Potential energy curves and dissociation energies of NbO,SiC, CP,PH+, SiF+, and NH+

The potential energy curves for the electronic ground states of astrophysically important NbO, SiC, CP, PH⁺, SiF⁺, and NH⁺ molecules are constructed by the RKRV method. The dissociation energies are determined by curve-fitting techniques using the five-parameter Hulburt-Hirschfelder function. The estimated dissociation energies are 7.86±0.16, 3.66±0.09, 5.12±0.12, 3.08±0.09, 6.46±0.14, and 3.02±0.09 eV for NbO, SiC, CP, PH⁺, SiF⁺, and NH⁺, respectively. The estimatedD ₀ values are in reasonably good agreement with literature values. If we utilizeD ₀ values of PH⁺, SiF⁺, and NH⁺, ionization potentials for PH, SiF, and NH are derived. The ionization potentials are 10.12, 7.13, and 13.66 eV, respectively, for PH, SiF, and NH. Dissociation energies for the above molecules are also estimated by use of the Birge-Sponer extrapolation and Hildenbrand and Murad methods.     

Astrophysical Molecules AlD and CaH: Transition Probabilities and Dissociation Energy

The Franck-Condon (FC) factors and r-centroids for the bands systemC ¹ Σ ⁺ → X ¹ Σ ⁺ of AlD and E ² Π → X ² Σ ⁺ of CaH have been evaluated by means of a reliable numerical integration procedure by using a suitable potential. The dissociation energy, D _e, for the electronic ground states of AlD and CaH have been estimated by the curve fitting method to the RKRV experimental potential curve turning out to be 3.01 eV and 2.32 eV, respectively. This revised version was published online in July 2006 with corrections to the Cover Date.     

A comparison of the energy spectra of cosmic ray helium and heavy nuclei

Recent observations of the spectra of cosmic ray helium, M, LH and VH nuclei in the energy range from 200 MeV/nuc to>22 GeV/nuc are reported. The differential spectra of all of these groups of nuclei are found to have a maximum at 300–400 MeV/nuc at sunspot minimum. The average exponents on the integral rigidity spectra in the range 5 to 50 GV are 1.54±0.03 for He nuclei, 1.50±0.04 for M nuclei, 1.47±0.06 for LH nuclei and 1.40±0.08 for VH nuclei. The spectra of these groups of nuclei are compared and it is found that the average He/M, He/LH and He/VH ratios are 16±1, 70±3 and 200±15 respectively. These values are reasonably constant from the highest down to the lowest energies measured although some evidence for a dip is present in the 500–1000 MeV/nuc range for both the He/LH and He/VH ratios. Solar modulation effects on these ratios are discussed and it is concluded that the ratios measured at earth are representative of those existing in interstellar space only if energy loss processes in interplanetary space are unimportant. The influence of interstellar propagation on the spectra and charge ratios at low energies arising from ionization energy loss and nuclear spallation during matter traversal is examined. It is found that propagation models that contain a large number of relatively short path lengths significantly modify the expected effects of ionization energy loss at low energies. Specifically it is suggested that the presently measured charge ratios are consistent with the passage of the average cosmic radiation through enough matter to reproduce the abundances of the so-called fragmentation nuclei, Li, Be, B and He³. Two component models are not required to explain our data. Rather we feel that a better representation of the situation results from considering a continuous spatial distribution of sources which, along with the actual interstellar propagation conditions, leads to a particular distribution of matter path lengths. It is pointed out that large differences exist in the approaches used in the literature to calculate the effects of matter traversal in interstellar space at low energies. These differences play an important role in the interpretation of the experimental results. Significant modifications of the charge ratios at low energies can also be obtained by requiring that some of the matter traversal occur in the cosmic ray sources themselves during the cosmic ray acceleration process. This may be sufficient to produce charge ratios that are essentially flat at low energies even in the presence of interstellar ionization loss.     

Estimation of potential energy curves, dissociation energies, franck-condon factors and r-centroids of comet interesting molecules

The experimental potential energy curves for the different electronic states of molecules like CN, CO and CS observed in comets are constructed by using the Rydberg-Klein-Rees method as modified by Vanderslice et al. The ground state dissociation energies are determined by curve fitting technique using the five parameter Hulburt-Hirschfelder (H-H)function. The estimated dissociation energies are 7.63 ± 0.187, 10.95 ±0.224 and 7.27 ± 0.152 eV for CN, CO and CS respectively. These values are in good agreement with the literature values. Estimated dissociation energies of CN, CO and CS are used in the relation given by Gaydon and ionization potentials are evaluated for CO and CS molecules. The estimated ionization potentials are 13.92and 12.15 eV for CO and CS molecules respectively. The r-centroids and Franck-Condon factors (FC Factors) for the band system of a ³Π_r – X¹Σ⁺ (a – X) and A¹Π – X ¹Σ⁺ (A -X) of CN, A ²Π_i – X²Σ⁺ (A – X) and B²Σ⁺-X²Σ⁺ (B – X) of CO and a ³Π_r – X¹Σ⁺ (a – X) of CS molecules have been calculated employing an approximate analytical methods of Jarmain and Fraser and Nicholls and Jarmain. The absence of the bands in these systems are explained. This revised version was published online in July 2006 with corrections to the Cover Date.     

