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 | |
Spectral type | B2 Ib[3] |
U−B color index | −0.54[4] |
B−V color index | +0.30[4] |
Variable type | α Cyg[2] |
Astrometry | |
Radial velocity (Rv) | −13.50 ± 0.8[5] 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[6] 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[7] | |
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 | |
Database references | |
SIMBAD | data |
9 Cephei (9 Cep), also known as V337 Cephei, is a variable star in the constellation Cepheus.
9 Cephei was given the name V337 Cephei and classified as an α Cygni variable in 1967.[9] 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.[10]
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 gives a temperature of 19,200 K, radius of 32 R☉, luminosity of 129,000 L☉, and mass of 12 M☉.[7]
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