A high-energy component in the radio galaxy Centaurus A was reported after analysing four years of Fermi data. The spectrum of this component is described by means of a broken power law with a break ...energy of 4 GeV and, below and above spectral indices of α1 = 2.74 ± 0.03 and α2 = 2.09 ± 0.20, respectively. Also a faint γ-ray flux at TeV energies was detected by High Energy Stereoscopic System. In this paper, we show that the spectrum at GeV–TeV energies is described through synchrotron self-Compton emission up to a few GeV (∼4 GeV) and π0 decay products up to TeV energies, although the emission of synchrotron radiation by muons could contribute to the spectrum at GeV energies, if they are rapidly accelerated. Muons and π0s are generated in the interactions of accelerated protons with two populations of seed photons which were reported by Compton Gamma-Ray Observatory: one population at intermediate-state emission with energy peak of 0.15 MeV and another at low-state emission with energy peak of 0.59 MeV. In addition, we show that the reported observations of ultrahigh-energy cosmic rays and non-high-energy neutrino detection around Centaurus A can be explained through these interactions, assuming that proton spectrum is extended up to ultrahigh energies.
Gamma-ray Bursts (GRBs) are highly energetic events that can be observed at extremely high redshift. However, inherent bias in GRB data due to selection effects and redshift evolution can ...significantly skew any subsequent analysis. We correct for important variables related to the GRB emission, such as the burst duration, T90*, the prompt isotropic energy, Eiso, the rest-frame end time of the plateau emission, Ta,radio*, and its correspondent luminosity La,radio, for radio afterglow. In particular, we use the Efron–Petrosian method presented in 1992 for the correction of our variables of interest. Specifically, we correct Eiso and T90* for 80 GRBs, and La,radio and Ta,radio* for a subsample of 18 GRBs that present a plateau-like flattening in their light curve. Upon application of this method, we find strong evolution with redshift in most variables, particularly in La,radio, with values similar to those found in past and current literature in radio, X-ray and optical wavelengths, indicating that these variables are susceptible to observational bias. This analysis emphasizes the necessity of correcting observational data for evolutionary effects to obtain the intrinsic behavior of correlations to use them as discriminators among the most plausible theoretical models and as reliable cosmological tools.
Abstract
Cosmological models and their parameters are widely debated, especially about whether the current discrepancy between the values of the Hubble constant,
H
0
, obtained by Type Ia supernovae ...(SNe Ia) and the Planck data from the cosmic microwave background radiation could be alleviated when alternative cosmological models are considered. Thus, combining high-redshift probes, such as gamma-ray bursts (GRBs) and quasi-stellar objects (QSOs, or quasars), together with baryon acoustic oscillations and SNe Ia is important to assess the viability of these alternative models and whether they can cast further light on the Hubble tension. In this work, for GRBs, we use a three-dimensional relation between the peak prompt luminosity, the rest-frame time at the end of the X-ray plateau, and its corresponding luminosity in X-rays: the 3D Dainotti fundamental plane relation. Regarding QSOs, we use the Risaliti−Lusso relation among the UV and X-ray luminosities for a sample of 2421 sources. We correct both the QSO and GRB relations by accounting for selection and evolutionary effects with a reliable statistical method. We here use both the traditional Gaussian likelihoods (
) and the new best-fit likelihoods (
) to infer cosmological parameters of nonflat Lambda cold dark matter (ΛCDM) and flat
w
CDM models. We obtain for all the parameters reduced uncertainties, up to 35% for
H
0
, when applying the new
likelihoods in place of the Gaussian ones. Our results remain consistent with a flat ΛCDM model, although with a shift of the dark energy parameter
w
toward
w
< −1 and a curvature density parameter toward Ω
k
< 0.
