Search for intra-day optical variability in Mrk 501

Abstract

We present our observations of the optical intra-day variability (IDV) in $\gamma$-ray BL Lac object Mrk 501. The observations were run with the 1.02 m and 2.4 m optical telescopes at Yunnan Observatories from 2005 April to 2012 May. The light curve at the $R$ band on 2010 May 15 passes both variability tests (the $F$ test and the ANOVA test). A flare within the light curve on 2010 May 15 has a magnitude change $\Delta m=0.03\pm 0.005_{\mathrm{stat}}\pm 0.007_{\mathrm{sys}}$ mag, \textbf{a darkening timescale of ${\tau }_{\mathrm{d}}=$ 26.7 minutes}, and an amplitude of IDV $Amp=2.9\%\pm 0.7\%$. A decline \textbf{described by 11 consecutive flux measurements} within the flare can be fitted linearly with a Pearson's correlation coefficient $r=0.945$ at the confidence level of $>99.99\%$. Under the assumptions that the IDV is tightly connected to the mass of the black hole, \textbf{and that the flare duration, being two times ${\tau }_{\mathrm{d}}$, is representative of the minimum characteristic timescale, we can derive upper bounds to the mass of the black hole}. In the case of the Kerr black hole, the timescale of $\Delta t_{\min }^{\mathrm{ob}}=$ 0.89 hours gives $M_{\bullet}\la 10^{9.20} M_{\odot}$, which is consistent with measurements reported in the literature. This agreement indicates that the hypothesis about $M_{\bullet }$ and $\Delta t_{\min }^{\mathrm{ob}}$ is consistent with the measurements/data.

accepted for publication in ApJ; 7 figures, 2 tables

References in corpus (13)

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Cited by in corpus (3)

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• Reverberation Mapping of Changing-look Active Galactic Nucleus NGC 3516
• Microvariability in AGNs: study of different statistical methods II. Light curves from simulated images