Spectroscopic Binaries in the alpha Persei Cluster
Abstract
An average of 16 radial velocity measures for each of the 28 brightest (B3-A2) cluster members and found four binaries was obtained. The resulting binary frequency of 14 percent is, like the previous 20 percent for the B6-A1 stars in the Pleiades, unusually low compared with a typical 30 percent for early-type field stars or with 30 percent or more in other open clusters. These two clusters are the only known ones with unusually high mean rotational velocities. It is suspected that the mean rotational velocities are high either because these clusters lack short-period binaries or are not old enough for synchronization of rotational and orbital velocities to have occurred. The four Alpha Persei binaries are all relatively wide ones (greater than 20 d) and with small mass ratios (0.1-0.5). The same results apply to the young Orion Nebula cluster. These results can be explained in terms of the formation of binaries by capture in that during the first free-fall time, capture will produce wide binaries with small mass ratios, as in the Orion Nebula and Alpha Persei clusters, but repeated captures and disruptions will produce more closely spaced binaries with many mass ratios near 1.0, as in IC 4665.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 1992
- DOI:
- 10.1086/171534
- Bibcode:
- 1992ApJ...393..666M
- Keywords:
-
- Binary Stars;
- Open Clusters;
- Orion Nebula;
- Pleiades Cluster;
- Stellar Rotation;
- Stellar Spectra;
- Interstellar Matter;
- Radial Velocity;
- Stellar Mass;
- Astrophysics