BX Andromedae

BX Andromedae (BX And) is an eclipsing binary star in the constellation Andromeda. Its maximum apparent visual magnitude is 8.87. Within a cycle of approximately 14.6 hours, the brightness drops down to a magnitude of 9.53 during the main eclipse, and to a magnitude of 9.12 during the secondary one. It is classified as a Beta Lyrae variable.[2]

BX Andromedae
Observation data
Epoch J2000      Equinox J2000
Constellation Andromeda
Right ascension 02h 09m 03.42126s[1]
Declination +40° 47′ 39.16539″[1]
Apparent magnitude (V) 8.87 – 9.53 variable [2]
Characteristics
Spectral type F2V[2]
Apparent magnitude (B) 9.37[3]
Apparent magnitude (V) 8.98[3]
Apparent magnitude (G) 8.8903[1]
Apparent magnitude (J) 8.487[4]
Apparent magnitude (H) 8.229[4]
Apparent magnitude (K) 8.134[4]
B−V color index 0.3927[5]
Variable type EB[2]
Astrometry
Radial velocity (Rv)−45.10±2.6[6] km/s
Proper motion (μ) RA: 9.860±0.080 [1] mas/yr
Dec.: −8.307±0.078[1] mas/yr
Parallax (π)5.4529 ± 0.0558[1] mas
Distance598 ± 6 ly
(183 ± 2 pc)
Orbit[7]
Period (P)0.61011240 days
Semi-major axis (a)4.424 R☉
Inclination (i)75.862°
Semi-amplitude (K1)
(primary)		106.35±0.61 km/s
Semi-amplitude (K2)
(secondary)		233.58±1.77 km/s
Details[7]
Primary
Mass2.148 M☉
Radius2.01 R☉
Luminosity7.08 L☉
Temperature6,650 K
Secondary
Mass0.977 M☉
Radius1.40 R☉
Luminosity0.90 L☉
Temperature4,758 K
Other designations
2MASS J02090342+4047392, BD+40 442, HD 13078, HIP 10027, SAO 37805, TYC 2833-1436-1
Database references
SIMBADdata

Variability

BX Andromedae, like all Beta Lyrae variables, shows a primary and a secondary minimum when, respectively, the most luminous and the less luminous component of the pair is eclipsed by the other. The brightness however changes smoothly, so there is no onset and an end time for the eclipses. This cycle repeats approximately every 14.6 hours.[2]

System

The two stars in the system are orbiting so close to each other that they retain an ellipsoidal shape. The spectrum of the two stars hasn't been separated yet; as a whole, the system has a spectral type F2V.[2] The physical parameters of the stars (like mass, radius, and temperature) can be inferred from the light curve.

BX Andromedae, however, may be a quadruple system. This system shows slight orbital period variations that could be induced by a third faint body in the system with an orbital period of 62 years.[8] There is also a visual companion star TYC 2833-53-1 of 10.85 magnitude only 20 arcseconds away with a common proper motion and a distance (measured with parallax) compatible with the one of BX Andromedae, and has an estimated mass of 1.04 M☉.[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. BX 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. "BX And". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved October 26, 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. 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.
  6. Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35495 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.
  7. Siwak, M.; Zola, S.; Koziel-Wierzbowska, D. (2010). "A Study of Contact Binaries with Large Temperature Differences between Components". Acta Astronomica. 60 (4): 305–336. arXiv:1011.5682. Bibcode:2010AcA....60..305S.
  8. Pribulla, T.; Rucinski, S. M. (2006). "Contact Binaries with Additional Components. I. The Extant Data". The Astronomical Journal. 131 (6): 2986–3007. arXiv:astro-ph/0601610. Bibcode:2006AJ....131.2986P. doi:10.1086/503871. S2CID 15762240.
  9. Database entry, Updated Multiple Star Catalog (MSC, 2018), A. Tokovinin CDS ID J/ApJS/235/6 Accessed on line 2018-10-29.
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