The solar O i λ 7773 triplet

The reduction of observations of the O i 7773 triplet obtained at high spatial resolution (0.5) at two disk positions is described. Two sets of triplet profile data are presented at each disk position. One set represents data taken from 0.5 regions centered on the brightest granules, while the other set represents data taken from 0.5 regions centered on the cooler infalling intergranular material.     

Systematic reductions of 19th century planetary observations

Systematic reductions of nineteenth century observations to the system of the FK4 are discussed. Reductions made on a nightly basis are described and compared with the results obtained through the use of conventional tables. The series of observations made at the Paris Observatory from 1837 to 1881 was used to compare the two methods, and a combined system of 24 000 FK4, FK4 Sup and AGK 3R positions and proper motions provided the reference stars. The results show that for Uranus the mean error of a single observation in right ascension is ±1..33 when tables are used for the reductions, and ±1.12 when nightly reductions are made, while in declination the corresponding mean errors are ±0.88 and ±0.80. The observations of Neptune show an even greater difference between the two methods; the mean errors for the tabular and nightly reductions are ±1.57 and ±1.09 in right ascension and ±0.88 and ±0.75 in declination. Secular rates in the (0–C)'s of Uranus of –0.029/year in right ascension and ±0.030/year in declination are present when the observations are reduced with tables. These rates are reduced to –0.007/year and +0.015/year, respectively, when nightly reductions are made.Presented at the Symposium Star Catalogues, Positional Astronomy and Celestial Mechanics, held in honor of Paul Herget at the U.S. Naval Observatory, Washington, November 30, 1978.     

Two Offner-based IR camera optical designs

Tracing results for two designs based on the Offner reimager are given: a practical 256×256 NICMOS-3 IR/CCD I-K camera designed for use on a f/13.5 1-m telescope yielding a 154×154 field, and a hypothetical 1024×1024 pixel nextgeneration IR camera for a f/7.5 2.5-m telescope yielding a 244×244 field. Both designs produce near-diffration limited results.     

The oscillatory velocity field observed in a unipolar sunspot region

The velocity field has been mapped for 42 min in an area 80 by 85 containing a unipolar sunspot. Apparent shifts of Fe i 5233 were measured photoelectrically using a rectangular scanning aperture 1.6 × 4.0. The sunspot did not exert a marked influence on the generally random pattern of oscillations at a period of 300 s. Discrete periods of oscillation both longer and shorter than 300 s were excited within the enhanced magnetic field boundaries of this spot. Umbral oscillations at periods near 180 s were detected in agreement with independent observations of the same spot during the previous solar rotation.NRC Postdoctoral Fellow, 1969–71.     

Recent results on the solar diameter

Using optically identical telescopes at different sites, we have measured the solar diameter with a drift-scan technique. In order to investigate the cause of the observed fluctuations, we not only compare observations made simultaneously by different observers at the same telescope, but also observations made simultaneously at two different sites. Our main results are: (a) The mean error of a single drift time measurement is ±0.08s(or ± 1.1) at Izaña and ±0.11 s (or ± 1.7) at Locarno; this closely corresponds to the angular resolution at those two sites under normal seeing conditions, (b) We find no correlation between observations at different sites; a significant correlation exists, however, between observations made simultaneously by different observers at the same site: This indicates that most of the observed fluctuations are due to atmospheric effects (image motion) rather than personality effects, (c) The mean solar semi-diameter derived from a total of 1122 observations made in 1990 (472 at Izaña, 650 at Locarno) is R = (960.56 ± 0.03) (Izaña: 960.51, Locarno: 960.59); this may be compared with R = (960.32 ± 0.02) which is obtained from a re-analysis of 1773 observations made in 1981 (Izaña: 960.16, Locarno: 960.38). Although a small residual increase of the solar diameter during the last ten years seems to be indicated, we conclude that most - if not all - of the observed variations are due to variable seeing conditions, and that there is still no conclusive evidence for a genuine solar variation with amplitudes in excess of about ±0.3.     

CASPIR: A cryogenic array spectrometer imager for the MSSSO 2.3 m telescope

CASPIR is a near-infrared spectrometer/imager being built for the Mount Stromlo and Siding Spring Observatories' 2.3 m telescope. The instrument is based on a SBRC 256×256 InSb detector array and uses AR-coated Sapphire, MgO, CaF₂, and BaF₂ optics to produce two imaging focal plane scales with 0.5/pixel and 0.25/pixel. Spectral resolving powers of 500 will be achieved through a 1×128 slit with three grisms designed for the J, H, and K bands. IJ, JH, and HK cross-dispersed échelle grisms will achieve resolving powers of 1100 through a 1×15 slit. Coronograph and imaging polarimetry modes will also be available. The various observing configurations are selected via five remotely controlled wheels. The instrument design and system architecture are discussed, and preliminary detector performance figures reported.     

