Extended structures around yso in Mid-IR broad emission features     

Lynne K. Deutsch  Joseph L. Hora  Harold M. Butner  William F. Hoffmann  Giovanni G. Fazio 《Astrophysics and Space Science》1995,231(1-2):89-92

We present CO(1-0) observations toward the soft gamma-ray repeater SGR 1806-20. We discuss the implications on the distance to the X-ray counterpart: AX 1805.7-2025. We also present an upper limit at = 1.3 mm for the thermal emission from dust and high resolution IRAS maps of the region. SGR 1806-20 is very likely associated with the H II complex W31. The G10.0-0.3 supernova remnant (SNR) could be expanding in the very low density region produced by the wind of the bright O9-B2 star recently detected.National Academy of Sciences / National Research Council Resident Research Associate  相似文献   

Search for GRB counterparts in the optical     

René Hudec 《Astrophysics and Space Science》1995,231(1-2):239-246

The history and recent results of searches for optical counterparts to gamma ray burst sources in all three categories (i.e. flaring, fading and quiet) are outlined. The related problems such as background triggers and advantages and drawbacks of previous and recent approaches and investigations are discussed. Although there are some promising results especially in the appearance of optical transients i.e. short-lived star-like objects found in or close to the error boxes of some GRB, there is a need for more and better optical data, especially taken at or close to the times of GRB. Based on recent results, a strategy for further works in this direction is suggested with emphasis on obtaining of simultaneous (wide-field CCD experiments) and quasisimultaneous (robotic telescopes automatically pointed to the positions of newly detected GRB by Internet link) optical data.  相似文献   

The Claire gondola: Testing the first gamma-ray lens on a stratospheric balloon     

Ph. Laporte  J. Evrard  A. Laurens 《Experimental Astronomy》2005,20(1-3):447-454

For more than 40 years CNES has flown scientific balloon flights to perform measurements in a near space environment. The CNES balloon team provides the scientific teams with expertise in the construction of the gondola, the link between the instrument and the balloon. This gondola provides to the scientific instrument power supply, thermal and landing protection, attitude measurement and also pointing capability where needed.The project CLAIRE provides a good illustration of the CNES expertise in this domain. The goal of this project was to demonstrate that it is possible to focus a gamma-ray beam intercepted by a large area onto a small focal point. The concept has been demonstrated on ground in the 90s, but a validation under space conditions was necessary to measure the performance of such a telescope for a source at infinity.  相似文献   

Preliminary results on VLT K-band imaging observations of GRB host galaxies     

E. Le Floc’h  I. F. Mirabel  P. -A. Duc 《Journal of Astrophysics and Astronomy》2002,23(1-2):119-122

We have obtainedK-band imaging observations of Gamma-Ray Burst (GRB) host galaxies with the near-infrared spectro-imager ISAAC installed on the Very Large Telescope at Paranal (Chile). The derivedK magnitudes, combined with other photometric data taken from the literature, are used to investigate theR-K colors of GRB hosts. We do not find any extremely reddened starbursts in our sample, despite the capability of GRBs to trace star formation even in dusty regions. The observedR-K colors are on the contrary typical of irregular and spiral blue galaxies at high redshift.  相似文献   

The star formation history inferred from long gamma-ray bursts with high pseudo-redshifts     

《New Astronomy》2015

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Derivation of elemental abundance maps at intermediate resolution from optical interpolation of lunar prospector gamma-ray spectrometer data     

Yuriy G. Shkuratov  Vadim G. Kaydash  Larissa V. Starukhina  Serge D. Chevrel 《Planetary and Space Science》2005,53(12):1287-1301

We propose a technique that interpolates available lunar prospector gamma-ray spectrometer (GRS) data using Clementine UVVIS spectral reflectance images. The main idea is to use low resolution GRS data as a “ground truth” to establish relationships linking optical data and geochemical information maximizing the respective correlation coefficients. Then the relationships and Clementine UVVIS data are used to derive elemental abundance maps with significantly improved spatial resolution. The main limitation of the technique is its dependence on how well the abundance of the elements correlates with the Clementine UVVIS data. The technique can also be applied to analysis of coming D-CIXS/Smart-1 and AMIE/Smart-1 data to increase resolution of lunar compositional maps. As an illustration of the suggested technique, maps for the elements Fe, Ti, O, Al, Ca, and Mg with pixel size 15 km×15 km are presented. The Fe and Ti distributions resemble qualitatively to the maps obtained with the well-known technique by lucey et al. (2000a. Lunar iron and titanium abundance algorithms based on final processing of Clementine ultraviolet-visible images. J. Geophys. Res. 105, 20,297-20,306), though in our case the ranges of Fe and Ti variations are, respectively, wider and narrower than for lucey's maps. New maps for the elements Fe, Ti, O, Al, Ca, and Mg appear to be informative. For instance, the map of oxygen abundance demonstrates an anomaly in the crater Tycho. The maps of Fe and Al contents show for highland regions slight variations related to maturity degree. Reliability of this relation is confirmed with lunar sample data. The reason of the correlation between chemical composition and exposition age of the lunar surface can be the global transport of the lunar surface material due to meteorite impacts.  相似文献   

3-D Rpic Simulations of Relativistic Jets: Particle Acceleration, Magnetic Field Generation, and Emission     

K.-I. Nishikawa  C. B. Hededal  P. E. Hardee  G. J. Fishman  C. Kouveliotou  Y. Mizuno 《Astrophysics and Space Science》2007,307(1-3):319-323

