V915 Scorpii

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V915 Scorpii
Position of V915 Scorpii (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Scorpius
Right ascension 17h 14m 27.65508s[1]
Declination −39° 45′ 59.9378″[1]
Apparent magnitude (V) 6.22 - 6.64[2]
Characteristics
Evolutionary stage K-type hypergiant
Spectral type K0Ia-0[3]
U−B color index 2.48[4]
B−V color index 2.21[5]
Variable type SRd[6]
Astrometry
Radial velocity (Rv)46.00[7] km/s
Proper motion (μ) RA: −0.758[1] mas/yr
Dec.: −1.466[1] mas/yr
Parallax (π)0.5485 ± 0.0525 mas[1]
Distance5600+570
−370 ly
(1718+175
−115 pc)[8]
Details
Mass8.5[9] or 14.7[10] M☉
Radius685.6[1] R☉
Luminosity74,100[11] L☉
Surface gravity (log g)0.003[1] cgs
Temperature4,573[1] K
Metallicity [Fe/H]0.3491[1] dex
Other designations
HR 6392, HD 155603, HIP 84322, CD−39°11212, IRAS 17109-3942, 2MASS J17142765-3945599, WDS J17145-3946
Database references
SIMBADdata

V915 Scorpii (HR 6392, HD 155603) is an orange hypergiant and a semiregular variable star, located 1,718 parsecs (5,600 ly) away in the constellation Scorpius. Its apparent magnitude varies between 6.22 and 6.64, being heavily diminshed by 2.93 magnitudes due to interstellar extinction.

Surroundings[edit]

V915 Scorpii and its companions resolved by the Hubble Space Telescope

V915 Scorpii is surrounded by the sparse OB association Moffat 2.[12] It is also surrounded by an envelope of dust and gas, producing a significant infrared excess.[13]

V915 Sco has been classified as a triple star. 15" away is the Wolf-Rayet star WR 85, one of the most luminous stars known, but still visually four magnitudes fainter than V915 Sco.[14] Component C is a 10th magnitude K class star 17" away.[15] There is also a 14th magnitude star 22" away. Photometry and space motions suggest that only V915 Sco and WR 85 lie at the same distance, while the other two stars are foreground objects. Assumptions about the brightness of each star suggest a distance of 2,600 pc, and a projected separation of 0.2 pc.[16]

Four arc minutes distant are two other assumed members of the association, a 10th magnitude B0 giant and an 11th magnitude OB star. Fitting the association members to a main sequence gives a highly uncertain distance of 1.8 kpc.[12] A kinematical distance has been calculated for the bubble around WR 85 at 2.8 kpc.[17] The distance to V915 Scorpii derived assuming minimal interstellar extinction is 7,300 pc.[13] However, the star is considerably reddened and this results in a distance of 2,630 pc.[16] Analysis of WR 85 as a luminous hydrogen-rich star gives a distance of 6,600 pc.[14] Bailer-Jones et al. 2018 estimates a distance of 1,720 pc.[8] The parallax for WR 85 is considerably reliable and suggests a distance of around 2,400 pc.[18]

Variability[edit]

A light curve for V915 Scorpii, plotted from Hipparcos data[19]

V915 Scorpii is classified as a semiregular variable, with an apparent magnitude that varies between 6.22 and 6.64.[6] Any period associated with the variation is longer than 600 days.[20]

The variability of V915 Scorpii was first announced by the Konkoly Observatory in 1979. It was given the variable-star designation V915 Scorpii in 1978.[21]

Properties[edit]

V915 Scorpii has a spectral classification of K0 Ia-0,[22] meaning that is a hypergiant star with a K spectral type. The mass of the star is estimated at 8.5[9] or 14.7 times[10] the solar mass, while its radius is estimated at about 690 R☉, thus giving a volume equivalent to about 330 million times that of the Sun.[1] A 2001 paper publised an angular diameter of 0.0032 arcseconds for this star.[23] V915 Scorpii is radiating a luminosity equivalent to 74,000 times the solar luminosity.[9] It has a surface effective temperature of 4,600 K, giving it the typical orange color of a K-type star.[1][24]

Despite being a K-type star, it is seen as red in the sky, with a B-V color index of 2.21.[5][a] This happens because of massive interstellar reddenning between Earth and the star,[24] its apparent brightness is diminished by 2.93 magnitudes due to interstellar dust.[1]

The spectral type of V915 Scorpii was determined to be G5Ia in 1954,[25] G5Ia-0 in 1973,[26] G8Ia in 1977,[12] K0Ia in 1982,[27] and K0Ia-0 in 1989,[3] all indicative of a luminous supergiant or hypergiant.

