Discussion following the presentation by F. Deubner

1977 ◽  
Vol 36 ◽  
pp. 69-74
Keyword(s):  
List Type ◽  
The Sun ◽  
Type Number ◽  
Harmonic Motion ◽  
Locally Excited ◽  
Long Period ◽  
Coherent Wave ◽  
Short Period ◽  
Global Modes

The discussion was separated into 3 different topics according to the separation made by the reviewer between the different periods of waves observed in the sun :1) global modes (long period oscillations) with predominantly radial harmonic motion.2) modes with large coherent - wave systems but not necessarily global excitation (300 s oscillation).3) locally excited - short period waves.

scholarly journals The Evolution of Comet Orbits

1976 ◽  
Vol 25 (Part1) ◽  
pp. 445-464 ◽  
Author(s):  
Edgar Everhart
Keyword(s):  
Solar System ◽  
Body Problem ◽  
List Type ◽  
Type Number ◽  
Distant Source ◽  
Origin And Evolution ◽  
Long Period ◽  
Jacobi Integral ◽  
Short Period ◽  
Stellar Perturbations

AbstractThis review states and defends seven conclusions on the origin of comets and the evolution of their orbits:1.There is a N-½ law of survival of comets against ejection on hyperbolic orbits, where N is the number of perihelion passages.2.The short-period comets are not created by single close encounters of near-parabolic comets with Jupiter.3.Observable long-period comets do not evolve into observable short-period comets.4.Unobservable long-period comets with perihelia near Jupiter can evolve into observable short-period comets.5.Long-period comets cannot have been formed or created within the planetary region of the solar system. (This conclusion is somewhat qualified because of possible effects of stellar perturbations. )6.It is possible that some of ths short-period comets could have been formed inside the orbit of Neptune, but it is certain that others have the same distant source as the long-period comets.7.The circularly-restricted 3-body problem, and its associated Jacobi integral, are not valid approximations to use in studying origin and evolution of comets.

scholarly journals Observations of Southern Dwarf Novae

1979 ◽  
Vol 53 ◽  
pp. 497-497
Author(s):  
N. Vogt
Keyword(s):  
Orbital Period ◽  
White Dwarf ◽  
Photometric Data ◽  
Emission Lines ◽  
List Type ◽  
Type Number ◽  
Dwarf Novae ◽  
Broad Emission ◽  
Cataclysmic Binaries ◽  
Short Period

Preliminary results of spectroscopic and photometric data for five dwarf novae are presented : 1) V 436 Cen. The orbital period of 0.0669 days was determined from radial velocity variations. The RV half amplitude of the primary, K1. = 159 km/s, implies very small masses of M1 ≲ 0.20 M⊙ and M2 = 0.18 M⊙ for the binary components.2) Z Cha. Broad emission (Hβ, Hγ, Hδ) and superimposed narrow absorption lines of Hβ-HII, HeI 4471, Cal 4427 and Call K characterize the spectrum during quiescence. Apparently, the cool, optically thin outer disc is seen on the background of a hot continuum, originating from the white dwarf or the inner disc. The RV half amplitude K1 = 87 km/s results in masses of M1 = 1.10 M⊙ and M⊙ = 0.21 M⊙.3) EX Hya. The RV half amplitude K1 = 68 km/s reveals masses of M1 = 1.4 M⊙ and M2 = 0.19 M⊙ The equivalent widths of the emission lines of H, HeI 4471 and HeII 4686 vary with the phase of the recently detected 67 minute cycle (maximal EW coincides nearly with maximal continuum intensity).4) 0Y Car is an eclipsing binary with an orbital period of 0.0631 days. The eclipses show strong variations in shape and amplitude in the course of an outburst, similar as those of Z Cha. The observations seem to confirm that the location of the eruption is the central part of the disc which increases in size and luminosity.5) EK TrA shows periodic superhumps (P = 0.0645 days) during supermaximum, and therefore belongs to the SU UMa sub-group of dwarf novae which are also characterized by a quasi-periodic occurence of super-maxima. The SU UMa sub-group comprises 70% of the ultra-short period cataclysmic binaries, and at least 18% of all dwarf novae.

scholarly journals New Trends in the Discovery of Comets by Amateurs

1988 ◽  
Vol 98 ◽  
pp. 163-163 ◽  
Author(s):  
J.C. Merlin
Keyword(s):  
Strong Correlation ◽  
Considerable Proportion ◽  
The Sun ◽  
Long Period ◽  
Short Period

AbstractThe ways in which amateurs may increase their chances of discovering comets were described. Amateurs discover a considerable proportion of comets, but their contribution is greater among long-period comets. The relative proportions of short-period comets is revealing: 1 in 2 for professional astronomers, 1 in 8 for amateurs. Professional discoveries are largely a by-product of searches for asteroids: the comets have low inclinations (i < 30°) and are faint (m1 > 14). Amateurs are most successful in areas close (<60°) to the Sun. Typical apertures are 150-mm, and most comets are brighter than magnitude 10.Past results show that there is a strong correlation between number of observers and number of discoveries. Several amateurs have discovered comets at great elongations with larger telescopes (≥ 400 mm). The comets tend to be fainter (10 < m1 < 12). Several comets have been discovered with simple equipment (200- or 300-mm telephoto lenses) down to magnitude 13.Calculations of the distribution of discoverable comets show that an average of 14 comets (9 < m1 < 14) are missed per year.

