offer new avenues for testing gravity in strong-field regimes.

Abstract We detail new force-free simulations to investigate magnetosphere evolution and precursor electromagnetic (EM) signals from binary neutron stars. Our simulations fully follow a representative inspiral motion, capturing the intricate magnetospheric dynamics and their impact on EM outflows. We explore a range of stellar magnetic moment orientations and relative strengths, finding that the magnetospheres and Poynting flux evolution are strongly configuration dependent. The Poynting flux exhibits pulsations at twice the orbital frequency, 2Ω, and is highly anisotropic, following a power-law dependence on orbital frequency. The index ranges from 1 to 6, shaped by the intricate dynamics of the magnetospheres. Furthermore, we present the first computation of (1) the EM forces acting on the star surfaces, revealing the presence of torques that, for highly magnetized stars, could influence the orbital dynamics or break the crust; (2) the high-energy emission signals from these systems by adopting the established isolated pulsar theory. Assuming curvature radiation in the radiation-reaction limit, we find that photons could reach TeV–PeV energies in the last ∼ms for magnetic field strengths 10 10 –10 15 G. However, our analysis of single photon magnetic pair production suggests that these photons are unlikely to escape, with the MeV band emerging as a promising observational window for precursor high-energy emission. In this framework, we construct high-energy emission skymaps and light curves, exploring observational implications. Finally, we propose potential precursor radio emission and delayed afterglow echoes from magnetized outflows, which may contribute to late-time rebrightening in short gamma-ray bursts or to orphan afterglows.

Abstract The Fe xxii doublet has been previously used to determine the density of collisionally ionized emission from magnetic cataclysmic variable stars. We test how this diagnostic doublet behaves for a photoionized plasma with the spectral energy distribution (SED) of an active galactic nucleus (AGN). We use the photoionized plasma code pion and ∼440 ks of archival Chandra High Energy Transmission Grating observations for the well-known Seyfert 2 galaxy NGC 1068 to test the behaviour of the Fe xxii doublet in the context of an AGN. This marks the first time these data have been examined with pion . We find that in a photoionized plasma, the Fe xxii doublet is dependent on the density, ionization state, and SED used. Thus, this density diagnostic remains model-dependent. In the context of NGC 1068 the doublet predicts an emission region ∼100 r g from the central black hole. This would require a direct line of sight to the central engine, which is at odds with the Seyfert 2 nature of this source. In practice, these results highlight the complexities and challenges of applying photoionized models. With these data, we cannot exclude the possibility of a direct line of sight to the central engine of NGC 1068, but we cannot confirm it. Future observations with instruments such as Athena are needed to explore the Fe xxii doublet further.

Abstract We report the detection of mHz quasiperiodic oscillations (QPOs) in four Nuclear Spectroscopic Telescope Array observations of 4U 1626–67 during its recent spin-down episode. By using a novel method based on the Hilbert–Huang transform, we present the first QPO-phase-resolved timing and spectral analysis of accreting X-ray pulsars in low-mass X-ray binaries. Broadband QPO waveforms have been reconstructed and exhibit approximately sinusoidal shapes, with fractional amplitudes that vary with energy. In addition, we find that spin pulse profiles exhibit stable shapes between different QPO phases with different instantaneous fluxes, while the fractional rms is distinct for different observations. In this source, both QPO-phase-resolved and averaged spectra can be modeled with a negative and positive power-law exponential model, and their spectral evolutions show a similar trend, suggesting that the QPO modulation is caused by accretion rate variability instead of a geometric obscuration. These results provide new constraints on accretion physics in strongly magnetized neutron stars and the underlying mechanisms of QPOs.

Abstract Ap stars are a subclass of early-type chemically peculiar stars characterized by abnormal surface elemental abundances and strong, global magnetic fields. These features make them valuable tracers for studying stellar magnetic field origins and evolution. In recent years, the identification of Ap stars has become a research hotspot. We present a novel method using low-resolution LAMOST DR12 spectra. We developed ECACNet, a deep neural network incorporating the ECA mechanism to enhance sensitivity to key spectral features of magnetic Ap stars. On a balanced dataset covering seven stellar classes, ECACNet achieved 96.80% precision and 94.05% recall. Evaluated on seven independent validation sets, it maintained robust performance (96.13% precision, 92.03% recall), significantly outperforming conventional methods. Applying the model to LAMOST DR12 B- to F-type spectra identified 8,130 high-confidence spectra. Visual inspection confirmed 4,826 unique Ap candidates via the characteristic 5200 Å flux depression and metallic lines. Cross-matching with eight catalogs revealed 4,032 known and 794 new candidates. MKCLASS refined the new candidates’ spectral classifications. Statistical analyses of atmospheric parameters (Teff, log g, and [Fe/H]) for the new candidates showed distributions consistent with known Ap stars, further validating our method’s reliability.

