Preirradiation history of Djermaia (H) chondritic breccia

Djermaia is a unique case among gas-rich chondrites. Twelve light xenoliths studied so far in the two available stones show unequivocal evidences of large preirradiation effects, which stand out most clearly when both cosmic-ray track and spallogenic rare-gas data are considered and compared to data from chondrites with a simple radiation history. Each of the two stones studied displays a specific xenolith population with distinct morphological and preirradiation characteristics. The first population consists of rounded and more- or less-shocked xenoliths which show evidences of short solar-flare irradiation (<1 my) and a longer residence under heavier shielding (～50 g/cm²). The second population shows neither clear indication of surface erosion nor evidence of solar-flare effects, and its preirradiation occured in deep-seated locations (～150 g/cm²).The size distribution of xenoliths is also different for the two populations, indicative of more active reworking processes in the top ～20 cm of the Djermaia regolith than at a depth of ～50 cm. The amount of ²¹Ne_sp accumulated during the preirradiation stage is substantial (25–60% of total ²¹Ne_sp), corresponding to a formal preexposure time of ～15 my for both stones, assuming static irradiation conditions. These results give an insight into the dynamics of the upper levels of the H-asteroid regolith, which appears to be in good agreement with the model of Housen, Wilkening, Chapman, and Greenberg (Icarus, 1979, 39, 317–351).     

Exposure history of the Peekskill (H6) meteorite

Abstract— The Peekskill H6 meteorite fell on 1992 October 9. We report extensive measurements of cosmic-ray produced stable nuclides of He, Ne, and Ar, of the radionuclides ²²Na, ⁶⁰Co, ¹⁴C, ³⁶Cl, ²⁶Al, and ¹⁰Be, and of cosmic-ray track densities. After correction for shielding via the ²²Ne/²¹Ne ratio, the concentrations of cosmic-ray produced ³He, ²¹Ne and ³⁸Ar give an average exposure age of 25 Ma, which is considered to be a lower limit on the true value. The ¹⁰Be/²¹Ne age is 32 Ma and falls onto a peak in the H-chondrite exposure age distribution. The activities of ²⁶Al, ¹⁴C, ³⁶Cl, and ¹⁰Be are all close to the maximum values expected for H-chondrites. Together with cosmic-ray track densities and the ²²Ne/²¹Ne ratio, these radionuclide data place the samples at a depth >20 cm in a meteoroid with a radius >40 cm. In contrast, the ⁶⁰Co activity requires a near-surface location and/or a much smaller body. Calculations show that a flattened geometry for the Peekskill meteoroid does not explain the observations in the context of a one-stage irradiation. A two-stage model can account for the data. We estimate an upper bound of 70 cm on the radius of the earlier stage of irradiation and conclude that Peekskill's radius was <70 cm when it entered the Earth's atmosphere. This size limit is somewhat smaller than the dynamic determinations (Brown et al., 1994).     

The Effelsberg Bonn H I Survey (EBHIS)

The Effelsberg‐Bonn H I survey (EBHIS) comprises an all‐sky survey north of Dec = –5° of the Milky Way and the local volume out to a red‐shift of z ≃ 0.07. Using state of the art Field Programmable Gate Array (FPGA) spectrometers it is feasible to cover the 100 MHz bandwidth with 16.384 spectral channels. High speed storage of H I spectra allows us to minimize the degradation by Radio Frequency Interference (RFI) signals. Regular EBHIS survey observations started during the winter season 2008/2009 after extensive system evaluation and verification tests. Until today, we surveyed about 8000 square degrees, focusing during the first all‐sky coverage of the Sloan‐Digital Sky Survey (SDSS) area and the northern extension of the Magellanic stream. The first whole sky coverage will be finished in 2011. Already this first coverage will reach the same sensitivity level as the Parkes Milky Way (GASS) and extragalactic surveys (HIPASS). EBHIS data will be calibrated, stray‐radiation corrected and freely accessible for the scientific community via a webinterface. In this paper we demonstrate the scientific data quality and explore the expected harvest of this new all‐sky survey (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Detection of interstellar ethylene oxide (c-C2H4O)

