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Journal articles on the topic 'Astrometric'

Author: Grafiati

Published: 4 June 2021

Last updated: 10 March 2023

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1

Klioner, S. A. "Relativistic astrometry and astrometric relativity." Proceedings of the International Astronomical Union 3, S248 (October 2007): 356–62. http://dx.doi.org/10.1017/s174392130801956x.

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AbstractThe interplay between modern astrometry and gravitational physics is very important for the progress in both these fields. Below some threshold of accuracy, Newtonian physics fails to describe observational data and the Einstein's relativity theory must be used to model the data adequately. Many high-accuracy astronomical techniques have already passed this threshold. Moreover, modern astronomical observations cannot be adequately modeled if relativistic effects are considered as small corrections to Newtonian models. The whole way of thinking must be made compatible with relativity: t

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Tubbs, R., N. M. Elias, R. Launhardt, S. Reffert, F. Delplancke, A. Quirrenbach, T. Henning, and D. Queloz. "ESPRI data-reduction strategy and error budget for PRIMA." Proceedings of the International Astronomical Union 3, S248 (October 2007): 132–33. http://dx.doi.org/10.1017/s1743921308018887.

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AbstractThe Exoplanet Search with PRIma (ESPRI) will use the PRIMA dual-feed astrometric capability on the Very Large Telescope Interferometer (VLTI) to perform astrometric detections of extra-solar planets. We present an overview of our data-reduction strategy for achieving 10-μarcsecond accuracy narrow-angle astrometry using the PRIMA instrument. We discuss the error budget for astrometric measurements, and those aspects of our strategy which are designed to minimise the astrometric measurement errors.

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Seidelmann, P. K. "Space Astrometry and the HST Wide Field/Planetary Camera." Symposium - International Astronomical Union 141 (1990): 347–54. http://dx.doi.org/10.1017/s0074180900087040.

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The launch of the Hipparcos spacecraft marked the beginning of space astrometry. Hopefully, this will be followed in the near future by the launch of the Hubble Space Telescope, which is not primarily an astrometric instrument, but has astrometric capabilities which will be described in this paper. In addition, there are plans and proposals for future astrometric spacecraft. These include the launch of a radio antenna, which combined with Earth-based antennae would provide a very, very long base line interferometer (Levy, 1986, 1988). There are proposals for launching optical interferometers,

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Sakai, N. "SYNERGY BETWEEN OPTICAL (GAIA) AND RADIO (VLBI)ASTROMETRIC RESEARCHES." Revista Mexicana de Astronomía y Astrofísica Serie de Conferencias 52 (October 5, 2020): 9–11. http://dx.doi.org/10.22201/ia.14052059p.2020.52.03.

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Optical and radio astrometry have become significant for mapping the Milky Way. We introduce an example of synergy between optical and radio astrometry on a research of the Galactic spiral arms. Kinematics and spatial distribution of star and gas indicate a new and complex picture of the Galactic spiral arms. Synergy of astrometric study at multi-wavelength would be enhanced thanks to future infrared astrometric projects (e.g.,Small Jasmine; GaiaNIR) in 2020-2030s.

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Schilbach, E., Wenjing Jin, M. Crézé, P. D. Hemenway, I. I. Kumkova, I. K. Platais, S. Röser, C. Turon, and J. J. Wang. "Commission 24: Photographic Astrometry: (Astrometrie Photographique)." Transactions of the International Astronomical Union 24, no. 1 (2000): 48–59. http://dx.doi.org/10.1017/s0251107x00002571.

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The scope of scientific interests of about 130 Commission members is much more complex than one may expect from the title of the commission. Besides traditional topics like the compilation of astrometric catalogues and the construction of an inertial reference system, more and more investigations performed by our members have been dedicated to the astrophysical interpretation of observations including among others astrometric data.

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Fey, Alan L. "Limits on Astrometric Accuracy." International Astronomical Union Colloquium 180 (March 2000): 20–28. http://dx.doi.org/10.1017/s0252921100000063.

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AbstractA general overview of the various factors limiting the accuracy to which astrometric observations can be made is presented. Since this is a very broad topic, it is limited primarily to radio astrometry of extragalactic objects.

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Hobbs, David, Berry Holl, Lennart Lindegren, Frédéric Raison, Sergei Klioner та Alexey Butkevich. "Determining PPN γ with Gaia's astrometric core solution". Proceedings of the International Astronomical Union 5, S261 (квітень 2009): 315–19. http://dx.doi.org/10.1017/s1743921309990561.

