Some requirements of a colliding comet source of gamma ray bursts

Colliding comets in the Solar System may be an important source of gamma ray bursts. The spherical gamma ray comet cloud required by the results of the Venera Satellites (Mazets and Golenetskii, 1987) and the BATSE detector on the Compton Satellite (Meeganet al., 1992a, b) is neither the Oort Cloud nor the Kuiper Belt. To satisfy observations ofN(>P _max) vsP _max for the maximum gamma ray fluxes,P _max > 10^–5 erg cm^–2 s^–1 (about 30 bursts yr^–1), the comet density,n, should increase asn a ¹ from about 40 to 100 AU wherea is the comet heliocentric distance. The turnover above 100 AU requiresn a ^–1/2 to 200 AU to fit the Venera results andn a ^1/4 to 400 AU to fit the BATSE data. Then the masses of comets in the 3 regions are from: 40–100 AU, about 9 earth masses,m _E; 100–200 AU about 25m _E; and 100–400 AU, about 900m _E. The flux of 10^–5 erg cm^–2 s^–1 corresponds to a luminosity at 100 AU of 3 × 10²⁶ erg s^–1. Two colliding spherical comets at a distance of 100 AU, each with nucleus of radiusR of 5 km, density of 0.5 g cm^–3 and Keplerian velocity 3 km s^–1 have a combined kinetic energy of 3 × 10²⁸ erg, a factor of about 100 greater than required by the burst maximum fluxes that last for one second. Betatron acceleration in the compressed magnetic fields between the colliding comets could accelerate electrons to energies sufficient to produce the observed high energy gamma rays. Many of the additional observed features of gamma ray bursts can be explained by the solar comet collision source.     

Flare-associated high-speed solar plasma streams

Characteristics of flare-associated high-speed solar plasma streams are investigated using measurements from space probes and Earth-orbiting spacecraft for the period 1964–1982. The maximum observed velocity (V _m) of these streams range from 400 to 850 km s^–1} with peak probability for 600 km s^–1}. These remain for the period of 1–10 days with the peak occurrence 3 days. The difference between the pre-stream velocity (V ₀) and the maximum velocity (V _m) of any high-speed stream serves as the measure of its intensity. For about 60% of the flare associated streams, (V _m-V ₀) is well in excess of 200 km s^–1} and in some cases becomes as large as 450 km s^–1}. The yearly percentage occurrence, total duration and the product of mean (V _m - V ₀) with total duration of the high-speed streams during the year correlates well with solar activity, e.g., maximum during high solar activity period and minimum during low solar activity. The study suggests that presence of sunspots plays a significant role in the generation of flare associated high-speed solar streams.     

Spectroscopic observations of delta orionis

The H profile in the spectrum of Orionis shows phase-dependent changes, with a period of variation equal to the orbital period fo the binary system. The profile shape changes from a normal absorption profile at zero phase to a P Cygni-type at a later phase, to an absorption profile having emission at the centre of the profile, to a normal absorption profile at the end of the period. The spectra have been obtained at the Cassegrain focus of Kavalur Observatory telescopes (50 and 100 cm) at 17.2 Å mm^–1 reciprocal dispersion and resolution 0.3 Å at 6562.817 Å. Assuming that the P Cygni profile is formed by a spherically-symmetrical region, the analysis gives a shell radius of 2.18 stellar radius and an electron density in the shell equal to 6.54×10^–9 cm^–3, with the observed expansion velocity of 50 km/s^–1, a mass loss of 1.3×10^–7 M per year.An analysis has been carried on the radial velocity data of earlier observers and the present radial velocity data. It is found that the orbital elements change. The presence of apsidal motion is confirmed by the increasing value of . The radial velocity of the centre of mass, , shows periodic variation. These observations confirm the presence of a third body. The values ofK (mean amplitude),P (period),a sini, and mass functionf(m), indicate a regular decrease, thereby confirming the mass transfer/mass loss from the system.     