Abstract
The Neil Gehrels Swift observatory observes gamma-ray burst (GRB) plateaus in X-rays. We test the reliability of the closure relations through the fireball model when dealing with GRB ...plateau emissions. We analyze 455 X-ray light curves collected by Swift from 2005 January until 2019 August for which the redshifts are either known or unknown using the phenomenological Willingale 2007 model. Using these fits, we analyze the emission mechanisms and astrophysical environments of these GRBs through the closure relations within the time interval of the plateau emission. Finally, we test the three-dimensional fundamental plane relation (Dainotti relation) which connects the prompt peak luminosity, the time at the end of the plateau (rest frame), and the luminosity at that time, for the GRBs with redshift, concerning groups determined by the closure relations. This allows us to check if the intrinsic scatter σint of any of these groups is reduced compared to previous literature. The most fulfilled environments for the electron spectral distribution, p > 2, are wind slow cooling (SC) and interstellar material (ISM) slow cooling for cases in which the parameter q, which indicates the flatness of the plateau emission and accounts for the energy injection, is 0 and 0.5, respectively, in cases with both known and unknown redshifts. We also find that for short GRBs all ISM environments with q = 0 have the smallest σint = 0.04 ± 0.15 in terms of the fundamental plane relation holding a probability of occurring by chance of p = 0.005. We have shown that the majority of GRBs presenting plateau emission fulfill the closure relations, including the energy injection, with a particular preference for the wind SC environment. The subsample of GRBs that fulfill the given relations can be used as possible standard candles and can suggest a way to reduce the intrinsic scatter of these studied relationships.
A state-of-the-art semi-analytic gamma-ray burst (GRB) afterglow model with synchrotron self-Compton (SSC) emission has been applied for the first time for parameter inference using real GRB data. We ...analyzed the famous GRB 190114C as a case study. GRB 190114C, characterized by its long duration and high luminosity, was observed by many ground-based and orbiting telescopes spanning a wide range of electromagnetic wavelengths, from radio to GeV gamma rays. We used two advanced algorithms for inference: a nested sampling algorithm called UltraNest and an MCMC algorithm emcee. Evoking the standard afterglow model, the inference result and the best-fit values lead to an initial bulk Lorentz factor (a rough estimate of Γ=526), which aligns with the values often seen in GRBs identified by the Fermi-LAT instrument. Similarly to the best-fit values of other studies in the literature, the derived values of microphysical parameters, the circumburst density, and the kinetic efficiency are consistent with those found after modeling the multi-wavelength observations in GRB 190114C. We show that the SSC from the forward-shock region can only describe the highest-energy photons above a few GeVs.
Numerous studies suggest that high-energy (HE) neutrinos and ultra-high-energy (UHE) cosmic rays could originate from extremely high-synchrotron peaked (EHSP) BL Lacs, which have been identified as ...effective particle accelerators. Due to the discovery of HE-neutrinos by the IceCube telescope, these hypotheses may shortly have the opportunity to be tested. In this work, we use a two-zone leptohadronic model to explain the spatial coincidence of three EHSP BL Lac: 1RXS J09462.5+010459, 1ES 1101-232, and 3HSP J095507.9+355101 with the arrival of track-like neutrinos. Our results for 1RXS J09462.5+010459 and 1ES 1101-232 indicate that the model accurately describes the electromagnetic emission and neutrino events without increasing the fluxes in the measured bands. In addition, the X-ray flaring state of 3HSP J095507.9+355101 can be explained by our model, but the measured ultraviolet flux during the neutrino arrival time window cannot be explained. For all cases, the broadband emission and neutrino arrival are better described by hard proton distributions ≈1.5. Finally, the proton luminosity required to explain the neutrino fluxes is slightly higher than the Eddington limit with a photopion efficiency of ≈0.1 for non-flaring state cases. On the other hand, for the flaring state of 3HSP J095507.9+355101, the proton luminosity must be higher than the Eddington limit at least by one order of magnitude, even if the photopion efficiency reaches unity.
Gamma-ray bursts (GRBs) are brief, intense pulses of high-energy emission associated with extreme astrophysical phenomena, e.g. the death of massive stars or the coalescence of compact objects. They ...have been observed at high energies by the Fermi Large Area Telescope (LAT), which detects GRBs in the 20 MeV–300 GeV energy range. The Fermi-LAT Second GRB Catalog (2FLGC) presents information on 186 GRBs observed from 2008 to 2018. We consider the GRBs that have been fitted in the 2FLGC with a broken (21 GRBs) or simple power law (65 GRBs), compiling a total sample of 86 GRBs. We analyze the relationship between the spectral and temporal indices using closure relations according to the synchrotron forward-shock model evolving in stratified environments (n∝r−k). We find that the model without energy injection is preferred over the one with energy injection. There is a clear preference for the cooling conditions ν> max{νc,νm} and νm<ν<νc (where νc and νm are the cooling and characteristic frequencies, namely the frequency at the spectral break). Within these cooling conditions, density profiles r−k with values of k=1.5 and 2 generally have a higher rate of occurrence when considering relations with and without energy injection.