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AbstractThe ESA space astrometry mission Gaia, due for launch in early 2012, will in addition to its huge output of fundamental astrometric and astrophysical data also provide stringent tests of general relativity. In this paper we present an updated analysis of Gaia's capacity to measure the PPN parameter γ as part of its core astrometric solution. The analysis is based on small-scale astrometric solutions taking into account the simultaneous determination of stellar astrometric parameters and the satellite attitude. In particular, the statistical correlation between PPN γ and the stellar par

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Platais, I., A. L. Fey, S. Frey, S. G. Djorgovski, C. Ducourant, Ž. Ivezić, A. Rest, C. Veillet, R. F. G. Wyse, and N. Zacharias. "Deep Astrometric Standards." Proceedings of the International Astronomical Union 3, S248 (October 2007): 320–23. http://dx.doi.org/10.1017/s1743921308019455.

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AbstractThe advent of next-generation telescopes with very wide fields-of-view creates a need for deep and precise reference frames for astrometric calibrations. The Deep Astrometric Standards (DAS) program is designed to establish such a frame, by providing absolute astrometry at the 5–10 mas level in four 10 deg2 Galactic fields, to a depth of V=25. The source of our basic reference frame is the UCAC2 catalog, significantly improved by additional observations, and new VLBI positions of radio-loud and optically visible QSOs. We describe all the major steps in the construction of the DAS field

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Zhang, Yigong, Jiancheng Wang, Jie Su, Xiangming Cheng, and Zhenjun Zhang. "Astrometric Observations of a Near-Earth Object Using the Image Fusion Technique." Astronomical Journal 162, no. 6 (November 19, 2021): 250. http://dx.doi.org/10.3847/1538-3881/ac2c6f.

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Abstract The precise astrometric observation of small near-Earth objects (NEOs) is an important observational research topic in the astrometric discipline, which greatly promotes multidisciplinary research, such as the origin and evolution of the solar system, the detection and early warning of small NEOs, and deep-space navigation. The characteristics of small NEOs, such as faintness and fast moving speed, restrict the accuracy and precision of their astrometric observations. In the paper, we present a method to improve the accurate and precise astrometric positions of NEOs based on image fus

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Neuhäuser, R., A. Seifahrt, T. Röll, A. Bedalov, and M. Mugrauer. "Detectability of Planets in Wide Binaries by Ground-Based Relative Astrometry with AO." Proceedings of the International Astronomical Union 2, S240 (August 2006): 261–63. http://dx.doi.org/10.1017/s1743921307004139.

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AbstractMany planet candidates have been detected by radial-velocity variations of the primary star; they are planet candidates, because of the unknown orbit inclination. Detection of the wobble in the two other dimensions, to be measured by astrometry, would yield the inclination and, hence, true mass of the companions. We aim to show that planets can be confirmed or discovered in a close visual stellar binary system by measuring the astrometric wobble of the exoplanet host star as a periodic variation of the separation, even from the ground. We test the feasibility with HD 19994, a visual bi

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Everall, Andrew, Douglas Boubert, Sergey E. Koposov, Leigh Smith, and Berry Holl. "Completeness of the Gaia-verse – IV. The astrometry spread function of Gaia DR2." Monthly Notices of the Royal Astronomical Society 502, no. 2 (February 1, 2021): 1908–24. http://dx.doi.org/10.1093/mnras/stab041.

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ABSTRACT Gaia Data Release 2 (DR2) published positions, parallaxes, and proper motions for an unprecedented 1331 909 727 sources, revolutionizing the field of Galactic dynamics. We complement this data with the astrometry spread function (ASF), the expected uncertainty in the measured positions, proper motions, and parallax for a non-accelerating point source. The ASF is a Gaussian function for which we construct the 5D astrometric covariance matrix as a function of position on the sky and apparent magnitude using the Gaia DR2 scanning law and demonstrate excellent agreement with the observed

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Sahlmann, J., A. J. Burgasser, D. C. Bardalez Gagliuffi, P. F. Lazorenko, D. Ségransan, M. R. Zapatero Osorio, C. H. Blake, C. R. Gelino, E. L. Martín, and H. Bouy. "Astrometric orbits of spectral binary brown dwarfs – I. Massive T dwarf companions to 2M1059−21 and 2M0805+48." Monthly Notices of the Royal Astronomical Society 495, no. 1 (May 6, 2020): 1136–47. http://dx.doi.org/10.1093/mnras/staa1235.

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ABSTRACT Near-infrared spectroscopic surveys have uncovered a population of short-period, blended-light spectral binaries composed of low-mass stars and brown dwarfs. These systems are amenable to orbit determination and individual mass measurements via astrometric monitoring. Here, we present first results of a multiyear campaign to obtain high-precision absolute astrometry for spectral binaries using the Gemini-South and Gemini-North GMOS imagers. We measure the complete astrometric orbits for two systems: 2M0805+48 and 2M1059−21. Our astrometric orbit of 2M0805+48 is consistent with its 2-y

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Sowmya, K., N. E. Nèmec, A. I. Shapiro, E. Işık, N. A. Krivova, and S. K. Solanki. "Predictions of Astrometric Jitter for Sun-like Stars. III. Fast Rotators." Astrophysical Journal 934, no. 2 (August 1, 2022): 146. http://dx.doi.org/10.3847/1538-4357/ac79b3.

