Z Andromedae
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Double star Z Andromedae |
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| Light curve from Z Andromedae 1976 to 2014 | |||||||||||||||
| AladinLite | |||||||||||||||
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Observation dates equinox : J2000.0 , epoch : J2000.0 |
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| Constellation | Andromeda | ||||||||||||||
| Right ascension | 23 h 19 m 49.93 s | ||||||||||||||
| declination | + 21 ° 56 ′ 52.2 ″ | ||||||||||||||
| Apparent brightness | 8.00 (7.7 to 11.3) mag | ||||||||||||||
| Typing | |||||||||||||||
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rel. Brightness (G-band) |
(9.10 ± 0.01) mag | ||||||||||||||
| rel. Brightness (J-band) |
(6.19 ± 0.02) mag | ||||||||||||||
| B − V color index | (+1.35) | ||||||||||||||
| U − B color index | (−0.49) | ||||||||||||||
| Spectral class | M2 III + B1 eq | ||||||||||||||
| Variable star type | ZAND | ||||||||||||||
| Astrometry | |||||||||||||||
| Radial velocity | (−0.59 ± 0.17) km / s | ||||||||||||||
| parallax | (0.51 ± 0.03) mas | ||||||||||||||
| distance | (6,500) ly 2,000 pc |
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| Proper movement | |||||||||||||||
| Rec. Share: | (−1.61 ± 0.05) mas / a | ||||||||||||||
| Dec. portion: | (−2.97 ± 0.04) mas / a | ||||||||||||||
| Physical Properties | |||||||||||||||
| Dimensions | (2 / 0.75) M ☉ | ||||||||||||||
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Other names and catalog entries |
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Z Andromedae is a double star in the constellation Andromeda at a distance of about 6500 light years . The system is the prototype of the Z-Andromedae stars, which are also called symbiotic stars . It consists of a red giant of the spectral class M2 and a white dwarf of the spectral class B1eq.
discovery
In 1901 Williamina Fleming discovered the star. The striking spectrum showed similarities to those of the recently discovered Nova Persei 1901 and RS Ophiuchi .
properties
The two stars orbit each other every 759 days. The red giant loses mass through stellar winds and the white dwarf accretes mass.
spectrum
The system shows peculiar properties in the optical spectrum and changes depending on the activity of the system. In the X-ray range, like many symbiotic stars, the system shows little or no activity, presumably because the fog surrounding the system absorbs this radiation.
outbreaks
The system shows breakouts at irregular intervals, whereby the apparent brightness can increase by up to 4 magnitudes. Since the system varies widely and has been known for a long time, several larger outbreaks have been observed. For example in the years 1900, 1915, 1939, 1959 and 1967/1968. Even in more recent times since 2000, the system has been active again and again and has shown such major outbreaks. During these eruptions, the radius (0.03 to 0.36 R ☉ ), the effective temperature (90,000 to 160,000 Kelvin ) and also the luminosity (200 to 10,000 L ☉ ) of the white dwarf can fluctuate greatly.
Individual evidence
- ↑ a b c d e f g h i j Z And. In: SIMBAD . Center de Données astronomiques de Strasbourg , accessed October 10, 2019 .
- ↑ a b Z And. In: VSX. AAVSO , accessed October 10, 2019 .
- ↑ a b Francis C Fekel, Kenneth H Hinkle, Richard R Joyce, Michael F Skrutskie: Infrared Spectroscopy of Symbiotic Stars. II. Orbits for Five S-Type Systems with Two-Year Periods . In: The Astronomical Journal . 120, No. 6, 2000, p. 3255. bibcode : 2000AJ .... 120.3255F . doi : 10.1086 / 316872 .
- ^ A b c Z Andromedae: The Prototype of the Symbiotic Class. AAVSO, accessed October 10, 2019 .
- ↑ JL Sokoloski, SJ Kenyon, BR Espey, Charles D Keyes, SR McCandliss, AK H Kong, JP Aufdenberg, AV Filippenko, W Li, C Brocksopp, Christian R Kaiser, PA Charles, MP Rupen, RP S Stone: A Combination Nova Outburst in Z Andromedae: Nuclear Shell Burning Triggered by a Disk Instability . In: The Astrophysical Journal . 636, No. 2, 2006, p. 1002. arxiv : astro-ph / 0509638 . bibcode : 2006ApJ ... 636.1002S . doi : 10.1086 / 498206 .