XMM-Newton detection of soft time lags in the TDE candidate AT 2018fyk

Abstract

In this letter we report a tentative detection of soft time lags (i.e. variability of softer photons lags behind the variability of harder photons) in one $XMM-Newton$ observation of the tidal disruption event (TDE) candidate AT 2018fyk while the source was in the hard spectral state. The lags are detected at $6.51\times 10^{-5}\mathrm{Hz}$. The amplitude of the lags with respect to 0.5$-$1 keV monotonically decreases with the photon energy, from $\sim 1200\mathrm{s}$ at 0.3$-$0.5 keV to $\sim -4200\mathrm{s}$ at 3$-$5 keV (in our convention a positive lag means lagging behind the reference band). We find that the amplitude is proportional to the logarithm of the energy separation between the examined band and the reference band. The energy-dependent covariance spectrum indicates that the correlated variability is more likely to be associated with the non-thermal radiation. The soft lags are difficult to reconcile with the reverberation scenario that are used to explain the soft lags in active galactic nuclei. On the other hand, the observed soft lags are consistent with the picture that the soft X-rays are down-scattered hard X-rays by the outflow as predicted by ``unification'' models of TDEs.

arXiv comment5 pages, 3 figures; accepted for publication in MNRAS Letters

References in corpus (35)

• RXTE Observation of Cygnus X-1: II. Timing Analysis
• Tidal Disruption Events
• Combined Long and Short Timescale X-ray Variability of NGC4051 with RXTE and XMM-Newton
• A unified model for tidal disruption events
• Discovery of a relation between black hole mass and soft X-ray time lags in active galactic nuclei
• The causal connection between disc and power-law variability in hard state black hole X-ray binaries
• A Dark Year for Tidal Disruption Events
• Accretion disc variability in the hard state of black hole X-ray binaries
• Evidence for rapid disk formation and reprocessing in the X-ray bright tidal disruption event AT 2018fyk
• From ultraluminous X-ray sources to ultraluminous supersoft sources: NGC 55 ULX, the missing link
• Long XMM observation of the Narrow-Line Seyfert 1 galaxy IRAS13224-3809: rapid variability, high spin and a soft lag
• Frequency-dependent time lags in the X-ray emission of the Seyfert galaxy NGC 7469
• Rapid accretion state transitions following the tidal disruption event AT2018fyk
• A soft X-ray reverberation lag in the AGN ESO 113-G010
• Spectral-timing evidence for a Very High State in the Narrow Line Seyfert 1 Ark 564
• X-ray Variability of the Seyfert 1 Markarian 335: Power Spectrum and Time Lags
• Evolution of the reverberation lag in GX 339-4 at the end of an outburst
• Energy and time-lag spectra of black-hole systems in the low state
• Phase Lags and Coherence of X-Ray Variability in Black Hole Candidates
• The linear rms-flux relation in an Ultraluminous X-ray Source
• X-ray Reverberation close to the black hole in RE J1034+396
• Fainter harder brighter softer: a correlation between ${\alpha }_{\mathrm{ox}}$ , X-ray spectral state and Eddington ratio in tidal disruption events
• Phase Lag and Coherence Function of X-ray emission from Black Hole Candidate XTE J1550-564
• Time lags in the ultraluminous X-ray source NGC 5408 X-1: implications for the black hole mass
• X-ray time delays in the Narrow Line Seyfert 1 galaxy PG 1244+026
• The evolution of the X-ray phase lags during the outbursts of the black hole candidate GX 339-4
• Hard X-ray Lags in Cygnus X-1
• X-ray time lags and nonlinear variability in the ultraluminous X-ray sources NGC 5408 X-1 and NGC 6946 X-1
• Statistical properties of Fourier-based time-lag estimates
• Discovery of a soft X-ray lag in the Ultraluminous X-ray Source NGC 1313 X-1
• Energy Dependent time lags in the Seyfert 1 galaxy NGC 4593
• The X-ray continuum time-lags and intrinsic coherence in AGN
• The rare X-ray flaring activity of the Ultraluminous X-ray source NGC 4559 X7
• The long term X-ray time-lags of NGC 4051
• Evidence for Fe K${}_{\alpha }$ line and soft X-ray lag in NGC 7456 ULX-1

Cited by in corpus (3)

• Live to die another day: the rebrightening of AT2018fyk as a repeating partial tidal disruption event
• AT2018fyk: Candidate Tidal Disruption Event by a (Super)massive Black Hole Binary
• In-flight Timing Calibration of the Follow-up X-Ray Telescope on Board the Einstein Probe