| Speaker: | Pavan Vynathea (CITA) |
|---|---|
| Title: | Asymmetrical supernovae triggered by the tidal disruption of white dwarfs |
| Date (JST): | Tue, Mar 03, 2026, 11:00 - 12:00 |
| Place: | Seminar Room A |
| Abstract: |
In this era of transient astronomy, we expect to discover exotic transients such as tidal disruption events (TDEs) of white dwarfs (WDs). A WD TDE can occur in dense stellar cluster cores, where a WD passes within the tidal radius of a black hole (BH). Unlike standard TDEs, very close encounters cause tidal compression in the WD, raising temperatures and pressures enough to ignite runaway fusion and trigger an asymmetric thermonuclear supernova (SN). We use the hydrodynamics code AREPO, equipped with a nuclear reaction network, to simulate TDEs of a carbon-oxygen WD due to an intermediate-mass BH for different scaled impact parameters b, defined as the ratio of periapsis distance to tidal radius. Wider encounters (b = 0.20) lead to standard TDEs, while closer ones produce produce combined TDE–SN events, converting C-12 and O-16 into heavier isotopes up to Ni-56 and ejecting material asymmetrically. The Ni-56 fraction rises from 8% at b = 0.18 to 80% at b = 0.10. We feed the AREPO data into the 1D and 2D radiative-transfer codes CMFGEN and LONG_POL to model light curves and spectra. Bolometric luminosities peak 14–23 days after disruption, with lower-b cases peaking higher and later. Models with larger Ni-56 masses show stronger Fe and Co lines and weaker O, Si, and Ca lines. The 2D spectra reveal viewing-angle–dependent brightness and Doppler shifts, highlighting the impact of ejecta asymmetry. The diversity of spectra from WD TDEs suggests they may account for a wide range of observed transients. |
