Astronomy:HD 4778

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Short description: Star in the constellation Andromeda
HD 4778
GOAndLightCurve.png
A light curve for GO Andromedae, plotted from TESS data[1]
Observation data
Equinox J2000.0]] (ICRS)
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[2] mas
Distance350 ± 3 ly
(107 ± 1 pc)
Absolute magnitude (MV)1.18[7]
Details
Mass2.24±0.09[7] M☉
Radius2.36±0.12[8] R☉
Luminosity34.9±4.3[8] L☉
Surface gravity (log g)4.12±0.09[7] cgs
Temperature9,135±400[8] K
Rotation2.5616[7] days
Rotational velocity (v sin i)33[4] km/s
Age77[9] Myr
Other designations
GO Andromedae, BD+44° 176, FK5 2055, HD 4778, HIP 3919, HR 234, SAO 36702, PPM 43369[10]
Database references
SIMBADdata

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]

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

  1. ↑ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G. 
  3. ↑ 3.0 3.1 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A. 
  4. ↑ 4.0 4.1 4.2 Abt, Helmut A.; Morrell, Nidia I. (1995). "The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars". Astrophysical Journal Supplement 99: 135. doi:10.1086/192182. Bibcode: 1995ApJS...99..135A. 
  5. ↑ 5.0 5.1 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. doi:10.1134/S1063772917010085. Bibcode: 2017ARep...61...80S. 
  6. ↑ 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. doi:10.1002/asna.200710776. Bibcode: 2007AN....328..889K. 
  7. ↑ 7.0 7.1 7.2 7.3 7.4 7.5 7.6 North, P. (June 1998), "Do SI stars undergo any rotational braking?", Astronomy and Astrophysics 334: 181–187, Bibcode: 1998A&A...334..181N 
  8. ↑ 8.0 8.1 8.2 8.3 8.4 Perraut, K. et al. (October 2020), "Benchmarking the fundamental parameters of Ap stars with optical long-baseline interferometric measurements", Astronomy & Astrophysics 642: 13, doi:10.1051/0004-6361/202038753, A101, Bibcode: 2020A&A...642A.101P. 
  9. ↑ 9.0 9.1 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. doi:10.1088/0004-637X/804/2/146. Bibcode: 2015ApJ...804..146D. 
  10. ↑ "HD 3167". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+3167. 
  11. ↑ VSX (4 January 2010). "GO Andromedae". AAVSO Website. American Association of Variable Star Observers. http://www.aavso.org/vsx/index.php?view=detail.top&oid=197. 
  12. ↑ 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. 
  13. ↑ 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. 



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