Millisecond pulsars (MSPs) are evolved neutron stars along with short spin periods that have gone through a long period of bulk transfer in a low-mass X-ray binary phase.
Globular groupings (GCs)— conglomerations of thousands or millions of stars— are usually prolific environments for the development of MSPs. However , within NGC 6397— one of two GCs closest to Earth— only one MSP had been identified until recently.
At this point, researchers have not only found a second pulsar in our neighboring GC but have a much better idea why other pulsars have “ gone lacking. ”
Utilizing the Parkes radio telescope nationwide to observe NGC 6397, Doctor Zhang Lei from the National Astronomical Observatories of the Chinese Academy of Sciences (NAOC) discovered a new 5. 79 ms-period MSP, named PSR J1740-5340B (NGC 6397B), within an eclipsing binary system. This discovery was confirmed with the MeerKAT radio telescope within South Africa.
NGC 6397B is detectable only when the pulsar is quietly of its orbit closest towards the observer. Its measured orbital period of 1 . 97 days is the longest among most eclipsing binaries in GCs. This orbital time period is also in line with that of the previously discovered X-ray source U18, which was once considered a “ concealed MSP. ” U18 has been confirmed by the current research to be NGC 6397B.
The work had been published in The Astrophysical Journal Letters on July twenty-eight.
Prof. Li Di of NAOC, the particular corresponding author, organized the first coherently de-dispersed search for new pulsars in NGC 6397 using the ua-wideband low (UWL) receiver system recently attached to the Parkes radio telescope.
Using information from the first observation by Parkes radio telescope upon April 12, 2019, Doctor Zhang discovered the new pulsar . In total, 39 observations were manufactured by the Parkes radio telescope over a period of three years along with two observations by the MeerKAT radio telescope.
The notable characteristic of NGC 6397B is the faintness of its radio signal and prolonged radio-quiescent periods. The researchers suggested that NGC 6397B may be representative of a subgroup of extremely faint and heavily obscured binary pulsars. The researchers said this might explain the apparent overabundance of isolated pulsars in the dense cores of GCs, where stellar interactions are expected to preferentially result in binaries. In other words, binaries may not be absent— they may just be hard to detect.
According to the experts, these faint pulsars are usually hard to pick up in stereo bands either because they are embedded in clouds of flat screen or are actively accreting matter due to their companion stars.
Future research may test whether these types of explanations correctly describe why few binary pulsars have already been found in GCs.