G 117-B15A

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 15.25s[2]
Declination +35° 16′ 51.4″[2]
Apparent magnitude (V) 15.5[3]
Characteristics
Spectral type DAV4[3]
U−B color index −0.6[3]
B−V color index +0.2[3]
Variable type DAV[3]
Astrometry
Proper motion (μ) RA: −145.181[2] mas/yr
Dec.: −0.053[2] mas/yr
Parallax (π)17.3947 ± 0.0452 mas[2]
Distance187.5 ± 0.5 ly
(57.5 ± 0.1 pc)
Absolute magnitude (MV)11.79[4]
Details
Mass0.69[4] M☉
Surface gravity (log g)8.14[4] cgs
Temperature12,400[5] K
Other designations
RY LMi, EGGR 65, WD 0921+354[6]
Database references
SIMBADdata

G117-B15A[7] 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,[8] and this was confirmed in 1976 by McGraw and Robinson.[9] 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.[7] Its age is estimated at 400 million years.[10] Its light curve has a dominant period of 215.2 seconds,[7] which is estimated to increase by approximately one second each 14 million years.[11] G117-B15A has been claimed to be the most stable optical clock ever found, much more stable than the ticks of an atomic clock.[12] It is also the first pulsating white dwarf to have its main pulsation mode index identified.[7]

An X-ray source in the constellation Leo Minor is the white dwarf G117-B15A.[13]

  1. ^ Cite error: The named reference Chote was invoked but never defined (see the help page).
  2. ^ a b c d e Cite error: The named reference dr3 was invoked but never defined (see the help page).
  3. ^ a b c d e Cite error: The named reference villanovar4 was invoked but never defined (see the help page).
  4. ^ a b c Cite error: The named reference gianninas2011 was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference kepler2021 was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference simbad was invoked but never defined (see the help page).
  7. ^ 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.
  8. ^ 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.
  9. ^ 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.
  10. ^ Pivetta, Marcos (January 2006). "The star of the moment". Retrieved 2007-06-06.
  11. ^ From Ṗ=2.3·10−15 in Kepler et al.
  12. ^ McDonald Observatory. "Astronomers Find Most Stable Optical Clock in Heavens; Aids Understanding of Stars' Lives". McDonald Observatory. Retrieved 2007-06-06.[permanent dead link]
  13. ^ Kepler SO (December 5, 2005). "Astronomers Find Most Stable Optical Clock In Heavens".