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Abstract A breakthrough in exoplanet detections is foreseen with the unprecedented astrometric measurement capabilities offered by instrumentation aboard the Gaia space observatory. Besides, astrometric discoveries of exoplanets are expected from the planned space mission, Small-JASMINE. In this setting, the present series of papers focuses on estimating the effect of the magnetic activity of G2V-type host stars on the astrometric signal. This effect interferes with the astrometric detections of Earth-mass planets. While the first two papers considered stars rotating at the solar rotation rate

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Brown, A. G. A. "Getting ready for the micro-arcsecond era." Proceedings of the International Astronomical Union 3, S248 (October 2007): 567–76. http://dx.doi.org/10.1017/s1743921308020176.

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AbstractAs the title of this symposium implies, one of the aims is to examine the future of astrometry as we move from an era in which thanks to the Hipparcos Catalogue everyone has become familiar with milliarcsecond astrometry to an era in which microarcsecond astrometry will become the norm. I will take this look into the future by first providing an overview of present astrometric programmes and how they fit together and then I will attempt to identify the most promising future directions. In addition I discuss the important conditions for the maximization of the scientific return of futur

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Bernstein, H. H. "Derivation of orbital parameters of very low mass companions in double stars from radial velocities and observations of space astrometry missions like HIPPARCOS, DIVA and GAIA." International Astronomical Union Colloquium 170 (1999): 410–15. http://dx.doi.org/10.1017/s0252921100048843.

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AbstractRadial velocity measurements are a well known high-precision method to obtain the orbits of extrasolar planets or brown dwarfs. However, this method is not able to determine the inclination which could be derived from astrometry. The astrometric effects of those objects are very minute, wherefore the interest of astronomers in astrometric techniques was very poor. This situation changes fundamentally since space astrometry observations are available. HIPPARCOS demonstrated the power of space astrometry and the extremely high accuracy of the DIVA, and especially the GAIA observations al

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Yano, T., N. Gouda, H. Ueda, H. Koyama, Y. Kan-ya, and A. Taruya. "Elucidation of kinematical and dynamical structure of the Galactic bulge." Proceedings of the International Astronomical Union 3, S245 (July 2007): 39–44. http://dx.doi.org/10.1017/s1743921308017249.

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AbstractFuture space mission of astrometric satellite, GAIA and JASMINE (Japan Astrometry Satellite Mission for Infrared Exploration), will produce astrometric parameter, such as positions, parallaxes, and proper motions of stars in the Galactic bulge. Then kinematical information will be obtained in the future. Accordingly it is expected that our understanding of the dynamical structure will be greatly improved. Therefore it is important to make a method to construct a kinematical and dynamical structure of the Galactic bulge immediately.

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Fresneau, Alain. "Space Telescope Motion Limitations for Fine Guidance Sensor Astrometry." Symposium - International Astronomical Union 109 (1986): 643–47. http://dx.doi.org/10.1017/s0074180900077147.

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Basic Fine Guidance Sensor data have been simulated to correlate the Power Spectrum Densities (PSD) of the Space Telescope motion disturbances with the “seeing” of an astrometric target. The goal of this study is to describe whether a complete identification of the jitter of the line of sight during an astrometric observation is required to improve the precision of this observation. The present preliminary results indicate that the performance in Astrometry are close to the predictions.

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Gai, Mario, Alberto Vecchiato, Alessandro Sozzetti, Sebastiano Ligori, and Mario G. Lattanzi. "Gravitation Astrometric Measurement Experiment (GAME)." Proceedings of the International Astronomical Union 6, S276 (October 2010): 535–36. http://dx.doi.org/10.1017/s1743921311021119.

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AbstractGAME (Gravitation Astrometric Measurement Experiment) is a mission concept based on astronomical techniques for high precision measurements of interest to Fundamental Physics and cosmology, in particular the γ and β parameters of the Parameterized Post-Newtonian formulation of gravitation theories extending the General Relativity.High precision astrometry also provides the light deflection induced by the quadrupole moment of Jupiter and Saturn, and, by high precision determination of the orbits of Mercury and high elongation asteroids, the PPN parameter β.The astrometric and photometri

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White, Richard L., Stephen H. Lubow, and Bernie Shiao. "Improvements to Pan-STARRS1 Astrometry. II. Corrections for Differential Chromatic Refraction." Astronomical Journal 164, no. 2 (August 1, 2022): 73. http://dx.doi.org/10.3847/1538-3881/ac7ab6.

