U Equulei
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Equuleus |
| Right ascension | 20h 57m 16.2s |
| Declination | 02° 58′ 45″ |
| Apparent magnitude (V) | 14.5 |
| Characteristics | |
| Spectral type | M[1] |
| Variable type | irregular variable |
| Astrometry | |
| Radial velocity (Rv) | 78 km/s |
| Distance | 5000 ly (1500 pc) |
| Other designations | |
IRAS 20547+0247 | |
U Equulei (U Equ / IRAS 20547 +0247) is a variable star in the constellation of Equuleus of an apparent magnitude of +14.50 in the B band. It lies at an estimated distance of 5,000 light-years (1,500 parsecs ) of the Solar System.
Properties
U Equulei is a peculiar star whose optical spectrum is one of the strangest observed. Their spectra, obtained in 1994, are dominated by strong absorption units metallic oxides[2] somewhat similar to red giant of spectral type M. The bands due to TiO, AlO, and appear to have a source VO-from circumstellar material surrounding the star-and photospheric . There appears to be falling into the star material or mass ejection therefrom, it is thought that gas can be contained in a disk-shaped structure. U Equulei also shows other peculiarities. Its emissions maser of OH and H2O[2] vary in speed and intensity. Also, its high radial velocity (78 km / s) and galactic latitude (-26 °) suggest a link with the population of galactic halo.
U Equulei is ranked as an irregular variable of long period (LB) whose brightness-B-band magnitude varies between +14.5 and +15.5. Although in 1994 the visual magnitude was about +9, post - 1996, 1998 and 1999 - showed a decrease in magnitude to +13. Variations in visual magnitude and the origin of circumstellar material remain unexplained, however, the strange nature of its optical spectrum suggests that the star may have entered a stage of rapid development.
Theoretical Planet
Lionel Siess and Mario Livio suggested that the accretion of a giant planet towards increasing red giant has been able to make the star's outer layers rotate fast enough to cause an outpouring equatorial-or disk-expansion, responsible for the peculiar environment U Equulei.[3]
See also
References
- ↑ "V*U Equ -- Post-AGB Star", SIMBAD Astronomical Database(Centre de donées astronomiques de Strasbourg), retrieved 2012-09-23
- ↑ 2.0 2.1 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: 983–984, arXiv:astro-ph/0502154, Bibcode:2005ApJ...624..983G, doi:10.1086/429369
- ↑ 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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