We propose a scenario to account for the surprising orbital properties of the planet orbiting the metal poor red horizontal branch star HIP 13044. The orbital period of 16.2 days implies that the planet went through a common envelope phase inside the red giant branch (RGB) stellar progenitor of HIP 13044. The present properties of the star imply that the star maintained a substantial envelope mass of 0.3Mo, raising the question of how the planet survived the common envelope before the envelope itself was lost? If such a planet enters the envelope of an RGB star, it is expected to spiral-in to the very inner region within <100yr, and be evaporated or destructed by the core. We speculate that the planet was engulfed by the star as a result of the core helium flash that caused this metal poor star to swell by a factor of ~3-4. The evolution following the core helium flash is very rapid, and some of the envelope is lost due to the interaction with the planet, and the rest of the envelope shrinks within about a hundred years. This is about equal to the spiraling-in time, and the planet survived.
We report the discovery of a substellar companion around the giant star HIP67537. Based on precision radial velocity measurements from CHIRON and FEROS high-resolution spectroscopic data, we derived the following orbital elements for HIP67537$\,b$: m$_b$sin$i$ = 11.1$^{+0.4}_{-1.1}$ M$_{\rm {\tiny jup}}$, $a$ = 4.9$^{+0.14}_{-0.13}$ AU and $e$ = 0.59$^{+0.05}_{-0.02}$. Considering random inclination angles, this object has $\gtrsim$ 65% probability to be above the theoretical deuterium-burning limit, thus it is one of the few known objects in the planet to brown-dwarf transition region. In add…
The census of stellar and substellar companions of nearby stars is largely incomplete. It is, however, fundamentally important in the understanding of the stellar and planetary formation and evolution mechanisms. We aim to characterize the presence of physical companions in orbit around nearby stars. Orbiting secondary bodies influence the proper motion (PM) of their parent star through their gravitational reflex motion. Using the Hipparcos catalog and Gaia's second data release (GDR2), we determined the long-term PM of the stars common to these two catalogs. We then searched for a PM anomaly …
We present the direct-imaging discovery of a substellar companion in orbit around a Sun-like star member of the Hyades open cluster. So far, no other substellar companions have been unambiguously confirmed via direct imaging around main-sequence stars in Hyades. The star HIP 21152 is an accelerating star as identified by the astrometry from the Gaia and Hipparcos satellites. We have detected the companion, HIP 21152 B, in multi-epoch using the high-contrast imaging from SCExAO/CHARIS and Keck/NIRC2. We have also obtained the stellar radial-velocity data from the Okayama 188cm telescope. The CH…
Study of the impact of the post-MS evolution of the host star on the orbits of close-in planets. II. A giant planet in a close-in orbit around the RGB star HIP63242
OASIS Survey Direct Imaging and Astrometric Discovery of HIP 71618 B: A Substellar Companion Suitable for the Roman Coronagraph Technology Demonstration
HIP 67522 b is a 17 Myr old, close-in ($P_{orb} = 6.96$ d), Jupiter-sized ($R = 10\,R_{\oplus}$) transiting planet orbiting a Sun like star in the Sco-Cen OB association. We present our measurement of the system's projected orbital obliquity via two spectroscopic transit observations using the CHIRON spectroscopic facility. We present a global model that accounts for large surface brightness features typical of such young stars during spectroscopic transit observations. With a value of $|λ| = 5.8^{+2.8\,\circ}_{-5.7}$, it is unlikely that this well-aligned system is the result of a high eccent…