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Abstract In a previous paper, we applied the Gaia DR2 catalog to improve the astrometric accuracy of about 1.7 billion objects in Pan-STARRS1 Data Release 2 (PS1 DR2). We report here on further improvements made by utilizing Gaia EDR3 and correcting for the effects of differential chromatic refraction (DCR) in decl. We extend the correction algorithm in Paper I by iteratively subtracting color- and decl.-dependent PS1/Gaia EDR3 decl. residuals. We determine the astrometric improvement for ∼440 million reference objects that are point-like and cross-match to Gaia EDR3. For this set of objects,

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Kaplan, G. H. "Astrometric Interferometry — Can It Establish a Fundamental System?" Symposium - International Astronomical Union 141 (1990): 241–50. http://dx.doi.org/10.1017/s0074180900086897.

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The astrometric optical interferometer on Mt. Wilson is providing a new source of astrophysical and astrometric data on bright stars. The instrument, with 12-meter baselines, has been in operation since late 1986. The interferometer is capable of wide-angle astrometry, that is, the determination of very precise stellar positions within a reference frame defined by bright stars spread across a large area (of order one steradian) of the sky. This paper addresses the question of whether such an instrument can be used to establish a fundamental system — that is, one tied to the Earth in some well-

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Crosta, M. T., B. Bucciarelli, F. de Felice, M. G. Lattanzi, and A. Vecchiato. "Astrometric observable and relativistic astrometric catalogues." EAS Publications Series 30 (2008): 345–48. http://dx.doi.org/10.1051/eas:0830058.

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Lindegren, L., J. Hernández, A. Bombrun, S. Klioner, U. Bastian, M. Ramos-Lerate, A. de Torres, et al. "Gaia Data Release 2." Astronomy & Astrophysics 616 (August 2018): A2. http://dx.doi.org/10.1051/0004-6361/201832727.

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Context. Gaia Data Release 2 (Gaia DR2) contains results for 1693 million sources in the magnitude range 3 to 21 based on observations collected by the European Space Agency Gaia satellite during the first 22 months of its operational phase. Aims. We describe the input data, models, and processing used for the astrometric content of Gaia DR2, and the validation of these resultsperformed within the astrometry task. Methods. Some 320 billion centroid positions from the pre-processed astrometric CCD observations were used to estimate the five astrometric parameters (positions, parallaxes, and pro

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Benedict, G. F., J. T. McGraw, and T. R. Hess. "Relative Astrometry with Imaging Transit Telescopes." Symposium - International Astronomical Union 166 (1995): 9–12. http://dx.doi.org/10.1017/s0074180900227757.

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A CCD/Transit Instrument (CTI) has produced relative astrometry with standard errors less than 2.6% of a 1.55 arcsecond pixel for stars with V ≤ 17. Additional astrometric studies with existing data are required to better understand the ultimate contribution these devices can make to our science.The CTI is presently dismantled, awaiting a move to a new site. We briefly discuss the potential astrometric scientific returns from the exisiting data set, from a refurbished CTI, and from a similar device emplaced on the Moon.

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Zacharias, Norbert, Valeri V. Makarov, Charles T. Finch, Hugh C. Harris, Jeffrey A. Munn, and John P. Subasavage. "USNO Bright Star Catalog, Version 1." Astronomical Journal 164, no. 2 (July 5, 2022): 36. http://dx.doi.org/10.3847/1538-3881/ac686d.

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Abstract The USNO Bright Star Catalog (UBSC) is a new astrometric catalog of the 1423 brightest stars covering the entire sky, which is published online. It is nearly complete to V = 3 mag except for three stellar systems. A combined astrometric solution of the Hipparcos Intermediate Astrometry Data and two dedicated ground-based campaigns in 2013–2020 is the basis for this catalog. The astrometric parameters for each star include position coordinates, parallax, and proper motion components, and their covariances on the Hipparcos mean epoch 1991.25. 64% of the catalog are flagged as known or s

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Brandt, G. Mirek, Daniel Michalik, Timothy D. Brandt, Yiting Li, Trent J. Dupuy, and Yunlin Zeng. "htof: A New Open-source Tool for Analyzing Hipparcos, Gaia, and Future Astrometric Missions." Astronomical Journal 162, no. 6 (November 5, 2021): 230. http://dx.doi.org/10.3847/1538-3881/ac12d0.

