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We present the results of a broadband simultaneous campaign on the nearby low-luminosity active galactic nucleus M81*. From February through August 2005, we observed M81* five times using the Chandra X-ray Observatory with the High-Energy Transmission Grating Spectrometer, complemented by ground-based observations with the Giant Meterwave Radio Telescope, the Very Large Array and Very Large Baseline Array, the Plateau de Bure Interferometer at IRAM, the Submillimeter Array and Lick Observatory. We discuss how the resulting spectra vary over short and longer timescales compared to previous results, especially in the X-rays where this is the first ever longer-term campaign at spatial resolution high enough to nearly isolate the nucleus (17pc). We compare the spectrum to our Galactic center weakly active nucleus Sgr A*, which has undergone similar campaigns, as well as to weakly accreting X-ray binaries in the context of outflow-dominated models. In agreement with recent results suggesting that the physics of weakly-accreting black holes scales predictably with mass, we find that the exact same model which successfully describes hard state X-ray binaries applies to M81*, with very similar physical parameters.
We report first results from a large project to measure black hole (BH) mass in high accretion rate active galactic nuclei (AGNs). Such objects may be different from other AGNs in being powered by slim accretion disks and showing saturated accretion
For most of their lifetime, super-massive black holes (SMBHs) commonly found in galactic nuclei obtain mass from the ambient at a rate well below the Eddington limit, which is mediated by a radiatively inefficient, hot accretion flow. Both theory and
Intermediate-mass black holes (IMBHs), with masses in the range $100-10^{6}$ M$_{odot}$, are the link between stellar-mass BHs and supermassive BHs (SMBHs). They are thought to be the seeds from which SMBHs grow, which would explain the existence of
We present new and stronger evidence for a previously reported relationship between galactic spiral arm pitch angle P (a measure of the tightness of spiral structure) and the mass M_BH of a disk galaxys nuclear supermassive black hole (SMBH). We use
Nantais et al. used the Hubble Space Telescope to localize probable globular clusters (GCs) in M81, a spiral galaxy at a distance of 3.63 Mpc. Theory predicts that GCs can host intermediate-mass black holes (IMBHs) with masses M_BH sim 100 - 100,000