GY Andromedae
| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Andromeda |
| Right ascension | 01h 38m 31.82463s[1] |
| Declination | +45° 23′ 58.9324″[1] |
| Apparent magnitude (V) | 6.36[2] |
| Characteristics | |
| Spectral type | B9 pe[3] |
| U−B color index | -0.10[2] |
| B−V color index | +0.04[2] |
| Variable type | α2 CVn |
| Astrometry | |
| Radial velocity (Rv) | +3.0[4] km/s |
| Proper motion (μ) | RA: -15.64[1] mas/yr Dec.: -0.77[1] mas/yr |
| Parallax (π) | 6.23 ± 0.72[1] mas |
| Distance | approx. 520 ly (approx. 160 pc) |
| Details | |
| Surface gravity (log g) | 3.7[5] |
| Temperature | 10,723[5] K |
| Metallicity [Fe/H] | 0.86[5] dex |
| Rotational velocity (v sin i) | 31[6] km/s |
| Orbit[7] | |
| Companion | GY And B |
| Period (P) | 272.99 days |
| Semimajor axis (a) | > 0.25 AU |
| Eccentricity (e) | 0.47 |
| Argument of periastron (ω) (secondary) |
17.7° |
| Other designations | |
| Database references | |
| SIMBAD | data |
GY Andromedae (GY And) is an α2 Canum Venaticorum type variable star in the northern constellation Andromeda. Its brightness fluctuates in visual magnitude between 6.27m and 6.41m, making it a challenge to view with the naked eye even in good seeing conditions. The magnetic activity on this star shows an unusually long period of variability, cycling about once every 23 years.[8] Based upon parallax measurements, this star is located at a distance of about 520 light-years (160 parsecs) from the Earth.[1]
This is classified as an Ap/Bp star, with a peculiar spectrum[8] showing lines of chromium and europium that change in intensity over a period matching the variability cycle, although opposite in phase.[9] Its most striking characteristic is the presence of the unstable element promethium in its emission spectrum. All isotopes of this element are radioactive with half lives of 17.7 years or less. The promethium in the outer envelope may be generated by the spontaneous fission of higher mass transuranic elements.[10]
In 1958, American astronomer Horace W. Babcock discovered that this is a spectroscopic binary star. It has an orbital period of 273 days with a large eccentricity of 0.47. The two components are separated by an estimated distance of at least 3.74 × 107 km, or 0.25 Astronomical Units.[7]
[edit] References
- ^ a b c d e f van Leeuwen, F. (November 2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653–664. Bibcode 2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
- ^ a b c Nicolet, B. (1978). "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System". Astronomy and Astrophysics Supplement Series 34: 1–49. Bibcode 1978A&AS...34....1N.
- ^ a b "V* GY And -- Variable Star of alpha2 CVn type", SIMBAD (Centre de Données astronomiques de Strasbourg), http://simbad.u-strasbg.fr/simbad/sim-id?Ident=GY+Andromedae, retrieved 2012-01-01
- ^ Wilson, R. E. (1953), General Catalogue of Stellar Radial Velocities, Carnegie Institute of Washington, D.C., Bibcode 1953GCRV..C......0W
- ^ a b c Aller, M. F. (July 1972), "A model atmosphere analysis of the Ap star HR 465", Astronomy and Astrophysics 19: 248–260, Bibcode 1972A&A....19..248A
- ^ Royer, F. et al. (October 2002), "Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i", Astronomy and Astrophysics 393: 897–911, Bibcode 2002A&A...393..897R, doi:10.1051/0004-6361:20020943
- ^ a b Scholz, G. (1978), "Spectroscopic investigations of the magnetic AP star HD 9996", Astronomische Nachrichten 299 (2): 81–85, Bibcode 1978AN....299...81S
- ^ a b Leroy, J. L. (November 1995), "Linear polarimetry of AP stars. V. A general catalogue of measurements", Astronomy and Astrophysics Supplement 114: 79, Bibcode 1995A&AS..114...79L
- ^ Preston, Sidney C.; Wolff (1970), "The Very Slow Spectrum, Magnetic, and Photometric Variations of HD 9996", Astrophysical Journal 160: June, Bibcode 1970ApJ...160.1071P, doi:10.1086/150494
- ^ Mitalas, R.; Marlborough, J. M. (April 1973), "Some tests and consequences of the identification of promethium in HR 465", Astrophysical Journal 181: 475–480, Bibcode 1973ApJ...181..475M
[edit] External links
- Astronomie: Die Sterne - Special Stars: GY Andromedae
- Aladin previewer - Image V* GY And
