The e-ASTROGAM gamma-ray space observatory for the multimessenger astronomy of the 2030s

Tatischeff, V.; Angelis, A. De; Tavani, M.; Grenier, I. A.; Oberlack, U.; Hanlon, L.; Walter, R.; Argan, A.; Ballmoos, P. von; Bulgarelli, A.; Donnarumma, I.; Hernanz, M.; Kuvvetli, I.; Mallamaci, M.; Pearce, Mark; Zdziarski, A. A.; Aboudan, A.; Ajello, M.; Ambrosi, G.; Bernard, D.; Bernardini, E.; Bonvicini, V.; Brogna, A.; Branchesi, M.; Budtz-Jørgensen, Carl; Bykov, A. M.; Campana, R.; Cardillo, M.; Ciprini, S.; Coppi, P.; Cumani, P.; Silva, R.M. Curado da; Martino, D. de; Diehl, R.; Doro, M.; Fioretti, V.; Funk, S.; Ghisellini, G.; Giordano, F.; Grove, J. E.; Hamadache, C.; Hartmann, D. H.; Hayashida, M.; Isern, J.; Kanbach, G.; Kiener, J.; Knödlseder, J.; Labanti, C.; Laurent, P.; Leising, M. D.; Limousin, O.; Longo, F.; Mannheim, K.; Marisaldi, M.; Martı́nez, M.; Mazziotta, M. N.; McEnery, J. E.; Mereghetti, S.; Minervini, G.; Моисеев, А. А.; Morselli, A.; Nakazawa, K.; Orleański, P.; Paredes, J. M.; Patricelli, B.; Peyré, J.; Piano, G.; Pohl, Martin; Rando, R.; Roncadelli, M.; Tavecchio, F.; Thompson, D. J.; Turolla, R.; Ulyanov, A.; Vacchi, A.; Wu, Xiaodong; Zoglauer, Andreas

doi:10.48550/arxiv.1805.06435

Cited by 5 publications

(27 citation statements)

References 31 publications

(13 reference statements)

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“…We have considered three energy ranges: (i) X-ray band (10 −3 keV−10 2 keV), (ii) HE band (10 −1 MeV − 10 4 MeV), (iii) VHE band (10 −2 TeV − 10 3 TeV). While our results about the first two energy ranges can be tested by current and planned observatories [45][46][47][48][49][50], our findings in the VHE band are currently of theoretical nature. We have checked that our results about P γ→γ and Π L satisfy the theorems linking conversion/survival probability and photon polarization, which have been enunciated and demonstrated in [67].…”

Section: Discussionmentioning

confidence: 96%

“…As discussed above, observatories in the X-ray and HE bands [45][46][47][48][49][50] are expected to possess a sufficient energy resolution to be able to detect the photon polarization features induced by ALPs and analyzed in this paper (see also [117]). Still, we plan to study the actual detectability in a further publication.…”

Section: Discussionmentioning

confidence: 99%

“…What we have discussed in the X-ray energy band extends in the HE range about the possibility to detect the polarization features described in this subsection. Thus, by considering the energy resolution of planned flux-measuring observatories in the HE range [48,49], we expect a polarimeter energy resolution of 8 − 10 energy bins per decade. Therefore, observatories like COSI [47], e-ASTROGAM [48,49] and AMEGO [50] are expected to be able to detect the ALP-induced modifications to photon polarization.…”

Section: B High-energy Bandmentioning

confidence: 99%

“…First of all, we want to stress that, while for the X-ray and the HE bands our findings can be tested by current and planned observatories [45][46][47][48][49][50], our results about the photon polarization in the VHE range are nowadays purely theoretical. However, as it will be clear below, some important features about photon polarization linked to the photon-ALP interaction arise.…”

Section: Very-high-energy Bandmentioning

confidence: 99%

“…in [39][40][41][42][43][44]. In addition, new attention on this topics has been recently paid because of some existing or proposed experiments that measure the polarization of cosmic photons in the X-ray band like IXPE [45] and Polstar [46] and in the high-energy (HE) band such as COSI [47], e-ASTROGAM [48,49] and AMEGO [50].…”

Section: Introductionmentioning

confidence: 99%

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Photon-ALP oscillations inducing modifications to photon polarization

