EU Andromedae

EU Andromedae

A visual band light curve for EU Andromedae, plotted from ASAS-SN data.[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Andromeda
Right ascension 23h 19m 58.8815s[2]
Declination +47° 14′ 34.576″[2]
Apparent magnitude (V) 10.7 – 11.8 variable [3]
Characteristics
Spectral type C-J5− C25 j3.5[4]
Apparent magnitude (B) 12.84[5]
Apparent magnitude (V) 10.38[5]
Apparent magnitude (G) 9.0005[2]
Apparent magnitude (J) 5.526[6]
Apparent magnitude (H) 4.492[6]
Apparent magnitude (K) 4.018[6]
B−V color index 2.5687[5]
Variable type Lb?[3]
Astrometry
Proper motion (μ) RA: 2.062±0.080 [2] mas/yr
Dec.: −3.263±0.072[2] mas/yr
Parallax (π)0.6515 ± 0.0561 mas[2]
Distance5,000 ± 400 ly
(1,500 ± 100 pc)
Details
Radius82[2] R☉
Luminosity983[2] L☉
Temperature3,579[2] K
Other designations
2MASS J23195888+4714345, TYC 3640-752-1
Database references
SIMBADdata

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.[3]

EU Andromedae was reported to be a carbon star by Oliver J. Lee et al. in 1947, based on objective prism observations undertaken as part of a Dearborn Observatory study of faint red stars.[7][8] Years later, the variability of EU Andromedae was discovered by French amateur astronomer Roger Weber, who examined the star on photographic plates that he and Giuliano Romano had taken from May 1959 through October 1961. Weber announced the discovery in 1962 and noted that it was probably a long period variable, but he could not determine if it was a semi-regular or a Mira variable. It is number 149 in his catalog.[9][10] There is some disagreement in the literature about what class of variable star EU Andromedae belongs to, with some researchers listing it as a slow irregular variable,[3] and others listing it as a semi-regular variable.[11]

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.[8] 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.[12][13]

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.[4]

  1. ^ Cite error: The named reference ASAS-SN was invoked but never defined (see the help page).
  2. ^ a b c d e f g h i Cite error: The named reference Gaia was invoked but never defined (see the help page).
  3. ^ a b c d Cite error: The named reference GCVS was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference barnbaum was invoked but never defined (see the help page).
  5. ^ a b c Cite error: The named reference TYCHO was invoked but never defined (see the help page).
  6. ^ a b c Cite error: The named reference 2MASS Cat was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference Lee was invoked but never defined (see the help page).
  8. ^ a b Cite error: The named reference Benson1987 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference Weber was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Schweitzer was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Dimitrov was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Ohnaka2008 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference silicate was invoked but never defined (see the help page).