HD 4778, also known as HR 234 and GO Andromedae, is a variable star in the constellation Andromeda. Its magnitude varies by 0.04 magnitudes from the median of 6.12 with a period of approximately 2.55 days.[11] The star is located 350 light years away, as determined from its annual parallax shift of 9.32 mas.[2]
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Andromeda |
| Right ascension | 00h 50m 18.26563s[2] |
| Declination | +45° 00′ 08.1439″[2] |
| Apparent magnitude (V) | 6.13[3] |
| Characteristics | |
| Spectral type | A3VpSiSrCrEuKsn[4] |
| B−V color index | 0.043±0.004[3] |
| Variable type | α2 CVn[5] |
| Astrometry | |
| Radial velocity (Rv) | 1.60[6] km/s |
| Proper motion (μ) | RA: 65.353[2] mas/yr Dec.: 4.133[2] mas/yr |
| Parallax (π) | 9.3224 ± 0.0916 mas[2] |
| Distance | 350 ± 3 ly (107 ± 1 pc) |
| Absolute magnitude (MV) | 1.18[7] |
| Details | |
| Mass | 2.24±0.09[7] M☉ |
| Radius | 2.36±0.12[8] R☉ |
| Luminosity | 34.9±4.3[8] L☉ |
| Surface gravity (log g) | 4.12±0.09[7] cgs |
| Temperature | 9,135±400[8] K |
| Rotation | 2.5616[7] days |
| Rotational velocity (v sin i) | 33[4] km/s |
| Age | 77[9] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
This is an Ap star with a stellar classification of A3VpSiSrCrEuKsn,[4] showing chemical peculiarities in its spectrum from strontium, chromium, and europium.[12] It is an Alpha2 Canum Venaticorum variable[5] with a magnetic field that varies across the range +1,400 to −1,100 G.[13] This rotation-modulated variability allows direct determination of the rotation rate of 2.5616 days.[7]
HD 4778 has 2.24[7] times the mass of the Sun and 2.36[8] times the Sun's radius. The star is radiating 35[8] times the Sun's luminosity from its photosphere at an effective temperature of 9,375 K.[7] It is about 77[9] million years old.
References
edit- ^ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 8 December 2021.
- ^ a b c d e f Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051.
- ^ a b Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
- ^ a b c Abt, Helmut A.; Morrell, Nidia I. (1995). "The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars". Astrophysical Journal Supplement. 99: 135. Bibcode:1995ApJS...99..135A. doi:10.1086/192182.
- ^ a b Samus, N. N.; Kazarovets, E. V.; Durlevich, O. V.; Kireeva, N. N.; Pastukhova, E. N. (2017). "General Catalogue of Variable Stars". Astronomy Reports. GCVS 5.1. 61 (1): 80–88. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085. S2CID 125853869.
- ^ Kharchenko, N. V.; et al. (2007). "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ~55000 stars and mean radial velocities of 516 Galactic open clusters and associations". Astronomische Nachrichten. 328 (9): 889. arXiv:0705.0878. Bibcode:2007AN....328..889K. doi:10.1002/asna.200710776. S2CID 119323941.
- ^ a b c d e f g North, P. (June 1998), "Do SI stars undergo any rotational braking?", Astronomy and Astrophysics, 334: 181–187, arXiv:astro-ph/9802286, Bibcode:1998A&A...334..181N
- ^ a b c d e Perraut, K.; et al. (October 2020), "Benchmarking the fundamental parameters of Ap stars with optical long-baseline interferometric measurements", Astronomy & Astrophysics, 642: 13, Bibcode:2020A&A...642A.101P, doi:10.1051/0004-6361/202038753, A101.
- ^ a b David, Trevor J.; Hillenbrand, Lynne A. (2015). "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets". The Astrophysical Journal. 804 (2): 146. arXiv:1501.03154. Bibcode:2015ApJ...804..146D. doi:10.1088/0004-637X/804/2/146. S2CID 33401607.
- ^ "HD 3167". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved October 6, 2018.
- ^ VSX (4 January 2010). "GO Andromedae". AAVSO Website. American Association of Variable Star Observers. Retrieved 25 May 2014.
- ^ Panek, R. J. (October 1980). "Periodic spectral variability of the AP star HR 234". Astronomy and Astrophysics. 90 (3): 341–343. Bibcode:1980A&A....90..341P.
- ^ Bohlender, D. A. (August 1989). "The magnetic field and rotation period of the AP star HD 4778". Astronomy and Astrophysics. 220: 215–217. Bibcode:1989A&A...220..215B.