We propose a self-consistent approach of the CP star phenomenon and try to solve simultaneously the problems of abundance spots, wind and X-ray emission from these stars. We also discuss the periodic X-ray emission from the 07V star θ1 Orionis C and its link with Bp stars.

Diagnosis of Ap star magnetic fields through spectroscopic methods is a broad topic, which cannot be fully covered within the rather tight limits of this contribution. Accordingly, the latter is devoted to only one particular approach, namely the determination of the mean magnetic field modulus from the observation of resolved magnetically split lines in high-dispersion spectra taken in unpolarized light. This determination is straightforward, mostly approximation free and model independent. The derived quantity, the mean magnetic field modulus, is the line-intensity weighted average over the visible stellar hemisphere of the modulus of the magnetic vector.

The observational quantities commonly used to study the magnetic field of CP stars – the mean field modulus and the mean longitudinal field, as well as the ‘mean asymmetry of the longitudinal field’ and the ‘mean quadratic field’ recently introduced by Mathys (1995a,b) – are based either on the Stokes parameter / or on the Stokes parameter V. However, a complete description of polarized radiation requires the knowledge of the full Stokes vector: in other words, we should expect that useful information is also contained in linear polarization (the Stokes parameters Q and U); or rather we should expect the information contained in (Q, U) and in V to be complementary, since linear and circular polarization are basically related to the transverse and the longitudinal component of the magnetic field, respectively.

This group of metal poor stars were introduced with the identification of an ‘abnormal’ spectrum for λBoõtis in the famous classification survey of Morgan, Keenan & Kellman (1943) based on a blue sensitive photographic emulsion. More stars were discovered with comparable spectra and with other peculiarities, in particular when the available spectral region was extended to the red and beyond the optical region towards the IR and to the UV.

Until the rapid oscillations in Przybylski’s star, HD 101065, were discovered by Kurtz in 1978, chemical peculiarity and pulsation were thought to be mutually exclusive. Though the location of the Ap stars in the HR diagram overlaps with that of the Delta Scuti stars, no Ap stars were known to pulsate, and the Delta Scuti type pulsating stars, with a few exceptions, were not claimed to reveal chemical peculiarity. The striking impact of the discovery of the rapid oscillations of Ap stars is that the basic conception of the exclusiveness of the chemical peculiarity and the pulsation was broken. So far, twenty-nine Ap stars have been discovered to be rapidly oscillating Ap (roAp) stars (Kurtz 1997). The observed pulsations of Ap stars are, however, different from those of the Delta Scuti stars in various aspects. The pulsation periods of roAp stars are typically 10.minutes and are much shorter than those of the Delta Scuti stars, which are typically 2 hrs. In some cases, the amplitudes are modulated with the same period and phase as the magnetic strength variation. The amplitudes of some of the roAp stars are very stable, while some others show a fairly short-term variation of a time scale of a day. Some of the roAp stars show a long-term variation of the frequency with a time scale of years.

Let me first remind you of the subject of the present Joint Discussion. It is about spectroscopy with large telescopes. As I have never done any spectroscopic research of my own and I have never observed with a very large telescope, I am certainly the right person to summarize the most recent results in this area.

With the achievements obtained in the last few years, in particular most recently, I arrived at the following three hypotheses which seem to combine some major problems of ancient Chinese astronomy on a common historical basis.

In this talk we will discuss some aspects of the exchange of astronomical knowledge that took place between the Muslim world and China in the thirteenth and fourteenth century. In that period both the eastern part of the Muslim world, consisting of Persia and surrounding countries, and China, ruled by the Yuan Dynasty, were part of the Mongol world empire. In particular in the period between 1260 and 1280, astronomers as well as astronomical books and instruments were exchanged between Persia and China. As a result, extensive descriptions of a Chinese luni-solar calendar can be found in Arabic and Persian astronomical works from the Mongol period, whereas a Chinese text entitled Huihui Li (“Islamic Calendar”) can be seen to be a translation of a typical Islamic astronomical handbook with tables and explanatory text, in Arabic and Persian called zīj. Islamic astronomy had a good name in China because of its accurate prediction of eclipses, and the Huihui li was used parallel with the official Chinese calendar for almost 300 years.

Na๣īr al-Dīn al-Ṭūsī (1201-1274) composed his Tadhkira at Marāgha in 1261 and altered it with his students and produced his “final version” at Baghdad in 1274. The Baghdad version with all its differences from the Marāgha version was published by Ragep [1993]. That the Tadhkira was considered important by astronomers writing in Arabic is amply attested to by the fact that Ragep [1993] can list fourteen commentaries and supercommentaries as well as refer to numerous other derivative texts.

Indian astronomy was introduced into China along with the intrusion of Buddhism. This process lasted about one thousand years in the Mediaeval age. For the study of this process, there are a lot of materials in ancient Chinese historic texts, while the Buddhist scriptures in Chinese translation are very important first-hand materials.

In this paper a survey of three star maps produced in Korea in the mid-18th century as the results of interaction with the Jesuits in Beijing is briefly outlined. The first of these is the Honchŏn Jŏndo (abbreviated to HJ), a wood-cut print. The other two are large screen star maps, each consisting of 8 panels of a folding screen, called Screen Star Map Type 1 (abbreviated to SSM1) and Screen Star Map Type 2 (abbreviated to SSM2). On each of these three star maps there are detailed explanatory texts, which provide information on the transmission of wetern astronomy to Korea by the Royal astronomers.

