Related papers: On the lensed blazar B0218+357

The classification of gamma-ray-detected blazar candidates of uncertain type (BCU) is a relevant problem in extragalactic gamma-ray astronomy. Here we report the optical spectroscopic characterization, using two 3-4~m class telescopes,…

We obtained MMT spectra of the gravitational lens candidate UM425 to compare the redshifts and line profile structures of lens components A and B, which are separated by ~6.5". The CIV lambda 1550 A emission in both A and B exhibits Broad…

We present Keck Cosmic Web Imager spectroscopy of the four putative images of the lensed quasar candidate J014709+463037 recently discovered by Berghea et al. (2017). The data verify the source as a quadruply lensed, broad absorption-line…

We present high-resolution imaging and low-resolution spectroscopy of the BL Lac object PKS 0537-441 (z = 0.893) and its environment. The observations were designed to clarify, whether the properties of PKS 0537-441 are affected by…

We searched for 21-cm absorption associated with the z_abs = 1.3647 absorption system toward PKS 0237-233 using the GMRT. A high quality UVES spectrum shows that C I and C I* are detected at this redshift together with C II*, Mg I, Mg II,…

(Abridged) We perform a detailed analysis of the optical gravitational lens ER 0047-2808 imaged with WFPC2 on the Hubble Space Telescope. Using software specifically designed for the analysis of resolved gravitational lens systems, we focus…

We report observations of the z = 3.87 broad absorption line quasar APM 08279+5255 (Irwin et al. 1998) with the Adaptive Optics Bonnette (AOB) of the Canada-France-Hawaii Telescope. The object is found to be a double source. The separation…

We investigate potential $\gamma-\gamma$ absorption of gamma-ray emission from blazars arising from inhomogeneities along the line of sight, beyond the diffuse Extragalactic Background Light (EBL). As plausible sources of excess…

We present the first results from a program of near-infrared spectroscopy aimed at studying the familiar rest-frame optical emission lines from the H II regions of Lyman break galaxies at z = 3. By targeting redshifts which bring the lines…

We present the observations of the gravitationally lensed system QSO 2237+0305 performed with the Chandra X-ray Observatory on 2000 Sept. 6, and on 2001 Dec. 8 for 30.3 ks and 9.5 ks, respectively. Imaging analysis resolves the four X-ray…

In a recent paper Pello et al. reported observations of a faint galaxy, gravitationally lensed by the galaxy cluster Abell 1835. Deep J-band spectroscopy revealed a weak emission line near 1.34 microns, detected in two spectra with…

We present the results of the first long-term (2.2 years) spectroscopic monitoring of a gravitationally lensed quasar, namely the Einstein Cross Q2237+0305. We spatially deconvolve deep VLT/FORS1 spectra to accurately separate the spectrum…

We use high-resolution UV spectra of the radio-quiet QSO H1821+643 (z_em = 0.297), obtained with STIS and FUSE, to study the ionization and metallicity of an intervening O VI absorption line system at z(abs) = 0.1212. This absorber has the…

We report the discovery of a new low-redshift galaxy-scale gravitational lens, identified from a systematic search of publicly available MUSE observations. The lens galaxy, 2MASXJ04035024-0239275, is a giant elliptical at $z$ = 0.06604 with…

We present UV spectroscopy from HST/GHRS and reanalyze existing H_alpha images of the quasar/galaxy pair 3C 232/NGC 3067 and of the halo gas associated with NGC 3067. The spectra permit measurement of, or limits on, the column densities of…

We report a tentative detection with the IRAM 30m telescope of the LiH molecule in absorption in front of the lensed quasar B0218+357. We have searched for the J = 0 -- 1 rotational line of lithium hydride at 444 GHz (redshifted to 263…

In recent years, changing-look blazars have called the traditional view of BL Lacs-flat spectrum radio quasars into question within the empirical classification of blazars. Based on the intensity of optical lines, they appear to transition…

We discuss observational properties of strong emission-line galaxies at low redshift found by our deep imaging survey for high-redshift Ly alpha emitters. In our surveys, we used the narrowband filter, NB816 (lambda_center=8150A with FWHM =…

We present the observation of a new intermediate redshift damped Lyman-alpha absorption system candidate, discovered in the course of a spectroscopic follow-up for identifying the sources detected in a 150 A wide bandpass UV-imaging survey…

The blazar zone in quasars is commonly assumed to be located inside the broad-line region at some hundreds of Schwartzschild radii from the central black hole. Now, the simultaneous Fermi/LAT and MAGIC observations of a strong flare in the…