12 Lacertae

12 Lacertae is a wide binary star[3] system in the northern constellation of Lacerta, located roughly 1,090 light years away from the Sun based on parallax.[1] It is visible to the naked eye as a dim, blue-white hued point of light with a baseline apparent visual magnitude of 5.23.[2] The system is drifting closer to the Earth with a mean heliocentric radial velocity of –12.5.[6] It is a probable member of the I Lacertae OB association (Lac OB1).[13][14][15]

12 Lacertae
Observation data
Epoch J2000      Equinox J2000
Constellation Lacerta
Right ascension  22h 41m 28.64920s[1]
Declination +40° 13′ 31.6192″[1]
Apparent magnitude (V) 5.228[2] + 9.2[3]
Characteristics
Spectral type B1.5III[4] + A3V[3]
B−V color index −0.142[2]
Variable type β Cep[5]
Astrometry
Radial velocity (Rv)−12.5±2.2[6] km/s
Proper motion (μ) RA: −1.761[1] mas/yr
Dec.: −5.102[1] mas/yr
Parallax (π)3.1131 ± 0.2529[1] mas
Distance1,050 ± 90 ly
(320 ± 30 pc)
Absolute magnitude (MV)–3.02[6]
Details
Mass9.5±0.3[7] M☉
Radius8.4[8] R☉
Luminosity (bolometric)8,877[2] L☉
Surface gravity (log g)3.817±0.047[9] cgs
Temperature23,809±450[9] K
Metallicity [Fe/H]−0.41[10] dex
Rotational velocity (v sin i)44±6[11] km/s
Age21.8±3.1[7] Myr
Other designations
12 Lac, DD Lac, BD+39°4912, GC 31670, HD 214993, HIP 112031, HR 8640, SAO 72627, WDS J22415+4014A[12]
Database references
SIMBADdata

The primary component is a Beta Cephei variable[5] with a stellar classification of B1.5III,[4] matching a B-type star with the luminosity class of a giant star. It has been known to be variable for more than a century and has been extensively studied.[16] The variable radial velocity of the star was discovered by W. S. Adams in 1912, and the light variations were established by 1919. The pulsational nature of the variability was shown by P. Ledoux in 1951, which led to one of the first world-wide observing campaigns with the star as its target. Dutch mathematician F. J. M. Barning analyzed the resulting data in 1963 and found four separate cycles of variation. By 1994, six periods had been confirmed.[5]

The variable star designation of the primary is DD Lacertae,[17] while 12 Lacertae is the Flamsteed designation.[12] In general terms it varies in magnitude from 5.16 down to 5.28 with a period of 4.63 hours.[17] As many as eleven different frequencies have been detected, with the dominant cycle showing a frequency of 5.179034 cycles per day. Curiously, three of the frequencies form an equally-spaced triplet with cycles of 5.179, 5.334, and 5.490 per day, although this alignment appears to be a coincidence.[5] It is a hybrid pulsator, showing mixed behaviors of a Beta Cephei variable and a slowly pulsating B-type star.[18]

The primary is a massive star, having 9.5[7] times the mass of the Sun and an age of only 22[7] million years old. It has about 8.4[8] times the girth of the Sun. The averaged quadratic field strength of the surface magnetic field is (2,352.3±1,604.9)×10−4 T.[19] It is radiating 8,877[2] times the luminosity of the Sun from its photosphere at an effective temperature of 23,809 K.[9] The estimated rotational velocity of the primary at the equator is 52±5 km/s;[20] about 10% of its break-up velocity.[18] However, seismic models suggest the core region is rotating much more rapidly with a rotational velocity of up to 100 km/s, and thus the star is undergoing differential rotation.[20]

The companion is an A-type main-sequence star with a stellar classification of A3V and visual magnitude 9.2. As of 2008, it had an angular separation of 69″ from the primary.[3] There is a faint infrared nebulosity at a separation of 0.6 light-years from the pair that is most likely a bow shock.[21]

