The Program to Link the HIPPARCOS Reference Frame to an Extragalactic Reference System Using the Fine Guidance Sensors of the Hubble Space Telescope

Hemenway, P. D.; Duncombe, R. L.; Bozyan, E. P.; Lalich, A. M.; Argue, A. N.; Franz, O. G.; McArthur, B.; Nelan, Edmund; Taylor, D. B.; White, G.; Benedict, G. F.; Crifo, F.; Fredrick, L. W.; Jefferys, W. H.; Johnston, K.; Kovalevsky, J.; Kristian, J.; Perryman, M. A. C.; Preston, R. A.; Shelus, P. J.; Turon, C.; Altena, W. van

doi:10.1086/118688

Cited by 6 publications

(5 citation statements)

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“…As part of the Hipparcos to ICRF coordinate system link the separation between pairs of selected QSOs and nearby Hipparcos stars was measured with the HST Fine Guidance Sensors (FGS) (Hemenway et al 1997). System orientation and rotation (spin) angles (6 parameters) were determined with an accuracy of about 2 mas (2.5 mas/yr) from observations of about 40 pairs.…”

Section: Comparison To Other Projectsmentioning

confidence: 99%

Radio-Optical Reference Frame Link Using the U.S. Naval Observatory Astrograph and Deep CCD Imaging

Zacharias

2014

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Between 1997 and 2004 several observing runs were conducted mainly with the CTIO 0.9 m to image ICRF counterparts (mostly QSOs) in order to determine accurate optical positions. Contemporary to these deep CCD images the same fields were observed with the US Naval Observatory (USNO) astrograph in the same bandpass. They provide accurate positions on the Hipparcos/Tycho-2 system for stars in the 10 to 16 magnitude range used as reference stars for the deep CCD imaging data. Here we present final optical position results of 413 sources based on reference stars obtained by dedicated astrograph observations which were reduced following 2 different procedures. These optical positions are compared to radio VLBI positions. The current optical system is not perfectly aligned to the ICRF radio system with rigid body rotation angles of 3 to 5 mas (= 3 σ level) found between them for all 3 axes. Furthermore, statistically, the optical−radio position differences are found to exceed the total, combined, known errors in the observations. Systematic errors in the optical reference star positions as well as physical offsets between the centers of optical and radio emissions are both identified as likely causes. A detrimental, astrophysical, random noise (DARN) component is postulated to be on about the 10 mas level. If confirmed by future observations, this could severely limit the Gaia to ICRF reference frame alignment accuracy to an error of about 0.5 mas per coordinate axis with the current number of sources envisioned to provide the link. A list of 36 ICRF sources without the detection of an optical counterpart to a limiting magnitude of about R=22 is provided as well.

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Section: Comparison To Other Projectsmentioning

confidence: 99%

Radio-Optical Reference Frame Link Using the U.S. Naval Observatory Astrograph and Deep CCD Imaging

Zacharias

2014

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“…This mode is employed when individual stellar positions are desired, for instance, as part of a parallax study. A detailed discussion of the way in which x, y values are obtained in POS mode has been provided in Hemenway et al (1997), so only a brief overview is given here. In this mode only one star is observed at a time.…”

Section: Datamentioning

confidence: 99%

The Internal Proper Motions of Stars in the Open Cluster M35

McNamara

Harrison

McArthur³

et al. 2011

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Relative proper motions, based on 108 orbits of Hubble Space Telescope Fine Guidance Sensor data extending from 1992 to 2006, are reported for 74 stars in the open cluster M35 (NGC 2168). A subset of 22 of these objects are then used to compute the cluster's internal proper motion dispersions in both right ascension and declination. We find that these dispersions are equal to within their measurement errors. The average one-dimensional dispersion is 0.018 ± 0.002 arcsec century −1 . When combined with the M35 radial velocity dispersion of 0.65 ± 0.10 km s −1 found by Geller et al., this produces a cluster distance of 762 ± 145 pc. Using isochrone fits to the cluster main sequence, this distance suggests that M35 has an age of about 133 Myr. Although this age is consistent with that typically found for M35, the formal error in the dynamical distance of ±19% can accommodate ages between 65 Myr and 201 Myr.

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“…No evidence of another set of lines was found down to the level of the noise, at about 10% of the brightness of the primary. In addition, Hemenway et al (1997) reported an observation of HIP 50796 by speckle interferometry in which no companions were apparently seen in the range from 30 mas to 0B7. Details of this measurement are unavailable.…”

Section: The Nature Of the Companionmentioning

confidence: 99%

The Astrometric-Spectroscopic Binary System HIP 50796: An Overmassive Companion

Torres¹

2006

Astron J

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We report spectroscopic observations of the star HIP 50796, previously considered ( but later rejected) as a candidate member of the TW Hya association. Our measurements reveal it to be a single-lined binary with an orbital period of 570 days and an eccentricity of e ¼ 0:61. The astrometric signature of this orbit was previously detected by Hipparcos in the form of curvature in the proper-motion components, although the period was unknown at the time. By combining our radial velocity measurements with the Hipparcos intermediate data (abscissa residuals) we are able to derive the full three-dimensional orbit and determine the dynamical mass of the unseen companion, as well as a revised trigonometric parallax that accounts for the orbital motion. Given our primary mass estimate of 0.73 M (mid-K dwarf ), the companion mass is determined to be 0.89 M , or $20% larger than the primary. The likely explanation for the larger mass without any apparent contribution to the light is that the companion is itself a closer binary composed of M dwarfs. The near-infrared excess and X-ray emission displayed by HIP 50796 support this. Our photometric modeling of the excess leads to a lower limit to the mass ratio of the close binary of q $ 0:8 and individual masses of 0.44-0.48 and 0.41-0.44 M . The new parallax ( ¼ 20:6 AE 1:9 mas) is significantly smaller than the original Hipparcos value and more precise.

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The Program to Link the HIPPARCOS Reference Frame to an Extragalactic Reference System Using the Fine Guidance Sensors of the Hubble Space Telescope

Cited by 6 publications

References 0 publications

Radio-Optical Reference Frame Link Using the U.S. Naval Observatory Astrograph and Deep CCD Imaging

Radio-Optical Reference Frame Link Using the U.S. Naval Observatory Astrograph and Deep CCD Imaging

The Internal Proper Motions of Stars in the Open Cluster M35

The Astrometric-Spectroscopic Binary System HIP 50796: An Overmassive Companion

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