Intranight Variability Research Articles

Are there broad absorption-line blazars?

Abstract We report the first systematic search for blazars among broad-absorption-line (BAL) quasars. This is based on our intranight optical monitoring of a well-defined sample of 10 candidates selected on the criteria of a flat spectrum and an abnormally high linear polarization at radio wavelengths. A small population of BAL blazars can be expected in the ‘polar model’ of BAL quasars. However, no such case is found, since none of our 30 monitoring sessions devoted to the 10 candidates yielded a positive detection of intra-night optical variability (INOV), which is uncharacteristic of blazars. This lack of INOV detection contrasts with the high duty cycle of INOV observed for a comparison sample of 15 ‘normal’ (i.e., non-BAL) blazars. Some possible implications of this are pointed out.

Nocturnal low-level clouds in the atmospheric boundary layer over southern West Africa: an observation-based analysis of conditions and processes

Abstract. During the West African summer monsoon season, extended nocturnal stratiform low-level clouds (LLCs) frequently form in the atmospheric boundary layer over southern West Africa and persist long into the following day affecting the regional climate. A unique data set was gathered within the framework of the Dynamics–Aerosol–Chemistry–Cloud Interactions in West Africa (DACCIWA) project, which allows, for the first time, for an observational analysis of the processes and parameters crucial for LLC formation. In this study, in situ and remote sensing measurements from radiosondes, ceilometer, cloud radar and energy balance stations from a measurement site near Savè in Benin are analyzed amongst others for 11 nights. The aim is to study LLC characteristics, the intranight variability of boundary layer conditions and physical processes relevant for LLC formation, as well as to assess the importance of these processes. Based on the dynamic and thermodynamic conditions in the atmospheric boundary layer we distinguish typical nocturnal phases and calculate mean profiles for the individual phases. A stable surface inversion, which forms after sunset, is eroded by differential horizontal cold air advection with the Gulf of Guinea maritime inflow, a cool air mass propagating northwards from the coast in the late afternoon and the evening, and shear-generated turbulence related to a nocturnal low-level jet. The analysis of the contributions to the relative humidity changes before the LLC formation reveals that cooling in the atmospheric boundary layer is crucial to reach saturation, while specific humidity changes play a minor role. We quantify the heat budget terms and find that about 50 % of the cooling prior to LLC formation is caused by horizontal cold air advection, roughly 20 % by radiative flux divergence and about 22 % by sensible heat flux divergence in the presence of a low-level jet. The outcomes of this study contribute to the development of a conceptual model on LLC formation, maintenance and dissolution over southern West Africa.

Intra-night optical variability of misaligned active galaxies

The majority of the γ-ray sources detected by the Fermi Gamma-ray Space Telescope belong to the blazar class of active galactic nuclei (AGNs). In addition to blazars, a minority of non-blazar AGNs is also found to be γ-ray emitters. A class of AGNs with large jet to line-of-sight angle are termed as misaligned AGNs (MAGNs). A significant fraction of γ-ray emitting non-blazar AGNs belong to this class. The detection of these sources in γ-rays suggests that most of their emission originate in the jet. Considering jet origin of intra-night optical variability (INOV), one thus can expect to observe strong presence of INOV in these γ-ray detected MAGN. However, no observations exist on their INOV nature. We therefore, have carried out a first search for INOV on a sample of six MAGN, that comprises three FR I, two Steep Spectrum Radio Quasars (SSRQs)/Compact Steep Spectrum (CSS) and one FR II galaxy. Our observations carried out on a total of eight nights for a duration of ∼29 h, reveal that MAGNs show large amplitude (between 2 and 10 per cent) INOV with a duty cycle of about 50 per cent, including both variable and probably variable sources, which is similar to that shown by blazars. Though INOV has been detected in MAGNs, differences if any between the INOV characteristics of FR I, SSRQs/CSS, and FR II types of MAGNs could not be unambiguously established owing to limited observations. Nevertheless, the first detection of INOV in MAGNs points to their jet based origin.

