An 86-GHz search for Pulsars in the Galactic Center with the Atacama Large Millimeter/submillimeter Array

TL;DR

This study conducted the first millimeter-wavelength pulsar survey of the Galactic Center using ALMA, detecting the polarization of a magnetar and assessing the survey's sensitivity to luminous pulsars and orbital motion.

Contribution

It introduces a novel millimeter-wave pulsar search method with ALMA, including polarization measurements and sensitivity analysis for detecting pulsars near Sgr A*.

Findings

First polarization profile of GC magnetar at mm-wavelengths.

Survey sensitive only to the most luminous pulsars.

Future Band-1 observations will improve sensitivity significantly.

Abstract

We report on the first pulsar and transient survey of the Galactic Center (GC) with the Atacama Large Millimeter/submillimeter Array (ALMA). The observations were conducted during the Global Millimeter VLBI Array campaign in 2017 and 2018. We carry out searches using timeseries of both total intensity and other polarization components in the form of Stokes parameters. We incorporate acceleration and its derivative in the pulsar search, and also search in segments of the entire observation to compensate for potential orbital motion of the pulsar. While no new pulsar is found, our observations yield the polarization profile of the GC magnetar PSR J1745-2900 at mm-wavelength for the first time, which turns out to be nearly 100 % linearly polarized. Additionally, we estimate the survey sensitivity placed by both system and red noise, and evaluate its capability of finding pulsars in orbital motion with either Sgr A* or a binary companion. We show that the survey is sensitive to only the most luminous pulsars in the known population, and future observations with ALMA in Band-1 will deliver significantly deeper survey sensitivity on the GC pulsar population.