XMM–Newton observations of soft gamma-ray repeaters     

Sandro Mereghetti  Paolo Esposito  Andrea Tiengo 《Astrophysics and Space Science》2007,308(1-4):13-23

All the confirmed Soft Gamma-ray Repeaters have been observed with the EPIC instrument on the XMM–Newton satellite. We review the results obtained in these observations, providing the most accurate spectra on the persistent X-ray emission in the 1–10 keV range for these objects, and discuss them in the context of the magnetar interpretation.   相似文献   

Saturn's auroral/polar H₃ infrared emission: I. General morphology and ion velocity structure     

Tom Stallard  Steve Miller  Makenzie Lystrup  Nicholas Achilleos 《Icarus》2007,189(1):1-13

  相似文献   

Total electron content processing from GPS observations to facilitate ionospheric modeling   总被引：2，自引：1，他引：1  

Angeline G. Burrell  Nelson A. Bonito  Charles S. Carrano 《GPS Solutions》2009,13(2):83-95

With the increasing global distribution of high rate dual-frequency global positioning system (GPS) receivers, the production of a real-time atmospheric constituent definition, total electron content (TEC), has become a beneficial contributor to the modeling applications used in the assessment of GPS position accuracy and the composition of the ionosphere, plasmasphere, and troposphere. Historically, TEC measurements have been obtained through post processing techniques to produce the quality of data necessary for modeling applications with rigorous error estimate requirements. These procedures necessitated the collection of large volumes of data to address the various abnormalities in the computation of TEC associated with the use of greater data quality controls and source selection while real-time modeling environments must rely on autonomous controls and filtration techniques to prevent the production of erroneous model results. In this paper we present methods for processing TEC in real time, which utilize several procedures including the application of an ionospheric model to automatically perform quality control on the TEC output and the computational techniques used to address receiver multipath, faulty receiver observations, cycle-slips, segmented processing, and receiver calibrations. The resulting TEC measurements are provided with rigorous error estimates validated using the vertical TEC from the Jason satellite mission.

Nelson A. BonitoEmail:

  相似文献   

MATLAB软件在测量平差中的应用     

卓力格图  詹洁晖 《大地测量与地球动力学》2000,20(3):75-80

阐述了如何利用 MATLAB软件处理观测数据。 MATLAB是目前在大学和研究机构广泛应用的一种数值计算及图形工具软件 ,它的特点是语法结构简明 ,数值计算高效 ,图形功能完备 ,特别适合非专业编程人员完成数值计算、科学试验数据处理等任务。给出了一个水准网无约束平差算例及其源程序  相似文献   

SWAS observations of water vapor in the Venus mesosphere     

Mark A. Gurwell  Gary J. Melnick  Edwin A. Bergin 《Icarus》2007,188(2):288-304

We present the first detections of the ground-state H₂¹⁶O (₁₁₀-₁₀₁) rotational transition (at 556.9 GHz) and the ¹³CO (5-4) rotational transition from the atmosphere of Venus, measured with the Submillimeter Wave Astronomy Satellite (SWAS). The observed spectral features of these submillimeter transitions originate primarily from the 70-100 km altitude range, within the Venus mesosphere. Observations were obtained in December 2002, and January, March, and July 2004, coarsely sampling one Venus diurnal period as seen from Earth. The measured water vapor absorption line depth shows large variability among the four observing periods, with strong detections of the line in December 2002 and July 2004, and no detections in January and March 2004. Retrieval of atmospheric parameters was performed using a multi-transition inversion algorithm, combining simultaneous retrievals of temperature, carbon monoxide, and water profiles under imposed constraints. Analysis of the SWAS spectra resulted in measurements or upper limits for the globally averaged mesospheric water vapor abundance for each of the four observation periods, finding variability over at least two orders of magnitude. The results are consistent with both temporal and diurnal variability, but with short-term fluctuations clearly dominating. These results are fully consistent with the long-term study of mesospheric water vapor from millimeter and submillimeter observations of HDO [Sandor, B.J., Clancy, R.T., 2005. Icarus 177, 129-143]. The December 2002 observations detected very rapid change in the mesospheric water abundance. Over five days, a deep water absorption feature consistent with a water vapor abundance of 4.5±1.5 parts per million suddenly gave way to a significantly shallower absorption, implying a decrease in the water vapor abundance by a factor of nearly 50 in less that 48 h. In 2004, similar changes in the water vapor abundance were measured between the March and July SWAS observing periods, but variability on time scales of less than a week was not detected. The mesospheric water vapor is expected to be in equilibrium with aerosol particles, primarily composed of concentrated sulfuric acid, in the upper haze layers of the Venus atmosphere. If true, moderate amplitude (10-15 K) variability in mesospheric temperature, previously noted in millimeter spectroscopy observations of Venus, can explain the rapid water vapor variability detected by SWAS.  相似文献   

A broad-band spectroscopic search for CO line emission in HDF850.1: the brightest submillimetre object in the Hubble Deep Field-North     

J. Wagg  D. H. Hughes  I. Aretxaga  E. L. Chapin  J. S. Dunlop  E. Gaztañaga  M. Devlin 《Monthly notices of the Royal Astronomical Society》2007,375(2):745-752

  相似文献   

High-resolution imaging of the anomalous flux ratio gravitational lens system CLASS B2045+265: dark or luminous satellites?     