See also[edit]

Notes[edit]

  1. ^ See the color index article

References[edit]

  1. ^ a b c d e f g h i j k l 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.
  2. ^ 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.
  3. ^ a b Keenan, Philip C.; McNeil, Raymond C. (1989). "The Perkins catalog of revised MK types for the cooler stars". Astrophysical Journal Supplement Series. 71: 245. Bibcode:1989ApJS...71..245K. doi:10.1086/191373. S2CID 123149047.
  4. ^ 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: 0. Bibcode:2002yCat.2237....0D.
  5. ^ a b Hunsch, M.; Schmitt, J. H. M. M.; Voges, W. (1998-01-01). "The ROSAT all-sky survey catalogue of optically bright late-type giants and supergiants". Astronomy and Astrophysics Supplement Series. 127 (2): 251–255. Bibcode:1998A&AS..127..251H. doi:10.1051/aas:1998347. ISSN 0365-0138.
  6. ^ a b "VSX : Detail for V0915 Sco". www.aavso.org. Retrieved 2024-05-19.
  7. ^ Barbier-Brossat, M.; Petit, M.; Figon, P. (1994). "Third bibliographic catalogue of stellar radial velocities (Text in French)". Astronomy and Astrophysics Supplement Series. 108: 603. Bibcode:1994A&AS..108..603B.
  8. ^ a b Bailer-Jones, C. A. L.; Rybizki, J.; Fouesneau, M.; Demleitner, M.; Andrae, R. (2021-03-01). "Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3". The Astronomical Journal. 161 (3): 147. arXiv:2012.05220. Bibcode:2021AJ....161..147B. doi:10.3847/1538-3881/abd806. ISSN 0004-6256. Data about this star can be seen here.
  9. ^ a b c Anders, F.; Khalatyan, A.; Chiappini, C.; Queiroz, A. B.; Santiago, B. X.; Jordi, C.; Girardi, L.; Brown, A. G. A.; Matijevič, G.; Monari, G.; Cantat-Gaudin, T.; Weiler, M.; Khan, S.; Miglio, A.; Carrillo, I.; Romero-Gómez, M.; Minchev, I.; De Jong, R. S.; Antoja, T.; Ramos, P.; Steinmetz, M.; Enke, H. (2019). "Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia DR2 stars brighter than G = 18". Astronomy and Astrophysics. 628: A94. arXiv:1904.11302. Bibcode:2019A&A...628A..94A. doi:10.1051/0004-6361/201935765. S2CID 131780028. V915 Scorpii's database entry at VizieR.
  10. ^ a b Kervella, Pierre; Arenou, Frédéric; Mignard, François; Thévenin, Frédéric (2019-03-01). "Stellar and substellar companions of nearby stars from Gaia DR2. Binarity from proper motion anomaly". Astronomy and Astrophysics. 623: A72. arXiv:1811.08902. Bibcode:2019A&A...623A..72K. doi:10.1051/0004-6361/201834371. ISSN 0004-6361. V915 Scorpii's database entry at VizieR.
  11. ^ Dorn-Wallenstein, Trevor Z.; Levesque, Emily M.; Neugent, Kathryn F.; Davenport, James R. A.; Morris, Brett M.; Gootkin, Keyan (2020). "Short-term Variability of Evolved Massive Stars with TESS. II. A New Class of Cool, Pulsating Supergiants". The Astrophysical Journal. 902 (1): 24. arXiv:2008.11723. Bibcode:2020ApJ...902...24D. doi:10.3847/1538-4357/abb318. S2CID 221340538. V915 Scorpii's database entry at VizieR.
  12. ^ a b c Moffat, A. F. J.; Fitzgerald, M. P. (1977). "Some very luminous supergiants associated with compact groups of luminous OB stars". Astronomy and Astrophysics. 54: 263. Bibcode:1977A&A....54..263M.
