Optical Modulation in the X-Ray Binary 4U 1543–624 Revisited
Author(s)Wang, Z.; Tziamtzis, A.; Kaplan, D. L.; Chakrabarty, Deepto
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The X-ray binary 4U 1543–624 has been provisionally identified as an ultra-compact system with an orbital period of ≃ 18 min. We have carried out time-resolved optical imaging of the binary to verify the ultra-short orbital period. Using 140 min of high-cadence r′-band photometry, we recover the previously-seen sinusoidal modulation and determine a period P = 18.20 ± 0.09 min. In addition, we also see a 7.0 × 10⁻⁴ mag min⁻¹ linear decay, likely related to variations in the source's accretion activity. Assuming that the sinusoidal modulation arises from X-ray heating of the inner face of the companion star, we estimate a distance of 6.0–6.7 kpc and an inclination angle of 34°–61° (90% confidence) for the binary. Given the stability of the modulation, we can confirm that the modulation is orbital in origin and 4U 1543–624 is an ultra-compact X-ray binary.
DepartmentKavli Institute for Astrophysics and Space Research; Massachusetts Institute of Technology. Department of Physics
Publications of the Astronomical Society of Australia
Wang, Z.; Tziamtzis, A.; Kaplan, D. L. and Chakrabarty, D. “Optical Modulation in the X-Ray Binary 4U 1543–624 Revisited.” Publications of the Astronomical Society of Australia 32 (2015). © 2015 Astronomical Society of Australia
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