LS 5039 is a system hosting a high-mass star and a compact object of unclear nature. There are hints that the system may host a strongly magnetized neutron star, a scenario that requires a mechanism to power its persistent and strong nonthermal emission. We investigate a mechanism in which the nonsteady interaction structure of the stellar and the compact object winds can regularly excite neutron star magnetospheric activity, which can release extra energy and fuel the source nonthermal emission. The neutron star wind shocked by the stellar wind can recurrently touch the neutron star magnetosphere, triggering magnetic instabilities whose growth can release extra energy into the neutron star wind in a cyclic manner. To illustrate and study the impact of these cycles on the two-wind interaction structure on different scales, we performed relativistic hydrodynamics simulations in two and three dimensions with periods of an enhanced power in the neutron star wind along the orbit. We also used analytical tools to characterize processes near the neutron star relevant for the nonthermal emission. As the neutron star wind termination shock touches the magnetosphere energy dissipation occurs, but the whole shocked two-wind structure is eventually driven away, stopping the extra energy injection. However, due to the corresponding drop in the neutron star wind ram pressure, the termination shock propagates back toward the magnetosphere, resuming the process. These cycles of activity excite strong waves in the shocked flows, intensifying their mixing and the disruption of their spiral-like structure produced by orbital motion. Further downstream, the shocked winds can become a quasi-stable, relatively smooth flow. The recurrent interaction between the neutron star magnetosphere and a shocked wind can fuel a relativistic outflow powerful enough to explain the nonthermal emission of LS 5039. A magnetospheric multipolar magnetic field much stronger than the dipolar one may provide the required energetics, and help to explain the lack of evidence of a recent supernova remnant.

At this time, the list of known magnetic δ Scuti stars is extremely limited, with only a select number of well-studied examples. We seek to expand this list, by retrieving targets from a variety of sources and demonstrating that they present simultaneously a surface magnetic field signature and δ Scuti pulsations. We obtained archival and new spectropolarimetric datasets for a variety of known δ Scuti stars and analysed them using the least squares deconvolution method to generate mean Stokes I and V profiles for each target, from which we can determine longitudinal magnetic field measurements. Additionally, we assessed photometric data from the TESS satellite to discern frequency peaks consistent with δ Scuti pulsations in known magnetic stars, and to identify magnetic candidates via rotational modulation. We present a compiled list of all the confirmed magnetic δ Scuti stars discovered to date, containing 13 stars. The majority of this sample lies outside the usual δ Scuti instability strip in the Hertzsprung-Russell diagram, though we do not observe any specific correlations between magnetic field strength and various stellar parameters. This indicates that strong global magnetic fields play a fundamental role in shaping interior structure and processes. Magnetic fields thus must be included in realistic stellar models in order to more accurately predict structure and evolution. This work constitutes the largest database to date of strongly magnetic δ Scuti stars, one that will continue to grow over time with subsequent studies.

In the framework of generalized non-relativistic Fermi-liquid approach analytic expressions have been derived for functions Tc(+)(n, H; Ec) and Tc(–)(n, H; Ec), which are phase transition (PT) temperatures of superdense spatially uniform pure neutron matter from normal to superfluid states with anisotropic spin-triplet p-wave pairing (similar to anisotropic superfluid phases 3He–A1 and 3He–A2) in steady and homogeneous superstrong magnetic fields H ≡ Z⋅1017 G (here 1 ≤ Z ≤ 10; the magnitude of the Zeeman energy of a neutron is |μn|⋅H < Ec ≪ ɛF(n), where μn < 0 is the magnetic dipole moment of a neutron, Ec = 16 and 10 MeV have been selected as two alternative versions of the cutoff energy, ɛF(n) is the Fermi energy of neutron matter at supranuclear densities n > n0, n0 = 0.17 fm−3). These functions Tc(±), which are valid for BSk parametrizations of the unconventional Skyrme forces from the so-called BSk family of the Brussels–Montreal group, depend nonlinearly on density n of neutron matter. The obtained formulas for Tc(±) contain not only terms with symmetrical and linearly field dependent splitting (as had been already derived for the “moderately strong” fields H ≡ Z⋅1017 G with 0 < Z ≤ 1), but also additional terms quadratically dependent on superstrong magnetic field H (in the range with 1 < Z ≤ 10), which lead to asymmetry and nonlinearity in splitting of phase transition temperatures Tc(±)(n, H; Ec) relative to the PT temperature Tc0(n; Ec) in zero field. Using the example of the unconventional BSk21 parameterization of Skyrme forces in superfluid neutron matter (SNM), it was found that the character of the behavior of the asymmetry in the splitting of the PT temperatures depending on the density of SNM also depends on the value of the cutoff energy Ec not only quantitatively, but also qualitatively. Phase transitions to superfluid states of such type might occur in liquid outer core of magnetars (strongly magnetized neutron stars) at n>∼⁡n0.