We report the identification of 10 transitions that support the detection of the small cyclic molecule ethylene oxide (c-C2H4O) in Sgr B2N. Although one of these transitions is severely blended, so that an accurate intensity and line width could not be determined, and two other lines are only marginally detected, we have done Gaussian fits to the remaining seven lines and have performed a rotation diagram analysis. Our results indicate a rotation temperature T(rot) = 18 K and a molecular column density N(c-C2H4O) = 3.3 x 10(14) cm-2, corresponding to a fractional abundance relative to molecular hydrogen of order 6 x 10(-11). This is a factor of more than 200 higher than the abundance for this molecule suggested by the "new standard" chemistry model of Lee, Bettens, & Herbst. This result suggests that grain chemistry might play an effective role in the production of c-C2H4O. No transitions of this molecule were detected in either Sgr B2M or Sgr B2NW.     

The H− equilibrium using coupled rate equations for H−, H,H+, H2, and H2 +

We formulate rate equations for the reaction network coupling H, H^–, H⁺, H₂, and H₂ ⁺. We attempt to systematize the notation, and to write the equations in a form suitable for modern computational methods of handling the coupled rate equations and radiative transfer equations, for both dynamical and static atmospheres. We have accounted for more processes than are generally considered in most current work; some of these may have an impact on the equilibrium of H^– (hence its opacity) and on charge conservation (hence the proton density) in the atmospheres of solar-type stars.Operated by the Association of Universities for Research in Astronomy, Inc. under Contract AST 78-17292 with the National Science Foundation.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

Analyses of the chondritic meteorite Orvinio (H6): Insight into the origins and evolution of shocked H chondrite material

Abstract— We have studied the petrography, reflectance spectra, and Ar‐Ar systematics of the Orivinio meteorite. Orvinio is an H chondrite not an L chondrite as sometimes reported. The material in the meteorite was involved in several impact events. One impact event produced large swaths of impact melt from H chondrite material surrounding relict clasts of chondrule‐bearing material. Not only were portions of a bulk H chondrite planestesimal melted during the impact event, but shock redistribution of metal and sulfide phases in the meteorite dramatically altered its reflectance spectra. Both the melt and relict clasts are darker than unshocked H chondrite material, bearing spectral similarities to some C‐class asteroids. Such shock metamorphism, which lowers the albedo of an object without increasing its spectral slope, may partially explain some of the variation among S‐class asteroids and some of the trends seen on asteroid 433 Eros. Noble gases record the evidence of at least two, and perhaps three, impact events in the meteorite and its predecessor rocks. The most significant evidence is for an event that occurred 600 Ma ago or less, perhaps ?325 Ma ago or less. There is also a signature of 4.2 Ga in the Ar‐Ar systematics, which could either reflect complete degassing of the rock at that time or partial degassing of even the most retentive sites in the more recent event.     

Exposure history of the St‐Robert (H5) fall

Abstract— The compositionally typical H5 chondrite St‐Robert has an exposure age, 7.8 Ma, indistinguishable from that of the main cluster of H chondrites. Small values of the cosmogenic ²²Ne/²¹Ne ratio in interior samples imply a pre‐atmospheric radius on the order of 40 cm. Sample depths based on tracks and the production rates of Bhattacharya et al. (1973) range from 6 to ～40 cm and are generally larger than depths estimated from published ⁶⁰Co activities, perhaps because the track production rates adopted are too high. Depth profiles of the production rates of ¹⁴C, ³⁶Cl, ²⁶Al, ¹⁰Be, and ²¹Ne in stony material show increases with depth and reach levels 5% to 15% higher than expected from modeling calculations. The maximum concentrations in St‐Robert are, however, generally comparable to those measured for the L5 chondrite, Knyahinya, whose pre‐atmospheric radius of ～45 cm is thought to lead to the maximum possible production rates in chondrites. We infer that the pre‐atmospheric radius of St‐Robert was within 5 cm of the value that supports maximum production rates (i.e., 45 ± 5 cm). This radius corresponds to a pre‐atmospheric mass of (1.3 ± 0.4) × 10³ kg. The agreement of exposure ages for St‐Robert obtained in several different ways and the similarity of the depth profiles for ¹⁴C, ²⁶Al, ¹⁰Be, and ²¹Ne argue against a lengthy pre‐exposure of St‐Robert on the parent body and against a two‐stage exposure after launch from the parent body. Following Morbidelli and Gladman (1998), we suggest that St‐Robert was chipped from deep in its parent body, spent the next 7–8 Ma without undergoing a major collision, was nudged gradually into an orbital resonance with Jupiter, and then traveled quickly to Earth.     

