Gamma-ray Connection Research Articles

ALMA and NOEMA constraints on synchrotron nebular emission from embryonic superluminous supernova remnants and radio–gamma-ray connection

ABSTRACT Fast-rotating pulsars and magnetars have been suggested as the central engines of superluminous supernovae (SLSNe) and fast radio bursts, and this scenario naturally predicts non-thermal synchrotron emission from their nascent pulsar wind nebulae (PWNe). We report results of high-frequency radio observations with ALMA and NOEMA for three SLSNe (SN 2015bn, SN 2016ard, and SN 2017egm), and present a detailed theoretical model to calculate non-thermal emission from PWNe with an age of ∼1−3 yr. We find that the ALMA data disfavours a PWN model motivated by the Crab nebula for SN 2015bn and SN 2017egm, and argue that this tension can be resolved if the nebular magnetization is very high or very low. Such models can be tested by future MeV–GeV gamma-ray telescopes such as AMEGO.

Hidden Cores of Active Galactic Nuclei as the Origin of Medium-Energy Neutrinos: Critical Tests with the MeV Gamma-Ray Connection

Mysteries about the origin of high-energy cosmic neutrinos have deepened by the recent IceCube measurement of a large diffuse flux in the 10-100TeV range. Based on the standard disk-corona picture of active galactic nuclei (AGN), we present a phenomenological model enabling us to systematically calculate the spectral sequence of multimessenger emission from the AGN coronae. We show that protons in the coronal plasma can be stochastically accelerated up to PeV energies by plasma turbulence, and find that the model explains the large diffuse flux of medium-energy neutrinos if the cosmic rays carry only a few percent of the thermal energy. We find that the Bethe-Heitler process plays a crucial role in connecting these neutrinos and cascaded MeV gamma rays, and point out that the gamma-ray flux can even be enhanced by the reacceleration of secondary pairs. Critical tests of the model are given by its prediction that a significant fraction of the MeV gamma-ray background correlates with ∼10 TeV neutrinos, and nearby Seyfert galaxies including NGC 1068 are promising targets for IceCube, KM3Net, IceCube-Gen2, and future MeV gamma-ray telescopes.

Breaking the radio – gamma-ray connection in Arp 220

Recent analyses of the gamma-ray spectrum from the ultra-luminous infrared galaxy Arp 220 have revealed a discrepancy in the cosmic ray energy injection rates derived from the gamma-rays versus the radio emission. While the observed radio emission is consistent with the star formation rate inferred from infrared observations, a significantly higher cosmic ray population is necessary to accurately model the measured gamma-ray flux. To resolve this discrepancy between the radio and gamma-ray observations, we find that we must increase the cosmic ray energy injection rate and account for an infrared optical depth greater than unity. Raising the energy injection rate naturally raises the total gamma-ray flux but also raises the radio flux unless there is also an increase in the energy loss rate for cosmic ray leptons. A optically thick medium results in an increase in energy losses via inverse Compton for cosmic ray leptons and preserves agreement with submillimeter, millimeter, and infrared wavelength observations.

THE RADIO AND GAMMA-RAY CONNECTION OF EGRET BLAZARS: CORRELATION, REGRESSION, AND MONTE CARLO ANALYSIS

A comprehensive statistical analysis of the broadband properties of Energetic Gamma-Ray Experiment Telescope blazars is presented. This analysis includes sources identified as blazars in the Sowards-Emmerd publications. Using this sample of 122 sources, we find that there is a relationship L γ Lr 0.77±0.03, as well as a correlation between α og and α ro , and a correlation between radio luminosity and α og . Through the use of Monte Carlo simulations, we can replicate the observed luminosity relationship if a synchrotron self-Compton model is assumed. However, this relationship cannot be replicated if an external Compton scattering model is assumed. These differences are primarily due to beaming effects. In addition, it has been determined that the intrinsic radio luminosity of the parent sample falls in the range 1021 < L < 1030 W Hz-1 and that the bulk of the Lorentz factors of the source are in the range 1 < Γ < 30, in agreement with very long baseline interferometry observations. Finally, we discuss implications for the Gamma Ray Large Area Space Telescope, successfully launched in 2008 June.

New superluminal quasar 1633 + 382 and the blazar-gamma-ray connection

view Abstract Citations (35) References (48) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS New Superluminal Quasar 1633+382 and the Blazar--Gamma-Ray Connection Barthel, P. D. ; Conway, J. E. ; Myers, S. T. ; Pearson, T. J. ; Readhead, A. C. S. Abstract We report detection of superluminal motion in the core of 4C 38.41, associated with the z = 1.814 quasar 1633 + 382. The dominant nucleus in the ~30 kpc triple morphology of the radio source displays a core-jet structure on the milliarcsecond scale, and a jet component is found moving outward at 6.1 h^-1^c (H_0_ = 100 h km s^-1^ Mpc^-1^, q_0_ = 0.5). Quasar 1633+382 is a highly variable object, in both the radio and the optical wavebands, and in addition an extremely luminous gamma-ray emitter. It is the ninth gamma-ray blazar displaying superluminal motion. We point out that all gamma-ray active galactic nuclei (AGNs) which have been observed with VLBI sufficiently well have been found to show superluminal expansion. This provides strong support for the commonly accepted hypothesis that AGN gamma-ray emission is produced in a beamed relativistic jet. Publication: The Astrophysical Journal Pub Date: May 1995 DOI: 10.1086/187850 Bibcode: 1995ApJ...444L..21B Keywords: Active Galactic Nuclei; Blazars; Gamma Rays; Quasars; Radio Jets (Astronomy); Radio Observation; Variability; Data Correlation; Image Analysis; Luminosity; Radiant Flux Density; Red Shift; Astronomy; GALAXIES: JETS; GALAXIES: QUASARS: INDIVIDUAL ALPHANUMERIC: 1633; 382; GAMMA RAYS: THEORY; RADIO CONTINUUM: GALAXIES full text sources ADS | data products SIMBAD (13) NED (1)