Ultra-short period (USP) planets are a class of exoplanets with periods shorter than one day. The origin of this sub-population of planets is st ill unclear, with different formation scenarios highly dependent on the composition of the USP planets. A better understanding of this class of exoplanets will, therefore, require an increase in the sample of such planets that have accurate and precise masses and radii, which also includes estimates of the level of irradiation and information about possible companions. Here we report a detailed characterization of a USP planet around the solar-type star HD 80653 = EP 251279430 using the K2 light curve and 108 precise radial velocities obtained with the HARPS-N spectrograph, installed on the Telescopio Nazionale Galileo. From the K2 C16 data, we found one super-Earth planet (Rb=1.613+/-0.071R_{Earth}_) transiting the star on a short-period orbit (Pb=0.719573+/-0.000021d). From our radial velocity measurements, we constrained the mass of HD 80653 b to Mb=5.60+/-0.43M_{Earth}_. We also detected a clear longterm trend in the radial velocity data. We derived the fundamental stellar parameters and determined a radius of R*=1.22+/-0.01R_{sun}_ and mass of M*=1.18+/-0.04M_{sun}_, suggesting that HD 80653 has an age of 2.7+/-1.2Gyr. The bulk density (rho_b_=7.4+/-1.1g/cm^3^) of the planet is consistent with an Earth-like composition of rock and iron and no thick atmosphere. Our analysis of the K2 photometry also suggests hints of a shallow secondary eclipse with a depth of 8.1+/- 3.7ppm. Flux variations along the orbital phase are consistent with zero. The most important contribution might come from the day-side thermal emission from the surface of the planet at T=3480K.
HD 50138 presents the B[e] phenomenon, but its nature is not clear yet. This star is known to present spectral variations, which have been associated with outbursts and shell phases. We analyze the line profile variability of HD 50138 and its possible origin, which provide possible hints to its evolutionary stage, so far said to be close to the end of (or slightly beyond) the main sequence.
Since 2011, the SOPHIE spectrograph has been used to search for Neptunes and super-Earths in the northern hemisphere. As part of this observational program, 290 radial velocity measurements of the 6.4 V magnitude star HD 158259 were obtained. Additionally, TESS photometric measurements of this target are available. We present an analysis of the SOPHIE data and compare our results with the output of the TESS pipeline. The radial velocity data, ancillary spectroscopic indices, and ground-based photometric measurements were analyzed with classical and l_1_ periodograms. The stellar activity was modeled as a correlated Gaussian noise and its impact on the planet detection was measured with a new technique. The SOPHIE data support the detection of five planets, each with msini~=6M_{Earth}_, orbiting HD 158259 in 3.4, 5.2, 7.9, 12, and 17.4 days. Though a planetary origin is strongly favored, the 17.4 d signal is classified as a planet candidate due to a slightly lower statistical significance and to its proximity to the expected stellar rotation period. The data also present low frequency variations, most likely originating from a magnetic cycle and instrument systematics. Furthermore, the TESS pipeline reports a significant signal at 2.17 days corresponding to a planet of radius ~=1.2R_{Earth}_. A compatible signal is seen in the radial velocities, which confirms the detection of an additional planet and yields a ~=2M_{Earth}_ mass estimate. We find a system of five planets and a strong candidate near a 3:2 mean motion resonance chain orbiting HD 158259. The planets are found to be outside of the two and three body resonances.
High-resolution spectral observations during 1994-2017 are analysed in order to reveal long- and short-term changes in the spot activity of the FK Comae-type subgiant HD 199178. Most of the observations were collected with the Nordic Optical Telescope high resolution spectrographs SOFIN (34 sets) and FIES (6 sets). One set was obtained at the NAO (Rozhen), Bulgaria. The spectra were used to calculate Doppler imaging temperature maps for HD 199178 covering the years 1994-2017.
Hot Jupiters are surrounded by extended atmospheres of neutral hydrogen. Observations have provided evidence for in-transit hydrogen H{alpha} absorption as well as variable pre-transit absorption signals. These have been interpreted in terms of a bow shock or an accretion stream that transits the host star before the planet. We test the hypothesis of planetary related H{alpha} absorption by studying the time variability of the H{alpha} and stellar activity-sensitive calcium lines in high-resolution spectra of the planet host HD189733. In the framework of an observing campaign spanning several months, the host star was observed several times per week randomly sampling the orbital phases of the planet. We determine the equivalent width in the H{alpha}, Ca H&K and Ca IRT lines, and subtract stellar rotationally induced activity from the H{alpha} time series via its correlation with the IRT evolution. The residuals are explored for significant differences between the pre-, in-, and out-of-transit phases. We find strong stellar rotational variation with a lifetime of about 20-30 days in all activity indicators, but the corrected H{alpha} time series exhibits no significant periodic variation. We exclude the presence of more than 6.2m{AA}A pre-transit absorption and 5.6m{AA} in-transit absorption in the corrected H{alpha} data at a 99% confidence level. Previously observed H{alpha} absorption signals exceed our upper limits, but they could be related to excited atmospheric states. The H{alpha} variability in the HD189733 system is dominated by stellar activity, and observed signals around the planetary transit may well be caused by short term stellar variability.
