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G 117-B15A

A light curve for RY Leonis Minoris, plotted from data published by Chote et al. (2014)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Leo Minor
Right ascension	09 24 15.25
Declination	+35° 16′ 51.4″
Apparent magnitude (V)	15.5
Characteristics
Spectral type	DAV4
U−B color index	−0.6
B−V color index	+0.2
Variable type	DAV
Astrometry
Proper motion (μ)	RA: −145.181 mas/yr Dec.: −0.053 mas/yr
Parallax (π)	17.3947 ± 0.0452 mas
Distance	187.5 ± 0.5 ly (57.5 ± 0.1 pc)
Absolute magnitude (MV)	11.79
Details
Mass	0.69 M☉
Surface gravity (log g)	8.14 cgs
Temperature	12,400 K
Other designations
RY LMi, EGGR 65, WD 0921+354
Database references
SIMBAD	data

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

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

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. arXiv:1412.5724. doi:10.1093/mnras/stu348.
2. ^ Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
3. ^ McCook, George P.; Sion, Edward M. (March 1999). "A Catalog of Spectroscopically Identified White Dwarfs". Astrophysical Journal Supplement. 121 (1): 1–130. Bibcode:1999ApJS..121....1M. doi:10.1086/313186. S2CID 122286998. CDS ID III/210.
4. ^ Gianninas, A.; Bergeron, P.; Ruiz, M. T. (2011). "A Spectroscopic Survey and Analysis of Bright, Hydrogen-rich White Dwarfs". The Astrophysical Journal. 743 (2): 138. arXiv:1109.3171. Bibcode:2011ApJ...743..138G. doi:10.1088/0004-637X/743/2/138. S2CID 119210906.
5. 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 (1): 7. arXiv:2010.16062. Bibcode:2021ApJ...906....7K. doi:10.3847/1538-4357/abc626. S2CID 226222216.
6. "V* RY LMi". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2023-01-30.
7. ^ 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 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.
13. Kepler SO (December 5, 2005). "Astronomers Find Most Stable Optical Clock In Heavens".

See also

• Ross 548

v t e Constellation of Leo Minor
List of stars in Leo Minor Leo Minor in Chinese astronomy
Stars	Bayer β Flamsteed 7 8 9 10 11 13 16 17 19 20 21 22 23 24 26 27 28 29 30 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 (Praecipua) 48 50 51 Variable R RW RY RZ SX VW YZ AS HR 3979 3993 HD 82886 (Illyrian) 87883 93521 Other NGC 3382
Exoplanets HD 87883 b
Galaxies	NGC 2859 3003 3021 3245 3254 3294 3344 3395 3396 3414 3430 3432 3486 3504 Other 3C 223 3C 236 AGC 198691 Arp 107 IC 2497
Category

• Pulsating white dwarfs
• Leo Minor
• Astronomical X-ray sources
• X-ray astronomy
• Objects with variable star designations