A variable-frequency HFQPO in GRS 1915+105 as observed with Astrosat

Abstract

From the analysis of more than 92 ks of data obtained with the laxpc instrument on board Astrosat we have detected a clear high-frequency QPO whose frequency varies between 67.4 and 72.3 Hz. In the classification of variability classes of GRS 1915+105, at the start of the observation period the source was in class omega and at the end the variability was that of class mu: both classes are characterized by the absence of hard intervals and correspond to disk-dominated spectra. After normalization to take into account time variations of the spectral properties as measured by X-ray hardness, the QPO centroid frequency is observed to vary along the hardness-intensity diagram, increasing with hardness. We also measure phase lags that indicate that HFQPO variability at high energies lags that at lower energies and detect systematic variations with the position on the hardness-intensity diagram. This is the first time that (small) variations of the HFQPO frequency and lags are observed to correlate with other properties of the source. We discuss the results in the framework of existing models, although the small (7%) variability observed is too small to draw firm conclusions.

arXiv comment7 pages, 9 figures; Accepted in MNRAS. Some figures are at lower resolution than journal version

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Cited by in corpus (15)

• A review of quasi-periodic oscillations from black hole X-ray binaries: observation and theory
• Large Area X-ray Proportional Counter (LAXPC) in Orbit Performance : Calibration, background, analysis software
• AstroSat view of GRS 1915+105 during the Soft State: Detection of HFQPOs and estimation of Mass and Spin
• Confrontation of Observation and Theory: High Frequency QPOs in X-ray Binaries, Tidal Disruption Events, and Active Galactic Nuclei
• Re-observing the NLS1 Galaxy RE J1034+396. I. the Long-term, Recurrent X-ray QPO with a High Significance
• Re-observing the NLS1 Galaxy RE J1034+396. II. New Insights on the Soft X-ray Excess, QPO and the Analogy with GRS 1915+105
• Wide-band view of High Frequency QPOs of GRS 1915+105 in 'softer' variability classes observed with AstroSat
• The INTEGRAL view on Black Hole X-ray Binaries
• Unraveling the foretime of GRS 1915+105 using AstroSat observations: Wide-band spectral and temporal characteristics
• Broadband Spectral and Timing Properties of MAXI J1348-630 using AstroSat and NICER Observations
• A Machine Learning approach for classification of accretion states of Black hole binaries
• Correlations between QPO frequencies and spectral parameters of GRS 1915+105 using AstroSat observations
• Probing black-hole accretion through time variability
• Discovery of a new flaring class in GRS 1915+105 using AstroSat
• LAXPC instrument onboard AstroSat: Five exciting years of new scientific results specially on X-ray Binaries