U Equulei
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Equuleus |
| Right ascension | 20h 57m 16.28s[1] |
| Declination | 02° 58′ 44.6″[1] |
| Apparent magnitude (V) | 9 - 13[2] |
| Characteristics | |
| Evolutionary stage | (post?) AGB[3] |
| Spectral type | G - K III[3] |
| B−V color index | +1.6[3] |
| Variable type | Lb[2] |
| Astrometry | |
| Radial velocity (Rv) | 78 km/s |
| Distance | 5,000 ly (1,500[3] pc) |
| Other designations | |
| Database references | |
| SIMBAD | data |
U Equulei (U Equ / IRAS 20547 +0247) is a variable star in the Equuleus constellation with an apparent magnitude of +14.50 in the B band. It lies at an estimated distance of 5,000 light-years (1,500 parsecs ) from the Solar System.
Properties
U Equulei is, or was, an OH/IR star, and strong OH and H2O masers have been observed. These vary to a greater extent than almost any other star observed, and it is possible that the stage of maser activity is essentially finished.[4]
Theoretical Planet
Lionel Siess and Mario Livio suggested that the accretion of a giant planet towards the increasing red giant has made the star's outer layers rotate fast enough to cause an outpouring equatorial- or disk-expansion, responsible for the star's peculiar environment.[5]
See also
References
- 1 2 Cutri, R. M.; Skrutskie, M. F.; Van Dyk, S.; Beichman, C. A.; Carpenter, J. M.; Chester, T.; Cambresy, L.; Evans, T.; Fowler, J.; Gizis, J.; Howard, E.; Huchra, J.; Jarrett, T.; Kopan, E. L.; Kirkpatrick, J. D.; Light, R. M.; Marsh, K. A.; McCallon, H.; Schneider, S.; Stiening, R.; Sykes, M.; Weinberg, M.; Wheaton, W. A.; Wheelock, S.; Zacarias, N. (2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". VizieR On-line Data Catalog: II/246. Originally published in: 2003yCat.2246....0C. 2246. Bibcode:2003yCat.2246....0C.
- 1 2 Geballe, T.R.; Barnbaum, C.; Noll, Keith S.; Morris, M. (September 2012), "Infrared Spectroscopy of U Equulei's Warm Circumstellar Gas", The Astrophysical Journal, 624 (2): 983–984, arXiv:astro-ph/0502154
, Bibcode:2005ApJ...624..983G, doi:10.1086/429369 - 1 2 3 4 Barnbaum, C.; Omont, A.; Morris, M. (1996). "The unusual circumstellar environment of the evolved star, U Equulei". Astronomy and Astrophysics. 310: 259. Bibcode:1996A&A...310..259B.
- ↑ Lewis, B. M. (2002). "On Dead OH/IR Stars". The Astrophysical Journal. 576: 445. Bibcode:2002ApJ...576..445L. doi:10.1086/341534.
- ↑ Siess, Lionel; Mario Livio (October 1999). "The accretion of brown dwarfs and planets by giant stars – II. Solar-mass stars on the red giant branch". Monthly Notices of the Royal Astronomical Society. 308 (4): 1133–1149. arXiv:astro-ph/9905235. Bibcode:1999MNRAS.308.1133S. doi:10.1046/j.1365-8711.1999.02784.x.
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