ET Andromedae

The visual band light curve of ET Andromedae, adapted from Blanco et al. (1980)[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Andromeda
Right ascension 23h 17m 56.011185s[2]
Declination +45° 29′ 20.1197″[2]
Apparent magnitude (V) 6.48[3]
Characteristics
Spectral type A0 Vp SiSr[4] or B9p SI[5]
B−V color index −0.037±0.006[3]
Variable type α2 CVn
Astrometry
Radial velocity (Rv)−0.30±4.10[3] km/s
Proper motion (μ) RA: +24.740[2] mas/yr
Dec.: −11.038[2] mas/yr
Parallax (π)5.4200 ± 0.0572 mas[2]
Distance602 ± 6 ly
(185 ± 2 pc)
Absolute magnitude (MV)0.58[6]
Orbit[7]
Period (P)48.304±0.007 d
Eccentricity (e)0.50±0.05
Periastron epoch (T)2443720.11±0.64 JD
Argument of periastron (ω)
(secondary)		49.8±6.0°
Semi-amplitude (K1)
(primary)		25.7±2.0 km/s
Details
Mass3.25[8] M☉
Radius2.7[9] R☉
Luminosity91.06[3] L☉
Surface gravity (log g)3.81[10] cgs
Temperature11,444[10] K
Rotation1.62 d[11]
Rotational velocity (v sin i)65[12] km/s
Age284[6] Myr
Other designations
AG+45° 2124, BD+44° 4373, HD 219749, HIP 115036, HR 8861, SAO 52876, PPM 64037, TYC 3636-2562-1, GSC 03636-02562, 2MASS J23175600+4529201[13]
Database references
SIMBADdata

ET Andromedae is a binary star system star in the northern constellation of Andromeda.[14] It has an apparent visual magnitude of 6.48,[3] placing it at the nominal limit for visibility with the naked eye. The distance to this system can be estimated from its annual parallax shift of 5.42 mas,[2] which yields a value of 602 light years.

Variations in the radial velocity of this star suggest it is a single-lined spectroscopic binary system. This yields orbital elements with a period of 48.3 days and an eccentricity of 0.50. The a sin i value for the primary is 14.8 Gm (0.099 AU), where a is the semimajor axis and i is the (unknown) orbital inclination.[7]

The visible component is a well-studied magnetic chemically peculiar star[15] with a stellar classification of A0 Vp SiSr.[4] The SiSr notation indicates unusual abundances of silicon and strontium in the spectrum. It has a magnetic field with an average surface value of 3.2 kT.[16] The abundance of silicon varies depending on the viewing angle.[15] The star is an Alpha2 Canum Venaticorum variable with a period of 1.618875 days.[17]

References

  1. ↑ Blanco, C.; Catalano, F. A.; Strazzulla, G. (January 1980). "The light variations of the Ap Star HR 8861". Astronomy & Astrophysics Supplement Series. 39: 127–128. Retrieved 8 October 2021.
  2. 1 2 3 4 5 6 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.
  3. 1 2 3 4 5 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
  4. 1 2 Abt, Helmut A.; Morrell, Nidia I. (1995). "The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars". Astrophysical Journal Supplement. 99: 135. Bibcode:1995ApJS...99..135A. doi:10.1086/192182.
  5. ↑ Cowley, A.; et al. (April 1969). "A study of the bright A stars. I. A catalogue of spectral classifications". Astronomical Journal. 74: 375–406. Bibcode:1969AJ.....74..375C. doi:10.1086/110819.
  6. 1 2 Gontcharov, G. A. (November 2012). "Spatial distribution and kinematics of OB stars". Astronomy Letters. 38 (11): 694–706. arXiv:1606.09028. Bibcode:2012AstL...38..694G. doi:10.1134/S1063773712110035. S2CID 119108982.
  7. 1 2 Ouhrabka, M.; Grygar, J. (May 1979). "Spectroscopic evidence for the binary nature of the Ap star". Information Bulletin on Variable Stars. 1600: 1. Bibcode:1979IBVS.1600....1O.
  8. ↑ Ducati, J. R.; et al. (2011). "The mass ratio and initial mass functions in spectroscopic binaries" (PDF). Astronomy and Astrophysics. 525: A26. Bibcode:2011A&A...525A..26D. doi:10.1051/0004-6361/200913895.
  9. ↑ Pasinetti Fracassini, L. E.; et al. (2001). "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)". Astronomy & Astrophysics (Third ed.). 367 (2): 521–24. arXiv:astro-ph/0012289. Bibcode:2001A&A...367..521P. doi:10.1051/0004-6361:20000451. S2CID 425754.
  10. 1 2 Adelman, Saul J. (2002). "On the Periods of the Magnetic CP Stars". Baltic Astronomy. 11: 475–485. Bibcode:2002BaltA..11..475A.
  11. ↑ Kreidl, T. J. (October 1993), "A Null Detection of Rapid Oscillations in the Ap Star ET And", Information Bulletin on Variable Stars, 3945: 1, Bibcode:1993IBVS.3945....1K
  12. ↑ Strom, Stephen E.; et al. (2005). "B Star Rotational Velocities in h and χ Persei: A Probe of Initial Conditions during the Star Formation Epoch?". The Astronomical Journal. 129 (2): 809–828. arXiv:astro-ph/0410337. Bibcode:2005AJ....129..809S. doi:10.1086/426748. S2CID 15059129.
  13. ↑ "HD 13530". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 20 August 2018.
  14. ↑ Watson, Christopher (4 February 2010). "ET Andromedae". AAVSO Website. American Association of Variable Star Observers. Retrieved 5 November 2014.
  15. 1 2 Adelman, Saul J. (May 2000). "UVBY photometry of the magnetic CP stars HD 36668, 36 Lyncis, HD 86592, and HR 8861". Astronomy and Astrophysics. 357: 548–552. Bibcode:2000A&A...357..548A.
  16. ↑ Glagolevskij, Yu. V. (September 2007). "Magnetic-field dependence of chemical anomalies in CP stars". Astrophysical Bulletin. 62 (3): 244–256. Bibcode:2007AstBu..62..244G. doi:10.1134/S1990341307030054. S2CID 122706004.
  17. ↑ Samus', N. N.; Kazarovets, E. V.; Durlevich, O. V.; Kireeva, N. N.; Pastukhova, E. N. (2017), "General catalogue of variable stars: Version GCVS 5.1", Astronomy Reports, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
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