Michael A. Nowak

Exploring accretion and disk-jet connections in the LLAGN M81*

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.

Cygnus X-1: shedding light on the spectral variability of the hard state of black holes

E-mail: Victoria.Grinberg@sternwarte.uni-erlangen.de 1Remeis-Observatory/ECAP/FAU, Bamberg, Germany 2CRESST/NASA-GSFC, Greenbelt, MD, USA 3UMBC, Baltimore, MD, USA 4GMU, Fairfax, VA, USA 5ESAC, Madrid, Spain 6UMCP, College Park, MD, USA 7MIT Kavli Institute, Cambridge, MA, US 8UVA, Amsterdam, NL 9UCSD, La Jolla, CA, USA 10SSL, UC Berkeley, Berkeley, CA, USA 11DSM/DAPNIA/SAp, CEA Saclay, France 12University of Cambridge, Cambridge, UK

Properties of a fast state transition in Cygnus X‐1

In 2005 February we observed the microquasar Cygnus X‐1 for a total of 10 days quasi‐continuously with the Rossi X‐ray Timing Explorer and the Ryle telescope. During that period of time Cyg X‐1 was very variable and covered a large fraction of its total variability found during our years long monitoring. A full transition from the hard to the soft state occured within less than 2.5 hours. We present results of the spectral and timing analysis, compare them with the long‐term behavior and discuss the discovered energy dependence of the power spectra.

Fitting along the Fundamental Plane: New comparisons of jet physics across the black hole mass scale

Correlations between the radio and X-ray bands in the hard state of black hole X-ray binaries (BHBs) have led to the discovery of the Fundamental Plane of black hole accretion, linking accretion-driven radiative attributes to black hole mass. Although this discovery has led to new constraints on radiative efficiencies, there is still significant degeneracy in terms of understanding the governing physics. I present several new results exploring the processes driving the Fundamental Plane over the black hole mass range. These include the first ever homogeneous fits of sources at approximately the same Eddington luminosity but millions of times different in mass, which I focus on for this proceeding article.

Modelling a Simultaneous Radio/X-Ray Flare from Cyg X-1

The long-term monitoring campaign of Cyg X-1 has provided the detection of the first simultaneous radio/X-ray flare seen from that source. We investigate the physical characteristics of the event in terms of emission from a homogeneous, expanding blob of pair-plasma, superimposed on a baseline flux in both bands. We find that while the radio flare can be reconstructed under various configurations of a cooling blob, continuous (re)acceleration of particles inside the jet is necessary to sustain X-ray emission at the levels implied by the data, for the observed duration. We present major results of the modelling and discuss implications for the role of microquasar jets.