Discrepant measurements of the radial velocities of SS cygni: solution to the problem

We show that the discrepancies among the various measurements of the radial velocity curve of the K5 V star in the dwarf nova SS Cyg have been caused by (1) poor choices of lines for measuring its velocity and (2) large distortions in its velocity caused by heating from the white dwarf and its accretion disk. The correctK velocity of the center of mass of the K5 V star is 158±3km s ^–1.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Development, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986.     

A study of non-thermal radio emission features using fine spectral BAO and high-sensitivity RATAN observations of a solar active region

Based on spectral observations of active region NOAA 8545 on 19 May 1999, we describe the processes responsible for non-thermal long-lasting radio emission and for narrow-band non-drifting bursts observed at the same time. Non-thermal long-lasting radio emission consisted of two components: short-duration (1–2 s) microbursts with fluxes about 0.001 s.f.u. and continuum emission with growing spectrum in the range of 1000–2000 MHz. Energetic electrons continuously existed in the active region for more than 2.2 hours. The nature and parameters of microbursts were discussed by Bogod, Mercier, and Yasnov (2001). Here we consider the continuum source nature. It is shown that the model, taking into account the cyclotron loss-cone instability of hot electrons and the generation of plasma waves at the upper hybrid frequency, may explain the observed continuum source parameters. For the narrow-band non-drifting bursts we consider two models: the first taking into account an excitation of weak shock waves across the magnetic field and the second with an excitation of the upper hybrid waves under the double plasma resonance. Continuum source parameters are close to the last model. Our estimations for the magnetic field strength are as follows: H=120–126 G, which is valid for the region where the electron density of background plasmas n=(1.4–1.9) ×10⁹ cm^–3; H=180–190 G for the region where n=(3.0–4.3) ×10⁹ cm^–3; H=290 G for the region where n _e=2.5×10¹⁰ cm^–3; and H=350 G for the region where n _e=3.5×10¹⁰ cm^–3. The speed of the fast electrons is about 0.10–0.14 c.     

Identification of some diffuse interstellar features

Twenty-eight of the thirty-nine diffuse interstellar bands identified by Herbig (1975) are shown to constitute three vibronic systems with origins at 14 321, 15 153, and 15 343 cm^–1 (vac). Structure within these three systems arises from the excitation of vibrational modes withv ₁=275 cm^–1,v ₂=445.5 cm^–1, andv ₃=793 cm^–1. The electronic origins at 14 321 and 15 343 cm^–1 correspond to narrow lines observed in the spectrum of Cr³⁺ ions at cubic sites in MgO solids while the 15 153 cm^–1 origin arises in Mn⁴⁺ : MgO. Hence, many of the diffuse bands in the visible likely are due to small MgO particles containing these ions. This observation is compatible with recent experimental data showing broad bands at 160 nm and 220 nm from finely divided MgO solids that match features in the interstellar extinction curve.     

A window on the plasma universe: the very large array

For nearly two decades, the aperature synthesis telescope known as the Very Large Array (VLA) has been providing a wealth of data on all types of astronomical objects. This telescope fills the need for more powerful and more sensitive instruments to gather data on a vast range of plasma phenomena in astrophysical settings. Currently the VLA is capable of observing at eight radio frequency bands (four corresponding to important spectral lines) with sensitivities on the order of 10^–29 Wm ^–2 Hz ^–1, or 10^–3 Jansky (1 mJy), and noise levels ten times lower. This paper describes the VLA and its capabilities, and describes how researchers interested in plasma astrophysics can use the instrument.     

