English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

A major question in the study of black hole binaries involves ourunderstanding of the accretion geometry when the sources are in the hard state.In this state, the X-ray energy spectrum is dominated by a hard power-lawcomponent and radio observations indicate the presence of a steady and powerfulcompact jet. Although the common hard state picture is that the accretion diskis truncated, perhaps at hundreds of gravitational radii from the black hole,recent results for the recurrent transient GX 339-4 by Miller and co-workersshow evidence for optically thick material very close to the black hole'sinnermost stable circular orbit. That work focused on an observation of GX339-4 at a luminosity of about 5% of the Eddington limit and used parametersfrom a relativistic reflection model and the presence of a soft, thermalcomponent as diagnostics. In this work, we use similar diagnostics, but extendthe study to lower luminosities (2.3% and 0.8% Ledd) using Swift and RXTEobservations of GX 339-4. We detect a thermal component with an inner disktemperature of ~0.2 keV at 2.3% Ledd. We detect broad features due to ironKalpha that are likely related to reflection of hard X-rays off the opticallythick material. If these features are broadened by relativistic effects, theyindicate that optically thick material resides within 10 Rg down to 0.8% Ledd,and the measurements are consistent with the inner radius of the disk remainingat ~4 Rg down to this level. However, we also discuss an alternative model forthe broadening, and we note that the evolution of the thermal component is notentirely consistent with the constant inner radius interpretation. Finally, wediscuss the results in terms of recent theoretical work on the possibility thatmaterial may condense to maintain an inner optically thick disk.

Broadband X-ray Spectra of GX 339-4 and the Geometry of Accreting Black Holes in the Hard State