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G117-B15A[5] is a small, well-observed variable white dwarf star of the DAV, or ZZ Ceti, type in the constellation of Leo Minor.

G 117-B15A

A light curve for RY Leonis Minoris, plotted from data published by Chote et al. (2014)[1]
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Leo Minor
Right ascension 09h 24m 16s[2]
Declination +35° 16.9′[2]
Apparent magnitude (V) 15.5[2]
Characteristics
Spectral type DAV4[2]
U−B color index -0.6[2]
B−V color index 0.2[2]
Variable type DAV[2]
Astrometry
Proper motion (μ) RA: -136[3] mas/yr
Dec.: 22[3] mas/yr
Details
Temperature12400[4] K
Other designations
RY LMi, EGGR 65, WD 0921+354
Database references
SIMBADdata

G117-B15A was found to be variable in 1974 by Richer and Ulrych,[6] and this was confirmed in 1976 by McGraw and Robinson.[7] 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.[5] Its age is estimated at 400 million years.[8] Its light curve has a dominant period of 215.2 seconds,[5] which is estimated to increase by approximately one second each 14 million years.[9] G117-B15A has been claimed to be the most stable optical clock ever found, much more stable than the ticks of an atomic clock.[10] It is also the first pulsating white dwarf to have its main pulsation mode index identified.[5]


X-ray source


An X-ray source in the constellation Leo Minor is the white dwarf G117-B15A.[11]


Notes


  1. Chote, P.; Sullivan, D. J.; Brown, R.; Harrold, S. T.; Winget, D. E.; Chandler, D. W. (May 2014). "Puoko-nui: a flexible high-speed photometric system". Monthly Notices of the Royal Astronomical Society. 440 (2): 1490–1497. doi:10.1093/mnras/stu348. Retrieved 16 January 2022.
  2. 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.
  3. "V* RY LMi". SIMBAD. Centre de données astronomiques de Strasbourg.
  4. 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.
  5. 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.
  6. 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.
  7. 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.
  8. Pivetta, Marcos (January 2006). "The star of the moment". Retrieved 2007-06-06.
  9. From Ṗ=2.3·10−15 in Kepler et al.
  10. McDonald Observatory. "Astronomers Find Most Stable Optical Clock in Heavens; Aids Understanding of Stars' Lives". McDonald Observatory. Retrieved 2007-06-06.[permanent dead link]
  11. Kepler SO (December 5, 2005). "Astronomers Find Most Stable Optical Clock In Heavens".

See also



На других языках

- [en] G 117-B15A

[es] RY Leonis Minoris

RY Leonis Minoris (RY LMi / G 117-15A / WD 0921+354)[1] es una enana blanca situada en la constelación de Leo Minor a 150 años luz de distancia del Sistema Solar.[2] Con una edad estimada de 400 millones de años,[2] tiene una temperatura efectiva entre 11.600 y 12.400 K.[3]


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