The thermal and physical characteristics of the Gao-Guenie (H5) meteorite

Measurements of the bulk density, grain density, porosity, and magnetic susceptibility of 19 Gao-Guenie H5 chondrite meteorite samples are presented. We find average values of bulk density 〈ρ_bulk〉=3.46±0.07 g/cm³, grain density 〈ρ_grain〉=3.53±0.08 g/cm³, porosity 〈P(%)〉=2.46±1.39, and bulk mass magnetic susceptibility 〈log χ〉=5.23±0.11. Measurements of the specific heat capacity for a 3.01-g Gao-Guenie sample, a 61.37-g Gao-Guenie sample, a 62.35-g Jilin H5 chondrite meteorite sample, and a 51.37-g Sikhote-Alin IIAB Iron meteorite sample are also presented. Temperature interpolation formula are further provided for the specific heat capacity, thermal conductivity, and thermal diffusivity of the 3.01-g Gao-Guenie sample in the temperature range 300<T (K)<800. We briefly review the possible effects of the newly deduced specific heat and thermal conductivity values on the ablation of meteoroids within the Earth's atmosphere, the modeling of asteroid interiors and the orbital evolution of meteoroids through the Yarkovsky-O’Keefe-Radzievskii-Paddack (YORP) effect.     

NOBLE GASES IN THE BELLS (C2) AND SHARPS (H3) CHONDRITES

Bells and Sharps have some mineralogical and chemical peculiarities that make their classification uncertain. For Bells, the⁴⁰ Ar content at 890 × 10^?8 cm³ STP/g is greater than the highest C1 chondrite value (Ivuna; 640), but close to the mean value for C2's (880). The²¹ Ne-exposure age of 0.38 ± 0.07 Ma is very short, and coincides with the distinctive cluster of five C2's (0.17 to 0.76 Ma). Very likely Bells belongs to the same cluster, in which case it comes from the C2 parent body. Hence the C2 parent body seems to contain transitional C1-C2 material, like Bells, within a few km of the region of C2 chondrites proper. Thus the radiogenic and especially the cosmogenic gases link Bells to the C2 group. For Sharps, the elemental concentrations of primordial Ar, Kr and Xe (127, 0.76 and 0.59, all 10^?8 cc/g) are ～ 3 x higher than for any other H3 chondrite. While Sharps is classified as 3.4 based on five indicators of metamorphism, the very high concentration of remaining two parameters of the Sears et al. (1980) scheme — C and primordial³⁶ Ar — (together with the high concentration of the volatile trace elements Bi, In and Tl) implies a classification of 3.0 for its volatile element content. The²¹ Ne-exposure age is 25.5 ± 2.5 Ma, placing Sharps in the second largest peak of the H-chondrite distribution. The nominal K-Ar and U, Th-He ages are 4.6 ± 0.2 and 4.2 ± 1.5 Ga, suggesting that Sharps has remained at low temperatures since its beginnings.     

On the line intensity ratios E(Hα)/E(D3) and E(Hβ)/E(D3) in prominences

The intensity ratios E(H)/E(D3) and E(H)/E(D3) in prominences depend on the total optical thickness in H of the layer. The emission of the He D3 line appears relatively enhanced in thin layers and in outer parts of the prominences.     

