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Micro-arcsecond relative astrometry by ground-based and single-aperture observations

Published online by Cambridge University Press:  01 October 2007

T. Röll ,
A. Seifahrt  and
R. Neuhäuser
T. Röll
Affiliation:
Astrophysikalisches Institut und Universitäts-Sternwarte Jena, email: [email protected], [email protected]
A. Seifahrt
Affiliation:
Astrophysikalisches Institut und Universitäts-Sternwarte Jena, email: [email protected], [email protected] Institut für Astrophysik, Göttingen email: [email protected]
R. Neuhäuser
Affiliation:
Astrophysikalisches Institut und Universitäts-Sternwarte Jena, email: [email protected], [email protected]
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Abstract

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We present an observation method to obtain a relative astrometric precision of about 100 . . . 150 μas with ground-based and single-aperture observations. By measuring the separation of double or triple stars we want to determine the astrometric signal of an unseen substellar companion as a periodic change in the separation between the stellar components. Using an adaptive optics system we correct for atmospheric turbulences and furthermore by using a narrow band filter in the near infrared we can suppress differential chromatic refraction effects. To reach a high precision we use a statistical approach. Using the new observation mode “cube-mode” (where the frames were directly saved in cubes with nearly no loss of time during the readout), we obtain several thousand frames within half an hour. After the verification of the Gaussian distributed behaviour of our measurements (done with a Kolmogorov-Smirnov-Test) the measurement precision can be calculated as the standard deviation of our measurements divided by the square root of the number of frames.

To monitor the stability of the pixel scale between our observations, we use the old globular cluster 47 Tuc as a calibration system.

Keywords

astrometrymethods: statisticalinstrumentation: adaptive opticsbinaries: generalplanetary systemsglobular clusters: individual (47 Tuc)
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 3 , Symposium S248: A Giant Step: from Milli- to Micro-arcsecond Astrometry , October 2007 , pp. 48 - 51
Copyright
Copyright © International Astronomical Union 2008

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