Publications
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| EAS Tycho Brahe Prize Lecture 2011 - Hipparcos: a Retrospective |
Preprint. Paper to appear in Astronomy and Astrophys Review, 2011. The Hipparcos satellite was launched in 1989. It was the first, and remains to date the only, attempt at performing large-scale astrometric measurements from space. Hipparcos marked a fundamentally new approach to the field of astrometry, revolutionising our knowledge of the positions, distances, and space motions of the stars in the solar neighbourhood. In this retrospective, I look back at the processes which led to the mission's acceptance, provide a short summary of the underlying measurement principles and the experiment's scientific achievements, and a conclude with a brief summary of its principal legacy - the Gaia mission. |
| Publication date: 30 Sep 2011 |
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| Astronomical Applications of Astrometry: Ten Years of Exploitation of the Hipparcos Satellite Data |
The Hipparcos satellite, developed and launched by the European Space Agency (ESA) in 1989, was the first space mission dedicated to astrometry - the accurate measurement of positions, distances, and proper motions of stars. Amongst the key achievements of its measurements are refining the cosmic distance scale, characterising the large-scale kinematic motions in the Solar neighbourhood, providing precise luminosities for stellar modelling, and confirming Einstein's prediction of the effect of gravity on starlight. This authoritative account of the Hipparcos contributions over the last decade is an outstanding reference for astronomers, astrophysicists and cosmologists. It reviews the applications of the data in different areas, describing the subject and the state-of-the-art before Hipparcos, and summarising all major contributions to the topic made by Hipparcos. It contains a detailed overview of the Hipparcos and Tycho Catalogues, their annexes and their updates. Each chapter ends with comprehensive references to relevant literature.
Table of Contents
1. The Hipparcos and Tycho catalogues;
2. Derived catalogues and applications;
3. Double and multiple stars;
4. Photometry and variability;
5. Luminosity calibration and distance scale;
6. Open clusters, groups and associations;
7. Stellar structure and evolution;
8. Specific stellar types and the ISM;
9. Structure of the Galaxy;
10. Solar System and exo-planets;
Index.
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| Publication date: 01 Dec 2008 |
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| Hipparcos, the New Reduction of the Raw Data |
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| Publication date: 27 Sep 2007 |
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| ESA SP-1296: ESA's Report to the 36th COSPAR Meeting |
Scientific editor: R. Marsden
Editor: A. Wilson
The report for the 36th COSPAR Meeting covers, as in previous issues, the missions of the Scientific Programme of ESA in the areas of astronomy, Solar System science and fundamental physics. This year's COSPAR meeting will take place only weeks before the end of the SMART-1 mission to the Moon, a technology project that provided the first European look at our natural satellite from lunar orbit.In October of this year, a new mission will be launched: COROT. ESA, together with a number of countries, is contributing to this unique, French-led project that will provide an insight into the interior of the stars, by means of the asteroseismology technique successfully applied by SOHO. COROT will also perform a systematic search for new extrasolar planets using photometric transits.
The record number of ESA Science Programme missions in operation established at the time of the last report was maintained in 2006 (Huygens having been replaced in the list by Venus Express). Eleven different missions, involving 14 operating spacecraft, are providing excellent science to the worldwide scientific community. The Research and Scientific Support Department (RSSD) is responsible for the science operations of these missions and makes every effort to ensure the best possible science return. The Department also supports the realisation of approved projects in all phases of their development. |
| Publication date: 15 Jun 2006 |
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| Unexpected stellar velocity distribution in the warped Galactic disk |
| It is now over 40 years since the gaseous disc of our galaxy was discovered to be warped from radio observations of neutral hydrogen [1]. Subsequently the warp has been detected in the distribution of galactic dust [2], molecular clouds [3], and luminous stars [4,5]. Roughly half of all spiral galaxies have similarly warped discs, which suggests that warps are common and long-lived phenomenon. However, there is still no consensus as to what induces galactic discs to become warped: intergalactic winds, tidal interactions with satellites, magnetic pressure and massive dark halos have all been proposed as causative agents. Here we use data from the Hipparcos satllite [6] to probe the Milky Way's warp. |
| Publication date: 02 Apr 1998 |
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| The Hyades: distance, structure, dynamics, and age |
| We use absolute trigonometric parallaxes from the Hipparcos Catalogue to determine individual distances to members
of the Hyades cluster, from which the 3-dimensional structure of the cluster can be derived. Inertially-referenced proper
motions are used to rediscuss distance determinations based on convergent-point analyses. A combination of parallaxes and
proper motions from Hipparcos, and radial velocities from ground-based observations, are used to determine the position
and velocity components of candidate members with respect to the cluster centre, providing new information on cluster membership: 13 new candidate members within 20 pc of the cluster centre have been identified. Farther from the cluster centre there is a gradual merging between certain cluster members and field stars, both spatially and kinematically. |
| Publication date: 01 Mar 1998 |
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| Timing the Geminga Pulsar with Gamma-Ray Observations |
| We present the COS B/EGRET 1997 ephemeris for the rotation of the Geminga pulsar. This ephemeris is derived from high-energy gamma -ray observations that span 24 yr. The recently obtained accurate position and proper motion are assumed. A cubic ephemeris predicts the rotational phase of Geminga with errors smaller than 50 milliperiods for all existing high-energy gamma -ray observations that span a 24.2 yr timing baseline. The braking index obtained is 17 +/- 1. Further observation is required to ascertain whether this high value truly reflects the rotational energy loss mechanism, or whether it is a manifestation of timing noise. The ephemeris parameters are sufficiently constrained so that timing noise will be the limitation on forward extrapolation. If Geminga continues to rotate without a glitch, as it has for at least 23 yr, we expect this ephemeris to continue to describe the phase, with an error of less than 100 milliperiods, until 2008. Statistically significant timing residuals are detected in the EGRET data that depart from the cubic ephemeris at a level of 30 milliperiods. Although this could simply be an additional manifestation of timing noise, the EGRET timing residuals appear to have a sinusoidal modulation that is consistent with a planet of mass 1.7/sin i MSun orbiting Geminga at a radius of 3.3 AU. |
| Publication date: 01 Feb 1998 |
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| Hipparcos positioning of Geminga: how and why |
| Accuracy in the absolute position in the sky is one of the limiting factors for pulsar timing, and timing parameters have a direct impact on the understanding of the physics of Isolated Neutron Stars (INS). We report here on a high-accuracy measurement of the optical position of Geminga (mv=25.5), the only known radio-quiet INS. The procedure combines the Hipparcos and Tycho catalogues, ground-based astrometric data,and Hubble Space Telescope (HST) Wide Field Planetary Camera (WFPC2) images, to yield Geminga's absolute position to within ~ 40 mas (per coordinate). Such a positional accuracy, unprecedented for the optical position of a pulsar or an object this faint, is needed to combine in phase gamma -ray photons collected over more than 20 years, i.e. over 2.5 billions of star' revolutions. Although quite a difficult task, this is the only way to improve our knowledge of the timing parameters of this radio silent INS. Based on Observation with the ESA Hipparcos satellite. |
| Publication date: 05 Jan 1998 |
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