Intranight optical variability of radio-quiet BL Lacertae objects

Abstract

Aims. Intranight variation (or microvariation) is a common phenomenon of radio-loud BL Lac objects. However, it is not clear whether the recently found radio-quiet BL Lac objects have the same properties. The occurrence rate of intranight variation is helpful in distinguishing the mechanism of the continuum of radio-quiet BL Lac objects. Methods. We conducted a photometric monitoring of 8 radio-quiet BL Lac objects by the Xinglong 2.16 m and Lijiang 2.4 m telescopes. The differential light curves are calculated between each target and two comparison stars. To quantify the variation, the significance of variation is examined by a scaled F-test. Results. No significant variation is found in the 11 sessions of light curves of 8 radio-quiet BL Lac objects (one galactic source is excluded). The lack of microvariation in radio-quiet BL Lac objects is consistent with the detection rate of microvariation in normal radio-quiet AGNs, but much lower than for radio-loud AGNs. This result indicates that the continua of the radio-quiet BL Lac objects are not dominated by jets that will induce frequent microvariations.

The Covering Factor of Warm Dust in Weak Emission-Line Active Galactic Nuclei

“…They claimed that their variability duty cycles are higher than for radio-quiet quasars and radio lobe-dominated quasars. However, Liu et al (2015) have not detected significant microvariations in eight WLAGNs. The properties of WLAGNs are different from those of BL Lac objects, but consistent with normal AGNs in most respects except for their featureless spectra.…”

Resveratrol Directly Controls the Activity of Neuronal Ryanodine Receptors at the Single-Channel Level

“…The goal of our study was to identify and measure the control of brain RyR activity by one such molecule with potential pharmacological benefits for the therapy of neurodegenerative processes, trans-resveratrol. As a naturally occurring stilbenoid compound with multiple potential medicinal applications in cardiovascular, neurological and inflammatory disorders (51)(52)(53)(54)(55), trans-resveratrol affects several cellular signaling pathways involved in disease pathogenesis, most notably through its antioxidant properties by directly scavenging reactive oxygen species and by upregulating neuronal antioxidant proteins, such as quinone reductase 2 and heme oxygenase 1 (56)(57)(58)(59)(60), but also by a range of pleiotropic effects such as inhibiting pro-inflammatory signaling and enhancing NF-κB signaling (54,58,61). While trans-resveratrol directly attenuates programmed cell death and calcium toxicity induced by oxygen-glucose deprivation in primary neurons (62), it also stimulates cell cycle arrest, caspase activation, cytochrome c release and apoptosis in a range of cancer cell lines (63)(64)(65)(66)(67).…”

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

“…These are the two main characteristic properties of BL Lac objects; namely an optical polarisation, p > 3% (e.g., Heidt & Nilsson 2011) and an INOV duty cycle approaching the level of ∼50 percent (at an INOV amplitude ψ > 3%) (e.g, Gopal-Krishna et al 2003;Sagar et al 2004;Stalin et al 2004a,b;Gopal-Krishna et al 2011;Goyal et al 2012). To characterize INOV of RQWLQs, our group has recently analysed a sample of 70 intranight light curves of 34 RQWLQs (Gopal-Krishna et al 2013;Chand et al 2014;Kumar et al 2015Kumar et al , 2016Kumar et al , 2017 and re-ported that two of the RQWLQs in two separate sessions exhibited strong INOV with ψ > 10%, like that of BL Lacs, though the duty cycle of INOV was found to be only about ∼ 5% which is typical of normal radioquiet QSOs (Kumar et al 2017, and references therein, see also Liu et al 2015). On the other hand, efforts for a systematic polarimetric characterization of radio-quiet BL Lac candidates have been quite limited, although polarimetric surveys have been reported for WLQs in general (e.g, Smith et al 2007;Heidt & Nilsson 2011).…”