Synchrotron emission from the shocked regions in supernova remnants provides, through its polarization, crucial details about the magnetic field strength and orientation in these regions. This, in turn, provides information on particle acceleration in these shocks. Due to the rapid losses of the highest-energy relativistic electrons, X-ray polarization measurements allow for investigations of the magnetic field to be carried outvery close to the sites of particle acceleration. Measurements of both the geometry of the field and the levels of turbulence implied by the observed polarization degree thus provide unique insights into the conditions leading to efficient particle acceleration in fast shocks. The Imaging X-ray Polarimetry Explorer (IXPE) has carried out observations of multiple young SNRs, including Cas A, Tycho, SN 1006, and RX J1713.7-3946. In each, significant X-ray polarization detections provide measurements of magnetic field properties that show some common behavior but also considerable differences between these SNRs. Here, we provide a summary of results from IXPE studies of young SNRs, providing comparisons between the observed polarization and the physical properties of the remnants and their environments.
Probing the emission geometry of the X-ray pulsar 2S 1417$-$624 during a weak outburst with NICER, IXPE, and NuSTAR
Institut für Astronomie und Astrophysik, Universität Tübingen（蒂宾根大学天文与天体物理研究所）；Research Center of Astronomy, QingHai University（青海大学天文研究中心）；Department of Physics and Astronomy, QingHai University（青海大学物理与天文系）；Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所粒子天体物理重点实验室）；University of Chinese Academy of Sciences, Chinese Academy of Sciences（中国科学院大学）
As supernova remnants (SNRs) age, they become efficient cosmic ray accelerators at their outer shell shocks. The current paradigm for shock acceleration theory favors turbulent field environs in the proximity of these shocks, turbulence driven by current instabilities involving energetic ions. With the imminent prospect of dedicated X-ray polarimeters becoming a reality, the possibility looms of probing turbulence on scales that couple to the super-TeV electrons that emit X-rays. This paper presents model X-ray polarization signatures from energetic electrons moving in simulated MHD turbulence…
We present a comprehensive study of interstellar X-ray extinction using the extensive Chandra supernova remnant archive and use our results to refine the empirical relation between the hydrogen column density and optical extinction. In our analysis, we make use of the large, uniform data sample to assess various systematic uncertainties in the measurement of the interstellar X-ray absorption. Specifically, we address systematic uncertainties that originate from (i) the emission models used to fit supernova remnant spectra, (ii) the spatial variations within individual remnants, (iii) the physi…
The investigation of extragalactic Supernova Remnants (SNRs) gives us the advantage of surmounting the challenges we are usually confronted with when observing Galactic SNRs, most notably Galactic extinction and distance uncertainties. At the same time, by obtaining larger samples of SNRs, we are allowed to cover a wider range of environments and Interstellar Medium (ISM) parameters than our Galaxy, providing us a more complete and representative picture of SNR populations. I will outline the recent progress on extragalactic surveys of SNR populations focusing on the optical, radio, and X-ray …
X-ray polarimetry promises us an unprecedented look at the structure of magnetic fields and on the processes at the base of acceleration of particles up to ultrarelativistic energies in relativistic jets. Crucial pieces of information are expected from observations of blazars (that are characterized by the presence of a jet pointing close to the Earth), in particular of the subclass defined by a synchrotron emission extending to the X-ray band (so-called high synchrotron peak blazars, HSP). In this review, I give an account of some of the models and numerical simulations developed to predict t…
The new generation of X-ray polarisation detectors, gas pixel detectors, which will be employed by the future space missions IXPE and eXTP, allows for spatially resolved X-ray polarisation studies. This will be of particular interest for X-ray synchrotron emission from extended sources like young supernova remnants and pulsar wind nebulae. Here we report on employing a polarisation statistic that can be used to makes maps in the Stokes I, Q, and U parameters, a method that we expand by correcting for the energy-dependent instrumental modulation factor, using optimal weighting of the signal. In…
The shell-type supernova remnant HESS J1731$-$347 emits TeV gamma-rays, and is a key object for the study of the cosmic ray acceleration potential of supernova remnants. We use 0.5-1 arcminute Mopra CO/CS(1-0) data in conjunction with HI data to calculate column densities towards the HESS J1731$-$347 region. We trace gas within at least four Galactic arms, typically tracing total (atomic+molecular) line-of-sight H column densities of 2-3$\times$10$^{22}$ cm$^{-2}$. Assuming standard X-factor values and that most of the HI/CO emission seen towards HESS J1731$-$347 is on the near-side of the Gal…
Thin non-thermal X-ray filaments are often seen in young supernova remnants. We used data from the 1 Ms Chandra observation of Cassiopeia A to study spectral properties of some of the filaments in this remnant. For all the cases that we examined, the X-ray spectrum across the filaments hardens, at about 10% level, going outward, while observed filament widths depend only weakly on the photon energy. Using a model that includes radiative cooling, advection and diffusion of accelerated particles behind the shock, we estimated the magnetic field, turbulence level and shock obliquity.
