The interaction between low-mass companions and the debris disks they reside in is still not fully understood. A debris disk can evolve due to self-stirring, a process in which planetesimals can excite their neighbours to the point of destructive collisions. On top of this, the presence of a companion could further stir the disk (companion-stirring). Additional information is necessary to understand this fundamental step in the formation and evolution of a planetary system, and at the moment of writing only a handful of systems are known in which both a companion and a debris disk have been detected and studied at the same time. Our primary goal is to augment the sample of such systems and understand the relative importance between self-stirring and companion-stirring. In the course of the VLT/NaCo-ISPY Imaging Survey for Planets around Young stars, we observed HD 193571, an A0 debris disk hosting star at a distance of 68 pc with an age between 60-170Myr. We obtained two sets of observations in L' band and a third epoch in H band using the GPI instrument at Gemini-South. A companion was detected in all three epochs at a projected separation of 11au (0.17-arcsec), and co-motion was confirmed through proper motion analysis. Given the inferred disk size of 120au, the companion appears to reside within the gap between the host star and the disk. Comparison between the L' and H band magnitude and evolutionary tracks suggests a mass of 0.31-0.39M_{sun}_. We discovered a previously unknown M-dwarf companion around HD 193571, making it the third low-mass stellar object discovered within a debris disk. Comparison to self- and companion-stirring models suggests that the companion is likely responsible for the stirring of the disk.
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.
The observed orbital characteristics of post-asymptotic giant branch (post-AGB) and post-red giant branch (post-RGB) binaries are not understood. We suspect that the missing ingredients to explain them probably lie in the continuous interaction of the central binary with its circumstellar environment. We aim at studying the circumbinary material in these complex systems by investigating the connection between the innermost and large-scale structures. We perform high-angular resolution observations in the near-infrared continuum of HD101584, which has a complex structure as seen at millimeter wavelengths with a disk-like morphology and a bipolar outflow due to an episode of strong binary interaction. To account for the complexity of the target we first perform an image reconstruction and use this result to fit a geometrical model to extract the morphological and thermal features of the environment. The image reveals an unexpected double-ring structure. We interpret the inner ring to be produced by emission from dust located in the plane of the disk and the outer ring to be produced by emission from dust that is located 1.6[D/1kpc] au above the disk plane. The inner ring diameter (3.94[D/1kpc] au), and temperature (T=1540+/-10K) are compatible with the dust sublimation front of the disk. The origin of the out-of-plane ring (with a diameter of 7.39[D/1kpc] au and a temperature of 1014+/-10K) could be due to episodic ejection or a dust condensation front in the outflow. The observed outer ring is possibly linked with the blue-shifted side of the large scale outflow seen by ALMA and is tracing its launching location to the central star. Such observations give morphological constraints on the ejection mechanism. Additional observations are needed to constrain the origin of the out-of-plane structure.
The occurrence rate of hot Jupiters from the Kepler transit survey is roughly half that of radial velocity surveys targeting solar neighborhood stars. One hypothesis to explain this difference is that the two surveys target stars with different stellar metallicity distributions. To test this hypothesis, we measure the metallicity distribution of the Kepler targets using the Hectochelle multi-fiber, high-resolution spectrograph. Limiting our spectroscopic analysis to 610 dwarf stars in our sample with logg>3.5, we measure a metallicity distribution characterized by a mean of [M/H]_mean_=-0.045+/-0.009, in agreement with previous studies of the Kepler field target stars. In comparison, the metallicity distribution of the California Planet Search radial velocity sample has a mean of [M/H]_CPS,mean_=-0.005+/-0.006, and the samples come from different parent populations according to a Kolmogorov-Smirnov test. We refit the exponential relation between the fraction of stars hosting a close-in giant planet and the host star metallicity using a sample of dwarf stars from the California Planet Search with updated metallicities. The best-fit relation tells us that the difference in metallicity between the two samples is insufficient to explain the discrepant hot Jupiter occurrence rates; the metallicity difference would need to be ~0.2-0.3dex for perfect agreement. We also show that (sub)giant contamination in the Kepler sample cannot reconcile the two occurrence calculations. We conclude that other factors, such as binary contamination and imperfect stellar properties, must also be at play.
Elemental abundance studies of solar twin stars suggest that the solar chemical composition contains signatures of the formation of terrestrial planets in the solar system, namely small but significant depletions of the refractory elements. To test this hypothesis, we study stars which, compared to solar twins, have less massive convective envelopes (therefore increasing the amplitude of the predicted effect) or are, arguably, more likely to host planets (thus increasing the frequency of signature detections). We measure relative atmospheric parameters and elemental abundances of a late-F type dwarf sample (52 stars) and a sample of metal-rich solar analogs (59 stars). We detect refractory-element depletions with amplitudes up to about 0.15dex. The distribution of depletion amplitudes for stars known to host gas giant planets is not different from that of the rest of stars. The maximum amplitude of depletion increases with effective temperature from 5650K to 5950K, while it appears to be constant for warmer stars (up to 6300K). The depletions observed in solar twin stars have a maximum amplitude that is very similar to that seen here for both of our samples. Gas giant planet formation alone cannot explain the observed distributions of refractory-element depletions, leaving the formation of rocky material as a more likely explanation of our observations. More rocky material is necessary to explain the data of solar twins than metal-rich stars, and less for warm stars. However, the sizes of the stars' convective envelopes at the time of planet formation could be regulating these amplitudes. Our results could be explained if disk lifetimes were shorter in more massive stars, as independent observations indeed seem to suggest.