Context . About 12% of the early-type Be stars, which are not known X-ray binaries, exhibit an unusually hard and bright thermal X-ray emission. The X-ray emission of these so-called γ Cas stars could result from accretion onto a white dwarf companion or from magnetic interactions between the Be star and its decretion disc. Aims . Exploring the full power of high-resolution X-ray spectroscopy of γ Cas stars requires the comparison of observations of the fluorescent Fe K α emission lines near ~6.4keV with synthetic lines simulated for both scenarios. Methods . We computed synthetic profiles of this line complex within the framework of the magnetic interaction and the accreting white dwarf scenarios. For the latter, we further distinguished between accretion onto a non-magnetic and a magnetic white dwarf. The various models account for different reservoirs of reprocessing material: the Be circumstellar decretion disc, the Be photosphere, an accretion disc around the putative white dwarf companion, a magnetically channelled accretion flow, and the white dwarf photosphere. Results . We find considerably different line properties for the different scenarios. For a non-magnetic accreting white dwarf, the global Fe K α complex is extremely broad, reaching a full width of 140 eV, whilst it is ~40 eV for the magnetic star–disc interaction and the magnetic accreting white dwarf cases. In the magnetic star-disc interaction, the line centroid is expected to follow the orbital motion of the Be star, whereas it should move along with the white dwarf in the case of an accreting white dwarf. For γ Cas, given the ~15× larger amplitude of the white dwarf orbital motion, the shift in position for an accreting white dwarf should be easily detectable with high-resolution spectrographs such as Resolve on XRISM , but remains essentially undetectable for the magnetic star-disc interaction. Conclusions . Upcoming high-resolution spectroscopy of the fluorescent Fe K α emission lines in the X-ray spectra of γ Cas stars will offer important insights into the properties of the primary X-ray source and of the illuminated material, allowing us to distinguish between the competing scenarios.

Investigated features of the magnetic field and other properties of the star HD149438. It is shown that this star corresponds to other known magnetic O-stars in all respects. At the same time, all known O-stars have the same properties as SrCrEu+Si+He-w+He-r objects, which allows us to assume their same origin and evolution. There are data on the fact that the hypotheses of the origin of magnetic stars from close binary systems discussed in the literature are not supported by observations.

Detecting coherent radio bursts from nearby M dwarfs provides opportunities for exploring their magnetic activity and interaction with orbiting exoplanets. However, it remains uncertain whether the emission is related to flare-like activity similar to the Sun or magnetospheric process akin to magnetized planets. Using observations (1.0 to 1.5 gigahertz) taken by the Five-hundred-meter Aperture Spherical radio Telescope, we found a type of millisecond-scale radio bursts with exceptionally high-frequency drift rates (~8 gigahertz per second) from an active M dwarf, AD Leo. The ultrafast drift rates point to a source region with a notably low magnetic scale height (<0.15 , as the stellar radius), a feature not expected in a commonly assumed dipole-like global field but highly possible in localized strong-field structures, i.e., starspots. Our findings suggest that a concentrated magnetic field above starspots could be responsible for some of the most intense radio bursts from M dwarfs, supporting a solar-like electron acceleration mechanism.

Abstract Fast radio bursts (FRBs) are among the most energetic and enigmatic transients in the radio sky, with mounting evidence suggesting newborn, highly magnetized neutron stars formed in core-collapse supernovae (CCSNe) as their sources. A definitive spatial association between an FRB and a historic CCSN would confirm this link and tightly constrain young neutron-star source models. Here we report on the first systematic crossmatching of 886 spectroscopically classified CCSNe in the local Universe (z ≤ 0.043) against 241 CHIME/FRB Catalog 1 events, applying rigorous spatial, dispersion measure (DM), and scattering time (τ) criteria. We identify four positional overlaps, all consistent with a chance alignment; however, one pair, FRB 20190412B–SN 2009gi, also satisfies independent host-DM and τ constraints, making it a promising candidate for targeted follow-up. Next, we search for compact (persistent or transient) radio emission at all matched supernova sites using multiepoch Very Large Array Sky Survey data and detect none. Treating every CCSN sight line as a nondetection, we derive Poisson upper limits on the FRB burst rate at these locations, which lie well below the rates observed for the most active repeaters unless their activity is heavily suppressed by beaming, intermittency, or residual free–free absorption. We then develop a galaxy-integrated FRB-rate model that incorporates an intrinsic spectral index, secular magnetar-activity decay, and frequency-dependent free–free opacity. Applying this formalism to existing FRB data shows that reproducing the observed CHIME/CRAFT all-sky rate ratio requires a steep decline in magnetar burst rate with age. Finally, our work underscores the necessity of subarcsecond localizations and multiwavelength follow-up to definitively test the young neutron star source hypothesis.