Observation data Epoch J2000.0 Equinox J2000.0 | |
---|---|
Constellation | Cepheus |
Right ascension | 22h 46m 54.111s [2] |
Declination | +58° 05′ 03.53″ [2] |
Apparent magnitude (V) | 8.61 [3] (8.63 – 8.70) [4] |
Characteristics | |
Evolutionary stage | Main sequence |
Spectral type | O5.5 V + O6 V [5] |
B−V color index | 0.334±0.041 [6] |
Variable type | Ellipsoidal [7] [4] |
Astrometry | |
Radial velocity (Rv) | −33.4±3.2 [6] km/s |
Proper motion (μ) |
RA: −2.599
mas/
yr
[2] Dec.: −2.236 mas/ yr [2] |
Parallax (π) | 0.3397 ± 0.0138 mas [2] |
Distance | 9,600 ± 400
ly (2,900 ± 100 pc) |
Absolute magnitude (MV) | −4.66±0.25 (A) −4.55±0.25 (B) [8] |
Orbit [3] | |
Period (P) | 2.11095 d |
Semi-major axis (a) | ≥9.79±0.17 R☉ |
Eccentricity (e) | 0.0 (fixed) |
Periastron epoch (T) | 2,456,525.564±0.006 HJD |
Details [3] | |
A | |
Mass | 25.0
[9] or 38.4±2.5 M☉ |
Radius | 8.31 [9] R☉ |
Luminosity | 2.34×105 [9] L☉ |
Surface gravity (log g) | 4.3±0.3 cgs |
Temperature | 44,000 K |
Rotational velocity (v sin i) | 175 km/s |
B | |
Mass | 16.8
[9] or 33.4±2.2 M☉ |
Radius | 7.76 [9] R☉ |
Luminosity | 1.86×105 [9] L☉ |
Surface gravity (log g) | 4.3±0.2 cgs |
Temperature | 43,000 K |
Rotational velocity (v sin i) | 160 km/s |
Other designations | |
Database references | |
SIMBAD | data |
DH Cephei is a variable binary star [5] system in the northern circumpolar constellation of Cepheus, positioned about two degrees to the east of the star system Delta Cephei. [10] With an apparent visual magnitude of 8.61, [3] it is too faint to be visible without a telescope. Based on parallax measurements, this system is located at a distance of approximately 9.6 kilolight-years (2.9 kiloparsecs) from the Sun. [2] At present it is moving closer to the Earth with a radial velocity of −33 km/s. [6]
This is a double-lined spectroscopic binary system consisting of two near-identical, massive, O-type main sequence stars. [5] Evolutionary tracks place the stars close to the zero age main sequence, with an age of less than two million years. [12] This is a detached binary [12] with a close orbit having a period of 2.11 days, and the orbit is assumed to have circularized. The orbital plane is estimated to be inclined by an angle of 47°±1° to the line of sight from the Earth, which yields mass estimates of 38 and 34 times the mass of the Sun. [3] Although initially suspected to be an eclipsing binary and given a variable star designation, [8] it doesn't appear to be eclipsing. [3] Instead, the system displays ellipsoidal light variations that are caused by tidal distortions. [7]
This system lies at the center of the young open cluster NGC 7380. It is the primary ionizing source for the surrounding H II region designated S142. The pair are a source of X-ray emission, which may be the result of colliding stellar winds. [13] Their measured X-ray luminosity is 3.2×1031 erg s−1. [9] The location and rare class of these stars make them an important object for astronomical studies. [8]
{{
cite web}}
: CS1 maint: postscript (
link)