Solar neutrino measurement with the radiochemical gallium detector (GALLEX)

The GALLEX experiment for the detection of solar neutrinos by means of a radiochemical gallium detector is operated by groups from Italy, France, Germany, Israel and the USA in the Gran Sasso underground laboratory (LNGS) near L'Aquila (Italy). It consists of (i) the technical scale tank made of glass fiber reinforced polyester fabric containing 101 tonnes (54 m³) of a highly concentrated (8 moll^–1) GaCl₃ solution; (ii) a gas sparging system for desorption of GeCl₄ which has been formed by interaction of the neutrinos with gallium according to⁷¹Ga + _e ⁷¹Ge + e^– and by addition of ca. 1 mg of a stable Ge isotope; (iii) the absorption columns for concentration of GeCl₄ into a volume of 1 l of water; (iv) the laboratory scale apparatus for conversion of GeCl₄ to GeH₄ and mixing with the counting gas Xe; (v) the counter filling station, and (vi) the low level proportional counters.Contributions of possible side reactions which have to be corrected for, e.g. by cosmic muons, fast neutrons and-emitters are discussed, as well as the purification of the target solution from long-lived (t _1/2 = 271 d) cosmogenic⁶⁸Ge. A first preliminary result after one year of solar neutrino measurement is presented. This constitutes the first direct measurement of the basic proton-proton fusion reaction in the core of the sun. This result, appreciably below the predictions of the standard solar model (SSM) (132 SNU) can be interpreted, together with the results of the chlorine and KAMIOKANDE experiments either by astrophysics or by neutrino oscillations (MSW effect). The solar neutrino measurements are continuing and a calibration experiment with a⁵¹Cr source is in preparation.Presented at the 2nd UN/ESA Workshop, held in Bogotá, Colombia, 9–13 November, 1992.for the GALLEX Collaboration: P. Anselmann, W. Hampel, G. Heusser, J. Kiko, T. Kirsten, E. Pernicka, R. Plaga, U. Ronn, M. Sann, C. Schlosser, R. Wink, M. Wojcik (Max Planck Institut fur Kernphysik, Heidelberg); R. v. Ammon, K.H. Ebert, T. Fritsch, K. Hellriegel, E. Henrich, L. Stieglitz, F. Weirich (Kernforschungszentrum Karlsruhe, Institut für Heisse Chemie); M. Balata, E. Bellotti, N. Ferrari, H. Lalla, T. Stolarczyk (INFN-Laboratori Nazionali del Gran Sasso); C. Cattadori, O. Cremonesi, E. Fiorini, S. Pezzoni, L. Zanotti (Universita di Milano und INFN); F. von Feilitzsch, R. Mößbauer, U. Schanda (TU München, Garching); G. Berthomieu, E. Schatzman (Observatoire Nizza); I. Carmi, I. Dostrovsky (Weizman Institut, Rehovot); C. Bacci, P. Belli, R. Bernabei, S. d'Angelo, L. Paoluzi (Universita di Roma und INFN); S. Carbit,M. Cribier, G. Dupont, L. Gosset, J. Rich, M. Spiro, C. Tao, D. Vignaud (CEN Saclay); R.L. Hahn, F.X. Hartmann, J.K. Rowley, R.W. Stoenner, J. Weneser (Brookhaven National Laboratory).     

71 GHz (4.2 mm) solar radio bursts in the period July 1967 to December 1969

The results of 2 1/2 years (July 1967 – December 1969) monitoring of solar radio bursts at 71 GHz ( = 4.2 mm) at the Radio and Space Research Station, Slough are presented. During this period only seven events were positively identified as 71 GHz bursts. One of these events (6 July, 1968) is among the largest solar bursts ever recorded anywhere in the microwave-millimetre wave band (47000 × 10^–22Wm^–2Hz^–1), and the associated magnetic field may possibly have exceeded 7200 G. Another event (27 March, 1969) has demonstrated that bursts at 71 GHz can be both intense (4700 × 10^–22Wm^–2Hz^–1) and complex. On other occasions, the absence of any detectable event at 71 GHz helps to define the high frequency spectrum of the burst, this being an important factor in determining the initial energy distribution of the electrons ejected by the associated flare. On one such occasion (21 March, 1969) the derived energy distribution index is 8, in contrast with the more usual values of 2–4.1969–1970 NCR-OAR Senior Post-Doctoral Research Associate at Air Force Cambridge Research Laboratories, L. G. Hanscom Field, Bedford, Mass., U.S.A.     

