K2 & TESS observations of symbiotic X-ray binaries: GX 1+4 and IGR J16194-2810

Abstract

I analyze the K2 and TESS data taken in 2016, 2019 and 2021 of the symbiotic X-ray binaries GX 1+4 and IGR J16194-2810. GX 1+4 consists of a pulsar accreting from a red giant companion in a 1160 days orbit. Since 1984, the pulsar has shown a continuous spin-down rate of $\dot{P}$=-0.1177(3) mHZ/yr. I report the detection of the spin period at an average value of 180.426(1) seconds as observed with the K2 mission and confirm that the spin period continues to increase at a rate of $\sim$1.61$\times$10${}^{-7}$ s/s. The K2 and hard X-rays, as observed with Swift/BAT, varied in tandem, in agreement with other authors who proposed that the optical light arise from reprocessed X-ray emission. In the case of IGR J16194-2810, the X-ray and optical spectroscopy have been interpreted as arising from a neutron star accreting from a M2 III red giant companion. Its orbital period is unknown, while I report here the detection of a modulation with a period of 242.837 min, interpreted as the neutron star spin period. IGR J16194-2810 is thus the second symbiotic X-ray binary where the spin period is detected in optical wavelengths. This period, however, was only detected during the TESS observations of Sector 12 in 2019. The non-detection of this modulation during the observations of Sector 39 in 2021 is perhaps related with the orbital modulation, i.e. a low inclination of the orbit.

arXiv commentaccepted in A&A Letters

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Cited by in corpus (4)

• Symbiotic stars in the era of modern ground- and space-based surveys
• The Symbiotic X-ray Binary IGR J16194-2810: A Window on the Future Evolution of Wide Neutron Star Binaries From Gaia
• A Two-Stage Kick Scenario for the Peculiar LMXB GX 1+4
• A TESS View of Post-Eruption Variability in the Novae V1405 Cas,V1716 Sco, and V1674 Her