Abstracts of Interest
Selected by:
Teddy McKennall
Abstract: 2409.07515
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Anomalous Ionization in the Central Molecular Zone by sub-GeV Dark Matter
View PDF HTML (experimental)Abstract:We demonstrate that the anomalous ionization rate observed in the Central Molecular Zone can be attributed to MeV dark matter annihilations into $e^+e^-$ pairs for galactic dark matter profiles with slopes $\gamma>1$. The low annihilation cross-sections required avoid cosmological constraints and imply no detectable inverse Compton, bremsstrahlung or synchrotron emissions in radio, X and gamma rays. The possible connection to the source of the unexplained 511 keV line emission in the Galactic Center suggests that both observations could be correlated and have a common origin.
Abstract: 2409.07511
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Initial performance of the Radar Echo Telescope for Cosmic Rays, RET-CR
View PDF HTML (experimental)Abstract:The Radar Echo Telescope for Cosmic Rays (RET-CR), a pathfinder instrument for the radar echo method of ultrahigh energy (UHE) neutrino detection, was initially deployed near Summit Station, Greenland, in May 2023. After a 4 week commissioning period, 9 days of data were taken before the instrument went offline. In this article, we describe the instrument as it was deployed, and the initial performance of the detector. We show that the technical aspects of running a radar based particle cascade detector in the ice have been demonstrated. Analysis of the 2023 data informed improvements that were incorporated into the May-August 2024 deployment, which has just concluded at time of writing. Results from the 2024 run will be presented in forthcoming publications.
Abstract: 2409.06841
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Resolution of (Heavy) Primaries in Ultra High Energy Cosmic Rays
View PDF HTML (experimental)Abstract:Measurements of Ultra-High Energy Cosmic Rays (UHECR) suggest a complex composition with significant contributions from heavy nuclei at the highest energies. We systematically explore how the selection and number of primary nuclei included in the analysis impact the inferred UHECR mass composition. Introducing a distance measure in the space of $X_{\rm max}$ distribution moments, we demonstrate that limiting the analysis to a few primaries can introduce significant biases, particularly as observational data improves. We provide lists of primaries approximately equidistant in the new measure, which guaranty unbiased results at given statistical confidence. Additionally, we explore consistent inclusion of nuclei heavier than iron and up to plutonium, deriving first observational upper bounds on their contributions to UHECR with the Pierre Auger Open Data.
Abstract: 2409.06435
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:CTC and CT5TEA: an advanced multi-channel digitizer and trigger ASIC for imaging atmospheric Cherenkov telescopes
View PDF HTML (experimental)Abstract:We have developed a new set of Application-Specific Integrated Circuits (ASICs) of the TARGET family (CTC and CT5TEA), designed for the readout of signals from photosensors in cameras of Imaging Atmospheric Cherenkov Telescopes (IACTs) for ground-based gamma-ray astronomy. We present the performance and design details. Both ASICs feature 16 channels, with CTC being a Switched-Capacitor Array (SCA) sampler at 0.5 to 1 GSa/s with a 16,384 sample deep storage buffer, including the functionality to digitize full waveforms at arbitrary times. CT5TEA is its companion trigger ASIC (though may be used on its own), which provides trigger information for the analog sum of four (and 16) adjacent channels. Since sampling and triggering takes place in two separate ASICs, the noise due to interference from the SCA is suppressed, and allows a minimal trigger threshold of $\leq$ 2.5 mV (0.74 photo electrons (p.e.)) with a trigger noise of $\leq$ 0.5 mV (0.15 p.e.). For CTC, a maximal input voltage range from $-$0.5 V up to 1.7 V is achieved with an effective bit range of $>$ 11.6 bits and a baseline noise of 0.7 mV. The cross-talk improved to $\leq$ 1% over the whole $-$3 dB bandwidth of 220 MHz and even down to 0.2% for 1.5 V pulses of 10 ns width. Not only is the performance presented, but a temperature-stable calibration routine for pulse mode operation is introduced and validated. The resolution is found to be $\sim$ 2.5% at 33.7 mV (10 p.e.) and $\leq$ 0.3% at 337 mV (100 p.e.) with an integrated non-linearity of $<$ 1.6 mV. Developed for the Small-Sized Telescope (SST) and Schwarzschild-Couder Telescope (SCT) cameras of the Cherenkov Telescope Array Observatory (CTAO), CTC and CT5TEA are deployed for both prototypes and shall be integrated into the final versions.