Studies of some diatomic molecules in the F- and early G-type dwarf stars

A critical analysis of CH, NH, OH, C₂, and CN molecules/radicals has been made in twenty-four F- and early G-type dwarfs at different effective temperature as well as in new constructed model atmosphere. Molecular indices of bandheads ofA-X system of CH, NH, OH, C₂, and CN have been obtained by using the data available in the literature (thirteen-colour and eight-colour photometry).Besides, some interesting plots of the molecular indices vs _eff, molecular abundances and molecular indices vs dissociation energy, reduced equivalent widths and FCF's vs dissociation energy for respective molecules have also been enumerated. It is found that the molecular indices at bandheads ofA-X system of CH, NH, OH, C₂, and CN are approximately constant (5810–6570 K). It is to be noted that the molecular indices decrease in the order OH, NH, CH, C₂, and CN at a given temperature.The dissociation equilibrium of CH, NH, OH, C₂, and CN is considered at 5810, 6570, and 7160 K phases in model atmosphere. At standard scale of abundance the molecular abundance and molecular index decrease in the order OH, NH, CH, C₂, and CN at any given phase, however, CN abundance and index increase (_eff=0.867-0.767). The amplitude of abundance and index variation decrease in the order NH, OH, CH, C₂, and CN (_eff=0.767-0.704).The reduced equivalent width decrease in the order OH, NH, CH, and C₂ and FCF's decrease in the order CH, OH, NH, CN, and C₂.The confrontation of models and observations of spectra of F- and early G-type dwarfs of parent molecules is of primary importance to investigate the physical conditions within atmospheres. Reliable excitation models are also requisite for interpreting spectroscopic observations of parent molecules and deriving molecular abundances.     

Bond dissociation energies and bond orders for some astrophysical molecules

The bond dissociation energies for astrophysically important diatomic molecules have been estimated based on the derived relation D_AB = D_AB + 32.058 Δ_χ where D_AB = (D_AA D_BB)1/2, Δ_χ represents Pauling electronegativity difference χ_A – χ_B) Based on the formula suggested by Reddyet al., bond orders are estimated. The ambiguity arising from Parr & Borkman relation is discussed. The present study supports the view of Politzer thatq/(0.5r _e)² is the correct definition of bond order. The estimated bond energies are in reasonably good agreement with the values in the literature. The bond energies estimated with the relation we suggested, for the molecules in the present study, give an error of 8.0 per cent. The corresponding error associated with Pauling’s equation is 26.8 per cent.     

Cross-sections for the (4He, 3H) stripping reaction on Fe,Al, C and glass targets at an energy of 120 MeV

Fe, Al, C and Glass targets have been irradiated with 120 MeV helium ions. The cross sections for the stripping reaction (⁴He, ³H) on these target nuclei have been determined, with nuclear emulsions, as 85 ± 30, 65 ± 20, 38 ± 15 and 41 ± 15 mb, respectively.     

Solar photo rates for planetary atmospheres and atmospheric pollutants

Unattenuated solar photo rate coefficients and excess energies for dissociation, ionization, and dissociative ionization are presented for atomic and molecular species that have been identified or are suspected to exist in the atmospheres of planets, satellites (moons), comets, or as pollutants in the Earth atmosphere. The branching ratios and cross sections with resonances have been tabulated to the greatest detail possible and the rate coefficients and excess energies have been calculated from them on a grid of small wavelength bins for the quiet and the active Sun at 1 AU heliocentric distance.     

Lightcurves and poles of seven asteroids

The Asteroids 5 Astraea, 19 Fortuna, 51 Nemausa, 68 Leto, 138 Tolosa, 196 Philomela and 409 Aspasia have been studied using Strömgren photometry observations made in 1997. Simultaneous lightcurves in the uvby Strömgren filters of synodic periods of 0.70004±0.00020, 0.31013±0.00003, 0.32400±0.00020, 0.61910±0.00100, 0.42087±0.00009, 0.34750±0.00020 and 0.37576±0.00060 days, and amplitudes, in the y filter, of 0.^m16±0.^m05, 0.^m30±0.^m02, 0.^m15±0.^m04, 0.^m29±0.^m02, 0.^m43±0.^m03, 0.^m30±0.^m04 and 0.^m15±0.^m06 have been found for 5 Astraea, 19 Fortuna, 51 Nemausa, 68 Leto, 138 Tolosa, 196 Philomela and 409 Aspasia, respectively. Additional observations of 138 Tolosa and 196 Philomela during February 2000, show lightcurve amplitudes equal or greater than 0.^m15 for 138 Tolosa and of 0.^m45 for 196 Philomela in 2000 opposition.Solutions for the sense of rotation, sidereal period, pole orientation and shape properties have been proposed for the first time for 138 Tolosa and improved solutions have been obtained for 5 Astraea, 19 Fortuna, 51 Nemausa, 196 Philomela and 409 Aspasia.     

