Aquila X-1 (frequently abbreviated to Aql X-1) is a low-mass x-ray binary (LMXB) and the most luminous X-Ray source in the constellation Aquila. It was first observed by the satellite Vela 5B which detected several outbursts from this source between 1969 and 1976.[4] Its optical counterpart is variable, so it was named V1333 Aql according to the IAU standards. The system hosts a neutron star that accretes matter from a main sequence star of spectral type K4.[3] The binary's orbital period is 18.9479 hours.[1]
The neutron star radiation flux is slightly variable due to the nuclear burning of the accreted helium on the surface.[6]
^Mancuso, G. C.; Altamirano, D.; Méndez, M.; Lyu, M.; Combi, J. A. (2021), "Drifts of the marginally stable burning frequency in the X-ray binaries 4U 1608–52 and Aql X–1", Monthly Notices of the Royal Astronomical Society, 502 (2): 1856–1863, arXiv:2102.01181, doi:10.1093/mnras/stab159