2019/06/30 by P. G. Jonker, N. C. Stone, Nicholas C. Stone +6
Physics and Astronomy · #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Black hole (networking) #Brightness #Gamma-ray bursts and supernovae #Luminosity #Physics #Power law #Pulsars and Gravitational Waves Research #Statistics #astro-ph.HE
paper · pdf · doi:10.3847/1538-4357/ab659c
Accepted for publication to ApJ, 18 pages, 4 figures
openalex created_date 2019/07/12 · arxiv created 2019/12/24 · openalex publication_date 2020/02/01 · arxiv updated 2020/02/12 · openalex updated_date 2026/08/05
Abstract We present Chandra X-ray observations of four optically selected tidal disruption events (TDEs) obtained 4–9 yr after discovery. Three sources were detected with luminosities between 9 × 10 40 and 3 × 10 42 erg s −1 . The spectrum of PTF09axc is consistent with a power law of index 2.5 ± 0.1, whereas the spectrum of PTF09ge is very soft. The power-law spectrum of PTF09axc and prior literature findings provide evidence that TDEs transition from an early-time soft state to a late-time hard state many years after disruption. We propose that the time to peak luminosity for optical and X-ray emission may differ substantially in TDEs, with X-rays being produced or becoming observable later. This delay helps explain the differences in observed properties such as L opt / L X of optically and X-ray-selected TDEs. We update TDE rate predictions for the eROSITA instrument: it ranges from 3 to 990 yr −1 , depending sensitively on the distribution of black hole spins and the time delay between disruption and peak X-ray brightness. We further predict an asymmetry in the number of retrograde and prograde disks in samples of optically and X-ray-selected TDEs. The details of the observational biases can contribute to observed differences between optically and X-ray-selected TDEs (with optically selected TDEs being fainter in X-rays for retrograde TDE disks).