Velocity structure of the shallow lunar crust

The data from the Apollo-14 and Apollo-16 Active Seismic Experiments have been reanalyzed and show that a power-law velocity variation with depth,v(z)110z ^1/6 m s^–1 (0<z<10 m), is consistent with both the travel times and amplitudes of the first arrivals for source-to-geophone separations up to 32 m. The data were improved by removing spurious glitches, by filtering and stacking. While this improved the signal-to-noise ratios, it was not possible to measure the arrival times or amplitudes of the first arrivals beyond 32 m. The data quality precludes a definitive distinction between the power-law velocity variation and the layered-velocity model proposed previously. However, the physical evidence that the shallow lunar regolith is made up of fine particles adds weight to the 1/6-power velocity model because this is the variation predicted theoretically for self-compacting spheres.The 1/6-power law predicts the travel time,t(x), varies with separation,x, ast(x)=t ₀(x/x ₀)^5/6 and, using a first-order theory, the amplitude,A(x), varies asA(x)=A ₀(x/x ₀)^{–(13–m)/12},m>1; the layervelocity model predictst(x)=t ₀(x/x ₀) andA(x)=A ₀(x/x ₀)^–2, respectively. The measured exponents for the arrival times were between 0.63 and 0.84 while those for the amplitudes were between –1.5 and –2.2. The large variability in the amplitude exponent is due, in part, to the coarseness with which the amplitudes are measured (only five bits are used per amplitude measurement) and the variability in geophone sensitivity and thumper-shot strengths.A least-squares analysis was devised which uses redundancy in the amplitude data to extract the geophone sensitivities, shot strengths and amplitude exponent. The method was used on the Apollo-16 ASE data and it indicates there may be as much as 30 to 40% variation in geophone sensitivities (due to siting and coupling effects) and 15 to 20% variability in the thumper-shot strengths. However, because of the low signal-to-noise ratios in the data, there is not sufficient accuracy or redundancy in the data to allow high confidence in these results.     

Dependence of the meridional motions of sunspot groups on life spans and age of the groups,and on the phase of the solar cycle

We have analyzed data on sunspot groups compiled during 1874–1981 and investigated the following: (i) dependence of the `initial' meridional motion (v <sub>ini</sub>()) of sunspot groups on the life span () of the groups in the range 2–12 days, (ii) dependence of the meridional motion (v(t)) of sunspot groups of life spans 10–12 days on the age (t) of the spot groups, and (iii) variations in the mean meridional motion of spot groups of life span 2–12 days during the solar cycle. In each of the latitude intervals 0°–10°, 10°–20° and 20°–30°, the values of both v <sub>ini</sub>() and v(t) often differ significantly from zero. In the latitude interval 20°–30°, the forms of v <sub>ini</sub>() and v(t) are largely systematic and mutually similar in both the north and south hemispheres. The form of v(t) suggests existence of periodic variation in the solar meridional motion with period of 4 days and amplitude 10–20 m s<sup>–1</sup>. Using the anchoring depths of magnetic structures for spot groups of different and testimated earlier, (Javaraiah and Gokhale, 1997), we suggest that the forms of v <sub>ini</sub>() and v(t) may represent radial variation of meridional flow in the Sun's convection zone, rather than temporal variation of the flow. The meridional flows (v <sub>e</sub>(t)) determined from the data during the last few days (i.e., age t: 10–12 days) of spot groups of life spans of 10–12 days are found to have magnitudes (10–20 m s<sup>–1</sup>) and directions (poleward) similar to the those of the surface meridional plasma flows determined from the Dopplergrams and magnetograms. The mean meridional velocity of sunspot groups living 2–12 days seems to vary during the solar cycle. The velocity is not significantly different from zero during the rising phase of the cycle and there is a suggestion of equatorward motion (a few m s<sup>–1</sup>at lower latitudes and 10 m s<sup>–1</sup>at higher latitudes) during the declining phase (last few years) of the cycle. The variation during the odd numbered cycles seems to anticorrelate with the variation during the even numbered cycles, suggesting existence of 22-year periodicity in the solar meridional flow. The amplitude of the anticorrelation seems to be depending on latitude and the cycle phase. In the latitude interval 20°–30° the `surface plasma meridional motion', v _e(t), is found to be poleward during maximum years (v _e(t) 20 m s^–1at 4th year) and equatorward during ending years of the cycle (v _e(t) –17 m s^–1at 10th year).     