scholarly journals 40. Investigation of minor meteor streams

1968 ◽  
Vol 33 ◽  
pp. 408-427 ◽  
Author(s):  
A. K. Terenteva
Keyword(s):  
Numerical Integration ◽  
Electronic Computer ◽  
Equations Of Motion ◽  
Time Interval ◽  
List Type ◽  
Type Number ◽  
Meteor Streams ◽  
Long Period ◽  
The Earth ◽  
Meteor Body

The paper consists of three sections: (1)In continuation of a previous paper by the author, on 154 minor meteor streams, elements of orbits and other data are presented for an additional 95 minor streams (most of them less active). These streams have been found both by the studies of the photographic orbits of meteor bodies known before, and from the visual radiants of faint showers.(2)The problems of a possible family of six minor meteor streams associated with the Lexell comet 1770-I, and the connection between nine other minor streams and long-period comets, are examined. The assumption is made that nearly-parabolic comets may be accompanied by meteor streams of considerable width.(3)Radiants and elements of the orbits for 30 meteor bodies of the Cyclids are described, as were established by photographic data. Perturbed motion of one such meteor body is investigated by numerical integration of differential equations of motion on the electronic computer BESM-2, using Cowell's method of quadratures and taking account of perturbations from six planets (Venus–Uranus) and of high-order terms through to the 4th order. Over the time interval studied of 45 years the orbit of the Cyclids has been stable. Perturbing action of the Earth does not lead to any substantial changes in the elements of the orbits. Even at close approaches of the order of 0–003 AU the changes in the angular elements are not greater than about 1°.

A Magneto-Hydrodynamic Study of Pre-Flare Loops

1979 ◽  
Vol 44 ◽  
pp. 233-236 ◽  
Author(s):  
S.S. Hasan
Keyword(s):  
List Type ◽  
The Sun ◽  
Type Number ◽  
Flare Loops ◽  
Hydrodynamic Study

The aim of this paper is to discuss the equilibrium and stability of a configuration which may apply to pre-flare loops on the Sun. The analysis is based on the following working scenario:a)The loops exist much prior to the flare and in equilibrium with their surroundings.b)Gradually, starting probably a few hours before the flare, the configuration acquires energy in the form of currents.c)During the period of energy build-up, the loops are MHD stable.d)The flare occurs only after there is adequate energy in the currents.

Differential Curve-of-Growth Analyses of Mn-Hg Stars

1976 ◽  
Vol 32 ◽  
pp. 521-531
Author(s):  
Keiichi Kodaira
Keyword(s):  
Chemical Composition ◽  
Effective Temperature ◽  
Narrow Range ◽  
Enrichment Factors ◽  
Surface Gravity ◽  
List Type ◽  
The Sun ◽  
Type Number ◽  
Growth Method ◽  
Growth Analyses

SummarySpectra of eleven Mn-Hg stars (α And,μ Lep, 129 Tau, 14 Hya,κCnc, 30 UMa, πBoo, ι CrB, ϕ Her, ν Her, 46 Dra) are analyzed by the curve-of-growth method. The effective temperature and the surface gravity are estimated from the |u-b|- and the β-indexes and fall into ranges O.346 ≤ θe≤0.451 and 3.4≤log g≤3.8. The microturbulence velocity is found to be in a narrow range of 2 ≲ vt≲ 4.5 km/sec. The resulting chemical composition is very similar among the eleven Mn-Hg stars and shows following characteristics:1)The abundance ratios N(C):N(Si):N(Ca):N(Fe), N(Ti):N(Cr) and N(Sr):N(Y):N(Zr) are nearly identical to those of the sun.2)The enrichment factors relative to Fe are about 10 for Ti and Cr, about 100 for P, Sc, Mn, Sr, Y, and Zr, about 105for Ga, and about 103~106(varying among stars) for Hg.

scholarly journals Flare Star Observations in the Praesepe Region

1977 ◽  
Vol 42 ◽  
pp. 120-125
Author(s):  
I. Jankovics
Keyword(s):  
Observational Data ◽  
Flare Star ◽  
Flare Activity ◽  
List Type ◽  
The Sun ◽  
Type Number ◽  
Orion Association ◽  
Order Of Magnitude ◽  
Photographic Survey ◽  
Flare Stars

In a program of systematic search for flare stars in clusters and associations we have carried out a photographic survey in the region of Praesepe. The previously obtained interesting results in the Pleiades cluster and the Orion association stimulated us to continue the work of Haro (1968) and Rosino (1966) in Praesepe. The importance of observations in this cluster is obvious if we consider the following circumstances: 1. Praesepe and Pleiades have nearly the same distance from the Sun, 160 and 125 pc, respectively.2. There exists a difference in age between the 2 clusters of at least one order of magnitude.3. The use of Schmidt telescopes allows observations in large cluster regions.A great number of observational data are desirable for comparison of flare activity in the regions of Pleiades and Praesepe.

