G 117-B15A

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G 117-B15A
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Leo Minor
Right ascension 09h 24m 16s[1]
Declination +35° 16.9′[1]
Apparent magnitude (V) 15.5[1]
Characteristics
Spectral type DAV4[1]
U−B color index -0.6[1]
B−V color index 0.2[1]
Variable type DAV[1]
Astrometry
Proper motion (μ) RA: -136[2] mas/yr
Dec.: 22[2] mas/yr
Details
Temperature12400[3] K
Other designations
RY LMi, EGGR 65, WD 0921+354
Database references
SIMBADdata

G117-B15A[4] is a small, well-observed variable white dwarf star of the DAV, or ZZ Ceti, type in the constellation of Leo Minor.

G117-B15A was found to be variable in 1974 by Richer and Ulrych,[5] and this was confirmed in 1976 by McGraw and Robinson.[6] In 1984 it was demonstrated that the star's variability is due to nonradial gravity wave pulsations. As a consequence, its timescale for period change is directly proportional to its cooling timescale, allowing its cooling rate to be measured using astroseismological techniques.[4] Its age is estimated at 400 million years.[7] Its light curve has a dominant period of 215.2 seconds,[4] which is estimated to increase by approximately one second each 14 million years.[8] G117-B15A has been claimed to be the most stable optical clock ever found, much more stable than the ticks of an atomic clock.[9] It is also the first pulsating white dwarf to have its main pulsation mode index identified.[4]

X-ray source[]

An X-ray source in the constellation Leo Minor is the white dwarf G117-B15A.[10]

Notes[]

  1. ^ a b c d e f g A Catalog of Spectroscopically Identified White Dwarfs, George P. McCook and Edward M. Sion, Astrophysical Journal Supplement 121, #1 (March 1999), pp. 1–130. CDS ID III/210. Astrometric data updated to J2000.0.
  2. ^ a b "V* RY LMi". SIMBAD. Centre de données astronomiques de Strasbourg.
  3. ^ Kepler, S. O.; Winget, D. E.; Vanderbosch, Zachary P.; Castanheira, Barbara Garcia; Hermes, J. J.; Bell, Keaton J.; Mullally, Fergal; Romero, Alejandra D.; Montgomery, M. H.; Degennaro, Steven; Winget, Karen I.; Chandler, Dean; Jeffery, Elizabeth J.; Fritzen, Jamile K.; Williams, Kurtis A.; Chote, Paul; Zola, Staszek (2020). "The Pulsating White Dwarf G117-B15A: Still the Most Stable Optical Clock Known". The Astrophysical Journal. 906: 7. arXiv:2010.16062. Bibcode:2021ApJ...906....7K. doi:10.3847/1538-4357/abc626. S2CID 226222216.
  4. ^ a b c d Kepler, S. O.; et al. (2000-05-10). "Evolutionary Timescale of the Pulsating White Dwarf G117-B15A: The Most Stable Optical Clock Known". The Astrophysical Journal Letters. 534 (2): L185–L188. arXiv:astro-ph/0003478. Bibcode:2000ApJ...534L.185K. doi:10.1086/312664. PMID 10813678. S2CID 14540467.
  5. ^ High-frequency optical variables. II. Luminosity-variable white dwarfs and maximum entropy spectral analysis, H. B. Richer and T. J. Ulrych, Astrophysical Journal 192 (September 1974), pp. 719–730.
  6. ^ High-speed photometry of luminosity-variable DA dwarfs: R808, GD 99, and G 117-B15A, J. T. McGraw and E. L. Robinson, Astrophysical Journal 205 (May 1976), pp. L155–L158.
  7. ^ Pivetta, Marcos (January 2006). "The star of the moment". Retrieved 2007-06-06.
  8. ^ From Ṗ=2.3·10−15 in Kepler et al.
  9. ^ McDonald Observatory. "Astronomers Find Most Stable Optical Clock in Heavens; Aids Understanding of Stars' Lives". McDonald Observatory. Retrieved 2007-06-06.[permanent dead link]
  10. ^ Kepler SO (December 5, 2005). "Astronomers Find Most Stable Optical Clock In Heavens".

See also[]

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