GR Andromedae

GR Andromedae (often abbreviated to GR And) is a variable star in the constellation Andromeda. Its apparent visual magnitude varies between 6.87 and 6.95 in a cycle of 518.2 days.[9] It is classified as an α2 Canum Venaticorum variable.[2]

GR Andromedae
Observation data
Epoch J2000      Equinox J2000
Constellation Andromeda
Right ascension 00h 28m 28.5694s[1]
Declination +32° 26′ 15.8791″[1]
Apparent magnitude (V) 6.87 – 6.95 variable[2]
Characteristics
Spectral type A2pSrCrEu[2]
Apparent magnitude (B) 6.99[3]
Apparent magnitude (V) 6.91[3]
Apparent magnitude (G) 6.8449[1]
Apparent magnitude (J) 6.708[4]
Apparent magnitude (H) 6.765[4]
Apparent magnitude (K) 6.739[4]
Variable type α2 CVn[2]
Astrometry
Radial velocity (Rv)−18.2±0.7[5] km/s
Proper motion (μ) RA: −28.861±0.093 [1] mas/yr
Dec.: −20.308±0.070[1] mas/yr
Parallax (π)5.3516 ± 0.0704[1] mas
Distance609 ± 8 ly
(187 ± 2 pc)
Absolute magnitude (MV)+0.88[6]
Details
Mass2.24[6] M☉
Radius2.24[7] R☉
Luminosity37[6] L☉
Surface gravity (log g)3[8] cgs
Temperature8,542[8] K
Metallicity [Fe/H]1[8] dex
Rotation518.2 days[9]
Rotational velocity (v sin i)< 6[7] km/s
Age525[6] Myr
Other designations
2MASS J00282858+3226159, BD+31 59, HD 2453, HIP 2243, SAO 53921, TYC 2266-725-1
Database references
SIMBADdata

Spectrum

The radiation emitted by GP Andromedae is a typical stellar blackbody with absorption lines from various elements, which gives to the star a spectral type A2pSrCrEu, meaning that unusually strong lines of strontium, chromium and europium can be observed.[2] GP Andromedae is thus classified as an Ap star. The intensity and profile of the spectral lines varies within a cycle with the same period as the brightness variations.[7]

Variability

Photometric and spectral variability of GR Andromedae is typical of a star with a strong and variable magnetic field. This way, the 518.2 days periodicity can be identified as the rotation period of the star.[7] It's among the slowest rotators in the category of magnetic chemically peculiar stars, with a calculated equatorial rotation rate of only 0.2 km/s.[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. Gaia DR2 record for this source at VizieR.
  2. GR 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. "GR And". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved November 8, 2018.
  4. 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.
  5. Gontcharov, G. A. (November 2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. S2CID 119231169.
  6. Kochukhov, O.; Bagnulo, S. (2006). "Evolutionary state of magnetic chemically peculiar stars". Astronomy and Astrophysics. 450 (2): 763. arXiv:astro-ph/0601461. Bibcode:2006A&A...450..763K. doi:10.1051/0004-6361:20054596. S2CID 18596834.
  7. Catalano, F. A.; Leone, F. (June 1990). "Photoelectric photometry of chemically peculiar stars at the Catania astrophysical observatory. Observatory of HD 2453, HD 71866, HD 72968 and HD 126515". Astronomy and Astrophysics Supplement Series. 83: 491. Bibcode:1990A&AS...83..491C.
  8. Soubiran, Caroline; et al. (2016), "The PASTEL catalogue: 2016 version", Astronomy & Astrophysics, 591: A118, arXiv:1605.07384, Bibcode:2016A&A...591A.118S, doi:10.1051/0004-6361/201628497, S2CID 119258214.
  9. Pyper, D. M.; Adelman, S. J. (October 2017). "On the Photometric Variability of Very Sharp-lined Cool mCP Stars". Publications of the Astronomical Society of the Pacific. 129 (980): 104203. Bibcode:2017PASP..129j4203P. doi:10.1088/1538-3873/aa7c9e.
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