Further evidence for intra-night optical variability of radio-quiet quasars

Although well established for BL Lac objects and radio-loud quasars, the occurrence of intra-night optical variability (INOV) in radio-quiet quasars is still debated, primarily since only a handful of INOV events with good statistical significance, albeit small amplitude, have been reported so far. This has motivated us to continue intra-night optical monitoring of bona-fide radio-quiet quasars (RQQs). Here we present the results for a sample of 11 RQQs monitored by us on 19 nights. On 5 of these nights a given RQQ was monitored simultaneously from two well separated observatories. In all, two clear cases and two probable case of INOV were detected. From these data, we estimate an INOV duty cycle of $\sim$8% for RQQs which would increase to 19% if the `probable variable' cases are also included. Such comparatively small INOV duty cycles for RQQs, together with the small INOV amplitudes ($\sim$1%), are in accord with the previously deduced characteristics of this phenomenon.Comment: 15 Pages, 4 Tables, 24 Figures; Accepted in BAS

Comparison of fasting and non-fasting serum lipid profile in healthy population

Background: Serum lipids are routinely used for the assessment of cardiovascular risk. The test is usually performed under fasting condition. However, recently non-fasting lipid profile is also measured in certain cases. The present study was intended to estimate the concentration of total cholesterol (TC), triglyceride (TG), HDL cholesterol (HDL-C), LDL cholesterol (LDL-C) and VLDL cholesterol (VLDL-C) in fasting as well as non-fasting blood samples of a group of normal male and female subjects.Methods: The study recruited 50 normal healthy male and female subjects within the age group of 12-48 years. The concentration of TC, TG, HDL-C, LDL-C and VLDL-C in serum of these subjects were quantitatively determined using the commercially available kits based on CHOD/POD method.Results: The mean concentration of non-fasting TC, TG, HDL-C, LDL-C and VLDL-C was found to be 141.20 mg/dl, 132.20 mg/dl, 50.39 mg/dl, 64.30 mg/dl, 26.44 mg/dl respectively. On the other hand, the mean concentration of fasting TC, TG, HDL-C, LDL-C and VLDL-C was found to be 112.37 mg/dl, 100.90 mg/dl, 38.59 mg/dl, 53.59 mg/dl and 20.18 mg/dl respectively. The concentration of fasting lipid profile parameters was significantly low from the respective parameters of non-fasting lipid profile.Conclusions: The present study reveals that there was an increase in the levels of TC, TG, HDL-C, LDL-C, and VLDL-C in non-fasting state compared to the fasting state. Measuring the lipid profile parameters under non-fasting state cannot be usually considered for assessment of cardiovascular risk and for other clinical purposes

SYNTHESIS AND EVALUATION OF SOME BENZOTHIAZOLE DERIVATIVES AS ANTIDIABETIC AGENTS

Objective: The objective of the present research investigation involves synthesis and biological evaluation of antidiabetic activity of benzothiazole derivatives.Methods: A novel series of benzothiazole derivatives 7(a-l) were synthesised and synthesised compounds were characterised for different physical and chemical properties like molecular formula, molecular weight, melting point, percentage yield, Rf value, IR, 1HNMR, 13CNMR and mass spectroscopy. The newly synthesised benzothiazole derivatives were subsequently assayed in vivo to investigate their hypoglycemic activity by the alloxan-induced diabetic model in rats. Results: All the synthesised derivatives showed significant biological efficacy. The compound 7d at 350 mg/kg exerted maximum glucose lowering effects whereas 7c showed minimum glucose lowering effects. All the compounds were effective, and experimental results were statistically significant at p<0.01 and p<0.05 level.Conclusion: From the results, it is clear that compound 7d demonstrated potent anti-diabetic activity and would be of better use in drug development to combat the metabolic disorder in future

Intra-night optical variability of core dominated radio quasars: the role of optical polarization

Context. Rapid variations in optical flux are seen in many quasars and all blazars. The amount of variability in different classes of active galactic nuclei has been studied extensively but many questions remain unanswered. Aims. We present the results of a long-term programme to investigate the intra-night optical variability (INOV) of powerful flat spectrum radio core-dominated quasars (CDQs), with a focus on probing the relationship of INOV to the degree of optical polarization. Methods. We observed a sample of 16 bright CDQs showing strong broad optical emission lines and consisting of both high and low optical polarization quasars (HPCDQs and LPCDQs). In this first systematic study of its kind, we employed the 104-cm Sampurnanand telescope, the 201-cm Himalayan Chandra telescope and the 200-cm IUCAA-Girawali Observatory telescope, to carry out R-band monitoring on a total of 47 nights. Using the CCD as an N-star photometer to densely monitor each quasar for a minimum duration of about 4 h per night, INOV exceeding ~1–2 per cent could be reliably detected. Combining these INOV data with those taken from the literature, after ensuring conformity with the basic selection criteria we adopted for the 16 CDQs monitored by us, we were able to increase the sample size to 21 CDQs (12 LPCDQs and 9 HPCDQs) monitored on a total of 73 nights. Results. As the existence of a prominent flat-spectrum radio core signifies that strong relativistic beaming is present in all these CDQs, the definitions of the two sets differ primarily in fractional optical polarization, with the LPCDQs showing a very low median Pop ≃ 0.4 per cent. Our study yields an INOV duty cycle (DC) of ~28 per cent for the LPCDQs and ~68 percent for HPCDQs. If only strong INOV with fractional amplitude above 3 per cent is considered, the corresponding DCs are ~7 per cent and ~40 per cent, respectively. Conclusions. From this strong contrast between the two classes of luminous, relativistically beamed quasars, it is apparent that relativistic beaming is normally not a sufficient condition for strong INOV and a high optical polarization is the other necessary condition. Moreover, the correlation is found to persist for many years after the polarization measurements were made. Some possible implications of this result are pointed out, particularly in the context of the recently detected rapid γ-ray variability of blazars

