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Temporal Variation of the Coronal Parameter in a Jetted Tidal Disruption Event: Swift J1644+57

Arka Chatterjee, Kimitake Hayasaki, Prantik Nandi, Neeraj Kumari, Skye R. Heiland, Arghajit Jana, Sachindra Naik, Samar Safi-Harb

Abstract

Tidal Disruption Events are exotic astrophysical phenomena where matter from a star or the interstellar medium is captured by a supermassive black hole. The process liberates enormous energy, within a few months to a year timescale, enough to detect dormant black holes in near as well as the farthest galaxies. We revisit the long-term spectral variabilities associated with the jetted Tidal Disruption Event \source~by exploring the archival X-ray data obtained with MAXI/GSC, Swift/XRT, and XMM-Newton observatories. Our analysis reveals that the spectral indices decrease non-monotonically as \source~evolves with time. We also find that the soft (0.3-1.5 keV) and hard (1.5-10 keV) X-ray photon counts are highly correlated with a maximum correlation coefficient of 0.95 and peak at {\it zero} lag. Moreover, the soft and hard band variabilities obtained from XMM-Newton observations are highly correlated with a Pearson cross-correlation coefficient of 0.96. This indicates that the soft and hard X-ray photons are emitted from the same site, which is most likely a Compton cloud, i.e., the corona. Assuming the hard X-ray photons originate from the corona, we find that the coronal parameter undergoes rapid expansion during the early phases when accompanied by a relativistic jet launching and subsequently evolves toward a state of saturation with minor fluctuations in the latter stages. The temporal variation of the coronal size is consistent with a simple theoretical conjecture. We also discuss the application of our analytical outcomes to other jetted and non-jetted tidal disruption events.

Temporal Variation of the Coronal Parameter in a Jetted Tidal Disruption Event: Swift J1644+57

Abstract

Tidal Disruption Events are exotic astrophysical phenomena where matter from a star or the interstellar medium is captured by a supermassive black hole. The process liberates enormous energy, within a few months to a year timescale, enough to detect dormant black holes in near as well as the farthest galaxies. We revisit the long-term spectral variabilities associated with the jetted Tidal Disruption Event \source~by exploring the archival X-ray data obtained with MAXI/GSC, Swift/XRT, and XMM-Newton observatories. Our analysis reveals that the spectral indices decrease non-monotonically as \source~evolves with time. We also find that the soft (0.3-1.5 keV) and hard (1.5-10 keV) X-ray photon counts are highly correlated with a maximum correlation coefficient of 0.95 and peak at {\it zero} lag. Moreover, the soft and hard band variabilities obtained from XMM-Newton observations are highly correlated with a Pearson cross-correlation coefficient of 0.96. This indicates that the soft and hard X-ray photons are emitted from the same site, which is most likely a Compton cloud, i.e., the corona. Assuming the hard X-ray photons originate from the corona, we find that the coronal parameter undergoes rapid expansion during the early phases when accompanied by a relativistic jet launching and subsequently evolves toward a state of saturation with minor fluctuations in the latter stages. The temporal variation of the coronal size is consistent with a simple theoretical conjecture. We also discuss the application of our analytical outcomes to other jetted and non-jetted tidal disruption events.
Paper Structure (13 sections, 9 equations, 9 figures, 4 tables)

This paper contains 13 sections, 9 equations, 9 figures, 4 tables.

Table of Contents

  1. Introduction
  2. Data Analysis Process
  3. Swift/XRT
  4. XMM-Newton
  5. Results
  6. Light curves
  7. Spectra
  8. Optxagnf
  9. Discussion
  10. Nuclear Properties
  11. Coronal Variations
  12. Viability of TDE Corona Models
  13. Summary

Figures (9)

  • Figure 1: Upper Panel: X-ray light curves of Swift J1644+57, obtained from the Swift/XRT, are presented for 0.3--1.5 keV (square-light-salmon) and 1.5--10 keV energy bands (diamond-greenish-blu-e points). Lower panel:$\zeta$-DCF cross-correlation between 0.3-1.5 keV and 1.5--10 keV ranges are presented for Swift J1644+57 using Swift/XRT data. Both the energy bands are highly correlated ($\rho_{max}=0.95$). Considering the error bars, no delay is observed between the two X-ray bands.
  • Figure 2: Left Panel: Hardness ratio of Swift J1644+57 is presented. The source exhibited hard spectra throughout the tidal disruption event. The colorbar on top represents the MJD from the start of the event. Right Panel: Correlated variability between 0.2--2 keV and 3--10 keV is observed from XMM-Newton data. The Pearson correlation coefficient is 0.96.
  • Figure 3: left to right: XRT2, XRT6, and XRT10 fitted unfolded spectra are presented for various models. The red line represents the Optxagnf , green represents the Nthcomp, and orange represents the powerlaw model. Corresponding residues are plotted in the bottom panels.
  • Figure 4: Contours of confidence are plotted for Swift /XRT observations fitted with powerlaw and Optxagnf model.
  • Figure 5: Variation of spectral parameters of Swift J1644+57 are presented for powerlaw and optxagnf model. Only stacked Swift/XRT data are employed to fit optxagnf model.
  • ...and 4 more figures