scholarly journals Cataclysmic Binaries: Optical and Geometrical Thickness of Disks and the Visibility of the Primary Components

1992 ◽  
Vol 151 ◽  
pp. 83-90
Author(s):  
Józef. I. Smak
Keyword(s):  
Accretion Disks ◽  
White Dwarf ◽  
Vertical Direction ◽  
Central Star ◽  
List Type ◽  
Type Number ◽  
Dwarf Novae ◽  
Long Period ◽  
Cataclysmic Binaries ◽  
Inner Parts

Accretion disks in cataclysmic binaries are optically thick (in the vertical direction), except for the case of inner parts of cool disks in dwarf novae at quiescence, which are optically thin. In long period Algols disks are cool and optically thick; their atmospheres can be quite extensive.Except for inclinations close to i = 0°, disks obscure either one or both hemispheres of the central star, the obscuration being either partial or total. In particular: (a)In stationary accretion cataclysmic binaries (old novae and nova-like systems), at inclinations close to 90° the white dwarf is fully obscured; at i < 85° only its top hemisphere becomes visible.(b)In dwarf novae at quiescence, at inclinations close to 90°, the obscuration of the white dwarf is either complete (for disk radii Rd ≥ 4 × 1010 cm), or limited to its equatorial parts (for Rd ≤ 2 × 1010 cm); at i ≈ 85 – 88° the top hemisphere becomes fully visible, while the bottom hemisphere is fully obscured; at i < 85°, due to the low optical thickness of the inner disk, parts of the bottom hemisphere near the equator also become visible.(c)In long period Algols the situations is similar as under (a); in addition, depending on inclination, part of the obscuration can be due to the atmosphere of the disk.

scholarly journals 25. Orbits of photographic meteors

1968 ◽  
Vol 33 ◽  
pp. 265-279 ◽  
Author(s):  
R. E. McCrosky
Keyword(s):  
Marked Decrease ◽  
High Elevation ◽  
Similar Distribution ◽  
List Type ◽  
Long Period ◽  
Short Period ◽  
Meteorite Fall ◽  
Inappropriate Choice ◽  
Better Than ◽  
Meteor Data

New photographic observations of meteors in the brightness range −5 > Mp > −18 (?) and with a median value of M = −8·5 have yielded orbits with a precision of better than 1° in the angular elements and of about 0·05 in e and 1/a. A comparison of 100 of these fireball orbits with Super-Schmidt orbits shows: (1)A class of orbits, comprising about 25% of the faint meteors, of long period, is almost completely absent among the fireballs.(2)Small perihelion distances (q < 0·2 AU) are not found. A maximum at q ~ 0·7 AU, which also appears in the Super-Schmidt orbits of short period, corresponds to the perihelion distances of all but two of the Apollo objects.(3)The distribution of aphelia shows a marked decrease at Jupiter when compared to a similar distribution of small, faint meteor orbits. With the existing material, we cannot determine whether this represents an important evolutionary distinction between meteoroids of different mass or is simply the result of an inappropriate choice of the division between ‘large’ and ‘small’ orbits in the faint meteor data.Provisional values of the bulk density of 28 of the fireballs as determined from the photometric mass and the observed mass-area ratio indicate that these meteoroids do not differ significantly from those observed with the Super-Schmidt cameras. Evidence of gross fragmentation of these large objects at high elevation and evidence of small or negligible terminal masses suggest that the material is friable. There is no certain evidence that any appreciable fraction of fireballs is produced by high-density, cohesive material.If the above analysis is correct, we should expect an occasional (1 year−1 106 km−2?) meteorite fall of discoverable size originating from a low-density meteoroid.

scholarly journals Report to the solar physics committee on a comparison between apparent inequalities of short period in sun-spot areas and in diurnal temperature-ranges at Toronto and Kew

1884 ◽  
Vol 37 (232-234) ◽  
pp. 290-316
Keyword(s):  
Solar Physics ◽  
The State ◽  
The Sun ◽  
Diurnal Temperature ◽  
Terrestrial Magnetism ◽  
Long Period ◽  
Short Period ◽  
Temperature Ranges

1. It has been known for some time, through the researches of Sabine and others, that there is a close connexion between the Inequalities in the state of the sun’s surface as denoted by sun-spot areas and those in terrestrial magnetism as denoted by the diurnal ranges of oscillation of the declination magnet; and moreover, the observations,of Baxendell, Meldrum, and various other meteorologists have induced us to suspect that there may likewise be a connexion between solar inequalities and those in terrestrial meteorology. This latter connexion, however, assuming it to exist, is not so well established as the former—at least if we compare together Inequalities of long period. Attempts have been made to explain this by imagining that for long periods the state of the atmosphere, as regards absorption, may change in such a manner as to diminish or even cloak the effects of solar variation by increasing the absorption when the sun is strongest and diminishing the absorption when the sun is weakest.

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