4-8 GHz Fourier-domain Searches for Galactic Center Pulsars

TL;DR

This study conducted the most sensitive 4-8 GHz pulsar survey of the Galactic Center, detecting a known magnetar but finding no new pulsars, suggesting limitations in current sensitivity or environmental effects on pulsar populations.

Contribution

It presents the deepest 4-8 GHz pulsar search in the Galactic Center to date, incorporating advanced Fourier domain analysis for pulsar detection.

Findings

Detected the GC magnetar PSR J1745-2900

No new pulsars detected above 6σ threshold

Results suggest possible environmental effects or sensitivity limits

Abstract

The Galactic Center (GC), with its high density of massive stars, is a promising target for radio transient searches. In particular, the discovery and timing of a pulsar orbiting the central supermassive black hole (SMBH) of our Galaxy will enable stringent strong-field tests of gravity and accurate measurements of SMBH properties. We performed multi-epoch 4-8 GHz observations of the inner $\approx$ 15 pc of our Galaxy using the Robert C. Byrd Green Bank Telescope in 2019 August-September. Our investigations constitute the most sensitive 4-8 GHz GC pulsar survey conducted to date, reaching down to a 6.1 GHz pseudo-luminosity threshold of $\approx$ 1 mJy kpc$^2$ for a pulse duty cycle of 2.5$\%$. We searched our data in the Fourier domain for periodic signals incorporating a constant or linearly changing line-of-sight pulsar acceleration. We report the successful detection of the GC magnetar PSR J1745$-$2900 in our data. Our pulsar searches yielded a non-detection of novel periodic astrophysical emissions above a 6$\sigma$ detection threshold in harmonic-summed power spectra. We reconcile our non-detection of GC pulsars with inadequate sensitivity to a likely GC pulsar population dominated by millisecond pulsars. Alternatively, close encounters with compact objects in the dense GC environment may scatter pulsars away from the GC. The dense central interstellar medium may also favorably produce magnetars over pulsars.