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This content will become publicly available on April 2, 2026

Title: Eight Years of Light from ASASSN-15oi: Toward Understanding the Late-time Evolution of TDEs
Abstract We present results from an extensive follow-up campaign of the tidal disruption event (TDE) ASASSN-15oi spanningδt ∼ 10–3000 days, offering an unprecedented window into the multiwavelength properties of a TDE during its first ≈8 yr of evolution. ASASSN-15oi is one of the few TDEs with strong detections at X-ray, optical/UV, and radio wavelengths and it also featured two delayed radio flares atδt ∼ 180 days andδt ∼ 1400 days. Our observations atδt > 1400 days reveal an absence of thermal X-rays, a late-time variability in the nonthermal X-ray emission, and sharp declines in the nonthermal X-ray and radio emission atδt ∼ 2800 days and ∼3000 days, respectively. The UV emission shows no significant evolution atδt > 400 days and remains above the pre-TDE level. We show that a cooling envelope model can explain the thermal emission consistently across all epochs. We also find that a scenario involving episodic ejection of material due to stream–stream collisions can possibly explain the first radio flare. Given the peculiar spectral and temporal evolution of the late-time emission, however, constraining the origins of the second radio flare and the nonthermal X-rays remains challenging. Our study underscores the critical role of long-term, multiwavelength follow-up to fully characterize the extended evolutionary phases of a TDE.  more » « less
Award ID(s):
2224255 2307668 2307710 2206243
PAR ID:
10613960
Author(s) / Creator(s):
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more » ; ; ; ; ; ; ; ; ; « less
Publisher / Repository:
ApJ
Date Published:
Journal Name:
The Astrophysical Journal
Volume:
983
Issue:
1
ISSN:
0004-637X
Page Range / eLocation ID:
29
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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