Matter Ejection Explains Strange High-low Mode Changes in Distant Millisecond Pulsars

The millisecond pulsar PSR J1023+0038 is known to switch between two luminance modes almost constantly, but this has been a mystery until now. PSR J1023+0038 is a 1.69 ms radio pulsar located in the sextant about 4,500 light-years away. Discovered in 2007, the star orbits its low-mass (0.2 solar-mass) companion in an orbital period of only 4.75 hours. Over the past decade, PSR J1023+0038 has been actively plucking material from its companion star, which accumulates in the accretion disk around the pulsar and slowly falls toward it. Since this process of matter accumulation began, the sweeping beam has effectively disappeared and the pulsar has begun to switch constantly between her two modes. In “high” mode, the pulsar emits bright X-rays, ultraviolet and visible light, while in “low” mode these frequencies are weakened and emit more radio waves. The Pulsar stays in each mode for seconds or minutes, then switches to the other mode in just a few seconds. This change has puzzled astronomers. “We have observed an extraordinary cosmic event in which a large amount of material, resembling a cosmic cannonball, is ejected into space in a very short span of a few tens of seconds from a small, dense object rotating at an incredibly high speed. I saw it,” said Dr. Maria Cristina Barrio, astronomer at New York University Abu Dhabi and the Italian National Institute of Astrophysics. Dr. Baglio and her colleagues conducted the most extensive multi-wavelength campaign ever conducted on the Transition Pulsar, from radio to her X-rays. The campaign includes 12 different arrays, including ESA’s XMM Newton Observatory, NASA/ESA’s Hubble Space Telescope, ESO’s Very Large Telescope’s FORS2 instrument, the Atacama Large Millimeter/Submillimeter Wave Array, and the Karl G. Jansky Very Large Array. Telescopes and instruments were involved. NSF, and fast. Over two nights in June 2021, astronomers observed more than 280 changes between the high and low modes of PSR J1023+0038. “We found that the mode change was due to a complex interaction between the pulsar wind, the flow of high-energy particles blown away by the pulsar, and the matter flowing towards the pulsar,” he said. Francesco Coti Zerati, astronomer at the Institute of Space and Astronautical Science in Barcelona and the Italian National Institute of Astrophysics. In low mode, material flowing towards the pulsar is ejected as a narrow jet perpendicular to the disk. Gradually, this material accumulates closer and closer to the pulsar, and the wind from the pulsating star heats the material. The system is now in high mode and glows brightly in X-ray, UV and visible light. Ultimately, this hot blob of matter is removed by a pulsar through a jet. With less hot material in the disc, the system dims and returns to low mode. “Our results demonstrate that multi-wavelength campaigns combining different observational techniques provide a powerful tool for deciphering the nature of elusive objects like transition millisecond pulsars.” said the astronomers.


the journal Astronomy & Astrophysics. _____ M.C. Baglio et al. 2023. Matter ejections behind the highs and lows of the transitional millisecond pulsar PSR J1023+0038. A&A 677, A30; doi: 10.1051/0004-6361/202346418