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Abstract We present htof, an open-source tool for interpreting and fitting the intermediate astrometric data (IAD) from both the 1997 and 2007 reductions of Hipparcos, the scanning law of Gaia, and future missions such as the Nancy Grace Roman Space Telescope (NGRST). htof solves the astrometric parameters of any system for any arbitrary combination of absolute astrometric missions. In preparation for later Gaia data releases, htof supports arbitrarily high-order astrometric solutions (e.g., five-, seven-, and nine-parameter fits). Using htof, we find that the IAD of 6617 sources in Hipparcos

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Rioja, M., R. Dodson, G. Orosz, and H. Imai. "MultiView High Precision VLBI Astrometry at Low Frequencies." Proceedings of the International Astronomical Union 13, S336 (September 2017): 439–42. http://dx.doi.org/10.1017/s1743921317010560.

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AbstractObservations at low frequencies (<8GHz) are dominated by distinct direction dependent ionospheric propagation errors, which place a very tight limit on the angular separation of a suitable phase referencing calibrator and astrometry. To increase the capability for high precision astrometric measurements an effective calibration strategy of the systematic ionospheric propagation effects that is widely applicable is required. The MultiView technique holds the key to the compensation of atmospheric spatial-structure errors, by using observations of multiple calibrators and two dimensio

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Shao, M., M. Colavita, D. Staelin, R. Simon, and K. Johnston. "Present Status and Future Plans for the Two Color Astrometric Interferometer Project." Symposium - International Astronomical Union 109 (1986): 331–40. http://dx.doi.org/10.1017/s0074180900076750.

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A 3-meter two telescope stellar interferometer has been used to observe fringes for the past year in order to study the feasibility of using long baseline interferometers for astrometry. We have demonstrated that two color fringe measurements are capable of significantly reducing the astrometric error due to atmospheric turbulence. Currently, we are investigating the thermal and mechanical sources of error in the instrument. The results of our study will be incorporated into the design of the 20 meter astrometric interferometer which will be built in the next 1–2 years. The key to the 20-meter

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Meunier, N., A. M. Lagrange, and S. Borgniet. "Activity time series of old stars from late F to early K." Astronomy & Astrophysics 644 (December 2020): A77. http://dx.doi.org/10.1051/0004-6361/202038710.

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Context. Stellar activity strongly affects and may prevent the detection of Earth-mass planets in the habitable zone of solar-type stars with radial velocity technics. Astrometry is in principle less sensitive to stellar activity because the situation is more favourable: the stellar astrometric signal is expected to be fainter than the planetary astrometric signal compared to radial velocities. Aims. We quantify the effect of stellar activity on high-precision astrometry when Earth-mass planets are searched for in the habitable zone around old main-sequence solar-type stars. Methods. We used a

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Hyland, L. J., M. J. Reid, S. P. Ellingsen, M. J. Rioja, R. Dodson, G. Orosz, C. R. Masson, and J. M. McCallum. "Inverse Multiview. I. Multicalibrator Inverse Phase Referencing for Microarcsecond Very Long Baseline Interferometry Astrometry." Astrophysical Journal 932, no. 1 (June 1, 2022): 52. http://dx.doi.org/10.3847/1538-4357/ac6d5b.

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Abstract Very Long Baseline Interferometry (VLBI) astrometry is a well established technique for achieving ±10 μas parallax accuracies at frequencies well above 10 GHz. At lower frequencies, uncompensated interferometer delays associated with the ionosphere play the dominant role in limiting the astrometric accuracy. Multiview is a novel VLBI calibration method, which uses observations of multiple quasars to accurately model and remove time-variable, directional-dependent changes to the interferometer delay. Here we extend the Multiview technique by phase-referencing data to the target source

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Mishra-Sharma, Siddharth. "Inferring dark matter substructure with astrometric lensing beyond the power spectrum." Machine Learning: Science and Technology 3, no. 1 (January 19, 2022): 01LT03. http://dx.doi.org/10.1088/2632-2153/ac494a.

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Abstract Astrometry—the precise measurement of positions and motions of celestial objects—has emerged as a promising avenue for characterizing the dark matter population in our Galaxy. By leveraging recent advances in simulation-based inference and neural network architectures, we introduce a novel method to search for global dark matter-induced gravitational lensing signatures in astrometric datasets. Our method based on neural likelihood-ratio estimation shows significantly enhanced sensitivity to a cold dark matter population and more favorable scaling with measurement noise compared to exi

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Honma, Mareki, Takumi Nagayama, Tomoya Hirota, Naoko Matsumoto, Nobuyuki Sakai, and Noriyuki Kawaguchi. "Maser astrometry with VERA and Galactic structure." Proceedings of the International Astronomical Union 8, S287 (January 2012): 386–90. http://dx.doi.org/10.1017/s174392131200734x.

