The Orbit and Companions of the Classical Cepheid FF AQL
Abstract
New radial velocities of the classical Cepheid FF Aql have been obtained and combined with previous observations to provide a revised orbit. A companion has been detected at 1800 A in IUE spectra with a spectral type of A9 V to F3 V. If the Cepheid has an evolutionary mass, then the mass ratio is M1/M2 = 3.8. A companion recently detected by speckle interferometry is in a longer-period orbit if it is a physical companion. In this case it is also an evolved star. The possible fourth member of the system, the visual companion, is unlikely to be a member of the system. The companion at 6 arcsec is unlikely to be a physical companion. Cepheids (in the 'free-fall' descending branch of the light curve) and nonvariable supergiants are shown to have a different spectral slope between 2900 and 1800 A for the same (B-V)0. IUE spectra of Polaris are rediscussed using other Cepheid spectra as comparison stars, and it is concluded that there is probably no sign of a companion.
- Publication:
-
The Astronomical Journal
- Pub Date:
- May 1990
- DOI:
- 10.1086/115442
- Bibcode:
- 1990AJ.....99.1598E
- Keywords:
-
- Cepheid Variables;
- Companion Stars;
- Stellar Orbits;
- Iue;
- Speckle Interferometry;
- Stellar Evolution;
- Stellar Luminosity;
- Stellar Mass;
- Supergiant Stars;
- Astrophysics;
- STARS: CEPHEIDS;
- STARS: INDIVIDUAL