EU Andromedae

EU Andromedae (often abbreviated to EU And) is a carbon star in the constellation Andromeda. Its apparent visual magnitude varies in an irregular manner between 10.7 and 11.8.[2]

EU Andromedae
Observation data
Epoch J2000      Equinox J2000
Constellation Andromeda
Right ascension  23h 19m 58.8815s[1]
Declination +47° 14′ 34.576″[1]
Apparent magnitude (V) 10.7 – 11.8 variable [2]
Characteristics
Spectral type C-J5− C25 j3.5[3]
Apparent magnitude (B) 12.84[4]
Apparent magnitude (V) 10.38[4]
Apparent magnitude (G) 9.0005[1]
Apparent magnitude (J) 5.526[5]
Apparent magnitude (H) 4.492[5]
Apparent magnitude (K) 4.018[5]
B−V color index 2.5687[4]
Variable type Lb?[2]
Astrometry
Proper motion (μ) RA: 2.062±0.080 [1] mas/yr
Dec.: −3.263±0.072[1] mas/yr
Parallax (π)0.6515 ± 0.0561[1] mas
Distance5,000 ± 400 ly
(1,500 ± 100 pc)
Details
Radius82[1] R☉
Luminosity983[1] L☉
Temperature3,579[1] K
Other designations
2MASS J23195888+4714345, TYC 3640-752-1
Database references
SIMBADdata

Infrared observations of EU Andromedae show the presence of silicate grains, indicating the presence of an oxygen-rich circumstellar shell around the star, a combination known as a silicate star. Subsequently, a water maser was detected around this star (and for the first time around a carbon star), confirming the existence of the shell.[6] The most recent observations suggest that the maser originated in a circumstellar disc, seen nearly edge-on, around an unseen companion with a minimum mass of 0.5 M☉. Carbon dioxide has been detected for the first time in a silicate carbon star around EU Andromedae.[7][8]

EU Andromedae is given as the standard star for the C-J5− spectral class. C-J spectral types are assigned to stars with strong isotopic bands of carbon molecules, defined as the ratio of 12
C
 to 13
C
 being less than four. A more complete spectral type includes the abundance indices C25 j3.5, which indicate the Swan band strength and the isotopic band ratio.[3]

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. Gaia DR2 record for this source at VizieR.
  2. EU 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 Accessed on line 2018-10-17.
  3. Barnbaum, Cecilia; Stone, Remington P. S.; Keenan, Philip C. (1996). "A Moderate-Resolution Spectral Atlas of Carbon Stars: R, J, N, CH, and Barium Stars". The Astrophysical Journal Supplement Series. 105: 419. Bibcode:1996ApJS..105..419B. doi:10.1086/192323.
  4. Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (2000), "The Tycho-2 catalogue of the 2.5 million brightest stars", Astronomy & Astrophysics, 355: L27–L30, Bibcode:2000A&A...355L..27H.
  5. Cutri, R. M.; Skrutskie, M. F.; Van Dyk, S.; et al. (June 2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". CDS/ADC Collection of Electronic Catalogues (2246): II/246. Bibcode:2003yCat.2246....0C.
  6. Benson, P. J.; Little-Marenin, I. R. (1987). "A Water Maser Associated with EU Andromedae: A Carbon Star near an Oxygen-rich Circumstellar Shell". Astrophysical Journal Letters. 316: L37. Bibcode:1987ApJ...316L..37B. doi:10.1086/184887.
  7. Ohnaka, K.; Boboltz, D. A. (2008). "Imaging the oxygen-rich disk toward the silicate carbon star EU Andromedae". Astronomy and Astrophysics. 478 (3): 809–814. arXiv:0712.2395. Bibcode:2008A&A...478..809O. doi:10.1051/0004-6361:20079030.
  8. Lloyd Evans, T. (1990). "Carbon stars with silicate dust shells - I. Carbon stars with enhanced 13C (J stars)". Monthly Notices of the Royal Astronomical Society. 243: 336. Bibcode:1990MNRAS.243..336L.
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