Morphological properties and origin of the photospheric facular granules

From time series of high resolution photographs, morphological properties of the photospheric facular granules were derived. The facular granules are cells of the common granular pattern, brighter than the normal granules when seen between cos = 0.6 and the limb. Their apparent diameter, which decreases towards the limb, is smaller than that of the normal granules: 0.65 and 1.25 respectively at cos = 0.55; their lifetime is 25 min but their bright stage lifetime is only 15 min; they are visible closer to the limb than the normal granules: 1.2 compared to 2–5; the brightening of the facular granules occurs at a faster rate than their fading. From the great similitude of both morphological properties and temperature models of facular and normal granules, it appears possible that the photospheric facular granules are convective cells modified by the presence of a magnetic field of some hundreds Gauss.     

The Hard X-ray Imaging Spectrometer (HXIS)

The HXIS, a joint instrument of the Space Research Laboratory at Utrecht, The Netherlands, and the Department of Space Research of the University of Birmingham, U.K., images the Sun in hard X-rays: Six energy bands in energy range 3.5–30 keV, spatial resolution 8 over Ø 240 and 32 over Ø 624 field of view, and time resolution of 0.5–7 s depending on the mode of operation. By means of a flare flag it alerts all the other SMM instruments when a flare sets in and informs them about the location of the X-ray emission. The experiment should yield information about the position, extension and spectrum of the hard X-ray bursts in flares, their relation to the magnetic field structure and to the quasi-thermal soft X-rays, and about the characteristics and development of type IV electron clouds above flare regions.     

Corrections to the lunisolar precession and the motion of the equinox from proper motions of Cepheids

Corrections to Newcomb's lunisolar precession and to motion of the equinox are evaluated from proper motions of 77 Cepheids, employing recently determined values of their distances. Results are diverse, depending on the weighting method. If the effect of the cosmic dispersion is neglected and ₀ is imposed to be 25 km/s/kpc, thenp ₁=1.1±0.2 and +e = 1.0 ± 0.1 per century in the FK4 system.Presented at IAU Colloquium No. 9, The IAU System of Astronomical Constants, Heidelberg, Germany, August 12–14, 1970.     

VLA and Trieste observations of type I storms,type IV and pulsations

A prime objective of this experiment was to determine whether type I or IV sources at 333 MHz contain features of small (arc sec) scale. With the VLA, our resolution was better than 4. However, we never observed any structure of size smaller than about 30, with the typical source sizes being between about 40 and 90.Many observations were simultaneous with the Trieste Astronomical Observatory records at 327 MHz. The observations were made on two days in November 1988. On 8 November the observations were of a type I storm about two hours after a major flare. On 14 November they were mostly of the main phase of a type IV event, including pulsations of a kind rarely seen, strongly circularly polarized, and having a well-defined period of about 12 s. The size of the pulsating source was about 40 by 60, and the brightness temperature was about 10⁹ K. We compare these pulsations with those observed earlier.     

Location of type I radio continuum and bursts on Yohkoh soft X-ray maps

A solar type I noise storm was observed on 30 July, 1992 with the radio spectrometer Phoenix of ETH Zürich, the Very Large Array (VLA) and the soft X-ray (SXR) telescope on board theYohkoh satellite. The spectrogram was used to identify the type I noise storm. In the VLA images at 333 MHz a fully left circular polarized (100% LCP) continuum source and several highly polarized (70% to 100% LCP) burst sources have been located. The continuum and the bursts are spatially separated by about 100 and apparently lie on different loops as outlined by the SXR. Continuum and bursts are separated in the perpendicular direction to the magnetic field configuration. Between the periods of strong burst activities, burst-like emissions are also superimposed on the continuum source. There is no obvious correlation between the flux density of the continuum and the bursts. The burst sources have no systematic motion, whereas the the continuum source shows a small drift of 0.2 min^–1 along the X-ray loop in the long-time evolution. The VLA maps at higher frequency (1446 MHz) show no source corresponding to the type I event. The soft X-ray emission measure and temperature were calculated. The type I continuum source is located (in projection) in a region with enhanced SXR emission, a loop having a mean density of n _e = (1.5 ± 0.4) × 10⁹ cm^–3 and a temperature ofT = (2.1 ± 0.1) × 10⁶ K. The centroid positions of the left and right circularly polarized components of the burst sources are separated by 15–50 and seem to be on different loops. These observations contradict the predictions of existing type I theories.Presented at the CESRA-Workshop on Coronal Magnetic Energy Release at Caputh near Potsdam in May 1994.     

A deeply embedded companion to LKHα198

The region around the Herbig Ae/Be star LkH198 was imaged at 10m with the CAMIRAS camera at the Canada-France-Hawaii Telescope and the Nordic Optical Telescope. We discovered a deeply embedded companion 6 north of LkH198, which may be responsible for most of the far-infrared emission in the region and for driving the molecular flow. LkH198 appears point-like at our resolution (FWHM 1.3), excluding an extended envelope of transiently heated small grains as the dominant origin of the mid-infrared excess in that star.     

