Astronomy:Mira B
280px The red giant star Mira (right), and its companion Mira B on the left. Taken on December 11, 1995, by the Hubble Space Telescope using the Faint Object Camera. | |
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Cetus |
| Right ascension | 02h 19m 20.80s[1] |
| Declination | −02° 58′ 40.0″[1] |
| Apparent magnitude (V) | 9.5–12.0[2] |
| Characteristics | |
| Evolutionary stage | white dwarf[3] |
| Variable type | unique[2] |
| Astrometry | |
| Distance | approx. 300[4] ly (approx. 90 pc) |
| Details | |
| Mass | 0.24±0.04 or 0.42±0.04[3]: 6 M☉ |
| Radius | 0.015 or 0.020[3]: 3 R☉ |
| Temperature | 14,000[5] K |
| Other designations | |
| Database references | |
| SIMBAD | data |
Mira B, also known as VZ Ceti, is the companion star to the variable star Mira, probably a white dwarf. The two are separated by around 100 astronomical unit|AU. Suspected as early as 1918, it was visually confirmed in 1923 by Robert Grant Aitken, and has been observed more or less continually since then, most recently by the Chandra X-Ray Observatory.[6]
Long known to be erratically variable itself, its fluctuations seem to be related to its accretion of matter from Mira's stellar wind, which makes it a symbiotic star.[7]
Orbit
The exact orbit around Mira is poorly known due to its long period,[8] though a commonly cited estimate of 497.9 years was published by Prieur et al in 2002.[9] Assuming the distance in the Hipparcos catalog and orbit are correct, Mira A and B are separated by an average of 100 AU.[10]
Physical properties
In January 2007, astronomers at the Keck Observatory announced the discovery of a protoplanetary disk around Mira B. Discovered via infrared data, the disk is apparently derived from captured material from Mira itself; Mira B accretes as much as one percent of the matter lost by its primary. Though planetary formation is perhaps unlikely as long as the disk is in active accretion, it may proceed apace once Mira A completes its red giant phase and becomes a white dwarf.[11]
Mira B was long suspected to itself be a white dwarf. Several factors, such as its low x-ray luminosity, suggested that Mira B could instead be a normal main-sequence star of spectral type K and with a mass of roughly 0.7 M☉. However, a 2010 analysis of rapid optical brightness variations indicated that Mira B is, in fact, a white dwarf.[5] Although most white dwarfs have masses close to 0.6 M☉, Mira B's accretion rate suggest a mass of either 0.24±0.04 M☉ in the case of accretion through overflow of the red giant's Roche lobe by its stellar wind, or 0.42±0.04 M☉ in the case of Bondi–Hoyle–Lyttleton accretion. Mass-radius relations give radii of 0.020 or 0.015 R☉, respectively. The case of wind roche lobe overflow is more probable, so Mira B is likely an extremely low-mass white dwarf.[3]
External links
- From the AAVSO Variable Star of the Month: Mira
- Sixth Orbit Catalog
- Chandra Photo Album, Mira press release
- Born Again Protoplanetary Disk Around Mira B
References
- ↑ 1.0 1.1 Skiff, B. A. (2014). "VizieR Online Data Catalog: Catalogue of Stellar Spectral Classifications". VizieR On-line Data Catalog 1. Bibcode: 2014yCat....1.2023S.
- ↑ 2.0 2.1 Samus', N. N. (2003). "An Electronic Version of the Second Volume of the General Catalogue of Variable Stars with Improved Coordinates". Astronomy Letters 29 (7): 468–479. doi:10.1134/1.1589864. Bibcode: 2003AstL...29..468S.
- ↑ 3.0 3.1 3.2 3.3 Zamanov, R. K.; Irincheva, V.; Spassov, B.; Kurtenkov, A.; Marchev, D.; Minev, M.; Bode, M. F.; Dankova, L.; Borisov, B. (2026-02-25). "Is Mira B a low mass white dwarf?". arXiv:2602.21725 [astro-ph.SR].
- ↑ van Leeuwen, F. (November 2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653–664. doi:10.1051/0004-6361:20078357. Bibcode: 2007A&A...474..653V.
- ↑ 5.0 5.1 5.2 J. L. Sokoloski; Lars Bildsten (2010). "Evidence for the White Dwarf Nature of Mira B". The Astrophysical Journal 723 (2): 1188–1194. doi:10.1088/0004-637X/723/2/1188. Bibcode: 2010ApJ...723.1188S.
- ↑ Robert Burnham (15 April 2013). Burnham's Celestial Handbook, Volume One: An Observer's Guide to the Universe Beyond the Solar System. Courier Corporation. ISBN 978-0-486-31902-5. https://books.google.com/books?id=z3_CAgAAQBAJ.
- ↑ James B. Kaler (7 May 2006). The Hundred Greatest Stars. Springer Science & Business Media. ISBN 978-0-387-21625-6. https://books.google.com/books?id=jmoQBwAAQBAJ.
- ↑ Wood, Brian E.; Karovska, Margarita (20 September 2006). "Mira B Rejuvenated". The Astrophysical Journal 649 (1): 410–414. doi:10.1086/506383.
- ↑ Prieur, J. L.; Aristidi, E.; Lopez, B.; Scardia, M.; Mignard, F.; Carbillet, M. (March 2002). "High Angular Resolution Observations of Late-Type Stars". The Astrophysical Journal Supplement Series 139 (1): 249–258. doi:10.1086/338029.
- ↑ "Sixth Catalog of Orbits of Visual Binary Stars". United States Naval Observatory. http://www.usno.navy.mil/USNO/astrometry/optical-IR-prod/wds/orb6.
- ↑ Ireland, M. J; Monnier, J. D; Tuthill, P. G; Cohen, R. W; De Buizer, J. M; Packham, C; Ciardi, D; Hayward, T et al. (2007). "Born-Again Protoplanetary Disk around Mira B". The Astrophysical Journal 662 (1): 651–657. doi:10.1086/517993. Bibcode: 2007ApJ...662..651I.
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