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561. Optical identifications of radio sources
ID:
ivo://CDS.VizieR/J/A+AS/115/11
Title:
Optical identifications of radio sources
Short Name:
J/A+AS/115/11
Date:
21 Oct 2021
Publisher:
CDS
Description:
CCD images of the fields of 115 radio sources from the 1Jy, S4 and S5 catalogues are presented. New optical counterparts have been found for a total of 34 sources, a large fraction of which had as yet only been described as empty fields on Sky Survey Plates. Of the 54 radio sources with previously published identifications, 50 optical counterparts have been confirmed while for 4 sources new identifications are proposed. R band magnitudes, derived from the CCD images, are provided for all but a few identified optical counterparts. The fields at the positions of 27 radio sources are still empty down to a limiting magnitude of at least m_R_=22mag, requiring much deeper optical as well as additional infrared images for establishing their optical counterparts.
562. Optical-infrared colors of CORALS QSOs
ID:
ivo://CDS.VizieR/J/AJ/130/1345
Title:
Optical-infrared colors of CORALS QSOs
Short Name:
J/AJ/130/1345
Date:
21 Oct 2021
Publisher:
CDS
Description:
The presence of dust in quasar absorbers, such as damped Ly{alpha} (DLA) systems, may cause the background QSO to appear reddened. We investigate the extent of this potential reddening by comparing the optical-to-infrared colors of QSOs with and without intervening absorbers. Our QSO sample is based on the Complete Optical and Radio Absorption Line System (CORALS) survey of Ellison and coworkers. The CORALS data set consists of 66 radio-selected QSOs at z_em_>=2.2 with complete optical identifications. We have obtained near-simultaneous B- and K-band magnitudes for a subset of the CORALS sample and supplemented our observations with further measurements published in the literature. In total, we have B-K colors for 42 of the 66 QSOs, of which 14 have intervening DLA systems. To account for redshift-related color changes, the B-K colors are normalized using the Sloan Digital Sky Survey QSO composite.
563. Optical/IR observ. of Radio Galaxies and QSOs
ID:
ivo://CDS.VizieR/J/MNRAS/238/1171
Title:
Optical/IR observ. of Radio Galaxies and QSOs
Short Name:
J/MNRAS/238/1171
Date:
21 Oct 2021
Publisher:
CDS
Description:
This catalog reports on an extensive optical and infrared study of the 178 radio sources in the Parkes Selected Regions (S > 100 mJy at 2.7 GHz). CCD observations have resulted in the essential completion (95 percent) of optical identifications and have provided B and R photometry. In addition, K photometry has been completed for four of the six selected regions.
564. Optical LCs of QSO J0924+0219 lensed quasar
ID:
ivo://CDS.VizieR/J/ApJ/806/258
Title:
Optical LCs of QSO J0924+0219 lensed quasar
Short Name:
J/ApJ/806/258
Date:
21 Oct 2021
Publisher:
CDS
Description:
We analyze the optical, UV, and X-ray microlensing variability of the lensed quasar SDSS J0924+0219 using six epochs of Chandra data in two energy bands (spanning 0.4-8.0keV, or 1-20keV in the quasar rest frame), 10 epochs of F275W (rest-frame 1089{AA}) Hubble Space Telescope data, and high-cadence R-band (rest-frame 2770{AA}) monitoring spanning 11 years. Our joint analysis provides robust constraints on the extent of the X-ray continuum emission region and the projected area of the accretion disk. The best-fit half-light radius of the soft X-ray continuum emission region is between 5x10^13^ and 10^15^cm, and we find an upper limit of 10^15^cm for the hard X-rays. The best-fit soft-band size is about 13 times smaller than the optical size, and roughly 7GM_BH_/C^2^ for a 2.8x10^8^M_{sun}_ black hole, similar to the results for other systems. We find that the UV emitting region falls in between the optical and X-ray emitting regions at 10^14^cm<r_1/2.UV_<3x10^15^cm. Finally, the optical size is significantly larger, by 1.5{sigma}, than the theoretical thin-disk estimate based on the observed, magnification-corrected I-band flux, suggesting a shallower temperature profile than expected for a standard disk.