  13. ^ a b Odenwald, S. F. (1986). "An IRAS survey of IR excesses in G-type stars". Astrophysical Journal. 307: 711. Bibcode:1986ApJ...307..711O. doi:10.1086/164456.
  14. ^ a b Hamann, W.-R.; Gräfener, G.; Liermann, A. (2006). "The Galactic WN stars. Spectral analyses with line-blanketed model atmospheres versus stellar evolution models with and without rotation". Astronomy and Astrophysics. 457 (3): 1015. arXiv:astro-ph/0608078. Bibcode:2006A&A...457.1015H. doi:10.1051/0004-6361:20065052. S2CID 18714731.
  15. ^ Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal. 122 (6): 3466. Bibcode:2001AJ....122.3466M. doi:10.1086/323920.
  16. ^ a b Andrews, J. P. (1977). "HR 6392 - A double star with very high luminosities". Monthly Notices of the Royal Astronomical Society. 178 (2): 131–136. Bibcode:1977MNRAS.178..131A. doi:10.1093/mnras/178.2.131.
  17. ^ Vasquez, J.; Cappa, C.; McClure-Griffiths, N. M. (2005). "An HI interstellar bubble surrounding WR85 and RCW118". Monthly Notices of the Royal Astronomical Society. 362 (2): 681–688. arXiv:astro-ph/0507481. Bibcode:2005MNRAS.362..681V. doi:10.1111/j.1365-2966.2005.09349.x. S2CID 16064834.
  18. ^ 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.
  19. ^ "Hipparcos Tools Interactive Data Access". Hipparcos. ESA. Retrieved 8 December 2021.
  20. ^ ESA (1997). "The HIPPARCOS and TYCHO catalogues. Astrometric and photometric star catalogues derived from the ESA HIPPARCOS Space Astrometry Mission". The Hipparcos and Tycho Catalogues. Astrometric and Photometric Star Catalogues Derived from the ESA Hipparcos Space Astrometry Mission. 1200. Bibcode:1997ESASP1200.....E.
  21. ^ Kholopov, P. N.; Kukarkina, N. P.; Perova, N. B. (1979-04-01). "64th Name-List of Variable Stars". Information Bulletin on Variable Stars. 1581: 1. Bibcode:1979IBVS.1581....1K. ISSN 0374-0676.
  22. ^ "V915 Sco". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved May 19, 2024.
  23. ^ Pasinetti Fracassini, L. E.; Pastori, L.; Covino, S.; Pozzi, A. (2001-02-01). "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics". Astronomy and Astrophysics. 367 (2): 521–524. arXiv:astro-ph/0012289. Bibcode:2001A&A...367..521P. doi:10.1051/0004-6361:20000451. ISSN 0004-6361. V915 Scorpii's database entry at VizieR.
  24. ^ a b "Colour of Stars". 6 March 2024.
  25. ^ Bidelman, William P. (1954). "Spectral Classification of Southern Stars of High Luminosity". Publications of the Astronomical Society of the Pacific. 66 (392): 249. Bibcode:1954PASP...66..249B. doi:10.1086/126709.
  26. ^ Warren, P. R. (1973). "A model atmosphere analysis of the super-supergiant HR 5171". Monthly Notices of the Royal Astronomical Society. 161 (4): 427–444. Bibcode:1973MNRAS.161..427W. doi:10.1093/mnras/161.4.427.
  27. ^ Houk, N. (1982). "Michigan Catalogue of Two-dimensional Spectral Types for the HD stars. Volume_3. Declinations -40_ƒ0 to -26_ƒ0". Michigan Catalogue of Two-dimensional Spectral Types for the HD stars. Volume_3. Declinations -40_ƒ0 to -26_ƒ0. Bibcode:1982mcts.book.....H.
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