Separating states in astronomical sources using hidden Markov models: with a case study of flaring and quiescence on EV Lac
File(s)
Published version
Author(s)
Zimmerman, Robert
van Dyk, David
Kashyap, Vinay
Siemiginowska, Aneta
Type
Journal Article
Abstract
We present a new method to distinguish between different states (e.g. high and low, quiescent and flaring) in astronomical sources with count data. The method models the underlying physical process as latent variables following a continuous-space Markov chain that determines the expected Poisson counts in observed light curves in multiple passbands. For the underlying state process, we consider several autoregressive processes, yielding continuous-space hidden Markov models of varying complexity. Under these models, we can infer the state that the object is in at any given time. The continuous state predictions from these models are then dichotomized with the help of a finite mixture model to produce state classifications. We apply these techniques to X-ray data from the active dMe flare star EV Lac, splitting the data into quiescent and flaring states. We find that a first-order vector autoregressive process efficiently separates flaring from quiescence: flaring occurs over 30 per cent–40 per cent of the observation durations, a well-defined persistent quiescent state can be identified, and the flaring state is characterized by higher plasma temperatures and emission measures.
Date Issued
2024-11
Date Acceptance
2024-08-30
Citation
Monthly Notices of the Royal Astronomical Society, 2024, 534 (3), pp.2142-2167
ISSN
0035-8711
Publisher
Oxford University Press
Start Page
2142
End Page
2167
Journal / Book Title
Monthly Notices of the Royal Astronomical Society
Volume
534
Issue
3
Copyright Statement
© 2024 The Author(s).
Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium,
provided the original work is properly cited.
Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium,
provided the original work is properly cited.
License URL
Identifier
https://academic.oup.com/mnras/article/534/3/2142/7754163
Publication Status
Published
Article Number
stae2082
Date Publish Online
2024-09-09