LQ Andromedae

LQ Andromedae (shortened as LQ And, also known as HR 9070 in the Bright Star Catalogue) is a variable star in the constellation Andromeda. Its maximum apparent visual magnitude is 6.5, placing it at the limit of the visibility to the naked eye. The brightness, however, drops down to 6.66 with a periodic cycle of roughly 7.44 hours.[2]

LQ Andromedae
Observation data
Epoch J2000      Equinox J2000
Constellation Andromeda
Right ascension  23h 58m 46.4391s[1]
Declination +46° 24′ 47.44272″[1]
Apparent magnitude (V) 6.5 – 6.66 variable [2]
Characteristics
Spectral type B4Ven[2]
Apparent magnitude (U) 5.84[3]
Apparent magnitude (B) 6.444[4]
Apparent magnitude (V) 6.538[4]
Apparent magnitude (G) 6.4666[1]
Apparent magnitude (J) 6.588[5]
Apparent magnitude (H) 6.617[5]
Apparent magnitude (K) 6.545[5]
B−V color index 0.098[6]
Variable type Be star
Astrometry
Radial velocity (Rv)−51.27±0.42[7] km/s
Proper motion (μ) RA: 15.419±0.081 [1] mas/yr
Dec.: 0.574±0.060[1] mas/yr
Parallax (π)2.4169 ± 0.0519[1] mas
Distance1,350 ± 30 ly
(414 ± 9 pc)
Orbit
Period (P)7.413 days[8]
Details[6]
Mass8.0±0.5 M☉
Radius3.4±1[8] R☉
Luminosity (bolometric)2,559 L☉
Surface gravity (log g)3.49±0.37 cgs
Temperature17260±520 K
Rotational velocity (v sin i)300±25 km/s
Other designations
2MASS J23584644+4624474, BD+45 4381, HD 224559, HIP 118214, HR 9070, SAO 53540, TYC 3639-164-1
Database references
SIMBADdata

The stellar classification of this star is B4Ven,[2] so it is a main sequence star that shows emission lines and broadened absorption lines induced by the fast projected rotational velocity of 300 km/s (the angle between the rotation axis and our line of sight has been estimated with a value of 72°).[6] This leads to the classification of the star as a Be star. Further proof is the compatibility between the rotational and luminosity variability periods.[8]

LQ Andromedae is also a spectroscopic binary with an orbital period of 7.413 days. Not much is known about the secondary component, but it is likely a low-mass companion (M<0.5 M☉). A circumstellar disk is also present in the system.[8]

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. LQ 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. "LQ And". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved October 18, 2018.
  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. Zorec, J.; Frémat, Y.; Domiciano de Souza, A.; Royer, F.; Cidal, L.; Hubert, A. -M.; Seemann, T.; Martayan, C.; Cochetti, Y. R.; Arias, M. L.; Aidelman, Y.; Stee, P. (November 2016). "Critical study of the distribution of rotational velocities of Be stars. I. Deconvolution methods, effects due to gravity darkening, macroturbulence, and binarity". Astronomy & Astrophysics. 595: 26 pp. arXiv:1702.07684. Bibcode:2016A&A...595A.132Z. doi:10.1051/0004-6361/201628760.
  7. de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, A61.
  8. Matthews, J. M.; Harmanec, P.; Walker, G. A. H.; Yang, S.; Wehlau, W. H. (February 1991). "Spectroscopic variations of the Be star LQ And : binarity and rotation". Monthly Notices of the Royal Astronomical Society. 248: 787. Bibcode:1991MNRAS.248..787M. doi:10.1093/mnras/248.4.787.
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