New planets around K giant stars

Unexpected find and seemingly overlooked discovery (January 2020!), unless previously posted. Otherwise, please, merge the topics.

A SEARCH FOR EXOPLANETS AROUND NORTHERN CIRCUMPOLAR STARS VI. DETECTION OF PLANETARY COMPANIONS ORBITING THE GIANTS HD 60292 AND HD 112640

Quote :

We report the detection of exoplanet candidates in orbits around HD 60292 and HD 112640 from a radial velocity (RV) survey. The stars exhibit RV variations with periods of 495 ±3 days and 613±6 days, respectively. These detections are part of the Search for Exoplanets around Northern Circumpolar Stars (SENS) survey using the fiber-fed Bohyunsan Observatory Echelle Spectrograph installed at the 1.8-m telescope of the Bohyunsan Optical Astronomy Observatory in Korea. The aim of the survey is to search for planetary or substellar companions. We argue that the periodic RV variations are not related to surface inhomogeneities; rather, Keplerian motions of planetary companions are the most likely interpretation. Assuming stellar masses of 1.7 ± 0.2M⊙ (HD 60292) and 1.8 ± 0.2M⊙ (HD 112640), we obtain minimum planetary companion masses of 6.5 ± 1.0MJup and 5.0 ± 1.0MJup, and periods of 495.4 ± 3.0 days and 613.2 ± 5.8 days, respectively.

Open-access too, not paywalled.

Amazing! Thank-you for pointing this out. I think this totally escaped my notice.

Waiting for more solid updates...

Chemical abundances of three new Ba stars from the Keck/HIRES spectra

Quote :

Based on high resolution, high signal-to-noise (S/N) ratio spectra from Keck/HIRES, we have determined abundances of 20 elements for 18 Ba candidates. The parameter space of these stars is in the range of 4880 ≤ T eff ≤ 6050 K,  2.56≤logg≤4.53dex  and - 0.27 ≤ [Fe/H] ≤ 0.09 dex. It is found that four of them can be identified as Ba stars with [s/Fe] > 0.25 dex (s: Sr, Y, Zr, Ba, La, Ce and Nd), and three of them are newly discovered, which include two Ba giants (HD 16178 and HD 22233) and one Ba subgiant (HD 2946). Our results show that the abundances of α, odd and iron-peak elements (O, Na, Mg, Al, Si, Ca, Sc, Ti, Mn, Ni and Cu) for our program stars are similar to those of the thin disk, while the distribution of [hs/ls] (hs: Ba, La, Ce and Nd, ls: Sr, Y and Zr) ratios of our Ba stars is similar to those of the known Ba objects. None of the four Ba stars show clear enhancement in carbon including the known CH subgiant HD 4395. It is found that three of the Ba stars present clear evidence of hosting stellar or sub-stellar companions from the radial velocity data.

Emphasis mine. No orbital solution is provided yet.
As stated in the paper, possible host stars are the following ones:

Quote :

Three of our four Ba stars, HD 4395, HD 16178 and HD 22233, have clear evidences of hosting stellar or sub-stellar companions in long-term radial velocity data, and the binarity for the Ba subgiant HD 2946 cannot be excluded

Personal musings: if barium stars have usually a WD binary companion responsible for observed barium excess, any putative substellar companion might represent a "second generation planet/companion".

Third inner planet detected in HD 33142 system, yet EPE was already listing 3 planets but one of them seems repeated

A new third planet and the dynamical architecture of the HD33142 planetary system

Quote :

Based on recently-taken and archival HARPS, FEROS and HIRES radial velocities (RVs), we present evidence for a new planet orbiting the first ascent red giant star HD33142 (with an improved mass estimate of 1.52±0.03 M⊙), already known to host two planets. We confirm the Jovian mass planets HD33142 b and c with periods of Pb = 330.0+0.4−0.4 d and Pc = 810.2+3.8−4.2 d and minimum dynamical masses of mbsini = 1.26+0.05−0.05 MJup and mcsini = 0.89+0.06−0.05 MJup. Furthermore, our periodogram analysis of the precise RVs shows strong evidence for a short-period Doppler signal in the residuals of a two-planet Keplerian fit, which we interpret as a third, Saturn-mass planet with mdsini = 0.20+0.02−0.03 MJup on a close-in orbit with an orbital period of Pd =89.9+0.1−0.1 d. We study the dynamical behavior of the three-planet system configurations with an N-body integration scheme, finding it long-term stable with the planets alternating between low and moderate eccentricities episodes. We also performed N-body simulations, including stellar evolution and second-order dynamical effects such as planet-stellar tides and stellar mass-loss on the way to the white dwarf phase. We find that planets HD33142 b, c and d are likely to be engulfed near the tip of the red giant branch phase due to tidal migration. These results make the HD33142 system an essential benchmark for the planet population statistics of the multiple-planet systems found around evolved stars.

