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HD 50138

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HD 50138
Observation data
Epoch J2000      Equinox J2000
Constellation Monoceros
Right ascension 06h 51m 33.399s[1]
Declination −06° 57′ 59.45″[1]
Apparent magnitude (V) 6.58[2]
Characteristics
Spectral type B8[3]
B−V color index 0.030±0.008[2]
Variable type γ Cas[4] or FS CMa[5]
Astrometry
Radial velocity (Rv)40.8±0.2[5] km/s
Proper motion (μ) RA: −3.678 mas/yr
Dec.: 4.178 mas/yr
Parallax (π)2.8487 ± 0.0459 mas[1]
Distance1,140 ± 20 ly
(351 ± 6 pc)
Absolute magnitude (MV)0.22[2]
Details
Mass6[3] M☉
Radius7.0±2.1[3] R☉
Luminosity(1.2±0.4)×103[3] L☉
Surface gravity (log g)4.63±0.16[6] cgs
Temperature6,391±241[6]
13,000[3] K
Metallicity [Fe/H]0.18±0.04[2] dex
Rotational velocity (v sin i)1.81389[6] km/s
Other designations
MWC 158, V743 Mon, BD−06°1775, GC 8983, HD 50138, HIP 32923, SAO 133781, PPM 189615[7]
Database references
SIMBADdata

HD 50138 is a peculiar star in the equatorial constellation of Monoceros, the unicorn. It has the variable star designation V743 Monocerotis. The typical apparent visual magnitude of this star is 6.58,[2] placing it near the lower limit for visibility to the naked eye.[2] Based on parallax measurements,[1] this star is located at a distance of approximately 1,140 light years. It is drifting further away with a heliocentric radial velocity of 41 km/s.[5] This is an isolated star, being located far from any star forming region and having a low proper motion.[5]

Observations

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In 1921 at the Mount Wilson Observatory, a search for B-type stars with Hydrogen-alpha emission lines identified HD 50138.[8][9] P. W. Merrill classified it as a Be star with a spectral type of B8e.[10][11] The structure of its bright hydrogen lines was found to vary with a period of around 12 days.[12] This was revised in 1933 to two periods: the first is five years long and the second is thirty days.[5] In 1949, Merrill noted the star displays a shell spectra, with narrow lines having been formed from a low density strata above the star's photosphere.[13] Metallic lines were found to undergo significant variation in intensity, appearing to roughly vary as a group.[9]

A radial velocity study of the star by V. Doazan in 1965 demonstrated that the star is surrounded by an expanding envelope. This expansion undergoes a variation with a period of around 50 days.[14] D. A. Allen found an excess of infrared emission in 1973, and also noticed that the star is photometrically variable.[15] A mass loss rate of 6.2×10−4 M☉·yr−1 was reported in 1975.[16] To explain the observations, a model was proposed consisting of a B8V class star surrounded by a shell of ionized hydrogen. It was also noticed how much the variable spectrum resembled that of AB Aurigae, a young Herbig Ae star.[17] Based on the spectrum, HD 50138 was then classed as a B[e] star, in the same group as FS Canis Majoris.[18]

In spite of its isolation from any star formation, the properties of this star continue to closely resemble a Herbig Be star. Some spectral features indicated the star is undergoing accretion. At the same time, the surrounding envelope showed gas expulsion in the outer regions. The envelope appears concentrated around the equator, suggesting an opaque circumstellar disk. The gas shell surrounding the star also appears to include local inhomogeneities or condensations.[19] The morphology of the circumstellar environment within an astronomical unit of the star was found to vary on time scales of days or weeks.[20] The formation of a new shell was observed around 1991.[21]

Polarization measurements show that the star is also polarimetrically variable, which could be explained by a dusty disk or a binary companion. A binary system is a favored scenario for its classification as a FS Canis Majoris variable. The large amount of circumstellar matter can then be explained as a result of a mass transfer between the two stars. The companion may be much fainter than the primary, which is why it has not been detected.[21] However, the changes in the circumstellar materials are difficult to explain with a binary model. Instead, the variability may be explained by a disk with a hot spot.[20] The large amount of circumstellar matter has made it difficult to obtain any direct information about the central star.[21] However, the star is most likely in an evolved state, rather than being pre-main-sequence.[3]