565. Optical light curves of PHL1811 and 3C273
ID:
ivo://CDS.VizieR/J/ApJS/213/26
Title:
Optical light curves of PHL1811 and 3C273
Short Name:
J/ApJS/213/26
Date:
21 Oct 2021
Publisher:
CDS
Description:
Variability is one of the most observable characteristics of active galactic nuclei, and it is important when considering the emission mechanism. In this paper, we report optical photometry monitoring of two nearby brightest quasars, PHL 1811 and 3C 273, using the ST-6 camera attached to the Newtonian focus and the Ap6E CCD camera attached to the primary focus of the 70cm meniscus telescope at the Abastumani Observatory, Georgia. PHL 1811 was monitored during the period from 2002 September to 2012 December, while 3C 273 was monitored during the period from 1998 February to 2008 May. During our monitoring period, the two sources did not show any significant intra-day variability. The largest detected variations are {Delta}R=0.112+/-0.010mag. for PHL 1811, {Delta}B=0.595+/-0.099mag, {Delta}V=0.369+/-0.028mag, {Delta}R=0.495+/-0.076mag, and {Delta}I=0.355+/-0.009mag for 3C 273. When the periodicity analysis methods are adopted for the observations of the sources, a period of p=5.80+/-1.12yr is obtained for PHL 1811 in the R light curve in the present work, and periods of p=21.10+/-0.14, 10.00+/-0.14, 7.30+/-0.09, 13.20+/-0.09, 2.10+/-0.06, and 0.68+/-0.05yr are obtained for 3C 273 based on the data in the present work combined with historical works.
566. Optical linear polarization at McDonald Obs.
ID:
ivo://CDS.VizieR/J/ApJS/194/19
Title:
Optical linear polarization at McDonald Obs.
Short Name:
J/ApJS/194/19
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present 976 previously unpublished optical linear polarization measurements of quasars, active galactic nuclei, and some stars observed for interstellar polarization. The observations, covering the period 1981-2000, were made with McDonald Observatory's 2.1m Struve reflector and the Breger photopolarimeter.
567. Optically bright AGN in ROSAT-FSC
ID:
ivo://CDS.VizieR/J/A+A/414/487
Title:
Optically bright AGN in ROSAT-FSC
Short Name:
J/A+A/414/487
Date:
21 Oct 2021
Publisher:
CDS
Description:
To build a large, optically bright, X-ray selected AGN sample we have correlated the ROSAT-FSC (<IX/29>) catalogue of X-ray sources with the USNO (<I/252>) catalogue limited to objects brighter than O=16.5 and then with the APS (<VII/214>) database. Each of the 3212 coincidences was classified using the slitless Hamburg spectra. 493 objects were found to be extended and 2719 starlike. Using both the extended objects and the galaxies known from published catalogues we built up a sample of 185 galaxies with O(APS)<17.0mag, which are high-probability counterparts of RASS-FSC X-ray sources. 130 galaxies have a redshift from the literature and for another 34 we obtained new spectra. The fraction of Seyfert galaxies in this sample is 20%. To select a corresponding sample of 144 high-probability counterparts among the starlike sources we searched for very blue objects in an APS-based color-magnitude diagram. Forty-one were already known AGN and for another 91 objects we obtained new spectra, yielding 42 new AGN, increasing their number in the sample to 83. This confirms that surveys of bright QSOs are still significantly incomplete. On the other hand we find that, at a flux limit of 0.02ct/s and at this magnitude, only 40% of all QSOs are detected by ROSAT.
568. Optically faint obscured quasars
ID:
ivo://CDS.VizieR/J/A+A/424/545
Title:
Optically faint obscured quasars
Short Name:
J/A+A/424/545
Date:
21 Oct 2021
Publisher:
CDS
Description:
We use Virtual Observatory (VO) tools to identify optically faint, obscured (i.e., type 2) active galactic nuclei (AGN) in the two Great Observatories Origins Deep Survey (GOODS) fields. By employing publicly available X-ray and optical data and catalogues we discover 68 type 2 AGN candidates.
569. Optically selected BL Lac objects from SDSS-DR7
ID:
ivo://CDS.VizieR/J/AJ/139/390
Title:
Optically selected BL Lac objects from SDSS-DR7
Short Name:
J/AJ/139/390
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a sample of 723 optically selected BL Lac candidates from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7) spectroscopic database encompassing 8250deg^2^ of sky; our sample constitutes one of the largest uniform BL Lac samples yet derived. Each BL Lac candidate has a high-quality SDSS spectrum from which we determine spectroscopic redshifts for ~60% of the objects. Redshift lower limits are estimated for the remaining objects utilizing the lack of host galaxy flux contamination in their optical spectra; we find that objects lacking spectroscopic redshifts are likely at systematically higher redshifts.
570. Optically thick absorbers near luminous quasars
ID:
ivo://CDS.VizieR/J/ApJ/651/61
Title:
Optically thick absorbers near luminous quasars
Short Name:
J/ApJ/651/61
Date:
21 Oct 2021
Publisher:
CDS
Description:
With close pairs of quasars at different redshifts, a background quasar sight line can be used to study a foreground quasar's environment in absorption. We search 149 moderate-resolution background quasar spectra from Gemini, Keck, the MMT, and the SDSS to survey Lyman limit systems (LLSs) and damped Ly{alpha} systems (DLAs) in the vicinity of 1.8<z<4.0 luminous foreground quasars. A sample of 27 new quasar-absorber pairs is uncovered with column densities 10^17.2^cm^-2^<NH<10^20.9^cm^-2^ and transverse (proper) distances of 22h^-1^kpc<R<1.7h^-1^Mpc from the foreground quasars.