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X-Ray Intraday Variability of the Blazar OJ 287 Observed with XMM-Newton

Tao Huang, Alok C. Gupta, Lang Cui, Ashutosh Tripathi, Yongfeng Huang, P. U. Devanand, Xiang Liu

Abstract

We present X-ray intraday variability, cross-correlated variability, and power spectrum density analysis of the binary black hole blazar candidate OJ 287. The X-ray pointed observations of the source were carried out on eight occasions by the EPIC-pn camera on board the XMM-Newton satellite from November 2005 to November 2022. These good time intervals range between 3.6 hours and 24.1 hours. Three energy bands -- 0.2-2 keV (soft), 2-10 keV (hard), and 0.2-10 keV (total) -- have been used to estimate variability. Low amplitude variations are observed in 4, 5, and 6 light curves in soft, hard, and total energy bands, respectively. Only two observation IDs has shown variation in the all energy bands. The discrete correlation function of the light curves in soft and hard energy bands peaks at zero lag, suggesting that the emission in both bands was cospatial and came from the same population of leptons. Red noise dominates the power spectral densities of variable light curves. According to our flux and spectrum investigations, both particle acceleration and synchrotron cooling mechanisms contribute significantly to the emission from this blazar.

X-Ray Intraday Variability of the Blazar OJ 287 Observed with XMM-Newton

Abstract

We present X-ray intraday variability, cross-correlated variability, and power spectrum density analysis of the binary black hole blazar candidate OJ 287. The X-ray pointed observations of the source were carried out on eight occasions by the EPIC-pn camera on board the XMM-Newton satellite from November 2005 to November 2022. These good time intervals range between 3.6 hours and 24.1 hours. Three energy bands -- 0.2-2 keV (soft), 2-10 keV (hard), and 0.2-10 keV (total) -- have been used to estimate variability. Low amplitude variations are observed in 4, 5, and 6 light curves in soft, hard, and total energy bands, respectively. Only two observation IDs has shown variation in the all energy bands. The discrete correlation function of the light curves in soft and hard energy bands peaks at zero lag, suggesting that the emission in both bands was cospatial and came from the same population of leptons. Red noise dominates the power spectral densities of variable light curves. According to our flux and spectrum investigations, both particle acceleration and synchrotron cooling mechanisms contribute significantly to the emission from this blazar.
Paper Structure (18 sections, 19 equations, 10 figures)

This paper contains 18 sections, 19 equations, 10 figures.

Table of Contents

  1. Introduction
  2. Data Selection and Reduction
  3. Data Selection
  4. Data Reduction
  5. Analytical Methods
  6. Excess Variance and Fractional Variability
  7. Flux Variability Timescale
  8. Power Spectral Density
  9. Discrete Correlation Function
  10. Hardness Ratio
  11. Results
  12. Intraday Variation In X-ray Flux
  13. Intraday Spectral Variability
  14. Power Spectral Density Analysis
  15. Intraday cross-correlated variability
  16. ...and 3 more sections

Figures (10)

  • Figure 1: XMM-Newton observations of OJ 287: LCs for all observation IDs in the total band (0.2 -- 10 keV).
  • Figure 2: Light curves (LCs) from 8 pointed XMM-Newton observations are shown in the soft (red points) and hard (blue points) bands. The corresponding observation IDs are indicated above each plot.
  • Figure 3: HR plots for all observations by XMM-Newton.
  • Figure 4: The PSD of all LCs (variable) in the soft energy band from XMM-Newton observations. The Obs ID and spectral index are labeled. The solid line represents the power-law fit to the red noise. The red dashed curve represents the 3$\sigma$ level of the red noise, and the dashed horizontal line indicates the Poisson noise level.
  • Figure 5: The PSD of all LCs (variable) in the hard energy band from XMM-Newton observations. The Obs ID and spectral index are labeled. The solid line represents the power-law fit to the red noise. The red dashed curve represents the 3$\sigma$ level of the red noise, and the dashed horizontal line indicates the Poisson noise level.
  • ...and 5 more figures