Optical Identification of New Quasi-Stellar Radio Sources.

Sandage, Allan; Véron, Philippe; Wyndham, John

doi:10.1086/148415

Cited by 35 publications

(22 citation statements)

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“…The post‐1965 maximum optical variation, Δ B =5.88 mag [from 18.01 mag (Sandage et al 1965) to 12.13 mag (Webb et al 1990)], is greater than that in the infrared (Δ K =4.59 mag). During the 1952–75 period, there are a few optical records of observations, and only one event, in 1974 May, indicates 3C 279 to be brighter than B =15.5: B =15.68 in 1966 December, while B =13.6 in 1974 May (Eachus & Liller 1975).…”

Section: Discussionmentioning

confidence: 99%

“…Simultaneous multiwavelength observations have been carried out by many groups (Kidger et al 1992a, and references therein;Shrader et al 1994;Hartman et al 1996). The post-1965 maximum optical variation, DB 5X88 mag [from 18.01 mag (Sandage et al 1965) to 12.13 mag (Webb et al 1990, is greater than that in the infrared DK 4X59 mag. During the 1952±75 period, there are a few optical records of observations, and only one event, in 1974 May, indicates 3C 279 to be brighter than B 15X5 : B 15X68 in 1966 December, while B 13X6 in 1974 May (Eachus & Liller 1975).…”

Section: Discussionmentioning

confidence: 99%

“…For comparison, the optical data have also been compiled and analysed using the Jurkevich method. The optical data are from the literature (Sandage, Veron & Wyndham 1965;Tritton & Selmes 1971;Visanathan 1973;O'Dell et al 1978;Sitko et al 1982;Carini & Miller 1988;Kidger & Allan 1988;Sadun 1988;Webb 1988;Brown et al 1989a;Sadun & Carini 1989;Mead et al 1990;Webb et al 1990;Kidger et al 1992a). When the infrared data (Neugebauer et al 1979) are converted into optical data with an adopted optical±near-infrared spectral index of 21X6 (Sitko et al 1982) (see Webb et al 1990) and the Jurkevich method is used for the optical data, similar results to those for the near-infrared are q 1999 RAS, MNRAS 308, 1032±1036 obtained and shown in Fig.…”

Section: Periodicitymentioning

confidence: 99%

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Infrared variability properties of the blazar 3C 279

Jiang

1999

Monthly Notices of the Royal Astronomical Society

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The long‐term (about 27 years) near‐infrared K light curve is constructed from the published literature for the blazar 3C 279. The Jurkevich method is adopted to analyse the periodicity, and a strong 7.1±0.44 yr period is found, suggesting that the next near‐infrared outburst will occur in 2002/03. The correlation between colour index (spectral index) and magnitude is discussed, and a significant correlation between (J−H) and K is found with a correlation coefficient r=0.72 (p=2.0×10−10), which is consistent with Brown et al.’s proposal.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Periodicitymentioning

confidence: 99%

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Infrared variability properties of the blazar 3C 279

Jiang

1999

Monthly Notices of the Royal Astronomical Society

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“…On the other hand, multiwavelength observations suggest that the jet component contributes to the core flux from radio to X-rays. Significant variability of core flux with a factor ≃ 2 at timescale of years has been observed in radio and optical bands (Sandage et al 1965;Hough et al 2002;Schneider et al 2010). And the spectrum of the core X-ray emission is very hard (Γ ≃ 1.5).…”

Section: Summary and Discussionmentioning

confidence: 99%

DISCOVERY OFγ-RAY EMISSION FROM THE STRONGLY LOBE-DOMINATED QUASAR 3C 275.1

Liao¹,

Xin²,

Li³

et al. 2015

ApJ

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We systematically analyze the 6-year Fermi/LAT data of the lobe-dominated quasars (LDQs) in the complete LDQ sample from 3CRR survey and report the discovery of high-energy γ-ray emission from 3C 275.1. The γ-ray emission of 3C 207 is confirmed and significant variability of the lightcurve is identified. We do not find statistically significant γ-ray emission from other LDQs. 3C 275.1 is the known γ-ray quasar with the lowest core dominance parameter (i.e., R = 0.11). We also show that both the northern radio hotspot and parsec jet models can reasonably reproduce the γ-ray data. The parsec jet model, however, is favored by the potential γ-ray variability at the timescale of months. We suggest that some dimmer γ-ray LDQs will be detected in the future and LDQs could contribute non-negligibly to the extragalactic γ-ray background.

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“…All these studies benefit from efficient and/or complete selection of large quasar samples. Sandage et al (1965) pioneered quasar selection through the use of multicolor imaging data. Because quasars are not characterized by a single temperature like stars, they usually occupy different regions of color space.…”

Section: Introductionmentioning

confidence: 99%

A Study of Quasar Selection in the Supernova Fields of the Dark Energy Survey

Tie¹,

Martini²,

Mudd³

et al. 2017

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We present a study of quasar selection using the supernova fields of the Dark Energy Survey (DES). We used a quasar catalog from an overlapping portion of the SDSS Stripe 82 region to quantify the completeness and efficiency of selection methods involving color, probabilistic modeling, variability, and combinations of color/ probabilistic modeling with variability. In all cases, we considered only objects that appear as point sources in the DES images. We examine color selection methods based on the Wide-field Infrared Survey Explorer2 color, a mixture of WISE and DES colors (g − i andiW 1), and a mixture of Vista Hemisphere Survey and DES colors (g − i and i − K ). For probabilistic quasar selection, we used XDQSO, an algorithm that employs an empirical multi-wavelength flux model of quasars to assign quasar probabilities. Our variability selection uses the multi-band χ 2 -probability that sources are constant in the DES Year 1 griz-band light curves. The completeness and efficiency are calculated relative to an underlying sample of point sources that are detected in the required selection bands and pass our data quality and photometric error cuts. We conduct our analyses at two magnitude limits, i<19.8 mag and i<22 mag. For the subset of sources with W1 and W2 detections, the -W W 1 2 color or XDQSOz method combined with variability gives the highest completenesses of >85% for both i-band magnitude limits and efficiencies of >80% to the bright limit and >60% to the faint limit; however, the giW1 and giW1+variability methods give the highest quasar surface densities. The XDQSOz method and combinations of W1W2/giW1/XDQSOz with variability are among the better selection methods when both high completeness and high efficiency are desired. We also present the OzDES Quasar Catalog of 1263 spectroscopically confirmed quasars from three years of OzDES observation in the 30 deg 2 of the DES supernova fields. The catalog includes quasars with redshifts up to z∼4 and brighter than i = 22 mag, although the catalog is not complete up to this magnitude limit.

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Optical Identification of New Quasi-Stellar Radio Sources.

Cited by 35 publications

References 0 publications

Infrared variability properties of the blazar 3C 279

Infrared variability properties of the blazar 3C 279

DISCOVERY OFγ-RAY EMISSION FROM THE STRONGLY LOBE-DOMINATED QUASAR 3C 275.1

A Study of Quasar Selection in the Supernova Fields of the Dark Energy Survey

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