Far Ultraviolet Variability on Timescales of a Few hours in the Recurrent Nova M31N 2008-12a: Origin and Implications
Abstract
The fate of the accretion disk during nova eruptions remains an open question, particularly in rapidly recurring novae, where high accretion rates and low ejecta masses may allow the disk to survive the eruption. M31N 2008-12a, the most rapidly recurring nova currently known, provides an ideal laboratory for investigating this process. We present high-cadence AstroSat/UVIT observations obtained during eruptions between 2019 and 2023. Complementary multiwavelength observations of the 2023-2025 eruptions are also presented, which are broadly consistent with prior outbursts. The main result is the early onset of intrinsic far-ultraviolet variability on a timescale of a few hours, approximately 4-5 days after eruption, which is of astrophysical origin. A periodicity search suggests a tentative signal at 4.60 (+0.25,-0.15) hr at 2.3 sigma confidence, detected in high-cadence UVIT/FUV observations. We show that a Keplerian orbit of this timescale lies not only within the Roche lobe of the white dwarf in M31N 2008-12a, but also within the circularisation radius. A disk-related origin is, thus, physically plausible. The presence of this UV variability so soon after eruption suggests that accretion structures may already exist during the early post-eruption phase, supporting the disk-survival hypotheses. If confirmed by future observations, this method may provide a new dynamical probe of accretion disk survival in rapidly recurring novae.
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BibTeX
@misc{basu2026ultraviolet,
title = {{Far Ultraviolet Variability on Timescales of a Few hours in the Recurrent Nova M31N 2008-12a: Origin and Implications}},
author = {Judhajeet Basu and Sudhanshu Barway and G. C. Anupama and Shatakshi Chamoli and Kulinder Pal Singh and Varun Bhalerao and M. Pavana and Vishwajeet Swain},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.33844},
eprint = {2610.33844},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.33844},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Far Ultraviolet Variability on Timescales of a Few hours in the Recurrent Nova M31N 2008-12a: Origin and Implications
AU - Judhajeet Basu
AU - Sudhanshu Barway
AU - G. C. Anupama
AU - Shatakshi Chamoli
AU - Kulinder Pal Singh
AU - Varun Bhalerao
AU - M. Pavana
AU - Vishwajeet Swain
PY - 2026
DA - 2026/10/24
PB - arXiv
DO - 10.48550/arxiv.2610.33844
UR - https://arxiv.org/abs/2610.33844
AB - The fate of the accretion disk during nova eruptions remains an open question, particularly in rapidly recurring novae, where high accretion rates and low ejecta masses may allow the disk to survive the eruption. M31N 2008-12a, the most rapidly recurring nova currently known, provides an ideal laboratory for investigating this process. We present high-cadence AstroSat/UVIT observations obtained during eruptions between 2019 and 2023. Complementary multiwavelength observations of the 2023-2025 eruptions are also presented, which are broadly consistent with prior outbursts. The main result is the early onset of intrinsic far-ultraviolet variability on a timescale of a few hours, approximately 4-5 days after eruption, which is of astrophysical origin. A periodicity search suggests a tentative signal at 4.60 (+0.25,-0.15) hr at 2.3 sigma confidence, detected in high-cadence UVIT/FUV observations. We show that a Keplerian orbit of this timescale lies not only within the Roche lobe of the white dwarf in M31N 2008-12a, but also within the circularisation radius. A disk-related origin is, thus, physically plausible. The presence of this UV variability so soon after eruption suggests that accretion structures may already exist during the early post-eruption phase, supporting the disk-survival hypotheses. If confirmed by future observations, this method may provide a new dynamical probe of accretion disk survival in rapidly recurring novae.
ER -