# First detection of PSR B1259-63/LS 2883 in the Millimeter and Submillimeter Wavelengths with ALMA

## TL;DR

This study reports the first detection of the PSR B1259-63/LS 2883 binary system in millimeter/submillimeter wavelengths using ALMA, revealing new insights into its emission properties and magnetic environment post-periastron.

## Contribution

It provides the first millimeter/submillimeter observations of the system, constrains magnetic fields and electron energies, and compares spectral behavior across different periastron passages.

## Key findings

- Detected radio continuum emission at 97 GHz post-periastron
- No correlation between millimeter flux and GeV gamma-ray flares
- Observed excess flux at 343 GHz likely from the Be star's circumstellar disk

## Abstract

We report Atacama Large Millimeter/submillimeter Array (ALMA) observations of the binary system containing the pulsar PSR B1259-63 orbiting around a Be star LS 2883 after the 2017 periastron passage. We detected radio continuum emission from the binary system in the millimeter/submillimeter wavelengths for the first time. At Band 3 (97 GHz), the flux 84 days after the periastron is almost the same as that 71 days after the periastron. Although the binary system showed intense GeV gamma-ray flares during our observations, the Band 3 flux did not indicate any time correlation with them. The Band 3 fluxes are consistent with an extrapolation of the radio spectrum at lower frequencies. Assuming that it is synchrotron emission, we constrain magnetic fields ($\lesssim 0.6$ G) and the high-energy cutoff of the electrons ($\gamma \gtrsim 360$). The flux at Band 7 (343 GHz) 69 days after the periastron shows a significant excess from the extrapolation of the radio spectrum at lower frequencies. The flux may be associated with the circumstellar disk around the Be star. We also present the results of Australian Telescope Compact Array (ATCA) observations at 94 GHz for the 2014 periastron passage, which show that the radio spectrum was relatively soft when the pulsar passed the disk.