| |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Draco |
| Right ascension | 18h46m 43.089s[3] |
| Declination | +52° 59′ 16.65″[3] |
| Apparent magnitude (V) | 5.68 to 5.99[4] |
| Characteristics | |
| Spectral type | B2.5 V + F5 III[5] |
| Variable type | γ Cas + rotating ellipsoidal[4] |
| Astrometry | |
| Radial velocity (Rv) | −2.1±2.3[6] km/s |
| Proper motion (μ) | RA: 10.965 mas/yr[3] Dec.: −4.920 mas/yr[3] |
| Parallax (π) | 2.8262 ± 0.0587 mas[3] |
| Distance | 1,150 ± 20 ly (354 ± 7 pc) |
| Orbit[7] | |
| Period (P) | 6.695957±0.000043 d |
| Semi-major axis (a) | ≥ 3.253 Gm[8] |
| Eccentricity (e) | 0.052±0.006 |
| Inclination (i) | 52 to 55° |
| Periastron epoch (T) | 2,442,549.48±0.24 HJD |
| Argument of periastron (ω) (secondary) | 267.9±6.4° |
| Semi-amplitude (K1) (primary) | 33.66±0.86 km/s |
| Semi-amplitude (K2) (secondary) | 145.92±0.82 km/s |
| Details | |
| Primary | |
| Mass | 7.3[9] M☉ |
| Surface gravity (log g) | 3.71±0.27[10] cgs |
| Temperature | 19,580±640[10] K |
| Rotational velocity (v sin i) | 163±10[10] km/s |
| Secondary | |
| Mass | ~1.7[9] M☉ |
| Temperature | 6,500[11] K |
| Rotational velocity (v sin i) | ~65[11] km/s |
| Other designations | |
CX Dra, BD+52°2280, FK5 1492, GC 25757, HD 174237, HIP 92133, HR 7084, SAO 31165[12] | |
| Database references | |
| SIMBAD | data |
CX Draconis is an interacting binary star system in the northern constellationofDraco, abbreviated CX Dra. It has the designation HD 174237 in the Henry Draper Catalogue; CX Draconis is the variable star designation. This is a double-lined spectroscopic binary system with a near circular orbit.[7] The brightness of the system undergoes long-term irregular fluctuations,[11] ranging from an apparent visual magnitude of 5.68 down to 5.99.[4] Based on parallax measurements, it is located at a distance of approximately 1,150 light years from the Sun.[3]
In 1921, this target was found to have a varying radial velocitybyJ. S. Plaskett and associates.[13][14] It was shown to be a Be starbyO. C. Mohler in 1940,[15] and in 1965 M. Lacoarret studied variations in the hydrogen alpha emission profiles from the target. This system was discovered to be a photometric variable by P. Merlin in 1975.[14] P. Koubský measured the radial velocity variations in 1976,[16] and in 1978 published orbital elements for this binary system with a period of 6.696 days.[17] He found that the variation in emission lines matched the time scale of the orbit, indicating that this is an interacting binary.[11]
Using observations from the Einstein Observatory, in 1984 this system was shown to be an X-ray sourcebyE. F. Guinan and associates. This emission may be coming from the cooler secondary that is phase-locked with the primary and is magnetically active due to rapid rotation.[18] In 1992, J. Horn and associates determined that the secondary component is an evolved F-type giant star. Evidence suggests this star is overflowing its Roche lobe with gas streaming toward the primary.[11]
Models indicate that the main source of the H-alpha emission is located mid-way between the two stars, with other emission lines originating from an accretion disk orbiting the primary. The circumstellar environment is changing in cycles lasting hundreds of days.[7] Infrared emission to the northeast of the system suggests it may be undergoing systematic mass loss.[19]
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