Pulkovo astronegatives collection in the Gaia era: from astrometry to the Galactic and Solar System dynamics

Максим Юрьевич Ховричев (Докладчик)

Деятельность: выступлениевыступление с приглашенным докладом/лекцией


Photographic observations performed with the Normal Astrograph in 1890s resulted in creation of the Pulkovo collection of astronegatives. Accumulation of the plates had been going on during the whole XX century. Pulkovo Normal Astrograph and 26-inch refractor were the main instruments used in the process. Small part of the archive was produced with the telescopes of Chilean, Bolivian and other projects of the Pulkovo Observatory. To this day the plates archive has more than 50000 astronegatives. Basic qualities of the material were caused by scientific aims and telescope’s parameters. A wide program of observations consisted of the proper motion surveys of the selected sky areas and open clusters, astrometric observations of the Solar System bodies, photographic surveys in order to construct astrometric catalogues. One of the primary goals of the Pulkovo observations was to determine the orbital parameters and masses of binary stars, therefore the archive is half composed of the 26-inch refractor plates (plate size is 130x180 mm, scale is 19.81 arcsec/mm). About the third of the archive consists of the Normal Astrograph plates (plate size is 160x160 mm, scale is 59.56 arcsec/mm). Limiting magnitude of stars depended on scientific goals. The deepest plates taken with the Normal Astrograph contain stars up to 17 mag. The 26-inch refractor plates are limited by 10 to 12 mag. Significant fraction of the material has been measured manually at the 3 mkm level of accuracy. А number of the plates with binaries has been processed with the automatic machines with the accuracy of 1 mkm. Thus, we see that the Pulkovo plate collection is a rich source of astronomical data in the epoch of high precision digitalizing machines and Gaia accurate and dense grid of reference stars. Statistical properties of the binary stars population in the solar neighborhood (distribution of orbital parameters, binary fraction) reflect the dynamics of star formation and further dynamical evolution of binaries. Present day catalogues of binaries contain billions of records, but the orbital parameters are known only for a small part of them due to 'poor observational history'. Analysis of the long term effects in the motions of planetary satellites and resonant asteroids, as well as the investigation of a long-term photometric behavior of variable stars, transients and microlensing events, is also complicated by data deficit. Current digitization and analysis of the Pulkovo plates are performed to support the progress in achieving the described goals. A combination of high accuracy machine measurements, fast imaging process and suitable full format camera is used to extract new astronomical results from Pulkovo astronegatives. Templates and a number of astronegatives have been measured with the accuracy of 0.1 mkm using the high quality digitizer. Fast scanning of a large area of the plate is performed with MDD-camera. Templates allow us to construct a field distortion pattern of the lens and take into account corresponding systematic errors. As a result, the accuracy of the plate x,y is about 1 mkm. Equatorial coordinates and proper motions from the Gaia catalogue are used to make astrometric calibration. The final astrometric accuracy has been improved up to 10 – 30 mas for binaries and to 50 – 100 mas for planetary satellites. Described approach allows us to achieve the high accuracy in relatively small areas. That is why binaries are considered to be high priority objects. About 9000 of plates have been digitized. The results of the measurements have been combined with the data of CCD-observations performed using the 26-inch refractor. Finally, the orbital parameters of 451 binaries have been determined. The relative positions and proper motions calculated with these orbital parameters are in good agreement with the Gaia data (differences are less than 5 mas and 0.5 mas/yr correspondingly). Relatively large values of differences might be caused by the presence of previously unknown components. The eccentricity distribution supports the 'thermal distribution hypothesis' (f=2e). Only few hundreds of the plates with the images of Solar System bodies have been digitized. The equatorial coordinates of these objects referred to HCRF/UCAC4 have been published, but we plan to improve them using Gaia reference stars. Web-representation of the Pulkovo collection is available via http://www.puldb.ru/db/plates/index.php. The reported study was funded by RFBR according to the research project 19-02-00843 А.
Период24 июн 201928 июн 2019
Название событияThe European Week of Astronomy and Space Science: null
Тип мероприятияконференция
МестонахождениеLyon, Франция