The ongoing radio continuum TIFR GMRT Sky Survey (TGSS) using the Giant Metrewave Radio Telescope (GMRT) at 150MHz offers an unprecedented opportunity to undertake a fairly deep search for low-frequency radio emission from nearby extrasolar planets. Currently TGSS images are available for a little over a steradian, encompassing 175 confirmed exoplanetary systems. We have searched for their radio counterparts in the TGSS (150MHz), supplemented with a search in the NRAO VLA Sky Survey (NVSS) and the VLA FIRST survey at 1.4GHz. For 171 planetary systems, we find no evidence of radio emission in the TGSS maps, placing a 3{sigma} upper limit between 8.7mJy and 136mJy (median ~24.8mJy) at 150MHz.
We report 312 micrometer measurements of 155 visual double stars made with the 50 cm refractor at the Cote D'Azur observatory (Nice, France) and with the 152 cm telescope at Calar Alto observatory (Almeria, Spain).
We present a high spatial resolution, 10-20{mu}m survey of 65 T Tauri binary stars in Taurus, Ophiuchus, and Corona Australis using the Keck 10m telescopes. Designed to probe the inner ~1AU region of the circumstellar disks around the individual stellar components in these binary systems, this study increases the number of binaries with spatially resolved measurements at 10{mu}m by a factor of ~5.
We present a high angular resolution millimeter-wave dust continuum imaging survey of circumstellar material associated with the individual components of 23 multiple star systems in the Taurus-Auriga young cluster. Combined with previous measurements in the literature, these new data permit a comprehensive look at how the millimeter luminosity (a rough tracer of disk mass) relates to the separation and mass of a stellar companion. Approximately one-third (28%-37%) of the individual stars in multiple systems have detectable millimeter emission, an incidence rate half that for single stars (~62%) which does not depend on the number of companions. There is a strong, positive correlation between the luminosity and projected separation (a_p_) of a stellar pair. Wide pairs (a_p_>300AU) have a similar luminosity distribution as single stars, medium pairs (a_p_{approx}30-300AU) are a factor of five fainter, and close pairs (a_p_<30AU) are ~5x fainter yet (aside from a small, but notable population of bright circumbinary disks). In most cases, the emission is dominated by a disk around the primary (or a wide tertiary in hierarchical triples), but there is no clear relationship between luminosity and stellar mass ratio.
We present high-contrast Magellan adaptive optics images of HD 7449, a Sun-like star with one planet and a long-term radial velocity (RV) trend. We unambiguously detect the source of the long-term trend from 0.6-2.15{mu}m at a separation of ~0.54". We use the object's colors and spectral energy distribution to show that it is most likely an M4-M5 dwarf (mass ~0.1-0.2M_{sun}_) at the same distance as the primary and is therefore likely bound. We also present new RVs measured with the Magellan/MIKE and Planet Finder Spectrograph (PFS) spectrometers and compile these with archival data from CORALIE and HARPS. We use a new Markov chain Monte Carlo procedure to constrain both the mass (>0.17M_{sun}_ at 99% confidence) and semimajor axis (~18 AU) of the M dwarf companion (HD 7449B). We also refine the parameters of the known massive planet (HD 7449Ab), finding that its minimum mass is 1.09_-0.19_^+0.52^M_J_, its semimajor axis is 2.33_-0.02_^+0.01^AU, and its eccentricity is 0.8_-0.06_^+0.08^. We use N-body simulations to constrain the eccentricity of HD 7449B to <~0.5. The M dwarf may be inducing Kozai oscillations on the planet, explaining its high eccentricity. If this is the case and its orbit was initially circular, the mass of the planet would need to be <~1.5M_J_. This demonstrates that strong constraints on known planets can be made using direct observations of otherwise undetectable long-period companions.
The spectral types listed here represent about one-third of a program of MK classification of all the Northern (Dec>-30deg) visual components brighter than B~8.0mag. The spectra used were obtained in 1969-1980 with the Cassegrain spectrograph attached to the Kitt Peak No.2 91-cm telescope. The grating spectra have a dispersion of 128{AA}/mm, and are 1.2mm wide; they are overexposed and underdeveloped to minimize grain. The spectra were classified against standards of the "Revised MK Spectral Atlas for stars earlier than the Sun" by Morgan, Abt and Tapscott (Yerkes Obs. 1978) and of the "Spectral classification" of Morgan and Keenan (1973ARA&A..11...29M). Accurate positions, V magnitudes rounded to 0.1 mag, and remarks were added by B. Skiff in June 2004 as the file "more.dat"; some typos in the catalog were also corrected (see the "History" section below).
Each component of 170 close visual binaries has been classified with new procedures for controlling contamination problems. These classifications are shown to be on the MK system. Two sources of area scanner UBV photometry were compared in order to establish homogeneous photometric as well as spectroscopic data. From a consideration of systematic errors in the V magnitude difference between components the photometry of Hurly and Warner is to be preferred. Absolute magnitudes for each binary are derived from magnitude difference via a tested MK-Mv map.
In this third of three parts of MK classifications of the components brighter than about B=8mag in Aitken's Catalogue (ADS, 1932) new classifications are given for 546 stars. Included in this section are 15 Ap stars, 33 Am stars, 18 stars with composite spectra, three stars with shell spectra, and two SB2s.