Theorie litterale du neuvieme satellite de Saturne,Phoebe

We study a theory for the ninth satellite of Saturn, Phoebe, based on the literal solution we have obtained in the main problem of the lunar theory.These series were computed by solving, by successive approximations, the Lagrange's equations expressed in variables, functions of the elliptic elements.We may consider the case of Phoebe simpler than a lunar case because we seek less precision (1/10 geocentric) than in the Lunar case, although the eccentricity of Phoebe is stronger.Main problem: our series are computed to the complete seventh order and a great part of the perturbations of the eighth and ninth order, where we have attributed to the small lunar parameters the order 1 tom ₀=n/n ₀,e ₀,e, sin (i ₀/2), the order 2 to ₀=(a ₀/a)((M ₁–)/(M ₁+M)) and the order 4 toµ ₀(a ₀/a)M ₁ M/M ₁ ² –M ².In the case of Phoebe,µ ₀ equal zero and ±₀ is the ratioa ₀/a.We study the further development of these series by using, instead of parameterm ₀, the quantity m ₀=n/n ₀–m ₁ wherem ₁ is an approached value ofm ₀, in order to accelerate the convergence of the series with respect tom ₀.Comparison with a numerical integration we are adjusting a numerical integration to the observations. We have already more than 100 observations, for the period 1900–1957.At first, we compare the series of the main problem to a numerical integration of the Keplerian problem.

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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.     

On the relative roles of unipolar and mixed-polarity fields

Away from plages, solar magnetic fields may be classified as unipolar or as of mixed polarity, though the distinction is strictly arbitrary. The dividing line used here is 0.4 ¦B _minor/B _major¦ 1, where average fields of major and minor polarities are measured over large areas. Some of their statistical properties and cyclical variations are detailed. In unipolar regions, 3 B _major 50 G, B _minor 0.1 B _major, and ¦B¦ 1.1 B _major. In regions of mixed polarity, 3.5 ¦B¦ 10 G.Below latitudes of ± 60°, mixed polarities predominate for about 5 yr around sunspot minimum. For several years around sunspot maximum, unipolar fields fill the 20°–40° zone completely, and occupy about 75% of the 0°–20° and 40°–60° zones.The polar unipolar fields are weak on the whole (Bmajor 4 G for 6 typical days in 1976–79), with small regions having stronger fields at times, probably not exceeding B _major = 10 G. Again B _minor 0.1 B _major. There is no direct way at present of measuring properties of polar mixed fields, such as may occur around sunspot maximum, but by inference ¦B¦ 2 to 5 G.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.     

The creation of magnetic monopoles in outer gaps of pulsars

The production of magnetic monopoles-antimonopoles pairs is expected in the interactions of highly energetic particles in the outer gaps of a pulsar. We estimate upper limit for production of monopoles withm _g 10⁴ GeV _c ^–2 ine ⁺ e ^– interactions of the order _ee 10^–32 cm^–2.     

Additional measurements of the high-latitude sunspot rotation rate

We report measurements of the sunspot rotation rate at high sunspot latitutdes for the years 1966–1968. Ten spots at ¦latitude¦ 28 deg were found in our Mees Solar Observatory H patrol records for this period that are suitable for such a study. On the average we find a sidereal rotation rate of 13.70 ± 0.07 deg day^-1 at 31.05 ± 0.01 deg. This result is essentially the same as that obtained by Tang (1980) for the succeeding solar cycle, and significantly larger than Newton and Nunn's (1951) results for the 1934–1944 cycle. Taken together, the full set of measurements in this latitude regime yield a rotation rate in excellent agreement with the result =14^°.37₇–2^°.77 sin², derived by Newton and Nunn from recurrent spots predominatly at lower latitudes throughout the six cycles from 1878–1944.Summer Research Assistant.     

