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Transient Large-Scale Anisotropy in TeV Cosmic Rays due to an Interplanetary Coronal Mass Ejection
No full textInternational audienceLarge- or medium-scale cosmic ray anisotropy at TeV energies has not previously been confirmed to vary with time. Transient anisotropy changes have been observed below 150 GeV, especially near the passage of an interplanetary shock and coronal mass ejection containing a magnetic flux rope ejected by a solar storm, which can trigger a geomagnetic storm with practical consequences. In such events, cosmic rays provide remote sensing of the magnetic field properties. Here we report the observation of transient large-scale anisotropy in TeV cosmic ray ions using data from the Large High Altitude Air Shower Observatory (LHAASO). We analyze hourly skymaps of the transient cosmic ray intensity excess or deficit, the gradient of which indicates the direction and magnitude of transient large-scale anisotropy across the field of view. We observe enhanced anisotropy above typical hourly fluctuations with 5 significance during some hours of November 4, 2021, in separate data sets for four primary cosmic ray energy ranges of median energy from =0.7 to 3.1 TeV. The gradient varies with energy as , where . At a median energy 1.0 TeV, this gradient corresponds to a dipole anisotropy of at least 1%, or possibly a weaker anisotropy of higher order. This new type of observation opens the opportunity to study interplanetary magnetic structures using air shower arrays around the world, complementing existing in situ and remote measurements of plasma properties
Planetary, Solar and Heliospheric Radio Emissions X
No full textInternational audienceThe 10th edition of the international workshop on "Planetary, Solar and Heliospheric Radio Emissions” was held in June 2025 in Marseille, France, in continuation of a series of previous workshops successively held in Graz (Austria) in 1984, 1987, 1991, 1996, 2001, 2005, 2010 and 2016 and in Ireland (Dublin) in 2022. The proceedings of this workshop have been double peer-reviewed under the responsability of a scientific editorial committee composed of L. Lamy, C. K. Louis, G. Fischer, D. Morosan and P. Zarka and are published as a digital book entitled “Planetary, Solar and Heliospheric Radio Emissions X”
H.E.S.S. detection and multi-wavelength study of the 1 blazar PKS 034627
No full textInternational audiencePKS 0346-27 is a Low Synchrotron Peaked (LSP) blazar at redshift 0.991. The very-high-energy (VHE, E > 100 GeV) spectra of blazars are always affected by absorption by the Extragalactic Background Light (EBL) and subsequently, no blazars have been detected in VHE -rays at redshifts exceeding 1. Extending the redshift range of VHE-detected blazars to will yield insights into the cosmological evolution of both the VHE blazar population and the EBL. This is the goal of a target-of-opportunity (ToO) programme by H.E.S.S. to observe flaring high-redshift () blazars. We report on H.E.S.S. ToO and multi-wavelength observations of the blazar PKS 034627. Along with H.E.S.S., simultaneous data from {\it Fermi}-LAT, {\it Swift} (XRT and UVOT), and ATOM have been analysed and modelled using single-zone leptonic and hadronic models. PKS~0346-27 has been detected by H.E.S.S at a significance of 6.3 during one night, on 3 November 2021, while for other nights before and after this day, upper limits on the VHE flux are determined. No evidence for intra-night -ray variability has been found. A flare in high-energy (HE, ~MeV) -rays detected by {\it Fermi}-LAT preceded the H.E.S.S. detection by 2 days. A fit with a single-zone emission model to the contemporaneous spectral energy distribution during the detection night was possible with a proton-synchrotron-dominated hadronic model, requiring a proton-kinetic-energy-dominated jet power temporarily exceeding the source's Eddington limit, although alternative (e.g. multi-zone) models can not be ruled out. A one-zone leptonic model is, in principle, also able to fit the flare-state SED, however, requiring implausible parameter choices, in particular, extreme Doppler and bulk Lorentz factors of
Energy-Dependent Shifts of Medium-Scale Anisotropies in Very-High-Energy Cosmic Rays Observed by LHAASO-KM2A
No full textInternational audienceSmall deviations from isotropy in the arrival directions of Galactic cosmic rays serve as a unique probe of the local magnetic environment. In this Letter, we report observations of medium-scale anisotropies (MSA) at energies above 10 TeV using the LHAASO-KM2A array. Our analysis identifies four regions of excess and four regions of deficit, each spanning angular scales of approximately ten degrees. Crucially, we detect significant energy-dependent shifts in the centroids of two excess regions: Region B and the newly identified Region . We also characterize the energy evolution of the fractional relative intensity across both excess and deficit regions. These findings imply that the observed anisotropies are shaped by the specific realization of the local turbulent magnetic field within the cosmic ray scattering length. Such energy-dependent behaviors impose strict constraints on local turbulence models and cosmic ray propagation theories
