Relativistic Line Reverberation in Tidal Disruption Events

When normal stars run into those supermassive black holes at the centers of normal galaxies, they could be totally or partly disrupted by the tidal force from the black holes. Part of the debris of the disrupted stars would be accreted by the central black holes, causing the so-called Tidal Disruption Flares (TDFs) associated with Tidal Disruption Events (TDEs). These TDFs provide great opportunities for us to probe those dormant SMBHs (or IMBHs) at the centers of normal galaxies, which represent the majority of those SMBHs in our universe. Relativistic line reverberation, probably in the X-ray and UV band, will be able to probe the mass and spin of the SMBHs as well as General Relativistic (GR) effects (e.g., Lense-Thirring precession and Bardeen-Petterson effect).

We have initiated an internationally competitive efforts to perform X-ray line reverberation in the early phase of TDFs aiming at the above goals since late 2010. Target-of-Opportunity (ToO) X-ray observations with current Swift and XMM-Newton are very necessary, but we need to trigger such observations at much earlier times - the most promising trigger would be from sensitive, wide Field-of-View (FoV) radio monitoring facilities, such as the Square Kilometer Array (SKA) (see Yu et al. 2015).

The sensitive wide field-of-view monitoring of the SKA in the radio band will be able to detect jet activities due to the accretion of the debris flow of disrupted stars onto the SMBH at the very early stage when the mass accretion rate is very low. The SKA’s detections will give future missions such as Athena+ or eXTP enough time to respond and perform observations X-ray spectral observations to detect possible X-ray line signatures expected at the very early stages, allowing us to probe the mass and the spin of those SMBHs and detect GR effects with great details.

We make use of space observatories such as Swift and XMM-Newton to study the X-ray spectra at the early phase of TDFs. In the future, we look forward to future X-ray timing/spectral missions: eXTP, LOFT and several other X-ray telescopes.

Here below are the reviews/papers about the field:

• X-ray reverberation around accreting black holes (Uttley, P. et al. 2014, ARAA, 22, 72)

Representative Publications:

• Prediction of relativistic line reverberation in TDFs

  • Zhang, Wenda; Yu, Wenfei; Karas, Vladimír; Dovčiak, Michal "Predictions for the Reverberating Spectral Line from a Newly Formed Black Hole Accretion Disk: Case of Tidal Disruption Flares" 2015ApJ...807...89Z

• Early phase discovery of Galactic and extraGalactic black hole transients

  • Yu, W., Zhang, H., Yan, Z. And Zhang, W. “Early Phase Detection and Coverage of Extragalactic and Galactic Black Hole X-ray Transients with SKA” SKA white book chapter

Here below are relevant space observation programs:

• XMM-Newton AO-17: our proposal on extragalactic transients is awarded time again for joint XMM/Swift observations of a future TDE flare

  • XMM-Newton AO17 accepted observations
  • Science: relativistic astrophysics during the very early phase of a future TDE flare !!!

• XMM-Newton AO-13: joint XMM-Newton/Swift ToO program, performed in early 2017

  • XMM-Newton AO13 accepted observations

[ version last updated: 2017.10.10 wenfei @shao.ac.cn ]