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.     

On the feasibility of correlation tracking at moderate resolution

The SOUP experiment demonstrated that photospheric surface flows can be measured by correlation tracking of white-light intensity features at high resolution (November et al., 1987). In order to assess the feasibility of this technique with observations made at lower resolution, we have applied it to the same SOUP data artificially degraded, but still free of seeing distortion. Comparison with the velocity structures inferred from the original data shows generally good agreement when the resolution is better than about 2. The radial outflow from a sunspot penumbra, however, can only be seen with resolution of better than 1. With resolution of worse than 2, the inferred velocity fields rapidly lose coherence, while resolution of better than 1 yields little improvement. We conclude that apertures as small as 10–14 cm on a space-based platform will be useful for the measurement of large-scale horizontal motions.     

3D: The new MPE near-infrared field imaging spectrometer

3D, the next-generation near-IR spectrometer developed at the MPE, produces in a single integration, a datacube of a 8×8 field characterised by 0.5 resolution in image space and a resolving power of R=1000 over the entire K-band in wavelength space.A detailed account of this work, including results of the first test measurements, will be presented elsewhere (Weitzel et al., in preparation).     

The large-scale pattern formed by the spatial distribution of granules

The spatial distribution of granule sizes at the surface of the sun is investigated. Granules have been separated into two classes: those larger than 1.37 and those smaller, where 1.37 is the critical scale defined by Roudier and Muller (1986). It is found that granules are not distributed at random: large granules appear to be clustered, forming a cellular pattern with a characteristic scale of 7; small granules form a similar and complementary pattern. These patterns are probably related to the mesogranulation.     

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.     

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.     

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.     

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.     

Theorie des planetes inferieures

Resumé La construction de théories planétaires a été entreprise au Bureau des Longitudes pour l'ensemble du système solaire. Il s'agit de théories semi-analytiques à variations séculaires ce qui signifie que les termes à longues périodes (périodes des périhélies et des noeuds comprises entre 50 000 ans et 2 000 000 d'années) ont été développés par rapport au temps. Ce sont donc des théories du type de celles de Le Verrier ou de Newcomb.Les théories de Le Verrier et de Newcomb ont une précision interne d'environ 0,1 pour les planètes inférieures. La théorie de Le Verrier-Gaillot a une précision interne de quelques secondes pour les grosses planètes. Mais les constantes d'intégration de, ces théories, la dégradation des éléments moyens due à l'imprécision des termes séculaires calculés font que la précision réelle est comprise entre quelques 0,1 et plusieurs secondes. La précision de la théorie du soleil de Newcomb, par exemple, est de l'ordre de 0,8.Les objectifs que nous nous sommes fixés sont d'atteindre en précision; pour les planètes inférieures 0,001 sur plusieurs siècles; pour les grosses planètes 0,01 sur un siècle, 0,1 sur 1000 ans.Cela implique de déterminer les perturbations au moins jusqu'a l'ordre 3 des masses pour les planètes inférieures et jusqu'à l'ordre 6 pour les grosses planètes.

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Theory of the inner planets

In the contruction of planetary theories for the whole of the solar system undertaken at the Bureau des Longitudes, the aim is to obtain the precision of: for the inner planets 0.001 over several centuries; for the outer planets 0.01 over one century, 0.1 over 1000 years. To get these precisions one must compute the perturbations at least to the 3rd order of the masses for the inner planets and to the 6th order of the masses for the outer planets.We have used an iterative method which has given the perturbations up to the 6th order of the masses for the outer planets and a method working order after order with respect to the masses. Through the latter, we have built the perturbations up to the 3rd order with respect to the masses for all the planets.In the mean longitudes the precision now obtained is of 0.0005 for Mercury, 0.0030 for Venus and the Earth and 0.0047 for Mars.For Mercury, the obtained precision is about 130 meters. One has therefore to introduce besides the advance of the perihelium due to relativity, the periodic relativistic corrections, whose amplitude is over 3000 meters for that planet.We have completed our theory of the Earth-Moon barycenter by the relativistic effects, as well as by the perturbations due to the Moon. As a whole, our solution is about 100 times better than that of Newcomb. Our solution for the variablesq andp of the Earth shows that the equinox is moved by a periodic motion of 0.04 amplitude and with a period of 883 year-a thing not considered generally.the precision of our solution for the mean longitude of Mars is 0.0047, which means a real progress over the theory of Clemence. We have indeed noticed many arguments missing in that theory we last mentioned. For the years to come we intend to replace to theories of Le Verrier by these solutions in the ephemerides published by the Bureau des Longitudes. Beforehand we are going to improve the constants of integration by a comparison to numerical integrations or directly to observation.

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Proceedings of the Conference on Analytical Methods and Ephemerides: Theory and Observations of the Moon and Planets. Facultés universitaires Notre Dame de la Paix, Namur, Belgium, 28–31 July, 1980.     

