Monthly Notices of the Royal Astronomical Society
We have obtained optical spectroscopy of the X-ray burst source 4U1735 – 44 with spectral resolution of ∼ 1.6 Å and a time resolution of ∼ 30 min. There is strong evidence for cyclic He II velocity variations, but we are unable to confirm or deny either of the previously reported possible binary periodicities in the source. However, kinematic arguments suggest that the companion can be classified as being of spectral type F0–K5 V and the presence of the Ca II K interstellar absorption line at λ 3933 leads to a lower limit on the distance of the source of ∼ 2.0 kpc.
Smale, A. P.; Charles, P. A.; Tuohy, I. R.; and Thorstensen, J. R., "Spectroscopic Studies of 4U1735 – 44; Evidence for Binary Motion" (1984). Open Dartmouth: Faculty Open Access Articles. 1884.