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First Massive Binary Star Found Where Both Stars Have Magnetic Fields

A binary star is a star system consisting of two or more stars, orbiting around their common center of mass. Matt Schulz, a PhD candidate, has discovered the first occurence of a binary star where both stars have magnetic fields. The binary star which he discovered is called epsilon Lupi.

The BinaMIcS (Binarity and Magnetic Interactions in various classes of Stars) collaboration has spent several years trying to find such an object but hasn’t succeeded until now. The epsilon Lupi discovery was made with use of the Canada-France-Hawaii Telescope.

Mr. Shultz (Physics, Engineering Physics and Astronomy) said: “The origin of magnetism amongst massive stars is something of a mystery and this discovery may help to shed some light on the question of why these stars have magnetic fields.”

Stars such as the Sun generate magnetic fields by a convection in the outer portion of the star but massive stars have no convection in their outer layers which means that they have no support for a magnetic dynamo but still almost 10% of massive stars have a strong magnetic field.

There are two hypothesis as to why these stars have magnetic fields and both are based on a so-called “fossil” magnetic field. A fossil magnetic field is a field that was generated sometime in the stars past and was then locked into this stars outer portion.

The first of these two hypothesis claims that the magnetic field appears when the star is being born and the second one claims that the magnetic field is created by the mixing of stellar plasma when two stars in a close binary merge.

Mr. Shultz explained that the researchers still don’t know why there are so few magnetic, massive stars in close binaries.

The study shows that the magnetic fields on both stars are very similar and that they have their magnetic axes anti-aligned. What that means is that the south pole of one star is pointing in the direction of the north pole of the other star. Shultz said: “We’re not sure why that is yet, but it probably points to something significant about how the stars are interacting with one another. We’ll need to collect more data.”

The study was published in Monthly Notices of the Royal Astronomical Society under Confirming HD 23478 as a new magnetic B star hosting an H -bright centrifugal magnetosphere.

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  • astrofrog

    The journal reference is incorrect.

    • TheLatestNews

      What seems to be wrong with it?

      • astrofrog

        “Confirming HD 23478 as a new magnetic B star hosting an H -bright centrifugal magnetosphere.”

        is wrong, and

        “Detection of magnetic fields in both B-type components of the $epsilon$ Lupi system: a new constraint on the origin of fossil fields?”

        is correct.