HD 37974

HD 37974 (or R 126) a variable B[e] hypergiant in the Large Magellanic Cloud. It is surrounded by an unexpected dust disk.

HD 37974

Artist concept of the stars, Sun and planets not drawn to scale
Observation data
Epoch J2000      Equinox J2000
Constellation Dorado
Right ascension 05h 36m 25.843s[1]
Declination –69° 22′ 55.90″[1]
Apparent magnitude (V) 10.95[2]
Characteristics
Spectral type B0.5Ia+[3]
U−B color index −0.88[2]
B−V color index +0.15[2]
Variable type LBV?[4][5]
Astrometry
Radial velocity (Rv)258[6] km/s
Proper motion (μ) RA: -1.8[1] mas/yr
Dec.: -15.1[1] mas/yr
Parallax (π)0.22 ± 0.42 mas[7]
Absolute magnitude (MV)−8.4[4]
Details[3]
Mass70 M☉
Luminosity1,400,000 L☉
Temperature22,500 K
Other designations
RMC 126, R 126, HD 37964, GSC 09167-00518, AL 361, GV 408, MSX LMC 890, CPD-69°420, MWC 123, LHA 120-S 127, LI-LMC 1413, LMC V3566; 2MASS J05362586-6922558[5]
Database references
SIMBADdata

Properties

R126, formally RMC (Radcliffe observatory Magellanic Cloud) 126, is a massive luminous star with several unusual properties. It exhibits the B[e] phenomenon where forbidden emission lines appear in the spectrum due to extended circumstellar material. Its spectrum also shows normal (permitted) emission lines formed in denser material closer to the star, indicative of a power stellar wind.[8] The spectra include silicate and polycyclic aromatic hydrocarbon (PAH) features that suggest a dusty disc.[3]

The star itself is a hot supergiant thought to be seventy times more massive than the Sun and over a million times more luminous. It has evolved away from the main sequence (being an O-class star, when it was in MS) and is so luminous and large that it is losing material through its stellar wind over a billion times faster than the Sun. It would lose more material than the Sun contains in about 25,000 years.[9]

It is expected to evolve into Wolf–Rayet star in several hundred thousand years.

Dusty disc

The dust cloud around R126 is surprising because stars as massive as these were thought to be inhospitable to planet formation due to powerful stellar winds making it difficult for dust particles to condense. The nearby hypergiant HD 268835 shows similar features and is also likely to have a dusty disc, so R126 is not unique.[3]

The disc extends outwards for 60 times the size of Pluto's orbit around the Sun, and probably contains as much material as the entire Kuiper belt. It is unclear whether such a disc represents the first or last stages of the planet-forming process.[10]

Variability
A light curve for HD 37974, adapted from Pedersen et al. (2019)[11]

The brightness of R126 varies in an unpredictable way by around 0.6 magnitude over timescales of tens to hundreds of days. The faster variations are characteristic of α Cygni variables, irregular pulsating supergiants. The slower variations are accompanied by changes in the colour of the star, with it being redder when it is visually brighter, typical of the S Doradus phases of luminous blue variables.[4]

See also

References
  1. 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 and Astrophysics. 355: L27. Bibcode:2000A&A...355L..27H. doi:10.1888/0333750888/2862.
  2. Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237. Bibcode:2002yCat.2237....0D.
  3. Kastner, J. H.; Buchanan, C. L.; Sargent, B.; Forrest, W. J. (2006). "SpitzerSpectroscopy of Dusty Disks around B\e] Hypergiants in the Large Magellanic Cloud". The Astrophysical Journal. 638 (1): L29–L32. Bibcode:2006ApJ...638L..29K. doi:10.1086/500804.
  4. Van Genderen, A. M.; Sterken, C. (2002). "Light variations of massive stars (alpha Cyg variables). XVIII. The B[e] supergiants S 18 in the SMC and R 66 = HDE 268835 and R 126 = HD 37974 in the LMC". Astronomy and Astrophysics. 386 (3): 926. Bibcode:2002A&A...386..926V. doi:10.1051/0004-6361:20020360.
  5. Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
  6. Feast, M. W.; Thackeray, A. D.; Wesselink, A. J. (1960). "The brightest stars in the Magellanic Clouds". Monthly Notices of the Royal Astronomical Society. 121 (4): 337. Bibcode:1960MNRAS.121..337F. doi:10.1093/mnras/121.4.337.
  7. Gaia Collaboration (2016). "VizieR Online Data Catalog: Gaia DR1 (Gaia Collaboration, 2016)". VizieR On-line Data Catalog: I/337. Originally Published in: Astron. Astrophys. 1337. Bibcode:2016yCat.1337....0G.
  8. Levato, H.; Miroshnichenko, A. S.; Saffe, C. (2014). "New objects with the B[e] phenomenon in the Large Magellanic Cloud". Astronomy & Astrophysics. 568: A28. Bibcode:2014A&A...568A..28L. doi:10.1051/0004-6361/201423846.
  9. Zsargó, J.; Hillier, D. J.; Georgiev, L. N. (2008). "Axi-symmetric models of B[e] supergiants. I. The effective temperature and mass-loss dependence of the hydrogen and helium ionization structure". Astronomy and Astrophysics. 478 (2): 543. arXiv:0712.0870. Bibcode:2008A&A...478..543Z. doi:10.1051/0004-6361:20078293. S2CID 55234776.
  10. NASA's Spitzer Uncovers Hints of Mega Solar Systems, Nasa.gov, accessed 11 Feb 2006
  11. Pedersen, May G.; Chowdhury, Sowgata; Johnston, Cole; Bowman, Dominic M.; Aerts, Conny; Handler, Gerald; De Cat, Peter; Neiner, Coralie; David-Uraz, Alexandre; Buzasi, Derek; Tkachenko, Andrew; Simón-Díaz, Sergio; Moravveji, Ehsan; Sikora, James; Mirouh, Giovanni M.; Lovekin, Catherine C.; Cantiello, Matteo; Daszyńska-Daszkiewicz, Jadwiga; Pigulski, Andrzej; Vanderspek, Roland K.; Ricker, George R. (February 10, 2019). "Diverse Variability of O and B Stars Revealed from 2-minute Cadence Light Curves in Sectors 1 and 2 of the TESS Mission: Selection of an Asteroseismic Sample". The Astrophysical Journal Letters. 872 (1): L9. arXiv:1901.07576. Bibcode:2019ApJ...872L...9P. doi:10.3847/2041-8213/ab01e1. S2CID 118963697.
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