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Exploring the variability of the symbiotic X-ray binary GX 1+4 with NICER, Chandra, and NuSTAR

Presentation #107.10 in the session Stellar/Compact Objects - Poster Session.

Published onMay 03, 2024
Exploring the variability of the symbiotic X-ray binary GX 1+4 with NICER, Chandra, and NuSTAR

Low Mass X-ray Binaries comprise a low mass star and a compact object in orbit. GX 1+4 belongs to the rare sub-class of symbiotic X-ray binaries where X-rays are generated as the compact object accretes material from a dust-driven wind launched by the low mass star which has evolved beyond the main sequence. We carried out a monitoring campaign with NICER and of high-resolution spectra from Chandra/HETG to characterize the properties of the accretion flow and the modalities of the mass transfer and loss. Following, NuStar Stray Light observations will be analyzed to generate pulse profiles as well as observe absorption in higher energies ~3-40 keV. The NICER monitoring revealed the presence of strong iron line emission and large absorption. The EW of the iron line ranges from ~0.1-2.5 keV and the hydrogen column density ranges from a few 1022 to 1023. The strong absorption leads to intense fluctuations in the observed spectra within the energy range examined by NICER and Chandra, like that seen in strongly absorbed wind-accreting high mass X-ray binaries. The pulsar is continuously spinning down and shows a period of ~250 s around the time of the NICER observations, nearly twice its period at its discovery in 1969. Preliminary analysis reveals no strong pulsations in the NICER light curves, probably because the observations were carried out during an extended low state of GX 1+4 as seen with SWIFT/BAT. The Chandra data taken a year later from NICER also show similar flux variability and a similar broad iron K α line, with a sharp K α edge. With Chandra gratings data, we explore the evolution of high-resolution features, like a Compton shoulder and absorption edges, in the context of the X-ray variability of this rare system.

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