HD 183143

HD 183143 (HT Sagittae) is a blue hypergiant star located in the constellation of Sagitta.

HD 183143

A visual band light curve for HT Sagittae, plotted from ASAS-SN data[1]
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Sagitta
Right ascension 19h 27m 26.5636s[2]
Declination +18° 17′ 45.193″[2]
Apparent magnitude (V) 6.71 - 6.95[3]
Characteristics
Spectral type B6-8 Ia-0[4]
Apparent magnitude (B) 8.08
Apparent magnitude (J) 4.13
Apparent magnitude (K) 3.46
U−B color index +0.2[5]
B−V color index +1.2[5]
Variable type α Cyg?[3]
Astrometry
Proper motion (μ) RA: −1.004[2] mas/yr
Dec.: −5.703[2] mas/yr
Parallax (π)0.4296 ± 0.0243 mas[2]
Distance7,600 ± 400 ly
(2,300 ± 100 pc)
Absolute magnitude (MV)−8.7[4]
Details
Mass24.2[5] M☉
Radius109[5] R☉
Luminosity288,000[5] L☉
Surface gravity (log g)1.40[6] cgs
Temperature11,500[6] K
Rotational velocity (v sin i)37[6] km/s
Age7.6[5] Myr
Other designations
HT Sge, BD+18°4085, HD 183143, HIP 95657, SAO 104860
Database references
SIMBADdata

This star has an apparent magnitude of 6.9, meaning that can be seen with the naked eye under very dark skies and that is an easy target for binoculars or a small telescope.

Observations

HD 183143 was included in the first catalogue of Be stars, with distinct Hα emission lines.[7] When emission lines in hot supergiant stars were investigated as indicators of expanding atmospheres and mass loss, HD 183143 was found to have Hα lines with P Cygni profiles, but indications of only modest mass loss.[8] Modern high-resolution spectra show emission in lines from Hα, Hβ, Hγ, and Hδ, formed by the strong stellar wind.[6]

The introduction of spectral standards for supergiants gave HD 183143 as the standard star for the class B7Ia.[9] The spectral type is sometimes given as B7Iae to indicate the presence of the emission lines.[10]

HD 183143 was listed as being variable in 1976, with a very small amplitude.[11] During the Hipparcos mission, its brightness was observed to vary between magnitude 6.71 and 6.95. ASAS-3 photometry shows a period of 40.44 days.[3] HD 183143 was formally announced as a variable star, probably of the α Cygni type, in 1979 and given the variable star designation HT Sagittae.[12]

HD 183143 has been extensively studied because of the diffuse interstellar bands visible in its spectrum. The strongest lines are caused by interstellar atomic iron, potassium, lithium, sodium, and calcium, as well as ionised calcium, and CH and CN molecules.[13] Infrared bands of ionised buckminsterfullerene have also been found in its spectrum.[14] HD 183143 has been proposed as a reference standard for interstellar polarisation. It shows 6% polarisation.[15]

A 2004 study reclassified the spectral type of HD 183143 as B6.8 Ia-0, a hypergiant. The parallax from the original Hipparcos catalogue was 2.70 mas, indicating a distance around 370 pc, but the revised Hipparcos parallax and the Gaia Data Release 3 parallax both indicate distances around 2,000 pc.[2] Comparison of the space velocity and interstellar spectral lines produce a similar distance, with the star lying between the Orion-Cygnus Arm and the Carina–Sagittarius Arm.[4] At that distance, HD 183143 is an extremely luminous star, around 288,000 L☉, with correspondingly high mass and radius.[5]

