Astrophysical Energies Research Articles

Overestimation of Astrophysical Gamma-Ray Energies during Thunderstorms: Synergy of Galactic and Atmospheric Accelerators

Particle accelerators abound in space plasmas, saturating the cosmos with fully stripped nuclei and gamma rays, with energies surpassing the capabilities of human-made accelerators by orders of magnitude. Upon reaching Earth’s atmosphere, these particles trigger extensive air showers (EASs), generating millions of secondary cosmic rays of lower energies. Free electrons from EASs developing in the atmosphere are seeds for atmospheric electron accelerators. Strong atmospheric electric fields (AEFs) evolving during thunderstorms act as accelerators, amplifying the intensity of electrons many times, significantly enlarging the EAS size (number of electrons). Thus, the energy of the primary cosmic ray recovered by EAS size can be significantly overestimated. Recently discovered by high-altitude EAS arrays, PeVatron candidates (ultra–high-energy (UHE) astrophysical gamma-ray sources) must be carefully examined according to the atmospheric conditions during EAS detection. Large High Altitude Air Shower Observatory and High-Altitude Water Cherenkov Observatory arrays are located in regions of frequent thunderstorms, and an AEF’s strength can reach and surpass the critical strength to start relativistic runaway electron avalanches. A few registered UHE gamma rays from stellar sources can be registered at just this time when the AEF highly enhances the EAS size. Thunderstorm ground enhancements are copiously registered at mountain peaks of Eastern Europe, Germany, and Armenia, with energies well above the threshold energy of EAS array scintillators. Thus, the overestimation of the energy of primary particles is not an exotic process but a consequence of already well-established physical phenomena. Consequently, a report on each registered UHE gamma ray should include the recorded time and corresponding weather conditions.

Indirect Measurement of the 3He(n,p)3H Reaction Cross Section at Big Bang Energies

Abstract Neutron-induced nuclear reactions play an important role in the Big Bang Nucleosynthesis. Their excitation functions are, from an experimental point of view, usually difficult to measure. Nevertheless, in the last decades, big efforts have led to a better understanding of their role in the primordial nucleosynthesis network. In this work, we apply the Trojan Horse Method to extract the cross section at astrophysical energies for the 3He(n,p)3H reaction after a detailed study of the 2H(3He,pt)H three-body process. Data extracted from the present measurement are compared with other published sets. The reaction rate is also calculated, and the impact on the Big Bang nucleosynthesis is examined in detail.

Direct and Indirect Measurements of the 19F(p,α)16O Reaction at Astrophysical Energies Using the LHASA Detector and the Trojan Horse Method

Fluorine is one of the most interesting elements in nuclear astrophysics. Its abundance can provide important hints to constrain the stellar models since fluorine production and destruction are strictly connected to the physical conditions inside the stars. The 19F(p,α)16O reaction is one of the fluorine burning processes and the correction evaluation of its reaction rate is of pivotal importance to evaluate the fluorine abundance. Moreover, the 19F(p,α)16O reaction rate can have an impact for the production of calcium in the first-generation of Population III stars. Here, we present the AsFiN collaboration efforts to the study of the 19F(p,α)16O reaction by means of direct and indirect measurements. On the direct measurements side, an experimental campaign aimed to the measurement of the 19F(p,α0,π)16O reaction is ongoing, taking advantage of the new versatile arrays of silicon strip detectors, LHASA and ELISSA. Moreover, the Trojan Horse Method (THM) was used to determine the 19F(p,α0)16O reaction S(E)-factor in the energy range of astrophysical interest (Ecm≈ 0–1 MeV), showing, for the first time, the presence of resonant structures within the astrophysical energy range. THM has been also applied for the study of the 19F(p,απ)16O reaction; data analysis is ongoing.

Experimental Determination of α Widths of ^{21}Ne Levels in the Region of Astrophysical Interest: New ^{17}O+α Reaction Rates and Impact on the Weak s Process.