Distribution of gravitational potential energy within the solar system

The orbital gravitational potential energies of the planets and of the satellites have been estimated and compared to the gravitational potential energies of the bodies themselves and to the gravitational potential energy of the Sun. From the point of view of the gravitational potential energy distribution two quite different groups of the planets can be distinguished clearly. However, the gravitational potential energy of the systems is mainly concentrated within the central bodies, only about 10^–5 in orbiting bodies.     

Measurements of radio emission from the compact source in the Crab nebula with the uran-1 interferometer at 16.7, 20 and 25 MHz

This paper presents the results of measurements of the Crab nebula in the decametre range with an interferometer whose baseline is 2.4–3.5×10³ of the wavelength. Visibility function values, which in these observations determine the contribution by the compact source to the total nebula flux, have been measured at frequencies 16.7, 20 and 25 MHz to be 0.64±0.07, 0.43±0.04 and 0.31±0.03, respectively. The spectral index of the spectrum obtained for the compact source in the range 16.7–122 MHz is 2.09±0.04. Flattening of the nebula spectrum without the compact source has been confirmed for the decametre range.     

VLA observations of Jupiter’s synchrotron radiation at 15 and 22 GHz

We observed Jupiter’s synchrotron radiation at frequencies of 15 and 22 GHz using the VLA (Very Large Array) in its most compact configuration (D-array) in March 1991. The spatial brightness distribution of the emission at these high frequencies appears to be very similar to that seen at lower frequencies (5 GHz down to 330 MHz). We measured a total nonthermal flux density at 15 and 22 GHz of 1.5 ± 0.15 Jy and 1.5 ± 0.4 Jy, respectively (both normalized to a geocentric distance of 4.04 AU). These numbers agree well with model spectra of Jupiter’s synchrotron radiation that were obtained by fitting the planet’s nonthermal radio emission between 74 MHz and 8 GHz and suggest a maximum cutoff in electron energies at ∼100 MeV. The degree of linear polarization observed with the VLA is 21.5 ± 1.9% at 15 GHz.     

Water vapor abundance in Venus' middle atmosphere from Pioneer Venus OIR and Venera 15 FTS measurements

The Pioneer Venus Orbiter Infrared Radiometer and Venera 15 Fourier Transform Spectrometer observations of thermal emission from Venus' middle atmosphere between 10° S and 50° N have been independently re-analyzed using a common method to determine global maps of temperature, cloud optical depth, and water vapor abundance. The spectral regions observed include the strong 15 μm carbon dioxide band and the 45 μm fundamental rotational water band. The different spatial and spectral resolutions of the two instruments have necessitated the development of flexible analysis tools. New radiative transfer and retrieval models have been developed for this purpose based on correlated-k absorption tables calculated with up-to-date spectral line data. The common analysis of these two sets of observations has hence been possible for the first time. From the PV OIR observations, the cloud-top unit optical depth pressure showed a minimum of ∼110±10 mbars in the evening equatorial region and a maximum of ∼160±12 mbars in the morning mid-latitude regions. From the Venera 15 FTS spectra, the cloud-top pressure was found to increase from morning values of ∼120±10 to 200±30 mbars in the late afternoon/early evening region. The cloud-top water vapor abundances observed by the PV OIR instrument were found to fluctuate from 10±5 ppm at night up to 90±15 ppm in the equatorial cloud-top region shortly after the sub-solar point. The mean Venera 15 FTS water vapor abundances were found to be 12±5 ppm with only a slight enhancement over the equatorial latitude bands and no clear day-night distinction. The common analysis of these two sets of observations broadly validates previously published individual findings. The differences in the retrieved atmospheric state can no longer be attributed to radiative transfer modeling bias and suggest significant temporal variability in the middle atmosphere of Venus.     

Differential rotation of coronal holes

Using KPNO helium 10830 Å synoptic charts of Carrington rotations 1716 through 1739, and by assembling a time sequence representing single latitude zone, rotational properties of coronal holes for five zones of latitudes (±10°, ±20° – ±40°, and ±40° – ±60°) have been examined. It seems that the rotation period of coronal holes is a function of latitude, thus reflecting differential rotation of coronal holes.     