The construction of a new museum of astronomy is planned by the present author in Yecheon Prefecture (λ = 128°28’ E, (ϕ> = 36°39’ N), Korea, with the openning date set in October, 1999. The aims of the museum directed in three area: (1) to exhibit astronomical works available in Korea, China, Japan and other regions of the Far East; (2) to serve the publics with written material for the study of history of Oriental astronomy; and (3) to operate a 40-cm reflecting telescope for researches of both professionals and amateur astronomers. A long-term project of the reconstruction of King Sejong’s instruments, which were made in the 15th century in the Kyongbok Palace, Seoul, is also an important subject of this museum.

The following is a summary of recent research which I have undertaken on the eclipse records in the Koryo-sa. This work is based on a careful examination of the astrological treatise of the Koryo-sa. I have compared each of the many solar and lunar eclipse accounts with the results of computation and based deductions on these comparisons.

The celestial map of the Chunyou stone inscription in Suzhou and that contained in the Xin yixiang fayao (), both belonging to the Song () Dynasty, are among the oldest of the extant celestial maps in China. The former has a circular form, and the latter is in two forms, circular and rectangular. I have been wondering which projection methods were used in these star maps, or rather, whether they were ever drawn accurately enough for us to be able to discuss their projection methods. While the stone inscription in Suzhou remains original without any change, we are not sure to which extent the star map in the Xin yixiang fayao maintains its original form, because the text underwent frequent reimpressions.

This study was originally motivated from the discussion of the obliquity of the ecliptic, e, in the work of Needham (1959) and his collaborators, and the article, “An 8-th Century Meridian Line,” by Beer et al. (1961). A search in the historical records yields values of e in addition to the published values in the literatures.

In this paper, I would like to discuss some topics about the Vedāṅga astronomy, which is a kind of ancient Indian astronomy.

The Vedāṅga (limb of the Veda) is a class of works regarded as auxiliary to the Veda. It consists of six divisions, one of which is astronomy (jyotiŢa).

Although the methods of plane trigonometry became the cornerstone of classical Indian mathematical astronomy, the corresponding techniques for exact solution of triangles on the sphere’s surface seem never to have been independently developed within this tradition. Numerous rules nevertheless appear in Sanskrit texts for finding the great-circle arcs representing various astronomical quantities; these were presumably derived not by spherics per se but from plane triangles inside the sphere or from analemmatic projections, and were supplemented by approximate formulas assuming small spherical triangles to be plane.

All 13 Shang dynasty oracle bone eclipse records have been uniquely matched to 6 solar and 7 lunar eclipses in the 14-12th centuries B.C. The King Zhong Kang 5th year autumnal (Oct. 16, 1876 B.C.) and King Yu 3rd year “double sunset” (Sept. 24, 1912 B.C.) eclipses confirm the accuracy of the revised Bamboo Annals Xia dynasty chronology (Nivision and Pang, Early China 15, 1990, 87). The eclipse dates are plotted against the number of generations before 841 B.C. (earliest accurate date), the respective kings ruled. The curve of benefit has both the strengths of verified royal genealogy – continuity – and eclipse dating – accuracy. It is 99% accurate, and can be confidently used as a foundation for building a detailed absolute chronology for the Xia, Shang and Zhou dynasties, an important project in China’s new 5-Year Plan (Song, Sci. Tech. Daily, May 17, 1996; Newsweek, July 7, 1997).

In November of 1730 the Portuguese astronomer Pedro da Silva arrived in Jayasiṃha’s court bearing, among other books, a copy of the second edition of Philippe de La Hire’s Tabulae Astro-nomicae, published in Paris in 1727. The choice of this text as the representative of contemporary European astronomy being sent to the Maharaja was apparently due to the fact that de La Hire, finding fault with the Rudolphine Tables, whose alleged errors he attributes to Kepler’s hypotheses, claims: Quamobrem id statui Tabulas meas nulli hypothesi, sed observationibus tantummodò superstruere, nulla cuius vis Systematis habita ratione. This abjuring of adhesion to an “heretical” astronomy must have pleased the Jesuits who chose the book. This aspect of the Tabulae Astronomicae (though in fact de La Hire does adhere to an astronomical hypothesis, the heliocentric) appealed also to Jospeh Dubois, who wrote at the beginning of the Jayapura copy on September 1732: Tabulae Astronomicae in quibus Solis, Lunae, reliquorum planetarum motus ex ipsis observationibus nulla adhibita hypotesi traduntur. This same propaganda explains the title, Drkpaksasâranï, given to the adaption of the Tabulae Astronomicae written in Sanskrit verse by Kevalarama, Jayasimha’s jyotisarãja, in or after 1733 when the new city of Jayapura, to which he refers, began to be occupied, and the astonishing fact that Kevalrarãma nowhere in this work mentions the heliocentric theory though the computations that he prescribes are based upon it.

The Period from 1858 to 1947 is known as the British Period of Indian History. After the fall of Mughal empire, when the first war of independence against British colonisers failed in 1857, and the East India Company’s Government was transferred to the British Crown in 1858. However only in 1910, a Department of Education was established by the (British) Govt, of India and in the following decades modern universities were established in various important Indian towns, wherein Western / European type education and training with English as medium of instruction were imparted. However more than a century before, Indian scholar’s came into contact with the scholars – administrators of East India Company, either through employment or social interaction. Thereby, Indians became acquainted with the scientific (also technological) advances in Europe. A few of them visited England and other European countries, Portugal, Prance etc. already in the last quarter of 18th century, in order to experience and to learn firsthand the European sciences.