On the accelerations of the Moon and Sun,the constant of gravitation,and the origin of mountains

In a previous paper Lyttleton (1976) has shown that the apparent secular accelerations of the Sun and Moon, as given by de Sitter, can be largely explained if the Earth is contracting at the rate required by the phase-change hypothesis for the nature of the core. More reliable values for these accelerations have since become available which warrant a redetermination of the various effects concerned on the basis of constantG, and this is first carried out in the present paper. The lunar tidal couple, which is the same whetherG is changing or not, is found to be (4.74±0.38)×10²³ cgs, about three-quarters that yielded by the de Sitter values, while within the theory the Moon would take correspondingly longer to reach close proximity to the Earth at about 1.5×10⁹ years ago.The more accurate values of the accelerations enable examination to be made of the effects that a decreasingG would have, and it is shown that a valueG/G=–3×10^–11 yr^–1 can be weakly satisfied compared with the close agreement found on the basis of constantG, while a value as large numerically asG/G=–6×10^–11 yr^–1 seems to be definitely ruled out. On the iron-core model, an intrinsic positive component of acceleration of the angular velocity cannot be reconciled at all with the secular accelerations even for constantG, and far less so ifG is decreasing at a rate suggested by any recent cosmological theory.ItG=0, the amount of contraction available for mountain-building would correspond to a reduction of surface area of about 49×10⁶ km² and a volume to be redistributed of 160×10⁹ km³ if the time of collapse were 2.5×10⁹ years ago. For earlier times, the values are only slightly reduced. IfG/G=–3×10^–11 yr^–1, the corresponding values are 44×10⁶ km² and 138×10⁹ km³ for collapse at –2.5×10⁹ yr, and not importantly smaller at 38×10⁶ km² and 122×10⁹ km³ for collapse at –4.5×10⁹ yr. Any of these values would suffice to account in order of magnitude for all the eras of mountain-building. An intense brief period of mountain-building on an immense scale would result from the Ramsey-collapse at whatever time past it may have occurred.     

Global Oscillations at Low Frequency from the SOHO mission (GOLF)

The GOLF experiment on the SOHO mission aims to study the internal structure of the sun by measuring the spectrum of global oscillations in the frequency range 10^–7 to 10^–2 Hz. Bothp andg mode oscillations will be investigated, with the emphasis on the low order long period waves which penetrate the solar core. The instrument employs an extension to space of the proven ground-based technique for measuring the mean line-of-sight velocity of the viewed solar surface. By avoiding the atmospheric disturbances experienced from the ground, and choosing a non-eclipsing orbit, GOLF aims to improve the instrumental sensitivity limit by an order of magnitude to 1 mm s^–1 over 20 days for frequencies higher than 2.10^–4 Hz. A sodium vapour resonance cell is used in a longitudinal magnetic field to sample the two wings of the solar absorption line. The addition of a small modulating field component enables the slope of the wings to be measured. This provides not only an internal calibration of the instrument sensitivity, but also offers a further possibility to recognise, and correct for, the solar background signal produced by the effects of solar magnetically active regions. The use of an additional rotating polariser enables measurement of the mean solar line-of-sight magnetic field, as a secondary objective.     

Motion of Dust Structures in the Circumnuclear Region of Comet Hale–Bopp and Rotation of the Cometary Nucleus

The motion of dust structures in the circumnuclear region of comet Hale–Bopp is studied. About 270 envelope images were obtained with the AZT-8 reflector (D = 0.7 m, F = 28 m) and the Filin-3 image intensifier. We carried out our observations at the observational station of the Astronomical Observatory of Shevchenko Kiev State University in the village of Lesniki (near Kiev). The recording from the image-intensifier screen was made on Foto-100 film during 23 nights from March 24 to May 10, 1997. The circumnuclear region was imaged both in white light (without filters) and with IHW CO⁺ (_ef = 426 nm), C₃ (_ef = 496 nm), C₂ (_ef = 514 nm), and RC (red continuum, _ef = 684 nm) narrow-band interference filters. Based on our measurements of the radial expansion of dust structures, we determined the velocities, 0.61–1.99 km s^–1; accelerations, from –18.3 × 10^–3 to 4.0 × 10^–3 m s^–2; and rotation period of the cometary nucleus, 111.41^h ± 0.05^h.     

