Delta Scorpii
A List of Comparison Stars for Spectroscopy
| Star | Type | R.A. (2000) | Dec. (2000) | V-mag | Sp.T. | RV, km/s |
| Alpha Ser | RV standard | 15:44:16 | +06:25:32 | 2.65 | K2 III | + 2.6±0.2 |
| Delta Oph | RV standard | 16:14:21 | –03:41:40 | 2.74 | M0.5 III | –19.6±0.3 |
| Gamma Lib | Comparison star | 15:35:32 | –14:47:22 | 3.93 | K0 III | –27.5±0.9 |
| Theta Lib | Comparison star | 15:53:50 | –16:43:46 | 4.15 | K0 III | + 3.4 |
Comments:
Constancy of the radial velocity of Alpha Ser and Delta Oph has been established by long-term observations.
Delta Oph is the least recommended as many of its spectral lines blend even at a resolving power of ~17000.
Radial velocity of Gamma Lib and Theta Lib has been measured in several papers with a low scatter.
Theta Lib is the closest to Delta Sco star with an appropriate spectral type that is also bright enough to be used for the radial velocity calibration.
Binarity or multiplicity of Alpha Ser, Delta Oph, and Gamma Lib mentioned in SIMBAD does not affect their radial velocity, because all the systems are wide visual binaries/multiples.
Spectral line identification for the comparison stars will be provided later.
Last updated: 4-Feb-2011