TY - JOUR
T1 - GRS 1915+105
T2 - The distance, radiative processes and energy-dependent variability
AU - Zdziarski, Andrzej A.
AU - Gierliński, Marek
AU - Rao, A. R.
AU - Vadawale, S. V.
AU - Mikolajewska, Joanna
PY - 2005/7/1
Y1 - 2005/7/1
N2 - We present an exhaustive analysis of five broad-band observations of GRS 1915+105 in two variability states, x and ω, observed simultaneously by the Proportional Counter Array (PCA) and High-Energy X-ray Timing Experiment (HEXTE) detectors aboard the Rossi X-ray Timing Explorer, and the Oriented Scintillation Spectrometer Experiment (OSSE) detector aboard the Compton Gamma-ray Observatory. We find all the spectra well fitted by Comptonization of disc blackbody photons, with very strong evidence for the presence of a non-thermal electron component in the Comptonizing plasma. Both the energy and the power spectra in the x state are typical of the very high/intermediate state of black hole binaries. The spectrum of the ω state is characterized by a strong blackbody component Comptonized by thermal electrons and a weak non-thermal tail. We then calculate rms spectra (fractional variability as functions of energy) for the PCA data. We accurately model the rms spectra by coherent superposition of variability in the components implied by the spectral fits, namely a less variable blackbody and more variable Comptonization. The latter dominates at high energies, resulting in a flattening of the rms at high energies in most of the data. This is also the case for the spectra of the quasiperiodic oscillations present in the x state. Then, some of our data require a radial dependence of the rms of the disc blackbody. We also study the distance to the source, and find d ≃ 11 kpc as the most likely value, contrary to a recent claim of a much lower value.
AB - We present an exhaustive analysis of five broad-band observations of GRS 1915+105 in two variability states, x and ω, observed simultaneously by the Proportional Counter Array (PCA) and High-Energy X-ray Timing Experiment (HEXTE) detectors aboard the Rossi X-ray Timing Explorer, and the Oriented Scintillation Spectrometer Experiment (OSSE) detector aboard the Compton Gamma-ray Observatory. We find all the spectra well fitted by Comptonization of disc blackbody photons, with very strong evidence for the presence of a non-thermal electron component in the Comptonizing plasma. Both the energy and the power spectra in the x state are typical of the very high/intermediate state of black hole binaries. The spectrum of the ω state is characterized by a strong blackbody component Comptonized by thermal electrons and a weak non-thermal tail. We then calculate rms spectra (fractional variability as functions of energy) for the PCA data. We accurately model the rms spectra by coherent superposition of variability in the components implied by the spectral fits, namely a less variable blackbody and more variable Comptonization. The latter dominates at high energies, resulting in a flattening of the rms at high energies in most of the data. This is also the case for the spectra of the quasiperiodic oscillations present in the x state. Then, some of our data require a radial dependence of the rms of the disc blackbody. We also study the distance to the source, and find d ≃ 11 kpc as the most likely value, contrary to a recent claim of a much lower value.
KW - Accretion, accretion discs
KW - Binaries: general
KW - Black hole physics
KW - Radiation mechanisms: non-thermal
KW - Stars: individual: GRS 1915+105
KW - X-rays: Stars
UR - http://www.scopus.com/inward/record.url?scp=22144452560&partnerID=8YFLogxK
U2 - 10.1111/j.1365-2966.2005.09112.x
DO - 10.1111/j.1365-2966.2005.09112.x
M3 - Article
AN - SCOPUS:22144452560
VL - 360
SP - 825
EP - 838
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
SN - 0035-8711
IS - 3
ER -