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It is generally recognised that the Working Group on the Rotation of the Earth that was set up after IAU Symposium No. 82 has successfully achieved its principal objectives, namely: “to make recommendations on … future international services on earth-rotation” and “to obtain and analyse data on earth-rotation by both current and new methods …”. In particular, by organising Project MERIT, it has stimulated the development and use of new techniques and it has brought together in fruitful collaboration scientists from many countries and disciplines. Other subsidiary objectives have also been achieved and the project has been extended through cooperation with the COTES Working Group on the terrestrial reference system. The possible reasons for this success are also reviewed in the expectation that the conclusions will be relevant to other future projects.
We present results from our ongoing monitoring programs aimed at identifying and understanding Active Galactic Nuclei (AGN) in extreme flux and spectral states. Observations of AGN in extreme states can reveal the nature of the inner accretion flow, the physics of matter under strong gravity, and they provide insight on the properties of ionized absorbers and outflows launched near supermassive black holes (SMBHs). We present new results from our long-term monitoring of IC 3599, WPVS007, and Mrk 335, multi-wavelength follow-ups of the newly identified changing-look AGN HE 1136–2304, and UV–X-ray follow-ups of the binary SMBH candidate OJ 287 after its 2015 optical maximum, now in a new optical-X-ray–high-state.
The aims of this report are, firstly, to review the activities of Commission 5 during the period since the IAU General Assembly in Delhi in November 1985 and, secondly, to draw attention to other relevant activities. It is based mainly on contributions from the Chairmen of the working groups and other members of the Commission, but it also includes some items of general interest that have been taken from the Commission’s Newsletter. The Working Groups and their Chairmen are as follows:
During the period under review two issues of the Astronomical Yearbook of the U.S.S.R. for the years 1971, 1972 have been published, and that for 1973 is in preparation. The positions and proper motions of the stars are in the FK4 system as recommended by Commission 4 in 1961. Further, as recommended at the meeting in Hamburg in 1964 (Trans. IAU, 12 B (1964), 105,1966) the IAU System of Astronomical Constants has been introduced into the tabulations of the day numbers, solar and lunar eclipses, ephemerides for physical observations of planets, and the factors S &C. The corresponding differential corrections to the Moon’s ephemeris as well as re-calculated eclipse data for 1971 have been tabulated separately in the Appendix to the Yearbook for 1971. As from the edition of the Yearbook for 1972, the lunar ephemeris j = 2 will be published in accordance with the recommendations adopted in Prague in 1967.
The regular publication of the ephemeris of the lunar crater Mösting A has been continued in the editions of the Yearbook mentioned above.
Fundamental ephemerides of the Sun, Moon, and planets have been printed in full conformity with the first part of the Astronomical Ephemeris circulated in advance by H. M. Nautical Almanac Office, Royal Greenwich Observatory.
Because of unforeseen difficulties, Dr Sinzi, President of the Commission, was not able to prepare this Report. It was then too late for asking the Directors of the almanac offices and the other Members of the Commission for informations. This Report is therefore based on the material just available, and it must be apologized for some lack from which it necessarily suffers. If possible, any omitted facts which appear to be serious, may be included in the Report for the following triennium.
The period of this Report includes 1984 January 1, the date which was probably the most drastic caesura in the history of astronomical almanacs. It seemed, therefore, appropriate to concentrate here to the general aspects rather than to describe the works going on at the particular almanac offices. It is, however, hoped that the past years with their developments and changes will be followed by a period of consolidation and continuity. This would be also of great benefit for the users of the almanacs who still need some time for getting accustomed to so many innovations.
The appended reports of the directors of the national ephemeris offices provide a record of the current activity in the publication and preparation of astronomical ephemerides, including those published for use by navigators and surveyors and those prepared for astronomers whose special needs are not met in the printed almanacs. A brief review of the relevant work of other institutions and individuals is also given in the appendix. The reports also cover to some extent activities in positional astronomy and celestial mechanics (i.e. in the fields of interest of Commissions 7, 8, 17, 19, 20 and 31). This report is therefore restricted to reviewing, firstly, the action that has been taken on matters raised at and since the 1967 meetings of the Commission and, secondly, the matters that will require attention at and after the 1970 meetings.
Before that review, it is appropriate to pay tribute to the memory of that almost legendary astronomer, Gaston Fayet, who died on 27 December 1967 at the advanced age of 93. As member of the Bureau des Longitudes responsible for the production of the Connaissance des Temps from 1930 to 1961, and President of Commission 4 from 1938 to 1952, he contributed greatly to our subject, in addition to his researches in other fields particularly in respect of the minor planets.
During the period, there have been several major events which have effected the scope and interest of Commission 19. The most significant of these has been the dissolution of the BIH and IPMS and their replacement by the International Earth Rotation Service (IERS). The correlation of higher frequency fluctuations in the Earth’s rotation rate with changes in the Earth’s Atmospheric Angular Momentum is also significant. Many investigators now seem to believe that the “decade variations„ in the Earth’s rotation rate are caused by torques between the core and mantle caused by the uneven motions at the core-mantle boundary. These events and discoveries have made this an exciting period. It seems that the future holds more in the way of discovery due to the utilization of the more accurate and precise Earth rotation data coming from the modern observing techniques.
The report period 1982-84 was characterized by an again increased volume of material processed in data and abstracting centers, and by a growing clientele particularly of online services. The Working Groups of Commission 5 seek continued consultation with research object commissions so that the advanced documentation technology be efficiently employed toward specific demands of subject areas as to indexing, tagging, comprehensive, selective and inter-discliplinary retrievals. The guideline library for these purposes has been augmented by the First Dictionary of the Nomenclature of Celestial Objects by A. Fernandez, M.-C. Lortet and F. Spite (Astr. Astrophys. Suppl. 52 no.4, 1983) and by the Guide to the Presentation of Astronomical Data by G.A. Wilkins (CODATA Bull.46 1982); a new draft of the IAU Style Manual is before the IAU EC.