KZ Andromedae

KZ Andromedae (often abbreviated to KZ And) is a double lined spectroscopic binary in the constellation Andromeda. Its apparent visual magnitude varies between 7.91 and 8.03 during a cycle slightly longer than 3 days.

KZ Andromedae
Observation data
Epoch J2000      Equinox J2000
Constellation Andromeda
Right ascension  23h 09m 57.3642s[1]
Declination +35° 32′ 55.65804″[1]
Apparent magnitude (V) 7.91 – 8.03 variable[2]
Characteristics
Spectral type K2Ve+K2Ve[2]
Apparent magnitude (B) 8.81[3]
Apparent magnitude (V) 7.93[3]
Apparent magnitude (G) 7.6580[1]
Apparent magnitude (J) 6.225[4]
Apparent magnitude (H) 5.778[4]
Apparent magnitude (K) 5.659[4]
Variable type BY Dra[2]
Astrometry
Radial velocity (Rv)−5.818±0.026[5] km/s
Proper motion (μ) RA: 150.123±0.063 [1] mas/yr
Dec.: 1.226±0.059[1] mas/yr
Parallax (π)32.8449 ± 0.0369[1] mas
Distance99.3 ± 0.1 ly
(30.45 ± 0.03 pc)
Orbit[5]
Period (P)3.03291126±0.00000046 days
Eccentricity (e)0.01174±0.00056
Periastron epoch (T)HJD 2455133.480±0.020
Argument of periastron (ω)
(secondary)		7.11±2.35°
Semi-amplitude (K1)
(primary)		69.362±0.046 km/s
Semi-amplitude (K2)
(secondary)		71.300±0.054 km/s
Details[5]
Primary
Radius0.77±0.07 R☉
Luminosity0.34±0.06 L☉
Rotational velocity (v sin i)12.5 km/s
Secondary
Radius0.66±0.06 R☉
Luminosity0.25±0.04 L☉
Rotational velocity (v sin i)12.2 km/s
Other designations
2E 4687, 2MASS J23095734+4757300, BD+47 4058, EUVE J2309+47.9, HD 218738, HIP 114379, GJ 4315, TYC 3627-1822-1, NLTT 2314, SAO 52753, WDS J23100+4758B
Database references
SIMBADdata

System

Both stars in the KZ Andromedae system are main sequence stars of spectral type K2Ve, meaning that the spectrum shows strong emission lines.[2] This is caused by their active chromosphere that cause large spots on the surface.[5]

KZ Andromedae is listed in the Washington Double Star Catalog as the secondary component in a visual binary system, with the primary being HD 218739. In 50 years of observations, there is little evidence of relative motion between the two stars; however, they have a common proper motion and a similar radial velocity.[5]

Variability

The rotational velocity of both stars is consistent with a synchronous rotation of the pair, and the rotational period is itself comparable to the brightness variation period. KX Andromedae is thus classified as a BY Draconis variable, and the variability is caused by the large spots on the surface.[5]

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. N. N. Samus; O. V. Durlevich; et al. "KZ And database entry". Combined General Catalog of Variable Stars (2004 ed.). CDS. Retrieved 2018-11-12.
  3. "KZ And". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved November 12, 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. Fekel, F. C.; Henry, G. W.; Tomkin, J. (September 2017). "New Precision Orbits of Bright Double-lined Spectroscopic Binaries. X. HD 96511, HR 7578, and KZ Andromedae". The Astronomical Journal. 154 (3): 13. Bibcode:2017AJ....154..120F. doi:10.3847/1538-3881/aa816e. 120.
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