| Name: Mainak Chatterjee |
| Affiliation: Ashoka University |
| Conference ID: ASI2026_940 |
| Title: QPO polarization in Black Hole binaries. |
| Abstract Type: Poster |
| Abstract Category: High Energy Phenomena, Fundamental Physics and Astronomy |
| Author(s) and Co-Author(s) with Affiliation: Mainak Chatterjee(Ashoka University, Rajiv Gandhi Education City, Rai, Sonipat, Haryana 131021, India), Dipankar Bhattacharya(Ashoka University, Rajiv Gandhi Education City, Rai, Sonipat, Haryana 131021, India) |
| Abstract: We study the polarization of quasi-periodic oscillations (QPO) in the X-ray emission from accreting black hole binary systems. The QPO, commonly attributed to relativistic precession of the inner accretion flow, has been expected to exhibit a significant polarization modulation. Recent observations from the IXPE mission, however, place upper limits well below the expected levels.
In this work, we explore the effects of an additional comptonizing medium in the form of a hot corona surrounding the inner precessing flow, in a geometry inspired by the model of Karpouzas et al. [1,2]. We consider seed photons to originate from a narrow annular region of the precessing inner disk, with an assumed degree of polarization, which are then upscattered by the surrounding spherical stationary corona.
We compute the resulting polarization degree and polarization angle and examine their spectral and temporal variations. Using a weighted Monte Carlo simulation technique, we predict polarization variability and spectral lags as functions of QPO frequency and source state in the hardness-intensity diagram. By combining key elements of QPO origin with the Karpouzas et al. model, this work aims to develop a unified diagnostic linking timing, spectroscopy and polarimetry, and make testable predictions for current and future X-ray polarimetry missions.
References:
[1] Karpouzas, K., et al. (2020). The Comptonizing medium of the neutron star in 4U 1636–53 through its lower kilohertz quasi-periodic oscillations. Monthly Notices of the Royal Astronomical Society, 492(1), 1399–1415.
[2] Karpouzas, K., et al. (2021). A variable corona for GRS 1915+105. Monthly Notices of the Royal Astronomical Society, 503(4), 5522–5533.
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