The efficiency of the weak s process in low-metallicity rotating massive stars depends strongly on the rates of the competing ^{17}O(α,n)^{20}Ne and ^{17}O(α,γ)^{21}Ne reactions that determine the potency of the ^{16}O neutron poison. Their reaction rates are poorly known in the astrophysical energy range of interest for core helium burning in massive stars because of the lack of spectroscopic information (partial widths, spin parities) for the relevant states in the compound nucleus ^{21}Ne. In this Letter, we report on the first experimental determination of the α-particle spectroscopic factors and partial widths of these states using the ^{17}O(^{7}Li,t)^{21}Ne α-transfer reaction. With these the ^{17}O(α,n)^{20}Ne and ^{17}O(α,γ)^{21}Ne reaction rates were evaluated with uncertainties reduced by a factor more than 3 with respect to previous evaluations and the present ^{17}O(α,n)^{20}Ne reaction rate is more than 20 times larger. The present (α,n)/(α,γ) rate ratio favors neutron recycling and suggests an enhancement of the weak s process in the Zr-Nd region by more than 1.5 dex in metal-poor rotating massive stars.

$$^6{\textrm{Li}}$$ as a Three-Body System in the (p,$$^3{\textrm{He}}$$) Reaction at Astrophysical Energies

$$^6{\textrm{Li}}$$ as a Three-Body System in the (p,$$^3{\textrm{He}}$$) Reaction at Astrophysical Energies

Shedding light on 17O(n,α)14C reaction at astrophysical energies with Trojan Horse Method and Asymptotic Normalization Coefficient

Shedding light on ¹⁷O(n,α)¹⁴C reaction at astrophysical energies with Trojan Horse Method and Asymptotic Normalization Coefficient

Using indirect methods to explore low-energy fusion cross sections in nuclear astrophysics

Nuclear reactions within stellar environments typically manifest at energies well below 1 MeV. As a consequence, the Coulomb barrier strongly suppresses the cross section, diminishing it to values as minute as a few nanobarns for charged particles. This challenge in obtaining precise input data for astrophysics has prompted the utilization of indirect methodologies. Specifically, approaches such as ANC and THM have been employed to ascertain cross sections for reactions involving photons and charged particles in the exit channel, respectively, obviating the necessity for extrapolation. The discourse explores recent findings arising from the application of these methodologies. For example, the measurement of 6Li(3He,d)7Be is employed to infer the ANC’s of the 3He+4He→ 7Be and p+6Li→ 7Be channels, along with their corresponding radiative-capture cross sections. Furthermore, the THM measurement of the 27Al(p, α)24Mg cross section via the 2H(27Al,α 24Mg)n reaction is emphasized. In both instances, the cross section at astrophysical energies has been ascertained with unparalleled precision.

The Virtual Research Environment: A multi-science analysis platform

One of the objectives of the ESCAPE collaboration, within the context of the implementation of the European Open Science Cloud, is integrating analysis workflows from Cosmology, Astrophysics and High Energy Physics into a common framework, making it easier for researchers to share data, software and analysis code. The development of the ESCAPE Science Projects (Dark Matter and Extreme Universe) relies on the implementation of the Virtual Research Environment, a prototype analysis platform deployed in the respect of FAIR data principles. The Virtual Research Environment’s main components are (1) an Authentication and Authorization layer, (2) a federated distributed storage solution, providing functionalities for data injection and replication through a Data Management and Orchestration software, (3) an interactive notebook interface that hides the complexity of the underlying infrastructure and facilitates browsing data catalogues and (4) computing processing power to run full end-to-end analyses through workflow schedulers and resource managers that also allow for pipelines’ preservation. This contribution will depict the collection of services and technologies that compose the Virtual Research Environment, hosted on a cloud infrastructure and managed by an open source, publicly available repository.