We have applied numerical simulations and modeling to the particle acceleration, magnetic field generation, and emission from relativistic shocks. We investigate the nonlinear stage of theWeibel instability and compare our simulations with the observed gamma-ray burst emission. In collisionless shocks, plasma waves and their associated instabilities (e.g., the Weibel, Buneman and other two-stream instabilities) are responsible for particle (electron, positron, and ion) acceleration and magnetic field generation. 3-D relativistic electromagnetic particle (REMP) simulations with three different electron-positron jet velocity distributions and also with an electron-ion plasma have been performed and show shock processes including spatial and temporal evolution of shocks in unmagnetized ambient plasmas. The growth time and nonlinear saturation levels depend on the initial jet parallel velocity distributions. Simulations show that the Weibel instability created in the collisionless shocks accelerates jet and ambient particles both perpendicular and parallel to the jet propagation direction. The nonlinear fluctuation amplitude of densities, currents, electric, and magnetic fields in the electron-positron shocks are larger for smaller jet Lorentz factor. This comes from the fact that the growth time of the Weibel instability is proportional to the square of the jet Lorentz factor. We have performed simulations with broad Lorentz factor distribution of jet electrons and positrons, which is assumed to be created by photon annihilation. Simulation results with this broad distribution show that the Weibel instability is excited continuously by the wide-range of jet Lorentz factor from lower to higher values. In all simulations the Weibel instability is responsible for generating and amplifying magnetic fields perpendicular to the jet propagation direction, and contributes to the electron’s (positron’s) transverse deflection behind the jet head. This small scale magnetic field structure contributes to the generation of “jitter” radiation from deflected electrons (positrons), which is different from synchrotron radiation in uniform magnetic fields. The jitter radiation resulting from small scale magnetic field structures may be important for understanding the complex time structure and spectral evolution observed in gamma-ray bursts or other astrophysical sources containing relativistic jets and relativistic collisionless shocks. The detailed studies of shock microscopic process evolution may provide some insights into early and later GRB afterglows.  相似文献   

The measurement of gamma-emitting radionuclides in beach sand cores of coastal regions of Ramsar,Iran using HPGe detectors     

Marziyeh Tari  Sayyed Ali Moussavi Zarandi  Kheirollah Mohammadi  Mohammad Reza Zare 《Marine pollution bulletin》2013

Radionuclides which present in different beach sands are sources of external exposure that contribute to the total radiation exposure of human. ²²⁶Ra, ²³⁵U, ²³²Th, ⁴⁰K and ¹³⁷Cs analysis has been carried out in sand samples collected at six depth levels, from eight locations of the northern coast of Iran, Ramsar, using high-resolution gamma-ray spectroscopy. The average Specific activities of natural radionuclides viz., ²²⁶Ra, ²³⁵U, ²³²Th, ⁴⁰K and ¹³⁷Cs, in the 0–36 cm depth sand were found as: 19.2 ± 0.04, 2.67 ± 0.17, 17.9 ± 0.06, 337.5 ± 0.61 and 3.35 ± 0.12 Bq kg⁻¹, respectively. The effects of organic matter content and pH value of sand samples on the natural radionuclide levels were also investigated. Finally, the measured radionuclide concentrations in the Ramsar beach were compared with the world average values, as reported by UNSCEAR (2000). None of the studied beaches were considered as a radiological risk.  相似文献   

Systematics in the interpretation of aggregated neutrino flux limits and flavor ratios from gamma-ray bursts     

Philipp Baerwald Svenja Hümmer  Walter Winter 《Astroparticle Physics》2012,35(8):508-529

Gamma-ray burst analyses at neutrino telescopes are typically based on diffuse or stacked (i.e., aggregated) neutrino fluxes, because the number of events expected from a single burst is small. The interpretation of aggregated flux limits implies new systematics not present for a single burst, such as by the integration over parameter distributions (diffuse fluxes), or by the low statistics in small burst samples (stacked fluxes). We simulate parameter distributions with a Monte Carlo method computing the spectra burst by burst, as compared to a conventional Monte Carlo integration. With this approach, we can predict the behavior of the flux in the diffuse limit as well as in low statistics stacking samples, such as used in recent IceCube data analyses. We also include the flavor composition at the detector (ratio between muon tracks and cascades) into our considerations. We demonstrate that the spectral features, such as a characteristic multi-peak structure coming from photohadronic interactions, flavor mixing, and magnetic field effects, are typically present even in diffuse neutrino fluxes if only the redshift distribution of the sources is considered, with z ? 1 dominating the neutrino flux. On the other hand, we show that variations of the Lorentz boost can only be interpreted in a model-dependent way, and can be used as a model discriminator. For example, we illustrate that the observation of spectral features in aggregated fluxes will disfavor the commonly used assumption that bursts with small Lorentz factors dominate the neutrino flux, whereas it will be consistent with the hypothesis that the bursts have similar properties in the comoving frame.  相似文献   

航空物探综合站测量在多宝山斑岩铜矿上的应用效果   总被引：2，自引：2，他引：0  

范正国  赵玉刚  卢建忠 《地质与勘探》2004,40(4):60-63

文章介绍了多宝山和铜山斑岩型铜(钼)矿床的高精度航空物探综合异常:高精度航磁为弱正异常;航空伽玛能谱测量总道、钾道、铀道为弱相对高异常,钍道为弱相对低异常, F参数有明显相对高异常;航电异常实分量为高(峰)值异常、虚分量为低(谷)值异常.根据多宝山和铜山斑岩型铜(钼)矿床产出的地质环境、岩石蚀变特点,以及实测的岩(矿)石物性参数和航空物探综合异常特征,探讨了斑岩型铜(钼)矿床引起航空物探综合异常的前提条件,并认为航空物探综合站测量是普查斑岩型铜(钼)矿的一种有效的物探方法组合.  相似文献