Abstracts of Interest
Selected by:
Ryan Burley
Abstract: 2304.02684
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Cosmic ray propagation in turbulent magnetic fields
Download PDFAbstract: Propagation of cosmic rays (CRs) in turbulent and magnetized astrophysical media is a long-standing problem that requires both understanding of the properties of turbulent magnetic fields and their interaction with energetic particles. This review focuses on selected recent theoretical findings made based on the progress in understanding and simulating magnetohydrodynamic (MHD) turbulence. In particular, we address the problem of perpendicular and parallel propagation of CRs and identify the conditions when the perpendicular propagation is superdiffusive and diffusive. For the parallel diffusion, we discuss the problems of the traditionally used diffusion mechanism arising from pitch angle scattering and the possible solutions provided by the recently identified ``mirror diffusion" in the presence of turbulent magnetic mirrors.
Abstract: 2304.02719
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:The Large Array Survey Telescope -- Science Goals
Download PDFAbstract: The Large Array Survey Telescope (LAST) is designed to survey the variable and transient sky at high temporal cadence. The array is comprised of 48 F/2.2 telescopes of 27.9cm aperture, coupled to full-frame backside-illuminated cooled CMOS detectors with $3.76$$\mu$m pixels, resulting in a pixel scale of $1.25\mathrm{arcsec}$. A single telescope with a field of view of $7.4\mathrm{deg}^2$ reaches a $5\sigma$ limiting magnitude of $19.6$ in $20$s. LAST 48 telescopes are mounted on 12 independent mounts -- a modular design which allows us to conduct optimized parallel surveys. Here we provide a detailed overview of the LAST survey strategy and its key scientific goals. These include the search for gravitational-wave (GW) electromagnetic counterparts with a system that can cover the uncertainty regions of the next-generation GW detectors in a single exposure, the study of planetary systems around white dwarfs, and the search for near-Earth objects. LAST is currently being commissioned, with full scientific operations expected in mid 2023. This paper is accompanied by two complementary publications in this issue, giving an overview of the system (Ofek et al. 2023a) and of the dedicated data reduction pipeline (Ofek et al. 2023b).
Abstract: 2304.02761
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:$\mathbf {SU(\infty)}$-QGR Quantumania: Everything, Everywhere, All At Once
Download PDFAbstract: $SU(\infty)$-QGR is a quantum approach to Universe and gravity. Its main assumption is infinite mutually commuting observables in the Universe, leading to representation of $SU(\infty)$ by its Hilbert spaces and those of its subsystems. The Universe as a whole is static, topological, and characterized by two continuous parameters. Nonetheless, quantum fluctuations induce clustering and finite rank internal symmetries, which approximately divide the Universe to infinite interacting subsystems. Their Hilbert space depends on an additional dimensionful parameter, and selection of a subsystem as clock induces a relative dynamics, with $SU(\infty)$ sector as gravity. The Lagrangian defined on the (3+1)-dimensional parameter space is Yang-Mills for both symmetries. When quantumness of gravity is undetectable, it is perceived as curvature of an effective spacetime.
Abstract: 2304.02756
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Upper limits on transmitter rate of extragalactic civilizations placed by Breakthrough Listen observations
Download PDFAbstract: The Search for Extra-Terrestrial Intelligence (SETI) has been conducted for over sixty years, yet no technosignatures have been identified. Previous studies have focused on stars in our galaxy, with few searches in the extragalactic Universe despite a larger volume being available. Civilizations capable of harvesting energy from a star or a galaxy are classified as KII or KIII on the Kardashev scale, respectively. Technosignatures from such advanced civilizations would be extremely luminous and detectable by current radio telescopes, even from distant galaxies. To explore the frontier of extragalactic SETI, we investigate the likely prevalence of extragalactic civilizations possessing a radio transmitter, known as the transmitter rate, based on observational results from the Breakthrough Listen (BL) observations. We calculated the transmitter rate by considering the background galaxies in the field of view of target stars in BL observations. We used a statistical method to derive the total mass of stars in those background galaxies from a galaxy stellar mass function. Our statistical method suggests that less than one in hundreds of trillions of extragalactic civilizations within 969 Mpc possess a radio transmitter above 7.7$\times$10$^{26}$ W of power, assuming one civilization per one-solar-mass stellar system. Additionally, we cross-matched the BL survey fields with the WISE$\times$SuperCOSMOS Photometric Redshift Catalogue and compared with the statistical method. Our result sets the strictest limits to date on the transmitter rate at such high power levels, emphasizing the high efficiency of searching for radio transmitters in galaxies and the rarity of technologically advanced civilizations in our Universe.