Abstract: 2409.05932
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Effect of inelastic scattering on cosmic-ray-boosted dark matter
View PDF HTML (experimental)Abstract:Sub-GeV dark matter particles evade standard direct detection studies since their typical energies in the galactic halo do not allow for detectable recoil of the heavy nuclei in the detectors. However, it was noted that if the dark matter particles have sizable couplings to nucleons, they can be boosted by interactions with galactic cosmic rays and probed by experiments like Xenon-1T. We revisit the resulting bounds on DM-nucleon interaction and improve on previous works by considering the DM-nucleus inelastic cross sections provided by the GENIE interaction event generator. Including inelastic scattering in the process of dark matter boosting increases the flux of high-energy dark matter coming to Earth. Additionally, allowing for inelastic scattering with nuclei is important for a realistic description of the dark matter interacting in the Earth's crust. We demonstrate these effects on a benchmark model where dark matter interactions are mediated by a dark U(1) vector boson.
Abstract: 2409.05739
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Exploring the intermittency of magnetohydrodynamic turbulence by synchrotron polarization radiation
View PDF HTML (experimental)Abstract:Magnetohydrodynamic (MHD) turbulence plays a critical role in many key astrophysical processes such as star formation, acceleration of cosmic rays, and heat conduction. However, its properties are still poorly understood. We explore how to extract the intermittency of compressible MHD turbulence from the synthetic and real observations. The three statistical methods, namely the probability distribution function, kurtosis, and scaling exponent of the multi-order structure function, are used to reveal the intermittency of MHD turbulence. Our numerical results demonstrate that: (1) the synchrotron polarization intensity statistics can be used to probe the intermittency of magnetic turbulence, by which we can distinguish different turbulence regimes; (2) the intermittency of MHD turbulence is dominated by the slow mode in the sub-Alfv{é}nic turbulence regime; (3) the Galactic interstellar medium (ISM) at the low latitude region corresponds to the sub-Alfvénic and supersonic turbulence regime. We have successfully measured the intermittency of the Galactic ISM from the synthetic and realistic observations.
Abstract: 2409.05509
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Origin of the break in the cosmic-ray electron plus positron spectrum at ~ 1 TeV
View PDF HTML (experimental)Abstract:Recent measurements of the cosmic-ray electron plus positron spectrum by several experiments have confirmed the presence of a break at $\sim\,1$ TeV. The origin of the break is still not clearly understood. In this work, we explore different possibilities for the origin which include an electron source spectrum with a broken power-law, a power-law with an exponential or super-exponential cut-offs and the absence of potential nearby cosmic-ray sources. Based on the observed electron plus positron data from the DAMPE and the H.E.S.S experiments, and considering supernova remnants as the main sources of cosmic rays in the Galaxy, we find statistical evidence in favour of the scenario with a broken power-law source spectrum with the best-fit source parameters obtained as $\Gamma=2.39$ for the source spectral index, $E_0\approx 1.6$ TeV for the break energy and $f=1.59\times 10^{48}$ ergs for the amount of supernova kinetic energy injected into cosmic-ray electrons. Such a power-law break in the spectrum has been predicted for electrons confined inside supernova remnants after acceleration via diffusive shock acceleration process, and also indicated by the multi-wavelength study of supernova remnants. All these evidences have shown that the observed spectral break provides a strong indication of a direct link between cosmic-ray electrons and their sources. Our findings further show that electrons must undergo spectral changes while escaping the source region in order to reconcile the difference between the spectral index of electrons observed inside supernova remnants and that obtained from Galactic cosmic-ray propagation studies.
