GJ 687 b - 38 day Neptune-mass planet

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GJ 687 b - 38 day Neptune-mass planet

Post by Sirius_Alpha on 13th May 2014, 8:25 pm

The Lick-Carnegie Exoplanet Survey: Gliese 687b: A Neptune-Mass Planet Orbiting a Nearby Red Dwarf
http://arxiv.org/abs/1405.2929

Precision radial velocities from the Automated Planet Finder and Keck/HIRES reveal an M*sin(i) =18 +/- 2 Earth mass planet orbiting the nearby M3V star GJ 687. This planet has an orbital period, P = 38.14 days, and a low orbital eccentricity. Our Stromgren b and y photometry of the host star suggests a stellar rotation signature with a period of P = 60 days. The star is somewhat chromospherically active, with a spot filling factor estimated to be several percent. The rotationally{induced 60-day signal, however, is well-separated from the period of the radial velocity variations, instilling confidence in the interpretation of a Keplerian origin for the observed velocity variations. Although GJ 687b produces relatively little specific interest in connection with its individual properties, a compelling case can be argued that it is worthy of remark as an eminently typical, yet at a distance of 4.52 pc, a very nearby representative of the galactic planetary census. The detection of GJ 687b indicates that the APF telescope is well suited to the discovery of low-mass planets orbiting low-mass stars in the as-yet relatively un-surveyed region of the sky near the north celestial pole.

As discussed here.
http://solar-flux.forumandco.com/t303-mess-new-spectrograf-california-group-finds-exo-earths-or-apf-rpf#10321

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Re: GJ 687 b - 38 day Neptune-mass planet

Post by Shellface on 13th May 2014, 9:08 pm

I think it's notable that we're still discovering planets around such nearby stars ("still" refers to this and Gliese 682 bc from this year, etc.). A census of ≥Super-Earth-mass/size planets around, say, all ≥M5 stars closer than 10 parsecs would sure be interesting, but it looks like that's not going to be happening for a while.

But yes. Here's a typical planet around a typical star. One more for the statistics.

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Re: GJ 687 b - 38 day Neptune-mass planet

Post by Sirius_Alpha on 13th May 2014, 9:11 pm

Indeed. Maybe I've become desensitised to the discoveries of Kepler, but nothing excites me as much as discoveries of planets in the much closer solar neighbourhood.

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Re: GJ 687 b - 38 day Neptune-mass planet

Post by Lazarus on 16th May 2014, 2:42 pm

Raises the question about what constitutes an interesting exoplanet these days.

For example, barring the odd cluster planet (e.g. HD 285507b), it looks like no-one's still publishing RV-only hot Jupiters. Is that because all the HJs have been found in the sample of stars its worth doing RV measurements on, or because they are no longer sufficiently interesting to publish?

And even the super-Earths are now "becoming statistical"...
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Re: GJ 687 b - 38 day Neptune-mass planet

Post by Shellface on 16th May 2014, 3:13 pm

it looks like no-one's still publishing RV-only hot Jupiters.
Eh, there was that SOPHIE paper with three new ones a while back. Though I guess all of those systems have additional companions…

Is that because all the HJs have been found in the sample of stars its worth doing RV measurements on, or because they are no longer sufficiently interesting to publish?
I lean towards the former. Hot Jupiters are far rarer than transit surveys make them out to be; in the HARPS-GTO sample of 451 stars (list here, etc.) there are… what, four systems with HJs? Except for SOPHIE, none of the major spectrographs have noticeably expanded their samples recently, and because HJs are extremely easily identified and characterised, you shouldn't expect any new ones from a spectrograph that has been observing for more than a year or two (SOPHIE's an oddball because it's the Geneva team, and they're slllooowwww). We also haven't seen any targeted surveys like N2K recently, possibly because N2K detected like 10 planets rather than 2000, so no HJs there either.

And even the super-Earths are now "becoming statistical"...
Kepler's a very indulging short-cut, huh. Though, RV super-earths (and earths, however we're going to define that) are still quite exciting for me!

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