The first super-Earth Detection from the High Cadence and High Radial Velocity Precision Dharma Planet Survey

The Dharma Planet Survey (DPS) aims to monitor about 150 nearby very bright FGKM dwarfs (within 50 pc) during 2016$-$2020 for low-mass planet detection and characterization using the TOU very high resolution optical spectrograph (R$\approx$100,000, 380-900nm). TOU was initially mounted to the 2-m Automatic Spectroscopic Telescope at Fairborn Observatory in 2013-2015 to conduct a pilot survey, then moved to the dedicated 50-inch automatic telescope on Mt. Lemmon in 2016 to launch the survey. Here we report the first planet detection from DPS, a super-Earth candidate orbiting a bright K dwarf star, HD 26965. It is the second brightest star ($V=4.4$ mag) on the sky with a super-Earth candidate. The planet candidate has a mass of 8.47$\pm0.47M_{\rm Earth}$, period of $42.38\pm0.01$ d, and eccentricity of $0.04^{+0.05}_{-0.03}$. This RV signal was independently detected by Diaz et al. (2018), but they could not confirm if the signal is from a planet or from stellar activity. The orbital period of the planet is close to the rotation period of the star (39$-$44.5 d) measured from stellar activity indicators. Our high precision photometric campaign and line bisector analysis of this star do not find any significant variations at the orbital period. Stellar RV jitters modeled from star spots and convection inhibition are also not strong enough to explain the RV signal detected. After further comparing RV data from the star's active magnetic phase and quiet magnetic phase, we conclude that the RV signal is due to planetary-reflex motion and not stellar activity.Comment: 13 pages, 17 figures, Accepted for publication in MNRA

TOI 694b and TIC 220568520b: Two Low-mass Companions near the Hydrogen-burning Mass Limit Orbiting Sun-like Stars

We report the discovery of TOI 694 b and TIC 220568520 b, two low-mass stellar companions in eccentric orbits around metal-rich Sun-like stars, first detected by the Transiting Exoplanet Survey Satellite (TESS). TOI 694 b has an orbital period of 48.05131 +- 0.00019 days and eccentricity of 0.51946 +- 0.00081, and we derive a mass of 89.0 +- 5.3 MJup (0.0849 +- 0.0051 M☉) and radius of 1.111 +- 0.017 RJup (0.1142 +- 0.0017 R☉). TIC 220568520 b has an orbital period of 18.55769 +- 0.00039 days and eccentricity of 0.0964 +- 0.0032, and we derive a mass of 107.2 +- 5.2 MJup (0.1023 +- 0.0050 M☉) and radius of 1.248 +- 0.018 RJup (0.1282 +- 0.0019 R☉). Both binary companions lie close to and above the hydrogen-burning mass threshold that separates brown dwarfs and the lowest-mass stars, with TOI 694 b being 2σ above the canonical mass threshold of 0.075 M☉. The relatively long periods of the systems mean that the magnetic fields of the low-mass companions are not expected to inhibit convection and inflate the radius, which according to one leading theory is common in similar objects residing in short-period tidally synchronized binary systems. Indeed we do not find radius inflation for these two objects when compared to theoretical isochrones. These two new objects add to the short but growing list of low-mass stars with well-measured masses and radii, and highlight the potential of the TESS mission for detecting such rare objects orbiting bright stars.M.N.G. acknowledges support from MIT’s Kavli Institute as a Torres postdoctoral fellow. L.A.dS. is supported by funding from the European Research Council (ERC) under the European Unionʼs Horizon 2020 research and innovation program (project FOUR ACES; grant agreement No 724427). A.J. acknowledges support from FONDECYT project 1171208 and by the Ministry for the Economy, Development, and Tourism’s Programa Iniciativa Científica Milenio through grant IC 120009, awarded to the Millennium Institute of Astrophysics (MAS)

The first super-Earth detection from the high cadence and high radial velocity precision Dharma Planet Survey

The Dharma Planet Survey (DPS) aims to monitor about 150 nearby very bright FGKM dwarfs (within 50 pc) during 2016–2020 for low-mass planet detection and characterization using the TOU very high resolution optical spectrograph (⁠R≈100000⁠, 380–900 nm). TOU was initially mounted to the 2-m Automatic Spectroscopic Telescope at Fairborn Observatory in 2013–2015 to conduct a pilot survey, then moved to the dedicated 50-inch automatic telescope on Mt. Lemmon in 2016 to launch the survey. Here, we report the first planet detection from DPS, a super-Earth candidate orbiting a bright K dwarf star, HD 26965. It is the second brightest star (V = 4.4 mag) on the sky with a super-Earth candidate. The planet candidate has a mass of 8.47 ± 0.47MEarth, period of 42.38 ± 0.01 d, and eccentricity of 0.04+0.05−0.03⁠. This radial velocity (RV) signal was independently detected by Díaz et al., but they could not confirm if the signal is from a planet or stellar activity. The orbital period of the planet is close to the rotation period of the star (39–44.5 d) measured from stellar activity indicators. Our high precision photometric campaign and line bisector analysis of this star do not find any significant variations at the orbital period. Stellar RV jitters modelled from star-spots and convection inhibition are also not strong enough to explain the RV signal detected. After further comparing RV data from the star’s active magnetic phase and quiet magnetic phase, we conclude that the RV signal is due to planetary-reflex motion and not stellar activity

Exploring the brown dwarf desert : new substellar companions from the SDSS-III MARVELS survey

Planet searches using the radial velocity technique show a paucity of companions to solar-type stars within ∼5 au in the mass range of ∼10–80 MJup. This deficit, known as the brown dwarf desert, currently has no conclusive explanation. New substellar companions in this region help assess the reality of the desert and provide insight to the formation and evolution of these objects. Here, we present 10 new brown dwarf and 2 low-mass stellar companion candidates around solar-type stars from the Multi-object APO Radial Velocity Exoplanet Large-Area Survey (MARVELS) of the Sloan Digital Sky Survey III. These companions were selected from processed MARVELS data using the latest University of Florida Two Dimensional pipeline, which shows significant improvement and reduction of systematic errors over previous pipelines. The 10 brown dwarf companions range in mass from ∼13 to 76 MJup and have orbital radii of less than 1 au. The two stellar companions have minimum masses of ∼98 and 100 MJup. The host stars of the MARVELS brown dwarf sample have a mean metallicity of [Fe/H] = 0.03 ± 0.08 dex. Given our stellar sample we estimate the brown dwarf occurrence rate around solar-type stars with periods less than ∼300 d to be ∼0.56 per cent