HD 3167 - Two transiting super-Earths around V = 8.94 star

Two Small Planets Transiting HD 3167
http://arxiv.org/abs/1607.05248

Quote :

We report the discovery of two super-Earth-sized planets transiting the bright (V = 8.94, K = 7.07) nearby late G-dwarf HD 3167, using data collected by the K2 mission. The inner planet, HD 3167 b, has a radius of 1.6 R_e and an ultra-short orbital period of only 0.96 days. The outer planet, HD 3167 c, has a radius of 2.9 R_e and orbits its host star every 29.85 days. At a distance of just 45.8 +/- 2.2 pc, HD 3167 is one of the closest and brightest stars hosting multiple transiting planets, making HD 3167 b and c well suited for follow-up observations. The star is chromospherically inactive and slowly rotating, ideal for radial velocity observations to measure the planets' masses. The outer planet is large enough that it likely has a thick gaseous envelope which could be studied via transmission spectroscopy. Planets transiting bright, nearby stars like HD 3167 are valuable objects to study leading up to the launch of the James Webb Space Telescope.

The Campaign 8 data was released on the 1st of this month. That's discovery, follow-up, writing, submission, and publication in under 3 weeks.

This system seems quite similar to Kepler-10, but ~2.5 magnitudes brighter. The star is inactive, so I expect strong mass measurements will be published within a couple of years.

Well we do not need really to wait for RV measurement .First planet is so close that surely lost all volatiles and water if it ever had being dense rocky world and second is too large and surely has low density and thick atmosphere

RV data is available, confirming the b planet is a rocky super-Earth and the c planet is a low-density sub-Neptune. They also uncover a third non-transiting planet between the two transiting planets with a minimum mass of 6.9±0.71 Earth-masses.

Three's Company: An additional non-transiting super-Earth in the bright HD 3167 system, and masses for all three planets
https://arxiv.org/abs/1706.01892

I would rule out any volatiles on planet b .Core mass fraction (15%) much smaller than Earth seems quite common for planets larger than Earth HD 219134b kepler 97 b are examples

Another paper on this system

The transiting multi-planet system HD3167: a 5.7 MEarth Super-Earth and a 8.3 MEarth mini-Neptune
https://arxiv.org/abs/1706.02532

Quote :

D3167 is a bright (V=8.9 mag) K0V star observed by the NASA's K2 space mission during its Campaign 8. It has been recently found to host two small transiting planets, namely, HD3167b, an ultra short period (0.96 d) super-Earth, and HD3167c, a mini-Neptune on a relatively long-period orbit (29.85 d). Here we present an intensive radial velocity follow-up of HD3167 performed with the FIES@NOT, HARPS@ESO-3.6m, and HARPS-N@TNG spectrographs. We revise the system parameters and determine radii, masses, and densities of the two transiting planets by combining the K2 photometry with our spectroscopic data. With a mass of 5.69+/-0.44 MEarth, radius of 1.574+/-0.054 REarth, and mean density of 8.00(+1.0)(-0.98) g/cm^3, HD3167b joins the small group of ultra-short period planets known to have a rocky terrestrial composition. HD3167c has a mass of 8.33 (+1.79)(-1.85) MEarth and a radius of 2.740(+0.106)(-0.100) REarth, yielding a mean density of 2.21(+0.56)(-0.53) g/cm^3, indicative of a planet with a composition comprising a solid core surrounded by a thick atmospheric envelope. The rather large pressure scale height (about 350 km) and the brightness of the host star make HD3167c an ideal target for atmospheric characterization via transmission spectroscopy across a broad range of wavelengths. We found evidence of additional signals in the radial velocity measurements but the currently available data set does not allow us to draw any firm conclusion on the origin of the observed variation.

So we have 2 transiting planets 1 day and 28 days orbit, 1 non transiting 8 days and 2 putative planets also non transiting with periods 6 and 10.7 days .System is getting more and more interesting

So Keck/HIRES+APF/Levy+HARPS-N gives one result, FIES+HARPS+HARPS-N gives another.

This does not mean two additional planets. For starters, the paper notes that the 10.7-day period and the 8.4-day period appear to be aliases of each other - the beat frequency corresponds to one of the peaks in the window function. Their analysis prefers the 10.7-day period over the 8.4-day period. (Section 5.4)

tommi59 wrote:

System is getting more and more interesting

Nearly Polar orbit of the sub-Neptune HD3167 c: Constraints on a multi-planet system dynamical history
https://arxiv.org/abs/1906.11013

Quote :

We present the obliquity measurement i.e. the angle between the normal of the planet orbital plane and stellar spin axis of the sub-Neptune planet HD3167 c that transits a bright, nearby K0 star. New observations obtained with HARPS-N at Telescopio Nazionale Galileo (TNG) are employed for our analysis. We study the orbital architecture of this multi-planet system to understand its dynamical history. We also put constraints on the obliquity of planet d from the geometry of the planetary system and the dynamical study of the system. The sky-projected obliquity is measured using three different methods, i.e Rossiter-McLaughlin anomaly, Doppler tomography and Reloaded Rossiter-McLaughlin techniques. We perform the stability analysis of the system and investigate the dynamical interactions between the planets and star. HD3167 c is found to be nearly polar with sky-projected obliquity, λ = -98∘±23∘. This misalignment of the orbit of planet c with the spin axis of the host star is detected with 97% confidence. The analysis of the dynamics of this system yields coplanar orbits of planets c and d. It also shows that it is unlikely that the currently observed system can, by itself, generate such a large obliquity for planets c and d. However, the polar orbits of planets c and d could be explained by the presence of an outer companion in the system. Follow-up observations of the system are required to confirm such a long period companion.

Bourrier et al. (2022) "A CHEOPS-enhanced view of the HD3167 system"
https://doi.org/10.1051/0004-6361/202243778

The system contains an additional non-transiting fourth planet HD 3167 e in a 102-day orbit, likely coplanar with planets c and d. The ultra-short period planet b has a density too low to be a pure rock planet, indicating a non-zero water mass fraction (possibly mixed in with the magma ocean). Planet d is predicted to have undergone a similar atmospheric evolution, while planets c and e are likely to have suffered minimal mass loss and retained primordial H/He atmospheres.

Lazarus wrote:

Bourrier et al. (2022) "A CHEOPS-enhanced view of the HD3167 system"
https://doi.org/10.1051/0004-6361/202243778

The system contains an additional non-transiting fourth planet HD 3167 e in a 102-day orbit, likely coplanar with planets c and d. The ultra-short period planet b has a density too low to be a pure rock planet, indicating a non-zero water mass fraction (possibly mixed in with the magma ocean). Planet d is predicted to have undergone a similar atmospheric evolution, while planets c and e are likely to have suffered minimal mass loss and retained primordial H/He atmospheres.

Great premiere, Lazarus!

Lazarus wrote:

Bourrier et al. (2022) "A CHEOPS-enhanced view of the HD3167 system"
https://doi.org/10.1051/0004-6361/202243778

The system contains an additional non-transiting fourth planet HD 3167 e in a 102-day orbit, likely coplanar with planets c and d. The ultra-short period planet b has a density too low to be a pure rock planet, indicating a non-zero water mass fraction (possibly mixed in with the magma ocean). Planet d is predicted to have undergone a similar atmospheric evolution, while planets c and e are likely to have suffered minimal mass loss and retained primordial H/He atmospheres.

Here is arXiv preprint too