Abstract: 2304.01174
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:IceCat-1: the IceCube Event Catalog of Alert Tracks
Download PDFAbstract: We present a catalog of likely astrophysical neutrino track-like events from the IceCube Neutrino Observatory. IceCube began reporting likely astrophysical neutrinos in 2016 and this system was updated in 2019. The catalog presented here includes events that were reported in real-time since 2019, as well as events identified in archival data samples starting from 2011. We report 275 neutrino events from two selection channels as the first entries in the catalog, the IceCube Event Catalog of Alert Tracks, which will see ongoing extensions with additional alerts. The gold and bronze alert channels respectively provide neutrino candidates with 50\% and 30\% probability of being astrophysical, on average assuming an astrophysical neutrino power law energy spectral index of 2.19. For each neutrino alert, we provide the reconstructed energy, direction, false alarm rate, probability of being astrophysical in origin, and likelihood contours describing the spatial uncertainty in the alert's reconstructed location. We also investigate a directional correlation of these neutrino events with gamma-ray and X-ray catalogs including 4FGL, 3HWC, TeVCat and Swift-BAT.
Abstract: 2304.03023
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Pitch-angle diffusion through localized interactions with sharp magnetic field bends in MHD turbulence
Download PDFAbstract: When a particle crosses a region of space where the curvature radius of the magnetic field line shrinks below the gyroradius $r_{\rm g}$, it experiences a non-adiabatic (magnetic moment violating) change in pitch-angle. The present paper carries that observation into MHD turbulence to examine the influence of intermittent, sharp bends of the magnetic field lines on particle transport. On the basis of dedicated measurements in a simulation of incompressible turbulence, it is argued that regions of sufficiently large curvature may exist in sufficient numbers on all scales to promote pitch-angle diffusion. The parallel mean free path predicted by the powerlaw statistics of the curvature strength scales as $\sim r_{\rm g}^{0.3}\,\ell_{\rm c}^{0.7}$ ($\ell_{\rm c}$ coherence scale of the turbulence), of direct interest to cosmic-ray phenomenology. Particle tracking in that numerical simulation confirms that the magnetic moment diffuses through localized, violent interactions, in agreement with the above picture. Correspondingly, the overall transport process is non-Brownian up to length scales $\gtrsim\ell_{\rm c}$.
Abstract: 2304.02988
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Azimuthal fluctuations and number of muons at the ground in muon-depleted proton air showers at PeV energies
Download PDFAbstract: Muon counting is an effective strategy for discriminating between gamma and hadron-initiated air showers. However, their detection, which requires shielded detectors, is highly costly and almost impossible to implement in large ${\rm km^2}$ environmentally sensitive areas. This work shows that the gamma/hadron discriminators, based on the new $LCm$ variable and the number of muons, have equivalent proton rejection levels at the PeV energies. It is, therefore, possible to build, at an affordable cost, a large, high-performant, wide field-of-view gamma-ray observatory.
Abstract: 2304.04796
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:The Large Array Survey Telescope -- System Overview and Performances
Download PDFAbstract: The Large Array Survey Telescope (LAST) is a wide-field visible-light telescope array designed to explore the variable and transient sky with a high cadence. LAST will be composed of 48, 28-cm f/2.2 telescopes (32 already installed) equipped with full-frame backside-illuminated cooled CMOS detectors. Each telescope provides a field of view (FoV) of 7.4 deg^2 with 1.25 arcsec/pix, while the system FoV is 355 deg^2 in 2.9 Gpix. The total collecting area of LAST, with 48 telescopes, is equivalent to a 1.9-m telescope. The cost-effectiveness of the system (i.e., probed volume of space per unit time per unit cost) is about an order of magnitude higher than most existing and under-construction sky surveys. The telescopes are mounted on 12 separate mounts, each carrying four telescopes. This provides significant flexibility in operating the system. The first LAST system is under construction in the Israeli Negev Desert, with 32 telescopes already deployed. We present the system overview and performances based on the system commissioning data. The Bp 5-sigma limiting magnitude of a single 28-cm telescope is about 19.6 (21.0), in 20 s (20x20 s). Astrometric two-axes precision (rms) at the bright-end is about 60 (30)\,mas in 20\,s (20x20 s), while absolute photometric calibration, relative to GAIA, provides ~10 millimag accuracy. Relative photometric precision, in a single 20 s (320 s) image, at the bright-end measured over a time scale of about 60 min is about 3 (1) millimag. We discuss the system science goals, data pipelines, and the observatory control system in companion publications.