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AbstractSince 2007 VERA (VLBI Exploration of Radio Astrometry) has been producing astrometric results (distances and/or proper motions) for Galactic maser sources. Nearly 30 parallaxes have been obtained for star-forming regions and late-type stars. By using VERA's astrometric results for star-forming regions, combined with those obtained with VLBA and EVN, fundamental Galactic parameters and Galactic structure may be derived. Our results show that R0 = 8.4 ± 0.4 kpc and Ω⊙ ≡ Ω0 + V⊙/R0=30.7±0.8 km s−1 kpc−1, and also show that the rotation curve of the Galaxy is nearly flat. The determination

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Sergienko, V. I., A. G. Radchuk, B. A. Pavlov, and V. S. Kudeeva. "A Fully-Automated System of Astrometric Data Collection and Processing." Symposium - International Astronomical Union 109 (1986): 795–98. http://dx.doi.org/10.1017/s0074180900077342.

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The automated astronomical system “Astrometrist” for the determination of the parameters of terrestrial rotation (DTRP) is intended for astrometric and meteorological data collection and on-line processing and feedback to the user by a computer.

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Høg, Erik. "GIER: A Danish computer from 1961 with a role in the modern revolution of astronomy - II." Proceedings of the International Astronomical Union 12, S330 (April 2017): 92–93. http://dx.doi.org/10.1017/s1743921317005336.

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AbstractA Danish computer, GIER, from 1961 played a vital role in the development of a new method for astrometric measurement. This method, photon counting astrometry, ultimately led to two satellites with a significant role in the modern revolution of astronomy. A GIER was installed at the Hamburg Observatory in 1964 where it was used to implement the entirely new method for the measurement of stellar positions by means of a meridian circle, at that time the fundamental instrument of astrometry. An expedition to Perth in Western Australia with the instrument and the computer was a success. Th

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Lloyd, James P., Ben R. Oppenheimer, and James R. Graham. "The Potential of Differential Astrometric Interferometry from the High Antarctic Plateau." Publications of the Astronomical Society of Australia 19, no. 3 (2002): 318–22. http://dx.doi.org/10.1071/as01072.

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AbstractThe low infrared background and high atmospheric transparency are the principal advantages of Antarctic Plateau sites for astronomy. However, the poor seeing (between 1 and 3 as) negates much of the sensitivity improvements that the Antarctic atmosphere offers, compared to mid-latitude sites such as Mauna Kea or Cerro Paranal. The seeing at mid-latitude sites, though smaller in amplitude, is dominated by turbulence at altitudes of 10–20 km. Over the Antarctic Plateau, virtually no high altitude turbulence is present in the winter. The mean square error for an astrometric measurement wi

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Dravins, D., L. Lindegren, S. Madsen, and J. Holmberg. "Astrometric Radial Velocities From Hipparcos." Highlights of Astronomy 11, no. 1 (1998): 564. http://dx.doi.org/10.1017/s153929960002219x.

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AbstractSpace astrometry now permits accurate determinations of stellar radial motion, without using spectroscopy. Although the feasibility of deducing astrometric radial velocities from geometric projection effects was realized already by Schlesinger (1917), only with Hipparcos has it become practical. Such a program has now been carried out for the moving clusters of Ursa Major, Hyades, and Coma Berenices. Realized inaccuracies reach about 300 m/s (Dravins et al. 1997).Discrepancies between astrometric and spectroscopic radial velocities reveal effects (other than stellar motion) that affect

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Kaplan-Lipkin, Avi, Bruce Macintosh, Alexander Madurowicz, Krishnamurthy Sowmya, Alexander Shapiro, Natalie Krivova, and Sami K. Solanki. "Multiwavelength Mitigation of Stellar Activity in Astrometric Planet Detection." Astronomical Journal 163, no. 5 (April 11, 2022): 205. http://dx.doi.org/10.3847/1538-3881/ac56e0.

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Abstract Astrometry has long been a promising technique for exoplanet detection. At the theoretical limits, astrometry would allow for the detection of smaller planets than previously seen by current exoplanet search methods, but stellar activity may make these theoretical limits unreachable. Astrometric jitter of a Sun-like star due to magnetic activity in its photosphere induces apparent variability in the photocenter of order 0.5 mR ⊙. This jitter creates a fundamental astrophysical noise floor preventing detection of lower-mass planets in a single spectral band. By injecting planet orbits

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Taheri, Mojtaba, Alan W. McConnachie, Paolo Turri, Davide Massari, David Andersen, Giuseppe Bono, Giuliana Fiorentino, Kim Venn, Jean-Pierre Véran, and Peter B. Stetson. "Optimal Differential Astrometry for Multiconjugate Adaptive Optics. I. Astrometric Distortion Mapping using On-sky GeMS Observations of NGC 6723." Astronomical Journal 163, no. 4 (March 23, 2022): 187. http://dx.doi.org/10.3847/1538-3881/ac5747.