Intra-night optical monitoring of three γ-ray detected narrow-line Seyfert 1 galaxies

For 3 radio-loud $\gamma$-ray detected Narrow-Line Seyfert 1 ($\gamma$-ray NLSy1) galaxies, we report optical variability on intra-night and/or week-like time scales, based on five $\geq$ 3 hours long monitoring sessions for each galaxy. The radio-loudness factors (R$_{1.4 GHz}$) for these galaxies, namely 1H 0323$+$342 (z = 0.0629), PKS J1222$+$0413 (z = 0.966) and PKS J1505$+$0326 (z = 0.408) are $\sim$318, $\sim$1534 and $\sim$3364 at 1.4 GHz, respectively. For the most distant $\gamma$-ray NLSy1, PKS J1222$+$0413, Intra-Night Optical Variability (INOV) characterisation is presented for the first time. The blazar-like behaviour of the nearest $\gamma$-ray NLSy1 1H 0323$+$342, which showed strong INOV on 4 of the 5 nights, was unexpected in view of its recent reclassification as `radio intermediate' (R$_{5 GHz}$ $\lesssim$ 25). Its particularly violent INOV is manifested by two optical outbursts lasting $\sim$ 1 hour, whose rapid brightening phase is shown to imply a doubling time of $\sim$ 1 hour for the optical synchrotron flux, after (conservatively) deducting the thermal optical emission contributed by the host galaxy and the Seyfert nucleus. A more realistic `decontamination' could well reduce substantially the flux doubling time, bringing it still closer in rapidity to the ultra-fast VHE ($>$ 100 GeV) flares reported for the blazars PKS 1222$+$216 and PKS 2155$-$304. A large contamination by thermal optical emission may, in fact, be common for NLSy1s as they are high Eddington rate accretors. The present study further suggests that superluminal motion in the radio jet could be a robust diagnostic of INOV.

Optical Variability in IBL S5 0716+714 during the 2013–2015 Outbursts

Abstract With an aim to explore optical variability at diverse timescales in BL Lac source S5 0716+714, it was observed for 46 nights during 2013 January 14 to 2015 June 01 when it underwent two major outbursts. The observations were made using the 1.2 m Mount Abu InfraRed Observatory telescope mounted with a CCD camera. On 29 nights, the source was monitored for more than 2 hr, resulting in 6256 data points in the R band, to check for the intra-night variability (INV). Observations in the B, V, and I bands with 159, 214, and 177 data points, respectively, along with daily averaged R-band data are used to address inter-night and long-term variability and the color behavior of S5 0716+71. The study suggests that the source shows significant INV with a duty cycle of more than 31% and night-to-night variations. The average brightness magnitudes in the B, V, R, and I bands were found to be 14.42(0.02), 14.02(0.01), 13.22(0.01), and 13.02(0.03), respectively, while S5 0716+714 was historically brightest with R = 11.68 mag on 2015 January 18, indicating that the source was in a relatively high state during this period. A mild bluer-when-brighter behavior, typical of BL Lacs, supports the shock-in-jet model. We noticed larger amplitudes of variation when the source was relatively brighter. Based on the shortest timescale of variability and causality argument, the upper bound on the size of the emission region is estimated to be 9.32 × 1014 cm, and the mass of the black hole is estimated to be 5.6 × 108 M ⊙.

F25. Intranight variability of AHI can affect the efficiency of CPAP treatment

Introduction Obstructive sleep apnea (OSA) is a common disease with severe health consequences most commonly treated with continuous positive airway pressure (CPAP) device. However, the adherence to CPAP treatment is often limited and the usage of the CPAP device can be only around 4 h per night after 1 month usage ( Chai-Coetzer et al., 2013 ). Possibly for this reason the benefits of the CPAP usage in terms of cardiovascular outcomes are not always obvious ( McEvoy et al., 2016 ). The severity of OSA is estimated with apnea-hypopnea-index (AHI) together with daytime symptoms. AHI may vary hour by hour during the night. In the current study, the aim was to investigate whether there is a difference in AHI during the first 4 h of sleep (possible CPAP adherence) and during the worst 4 h during the night. Methods 2002 ambulatory polygraphic recordings of suspected OSA patients were evaluated. The patients were divided into normal, mild, moderate and severe OSA categories based on their total AHI. Total AHI, AHI during the first 4 h and AHI during the worst 4 h during the recording were analyzed. AHI during the first and the worst 4 h were then compared. Wilcoxon signed ranks test was used to estimate the statistical significance of the differences. p Results There were 972, 508, 260 and 262 patients in normal, mild, moderate and severe OSA categories, respectively. We found a trend of increasing AHI towards the end of the night. The median total AHI in these categories were 1.5, 8.7, 20.7 and 47.6 events/h, respectively. The median differences between the AHI during the worst 4 h and the first 4 h of the recording were 0.8, 4.8, 10.4 and 9.8 events/h ( p Conclusion There were statistically and clinically significant differences between the median AHI values of the worst 4 h and the first 4 h of the night in all OSA severity categories. CPAP adherence has been reported to be around 4 h per night ( Chai-Coetzer et al., 2013 ) and the CPAP usage is probably typically focused on the first hours from the beginning of the night. For these reasons the benefits of the CPAP usage are probably not as linear as the simple time of adherence indicates. With limited adherence time, CPAP treatment is not always able to prevent severe cardiovascular outcomes ( McEvoy et al., 2016 ). If the CPAP usage could be directed to the worst hours of the night at the same adherence level it might provide better treatment results. The total AHI would decrease more when CPAP would be used during the worst hours instead the first hours of the night.

