Circumstellar Disc and X-ray Variability in the Be/X-ray Binary SXP 5.05 During its 2024 Outburst

@misc{patel2026circumstellar,
  title = {{Circumstellar Disc and X-ray Variability in the Be/X-ray Binary SXP 5.05 During its 2024 Outburst}},
  author = {Chintan Patel and Sayantan Bhattacharya and Karan Akbari and Rajapandi Nadar and Sudip Bhattacharyya and Manojendu Choudhury},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2607.19373},
  eprint = {2607.19373},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2607.19373},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - Circumstellar Disc and X-ray Variability in the Be/X-ray Binary SXP 5.05 During its 2024 Outburst
AU  - Chintan Patel
AU  - Sayantan Bhattacharya
AU  - Karan Akbari
AU  - Rajapandi Nadar
AU  - Sudip Bhattacharyya
AU  - Manojendu Choudhury
PY  - 2026
DA  - 2026/09/30
PB  - arXiv
DO  - 10.48550/arxiv.2607.19373
UR  - https://arxiv.org/abs/2607.19373
AB  - Be/X-ray binaries provide a unique opportunity to study the interaction between neutron stars and circumstellar discs. SXP 5.05 is a particularly rare system, exhibiting eclipse-like X-ray variability attributed to obscuration by the Be star disc rather than a simple stellar eclipse. Motivated by its unusual geometry and the well-studied 2013 outburst, we present a multiwavelength analysis of its 2024 outburst using NICER X-ray observations and long-term optical monitoring from OGLE. The X-ray light curve shows a declining outburst with lower peak intensity and shorter duration compared to 2013, indicating a reduced accretion episode. The spectral evolution, characterized through hardness ratios, reveals a transition from a soft, high-intensity state to a harder, low-intensity state. Coherent pulsations near 5.05 s are detected throughout the observations, with properties consistent with previous measurements. The optical light curves show a reduced variability amplitude relative to 2013, possibly from a less extended or less dense circumstellar disc. Orbital-phase-folded optical profiles reveal a persistent, phase-locked dip structure, indicating a stable non-axisymmetric disc component that evolves across outburst phases. Together, these results support a picture in which the observed variability is driven by changes in disc structure and viewing geometry. SXP 5.05 thus remains a key system for probing the time-dependent properties of Be star discs through combined X-ray and optical observations.
ER  -