New method leads to discovery of extremely massive neutron star

Method is specifically devised to measure stellar remnants in close binary systems.

Using an innovative method that yields higher accuracy than any previous one, a team of astronomers discovered one of the most massive neutron stars observed to date.

Also known as pulsars, neutron stars are the remnants of 10-30 solar-mass stars that died in supernova explosions. Although these stellar remnants are small in size, with diameters of about 12.4 miles (20 km), they are more massive than the Sun and thus very dense.

Researchers from the Astronomy and Astrophysics Group of the Universitat Politecnica de Catalunya (UPC) in Barcelona, Spain, and of the Canary Islands Institute of Astrophysics (IAC) found this particular neutron star, known as PSR J2215+5135, to have approximately 2.3 solar masses.

This makes it one of the most massive of the 2,000 plus neutron stars scientists have discovered.

PSR J2215+5135 is part of a close binary star system, for which the new method is aimed. Its companion is a Sun-like star, which the neutron star bombards with radiation.

Because the two stars orbit a common center of mass, known as a barycenter, the more massive the neutron star is, the faster the regular star moves.

With the new method, scientists use the spectral lines of hydrogen and magnesium in the companion star to measure the speed at which both sides of the companion star travel. By measuring the companion’s irradiated and non-irradiated sides, researchers can then determine the mass of the neutron star.

For the study, the research team used data collected by the Gran Telescopio Canarias (GTC), which is the world’s larges optical and infrared telescopes; the William Herschel Telescope (WHT); the Isaac Newton Telescope Group (ING), and the IAC-80 telescope, all located in Spain’s Canary Islands, as well as computer models of binary star systems with irradiation.

As a next step, scientists plan to use this method to measure the many similar neutron stars discovered within the last ten years as well as stellar mass black holes, which are also supernova remnants, and white dwarfs, the remnants of lower-mass stars, in binary systems.

A paper detailing the study has been published in the Astrophysical Journal.



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