TY - JOUR

T1 - Superradiance in rotating stars and pulsar-timing constraints on dark photons

AU - Cardoso, Vitor

AU - Pani, Paolo

AU - Yu, Tien-Tien

PY - 2017/6/30

Y1 - 2017/6/30

N2 - In the presence of massive bosonic degrees of freedom, rotational superradiance can trigger an instability that spins down black holes. This leads to peculiar gravitational-wave signatures and distribution in the spin-mass plane, which in turn can impose stringent constraints on ultralight fields. Here, we demonstrate that there is an analogous spindown effect for conducting stars. We show that rotating stars amplify low-frequency electromagnetic waves, and that this effect is largest when the time scale for conduction within the star is of the order of a light crossing time. This has interesting consequences for dark photons, as massive dark photons would cause stars to spin down due to superradiant instabilities. The time scale of the spindown depends on the mass of the dark photon, and on the rotation rate, compactness, and conductivity of the star. Existing measurements of the spindown rate of pulsars place direct constraints on models of dark sectors. Our analysis suggests that dark photons of mass m(V) similar to 10(-12) eV are excluded by pulsar-timing observations. These constraints also exclude superradiant instabilities triggered by dark photons as an explanation for the spin limit of observed pulsars.

AB - In the presence of massive bosonic degrees of freedom, rotational superradiance can trigger an instability that spins down black holes. This leads to peculiar gravitational-wave signatures and distribution in the spin-mass plane, which in turn can impose stringent constraints on ultralight fields. Here, we demonstrate that there is an analogous spindown effect for conducting stars. We show that rotating stars amplify low-frequency electromagnetic waves, and that this effect is largest when the time scale for conduction within the star is of the order of a light crossing time. This has interesting consequences for dark photons, as massive dark photons would cause stars to spin down due to superradiant instabilities. The time scale of the spindown depends on the mass of the dark photon, and on the rotation rate, compactness, and conductivity of the star. Existing measurements of the spindown rate of pulsars place direct constraints on models of dark sectors. Our analysis suggests that dark photons of mass m(V) similar to 10(-12) eV are excluded by pulsar-timing observations. These constraints also exclude superradiant instabilities triggered by dark photons as an explanation for the spin limit of observed pulsars.

KW - GRAVITATIONAL-WAVES

KW - ELECTRICAL-CONDUCTIVITY

KW - NEWTONIAN DYNAMICS

KW - NEUTRON-STARS

KW - BLACK-HOLE

KW - RADIATION

KW - SPIN

U2 - 10.1103/PhysRevD.95.124056

DO - 10.1103/PhysRevD.95.124056

M3 - Journal article

VL - 95

JO - Physical Review D

JF - Physical Review D

SN - 2470-0010

IS - 12

M1 - 124056

ER -