Intra-night optical variability characteristics of different classes of narrow line Seyfert 1 galaxies
2016
In a first systematic effort to characterize the intra-night optical variability (INOV) of different classes of narrow line Seyfert 1 (NLSy1)
galaxies, we have carried out observations on a sample of radio-
loud(RL) and radio-quiet (RQ) NLSy1
galaxies. The RL-NLSy1
galaxiesare further divided into {\gamma}-ray
loud(GL) and {\gamma}-ray quiet (GQ) NLSy1
galaxies. Our sample consists of four
sets, each
setconsisting of a RQ-NLSy1, a GQ-NLSy1 and a GL-NLSy1
galaxy, closely matched in redshift and optical luminosity. Our observations on both RQ and GQ-NLSy1
galaxiesconsist of a total of 19 nights, whereas the data for GL-NLSy1
galaxies(18 nights) were taken from literature published earlier by us. This enabled us to do a comparison of the duty cycle (DC) of different classes of NLSy1
galaxies. Using power-enhanced F-test, with a variability threshold of 1%, we find DCs of about 55%, 39% and 0% for GL, GQ and RQ-NLSy1
galaxiesrespectively. The high DC and large amplitude of INOV (24.0 +/- 13.7%) shown by GL-NLSy1
galaxiesrelative to the other two classes might be due to their inner aligned relativistic jets having large bulk
Lorentz factors. The null DC of RQ-NLSy1
galaxiescould mean the presence of low power and/or largely misaligned jets in them. However, dividing RL-NLSy1
galaxiesinto low and high optical polarization sources, we find that sources with large polarization show somewhat higher DCs (69%) and amplitudes (29%) compared to those with low polarization. This points to a possible link between INOV and optical polarization.
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