陕西天文台守时用氢原子钟

本文介绍了陕西天文台守时用氢原子钟（Ｈ２）的改进、分项误差、准确度及在国际时间局（ＢＩＰＭ）公报中取权情况．Ｈ２自１９９１年开始连续运转至今已两年多了。１９９１年３月开始每月向ＢＩＰＭ报送数据，１９９１年９月开始取权１．Ｈ２是我国唯一的一台在ＢＩＰＭ公报上取权的氢钟．     

On the relation between filaments (prominences) and Hα loops

The relation between occurrence of H loops and filaments is discussed on the occasion of the observation of a new type of transient loops during a flare associated filament activation. Considering all known types of loop systems crossing neutral lines it is concluded that concurrent existence of stable filaments and H loops is incompatible.Mitt. aus dem Fraunhofer Institut No. 112.     

Near-infrared imaging in H2 of molecular (CO) outflows from young stars

We have imaged several known molecular (CO) outflows in H₂ v=1-0 S(1) and wide-band K in order to identify the molecular shocks associated with the acceleration of ambient gas by outflows from young stars. We detected H₂ line emission in all the flows we observed: L 1157, VLA 1623, NGC 6334I, NGC 2264G, L 1641N and Haro 4-255. A comparison of the H₂ data with CO outflow maps strongly suggests that prompt entrainment near the head of a collimated jet probably is the dominant mechanism for producing the CO outflows in these sources.     

On the nature of the unique eclipsing system H 187 (HMW 15)

We present our photometric observations of the T Tauri star H 187. They confirm our conclusion that a new extended eclipse has begun in this young object. By the end of 2005, H 187 reached its minimum light following which its brightness began to slowly increase. Comparison with the previous ～3.5-yr-long eclipse observed by Cohen et al. shows that the new eclipse follows the previous eclipse fairly closely and, hence, it was caused by a second passage of the same extended dust or gas-dust cloud around the object. We have estimated the period between these events to be 4.7 yr. The object reddened during the eclipse, suggesting that the extinction was produced by small grains ～0.1μm in size. Possible mechanisms of such unusual eclipses are discussed. We draw an analogy between these eclipses and the cycles of photometric activity observed in UX Ori stars. Light curves similar to those observed for H 187 are shown to be obtained in the model of a young binary system with a low-mass companion accreting matter from the remnants of a protostellar cloud at a rate of ～10^?9 M _⊙ yr^?1.     

On the non-linear relationships between N(CaII), N(KI) and N(H)

Calculations by Penstonet al. (1969) of the mass distribution of interstellar clouds are reexamined in the light of Hobbs's data on the relationship between N(Caii) and N(H). The mass spectrum is calculated using two different sets of simple assumptions. Two possible explanations of the quadratic dependence of N(Ki) on N(H) are briefly examined.     

Chemical and isotopic characteristics of the Didwana‐Rajod (H5) chondrite

Abstract— The mineralogical and chemical characteristics of the Didwana‐Rajod chondrite are described. The mean mineral composition is found to be olivine (Fo_83.2) and pyroxene (En_83.5Wo_0.7Fs_15.8), and feldspar is mainly oligoclase. Oxygen isotopic analysis shows δ¹⁸O = +3.8%0 and δ¹⁷O = +2.59%0. The nitrogen content of Didwana‐Rajod is ～2 ppm with δ¹⁵N ? 3.4%0. Based on microscopic, chemical, isotopic and electron probe microanalysis, the meteorite is classified as an H5 chondrite. Cosmogenic tracks, radionuclides and the isotopic composition of rare gases were also measured in this meteorite. The track density in olivines varies in a narrow range with an average value of (6.5 ± 0.5) × 10⁵/cm² for four spot samples taken at the four corners of the stone. The cosmic‐ray exposure age based on neon and argon is 9.8 Ma. ²²Na/²⁶Al ? 0.94 is lower than the solar‐cycle average value of ～1.5 and is consistent with irradiation of the meteoroid to lower galactic cosmic‐ray fluxes as expected at the solar maximum. The track density, rare gas isotopic ratios, ⁶⁰Co activity and other radionuclide data are consistent with a preatmospheric radius of ～15 cm, corresponding to a mass of ～50 kg. The cosmogenic properties are consistent with a simple exposure history in interplanetary space.