The 19F(p, α1,2) reaction studied via Trojan Horse Method in astrophysical range of interest

The complex reaction network connected to the 19F stellar abundance is very sensitive to the physical condition in stars. To overcome difficulties present in the direct measurements, mainly the very low cross section in the astrophysical energy range due to the Coulomb repulsion, an indirect measurement of the 19F(p, α) reaction, with the Trojan Horse Method (THM), was performed at INFN-LNS. While the method had been successfully used to study α0 channel, in the present analysis focus was given to the α1,2 channels, where better knowledge of the reaction rates at low energies is required, obtainable by employing the THM method.

Analysis of fusion cross-section and S-factor of 13C + 12,13C reactions for different density distributions at astrophysical energies

The effect of the various density distributions on 13C + 12,13C reactions is investigated by using the optical model at energies near and below Coulomb barrier. For this purpose, five different density distributions of the 12C and 13C nuclei are used to produce the real potential over the double folding model. To make a comprehensive analysis, the fusion cross-sections, S-factor and elastic cross-sections are simultaneously analyzed at astrophysical energies. It is seen that the theoretical results are in good agreement with the experimental data. In this study, the hindrance characteristics of the S-factors for the 13C + 12,13C reactions are also examined at low energies, and hindrance behavior is not observed.

Cosmic implications of the reaction: a nuclear astrophysical perspective

We conducted a comprehensive study of the neutron capture cross section of within the relevant astrophysical energy range. Through rigorous R-matrix analysis, we determined the Maxwellian-averaged cross section to be 11.98 0.25 μb at kT = 30 keV. This result is approximately four times higher than the thermal neutron capture cross section estimated in earlier studies assuming the law. The implications of our findings extend to the region of inhomogeneous Big-Bang models in nuclear astrophysics, where understanding the behaviour of neutron capture cross sections plays a crucial role in elucidating the intricate processes that shaped the early universe.

Triton-alpha radiative capture reaction at astrophysical energies

Triton-alpha radiative capture reaction at astrophysical energies

Investigation of the 121Sb(α,γ)125I reaction cross-section calculations at astrophysical energies

Investigation of the 121Sb(α,γ)125I reaction cross-section calculations at astrophysical energies

IceCat-1: The IceCube Event Catalog of Alert Tracks

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 a 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.

Lithium photodisintegration with linearly polarized photons at astrophysical energies

ABSTRACT We present here a model-independent theoretical discussion of differential cross-sections in photodisintegration of lithium with unpolarized and linearly polarized photons. In recent years, experimental measurements are being carried out on the photodisintegration of lithium in the reaction channel 7Li(γ, n)6Li to study the angular dependence of cross-section. In this regard, we have studied the spin structure of amplitudes in 7Li(γ, n)6Li by expressing the differential cross-section in terms of Legendre polynomials.

Estimation of the S34(0) S-factor for 3He(α, γ)7Be reaction by using distorted wave born approximation and artificial neural network

The astrophysical S-factor and total cross-section of radiative capture reaction are analyzed using the first-order distorted wave born approximation and artificial neural network. To make estimations of S34(0) at energies going to zero, we have used an artificial neural network model as a new approximation in this area. First, we obtain distorted wave born approximation results using the Gaussian and Woods-Saxon potentials. After, we evaluate artificial neural network approximation to analyze reaction observables of the system. Our results show that artificial neural network model is a powerful candidate as an extrapolation model for astrophysical energies for estimating of the S-factor observable.

Elastic Scattering of Proton from Oxygen at Astrophysical Energies

Elastic Scattering of Proton from Oxygen at Astrophysical Energies

Retraction Note: Direct measurements of the 12C + 12C reactions cross-sections towards astrophysical energies

Retraction Note: Direct measurements of the 12C + 12C reactions cross-sections towards astrophysical energies

Waveform uncertainty quantification and interpretation for gravitational-wave astronomy

