Observation of the Comet Kohoutek (1973f) in the resonance light (A2Σ+−X2 ∏) of the OH radical

Two monochromatic pictures of the Comet Kohoutek (1973f) were taken on January 15, 1974 in the resonance light (A²Σ ? X² ∏) of the radical OH with a photographic telescope placed on board the NASA 990 Convair airplane. From an intensity profile we derive the production rate of OH radicals Q_OH = 4 xsx 10²⁸ moleculesec ^?1sr^?1 at 0.6 AU and the lifetime of the OH radical which is τ_OH = 4.5 × 10⁴ sec at 0.6 AU. This short lifetime (very similar to the lifetime of H₂O) combined with the high total production rate of gas in comets can explain the observed velocity of 8km sec^?1 for the H-atoms: The H-atoms produced by photodissociation of H₂O are thermalized at short distancesfrom the nucleus; the H-atoms produced by photodissociation of OH have a velocity of ?8km sec^?1 and can reach the outer part of the hydrogen envelope.     

Astrophysically useful radiative transition parameters for?the?e1Π–X1Σ+ and 1Σ+–X1Σ+ systems of zirconium oxide

The zirconium oxide (ZrO) is well known for its astrophysical importance. The radiative transition parameters that include Franck-Condon (FC) factor, r-centroid, electronic transition moments, Einstein coefficient, band oscillator strengths, radiative life time and effective vibrational temperature have been estimated for e ¹Π–X ¹Σ⁺ and ¹Σ⁺–X ¹Σ⁺ band systems of ⁹⁰ZrO molecule for the experimentally known vibrational levels using RKR potential energy curves. A reliable numerical integration method has been used to solve the radial Schr?dinger equation for the vibrational wave functions of upper and lower electronic states based on the latest available spectroscopic data and known wavelengths. The estimated radiative transition parameters are tabulated. The effective vibrational temperatures of these band systems of ⁹⁰ZrO molecule are found to be below 4200 K. Hence, the radiative transition parameters help us to ascertain the presence of ⁹⁰ZrO molecule in the interstellar medium, S stars and sunspots.     

High spectral resolution ground-based observations of Venus in the 450- to 1250-cm−1 region

Ground-based observations of Venus were made with a 5-cm drive Michelson interferometer during December 1970 and December 1973. The thermal emission spectrum of the central portion of the apparent disk was recorded from 450–1250 cm^?1 with an apodized spectral resolution of 0.25 cm^?1. All statistically significant sharp line absorption features in the spectrum have been identified with gaseous CO₂. Comparison between the observed spectrum and a synthetic spectrum computed from a model atmosphere, assuming gaseous CO₂ and a sulfuric acid haze as opacity sources, indicates good agreement. A broad diffuse absorption feature associated with the sulfuric acid haze is evident in the 870- to 930 cm^?1 region. With the exception of the rotational lines of the 927-cm^?1 CO₂ band, the above feature appears as a continuum down to 0.25 cm^?1 resolution. In the 750- to 1250-cm^?1 range, the spectrum exhibits moderate thermal contrast with maximum brightness temperatures of 234–238°K occurring near 825 cm^?1. These temperatures are in general agreement with previous measurements.     

Five-dimensional Brans–Dicke M1×R3×S1 cosmology with?chameleon scalar field

We investigate five-dimensional Brans–Dicke cosmology with spacetime described by the homogeneous, anisotropic and flat spacetime with the topology M ¹×R ³×S ¹ where S ¹ is taken in the form of a circle. We conjecture throughout this letter that the extra-dimension compactifies as the visible dimensions expand like b(t)≈a ⁻¹(t) and that the non-minimal coupling between the scalar field and the matter is of the form f(φ)∝ φ ². The model gives rise to a transition from a decelerated epoch to an accelerated epoch for large values of the Brans–Dicke parameter ω. The model predicts crossing of the phantom divided barrier unless the universe is governed by a growing matter field.     