The solar minimum temperature determined by the CO (A 1Π-X 1Σ)

The synthetic Voigt profile of the following transitions (v=0,v=0), (v=0,v=1), (v=1,v=1), (v=1,v=0) have been computed for different concentrations and temperatures of CO and compaed to the measured intensities of the UV sunspot spectrum by a high resolution spectrograph. From this comparison the solar minimum temperature has been determined.     

Sub-arcsec 10 μm imaging of β pictoris and other star disk candidates

We have used the ESO 10 m camera, TIMMI, to image with a very high angular resolution (PFoV: 0.3; FWHM:0.9) several main-sequence star disk candidates. Information on the -Pictoris dust disk has been obtained in a region largely inaccessible to previous observations: 0–80 AU, with a resolution of about 5 AU after deconvolution. Another promising target for 10 m imaging, 51 Ophiuchi, appears point-like.based on data collected at the European Southern Observatory (ESO), La Silla, Chile     

The Tokyo PMC catalog 85

The catalog of positions of 1007 stars (792 FK4 and FK4S stars, 57 OB stars, 49 NPZT stars, and 109 SAO stars) is presented. They were observed during the period from December 1984 to September 1985 with the Tokyo Photoelectric Meridian Circle (Tokyo PMC). The positions in the catalog are referred to the equinox and equator of J2000, and are based on the FK4 system. The internal errors of a single observation were estimated to be ( cos, )=(0.16, 0.19), whereas the mean internal errors of the catalog positions were (0.08, 0.08) for FK4 stars and (0.09, 0.11) for FK4S stars. A comparison of the positions of the FK4 stars in the present catalog with those of the FK4 catalog shows significant differences cos and in some declination zones. Some of those differences are commonly found in other recent catalogs. Thus they may be considered to be real systematic errors in the FK4 system. Neither significant magnitude nor color equations exist in the Tokyo PMC 85 catalog.     

Radial pulsation of less-massive yellow supergiants

The conclusions of the present paper broadly are: (a) The galactic concentration of doubles by comparing the distributions in galactic latitudes 0°<20° and >40° is nearly twice as large as the galactic concentration of stars in general. (b) The astrographic catalogues are not complete in the fainter magnitudes. (c) The large value of the ratioT:O _k (observed to optical number of pairs) from Kreiken's formula shows that almost all stars in the group 0<d5 and quite a few in the other two groups, viz., 5<d10 and 10<d15 might be shown true binaries. Consequently, Aitken's working definition of a true binary should be extended if it were to include all true binaries. (d) The doubles are probably stars of Population I. (e) The logarithm to the base 10 of the cumulative counts can be represented by an empirical relationA+B(m–1.5)+C(m–1.5)².Communication presented at the International Conference on Astrometric Binaries, held on 13–15 June, 1984, at the Remeis-Sternwarte Bamberg, Germany, to commemorate the 200th anniversary of the birth of Friedrich Wilhelm Bessel (1784–1846)     

Global astrometry by space techniques

The European Space Agency project of an astrometric satellite-HIPPARCOS-is shortly described. It will measure the angles between stars situated in fields separated by about 70°. The precision of the elementary measurements is expected to be of the order of 0.005. A similar accuracy is found to apply to the basic reduction giving the abcissae of stars referred to great circles on the sky. The final overall reduction should yield accuracies better than 0.002 in position and parallaxes and 0.002 per year in proper motions.The main features of the final catalogue are described and some possible consequences for fundamental astronomy are given.Presented at the Symposium Star Catalogues, Positional Astronomy and Celestial Mechanics, held in honor of Paul Herget at the U.S. Naval Observatory, Washington, November 30, 1978.     

On the size of the structure elements in the solar chromosphere

Photometric reductions of the spectrograms obtained during the third flight of the Soviet Stratopsheric Solar Station are discussed. A comparison of photometric scans in H and its far wings near to the continuum leads to the conclusion that chromospheric mottles are at least several times broader than photospheric granules. The optimum size of mottles is about 0.8–1.1. The H profiles of mottles are practically the same as those obtained from the ground observations. The broadening of mottles is considered as an effect of expansion of magnetic arcs growing up to chromospheric levels.     

Dependence of the correlation of small scale photospheric structures upon resolution

Correlations between continuum intensity, velocity, and equivalent widths of two Mn i lines as observed with two different entrance apertures tend to deteriorate with improvement in spatial resolution. The KPNO multichannel magnetograph was used to make area scans at the center of the disk with entrance apertures 3.5×2.5 arc and 1×1 arc. A coherence analysis shows that this effect is caused by marked differences of fluctuations in temperature and temperature gradients as well as in the velocity structure of photospheric elements of various sizes.     

The jump of the second derivative of the Moon's elongation

We present some results of new calculations ofD(t)-the second derivative of the Moon's elongation as a function of time. The paper contains an explanation of the well-known R. Newton's effecthe rapid decline inD(t) from about 700 yr to about 1300 yr. The new graph ofD is based on the revised dates of the ancient eclipses and has a qualitatively different character; in particular, the decline inD(t) vanishes completely andD(t) oscillates at a roughly constant value, which coincides with the modern one. This fact agrees with the independent chronological results in the author's [7] paper.