Coronal Mass Ejection of 15 May 2001: I. Evolution of Morphological Features of the Eruption

We study the initiation and development of the limb coronal mass ejection (CME) of 15 May 2001, utilizing observations from Mauna Loa Solar Observatory (MLSO), the Solar and Heliospheric Observatory (SOHO), and Yohkoh. The pre-eruption images in various spectral channels show a quiescent prominence imbedded in the coronal void, being overlaid by the coronal arch. After the onset of rapid acceleration, this three-element structure preserved its integrity and appeared in the MLSO MK-IV coronagraph field of view as the three-part CME structure (the frontal rim, the cavity, and the prominence) and continued its motion through the field of view of the SOHO/LASCO coronagraphs up to 30 solar radii. Such observational coverage allows us to measure the relative kinematics of the three-part structure from the very beginning up to the late phases of the eruption. The leading edge and the prominence accelerated simultaneously: the rapid acceleration of the frontal rim and the prominence started at approximately the same time, the prominence perhaps being slightly delayed (4 – 6 min). The leading edge achieved the maximum acceleration a_max 600 ± 150 m s^–2 at a heliocentric distance 2.4 –2.5 solar radii, whereas the prominence reached a_max 380± 50 m s^–2, almost simultaneously with the leading edge. Such a distinct synchronization of different parts of the CME provides clear evidence that the entire magnetic arcade, including the prominence, erupts as an entity, showing a kind of self-similar expansion. The CME attained a maximum velocity of v_max 1200 km s^–1 at approximately the same time as the peak of the associated soft X-ray flare. Beyond about 10 solar radii, the leading edge of the CME started to decelerate at a–20 m s^–2, most likely due to the aerodynamic drag. The deceleration of the prominence was delayed for 10 –30 min, which is attributed to its larger inertia.     

Neutralization and stabilization of particle streams in the corona and type III radio bursts

The processes by which streams of charged particles become charge and current neutralized in the corona are investigated. It is shown that a large amplitude plasma wave, which is related to precursor phenomenon in type III bursts and possibly plasma radiation from type IV bursts, will be excited at the head of the stream. The energy extracted from the stream to produce this plasma wave is computed and used to set conservative upper limits on the densities of possible excitors for type III bursts. For electron streams the density n _s < 10^–5 n _e, where n _e is the density of the background plasma. For proton streams n _s < 1.8 × 10^–2 n _e. The energy extracted from the stream is also used to set upper limits on the lifetimes of relativistic electrons stored in the corona and it is concluded that for n _e > 10² cm^–3 this loss must be taken into account. Since electron streams cannot produce their own stabilizing ionacoustic waves because they would violate the condition n _s < 10^–5 n _e, other mechanisms for producing ion-acoustic waves in the corona are examined. Another stabilization mechanism due to velocity inhomogeneity is investigated.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

A possible interpretation of the optical spectrum for BL Lac-type objects

On the basis of Sobolev's method, the population of 30 levels of hydrogen atom is determined allowing for the radiative and collision processes of the heating and ionization of the medium with velocity gradient gradv=10^–9–10^–11s^–1, electron temperatureT _e=10⁴ K-2×10⁴ K and electron densityN _e=10¹⁰ cm^–3–10¹¹ cm^–3. The central source radiation is characterized by a power spectrum with spectral indices varying from 0 to 2. A region of possible physical conditions is found where the thermal diffuse radiation of the envelope exceeds the emission in the Balmer H line.     

Spectral classification of Be stars

In the course of observations of the LMC with the Glazar space telescope it was found that the star HD 269665 is unusually bright at 1640 A:m ₁₆₄₀ = 5 _. ^m ± 0 _. ^m 1,m ₁₆₄₀ –V = –6 _. ^m 2.     