Intra-Night Variability of OJ 287 with Long-Term Multiband Optical Monitoring

We present long-term optical multi-band photometric monitoring of the blazar OJ 287 from 6 March 2010 to 3 April 2016, with high temporal resolution in the V R I -bands. The flux variations and colour-magnitude variations on long and short timescales were investigated to understand the emission mechanisms. In our observation, the major outbursts occurred in January 2016, as predicted by the binary pair of black holes model for OJ 287, with F v a r of 1.3∼2.1%, and variability amplitude (Amp) of 5.8∼9.0%. The intra-night variability (IDV) durations were from 18.5 to 51.3 min, and the minimal variability timescale was about 4.7 min. The colour-magnitude variation showed a weak positive correlation on the long timescale with Pearson’s r = 0 . 450 , while a negative correlation was found on intra-night timescales. We briefly discuss the possible physical mechanisms that are most likely to be responsible for the observed flux and colour-magnitude correlation variability.

Impact of seeing and host galaxy into the analysis of photo-polarimetric microvariability in blazars

Blazars, a type of Active Galactic Nuclei, present a particular orientation of their jets close to the line ofsight. Their radiation is thus relativistically beamed, giving rise to extreme behaviors, specially strong variability on very short time-scales (i.e., microvariability). Here we present simultaneous photometric and polarimetric observations of two relatively nearby blazars, 1ES 1959+650 and HB89 2201+044, that were obtained using the Calar Alto Faint Object Spectrograph mounted at the 2.2 m telescope in Calar Alto, Spain. An outstanding characteristic of these two blazars is the presence of well resolved host galaxies. This particular feature allows us to produce a study of their intrinsic polarization, a measurement of the polarization state of the galactic nucleus unaffected by the host galaxy. To carry out this work, we computed photometric fluxes from which we calculated the degree and orientation of the blazars polarization. Then, we analyzed the depolarizing effect introduced by the host galaxy with the main goal to recover the intrinsic polarization of the galactic nucleus, carefully taking into consideration the spurious polarimetric variability introduced by changes in seeing along the observing nights. We find that the two blazars do not present intra-night photo-polarimetric variability, although we do detect a significant inter-night variability. Comparing polarimetric values before and after accounting for the host galaxies, we observe a significant difference in the polarization degree of about 1 % in the case of 1ES 1959+650, and 0.3 % in the case of HB89 2201+044, thus evidencing the non-negligible impact introduced by the host galaxies. We note that this host galaxy effect depends on the weaveband, and varies with changing seeing conditions, so it should be particularly considered when studying frequency-dependent polarization in blazars.

OISTER optical and near-infrared monitoring observations of peculiar radio-loud active galactic nucleus SDSS J110006.07+442144.3

Abstract We present monitoring campaign observations at optical and near-infrared (NIR) wavelengths for a radio-loud active galactic nucleus (AGN) at z = 0.840, SDSS J110006.07+442144.3 (hereafter, J1100+4421), which was identified during a flare phase in late 2014 February. The campaigns consist of three intensive observing runs from the discovery to 2015 March, mostly within the scheme of the OISTER collaboration. Optical–NIR light curves and simultaneous spectral energy distributions (SEDs) are obtained. Our measurements show the strongest brightening in 2015 March. We found that the optical–NIR SEDs of J1100+4421 show an almost steady shape despite the large and rapid intranight variability. This constant SED shape is confirmed to extend to ∼5 μm in the observed frame using the archival WISE data. Given the lack of absorption lines and the steep power-law spectrum of αν ∼ −1.4, where $f_{\nu }\propto \nu ^{\alpha _{\nu }}$, synchrotron radiation by a relativistic jet with no or small contributions from the host galaxy and the accretion disk seems most plausible as an optical–NIR emission mechanism. The steep optical–NIR spectral shape and the large amplitude of variability are consistent with this object being a low νpeak jet-dominated AGN. In addition, sub-arcsecond resolution optical imaging data taken with Subaru Hyper Suprime-Cam does not show a clear extended component and the spatial scales are significantly smaller than the large extensions detected at radio wavelengths. The optical spectrum of a possible faint companion galaxy does not show any emission lines at the same redshift, and hence a merging hypothesis for this AGN-related activity is not supported by our observations.