Outstanding find. So multi-planet systems around giant stars are not uncommon

A Trio of Giant Planets Orbiting Evolved Star HD 184010
https://arxiv.org/abs/2209.09426

Astonishing!

High resolution ALMA and HST imaging of κCrB: a broad debris disc around a post-main sequence star with low-mass companions

Quote :

κ CrB is a ∼2.5Gyr old K1 sub-giant star, with an eccentric exo-Jupiter at ∼2.8au and a debris disc at tens of au. We present ALMA Band 6 (1.3mm) and HST scattered light (0.6μm) images, demonstrating κ CrB's broad debris disc, covering an extent 50−180au in the millimetre (peaking at 110au), and 51−280au in scattered light (peaking at 73au). By modelling the millimetre emission, we estimate the dust mass as ∼0.016M⊕, and constrain lower-limit planetesimal sizes as D_max>1km and the planetesimal belt mass as M_disc>1M⊕. We constrain the properties of an outer body causing a linear trend in 17 years of radial velocity data to have a semi-major axis 8−66au and a mass (0.4−120)M_Jup. There is a large inner cavity seen in the millimetre emission, which we show is consistent with carving by such an outer massive companion with a string of lower mass planets. Our scattered light modelling shows that the dust must have a high anisotropic scattering factor (g∼0.8−0.9) but an inclination (i ∼ 30-40 degrees) that is inferred to be significantly lower than the i ∼ 61 degrees millimetre inclination. The origin of such a discrepancy is unclear, but could be caused by a misalignment in the micron and millimetre sized dust. We place an upper limit on the CO gas mass of M_CO<(4.2-13)×10^-7 M⊕, and show this to be consistent with levels expected from planetesimal collisions, or from CO-ice sublimation as κCrB begins its giant branch ascent.

Modelled second giant planet with m_c sin i = 0.39 M_Jup at a_c = 6 AUs. But that's not all:

Quote :

Thirdly for the disc to be producing visible levels of dust, it is possible that this disc is being stirred by a planet. There is however only one known planet, the inner exo-Jupiter κ CrB b, and this planet alone could not be responsible for the observed disc architecture. [...] We note here however, that since the cavity may have formed much earlier in the system’s lifetime (and the equations of Shannon et al. (2016) are based on the age of the system) fewer planets with a greater total mass could have been responsible for the observed cavity i.e., the above planet mass estimates should be seen as lower limits. Since the putative RV companion could however be anywhere between 8-66 au (rather than at either limit) these two example calculations serve to demonstrate that in addition to κ CrB b and the putative RV planet, a significant number of additional planets may be required to produce the observed disc morphology if planet sculpting from non-migrating planets is the main cause of the observed cavity.

Edasich wrote:

Modelled second giant planet with m_c sin i = 0.39 M_Jup at a_c = 6 AUs.

Unfortunately that one doesn't seem too plausible.

Quote :

Whilst this model comparison investigation suggests that a 2-planet configuration is statistically favoured, we argue against such a configuration on dynamical grounds. In the modelled scenario, whilst the inner planet remains in the same location, the model derives the outer planet mass as M_{pl c} sin i=0.39±0.10 M_Jup, the semimajor axis as a=6.0±0.4 au, and the eccentricity as e=0.78±0.13. Such an eccentricity and orbital radius result in this body having a periastron at ∼1.3 au, i.e., inside the 2.8 au orbit of the exo-Jupiter, κ CrB b, which we deem an unstable configuration over the 2.5 Gyr age of the system.