RR Lyrae
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Star RR Lyrae |
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Observation dates equinox : J2000.0 , epoch : J2000.0 |
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| Constellation | lyre | ||||||||||||||
| Right ascension | 19 h 25 m 27.91 s | ||||||||||||||
| declination | + 42 ° 47 ′ 3.7 ″ | ||||||||||||||
| Apparent brightness | (+7.17 to +8.14) mag | ||||||||||||||
| Typing | |||||||||||||||
| B − V color index | (0.3) | ||||||||||||||
| R − I index | (0.2) | ||||||||||||||
| Spectral class | A5 to F7 | ||||||||||||||
| Variable star type | RRAB / BL | ||||||||||||||
| Astrometry | |||||||||||||||
| Radial velocity | (−72.2 ± 0.8) km / s | ||||||||||||||
| parallax | 3.64 ± 0.23 mas | ||||||||||||||
| distance | (900) ly (270) pc |
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| Physical Properties | |||||||||||||||
| Dimensions | (0.65) M ☉ | ||||||||||||||
| radius | (5.1 to 5.6) R ☉ | ||||||||||||||
| Luminosity |
(49 ± 5) L ☉ |
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| Effective temperature | (6125 ± 50) K. | ||||||||||||||
| Metallicity [Fe / H] | (−1.16) | ||||||||||||||
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Other names and catalog entries |
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RR Lyrae is a giant star about 900 light years away . It is the prototype of the so-called RR Lyrae stars , which belong to the pulsation-variable stars .
The special significance of the RR Lyrae stars is that they are suitable as standard candles to determine distances.
history
In 1901, Williamina Fleming discovered that the star is a variable star . RR Lyrae's distance was uncertain for a long time. Measurements with the Hubble space telescope and the Hipparcos astrometry satellite finally narrowed the range down to around 850 light years. Recent measurements with Gaia indicate a distance of 850 to 950 light years.
properties
The star has already passed the red giant phase and is in the helium-burning stage in the core. After the star moved along the horizontal branch in the HR diagram , it landed in the instability strip . Therefore, the star pulsates with a period of about 0.57 days (13.6 hours) between a magnitude of 7.06 to 8.12. The radius fluctuates between 5.1 and 5.6 solar radii (R ☉ ). The star is a very old star with low metallicity and belongs to the Population II stars
Web links
Individual evidence
- ↑ a b c d e RR Lyr. In: SIMBAD . Center de Données astronomiques de Strasbourg (CDS), accessed September 8, 2018 .
- ↑ a b c d RR Lyr. In: The International Variable Star Index (VSX). AAVSO , accessed September 8, 2018 .
- ↑ a b c d e K. Kolenberg, L. Fossati, D. Shulyak, H. Pikall, TG Barnes, O. Kochukhov, V. Tsymbal: An in-depth spectroscopic analysis of the Blazhko star RR Lyrae. I. Characterization of the star: abundance analysis and fundamental parameters . In: Astronomy & Astrophysics . 519, September 2010, p. A64. arxiv : 1004.5156 . bibcode : 2010A & A ... 519A..64K . doi : 10.1051 / 0004-6361 / 201014471 .
- ↑ M. Catelan, C. Cortés: Evidence for an Overluminosity of the Variable Star RR Lyrae, and a Revised Distance to the LMC . In: The Astrophysical Journal . 676, No. 2, April 2008, pp. L135-L138. arxiv : 0802.2063 . bibcode : 2008ApJ ... 676L.135C . doi : 10.1086 / 587515 .
- ↑ Burnham, Robert, Jr .: Burnham's Celestial Handbook . Ed .: Dover Publications . tape 2 , 1978, ISBN 0-486-23568-8 ( google.com ).