Neptunes at HD 42618, HD 164922 and Rho CrB

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Neptunes at HD 42618, HD 164922 and Rho CrB

Post by Sirius_Alpha on 3rd July 2016, 11:35 pm

Three Temperate Neptunes Orbiting Nearby Stars
http://arxiv.org/abs/1607.00007

We present the discovery of three modestly-irradiated, roughly Neptune-mass planets orbiting three nearby Solar-type stars. HD 42618 b has a minimum mass of 15.4±2.4 M⊕, a semi-major axis of 0.55 AU, an equilibrium temperature of 337 K, and is the first planet discovered to orbit the solar analogue host star, HD 42618. We also discover new planets orbiting the known exoplanet host stars HD 164922 and HD 143761 (ρ CrB). The new planet orbiting HD 164922 has a minimum mass of 12.9±1.6 M⊕ and orbits interior to the previously known Jovian mass planet orbiting at 2.1 AU. HD 164922 c has a semi-major axis of 0.34 AU and an equilibrium temperature of 418 K. HD 143761 c orbits with a semi-major axis of 0.44 AU, has a minimum mass of 25±2 M⊕, and is the warmest of the three new planets with an equilibrium temperature of 445 K. It orbits exterior to the previously known warm Jupiter in the system. A transit search using space-based CoRoT data and ground-based photometry from the Automated Photometric Telescopes (APTs) at Fairborn Observatory failed to detect any transits, but the precise, high-cadence APT photometry helped to disentangle planetary-reflex motion from stellar activity. These planets were discovered as part of an ongoing radial velocity survey of bright, nearby, chromospherically-inactive stars using the Automated Planet Finder (APF) telescope at Lick Observatory. The high-cadence APF data combined with nearly two decades of radial velocity data from Keck Observatory and gives unprecedented sensitivity to both short-period low-mass, and long-period intermediate-mass planets.

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Re: Neptunes at HD 42618, HD 164922 and Rho CrB

Post by Edasich on 4th July 2016, 4:19 am

I was sure that Rho CrB b would have come back somehow, sometime. Very Happy Wink

Plus accounting the inner stellar companion astrometrically confirmed (0.17 MSol), the brand new Rho CrB b should be labelled as "Rho CrB (AB)b" and even assuming coplanarity and face-on configuration (i = ca. 0.4-0.5°) it would always lie in planetary domain (m < 12 MJup). Would that be the first RV detected circumbinary exoplanet? Surprised
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Re: Neptunes at HD 42618, HD 164922 and Rho CrB

Post by Lazarus on 4th July 2016, 6:52 am

Edasich wrote:Plus accounting the inner stellar companion astrometrically confirmed (0.17 MSol), the brand new Rho CrB b should be labelled as "Rho CrB (AB)b" and even assuming coplanarity and face-on configuration (i = ca. 0.4-0.5°) it would always lie in planetary domain (m < 12 MJup). Would that be the first RV detected circumbinary exoplanet? Surprised
Well as noted in §4.4, the observations seem to exclude stellar companions close to ρ CrB, and stability considerations rule out the near face-on astrometric orbit for ρ CrB b.

The lower limit of 4° on the inclination given in §4.4.2 translates to masses of 15.0 and 1.1 Jupiter masses for ρ CrB b and c respectively.
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Re: Neptunes at HD 42618, HD 164922 and Rho CrB

Post by Shellface on 4th July 2016, 9:57 am

Hmm. I was in favour of the stellar interpretation of the companion, but making it a multi-planet system certainly goes against that. Even more odd is that it appears to be an evolving 0.9 Msol star…

In the introduction the Eta-Earth survey is described in the past tense, so I take it that it has been completed. A recent paper made that data publicly available for a considerable number of stars, as well. I wonder if the team are going to present their final results from the survey.

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Re: Neptunes at HD 42618, HD 164922 and Rho CrB

Post by Edasich on 4th July 2016, 12:05 pm

The lower limit of 4° on the inclination given in §4.4.2 translates to masses of 15.0 and 1.1 Jupiter masses for ρ CrB b and c respectively.

Wasn't the stellar nature of ρ CrB b (or B) ascertained and confirmed once for all with astrometric measurements? Rolling Eyes
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Re: Neptunes at HD 42618, HD 164922 and Rho CrB

Post by Lazarus on 4th July 2016, 4:43 pm

Apparently the result may be less secure than it originally appeared. Not sure if ρ CrB is faint enough for Gaia to get useful results for.
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Re: Neptunes at HD 42618, HD 164922 and Rho CrB

Post by Edasich on 5th July 2016, 4:50 am

Well in case of stellar nature for "b", I would not discard the "circumbinary planet" solution (which intrigues me much). Of course I would neither be displeased of the "2-planets" one disproving previous astrometric conclusions. Smile
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Re: Neptunes at HD 42618, HD 164922 and Rho CrB

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