The absence of a thin disc in M81

Abstract

We present the results of simultaneous Suzaku and NuSTAR observations of the nearest Low-Luminosity Active Galactic Nucleus (LLAGN), M81*. The spectrum is well described by a cut-off power law plus narrow emission lines from Fe K$\alpha$, Fe XXV and Fe XXVI. There is no evidence of Compton reflection from an optically thick disc, and we obtain the strongest constraint on the reflection fraction in M81* to date, with a best-fit value of $R=0.0$ with an upper limit of $R<0.1$. The Fe K$\alpha$ line may be produced in optically thin, $N_H=1\times 10^{23}$ cm${}^{-2}$, gas located in the equatorial plane that could be the broad line region. The ionized iron lines may originate in the hot, inner accretion flow. The X-ray continuum shows significant variability on $\sim 40$ ks timescales suggesting that the primary X-ray source is $\sim 100$s of gravitational radii in size. If this X-ray source illuminates any putative optically thick disc, the weakness of reflection implies that such a disc lies outside a few $\times 10^3$ gravitational radii. An optically thin accretion flow inside a truncated optically thick disc appears to be a common feature of LLAGN that are accreting at only a tiny fraction of the Eddington limit.

arXiv comment7 pages, 7 figures, to appear in MNARS

References in corpus (21)

• An XMM-Newton survey of broad iron lines in Seyfert galaxies
• The Supermassive Black Hole at the Galactic Center
• An X-ray Spectral Model for Compton-Thick Toroidal Reprocessors
• Piecing Together the X-ray Background: Bolometric Corrections for Active Galactic Nuclei
• Space Telescope and Optical Reverberation Mapping Project. III. Optical Continuum Emission and Broad-Band Time Delays in NGC 5548
• The XXL Survey: I. Scientific motivations - XMM-Newton observing plan - Follow-up observations and simulation programme
• The Nature of the Compton-thick X-ray Reprocessor in NGC 4945
• On the Iwasawa-Taniguchi effect of radio-quiet AGN
• General relativistic modelling of the negative reverberation X-ray time delays in AGN
• A Stationary Core with a One-sided Jet in the Center of M81
• Iron line profiles in Suzaku spectra of bare Seyfert galaxies
• X-ray spectral properties of the AGN sample in the northern XMM-XXL field
• Long-term X-Ray Spectral Variability in AGN from the Palomar sample observed by Swift
• The Seyfert 2 galaxy NGC 2110: hard X-ray emission observed by NuSTAR and variability of the iron K$\alpha$ line
• Evidence for a Truncated Accretion Disc in the Low Luminosity Seyfert Galaxy, NGC 7213?
• Exploring Accretion and Disk-Jet Connections in the LLAGN M81*
• Probing Unification With Chandra HETGS and XMM-Newton EPIC And RGS Spectroscopy of the Narrow Emission Line Galaxy NGC 2110
• Highly ionized Fe K emission lines from the LINER galaxy M 81
• X-ray emission line gas in the LINER galaxy M81
• Very fast X-ray spectral variability in Cygnus X-1: Origin of the hard and soft-state emission components
• Kinematics of the Broad Line Region in M81

Cited by in corpus (11)

• Relations between phenomenological and physical parameters in the hot coronae of AGNs computed with the MoCA code
• NuSTAR Hard X-ray View of Low-luminosity Active Galactic Nuclei: High-energy Cutoff and Truncated Thin Disk
• Properties of the Obscuring Torus in NGC 1052 from Multi-epoch Broadband X-ray Spectroscopy
• Constraining X-ray reflection in the low-luminosity AGN NGC 3718 using NuSTAR and XMM--Newton
• Inflowing Gas in the Central Parsec of M81
• Universality of coronal properties in accreting black holes across mass and accretion rate
• Tracking X-ray Variability in Next Generation EHT LLAGN Targets
• X-ray flares in the long-term light curve of low-luminosity Active Galactic Nucleus M81*
• The X-ray variation of M81* resolved by Chandra and NuSTAR
• Hard X-ray view of two $\gamma$-ray detected low-luminosity active galactic nuclei: NGC 315 and NGC 4261
• An Energetic Hot Wind from the Low-luminosity Active Galactic Nucleus M81*