Abstract: 2304.04864
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Simulated observations of star formation regions: infrared evolution of globally collapsing clouds
Download PDFAbstract: The direct comparison between hydrodynamical simulations and observations is needed to improve the physics included in the former and test biases in the latter. Post-processing radiative transfer and synthetic observations are now the standard way to do this. We report on the first application of the \texttt{SKIRT} radiative transfer code to simulations of a star-forming cloud. The synthetic observations are then analyzed following traditional observational workflows. We find that in the early stages of the simulation, stellar radiation is inefficient in heating dust to the temperatures observed in Galactic clouds, thus the addition of an interstellar radiation field is necessary. The spectral energy distribution of the cloud settles rather quickly after $\sim3$ Myr of evolution from the onset of star formation, but its morphology continues to evolve for $\sim8$ Myr due to the expansion of \textsc{Hii} regions and the respective creation of cavities, filaments, and ridges. Modeling synthetic \textit{Herschel} fluxes with 1- or 2-component modified black bodies underestimates total dust masses by a factor of $\sim2$. Spatially-resolved fitting recovers up to about $70\%$ of the intrinsic value. This ``missing mass'' is located in a very cold dust component with temperatures below $10$ K, which does not contribute appreciably to the far-infrared flux. This effect could bias real observations if such dust exists in large amounts. Finally, we tested observational calibrations of the SFR based on infrared fluxes and concluded that they are in agreement when compared to the intrinsic SFR of the simulation averaged over $\sim100$ Myr.
Abstract: 2304.04869
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:The James Webb Space Telescope Mission
Download PDFAbstract: Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least $4m$. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the $6.5m$ James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.
Abstract: 2304.05168
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Diffusive Shock Acceleration of Cosmic Rays -- Quasi-thermal and Non-thermal Particle Distributions
Download PDFAbstract: A well-known paradigm about the origin of Galactic cosmic rays (CRs) is that these high-energy particles are accelerated in the process of diffusive shock acceleration (DSA) at collisionless shocks (at least up to the so-called "knee"energy of $10^{15}$ eV). Knowing the details of injection of electrons, protons and heavier nuclei into the DSA, their initial and the resulting spectrum, is extremely important in many "practical" applications of the CR astrophysics, e.g. in modelling of the gamma or synchrotron radio emission of astrophysical sources. In this contribution I we will give an overview of the DSA theory and the results of observations and kinetic Particle-In-Cell (PIC) simulations that support the basic theoretical concepts. PIC simulations of quasi-parallel collisionless shocks show that thermal and supra-thermal proton distribution functions at the shock can be represented by a single quasi-thermal distribution - the $\kappa$-distribution that is commonly observed in out-of-equilibrium space plasmas. Farther downstream, index $\kappa$ increases and the low-energy spectrum tends to Maxwell distribution. On the other hand, higher-energy particles continue through the acceleration process and the non-thermal particle spectrum takes a characteristic power-law form predicted by the linear DSA theory. In the end, I will show what modification of the spectra is expected in the non-linear DSA, when CR back-reaction to the shock is taken into account.
Abstract: 2304.05348
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Applications of the gamma/hadron discriminator $LCm$ to realistic air shower array experiments
Download PDFAbstract: In this article, it is shown that the $C_k$ and $LCm$ variables, recently introduced as an effective way to discriminate gamma and proton-induced showers in large wide-field gamma-ray observatories, can be generalised to be used in arrays of different detectors and variable fill factors. In particular, the $C_k$ profile discrimination capabilities are evaluated for scintillator and water Cherenkov detector arrays.