We have used 46 high-resolution echelle spectra of the Wolf-Rayet star HD 192163 taken in 2005-2009 at the Cassegrain focus of the 2-m Zeiss-2000 telescope of the Shamakha Astrophysical Observatory to study profiles of the five strongest emission lines (HeII 4859, HeII 5411, CIV 5808, HeI 5875, (HeII+Halpha) 6560). We also obtained four echelle spectrograms of the Wolf-Rayet star HD 191765 for a comparative study of the NaI 5890 (D2) and NaI 5896 (D1) interstellar absorption lines. The echelle spectrograms were reduced using the DECH20 code. We determined the equivalent widths, radial velocities, central intensities, and half-widths of the emission lines. We We also studied the NaI 5890 (D2) and NaI 5896 (D1) interstellar absorption lines, which are important for understanding the nature of the nebula NGC 6888, whose origin is related to HD 192163.
The metal-poor post-asymptotic giant branch (AGB) star HD 46703 is shown to be a single-line spectroscopic binary with a period of 600-days, a high velocity of -94km/s, and an orbital eccentricity of 0.3. Light-curve studies show that it also pulsates with a period of 29-days. High-resolution, high signal-to-noise spectra were used for a new abundance study.
Debris disks offer valuable insights into the latest stages of circumstellar disk evolution, and can possibly help us to trace the outcomes of planetary formation processes. In the age range 10 to 100Myr, most of the gas is expected to have been removed from the system, giant planets (if any) must have already been formed, and the formation of terrestrial planets may be on-going. Pluto-sized planetesimals, and their debris released in a collisional cascade, are under their mutual gravitational influence, which may result into non-axisymmetric structures in the debris disk. Here we present new VLT/SPHERE and ALMA observations of the debris disk around the 40Myr-old solar-type star HD61005. We resolve the disk at unprecedented resolution both in the near-infrared (in scattered and polarized light) and at millimeter wavelengths. We perform a detailed modeling of these observations, including the spectral energy distribution. Thanks to the new observations, we propose a solution for both the radial and azimuthal distribution of the dust grains in the debris disk. We find that the disk has a moderate eccentricity and that the dust density is two times larger at the pericenter compared to the apocenter. With no giant planets detected in our observations, we investigate alternative explanations besides planet-disk interactions to interpret the inferred disk morphology. We postulate that the morphology of the disk could be the consequence of a massive collision between 1000km-sized bodies at 61 au. If this interpretation holds, it would put stringent constraints on the formation of massive planetesimals at large distances from the star.
In this paper we present the results of the SPHERE observation of the HD 284149 system, aimed at a more detailed characterisation of both the primary and its brown dwarf companion. We observed HD 284149 in the near-infrared with SPHERE, using the imaging mode (IRDIS+IFS) and the long-slit spectroscopy mode (IRDIS-LSS). The data were reduced using the dedicated SPHERE pipeline, and algorithms such as PCA and TLOCI were applied to reduce the speckle pattern. The IFS images revealed a previously unknown low-mass (~0.16M_{sun}_) stellar companion (HD 294149 B) at ~0.1", compatible with previously observed radial velocity differences, as well as proper motion differences between Gaia and Tycho-2 measurements. The known brown dwarf companion (HD 284149 b) is clearly visible in the IRDIS images. This allowed us to refine both its photometry and astrometry. The analysis of the medium resolution IRDIS long slit spectra also allowed a refinement of temperature and spectral type estimates. A full reassessment of the age and distance of the system was also performed, leading to more precise values of both mass and semi-major axis. As a result of this study, HD 284149 ABb therefore becomes the latest addition to the (short) list of brown dwarfs on wide circumbinary orbits, providing new evidence to support recent claims that object in such configuration occur with a similar frequency to wide companions to single stars.
Young planets are expected to cause cavities, spirals, and kinematic perturbations in protostellar disks that may be used to infer their presence. However, a clear detection of still-forming planets embedded within gas-rich disks is still rare. HD169142 is a very young Herbig Ae-Be star surrounded by a pre-transitional disk, composed of at least three rings. While claims of sub-stellar objects around this star have been made previously, follow-up studies remain inconclusive. The complex structure of this disk is not yet well understood. We used the high contrast imager SPHERE at ESO Very large Telescope to obtain a sequence of high-resolution, high-contrast images of the immediate surroundings of this star over about three years in the wavelength range 0.95-2.25um. This enables a photometric and astrometric analysis of the structures in the disk. While we were unable to definitively confirm the previous claims of a massive sub-stellar object at 0.1-0.15arcsec from the star, we found both spirals and blobs within the disk. The spiral pattern may be explained as due to the presence of a primary, a secondary, and a tertiary arm excited by a planet of a few Jupiter masses lying along the primary arm, likely in the cavities between the rings. The blobs orbit the star consistently with Keplerian motion, allowing a dynamical determination of the mass of the star. While most of these blobs are located within the rings, we found that one of them lies in the cavity between the rings, along the primary arm of the spiral design. This blob might be due to a planet that might also be responsible for the spiral pattern observed within the rings and for the cavity between the two rings. The planet itself is not detected at short wavelengths, where we only see a dust cloud illuminated by stellar light, but the planetary photosphere might be responsible for the emission observed in the K1 and K2 bands. The mass of this putative planet may be constrained using photometric and dynamical arguments. While uncertainties are large, the mass should be between 1 and 4 Jupiter masses. The brightest blobs are found at the 1:2 resonance with this putative planet.