9 Cephei
Star in the constellation Cepheus
From Wikipedia, the free encyclopedia
9 Cephei (9 Cep), also known as V337 Cephei, is a variable star in the constellation Cepheus. It is visible to the naked eye.
  | |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Cepheus |
| Right ascension | 21h 37m 55.22469s[1] |
| Declination | +62° 04′ 54.9825″[1] |
| Apparent magnitude (V) | 4.69 - 4.78[2] |
| Characteristics | |
| Evolutionary stage | supergiant[3][4] |
| Spectral type | B2 Ib[3] |
| U−B color index | −0.54[5] |
| B−V color index | +0.30[5] |
| Variable type | α Cyg[2] |
| Astrometry | |
| Radial velocity (Rv) | −13.50±0.8[6] km/s |
| Proper motion (μ) | RA: −1.64±0.17[1] mas/yr Dec.: −3.02±0.16[1] mas/yr |
| Parallax (π) | 0.48±0.14 mas[1] |
| Distance | 950[7] pc |
| Absolute magnitude (MV) | −6.44[3] |
| Details | |
| Searle et al 2008[3] | |
| Mass | 21 M☉ |
| Radius | 39.8 R☉ |
| Luminosity | 151,000 L☉ |
| Surface gravity (log g) | 2.50 cgs |
| Temperature | 18,000 K |
| Rotational velocity (v sin i) | 73 km/s |
| Markova & Puls 2008[4] | |
| Mass | 12 M☉ |
| Radius | 32 R☉ |
| Luminosity | 129,000 L☉ |
| Surface gravity (log g) | 2.50 cgs |
| Temperature | 19,200 K |
| Rotational velocity (v sin i) | 45 km/s |
| Other designations | |
| 9 Cephei, V337 Cephei, BD+61°2169, HD 206165, HIP 106801, HR 8279, GSC 04253-02243, 2MASS J21375521+6204548 | |
| Database references | |
| SIMBAD | data |
In 1967, Graham Hill announced his discovery that 9 Cephei is a variable star.[9] 9 Cephei was given the name V337 Cephei and classified as an α Cygni variable in 1979.[10] It varies irregularly between magnitude 4.69 and 4.78.[2] A study of the Hipparcos satellite photometry showed an amplitude of 0.56 magnitudes, but could find no periodicity.[11]
9 Cephei is considered to be a member of the Cepheus OB2 stellar association, a scattering of massive bright stars around a thousand parsecs away in the southern part of the constellation Cepheus.[3]
Calculations of the physical properties of 9 Cephei vary considerably even from broadly similar observational data. Modelling using the non-LTE line-blanketed CMFGEN atmospheric code gives a temperature of 18,000 K, radius of 40 R☉, luminosity of 151,000 L☉, and mass of 21 M☉.[3] Calculations using the FASTWIND model give a temperature of 19,200 K, radius of 32 R☉, luminosity of 129,000 L☉, and mass of 12 M☉.[4]