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Abstract The Extremely Large Telescope and the Thirty Meter Telescope will use state of the art multiconjugate adaptive optics (MCAO) systems to obtain the full D 4 advantage that their apertures can provide. However, to reach the full astrometric potential of these facilities for on-sky science requires understanding any residual astrometric distortions from these systems and find ways to measure and eliminate them. In this work, we use Gemini multiconjugate adaptive optic system (GeMS) observations of the core of NGC 6723 to better understand the on-sky astrometric performance of MCAO. We de

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Ducourant, C., O. Wertz, A. Krone-Martins, R. Teixeira, J. F. Le Campion, L. Galluccio, J. Klüter, et al. "Gaia GraL: Gaia DR2 gravitational lens systems." Astronomy & Astrophysics 618 (October 2018): A56. http://dx.doi.org/10.1051/0004-6361/201833480.

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Context. Thanks to its spatial resolution, the ESA/Gaia space mission offers a unique opportunity to discover new multiply imaged quasars and to study the already known lensed systems at sub-milliarcsecond astrometric precisions. Aims. In this paper, we address the detection of the known multiply imaged quasars from the Gaia Data Release 2 (DR2) and determine the astrometric and photometric properties of the individually detected images found in the Gaia DR2 catalogue. Methods. We have compiled an exhaustive list of quasar gravitational lenses from the literature to search for counterparts in

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Gai, M., A. Vecchiato, A. Riva, D. Busonero, M. Lattanzi, B. Bucciarelli, M. Crosta, and Z. Qi. "Astrometric Precision Tests on TESS Data." Publications of the Astronomical Society of the Pacific 134, no. 1033 (March 1, 2022): 035004. http://dx.doi.org/10.1088/1538-3873/ac584a.

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Abstract Astrometry at or below the microarcsec level with an imaging telescope assumes that the uncertainty on the location of an unresolved source can be an arbitrarily small fraction of the detector pixel, given a sufficient photon budget. This paper investigates the geometric limiting precision, in terms of CCD pixel fraction, achieved by a large set of star field images, selected among the publicly available science data of the Transiting Exoplanet Survey Satellite (TESS) mission. The statistics of the distance between selected bright stars (G ≃ 5 mag), in pixel units, is evaluated, using

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Tichý, Miloš, Jana Tichá, and Michal Kočer. "KLENOT PROJECT - NEAR EARTH OBJECTS FOLLOW-UP PROGRAM." Proceedings of the International Astronomical Union 10, S318 (August 2015): 319–20. http://dx.doi.org/10.1017/s1743921315007176.

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AbstractNEO research is a great challenge just now - for science, for exploration and for planetary defence. Therefore NEO discoveries, astrometric follow-up, orbit computations as well as physical studies are of high interest both to science community and humankind.The KLENOT Project of the Klet Observatory, South Bohemia, Czech Republic pursued the confirmation, early follow-up, long-arc follow-up and recovery of Near Earth Objects since 2002. Tens of thousands astrometric measurements helped to make inventory of NEOs as well as to understand the NEO population. It ranked among the world mos

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Sahlmann, J., E. G. Nelan, P. Chayer, B. McLean, and M. Lallo. "Optimisation of JWST operations with the help of Gaia." Proceedings of the International Astronomical Union 12, S330 (April 2017): 98–99. http://dx.doi.org/10.1017/s1743921317006275.

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AbstractThe James Webb Space Telescope (JWST) is scheduled for launch in 2018. To operate and observe efficiently, JWST will rely on various external astrometric and photometric catalogues, in particular the HST Guide Star Catalog (GSC), for instance to locate sources accurately on the sky. The incorporation of the Gaia astrometric catalog will improve the absolute astrometry of the GSC and is therefore relevant for JWST operations. We outline how the JWST Science and Operations Center hosted at the Space Telescope Science Institute (STScI) intends to use the Gaia survey results to improve upo

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Dravins, Dainis. "Absolute Wavelength Shifts — A New Diagnostic for Rapidly Rotating Stars." Symposium - International Astronomical Union 215 (2004): 27–32. http://dx.doi.org/10.1017/s0074180900195130.

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Accuracies reached in space astrometry now permit the accurate determination of astrometric radial velocities, without any use of spectroscopy. Knowing this true stellar motion, spectral shifts intrinsic to stellar atmospheres can be identified, for instance gravitational redshifts and those caused by velocity fields on stellar surfaces. The astrometric accuracy is independent of any spectral complexity, such as the smeared-out line profiles of rapidly rotating stars. Besides a better determination of stellar velocities, this permits more precise studies of atmospheric dynamics, such as possib

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Unwin, Stephen C. "Precision Astrometry with the Space Interferometry Mission." Symposium - International Astronomical Union 202 (2004): 474–76. http://dx.doi.org/10.1017/s0074180900218548.

