scholarly journals Gaia Data Release 2

2018 ◽  
Vol 616 ◽  
pp. A1 ◽  
Author(s):  
◽  
A. G. A. Brown ◽  
A. Vallenari ◽  
T. Prusti ◽  
J. H. J. de Bruijne ◽  
...  
Keyword(s):  
Solar System ◽  
Reference Frame ◽  
Broad Band ◽  
Radial Velocities ◽  
Minor Planets ◽  
Major Advance ◽  
Photometric System ◽  
Proper Motions ◽  
Apparent Brightness ◽  
Data Release

Context. We present the second Gaia data release, Gaia DR2, consisting of astrometry, photometry, radial velocities, and information on astrophysical parameters and variability, for sources brighter than magnitude 21. In addition epoch astrometry and photometry are provided for a modest sample of minor planets in the solar system. Aims. A summary of the contents of Gaia DR2 is presented, accompanied by a discussion on the differences with respect to Gaia DR1 and an overview of the main limitations which are still present in the survey. Recommendations are made on the responsible use of Gaia DR2 results. Methods. The raw data collected with the Gaia instruments during the first 22 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium (DPAC) and turned into this second data release, which represents a major advance with respect to Gaia DR1 in terms of completeness, performance, and richness of the data products. Results. Gaia DR2 contains celestial positions and the apparent brightness in G for approximately 1.7 billion sources. For 1.3 billion of those sources, parallaxes and proper motions are in addition available. The sample of sources for which variability information is provided is expanded to 0.5 million stars. This data release contains four new elements: broad-band colour information in the form of the apparent brightness in the GBP (330–680 nm) and GRP (630–1050 nm) bands is available for 1.4 billion sources; median radial velocities for some 7 million sources are presented; for between 77 and 161 million sources estimates are provided of the stellar effective temperature, extinction, reddening, and radius and luminosity; and for a pre-selected list of 14 000 minor planets in the solar system epoch astrometry and photometry are presented. Finally, Gaia DR2 also represents a new materialisation of the celestial reference frame in the optical, the Gaia-CRF2, which is the first optical reference frame based solely on extragalactic sources. There are notable changes in the photometric system and the catalogue source list with respect to Gaia DR1, and we stress the need to consider the two data releases as independent. Conclusions. Gaia DR2 represents a major achievement for the Gaia mission, delivering on the long standing promise to provide parallaxes and proper motions for over 1 billion stars, and representing a first step in the availability of complementary radial velocity and source astrophysical information for a sample of stars in the Gaia survey which covers a very substantial fraction of the volume of our galaxy.

scholarly journals Esiderata for nearby - star quantities observable with small telescope

1986 ◽  
Vol 118 ◽  
pp. 247-249
Author(s):  
W. Gliese
Keyword(s):  
Broad Band ◽  
Radial Velocities ◽  
General Assembly ◽  
New Delhi ◽  
Proper Motions ◽  
Nearby Star ◽  
Small Telescope ◽  
General Catalogue ◽  
Nearby Stars

At the General Assembly of the IAU at New Delhi van Altena reported on the new General Catalogue of Trigonometric Stellar Parallaxes (GCTSP) which was completed recently at the Yale Observatory. Time seems to be ripe now for the compilation of a Third Catalogue of Nearby Stars which will include all objects known to be nearer than 25 parsecs. This catalogue will contain positions, proper motions, radial velocities, spectral types, broad-band photometry, and parallaxes - quantities won by observations.

scholarly journals Galactic Archeology with RAVE and TGAS

2017 ◽  
Vol 13 (S334) ◽  
pp. 116-119
Author(s):  
Matthias Steinmetz ◽  
Keyword(s):  
Radial Velocities ◽  
Proper Motions ◽  
Basic Properties ◽  
Gaia Dr1 ◽  
Disk Structure ◽  
Data Release ◽  
Data Products ◽  
Derived Data ◽  
Astrometric Data

AbstractThe 5th RAVE data release is based on 520,781 spectra (R ≈ 7500 in the CaT region at 8410 - 8795Å) of 457,588 unique stars. RAVE DR5 provides radial velocities, stellar parameters and individual abundances for up to seven elements and distances found using isochrones for a considerable subset of these objects. In particular, RAVE DR5 has 255,922 stellar observations that also have parallaxes and proper motions from the Tycho-Gaia astrometric solution (TGAS) in Gaia DR1. The combination of RAVE and TGAS thus provides the currently largest overlap of spectroscopic and space-based astrometric data and thus can serve as a formidable preview of what Gaia is going to deliver in coming data releases. Basic properties of the RAVE+TGAS survey and its derived data products are presented as well as first applications w.r.t wave-like patterns in the disk structure. An outlook to the 6th RAVE data release is given.