Transition probabilities and dissociation energy of astrophysical molecule GeH

The Franck-Condon factors andr-centroids, which are very closely related to vibrational transition probabilities, have been evaluated by the more reliable numerical integration procedure for the bands of A ² Δ - X² π_r system of astrophysical molecule GeH, using a suitable potential. The dissociation energy for the electronic ground state of astrophysical molecule GeH has been estimated precisely as D ⁰ ₀ = 2.69 ± 0.05 eV by fitting the empirical potential function to the experimental potential energy curve using correlation coefficient. This revised version was published online in July 2006 with corrections to the Cover Date.     

The orbital period and variability of the dwarf nova ES Draconis

A radial velocity study of the cataclysmic variable ES Dra (PG 1524+622) is presented. ES Dra is found to have an orbital period of 0.17660 ± 0.00006 day (4.2384 ± 0.0014 h). The mass-losing secondary star of ES Dra is detectable in the spectrum, and it has a spectral type of M2 ± 1. From this, we estimate the absolute magnitude of ES Dra during our spectroscopic observations to have been M_R = 6.5 ± 0.5, and its distance to be 720 ± 150 pc. The long-term light curve of ES Dra compiled by the American Association of Variable Star Observers (AAVSO) shows that ES Dra is a Z Cam star, which between 1995 and 2009 spent most of its time in standstill.     

Secular Decrease and Random Variations of the Flux Density of Cas a at 927, 290, 151.5, and 38 MHZ from Long-Term Measurements

Long-term measurements of the radio flux density of Cassiopeia A relative to Cygnus A have been carried out at 927, 290, 151.5, and 38 MHz. The mean secular decreases in the radio flux of Cas A are d927 = -(0.73±0.05)% year-1 (for the period 1977.8-1996.8), d290 = -(0.66 ± 0.07)% year-1 (1978.8-1996.85), and d151.5 = -(1.11 ± 0.22)% year-1 (1980.9-1994.8). Using also the results of other studies, d38 = -(.66 ± 0.17)% year-1 (1956-1995.6) and d151.5 = -(.86 ± 0.09)% year-1 (1966.5-1994.8). The temporal nonuniformity of the Cas A flux density decrease is most likely due to random changes in the integrated radio emission of the approximately 300 compact features observed in this source.     

Performance of the MAGIC stereo system obtained with Crab Nebula data

MAGIC is a system of two Imaging Atmospheric Cherenkov Telescopes located in the Canary island of La Palma. Since autumn 2009 both telescopes have been working together in stereoscopic mode, providing a significant improvement with respect to the previous single-telescope observations. We use observations of the Crab Nebula taken at low zenith angles to assess the performance of the MAGIC stereo system. The trigger threshold of the MAGIC telescopes is 50 − 60 GeV. Advanced stereo analysis techniques allow MAGIC to achieve a sensitivity as good as (0.76 ± 0.03)% of the Crab Nebula flux in 50 h of observations above 290 GeV. The angular resolution at those energies is better than ∼0.07°. We also perform a detailed study of possible systematic effects which may influence the analysis of the data taken with the MAGIC telescopes.     

Spectroscopic Studies on Astrophysically Interesting TaO TaS, ZrS and SiO+ Molecules

The true experimental potential energy curves for the electronic ground states of astrophysically important TaO, TaS, ZrS and SiO⁺molecules are constructed by using the Rydberg–Klein–Rees method as modified by Vanderslice et al. The ground state dissociation energies are determined by curve fitting techniques using the five parameters Hulburt-Hirschfelder (H-H) function. The estimated dissociation energies are 8.19 ± 0.17, 6.9 ±0.14, 5.89 ± 0.12 and 5.75 ± 0.12 eVfor TaO, TaS, ZrS and SiO⁺ respectively. These values are in good agreement with the literature values. The r-centriods and Franck–Condon factors (FC Factors) for the bands of K ² φ _5/2 - X ² Δ _3/2 (K-X) system of TaO, A-X ² Δ (A-X) and B-X ² Δ (B-X)systems of TaS, B ¹ Π - X¹ Σ⁺ (B-X) system of ZrS and B ²Σ⁺ - X² Σ⁺ (B-X) and A ² Π - X² Σ⁺ (A-X)systems of SiO⁺ molecules have been calculated. The Franck–Condon factors (FC factors) are evaluated by the approximate analytical methods of Jarmain and Fraser. The absence of the bands of these systems is explained. This revised version was published online in July 2006 with corrections to the Cover Date.     

North-south asymmetries in the green corona brightness between 1947 and 1976

The north-south asymmetry has been studied using the green emission corona brightness in the period of 1947–1976. (N - S)/(N + S) values are constructed with the 5-deg opposite coronal belts brightnesses between ± 5 and ± 60 deg. Power spectra analyses were performed to study periodicities of these (N - S)/(N + S) values. Two noticeable periodicities (14.5 and 5 yr) have been found.