While supernova remnants (SNRs) are widely thought to be powerful accelerators, evidence comes largely from a small number of well-studied cases. Here we systematically determine the gamma-ray emission from all known Galactic SNRs, disentangling them from the sea of Galactic cosmic rays. Using Fermi LAT data we have characterized the GeV emission in all regions containing SNRs, accounting for systematic uncertainties caused by source confusion, diffuse emission modeling, and instrumental response. More than a dozen remnants are identified through spatial extension or detection at TeV energies,…
We report on a $\sim 5σ$ detection of polarized 3-6 keV X-ray emission from the supernova remnant Cassiopeia A with the Imaging X-ray Polarimetry Explorer (IXPE). The overall polarization degree of $1.8 \pm 0.3$% is detected by summing over a large region, assuming circular symmetry for the polarization vectors. The measurements imply an average polarization degree for the synchrotron component of $\sim 2.5$%, and close to 5% for the X-ray synchrotron-domimated forward-shock region. These numbers are based on an assessment of the thermal and non-thermal radiation contributions, for which we us…
We present a proof-of-concept study, based on numerical-relativity simulations, of how gravitational waves (GWs) from neutron star merger remnants can probe the nature of matter at extreme densities. Phase transitions and extra degrees of freedom can emerge at densities beyond those reached during the inspiral, and typically result in a softening of the equation of state (EOS). We show that such physical effects change the qualitative dynamics of the remnant evolution, but they are not identifiable as a signature in the GW frequency, with the exception of possible black-hole formation effects.…
We address the question of regular primordial black holes with de Sitter interior, their remnants and gravitational vacuum solitons G-lumps as heavy dark matter candidates providing signatures for inhomogeneity of early universe, which is severely constrained by the condition that the contribution of these objects in the modern density does not exceed the total density of dark matter. Primordial black holes and their remnants seem to be most elusive among dark matter candidates. However, we reveal a nontrivial property of compact objects with de Sitter interior to induce proton decay or decay …
Polarimetric measurements, especially if extended at high energy, are expected to provide important insights into the mechanisms underlying the acceleration of relativistic particles in jets. In a previous work we have shown that the polarization of the synchrotron X-ray emission produced by highly energetic electrons accelerated by a mildly relativistic shock carries essential imprints of the geometry and the structure of the magnetic fields in the downstream region. Here we present the extension of our analysis to the non-stationary case, especially suitable to model the highly variable emis…
In this work we present a procedure to infer the mass of progenitors and remnants of Gamma Ray Bursts (GRB), starting from the observed energy $E_{iso}^{GRB}$ emitted isotropically and considering the associated emission of Gravitational Waves (GW) $ E_{iso}^{GW}$ in the different phases. We assume that the GW energy of the progenitor $E_{PROG}^{GW}$ is emitted partially during a star collapse, and the residual energy is related to the GW energy emitted by the remnant. We take a sample of $237$ Long GRB, and use an hybrid Montecarlo procedure to explore, for each of them, a region of possible …
Probing the Diversity of Type Ia Supernova Remnants in 3-D Hydrodynamic Simulations with X-ray Spectral Synthesis
Kyoto University（京都大学）；The University of Tokyo（东京大学）；Kavli Institute for the Physics and Mathematics of the Universe (WPI)（宇宙物理与数学惠特尼研究所）；The University of Manitoba（曼尼托巴大学）；RIKEN Center for Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS)（理化学研究所跨学科理论与数学科学中心）；Smithsonian Astrophysical Observatory（史密森尼天体物理台）；Astrophysical Big Bang Laboratory (ABBL), RIKEN Pioneering Research Institute (PRI)（大爆炸天体物理学实验室（先进研究院））；Okinawa Institute of Science and Technology Graduate University (OIST)（冲绳科学技术大学院大学）；University of California, Berkeley（加州大学伯克利分校）；Max-Planck-Institut für Astrophysik（马克斯·普朗克天体物理研究所）
Located in a dense complex environment, W51C provides an excellent scenario to probe accelerated protons in SNRs and their interaction with surrounding target material. Here we report the observation of extended Very High Energy (VHE) gamma-ray emission from the W51C supernova remnant (SNR) with MAGIC. Detections of extended gamma-ray emission in the same region have already been reported by the Fermi and H.E.S.S. collaborations. Fermi/LAT measured the source spectrum in the energy range between 0.2 and 50 GeV, which was found to be well fit by a hadronic neutral-pion decay model. The VHE obse…