Intergalactic suprathermal grains

The physical conditions under which suprathermal grains may loose energy and the processes involving the grains (a3×10^–6 cm) destruction are investigated. It is found that the dust grain once attaining the velocityU (10⁵ cm s^–1) may attain suprathermal energy (v _g3×10⁸ cm s^–1) and subsequently may also attain relativistic energy are almost indestructible in the accelerating phase.     

Models of the universe compatible with present observations

It is shown that cosmic radiation almost follows a Planck distribution, because just as matter is formed, its density of energy is negligible in comparison with that of radiation, and that the present age of the Universe does not depend on the particular manner in which the matter is formed.Thus, if the results of the latest observations (which imply a deceleration parameterq=1.6) are combined with the assumption that the present age of the Universe is at least 12×10⁹ yr, they lead to a hyperbolic oscillating universe with a negative cosmological constant (<–1.53×10^–56 cm^–2) and a present mass-density _m of less than 1.2×10^–30 g cm^–3. If the cosmological constant is taken to be zero, a solution is only possible if we are prepared to admit a rate of evolution of galaxies with a deceleration parameterq<0.52. Three types of oscillating universe are then possible, but the heperbolic type is the most probable. If Hubble's constant is greater than 63.4 km s^–1 Mpc^–1, the solutions are only hyperbolic universes with <+0.45×10^–56 cm^–2 and _m <4.8×10^-30g cm^-3.

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Sommaire On montre que le rayonnement cosmique général suit pratiquement une loi de Planck parce que la densité d'énergie de la matière au moment de sa formation est négligeable à côté de celle du rayonnement et que l'âge actuel de l'Univers ne dépend pas du mode de formation de la matière.Dans ces conditions, si l'on combine les derniers résultats d'observations (qui impliquent un paramètre de décélérationq=1.6) avec l'hypothèse que l'âge actuel de l'Univers est au moins de 12×10⁹ années on est conduit à un Univers hyperbolique oscillant à constante cosmologique négative (<–1.53×10^–56 cm^–2) et où l'actuelle densité de matière _m est moindre que 1.2×10^–30 g cm^–3. Si la constante cosmologique est supposée nulle, une solution ne peut être obtenue que si l'on admet un certain taux d'évolution des Galaxies et un paramètre de décélérationq<0.52. Alors, les trois types d'Univers oscillants sont possibles, mains les Univers hyperboliques paraissent plus probables. Enfin, si la constante de Hubble est plus grande que 63.4 km s^–1 Mpc^–1 les solutions ne peuvent être que des Univers hyperboliques avec <+0.45×10^–56 cm^–2 et _m <4.8×10^-30g cm^-3.

     

V792 Her=HD 155638: A totally eclipsing RS CVn binary

Photometry of HD 155638=V792 Her has been analyzed to determine the elements of this totally eclipsing RS CVn binary. The light variation outside eclipse was found to have a period of 27^d.07±0^d.07, which is slightly different from the 27^d.5384±0^d.0045 orbital period. Analysis of the eclipses was achieved by a modification of the Russell-Merrill technique. With the aid of radial velocity measures, absolute elements were obtained for the hot and cool stars, respectively;R _h=2.58R ,R _c=12.28R ,M _h=1.40M ,M _c=1.46M ,i=80^o.61 and velocity semi-amplitudesK _c=48.36 km s^–1±0.79 km s^–1, andK _h=50.50 km s^–1±0.33 km s^–1. The apparent magnitudes areV _h=9 ^m .73 andV _c=8 ^m .48. The distance to HD 155638 was estimated to be 310 parsecs.     