Abstract: 2303.05712
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Detection of a new molecular cloud in the LHAASO J2108+5157 region supporting a hadronic PeVatron scenario
Download PDFAbstract: PeVatrons are the most powerful naturally occurring particle accelerators in the Universe. The identification of counterparts associated to astrophysical objects such as dying massive stars, molecular gas, star-forming regions, and star clusters is essential to clarify the underlying nature of the PeV emission, i.e., hadronic or leptonic. We present $^{12,13}$CO(J=2$\rightarrow$1) observations made with the 1.85~m radio-telescope of the Osaka Prefecture University toward the Cygnus OB7 molecular cloud, which contains the PeVatron candidate LHAASO J2108+5157. We investigate the nature of the sub-PeV (gamma-ray) emission by studying the nucleon density determined from the content of HI and H$_2$, derived from the CO observations. In addition to MML[2017]4607, detected via the observations of the optically thick $^{12}$CO(J=1$\rightarrow$0) emission, we infer the presence of an optically thin molecular cloud, named [FKT-MC]2022, whose angular size is 1.1$\pm$0.2$^{\circ}$. We propose this cloud as a new candidate to produce the sub-PeV emission observed in LHAASO J2108+5157. Considering a distance of 1.7 kpc, we estimate a nucleon (HI+H$_2$) density of 37$\pm$14 cm$^{-3}$, and a total nucleon mass(HI+H$_2$) of 1.5$\pm$0.6$\times$10$^4$ M$_{\odot}$. On the other hand, we confirm that Kronberger 82 is a molecular clump with an angular size of 0.1$^{\circ}$, a nucleon density $\sim$ 10$^3$ cm$^{-3}$, and a mass $\sim$ 10$^3$ M$_{\odot}$. Although Kronberger 82 hosts the physical conditions to produce the observed emission of LHAASO J2108+5157, [FKT-MC]2022 is located closer to it, suggesting that the latter could be the one associated to the sub-PeV emission. Under this scenario, our results favour a hadronic origin for the emission.
Abstract: 2303.13576
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Gamma-rays and neutrinos from supernovae of Type Ib/c with late time emission
Download PDFAbstract: Observations of some supernovae (SNe), such as SN 2014C, in the X-ray and radio wavebands revealed a rebrightening over a timescale of about a year since their detection. Such a discovery hints towards the evolution of a hydrogen-poor SN of Type Ib/c into a hydrogen-rich SN of Type IIn, the late time activity being attributed to the interaction of the SN ejecta with a dense hydrogen-rich circumstellar medium (CSM) far away from the stellar core. We compute the neutrino and gamma-ray emission from these SNe, considering interactions between the shock accelerated protons and the non-relativistic CSM protons. Assuming three CSM models inspired by recent electromagnetic observations, we explore the dependence of the expected multi-messenger signals on the CSM characteristics. We also investigate the detection prospects of current and upcoming gamma-ray (Fermi-LAT and Cerenkov Telescope Array) and neutrino (IceCube, IceCube-Gen2 and KM3NeT) telescopes. Our findings are in agreement with the non-detection of neutrinos and gamma-rays from past SNe exhibiting late time emission. Nevertheless, the detection prospects of SNe with late time emission in gamma-rays and neutrinos with the Cerenkov Telescope Array and IceCube-Gen2 (Fermi and IceCube) are promising and could potentially provide new insight into the CSM properties, if the SN burst should occur within $10$ Mpc ($4$ Mpc).
Abstract: 2304.00730
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:The High-Altitude Water Cherenkov (HAWC) Observatory in México: The Primary Detector
Download PDFAbstract: The High-Altitude Water Cherenkov (HAWC) observatory is a second-generation continuously operated, wide field-of-view, TeV gamma-ray observatory. The HAWC observatory and its analysis techniques build on experience of the Milagro experiment in using ground-based water Cherenkov detectors for gamma-ray astronomy. HAWC is located on the Sierra Negra volcano in México at an elevation of 4100 meters above sea level. The completed HAWC observatory principal detector (HAWC) consists of 300 closely spaced water Cherenkov detectors, each equipped with four photomultiplier tubes to provide timing and charge information to reconstruct the extensive air shower energy and arrival direction. The HAWC observatory has been optimized to observe transient and steady emission from sources of gamma rays within an energy range from several hundred GeV to several hundred TeV. However, most of the air showers detected are initiated by cosmic rays, allowing studies of cosmic rays also to be performed. This paper describes the characteristics of the HAWC main array and its hardware.
