相关论文: Variable Extended Objects in SA 57

Variability selection has been proposed as a powerful tool for identifying both low-luminosity AGN and those with unusual SEDs. However, a systematic study of sources selected in such a way has been lacking. In this paper, we present the…

With upcoming all sky surveys such as LSST poised to generate a deep digital movie of the optical sky, variability-based AGN selection will enable the construction of highly-complete catalogs with minimum contamination. In this study, we…

We present results from a study to detect variable galaxies in the Hubble Deep Field North. The goal of this project is to investigate the number density of AGN at z=1 through the detection of variable galaxy nuclei. The advantage of HST is…

Methane brown dwarfs, i.e. objects similar to the low mass star Gliese 229B, are characterized by very unusual colours: J-K<~0 and I-J>~5. An analysis of the ESO public images, which cover an area of 37 sq. arcmin in the three filters,…

We describe the selection of a sample of photometrically-defined Lyman break galaxies (LBGs) at z~5 using the multi-wavelength imaging data of the ESO Remote Galaxy Survey (ERGS). The data is drawn from ten widely-separated fields covering…

This paper presents the analysis of a statistically complete sample of 28 serendipitous X-ray sources selected in 82 pointed XMM-Newton fields down to a count-rate of 0.002 counts s^-1(4.5-7.5 keV energy band). This is the first sample…

We explore the properties of X-ray Bright Optically Inactive Galaxies (XBONG) detected in the 0.5-8 keV spectral band in 20 public XMM fields overlapping with the SDSS. We constrain our sample to optically extended systems with log (f_X/f_o…

Aims: We used data from the 58 month long, continuous Swift/Burst Alert Telescope (BAT) observations of the five brightest Seyfert galaxies at hard X-rays, to study their flux and spectral variability in the 20-100 keV energy band. The…

[ABRIGED] We present the optical identification of a sample of 695 X-ray sources detected in the first 1.3 deg^2 of the XMM-COSMOS survey, down to a 0.5-2 keV (2-10 keV) limiting flux of ~10^-15 erg cm-2 s-1 (~5x10^-15 erg cm^-2 s-1). We…

Low luminosity active galactic nuclei (LLAGN) probe accretion physics in the low Eddington regime and can provide additional clues about galaxy evolution. AGN variability is ubiquitous and thus provides a reliable tool for finding AGN. We…

We present optical spectroscopy of a sample of 77 luminous AGN and quasars selected on the basis of their mid-infrared colors. Our objects are selected from the Spitzer Extragalactic First Look Survey and SWIRE XMM-LSS fields, with a…

We have detected a population of predominantly blue (B-V <= 1.1) stars in the direction l = 167 deg., b = -35 deg. (Kapteyn Selected Area 71) that cannot be accounted for by standard starcount models. Down to V ~ 20, the colors and…

The Two Micron All-Sky Survey (2MASS) has provided a uniform photometric catalog to search for previously unknown red AGN and QSOs. We have extended the search to the southern equatorial sky by obtaining spectra for 1182 AGN candidates…

We observed 37 AGN candidates and classified them on the basis of their spectroscopic properties; three are confirmed QSOs, one is a BL Lac object, nine are Seyfert 1 galaxies, four Seyfert 2s, while twenty are HII regions.

Variability across the electromagnetic spectrum is a property of AGN that can help constraining the physical properties of these galaxies. This is the third of a serie of papers with the aim of studying the X-ray variability of different…

Compact Symmetric Objects (CSOs) are a distinct category of jetted active galactic nuclei (AGN) whose optical variability characteristics have not been well investigated. We present here the results of our investigation on the optical flux…

We present the results of X-ray spectral analysis of 22 active galactic nuclei (AGNs) with a small scattering fraction selected from the Second XMM-Newton Serendipitous Source Catalogue using hardness ratios. They are candidates of buried…

We present variability analysis of data from the Northern Sky Variability Survey (NSVS). Using the clustering method which defines variable candidates as outliers from large clusters, we cluster 16,189,040 light curves, having data points…

Quasi-stellar objects (QSOs) whose spectral energy distributions (SEDs) are reddened by dust either in their host galaxies or in intervening absorber galaxies are to a large degree missed by optical color selection criteria like the one…

The main criterium for the selection of active objects in the First Byurakan Survey was the presence of uv-excess on low-dispersion spectra registered on photographic plates obtained with the 1m Shmidt type Byurakan telescope. Using the…