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 mean Jovian temperature structure derived from spectral observations from 105 to 630 cm−1

New far-infrared observations of the NH₃ rotation-inversion manifolds in the spectrum of Jupiter have been inverted with the use oftthe detailed ammonia line opacity. A temperature of 160°K at a 1-bar pressure level and a temperature of 105°K for the minimum temperature of the inversion level at 0.15 bars have been derived for gaseous absorption due to NH₃, H₂, and He. The overall fit to the brightness temperature as a function of frequency σ is within ±1°K for 100 ≤ σ ≤ 400 cm^?1 except for the centers of the NH₃ rotation-inversion manifolds where for J ≥ 7 the fit is about 5°K too high. In the continuum for 400 ≤ σ ≤ 630 cm^?1 the fit is within 2.5°K. Consideration of an ammonia ice haze, photodissociation of NH₃ by uv radiation, NH₃ abundance variation, different He/H₂ ratios, and uncertainties in the data effect the temperatures at 1 bar and the temperature at the inversion layer by <7°K. The presently derived temperature at 1 bar of 160°K is consistent with Jovian interior models which can match the gravitational moment, J₂.     

Large-scale mapping of the IRAS 0042 + 5530 region in the 12CO (J = 1−0) and 13CO (J = 1−0) molecular lines

We present new radio observations of molecular lines in the region of high mass star formation, namely G122.0-7.1. A large-scale map of the emission observed in the ¹²CO (J = 1−0) and ¹³CO (J = 1−0) lines covers the area of 15′ × 9′, revealing two dense regions. The molecular bipolar outflows have been resolved in ASO1 region. It is associated with the known candidate YSO nearby IRAS 0042 + 5530. Also, a new dense region has been discovered in the North-Western part of the G122.0-7.1 at a distance of 5′ from IRAS 0042 + 5530. Its position is close to the peak of 4850 MHz emission. The text was submitted by the authors in English.     

Chirikov diffusion in the asteroidal three-body resonance (5, −2, −2)

The theory of diffusion in many-dimensional Hamiltonian system is applied to asteroidal dynamics. The general formulation developed by Chirikov is applied to the Nesvorny-Morbidelli analytic model of three-body (three-orbit) mean-motion resonances (Jupiter-Saturn-asteroid). In particular, we investigate the diffusion along and across the separatrices of the (5, −2, −2) resonance of the (490) Veritas asteroidal family and their relationship to diffusion in semi-major axis and eccentricity. The estimations of diffusion were obtained using the Melnikov integral, a Hadjidemetriou-type sympletic map and numerical integrations for times up to 10⁸ years.     

ETON 2: Quenching parameters for the proposed precursors of O2(b1Σg+) and O(1S) in the terrestrial nightglow

Volume emission profiles of the O₂(b¹Σ_g⁺−X³Σ_g^t-)(O-O) Atmospheric Band and the O(¹S-¹D) green line are used together with coordinated measurements of the atomic oxygen concentrations to test the hypothesis that both emissions are excited by Barth type mechanisms. By considering O₂(b¹Σ_g⁺) to be produced from an excited O₂ precursor, with O₂ as transfer agent, and O(¹S) to be formed from a similar precursor with atomic oxygen as the transfer agent, precursor quenching rates are obtained as a function of altitude. These quenching profiles can be well resolved into components corresponding to collisional deactivation by O(³P) and O₂ (or N₂), and support the suggestion that Barth type mechanisms are involved. Minimum efficiencies for the production of the two precursors in oxygen atom recombination and ratios for the quenching of each by O(³P) and O₂ (or N₂) are deduced. Differences in the quenching coefficients for the two precursors are discussed.     

