}}{{Starbox reference
| Simbad = HD+4778
}}{{Starbox end}}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.[16] The star is located 350 light years away, as determined from its annual parallax shift of {{Val|9.32|ul=mas}}.[1]This is an Ap star with a stellar classification of A3VpSiSrCrEuKsn,[4] showing chemical peculiarities in its spectrum from strontium, chromium, and europium.[19] It is a Alpha2 Canum Venaticorum variable[6] with a magnetic field that varies across the range {{Val|+1400|to|−1100|ul=G|fmt=commas}}.[21] This rotation-modulated variability allows direct determination of the rotation rate of 2.5616 days.[11]
HD 4778 has 2.24 times the mass of the Sun and 2.2 times the Sun's radius. The star is radiating 32 times the Sun's luminosity from its photosphere at an effective temperature of 9,375 K.[11] It is about 77[14] million years old.
References
1. ^1 2 3 4 5 6 {{cite DR2}}
2. ^1 2 {{citation | title=XHIP: An extended hipparcos compilation | last1=Anderson | first1=E. | last2=Francis | first2=Ch. | journal=Astronomy Letters | volume=38 | issue=5 | pages=331 | year=2012 | bibcode=2012AstL...38..331A | doi=10.1134/S1063773712050015 | arxiv=1108.4971 | postscript=. }}
3. ^1 2 {{cite journal | last1=Samus | first1=N. N. | last2=Kazarovets | first2=E. V. | last3=Durlevich | first3=O. V. | last4=Kireeva | first4=N. N. | last5=Pastukhova | first5=E. N. | title=General Catalogue of Variable Stars | version=GCVS 5.1 | journal=Astronomy Reports | year=2017 | volume=61 | issue=1 | pages=80–88 | bibcode=2017ARep...61...80S }}
4. ^1 {{cite journal | title=The magnetic field and rotation period of the AP star HD 4778 | last1=Bohlender | first1=D. A. | journal=Astronomy and Astrophysics | volume=220 | pages=215–217 | date=August 1989 | bibcode=1989A&A...220..215B }}
5. ^1 2 3 4 {{citation | last1=North | first1=P. | title=Do SI stars undergo any rotational braking? | journal=Astronomy and Astrophysics | volume=334 | pages=181–187 |date=June 1998 | bibcode=1998A&A...334..181N | arxiv=astro-ph/9802286 }}
6. ^1 {{cite web | title=GO Andromedae | author=VSX | date=4 January 2010 | work=AAVSO Website | publisher=American Association of Variable Star Observers | url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=197 | accessdate=25 May 2014 }}
7. ^1 {{Cite journal | title=Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ∼55000 stars and mean radial velocities of 516 Galactic open clusters and associations | journal=Astronomische Nachrichten | volume=328| issue=9| pages=889| year=2007 | display-authors=1 | last1=Kharchenko | first1=N. V. | last2=Scholz | first2=R. -D. | last3=Piskunov | first3=A. E. | last4=Röser | first4=S. | last5=Schilbach | first5=E. | arxiv=0705.0878 | bibcode=2007AN....328..889K | doi=10.1002/asna.200710776 }}
8. ^1 2 3 {{cite journal | last1=Abt | first1=Helmut A. | last2=Morrell | first2=Nidia I. | title=The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars | journal=Astrophysical Journal Supplement | volume=99 | pages=135 | year=1995 | bibcode=1995ApJS...99..135A | doi=10.1086/192182 }}
9. ^1 2 {{cite journal | last1=David | first1=Trevor J. | last2=Hillenbrand | first2=Lynne A. | title=The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets | journal=The Astrophysical Journal | volume=804 | issue=2 | pages=146 | year=2015 | bibcode=2015ApJ...804..146D | doi=10.1088/0004-637X/804/2/146 | arxiv=1501.03154 }}
10. ^1 {{cite journal | title=Periodic spectral variability of the AP star HR 234 | last1=Panek | first1=R. J. | journal=Astronomy and Astrophysics | volume=90 | issue=3 | date=October 1980 | pages=341–343 | bibcode=1980A&A....90..341P }}