Evidence for the Most Powerful Pulsar in a Faraway Galaxy is Found by Astronomers


One of the newest neutron stars, which is the superdense relic of a massive star that burst as a supernova, has been found by astronomers who are studying data from the VLA Sky Survey (VLASS). The intense radio emission driven by the spinning pulsar's magnetic field has only just been seen through a thick shell of supernova explosion debris, according to images from the Karl G. Jansky Very Large Array (VLA) of the National Science Foundation.

The object, designated VT 1137-0337, is located 395 million light-years away from Earth in a dwarf galaxy. It initially appeared in a January 2018 VLASS picture. It wasn't seen in a picture of the same area taken in 1998 by the FIRST Survey of the VLA. Later VLASS observations in 2018 and later ones in 2019, 2020, and 2022 still showed it.

According to Dillon Dong, a graduate student at Caltech who will start a Jansky Postdoctoral Fellowship at the National Radio Astronomy Observatory (NRAO) later this year, "What we're most likely witnessing is a pulsar wind nebula." When the surrounding charged particles are accelerated to almost the speed of light by a neutron star's strong magnetic field, a pulsar wind nebula is produced.

Gregg Hallinan, Dong's Ph.D. adviser at Caltech, said: "Based on its characteristics, this is a very young pulsar — maybe as young as about 14 years, but no older than 60 to 80 years."

In data from VLASS, an NRAO initiative that started in 2017 to survey the entire sky viewable from the VLA (about 80% of the sky), Dong and Hallinan found the object. VLASS is doing a thorough scan of the sky three times over the course of seven years, with the goal of discovering transitory objects. In the initial VLASS survey from 2018, astronomers discovered VT 1137-0337.

20 very brilliant transient objects that could be linked to well-known galaxies were discovered by comparing the data from that VLASS scan to those from the FIRST VLA sky survey. This one stood out due to both the features of its radio emission and the fact that its galaxy is undergoing a surge of star creation, according to Dong. Its name is SDSS J113706.18-033737.1, and it is a dwarf galaxy with a mass that is around 100 million times that of the Sun.

The researchers looked at a number of possibilities for VT 1137-0337's features, including supernova, gamma ray burst, and tidal disruption events, in which a star is torn apart by a supermassive black hole. They came to the conclusion that a pulsar wind nebula is the most viable theory.

In this case, a star that was far more massive than the Sun went supernova and left a neutron star in its wake. A shell of debris made up primarily of the original star's mass was flung outward. The neutron star spins quickly, accelerating charged particles and producing tremendous radio emission as its strong magnetic field sweeps over the surrounding universe. 

The shell of explosion debris first obscured the radio transmission from vision. The density of that shell decreased as it grew, finally allowing radio waves from the pulsar wind nebula to flow through. Between the FIRST observation in 1998 and the VLASS observation in 2018, this occurred, according to Hallinan.

The Crab Nebula in the constellation Taurus, which was created by a supernova that flashed brightly in the year 1054, is most likely the most well-known illustration of a pulsar wind nebula. Small telescopes may easily see the crab today. According to Dong, the item they discovered has a greater magnetic field and looks to be 10,000 times more active than the Crab. 

He said, "It's probably an emerging'super Crab'." While Dong and Hallinan believe it is most likely a pulsar wind nebula, it is also feasible that the neutron star's magnetic field is powerful enough to make it a magnetar, a type of super-magnetic object. The unexplained Fast Radio Bursts are currently the subject of significant investigation, and magnetars are a prominent possibility for their origin.

If so, Dong added, "in that scenario, this would be the first magnetar seen while it was emerging, and that, too, is really interesting." In fact, it has been discovered that some fast radio bursts are connected to mysterious persistent radio sources. They have many characteristics with VT 1137-0337, although they don't appear to be particularly variable.

The radio sources connected to FRBs may also be brilliant pulsar wind nebulae, according to Dong's finding of a very similar source that was switching on.

In order to understand the item better and to track its evolution over time, the astronomers intend to make further observations.