Planet at GU Psc

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Planet at GU Psc

Post by Edasich on 29th April 2014, 6:29 am

Listed first in EPE:

http://exoplanet.eu/catalog/gu_psc_b/

Paper abstract (prepring coming soon, I hope).

Discovery of a Wide Planetary-mass Companion to the Young M3 Star GU Psc

We present the discovery of a comoving planetary-mass companion ~42'' (~2000 AU) from a young M3 star, GU Psc, a likely member of the young AB Doradus Moving Group (ABDMG). The companion was first identified via its distinctively red i z color (>3.5) through a survey made with Gemini-S/GMOS. Follow-up Canada-France-Hawaii Telescope/WIRCam near-infrared (NIR) imaging, Gemini-N/GNIRS NIR spectroscopy and Wide-field Infrared Survey Explorer photometry indicate a spectral type of T3.5 1 and reveal signs of low gravity which we attribute to youth. Keck/Adaptive Optics NIR observations did not resolve the companion as a binary. A comparison with atmosphere models indicates T eff = 1000-1100 K and log g = 4.5-5.0. Based on evolution models, this temperature corresponds to a mass of 9-13 M Jup for the age of ABDMG (70-130 Myr). The relatively well-constrained age of this companion and its very large angular separation to its host star will allow its thorough characterization and will make it a valuable comparison for planetary-mass companions that will be uncovered by forthcoming planet-finder instruments such as Gemini Planet Imager and SPHERE.
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Re: Planet at GU Psc

Post by Lazarus on 29th April 2014, 2:57 pm

Mass ratio ~30 at a separation of ~2000 AU.
The authors at least seem to be hedging their bets about calling this one a planet...

(not read the paper because of the paywall, so the following could well be ruled out)

I suppose it could be an outward-scattered superplanet, but in that case there would likely be another planet of comparable mass closer to the star (or perhaps even engulfed by it, which would make testing things more difficult). In which case GU Psc is the most extreme planetary system yet found around an M-dwarf in terms of total planet mass.

Doesn't smell particularly planetary to me, but these wide-orbit companions are rather problematic to explain.
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Re: Planet at GU Psc

Post by Stalker on 30th April 2014, 3:10 am

This star is listed as a RS CVn variable, a close spotted binary.

http://simbad.u-strasbg.fr/simbad/sim-id?protocol=html&Ident=1RXS+J011235.6%2B170401

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Re: Planet at GU Psc

Post by Sirius_Alpha on 30th April 2014, 6:18 am

Lazarus wrote:Mass ratio ~30 at a separation of ~2000 AU.... Doesn't smell particularly planetary to me, but these wide-orbit companions are rather problematic to explain.

I agree completely. For a little fun exercise, I dug through the EPE, took all their planets with separations > 5 AU, and plotted the star/planet mass ratio on the x-axis and the separation (divided by the stellar mass to try to account for such things since the orbital period is unknown) on the y-axis. Solar system planets are marked in red, and the planets of HR 8799 are marked in blue. GU Psc is independently labelled. It looks like two separate populations. I'd be fine with dismissing the planetary status of the top group of planets. It'll be interesting to see how well segregated these two groups really are as we discover more objects in this parameter space.


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Re: Planet at GU Psc

Post by Edasich on 30th April 2014, 8:50 am

The largest separation planetary-mass objects are indeed WD 0806-661 b (2,500 AUs) and HIP 77900 b (3,200 AUs).
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Re: Planet at GU Psc

Post by Lazarus on 30th April 2014, 5:45 pm

Interesting diagram. It does seem suggestive but I wonder how much of that gap is real and how much is due to detection biases at intermediate separations where direct imaging becomes difficult and RV hasn't been going long enough to reach.
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Re: Planet at GU Psc

Post by Sirius_Alpha on 13th May 2014, 8:24 pm

Here's the paper on arXiv.
http://arxiv.org/abs/1405.2932

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Re: Planet at GU Psc

Post by Led_Zep on 14th May 2014, 5:58 am

A good target for SPHERE...

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Re: Planet at GU Psc

Post by Lazarus on 14th May 2014, 6:18 am

News release from Gemini Observatory, with the image from figure 1 and the usual artistic view.

Odd planet, so far from its star...
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