Flares during eclipses of high-mass X-ray binary systems Vela X-1, 4U 1700?37, and LMC X-4

Title

Flares during eclipses of high-mass X-ray binary systems Vela X-1, 4U 1700?37, and LMC X-4

Creator

Rikame K.; Paul B.; Sharma R.; Jithesh V.; Paul K.T.

Description

In eclipsing X-ray binary systems, the direct X-ray emission is blocked by the companion star during the eclipse. We observe only reprocessed emission that contains clues about the environment of the compact object and its chemical composition, ionization levels, etc. We have found flares in some X-ray binaries during their eclipses. The study of eclipse flares provides additional clues regarding the size of the reprocessing region and helps distinguish between different components of the X-ray spectrum observed during the eclipse. In the archival data, we searched for flares during eclipses of high-mass X-ray binaries and found flares in three sources: Vela X-1, LMC X-4, and 4U 1700?37. Comparing spectral properties of the eclipse flare and non-flare data, we found changes in the power-law photon index in all three sources and multiple emission lines in Vela X-1 and 4U 1700-37. The fluxes of prominent emission lines showed a similar increase as the overall X-ray flux during the eclipse flare, suggesting the lines originate in the binary environment and not in the interstellar medium. We also observed a soft excess in 4U 1700-37 that remains unchanged during both eclipse flare and non-flare states. Our analysis suggests that this emission originates from the extremely thin shell of the stellar wind surrounding the photosphere of its companion star. The detection of short (100200 s) count-rate doubling time-scale in 4U 1700?37 and LMC X-4 indicates that the eclipse reprocessing occurs in a region larger than, but comparable to the size of the companion star. 2024 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society.

Source

Monthly Notices of the Royal Astronomical Society, Vol-529, No. 4, pp. 3360-3371.

Date

2024-01-01

Publisher

Oxford University Press

Subject

4U 1700?37; pulsars: general; stars: neutron; X-rays: binaries; X-rays: individual: LMC X-4, Vela X-1

Coverage

Rikame K., Department of Physics and Electronics, CHRIST (Deemed to be University), Karnataka, Bangalore, 560029, India, Raman Research Institute, Astronomy and Astrophysics, C.V. Raman Avenue, Karnataka, Bangalore, 560080, India; Paul B., Raman Research Institute, Astronomy and Astrophysics, C.V. Raman Avenue, Karnataka, Bangalore, 560080, India; Sharma R., Raman Research Institute, Astronomy and Astrophysics, C.V. Raman Avenue, Karnataka, Bangalore, 560080, India; Jithesh V., Department of Physics and Electronics, CHRIST (Deemed to be University), Karnataka, Bangalore, 560029, India; Paul K.T., Department of Physics and Electronics, CHRIST (Deemed to be University), Karnataka, Bangalore, 560029, India

Rights

All Open Access; Gold Open Access; Green Open Access

Relation

ISSN: 358711; CODEN: MNRAA

Format

Online

Language

English

Type

Article

Identifier

https://doi.org/10.1093/mnras/stae739

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