1998/09/08 by John A. Tomsick, Philip Kaaret, Richard A. Kroeger +1 · 2 citations
Physics and Astronomy · #Astrophysical Phenomena and Observations #Black hole (networking) #Eddington luminosity #Flux (metallurgy) #Gamma-ray bursts and supernovae #K-line #Line (geometry) #Luminosity #Photon #Pulsars and Gravitational Waves Research #Spectral index #Spectral line #astro-ph
paper · pdf · doi:10.1086/306797
20 pages, 5 figures, Accepted for publication in the Astrophysical Journal
arxiv created 1998/09/08 · openalex publication_date 1999/02/20 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06
We present broadband (2 keV-2 MeV) X-ray spectra of GRO J1655-40, a luminous X-ray transient and occasional source of relativistic radio jets, obtained with the Rossi X-Ray Timing Explorer ( RXTE ) and the Oriented Scintillation Spectrometer Experiment. In one observation, the luminosity is found to be 18% of the Eddington limit, which is one of the highest luminosities ever observed from GRO J1655-40. For this observation, we find that an adequate fit is obtained when a broad iron line and a reflection component are added to a model consisting of a power law plus a soft excess component. The 95% confidence lower limit on the rms line width is 0.86 keV. The power-law component has a photon index of 2.72 and extends to at least 800 keV without a cutoff. After this observation, a significant drop in the (5-12 keV)/(1.5-5 keV) hardness ratio occurred on a timescale less than 2 hr. From an RXTE observation of GRO J1655-40 made after the hardness transition, we find that the power-law index is harder (α=2.415±0.011), the flux of the power-law component is lower, and the total luminosity is 10% of the Eddington limit. The change in the power-law component is consistent with the correlation between the spectral index and power-law flux previously reported for GRO J1655-40.