The optical spectrum of nova LW Serpentis 1978

We present optical spectroscopic data on the nova LW Serpentis 1978, covering its diffuse-enhanced phase until the onset of [OI] flash. The spectra cover a range of 4000–8700 A, at dispersions ranging from 83–675 A mm^–1.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986.     

X-ray observation of the Jovian impacts of comet Shoemaker - Levy 9

An ASCA observation of the Jovian impact of the comet Shoemaker-Levy 9 is reported. Four impacts of H, L, Q1 and R were observed and four impacts of B, C, G, and Q2 were observed within 60 minutes after their impacts. No significant flaring of X-ray emission was observed. Upper limit X-ray fluxes of 90 % confidence level, averaged 5 minutes just after the impacts, were 2.4 × 10^–13 erg sec^–1 cm^–2, 3.5 × 10^–13 erg sec^–1 cm^–2, 1.6 × 10^–13 erg sec^–1 cm^–2 and 2.9 × 10^–13 erg sec^–1 cm^–2 for the impacts of H, L, Q1 and R, respectively, in the 0.5(0.7 for H and Q1)–10 keV energy range. However, a hint of X-ray enhancement around Jupiter from July 17 to July 19 was detected with about 2 6 × 10^–14 erg sec^–1 cm^–2 in the 0.5–10 keV energy range.     

Radio emission of the NGC 1499 nebula at decametric wavelengths

Observations of the ionized hydrogen region NGC 1499 have been carried out with the radio telescope UTR-2 at frequencies 12.6, 14.7, 16.7, 20 and 25 MHz. The half-power resolution of the instrument to zenith is 28×34 at 25 MHz. The average volume density of the non-thermal radio emission between the Sun and the nebula (1.75×10^–40 W m^–3 Hz^–1 ster^–1 at 25 MHz), the electron temperature of the HII nebula (T _e =4400 K), the measure of emission (ME=1500 cm^–6 pc) and other parameters have been obtained. Maps of brightness distribution over the source are presented for each observation frequency. The results are compared with previously obtained data.     

Some Characteristics of the Circumstellar Shells of Stars with Variability of the R Coronae Borealis Type

The transformation of the line and molecular spectra of R CrB from absorption to emission at the 1985 minimum is traced from spectroscopic observations, and it is concluded for the first time, from a comparison with light curves and color indices, that the rapid variation of the color index U – B by –0^m.6 during fading is due exclusively to this transformation. The transformation of the spectrum can result in an increase in the star's brightness in the UBV photometric bands by about 1^m.4, 0^m.75, and up to 0^m.75, respectively. This removes one of the main objections to using the concept of a homogeneous spherical shell to interpret the R Coronae Borealis phenomenon. High-resolution spectroscopic observations of SV Sge, a star with variability of the R Coronae Borealis type, showed the presence of an intense circumstellar component in Na I D lines with a violet shift corresponding to 240 km/sec, which is unrelated to visible brightness minima. It is suggested that a stream of matter with such a velocity through the star's vicinity is the cause of the excitation not only of the broad emission features observed during brightness minima upon fading of the photospheric emission but also of the narrow ones. Assuming that a brightness minimum is associated with the temporary formation of another spherical screening shell, some characteristics of the permanent shell are determined. Its optical depth and geometrical thickness are 0.2-0.7 and at least 0.4 of its radius, respectively.     