Airglow O2(1Σ) atmospheric band at 8645 Å and the rotational temperature observed at 23°S

Regular observations of theO₂(¹Σ), 0–1) atmospheric band at 8645 Å [O₂A(0, 1)] and the rotational temperature, together with the OH(9,4) band and OI 5577 Å airglow emissions, using multichannel tilting filter type photometers, have been carried out at Cachoeira Paulista (22.7°S, 45.0°W), Brazil, since February 1983. The O₂A(0, 1) band intensities occasionally vary from 200 to 1000 R during a night. Covariations in nocturnal and seasonal variation with the OI 5577 A emission were observed. The temperatures determined from the P branch of the O₂A(0, 1) band vary between 180 and 230 K. The amplitude of the nocturnal temperature variation is sometimes larger than that determined from the OH emission, and the phase of the variation, on some occasions, leads that of the OH.     

Collision induced rotational excitation of AlF (X 1Σ+) by para-H2 (j=0)

Rotational excitation cross sections and rate coefficients of AlF collisions with para-H₂ are computed at low temperature, i.e., for T≤70 K. Prior to collisional calculations, a four-dimensional (4D) potential energy surface (PES) for the AlF-H₂ system is calculated at the ab initio Coupled-Cluster level of the theory with an aug-cc-pVQZ Gaussian basis set. This 4D-PES is further reduced to a two-dimensional (2D) PES based on the considerations related to collisional studies with para-H₂. The [Al-F] and [H-H] bond lengths are frozen at their experimental equilibrium value r _e =1.654369 bohr and r _e =1.4011 bohr respectively. The interaction energy presents a global minimum located ∼63 cm⁻¹ below the AlF-H₂ dissociation limit. With this PES, cross sections are determined in the Close-Coupling (CC) approach and rate coefficients are inferred by averaging the cross sections over a Maxwell-Boltzman distribution of kinetic energies. These quantities are significantly magnified in comparison with their AlF-He counterparts. The already observed propensity towards ΔJ=1 transitions for AlF-He remains.     

Lineaments on the Surface of the Consolidated Material of the Comet 67P/Churyumov−Gerasimenko Nucleus

Morphologic analysis of the fragments (500 × 500 pixels) of images of comet 67P/Churyumov? Gerasimenko obtained with the OSIRIS camera for 18 regions, where the consolidated material is exposed on the surface, has been carried out. In terms of resolution, the images form a series from 0.04 to 1.29 m/pixel; consequently, the areas covered by these fragments vary from 400 to ~400000 m². In all of the regions, lineaments resembling tension fractures—several dozens of structures per region—are seen; and their number scarcely changes when passing from high-resolution images to lower-resolution ones. It is clear that relatively small lineaments cease to be reliably distinguished when the image resolution worsens, but the largest and well-defined ones remain observable, while the number of larger lineaments grows proportionally to the survey area increasing. Undoubtedly, this is an observational effect, which was demonstrated by examples with an artificially worsened resolution. However, on the other hand, this means that the tension fractures of the consolidated nucleus material represent a hierarchic population of smaller (meters long) to larger (decameters and longer) features. The lineaments seen in the analyzed fragments of images were counted, their lengths were measured, and the spacings (the mean distances between lineaments) and, from them, the depths of penetration of fractures into the nucleus material were estimated. It has been shown that the mean length of lineaments within each studied region depends on its area (which here correlates with the image resolution) and the depths of fracture penetration into the nucleus body depends on the mean length of lineaments. Both dependences are close to a power law. In the images of four regions covering the areas from 100000 to 400000 m² with a resolution of 0.66?1.29 m/pixel, the structures that look like layering or sheet jointing are seen in addition to fracture lineaments. The tension fractures are apparently formed due to seasonal and diurnal variations of the temperature, while the nature of the formation of the layer-like structures is not yet fully understood.     

