GD 66

{{Short description|Star in the constellation Auriga}}

{{Starbox begin |

name=GD 66 }}

{{Starbox image

| image = 250px

| caption = A light curve for GD 66, adapted from Fontaine et al. (1985)

}}

{{Starbox observe |

epoch=J2000 |

ra={{RA|05|20|38.31}}{{cite simbad|title=V* V361 Aur|access-date=2008-12-19}} |

dec= {{DEC|+30|48|24.1}} |

appmag_v=15.56 |

constell=Auriga }}

{{Starbox character |

class=DA |

r-i = |

v-r = |

b-v = 0.22 |

u-b = -0.59{{citation needed|date=December 2008}} |

variable=Pulsating white dwarf }}

{{Starbox astrometry |

radial_v= |

prop_mo_ra=54 |

prop_mo_dec=−120 |

dist_ly=170{{cite journal|author=Mullally, F.|display-authors=etal|title=Limits on Planets around Pulsating White Dwarf Stars|journal=The Astrophysical Journal|volume=676|issue=1|pages=573–583|date=2008|doi=10.1086/528672|bibcode=2008ApJ...676..573M|arxiv=0801.3104|s2cid=123684051 }} |

dist_pc=51 |

absmag_v=12 }}

{{Starbox detail|

mass=0.64 ± 0.03{{cite journal|title=Spitzer Planet Limits around the Pulsating White Dwarf GD66|author=Mullally, F.|display-authors=etal|year=2009|doi=10.1088/0004-637X/694/1/327|journal=The Astrophysical Journal|volume=694|issue=1 |pages=327–331|arxiv=0812.2951|bibcode = 2009ApJ...694..327M |s2cid=16241754}} |

temperature=11980{{cite journal|title=On the Purity of the ZZ Ceti Instability Strip: Discovery of More Pulsating DA White Dwarfs on the Basis of Optical Spectroscopy|author=Bergeron, P.|display-authors=etal|date=2004|journal=The Astrophysical Journal|volume=600|issue=1|pages=404–408|doi=10.1086/379808|bibcode=2004ApJ...600..404B|arxiv = astro-ph/0309483 |s2cid=16636294}} |

gravity= 8.05 |

age= 1.2–1.7 billion}}

{{Starbox catalog |

names=V361 Aurigae, GD 66, 2MASS J05203829+3048239, WD 0517+30, EGGR 572, WD 0517+307 }}

{{Starbox reference |

Simbad=GD+66

| ARICNS = }}

{{Starbox end}}

GD 66 or V361 Aurigae is a 0.64 solar mass ({{Solar mass|link=y}}) pulsating white dwarf star located 170 light years from Earth in the Auriga constellation. The estimated cooling age of the white dwarf is 500 million years. Models of the relationship between the initial mass of a star and its final mass as a white dwarf star suggest that when the star was on the main sequence it had a mass of approximately 2.5 {{Solar mass|link=y}}, which implies its lifetime was around 830 million years. The total age of the star is thus estimated to be in the range 1.2 to 1.7 billion years.

In 1983, Noël Dolez et al. discovered that GD 66 is a variable star, from photometric data obtained at Haute-Provence Observatory. It was given its variable star designation, V361 Aurigae, in 1985. The star is a pulsating white dwarf of type DAV, with an extremely stable period. Small variations in the phase of pulsation led to the suggestion that the star was being orbited by a giant planet which caused the pulsations to be delayed due to the varying distance to the star caused by the reflex motion about the system's centre-of-mass. Observations with the Spitzer Space Telescope failed to directly detect the planet, which put an upper limit on the mass of 5–6 Jupiter masses. Investigation of a separate pulsation mode revealed timing variations in antiphase with the variations in the originally-analysed pulsation mode.{{cite conference|author=Hermes, James J.|title=Complications to the Planetary Hypothesis for GD 66|date=2013|publisher=American Astronomical Society|conference=AAS Meeting #221|bibcode=2013AAS...22142404H}} This would not be the case if the variations were caused by an orbiting planet, and thus the timing variations must have a different cause. This illustrates the potential dangers of attempting to detect planets by white dwarf pulsation timing.{{cite conference|author=Hermes, J. J. |title=8 Years On: A Search for Planets Around Isolated White Dwarfs |date=2012 |conference=Planets around Stellar Remnants |conference-url=http://www.mpia-hd.mpg.de/PLANETS2012/ |url=http://www.mpia-hd.mpg.de/PLANETS2012/presentations/Hermes_Talk.pdf |url-status=dead |archive-url=https://web.archive.org/web/20141227054532/http://www.mpia-hd.mpg.de/PLANETS2012/presentations/Hermes_Talk.pdf |archive-date=2014-12-27 }}