Located in a dense complex environment, W51C provides an excellent scenario to probe accelerated protons in SNRs and their interaction with surrounding target material. Here we report the observation of extended Very High Energy (VHE) gamma-ray emission from the W51C supernova remnant (SNR) with MAGIC. Detections of extended gamma-ray emission in the same region have already been reported by the Fermi and H.E.S.S. collaborations. Fermi/LAT measured the source spectrum in the energy range between 0.2 and 50 GeV, which was found to be well fit by a hadronic neutral-pion decay model. The VHE obse…
X-Ray Polarization from the Atoll 4U 1735-44 Suggests a Low Inclination
University of Turku（图尔库大学）；Nordic Optical Telescope（北欧光学望远镜）；NASA Marshall Space Flight Center（美国宇航局马歇尔太空飞行中心）；Università degli Studi Roma Tre（罗马第三大学）；INAF Istituto di Astrofisica e Planetologia Spaziali（意大利国家天体物理研究所空间天体物理学和行星科学研究所）
One of the most essential but uncertain processes for producing cosmic-rays (CRs) and their spectra is how accelerated particles escape into the interstellar space. We propose that the CR electron spectra at >~TeV energy can provide a direct probe of the CR escape complementary to the CR nuclei and gamma-rays. We calculate the electron spectra from a young pulsar embedded in the supernova remnant (SNR), like Vela, taking into account the energy-dependent CR escape. SNRs would accelerate and hence confine particles with energy up to 10^{15.5}eV. Only energetic particles can escape first, while …
The dissipation of energy flux in blazar jets plays a key role in the acceleration of relativistic particles. Two possibilities are commonly considered for the dissipation processes, magnetic reconnection -- possibly triggered by instabilities in magnetically-dominated jets -- , or shocks -- for weakly magnetized flows. We consider the polarimetric features expected for the two scenarios analyzing the results of state-of-the-art simulations. For the magnetic reconnection scenario we conclude, using results from global relativistic MHD simulations, that the emission likely occurs in turbulent r…
A supernova remnant (SNR) candidate SRGe~J0023+3625 = G116.6-26.1 was recently discovered in the \textit{SRG}/eROSITA all-sky X-ray survey. This large ($\sim 4$ deg in diameter) SNR candidate lacks prominent counterparts in other bands. Here we report detection of radio emission from G116.6-26.1 in the LOFAR Two-metre Sky Survey (LoTTS-DR2). Radio images show a shell-like structure coincident with the X-ray boundary of the SNR. The measured surface brightness of radio emission from this SNR is very low. Extrapolation of the observed surface brightness to 1~GHz places G116.6-26.1 well below oth…
The characteristic two-component blazar spectral energy distribution (SED) can be of either leptonic and/or hadronic origins. The potential association of the high-energy neutrino event IceCube-170922A with the flaring blazar TXS~0506+056 indicates that hadronic processes may operate in a blazar jet. Despite multi-wavelength follow-ups of the event and extensive theoretical modelings, the radiation mechanisms and the underlying magnetic field strength and configuration remain poorly understood. In this paper, we consider generic leptonic and hadronic blazar spectral models with distinct magnet…
Supernovae shape the interstellar medium, chemically enrich their host galaxies, and generate powerful interstellar shocks that drive future generations of star formation. The shock produced by a supernova event acts as a type of time machine, probing the mass loss history of the progenitor system back to ages of $\sim$ 10 000 years before the explosion, whereas supernova remnants probe a much earlier stage of stellar evolution, interacting with material expelled during the progenitor's much earlier evolution. In this chapter we will review how observations of supernova remnants allow us to in…
Observations of young supernova remnants (SNRs) in X-rays and gamma-rays have provided conclusive evidence for particle acceleration to at least TeV energies. Analysis of high spatial resolution X-ray maps of young SNRs has indicated that the particle acceleration process is accompanied by strong non-adiabatic amplification of magnetic fields. If Fermi acceleration is the mechanism producing the energetic cosmic rays (CRs), the amplified magnetic field must be turbulent and CR-driven instabilities are among the most probable mechanisms for converting the shock ram pressure into the magnetic tu…