Rapid optical variability of TeV blazars

In this first systematic attempt to characterise the intranight optical variability (INOV) of TeV detected blazars, we have monitored a well defined set of 9 TeV blazars on total 26 nights during 2004-2010. In this R (or V)-band monitoring programme only one blazar was monitored per night for a minimum duration of 4 hours. Using the CCD, an INOV detection threshold of ~ 1-2 % was achieved in the densely sampled DLCs. We have further expanded the sample by including another 13 TeV blazars from literature. This enlarged sample of 22 TeV blazars, monitored on a total of 116 nights (including 55 nights newly reported here), has enabled us to arrive at the first estimate of the INOV duty cycle of TeV detected blazars. Applying the C-test, the INOV DC is found to be 59 %, which decreases to 47 % if only INOV fractional amplitudes above 3 % are considered. These observations also permit, for the first time, a comparison of the INOV characteristics of the two major subclasses of TeV detected BL Lacs, namely LBLs and HBLs, for which we find the INOV DCs to be ~ 63 % and ~ 38 %, respectively. This demonstrates that the INOV differential between LBLs and HBLs persists even when only their TeV detected subsets are considered. Despite dense sampling, the intranight light curves of the 22 TeV blazars have not revealed even a single feature on time scale substantially shorter than 1 hour, even though the inner jets of TeV blazars are believed to have exceptionally large bulk Lorentz factors (and correspondingly stronger time compression). An intriguing feature, clearly detected in the light curve of the HBL J1555+1111, is a 4 per cent `dip' on a 1 hour timescale. This unique feature could have arisen from absorption in a dusty gas cloud, occulting a superluminally moving optical knot in the parsec scale jet of this relatively luminous BL Lacs object.Comment: 39 pages, 3 figures, accepted for publication in MNRA

Optical variability of radio-intermediate quasars

We report the results of our intensive intranight optical monitoring of 8 `radio-intermediate quasars' (RIQs) having flat or inverted radio spectra. The monitoring was carried out in {\it R-} band on 25 nights during 2005-09. An intranight optical variability (INOV) detection threshold of $\sim$ 1--2% was achieved for the densely sampled differential light curves (DLCs). These observations amount to a large increase over those reported hitherto for this rare and sparsely studied class of quasars which can, however, play an important role in understanding the link between the dominant varieties of powerful AGN, namely the radio-quiet quasars (RQQs), radio-loud quasars (RLQs) and blazars. Despite the probable presence of relativistically boosted nuclear jets, clear evidence for INOV in our extensive observations was detected only on one night. These results demonstrate that as a class, RIQs are much less extreme in nuclear activity compared to blazars. The availability in the literature of INOV data for another 2 RIQs conforming to our selection criteria allowed us to enlarge the sample to 10 RIQs (monitored on a total of 42 nights for a minimum duration of $\sim 4$ hours per night). The absence of large amplitude INOV $(\psi > 3$ persists in this enlarged sample. This extensive database has enabled us to arrive at the first estimate for the INOV Duty Cycle (DC) of RIQs. The DC is found to be small ($\sim$ 9%). The corresponding value is known to be $\sim 60$ for BL Lacs and $\approx 15$ for RLQs and RQQs. On longer-term, the RIQs are found to be fairly variable with typical amplitudes of $\approx$ 0.1-mag. The light curves of these RIQs are briefly discussed in the context of a theoretical framework proposed earlier for linking this rare kind of quasars to the much better studied dominant classes of quasars.Comment: 35 pages, 2 figures, 3 tables, accepted for publication in MNRA

Unusual optical quiescence of the classical BL Lac object PKS 0735+178 on intranight time-scale

We present the result of our extensive intranight optical monitoring of the well-known low-energy peaked BL Lac (LBL) object PKS 0735+178. This long-term follow-up consists of R -band monitoring for a minimum duration of ∼4 hours, on 17 nights spanning 11 years (1998–2008). Using the CCD as an N-star photometer, a detection limit of around 1 per cent was attained for the intranight optical variability (INOV). Remarkably, an INOV amplitude of ≥3 per cent on hour-like time-scale was not observed on any of the 17 nights, even though the likelihood of a typical LBL showing such INOV levels in a single session of >4 hours duration is known to be high (∼50 per cent) . Our observations have thus established a peculiar long-term INOV quiescence of this radio-selected BL Lac object. Moreover, the access to unpublished optical monitoring data of similarly high sensitivity, acquired in another programme, has allowed us to confirm the same anomalous INOV quiescence of this LBL all the way back to 1989, the epoch of its historically largest radio outburst. Here, we present observational evidence revealing the very unusual INOV behaviour of this classical BL Lac object and discuss this briefly in the context of its other known exceptional properties.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74920/1/j.1365-2966.2009.15385.x.pd