Abstract: 2304.05406
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Galactic ChitChat: Using Large Language Models to Converse with Astronomy Literature
Download PDFAbstract: We demonstrate the potential of the state-of-the-art OpenAI GPT-4 large language model to engage in meaningful interactions with Astronomy papers using in-context prompting. To optimize for efficiency, we employ a distillation technique that effectively reduces the size of the original input paper by 50\%, while maintaining the paragraph structure and overall semantic integrity. We then explore the model's responses using a multi-document context (ten distilled documents). Our findings indicate that GPT-4 excels in the multi-document domain, providing detailed answers contextualized within the framework of related research findings. Our results showcase the potential of large language models for the astronomical community, offering a promising avenue for further exploration, particularly the possibility of utilizing the models for hypothesis generation.
Abstract: 2304.05953
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Ice, Ice, Maybe? Investigating 46P/Wirtanen's Inner Coma For Icy Grains
Download PDFAbstract: The release of volatiles from comets is usually from direct sublimation of ices on the nucleus, but for very or hyper-active comets other sources have to be considered to account for the total production rates. In this work, we present new near-infrared imaging and spectroscopic observations of 46P/Wirtanen taken during its close approach to the Earth on 2018 December 19 with the MMIRS instrument at the MMT Observatory to search for signatures of icy or ice-rich grains in its inner coma that might explain its previously reported excess water production. The morphology of the images does not suggest any change in grain properties within the field of view, and the NIR spectra do not show the characteristic absorption features of water ice. Using a new MCMC-based implementation of the spectral modeling approach of Protopapa et al. (2018), we estimate the areal water ice fraction of the coma to be less than 0.6%. When combined with slit-corrected Afrho values for the J, H, and K bands and previously measured dust velocities for this comet, we estimate an icy grain production rate of less than 4.6 kg/s. This places a strict constraint on the water production rate from pure icy grains in the coma, and in turn we find that for the 2018-2019 apparition approximately 64% of 46P's surface was sublimating water near perihelion. WE then discuss 46P's modern properties within the context of other (formerly) hyper-active comets to understand how these complex objects evolve.
Abstract: 2201.03996
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Modelling the propagation of very-high-energy gamma rays with the CRbeam code: Comparison with CRPropa and ELMAG codes
Download PDFAbstract: Very-high-energy gamma rays produce electron positron pairs in interactions with low-energy photons of extragalactic background light during propagation through the intergalactic medium. The electron-positron pairs generate secondary gamma rays detectable by gamma-ray telescopes. This secondary emission can be used to detect intergalactic magnetic fields (IGMF) in the voids of large-scale structure. A new gamma-ray observatory, namely, Cherenkov Telescope Array (CTA), will provide an increase in sensitivity for detections of these secondary gamma-ray emission and enable the measurement of its properties for sources at cosmological distances. The interpretation of the CTA data, including detection of IGMF and study of its properties and origins, will require precision modeling of the primary and secondary gamma-ray fluxes. We asses the precision of the modeling of the secondary gamma-ray emission using model calculations with publicly available Monte-Carlo codes CRPropa and ELMAG and compare their predictions with theoretical expectations and with model calculations of a newly developed CRbeam code. We find that model predictions of different codes differ by up to 50% for low-redshift sources, with discrepancies increasing up to order-of-magnitude level with the increasing source redshifts. We identify the origin of these discrepancies and demonstrate that after eliminating the inaccuracies found, the discrepancies between the three codes are reduced to 10% when modeling nearby sources with z~0.1. We argue that the new CRbeam code provides reliable predictions for spectral, timing and imaging properties of the secondary gamma-ray signal for both nearby and distant sources with z~1. Thus, it can be used to study gamma-ray sources and IGMF with a level of precision that is appropriate for the prospective CTA study of the effects of gamma-ray propagation through the intergalactic medium.
Abstract: 2205.11538
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Interpretation of the observed neutrino emission from three Tidal Disruption Events
Download PDFAbstract: Three Tidal Disruption Event (TDE) candidates (AT2019dsg, AT2019fdr, AT2019aalc) have been associated with high energy astrophysical neutrinos in multi-messenger follow-ups. In all cases, the neutrino observation occurred O(100) days after the maximum of the optical-ultraviolet (OUV) luminosity. We discuss unified fully time-dependent interpretations of the neutrino signals where the neutrino delays are not a statistical effect, but rather the consequence of a physical scale of the post-disruption system. Noting that X-rays flares and infrared (IR) dust echoes have been observed in all cases, we consider three models in which quasi-isotropic neutrino emission is due to the interactions of accelerated protons of moderate, medium, and ultra-high energies with X-rays, OUV, and IR photons, respectively. We find that the neutrino time delays can be well described in the X-ray model assuming magnetic confinement of protons in a calorimetric approach if the unobscured X-ray luminosity is roughly constant over time, and in the IR model, where the delay is directly correlated with the time evolution of the echo luminosity (for which a model is developed here). The OUV model exhibits the highest neutrino production efficiency. In all three models, the highest neutrino fluence is predicted for AT2019aalc, due to its high estimated supermassive black hole mass and low redshift. All models result in diffuse neutrino fluxes that are consistent with observations.
