TY - JOUR
T1 - Circularization of tidal debris around white dwarfs
T2 - Implications for gas production and dust variability
AU - Malamud, Uri
AU - Grishin, Evgeni
AU - Brouwers, Marc
N1 - Publisher Copyright:
© 2020 The Author(s).
Copyright:
Copyright 2021 Elsevier B.V., All rights reserved.
PY - 2021/3/1
Y1 - 2021/3/1
N2 - White dwarf (WD) pollution is thought to arise from the tidal disruption of planetary bodies. The initial fragment stream is extremely eccentric, while observational evidence suggest that discs are circular or nearly so. Here, we propose a novel mechanism to bridge this gap and show that the fragments can rapidly circularize through dust or gas drag when they interact with a pre-existing compact disc. We assume that the tidal stream mainly consists of small cohesive fragments in the size range 10-1000 m, capable of resisting the WD tidal forces, whereas the compact discs span a wide mass range. We provide an analytical model, accompanied by N-body simulations, and find a large parameter space in fragment sizes and orbital separation that leads to full circularization. Partial circularization is possible for compact discs that are several orders of magnitudes less massive. We show that dust-induced circularization inherently produces gas as tidal fragments collisionally vapourize the pre-existing dust along their path. We show that ongoing gas production has a higher probability to occur during the early stages of tidal disruption events, resulting from the fact that smaller fragments are the first to circularize. Intermittent gas production however becomes more likely as the tidal stream matures. This could explain why only a small subset of systems with dusty compact discs also have an observed gaseous component. Additionally, the interaction yields fragment erosion by collisional shattering, sputtering, sublimation, and possibly ram pressure. Material scattered by the collisions might form a thin dusty halo that evolves through Poynting-Robertson drag, in compatibility with observed infrared variability.
AB - White dwarf (WD) pollution is thought to arise from the tidal disruption of planetary bodies. The initial fragment stream is extremely eccentric, while observational evidence suggest that discs are circular or nearly so. Here, we propose a novel mechanism to bridge this gap and show that the fragments can rapidly circularize through dust or gas drag when they interact with a pre-existing compact disc. We assume that the tidal stream mainly consists of small cohesive fragments in the size range 10-1000 m, capable of resisting the WD tidal forces, whereas the compact discs span a wide mass range. We provide an analytical model, accompanied by N-body simulations, and find a large parameter space in fragment sizes and orbital separation that leads to full circularization. Partial circularization is possible for compact discs that are several orders of magnitudes less massive. We show that dust-induced circularization inherently produces gas as tidal fragments collisionally vapourize the pre-existing dust along their path. We show that ongoing gas production has a higher probability to occur during the early stages of tidal disruption events, resulting from the fact that smaller fragments are the first to circularize. Intermittent gas production however becomes more likely as the tidal stream matures. This could explain why only a small subset of systems with dusty compact discs also have an observed gaseous component. Additionally, the interaction yields fragment erosion by collisional shattering, sputtering, sublimation, and possibly ram pressure. Material scattered by the collisions might form a thin dusty halo that evolves through Poynting-Robertson drag, in compatibility with observed infrared variability.
KW - planet-disc interactions
KW - transients: Tidal disruption events
KW - white dwarfs
UR - http://www.scopus.com/inward/record.url?scp=85100306513&partnerID=8YFLogxK
U2 - 10.1093/mnras/staa3940
DO - 10.1093/mnras/staa3940
M3 - Article
AN - SCOPUS:85100306513
SN - 0035-8711
VL - 501
SP - 3806
EP - 3824
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 3
ER -