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تسجيل مستخدم جديدReport of IAU Commission 30 on Radial Velocities (2009-2012)
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Brief summaries are given of the following subjects of interest to IAU Commission 30: Large-scale radial-velocity surveys; The role of radial-velocity measurements in studies of stellar angular momentum evolution and stellar age; Radial velocities in open clusters; Toward higher radial-velocity precision; High-precision radial velocities applied to studies of binary stars; Doppler boosting effect; Working groups (Stellar radial velocity bibliography; Radial velocity standards; Catalogue of orbital elements of spectroscopic binaries [SB9]).
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Commission 8 has regularly published triennial reports in the past and the current OC therefore voted to adopt a traditional format also for this special Legacy issue of the IAU Transactions. The outgoing President is grateful for the support of many
Commission members who contributed to this report. Our contribution consists of 3 parts: 1) this introduction, providing a general overview and highlights of recent research in astrometry, 2) a summary of the astrometry business and science meeting at the 2015 IAU General Assembly, and 3) the activity report of our Commisson covering the mid-2012 to mid-2015 period.
This hexennial report covers the activities of IAU Commission 36 -- Theory of Stellar Atmospheres -- during the years 2009 to 2015, and will be the last report from this Commission, being replaced by Commission C.G5. After outlining the composition
of the Organization Committee(s), we list the scientific meetings held between 2009 and 2015 that were of relevance for our Commission members, and comment on the establishment and objectives of the new Commission C.G5 (Stellar and Planetary Atmospheres) within the re-structuring process of the IAU. In the main part of the report, we briefly review specific contributions and achievements within our research field during the last six years, concentrating on the theoretical aspect, and dividing between late-type and massive star atmospheres. We also provide a more general overview of primary research areas, and finish our report with a collection of useful web links.
After more than half a century of community support related to the science of solar activity, IAUs Commission 10 was formally discontinued in 2015, to be succeeded by C.E2 with the same area of responsibility. On this occasion, we look back at the gr
owth of the scientific disciplines involved around the world over almost a full century. Solar activity and fields of research looking into the related physics of the heliosphere continue to be vibrant and growing, with currently over 2,000 refereed publications appearing per year from over 4,000 unique authors, publishing in dozens of distinct journals and meeting in dozens of workshops and conferences each year. The size of the rapidly growing community and of the observational and computational data volumes, along with the multitude of connections into other branches of astrophysics, pose significant challenges; aspects of these challenges are beginning to be addressed through, among others, the development of new systems of literature reviews, machine-searchable archives for data and publications, and virtual observatories. As customary in these reports, we highlight some of the research topics that have seen particular interest over the most recent triennium, specifically active-region magnetic fields, coronal thermal structure, coronal seismology, flares and eruptions, and the variability of solar activity on long time scales. We close with a collection of developments, discoveries, and surprises that illustrate the range and dynamics of the discipline.
The IAU Commission 4 Working Group on Standardizing Access to Ephemerides recommends the use of the Spacecraft and Planet Kernel (SPK) format as a standard format for the position ephemerides of planets and other natural solar system bodies, and the
use of the Planetary Constants Kernel (PCK) format for the orientation of these bodies. It further recommends that other supporting data be stored in a text PCK. These formats were developed for use by the SPICE Toolkit by the Navigation and Ancillary Information Facility of NASAs Jet Propulsion Laboratory (JPL). The CALCEPH library developed by the Institut de mecanique celeste de calcul des ephemerides (IMCCE) is also able to make use of these files. High accuracy ephemerides available in files conforming to the SPK and PCK formats include: the Development Ephemerides (DE) from JPL, Integrateur Numerique Planetaire de lObservatoire de Paris (INPOP) from IMCCE, and the Ephemerides Planets and the Moon (EPM), developed by the Institute for Applied Astronomy (IAA). The bulk of this report is a description of the portion of PCK and SPK formats required for these ephemerides. New SPK and PCK data types, both called Type 20: Chebyshev (Velocity Only), have been added. Other changes to the specification are (i) a new object identification number for coordinate time ephemerides and (ii) a set of three new data types that use the TCB rather than the TDB time scale for the ephemerides, but are otherwise identical to their T
It is widely accepted that stars do not form in isolation but result from the fragmentation of molecular clouds, which in turn leads to star cluster formation. Over time, clusters dissolve or are destroyed by interactions with molecular clouds or tid
al stripping, and their members become part of the general field population. Star clusters are thus among the basic building blocks of galaxies. In turn, star cluster populations, from young associations and open clusters to old globulars, are powerful tracers of the formation, assembly, and evolutionary history of their parent galaxies. Although their importance had been recognised for decades, major progress in this area has only become possible in recent years, both for Galactic and extragalactic cluster populations. Star clusters are the observational foundation for stellar astrophysics and evolution, provide essential tracers of galactic structure, and are unique stellar dynamical environments. Star formation, stellar structure, stellar evolution, and stellar nucleosynthesis continue to benefit and improve tremendously from the study of these systems. Additionally, fundamental quantities such as the initial mass function can be successfully derived from modelling either the H-R diagrams or the integrated velocity structures of, respectively, resolved and unresolved clusters and cluster populations. Star cluster studies thus span the fields of Galactic and extragalactic astrophysics, while heavily affecting our detailed understanding of the process of star formation in dense environments.This report highlights science results of the last decade in the major fields covered by IAU Commission 37: Star clusters and associations.
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