Long-term Optical Polarization Variability and Multiwavelength Analysis of Blazar Mrk 421

Abstract The results of 8 yr R-band photopolarimetric data of blazar Mrk 421 collected from 2008 February to 2016 May are presented, along with extensive multiwavelength observations covering radio to TeV γ-rays around the flares observed in 2008 May, 2010 March, and 2013 April. The most important results are found in 2013, when the source displayed in the R band a very high brightness state of 11.29 ± 0.03 mag (93.60 ± 1.53 mJy) on April 10 and a polarization degree of 11.00% ± 0.44% on May 13. The analysis of the optical data shows that the polarization variability is due to the superposition of two polarized components that might be produced in two distinct emitting regions. An intranight photopolarimetric variability study carried out over seven nights after the 2013 April maximum found flux and polarization variations on the nights of April 14, 15, 16, and 19. In addition, the flux shows a minimum variability timescale of Δt = 2.34 ± 0.12 hr, and the polarization degree presents variations of ∼1%–2% on a timescale of Δ t ∼ minutes. Also, a detailed analysis of the intranight data shows a coherence length of the large-scale magnetic field of pc, which is the same order of magnitude as the distance traveled by the relativistic shocks. This result suggests that there is a connection between the intranight polarimetric variations and spatial changes of the magnetic field. Analysis of the complete R-band data along with the historical optical light curve found for this object shows that Mrk 421 varies with a period of 16.26 ± 1.78 yr.

Intra-night variability of the blazar CTA 102 during its 2012 and 2016 giant outbursts

We obtained and analyzed more than 100 hours of multicolour optical time series of the blazar CTA 102 during its 2012 and 2016 outbursts. The object reached almost 11-th mag at the end of 2016, which is perhaps the brightest blazar state ever observed! During both outbursts, CTA 102 showed significant and rapid variability on intra-night time scales, reaching up to 0.2 mag for 30 min on some occasions. The "rms-flux" relation, built for all datasets, shows a large scatter and no apparent saturation on the magnitude scale. The ensemble structure function of the light curves can be fitted well with a straight line of a slope of $\sim$0.4. The time lags between the different optical bands appear to be consistent with zero, taking into account our time resolution. We discuss different variability scenarios and favor the changing Doppler factor of the emitting blobs as the most plausible one to account for the observed intra-night variability.

Intra-night Optical Variability Monitoring of Fermi Blazars: First Results from 1.3 m J. C. Bhattacharya Telescope

Abstract We report the first results obtained from our campaign to characterize the intra-night-optical variability (INOV) properties of Fermi detected blazars, using the observations from the recently commissioned 1.3 m J. C. Bhattacharya telescope (JCBT). During the first run, we were able to observe 17 blazars in the Bessel R filter for ∼137 hr. Using C- and scaled F-statistics, we quantify the extent of INOV and derive the duty cycle (DC), which is the fraction of time during which a source exhibits a substantial flux variability. We find a high DC of 40% for BL Lac objects and the flat spectrum radio quasars are relatively less variable (DC ∼ 15%). However, when estimated for blazars sub-classes, a high DC of ∼59% is found in low synchrotron peaked (LSP) blazars, whereas, intermediate and high synchrotron peaked objects have a low DC of ∼11% and 13%, respectively. We find evidence of the association of the high amplitude INOV with the γ-ray flaring state. We also notice a high polarization during the elevated INOV states (for the sources that have polarimetric data available), thus supporting the jet based origin of the observed variability. We plan to enlarge the sample and utilize the time availability from the small telescopes, such as 1.3 m JCBT, to strengthen/verify the results obtained in this work and those existing in the literature.

