A NICER Discovery of a Low-frequency Quasi-periodic Oscillation in the Soft-intermediate State of MAXI J1535-571
Abstract
We present the discovery of a low-frequency ≈5.7 Hz quasi-periodic oscillation (QPO) feature in observations of the black hole X-ray binary MAXI J1535-571 in its soft-intermediate state, obtained in 2017 September-October by the Neutron Star Interior Composition Explorer. The feature is relatively broad (compared to other low-frequency QPOs; quality factor Q ≈ 2) and weak (1.9% rms in 3-10 keV), and is accompanied by a weak harmonic and low-amplitude broadband noise. These characteristics identify it as a weak Type A/B QPO, similar to ones previously identified in the soft-intermediate state of the transient black hole X-ray binary XTE J1550-564. The lag-energy spectrum of the QPO shows increasing soft lags toward lower energies, approaching 50 ms at 1 keV (with respect to a 3-10 keV continuum). This large phase shift has similar amplitude but opposite sign to that seen in Rossi X-Ray Timing Explorer data for a Type B QPO from the transient black hole X-ray binary GX 339-4. Previous phase-resolved spectroscopy analysis of the Type B QPO in GX 339-4 pointed toward a precessing jet-like corona illuminating the accretion disk as the origin of the QPO signal. We suggest that this QPO in MAXI J1535-571 may have the same origin, with the different lag sign depending on the scale height of the emitting region and the observer inclination angle.
- Publication:
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The Astrophysical Journal
- Pub Date:
- October 2018
- DOI:
- 10.3847/2041-8213/aae1a4
- arXiv:
- arXiv:1809.07556
- Bibcode:
- 2018ApJ...865L..15S
- Keywords:
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- accretion;
- accretion disks;
- black hole physics;
- stars: black holes;
- X-rays: binaries;
- X-rays: individual: MAXI J1535;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- Accepted for publication in ApJ Letters