The thin and medium filters of the EPIC camera on-board XMM-Newton: measured performance after more than 15 years of operation     

Marco Barbera  Fabio Gastaldello  Luisa Sciortino  Simonpietro Agnello  Gianpiero Buscarino  Alfonso Collura  Nicola La Palombara  Ugo Lo Cicero  Nicola Sartore  Andrea Tiengo  Salvatore Varisco  Anna Maria Venezia 《Experimental Astronomy》2016,42(2):179-197

After more than 15 years of operation of the EPIC camera on board the XMM-Newton X-ray observatory, we have reviewed the status of its Thin and Medium filters. We have selected a set of Thin and Medium back-up filters among those still available in the EPIC consortium and have started a program to investigate their status by different laboratory measurements including: UV/VIS transmission, Raman scattering, X-Ray Photoelectron Spectroscopy, and Atomic Force Microscopy. Furthermore, we have investigated the status of the EPIC flight filters by performing an analysis of the optical loading in the PN offset maps to gauge variations in the optical and UV transmission. We both investigated repeated observations of single optically bright targets and performed a statistical analysis of the extent of loading versus visual magnitude at different epochs. We report the results of the measurements conducted up to now. Most notably, we find no evidence for change in the UV/VIS transmission of the back-up filters in ground tests spanning a 2 year period and we find no evidence for change in the optical transmission of the thin filter of the EPIC-pn camera from 2002 to 2012. We point out some lessons learned for the development and calibration programs of filters for X-ray detectors in future Astronomy missions.  相似文献   

Hydrological and biogeochemical features of the Northern Adriatic Sea in the period 2003–2006     

Giorgio Socal  Francesco Acri  Mauro Bastianini  Fabrizio Bernardi Aubry  Franco Bianchi  Daniele Cassin  Joan Coppola  Amelia De Lazzari  Vinko Bandelj  Gianpiero Cossarini  Cosimo Solidoro 《Marine Ecology》2008,29(4):449-468

This paper reports on the main biogeochemical properties of the Northern Adriatic Sea in the period May 2003–November 2006 within the framework of the European program INTERREG III Italy‐Slovenia. Spatial and temporal distributions of water density, dissolved oxygen, nutrients (nitrogen, phosphorous and silicon) and chlorophyll a are presented. Multivariate methods such as fuzzy k‐means, self‐organising maps and cluster analysis were used to identify the different water masses and to characterise the temporal and spatial variability of the main biogeochemical features present in the area. The results confirm that the Po River outflows and the meteorological forcing factors are the main components triggering the alternation of stratification and mixing of the water column and that strongly affect the trophic state of the basin. In general, oligotrophic conditions dominate, and were more pronounced offshore, but mesotrophy occurred episodically in May 2004 and July 2005, when phytoplankton blooms were observed concomitant with vertical stability of the water column. A marked interannual variability was also observed, supporting the importance of maintaining long‐term observations of the basin.  相似文献   

BeppoSAX observations of 1-Jy BL Lacertae objects – I     

Paolo Padovani †‡  Luigi Costamante  Paolo Giommi  Gabriele Ghisellini  rea Comastri  Anna Wolter  Laura Maraschi  Gianpiero Tagliaferri  C. Megan Urry 《Monthly notices of the Royal Astronomical Society》2001,328(3):931-943

We present new BeppoSAX observations of seven BL Lacertae objects selected from the 1-Jy sample plus one additional source. The collected data cover the energy range     (observer's frame), reaching ∼50 keV for one source (BL Lac). All sources characterized by a peak in their multifrequency spectra at infrared/optical energies (i.e., of the low-energy peaked BL Lac type, LBL) display a relatively flat     X-ray spectrum, which we interpret as inverse Compton emission. Four objects (two-thirds of the LBLs) show some evidence for a low-energy steepening, which is probably due to the synchrotron tail merging into the inverse Compton component around ∼     . If this were generally the case with LBLs, it would explain why the     ROSAT spectra of our sources are systematically steeper than the BeppoSAX ones     . The broad-band spectral energy distributions fully confirm this picture, and a synchrotron inverse Compton model allows us to derive the physical parameters (intrinsic power, magnetic field, etc.) of our sources. Combining our results with those obtained by BeppoSAX on BL Lacs covering a wide range of synchrotron peak frequency, ν _peak, we confirm and clarify the dependence of the X-ray spectral index on ν _peak originally found in ROSAT data.  相似文献   

Detection of Variations in Air Temperature at Different Time Scales During the Period 1889–1998 at Firenze, Italy     

P. Vijaya Kumar  Marco Bindi  Alfonso Crisci  Giampiero Maracchi 《Climatic change》2005,72(1-2):123-150

In an attempt to contribute to studies on global climatic change, 110 years of temperature data for Firenze, Italy, were analysed. Means and trends of annual and monthly temperatures (minimum, maximum and average) were analysed at three different time scales: short (20 years), medium (36–38 years) and long (55 years). Comparative changes in extreme events viz. frosts in the first and second parts of the 20th century were also analysed. At short time scales, climatic change was found in minimum and average temperatures but not in maximum temperatures. At all three time scales, the annual means of minimum, maximum and average temperatures were significantly warmer in the last part than in the early part of the 20th century. The monthly mean temperatures showed significant warming of winter months. Over the last four decades, minimum, maximum and average temperatures had warmed by 0.4, 0.43 and 0.4 ∘C per decade, respectively, and if this trend continues, they will be warmer by 4 ∘C by the end of the 21st century. The significant decline in days with subzero temperatures and frosts in the last half of the 20th century, further substantiated the occurrence of climate change at this site.  相似文献