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Register a new userDetection of an exoplanet around the evolved K giant HD 66141
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Aims. We have been carrying out a precise radial velocity (RV) survey for K giants to search for and study the origin of the lowamplitude and long-periodic RV variations. Methods. We present high-resolution RV measurements of the K2 giant HD 66141 from December 2003 to January 2011 using the fiber-fed Bohyunsan Observatory Echelle Spectrograph (BOES) at Bohyunsan Optical Astronomy Observatory (BOAO). Results. We find that the RV measurements for HD 66141 exhibit a periodic variation of 480.5 +/- 0.5 days with a semi-amplitude of 146.2 +/- 2.7 m/s. The Hipparcos photometry and bisector velocity span (BVS) do not show any obvious correlations with RV variations. We find indeed 706.4 +/- 35.0 day variations in equivalent width (EW) measurements of H_alpha line and 703.0 +/- 39.4 day variations in a space-born measurements 1.25{mu} flux of HD 66141 measured during COBE/DIRBE experiment. We reveal that a mean value of long-period variations is about 705 +/- 53 days and the origin is a rotation period of the star and variability that is caused by surface inhomogeneities. For the 480 day periods of RV variations an orbital motion is the most likely explanation. Assuming a stellar mass of 1.1 +/- 0.1 M_Sun? for HD 66141, we obtain a minimum mass for the planetary companion of 6.0 +/- 0.3 M_Jup with an orbital semi-major axis of 1.2 +/- 0.1 AU and an eccentricity of 0.07 +/- 0.03.
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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 TUB.ITAK 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 with a minimum mass of m2sini=1.40MJ, which is relatively low compared to those of known planets orbiting evolved intermediate-mass stars. The planet is in a nearly circular orbit with a period of P=353 days at about 1 AU distance from the host star. The star is metal rich and located at the early phase of ascent along the red giant branch. The photometric observations of the star at Ankara University Kreiken Observatory (AUKR) and the HIPPARCOS photometry show no sign of variation with periods associated with the RV variation. Neither bisector velocity analysis nor analysis of the Ca II and Halpha lines shows any correlation with the RV measurements.
HD 95086 is an intermediate-mass debris-disk-bearing star. VLT/NaCo $3.8 mu m$ observations revealed it hosts a $5pm2 mathrm{M}_{Jup}$ companion (HD 95086 b) at $simeq 56$ AU. Follow-up observations at 1.66 and 2.18 $mu m$ yielded a null detection, suggesting extremely red colors for the planet and the need for deeper direct-imaging data. In this Letter, we report H- ($1.7 mu m$) and $mathrm{K}_1$- ($2.05 mu m$) band detections of HD 95086 b from Gemini Planet Imager (GPI) commissioning observations taken by the GPI team. The planet position in both spectral channels is consistent with the NaCo measurements and we confirm it to be comoving. Our photometry yields colors of H-L= $3.6pm 1.0$ mag and K$_1$-L=$2.4pm 0.7$ mag, consistent with previously reported 5-$sigma$ upper limits in H and Ks. The photometry of HD 95086 b best matches that of 2M 1207 b and HR 8799 cde. Comparing its spectral energy distribution with the BT-SETTL and LESIA planet atmospheric models yields T$_{mathrm{eff}}sim$600-1500 K and log g$sim$2.1-4.5. Hot-start evolutionary models yield M=$5pm2$ M$_{Jup}$. Warm-start models reproduce the combined absolute fluxes of the object for M=4-14 M$_{Jup}$ for a wide range of plausible initial conditions (S$_{init}$=8-13 k$_{B}$/baryon). The color-magnitude diagram location of HD 95086 b and its estimated T$_{mathrm{eff}}$ and log g suggest that the planet is a peculiar L-T transition object with an enhanced amount of photospheric dust.
The Transiting Exoplanet Survey Satellite (TESS) is an all-sky survey mission aiming to search for exoplanets that transit bright stars. The high-quality photometric data of TESS are excellent for the asteroseismic study of solar-like stars. In this work, we present an asteroseismic analysis of the red-giant star HD~222076 hosting a long-period (2.4 yr) giant planet discovered through radial velocities. Solar-like oscillations of HD~222076 are detected around $203 , mu$Hz by TESS for the first time. Asteroseismic modeling, using global asteroseismic parameters as input, yields a determination of the stellar mass ($M_star = 1.12 pm 0.12, M_odot$), radius ($R_star = 4.34 pm 0.21,R_odot$), and age ($7.4 pm 2.7,$Gyr), with precisions greatly improved from previous studies. The period spacing of the dipolar mixed modes extracted from the observed power spectrum reveals that the star is on the red-giant branch burning hydrogen in a shell surrounding the core. We find that the planet will not escape the tidal pull of the star and be engulfed into it within about $800,$Myr, before the tip of the red-giant branch is reached.
The Transiting Exoplanet Survey Satellite (TESS) is performing a near all-sky survey for planets that transit bright stars. In addition, its excellent photometric precision enables asteroseismology of solar-type and red-giant stars, which exhibit convection-driven, solar-like oscillations. Simulations predict that TESS will detect solar-like oscillations in nearly 100 stars already known to host planets. In this paper, we present an asteroseismic analysis of the known red-giant host stars HD 212771 and HD 203949, both systems having a long-period planet detected through radial velocities. These are the first detections of oscillations in previously known exoplanet-host stars by TESS, further showcasing the missions potential to conduct asteroseismology of red-giant stars. We estimate the fundamental properties of both stars through a grid-based modeling approach that uses global asteroseismic parameters as input. We discuss the evolutionary state of HD 203949 in depth and note the large discrepancy between its asteroseismic mass ($M_ast = 1.23 pm 0.15,{rm M}_odot$ if on the red-giant branch or $M_ast = 1.00 pm 0.16,{rm M}_odot$ if in the clump) and the mass quoted in the discovery paper ($M_ast = 2.1 pm 0.1,{rm M}_odot$), implying a change $>30,%$ in the planets mass. Assuming HD 203949 to be in the clump, we investigate the planets past orbital evolution and discuss how it could have avoided engulfment at the tip of the red-giant branch. Finally, HD 212771 was observed by K2 during its Campaign 3, thus allowing for a preliminary comparison of the asteroseismic performances of TESS and K2. We estimate the ratio of the observed oscillation amplitudes for this star to be $A_{rm max}^{rm TESS}/A_{rm max}^{rm K2} = 0.75 pm 0.14$, consistent with the expected ratio of $sim0.85$ due to the redder bandpass of TESS.
Photometry of the A0 V main-sequence star HD 106797 with AKARI and Gemini/T-ReCS is used to detect excess emission over the expected stellar photospheric emission between 10 and 20 micron, which is best attributed to hot circumstellar debris dust surrounding the star. The temperature of the debris dust is derived as Td ~ 190 K by assuming that the excess emission is approximated by a single temperature blackbody. The derived temperature suggests that the inner radius of the debris disk is ~ 14 AU. The fractional luminosity of the debris disk is 1000 times brighter than that of our own zodiacal cloud. The existence of such a large amount of hot dust around HD 106797 cannot be accounted for by a simple model of the steady state evolution of a debris disk due to collisions, and it is likely that transient events play a significant role. Our data also show a narrow spectral feature between 11 and 12 micron attributable to crystalline silicates, suggesting that dust heating has occurred during the formation and evolution of the debris disk of HD 106797.
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