The photospheric velocity field of Procyon

BUSS observations of the profiles of two well observed spectral lines in the ultraviolet spectrum of CMi (Procyon; F5 IV–V) are analysed with a Fourier transform method in order to determine values of various parameters of the velocity field of the upper photosphere. We find a microturbulent line-of-sight velocity componentL = 0.9 ± 0.4 km s^–1, a macroturbulent velocity componentL _M = 5.3 ± 0.2 km s^–1, and a rotational velocity componentv _R sini=10.0±1.2 km s^–1. In these calculations a single-moded sinusoidal isotropic macroturbulent velocity function was assumed. The result appears to be sensitive to the assumed shape of the macroturbulence function: for an assumed Gaussian shape the observations can be described withv _R sini=4 km s^–1 andL _M = 11.6 ± 2.7 km s^–1. A comparison is made with other results and theoretical predictions.     

A quantitative analysis of the prototype [WCL] star CPD-56° 8032

We present a detailed, quantitative study of the standard [WC10] Wolf-Rayet central star CPD-56^o 8032 based on new high resolution AAT UCLES observations and the Hillier (1990) WR standard model. Our analysis of CPD-56^o 8032 gives the wind properties (T _*=34500K, lg (L/L )=3.8, lg (M/M a^–1)=–5.4,v =225 km s^–1) and chemistry (C/He=0.5, O/He=0.1, by number), the latter suggesting an intimate relationship with the Ovi PN central stars and the PG 1159-035 objects. A comparison between the wind properties of CPD-56^o 8032 and Sk-66^o 40 (WN 10) indicates that low excitation, low wind velocity WR winds are common to both low mass PN central stars (WC sequence) and high mass post-LBV's (WN sequence).     

Das ProduktAR 0 und Weitere Galaktische Parameter

According to the tangential method the productAR ₀ is determined with 145.7 km s^–1 from measurements of the line profiles of the 21-cm line of the neutral hydrogen by Weaver and Williams (1973). The recent individual measurements of Oort's constantA and of the distanceR ₀ of the Sun from the galactic centre yields 138.5 km s^–1. The mean value 142.1 kms^–1 leads toA=14.56 km s^–1 kpc^–1 andR ₀=9.76 kpc. At the galactocentric distanceR nearR ₀ the angular velocity is represented by (R)=25.84–2.98 (R–9.76)+0.075 (R–9.76)². The mass of the Galaxy amounts to 1-92×10¹¹ .

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Herrn Kollegen Prof. Dr W. Gleisberg zum 70. Geburtstag am 26.12.1973 gewidmet.

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Mitteilungen Serie A.     

Statistical survey of planetary nebulae: Distances,masses, and distribution in the galaxy

On the basis of empirical (D)-dependency at the frequency of 5 GHz constructed using 15 planetary nebulae with the independently measured distances (10^–171×10^–20 W m^–2 Hz^–1 ster^–1), we evaluated distances of 335 objects. Independent evidence of the correctness of the accepted scale are given. Then(D)-dependency is constructed and it is shown that atD<0.08 pc the mean electron density is higher than the one determined by the Seaton method. We showed that the filling factor diminishes with the increase of the PN diameter (1 atD0.08 pc and 0.2 atD0.4 pc). the ionized mass of 33 PNs is determined. With the diameter increase the ionized mass grows and atD0.4 pc reaches the valueM0.07M . We used the new distance scale when investigating the space distribution of PNs. The mean scale height =130±15 pc and the mean gradient of the change of surface densitym=0.37, which allowed us to estimate the total number of nebulae in the GalaxyN4×10⁴. We divided the PNs according to their velocities (withV _LSR>35 km s^–1 andV _LSR<35 km s^–1) and permitted us to confirm that the PN belong to different sub-systems of the Galaxy. The estimated local formation rate of PNs [=(4.6±2.2)×10^–12 pc^–3 yr^–1] is a little higher than the one of the white dwarfs. That can be explained by a large number of PNs having binary cores, which used in our sample. The statistical estimation of PN expansion velocity showed thatV _ex increases from 5–7 km s^–1 (atD0.03 pc) to 40–50 km s^–1 (atD0.8 pc).