Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Cygnus |
Right ascension | 20h 09m 25.61909s [2] |
Declination | +36° 50′ 22.5961″ [2] |
Apparent magnitude (V) | 4.93 [3] |
Characteristics | |
Spectral type | B2.5 V [4] or B2 IV(e) [5] + sdO [6] |
B−V color index | −0.139±0.004 [3] |
Variable type | SX Ari [7] |
Astrometry | |
Radial velocity (Rv) | −0.36±2.59 [8] km/s |
Proper motion (μ) |
RA: +2.728
[2]
mas/
yr Dec.: +15.562 [2] mas/ yr |
Parallax (π) | 5.2947 ± 0.2255 mas [2] |
Distance | 620 ± 30
ly (189 ± 8 pc) |
Absolute magnitude (MV) | −2.56 [3] |
Details | |
Mass | 9.5±0.3 [9] M☉ |
Radius | 5.7 [10] R☉ |
Luminosity | 1,353.22 [11] L☉ |
Surface gravity (log g) | 3.983 [12] cgs |
Temperature | 11,338 [11] K |
Rotational velocity (v sin i) | 320 [10] km/s |
Age | 22.1±2.8 [9] Myr |
Other designations | |
Database references | |
SIMBAD | data |
28 Cygni is a binary [6] star in the northern constellation of Cygnus. It is a faint blue-white hued star but visible to the naked eye with an apparent visual magnitude of 4.93. [3] The distance to 28 Cyg, as estimated from its annual parallax shift of 5.3 mas, [2] is around 620 light years. It has an absolute magnitude of −2.56, [3] which means that if the star were just 10 parsecs (33 light-years) away it would be brighter than Sirius, the brightest star in the night sky.
This primary object is a B-type main-sequence star with a stellar classification of B2.5 V, per Lesh (1968). [4] Slettebak (1982) found a class of B2 IV(e), [5] which would suggest this is a more evolved subgiant star. It is a Be star, which means the spectrum displays emission lines due a disk of ejected gas in a Keplerian orbit around the star. The star displays short-term variability with two or more periods, [10] and is classified as an SX Arietis variable by Samus et al. (2017). [7] It is spinning rapidly with a projected rotational velocity of 320 km/s; estimated at round 80% of the critical rotation rate. This is giving the star an oblate shape with an equatorial bulge out to 6.5 times the Sun's radius, compared to 5.7 at the poles. [10] The central star is orbited by a secondary companion star, which is a subdwarf O star. [6] After previous failed attempts to find the star, [14] the companion was detected using interferometry, but the orbital parameters are unknown. [6]
Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Cygnus |
Right ascension | 20h 09m 25.61909s [2] |
Declination | +36° 50′ 22.5961″ [2] |
Apparent magnitude (V) | 4.93 [3] |
Characteristics | |
Spectral type | B2.5 V [4] or B2 IV(e) [5] + sdO [6] |
B−V color index | −0.139±0.004 [3] |
Variable type | SX Ari [7] |
Astrometry | |
Radial velocity (Rv) | −0.36±2.59 [8] km/s |
Proper motion (μ) |
RA: +2.728
[2]
mas/
yr Dec.: +15.562 [2] mas/ yr |
Parallax (π) | 5.2947 ± 0.2255 mas [2] |
Distance | 620 ± 30
ly (189 ± 8 pc) |
Absolute magnitude (MV) | −2.56 [3] |
Details | |
Mass | 9.5±0.3 [9] M☉ |
Radius | 5.7 [10] R☉ |
Luminosity | 1,353.22 [11] L☉ |
Surface gravity (log g) | 3.983 [12] cgs |
Temperature | 11,338 [11] K |
Rotational velocity (v sin i) | 320 [10] km/s |
Age | 22.1±2.8 [9] Myr |
Other designations | |
Database references | |
SIMBAD | data |
28 Cygni is a binary [6] star in the northern constellation of Cygnus. It is a faint blue-white hued star but visible to the naked eye with an apparent visual magnitude of 4.93. [3] The distance to 28 Cyg, as estimated from its annual parallax shift of 5.3 mas, [2] is around 620 light years. It has an absolute magnitude of −2.56, [3] which means that if the star were just 10 parsecs (33 light-years) away it would be brighter than Sirius, the brightest star in the night sky.
This primary object is a B-type main-sequence star with a stellar classification of B2.5 V, per Lesh (1968). [4] Slettebak (1982) found a class of B2 IV(e), [5] which would suggest this is a more evolved subgiant star. It is a Be star, which means the spectrum displays emission lines due a disk of ejected gas in a Keplerian orbit around the star. The star displays short-term variability with two or more periods, [10] and is classified as an SX Arietis variable by Samus et al. (2017). [7] It is spinning rapidly with a projected rotational velocity of 320 km/s; estimated at round 80% of the critical rotation rate. This is giving the star an oblate shape with an equatorial bulge out to 6.5 times the Sun's radius, compared to 5.7 at the poles. [10] The central star is orbited by a secondary companion star, which is a subdwarf O star. [6] After previous failed attempts to find the star, [14] the companion was detected using interferometry, but the orbital parameters are unknown. [6]