The HPMS3 catalog is a comprehensive list of 90455 stars south of the J2000 celestial equator that have proper motions larger than 150mas/yr. The catalog has been generated as counter-part of the I/298 LSPM-North Catalog by systematic search for high proper motion stars in the GAIA DR2 catalog (Cat. I/345) with Dec<0. The HPMS3 catalog considerably expands the number of high proper motion stars over the existing high proper motion SIMBAD objects in the southern sky by about a factor 2.5. We also provide an estimated V magnitude for all catalog entries mostly calculated from GAIA G-, B- and R-magnitudes. The catalog is estimated to be over 99% complete down to a magnitude V=20 with a gap of about 300 to 400 very high (larger than 600mas/yr) proper motion stars not covered by GAIA DR2. The catalog was cross-matched with other catalogs (2MASS, UCAC4, PS1 and GAIA DR1) and then searched for pairs with a separation of up to 60-arcseconds. 4412 such pairs were identified and assessed for common proper motion and potential gravitational relationship. These pairs were then cross-matched with the Washington Double Star catalog to identify double stars already known resulting in 1623 matches. From the rest we eliminated all pairs with potentially suspect data, especially objects with negative parallaxes or parallaxes smaller than 3 times the given Plx error. In the next steps we eliminated all pairs with parallaxes too different to allow for gravitational relationship considered to be optical even if proper motion data suggested common proper motion pairs. Finally 721 pairs remained considered to be most probably physical pairs or multiples by means of common proper motion and potential gravitational relationship. Additionally 215 pairs with slightly different proper motion data are also considered probably physical as minor differences in proper motion values are probably caused by orbits overlapping the proper motion of the double or multiple star system.
This catalog contains a high resolution atlas of both northern and southern sky symbiotic stars. It represents an all-sky optical survey of symbiotic stars using Echelle spectrometers. A summary of the stars with positions and a summary of spectra available are included. The wavelength resolution is better than 0.01 nm. The emission lines in this catalog were chosen to allow the determination of global values for the density and temperature of the nebula, as well as the temperature of the ionizing source. Note that some of the spectra with date marked by "++++" in the "ObsDate" column of the "spectra.dat" file are not in the original publications (mostly "low resolution" spectra)
Wide binaries are a potential pathway for the formation of hot Jupiters. The binary fraction among host stars is an important discriminator between competing formation theories, but has not been well characterised. Additionally, contaminating light from unresolved stars can significantly affect the accuracy of photometric and spectroscopic measurements in studies of transiting exoplanets. We observed 101 transiting exoplanet host systems in the Southern hemisphere in order to create a homogeneous catalogue of both bound companion stars and contaminating background stars, in an area of the sky where transiting exoplanetary systems have not been systematically searched for stellar companions. We investigate the binary fraction among the host stars in order to test theories for the formation of hot Jupiters. Lucky imaging observations from the Two Colour Instrument on the Danish 1.54m telescope at La Silla were used to search for previously unresolved stars at small angular separations. The separations and relative magnitudes of all detected stars were measured. For 12 candidate companions to 10 host stars, previous astrometric measurements were used to evaluate how likely the companions are to be physically associated. We provide measurements of 499 candidate companions within 20 arcseconds of our sample of 101 planet host stars. 51 candidates are located within 5 arcseconds of a host star, and we provide the first published measurements for 27 of these. Calibrations for the plate scale and colour performance of the Two Colour Instrument are presented. We find that the overall multiplicity rate of the host stars is 38+17%, consistent with the rate among solar-type stars in our sensitivity range, suggesting that planet formation does not preferentially occur in long period binaries compared to a random sample of field stars. Long period stellar companions (P>10yr) appear to occur independently of short period companions, and so the population of close-in stellar companions is unconstrained by our study.
The comparison of the proper motions constructed from positions spanning a short (Hipparcos) or long time (Tycho-2) makes it possible to uncover binaries with periods of the order of or somewhat larger than the short time span (in this case, the 3 yr duration of the Hipparcos mission), since the unrecognised orbital motion will then add to the proper motion. A list of candidate proper motion binaries is constructed from a chi-square test evaluating the statistical significance of the difference between the Tycho-2 and Hipparcos proper motions for 103134 stars in common between the two catalogues (excluding components of visual systems). The present paper focuses on the evaluation of the detection efficiency of proper-motion binaries, using different kinds of control data (mostly radial velocities). The detection rate for entries from the Ninth Catalogue of Spectroscopic Binary Orbits (SB9) is evaluated, as well as for stars like barium stars, which are known to be all binaries, and finally for spectroscopic binaries identified from radial velocity data in the Geneva-Copenhagen survey of F and G dwarfs in the solar neighbourhood. Proper motion binaries are efficiently detected for systems with parallaxes in excess of 20mas, and periods in the range 1000-30000d. The shortest periods in this range (1000-2000d, i.e., once to twice the duration of the Hipparcos mission) may appear only as DMSA/G binaries (accelerated proper motion in the Hipparcos Double and Multiple System Annex). Proper motion binaries detected among SB9 systems having periods shorter than about 400d hint at triple systems, the proper-motion binary involving a component with a longer orbital period. A list of 19 candidate triple systems is provided. Binaries suspected of having low-mass (brown-dwarf-like) companions are listed as well. Among the 37 barium stars with parallaxes larger than 5mas, only 7 exhibit no evidence for duplicity whatsoever (be it spectroscopic or astrometric). Finally, the fraction of proper-motion binaries shows no significant variation among the various (regular) spectral classes, when due account is taken for the detection biases.
We present improved Hipparcos astrometry for 257 Hipparcos stars, resolved into 342 components. For 64 of the stars no astrometry was obtained in the Hipparcos Catalogue, while for the remaining stars additional components have been added by this solution or the positions have been revised considerably. We have used the published Hipparcos transit data for the new solutions, together with results from the second reduction of the Tycho data for defining better initial values.
