Twenty-seven sources of brief radio pulses have been spotted in the Milky Way.
The discovery comes from MeerTRAP, a program that searches for very short radio signals while the MeerKAT radio telescope carries out other observations. Located in South Africa, MeerKAT combines numerous antennas to observe the sky with high sensitivity.
Image by Danielle Futselaar
These 27 objects belong to a family called rotating radio transients. They emit pulses spaced far enough apart to go unnoticed during a conventional observation. Their behavior is generally associated with neutron stars, the extremely dense remnants left behind by certain stars after they explode.
For 14 of the new sources, the researchers were able to determine their position in the sky with a precision of about one arcsecond. One arcsecond corresponds to 1/3600 of a degree. Such precise localization makes it easier to carry out targeted observations with MeerKAT or other instruments.
The researchers also estimated the rotation period of eight objects using the arrival times of several pulses. The periods obtained range from 0.78 to 4 seconds. In other words, these stars complete one rotation in just a few seconds.
Why, then, do we receive their signals intermittently? A neutron star can produce a radio beam that sweeps through space at the rate of its rotation. If this beam crosses Earth, a radio telescope detects a pulse. In some sources, these emissions become rare or irregular.
The boundary with classical pulsars appears less clear-cut than expected. During follow-up observations, four new sources produced regular pulses resembling the usual behavior of a pulsar. Their classification therefore also depends on the duration and sensitivity of the available observations.
For four objects, the team obtained sufficiently precise monitoring to characterize their rotation over an extended period. These measurements make it possible to compare them with the known population of neutron stars in our Galaxy and to study whether intermittent sources truly constitute a distinct population.
The program also continued observing a previously announced source, MTP0040, also called PSR J1357-6507. New pulses made it possible to refine its position and period. Future campaigns may apply the same method to the newly discovered objects in order to track changes in their emissions.