Optical variability of the high synchrotron energy peaked blazar 1ES 1959+650 on various time-scales

We report the results of optical monitoring of the high synchrotron energy peaked blazar (HSP), 1ES 1959+650, performed with the 80-cm optical telescope at Xinglong Optical Observatory in 2010–2016. Our study was focused on the optical variability of the source on diverse time-scales over about 6 yr, which is helpful in understanding the variability mechanisms of blazars. Over 19 nights of intense photometric observations, we obtained 38 intranight light curves in the different bands. Intranight variability was not detected from all of these light curves. However, 1ES 1959+650 exhibited significant variations on the short-term (months) and long-term (years) time-scales. During the whole period of our monitoring, the maximum changes in the brightness of the source was 1.38 ± 0.05 and 1.17 ± 0.03 mag in the B and R waveband, respectively. The larger variability amplitude in the blue band than in the red one is demonstrated by the bluer-when-brighter spectral trend. The B − R colour index showed a change of 0.21 ± 0.06 mag across our monitoring period. The non-detection of intranight variations of 1ES 1959+650 is in agreement with previous observations, showing that the optical fluxes of HSPs are less variable than those of intermediate/low synchrotron energy peaked blazars (ISPs/LSPs) on time-scales of hours. In contrast, the detections of significant short-term and long-term variability of the source suggest that the optical variability of HSPs might not be very different from those of ISPs/LSPs on time-scales of months and years. Finally, we discuss some possible scenarios for the differences and the similarities of optical variability on various time-scales between the two blazar subclasses.

Flux and Polarization Variability of OJ 287 during the Early 2016 Outburst

Abstract The gamma-ray blazar OJ 287 was in a high activity state during 2015 December–2016 February. Coinciding with this high brightness state, we observed this source for photometry on 40 nights in R-band and for polarimetry on nine epochs in UBV RI bands. During the period of our observations, the source brightness varied from 13.20 ± 0.04 mag to 14.98 ± 0.04 mag and the degree of polarization (P) fluctuated between 6.0% ± 0.3% and 28.3% ± 0.8% in R-band. Focusing on intranight optical variability (INOV), we find a duty cycle of about 71% using χ 2-statistics, similar to that known for blazars. From INOV data, the shortest variability timescale is estimated to be 142 ± 38 minutes, yielding a lower limit of the observed Doppler factor δ 0 = 1.17, the magnetic field strength B ≤ 3.8 G, and the size of the emitting region R s < 2.28 × 1014 cm. On internight timescales, a significant anticorrelation between R-band flux and P is found. The observed P at U-band is generally larger than that observed at longer-wavelength bands, suggesting a wavelength-dependent polarization. Using V-band photometric and polarimetric data from Steward Observatory obtained during our monitoring period, we find a varied correlation between P and V-band brightness. While an anticorrelation is sometimes seen between P and V-band magnitude, no correlation is seen at other times, thereby suggesting the presence of more than one short-lived shock component in the jet of OJ 287.

Intra-night optical variability characteristics of different classes of narrow-line Seyfert 1 galaxies

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 galaxies are further divided into {\gamma}-ray loud (GL) and {\gamma}-ray quiet (GQ) NLSy1 galaxies. Our sample consists of four sets, each set consisting 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 galaxies consist 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 galaxies respectively. The high DC and large amplitude of INOV (24.0 +/- 13.7%) shown by GL-NLSy1 galaxies relative 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 galaxies could mean the presence of low power and/or largely misaligned jets in them. However, dividing RL-NLSy1 galaxies into 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.

The DOHA algorithm: a new recipe for cotrending large-scale transiting exoplanet survey light curves

We present DOHA, a new algorithm for cotrending photometric light curves obtained by transiting exoplanet surveys. The algorithm employs a novel approach to the traditional "differential photometry" technique, by selecting the most suitable comparison star for each target light curve, using a two-step correlation search. Extensive tests on real data reveal that DOHA corrects both intra-night variations and long-term systematics affecting the data. Statistical studies conducted on a sample of 9500 light curves from the Qatar Exoplanet Survey reveal that DOHA-corrected light curves show an RMS improvement of a factor of 2, compared to the raw light curves. In addition, we show that the transit detection probability in our sample can increase considerably, even up to a factor of 7, after applying DOHA.

