Probing the Pulsar Explanation of the Galactic-Center GeV Excess Using Continuous Gravitational-Wave Searches

Area of Science:

• Astrophysics
• Cosmology
• Gravitational Wave Astronomy

Background:

• An excess of GeV gamma rays from the Galactic Center, observed by Fermi, has two main proposed origins: dark matter annihilation or millisecond pulsars.
• Millisecond pulsars are rapidly rotating neutron stars, and their potential contribution to the observed gamma-ray excess remains a topic of investigation.

Purpose of the Study:

• To investigate whether unresolved millisecond pulsars could account for the observed GeV gamma-ray excess from the Galactic Center.
• To constrain the population of millisecond pulsars using recent gravitational wave data.

Main Methods:

• Utilized LIGO and Virgo's O3 all-sky search results for continuous gravitational waves from isolated neutron stars.
• Defined a luminosity function to estimate the number of millisecond pulsars needed to explain the gamma-ray excess.
• Modeled millisecond pulsar deformations to determine their ellipticity distributions and gravitational-wave emission.

Main Results:

• Null results from the O3 continuous gravitational wave search excluded a substantial parameter space within the pulsar luminosity function.
• The study evaluated how different model choices impact these exclusion regions.

Conclusions:

• The findings challenge the hypothesis that millisecond pulsars are the primary source of the Galactic Center's GeV gamma-ray excess.
• This research establishes a novel connection between gamma-ray astrophysics, gravitational wave astronomy, and dark matter physics.