Abstract: 2409.05256
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:3D hybrid fluid-particle jet simulations and the importance of synchrotron radiative losses
View PDF HTML (experimental)Abstract:Context. Relativistic jets in active galactic nuclei are known for their exceptional energy output, and imaging the synthetic synchrotron emission of numerical jet simulations is essential for a comparison with observed jet polarization emission. Aims. Through the use of 3D hybrid fluid-particle jet simulations (with the PLUTO code), we overcome some of the commonly made assumptions in relativistic magnetohydrodynamic (RMHD) simulations by using non-thermal particle attributes to account for the resulting synchrotron radiation. Polarized radiative transfer and ray-tracing (via the RADMC-3D code) highlight the differences in total intensity maps when (i) the jet is simulated purely with the RMHD approach, (ii) a jet tracer is considered in the RMHD approach, and (iii) a hybrid fluid-particle approach is used. The resulting emission maps were compared to the example of the radio galaxy Centaurus A. Methods. We applied the Lagrangian particle module implemented in the latest version of the PLUTO code. This new module contains a state-of-the-art algorithm for modeling diffusive shock acceleration and for accounting for radiative losses in RMHD jet simulations. The module implements the physical postulates missing in RMHD jet simulations by accounting for a cooled ambient medium and strengthening the central jet emission. Results. We find a distinction between the innermost structure of the jet and the back-flowing material by mimicking the radio emission of the Seyfert II radio galaxy Centaurus A when considering an edge-brightened jet with an underlying purely toroidal magnetic field. We demonstrate the necessity of synchrotron cooling as well as the improvements gained when directly accounting for non-thermal synchrotron radiation via non-thermal particles.
Abstract: 2409.04580
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:GRB 221009A: the B.O.A.T Burst that Shines in Gamma Rays
View PDF HTML (experimental)Abstract:We present a complete analysis of Fermi Large Area Telescope (LAT) data of GRB 221009A, the brightest Gamma-Ray Burst (GRB) ever detected. The burst emission above 30 MeV detected by the LAT preceded by 1 s the low-energy (< 10 MeV) pulse that triggered the Fermi Gamma-Ray Burst Monitor (GBM), as has been observed in other GRBs. The prompt phase of GRB 221009A lasted a few hundred seconds. It was so bright that we identify a Bad Time Interval (BTI) of 64 seconds caused by the extremely high flux of hard X-rays and soft gamma rays, during which the event reconstruction efficiency was poor and the dead time fraction quite high. The late-time emission decayed as a power law, but the extrapolation of the late-time emission during the first 450 seconds suggests that the afterglow started during the prompt emission. We also found that high-energy events observed by the LAT are incompatible with synchrotron origin, and, during the prompt emission, are more likely related to an extra component identified as synchrotron self-Compton (SSC). A remarkable 400 GeV photon, detected by the LAT 33 ks after the GBM trigger and directionally consistent with the location of GRB 221009A, is hard to explain as a product of SSC or TeV electromagnetic cascades, and the process responsible for its origin is uncertain. Because of its proximity and energetic nature, GRB 221009A is an extremely rare event.
Abstract: 2409.05501
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:On the model uncertainties for the predicted maximum depth of extensive air showers
View PDF HTML (experimental)Abstract:A quantitative analysis of model uncertainties for calculations of the maximum depth of proton-initiated extensive air showers (EAS) has been performed. Staying within the standard physics picture and using the conventional approach to the treatment of high energy interactions, we found that present uncertainties on the energy dependence of the inelastic cross section, the rate of diffraction, and the inelasticity of hadronic collisions allow one to increase the predicted average EAS maximum depth by about 10 g/cm$^2$. Invoking more exotic assumptions regarding a potentially significant modification of the parton hadronization procedure by hypothetical collective effects, we were able to change drastically the predicted energy dependence of the inelasticity of proton-air interactions and to increase thereby the predicted EAS maximum depth by up to $\simeq 30$ g/cm$^2$. However, those latter modifications are disfavored by the data of the LHCf experiment, regarding forward neutron production in proton-proton collisions at the Large Hadron Collider, and by measurements of the muon production depth by the Pierre Auger Observatory.
