Constraints on ultralight scalars from compact stars

Ultralight scalar fields with electromagnetic and electrophilic
couplings to Standard Model particles can be sourced by compact stars,
giving rise to long-range interactions that mediate forces between stars
in
binary systems. In certain scenarios, these scalars can also be radiated
from the stars, leading to observable effects. I will present constraints
on such ultralight scalars using measurements of pulsar spin-down rates,
orbital period loss in binaries, and characteristic parameters of pulsars,
considering Crab pulsar, PSR J0737-3039, etc. Additionally, I will discuss
how the presence of a cosmic neutrino background can quench these
constraints. Future radio observations and precision measurements will
strengthen the bounds by several orders of magnitude