U Andromedae

U Andromedae is a variable star in the constellation of Andromeda, at a distance of approximately 2,200 ly. It is a star of spectral type M6e and it is classified as a Mira variable.

Not to be confused with υ (Upsilon) Andromedae.
U Andromedae
Observation data
Epoch J2000      Equinox J2000
Constellation Andromeda
Right ascension  01h 15m 29.69623s[1]
Declination +40° 43′ 08.3932″[1]
Apparent magnitude (V) 9.0 to 15.0[2]
Characteristics
Spectral type M6e[2]
Variable type Mira[2]
Astrometry
Radial velocity (Rv)−4.0±5[3] km/s
Proper motion (μ) RA: 11.416±0.321[1] mas/yr
Dec.: −8.392±0.297[1] mas/yr
Parallax (π)1.4745 ± 0.1511[1] mas
Distanceapprox. 2,200 ly
(approx. 680 pc)
Details
Temperature3,288[1] K
Other designations
HD 7482, BD+39°291a, 2MASS J01152971+4043082, IRAS 01126+4027[4]
Database references
SIMBADdata

U Andromedae is the variable star designation of this star. Its brightness varies by several magnitudes with a mean period of 347.7 d, although the exact length of each cycle is somewhat variable. Similarly, the magnitude of each maximum and minimum varies. The mean apparent magnitude is 11.6, with a mean maximum magnitude of 9.9.[5] The brightest recorded maxima are at magnitude 9.0, and the faintest minima at magnitude 15.0.[2] The rise to maximum brightness is faster than the fall to minimum, taking on average 40% of the period.[6]

The large amplitude, long period, and shape of the light curve mean that U Andromedae is classified as a Mira variable, a type of pulsating asymptotic giant branch (AGB) star.[2] It was first observed to be variable by Thomas D. Anderson during 1894 and 1895.[7][8] AGB stars have exhausted both hydrogen and helium in their cores and are not massive enough to fuse carbon and oxygen, so they erratically fuse helium and hydrogen shells outside the core.[9]

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051.
  2. U And, database entry, Combined General Catalog of Variable Stars (GCVS4.2, 2004 Ed.), N. N. Samus, O. V. Durlevich, et al., CDS ID II/250.
  3. Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Carnegie Institute Washington D.C. Publication. Bibcode:1953GCRV..C......0W.
  4. "U And". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved October 8, 2018.
  5. Clayton, M. L.; Feast, M. W. (1969). "Absolute Magnitudes of Mira Variables from Statistical Parallaxes". Monthly Notices of the Royal Astronomical Society. 146 (4): 411–421. Bibcode:1969MNRAS.146..411C. doi:10.1093/mnras/146.4.411.
  6. "U Andromedae". The International Variable Star Index. Retrieved 2019-09-17.
  7. Anderson, Thomas D. (1895). "New variable star in Andromeda". Astronomische Nachrichten. 139: 117. Bibcode:1895AN....139Q.117A.
  8. Chandler, S. C. (1896). "Third catalogue of variable stars". The Astronomical Journal. 16: 145. Bibcode:1896AJ.....16..145C. doi:10.1086/102484.
  9. Woźniak, P. R.; Williams, S. J.; Vestrand, W. T.; Gupta, V. (2004). "Identifying Red Variables in the Northern Sky Variability Survey". The Astronomical Journal. 128 (6): 2965. Bibcode:2004AJ....128.2965W. doi:10.1086/425526.
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