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SIM - the Space Interferometry Mission - will be the first of a new generation of space instruments using interferometry. Designed for precision astrometry, it will be a 10-meter optical interferometer providing 4 microarcsecond (μas) absolute position measurements over the whole sky, using a grid of stars (and quasars) for a reference frame. Maintaining its astrometric precision on stars as faint as 20 magnitude, it will far surpass the capability of ground-based astrometry, opening up a new era of space-based astrometry. A wide range of astrophysics problems will be addressed by SIM, includi

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McNally, Derek. "Astrometric angles." Nature 319, no. 6056 (February 1986): 824. http://dx.doi.org/10.1038/319824a0.

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Nucita, A. A., F. De Paolis, G. Ingrosso, M. Giordano, and L. Manni. "Astrometric microlensing." International Journal of Modern Physics D 26, no. 05 (April 2017): 1741015. http://dx.doi.org/10.1142/s0218271817410152.

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In the next future, astrometric microlensing will offer a new channel for investigating the nature of both lenses and sources involved in a gravitational microlensing event. The effect, corresponding to the shift of the position of the multiple image centroid with respect to the source star location, is expected to occur on scales from micro-arcoseconds to milli-arcoseconds depending on the characteristics of the lens-source system. Here, we consider different classes of events (single/binary lens acting on a single/binary source) also accounting for additional effects including the finite sou

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Seidelmann, P. K. "Prospects for Future Astrometric Missions." Symposium - International Astronomical Union 179 (1998): 79–85. http://dx.doi.org/10.1017/s0074180900128232.

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Hipparcos and the Hubble Space Telescope have demonstrated the astrometric capabilities in space. SIM and GAIA are being studied for future missions. There have been many proposals for new astrometry missions from many different countries, but most of them have not been funded.The best possibility for a mission within the next five years would be through a collaborative effort for a small, fast, cheap spacecraft which could be a precursor for future, larger, more accurate missions, which are under study.

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Colomer, F., D. Graham, T. Krichbaum, B. O. Rönnäng, P. de Vicente, A. Barcia, R. S. Booth, A. Witzel, J. Gómez-González та A. Baudry. "Astrometry of SiO Masers: First detections of circumstellar SiO maser emission at λ = 7 mm using three European VLBI stations". International Astronomical Union Colloquium 131 (1991): 338–41. http://dx.doi.org/10.1017/s0252921100013592.

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The positions of circumstellar molecular masers relative to each other, to the central star, and to the compact extragalactic sources are of astrophysical and astrometrical interest. The SiO masers at λ = 7 mm are especially interesting as the maser spots are located very close to the photosphere of the star. For astrometry we would like to see a proper distribution of the maser spots and several epochs of observations in order to estimate the position of the central star and eventual motions of the spots.The optical position of this star can be determined with ground-based astrometric facilit

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Rodeghiero, G., M. Sawczuck, J. U. Pott, M. Glück, E. Biancalani, M. Häberle, H. Riechert, et al. "Development of the Warm Astrometric Mask for MICADO Astrometry Calibration." Publications of the Astronomical Society of the Pacific 131, no. 999 (April 12, 2019): 054503. http://dx.doi.org/10.1088/1538-3873/ab0c40.

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Lindegren, Lennart, and Dainis Dravins. "Astrometric radial velocities for nearby stars." Astronomy & Astrophysics 652 (August 2021): A45. http://dx.doi.org/10.1051/0004-6361/202141344.

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Context. Under certain conditions, stellar radial velocities can be determined from astrometry, without any use of spectroscopy. This enables us to identify phenomena, other than the Doppler effect, that are displacing spectral lines. Aims. The change of stellar proper motions over time (perspective acceleration) is used to determine radial velocities from accurate astrometric data, which are now available from the Gaia and HIPPARCOS missions. Methods. Positions and proper motions at the epoch of HIPPARCOS are compared with values propagated back from the epoch of the Gaia Early Data Release 3

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Geisler, R., J. Setiawan, Th Henning, D. Queloz, A. Quirrenbach, R. Launhardt, A. Müller, S. Reffert, and P. Weise. "Preparing the exoplanet search with PRIMA: searching for reference stars and target characterization." Proceedings of the International Astronomical Union 3, S249 (October 2007): 61–63. http://dx.doi.org/10.1017/s1743921308016384.

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AbstractThe PRIMA (Phase-Referenced Imaging and Micro-arcsecond Astrometry) facility at ESO VLTI (Paranal observatory) is expected to be commissioned in mid 2008. The ESPRI (Exoplanet Search with PRIMA) consortium is currently preparing an astrometric survey to search for extrasolar planets. To achieve the scientific goal of this survey, a careful selection of target and reference stars is necessary. Apart from catalog search and modelling, extensive and dedicated preparatory observations are indispensable. Here we present two aspects of the preparatory observation programs: A high dynamic ran

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