RATAN-600 7.6-cm deep sky strip surveys at the declination of the SS433 source during the 1980–1999 period. Data reduction and the catalog of radio sources in the right-ascension interval 7h ≤ R.A. < 17h

We use two independent methods to reduce the data of the surveys made with RATAN-600 radio telescope at 7.6 cm in 1988–1999 at the declination of the SS433 source. We also reprocess the data of the “Cold” survey (1980–1981). The resulting RCR (RATAN COLD REFINED) catalog contains the right ascensions and fluxes of objects identified with those of the NVSS catalog in the right-ascension interval 7 ^h ≤ R.A. < 17 ^h . We obtain the spectra of the radio sources and determine their spectral indices at 3.94 and 0.5 GHz. The spectra are based on the data from all known catalogs available from the CATS, Vizier, and NED databases, and the flux estimates inferred from the maps of the VLSS and GB6 surveys. For 245 of the 550 objects of the RCR catalog the fluxes are known at two frequencies only: 3.94 GHz (RCR) and 1.4 GHz (NVSS). These are mostly sources with fluxes smaller than 30mJy. About 65% of these sources have flat or inverse spectra (α > −0.5). We analyze the reliability of the results obtained for the entire list of objects and construct the histograms of the spectral indices and fluxes of the sources. Our main conclusion is that all 10–15 mJy objects found in the considered right-ascension interval were already included in the decimeter-wave catalogs.     

Luminosity–redshift (L−z) relation and the blazar sequence for low power blazars

This paper presents an alternative interpretation for the wide scatter and apparent lack of anti-correlation in the relationship between the spectral luminosity (L _ν ) and synchrotron peak frequency (ν _peak ) in a sample of BL Lac Objects contained in Wu et al. (Astron. Astrophys. 466:43, 2007) compilation. The apparent lack of correlation between the parameters contradicts the blazar sequence proposed by Fossati et al. (in Mon. Not. R. Astron. Soc. 299:433, 1998), which predicts a general decline in L _ν with increasing ν _peak . Analysis of the radio luminosity and synchrotron peak frequency data of the sample reveals a strong selection effect, due to Malmquist bias. We show that a clear anti-correlation (r～?0.7) between the radio luminosity at synchrotron peak (L _peak ) and ν _peak exists for the BL Lac sample above some redshift cut-off (z _c =0.3), which may correspond to the flux limit of the sample. The results are not only in agreement with FRI–BL Lac unification, but also suggest that the present data is consistent with the blazar sequence.     

Sub-iron to iron nuclei in low-energy (50–200 MeV nucl−1) cosmic rays as observed in the Skylab experiment

In this paper we present our most recent results on the sub-iron (Sc to Cr) to Fe nuclei abundance ratios in the low-energy cosmic rays of 50 to 250 MeV nucl.^–1 and their implications as observed in theSkylab experiment. In view of the importance of this ratio in determining the cosmic-ray pathlength in interstellar medium, we have obtained additional data in the same detector module and the results of final analysis are reported. Charge determinations in the Lexan detector were made from an average of about four independent measurements ofZ for each of the cosmic-ray events and the mean charge resolution is obtained asZ/Z0.2. From about 100 events of calcium to nickel in low-energy cosmic rays, sub-iron (Sc to Cr) to Fe–Co ratio is determined as 1.43±0.40 in 50–250 MeV nucl.^–1. This shows a large energy dependence of the ratio as compared to the value of 0.4–0.8 in 200–1000 MeV nucl.^–1 as measured by many investigators. The origin of this large enhancement of the ratios in low-energy cosmic rays is not known at present. Some possible suggestions are briefly mentioned.     

The comparison of H_2CO(1_(10)–1_(11)),C~(18)O(1–0) and the continuum towards molecular clouds

We present large scale observations of C18O(1–0) towards four massive star forming regions: MON R2,S156,DR17/L906 and M17/M18. The transitions of H2CO(110–111),C18O(1–0) and the 6 cm continuum are compared in these four regions. Our analysis of the observations and the results of the Non–LTE model shows that the brightness temperature of the formaldehyde absorption line is strongest in a background continuum temperature range of about 3 – 8 K. The excitation of the H2 CO absorption line is affected by strong background continuum emission. From a comparison of H2 CO and C18 O maps,we found that the extent of H2 CO absorption is broader than that of C18 O emission in the four regions. Except for the DR17 region,the maximum in H2 CO absorption is located at the same position as the C18 O peak. A good correlation between intensities and widths of H2 CO absorption and C18 O emission lines indicates that the H2 CO absorption line can trace the dense,warm regions of a molecular cloud. We find that N(H2CO) is well correlated with N(C18O) in the four regions and that the average ratio of column densities is N(H2CO)/N(C18O) ～ 0.03.     