We demonstrate how to quantify the frequency-domain amplitude and phase accuracy of waveform models, and δφ, in a form that could be marginalized over in gravitational-wave inference using techniques currently applied for quantifying calibration uncertainty. For concreteness, waveform uncertainties affecting neutron-star inspiral measurements are considered, and post-hoc error estimates from a variety of waveform models are made by comparing time-domain and frequency-domain analytic models with multiple-resolution numerical simulations. These waveform uncertainty estimates can be compared to GW170817 calibration envelopes or to Advanced LIGO and Virgo calibration goals. Signal-specific calibration and waveform uncertainties are compared to statistical fluctuations in gravitational-wave observatories, giving frequency-dependent modeling requirements for detectors such as Advanced LIGO Plus, Cosmic Explorer, or Einstein Telescope. Finally, the distribution of waveform error for the GW170817 posterior is computed from tidal models and compared to the constraints on δφ or from GWTC-1 by Edelman et al. In general, δφ and can also be interpreted in terms of unmodeled astrophysical energy transfer within or from the source system.

Proton decays from α -unbound states in Mg22 and the Ne18(α,p0)21Na cross section

Background: Type I x-ray bursts provide an opportunity to constrain the equation of state of nuclear matter. Observations of the light curves from these bursts allow the compactness of neutron stars to be constrained. However, the behavior of these light curves also depends on a number of important thermonuclear reaction rates. One of these reactions, $^{18}\mathrm{Ne}(\ensuremath{\alpha},p)^{21}\mathrm{Na}$, has been extensively studied but there is some tension between the rate calculated from spectroscopic information of states above the $\ensuremath{\alpha}$-particle threshold in $^{22}\mathrm{Mg}$ and the rate determined from time-reversed measurements of the cross section.Purpose: The time-reversed measurement of the cross section is only sensitive to the ground state-to-ground state contribution. Therefore, corrections must be made to this reaction rate to account for the contribution of branches to excited states in $^{21}\mathrm{Na}$. At present this is done with statistical models which may not be applicable in such light nuclei. Basing the correction of the time-reversed cross section on experimental data is much more robust.Method: The $^{24}\mathrm{Mg}(p,t)^{22}\mathrm{Mg}$ reaction was used to populate states in $^{22}\mathrm{Mg}$. The reaction products from the reaction were analysed by the K600 magnetic spectrometer at iThemba Laboratories, South Africa. Protons decaying from excited states of $^{22}\mathrm{Mg}$ (${S}_{p}=5502$ keV) were detected in an array of five double-sided silicon strip detectors placed at backward angles. The branching ratio for proton decays to the ground state of $^{21}\mathrm{Na}, {B}_{{p}_{0}}$, was determined by comparing the inclusive (triton-only focal-plane) and exclusive (focal-plane gated on a specific proton decay) spectra.Results: The experimental proton decay branching ratio to the ground state of $^{21}\mathrm{Na}$ from excited states in $^{22}\mathrm{Mg}$ were found to be a factor of about two smaller than the ratios predicted by Hauser-Feshbach models. Using the experimental branchings for a recalculation of the $^{18}\mathrm{Ne}(\ensuremath{\alpha},{p}_{0})^{21}\mathrm{Na}$ cross section leads to a considerably improved agreement with previous reaction data. Updated information on the disputed number of levels around ${E}_{x}\ensuremath{\approx}9$ MeV and on the possible $^{18}\mathrm{Ne}(\ensuremath{\alpha},2p)^{20}\mathrm{Ne}$ cross section at astrophysical energies is also reported.Conclusions: The proton decay branching of excited states in $^{22}\mathrm{Mg}$ to the ground state of $^{21}\mathrm{Na}$ have been measured using the K600 Q2D spectrometer at iThemba Laboratories coupled to the double-sided silicon-strip detector array CAKE. Using these experimental data, the modeling of the $^{18}\mathrm{Ne}(\ensuremath{\alpha},{p}_{0})^{21}\mathrm{Na}$ cross section has been improved. The result is not only in better agreement with previous cross section data but also consistent with a recent direct measurement of $^{18}\mathrm{Ne}(\ensuremath{\alpha},p)^{21}\mathrm{Na}$. This strengthens the case for the application of statistical models for these reactions.