Abstract: 2304.06068
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Probing neutrino production in high-energy astrophysical neutrino sources with the Glashow Resonance
Download PDFAbstract: The flavor composition of high-energy neutrinos carries important information about their birth. However, the two most common production scenarios, $pp$ (hadronuclear) and $p\gamma$ (photohadronic) processes, lead to the same flavor ratios when neutrinos and antineutrinos cannot be distinguished. The Glashow resonant interaction $\bar{\nu}_e+e^- \rightarrow W^-$ becomes a window to differentiate the antineutrino contribution from the total diffuse neutrino flux, thus lifting this degeneracy. We examine the power of Glashow resonant events in measuring the fraction of the $\bar{\nu}_e$ flux with current IceCube data, and produce projected sensitivities based on the combined exposure of planned Cherenkov neutrino telescopes around the globe. We find that $pp$ and $p\gamma$ can be distinguished at a 2$\sigma$ significance level in the next decades, in both an event-wise analysis and a more conservative statistical analysis, even with pessimistic assumptions on the spectral index of the astrophysical flux. Finally, we consider the sensitivity of future experiments to mixed production mechanisms.
Abstract: 2304.06271
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:A Contribution of the HAWC Observatory to the TeV era in the High Energy Gamma-Ray Astrophysics: The case of the TeV-Halos
Download PDFAbstract: We present a short overview of the TeV-Halos objects as a discovery and a relevant contribution of the High Altitude Water Čerenkov (HAWC) observatory to TeV astrophysics. We discuss history, discovery, knowledge, and the next step through a new and more detailed analysis than the original study in 2017. TeV-Halos will contribute to resolving the problem of the local positron excess observed on the Earth. To clarify the latter, understanding the diffusion process is mandatory.
Abstract: 2304.06291
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Far-infrared Polarization of the Supernova Remnant Cassiopeia A with SOFIA HAWC+
Download PDFAbstract: We present polarization observations of the young supernova remnant (SNR) Cas A using the High-resolution Airborne Wideband Camera-Plus (HAWC+) instrument onboard the Stratospheric Observatory for Infrared Astronomy (SOFIA). The polarization map at 154 microns reveals dust grains with strong polarization fractions (5 - 30 percent), supporting previous measurements made over a smaller region of the remnant at 850 microns. The 154 microns emission and the polarization signal is coincident with a region of cold dust observed in the southeastern shell and in the unshocked central ejecta. The highly polarized far-IR emission implies the grains are large (greater than 0.14 microns) and silicate-dominated. The polarization level varies across the SNR, with an inverse correlation between the polarization degree and the intensity and smaller polarization angle dispersion for brighter SNR emission. Stronger polarization is detected between the bright structures. This may result from a higher collision rate between the gas and dust producing a lower grain alignment efficiency where the gas density is higher. We use the dust emission to provide an estimate of the magnetic field strength in Cas A using the Davis-Chandrasekhar-Fermi method. The high polarization level is direct evidence that grains are highly elongated and strongly aligned with the magnetic field of the SNR. The dust mass from the polarized region is 0.14+-0.04 Msun, a lower limit of the amount of dust present within the ejecta of Cas A. This result strengthens the hypothesis that core-collapse SNe are an important contributor to the dust mass in high redshift galaxies.
