Optical Modulation in the X-Ray Binary 4U 1543–624 Revisited*. (7th October 2015)

• Record Type: Journal Article
• Authors: Wang, Z.; Tziamtzis, A.; Kaplan, D. L.; Chakrabarty, D.
• Is Part Of: Publications of the Astronomical Society of Australia. Volume 32(2015)
• Publication Date: 2015-10-07
• Subjects: binaries: close – stars: individual (4U 1543–624) – stars: low-mass– stars: neutron – X-rays: binaries; Astronomy -- Periodicals; Southern sky (Astronomy) -- Periodicals; Astrophysics -- Periodicals; Periodicals; 520.5
• DOI: 10.1017/pasa.2015.36
• Languages: English
• ISSNs: 1323-3580

Abstract

Abstract: 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.