Related papers: Astrophysical Axion Bounds
Relativistic axions are good candidates for the dark radiation for which there are mounting observational hints. The primordial decays of heavy fields produce axions which are ultra-energetic compared to thermalised matter and inelastic…
We study early and late time signatures of both QCD axion strings and hyperlight axion strings (axiverse strings). We focus on charge deposition onto axion strings from electromagnetic fields and subsequent novel neutralizing mechanisms due…
The energy released by Active Galactic Nuclei (AGN) in the form of radiation, winds, or radio plasma jets, is known to impact on the surrounding interstellar medium. The result of these processes, known as AGN (negative) feedback, is…
Cosmological precision data can be used to set very strict constraints on Axions and Axion-like particles (ALPs) produced thermally in the big bang. We briefly review the known bounds and propose two new constraints for Axions and ALPs…
The anomalous orbits of Trans-Neptunian Objects (TNOs) can be explained by the Planet 9 hypothesis. We propose that the Planet 9 can be an axion star. Axion stars are gravitational bound clusters condensed by QCD axions or axion-like…
In many X-ray point sources on the sky, the X-ray emission arises because hydrogen and/or helium is accreted onto a neutron star from a nearby donor star. When this matter settles on the neutron star surface, it will undergo nuclear fusion.…
We determine limits from SN 1987A on massive axion-like particles (ALPs) with masses in the 10 keV - 100 MeV range and purely coupled to two photons. ALPs produced in the core collapse escape from the star and decay into photons that can be…
We study parametric instability of compact axion dark matter structures decaying to radiophotons. Corresponding objects - Bose (axion) stars, their clusters, and clouds of diffuse axions - form abundantly in the postinflationary…
We discuss the phenomenology of neutrino mixing with bulk fermions in the context of supernova physics. The constraints on the parameter space following from the usual energy loss argument can be relaxed by four orders of magnitude due to a…
We observed several nearby face-on spiral galaxies with the ROSAT PSPC to study their 0.1-2.0 keV diffuse emission. After the exclusion of resolved discrete sources, there is unresolved X-ray emission in all the galaxies observed. Since…
Axion-like particles (ALPs) coupled to nucleons might be copiously emitted from a supernova (SN) core. We extend existing bounds on free-streaming ALPs to the case in which these are so strongly-interacting with the nuclear matter to be…
Axion-like particles are hypothetical new light (sub-eV) bosons predicted in some extensions of the Standard Model of particle physics. In astrophysical environments comprising high-energy gamma rays and turbulent magnetic fields, the…
To date more than half a dozen X-ray dim isolated neutron stars are known. Their X-ray spectra are characterized by soft blackbody-like emission (kT about 50-120 eV) without indication for harder, non-thermal components. These stars…
The superradiant instability can lead to the generation of extremely dense axion clouds around rotating black holes. We show that, despite the long lifetime of the QCD axion with respect to spontaneous decay into photon pairs, stimulated…
We investigate the impact of a presumed axion-like-particle (ALP) emission in a core-collapse supernova explosion on neutrino luminosities and mean energies employing a relatively simple analytic description. We compute the nuclear…
One of the most dramatic possible consequences of stellar rotation is its influence on stellar death, particularly of massive stars. If the angular momentum of the iron core when it collapses is such as to produce a neutron star with a…
We update cosmological hot dark matter constraints on neutrinos and hadronic axions. Our most restrictive limits use 7-year data from the Wilkinson Microwave Anisotropy Probe for the cosmic microwave background anisotropies, the halo power…
Axions are well-motivated candidates for dark matter. Recently, much interest has focused on the detection of photons produced by the resonant conversion of axion dark matter in neutron star magnetospheres. Various groups have begun to…
We present a brief overview of the ongoing searches for the axion particle via its coupling to photons. Both the classical QCD axions and more recently proposed Axion-Like-Particles are considered. Astrophysical bounds on the axion-photon…
It is likely that one or more gamma-ray bursts within our galaxy have strongly irradiated the Earth in the last Gy. This produces significant atmospheric ionization and dissociation, resulting in ozone depletion and DNA-damaging ultraviolet…