Intranight optical variability of radio-quiet weak emission line quasars – IV

We report an extension of our program to search for radio-quiet BL Lac candidates using intra-night optical variability (INOV) as a probe. The present INOV observations cover a well-defined representative set of 10 `radio-quiet weak-emission-line quasars' (RQWLQs), selected from a newly published sample of 46 such sources, derived from the Sloan Digital Sky Survey (Data release 7). Intra-night CCD monitoring of the 10 RQWLQs was carried out in 18 sessions lasting at least 3.5 hours. For each session, differential light curves (DLCs) of the target RQWLQ were derived relative to two steady comparison stars monitored simultaneously. Combining these new data with those already published by us for 15 RQWLQs monitored in 30 sessions, we estimate an INOV duty cycle of $\sim 3\%$ for the RQWLQs, which appears inconsistent with BL Lacs. However, the observed INOV events (which occurred in just two of the sessions) are strong (with a fractional variability amplitude $\psi >$ 10\%), hence blazar-like. We briefly point out the prospects of an appreciable rise in the estimated INOV duty cycle for RQWLQs with a relatively modest increase in sensitivity for monitoring these rather faint objects.

Detecting microvariability in type 2 quasars using enhanced F-test

Microvariability (intra-night variability) is a low amplitude flux change at short time scales (i.e. hours). It has been detected in unobscured type 1 AGNs and blazars. However in type 2 AGNs, the detection is hampered by the low contrast between the presumably variable nucleus and the host galaxy. In this paper, we present a search for microvariability in a sample of four type 2 quasars as an astrostatistical problem. We are exploring the use of a newly introduced enhanced F-test, proposed by de Diego 2014. The presented results show that out of our four observed targets, we were able to apply this statistical method to three of them. Evidence of microvariations is clear in the case of quasar J0802+2552 in all used filters (g',r' and i') during both observing nights, the microvariations are present in one of the nights of observations of J1258+5239 in one filter (i'), while for the J1316+4452, there is evidence for microvariability within our detection levels during one night and two filters (r' and i'). We demonstrate the feasibility of the enhanced F-test to detect microvariability in obscured type 2 quasars. At the end of this paper, we discuss possible causes of microvariability. One of the options is the misclassification of the targets. A likely scenario for explanation of the phenomenon involves optically thin gaps in a clumpy obscuring medium, in accordance with the present view of the circumnuclear region. There is a possible interesting connection between the merging state of the targets and detection of microvariability.

BROADBAND OBSERVATIONS OF THE GAMMA-RAY EMITTING NARROW LINE SEYFERT 1 GALAXY SBS 0846+513

ABSTRACT We present the results of our broadband study of the γ-ray emitting narrow line Seyfert 1 (NLSy1) galaxy SBS 0846+513 (z = 0.585). This includes multiband flux variations, γ-ray spectral analysis, broadband spectral energy distribution (SED) modeling, and intranight optical variability (INOV) observations carried out over six nights between 2012 November and 2013 March using the 2 m Himalayan Chandra Telescope and the 1.3 m telescope at Devasthal, India. Multiple episodes of flaring activity are seen in the γ-ray light curve of the source which are also reflected in the observations at lower frequencies. A statistically significant curvature is noticed in the seven years averaged γ-ray spectrum, thus indicating its similarity with powerful flat spectrum radio quasars (FSRQs). Modeling the SEDs with a one-zone leptonic emission model hints that the optical UV spectrum is dominated by synchrotron radiation, whereas inverse Compton scattering of broad line region photons reproduces the γ-ray part of the SEDs. The source was found to be variable on all the six nights of optical observations with a variation of ∼0.3 mag within a single night, coinciding with a high γ-ray activity state. The observed large amplitude INOV clearly indicates the presence of a closely aligned beamed relativistic jet in SBS 0846+513. Our broadband study supports the recent claims in literature that γ-ray emitting NLSy1 galaxies are similar to blazars and constitute the low black hole mass counterparts to FSRQs.

Optical monitoring observations of two γ-ray narrow-line Seyfert 1 galaxies

1H 0323+342 is a rather radio-loud narrow-line Seyfert 1 galaxy (NLS1) with γ-ray emission. Optical observations were carried out in B and R bands which covered 6 nights in 2011 to obtain light curves of 1H 0323+342. The difference image subtraction method was used to deal with the data of 1H 0323+342 because of the existence of extended host galaxy. Optical variability on day timescale was reported here. We also monitored the first γ-ray NLS1 SDSS J094857.3+002225 and confirmed the existence of intranight optical variability (INOV). These indicated the existence of a relativistic jet in these NLS1s.