1998/01/24 by T. Shahbaz, J. R. Thorstensen, P. A. Charles +1 · 2 citations
Physics and Astronomy · #Advanced X-ray Imaging Techniques #Astrophysical Phenomena and Observations #Particle Detector Development and Performance #astro-ph
paper · pdf · doi:10.1046/j.1365-8711.1998.01474.x
4 pages text, 3 figures, to appear in MNRAS
arxiv created 1998/01/24 · openalex publication_date 1998/06/01 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We have obtained I-band photometry of the neutron star X-ray transient Aql X-1 during quiescence. We find a periodicity at 2.487 cycles d−1, which we interpret as twice the orbital frequency (19.30±0.05 h). Folding the data on the orbital period, we model the light-curve variations as the ellipsoidal modulation of the secondary star. We determine the binary inclination to be 20°–30° (90 per cent confidence) and also determine the 95 per cent upper limits to the radial velocity semi-amplitude and rotational broadening of the secondary star to be 117 and 50 km s−1, respectively.