The Astrophysical Journal, vol. 959, no. 1, pp. 14(27pp)

Authors:

  • Pablo Torne
  • Kuo Liu
  • Ralph P. Eatough
  • Jompoj Wongphechauxsorn
  • James M. Cordes
  • Gregory Desvignes
  • Mariafelicia De Laurentis
  • Michael Kramer
  • Scott M. Ransom
  • Shami Chatterjee
  • Robert Wharton
  • Ramesh Karuppusamy
  • Lindy Blackburn
  • Michael Janssen
  • Chi-kwan Chan
  • Geoffrey, B. Crew
  • Lynn D. Matthews
  • Ciriaco Goddi
  • Helge Rottmann
  • Jan Wagner
  • Salvador Sánchez
  • Ignacio Ruiz
  • Federico Abbate
  • Geoffrey C. Bower
  • Juan J. Salamanca
  • Arturo I. Gómez-Ruiz
  • Alfredo Herrera-Aguilar
  • Wu Jiang
  • Ru-Sen Lu
  • Ue-Li Pen
  • Alexander W. Raymond
  • Lijing Shao
  • Zhiqiang Shen
  • Gabriel Paubert
  • Miguel Sanchez-Portal
  • Carsten Kramer
  • Manuel Castillo
  • Santiago Navarro
  • David John
  • Karl-Friedrich Schuster
  • Michael D. Johnson
  • Kazi L. J. Rygl
  • The Event Horizon Telescope Collaboration

URL:

Abstract:

In 2017 the Event Horizon Telescope (EHT) observed the supermassive black hole at the center of the Milky Way, Sagittarius A$^\ast$ (Sgr A*), at a frequency of 228.1 GHz ($łambda=1.3 mm$). 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 ($łesssim 2.2 %$) of the pulsars that may exist close to Sgr A*, motivating further searches for fainter pulsars in the region.