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Stickel, Eberhard; Groffmann, Hans-Dieter; Rau, Karl-Heinz

doi:10.1007/978-3-663-12126-8_8

Cited by 38 publications

(63 citation statements)

References 1 publication

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“…At most two of these, one CDQ (1225+317, with z = 2.219) and possibly one BL Lac (0735+178, with z > 0.424), lie at z > 1, so this sample provides a fairly even coverage of the redshift range up to z = 1 for each blazar subclass. Note that we have adopted a BL Lac classification for B2 1308+326, following the 1-Jy (Stickel, Fried & Kühr 1993) and Padovani & Giommi (1995) catalogues, even though it is classified as a CDQ in the Véron-Cetty & Véron (1998) catalogue. Also, for the BL Lac object PKS 0735+178 we have adopted a redshift z = 0.424, though formally the published value is z > 0.424 (see Véron-Cetty & Véron 1998).…”

Section: S a M P L E O B S E Rvat I O N S A N D R E D U C T I O N Smentioning

confidence: 99%

Intranight optical variability of blazars

Sagar

Stalin

Gopal-Krishna

et al. 2004

Monthly Notices of the Royal Astronomical Society

109

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We present results of a multi‐epoch intranight optical monitoring of 11 blazars consisting of six BL Lac objects and five radio core‐dominated quasars (CDQs). These densely sampled and sensitive R‐band CCD observations, carried out from 1998 November to 2002 May during a total of 47 nights with an average of 6.5 h per night, have enabled us to detect variability amplitudes as low as ∼1 per cent on intranight time‐scales. A distinction is found for the first time between the intranight optical variability (INOV) properties of the these two classes of relativistically beamed radio‐loud active galactic nuclei (AGNs). BL Lacs are found to show a duty cycle (DC) of INOV of ∼60 per cent, in contrast to CDQs, which show a much smaller INOV DC of ∼20 per cent, the difference being attributable mainly to the weakly polarized CDQs. On longer time‐scales (i.e. between a week to a few years) variability is seen from all the CDQs and BL Lacs in our sample. The results reported here form part of our long‐term programme to understand the intranight optical variability characteristics of the four main classes of luminous AGNs, i.e. radio‐quiet quasars (RQQs) and radio lobe‐dominated quasars (LDQs), as well as CDQs and BL Lac objects.

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Section: S a M P L E O B S E Rvat I O N S A N D R E D U C T I O N Smentioning

confidence: 99%

Intranight optical variability of blazars

Sagar

Stalin

Gopal-Krishna

et al. 2004

Monthly Notices of the Royal Astronomical Society

109

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“…These include the 3CR (Laing, Riley & Longair 1983) and MRC (Large et al 1981;Kapahi et al 1998a,b) samples selected at low radio frequencies, the 2-Jy all-sky survey at 2.7 GHz (Wall & Peacock 1985, and references therein), the PKS 100-mJy deep survey (Dunlop et al 1989) Wall & Peacock (1985) and the Dunlop et al (1989) surveys. It covers the region between 1358 # d # 1708 and consists of 270 sources with jb II j $ 108X This complete sample, with updates of the optical identifications and redshifts, has been presented by Stickel & Ku Èhr (1994).…”

Section: T H E S 4 S a M P L E O F R A D I O S O U R C E Smentioning

confidence: 99%

“…To improve the statistics for high-luminosity sources, we have also considered the complete sample of S4 radio sources (Kapahi 1981;Stickel & Ku Èhr 1994) with a 5000 ,1400 $ 0X5 and luminosity at 5000 MHz $ 5 Â 10 24 W Hz 21 sr 21 X The luminosity cut-off at 5000 MHz is similar to that at 178 MHz for a source with a spectral index of 0.8. In addition, we have considered the 3C and Peacock & Wall (1982, hereinafter referred to as PW) samples of CSS sources (Spencer et al 1989) satisfying the above luminosity cut-offs.…”

Section: S a M P L E O F S O U R C E S A N D T H E I R S Y M M E T R mentioning

confidence: 99%

Compact steep-spectrum sources from the S4 sample

Saikia

Jeyakumar

Salter

et al. 2001

Monthly Notices of the Royal Astronomical Society

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We present the results of 5-GHz observations with the VLA A-array of a sample of candidate Compact Steep Spectrum sources (CSSs) selected from the S4 survey. We also estimate the symmetry parameters of high-luminosity CSSs selected from different samples of radio sources, and compare these with the larger sources of similar luminosity to understand their evolution and the consistency of the CSSs with the unified scheme for radio galaxies and quasars. The majority of CSSs are likely to be young sources advancing outwards through a dense asymmetric environment. The radio properties of CSSs are found to be consistent with the unified scheme, in which the axes of the quasars are observed close to the line of sight, while radio galaxies are observed close to the plane of the sky.Comment: accepted for publication in mnras; 8 pages, figure 1 with 21 images, and two additional figures; 2 table

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“…Hardcastle (1998), however, showed that the WAT 3C 130 (z = 0.109) exhibits C 2004 RAS Notes. Redshifts are taken from Owen, Ledlow & Keel (1995), except for that of 0647+693 (Stickel & Kühr 1994) and 1610−608 (the cluster redshift, corrected for Local Group motions, from Struble & Rood (1999)). 1.4-GHz flux densities are from , except for 1610−608, where the flux density is from Christiansen et al (1977).…”

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confidence: 99%

Jet termination in wide-angle tail radio sources

Hardcastle

Sakelliou

2004

Monthly Notices of the Royal Astronomical Society

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Wide‐angle tail radio galaxies (WATs) are an uncommon class of radio sources with luminosities near the FR I/FR II break, and are usually associated with central cluster galaxies. Their defining characteristic when imaged sensitively at high resolution is their twin, well‐collimated jets, which can persist with low opening angle for tens of kiloparsecs before flaring into long, often bent, plumes. Although several models for the jet termination have been proposed, the majority of them are unsatisfactory when confronted with observations. Here we present the results of a programme of radio observations made with the aims of showing that objects classified as WATs do all have well‐collimated jets and of seeing in detail how the jets disrupt as they enter the plumes. We show that compact, ‘hotspot‐like’ features at the ends of the jets are common but by no means universal, and discuss the constraints that this places on models of the jet–plume transition. We discuss the properties of the observed well‐collimated jets, and, using relativistic beaming models, estimate their speed to be ∼0.3c. Finally, we show that the distance from the galactic centre at which the base of the plume is found is related to the temperature of the host cluster.

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H

Cited by 38 publications

References 1 publication

Intranight optical variability of blazars

Intranight optical variability of blazars

Compact steep-spectrum sources from the S4 sample

Jet termination in wide-angle tail radio sources

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