相关论文: A survey of hard spectrum ROSAT sources 2: optical…

The ROSAT Deep Survey in the Lockman Hole contains a complete sample of 50 X-ray sources with fluxes in the 0.5-2.0 keV band larger than 5.5E-15 erg/cm2/s. Previous work has provided optical identification of 46 of the 50 X-ray sources;…

We present the X-ray data and the optical identifications for a deep ROSAT PSPC observation in the "Marano field". In the inner region of the ROSAT field (15' radius) we detected 50 X-ray sources with Sx >= 3.7x10^(-15) erg/cm^2/s. When…

We have identified a population of blank field sources (or `blanks') among the ROSAT bright unidentified X-ray sources with faint optical counterparts. The extreme X-ray over optical flux ratio of blanks is not compatible with the main…

Hard X-ray selection is the most efficient way to discriminate between accretion-powered sources, such as AGN, from sources dominated by starlight. Hard X-rays are also less affected than other bands by obscuration. We have then carried out…

Results are presented of extended and refined optical identification of 181 radio/X-ray sources in the RASS-Green Bank (RGB) catalog which have been spectroscopically observed in the Sloan digital sky survey (SDSS) DR5. For 72 sources, the…

We present an analysis of the X-ray spectral properties of 61 hard X-ray selected (2-8 keV) sources from the bright ($f_{2-8 keV}>10^{-14}$ \funits) {\it XMM-Newton}/2dF survey. This comprises of 9 {\it XMM-Newton} pointings in the North…

The ROSAT Bright Survey (RBS) aims to completely optically identify the more than 2000 brightest sources detected in the ROSAT all-sky survey at galactic latitudes |b| > 30 degr (excluding LMC, SMC, Virgo cluster). This paper presents a…

We present a catalogue of 147 serendipitous X-ray sources selected to have hard spectra (alpha < 0.5) from a survey of 188 ROSAT fields. Such sources must be the dominant contributors to the X-ray background at faint fluxes. We have used…

We present ASCA GIS observations (total exposure 100-200 ksec) of three fields which form part of our deep ROSAT survey. We detect 26 sources down to a limiting flux (2-10 keV) of 5x10^{-14} erg cm-2 s-1. Sources down to this flux level…

The optical identification of large number of X-ray sources such as those from the ROSAT All-Sky Survey is challenging with conventional spectroscopic follow-up observations. We investigate two ROSAT All-Sky Survey fields of size 10 * 10…

The ROSAT Ultradeep HRI survey in the Lockman Hole contains a complete sample of 91 X-ray sources with fluxes in the 0.5-2 keV band larger than 1.2 times 10e-15 erg cm-2 s-1, where over about 75 per cent of the sources are quasars or…

The ROSAT Deep Survey includes a complete sample of 50 X-ray sources with fluxes in the $0.5 - 2$ keV band larger than 5.5 $10^{-15}$ erg cm$^{-2}$ s$^{-1}$ in the Lockman field (Hasinger et al., Paper I). We have obtained deep broad-band…

We present the X-ray spectra of 86 optically-identified sources in the 13H XMM-Newton/Chandra deep field which have >70 X-ray counts. The sample consists of 50 broad line AGN, 25 narrow emission line galaxies, 6 absorption line galaxies,…

The nature of the low- to intermediate-luminosity (Lx$\,\sim 10^{32-34}$ erg s$^{-1}$) source population revealed in hard band (2-10 keV) X-ray surveys of the Galactic Plane is poorly understood. To overcome such problem we cross-correlated…

We analyse the ROSAT PSPC spectrum of 19 X-ray selected Narrow Emission Line Galaxies (NELGs) discovered during the optical identification of sources in the ROSAT UK Deep Survey. Their properties are compared to those of broad line Active…

We present optical and X-ray data for a sample of serendipitous XMM-Newton sources that are selected to have 0.5-2 keV vs 2-4.5 keV X-ray hardness ratios which are harder than the X-ray background. The sources have 2-4.5 keV X-ray flux >=…

We present X-ray and optical analysis of 188 AGN identified from 497 hard X-ray (f (2.0-8.0 keV) > 2.7x10^-15 erg cm^-2 s^-1) sources in 20 Chandra fields (1.5 deg^2) forming part of the Chandra Multi-wavelength Project. These medium depth…

We report on optical searches in the error circles of 93 ROSAT survey sources located at low galactic latitudes (|b| < 20 deg). These sources were extracted from the ROSAT Galactic Plane Survey using various selection criteria on hardness…

We present an X-ray and optical analysis of a 2-8 keV flux limited (fx > 10e-14 erg s^-1 cm^-2) sample of 126 AGN detected in 16 Chandra fields. This work represents a small though significant subset of the Chandra Multiwavelength Project…

We selected a sample of sources with high X-ray over optical flux ratio from the ROSAT PSPC archives. Out of the 16 sources in our sample, one is a (possibly extreme) BL Lac and two are AGNs. Six more sources are tentatively classified as…