We report on anomalously long duration (2 ms) count rate bursts following the impact of cosmic ray showers near a 7.62 cm x⊘7.62 cm LaBr3 scintillation detector at the High Altitude Water Cherenkov ...array in Mexico, previously described by Stenkin et al. (2001), and termed “neutron bursts.” The largest burst produced 198 counts within 2 ms in our LaBr3 detector. We simulate the neutron burst albedo flux (that is, secondary emissions from an extensive air shower core impacting the ground), and show that (1) the characteristic spectra and count rates are well explained by neutron absorption in the ground and (2) any cosmic ray secondary that produces neutrons, either through hadron inelastic collisions, or photoneutron production by gamma‐rays, produces the same characteristic spectra. This implies that other natural phenomena that produce downward beams of gamma‐rays, like Terrestrial gamma ray flashes, should produce a similar “neutron burst” signature from the photoneutron reactions occurring in the soil.
Plain Language Summary
When very large cosmic ray showers (CRS) impact the ground, neutrons are produced in the soil that will rattle around until they become captured by soil particles and release energetic gamma‐rays. This produces a slow explosion of particles emanating from the ground following a CRS impact, and is termed a 'neutron burst'. We present recent observations of neutron bursts from a hand held sized gamma‐ray detector at the High Altitude Water Cherenkov (HAWC) array in Mexico, that exhibit interesting spectral features (the presence of positron annihilation), and an interesting time structure (hundreds of counts within a few ms). Our simulations indicate that Terrestrial gamma‐ray flashes (TGFs, bursts of gamma‐rays associated with lightning) should also produce these neutron bursts. An implication of this work is that existing deployments of ground based TGF instruments, comprised of small gamma‐ray detectors, can additionally be used to observe signatures of large cosmic ray showers on clear days.
Key Points
We report on fairweather count rate bursts with 2 ms duration following the impact of a large cosmic ray shower near a small scintillation detector at HAWC
Simulations show that the spectra and decay time can be produced by either hadronic interactions, or photoneutron reactions from gamma‐rays
These results imply that downward TGFs could produce a similar delayed neutron signature in the soil near ground based detectors
Long gamma-ray bursts have been widely associated with collapsing massive stars in the framework of collapsar model. High-energy neutrinos and photons can be produced in the internal shocks of middle ...relativistic jets from core-collapse supernova. Although photons can hardly escape, high-energy neutrinos could be the only signature when the jets are hidden. We show that using suitable parameters, high-energy neutrinos in GeV-PeV range can be produced in the hidden jet inside the collapsar, thus demonstrating that these objects are candidates to produce neutrinos with energies between 1 and 10 PeV which were observed with IceCube. On the other hand, due to matter effects, high-energy neutrinos may oscillate resonantly from one flavour to another before leaving the star. Using two- (solar, atmospheric and accelerator parameters) and three-neutrino mixing, we study the possibility of resonant oscillation for these neutrinos created in internal shocks. Also we compute the probabilities of neutrino oscillations in the matter at different distances along the jet (before leaving the star) and after in vacuum, on their path to Earth. Finally, neutrino flavour ratios on Earth are estimated.
High-energy neutrinos generated in collimated jets inside the progenitors of gamma-ray bursts (GRBs) have been related to the events detected by IceCube. These neutrinos, produced by hadronic ...interactions of Fermi-accelerated protons with thermal photons and hadrons in internal shocks, are the only signature when the jet has not broken out or failed. Taking into account that the photon field is thermalized at keV energies and the standard assumption that the magnetic field maintains a steady value throughout the shock region (with a width of 1010–1011 cm in the observed frame), we study the effect of thermal and magnetized plasma generated in internal shocks on the neutrino oscillations. We calculate the neutrino effective potential generated by this plasma, the effects of the envelope of the star, and the vacuum on the path to Earth. By considering these three effects, the two (solar, atmospheric and accelerator parameters) and three neutrino mixing, we show that although GeV–TeV neutrinos can oscillate resonantly from one flavour to another, a non-significant deviation of the standard flavour ratio (1: 1: 1) could be expected on Earth.