ABSTRACT
The recent discovery of gravitational waves from stellar-mass binary black hole mergers by the Laser Interferometer Gravitational-wave Observatory opened the door to alternative probes of stellar and galactic evolution, cosmology and fundamental physics. Probing the origin of binary black hole mergers will be difficult due to the expected lack of electromagnetic emission and limited localization accuracy. Associations with rare host galaxy types-such as active galactic nuclei-can nevertheless be identified statistically through spatial correlation. Here we establish the feasibility of statistically proving the connection between binary black hole mergers and active galactic nuclei as hosts, even if only a sub-population of mergers originate from active galactic nuclei. Our results are the demonstration that the limited localization of gravitational waves, previously written off as not useful to distinguish progenitor channels, can in fact contribute key information, broadening the range of astrophysical questions probed by binary black hole observations.Binary black hole mergers have recently been observed through the detection of gravitational wave signatures. The authors demonstrate that their association with active galactic nuclei can be made through a statistical spatial correlation.
ABSTRACT
The tidal disruption of a star by a supermassive black hole leads to a short-lived thermal flare. Despite extensive searches, radio follow-up observations of known thermal stellar tidal disruption flares (TDFs) have not yet produced a conclusive detection. We present a detection of variable radio emission from a thermal TDF, which we interpret as originating from a newly launched jet. The multiwavelength properties of the source present a natural analogy with accretion-state changes of stellar mass black holes, which suggests that all TDFs could be accompanied by a jet. In the rest frame of the TDF, our radio observations are an order of magnitude more sensitive than nearly all previous upper limits, explaining how these jets, if common, could thus far have escaped detection.
ABSTRACT
OBJECTIVES: To review the clinical outcome of arthrodesis of the foot in patients with diabetic Charcot arthropathy and to review the pathophysiology, clinical and radiographic features of Charcot arthropathy. DESIGN: A retrospective review and clinical follow-up of a series of patients. SETTING: St. Michael's Hospital, Toronto, a tertiary care teaching hospital. PATIENTS: Ten diabetic patients treated between 1996 and 1998 who required an arthrodesis of the midfoot or hindfoot secondary to deformity of diabetic neuropathic joints. INTERVENTIONS: Three midfoot (Lisfranc) and 7 hindfoot arthrodeses with autogenous iliac-crest bone grafting and internal fixation. OUTCOME MEASURES: Patient satisfaction, maintenance of the correction of the deformity and avoidance of amputation. Western Ontario/McMaster University score and midfoot/hindfoot American Orthopaedic Foot and Ankle Society foot ratios. Clinical examination including E-MED pedographic examination. Correction and evidence of bony or fibrous union assessed radiologically. RESULTS: The postoperative correction was maintained, no further skin ulceration occurred and amputation was avoided in 9 of 10 patients. Because this is a salvage procedure and there was often significant concomitant illness, the results of clinical rating systems were poor. Five of 9 patients had clinical and radiographic evidence of a solid bony arthrodesis; 4 had a stable fibrous union. CONCLUSIONS: With careful surgical technique, a reasonable number of feet can be salvaged by an arthrodesis of a diabetic neuropathic joint when nonoperative measures fail. Patient selection is important because there is a significant complication rate.
