A Library of Synthetic X-Ray Spectra for Fitting Tidal Disruption Events

Abstract

We present a tabulated version of our slim-disk model for fitting tidal disruption events (TDEs). We create a synthetic X-ray spectral library by ray-tracing stationary general relativistic slim disks and including gravitational redshift, Doppler, and lensing effects self-consistently. We introduce the library to reduce computational expense and increase access for fitting future events. Fitting requires interpolation between the library spectra; the interpolation error in the synthetic flux is generally <10% (it can rise to 40% when the disk is nearly edge-on). We fit the X-ray spectra of the TDEs ASASSN-14li and ASASSN-15oi, successfully reproducing our earlier constraints on black hole mass M • and spin a • from full on-the-fly ray-tracing. We use the library to fit mock observational data to explore the degeneracies among parameters, finding that (1) spectra from a hotter thermal disk and edge-on inclination angle offer tighter constraints on M • and a •; (2) the constraining power of spectra on M • and a • increases as a power law with the number of X-ray counts, and the index of the power law is higher for hotter thermal disk spectra; (3) multiepoch X-ray spectra partially break the degeneracy between M • and a •; (4) the time-dependent level of X-ray absorption can be constrained from spectral fitting. The tabulated model and slim-disk model are available at https://doi.org/10.25739/hfhz-xn60.

A Census of Archival X-Ray Spectra for Modeling Tidal Disruption Events

“…At the time of writing, only 3 of the 100+ known TDEs in our new TDE catalog have been successfully analyzed for M • and a • using the techniques in Wen et al (2020Wen et al ( , 2021 and Cao et al (2023): Each of these analyses required a minimum computational time of 10 4 CPU hours. However, new interpolation techniques are now able to closely mirror those prior results at much less computational expense (∼10 CPU hours) (Wen et al 2022b). The large number of TDEs with archival X-ray spectra in our new catalog, as well as the expected growth in discovery rates (∼10 2 -10 3 per year), shows the utility of the new interpolation methods for constraining the distributions of M • and a • for TDEs for the first time.…”

“…From our past work (Wen et al 2022b) and, as shown later in Figure 2, we have learned that this exposure time produces counts in most nearby TDEs that are adequate to constrain M • and a • . 2.…”

“…The spectra of TDEs disrupted by higher-mass SMBHs evolve on shorter timescales than those originating from less-massive IMBHs (Hayasaki et al 2013;Shen & Matzner 2014;Shiokawa et al 2015;Bonnerot et al 2016;Hayasaki et al 2016). For black holes of the same mass, tighter constraints on M • and a • from TDE spectra arise from epochs of super-Eddington accretion than at later times (Wen et al 2022b).…”

“…New stationary general-relativistic slim-disk accretion models that have been adapted for sub-and super-Eddington accretion rates show promising results in constraining M • and a • by fitting observed X-ray spectra from TDEs (SMBHs in Wen et al 2020 and intermediate-mass (10 2 M e  M •  10 5 M e ) black holes or IMBHs in Wen et al 2021 andCao et al 2023). Analysis of synthetic TDE X-ray spectra via the slim-disk model by Wen et al (2022b) shows that the useful constraints on M • and a • arise from TDEs with (1) lower black hole mass, (2) higher black hole spin, and either (3a) (at least) a singular observation with high counts from an early super-Eddington accretion period or, barring that, (3b) multiple observations with high counts from later lower accretion rate periods. We therefore consider TDEs with deep, multiepoch archival X-ray spectra, particularly at early times (i.e., within the first ∼100 days of discovery), prime candidates for slimdisk model fitting.…”

Extreme accretion events: TDEs and changing‐look AGN

“…Meanwhile, TDE statistics and the physics in their different regimes of evolution (Figure 1), allow us to address many more questions of broad relevance for extragalactic astrophysics (Section 2.2). These are aided by simulations that have not only allowed to confirm some of the assumptions in the early analytical models but have also allowed to expand the regime of TDE parameter space to include different types of disrupted stars, different stellar orbits including high penetration factors, extreme stellar compression, spinning and non‐spinning SMBHs, single and binary stars, and single and binary SMBHs; some regimes only accessible numerically in very advanced computer simulations (Andalman et al 2022; Bonnerot & Wenbin 2022; Bu et al 2022; Coughlin & Nixon 2022; Cufari et al 2022; Ryu et al 2022b; Wen et al 2022, and references therein) with many new predictions of observable facets of TDEs.…”