Model-independent ZH production cross section at FCC-ee
No full textInternational audienceThis paper presents prospects for a model-independent measurement of the production cross section at the FCC-ee using the recoil-mass technique at center-of-mass energies of and GeV. The analysis considers the muon, electron, and hadronic decay modes of the associated boson. Event selections rely primarily on the kinematic properties of the reconstructed decay products, ensuring maximal independence from specific Higgs boson decay modes, while multivariate techniques are employed to further enhance sensitivity. Statistical interpretations of the individual final states yield relative precisions of for the combined leptonic channels and for the hadronic channel at GeV with an integrated luminosity of ab. Their full statistical combination leads to total uncertainties of at GeV and at GeV with ab. Dedicated statistical tests demonstrate model independence at the level of the obtained precision. This study presents, for the first time, a consistent and combined analysis of the leptonic and hadronic final states, achieving the most precise projected determination of the production cross section at future lepton colliders, with model independence demonstrated within the statistical precision
Nonlinear Relativistic Tidal Response of Neutron Stars
No full textInternational audienceWe investigate the nonlinear tidal response of relativistic neutron stars by computing the fully relativistic, static, quadratic Love numbers. Using both the worldline effective field theory for extended gravitating bodies and second-order perturbations of relativistic stellar models, we derive the nonlinear tidal deformation induced by an external gravito-electric tidal field to quadratic order. Through a suitable matching procedure, we provide for the first time the leading nonlinear tidal corrections to the conservative dynamics and gravitational-wave signal of binary systems. Quadratic Love numbers are enhanced more than the linear ones in the small-compactness limit. Because of this, despite entering the gravitational-wave phase at 8th post-Newtonian (PN) order, the leading quadratic Love number can be as important as the next-to-next-to-leading order linear tidal correction, which enters at 7th PN order, and is larger than the subleading point-particle contribution entering at 4th PN order. In particular, quadratic Love numbers can be as large as ~10% of the linear Love numbers in the late inspiral phase. Our approach provides a framework to also compute the (subleading) nonlinear effects induced by magnetic tidal fields and higher multipole moments, and sets the foundations for incorporating nonlinear tidal effects in high-precision gravitational-wave modeling
Optical Follow-Up Strategies for the Next Neutrino-Detected Galactic Core-Collapse Supernova
No full textInternational audienceCore-collapse supernovae (CCSNe) are expected to produce intense bursts of neutrinos preceding the emergence of their electromagnetic (EM) counterparts. The prompt detection of such neutrino signals offers a unique opportunity to trigger early follow-up observations in the EM domain. We aim to assess the feasibility and efficiency of an optical-NIR follow-up strategy for CCSNe discovered via neutrino bursts, by modelling the spatial distribution of events and simulating realistic observational campaigns taking into account the size of the localization error box generated by triangulating the neutrino burst. We modelled the Galactic distribution of CCSNe, including the effects of interstellar extinction, and considered three main progenitor types: Wolf-Rayet stars, red and blue supergiants. We included the shock breakout in the EM signatures that could be detected following the neutrino burst. A population of CCSNe was generated and detected by different networks of neutrino observatories, including IceCube, KM3NeT, Super-Kamiokande, Hyper-Kamiokande, and JUNO. The resulting skymaps were used as input for GWEMOPT to produce optimized follow-up plans with two optical facilities: LSST and the TAROT robotic telescopes. Both LSST and TAROT exhibit comparable detection efficiencies for the simulated CCSN population. However, the TAROT network achieves similar success rates while requiring fewer pointings to cover the CCSN skymap. Our simulations demonstrate that neutrino follow-up campaigns can effectively CCSN optical counterparts using both large and small facilities. Depending on the neutrino network, the median number of pointings for the two tested optical facilities is of the order of 20 to 100 to find the EM emission. The number of images is larger for LSST than for TAROT by a factor of 2 to 4