J. P. McKean  L. V. E. Koopmans  C. E. Flack  C. D. Fassnacht  D. Thompson  K. Matthews  R. D. Blandford  A. C. S. Readhead  B. T. Soifer 《Monthly notices of the Royal Astronomical Society》2007,378(1):109-118

  相似文献   

Wide-field mid-infrared and millimetre imaging of the high-redshift radio galaxy, 4C 41.17     

T. R. Greve  D. Stern  R. J. Ivison  C. De Breuck  A. Kovács  F. Bertoldi 《Monthly notices of the Royal Astronomical Society》2007,382(1):48-66

  相似文献   

Star formation in galaxies along the Pisces-Cetus Supercluster filaments     

Scott C. Porter  Somak Raychaudhury 《Monthly notices of the Royal Astronomical Society》2007,375(4):1409-1417

We investigate the variation of current star formation in galaxies as a function of distance along three supercluster filaments, each joining pairs of rich clusters, in the Pisces-Cetus supercluster, which is part of the two-degree Field Galaxy Redshift Survey (2dFGRS). We find that even though there is a steady decline in the rate of star formation, as well as in the fraction of star-forming galaxies, as one approaches the core of a cluster at an extremity of such a filament, there is an increased activity of star formation in a narrow distance range between 3 and  4  h ⁻¹₇₀ Mpc  , which is 1.5–2 times the virial radius of the clusters involved. This peak in star formation is seen to be entirely due to the dwarf galaxies  (−20 < M _B ≤−17.5)  . The position of the peak does not seem to depend on the velocity dispersion of the nearest cluster, undermining the importance of the gravitational effect of the clusters involved. We find that this enhancement in star formation occurs at the same place for galaxies which belong to groups within these filaments, while group members elsewhere in the 2dFGRS do not show this effect. We conclude that the most likely mechanism for this enhanced star formation is galaxy–galaxy harassment, in the crowded infalling region of rich clusters at the extremities of filaments, which induces a burst of star formation in galaxies, before they have been stripped of their gas in the denser cores of clusters. The effects of strangulation in the cores of clusters, as well as excess star formation in the infalling regions along the filaments, are more pronounced in dwarfs since they more vulnerable to the effects of strangulation and harassment than giant galaxies.  相似文献   

Deep-sea reef fish assemblage patterns on the Blake Plateau(Western North Atlantic Ocean)     

Steve W. Ross  & Andrea M. Quattrini 《Marine Ecology》2009,30(1):74-92

Deep‐water coral habitats are scattered throughout slope depths (360–800 m) off the Southeastern United States (SEUS, Cape Lookout, North Carolina, to Cape Canaveral, Florida), contributing substantial structure and diversity to bottom habitats. In some areas (e.g. off North Carolina) deep corals form nearly monotypic (Lophelia pertusa) high profile mounds, and in other areas (e.g. off Florida) many species may colonize hard substrata. Deep coral and hard substrata ecosystems off the SEUS support a unique fish assemblage. Using the Johnson‐Sea‐Link submersible (in 2000–2005, 65 dives), and a remotely operated vehicle (in 2003, five dives), fishes were surveyed in nine deep reef study areas along the SEUS slope. Forty‐two benthic reef fish species occurred in deep reef habitats in these study areas. Species richness was greatest on the two coral banks off Cape Lookout, North Carolina (n = 23 and 27 species) and lowest on the two sites off Cape Canaveral, Florida (n = 7 and 8 species). Fish assemblages exhibited significantly (ANOSIM, Global R = 0.69, P = 0.001) different patterns among sites. Stations sampled off North Carolina (three study areas) formed a distinct group that differed from all dives conducted to the south. Although several species defined the fish assemblages at the North Carolina sites, Laemonema barbatulum, Laemonema melanurum, and Helicolenus dactylopterus generally had the most influence on the definition of the North Carolina group. Fish assemblages at three sites within the central survey area on the Blake Plateau were also similar to each other, and were dominated by Nezumia sclerorhynchus and L. melanurum. Synaphobranchus spp. and Neaumia sclerorhynchus differentiated the two southern sites off Cape Canaveral, Florida, from the other station groups. Combinations of depth and habitat type had the most influence on these station groups; however, explicit mechanisms contributing to the organization of these assemblages remain unclear.  相似文献