Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · 1304.3272

Gamma-ray emission from proton-proton interactions in hot accretion flows

Andrzej Niedzwiecki·Fu-Guo Xie·Agnieszka Stepnik
View original source ↗Read source document ↗Export metadata ↓

Abstract

We present a model of gamma-ray emission through neutral pion production and decay in two-temperature accretion flows around supermassive black holes. We refine previous studies of such a hadronic gamma-ray emission by taking into account (1) relativistic effects in the photon transfer and (2) absorption of gamma-ray photons in the radiation field of the flow. We use a fully general relativistic description of both the radiative and hydrodynamic processes, which allows us to study the dependence on the black hole spin. The spin value strongly affects the gamma-ray emissivity within ~10 gravitational radii. The central regions of flows with the total luminosities L < 0.001 of the Eddington luminosity are mostly transparent to photons with energies below 10 GeV, permitting investigation of the effects of space-time metric. For such L, an observational upper limit on the gamma-ray (0.1-10 GeV) to X-ray (2-10 keV) luminosity ratio of L_{0.1-10 GeV}/L_{2-10 keV} << 0.1 can rule out rapid rotation of the black hole; on the other hand, a measurement of L_{0.1-10 GeV}/L_{2-10 keV} ~ 0.1 cannot be regarded as the evidence of rapid rotation, as such a ratio can also result from a flat radial profile of gamma-ray emissivity (which would occur for nonthermal acceleration of protons in the whole body of the flow). At L > 0.01 of the Eddington luminosity, the gamma-ray emission from the innermost region is strongly absorbed and the observed gamma-rays do not carry information on the value of the black hole spin. We note that if the X-ray emission observed in Centaurus A comes from an accretion flow, the hadronic gamma-ray emission from the flow should contribute significantly to the MeV/GeV emission observed from the core of this object, unless it contains a slowly rotating black hole and protons in the flow are thermal.

Explore related subjects

astro-ph.HE

Keep this discovery

BibTeXRIS

Andrzej Niedzwiecki, Fu-Guo Xie, Agnieszka Stepnik. 2013-04-11. Gamma-ray emission from proton-proton interactions in hot accretion flows. https://doi.org/10.1093/mnras%2Fstt573

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

IceCube neutrino point-source searches in the direction of the KM3NeT ultra-high-energy event

While still under construction, the KM3NeT Astroparticle Research with Cosmics in the Abyss (ARCA) detector recorded a $\sim$200 PeV neutrino on February 13th, 2023. This event is the highest-energy neutrino reported. IceCube, a cubic kilometer neutrino detector located at the geographic South Pole, has previously detected neutrinos up to approximately 10 PeV. We search for high-energy neutrinos from the location of the KM3NeT event using 15 years of IceCube data and considering three temporal hypotheses: steady or flaring in time coincidence, or at an arbitrary time. We find no evidence for neutrino emission for any of the studies performed. Correspondingly, we set upper limits on the neutrino flux from a point source in the direction of KM3-230213A. We compare these limits to KM3NeT's estimated flux and show that an astrophysical explanation of this event is strongly constrained for a variety of spectral assumptions for a steady or transient point source with the flux inferred from the single KM3NeT ultra-high-energy event assuming a spectral index of 2.0.

astro-ph.HE↗
arXiv2026

Evidence for the binary nature of the long-period radio transient ASKAP/DART J1832-0911

Long-period transients are a class of periodic pulsed radio source repeating on the minute to hour timescale. Recently, an increasing number of them are being identified as binary systems, specifically white dwarfs with low-mass main-sequence companions. In this work we analyse the most luminous long-period transient discovered to date, ASKAP/DART J1832-0911, with two years of radio data, and propose that it, too, may be a white dwarf system, although in a far more compact orbit than the aforementioned. The pulses are composed of quasi-periodic components which evolve in a systematic way over days and months. The source is highly linearly or elliptically polarised and its brightness enabled very high signal-to-noise measurement of the time-resolved Faraday rotation measure, which was found to vary across pulse phase. The linear polarisation position angle, circular polarised fraction, and spectral index also varied systematically in ways not typical of pulsars and magnetars. We show that an ultra-compact asynchronous polar explains much of the phenomenology of ASKAP/DART J1832-0911, in particular the evolution of the pulse morphology, rotation measure variation, and periodic X-ray emission, although we cannot conclusively prove a binary nature. However, our model makes testable predictions.

astro-ph.HE↗
arXiv2026

Nonbirefringent model of orthogonal polarization modes in radio pulsars - New view on S swing and mode structure in pulsar beam

Two orthogonal polarization modes observed in radio pulsar signals have long been attributed to proper modes of wave oscillation in strongly magnetized plasma. Yet it has been shown recently that they show up readily for extended emission regions that produce incoherently-superposed polarization signal. In this paper we present a two-dimensional polarization model based on incoherent superposition of radio signals. The model involves a single proper mode, say the O mode, but leads to the appearance of two orthogonal polarization tracks and naturally produces the triple form of polarization mode segregation in averaged profiles (central mode flanked on boths sides by another mode), as well as the displacement of modes in latitude, previously inferred from beam mapping. In the case of conal emission regions, the modelled polarization tends to mimic general polarization properties of the rotating vector model (RVM). However, the reason for this is the symmetry of the emission region - not the usual projection of dipolar magnetic azimuths. Thus the emerging RVM parameters reveal geometry of the emission region, not of the dipolar magnetic field. The results strongly support the vital role of nonbirefringent modal effects in radio pulsar profiles. Two proper modes may not be needed to explain observations of two orthogonal polarization tracks.

astro-ph.HE↗