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American Astronomical Society, Astrophysical Journal, 1(959), p. 14, 2023

DOI: 10.3847/1538-4357/acf4f2

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A Search for Pulsars around Sgr A* in the First Event Horizon Telescope Data Set

Journal article published in 2023 by Pablo Torne ORCID, Kuo Liu ORCID, Ralph P. Eatough ORCID, Jompoj Wongphechauxsorn ORCID, James M. Cordes ORCID, Gregory Desvignes ORCID, Mariafelicia De Laurentis ORCID, Michael Kramer ORCID, Scott M. Ransom ORCID, Shami Chatterjee ORCID, Robert Wharton ORCID, Ramesh Karuppusamy ORCID, Lindy Blackburn ORCID, Michael Janssen ORCID, Chi-Kwan Chan ORCID and other authors.
This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Abstract

Abstract In 2017 the Event Horizon Telescope (EHT) observed the supermassive black hole at the center of the Milky Way, Sagittarius A* (Sgr A*), at a frequency of 228.1 GHz (λ = 1.3 mm). The fundamental physics tests that even a single pulsar orbiting Sgr A* would enable motivate searching for pulsars in EHT data sets. The high observing frequency means that pulsars—which typically exhibit steep emission spectra—are expected to be very faint. However, it also negates pulse scattering, an effect that could hinder pulsar detections in the Galactic center. Additionally, magnetars or a secondary inverse Compton emission could be stronger at millimeter wavelengths than at lower frequencies. We present a search for pulsars close to Sgr A* using the data from the three most sensitive stations in the EHT 2017 campaign: the Atacama Large Millimeter/submillimeter Array, the Large Millimeter Telescope, and the IRAM 30 m Telescope. We apply three detection methods based on Fourier-domain analysis, the fast folding algorithm, and single-pulse searches targeting both pulsars and burst-like transient emission. We use the simultaneity of the observations to confirm potential candidates. No new pulsars or significant bursts were found. Being the first pulsar search ever carried out at such high radio frequencies, we detail our analysis methods and give a detailed estimation of the sensitivity of the search. We conclude that the EHT 2017 observations are only sensitive to a small fraction (≲2.2%) of the pulsars that may exist close to Sgr A*, motivating further searches for fainter pulsars in the region.