AAS 195th Meeting, January 2000
Session 37. Stellar Mass Black Holes
Display, Thursday, January 13, 2000, 9:20am-6:30pm, Grand Hall

[Previous] | [Session 37] | [Next]

[37.03] Implications of Thermal/Non-thermal Comptonization Spectral Fits for GRS 1915+105

T.J. Maccarone, P.S. Coppi (Yale University), R.E. Taam (Northwestern University)

We present the results of spectral fits of PCA and HEXTE observations from RXTE of GRS 1915+105 using the EQPAIR model of Coppi et al to assess the effects of thermal and non-thermal Comptonization, as well as reflection. We note that such self-consistent models result in larger inner disk radii and lower disk temperatures than the previous fits based on multi-temperature blackbody and power law models, thus alleviating the problem of small inner disk radii (less than about 1 Schwarzchild radius) occassionally inferred from such models.

We also note that the spectral fits are generally much better for the radio low states of GRS 1915+105 than the radio high states. For the radio high states, the lower energy PCA data appear to require a very small nonthermal component in the Comptonization spectrum. Adopting this model, however, the HEXTE data then show an excess of hard emission above 50 keV. This hard excess can be accounted for by adding an additional power law component, with a typical spectral index of 1.5. Such an index is typical of what is found in the rising portion of the spectrum of the Compton bump in a synchrotron self-Compton (SSC) emission model. We discuss the range of disk and jet parameters necessary for this power law component to be interpreted as emission from Compton scattering in the jet as well as the observations that can be used to test this intepretation of the spectrum.

The author(s) of this abstract have provided an email address for comments about the abstract: maccaron@astro.yale.edu

[Previous] | [Session 37] | [Next]