Astrometric surveys in the Gaia era

2017 ◽  
Vol 12 (S330) ◽  
pp. 49-58
Author(s):  
Norbert Zacharias
Keyword(s):  
Reference Frame ◽  
Wide Field ◽  
Proper Motions ◽  
Gaia Dr1 ◽  
Data Release ◽  
Optical Reference ◽  
Trigonometric Parallaxes ◽  
Astrometric Data ◽  
Interim Period

AbstractThe Gaia first data release (DR1) already provides an almost error free optical reference frame on the milli-arcsecond (mas) level allowing significantly better calibration of ground-based astrometric data than ever before. Gaia DR1 provides positions, proper motions and trigonometric parallaxes for just over 2 million stars in the Tycho-2 catalog. For over 1.1 billion additional stars DR1 gives positions. Proper motions for these, mainly fainter stars (G ≥ 11.5) are currently provided by several new projects which combine earlier epoch ground-based observations with Gaia DR1 positions. These data are very helpful in the interim period but will become obsolete with the second Gaia data release (DR2) expected in April 2018. The era of traditional, ground-based, wide-field astrometry with the goal to provide accurate reference stars has come to an end. Future ground-based astrometry will fill in some gaps (very bright stars, observations needed at many or specific epochs) and mainly will go fainter than the Gaia limit, like the PanSTARRS and the upcoming LSST surveys.

scholarly journals Exploring the Solar System with the NOIRLab Source Catalog I: Detecting Objects with CANFind

2021 ◽  
Vol 162 (6) ◽  
pp. 244
Author(s):  
Katie M. Fasbender ◽  
David L. Nidever
Keyword(s):  
Solar System ◽  
Proper Motion ◽  
Kuiper Belt ◽  
Moving Object ◽  
Proper Motions ◽  
Clustering Method ◽  
Main Belt ◽  
Relative Proximity ◽  
Solar System Objects ◽  
Data Release

Abstract Despite extensive searches and the relative proximity of solar system objects (SSOs) to Earth, many remain undiscovered and there is still much to learn about their properties and interactions. This work is the first in a series dedicated to detecting and analyzing SSOs in the all-sky NOIRLab Source Catalog (NSC). We search the first data release of the NSC with CANFind, a Computationally Automated NSC tracklet Finder. NSC DR1 contains 34 billion measurements of 2.9 billion unique objects, which CANFind categorizes as belonging to “stationary” (distant stars, galaxies) or moving (SSOs) objects via an iterative clustering method. Detections of stationary bodies for proper-motion μ ≤ 2.″5 hr−1 (0.°017 day−1) are identified and analyzed separately. Remaining detections belonging to high-μ objects are clustered together over single nights to form “tracklets.” Each tracklet contains detections of an individual moving object, and is validated based on spatial linearity and motion through time. Proper motions are then calculated and used to connect tracklets and other unassociated measurements over multiple nights by predicting their locations at common times, forming “tracks.” This method extracted 527,055 tracklets from NSC DR1 in an area covering 29,971 square degrees of the sky. The data show distinct groups of objects with similar observed μ in ecliptic coordinates, namely Main Belt Asteroids, Jupiter Trojans, and Kuiper Belt Objects. Apparent magnitudes range from 10 to 25 mag in the ugrizY and VR bands. Color–color diagrams show a bimodality of tracklets between primarily carbonaceous and siliceous groups, supporting prior studies.

scholarly journals Gaia Data Release 2

2018 ◽  
Vol 616 ◽  
pp. A17 ◽  
Author(s):  
F. Arenou ◽  
X. Luri ◽  
C. Babusiaux ◽  
C. Fabricius ◽  
A. Helmi ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Solar System ◽  
Spectroscopic Data ◽  
Statistical Properties ◽  
Radial Velocities ◽  
Systematic Analysis ◽  
External Data ◽  
Accuracy And Precision ◽  
Solar System Objects ◽  
Data Release

Context. The second Gaia data release (DR2) contains very precise astrometric and photometric properties for more than one billion sources, astrophysical parameters for dozens of millions, radial velocities for millions, variability information for half a million stars from selected variability classes, and orbits for thousands of solar system objects. Aims. Before the catalogue was published, these data have undergone dedicated validation processes. The goal of this paper is to describe the validation results in terms of completeness, accuracy, and precision of the various Gaia DR2 data. Methods. The validation processes include a systematic analysis of the catalogue content to detect anomalies, either individual errors or statistical properties, using statistical analysis and comparisons to external data or to models. Results. Although the astrometric, photometric, and spectroscopic data are of unprecedented quality and quantity, it is shown that the data cannot be used without dedicated attention to the limitations described here, in the catalogue documentation and in accompanying papers. We place special emphasis on the caveats for the statistical use of the data in scientific exploitation. In particular, we discuss the quality filters and the consideration of the properties, systematics, and uncertainties from astrometry to astrophysical parameters, together with the various selection functions.