References

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  1. ^ a b c d Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  2. ^ a b c d e f 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, S2CID 119257644.
  3. ^ a b c d e f Koutoulaki, M.; et al. (June 2018), "The circumstellar environment of HD 50138 revealed by VLTI/AMBER at high angular resolution", Astronomy & Astrophysics, 614, id. A90, arXiv:1805.01432, Bibcode:2018A&A...614A..90K, doi:10.1051/0004-6361/201832814.
  4. ^ Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, GCVS 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, retrieved 2024-11-14.
  5. ^ a b c d e Sandell, Göran; Salyk, C.; van den Ancker, M.; de Wit, W. -J.; Chambers, E.; Güsten, R.; Wiesemeyer, H.; Richter, H. (September 2018), "Velocity-resolved [O I] 63 μm Emission in the HD 50138 Circumstellar Disk", The Astrophysical Journal, 864 (2), id. 104, arXiv:1807.09815, Bibcode:2018ApJ...864..104S, doi:10.3847/1538-4357/aad639.
  6. ^ a b c Jönsson, Henrik; et al. (August 17, 2020), "APOGEE Data and Spectral Analysis from SDSS Data Release 16: Seven Years of Observations Including First Results from APOGEE-South", The Astronomical Journal, 160 (3), American Astronomical Society: 120, arXiv:2007.05537, Bibcode:2020AJ....160..120J, doi:10.3847/1538-3881/aba592, ISSN 0004-6256.
  7. ^ "HD 50138". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2024-11-12.
  8. ^ Humason, M. L.; Merrill, P. W. (April 1921), "Ten Stars of Class B having the Hα Line Bright; 2nd List", Publications of the Astronomical Society of the Pacific, 33 (192): 112, Bibcode:1921PASP...33..112H, doi:10.1086/123052.
  9. ^ a b Merrill, Paul W. (November 1952), "Measurements in the Spectra of Ten Shell Stars", Astrophysical Journal, 116: 501, Bibcode:1952ApJ...116..501M, doi:10.1086/145642.
  10. ^ Merrill, Paul W. (June 1931), "The Spectrum of H. D. 50138", Astrophysical Journal, 73: 348, Bibcode:1931ApJ....73..348M, doi:10.1086/143314.
  11. ^ Merrill, Paul W.; Burwell, Cora G. (September 1933), "Catalogue and Bibliography of Stars of Classes B and A whose Spectra have Bright Hydrogen Lines", Astrophysical Journal, 78: 87, Bibcode:1933ApJ....78...87M, doi:10.1086/143490.
  12. ^ Merrill, P. W.; et al. (June 1925), "Discovery and Observations of Stars of Class Be", Astrophysical Journal, 61: 389–417, Bibcode:1925ApJ....61..389M, doi:10.1086/142899.
  13. ^ Merrill, Paul W. (February 1949), "Stars Having Shell Spectra", Publications of the Astronomical Society of the Pacific, 61 (358): 38, Bibcode:1949PASP...61...38M, doi:10.1086/126118.
  14. ^ Doazan, V. (1965), "Etude de l'etoile a enveloppe HD 50138, caracteristiques physiques etcinematiques.", Annales d'Astrophysique, 28: 1, Bibcode:1965AnAp...28....1D.
  15. ^ Allen, D. A. (1973), "Near infra-red magnitudes of 248 early-type emission-line stars and related objects.", Monthly Notices of the Royal Astronomical Society, 161 (2): 145–166, Bibcode:1973MNRAS.161..145A, doi:10.1093/mnras/161.2.145.
  16. ^ Kuan, P.; Huhi, L. V. (July 1975), "P Cygni stars and mass loss.", Astrophysical Journal, 199: 148–149, Bibcode:1975ApJ...199..148K, doi:10.1086/153675.
  17. ^ Hutsemekers, D. (June 1985), "The ultraviolet spectrum of the Be star HD 50138", Astronomy and Astrophysics, Supplement Series', 60: 373–388, Bibcode:1985A&AS...60..373H.
  18. ^ Bopp, B. W. (January 1993), "Spectroscopy of the B[e] Star HD 50138 (MWC 158)", Information Bulletin on Variable Stars, 3834: 1, Bibcode:1993IBVS.3834....1B.
  19. ^ Pogodin, M. A. (January 1997), "Circumstellar peculiarities in the unusual Be star HD 50138.", Astronomy and Astrophysics, 317: 185–192, Bibcode:1997A&A...317..185P.
  20. ^ a b Kluska, J.; et al. (June 2016), "A disk asymmetry in motion around the B[e] star MWC158", Astronomy & Astrophysics, 591, id. A82, arXiv:1605.05262, Bibcode:2016A&A...591A..82K, doi:10.1051/0004-6361/201527924.
  21. ^ a b c Jeřábková, T.; et al. (February 2016), "Time-dependent spectral-feature variations of stars displaying the B[e] phenomenon. III. HD 50138", Astronomy & Astrophysics, 586, id. A116, arXiv:1512.02506, Bibcode:2016A&A...586A.116J, doi:10.1051/0004-6361/201526290.

Further reading

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