Comparative intranight optical variability of X-ray and γ-ray-detected narrow-line Seyfert 1 galaxies

Abstract

In a systematic program to characterise the intra-night optical variability (INOV) of different classes of narrow-line Seyfert 1 galaxies (NLSy1s), we report here the first comparative INOV study of NLSy1 sets detected in the X-ray and γ-ray bands. Our sample consists of 18 sources detected in X-ray but not in γ-rays (hereafter x NLSy1s) and 7 sources detected in γ-rays (hereafter g NLSy1s), out of which 5 are detected also in X-rays. We have monitored these two sets of NLSy1s, respectively, in 24 and 21 sessions of a minimum of 3 hours duration each. The INOV duty cycles for these two sets are found to be 12% and 53%, respectively (at a 99% confidence level). In the set of 18 x NLSy1s, INOV duty cycle is found to be zero for the 13 radio-quiet members (monitored in 14 sessions) and 43% for the 5 radio-loud members (10 sessions). The latter is very similar to the aforementioned duty cycle of 53% found here for the set of g NLSy1s (all of which are radio-loud). Thus it appears that the radio loudness level is the prime factor behind the INOV detection and the pattern of the high-energy radiation plays only a minor role.

Jetted Narrow-Line Seyfert 1 Galaxies & Co.: Where Do We Stand?

“…Other studies at infrared/optical wavelengths [18,[269][270][271][272][273][274][275][276][277][278][279] and at X-rays [254,280,281] have been done.…”

Intra-night optical variability of $γ-$ray detected narrow-line Seyfert 1 galaxies

“…This source is known to exhibit strong optical variability on longer time scales as well (Maune et al 2013). Nonetheless, as an AGN class, γ-ray NLSy1s are marked by rather poorly known INOV characteristics, primarily because INOV observations have so far been reported for just 6 3 of them (Liu et al 2010;Paliya et al 2013aPaliya et al , 2016Kshama et al 2017;Ojha et al 2019Ojha et al , 2020b. Therefore, the primary aim of the present study is to bridge this knowledge gap, by determining the INOV characteristics of this rare and enigmatic class of AGN.…”

“…The possibility that misaligned relativistic jets could be hidden among radio-quiet AGNs has also been noted in the context of NLSy1 galaxies (e.g., Foschini 2011;Berton et al 2018). Nonetheless, INOV studies of these (low-luminosity) AGNs continue to be sparse and have been limited to a small data set (Miller et al 2000;Ferrara et al 2001;Klimek et al 2004;Liu et al 2010;Paliya et al 2013a;Kshama et al 2017;Ojha et al 2018;Paliya 2019;Ojha et al 2020b), even though they were discovered over 3 decades ago (Osterbrock & Pogge 1985) and basically defined by the rather small width of the optical Balmer emission lines, with full width at half-maximum (FWHM) being < 2000 km s −1 for Hβ (Osterbrock & Pogge 1985;, stronger permitted Fe II, and weak [O I I I ] emission lines such that the flux ratio of [O I I I ] λ5007 /Hβ is < 3 (Shuder & Osterbrock 1981). With some possible exceptions, they also show strong [Fe VII] and [Fe X] emission lines (Pogge 2011, see, however, Cracco et al 2016.…”

Intra-night optical variability study of a non-jetted narrow-line Seyfert 1 galaxy: SDSS J163401.94+480940.1

“…In addition to the criterion of FWHM(Hβ), two extreme optical characteristics such as relatively weak [O III ] and strong permitted Fe ii emission lines with [O III ] λ5007 /Hβ < 3 are used to define the NLSy1 galaxy (Shuder & Osterbrock, 1981). Moreover, NLSy1 galaxies (NLSy1s) also display other utmost observational characteristics such as steep soft X-ray spectra, rapid X-ray (in optical sometimes) flux variability, strong soft X-ray excess below 2 keV, and blue-shifted line profile (e.g., Brandt et al, 1997;Leighly, 1999;Vaughan et al, 1999;Komossa & Meerschweinchen, 2000;Miller et al, 2000;Zamanov et al, 2002;Klimek et al, 2004;Leighly & Moore, 2004;Boroson, 2005;Liu et al, 2010;Paliya et al, 2013a;Kshama et al, 2017;Ojha et al, 2019Ojha et al, , 2020b. It is believed that NLSy1s are young active galactic nuclei (AGNs) and represents an earlier stage in their evolution (e.g., Mathur, 2000;Sulentic et al, 2000;Mathur et al, 2001;Fraix-Burnet et al, 2017;Komossa, 2018;Paliya, 2019).…”