Exploring Accretion and Disk-Jet Connections in the Llagn M81*

Abstract

We report on a year-long effort to monitor the central supermassive black hole in M81 in the X-ray and radio bands. Using Chandra and the Very Large Array, we obtained quasi-simultaneous observations of M81* on seven occasions during 2006. The X-ray and radio luminosity of M81* are not strongly correlated on the approximately 20 day sampling timescale of our observations, which is commensurate with viscous timescales in the inner flow and orbital timescales in a radially truncated disk. This suggests that short-term variations in black hole activity may not be rigidly governed by the "fundamental plane," but rather adhere to the plane in a time-averaged sense. Fits to the X-ray spectra of M81* with bremsstrahlung models give temperatures that are inconsistent with the outer regions of very simple advection-dominated inflows. However, our results are consistent with the X-ray emission originating in a transition region where a truncated disk and advective flow may overlap. We discuss our results in the context of models for black holes accreting at small fractions of their Eddington limit and the fundamental plane of black hole accretion.

Detection of jet precession in the active nucleus of M 81

“…However, the parametric space of very-low accretion flows in AGNs (e.g., LLAGN) is not fully characterized observationally. Although Markoff et al (2008) and Miller et al (2010) were able to fit average broadband spectra of M 81* in the frame of the fundamental-plane model of disk-jet connection, no clear correlation between the variabilities in the X-rays and radio was observed unlike in microquasars (Mirabel et al 1998) and AGNs (Marscher et al 2002). In the present paper, we report on a very long flare of M 81* at radio frequencies, beginning around mid 1997, which lasted nearly four years.…”

A universal scaling law of black hole activity including gamma-ray bursts

“…Interestingly, NGC 7213 lies very close to the best-fitting correlation of the fundamental plane. Miller et al (2010) proposed that an individual source might not be rigidly governed by the fundamental plane on short timescales. But it follows the fundamental plane in a time-averaged sense.…”

Nuclear Radio Jet From a Low-Luminosity Active Galactic Nucleus in NGC 4258

“…Using our finding, the VLBI results, and the SED model, two predictions can be made for future observations: (1) the radio spectral variation will not be so promptly correlated with those in the infrared or X-ray regimes (cf. Miller et al 2010, for M81) because of significantly different linear scales of emitting sites and (2) the outer jet component will provide a contribution comparable with that of the jet base at submillimeter wavelengths, which implies a spectral upswing from α ≈ 0.3 at lower frequencies to α 2.5 at higher frequencies rather than a spectral turnover.…”

“…To calculate R F of M81, we adopted a peak intensity of ∼100 mJy beam −1 and three times the image noise of σ ∼ 0.2 mJy beam −1 in the images at 8.4 GHz by Bietenholz et al (2000). To calculate R X , we used observed flux densities at 22 GHz of typically ∼3 mJy and ∼100 mJy for NGC 4258 (Table 2) and M81 (e.g., Bietenholz et al 2000), respectively, as representative of radio data because of similar spectral indices (α ≈ 0.3) and 2-10 keV X-ray luminosities typically ∼1×10 41 erg s −1 and ∼2×10 40 erg s −1 for NGC 4258 (Makishima et al 1994;Fruscione et al 2005;Yamada et al 2009) and M81 (Ishisaki et al 1996;Markoff et al 2008;Miller et al 2010), respectively. In the present paper, we demonstrate that the differences in (1)-(3) can be attributed to inclination effects by following discussions; M81 is presumably a pole-on viewed system at an inclination of θ = 14…”