Title:	A comprehensi v e study of orbital ev olution of LMC X-4: existence of a second deri v ati v e of the orbital period
Authors:	Jain, Chetana Sharma, Rahul Paul, Biswajit
Keywords:	X-rays: binaries –(stars) pulsars general –stars neutron –X-rays –individual LMC X-4
Issue Date:	18-Mar-2024
Publisher:	Oxford University Press on behalf of Royal Astronomical Society
Citation:	Monthly Notices of the Royal Astronomical Society, 2024, Vol.529, p4056
Abstract:	We report here results from pulse arri v al time delay analysis of the eclipsing high-mass X-ray binary (HMXB) pulsar LMC X-4 using observations made with the Rossi X-ray Timing Explorer , XMM –Newton, NuSTAR ( Nuclear Spectroscopic Telescope ARray ), and AstroSat . Combining the orbital parameters determined from these observations with the historical measurements dating back to 1998, we have extended the T π/2 epoch history of LMC X-4 by about 4600 binary orbits spanning about 18 yr. We also report mid-eclipse time measurements ( T ecl ) using data obtained from wide-field X-ray monitors of MAXI -GSC (Monitor of All-sky X ray Image –Gas Slit Camera) and Swift - BAT ( Burst Alert Telescope ). Combining the new T π/2 and T ecl estimates with all the previously reported values, we have significantly improved the orbital evolution measurement, which indicates that the orbital period is evolving at a time-scale ( P orb / ˙P orb ) of about 0.8 Myr. For the first time in an accreting X-ray pulsar system, we confirm the existence of a second deri v ati ve of the orbital period, having an evolution time-scale ( ˙P orb / ¨P orb ) of about 55 yr. Detection of a second deri v ati ve of the orbital period in LMC X-4 makes its orbital evolution time-scale more uncertain, which may also be true for other HMXBs. Independent solutions for the orbital evolution measurement using the mid-eclipse data and the pulse timing data are consistent with each other, and help us put an upper limit of 0.009 on the eccentricity of the binary system.
Description:	Open Access
URI:	http://hdl.handle.net/2289/8281
Alternative Location:	https://ui.adsabs.harvard.edu/abs/2024MNRAS.529.4056J/abstract https://arxiv.org/abs/2403.09595 https://doi.org/10.1093/mnras/stae784
Copyright:	2024, The Author(s)
Appears in Collections:	Research Papers (A&A)

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