HIP 41378 - Multi-Planet System from K2

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HIP 41378 - Multi-Planet System from K2

Post by Sirius_Alpha on 28th June 2016, 8:46 pm

Wow!

Five Planets Transiting a Ninth Magnitude Star
http://arxiv.org/abs/1606.08441

The Kepler mission has revealed a great diversity of planetary systems and architectures, but most of the planets discovered by Kepler orbit faint stars. Using new data from the K2 mission, we present the discovery of a five planet system transiting a bright (V = 8.9, K = 7.7) star called HIP 41378. HIP 41378 is a slightly metal-poor late F-type star with moderate rotation (v sin(i) = 7 km/s) and lies at a distance of 116 +/- 18 from Earth. We find that HIP 41378 hosts two sub-Neptune sized planets orbiting 3.5% outside a 2:1 period commensurability in 15.6 and 31.7 day orbits. In addition, we detect three planets which each transit once during the 75 days spanned by K2 observations. One planet is Neptune sized in a likely ~160 day orbit, one is sub-Saturn sized likely in a ~130 day orbit, and one is a Jupiter sized planet in a likely ~1 year orbit. We show that these estimates for the orbital periods can be made more precise by taking into account dynamical stability considerations. We also calculate the distribution of stellar reflex velocities expected for this system, and show that it provides a good target for future radial velocity observations. If a precise orbital period can be determined for the outer Jovian planet through future observations, it will be an excellent candidate for follow-up transit observations to study its atmosphere and measure its oblateness.

Admin note: This has been extracted from the Kepler-K2 Results thread since it deserves its own thread.


Last edited by Sirius_Alpha on 30th September 2018, 8:31 pm; edited 1 time in total

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Re: HIP 41378 - Multi-Planet System from K2

Post by Lazarus on 29th June 2016, 2:47 am

Interesting discovery, looking forward to follow-up on this one. Looks like they're all too close to the star to be habitable (though the uncertainties on the outer planet are quite large), maybe there's enough space between HIP 41378 f and the HZ for a planet to be stable there.
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Re: HIP 41378 - Multi-Planet System from K2

Post by Shellface on 29th June 2016, 3:23 pm

A week ago, I posted an independent study of this system to Planet Hunters. Vanderburg emailed me not long after, commenting that the results I reached were quite similar to those in this paper. I had no idea it was so close to being put to the presses, however! Martti, the third name on the author list, is a prominent member at PH, and I congratulate him on the recognition.

As far as I am aware, this is the second-brightest K2 system in the V-band. It is also the highest multiplicity planetary system identified by K2 to date - if K2 observations had been at a different time, it is quite likely that at least one of the mono-transiters would have been missed, so there is certainly some serendipity in these results

As it is bright and observable from most of the Earth, this is an exemplary system for planet characterisation. Mass measurements for all planets are plausible with modern technology, and atmospheric observations will be possible in the near future. In particular this is currently the brightest star with a transiting AU Jovian, so f is an excellent target for many projects; observing its Rossiter-McLaughlin effect, determining its oblateness, attempting to detect moons, to name a few. Determining the outer orbital periods is a priority, and I understand dedicated RV observations are underway.

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HIP 41378 - Multi-Planet System from K2

Post by Shellface on 8th July 2016, 3:06 pm

HIP 41378 becomes K2-93. Apparently ~50 systems are to be confirmed in the near future.

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Re: HIP 41378 - Multi-Planet System from K2

Post by Sirius_Alpha on 30th September 2018, 8:35 pm

A couple of updates to this system (which I just split from the K2 News and Results thread). The system was observed again by K2 in Campaign 18, revealing new transits of the d and f planets. This has allowed for discrete limits on what their orbital periods are. There's also TTV in the orbit of the c planet detected by Spitzer + Kepler-K2, which could be from the d, e or f planet.

A Discrete Set of Possible Transit Ephemerides for Two Long Period Gas Giants Orbiting HIP 41378
https://arxiv.org/abs/1809.10688

Revisiting the HIP41378 system with K2 and Spitzer
https://arxiv.org/abs/1809.11116

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