Cosmic cannibals: astronomers have discovered an unusual representative of the “black widow” – pulsars that destroy their companion star. With an orbital period of just 62 minutes, the pulsar and its companion star are the closest and fastest pair of their kind. However, the absence of X-rays, the third star in the Bunde and the origin of this system in the globular mass migrating through the galaxy makes it mysterious and unusual.
It also carries the spider of the same name Cosmic Black Widow The death of their astral partner. These fast-rotating pulsars form binary systems with low-mass companion stars, but over time they destroy their stellar partners. The reason for this is the pulsar’s intense, high-energy radiation and its powerful stellar winds, which gradually erode the companion star. So far, only twenty “spider” pulsars are known.
Flashing mark
But astronomers have now discovered a “black widow” that is unusual in many ways. It started with their discovery: Kevin Bridge of the Massachusetts Institute of Technology (MIT) in Cambridge and his team discovered the pulsar system not through the pulsar’s X-ray and gamma rays, but by the flash of its companion star. Since the side facing the pulsar is hotter than the side facing it, its brightness should vary rapidly and widely with direction.
For their search for “spider pulsars,” Bridge and his team evaluated observational data from the Zwicky Transit Facility in California, a telescope that scans large swaths of the sky for changes or emerging phenomena. In data about 20 million stars, astronomers have looked for objects whose brightness fluctuates by a factor of ten or more at intervals of an hour or less.
Pulsar cannibal with close friends
In fact, the researchers found what they were looking for: They found something about 3,000 light-years away that became about 13 times brighter every 62 minutes and then faded away again. According to astronomers, the patterns and spectral features of this system suggest it is a binary system in which one pair is heated from one side – as in the case of the cosmic black widow.
“What we know for sure is that what we see here is a star that is hotter on the day side than the night side, and orbits something else for 62 minutes,” said Bridge. “Everything seems to indicate that this is a black widow pulsar.” If so, the system, called ZTF J1406 + 1222, would be the first pulsar to be discovered through visible light observations. It will also be the pulsar system with the shortest known orbital period.
Lost radiation and third parties
But that’s not all: “There are a few things that are unusual about this system, so it might as well be something completely new,” explains Bridge. So far, no X-rays or gamma rays emitted from this system have been detected, and no radiation source can be identified at this position in the archived radio data. It is not clear why this radiation, which is typical for pulsars, disappears from ZTF J1406 + 1222.
Unusual third parties too: Additional observational data from the Sloan Digital Sky Survey reveals that a nearby, rapidly orbiting pair is orbiting a very distant third star. This mineral-rich dwarf is about 600 AU away and takes about 12,000 years to rotate – and is thus much more closely related than the inner pair.
Unique among pulsars
Astronomers show that this triple hierarchical configuration, together with the pulsar’s short orbital period and inner pair, distinguishes this black widow from all previously known spider pulsars. In addition, spectroscopic analysis indicates that ZTF J1406 + 1222 may be older than our solar system. This raises the question of where and how this strange system came about.
The team concluded from their data that the pulsar and its companions were originally in a globular cluster on the edge of the Milky Way. However, this star cluster must have reached the center of the galaxy, where it was torn apart by gravitational disturbances. Astronomers have long speculated that the millisecond pulsars detected near the galactic center could also be from the disturbed globular cluster.
“So this system is unique for the black widow because we detect it in visible light, it has an additional distant companion, and because it exits the galactic center,” Bridge said. “There’s still a lot we don’t understand about this system” (Alam, 2022; doi: 10.1038 / s41586-022-04551-1)
Source: Massachusetts Institute of Technology
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