Abstract: 2212.10059
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:CosmoDRAGoN simulations -- I. Dynamics and observable signatures of radio jets in cosmological environments
Download PDFAbstract: We present the Cosmological Double Radio Active Galactic Nuclei (CosmoDRAGoN) project: a large suite of simulated AGN jets in cosmological environments. These environments sample the intra-cluster media of galaxy clusters that form in cosmological smooth particle hydrodynamics (SPH) simulations, which we then use as inputs for grid-based hydrodynamic simulations of radio jets. Initially conical jets are injected with a range of jet powers, speeds (both relativistic and non-relativistic), and opening angles; we follow their collimation and propagation on scales of tens to hundreds of kiloparsecs, and calculate spatially-resolved synthetic radio spectra in post-processing. In this paper, we present a technical overview of the project, and key early science results from six representative simulations which produce radio sources with both core- (Fanaroff-Riley Type I) and edge-brightened (Fanaroff-Riley Type II) radio morphologies. Our simulations highlight the importance of accurate representation of both jets and environments for radio morphology, radio spectra, and feedback the jets provide to their surroundings.
Abstract: 2304.06905
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:How the Moon Impacts Subsea Communication Cables
Download PDFAbstract: We report tidal-induced latency variations on a transpacific subsea cable. Week-long recordings with a precision phase meter suggest length changes in the sub-meter range caused by the Poisson effect. The described method adds to the toolbox for the new field >>optical oceanic seismology<<.
Abstract: 2304.07055
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Optical characteristics and capabilities of the successive versions of Meudon and Haute Provence H$α$ heliographs (1954-2004)
Download PDFAbstract: H$\alpha$ heliographs are imaging instruments designed to produce monochromatic images of the solar chromosphere at fast cadence (60 s or less). They are designed to monitor efficiently dynamic phenomena of solar activity, such as flares or material ejections. Meudon and Haute Provence observatories started systematic observations in the frame of the International Geophysical Year (1957) with Lyot filters. This technology evolved several times until 1985 with tunable filters allowing to observe alternatively the line wings and core (variable wavelength). More than 6 million images were produced during 50 years, mostly on 35 mm films (catalogs are available on-line). We present in this paper the optical characteristics and the capabilities of the successive versions of the H$\alpha$ heliographs in operation between 1954 and 2004, and describe briefly the new heliograph (MeteoSpace) which will be commissioned in 2023 at Calern observatory.
Abstract: 2304.07179
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Results from the ARIANNA high-energy neutrino detector
Download PDFAbstract: The ARIANNA in-ice radio detector explores the detection of UHE neutrinos with shallow detector stations on the Ross Ice Shelf and the South Pole. Here, we present recent results that lay the foundation for future large-scale experiments. We show a limit on the UHE neutrino flux derived from ARIANNA data, measurements of the more abundant air showers, results from in-situ measurement campaigns, a study of a potential background from internal reflection layers, and give an outlook of future detector improvements.
Abstract: 2304.07321
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Constraints on the proton fraction of cosmic rays at the highest energies and the consequences for cosmogenic neutrinos and photons
Download PDFAbstract: Over the last decade, observations have shown that the mean mass of ultra-high-energy cosmic rays (UHECRs) increases progressively toward the highest energies. However, the precise composition is still unknown, and several theoretical studies hint at the existence of a subdominant proton component up to the highest energies. Motivated by the exciting prospect of performing charged-particle astronomy with ultra-high-energy (UHE) protons we quantify the level of UHE-proton flux that is compatible with present multimessenger observations and the associated fluxes of neutral messengers produced in the interactions of the protons. We study this scenario with numerical simulations of two independent populations of extragalactic sources and perform a fit to the combined UHECR energy spectrum and composition observables, constrained by diffuse gamma-ray and neutrino observations. We find that up to of order $10\%$ of the cosmic rays at the highest energies can be UHE protons, although the result depends critically on the selected hadronic interaction model for the air showers. Depending on the maximum proton energy ($E_\text{max}^\text{p}$) and the redshift evolution of sources, the associated flux of cosmogenic neutrinos and UHE gamma rays can significantly exceed the multimessenger signal of the mixed-mass cosmic rays. Moreover, if $E_\text{max}^\text{p}$ is above the GZK limit, we predict a large flux of UHE neutrinos above EeV energies that is absent in alternate scenarios for the origin of UHECRs. We present the implications and opportunities afforded by these UHE proton, neutrino and photon fluxes for future multimessenger observations.
