Radio Galaxy Zoo Talk

ARG0003b2j - a purple star

  • Dolorous_Edd by Dolorous_Edd

    Not a source of radio emission, but

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    SDSS J155404.94+071103.3 - 1237662198825222287

    Is a M5III according to SDSS spectrum, but IMHO doesn't look like one not visually (should be red ) not by spec

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    Here is SDSS Spectral cross-correlation template for M5 star

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    QSO? Star? Blend?

    Posted

  • JeanTate by JeanTate in response to Dolorous_Edd's comment.

    Cool! 😃

    I think this may be a binary, a red dwarf and a white dwarf; these are much sought after by astronomers (the extreme width of the H Balmer absorption lines speaks to extreme gravity) ... the 'U shaped' continuum is almost certainly due to a blend of a hot source (continuum rising to the blue) and cool (red). These weird systems are called symbiotic stars.

    Posted

  • Dolorous_Edd by Dolorous_Edd

    blend of a hot source (continuum rising to the blue) and cool (red)

    It makes sense hence the purple color

    I think this may be a binary

    Has to be a very close binary since companion is not seen even in the UKIDSS image

    UKIDSS K-band / Red circles are UKIDSS sources

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    It is also a UV source seen in Galex Near UV and Far UV

    Near UV / Far UV

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    Posted

  • JeanTate by JeanTate in response to Dolorous_Edd's comment.

    The two stars in symbiotic binaries are quite close together, far too close to be seen as separate objects (though the Hubble may split the nearest). Sometimes they're so close that matter coming off one (the big, red component) is captured by the other and forms an accretion disk. If so, then you get Balmer emission lines instead, and a very strange spectrum. Such as the one mitch came across, back in 2009, in the GZ forum (here is a post by NGC3314 explaining what mitch had found; there are several posts in the GZ forum on these stars).

    Posted

  • Dolorous_Edd by Dolorous_Edd

    The two stars in symbiotic binaries are quite close together,

    Yeah, like contact binaries only separation a tiny bit wider

    About visibility in Galex UV is that due to presence of the hot companion right?

    M dwarf by itself does not radiate that much in UV?

    Posted

  • JeanTate by JeanTate in response to Dolorous_Edd's comment.

    About visibility in Galex UV is that due to presence of the hot companion right?

    Yes, especially as there are no emission lines, so there's likely only, at best, a weak accretion disk (they can radiate in the UV).

    M dwarf by itself does not radiate that much in UV?

    Right; M dwarfs are essentially invisible in the UV (except, perhaps, when they have strong flares?)

    Posted