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. Hohle, M. M.; Neuhäuser, R.; Schutz, B. F. (2010), "Masses and luminosities of O- and B-type stars and red supergiants", Astronomische Nachrichten, 331 (4): 349–360, arXiv:1003.2335, Bibcode:2010AN....331..349H, doi:10.1002/asna.200911355.
  3. Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x.
  4. Lesh, Janet Rountree (December 1968), "The Kinematics of the Gould Belt: an Expanding Group?", Astrophysical Journal Supplement, 17: 371, Bibcode:1968ApJS...17..371L, doi:10.1086/190179.
  5. Handler, G.; et al. (January 2006), "Asteroseismology of the β Cephei star 12 (DD) Lacertae: photometric observations, pulsational frequency analysis and mode identification", Monthly Notices of the Royal Astronomical Society, 365 (1): 327–338, arXiv:astro-ph/0510326, Bibcode:2006MNRAS.365..327H, doi:10.1111/j.1365-2966.2005.09728.x.
  6. 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.
  7. Tetzlaff, N.; et al. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society, 410 (1): 190–200, arXiv:1007.4883, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x.
  8. Pasinetti Fracassini, L. E.; et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)", Astronomy and Astrophysics (Third ed.), 367: 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451.
  9. Huang, W.; et al. (2010), "A Stellar Rotation Census of B Stars: From ZAMS to TAMS", The Astrophysical Journal, 722 (1): 605–619, arXiv:1008.1761, Bibcode:2010ApJ...722..605H, doi:10.1088/0004-637X/722/1/605.
  10. Gies, Douglas R.; Lambert, David L. (March 1992), "Carbon, nitrogen, and oxygen abundances in early B-type stars", Astrophysical Journal, Part 1, 387: 673–700, Bibcode:1992ApJ...387..673G, doi:10.1086/171116
  11. Lefever, K.; et al. (June 2010), "Spectroscopic determination of the fundamental parameters of 66 B-type stars in the field-of-view of the CoRoT satellite", Astronomy and Astrophysics, 515: A74, arXiv:0910.2851, Bibcode:2010A&A...515A..74L, doi:10.1051/0004-6361/200911956.
  12. "12 Lac". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-06-27.
  13. Lesh, J. R. (September 1969), "Internal motions in the associations II Per and I Lac.", Astronomical Journal, 74: 891–898, Bibcode:1969AJ.....74..891L, doi:10.1086/110878.
  14. Wolff, S. C.; Strom, S. E.; Dror, D.; Venn, K. (March 2007), "Rotational Velocities for B0-B3 Stars in Seven Young Clusters: Further Study of the Relationship between Rotation Speed and Density in Star-Forming Regions", The Astronomical Journal, 133 (3): 1092–1103, arXiv:astro-ph/0702133, Bibcode:2007AJ....133.1092W, doi:10.1086/511002.
  15. Kaltcheva, Nadia (October 2009), "Lacerta OB1 Revisited", Publications of the Astronomical Society of the Pacific, 121 (884): 1045, Bibcode:2009PASP..121.1045K, doi:10.1086/606037.
  16. Desmet, M.; et al. (July 2009), "An asteroseismic study of the β Cephei star 12 Lacertae: multisite spectroscopic observations, mode identification and seismic modelling", Monthly Notices of the Royal Astronomical Society, 396 (3): 1460–1472, arXiv:0903.5477, Bibcode:2009MNRAS.396.1460D, doi:10.1111/j.1365-2966.2009.14790.x.
  17. Samus', N. N; Kazarovets, E. V; Durlevich, O. V; Kireeva, N. N; Pastukhova, E. N (2017), "General catalogue of variable stars", Astronomy Reports, 5.1, 61 (1): 80, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085.
  18. Daszyńska-Daszkiewicz, J.; et al. (June 2013), "The β Cep/SPB star 12 Lacertae: extended mode identification and complex seismic modelling", Monthly Notices of the Royal Astronomical Society, 431 (4): 3396–3407, arXiv:1304.4049, Bibcode:2013MNRAS.431.3396D, doi:10.1093/mnras/stt418.
  19. Bychkov, V. D.; et al. (August 2003), "Catalogue of averaged stellar effective magnetic fields. I. Chemically peculiar A and B type stars", Astronomy and Astrophysics, 407 (2): 631–642, arXiv:astro-ph/0307356, Bibcode:2003A&A...407..631B, doi:10.1051/0004-6361:20030741.
  20. Dziembowski, W. A.; Pamyatnykh, A. A. (April 2008), "The two hybrid B-type pulsators: ν Eridani and 12 Lacertae", Monthly Notices of the Royal Astronomical Society, 385 (4): 2061–2068, arXiv:0801.2451, Bibcode:2008MNRAS.385.2061D, doi:10.1111/j.1365-2966.2008.12964.x.
  21. Bodensteiner, J.; et al. (October 2018), "Infrared nebulae around bright massive stars as indicators for binary interactions", Astronomy & Astrophysics, 618: 13, arXiv:1806.01294, Bibcode:2018A&A...618A.110B, doi:10.1051/0004-6361/201832722, A110.
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