Polarimetric and spectroscopic study of radio-quiet weak emission line quasars

Abstract

A small subset of optically selected radio-quiet quasars showing weak or no emission lines may turn out to be the elusive radio-quiet BL Lac objects, or simply be radio-quiet QSOs with a still-forming/shielded broad line region (BLR). High polarisation ($p$ $>$ 3$-$4$\%$), a hallmark of BL Lacs, can be used to test whether some optically selected `radio-quiet weak emission line quasars' (RQWLQs) show a fractional polarisation high enough to qualify as radio-quiet analogs of BL Lac objects. Out of the observed six RQWLQs candidates showing an insignificant proper motion, only two are found to have $p$ $>$ 1$\%$. For these two RQWLQs, namely J142505.59$+$035336.2, J154515.77+003235.2, we found polarisation of 1.03$\pm$0.36$\%$, 1.59$\pm$0.53$\%$ respectively, which again is too modest to justify a (radio-quiet) BL Lac classification. We also present here a statistical comparison of the optical spectral index, for a set of 40 RQWLQs with redshift-luminosity matched control sample of 800 QSOs and an equivalent sample of 120 blazars. The spectral index distribution of RQWLQs is found to differ, at a high significance level, from that of blazars and is consistent with that of the ordinary QSOs. Likewise, a structure-function analysis of photometric light curves presented here suggests that the mechanism driving optical variability in RQWLQs is similar to that operating in QSOs and different from that of blazars. These findings are consistent with the common view that the central engine in RQWLQs, as a population, is akin to that operating in normal QSOs and the primary differences between them might be related to differences in the BLR.

arXiv comment9 pages, 5 figures, Accepted for publication in MNRAS

References in corpus (38)

• The Sloan Digital Sky Survey: Technical Summary
• The Gaia mission
• The Seventh Data Release of the Sloan Digital Sky Survey
• Unified Schemes for Radio-Loud Active Galactic Nuclei
• First Results from the Catalina Real-time Transient Survey
• Spectral Classification and Redshift Measurement for the SDSS-III Baryon Oscillation Spectroscopic Survey
• The Connection between X-ray- and Radio-Selected BL Lacertae Objects
• On the Disappearance of the Broad-Line Region in Low-Luminosity Agns
• High-Redshift SDSS Quasars with Weak Emission Lines
• Selecting Quasars by their Intrinsic Variability
• The Lack of BLR in Low Accretion Rate AGN as Evidence of their Origin in the Accretion Disk
• Variability in active galactic nuclei: confrontation of models with observations
• Optically Selected BL Lacertae Candidates from the Sloan Digital Sky Survey Data Release Seven
• Cold Accretion Disks and Lineless Quasars
• Optically identified BL Lacertae objects from the Sloan Digital Sky Survey
• A novel variability-based method for quasar selection: evidence for a rest frame ~54 day characteristic timescale
• Intranight optical variability of Blazars
• Clear Evidence for Intranight Optical Variability in Radio-quiet Quasars
• Intranight optical variability of radio-quiet and radio lobe dominated quasars
• Multiwavelength Observations of Radio-quiet Quasars with Weak Emission Lines
• SDSS J094533.99+100950.1 - the remarkable weak emission line quasar
• Intra-night optical variability of core dominated radio quasars: the role of optical polarization
• Dusty torus formation by anisotropic radiative pressure feedback of active galactic nuclei
• A large sample of Kohonen-selected SDSS quasars with weak emission lines: selection effects and statistical properties
• Highly Polarized Optically-Selected BL Lacertae Objects
• Optical variability properties of high luminosity AGN classes
• The 2dF BL Lac Survey
• Rapid optical variability of TeV blazars
• Polarimetry of optically selected BL Lac candidates from the SDSS
• Intranight Optical Variability of Radio-Quiet Weak Emission Line Quasars-III
• The environment of weak emission-line quasars
• Intranight Optical Variability of Radio-Quiet Weak Emission Line Quasars
• Long-term optical photometric monitoring of the quasar SDSS J153259.96-003944.1
• Intranight Optical Variability of Radio-Quiet Weak Emission Line Quasars-II
• Intranight Optical Variability of Radio-Quiet Weak Emission Line Quasars-IV
• Multi-epoch intra-night optical monitoring of 8 radio-quiet BL Lac candidates
• On the signatures of flare-induced global waves in the Sun: GOLF and VIRGO observations
• Intranight optical variability of radio-quiet BL Lacertae objects

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