Volume 386, Number 1, April IV 2002
|Page(s)||271 - 279|
|Section||Interstellar and circumstellar matter|
|Published online||15 April 2002|
Energy dependence of a low frequency QPO in GRS 1915+105
DSM/DAPNIA/Service d'Astrophysique (CNRS URA 2052), CEA Saclay, 91191 Gif-sur-Yvette, France
2 Instituto de Astronomía y Física del Espacio/CONICET, Buenos Aires, Argentina
3 Institute of Space and Astronautical Science, Yoshinodai 3-1-1, Sagamihara, Kanagawa 229-8510, Japan
4 RIKEN The Institute of Physical and Chemical Research, Hirosawa 2-1, Wako, Saitama 351-0198, Japan
Corresponding author: J. Rodriguez, firstname.lastname@example.org
Accepted: 5 February 2002
We analyze a set of three RXTE Target of Opportunity observations of the Galactic microquasar GRS 1915+105, observed on April 2000, during a multi-wavelength campaign. During the three observations, a strong, variable low frequency ( Hz) quasi periodic oscillation (hereafter QPO), often referred to as the ubiquitous QPO, is detected together with its first harmonic. We study the spectral properties of both features, and show that: 1) their frequency variations are better correlated with the soft X-ray flux ( keV), favoring thus the location of the QPO in the accretion disk; 2) the QPO affects more the hard X-rays, usually taken as the signature of an inverse Compton scattering of the soft photons in a corona; 3) the fundamental and its harmonic do not behave in the same manner: the fundamental sees its power increase with the energy up to 40 keV, whereas the harmonic increases up to ~10 keV. The results presented here could find an explanation in the context of the Accretion-Ejection Instability, which could appear as a rotating spiral or hot point located in the disk, between its innermost edge and the co-rotation radius. The presence of the harmonic could then be a signature of the non-linear behavior of the instability. The high-energy (>40 keV) decrease of the fundamental would favor an interpretation where most or all of the quasi-periodic modulation at high energies comes not from the comptonized corona as usually assumed, but from a hot point in the optically thick disk.
Key words: stars: individual: GRS 1915+105 / X-rays: binaries
© ESO, 2002
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.