Abstract: 2409.04472
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Study of acoustic neutrino detection in O$ν$DE-2 raw acoustic data
View PDF HTML (experimental)Abstract:Research suggests that acoustic technology may be able to detect ultra-high-energy neutrinos if a large amount of non-linear fluid is analyzed. When a neutrino interacts in water, it creates a quasi-instantaneous cascade of particles, heating that region of the fluid and emitting a tiny acoustic signal. This rapid heating produces a thermoacoustic Bipolar Pulse (BP) with unique characteristics such as a wide bandwidth and a narrow directivity for these frequencies. While dedicated devices for acoustic neutrino detection are currently non-existent, there are a few underwater neutrino telescopes that utilize optical technology, but often with an acoustic positioning system that deploys hydrophones in the infrastructure. The possibility of using them to study a BP caused by a neutrino interaction is currently being discussed. This study aims to evaluate the implementation of a trigger system to detect a possible BP in deep-sea hydrophones. For this, up to 24 hours of the raw acoustic signal recorded by the O$\nu$DE-2 station, which was located 25 km off-shore from Catania in the Western Ionian Sea, at 2100 m depth, is analyzed. The station used calibrated hydrophones from a few Hz to 70 kHz. In this work, a synthetic BP is created and added to the experimental data, allowing the study of its detection and the calculation of precision and recall.
Abstract: 2409.04165
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Multi-epoch leptohadronic modeling of neutrino source candidate blazar PKS 0735+178
View PDF HTML (experimental)Abstract:The origin of the astrophysical neutrino flux discovered by IceCube remains largely unknown. Several individual neutrino source candidates were observed. Among them is the gamma-ray flaring blazar TXS 0506+056. A similar coincidence of a high-energy neutrino and a gamma-ray flare was found in blazar PKS 0735+178. By modeling the spectral energy distributions of PKS 0735+178, we expect to investigate the physical conditions for neutrino production during different stages of the source activity. We analyze the multi-wavelength data during the selected periods of time. Using numerical simulations of radiation processes in the source, we study the parameter space of one-zone leptonic and leptohadronic models and find the best-fit solutions that explain the observed photon fluxes. We show the impact of model parameter degeneracy on the prediction of the neutrino spectra. We show that the available mutli-wavelength data are not sufficient to predict the neutrino spectrum unambiguously. Still, under the condition of maximal neutrino flux, we propose a scenario in which 0.2 neutrino events are produced during the 50 days flare.
Abstract: 2409.03854
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Progress towards an array-wide diffuse UHE neutrino search with the Askaryan Radio Array
View PDF HTML (experimental)Abstract:The Askaryan Radio Array (ARA) is an in-ice ultrahigh energy (UHE) neutrino experiment at the South Pole. ARA aims to detect the radio emissions from neutrino-induced particle showers using in-ice clusters of antennas buried ${\sim}200$ m deep on a roughly cubical lattice with side length of ${\sim}10$ m. ARA has five such independent stations which have collectively accumulated ${\sim}30$ station-years of livetime through 2023. The fifth station of ARA has an additional sub-detector, known as the phased array, which pioneered an interferometric trigger constructed by beamforming the signals of $7$ tightly packed, vertically-polarized antennas. This scheme has been demonstrated to significantly improve the trigger efficiency for low SNR signals. In this talk, we will present the current state of the first array-wide diffuse neutrino search using $24$ station-years of data (through 2021). We anticipate that this analysis will result in the first UHE neutrino observation or world-leading limits from a radio neutrino detector below $100$ EeV. Additionally, this analysis will demonstrate the feasibility for multi-station in-ice radio arrays to successfully conduct an array-wide neutrino search -- paving the way for future, large detector arrays such as RNO-G and IceCube-Gen2 Radio.
