Search Publications
Astrometry as a Tool for Discovering and Weighing Faint Companions to Nearby Stars
Brandt, Timothy D.
This tutorial covers the use of absolute astrometry, in particular from the combination of the Hipparcos and Gaia missions, to identify faint companions to nearby stars and to measure the masses and orbits of those companions. Absolute astrometry has been used with increasing success to discover new planets and brown dwarfs and to measure masses a…
Global and Local Three-dimensional Studies of The Residual Vector Field from 2MASS and Hipparcos-2 Catalog
Marco, F. J.; Martínez, M. J.; López, J. A.
The Gaia mission will provide a six-parameter solution for millions of stars, including a tridimensional map of our Galaxy. The estimation of distances has been made for the Tycho-Gaia Astrometric Solution (TGAS), while to contrast the proper motions it is interesting to consider positions from the different Gaia Data Release with older ones given…
A Binary Nature of the Marginal CP Star Sigma Sculptoris
Krtička, Jiří; Paunzen, Ernst; Adam, Christian +7 more
The A2 V star σ Scl was suspected of being a low-amplitude rotating variable of the Ap-type star by several authors. Aiming to decide whether the star is a variable chemically peculiar (CP) star, we searched for the photometric and spectroscopic variability, and determined chemical abundances of σ Scl. The possible variability was tested using sev…
Variability Analysis of δ Scuti Candidate Stars
Tautvaišienė, Gražina; Pakštienė, Erika; Janulis, Rimvydas +5 more
The Hipparcos catalog contains stars suspected to be δ Scuti variables for which extensive ground-based observations and characterization of variability are necessary. Our aim was to characterize variability of 13 candidates to δ Scuti type stars. We obtained 24 215 CCD images and analyzed stellar light curves using the Period04 program. Twelve δ …
The Breakthrough Listen Search for Intelligent Life: Target Selection of Nearby Stars and Galaxies
DeBoer, David; Marcy, Geoffrey W.; Siemion, Andrew P. V. +10 more
We present the target selection for the Breakthrough Listen search for extraterrestrial intelligence during the first year of observations at the Green Bank Telescope, Parkes Telescope, and Automated Planet Finder. On the way to observing 1,000,000 nearby stars in search of technological signals, we present three main sets of objects we plan to ob…
Comparison of Hipparcos Trigonometric and Mount Wilson Spectroscopic Parallaxes for 90 Subgiants that Defined the Class in 1935
Majewski, Steven R.; Beaton, Rachael L.; Sandage, Allan
A history is given of the discovery between 1914 and 1935 of stars of intermediate luminosity between giants and dwarfs with spectral types between G0 to K3. The Mount Wilson spectroscopists identified about 90 such stars in their 1935 summary paper of spectroscopic absolute magnitudes for 4179 stars. Called “subgiants” by Strömberg, these 90 star…
Revised Filter Profiles and Zero Points for Broadband Photometry
Mann, Andrew W.; von Braun, Kaspar
Estimating accurate bolometric fluxes for stars requires reliable photometry to absolutely flux calibrate the spectra. This is a significant problem for studies of very bright stars, which are generally saturated in modern photometric surveys. Instead we must rely on photometry with less precise calibration. We utilize precisely flux-calibrated sp…
A Combined Astrometric and Spectroscopic Study of Metal-Poor Binaries
Sozzetti, A.; Santos, N. C.; Latham, D. W. +1 more
In this work we present a study of binary systems in a metal-poor sample of solar type stars. The stars analyzed were rejected from two planet search samples because they were found to be binaries. Using available radial velocity and Hipparcos astrometric data, we apply different methods to find, for every binary system, a possible range of soluti…
Nitrogen Abundances and the Distance Moduli of the Pleiades and Hyades
King, Jeremy R.; Boesgaard, Ann M.; Chen, Yu +1 more
Recent reanalyses of HIPPARCOS parallax data confirm a previously noted discrepancy with the Pleiades distance modulus estimated from main-sequence fitting in the color-magnitude diagram. One proposed explanation of this distance modulus discrepancy is a Pleiades He abundance that is significantly larger than the Hyades value. We suggest that, bas…
Spectrophotometric Libraries, Revised Photonic Passbands, and Zero Points for UBVRI, Hipparcos, and Tycho Photometry
Murphy, Simon; Bessell, Michael
We have calculated improved photonic passbands for the UBVRI, Hipparcos Hp, and Tycho BT and VT standard systems using the extensive spectrophotometric libraries of NGSL and MILES. Using the Hp passband, we adjusted the absolute flux levels of stars in the spectrophotometric libraries so that their synth…