The GAPS programme at TNG LXXI. A sub-Neptune suitable for atmospheric characterization in a multiplanet and mutually inclined system orbiting the bright K dwarf TOI-5789 (HIP 99452)
INAF - Osservatorio Astrofisico di Torino（意大利国家天体物理研究所都灵天文台）；INAF - Osservatorio Astronomico di Palermo（意大利国家天体物理研究所巴勒莫天文台）；Instituto de Astrofísica de Canarias (IAC)（加那利天体物理学研究所）；Departamento de Astrofísica, Universidad de La Laguna (ULL)（拉帕马大学天体物理学系）；INAF-Osservatorio Astronomico di Roma（意大利国家天体物理研究所罗马天文台）；Space Research Institute, Austrian Academy of Sciences（奥地利科学院空间研究所）
A metallicity, chemical composition, and kinematic survey has been conducted for a sample of 340 candidate field red horizontal branch stars. High resolution, high signal-to-noise spectra were gathered with the McDonald Observatory 2.7m Tull and the Hobby-Eberly Telescope echelle spectrographs, and were used to determine effective temperatures, surface gravities, microturbulent velocities, [Fe/H] metallicities, and abundance ratios [X/Fe] for seven $α$ and Fe-group species. The derived temperatures and gravities confirm that at least half of the candidates are true RHB stars, with (average) pa…
We have been conducting a exoplanet search survey using Bohyunsan Observatory Echelle Spectrograph (BOES) for the last 18 years. We present the detection of exoplanet candidate in orbit around HD 18438 from high-precision radial velocity (RV) mesurements. The target was already reported in 2018 (Bang et al. 2018). They conclude that the RV variations with a period of 719 days are likely to be caused by the pulsations because the Lomb-Scargle periodogram of HIPPARCOS photometric and Ha EW variations for HD 18438 show peaks with periods close to that of RV variations and there were no correlatio…
Discovery of a Low-Mass Companion to the Accelerating Star HIP 53005 with Strongly Conflicting Mass Estimates
Astrobiology Center（天体生物学中心）；National Astronomical Observatory of Japan（日本国立天文台）；Department of Physics and Astronomy, University of Texas-San Antonio（德克萨斯大学圣安东尼奥分校物理与天文系）；Subaru Telescope, National Astronomical Observatory of Japan, National Institutes of Natural Sciences（国立研究开发法人自然科学研究机构国立天文台昴星团望远镜）；Department of Astronomy, California Institute of Technology（加州理工学院天文学系）；Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles（加州大学洛杉矶分校地球、行星与空间科学系）；European Southern Observatory（欧洲南方天文台）；Department of Physics, University of California, Santa Barbara（加州大学圣塔芭芭拉分校物理系）；LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université Paris Cité（巴黎天文台LESIA实验室，巴黎文理研究大学，法国国家科学研究中心，索邦大学，巴黎西岱大学）；INAF – Osservatorio Astronomico di Padova（意大利国家天体物理研究所帕多瓦天文台）
Connecting planets around horizontal branch stars with known exoplanets
我们研究了主序（MS）恒星周围系外行星的分布，并将我们的结果应用于极端水平分支（EHB; sdO; sdB;热次矮星）恒星形成的二元模型。通过双星模型，我们指的是恒星和亚恒星的同伴，提高质量损失率，其中亚恒星的同伴代表大质量行星和褐矮星。我们的结论是sdB（EHB）恒星是行星搜索的主要目标。我们得出这一结论是因为我们注意到，行星围绕恒星的双峰分布相对于参数M_p*a^2在质量范围为1 Mo < M < 1.5Mo的恒星中最为显著; 'a'是轨道间距，'M'是恒星质量，'M_p'是行星质量。这也是EHB恒星的祖先的质量范围，这些恒星是通过它们的祖先与行星的相互作用形成的（假设EHB的形成机制是双星模型）。在EHB星形成的双星模型中，与双星伴星或亚恒星物体（行星或棕矮星）的相互作用，导致其前身在红巨星分支（RGB）阶段失去了大部分的包层质量。因此，后代HB星是热的，即，一颗EHB（sdB）星。双峰分布表明，即使形成EHB恒星的近距离行星没有在其RGB共同包层演化中幸存下来，也可能有一颗或多颗行星在>1AU的位置幸存下来。此外，如果一颗或更多的行星在大于1AU的位置被观测到，那么有可能是一颗更近的大质量行星在共同包层阶段幸存下来，并且它以数小时到数天的轨道周期绕着EHB运行。