Abstract: 2409.07916
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Follow-up of Neutron Star Mergers with CTA and Prospects for Joint Detection with Gravitational-Wave Detectors
View PDF HTML (experimental)Abstract:The joint gravitational wave (GW) and electromagnetic observations of the binary neutron star (BNS) merger GW170817 marked a giant leap in multi-messenger astrophysics. The extensive observation campaign of the associated Gamma-Ray Burst (GRB) and its afterglow has strengthened the hypothesis associating GRBs with BNS mergers and provided insights on mass ejection, particularly the relativistic outflow launched in BNS mergers. In this paper, we investigate the joint detection probabilities of BNS mergers by GW detectors and the upcoming ground-based very-high-energy (VHE) $\gamma$-ray instrument, the Cherenkov Telescope Array (CTA). Using an empirical relation that constrains the distance-inclination angle plane, we simulated BNS mergers detectable in the O5 run of the LIGO/Virgo/Kagra (LVK) network with $300$~Mpc BNS horizon. Assuming Gaussian structured jets and ignoring large sky localization challenges of GW detectors, we estimated VHE afterglow detection probability by CTA. We have explored the afterglow parameter space to identify conditions favourable for detecting synchrotron self-Compton emission by CTA. Our study reveals that events viewed at angles $\lesssim3$ times the jet core angle are detectable by CTA when the initial bulk Lorentz factor at the jet axis ranges between 100 and 800. We find high kinetic energy ($E_k>10^{50}$ erg), ambient density ($n_0>10^{-1}$ $cm^{-3}$), and energy content in non-thermal electrons significantly enhance the likelihood of CTA detection within 300 Mpc. The joint detection rate varies significantly with afterglow parameter distributions, ranging from $0.003$ to $0.5$ per year.
Abstract: 2409.07905
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Supernova remnants in clumpy medium: A model of hydrodynamic and radio synchrotron evolution
View PDF HTML (experimental)Abstract:We present an analytical model of $\Sigma-D$ relation for supernova remnants (SNRs) evolving in a clumpy medium. The model and its approximations were developed using the hydrodynamic simulations of SNRs in environments of low-density bubbles and clumpy media with different densities and volume-filling factors. For calculation of SNR luminosities we developed the synchrotron emission model, implying the test-particle approximation. The goal of this work is to explain the flattened part of $\Sigma-D$ relation for Galactic SNRs at $D\approx14-50$ pc. Our model shows that the shock collision with the clumpy medium initially enhances the brightness of individual SNRs, which is followed by a steeper fall of their $\Sigma-D$ curve. We used the analytical model to generate large SNR samples on $\Sigma-D$ plane, within a span of different densities and distances to clumpy medium, keeping the observed distribution of diameters. After comparison with the Galactic sample, we conclude that the observed $\Sigma-D$ flattening and scatter originates in sporadic emission jumps of individual SNRs while colliding with the dense clumps. Statistically, the significant impact of the clumps starts at diameters of $\approx14$ pc, up to $\sim70$ pc, with the average density jump at clumpy medium of $\sim2-20$ times, roughly depending on the low density of circumstellar region. However, additional analysis considering the selection effects is needed, as well as the improvement of the model, considering radiation losses and thermal conduction.
Abstract: 2409.05505
Full Text: [ PostScript, PDF]
Full Text: [ PostScript, PDF]
Title:Astroaccesible: A multi-messenger outreach for a multi-messenger science
View PDF HTML (experimental)Abstract:This contribution summarizes the main activities and objectives of the outreach project Astroaccesible, whose main aim is to carry the teaching and diffusion of astronomy among all kinds of collectives, focusing on blind and visually impaired (BVI) people. This project is led by a blind astronomer and aims to use a variety of resources based on different sensory channels, avoiding limiting the transmission of concepts to visual perception. This principle favors inclusion and benefits everyone, as the information is not presented using just one channel. This strategy is especially convenient for the nowadays typical data acquisition, where a variety of sources of information, not solely based on the collection of different spectral domains of electromagnetic radiation, is used. Moreover, the study of new multi-messenger astronomy could be much better understood using a multi-messenger teaching approach, favoring inclusion, motivation, and creativity.
This page created: Mon Sep 16 10:23:41 ACST 2024 by Teddy McKennall
For a printable title listing click here
For details on generating this page see the instructions. If there are problems with this page contact Violet.
For previous lists of abstracts of interest click Previous abstracts of interest