Astronomy:G 117-B15A
| Observation data Epoch J2000.0 Equinox (celestial coordinates) | |
|---|---|
| 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[2] mas |
| Distance | 187.5 ± 0.5 ly (57.5 ± 0.1 pc) |
| Absolute magnitude (MV) | 11.79[4] |
| Details | |
| Mass | 0.69[4] M☉ |
| Surface gravity (log g) | 8.14[4] cgs |
| Temperature | 12,400[5] K |
| Other designations | |
| Database references | |
| SIMBAD | data |
G117-B15A[6] 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,[7] and this was confirmed in 1976 by McGraw and Robinson.[8] 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.[6] Its age is estimated at 400 million years.[9] Its light curve has a dominant period of 215.2 seconds,[6] which is estimated to increase by approximately one second each 14 million years.[10] G117-B15A has been claimed to be the most stable optical clock ever found, much more stable than the ticks of an atomic clock.[11] It is also the first pulsating white dwarf to have its main pulsation mode index identified.[6]
An X-ray source in the constellation Leo Minor is the white dwarf G117-B15A.[12]
Notes
- ↑ 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.
- ↑ 2.0 2.1 2.2 2.3 2.4 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940 Gaia DR3 record for this source at VizieR.
- ↑ 3.0 3.1 3.2 3.3 3.4 McCook, George P.; Sion, Edward M. (March 1999). "A Catalog of Spectroscopically Identified White Dwarfs". Astrophysical Journal Supplement 121 (1): 1–130. doi:10.1086/313186. Bibcode: 1999ApJS..121....1M. CDS ID III/210.
- ↑ 4.0 4.1 4.2 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. doi:10.1088/0004-637X/743/2/138. Bibcode: 2011ApJ...743..138G.
- ↑ Kepler, S. O.; Winget, D. E.; Vanderbosch, Zachary P.; Castanheira, Barbara Garcia; Hermes, J. J.; Bell, Keaton J.; Mullally, Fergal; Romero, Alejandra D. et al. (2020). "The Pulsating White Dwarf G117-B15A: Still the Most Stable Optical Clock Known". The Astrophysical Journal 906 (1): 7. doi:10.3847/1538-4357/abc626. Bibcode: 2021ApJ...906....7K.
- ↑ 6.0 6.1 6.2 6.3 Kepler, S. O. (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. doi:10.1086/312664. PMID 10813678. Bibcode: 2000ApJ...534L.185K.
- ↑ 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.
- ↑ 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.
- ↑ Pivetta, Marcos (January 2006). "The star of the moment". http://www.revistapesquisa.fapesp.br/?art=1620&bd=1&pg=1&lg=en. Retrieved 2007-06-06.
- ↑ From Ṗ=2.3·10−15 in Kepler et al.
- ↑ McDonald Observatory. "Astronomers Find Most Stable Optical Clock in Heavens; Aids Understanding of Stars' Lives". McDonald Observatory. http://www.spaceref.ca/news/viewpr.html?pid=18424. Retrieved 2007-06-06.[yes|permanent dead link|dead link}}]
- ↑ Kepler SO (December 5, 2005). "Astronomers Find Most Stable Optical Clock In Heavens". http://www.physorg.com/news8712.html.
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