Resonant conversion of dark matter oscillons in pulsar magnetospheres

Abstract

Due to their high magnetic fields and plasma densities, pulsars provide excellent laboratories for tests of beyond Standard Model (BSM) physics. When axions or axion-like particles (ALPs) approach closely enough to pulsars, they can be resonantly converted to photons, yielding dramatic electromagnetic signals. We discuss the possibility of detecting such signals from bound configurations of axions, colliding with pulsar magnetospheres. We find that all but the densest axion stars, oscillons, are tidally destroyed well before resonant conversion can take place. Oscillons can be efficiently converted to photons, leading to bright, ephemeral radio flashes. Observation of the galactic bulge using existing (Very Large Array and LOFAR) and forthcoming (Square Kilometer Array) radio missions has the potential to detect such events for axion masses in the range m a ∈ [0.1 µeV, 30 µeV], even if oscillons make up a negligible fraction of dark matter.

Dipole radiation and beyond from axion stars in electromagnetic fields

“…Alternatively, if axions were produced in the early universe and survive today as dark matter, then the flux of these cold axions onto magnetized compact stars could result in a distinctive radio emission [58][59][60][61][62][63][64][65]. As much as an O(1) fraction of the axion dark matter could be in the form of axion stars, and therefore it is also important to develop strategies for detecting the encounter of axion stars with magnetized compact stars [66][67][68][69][70][71][72][73][74][75][76][77][78]. Furthermore, the collision of and collapse of axion stars can amplify even small fluctuations in the electromagnetic fields [41,53,66,79].…”

Radio line properties of axion dark matter conversion in neutron stars

“…One way to search for axion dark matter is by observing its decay into two photons [13][14][15][16][17][18][19][20][21][22][23][24]. However, compact objects have long been known to offer a useful avenue in which to probe axions and ALPs in a variety of ways [25][26][27][28][29][30][31][32][33]. Neutron stars (NSs) in particular offer an exciting opportunity for increasing the possibility to detect axion dark matter by allowing axions to resonantly convert into radio photons in their magnetospheres.…”

Radio Line Properties of Axion Dark Matter Conversion in Neutron Stars

“…At this point, it is also interesting to relate the expression (24) to the refractive index appearing in eq. ( 12) which can be read off from eq.…”

“…One way to search for axion dark matter is by observing its decay into two photons [10][11][12][13][14][15][16][17][18][19]. However, compact objects have long been known to offer a useful avenue in which to probe axions and ALPs in a variety of ways [20][21][22][23][24][25][26][27][28]. Neutron stars (NSs) in particular offer an exciting opportunity for increasing the possibility to detect axion dark matter by allowing axions to resonantly convert into radio photons in their magnetospheres.…”