Theoretical emission line ratios for Si XIII compared to solar observations

The electron collision excitation rates recently calculated for transitions in Si xiii by Keenan et al. (1987) are used to derive the electron temperature sensitive ratio G(=(f + i)/r and the density sensitive ratio R(=f/i), where i, f, and r are the intercombination (1s ^{2 1} S – 1s2p ³ P _{1, 2}) forbidden (1s ^{2 1} S – 1s2s ³ S), and resonance (1s ^{2 1} S – 1s2p ¹ P), transitions respectively. Also estimated are the values of R in the low-density limit (R ₀) as a function of electron temperature. The theoretical G ratio at the temperature of maximum emissivity for Si xiii, G(T _m) = 0.70, is in much better agreement with the observed G for the 1985, May 5 flare determined by McKenzie et al. (G = 0.60 ± 0.07) than is the earlier calculation of Pradhan, who derived G(T _m) = 0.85. The error in the observed R ₀ ratio is so large that both our result and Pradhan's fall within the acceptable limits of uncertainty and hence one cannot estimate which of the two is the more accurate.     

The size of antimatter bodies and the primary very high energy cosmic ray flux

The consequences of antimatter bodies on the very high energy primary cosmic ray flux are considered. The effects of various models of cosmic ray origin and properties of astrophysical parameters are discussed. A simple expression for the production of antiprotons inN–N collisions as a function of energy of the incident proton is obtained by utilizing characteristics of particles produced in high energy collisions. It is assumed that sufficient time will have elapsed for all antibaryons to decay to antiprotons. It is shown that the measurement of antinuclei in the primary cosmic ray spectrum above 10¹⁷ eV could help to establish the size of antimatter bodies.This research was supported by A.F.O.S.R. Grant No. F-44620-69-C-0019.     

The frequency of novae in the Galaxy

Recent statistics indicate that each year an average of 3.5 novae or nova-like objects are discovered in the Galaxy. With reasonable assumptions about the completeness of the surveys, we arrive at an overall galactic production rate of 76±38 y^–1. When recurrent novae are omitted, this rate drops to 60±30 y^–1. Hence, it seems that our Galaxy is more prolific than M31 in nova production. The total amount of material released into galactic space by novae each year is about one-tenth that ejected by supernovae.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986.     

The effect of upwelling on the distribution and stable isotope composition of Globigerina bulloides and Globigerinoides ruber (planktic foraminifera) in modern surface waters of the NW Arabian Sea

Hydrographic changes in the NW Arabian Sea are mainly controlled by the monsoon system. This results in a strong seasonal and vertical gradient in surface water properties, such as temperature, nutrients, carbonate chemistry and the isotopic composition of dissolved inorganic carbon (δ¹³C_DIC). Living specimens of the planktic foraminifer species Globigerina bulloides and Globigerinoides ruber, were collected using depth stratified plankton tows during the SW monsoon upwelling period in August 1992 and the NE monsoon non-upwelling period in March 1993. We compare their distribution and the stable isotope composition to the seawater properties of the two contrasting monsoon seasons. The oxygen isotope composition of the shells (δ¹⁸O_shell) and vertical shell concentration profiles indicate that the depth habitat for both species is shallower during upwelling (SW monsoon period) than during non-upwelling (NE monsoon period). The calcification temperatures suggest that most of the calcite is precipitated at a depth level just below the deep chlorophyll maximum (DCM), however above the main thermocline. Consequently, the average calcification temperature of G. ruber and G. bulloides is lower than the sea surface temperature by 1.7±0.8 and 1.3±0.9 °C, respectively. The carbon isotope composition of the shells (δ¹³C_shell) of both species differs from the in situ δ¹³C_DIC found at the calcification depths of the specimens. The observed offset between the δ¹³C_shell and the ambient δ¹³C_DIC results from (1) metabolic/ontogenetic effects, (2) the carbonate chemistry of the seawater and, for symbiotic G. ruber, (3) the possible effect of symbionts or symbiont activity. Ontogenetic effects produce size trends in Δδ¹³C_shell–DIC and Δδ¹⁸O_shell–w: large shells of G. bulloides (250–355μm) are 0.33‰ (δ¹³C) and 0.23‰ (δ¹⁸O) higher compared to smaller ones (150–250 μm). For G. ruber, this is 0.39‰ (δ¹³C) and 0.17‰ (δ¹⁸O). Our field study shows that the δ¹³C_shell decreases as a result of lower δ¹³C_DIC values in upwelled waters, while the effects of the carbonate system and/or temperature act in an opposite direction and increase the δ¹³C_shell as a result lower [CO₃²⁻] (or pH) values and/or lower temperature. The Δδ¹³C_shell–DIC [CO₃²⁻] slopes from our field data are close to those reported literature from laboratory culture experiments. Since seawater carbonate chemistry affects the δ¹³C_shell in an opposite sense, and often with a larger magnitude, than the change related to productivity (i.e. δ¹³C_DIC), higher δ¹³C_shell values may be expected during periods of upwelling.     

