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Fourier Analysis of Hubble Space Telescope Fine Guidance Sensor Data of Binary Stars and Application to the Multiple System HD 157948
A Fourier-based method is presented for the analysis of binary andmultiple star data taken with the Hubble Space Telescope Fine GuidanceSensors (FGSs). Relative astrometry and magnitude differences areobtained as with standard FGS analysis techniques, and although the FGSsystem is essentially unfiltered, this method also permits thecharacterization of color differences between components of binary ormultiple star systems based on the wavelength dependence of theinterference fringes produced by the instrument. Using the multiplesystem HD 157948, we show that the method produces astrometric andphotometric measurements that are consistent with previous FGS analysisfor the three components that lie within the field of view of FGS andgives color differences relative to the primary for two of the threeknown companions. Speckle observations of the system with the WIYN 3.5 mtelescope at Kitt Peak National Observatory are also presented, which,in combination with the FGS results and other data available in theliterature, permit B-V colors and absolute V magnitudes to be obtainedof all four components in the system. Their colors and magnitudes areplotted on the H-R diagram, and a comparison with theoretical isochronesindicates that the results are consistent with theory for a relativelyyoung, somewhat metal-poor system.Based on observations made with the NASA/ESA Hubble Space Telescope,obtained at the Space Telescope Science Institute, which is operated bythe Association of Universities for Research in Astronomy, Inc., underNASA contract NAS5-26555.
| Dynamical Masses of Young Stars in Multiple Systems
We present recent measurements of the orbital motion in the youngbinaries DF Tau and ZZ Tau and the hierarchical triple Elias 12 thatwere obtained with the Fine Guidance Sensors on the Hubble SpaceTelescope and at the Keck Observatory using adaptive optics. Combiningthese observations with previous measurements from the literature, wecompute preliminary orbital parameters for DF Tau and ZZ Tau. We findthat the orbital elements cannot yet be determined precisely because theorbital coverage spans only ~90° in position angle. Nonetheless, therange of possible values for the period and semimajor axis alreadydefines a useful estimate for the total mass in DF Tau and ZZ Tau, withvalues of 0.90+0.85-0.35 and0.81+0.44-0.25 Msolar, respectively, ata fiducial distance of 140 pc.
| The Program to Link the HIPPARCOS Reference Frame to an Extragalactic Reference System Using the Fine Guidance Sensors of the Hubble Space Telescope
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....114.2796H&db_key=AST
| The space distribution of late type stars in a North galactic pole region.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1962AJ.....67...37U&db_key=AST
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Observation and Astrometry data
| Constellation: | Grande Ourse |
| Right ascension: | 11h52m54.19s |
| Declination: | +49°23'45.3" |
| Apparent magnitude: | 9.509 |
| Proper motion RA: | 6.9 |
| Proper motion Dec: | -13.6 |
| B-T magnitude: | 11.32 |
| V-T magnitude: | 9.659 |
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INHABITED SKY