The influence of the 3D Galactic gas structure on cosmic-ray transport and gamma-ray emission
No full textInternational audienceCosmic rays (CRs) play a major role in the dynamics of the interstellar medium (ISM). Their interactions and transport ionize, heat, and push the ISM thereby coupling different regions of it. The spatial distribution of CRs depends on the distribution of their sources as well as the ISM constituents they interact with, such as gas, starlight, and magnetic fields. Particularly, gas interacts closely with CRs, influencing CR fluxes and gamma -ray emission. We illustrate the influence of 3D gas structures on CR transport and gamma -ray emission. We use the PICARD code and multiple samples of recent 3D reconstructions of the HI and H Galactic gas constituents to investigate the impact on the transport of CRs and emission of gamma -rays. We find the necessary transport parameters to reproduce local measurements of CR fluxes, and see that they depend on the local distribution of gas density and structure. The distribution of CR fluxes exhibits energy-dependent structures that vary for all CR species due to their corresponding loss processes. Regions of enhanced secondary (primary) species are spatially correlated (anti-correlated) with the gas density. We observe a high sensitivity of the gamma -ray emission on the contrast of gas structures, as those determine the 3D spatial distributions of hadronic interactions and bremsstrahlung. We find that corresponding gas-induced structures in the distribution of CR electrons are also visible in Inverse Compton (IC) emission. Due to the aforementioned sensitivity, the analysis of CR data for CR sources and transport parameters requires the usage of accurate 3D gas maps
Euclid: Early Release Observations. A combined strong and weak lensing solution for Abell 2390 beyond its virial radius
No full textInternational audienceEuclid is presently mapping the distribution of matter in the Universe in detail via the weak lensing (WL) signature of billions of distant galaxies. The WL signal is most prominent around galaxy clusters, and can extend up to distances well beyond their virial radius, thus constraining their total mass. Near the centre of clusters, where contamination by member galaxies is an issue, the WL data can be complemented with strong lensing (SL) data which can diminish the uncertainty due to the mass-sheet degeneracy and provide high-resolution information about the distribution of matter in the centre of clusters. Here we present a joint SL and WL analysis of the Euclid Early Release Observations of the cluster Abell 2390 at z=0.228. Thanks to Euclid's wide field of view of 0.5 deg^2, combined with its angular resolution in the visible band of 0."13 and sampling of 0."1 per pixel, we constrain the density profile in a wide range of radii, 30 kpc < r < 2000 kpc, from the inner region near the brightest cluster galaxy to beyond the virial radius of the cluster. We find consistency with earlier X-ray results based on assumptions of hydrostatic equilibrium, thus indirectly confirming the nearly relaxed state of this cluster. We also find consistency with previous results based on weak lensing data and ground-based observations of this cluster. From the combined SL+WL profile, we derive the values of the viral mass M_{200} = (1.48 \pm 0.29)\times10^{15}\, \Msun, and virial radius ), with error bars representing one standard deviation. The profile is well described by an NFW model with concentration c=6.5 and a small-scale radius of 230 kpc in the 30 kpc < r < 2000 kpc range that is best constrained by SL and WL data. Abell 2390 is the first of many examples where Euclid data will play a crucial role in providing masses for clusters
Detection of Oscillations in a Type I X-Ray Burst of 4U 0614+091 with SVOM/ECLAIRs
No full textInternational audienceOn 2025 January 10, a thermonuclear (Type I) X-ray burst from the neutron star low-mass X-ray binary (LMXB) 4U 0614+091 was detected with the ECLAIRs instrument on board the Space-based multiband astronomical Variable Object Monitor mission. We present here a time-resolved spectroscopic analysis of the burst, along with the detection of burst oscillations within a 51 s interval during the decay phase. The oscillation frequency is measured to be ν = 413.674 ± 0.002 Hz, consistent with previous reports. However, we detect a significant downward frequency drift over the burst duration, characterized by ν̇=(−4.7±0.3)×10−3Hzs−1. This frequency evolution is atypical compared to those observed in similar burst oscillation sources. We tentatively attribute the observed drift to a Doppler shift induced by orbital motion. Under this interpretation, the inferred orbital period must be shorter than 20 minutes, placing 4U 0614+091 among the most compact known LMXBs