Advances in gamma-ray burst astronomy

Work at Goddard is preséntly being carried out in three major areas of gamma-ray burst research: (1) A pair of simultaneously operating 0.8-m² burst detectors were successfully balloon-borne at locations 800 miles apart on 9 May, 1975, each to atmospheric depths of 3 to 4 g cm^–2, for a 20-h period of coincident data coverage. This experiment investigates the size spectrum of bursts in the 10^–7 to 10^–6 erg cm^–2 size region where dozens of events per day are expected on a –1.5 index integral power-law extrapolation. Considerable separation in latitude was used to avoid possible atmospheric and auroral secondary effects. Its results are not yet available. This experiment is the sequel to a single balloon flight in May 1974, in which candidate events were found to fit the –1.5 spectral extrapolation, indicating the need for positive event identification. (2) A deep-space burst detector, the first spacecraft instrument built specifically for gamma-ray burst studies, was recently successfully integrated into the Helios-B space probe. Its use at distances of up to 2 AU will make possible the first high-resolution directional study of gamma-ray burst source locations. Similar modifications to several other space vehicles are also being prepared. (3) Our gamma-ray instrument on the IMP-7 satellite is presently the most sensitive burst detector still operating in orbit. Its results have shown that all measured event-average energy spectra are consistent with being alike. Using this characteristic spectrum to select IMP-7 candidate events of smaller size than those detected using other spacecraft in coincidence, a size spectrum is constructed which fits the –1.5 index power law down to 2.5×10^–5 erg cm^–2 per event, at an occurrence rate of about once per month.Paper presented at the COSPAR Symposium on Fast Transients in X-and Gamma-Rays, held at Varna, Bulgaria, 29–31 May, 1975.     

Simulation of the Ion Modification Processes in the Silicate Dust of Protoplanetary Disks

The modification of crystalline olivine under irradiation with 1.43-MeV deuterons was studied experimentally. For the first time, the partial destruction of olivine in the surface (100–200 nm) layer was found at a current density of 5–10 A/cm². This effect is caused by ionization and desorption of Mg and Fe atoms at deuteron fluences (3–8 × 10¹⁶cm^–2) which are substantially below the amorphization threshold. It was suggested that the negative charge of the anion group SiO₄ ^4–is neutralized by the interaction with the deuterium ions and Frenkel pairs. The mechanism of sputtering of the crystalline olivine surfaces under irradiation with H, D, He, and Ar ions was studied using of the TRIM 98 program.     

The spectrum of nova vulpeculae 1984 No2 at nebular phase

Nova Vul 1984 n^o2 has been again observed at Observatoire de Haute-Provence in the autumn of 1985, i.e. 270–295 days after maximum. It was then in the nebular phase. The spectra cover the blue-violet and the near infrared regions. Over 50 lines and blends have been identified and are given in Table 2. No clear pattern is observed in the emission bands of a width of about 1450 km/sec. The most conspicuous features observed are the forbidden NeIII and NeV lines. The infrared region is dominated by a very strong He I 1083nm emission.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986.