Supernova Remnants and Pulsar Wind Nebulae are among the most significant sources of non-thermal X-rays in the sky, and the closest laboratories where relativistic plasma dynamics and particle acceleration can be investigated. Being strong synchrotron emitters, they are ideal candidates for X-ray polarimetry, and indeed the Crab nebula is up to present the only object where X-ray polarization has been detected with a high level of significance. Future polarimetric measures will likely provide us crucial informations on the level of turbulence that is expected at the particle acceleration sites…
Probing millisecond magnetar formation in binary neutron star mergers through X-ray follow-up of gravitational wave alerts
Université Paris-Saclay（巴黎萨克雷大学）；Université Paris Cité（巴黎西岱大学）；CEA（法国原子能和替代能源委员会）；CNRS（法国国家科学研究中心）；Max Planck Institute for Gravitational Physics (Albert Einstein Institute)（马克斯·普朗克引力物理研究所（爱因斯坦研究所））；CNRS/IN2P3, IJCLab（法国国家科学研究中心/法国国家核物理与粒子物理研究所，IJCLab实验室）；Institut d’Astrophysique de Paris（巴黎天文物理研究所）；Sorbonne Université（索邦大学）；Università di Torino（都灵大学）
We investigate pulsar timing residuals due to the coupling effect of the pulsar transverse acceleration and the R$\rm{\ddot{o}}$mer delay. The effect is relatively small and usually negligible. Only for pulsars in globular clusters, it is possibly important. The maximum residual amplitude, which is from the pulsar near the surface of the core of the cluster, is about tens nanoseconds, and may hardly be identified for most of the globular clusters currently. However, an intermediate-mass black hole in the centre of a cluster can increase apparently the timing residual magnitudes. Particularly f…
The newly discovered Be/X-ray binary in the Small Magellanic Cloud, SXP 1062, provides the first example of a robust association with a supernova remnant (SNR). The short age estimated for the SNR qualifies SXP 1062 as the youngest known source in its class, tau ~ 1e4 yr. As such, it allows to test current models of magneto-rotational evolution of neutron stars ina still unexplored regime. Here we discuss possible evolutionary scenarios for SXP 1062 in the attempt to reconcile its long spin period, P=1062 s, and short age. Although several options can be considered, like an anomalously long in…
What's the Buzz About GX 13+1? Constraining Coronal Geometry with QUEEN-BEE: A Bayesian Nested Sampling Framework for X-ray Polarization Rotation Analysis
本文提出贝叶斯嵌套采样框架 QUEEN-BEE，用于分析 IXPE 数据中 GX 13+1 的 X 射线偏振旋转，首次约束其冕几何为片状，并展示其在低信噪比下识别演化偏振特征的能力。
The measurement of an excess in the cosmic-ray electron spectrum between 300 and 800 GeV by the ATIC experiment has - together with the PAMELA detection of a rise in the positron fraction up to 100 GeV - motivated many interpretations in terms of dark matter scenarios; alternative explanations assume a nearby electron source like a pulsar or supernova remnant. Here we present a measurement of the cosmic-ray electron spectrum with H.E.S.S. starting at 340 GeV. While the overall electron flux measured by H.E.S.S. is consistent with the ATIC data within statistical and systematic errors, the H.E.…
Probing the Dispersion and Rotation Measure Contributions from Supernova Remnants in Fast Radio Burst Source Environments with 1D SNR Simulation
Theoretical Astrophysics, Department of Earth and Space Science, The University of Osaka（大阪大学地球惑星科学部理论天体物理学）；Department of Astronomy, Kyoto University（京都大学天文学系）；Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo（东京大学宇宙物质前沿研究机构（WPI））；Theoretical Joint Research, Forefront Research Center, Graduate School of Science, The University of Osaka（大阪大学大学院理学研究科前沿研究中心理论联合研究）；Kavli IPMU (WPI), UTIAS, The University of Tokyo（东京大学UTIAS卡弗里宇宙物理与数学研究所（WPI））；Department of Physics & Astronomy, University of Nevada, Las Vegas（内华达大学拉斯维加斯分校物理与天文系）；Nevada Center for Astrophysics, University of Nevada, Las Vegas（内华达大学拉斯维加斯分校内华达天体物理学中心）；The Hong Kong Institute for Astronomy and Astrophysics, The University of Hong Kong（香港大学香港天体物理学研究所）
The IceCube Collaboration has recently reported evidence for a high-energy extraterrestrial neutrino flux. During two years of operation 28 events with energies between 30 TeV and 1.2 PeV were observed while only 10.6 events were expected from conventional atmospheric backgrounds. The hadronic interactions responsible for this IceCube excess will also produce a flux of high-energy gamma-rays that can serve as a probe of source direction and distance. We show that existing TeV to PeV diffuse gamma-ray limits support the interpretation that the IceCube excess is mostly of extragalactic origin. H…
Supernova remnants (SNRs) have been regarded as major acceleration sites of Galactic cosmic rays. Recent X-ray studies revealed neutral Fe K$α$ line emission from dense gas in the vicinity of some SNRs, which can be best interpreted as K-shell ionization of Fe atoms in the gas by sub-relativistic particles accelerated in the SNRs. In this Letter, we propose a novel method of constraining the composition of particles accelerated in SNRs, which is currently unknown. When energetic heavy ions collide with target atoms, their strong Coulomb field can easily cause simultaneous ejection of multiple …