We report the confirmation and mass determination of three hot Jupiters discovered by the Transiting Exoplanet Survey Satellite (TESS) mission: HIP 65Ab (TOI-129, TIC-201248411) is an ultra-short-period Jupiter orbiting a bright (V=11.1 mag) K4-dwarf every 0.98 days. It is a massive 3.213 +/- 0.078 Mjup planet in a grazing transit configuration with an impact parameter of b = 1.17 +0.10/-0.08. As a result the radius is poorly constrained, 2.03 +0.61/-0.49 Rjup. The planet's distance to its host star is less than twice the separation at which it would be destroyed by Roche lobe overflow. It is …
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…
Brown dwarfs with well-determined ages, luminosities, and masses provide rare but valuable tests of low-temperature atmospheric and evolutionary models. We present the discovery and dynamical mass measurement of a substellar companion to HD 47127, an old ($\approx$7-10 Gyr) G5 main sequence star with a mass similar to the Sun. Radial velocities of the host star with the Harlan J. Smith Telescope uncovered a low-amplitude acceleration of 1.93 $\pm$ 0.08 m s$^{-1}$ yr$^{-1}$ based on 20 years of monitoring. We subsequently recovered a faint ($ΔH$=13.14 $\pm$ 0.15 mag) co-moving companion at 1.95…
The Pan-Pacific Planet Search -- IX. A menagerie of companions orbiting evolved stars
University of Southern Queensland（南昆士兰大学）；Max Planck Institute for Astronomy（马克斯·普朗克天文学研究所）；Department of Astronomy & Astrophysics, University of Chicago（芝加哥大学天文与天体物理系）；Department of Physical Sciences, Kutztown University（库茨敦大学物理科学系）；Sydney Institute for Astronomy (SIfA), School of Physics, University of Sydney（悉尼大学物理学院悉尼天体物理研究所）；Institute for Astronomy, University of Hawai‘i（夏威夷大学天体物理研究所）；School of Physics, UNSW Sydney（新南威尔士大学悉尼分校物理学院）；Department of Physics, National University of Singapore（新加坡国立大学物理系）
Exoplanet systems with multiple transiting planets are natural laboratories for testing planetary astrophysics. One such system is HD 191939 (TOI-1339), a bright (V=9) and Sun-like (G9V) star, which TESS found to host three transiting planets (b, c, and d). The planets have periods of 9, 29, and 38 days each with similar sizes from 3 to 3.4 $R_{\oplus}$. To further characterize the system, we measured the radial velocity (RV) of HD 191939 over 415 days with Keck/HIRES and APF/Levy. We find that $M_b = 10.4 \pm 0.9 M_{\oplus}$ and $M_c = 7.2 \pm 1.4 M_{\oplus}$, which are low compared to most k…
We present the discovery of a transiting hot Jupiter orbiting HIP 67522 ($T_{eff}\sim5650$ K; $M_* \sim 1.2 M_{\odot}$) in the 10-20 Myr old Sco-Cen OB association. We identified the transits in the TESS data using our custom notch-filter planet search pipeline, and characterize the system with additional photometry from Spitzer, spectroscopy from SOAR/Goodman, SALT/HRS, LCOGT/NRES, and SMARTS/CHIRON, and speckle imaging from SOAR/HRCam. We model the photometry as a periodic Gaussian process with transits to account for stellar variability, and find an orbital period of 6.9596$^{+0.000016}_{-0…
The OATMEAL Survey. III. An Aligned Transiting Warm Brown Dwarf and Evidence for Quiescent Brown Dwarf Migration
Michigan State University（密歇根州立大学）；University of Illinois at Urbana-Champaign（伊利诺伊大学厄巴纳-香槟分校）；Center for Astrophysics | Harvard & Smithsonian（哈佛与史密森尼天体物理中心）；University of Southern Queensland（昆士兰南方大学）；University of Hawai‘i（夏威夷大学）；California Institute of Technology（加州理工学院）；The Observatories of the Carnegie Institution for Science（卡内基科学促进会天文台）
In this study, we independently test the presence of an exoplanet around the binary KIC 9472174, which is composed of a red dwarf and a pulsating type B subdwarf. We also present the results of our search for Jupiter-mass objects orbiting near to the eclipsing binary KIC 7975824, which is composed of a white dwarf and type B subdwarf, and the pulsating white dwarf KIC 8626021. The goal is to test analytical techniques and prepare the ground for a larger search for possible substellar survivors on tight orbits around post-common envelope binaries and stars at the end of their evolution, that is…
