Optical Monitoring of OT 546 in 2009
aa r X i v : . [ a s t r o - ph . S R ] M a y J. Astrophys. Astr. (0000) , 000–000 Optical Monitoring of OT 546 in 2009
Difu Guo ∗ , Shaoming Hu & Xu Chen School of Space Science and Physics, Shandong University, Weihai,180 Cultural West Road, Weihai, Shandong 264209, China.
Abstract.
We reported the monitoring results of OT 546 in V, R andI bands, observed on 22 nights from February 16 to July 1 in 2009 atWeihai Observatory of Shandong University. During our monitoring,its variability amplitude was small and a possible microvariability wasdetected on one night using both C and F tests.
Key words : AGN: blazar – BL lac: individual: OT 546.
1. Introduction
OT 546 (ZW I 187) was classified as a BL Lac object by Angel & Stockmann(1980). An optical variation of 2.1 mag was found in B band (Hall & Usher, 1972),but its variability amplitude was small recently. The average brightness in V and Bbands were near 16 mag (Kinman , 1976) and 16.7 mag (Pica et al., 1988) respec-tively. Rapid short term variability was reported by Pica et al. (1988).
2. Observations and results
The optical observations were carried out at Weihai Observatory of Shandong Uni-versity, using 1.0-m telescope equipped with a back illuminated PIXIS 2048B CCDcamera at the cassegrain focus. The field of view was about 12 ′ × ′ . StandardJohnson Cousins filters were used in our observations. The data reduction was car-ried out following the standard procedure of the IRAF packages. All images wereprocessed by bias and flat-field correction. Then, aperture photometry was used toobtain the instrumental magnitudes for the target and the comparison stars. Com-parison stars B, H and L taken from Fiorucci & Tosti (1996) were used, and themagnitude of the source was derived by di ff erential photometry.Light curves of the source in V, R and I bands were shown in Figure 1. Dur-ing our observations, the variability amplitude was small, similar to recent ob-servations (Fiorucci & Tosti, 1996; Katajainen et al., 2000; Xie et al., 2004). The ∗ e-mail:[email protected] Guo et al.
JD 2454870+ M a g . V R I
Figure 1.
Light curves of OT 546 in V, R and I bands. brightness variation in V band was between 15.72 (JD 2454978.142) and 16.05 (JD2454907.304) mag with an average brightness of 15.92 mag. The observed largestintra-night variability amplitudes in V, R and I bands were ∆ V ∼ ∆ R ∼ ∆ I ∼ Acknowledgements:
This work was partially supported by the NSFC (Nos. 11143012, 11203016, 10778619and 10778701), and by the NSF of Shandong Province (No. ZR2012AQ008).
References
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