References
  1. "ASAS-SN Variable Stars Database". ASAS-SN Variable Stars Database. ASAS-SN. Retrieved 6 January 2022.
  2. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  3. Watson, C. L. (2006). "The International Variable Star Index (VSX)". The Society for Astronomical Sciences 25th Annual Symposium on Telescope Science. Held May 23–25. 25: 47. Bibcode:2006SASS...25...47W.
  4. Chentsov, E. L. (2004). "HD 183143: A Hypergiant". Astronomy Letters. 30 (5): 325–331. Bibcode:2004AstL...30..325C. doi:10.1134/1.1738155. S2CID 121435951.
  5. Weßmayer, D.; Przybilla, N.; Butler, K. (2022). "Quantitative spectroscopy of B-type supergiants". Astronomy & Astrophysics. 668: A92. arXiv:2208.02692. Bibcode:2022A&A...668A..92W. doi:10.1051/0004-6361/202243973. S2CID 251320457.
  6. Galazutdinov, G. A.; Shimansky, V. V.; Bondar, A.; Valyavin, G.; Krełowski, J. (2017). "C60+ - looking for the bucky-ball in interstellar space". Monthly Notices of the Royal Astronomical Society. 465 (4): 3956. arXiv:1612.08898. Bibcode:2017MNRAS.465.3956G. doi:10.1093/mnras/stw2948. S2CID 118971571.
  7. Merrill, P. W.; Humason, M. L.; Burwell, C. G. (1925). "Discovery and Observations of Stars of Class Be". Astrophysical Journal. 61: 389. Bibcode:1925ApJ....61..389M. doi:10.1086/142899.
  8. Hutchings, J. B. (1970). "Expanding atmospheres in OB supergiants - IV". Monthly Notices of the Royal Astronomical Society. 147 (2): 161. Bibcode:1970MNRAS.147..161H. doi:10.1093/mnras/147.2.161.
  9. Morgan, W. W.; Roman, Nancy G. (1950). "Revised Standards for Supergiants on the System of the Yerkes Spectral Atlas". Astrophysical Journal. 112: 362. Bibcode:1950ApJ...112..362M. doi:10.1086/145351.
  10. Kohoutek, L.; Wehmeyer, R. (1997). "Catalogue of stars in the Northern Milky Way having H-alpha in emission". Abhandlungen aus der Hamburger Sternwarte. 11: 1. Bibcode:1997AAHam..11.....K.
  11. Hill, G.; Hilditch, R. W.; Pfannenschmidt, E. L. (1976). "Photoelectric measures of variable stars observed at Mt. Kobau (1970 - 73)". Publications of the Dominion Astrophysical Observatory Victoria. 15: 1. Bibcode:1976PDAO...15....1H.
  12. Kholopov, P. N.; Kukarkina, N. P.; Perova, N. B. (1979). "64th Name-List of Variable Stars". Information Bulletin on Variable Stars. 1581: 1. Bibcode:1979IBVS.1581....1K.
  13. Hobbs, L. M.; York, D. G.; Thorburn, J. A.; Snow, T. P.; Bishof, M.; Friedman, S. D.; McCall, B. J.; Oka, T.; Rachford, B.; Sonnentrucker, P.; Welty, D. E. (2009). "Studies of the Diffuse Interstellar Bands. III. HD 183143". The Astrophysical Journal. 705 (1): 32–45. arXiv:0910.2983. Bibcode:2009ApJ...705...32H. doi:10.1088/0004-637X/705/1/32. S2CID 3752303.
  14. Walker, G. A. H.; Bohlender, D. A.; Maier, J. P.; Campbell, E. K. (2015). "Identification of More Interstellar C60+ Bands". The Astrophysical Journal Letters. 812 (1): L8. arXiv:1509.06818. Bibcode:2015ApJ...812L...8W. doi:10.1088/2041-8205/812/1/L8. S2CID 118598331.
  15. Wisniewski, John P.; Babler, Brian L.; Bjorkman, Karen S.; Kurchakov, Anatoly V.; Meade, Marilyn R.; Miroshnichenko, Anatoly S. (2006). "The Asymmetrical Wind of the Candidate Luminous Blue Variable MWC 314". The Publications of the Astronomical Society of the Pacific. 118 (844): 820. arXiv:astro-ph/0605602. Bibcode:2006PASP..118..820W. doi:10.1086/506182. S2CID 14164638.
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