For over 10 years, we have carried out a precise radial velocity (RV) survey to find substellar companions around evolved G,K-type stars to extend our knowledge of planet formation and evolution. We performed high precision RV measurements for the giant star HD 208897 using an iodine (I2) absorption cell. The measurements were made at TÜBİTAK National Observatory (TUG, RTT150) and Okayama Astrophysical Observatory (OAO). For the origin of the periodic variation seen in the RV data of the star, we adopted a Keplerian motion caused by an unseen companion. We found that the star hosts a planet wi…
Small planets are common around late-M dwarfs and can be detected through highly precise photometry by the transit method. Planets orbiting nearby stars are particularly important as they are often the best-suited for future follow-up studies. We present observations of three nearby M-dwarfs referred to as EIC-1, EIC-2, and EIC-3, and use them to search for transits and set limits on the presence of planets. On most nights our observations are sensitive to Earth-sized transiting planets, and photometric precision is similar to or better than TESS for faint late-M dwarfs of the same magnitude (…
We present the discovery of TOI-197.01, the first transiting planet identified by the Transiting Exoplanet Survey Satellite (TESS) for which asteroseismology of the host star is possible. TOI-197 (HIP116158) is a bright (V=8.2 mag), spectroscopically classified subgiant which oscillates with an average frequency of about 430 muHz and displays a clear signature of mixed modes. The oscillation amplitude confirms that the redder TESS bandpass compared to Kepler has a small effect on the oscillations, supporting the expected yield of thousands of solar-like oscillators with TESS 2-minute cadence o…
As part of the search for planets around evolved stars, we can understand planet populations around significantly higher-mass stars than the Sun on the main sequence. This population is difficult to study any other way, particularly with radial-velocities since these stars are too hot and rotate too fast to measure precise velocities. Here we estimate stellar parameters for all of the giant stars from the EXPRESS project, which aims to detect planets orbiting evolved stars, and study their occurrence rate as a function of stellar mass. We analyse high resolution echelle spectra of these stars,…
Aims. The project aims to understand better the role of wide brown dwarf companions on planetary systems. Methods. We obtained high-resolution spectra of six bright stars with co-moving wide substellar companions with the SONG, CARMENES, and STELLA high-resolution spectrographs. We used these spectra to derive radial velocities together with a complete set of stellar physical parameters. We then investigated radial velocities signals and discussed the fraction of planets in such systems. We also re-analyzed the ages of our targets, which were used to derive the physical parameters of wide brow…
An Outer Giant Planet or Brown Dwarf in the 51 Pegasi System?
University of California, Santa Barbara（加州大学圣塔芭芭拉分校）；University of California, Santa Cruz（加州大学圣克鲁兹分校）；University of Hawai’i at Mänoa（夏威夷大学马诺阿分校）；Yale University（耶鲁大学）；The University of Texas at Austin（德克萨斯大学奥斯汀分校）；University of California Los Angeles（加州大学洛杉矶分校）；Michigan State University（密歇根州立大学）