scholarly journals Solar system objects observed by Hipparcos

1996 ◽  
Vol 172 ◽  
pp. 437-442
Author(s):  
D. Hestroffer ◽  
B. Morando
Keyword(s):  
Solar System ◽  
Reference Frame ◽  
Minor Planets ◽  
Solar System Objects ◽  
Normal Place ◽  
Natural Satellites

The ESA satellite Hipparcos provides valuable photometric and astrometric results on minor planets and natural satellites. Observations of 48 asteroids, JII-Europa, S VI-Titan and S VIII-Iapetus were made from November 1989 to March 1993. A twenty seconds averaged normal place is constructed, providing thus positions accurate to a few hundredths of arcseconds and relative to a very precise and homogeneous reference frame.

scholarly journals Galactocentric acceleration in VLBI analysis

2019 ◽  
Vol 630 ◽  
pp. A93 ◽  
Author(s):  
D. S. MacMillan ◽  
A. Fey ◽  
J. M. Gipson ◽  
D. Gordon ◽  
C. S. Jacobs ◽  
...  
Keyword(s):  
Solar System ◽  
Reference Frame ◽  
Working Group ◽  
Galactic Center ◽  
Proper Motions ◽  
Data Set ◽  
Global Parameter ◽  
Geodetic Vlbi ◽  
Acceleration Vector ◽  
Group Members

Aims. The IVS Working Group on Galactic Aberration (WG8) was established to investigate issues related to incorporating the effect of Galactic aberration in IVS analysis. The circular motion of the solar system barycenter around the Galactic center causes a change in aberration, which in the case of geodetic VLBI observing is over time scales of several decades. One of the specific goals was to recommend a Galactic aberration model to be applied by the IAU ICRF3 working group in the generation of ICRF3 as well as in other IVS analysis. Studies made by working group members have shown that the three-dimensional acceleration vector of the solar system barycenter can be estimated from VLBI delay observations. Methods. Among the working group members, three methods were used to estimate the acceleration vector. One is to directly estimate the acceleration vector as a global parameter. The second is to estimate the acceleration vector from source proper motions determined from estimated source position time series. A third method estimated a global reference frame scale parameter for each source and derived the acceleration vector from these estimates. The acceleration vector estimate consists of a galactocentric component along with the non-galactocentric components. Results. The geodetic reference frame VLBI estimates of the galactocentric aberration constant from the different working group members are in the range 5.1–6.4 μas yr−1. These estimates are relatively close to independent estimates of 4.8–5.4 μas yr−1 that can be derived from astrometric measurements of proper motions and parallaxes of masers in the Milky Way galaxy. Based on the most recent geodetic VLBI solutions, we find an upper bound of 0.8 μas yr−1 for the non-galactocentric component of the secular aberration. Conclusions. The working group made a recommendation only for the galactocentric component of the observed acceleration vector. For the recommended galactocentric aberration constant, the working group chose a geodetic value to be consistent with geodetic VLBI applications. The recommended value 5.8 μas yr−1 was estimated directly in a global solution that used the ICRF3 solution data set: 1979–May 2018.

scholarly journals Improving the dynamical reference frame through minor planet orbit correction using crossing point observations

1988 ◽  
Vol 128 ◽  
pp. 55-60
Author(s):  
Arthur L. Whipple ◽  
Raynor L. Duncombe ◽  
Paul D. Hemenway
Keyword(s):  
Computer Program ◽  
Reference Frame ◽  
Reference System ◽  
Hubble Space Telescope ◽  
Simulated Data ◽  
Minor Planet ◽  
Minor Planets ◽  
Space Telescope ◽  
Orbit Correction ◽  
Crossing Point

We have begun a program to establish a dynamical reference frame based on the motions of minor planets. The program will utilize observations from the Hubble Space Telescope, and will ultimately tie the HIPPARCOS reference system to a dynamical base. Thirty-four minor planets, 20 of which are suitable for observation with the Hubble Space Telescope, have been selected. Ground based observations, particularly crossing-point observations with long focus reflectors, have been initiated.A computer program to simultaneously solve for the corrections of the orbits of the 34 minor planets including the crossing-point observations, was successfully run. The observations are treated by the method of W. H. Jeffreys. Using simulated data, solutions with and without crossing point observations demonstrate the value of those observations to produce a homogeneous and coherent set of results.

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