Kavli Affiliate: Bradford A. Benson
| First 5 Authors: Pablo Torne, Kuo Liu, Ralph P. Eatough, Jompoj Wongphechauxsorn, James M. Cordes
| Summary:
The Event Horizon Telescope (EHT) observed in 2017 the supermassive black
hole at the center of the Milky Way, Sagittarius A* (Sgr A*), at a frequency of
228.1 GHz ($lambda$=1.3 mm). The fundamental physics tests that even a single
pulsar orbiting Sgr A* would enable motivate searching for pulsars in EHT
datasets. 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 search targeting both pulsars and
burst-like transient emission; using 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 ($lesssim$2.2%) of the pulsars that may exist
close to Sgr A*, motivating further searches for fainter pulsars in the region.
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