Galanti¹

2022

Preprint

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Axion-like particles (ALPs) are very light, neutral, spin zero bosons predicted by many theories which try to extend and complete the standard model of elementary particles. ALPs interact primarily with two photons and can generate photon-ALP oscillations in the presence of an external magnetic field. They are attracting increasing interest since photon-ALP oscillations produce deep consequences in astrophysics particularly in the very-high-energy (VHE) band, where they increase the transparency of the Universe to VHE photons by partially preventing absorption caused by the extragalactic background light. Furthermore, ALPs explain why photons coming from flat spectrum radio quasars (a particular class of active galactic nuclei, AGN) have been observed for energies above 20 GeV -which represents a first hint for the existence of an ALP. In addition, ALPs solve an anomalous redshift dependence of blazar (an AGN class) spectra -which represents a second hint for the existence of an ALP. In this paper, we study another effect of the photon-ALP interaction: the change of the polarization state of photons. In particular, we study the propagation of the photon-ALP beam starting where photons are produced -we consider photons generated in a galaxy cluster or in the jet of a blazar -crossing several magnetized media (blazar jet, host galaxy, galaxy cluster, extragalactic space, Milky Way) up to their arrival at the Earth, where photons can be detected. In the presence of photon-ALP interaction, we analyze the photon survival probability Pγ→γ and the corresponding photon degree of linear polarization ΠL for observed energies in the range (1 − 10 15 ) eV dividing it into three energy bands: (i) X-ray band (10 −3 keV − 10 2 keV), (ii) high-energy (HE) band (10 −1 MeV − 10 4 MeV), (iii) VHE band (10 −2 TeV − 10 3 TeV). We observe that photons, which are expected as unpolarized in the absence of ALPs, are made partially polarized by photon-ALP interaction, which generally modifies the initial photon degree of linear polarization ΠL,0 in a sizable and measurable way. Our findings about the X-ray and HE bands can be tested by current and planned observatories like IXPE, Polstar, COSI, e-ASTROGAM and AMEGO. A possible detection of a departure of the photon polarization from the standard expectations would represent an additional hint for the existence of an ALP. We also discover a peculiar feature in the VHE band, where photons at energies above ∼ 1 TeV are fully polarized because of photon-ALP interaction. A possible detection of this feature would represent a proof for the existence of an ALP, but, unfortunately, current technologies do not allow yet to detect photon polarization up to so high energies.

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Section: Discussionmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 99%

Section: B High-energy Bandmentioning

confidence: 99%

Section: Very-high-energy Bandmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Photon-ALP oscillations inducing modifications to photon polarization

Galanti¹

2022

Preprint

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Behavior of axionlike particles in smoothed out domainlike magnetic fields

Galanti

Roncadelli

2018

Phys. Rev. D

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The existence of axion-like particles (ALPs) is predicted by many extensions of the standard model of elementary particles and in particular by theories of superstrings and superbranes. ALPs are very light, neutral, pseudo-scalar bosons which are supposed to interact with two photons. They can play an important role in high-energy astrophysics. Basically, in certain circumstances ALPs substantially enhance the photon survival probability Pγ→γ(E) of a beam emitted by a far-away source through the mechanism of photon-ALP oscillations (E denotes the energy). But in order for this to work, an external magnetic field B must be present. In several cases B is modeled as a domain-like network with 'sharp edges': all domains have the same size L dom (set by the B coherence length) and the same strength B, but the direction of B changes randomly and abruptly from one domain to the next. While this model has repeatedly been used so far since it greatly simplifies the calculations, it is obviously a highly mathematical idealization wherein the components of B are discontinuous across the edges (whence the name sharp edges). It is therefore highly desirable to go a step further, and to find out what happens when the edges are smoothed out, namely when the abrupt change of B is replaced by a smooth one. Moreover, this step becomes compelling when the photon-ALP oscillation length losc turns out to be comparable to -or smaller than -L dom , because in this case the photon survival probability Pγ→γ(E) critically depends on the domain shape. Finally, it would be more realistic to have L dom randomly changing within a given range, since it looks rather unlikely that the coherence length of B should be everywhere the same especially when its source is sufficiently extended. In the present paper we propose a smoothed out version of the previous domain-like structure of B which incorporates the above changes, and we work out its implications. Even in the present case we are able to solve analytically and exactly the propagation equation of a monochromatic photon/ALP beam of energy E inside a single smoothed out domain, thereby ultimately evaluating the corresponding photon survival probability Pγ→γ(E) exactly. This fact has the great advantage to drastically shorten the computation time in the applications involving computer simulations as compared to a numerical solution of the beam propagation equation. Actually, it turns out that the condition losc L dom takes place when a photon/ALP beam of either very low E or very large E -both in the gamma-ray band -crosses a variety of astronomical objects, like radio lobes of flat spectrum radio quasars, spiral galaxies, starburst galaxies, elliptical galaxies and extragalactic space. Thus, the use of our model becomes compelling in all these instances, since the sharp edges model would yield unphysical results. The case of extragalactic space is of particular importance in view of the new generation of gamma-ray observatories like CTA, HAWC, GAMMA-400, LHAASO and TAIGA-HiSCORE, since in suc...

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Axion-like Particles Implications for High-Energy Astrophysics

Galanti

Roncadelli

2022

Universe

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We offer a pedagogical introduction to axion-like particles (ALPs) as far as their relevance for high-energy sstrophysics is concerned, from a few MeV to 1000 TeV. This review is self-contained, in such a way to be understandable even to non-specialists. Among other things, we discuss two strong hints at a specific ALP that emerge from two very different astrophysical situations. More technical matters are contained in three Appendices.

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The e-ASTROGAM gamma-ray space observatory for the multimessenger astronomy of the 2030s

Cited by 5 publications

References 31 publications

Photon-ALP oscillations inducing modifications to photon polarization

Photon-ALP oscillations inducing modifications to photon polarization

Behavior of axionlike particles in smoothed out domainlike magnetic fields

Axion-like Particles Implications for High-Energy Astrophysics

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