Radio Galaxy Zoo Talk

A radio star?

  • planetaryscience by planetaryscience

    Not sure if this project is still active, but I have a question for an object outside the project, fount with the NVSS survey.

    Radio stars aren't a thing, right? This star has a noticeable proper motion, and is noticeably emitting radio waves at the 1.4 GHz/21 cm frequency. How could this happen?

    305.0475 9.895

    Posted

  • Dolorous_Edd by Dolorous_Edd

    Not sure if this project is still active,

    Pretty active, I would say

    Radio stars aren't a thing, right?

    Well, they are the thing, but they are rare & ambiguous

    see : https://arxiv.org/abs/0906.3030

    How could this happen?

    I don't like few things

    1. Only covered by NVSS and NVSS has poor resolution hence impossible to tell if it is really a host

    2. Could be easily explained by distant background source (tm) i.e. high z galaxy

    Posted

  • planetaryscience by planetaryscience

    Thanks for the quick response- I did a survey of my own and was able to turn up 4 other stars with high proper motion that also appeared to emit radio waves. NVSS seems to scale its error size by the strength of the signal, and one is emitting over 100 mJy, and has sub-arcsecond error- FIRST then detected it at a different location outside of that error range, in the area the high-PM star had moved to.

    That's partially why I searched for high proper motion stars, because followup observations could confirm if the radio source appeared to move, effectively ruling out a background source. The paper you cited seems very vague in their description of what constitutes a radio star (other than radio emission, of course)- is it simply a "strong magnetic field" or did I miss something?

    Posted

  • JeanTate by JeanTate

    I'm a bit late to this party, but here's my $0.02's worth:

    • yes, RGZ is still an active project
    • perhaps almost all stars are radio sources (our own Sun is, after all)
    • however, there are very few with sufficient radio luminosity to be detected in the big surveys published to date (e.g. FIRST, NVSS, SUMS, VLSSr, GLEAM, TGSS)
    • (this may change soon)
    • NVSS has a ~45" resolution
    • just like in the optical, you can make an estimate of position well below the resolution ...
    • ... however, you need to have a good handle on the PSF ("beam" in radio astronomy)
    • AND your estimate is source model-dependent (stars are easy, just point sources!)
    • some radio sources in NVSS are likely to be point sources
    • but many, perhaps most, are not

    "Photobombing" is common ... lots of FIRST sources in RGZ fields appear to be "close to" interesting galaxies (etc), but a more detailed look shows many are chance alignments. Common radio sources (e.g. radio loud cD galaxies) are "visible" to far higher redshift than can be seen in SDSS images (and I note that your field is outside the SDSS footprint), and even the WISE one.

    Hope this helps, and happy hunting! 😃

    Posted