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    Controversy of the GRO J1655-40 Black Hole Mass and Spin Estimates and Its Possible Solutions

    Zdeněk Stuchlík · Červenec 01, 2016 · Fyzika · 0 comments
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    Publication date: Jul 2016

    Abstract:
    Estimates of the black hole mass M and the dimensionless spin a in the
    microquasar GRO J1655-40 implied by strong gravity effects related to
    the timing and spectral measurements are controversial, if the mass
    restriction determined by the dynamics related to independent optical
    measurements, M opt = (5.4 ± 0.3) M ☉, is applied.
    The timing measurements of twin high-frequency (HF) quasiperiodic
    oscillations (QPOs) with the frequency ratio 3:2 and the simultaneously
    observed low-frequency (LF) QPO imply spin in the range ain
    (0.27{–}0.29) if models based on the frequencies of geodesic epicyclic
    motion are used to fit the timing measurements, and the correlated
    creation of the twin HF QPOs and the LF QPO at a common radius is
    assumed. On the other hand, the spectral continuum method implies ain
    (0.65{–}0.75), and the Fe-line-profile method implies ain
    (0.94{–}0.98). This controversy can be cured if we abandon the
    assumption of the occurrence of the twin HF QPOs and the simultaneously
    observed LF QPO at a common radius. We demonstrate that the epicyclic
    resonance model of the twin HF QPOs is able to predict the spin in
    agreement with the Fe-profile method, but no model based on the geodesic
    epicyclic frequencies can be in agreement with the spectral continuum
    method. We also show that the non-geodesic string loop oscillation model
    of twin HF QPOs predicts spin a > 0.3 under the optical measurement
    limit on the black hole mass, which is in agreement with both the
    spectral continuum and Fe-profile methods.

    Authors:
    Stuchlík, Z.; Kološ, M.;

    https://ui.adsabs.harvard.edu/abs/2016ApJ…825…13S

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