Abstract: 2304.08132
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Prospects for ultra-high-energy particle acceleration at relativistic shocks
Download PDFAbstract: We study the acceleration of charged particles by ultra-relativistic shocks using test-particle Monte-Carlo simulations. Two field configurations are considered: (i) shocks with uniform upstream magnetic field in the plane of the shock, and (ii) shocks in which the upstream magnetic field has a cylindrical geometry. Particles are assumed to diffuse in angle due to frequent non-resonant scattering on small-scale fields. The steady-state distribution of particles' Lorentz factors is shown to approximately satisfy $dN/d\gamma \propto \gamma^{-2.2}$ provided the particle motion is scattering dominated on at least one side of the shock. For scattering dominated transport, the acceleration rate scales as $t_{\rm acc}\propto t^{1/2}$, though recovers Bohm scaling $t_{\rm acc}\propto t$ if particles become magnetised on one side of the shock. For uniform field configurations, a limiting energy is reached when particles are magnetised on both sides of the shock. For the cylindrical field configuration, this limit does not apply, and particles of one sign of charge will experience a curvature drift that redirects particles upstream. For the non-resonant scattering model considered, these particles preferentially escape only when they reach the confinement limit determined by the finite system size, and the distribution approaches the escapeless limit $dN/d\gamma \propto \gamma^{-1}$. The cylindrical field configuration resembles that expected for jets launched by the Blandford $\&$ Znajek mechanism, the luminous jets of AGN and GRBs thus provide favourable sites for the production of ultra-high energy cosmic rays.
Abstract: 2304.08202
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Prospects for annihilating dark matter from M31 and M33 observations with the Cherenkov Telescope Array
Download PDFAbstract: M31 and M33 are the closest spiral galaxies and the largest members (together with the Milky Way) of the Local group, which makes them interesting targets for indirect dark matter searches. In this paper we present studies of the expected sensitivity of the Cherenkov Telescope Array (CTA) to an annihilation signal from weakly interacting massive particles from M31 and M33. We show that a 100 h long observation campaign will allow CTA to probe annihilation cross-sections up to $\langle\sigma\upsilon\rangle\approx 5\cdot10^{-25}~\mathrm{cm^{3}s^{-1}}$ for the $\tau^{+}\tau^{-}$ annihilation channel (for M31, at a DM mass of 0.3 TeV), improving the current limits derived by HAWC by up to an order of magnitude. We present an estimate of the expected CTA sensitivity, by also taking into account the contributions of the astrophysical background and other possible sources of systematic uncertainty. We also show that CTA might be able to detect the extended emission from the bulge of M31, detected at lower energies by the Fermi/LAT.
Abstract: 2302.07723
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Search for neutrino counterparts to the gravitational wave sources from LIGO/Virgo O3 run with the ANTARES detector
Download PDFAbstract: Since 2015 the LIGO and Virgo interferometers have detected gravitational waves from almost one hundred coalescences of compact objects (black holes and neutron stars). This article presents the results of a search performed with data from the ANTARES telescope to identify neutrino counterparts to the gravitational wave sources detected during the third LIGO/Virgo observing run and reported in the catalogues GWTC-2, GWTC-2.1, and GWTC-3. This search is sensitive to all-sky neutrinos of all flavours and of energies $>100$ GeV, thanks to the inclusion of both track-like events (mainly induced by $\nu_\mu$ charged-current interactions) and shower-like events (induced by other interaction types). Neutrinos are selected if they are detected within $\pm 500$ s from the GW merger and with a reconstructed direction compatible with its sky localisation. No significant excess is found for any of the 80 analysed GW events, and upper limits on the neutrino emission are derived. Using the information from the GW catalogues and assuming isotropic emission, upper limits on the total energy $E_{\rm tot, \nu}$ emitted as neutrinos of all flavours and on the ratio $f_\nu = E_{\rm tot, \nu}/E_{\rm GW}$ between neutrino and GW emissions are also computed. Finally, a stacked analysis of all the 72 binary black hole mergers (respectively the 7 neutron star - black hole merger candidates) has been performed to constrain the typical neutrino emission within this population, leading to the limits: $E_{\rm tot, \nu} < 4.0 \times 10^{53}$ erg and $f_\nu < 0.15$ (respectively, $E_{\rm tot, \nu} < 3.2 \times 10^{53}$ erg and $f_\nu < 0.88$) for $E^{-2}$ spectrum and isotropic emission. Other assumptions including softer spectra and non-isotropic scenarios have also been tested.
This page created: Thu Apr 20 11:03:37 ACST 2023 by rburley
For a printable title listing click here
For details on generating this page see the instructions. If there are problems with this page (and I expect there will be from time to time) contact Jose.
For previous lists of abstracts of interest click Previous abstracts of interest