Goyal, Arti ; Mhaskey, Mukul ; Gopal-Krishna, * ; Wiita, Paul J. ; Stalin, C. S. ; Sagar, Ram (2013) On the photometric error calibration for the differential light curves of point-like active galactic nuclei Journal of Astrophysics and Astronomy, 34 (3). pp. 273-296. ISSN 0250-6335
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Official URL: http://www.ias.ac.in/jaa/sep2013/jaa-d-13-00037.pd...
Related URL: http://dx.doi.org/10.1007/s12036-013-9183-7
Abstract
It is important to quantify the underestimation of rms photometric errors returned by the commonly used APPHOT algorithm in the IRAF software, in the context of differential photometry of point-like AGN, because of the crucial role it plays in evaluating their variability properties. Published values of the underestimation factor, η, using several different telescopes, lie in the range 1.3–1.75. The present study aims to revisit this question by employing an exceptionally large data set of 262 differential light curves (DLCs) derived from 262 pairs of non-varying stars monitored under our ARIES AGN monitoring program for characterizing the intra-night optical variability (INOV) of prominent AGN classes. The bulk of these data were taken with the 1-m Sampurnanad Telescope (ST). We find η = 1.54±0.05 which is close to our recently reported value of η = 1.5. Moreover, this consistency holds at least up to a brightness mismatch of 1.5 mag between the paired stars. From this we infer that a magnitude difference of at least up to 1.5 mag between a point-like AGN and comparison star(s) monitored simultaneously is within the same CCD chip acceptable, as it should not lead to spurious claims of INOV.
Item Type: | Article |
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Source: | Copyright of this article belongs to Indian Academy of Sciences. |
Keywords: | Photometry: optical; photometry: methods: data analysis; optical: variability; AGN |
ID Code: | 98436 |
Deposited On: | 21 Jul 2014 09:56 |
Last Modified: | 19 May 2016 10:26 |
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