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.     

CH3CN J = 8 − 7 and CS J = 3 − 2 emission in orion KL

The data of the line series CH₃CN 8(K) – 7(K) K = 0 – 7 and line CS J = 3 – 2 were taken simultaneously. At beam size of 16 the emissions of CH₃CN and CS have a common center position located near IRc2 with deviations -8 and 5. The observed data show that in Orion KL core the integrated intensities of the two species have double peaks separated by a space of 14. The 2-dimension Gaussian fitting plots (FWHM) are ellipses ofD _maj = 26 andD _min = 22 for CH₃CN 8(K) – 7(K) K = 3 – 6 andD_maj = 39 D_min = 31 for CS J = 3 – 2 at a distance about 450 pc. Towards the multiple line emission region of CH₃CN 8(K) – 7(K) K = 3 – 6, using a simplified very large velocity gradient model to solve the statistical equilibrium and radiative transfer equations, we find to fit the observed results, the optimum physical parameters and kinetic temperatureT _k 120 K, densityn(H _a) 1.2 × 10⁵ cm^–3, velocity gradientV _gr 92 km s^–1 pc^–1 and the local abundance of CH₃CNF _ab 3 × 10^–8. However towards the region of single line emission of CS J = 3 – 2 we have to use LTE and the optical thin approximation on the assumption ofT _k= 120 K to obtain the lower limits of column density and then, an averaged abundance of CS of 6 × 10^–8.     

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.     

Fine-scan velocity and magnetic-field measurements in solar active regions

Fine scan (5 × 5 aperture) simultaneous Doppler and magnetograms have been obtained over solar active regions near the central meridian passage. Besides the mainly horizontal Evershed motion in sunspots, there appears a conspicuous descending motion over all active regions. A comparison of H-filtergrams with the fine scan magnetograms shows that dark filaments generally lie along the neutral longitudinal magnetic zone, while the H-fibrils lie along the field lines, joining regions of opposite polarity.     

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.     

The physical librations of the moon,including higher harmonic effects

The equations of the physical libration of the Moon are developed using a representation of the Earth-Moon orbit as a Kepler ellipse referred to the lunar equator and expanding the lunar potential in terms of these Kepler elements. TheImproved Lunar Ephemeris is used to calculate solar perturbations, and a linear integration of all effects arising from lunar gravitational harmonics through the fourth degree performed. Aside from unobservable constant offsets of the principal axes, the main effects of the higher harmonics on longitude are: 10 six-yearly (argument), 1.2 three-yearly, 0.5 annual, and 0.1 monthly; on pole direction they are on the order of 0.5 six-yearly and 1.0 monthly. The higher harmonics must hence be taken into account in analyzing ranging data of 10 cm accuracy.Paper dedicated to Prof. Harold C. Urey on the occasion of his 80th birthday on 29 April 1973.     

High-resolution spectral observation during the impulsive phase of a flare

High-resolution observations of the flare on October 21, 1989 were made with the Domeless Solar Telescope of the Hida Observatory. The following new results have been obtained: (a) during the impulsive phase of the flare, the spectral line asymmetry has spatial fine structures of 1–2; (b) for several points in the flare region the line profile alternatively changes between blue asymmetry and red asymmetry within a few seconds. A possible explanation has been suggested.     

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)     

Polarization properties of spherical interstellar grains on light scattering

On the basis of the Mie theory, the differential cross-section for polarization and the polarization efficiency are calculated for some spherical interstellar grains consisting of ice, silicate, or graphite in the ultraviolet, optical, and near infrared wavelengths. As far as the polarization due to scattering is concerned, these particles scatter light as Rayleigh scattering for 0<x1, wherex is the dimensionless size parameter. The polarization efficienties depend strongly on the value of the imaginary part (m) of the refractive index of grain material whenx1: the efficiency takes a maximum value atx1 and decreases to zero asx approaches zero for the absorbing sphere such as the dielectric particle withm0.1 or the graphite grain in the infrared wavelengths.     

Compact,variable sources on the Sun at 2 centimeter wavelength

Very Large Array (VLA) observations of compact transient sources on the Sun at 2 cm wavelength are presented. These sources have angular sizes of 5–25, brightness temperatures of T _B 1–3 × 10⁵ K, and lifetimes ranging between a few minutes to several hours. The emission originates in regions of diffuse plage and quiet Sun, where the photospheric magnetic fields are relatively weak (H 100 G). In some cases the 2 cm radiation may be explained as the thermal bremsstrahlung of a dense (N _e 10¹⁰ cm^-3) plasma in the transition region. For other sources, the relatively high circular polarization ( _c 40–50 %) suggests a nonthermal emission mechanism, such as the gyrosynchrotron radiation of mildly relativistic electron with a power-law spectrum.     

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.