Recent efforts in cosmic ray (CR) confinement and transport theory are discussed. Three problems are addressed as being crucial for understanding the present day observations and their possible telltale signs of the CR origin. The first problem concerns CR behavior right after their release from a source, such as a supernova remnant (SNR). At this phase the CRs are confined near the source by self-emitted Alfven waves. The second is the problem of diffusive propagation of CRs through the turbulent ISM. This is a seemingly straightforward and long-resolved problem, but it remains controversial …
Supernova remnants (SNRs) are important objects in investigating the links among supernova (SN) explosion mechanism(s), progenitor stars, and cosmic-ray acceleration. Non-thermal emission from SNRs is an effective and promising tool for probing their surrounding circumstellar media (CSM) and, in turn, the stellar evolution and mass-loss mechanism(s) of massive stars. In this work, we calculate the time evolution of broadband non-thermal emissions from Type Ib/c SNRs whose CSM structures are derived from the mass-loss history of their progenitors. Our results predict that Type Ib/c SNRs make a …
Supernova remnants (SNRs) are thought to be one of the major acceleration sites of galactic cosmic rays (CRs) and an important class of objects for high-energy astrophysics. SNRs produce multi-wavelength, non-thermal emission via accelerated particles at collisionless shocks generated by the interactions between the SN ejecta and the circumstellar medium (CSM). Although it is expected that the rich diversities observed in supernovae (SNe) and their CSM can result in distinct very-high-energy (VHE) electromagnetic signals in the SNR phase, there are only a handful of SNRs observed in both GeV a…
The contribution of galactic supernova remnants (SNRs) to the origin of cosmic rays (CRs) is an important open question in modern astrophysics. Broadband non-thermal emission is a useful proxy for probing the energy budget and production history of CRs in SNRs. We conduct hydrodynamic simulations to model the long-term SNR evolution from explosion all the way to the radiative phase (or $3\times10^5$ yrs at maximum), and compute the time evolution of the broadband non-thermal spectrum to explore its potential applications on constraining the surrounding environments as well as the natures and m…
Probing ultralight bosons with LISA observations of spinning black hole mergers and follow-up searches of merger remnants
Perimeter Institute for Theoretical Physics（Perimeter理论物理研究所）；University of Waterloo（滑铁卢大学）；Max Planck Institute for Gravitational Physics (Albert Einstein Institute)（马克斯·普朗克引力物理学研究所（爱因斯坦研究所））
Supernova remnants (SNRs) have been regarded for many decades as the sources of Galactic cosmic rays (CRs) up to a few PeV. However, only with the advent of Fermi-LAT it has been possible to detect - at least in some SNRs - γ-rays whose origin is unequivocally hadronic, namely due to the decay of neutral pions produced by collisions between relativistic nuclei and the background plasma. When coupled with observations in other bands (from radio to TeV γ-rays), Fermi-LAT data present evidence for CR spectra significantly steeper than the standard prediction of diffusive shock acceleration, forci…
The galactic cosmic rays are generally believed to be originated in supernova remnants (SNRs), produced in diffusive shock acceleration (DSA) process in supernova blast waves driven by expanding SNRs. One of the key unsettled issue in SNR origin of cosmic ray model is the maximum attainable energy by a cosmic ray particle in the supernova shock. Recently it has been suggested that an amplification of effective magnetic field strength at the shock may take place in young SNRs due to growth of magnetic waves induced by accelerated cosmic rays and as a result the maximum energy achieved by cosmic…
4FGL J0822.8-4207 is a point source found in the 4FGL-DR2 catalog by the gamma-ray observatory Fermi-LAT and has no known association. We carry out X-ray observations of 4FGL J0822.8-4207 to help understand its nature. We explore two scenarios for the origin of 4FGL J0822.8-4207. In the first case we study the possibility that cosmic rays from the supernova remnant (SNR) Puppis A, seen nearby in the sky, reach the dense gas at the location of the source and produce the gamma-rays through inelastic proton-proton collisions. We apply a standard model for particle diffusion in the interstellar me…