Stellar disruption by a supermassive black hole: is the light curve really proportional to t−5/3?

In this paper, we revisit the arguments for the basis of the time evolution of the flares expected to arise when a star is disrupted by a supermassive black hole. We present a simple analytic model relating the light curve to the internal density structure of the star. We thus show that the standard light curve proportional to   t ^−5/3  only holds at late times. Close to the peak luminosity the light curve is shallower, deviating more strongly from   t ^−5/3  for more centrally concentrated (e.g. solar type) stars. We test our model numerically by simulating the tidal disruption of several stellar models, described by simple polytropic spheres with index γ. The simulations agree with the analytical model given two considerations. First, the stars are somewhat inflated on reaching pericentre because of the effective reduction of gravity in the tidal field of the black hole. This is well described by a homologous expansion by a factor which becomes smaller as the polytropic index becomes larger. Secondly, for large polytropic indices wings appear in the tails of the energy distribution, indicating that some material is pushed further away from parabolic orbits by shocks in the tidal tails. In all our simulations, the   t ^−5/3  light curve is achieved only at late stages. In particular, we predict that for solar-type stars, this happens only after the luminosity has dropped by at least 2 mag from the peak. We discuss our results in the light of recent observations of flares in otherwise quiescent galaxies and note the dependence of these results on further parameters, such as the star/hole mass ratio and the stellar orbit.     

Stellar sources in the isogal inner galactic bulge field (l=0°,b= − 1°)

ISOGAL is a survey at 7 and 15 μm with ISOCAM of the inner galactic disk and bulge of our Galaxy. The survey covers ∼ 22 deg² in selected areas of the centrall = ±30 degree of the inner Galaxy. In this paper, we report the study of a small ISOGAL field in the inner galactic bulge (l = 0°,b = −1°, area = 0.033deg²). Using the multicolor nearinfrared data (IJK_s) of DENIS (DEep Near Infrared Southern Sky Survey) and mid-infrared ISOGAL data, we discuss the nature of the ISOGAL sources. The various color-color and color-magnitude diagrams are discussed in the paper. While most of the detected sources are red giants (RGB tip stars), a few of them show an excess in J-K_s and K_s-[15] colors with respect to the red giant sequence. Most of them are probably AGB stars with large mass-loss rates.     

A laboratory atlas of the 5ν1 NH3 absorption band at 6475 Å with applications to Jupiter and Saturn

The 5ν₁ absorption band of NH₃ is displayed from 6418 to 6550 Å. The total band intensity has been measured: S_B = 0.66 cm^?1m^?1amagat^?1. Line intensities and self-broadening coefficients have been measured for some of the prominent lines. Our line intensities are in good agreement with those of Rank et al. (1966), but are about 2 times greater than those of Mason (1970). The spectrum displayed was obtained photoelectrically at a pressure of 0.061 atm, and shows many more lines than the spectrum obtained by McBride and Nicholls (1972a) at a pressure of 0.39 atm. Therefore, our new measurements can provide the basis for making a more complete rotational analysis than those of McBride and Nicholls (1972a).Since the total band absorption has previously been measured by others on moderate resolution photoelectric scans of the spectra of Jupiter and Saturn, we can use the band intensity to derive the NH₃ abundance in the atmospheres of these two planets. The NH₃ abundances in a single vertical path obtained by this method are about 10m amagat for Jupiter and 2m amagat for Saturn. These results are in agreement with previous results obtained from higher resolution photographic spectra.